Objective: Circulatory shock results in hypoxia/reoxygenation processes that lead to the release of reactive oxygen species, endothelial injury, and multiple organ failure. Previous data suggest that beta2-adrenergic agonists prevent endothelial dysfunction. The study aimed at determining whether the beta2-adrenergic agonist formoterol protects endothelial cells against hypoxia/reoxygenation injury in vitro.
Design: Prospective controlled trial.
Setting: University hospital research laboratory.
Subjects: Cultured human umbilical vein endothelial cells (HUVECs).
Interventions: Confluent HUVECs were sealed in a flow-through chamber mounted on an inverted microscope and perfused with a constant flow of Krebs medium. After 1 hr of equilibration, HUVECs underwent 2 hrs of hypoxia and 1 hr of reoxygenation. Cell death at the end of reoxygenation and reactive oxygen species formation were assessed with fluorescent probes propidium iodide and 2',7'-dichlorodihydrofluorescein diacetate, respectively. The effects of the beta2-adrenergic agonist formoterol, the beta2-adrenergic antagonist ICI 118,551 and the nitric oxide synthase inhibitor L-NNA were investigated. Statistical analysis was performed with analysis of variance followed by post hoc Fisher's test.
Measurements and main results: Hypoxia/reoxygenation increased cell death (hypoxia/reoxygenation 29 +/- 4% vs. control 1 +/- 5%, p < .05) and endothelial reactive oxygen species production (hypoxia/reoxygenation 126 +/- 4% vs. control 108 +/- 4%, p < .05). Formoterol reduced cell death in a concentration-dependent manner (EC95 = 10 mol/L) and reduced endothelial reactive oxygen species production (hypoxia/reoxygenation + formoterol EC95 109 +/- 4% vs. hypoxia/reoxygenation 126 +/- 4%, p < .05). When added to formoterol EC95, ICI 118,551 and L-NNA abolished the formoterol-induced cell protection and reduced reactive oxygen species production.
Conclusions: These results indicate that formoterol reduces endothelial cell death and reactive oxygen species production in this in vitro hypoxia/reoxygenation model. These effects are beta2-adrenergic specific and are partially mediated by nitric oxide synthase.