To Investigate The Effect Of PM_2.5 Exposure On Diaphragm In Mice

Objective PM2.5 exposure can cause cardiopulmonary injury,leading to cardiovascular disease and chronic respiratory diseases.Such diseases are often accompanied by symptoms such as respiratory restriction and excessive lung inflation.Excessive inflation of the lung can easily lead to flattened diaphragm muscles,shortened muscle fibers,and mating area These changes in morphology are closely related to diaphragmatic dysfunction.The diaphragm,as the main respiratory muscle,plays an important role in the body’s breathing movement and oxygen transport in the blood.At present,there are few studies on the effects of PM2.5 exposure on diaphragm Therefore,in this experiment,PM2.5 tracheal instillation was used to preliminary investigate the effect of PM2.5 exposure on the diaphragm in mice.Methods Twenty 8-week-old male C57 / BL6 mice were randomly divided into control group(FA)and PM2.5 tracheal infusion group(PM2.5),with 10 mice in each group.The experimental group used tracheal instillation.After exposure to PM2.5(10 mg / kg),the control group was instilled with the same volume of control extract by trachea,instilled once every other day for 4 weeks,and executed 24 hours after the last infusion.DHE(Dihydroethidium)staining was used to determine the changes of superoxide anion in oxidative stress products.Picrosirius red staining was used to observe the degree of fibrosis of mouse diaphragm muscle,and HE staining was used to observe the changes in morphological structure of mouse diaphragm muscle tissue.Western blot was used to determine the expression of antioxidant proteins in mouse diaphragm muscle tissues.q PCR(polymerase chain reaction)was used to detect the transcription levels of antioxidant proteinases,related inflammatory factors,and collagen fiber genes in mouse diaphragm muscle tissues.Results(1)HE(hematoxylin-eosin)staining to detect the morphological structure of mouse diaphragm muscles: Observation of the paraffin section under a light microscope show that the muscle fibers in the longitudinal section of diaphragm muscles in the FA group were arranged neatly and tightly,with less interstitial cells and regular muscle striations,and the muscle fibers in transverse section had the same size.However,in the PM2.5 group,the muscle fibers in the longitudinal section of the diaphragm were different in size and some of them were twisted,the muscle striations were disordered,the connective tissue between the muscles was increased,the muscle fibers in the cross section were incomplete,and the muscle fiber gap was increased.(2)DHE(Dihydroethidium)staining to determine the changes in oxidative stress products: The results showed that the levels of superoxide anions in the diaphragm muscle tissue of the PM2.5 group were remarkably increased compared with the FA group(P <0.01).(3)Picrosirius red(PSR)staining to detect diaphragmatic fibrosis in mice:Compared with the FA group,the degree of fibrosis in the diaphragmatic tissue of mice in the PM2.5 group was significantly increased(P <0.05).(4)Polymerase chain reaction(q PCR)to detect oxidative stress,inflammation and fibrosis: Compared with the FA group,the transcription level of SOD1,SOD2 and SOD3(superoxide dismutase)in the PM2.5 group was greatly reduced(P < 0.05).The transcription levels of IL-1b,TNF-α,TGF-β,CD14 and other related inflammatory factors were significantly increased(P <0.05).The transcription levels of collagen genes including CollagenⅠ,CollagenⅢ were remarkably increased(P<0.05).(5)Western blotting was used to detect the expression of antioxidant enzymes related to mitochondria in the diaphragm of mice: Compared with the FA group,the expression level of Prdx1 in the PM2.5 group had no obviously change(P> 0.05),and the expression levels of Prdx5 and Trxr2 were reduced greatly(P <0.05).Conclusion(1)Four weeks of PM2.5 exposure can cause increased interstitial tissue in the diaphragm muscles of mice,promote distortion and disturbance of muscle fibers,and induce structural damage in the diaphragm muscles of mice.(2)Four weeks of PM2.5 exposure may inhibit oxidation-reduction protease activity,unbalance redox levels in mice,and induce oxidative stress in the diaphragm muscles of mice.(3)Four weeks of PM2.5 exposure may induce the inflammation of diaphragm muscle by up-regulating the transcription of CD14 and other inflammation-related factors.(4)Four weeks of PM2.5 exposure may promote the fibrosis of the diaphragm by promoting the transcription of collagen genes CollagenⅠ and Collagen Ⅲ.