Role of glycogen synthase kinase-3β and PPAR-γ on epithelial-to-mesenchymal transition in DSS-induced colorectal fibrosis

Abstract

BackgroundIntestinal fibrosis is characterized by abnormal production and deposition of extracellular matrix (ECM) proteins by activated myofibroblasts. The main progenitor cells of activated myofibroblasts are the fibroblasts and the epithelial cells, the latter through the epithelial-mesenchymal transition (EMT).AimTo evaluate the action of the new PPAR-γ modulator, GED-0507-34 Levo (GED) on the expression of EMT associated and regulatory proteins such as TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, and GSK-3β, in a mouse model of DSS-induced intestinal fibrosis.MethodsChronic colitis and fibrosis were induced by oral administration of 2.5% DSS (w/v) for 6 weeks. GW9662 (GW), a selective PPAR-γ inhibitor, was also administered by intraperitoneal injection at the dose of 1 mg/kg/day combined with GED treatment. All drugs were administered at the beginning of the second cycle of DSS (day 12). 65 mice were randomly divided into five groups (H2O as controls n = 10, H2O+GED n = 10, DSS n = 15, DSS+GED n = 15, DSS+GED+GW n = 15). The colon was excised for macroscopic examination and histological and morphometric analyses. The level of expression of molecules involved in EMT and fibrosis, like TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, GSK-3β and PPAR-γ, was assessed by immunohistochemistry, immunofluorescence, western blot and Real Time PCR.ResultsGED improved the DSS-induced chronic colitis and fibrosis. GED was able to reduce the expression of the main fibrosis markers (α-SMA, collagen I-III and fibronectin) as well as the pivotal pro-fibrotic molecules IL-13, TGF-β and Smad3, while it increased the anti-fibrotic PPAR-γ. All these GED effects were nullified by co-administration of GW with GED. Furthermore, GED was able to normalize the expression levels of E-cadherin and β-catenin and upregulated GSK-3β, that are all known to be involved both in EMT and fibrosis.ConclusionsThe DSS-induced intestinal fibrosis was improved by the new PPAR-γ modulator GED-0507-34 Levo through the modulation of EMT mediators and pro-fibrotic molecules and through GSK-3β induction.

Crosstalk Between Peroxisome Proliferator-Activated Receptor Gamma and the Canonical WNT/β-Catenin Pathway in Chronic Inflammation and Oxidative Stress During Carcinogenesis

“…Troglitazones (anti-inflammatory drugs) can decrease c-Myc levels ( 84 ). Intestinal fibrosis presents an activation of the WNT/β-catenin pathway, and the use of PPARγ agonists can decrease it and diminish fibrosis formation ( 85 ). PPARγ agonists activate Dickkopf-1 (DKK1, a WNT inhibitor) activity to decrease the canonical WNT/β-catenin pathway and then inhibit the fibroblasts differentiation ( 86 ).…”

Precancerous niche (PCN), a product of fibrosis with remodeling by incessant chronic inflammation

“…Increased GSK-3b expression is associated with the lesion grade in cervical cancer and inversely correlated with Cyclin D1 [32]. Dextran sulfate sodium (DSS)induced intestinal fibrosis was improved via GSK-3b signaling and after the use of the peroxisome proliferator-activated receptor gamma (PPAR-g) modulator, GED-0507-34 Levo [33].…”

Interactions between TGF-β1, canonical WNT/β-catenin pathway and PPAR γ in radiation-induced fibrosis

“…Troglitazone, a PPAR γ agonist, can decrease c-Myc levels [ 303 ]. In intestinal fibrosis, the activation of WNT/β-catenin has been observed and the use of PPAR γ agonist can inhibit WNT/β-catenin pathway activation and then can repress fibrosis [ 304 ]. PPAR γ agonists stimulate Dickkopf-1 (DKK1) activity, which inhibits the canonical WNT pathway and then block fibroblast differentiation [ 305 ].…”