Protective effect of miR-34b-5p on sepsis-induced acute lung injury in rats and the underlying mechanism

TANG Yongjun; ZHANG Hongyu; LI Xin

doi:10.3969/j.issn.1002-7386.2025.07.002

Abstract：Objective To explore the protective effect of miR-34b-5p on sepsis-induced acute lung injury(ALI)in rats and its impact on the phosphatase and tensin homolog(PTEN)/protein kinase B(Akt)/mechanistic target of rapamycin(mTOR)signaling pathway.Methods A total of 80 specific-pathogen free(SPF)grade male Sprague-Dawley(SD)rats were randomly divided into sham group,model group,empty vector group,and miR-34b-5p group,with 20 rats in each group.Rats in the sham group were only treated with laparotomy,while the remaining rats were subjected to cecal ligation and perforation to prepare a sepsis model.After sepsis modeling,rats in the empty vector group and miR-34b-5p group were injected with empty vectors and miR-34b-5p overexpression plasmids through the tail vein,respectively.Rats in the model group and sham group were injected with equal amounts of 0.9％NaCl solution.After 3 days of injection,enzyme-linked immunosorbent assay(ELISA)was used to determine peripheral blood levels of interleukin-1 beta(IL-1β)and IL-6.The wet-to-dry(W/D)value of rat lung tissue was calculated.The pathological changes of rat lung tissue were observed by hematoxylin and eosin(H&E)staining.The apoptotic rate of lung tissue was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling(TUNEL)assay.The mRNA levels of miR-34b-5p,IL-1β and IL-6 in lung tissue were detected by quadruplex real-time quantitative polymerase chain reaction(qRT-PCR).Western blot was used to detect the protein levels of PTEN,p-AKT,p-mTOR,AKT,mTOR,Bax,Bcl-2,and Caspase-3.Results The alveoli of rats in the sham group were normal,while those in the model group and empty vector group had alveolar collapse,thickening of alveolar walls,vascular congestion,pulmonary interstitial congestion,edema,and inflammatory cell infiltration.The infiltration of inflammatory cells in rat lung tissue the miR-34b-5p group was reduced,and alveolar damage was significantly improved.Compared with the sham group,rats in the model group had significantly higher protein and mRNA levels of IL-1 β and IL-6,number of apoptotic cells,protein levels of Bax,Caspase-3 and PTEN,and W/D of lung tissue,but lower miR-34b-5p level,protein level of Bel-2,p-AKT/AKT and p-mTOR/mTOR(P＜0.01).Compared with the empty vector group,miR-34b-5p group had significantly higher miR-34b-5p level,protein level of Bcl-2,p-AKT/AKT and p-mTOR/mTOR,but lower protein and mRNA levels of IL-1β and IL-6,number of apoptotic cells,protein levels of Bax,Caspase-3 and PTEN,and W/D of lung tissue(P＜0.01).Conclusion MiR-34b-5p can alleviate pulmonary inflammation and cell apoptosis of ALI in sepsis rats through the PTEN/AKT/mTOR signaling pathway.