Reactive Oxygen Species-Mediated Pancreatic β-Cell Death Is Regulated by Interactions between Stress-Activated Protein Kinases, p38 and c-Jun N-Terminal Kinase, and Mitogen-Activated Protein Kinase Phosphatases

Abstract

Pancreatic beta-cells are susceptible to reactive oxygen species (ROS), which are known to be generated by high or low glucose (LG), hypoxic, or cytokine-producing conditions. When we cultured mouse beta-cell-derived MIN6 cells in a LG condition, we detected a significant generation of ROS, including hydrogen peroxide, which was comparable to the ROS production in hypoxic or cytokine-treated conditions. ROS accumulation induced by the LG culture led to cell death, which was prevented by the ROS scavengers N-acetylcysteine and manganese(III)tetrakis(4-benzoic acid) porphyrin. We next investigated the mechanism of stress-activated protein kinases (SAPKs), c-jun N-terminal kinase (JNK) and p38, in ROS-induced MIN6 cell death. Activation of p38 occurred immediately after the LG culture, whereas JNK activation increased slowly 8 h later. Adenoviral p38 expression decreased MIN6 cell death, whereas the JNK expression increased it. Consistently, blocking p38 activation by inhibitors increased beta-cell death, whereas JNK inhibitors decreased it. We then examined the role of MAPK phosphatases (MKPs) specific for stress-activated protein kinases in beta-cell death. We found that MKP-1 presented an increase in its oxidized product after the LG culture. ROS scavengers prevented the appearance of this oxidized product and JNK activation. Thus, ROS-induced MKP inactivation causes sustained activation of JNK, which contributes to beta-cell death. Adenoviral overexpression of MKP-1 and MKP-7 prevented the phosphorylation of JNK at 36 h after the LG culture, and decreased MIN6 beta-cell death. We suggest that beta-cell death is regulated by interactions between JNK and its specific MKPs.

Proteasome assembly defect due to a proteasome subunit beta type 8 (PSMB8) mutation causes the autoinflammatory disorder, Nakajo-Nishimura syndrome

“…4D), although it remains unknown precisely how attenuation of proteasome activity causes accumulation of p-p38 in the nucleus. The accumulation of oxidized proteins and/or ROS in NNS fibroblasts may be one of the mechanisms responsible for the accumulation of p-p38 (29,30,38,39). Increased p-p38 levels are in agreement with the proposed mechanism for TNFR1-associated periodic syndrome (TRAPS), which is another autoinflammatory syndrome (40).…”

Oxidative Modification of Nuclear Mitogen-activated Protein Kinase Phosphatase 1 Is Involved in Transforming Growth Factor β1-induced Expression of Plasminogen Activator Inhibitor 1 in Fibroblasts

“…Nonetheless, although no data are available in the literature showing that TGF-␤ inhibits MKP-1 activity, ROS generated by other stimuli have been reported to inactivate MKP-1. Hou et al (43) showed that treatment of pancreatic ␤-cells with low glucose induced ROS production, JNK and p38 phosphorylation, and MKP-1 oxidation, whereas ROS scavengers prevented MKP-1 oxidation and JNK activation. Interestingly, Mishra et al (44) reported that exposure of newborn piglets to hypoxia increased MKP-1 and MKP-3 protein levels but decreased their activities in the neuronal nucleus.…”

Gene Silencing of Phogrin Unveils Its Essential Role in Glucose-Responsive Pancreatic β-Cell Growth

“…Control cell lines (wild type) were from littermates of ␤IRKO mice. Mouse pancreatic islets were isolated and cultured as described previously (38). Adenovirus production.…”