Olmesartan Attenuates Single-lung Ventilation Induced Lung Injury Via Regulating Pulmonary Microbiota

Background and PurposeSingle-lung ventilation(SLV)is a conventional ventilation procedure used for thoracic surgery.Although it has many advantages for the improvement of assess to the operation field,SLV can result in acute lung injury,which may further develop into lethal acute respiratory distress syndrome(ARDS),which could raise the death rate to almost 40%.And SLV associated acute lung injury is similar to ischemia reperfusion(IR)injury.Olmesartan(Olm),a novel angiotensin receptor blocker(ARB),has been reported to ameliorate organ IR injury.Several recent studies have shown that lung microbiota may be involved in pulmonary diseases,but the effect of pulmonary microbiota in SLV-induced lung injury has not been reported.This study aims to determine the mechanism of how Olm attenuates SLV induced lung injury.MethodsSprague Dawley(SD)rat and cell hypoxia reoxygenation model was used to construct in vivo and in vitro models of SLV.Hematoxylin-eosin(HE)staining was used to assess the pathological score of lung injury.Wet/Dry(W/D)ratio was used to assess pulmonary edema.The content of cytokines was detected by ELISA.Reactive oxygen species(ROS)and malondialdehyde(MDA)were used to assess the degree of oxidative stress.16S rDNA and Liquid chromatography tandem mass spectrometry(LC-MS)were used for microbiota and metabolomics analysis.Correlational analysis and bioinformatics analysis were used to illustrate the relationship and mechanism of respiratory microbiota and its metabolites in Olm mitigating SLV-induced lung injury.ResultsFirstly,we found that Olm treatment before modeling markedly alleviated SLV-induced lung injury by suppressing inflammation and reactive oxygen species.Bronchoalveolar lavage fluid samples from the injured side were collected for 16S rDNA gene-based sequencing analysis.We found that SLV induced lung injury could disturb the balance of pulmonary microbiota,and after Olm's treatment rebalance the procedure.At the levels of Genus and Species,24 different bacteria at the genus level and 29 different bacteria at the species level were identified,which could play the critical roles in these procedures.Furthermore,the injured lung samples were collected for metabolomics analysis using liquid chromatography-mass spectrometry analyses to explore differential metabolites among all groups.And gamma-Linolenic acid(GLA),which found from differential metabolites among all groups,was proven that it plays an important role in keeping lung from SLV induced lung injury.To explore the relationship between related metabolites and cellular immunity,we analyze the correlation between differential metabolites and lung microbiota.A total of 24 pathways were both identified by analyzing either metabolites or microbiota,which may be the potential mechanism of how Olm attenuates SLV induced lung injury.ConclusionBesides classical blockage of the renin-angiotensin II system to inhibit oxidative stress and inflammation,Olm could also alleviate SLV-induced lung injury by rewiring the interaction between pulmonary microbiota and metabolites(such as up-regulating the level of GLA).