Calcitonin gene‐related peptide and adrenomedullin modulate cytokine‐induced microvascular endothelial cell cellular adhesion molecule expression and NF‐κB activation

Abstract

AM and the sensory neuropeptide CGRP are potent vasoactive mediators that activate high‐affinity G‐protein‐coupled receptors consisting of receptor‐activity modifying proteins (RAMPs) and a seven‐transmembrane domain calcitonin receptor‐like receptor (CRLR) with RAMP‐1/CRLR as CGRP and RAMP2 or ‐3/CRLR as AM receptors. In this study, we have examined the possibility that AM or CGRP modulate dermal microvascular EC adhesion molecule (ICAM‐1 and VCAM‐1) expression. Primary HDMEC or cells of the EC line HMEC‐1 were transfected with cDNA expression vectors for an EGFP control, RAMP‐1, RAMP‐2 and CRLR by electroporation, or left untransfected. Stimulation of EC‐overexpressing R1/CRLR or R2/CRLR with CGRP or AM (0.01–1000 nm) resulted in a dose‐dependent upregulation of intracellular cAMP. Importantly, when HDMEC transfected with R1/CRLR or R2/CRLR were treated with TNFα in combination with CGRP or AM, these peptides interfered with the TNF‐induced expression of ICAM‐1 and VCAM‐1 as well as the adhesion of lymphoblastoid cell lines to HDMEC monolayer in a biphasic manner. Likewise, AM and CGRP modulated the activation of nuclear factor κB (NF‐κB) partly by inhibiting the TNFα‐induced degradation of cytosolic IκBα. Neither transfection with the orphan CRLR nor RAMPs alone was capable of mediating a full reduction of TNFα‐induced ICAM‐1 or VCAM‐1 expression. In conclusion, CGRP and more pronounced AM are capable of modulating TNFα‐induced EC CAM expression, which may be of importance for the regulation of leucocyte–endothelial cell interaction during cutaneous neurogenic inflammation.This study was supported by the “Medizinische Forschungsgesellschaft Salzburg” and a grant of the Austrian Science Foundation (P14906).