engleski

Human amylin induces activation of mitogen-activated protein kinases and caspases in RINm5F cell line

Amylin is a 37-amino acid peptide that is co-stored and co-secreted with insulin in pancreatic beta-cells. Amylin is the major component of islet amyloid found in the pancreas of >90% patients with non-onsulin-dependent diabetes mellitus (NIDDM). The increase of the pancreatic amyloid deposits is correlated with the gradual destruction of beta-cells of individuals with NIDDM. In this study we addressed the question whether the mechanism underlying promotion of islet beta-cell death by human amylin involves activation of mitogen-activated protein kinases (MAPK) family members and/or caspase machinery. We employed rat insulinoma RINm5F cells as a model cell line to assess the alterations in these signalling pathways. Nanomolar concentrations of human amylin induced RINm5F cell death in a time and in a concentration dependent manner. Morphological changes of membrane and chromatin integrity suggested that the cells were predominantly dying by the process of apoptosis. However, amylin also caused impairments of the cell membrane integrity, as seen by LDH leakage, indicative of necrotic cell death. Activation of caspase-3 and MAPKs was detected by Western blot analysis. Human amylin induced significant activation of caspase-3 and strong and sustained phosphorylation of stress-activated protein kinases. JNK and p38 activation was sensitive to caspase inhibitor DEVD-fmk. Our data suggest that activation of caspase-3 and stress-activated protein kinases is involved in human amylin-induced cytotoxicity of RINm5F cells.

amylin; MAPK; caspase; RINm5F cells

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