Abstract 166: The Co-releasing Molecule CORM-3 Protects Adult Cardiomyocytes Against Hypoxia Reoxygenation by Inhibiting Na+/HCO3- Symporter
Several studies have reported that CORM-3, a water-soluble carbon monoxide (CO)-releasing molecule, elicits cardioprotection against myocardial infarction but the mechanism of its beneficial action remains to be elucidated. Considerable evidence also indicates that inhibition of two pH regulators, the Na+/H+ exchanger (NHE) and Na+/HCO3- symporter (NBS), protect cardiomyocytes from hypoxia/reoxygenation injury by delaying the intracellular pH (pHi) recovery at the time of reperfusion. Thus the aim of this study was to explore whether CORM-3-mediated cytoprotection involves the modulation of NBS and other well-known cardioprotective targets such as mitochondrial ATP-dependent K+ channels (mKATP) and ERK 1/2 pathway. Therefore cardiomyocytes freshly isolated from adult mice (C57BL6J) were submitted to a sequence of 3h hypoxia followed by 2h of reoxygenation. CORM-3 (20, 50 and 100 µM) was added at the time of reoxygenation and cell viability was assessed using trypan blue. NBS activity was modulated using different experimental conditions: 1) medium with or without bicarbonate since NBS is inhibited in bicarbonate-free medium; 2) hypoxia performed with extracellular pH (pHo) either at 7.4 or 6.2, followed by a reoxygenation phase at pHo 7.4. The contribution of NBS is of major importance for acid-extrusion when pHo at the end of hypoxia is close to neutrality but is rather low when pHo is acidic. CORM-3 reduced by an average of 14% (p<0.05, n=15) the mortality of cardiomyocytes placed in bicarbonate-buffered solution and exposed to hypoxia at pHo 7.4. Under acidic conditions during hypoxia, the extent of cardioprotection was weaker. Interestingly, the cardioprotective effect of CORM-3 was abolished by switching to a bicarbonate-free medium (i.e. NBS inhibition), independently from pHo used during hypoxia. Furthermore, the beneficial effect of CORM-3 was also inhibited by 5-hydroxydecanoate (mKATP inhibitor, 500 µM) or PD098059 (ERK 1/2 inhibitor, 10 µM). In conclusion, mKATP channels opening, activation of ERK 1/2 pathway and inhibition of Na+/HCO3- symporter at reoxygenation contribute to the cardioprotection conferred by CORM-3.
- © 2012 by American Heart Association, Inc.