Involvement of oxidative stress-induced ERK/JNK activation in the Cu(2+)/pyrrolidine dithiocarbamate complex-triggered mitochondria-regulated apoptosis in pancreatic β-cells

Abstract

Oxidative stress was demonstrated to promote the progression of diabetes mellitus (DM). It has been suggested that copper may play a specific role in the progression and pathogenesis of DM. Pyrrolidine dithiocarbamate (PDTC), a widely apply to the medicine, was known to be capable of enhancing copper accumulation. In this study, we investigated the effect of submicromolar-concentration Cu(2+)/PDTC complex on pancreatic β-cell damage and evaluated the role of oxidative stress in this effect. CuCl(2) (0.01-300μM) did not affect the cell viability in β-cell line RIN-m5F cells. However, combination of CuCl(2) (0.5μM) and PDTC (0.3μM) markedly reduced RIN-m5F cell viability. Cu(2+)/PDTC complex could also increase the LPO and decrease the intracellular reduced GSH levels, and display several features of apoptosis signals including: increase in sub-G1 cell population, annexin-V binding, and caspase-3 activity, mitochondrial dysfunctions, and the activation of PARP and caspase cascades, which accompanied with the marked increase the intracellular Cu(2+) levels. These apoptotic-related responses of Cu(2+)/PDTC complex-induced could be effectively prevented by antioxidant N-acetylcysteine (NAC). Furthermore, Cu(2+)/PDTC complex was capable of increasing the phosphorylations of ERK1/2 and JNK, and its upstream kinase MEK1/2 and MKK4, which could be reversed by NAC. Transfection with ERK2- and JNK-specific si-RNA and specific inhibitors SP600125 and PD98059 could inhibit ERK1/2 and JNK activation and attenuate MMP loss and caspase-3 activity induced by the Cu(2+)/PDTC complex. Taken together, these results are the first report to demonstrate that the Cu(2+)/PDTC complex triggers a mitochondria-regulated apoptosis via an oxidative stress-induced ERK/JNK activation-related pathway in pancreatic β-cells.