Role Of Histone Deacetylases Research Articles

Downregulation of HDAC1 Is Involved in the Cardiomyocyte Differentiation from Mesenchymal Stem Cells in a Myocardial Microenvironment

Under myocardial microenvironment, bone marrow-derived mesenchymal stem cells (MSCs) can transdifferentiate into cardiomyocytes (CMs). However, the role of histone deacetylase 1 (HDAC1) in this directed differentiation process remains unclear. The current study is to determine the acetylation regulatory mechanisms that may be involved in the directed CM differentiation from MSCs. MSCs isolated from male Sprague-Dawley (SD) rats were marked with Ad-EGFP and co-cultured with CMs. Flow cytometry was used to sort EGFP-positive (EGFP+) MSCs from the co-culture system. Then, the expression of cardiac troponin T (cTnT) in these MSCs was detected by immunofluorescence assay. In addition, HDAC1 levels at different co-culture times were measured by quantitative real-time polymerase chain reaction (QT-PCR) and Western blotting. At 4 days after co-culture with CMs, the MSCs began to expression detectable levels of cTnT. The expression of HDAC1 in CMs was much lower than that in MSCs. After co-culture with CMs, the expression of HDAC1 in MSCs was significantly decreased in a time dependent manner. In addition, our recent study has also identified that knockdown of the HDAC1 could promote the directed differentiation of MSCs into CMs. The results suggest that HDAC1 has a negative correlation with cardiac cell differentiation from MSCs under a myocardial microenvironment. HDAC1 might play an important role in the directed differentiation of MSCs into CMs in heart.

Role for histone deacetylases in regulating angiotensinogen expression mediated by the JAK‐STAT pathway by suppressor of cytokine signaling in renal proximal tubular cells (1173.2)

Activated JAK‐STAT pathway stimulates SOCS expression, which inhibits JAK‐STAT pathway as a negative‐feedback system. Elevated SOCS limits AGT augmentation in PTC, suggesting that induction of SOCS elevation is an effective strategy to treat the renin‐angiotensin system (RAS) associated diseases. Thus, establishment of an approach to elevate SOCS without activation of the JAK‐STAT pathway is required. The aim of this study was to demonstrate that epigenetic modification by pharmacological treatments induces SOCS elevation leading to AGT suppression in PTC. Rat PTC were treated with sodium butyrate (NaB), a non‐selective HDAC inhibitor, for 6 hours. NaB induced SOCS1 (1.71 ± 0.04, ratio to control) and SOCS3 (1.67 ± 0.2) mRNA elevation in PTC. In the NaB‐treated cells, decreases in STAT3 phosphorylation levels (0.56 ± 0.02), AGT mRNA (0.19 ± 0.04) and protein (0.76 ± 0.04) levels were observed. PCI‐34051, an HDAC inhibitor exhibiting higher affinity to HDAC8 than other HDACs, also suppressed AGT expression. Inversely, Inhibition of class IIa HDACs by TMP269 increased AGT expression, indicating that class IIa HDACs include a repressor of AGT expression. These results suggest that an important role for HDACs, particularly HDAC8, in regulating AGT expression via the JAK‐STAT pathway in PTC. The findings will provide a more effective approach to treat RAS associated diseases by SOCS elevation.

79. Investigation of the Role of Histone Deacetylases in Rheumatoid Arthritis Synovial Fibroblasts

79. Investigation of the Role of Histone Deacetylases in Rheumatoid Arthritis Synovial Fibroblasts

Role of anoctamins in cancer and apoptosis

Anoctamin 1 (TMEM16A, Ano1) is a recently identified Ca(2+)-activated chloride channel and a member of a large protein family comprising 10 paralogues. Before Ano1 was identified as a chloride channel protein, it was known as the cancer marker DOG1. DOG1/Ano1 is expressed in gastrointestinal stromal tumours (GIST) and particularly in head and neck squamous cell carcinoma, at very high levels never detected in other tissues. It is now emerging that Ano1 is part of the 11q13 locus, amplified in several types of tumour, where it is thought to augment cell proliferation, cell migration and metastasis. Notably, Ano1 is upregulated through histone deacetylase (HDAC), corresponding to the known role of HDAC in HNSCC. As Ano1 does not enhance proliferation in every cell type, its function is perhaps modulated by cell-specific factors, or by the abundance of other anoctamins. Thus Ano6, by regulating Ca(2+)-induced membrane phospholipid scrambling and annexin V binding, supports cellular apoptosis rather than proliferation. Current findings implicate other cellular functions of anoctamins, apart from their role as Ca(2+)-activated Cl(-) channels.

New Insights into the Role of Histone Deacetylases as Coactivators of Inflammatory Gene Expression

The expression and/or activity of histone deacetylases (HDACs) can be regulated by a variety of environmental conditions, including inflammation and oxidative stress. These events result in diminished or exaggerated protein acetylation, both of which can be causative for many ailments. While the anti-inflammatory activity of HDAC inhibitors (HDACis) is well known, recent studies started unraveling details of the molecular mechanisms underlying the pro-inflammatory function of HDACs. Recent evidence shows that HDACs are found in association with transcribed regions and ensure proper transcription by maintaining acetylation homeostasis. We also discuss current insights in the molecular mechanisms mediating acetylation-dependent inhibition of pro-inflammatory transcription factors of the NF-κB, HIF-1, IRF, and STAT families. The high number of acetylations and the complexity of the regulatory consequences make it difficult to assign biological effects directly to a single acetylation event. The vast majority of acetylated proteins are nonhistone proteins, and it remains to be shown whether the therapeutic effects of HDACis are attributable to altered histone acetylation. In the traditional view, only exaggerated acetylation is harmful and causative for diseases. Recent data show the relevance of acetylation homeostasis and suggest that both diminished and inflated acetylation can enable the development of ailments. Since acetylation of nonhistone proteins is essential for the induction of a substantial part of the inflammatory gene expression program, HDACis are more than "epigenetic drugs." The identification of substrates for individual HDACs will be the prerequisite for the adequate use of highly specific HDACis.

Ribosomal Protein S6, a Target of Rapamycin, Is Involved in the Regulation of rRNA Genes by Possible Epigenetic Changes in Arabidopsis

The target of rapamycin (TOR) kinase pathway regulates various biological processes, including translation, synthesis of ribosomal proteins, and transcription of rRNA. The ribosomal protein S6 (RPS6) is one of the well known downstream components of the TOR pathway. Ribosomal proteins have been known to have diverse functions in regulating cellular metabolism as well as protein synthesis. So far, however, little is known about other possible role(s) of RPS6 in plants, besides being a component of the 40 S ribosomal subunit and acting as a target of TOR. Here, we report that RPS6 may have a novel function via interaction with histone deacetylase 2B (AtHD2B) that belongs to the plant-specific histone deacetylase HD2 family. RPS6 and AtHD2B were localized to the nucleolus. Co-expression of RPS6 and AtHD2B caused a change in the location of both RPS6 and AtHD2B to one or several nucleolar spots. ChIP analysis suggests that RPS6 directly interacts with the rRNA gene promoter. Protoplasts overexpressing both AtHD2B and RPS6 exhibited down-regulation of pre-18 S rRNA synthesis with a concomitant decrease in transcription of some of the ribosomal proteins, suggesting their direct role in ribosome biogenesis and plant development. This is consistent with the mutation in rps6b that results in reduction in 18 S rRNA transcription and decreased root growth. We propose that the interaction between RPS6 and AtHD2B brings about a change in the chromatin structure of rDNA and thus plays an important role in linking TOR signaling to rDNA transcription and ribosome biogenesis in plants.

Histone deacetylase activity is required for embryonic posterior lateral line development

The posterior lateral line (PLL) system in zebrafish has recently become a model for investigating tissue morphogenesis. PLL primordium periodically deposits neuromasts as it migrates along the horizontal myoseptum from head to tail of the embryonic fish, and this migration requires activity of various molecular mechanisms. Histone deacetylases (HDACs) have been implicated in numerous biological processes of development, by regulating gene transcription, but their roles in regulating PLL during embryonic development have up to now remained unexplored. In this study, we used HDAC inhibitors to investigate the role of HDACs in early development of the zebrafish PLL sensory system. We further investigated development of the PLL by cell-specific immunostaining and in situ hybridization. Our analysis showed that HDACs were involved in zebrafish PLL development as pharmacological inhibition of HDACs resulted in its defective formation. We observed that migration of PLL primordium was altered and accompanied by disrupted development of PLL neuromasts in HDAC inhibitor-treated embryos. In these, positions of PLL neuromasts were affected. In particular, the first PLL neuromast was displaced posteriorly in a treatment dose-dependent manner. Primordium cell proliferation was reduced upon HDAC inhibition. Finally, we showed that inhibition of HDAC function reduced numbers of hair cells in PLL neuromasts of HDAC inhibitor-treated embryos. Here, we have revealed a novel role for HDACs in orchestrating PLL morphogenesis. Our results suggest that HDAC activity is necessary for control of cell proliferation and migration of PLL primordium and hair cell differentiation during early stages of PLL development in zebrafish.

Histone Deacetylase 6 (HDAC6) Influences T-Cell Activation and Survival: Implications For Cancer Immunotherapy

The role of histone deacetylases (HDACs) as epigenetic regulators of immune function is becoming increasingly clear. Recently, the role of specific HDACs in orchestrating T-cell maturation, survival and function has begun to emerge, giving rationale to selective therapy to direct immune responses in different disease settings, including cancer. In particular, HDAC6 has recently been characterized as a negative regulator of regulatory T-cell suppressive activity (de Zoeten, Molecular and Cellular Biology, 2011). Here we report an expanded, novel role of HDAC6 in regulating T-cell survival and activation. First, the relative expression of the eleven classic HDACs was evaluated in resting and activated T-cells from mouse and human samples. It was found that the majority of HDACs decrease in expression following activation, including HDAC6. Next, in a HDAC6KO mouse model, it was found that T-cells lacking HDAC6 had skewed survival when compared to wild-type murine T-cells. This difference seems to be the result of an increased CD4+ T-cells population in the lymph nodes, with a concomitant decrease in viable CD8+ T-cells. To determine whether this population skewing was the consequence of defects in HDAC6KO mice T-cell development, wild-type murine T-cells were treated with an isotype-selective HDAC6 inhibitor. The results seen in HDAC6KO T-cells were recapitulated when wild-type T-cells were activated and treated with HDAC6 specific inhibitors, indicating a role of HDAC6 outside of thymic development in promoting CD4+ T-cell survival at the expense of CD8+ T-cells. Interestingly, it was found that activated CD4+ T-cells displayed decreased expression of the apoptosis signaling receptor FAS after HDAC6 inhibition while no differences were observed in CD8+ T-cells under the same conditions. In addition to these results implicating HDAC6 in regulating T-cell survival, expression of surface markers was altered in both CD8+ and CD4+ T-cells, including enhanced expression of the activation molecule CD69 in stimulated T-cells treated with an isotype-selective HDAC6 inhibitor. Finally, in vivo studies in tumor-bearing HDAC6KO mice revealed a significantly delayed in tumor progression. Similar results were observed in lymphoma-bearing mice treated with HDAC6 specific inhibitors. Taken together, this data shows that HDACs are dynamic in expression with regards to T-cell activation state. More specifically, we have unveiled hereto-unexplored roles of HDAC6 in regulating T-cell survival and function, pointing at this specific HDAC as an appealing target to harness T-cell immunity in hematologic malignancies. Disclosures:No relevant conflicts of interest to declare.

Role of histone deacetylases in regulation of phenotype of ovine newborn pulmonary arterial smooth muscle cells

Pulmonary arterial hypertension, characterized by pulmonary vascular remodelling and vasoconstriction, is associated with excessive proliferative changes in pulmonary vascular walls. However, the role of HDACs in the phenotypic alteration of pulmonary arterial smooth muscle cells (PASMC) is largely unknown. Pulmonary arterial smooth muscle cells were isolated from newborn sheep. Cell cycle analysis was performed by flow cytometry. mRNA and protein expression were measured by real-time PCR and Western blot analysis. Wound-healing scratch assay was used to measure cell migration. Contractility of newborn PASMCs was determined by gel contraction assay. Chromatin immunoprecipitation was used to examine histone modifications along the p21 promoter region. Global DNA methylation was measured by liquid chromatography-mass spectroscopy. Inhibition of class I and class II HDACs by apicidin and HDACi VIII suppressed proliferation of newborn PASMC and induced cell cycle arrest in G1 phase. Acetyl H3 levels were higher in newborn PASMC treated with apicidin and HDACi VIII. This was accompanied by increased expression of p21 and reduced expression of CCND1 but not p53. HDAC inhibition altered histone codes around the p21 promoter region in NPASMC. Apicidin inhibited serum-induced cell migration, and modulated profiling of expression of genes encoding pro-oxidant and antioxidant enzymes. Contractility and global DNA methylation levels of newborn PASMCs were also markedly modulated by apicidin. Our results demonstrate that class I HDACs are clearly involved in phenotypic alteration of newborn PASMC.

Roles of Histone Deacetylases in Angiogenic Cellular Processes

Roles of Histone Deacetylases in Angiogenic Cellular Processes

Dimethyl fumarate regulates histone deacetylase expression in astrocytes

We previously showed that dimethyl fumarate (DMF) reduces inflammatory activation in astrocytes, involving activation of transcription factor Nrf2. However, the pathways causing Nrf2 activation were not examined. We now show that DMF modifies expression of histone deacetylases (HDACs) in primary rat astrocytes. After 4h incubation, levels of HDAC1, 2, and 4 mRNAs were increased by DMF; however, after 24h, levels returned to or were below control values. At that time, HDAC protein levels and overall activity were also reduced by DMF. Stimulation of astrocytes with pro-inflammatory cytokines significantly increased HDAC mRNA levels after 24h, although protein levels were not increased at that time point. In the presence of cytokines, DMF reduced HDAC mRNAs, proteins, and activity. Proteomic analysis of DMF-treated astrocytes identified 8 proteins in which lysine acetylation was increased by DMF, including histones H2a.1 and H3.3. A role for HDACs in mediating DMF actions is suggested by findings that the selective HDAC inhibitor SAHA increased nuclear Nrf2:DNA binding activity, reduced inflammatory activation of astrocytes which was reversed by a selective inhibitor of the Nrf2 target gene heme-oxygenase 1. These data show that DMF regulates astrocyte HDAC expression, which could contribute to Nrf2 activation, suppression of inflammatory responses and cause long-lasting changes in gene expression.

A novel hydroxysuberamide derivative potentiates MG132‐mediated anticancer activity against human hormone refractory prostate cancers—the role of histone deacetylase and endoplasmic reticulum stress

Histone deacetylase (HDAC) inhibitors are successful for treatment of advanced cutaneous T-cell lymphoma but only show modest effect in solid tumors. Approaches for HDAC inhibitors to improve activity against solid tumors are necessary. Sulforhodamine B assay and flow cytometric analysis detected cell proliferation and cell-cycle progression, respectively. Protein expression was determined by Western blotting. Comet assay and DNA end-binding activity of Ku proteins detected DNA damage and DNA repair activity, respectively. siRNA technique was used for knockdown of specific cellular target. WJ25591 displayed inhibitory activity against HDAC1 and cell proliferation in human hormone-refractory prostate cancers PC-3 and DU-145. WJ25591 caused an arrest of cell-cycle at both G1- and G2-phase and increased protein expressions of p21 and cyclin E, followed by cell apoptosis. WJ25591-induced Bcl-2 down-regulation and activation of caspase-9, -8, and -3, suggesting apoptotic execution through both intrinsic and extrinsic apoptotic pathways. WJ25591 also significantly inhibited DNA repair activity but not directly induced DNA damage. Moreover, the proteasome inhibitor MG-132 dramatically sensitized WJ25591-induced cell apoptosis. The siRNA technique demonstrated that endoplasmic reticulum (ER) stress, in particular CHOP/GADD153 up-regulation, contributed to the synergistic effect. The data suggest that WJ25591 inhibited HDAC activity, leading to cell-cycle arrest and inhibition of DNA repair. Caspase cascades are subsequently triggered to execute cell apoptosis. MG-132 dramatically sensitizes WJ25591-mediated apoptosis, at least partly, through ER stress response. The data also reveal that combination of HDAC inhibitors and proteasome inhibitors may be a potential strategy against hormone-refractory prostate cancers.

A new role for histone deacetylase 5 in the maintenance of long telomeres

Telomeres are major regulators of genome stability and cell proliferation. A detailed understanding of the mechanisms involved in their maintenance is of foremost importance. Of those, telomere chromatin remodeling is probably the least studied; thus, we intended to explore the role of a specific histone deacetylase on telomere maintenance. We uncovered a new role for histone deacetylase 5 (HDAC5) in telomere biology. We report that HDAC5 is recruited to the long telomeres of osteosarcoma- and fibrosarcoma-derived cell lines, where it ensures proper maintenance of these repetitive regions. Indeed, depletion of HDAC5 by RNAi resulted in the shortening of longer telomeres and homogenization of telomere length in cells that use either telomerase or an alternative mechanism of telomere maintenance. Furthermore, we present evidence for the activation of telomere recombination on depletion of HDAC5 in fibrosarcoma telomerase-positive cancer cells. Of potential importance, we also found that depletion of HDAC5 sensitizes cancer cells with long telomeres to chemotherapeutic drugs. Cells with shorter telomeres were used to control the specificity of HDAC5 role in the maintenance of long telomeres. HDAC5 is essential for the length maintenance of long telomeres and its depletion is required for sensitization of cancer cells with long telomeres to chemotherapy.

The role of histone deacetylases in rheumatoid arthritis fibroblast-like synoviocytes

RA (rheumatoid arthritis) is an inflammatory disease of synovial joints affecting approximately 1% of the population. One of the main cell typesinvolved in damage to RA joint tissue is the FLSs (fibroblast-like synoviocytes). These have a semi-transformed, auto-aggressive phenotype typified by loss of contact inhibition, reduced apoptosis and the production of matrix-degrading enzymes. The mechanisms involved in the development of this phenotype are unclear; however, increasing evidence implicates alterations in the epigenetic regulation of gene expression. Reduced acetylation of amino acids in the tails of histone proteins is an epigenetic mark associated with transcriptional repression and is controlled by the HDAC (histone deacetylase) enzyme family. To date, evidence has implicated HDACs in the auto-aggressive phenotype of FLSs, and administration of HDAC inhibitors to both animal models of RA and individuals with juvenile arthritis has shown efficacy in attenuating inflammation and tissue damage. This highlights a role for HDACs in disease pathogenesis and, more importantly, that HDACs are potential novel therapeutic targets.

HDAC6 Regulates Mutant SOD1 Aggregation through Two SMIR Motifs and Tubulin Acetylation

Histone deacetylase 6 (HDAC6) is a tubulin deacetylase that regulates protein aggregation and turnover. Mutations in Cu/Zn superoxide dismutase (SOD1) linked to familial amyotrophic lateral sclerosis (ALS) make the mutant protein prone to aggregation. However, the role of HDAC6 in mutant SOD1 aggregation and the ALS etiology is unclear. Here we report that HDAC6 knockdown increased mutant SOD1 aggregation in cultured cells. Different from its known role in mediating the degradation of poly-ubiquitinated proteins, HDAC6 selectively interacted with mutant SOD1 via two motifs similar to the SOD1 mutant interaction region (SMIR) that we identified previously in p62/sequestosome 1. Expression of the aggregation-prone mutant SOD1 increased α-tubulin acetylation, and the acetylation-mimicking K40Q α-tubulin mutant promoted mutant SOD1 aggregation. Our results suggest that ALS-linked mutant SOD1 can modulate HDAC6 activity and increase tubulin acetylation, which, in turn, facilitates the microtubule- and retrograde transport-dependent mutant SOD1 aggregation. HDAC6 impairment might be a common feature in various subtypes of ALS.

Abstract 5246: Histone deacetylase 6 (HDAC6) as a new modulator of the JAK/STAT pathway in melanoma.

Abstract There is a crescent interest to understand the cellular and molecular processes involved in the progression of melanoma. Such knowledge is crucial for the development of more efficacious treatments and improved diagnostics. Acetylation and deacetylation of proteins plays a crucial role in the control of important cellular pathways, such as transcriptional control, proliferation, apoptosis, immunogenicity, etc. Specifically, histone deacetylases (HDACs) have garnered significant interest due to the availability of drugs that selectively inhibits HDAC. We recently investigated the effect of HDAC6 selective inhibitor(s) (HDAC6i) in human melanoma cell lines (WM164, WM983A and SKMEL21) with regards to proliferation and cell cycle profile. Pharmacological inhibition of HDAC6 resulted in a delayed proliferation and G1 cell cycle arrest in all melanoma cell lines analyzed. In addition to the pharmacological inhibition of HDAC6, we explored the effect of HDAC6 knock-down using specific shRNA (HDAC6KD). In agreement with the previous data from pharmacological inhibition of HDAC6, the proliferation of HDAC6KD melanoma cells was diminished when compared to wild-type and non-target shRNA control cells. Likewise, we observed a similar G1 arrest in the cell cycle that was attained with the use of HDAC6 specific inhibitors. Our data has also implicated HDAC6 in the regulation of the STAT1 and STAT3 pathways in melanoma cells. After cytokine IL-6 and IFN-γ stimulation of melanoma cells we found significant changes in the phosphorylation and acetylation status of STAT3 and STAT1 proteins in KDHDAC6 cells and/or treated with HDAC6i. Supporting this data, we observed important changes in the expression of STAT1 and STAT3 target genes, including essential genes involved in cell cycle control and immune regulation. Moreover, we observed a delay in tumor growth in C57BL/6 mice challenged in vivo with B16 cells lacking HDAC6 when compared to wild type B16 cells. These studies provide critical insights into the molecular pathways and/or partners that are involved in the regulatory role of HDAC6 in cell proliferation survival and cytokine signaling of human melanoma cells. Collectively, our data has identified HDAC6 as an attractive therapeutic target in melanoma due to its ability to delay tumor growth and target the JAK/STAT pathways, known to be altered in several melanoma malignancies. Citation Format: Maritza Lienlaf, Patricio Perez-Villarroel, Jorge Canales, Tessa Knox, Fengdong Cheng, Danay Marante, David Woods, Karrune Woan, HongWei Wang, Ed Seto, Jeffrey S. Weber, Eduardo M. Sotomayor, Alejandro Villagra. Histone deacetylase 6 (HDAC6) as a new modulator of the JAK/STAT pathway in melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5246. doi:10.1158/1538-7445.AM2013-5246

Abstract 1742: Potential roles of histone deacetylase 11 in cell cycle regulation and cancer.

Abstract Histone deacetylases (HDACs) are enzymes that deacetylate lysine residues on histone and non-histone proteins. They regulate various cellular functions including transcriptional regulation, cell proliferation, apoptosis, and cellular metabolism. Broad spectrum HDAC inhibitors, including Vorinostat and Romidepsin, have been approved for cancer therapy, but their use is limited due to toxicity and side effects. A deeper understanding of the function of individual histone deacetylases could lead to the development of more specific and potentially more effective anti-cancer agents. In this context, Histone Deacetylase 11 (HDAC11) could be a potential target for anticancer therapeutics. HDAC11 is the most recently discovered Histone Deacetylase and, therefore, the least characterized among the 18 HDACs. Its expression is altered in various cancers and recent studies have suggested that HDAC11 might inhibit the activity and function of the DNA replication licensing factor Cdt1. To examine whether HDAC11 controls Cdt1-mediated cell cycle regulation, HDAC11 was overexpressed in human U87 glioblastoma cells. We found that overexpression of HDAC11 represses Cdt1 expression levels. Most importantly, we observed that HDAC11 overexpression promotes earlier cell entry into the G2/M phase of the cell cycle than non-HDAC11-overexpressed cells. Finally, we discovered that HDAC11 levels change throughout the cell cycle in a manner that is contrary to the Cdt1 expression levels. These results indicate that HDAC11 negatively regulates Cdt1, and uncover an important and previously unknown role of this enzyme in cell cycle regulation. Together, our findings suggest that development of drugs that target HDAC11 might be a viable strategy for overcoming cancers where this protein is overexpressed. Citation Format: Thejal Srikumar, Elphine Telles, Edward Seto. Potential roles of histone deacetylase 11 in cell cycle regulation and cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1742. doi:10.1158/1538-7445.AM2013-1742

Enhancement of Inflammatory Protein Expression and Nuclear Factor Κb (NF-Κb) Activity by Trichostatin A (TSA) in OP9 Preadipocytes

The production of inflammatory proteins such as interleukin-6 (IL-6) by preadipocytes and mature adipocytes is closely associated with the impairment of systemic glucose homeostasis. However, precisely how the production is regulated and the roles of histone deacetylases (HDACs) remain largely unknown. The aim of this study was to establish whether HDAC inhibitors affect the expression of inflammatory proteins in pre/mature adipocytes, and, if so, to determine the mechanism involved. Trichostatin A (TSA), an HDAC inhibitor, enhanced lipopolysaccharide (LPS)-induced production of IL-6 in OP9 preadipocytes but not the mature adipocytes. Moreover, TSA also enhanced palmitic acid-induced IL-6 production and the expression of inflammatory genes induced by LPS in preadipocytes. Although TSA did not affect TLR4 mRNA expression or the activation of MAPKs, a reporter gene assay revealed that the LPS-induced increase in nuclear factor κB (NF-κB) activity was enhanced by TSA. Moreover, TSA increased the level of NF-κB p65 acetylation at lysine 310 and duration of its translocation into the nucleus, which leads to enhancement of NF-κB activity and subsequently expression of inflammatory genes. These findings shed new light on the regulatory roles of HDACs in preadipocytes in the production of inflammatory proteins.

Abstract TMP71: Role Of Histone Deacetylases in Stroke-induced Oligodendrogenesis

Background: Histone deacetylases (HDACs) are a superfamily of isoforms that deacetylate lysine residues in histones. HDAC activity is essential for oligodendrocyte (OLG) differentiation. The present study measured spatial profiles of individual HDACs in white matter during brain repair after stroke. Methods and Results: Adult male Wistar rats (n=8) were subjected to permanent right MCA occlusion and sacrificed 8 days later. Immunohistochemistry was performed on brain coronal sections with antibodies against HDACs, NG2 (a marker of oligodendrocyte progenitor cells, OPCs), and APC (a marker of OLGs). The numbers of immunoreactive cells were counted in peri-infarct and contralateral corpus callosum. Double immunofluorescent staining revealed that stroke significantly (p<0.05) increased the number of HDAC1 (HDAC1+/NG2+ cells, 166±7 vs.105±6 in contralateral), HDAC2 (HDAC2+/NG2+ cells, 130±4 vs. 98±2), and HDAC4 (HDAC4+/NG2+ cells, 74±5 vs. 56±4) positive OPCs, but did not significantly change HDAC5 positive OPCs. However, stroke only significantly increased the number of HDAC2 positive OLGs (HDAC2+/APC+ cells, 466 ±15 vs. 420±10), whereas the number of HDAC1 positive OLGs significantly decreased (HDAC1+/APC cells, 438±24 vs. 533±15, p<0.05). HDAC activity affects the acetylation (Ac) status of histone proteins (HH) within chromatin. We found stroke significantly decreased Ac-HH3+ OPCs (49±2 vs. 64±2) and Ac-HH3+ OLGs (311±16 vs. 356±13), which is consistent with elevation of HDAC activity in both cell types. Conclusion: Our data indicate that stroke induces different expression profiles of class I (1 and 2) and II (4 and 5) HDACs in OPCs and OLGs, suggesting that these HDACs could play distinct roles in stroke-induced oligodendrogenesis.

The HDAC interaction network

The HDAC interaction network