P2Y2 Receptor Dependent Modulation of Microvascular Barrier Function

That P2Y2 nucleotide receptor (P2Y2R) is critical to endothelial‐dependent inflammatory vascular responses including leukocyte recruitment and filtration was revealed by abolishment of inflammatory responses in P2Y2R‐deficient mice. The role of P2Y2R in the mediation of microvascular permeability, however, remains to be investigated. Both in vivo and in vitro approaches were used to test the hypothesis that P2Y2R activation would increase vascular permeability. We measured in vivo cremaster venular permeability to albumin ( P s ) in response to UTP, a P2Y2R agonist, in wild type (WT) and P2Y2R‐deficient mice. UTP (10 − 5 M) induced 5.2 ± 1.7‐fold (n=5) transient increase in cremaster venular P s from basal levels in WT mice; this response was absent (P test /P control = 0.92 ±0.07, n=4) in the P2Y2R‐deficient mice. The increased P s in response to UTP in WT mice was inhibited by the ROCK blocker, Y27632 (10 −5 M). We established primary cultured microvascular endothelial cells (EC) derived from the same origin as cremaster microvessels to test the signaling mechanisms underlying P2Y2R‐dependent modulation of P s . The level of focal adhesion kinase (FAK) expression and phosphorylated FAK at tyrosine‐397 increased in EC following UTP treatment. The findings demonstrate that P2Y2R activation elevates vascular P s , which is consistent with the hypothesis. The UTP‐induced increase in P s is mediated by RhoA‐ROCK pathway and is also associated with reorganization of cell‐matrix adhesion.