Background: Studies have described polymorphisms in genes involved with both leukotriene synthesis and remodeling. Leukotriene C4 synthase (LTC4S) is the critical terminal pathway enzyme involved in regulation of cysteinyl leukotriene (CysLT) synthesis. An A-to-C base exchange in the promoter region of the LTC4S gene influences its expression. The plasminogen activator inhibitor (PAI) 1 gene is associated with tissue fibrosis. The presence of either 4G or 5G residues in the promoter region has been associated with altered transcription. The role of these polymorphisms was investigated in patients with sinusitis and polyps. We performed a prospective study of patients undergoing endoscopic sinus surgery at a university hospital between 1996 and 2004.
Methods: Demographic data and sinus tissue were collected from patients. Patients were classified into four groups: controls, chronic hyperplastic eosinophilic sinusitis (CHES), aspirin exacerbated respiratory disease (AERD), and chronic inflammatory sinusitis (CIS). DNA was analyzed for the LTC4S and the PAI-1 promoter polymorphisms using standard PCR techniques.
Results: There were 133 patients with 76 women and 57 men (mean age, 42 years). Sixty-six people were in the control group, 16 people were in the CIS group, 51 people were in the CHES group, and 22 people were in the AERD group. The LTC4S allelic frequencies were controls, A = 0.81 and C = 0.19; CIS, A = 0.73 and C = 0.27; CHES, A = 0.69 and C = 0.31; AERD, A = 0.67 and C = 0.33. The C allele was more frequent in CHES versus controls (p = 0.04). The PAI-1 allele frequencies were controls, 5G = 0.55 and 4G = 0.45; CIS, 5G = 0.47 and 4G = 0.53; CHES, 5G = 0.56 and 4G = 0.44; AERD, 5G = 0.54 and 4G = 0.46. Increased expression of the 4G allele of the PAI-1 gene was observed in CIS; however, this genetic variance between the four groups was not statistically different (p > 0.05).
Conclusion: There appears to be a genetic component that contributes to nasal polyp formation in sinusitis. Although the LTC4S polymorphism has previously been associated with aspirin-sensitive asthma, this is the first demonstration that the polymorphism is associated with CHES and this is independent of aspirin sensitivity.