The red‐vine‐leaf extract AS195 increases nitric oxide synthase–dependent nitric oxide generation and decreases oxidative stress in endothelial and red blood cells

The red‐vine‐leaf extract AS195 improves cutaneous oxygen supply and the microcirculation in patients suffering from chronic venous insufficiency. Regulation of blood flow was associated to nitric oxide synthase (NOS)‐dependent NO (nitric oxide) production, and endothelial and red blood cells (RBC) have been shown to possess respective NOS isoforms. It was hypothesized that AS195 positively affects NOS activation in human umbilical vein endothelial cells (HUVECs) and RBC. Because patients with microvascular disorders show increased oxidative stress which limits NO bioavailability, it was further hypothesized that AS195 increases NO bioavailability by decreasing the content of reactive oxygen species (ROS) and increasing antioxidant capacity. Cultured HUVECs and RBCs from healthy volunteers were incubated with AS195 (100 μmol/L), tert‐butylhydroperoxide (TBHP, 1 mmol/L) to induce oxidative stress and with both AS195 and TBHP. Endothelial and red blood cell–nitric oxide synthase (RBC‐NOS) activation significantly increased after AS195 incubation. Nitrite concentration, a marker for NO production, increased in HUVEC but decreased in RBC after AS195 application possibly due to nitrite scavenging potential of flavonoids. S‐nitrosylation of RBC cytoskeletal spectrins and RBC deformability were increased after AS195 incubation. TBHP‐induced ROS were decreased by AS195, and antioxidative capacity was significantly increased in AS195‐treated cells. TBHP also reduced RBC deformability, but reduction was attenuated by parallel incubation with AS195. Adhesion of HUVEC was also reduced after AS195 treatment. Red‐vine‐leaf extract AS195 increases NOS activation and decreases oxidative stress. Both mechanisms increase NO bioavailability, improve cell function, and may thus account for enhanced microcirculation in both health and disease.