The ADMA/DDAH/NO pathway in human vein endothelial cells exposed to arsenite.

Inorganic arsenic (iAs) exposure is related to cardiovascular disease, which is characterized by endothelial dysfunction and nitric oxide (NO) depletion. The mechanisms underlying NO depletion as related to iAs exposure are not fully understood. The endogenous inhibitor of nitric oxide synthase, asymmetric dimethylarginine (ADMA), might be a molecular target of iAs. ADMA concentrations are regulated by proteins involved in its synthesis (arginine methyl transferase 1 [PRMT-1]) and degradation (dimethylarginine dimethylaminohydrolase [DDAH]). Both, ADMA and NO are susceptible to oxidative stress. We aimed to determine the ADMA/DDAH/NO pathway in human vein endothelial cells (HUVEC-CS) exposed to arsenite. We exposed HUVEC-CS cells to 1, 2.5 and 5µM of arsenite for 24h. We proved that arsenite at 5µM was able to decrease NO levels with an associated increase in ADMA and depletion of l-arginine in HUVEC-CS cells. We also found a decrease in DDAH-1 protein expression with 5µM of arsenite compared to the control group. However, we did not observe significant differences in PRMT-1 protein expression at any of the concentrations of arsenite employed. Finally, arsenite (2.5 and 5µM) increased NADPH oxidase 4 protein levels compared with the control group. We conclude that ADMA, l-arginine and DDAH are involved in NO depletion produced by arsenite, and that the mechanism is related to oxidative stress.

Exercise capacity in polycystic kidney disease.

BACKGROUND: Reports about exercise performance in autosomal dominant polycystic kidney disease (ADPKD) are scarce. We aimed to evaluate exercise capacity and levels of nitric oxide and asymmetric dimethylarginine (ADMA) in normotensive patients with ADPKD. STUDY DESIGN: Prospective controlled cohort study. SETTING & PARTICIPANTS: 26 patients with ADPKD and 30 non-ADPKD control participants (estimated glomerular filtration rate>60 mL/min/1.73 m2, aged 19-39 years, and blood pressure [BP]<140/85 mmHg). We excluded smokers, obese people, and individuals with associated diseases. PREDICTOR: ADPKD versus control. OUTCOMES: Exercise capacity and nitric oxide and ADMA levels in response to exercise. MEASUREMENTS: Cardiopulmonary exercise testing and serum and urinary nitric oxide, plasma ADMA, and BP levels before and after exercise. RESULTS: Mean basal systolic and diastolic BP, estimated glomerular filtration rate, and age did not differ between the ADPKD and control groups (116±12 vs. 110±11 mmHg, 76±11 vs 71±9 mmHg, 113±17 vs. 112±9.6 mL/min/1.73 m2, and 30±8 vs. 28.9±7.3 years, respectively). Peak oxygen uptake and anaerobic threshold were significantly lower in the ADPKD group than in controls (22.2±3.3 vs. 31±4.8 mL/kg/min [P<0.001] and 743.6±221 vs. 957.4±301 L/min [P=0.01], respectively). Postexercise serum and urinary nitric oxide levels in patients with ADPKD were not significantly different from baseline (45±5.1 vs. 48.3±4.6 µmol/L and 34.7±6.5 vs. 39.8±6.8 µmol/mg of creatinine, respectively), contrasting with increased postexercise values in controls (63.1±1.9 vs. 53.9±3.1 µmol/L [P=0.01] and 61.4±10.6 vs. 38.7±5.6 µmol/mg of creatinine [P=0.01], respectively). Similarly, whereas postexercise ADMA level did not change in the ADPKD group compared to those at rest (0.47±0.04 vs. 0.45±0.02 µmol/L [P=0.6]), it decreased in controls (0.39±0.02 vs. 0.47±0.02 µmol/L [P=0.006]), as expected. A negative correlation between nitric oxide and ADMA levels after exercise was found in only the control group (r = -0.60; P<0.01). LIMITATIONS: Absence of measurements of flow-mediated dilatation and oxidative status. CONCLUSIONS: We found lower aerobic capacity in young normotensive patients with ADPKD with preserved kidney function and inadequate responses of nitric oxide and ADMA levels to acute exercise, suggesting the presence of early endothelial dysfunction in this disease.