Heart Damage Mechanism Research Induced By Oxidative Stress In Hot And Humid Environment

Research backgroundHeatstroke is refers to the human body under the hot and humid environment of high temperature,high humidity,due to loss excessive water and electrolyte,heat dissipation function failure caused to the central nervous system,the cardiovascular system,the digestive system et al,the main performance of the system dysfunction disease induced by hot and humid stress.According to the diagnostic standard of management of occupational heat stroke(GB11508-89)heat stroke can be divided into the following three grade:mild heat stroke and moderate heat stroke and heat stroke.Severe heatstroke have three categories:heat cramps,heat exhaustion and heat stroke,in which heat stroke can be deadly.In the south of China,damp and hot is the mainstream of the summer climate,according to incomplete statistics,China heat stroke mortality rate could be as high as 10?15%;Epidemiological data showed that during the period of extremely hot,urban areas heat stroke incidence is 20/100000 in the United States,its potential mortality rate is about 40%,and the fatality rate of about 50%in Saudi Arabia.Current research suggests that hot and humid environment lead to heat stroke mainly for multiple organ dysfunction syndrome and multiple organ failure,and cardiovascular system is considered to be the first to be affected,but for its damage and damage mechanism research is less,and lack of targeted therapy,the study will further to reveal the pathogenesis of cardiac injury in hot and humid environment establish the theory foundation,for further research and clinical prevention and treatment of damp and hot stress related heart function damage.Objective1.To investigate the heat stroke(heat stroke,HS)rat myocardial injury and risk factors of death;2.To explore the damp and hot stress cause rat myocardial tissue damage and heart function damage mechanism;3.To explore reactive oxygen species(ROS),Angiotensin?(Ang?)the role and the mechanism with the process of myocardial injury in heat stroke(damp and hot stress);4.For further research and clinical prevention and treatment of heat stroke related heart function damage provide theoretical basis.Methods1.Experimental rats groups:Specefic pathogen Free(SPF)level Sprague Dawley(SD)rats(48),weight 278?278g,which feeding in Guang zhou military area commands 1 week,Guang zhou general hospital laboratory animal center temperature of 23?,humidity(50+5)%,12h day/night cycle,the experimental rats were randomly divided into normal Control group(Control group C),Heat stroke group(Heat stroke,HS group),the Heat stroke of vitamin E treatment group(Heat stroke of vitaminE,VitEHS group),the Heat stroke of valsartan treatment group(Heat stroke of valsartan,ValsartanHS group),12 rats each group of.2.Heat stroke rats animal model:The rats are put in simulated hot climate animals capsule,which were to preheat temperature:40?,humidity:65%.Diagnostic criteria of the HS:anal temperature of(42.5+0.2)?,at the same time weakness of the limb,can't crawl.3.The recovery process:each group rats were weighed and record the weight change before and after hit,formula:weight rate=(weight changes(the weight of before heat and humid stress-the weight of maximum core body temperature)/the weight of before heat and humid stress)×100%;Restore food,water,the body temperature were detection every 30 minutes in the process of recovery,after 3 hours change to every 6 hours;The weight were record every 12 hours;VitEHS,ValsartanHS group were given VitEl00mg/kg/day(dissolved to 1 ml),Valsartanl6mg/kg/day(dissolved to 1 ml)to fill the stomach,the group C,the HS group were given saline 1 ml/day to fill the stomach,the experiments were terminated after 72 hours.Kanplan-Meier curve is draw and the mortality is calculate.4.Histopathological detection:the myocardial tissue specimens(apex)were return,paraffin section,using HE staining observation each groups myocardial specimen pathological change,TUNEL method is used to detect myocardial cell apoptosis;The other do myocardial tissue electron microscope slices,myocardial tissue ultrastructure were observed with electron microscopy.5.Serum detection:Blood specimens were returned with blood collection by abdominal aortic,using the kits in serum Creatine Kinase isoenzyme MB(CreatineKinase-MB,CK-MB),hypersensitive c-reactive protein(hypersensitive C-reactive protein,the hs-CRP),cardiac troponin I(cardiac troponin,cTn-I)and Acetylcholine(Acetylcholine,Ach),Ang?,etc.6.Oxidative stress test:The myocardial tissue of rats were return,at-70?refrigerator cryogeniced,the myocardial tissue glutathione(glutathione,GSH),malondialdehyde,malondialdehyde(MDA),Total Antioxidant Capacity(Total Antioxidant Capacity,T-AOC),Total Superoxide Dismutase(SOD)(Total Superoxide Dismutase,T-SOD)were test using the kits.7.Use SPSS19.0 Statistical processing,the data statistics software,measurement data with mean±standard deviation(X±S),comparison between the two groups of mean using t test,multiple sets of comparison between mean using analysis of variance(one-way ANOVA),Kanplan-Meier method and survivalcurve,compare the log-rank ?2 test,the analysis of the factors affecting the COX regression model,P<0.05 for the difference was statistically significant.Results1.The in rats heat stroke model were successful built,the average onset time between the HS,VitEHS group,ValsartanHS group is no difference,there was no statistically significant difference(P>0.05).Weight change rate of group C are smaller than the HS group,VitEHS group,ValsartanHS group,the difference was statistically significant(P<0.05),but the HS group,VitEHS group,ValsartanHS group,the weight rate differences between groups have no statistical significance(P>0.05).2.The HS group,VitEHS group,ValsartanHS Kanplan-Meier survival analysis of 72 hours were found that there was no statistically significant difference between groups mortality(P>O.05),but data shows deaths occurred mainly within 24 hours after the onset.The major risk factor for heat stroke model in rats death is hypothermia after the onset and longer time hit display by COX regression model,but relatively higher weight rate on the survival of the heat stroke model in rats has certain protective effect.3.The myocardial tissue is HE staining,basic normal myocardial tissue structure of group C,myocardial cells are round,center nucleus and cytoplasm are dyed,no inflammatory cell infiltration and hemorrhage;Some disordered arrangement of myocardial cells in HS group,form irregular or blurred,part of the cytoplasmic hyperchromatic,myocyte hypertrophy,interstitial cells visible scattered hemorrhage,edema and inflammatory cell infiltration;VitEHS group of.myocardial cells arranged neatly with the HS group,the number of hypertrophy of cardiac muscle cells are decreased,mesenchymal cells are still visible scattered hemorrhage and edema and inflammatory cells infiltration,but reduce with the HS group;ValsartanHS group compared with the HS group cell arrangement is neat,hypertrophy of cardiac muscle cells,cells in interstitial sites,inflammatory cells infiltration quantity reduced,interstitial edema degree of ease,but no significant difference compared with VitEHS group.4.Group C rats myocardial tissue sarcomere neatly,Z line is clear,did not seen muscle wire fracture,dissolved,mitochondria swelling,crest clarity,closely packed neatly,cell nuclear chromatin evenly,did not see chromatin pyknosis,edge set,no cavitation degeneration;HS group rats myocardial tissue shows partial muscle microfilament loose,fuzzy,Z line is not obvious,mitochondria swelling and cristae blur,visible vacuolation,irregular,nuclear shape nuclear weeks gap widened,nuclear chromatin condensed and fixation appear edge clustering phenomenon by transmission electron microscope,the above change did not improve in the HS group 24 hours,48 hours,72 hours.VitEHS group sarcomere neatly,Z line clear,mitochondria swelling,alleviate and crest is relatively clear,mitochondria,vacuoles obviously reduced,the nuclear shape is neat,the cell nuclear chromatin is uniform,occasional nuclear weeks widened slightly and edge clustering phenomenon with the HS group;ValsartanHS group compared with the HS group sarcomere is neat,Z line is clear,mitochondria swelling,alleviate and crest is clear,did not see clear vacuoles mitochondrial and nuclear shape is neat,the nucleus is relatively uniform,occasional nuclear chromatin weeks widened slightly and edge clustering phenomenon;ValsartanHS group no significant difference compared with VitEHS group.5.Only see a minority of myocardial cell apoptosis in group C,HS group,VitEHS group,ValsartanHS group dramatic increase in the number of myocardialcell apoptosis by analysis of variance(one-way ANOVA),the difference was statistically significant(P<0.05);The number of myocardial cell apoptosis in ValsartanHS group and VitEHS group were decreased than the HS group,but still higher than that of group C number of myocardial cell apoptosis,the difference was statistically significant(P<0.05);VitEHS group compared with ValsartanHS group,two groups of myocardial cell apoptosis number has no statistically significant difference(P>0.05).6.The HS group compared with group C the serum content of Ach decreased significantly,the difference was statistically significant(P<0.05).7.The myocardial apoptosis number(AI)of VitEHS group and ValsartanHS group is less than the HS group,but more than C group,the difference was statistically significant(P<0.05),VitEHS and ValsartanHS group are no difference between the number of myocardial cell apoptosis.8.Groups of cardiac muscle creatine kinase isoenzyme MB(CK-MB)content,serum cardiac troponin I(cTn-I)content,no significant difference(P>0.05).9.The HS group,VitEHS group,ValsartanHS group serum hypersensitive c-reactive protein(HS-CRP)content increased significantly compared with the C group,the difference was statistically significant(P<0.05);VitEHS and ValsartanHS group serum hypersensitive c-reactive protein(hs-CRP)content is less than the HS group,but still higher than that of group C,the difference was statistically significant(P<0.05);VitEHS group compared with ValsartanHS group,there was no statistically significant difference(P>0.05).10.The Serum angiotensin ?(Ang?)content of group C is relatively less,the HSgroup,VitEHS and ValsartanHS group serum angiotensin?(Ang?)content increased significantly,the difference was statistically significant(P<0.05);ValsartanHS group serum angiotensin ?(Ang?)content is a little higher than the HS group and VitEHS group,the difference was statistically significant(X<0.05);The HS group compared with VitEHS group,there was no statistically significant difference(P>0.05).11.The myocardial tissue of glutathione(GSH)and total antioxidant capacity(T-AOC)and total superoxide dismutase(T-SOD)content of Group C is more compared with the HS group,the VitEHS group and ValsartanHS group,by the analysis of variance(one-way ANOVA),the difference was statistically significant(P<0.05);VitEHS group and ValsartanHS of GSH,T-AOC,T-SOD content were increased than the HS group,but still lower than that of group C,the difference was statistically significant(P<0.05);VitEHS group compared with ValsartanHS group,GSH,T-AOC,T-SOD content differences had no statistical significance(P>0.05);The HS group,VitEHS group,ValsartanHS group of myocardial tissue malondialdehyde(MDA)content increased significantlythan the C group,through the analysis of variance(one-way ANOVA),the difference was statistically significant(P<0.05;The MDA content of VitEHS group and ValsartanHS group were decreased than the HS group,but still higher than that of group C,the difference was statistically significant(P<0.05);VitEHS group compared with ValsartanHS group,there was no statistically significant difference(P>0.05).Conclusion1.The study found that the heat stroke model in rats of death main within 24 hours after the onset time,the main risk factors may be related to recovery of low temperature and longer fight time closely related,and relatively high weight rate on the survival of the heat stroke model in rats has certain protective effect.2.This study further clear about that the high temperature and high humidity environment can be caused to myocardial tissue damage,but the study did not find the presence of myocardial tissue necrosis,the myocardial tissue damage may be related to myocardial apoptosis induced by Ang? and reactive oxygen species;Ang?? reactive oxygen species(ROS)? oxidative stress(oxidative stress)?mitochondrial damage?the myocardial cell apoptosis?myocardial injury,may be one of the signaling pathway of myocardial tissue damage by the high temperature and high humidity lead to heat stroke,through antagonist of angiotensin ? with AT1 receptor and remove excessive reactive oxygen species may be can reduce myocardial tissue damage caused by heat and humid stress.