GLYCOGEN SYNTHASE KINASE 3β AS A TARGET FOR THE THERAPY OF... : Shock (original) (raw)
INTRODUCTION
The regulation of glycogen synthase, the enzyme catalyzing the last step of glycogen synthesis, has been widely studied for many years. In 1980, Embi et al. (1) identified glycogen synthase kinase (GSK) 3 as one of the protein kinases able to phosphorylate glycogen synthase. Initially, the functions of GSK-3 were thought to be limited to glycogen metabolism; however, 20 years after its discovery, we know that this kinase is involved in the regulation of many cell functions, including the specification of cell fate during embryonic development, cell division and apoptosis, and signaling by insulin, growth factors, and nutrients (2). Moreover, GSK-3 is involved in the regulation of several signal transduction pathways, the dysregulation of which has been implicated in the development of cancer, diabetes, neurodegenerative diseases, and bipolar disorder (see Table 1 for a list of GSK-3 substrates). For these reasons, GSK-3 has become a novel and important therapeutic target, and several inhibitors of this kinase have been developed and studied in vitro and in preclinical studies in vivo (3).
Substrates of GSK-3.
Two mammalian isoforms of GSK-3 are known: GSK-3α and GSK-3β. These isoforms are encoded by distinct genes and have molecular weights of 51 and 47 kDa, respectively (4). Homologues of GSK-3 exist in all eukaryotes examined to date, as reviewed in the article of Ali et al. (5). The reported degree of homology between species is very high indeed. The isoforms GSK-3α and GSK-3β are constitutively expressed and have similar, but not identical, functions. The crystal structure of GSK-3 has been identified (6-8) and has provided important information about the regulation of the kinase and the mode of action of its inhibitors.
GSK-3 regulation
In contrast to most other kinases, GSK-3 is active when the cell is in a resting state. The inactivation of GSK-3 can be induced by phosphorylation at one of its N-terminal serine (Ser) residues: Ser21 for GSK-3α and Ser9 for GSK-3β (9). This phosphorylation can be mediated by several kinases, including mitogen-activated protein kinase (MAPK)-activated protein kinase 1 (p90Rsk), p70 S6 kinase, Akt (protein kinase B [PKB]), some isoforms of protein kinase C (PKC), and cyclic AMP (cAMP)-dependent protein kinase (protein kinase A [PKA]) (10-12). Insulin inhibits the activity of GSK-3, and this effect has been correlated with the phosphorylation of Ser9/21 (13). As shown in Figure 1, the insulin-dependent inactivation of GSK-3 is mediated by Akt, one of the most important physiological mediators of the phosphatidylinositol 3 kinase (PI3K) survival pathway. Both in vitro and in vivo studies have demonstrated that activated Akt inactivates GSK-3 by inducing the phosphorylation of Ser21 on GSK-3α and of Ser9 on GSK-3β (13-15). Moreover, van Weeren et al. (16) observed a direct interaction between insulin and Akt, showing that the inhibitory effect of insulin on GSK-3β is mediated by direct phosphorylation by Akt.
Regulation of GSK-3 activity by phosphorylation. Several signaling cascades initiate the phosphorylation of GSK-3 on its regulatory N-terminal serine residue. Insulin receptor substrate activation results in sequential activation of PI3K, 3-phosphatidylinositol-dependent kinase 1, and Akt. Activated Akt phosphorylates GSK-3 on serine residue 21 (α) or 9 (β), resulting in GSK-3 inhibition. In addition, the activation of G protein-coupled receptor linked to heterotrimeric G proteins (subunits α, β, and γ) that activate phospholipase and cause the hydrolysis of phosphatidylinositol 4,5-biphosphate to two second messengers, inositol triphosphate, which increases intracellular Ca++ levels, and diacylglycerol. These messengers induce the activation of PKC, which ultimately phosphorylates GSK-3. Similarly, the binding to the G protein-coupled receptor of ligands, coupled with G proteins that activate adenyl cyclase to produce cAMP, leads to the activation of PKA that also phosphorylates GSK-3. The reactivation of GSK-3 is dependent on specific phosphatases. Many substrates of GSK-3 need to be prephosphorylated at a serine or threonine residue as an additional regulatory mechanism controlling GSK-3 activity. Glycogen synthase is prephosphorylated by casein kinase II before GSK-3 can phosphorylate it and downregulate its activity. The CREB must be first phosphorylated by PKA to enable the phosphorylation of CREB by GSK-3. In addition, the prephosphorylation of the microtubule-associated protein tau by other kinases (including Cdk5) facilitates the subsequent phosphorylation of tau by GSK-3, which decreases the ability of tau to bind and stabilize the microtubules.
In contrast to the inhibitory effect obtained after serine phosphorylation on GSK-3, the phosphorylation of tyrosine residues 216 on GSK-3β and 279 on GSK-3α increase the activity of this enzyme (17). Signals different from those involved in serine phosphorylation lead to tyrosine phosphorylation of GSK-3. The mechanism by which tyrosine phosphorylation of GSK-3 takes place in cells is largely unclear (18-20).
The activity of GSK-3 can also be regulated by the formation of protein complexes (protein-protein interactions) with specific binding proteins (21). These include GSK-3β-binding protein, axin and the axin-related protein axil, and conductin (21-23). These interactions result in the inhibition of GSK-3 activity, which, in turn, leads to the stabilization of β-catenin levels because of the reduced GSK-3-facilitated degradation of β-catenin (21, 24). The ability to form protein complexes is an additional regulatory system for GSK-3 activity, integrated with serine and tyrosine phosphorylation, to provide a precise and, possibly, signal and/or substrate-specific mechanism for the modulation of the activity of this kinase.
Glycogen synthase kinase 3β is an important mediator in the Wnt pathway and is a critical component of the adenomatous polyposis coli-β-catenin destruction complex, especially important in initiating the phosphorylation-dependent degradation of β-catenin (Fig. 2) (25). Interestingly, mice lacking the gene for GSK-3β do not show any defect in the Wnt pathway (26). This indicates that axin switches from binding both GSK-3α and GSK-3β to binding only the isoform α. The GSK-3α concentration in the cytoplasm is higher than that of axin; thus, there is abundance of GSK-3α molecules for axin to bind to (27). The lack of discrimination between GSK-3α and GSK-3β in the Wnt pathway is not observed in other cellular pathways in which the kinase is involved, as reported by Hoeflich et al. (26). In addition, the two GSK-3 isoforms α and β, at least in the specific pathway analyzed, show distinct biological roles, and the isoform α is not able to compensate for the loss of GSK-3β (26, 27).
The Wnt pathway. In the absence of the Wnt ligand, GSK-3 is bound in a complex with axin, β-catenin, and adenomatous polyposis coli protein. β-Catenin is prephosphorylated by casein kinase I to prime it for phosphorylation by GSK-3 and for its subsequent proteosomal degradation. Stimulation by Wnt of the Frizzled receptor results in the recruitment of FRAT (frequently rearranged in advanced T-cell lymphomas) and in the disheveling into the GSK-3 complex. This prevents the phosphorylation of β-catenin by GSK-3 and results in its accumulation and translocation to the nucleus, where it binds to the cotranscriptional activator of T-cell factor/lymphocyte enhancer-binding factor, starting target genes transcription.
Regulation of nuclear factor κB activity by GSK-3
In the year 2000, GSK-3β was identified as a new fundamental player for cell survival. Hoeflich et al. (26) showed that GSK-3β is required for the nuclear factor (NF) κB-mediated survival response after tumor necrosis factor (TNF) α stimulation. To study the role of GSK-3 in mammalian development, the GSK-3 gene in murine embryonic stem cells was disrupted. The GSK-3β+/− male and female mice generated were healthy; however, the GSK-3β−/− embryos were not viable and died between 13.5 and 14.5 days into gestation (26). The analysis of the embryos revealed a multifocal hemorrhagic degeneration in the livers of GSK-3β−/− embryos, the hepatocytes showing signs of apoptosis. This phenotype was similar to mice in which the gene for p65 or IκB kinase (IKK) 2 (and hence, the activation of NF-κB) had been deleted (26, 28, 29). This finding formed the basis for the hypothesis that GSK-3β may play a pivotal role in the regulation of the activation of NF-κB and, hence, inflammatory response. Interestingly, the apoptotic hepatocytes in GSK-3β−/− embryos could be rescued by inhibiting the formation of endogenous TNF-α with injections of an antimurine TNF-α monoclonal antibody. This data pointed to a role for GSK-3 in suppressing TNF-α-induced apoptosis. Since these early observations, a number of studies have confirmed the involvement of GSK-3β in the regulation of NF-κB activation (Fig. 3). Schwabe and Brenner (30) reported the effect of the pharmacological inhibition of GSK-3β in primary hepatocytes. After stimulation with TNF-α, the cells were treated with the specific GSK-3β inhibitor lithium chloride. Treatment of TNF-α-stimulated cells with lithium chloride resulted in a decrease of the NF-κB-dependent gene transcription. Moreover, the authors demonstrated that lithium chloride did not affect IκB-α degradation or IKK activity, translocation of the NF-κB heterodimer into the nucleus, or its binding to DNA. This study also indicated four potential phosphorylation sites for GSK-3β on NF-κB subunit p65 (30).Takada and colleagues (31) demonstrated that NF-κB activation induced by lipopolysaccharide (LPS), interleukin (IL) 1β, or cigarette smoke was abolished in GSK-3β−/− cells. In this study, the authors found that the genetic depletion of GSK-3β also suppressed the TNF-α-induced IKK activation, IκB-α phosphorylation, and IκB-α ubiquitination (31). A different approach into the investigation of the GSK-3β activity was used by Sanchez et al. (32), who measured the effect of GSK-3β on NF-κB in primary astrocytes obtained from 1-day-old rats. Interestingly, the overexpression of constitutively active GSK-3β resulted in astrocyte cell death. This effect is probably due to the ability of GSK-3β to induce apoptosis through the disruption of a cell survival pathway regulated by NF-κB. In agreement with Takada and colleagues, GSK-3β was found to block NF-κB-dependent transcription and DNA binding activity by preventing the phosphorylation and degradation of IκBα after TNF-α challenge (32).
Possible sites for GSK-3 activity on NF-κB regulation. After cellular stimulation (TNF, LPS), IκBα is phosphorylated and the p50/p65 heterodimer translocates into the nucleus. Different reports indicate that GSK-3 is able to affect NF-κB activity at different sites: (1) phosphorylation of IκBα, (2) translocation of p50/p65 to the nucleus and its binding to DNA, or (3) phosphorylation of p65 (see text for details).
Another possible model for the regulation of NF-κB by GSK-3β was proposed by Demarchi et al. (33). The authors found a role for the kinase in the regulation of the stability of p105, precursor of the NF-κB component p50. They demonstrated that in cells lacking GSK-3β, the constitutive p105 processing to p50 occurred faster than in wild-type fibroblasts. With the reintroduction of GSK-3β by transfection, the processing rate was reduced. Moreover, GSK-3β was necessary to prime and then phosphorylate p105 after stimulation of the cells with TNF-α. On the basis of the observation that TNF-α stimulation determines both IKK activation and GSK-3β inhibition, the authors proposed that after the challenge with TNF-α, GSK-3β is inhibited and therefore cannot phosphorylate the newly synthesized p150 dimers. The p105 subunits are then excluded from the degradation pathway, and this leads to an overall decrease of the NF-κB pathway activation (33).
Following the growing evidence indicating a role for GSK-3β in the activation of NF-κB, different groups have tried to determine the relevant site(s) for the phosphorylation of the subunit p65 by GSK-3β. Glycogen synthase kinase 3β has been shown to phosphorylate a glutathione _S_-transferase-p65 fusion protein in vitro, but the exact site was not determined and it was still unclear if p65 was a physiological substrate for GSK-3β in vivo (30). The serine residue 468 on p65 was proposed as a phosphorylation site for GSK-3β in a study conducted in HeLa cells stimulated with IL-1 (34). The same study reported that phosphorylation of serine residue 468 of p65, induced by the PP1/PP2A phosphatase inhibitor calyculin A, was inhibited by the GSK-3β inhibitor lithium chloride (34). The effect of GSK-3β on the regulation of NF-κB raised an interest in the investigation of the role of this kinase in diseases where NF-κB activation plays a fundamental role, including inflammation and sepsis. Excessive inflammation and the activation of the NF-κB pathway are important components in the pathophysiology of sepsis and septic shock (35-39).
Martin et al. (40) recently reported the effects of inhibition of GSK-3β activity on the production of proinflammatory and anti-inflammatory cytokines after stimulation of cells with LPS. They used both wild-type mouse embryonic fibroblast (MEF) treated with an inhibitor of GSK-3β, and GSK-3β−/− MEFs. After stimulation of GSK-3β−/− MEFs with LPS, they found a reduction in the production of the proinflammatory cytokines TNF-α and IL-6, and an increase in the formation of the anti-inflammatory cytokine IL-10, compared with wild-type MEFs not challenged with LPS. This study showed a correlation between GSK-3-induced modulation of proinflammatory and anti-inflammatory cytokine production and the toll-like receptors (TLRs) signaling pathways. Using selective agonists for TLR2 (lipoteichoic acid from Streptococcus pneumoniae), TLR4 (synthetic lipid A; compound 506), TLR5 (flagellin protein FljB from Salmonella typhimurium), and TLR9 (human CpG), the authors assessed whether the inhibition of GSK-3 in conjunction with a specific TLR agonist affected the inflammatory response (40). The specific GSK-3 inhibitor SB216763 reduced the production of the proinflammatory cytokines IL-1β, interferon gamma, IL-12p40, and IL-6 in human peripheral blood mononuclear cells stimulated with a TLR2, TLR4, TLR5, or TLR9 agonists. In contrast, the production of the anti-inflammatory cytokine IL-10 was increased compared with that of controls stimulated with any of the TLR agonist (40).
Martin et al. (40) also sought to elucidate which step(s) of the NF-κB pathway could be affected by GSK-3 inhibition. The presence of the GSK-3 inhibitor SB216763 failed to alter the rate or extent of degradation or resynthesis of IκBα and IκBβ. Neither the amount nor the duration of p65 phosphorylation (Ser276 or Ser536) was affected after stimulation of human monocytes with LPS in the presence of the GSK-3 inhibitor SB216763 compared with that of cultures stimulated with LPS alone. No alterations were found in the amount of nuclear p50 or p65, or in the DNA binding of nuclear p50 or p65 in unstimulated cells treated with SB216763 alone compared with that of untreated control. What, then, are the mechanism(s) regulating the activation of NF-κB-dependent gene transcription after binding of the active p50/p65 heterodimer to the promoter region of its target genes? There is evidence that (1) the cellular coactivator cAMP response element-binding protein (CREB)-binding protein (CBP) functions as a transcriptional coactivator of NF-κB, (2) CREB binds to phosphorylated p65, and (3) CREB may compete with (phosphorylated) p65 for CBP binding. Interestingly, stimulation of cells with LPS increased the binding of CBP to p65, whereas inhibition of the activity of GSK-3β with SB216763 not only attenuated the LPS-stimulated binding of p65 to CREB but also increased CREB-binding to CBP (40, 41). Thus, it seems that GSK-3 regulates, at least in MEF, the degree of phosphorylation of CREB, which then binds to CBP and removes this transcriptional coactivator of NF-κB from the p65 subunit, resulting in a reduction in the activation of NF-κB.
High levels of β-catenin that occur after the inhibition of both GSK-3 protein isoforms are reported to inhibit NF-κB activity at the level of DNA binding, although the mechanism by which this occurs has not been established (42, 43). Two cell lines, MEFs and nontransformed rat intestinal epithelial cells, have been shown not to exhibit elevated levels of β-catenin as a result of decreased GSK-3 activity compared with control cells and, therefore, provide diverse model systems for the investigation of the influence of GSK-3 on NF-κB activity. These cell lines were used in a recent study (44), providing evidence that GSK-3β is necessary for the efficient localization of p65 to the promoter region of NF-κB-regulated genes during cytokine stimulation. Several genes, including monocyte chemoattractant protein (MCP) 1 and IL-6, were poorly induced in cells lacking GSK-3β, in response to TNF-α stimulation. These genes were substantially upregulated in wild-type fibroblast treated with TNF-α. Moreover, this study showed that the activation of IKK was not disrupted in cells lacking GSK-3β, which was consistent with earlier studies discussed previously (26, 30) (Fig. 3).
Inhibitors of GSK-3ββ
The alkali metal lithium has been used in various formulations for the cure of several human diseases (45). In particular, after the studies conducted in the early 1950s, lithium was introduced as an effective therapy for bipolar affective disorder (46). More recently, lithium has been shown to affect the development of several organisms (47, 48), with a similar pattern resulting with the embryonic disruption of GSK-3 gene in Dictyostelium or ectopic expression of Wnt genes in Xenopus embryos (49, 50). The link between lithium and the Wnt pathway was revealed by the finding that lithium inhibits the activity of purified GSK-3α and GSK-3β, and their functions in intact cells (51, 52). Lithium is very selective for GSK-3 and has been used as a pharmacological tool to investigate the role of the kinase in various cellular processes (53). Similar to lithium, valproic acid, a rather old drug with a good safety profile and widely used as an anticonvulsant, is capable of inhibiting GSK-3 (54-56). Valproic acid inhibits-concentration dependently-both GSK-3α and GSK-3β. The inhibition of GSK-3β in the central nervous system may underlie some of the long-term therapeutic effects of mood-stabilizing agents lithium and valproic acid (54). Glycogen synthase kinase 3 was nearly ignored as a drug target until the late 1990s when its potentially important role in Alzheimer disease was discovered. The development of new molecules able to inhibit GSK-3 was initially addressed to the therapy for central nervous system disorders and diabetes. Increased GSK-3 levels have been found in postmortem brain analysis of patients with Alzheimer disease: an increase in GSK-3β activity was associated with the progression of neurofibrillary tangle and neurodegeneration (57, 58). Inhibition of the activity of GSK-3 in diabetes, on the other hand, may be beneficial for several reasons. We know that insulin is an endogenous inhibitor of GSK-3 and that the expression of GSK-3 is elevated in diabetic muscle (59, 60). It is therefore possible that drugs inhibiting GSK-3 mimic the effect of insulin to promote the conversions of glucose to glycogen and overcome the resistance to insulin, which characterize type 2 diabetes. Insulin resistance (together with hyperglycemia) is also a common symptom present in some critically ill patients (61). Thus, it is conceivable that insulin, which is used already in the therapy for sepsis, may exert its beneficial effects in conditions associated with systemic inflammation by inhibiting the activity of GSK-3 (62).
A series of adenosine triphosphate (ATP)-competitive GSK-3 inhibitors were identified during screenings of other protein kinases inhibitors. Some indirubins, paullones, hymenialdisine, and staurosporine derivatives have shown a higher inhibitory profile for GSK-3 than for the other kinases, with the 50% inhibitory concentration values in the nanomolar range (63). More recently, Coghlan et al. (64) reported the identification of SB216763 and SB415286, two structurally distinct maleimides, which have similar inhibitory effects on both GSK-3α and GSK-3β in an ATP-competitive manner. These compounds did not significantly inhibit any other of the 24 protein kinases tested, and possessed a higher nanomolar potency when compared with the other classes of GSK-3 inhibitors mentioned (64). In the last few years, several potent and specific inhibitors of GSK-3 have been developed by the pharmaceutical industry not only for the treatment of Alzheimer and diabetes but also for their ability to inhibit the activation of NF-κB and, hence, their potential to be of benefit in a vast number of diseases associated with local and systemic inflammation, including sepsis and cancer (3, 65).
The study by Hoeflich et al. (26) specifies a role for the isoform β of the kinase in the activation of NF-κB. Consequently, the role of GSK-3β was studied more intensely in the pathophysiology of the diseases in which NF-κB activation is involved. With the publication of the crystal structure of GSK-3β (7), it was possible to develop molecules specifically and selectively targeting GSK-3β. In 2002, Martinez et al. (66) described the synthesis, structure-activity relationships, and a hypothetical binding mode of new, small heterocyclic thiadiazolidinones (TDZD) as the first non-ATP-competitive selective GSK-3β inhibitors. Of these, TDZD-8 was the most effective (66).
Inhibitors of GSK-3β reduce the morbidity and mortality in animal models of shock
We have recently reported the beneficial effects of a number of distinct inhibitors of GSK-3β in rodent models of shock invivo (67). In a rat model of endotoxemia, two chemically distinct inhibitors of GSK-3β (TDZD-8 and SB216763) attenuated the renal dysfunction, hepatocellular injury, pancreatic injury, and neuromuscular injury, as indicated by the reduced plasma levels of creatinine, aspartate aminotransferase, alanine aminotransferase, lipase, and creatine kinase in treated animals. Administration of the GSK-3β inhibitor SB216763 also decreased the mortality rate in mice challenged with a lethal dose of LPS when compared with the LPS control group (40). This beneficial effect of SB216763 was associated with a reduction in the formation of IL-6 and TNF-α, and with an increase in the formation of IL-10 (40).
To rule out the possibility that the beneficial effect of GSK-3β inhibition were due to the prevention of the hypotension induced by LPS, we also investigated the effects of TDZD-8 and SB415286 in a rat model of systemic inflammation without hypotension, induced by the coadministration of low-dose LPS and peptidoglycan (67). We have previously reported that the administration of peptidoglycan, a cell wall component of Gram-positive and (to a much lesser extent) Gram-negative bacteria, synergizes with LPS (from Gram-negative bacteria) to cause the release of inflammatory mediators and multiple organ injury/dysfunction in vivo (68, 69). Interestingly, both TDZD-8 and SB415286 also attenuated the multiple organ injury/dysfunction caused by the coadministration of LPS and peptidoglycan, indicating that the observed protective effect was not solely due to a favorable hemodynamic effect. Because there is good evidence that the activation of NF-κB plays a fundamental role in the development of the multiple organ injury and dysfunction syndrome in systemic inflammation caused by endotoxemia or coadministration of LPS and peptidoglycan in vivo (69, 70), we also investigated whether the inhibition of GSK-3β would affect the expression of NF-κB-dependent genes, such as the proinflammatory cytokines IL-1β and IL-6, adhesion molecules ICAM-1 and VCAM-1, and the chemokine MCP-1. We found that the coadministration of LPS and peptidoglycan resulted in significant increases in the expression of the mRNA of these proinflammatory mediators in the lung. Most notably, pretreatment with the GSK-3β inhibitor TDZD-8 abolished the upregulated mRNA expression of these NF-κB-dependent genes. Similarly, the increase in IL-6 and MCP-1 mRNA expression was strongly elevated in wild-type MEFs after treatment with TNF-α, and completely absent (IL-6) or minimally induced (MCP-1) in GSK-3−/− stimulated with TNF-α (44). Interestingly, the mRNA expression of other mediators of inflammation, including IL-2 and RANTES (regulated on activation, normal T cells expressed and secreted), are also downregulated by the inhibition of GSK-3β via Ser9 phosphorylation in vitro (71, 72).
Subsequently, we evaluated the effects of TDZD-8 on the NF-κB/DNA binding in the lungs of rats, which had received LPS and peptidoglycan, and found that the NF-κB binding to the DNA was not affected by inhibition of GSK-3 activity (67). This finding is not entirely surprising because the nuclear translocation of the p50/p65 heterodimer is also not affected in cells that lack active GSK-3β (26, 44). Coadministration of LPS and peptidoglycan also caused a significant increase in the phosphorylation of Ser536 on p65 in the lung, and pretreatment with the GSK-3β inhibitor TDZD-8 significantly inhibited this phosphorylation (67). In an in vitro study on HEK293 cells, we also demonstrated that the inhibitors were able to phosphorylate the Ser9 residue on GSK-3β, the key site that determines kinase activity. Moreover, in support of the in vivo data, we found that the increase of p65 activity in the HEK293 cells, induced by treatment with IL-1β, was markedly reduced by the three inhibitors of GSK-3β used.
There is good evidence that severe hemorrhage and resuscitation also leads to the activation of NF-κB (73-75) and that a number of interventions inhibiting the activation of NF-κB, including calpain inhibitor I, the ROS-scavenger tempol, and the PPAR-γ agonists 15-d-PGJ2, reduce both systemic inflammation and organ injury in animal models of hemorrhagic shock (74, 76, 77). Thus, we investigated whether the inhibition of GSK-3β activity with TDZD-8 and SB216763 attenuates the multiple organ injury and dysfunction caused by severe hemorrhage and resuscitation in the rat (78). Administration of the selective GSK-3β inhibitors TDZD-8 or SB216763, 5 min before the onset of resuscitation, attenuates the renal dysfunction and the hepatocellular injury caused by hemorrhage and resuscitation in the rat. Using an extensive histological analysis of biopsies obtained from lung, liver, and kidneys, we confirmed that hemorrhage and resuscitation resulted in renal and liver injury and in infiltration with neutrophils and macrophages, particularly in the lung and, to a lesser extent, in the liver. Trauma and hemorrhage result in the release of a number of proinflammatory cytokines (79-81). The plasma levels of the circulating proinflammatory cytokine IL-6 increased significantly in our study after hemorrhage and resuscitation, and the administration of TDZD-8 and SB216763 significantly attenuated the increase in the plasma levels of IL-6 (78).
It should be noted that other mechanisms and signaling pathways may also be involved in the protective effects of GSK-3β inhibitors observed in this study. In intact cells, different protein kinases, such as PKB, PKC, and PKA, are able to phosphorylate GSK-3β on Ser9 (82). The activation of these protein kinases is dependent on the external stimuli. However, although the signaling pathways converge at GSK-3, the phosphorylation of the enzyme by a certain signal will not lead to the activation of all targets but to a selected target determined by the type of signal (82).
Anti-inflammatory effects of GSK-3ββ inhibition in colitis
In a classic model of severe inflammation, trinitrobenzene sulphonic acid-induced colitis in the rat, the administration of two different GSK-3β inhibitors caused a dose-dependent reduction in the colonic inflammation and reduced the decline in body weight. In addition, the observed increase in the levels of the proinflammatory cytokine TNF-α in the inflamed colon was significantly reduced by TDZD-8 and SB415286 at the highest dose used (1 mg/kg, s.c.). Interestingly, in this study, the nuclear translocation of the NF-κB subunit p65 in the colon (using Western blot analysis of nuclear extracts) was dose-dependently reduced by TDZD-8 or SB415286, indicating that the mechanism underlying the anti-inflammatory effects of these compounds in this preclinical model of colitis may be secondary to the inhibition of NF-κB activity (83).
Effects of insulin in sepsis and inflammation: role of GSK-3β
The pathways leading to the phosphorylation/inhibition of GSK-3 can be initiated by several cellular stimuli. Insulin is one of the main physiological signaling factors responsible for the regulation of GSK-3, which, in turn, is responsible for the activity of glycogen synthase (Fig. 1) (13). Interesting results regarding the role of GSK-3 in the regulation of insulin activity have been reported by McManus et al. (84), who generated homozygous knockin mice in which the phosphorylation site on GSK-3α and GSK-3β by PKB was changed from serine to alanine. The mice were viable and the authors demonstrated that inactivation of GSK-3β, rather than GSK-3α, is the main route by which insulin inactivates glycogen synthase in the skeletal muscle.
In the recent years, insulin has been increasingly studied and therapeutically used not only for decreasing the blood glucose levels in diabetes and shock (see succeeding sections) but also for its important anti-inflammatory effects. Hyperglycemia associated with insulin resistance is common in critically ill patients. Although hyperglycemia of the critically ill was thought to be a normal adaptive response to injury and sepsis, there is now good evidence that hyperglycemia in critically ill patients is not an adaptive but rather a harmful response that should be treated (tight insulin control) (85).
A large-scale, randomized clinical trial conducted by Greet van den Berghe et al. has demonstrated that controlling blood glucose levels by intensive insulin therapy significantly decreases mortality and morbidity in septic patients in surgical intensive care units (ICUs) (89). In fact, insulin therapy reduced not only the mortality rate but also the requirement of long-term mechanical ventilation and transfusion, the incidence rate of acute renal failure requiring dialysis or hemofiltration, the prevalence of bloodstream infections, and the incidence rate of polyneuropathy. In a subsequent, more comprehensive analysis of these results, van den Berghe et al. (90) showed that insulin treatment suppressed the hepatic acute-phase response, as indicated by circulating levels of C-reactive protein, which may contribute to the beneficial effects observed in critically ill patients. On the basis of the evidence published, the Surviving Sepsis Campaign guidelines for the management of severe sepsis and septic shock (91) currently indicate that after the initial stabilization of the patient, blood glucose levels should be maintained at less than 150 mg/dL. The usual protocol of treatment for glycemic control in sepsis involves continuous infusion of insulin and glucose. Glucose should be monitored frequently after the initiation of treatment and regularly once the blood glucose concentration is stable (91). A recent study from the same group investigated the effects of intensive insulin therapy in patients in medical ICUs, who were considered to need intensive care for at least 3 days (92). Intensive insulin therapy significantly reduced the morbidity and mortality rate in patients who stayed in the medical ICU for 3 or more days, whereas the beneficial effects of intensive insulin therapy in patients who stayed in the ICU for less than 3 days were less clear (92).
Clinical trials investigating the effect of insulin on cardiac performance during myocardial injury have adopted an approach involving the administration of insulin as a part of glucose-insulin-potassium (GIK) solution (93, 94). The beneficial effects of the infusion of GIK as a polarizing agent to promote electrical stability in patients with acute myocardial infarction were first proposed in 1962 (95). Later, several clinical studies used the GIK infusion, using different doses and obtaining contrasting results (96-98). In some studies, patients affected by acute myocardial infarction benefited from GIK treatment, whereas no benefit was observed in others (94, 96-98). The variability of the results obtained has been attributed to the differences in the GIK administration regime, patient characteristics, and reperfusion strategies (94, 96-98). Malmberg et al. (99, 100) showed in two separate clinical trials that diabetic patients with acute myocardial infarction can benefit more from GIK treatment than do nondiabetic patients (94, 96-98). This was suggested to be associated with the differences in the metabolism of diabetic individuals versus nondiabetic ones, and in the response of these patients to traumatic insults (101-104).
Mechanism of action
A number of clinical trials, supported by a variety of in vitro and in vivo studies, propose an important role for insulin in the modulation of the inflammatory response (105-109). However, despite extensive research, the mechanism(s) underlying the anti-inflammatory effects of insulin in sepsis (or, indeed, other conditions associated with local or systemic inflammation) are not clear. Although there is no doubt that the reduction of plasma glucose by insulin importantly contributes to the beneficial effects of insulin in patients with septic shock, it is also possible that other effects of insulin may contribute to the beneficial effects of insulin in shock and ischemia-reperfusion injury. These beneficial effects of insulin may be secondary to the activation of the survival kinase Akt. One proposed mechanism involves the antiapoptotic effect of insulin (110) because insulin prevents apoptotic cell death from numerous stimuli by activating the PI3K-Akt pathway. However, strict glycemic control has been one hypothesis of the protective mechanism of insulin in sepsis to date. Correcting hyperglycemia has been proposed to restore impaired neutrophil function in septic patients and improve bacterial phagocytosis (111). However, it is still unclear whether the beneficial effects of insulin therapy in sepsis are due to the control of blood glucose alone or are due-at least in part-to a direct effect of insulin on cell function and survival. A number of studies have shown a role for insulin in the regulation of the inflammatory cascade (112, 113). Insulin is able to decrease the production of proinflammatory cytokines, such as TNF-α, IL-1β, and IL-6, and to increase the expression of anti-inflammatory cytokines, such as IL-2, IL-4, and IL-10, in animal and human studies (105, 106, 114, 115). Jeschke and other investigators studied the role of insulin in rat models of sepsis and thermal trauma (105, 106,). In these studies, insulin attenuated the formation of proinflammatory cytokines and increased the expression of anti-inflammatory cytokines.
Another study from the same group (107) investigated the effect of insulin administration in a rat model of thermal injury, showing how insulin decreased the hepatic proinflammatory cytokines mRNA expression. Insulin seems to improve organ function and protein synthesis during the hypermetabolic response through the modulation of proinflammatory and anti-inflammatory transcription factors (107, 116, 117). Insulin treatment also caused amelioration of thermal injury in severely burned pediatric patients (115). In addition, in this study, insulin attenuated the inflammatory response by decreasing the proinflammatory and increasing the anti-inflammatory cascade, thus restoring systemic homeostasis (115). In the previously mentioned studies, the glucose levels were kept in the same range in insulin-treated and control groups, indicating a direct anti-inflammatory mechanism of insulin through modulation of cellular pathways, rather than an indirect mechanism through the modulation of blood glucose concentration (115).
Brix-Christensen et al. (114) investigated the effect of hyperinsulinemia on the systemic cytokine response and neutrophil function during endotoxin-induced systemic inflammation in the pig. Lipopolysaccharide infusion caused an increase in plasma IL-6, IL-8, IL-10, and TNF-α, whereas insulin infusion attenuated the increase in IL-6 and TNF-α caused by LPS; however, there was no significant difference in the plasma levels of IL-8 and IL-10 between the LPS-treated pigs and the LPS + insulin group (114). Plasma glucose levels were comparable in all groups, indicating in this study, as in the previous studies, that the beneficial effect of insulin was not dependent on the regulation of blood glucose (105, 106, 114, 115).
The effects of insulin on the activation of specific members of the MAPK pathway were investigated in a rat model of cecal ligation and puncture (118). In this study, the insulin pretreatment decreased the p38 MAPK activation observed in the early stages of cecal ligation and puncture and increased the activation of p42/44 MAPK (118).
On the basis of our previous report showing the role of chemically different inhibitors of GSK-3β in the regulation of NF-κB in vivo (67), we were intrigued by the link between insulin and GSK-3 and conducted a follow-up study to investigate (1) whether insulin does reduce the organ injury and systemic inflammation caused by the coadministration of LPS and peptidoglycan in the rat, and (2) whether any of the observed effects of insulin were similar to the effects of the selective GSK-3β inhibitor TDZD-8 (62). In this study, insulin, administered as either pretreatment or post-treatment at the dose of 1.4 U/kg i.v., significantly reduced the organ injury and dysfunction caused by the coadministration of LPS and peptidoglycan in the rat. In this model of systemic inflammation, which elicits a persistent hypoglycemia in response to the coadministration of LPS and peptidoglycan, the protective effects of insulin were independent of alterations in blood glucose levels, and glucose administration alone had no effect on the organ injury/dysfunction. Moreover, in human embryonic tubular cells, insulin or TDZD-8 similarly increased the phosphorylation of Ser9 on GSK-3β, the key site determining the activity of this kinase (62). Our study, in agreement with those discussed previously, also showed that insulin treatment reduced the plasma levels of IL-1β. Interestingly, the effects of TDZD-8 and insulin were qualitatively and quantitatively very similar indeed. Taken together, these results suggest that insulin elicits a direct protective effect against the organ injury and dysfunction associated with the systemic inflammatory response caused by the coadministration of LPS and peptidoglycan, which is associated with the inhibition of the activity GSK-3β but independent of alterations in blood glucose levels (62).
CONCLUSION
In the last few years, GSK-3 has emerged as an important target for drug development because (1) the inhibitors of this kinase are commercially available (lithium chloride, valproic acid, TDZD-8, SB216763, to name but a few), and (2) the inhibitors of this kinase have been reported to exert beneficial effects in many different, preclinical animal models of the disease. Because of the heterogeneity of the tissue distribution of GSK-3 and because of the involvement of this kinase in many different cellular pathways, GSK-3 has been the object of studies on inflammation, shock, diabetes, cancer, and neuronal degeneration. GSK-3 phosphorylates and regulates the activity of a number of metabolic and signaling proteins, structural proteins, and transcription factors; hence, it is not entirely surprising that GSK-3 has a number of important effects in physiology and pathophysiology. There is considerable evidence, for example, that GSK-3β modulation of the activity of the cytoskeletal protein tau may contribute to the neuropathology of Alzheimer disease (119, 120). Moreover, GSK-3 has been recognized as an important mediator of apoptosis. Activation of GSK-3 has been linked (via Akt/protein kinase B) to cell survival and directly linked to neuronal survival. Glycogen synthase kinase 3 downregulates the activities of many transcription factors, including those of heat shock factor 1, CREB, and, most importantly, NF-κB. Interestingly, the GSK-3 inhibitor lithium is known for its neuroprotective and antiapoptotic effects, which are likely to be due to the inhibition of this kinase (121).
We have recently reported an important role for GSK-3 in the regulation of the inflammatory process. Most notably, we have provided evidence (reviewed in this article) that various chemically distinct inhibitors of this kinase reduce systemic and local inflammation and the associated tissue/organ injury (67, 78). We have also proposed that the protective effect of GSK-3β inhibition is due to the downregulation of NF-κB activity, and this hypothesis is supported by several recent studies. Taken together, all these findings suggest that the inhibition of GSK-3β is a novel target of the therapy for sepsis and inflammation. Moreover, the inhibition of the activity of GSK-3 may be the mechanism of action through which insulin, already clinically used in the treatment of septic shock, may exert its beneficial effects (62). Previous studies established the beneficial effects of insulin, and clinical trials led to the use of insulin therapy for the treatment of patients affected by sepsis; however, those studies did not clarify the mechanism of the protective effects of insulin and/or the mechanism(s) by which insulin exerts its anti-inflammatory effect. The finding that insulin may exert its anti-inflammatory effect through the regulation of GSK-3β may well turn out to be a novel and exciting explanation for the beneficial effects of insulin in inflammation, ischemia-reperfusion injury, and shock.
It is likely that in the next few years, we will see the emergence of a large number of molecules (lead compounds) designed to inhibit the activity of GSK-3 (or its specific isoforms) and/or the activation of NF-κB caused by GSK-3β. Because GSK-3 is involved in a large number of cell signaling events, one of the challenges of the next few years will be to determine which of the effects of these new, potent, and selective inhibitors of this kinase are beneficial and which are (potentially) harmful.
REFERENCES
1. Embi N, Rylatt DB, Cohen P: Glycogen synthase kinase-3 from rabbit skeletal muscle. Separation from cyclic-AMP-dependent protein kinase and phosphorylase kinase. Eur J Biochem 107:519-527, 1980.
2. Frame S, Cohen P: GSK3 takes centre stage more than 20 years after its discovery. Biochem J 359:1-16, 2001.
3. Cohen P, Goedert M: GSK3 inhibitors: development and therapeutic potential. Nat Rev Drug Discov 3:479-487, 2004.
4. Woodgett JR: Molecular cloning and expression of glycogen synthase kinase-3/factor A. EMBO J 9:2431-2438, 1990.
5. Ali A, Hoeflich KP, Woodgett JR: Glycogen synthase kinase-3: properties, functions, and regulation. Chem Rev 101:2527-2540, 2001.
6. Bax B, Carter PS, Lewis C, Guy AR, Bridges A, Tanner R, Pettman G, Mannix C, Culbert AA, Brown MJ, et al: The structure of phosphorylated GSK-3beta complexed with a peptide, FRATtide, that inhibits beta-catenin phosphorylation. Structure (Camb) 9:1143-1152, 2001.
7. Dajani R, Fraser E, Roe SM, Young N, Good V, Dale TC, Pearl LH: Crystal structure of glycogen synthase kinase 3 beta: structural basis for phosphate-primed substrate specificity and autoinhibition. Cell 105:721-732, 2001.
8. ter Haar E, Coll JT, Austen DA, Hsiao HM, Swenson L, Jain J: Structure of GSK3beta reveals a primed phosphorylation mechanism. Nat Struct Biol 8:593-596, 2001.
9. Plyte SE, Hughes K, Nikolakaki E, Pulverer BJ, Woodgett JR: Glycogen synthase kinase-3: functions in oncogenesis and development. Biochim Biophys Acta 1114:147-162, 1992.
10. Eldar-Finkelman H, Seger R, Vandenheede JR, Krebs EG: Inactivation of glycogen synthase kinase-3 by epidermal growth factor is mediated by mitogen-activated protein kinase/p90 ribosomal protein S6 kinase signaling pathway in NIH/3T3 cells. J Biol Chem 270:987-990, 1995.
11. Stambolic V, Woodgett JR: Mitogen inactivation of glycogen synthase kinase-3 beta in intact cells via serine 9 phosphorylation. Biochem J 303(Pt 3):701-704, 1994.
12. Sutherland C, Leighton IA, Cohen P: Inactivation of glycogen synthase kinase-3 beta by phosphorylation: new kinase connections in insulin and growth-factor signalling. Biochem J 296(Pt 1):15-19, 1993.
13. Cross DA, Alessi DR, Cohen P, Andjelkovich M, Hemmings BA: Inhibition of glycogen synthase kinase-3 by insulin mediated by protein kinase B. Nature 378:785-789, 1995.
14. Hurel SJ, Rochford JJ, Borthwick AC, Wells AM, Vandenheede JR, Turnbull DM, Yeaman SJ: Insulin action in cultured human myoblasts: contribution of different signalling pathways to regulation of glycogen synthesis. Biochem J 320(Pt 3):871-877, 1996.
15. Moule SK, Welsh GI, Edgell NJ, Foulstone EJ, Proud CG, Denton RM: Regulation of protein kinase B and glycogen synthase kinase-3 by insulin and beta-adrenergic agonists in rat epididymal fat cells. Activation of protein kinase B by wortmannin-sensitive and -insensitive mechanisms. J Biol Chem 272:7713-7719, 1997.
16. van Weeren PC, de Bruyn KM, Vries-Smits AM, van Lint J, Burgering BM: Essential role for protein kinase B (PKB) in insulin-induced glycogen synthase kinase 3 inactivation. Characterization of dominant-negative mutant of PKB. J Biol Chem 273:13150-13156, 1998.
17. Hughes K, Nikolakaki E, Plyte SE, Totty NF, Woodgett JR: Modulation of the glycogen synthase kinase-3 family by tyrosine phosphorylation. EMBO J 12:803-808, 1993.
18. Murai H, Okazaki M, Kikuchi A: Tyrosine dephosphorylation of glycogen synthase kinase-3 is involved in its extracellular signal-dependent inactivation. FEBS Lett 392:153-160, 1996.
19. Wang QM, Fiol CJ, DePaoli-Roach AA, Roach PJ: Glycogen synthase kinase-3 beta is a dual specificity kinase differentially regulated by tyrosine and serine/threonine phosphorylation. J Biol Chem 269:14566-14574, 1994.
20. Cole A, Frame S, Cohen P: Further evidence that the tyrosine phosphorylation of glycogen synthase kinase-3 (GSK3) in mammalian cells is an autophosphorylation event. Biochem J 377:249-255, 2004.
21. Yost C, Farr GH III, Pierce SB, Ferkey DM, Chen MM, Kimelman D: GBP, an inhibitor of GSK-3, is implicated in Xenopus development and oncogenesis. Cell 93:1031-1041, 1998.
22. Ikeda S, Kishida S, Yamamoto H, Murai H, Koyama S, Kikuchi A: Axin, a negative regulator of the Wnt signaling pathway, forms a complex with GSK-3beta and beta-catenin and promotes GSK-3beta-dependent phosphorylation of beta-catenin. EMBO J 17:1371-1384, 1998.
23. Yamamoto H, Kishida S, Uochi T, Ikeda S, Koyama S, Asashima M, Kikuchi A: Axil, a member of the Axin family, interacts with both glycogen synthase kinase 3beta and beta-catenin and inhibits axis formation of Xenopus embryos. Mol Cell Biol 18:2867-2875, 1998.
24. Farr GH, Ferkey DM, Yost C, Pierce SB, Weaver C, Kimelman D: Interaction among GSK-3, GBP, axin, and APC in Xenopus axis specification. J Cell Biol 148:691-702, 2000.
25. Rubinfeld B, Albert I, Porfiri E, Fiol C, Munemitsu S, Polakis P: Binding of GSK3beta to the APC-beta-catenin complex and regulation of complex assembly. Science 272:1023-1026, 1996.
26. Hoeflich KP, Luo J, Rubie EA, Tsao MS, Jin O, Woodgett JR: Requirement for glycogen synthase kinase-3beta in cell survival and NF-kappaB activation. Nature 406:86-90, 2000.
27. Woodgett JR: Judging a protein by more than its name: GSK-3. Sci STKE 2001:RE12-RE22, 2001.
28. Beg AA, Sha WC, Bronson RT, Ghosh S, Baltimore D: Embryonic lethality and liver degeneration in mice lacking the RelA component of NF-kappa B. Nature 376:167-170, 1995.
29. Li Q, Van Antwerp D, Mercurio F, Lee KF, Verma IM: Severe liver degeneration in mice lacking the IkappaB kinase 2 gene. Science 284:321-325, 1999.
30. Schwabe RF, Brenner DA: Role of glycogen synthase kinase-3 in TNF-alpha-induced NF-kappaB activation and apoptosis in hepatocytes. Am J Physiol Gastrointest Liver Physiol 283:G204-G211, 2002.
31. Takada Y, Fang X, Jamaluddin MS, Boyd DD, Aggarwal BB: Genetic deletion of glycogen synthase kinase-3beta abrogates activation of IkappaBalpha kinase, JNK, Akt, and p44/p42 MAPK but potentiates apoptosis induced by tumor necrosis factor. J Biol Chem 279:39541-39554, 2004.
32. Sanchez JF, Sniderhan LF, Williamson AL, Fan S, Chakraborty-Sett S, Maggirwar SB: Glycogen synthase kinase 3beta-mediated apoptosis of primary cortical astrocytes involves inhibition of nuclear factor kappaB signaling. Mol Cell Biol 23:4649-4662, 2003.
33. Demarchi F, Bertoli C, Sandy P, Schneider C: Glycogen synthase kinase-3 beta regulates NF-kappa B1/p105 stability. J Biol Chem 278:39583-39590, 2003.
34. Buss H, Dorrie A, Schmitz ML, Frank R, Livingstone M, Resch K, Kracht M: Phosphorylation of serine 468 by GSK-3beta negatively regulates basal p65 NF-kappaB activity. J Biol Chem 279:49571-49574, 2004.
35. Brouard S, Berberat PO, Tobiasch E, Seldon MP, Bach FH, Soares MP: Heme oxygenase-1-derived carbon monoxide requires the activation of transcription factor NF-kappa B to protect endothelial cells from tumor necrosis factor-alpha-mediated apoptosis. J Biol Chem 277:17950-17961, 2002.
36. Christman JW, Lancaster LH, Blackwell TS: Nuclear factor kappa B: a pivotal role in the systemic inflammatory response syndrome and new target for therapy. Intensive Care Med 24:1131-1138, 1998.
37. Gadjeva M, Tomczak MF, Zhang M, Wang YY, Dull K, Rogers AB, Erdman SE, Fox JG, Carroll M, Horwitz BH: A role for NF-kappa B subunits p50 and p65 in the inhibition of lipopolysaccharide-induced shock. J Immunol 173:5786-5793, 2004.
38. Wang X, Li W, Lu J, Li N, Li J: Lipopolysaccharide suppresses albumin expression by activating NF-kappaB in rat hepatocytes. J Surg Res 122:274-279, 2004.
39. Weih F, Carrasco D, Durham SK, Barton DS, Rizzo CA, Ryseck RP, Lira SA, Bravo R: Multiorgan inflammation and hematopoietic abnormalities in mice with a targeted disruption of RelB, a member of the NF-kappa B/Rel family. Cell 80:331-340, 1995.
40. Martin M, Rehani K, Jope RS, Michalek SM: Toll-like receptor-mediated cytokine production is differentially regulated by glycogen synthase kinase 3. Nat Immunol 6:777-784, 2005.
41. Sheppard KA, Rose DW, Haque ZK, Kurokawa R, McInerney E, Westin S, Thanos D, Rosenfeld MG, Glass CK, Collins T: Transcriptional activation by NF-kappaB requires multiple coactivators. Mol Cell Biol 19:6367-6378, 1999.
42. Deng J, Miller SA, Wang HY, Xia W, Wen Y, Zhou BP, Li Y, Lin SY, Hung MC: Beta-catenin interacts with and inhibits NF-kappa B in human colon and breast cancer. Cancer Cell 2:323-334, 2002.
43. Deng J, Xia W, Miller SA, Wen Y, Wang HY, Hung MC: Crossregulation of NF-kappaB by the APC/GSK-3beta/beta-catenin pathway. Mol Carcinog 39:139-146, 2004.
44. Steinbrecher KA, Wilson W III, Cogswell PC, Baldwin AS: Glycogen synthase kinase 3β functions to specify gene-specific, NF-κB-dependent transcription. Mol Cell Biol 25:8444-8455, 2005.
45. Johnson G: Lithium. Med J Aust 141:595-601, 1984.
46. Cade JF: Lithium salts in the treatment of psychotic excitement. 1949. Bull World Health Organ 78:518-520, 2000.
47. Kao KR, Elinson RP: The entire mesodermal mantle behaves as Spemann's organizer in dorsoanterior enhanced Xenopus laevis embryos. Dev Biol 127:64-77, 1988.
48. Maeda Y: Influence of ionic conditions on cell differentiation and morphogenesis of the cellular slime molds. Dev Growth Differ 12:217-227, 1970.
49. Harwood AJ, Plyte SE, Woodgett J, Strutt H, Kay RR: Glycogen synthase kinase 3 regulates cell fate in Dictyostelium. Cell 80:139-148, 1995.
50. McMahon AP, Moon RT: Ectopic expression of the proto-oncogene int-1 in Xenopus embryos leads to duplication of the embryonic axis. Cell 58:1075-1084, 1989.
51. Klein PS, Melton DA: A molecular mechanism for the effect of lithium on development. Proc Natl Acad Sci U S A 93:8455-8459, 1996.
52. Stambolic V, Ruel L, Woodgett JR: Lithium inhibits glycogen synthase kinase-3 activity and mimics wingless signalling in intact cells. Curr Biol 6:1664-1668, 1996.
53. Chalecka-Franaszek E, Chuang DM: Lithium activates the serine/threonine kinase Akt-1 and suppresses glutamate-induced inhibition of Akt-1 activity in neurons. Proc Natl Acad Sci U S A 96:8745-8750, 1999.
54. Chen G, Huang LD, Jiang YM, Manji HK: The mood-stabilizing agent valproate inhibits the activity of glycogen synthase kinase-3. J Neurochem 72:1327-1330, 1999.
55. De SP, Li X, Jope RS: Regulation of Akt and glycogen synthase kinase-3 beta phosphorylation by sodium valproate and lithium. Neuropharmacology 43:1158-1164, 2002.
56. Fink MP: What do insulin, estrogen, valproic acid, and TDZD-8 have in common? Crit Care Med 33:2115-2117, 2005.
57. Leroy K, Boutajangout A, Authelet M, Woodgett JR, Anderton BH, Brion JP: The active form of glycogen synthase kinase-3beta is associated with granulovacuolar degeneration in neurons in Alzheimer's disease. Acta Neuropathol (Berl) 103:91-99, 2002.
58. Pei JJ, Tanaka T, Tung YC, Braak E, Iqbal K, Grundke-Iqbal I: Distribution, levels, and activity of glycogen synthase kinase-3 in the Alzheimer disease brain. J Neuropathol Exp Neurol 56:70-78, 1997.
59. Eldar-Finkelman H, Schreyer SA, Shinohara MM, LeBoeuf RC, Krebs EG: Increased glycogen synthase kinase-3 activity in diabetes- and obesity-prone C57BL/6J mice. Diabetes 48:1662-1666, 1999.
60. Nikoulina SE, Ciaraldi TP, Mudaliar S, Mohideen P, Carter L, Henry RR: Potential role of glycogen synthase kinase-3 in skeletal muscle insulin resistance of type 2 diabetes. Diabetes 49:263-271, 2000.
61. Eldar-Finkelman H, Krebs EG: Phosphorylation of insulin receptor substrate 1 by glycogen synthase kinase 3 impairs insulin action. Proc Natl Acad Sci U S A 94:9660-9664, 1997.
62. Dugo L, Collin M, Allen DA, Murch O, Foster SJ, Yaqoob MM, Thiemermann C: Insulin reduces the multiple organ injury and dysfunction caused by co-administration of LPS and peptidoglycan independently of blood glucose: role of glycogen synthase kinase-3b inhibition. Crit Care Med 34:1489-1496, 2006.
63. Van Wauwe J, Haefner B: Glycogen synthase kinase-3 as drug target: from wallflower to center of attention. Drug News Perspect 16:557-565, 2003.
64. Coghlan MP, Culbert AA, Cross DA, Corcoran SL, Yates JW, Pearce NJ, Rausch OL, Murphy GJ, Carter PS, Roxbee CL, et al: Selective small molecule inhibitors of glycogen synthase kinase-3 modulate glycogen metabolism and gene transcription. Chem Biol 7:793-803, 2000.
65. Haefner B: NF-kappa B: arresting a major culprit in cancer. Drug Discov Today 7:653-663, 2002.
66. Martinez A, Alonso M, Castro A, Perez C, Moreno FJ: First non-ATP competitive glycogen synthase kinase 3 beta (GSK-3beta) inhibitors: thiadiazolidinones (TDZD) as potential drugs for the treatment of Alzheimer's disease. J Med Chem 45:1292-1299, 2002.
67. Dugo L, Collin M, Allen DA, Patel NS, Bauer I, Mervaala EM, Louhelainen M, Foster SJ, Yaqoob MM, Thiemermann C: GSK-3beta inhibitors attenuate the organ injury/dysfunction caused by endotoxemia in the rat. Crit Care Med 33:1903-1912, 2005.
68. Dugo L, Collin M, Cuzzocrea S, Thiemermann C: 15d-Prostaglandin J(2) reduces multiple organ failure caused by wall-fragment of Gram-positive and Gram-negative bacteria. Eur J Pharmacol 498:295-301, 2004.
69. Wray GM, Foster SJ, Hinds CJ, Thiemermann C: A cell wall component from pathogenic and non-pathogenic Gram-positive bacteria (peptidoglycan) synergises with endotoxin to cause the release of tumour necrosis factor-alpha, nitric oxide production, shock, and multiple organ injury/dysfunction in the rat. Shock 15:135-142, 2001.
70. Wang JE, Dahle MK, Yndestad A, Bauer I, McDonald MC, Aukrust P, Foster SJ, Bauer M, Aasen AO, Thiemermann C: Peptidoglycan of Staphylococcus aureus causes inflammation and organ injury in the rat. Crit Care Med 32:546-552, 2004.
71. Gong R, Rifai A, Dworkin LD: Activation of PI3K-Akt-GSK3beta pathway mediates hepatocyte growth factor inhibition of RANTES expression in renal tubular epithelial cells. Biochem Biophys Res Commun 330:27-33, 2005.
72. Jhun BS, Oh YT, Lee JY, Kong Y, Yoon KS, Kim SS, Baik HH, Ha J, Kang I: AICAR suppresses IL-2 expression through inhibition of GSK-3 phosphorylation and NF-AT activation in Jurkat T cells. Biochem Biophys Res Commun 332:339-346, 2005.
73. Hierholzer C, Harbrecht B, Menezes JM, Kane J, MacMicking J, Nathan CF, Peitzman AB, Billiar TR, Tweardy DJ: Essential role of induced nitric oxide in the initiation of the inflammatory response after hemorrhagic shock. J Exp Med 187:917-928, 1998.
74. McDonald MC, Mota-Filipe H, Paul A, Cuzzocrea S, Abdelrahman M, Harwood S, Plevin R, Chatterjee PK, Yaqoob MM, Thiemermann C: Calpain inhibitor I reduces the activation of nuclear factor-kappaB and organ injury/dysfunction in hemorrhagic shock. FASEB J 15:171-186, 2001.
75. Meldrum DR, Shenkar R, Sheridan BC, Cain BS, Abraham E, Harken AH: Hemorrhage activates myocardial NFkappaB and increases TNF-alpha in the heart. J Mol Cell Cardiol 29:2849-2854, 1997.
76. Abdelrahman M, Collin M, Thiemermann C: The peroxisome proliferator-activated receptor-gamma ligand 15-deoxyDelta12,14 prostaglandin J2 reduces the organ injury in hemorrhagic shock. Shock 22:555-561, 2004.
77. Mota-Filipe H, McDonald MC, Cuzzocrea S, Thiemermann C: A membrane-permeable radical scavenger reduces the organ injury in hemorrhagic shock. Shock 12:255-261, 1999.
78. Dugo L, Abdelrahman M, Murch O, Mazzon E, Cuzzocrea S, Thiemermann C: Glycogen synthase kinase-3beta inhibitors protect against the organ injury and dysfunction caused by hemorrhage and resuscitation. Shock 25:485-491, 2006.
79. Ayala A, Perrin MM, Meldrum DR, Ertel W, Chaudry IH: Hemorrhage induces an increase in serum TNF which is not associated with elevated levels of endotoxin. Cytokine 2:170-174, 1990.
80. Rhee P, Waxman K, Clark L, Kaupke CJ, Vaziri ND, Tominaga G, Scannell G: Tumor necrosis factor and monocytes are released during hemorrhagic shock. Resuscitation 25:249-255, 1993.
81. Zingarelli B, Squadrito F, Altavilla D, Calapai G, Di Rosa M, Caputi AP: Role of tumor necrosis factor-alpha in acute hypovolemic hemorrhagic shock in rats. Am J Physiol 266:H1512-H1515, 1994.
82. Eldar-Finkelman H: Glycogen synthase kinase 3: an emerging therapeutic target. Trends Mol Med 8:126-132, 2002.
83. Whittle B, Varga C, Posa A, Molnar A, Collin M, Thiemermann C: Reduction of experimental colitis in the rat by inhibitors of glycogen synthase kinase-3beta. Br J Pharmacol 147:575-582, 2005.
84. McManus EJ, Sakamoto K, Armit LJ, Ronaldson L, Shpiro N, Marquez R, Alessi DR: Role that phosphorylation of GSK3 plays in insulin and Wnt signalling defined by knockin analysis. EMBO J 24:1571-1583, 2005.
85. Summers SA, Kao AW, Kohn AD, Backus GS, Roth RA, Pessin JE, Birnbaum MJ: The role of glycogen synthase kinase 3beta in insulin-stimulated glucose metabolism. J Biol Chem 274:17934-17940, 1999.
86. Agwunobi AO, Reid C, Maycock P, Little RA, Carlson GL: Insulin resistance and substrate utilization in human endotoxemia. J Clin Endocrinol Metab 85:3770-3778, 2000.
87. Khaodhiar L, McCowen K, Bistrian B: Perioperative hyperglycemia, infection or risk? Curr Opin Clin Nutr Metab Care 2:79-82, 1999.
88. McCowen KC, Ling PR, Ciccarone A, Mao Y, Chow JC, Bistrian BR, Smith RJ: Sustained endotoxemia leads to marked down-regulation of early steps in the insulin-signaling cascade. Crit Care Med 29:839-846, 2001.
89. van den Berghe G, Wouters P, Weekers F, Verwaest C, Bruyninckx F, Schetz M, Vlasselaers D, Ferdinande P, Lauwers P, Bouillon R: Intensive insulin therapy in the critically ill patients. N Engl J Med 345:1359-1367, 2001.
90. van den Berghe G, Wouters PJ, Bouillon R, Weekers F, Verwaest C, Schetz M, Vlasselaers D, Ferdinande P, Lauwers P: Outcome benefit of intensive insulin therapy in the critically ill: insulin dose versus glycemic control. Crit Care Med 31:359-366, 2003.
91. Dellinger RP, Carlet JM, Masur H, Gerlach H, Calandra T, Cohen J, Gea-Banacloche J, Keh D, Marshall JC, Parker MM, et al: Surviving Sepsis Campaign guidelines for management of severe sepsis and septic shock. Crit Care Med 32:858-873, 2004.
92. van den Berghe G, Wilmer A, Hermans G, Meersseman W, Wouters PJ, Milants I, Van WE, Bobbaers H, Bouillon R: Intensive insulin therapy in the medical ICU. N Engl J Med 354:449-461, 2006.
93. Fath-Ordoubadi F, Beatt KJ: Glucose-insulin-potassium therapy for treatment of acute myocardial infarction: an overview of randomized placebo-controlled trials. Circulation 96:1152-1156, 1997.
94. Pache J, Kastrati A, Mehilli J, Bollwein H, Ndrepepa G, Schuhlen H, Martinoff S, Seyfarth M, Nekolla S, Dirschinger J, et al: A randomized evaluation of the effects of glucose-insulin-potassium infusion on myocardial salvage in patients with acute myocardial infarction treated with reperfusion therapy. Am Heart J 148:105, 2004.
95. Sodi-Pallares D, Testelli MR, Fishleder BL, Bisteni A, Medrano GA, Friedland C, De Micheli A: Effects of an intravenous infusion of a potassium-glucose-insulin solution on the electrocardiographic signs of myocardial infarction. A preliminary clinical report. Am J Cardiol 9:166-181, 1962.
96. Ceremuzynski L, Budaj A, Czepiel A, Burzykowski T, Achremczyk P, Smielak-Korombel W, Maciejewicz J, Dziubinska J, Nartowicz E, Kawka-Urbanek T, et al: Low-dose glucose-insulin-potassium is ineffective in acute myocardial infarction: results of a randomized multicenter Pol-GIK trial. Cardiovasc Drugs Ther 13:191-200, 1999.
97. Diaz R, Paolasso EA, Piegas LS, Tajer CD, Moreno MG, Corvalan R, Isea JE, Romero G: The ECLA (Estudios Cardiologicos Latinoamerica) Collaborative Group. Metabolic modulation of acute myocardial infarction. Circulation 98:2227-2234, 1998.
98. van der Horst I, Zijlstra F, van't Hof AW, Doggen CJ, de Boer MJ, Suryapranata H, Hoorntje JC, Dambrink JH, Gans RO, Bilo HJ: Glucose-insulin-potassium infusion inpatients treated with primary angioplasty for acute myocardial infarction: the glucose-insulin-potassium study: a randomized trial. J Am Coll Cardiol 42:784-791, 2003.
99. Malmberg K, Ryden L, Efendic S, Herlitz J, Nicol P, Waldenstrom A, Wedel H, Welin L: Randomized trial of insulin-glucose infusion followed by subcutaneous insulin treatment in diabetic patients with acute myocardial infarction (DIGAMI study): effects on mortality at 1 year. J Am Coll Cardiol 26:57-65, 1995.
100. Malmberg K: DIGAMI (Diabetes Mellitus, Insulin Glucose Infusion in Acute Myocardial Infarction) Study Group. Prospective randomised study of intensive insulin treatment on long term survival after acute myocardial infarction in patients with diabetes mellitus. BMJ 314:1512-1515, 1997.
101. Davi G, Catalano I, Averna M, Notarbartolo A, Strano A, Ciabattoni G, Patrono C: Thromboxane biosynthesis and platelet function in type II diabetes mellitus. N Engl J Med 322:1769-1774, 1990.
102. Jain SK, Nagi DK, Slavin BM, Lumb PJ, Yudkin JS: Insulin therapy in type 2 diabetic subjects suppresses plasminogen activator inhibitor (PAI-1) activity and proinsulin-like molecules independently of glycaemic control. Diabet Med 10:27-32, 1993.
103. Pickup JC, Chusney GD, Thomas SM, Burt D: Plasma interleukin-6, tumour necrosis factor alpha and blood cytokine production in type 2 diabetes. Life Sci 67:291-300, 2000.
104. Sobrevia L, Mann GE: Dysfunction of the endothelial nitric oxide signalling pathway in diabetes and hyperglycaemia. Exp Physiol 82:423-452, 1997.
105. Jeschke MG, Einspanier R, Klein D, Jauch KW: Insulin attenuates the systemic inflammatory response to thermal trauma. Mol Med 8:443-450, 2002.
106. Jeschke MG, Klein D, Bolder U, Einspanier R: Insulin attenuates the systemic inflammatory response in endotoxemic rats. Endocrinology 145:4084-4093, 2004.
107. Klein D, Schubert T, Horch RE, Jauch KW, Jeschke MG: Insulin treatment improves hepatic morphology and function through modulation of hepatic signals after severe trauma. Ann Surg 240:340-349, 2004.
108. Lewis KS, Kane-Gill SL, Bobek MB, Dasta JF: Intensive insulin therapy for critically ill patients. Ann Pharmacother 38:1243-1251, 2004.
109. Vanhorebeek I, De Vos R, Mesotten D, Wouters PJ, Wolf-Peeters C, van den Berghe G: Protection of hepatocyte mitochondrial ultrastructure and function by strict blood glucose control with insulin in critically ill patients. Lancet 365:53-59, 2005.
110. Gao F, Gao E, Yue TL, Ohlstein EH, Lopez BL, Christopher TA, Ma XL: Nitric Oxide mediates the antiapoptotic effect of insulin in myocardial ischemia-reperfusion: the roles of PI3-Kinase, AKt, and endothelial nitric oxide synthase phosphorylation. Circulation 105:1997-1502, 2002.
111. Mazade MA, Edwards MS: Impairment of type III group B Streptococcus- stimulated superoxide production and opsonophagocytosis by neutrophils in diabetes. Mol Genet Metab 73:259-267, 2001.
112. Aljada A, Ghanim H, Saadeh R, Dandona P: Insulin inhibits NFkappaB and MCP-1 expression in human aortic endothelial cells. J Clin Endocrinol Metab 86:450-453, 2001.
113. Dandona P, Aljada A, Mohanty P, Ghanim H, Hamouda W, Assian E, Ahmad S: Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect? J Clin Endocrinol Metab 86:3257-3265, 2001.
114. Brix-Christensen V, Andersen SK, Andersen R, Mengel A, Dyhr T, Andersen NT, Larsson A, Schmitz O, Orskov H, Tonnesen E: Acute hyperinsulinemia restrains endotoxin-induced systemic inflammatory response: an experimental study in a porcine model. Anesthesiology 100:861-870, 2004.
115. Jeschke MG, Klein D, Herndon DN: Insulin treatment improves the systemic inflammatory reaction to severe trauma. Ann Surg 239:553-560, 2004.
116. Emanuelli B, Peraldi P, Filloux C, Sawka-Verhelle D, Hilton D, Van OE: SOCS-3 is an insulin-induced negative regulator of insulin signaling. J Biol Chem 275:15985-15991, 2000.
117. Ogle CK, Kong F, Guo X, Wells DA, Aosasa S, Noel G, Horseman N: The effect of burn injury on suppressors of cytokine signalling. Shock 14:392-398, 2000.
118. Maitra SR, Chen E, Rosa D, Valane PD, El-Maghrabi MR, Brathwaite CE: Modulations of signal transduction pathways during sepsis and the effects of insulin and mifepristone. Acad Emerg Med 10:1-8, 2003.
119. Hanger DP, Hughes K, Woodgett JR, Brion JP, Anderton BH: Glycogen synthase kinase-3 induces Alzheimer's disease-like phosphorylation of tau: generation of paired helical filament epitopes and neuronal localisation of the kinase. Neurosci Lett 147:58-62, 1992.
120. Ishiguro K, Shiratsuchi A, Sato S, Omori A, Arioka M, Kobayashi S, Uchida T, Imahori K: Glycogen synthase kinase 3 beta is identical to tau protein kinase I generating several epitopes of paired helical filaments. FEBS Lett 325:167-172, 1993.
121. Bijur GN, De SP, Jope RS: Glycogen synthase kinase-3beta facilitates staurosporine- and heat shock-induced apoptosis. Protection by lithium. J Biol Chem 275:7583-7590, 2000.
Keywords:
Glucose; insulin; TDZD-8; LPS; hemorrhagic shock; colitis; cytokines; GSK-3; SB216763; SB415286
©2007The Shock Society