叶黄素与叶酸的研究

叶黄素（Lutein）又名植物黄体素,分子式C40H50O2,易溶于氯仿、CO2,微溶于醇、醚,被认为是维生素的一个新品种。在复合维生素中加入一定比例的叶黄素对人体的保健起着重要作用。特别是在抗视力疲劳方面显现出一定的功效。在人的视网膜中除了特有的视紫红质（rhodopsin）之外,还含有叶黄素,一旦缺乏叶黄素必将引起视黄斑退化,损害视力,其致病机理和缺乏维生素A引起夜盲症类似。在美国,65岁以上的老人视黄斑退化占10％以上。除此之外,叶黄素在防病、抗癌和增强免疫力方面的作用也不可小视。它是人血液中主要类胡萝b素之一,对直肠癌、皮肤癌等多种癌症有抑制作用,例如它可保护皮肤不受紫外线照射的损伤,能大大减少皮肤癌的发生率,机体免疫力增强了。在膳食中摄入叶黄素不仅可以抑制肿瘤,还能预防肿瘤的发生。叶黄素还有利于预防心血管病的发生,延缓早期动脉硬化。这些充分显示了叶黄素对人体保健方面的重要价值。     

新型癌症疫苗有望用于治疗前列腺癌

最近英国报道,研究人员开发出一种制作癌症疫苗的新方法,由此制成的疫苗对患有前列腺癌的实验鼠治愈率较高,将来还有望用这种方法制造出能治疗其他癌症的疫苗。与普通疫苗起预防感染的作用不同,癌症疫苗的作用是诱使免疫系统攻击已经存在的肿瘤,从而帮助治疗癌症。     

氢分子在癌症防治中的应用进展

氢分子作为新型抗氧化剂,对多种由氧化应激和炎症引起的疾病具有良好的治疗效果。肿瘤发病机制复杂,预防和治疗难度大,一些恶性肿瘤的发生与慢性炎症和氧化应激相关,氢分子是否能够通过发挥抗炎症和抗氧化的作用预防癌症的发生并抑制肿瘤的发展得到广泛关注。现有研究表明,氢分子对多种肿瘤具有一定的预防和治疗作用,并能在肿瘤放化疗中起到减副增效的作用,提高患者生存质量。围绕氢分子在癌症预防和治疗方面的发展现状,综述了近年来氢分子在肿瘤研究方面的进展,并对未来的发展方向进行了展望,以期为氢分子在癌症防治中的应用提供参考。     

植物光破坏防御机制研究进展

光破坏防御机制是植物为应对复杂多变的自然环境而产生的保护措施,这些措施从形态、生理和生化等方面反映了植物对环境的适应能力。本文根据光抑制的机理,对近年来植物的光破坏防御机制以及高等植物叶黄素循环机制的研究现状进行综述,认为叶黄素循环防御机制是植物光保护作用的重要措施之一。     

叶酸在人体内作用的研究进展

叶酸Floic Acid是维生素B族中的一种,也是人体不可缺少的维生素,但人体不能合成,需由食物中获取。研究表明,叶酸缺乏可导致畸形儿出生、儿童肾衰、癌症、心血管疾病、老年性痴呆等疾病的发病率增高,补充叶酸除能有效减少上述疾病外,还有提高男性生育率,增强记忆力,预防硝酸甘油耐药性等效用。开发叶酸产品的前景看好。     

原花青素防癌抗癌作用研究进展

综述了原花青素对各种癌症的预防或治疗作用。     

叶黄素对人RPE细胞氧化应激损伤的保护作用

目的：外源性给予过氧化氢（H2O2）诱导构建人视网膜色素上皮细胞（Retinal pigment epithelial,RPE）细胞氧化损伤模型,探究H2O2的最佳建模浓度,并探讨叶黄素对H2O2诱导人RPE细胞氧化损伤的保护作用。方法：本研究以人RPE细胞为实验对象。不同浓度H2O2（0、50、100、200、400、600μmol/L）处理RPE细胞1 h后,观察细胞形态的改变,并测定细胞生存率和细胞内ROS浓度进而确定H2O2的最佳建模浓度。不同剂量叶黄素（1、2.5、5、7.5、10μg/mL）预处理RPE细胞24h,随后给予100μmol/L H2O2作用1h,测定各组细胞生存率和细胞内活性氧（ROS）浓度,从而评价叶黄素对RPE细胞氧化损伤的作用。结果：H2O2作用后,随H2O2浓度的增加,RPE细胞生存率逐步下降;细胞内ROS浓度随H2O2的浓度增加而显著升高。与损伤对照组相比,各叶黄素处理组RPE细胞生存率显著升高,同时细胞内ROS浓度显著下降。结论：H2O2可导致RPE细胞出现氧化应激损伤,细胞ROS含量显著增加。叶黄素干预后可显著减缓H2O2诱导的氧化应激反应,提示其可通过提高RPE细胞的生存率、抑制细胞内ROS浓度,保护RPE细胞免受氧化损伤,从而对年龄相关性黄斑变性等眼部退行性疾病起到预防和减缓作用。     

抗癌药物作用预测计算方法的研究现状与展望

对精准医疗即个体化医疗理念的探讨与实践是当下医学研究的热门课题,如果精准医疗的设想实现可为患者提供更加精确有效的治疗方案,而对癌症的研究是医学界尚未攻破且意义重大的研究课题,也是和精准医疗结合最密切的课题之一。应用生物信息学的计算方法可以通过分析患者的概况来为癌症患者的药物选择提供有效方案,从而提高癌症患者的生存率。通过参考多篇使用计算方法研究抗癌药物作用的研究成果,从数据源和网络分析、机器学习和深度学习等计算方法两个方面总结了当前的研究成果,并对该课题存在的问题与未来发展趋势做出了分析与展望。     

免疫疗法治疗癌症

开始是手术,然后是化学疗法和放射疗法。现在,研究人员已经突破了过去30年的传统思维,成功发现治疗癌症的第四种方法。该方法利用癌症疫苗,意在治疗癌症而不是预防癌症。     

关于癌病毒的探讨——从猴到人

<正>病毒作为癌症病原之一,是本世纪初,与化学物质同时提出来的问题。如果病毒能引起癌症,即使不同于一般病毒,也会有传染途径。那么,切断传染途径,能否预防。在免疫学上对病毒能否预防、诊断、治疗,这就是对所谓“癌病毒说”的一般期望。 但是,对癌症病毒的研究,特别是人癌病毒的研究,决不是容易研究的领域。1950年以前,停留在单纯的“癌病毒说”上,这     

Carotenoid actions and their relation to health and disease

Based on extensive epidemiological observation, fruits and vegetables that are a rich source of carotenoids are thought to provide health benefits by decreasing the risk of various diseases, particularly certain cancers and eye diseases. The carotenoids that have been most studied in this regard are β-carotene, lycopene, lutein and zeaxanthin. In part, the beneficial effects of carotenoids are thought to be due to their role as antioxidants. β-Carotene may have added benefits due its ability to be converted to vitamin A. Additionally, lutein and zeaxanthin may be protective in eye disease because they absorb damaging blue light that enters the eye. Food sources of these compounds include a variety of fruits and vegetables, although the primary sources of lycopene are tomato and tomato products. Additionally, egg yolk is a highly bioavailable source of lutein and zeaxanthin. These carotenoids are available in supplement form. However, intervention trials with large doses of β-carotene found an adverse effect on the incidence of lung cancer in smokers and workers exposed to asbestos. Until the efficacy and safety of taking supplements containing these nutrients can be determined, current dietary recommendations of diets high in fruits and vegetables are advised.     

Resonance Raman measurement of macular carotenoids in the living human eye

There is growing evidence that high levels of the macular xanthophyll carotenoids lutein and zeaxanthin may be protective against visual loss from age-related macular degeneration. To study this protective effect further, it is important to measure macular carotenoid levels noninvasively in a wide variety of subjects. We have developed and validated resonance Raman spectroscopy as a sensitive and specific objective method to measure macular carotenoid levels in the living human eye. In this minireview, the principles and implementation of ocular carotenoid resonance Raman spectroscopy are reviewed, and the results of observational cross-sectional studies and of prospective supplementation studies on subjects with and without macular pathology are summarized. We have recently extended this technology to an imaging mode which will further enhance our understanding of the roles of lutein and zeaxanthin in normal macular function and in the prevention of age-related visual loss.     

The anticancer activity of propolis

Propolis and its compounds have been the subject of many studies due to their antimicrobial and antiinflammatory activity; however, it is now known that they also possess antitumor properties. This review aims to summarize the results of studies on the mechanism of activity of propolis and its active compounds such as CAPE and chrysin in the apoptotic process, and their influence on the proliferation of cancer cells. Our review shows that propolis and its presented compounds induce apoptosis pathways in cancer cells. The antiproliferative effects of propolis, CAPE or chrysin in cancer cells are the result of the suppression of complexes of cyclins, as well as cell cycle arrest. The results of in vitro and in vivo studies suggest that propolis, CAPE and chrysin may inhibit tumor cell progression and may be useful as potential chemotherapeutic or chemopreventive anticancer drugs.     

The photoprotective role of carotenoids in higher plants

Carotenoids have two important roles in photosynthetic organisms. First, they act as accessory light-harvesting pigments, effectively extending the range of light absorbed by the photosynthetic apparatus. Secondly, they perform an essential photoprotective role by quenching triplet state chlorophyll molecules and scavenging singlet oxygen and other toxic oxygen species formed within the chloroplast. Only recently an additional, novel, protective role has been proposed for the carotenoid zeaxanthin, involving the dissipation of harmful excess excitation energy under stress conditions. Zeaxanthin may be formed through de novo synthesis in response to long-term environmental stress, and through the rapid enzymic de-epoxidation of the carotenoid violaxanthin (the xanthophyll cycle) in response to short-term alterations in the plant's light environment. Interspecific differences occur in the ability of plants and algae to produce zeaxanthin under stress conditions, and hence the ability to photoprotect the photosynthetic apparatus through this means varies from species to species. The ability of a plant to respond to light-mediated environmental stress by producing zeaxanthin may therefore affect, at least in part, the ability of that plant to inhabit or colonise certain habitats (e.g. sun or shade conditions).     

Cancer prevention by natural carotenoids

Various natural carotenoids were proven to have anticarcinogenic activity. Epidemiological investigations have shown that cancer risk is inversely related to the consumption of green and yellow vegetables and fruits. Since beta-carotene is present in abundance in these vegetables and fruits, it has been investigated extensively as possible cancer preventive agent. However, various carotenoids which co-exist with beta-carotene in vegetables and fruits also have anti-carcinogenic activity. And some of them, such as alpha-carotene, showed higher potency than beta-carotene to suppress experimental carcinogenesis. Thus, we have carried out more extensive studies on cancer preventive activities of natural carotenoids in foods; i.e., lutein, lycopene, zeaxanthin and beta-cryptoxanthin. Analysis of the action mechanism of these natural carotenoids is now in progress, and some interesting results have already obtained; for example, beta-cryptoxanthin was suggested to stimulate the expression of RB gene, an anti-oncogene, and p73 gene, which is known as one of the p53-related genes. Based on these results, multi-carotenoids (mixture of natural carotenoids) seems to be of interest to evaluate its usefulness for practice in human cancer prevention.     

Synergistic effects of zeaxanthin and its binding protein in the prevention of lipid membrane oxidation

There is growing evidence that high levels of the macular xanthophyll carotenoids lutein and zeaxanthin may be protective against visual loss due to age-related macular degeneration, but the actual mechanisms of their protective effects are still poorly understood. We have recently purified, identified and characterized a pi isoform of glutathione S-transferase (GSTP1) as a zeaxanthin-binding protein in the macula of the human eye which specifically and saturably binds to the two forms of zeaxanthin endogenously found in the foveal region. In this report, we studied the synergistic antioxidant role of zeaxanthin and GSTP1 in egg yolk phosphatidylcholine (EYPC) liposomes using hydrophilic 2,2'-azobis(2-methyl-propionamidine) dihydrochloride (AAPH) and lipophilic 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) as lipid peroxyl radical generators. The two zeaxanthin diastereomers displayed synergistic antioxidant effects against both azo lipid peroxyl radical generators when bound to GSTP1. In the presence of GSTP1, nondietary (3R,3'S-meso)-zeaxanthin was observed to be a better antioxidant than dietary (3R,3'R)-zeaxanthin. This effect was found to be independent of the presence of glutathione. Carotenoid degradation profiles indicated that the zeaxanthin diastereomers in association with GSTP1 were more resistant to degradation which may account for the synergistic antioxidant effects.     

Location of macular xanthophylls in the most vulnerable regions of photoreceptor outer-segment membranes

Lutein and zeaxanthin are two dietary carotenoids that compose the macular pigment of the primate retina. Another carotenoid, meso-zeaxanthin, is formed from lutein in the retina. A membrane location is one possible site where these dipolar, terminally dihydroxylated carotenoids, named macular xanthophylls, are accumulated in the nerve fibers and photoreceptor outer segments. Macular xanthophylls are oriented perpendicular to the membrane surface, which ensures their high solubility, stability, and significant effects on membrane properties. It was recently shown that they are selectively accumulated in membrane domains that contain unsaturated phospholipids, and thus are located in the most vulnerable regions of the membrane. This location is ideal if they are to act as lipid antioxidants, which is the most accepted mechanism through which lutein and zeaxanthin protect the retina from age-related macular degeneration. In this mini-review, we examine published data on carotenoid-membrane interactions and present our hypothesis that the specific orientation and location of macular xanthophylls maximize their protective action in membranes of the eye retina.     

Carotenoids are degraded by free radicals but do not affect lipid peroxidation in unilamellar liposomes under different oxygen tensions

It has been questioned whether carotenoids can act as antioxidants in biological membranes. Biological membranes can be modeled for studies of lipid peroxidation using unilamellar liposomes. Both carotenoid depletion and lipid peroxidation were increased with increasing oxygen tension in unilamellar liposomes. Carotenoids in such liposomes were found to be very sensitive to degradation by free radicals generated from iron and 2,2'-azobis(2-amidinopropane) dihydrochloride, but they were not protective against lipid peroxidation. Lycopene and beta-carotene were more sensitive to free radical attack than lutein, zeaxanthin, and beta-cryptoxanthin.     

The synthesis of NPQ-effective zeaxanthin depends on the presence of a transmembrane proton gradient and a slightly basic stromal side of the thylakoid membrane

In the present study we address the question which factors during the synthesis of zeaxanthin determine its capacity to act as a non-photochemical quencher of chlorophyll fluorescence. Our results show that zeaxanthin has to be synthesized in the presence of a transmembrane proton gradient. However, it is not essential that the proton gradient is generated by the light-driven electron transport. NPQ-effective zeaxanthin can also be formed by an artificial proton gradient in the dark due to ATP hydrolysis. Zeaxanthin that is synthesized in the dark in the absence of a proton gradient by the low pH-dependent activation of violaxanthin de-epoxidase is not able to induce NPQ. The second important factor during the synthesis of zeaxanthin is the pH-value of the stromal side of the thylakoid membrane. Here we show that the stromal side has to be neutral or slightly basic in order to generate zeaxanthin which is able to induce NPQ. Thylakoid membranes in reaction medium pH 5.2, which experience low pH-values on both sides of the membrane, are unable to generate NPQ-effective zeaxanthin, even in the presence of an additional light-driven proton gradient. Analysing the pigment contents of purified photosystem II light-harvesting complexes we are further able to show that the NPQ ineffectiveness of zeaxanthin formed in the absence of a proton gradient is not caused by changes in its rebinding to the light-harvesting proteins. Purified monomeric and trimeric light-harvesting complexes contain comparable amounts of zeaxanthin when they are isolated from thylakoid membranes enriched in either NPQ-effective or ineffective zeaxanthin.