Arylamine N-acetyltransferase (NAT2) gene mutations in children with allergic diseases

Current insights into the genetics of food allergy

Food allergy (FA), a growing public health burden in the United States, and familial aggregation studies support strong roles for both genes and environment in FA risk. Deepening our understanding of the molecular and cellular mechanisms driving FAs is paramount to improving its prevention, diagnosis, and clinical management. In this review, we document lessons learned from the genetics of FA that have aided our understanding of these mechanisms. Although current genetic association studies suffer from low power, heterogeneity in definition of FA, and difficulty in our ability to truly disentangle FA from food sensitization (FS) and general atopy genetics, they reveal a set of genetic loci, genes, and variants that continue to implicate the importance of barrier and immune function genes across the atopic march, and FA in particular. The largest reported effects on FA are from MALT1 (odds ratio, 10.99), FLG (average odds ratio, ∼2.9), and HLA (average odds ratio, ∼2.03). The biggest challenge in the field of FA genetics is to elucidate the specific mechanism of action on FA risk and pathogenesis for these loci, and integrative approaches including genetics/genomics with transcriptomics, proteomics, and metabolomics will be critical next steps to translating these genetic insights into practice.

Case Study 10: A Case to Investigate Acetyl Transferase Kinetics

Major routes of metabolism for marketed drugs are predominately driven by enzyme families such as cytochromes P450 and UDP-glucuronosyltransferases. Less studied conjugative enzymes, like N-acetyltransferases (NATs), are commonly associated with detoxification pathways. However, in the clinic, the high occurrence of NAT polymorphism that leads to slow and fast acetylator phenotypes in patient populations has been linked to toxicity for a multitude of drugs. A key example of this is the observed clinical toxicity in patients who exhibit the slow acetylator phenotype and were treated with isoniazid. Toxicity in patients has led to detailed characterization of the two NAT isoforms and their polymorphic genotypes. Investigation in recombinant enzymes, genotyped hepatocytes, and in vivo transgenic models coupled with acetylator status-driven clinical studies have helped understand the role of NATs in drug development, clinical study design and outcomes, and potential roles in human disease models. The selected case studies herein document NAT enzyme kinetics to explore substrate overlap from two human isoforms, preclinical species considerations, and clinical genotype population concerns.

N-acetyltransferase: the practical consequences of polymorphic activity in man

Over the years, numerous studies have supported the premise that individuals possessing the "slow acetylator" phenotype are more at risk from developing drug side-effects. Most prominent amongst these reports are those concerned with hepatotoxicity and peripheral neuropathy following treatment with isoniazid, lupus-like symptoms during procainamide therapy and experiencing hypersensitivity reactions to the various sulphonamide derivatives. Similarly, "slow acetylators" undergoing heavy exposure to arylamines and related carcinogens are more likely to develop bladder cancer. Contrariwise, there appears a slight risk of "rapid acetylators" developing pancreatic tumours.Other therapeutic agents for which polymorphic N-acetylation plays a minor role in their metabolism have been investigated but any impact of this metabolic difference on clinical efficacy or associated toxicity is still under question. In the search for clues as to the underlying aetiology, patient groups with many disease states have been examined for association with differences in N-acetylation and the majority have provided data that could be interpreted as equivocal. Studies have given contradictory, often opposing, results, calculated risk factors that are (perhaps) just significant but certainly not high, and patients within the cohorts who are always exceptions. Undoubtedly, other as yet unappreciated factors are at play.

The role of lysine(100) in the binding of acetylcoenzyme A to human arylamine N-acetyltransferase 1: implications for other acetyltransferases

The arylamine N-acetyltransferases (NATs) catalyze the acetylation of aromatic and heterocyclic amines as well as hydrazines. All proteins in this family of enzymes utilize acetyl coenzyme A (AcCoA) as an acetyl donor, which initially binds to the enzyme and transfers an acetyl group to an active site cysteine. Here, we have investigated the role of a highly conserved amino acid (Lys(100)) in the enzymatic activity of human NAT1. Mutation of Lys(100) to either a glutamine or a leucine significantly increased the Ka for AcCoA without changing the Kb for the acetyl acceptor p-aminobenzoic acid. In addition, substrate inhibition was more marked with the mutant enzymes. Steady state kinetic analyzes suggested that mutation of Lys(100) to either leucine or glutamine resulted in a less stable enzyme-cofactor complex, which was not seen with a positively charged arginine at this position. When p-nitrophenylacetate was used as acetyl donor, no differences were seen between the wild-type and mutant enzymes because p-nitrophenylacetate is too small to interact with Lys(100) when bound to the active site. Using 3'-dephospho-AcCoA as the acetyl donor, kinetic data confirmed that Ly(100) interacts with the 3'-phosphoanion to stabilize the enzyme-cofactor complex. Mutation of Lys(100) decreases the affinity of AcCoA for the protein and increases the rate of CoA release. Crystal structures of several other unrelated acetyltransferases show a lysine or arginine residue within 3Å of the 3'-phosphoanion of AcCoA, suggesting that this mechanism for stabilizing the complex by the formation of a salt bridge may be widely applicable in nature.

Ontogeny of mammalian metabolizing enzymes in humans and animals used in toxicological studies

It is well recognized that expression of enzymes varies during development and growth. However, an in-depth review of this acquired knowledge is needed to translate the understanding of enzyme expression and activity into the prediction of change in effects (e.g. kinetics and toxicity) of xenobiotics with age. Age-related changes in metabolic capacity are critical for understanding and predicting the potential differences resulting from exposure. Such information may be especially useful in the evaluation of the risk of exposure to very low (µg/kg/day or ng/kg/day) levels of environmental chemicals. This review is to better understand the ontogeny of metabolizing enzymes in converting chemicals to either less-toxic metabolite(s) or more toxic products (e.g. reactive intermediate[s]) during stages before birth and during early development (neonate/infant/child). In this review, we evaluated the ontogeny of major "phase I" and "phase II" metabolizing enzymes in humans and commonly used experimental animals (e.g. mouse, rat, and others) in order to fill the information gap.

N-acetyltransferase-2 genotypes among patients with rheumatoid arthritis attending Jordan University Hospital

AIM

To determine the frequency of major N-acetyltransferase (NAT2) alleles and genotypes among Jordanian patients with rheumatoid arthritis (RA).

METHODS

The study was approved by the IRB of the Jordan University Hospital. An informed consent was signed by every patient. DNA samples from 150 healthy volunteers and 108 patients with RA were analyzed by polymerase chain reaction followed by a restriction fragment length polymorphism assay (PCR-RFLP) to determine the frequency of four major alleles: NAT2*4, NAT2*5, NAT2*6, and NAT2*7.

RESULTS

The most prevalent genotypes are those that encode the slow acetylation phenotype. About 59.3% of the patients with RA carried the slow, 33.3% the intermediate, and 7.4% the fast-encoding genotypes. The frequency of NAT2 alleles was 0.241 (95% confidence interval [CI] 0.184-0.298) for NAT2*4, 0.449 (95% CI 0.383-0.515) for NAT2*5, 0.273 (95% CI 0.214-0.332) for NAT2*6, and 0.037 (95% CI 0.012-0.062) for NAT2*7 allele. The overall frequency of the slow acetylation genotype in patients with RA is similar to that in healthy Jordanian volunteers. However, the NAT2*5/7 genotype was found in seven patients (6.5%) with RA and was absent in Jordanian volunteers, and the z test revealed that the difference was statistically significant. This genotype constituted 10.9% of the genotypes encoding slow acetylation.

CONCLUSION

The overall acetylator genotype in RA is similar to that in healthy volunteers. The overall slow acetylator genotypes do not seem to be a genetic risk factor for RA among Jordanians. However, the NAT2*5/7 genotype seems to be related to RA. The nature of this relationship needs further clarification.

Genetic factors in contact allergy--review and future goals

The genetics of contact allergy are still only partly understood, despite decades of research; this might be a consequence of inadequately defined phenotypes used in the past. A recommendation is to study an extreme phenotype, namely, polysensitization (sensitization to three or more unrelated allergens). Another approach to unravel the genetics of contact allergy is the study of candidate genes. In this review, we summarize studies on the associations between genetic variation (e.g. single-nucleotide polymorphisms) in certain candidate genes and contact allergy. Polymorphisms and mutations affecting the following proteins were studied: (i) filaggrin; (ii) N-acetyltransferase (NAT) 1 and 2; (iii) glutathione-S-transferase (GST) M and T; (iv) manganese superoxide dismutase; (v) angiotensin-converting enzyme (ACE); (vi) tumour necrosis factor (TNF); and (vii) interleukin-16 (IL-16). The polymorphisms of NAT1, NAT2, GSTM, GSTT, ACE, TNF and IL-16 were shown to be associated with an increased risk of contact allergy. In one of our studies, the increased risk conferred by the TNF and IL-16 polymorphisms was confined to polysensitized individuals. Other relevant candidate genes may be identified by studying diseases related to contact allergy in terms of clinical symptoms, a more general pathology (inflammation), and possibly an overlapping genetic background, such as irritant contact dermatitis.

Genetics of food allergy

PURPOSE OF REVIEW

Food allergy, a growing clinical and public health problem in the United States and worldwide, is likely determined by multiple environmental and genetic factors. The purpose of this review is to summarize recent advances in food allergy genetic research.

RECENT FINDINGS

There is compelling evidence that genetic factors may play a role in food allergy. However, the specific genetic loci that may modulate individual risk of food allergy remain to be identified. To date, only a limited number of candidate gene association studies of food allergy have been reported. Polymorphism(s) in nine genes have been associated with the incidence of food allergy or food allergy severity in at least one study. But most of these findings remain to be replicated in independent populations. In contrast, there are considerable advances in genetics of other allergic diseases such as asthma and atopic dermatitis. Although asthma and atopic dermatitis often coexist with food allergy, the relevance of their candidate genes to food allergy remains to be evaluated.

SUMMARY

Genetics in food allergy is a promising research area but is still in its infancy. More studies are needed to dissect susceptible genes of food allergy. A genome-wide association approach may serve as a powerful tool to identify novel genes related to food allergy. Furthermore, the role of gene-environment interaction, gene-gene interaction, and epigenetics in food allergy remains largely unexplored. Given the complex nature of food allergy, future studies need to integrate environment, genomics, and epigenomics in order to better understand the multifaceted etiology and biological mechanisms of food allergy.

N-acetyltransferase 2 (NAT2) polymorphism in patients with atopic asthma

BACKGROUND AND AIMS

Allergic asthma is a chronic inflammatory disorder of the airways where, on exposure to allergens, the body mounts an immune response. The etiology of asthma is complex and multifactorial. Rapid and slow acetylators reflect the genetically determined variation in the elimination of xenobiotics. Recent advances have demonstrated the importance of genetic and environmental factors in the development of atopic asthma. Hepatic arylamine N-acetyltransferase 2 (NAT2) takes part in the detoxification of some drugs and arylamine xenobiotics. The aim of the present study was to determine the NAT2 polymorphism in patients with atopic asthma.

METHODS

In the study, 184 unrelated asthmatic patients and 181 healthy controls were included. The mutations at positions 481T, 803G, 590A and 857A of the NAT2 gene were determined by a polymerase chain reaction-restriction fragment length polymorphism assay (PCR-RFLP).

RESULTS

The frequency of homozygous fast acetylators did not differ significantly between patients and controls. Compared with the control population, the significant prevalence of slow acetylators in the group of patients with atopic asthma was observed. There was a statistically significant prevalence of subjects with NAT2*5/NAT2*5 and NAT2*5/NAT2*6 genotypes. The risk of an atopic asthma development was 3.4 times greater in slow than in fast acetylators (OR = 3.3657; p <0.000001, 95% CI = 2.1282-5.3228).

CONCLUSIONS

These results suggest that NAT2 polymorphism may be involved in the pathogenesis of atopic asthma.

Genetic susceptibility to atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder with an increasing prevalence in industrialized countries. AD belongs to the group of allergic disorders that includes food allergy, allergic rhinitis, and asthma. A multifactorial background for AD has been suggested, with genetic as well as environmental factors influencing disease development. Recent breakthroughs in genetic methodology have greatly augmented our understanding of the contribution of genetics to susceptibility to AD. A candidate gene association study is a general approach to identify susceptibility genes. Fifty three candidate gene studies (50 genes) have identified 19 genes associated with AD risk in at least one study. Significant associations between single nucleotide polymorphisms (SNPs) in chemokines (chymase 1-1903A > G), cytokines (interleukin13 Arg144Gln), cytokine receptors (interleukin 4 receptor 1727G > A) and SPINK 1258G > A have been replicated in more than one studies. These SNPs may be promising for identifying at-risk individuals. SNPs, even those not strongly associated with AD, should be considered potentially important because AD is a common disease. Even a small increase in risk can translate to a large number of AD cases. Consortia and international collaborative studies, which may maximize study efficacy and overcome the limitations of individual studies, are needed to help further illuminate the complex landscape of AD risk and genetic variations.

Lack of impact of artesunate on the disposition kinetics of sulfadoxine/pyrimethamine when the two drugs are concomitantly administered

OBJECTIVE

To determine the effect of artesunate (AT) on the disposition kinetics of sulfadoxine/pyrimethamine (SP) in humans.

METHODS

In a randomized cross-over study, 16 healthy volunteers were given a dose of three SP tablets containing 500 mg of sulfadoxine (SDX) and 25 mg of pyrimethamine (PYR) (=SP group), while the second arm received three SP tablets + two AT tablets of 200 mg in total followed by 100 mg AT for the next 4 days (SP+AT group). Blood samples (100 microl) were collected by means of a finger prick and dried on filter paper. The blood spots were wrapped in polythene folders and stored at room temperature until analysis. The samples were assayed using high-performance liquid chromatographic methods.

RESULTS

The peak concentration C(max)), time required to attain peak concentration (T(max)), half-life (t ((1/2))) and area under the plasma concentration-time curve (AUC) were determined. The C(max) of SDX were 92.9 and 98.9 microg/ml for the SP and SP+AT arms, respectively; for PYR, these were 0.86 and 0.79 microg/ml, respectively. The T(max) of SDX were 10 and 8 h for the SP and SP+AT arms, respectively; for PYR, these were 4.0 and 3.0 h, respectively. The AUC(0-288) of SDX were 15,840 and 18,876 microg/ml h for the SP and SP+AT arms, respectively; for PYR, they were 124 and 112 microg/ml h, respectively. The t ((1/2)) of values for SDX were 165 and 180 h for the SP and SP+AT arms, respectively; for PYR, these were 158 and 177 h, respectively. There was no statistically significant difference between the C(max), T(max), AUC(0-288) and t ((1/2)) between the two arms (p > 0.05).

CONCLUSION

Taking AT concomitantly with SP does not have any impact in the disposition of SP.

Arylamine N-acetyltransferase gene polymorphisms: markers for atopic asthma, serum IgE and blood eosinophil counts

INTRODUCTION

Polymorphisms in N-acetyltransferase 2 (NAT2), present on chromosome 8p22, are responsible for the N-acetylation variants, which segregate human populations into rapid, intermediate and slow acetylators and influence the susceptibility towards atopic disorders. We have undertaken a study of the North Indian population to screen for various NAT2 polymorphisms and to investigate their association with atopic asthma and related phenotypes.

METHODS

First, to establish linkage of the 8p22 region with asthma, 158 families were recruited from North India. Next, a total of 219 unrelated atopic asthmatics and 210 unrelated healthy controls were recruited for case-control disease association studies.

RESULTS

A suggestive linkage was observed with microsatellite marker D8S549, 2.6 MB upstream of NAT2. By sequencing the DNA of 40 individuals, the T111C, G191A, A434C and C759T single nucleotide polymorphisms (SNPs) in NAT2 were found to be nonpolymorphic in our population and a pattern of strong linkage disequilibrium was observed among the T341C, C481T and A803G polymorphisms. Thus, a total of 429 individuals were genotyped for the C481T and unlinked C282T polymorphisms. The C481T polymorphism was found to be significantly associated with asthma in our case-control studies at the genotype level (Armitage p = 0.00027). C481T also showed a marginal association with serum total IgE (TsIgE) (p = 0.022). Furthermore, percent blood eosinophil counts were found to be significantly higher in patients carrying the 481T allele (p = 0.0037). Significant association was also detected with respect to the C282T polymorphism and TsIgE (p = 0.008). Moreover, C_T was found to be an important risk (p = 0.001), while C_C was a major protective haplotype (p = 0.0005). The associations remained significant after Bonferroni correction for multiple testing.

CONCLUSION

In summary, the genetic variants of the NAT2 gene do not seem to affect asthma alone, but act as modulators of asthma-related traits, such as serum IgE and blood eosinophil counts, and therefore could serve as genetic markers.

Human arylamine N-acetyltransferase 2 polymorphism and susceptibility to allergic contact dermatitis

BACKGROUND

N-acetyltransferase 2 (NAT2) polymorphism may be involved in the pathogenesis of allergic contact dermatitis.

OBJECTIVE

The present study was designed to evaluate whether acetylation polymorphism plays a role in the susceptibility to p-Phenylenediamine (PPD) sensitization.

METHODS

The frequencies of seven NAT2 point mutations, namely G191A, C282T, T341C, C481T, G590A, A803G, and G857A, and genotypes were determined by PCR/RFLP in a total of 70 patients with allergic contact dermatitis to PPD and 100 control subjects with no history of allergy, atopy, lung disease, diabetes mellitus and cancer.

RESULTS

Genotypes coding rapid acetylation were detected in 52.9% and 37.0% of patients with contact dermatitis and control subjects, respectively (P = 0.04). The frequency of the NAT2*4 allele and NAT2*4/*4 genotype, coding for rapid acetylation, were also significantly higher in the contact dermatitis patients than in the control subjects (P = 0.003).

CONCLUSION

Our results suggest an association between rapid acetylation polymorphism and susceptibility to PPD sensitization.

N-acetyltransferase 2 phenotype may be associated with susceptibility to age-related cataract

Free radicals and oxidative damage play roles in aging and age-related ocular diseases such as cataracts, so defensive mechanisms become important factors for protection. Because N-acetylation is involved in a wide variety of detoxification processes, this study was conducted to examine the relationship between the acetylator phenotypes and genotypes in a group of patients with age-related cataract. Sixty-one cases of age-related cataract and 104 controls were included in this study. Blood was collected in EDTA-containing tubes, and genomic DNA was extracted from the white blood cells by high pure PCR template preparation kit. Genotyping of NAT2 polymorphisms were detected by using a LightCycler-NAT2 mutation detection kit in real-time PCR. There was a significant difference in the distribution of the NAT2*6A acetylator phenotype between cases and the controls. The odds ratio of cataract for the NAT2*6A slow phenotype was 3.8 (95% CI = 1.08 to 13.11, p = 0.032) compared with the fast type. Our results suggest that slow acetylators are at higher risk of developing age-related cataracts than fast acetylators. As NAT2 is an important xenobiotic-metabolizing enzyme and theoretically xenobiotics such as ultraviolet B radiation, smoking, and alcohol use may induce cataract formation, NAT2 gene polymorphisms may be associated with genetic susceptibility of cataract.

Ontogeny of drug metabolizing enzymes in the neonate

Fetal exposure to xenobiotics is modulated to a considerable degree by the metabolic capabilities of the mother and the placenta. However, once liberated from the uterine environment the neonate is instantly exposed to a wide array of new macromolecules in the form of byproducts of cellular metabolism, dietary constituents, environmental toxins and pharmacologic agents. The rapid and efficient biotransformation of these compounds by Phase I and Phase II drug-metabolizing enzymes is an essential process if the infant is to avoid the accumulation of reactive compounds that could produce cellular injury or tissue dysfunction. Genetic polymorphisms and environmental factors are known to contribute dramatically to individual variation in the activity of drug-metabolizing enzymes. More recently, it has become apparent that programmed, developmental, regulatory events occur - independent of genotype - which further add to individual variation in drug metabolism. An appreciation of the impact of ontogeny on the expression and functional activity of the major drug-metabolizing enzymes enables the practicing clinician to predict the ultimate consequence of drug administration in the neonate to help guide optimal drug therapy.

Protective role of glutathione S-transferase P1 (GSTP1) Val105Val genotype in patients with bronchial asthma

BACKGROUND

Glutathione S-transferase P1 (GSTP1), the abundant isoform of glutathione S-transferases (GSTs) in lung epithelium, plays an important role in cellular protection against oxidative stress and toxic foreign chemicals. It has been suggested that polymorphisms in the GSTP1 gene are associated with asthma and related phenotypes. As significant interindividual and interethnic differences exist in the distribution of xenobiotic-metabolizing enzymes, we have studied the GSTP1 Ile105Val polymorphism in patients with asthma in a Turkish sample.

METHODS

GSTP1 Ile105Val polymorphism in exon 5 was determined in 210 patients with asthma (112 extrinsic and 108 intrinsic) and 265 control individuals without lung diseases and without history of allergy or atopy, using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) techniques.

RESULTS

The proportion of GSTP1 Val105 homozygotes was significantly lower in the patients with asthma than in the control individuals (3.8% vs 12.1%). The odds ratio for GSTP1 Val105 homozygotes vs all other genotypes was 0.29 (95%CL 0.13-0.64, p = 0.01) for asthmatics. The distribution of GSTP1 Ile105Val genotypes and the frequency of GSTP1 Val105Val homozygotes (3.7% vs 3.9%) was not significantly different between extrinsic and intrinsic asthmatics.

CONCLUSION

These results suggest a significant association between GSTP1 Ile105Val polymorphism and susceptibility to asthma and that the GSTP1 Val105Val genotype may be protective against developing this disease.

Association studies for asthma and atopic diseases: a comprehensive review of the literature

Hundreds of genetic association studies on asthma-related phenotypes have been conducted in different populations. To date, variants in 64 genes have been reported to be associated with asthma or related traits in at least one study. Of these, 33 associations were replicated in a second study, 9 associations were not replicated either in a second study or a second sample in the same study, and 22 associations were reported in just a single published study. These results suggest the potential for a great amount of heterogeneity underlying asthma. However, many of these studies are methodologically limited and their interpretation hampered by small sample sizes.

NAT2 slow acetylator function as a risk indicator for age-related cataract formation

OBJECTIVES

To show that the slow arylamine N-acetyltransferase type 2 (NAT2) catalysed acetylator function is associated with the development of age-related cataracts.

METHODS

Both the acetylator phenotype and genotype of 139 patients with age-related cataracts were determined, and the distribution of the acetylator subtypes in the case population was compared with the distribution in the general (control) population. The genotype was determined by restriction-enzyme analysis of DNA, and the phenotype was determined using the elimination characteristics of isoniazid as discriminant.

RESULTS

The frequency of alleles coding for slow acetylator characteristics was higher in the patients than in the controls, and the difference was significant (P = 0.013).

CONCLUSIONS

Slow acetylators are at higher risk of developing age-related cataracts than fast acetylators and we suggest that exogenous factors, which can be detoxified by acetylation, are aetiological agents for cataract formation. Identification of and avoidance of such (environmental) agents should reduce the incidence of age-related cataracts.

Association between the N-acetylation genetic polymorphism and bronchial asthma

AIMS

Since polymorphic N-acetyltransferase 2 (NAT2) has been suggested as a susceptibility factor for atopic diseases, the study was undertaken to investigate whether an association exists between acetylation polymorphism and asthma patients with atopy.

METHODS

The frequencies of NAT2 alleles and genotypes were determined by PCR/RFLP in a total of 210 asthma patients (extrinsic (n = 108) and intrinsic (n = 102) asthmatics) and 240 control subjects. Presence of the NAT2*4 (wild-type) allele defined a NAT2 genotype as rapid and combinations of mutant alleles NAT2*5 A, *5B, *5C, *6 A, and *7B as slow.

RESULTS

Genotypes coding for slow acetylation were detected in 70.4, 58.4 and 58.3% of extrinsic asthmatics, but intrinsic asthmatics and control subjects, respectively. The frequency of slow acetylators was higher among extrinsic asthmatics than intrinsic asthmatics, this difference did not reach statistical significance (odds ratio 1.02, 95% confidence interval 0.64, 1.63, P = 0.085). However, we found a relatively moderate, but significantly higher, increased frequency of slow acetylators among extrinsic asthma patients compared with control subjects (odds ratio 1.70, 95% confidence interval 1.04, 2.76, P = 0.042).

CONCLUSIONS

This study shows an association between acetylation polymorphism and susceptibility to extrinsic asthma, but not to intrinsic asthma, suggesting a minor role of the NAT2 polymorphism in the development of atopic asthma.

Lack of association between arylamine N-acetyltransferase 2 (NAT2) polymorphism and systemic lupus erythematosus

The slow arylamine -acetyltransferase 2 (NAT2) phenotype frequently has been assumed to be associated with an elevated risk to develop a lupus-like syndrome after administration of drugs such as procainamide or hydralazine. Moreover, there are conflicting data on the role of acetylator phenotype as a susceptibility factor for systemic lupus erythematosus (SLE). Because most investigations have previously been conducted with relatively small sample sizes, the present study was performed to clarify the possible association between genotypes and SLE among a large European cohort. In a case-control study, 209 patients with SLE (194 women, 15 men) were enrolled and matched by gender to 209 controls without clinical signs of inflammatory diseases. All SLE patients fulfilled at least four of the revised American College of Rheumatology classification criteria of SLE. was genotyped for seven known mutations by polymerase chain reaction/restriction fragment length polymorphism. The frequency of slow acetylation genotypes in SLE patients (59.8%) did not differ significantly from controls (56.5%). The adjusted odds ratio (OR) was 0.95 (95% confidence interval, 0.59-1.53). Further differentiation to gender, cigarette consumption, allergic disorders and specific SLE manifestations revealed an equal distribution of genotypes in all subgroups. We conclude that this large genotyping study in a Caucasian population demonstrated a lack of evidence for an association of the slow acetylator genotype with SLE.

N-acetyltransferase 1 and 2 polymorphisms in para-substituted arylamine-induced contact allergy

Sensitization to arylamines such as p-phenylenediamine is frequently diagnosed in patients with allergic contact dermatitis. Reactive metabolites of p-phenylenediamine might be produced in the skin by O-acetylation of N-hydroxylamines catalysed by local N-acetyltransferases (NATs). In this study, we tested whether genetic polymorphisms of NATs, which are known to affect enzyme activity, may influence the susceptibility to para-substituted arylamine-induced contact eczema. Using polymerase chain reaction and restriction enzyme analysis, the distribution of polymorphisms of NAT1 and NAT2 was investigated in 88 patients sensitized to para-substituted aryl compounds and 123 healthy controls. NAT2 rapid acetylators, i.e. carriers of the NAT2*4 wild-type allele, were more common in the contact allergy (44%) than in the healthy control group [30%; P = 0.042, odds ratio 1.9 (95% confidence interval, CI 1. 05-3.27)]. Slow acetylators carrying the NAT2*5b/2*6a genotype were significantly less frequent among patients [13% vs. 38% in controls; P = 0.009, odds ratio 0.39 (95% CI 0.19-0.78)]. The carriage rate of the NAT1*10 allele, which is supposed to encode for a rapid NAT1 phenotype, was not significantly different between patients and controls [43% vs. 36%; odds ratio 1.5 (95% CI 0.88-2.68)]. Interactions between NAT2*4 and NAT1*10 were suggested by the increased frequency of the NAT2*4/NAT1*10 haplotype in patients (27%) compared with controls [15%; P = 0.039, odds ratio 2.1 (95% CI 1.04-4.04)]. As the NAT1 and NAT2 encoding genes are located in close proximity on chromosome 8p22, the latter finding could at least partly be due to genetic linkage. In fact, a linkage disequilibrium between NAT2*4 and NAT1*10 was observed in the contact allergy (P = 0.0025) and in the control group (P = 0.042). Our data indicate an association between the NAT2*4/NAT1*10 haplotype and contact sensitization to para-substituted aryl compounds. Therefore, acetylation may either enhance contact sensitization or NAT2*4 and NAT1*10 might be linked to an unknown susceptibility factor.

Gender-specific effects of NAT2 and GSTM1 in bladder cancer

One approach for risk assessment of cancer is the evaluation of polymorphic enzymes involved in cancer using molecular tools. Phase II enzymes are involved in the detoxification of several drugs, environmental substances and carcinogenic compounds. Here, we analyzed enzymes for their putative relevance in urinary bladder cancer. The hereditable enzyme polymorphism of arylamine N-acetyltransferase 2 (NAT2) and glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) was studied in 157 hospital-based patients and in 223 control subjects. Slow acetylation was not observed to be a significant risk factor of developing bladder cancer (OR: 1.33; 95% CI 0.85-2.09). One genotype responsible for slow acetylation (NAT2*5B/*6A) was observed significantly more frequently in bladder cancer patients compared with control subjects (OR: 1.63; 95% CI 1.03-2.58). Gender-specific effects were observed when patients were divided into subgroups. In male patients, slow acetylators were identified as carrying a significant increased risk of developing bladder cancer, in particular when the genotype NAT2*5B/*6A was combined with the GSTM1 null genotype (OR: 4.39; 95% CI 1.98-9.74). By contrast, the same genotype combination significantly protected female patients from bladder cancer (OR: 0.21; 95% CI 0.06-0.80).

Comparison of acetylation phenotype with genotype coding for N-acetyltransferase (NAT2) in children

The present study focused on evaluation of the extent to which genotype coding for N-acetyltransferase agrees with acetylation phenotype in children at various ages. In 82 Caucasian children aged from 1 mo to 17 y (57 boys and 25 girls) and including 37 infants, the acetylation phenotype was evaluated from the urinary metabolic ratio of 5-acetylamino-6-formylamino-3-methyluracil (AFMU) to 1-methylxanthine (1X) after oral administration of caffeine. At the same time, by use of PCR and restriction analysis of amplified fragments of the N-acetyltransferase gene, four nucleotide transitions were identified: 481C-->T (KpnI), 590 G-->A (TaqI), 803 A-->G (DdeI), and 857 G-->A (BamHI). The wild-type allele was detected in 27 (33%) children, and the slow acetylation genotype was found in 55 (67%) children. The results of the study show that the metabolic ratio AFMU/1X could be calculated only in 72 children, because in 10 (14%) infants <20 wk of age, AFMU was not detected. Determination of the relation between the acetylation phenotype and genotype revealed that 18 children (23%) containing at least one wild-type allele had AFMU/1X <0.4 (slow acetylation activity) and 7 (8%) of genotypically slow acetylators presented high metabolic ratio (high acetylation activity). We concluded that the disagreement between the acetylation phenotype and genotype is more often found in the group of children characterized by low AFMU/1X and that in small children only N-acetyltransferase genotype studies enable the detection of genetic acetylation defect.