Histamine pharmacogenomics

Involvement of human histamine N-methyltransferase gene polymorphisms in susceptibility to atopic dermatitis in korean children

Purpose

Histamine N-methyltransferase (HNMT) catalyzes one of two major histamine metabolic pathways. Histamine is a mediator of pruritus in atopic dermatitis (AD). The aim of this study was to evaluate the association between HNMT polymorphisms and AD in children.

Methods

We genotyped 763 Korean children for allelic determinants at four polymorphic sites in the HNMT gene: -465T>C, -413C>T, 314C>T, and 939A>G. Genotyping was performed using a TaqMan fluorogenic 5' nuclease assay. The functional effect of the 939A>G polymorphism was analyzed.

Results

Of the 763 children, 520 had eczema and 542 had atopy. Distributions of the genotype and allele frequencies of the HNMT 314C>T polymorphism were significantly associated with non-atopic eczema (P=0.004), and those of HNMT 939A>G were significantly associated with eczema in the atopy groups (P=0.048). Frequency distributions of HNMT -465T>C and -413C>T were not associated with eczema. Subjects who were AA homozygous or AG heterozygous for 939A>G showed significantly higher immunoglobulin E levels than subjects who were GG homozygous (P=0.009). In U937 cells, the variant genotype reporter construct had significantly higher mRNA stability (P<0.001) and HNMT enzyme activity (P<0.001) than the common genotype.

Conclusions

Polymorphisms in HNMT appear to confer susceptibility to AD in Korean children.

Association of single nucleotide polymorphisms in the diamine oxidase gene with diamine oxidase serum activities

BACKGROUND

Histamine intolerance (HIT) is associated with an excess of histamine because of an impaired function of the histamine-degrading enzyme diamine oxidase (DAO). The genetic background of HIT is unknown yet.

METHODS

Case-control association study of all haplotype tagging and four previously reported DAO SNPs and one HNMT Single nucleotide polymorphism with symptoms of HIT and DAO serum activity in 484 German individuals including 285 patients with clinical symptoms of HIT and 199 controls.

RESULTS

Diamine oxidase serum activity was significantly associated with seven SNPs within the DAO gene. The minor allele at rs2052129, rs2268999, rs10156191 and rs1049742 increased the risk for a reduced DAO activity whereas showing a moderate protective effect at rs2071514, rs1049748 and rs2071517 in the genotypic (P = 2.1 × 10(-8) , 7.6 × 10(-10) , 8.3 × 10(-10) , 0.009, 0.005, 0.00001, 0.006, respectively) and allelic genetic model (P = 2.5 × 10(-11) , 5.4 × 10(-13) , 8.9 × 10(-13) , 0.00002, 0.006, 0.0003, 0.005, respectively). Reporter gene assays at rs2052129 revealed a lower promoter activity (P = 0.016) of the minor allele. DAO mRNA expression in peripheral blood mononuclear cells of homozygous carriers of the minor allele at rs2052129, rs2268999, rs10156191 was lower (P = 0.002) than homozygous carriers of the major allele. Diamine oxidase variants were not associated with the HIT phenotype per se, only with DAO activity alone and the subgroup of HIT patients displaying a reduced DAO activity.

CONCLUSIONS

DAO gene variants strongly influence DAO expression and activity but alone are not sufficient to fully effectuate the potentially associated disease state of HIT, suggesting an interplay of genetic and environmental factors.

Assessment of nonsteroidal anti-inflammatory drug-induced hepatotoxicity

INTRODUCTION

Liver toxicity related to NSAIDs is of outstanding importance because of the wide use of these drugs. NSAIDs are responsible for roughly 10% of the total of cases of drug-induced hepatotoxicity. The assessment of NSAID-induced hepatotoxicity, presently based on clinical and analytical biomarkers, is critical for early diagnosis and immediate withdrawal of the causing drug.

AREAS COVERED

The review presents an overview of current knowledge of the assessments of NSAID-induced hepatotoxicity with emphasis on the causative drugs, the NSAID-specific mechanisms involved, and a summary of genetic and non-genetic risk factors. Additionally, the authors discuss genetic factors which show NSAID-specific risk, namely CYP2C, UGT2B7, GSTM1 and GSTT1, as well as HLA alleles. The paper includes a list of the NSAID 'usual suspects' that cause hepatotoxicity based on the integrated information of drug-induced hepatotoxicity databases.

EXPERT OPINION

The ultimate goal of this research is pre-prescription testing. Unfortunately, genetic testing, alone, is not sufficient to predict NSAID-induced hepatotoxicity. The development of genetic biomarkers capable of identifying at-risk individuals will not be complete until we develop the ability to fully characterize patients' phenomes and the phenome-genome interaction in patients with NSAID-induced hepatotoxicity. Additionally, a characterization of the metabolic profile of the causative drug in patients with NSAID-induced hepatotoxicity would add crucial information which is presently disregarded in most studies. The full development of robust biomarkers will require the combination of several disciplines including causal statistics, phenomics, genomics, transcriptomics and metabonomics.

Variability of the L-Histidine decarboxylase gene in allergic rhinitis

BACKGROUND

Nonsynonymous polymorphisms in genes coding for histamine-metabolizing enzymes, diamine oxidase and histamine N-methyltransferase are related to the risk of developing allergic diseases. The role of polymorphisms in the histidine decarboxylase gene remains unexplored. The objective of this study is to identify novel polymorphisms in the human histidine decarboxylase gene and to analyse the clinical association of nonsynonymous polymorphisms with rhinitis.

METHODS

We performed a single-strand conformational polymorphism analysis of the histidine decarboxylase gene sequence. The presence of two nonsynonymous polymorphisms Thr31Met (rs17740607) and Glu644Asp (rs2073440) was analysed in 442 unrelated patients with allergic rhinitis, 233 of whom also had asthma, and in 486 healthy subjects.

RESULTS

We observed three novel polymorphisms designated as ss50402829, ss50402830 and ss50402831-(rs17740607) with allele frequencies = 0.005, 0.208 and 0.073, respectively. Statistically significant differences were observed for the histidine decarboxylase Glu644Asp (rs2073440) polymorphism, with OR (95% CI) values for homozygous carriers of the Glu644 allele equal to 3.12 (1.75-5.56, P < 0.00005) for all patients, 3.38 (1.54-7.44, P = 0.002) for patients with rhinitis alone, and 2.92 (1.43-5.95), P = 0.003 for patients with rhinitis + asthma, when compared with healthy controls. A significant Glu644 gene-dose effect was observed for overall patients (P = 0.0001), for patients with rhinitis alone (P = 0.005) and for patients with rhinitis + asthma (P = 0.010).

CONCLUSIONS

The HDC allele Glu644 in homozygosity increases the risk of developing rhinitis in the studied population. This adds to increasing evidence supporting a prominent role of genetic variations related to histamine homeostasis in the risk to develop allergic diseases.

Polymorphisms of two histamine-metabolizing enzymes genes and childhood allergic asthma: a case control study

Background

Histamine-metabolizing enzymes (N-methyltransferase and amiloride binding protein 1) are responsible for histamine degradation, a biogenic amine involved in allergic inflammation. Genetic variants of HNMT and ABP1 genes were found to be associated with altered enzyme activity. We hypothesized that alleles leading to decreased enzyme activity and, therefore, decreased inactivation of histamine may be responsible for altered susceptibility to asthma.

Methods

The aim of this study was to analyze polymorphisms within the HNMT and ABP1 genes in the group of 149 asthmatic children and in the group of 156 healthy children. The genetic analysis involved four polymorphisms of the HNMT gene: rs2071048 (-1637T/C), rs11569723 (-411C/T), rs1801105 (Thr105Ile = 314C/T) and rs1050891 (1097A/T) and rs1049793 (His645Asp) polymorphism for ABP1 gene. Genotyping was performed with use of PCR-RFLP. Statistical analysis was performed using Statistica software; linkage disequilibrium analysis was done with use of Haploview software.

Results

We found an association of TT genotype and T allele of Thr105Ile polymorphism of HNMT gene with asthma. For other polymorphisms for HNMT and ABP1 genes, we have not observed relationship with asthma although the statistical power for some SNPs might not have been sufficient to detect an association. In linkage disequilibrium analysis, moderate linkage was found between -1637C/T and -411C/T polymorphisms of HNMT gene. However, no significant differences in haplotype frequencies were found between the group of the patients and the control group.

Conclusions

Our results indicate modifying influence of histamine N-methyltransferase functional polymorphism on the risk of asthma. The other HNMT polymorphisms and ABP1 functional polymorphism seem unlikely to affect the risk of asthma.

Analysis of a non-synonymous single nucleotide polymorphism of the human diamine oxidase gene (ref. SNP ID: rs1049793) in patients with Crohn's disease

OBJECTIVE

To analyse the possible influence of a non-synonymous single nucleotide polymorphism (SNP) of the histamine-degrading enzyme diamine oxidase (DAO) on genetic susceptibility to Crohn's disease (CD).

MATERIAL AND METHODS

In this prospective, case-control study, 210 unrelated Caucasian consecutive CD patients were recruited at the Inflammatory Bowel Disease Unit of a single tertiary centre (Hospital Clínico San Carlos) in Madrid, Spain. A total of 261 healthy volunteers from the same geographic area were also recruited and matched with patients. Both cases and controls were analysed for the presence of a non-synonymous SNP (rs1049793) of DAO using amplification-restriction procedures of the genotype obtained in a blood sample.

RESULTS

No significant differences were found in the distribution of carriers of the non-synonymous SNP of DAO between CD patients and controls (OR 1.2 (95% CI 0.9-1.6; p=0.3)). Nor were any differences found between carriers and non-carriers of the non-synonymous SNP in demographic characteristics, phenotypes, complications or treatment of CD.

CONCLUSIONS

The study of a non-synonymous SNP (rs1049793) of DAO does not seem to be of use in assessing susceptibility to CD, either as a marker of disease activity or as a marker of clinical behaviour in patients with the disease.