Effects And Mechanisms Of MMP16 On Chronic Obstructive Pulmonary Diseases Based On Model Induced By NO₂

BACKGROUDBased on our previous epidemiology studies and evidences,we reported that Nitrogen Dioxide(NO2)could indeed contribute to the pathogenesis of emphysema,but the underlying mechanisms remains largely unknown and requires further investigation.OBJECTIVETo explore the pathogenic roles of NO2 in emphysema by employing Matrix Metalloproteinase(MMPs)and its inhibitor tissue inhibitor of Metalloproteinase(TIMPs).METHODSIn this project,four parts of study were conducted to determine the underlying mechanisms of emphysema:1.Acute/chronic exposure of NO2-induced rat models were established to investigate the physiological and pathophysiological effects of NO2 on lung damage.Spirometry,hematoxylin and Eosin(H&E)staining on lung tissues,inflammatory counts of BALF and peripheral venous blood,immunofluorescence of CD68 macrophages,as well blood coagulation function,blood lipid and blood glucose levels testing were performed.2.Mechanisms exploration.Based on the animal model described above,the influences of NO2 on pulmonary system were therefore investigated.In parallel,a NaNO2-induced cell models were also established for in vitro study of molecular mechanisms.Levels of oxidative stress and nitrification stress,as well MMPs/TIMPs expressions were tested thereafter.3.The above results verified by using the GIRD COPD Biobank based blood samples.Whole Genome Sequencing on pedigree emphysema and further verification test on enlarged emphysema patients without blood-related were conducted.4.Further functional study were also performed on MMP16 rs2664370 T>C."MMP16--hsa-miR-576-5p--functional study" relationship was tested to comfirm if MMP16 plays a great influence on emphysema by binding with hsa-miR-576-5p.RESULTS1.Chronic exposure of NO2 led to emphysema in rats but without a collection of inflammatory cells.NO2 exposure could cause hematological derangement,blood viscosity,elevated blood lipids,and increased GLU levels that persisted(P<0.05).At longer time points post NO2 cessation,the lung function and hematological function were greatly improved,likely due to a better repair that lasts long enough.2.MMP16 might be one of the biomarkers in emphysema,and its levels were increased caused by toxic gas or particles exposure such as NO2,PM2.5 and CSE(P<0.05).3.MMP16 rs2664370 T>C was the common mutation among pedigree emphysema and enlarged emphysema patients without blood-related.Rs2664370 CC was a protective mutation under recessive mode,and it was possible that rs2664370 CC played its pivotal protective role by improving respiratory function in human.4.The C variants could also decrease emphysema risk,likely by binding with hsa-miR-576-5p,thus led to downregulated MMP16 expression.CONCLUSIONS1.NO2 exposure could cause emphysema,and elevated MMP16 expression might be the possible underlying mechanism in emphysema by degrading extracellular matrix and basement membrane in pulmonary tissue.2.It was possible that the C variants of rs2664370 decreased emphysema risk likely by binding with hsa-miR-576-5p which led to downregulated MMP16 expression,or played its pivotal protective role on human by improved respiratory function in emphysema.