Lipid mediators in innate immunity against tuberculosis: opposing roles of PGE(2) and LXA(4) in the induction of macrophage death

Virulent Mycobacterium tuberculosis (Mtb) induces a maladaptive cytolytic death modality, necrosis, which is advantageous for the pathogen. We report that necrosis of macrophages infected with the virulent Mtb strains H37Rv and Erdmann depends on predominant LXA(4) production that is part of the antiinflammatory and inflammation-resolving action induced by Mtb. Infection of macrophages with the avirulent H37Ra triggers production of high levels of the prostanoid PGE(2), which promotes protection against mitochondrial inner membrane perturbation and necrosis. In contrast to H37Ra infection, PGE(2) production is significantly reduced in H37Rv-infected macrophages. PGE(2) acts by engaging the PGE(2) receptor EP2, which induces cyclic AMP production and protein kinase A activation. To verify a role for PGE(2) in control of bacterial growth, we show that infection of prostaglandin E synthase (PGES)(−/−) macrophages in vitro with H37Rv resulted in significantly higher bacterial burden compared with wild-type macrophages. More importantly, PGES(−/−) mice harbor significantly higher Mtb lung burden 5 wk after low-dose aerosol infection with virulent Mtb. These in vitro and in vivo data indicate that PGE(2) plays a critical role in inhibition of Mtb replication.