Protective effect of hypoxylonol C and 4,5,4 ',5 '-tetrahydroxy-1,1 '-binaphthyl isolated from Annulohypoxylon annulatum against streptozotocin-induced damage in INS-1 cells

Abstract

We evaluated the protective effects of hypoxylonol C and 4,5,4', 5'-tetrahydroxy-1,1'-binaphthyl (BNT) isolated from Annulohypoxylon annulatum on pancreatic beta-cell apoptosis, using the beta-cell toxin streptozotocin (STZ). Hypoxylonol C and BNT restored the STZ-induced decrease in INS-1 cell viability in a dose-dependent manner. In addition, treatment of INS-1 cells with 50 mu M STZ resulted in an increase in apoptotic cell death, which was observed as annexin V fluorescence intensity. Apoptotic cell death was decreased by co-treatment with 100 mu M hypoxylonol C and 100 mu M BNT. Similarly, STZ caused a marked increase in the expression of cleaved caspase-8, caspase-3, Bax, and poly (ADP-ribose) polymerase (PARP), as well as a decrease in the expression of B-cell lymphoma 2 (Bcl-2), which was reversed by co-treatment with 100 mu M hypoxylonol C and 100 mu M BNT. These findings suggest that hypoxylonol C and BNT play an important role in protecting pancreatic beta-cells against apoptotic damage.