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Published on: May 14, 2017
Mitochondrial oxidative stress in human hepatoma cells exposed to stavudine
Leonard W Velsor1, Miro Kovacevic, Mark Goldstein
1Department of Medicine, National Jewish Medical and Research Center, Denver, CO 80206, USA.
Abstract:
The toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is linked to altered mitochondrial DNA (mtDNA) replication and subsequent disruption of cellular energetics. This manifests clinically as elevated concentrations of lactate in plasma. The mechanism(s) underlying how the changes in mtDNA replication lead to lactic acidosis remains unclear. It is hypothesized that mitochondrial oxidative stress links the changes in mtDNA replication to mitochondrial dysfunction and ensuing NRTIs toxicity. To test this hypothesis, changes in mitochondrial function, mtDNA amplification efficiency, and oxidative stress were assessed in HepG2-cultured human hepatoblasts treated with the NRTI stavudine (2',3'-didehydro-2',3'-deoxythymidine or d4T) for 48 h. d4T produced significant mitochondrial dysfunction with a 1.5-fold increase in cellular lactate to pyruvate ratios. In addition, d4T caused a dose-dependent decrease in mtDNA amplification and a correlative increase in abundance of markers of mitochondrial oxidative stress. Manganese (III) meso-tetrakis (4-benzoic acid) porphyrin, MnTBAP, a catalytic antioxidant, ameliorated or reversed d4T-induced changes in cell injury, energetics, mtDNA amplification, and mitochondrial oxidative stress. In conclusion, d4T treatment elevates mitochondrial reactive oxygen species (ROS), enhances mitochondrial oxidative stress, and contributes mechanistically to NRTI-induced toxicity. These deleterious events may be potentiated in acquired immunodeficiency syndrome (AIDS) by human immunodeficiency virus (HIV) infection itself, coinfection (e.g., viral hepatitis), aging, substance, and alcohol use.
Insights
Nucleoside reverse transcriptase inhibitor (NRTI) toxicity, causing lactic acidosis, is linked to mitochondrial damage. Stavudine (d4T) increases oxidative stress and disrupts cellular energy, but an antioxidant reversed these effects.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Nucleoside reverse transcriptase inhibitors (NRTIs) can cause toxicity, potentially linked to mitochondrial DNA (mtDNA) replication issues and impaired cellular energy metabolism, leading to elevated plasma lactate.
- The precise mechanisms connecting mtDNA replication changes to lactic acidosis in NRTI toxicity are not fully understood.
Purpose of the Study:
- To investigate the hypothesis that mitochondrial oxidative stress mediates the link between altered mtDNA replication and mitochondrial dysfunction in NRTI toxicity.
- To assess the effects of stavudine (d4T), an NRTI, on mitochondrial function, mtDNA amplification, and oxidative stress in human hepatoblasts.
Main Methods:
- HepG2-cultured human hepatoblasts were treated with stavudine (d4T) for 48 hours.
- Assessed mitochondrial function (lactate to pyruvate ratio), mtDNA amplification efficiency, and markers of mitochondrial oxidative stress.
- Evaluated the effect of Manganese (III) meso-tetrakis (4-benzoic acid) porphyrin (MnTBAP), a catalytic antioxidant, on d4T-induced changes.
Main Results:
- d4T treatment resulted in significant mitochondrial dysfunction, indicated by a 1.5-fold increase in cellular lactate to pyruvate ratios.
- A dose-dependent decrease in mtDNA amplification and a corresponding increase in mitochondrial oxidative stress markers were observed with d4T.
- MnTBAP treatment ameliorated or reversed the d4T-induced cellular injury, energetic deficits, and oxidative stress.
Conclusions:
- Stavudine (d4T) treatment elevates mitochondrial reactive oxygen species (ROS) and enhances mitochondrial oxidative stress, contributing to NRTI-induced toxicity.
- These toxic effects may be exacerbated by factors such as HIV infection, coinfections, aging, and substance use.
