Mihaela Mocanu - Academia.edu (original) (raw)

Papers by Mihaela Mocanu

Research paper thumbnail of Pioglitazone Mimics Preconditioning in the Isolated Perfused Rat Heart: A Role for the Prosurvival Kinases PI3K and P42/44MAPK

Journal of Cardiovascular Pharmacology, Dec 1, 2005

Ischemic preconditioning, the most powerful protection against infarction, activates PI3Kinase (P... more Ischemic preconditioning, the most powerful protection against infarction, activates PI3Kinase (PI3K)/AKT and P42/44MAPK. Pioglitazone, a thiazolidinedione and PPARgamma receptor agonist used in Type II diabetes treatment, has been shown to activate these kinase cascades. We therefore hypothesized that pioglitazone could protect the myocardium when given prior to myocardial ischemia/reperfusion injury. Langendorff perfused rat hearts underwent 40 minutes of stabilization then 35 minutes of regional ischemia and 120 minutes of reperfusion (control) or Pioglitazone (1, 2, 5, and 10 microM)-given before ischemia. Additional groups underwent the same protocol but with either PI3K inhibitors (15 microM LY294002 or 100 nM wortmannin) or P42/44MAPK inhibitors (10 microM U0126 or 10 microM PD98059) given either during stabilization or at reperfusion. Infarct size was determined as a percentage of risk zone (I/R%). Pioglitazone (2 microM) significantly reduced I/R% compared with control (25.4 +/- 3.1 versus 47.3 +/- 3.4; P < 0.05). This protection was abolished by PI3K inhibitors (pioglitazone+LY294002 46.5 +/- 5.0, pioglitazone + wortmannin 48.8 +/- 4.6 versus pioglitazone alone 25.4 +/- 3.1; P < or = 0.05) but not by P42/44MAPK inhibitors (pioglitazone+U0126 30.7 +/- 5.7, pioglitazone + PD98059 28.5 +/- 6.3 versus pioglitazone alone 25.4 +/- 3.1; P < or = 0.05) given in stabilization. However when the inhibitors were given at reperfusion, the protection was abrogated by blocking either pathway (pioglitazone+LY294002 49.8 +/- 3.1, pioglitazone+U0126 48.7 +/- 3.7 versus pioglitazone alone 25.4 +/- 3.1; P < or = 0.05). In conclusion pioglitazone induced significant protection against ischemia/reperfusion injury when administered prior to ischemia. This protection appears to involve PI3K and P42/44MAPK.

Research paper thumbnail of Leptin, the obesity-related adipocytokine, protects the myocardium against ischaemia–reperfusion injury

Journal of Molecular and Cellular Cardiology

Research paper thumbnail of Failure of the adipocytokine, resistin, to protect the heart from ischemia-reperfusion injury

Journal of cardiovascular pharmacology and therapeutics, 2011

Experimental studies have linked the adipocytokines with acute cardioprotection. Whether the adip... more Experimental studies have linked the adipocytokines with acute cardioprotection. Whether the adipocytokine, resistin, confers protection is, however, debatable. In the current study, the actions of resistin, administered at reperfusion, were investigated in in vivo and in vitro rodent and in vitro human models of myocardial ischemia-reperfusion (I/R) injury. Resistin did not reduce infarct size in Langendorff-perfused rat hearts or murine hearts perfused in vivo. Resistin also did not protect human atrial muscle subjected to hypoxia-reoxygenation. Although cyclosporin A delayed mitochondrial permeability transition pore (MPTP) opening in murine cardiomyocytes, resistin was ineffective. Western blot analysis revealed that resistin treatment was associated with enhanced phosphorylation of Akt, at both the serine-473 (+ 51.9%, P = .01) and threonine-308 (+107%, P < .01) phosphorylation sites, although not to the extent seen with ischemic preconditioning (+132.5%, P = .002 and +389.1...

Research paper thumbnail of AMPK activation at reperfusion: A novel cardioprotective target?

Journal of Molecular and Cellular Cardiology, 2007

UCL logo UCL Discovery. ...

Research paper thumbnail of The Diabetic Heart: Too Sweet for Its Own Good?

Cardiology Research and Practice, 2012

Diabetes mellitus is a major risk factor for ischemic heart disease (IHD). Patients with diabetes... more Diabetes mellitus is a major risk factor for ischemic heart disease (IHD). Patients with diabetes and IHD experience worse clinical outcomes, suggesting that the diabetic heart may be more susceptible to ischemia-reperfusion injury (IRI). In contrast, the animal data suggests that the diabetic heart may be either more, equally, or even less susceptible to IRI. The conflicting animal data may be due to the choice of diabetic and/or IRI animal model. Ischemic conditioning, a phenomenon in which the heart is protected against IRI by one or more brief nonlethal periods of ischemia and reperfusion, may provide a novel cardioprotective strategy for the diabetic heart. Whether the diabetic heart is amenable to ischemic conditioning remains to be determined using relevant animal models of IRI and/or diabetes. In this paper, we review the limitations of the current experimental models used to investigate IRI and cardioprotection in the diabetic heart.

Research paper thumbnail of Metformin protects against myocardial infarction independent of its glucose lowering effects

Journal of Molecular and Cellular Cardiology, 2008

Journal of Molecular and Cellular Cardiology, Volume 44, Issue 4, Pages 748, April 2008, Authors:... more Journal of Molecular and Cellular Cardiology, Volume 44, Issue 4, Pages 748, April 2008, Authors:Marta Paiva; Lino Gonçalves; Luís Providência; Mihaela M. Mocanu; Derek M. Yellon.

Research paper thumbnail of The adipocytokine, resistin, is not cardioprotective despite activating components of the risk pathway

Journal of Molecular and Cellular Cardiology, 2008

Research paper thumbnail of Metformin cardioprotects the diabetic heart by inhibiting mPTP opening via the risk pathway

Journal of Molecular and Cellular Cardiology, 2007

Research paper thumbnail of The metabolic syndrome raises the threshold for cardioprotection

Journal of Molecular and Cellular Cardiology, 2007

... The metabolic syndrome raises the threshold for cardioprotection. Hausenloy, DJ and Wynne, A ... more ... The metabolic syndrome raises the threshold for cardioprotection. Hausenloy, DJ and Wynne, A and Mocanu, MM and Yellon, DM (2007) The metabolic syndrome raises the threshold for cardioprotection. In: JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY. (pp. ...

Research paper thumbnail of Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart

Journal of Molecular and Cellular Cardiology, 2007

... Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart. Wynne, ... more ... Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart. Wynne, A and Hausenloy, DJ and Mocanu, NM and Yellon, DM (2007) Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart. ...

Research paper thumbnail of PI3 Kinase and not p42/p44 Appears to be Implicated in the Protection Conferred by Ischemic Preconditioning

Journal of Molecular and Cellular Cardiology, 2002

M. M. MOCANU, R. M. BELL AND D. M. YELLON. PI3 Kinase and not p42/p44 Appears to be Implicated in... more M. M. MOCANU, R. M. BELL AND D. M. YELLON. PI3 Kinase and not p42/p44 Appears to be Implicated in the Protection Conferred by Ischemic Preconditioning. Journal of Molecular and Cellular Cardiology (2002) 34, 661À À668. Ischemic preconditioning results in an immediate phase of protection against lethal ischemia/ reperfusion injury that is comprised of both irreversible necrosis and programmed cell death, apoptosis. We hypothesized that preconditioning may activate putative anti-apoptotic pathways, through the induction of either phosphatidyl inositol 3-OH kinase (PI3 kinase) or p42/p44 extracellular receptor kinase, attenuating total cell death. Isolated perfused rat hearts were preconditioned with two cycles of 5 min ischemia and 10 min reperfusion. Then they were frozen for Western blot analysis or subjected to 35 min regional ischemia and 120 min reperfusion prior to infarct size assessment. Selective PI3 kinase inhibitors, wortmannin (W, 100 nM) and LY294002 (LY, 15 "M) and the p42/p44 inhibitor, PD 98059 (PD, 10 and 50 "M), were individually infused during the preconditioning protocol. One further group of hearts received both inhibitors (W and PD). The results were expressed as percentage of infarction within the risk zone. Inhibition of PI3 kinase by either W or LYpartially abrogated the infarct sparing effect of ischemic preconditioning (I/R%: 44.6 AE 2.7 in C, 17.6 AE 2.0 in IP, vs 32.2 AE 4.2 in W, and 30.9 AE 2.6 in LY, P , 0.05). Inhibition of ERK phosphorylation however, had no signi®cant effect upon infarct size reduction (17.6 AE 2.0 in ischemic preconditioning vs 21.4 AE 3.0 in IP 10 "M PD and 15.2 AE 1.4 in IP 50 "M PD, P . 0.05). Western blot analysis con®rmed that PD abrogated the phosphorylation of p42/p44 and LY the phosphorylation of AKT. Combined inhibition with PD W failed to further attenuate protection (27.6 AE 1.3%, P . 0.1). These data appear to demonstrate that the PI3 kinase, but not the p42/p44 cascade, is implicated in early ischemic preconditioning.

Research paper thumbnail of The Akt1 isoform is an essential mediator of ischaemic preconditioning

Journal of Cellular and Molecular Medicine, 2012

Phosphatidyl-inositol-3-kinase (PI3K)-Akt pathway is essential for conferring cardioprotection in... more Phosphatidyl-inositol-3-kinase (PI3K)-Akt pathway is essential for conferring cardioprotection in response to ischaemic preconditioning (IPC) stimulus. However, the role of the individual Akt isoforms expressed in the heart in mediating the protective response to IPC is unknown. In this study, we investigated the specific contribution of Akt1 and Akt2 in cardioprotection against ischaemia-reperfusion (I-R) injury. Mice deficient in Akt1 or Akt2 were subjected to in vivo regional myocardial ischaemia for 30 min. followed by reperfusion for 2 hrs with or without a prior IPC stimulus. Our results show that mice deficient in Akt1 were resistant to protection with either one or three cycles of IPC stimulus (42.7 ± 6.5% control versus 38.5 ± 1.9% 1 χ IPC, N = 6, NS; 41.4 ± 6.3% control versus 32.4 ± 3.2% 3 χ IPC, N = 10, NS). Western blot analysis, performed on heart samples taken from Akt1(-/-) mice subjected to IPC, revealed an impaired phosphorylation of GSK-3β, a downstream effector of Akt, as well as Erk1/2, the parallel component of the reperfusion injury salvage kinase pathway. Akt2(-/-) mice, which exhibit a diabetic phenotype, however, were amenable to protection with three but not one cycle of IPC (46.4 ± 5.6% control versus 35.9 ± 5.0% in 1 χ IPC, N = 6, NS; 47.0 ± 6.0% control versus 30.8 ± 3.3% in 3 χ IPC, N = 6; *P = 0.039). Akt1 but not Akt2 is essential for mediating a protective response to an IPC stimulus. Impaired activation of GSK-3β and Erk1/2 might be responsible for the lack of protective response to IPC in Akt1(-/-) mice. The rise in threshold for protection in Akt2(-/-) mice might be due to their diabetic phenotype.

Research paper thumbnail of Metformin Prevents Myocardial Reperfusion Injury by Activating the Adenosine Receptor

Journal of Cardiovascular Pharmacology, 2009

Metformin improves cardiovascular outcomes in patients with type 2 diabetes compared with other g... more Metformin improves cardiovascular outcomes in patients with type 2 diabetes compared with other glucose-lowering drugs. Experimental studies have shown that metformin can increase the intracellular concentration of adenosine monophosphate, which is a major determinant of the intracellular formation of adenosine. We hypothesize that metformin, given at reperfusion, can limit myocardial infarct size due to increased adenosine receptor stimulation. Isolated perfused hearts from Sprague-Dawley rats were subjected to 35 minutes of regional ischemia and 120 minutes of reperfusion. Perfusion with metformin (50 microM) for the first 15 minutes of reperfusion reduced infarct size (percent area at risk) from 42% +/- 2% to 19% +/- 4% (n &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;or= 6; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), which was blocked by a concomitant perfusion with the adenosine receptor antagonist 8-p-sulfophenyltheophylline (100 microM; 43% +/- 3%) or nitrobenzylthioinosine (a blocker of transmembranous adenosine transport; 1 microM; 45% +/- 5%). In addition, intravenous administration of metformin (5 mg/kg) reduced infarct size in a rat in situ model of myocardial infarction (34% +/- 6% vs. 62% +/- 5%; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), which was completely abolished by 8-p-sulfophenyltheophylline (61% +/- 3%). We conclude that metformin, given at reperfusion, reduces infarct size in a rat model of myocardial infarction, which is critically dependent on adenosine receptor stimulation, probably via increased intracellular formation of adenosine.

Research paper thumbnail of BAS/BSCR34 Is an increased AMPK activation during ischaemia essential for the protection of the heart against infarction?

Heart, 2010

BackgroundDuring ischaemia, AMPK activation occurs in order to provide energy from alternative re... more BackgroundDuring ischaemia, AMPK activation occurs in order to provide energy from alternative resources. However, AMPK activity is known to be impaired in diabetes. We hypothesised that enhancing AMPK activation above physiological levels during ischaemia would protect both the normoglycaemic and the diabetic heart.MethodologyHearts from Wistar and Goto Kakizaki rats (GK, a mildly diabetic rat strain) were subjected to 35 min

Research paper thumbnail of Synthesis and characterization of some new complexes of Cu(II), Ni(II) and V(IV) with Schiff base derived from indole-3-carboxaldehyde. Biological activity on prokaryotes and eukaryotes

European Journal of Medicinal Chemistry, 2012

Six new Cu(II), Ni(II), and VO(II) complexes (1-6) with Schiff base 1-phenyl-2,3-dimethyl-4-(1H-i... more Six new Cu(II), Ni(II), and VO(II) complexes (1-6) with Schiff base 1-phenyl-2,3-dimethyl-4-(1H-indole-3-carboxaldehyde)-3-pyrazolin-5-one (HL) were synthesized. The Schiff base was prepared through the condensation of 1-phenyl-2,3-dimethyl-4-amino-3-pyrazolin-5-one (antipyrine) with 1H-indole-3-carboxaldehyde. The new obtained compounds were characterized by (1)H NMR, (13)C NMR, UV-VIS, IR, EPR spectroscopy, elemental analysis, molar electric conductibility, magnetic susceptibility and thermal gravimetric analysis. In addition, the structure of the ligand HL has been determined by X-ray diffraction methods. The biological activity of complex compounds was investigated in terms of antibacterial effect on prokaryotic cells, by using paper disc diffusion technique, and for antiproliferative effect on eukaryotic cells, by monitoring mitotic activity in timelapse videomicroscopy experiments. The compounds were screened for their antibacterial activity against gram-positive bacteria (Staphylococcus aureus var. Oxford 6538, Klebsielle pneumoniae ATCC 100131 and Legionella monocytogenes ATCC 35182), gram-negative bacteria (Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 9027 and Salmonella typhimurium ATCC 14028) and anti-fungal activity (Candida albicans and Aspergillus flavus) using paper disc diffusion technique. The minimum inhibitory concentrations (MICs) of the compounds were also determined by agar streak dilution method. Compounds 3 and 4 proved to be the most effective as antibacterial agents. The antiproliferative activity was investigated by counting the number of mitoses for HeLa, and MCF7 cells. No significant antiproliferative effect was noted for HL and complex 2, for both used cell types. For complexes 1 and 3 complete inhibition of cell proliferation was observed in the case of HeLa cells, while the effects on MCF7 cell proliferation were lower. In conclusion, six new complex compounds were synthesized, and their biological activity investigated on both prokaryotic and eukaryotic cells, proving that some of them could be putative therapeutic substances.

Research paper thumbnail of Preconditioning the Diabetic Heart: The Importance of Akt Phosphorylation

Diabetes, 2005

Conflicting evidence exists whether diabetic myocardium can be protected by ischemic precondition... more Conflicting evidence exists whether diabetic myocardium can be protected by ischemic preconditioning (IPC). The phosphatidylinositol 3-kinase (PI3K)-Akt pathway is important in IPC. However, components of this cascade have been found to be defective in diabetes. We hypothesize that IPC in diabetic hearts depends on intact signaling through the PI3K-Akt pathway to reduce myocardial injury. Isolated perfused Wistar (normal) and Goto-Kakizaki (diabetic) rat hearts were subjected to 1) 35 min of regional ischemia and 120 min of reperfusion with infarct size determined; 2) preconditioning (IPC) using 5 min of global ischemia followed by 10 min of reperfusion performed one, two, or three times before prolonged ischemia; or 3) determination of Akt phosphorylation after stabilization or after one and three cycles of IPC. In Wistar rats, one, two, and three cycles of IPC reduced infarct size 44.7 +/- 3.8% (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), 31.4 +/- 4.9% (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), and 34.3 +/- 6.1% (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), respectively, compared with controls (60.7 +/- 4.5%). However, in diabetic rats only three cycles of IPC significantly reduced infarction to 20.8 +/- 2.6% from 46.6 +/- 5.2% in controls (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), commensurate with significant Akt phosphorylation after three cycles of IPC. To protect the diabetic myocardium, it appears necessary to increase the IPC stimulus to achieve the threshold for cardioprotection and a critical level of Akt phosphorylation to mediate myocardial protection.

Research paper thumbnail of Glucagon-like Peptide 1 Can Directly Protect the Heart Against Ischemia/Reperfusion Injury

Diabetes, 2005

Glucagon-like peptide 1 (GLP-1), a gut incretin hormone that stimulates insulin secretion, also a... more Glucagon-like peptide 1 (GLP-1), a gut incretin hormone that stimulates insulin secretion, also activates antiapoptotic signaling pathways such as phosphoinositide 3-kinase and mitogen-activated protein kinase in pancreatic and insulinoma cells. Since these kinases have been shown to protect against myocardial injury, we hypothesized that GLP-1 could directly protect the heart against such injury via these prosurvival signaling pathways. Both isolated perfused rat heart and whole animal models of ischemia/reperfusion were used, with infarct size measured as the end point of injury. In both studies, GLP-1 added before ischemia demonstrated a significant reduction in infarction compared with the valine pyrrolidide (an inhibitor of its breakdown) or saline groups. This protection was abolished in the in vitro hearts by the GLP-1 receptor antagonist exendin (9-39), the cAMP inhibitor Rp-cAMP, the PI3kinase inhibitor LY294002, and the p42/44 mitogen-activated protein kinase inhibitor UO126. Western blot analysis demonstrated the phosphorylation of the proapoptotic peptide BAD in the GLP-1-treated groups. We show for the first time that GLP-1 protects against myocardial infarction in the isolated and intact rat heart. This protection appears to involve activating multiple prosurvival kinases. This finding may represent a new therapeutic potential for this class of drug currently undergoing clinical trials in the treatment of type 2 diabetes.

Research paper thumbnail of Glimepiride, a Novel Sulfonylurea, Does Not Abolish Myocardial Protection Afforded by Either Ischemic Preconditioning or Diazoxide

Circulation, 2001

Background-The sulfonylurea glibenclamide (Glib) abolishes the cardioprotective effect of ischemi... more Background-The sulfonylurea glibenclamide (Glib) abolishes the cardioprotective effect of ischemic preconditioning (IP), presumably by inhibiting mitochondrial K ATP channel opening in myocytes. Glimepiride (Glim) is a new sulfonylurea reported to affect nonpancreatic K ATP channels less than does Glib. We examined the effects of Glim on IP and on the protection afforded by diazoxide (Diaz), an opener of mitochondrial K ATP channels. Methods and Results-Rat hearts were Langendorff-perfused, subjected to 35 minutes of regional ischemia and 120 minutes of reperfusion, and assigned to 1 of the following treatment groups: (1) control;

Research paper thumbnail of Cross-talk between the survival kinases during early reperfusion: its contribution to ischemic preconditioning

Cardiovascular Research, 2004

Recruitment of the survival kinase cascades, PI3K-Akt and Raf-MEK1/2-Erk1/2, at the time of reper... more Recruitment of the survival kinase cascades, PI3K-Akt and Raf-MEK1/2-Erk1/2, at the time of reperfusion, following a lethal ischemic insult, may mediate the protection associated with ischemic preconditioning (IPC). The exact interplay between these two kinase cascades in mediating this effect is not clear. We examine the &amp;amp;amp;amp;amp;amp;amp;amp;#39;cross-talk&amp;amp;amp;amp;amp;amp;amp;amp;#39; between these kinase cascades in their contribution to IPC-induced protection. In isolated perfused rat hearts subjected to 35 min of lethal ischemia +/- ischemic preconditioning, the phosphorylation states of Akt, Erk1/2, p70S6K were determined after 15 min of reperfusion, and infarct size was measured after 120 min of reperfusion. IPC induced a threefold increase in Akt, Erk1/2, and p70S6K phosphorylation, at reperfusion. We found that inhibiting the PI3K-Akt (using LY294008) at reperfusion induced the phosphorylation of Erk1/2-p70S6K, and conversely, that inhibiting the MEK1/2-Erk1/2 pathway (using PD 98059) at reperfusion, induced the phosphorylation of Akt, suggesting &amp;amp;amp;amp;amp;amp;amp;amp;#39;cross-talk&amp;amp;amp;amp;amp;amp;amp;amp;#39; between the two kinase pathways. However, this effect was not accompanied by a reduction in infarct size (43.1 +/- 7.2% with LY 294008 and 57.7 +/- 7.0% with PD 98059 vs. 46.3 +/- 5.8% in control; P = NS), suggesting that both the kinase cascades may need to be activated to mediate IPC-induced protection. IPC reduced the infarct-risk volume ratio to 17.8 +/- 2.3% from 46.3 +/- 5.8% in control (P &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Inhibiting p70S6K, a kinase situated downstream of both PI3K and Erk1/2, using rapamycin, abolished IPC-induced protection (46.0 +/- 7.7% with IPC+RAPA vs. 17.8 +/- 2.3% with IPC; P &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). We report that, the survival kinase cascades PI3K-Akt and MEK1/2-Erk1/2, which are recruited at the time of reperfusion in response to ischemic preconditioning, exhibit &amp;amp;amp;amp;amp;amp;amp;amp;#39;cross-talk&amp;amp;amp;amp;amp;amp;amp;amp;#39; such that inhibiting one cascade activates the other and vice versa. Furthermore, at the time of reperfusion, these kinase cascades mediate IPC-induced protection, by acting in concert via p70S6K.

Research paper thumbnail of The Cardioprotective Effect of Necrostatin Requires the Cyclophilin-D Component of the Mitochondrial Permeability Transition Pore

Cardiovascular Drugs and Therapy, 2007

Necrostatin (Nec-1) protects against ischemia-reperfusion (IR) injury in both brain and heart. We... more Necrostatin (Nec-1) protects against ischemia-reperfusion (IR) injury in both brain and heart. We have previously reported in this journal that necrostatin can delay opening of the mitochondrial permeability transition pore (MPTP) in isolated cardiomyocytes. The aim of the present study was to investigate in more detail the role played by the MPTP in necrostatin-mediated cardioprotection employing mice lacking a key component of the MPTP, namely cyclophilin-D. Anaesthetized wild type (WT) and cyclophilin-D knockout (Cyp-D-/-) mice underwent an open-chest procedure involving 30 minutes of myocardial ischemia and 2 hours of reperfusion, with subsequent infarct size assessed by triphenyltetrazolium staining. Nec-1, given at reperfusion, significantly limited infarct size in WT mice (17.7±3% vs. 54.3±3%, P<0.05) but not in Cyp-D−/− mice (28.3±7% vs. 30.8±6%, P>0.05). In conclusion, the data obtained in Cyp-D−/− mice provide further evidence that Nec-1 protects against myocardial IR injury by modulating MPTP opening at reperfusion.

Research paper thumbnail of Pioglitazone Mimics Preconditioning in the Isolated Perfused Rat Heart: A Role for the Prosurvival Kinases PI3K and P42/44MAPK

Journal of Cardiovascular Pharmacology, Dec 1, 2005

Ischemic preconditioning, the most powerful protection against infarction, activates PI3Kinase (P... more Ischemic preconditioning, the most powerful protection against infarction, activates PI3Kinase (PI3K)/AKT and P42/44MAPK. Pioglitazone, a thiazolidinedione and PPARgamma receptor agonist used in Type II diabetes treatment, has been shown to activate these kinase cascades. We therefore hypothesized that pioglitazone could protect the myocardium when given prior to myocardial ischemia/reperfusion injury. Langendorff perfused rat hearts underwent 40 minutes of stabilization then 35 minutes of regional ischemia and 120 minutes of reperfusion (control) or Pioglitazone (1, 2, 5, and 10 microM)-given before ischemia. Additional groups underwent the same protocol but with either PI3K inhibitors (15 microM LY294002 or 100 nM wortmannin) or P42/44MAPK inhibitors (10 microM U0126 or 10 microM PD98059) given either during stabilization or at reperfusion. Infarct size was determined as a percentage of risk zone (I/R%). Pioglitazone (2 microM) significantly reduced I/R% compared with control (25.4 +/- 3.1 versus 47.3 +/- 3.4; P < 0.05). This protection was abolished by PI3K inhibitors (pioglitazone+LY294002 46.5 +/- 5.0, pioglitazone + wortmannin 48.8 +/- 4.6 versus pioglitazone alone 25.4 +/- 3.1; P < or = 0.05) but not by P42/44MAPK inhibitors (pioglitazone+U0126 30.7 +/- 5.7, pioglitazone + PD98059 28.5 +/- 6.3 versus pioglitazone alone 25.4 +/- 3.1; P < or = 0.05) given in stabilization. However when the inhibitors were given at reperfusion, the protection was abrogated by blocking either pathway (pioglitazone+LY294002 49.8 +/- 3.1, pioglitazone+U0126 48.7 +/- 3.7 versus pioglitazone alone 25.4 +/- 3.1; P < or = 0.05). In conclusion pioglitazone induced significant protection against ischemia/reperfusion injury when administered prior to ischemia. This protection appears to involve PI3K and P42/44MAPK.

Research paper thumbnail of Leptin, the obesity-related adipocytokine, protects the myocardium against ischaemia–reperfusion injury

Journal of Molecular and Cellular Cardiology

Research paper thumbnail of Failure of the adipocytokine, resistin, to protect the heart from ischemia-reperfusion injury

Journal of cardiovascular pharmacology and therapeutics, 2011

Experimental studies have linked the adipocytokines with acute cardioprotection. Whether the adip... more Experimental studies have linked the adipocytokines with acute cardioprotection. Whether the adipocytokine, resistin, confers protection is, however, debatable. In the current study, the actions of resistin, administered at reperfusion, were investigated in in vivo and in vitro rodent and in vitro human models of myocardial ischemia-reperfusion (I/R) injury. Resistin did not reduce infarct size in Langendorff-perfused rat hearts or murine hearts perfused in vivo. Resistin also did not protect human atrial muscle subjected to hypoxia-reoxygenation. Although cyclosporin A delayed mitochondrial permeability transition pore (MPTP) opening in murine cardiomyocytes, resistin was ineffective. Western blot analysis revealed that resistin treatment was associated with enhanced phosphorylation of Akt, at both the serine-473 (+ 51.9%, P = .01) and threonine-308 (+107%, P < .01) phosphorylation sites, although not to the extent seen with ischemic preconditioning (+132.5%, P = .002 and +389.1...

Research paper thumbnail of AMPK activation at reperfusion: A novel cardioprotective target?

Journal of Molecular and Cellular Cardiology, 2007

UCL logo UCL Discovery. ...

Research paper thumbnail of The Diabetic Heart: Too Sweet for Its Own Good?

Cardiology Research and Practice, 2012

Diabetes mellitus is a major risk factor for ischemic heart disease (IHD). Patients with diabetes... more Diabetes mellitus is a major risk factor for ischemic heart disease (IHD). Patients with diabetes and IHD experience worse clinical outcomes, suggesting that the diabetic heart may be more susceptible to ischemia-reperfusion injury (IRI). In contrast, the animal data suggests that the diabetic heart may be either more, equally, or even less susceptible to IRI. The conflicting animal data may be due to the choice of diabetic and/or IRI animal model. Ischemic conditioning, a phenomenon in which the heart is protected against IRI by one or more brief nonlethal periods of ischemia and reperfusion, may provide a novel cardioprotective strategy for the diabetic heart. Whether the diabetic heart is amenable to ischemic conditioning remains to be determined using relevant animal models of IRI and/or diabetes. In this paper, we review the limitations of the current experimental models used to investigate IRI and cardioprotection in the diabetic heart.

Research paper thumbnail of Metformin protects against myocardial infarction independent of its glucose lowering effects

Journal of Molecular and Cellular Cardiology, 2008

Journal of Molecular and Cellular Cardiology, Volume 44, Issue 4, Pages 748, April 2008, Authors:... more Journal of Molecular and Cellular Cardiology, Volume 44, Issue 4, Pages 748, April 2008, Authors:Marta Paiva; Lino Gonçalves; Luís Providência; Mihaela M. Mocanu; Derek M. Yellon.

Research paper thumbnail of The adipocytokine, resistin, is not cardioprotective despite activating components of the risk pathway

Journal of Molecular and Cellular Cardiology, 2008

Research paper thumbnail of Metformin cardioprotects the diabetic heart by inhibiting mPTP opening via the risk pathway

Journal of Molecular and Cellular Cardiology, 2007

Research paper thumbnail of The metabolic syndrome raises the threshold for cardioprotection

Journal of Molecular and Cellular Cardiology, 2007

... The metabolic syndrome raises the threshold for cardioprotection. Hausenloy, DJ and Wynne, A ... more ... The metabolic syndrome raises the threshold for cardioprotection. Hausenloy, DJ and Wynne, A and Mocanu, MM and Yellon, DM (2007) The metabolic syndrome raises the threshold for cardioprotection. In: JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY. (pp. ...

Research paper thumbnail of Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart

Journal of Molecular and Cellular Cardiology, 2007

... Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart. Wynne, ... more ... Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart. Wynne, A and Hausenloy, DJ and Mocanu, NM and Yellon, DM (2007) Glimepiride reduces the threshold for ischemic preconditioning in the diabetic heart. ...

Research paper thumbnail of PI3 Kinase and not p42/p44 Appears to be Implicated in the Protection Conferred by Ischemic Preconditioning

Journal of Molecular and Cellular Cardiology, 2002

M. M. MOCANU, R. M. BELL AND D. M. YELLON. PI3 Kinase and not p42/p44 Appears to be Implicated in... more M. M. MOCANU, R. M. BELL AND D. M. YELLON. PI3 Kinase and not p42/p44 Appears to be Implicated in the Protection Conferred by Ischemic Preconditioning. Journal of Molecular and Cellular Cardiology (2002) 34, 661À À668. Ischemic preconditioning results in an immediate phase of protection against lethal ischemia/ reperfusion injury that is comprised of both irreversible necrosis and programmed cell death, apoptosis. We hypothesized that preconditioning may activate putative anti-apoptotic pathways, through the induction of either phosphatidyl inositol 3-OH kinase (PI3 kinase) or p42/p44 extracellular receptor kinase, attenuating total cell death. Isolated perfused rat hearts were preconditioned with two cycles of 5 min ischemia and 10 min reperfusion. Then they were frozen for Western blot analysis or subjected to 35 min regional ischemia and 120 min reperfusion prior to infarct size assessment. Selective PI3 kinase inhibitors, wortmannin (W, 100 nM) and LY294002 (LY, 15 "M) and the p42/p44 inhibitor, PD 98059 (PD, 10 and 50 "M), were individually infused during the preconditioning protocol. One further group of hearts received both inhibitors (W and PD). The results were expressed as percentage of infarction within the risk zone. Inhibition of PI3 kinase by either W or LYpartially abrogated the infarct sparing effect of ischemic preconditioning (I/R%: 44.6 AE 2.7 in C, 17.6 AE 2.0 in IP, vs 32.2 AE 4.2 in W, and 30.9 AE 2.6 in LY, P , 0.05). Inhibition of ERK phosphorylation however, had no signi®cant effect upon infarct size reduction (17.6 AE 2.0 in ischemic preconditioning vs 21.4 AE 3.0 in IP 10 "M PD and 15.2 AE 1.4 in IP 50 "M PD, P . 0.05). Western blot analysis con®rmed that PD abrogated the phosphorylation of p42/p44 and LY the phosphorylation of AKT. Combined inhibition with PD W failed to further attenuate protection (27.6 AE 1.3%, P . 0.1). These data appear to demonstrate that the PI3 kinase, but not the p42/p44 cascade, is implicated in early ischemic preconditioning.

Research paper thumbnail of The Akt1 isoform is an essential mediator of ischaemic preconditioning

Journal of Cellular and Molecular Medicine, 2012

Phosphatidyl-inositol-3-kinase (PI3K)-Akt pathway is essential for conferring cardioprotection in... more Phosphatidyl-inositol-3-kinase (PI3K)-Akt pathway is essential for conferring cardioprotection in response to ischaemic preconditioning (IPC) stimulus. However, the role of the individual Akt isoforms expressed in the heart in mediating the protective response to IPC is unknown. In this study, we investigated the specific contribution of Akt1 and Akt2 in cardioprotection against ischaemia-reperfusion (I-R) injury. Mice deficient in Akt1 or Akt2 were subjected to in vivo regional myocardial ischaemia for 30 min. followed by reperfusion for 2 hrs with or without a prior IPC stimulus. Our results show that mice deficient in Akt1 were resistant to protection with either one or three cycles of IPC stimulus (42.7 ± 6.5% control versus 38.5 ± 1.9% 1 χ IPC, N = 6, NS; 41.4 ± 6.3% control versus 32.4 ± 3.2% 3 χ IPC, N = 10, NS). Western blot analysis, performed on heart samples taken from Akt1(-/-) mice subjected to IPC, revealed an impaired phosphorylation of GSK-3β, a downstream effector of Akt, as well as Erk1/2, the parallel component of the reperfusion injury salvage kinase pathway. Akt2(-/-) mice, which exhibit a diabetic phenotype, however, were amenable to protection with three but not one cycle of IPC (46.4 ± 5.6% control versus 35.9 ± 5.0% in 1 χ IPC, N = 6, NS; 47.0 ± 6.0% control versus 30.8 ± 3.3% in 3 χ IPC, N = 6; *P = 0.039). Akt1 but not Akt2 is essential for mediating a protective response to an IPC stimulus. Impaired activation of GSK-3β and Erk1/2 might be responsible for the lack of protective response to IPC in Akt1(-/-) mice. The rise in threshold for protection in Akt2(-/-) mice might be due to their diabetic phenotype.

Research paper thumbnail of Metformin Prevents Myocardial Reperfusion Injury by Activating the Adenosine Receptor

Journal of Cardiovascular Pharmacology, 2009

Metformin improves cardiovascular outcomes in patients with type 2 diabetes compared with other g... more Metformin improves cardiovascular outcomes in patients with type 2 diabetes compared with other glucose-lowering drugs. Experimental studies have shown that metformin can increase the intracellular concentration of adenosine monophosphate, which is a major determinant of the intracellular formation of adenosine. We hypothesize that metformin, given at reperfusion, can limit myocardial infarct size due to increased adenosine receptor stimulation. Isolated perfused hearts from Sprague-Dawley rats were subjected to 35 minutes of regional ischemia and 120 minutes of reperfusion. Perfusion with metformin (50 microM) for the first 15 minutes of reperfusion reduced infarct size (percent area at risk) from 42% +/- 2% to 19% +/- 4% (n &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;or= 6; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), which was blocked by a concomitant perfusion with the adenosine receptor antagonist 8-p-sulfophenyltheophylline (100 microM; 43% +/- 3%) or nitrobenzylthioinosine (a blocker of transmembranous adenosine transport; 1 microM; 45% +/- 5%). In addition, intravenous administration of metformin (5 mg/kg) reduced infarct size in a rat in situ model of myocardial infarction (34% +/- 6% vs. 62% +/- 5%; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), which was completely abolished by 8-p-sulfophenyltheophylline (61% +/- 3%). We conclude that metformin, given at reperfusion, reduces infarct size in a rat model of myocardial infarction, which is critically dependent on adenosine receptor stimulation, probably via increased intracellular formation of adenosine.

Research paper thumbnail of BAS/BSCR34 Is an increased AMPK activation during ischaemia essential for the protection of the heart against infarction?

Heart, 2010

BackgroundDuring ischaemia, AMPK activation occurs in order to provide energy from alternative re... more BackgroundDuring ischaemia, AMPK activation occurs in order to provide energy from alternative resources. However, AMPK activity is known to be impaired in diabetes. We hypothesised that enhancing AMPK activation above physiological levels during ischaemia would protect both the normoglycaemic and the diabetic heart.MethodologyHearts from Wistar and Goto Kakizaki rats (GK, a mildly diabetic rat strain) were subjected to 35 min

Research paper thumbnail of Synthesis and characterization of some new complexes of Cu(II), Ni(II) and V(IV) with Schiff base derived from indole-3-carboxaldehyde. Biological activity on prokaryotes and eukaryotes

European Journal of Medicinal Chemistry, 2012

Six new Cu(II), Ni(II), and VO(II) complexes (1-6) with Schiff base 1-phenyl-2,3-dimethyl-4-(1H-i... more Six new Cu(II), Ni(II), and VO(II) complexes (1-6) with Schiff base 1-phenyl-2,3-dimethyl-4-(1H-indole-3-carboxaldehyde)-3-pyrazolin-5-one (HL) were synthesized. The Schiff base was prepared through the condensation of 1-phenyl-2,3-dimethyl-4-amino-3-pyrazolin-5-one (antipyrine) with 1H-indole-3-carboxaldehyde. The new obtained compounds were characterized by (1)H NMR, (13)C NMR, UV-VIS, IR, EPR spectroscopy, elemental analysis, molar electric conductibility, magnetic susceptibility and thermal gravimetric analysis. In addition, the structure of the ligand HL has been determined by X-ray diffraction methods. The biological activity of complex compounds was investigated in terms of antibacterial effect on prokaryotic cells, by using paper disc diffusion technique, and for antiproliferative effect on eukaryotic cells, by monitoring mitotic activity in timelapse videomicroscopy experiments. The compounds were screened for their antibacterial activity against gram-positive bacteria (Staphylococcus aureus var. Oxford 6538, Klebsielle pneumoniae ATCC 100131 and Legionella monocytogenes ATCC 35182), gram-negative bacteria (Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 9027 and Salmonella typhimurium ATCC 14028) and anti-fungal activity (Candida albicans and Aspergillus flavus) using paper disc diffusion technique. The minimum inhibitory concentrations (MICs) of the compounds were also determined by agar streak dilution method. Compounds 3 and 4 proved to be the most effective as antibacterial agents. The antiproliferative activity was investigated by counting the number of mitoses for HeLa, and MCF7 cells. No significant antiproliferative effect was noted for HL and complex 2, for both used cell types. For complexes 1 and 3 complete inhibition of cell proliferation was observed in the case of HeLa cells, while the effects on MCF7 cell proliferation were lower. In conclusion, six new complex compounds were synthesized, and their biological activity investigated on both prokaryotic and eukaryotic cells, proving that some of them could be putative therapeutic substances.

Research paper thumbnail of Preconditioning the Diabetic Heart: The Importance of Akt Phosphorylation

Diabetes, 2005

Conflicting evidence exists whether diabetic myocardium can be protected by ischemic precondition... more Conflicting evidence exists whether diabetic myocardium can be protected by ischemic preconditioning (IPC). The phosphatidylinositol 3-kinase (PI3K)-Akt pathway is important in IPC. However, components of this cascade have been found to be defective in diabetes. We hypothesize that IPC in diabetic hearts depends on intact signaling through the PI3K-Akt pathway to reduce myocardial injury. Isolated perfused Wistar (normal) and Goto-Kakizaki (diabetic) rat hearts were subjected to 1) 35 min of regional ischemia and 120 min of reperfusion with infarct size determined; 2) preconditioning (IPC) using 5 min of global ischemia followed by 10 min of reperfusion performed one, two, or three times before prolonged ischemia; or 3) determination of Akt phosphorylation after stabilization or after one and three cycles of IPC. In Wistar rats, one, two, and three cycles of IPC reduced infarct size 44.7 +/- 3.8% (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), 31.4 +/- 4.9% (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), and 34.3 +/- 6.1% (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), respectively, compared with controls (60.7 +/- 4.5%). However, in diabetic rats only three cycles of IPC significantly reduced infarction to 20.8 +/- 2.6% from 46.6 +/- 5.2% in controls (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01), commensurate with significant Akt phosphorylation after three cycles of IPC. To protect the diabetic myocardium, it appears necessary to increase the IPC stimulus to achieve the threshold for cardioprotection and a critical level of Akt phosphorylation to mediate myocardial protection.

Research paper thumbnail of Glucagon-like Peptide 1 Can Directly Protect the Heart Against Ischemia/Reperfusion Injury

Diabetes, 2005

Glucagon-like peptide 1 (GLP-1), a gut incretin hormone that stimulates insulin secretion, also a... more Glucagon-like peptide 1 (GLP-1), a gut incretin hormone that stimulates insulin secretion, also activates antiapoptotic signaling pathways such as phosphoinositide 3-kinase and mitogen-activated protein kinase in pancreatic and insulinoma cells. Since these kinases have been shown to protect against myocardial injury, we hypothesized that GLP-1 could directly protect the heart against such injury via these prosurvival signaling pathways. Both isolated perfused rat heart and whole animal models of ischemia/reperfusion were used, with infarct size measured as the end point of injury. In both studies, GLP-1 added before ischemia demonstrated a significant reduction in infarction compared with the valine pyrrolidide (an inhibitor of its breakdown) or saline groups. This protection was abolished in the in vitro hearts by the GLP-1 receptor antagonist exendin (9-39), the cAMP inhibitor Rp-cAMP, the PI3kinase inhibitor LY294002, and the p42/44 mitogen-activated protein kinase inhibitor UO126. Western blot analysis demonstrated the phosphorylation of the proapoptotic peptide BAD in the GLP-1-treated groups. We show for the first time that GLP-1 protects against myocardial infarction in the isolated and intact rat heart. This protection appears to involve activating multiple prosurvival kinases. This finding may represent a new therapeutic potential for this class of drug currently undergoing clinical trials in the treatment of type 2 diabetes.

Research paper thumbnail of Glimepiride, a Novel Sulfonylurea, Does Not Abolish Myocardial Protection Afforded by Either Ischemic Preconditioning or Diazoxide

Circulation, 2001

Background-The sulfonylurea glibenclamide (Glib) abolishes the cardioprotective effect of ischemi... more Background-The sulfonylurea glibenclamide (Glib) abolishes the cardioprotective effect of ischemic preconditioning (IP), presumably by inhibiting mitochondrial K ATP channel opening in myocytes. Glimepiride (Glim) is a new sulfonylurea reported to affect nonpancreatic K ATP channels less than does Glib. We examined the effects of Glim on IP and on the protection afforded by diazoxide (Diaz), an opener of mitochondrial K ATP channels. Methods and Results-Rat hearts were Langendorff-perfused, subjected to 35 minutes of regional ischemia and 120 minutes of reperfusion, and assigned to 1 of the following treatment groups: (1) control;

Research paper thumbnail of Cross-talk between the survival kinases during early reperfusion: its contribution to ischemic preconditioning

Cardiovascular Research, 2004

Recruitment of the survival kinase cascades, PI3K-Akt and Raf-MEK1/2-Erk1/2, at the time of reper... more Recruitment of the survival kinase cascades, PI3K-Akt and Raf-MEK1/2-Erk1/2, at the time of reperfusion, following a lethal ischemic insult, may mediate the protection associated with ischemic preconditioning (IPC). The exact interplay between these two kinase cascades in mediating this effect is not clear. We examine the &amp;amp;amp;amp;amp;amp;amp;amp;#39;cross-talk&amp;amp;amp;amp;amp;amp;amp;amp;#39; between these kinase cascades in their contribution to IPC-induced protection. In isolated perfused rat hearts subjected to 35 min of lethal ischemia +/- ischemic preconditioning, the phosphorylation states of Akt, Erk1/2, p70S6K were determined after 15 min of reperfusion, and infarct size was measured after 120 min of reperfusion. IPC induced a threefold increase in Akt, Erk1/2, and p70S6K phosphorylation, at reperfusion. We found that inhibiting the PI3K-Akt (using LY294008) at reperfusion induced the phosphorylation of Erk1/2-p70S6K, and conversely, that inhibiting the MEK1/2-Erk1/2 pathway (using PD 98059) at reperfusion, induced the phosphorylation of Akt, suggesting &amp;amp;amp;amp;amp;amp;amp;amp;#39;cross-talk&amp;amp;amp;amp;amp;amp;amp;amp;#39; between the two kinase pathways. However, this effect was not accompanied by a reduction in infarct size (43.1 +/- 7.2% with LY 294008 and 57.7 +/- 7.0% with PD 98059 vs. 46.3 +/- 5.8% in control; P = NS), suggesting that both the kinase cascades may need to be activated to mediate IPC-induced protection. IPC reduced the infarct-risk volume ratio to 17.8 +/- 2.3% from 46.3 +/- 5.8% in control (P &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Inhibiting p70S6K, a kinase situated downstream of both PI3K and Erk1/2, using rapamycin, abolished IPC-induced protection (46.0 +/- 7.7% with IPC+RAPA vs. 17.8 +/- 2.3% with IPC; P &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). We report that, the survival kinase cascades PI3K-Akt and MEK1/2-Erk1/2, which are recruited at the time of reperfusion in response to ischemic preconditioning, exhibit &amp;amp;amp;amp;amp;amp;amp;amp;#39;cross-talk&amp;amp;amp;amp;amp;amp;amp;amp;#39; such that inhibiting one cascade activates the other and vice versa. Furthermore, at the time of reperfusion, these kinase cascades mediate IPC-induced protection, by acting in concert via p70S6K.

Research paper thumbnail of The Cardioprotective Effect of Necrostatin Requires the Cyclophilin-D Component of the Mitochondrial Permeability Transition Pore

Cardiovascular Drugs and Therapy, 2007

Necrostatin (Nec-1) protects against ischemia-reperfusion (IR) injury in both brain and heart. We... more Necrostatin (Nec-1) protects against ischemia-reperfusion (IR) injury in both brain and heart. We have previously reported in this journal that necrostatin can delay opening of the mitochondrial permeability transition pore (MPTP) in isolated cardiomyocytes. The aim of the present study was to investigate in more detail the role played by the MPTP in necrostatin-mediated cardioprotection employing mice lacking a key component of the MPTP, namely cyclophilin-D. Anaesthetized wild type (WT) and cyclophilin-D knockout (Cyp-D-/-) mice underwent an open-chest procedure involving 30 minutes of myocardial ischemia and 2 hours of reperfusion, with subsequent infarct size assessed by triphenyltetrazolium staining. Nec-1, given at reperfusion, significantly limited infarct size in WT mice (17.7±3% vs. 54.3±3%, P<0.05) but not in Cyp-D−/− mice (28.3±7% vs. 30.8±6%, P>0.05). In conclusion, the data obtained in Cyp-D−/− mice provide further evidence that Nec-1 protects against myocardial IR injury by modulating MPTP opening at reperfusion.