Enhanced Expression of the Leukotriene C₄Synthase Due to Overactive Transcription of an Allelic Variant Associated with Aspirin-Intolerant Asthma

Abstract

Aspirin-intolerant asthma (AIA), a distinct clinical syndrome affecting about 10% of adult asthmatics, appears to be unusually dependent on cysteine leukotriene (cys-LT) overproduction by pulmonary eosinophils. The gene coding for leukotriene (LT) C(4) synthase (LTC(4)S), the enzyme controlling cys-LT biosynthesis, exists as two common alleles distinguished by an A to C transversion at a site 444 nucleotides upstream of the translation start. We tested the hypothesis that this single nucleotide polymorphism (SNP) affects binding of transcription factors and influences the transcription rate, predisposing to AIA. Gel shift assay studies revealed that the (-444)C allele, conferring an activator protein-2 binding sequence, is an additional target for a transcription factor of histone H4 consensus. Introduction of the H4TF-2 decoy oligonucleotide into LTC(4)S-positive, differentiated HL-60 cells decreased accumulation of LTC(4) to 68%. Transfection of COS-7 with promoter construct increased expression of beta-galactosidase reporter for the (-444)C variant. The (-444)C allelic frequency was significantly higher in AIA patients (n = 76) as compared with matched aspirin-tolerant asthmatics (n = 110) and healthy controls (n = 75). Patients with AIA had also upregulated LTC(4)S messenger RNA expression in peripheral blood eosinophils. An inhaled provocation test with lysine-aspirin led to an increase in urinary output of LTE(4), which reached statistical significance only in carriers of the (-444)C allele. Our results suggest that a transcription factor, present in dividing and bone marrow resident progenitors of eosinophils, triggers LTC(4)S transcription in carriers of a common (-444)C allele due to binding with the histone H4 promoter element of the gene. Genetic predisposition to cys-LT pathway upregulation, a hallmark of AIA, can be related to overactive expression of the LTC(4)S (-444)C allele.

Leukotriene pathway genetics and pharmacogenetics in allergy

“…LTC4S encodes for the main enzyme specific to CysLT synthesis and has been extensively studied, especially a Duroudier et al polymorphism located )444 upstream of the ATG translation start site ()444 A>C, rs730012). Approximately half of the published genetic studies found the C allele associated with asthma, asthma severity or aspirin intolerance (105,(115)(116)(117)(118). The other studies, including two also investigating another promoter polymorphism ()1072 G>A) did not detect an association with those same phenotypes (109,(119)(120)(121)(122)(123)(124)(125)) (see Table 3).…”

Local genetic and environmental factors in asthma disease pathogenesis: chronicity and persistence mechanisms

“…BHR) and disease severity (e.g. treatment requirements) include the b 2 -adrenoceptor (Gly 16 Arg, Gln 27 Gly and Thr 64 Ile) [57], TGF-b (C509T, 72 Ins C, T869C and G915C) [58,59], LT C4 synthase (A-444C) [60], glutathione-S-transferase (GST P1: Val 105 Leu) [61], TNF-a (G-308A), TNF-b (LTa NcoI) [62] and neuronal NOS (CA 18 allele) [63]. In other cases, genetic variation in specific genes have effects on both immunological/inflammatory and structural cells, such as IL-4, -9, -13, and their respective receptors and intracellular signalling molecules, such as signal transducer and activator of transcription (STAT)-6, suppressor of cytokine signalling (SOCS)-1, SOCS box and, most recently, the identification of TLRs on epithelial cells and smooth muscle [64].…”

Lack of an Association between a Newly Identified Promoter Polymorphism (-1702G > A) of the Leukotriene C4 Synthase Gene and Aspirin-Intolerant Asthma in a Korean Population

“…It has been reported that LTC4S was expressed five times more strongly in bronchial biopsies from AIA patients compared to ATA and normal controls (Cowburn et al 1998). Sanak et al (1997Sanak et al ( , 2000 showed that AIA was associated with the genetic polymorphism of LTC4S -444A>C, which has an additional responsive element to histone H4 transcription factor-2, and increases the transcription rate of the gene in vitro and in vivo in a Polish population. Furthermore, the variant C allele was not associated with mild asthmatics having AIA who did not require oral steroids to control their asthma symptoms, suggesting that it is a marker of the severe, steroid-dependent phenotype of AIA.…”

“…The genetic polymorphism of LTC4S -444A>C is strongly associated with the AIA phenotype in a Polish population, which is supported by functional data demonstrating an additional transcription factor binding site to increase the transcription rate of this gene (Sanak et al 1997(Sanak et al , 2000. In contrast, no significant associations were detected in American (Van Sambeek et al 2000), Japanese (Kawagishi et al 2002), Australian (Kedda et al 2004), or Spanish (Isidoro-García et al 2005 populations.…”