Mechanism Of Sepsis-Induced Myocardial Dysfunction Based On CaMKⅡ/MPTP Pathway

Background Sepsis,multiple organ dysfunction and even septic shock have become the most common diseases with high mortality in intensive care units,And sepsis-induced myocardial dysfunction is the main target organ injury.After the active anti-infection,aggressive fluid resuscitation and multi-organ protection,despite cardiac preload have recovered,a proportion of patients with sepsis return to cardiac preload,hemodynamics of some sepsis patients still show low-output and highresistance（increased peripheral vascular resistance and decreased cardiac output）,which may be attributed to the fact that the myocardial mitochondrial damage has not been recovered.Objective The rat model of sepsis was established by Caecal Ligation and Perforation,to investigate whether calcium/calmodulin-dependent protein kinaseⅡ,Ca²⁺-ATPASE and mitochondrial permeability transition pore are involved in sepsis-induced myocardial dysfunction in rats with sepsis,and confirm that CaMKⅡ/MPTP pathway is one of the mechanisms that mediate sepsis-induced myocardial dysfunction in rats.Methods Forty-eight healthy male sprague-dawley（SD）rats with body weight between230g and 250g were randomly divided into Sham group,CaMKⅡinhibitor group and CLP group.The operation is found by the same person using the same method to find the cecum.Rats in the Sham group were not ligated or perforated in cecum;rats in the CLP group were treated with CLP to establish septic rat model;rats in the CaMKⅡinhibitor group were treated with intraperitoneal injection of KN93（10μmol/kg）after CLP.The following indicators were observed and detected:（1）Symptoms of sepsis in rats:general conditions（postoperative activity,spirit,water intake,reaction to stimulation,etc.）and survival of rats;The abdominal cavity of rats was dissected 36 hours after operation to observe the infection,Detection of Procalcitonin（PCT）in rat serum by Enzyme Linked Immunosorbent Assay.（2）Myocardial injury:Echocardiography of rats was detected 36 hours after operation.Cardiac troponin I（c Tn I）and N Terminal Pro B type Natriuretic Peptid（NT-pro BNP）were detected by（ELISA）in rat serum.Meanwhile,the activity of Ca²⁺-ATPase(Ca²⁺,Cardiac Muscle,Slow Twitch,Ca²⁺-ATPase)in rat heart tissue was detected by ELISA,MPTP openness of rat septic cardiomyocytes was measured by mitochondrial swelling method.HE staining was used to observe myocardial cell injury in rats with sepsis,The expression of CaMKⅡin rat heart tissue was detected by Western blot.Results（1）Signs of sepsis of rats in each group:Compared with the Sham group,the CLP group gradually showed a significant decrease in activity,intake of water,mental condition and response to stimuli after operation;Compared with CLP group,CaMKⅡinhibitor group had a slight decrease activity,intake of water,mental condition and response to stimuli after operation.Thirty-six hours after the operation,the survival rate was 100%in Sham group,75%in CaMKⅡinhibitor group and 37.5%in CLP group.Dissection of abdominal cavity revealed no obvious abnormalities in Sham group,while compared with Sham group,the abdominal cavity structure of rats in CLP group was unclear,with obvious odor,ascites,black necrosis and intestinal edema and adhesion after the operation 36 hours;Compared with the CLP group,the abdominal cavity structure of the CaMKⅡinhibitor group was clear after the operation 36 hours,with slight black necrosis and slight edema and adhesion of the cecum.The PCT of each group was compared 36 hours after operation,compared with Sham group,PCT in CLP group was significantly increased（P<0.05）;Compared with CLP group,PCT in CaMKⅡinhibitor group was significantly decreased（P<0.05）.（2）Myocardial injury of rats in each group:Compared with Sham group,LVEF of the heart in CLP group was significantly decreased（P<0.05）,Compared with CLP group,LVEF of the heart in CaMKⅡinhibitor group was significantly recovered（P<0.05）.Compared with Sham group,serum c Tn I and NT-pro BNP in CLP group were significantly increased（P<0.05）.Compared with CLP group,serum c Tn I and Nt-pro BNP in CaMKⅡinhibitor group were significantly decreased（P<0.05）.Compared with Sham group,Ca²⁺-ATPase activity in CLP group was significantly decreased（P<0.05）;Compared with CLP group,Ca2⁺-ATPase activity of CaMKⅡinhibitor group was significantly recovered（P<0.05）.Compared with Sham group,the expression of CaMKⅡin CLP group was significantly increased（P<0.05）;Compared with CLP group,the expression of CaMKⅡin CaMKⅡinhibitor group was significantly decreased（P<0.05）.Compared with Sham group,rats in CLP group had higher abnormal MPTP openness（P<0.05）,On the contrary,compared with CLP group,the abnormal openness of MPTP in CaMKⅡinhibitor group was decreased（P<0.05）.HE staining results of rat heart tissue suggested that compared with Sham group,myocardial cells in CLP group had incomplete epicardial structure,a large number of neutrophils and lymphocytes exudated,myocardial cells were obviously edema,and blood vessels were obviously dilated;Compared with CLP group,the epicardial structure of rats in CaMKⅡinhibitor group was intact,with only a few neutrophils and lymphocytes exudating,mild edema of myocardial cells and no vascular dilation.Conclusion CaMKⅡ、Ca²⁺-ATPase and MPTP were associated with sepsis-induced myocardial dysfunction in rats,CaMKⅡ/MPTP pathway is one of the mechanisms of sepsis-induced myocardial dysfunction in rats.