Angioedema and Shear Stress Modulate Endothelial Permeability Through gC1qR

Angioedema is characterized by swelling in the dermis, oropharyngolaryngeal tissue and/or gastrointestinal wall. In angioedema (AE), vascular wall permeability increases, which is largely due to the overproduction of bradykinin, an inflammatory mediator and vasodilator. The receptor for C1q, gC1qR, has also been identified to play important roles in many physiological/pathological responses. High molecular weight kininogen (HK) can bind to gC1qR on the surface of vascular wall endothelial cells, resulting in the assembly and activation of the kinin/kallikrein system, culminating in bradykinin production. Endothelial cells are sensitive to blood flow‐induced shear stress. It has been established that low shear stress can lead to endothelial cell inflammation and gC1qR upregulation. The goals of the present study are: 1) to investigate how bradykinin and angioedema patients' plasma impair vascular endothelial cell permeability under various shear stress conditions (physiological and pathological); and 2) to determine if a monoclonal antibody (mAb) 74.5.2 known to block the gC1qR/HK interaction can also effectively block this response. To this end, human umbilical vein endothelial cells (HUVECs) were grown to confluence in polycarbonate transwell plates and exposed to 30 minutes of shear stress (1, 5 and 10 dynes/cm 2 ) in the presence or absence of bradykinin or angioedema patients' plasma. FITC‐conjugated bovine serum albumin (BSA) was added to the upper chamber of the transwells before shearing. Endothelial cell permeability was measured by the amount of FITC‐BSA leaked to the bottom chamber of the transwell at the end of the experiment. Cell surface gC1qR expression was measured using a solid‐phase ELISA. Endothelial cell morphology following treatment (shear stress, bradykinin and AE plasma) was quantified using immunofluorescence microscopy. To confirm that mAb 74.5.2 can effectively block HK binding to gC1qR, purified gC1qR was coated on a 96‐well microtiter plate. After incubation with 74.5.2, HK binding was measured using ELISA. The results demonstrated that both bradykinin and AE plasma can significantly enhance gC1qR expression and damage endothelial cell integrity (i.e. permeability), especially under low shear stress (1 dynes/cm 2 ). Monoclonal antibody 74.5.2 could significantly inhibit HK binding to immobilized gC1qR (by more than 40%). These results suggest that gC1qR is a major mediator in angioedema, especially under pathological low shear stress. Inhibiting HK binding to gC1qR using 74.5.2 could be an effective therapeutic solution to prevent angioedema. Support or Funding Information Research funded by Berhane Ghebrehiwet through NIH Grant: 1 R56 AI122376‐01A1 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .