Imbalance of Wnt/Dkk Negative Feedback Promotes Persistent Activation of Pancreatic Stellate Cells in Chronic Pancreatitis

Abstract

The role of persistent activation of pancreatic stellate cells (PSCs) in the fibrosis associated with chronic pancreatitis (CP) is increasingly being recognized. Recent studies have shown that Wnt signaling is involved in the development of fibrosis in multiple organs, however, the role of specific Wnts in pancreatic fibrosis remains unknown. We investigated the role of Wnt signaling during PSC activation in CP and the effect of β-catenin inhibition and Dickkopf-related protein 1 (Dkk1) restoration on the phenotype of PSCs. CP was induced in mice by repetitive caerulein injection and mouse PSCs were isolated and activated in vitro. The expression of Wnts, β-catenin, secreted frizzled-related proteins (sFRPs) and Dkks was analyzed by quantitative RT-PCR and western blotting. The canonical Wnt signaling pathway was examined by immunofluorescence and western blot detection of nuclear β-catenin expression. The effect of recombinant mouse Dkk-1 (rmDkk-1) on cell proliferation and apoptosis was assessed by flow cytometry, immunofluorescence, immunocytochemistry and Cell Counting Kit-8 (CCK-8) analysis. The expression of β-catenin, collagen1α1, TGFβRII, PDGFRβ and α-SMA in PSCs treated with different concentrations of rmDkk-1 or siRNA against β-catenin was determined by quantitative RT-PCR and western blotting. Wnt2 was the only Wnt whose expression was significantly upregulated in response to PSC activation, and Wnt2 and β-catenin protein levels were significantly increased in the pancreas of CP mice, whereas Dkk-1 expression was evidently decreased. Nuclear β-catenin levels were markedly increased in activated PSCs, and rmDkk-1 suppressed the nuclear translocation of β-catenin and the proliferation and extracellular matrix production of PSCs through the downregulation of PDGFRβ and TGFβRII. Upregulation of Dkk-1 expression increased apoptosis in cultured PSCs. These results indicate that Wnt signaling may mediate the profibrotic effect of PSC activation, and Wnt2/Dkk-1 could be potential therapeutic targets for CP.

Role of the Wnt/β-catenin pathway in gastric cancer: An in-depth literature review

“…Some Wnt-target genes, such as Dkk-1, Axin, Nemo kinase, etc., have shown to cause inhibition of Wnt signaling itself [114,115] . These Wnt-antagonists are initially upregulated in response to Wnt signaling activation, initiating a negative feedback loop [116] . However, in certain tumor cells, the epigenetic silencing of Dkk-1 by promoter hypermethylation or loss of heterozygosity, produces an imbalance of Wnt/Dkk negative feedback, therefore contributing to persistent activation of Wnt/ b-catenin signaling [117,118] .…”

Genetic sharing with coronary artery disease identifies potential novel loci for bone mineral density

“…Strong interactions were detected between proteins produced by cFDR-significant genes, especially among WNT4, SFRP4, WLS, JAG1, MEPE, ESR1, TNFRSF11B, TNFSF11 and SOST. For example, protein produced by SFRP4 regulates Wnt signaling through direct interaction [32], JAG1 encodes Jagged1 protein, Jagged1-Notch1 signaling induces the expression of WNT4 in encocardial cells [33]. SOST inhibits Wnt signaling and negatively regulates bone formation [34], TNFRSF11B is the decoy receptor for TNFSF11 and neutralizes its function in osteoclastogenesis [35].…”

Wnt/β-catenin signalling plays diverse functions during the process of fibrotic remodelling in the exocrine pancreas

“…After deparaffination and antigen unmasking in citrate buffer (pH 6.0) 5 µm-thick tissue slices of the human pancreatic samples were probed with rabbit primary antibodies against selected Wnt/β-catenin pathway proteins. The selection 5 was made based on previous studies on their involvement in pancreatic physiology and/or pathophysiology [11,13,16,21,22]. Anti-β-catenin (ab16051), anti-Wnt2 (ab109222) and anti-SFRP4 (ab154167) antibodies were purchased from Abcam, Cambridge, UK and the one against Wnt5a (PA5-72454) was from Thermo Fisher Scientific, Rockford, IL.…”

“…Pancreatic stellate cells (PSCs) are central contributors to the fibrotic remodelling of the stromal compartment in pancreatitis and cancer [20]. Their persistent activation in chronic pancreatitis has been associated with aberrant regulation of Wnt/β-catenin signalling [21,22]. Suppression of Wnt/β-catenin signalling in PSCs has been shown to inhibit their activation and to ameliorate fibrosis in pancreatic diseases [16,22].…”