P50 Is cigarette smoking exacerbating the effect of non-alcoholic fatty liver disease (NAFLD) on CYP3A- and CYP2C-mediated drug metabolism?

Jessica Virgili , Université Laval, Québec, QC, Canada
Sylvie Pilote , CRIUCPQ, Québec, QC, Canada
Camille Thibault , Université Laval, Québec, QC, Canada
Éric Jubinville , CRIUCPQ, Québec, QC, Canada
Joanie Routhier , Université Laval, Québec, QC, Canada
Benoît Drolet , Université Laval, Québec, QC, Canada
Mathieu C. Morissette , Université Laval, Québec, QC, Canada
Chantale Simard , Université Laval, Québec, QC, Canada
Background and objectives: Cigarette smoking is a worldwide health problem contributing to cardiovascular morbidity and mortality. It has been reported that tobacco smoke has the ability to modulate the expression of certain genes, including cytochrome P450 enzymes. Indeed, cigarette smoke contains numerous cytochrome P450 inducers, substrates and inhibitors.1 Besides, non-alcoholic fatty liver disease (NAFLD) is a common disorder strongly associated with metabolic syndrome components such as abdominal obesity and type II diabetes. Due to the rising tide of obesity, the burden of NAFLD is still increasing. NAFLD patients exposed to cigarette smoke frequently use numerous drugs to manage comorbidities. Little is known about the effects of NAFLD and cigarette smoke on drug disposition and metabolism. A NAFLD animal model generated by T0901317, a liver X-receptor agonist, was used to evaluate the combined impact of NAFLD and cigarette smoke on drug metabolism. The function of two major hepatic cytochrome P450 subfamilies (CYP3A and CYP2C) was evaluated. Methods: Seven to nine-week old female C57BL/6 mice, either exposed to ambient air or cigarette smoke during 2 h, once daily, were injected intraperitoneally daily for 4 days with either vehicle or T0901317 20 mg/kg (4 groups, n=5/group). Livers were collected, washed, weighted and snap frozen in liquid nitrogen. Frozen optical cutting temperature-embedded liver sections were stained with Oil red O. Microsomes were extracted, the protein content was determined and standard incubations were performed with either testosterone, a CYP3A probe substrate or tolbutamide, a CYP2C probe substrate. Results: A marked lipid infiltration in the cytosol of hepatocytes, a hallmark of NAFLD, was seen in T0-treated mice. Significant increase in total hepatic weight and significant decrease in hepatic activities of CYP3A and CYP2C were observed in T0901317-treated compared to vehicle-treated mice.

Room air exposure

Cigarette smoke exposure

Vehicle treated-mice

T0901317

treated-mice

Vehicle treated-mice

T0901317

treated-mice

Normalized liver weight

1.00±0.07

1.8±0.08***

0.80±.010

1.46±0.06 *** §§§

Normalized CYP3A activity

1.00±0.08

0.22±0.04***

1.15±0.38

0.04±0.02***

§§

Normalized CYP2C activity

1.00±0.11

0.10±0.02**

0.89±0.26

0.00**

§§

** p<0.01, ***p<0.001 when compared to vehicle-treated-mice exposed to room air

§§ p<0.01, §§§ p<0.001 when compared to vehicle-treated-mice exposed to cigarette smoke

Conclusions: Drug metabolism mediated by CYP3A and CYP2C subfamilies was drastically impaired in the T0901317-treated mouse. These results reinforce the notion that liver conditions and hepatic lipid accumulation impact the metabolism of xenobiotics. Exposure to cigarette smoke appears to exacerbate the impact of NAFLD on drug metabolism. Keeping in mind that CYP3A and CYP2C cytochrome P450 subfamilies together are involved in the disposition of nearly more than 50% of currently marketed drugs, these striking results warrant further investigations to evaluate the potential clinical consequences of combined NAFLD and tobacco use on drug disposition, efficacy and toxicity.

  1. Czekaj P et al. (2004) Tobacco smoke-dependent changes in cytochrome P450 1A1, 1A2, and 2E1 protein expressions in fetuses, newborns, pregnant rats, and human placenta. Arch Toxicol. 79: 13-24.