The PlGF-NRP1 pathway primes splenic immune response to increase blood pressure

Introduction T lymphocytes and Dendritic Cells (DCs) play crucial roles in hypertension(1,2). Placental Growth Factor (PlGF) is a neuroimmune mediator that promotes T lymphocytes egression from the spleen and infiltration in target organs of elevated blood pressure (BP) (1). We demonstrated that Neuropilin-1 (NRP1) expressed by myeloid cells is a crucial mediator of PlGF effect on immune responses in cardiovascular diseases(3). Hypothesis: We explored the cellular mechanism downstream to PlGF responsible for lymphocytes priming in hypertension. We hypothesized that PlGF released in the spleen after sympathetic discharge induced by hypertensive stimuli, primes splenic immune response through its receptor NRP1 expressed by DCs precursors contributing to BP increase. Methods We used flow cytometry, immunohistochemistry, in vitro cell culture and tail cuff plethysmography to evaluate the involvement of PlGF-NRP1 pathway in splenic immune response in hypertension. Results DCs subsets have different developmental origins and phenotypes playing crucial roles in immune responses in pathological conditions. Here we identified a DCs subset originating from Ly6C+ monocyte-DC (MoDCs) progenitors involved in T cells priming in the spleen and contributing to BP dysregulation. To explore the role of NRP1 in different stages of DCs maturation, we took advantage of two mouse models lacking NRP1 in myeloid MoDCs progenitors (NRP1myeKO mice) and in mature DCs (NRP1DC-KO mice). In vitro, we induced the differentiation of splenic MoDCs progenitors in mature DC by using a standard differentiation protocol of monocytes in DCs. We observed that CD86 and MHCII expression was upregulated in MoDCs from WT and NRP1DC-KO mice cultured in the standard medium plus recombinant PlGF (rPlGF). On the contrary, rPlGF didn't increase CD86 and MHCII expression in MoDCs from NRP1myeKO mice suggesting that PlGF-NRP1 signaling is involved in the maturation and activation of MoDCs, since the absence of NRP1 in MoDCs progenitors, but not in mature DCs, abolished this process. To explore the involvement of NRP1 in transducing the effect of PlGF in hypertension, we stimulated mice with AngII, finding that NRP1DC-KO mice increased BP similarly to WT; on the contrary, NRP1myeKO mice were protected from AngII-hypertension. In addition, AngII increased the expression of costimulation molecules in splenic MoDCs from WT mice; the selective deletion of NRP1 in MoDCs progenitors hampered the maturation of MoDCs and the expression of costimulation molecules. NRP1myeKO mice were also protected from T cells egression from the spleen and infiltration in target organs of hypertension. Conclusions PlGF-NRP1 pathway is involved in MoDCs maturation to promote T cells priming and migration toward peripheral vasculature where they affect BP contributing to hypertension.​ The selective deletion of NRP1 in MoDCs progenitors protects from BP increase and related organ damage.