Neuroprotective effects of the Phellinus linteus ethyl acetate extract against H2O2-induced apoptotic cell death of SK-N-MC cells

Numerous studies have suggested that neuronal cells are protected against oxidative stress-induced cell damage by antioxidants, such as polyphenolic compounds. Phellinus linteus (PL) has traditionally been used to treat various symptoms in East Asian countries. In the present study, we prepared an ethyl acetate extract from the fruiting bodies of PL (PLEA) using hot water extraction, ethanol precipitation, and ethyl acetate extraction. The PLEA contained polyphenols as its major chemical component, and thus, we predicted that it may exhibit antioxidant and neuroprotective effects against oxidative stress. The results showed that the pretreatment of human brain neuroblastoma SK-N-MC cells with the PLEA (0.1-5 μg/mL) significantly and dose-dependently reduced the cytotoxicity of H2O2 and the intracellular ROS levels and enhanced the expression of HO-1 (heme oxygenase-1) and antioxidant enzymes, such as CAT (catalase), GPx-1 (glutathione peroxidase-1), and SOD-1 and -2 (superoxide dismutase-1 and -2). The PLEA also directly scavenged free radicals. PLEA pretreatment also significantly attenuated DNA fragmentation and suppressed the mRNA expression and activation of mitogen-activated protein kinases extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 kinase, which are induced by oxidative stress and lead to cell death. PLEA pretreatment inhibited the activation of the apoptosis-related proteins caspase-3 and poly (ADP-ribose) polymerase. These results demonstrate that the PLEA has neuroprotective effects against oxidative stress (H2O2)–induced neuronal cell death via its antioxidant and anti-apoptotic properties. PLEA should be investigated in an in vivo model on its potential to prevent or ameliorate neurodegenerative disease.