Human Arylamine N-Acetyltransferase 1 Is Inhibited by the Dithiocarbamate Pesticide Thiram

Abstract

Thiram (tetramethylthiuram disulfide) is a representative dithiocarbamate (DTC) pesticide used in both the field and as a seed protectant. The widespread use of Thiram and other DTC pesticides has raised concerns for health, because these compounds can exert neuropathic, endocrine disruptive, and carcinogenic effects. These toxic effects are thought to rely, at least in part, on the reaction of Thiram (and certain of its metabolites) with cellular protein thiols with subsequent loss of protein function. So far, a limited number of molecular targets of Thiram have been reported, including few enzymes such as dopamine -hydroxylase, 11-hydroxysteroid dehydrogenase, and brain glycogen phosphorylase. We provide evidence that Thiram is an inhibitor ( = 23 M; = 0.085 second; / = 3691 M⋅s) of human arylamine -acetyltransferase 1 (NAT1), a phase II xenobiotic-metabolizing enzyme that plays a key role in the biotransformation of aromatic amine xenobiotics. Thiram was found to act as an irreversible inhibitor through the modification of NAT1 catalytic cysteine residue as also reported for other enzymes targeted by this pesticide. We also showed using purified NAT1 and human keratinocytes that Thiram impaired the-acetylation of 3,4-dichloroaniline (3,4-DCA), a major toxic metabolite of aromatic amine pesticides (such as Diuron or Propanil). As coexposure to different classes of pesticides is common, our data suggest that pharmacokinetic drug-drug interactions between DTC pesticides such as Thiram and aromatic amine pesticides may occur through alteration of NAT1 enzymes functions.

Population variability of rhesus macaque (Macaca mulatta) NAT1 gene for arylamine N-acetyltransferase 1: Functional effects and comparison with human

“…Our observations were consistent with protein aggregation involving misfolded recombinant (MACMU)NAT1 unstable variants, both during expression (in the form of bacterial inclusion bodies), as well as in cell lysates and during purification (in the form of soluble and insoluble complexes with native Escherichia coli proteins) 75–77 . Although a variety of approaches are available for overcoming recombinant protein aggregation 75 , optimizing the expression/purification conditions for individual (MACMU)NAT1 variants was beyond the scope of this study, which focused on comparison of SNV effects using a standard procedure widely employed by NAT researchers performing similar work 27,35,64,78–87 . As expression of mammalian proteins in E .…”

Effect of thiram on rat kidney: inhibition of brush border membrane and antioxidant enzymes, diminution of antioxidant capacity, enhanced DNA damage and DNA-protein cross-linking

“…ALP and LAP are metalloproteins whereas maltase and GGT have cysteine residues that are involved in binding of substrate at the enzyme active site. The decrease in the activities of BBM marker enzymes could either be due to metal chelating property of thiram or by formation of mixed disul de with the critical cysteine residues, or their oxidation, present at the active site of enzyme (Marikovsky, 2002;Xu et al, 2017). Another reason could be loss of the enzymes into the lumen of the tubule upon membrane damage.…”

“…Thiram exposure is associated with several toxicological effects including endocrine disruption (Chen et al, 2018), hepatotoxicity (Saqib et al, 2005) neurotoxicity (Agrawal et al, 1997) and genotoxicity (Perocco et al, 1989). Thiram also interferes with the metabolism of xenobiotic compounds by inhibiting the enzyme arylamine N-acetyltransferase-1 (Xu et al, 2017). Thiram and ziram induce neurotoxicity by increasing the intracellular level of Ca 2+ through non-selective cation channels (Han et al, 2003).…”

Assessment of N-acetyltransferase 2 (NAT2) gene polymorphisms in bladder cancer patients

“…Positive cytology 20 (57%) 0 (0%) 0 (0%) NATs are phase II metabolic enzymes. They catalyse the acetylation of aromatic and heterocyclic amine carcinogens (9). Their activity is encoded by 2 distinct genes, named NAT1 and NAT2.…”