Role of polymorphic and monomorphic human arylamine N-acetyltransferases in determining sulfamethoxazole metabolism

doi:10.1016/0006-2952(93)90280-A

Biochemical Pharmacology

Volume 45, Issue 6, 24 March 1993, Pages 1277-1282

https://doi.org/10.1016/0006-2952(93)90280-A Get rights and content

Abstract

Sulfonamides are associated with a variety of adverse reactions, some of which have been linked with the classical acetylator phenotypes. Although the slow acetylator phenotype has been identified as a risk factor for hypersensitivity reactions to sulfamethoxazole (SMX), the disposition of this compound appears not to be affected by the acetylation polymorphism in vivo in humans. We therefore investigated the acetylation of SMX by monomorphic (NAT1) and polymorphic (NAT2) arylamine N-acetyltransferases in humans with the objective of determining their role in the metabolism of SMX. SMX was acetylated by both NAT1 and NAT2. K_m values determined in hepatic cytosol for NAT1- and NAT2-mediated acetylation of SMX were 1.2 mM and approximately 5 mM, respectively, at an acetyl coenzyme A concentration of 100 μM. Mononuclear leukocytes, which contain only NAT1, had a K_m value of 1.2 mM. K_m values determined with recombinant NAT1 and NAT2 proteins expressed in Escherichia coli were 1.5 mM and approximately 15 mM, respectively. The higher affinity of NAT1 for SMX indicates that acetylation by this enzyme will predominate at therapeutic plasma concentrations, in agreement with the observed in vivo monomorphic acetylation of SMX. NAT1 may be the primary determinant of SMX systemic metabolic clearance. However, in the hepatocyte NAT2 variation may be an important competitive pathway which influences the extent of oxidative metabolism of SMX to its reactive hydroxylamine metabolite. Therefore, variation in both monomorphic and polymorphic N-acetyltransferases may play a role in determining susceptibility to sulfamethoxazole toxicity.

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The nitroso metabolite subsequently undergoes detoxification of by GSH [11]. The inactivation process of SMX also occurs through N-acetylation by two polymorphic enzymes, NAT1 and NAT2 [13]. It has been reported that patients with NAT2 slow acetylator genotypes were at a high risk with co-trimoxazole or SMX hypersensitivity [10,14].
Co-trimoxazole is mainly used as a first-line drug for treatment and prophylaxis against Pneumocystis jiroveci pneumonia. This drug, however, has been reported as the most common causative drug for severe cutaneous adverse reactions (SCARs). This study aimed to extensively elucidate the associations between genetic polymorphisms of HLA class I and genes involved in bioactivation and detoxification of co-trimoxazole on co-trimoxazole-induced SCARS in a large sample size and well-defined Thai SCARs patients. A total of 67 patients with co-trimoxazole-induced SCARs, consisting of 51 SJS/TEN patients and 16 DRESS patients, and 91 co-trimoxazole tolerant controls were enrolled in the study. The results clearly demonstrated that the HLA-B^∗13:01 allele was significantly associated with co-trimoxazole-induced SCARs, especially with DRESS (OR = 8.44, 95% CI = 2.66–26.77, P = 2.94 × 10⁻⁴, Pc = 0.0126). Moreover, the HLA-C^∗08:01 allele was significantly associated with co-trimoxazole-induced SJS/TEN in the HIV/AIDS patients with an OR of 8.51 (95% CI = 2.18–33.14, P = 8.60 × 10⁻⁴, Pc = 0.0241). None of the genes involved in the bioactivation and detoxification of co-trimoxazole investigated in this study play any major role in the development of all phenotypes of SCARs.
Reactive metabolites of the anticonvulsant drugs and approaches to minimize the adverse drug reaction
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From the middle of the 19th century to date, a number of anticonvulsant drugs were discovered and are categorized into different generations (Fig. 4) [22,33]. The presence of structural alerts in these drugs and their in vivo toxicity necessitates the discovery of the new drugs [34–36]. The anticonvulsant drugs act on different targets and some of these drugs acts on more than one targets such as voltage gated sodium channel (phenytoin, carbamazepine, valproic acid lamotrigine, topiramate, zonisamide and felbamate), GABA receptor (phenobarbital, primidone, benzodiazepines and valproic acid), calcium channel (ethosuximide, felbamate).
Several generations of antiepileptic drugs (AEDs) are available in the market for the treatment of seizures, but these are amalgamated with acute to chronic side effects. The most common side effects of AEDs are dose-related, but some are idiosyncratic adverse drug reactions (ADRs) that transpire due to the formation of reactive metabolite (RM) after the bioactivation process. Because of the adverse reactions patients usually discontinue the medication in between the treatment. The AEDs such as valproic acid, lamotrigine, phenytoin etc., can be categorized under such types because they form the RM which may prevail with life-threatening adverse effects or immune-mediated reactions. Hepatotoxicity, teratogenicity, cutaneous hypersensitivity, dizziness, addiction, serum sickness reaction, renal calculi, metabolic acidosis are associated with the metabolites of drugs such as arene oxide, N-desmethyldiazepam, 2-(1-hydroxyethyl)-2-methylsuccinimide, 2-(sulphamoy1acetyl)-phenol, E−2-en-VPA and 4-en-VPA and carbamazepine-10,11-epoxide, etc. The major toxicities are associated with the moieties that are either capable of forming RM or the functional groups may itself be too reactive prior to the metabolism. These functional groups or fragment structures are typically known as structural alerts or toxicophores. Therefore, minimizing the bioactivation potential of lead structures in the early phases of drug discovery by a modification to low-risk drug molecules is a priority for the pharmaceutical companies. Additionally, excellent potency and pharmacokinetic (PK) behaviour help in ensuring that appropriate (low dose) candidate drugs progress into the development phase. The current review discusses about RMs in the anticonvulsant drugs along with their mechanism vis-a-vis research efforts that have been taken to minimize the toxic effects of AEDs therapy.
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NAT was directly involved in transferring an acetyl group from Acetyl-CoA to aromatic amines substrates (Rodrigues-Lima et al., 2017), and some previous studies had confirmed that NAT was directly linked to sulfonamide metabolism and detoxification in humans and bacterium. Cloned NAT from Bacillus Anthracis could increase SMX resistance, and NAT from Bacillus anthracis showed a high catalytic efficiency from SMX to acetylate SMX (Cribb et al., 1993; Pluvinage et al., 2007, 2011). Cytochrome P450 (CYP450) had been proved to participate in N-hydroxylation of arylamines and heterocyclic arylamines in human body (Kim and Guengerich, 2005; Ott et al., 2014), and CYP450 of Pycnoporus sanguineus could also play roles in SMX biotransformation (Gao et al., 2018).
Sulfamethoxazole (SMX) has attracted much attention due to its high probability of detection in the environment. Marine bacteria Vibrio diabolicus strain L2–2 has been proven to be able to transform SMX. In this study, the potential resistance and biotransformation mechanism of strain L2–2 to SMX, and key genes responses to SMX at environmental concentrations were researched. KEGG pathways were enriched by down-regulated genes including degradation of L-Leucine, L-Isoleucine, and fatty acid metabolism. Resistance mechanism could be concluded as the enhancement of membrane transport, antioxidation, response regulator, repair proteins, and ribosome protection. Biotransformation genes might involve in arylamine N-acetyltransferases (nat), cytochrome c553 (cyc-553) and acyl-CoA synthetase (acs). At the environmental concentration of SMX (0.1–10 μg/L), nat was not be activated, which meant the acetylation of SMX might not occur in the environment; however, cyc-553 was up-regulated under SMX stress of 1 μg/L, which indicated the hydroxylation of SMX could occur in the environment. Besides, the membrane transport and antioxidation of strain L2–2 could be activated under SMX stress of 10 μg/L. The results provided a better understanding of resistance and biotransformation of bacteria to SMX and would support related researches about the impacts of environmental antibiotics.
Sex-related differences in disposition of sulfamethoxazole, N-acetyl-sulfamethoxazole and trimethoprim in yellow catfish (Pelteobagrus fulvidraco) following a single oral administration
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It was reported that the rate of N-acetylation depends on the drug categories and animal species (Bridges et al., 1968). Cribb et al. (1993) found that monomorphic arylamine N-acetyltransferases (NAT1) may be the primary determinant of SMZ systemic metabolic clearance. It is suggested that the significant differences of N-ac-SMZ concentrations in aquatic animals described above may be related to fish species and size, and more in depth explanation on differences may be due to NAT1 among aquatic animals.
The aim of this present study was to explore the sex-related differences in disposition regularities of sulfamethoxazole (SMZ), N-acetyl-sulfamethoxazole (N-ac-SMZ) and trimethoprim (TMP) in male and female yellow catfish. Concentrations of target compounds were determined using a reliable HPLC-MS/MS approach, which was validated according to the guidelines defined by FDA. The results showed that there are significant sex-associated differences in SMZ concentrations of muscle with skin and liver, in N-ac-SMZ levels of muscle with skin and kidney, and in TMP concentrations of muscle with skin, liver and kidney. Whereas, no significant sex differences were also observed in SMZ, N-ac-SMZ and TMP levels of plasma, in SMZ concentrations of kidney and in N-ac-SMZ concentrations of liver. Longer residue time of N-ac-SMZ than SMZ was observed in male and female yellow catfish. Withdrawal time (WT) of SMZ (N-ac-SMZ as the marker residue) calculated by the WT 1.4 software, was 11 days (male) and 9 days (female), respectively. By contrast, WT of SMZ (SMZ as the marker residue) was 9 days (male) and 7 days (female), respectively. These results could serve as reference data for establishing disparate use regimen and drug withdrawal time of SMZ and TMP in male and female yellow catfish.
Isolation and characterization of a marine bacterium Vibrio diabolicus strain L2-2 capable of biotransforming sulfonamides
2020, Environmental Research
Sulfonamides (SAs) have attracted much attention because of their high detection rates in natural water. In this study, a marine bacterium Vibrio diabolicus strain L2-2 was isolated which could metabolize 9 SAs to a different extent. Compared with SAs and their analogs, SAs with N-oxides of heterocyclic structure were easier to be transformed to their N⁴-acetylated metabolites or their isoxazole ring rearrangement isomers by strain L2-2. And, gene vdnatA and vdnatG were likely to be the key genes in SAs acetylation process, which might code Arylamine N-acetyltransferase. The biotransformation rates of sulfathiazole(STZ), sulfamonomethoxine(SMT), sulfadiazine(SDZ), sulfamethoxazole(SMX) and sulfisoxazole(SIX) could reach 29.39 ± 5.63, 24.97 ± 4.45, 79.41 ± 4.05, 64.64 ± 1.71, 32.82 ± 4.46% in 6 days, respectively. Besides, the overall optimal conditions for SAs biotransformation were less than 100 mg/L for total SAs in neutral or weakly alkaline medium with the salinity of 10–20‰ and additional nutrients like glucose, sucrose or glycerine. Furthermore, toxicity was demonstrated to be significantly reduced after biotransformation. Together, this study introduced a strategy to use V. diabolicus strain L2-2 to realize simultaneous removal and detoxification of multiple SAs in freshwater and seawater, and revealed SAs removal pathways and relevant molecular mechanism.
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^∗: Present address: Exploratory Biochemical Toxicology, Merck Research Laboratories, 44-L206, West Point, PA 19486, U.S.A.

^†: Scholar of the Medical Research Council of Canada.

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Biochemical Pharmacology

Abstract

References (27)

Cloning and expression of cDNAs for polymorphic and monomorphic arylamine N-acetyltransferases from human liver

J Biol Chem

Site-directed mutagenesis of recombinant human arylamine N-acetyltransferase expressed in Escherichia coli. Evidence for direct involvement of Cys⁶⁸ in the catalytic mechanism of polymorphic human NAT2

J Biol Chem

A rapid and sensitive method for the quanti tation of microgram quantities of protein utilizing the principle of protein-dye binding

Anal Biochem

Pharmacokinetics of sulfonamides revisited

Antibiot Chemother

N-Acetyltransferase

Pharmacol Ther

Differences in metabolism of sulfonamides predisposing to idiosyncratic toxicity

Ann Intern Med

Prominence of slow acetylator phenotype among patients with sulfonamide hypersensitivity reactions

Clin Pharmacol Ther

Drug disposition and drug hypersensitivity

Biochem Pharmacol

The immunological and metabolic basis of drug hypersensitivities

Annu Rev Pharmacol Toxicol

Hepatic microsomal metabolism of sulfamethoxazole to the hydroxylamine

Drug Metab Dispos

Peroxidase-dependent oxidation of sulfonamides by monocytes and neutrophils from humans and dogs

Mol Pharmacol

Sulfamethoxazole is metabolized to the hydroxylamine in humans

Clin Pharmacol Ther

Diagnosis of sulfonamide hypersensitivity reactions by in-vitro “rechallenge” with hydroxylamine metabolites

Ann Intern Med

Cited by (65)

Associations of HLA and drug-metabolizing enzyme genes in co-trimoxazole-induced severe cutaneous adverse reactions

Reactive metabolites of the anticonvulsant drugs and approaches to minimize the adverse drug reaction

Biotransformation mechanism of Vibrio diabolicus to sulfamethoxazole at transcriptional level

Sex-related differences in disposition of sulfamethoxazole, N-acetyl-sulfamethoxazole and trimethoprim in yellow catfish (Pelteobagrus fulvidraco) following a single oral administration

Isolation and characterization of a marine bacterium Vibrio diabolicus strain L2-2 capable of biotransforming sulfonamides

Metabolism of sulfamethoxazole in Arabidopsis thaliana cells and cucumber seedlings