Palmitate-induced apoptosis can occur through a ceramide-independent pathway

Cytotoxic accumulation of long chain fatty acids has been proposed to play an important role in the pathogenesis of diabetes mellitus and heart diseas e. To explore the mechanism of cellular lipotoxicity, we cultured Chinese h amster ovary cells in the presence of media supplemented with fatty acid. T he saturated fatty acid palmitate, but not the monounsaturated fatty acid o leate, induced programmed cell death as determined by annexin V positivity, caspase 3 activity, and DNA laddering. De novo ceramide synthesis increase d 2.4-fold with palmitate supplementation; however, this was not required f or palmitate-induced apoptosis, Neither biochemical nor genetic inhibition of de novo ceramide synthesis arrested apoptosis in Chinese hamster ovary c ells in response to palmitate supplementation. Rather, our data suggest tha t palmitate-induced apoptosis occurs through the generation of reactive oxy gen species. Fluorescence of an oxidant-sensitive probe was increased 3.5-f old with palmitate supplementation indicating that production of reactive i ntermediates increased. In addition, palmitate-induced apoptosis was blocke d by pyrrolidine dithiocarbamate and 4,5-dihydroxy-1,3-benzene-disulfonic a cid, two compounds that scavenge reactive intermediates. These studies sugg est that generation of reactive oxygen species, independent of ceramide syn thesis, is important for the lipotoxic response and may contribute to the p athogenesis of diseases involving intracellular lipid accumulation.