Abstract
Carboxylesterases constitute a class of enzymes that play important roles in the hydrolytic metabolism of drugs and other xenobiotics. Patients with liver conditions such as cirrhosis show increased secretion of proinflammatory cytokines [e.g., interleukin-6 (IL-6)] and decreased capacity of hydrolysis. In this study, we provide a molecular explanation linking cytokine secretion directly to the decreased capacity of hydrolytic biotransformation. In both primary hepatocytes and HepG2 cells, treatment with IL-6 decreased the expression of human carboxyl-esterases HCE1 and HCE2 by as much as 60%. The decreased expression occurred at both mRNA and protein levels, and it was confirmed by enzymatic assay. In cotransfection experiments, both HCE1 and HCE2 promoters were significantly repressed, and the repression was comparable with the decrease in HCE1 and HCE2 mRNA, suggesting that transrepression is responsible for the suppressed expression. In addition, pretreatment with IL-6 altered the cellular responsiveness in an opposite manner of overexpression of HCE1 and HCE2 toward various ester therapeutic agents (e.g., clopidogrel). Transfection of HCE1, for example, decreased the cytotoxicity induced by antithrombogenic agent clopidogrel, whereas pretreatment with IL-6 increased the cytotoxicity. Such a reversal was observed with other ester drugs, including anticancer agent irinotecan and anti-influenza agent oseltamivir. The altered cellular responsiveness was observed when drugs were assayed at sub- and low-micromolar concentrations, suggesting that suppressed expression of carboxylesterases by IL-6 has profound pharmacological consequences, particularly with those that are hydrolyzed in an isoform-specific manner.
Footnotes
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This work was supported by National Institutes of Health grants R01-ES07965, R01-GM61988, and F05-AT003019.
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Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
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doi:10.1124/mol.107.036889.
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ABBREVIATIONS: IL-6, interleukin-6; P450, cytochrome P450; HCE, human carboxylesterase; LPS, lipopolysaccharide; DRB, 5,6-dichlororibosidyl-benzi-midazole; GAPDH, glyceradehyde-3-phosphate dehydrogenase; PCR, polymerase chain reaction; DMEM, Dulbecco's modified Eagle's medium; PBS, phosphate-buffered saline; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium; OD, optical density; qRT-PCR, quantitative reverse transcription-polymerase chain reaction.
- Received April 5, 2007.
- Accepted May 30, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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