We have definitely demonstrated that endothelial cells (EC) from human dermis (HDMEC) display skin-specific phenotypic and functional characteristics in vitro, and that these characteristics are reflective of in vivo biology of skin. Because of their importance in the pathophysiology of inflammatory skin disease, we have targeted for study the regulated expression of cytokine inducible cell adhesion molecules in HDMEC. Vascular cell adhesion molecule 1 (VCAM-1) is regulated in HDMEC in a cell-and cytokine-specific fashion and the in vitro patterns of expression are consistent with observations of in vivo expression in skin inflammation. The mechanisms that mediate cell-specific regulatory features are important targets for novel anti-inflammatory therapies, since interruption of these pathways may allow for targeting therapies specifically to skin. Indeed, we have demonstrated that specific inhibition of VCAM-1 in HDMEC can be mediated by all-trans retinoic acid (t-RA) in a cell-specific fashion. We have partially characterized the tissue-specific regulatory pathways that mediate the fine specificity of expression, response, and suppression. These HDMEC specific regulatory functions appear to localize to two distinct domains of the VCAM-1 promoter that regulate unique responses to IL-1 and t-RA, respectively. We hypothesize that the unique features of VCAM-1 expression in HDMEC are the result of HDMEC-specific transcriptional regulation of the VCAM-1 gene, and that cell-specific regulation is controlled by definable regions in the VCAM-1 promoter and by cell-specific expression or function of transcription factors that interact with these domains. Defining how expression is controlled in a tissue-specific manner will provide invaluable insights for developing skin therapeutics. We therefore propose to: 1) identify regulatory elements in the VCAM-1 gene promoter that confer unresponsiveness for VCAM-1 gene transcription in HDMEC in a cytokine- and cell-specific fashion. 2) identify key differences between HDMEC and other cell types in their repertoire of expression and function of NF-kappaB proteins and define the functional relevance these differences as they relate to VCAM-1 gene expression. Understanding the mechanisms that dictate organ-and cell-specific regulation of VCAM-1 in HDMEC is clearly an extremely important avenue of research. Most directly, these studies will yield information on how inflammation is induced and regulated in the skin, but understanding these regulatory pathways will also provide us with novel cell- and tissue-specific targets for drug therapy.
