微囊藻毒素污染及其促肝癌作用研究进展

淡水水体的富营养化导致了蓝藻水华的普遍发生,微囊藻毒素是由蓝藻的部分藻属产生的环肽化合物,具有毒性大、分布广、结构稳定等特性,从而成为水环境中的重要潜在危害物质。微囊藻毒素已被证明具有明显的肝毒性,是肝肿瘤的促进剂之一。本文就微囊藻毒素的污染现状、肝毒性作用及其促肝癌机制等方面的研究进展进行了综述。     

藻类毒素对健康危害和控制的研究进展

近年来由于生活污染和工业污染加剧,人类向水体排放了大量含N、P的有机物,使水体富营养化程度加剧,造成藻类大量繁殖,藻类在代谢过程中或藻体破裂后向水体中排出藻毒素,主要有毒成分为微囊藻毒素(MC),MC是一类具有生物活性的环状七肽化合物.近几十年来,国内外动物试验、人群流行病学调查表明MC具有机体肝毒性、促癌、胚胎毒性、遗传毒性、免疫损害等作用,我们就有关藻毒素对健康影响的研究进展作一简要综述.     

微囊藻毒素的毒性及健康效应研究进展

由于水中氮、磷含量的急剧增加，导致水华在世界各地频频发生。除引起生态恶化外，因某些藻种所产生的藻毒素也给人类健康构成威胁。而淡水水华中目前最常见、对其毒性研究最为深入的是微囊藻毒素(Microcystin，MC)。且因其可能在饮用水中出现，世界卫生组织已把饮用水中MC的代表亚型MC-LR的基准值制订为1μg／L。本文对其理化性质、毒性表现、作用机制及流行病学调查的新进展作一综述。     

微囊藻毒素诱导细胞凋亡研究进展

由于工农业排污和生活排污日趋增多，水体污染日益严重。引发藻类水华频繁爆发，已成为全球广泛关注的环境问题。其中以铜绿微囊藻（Microcystin aeruginosa）、水花鱼腥藻（Anabaena flos-aquae）、颤藻（Oscilllation aeruginosa）等产生的有毒成分微囊藻毒素（microcystin．MC）对人体健康危害最为严重。近年来，对微囊藻毒素的毒性研究已受到关注并取得了初步成果，但具体的毒性机制尚未明确。研究认为，细胞凋亡是毒索发挥其毒性作用的关键所在，因而微囊藻毒素致细胞凋亡的研究是热点之一。本就相关研究进展作一综述。     

我国水源水及饮用水中微囊藻毒素的污染现状及影响因素研究

微囊藻毒素是地表水中常见的藻毒素,广泛分布于全世界各种类型的水域。目前已知微囊藻毒素-LR具有极强的肝毒性,达到极低浓度即可对人体健康造成严重危害,因此对于集中式供水水源地正遭受微囊藻毒素污染的报道尤为引人关注。本文综述了近年来关于我国水源水及出厂水中微囊藻毒素的污染现状及与疾病的关系,探讨了微囊藻毒素浓度变化的相关影响因素,为加强对水源水及饮用水中微囊藻毒素的监测和治理,保护人民群众的身心健康提供科学的依据。     

福建水华微囊藻毒素主要亚型及其亚慢性肝毒性

目的鉴定福建省某水库水华微囊藻毒素的主要亚型，研究该毒素对大鼠的亚慢性肝毒性。方法采集微囊藻水华，固相萃取法提取微囊藻毒素，以微囊藻毒素LR和RR纯毒素为标准，高效液相色谱法测定其亚型；SD大鼠0．42μg／（ks bw）MC-LR亚慢性染毒35d，观察血清酶学和组织病理学改变。结果该微囊藻水华检测出MC-LR，未检测出MC-RR；用藻细胞裂解液[相当于0．42μg／（ksbw））MC-LR]亚慢性染毒大鼠，血清SOD活性显著降低，SDH水平显著升高，肝脏系数显著增大，肝组织出现炎症样变化。结论福建某水库水华微囊藻毒素的主要亚型为MC-LR；亚慢性接触0．42μg／（ks bw）MC-LR的微囊藻毒素可引起肝损伤。     

上海淀山湖,黄浦江水系浮游藻类及藻类毒素的动态研究

通过对淀山湖，黄浦江水系浮游藻类的种群构成和蓝藻毒素的季节变化进行周年监测，发现淀山湖藻类及其毒素的污染具有明显的性，７－９月份蓝藻大量繁殖，形成了一年中污染的高峰，优势种群已由隐藻毒性较高的蓝藻所取代，而蓝藻中占优势的铜绿微囊藻，水华鱼腥藻等能产生一种具有强烈肝毒性的短肽，称为微囊藻毒素。     

饮水微囊藻毒素在实验性肝癌形成中对遗传物质的损伤作用

[目的]探讨饮水摄入微囊藻毒素在大鼠实验性肝癌形成模型中对遗传物质的损伤作用。[方法]建立微囊藻毒素促大鼠肝癌前病变的短期实验模型，检测饮水摄入低剂量微囊藻毒素在促肝癌作用的同时诱导骨髓嗜多染红细胞微核的作用。[结果]染毒组大鼹 骨髓嗜多染红细胞微核率明显升高。分别为：饮藻水 二乙基亚硝胺（DEN）启动组11.67‰，腹腔内注射微囊藻纯毒素 DEN启动组14.57‰，与DEN启动组6.80‰比较，有显著性差异。[结论]饮用受微囊藻毒素污染的水，可增强DEN对遗传物质的损伤。     

微囊藻毒素对鱼类免疫毒性的研究进展

微囊藻毒素(microcystins,MCs)是富营养化水体中最常见、毒性最强、研究最广泛的一类藻毒素,已经引起了广泛的关注。MCs除具有典型的肝毒性外,还具有免疫毒性。笔者主要从免疫器官的病理变化、免疫细胞、免疫相关酶以及基因等方面综述了MCs对鱼类免疫毒性的研究现状,进而系统梳理了MCs对鱼类的免疫毒性作用机制,可为有效预警环境中MCs的潜在风险提供支持。     

用血凝法检出淡水中的蓝藻毒素

在世界许多地区的淡水水域中,某些藻类可引起人、畜和水禽中毒,特别是藻花中的水华鱼腥藻(Anabaena flosaguae)和铜锈微囊藻(Microcystis aeruginosa)能产生小分子肽的致病毒素。此类毒素类似植物凝血素(Lectin),可以与人和动物的红细胞发生凝集反应。本实验根据此原理来定性检测自然淡水水体中此等藻类毒素存在与否。动物实验表明,这类小分子肽毒素主要引起肝中毒。并已知道不同的水华鱼腥藻菌株可产生鱼腥藻毒素(Anatoxin)a、-a(s)、b、-b(s)、-c和d六种毒素;铜锈微囊藻可产生一种微囊藻毒素(Microcystin)。检测的步骤是:采集、分离、浓集野外藻     

Microcystin Concentrations in the Nile River Sediments and Removal of Microcystin-LR by Sediments During Batch Experiments

During the present study, microcystin (MCYST) concentrations in the Nile River and irrigation canal sediments, Egypt, were investigated during the period January–December 2001. Batch experiments were also conducted to confirm the adsorption of MCYSTs on these sediments. The results of field study showed that MCYST concentrations in the sediments were correlated with total count of cyanobacteria, particularly Microcystis aeruginosa, and MCYST within phytoplankton cells in most sites. No detectable levels of MCYSTs were found in the cell-free water of all studied sites in the Nile River and irrigation canals during the entire study period. The data obtained from batch adsorption experiments confirmed the capability of the Nile River and irrigation canal sediments for MCYST adsorption; and that adsorption was sediment weight-dependent and thus fitted the Freundlich adsorption isotherm. The results also revealed that both adsorption capacity (K_f) and intensity (1/n) varied significantly with clay and organic matter contents of these sediments. The results of present study have two implications. First, the presence of cyanobacterial toxins in freshwater sediments can affect benthic organisms inhabiting these sediments, and thus it should be considered during biological monitoring of rivers and streams. Second, the ability of freshwater sediments to adsorb cyanobacterial toxins suggests that bank filtration could be used in developing countries (e.g., Egypt), which require an inexpensive and low-maintenance method for removing these toxins from drinking water.     

微囊藻毒素和水体有机污染物联合诱导SHE细胞转化及相关癌基因的变化

应用ＳＨＥ细胞体外二阶段转化实验和免疫组化方法，分析了上海淀山湖水体有机污染物和微囊藻毒素（ＭＣＹＳＴ）联合诱导ＳＨＥ细胞恶性转化的作用，发现微囊藻毒素单独作用不能诱发ＳＨＥ细胞转化，但可明显促进低剂量水体有机污染物启动的细胞恶性转化。在典型的Ⅲ型转化灶细胞中ｒａｓＰ２１蛋白表达明显增强。提示：微囊藻毒素具有促癌作用，二阶段诱导的转化细胞中ｒａｓ癌基因被激活。     

Bioaccumulation of microcystins by fish associated with a persistent cyanobacterial bloom in Lago de Patzcuaro (Michoacan, Mexico)

Lago de Patzcuaro is a historically important freshwater fishery in Mexico. The lake is presently characterized by a persistent bloom of cyanobacteria, specifically dominated by recognized producers of toxic microcystins (MCYSTs). We evaluated MCYSTs in sestonic and dissolved fractions of the water column, as well as representative fish species (silversides, Chirostoma spp.; Goodea sp.; and carp, Cyprinus carpio) obtained from local markets and small commercial catches during the bloom. Samples were evaluated primarily by enzyme-linked immunosorbent assay (ELISA), and secondarily by protein phosphatase (PPase) inhibition assay and liquid chromatography-mass spectrometry (LC-MS). Sestonic MCYST concentration (0.02-0.36 μg/L) generally correlated inversely with distance from the bloom, supporting the bloom as the source of the toxin. Several MCYST variants, including MC-LR, -LA and -LY, as well as didemethyl variants, were identified by LC-MS/MS analysis. All three species of fish bioaccumulated MCYSTs in relevant tissues, and toxin content correlated with trophic level, with highest and lowest levels measured in phytoplanktivorous and zooplanktivorous representatives, respectively. Detection of MCYST in silversides and Goodea sp. is particularly relevant because both are consumed in their entirety, including viscera (e.g., liver) known to primarily accumulate MCYST. These results indicate that Lago de Patzcuaro is indeed characterized by a toxigenic bloom, and that commercially important fish species from the lake accumulate toxic MCYST in tissues relevant to human consumption. As such, this system may represent an ideal model of the trophic transfer of MCYSTs and its relevance to human and environmental health.     

Depuration of microcystins in tilapia fish exposed to natural populations of toxic cyanobacteria: a laboratory study

Previous studies demonstrated that microcystins (MCYSTs) can be accumulated in different organs, particularly the liver, of tilapia fish (Oreochromis niloticus) in an Egyptian fish farm containing toxic blooms of Microcystis aeruginosa. In the present study, a microcosm experiment was conducted to examine the depuration of MCYSTs in tilapia fish from this fish farm. Fish were grown in a 100-L aerated recirculation tank containing dechlorinated water at room temperature (25+/-2 degrees C) for 96 h. MCYST concentrations in livers, intestines, and gallbladders of each daily sacrificed fish were determined by both enzyme-linked immunosorbent assay (ELISA) and protein phosphatase inhibition assay (PPIA). MCYST concentrations in the surrounding water were also determined by the same methods. The results showed that MCYST concentrations in the liver and intestine decreased gradually throughout the experimental period. This decrease was accompanied by an increase in MCYST concentrations in the gallbladder and surrounding water. The maximum value of MCYST in the surrounding water was obtained after 96 h at a level of 1.2 microg/L by ELISA, while it was obtained after 24 h at a level of 0.5 microg/L by PPIA and remained stable until the end of the experiment. The present study revealed that tilapia fish can depurate and excrete MCYSTs into the bile and surrounding water as a way to avoid toxicity from such a potent hepatotoxin.     

上海淀山湖、黄浦江水系浮游藻类及藻类毒素的动态研究

通过对淀山湖、黄浦江水系浮游藻类的种群构成和蓝藻毒素的季节变化进行周年监测，发现淀山湖藻类及其毒素的污染具有明显的季节性，７～９月份蓝藻大量繁殖，形成了一年中污染的高峰。优势种群已由隐藻被毒性较高的蓝藻所取代，而蓝藻中占优势的铜绿微囊藻、水华鱼腥藻等能产生一种具有强烈肝毒性的短肽，称为微囊藻毒素。应用ＥＬＩＳＡ方法对淀山湖水中的微囊藻毒素进行测定，结果表明水体中微囊藻毒素与蓝藻的变化规律呈正相关，夏、秋季水中毒素出现高峰，最高值达５５．４ｎｇ／ｍｌ，说明淀山湖藻类毒素的污染较为严重。通过对水体总磷、总氮、叶绿素ａ、ｐＨ值等因素的分析，讨论了影响该水系营养水平和藻类生长的主要因素。     

Microcystins (cyanobacterial toxins) in surface waters of rural Bangladesh: pilot study

In Bangladesh the exposure of millions of inhabitants to water from (shallow) tube wells contaminated with high geogenic loads of arsenic is a major concern. As an alternative to the costly drilling of deep wells, the return to the use of surface water as a source of drinking water is considered. In addition to the well-known hazards of water borne infectious diseases associated with the use of surface water, recently the potential public health implications of toxic cyanobacteria have been recognized. As a first step towards a risk assessment for cyanotoxins in Bangladesh surface waters, seston samples of 79 ponds were analysed in late summer 2002 for the presence of cyanobacteria and microcystins (MCYST), the most frequently detected cyanobacterial toxins worldwide. Microcystins could be detected in 39 ponds, mostly together with varying abundance of potentially microcystin-producing genera such as Microcystis, Planktothrix and Anabaena. Total microcystin concentrations ranged between <0.1 and > 1,000 microg l(-1), and more than half of the positive samples contained high concentrations of more than 10 microg l(-1). The results clearly show that concentrations of microcystins well above the provisional WHO guideline value of 1 microg l(-1) MCYST-LR can be frequently detected in Bangladesh ponds. Thus, an increasing use of surface water for human consumption introduces a risk of replacing one health hazard by another and therefore needs to be accompanied by cyanotoxin hazard assessments.     

First Report of a Microcystin-Containing Bloom of the Cyanobacteria <Emphasis Type="Italic">Microcystis</Emphasis> spp. in Lake Oubeira,Eastern Algeria

Lake Oubeira has been used as the main source of drinking water for many communities in the East of Algeria. In this lake, nutrient loading coupled with year-round warm weather favors the growth of cyanobacteria, several of which can produce cyanotoxins, especially the potent liver toxins called microcystins (MCYSTs). The present study evaluated microcystin levels and characterized the different microcystin variants present in the raw water during a 17-month period (April 2000–September 2001), as measured by protein phosphatase inhibition assays and by matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry, respectively. The results showed that microcystin concentrations in the lake water varied between 3 and 29,163 g microcystin-LR equivalent per liter. The microscopic examination of the phytoplankton samples showed the dominance of the Microcystis genus in the cyanobacterial bloom. The highest MCYST concentration was observed in August 2001, at 29,163 g/l. Therefore, the highest total MCYST content per phytoplankton biomass was found in August 2001, with 4,590 g MCYST-LR equivalents/g dried bloom material. Analysis of the field bloom extract by MALDI-TOF mass spectrometry demonstrated the presence of four variants of microcystins: microcystin-LR (MCYST-LR), microcystin-YR (MCYST-YR), microcystin-RR (MCYST-RR), and a demethylated variant of MCYST-LR (D-MCYST-LR).     

郑州市水源水藻类和藻类毒素污染调查

１９９６年－１９９７年对郑州市水源水藻类污染状况进行了连续检测,采用高敏感度ＥＬＩＳＡ方法测定了微囊藻毒素含量。结果表明,郑州市水源水藻类的生长有明显的季节特征,２月及１２月份,是藻类生长的两个高峰期,藻类总密度最高达到１０６８万个／Ｌ。１９９５年７月、１９９６年１月郑州水源厂调蓄池水微囊藻毒素含量均超过２００ｎｇ／Ｌ。按照Ｃａｒｌｓｏｎ提出的富营养化指数ＴＳＩ判定标准,结合总氮、总磷、ＣＯＤ及藻类密度等指标,认为郑州市水源水已呈现富营养化特征。建议对郑州市水源水藻类毒素的季节变化,浮游藻类的密度、组成及优势藻种的生长变化规律等做进一步的研究。     

Toxicity assessment of Clostridium difficile toxins in rodent models and protection of vaccination

Clostridium difficile is the leading cause of hospital-acquired diarrhea, also known as C. difficile associated diarrhea. The two major toxins, toxin A and toxin B are produced by most C. difficile bacteria, but some strains, such as BI/NAP1/027 isolates, produce a third toxin called binary toxin. The precise biological role of binary toxin is not clear but it has been shown to be a cytotoxin for Vero cells. We evaluated the toxicity of these toxins in mice and hamsters and found that binary toxin causes death in both animals similar to toxins A and B. Furthermore, immunization of mice with mutant toxoids of all three toxins provided protection upon challenge with native toxins. These results support the concept that binary toxin contributes to the pathogenicity of C. difficile and provide a method for monitoring the toxicity of binary toxin components in vaccines.     

实验条件下氮、磷对微囊藻毒素产生的影响

目的探讨在实验条件下氮、磷及氮磷比值对微囊藻毒素产生的影响。方法将经过扩大培养3次的铜绿微囊藻细胞接种于无氮、无磷的BG-11培养液中饥饿培养3天,分别接种到含有0、0.5、1.0、5.0、10.0mg/L磷的BG-11培养液中培养20天;接种于含磷0.05、5.0mg/L的BG-11培养液中,并分别按照氮:磷物质量比5∶1、10∶1、20∶1、50∶1、100∶1加入所需的NaNO3,培养20d。观察各组铜绿微囊藻细胞计数的变化。并于培养的第8、12、16、20天将藻细胞破碎,提取毒素,用高效液相色谱测定微囊藻毒素的量。结果当磷初始浓度低于5.0mg/L时,微囊藻毒素的产量随培养液中初始磷浓度的升高而增高。而当培养液中磷初始浓度为10.0mg/L时,磷对微囊藻毒素的产量产生了抑制作用。磷初始浓度为0.05mg/L的培养液中,氮磷比值在50:1时,细胞中微囊藻毒素的含量最高,在磷初始浓度为5.0mg/L的培养液中,氮磷比值为20:1时,细胞中微囊藻毒素的含量最高。与培养液中微囊藻细胞具有最大生物量时的氮磷比值相同。结论磷对于微囊藻毒素的产生具有十分重要的影响,应综合探讨磷浓度和氮磷比值对微囊藻毒素产生的影响。通过各种手段控制水体中的磷浓度可能是解决微囊藻毒素产生的有效途径。