Unquestionably, IL 8 mRNA expression was induced straight away right after the infection, but grew to become gradually weaker from eight to twelve h immediately after infection with the dotO mutant in Jurkat cells. L. pneumophila could also induce biphasic activation of NF B in T cells. The Dot Icm process was demonstrated to become vital for NF B activation in infections of read more human macrophages. Furthermore, the Corby strain was shown to have a severely decreased Dot Icm dependent NF B activation. Thus, the flaA mutant derived from Corby strain might be deficient in infecting T cells to produce IL 8. Along with flagellin, the Dot Icm procedure could also be essential for NF B activation and subsequent upregulation of IL 8 gene in infections of T cells. Together with NF B activation, MAPKs have also been implicated in the induction of IL 8 manufacturing.
The data presented here exhibiting that all 3 MAPKs have been consistently activated on infection with L. pneumophila in T cells, are in agreement with people published by quite a few groups who have also reported L. pneumophila dependent activation of those MAPKs in macrophages and lung epithelial cells. On the other hand, p38 and JNK activation is flagel lin independent in macrophages. Legionella defi cient in the Dot Icm procedure failed to activate p38 and JNK in macrophages. In lung epithelial cells, deletion of your Dot Icm didn't alter IL 8 manufacturing, whereas lack of flagellin decreased IL 8 release by Legio nella, although flagellin and Dot Icm dependency of MAPKs activation was not analyzed. It is actually most likely that L.
pneumophila flagellin provides signals to T cells as in lung epithelial cells because the flaA mutant failed to acti vate MAPKs in T cells. While it really is clear from this report that blockade of p38 with specific inhibitors but not that of ERK, diminishes IL eight mRNA expression and release in lung epithelial cells, the exact molecular mechanism underlying these inhibitions will not be clear however. We identified the two NF B and AP 1 binding internet sites around the five flanking region from the IL 8 promoter demanded for maximal induction of IL eight by L. pneumophila. Simply because we showed that L. pneumophila activated all three MAPKs, we also examined no matter whether L. pneumophila trig gers MAPKs mediated IL 8 production through activation of c Jun, JunD, CREB, and ATF1, which might bind on the AP 1 region inside the IL eight promoter, at the same time as its cell spe cificity.
By using precise kinase inhibitors, we also demonstrated that IL 8 expression and manufacturing in Jurkat cells was sensitive to inhibition of p38 and JNK but not ERK. Constant with these findings, L. pneumo phila stimulated phosphorylation of c Jun, CREB, and ATF1 was blocked by inhibitors of p38 and JNK but not ERK. Working with dominant detrimental mutant proteins of p38a and p38b, we showed that L. pneumophila induction of IL eight was also dependent within the p38 pathway.