| Diabetes mellitus is now taking its place as one of the main threats to human health in the 21st century. The global figure of people with diabetes is set to rise from the current estimate of 150 million to 220 million in 2010. Type 1 diabetes is primarily to autoimmune-mediated destruction of pancreatic β-cells, resulting in absolute insulin deficiency. Although type 1 diabetes accounts for only 10% of cases globally, it strongly affects human behavior and lifestyles. In addition, type 1 diabetes is the most common chronic disease of children.The underlying cause of this serious chronic illness is not well understood. Infiltration of islets of Langerhans by immune cells is likely to be an initial event in development of type 1 diabetes. Invading macrophages and T-cells may secrete proinflammatory cytokines such as interleukin-1β (IL-1β), interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α), promoting the destruction of insulin-producing β-cells. Chronic immune-mediated damage significantly reduces the β-cell mass and results in hyperglycemia. Recently, successful islet transplantation has raised hopes for curing this disease. However, even with newerimmunosuppressive medications and better understanding of islet transplantation technique, 30-40% of islet transplant recipients are insulin requiring after two years. Therefore, research aimed at characterizing the mechanism of the dysfunction in pancreatic P-cell are critical important both for understanding the pathogenesis of type 1 diabetes and improving outcomes in islet transplantation.Unlike COX-1, an enzyme that has constitutive expression in many tissues, cyclooxygenase-2 (COX-2) is induced by inflammatory stimuli like cytokines, lipopolysaccharide and free radicals. Both enzymes convert arachidonic acid (AA) to prostaglandin E2 (PGE2). PGE2 has long been known to impaired p-cell function. Pancreatic P-cells express low levels of COX-1 mRNA and higher levels of COX-2 mRNA in healthy p-cell. Upon stimulation with cytokine like IL-1β, COX-2 mRNA increases severalfold, whereas COX-1 mRNA expression remains unchanged. Prior studies demonstrated that PGE2 inhibited glucose-stimulated insulin secretion in rat islet, and this led to hypothesis that cytokine-induced pancreatic P-cell cytotoxicity was, in part, due to excessive PGE2 production. PGE2 may play a role in defective insulin secretion and glucose intolerance in diabetes mellitus. In spite of the established role of PGE2 in pancreatic p-cell, the exact cellular mechanism of PGE2-mediated inhibition of insulin secretion remains poorly understood. This study was deigned to understand the molecularmechanism underlying PGE2 induced pancreatic β-cell dysfunction and the correlation between COX-2/PGE2 and Akt/FKHR signaling pathway.The inhibitory and destructive effects of cytokines on β-cell function and islet viability are mediated, in part, through the expression of the inducible form of nitric oxide synthase (iNOS) and increased production of NO by β-cell. Moreover, NO has been found to modulate PGE2 synthesis in macrophage cell line and rat islet cells. In the present study, we tried to further investigate the role of NO in PGE2 formation and pathways that could be involved in cytokine-mediated dysfunction of pancreatic β-cells.This thesis consists two parts:Part 1 Potential role of NO in Modulation of COX-2 transcription, expression and PGE2 production in Pancreatic β-cellsTo investigate the role of NO in PGE2 formation and pathway that could be involved in cytokine-mediated dysfunction of pancreatic β-cells, the present study was designed to identify the precise mechanism of NO in COX-2 expression and PGE2 formation using IL-1β and NOS inhibitor NG-monomethyl-L-arginine (L-NMMA).Griess methods were used to determine stable metabolites of nitric oxide. Results showed that IL-1β increased NO production in a dose-dependent manner. The IL-1β (0.5ng/ml) induced maximum NOproduction, about 8 fold over the control value. The release of NO was completely inhibited by coincuba...
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