Protective Effects Of Astragaloside IV On Diabetic Vascular Remodeling And Its Mechanisms

Cardiovascular complications remain as the major cause of morbidity and mortalityin patients who suffer type 2 diabetes mellitus. As a common characteristic,hyperglycemia is an independent factor contributing to dysfunction of ECs andVSMCs.Vascular remodeling is a dynamic process that involves the structural alteration of avessel in response to hemodynamic and humoral stimuli. Different factors such ashyperglycemia, hyperinsulinemia, increased oxidative stress, and diabeticdyslipidemia can all contribute to alterations in the normal vessel wall andsubsequent vascular remodeling. Vascular remodeling, characterized byextracellular matrix deposition and an increased media-to-lumen ratio, occurs indiabetes and contributes to the development of complications. Vascular remodelinghas been postulated to be mediated by dysfunction of endothelial cells (ECs) and animbalance in the ratio proliferation/apoptosis of vascular smooth muscle cells(VSMCs) within the artery wall. Thus, in parallel with controlling blood glucoseconcentration, treatment of vascular complications is also important.In this study, real-time cell electrical sensing system (RT-CES^TM), which couldreflect cell biological conditions in real-time and label-free, was introduced toinvestigate the growth characteristics of VSMCs. Model of VSMC dysfunctioninduced by high glucose (25 mM) and method monitoring the VSMC growthdynamically were established as well. The whole process of electrode impedancealteration from cell adhesion, spreading, proliferation and confluence with thestimulation of high glucose was detected, indicating the dynamic changes of VSMCgrowth induced by high glucose. To ascertain that the RT-CES units of Cell Indexcorrelate with the number of the cells, comparative evaluation of impedancemeasurements and classic WST-1 assay was used. The model may be meaningful tostudy on mechanisms of diabetic vascular injury and screening of drugs for diabeticvascular complications.AstragalosideⅣ(3-O-β-D-xylopyranosyl-6-O-β-D-glucopyranosylcycloastra-genol)is a saponin extracted from radix astragali, which has been proved effective intreatment of diabetes, cardiovascular diseases and diabetic nephropathy. However, the effects of astragalosideⅣon the vascular remodeling in diabetic complicationsand the underlying mechanisms have not been well studied. We studied the effectsof astragalosideⅣon high glucose-induced alterations of proliferation andapoptosis in VSMCs. The results demonstrated that 50μg/mL astragalosideⅣreduced the viability of VSMCs enhanced the apoptotic rate of VSMCssignificantly(P＜0.01). These results indicated that astragalosideⅣcan inhibitVSMC proliferation through reducing cell viability and promoting the apoptotic rateof VSMCs. Inhibition of the DNA synthesis and the expression of antiapoptoticprotein Bcl-2 in VSMCs may be the underlying mechanisms. In addition,astragalosideⅣmay also resist from dedifferentiation induced by high glucose inVSMCs through enhancing the expression ofα-SMA. Our data showed thatastragalosideⅣpromoted the expression of PPAR-γmRNA in VSMCs. BecausePPAR-γplay an important role in regulation of the cell cycle and differentiation, ourresults indicated that the protective effects of astragalosideⅣon high glucoseinduced proliferation in VSMCs were closely related to the altered expression ofPPAR-γ. In order to assess the therapeutic potential on diabetic vascularcomplications of astragalosideⅣ, we investigated whether astragalosideⅣhad theeffects of endothelial protection. Our results proved that astragalosideⅣcouldimprove endothelial dysfunction induced by high glucose and does-dependentinhibit TNF-α-induced cell viability loss and apoptosis. The results indicated thatthe drugs had therapeutic potential to improve endothelial dysfunction and thus thediabetic vascular complications.In short, our study achieved the following novel findings: (1)Our study usedRT-CES monitoring the growth of VSMCs dynamically and established thereal-time detecting model which could screen and assess drugs for diabeticcomplications. The model will be helpful to related drug screening, exploitation andmechanism investigation. Based on this model, we investigated the protectiveeffects of astragalosideⅣon the dysfunction of ECs and VSMCs and its relatedmechanisms. (2)Our data demonstrated that astragalosideⅣcan exert vascularprotection by inhibiting VSMCs proliferation, enhancing apoptotic rate of VSMCs,inhibiting the endothelial barrier dysfunction and inhibiting the viability loss andapoptosis of ECs, all of which contributes to the inhibitive effects of astragalosideⅣon patholygical vascular remodeling. Our study used the model of dysfunction of ECs and VSMCs to evaluate the effects of astragalosideⅣon diabetic vascularremodeling and found that astragalosideⅣhad the inhibitive effects onpatholygical vascular remodeling and may be helpful to prevent the diabeticcomplications.