Studies on Cell Injury Induced by Hypoxia-Reoxygenation and Oxidized Low Density Lipoprotein With Special Reference to the Protectiove Effect of Mixed Tocopherols, Omega-3 Fatty Acids and Transforming Growth Factor-beta1

Abstract: Hypoxia-reoxygenation (H-R) injury is an important clinical phenomenon in patients with coronary artery disease (CAD). Endothelial injury is a critical step in the initiation and progression of atherosclerosis. Therefore, endothelial and cardiomyocyte protection has been considered an effective step in prevention and treatment of CAD.To investigate the cardioprotective effect of tocopherols, omega-3 fatty acid [eicosapentaenoic acid (EPA)] and transforming growth factor-?1 (TGF-?1) during H-R, calcium tolerant myocytes isolated from adult rats were cultured and subjected to hypoxia for 24 hrs followed by reoxygenation of 3 hrs. All strategies, including tocopherol preparations, EPA and TGF-?1, showed attenuation of H-R-induced myocyte injury indicated by reduction of lactate dehydrogenase (LDH) release. Both a-tocopherol and a mixed- tocopherols (?-, ?-, and ?-) decreased the effects of H-R on iNOS expression and SOD activity in cultured myocytes. The mixed-tocopherols was more potent than a-tocopherol alone. EPA inhibited H-R-induced lipid peroxidation, MMP-1 expression and p38MAPK phosphorylation. TGF-?1 blocked the increase in iNOS and PKB phosphorylation as well as the decrease in eNOS expression in cultured myocytes exposed to H-R. To further investigate the protective effect of omega-3 fatty acids [docosahexaenoic acid (DHA) and EPA] and TGF-?1, the cultured endothelial cells were exposed to oxidant injury mediated by oxidized low-density lipoprotein (ox-LDL). Ox-LDL markedly reduced TGF-?1 release, increased the expression of TGF-?1 receptors, upregulated the expression of adhesion molecules, P-selectin and ICAM-1, enhanced the adhesion of monocytes to endothelial cells, and decreased protein kinase B (PKB) activation. Both DHA and EPA blocked these effects of ox-LDL on endothelial cells. Exogenous recombinant TGF-?1 also ameliorated ox-LDL-induced expression of adhesion molecules and monocytes adhesion, which were blocked by antibodies to the TGF-?1 type 2, but not to the type 3 receptor.These observations provide mechanistic insights into H-R and oxidant injury and tissue protection by three different strategies.