Immunosuppressive and anti-inflammatory action of antioxidants in rat autoimmune diabetes

Oxidative stress makes an important contribution to the development of autoimmune diabetes. We therefore tested the possible therapeutic value of two anti-oxidants, butylated hydroxyanisole (BHA) and pyrrolidine dithiocarbamate (PDTC), in the animal model of diabetes induced in susceptible DA rats by multiple low doses of streptozotocin (MLD-SZ, 20 mg/kg/day for 5 days). Administration of either BHA, or PDTC (50 mg/kg/day for 7 days), after finishing MLD-SZ injections, attenuated both the development of hyperglycemia and insulitis. Ex vivo analysis revealed that BHA treatment reduced the proliferation of autoreactive lymphocytes and down-regulated their adhesion to endothelium. In addition, BHA markedly attenuated the production of proinflammatory cytokines IL-1beta and TNF-alpha by both islets of pancreas and peritoneal macrophages. In parallel, macrophage release of cytotoxic oxygen and nitrogen intermediates superoxide anion (O(2)*(-)) and nitric oxide (NO*), respectively, was significantly inhibited. Finally, BHA treatment reduced intrapancreatic expression of inducible NO synthase (iNOS) and consequent production of NO* by pancreatic islets. Together, these data indicate that antioxidant agents might be a feasible therapeutic tools to interfere with development of autoimmune diabetes at multiple levels, including lymphocyte proliferation and adhesion, as well as the production of proinflammatory and cytotoxic mediators.