Changes in inflammatory gene expression induced by hyperbaric oxygen treatment in human endothelial cells under chronic wound conditions

The antioxidant response element (ARE) is a transcriptional control element that mediates expression of a set of antioxidant proteins. NF-E2-related factor 2 (Nrf2) is a transcription factor that activates ARE-containing genes. In endothelial cells, the ARE-mediated genes are upregulated by atheroprotective laminar flow through a Nrf2-dependent mechanism. We tested the hypothesis that activation of ARE-regulated genes via adenovirus-mediated expression of Nrf2 may suppress redox-sensitive inflammatory gene expression. Expression of Nrf2 in human aortic endothelial cells (HAECs) resulted in a marked increase in ARE-driven transcriptional activity and protected HAECs from H2O2-mediated cytotoxicity. Nrf2 suppressed TNF-α-induced monocyte chemoattractant protein (MCP)-1 and VCAM-1 mRNA and protein expression in a dose-dependent manner and inhibited TNF-α-induced monocytic U937 cell adhesion to HAECs. Nrf2 also inhibited IL-1β-induced MCP-1 gene expression in human mesangial cells. Expression of Nrf2 inhibited TNF-α-induced activation of p38 MAP kinase. Furthermore, expression of a constitutively active form of MKK6 (an upstream kinase for p38 MAP kinase) partially reversed Nrf2-mediated inhibition of VCAM-1 expression, suggesting that p38 MAP kinase, at least in part, mediates Nrf2's anti-inflammatory action. In contrast, Nrf2 did not inhibit TNF-α-induced NF-κB activation. These data identify the Nrf2/ARE pathway as an endogenous atheroprotective system for antioxidant protection and suppression of redox-sensitive inflammatory genes, suggesting that targeting the Nrf2/ARE pathway may represent a novel therapeutic approach for the treatment of inflammatory diseases such as atherosclerosis.

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Frizzled-4 regulates β-catenin in endothelial cells exposed to disturbed flow via an atypical Wnt pathway leading to proinflammatory activation and increased permeability

10.1101/2021.11.12.468370 ◽

2021 ◽

Author(s):

Matthew Rickman ◽

Mean Ghim ◽

Kuin Tian Pang ◽

Ana Cristina von Huelsen Rocha ◽

Elena M Drudi ◽

...

Keyword(s):

Gene Expression ◽

Endothelial Cells ◽

Shear Stress ◽

Endothelial Dysfunction ◽

Wnt Pathway ◽

Molecular Mechanisms ◽

Cultured Cells ◽

Endothelial Permeability ◽

Inflammatory Gene Expression ◽

Inflammatory Gene

Objective: Endothelial cells are regulated by hemodynamic wall shear stress and multidirectional shear stress is known to promote endothelial dysfunction, although the molecular mechanisms are poorly defined. Wnt pathways play an important role in non-vascular mechanoresponsive cells. Here we investigated their role in endothelial mechanosignalling and endothelial dysfunction. Approach & Results: Human aortic endothelial cells were exposed to shear stress using an orbital shaker. The expression of Frizzled-4 receptors was significantly increased in endothelial cells exposed to low magnitude multidirectional flow (LMMF) relative to high magnitude uniaxial flow (HMUF). Increased expression was also detected in regions of the murine aortic arch exposed to LMMF. The increased Frizzled-4 expression in cultured cells was abrogated following knockdown of R-spondin-3 (RSPO-3) using RNA interference. LMMF also increased the stabilisation and nuclear localisation of β-catenin, an effect that was dependent on Frizzled-4 and RSPO-3. Inhibition of β-catenin using a small molecule inhibitor (iCRT5), or knockdown of Frizzled-4 or R-spondin-3 resulted in a significant reduction of pro-inflammatory gene expression in endothelial cells exposed to LMMF. Stabilisation of the β-catenin destruction complex using IWR-1 under LMMF also reduced pro-inflammatory gene expression, as did inhibition of Wnt5a signalling. Interestingly, inhibition of the canonical Wnt pathway had no effect. Inhibition of β-catenin signalling also reduced endothelial permeability; this was associated with altered junctional and focal adhesion organisation and cytoskeletal remodelling. Conclusions: These data suggest the presence of an atypical Wnt-β-catenin pathway in endothelial cells that promotes inflammatory activation and barrier disruption in response to LMMF.

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