All-Trans Retinoic Acid Induces TGF-β2 in Intestinal Epithelial Cells via RhoA- and p38α MAPK-Mediated Activation of the Transcription Factor ATF2

Abstract

ObjectiveWe have shown previously that preterm infants are at risk of necrotizing enterocolitis (NEC), an inflammatory bowel necrosis typically seen in infants born prior to 32 weeks’ gestation, because of the developmental deficiency of transforming growth factor (TGF)-β2 in the intestine. The present study was designed to investigate all-trans retinoic acid (atRA) as an inducer of TGF-β2 in intestinal epithelial cells (IECs) and to elucidate the involved signaling mechanisms.MethodsAtRA effects on intestinal epithelium were investigated using IEC6 cells. TGF-β2 expression was measured using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Western blots. Signaling pathways were investigated using Western blots, transiently-transfected/transduced cells, kinase arrays, chromatin immunoprecipitation, and selective small molecule inhibitors.ResultsAtRA-treatment of IEC6 cells selectively increased TGF-β2 mRNA and protein expression in a time- and dose-dependent fashion, and increased the activity of the TGF-β2 promoter. AtRA effects were mediated via RhoA GTPase, Rho-associated, coiled-coil-containing protein kinase 1 (ROCK1), p38α MAPK, and activating transcription factor (ATF)-2. AtRA increased phospho-ATF2 binding to the TGF-β2 promoter and increased histone H2B acetylation in the TGF-β2 nucleosome, which is typically associated with transcriptional activation.ConclusionsAtRA induces TGF-β2 expression in IECs via RhoA- and p38α MAPK-mediated activation of the transcription factor ATF2. Further studies are needed to investigate the role of atRA as a protective/therapeutic agent in gut mucosal inflammation.

Rho GTPase signaling promotes constitutive expression and release of TGF-β2 by human trabecular meshwork cells

“…Whereas induction of TGF-β2 expression by TGF-β1 or all- trans retinoic acid involves direct activation of RhoA/ROCK signaling in other cell types (Shimada et al , 2011; Namachivayam et al , 2015), a growing body of evidence further suggests that Rho GTPases may indirectly affect gene expression by facilitating serum response factor-mediated transcription of c-fos (Hill et al , 1995) or phosphorylation and activation of p38 MAP kinases (Charron et al , 2001; Marinissen et al , 2001). Consistent with these findings, we and others have previously reported a critical role for Rho GTPase signaling in facilitating TGF-β2 mediated induction of endothelin-1 (Von Zee et al , 2012), SPARC (Villarreal et al , 2014), and variety of extracellular matrix-associated genes (Pattabiraman and Rao, 2010; Pattabiraman et al , 2014).…”

Retinoic Acid, Leaky Gut, and Autoimmune Diseases

“…RA may mitigate IBD severity through various immunoregulatory mechanisms. RA could: (1) restore and/or reprogram the impaired Treg/Th17 lineage differentiation that is usually linked to IBD development [ 51 , 107 ] by inducing adaptive Treg cells and imprinting their gut-homing phenotype in response to inflammatory stimuli [ 108 ]; (2) modulate the recognition of different TLR ligands and control the activation of downstream transcription factor signaling [ 109 , 110 ]; (3) downregulate inflammatory signaling molecules like nitric oxide (NO) from PBMCs of IBD patients, even after the establishment of the pro-inflammatory niche [ 111 ]; (4) regulate the production of immunoregulatory cytokines, such as by enhancing the synthesis of IL-22 by γδ T cells and ILCs and consequently attenuating colitis [ 61 ]; and (5) synergize with immunoregulatory mediators like TGFβ for maintaining gut homeostasis [ 112 ].…”

SPOP promotes ATF2 ubiquitination and degradation to suppress prostate cancer progression

“…As shown if Fig. 5g , stably overexpression of SPOP-F133 L mutant markedly increased the mRNA expression of ATF2 downstream target genes involved in cancer cell proliferation and invasion, including SOX9 , MMP9 , and TGFB2 , [ 35 – 37 ], but this effect was largely abrogated by ATF2 depletion. Taken together, these results suggest that ATF2 is an important mediator of SPOP mutant-induced cell proliferation, migration and invasion.…”