Protective Effects Of Salidroside On Mitochondrial Functions Against Exertional Heat Stroke-Induced Organ Damage In The Rat

Exertional heat stroke(EHS)is the severe heatstroke when trained in high temperature and high humidity environments.Exertional heat stroke is characterized by high fever,coma,convulsions,rhabdomyolysis and multiple organ function failure.The mortality rate is as high as 50% if somebody are hitting on exertional heat stroke but not promptly treated.In addition to the high temperature damage,exertional heat stroke is also related to the oxygen deficit based on large load exercise.Both high temperature and oxygen deficit will damage mitochondrial function,increase the body’s oxygen deficit,make further deterioration.Protecting mitochondrial function in time will reduce exertional heat stroke on the body damage.Salidroside has been widely applied to improve myocardial ischemic injury which could inhibit hypoxia,the deficiency of mitochondrial membrane potential and the reducing of the activity caused by sugar damage.It could stabilize the mitochondrial membrane potential and inhibit cell apoptosis.Mitochondrial dysfunction included mitochondria swelling,ΔΨm,free calcium,respiratory control rate decrease,but ROS and MDA increase and antioxidant enzyme SOD reduction.Appropriate regulation of mitochondrial biogenesis and function is a critical component of adaptation to external conditions and prevention of pathogenesis.The present study was designed to evaluate the protective effects of salidroside on EHS by improving mitochondrial functions in the rat model.The purpose of these study was to established SD rats model of exertion heat stroke firstly and to explore the characteristics of mitochondrial in rat model by comparing with other control group rats.Further more,present study was designed to evaluate the protective effects of salidroside on exertion heat stroke rats.Part I The establishment of SD rat model of exertional heat stroke and the characteristic of mitochondris damageObjective:To establish a effective and stable rat model of exertional heat stroke and explore the characteristics of mitochondris damage in the rat.Methods:A total of 40 SD rats were randomly divided into 4 groups(n=10per group): control group(Group A),Exercise group(Group B),High temperature group(Group C),EHS group(Group D).Group A: rats were fed with normal standard method.Group B: in the SD animal room temperature(22°C),rats running on a treadmill(treadmill speed: 15m/min),given a electric stimulation(voltage 100V)when not run,after successive animals rest,and then continued to run until exhaustive.Group C: the thermostat inside temperature was adjusted to 45 °C,rats do not exercise until exhaustion.Group D: the thermostat inside temperature was adjusted to 45 °C and humidity was adjunted to 70%±5%.Rats running according to the first set of group B.Liver and heart mitochondria were observed by transmission electron microscopy and mitochondrial membrane potential(ΔΨm)was detected by a fluorescent probe.Intra-mitochondrial free Ca2+ concentration,mitochondrial respiratory control ratio(RCR),reactive oxygen species(ROS)levels,superoxide dismutase(SOD),and malondialdehyde(MDA)activity were detected by the corresponding kits Those relevant indicators(ΔΨm,RCR,SOD,MDA and Ca2+)were carried by comparative.To quantitatively estimate PGC-1α and Mn SOD m RNA expression in the rat hepatocytes and cardiomyocytes,real-time polymerase chain reaction(RT-PCR)was performed.Results: 1.Rat model of exertional heat stroke could established in the condition of 45 °C temperature and 70%±5% humidity and sustaining run in speeds 15m/min.2.It could observed by electron microscope that liver cells and cardiomyocytes from EHS group rats were swelling,mitochondrial myelin breakdown and together with disappearance of cristae matrix granules.In mitochondrial matrix or concentric cristae formed electron-lucent areas.3.Compared with control group,the mitochondrial membrane potential(ΔΨm),respiratory control ratio(RCR),intra-mitochondrial free Ca2+ concentration,superoxide dismutase(SOD)were lower significantly.But reactive oxygen species(ROS)levels and malondialdehyde(MDA)activity were higher significantly than those in control group.But the PGC-1α m RNA and Mn SOD m RNA level in hepatocytes and cardiomyocytes were down-regulation in EHS group than those in control group.Conclusions: The structure and function of mitochondria were damaged seriously in exertional heat stroke rats,which characteristic by reducing membrane potential(ΔΨm),respiratory control ratio(RCR),intra-mitochondrial free Ca2+ concentration and superoxide dismutase(SOD)and by increasing reactive oxygen species(ROS)levels and malondialdehyde(MDA)activity.The PGC-1α m RNA and Mn SOD m RNA level in hepatocytes and cardiomyocytes were down-regulation.Part II Protective effects of salidroside on mitochondrial functions against exertional heat stroke-induced mitochondrial damage in the rat.Objective:To explore the mechanism of the protective effects of salidroside on mitochondrial functions against exertional heat stroke-induced mitochondrial damage in the rat.Methods:A total of 50 SD rats were randomly divided into 5 groups(n=10 per group): control group(Group A),EHS group(Group B),salidroside low dose group(L,4 mg/kg,Group C),salidroside middle dose group(M,10 mg/kg,Group D)and salidroside middle High group(H,25mg/kg,Group E).Methods of establishing exertional heat stroke rat model were same as part I.Exercise distance,exercise time and body tempreture were observed.Liver and heart mitochondria were observed by transmission electron microscopy and mitochondrial membrane potential(ΔΨm)was detected by a fluorescent probe.Intra-mitochondrial free Ca2+ concentration,mitochondrial respiratory control ratio(RCR),reactive oxygen species(ROS)levels,superoxide dismutase(SOD),and malondialdehyde(MDA)activity were detected by the corresponding kits Those relevant indicators(ΔΨm,RCR,SOD,MDA and Ca2+)were carried by comparative.To quantitatively estimate PGC-1α and Mn SOD m RNA expression in the rat hepatocytes and cardiomyocytes,real-time polymerase chain reaction(RT-PCR)was performed.Results:1.Severity of mitochondrial injury in high dose salidroside group rats were lower than EHS group rats(group B).2.Compared with control group B,the mitochondrial membrane potential(ΔΨm),respiratory control ratio(RCR),intra-mitochondrial free Ca2+ concentration,superoxide dismutase(SOD)were higher significantly.But reactive oxygen species(ROS)levels and malondialdehyde(MDA)activity were lower significantly than those in group B.PGC-1α m RNA and Mn SOD m RNA level in hepatocytes and cardiomyocytes were up-regulation in group E than those in group B.Conclusion:High dose salidroside was able to relieve EHS damage by reducing the swelling of mitochondria,ROS levels and MDA activity,as well as increasing ΔΨm,RCR,free Ca 2+ concentration,SOD,PGC-1α and Mn SOD m RNA levels.In conclusion,salidroside has protective effects on mitochondrial functions against exertional heat stroke-induced organ damage in the rat.