Aberrant Activation of Notch1 Signaling in Glomerular Endothelium Induces Albuminuria

Glomerular capillaries are lined with a highly specialized fenestrated endothelium and contribute to the glomerular filtration barrier (GFB). The Notch signaling pathway is involved in regulation of GFB, but its role in glomerular endothelium has not been investigated due to the embryonic lethality of animal models with genetic modification of Notch pathway components in the endothelium. To determine the effects of aberrant activation of the Notch signaling in glomerular endothelium and the underlying molecular mechanisms. We established the ZEG-Notch1 intracellular domain (NICD1)/Tie2-tTA/Tet-O-Cre transgenic mouse model to constitutively activate Notch1 signaling in endothelial cells of adult mice. The triple transgenic mice developed severe albuminuria with significantly decreased VE-cadherin expression in the glomerular endothelium. In vitro studies showed that either NICD1 lentiviral infection or treatment with Notch ligand DLL4 markedly reduced VE-cadherin expression and increased monolayer permeability of human renal glomerular endothelial cells (HRGECs). In addition, Notch1 activation or gene knockdown of VE-cadherin reduced the glomerular endothelial glycocalyx. Further investigation demonstrated that activated Notch1 suppression of VE-cadherin was through the transcription factors SNAI1 and ERG, which bind to the -373 E-box and the -134/-118 ETS element of the VE-cadherin promoter, respectively. Our results reveal novel regulatory mechanisms whereby endothelial Notch1 signaling dictates the level of VE-cadherin through the transcription factors SNAI1 and ERG, leading to dysfunction of GFB and induction of albuminuria.