Studies On The Production Of IL-8 In Human Airway Epithelial Cells Induced By Mycobacterium Tuberculosis Supernatant And The Mechanisms Of Inflammatory Signaling Transduction

Objective This study was done to investigate the inflammatory response of human airway epithelial cells to the components in Mycobacterium tuberculosis supernatant and the mechanisms involved in the inflammatory signaling transduction.Methods Mycobacterium tuberculosis supernatant was prepared from the virulent laboratory strain H37R.V. Human lung epithelial cell lines SPC-A-1 and A549 were challenged with the supernatant and IL-8 secretion by the epithelial cells was assayed by using ELISA. In order to investigate whether MyD88 is involved in the inflammatory signaling pathway SPC-A-1 cells were transfected with an expression plasmid encoding dominant negative mutant MyD88. Western blot was used to determine MAPK phosphorylation of SPC-A-1 stimulated with the supernatant. Primary normal human airway epithelial cells cultured at usual culture system and air-liquid interface system were treated with the Mycobacterium tuberculosis supernatant. IL-8 secretion by the epithelial cells was assayed by using ELISA and MAPK phosphorylation was characterized by immunoblotting.Results Mycobacterium tuberculosis supernatant from H37Rv elicited production of IL-8 by SPC-A-1 and A549 cell lines. Expression of dominant negative mutant MyD88 in the SPC-A-1 cell line effectively blocked the production of IL-8 in response to Mycobacterium tuberculosis supernatant. The level of p- JNK and p-Erkl/2 increased dramatically after 10 minutes exposure of the SPC-A-1 cells to the supernatant. Also, IL-8 production in the primary human airway epithelial cells stimulated with Mycobacterium tuberculosis supernatant increased obviously. Phosphorylation of Erkl/2 was observed to rise significantly in 10 minutes of post-stimulation with the supernatant.Conclusion Components in Mycobacterium tuberculosis supernatant could induce IL-8 expression in both human airway epithelial cell lines and primary epithelial cells. Toll/IL-1 receptor pathway may be involved in the inflammatory signal transduction and transcriptional activation of IL-8 gene was concerned with the MAPK signal pathwayand and transcriptional factor AP-1. The production of inflammatory cytokines by the airway epithelial cells in response to Mycobacterium tuberculosis and/or its products may contribute to pathogenesis of pulmonary tuberculosis.