The Protective Effect Of CTRP3 On Vascular Endothelial Damage Induced By High Uric Acid And Its Mechanisms

BackgroundHyperuricemia(HUA)has been shown to be closely related to various cardiovascular diseases such as hypertension,atherosclerosis and coronary heart disease.Vascular endothelium is the first line of defense in preventing cardiovascular disease.Endothelial cells(ECs)can synthesize and secrete a variety of active substances to ensure the normal contraction and relaxation of blood vessels,and maintain vascular tension.Therefore,normal vascular endothelial cells have an important protective effect on the cardiovascular system.Existing studies have shown that high uric acid can cause vascular endothelial injury through a variety of mechanisms.Therefore,reducing vascular endothelial injury and improving endothelial function under high uric acid condition have great significance for the prevention and treatment of hyperuricemia related vascular lesions.C1q/tumor necrosis factor-related protein 3(CTRP3)is a new adipokine and a member of the adiponectin family.Recent studies have found that CTRP3 improves insulin sensitivity,regulates glucose and lipid metabolism,inhibits myocardial fibrosis,and promotes angiogenesis.However,it has not been reported whether CTRP3 can protect vascular endothelial injury induced by high uric acid.AimsThis study aimed to determine whether CTRP3 protects vascular endothelial cells injured by high uric acid,and whether this effect is mediated by down-regulating the toll-like receptor 4(TLR4)signal pathway and reducing the activity of xanthine oxidase to improve inflammatory responses and oxidative stress induced by high uric acid.MethodsIn vivo study,hyperuricemic animal model was established with male SD rats by drinking 10%fructose water for 12 weeks,then rats were given Ad-CTRP3 or Ad-GFP by a single tail vein injection.After 2 weeks,uric acid,hydroxyl radical scavenging activity,nitric oxide(NO),tumor necrosis factor-α(TNF-α),interleukin-6(IL-6)in serum and uric acid,reactive oxygen species(ROS),malondialdehyde(MDA)and xanthine oxidase(XO)activity in thoracic aorta were measured.The morphology of thoracic aorta and endothelial cell apoptosis were observed with haematoxylin-eosin(HE)and TUNEL methods.qRT-PCR was used to detect mRNA expression levels of eNOS,TNF-α and IL-6 in thoracic aorta.CTRP3 and TLR4 protein expression in the thoracic aorta were detected with western blot.In vitro study,human umbilical vein endothelial cells were transfected with Ad-CTRP3 or Ad-GFP firstly,then the cells were stimulated with 595μmol/L uric acid for 48 h.Some of the cells were pretreated with 1μM TAK242(TLR4 specific inhibitor)for 1 h.The level of NO in the supernatant of cell culture medium was detected.The concentration of MDA and the activity of XO were measured.The level of intracellular ROS was detected by flow cytometry.The cell apoptosis was observed by TUNEL method.The mRNA levels of eNOS,TNF-α and IL-6 were detected by qRT-PCR.Western blot was used to detect the protein expression of CTRP3 and TLR4.ResultsHyperuricemic rats showed impaired vascular endothelial function,increased inflammatory response,and higher oxidative stress status,which was accompanied by reduced CTRP3 and elevated TLR4 protein levels as well as upregulated xanthine oxidase activity in thoracic aorta.By contrast,CTRP3 overexpression decreased TLR4 protein and XO activity,reduced inflammatory cytokines and oxidative stress markers,and improved the morphology and function of aortic endothelium in rats with hyperuricemia.Similarly,CTRP3 overexpression abolished TLR4-mediated inflammation,abrogated XO-related oxidative stress,and rescued endothelial damage induced by uric acid in human umbilical vein endothelial cells.ConclusionCTRP3 ameliorates uric acid-induced inflammation and oxidative stress,which in turn protects endothelial function,maybe through the inhibition of TLR4-mediated inflammation and xanthine oxidase activity.