Recent data suggested a role of uric acid (UA) in the pathogenesis of cardiovascular and renal disease. Endothelial dysfunction, which is characterized by a decrease in nitric oxide, is regarded as the key mechanism of UA-induced vascular disease. Endo-MT is an early process of endothelial dysfunction, and is also known to play a role in the progression of renal fibrosis. Glycocalyx is a structure covering endothelium composed of membrane-bound proteoglycans and glycoproteins associated with adsorbed plasma components, which may lead to endothelial dysfunction via intraluminal shedding.Design and Method:
Endo-MT was evaluated by cell morphology and the expression of the endothelial markers, VE-cadherin or CD31 and the mesenchymal marker, α-SMA by real time PCR, western blotting (WB) and immunocytochemistry in HUVECs and animal model of hyperuricemia (Sprague-Dawley rats fed with 2% oxonic acid for 6 weeks). NAPDH oxidase (NOX) activity, reactive oxygen species (ROS) production, endothelial permeability and glycocalyx shedding were evaluated by WB and ELISA.Results:
Stimulation of HUVEC with UA resulted in an alteration of cell morphology into fibroblastoid cells associated with a decrease in CD31 and VE-cadherin and de-novo α-SMA expression from 24 hours. UA increased ROS production via NOX (15 min) and mitochondrial activation (6 hours) with an increase in glycocalyx shedding (6 hours), which were blocked by an inhibitor of organic anion transporter, probenecid (5 μM). Anti-oxidant treatment [NAC (5mM), apocynin (100 μM), and mitotempo (10 μM)] ameliorated endo-MT and glycocalyx shedding in HUVEC. Matrix metalloproteinase inhibitor, GM6001, also alleviated UA-induced endoMT. In the kidney of hyperuricemic rats, endothelial staining in peritubular capillaries was decreased with de-novo staining of α-SMA, which was ameliorated allopurinol treatment.Conclusions:
UA per se induced a phenotypic transition of endothelial cells via oxidative stress and glycocalyx shedding, which could be one of the mechanisms of UA-induced vascular disease.