Alcohol Up-Regulates TLR2 Through a NO/cGMP Dependent Pathway

Background: Heavy alcohol consumption is associated with severe bronchitis. This is likely, related to increased inflammation in the airways of alcohol abusers. Toll-like receptor 2 (TLR2) is an important mediator of inflammation in the airway epithelium. TLR2 initiates in inflammatory cascade in response to gram-positive bacteria. We have previously shown that alcohol up-regulates TLR2 in the airway epithelium. However, the mechanism of alcohol-mediated up-regulation of TLR2 has not been identified. Methods: A human airway epithelial cell line, 16HBE14o-, was exposed to biologically relevant concentrations of alcohol (100 mM) in the presence and absence of N(omega)-Nitro-L-arginine methyl ester hydrochloride, a nitric oxide (NO) synthase inhibitor,- and Rp-8-Br-cGMP-S. an antagonist analogue of cGMP. TLR2 was measured using real-time PCR and Western blots. In addition, 16HBE14o- cells were incubated with sodium nitroprusside (SNP),,in NO donor, and 8-Br-cGMP. a cGMP analogue. TLR2 was measured using real-time PCR. Results: N(omega)-Nitro-L-arginine methyl ester hydrochloride blocked the alcohol-medicated up)regulation or TLR2. This indicates that NO plays a key role in alcohol's up-regulation of TLR2. SNP, a NO donor, up-regulated TLR2. Rp-8-Br-CGMP-S attenuated alcohol's up-regulation Of TLR2, suggesting that NO was working through cGMP/PKG. 8-Br-cGMP up-regulated TLR2 also demonstrating the importance of cGMP/PKG. Conclusions: Alcohol upregulates TLR2 through a NO/cGMP/PKG dependent pathway in the airway epithelium. This is an important observation in the Understanding how alcolhol modulates ail-way inflammation. In addition, this is the first time that cyclic nucleotides have been shown to play a role in the regulation TLR2.