The Development Of Salt-sensitive Hypertension Regulated By Inflammation Via PSGL-1 And Platelets

ObjectionSalt-sensitive hypertension is characterized by increased arterial blood pressure due to the high salt intake,with complex pathological mechanism,which seriously endangers human health.Although the pathogenesis of hypertension has been made great progress in a long time study,the exactly molecular mechanism of salt-sensitive hypertension is still unknow.In recent years,a large number of studies suggest that inflammatory response and endothelial dysfunctioninduced by platelet activation are important factors in the development of cardiovascular disease.Clinical study shows that hypertensive patients exit abnormal platelet function and activation.High salt diet causes the development of high blood pressure as well as E-selectin expression on endothelial cells and inflammation.P-selectin glycoprotein ligand(PSGL-1)is a major selectin ligand on leukocyte,which plays a crucial role in leukocyte-endothelial cell adhesion and leukocyte infiltration as the initial step during inflammation,however the role of PSGL-1 and platelet in the development of salt-sensitive hypertension is still unknown.This study was designed to explore the role and mechanism of PSGL-1 and platelet-mediated inflammation and endothelial dysfunction in the development of salt-sensitive hypertension.MethodsIn vivo experiment one:PSGL-1 knockout(PSGL-1-/-)mice and control(PSGL-1+/+)mice were respectively given low-salt diet(0.4%NaCl)and high-salt diet(6%NaCl).After 3 months,carotid artery intubation was used to detect the blood pressures;the serum IL-1? and TNF-? level in peripheral blood was measured by ELISA;the percentage of immune cells and platelet-leukocyte aggregations in peripheral blood was detected by flow cytometry;infiltration of immune cells in skin and kidney was measured by immunohistochemistry;the expressions of IL-1?,IL-6 and TNF-? in kidney were detected by western blot.In vivo experiment two:Dahl salt-sensitive(Dahl SS)rats were randomly divided into three groups:low salt group(0.12%NaCl,LS),high salt group(8%NaCl,HS)and platelet inhibitor group(8%NaCl + bus,HS+bus)for 6 weeks.The arterial blood pressure was measured by tail-cuff method.The percentage of circulating leukocyte and platelet-leukocyte aggregation and the immune cells infiltrated into the aorta walls were measured by flow cytometry.The infiltration of immune cells in kidney was measured by immunohistochemistry.The expression of serum IL-6 was detected by enzyme-linked immunosorbent assay(ELISA).In vitro experiment:The human umbilical vein endothelial cells(HUVEC)was treated by different dose of NaCl.The expression of outer-membrane P-selectin and E-selectin were detected by flow cytometry;the expression of inflammatory cytokines IL-1? and NF-?B signaling proteins were detected by western blot.ResultsIn vivo experiment one:PSGL-1+/+ mice with high-salt diet,compared with low-salt diet group,presented high blood pressure and increased levels of IL-1? and TNF-? in serum and kidney,increased percentage of leukocyte and platelet-leukocyte aggregation in peripheral blood;more leukocyte infiltration in renal tubulointerstitial and skin vessels.However,the influence was not found in PSGL-1-/-mice with high-salt diet.In vivo experiment two:We found that Dahl SS rats in high salt group showed elevated blood pressure,increased proportion of circulating leukocyte(including T lymphocytes,B cells and Natural killer cells),platelet-leukocyte aggregationand serious immuno cells infiltrationon aortic walls,compared withlow-salt dietgroup,which were ameliorated by the platelet inhibitor busulfan.In vitro experiment:High salt intake increased the expressions of p-selectin,inflammatory cytokine IL-1?,stimulated the NF-?B signaling pathway in HUVEC.ConclusionOur findings suggest that high-salt diet may promote platelet-leukocyte aggregations via leukocyte PSGL-1 and inflammatory response to increase the blood pressure.PSGL-1 may be involved in the development of salt-sensitive hypertension.Platelet may play an important role in the development of salt-sensitive hypertension by promoting platelet-leukocyte aggregation,leukocyte infltration resulting in inflammation.High salt intake may directly stimulate vascular endothelial cells inflammation response and NF-?B signaling,to promote the vascular inflammation and the development of salt-sensitive hypertension.