Expression of isoforms of NADPH oxidase components in rat pancreatic islets

Increased oxidative stress plays a role in the pathogenesis of β-cell dysfunction and death. We studied isoforms of NADPH oxidase components in islets of Langerhans isolated from rat pancreas and tumoral rat β-cell line RINm5F cells by RT-PCR and sequencing of its products. RT-PCR revealed that isolated islets constitutively expressed mRNA of NADPH oxidase components, Nox1, Nox2, Nox4 and p22phox as membrane-associated components and p47phox, Noxo1 (homologue of p47phox), Noxa1 (homologue of p67phox), and p40phox as cytosolic components. RINm5F cells showed a similar pattern of expression but Nox2 mRNA was not detected. Expression of Nox1, Nox4, Noxo1 and Noxa1 was confirmed by sequencing the PCR products. Immunohistochemistry revealed the expression of NADPH oxidase component in β-cells of rat pancreatic islets. Glucose-stimulated insulin secretion from isolated islets was suppressed by diphenyleneiodonium, a flavocytochrome inhibitor, but not by apocynin, an inhibitor of p47phox translocation to membranes. Our results suggest that the functional significance of NADPH oxidase in insulin secretion may merit further investigation.