Helicobacter pylori-derived neutrophil-activating protein increases the lifespan of monocytes and neutrophils

An invariable feature of Helicobacter pylori-infected gastric mucosa is the persistent infiltration of inflammatory cells. The neutrophil-activating protein (HP-NAP) has a pivotal role in triggering and orchestrating the phlogistic process associated with H. pylori infection. Aim of this study was to address whether HP-NAP might further contribute to the inflammation by increasing the lifespan of inflammatory cells. We report that HP-NAP is able to prolong the lifespan of monocytes, in parallel with the induction of the anti-apoptotic proteins A1, Mcl-1, Bcl-2 and Bcl-X(L). This effect does not result from a direct action on the apoptotic machinery, but rather it requires the release of endogenous pro-survival factors, such as interleukin-1beta, which probably acts in synergy with other unidentified mediators. We also report that HP-NAP promotes the survival of Ficoll-purified neutrophils in a monocyte-dependent fashion: indeed, mononuclear cell depletion of Ficoll-purified neutrophils completely abolished the pro-survival effect by HP-NAP. In conclusion, our data reinforce the notion that HP-NAP has a pivotal role in sustaining a prolonged activation of myeloid cells.