Lacticaseibacillus rhamnosus attenuates acute lung inflammation in a murine model of acute respiratory distress syndrome: Relevance to cytokines associated to STAT4/T-bet and STAT3/RORɣt".

The Th1 cytokines production associated to signal transducer and activator of transcription 4 (STAT4) signaling amplifies the pro-inflammatory response in acute respiratory distress syndrome (ARDS). The anti-inflammatory action of commensal bacteria has been described as a secondary effect dependent on IL-10- secreting Treg cells that can act in organs far from the gut, including the lung. Despite it, no data is showing whether the previous reported anti-inflammatory action of probiotics is associated with its immunomodulatory effect dependent on Treg cells in a murine model of ARDS. Therefore, herein we focused on the short-term pretreatment effect with Lacticaseibacillus rhamnosus (Lr) in STAT4-associated Th1 cytokines as well as in population of IL-10- secreting Treg cells in a murine model of ARDS. Assays were performed in experimental groups divided into control, LPS, and Lr + LPS. Total and differential cells from bronchoalveolar lavage fluid (BALF) were counted through microscopy and the IL-10, IL-12, IL-17, IL-18, IL-22, IL-23, IL-27, IFN-γ, MMP-9, and TIMP were measured by ELISA. The peribronchial neutrophils were assessed using morphometry and for pulmonary edema was measured by Evans blue dye extravasation. The gene expression for STAT4, T-bet, STAT3, RORɣt, STAT5, and Foxp3 were measured by Real-Time PCR. Population of IL-10-secreting Treg cells was performed by flow cytometer. Data showed that pretreatment with Lr attenuated the number of inflammatory cells, secretion of both Th1 and Th17 cytokines, expression of STAT4/T-bet and STAT3/RORɣt in lung as well as alterations in lung morphometry. Otherwise, Lr was not efficient to restore mRNA expression for STAT5 and Foxp3 expression and population of IL-10-secreting Treg cells. Thus, beneficial effect of short-term pretreatment with Lr in murine model of ARDS is not dependent on an increased immunomodulatory action of IL-10-secreting Treg cells, however the anti-inflammatory effect of Lr has as target the Th1 and Th17 cytokines as well as signaling involving the STAT4/T-bet and STAT3/RORɣt.