Samul extract protects against the H2O2-induced apoptosis of H9c2 cardiomyoblasts via activation of extracellular regulated kinases (Erk) 1/2

Samul extract, containing Radix Rehmanniae, Radix Angelicae Gigantis, Radix Paeoniae, and Rhizoma Cnidii, has been traditionally used for treatment of ischemic heart and brain damages in Oriental medicine. However, little is known about the mechanism by which Samul rescues cells from cytotoxic damage. This study was designed to investigate the protective mechanisms of Samul on H2O2-induced death of H9c2 cells. Treatment with H2O2 markedly decreased the viability of H9c2 cells in a dose- and time-dependent manner, which was significantly prevented by pre-treatment with Samul. The nature of death of H9c2 cells by H2O2 was demonstrated by apoptotic features, including ladder-pattern fragmentation of genomic DNA and chromatin condensation, which were markedly abolished by pretreatment of Samul in H2O2-treated cells. We further demonstrated that MEK inhibitor, PD98059, dose-dependently attenuated the protective effects of Samul against H2O2, whereas inhibitors of Jnk and p38 did not. Consistently, Samul induced the early phosphorylation of Erk, p44, in H2O2-treated cells. In addition, treatment with Samul also resulted in an increase of expression of anti-apotogenic Bcl2 protein, which was decreased by H2O2. However, it inhibited the expression of apotogenic Bax protein in H2O2-treated cells. Taken together, these results suggest that the protective effects of Samul against oxidative damage may be achieved via activation of MAP kinase, Erk as well as Bcl2 family proteins.