The Bacterial Quorum-Sensing Signal 2-Aminoacetophenone Rewires Immune Cell Bioenergetics through the PGC-1α/ERRα Axis to Mediate Tolerance to Infection.

How bacterial pathogens exploit host metabolism to promote immune tolerance and persist in infected hosts remains elusive. To achieve this, we show that Pseudomonas aeruginosa (PA), a recalcitrant pathogen, utilizes the quorum sensing (QS) signal 2-aminoacetophenone (2-AA). Here, we unveil how 2-AA-driven immune tolerization causes distinct metabolic perturbations in macrophages' mitochondrial respiration and bioenergetics. We found that the 2-AA tolerization impairs oxidative phosphorylation (OXPHOS), leading to decreased generation of the crucial energy metabolite ATP and histone acetylation acetyl-CoA. We provide evidence that these effects result from reduced pyruvate flux into mitochondria due to the decreased expression of the mitochondrial pyruvate carrier (MPC1) mediated via the reduced expression and nuclear presence of its transcriptional regulator estrogen-related nuclear receptor (ERRα), leading to the weaker binding of ERRα to MPC1 promoter. This is the outcome of the hampered interaction of ERRα with the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) that ultimately leads to reduced pyruvate flux into mitochondria and ATP production in tolerized macrophages. Exogenously added ATP in 2-AA exposed macrophages restores the transcript levels of MPC1 and ERR-α and enhances cytokine production and intracellular bacterial clearance. Consistent with the in vitro findings, murine infection studies corroborate the 2-AA-mediated long-lasting decrease in ATP and acetyl-CoA and its association with PA persistence, further supporting this QS signaling molecule as the culprit of the host bioenergetic impairment and PA persistence. These findings unveil 2-AA as a negative modulator of cellular immunometabolism implicating the PGC-1α/ERRα axis in its influence on MPC1/OXPHOS-dependent energy production and PA clearance. These findings shed light on the underlying mechanisms of host tolerance and on potential therapeutic strategies to combat persistent PA infections.