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Clin. Vaccine Immunol. doi:10.1128/CVI.00178-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Expression and secretion of cathelicidin LL-37 in human epithelial cells by Mycobacterium bovis Bacillus Calmette-Guérin (BCG)

Departamento de Inmunología, Escuela Nacional de Ciencias Biológicas, IPN., Prol. Carpio y Plan de Ayala, México, D.F. 11340 México

^* To whom correspondence should be addressed. Email: pmendezs{at}bios.encb.ipn.mx.

	Abstract

The antimicrobial cathelicidin LL-37 is considered to play an important role in the innate immune response to tuberculosis infection. However, little is known about the induction and secretion of this antimicrobial peptide in A549 epithelial cells after infection with Mycobacterium bovis bacillus Calmette-Guérin (BCG), the world's most widely used tuberculosis vaccine. In this study, we investigated the effect of M.bovis BCG on LL-37 mRNA levels in A549 cells by real-time PCR, and protein levels by Western blot. Treatment of cells with M.bovis BCG up-regulates the LL-37 mRNA expression in a dose- and time-dependent manner. The quantitative analysis of LL-37 gene expression correlated with our Western blot results. Moreover, our results demonstrated that treatment of cells with the transcriptional inhibitor actinomycin D effectively inhibited in a concentration-dependent manner the ability of M.bovis BCG to induce LL-37 mRNA expression. Finally, inhibition of MEK1/2 and p38 MAPK signaling pathways reduced M.bovis BCG-mediated LL-37 mRNA expression. A reduction that correlated with the high level of downregulation observed for the LL-37 protein induction. Thus, these results indicate that the MEK1/2 and p38 MAPK signaling pathways play a critical role in the regulation of the inducible LL-37 gene expression in A549 cells infected with M.bovis BCG.