Experimental Research Of Myocardial Mitochondrial Injuries In Septic Rats

BackgroundSepsis is a complex condition that occurs as a result of the systemic manifestation of infection. It may cause severe sepsis, septic shock and MODS .Severe sepsis and septic shock are among the most important causes of morbidity and mortality in patients admitted to PICU.Recent reports indicate that mitochondria are rather important in the pathophysiology of sepsis, but the mechanism is unknowm. Cardiovascular dysfunction often occurs in patients with sepsis.If the patients are not treated in time,it may lead to heart failure.At present,the research about myocardial mitochondria injuries is less in sepsis,and the possible mechanism of myocardial mitochondria injuries is unknowm .ObjectiveIn order to find the method of prevent myocardial mitochondrial injury, we assessed the myocardial injuries and myocardial mitochondria, and evaluated the level of mitochondrial ROS and RNS to find out possible mechanisms of myocardial mitochondrial injuries in sepsis. Method1 .The animal modelFifty male SD rats were randomly divided into five groups according to the detected time. The rats in LPS groups received l0mg/kg lipopolysaccharide by intraperitoneal injection .2. Measurements and MethodsRectal temperature, heart rate and breathing rate were observed before intraperitoneal injection and at each time point after intraperitoneal injection.LPS was detected by tachypleus amebocyte lysate kinesis quantitative method.Serum CK,CK-MB and cTnI levels were detected by automatic biochemistry analyzer.The Pathological change of myocardial tissue was observed under light microscope.The myocardial mitochondrion were observed through electronic microscopy and the degree of injury was analyzed by Flameng semiquantitative evalution. At each time point, myocardial mitochondrion were isolated by differential centrifugation.The membrane potential and the swelling of myocardial mitochondrion were analyzed by FCM.The activity of Ca²⁺ - Mg²⁺ ATPase was tested.The activity of complexI^IV in mitochondrial respiratory chain were tested. The myocardial mitochondrial ROS and RNS were detected by chromatometry.RESULTS1.General state of animalsThe content of LPS in LPS groups was positive .Rats subjected to LPS intraperitoneal injection developed signs of sepsis.2. Myocardial injuriesCompared with control group, serum cTnI levels increased significantly in 24hLPS, 48hLPS and 72hLPS groups (P<0.01). Compared with 4hLPS group, the cTnI level increased in 24hLPS,48hLPS and 72hLPS groups ( P < 0. 05,P < 0. 01,P < 0. 01). Compared with control group,serum CK level increased significantly in 4hLPS , 24hLPS and 72hLPS groups ( P < 0. 01,P < 0. 01,P < 0. 05).Compared with control group,serum CK-MB level significantly increased in 4hLPS , 24hLPS and 72hLPS groups ( P < 0. 01,P < 0. 01,P < 0. 05). We can see inflammatory change of myocardial tissue in LPS groups , some myocardial cells degenerate.3.Myocardial mitochondrial injuriesâ‘´Morphology : There are obviously decrease of substrate density and swelling of mitochondria in 24hLPS and 72hLPS. Compared with control group, the semiquantitative evaluation of myocardial mitochondrion significantly increased in 72hLPS group .(P < 0. 01 ).Compared with control group ,the swelling of myocardial mitochondrion significantly increased in both 4hLPS and 72hLPS groups (P < 0. 01).⑵Function of myocardial mitochondrionNo statistically differences in the membrane potential of myocardial mitochondrion among five groups (P>0.05). Compared with control group, the activity of mitochondrial Ca²⁺ - Mg²⁺ ATPase significantly decreased in 24hLPS,48hLPS and 72hLPS groups (P < 0. 01 ). Compared with 4hLPS group, the activity of mitochondrial Ca²⁺ - Mg²⁺ ATPase significantly decreased in 24hLPS,48hLPS and 72hLPS groups (P < 0. 01 ).Compared with control group, the activity of mitochondrial complex I significantly decreased in 4hLPS, 24hLPS, 48hLPS and 72hLPS groups (P < 0. 01 ). Compared with 4hLPS group, the activity of mitochondrial complex I significantly decreased in 24hLPS, 48hLPS and 72hLPS groups (P < 0. 01 ). Compared with control group, the activity of mitochondrial complex III significantly decreased in 4hLPS, 24hLPS, 48hLPS and 72hLPS groups (P < 0. 01 ). No statistically differences in the activity of mitochondrial complex II and complex IV among five groups (P >0. 05). 4 The myocardial mitochondrial ROS and RNSCompared with control group, the activity of mitochondrial SOD did not significantly changed in LPS groups ( P>0. 05). Compared with 4hLPS group, the activity of mitochondrial SOD significantly increased in 48hLPS group ( P < 0. 05).Compared with control group, the content of mitochondrial MDA significantly increased in 48hLPS and 72hLPS groups ( P < 0. 05)Compared with control group, the activity of mitochondrial GSH did not significantly changed in LPS groups ( P>0. 05) Compared with 24hLPS group, the activity of mitochondrial GSH significantly decreased in 72hLPS group ( P < 0. 05).Compared with control group, the activity of mitochondrial iNOS significantly increased in24hLPS, 48hLPS and 72hLPS groups (P < 0. 01, P < 0. 01,P < 0. 05).Compared with 4hLPS group, the activity of mitochondrial iNOS significantly increased in24hLPS, 48hLPS and 72hLPS groups (P < 0. 01, P < 0. 01,P < 0. 05). No statistically differences in the activity of mitochondrial CAT among five groups (P >0. 05) .No statistically differences in the content of mitochondrial NO among five groups (P >0. 05).6. Correlation analysesThe level of mitochondrial MDA and iNOS was inversely correlated with the activity of mitochondrial complex I( r = - 0.450, P <0.05; r = - 0.613, P <0.01). The level of mitochondrial iNOS was inversely correlated with the activity of mitochondrial complex III (r = - 0.462, P <0.05).The serum cTnI level was inversely correlated with the activity of mitochondrial complex I (r = - 0.570, P <0.05).Conclusions1. Myocardial tissue is injured in sepsis.2. There are injuries of myocardial mitochondria in both function and morphology,and the injury of function is earlier .3. Myocardial mitochondria is in the condition of oxidative stress in sepsis . Oxidative stress is a major cause of mitochondrial injuries in heart .