Unfractionated Heparin Reduced Histone-induced Glycocalyx Degradation Of Mouse Pulmonary Endothelial Cells Via Heparinase Pathway

Objectives: Extracellular free histone is a significant mediator in sepsis.Endothelial glycocalyx degradation is thought to be the main pathophysiological mechanism in the development of sepsis.Unfractionated heparin(UFH)possesses beneficial effects on septic patients,but the specific mechanism is still unclear.This study aims to explore the damage effects of histone on the glycocalyx of endothelial cells and to investigate the protective effect and mechanism of UFH.Methods: Male mice(C57BL/6,8-10 weeks old,weighing 20-25 g)were randomly divided into five groups including control group,histone group,histone + UFH group,histone + Heparinase(HPA)inhibitor group,Histone + UFH + HPA inhibitor group.The mice were treated with HPA inhibitor(20 mg/kg)intraperitoneally and then injected with histone(50 mg/kg)via the tail vein immediately.UFH(400 U/kg)was injected via tail vein 1 h after histone administration.The other groups were injected with equal volume of sterile saline accordingly.Four hours after histone injection,the lungs of the mice were harvested and stained with hematoxylin and eosin(HE).The histopathological changes in lung tissue were observed under light microscope and the extent of lung injury was evaluated.The lung wet/dry weight ratio(W/D)and water content of lung tissue were measured.The m RNA expressions of tissue factor(TF)、fibrinogen(FIB)、Interleukin-1(IL-1)β、syndecan-1 and HPA in lung tissues were determined by real-time quantitative reverse transcription-polymerase chain reaction(RT-PCR).The positive expression of syndecan-1 in lung tissue and CD31 in lung endothelial cell was observed by immunofluorescence(IF).The protein expressions of syndecan-1 and HPA in lung tissue were observed by Western Blot(WB).Results: Histone induced lung injury and pulmonary edema in mice,promoted the expressions of TF,FIB and IL-1β in lung tissue,increased the expression of lung heparinase and led to the shedding of syndecan-1 in lung endothelial cells.UFH alleviated histone-induced expression of heparinase in the lung of mice,reduced the shedding of syndecan-1 in lung endothelial cells,inhibited the expressions of TF,FIB and IL-1β,and thus reduced the severity of lung injury and pulmonary edema.Conclusion: UFH may play a protective role by alleviating histone-induced destruction of glycocalyx in lung endothelial cells through heparinase pathway.