Background: Nebivolol is a third-generation beta-blocker used to treat hypertension. The vasodilation properties of nebivolol have been attributed to nitric oxide (NO) release. However, the kinetics and mechanism of nebivolol-stimulated bioavailable NO are not fully understood.
Methods: Using amperometric NO and peroxynitrite (ONOO⁻) nanosensors, β₃-receptor (agonist: L-755,507; antagonists: SR59230A and L-748,337), ATP efflux (the mechanosensitive ATP channel blocker, gadolinium) and P2Y-receptor (agonists: ATP and 2-MeSATP; antagonist: suramin) modulators, superoxide dismutase and a NADPH oxidase inhibitor (VAS2870), we evaluated the kinetics and balance of NO and ONOO⁻ stimulated by nebivolol in human umbilical vein endothelial cells (HUVECs). NO and ONOO⁻ were measured with nanosensors (diameter ~ 300 nm) placed 5 ± 2 μm from the cell membrane and ATP levels were determined with a bioluminescent method. The kinetics and balance of nebivolol-stimulated NO and ONOO⁻ were compared with those of ATP, 2-MeSATP, and L-755,507.
Results: Nebivolol stimulates endothelial NO release through β₃-receptor and ATP-dependent, P2Y-receptor activation with relatively slow kinetics (75 ± 5 nM/s) as compared to the kinetics of ATP (194 ± 10 nM/s), L-755,507 (108 ± 6 nM/s), and 2-MeSATP (105 ± 5 nM/s). The balance between cytoprotective NO and cytotoxic ONOO- was expressed as the ratio of [NO]/[ONOO⁻] concentrations. This ratio for nebivolol was 1.80 ± 0.10 and significantly higher than that for ATP (0.80 ± 0.08), L-755,507 (1.08 ± 0.08), and 2-MeSATP (1.09 ± 0.09). Nebivolol induced ATP release in a concentration-dependent manner.
Conclusion: The two major pathways (ATP efflux/P2Y receptors and β₃ receptors) and several steps of nebivolol-induced NO and ONOO⁻ stimulation are mainly responsible for the slow kinetics of NO release and low ONOO⁻. The net effect of this slow kinetics of NO is reflected by a favorable high ratio of [NO]/[ONOO⁻] which may explain the beneficial effects of nebivolol in the treatment of endothelial dysfunction, hypertension, heart failure, and angiogenesis.