Polymorphisms of Aspirin-Metabolizing Enzymes CYP2C9, NAT2 and UGT1A6 in Aspirin-Intolerant Urticaria

Acetyl salicylic acid (ASA) is metabolized by UDP-glucuronosyltransferase 1A6 (UGT1A6), cytochrome P4502C9 (CYP2C9), and N-acetyl transferase 2 (NAT2). Variations in the activities of these enzymes may modulate adverse ASA-related symptoms such as urticaria. We examined whether polymorphisms in the UGT1A6, CYP2C9, and NAT2 genes are related to ASA-intolerant urticaria (AIU). The genotypes of 148 subjects with AIU (AIU group) and 260 normal healthy control subjects (NC group) were analyzed with respect to the following single nucleotide polymorphisms: CYP2C9 -1188T>C and CYP2C9*3A1075C; UGT1A6 T181A A>G and UGT1A6 R184S A>C; and NAT2 9796A>T, NAT2 197G>A, NAT2 286G>A, NAT2 9601A>G, and NAT2 9306A>G. There were significant differences in the allele frequencies for the CYP2C9 polymorphisms between the two groups. The frequency of the minor allele CYP2C9 -1188T>C was significantly higher in the AIU group than in the NC group (P=0.005). The frequency of the variant genotype CC was higher in the AIU group compared with the controls in both the co-dominant (P=0.007) and recessive models (P=0.012). The frequency of haplotype 2 [CA] was also significantly higher in the AIU group in both the co-dominant (P=0.006) and dominant models (P=0.012). There was no significant difference in genotype frequencies for any of the UGT1A6 or NAT2 polymorphisms between the two groups. Clinical parameters did not differ according to genotype. These results suggest that the C allele of CYP2C9 -1188T>C may be associated with AIU

Genetic Mechanisms in Aspirin-Exacerbated Respiratory Disease

Aspirin-exacerbated respiratory disease (AERD) refers to the development of bronchoconstriction in asthmatics following the exposure to aspirin or other nonsteroidal anti-inflammatory drugs. The key pathogenic mechanisms associated with AERD are the overproduction of cysteinyl leukotrienes (CysLTs) and increased CysLTR1 expression in the airway mucosa and decreased lipoxin and PGE2 synthesis. Genetic studies have suggested a role for variability of genes in disease susceptibility and the response to medication. Potential genetic biomarkers contributing to the AERD phenotype include HLA-DPB1, LTC4S, ALOX5, CYSLT, PGE2, TBXA2R, TBX21, MS4A2, IL10, ACE, IL13, KIF3A, SLC22A2, CEP68, PTGER, and CRTH2 and a four-locus SNP set composed of B2ADR, CCR3, CysLTR1, and FCER1B. Future areas of investigation need to focus on comprehensive approaches to identifying biomarkers for early diagnosis

No evidence of association between interleukin-13 gene polymorphism in aspirin intolerant chronic urticaria

Aspirin-intolerant chronic urticaria (AICU) is a common condition among the chronic urticaria population, but the genetic mechanism is not yet understood. In this study, the genotypes and haplotypes of three interleukin (IL)-13 polymorphisms, -1510 A>C, -1055C>T, and Arg110Gln (110G>A), as well as their respective clinical phenotypes were examined to determine whether genetic variants of IL-13 play a role in AICU. Single-nucleotide polymorphism (SNP) genotyping was used to compare IL-13 genotype and allele frequencies among 135 patients with AICU, 146 with aspirin-tolerant chronic urticaria (ATCU), and 430 normal controls (NC). Relationships among the AICU phenotype, atopy, and total IgE level were also investigated. The results failed to show a significant difference in the allele or genotype frequencies between the AICU group and either the ATCU or NC group (P>0.05, respectively). Haplotype analysis confirmed that there was no significant difference among the three study groups (P>0.05), nor was there a significant difference in atopy or total IgE level according to the three genetic polymorphisms (P>0.05, respectively). Our data lead to the conclusion that there is no evidence supporting genetic polymorphisms in IL-13 as a genetic risk factor for the development of AICU

Update on Recent Advances in the Management of Aspirin Exacerbated Respiratory Disease

Aspirin intolerant asthma (AIA) is frequently characterized as an aspirin (ASA)-exacerbated respiratory disease (AERD). It is a clinical syndrome associated with chronic severe inflammation in the upper and lower airways resulting in chronic rhinitis, sinusitis, recurrent polyposis, and asthma. AERD generally develops secondary to abnormalities in inflammatory mediators and arachidonic acid biosynthesis expression. Upper and lower airway eosinophil infiltration is a key feature of AERD; however, the exact mechanisms of such chronic eosinophilic inflammation are not fully understood. Cysteinyl leukotriene over-production may be a key factor in the induction of eosinophilic activation. Genetic studies have suggested a role for variability of genes in disease susceptibility and response to medication. Potential genetic biomarkers contributing to the AERD phenotype include HLA-DPB1*301, LTC4S, ALOX5, CYSLT, PGE2, TBXA2R, TBX21, MS4A2, IL10 -1082A > G, ACE -262A > T, and CRTH2 -466T > C; the four-locus SNP set was composed of B2ADR 46A > G, CCR3 -520T > G, CysLTR1 -634C > T, and FCER1B -109T > C. Management of AERD is an important issue. Aspirin ingestion may result in significant morbidity and mortality, and patients must be advised regarding aspirin risk. Leukotriene receptor antagonists (LTRA) that inhibit leukotriene pathways have an established role in long-term AERD management and rhinosinusitis. Aspirin desensitization may be required for the relief of upper and lower airway symptoms in AERD patients. Future research should focus on identification of biomarkers for a comprehensive diagnostic approach

Biomarkers Predicting Isocyanate-Induced Asthma

Three diisocyanates can cause occupational asthma (OA): toluene diisocyanate (TDI), 4,4 diphenylmethane diisocyanate (MDI), and 1,6-hexamethylene diisocyanate (HDI). We analyzed potential biomarkers of isocyanate-induced OA, based on investigated immunologic, genetic, neurogenic, and protein markers, because there is no serological testing method. The prevalence of serum IgG to cytokeratin (CK)18 and CK19 in TDI-OA was significantly higher than in controls, although the prevalence of these antibodies was too low for them to be used as biomarkers. Another candidate biomarker was serum IgG to tissue transglutaminase (tTG), because the prevalence of serum specific IgG to tTG was significantly higher in patients with TDI-OA than in controls. The human leukocyte antigen (HLA) DRB1*1501-DQB1*0602-DPB1*0501 haplotype may be used as a genetic marker for TDI-OA in Koreans via enhanced specific IgE sensitization in exposed subjects. The genetic polymorphisms of catenin alpha 3, alpha-T catenin (CTNNA3) were significantly associated with TDI-OA. Additionally, examining the neurokinin 2 receptor (NK2R) 7853G>A and 11424 G>A polymorphisms, the NK2R 7853GG genotype had higher serum vascular endothelial growth factor (VEGF) levels than the GA or AA genotypes among Korean workers exposed to TDI. To identify new serologic markers using a proteomic approach, differentially expressed proteins between subjects with MDI-OA and asymptomatic exposed controls in a Korean population showed that the optimal serum cutoff levels were 69.8 ng/mL for ferritin and 2.5 µg/mL for transferrin. When these two parameters were combined, the sensitivity was 71.4% and the specificity was 85.7%. The serum cytokine matrix metalloproteinase-9 (MMP-9) level is a useful biomarker for identifying cases of TDI-OA among exposed workers. Despite these possible biomarkers, more effort should be focused on developing early diagnostic biomarkers using a comprehensive approach based on the pathogenic mechanisms of isocyanate-induced OA

Activation of Th2 cells downregulates CRTh2 through an NFAT1 mediated mechanism.

CRTh2 (encoded by PTGDR2) is a G-protein coupled receptor expressed by Th2 cells as well as eosinophils, basophils and innate lymphoid cells (ILC)2s. Activation of CRTh2, by its ligand prostaglandin (PG)D2, mediates production of type 2 cytokines (IL-4, IL-5 and IL-13), chemotaxis and inhibition of apoptosis. As such, the PGD2-CRTh2 pathway is considered important to the development and maintenance of allergic inflammation. Expression of CRTh2 is mediated by the transcription factor GATA3 during Th2 cell differentiation and within ILC2s. Other than this, relatively little is known regarding the cellular and molecular mechanisms regulating expression of CRTh2. Here, we show using primary human Th2 cells that activation (24hrs) through TCR crosslinking (αCD3/αCD28) reduced expression of both mRNA and surface levels of CRTh2 assessed by flow cytometry and qRT-PCR. This effect took more than 4 hours and expression was recovered following removal of activation. EMSA analysis revealed that GATA3 and NFAT1 can bind independently to overlapping sites within a CRTh2 promoter probe. NFAT1 over-expression resulted in loss of GATA3-mediated CRTh2 promoter activity, while inhibition of NFAT using a peptide inhibitor (VIVIT) coincided with recovery of CRTh2 expression. Collectively these data indicate that expression of CRTh2 is regulated through the competitive action of GATA3 and NFAT1. Though prolonged activation led to NFAT1-mediated downregulation, CRTh2 was re-expressed when stimulus was removed suggesting this is a dynamic mechanism and may play a role in PGD2-CRTh2 mediated allergic inflammation