Ceramide induces early and late apoptosis in human papilloma virus ⁺ cervical cancer cells by inhibiting reactive oxygen species decay, diminishing the intracellular concentration of glutathione and increasing nuclear factor-κB translocation

Ceramide is regarded as an important cellular signal for the induction of cell death. We have previously shown that ceramide induces the death of cervical tumor cells without biochemical and morphological markers of apoptosis. The mechanisms by which ceramide induces cell death are not understood, therefore we evaluated the effect of C6-ceramide, a synthetic cell-permeable analog of endogenous ceramides, in signaling pathways involved in the oxidative stress of three cervical human papilloma virus cancer cell lines. Reactive oxygen species production was determined by fluorescent 2,7-dichlorofluorescein, nitrite concentration by the Griess reaction (as an indirect measure of nitric oxide production), mitochondrial membrane potential by staining with Rh123, reduced-glutathione concentration by high-pressure liquid chromatography, nuclear factor-κB translocation by electrophoretic mobility shift assay, inhibitory protein of nuclear factor-κB expression by Western blot and cell death by a poly-caspases fluorochrome-labeled inhibitors of caspases apoptosis assay. C6-ceramide induced early and late apoptosis, which was associated with an increase in reactive oxygen species and nitric oxide production, a loss in mitochondrial membrane potential, an increase in nuclear factor-κB translocation, and a decrease in reduced glutathione concentration. C6-ceramide did not modify the expression of inhibitory protein of nuclear factor-κB and its antiproliferative effect was not abrogated by Bay 11-7082, an inhibitory protein of nuclear factor-κB kinase inhibitor. Our results suggest that oxidative stress might participate in the ceramide-induced damage to human papilloma virus cervical cancer cells.