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Alternative cyclosporine metabolic pathways and toxicity
1Institut für Allgemeine Pharmakologie, Medizinische Hochschule Hannover, Germany.
Clinical Biochemistry
|December 1, 1995
Summary
Aberrant cyclosporine metabolism may lead to toxic byproducts, especially when cytochrome P450 3A enzyme activity is low. Cyclized metabolites, potentially contributing to toxicity, are elevated in patients with early nephrotoxicity.
Area of Science:
- Pharmacology
- Drug Metabolism
- Nephrology
Background:
- Aberrant cyclosporine metabolism can produce toxic metabolites.
- Low cytochrome P450 3A (CYP3A) activity, due to genetic variability, ischemia, or drug interactions, impacts cyclosporine levels.
- Alternative metabolic pathways for cyclosporine may lead to the formation of cyclized metabolites.
Purpose of the Study:
- To investigate the role of alternative cyclosporine metabolic pathways and the formation of cyclized metabolites.
- To explore the potential contribution of these metabolites to cyclosporine toxicity, particularly nephrotoxicity.
- To understand the factors influencing CYP3A activity and their effect on cyclosporine metabolism.
Main Methods:
- In vitro studies using reconstituted purified enzymes or expressed P450 enzymes.
- Analysis of cyclosporine and its metabolites using High-Performance Liquid Chromatography (HPLC).
- Clinical studies correlating metabolite concentrations with clinical outcomes like nephrotoxicity.
Main Results:
- Alternative pathways involving inducible cytochrome P450 enzymes can produce cyclized cyclosporine metabolites.
- Cyclized metabolites have low affinity for cyclophilin and are primarily found in plasma.
- Elevated levels of the cyclized metabolite AM1c9 were observed during early nephrotoxicity in liver graft recipients.
Conclusions:
- Cyclization is a potential alternative pathway for cyclosporine metabolism, particularly when CYP3A activity is low.
- Cyclized metabolites, such as AM1c9, may contribute to cyclosporine-induced toxicity, including nephrotoxicity.
- Further research is needed to fully elucidate the role of these metabolites in cyclosporine toxicity and to quantify the complete P450 enzyme pattern.