Expression of inducible nitric oxide synthase (iNOS) mRNA in inflamed esophageal and colonic mucosa in a pediatric population

Objective: Increasing evidence suggests that nitric oxide participates in the pathophysiology of intestinal barrier function/dysfunction and inflammation. Increases in inducible nitric oxide synthase (iNOS) mRNA and protein expression have been observed in colonic mucosal biopsies of adults with inflammatory bowel disease (IBD). It is unclear whether iNOS induction is specific for IBD or a reflection of nonspecific mucosal inflammation. Furthermore, the characteristics of iNOS mRNA expression in pediatric patients with gastrointestinal disorders remains ill-defined. Our objective was to examine the relationship between iNOS mRNA expression and gastrointestinal mucosal inflammation in a pediatric population. Methods: Esophageal and colonic mucosal biopsies were obtained during endoscopy. Total RNA was isolated from these biopsies and reverse transcription-polymerase chain reaction (RT-PCR) performed (35 PCR cycles) using two 20-bp primers that amplified a predicted 372-bp conserved iNOS mRNA fragment. Results: Biopsies were obtained from 29 children (22 boys; mean age 10.6 yr [range 1.7-16.5 yr]). Endoscopic and histological findings included normal esophageal mucosa (n = 3), esophagitis (n = 10), normal rectal mucosa (n = 2), ulcerative colitis (n = 10), and Crohn disease (n = 4). Evidence of iNOS mRNA was detected by PCR amplification in six of 10 patients with ulcerative colitis and in two of four patients with Crohn disease. However, iNOS mRNA was not amplified in any esophageal biopsy or in rectal mucosa biopsies with normal histology. Conclusions: These data indicate that upregulation of iNOS mRNA expression in colonic mucosa is a feature of IBD in children. iNOS mRNA expression is not upregulated in esophageal mucosa or in the absence of colonic inflammation. Further studies designed to determine the site- and cell-specificity of iNOS mRNA upregulation in mucosal biopsies from children with IBD may further illuminate the pathophysiology of these disorders.