INFLAMMATORY RESPONSE TO Pseudomonas aeruginosa INCREASES THE ABILITY OF MACROPHAGES TO REMOVE APOPTOTIC CELLS

TRIBULATTI MARIA VIRGINIA; KIERBEL ARLINET; JAGER ADRIANA V; BROCCO MARCELA ADRIANA; ARIAS PAULA; PEPE MARIA VICTORIA

Virtual

Congreso; Congreso Conjunto SAIB-SAMIGE 2020; 2020

Pathogensphagocytosis and the uptake of apoptotic cells (efferocytosis) are essentialmacrophages tasks, classically considered as mutually exclusive. Macrophageshave been described to polarize into either pro-inflammatory/microbicidal oranti-inflammatory/efferocytic phenotypes. However, macrophages function implicatesmuch more complexity. Furthermore, little is known about regulation ofefferocytosis under inflammatory conditions. Pseudomonas aeruginosa is an opportunisticpathogen that primarily infects immune-compromised individuals and/or patientswith epithelial injury. While the epithelium provides a physical barrieragainst this gram-negative pathogen, innate immunity and, specifically,phagocytosis by neutrophils and macrophages are key determinants in the abilityof the host to control P. aeruginosa infection.Thus, the host inflammatory response is intimately connected to the phagocyticclearance of the bacteria. In this study, we aimed to elucidate the modulation ofmacrophage efferocytic function during P.aeruginosa inflammatory stimulus. For this purpose, we exposed primary bonemarrow-derived macrophages (BMDM) to apoptotic cells, bacteria andbacteria-laden apoptotic cells and examined their internalization(independently or in conjuction) by confocal microscopy and subsequent imageanalysis in order to investigate the phagocytic and efferocytic efficiencies.To study bacterial clearance, we measured intracellular survival over time.Also changes in cytokine expression levels were measured by real-time RT-PCR. Wefound that BMDM are very efficient in engulfing both the bacterial pathogen P. aeruginosa and apoptotic cells. BMDMshowed a high bactericidal capacity which is not affected by the concomitantpresence of apoptotic material. Plasticity in macrophageprogramming, in response to changing environmental cues, may modulateefferocytic capability. In this work we further showed that, afterphagocyting and processing P. aeruginosa,macrophages highly increase their efferocytic capacity without affecting theirphagocytic function. Moreover, we demonstrate that P. aeruginosa enhances efferocytosis of these phagocytes throughthe IL-6 signaling pathway. Our results show that, when confronted to thispathogen, macrophages respond through a pro-inflammatory response andmicrobicidal action to destroy the infectious agent. But, at the same time, theincrease of the pro-inflammatory response that follows the bacterial processingpromotes the clearance of apoptotic cells by these macrophages contributing tothe resolution of local inflammation.<!-- /* Font Definitions */@font-face{font-family:"Cambria Math";panose-1:2 4 5 3 5 4 6 3 2 4;mso-font-charset:0;mso-generic-font-family:auto;mso-font-pitch:variable;mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face{font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;mso-font-charset:0;mso-generic-font-family:auto;mso-font-pitch:variable;mso-font-signature:-536870145 1073786111 1 0 415 0;} /* Style Definitions */p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-unhide:no;mso-style-qformat:yes;mso-style-parent:"";margin-top:0cm;margin-right:0cm;margin-bottom:8.0pt;margin-left:0cm;line-height:107%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:Calibri;mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;mso-ansi-language:ES-AR;}.MsoChpDefault{mso-style-type:export-only;mso-default-props:yes;font-family:Calibri;mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;}size:595.0pt 842.0pt;margin:72.0pt 72.0pt 72.0pt 72.0pt;mso-header-margin:35.4pt;mso-footer-margin:35.4pt;mso-paper-source:0;}div.WordSection1{page:WordSection1;}