Protective Effect Of Angiopoietin-Like Protein 7 On LPS-Induced Alveolar Simplification In Neonatal Mice

BackgroundAlveolar simplification is the pathological manifestation of bronchopulmonary dysplasia(BPD)in preterm infants,characterized by reduced alveolar septal,larger alveolar airspace and decreased alveolar count.BPD is one of the most common complications of premature infants,with a high mortality rate.Survivors are often combined with long-term respiratory and nervous diseases,which greatly increases the mortality rate of premature infants and affects their quality of life.At present,there are no effective measures to prevent and treat BPD,so it is of great significance to find a potential measure that can alleviate alveolar simplification.ObjectiveThis study aims to investigate whether ANGPTL7 can reduce the apoptosis of type Ⅱ alveolar epithelial cells,alleviate the inflammatory response and thus improve the alveolar simplification in neonatal mice induced by LPS,providing a new direction for the prevention and treatment of BPD.Methods1.In vivo,C57BL/6J mice at 3 days after birth were randomly divided into three groups according to their sex and weight: control group,LPS group and LPS+Angptl7group.Each group of six mice.PBS,LPS or ANGPTL7 were injected intraperitoneally at the same time according to the different groups.HE staining of lung tissue was used to observe the lung morphology to assess the degree of alveolar simplification.Immunofluorescence was used to detected the infiltration of macrophages in lung tissue.The expression of inflammation factors(IL-6,MCP-1,IL-10)were detected by q RT-PCR,and the level of inflammatory cytokines(IL-6,MCP-1)in peripheral blood were detected by ELISA.2.In vitro,type Ⅱ alveolar epithelial cells(A549)were treated with LPS(100ng/ml)and the optimal concentration of ANGPTL7.The group was divided as A549+PBS;A549+LPS;A549+LPS+ANGPTL7.The apoptosis rate of A549 cells in each group was detected by Annexin V-APC/PI double staining and the survival rate of A549 cells was detected by CCK-8.Results1.In vivo,compared with the control group,LPS aggravated the level of alveolar simplification characteristic by the disordered alveolar structure,reduced alveolar septal,larger alveolar airspace and decreased alveolar number,which alleviated by ANGPTL7 intervention.In vitro,compared with the A549+PBS group,LPS could decrease the viability of A549 cells and increase the apoptosis rate of A549 cells,while the viability increased and the apoptosis rate decreased after treated with ANGLTL7.2.Scattered F4/80 positive cell staining was observed on the alveolar walls of mice in the control group,indicating a small number of macrophages.After LPS stimulation,the number of F4/80 positive cells in the alveolar wall were increased.However,after the intervention of ANGPTL7,the number of lung macrophages was reduced.3.Compared with the control group,the m RNA expressions of MCP-1 and IL-6 in the lung tissue in LPS group were increased,and the m RNA expressions of anti-inflammatory factor IL-10 were decreased,while the expressions of pro-inflammatory factor MCP-1 and IL-6 were decreased and the expression of IL-10 increased after the intervention of ANGPTL7.4.Compared with the control group,LPS stimulation increased the levels of MCP-1and IL-6 in peripheral blood,while reduced after ANGPTL7 intervention.ConclusionsANGPTL7 can reduce the apoptosis of type Ⅱ alveolar epithelial cells and reduce inflammatory response induced by LPS,thereby alleviating the alveolar simplification.