Protective Mechanism Of Secretory Phospholipase A2 Blocker On LPS-induced Lung Injury In Neonatal Rats By Reducing Lung Surfactant Degradation

Background:Acute respiratory distress syndrome(ARDS)refers to acute and progressive respiratory failure caused by a variety of pathogenic factors inside and outside the lungs other than cardiogenic.In 2017,the internationally established ARDS standard(Montreux standard)for the first time.Due to the special features of neonatal biology and pathophysiology,its pathogenesis is still unknown.We collected clinical data of 925 premature infants with respiratory distress from January 1,2014 to July 30,2017,grouped based on Montreux criteria,and found that compared with neonatal respiratory distress syndrome(NRDS),neonates with ARDS used trachea After intrapulmonary instillation of pulmonary surfactant,oxygenation improved and clinical symptoms improved,but the condition relapsed quickly,requiring multiple use of pulmonary surfactant.We speculate that there are components in children with ARDS that rapidly inactivate lung surfactants.We can improve clinical symptoms in neonatal with ARDS by blocking this active component.Studies have shown that secreted phospholipase A2(sPLA2)can change the composition of pulmonary surfactant phospholipids and reduce alveolar stability.It is a rate-limiting enzyme for a variety of inflammatory mediators.In addition,studies have shown that the uncontrolled inflammatory response during ARDS is closely related to the activation of P38 mitogen-activated protein kinase(MAPK)signaling pathway and nuclear factor-?B(NF-?B).In this study,the effects of secreted phospholipase A2 inhibitor(Varespladib)on dipalmitoylphosphatidylcholine(DPPC),lung surfactant protein A(SP-A),and the keysignaling molecules of signal pathway of neonatal rats with ARDS were investigated to explore the protective effect and possible mechanism of Varespladib on the lungs of neonatal rats with ARDS.Methods:Intraperitoneal injection of LPS was used to construct a neonatal ARDS model,which was divided into three groups according to the random number table:I control(38),? LPS(41),and ? LPS+sPLA2 blocker group(Varespladib)(40).HPLC was used to detect the content of DPPC in lung tissue;electronic balance was used to measure the wet weight of lung tissue,dried for 48 hours after weighing,weighed to calculate the wet/dry weight ratio of lung tissue;HE staining to observe pathological changes and calculate lung tissue injury score;ELISA was used to detect SP-A,IL-1 in serum of each group,IL-4,TNF-?,sPLA2 and SP-A expression in alveolar lavage fluid.RT-PCR and WB detection of SPLA2,p38 MAPK and NF-? B signaling pathway key factors(p38 MAPK,p-p38,NF-?B p65,p-NF-? B p65)in lung tissues;LPS intervention in lung ? epithelial cells A549 in vitro They were randomly divided into 5 groups:? control,?LPS,? LPS+Varespladib,IVLPS+Varespladib group+p38 MAPK agonist(Anisomycin),V LPS+Varespladib group+ NF-?B p65 agonist(Betulinic acid).The cell proliferation of each group was detected by CCK8,the expression of p38 MAPK,NF-?B p65 mRNA was detected by RT-PCR,and the expression of p38 MAPK,p-p38,NF-?B p65,and p-NF-?B p65 protein was detected by WB.Results:DPPC and SP-A were up-regulated while sPLA2 was down-regulated by Varespladib in LPS-induced newborn rats and LPS-induced A549 cells(P<0.05).and the expression of inflammatory factors such as IL-1,IL-4,TNF-?,and sPLA2 decrease was observed while sPLA2 was down-regulated by Varespladib.(P<0.05).The mRNA and Ratio of phosphorylated protein to total protein expression of P38 MAPK and NF-?B P65 decrease was observed while sPLA2 was downregulated by Varespladib in the lung tissue of LPS-induced newborn rats and LPS-induced A549 cells(P<0.05).Conclusion:Secreted phospholipase A2 inhibitors reduce the Pulmonary surfactant degradation and inflammatory damage of lung surfactant through the P38MAPK/NF-KB pathway in LPS-induced newborn rats and A549 cells.