Changes In Heat Shock Protein 27 Expression In Acute Coronary Syndrome And Its Correlation With Apoptosis Molecules

BackgroundCardiovascular diseases such as acute coronary syndrome（ACS）are the leading cause of death worldwide.ACS is caused by the rupture or erosion of unstable atherosclerotic plaques in coronary arteries,which results in thrombosis secondary to acute myocardial ischemia or necrosis,including acute myocardial infarction（AMI）and unstable angina（UA）pectoris.Although considerable progress has been made in the diagnosis,treatment,and prognosis of ACS in recent years,new diagnostic biomarkers and therapeutic interventions are urgently needed to reduce ACS-related morbidity and mortality.The main pathophysiological process of ACS involves myocardial tissue hypoxia caused by myocardial ischemia,which causes oxidative stress,apoptosis,and myocardial remodeling.Accumulating evidence has suggested that cardiomyocyte apoptosis mediates persistent damage to cardiac structure and function.Apoptosis is induced by extrinsic and mitochondrial pathways that activate the caspase cascade,leading to cellular damage.Fas ligand（FasL）is a cytokine that mediates apoptosis by binding to the Fas receptor.In addition,soluble Fas（sFas）and soluble Fas ligand（sFasL）have been recognized as circulating markers of apoptosis whose levels correlate with the clinical severity of cardiovascular disease.Heat shock protein 27（HSP27）is strongly induced during the stress response and protects cells from damage caused by multiple sources of stress by stabilizing the cytoskeleton,resisting oxidative stress,and resisting apoptosis.As an apoptosis-regulating protein,HSP27 interacts with key components of the apoptosis signaling pathway,especially in those that activate the caspase cascade;however,further studies are required to elucidate the regulatory relationship between HSP27 and Fas/FasL.For instance,it remains unclear whether HSP27 expression is related to Fas under hypoxic conditions,whether HSP27 expression is related to FasL in patients with ACS,and whether HSP27 can mediate ACS-induced apoptosis by regulating Fas/FasL.In addition,elucidating the regulatory relationship of apoptosis-related molecules in patients with ACS could enable HSP27 to be used as a potential therapeutic target in clinical practice.Research objectivesIn this study,an in vitro model of hypoxic injury in rat H9c2 cardiomyocytes was constructed using a hypoxia bag to determine whether hypoxia activated apoptosis and changes in HSP27 expression.Clinical experiments were also conducted to analyze the differences in serum HSP27,sFasL,and CK18-M30 expression levels in patients with ACS to determine their potential to predict the occurrence of ACS.Methods1.H9c2 cells were cultured with a hypoxia-generating bag to generate a hypoxic culture environment and to create a hypoxia model.Cell viability was detected using CCK-8 assays and intracellular reactive oxygen species（ROS）were detected using a DCFH-DA probe.TUNEL assays were used to detect apoptosis and to evaluate cell damage and apoptosis under hypoxic conditions.Western blotting was used to detect the expression levels of Caspase-3,Cleaved Caspase-3,Bc1-2,Bax,Fas,and HSP27.2.A total of 125 patients of the Department of Cardiovascular Medicine of the Second Hospital of Jilin University from March 1,2021,to September 30,2021,were selected as subjects for a cross-sectional study.A total of 95 patients had a definite ACS diagnosis（53 patients in the AMI group,42 patients in the UA group）and 30 patients were included in the control group who had been hospitalized in the Department of Cardiovascular Medicine during the same time period and received coronary angiography with no obvious coronary stenosis.Peripheral venous blood was collected from all patients and serum was obtained after centrifugation.Serum HSP27,sFasL,and CK18-M30 expression levels were detected using enzyme-linked immunosorbent assays.The correlation between serum HSP27,sFasL,and CK18-M30 expression levels was analyzed using Spearman’s rank correlation analysis.A receiver operating characteristic curve was produced,and the area under the curve was calculated to evaluate the predictive ability of serum HSP27,sFasL,and CK18-M30 levels for ACS,AMI,and UA.Results1.When incubated under hypoxic conditions for different lengths of time,the survival rate of H9c2 cells decreased and the levels of intracellular ROS and apoptosis increased in a time-dependent manner.In addition,prolonged hypoxia decreased the expression of the apoptosis-related protein Caspase-3 and the mitochondrial apoptosis protein Bcl-2,but increased the expression of Cleaved Caspase-3,Bax,the exogenous apoptosis protein Fas,and HSP27.2.Patients with ACS had higher serum HSP27,sFasL,and CK18-M30 expression levels than patients in the control group.HSP27,sFasL,and CK18-M30 expression were higher in the AMI and UA groups than in the control group,and HSP27 and sFasL expression were higher in the AMI group than in the UA group.In addition,serum HSP27 and sFasL expression correlated positively in patients with ACS,as did serum HSP27 and CK18-M30 expression levels.The best critical value of serum HSP27 expression for predicting ACS was 83.80 ng/mL,with a sensitivity of 78.95%and a specificity of 90%.The best critical value of serum HSP27 expression for predicting AMI was 94.51 ng/mL,with a sensitivity of 88.68%and a specificity of 100%.The best critical value of serum sFasL expression for predicting ACS was 82.14 pg/mL,with a sensitivity of 72.63%and a specificity of 86.67%.The best critical value of serum sFasL expression for predicting AMI was 91.72 pg/mL,with a sensitivity of 90.57%and a specificity of 93.33%.Conclusions1.Hypoxia can induce injury in rat H9c2 cardiomyocytes,potentially by triggering exogenous apoptosis.2.Serum HSP27 and sFasL expression were increased and positively correlated in patients with ACS,and thus could be used as biological markers to predict the occurrence of ACS and to distinguish between AMI and UA.Innovation and Research SignificanceIn this study,we first constructed a hypoxic environment to simulate the hypoxic state of cardiomyocytes in patients with ACS in order to explore the mechanism underlying hypoxia-induced cardiomyocyte apoptosis.Further clinical studies were conducted to explore the differences in the serum expression levels of HSP27 and apoptosis-related molecules,including sFasL,between the ACS and control groups.Thus,our findings provide new avenues for the development of biomarkers,such as serum HSP27 and sFasL expression,to predict ACS and AMI,and provide new options for treating patients with ACS.