| Lipopolysaccharide (LPS), the cytoderm component of Gram-negative bacteria,is a critical harmful factor to organism in septic shock, but the pathophysiology ofsepsis-induced myocardial dysfunction remains controversial. In previous research,it has been found that release of LPS by bacteria in sepsis can active immune systemand inflammatory reaction which will injure organism greatly; LPS also can decreasemyocardial contractility and heart rate that will cause cardiac dysfunction. It's notclear that whether LPS injure heart directly and the mechanism of this injury. As amajor component of myocardial cells, cytoskeleton proteins maintain theconstruction of myocardial cells and affect cardiac function. We presume that LPSnegative effect to construction and function of heart may be related with thecytoskeleton injury of myocardial cells. The aim of this study is to observe themyocardial desmin changes after stimulated by LPS in vivo and in vitro and toinvestigate the mechanism of LPS effects on myocardial cytoskeleton.There are two parts in the experiments. First, we observed the change of heartfunction in vivo after stimulating by LPS and Polydatin (a protective drug tomyocardial cells); second, to observe the change of distribution and quantity ofmyocardial cytoskeleton desmin in vitro after stimulating by LPS and calphostin C(inhibitor of PKC) and TPA (activator of PKC) and Y27632 (inhibitor ofRho-kinase).In the first experiment, Wistar rats were injected with LPS (Salmonellatyphosa, 10mg/kg weight) and then ventricular pressure be examined. We found that LVSP (110.53±10.32) began to decrease after 6h LPS stimulation compared tocontrol (128.09±16.83). Dp/dt max (3546.36±438.58) also began to decreasebut there is no significant difference compared to control (4043.96±1119.81 ) andLPS+PD and PD group. After 7h LPS stimulation, LVSP (48.31±11.03) decreasesignificantly compared to control (126.81±15.56) (p=0.022), dp/dt max(1089.69±403.81) also has significant difference compared to control(4000.36±1000.54 ) and LPS+PD (3817.05±951.83) and PD group(3704.35±234.05) (p=0.043). LVEDP and -dp/dt max after LPS stimulation haveno significant deviation compared to control and LPS+PD and PD group. Thecardiac function of the rats treated with LPS+PD also decrease greatly after 10hoursand die in final. These results demonstrate that LPS can decrease contractile functionmore significantly than diastolic function in vivo, PD can protect heart against LPSbut effect is temporal.The myocardial tissues were observed by light microscope andelectromicroscope after experiments. The results demonstrate that myocardial tissuebegan to disrupt and dissolve after LPS stimulation, capillary hemorrhage,accrementition of mitochondria and lysosome, the muscle fiber is destroyedsignificantly compared to the normal. The myocardial tissue after LPS+PDstimulating was also damaged but is minor to LPS stimulation. This resultdemonstrates that LPS can destroy myocardial tissue and have negative effect onheart construction and function.The morphological changes of desmin in rat cardiac muscle after differenttreatments were determined by immunohistochemical staining with anti-desminantibody. The distribution of desmin has no difference compared to normal, but theamount of desmin (114.56±9.58) decreased significantly compared to control(133.65±4.46), PD (132.10±3.82), and LPS+PD group(120.93±3.95) (P＜0.01). After stimulated with LPS for 4 hours in vitro, the distribution and amount ofdesmin in myocardial cells did not show significant difference compared to normalgroup or LPS+calphostinC group or LPS+Y27632 group. After stimulated with LPSfor 8 hours, the amount of desmin began to decrease significantly (31.33±2.23)compared to normal group (45.57±2.96, p=0.001) and LPS+calphostinC group(42.15±2.06, p=0.001) and LPS+Y27632 group (42.40±1.56, p=0.001). TPA,the activator of PKC, can destroy desmin in 4 fours (33.29±1.15, compare tocontrol p=0.001). These results demonstrate that LPS can destroy desmin inmyocardial cells, but it needs a few times. The tendency of desmin's damage by LPSis same as the decrease tendency of myocardial function in vivo by LPS, the damageof desmin maybe a factor of myocardial function decrease. The inhibitor of PKC andRho-kinase can relieve this damage affection and the activator of PKC show sameeffect as LPS, these results show that PKC and Rho-kinase phosphorylation pathwaymaybe involve in process of desmin's damage by LPS.In conclusion: LPS can damage myocardial function, it can induce decrease ofcontractile function, but it doesn't show significant effects to diastolic function invivo; LPS can damage to myocardial tissue, and cause capillary hemorrhage,accrementition of mitochondria and lysosome, the muscle fiber is destroyedsignificantly compared to normal; LPS also can damage to desmin by LPS after afew times, amount of desmin decrease and distribution is normal. The inhibitor ofPKC and Rho-kinase can relieve this damage affection and the activator of PKCshow same effect as LPS, these results show that PKC and Rho-kinasephosphorylation pathway maybe involve in process of desmin's damage by LPS.
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