A Preliminary Study On The Role Of FXR Induced Alveolar Cell Death In The Pathogenesis Of MAS

Background and objectiveMeconium aspiration syndrome(MAS)refers to the inhalation of meconium-stained amniotic fluid during the labor,caused by a series of inflammatory mediators,which can affect multiple systems of the body.The symptom varies according to the levels of inhalation and the meconium content.The pathogenesis of MAS is complex and not yet fully clear,severe MAS has multiple complications and the treatment of MAS is difficult.Therefore,MAS is still a hot topic that attracts the neonatologist.Cell death is the biological process of cell metabolism,the end of cell life,and also the game changer of the structure and function of the organ.Cell death and cell growth,value,differentiation,as are regulated by the body.The caspase cascade is a classic pathway of programmed cell death,with or without mitochondrial involvement.It is widely believed that necrosis is an accidental and unregulated event.However,there is growing evidence that the regulatory mechanism of cell death exists.Previous studies show that cholic acid can induce A549 cell death,low concentrations of bile acid induce apoptosis,and high concentrations of cholic acid induce necrotic apoptosis.But the underlying mechanism still needs to be elucidated.In the present study,we use human lung cancer cell line A549 as a tool cell.A549 cells and alveolar epithelial cell function similar.Based on this,we further explored the effects of lung-impairing factors such as meconium,cholic acid on cell death.The Farnesoid XR receptor(FXR)is an important regulator of several metabolic pathways.As a bile acid receptor and bile acid biosynthesis bioreceptor,the FXR influences the metabolism of bile acids,inflammation and cell cycle control.In recent years,a number of clinical studies have found that FXR plays an important role in the development of acute lung injury-ARDS,but themechanismis unclear.Previous studies have found that FXR may act as a nuclear receptor of cholic acid,mediating cholic acid-induced alveolar epithelial cells(AEC)death and inhibiting PS secretion.With understanding the effects of FXR on the regulation of inflammation and endothelial function,the mechanism of FXR action in the new born respiratory diseases needs further investigation.MethodsPart 1: Animal modeling of neonatal rat meconium aspiration syndrome through intratracheal injection of meconium;Part 2: A549 cells were stimulated with different concentrations of meconium suspension.Then we investigated the apoptosis and necrosis of the cells.To explore the role of FXR in the pathogenesis of neonatal meconium aspiration syndrome,the lung tissue and cells were measured of FXR and RIPK3 expressionby Wester blot and SDS-PAGE gel electrophoresis.;Part 3: Mechanical ventilation neonatal were recruited in the present study,and were divided into patients with pulmonary intubation group(P),the control group :Non pulmonary intubation patients.We collected alveolar lavage fluid cells and investigated the cell death ratio and type through flow cytology.Results(1)Meconium inhalation induces lung injury in the 2ml/ kg MAS tracheal intubationgroup,as reflectedby alterations of the wet / dry weight,chest X-ray,blood gas analysis and pathological morphological observations.(2)After treating A549 cells with different dose of meconium,the cell death increased in a dose-dependent manner.Compared with the C group and NS group,the expressions of FXR and RIPK3 in lung tissue of MAS group were increased.After treating A549 cells with different dose of meconium,the expressions of FXR and RIPK3 were increased.(3)The average cell death rate in the patients with pulmonary intubation group was about 25%(21%),and the average rate of cell death in non-pulmonary intubation was about 5%.The mean value of IL-6 in blood of patients with pulmonary intubation group was 533,which was significantly higher than that of the non-pulmonary intubation group.Conclusion:1.The meconium aspiration syndrome model can be successfully produced by injecting meconium suspension 2ml / kg into the tracheal tube,thus providing a better animal model for the study of meconium aspiration syndrome and the related diseases.2.The death of A549 cells was increased in a dose-dependent manner,and 20 mg / ml of meconium stimulation for 24 hours was a good choice for the animal model.The cell death rate was about 39% under such conditions.With the increase of meconium suspension concentration,the expressions of FXR and RIPK3 significantly increased.3.In patients with pulmonary intubation,the proportion of cell death was significantly higher than that of non-pulmonary tracheal intubation,and the death mode was mainly apoptotic cell death.