Similarities and differences in the biotransformation and transcriptomic responses of Caenorhabditis elegans and Haemonchus contortus to five different benzimidazole drugs

Abstract

We have undertaken a detailed analysis of the biotransformation of five of the most therapeutically important benzimidazole anthelmintics - albendazole (ABZ), mebendazole (MBZ), thiabendazole (TBZ), oxfendazole (OxBZ) and fenbendazole (FBZ) - in Caenorhabditis elegans and the ruminant parasite Haemonchus contortus. Drug metabolites were detected by LC-MS/MS analysis in supernatants of C. elegans cultures with a hexose conjugate, most likely glucose, dominating for all five drugs. This work adds to a growing body of evidence that glucose conjugation is a major pathway of xenobiotic metabolism in nematodes and may be a target for enhancement of anthelmintic potency. Consistent with this, we found that biotransformation of albendazole by C. elegans reduced drug potency. Glucose metabolite production by C. elegans was reduced in the presence of the pharmacological inhibitor chrysin suggesting that UDP-glucuronosyl/glucosyl transferase (UGT) enzymes may catalyze benzimidazole glucosidation. Similar glucoside metabolites were detected following ex vivo culture of adult Haemonchus contortus. As a step towards identifying nematode enzymes potentially responsible for benzimidazole biotransformation, we characterised the transcriptomic response to each of the benzimidazole drugs using the C. elegans resistant strain CB3474 ben-1(e1880)III. In the case of albendazole, mebendazole, thiabendazole, and oxfendazole the shared transcriptomic response was dominated by the up-regulation of classical xenobiotic response genes including a shared group of UGT enzymes (ugt-14/25/33/34/37/41/8/9). In the case of fenbendazole, a much greater number of genes were up-regulated, as well as developmental and brood size effects suggesting the presence of secondary drug targets in addition to BEN-1. The transcriptional xenobiotic response of a multiply resistant H. contortus strain UGA/2004 was essentially undetectable in the adult stage but present in the L3 infective stage, albeit more muted than C. elegans. This suggests that xenobiotic responses may be less efficient in stages of parasitic nematodes that reside in the host compared with the free-living stages.

Sub-lethal doses of albendazole induce drug metabolizing enzymes and increase albendazole deactivation in Haemonchus contortus adults

“…When C. elegans adults of the resistant strain CB3474 ben-1(e1880) III were exposed to ABZ and other benzimidazole anthelmintics (mebendazole, thiabendazole, and oxfendazole), the up-regulation of UGT genes (ugt-14/25/33/34/37/41/8/9) was observed. Surprisingly, the transcriptional xenobiotic response of H. contortus adults from the resistant strain UGA/2004 to anthelmintics exposure was undetectable [36]. Nevertheless, this discrepancy is probably based on the very high (lethal) concentrations (1.13 mM) of anthelmintics used in mentioned study.…”

Rapid determination of nematode cell and organ susceptibility to toxic treatments

“…Among the most significantly enriched genes in these 85 were a carbonic anhydrase gene (one of which may function in detoxification of cyanate in Ascaris lumbricoides ( Zolfaghari Emameh et al, 2015 )) and a dehydrogenase 7 (DHS-7) ortholog, which was one of five genes also upregulated at 2 h with both drugs. In both C. elegans and Haemonchus contortus , several dehydrogenases (dhs-23, dhs-27 and dhrs7b) were among 41 genes commonly upregulated in response to five different benzimidazole drugs ( Stasiuk et al, 2019 ).…”

Quantitative benzimidazole resistance and fitness effects of parasitic nematode beta-tubulin alleles

“…In addition to differential responses in the host species treated with albendazole or fenbendazole, parasitic nematodes respond differently to these two compounds. A recent study found that, in response to albendazole, fewer genes are differentially expressed compared to fenbendazole ( Stasiuk et al, 2019 ). Our study also found differential responses to albendazole and fenbendazole, where C. elegans was overall less susceptible to albendazole than fenbendazole.…”