Role Of HSP90 And Caveolin-1 In The Effect Of Homocysteine On The Vascular Endothelium Dysfunction

Homocyeteine(Hcy) is a sulfur-containing amino acid,generated as an intermediate product in the normal metabolism of the essential amino acid methionine.Hcy has been reported to be an independent risk factor of endothelial cell dysfunction. Endothelial cell dysfunction is the common characteristic of hypertention, coronary artery disease, artherosclerosis, stroke, diabetes and peripheral vascular disease. Endothelial nitric oxide synthase(eNOS) can generated nitric oxide(NO) which regulate the function of cardiovascular system.The decreasing activity of eNOS and superoxide anion generating(O2.-) contribute to endothelial cell dysfunction.The regulation of eNOS is a process containing eNOS transcription, translocation, protein interaction and phosphorylation. Heat shock protein 90 (HSP90) and Caveolin-1 are the important regulatory proteins.There are contradictory reports whether Hcy can affect the expressions of eNOSmRNA and protein. There was no report about the effect of Hcy on the expression of HSP90 and Caveolin-1.Object:In this experiment, human umbilical vein endothelial cell(HUVEC) was primary cultured in vitro,cultured with A23187,to study the effect of Hcy on the function of HUVEC and the expression of HSP90 and Caveolin-1, in order to investigate the mechanism of endothelial dysfunction induced by Hcy. Methods:Primary HUVECs were collected and cultured in vivo.The second passage of HUVEC were divided into four groups:(1)control group,(2)Hcy group,(3)A23187 group,(4)Hcy+A23187 group. After cultured 24h,the expression of HSP90,caveolin-1,phosphoryllated eNOS protein were detected by immunohistochemistry,the expression of eNOSmRNA were detected by reverse transcription-polymerase chain reaction(RT-PCR),and the contents of NO and MDA and the activities of eNOS and SOD were detected using the method of colorimetric method.Results:(1)Compared with control group,the activity of eNOS and the content of NO in Hcy group was significantly reduced but SOD and MDA was significanted increased(P<0.05),the activity of eNOS and the content of NO in A23187 group was increased significantly,MDA was decreased,SOD was increased.Compared with A23187 group, eNOS and NO was significantly reduced,MDA were increased, but SOD no change in Hcy+A23187 group.(2) Compared with control group, the expression of Caveolin-1 in Hcy group increased obviously(P<0.05);Compared with A23187 group, the expression of Caveolin-1 in Hcy+A23187 group was also increased obviously (P<0.05).(3)There was no difference on the expression of eNOSmRNA,HSP90 and P-eNOS protein in HUVEC in different groups(P>0.05).Conclusion:(1) In base and activated state,Hcy can induce NO and eNOS decreased,MDA and SOD increased.The mechanisms may be concerned with oxidation stress that can inhibit the activity of eNOS and lower the NO bioavailability.(2)There was no relationship between decreasing activity of eNOS induced by Hcy and eNOS transcription.(3)Hcy probably can decrease the association of HSP90 and eNOS by enhancing the expression of Caveolin-1 in HUVEC both in base and activated state, which can decrease the activity of eNOS.