Amylin-Induced Cytotoxicity Is Associated with Activation of Caspase-3 and MAP Kinases

Abstract

Nanomolar concentrations of human amylin promote death of RINm5F cells in a time and concentrationdependent manner. Morphological changes of chromatin integrity suggest that cells are predominantly undergoing apoptosis. Human amylin induces significant activation of caspase-3 and strong and sustained phosphorylation of stressactivated protein kinases, cJun Nterminal kinase (JNK) and p38, that precedes cell death. Extracellular signalregulated kinase (ERK) activation was not concomitant with JNK and/or p38 activation. Activation of caspase-3 and mitogenactivated protein kinases (MAPKs) was detected by Western blot analysis. Addition of the MEK1 inhibitor PD 98059 had no effect on amylininduced apoptosis, suggesting that ERK activation does not play a role in this apoptotic scenario. A correlative inhibition of JNK activation by the immunosuppressive drug FK506, as well as a selective inhibition of p38 MAPK activation by SB 203580, significantly suppressed procaspase-3 processing and the extent of amylininduced cell death. Moreover, simultaneous pretreatment with both FK506 and SB 203580, or with the caspase-3 inhibitor AcDEVDCHO alone, almost completely abolished procaspase-3 processing and cell death. Thus, our results suggest that amylininduced apoptosis proceeds through sustained activation of JNK and p38 MAPK followed by caspase-3 activation.