RNA FROM ESCHERICHIA COLI ENHANCE INFLAMMATORY RESPONSE IN A PNEUMONIA MURINE MODEL

PITTALUGA VILLARREAL JR; BIRNBERG-WEISS F; CASTRO, J; MARTIRE-GRECO D; FERNÁNDEZ G. C.; LANDONI V.I

San Luis

Congreso; LXXI REUNIÓN CIENTÍFICA ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI); 2023

SAI

Escherichia coli (ECO) is a Gram-negative bacteria member of the Enterobacteriaceae family, a well-known microorganism capable of causing multiple diseases. In particular, ECO is highly responsible for causing ventilator-associated pneumonias. Prokaryotic RNA has been previously established as an immune modulator. Our previous work demonstrated that depending on the bacterial species, RNA could act as both an inductor or an attenuator of inflammatory responses. In particular for the RNA from ECO (RNAECO), an inflammatory response was induced in vitro on human endothelial, lung epithelial cells and isolated neutrophils (PMN). For all these cell types, upregulation of activation proteins on their surface and secretion of chemotactic and pro-inflammatory cytokines have been shown after stimulation with RNAECO. Also PMN elimination of ECO was enhanced in the presence of RNAECO. The aim of this study was to determine the effects of RNAECO in vivo in the context of a lung infection using a murine model. For experimentation, 3 month-old female BALB/c mice were treated (intranasal, i.n) with PBS (Control) or RNAECO (10 µg), and bacterial infection was induced by administration of live ECO i.n. After 4 h post-infection bronchoalveolar lavage (BAL) and lung cells were obtained, and the number of PMN (GR1+-CD11b+ cells), secretion of inflammatory chemokines as well as bacterial clearance were determined. The number of migrated PMN was analyzed by flow cytometry, pro-inflammatory cytokines were measured using ELISA kits and bacterial clearance was determined counting the number of Colony Forming Units (CFU) of bacteria. Our results showed that RNAECO induced an increase in PMN in BAL and lung compared to control mice (p≤0.05). In line with this result, we observed an increase in the secretion of pro-inflammatory cytokines such as TNF-α and IL-6 in BAL (p≤0.05). Finally, we wondered whether this pro-inflammatory response in the lung elicited by RNAECO could affect bacterial clearance. The number of CFU in lung and BAL from mice treated with RNAECO were significantly reduced compared to mice challenged with ECO (p≤0.05). In conclusion, these results revealed that RNAECO is able to induce pro-inflammatory responses in the lungs that favors bacterial clearance during pneumonia. Further and detailed studies will allow us to determine whether the use of bacterial RNA could be implemented as a therapeutic strategy to improve bacterial clearance.