The Role Of MiR-29 In Lung Injury Caused By Air Pollution Among Schoolchildren

ObjectiveAir pollution has been classified as Group 1 carcinogen by the International Agency for Research on Cancer(IARC).Long-term exposure to air pollution is associated with an increased morbidity and mortality of respiratory diseases.Children are more susceptible to environmental chemicals because their immune system and lung function are not yet fully developed during the growth and development period.A number of epidemiological studies have shown that air pollution could cause lung function decline and respiratory diseases increased in children.Inflammatory response and immunologic injury are main mechanisms of lung injury caused by environmental pollutant.The immune system is very sensitive to environmental pollutants.Immunoglobulins and complements are the important components of humoral immunity,and play an important role in the immune function.Club cell protein(CC16)is a small molecule protein secreted by non-ciliated bronchiole cells,which has effects of anti-inflammatory,anti-oxidation and anti-fibrosis.CC16 is often used as an early sensitive marker for club cell damage and permeability changes in the lung blood barrier.C-reaction protein(CRP)is an acute phase response protein whose elevation reflects the body’s acute response to infection and injury.But there is lack of the systematic study of lung injury caused by air pollution among children.As one of the main mechanisms of epigenetics,microRNA(miRNA)can regulate the expression of target genes and affect many biological processes in vivo.Studies have shown that environmental pollution exposure can cause the expression levels of miRNA changed in occupation or general population,but there are few studies to investigate the miRNA expression changes caused by air pollution among children.To investigate the early effects of air pollution on children’s lung injury,we conducted a molecular epidemiological study among schoolchildren by observing immune system and lung injury biomarkers,analyzing the alternation in peripheral blood leucocyte miR-29 family and exploring the role of miR-29 in lung injury induced by air pollution among chi dren.MethodUsing a cross-sectional survey,two schools with different levels of pollution were selected as exposure group and control group.There were 163 children in exposure group and 110 children in control group.Air pollutant monitoring data including the concentration of PM2.5,PM10,NO2,CO were collected in the two areas.The concentration of serum IgE,IgA,IgG,IgM.complement C3 and C4 were detected by automatic immunoassay system.Serum CC16 level was detected by enzyme-linked immunosorbent assay.Serum hs-CRP level was detected by automatic biochemical analyzer.The expression of miR-29 family and target genes including phosphatase and tensin homolog chromosome 10(PTEN)were detected by RT-qPCR.We took the mediation analysis on the role of PTEN in miR-29 family and lung injury caused by air pollution among children.Result1.Immune and lung injury markers with air pollution exposure among childrenThe concentrations of PM2.5,PM10,NO2 and CO in the exposure group were significantly higher than those of the control group(P<0.001).After adjusting age,gender,BMI,and urinary cotinine levels,we found levels of serum complement C3 and C4 were lower in the exposure group than those of the control group(P = 0.001 and P<0.001,respectively):there is no statistically significant in serum hs-CRP levels in two groups(P = 0.07).After adjusting for age,gender,BMI,urinary cotinine levels,and serum creatinine,we found serum CC16 levels in the exposure group were increased than those of the control group(P = 0.008).Stratified by gender,BMI,and urinary cotinine levels,we found serum complement C4 levels in the exposure group were lower than that of the control group in boys(P =0.002).Serum hs-CRP and CC16 levels of the exposure group were higher than those of the control group in girls(P = 0.029,P = 0.004,respectively).In children with normal BMI,serum complement C3 and C4 levels in the exposure group were lower than those of the control group,but serum CC16 levels were higher than that of the control group(P= 0.043.P = 0.002,P = 0.002,respectively).In children with overweight,serum complement C4 levels were lower in the exposure group than that of the control group(P= 0.024).In children with urine cotinine<0.02 μg/mL,serum C4 levels were lower in the exposure group than those of the control group,but serum hs-CRP levels were higher than that of the control group(P = 0.019,P = 0.035,respectively).There was a significant negative correlation between complement C3,C4 and CC16 in all of the children(r =-0.201,P = 0.001;r =-0.201.P = 0.001,respectively).2.The expression of miR-29 family changes caused by air pollution among childrenThe expression levels of miR-29a-3p,miR-29b-3p and miR-29c-3p in the exposure group were 1.11,1.20,and 1.22 times higher than those of the control group,respectively(P= 0.024,P=0.002,P=0.007,respectively).We found that the expression levels of miR-29b-3p and miR-29c-3p in the exposure children were 1.30 times and 1.32 times higher than those of the control group in girls(P=0.006,P = 0.026,respectively).In children with normal BMI,the expression levels of miR-29b-3p in the exposure group was 1.17 times higher than that of the control group(P =0.015).In children with urine cotinine<0.02 μg/mL,the expression levels of mir-29a-3p,miR-29b-3p and miR-29c-3p in the exposure group were 1.13,1.20 and 1.23 times higher than those of the control group,respectively(P = 0.03 6.P = 0.010.P = 0.010.respectively).3.The role of miR-29 family in lung injury caused by air pollution among childrenThe expression level of PTEN mRNA was decreased in exposure group(P<0.001).We found that the PTEN mRNA expression level in the exposure group was lower than those of the control group by the stratification of BMI.urine cotinine(P values were 0.002,<0.001.0.004,and 0.008,respectively).There is a negatively correlation between the expression level of miR-29c-3p and serum CC16 in the exposcure group(r =-0.154.P = 0.05).But we did not find mediating effect of PTEN in miR-29 and serum CC16 elevation in our population.Conclusion(1)Air pollution may cause serum CC16 levels increase,which may be related to pulmonary blood barrier damage and increased vascular permeability of CC16.(2)The decrease of serum complement C3 and C4 may play a role in lung injury induced by air pollution.(3)Air pollution can cause the increase of miR-29a-3p,miR-29b-3p,and miR-29c-3p and decrease of PTEN in peripheral blood leukocytes among children.(4)There is a correlation between miR-29 family changes and lung injury marker,mainly as a negative correlation between miR-29c-3p and serum CC 16 in the exposure group.