Inhibition of mitophagy drives macrophage activation and anti-bacterial defense during sepsis
Résumé
Mitochondria have emerged as key actors of innate and adaptive immunity. Mitophagy has a pivotal role in cell homeostasis but its contribution to macrophage functions and host defense remains to be delineated. Here we showed that lipopolysaccharide (LPS) in combination with IFNγ, inhibits PINK1-dependent mitophagy in macrophages through a STAT1-dependent activation of the inflammatory caspases 1 and 11. In addition, we demonstrated that the inhibition of mitophagy triggers classical macrophage activation in a mitochondrial ROS-dependent manner. In a murine model of polymicrobial infection (cecal ligature and puncture, CLP), adoptive transfer of Pink1-deficient bone marrow or pharmacological inhibition of mitophagy promoted macrophage activation which favored bactericidal clearance and lead to a better survival. Reciprocally, mitochondrial uncouplers, that promote mitophagy, reverse LPS/IFNγ-mediated activation of macrophages and lead to immuno-paralysis with impaired bacterial clearance and lowered survival. In critically ill patients, we showed that mitophagy is inhibited in blood monocytes of patients with sepsis as compared to non-septic patients. Overall, this work demonstrates that the inhibition of mitophagy is a physiological mechanism that contributes to the activation of myeloid cells and improves the outcome of sepsis.