Background/Purpose: Endothelial dysfunction is a hallmark in the pathogenesis of many inflammatory diseases. The endothelial-to-mesenchymal transition (EndoMT) is a process where endothelial cells lose their endothelial features and acquire fibroblast-like phenotype. EndoMT has been associated with vasculopathy, atherogenesis, and it is promoted by several proinflammatory cytokines, such as tumor necrosis factor α (TNF-α). Protein tyrosine phosphatase 1B (PTP1B) modulates many signaling pathways associated with inflammatory mediators and has been associated with endothelial dysfunction and cardiovascular disturbances. However, it remains unclear the role of PTP1B in TNFα-induced EndoMT.

Objective. To characterize EndoMT promoted by TNF-α in human endothelial cells (ECs) and the putative role of PTP1B in this process.

Methods: Human aortic endothelial cells (HAECs) were used as model for in vitro induction of EndoMT. These ECs were incubated with human recombinant TNF-α (25 ng/mL) for 2 and 4 days. Expression of endothelial markers (eNOS, CD31, VE-cadherin) and mesenchymal marker (N-cadherin), and the transcription factors SNAI1, TWIST1 and ZEB1 along with PTP1B during EndoMT were evaluated by Western blot (WB). Canonical NF-κB pathway activation in EndoMT was assessed by phosphorylation of p65-Ser536, degradation of IkB-α and nuclear translocation of p65 by WB and immunofluorescence (IF). Inhibition of NF-kB pathway was assessed by using the IKK-β specific inhibitor BMS-345531 (5 µM).

Results: HAECs underwent EndoMT after 2- and 4-days TNF-α treatment. Expression of eNOS, CD31 and VE-cadherin were downregulated, and N-cadherin was upregulated as well as the transcription factors SNAI1, TWIST1 and ZEB1. Concomitant with this process, PTP1B increased its expression levels. TNF-α induced phosphorylation of NF-κB (p65-Ser 536) and degradation of IκB-α. Nuclear translocation of p65 was more evident 15 min after treatment. ECs pre-treated with BMS-345531 before TNF-α addition decreased TNF-α-induced phosphorylation of NF-κB (p65-Ser 536) and nuclear translocation of p65, and prevented degradation of IκB-α. Furthermore, decreased expression of N-cadherin, SNAI1 and TWIST1 was observed after 2 days of treatment with BMS-345531 + TNF-α.

Conclusion: TNF-α promotes EndoMT in human ECs by activating canonical NF-κB pathway. During this process PTP1B increases its expression levels. Pharmacological inhibition of IKK-β attenuated TNF-α-induced NF-kB activation with concomitant inhibition of EndoMT. These findings unveil an important pathway in endothelial dysfunction and vasculopathy associated with inflammatory conditions and suggest novel avenues for intervention.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tumor-necrosis-factor-%ce%b1-modulates-endothelial-to-mesenchymal-transition-and-increases-protein-tyrosine-phosphatase-1b/