Histone deacetylase inhibition promotes Caspase-independent cell death of ventral midbrain neurons

Inhibition of histone deacetylase (HDAC) activity results in dedifferentiation of various neural precursor cell populations, but is also known to promote neuronal differentiation. We sought to determine the effects of HDAC inhibition on differentiated and non-differentiated midbrain cells in order to examine more closely the consequences of HDAC inhibition on cell fate in a heterogeneous population. We demonstrate that HDAC inhibitor (HDACi) treatment causes a significant attenuation in the numbers of neurons, but not astrocytes, within 48 h, with no evidence of neuronal dedifferentiation. The loss of neurons is due to an initial morphological destabilization, which is not recoverable upon inhibitor removal, and ultimately leads to cell death. HDACi treatment results in progenitor cell cycle arrest and Caspase-dependent apoptosis. In contrast, the loss of midbrain neurons does not correlate with activated Caspase-3 expression. Treating cultures transiently with Caspase inhibitors blocks overall HDACi-induced cell death in the cultures, but does not prevent the loss of neurons. These data suggest that HDACi treated midbrain neurons undergo Caspase-independent cell death. Finally, we demonstrate that cortical neurons do not undergo cell death in response to HDACi treatment, suggesting that there may be tissue-specific or microenvironmental factors that promote the susceptibility of midbrain neurons to the neurotoxic effects of HDAC inhibition.     

Anti‐leukemic activity of valproic acid and imatinib mesylate on human Ph+ ALL and CML cells in vitro

The armamentarium of anti‐leukemic drugs has increased substantially since anti‐leukemic activities were recently found for a variety of non‐classical cytostatic drugs, among them the histone deacetylase (HDAC) inhibitor valproic acid (VPA). This study investigated the effect of VPA on proliferation and apoptosis of human Philadelphia chromosome‐positive (Ph+) acute lymphatic (ALL) and chronic myeloid leukemia (CML) cells and on colony formation of human chronic‐phase CML progenitor cells. Strong anti‐proliferative and pro‐apoptotic effects of VPA were observed on human ALL and CML cell lines at concentrations achievable in vivo. These effects were most pronounced in ALL cell lines as well as in primary ALL cells. Notably, VPA revealed enhanced activity with imatinib mesylate, nilotinib, the farnesyl transferase inhibitor SCH66336, interferon‐alpha and cytosine arabinoside. VPA inhibited the growth of colony‐forming cells from 12 Ph+ chronic‐phase CML patients but also of those from normal healthy controls in a dose‐dependent fashion. HDAC‐inhibiting activity of VPA was confirmed on ALL and CML cells. In conclusion, VPA, whether alone or in combination with other non‐classical anti‐leukemic compounds, exerts significant anti‐leukemic effects on human ALL and CML cells.     

Epigenetic impacts of endocrine disruptors in the brain

The acquisition of reproductive competence is organized and activated by steroid hormones acting upon the hypothalamus during critical windows of development. This review describes the potential role of epigenetic processes, particularly DNA methylation, in the regulation of sexual differentiation of the hypothalamus by hormones. We examine disruption of these processes by endocrine-disrupting chemicals (EDCs) in an age-, sex-, and region-specific manner, focusing on how perinatal EDCs act through epigenetic mechanisms to reprogram DNA methylation and sex steroid hormone receptor expression throughout life. These receptors are necessary for brain sexual differentiation and their altered expression may underlie disrupted reproductive physiology and behavior. Finally, we review the literature on histone modifications and non-coding RNA involvement in brain sexual differentiation and their perturbation by EDCs. By putting these data into a sex and developmental context we conclude that perinatal EDC exposure alters the developmental trajectory of reproductive neuroendocrine systems in a sex-specific manner.     

Modifying histones to tame cancer: clinical development of sodium phenylbutyrate and other histone deacetylase inhibitors

Compounds that inhibit histone deacetylase may enable the re-expression of silenced regulatory genes in neoplastic cells, reversing the malignant phenotype. Although several molecules that inhibit histone deacetylase are undergoing preclinical development, butyric acid derivatives have undergone clinical investigation for several years, initially for non-malignant indications and more recently for the treatment of cancer. Of the butyric acid derivatives, sodium phenylbutyrate has undergone the most extensive systematic investigation. Administration of phenylbutyrate by iv. and oral routes is well-tolerated clinically at concentrations which effect acetylation of histones in vitro. Higher doses lead to reversible CNS depression. The studies presented to date have been Phase I studies and do not enable assessment of efficacy. However, current development of phenylbutyrate is proceeding in combination with other agents based on rational biologically-based in vitro studies. The parallel development of combination therapy including phenylbutyrate and early clinical development of other, more potent histone deacetylase inhibitors will hopefully lead to feasible, clinically tolerable strategies for altering the malignant phenotype of cancer cells.     

Epigenetic mechanisms regulating learning and long-term memory

A balance between rapid, short lived, neuronal responses and prolonged ones fulfill the biochemical and cellular requirements for creating a molecular memory. I provide an overview of epigenetic mechanisms in the brain and discuss their impact on synaptic plasticity, cognitive functions, and discuss a recent example of how they can contribute to neurodegeneration and the cognitive decline associated with Alzheimer's disease.     

Studies on the chitin/chitosan binding properties of six cuticular proteins analogous to peritrophin 3 from Bombyx mori

Chitin deacetylation is required to make the cuticle rigid and compact through chitin chain crosslinking. Thus it is presumed that specialized proteins are required to bind deacetylated chitin chains together. However, deacetylated‐chitin binding proteins have not ever been reported. In a previous work, six cuticular proteins analogous to peritrophin 3 (CPAP3s) were found to be abundant in the moulting fluid of Bombyx mori. In this study, these BmCPAP3s (BmCPAP3‐A1, BmCPAP3‐A2, BmCPAP3‐B, BmCPAP3‐C, BmCPAP3‐D1 and BmCPAP3‐D2) were cloned and expressed in Escherichia coli and purified using metal‐chelating affinity chromatography. Their binding activities demonstrated that although all of the BmCPAP3s showed similar binding abilities toward crystalline chitin and colloidal chitin, they differed in their affinities toward partially and fully deacetylated chitin. Amongst them, BmCPAP3‐D1 exhibited the highest binding activity toward deacetylated chitin. The gene expression pattern of BmCPAP3‐D1 was similar to BmCPAP3‐A1 and BmCPAP3‐C at most stages except that it was dramatically upregulated at the beginning of the pupa to adult transition stage. This work is the first report of a chitin‐binding protein, BmCPAP3‐D1, which exhibits high binding affinity to deacetylated chitin.     

曲古菌素A诱导前列腺癌DU-145细胞有丝分裂的灾变

目的：研究组蛋白去乙酰化酶抑制剂（histone deacetylase inhibitor,HDACi）曲古菌素（trichostatina A,TSA）对前列腺癌DU145细胞有丝分裂的影响,探讨HDACi杀伤肿瘤细胞的新机制。方法：将前列腺癌DC-145细胞分成不加药对照组和不同剂量（100、200、300、400nmol/L）TSA加药组,药物作用一定时间后,MTT法检测TSA对DU145细胞的杀伤效应,瑞氏-姬姆萨染色观察细胞形态的变化,流式细胞术分析细胞周期的改变,免疫荧光染色观察DU145细胞异常的有丝分裂现象,Western blotting检测TSA处理对DU145细胞某些调控蛋白表达的影响。结果：TSA处理诱导DU145细胞发生有丝分裂,TSA处理24h后多核细胞数目由0.24%增加至1.21%。细胞周期计数结果显示,TSA处理后有丝分裂各期细胞比例发生明显改变,表现为有丝分裂前中期细胞所占比例增加,后末期细胞所占比例减少。免疫荧光染色显示,细胞出现多极纺锤体、染色体分离滞后等异常有丝分裂现象。TSA作用于DU145细胞后,能明显抑制Survivin蛋白的表达,增强细胞骨架蛋白Tubulin的乙酰化,并诱导P21蛋白高表达。结论：TSA能够诱使DU145细胞发生有丝分裂灾变,其机制可能与TSA降低Survivin蛋白的表达以及增强微管蛋白的乙酰化有关。     

组蛋白去乙酰酶抑制剂联合应用治疗肿瘤的研究进展

组蛋白去乙酰酶(histone deacetylase,HDAC)抑制剂可促进组蛋白乙酰化,调节染色质结构和基因转录。临床前研究,Ⅰ和(或)Ⅱ期临床试验都已证实,HDAC的小分子抑制剂能够有效地促进抑癌基因表达,抑制肿瘤生长并诱导细胞凋亡。在多种肿瘤中都已观察到,HDAC抑制剂与其他抗肿瘤药物联合应用,可在较低的剂量下产生更好的疗效,而不良反应减轻。     

胰腺导管内乳头状黏液性肿瘤组织DNMT1和HDAC1的表达及意义

目的:观察胰腺导管内乳头状黏液性肿瘤(IPMNs)组织DNA甲基化转移酶1(DNMT1)和组蛋白去乙酰化酶(HDACI)的表达,探讨其可能的临床意义.方法:免疫组织化学SP法检测DNMT1、HDAC1蛋白在48例IPMNs和54例胰腺导管腺癌(PDAC)组织中的表达并进行统计学分析.结果:DNMT和HDAC1阳性表达率在由正常胰腺导管→1PMA,IPMB→IPMC→PDAc的逐级进展过程中均逐渐升高,二者在IPMNs不同亚型中均有阳性表达.结论:DNMT1和HDAC1高表达是胰腺癌的早期事件,二者的表达水平能够反映IPMNs的恶性进展,但不能作为IPMNs的组织分型标志.