Histone Deacetylase Research Articles

Schlank orchestrates insect developmental transition by switching H3K27 acetylation to trimethylation in the prothoracic gland

Insect developmental transitions are precisely coordinated by ecdysone and juvenile hormone (JH). We previously revealed that accumulated H3K27 trimethylation (H3K27me3) at the locus encoding JH signal transducer Hairy is involved in the larval-pupal transition in insects, but the underlying mechanism remains to be fully defined. Here, we show in Drosophila and Bombyx that Rpd3-mediated H3K27 deacetylation in the prothoracic gland during the last larval instar promotes ecdysone biosynthesis and the larval-pupal transition by enabling H3K27me3 accumulation at the Hairy locus to induce its transcriptional repression. Importantly, we find that the homeodomain transcription factor Schlank acts to switch active H3K27 acetylation (H3K27ac) to repressive H3K27me3 at the Hairy locus by directly binding to the Hairy promoter and then recruiting the histone deacetylase Rpd3 and the histone methyltransferase PRC2 component Su(z)12 through physical interactions. Moreover, Schlank inhibits Hairy transcription to facilitate the larval-pupal transition, and the Schlank signaling cascade is suppressed by JH but regulated in a positive feedback manner by ecdysone. Together, our data uncover that Schlank mediates epigenetic reprogramming of H3K27 modifications in hormone actions during insect developmental transition.

Recent Molecular Targets and Their Ligands for the Treatment of Alzheimer Disease.

Alzheimer's disease is a multifaceted neurodegenerative disease. Cholinergic dysfunction, amyloid β toxicity, tauopathies, oxidative stress, neuroinflammation are among the main pathologies of the disease. Ligands targeting more than one pathology, multi-target directed ligands, attract attention in the recent years to tackle Alzheimer's disease. In this review, we aimed to cover different biochemical pathways, that are revealed in recent years for the pathology of the disease, as druggable targets such as cannabinoid receptors, matrix metalloproteinases, histone deacetylase and various kinases including, glycogen synthase kinase-3, mitogen-activated protein kinase and c-Jun N-terminal kinase, and their ligands for the treatment of Alzheimer's disease in the hope of providing more realistic insights into the field.

Postprandial cardiac hypertrophy is sustained by mechanics, epigenetic, and metabolic reprogramming in pythons

Constricting pythons, known for their ability to consume infrequent, massive meals, exhibit rapid and reversible cardiac hypertrophy following feeding. Our primary goal was to investigate how python hearts achieve this adaptive response after feeding. Isolated myofibrils increased force after feeding without changes in sarcomere ultrastructure and without increasing energy cost. Ca2+ transients were prolonged after feeding with no changes in myofibril Ca2+ sensitivity. Feeding reduced titin-based tension, resulting in decreased cardiac tissue stiffness. Feeding also reduced the activity of sirtuins, a metabolically linked class of histone deacetylases, and increased chromatin accessibility. Transcription factor enrichment analysis on transposase-accessible chromatin with sequencing revealed the prominent role of transcription factors Yin Yang1 and NRF1 in postfeeding cardiac adaptation. Gene expression also changed with the enrichment of translation and metabolism. Finally, metabolomics analysis and adenosine triphosphate production demonstrated that cardiac adaptation after feeding not only increased energy demand but also energy production. These findings have broad implications for our understanding of cardiac adaptation across species and hold promise for the development of innovative approaches to address cardiovascular diseases.

Epigenetic Modulations in Breast Cancer: An Emerging Paradigm in Therapeutic Implications.

Breast cancer, a heterogeneous and intricate disease, ranks among the leading causes of mortality in women. Restricted therapeutic choices, drug resistance, recurrence, and metastasis are the predominant conditions that lead to mortality. Accumulating evidence has shown breast cancer initiation and progression happen through a multifaceted and intricate process that involves numerous genetic and epigenetic alterations. The modulation of gene expression through epigenetic modifications, encompassing DNA methylation, histone alterations, and non-coding RNA regulation, has emerged as a fascinating field that represents a new avenue for breast cancer therapy. This review emphasizes various aberrant epigenetic regulations implicated in the onset and advancement of breast cancer. The critical epigenetic modifications closely associated with estrogen signaling, epithelial-to-mesenchymal transition (EMT), cancer stemness, and drug resistance have been discussed extensively. Moreover, it highlights current epi-drugs, including DNA modifying agents, histone acetyltransferase inhibitors, histone deacetylase inhibitors, histone methyltransferase inhibitors, and histone demethyltransferase inhibitors used for breast cancer treatment. Nonetheless, we described current investigations pertaining to combination therapy employing epi-drugs and future challenges.

Differential Expression of DNA Methyltransferase (DNMT1 and DNMT3), Histone Deacetylase (HDAC1 and HDAC2), and Upstream Target Regulators MiR-145 and Mir-152 among Oral Cancers

Epigenetic modulation of DNA and histones facilitated by and histone deacetylases (HDAC) is associated with the development and progression of many cancers, although less is known about DNA methyltransferase (DNMT) in oral cancers and the regulation of these targets. Using commercially available cell lines, oral squamous cell carcinomas (SCC4, SCC9, SCC15, SCC25, and CAL27), and normal gingival fibroblasts (HGF-1), growth assays and mRNA expression were evaluated using ANOVA. These results revealed homeostasis enzyme DNMT1 expression was significantly higher among slow-growing HGF-1 cells than among fast-growing oral cancers, p < 0.05. In contrast, DNMT3A and DNMT3B expression was significantly higher among oral cancers compared with HGF-1 cells, p < 0.05. However, differential expression of HDAC1 and HDAC2 was observed among SCC4, SCC25, and CAL27 cells. Further analysis of miR-152 (regulation and control of DNMT expression) and miR-21, miR-221, and miR-145 (regulation of HDAC expression) revealed all oral cancers produced miR-21, but none produced miR-221. However, differential expression of miR-145 (SCC15) and miR-152 (SCC25) suggested alternative epigenetic pathways and mechanisms of DNMT and HDAC regulation may be responsible for some of the observations revealed in this study.

The miR-26a/SIRT6/HIF-1α axis regulates glycolysis and inflammatory responses in host macrophages during Mycobacterium tuberculosis infection.

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis. Here, a macrophage infection model was used to unravel the role of the histone deacetylase sirtuin 6 (SIRT6) in Mtb-triggered regulation of the innate immune response. Mtb infection downregulated microRNA-26a and upregulated its target SIRT6. SIRT6 suppressed glycolysis and expression of HIF-1α-dependent glycolytic genes during infection. In addition, SIRT6 regulated the levels of intracellular succinate which controls stabilization of HIF-1α, as well as the release of interleukin (IL)-1β. Furthermore, SIRT6 inhibited inducible nitric oxide synthase (iNOS) and proinflammatory IL-6 but augmented anti-inflammatory arginase expression. The miR-26a/SIRT6/HIF-1α axis therefore regulates glycolysis and macrophage immune responses during Mtb infection. Our findings link SIRT6 to rewiring of macrophage signaling pathways facilitating dampening of the antibacterial immune response.

Comparative Analysis of Structural Analogs of Dipyridothiazines with m-Xylene and a Lutidine Moiety—In Silico, In Vitro, and Docking Studies

Dimers of dipyridothiazines with an m-xylene moiety are presented in terms of a comparative analysis with anticancer active structural analogs containing a lutidine system. The synthesis of new isomeric dimers was described, the structure of which was confirmed by 1H, 13C and 2D NMR, and HR MS spectroscopic methods. The preliminary prediction of the pharmacological profile using the Way2Drug server indicated the anticancer potential of the tested derivatives. In vitro biological activity tests were performed on a normal skin cell line (HaCaT) and five cancer cell lines, including human primary colon cancer (SW480), human metastatic colon cancer (SW620), human breast adenocarcinoma (MDA-MB-231), human lung carcinoma (A-549), and human glioblastoma (LN-229), which indicated low cytotoxic activity. In order to explain the surprisingly low activity, a comparative structural analysis of the tested analogs compared to the dimers with the lutidine system was performed using quantum mechanics and molecular docking in relation to histone deacetylase. Molecular docking indicated the different binding sites of the analyzed dimers, which explained the differences in the activity.

Development of peptoid-based heteroaryl-decorated histone deacetylase (HDAC) inhibitors with dual-stage antiplasmodial activity

Dynamics of epigenetic modifications such as acetylation and deacetylation of histone proteins have been shown to be crucial for the life cycle development and survival of Plasmodium falciparum, the deadliest malaria parasite. In this study, we present a novel series of peptoid-based histone deacetylase (HDAC) inhibitors incorporating nitrogen-containing bicyclic heteroaryl residues as a new generation of antiplasmodial peptoid-based HDAC inhibitors. We synthesized the HDAC inhibitors by an efficient multicomponent protocol based on the Ugi four-component reaction. The subsequent screening of 16 compounds from our mini-library identified 6i as the most promising candidate, demonstrating potent activity against asexual blood-stage parasites (IC50Pf3D7 = 30 nM; IC50PfDd2 = 98 nM), low submicromolar activity against liver-stage parasites (IC50PbEEF = 0.25 μM), excellent microsomal stability (t1/2 > 60 min), and low cytotoxicity to HEK293 cells (IC50 = 136 μM).

Vorinostat Treatment of Gastric Cancer Cells Leads to ROS-Induced Cell Inhibition and a Complex Pattern of Molecular Alterations in Nrf2-Dependent Genes.

Histone deacetylase inhibitors (HDACi) show high antineoplastic potential in preclinical studies in various solid tumors, including gastric carcinoma; however, their use in clinical studies has not yet yielded convincing efficacies. Thus, further studies on cellular/molecular effects of HDACi are needed, for improving clinical efficacy and identifying suitable combination partners. Here, we investigated the role of oxidative stress in gastric cancer cells upon treatment with HDACi. A particular focus was laid on the role of the Nrf2 pathway, which can mediate resistance to cell-inhibitory effects of reactive oxidative species (ROS). Using fluorescence-based ROS sensors, oxidative stress was measured in human gastric cancer cell lines. Activation of the Nrf2 pathway was monitored in luciferase reporter assays as well as by mRNA and proteomic expression analyses of Nrf2 regulators and Nrf2-induced genes. Furthermore, the effects of ROS scavenger N-acetyl-L-cysteine (NAC) and Nrf2-knockdown on HDACi-dependent antiproliferative effects were investigated in colorimetric formazan-based and clonogenic survival assays. HDACi treatment led to increased oxidative stress levels and consequently, treatment with NAC reduced cytotoxicity of HDACi. In addition, vorinostat treatment stimulated expression of a luciferase reporter under the control of an antioxidative response element, indicating activation of the Nrf2 system. This Nrf2 activation was only partially reversible by treatment with NAC, suggesting ROS independent pathways to contribute to HDACi-promoted Nrf2 activation. In line with its cytoprotective role, Nrf2 knockdown led to a sensitization against HDACi. Accordingly, the expression of antioxidant and detoxifying Nrf2 target genes was upregulated upon HDACi treatment. In conclusion, oxidative stress induction upon HDAC inhibition contributes to the antitumor effects of HDAC inhibitors, and activation of Nrf2 represents a potentially important adaptive response of gastric cancer cells in this context.

Light regulates widespread plant alternative polyadenylation through the chloroplast

Transcription of eukaryotic protein-coding genes generates immature mRNAs that are subjected to a series of processing events, including capping, splicing, cleavage, and polyadenylation (CPA), and chemical modifications of bases. Alternative polyadenylation (APA) greatly contributes to mRNA diversity in the cell. By determining the length of the 3' untranslated region, APA generates transcripts with different regulatory elements, such as miRNA and RBP binding sites, which can influence mRNA stability, turnover, and translation. In the model plant Arabidopsis thaliana, APA is involved in the control of seed dormancy and flowering. In view of the physiological importance of APA in plants, we decided to investigate the effects of light/dark conditions and compare the underlying mechanisms to those elucidated for alternative splicing (AS). We found that light controls APA in approximately 30% of Arabidopsis genes. Similar to AS, the effect of light on APA requires functional chloroplasts, is not affected in mutants of the phytochrome and cryptochrome photoreceptor pathways, and is observed in roots only when the communication with the photosynthetic tissues is not interrupted. Furthermore, mitochondrial and TOR kinase activities are necessary for the effect of light. However, unlike AS, coupling with transcriptional elongation does not seem to be involved since light-dependent APA regulation is neither abolished in mutants of the TFIIS transcript elongation factor nor universally affected by chromatin relaxation caused by histone deacetylase inhibition. Instead, regulation seems to correlate with changes in the abundance of constitutive CPA factors, also mediated by the chloroplast.

Sensitization of hepatocellular carcinoma cells to HDACi is regulated through hsa-miR-342-5p/CFL1

BackgroundIncreased prevalence of hepatocellular carcinoma (HCC) remains a global health challenge. HCC chemoresistance is a clinical obstacle for its management. Aberrant miRNA expression is a hallmark for both cancer progression and drug resistance. However, it is unclear which miRNAs are involved in HCC chemoresistance.MethodsMicroRNA microarray analysis revealed a differential expression profile of microRNAs between the hepatocellular carcinoma HA22T cell line and the HDACi-R cell line, which was validated by quantitative real-time PCR (qRT-PCR). To determine the biological function of miR-342-5p and the mechanism of the microRNA-342-5p/CFL1 axis in hepatocellular carcinoma HDACi resistance, loss- and gain-of-function studies were conducted in vitro.ResultsHere we demonstrated the molecular mechanism of histone deacetylase inhibitor (HDACi) resistance in HCC. Differential miRNA expression analysis showed significant down regulation of miR-342-5p in HDACi-R cells than in parental HA22T cells. Mimics of miR-342-5p enhanced apoptosis through upregulation of Bax, cyto-C, cleaved-caspase-3 expressions with concomitant decline in anti-apoptotic protein (Bcl-2) in HDACi-R cells. Although HDACi did not increase cell viability of HDACi-R, overexpression of miR-342-5p decreased cofilin-1 expression, upregulated reactive oxygen species (ROS) mediated apoptosis, and sensitized HDACi-R to HDACi in a dose-dependent manner.ConclusionOur findings demonstrated the critical role of miR-342-5p in HDACi resistance of HCC and that this mechanism might be attributed to miR-342-5p/cofilin-1 regulation.

Transcriptomic Heterogeneity of EGFR-Mutant Non-Small Cell Lung Cancer Evolution Toward Small-Cell Lung Cancer.

Histologic transformation from EGFR-mutant non-small cell lung cancer (NSCLC) to small-cell lung cancer (SCLC) is a key mechanism of resistance to EGFR tyrosine kinase inhibitors (TKI). However, transcriptomic changes between NSCLC and transformed SCLC (t-SCLC) remain unexplored. We conducted whole-transcriptome analysis of 59 regions of interest through the spatial profiling of formalin-fixed, paraffin-embedded tissues obtained from 10 patients (lung adenocarcinoma, 22; combined SCLC/NSCLC, 7; and t-SCLC, 30 regions of interests). Transcriptomic profiles and differentially expressed genes were compared between pre- and post-transformed tumors. Following EGFR-TKI treatment, 93.7% (15/16) of t-SCLC components evolved into neuroendocrine-high subtypes (SCLC-A or SCLC-N). The transition to t-SCLC occurred regardless of EGFR-TKI treatment and EGFR mutational status, with a notable decrease in EGFR expression (P < 0.001) at both mRNA and protein levels. Pathway analysis revealed that gene overexpression was related to epigenetic alterations in t-SCLC. Interestingly, histone deacetylase inhibitors restored EGFR expression in SNU-2962A cells and their organoid model. The synergistic effects of third-generation EGFR-TKI osimertinib and the histone deacetylase inhibitor fimepinostat were validated in both in vitro and in vivo models. Our study demonstrated that most t-SCLC cases showed neuronal subtypes with low EGFR expression. Differentially expressed gene analysis and t-SCLC preclinical models identified an epigenetic modifier as a promising treatment strategy for t-SCLC.

HDAC2 promotes autophagy-associated HCC malignant progression by transcriptionally activating LAPTM4B

Hepatocellular carcinoma (HCC) is a significant global health challenge. The activation of autophagy plays an essential role in promoting the proliferation and survival of cancer cells. However, the upstream regulatory network and mechanisms governing autophagy in HCC remain unclear. This study demonstrated that histone deacetylase 2 (HDAC2) regulates autophagy in HCC. Its expression was elevated in HCC tissues, and high HDAC2 expression was strongly associated with poor prognosis in individuals with HCC. Integrated in vitro and in vivo investigations confirmed that HDAC2 promotes autophagy and autophagy-related malignant progression in HCC. Mechanistically, HDAC2 bound specifically to the lysosome-associated protein transmembrane 4-β (LAPTM4B) promoter at four distinct binding sites, enhancing its transcriptional activation and driving autophagy-related malignant progression in HCC. These findings establish LAPTM4B as a direct target gene of HDAC2. Furthermore, the selective inhibitor of HDAC2 effectively alleviated the malignant development of HCC. In addition, multivariate Cox regression analysis of 105 human HCC samples revealed that HDAC2 expression is an independent predictor of HCC prognosis. This study underscores the crucial role of the HDAC2-LAPTM4B axis in regulating autophagy in the malignant evolution of HCC and highlights the potential of targeting HDAC2 to prevent and halt the malignant progression of HCC.

Searching for Novel HDAC6/Hsp90 Dual Inhibitors with Anti-Prostate Cancer Activity: In Silico Screening and In Vitro Evaluation.

Prostate cancer (PCA) is one of the most prevalent types of male cancers. While current treatments for early-stage PCA are available, their efficacy is limited in advanced PCA, mainly due to drug resistance or low efficacy. In this context, novel valuable therapeutic opportunities may arise from the combined inhibition of histone deacetylase 6 (HDAC6) and heat shock protein 90 (Hsp90). These targets are mutually involved in the regulation of several processes in cancer cells, and their inhibition is demonstrated to provide synergistic effects against PCA. On these premises, we performed an extensive in silico virtual screening campaign on commercial compounds in search of dual inhibitors of HDAC6 and Hsp90. In vitro tests against recombinant enzymes and PCA cells with different levels of aggressiveness allowed the identification of a subset of compounds with inhibitory activity against HDAC6 and antiproliferative effects towards LNCaP and PC-3 cells. None of the candidates showed appreciable Hsp90 inhibition. However, the discovered compounds have low molecular weight and a chemical structure similar to that of potent Hsp90 blockers. This provides an opportunity for structural and medicinal chemistry optimization in order to obtain HDAC6/Hsp90 dual modulators with antiproliferative effects against prostate cancer. These findings were discussed in detail in the study.

Sodium butyrate prevents cytokine-induced β-cell dysfunction through restoration of stromal interaction molecule 1 expression and activation of store-operated calcium entry.

Sodium butyrate (NaB) improves β-cell function in preclinical models of diabetes; however, the mechanisms underlying these beneficial effects have not been fully elucidated. In this study, we investigated the impact of NaB on β-cell function and calcium (Ca2+) signaling using exvivo and invitro models of diabetes. Our results show that NaB significantly improved glucose-stimulated insulin secretion in islets from human organ donors with type 2 diabetes and in cytokine-treated INS-1 β cells. Consistently, NaB improved glucose-stimulated Ca2+ oscillations in mouse islets treated with proinflammatory cytokines. Because the oscillatory phenotype of Ca2+ in the β cell is governed by changes in endoplasmic reticulum (ER) Ca2+ levels, we explored the relationship between NaB and store-operated calcium entry (SOCE), a rescue mechanism that acts to refill ER Ca2+ levels through STIM1-mediated gating of plasmalemmal Orai channels. We found that NaB treatment preserved basal ER Ca2+ levels and restored SOCE in IL-1β-treated INS-1 cells. Furthermore, we linked these changes with the restoration of STIM1 levels in cytokine-treated INS-1 cells and mouse islets, and we found that NaB treatment was sufficient to prevent β-cell death in response to IL-1β treatment. Mechanistic experiments revealed that NaB mediated these beneficial effects in the β-cell through histone deacetylase (HDAC) inhibition, iNOS suppression, and modulation of AKT-GSK-3 signaling. Taken together, these data support a model whereby NaB treatment promotes β-cell function and Ca2+ homeostasis under proinflammatory conditions through pleiotropic effects that are linked with maintenance of SOCE. These results also suggest a relationship between β-cell SOCE and gut microbiome-derived butyrate that may be relevant in the treatment and prevention of diabetes.

Entinostat as a combinatorial therapeutic for rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common childhood soft tissue sarcoma. For the alveolar subtype (ARMS), the presence of the PAX3::FOXO1 fusion gene and/or metastases are strong predictors of poor outcome. Metastatic PAX3::FOXO1+ ARMS often responds to chemotherapies initially, only to subsequently relapse and become resistant with most patients failing to survive beyond 8 years post-diagnosis. No curative intent phase II or phase III clinical trial has been available for patients in the past 10 years (ARST0921). Thus, metastatic ARMS represents a significantly unmet clinical need. Chemotherapy resistance in ARMS has previously been attributed to PAX3::FOXO1-mediated cell cycle checkpoint adaptation, which is mediated by an HDAC3-SMARCA4-miR-27a-PAX3::FOXO1 circuit that can be disrupted by HDAC3 inhibition. In this study, we investigated the therapeutic efficacy of combining the epigenetic regulator entinostat, a Class I Histone Deacetylase (HDAC1-3) inhibitor, with RMS-specific chemotherapies in patient derived xenograft (PDX) models of RMS. We identified single agent, additive or synergistic relationships between relapse-specific chemotherapies and clinically relevant drug exposures of entinostat in three PAX3::FOXO1+ ARMS mouse models. This preclinical data provides further rationale for clinical investigation of entinostat, already known to be well tolerated in a pediatric phase I clinical trial (ADVL1513).

Transcriptomic profiling reveals histone acetylation-regulated genes involved in somatic embryogenesis in Arabidopsis thaliana

BackgroundSomatic embryogenesis (SE) exemplifies the unique developmental plasticity of plant cells. The regulatory processes, including epigenetic modifications controlling embryogenic reprogramming of cell transcriptome, have just started to be revealed.ResultsTo identify the genes of histone acetylation-regulated expression in SE, we analyzed global transcriptomes of Arabidopsis explants undergoing embryogenic induction in response to treatment with histone deacetylase inhibitor, trichostatin A (TSA). The TSA-induced and auxin (2,4-dichlorophenoxyacetic acid; 2,4-D)-induced transcriptomes were compared. RNA-seq results revealed the similarities of the TSA- and auxin-induced transcriptomic responses that involve extensive deregulation, mostly repression, of the majority of genes. Within the differentially expressed genes (DEGs), we identified the master regulators (transcription factors - TFs) of SE, genes involved in biosynthesis, signaling, and polar transport of auxin and NITRILASE-encoding genes of the function in indole-3-acetic acid (IAA) biosynthesis. TSA-upregulated TF genes of essential functions in auxin-induced SE, included LEC1/LEC2, FUS3, AGL15, MYB118, PHB, PHV, PLTs, and WUS/WOXs. The TSA-induced transcriptome revealed also extensive upregulation of stress-related genes, including those related to stress hormone biosynthesis. In line with transcriptomic data, TSA-induced explants accumulated salicylic acid (SA) and abscisic acid (ABA), suggesting the role of histone acetylation (Hac) in regulating stress hormone-related responses during SE induction. Since mostly the adaxial side of cotyledon explant contributes to SE induction, we also identified organ polarity-related genes responding to TSA treatment, including AIL7/PLT7, RGE1, LBD18, 40, HB32, CBF1, and ULT2. Analysis of the relevant mutants supported the role of polarity-related genes in SE induction.ConclusionThe study results provide a step forward in deciphering the epigenetic network controlling embryogenic transition in somatic cells of plants.

Innovative Tools for DNA Topology Probing in Human Cells Reveal a Build-Up of Positive Supercoils Following Replication Stress at Telomeres and at the FRA3B Fragile Site.

Linear unconstrained DNA cannot harbor supercoils since these supercoils can diffuse and be eliminated by free rotation of the DNA strands at the end of the molecule. Mammalian telomeres, despite constituting the ends of linear chromosomes, can hold supercoils and be subjected to topological stress. While negative supercoiling was previously observed, thus proving the existence of telomeric topological constraints, positive supercoils were never probed due to the lack of an appropriate tool. Indeed, the few tools available currently could only investigate unwound (Trioxsalen) or overwound (GapR) DNA topology (variations in twist) but not the variations in writhe (supercoils and plectonemes). To address this question, we have designed innovative tools aimed at analyzing both positive and negative DNA writhe in cells. Using them, we could observe the build-up of positive supercoils following replication stress and inhibition of Topoisomerase 2 on telomeres. TRF2 depletion caused both telomere relaxation and an increase in positive supercoils while the inhibition of Histone Deacetylase I and II by TSA only caused telomere relaxation. Moving outside telomeres, we also observed a build-up of positive supercoils on the FRA3B fragile site following replication stress, suggesting a topological model of DNA fragility for this site.

Targeting SIRT2 in Aging-Associated Fibrosis Pathophysiology.

Aging is a complex biological process that involves multi-level structural and physiological changes. Aging is a major risk factor for many chronic diseases. The accumulation of senescent cells changes the tissue microenvironment and is closely associated with the occurrence and development of tissue and organ fibrosis. Fibrosis is the result of dysregulated tissue repair response in the development of chronic inflammatory diseases. Recent studies have clearly indicated that SIRT2 is involved in regulating the progression of fibrosis, making it a potential target for anti-fibrotic drugs. SIRT2 is a NAD+ dependent histone deacetylase, shuttling between nucleus and cytoplasm, and is highly expressed in liver, kidney and heart, playing an important role in the occurrence and development of aging and fibrosis. Therefore, we summarized the role of SIRT2 in liver, kidney and cardiac fibrosis during aging.

Suppressed testicular macrophage M1 polarization by HDAC5 enforces insensitivity to LPS-elicited blood-testis barrier damage

Infertility caused by lipopolysaccharide (LPS) exposure due to infection is endangering male fertility worldwide, but the mechanism remains unclear. The blood-testis barrier (BTB) is essential for maintaining spermatogenesis and male fertility. In the present study, we showed that LPS (5.0 mg/kg) treatment markedly down-regulated the expression of BTB-related proteins, expanded the biotin penetration distance and caused histopathological injury in seminiferous tubules in mouse testes. Notably, testicular macrophage M1 polarization induced by LPS seems to be related to BTB damage, which was well confirmed by co-culture of RAW264.7 and TM4 cells in vitro. Interestingly, a low-dose LPS (0.1 mg/kg) pretreatment attenuated down-regulation of BTB-related proteins expression and histopathological injury and shorten biotin penetration distance in seminiferous tubules caused by LPS. Correspondingly, a low-dose LPS pretreatment suppresses testicular macrophage M1 polarization induced by LPS in mouse testes. Further experiments revealed that histone deacetylase 5 (HDAC5) was markedly down-regulated at 2 h and slightly down-regulated at 8 h, but up-regulated at 24 h in mouse testes after LPS treatment. Additionally, low-dose LPS pretreatment against the down-regulation of HDAC5 protein caused by LPS treatment. Notably, the suppressed testicular macrophage M1 polarization by low-dose LPS pretreatment was broken by BRD4354, a specific inhibitor of HDAC5 in vitro. These results suggest suppressed testicular macrophage M1 polarization by HDAC5 enforces insensitivity to LPS-elicited BTB damage.