Inhibition of deoxycholate-induced apoptosis in iron-depleted HCT-116 cells

The bile acid, deoxycholate (DOC), can induce apoptosis in cells containing adequate amounts of all key nutrients, but it is unknown whether DOC-induced apoptosis can occur in cells lacking a single key nutrient. The aim of this study was to determine if DOC is able to induce apoptosis in HCT-116 colon epithelial cells depleted of iron. The cells were made iron-deficient by pre-treating them with the iron chelator, deferoxamine (DFO), before subsequent exposure to DOC. Mitochondrial dysfunction was detected in control cells exposed to DOC, but not in iron-depleted cells exposed to DOC. Moreover, characteristic features of apoptosis, namely, membrane blebbing, formation of apoptotic bodies, cytochrome c release into cytosol, generation of the activated form of caspase-3, chromatin condensation and fragmentation, and also plasma membrane phospholipid translocation, were all induced by DOC in control cells but not in iron-depleted cells. Treating DFO-pretreated cells with ferrous sulfate to replenish cellular iron restored the ability of DOC to induce apoptosis. In relating these findings to oxidative stress, it was found that DOC also induced the formation of reactive oxygen species and caused DNA damage in control cells, but not in iron-depleted cells. Collectively, the results suggest that in order for HCT-116 cells to undergo apoptosis when exposed to DOC, adequate amounts of intracellular iron must be present.