The Role Of Nitrosative Stress In The Post-cardiac Arrest Myocardial Dysfunction And Its Underlying Mechanism

BackgroundCardiac arrest(CA)refers to the disappearance of confirmed circulatory signs,the cessation of effective heart beat,or the sudden cessation of systemic blood flow directly caused by arrhythmia and/or the disappearance of effective heart beat.It is the disease with the highest mortality rate in China.The success rate of rescue in China is only 1%.It is one of the most critical situations in the field of public health and clinical medicine.Although patients with cardiac arrest recover their autonomic circulation after taking effective cardiopulmonary resuscitation measures,they still have varying degrees of coma and multiple organ dysfunction,which is called post cardiopulmonary resuscitation syndrome.Cardiac dysfunction is one of the important research contents in post cardiopulmonary resuscitation syndrome,and it is also the key reason for the low survival rate after cardiopulmonary resuscitation.When cardiac dysfunction occurs,myocardial microvascular blood perfusion decreases,microvascular endothelial function is damaged,vascular endothelial dependent relaxation function is weakened,and time-related abnormalities of cardiac systolic and diastolic function occur.Further research on cardiac dysfunction after cardiopulmonary resuscitation will help to improve the prognosis and survival rate of patients with cardiac arrest.Nitrosative stress is closely related to oxidative stress.It is a protein post-translational modification caused by the combined reaction of reactive nitrogen species and reactive oxygen species.Previous research results suggest that nitrosative stress is closely related to the occurrence and development of myocardial injury.On this basis,we further used the animal model of cardiac arrest to deeply study the pathological mechanism and intervention targets of nitrosative stress affecting the occurrence and development of visceral arrest.Objectives1.To determine whether nitrosative stress mediates myocardial dysfunction after CA/CPR.2.To clarify the effectiveness of treating CA/CPR with nitrosative stress as the intervention target.3.To further clarify the specific molecular mechanism of nitration modification after CA/CPR and explore its clinical transformation potential.Methods1.The animal model of cardiac arrest in Wistar rats established by asphyxia.2.Then rats were randomly divided into 4 groups,as follows:1)sham group,which only underwent surgical operation without CA/CPR;2)In CPR group,rats were given 6 minutes CA and CPR.The same volume of normal saline was injected intravenously 1 minute after ROSC;3)In CPR+FeTmPyP 1mg/kg group,the rats were treated with 6 minutes CA and CPR.The FeTmPyP was injected intravenously 1 minute after ROSC;4)In CPR+FeTmPyP 3mg/kg group,the rats were subjected to 6 minutes CA and CPR.The FeTmPyP was injected intravenously 1 minute after ROSC.3.The protein expression levels of 3-NT,bax,bcl-2 and cleaved caspase-3 were detected by Western blot.4.TUNEL staining was used to detect the apoptosis of rat myocardial tissue.5.The left ventricular function of rats was measured by small animal ultrasound.6.Record the heart rate and mean arterial pressure of rats.7.The structure of mitochondria in myocardial tissue was detected by transmission electron microscope.8.The survival time of rats within 72 hours after ROSC was recorded and the survival curve was drawn.9.CK-MB was detected after serum extraction.Results3-NT level was significantly increased in the heart after ROSC,and mainly appeared in the cytoplasm of cardiomyocytes.Administration of FeTMPyP(1 mg/kg or 3mg/kg)attenuated the increase of 3-NT in the myocardium.Inhibition of nitrosative stress improved survival and attenuated CA/CPR-induced reperfusion injury by maintaining the stability of MAP and HR,and reducing the accumulation of lactic acid.Post-cardiac arrest rats had higher serum CK-MB and Ang Ⅱ than healthy rats,while EF and FS were lower in healthy rats.Inhibition of nitrosative stress not only alleviated ischemic heart injury but also reduced the occurrence of CA/CPR-induced of arrhythmias.The results of Hematoxylin-eosin staining showed that there were inflammatory infiltration and abnormal morphological structure in myocardial tissue after CA/CPR,and FeTMPyP treatment could significantly improve the morphological damage of the myocardial tissue.Moreover,nitrosative stress mediated the upregulation of Cleaved caspase-3 and downregulation Bcl-2,which was abolished by FeTMPyP.ConclusionNitrosative stress plays an important role in the occurrence and development of myocardial injury after CA/CPR.Inhibition of nitrosative stress improves cardiac dysfunction after CA/CPR by reducing mitochondrial damage and inhibiting apoptosis.