Uric Acid And Vascular Endothelial Dysfunction Related Research

BackgroundUric acid is the product of purine metabolism. However, a higher level of serum uric acid is observed in human beings than that in other mammals because of genetic mutations. Hyperuricemia often comes with vascular and metabolic diseases. The incidences. of cardiovascular diseases and metabolic diseases are related to the elevation of serum uric acid in general population, but researchers have different opinions on the effects of serum uric acid on the endothelial function. Some observed that uric acid erased ROS as an antioxidant and endothelial protector. Some reported that hyperuricemia inhibited NO production and stimulated inflammation of the endothelium. Another group of studies even suggested that uric acid had different effects at different serum levels. Lipid disorders, which are recognized as risk factors for vascular injuries, often complicate with hyperuricemia. However, there are few reports on the interactive effect of lipid and uric acid on endothelial dysfunction. To study the interaction of uric acid and oxLDL on endothelial function may help to reveal the role of uric acid in vascular pathophysiology.Objective1) To determine the production of ROS and expression of eNOS mRNA and ET-1mRNA in Human Umbilical Vein Endothelial Cells（HUVEC） stimulated by uric acid and oxLDL solution with selected concentrations for24hours in vitro, focusing on the interaction of uric acid and oxLDL;2) To study the gene expression profile of HUVEC after72hours stimulation of uric acid with the latest Affymetrix gene-chip;3) To invesgate the relationship of hyperuricemia and lipid disorders in PUMCH staff during the annual health examination.Methods1) MTT test for toxicity on HUVEC stimulated by uric acid and oxLDL at stratified concentration in24and48hours. Stimulate HUVEC for24hours by uric acid and oxLDL with concentrations of0,5,20mg/dL and0,25and50μg/mL,respectively. Scan the cells by Confocul Fluorescent Microscopy to record the ROS production. RT-PCR and Real-Time PCR amplification to determine eNOS mRNA and ET-1mRNA expression at different UA/oxLDL concentrations.2) Affymetrix HG-U133_Plus₂genechip test and GCOS analysis for gene expression profile changes in HUVEC after72hours co-culture with uric acids at stratified concentrations. Sort out the genes with significant expression changes, and review the gene functions and relationships with systemic disease.3) Multiple variance analyis of the association of hyperuricemia and lipid disorders in PUMCH staff using health examination data.Results1) HUVEC viability significant decreased when oxLDL≥75μg/dL. After24h stimulation by uric acid/oxLDL, the mean intensity of ROS expression in HUVEC in vitro was significantly increased both by uric acid and oxLDL separately, and high level of uric acid had a tendency to discease the ROS stimulated by oxLDL（p=0.093）. eNOS mRNA expression was increased by uric acid alone and decreased by oxLDL alone. Uric acid at20mg/dL augmented eNOS downregulation by oxLDL. ET-1mRNA was increased by oxLDL, but not by uric acid alone, with an interaction between uric acid and oxLDL, which appeared as uric acid augmented ET-1upregulation by oxLDL.2) Uric acid stimulation with three concentrations had a common effect on HUVEC gene expression in72hours, with274genes epression significantly changed,133down and141up. The genes affected are involved in cell adherion, structure development, secretion, extracellular matrix and signal transduction, like CD51, matrix gla protein4, thrombomodulin（TM）, CD36, thrombospondin1, placental growth factor, endothelial lipase（LIPG）, corin, interleukin, signal transducer （gp130）, interlukine superfamily lagand, tumor necrosis factor （ligand）superfamily member4, chemokine （c-x-c motif） ligand, Bcl-2associated transcription repressor.3)14.3%subjects have hyperuricemia, and68.6%have dyslipidemia, in the PUMCH staff health examination. Hyperuricemia was related to abnormal serum LDL-C, HDL-C, TC and TG levels（OR1.85-3.09, p<0.01）. This association still existed by age, sex or BMI stratification, and after adjustment by fasting blood glucose, blood pressure and renal function. Conclusion1)24h stimulation of uric acid-oxLDL significantly increased ROS expression in HUVEC in vitro without significant interaction. Uric acid, which increased eNOS mRNA but did not affect ET-1mRNA alone, augmented eNOS downregulation and ET-1upregulation by oxLDL, at high concentration.2) HUVEC genes expression were changed by uric acid stimulation, which are involved in cell adhesion, extracellular matrix function, secretion and signal transduction, suggesting that uric acid may affect endothelium function via rounts other than ROS and inflammation.3) Hyperuricemia was significantly associated to dyslipidemia independently in the PUMCH staff health examination group.