Related Experiment Videos
Impairment by cyclosporine of membrane-mediated functions in kidney mitochondria
T Strzelecki1, S Kumar, R Khauli
1Division of Urology and Transplantation Surgery, University of Massachusetts Medical School, Worcester.
Abstract:
This study was performed to evaluate whether cyclosporine penetrates kidney mitochondria and impairs mitochondrial functions, causing nephrotoxicity. Exposure of rat kidney cortical mitochondria in vitro to cyclosporine had little effect on the oxidation of glutamate plus malate. Oxidation of succinate was markedly inhibited by a toxic level of cyclosporine (25 to 50 nmol/mg protein) under resting (State 4) and ADP-stimulated (State 3) conditions. Under uncoupling conditions, induced by the proton ionophore, CCCP or by the calcium ionophore, A23187 plus calcium, mitochondrial respiration was unchanged by cyclosporine. In mitochondria isolated from rats treated with an immunosuppressive dose of cyclosporine (25 mg/kg/day, p.o.), respiration was not significantly impaired. The respiration stimulated by ADP was only diminished in mitochondria from rats treated with 75 mg/kg. The rate of calcium uptake was unchanged by cyclosporine under in vitro and in vivo conditions. Kidney mitochondria of untreated rats maintained in a medium containing respiratory substrates and phosphate released spontaneously accumulated calcium that was accompanied by large amplitude swelling and enhanced respiration. Cyclosporine in vitro inhibited the process of spontaneous calcium discharge at the concentration range of 0.1 to 0.5 nmol/mg protein. Swelling and respiration induced by accumulated calcium was significantly diminished in kidney mitochondria isolated from cyclosporine-treated rats given doses of 25 or 75 mg/kg. The data obtained indicate that cyclosporine interacts with the membrane of kidney mitochondria in virtually the same way under in vitro and in vivo conditions. Cyclosporine at an immunosuppressive level impairs calcium-induced membrane permeability and at a toxic level, the rate of ADP phosphorylation.
Insights
Cyclosporine impairs kidney mitochondrial function and causes nephrotoxicity by affecting calcium levels and ADP phosphorylation. This drug interacts with kidney mitochondria similarly in vitro and in vivo.
Area of Science:
- Nephrology
- Mitochondrial Biology
- Pharmacology
Background:
- Cyclosporine is an immunosuppressant known to cause nephrotoxicity.
- The precise mechanisms underlying cyclosporine-induced nephrotoxicity, particularly its effects on kidney mitochondria, require further elucidation.
Purpose of the Study:
- To investigate the effects of cyclosporine on kidney mitochondria, specifically its penetration and impact on mitochondrial functions.
- To determine if cyclosporine impairs mitochondrial respiration, calcium handling, and membrane permeability, contributing to nephrotoxicity.
Main Methods:
- In vitro studies exposing isolated rat kidney cortical mitochondria to varying concentrations of cyclosporine.
- In vivo studies involving rats treated with immunosuppressive and toxic doses of cyclosporine.
- Assessment of mitochondrial respiration (State 3 and State 4), calcium uptake, and mitochondrial swelling.
Main Results:
- Toxic levels of cyclosporine inhibited succinate oxidation in mitochondria, while glutamate plus malate oxidation was largely unaffected.
- Cyclosporine inhibited spontaneous calcium release from mitochondria and diminished calcium-induced swelling and respiration.
- In vivo administration of cyclosporine impaired ADP-stimulated respiration at higher doses and affected calcium-induced mitochondrial permeability.
Conclusions:
- Cyclosporine interacts with kidney mitochondria in a manner consistent between in vitro and in vivo conditions.
- At immunosuppressive doses, cyclosporine impairs calcium-induced mitochondrial membrane permeability, and at toxic doses, it inhibits ADP phosphorylation, contributing to nephrotoxicity.