Naomie Turgeon

HDAC1 and HDAC2 Restrain the Intestinal Inflammatory Response by Regulating Intestinal Epithelial Cell Differentiation

Acetylation and deacetylation of histones and other proteins depends on histone acetyltransferases and histone deacetylases (HDACs) activities, leading to either positive or negative gene expression. HDAC inhibitors have uncovered a role for HDACs in proliferation, apoptosis and inflammation. However, little is known of the roles of specific HDACs in intestinal epithelial cells (IEC). We investigated the consequences of ablating both HDAC1 and HDAC2 in murine IECs. Floxed Hdac1 and Hdac2 homozygous mice were crossed with villin-Cre mice. Mice deficient in both IEC HDAC1 and HDAC2 weighed less and survived more than a year. Colon and small intestinal sections were stained with hematoxylin and eosin, or with Alcian blue and Periodic Acid Schiff for goblet cell identification. Tissue sections from mice injected with BrdU for 2 h, 14 h and 48 h were stained with anti-BrdU. To determine intestinal permeability, 4-kDa FITC-labeled dextran was given by gavage for 3 h. Microarray analysis was performed on total colon RNAs. Inflammatory and IEC-specific gene expression was assessed by Western blot or semi-quantitative RT-PCR and qPCR with respectively total colon protein and total colon RNAs. HDAC1 and HDAC2-deficient mice displayed: 1) increased migration and proliferation, with elevated cyclin D1 expression and phosphorylated S6 ribosomal protein, a downstream mTOR target; 2) tissue architecture defects with cell differentiation alterations, correlating with reduction of secretory Paneth and goblet cells in jejunum and goblet cells in colon, increased expression of enterocytic markers such as sucrase-isomaltase in the colon, increased expression of cleaved Notch1 and augmented intestinal permeability; 3) loss of tissue homeostasis, as evidenced by modifications of claudin 3 expression, caspase-3 cleavage and Stat3 phosphorylation; 4) chronic inflammation, as determined by inflammatory molecular expression signatures and altered inflammatory gene expression. Thus, epithelial HDAC1 and HDAC2 restrain the intestinal inflammatory response, by regulating intestinal epithelial cell proliferation and differentiation.

The acetylome regulators Hdac1 and Hdac2 differently modulate intestinal epithelial cell dependent homeostatic responses in experimental colitis

Histone deacetylases (Hdac) remove acetyl groups from proteins, influencing global and specific gene expression. Hdacs control inflammation, as shown by Hdac inhibitor-dependent protection from dextran sulfate sodium (DSS)-induced murine colitis. Although tissue-specific Hdac knockouts show redundant and specific functions, little is known of their intestinal epithelial cell (IEC) role. We have shown previously that dual Hdac1/Hdac2 IEC-specific loss disrupts cell proliferation and determination, with decreased secretory cell numbers and altered barrier function. We thus investigated how compound Hdac1/Hdac2 or Hdac2 IEC-specific deficiency alters the inflammatory response. Floxed Hdac1 and Hdac2 and villin-Cre mice were interbred. Compound Hdac1/Hdac2 IEC-deficient mice showed chronic basal inflammation, with increased basal disease activity index (DAI) and deregulated Reg gene colonic expression. DSS-treated dual Hdac1/Hdac2 IEC-deficient mice displayed increased DAI, histological score, intestinal permeability, and inflammatory gene expression. In contrast to double knockouts, Hdac2 IEC-specific loss did not affect IEC determination and growth, nor result in chronic inflammation. However, Hdac2 disruption protected against DSS colitis, as shown by decreased DAI, intestinal permeability and caspase-3 cleavage. Hdac2 IEC-specific deficient mice displayed increased expression of IEC gene subsets, such as colonic antimicrobial Reg3b and Reg3g mRNAs, and decreased expression of immune cell function-related genes. Our data show that Hdac1 and Hdac2 are essential IEC homeostasis regulators. IEC-specific Hdac1 and Hdac2 may act as epigenetic sensors and transmitters of environmental cues and regulate IEC-mediated mucosal homeostatic and inflammatory responses. Different levels of IEC Hdac activity may lead to positive or negative outcomes on intestinal homeostasis during inflammation.

The histone H3K27 methylation mark regulates intestinal epithelial cell density‐dependent proliferation and the inflammatory response

Polycomb‐group proteins form multimeric protein complexes involved in transcriptional silencing. The Polycomb Repressive complex 2 (PRC2) contains the Suppressor of Zeste‐12 protein (Suz12) and the histone methyltransferase Enhancer of Zeste protein‐2 (Ezh2). This complex, catalyzing the di‐ and tri‐methylation of histone H3 lysine 27, is essential for embryonic development and stem cell renewal. However, the role of Polycomb‐group protein complexes in the control of the intestinal epithelial cell (IEC) phenotype is not known. We show that Suz12 and Ezh2 were differentially expressed along the intestinal crypt‐villus axis. ShRNA‐mediated Suz12 depletion in the IEC‐6 rat crypt‐derived cell line decreased Ezh2 expression and H3K27 di‐trimethylation. Suz12‐depleted cells achieved higher cell densities after confluence, with increased cyclin D2 and cyclin D3 protein levels, and increased STAT3 activation in post‐confluent cells. Suz12 depletion specifically increased mostly developmental, cell adhesion and immune response gene expression, including neuronal and inflammatory genes. Suz12 depletion directly and indirectly de‐regulated the IL‐1β‐dependent inflammatory response, as demonstrated by decreased MAPK p38 activation as opposed to JNK activation, and altered basal and stimulated expression of inflammatory genes, including transcription factors such as C/EBPβ. Of note, this positive effect on cell proliferation and inflammatory gene expression was revealed in the absence of the cyclin‐dependent kinase inhibitor p16, a main target negatively regulated by PRC2. These results demonstrate that the PRC2 complex, in addition to keeping in check non‐IEC differentiation pathways, insures the proper IEC response to cell density as well as to external growth and inflammatory signals, by controlling specific signaling pathways. J. Cell. Biochem. 114: 1203–1215, 2013.

Regulation of C/EBPδ-dependent transactivation by histone deacetylases in intestinal epithelial cells

The C/EBPδ transcription factor is involved in the positive regulation of the intestinal epithelial cell acute phase response. C/EBPδ regulation by histone deacetylases (HDACs) during the course of inflammation remains to be determined. Our aim was to examine the effect of HDACs on C/EBPδ‐dependent regulation of haptoglobin, an acute phase protein induced in intestinal epithelial cells in response to pro‐inflammatory cytokines. HDAC1, HDAC3, and HDAC4 were expressed in intestinal epithelial cells, as determined by Western blot. GST pull‐down assays showed specific HDAC1 interactions with the transcriptional activation and the b‐ZIP C/EBPδ domains, while the co‐repressor mSin3A interacts with the C‐terminal domain. Immunoprecipitation assays confirmed the interaction between HDAC1 and the N‐terminal C/EBPδ amino acid 36–164 domain. HDAC1 overexpression decreased C/EBPδ transcriptional activity of the haptoglobin promoter, as assessed by transient transfection and luciferase assays. Chromatin immunoprecipitation analysis showed a displacement of HDAC1 from the haptoglobin promoter in response to inflammatory stimuli and an increased acetylation of histone H3 and H4. HDAC1 silencing by shRNA expression increased both basal and IL‐1β‐induced haptoglobin mRNA levels in epithelial intestinal cells. Our results suggest that interactions between C/EBPs and HDAC1 negatively regulate C/EBPδ‐dependent haptoglobin expression in intestinal epithelial cells. J. Cell. Biochem. 103: 1573–1583, 2008.

The histone deacetylase Hdac1 regulates inflammatory signalling in intestinal epithelial cells

BackgroundIt has recently been found that both nuclear epithelial-expressed histone deacetylases Hdac1 and Hdac2 are important to insure intestinal homeostasis and control the mucosal inflammatory response in vivo. In addition, HDAC inhibitors modulate epithelial cell inflammatory responses in cancer cells. However, little is known of the specific role of different HDAC, notably Hdac1, in the regulation of inflammatory gene expression in intestinal epithelial cells (IEC).MethodsWe investigated the role of Hdac1 in non-transformed IEC-6 rat cells infected with lentiviral vectors expressing specific Hdac1 shRNAs, to suppress Hdac1 expression. Proliferation was assessed by cell counting. Deacetylase activity was measured with a colorimetric HDAC assay. Cells were treated with IL-1β and/or the JQ1 bromodomain acetyl-binding inhibitor. Nuclear protein levels of Hdac1, Hdac2, phosphorylated or unphosphorylated NF-κB p65 or C/EBPβ, and NF-κB p50 and actin were determined by Western blot. Chemokine and acute phase protein expression was assessed by semi-quantitative RT-PCR analysis. Secreted cytokine and chemokine levels were assessed with a protein array. Chromatin immunoprecipitation experiments were done to assess RNA polymerase II recruitment.ResultsReduced Hdac1 protein levels led to Hdac2 protein increases and decreased cell proliferation. Hdac1 depletion prolonged nuclear IL-1β-induced phosphorylation of NF-κB p65 protein on Ser536 as opposed to total p65, and of C/EBPβ on Ser105. In addition, semi-quantitative RT-PCR analysis revealed three patterns of expression caused by Hdac1 depletion, namely increased basal and IL-1β-stimulated levels (Hp, Kng1), increased IL-1β-stimulated levels (Cxcl2) and decreased basal levels with normal IL-1β induction levels (Ccl2, Ccl5, Cxcl1, C3). Secreted cytokine and chemokine measurements confirmed that Hdac1 played roles both as an IL-1β signalling repressor and activator. Hdac1 depletion did not alter the JQ1 dependent inhibition of basal and IL-1β-induced inflammatory gene expression. Hdac1 depletion led to decreased basal levels of RNA polymerase II enrichment on the Ccl2 promoter, as opposed to the Gapdh promoter, correlating with decreased Ccl2 basal mRNA expression.ConclusionsHdac1 is a major nuclear HDAC controlling IL-1β-dependent inflammatory response in IEC, notably by regulating gene-specific transcriptional responses. Hdac1 may be important in restricting basal and inflammatory-induced gene levels to defined ranges of expression.

P2Y2 receptor expression is regulated by C/EBPβ during inflammation in intestinal epithelial cells

Inflammatory bowel diseases are characterized by relapses and remission periods during which numerous factors, including stress factors and nucleotides, are mobilized to re‐establish intestinal mucosal homeostasis. We have previously found that expression of the P2Y2 nucleotide receptor is increased in colonic tissue isolated from inflammatory bowel disease patients as well as in a mouse model of colitis, and that P2Y2 transcription is regulated in part by nuclear factor κB (NF‐κB) p65. Transcription factor DNA‐binding site analysis identified three potential CCAAT/enhancer‐binding protein β (C/EBPβ) binding sites in the P2Y2 proximal promoter. We then assessed the role of C/EBP transcription factors in the regulation of P2Y2 in intestinal epithelial cells (IECs). We identified a region between −229 and −220 bp upstream of the transcription initiation site as a DNA‐binding site for C/EBPβ, by electrophoretic mobility and supershift assays. Mutagenesis of this site decreased C/EBPβ‐dependent P2Y2 expression, as assessed by luciferase assays. In vivo, C/EBPβ as well as P2Y2 expression was increased in colonic IECs isolated from mice with dextran sulfate sodium‐induced acute colitis. In contrast, P2Y2 expression was decreased in C/EBPβ‐deficient mice treated with dextran sulfate sodium. Although C/EBPβ was sufficient to induce P2Y2 transcription, the effect of C/EBPβ and NF‐κB p65 on receptor transcription was synergistic. Chromatin immunoprecipitation assays revealed that both proteins simultaneously bind to the P2Y2 promoter. Thus, we have identified C/EBPβ as a novel regulator of P2Y2 expression.

Distinct Roles for Intestinal Epithelial Cell-Specific Hdac1 and Hdac2 in the Regulation of Murine Intestinal Homeostasis

The intestinal epithelium responds to and transmits signals from the microbiota and the mucosal immune system to insure intestinal homeostasis. These interactions are in part conveyed by epigenetic modifications, which respond to environmental changes. Protein acetylation is an epigenetic signal regulated by histone deacetylases, including Hdac1 and Hdac2. We have previously shown that villin‐Cre‐inducible intestinal epithelial cell (IEC)‐specific Hdac1 and Hdac2 deletions disturb intestinal homeostasis. To determine the role of Hdac1 and Hdac2 in the regulation of IEC function and the establishment of the dual knockout phenotype, we have generated villin‐Cre murine models expressing one Hdac1 allele without Hdac2, or one Hdac2 allele without Hdac1. We have also investigated the effect of short‐term deletion of both genes in naphtoflavone‐inducible Ah‐Cre and tamoxifen‐inducible villin‐CreER mice. Mice with one Hdac1 allele displayed normal tissue architecture, but increased sensitivity to DSS‐induced colitis. In contrast, mice with one Hdac2 allele displayed intestinal architecture defects, increased proliferation, decreased goblet cell numbers as opposed to Paneth cells, increased immune cell infiltration associated with fibrosis, and increased sensitivity to DSS‐induced colitis. In comparison to dual knockout mice, intermediary activation of Notch, mTOR, and Stat3 signaling pathways was observed. While villin‐CreER Hdac1 and Hdac2 deletions led to an impaired epithelium and differentiation defects, Ah‐Cre‐mediated deletion resulted in blunted proliferation associated with the induction of a DNA damage response. Our results suggest that IEC determination and intestinal homeostasis are highly dependent on Hdac1 and Hdac2 activity levels, and that changes in the IEC acetylome may alter the mucosal environment. J. Cell. Physiol. 231: 436–448, 2016.

GATA-4 modulates C/EBP-dependent transcriptional activation of acute phase protein genes.

C/EBP transcription factors are involved in the regulation of the intestinal epithelial cell response to inflammatory stimuli. GATA transcription factors modulate C/EBP-dependent transcriptional activation in various cell types. We thus determined whether GATA-4 whose expression is restricted to epithelial cells, modulate C/EBP transcriptional activity and C/EBP-dependent acute phase protein expression in intestinal epithelial cells. Interaction between C/EBPdelta and GATA-4 required both C/EBPdelta leucine zipper and basic DNA-binding domains, and the GATA-4 C-terminal region. C/EBP isoforms and GATA-4 synergistically activated the alpha-acid glycoprotein gene while GATA-4 repressed thiostatin and haptoglobin C/EBP-dependent transactivation. In GATA-4 expressing intestinal epithelial cells, GATA-4 led to decreased C/EBPbeta and C/EBPdelta protein levels, and decreased thiostatin expression in response to IL-1beta and dexamethasone. This correlated with decreased C/EBPdelta recruitment to the thiostatin promoter, as assessed by chromatin immunoprecipitation assays. In contrast, increased AGP expression in response to dexamethasone correlated with increased basal histone H4 acetylation. Thus, GATA-4 may be involved in the establishment of specific intestinal epithelial cell C/EBP-dependent and C/EBP-independent transcriptional responses.

Loss of histone deacetylase Hdac1 disrupts metabolic processes in intestinal epithelial cells

By using acetyl‐CoA as a substrate, acetyltransferases and histone deacetylases regulate protein acetylation by adding or removing an acetyl group on lysines. Nuclear‐located Hdac1 is a regulator of intestinal homeostasis. We have previously shown that Hdac1 define specific intestinal epithelial cell basal and inflammatory‐dependent gene expression patterns and control cell proliferation. We show here that Hdac1 depletionin cellulo leads to increased histone acetylation after metabolic stresses, and to metabolic disturbances resulting in impaired responses to oxidative stresses, AMPK kinase activation and mitochondrial biogenesis. Thus, nuclear Hdac1 may control intestinal epithelial cell metabolism by regulating the supply of acetyl groups.

A SILAC-Based Method for Quantitative Proteomic Analysis of Intestinal Organoids

Organoids have the potential to bridge 3D cell culture to tissue physiology by providing a model resembling in vivo organs. Long-term growing organoids were first isolated from intestinal crypt cells and recreated the renewing intestinal epithelial niche. Since then, this technical breakthrough was applied to many other organs, including prostate, liver, kidney and pancreas. We describe here how to apply a SILAC-based quantitative proteomic approach to measure protein expression changes in intestinal organoids under different experimental conditions. We generated SILAC organoid media that allow organoids to grow and differentiate normally, and confirmed the incorporation of isotopically labelled amino acids. Furthermore, we used a treatment reported to affect organoid differentiation to demonstrate the reproducibility of the quantification using this approach and to validate the identification of proteins that correlate with the inhibition of cellular growth and development. With the combined use of quantitative mass spectrometry, SILAC and organoid culture, we validated this approach and showed that large-scale proteome variations can be measured in an “organ-like” system.