Ouabain reduces the expression of the adhesion molecule CD18 in neutrophils

Ouabain, a hormone that inhibits Na⁺/K⁺-ATPase, modulates many aspects of the inflammatory response. It has been previously demonstrated that ouabain inhibits neutrophil migration in several inflammation models in vivo, but little is known about the mechanisms underlying this effect. Thus, this work aimed to evaluate the effect of ouabain on molecules related to neutrophil migration. For this purpose, neutrophils obtained from mouse bone marrow were treated with ouabain (1, 10, and 100 nM) in vitro. Neutrophil viability was assessed by annexin V/propidium iodide staining. Ouabain treatment did not affect neutrophil viability at different times (2, 4, and 24 h). However, basal neutrophil viability was decreased after 4 h. Thus, we assessed the effect of ouabain on the adhesion molecule CD18, an integrin β2 chain protein, and on the chemokine receptor CXCR2 after 2 h of treatment. CD18 expression was reduced (by 30%) by 1 nM ouabain. However, the expression of CXCR2 on the neutrophil membrane was not affected by ouabain treatment (1, 10, and 100 nM). Moreover, ouabain (1, 10, and 100 nM) did not modulate the zymosan-induced secretion of CXCL1 (a chemokine receptor CXCR2 ligand) in macrophage cultures. These data suggest that the inhibitory effect of ouabain on neutrophil migration is related to reduced CD18 expression, indicating a novel mechanism of action.