Endoplasmic Reticulum Stress-mediated Apoptosis In Different Heart Surgical Procedures

Objective:In the current research field of cardiac surgery, myocardial preservation is a key point. MIRI(Myocardial ischemic reperfusion injury), as a significant reason of myocardial damage, was put increasingly effort on research. As a multi-factor pathological process, was found several pathways as: calcium overload, mitochondrial pathway, injured capillary pathway, multi-path inflammatory responses and lipid oxidation pathway. It is found present that ERS(endoplasmic reticulum stress) puts an important role on cell apoptosis, related inflammatory response and MIRI. UPR(unfolded protein response) was activated in the initial phase of ERS to protect cells from damage and to revive cellular functions. GRP78(glucose regulated protein-78), as an activating signal of ERS, can combine and inactivate transmembrane-proteins that mediate apoptosis, therefore protect cells, revive the function of endoplasmic reticulum and accelerate the UPR. Caspase-12, as a specificity transmitter located in endoplasmic reticulum cytoplasm and only functional in ERS, can motivate Caspase-3 to activate the apoptosis procedure. Considered as a key factor in ERS-mediated inflammatory response, NF-kB(nuclear factor kappa B) is an multanimity nuclear transcription adjustment factor express in various stress response and previously reported as a protective and also traumatic factor in ERS. The research on the three factors above was only restricted in cellular level, and more research in animal experiment is still necessary. Beating heart during cardiopulmonary bypass surgery, since 1990s and enjoyed a dramatic development,can prevent MIRI and reduce myocardial cell injury by maintain the coronary artery flow, witch can also protect the brain, lungs and kidneys during the surgery procedure. This experiment use rabbit cardiopulmonary bypass model, and immunohistochemistry technique to explore the expression of GRP78, Caspase-12 and NF-kB in cardiomyocytes;To investigate the Endoplasmic reticulum stress-mediated apoptosis in different heart surgical procedures.Methods:Models of cardiopulmonary bypass surgery were established in rabbits,36 New Zealand White Rabbits were randomly separated into 3 groups (n=12):the AH group (CPB arrested heart group), the BT group (CPB beating heart group), and Sham. In BT group, he common carotid artery, and jugular vein were isolated to establish cardiopulmonary bypass, and aorta were not benn blocked when cardioplegia perfusion. Extracorporeal time was 120 min; The In AH group, the heart was paralleled loop for 15min after CPB, and aortic was cross-clamped when the temperature dropped to 28℃-30 ℃, and S0T.homas II cardioplegia (15 ml/kg,4℃) was infusion in the aortic root at Omin,30min (7.5 ml/kg) and 60min (7.5 ml / kg) each. After the final infusion, rewarm began; perfusion restored at 34℃; and cardiopulmonary bypass end after the heart resuscitation parallel loop and stable vital signs was showed, the experiment was successful when experimental animals were still alive after CPB end 1 hour, after the myocardial specimens were obtained. Methods of immunohistochemistry technique detection of rabbit cardiomyocytes GRP78, Caspase-12 and NF-kB expressions of the 3 above groups; In situ nick end labeling (TUNEL) assay were employed on observation of cardiomyocytes apoptosis rate.Results:(1) Apoptosis index (AI):BT group (4.27±0.61);AH group (10.09±0.49), Sham(1.33±0.35):The difference of AI among each groups were significant difference (P<0.05). (2) expression intension of GRP78:BT group (72.24%±7.89%), AH group(16.53%±2.59%), Sham(1.68%±1.19%); The difference between groups was statistically significant (P<0.01). (3) NF-kB expression levels:BT group (73.70%±6.70%), AH group(13.81%±1.79%), Sham(2.42%±1.42%); The difference between groups was statistically significant (P<0.01). (4) Caspase-12 expression levels:BT group (73.74%± 7.15%), AH group(14.49%±2.29%), Sham(2.46%±1.56%); The difference between groups was statistically significant (P<0.01).(5)Correlation analysis: the correlation coefficient between the apoptosis rate and caspase-12 expression level in BT group and AH group was separately 0.961 (P<0.01) and 0.912 (P <0.01) witch shows significant positive correlation; the correlation coefficient between the apoptosis rate and GRP78 expression level in BT group and AH group was separately0.827 (P< 0.01) and 0.831 (P<0.01) witch shows positive correlation; the correlation coefficient between the apoptosis rate and NF-kB expression level in BT group and AH group was separately 0.317 (P> 0.05) and 0.281 (P>0.05) witch shows no significant correlation;Conclusion:(1) GRP78 expression elevated in both groups infers that GRP78 played a role in cellar injury in cardiopulmonary bypass surgery.(2) Caspase-12 expression elevate in both groups demonstrates apoptosis exists in cellar injury during cardiopulmonary bypass surgery.(3) NF-kB expression elevated in both groups infers that ERS was strongly activated during cardiopulmonary bypass surgery; NF-kB was shows no significant correlation with Apoptosis index in same samples indicate NF-kB pathway is a complicated mechanism and may to some extent has a bidirectional regulation mechanism.(4)Apoptosis of myocardial cells can be significantly declined by beating heart surgery therefore myocardial cells were protected.