An Approach to Setting Vertebrate Animal-use Benchmarks for Agrochemical and GM Crop Testing to Facilitate Future Animal Reduction Efforts.

Agrochemical active ingredients are among the most toxicologically evaluated chemical substances, and genetically modified (GM) crops must be evaluated for safety and nutritional adequacy. Traditionally, these evaluations are conducted There are concerted efforts in the agrochemical sector to reduce animal testing, but there is also an emphasis on updating test guidelines and fulfilling new data package requirements, which can both result in increased animal testing. The purpose of this project was to generate benchmarks for the numbers of vertebrate animals used in: a) evaluating agrochemical pesticidal active ingredients for human health hazards; and b) assessing GM crops for safety and nutritional adequacy, based on guideline studies for data package requirements.

Altered regulation of hepatic efflux transporters disrupts acetaminophen disposition in pediatric nonalcoholic steatohepatitis.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, representing a spectrum of liver pathologies that include simple hepatic steatosis and the more advanced nonalcoholic steatohepatitis (NASH). The current study was conducted to determine whether pediatric NASH also results in altered disposition of acetaminophen (APAP) and its two primary metabolites, APAP-sulfate and APAP-glucuronide. Pediatric patients with hepatic steatosis (n = 9) or NASH (n = 3) and healthy patients (n = 12) were recruited in a small pilot study design.

Identification of a functional antioxidant response element within the eighth intron of the human ABCC3 gene.

The ATP-binding cassette (ABC) family of transporters, including ABCC3, is a large family of efflux pumps that plays a pivotal role in the elimination of xenobiotics from the body. ABCC3 has been reported to be induced during hepatic stress conditions and through the progression of some forms of cancer. Several lines of evidence have implicated the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in this induction.

Increased susceptibility to methotrexate-induced toxicity in nonalcoholic steatohepatitis.

Hepatic drug metabolizing enzymes and transporters play a crucial role in determining the fate of drugs, and alterations in liver function can place individuals at greater risk for adverse drug reactions (ADRs). We have shown that nonalcoholic steatohepatitis (NASH) leads to changes in the expression and localization of enzymes and transporters responsible for the disposition of numerous drugs. The purpose of this study was to determine the effect of NASH on methotrexate (MTX) disposition and the resulting toxicity profile.

Selective effects of a therapeutic protein targeting tumor necrosis factor-alpha on cytochrome P450 regulation during infectious colitis: Implications for disease-dependent drug-drug interactions.

We studied the impact of administering XPro1595, a novel antagonist of soluble tumor necrosis factor-α (TNFα), on the regulation of hepatic cytochrome P450 enzymes in the model of infectious colitis. XPro1595 was administered subcutaneously every three days throughout the infection, or as a single injection near the peak of infection. When given throughout the infection, XPro1595 selectively blocked the down-regulation of Cyp3a11 and 3a25 mRNAs, as well as the induction of Cyp2a4/5, without affecting the down-regulation of Cyp4a10, Cyp4a14, Cyp2b10 or flavin-mooxygenase-3.

Selective and cytokine-dependent regulation of hepatic transporters and bile acid homeostasis during infectious colitis in mice.

Various disease models have been shown to alter hepatic drug-metabolizing enzyme (DME) and transporter expression and to induce cholestasis through altered enzyme and transporter expression. Previously, we detailed the regulation of hepatic DMEs during infectious colitis caused by Citrobacter rodentium infection. We hypothesized that this infection would also modulate hepatic drug transporter expression and key genes of bile acid (BA) synthesis and transport.

Hepatic cytochrome P450s, phase II enzymes and nuclear receptors are downregulated in a Th2 environment during Schistosoma mansoni infection.

Inflammation and infection downregulate the activity and expression of cytochrome P450s (P450s) and other drug metabolizing enzymes (DMEs) involved in hepatic drug clearance. Schistosoma mansoni infection was reported to cause a downregulation of hepatic P450-dependent activities in mouse liver, but little is known about the specific enzymes affected or whether phase II DMEs are also affected. Here we describe the effect of murine schistosomiasis on the expression of hepatic P450s, NADPH-cytochrome P450 reductase (Cpr), phase II drug metabolizing enzymes, and nuclear receptors at 30 and 45 days postinfection (dpi).

Drug metabolism alterations in nonalcoholic fatty liver disease.

Drug-metabolizing enzymes play a vital role in the elimination of the majority of therapeutic drugs. The major organ involved in drug metabolism is the liver. Chronic liver diseases have been identified as a potential source of significant interindividual variation in metabolism.

The Nrf2 activator oltipraz also activates the constitutive androstane receptor.

Oltipraz (OPZ) is a well known inducer of NAD(P)H:quinone oxidoreductase (NQO1) along with other enzymes that comprise the nuclear factor E2-related factor 2 (Nrf2) battery of detoxification genes. However, OPZ treatment also induces expression of CYP2B, a gene regulated by the constitutive androstane receptor (CAR). Therefore, this study was designed to determine whether OPZ induces gene expression in the mouse liver through activation of CAR in addition to Nrf2.

Induction of drug metabolism enzymes and transporters by oltipraz in rats.

Coordinate regulation of Phase-I and -II enzymes with xenobiotic transporters has been shown after treatment with microsomal enzyme inducers. The chemopreventive agent oltipraz (OPZ) induces Phase-I and -II drug-metabolizing enzymes such as CYP2B and NQO1. The purpose of this study was to examine the regulation of drug-metabolizing enzymes and transporters in response to OPZ treatment and to investigate a potential role for constitutive androstane receptor (CAR) in OPZ-mediated induction.