Interleukin-10 stimulation of endogenous nitric oxide release from human saphenous veins diminishes immunocyte adherence

Interleukin-10 (IL-10) is described as a cytokine that exerts immune downregulating actions. In this regard, our study indicates that IL-10 activity on human saphenous veins is coupled to nitric oxide (NO) release. We demonstrated this phenomenon by using in vitro real-time amperometric measurement of NO levels in explanted human saphenous veins after IL-10 exposure. IL-10-induced NO release can inhibit the adherence of monocytes (75.7 ± 15 cells/600 μm² of endothelial surface) and granulocytes (65 ± 18 cells/600 μm² of endothelial surface) from control values (250-300 cells/600 μm² of endothelial surface; p < 0.005). This inhibition is directly sensitive to NO synthase inhibition. The specificity of the IL- 10 effects is shown by its sensitivity to antibody. In vivo measurement of IL- 10 levels during and after cardiopulmonary bypass surgery indicated that they are higher at 6 h after skin closure (1,400 pg/ml) compared with levels found during surgery (300 pg/ml). We surmise that the postsurgical increase of IL- 10 levels may be an immunoregulatory attempt to downregulate the diffuse intimation that has been shown to be associated with cardiopulmonary bypass surgery.