NOX2-Mediated Oxidative Stress Drives β-Cell Apoptosis and Insulin Secretory Dysfunction in an Experimental Streptozotocin-Induced Diabetic Rat Model

Background: Type 2 diabetes (T2D) is characterized by the combination of insulin resistance and progressive β-cell dysfunction, largely driven by oxidative stress. The present study addresses the β-cell oxidative-injury component of this process using a streptozotocin (STZ)-induced diabetic rat model, which reproduces glucotoxic β-cell damage but, in the absence of demonstrated peripheral insulin resistance, does not capture the insulin-resistance component of full T2D. NADPH oxidase 2 (NOX2) has recently emerged as a critical source of reactive oxygen species (ROS) in pancreatic β-cells, but its quantitative contribution to apoptosis and insulin secretory failure remains incompletely defined. Objective: To determine the contribution of NOX2 to β-cell apoptosis under glucotoxic stress and to evaluate the protective efficacy of broad-spectrum pharmacological NOX2-targeting agents. Methods: Isolated pancreatic islets from streptozotocin-induced diabetic rats (n = 24) were exposed to graded glucose concentrations (5.5 - 25 mM) with or without apocynin or diphenyleneiodonium (DPI). NOX2 and caspase-3 levels were quantified by ELISA in islet lysates, normalized to total protein content, and insulin secretion was measured in culture supernatants. Results: Hyperglycemia induced a dose-dependent increase in NOX2 and caspase-3 expression, with a strong positive correlation between NOX2 concentration and caspase-3 concentration (r = 0.93; p < 0.001) and an inverse correlation between caspase-3 and insulin secretion (r = ？0.95; p < 0.001). When apocynin and DPI were compared against untreated, glucose-matched controls at 15 μM, NOX2 and caspase-3 were consistently lower, and insulin secretion higher, in treated islets (p < 0.05 for 26 of 27 pairwise comparisons). Conclusion: NOX2 is a central determinant of β-cell apoptosis and insulin dysfunction in this experimental STZ-diabetic rat model. Broad-spectrum pharmacological perturbation of NOX2 activity attenuates oxidative stress-induced damage and represents a promising avenue for preserving β-cell mass, warranting further validation in models that also capture the insulin-resistance component of type 2 diabetes.