Association Between Achalasia and Nitric Oxide Synthase Gene Polymorphisms

Abstract

Our group previously reported the absence of nitric oxide synthase (NOS) in the gastroesophageal junction of patients with achalasia. NOS exists in three distinct isoforms: neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible isoform (iNOS). Some studies have shown that NO production is regulated by NOS polymorphisms. To assess whether some functional polymorphisms in the nNOS, iNOS, or eNOS genes are involved in susceptibility to suffer from achalasia. Genomic DNA from 80 unrelated Spanish Caucasian patients with sporadic achalasia and 144 healthy subjects matched for age (+/-5 yr) and gender was typed by PCR and RFLP methods for the 27-bp variable number of tandem repeat (VNTR) polymorphism in intron 4 of the eNOS gene, a CA microsatellite repeat and a Nla III (C-->T) restriction fragment length polymorphism (RFLP) in exon 29 of the nNOS gene, and two nucleotide substitutions located in exon 16 (C-->T) and exon 22 (G-->A) of the iNOS gene. No significant differences in carriage, genotype, and allele frequencies of the nNOS, iNOS, or eNOS gene polymorphisms were found between patients with achalasia and controls. Individuals homozygous for genotype iNOS22*A/A tended to be more frequent in achalasia (20%vs 11%, odds ratio [OR] 1.79, 95% confidence interval [CI] 0.89-3.59, p= 0.09) as were those homozygous for the rare eNOS*4a allele (6.2%vs 1.4%, OR 4.5, 95% CI 0.89-22.67, p= 0.1) although the difference did not reach statistical significance. No differences in genotype and allele distribution were found with respect to epidemiological and clinical characteristics of patients with achalasia. Our data suggest that NOS gene polymorphisms are not involved in the susceptibility to and nature of the clinical course of sporadic achalasia. However, studies in a greater number of patients are required to analyze the tendency toward a higher prevalence of genotypes iNOS22*A/A and eNOS*4a4a.