Abstract 5471: NAD(P)H Oxidase Nox4 in Vascular Endothelial and Smooth Muscle Cells May Be Involved in the Regulation of Basal Blood Pressure
Reactive oxygen species (ROS) play an important role in mediating changes in blood pressure, vascular remodeling, and arteriosclerosis. All vascular cell types including vascular endothelial cells (ECs) and smooth muscle cells (SMCs) produce ROS, primarily through NAD(P)H oxidase (Nox) family enzymes, including Nox1, Nox2 and Nox4. Nox4 is predominantly expressed in ECs and SMCs and its expression in the vasculature is upregulated by aging. In order to elucidate the function of Nox4 in blood vessels, we established transgenic mice with EC- and SMC-specific overexpression of wild-type Nox4 (EC-Nox4, SMC-Nox4) and dominant negative Nox4 (EC-DN-Nox4, SMC-DN-Nox4). EC- and SMC-specific overexpression was achieved with SM22α and Tie2 promoters, respectively. Enhanced expression of Nox4 or DN-Nox4 in ECs or SMCs was confirmed by immunostaining of blood vessels with a specific anti-Nox4 antibody. Superoxide producing activity in blood vessels was enhanced in EC-Nox4 (129.5±15.2%) and SMC-Nox4 (142.2±12.9%), and attenuated in EC-DN-Nox4 (30.6±4.9%) and SMC-DN-Nox4 (49.4±10.2%) compared to non-transgenic controls, as evaluated by dihydroethidium staining. At 3 months of age, EC-Nox4 exhibited significantly lower systolic blood pressure than WT (96.3±5.5 vs. 110.3±5.0 mmHg, p < 0.05) as determined by the tail-cuff method. Conversely, SMC-Nox4 exhibited significantly higher systolic blood pressure than WT (122.7±3.2 vs. 107.3±3.9 mmHg, p < 0.05). Blood pressure in EC-DN-Nox4 or SMC-DN-Nox4 was not statistically different from WT. At 3 months of age, none of the transgenic mouse lines exhibited obvious histopathological changes in vasculature, including aortas and arterioles in hearts and kidneys. Elevation of blood pressure induced by continuous infusion of angiotensin II (Ang II) (0.6 ng/g/min) in EC-Nox4 or SMC-Nox4 was not significantly different from WT at day 3, 7 and 14. Taken together, these results suggest that upregulation of Nox4 in SMCs and ECs increases superoxide production, thereby increasing or decreasing, respectively, blood pressure at baseline, without affecting Ang II-induced elevation in blood pressure.