VCAM-1 expression on human dermal microvascular endothelial cells is directly and specifically up-regulated by substance P.

Sensory nerves in skin are capable of releasing multiple neuropeptides, which modulate inflammatory responses by activating specific cutaneous target cells. Extravasation of particular subsets of leukocytes depends upon the regulated expression of cellular adhesion molecules such as VCAM-1 on microvascular endothelial cells. We examined the direct effect of cutaneous neuropeptides on the expression and function of human dermal microvascular endothelial cell (HDMEC) VCAM-1. A significant increase in VCAM-1 immunostaining of microvascular endothelium was observed in vivo following capsaicin application to human skin. Multiple cutaneous sensory C-fiber-released neuropeptides were evaluated for their ability to induce VCAM-1 cell surface expression on HDMEC. Only substance P (SP) was found to be capable of inducing HDMEC VCAM-1 expression. This SP-mediated VCAM-1 induction appeared to be a direct effect that did not require the release of other HDMEC-derived soluble factors. Increased HDMEC VCAM-1 mRNA expression was detected 1 h after the addition of SP, with peak mRNA increase at 6-9 h postinduction. FACS studies demonstrated a 6.5-fold increase in endothelial cell surface VCAM-1 expression detectable 16 h after addition of SP, which was specifically blocked by a neurokinin-1 receptor antagonist. Increased VCAM-1 cell surface expression on SP-treated HDMEC resulted in a 4-fold increase in the functional binding of 51Cr-labeled MOLT-4 T cells. These data indicate that SP is capable of directly and specifically up-regulating functional endothelial VCAM-1 expression and thus may play a key role in modulating certain inflammatory responses in the skin.

Neuropeptide regulation of human dermal microvascular endothelial cell ICAM-1 expression and function.

There is increasing evidence that sensory nerves may participate in cutaneous inflammatory responses by the release of neuropeptides such as substance P (SP). We examined the direct effect of SP on human dermal microvascular endothelial cell (HDMEC) intercellular adhesion molecule 1 (ICAM-1) expression and function. Our results indicated that, although cultured HDMEC expressed mRNA for neurokinin receptors 1, 2, and 3 (NK-1R, NK-2R, and NK-3R), SP initiated a rapid increase in HDMEC intracellular Ca2+ levels, primarily by the activation of NK-1R. Immunohistochemistry studies likewise demonstrated that HDMEC predominantly expressed NK-1R. The addition of SP to HDMEC resulted in a rapid increase in cellular ICAM-1 mRNA levels, followed by a fivefold increase in ICAM-1 cell surface expression. This functionally resulted in a threefold increase in 51Cr-labeled binding of J-Y lymphoblastoid cells to HDMEC. In vivo studies demonstrated a marked increase in microvascular ICAM-1 immunostaining 24 and 48 h after application of capsaicin to the skin. These results indicate that neuropeptides such as SP are capable of directly activating HDMEC to express increased levels of functional ICAM-1 and further support the role of the cutaneous neurological system in modulating inflammatory processes in the skin.