Neuronal nitric oxide synthase protects the pancreatic beta cell from glucolipotoxicity-induced endoplasmic reticulum stress and apoptosis

Abstract

Aims/hypothesis Cytokines stimulate nitric oxide production in pancreatic beta cells, leading to endoplasmic reticulum (ER) stress and apoptosis. Treatment of beta cells with glucose and NEFA induces nitric oxide synthase (NOS) as well as ER stress. However, the role of NO in glucolipotoxicity-induced ER stress in beta cells is not clear. Methods We studied the effect of high glucose and palmitate levels on NOS isoform production in rat and Psammomys obesus islets and in insulinoma-1E beta cells. The effects of neuronal NOS (nNOS) inhibition by small interfering RNA or by N ω -nitro-L-arginine methyl ester (L-NAME) on beta cell function, ER stress and apoptosis under conditions of glucolipotoxicity were investigated. Results Overnight incubation of rat and P. obesus islets at 22.2 mmol/l glucose with 0.5 mmol/l palmitate induced the production of nNOS but not inducible NOS (iNOS), in contrast with the robust stimulation of iNOS by cytokines. NOS inhibition by L-NAME did not prevent the decrease in glucose-stimulated insulin secretion and proinsulin biosynthesis or the depletion of islet insulin content observed under conditions of glucolipotoxicity. Moreover, treatment of beta cells with palmitate and L-NAME together resulted in marked activation of the IRE1α and PERK pathways of the unfolded protein response. This was associated with increased JNK phosphorylation and apoptosis in islets and beta cells. Moreover, partial nNos knockdown increased JNK phosphorylation and CHOP production, leading to apoptosis. Conclusions/interpretation In beta cells subjected to glucolipotoxic conditions, chronic inhibition of NOS exacerbates ER stress and activates JNK. Therefore, induction of nNOS is an adaptive response to glucolipotoxicity that protects beta cells from stress and apoptosis.

Dual Role of Nitric Oxide in Pancreatic β-Cells

“…Such an alteration might develop as a consequence of the diabetic state. In contrast, NOS1 activity and NO production were increased by the overnight exposure to high glucose and palmitate, while the inhibition of NOS1 by siRNA or l-NAME increased JNK phosphorylation and b-cell apoptosis (44). Thus, NOS1-derived NO seems to have an essential role in protecting b-cell function under conditions of glucolipotoxicity.…”

Bezafibrate prevents palmitate-induced apoptosis in osteoblastic MC3T3-E1 cells through the NF-κB signaling pathway

“…The palmitate-BSA solution was prepared as previously described (20). Briefly, the sodium salt of palmitate was dissolved at a concentration of 10 mM in 11% (w/v) BSA in a shaking waterbath at 37˚C overnight.…”

Regulation of pancreatic β-cell survival by nitric oxide

“…[15][16][17] Several activities related to cell survival are activated by NO, such as activation of signaling pathways and regulation of gene expression. This review therefore examines the role of NO in both scenarios.…”

“…15,17,104,127 The net yield of extracted islets basically depends on the characteristics of the donor and several parameters of the islet processing. Brain death in the donors promotes a rapid inflammatory response that predisposes islets to immune attack in the recipient patient after transplantation:…”