Substance P induces the expression of an endothelial-leukocyte adhesion molecule by microvascular endothelium.

Leukocyte trafficking in normal and diseased skin appears to be initially governed by endothelial surface glycoproteins that promote adhesive interactions with circulating leukocytes. In a separate study, we have demonstrated that one of these glycoproteins, endothelial-leukocyte adhesion molecule-1 (ELAM-1), is rapidly induced on postcapillary dermal venules as a direct consequence of experimentally-elicited degranulation of adjacent mast cells (Proc Natl Acad Sci USA 86:8972-8976, 1989). A principle endogenous mediator of mast cell degranulation is the neuropeptide substance P. In this study, we exposed organ cultures of neonatal human foreskins for 45 min to substance P or to a substance P analogue (D-pro4, D-trp7,9)SP(4-11) that binds to the identical mast cell surface receptor but which does not provoke histamine release. Dermal mast cells were uniformly degranulated only in explants exposed to substance P, as judged by ultrastructural analysis. After subsequent culture in medium alone for 6 h, superficial venules of explants exposed to substance P showed evidence of ELAM-1 induction, as documented histochemically using H4/18 monoclonal antibody. ELAM-1 was not induced by substance P analogue. Furthermore, preincubation of explants with analogue or with the mast cell inhibitor, cromolyn sodium, abrogated the ability of substance P to induce ELAM-1. From these results we suggest that substance P endogenously released by dermal nerve fibers upon physiologic or electrical stimulation may be important in the regulation of endothelial-leukocyte interactions in vivo. This concept provides further evidence for a neurogenic and psychogenic modulation of the immune response, and may be relevant to the course of naturally occurring dermatoses (e.g., psoriasis) that are commonly exacerbated by emotional stress.