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Metformin protects against myocardial reperfusion injury via PI3-kinase-dependent inhibition of mitochondrial permeability transition
ABSTRACTS / Journal of Molecular and Cellular Cardiology 40 (2006) 920 – 1015
112. Metformin protects against myocardial reperfusion injury via PI3-kinase-dependent inhibition of mitochondrial permeability transition Gurpreet S. Bhamra, Sean M. Davidson, Mihaela M. Mocanu, Derek M. Yellon. The Hatter Cardiovascular Institute, University College London Hospitals and Medical School, London, WC1E 6HX, UK The UKPDS study showed that metformin was associated with a reduced risk of heart disease. Previously, it has been demonstrated that the inhibition of the mitochondrial permeability transition pore (MPTP) induced protection against myocardial ischemia – reperfusion injury, and this was associated with a reduced myocardial infarct size. This protection has also been linked to up-regulation of the P13kinase/Akt survival pathway. Metformin is also known to inhibit MPTP opening and activate AMPK in different cell systems. Therefore, the aim of our study was to investigate whether metformin could directly reduce myocardial infarct size and whether any protection observed involved MPTP and the PI3kinase/Akt and AMPK signaling pathways. We measured infarct size in isolated perfused rat hearts subjected to 35 min ischemia and 120 min reperfusion with/ without metformin and the inhibitor of the P13kinase pathway, LY294002. We used Western blotting to assess the Akt and AMPK phosphorylation in these hearts and confocal microscopy to investigate the MPTP in isolated cardiomyocytes subjected to an oxidative injury in the presence of metformin. Metformin significantly reduced myocardial infarction (62.0 T 3.0% in control vs. 35.0 T 2.7%, P < 0.03) and increased the time to MPTP opening in rat cardiomyocytes (217 T 20 s to 343 T 29 s). These effects were abolished by LY294002. Akt, but not AMPK phosphorylation was increased andsustained in metformin treated hearts. This is the first study to demonstrate that metformin has direct cardioprotective properties and appears to act via inhibiting MPTP opening, linked to the PI3kinase/Akt pathway. These data may help explain some of the beneficial effects observed in the UKPDS study.
are unclear. We hypothesised that cGMP-dependent protein kinase (PKG) is a principal mediator of this cytoprotective response. A. Isolated neonatal rat cardiomyocytes in primary culture were subjected to 3 h simulated ischaemia and 2 h reoxygenation and the extent of irreversible cell injury was assessed using trypan blue uptake. Treatment throughout with the cGMP analogue 8Br-cGMP (10 nM) was protective and this action was abolished by the selective PKG inhibitor KT5823 (600 nM). Similarly the protective action of the NO-donor SNAP (1 mM) was abolished by the PKG inhibitor. B. In further studies, isolated perfused rat hearts were subjected to 30 min left coronary artery occlusion and 120 min reperfusion. Tetrazolium-determined infarct size was significantly reduced by treatment during ischaemia and early reperfusion with B-type natriuretic peptide (BNP, 10 nM). This protective effect was abolished by KT5823 while treatment with 8Br-cGMP was markedly protective. These data confirm previous observations that diverse cGMP-elevating agents are markedly protective against ischaemia –reperfusion injury. Furthermore, they implicate a key role of PKG as a mediator of protection.
doi:10.1016/j.yjmcc.2006.03.127
113. cGMP-dependent protein kinase mediates protection against ischaemia – reperfusion injury Zolta´n Giricz a, Aniko´ Go¨rbe a, Dwaine S. Burley b, Judit Pipis a, Pe´ter Ferdinandy a, Gary F. Baxter b. a Cardiovascular Research Group, Department of Biochemistry, University of Szeged, Szeged, Hungary. b The Royal Veterinary College, University of London, London, UK Elevation of intracellular [cGMP] as a result of soluble or particulate guanylate cyclase activation is associated with increased resistance to ischaemia– reperfusion injury but the downstream signaling pathways and effectors of protection
961
doi:10.1016/j.yjmcc.2006.03.128
112. Metformin protects against myocardial reperfusion injury via PI3-kinase-dependent inhibition of mitochondrial permeability transition Gurpreet S. Bhamra, Sean M. Davidson, Mihaela M. Mocanu, Derek M. Yellon. The Hatter Cardiovascular Institute, University College London Hospitals and Medical School, London, WC1E 6HX, UK The UKPDS study showed that metformin was associated with a reduced risk of heart disease. Previously, it has been demonstrated that the inhibition of the mitochondrial permeability transition pore (MPTP) induced protection against myocardial ischemia – reperfusion injury, and this was associated with a reduced myocardial infarct size. This protection has also been linked to up-regulation of the P13kinase/Akt survival pathway. Metformin is also known to inhibit MPTP opening and activate AMPK in different cell systems. Therefore, the aim of our study was to investigate whether metformin could directly reduce myocardial infarct size and whether any protection observed involved MPTP and the PI3kinase/Akt and AMPK signaling pathways. We measured infarct size in isolated perfused rat hearts subjected to 35 min ischemia and 120 min reperfusion with/ without metformin and the inhibitor of the P13kinase pathway, LY294002. We used Western blotting to assess the Akt and AMPK phosphorylation in these hearts and confocal microscopy to investigate the MPTP in isolated cardiomyocytes subjected to an oxidative injury in the presence of metformin. Metformin significantly reduced myocardial infarction (62.0 T 3.0% in control vs. 35.0 T 2.7%, P < 0.03) and increased the time to MPTP opening in rat cardiomyocytes (217 T 20 s to 343 T 29 s). These effects were abolished by LY294002. Akt, but not AMPK phosphorylation was increased andsustained in metformin treated hearts. This is the first study to demonstrate that metformin has direct cardioprotective properties and appears to act via inhibiting MPTP opening, linked to the PI3kinase/Akt pathway. These data may help explain some of the beneficial effects observed in the UKPDS study.
are unclear. We hypothesised that cGMP-dependent protein kinase (PKG) is a principal mediator of this cytoprotective response. A. Isolated neonatal rat cardiomyocytes in primary culture were subjected to 3 h simulated ischaemia and 2 h reoxygenation and the extent of irreversible cell injury was assessed using trypan blue uptake. Treatment throughout with the cGMP analogue 8Br-cGMP (10 nM) was protective and this action was abolished by the selective PKG inhibitor KT5823 (600 nM). Similarly the protective action of the NO-donor SNAP (1 mM) was abolished by the PKG inhibitor. B. In further studies, isolated perfused rat hearts were subjected to 30 min left coronary artery occlusion and 120 min reperfusion. Tetrazolium-determined infarct size was significantly reduced by treatment during ischaemia and early reperfusion with B-type natriuretic peptide (BNP, 10 nM). This protective effect was abolished by KT5823 while treatment with 8Br-cGMP was markedly protective. These data confirm previous observations that diverse cGMP-elevating agents are markedly protective against ischaemia –reperfusion injury. Furthermore, they implicate a key role of PKG as a mediator of protection.
doi:10.1016/j.yjmcc.2006.03.127
113. cGMP-dependent protein kinase mediates protection against ischaemia – reperfusion injury Zolta´n Giricz a, Aniko´ Go¨rbe a, Dwaine S. Burley b, Judit Pipis a, Pe´ter Ferdinandy a, Gary F. Baxter b. a Cardiovascular Research Group, Department of Biochemistry, University of Szeged, Szeged, Hungary. b The Royal Veterinary College, University of London, London, UK Elevation of intracellular [cGMP] as a result of soluble or particulate guanylate cyclase activation is associated with increased resistance to ischaemia– reperfusion injury but the downstream signaling pathways and effectors of protection
961
doi:10.1016/j.yjmcc.2006.03.128