Biology subjects

Barrionuevo, P.

Publications and source records attributed to Barrionuevo, P..

2 recordsLinked to original sources

bioRxiv2024

The RNA from Pseudomonas aeruginosa impairs neutrophil responses favoring bacterial survival

Epithelial and endothelial cells are essential in the modulation of innate immune responses in the lung, including the arrival of neutrophils (PMN), which are crucial cells for the antibacterial host defense. These cells are exposed to prokaryotic RNA (pRNA) during bacterial infections and pRNA has been shown to promote or attenuate the inflammatory response on different immune cells. Pseudomonas aeruginosa (PAE) can cause severe pneumonia and has several immune-evading mechanisms. The aim of this study was to determine the effects of the RNA from PAE (RNAPAE) on lung epithelial, endothelial cells and PMN, and its impact on bacterial elimination. For this purpose, we purified total RNAPAE, and used it as a stimulus to evaluate different functions on Calu-6, HMEC-1 and isolated human PMN. We found that RNAPAE neither induced a pro-inflammatory response on Calu-6 or HMEC-1, as measured by ICAM-1 surface expression, or IL-6 and IL-8 secretion. Also, RNAPAE failed to activate PMN, as measured by forward-scatter (FSC) increase, CD11b surface expression, chemotaxis and IL-8 secretion. Pre-stimulation with RNAPAE diminished CD11b surface expression, chemotaxis and microbicidal activity when PMN were challenged with live bacteria. Moreover, we found that phagocytosis was affected in the presence of RNAPAE. Fragments of short RNA (<200 bp) were responsible for the PMN microbicidal attenuation during bacterial elimination. In conclusion, our results indicated that short fragments of RNAPAE diminished the immune response on PMN even in the presence of live bacteria. AUTHOR SUMMARYPseudomonas aeruginosa (PAE) pneumonia constitutes a major problem for human health. Therapies are frequently inefficient due to immune evasion mechanisms of PAE. Therefore, it is imperative to understand the relationship between PAE (or its components) with the immune system to improve therapeutic strategies. Since some bacterial RNA are immunosuppressive, our hypothesis was that the RNA from PAE (RNAPAE) might negatively modulate the immune response in a lung infection. We investigated the effects of the RNAPAE on lung epithelial, and microvascular endothelial cells, central cells that respond to PAE early during infection, and on neutrophils (PMN), the first immune cell that arrives at the site of infection. We found that RNAPAE failed to induce any response on pulmonary epithelium, endothelium, or PMN. Moreover, RNAPAE-treated PMN showed reduced migration, activation, and bactericidal response against live bacteria. Exploring deeper into this phenomenon, we found that increased bacterial survival was due to a lower phagocytic capacity of RNAPAE-treated PMN. Our results indicate that RNAPAE may act as another evasion strategy to favor PAEs survival in a pulmonary infection. Understanding the mechanisms by which PAE reduces the response of cells that participate in pulmonary immunity is crucial for planning interventions that may benefit infected patients.

immunology↗

bioRxiv2019

Mycobacterium tuberculosis Modulates the Metabolism of Alternatively Activated Macrophages to Promote Foam Cell Formation and Intracellular Survival

The ability of Mycobacterium tuberculosis (Mtb) to persist inside host cells relies on metabolic adaptation, like the accumulation of lipid bodies (LBs) in the so-called foamy macrophages (FM). Indeed, FM are favorable to Mtb. The activation state of macrophages is tightly associated to different metabolic pathways, such as lipid metabolism, but whether differentiation towards FM differs between the macrophage activation profiles remains unclear. Here, we aimed to elucidate if distinct macrophage activation states exposed to a tuberculosis-associated microenvironment can accumulate LBs, and its impact on the control of infection. We showed that signal transducer and activator of transcription 6 (STAT6) activation in interleukin (IL)-4-activated human macrophages (M(IL-4)) prevents FM formation induced by pleural effusion from patients with tuberculosis. In these cells, LBs are disrupted by lipolysis, and the released fatty acids enter the {beta}-oxidation (FAO) pathway fueling the generation of ATP in mitochondria. We demonstrated that inhibition of the lipolytic activity or of the FAO drives M(IL-4) macrophages into FM. Also, exhibiting a predominant FAO metabolism, mouse alveolar macrophages are less prone to become FM compared to bone marrow derived-macrophages. Upon Mtb infection, M(IL-4) macrophages are metabolically re-programmed towards the aerobic glycolytic pathway and evolve towards a foamy phenotype, which could be prevented by FAO activation or inhibition of the hypoxia-inducible factor 1-alpha (HIF-1)-induced glycolytic pathway. In conclusion, our results demonstrate a role for STAT6-driven FAO in preventing FM differentiation, and reveal an extraordinary capacity by Mtb to rewire metabolic pathways in human macrophages and induce the favorable FM. IMPORTANCETuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb). While its treatment was already standardized, TB remains one of the top 10 death causes worldwide. A major problem is the efficient adaptation of Mtb to the macrophage intracellular milieu, which includes deregulation of the lipid metabolism leading to the formation of foamy macrophages (FM) which are favorable to Mtb. A critical aspect of our work is the use of tuberculous pleural effusions (TB-PE) -- human-derived biological fluid capable of mimicking the complex microenvironment of the lung cavity upon Mtb infection -- to study the FM metabolic modulation. We revealed how the STAT6 transcription factor prevents FM formation induced by PE-TB, and how Mtb counteracts it by activating another transcription factor, HIF-1, to re-establish FM. This study provides key insights in host lipid metabolism, macrophage biology and pathogen subversion strategies, to be exploited for prevention and therapeutic purposes in infectious diseases.

immunology↗