[Inhibitory effects of vasoactive intestinal peptide on superoxide anion generation from stimulated human...

Vasoactive intestinal peptide (VIP) is suspected to be a neurotransmitter of nonadrenergic and noncholinergic inhibitory nerves in human respiratory tracts. Although VIP affects T lymphocytes through its specific receptor, the effects of VIP on inflammatory cells except T lymphocytes are obscure. We investigated the effects of VIP on superoxide anion (O2-) generation from five kinds of human cells; neutrophils, eosinophils and mononuclear cells isolated from peripheral blood, alveolar macrophages obtained from the bronchoalveolar lavage, and human monocyte cell line, U937, the capacity of which for O2- generation was induced by interferon-gamma. O2- generation from human cells stimulated by 10(-5) M fMLP was measured by the cypridina luciferin analog, MCLA, -dependent chemiluminescence method. VIP inhibited O2- generation from fMLP-stimulated neutrophils, mononuclear cells and U937 in a dose-dependent manner. 3 x 10(-6) M VIP inhibited O2- generation from fMLP-stimulated eosinophils and alveolar macrophages significantly. These results indicate that VIP might inhibit the activation of inflammatory cells and act as an antiinflammatory agent.