Anti-fibrogenic effect of PPAR-γ agonists in human intestinal myofibroblasts

Abstract

BackgroundIntestinal fibrosis is a serious complication of inflammatory bowel disease, including Crohn’s disease and ulcerative colitis. There is no specific treatment for intestinal fibrosis. Studies have indicated that peroxisome proliferator-activated receptor- γ (PPAR-γ) agonists have anti-fibrogenic properties in organs besides the gut; however, their effects on human intestinal fibrosis are poorly understood. This study investigated the anti-fibrogenic properties and mechanisms of PPAR-γ agonists on human primary intestinal myofibroblasts (HIFs).MethodsHIFs were isolated from normal colonic tissue of patients undergoing resection due to colorectal cancer. HIFs were treated with TGF-β1 and co-incubated with or without one of two synthetic PPAR-γ agonists, troglitazone or rosiglitazone. mRNA and protein expression of procollagen1A1, fibronectin, and α-smooth muscle actin were determined by semiquantitative reverse transcription-polymerase chain reaction and Western blot. LY294002 (Akt inhibitor) was used to examine whether Akt phosphorylation was a downstream mechanism of TGF-β1 induced expression of procollagen1A1, fibronectin, and α-smooth muscle actin in HIFs. The irreversible PPAR-γ antagonist GW9662 was used to investigate whether the effect of PPAR-γ agonists was PPAR-γ dependent.ResultsBoth PPAR-γ agonists reduced the TGF-β1-induced expression of α-smooth muscle actin which was integrated into stress fibers in HIFs, as determined by actin microfilaments fluorescent staining and α-smooth muscle actin-specific immunocytochemistry. PPAR-γ agonists also inhibited TGF-β1-induced mRNA and protein expressions of procollagen1A1, fibronectin, and α-smooth muscle actin. TGF-β1 stimulation increased phosphorylation of downstream signaling molecules Smad2, Akt, and ERK. TGF-β1 induced synthesis of procollagen1A1, fibronectin, and α-smooth muscle actin through a phosphatidylinositol 3-kinase/Akt-dependent mechanism. PPAR-γ agonists down regulated fibrogenesis, as shown by inhibition of Akt and Smad2 phosphorylation. This anti-fibrogenic effect was PPAR-γ independent.ConclusionsTroglitazone and rosiglitazone suppress TGF-β1-induced synthesis of procollagen1A1, fibronectin, and α-smooth muscle actin in HIFs and may be useful in treating intestinal fibrosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12876-017-0627-4) contains supplementary material, which is available to authorized users.

Peroxisome Proliferator-Activated Receptors: Experimental Targeting for the Treatment of Inflammatory Bowel Diseases

“…On the other hand, PPARg agonists can decrease fibrogenesis by inhibiting the effects on TGF-b signaling (Kawai et al, 2009). Furthermore, some researchers have suggested that PPARg has both antiinflammatory and anti-fibrotic effects in the bowel (Speca et al, 2016;Koo et al, 2017). In this regard, natural and synthetic ligands of PPARg have been able to improve the fibrotic condition in both preliminary clinical trials and experimental models of intestinal fibrosis (Koo et al, 2017).…”

“…Furthermore, some researchers have suggested that PPARg has both antiinflammatory and anti-fibrotic effects in the bowel (Speca et al, 2016;Koo et al, 2017). In this regard, natural and synthetic ligands of PPARg have been able to improve the fibrotic condition in both preliminary clinical trials and experimental models of intestinal fibrosis (Koo et al, 2017). PPARg Reduce the state of activation of myofibroblasts and the expression of the main pro-fibrotic molecules as TGF-b, Smad3, IL-13, CTGF, and GSK-3b DSS-induced colitis mice Speca et al, 2016Di Gregorio et al, 2017 J11-Cl (Jasmonate) PPARg Decreases pro-inflammatory cytokines production DSS-induced colitis mice Choo et al, 2015 rSj16 (recombinant secreted protein of Schistosoma japonicum)…”

Fibrostenotic strictures in Crohn’s disease

“…48 TGF-β1-induced fibrogenesis is also mediated by Smad-independent pathways, including phosphorylation of extracellular signal regulated kinase, c-Jun N-terminal kinase, p38 mitogen-activated protein kinase (MAPK), and AKT. 26,[48][49][50] Another Smad-independent pathway is Ras homolog family member/Rho kinase/actin/myocardinrelated transcription factor/serum response factor (Rho/ ROCK/Actin/MRTF/SRF) pathway. 51,52 TGF-β1-induced activation of Rho and its effector ROCK, which promotes actin polymerization from globular actin to filamentous actin.…”

Fat fibrosis: friend or foe?

“…CP-544439-treated mice also have reduced expression of the key adipogenesis regulator PPARγ (120,(122)(123)(124). The antifibrotic effects of PPAR family proteins have been described in different tissue systems (125)(126)(127)(128)(129)(130). MMP-13-mediated regulation of PPAR expression in obese adipose tissue might therefore act as an important molecular switch that determines fibrogenic or adipogenic adipocyte progenitor fate.…”