Cytokine-induced apoptosis and necrosis are preceded by disruption of the mitochondrial membrane potential (Deltapsi(m)) in pancreatic RINm5F cells: prevention by Bcl-2

The mechanisms of cytokine-induced β-cell death are poorly characterised. In rat insulin-producing RINm5F cells, the combination of interleukin-1β, interferon-γ and tumour necrosis factor- presently induced disruption of the mitochondrial membrane potential (Δψ_m) as demonstrated by reduced JC-1 fluorescence. The reduction of Δψ_m was maximal after 8 h and was preceded by increased formation of reactive oxygen species (ROS), as assessed by dichlorofluorescein-diacetate (DCFH-DA) fluorescence. A nitric oxide synthase-, but not a ROS-inhibitor, prevented cytokine-induced loss of Δψ_m. Overexpression of the anti-apoptotic protein Bcl-2 increased both JC-1 and DCFH-DA fluorescence, which was paralleled by protection against cytokine-induced apoptosis and necrosis. It is concluded that cytokines induce a nitric oxide-dependent disruption of Δψ_m and that this may be a necessary event for both β-cell apoptosis and necrosis. Bcl-2 may prevent β-cell death by counteracting mitochondrial permeability transition.