A stop codon polymorphism of toll-like receptor 5 is associated with a stable course of chronic obstructive lung disease

Abstract

The etiology of chronic obstructive lung disease (COPD) is unclear. It is supposed to be the product of an exogenous antigenic stimulus, such as tobacco smoke, and an endogenous genetic susceptibility. Toll-like receptors (TLR) are signal molecules, essential for the cellular response to bacterial cell wall components. Lipopolysaccharide (LPS) binds to TLR4 and two different polymorphisms for the TLR4 gene (Asp299Gly and Thr399Ile) have recently been described. TLR5 is the receptor for flagellin, aconstituent of Gram-positive and -negative bacterial flagella. A functional relevant TLR5 polymorphism (TLR5392STOP) has already been identified. The coactivation of both TLR4 and 5 seems to play an important role in the mediation of host-defense mechanisms. We genotyped 138 Caucasian patients with COPD and 135 healthy controls for the TLR5 polymorphism TLR5392STOP respectively for Asp299Gly and Thr399Ile polymorphisms in theTLR4gene. Among COPD patients the prevalence for the TLR5 mutant allele was 9.42% (26/276). The prevalence for each Asp299Gly and Thr399Ile mutant allele was 4.71% (13/276). In the control group the TLR5 mutation prevalence was 5.19% (14/270) (P = 0.138), the prevalence of each TLR4 polymorphism was 2.96% (8/270) (p = 0.279). In the subgroup of 54 patients with a stable course of COPD, defined as less than three hospitalizations over the last three years due to COPD, we found a significant association with the TLR5392STOP gene polymorphism (P = 0.026). These data suggest that the TLR5392STOP polymorphism is associated with a stable course of COPD, whereas TLR4 polymorphisms have no impact neither on the onset nor on the course of COPD.