Restrain Stress Aggravates The Damage Of Heart In Rats With Crush Injury And Its Mechanism Of Endoplasmic Reticulum

Objective: In forensic practice,the number of nonfatal mechanicaldamage causing heart failure or even to dead is increasing. This kind of injuryoften happens in argument, fighting, non-violent torture, abusing and so on, ortraffic accident, earthquake. This kind of injury itself is not enough serious tolead to death, and even no obvious cardiovascular disease is observed. So thecauses of death often become intangible or controversial, which leads to thecase dragged and has a pernicious influence on society. In addition, in clinicalpractice, the slight wounds often happened to heart failure, which makes themedical staff unable to take effective action. So the research about nonfatalmechanical damage leading to heart failure or even to dead has becoming tobe focused issues..In addition to the direct effects of tissue injury on organism, the injuryitself, as a physical stressor, can cause the stress response. Besides, after theparties is damaged, the various reasons often caused anxious, depressed ornervous emotion, which is regarded to psychological stressor. When stressrespose occurs, both hypothalamic-pituitary-adrenal (HPA) axis and locuscereus norepinephrine axis (LC/NE) are activated. The levels of catecholaminein blood and urine are risen.[2]Moderate stress have defense meaning to body,but excessive stress may cause tissues and organs injury. Whether themechanism of nonfatal mechanical damage causing heart failure are related tostress remains unknown.Numerous studies have confirmed that endoplasmic reticulum stress(ERS)is one of the important cell responses.[4,5].The endoplasmic reticulum isresponsible for much of a cell’s protein synthesis and folding, and storage ofthe Ca2+. Various factors can disturbed protein folding and assembling, whichcan cause unfolded protein gathered in ER and activate unfolded protein response(UPR). This response can help the unfolded protein return normal,and prevent cells from damage. The growth of glucose-regulated protein（GRP78）is a marker protein in the activation of UPR. ER stress is necessaryto cells resisting injury, but excessive ERS can not only induce the expressionof genes encoding proteins with proapoptotic functions, such as CHOP, butalso activate inflammatory signaling pathway such as JNK pathway, whichcan cause tissues and cells damage. Some document reported that ERSparticipates in various cardiovascular disease.[4-6]But the processes of ERSparticipating in the non-lethal mechanical damage and causing myocardialdamage are unknown.In order to simulate the practical cases participated with mechanicaldamage and stress, our exercises established the complex model with crushinjury model and restraint stress model, and observed the effect of restrainstress on the damage of heart in rats with crush injury and its mechanism ofendoplasmic reticulum stress.Methods:1Grouping:36Sprague-Dawley rats (weight:200-220g), adaptively fedfor7days. Randomly divided into6groups: normal group(N); fasting watergroup(FW); restraint stress group(RS); composite model group(Com);4-PBA administration by intraperitoneal injection before restraint stress andcrush(Com+PBA). N: normal fed for24hours, weighted them with othergroup before and after exercises; FW: prohibit drinking and eating for8hours in the same time with restraint stress group: RS: restraint stress for8hours without drinking and eating, and freedom in other times, Continuouslyfor7days.④CR: fixed rats after narcosisING, overdraught24kg weight ontheir double hind legs for6hours, then removed the weight and let themfreedom.⑤Com: fixed rats after narcosisING, overdraught24kg weight ontheir double hind legs for6hours after restraint stress for7days, thenremoved the weight and let them freedom.⑥Com+PBA:4-PBAadministration by intraperitoneal injection30minutes before restraint stressand crush. 2Observe cardiac muscle tissue pathologic morphology according to HE3The protein expressions of GRP78, CHOP and caspase3, theendoplasmic reticulum stress markers, were determined byimmunohistochemistry. The protein levels of GRP78, CHOP and caspase3were examined by western blotting.4The cardiac muscle tissue homogenate IL-1 levels were tested byELISA.5The data were presented as Mean±SD and analyzed with one wayANOVA and least significant difference test (LSD) by SPSS16.0statisticalprogram. A level of p＜0.05was supposed to be statistically significant.Results:1There was no obvious pathological change in normal group and fastingwater group. Cardiac organizational structure is clear. Cytoplasm is loosen. Afew inflammatory cells infiltration were observed in restrain stress group.There is an intense eosinophilic of the contracted myocardial cells in crushgroup. Myofibrillar apparatus into cross-fiber, anomalous, and irregular orpathological bands. The most serious pathological changes such as a wavyappearance were showed in composite model group. In4-PBA administrationgroup, the myofibrillar apparatus into irregularly,but the number is obviouslydeduced compared to composite model group.2Immunohistochemistry staining indicated that GRP78, CHOP, thebiomarkers of ER stress, positive cells were significantly increased incomposite model group, compared with control group compared with restrainstress group, however, declined in Com+PBA group, compared withcomposite model group.3Similarly, the protein levels of GRP78, CHOP and caspase3detected bywestern blotting were also elevated composite model group, compared withcontrol group compared with restrain stress group, declined in Com+PBAgroup, compared with composite model group.4The cardiac muscle tissue homogenate IL-1levels tested by ELISA wereboth significantly increased in composite model group, compared with restrain stress group, however, declined in Com+PBA group, compared withcomposite model group.Conclusion:The present study set up the composit model of restraint stress and crushinjury successfully and observed cardiac muscle tissue pathologic morphology,detected the expressions of ERS mark protein and the levels of inflammatoryfactor IL-1. The conclusions were as followed:The restrain stress can aggravate the cardiac muscle tissue injure. Themechanism is associated with ERS-induced apoptosis and inflammation.