Related Experiment Videos
Nitric oxide-independent suppression of P450 2C11 expression by interleukin-1beta and endotoxin in primary rat
1Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322-3090, U.S.A.
Abstract:
Hepatic expression of multiple cytochrome P450 genes is suppressed in the livers of rats undergoing an inflammatory response. Nitric oxide (NO) released during inflammation has been implicated in the decreased activities and expression of several cytochrome P450 isozymes. We examined the role of cytokine-mediated NO release on cytochrome P450 2C11 expression in rat hepatocytes cultured on Matrigel. Lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha), but not interferon-gamma (IFN-gamma), suppressed the expression of P450 2C11 mRNA. Neither IL-6 nor IFN-gamma caused NO release into the medium or induction of inducible nitric oxide synthase (iNOS) mRNA. IL-1beta and LPS were the most effective in causing NO release and iNOS induction, and in down-regulating P450 2C11 mRNA expression. Combinations of the cytokines, IFN-gamma, and LPS produced an additive release of NO but did not synergize to further suppress P450 2C11 mRNA. To investigate the role of NO in the IL-1beta- or LPS-mediated suppression of P450 2C11, N-monomethyl-L-arginine (NMA) was administered at concentrations ranging from 30 to 300 microM. Three hundred micromolar NMA returned NO release back to control levels, but did not affect the IL-1beta- or LPS-mediated down-regulation of P450 2C11 mRNA or protein expression. Our results suggest that NO is not required for IL-1beta- or LPS-mediated down-regulation of P450 2C11 expression in cultured hepatocytes.
Insights
Inflammation suppresses cytochrome P450 2C11 expression in rat livers. While nitric oxide (NO) is implicated, this study found NO is not required for cytokine-induced P450 2C11 suppression.
Area of Science:
- Biochemistry
- Pharmacology
- Toxicology
Background:
- Hepatic cytochrome P450 (CYP450) gene expression is often suppressed during inflammatory responses.
- Nitric oxide (NO), a key inflammatory mediator, has been suggested to contribute to the decreased activity and expression of certain CYP450 isozymes.
Purpose of the Study:
- To investigate the role of cytokine-mediated nitric oxide (NO) release in the suppression of cytochrome P450 2C11 (P450 2C11) expression in rat hepatocytes.
- To determine if NO is a necessary mediator for the down-regulation of P450 2C11 by inflammatory stimuli like lipopolysaccharide (LPS) and interleukin-1beta (IL-1beta).
Main Methods:
- Primary rat hepatocytes were cultured on Matrigel.
- Hepatocytes were treated with various cytokines (LPS, IL-1beta, IL-6, TNF-alpha, IFN-gamma) individually and in combination.
- Nitric oxide (NO) release and inducible nitric oxide synthase (iNOS) mRNA expression were measured.
- The effect of N-monomethyl-L-arginine (NMA), a nitric oxide synthase inhibitor, on P450 2C11 mRNA and protein expression was assessed.
Main Results:
- Lipopolysaccharide (LPS), IL-1beta, IL-6, and TNF-alpha suppressed P450 2C11 mRNA expression, while IFN-gamma did not.
- IL-1beta and LPS were potent inducers of NO release and iNOS mRNA, and effectively suppressed P450 2C11 mRNA.
- Combinations of cytokines and LPS showed additive NO release but no synergistic suppression of P450 2C11 mRNA.
- Inhibition of NO production with NMA did not prevent the down-regulation of P450 2C11 mRNA or protein expression induced by IL-1beta or LPS.
Conclusions:
- Nitric oxide (NO) is not required for the suppression of cytochrome P450 2C11 expression by IL-1beta or LPS in cultured rat hepatocytes.
- The down-regulation of P450 2C11 during inflammation likely involves NO-independent mechanisms.