In severe food-induced anaphylaxis mast cell (MC)-derived mediators, including histamine, induce vasodilatation and fluid extravasation, causing cardiovascular collapse. Animal-based studies suggest that this is enhanced by IL-4; however, the contribution of vascular endothelium (VE) specific IL-4 signaling in fluid extravasation in IgE-mediated anaphylactic reactions is unknown.
To determine the requirement of IL-4Rα chain in vascular leakage we employed VE-specific IL-4Rα knockout (Cadherin-5Cre IL-4Rafl/fl:VEΔIL-4Rα) and iIL-9Tg VEΔIL-4Rα mice. In vitro, we measured transendothelial resistance (TER) in murine VE cell lines (mHEVCs) with shRNA-lentiviral knockdown of IL-4Rα, histamine receptors (H1R; H2R).
IL-4 treatment exacerbated histamine-induced hypothermia in VEIL-4Rα WT mice (-2.9 ± 0.7 ºC histamine vs. -5.4 ± 1.1 ºC IL4+histamine ; mean ± SD; p < 0.0001). VE-specific genetic deletion of IL-4Rα (VEDIL-4Rα mice) abolished the IL-4 amplification. Similarly, using a passive model of food-induced anaphylaxis, IL-4 amplified hypothermia following oral challenge with ovalbumin-TNP in iIL-9Tg VEIL-4Rα WT mice sensitized with anti-TNP IgE (-3.1 ± 0.9 ºC vs. -5.6 ± 1.3 ºC vehicle vs IL4 respectively; mean ± SD) but not in iIL-9Tg VEDIL-4Rα. In vitro, histamine increased VE permeability in mHEVC and this was enhanced with IL-4 (TER reduction percentage: -8.1 ± 2.5% histamine vs. -18.6 ± 5.3% IL-4+histamine; mean ± SD; p = 0.0002). shRNA-mediated knockdown of IL-4Rα, H1R, and H2R in mHEVCs revealed that IL-4+histamine–induced VE leakage is dependent on IL-4Rα and H1R.
Our data suggest a synergistic interaction between IL-4 and histamine through VE H1R and the IL-4Rα chain to modulate VE dysfunction and severity of anaphylaxis.