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Ceramide induces hepatocyte cell death through disruption of mitochondrial function in the rat
A S Arora1, B J Jones, T C Patel
1Center for Basic Research in Digestive Diseases, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
Abstract:
Although ceramide signaling pathways have been implicated in cell death, neither their role in hepatocellular death nor the cellular mechanisms mediating ceramide-induced cell death are known. The mitochondrial membrane permeability transition (MMPT) has been proposed as a common final pathway in cell death. Thus the aims of our study were to determine if ceramides cause hepatocellular death by necrosis and not apoptosis as confirmed by morphology and the absence of internucleosomal DNA cleavage. Ceramide-mediated hepatocyte necrosis was acyl chain-length, concentration, and time-dependent. Ceramides induced cell necrosis was associated with adenosine triphosphate (ATP) depletion and mitochondrial depolarization suggesting that ceramides caused mitochondrial dysfunction. In isolated mitochondria, ceramides induced the cyclosporine A-sensitive MMPT in an acyl chain-length and concentration dependent manner. Ceramide toxicity was specific as the less potent dihydro form did not induce cell necrosis, significant ATP depletion, mitochondrial depolarization nor the MMPT. In conclusion, ceramide induced cell death is acyl-chain length dependent and mediated by the MMPT. These data show for the first time that ceramide acts as a mediator of hepatocyte necrosis by causing mitochondrial failure.
Insights
Ceramides induce liver cell death (hepatocellular necrosis) by disrupting mitochondrial function, specifically triggering the mitochondrial membrane permeability transition (MMPT). This process is dependent on ceramide type and concentration.
Area of Science:
- Biochemistry
- Cell Biology
- Hepatology
Background:
- Ceramide signaling pathways are linked to cell death.
- The specific mechanisms of ceramide-induced hepatocellular death remain unclear.
- The mitochondrial membrane permeability transition (MMPT) is a proposed common pathway in cell death.
Purpose of the Study:
- To investigate if ceramides induce hepatocellular necrosis, not apoptosis.
- To elucidate the cellular mechanisms of ceramide-induced liver cell death.
- To determine the role of MMPT in ceramide-mediated hepatotoxicity.
Main Methods:
- Morphological analysis and DNA fragmentation assays to distinguish necrosis from apoptosis.
- Measurement of cellular adenosine triphosphate (ATP) levels and mitochondrial membrane potential.
- Assessment of MMPT induction in isolated mitochondria using cyclosporine A as an inhibitor.
Main Results:
- Ceramide-induced hepatocyte necrosis was dependent on acyl chain length, concentration, and time.
- Necrosis was associated with ATP depletion and mitochondrial depolarization.
- Ceramides induced cyclosporine A-sensitive MMPT in isolated mitochondria in a dose- and acyl chain-length-dependent manner.
- Dihydroceramides, a less potent form, did not induce necrosis or mitochondrial dysfunction.
Conclusions:
- Ceramide-induced liver cell death is mediated by the MMPT.
- Ceramide acts as a mediator of hepatocyte necrosis through mitochondrial failure.
- The mechanism is dependent on ceramide acyl chain length.