A Study Over The Effects Of Artificial Cold Spell/Heat Wave And PM_2.5 On Respiratory System Of COPD Rat And The Effect Intervenion Methods

ObjectivesThe purpose of this study are to study the effects of artificial cold spell/heat wave and fine particles(PM_2.5)on respiratory system of chronic obstructive pulmonary disease（COPD）rats and explore the related mechanism and the intervention methods.MethodsSelect 0℃ and 40℃ as the minimum temperature of artificial cold spell and the maximum temperature of artificial heat wave.The 0℃ simulates a cold spell process with the temperature drop of 20℃ in 8 hrs.The 40℃ simulates a heat wave process with a maximum daily temperature of 35℃ or above and a duration of 3 days.1.Particle sampling:PM_2.5 samples were collected and used for the analysis of endotoxin,OC/EC and PAHs with Chromogenic End-point（Tachypleus Amebocyte Lysate）TAL Kit,Thermal/Photocarbon Analysis System and Gas chromatography mass spectrometry.2.Artificial cold spell and PM_2.5 exposure:Healthy adult male Wistar rats were chosen to develop COPD rat model.Then,COPD rats were exposed to cold spell and PM_2.5（0,3.2,12.8mg/ml）with the intervention of valsartan.The lung function of each group was measured after the last exposure.Pathological sections were taken from the lung tissue and the lung tissue was detected by enzyme-linked immunosorbent assay（ELISA）.The concentrations of tumor necrosis factor（TNF-α）,monocyte chemoattractant protein（MCP-1）and angiotensin 2（Ang-II）were determined by enzyme-linked immunosorbent assay（ELISA）.Malondialdehyde（MDA）,superoxide dismutase（SOD）activity and inducible nitric oxide synthase（iNOS）content were detected by TBA method,WST-1 and colorimetric assay.The positive expression of 8-hydroxydeoxyguanosine（8-OHdG）,nuclear factorκB（NF-κB）and heme oxygenase（HO-1）were detected by immunohistochemical analysis and the protein expression of nuclear transcription factor 2（Nrf2）and HO-1 were detected by Western blotting.3.Artificial heat-wave and PM_2.5 exposure:COPD rats were exposed to artificially simulated heat wave and different doses of PM_2.5（0,3.2,12.8 mg/ml）with the intervention of Vitamin E.The lung function of each group was measured after the last exposure.Lung tissues were collected for pathological sections.ELISA was used to detect the concentrations of TNF-αand MCP-1 in lung tissue.The contents of MDA,SOD and iNOS in lung tissue were measured by TBA,WST-1 and colorimetry.The positive expression of NF-κB,8-OHdG and HO-1 was detected by immunohistochemistry.The protein expression of Nrf2 and HO-1 was detected by Western blotting.4.Cold spell and heat wave comparison experimental part:Based on the results of cold spell/heat wave and PM_2.5 exposure to COPD rat,data of lung function,TNF-α,MCP-1,MDA,SOD and iNOS were used to compare the effects of PM_2.5 on COPD rat lung under cold spell and heat wave.Results1.Particle sampling:The proportion of OC₂,OC₃,OC₄ and EC₁ in the 8 types of carbon components was the highest,and the ratio of OC to EC was 2.46.The endotoxin content in PM_2.5was（0.91±0.02）EU/mg.ANT and 2-EA were the highest proportions of 17 parent polycyclic aromatics and 19 oxygenated polycyclic aromatics respectively.2.Artificial cold spell experiment:Cold spell further significantly increased PM_2.5-induced increase in Ang-II,HO-1,and 8-OHdG levels and pathological damage,and reduced PM_2.5-induced decline in PIF,PEF,and SOD levels,which were more significant in COPD rats compared with healthy rats.Valsartan can significantly inhibit the decrease of PIF induced by PM_2.5 in COPD rats,but it can’t significantly inhibit the increase of Ang-II TNF-αand MCP-1induced by low temperature.3.Artificial heat-wave experiment:Heat wave further significantly reduced PM_2.5-induced PIF,PEF,SOD activity decline,inhibited Nrf2 and HO-1 protein expression,aggravated pathological lesions exposed to PM_2.5 and high temperature,the changes of which were more substantial in COPD rats.Vitamin E could significantly improve the reduction of PIF/PEF in COPD rats induced by PM_2.5,and it can also significantly antagonize the elevated TNF-α,MDA,and decreased SOD activity caused by heat wave.4.Comparison experiment:Cold spell and PM_2.5 mainly affect the COPD rat lung through aggravating inflammation and oxidative damage,while heat wave and PM_2.5 mainly through increasing oxidative damage.Conclusions1.The main source of PM_2.5 during the sampling period is the exhaust emissions from traffic,and the secondary organic carbon（SOC）in OC is an important pollution component.2.Cold spell can exacerbate lung injury induced by PM_2.5 in COPD rats.The mechanism is mainly through activating AngII/NF-κB inflammation related signaling pathways.Valsartan has limited effects on cold stress-induced inflammation and oxidative damage.3.The mechanism of heat wave exacerbating lung injury induced by PM_2.5 in COPD rats is mainly through inhibiting Nrf2/HO-1 signaling pathway and increasing oxidative stress.Vitamin E intervention can effectively suppress these changes.4.Compared with healthy rats,COPD rats are more susceptible to cold spell/heat wave and PM_2.5.