Research About The Effects Of Maternal NO₂ Exposure On Lung Development And The Related Molecular Mechanism

Nitrogen dioxide（NO₂）is an important precursor pollutant for the formation of fine particulate matter(PM_2.5)and ozone（O₃）.NO₂ exposure has a wide range of effects on human health.Both short-term and long-term exposure can cause damage to the organism’s respiratory system and then lead to an increased risk of irreversible respiratory diseases.The developmental origins of health and disease（DOHa D）hypothesis state that the adverse health effects of maternal air pollution exposure are inherently transgenerational and developing tissues and organs are hypersensitive to toxic damage.Therefore,maternal NO₂ exposure may lead to increased disease susceptibility or dysfunction in the offspring.However,embryonic development is a complex biological process,and the mechanism by maternal NO₂ exposure is associated with lung disease in offspring is unclear.Therefore,this study was based on a model of maternal NO₂ exposure with NO₂-induced lung developmental toxicity as the core,to investigate the health effects and related mechanisms of maternal NO₂ exposure interfering with lung development in offspring mice.The main findings are as follows:1.The biological processes and mechanisms associated with possible respiratory damage and disease risk from maternal NO₂ exposure based on the whole transcriptome have rarely been reported.To gain insight into NO₂ exposure pathways and toxicity transmission patterns,in this part of the study,a model of maternal NO₂ exposure was established and lung tissues of fetal/offspring mice were collected at different developmental windows to measure the dynamic developmental processes.Meanwhile,the body weight,embryo and fetal weight,placental weight,placental thickness,and placental diameter were recorded,while the intrauterine environment was assessed using enzyme-linked immunosorbent assay（ELISA）kits and reactive nitrogen species（RNS）kits.Then,whole-transcriptome sequencing（m RNA-seq）analysis was performed on the lung tissue of fetal/offspring mice.The underlying biological processes of differentially expressed genes（DEGs）were explored using gene ontology（GO）enrichment analysis and whole gene set enrichment analysis（GSEA）.Finally,the expression of the hub genes was verified using quantitative real-time PCR（q PCR）and immunohistochemical（IHC）staining.The lung development indicators and lung function in the asthma model mice were correlated using the mix Omics R package.The results showed that maternal NO₂exposure led to an abnormal intrauterine environment,reduced fetal weight,and interfered with fetal development.Time-series m RNA-seq analysis revealed that maternal NO₂exposure resulted in time-series changes in the expression profile of genes associated with pulmonary vein myocardial development of fetal/offspring mice.And most of the related genes in the NO₂-exposed group were repressed at mid-gestation and after birth.Further studies revealed that pulmonary vein myocardial development-related genes and transcription factors（TFs）were associated with lung function in the asthma model mice,and had similar expression trends.This part of the study provides experimental evidence to elucidate the mechanisms associated with maternal NO₂ exposure on lung tissue development in fetal/offspring and lung diseases in offspring.2.Long non-coding RNAs（lnc RNAs）have been shown to be closely associated with lung development.It’s still unclear whether the expression profiles of lnc RNAs in lung tissue at different developmental windows are altered by maternal NO₂ exposure.In this part of the study,on the basis of alveolarization assessment of lung tissues of offspring mice,the expression profiles of lnc RNAs in fetal/offspring lung tissues at different developmental windows were analyzed by lnc RNA-seq.On this basis,lnc RNAs were clustered and classified by weighted gene co-expression network analysis（WGCNA）.The lnc RNAs were then subjected to cis-and trans-target gene prediction and potential biological process analysis.The results showed that maternal NO₂ exposure induced hypoalveolarization at postnatal day 14（PND14）of offspring mice.The screened lnc RNAs had time-series expression patterns,and 2 of the modules of lnc RNAs and target genes were involved in developmentally relevant biological processes.Furthermore,some of these target genes were shown to be associated with abnormal vascular development and lung diseases.This part of the study indicates that maternal NO₂ exposure leads to abnormal lung development in fetal/offspring mice,which may be associated with altered expression profiles of time-series pattern lnc RNAs.The results of this study provide experimental evidence to explore the epigenetic mechanism of maternal NO₂ exposure and abnormal lung tissue development in offspring mice.In conclusion,this study aimed to resolve the correlation between maternal NO₂exposure and the developmental toxicity of offspring lung tissues and the origin of respiratory diseases.And to provide a theoretical basis for establishing a bridge between air pollutant exposure and adverse pregnancy outcomes at the microscopic level.