Levocarnitine Protects H9c2 Rat Cardiomyocytes from H(2)O(2)-induced Mitochondrial Dysfunction and Apoptosis

Background: Although the protective effects of levocarnitine in patients with ischemic heart disease are related to the attenuation of oxidative stress injury, the exact mechanisms involved have yet to be fully understood. Our aim was to investigate the potential protective effects of levocarnitine pretreatment against oxidative stress in rat H9c2 cardiomyocytes. Methods: Cardiomyocytes were exposed to H(2)O(2) to create an oxidative stress model. The cells were pretreated with 50, 100, or 200 μM levocarnitine for 1 hour before H(2)O(2) exposure. Results: H(2)O(2) exposure led to significant activation of oxidative stress in the cells, characterized by reduced viability, increased intracellular reactive oxygen species, lipid peroxidation, and reduced intracellular antioxidant activity. Mitochondrial dysfunction was also observed following H(2)O(2) exposure, reflected by the loss of mitochondrial transmembrane potential and intracellular adenosine triphosphate. These pathophysiological processes led to cardiomyocyte apoptosis through activation of the intrinsic apoptotic pathway. More importantly, the levocarnitine pretreatment attenuated the H(2)O(2)-induced oxidative injury significantly, preserved mitochondrial function, and partially prevented cardiomyocyte apoptosis during the oxidative stress reaction. Western blotting analyses suggested that levocarnitine pretreatment increased plasma protein levels of Bcl-2, reduced Bax, and attenuated cytochrome C leakage from the mitochondria in the cells. Conclusion: Our in vitro study indicated that levocarnitine pretreatment may protect cardiomyocytes from oxidative stress-related damage.