Nathan J Cherrington

PMID: 19326769;Abstract:

Xenobiotics, including drugs and environmental chemicals, can influence cytochrome P450 (CYP) levels by altering the transcription of CYP genes. To minimize potential drug-pesticide and pesticide-pesticide interactions it is important to evaluate the potential of pesticides to induce CYP isoforms and to cause cytotoxicity in humans. The present study was designed to examine chlorpyrifos and DEET mediated induction of CYP isoforms and also to characterize their potential cytotoxic effects on primary human hepatocytes. DEET significantly induced CYP3A4, CYP2B6, CYP2A6 and CYP1A2 mRNA expression while chlorpyrifos induced CYP1A1, CYP1A2 and CYP3A4 mRNA, and to a lesser extent, CYP1B1 and CYP2B6 mRNA in primary human hepatocytes. Chlorpyrifos and DEET also mediated the expression of CYP isoforms, particularly CYP3A4, CYP2B6 and CYP1A1, as shown by CYP3A4-specific protein expression, testosterone metabolism and CYP1A1-specific activity assays. DEET is a mild, while chlorpyrifos is a relatively potent, inducer of adenylate kinase and caspase-3/7, an indicator of apoptosis, while inducing 15-20% and 25-30% cell death, respectively. Therefore, DEET and chlorpyrifos mediated induction of CYP mRNA and functional CYP isoforms together with their cytotoxic potential in human hepatocytes suggests that exposure to chlorpyrifos and/or DEET should be considered in human health impact analysis. © Freund Publishing House Ltd., 2008.

Researchers who study acetaminophen (APAP) hepatotoxicity use either a 50% propylene glycol solution or saline as a diluent. Previous studies demonstrated differential expression of hepatobiliary transporter mRNA in mice treated with a toxic dose of APAP dissolved in 50% propylene glycol. The purpose of this study was to determine whether using saline as a diluent for APAP alters regulation of transporter gene expression during hepatotoxicity. Male C57BL/6J mice received acetaminophen (APAP 400 mg/kg, i.p. in saline) or saline (20 ml/kg). Plasma and liver samples were collected at 24 and 48 h for assessment of alanine aminotransferase (ALT) activity and gene expression. It was determined that plasma ALT activity was elevated at 24 and 48 h after APAP administration. Using the branched DNA signal amplification assay, reductions in organic anion-transporting polypeptides Oatp1a1, Oatp1b2, sodium/taurocholate-cotransporting polypeptide (Ntcp), and bile salt export pump (Bsep) mRNA were observed in APAP-treated mice. In contrast, multidrug resistance-associated proteins Mrp1, Mrp2, Mrp3, and Mrp4, as well as multidrug resistance proteins Mdr1a and Mdr1b genes, were increased following APAP. No changes in Oatp1a4, Mdr2, or breast cancer resistance protein (Bcrp) mRNA were observed. Alterations in transporter gene expression in this study were similar to those reported previously using propylene glycol as diluent. With the exceptions of Oatp1a1, Ntcp, and Mrp1, these data mirror previous results suggesting that the solution used to dissolve APAP may alter the susceptibility of mice to hepatotoxicity, but only minimally change the regulation of transporter gene expression.

Metabolic syndrome is a multifactorial disease associated with obesity, insulin resistance, diabetes, and the alteration of multiple metabolic hormones. Obesity rates have been rising worldwide, which increases our need to understand how this population will respond to drugs and exposure to other chemicals. The purpose of this study was to determine in lean and obese mice the ontogeny of clinical biomarkers such as serum hormone and blood glucose levels as well as the physiologic markers that correlate with nuclear receptor- and transporter-related pathways. Livers from male and female wild-type (WT) (C57BL/6) and ob/ob mice littermates were collected before, during, and after the onset of obesity. Serum hormone and mRNA levels were analyzed. Physiologic changes and gene expression during maturation and progression to obesity were performed and correlation analysis was performed using canonical correlations. Significant ontogenic changes in both WT and ob/ob mice were observed and these ontogenic changes differ in ob/ob mice with the development of obesity. In males and females, the ontogenic pattern of the expression of genes such as Abcc3, 4, Abcg2, Cyp2b10, and 4a14 started to differ from week 3, and became significant at weeks 4 and 8 in ob/ob mice compared with WT mice. In obese males, serum resistin, glucagon, and glucose levels correlated with the expression of most hepatic ATP-binding cassette (Abc) transporters, whereas in obese females, serum glucagon-like peptide 1 levels were correlated with most hepatic uptake transporters and P450 enzymes. Overall, the correlation between physiologic changes and gene expression indicate that metabolism-related hormones may play a role in regulating the genes involved in drug metabolism and transport.

PMID: 18189363;Abstract:

Obesity and type II diabetes pose a serious human health risk. Obese or diabetic patients usually take prescription drugs that require hepatic and renal metabolism and transport, and these patients sometimes display different pharmacokinetics of these drugs. Therefore, mRNA and protein expression of drug-metabolizing enzymes (DMEs) and transporters was measured in livers and kidneys of adult wild-type and ob/ob mice, which model obesity and diabetes. mRNA expression of numerous DMEs increased by at least 2-fold in livers of male ob/ob mice, including Cyp4a14, Cyp2b10, NAD(P)H:quinone oxidoreductase 1 (Nqo1), and sulfotransferase 2a1/2. In general, expression of uptake transporters was decreased in livers of ob/ob mice, namely organic anion-transporting polypeptides (Oatps) and sodium/taurocholate cotransporting polypeptide (Ntcp). In particular, Oatp1a1 mRNA and protein expression in livers of ob/ob mice was diminished to 5% and 15% of that in wild-types, respectively. Generally, the mRNA and protein expression of efflux transporters multidrug resistance-associated proteins (Mrps) was increased in livers of ob/ob mice, particularly with Mrp4 expression being elevated by at least 6-fold and Mrp2 expression at least 3-fold in livers of ob/ob mice. In kidney, Nqo1, Mrp3,4, Oatp1a1, and organic anion transporter 2 (Oat2) showed significant alterations with mRNA expression levels in ob/ob mice, being increased for Nqo1 and Mrp4 and decreased for Mrp3, Oatp1a1, and Oat2. In summary, the expression of a number of DMEs and transporters was significantly altered in livers and kidneys of ob/ob mice. Since expression of some DMEs and transporters is regulated similarly between mouse and human, the data from this study suggest that transporter expression in liver and kidney may be changed in patients presenting with obesity and/or type II diabetes. © 2008 American Chemical Society.

Nonalcoholic fatty liver disease is the most common chronic liver disease, which can progress to nonalcoholic steatohepatitis (NASH). Previous investigations demonstrated alterations in the expression and activity of hepatic drug transporters in NASH. Moreover, studies using rodent models of cholestasis suggest that compensatory changes in kidney transporter expression occur to facilitate renal excretion during states of hepatic stress; however, little information is currently known regarding extrahepatic regulation of drug transporters in NASH. The purpose of the current study was to investigate the possibility of renal drug transporter regulation in NASH across multiple experimental rodent models. Both rat and mouse NASH models were used in this investigation and include: the methionine and choline-deficient (MCD) diet, atherogenic diet, fa/fa rat, ob/ob and db/db mice. Histologic and pathologic evaluations confirmed that the MCD and atherogenic rats as well as the ob/ob and db/db mice all developed NASH. In contrast, the fa/fa rats did not develop NASH but did develop extensive renal injury compared with the other models. Renal mRNA and protein analyses of xenobiotic transporters suggest that compensatory changes occur in NASH to favor increased xenobiotic secretion. Specifically, both apical efflux and basolateral uptake transporters are induced, whereas apical uptake transporter expression is repressed. These results suggest that NASH may alter the expression and potentially function of renal drug transporters, thereby impacting drug elimination mechanisms in the kidney.