THE ROLE OF VASCULAR ENDOTHELIUM - FUNCTI ONAL-BEHAVIOR IN HUMAN NASAL-MUCOSA

Background: During the last decade the morphological structure of nasa l blood vessels was understood as a functional basis for different phy siological and immunological reactions. Results: Under normal conditio ns the vascular endothelium is involved in many activities including h emostasis, defense reactions, and angiogenesis during repair and patho logical events. Most of the required components are synthesized by the endothelium itself, including extracellular matrix components, coagul ation reactants, and growth factors. The complex vasculature of the hu man nasal mucosa plays an important role in the protection of the resp iratory tract by generation of nasal fluid under normal and pathologic conditions. Increased plasma exudation in inflammatory processes incl uding increased plasma protein concentrations binds cytokines, mediato rs, and cell release products and transports them to the respiratory l umen. During inflammation, endothelial cells stimulated by cytokines l ike TNF (tumor necrosis factor) regulate the recruitment of leukocytes by expression of certain surface proteins, called adhesion molecules. They also secrete chemokines like IL-8 (interleukin-8) and MCP (monoc yte chemotactic protein) to increase the affinity of adhesion molecule s, spread the leukocyte form to a flat, migrating one, and stimulate c ell locomotion. Last but not least, endothelial cells may also act as antigen presenting cells (APC), although antigen presentation by endot helium is not responsible for the generalized homing of T-cells once t he response is working. Conclusion: The new scientific results on the functional behaviour of vascular endothelium have opened new perspecti ves for our understanding of nasal blood vessels; it might also stimul ate and enable us to search for new therapeutical concepts based on th ese findings.