Polysaccharides from Opuntia milpa alta alleviate alloxan-induced INS-1 cells apoptosis via reducing oxidative stress and upregulating Nrf2 expression

Abstract The incidence and progression of type 2 diabetes are closely related to pancreatic β-cell damage. Oxidative stress may be one of the key factors contributing to β-cell apoptosis. Opuntia milpa alta polysaccharides (MAPs) are water-soluble macromolecular polysaccharides that have anti-diabetic effects in vivo. Therefore, we hypothesized that MAPs might effectively prevent β-cell apoptosis via the inhibition of oxidative damages. In this study, INS-1 cells were exposed to alloxan with different concentrations of MAPs in vitro, and the cell viability, oxidative enzyme activities, NO production, ROS production, apoptosis, and the expression of proteins in the antioxidant nucleus transcription factor NF-E2-related factor 2 (Nrf2) pathway and proteins related to apoptosis were measured to assess oxidative stress responses and apoptosis. The results indicated that INS-1 cells viabilities and SOD and GSH activities were significantly restored, while LDH releases and ROS, NO and MDA levels were greatly decreased after MAPs treatment. We showed that MAPs could attenuate alloxan-induced apoptosis by increasing the expression of Bcl-2 and decreasing the expression of Bax and the activities of caspase-3 and caspase-9. The results of Western blot revealed that MAPs suppressed the expression of cleaved caspase-3 and PARP and upregulated the expression of nucleus Nrf2 and its downstream protein. The findings indicated that MAPs could alleviate alloxan-induced β-cell damage by reducing oxidative stress and apoptosis and upregulating Nrf2 expression.