15-DEOXY-Δ12,14-PROSTAGLANDIN J2 (15D-PGJ2), A PEROXISOME... : Shock (original) (raw)
INTRODUCTION
Peroxisome proliferator-activated receptor-γ (PPARγ) is a member of the nuclear receptor superfamily and a ligand-activated transcription factor with effects on inflammation, atherosclerosis, and cell proliferation. PPARγ forms a heterodimer with the retinoid X receptor and upon ligand-activation binds to the PPAR response element in the promoter of genes to allow transcription (1, 2).
Several experimental studies have shown that the natural PPARγ ligand, 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2), has potent anti-inflammatory properties. 15d-PGJ2 is derived from arachidonic acid via the cyclo-oxygenase (COX) pathway through a series of dehydration steps. A structural characteristic of this prostaglandin is the cyclopentenone ring, which is thought to be actively taken up by cells, accumulates in the nucleus, and binds to the nuclear PPARγ (3). It has been shown that this natural PPARγ ligand inhibits the expression of several inflammatory response genes in activated macrophages, including the genes encoding inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNFα), gelatinase B, and COX-2, most probably by antagonizing activities of the transcription factors activator protein-1 (AP-1) and nuclear factor κB (NF-κB) (3, 4). We have also demonstrated that 15d-PGJ2 inhibits nitric oxide (NO) and thromboxane B2 production in macrophages stimulated with gram-positive and gram-negative bacterial stimuli (5). Furthermore, we have shown that 15d-PGJ2 exhibits potent anti-inflammatory properties in an in vivo experimental model of sepsis by inhibiting the NF-κB and AP-1 pathways (6). Other studies have proposed that the ability of 15d-PGJ2 to block cytokine-induced iNOS in macrophages is associated with the expression of heat shock protein (HSP) 70, a putative cytoprotective protein with antiapoptotic effects (7).
The expression of adhesion molecules such as E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cellular adhesion molecule-1 (VCAM-1) are involved in the recruitment of leukocytes to the vessel wall and play a critical step in the initiation of the inflammatory cascade. Adhesion molecule expression is regulated at the genetic level by several transcription factors including NF-κB (8). Under basal conditions NF-κB is localized in the cytosol in a nonDNA binding form complexed with its inhibitor κB (IκBα). NF-κB has been shown to be activated by the bacterial lipopolysaccharide (LPS) and inflammatory cytokines such as interleukin (IL) 6 and TNFα. Once activated NF-κB dissociates from IκBα and translocates into the nucleus where it binds to NF-κB elements and initiates transcription (9). Several in vitro studies have demonstrated that PPARγ is expressed on endothelial cells and may participate in the regulation of leukocyte recruitment (10, 11). However, the underlying molecular mechanisms of 15d-PGJ2 on neutrophil recruitment in vivo are not completely defined.
In the present study we investigated whether the PPARγ ligand, 15d-PGJ2, may decrease the inflammatory response of endotoxic shock by modulation of the expression of adhesion molecules. Furthermore, we investigated the in vivo molecular mechanisms of 15d-PGJ2 on the NF-κB pathway and the heat shock response.
MATERIALS AND METHODS
Endotoxic shock
Endotoxic shock was induced in male Swiss albino mice (25-30 g, Charles River Laboratories) by intraperitoneal (i.p.) injection of 25 mg/kg Escherichia coli lipopolysaccharide (LPS, Serotype 0111:B4). Two groups of mice were used in the experiment. The first group of mice (n = 20) was treated with 15d-PGJ2 (1 mg/kg i.p.) 3 hours after LPS administration and repeated doses of 15d-PGJ2 were given every 12 hours for a total of six doses. The second group of mice (n = 22) received an equal volume of vehicle (DMSO) 3 hours after LPS administration and was given repeated doses of vehicle every 12 hours for a total of six doses. All mice were monitored for survival for a total of 72 hours. In a separate experiment groups of mice were used (n = 4 for each group). A vehicle-treated group received LPS (25 mg/kg, i.p.) followed by administration of vehicle (DMSO) 3 hours after LPS. A 15d-PGJ2-treated group of animals received LPS followed by administration of 15d-PGJ2 3 hours later. Sham group of animals received saline solution (200 μL, i.p.) instead of LPS followed by administration of vehicle or 15d-PGJ2 and served as controls. Animals were sacrificed 6 hours after LPS administration. Plasma samples, lungs and small intestine were collected for biochemical studies and immunohistochemistry. The experiments were performed in adherence to the National Institutes of Health Guidelines on the Use of Laboratory Animals and the study was approved by our Institutional Animal Care and Use Committee.
Histology
Lungs were fixed in 4% paraformaldehyde and embedded in paraffin. Sections were stained with hematoxylin and eosin and evaluated by a pathologist blinded to the experimental protocol.
Myeloperoxidase activity
Myeloperoxidase activity was determined as an index of neutrophil accumulation as described previously (12). Small intestine and lung tissues were homogenized in a solution containing 0.5% hexa-decyl-trimethyl-ammonium bromide dissolved in 10 mM potassium phosphate buffer, pH 7, and centrifuged for 30 min at 20,000/g at 4°C. An aliquot of the supernatant was allowed to react with a solution of 1.6 mM tetra-methyl-benzidine and 0.1 mM H2O2. The rate of change in absorbance was measured by spectrophotometry at 650 nm. Myeloperoxidase activity was defined as the quantity of enzyme degrading 1 μmol of hydrogen peroxide/min at 37°C and expressed in units per 100 mg of tissue.
Subcellular fractionation and nuclear protein extraction
Tissue samples were homogenized with a Polytron homogenizer in a buffer containing 0.32 M sucrose, 10 mM Tris-HCL (pH 7.4), 1 mM EGTA, 2 mM EDTA, 5 mM NaN3, 10 mM β-mercaptoethanol, 20 μM leupeptin, 0.15 μM pepstatin A, 0.2 mM phenylmethanesulfonyl fluoride, 50 mM NaF, 1 mM sodium orthovanadate, and 0.4 nM microcystin. The homogenates were centrifuged (1,000 × g for 10 min), the supernatants (cytosol + membrane extracts) were collected for evaluation of IκBα, HSP70 and adhesion molecules. The pellets were solubilized in Triton buffer (1% Triton X-100, 150 mM NaCl, 10 mM Tris-HCl [pH 7.4], 1 mM EGTA, 1 mM EDTA, 0.2 mM sodium orthovanadate, 20 μM leupeptin A, 0.2 mM phenylmethanesulfonyl fluoride). The lysates were centrifuged (15,000 × g for 30 min, 4°C), and the supernatants (nuclear extracts) were collected for content of HSP70 and PPARγ, and for DNA binding of PPARγ and NF-κB.
Western blot analysis
Expression of ICAM-1, VCAM-1, E-selectin, HSP70, PPARγ and cytosol degradation of IκBα was determined by immunoblot analyses. Protein extracts were boiled in equal volumes of loading buffer (125 mM Tris-HCL, pH 6.8, 4% SDS, 20% glycerol, and 10% 2-mercaptoethanol) and 50 μg of protein was loaded per lane on an 8%-16% Tris-glycine gradient gel. Proteins were separated electrophoretically and transferred to nitrocellulose membranes. For immunoblotting, membranes were blocked with 5% nonfat dried milk in Tris-buffered saline for 1 hour and then incubated with primary antibodies against ICAM-1, VCAM-1, E-selectin, and IκBα for two hours, and HSP 70 and PPARγ for 1 hour. The membranes were washed in Tris-buffered saline with 0.1% Tween 20 and incubated with secondary peroxidase-conjugated antibody. Detection was enhanced by chemiluminescence and exposed to photographic film. Densitometric analysis of blots was performed using ImageQuant (Molecular Dynamics, Sunnyvale, CA).
Electrophoretic mobility shift assay (EMSA)
EMSAs were performed as described previously (6). An oligonucleotide probe corresponding to NF-κB consensus sequence (5′- AGT TGA GGG GAC TTT CCC ACG C-3′) and PPARs consensus sequence (5′-GAA AAC TAG GTC AAA GGT CA-3′) were labeled with [γ-32P]ATP using T4 polynucleotide kinase and purified in Bio-Spin chromatography columns (Bio-Rad, Hercules, CA). Ten micrograms of nuclear protein were preincubated with EMSA buffer (12 mM HEPES, pH 7.9, 4 mM Tris-HCl, pH 7.9, 25 mM KCl, 5 mM MgCl2, 1 mM EDTA, 1 mM dithiothreitol, 50 ng/ml poly[d(I-C)], 12% glycerol v/v, and 0.2 mM PMSF) on ice for 10 min before addition of the radiolabeled oligonucleotide for an additional 10 min. The specificity of the binding reactions was determined by coincubating duplicate nuclear extract samples with a 10-fold molar excess of respective unlabeled oligonucleotides (competitor assays; data not shown). Protein-nucleic acid complexes were resolved using a nondenaturing polyacrylamide gel consisting of 5% acrylamide (29:1 ratio of acrylamide:bisacrylamide) and run in 0.5X Tris borate-EDTA (45 mM Tris-HCl, 45 mM boric acid, and 1 mM EDTA) for 1 hour at constant current (30 mA). Gels were transferred to 3M paper (Whatman, Clifton, NJ), dried under a vacuum at 80°C for 1 hour, and exposed to photographic film at −70°C with an intensifying screen. Densitometric analysis was performed using ImageQuant (Molecular Dynamics).
Materials
The primary antibodies directed at IκBα, HSP70 and the oligonucleotide for NF-κB and PPARs were obtained from Santa Cruz Biotechnology, Inc. (Santa Cruz, CA). 15d-PGJ2 and the primary antibody for PPARγ were obtained from Biomol (Plymouth Meeting, PA). Secondary antibodies were obtained from Calbiochem (San Diego, CA).
Data analysis
All values in the figures and text are expressed as mean ± SEM of n observations (n = 3-4 animals for each group). The results were examined by analysis of variance followed by the Bonferroni's correction post hoc t test. Results from survival study were examined by Fisher's exact test. A P value less than 0.05 was considered significant.
RESULTS
Effect of 15d-PGJ2 on survival
Administration of LPS to Swiss Albino mice resulted in a survival rate of 9% at 72 hours. (i.e., 2 out of 22 mice survived the entire experimental period). Post-treatment with 15d-PGJ2 significantly improved the survival rate to 55%, and 11 out of 20 mice were still alive 72 hours after LPS administration (Fig. 1).
Effect of in vivo treatment with 15d-PGJ2 or vehicle on survival rate in mice subjected to endotoxic shock (LPS, 25 mg/kg). Data are expressed as percentage of initial survival rate (100%). *Represents P < 0.05 versus vehicle-treated mice.
Effect of 15d-PGJ2 on lung injury
At 6 hours after LPS administration, vehicle-treated mice exhibit marked lung injury characterized by disruption of lung architecture, extravasation of red cells, and accumulation of inflammatory cells. On the contrary the 15d-PGJ2 treated mice revealed a marked reduction of infiltrated inflammatory cells and amelioration of lung architecture and alveolar space (Fig. 2).
Effect of in vivo treatment with 15d-PGJ2 or vehicle on lung injury at 6 h after LPS administration. (A) Representative photomicrograph of histology showing normal lung architecture from sham mouse. (B) Interstitial hemorrhage and accumulation of inflammatory cells were observed in lung from a vehicle-treated mouse following LPS injection. (C) Lung section from a 15d-PGJ2-treated mouse demonstrates absence of hemorrhage and reduction of cell infiltrate. Treated mice received 15d-PGJ2 (1 mg/kg) or vehicle by intraperitoneal injection 3 h after LPS. Representative sections are illustrated; original magnification x100. A similar pattern was seen in n = 2-3 different tissue sections in each experimental group.
Effect of 15d-PGJ2 on tissue neutrophil infiltration
A serious complication of endotoxic shock is the occurrence of multiorgan failure, which is preceded by accumulation of neutrophils in several vital organs. Thus, we next quantified neutrophil infiltration on small intestine and lung by measurement of myeloperoxidase activity, an enzyme specific to granulocyte lysosomes. Analysis of myeloperoxidase activity indicated marked neutrophil infiltration in the small intestine and lung of vehicle-treated mice (64.2 ± 13.0 and 313.4 ± 48.5 U/100 mg tissue, respectively). In contrast, post-treatment with 15d-PGJ2 significantly reduced myeloperoxidase activity in the small intestine and lung (21.4 ± 6.2 and 180.7 ± 19.0 U/100 mg tissue, respectively; P < 0.05) (Fig. 3).
Effect of in vivo treatment with 15d-PGJ2 or vehicle on myeloperoxidase activity in the lung (A) and small intestine (B) of mice at 6 h after LPS administration. Each data point represents the mean ± SEM of 4 animals for each group. *Represents P < 0.05 versus sham mice; #represents P < 0.05 versus vehicle-treated mice. Treated mice received 15d-PGJ2 (1 mg/kg) or vehicle by intraperitoneal injection 3 h after LPS.
Effect of 15d-PGJ2 on expression of adhesion molecules
To further investigate the effect of PPARγ ligands on neutrophil infiltration, we evaluated expression of adhesion molecules by Western blot analysis. In lungs of vehicle-treated mice expression of VCAM-1, ICAM-1 and E-selectin were notably increased at 6 hours after LPS administration. A similar increase of VCAM-1 expression was observed in the small intestine. In vivo treatment with 15d-PGJ2 reduced expression of adhesion molecules both in the lung and small intestine (Fig. 4).
Effect of in vivo treatment with 15d-PGJ2 or vehicle on adhesion molecule expression in lung and small intestine. (A) Representative Western blot analysis for lung expression of VCAM-1, ICAM-1, and E-Selectin and gut VCAM-1. (B) Relative densitometric analysis of adhesion molecule content. *Represents P < 0.05 versus sham mice; #represents P < 0.05 versus vehicle-treated mice. Treated mice received 15d-PGJ2 (1 mg/kg) or vehicle by intraperitoneal injection 3 h after LPS.
Administration of LPS alters PPARγ expression and function
We next investigated whether induction of endotoxin shock was associated with changes in PPARγ expression and function. At Western blot analysis expression of PPARγ was decreased in the nuclear compartment in lungs of vehicle-treated mice at 6 hours after LPS. By EMSA we found that administration of LPS induced a slight increase in PPARγ DNA binding in vehicle-treated mice. In vivo treatment with 15d-PGJ2 increased PPARγ expression and DNA binding when compared with vehicle treatment (Fig. 5). These data suggest that the protective effect of the cyclopentenone prostaglandin is dependent, at least in part, on activation of PPARγ-regulated transcription.
Effect of in vivo treatment with 15d-PGJ2 or vehicle on nuclear expression and DNA binding of PPARγ. (A) Representative Western blot analysis for PPARγ in the nucleus (upper panel) and representative autoradiograph of electrophoretic mobility shift assay for PPARγ DNA binding (lower panel). (B) Relative densitometric analysis of PPARγ content (upper graphic) and DNA binding (lower graphic). *Represents P < 0.05 versus sham mice; #represents P < 0.05 versus vehicle-treated mice. Treated mice received 15d-PGJ2 (1 mg/kg) or vehicle by intraperitoneal injection 3 h after LPS.
Effects of 15d-PGJ2 on NF-κB pathway
To investigate the mechanism of action of 15d-PGJ2, we next evaluated the activation of the NF-κB pathway. In lungs of vehicle-treated mice NF-κB DNA binding was markedly increased at 6 hours after LPS administration. This effect was associated with degradation of IκBα as evaluated by Western blot analysis. In vivo treatment with 15d-PGJ2 significantly reduced NF-κB DNA binding in endotoxemic mice. However, treatment with 15d-PGJ2 did not inhibit LPS-induced IκBα degradation (Fig. 6). In vivo treatment with 15d-PGJ2 did not alter NF-κB DNA binding or cytosolic IκBα content in sham control animals. Thus, these data suggest that 15d-PGJ2 had a direct inhibitory effect on the nuclear activation of NF-κB.
Effect of in vivo treatment with 15d-PGJ2 or vehicle on activation of NF-κB pathway. (A) Representative Western blot analysis for IκBα in the cytosol (upper panel) and representative autoradiograph of electrophoretic mobility shift assay for NF-κB DNA binding (lower panel). (B) Relative densitometric analysis of IκBα (upper graphic) and NF-κB DNA binding (lower graphic). *Represents P < 0.05 versus sham mice; #represents P < 0.05 versus vehicle-treated mice. Results are representative of 3 separate experiments. Treated mice received 15d-PGJ2 (1 mg/kg) or vehicle by intraperitoneal injection 3 h after LPS.
Effect of 15d-PGJ2 on expression of HSP70
Recent in vitro studies have demonstrated that PPARγ ligands may induce expression of HSPs (7, 13). Thus, we next explored the hypothesis that anti-inflammatory effects of 15d-PGJ2 may be mediated by induction of the heat shock response. Western blot analyses indicated that administration of LPS induced a decrease in HSP70 expression in the nuclear and cytosol compartments in the lung of vehicle-treated mice. In vivo treatment with 15d-PGJ2 markedly increased HSP70 expression (Fig. 7).
Effect of in vivo treatment with 15d-PGJ2 or vehicle on HSP70. (A) Representative Western blot analysis for HSP70 in the cytosol and nucleus. (B) Relative densitometric analysis of HSP70 in the cytosol and nucleus. *Represents P < 0.05 versus sham mice; #represents P < 0.05 versus vehicle-treated mice. Results are representative of 3 separate experiments. Treated mice received 15d-PGJ2 (1 mg/kg) or vehicle by intraperitoneal injection 3 h after LPS.
DISCUSSION
The development of sepsis and multiorgan failure is a significant cause of mortality in critically ill patients (14). The Surviving Sepsis Campaign Management Guidelines Committee provides evidenced based guidelines for the management of sepsis and septic shock, unfortunately there are only a few recommendations that are supported by studies showing a difference in clinical outcome (15). We are then left with finding new therapeutic interventions, which have an impact on improving survival and reducing the organ dysfunction found in septic shock patients.
Previous studies have shown that PPARγ ligands may exert anti-inflammatory effects in experimental models of sepsis (2, 6, 16). We have demonstrated that in vivo treatment with PPARγ ligands, 15d-PGJ2 and the thiazolidinedione ciglitazone, improve survival, hemodynamic performance and reduce the inflammatory response in rats subjected to peritonitis by cecal ligation and puncture (6). Recent studies from Thiemermann's laboratory confirmed that pretreatment with 15d-PGJ2 ameliorates renal, liver and pancreatic dysfunction in models of endotoxemia and hemorrhagic shock in vivo (16, 17). However, the role of PPARγ activation and the precise molecular mechanisms of the natural PPARγ ligand, 15d-PGJ2, have not been fully determined in sepsis. In the present study, we have demonstrated that administration of 15d-PGJ2 improved survival, reduced lung injury and neutrophil trafficking to lung and small intestine in mice subjected to endotoxic shock. We have also demonstrated for the first time that 15d-PGJ2 enhanced the PPARγ function in the lung, thus suggesting that activation of PPARγ-regulated transcription contributes to its protective effects. Moreover, 15d-PGJ2 decreased NF-κB activity and enhanced the expression of the cytoprotective protein HSP70. A major finding of clinical relevance in our study is that administration of 15d-PGJ2 exerted beneficial effect when given as post-treatment 3 h after endotoxin challenge, i.e. when most of the adverse inflammatory effects of endotoxemia occurred or started to occur. Therefore, our data clearly indicate that enhancement of the PPARγ activation, which is associated with interruption of the NF-κB pathway, might be of clinical benefit in sepsis.
A relevant pathological condition that places patients at risk for development of multiple organ failure after endotoxemia is the generalized leukosequestration with resultant parenchymal cell injury. Neutrophils play a key role in the development of multiorgan failure in patients after sepsis, trauma and severe hemorrhage. It has been demonstrated that circulating neutrophils of severly injured patients have a primed phenotype. Upon adherence, this primed phenotype translates into a markedly increased release of lysosomal enzymes and production of oxidants, which contribute to organ injury (18, 19). These events are the consequence of a highly coordinated cascade of events leading to the reorientation of the cytoskeleton, firm adhesion and polarization and is regulated by adhesion molecules and chemokines (20, 21). Specifically, in the initial phase of inflammation a transient slowing and rolling of neutrophils in postcapillary venules, is mediated by selectins. In the presence of activator factors, such as cytokines and proinflammatory mediators, β2 and β1 integrins are activated on the leukocyte surface and firmly adhere to the vascular endothelial ligands, ICAM-1 and VCAM-1, thus allowing extravasation of leukocytes into the tissues. Activated neutrophils, then, release proteolytic enzymes, inflammatory cytokines and potent oxidizing molecules (21, 22). The expression of the cell surface receptor adhesion molecules is regulated at the genetic level by several transcription factors including NF-κB (9). In the current study we found that treatment with 15d-PGJ2 reduced neutrophil infiltration in the lung and small intestine. Reduction of accumulation of inflammatory cells was also associated with improvement of lung tissue damage. Furthermore, we observed a reduced expression of ICAM-1 and E-selectin in the lung and VCAM-1 in the lung and small intestine. Thus, our data suggest that the therapeutic effect of 15d-PGJ2 may be consequent to prevention of gene expression of molecules controlling neutrophil rolling, firm adhesion and transmigration. These data are consistent with other reports demonstrating that PPARγ modulates expression of adhesion molecules. In endothelial cells it has been demonstrated that PPARγ activation, pharmacologically or by genetic manipulation, significantly suppressed the expression of vascular adhesion molecules and the ensuing leukocyte recruitment in vitro (11, 23, 24). Similarly, we have recently demonstrated that in vivo treatment with PPARγ ligands suppress neutrophil recruitment in major organs in rats with polymicrobial sepsis (6).
Several cellular mechanisms, including the mode of gene regulation and signal transduction, may account for the anti-inflammatory properties of 15d-PGJ2 in endotoxic shock. NF-κB plays a critical role in the coordination of both innate and adaptive immune responses in sepsis by regulating the gene expression of many cellular mediators (9). Activation of this transcription factor is rapid and occurs within minutes after the microbial challenge (9, 25). The duration and the degree of NF-κB activity appear to correlate with the severity of the inflammatory response and to persist longer in nonsurviving than surviving patients with acute sepsis (26). In our study we have demonstrated that, in addition to PPARγ activation, regulation of signal transduction pathway of NF-κB accounts for the modulatory role of 15d-PGJ2 in neutrophil trafficking. Specifically, we found that in vivo treatment with 15d-PGJ2 decreased the nuclear activation of NF-κB. Interestingly, treatment with 15d-PGJ2 did not affect the cytosolic degradation of IκBα. Although this finding is in contrast with previous reports demonstrating that 15d-PGJ2 may inhibit NF-κB activation through inhibition of IκBα degradation and its regulatory kinase IKK (27, 28), several in vitro studies support the hypothesis that 15d-PGJ2 may directly interfere with the DNA binding activity of NF-κB via PPARγ-independent mechanisms. For example, 15d-PGJ2 has been demonstrated to inhibit NF-κB gene activation by covalent modification of cysteine residues in the DNA binding domain of the p65 (27) or the p50 NF-κB subunit and to reduce recombinant DNA binding in a dose-dependent manner (29). Furthermore, it is possible that 15d-PGJ2 may interfere with the DNA binding activity of NF-κB via a PPARγ-dependent mechanism. It has been proposed, in fact, that PPARγ may modulate expression of inflammatory genes by direct transrepression. PPARγ inhibited expression of the iNOS by direct interaction with CREB-binding protein, thus limiting its availability for NF-κB and AP-1 transcription (2, 30).
Another mechanism through which 15d-PGJ2 may exert its anti-inflammatory effects is through the heat shock response. The heat shock response is a highly conserved cellular defense mechanism to injury, which is characterized by the increased expression of chaperone proteins that provide cytoprotection from inflammatory insults, including oxidative stress, viral infection, and ischemia-reperfusion injury (31, 32). In our study, we found that treatment with 15d-PGJ2 and activation of PPARγ also led to enhancement of the heat shock response in the lung as demonstrated by the increased expression of HSP70, which correlated well with improvement of lung injury. Our data also supports previously published data by Weiss and colleagues demonstrating that expression of HSP70 in the lung is impaired in rats after cecal ligation and puncture (33). The importance of the heat shock response in the lung has been further demonstrated in an experimental acute respiratory distress syndrome in rats. An adenovirus-mediated gene therapy restored expression of HSP70 and resulted in improvement in lung injury and reduction in mortality (34). Our in vivo findings are in agreement with previous in vitro reports demonstrating that 15d-PGJ2 may induce expression of HSPs. Maggi and colleagues have proposed that the ability of 15d-PGJ2 to block cytokine-induced iNOS macrophages is associated with the expression of HSP70 (7). Similarly to our findings, Ianaro and colleagues have recently reported that in vivo treatment with 15d-PGJ2, its precursor PGD2, and the cyclopentenone ring structure itself, 2-cyclopenten-1-one, induces expression of HSP72 in inflamed tissue and that this effect is associated with the remission of the inflammatory reaction (35).
In conclusion, our data demonstrate that 15d-PGJ2 may counteract the inflammatory response probably through direct activation of PPARγ and inhibition of the NF-κB signaling pathway. Furthermore, it appears that this prostaglandin may affect inflammation also through activation of the cytoprotective pathway of the heat shock response. These novel pathophysiological insights may provide new basis for the development of tools for the treatment of sepsis.
ACKNOWLEDGMENTS
Funding for this study was provided by the National Institutes of Health to Dr. Basilia Zingarelli (grant R01 GM-67202).
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Keywords:
Endotoxic shock; nuclear factor-κB; heat shock protein 70; lung injury; adhesion molecules; neutrophils
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