Lack of association between slow acetylator status and spontaneous lupus erythematosus

Genetic Polymorphisms and the Clinical Response to Systemic Lupus Erythematosus Treatment Towards Personalized Medicine

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by a broad spectrum of clinical manifestations, an aberrant autoimmune response to self-antigens, which affect organs and tissues. There are several immune-pathogenic pathways, but the exact one is still not well known unless it is related to genetics. SLE and other autoimmune diseases are known to be inseparable from genetic factors, not only pathogenesis but also regarding the response to therapy. Seventy-one human studies published in the last 10 years were collected. Research communications, thesis publication, reviews, expert opinions, and unrelated studies were excluded. Finally, 32 articles were included. A polymorphism that occurs on the genes related to drugs pharmacokinetic, such as CYP, OATP, ABC Transporter, UGT, GST or drug-target pharmacodynamics, such as FCGR, TLR, and BAFF, can change the level of gene expression or its activity, thereby causing a variation on the clinical response of the drugs. A study that summarizes gene polymorphisms influencing the response to SLE therapy is urgently needed for personalized medicine practices. Personalized medicine is an effort to provide individual therapy based on genetic profiles, and it gives better and more effective treatments for SLE and other autoimmune disease patients.

Cigarette smoking, N-acetyltransferase 2 polymorphisms and systemic lupus erythematosus in a Japanese population

Cigarette smoking may be associated with an increased risk of systemic lupus erythematosus (SLE), but the underlying mechanism of this association remains unclear. N-acetyltransferase 2 (NAT2) is highly variable and detoxifies aromatic amines, an important class of carcinogens in tobacco smoke. Individuals who possess homozygous polymorphic alleles have a slower rate of metabolic detoxification of aromatic amines. We investigated the relationship of the NAT2 polymorphism to the risk of SLE with special reference to the interaction with cigarette smoking among 152 SLE cases and 427 controls in a female Japanese population. NAT2*4, NAT2*5B, NAT2*6A and NAT2*7B alleles were detected with polymerase chain reaction–restriction fragment length polymorphism. Individuals carrying the *4/*4 genotype are rapid acetylators, whereas those with homozygous non-*4 genotypes have a slow acetylator phenotype. Cigarette smoking was associated with an increased risk of SLE (odds ratio [OR] = 2.26; 95% confidence interval [CI] = 1.46–3.50). The slow acetylator genotype of NAT2 was significantly associated with an increased risk of SLE (OR = 2.34, 95% CI = 1.21–4.52) compared with the rapid acetylator genotype. A gene-environment interaction was suggested, with a combination of the NAT2 slow acetylator genotype and smoking conferring significantly higher risk (OR = 6.44, 95% CI = 3.07–13.52; attributable proportion due to interaction = 0.50, 95% CI = 0.12–0.88), compared with the NAT2 rapid acetylator genotype and no history of smoking. This study suggests that, in this Japanese population, the NAT2 slow acetylator status may be a determinant in susceptibility to SLE.

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.

Polymorphisms of the xenobiotic-metabolizing enzymes CYP1A1 and NAT-2 in systemic sclerosis and lupus erythematosus

The etiology of systemic autoimmune diseases, such as systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) is still unknown. In several cases, however, xenobiotics (i.e. drugs and occupational agents) were identified as etiologic agents and associations with certain polymorphic alleles of xenobiotic-metabolizing enzymes have been reported. Cytochrome P4501A1 (CYP1A1) and N-acetyltransferase 2 (NAT-2) are xenobiotic-metabolizing enzymes of phase 1- and phase 2-metabolism, respectively. CYP1A1 may activate drugs and other chemicals to reactive metabolites. NAT-2 is the most important enzyme in acetylation of aromatic amines, and thus may be responsible for detoxification of many of these compounds. Two polymorphisms of the human CYP1A1 gene, a point mutation in the 3' flanking region of the gene (Msp1) and a mutation in exon 7 leading to an isoleucine-valine-exchange in the heme-binding region of the enzyme, have been described and may lead to a higher basal and inducible enzyme activity. With respect to NAT-2, several alleles which combine for the two phenotypes "fast" and "slow" acetylators have been described. We analyzed the gene frequencies of the CYP1A1 polymorphisms and the phenotypes of NAT-2 in patients suffering from idiopathic SLE or SSc. CYP1A1 polymorphisms were analyzed in genomic DNA by PCR, whereas NAT-2 phenotypes were measured by the caffeine method. For CYP1A1 polymorphisms, 106 patients have been typed until now. The SLE group (n = 68) exhibited a significant increase (p < 0.05) in the mutant Val-allele (OR = 2.59) when compared to controls (n = 184). However, no significant differences in allele frequencies for MspI in the SLE group and for both CYP1A1 polymorphisms in the SSc group could be observed. Regarding the NAT-2 phenotype, patients suffering from SLE (n = 88) 75% and SSc (n = 26) 80.2%, respectively, were slow acetylators compared to 55% slow acetylators in the healthy German population (p < 0.05). The observed increased frequencies of the CYP1A1 mutant Val-allele and the slow actylator phenotype in idiopathic autoimmune disease support our concept that in slow acetylators non-acetylated xenobiotics may accumulate and are subsequently metabolized by other enzymes into reactive intermediates. Thus, enhanced formation of reactive metabolites could alter self-proteins presented to the immune system thus stimulating autoreactive T cells which induce autoimmunity.

Polymorphic acetylation: lack of influence of rheumatic disease activity and concomitant drug administration

Acetylation polymorphisms have been linked with a tendency to develop rheumatic diseases. We investigated the effect of changes in the disease activity of patients with rheumatoid arthritis (RA) during disease-modifying antirheumatic drug (DMARD) treatment, and on the capacity of these patients to acetylate the sulphonamide sulphadimidine. Fifty-four patients with RA treated with gold, sulphasalazine or D-penicillamine, 12 patients with AS and 16 patients with non-inflammatory arthritis (NI) were investigated over a 24-week period. The capacity of these individuals to acetylate sulphadimidine was determined at baseline and after 12 and 24 weeks. Although there was a tendency for sulphadimidine acetylation to increase in patients with RA from a median of 84.5% [interquartile range (IQR) 77.0-95.0%] at baseline to 90.5% (IQR 77.5-96.0%) at week 24, this failed to reach statistical significance. In contrast, the trend in patients with AS or NI was towards a decrease in acetylation. There was no correlation between changes in disease activity and sulphadimidine acetylation during DMARD intervention.

Major histocompatibility complex haplotypes and complement C4 alleles in systemic lupus erythematosus. Results of a multicenter study

In a multicenter study more than 300 central European systemic lupus erythematosus (SLE) patients were examined for HLA-B, HLA-DR, and complement C4 phenotypes. For 174 SLE patients MHC haplotypes were determined by family segregation analysis, and for 155 patients C4 gene deletions were determined by TaqI restriction fragment length polymorphism. Two haplotypes, B8-C4AQ0-C4B1-DR3 and B7-C4A3-C4B1-DR2, were identified as risk factors for SLE. These findings were confirmed by applying the haplotype frequency difference (HFD) method, which uses nontransmitted haplotypes from the family study as internal controls. Furthermore, only HLA-DR2, but not DR3, B7, or B8, was significantly increased in SLE patients independently of the two risk haplotypes. C4A gene deletions, but not silent C4AQ0 alleles, were increased in SLE patients and neither C4BQ0 alleles nor C4B gene deletions were increased. The observed frequencies of homozygosity and heterozygosity for the two haplotypes and the frequencies of homozygotes for C4AQ0 and C4A deletions did not differ from the expected values, indicating that the risk for SLE is conveyed by single allele effects. In conclusion, there are two MHC-linked susceptibility factors for Caucasian SLE patients carried by the haplotypes B7-DR2 and B8-DR3. The results argue against C4Q0 alleles being the decisive factors increasing susceptibility to SLE.

Systemic lupus erythematosus (SLE)-like syndromes associated with carbamazepine therapy

Records of 80 cases of systemic lupus erythematosus (SLE)-like syndromes associated with use of carbamazepine entered in the single case files of Central Drug Monitoring, Ciba-Geigy, Basel, were reviewed. Included in these were 11 cases reported in the literature. These were assessed in light of the current concepts of both idiopathic and drug-induced forms of SLE. Even allowing for under-reporting of adverse drug reactions, the number of such cases is far below the prevalence rates for SLE. This adverse drug reaction remains allocated to the category 'isolated cases' i.e. frequency is less than 0.001% of the cases treated. Antinuclear antibody (ANA) and anti-double-stranded DNA (anti-dsDNA) tests were not helpful in differentiating between idiopathic and drug-induced SLE. IgG antihistone antibodies in the absence of high titres of dsDNA antibodies is the only reliable test. Symptoms of SLE-like syndromes which manifest after carbamazepine therapy usually subside after discontinuation of the drug. Persistence of symptoms support the diagnosis of idiopathic SLE.