[In vitro effects of peptides of the corticostatin/defensin family on production of mitogen-induced cytokines].

Cytokines are autocrine, paracrine and endocrine glycoproteins that interact with specific cell receptors and have pleiotropic effects. Increasing evidence indicates that cytokines, immune interferon (IFN-gamma) and interleukin 6 (IL-6) among others, modulate hypothalamic-pituitary-adrenal function. Corticostatins/defensins are a family of cationic peptides recently isolated from phagocytic cells of myeloid lineage. Four peptides have been isolated from human neutrophils: HP-1, 2, 3 and 4. As defensins they participate in immunosurveillance against viruses, bacteria and fungi. Some members of the family are also able to inhibit ACTH-induced steroidogenesis. Among human peptides, only HP-4 is corticostatic. We previously demonstrated that HP-1 and HP-4 inhibit in vitro the spontaneous and cytokine-inducible natural killer activity of human peripheral blood mononuclear cells (PBMC) and potentiate cortisol-dependent inhibition. The present work was carried out to determine whether two human corticostatins/defensins, HP-1 and HP-4, were able to modulate in vitro IFN-gamma and IL-6 production by human PBMC stimulated with phytohemagglutinin or Concanavalin A. IFN-gamma was titrated using biological assay with WISH cells as indicators and vesicular stomatitis virus as the challenge virus. IL-6 was measured by means of enzyme amplified sensitivity immunoassay. Both HP-1 and HP-4 significantly reduced cytokine production. Our data indicate that HP-1 and HP-4 are novel modulators of lymphocyte functions in vitro. Their depressing properties on ACTH-induced steroidogenesis and on cytokine production add complexity to neuroendocrine-immune circuits involving hypothalamic-pituitary-adrenal function.