去乙酰化酶SIRT2及其抑制剂的研究进展

Sirtuin2(SIRT2)是一种烟酰胺腺嘌呤二核苷酸(NAD~+)依赖性的组蛋白去乙酰化酶,是沉默信息调节因子2(Sir2)相关蛋白家族的重要成员。SIRT2通过催化不同的底物去乙酰化参与了许多生物学过程,比如基因沉默、细胞周期调控、细胞代谢、细胞凋亡等。研究表明,在许多神经退行性疾病模型中,抑制SIRT2能够对神经元细胞产生明显的保护作用。因此,SIRT2有望成为治疗神经退行性疾病的重要靶点。本文主要对SIRT2的结构、功能、SIRT2与神经退行性疾病的关系、SIRT2抑制剂及其构效关系做一综述,旨在为以SIRT2为靶点的神经退行性疾病药物研发提供参考。     

SIRT1参与肝细胞癌发生发展和治疗的研究进展

肝细胞癌是严重影响人类健康的疾病,其发生发展机制尚不完全明确,治疗也面临众多的难题。SIRT1是Sirtuin家族中定位于细胞核的基因,主要参与细胞代谢、衰老、凋亡、分化、应激反应、能量代谢等生理活动,并与人类的多种肿瘤密切相关。研究显示,SIRT1在肝细胞癌中呈持续高表达,在肝癌的发生发展、侵袭、转移等多方面起到了重要的作用,并与肝细胞癌的诊治和预后相关。本文对SIRT1在肝癌发生发展以及诊治中的作用作一综述,为肝癌的实验及临床治疗研究提供参考依据。     

SIRT1的生理功能及其与肿瘤相关性的研究进展

沉默信息调节因子1(sileniinformationregulatorl,SIRT1)是一个具有NAD+依赖性的Ⅲ类组蛋白去乙酞化酶,属于SirtuinS 家族成员之一.人类SIRT1在细胞存活与代谢等过程中有着重要的生理功能.从而涉及了多种人类重大疾病如肿瘤、神经退行性疾病、心血管疾病等的发生、发展.随着对其研究的深入,SIRT1将有望在新药作用靶点及疾病治疗方面发挥作用.     

SIRT3在帕金森病发生中的作用研究进展

黑质致密部多巴胺能神经元退化及胞浆内α-突触核蛋白积聚是帕金森病(PD)的主要病理特征。线粒体在PD发病过程中发挥重要作用,线粒体功能障碍、氧化应激损伤与多巴胺能神经元丢失关系密切,线粒体损伤严重影响轴突形态和功能维持,神经毒素1-甲基-4-苯基-1,2,3,6-四氢吡啶(MPTP)和鱼藤酮可通过抑制线粒体电子传递链诱导PD症状发生,编码线粒体蛋白基因突变通过影响线粒体功能而引发家族性PD。SIRT3主要定位于线粒体,具有去乙酰化酶活性。越来越多研究报道线粒体蛋白SIRT3在神经相关疾病发生中的作用。SIRT3在神经退行性疾病中的神经保护作用机制主要与其改善线粒体功能、调节氧化应激与能量代谢、活性氧产生减少、ATP生成增加、抑制凋亡及炎性因子表达等相关,阐明SIRT3在这些神经疾病中的分子保护机制,可为SIRT3作为治疗靶点提供足够的证据。近年,SIRT3在PD发生中的作用研究越来越受到研究者关注,本文对相关文献综述后发现,MPTP注射小鼠中脑组织SIRT3表达减少,PD模型小鼠SIRT3基因缺失显著加剧黑质纹状体多巴胺能神经元退化,线粒体抗氧化酶SOD2、谷胱甘肽过氧化物酶表达均显著减少,说明SIRT3通过清除线粒体内自由基在MPTP诱导的神经退化中发挥一定保护作用。此外,SIRT3还通过增强线粒体柠檬酸合酶、异柠檬酸脱氢酶等酶的活性发挥多巴胺能神经元保护作用。SIRT3功能下降可增加PD动物模型黑质多巴胺能神经元线粒体氧化应激及细胞死亡。SIRT3还可通过促进自噬发生抵抗鱼藤酮诱导的神经细胞损伤。临床和实验研究表明,PD患者、PD细胞与动物模型大脑组织过氧化物酶体增殖活化受体γ共激活因子-1α(PGC-1α)表达均下降,过表达PGC-1α可抑制α-突触核蛋白聚集,减轻神经毒性。另有研究发现MPTP诱导的PD细胞模型中SIRT3表达显著减少,过表达SIRT3则抑制细胞凋亡,PGC-1α可促进SIRT3基因转录,通过去乙酰化激活SOD2和ATP合酶β,减少活性氧积聚和ATP消耗量,进而抑制多巴胺能神经元丢失。以上结果提示,线粒体蛋白SIRT3与PD发生具有一定的关系,但关于SIRT3在PD发展中具体作用分子机制的研究,还不够深入,未来可就这方面开展较多研究工作,为SIRT3作为PD病理机制研究与药物干预治疗新靶点提供更多新的科学证据。     

SIRT1、SIRT2和IL-37在子宫内膜异位症患者异位内膜组织的表达

目的 探讨 Sirtuin1（SIRT1）、Sirtuin2（SIRT2）及白细胞介素-37（IL-37）在正常子宫内膜组织及异位子宫 内膜组织表达的差异。方法 收集正常人子宫内膜组织及异位症患者异位内膜组织各 30例,采用免疫组织化学染 色检测 SIRT1、SIRT2及 IL-37蛋白的表达情况。结果 子宫内膜异位症患者异位内膜组织中 SIRT1、SIRT2、IL-37的 阳性表达率分别为 33.0%、20.0%、36.7%,均较正常子宫内膜组织（分别为 90.0%、86.7%、86.7%）显著降低（P＜0.05）。 不同月经周期对子宫内膜 SIRT1、SIRT2及 IL-37的表达无明显影响（P＞0.05）。结论 子宫内膜异位症患者异位内 膜中 SIRT1、SIRT2及 IL-37表达水平较低,提示子宫内膜异位症患者的异位内膜组织可能存在炎症反应。     

SIRT1在丙戊酸对肝细胞毒性中的作用研究

目的探讨沉默信息调节因子1(SIRT1)在丙戊酸对肝脏Hep G2细胞毒性中的作用。方法在Hep G2细胞中,丙戊酸(2 mmol·L-1)孵育6、12、24、48 h,或丙戊酸(0.5、1、2 mmol·L-1)分别孵育48 h,通过Western blot方法检测丙戊酸对SIRT1蛋白表达的影响;通过瞬时转染SIRT1表达质粒和si-SIRT1,采用SRB方法,观察对SIRT1基因进行过表达和抑制后,丙戊酸对Hep G2细胞毒性的改变情况。结果丙戊酸对SIRT1的表达有抑制作用,且具有时间和剂量依赖性。过表达SIRT1后,Hep G2细胞对丙戊酸的毒性敏感性下降,转染前后IC50分别为(4.025±0.47)、(10.87±1.50)mmol·L-1;而干扰SIRT1后,Hep G2细胞对丙戊酸的毒性敏感性增加,转染前后IC50分别为(1.938±0.16)、(0.663±0.05)mmol·L-1。结论丙戊酸可抑制SIRT1的蛋白表达,并且过表达SIRT1可拮抗丙戊酸对肝细胞的毒性作用。     

SIRT6在心血管疾病中的作用研究进展

心血管疾病以高发病率、高死亡率的特点成为危害人类健康的严重疾病。SIRT6作为组蛋白去乙酰化酶家族的重要成员,在动脉粥样硬化、心肌梗死以及缺血/再灌注损伤、病理性心肌肥大、心力衰竭等心血管疾病中发挥重要作用。该文主要针对SIRT6在心血管疾病中的作用进行综述,并对以SIRT6为靶点的激动剂和抑制剂的研究做一总结。     

瑞舒伐他汀通过UCP2-SIRT3信号调控脑I/R对神经元的损伤

目的:研究瑞舒伐他汀对脑缺血-再灌注损伤的保护作用及作用机制。方法:(1)建立脑梗死及OGD/R细胞模型,检测不同浓度瑞舒伐他汀对细胞增殖及细胞凋亡的影响;(2)用不同浓度瑞舒伐他汀处理OGD/R细胞模型,观察瑞舒伐他汀对细胞形态和细胞中UCP2/SIRT3表达和定位的影响;(3)构建UCP2沉默的细胞系,观察细胞线粒体形态和细胞中TOMM20及SIRT3分子表达与定位,研究瑞舒伐他汀在OGD/R细胞模型中发挥保护作用的通道和机制;(4)检测线粒体膜电位,PCR检测线粒体生成基因PGC1、Drp1和Opa1表达,研究瑞舒伐他汀对线粒体的保护作用。结果:(1)不同浓度瑞舒伐他汀均可以明显减低OGD/R细胞凋亡,提高细胞存活率;(2)瑞舒伐他汀通过影响细胞UCP2和SIRT3表达,进而发挥细胞保护作用,使细胞免受OGD/R损伤;(3)瑞舒伐他汀通过调控UCP2影响TOMM20表达,增加线粒体跨膜转运和能量代谢,增强线粒体功能,提高细胞存活;(4)瑞舒伐他汀阻止OGD/R细胞膜电位下降,保护线粒体,改善细胞状态,减少细胞凋亡。结论:瑞舒伐他汀通过调控UCP2/SIRT通路来抑制OGD/R细胞线粒体损伤,从而发挥神经元保护作用。     

糖尿病大鼠海马组织自噬减少与SIRT2下调有关

目的探讨自噬与SIRT2在糖尿病大鼠海马组织中的表达及意义。方法采用单次腹腔注射链脲佐菌素(STZ,60 mg/kg)建立1型糖尿病大鼠(T1DM)模型,采用激光共聚焦检测LC3蛋白表达,采用免疫组化检测海马SIRT2蛋白表达水平。结果与正常组相比,T1DM大鼠海马组织自噬减少,SIRT2表达降低,而胰岛素[4 U/(kg·d)]治疗后促进细胞自噬并上调SIRT2表达。结论高血糖下调海马神经元SIRT2表达并抑制自噬发生,这可能与糖尿病脑病的发生与发展相关。     

细胞色素氧化酶CYP 1A2基因多态性与物质代谢和癌症发生相关性的研究进展

细胞色素氧化酶CYP 1A2亚家族是近年来药物代谢研究领域较受关注的热点之一。该酶具有高度的个体间差异,并参与多种临床药物以及环境致癌物质的代谢,与癌症、炎症、心肌梗塞等疾病的发病易感性相关。CYP 1A2具有抗氧化作用;CYP 1A2基因多态性和表型差异的研究,可用于评价临床药物治疗效果;探针药物的应用是研究CYP 1A2活性的主要方法;人源化CYP 1A2转基因动物模型,是癌症发生研究中、新的研究手段。     

Can targeting SIRT-1 to treat type 2 diabetes be a good strategy? A review

Introduction: Dysregulation of metabolic pathways, caused by imbalances in energy homeostasis, leads to type 2 diabetes characterized by high glucose concentration in the blood due to insulin resistance which is a major disorder in developed countries.

Areas covered: One of the recent treatment strategies is using activators of SIRT1, which has been in clinical trials. Many of the cellular processes including insulin secretion, cell cycle, and apoptosis are imperatively regulated by a family of mediators called sirtuins. First known mammalian sirtuin, SIRT1 is a positive regulator of insulin secretion, which triggers glucose uptake and utilization. Since the past decade, a major outstanding question is whether SIRT1 activation is a safe therapy for human diseases such as type 2 diabetes? This review summarizes and discusses the advances of the past decade and the challenges that will brazen out perplexity about homeostasis and metabolic pathways linked to SIRT1 and type 2 diabetes. Furthermore, we described the interlink between SIRT1 metabolic pathways of various tissues such as pancreas, skeletal muscle, adipose tissue and liver.

Expert opinion: However be the complexity of the pathways involved, T2DM regulated by SIRT1 affected metabolism is dropping down progressively due to profound research. In the context of interlinking all the SIRT1 pathways in T2DM we found various crucial intermediaries in metabolic tissues, which can also be targeted for future prospects.     

Structure‐based discovery of new selective small‐molecule sirtuin 5 inhibitors

Human sirtuin 5 (SIRT5) is a protein deacylase regulating metabolic pathways and stress responses and is implicated in metabolism‐related diseases. Small‐molecule inhibitors for SIRT5 are sought as chemical tools and potential therapeutics. Herein, we proposed a customized virtual screening approach targeting catalytically important and unique residues Tyr102 and Arg105 of SIRT5. Of the 20 tested virtual screening hits, six compounds displayed marked inhibitory activities against SIRT5. For the hit compound 19 , a series of newly synthesized (E)‐2‐cyano‐N‐phenyl‐3‐(5‐phenylfuran‐2‐yl)acrylamide derivatives/analogues were carried out structure–activity relationship analyses, resulting in new more potent inhibitors, among which 37 displayed the most potent inhibition to SIRT5 with an IC₅₀ value of 5.59 ± 0.75 μM. The biochemical studies revealed that 37 likely acts via competitive inhibition with the succinyl‐lysine substrate, rather than the NAD⁺ cofactor, and it manifested substantial selectivity for SIRT5 over SIRT2 and SIRT6. This study will aid further efforts to develop new selective SIRT5 inhibitors as tools and therapeutics.     

A patent review of sirtuin activators: an update

Introduction : Reversible acetylation is a key post-translational modification of target proteins. Sirtuin deacetylases represent the homolog of the yeast silent information regulator (SIR2). Although seven sirtuins have been found in mammals, all sirtuin activators described to date act through SIRT1.

Areas covered : Areas covered in this paper include a review of the patent literature associated with SIRT1 activators, with a focus on therapeutic applications, primarily related to the use of pharmaceuticals and nutraceuticals containing resveratrol (RSV), and the development of second-generation activators unrelated to RSV. Also discussed is the current controversy over whether or not these molecules are actual SIRT1 activators.

Expert opinion : Developing effective strategies to protect against diet-induced metabolic imbalance is necessary to fight against current obesity rates. The hypothalamus is a candidate for developing drugs that suppress SIRT1 degradation, as a strategy for treating metabolic syndrome. Deciphering the basic mechanism of activators is essential to develop effective strategies to alter sirtuin activity. This is true regardless of the apparent controversy of whether in vitro activation of SIRT1 is direct or not, depending on the experimental design, and whether sirtuins may play a major role in longevity. The numerous studies on their positive effects against age-related diseases, obesity and other metabolic disorders are still valid, promising to positively influence the development of treatments to improve human health.     

Resveratrol is Not a Direct Activator of SIRT1 Enzyme Activity

Resveratrol is a plant polyphenol capable of exerting beneficial metabolic effects which are thought to be mediated in large by the activation of the NAD⁺‐dependent protein deacetylase SIRT1. Although resveratrol has been claimed to be a bona fide SIRT1 activator using a peptide substrate (Fluor de Lys‐SIRT1 peptide substrate), recent reports indicate that this finding might be an experimental artifact and need to be clarified. Here, we show that: (i) the Fluor de Lys‐SIRT1 peptide is an artificial SIRT1 substrate because in the absence of the covalently linked fluorophore the peptide itself is not a substrate of the enzyme, (ii) resveratrol does not activate SIRT1 in vitro in the presence of either a p53‐derived peptide substrate or acetylated PGC‐1α isolated from cells, and (iii) although SIRT1 deacetylates PGC‐1α in both in vitro and cell‐based assays, resveratrol did not activate SIRT1 under these conditions. Based on these observations, we conclude that the pharmacological effects of resveratrol in various models are unlikely to be mediated by a direct enhancement of the catalytic activity of the SIRT1 enzyme. In consequence, our data challenge the overall utility of resveratrol as a pharmacological tool to directly activate SIRT1.     

Non-specific SIRT inhibition as a mechanism for the cytotoxicity of ginkgolic acids and urushiols

Ginkgolic acids and urushiols are natural alkylphenols known for their mutagenic, carcinogenic and genotoxic potential. However, the mechanism of toxicity of these compounds has not been thoroughly elucidated so far. Considering that the SIRT inhibitory potential of anacardic acids has been hypothesized by in silico techniques, we herein demonstrated through both in vitro and computational methods that structurally related compounds such as ginkgolic acids and urushiols are able to modulate SIRT activity. Moreover, their SIRT inhibitory profile and cytotoxicity were comparable to sirtinol, a non-specific SIRT inhibitor (SIRT1 and SIRT2), and different from EX-527, a SIRT1 specific inhibitor. This is the first report on the SIRT inhibition of ginkgolic acids and urushiols. The results reported here are in line with previously observed effects on the induction of apoptosis by this class of compounds, and the non-specific SIRT inhibition is suggested as a new mechanism for their in vitro cytotoxicity.     

Discovery of 5-Benzylidene-2-phenyl-1,3-dioxane-4,6-diones as Highly Potent and Selective SIRT1 Inhibitors

SIRT1, a member of the sirtuin family, catalyzes the deacetylation of proteins with the transformation of NAD⁺ into nicotinamide and 2′-O-acetyl-ADP-ribose. Selective SIRT1/2 inhibitors have potential application in the chemotherapy of colorectal carcinoma, prostate cancer, and myelogenous leukemia. Here we identified novel SIRT1 inhibitors with the scaffold of 5-benzylidene-2-phenyl-1,3-dioxane-4,6-dione. The most potent inhibitor 12n displayed an IC₅₀ of 460 nM and a selectivity for SIRT1 over SIRT2, SIRT3, and SIRT5 of 113.5-, 254.3-, and 10.83-fold, respectively. It did not affect the activity of SIRT6. To elucidate the inhibitory mechanism, we determined the inhibition type of the inhibitor by enzyme kinetic analysis, showing that the inhibitor was competitive to the acetyl peptide and noncompetitive to NAD⁺. Further, the interaction of the inhibitor in SIRT1 was studied by using molecular docking, which was validated by the structure–activity relationship analysis of the inhibitors and the site-directed mutagenesis of SIRT1. Consistent with the in vitro assays, the inhibitors increased the acetylation level of p53 in a concentration-dependent manner in cells.     

17-β Oestradiol prevents cardiovascular dysfunction in post-menopausal metabolic syndrome by affecting SIRT1/AMPK/H3 acetylation

BACKGROUND AND PURPOSE

Oestrogen therapy is known to induce cardioprotection in post-menopausal metabolic syndrome (PMS). Hence, we investigated the effect of 17-β oestradiol (E2) on functional responses to angiotensin II and cardiovascular dysfunction in a rat model of PMS.

EXPERIMENTAL APPROACH

PMS was induced in ovariectomized rats by feeding a high-fat diet for 10 weeks. Isometric tension responses of aortic rings to angiotensin II were recorded using an isometric force transducer. TUNEL assay and immunoblotting was performed to assess apoptosis and protein expression respectively in PMS.

KEY RESULTS

Endothelial dysfunction in PMS was characterized by enhanced angiotensin II-induced contractile responses and impaired endothelial dependent vasodilatation. This was associated with an increased protein expression of AT₁ receptors in the aorta and heart in PMS. PMS induced cardiac apoptosis by activating Bax and PARP protein expression. These changes were associated with a down-regulation in the expression of silent information regulation 2 homologue (SIRT1)/P-AMP-activated PK (AMPK) and increased H3 acetylation in aorta and heart. E2 partially suppressed angiotensin II-induced contractions, restored the protein expression of SIRT1/P-AMPK and suppressed H3 acetylation. The role of SIRT1/AMPK was further highlighted by administration of sirtinol and compound C (ex vivo), which enhanced angiotensin II contractile responses and ablated the protective effect of E2 on PMS.

CONCLUSION AND IMPLICATIONS

Our results provide novel mechanisms for PMS-induced cardiovascular dysfunction involving SIRT1/AMPK/ histone H3 acetylation, which was prevented by E2. The study suggests that therapies targeting SIRT1/AMPK/epigenetic modifications may be beneficial in reducing the risk of cardiovascular disorders.     

Design and Evaluation of 3-(Benzylthio)benzamide Derivatives as Potent and Selective SIRT2 Inhibitors

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Second generation CB1 receptor blockers and other inhibitors of peripheral endocannabinoid overactivity and the rationale of their use against metabolic disorders

Introduction: Excessive abdominal obesity along with other risk factors results in the metabolic syndrome, which can lead to heart disease, Type-2 diabetes, and death. The endocannabinoid system (ECS) is composed of neutral lipids which signal through the G-protein coupled cannabinoid receptors CB1 and CB2. In abdominal obesity, the ECS is generally up-regulated in central and peripheral tissues and its blockade results in positive metabolic changes. Rimonabant (SR141716) was the first selective CB1 inverse agonist/antagonist marketed for the treatment of obesity; however, psychiatric side effects, which may result from its actions in the brain or its inverse agonism, resulted in its removal from the market. Recently, key metabolic-modulatory roles for the ECS within peripheral tissues have come to light. Thus there has been significant effort put forth by several laboratories to develop either neutral or peripherally restricted CB1 antagonists.

Areas covered: In this review we shall provide an overview of the roles the ECS plays outside the brain in regulating metabolism, and highlight the latest advances in the development of neutral and/or peripherally restricted CB1 antagonists, and other state of the art strategies that minimize endocannabinoid overactivity.

Expert opinion: The CB1 receptor is potentially a clinically relevant target for the design of therapies against metabolic syndrome, deserving the development and clinical testing of CB1-neutral antagonists which can pass the blood – brain barrier or of peripherally restricted inverse agonists/neutral antagonists. Furthermore, reducing endocannabinoid biosynthesis could represent an alternative strategy to counteract peripheral endocannabinoid overactivity through dietary n-3 polyunsaturated fatty acids or the development of diacylglycerol lipase inhibitors.