Mitochondrial dysfunction caused by bacterial outer membranes vesicles activates intrinsic apoptosis and inflammation

Sensing of microbes activates the immune system, depending on functional mitochondria. However, pathogenic bacteria inhibit mitochondria activity by delivering toxins via outer membrane vesicles (OMVs). How innate immune cells respond to pathogenic microbes that target mitochondria remains unclear. Here, we show that macrophages induce mitochondrial apoptosis and the NLRP3 inflammasome in response OMVs. Macrophages treated with OMVs and toxins that cause mitochondria dysfunction cease host protein translation which depletes pro-survival BCL-2 family member, MCL-1, and induces BAK-dependent mitochondrial apoptosis. Mitochondrial apoptosis and potassium ion efflux activate the NLRP3 inflammasome after OMV exposure. Importantly, mitochondrial apoptosis modulates IL-1 serum levels in response to OMVs. Our data highlight how innate immune cells sense infections by monitoring mitochondrial health.