Positively Charged Ceramide Is a Potent Inducer of Mitochondrial Permeabilization

Abstract

Ceramide-induced cell death is thought to be mediated by change in mitochondrial function, although the precise mechanism is unclear. Proposed models suggest that ceramide induces cell death through interaction with latent binding sites on the outer or inner mitochondrial membranes, followed by an increase in membrane permeability, as an intermediate step in ceramide signal propagation. To investigate these models, we developed a new generation of positively charged ceramides that readily accumulate in isolated and in situ mitochondria. Accumulated, positively charged ceramides increased inner membrane permeability and triggered release of mitochondrial cytochrome c. Furthermore, the positively charged ceramide-induced permeability increase was suppressed by cyclosporin A (60%) and 1,3-dicyclohexylcarbodiimide (90%). These observations suggest that the inner membrane permeability increase is due to activation of specific ion transporters, not the generalized loss of lipid bilayer barrier functions. The difference in sensitivity of ceramide-induced ion fluxes to inhibitors of mitochondrial transporters suggests activation of at least two transport systems: the permeability transition pore and the electrogenic H ؉ channel. Our results indicate the presence of specific ceramide targets in the mitochondrial matrix, the occupation of which triggers permeability alterations of the inner and outer mitochondrial membranes. These findings also suggest a novel therapeutic role for positively charged ceramides.

Role of human longevity assurance gene 1 and C18-ceramide in chemotherapy-induced cell death in human head and neck squamous cell carcinomas

“…Conventional short-chain ceramides, such as C 2 -and C 6 -ceramides, were shown to induce cell death in a variety of cancers. However, because of poor solubility and bioavailability of the conventional ceramides, novel pyridinium ceramides (Pyr-Cer) have been synthesized with greater water solubility and cell permeability (26,35,36). In addition, the positively charged pyridinium ring of these novel ceramides permits them to target and accumulate in negatively charged intracellular compartments, especially the mitochondria and nucleus (37).…”

Mitochondria as therapeutic targets for cancer chemotherapy

“…The specific physicochemical properties of the IM and the net deficit of positive charges on the inner side of the IM results in the DC m -driven accumulation of cationic lipophils in the mitochondrial matrix. Recently, cationic ceramide derivatives, but not their neutral counterparts, have been reported to buildup in isolated and in situ mitochondria in an energy-dependent manner (Novgorodov et al, 2005). Following the Nernst equation, positively charged agents sufficiently lipophilic to insert in or to cross cellular membranes enrich in IM and/or in the mitochondrial matrix.…”

Caspase-dependent and -independent cell death of Jurkat human leukemia cells induced by novel synthetic ceramide analogs

“…7 Positively charged ceramides also appear to trigger mitochondrial permeabilization. 15 One of the putative mechanisms that underlie these alterations is the increased endogenous ceramide level. Sustained elevation of ceramide was observed after treatment with our analogs: a finding also described with other ceramide mimics, including Nacylated-serinol, B13 and diene-ceramides.…”

“…Addition of synthetic short-chain ceramides, ceramines, C16-or C18-serinols, cationic ceramides as well as some other analogs was reported to mimic ceramide in inducing apoptosis in various cancer or leukemia cell lines, and, in some instances, to reduce the mass of xenografted tumors. [6][7][8][9][10][11][12][13][14][15] These observations have emphasized the potential usefulness of developing novel, ceramide-based chemotherapeutic agents for anticancer treatment.…”