THE TUBERCULOUS PLEURAL EFFUSION ALTERS THE METABOLIC REPROGRAMMING OF M1 ACTIVATED MACROPHAGES

JOSÉ LUIS MARÍN; MELANIE GENOULA; GABRIEL DUETTE; MALENA FERREYRA; GEANNCARLO LUGO-VILLARINO; OLIVIER NEYROLLES; EDUARDO JOSÉ MORAÑA; DOMINGO PALMERO; MARIA DEL CARMEN SASIAIN; PABLO SCHIERLOH; LUCIANA BALBOA

Cancún

Congreso; INMUNOMEXICO2018; 2018

Asociación Latinoamericana de Inmunología

Classically activated or M1 macrophages are key players of the first line of defense against bacterial infections such as Mycobacterium tuberculosis (Mtb), the etiological agent for tuberculosis (TB). Mtb infection remains a major health problem worldwide, with up to 2 billion people chronically infected. The chronic host-pathogen interaction in TB leads to extensivemetabolic remodeling in both the host and the pathogen1. In fact, the success of Mtb as a pathogen derives from its efficient adaptation to the intracellular milieu of human macrophages, displaying several strategies to circumvent the microbicidal activity in these cells. Normally, in response to infection, activation of the host immune cells is accompanied by a switch in the bioenergetic pathway from oxidative phosphorylation to aerobic glycolysis, which is required for the production of antimicrobial and pro-inflammatory effector molecules2,3. In this regard, M1 macrophages are known to obtain energy through glycolysis, displaying an increase in glucose uptake as well as the conversion of pyruvate to lactate4. A key transcription factor orchestrating the expression of glycolytic enzymes is the hypoxia-inducible factor-1 (HIF1), a heterodimer comprised of α (HIF-1α) and β (HIF-1β) subunits, being HIF-1α the regulated component of thecomplex5. The activation of HIF-1α results in the production of pro-inflammatory cytokines and other mediators of the M1 phenotype, such as glycolytic enzymes and the glucose transporter GLUT16. Moreover, at least two interruptions in the Krebs cycle were described in M1 macrophages, leading to the accumulation of intermediates such as succinate. Succinate was known to regulate the stability of HIF-1α driving a sustained production of the proinflammatory cytokine IL-1β7,8. Since M1 macrophage effector functions are deeply related to the metabolic program in course, we hypothesize that Mtb can perturb the metabolic reprogramming in M1 in order to facilitate its intracellular persistence. In this regard, previousreports have demonstrated that the infection with Mtb leads to glycolysis in bone-marrow derived macrophages9,10, in lungs of infected mice11, and in lung granulomas from patients with active TB12. Of note, it has shown that Mtb infection induced the increase of HIF-1α expression in IFN-γ-activated macrophages which is essential for IFN-γ-dependent control of infection13.Based on this knowledge, we decided to study whether the local microenvironment of the infection modulates the metabolic reprogramming in M1 macrophages and whether it impact on host defense against Mtb. To assess this issue, we polarized human M1 macrophages with IFN-γ and LPS, and then treated them with the acellular fraction of tuberculous pleural effusion (TBPE), which is genuine TB-derived microenvironment containing multiple soluble factors released locally during the infection. We found that the treatment with TB-PE increased the expression of the glucose transporter GLUT1, as well as the uptake and consumption of glucose in M1 macrophages. Surprisingly, the release of lactate was reduced in TB-PE-treated M1 macrophages, together with the expression of HIF-1α, the production of mitochondrial ROS, and the production of IL-1β. Finally, we demonstrated that the TB-PE-treated M1 macrophages contained higher bacillary loads. In conclusion, while TB-PE treatment promotes glucose uptake, this additional glucose is not used to fuel the aerobic glycolytic pathway associated with the microbicidal activity in M1 macrophages. Instead, aerobic glycolysis seems to be reduced by TBPE in association with a reduced ability to control the bacterial growth. Therefore, we propose that soluble factors released locally during the infection alter the metabolic reprogramming of M1 macrophages impacting on their ability to control the infection. The soluble mediators responsible for this metabolic alteration are still under study. We consider that a better understanding of the molecular mechanisms underlying host-pathogen interactions could provide a rational basis for the development of effective anti-TB therapeutics.