炎症诱发抑郁症：吲哚胺2,3 双加氧酶的激活是关键环节之一

本文通过回顾临床前期及临床期两阶段的文献,着重介绍炎症激活及抑郁症之间的相关联系并进一步探讨其机制。目前,抑郁症的机制研究热点之一是炎症反应又称为细胞因子假说,其中色氨酸--犬尿氨酸通路(KP)在该假说中的作用得到了越来越多的证实。该假说认为,色氨酸--犬尿氨酸途径是聚焦于抑郁症相关代谢产物改变的综合性通路。炎性抑郁症的产生是由于在免疫功能及神经递质改变下产生的炎性细胞因子激活了吲哚胺2,3-双加氧酶,从而进一步引发抑郁。吲哚胺2,3-双加氧酶的活性增加,不仅会导致色氨酸的衰竭同时还引起通过犬尿氨酸途径代谢的神经毒性产物的增加,而这两种改变都被认为与抑郁症的发病密切相关。在此基础上,我们主要聚焦于慢性病患者接受细胞因子治疗的相关研究,来探讨免疫激活病人中抑郁症发病的高风险性从而证明这一假说。这项工作的目的是希望通过对色氨酸--犬尿氨酸通路的研究,从吲哚胺2,3-双加氧酶的抑制,激活它的细胞因子的调节及寻找在犬尿氨酸途径中其它的靶点等方面来抗抑郁,从而为新型的抗抑郁药的发展提供新的方法途径。     

邻苯二酚2,3-双加氧酶的结构和功能研究进展

邻苯二酚是所有芳香族化合物降解过程中的重要的中间产物,其降解有邻位和间位裂解两条裂解途径,分别由邻苯二酚1,2-双加氧酶(C12O)和邻苯二酚2,3-双加氧酶(C23O)催化裂解。本综述简要介绍了邻苯二酚2,3-双加氧酶的结构和功能的研究进展。     

靶向色氨酸降解酶在肿瘤免疫治疗中的研究进展

免疫疗法为肿瘤患者带来了巨大希望。色氨酸作为人体必需氨基酸,在肿瘤免疫中具有重要意义。吲哚胺-2,3-双加氧酶1和2 (indoleamine-2,3-dioxygenase 1/2, IDO1/2)、色氨酸-2,3-双加氧酶2 (tryptophan-2,3-dioxygenase 2, TDO2)和白介素4诱导蛋白1 (interleukin-4-induced-1, IL4I1)是催化色氨酸降解的关键酶。研究表明靶向色氨酸降解酶能够恢复抗肿瘤免疫反应,并与其他免疫疗法(如免疫检查点抑制剂)具有协同作用,这给免疫肿瘤学领域带来了希望。然而,IDO1抑制剂的临床试验却带来了令人失望的结果。本综述将讨论色氨酸降解酶及其抑制剂在肿瘤免疫治疗中的潜在效果和问题,并提出了可选的规避方法。     

L-异亮氨酸和甘氨酸对大肠杆菌表达与分泌邻苯二酚2,3-双加氧酶的作用

证实了甘氨酸与L-异亮氨酸对大肠杆菌表达邻苯二酚2,3-双加氧酶(CatO_2ase)的促进作用和甘氨酸促使该酶分泌至胞外培养基中的作用.产酶量高低和分泌量多少与培养基种类、甘氨酸和L-异亮氨酸的浓度以及培养时间等因素有关.在甘氨酸存在的情况下,胞壁对溶菌酶的敏感性有所增加,超微形态似有变化,还存在其他物质的伴随分泌,故甘氨酸可能是引起细胞壁结构的改变而导致邻苯二酚2,3-双加氧酶等胞内容物被动分泌至胞外.     

L-异亮氨酸和甘氨酸对大肠杆菌表达与分泌邻苯二酚2,3-双加氧酶的作用

证实了甘氨酸与L-异亮氨酸对大肠杆菌表达邻苯二酚2,3-双加氧酶(CatO_2ase)的促进作用和甘氨酸促使该酶分泌至胞外培养基中的作用.产酶量高低和分泌量多少与培养基种类、甘氨酸和L-异亮氨酸的浓度以及培养时间等因素有关.在甘氨酸存在的情况下,胞壁对溶菌酶的敏感性有所增加,超微形态似有变化,还存在其他物质的伴随分泌,故甘氨酸可能是引起细胞壁结构的改变而导致邻苯二酚2,3-双加氧酶等胞内容物被动分泌至胞外.     

瑞香素及噁唑类小分子抑制吲哚胺-2,3-双加氧酶1(IDO1)的研究北大核心CSCD

吲哚胺-2,3-双加氧酶1(indoleamine 2,3-dioxygenase 1,IDO1)在肿瘤免疫中发挥了重要作用,为了获得新型的IDO1小分子抑制剂,本研究利用He La细胞系建立了IDO1抑制剂筛选模型,筛选抑制IDO1活性的天然小分子化合物。将He La细胞接种于48孔板中,加入干扰素-γ(IFN-γ)诱导He La细胞中IDO1的表达,检测HeLa细胞分泌IDO1的酶代谢活性。对化合物库筛选后发现瑞香素(Daphnetin)和一个噁唑类小分子ZH-26能够抑制IDO1酶活性,采用Graph Pad Prism计算瑞香素和ZH-26的IC50值,结果显示瑞香素的IC50为16. 50±0. 33μM,ZH-26的IC50为4. 68±0. 21μM。进一步在HEK-293A细胞中过表达IDO1,不同浓度瑞香素和ZH-26处理细胞后也表现出对IDO1活性的抑制作用。采用Western blot方法发现瑞香素显著下调IFN-γ诱导的IDO1蛋白表达,而ZH-26则对IFN-γ诱导的IDO1的表达没有影响。综上,瑞香素和ZH-26在He La细胞内没有发现明显的细胞毒作用。本实验首次发现了瑞香素和ZH-26具有抑制IDO1的活性,不但为了解瑞香素这一天然来源临床药物的抗肿瘤机制提供新的视角,也为开发新的靶向IDO1的肿瘤免疫治疗候选药物奠定了基础。     

邻苯二酚2,3—双加氧酶在大肠杆菌的表达与定域

本文在大肠杆菌/枮草芽孢杆菌间的穿梭质粒pTG 402的基础上构建了几个新的带有显色标志基闲xylE的表达质粒,摸索了该基因所编码的邻苯二酚2,3-双加氧酶(CatO_2ase)的表达条件,分析了该酶一级结构与二级结构的亲水性和疏水性,测定了它在大肠杆菌中的产量与分布。结果表明,CatO_2ase与各质粒的表达量不等,表达量高低与培养时间、宿主菌及诱导与否等影响因素有关;表达后有部分酶可在胞外测出,但大部分仍定域于膜内,亲、疏水性分析示该酶不具分泌性蛋白的显著特点。因该酶易于检测和定量,可作为一种选择性标记和监测指示系统在基因工程中推广应用,同时亦为用基因工程菌消除芳烃类化合物的污染提供了理论依据。     

吲哚胺2,3-双加氧酶基因转染对肝癌细胞凋亡的影响及相关机制研究

目的:通过细胞培养和在体实验探讨吲哚胺2,3-双加氧酶(indoleamine 2,3-dioxygenase,IDO)基因转染后对肝癌细胞凋亡的影响及相关细胞免疫机制的研究.方法:提取健康人外周血中的T细胞利用细胞培养和基因转染技术将T细胞和肝癌细胞混合培养.实验分为6组:根据是否加入D-1-MT分为未干预组和干预组...     

血红素加氧酶-1在中枢神经系统疾病中的作用

血红素加氧酶-1(heme oxygenase-1,HO-1)是一种应激蛋白,可将血红素降解为胆绿素、游离铁和一氧化碳。目前,国内外普遍认为HO-1在神经系统损伤后的应激反应中有至关重要的作用,其表达量与神经元凋亡和神经变性密切相关。本文对近年来HO-1在神经系统损伤性疾病中的现有研究结果进行了总结分析,旨在为相关研究的发展提供新的思路和方向。     

血红素加氧酶-1、树突状细胞和调节性T细胞在慢性气道炎症中的作用及相互关系

慢性气道炎症是多种肺部疾病的共同病理生理过程,是由多种炎症细胞、炎症介质及细胞因子相互作用所致的气道病变。血红素加氧酶(HO)-1、树突状细胞(DC)和调节性T细胞(Treg)参与了气道炎症并发挥不同的作用,表现在HO-1具有抗炎抗氧化及保护细胞的作用;DC除可导致或持续气道炎症反应外,也具有负向调控作用,可诱导免疫耐受而抑制炎症的发展;而Treg可发挥免疫调抑功能,以此维持免疫稳态及抑制气道炎症。HO-1、DC和Treg相互作用,影响着气道炎症的发生发展。现对三者在气道炎症中的作用及相互关系进行综述。     

Antitumour agents as inhibitors of tryptophan 2,3-dioxygenase

The involvement of tryptophan 2,3-dioxygenase (TDO) in cancer biology has recently been described, with the enzyme playing an immunomodulatory role, suppressing antitumour immune responses and promoting tumour cell survival and proliferation. This finding reinforces the need for specific inhibitors of TDO that may potentially be developed for therapeutic use. In this work we have screened ∼2800 compounds from the library of the National Cancer Institute USA and identified seven potent inhibitors of TDO with inhibition constants in the nanomolar or low micromolar range. All seven have antitumour properties, killing various cancer cell lines. For comparison, the inhibition potencies of these compounds were tested against IDO and their inhibition constants are reported. Interestingly, this work reveals that NSC 36398 (dihydroquercetin, taxifolin), with an in vitro inhibition constant of ∼16 μM, is the first TDO-selective inhibitor reported.     

Contributions of tryptophan 2,3-dioxygenase and indoleamine 2,3-dioxygenase to the conversion of d-tryptophan to nicotinamide analyzed by using tryptophan 2,3-dioxygenase-knockout mice

We investigated the contribution percentage of tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) to the conversion of d-tryptophan to nicotinamide in TDO-knockout mice. The calculated percentage conversions indicated that TDO and IDO oxidized 70 and 30%, respectively, of the dietary l-tryptophan. These results indicate that both TDO and IDO biosynthesize nicotinamide from d-tryptophan and l-tryptophan in mice.     

Biochemical mechanisms leading to tryptophan 2,3-dioxygenase activation

Tryptophan 2,3-dioxygenase (TDO) is the first enzyme in the tryptophan oxidation pathway. It is a hemoprotein and its heme prosthetic group is present as a heme-ferric (heme-Fe(3+)) form that is not active. To be able to oxidize tryptophan, the heme-Fe(3+) form of the enzyme must be reduced to a heme-ferrous (heme-Fe(2+)) form and this study describes conditions that promote TDO activation. TDO is progressively activated upon mixing with tryptophan in a neutral buffer, which leads to an impression that tryptophan is responsible for TDO activation. Through extensive analysis of factors resulting in TDO activation during incubation with tryptophan, we conclude that tryptophan indirectly activates TDO through promoting the production of reactive oxygen species. This consideration is supported by the virtual elimination of the initial lag phase when either pre-incubated tryptophan solution was used as the substrate or a low concentration of superoxide or hydrogen peroxide was incorporated into the freshly tryptophan and TDO mixture. However, accumulation of these reactive oxygen species also leads to the inactivation of TDO, so that both TDO activation and inactivation proceed with the specific outcome depending greatly on the concentrations of superoxide and hydrogen peroxide. As a consequence, the rate of TDO catalysis varies depending upon the proportion of the active to inactive forms of the enzyme, which is in a dynamic relationship in the reaction mixture. These data provide some insight towards elucidating the molecular regulation of TDO in vivo.     

The role of serine 167 in human indoleamine 2,3-dioxygenase: a comparison with tryptophan 2,3-dioxygenase

The initial step in the l-kynurenine pathway is oxidation of l-tryptophan to N-formylkynurenine and is catalyzed by one of two heme enzymes, tryptophan 2,3-dioxygenase (TDO) or indoleamine 2,3-dioxygenase (IDO). Here, we address the role of the conserved active site Ser167 residue in human IDO (S167A and S167H variants), which is replaced with a histidine in other mammalian and bacterial TDO enzymes. Our kinetic and spectroscopic data for S167A indicate that this residue is not essential for O 2 or substrate binding, and we propose that hydrogen bond stabilization of the catalytic ferrous-oxy complex involves active site water molecules in IDO. The data for S167H show that the ferrous-oxy complex is dramatically destabilized in this variant, which is similar to the behavior observed in human TDO [Basran et al. (2008) Biochemistry 47, 4752-4760], and that this destabilization essentially destroys catalytic activity. New kinetic data for the wild-type enzyme also identify the ternary [enzyme-O 2-substrate] complex. The data reveal significant differences between the IDO and TDO enzymes, and the implications of these results are discussed in terms of our current understanding of IDO and TDO catalysis.     

Comparative effects of oxygen on indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase of the kynurenine pathway

Indoleamine 2,3-dioxygenase (IDO) reacts with either oxygen or superoxide and tryptophan (trp) or other indoleamines while tryptophan 2,3-dioxygenase (TDO) reacts with oxygen and is specific for trp. These enzymes catalyze the rate-limiting step in the kynurenine (KYN) pathway from trp to quinolinic acid (QA) with TDO in kidney and liver and IDO in many tissues, including brain where it is low but inducible. QA, which does not cross the blood-brain barrier, is an excitotoxin found in the CNS during various pathologies and is associated with convulsions. We proposed that HBO-induced convulsions result from increased flux through the KYN pathway via oxygen stimulation of IDO. To test this, TDO and IDO of liver and brain, respectively, of Sprague Dawley rats were assayed with oxygen from 0 to 6.2 atm HBO. TDO activity was appreciable at even 30 microM oxygen and rose steeply to a maximum at 40 microM. Conversely, IDO had almost no detectable activity at or below 100 microM oxygen and maximum activity was not reached until about 1150 microM. (Plasma contains about 215 microM oxygen and capillaries about 20 microM oxygen when rats breathe air.) KYN was 60% higher in brains of HBO-convulsed rats compared to rats breathing air. While the oxygen concentration inside cells of rats breathing air or HBO is not known precisely, it is clear that the rate-limiting, IDO-catalyzed step in the brain KYN pathway (but not liver TDO) can be greatly accelerated in rats breathing HBO.     

Synthesis of novel tryptanthrin derivatives as dual inhibitors of indoleamine 2,3-dioxygenase 1 and tryptophan 2,3-dioxygenase

Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO) are promising drug development targets due to their implications in pathologies such as cancer and neurodegenerative diseases. The search for IDO1 inhibitor has been intensely pursued but there is a paucity of potent TDO and IDO1/TDO dual inhibitors. Natural product tryptanthrin has been confirmed to bear IDO1 and/or TDO inhibitory activities. Herein, twelve novel tryptanthrin derivatives were synthesized and evaluated for the IDO1 and TDO inhibitory potency. All of the compounds were found to be IDO1/TDO dual inhibitors, in particular, compound 9a and 9b bore IDO1 inhibitory activity similar to that of INCB024360, and compound 5a and 9b had remarkable TDO inhibitory activity superior to that of the well-known TDO inhibitor LM10. This work enriches the collection of IDO1/TDO dual inhibitors and provides chemical molecules for potential development into drugs.     

Evidence for a tumoral immune resistance mechanism based on tryptophan degradation by indoleamine 2,3-dioxygenase

T lymphocytes undergo proliferation arrest when exposed to tryptophan shortage, which can be provoked by indoleamine 2,3-dioxygenase (IDO), an enzyme that is expressed in placenta and catalyzes tryptophan degradation. Here we show that most human tumors constitutively express IDO. We also observed that expression of IDO by immunogenic mouse tumor cells prevents their rejection by preimmunized mice. This effect is accompanied by a lack of accumulation of specific T cells at the tumor site and can be partly reverted by systemic treatment of mice with an inhibitor of IDO, in the absence of noticeable toxicity. These results suggest that the efficacy of therapeutic vaccination of cancer patients might be improved by concomitant administration of an IDO inhibitor.     

Induction of tryptophan 2,3-dioxygenase in the mouse endometrium during implantation

Indoleamine 2,3-dioxygenase (IDO) is expressed in trophoblasts and defends the conceptus against rejection by reducing the tryptophan level and suppressing the T cell activity. We isolated a cDNA for tryptophan 2,3-dioxygenase (TDO), another key catabolizing enzyme of tryptophan, from a mouse uterus cDNA library enriched with pregnancy-induced genes. Northern blot and in situ hybridization analyses demonstrated that the TDO mRNA was induced in the decidualized stromal cells around the implanted embryo at the time of implantation. The expression was then upregulated and primarily localized at the mesometrial decidua. TDO mRNA was induced by deciduoma formation as well as embryo transfer but not by ovarian steroid hormones. These findings demonstrated that TDO is induced in the endometrial stromal cells concomitant with decidualization and suggested its involvement in the implantation process by regulating the tryptophan level at the implantation site.