Objective To explore the protective effect of L-carnitine on myocardial systolic dysfunction in sepsis and its underlying mechanism.Methods A mouse sepsis model was established by cecal ligation and puncture(CLP).Ten-week-old male SPF-grade C57BL/6 mice(body weight 20～30 g)were randomly divided into 5 groups via random number table:Sham group,Sepsis group,L-carnitine group,L-carnitine+Etomoxir(Eto)group,and Eto group.Echocardiography assessed cardiac function,ELISA measured serum creatine kinase isoenzyme MB(CK-MB)levels,and 72-hour survival rates were recorded to evaluate L-carnitine's effects on cardiac function.Cardiomyocytes were isolated,and a cell microtensiometer was used to detect cardiomyocyte contractile function and calcium transients.Myocardial tissues were collected from each group,and ELISA was used to determine the contents of triglyceride(TG),free fatty acid(FFA),and adenosine triphosphate(ATP).An in vitro sepsis model was constructed by stimulating HL-1 cardiomyocytes with lipopolysaccharide(LPS)for 12 hours,which was divided into 5 groups:control(CTRL)group,LPS group,L-carnitine group,L-carnitine+Eto group,and Eto group.ELISA was used to detect the contents of TG,FFA,and ATP as well as the activity of carnitine palmitoyltransferase 1A(CPT1A)in cardiomyocytes.A cellular energy metabolism analysis system was employed to measure fatty acid oxidation capacity,and Western blot was used to detect the protein expression of CPT1A in cardiomyocytes.BODIPY-FL-C16(green fluorescently labeled palmitic acid)was utilized to detect the distribution of fatty acids in the cytoplasm and mitochondria via immunofluorescence technology,thereby observing the ability of cells to transport fatty acids into mitochondria.Results Compared with the Sham group,cardiac function was significantly impaired in the Sepsis group,as evidenced by decreased ejection fraction and mean arterial pressure(P<0.05),along with elevated levels of the cardiac injury marker CK-MB(P<0.05).Treatment with L-carnitine significantly improved myocardial function,restored blood pressure in septic mice,and increased their survival rate from 12.50%to 81.25%(P<0.05).Compared with the Sham group,the contractile function and calcium transients of acutely isolated single cardiomyocytes were significantly reduced in the Sepsis group(P<0.05),while L-carnitine treatment remarkably restored the contractile function and calcium release capacity of septic cardiomyocytes(P<0.05).Both in vivo and in vitro experiments showed that TG and FFA levels were significantly increased(P<0.05),and ATP levels was significantly decreased(P<0.05)in the Sepsis and LPS groups—effects significantly reversed by L-carnitine treatment.Compared with the CTRL group,the basal oxidation rate and maximum oxidation capacity of fatty acids in cardiomyocytes of the LPS group were significantly reduced(P<0.05),and L-carnitine treatment notably improved these indicators.Compared with the CTRL group,the expression and activity of CPT1A in cardiomyocytes of the LPS group were significantly decreased(P<0.05),while L-carnitine treatment significantly increased the expression and activity of CPT1A(P<0.05).In LPS group cardiomyocytes,green fluorescently labeled palmitic acid primarily formed numerous granular/clumpy aggregates in the cytoplasm with minimal mitochondrial colocalization.In the L-carnitine group,the green fluorescent granules in the cytoplasm of cardiomyocytes were smaller,and colocalization with mitochondria was increased.However,the L-carnitine+Eto group exhibited similar phenomena to the LPS group.In addition,both in vivo and in vitro experiments demonstrated that treatment with the CPT1A inhibitor Eto reversed the effect of L-carnitine.Compared with the L-carnitine group,the ATP content in the L-carnitine+Eto group was significantly decreased(P<0.05),while the FFA content was significantly increased(P<0.05).Conclusion L-carnitine facilitates fatty acid entry into mitochondria for β-oxidation via a CPT1A-dependent mechanism,thereby ameliorating fatty acid oxidation dysfunction in septic cardiomyocytes and improving myocardial contractile function.

Objective To observe the improved effect of propofol on vascular hyporeactivity in septic rats and its underlying mechanism.Methods A total of 96 SD rats(12 weeks old,both genders,weighing 200～220 g)were randomly divided into sham group(n=16),sepsis group(n=16,cecal ligation and puncture),propofol group(n=16),propofol+ROCK inhibitor Y-27632 group(n=16),propofol+PKCαinhibitor GO6976 group(n=16),propofol+IP3 inhibitor 2-APB group(n=8)and propofol+gap junction inhibitor metoclopramide sodium(Movens)group(n=8).In vitro vascular ring reactivity and vascular calcium sensitivity were measured to observe the improved effects of propofol on vascular hyporeactivity in septic rats and its relationships with RhoA/ROCK,PKCα,IP3 and cell gap junction.Results Determination of in vitro vascular ring and calcium sensitivity showed that the contractile reactivity to norepinephrine(NE)and to calcium sensitivity were significantly decreased in the arterial rings isolated from the septic rats compared with those from the sham group,with the dose-response curve shifting to the right,and most significant decrease by 51.42％in the superior mesenteric artery(SMA,P＜0.05).Propofol treatment significantly improved the hyporeactivity and calcium sensitivity of the vessels isolated from the septic rats,especially those of the femoral artery with a recovery rate of 89.57％(P＜0.05).In comparison with the propofol group,the dose-response curves of the propofol+Y-27632 group and the propofol+GO6976 group were shifting to right,indicating that Y-27632 and GO6976 could significantly inhibit the amelioration of propofol on calcium sensitivity of SMA in severely septic rats with an inhibitory rate of 146.95％and 88.63％(P＜0.05),respectively.Isolated vascular reactivity measurement demonstrated that Y-27632 and Movens treatment significantly antagonized the ameliorated role of propofol on hyporeactivity of blood vessels from the septic rats with an inhibitory rate of 40.79％and 169.90％(P＜0.05),separately,while no such effect was observed in the propofol+GO6976 and propofol+2-APB groups.Conclusion Propofol treatment can significantly improve vascular hyporeactivity of septic rats,which may attribute to the increase of vascular calcium sensitivity through RhoA/ROCK pathway.

Objective To investigate the clearance capacity of cardiac resident macrophages in post-sepsis and its underlying mechanism.Methods A mouse model of sepsis was established using cecum perforation ligation.Thirty male C57BL/6 mice(8 weeks old,weighing 20～25 g)were randomly and equally divided into a sham operation group(sham group)and a model group(sepsis group).Immunofluorescence assay was employed to label the cardiomyocytes and macrophages to observe the apoptosis of cardiomyocytes and the phagocytosis by cardiac resident macrophages.Cardiac resident macrophages were extracted for transcriptomic sequencing to determine the functional changes of the cells after sepsis.Cardiac resident macrophage cell lines were established at the cellular level and served as the normal group(RAC group),and the RAC cells treated with LPS were subjected as the sepsis group(RAC+LPS group).Then the differences in the ability to clear apoptotic cardiomyocytes between the 2 groups were observed.Then DQ-BSA-RED lysosomal activity detection probe,Lyso-Sensor yellow/bule dye,ELISA,and Western blotting were applied to detect the lysosomal function of cardiac resident macrophages,activity and expression of important lysosomal hydrolases,changes in contents and related subunits of vacuolar-type adenosine triphosphatases(V-ATPase).Results Compared with the sham group,the sepsis group had larger number of apoptotic cardiomyocytes(P＜0.05)and increased phagocytosis of cardiomyocytes by cardiac macrophages(P＜0.05).The results of transcriptomic sequencing revealed a significant dysfunction of lysosome-associated functions of cardiac-resident macrophages after sepsis.In in vitro experiments,the RAC+LPS group had a reduced fragmentation capacity of apoptotic cardiomyocytes,reduction in the intensity of yellow fluorescence of lysosomes(P＜0.05),and decrease in lysosomal hydrolase activity(P＜0.05)when compared with the RAC group.In addition,LPS treatment significantly decreased the activity and expression of V-ATPase and its major subunit ATP6V1A in cardiac resident macrophages(P＜0.05).Conclusion Cardiac resident macrophages show reduced clearance of apoptotic cardiomyocytes after sepsis,which may be related to a decrease in the activity of ATP6V1A,an important subunit of its lysosomal V-ATPase,and reduced activity of lysosomal hydrolases.

Objective To observe the ameliorative effect of inhibiting acetyl-CoA carboxylase 2(ACC2)on cardiac dysfunction in septic mice and investigate its underlying mechanism.Methods Mouse model of sepsis was established by cecal ligation and perforation.A total of 24 male C57BL/6 mice(aged 8 weeks,weighing 20～25 g)were divided into sham operation group,sepsis group and ND-630+sepsis group.The cardiac specific ACC2 knockout(ACC2△CM)mice were constructed by Cre-LoxP recombinase system,and ACC2flox/flox Myh6-Cre-(ACC2fl/fl)mice were used as control.Several genetically engineered mice(8 weeks old,20～25 g,male)were divided into ACC2fl/fl+sham operation group,ACC2fl/fl+sepsis group,ACC2△CM+sepsis group,ACC2△CM+Mal-CoA+sepsis group,and ACC2△CM+sham operation group according to the random number table method.The contractile function and myofilament calcium sensitivity of cardiomyocytes were measured by a cell microtensiometer.Western blotting was used to detect the expression level of ACC2,and ELISA was employed to measure the level of malonyl-CoA(Mal-CoA)in myocardial tissue.The survival of the mice in 36 h after sepsis was observed.Results Compared with the sham operation group,the contraction amplitude of cardiomyocytes in sepsis group was decreased markedly,and the calcium sensitivity decreased significantly as well(P＜0.05).Based on the ACC2fl/fl+sham operation group,the ACC2△CM+sepsis group showed significant improvement in myocardial contraction compared with the ACC2fl/fl+sepsis group,with the contraction amplitude of cardiomyocytes recovered by 48.1％,and significantly restored calcium sensitivity(P＜0.05).ACC2△CM+Mal-CoA+sepsis group showed a notable decrease in myocardial cell contraction amplitude and a significant decrease in calcium sensitivity when compared to the ACC2△CM+sepsis group(P＜0.05).Compared with the sepsis group,the contraction amplitude of cardiomyocytes in the ND-630+sepsis group increased significantly,and the calcium sensitivity of myofilament also increased(P＜0.05).The expression level of ACC2 protein in the myocardial tissue of mice in the sepsis group increased compared to the sham operation group(P＜0.05).The level of myocardial Mal-CoA in the sepsis group was higher than that in the sham operation group(P＜0.05);Mal-CoA level in the myocardium of ACC2△CM+sepsis group mice was lower than that of sepsis group(P＜0.05).The 36-hour survival rate of the ACC2△CM+sepsis group.mice was 37.5％higher than that of the ACC2fl/fl+sepsis group mice.(P＜0.05).Conclusion Inhibition of ACC2 exerts a protective effect on myocardial contractility and calcium sensitivity in septic mice by reducing Mal-CoA.