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Journal of Diabetes Research
Volume 2014, Article ID 834528, 7 pages
http://dx.doi.org/10.1155/2014/834528
Research Article

P38 Plays an Important Role in Glucolipotoxicity-Induced Apoptosis in INS-1 Cells

Department of Endocrinology and Metabolism, Peking University People’s Hospital, Beijing 100044, China

Received 1 October 2013; Revised 27 January 2014; Accepted 30 January 2014; Published 5 March 2014

Academic Editor: Yanbing Li

Copyright © 2014 Lingli Zhou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objectives. The mechanism underlying the regulation of glucolipotoxicity-induced apoptosis by MAPKs was examined in INS-1 cells. Methods. The rat insulinoma cell line INS-1 was cotreated with glucose (30 mM) and palmitic acid (0.2 mM) (GLU+PA). Apoptosis was assessed by cell morphology and detection of PARP cleavage. The activation of MAPKs was examined by Western blotting using specific antibodies against the phosphorylated forms of JNK, ERK1/2, and P38. Results. (1) Live cell imaging studies showed that treatment with GLU+PA for 72 h induced significant cell death, concomitant with PARP-1 cleavage and caspase-3 activation, which peaked at 96 h of treatment. (2) Western blot analysis of the activation of MAPKs during GLU+PA-induced INS-1 cell apoptosis showed that phosphorylation of P38 increased gradually and reached a peak at 96 h, which coincided with PARP-1 cleavage. A transient increase of ERK activation was followed by a rapid decline at 96 h, whereas JNK phosphorylation status remained unchanged in response to GLU+PA. (3) Phosphorylation of insulin receptor substrate (IRS)-2 at 48 h of treatment triggered its degradation, which coincided with P38 activation. (4) Inhibition of P38, but not JNK or ERK, blocked GLU+PA-induced INS-1 cell apoptosis. Conclusions. P38 may be involved in the regulation of glucolipotoxicity-induced apoptosis through the phosphorylation of IRS-2.