Rainer Glauben

Histone Hyperacetylation Is Associated with Amelioration of Experimental Colitis in Mice

Inhibitors of histone deacetylases (HDAC) are being studied for their antiproliferative effects in preclinical cancer trials. Recent studies suggest an anti-inflammatory role for this class of compounds. Because inflammatory bowel disease is associated with an increased risk of malignancies, agents with antiproliferative and anti-inflammatory properties would be of therapeutic interest. HDAC inhibitors from various classes were selected and evaluated for their in vitro capacity to suppress cytokine production and to induce apoptosis and histone acetylation. Valproic acid (VPA) and suberyolanilide hydroxamic acid (SAHA) were chosen for further studies in dextran sulfate sodium- and trinitrobenzene sulfonic acid-induced colitis in mice. In vitro, inhibition of HDAC resulted in a dose-dependent suppression of cytokine synthesis and apoptosis induction requiring higher concentrations of HDAC inhibitors for apoptosis induction compared with cytokine inhibition. Oral administration of either VPA or SAHA reduced disease severity in dextran sulfate sodium-induced colitis. The macroscopic and histologic reduction of disease severity was associated with a marked suppression of colonic proinflammatory cytokines. In parallel to the beneficial effect observed, a dose-dependent increase in histone 3 acetylation at the site of inflammation was shown under VPA treatment. Furthermore, SAHA as well as VPA treatment resulted in amelioration of trinitrobenzene sulfonic acid-induced colitis, which was associated with an increase of apoptosis of lamina propria lymphocytes. Inhibitors of HDAC reveal strong protective effects in different models of experimental colitis by inducing apoptosis and suppressing proinflammatory cytokines, thereby representing a promising class of compounds for clinical studies in human inflammatory bowel disease.

Histone deacetylases: novel targets for prevention of colitis-associated cancer in mice

Objective: Inhibition of histone deacetylases, well known for its antiproliferative efficacy in vivo, was recently shown to ameliorate inflammation in experimental colitis. Since inflammatory bowel disease is associated with an increased risk of developing colon cancer, here the combined anti-inflammatory and proapoptotic efficacy of histone deacetylase inhibitors was studied in mouse models. Methods: The novel histone deacetylase inhibitor ITF2357 was compared with suberoylanilide hydroxamic acid in models of experimental colitis. Effects on tumour growth were studied after treatment of mice with azoxymethane and dextran sulphate sodium, and in interleukin 10 (IL10) knockout mice, respectively. Possible underlying mechanisms involving apoptosis and nuclear factor (NF)-κB activation were addressed by flow cytometry and western blot. Results: In dextran sulphate sodium- and trinitrobenzene sulphonic acid-induced colitis, treatment with ITF2357 was superior to suberoylanilide hydroxamic acid as shown by macroscopic and histological amelioration of inflammation, by reduced production of interferon γ (IFNγ) and by increased production of IL10. In both models of inflammation-mediated tumourigenesis, inhibition of histone deacetylases resulted in a significant suppression of tumour growth in terms of size and number, along with reduced signs of inflammation. As for potential mechanisms of ITF2357 action, increased acetylation of histone 3, reduced production of IFNγ and enhanced apoptosis in lamina propria mononuclear cells were found to accompany a histone deacetylase-dependent activation of NF-κB. Conclusions: These results indicate that inhibition of histone deactylases can attenuate inflammation-mediated tumour growth, which is paralled by an inhibition of NF-κB. Thus histone deacetylase inhibitors provide a promising strategy that combines anti-inflammatory and proapoptotic modes of action.

Leptin: A Critical Regulator of CD4+ T-cell Polarization in Vitro and in Vivo

Besides being mandatory in the metabolic system, adipokines like leptin directly affect immunity. Leptin was found to be necessary in T helper 1 (Th1)-dependent inflammatory processes, whereas effects on Th2 cells are rarely understood. Here, we focused on leptin in T-helper cell polarization and in Th2-mediated intestinal inflammation in vivo. The induction of cytokine-producing Th1 or Th2 cells from naive CD4(+) T cells under polarizing conditions in vitro was generally decreased in cells from leptin-deficient ob/ob mice compared with wild-type mice. To explore the in vivo relevance of leptin in Th2-mediated inflammation, the model of oxazolone-induced colitis was employed in wild-type, ob/ob, and leptin-reconstituted ob/ob mice. Ob/ob mice were protected, whereas wild-type and leptin-reconstituted ob/ob mice developed colitis. The disease severity went in parallel with local production of the Th2 cytokine IL-13. A possible explanation for the protection of ob/ob mice in Th1- as well as in Th2-dependent inflammation is provided by a decreased expression of the key transcription factors for Th1 and Th2 polarization, T-bet and GATA-3, in naive ob/ob T cells. In conclusion, these results support the regulatory function of the adipokine leptin within T-cell polarization and thus in the acquired immune system and support the concept that there is a close interaction with the endocrine system.

IκBNS Protein Mediates Regulatory T Cell Development via Induction of the Foxp3 Transcription Factor

Forkhead box P3 positive (Foxp3(+)) regulatory T (Treg) cells suppress immune responses and regulate peripheral tolerance. Here we show that the atypical inhibitor of NFκB (IκB) IκB(NS) drives Foxp3 expression via association with the promoter and the conserved noncoding sequence 3 (CNS3) of the Foxp3 locus. Consequently, IκB(NS) deficiency leads to a substantial reduction of Foxp3(+) Treg cells inxa0vivo and impaired Foxp3 induction upon transforming growth factor-β (TGF-β) treatment inxa0vitro. Moreover, fewer Foxp3(+) Treg cells developed from IκB(NS)-deficient CD25(-)CD4(+) Txa0cells adoptively transferred into immunodeficient recipients. Importantly, IκB(NS) was required for the transition of immature GITR(+)CD25(+)Foxp3(-) thymic Treg cell precursors into Foxp3(+) cells. In contrast to mice lacking c-Rel or Carma1, IκB(NS)-deficient mice do not show reduced Treg precursor cells. Our results demonstrate that IκB(NS) critically regulates Treg cell development in the thymus and during gut inflammation, indicating that strategies targeting IκB(NS) could modulate the Treg cell compartment.

HDAC inhibitors in models of inflammation-related tumorigenesis

Histone deacetylase (HDAC) inhibitors have been described in detail for their anti-proliferative potency. Recently, an anti-inflammatory property was characterized in vitro and in vivo. This dual efficacy of HDAC inhibitors is highly attractive, since chronic inflammations such as ulcerative colitis are associated with an increased risk of developing carcinomas. Additionally, in models of colitis and inflammation-induced tumorigenesis inflammation as well as tumor development was significantly inhibited by HDAC inhibitor treatment. The mechanisms involved reach beyond the simple regulation of histone acetylation and deacetylation. The currently known key target structures and mechanisms mediating this dual effect will be discussed in this review.

Toll-like receptor expression and response to specific stimulation in adipocytes and preadipocytes : On the role of fat in inflammation

Abstract:u2002 Data in this study indicate that both adipocytes and preadipocytes express abroad set of TLRs and they also respond to specific stimulation by cytokine production. The may be of relevance to Crohns disease and a suggests a closer link between adipose tissue and innate immunity.

Mesenteric fat—control site for bacterial translocation in colitis?

In Crohns disease bacteria could be detected in the adjacent mesenteric fat characterized by hypertrophy of unknown function. This study aimed to define effector responses of this compartment induced by bacterial translocation during intestinal inflammation. Dextran sulfate sodium-induced colitis served as a model of intestinal inflammation. Translocation of peptides and bacteria into mesenteric fat was evaluated. Innate functions of mesenteric fat and epithelium were characterized at whole tissue, cellular, and effector molecule levels. Orally applied peptides translocated in healthy wild-type (WT) mice. Bacterial translocation was not detected in healthy and acute but increased in chronic colitis. Mesenteric fat from colitic mice released elevated levels of cytokines and was infiltrated by immune cells. In MyD88−/− mice bacterial translocation occurred in health and increased in colitis. The exaggerated cytokine production in mesenteric fat accompanying colonic inflammation in WT mice was less distinct in MyD88−/− mice. In vitro studies revealed that fat not only increases cytokine production following contact with bacterial products, but also that preadipocytes are potent phagocytes. Colonic inflammation is accompanied by massive cytokine production and immune cell infiltration in adjacent adipose tissue. These effects can be considered as protective mechanisms of the mesenteric fat in the defense of bacterial translocation.

Histone deacetylase inhibitors modulate interleukin 6-dependent CD4+ T cell polarization in vitro and in vivo.

Background: HDAC inhibitors exert anti-inflammatory properties. Results: ITF2357 shifts the balance from Th17 cells toward regulatory T cells via suppression of the IL-6R expression on naïve T cells. Conclusion: The HDAC inhibitor ITF2357 modulates T cell polarization in experimental colitis. Significance: Learning the mode of action of this compound class will serve to optimize future therapeutic strategies. Histone deacetylase (HDAC) inhibitors have been associated primarily with an anti-proliferative effect in vitro and in vivo. Recent data provide evidence for an anti-inflammatory potency of HDAC inhibitors in models of experimental colitis. Because the balance of T cell subpopulations is critical for the balance of the mucosal immune system, this study explores the regulatory potency of HDAC inhibitors on T cell polarization as a mechanistic explanation for the observed anti-inflammatory effects. Although HDAC inhibition suppressed the polarization toward the pro-inflammatory T helper 17 (Th17) cells, it enhanced forkhead box P3 (FoxP3)+ regulatory T cell polarization in vitro and in vivo at the site of inflammation in the lamina propria. This was paralleled by a down-regulation of the interleukin 6 receptor (IL-6R) on naïve CD4+ T cells on the mRNA as well as on the protein level and changes in the chromatin acetylation at the IL6R gene and its promoter. Downstream of the IL-6R, HDAC inhibition was followed by a decrease in STAT3 phosphorylation as well as retinoic acid receptor-related orphan receptor γT (RORγT) expression, thus identifying the IL-6/STAT3/IL-17 pathway as an important target of HDAC inhibitors. These results directly translated to experimental colitis, where IL-6R expression was suppressed in naïve T cells, paralleled by a significant reduction of Th17 cells in the lamina propria of ITF2357-treated animals, resulting in the amelioration of disease. This study indicates that, in experimental colitis, inhibition of HDAC exerts an anti-inflammatory potency by directing T helper cell polarization via targeting the IL-6 pathway.

Histone deacetylase (HDAC) inhibitors modulate IL-6-dependent CD4+ T cell polarization in vitro and in vivo

Background: HDAC inhibitors exert anti-inflammatory properties. Results: ITF2357 shifts the balance from Th17 cells toward regulatory T cells via suppression of the IL-6R expression on naïve T cells. Conclusion: The HDAC inhibitor ITF2357 modulates T cell polarization in experimental colitis. Significance: Learning the mode of action of this compound class will serve to optimize future therapeutic strategies. Histone deacetylase (HDAC) inhibitors have been associated primarily with an anti-proliferative effect in vitro and in vivo. Recent data provide evidence for an anti-inflammatory potency of HDAC inhibitors in models of experimental colitis. Because the balance of T cell subpopulations is critical for the balance of the mucosal immune system, this study explores the regulatory potency of HDAC inhibitors on T cell polarization as a mechanistic explanation for the observed anti-inflammatory effects. Although HDAC inhibition suppressed the polarization toward the pro-inflammatory T helper 17 (Th17) cells, it enhanced forkhead box P3 (FoxP3)+ regulatory T cell polarization in vitro and in vivo at the site of inflammation in the lamina propria. This was paralleled by a down-regulation of the interleukin 6 receptor (IL-6R) on naïve CD4+ T cells on the mRNA as well as on the protein level and changes in the chromatin acetylation at the IL6R gene and its promoter. Downstream of the IL-6R, HDAC inhibition was followed by a decrease in STAT3 phosphorylation as well as retinoic acid receptor-related orphan receptor γT (RORγT) expression, thus identifying the IL-6/STAT3/IL-17 pathway as an important target of HDAC inhibitors. These results directly translated to experimental colitis, where IL-6R expression was suppressed in naïve T cells, paralleled by a significant reduction of Th17 cells in the lamina propria of ITF2357-treated animals, resulting in the amelioration of disease. This study indicates that, in experimental colitis, inhibition of HDAC exerts an anti-inflammatory potency by directing T helper cell polarization via targeting the IL-6 pathway.

Interleukin-7 links T lymphocyte and intestinal epithelial cell homeostasis

Interleukin-7 (IL-7) is a major survival factor for mature T cells. Therefore, the degree of IL-7 availability determines the size of the peripheral T cell pool and regulates T cell homeostasis. Here we provide evidence that IL-7 also regulates the homeostasis of intestinal epithelial cells (IEC), colon function and the composition of the commensal microflora. In the colon of T cell-deficient, lymphopenic mice, IL-7-producing IEC accumulate. IEC hyperplasia can be blocked by IL-7-consuming T cells or the inactivation of the IL-7/IL-7R signaling pathway. However, the blockade of the IL-7/IL-7R signaling pathway renders T cell-deficient mice more sensitive to chemically-induced IEC damage and subsequent colitis. In summary, our data demonstrate that IL-7 promotes IEC hyperplasia under lymphopenic conditions. Under non-lymphopenic conditions, however, T cells consume IL-7 thereby limiting IEC expansion and survival. Hence, the degree of IL-7 availability regulates both, T cell and IEC homeostasis.