Effects And Mechanisms Of Hydrogen-rich Saline On Alveolar Macrophages In Rats With Acute Lung Injury Induced By Sepsis

Objective: Sepsis is a serious systemic inflammatory response syndrome caused by infection,and the mortality rate remains high.Acute lung injury(ALI)and acute respiratory distress syndrome(ARDS)are common causes of death for septic patients.Hydrogen rich saline(HRS)has been proven a significant protective effect on the lung tissue of septic rats,however,the specific mechanisms are still not completely clear.Early over-activation and late suppression of the immune system is the core mechanism of septic organ injury,in which macrophages play a critical role.Recent studies have demonstrated that macrophages are key factors in the pathogenesis of ALI and ARDS.The polarization of alveolar macrophages(AMs)to proinflammatory phenotype contributes to ALI in sepsis.In addition,severe apoptosis of immune cells,including macrophages,caused by sepsis leads to immunosuppression and aggravation of infection.It is important to explore the effect and mechanism of HRS on polarization and apoptosis of AMs for ALI treatment.In addition,autophagy has been proven to be involved in the regulation of inflammation and immunization.Therefore,it is of great significance to explore whether HRS can affect the function of AMs through autophagy.Methods: Sepsis rat model was established by the intravenous administration of LPS,and HRS was injected intraperitoneally.NR8383 AMs were used for experimnets in vitro.(1)Lung injury was evaluated by pathological score and H-E staining.(2)The lung tissue was stained with immunofluorescence to detect the polarization,apoptosis and autophagy of AMs.(3)Western blot was used to detect the expression of marker proteins of M1/M2 polarization(i NOS and Arg-1),apoptosis(Bax,Bcl-2 and cleaved capase 3),and autophagy(LC3I,LC3 II and p62).(4)Flow cytometry was used to detect polarization and apoptosis of AMs.(5)Transmission electron microscope(TEM)was used to observe autophagosomes to evaluate the level of autophagy.(6)After administration of autophagy inhibitor 3-MA,the polarization and apoptosis of AMs in each group were detected by Western-blot and flow cytometry to evaluate the effecs of autophagy on polarization and apoptosis.Results:(1)The lung injury increased continuously at 4,8,12 and 24 hours postLPS challenge,and peaked at 24 hours.(2)HRS can attenuate LPS-induced ALI in rats.(3)HRS reversed the increase of M1 and decrease of M2 polarization of AMs induced by LPS.(4)HRS reduced apoptosis of AMs induced by LPS.(5)HRS suppressed LPS-induced autophagy in AMs of septic rats.(6)Inhibition of autophagy attenuated LPS induced apoptosis of AMs,reduced M1 polarization and increased M2 polarization.Conclusion:(1)HRS attenuates apoptosis,reduces M1 polarization and increases M2 polarization of AMs in septic rats with ALI.(2)HRS suppresses excessive autophagy of AMs in septic rats with ALI.(3)HRS attenuates ALI in septic rats through the regulation of AM polarization and a reduction in apoptosis by the suppression of autophagy.