IRON METABOLISM IN AN IN VITRO MODEL OF CARDIAC ISCHEMIA: HYPOXIC INJURY AND PROTECTIVE STRATEGIES

In the cardiac ischemia hypoxia and free iron appear to interact in causing the cellular death. Ischemia and re-establishment of blood flow cause the generation of reactive oxygen species catalysed by intracellular free iron with deleterious effects in post-ischemic reperfused tissue. In this study we have investigated the molecular mechanisms involved in the regulation of iron metabolism in cardiomiocytes exposed to hypoxia/reoxygenation and evaluated the relationships with cell viability parameters. We have demonstrated that oxygen, glucose and serum deprivation followed by reoxygenation affects the viability and survival of H9c2 cardiac cells. With regard to cellular iron homeostasis, IRPs activity appears to be differently regulated in hypoxia and reoxigenation. Regarding transferrin receptor the hypoxic conditions induced a reduction of its expression, while there was a significant increase during reoxygenation phases. Concerning ferritin cellular content, it resulted unchanged after 3h of OGSD, while there was a significant enhanced expression during reoxygenation. Interestingly, the reoxygenation-induced increase of ferritin content was less evident after an hypoxic exposure of 6h. In this in vitro experimental model of cardiac ischemia the “point of no return” of the H9c2 cardiac cells, is fixed approximately at 6 hours of hypoxic conditions. After this point, increased misregulations of iron metabolism coupled to reduction of oxygen availability caused permanent damages and impaired cell survival.