The Protective Effect Of Aerobic Intermittent Pre-exercise On The Lung Injury Of Rats Caused By Subacute Particulate Matter Exposure

In recent years,haze weather occurs frequently,The elevated concentration of fine particulate matter(PM_2.5)is an iconic feature,high concentration of fine particulate matter is closely related to the incidence rate and mortality rate of various respiratory diseases.Fine particulate matter seriously affects and threatens people's quality of life.Can the benefits of exercise protect against the effects of smog on the respiratory system?The purpose of this study was to explore the effects and related mechanisms of Aerobic interval exercise?AIT?against respiratory inflammation in rats.40 Wistar rats were randomly divided into four groups:Control group?Control group?C?,10?,Exercise intervention group?Exercise group?E?,10?,the Control+PM_2.5 exposure group(Control+PM_2.5 exposures(C+PM_2.5)group),10),Exercise intervention+PM_2.5 exposure group(Exercise+PM_2.5 exposures(E+PM_2.5 group),10).After one week of adaptive feeding,the maximal oxygen uptake of the rats was measured to determine the training intensity,and then the maximal oxygen uptake was measured every two weeks to adjust the exercise intensity.Starting from the middle of August 2018,I will conduct 8-week exercise training?5 days per week,1h per day?.According to Hong-Ke Jiang et al.High intensity aerobic interval training scheme^[1],this experiment set of experimental rats movement scheme as follows:first,to 12 m/min?50%?55%VO₂max?run speed for 5minutes,this one phase of the movement scheme is mainly to warm up,let rat can gradually adapt to the next exercise intensity,then 4 minutes of intense exercise:40m/min?80%?90%VO₂ max?,followed by 3min of 15m/min?65%?70%VO₂ max?low-intensity recovery exercise,repeat 7 stages in this cycle,and then finish at 12 m/min?50%?55%VO₂ max?treadmill speed for 5 minutes.After the exercise intervention,the control group+PM_2.5 exposure group adopted the online PM_2.5 concentration system developed by hui rong science and technology company.,It is to collect and concentrate atmospheric particles in the outdoor air,simulate the real exposure environment of PM_2.5particles,and carry out animal exposure.Starting from October 15,2018 to November 5,2018,6h/day for 22 consecutive days.Rats were raised normally during exposure.The control and exercise groups were exposed to clean air.After the exposure,lung function of the rats was determined.Hematein eosin?HE?staining was used to observe the changes in lung structure,the ultrastructure of lung tissue was observed by transmission electron microscopy,and Cyclooxygenase in lung tissue was determined by Western blot?WB?.COX-2),p38 mitogen activated protein kinase?p38MAPK?and phosphorylated p38 mitogen activated protein kinase?p-p38 mitogen activated protein kinase?p-p38MAPK?,and interleukin-1?IL-1??in lung gavage,Secretion levels of Tumor necrosis factor-alpha?TNF-??and Prostaglandin E2?PGE-2?.Results:?1?lung function:MVb??31%,P<0.05,ES=1.48?,TVb??29%,P<0.05,ES=1.5?,EF50??38%,P<0.05,ES=1.5?,PIFb??23%,P<0.05,ES=1.3?,PEFb??30%,P<0.05,ES=1.4?,PAU??16%,P<0.05,ES=1.7?,Te??28%,P<0.05?,ES=1.4?significantly increased.Compared with the C+PM_2.5 group,the E+PM_2.5 group showed a significant decrease in PAU??6%,P>0.05,ES=0.8?,Te??19%,P<0.05,ES=1.2?,MVb??40%,P<0.05,ES=0.9?,TVb??30%,P>0.05,ES=1.0?,EF50??56%,P<0.05,ES=1.0?,PIFb??32%,P<0.05,ES=1.2?,PEFb??40%,P>0.05?,ES=0.7)significantly increased.Compared with group C,Ti??14%,P<0.05,ES=1.5?in group E decreased significantly,while PIFb?17%?,P>0.05,ES=1.0?increased significantly.F?P>0.05,ES=0.43?,MVb?P>0.05,ES=0.54?,TVb?P>0.05,ES=0.09?,EF50?P>0.05,ES=0.43?,PAU?P>0.05,ES=0.18?,Te?P>0.05,ES=0.50?,PEFb?P>0.05,ES=0.52?showed no significant difference between the two groups.?2?Lung tissue morphology:observed under light microscope after HE staining,the alveolar structure of rats in group C and group E was complete,and the layers of pulmonary artery walls were clear and smooth,with no abnormalities.In group C,there was a small amount of hemorrhage and inflammatory infiltration in the lung tissue,and some tracheal cilia became shorter.In the rats of the C+PM_2.5 group,a large number of inflammatory cells gathered in the periphery of the alveolar cavity,pulmonary artery,bronchus and terminal bronchioles.The alveolar septa was thickened and some lung tissues showed obvious fibrosis.Compared with the C+PM_2.5 group,the overall lung structure of the rats in the E+PM_2.5 group was complete,and the local bleeding situation of the lung tissue,the degree of inflammatory infiltration and the degree of vascular wall lesions were significantly improved.Group C were observed under transmission electron microscope,the alveolar type?cellular structure is complete,the lumen is clear,but the cell surface microvilli significantly reduced,lamellar corpuscle decreased significantly.Group E of the lumen is clear,alveolar type?cell cytoplasm visible in many sizes,number of characteristic addicted to osmium lamellar corpuscle,mitochondria structure is clear,no swelling.Compared with group C,C+PM_2.5 group rat alveolar type?fracture significantly reduce cell surface microvilli,lamellar corpuscle decreased significantly,some cells degeneration,apoptosis and even collapse,mitochondria swelling and cristae broken,lung fibrosis.Compared with group C+PM_2.5,E+PM_2.5 group rats alveolar type?lamellar corpuscle cells increased obviously,mitochondria swelling,necrosis degree improved,there are still a small amount of blood cells and inflammatory cells within the lumen.?3?inflammatory factors:compared with the C+PM_2.5 group,rats in the C+PM_2.5 group had significantly higher IL-1?levels??30%,P<0.05,ES=1.2?and TNF-?levels??33%,P<0.05,ES=2.0?,and PGE2??33%,P<0.05,ES=0.98?.Compared with the C+PM_2.5 group,rats in the E+PM_2.5group had significantly lower IL-1?levels??21%,P<0.05,ES=1.1?,TNF-?levels??17%,P<0.05,ES=1.3?,and PGE2??23%,P<0.05,ES=0.9?.There was no significant difference between group E and group C in il-1??P>0.05,ES=0.14?,TNF-??P>0.05,ES=0.33?,and PGE2?P>0.05,ES=0.32??4?arachidonic acid-related pathway protein:compared with the C+PM_2.5 group,p-p38??37%,p<0.05,ES=0.82?and COX-2??41%,p<0.05,ES=1.3?in the lung tissues of the C+PM_2.5 group were significantly increased.Compared with C+PM_2.5,the lung tissues of E+PM_2.5 rats were significantly reduced by p-p38??31%,p<0.05,ES=1.1?and COX-2??25%,p<0.05,ES=2.0?.Compared with group C,p-p38??42%,P<0.05,ES=1.13?was significantly lower in group C than in group E.There was no significant difference between group E and group C in p38?P>0.05,ES=0.18?and COX-2?P>0.05,ES=0.28?.Conclusions:?1?aerobic intermittent pre exercise can effectively prevent the lung function decline induced by particulate matter exposure in rats.?2?aerobic intermittent pre exercise can effectively prevent the lung tissue structure damage induced by particulate matter exposure.?3?intermittent aerobic pre exercise can prevent the inflammatory response induced by inhalable particulate matter exposure,inhibit the activation of p38MAPK signaling pathway,maintain the normal level of COX-2 and PGE2,and thereby prevent the level of inflammation..