Hepatoprotective effect of apple polyphenols against concanavalin A-induced immunological liver injury in mice

Apple polyphenols (AP), a polyphenol extracted from the unripe apple, has been reported to improve acute hepatotoxicity induced by CCl4 in mice due to its significant antioxidant activity. In this study, the hepatoprotective effect of AP against concanavalin A (Con A)-induced immunological liver injury in mice was investigated. Mice were treated with AP daily for seven days prior to a single intravenous administration of Con A. The serum levels of AST, ALT, TP, Alb and histopathological changes were determined and the A/G ratio was calculated. Potential mechanisms were further explored by measuring TNF-α and IFN-γ levels, NO content as well as changes in the levels of endogenous oxidants and antioxidants. AP significantly improved the abnormal levels of ALT, AST, TP and Alb, and the A/G ratio. AP was also associated with improvement of liver histopathological changes after Con A-induced liver injury. Moreover, AP reduced serum levels of TNF-α and IFN-γ, decreased serum NO content, inhibited oxidative DNA single-strand breaks, and improved the abnormalities of MDA content, SOD activity and GSH level. These results suggest that AP exerts a protective effect against Con A-induced immunological liver injury through suppressing pro-inflammatory cytokines and activating the antioxidant system.