Backgrounds: Islets are known to contain low level of antioxidants which renders them vulnerable to oxidative stress. It is also known that islets are exposed to significant oxidative stress during the isolation and transplant. Nrf2 -Keap1 signaling pathway plays a central role in cell defense against oxidative stress. Activation of this pathway induces up-regulation of numerous genes encoding antioxidant and phase II detoxifying enzymes. However, little is known regarding a role of this pathway in human islet cells. Aims: To investigate the effect of Nrf2-keap1 pathway activation on human islets. Methods: Human islets were obtained from cadaveric donors. After treatment with the Nrf2 activator (NRA: a bardoxolone methyl analog), Nrf2 translocation, mRNA expression, and protein abundance of key anti-oxidants were evaluated by RT-PCR and Western blot. Cyto-protective effect of NRA on human Β cells against oxidative stress was evaluated using FACS. Inflammatory cytokines/chemokines form islets were measured in the supernatant. Results: The translocation of Nrf2 from cytoplasm to nucleus was observed by confocal microscope within 2 hours after NRA treatment. The mRNA expression of anti-oxidants, including GCLC, HO-1, and NQO1, was significantly increased in dose-dependent manner (GCLC: 1.7, 3.0, HO-1: 3.5, 10.3, NQO-1: 2.6, 5.0 times in response to 250 and 1000nM of NRA). Other Nrf2 targeted genes, such as catalase, SOD, GCLM, and GPx, were not significantly increased. Hydrogen peroxide was used to induce oxidative stress. After dissociation into single cells, cells were stained with 7-AAD, TMRE, and Newport Green (NG) and analyzed using FACS. The percentage of viable Β cells (7AAD-, NG+, TMRE+) was compared to evaluate the cyto-protective effect of NRA. The proportion of Β cells and their viability in the NRA-treated was higher than in the vehicle-treated cells. NRA decreased production of cytokines/chemokines including IL-1Β, IL-4, IL-6, and MCP-1. Conclusions: The in vitro treatment of human islets with NRA significantly increased expression of anti-oxidants and conferred protection against oxidative stress in Β cells. These results indicate that fortification of the antioxidant defense system by pharmacological activation of Nrf2-Keap1 pathway in human islets may be a promising strategy to improve the outcome in clinical islet cell transplantation.

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