Secretion of interleukin-8 by human-derived cell lines infected with Mycobacterium bovis.
BACKGROUND
The variable efficacy of bacillus Calmette-Guérin (Mycobacterium bovis BCG) in protecting humans against tuberculosis has prompted a search for the mechanisms through which BCG induces chemokines. In this study, our experiments were designed to determine the role of the transcription factor nuclear factor-kappaB (NF-kappaB) and intracellular calcium in the production of interleukin (IL)-8, a main chemotactic factor, by human-derived monocytic cell line U937 and by a human epithelial HEp-2 cell line infected with M. bovis BCG.


METHODS
The concentrations of IL-8 in culture supernatants of U937 cells or HEp-2 cells infected with M. bovis BCG were determined by enzyme-linked immunosorbent assay. We used sulfasalazine and curcumin, which are well-described inhibitors of NF-kappaB activity, and we used ethylenediamine tetraacetic acid to deplete extracellular Ca2+ or used the cell-permeable agent 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetra (acetoxymethyl) ester to chelate releasable intracellular stores of Ca2+ in order to investigate the mechanisms through which M. bovis BCG induces IL-8 secretion in our system.


RESULTS
The enzyme-linked immunosorbent assay showed that IL-8 protein secretion was elevated in M. bovis-infected cell lines. This effect was statistically significant (p < 0.01). When calcium influx was suppressed in M. bovis-infected cell lines, IL-8 secretion was inhibited. Notably, specific inhibitors of NF-kappaB (sulfasalazine and curcumin) inhibited M. bovis-induced IL-8 secretion from U937 cells or HEp-2 cells.


CONCLUSIONS
Collectively, these results indicate that activation of NF-kappaB is an important signal transduction pathway in M. bovis-induced IL-8 secretion in monocytic or epithelial cells. Furthermore, the results showed that calcium influx had a direct effect on IL-8 secretion in U937 cells or HEp-2 cells infected with M. bovis.
Méndez-Samperio
Patricia
P
Departmento de Inmunología, Escuela Nacional de Ciencias Biológicas, México, D F, México. pmendezs@bios.encb.ipn.mx
Palma-Barrios
Janet
J
Vázquez-Hernández
Abraham
A
García-Martínez
Elizabeth
E
D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism; D009163:Mycobacterium bovis; D016328:NF-kappa B / Q000378:metabolism; D015398:Signal Transduction; D014376:Tuberculosis / Q000378:metabolism*
D016209:Interleukin-8; D016328:NF-kappa B; D002118:Calcium