Characterization of the xenobiotic response of Caenorhabditis elegans to the anthelmintic drug albendazole and the identification of novel drug glucoside metabolites

Abstract

Knowledge of how anthelmintics are metabolized and excreted in nematodes is an integral part of understanding the factors that determine their potency, spectrum of activity and for investigating mechanisms of resistance. Although there is remarkably little information on these processes in nematodes, it is often suggested that they are of minimal importance for the major anthelmintic drugs. Consequently, we have investigated how the model nematode Caenorhabditis elegans responds to and metabolizes albendazole, one of the most important anthelmintic drugs for human and animal use. Using a mutant strain lacking the β-tubulin drug target to minimize generalized stress responses, we show that the transcriptional response is dominated by genes encoding XMEs (xenobiotic-metabolizing enzymes), particularly cytochrome P450s and UGTs (UDP-glucuronosyl transferases). The most highly induced genes are predominantly expressed in the worm intestine, supporting their role in drug metabolism. HPLC-MS/MS revealed the production of two novel glucoside metabolites in C. elegans identifying a major difference in the biotransformation of this drug between nematodes and mammals. This is the first demonstration of metabolism of a therapeutic anthelmintic in C. elegans and provides a framework for its use to functionally investigate nematode anthelmintic metabolism.

NHR-176 regulates cyp-35d1 to control hydroxylation-dependent metabolism of thiabendazole in Caenorhabditis elegans

“…Glucosidation is not a common pathway in mammals and has not been reported in any studies which have investigated metabolism of TBZ or ABZ in mammals [10,11,[46][47][48][49]. Interestingly, glucose conjugates of ABZ have also been reported in C. elegans and the parasitic nematode Haemonchus contortus which suggests that bio-transformation pathways could be conserved in strongylid nematodes [36,50]. Given that these nematodes include many human and veterinary parasites, revealing the components of these pathways could have important implications both for drug potency and for potential mechanisms of drug resistance.…”

“…Although metabolism of drugs has been extensively studied in mammals, the extent to which drugs are metabolized in nematodes remains to be determined [9,35,36]. Consequently we have investigated the metabolic pathway of TBZ in C. elegans and its regulation.…”

“…Interestingly, other TBZinducible CYP genes (cyp-35a3, cyp-35a5 and cyp-35-c1) showed a significantly stronger induction during RNAi knockdown of nhr-176 and cyp-35d1 than in the gfp control (P 0.05 and P 0.01; Figure 1), particularly after 6 h of TBZ exposure. Furthermore, microarray and GFP reporter analyses show the expression of both cyp-35c1 and cyp-35a5 are strongly induced under ABZ (albendazole) exposure [36] and may play an important role in oxidation of this BZ. This suggests compensatory regulation by other transcription factors during knockdown of both genes, which may allow some hydroxylation of TBZ to occur.…”

Phenobarbital Induction and Chemical Synergism Demonstrate the Role of UDP-Glucuronosyltransferases in Detoxification of Naphthalophos by Haemonchus contortus Larvae

“…UDPGT enzymes are also known to exist in nematodes, with the H. contortus genome possessing 34 UDPGT genes (26) and C. elegans known to possess 72 genes (47). While there are some reports of conjugation of glucose to benzimidazole anthelmintics in C. elegans (48) and H. contortus (49,50), there have, to our knowledge, been no reports of the conjugation of glucuronic acid, mediated by UDPGT enzymes, as a pathway of xenobiotic detoxification in parasitic worms prior to the present study.…”

Reliable reference gene selection for quantitative real time PCR in Haemonchus contortus

“…In a previous study, ABZ induced the transcriptional response of drug-metabolizing genes (e.g. cytochrome P450s and UDPglucosyl transferases) in Caenorhabitis elegans [12]. IVM is a macrocyclic lactone, which irreversibly binds to and activates ligand-gated chloride channels, resulting in paralysis of the body wall and pharyngeal muscles [13].…”