Abstract
Byline: Yao Gao, Vascular Biology Program, Dept of Surgery, Boston Children's Hosp, Harvard Med Sch, Boston, MA; David Li, Vascular Biology Program, Dept of Surgery, Boston Children's Hosp, Harvard Med Sch, Boston, MA; Dakshnapriya Balasubbramanian, Vascular Biology Program, Dept of Surgery, Boston Children's Hosp, Harvard Med Sch, Boston, MA; Asma Almazyad, Vascular Biology Program, Dept of Surgery, Boston Children's Hosp, Harvard Sch of Dental Medicine, Boston, MA; Hong Chen, Vascular Biology Program, Dept of Surgery, Boston Children's Hosp, Harvard Med Sch, Boston, MA; David Briscoe, Transplant Rsch Program, Dept of Pediatrics, Boston Children's Hosp, Harvard Med Sch, Boston, MA; Rosalyn Adam, Dept of Urology Rsch,Dept of Surgery, Boston Children's Hosp, Harvard Med Sch, Boston, MA; Diane Bielenberg, Vascular Biology Program, Dept of Surgery, Boston Children's Hosp, Harvard Med Sch, Boston, MA The endothelium mediates microvascular fluid exchange between the blood and the interstitial tissue compartments. Vascular endothelial growth factor (VEGF-A) mediates vascular permeability via its tyrosine kinase receptor VEGFR2. However, the role of Neuropilin-2 (Nrp2), a co-receptor for both VEGF-A and Semaphorin-3F (SEMA3F), in vascular leakage is less understood. Nrp2-deficient mice show enhanced and prolonged swelling in acute inflammation models. We hypothesize that endogenous Sema3F acts as a competitive ligand with VEGF-A for Nrp2 and that Sema3F/Nrp2 signaling reduces edema by inhibiting vascular permeability and promoting a quickened resolution of inflammation. To test our hypothesis we compared tissue thickness and vascular permeability in constitutive or tissue-specific, inducible Sema3F-deficient mice and control littermates under basal conditions or following cutaneous, acute delayed-type hypersensitivity reactions in the ear. Our results demonstrate that depletion of SEMA3F protein, either genetically using knockout mice or pharmacologically using systemic administration of SEMA3F neutralizing antibodies, significantly prolonged tissue swelling and increased vascular permeability compared to control mice during acute inflammation. Conversely, intravenous injection of SEMA3F adenovirus decreased ear swelling and edema during acute inflammation compared to control virus. Using proximity ligation assays, VEGFA/Nrp2 binding was found to be dramatically increased in Sema3F-knockout mice compared to wildtype mice. Taken together, our results demonstrate that the NRP2 signaling cascade mediates fluid homeostasis via its stimulatory (VEGFA) and inhibitory (SEMA3F) ligands during inflammatory reactions. SEMA3F acts as a competitive ligand with VEGFA binding to Nrp2 and promotes resolution by attenuating vascular permeability leading to reduced inflammation and edema. Our research suggests that the NRP2 axis may be a potential therapeutic target for inflammation-mediated diseases.