The present study was designed to evaluate protective activity of an ethanol extract of the stems ofSchisandra chinensis (SCE) and explore its possible molecular mechanisms on acetaminophen (APAP) induced hepatotoxicity in a mouse model.The results of HPLC analysis showed that the main components of SCE included schisandrol A,schisandrol B,deoxyschisandrin,schisandrin B,and sehisandrin C and their contents were 5.83,7.11,2.13,4.86,0.42 mg.g-1,respectively.SCE extract was given for 7 consecutive days before a single hepatotoxic dose of APAP (250 mg·kg-1) was injected to mice.Our results showed that SCE pretreatment ameliorated liver dysfunction and oxidative stress,which was evidenced by significant decreases in aspartate transaminase (AST),alanine aminotransferase (ALT),malondialdehyde (MDA) contents and elevations in reduced glutathione (GSH) and superoxide dismutase (SOD) levels.These findings were associated with the result that the SCE pretreatment significantly decreased expression levels of 4-hydroxynonenal (4-HNE) and 3-nitrotyrosine (3-NT).SCE also significantly decreased the expression levels of Bax,mitogen-activated protein kinase (MAPK),and cleaved caspase-3 by APAP exposure.Furthermore,supplementation with SCE suppressed the expression levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2),suggesting alleviation of inflammatory response.In summary,these findings from the present study clearly demonstrated that SCE exerted significant alleviation in APAP-induced oxidative stress,inflammation and apoptosis mainly via regulating MAPK and caspase-3 signaling pathways.