Pancreatic beta-cells express phagocyte-like NAD(P)H oxidase

The presence of a phagocyte-like NAD(P)H oxidase in pancreatic beta-cells was investigated. Three NAD(P)H oxidase components were found in pancreatic islets by RT-PCR: gp91(PHOX), p22(PHOX), and p47(PHOX). The components p67(PHOX) and p47(PHOX) were also demonstrated by Western blotting. Through immunohistochemistry, p47(PHOX) was mainly found in the central area of the islet, confirming the expression of this component by insulin-producing cells. Activation of NAD(P)H oxidase complex in the beta-cells was also examined by immunohistochemistry. The pancreatic islets presented slower kinetics of superoxide production than HIT-T15 cells, neutrophils, and macrophages, but they reached 66% that of the neutrophil nitroblue tetrazolium (NBT) reduction after 2 h of incubation. Glucose (5.6 mmol/l) increased NBT reduction by 75% when compared with control. The involvement of protein kinase C (PKC) in the stimulatory effect of glucose was confirmed by incubation of islets with phorbol myristate acetate (a PKC activator) and bysindoylmaleimide (GF109203X) (a PKC-specific inhibitor). Diphenylene iodonium [an NAD(P)H oxidase inhibitor] abolished the increase of NBT reduction induced by glucose, confirming the NAD(P)H oxidase activity in pancreatic islets. Because reactive oxygen species are involved in intracellular signaling, the phagocyte-like NAD(P)H oxidase activation by glucose may play an important role for beta-cell functioning.