Signaling pathways beyond prostaglandin formation in bradykinin induced skin edema in mice and humans.

• Applicant: Professor Georg Kojda, Ph.D.
• Subject Area: Pharmacology ; Dermatology ; Otolaryngology, Phoniatrics and Audiology
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 408212167

Endothelial permeability is a fundamental regulator of fluid and nutrient exchange between plasma and tissues. Destabilisation of this important blood-tissue interface by bradykinin can lead to recurrent and potentially life-threatening non-allergic angioedema, most commonly caused by ACE inhibitor therapy. The molecular mechanisms of the increase in permeability triggered by activation of endothelial bradykinin type 2 receptors (B2) have not yet been elucidated. The results of the completed project suggest that arachidonic acid metabolites such as prostacyclin play an important role. Preliminary work on this project proposal provides evidence that dexamethasone, in contrast to inhibition of COX or cPLA2α but similar to the B2 antagonist Icatibant, is able to almost completely inhibit B2-induced extravasation in C57BL/6 mice in vivo. After pre-treatment with dexamethasone, Icatibant showed no additional effect. Preliminary DNA microarray analyses of subcutaneous tissue from dexamethasone-treated C57BL/6 indicate the regulation of several proteins that may be involved in the cascade of B2 signal transduction. To date, there is no approved treatment for ACE inhibitor-induced non-allergic angioedema. Therefore, such patients usually receive a clinically untested combination of glucocorticoids and H1 antihistamines (standard of care treatment). The aim of this new project is to investigate the role of glucocorticoids in B2-induced extravasation in C57BL/6 and humans as well as B2-induced signalling in primary human and mouse microvascular dermal endothelial cells. To this end, Miles assays will be performed in C57BL/6 and annexin-A1 (cPLA2α inhibitor) deficient mice (ANXA1-/-) treated with dexamethasone and prednisolone to determine the time and concentration dependence as well as the involvement of glucocorticoid receptors. In addition, a change in prostacyclin is measured in skin samples. For endothelial cells, microarray analyses will be performed to assess similarities between changes in expression in vivo and in endothelial cells and complemented by Western blot and activity analyses for corresponding proteins such as cPLA2α. The ABRASE-2 study will investigate the effect of dexamethasone on B2-induced dermal extravasation in human volunteers. It is expected that the results of these studies may provide new targets for the treatment of the different forms of B2-induced angioedema. In addition, the studies in this new project may help to better justify the standard emergency treatment of non-allergic drug-induced angioedema with high-dose glucocorticoids.

• DFG Programme: Research Grants