Normalization of non-canonical Wnt signalings does not compromise blood-brain barrier protection conferred by upregulating endothelial Wnt/β-catenin signaling following ischemic stroke

摘要

Background Endothelial canonical (Wnt/β-catenin) and non-canonical Wnt signalings (Wnt/PCP and Wnt/Ca 2 ) promote blood-brain barrier (BBB) development and antagonize each other. However, the effects of ischemic stroke on endothelial canonical and non-canonical Wnt signalings are unclear. Further, how non-canonical Wnt signalings are influenced by upregulation of endothelial Wnt/β-catenin signaling and subsequently affect BBB function following ischemic stroke have not been studied. Methods First, we determined the levels of Wnt signaling markers including TCF/LEF1 transcription activity, Axin2 mRNA, phospho-JNK Thr183/Tyr185 , and NFAT in brain endothelial cells (ECs) with the deletion of Wnt receptor Frizzled (Fzd) 4 or Fzd6 , the two most abundant Fzds in brain ECs. Next, we observed the effect of ischemia/reperfusion injury on Wnt signalings in brain ECs and adult mice. Last, we assessed the changes of non-canonical Wnt signalings and BBB injury in the early stage of ischemic stroke in mice with endothelial β-catenin activation (β-cat mice). Results Fzd4 or Fzd6 deletion dampened both Wnt/β-catenin and Wnt/PCP signalings but enhanced Wnt/Ca 2 signaling in brain ECs. Both canonical and non-canonical Wnt signalings in brain ECs were downregulated after ischemia/reperfusion injury in vitro and in vivo . Upregulating endothelial Wnt/β-catenin signaling in β-cat mice normalized the downregulated non-canonical Wnt signalings, which did not compromise its protective effects on BBB integrity and endothelial tight junction following ischemic stroke. Conclusions The BBB protection induced by upregulation of endothelial Wnt/β-catenin signaling may be not interfered by the normalization of non-canonical Wnt signalings in the early stage of ischemic stroke.