Pathogenesis and protection of ischemia and reperfusion injury in myocardium.

The important factors that influence the progress of ischemic cardiac lesion are blood flow condition and abnormal cardiac metabolism. Myocardial ischemia is promoted by either an increase in oxygen demand or a shortage of oxygen supply. The Na(+)-Ca(++) ion exchange mechanism is very important for myocardial contraction and cell damage. Na(+)-K(+)ATPase and Ca(++)ATPase are enzyme histochemically localized in subsarcolemmal cisterns, sarcolemmal reticulum and capillary endothelium, and keep myocardial function. These ATPases are impaired by anoxia, superoxides and free radicals. The reduction of O(2) results in the production of superoxides as well as hydrogen peroxide (H(2)O(2)). H(2)O(2) is highly diffusible and induces cell damage. H(2)O(2) appears to affect not only lipids but also intramembranous proteins embedded in the cell membrane. The hydroxyl radical (OH) also participates in lipid hyperoxidation. In the pathogenesis of ischemic and/or reperfused heart disease, ischemia induces rapid or gradual changes in all membrane systems and causes reversible or irreversible injury including necrotic and apoptotic cell death. Advanced glycation end products (AGEs) accumulation induced by diabetic conditioning is an etiologic factor inducing cardiomyopathy. The AGEs protein affects cell changes such as increased number, transformation, functional disturbance and cytokine elimination. In coronary arteries, the migration of smooth muscle cells caused by the taking up of AGEs proteins through the receptor (RAGE), and cytokine discharge are suggested. AGEs accumulation may induce diabetic macroangiopathy through RAGE, and the increase in the level of RAGE expression by endothelial cells could be a reason that diabetes mellitus accelerates atherosclerosis. On the other hand, we also reported that hyperglycemia was a promoting factor of ischemic heart injury in diabetic animals. Ischemic preconditioning is a useful phenomenon that limits myocardial damage. We foused on protein kinase C (PKC), mitogen-activated protein kinase (MAPK) and mitochondrial ATP-dependent potassium (mitoK(ATP)) channel as mediator or end which effector are necessary for adaptation. The opening of the mitoK(ATP) channel induces the depolarization of mitochondria, reducing Ca(++)overload during reperfusion. The regeneration of myocardial cells is confirmed using embryonic stem cells. Myocardial cells that exhibit self-pulsation are generated from mesenchymal stem cells in mesodermal tissues of the bone marrow.