Blocking Notch in Endothelial Cells Prevents Arteriovenous Fistula Failure Despite CKD

Abstract

Neointima formation causes the failure of 60% of arteriovenous fistulas (AVFs) within 2 years. Neointimaforming mechanisms are controversial but possibly linked to excess proinflammatory responses and dysregulated Notch signaling. To identify how AVFs fail, we anastomosed the carotid artery to the internal jugular vein in normal and uremic mice and compared these findings with those in failed AVFs from patients with ESRD. Endothelial cells (ECs) of AVFs in uremic mice or patients expressed mesenchymal markers (FSP-1 and/or a-SMA) and exhibited increased expression and nuclear localization of Notch intracellular domain compared with ECs of AVFs in pair-fed control mice. Furthermore, expression of VE-Cadherin decreased, whereas expression of Notch1 and -4, Notch ligands, the downstream transcription factor of Notch, RBP-Jk, and Notch target genes increased in ECs of AVFs in uremic mice. In cultured ECs, ectopic expression of Notch ligand or treatment with TGF-b1 triggered the expression of mesenchymal markers and induced endothelial cell barrier dysfunction, both of which were blocked by Notch inhibition or RBP-Jk knockout. Furthermore, Notch-induced defects in barrier function, invasion of inflammatory cells, and neointima formation were suppressed in mice with heterozygous knockdown of endothelial-specific RBP-Jk. These results suggest that increased TGF-b1, a complication of uremia, activates Notch in endothelial cells of AVFs, leading to accelerated neointima formation and AVF failure. Suppression of Notch activation could be a strategy for improving AFV function in uremia.

Integrin β3 Mediates the Endothelial-to-Mesenchymal Transition via the Notch Pathway

“…1B). Our previous studies confirmed that SMA-α was also expressed in the endothelial layer of AVFs with severe neointima hyperplasia [6]. These results showed that the ECs of AVFs from ESRD patients express the mesenchymal cell marker, SMA-α.…”

“…Our data showed that overexpressed integrin β3 induced the EndMT through activation of the Notch signaling pathway. Elevated Notch signaling upregulates mesenchymal marker expression in ECs and leads to endothelial barrier dysfunction in AVFs [6]. Our findings explained the mechanism of neointimal formation in vascular disease regulated by integrin β3.…”

“…During the EndMT, ECs lose their endothelial-specific markers, gain mesenchymal markers, lose cell-cell junctions, and acquire invasive and migratory properties. The EndMT is not only critical to embryonic cardiac development [5], but is also involved in the pathogenesis of many diseases, including neointimal hyperplasia [6], fibrosis [7], and cancer [8]. Our previous studies reported that the ECs of the neointima of arteriovenous fistulas (AVFs) in uremic mice or end-stage renal disease (ESRD) patients expressed mesenchymal markers [6].…”

New Insights into Dialysis Vascular Access: Molecular Targets in Arteriovenous Fistula and Arteriovenous Graft Failure and Their Potential to Improve Vascular Access Outcomes

“…Another seminal study from Cheng and colleagues have shown that the endothelial barrier is dysfunctional after AVF creation and exacerbated in the setting of CKD, leading to increased neointimal hyperplasia development (23). Furthermore, this group has also demonstrated that signaling of the Notch pathway may play an important role in endothelial barrier dysfunction (24,25). Finally, Nath and colleagues have shown that generation of oxidant stress occurs within the AVF after AVF creation (26).…”

“…Genes in knockout mice that have been evaluated include HO-1 and HO-2 (15,16), MCP-1 (17), intermediate early response gene X-1 (IEX-1) (50), and elastin (51). Other recent studies in murine models have evaluated inhibition of specific genes, such as E26 transformation-specific sequence-1 (52) and Notch-1 (25).…”