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Iron-induced peroxidative injury to isolated rat hepatic mitochondria
Abstract:
Peroxidative injury to the mitochondrial inner membrane with resultant defects in oxidative metabolism may be partially responsible for hepatocellular injury in iron overload. We examined the effects of iron-induced lipid peroxidation in vitro on hepatic mitochondrial morphology and function and determined if various inhibitors of free-radical-mediated injury could be protective. Normal rat liver mitochondria were prepared by differential centrifugation and were incubated with 1, 2, and 3 microM Fe2+, NADPH, and with and without oxygen radical scavengers, iron chelators, and antioxidants. There was a direct linear relationship between the concentration of added iron and the degree of lipid peroxidation as measured by malondialdehyde (MDA) production (r = .85). With 3 microM Fe2+ there was a decrease in the respiratory control ratio (RCR) for all four substrates tested; this decrease in RCR was due to a decrease in the state 3 respiratory rate for all substrates, with no changes in the state 4 respiratory rate for glutamate, beta-hydroxybutyrate, or succinate. Oxygen radical scavengers failed to prevent iron-induced lipid peroxidation or to protect against associated mitochondrial dysfunction. Iron chelators and antioxidants prevented MDA formation and mitochondrial function was maintained. Iron-induced lipid peroxidation in vitro produces an irreversible inhibitory defect in mitochondrial electron transport that may be specific at complex IV (cytochrome oxidase).
Insights
Iron overload causes liver injury through mitochondrial damage. Iron chelators and antioxidants protect mitochondria from lipid peroxidation, preserving liver function.
Area of Science:
- Hepatology
- Mitochondrial Biology
- Oxidative Stress
Background:
- Hepatocellular injury in iron overload may stem from peroxidative damage to the mitochondrial inner membrane.
- Defects in oxidative metabolism are linked to mitochondrial dysfunction in iron overload conditions.
Purpose of the Study:
- To investigate the effects of iron-induced lipid peroxidation on hepatic mitochondrial morphology and function in vitro.
- To determine the protective potential of various inhibitors against free-radical-mediated injury in iron-loaded mitochondria.
Main Methods:
- Preparation of normal rat liver mitochondria via differential centrifugation.
- Incubation of mitochondria with varying concentrations of Fe2+, NADPH, and oxygen radical scavengers, iron chelators, or antioxidants.
- Measurement of lipid peroxidation via malondialdehyde (MDA) production and assessment of mitochondrial function using respiratory control ratio (RCR).
Main Results:
- A linear relationship was observed between iron concentration and MDA production (r = .85).
- High iron concentrations (3 microM Fe2+) decreased the RCR by reducing state 3 respiration without affecting state 4 respiration.
- Oxygen radical scavengers were ineffective, while iron chelators and antioxidants prevented MDA formation and maintained mitochondrial function.
Conclusions:
- Iron-induced lipid peroxidation causes irreversible mitochondrial electron transport defects, potentially at complex IV (cytochrome oxidase).
- Iron chelators and antioxidants demonstrate protective effects against iron-induced mitochondrial damage.