Effect Of Lipopolysaccharide-activated Complement On Endothelial Cell And The Effect Of Complement Inhibition On Lipopolysaccharide-induced Acute Lung Injury

Objective:To investigate the effect of lipopolysaccharide-activated complement on endothelial cell, and to evaluate the protective effect of the specific anticomplementary components on complement-injured endothelial cells and LPS-induced acute lung injury.Methods:The manner of LPS activating complement was characterized. Then the effects of LPS-activated complement on endothelial cells were determined. P-selectin, E-selectin and ICAM-1 were determined by ELISA. The activity of Caspase-3/7 was measured by chemiluminescence method. The growth of endothelial cells was measured by SRB method. Our previous work found that the polyphenol from the seed of Toona Sinensis could inhibit activation of complement. Protective effects of an anticomplementary polyphenol from the seed of Toona Sinensis on complement-injured endothelial cells were assessed by the change of P-selectin, E-selectin, ICAM-1 and Caspase-3/7. Rat acute lung injury model induced by LPS was used in this study. The anticomplementary proteins Atrase A and CVF were iv injected to rats 2 h and 24 h, respectively, prior to the administration of LPS. The samples of 1,6,12 h were collected, respectively. The total cell counts, the level of protein in bronchoaleolar lavage fluid, the water content and myeloperoxidase activity in lung tissue, the serum complement level and the concentrations of TNF-αand P-selectin in bronchoaleolar lavage fluid were measured. Pathological examination of lung tissue were performed.Results:LPS activated complement in a dose- and time-dependent manner. The incubation mixture of LPS and complement significantly induced the expression of P-selectin, E-selectin and ICAM-1 on endothelial cells. The activity of Caspase-3/7 was also significantly increased. The incubation mixture of LPS and complement showed no inhibition on the growth of endothelial cells. The anticomplementary polyphenol did not down-regulate the levels of adhesion molecule and apoptosis of endothelial cells by LPS-activated complement, showing no protective effect on complement-injured endothelial cells. In LPS-induced ALI model, rats given LPS showed typical ALI symptoms, and complement activity significantly decreased after LPS was administrated. Complement inhibition by Atrase A and CVF obviously reduced serum complement level, total amounts of cells, and myeloperoxidase activity. The anticomplementary protein could significantly down-regulate level of TNF-a and P-selectin in BALF, and mitigate inflammation in lung. Water content and protein content in lung tissue showed no significant difference.Conclusion:LPS-activated complement can activate endothelial cells, and significantly up-regulate the expression of adhesion molecules and apoptosis. The anticomplementary polyphenol strongly inhibits the haemolysis of the complement, but it nearly failure protect endothelial cells against injury by LPS-activated complement. In animal experiment, Atrase A and CVF can effectively reduce acute lung injury, but the effects showed obviously different, suggesting the special complement components that Atrase A act may play the key role in ALI.