金属硫蛋白基因表达水平评估青海不同地区的重金属污染程度

为揭示青海不同地区重金属污染的潜在生态风险,从玉树、果洛、海晏、刚察、共和5 个地区的牦牛肝脏样品中提取总RNA,在逆转录聚合酶的作用下生成cDNA,以逆转录产物为模板,利用实时定量PCR检测牦牛金属硫蛋白基因的表达水平。若将刚察地区牦牛肝脏金属硫蛋白cDNA实时荧光定量值作为对照组,2－ΔΔCt值设定为1时,则玉树、果洛、海晏、共和地区的牦牛肝脏金属硫蛋白cDNA实时荧光定量值分别为0.669、0.624、0.529、1.320,并且通过酶联免疫反应测定的牦牛体内金属硫蛋白的含量,相互印证,从而更加准确地评估青海不同地区牦牛机体重金属暴露水平,以便对牦牛产品安全进行评价。基因表达和酶联免疫反应的实验结果都表明,共和与刚察地区的重金属污染可能较为严重。     

Metals in aquatic ecosystems: mechanisms of uptake,accumulation and release‐Ecotoxicological perspectives

Metals are essential cofactors for bio‐chemical processes, including oxidative phosphorylation, gene regulation and free‐radical homeostasis. Abnormalities in metal ions concentration in organisms, lead towards the eco‐physiological hazards in the aquatics. In aquatic organisms, metal absorption involves transfer of metals to the circulatory system following : uptake by the apical membrane; movement through the cell as well as interaction with intracellular ligands and efflux across the basolateral membrane. Sequestration of metals in an immobilized form occurs throughout the various tissues and organs involved in pathways for metal uptake, transport, utilization and release. Metallothioneins, metal binding proteins, regulate the essential metals (Cu, Zn), detoxify the toxic metals (Cd, Hg) and play key role to the sequestering metals. Plasma proteins play the central role in metal transport in the vertebrates. Besides, blood cells in aquatic invertebrates, hemocytes in mollusks concentrate a variety of metals. Aquatic organisms utilize renal, digestive pathways and diapedesis for the excretion of a variety of metals.

This paper briefly reviews current information about the processes associated with metal uptake, transport, release, accumulation in the aquatic organisms and discuss about eco‐toxicological aspect of bio‐accumulation and suggest further necessary researches for future endeavor.     

A Zn(II)-glycine complex suppresses UVB-induced melanin production by stimulating metallothionein expression

Oxidative stress caused by ultraviolet (UV) radiation generates reactive oxygen species (ROS) in the skin, induces the secretion of melanocyte growth and activating factors from keratinocytes, which results in the formation of cutaneous hyper-pigmentation. Thus, increasing the anti-oxidative ability of skin cells is expected to be a good strategy for skin-lightening cosmetics. Metallothionein (MT) is one of the stress-induced proteins and is known to exhibit a strong anti-oxidative property. We previously reported that a zinc(II) complex with glycine (Zn(II)(Gly)(2)) effectively induces MT expression in cultured human keratinocytes. To determine its potential as a new skin lightening active, we examined whether Zn(II)(Gly)(2) regulates the release of melanocyte-activating factors from UVB-irradiated keratinocytes and affects melanin production in a reconstructed human epidermal equivalent. Conditioned medium from UVB-irradiated keratinocytes accelerated melanocyte proliferation to 110%, and that increase could be prevented by pre-treatment with Zn(II)(Gly)(2). In addition, Zn(II)(Gly)(2) significantly reduced both the production of prostaglandin E(2) and proopiomelanocortin expression in UVB-irradiated keratinocytes. Zn(II)(Gly)(2) also decreased melanin production in a reconstructed human epidermal equivalent. These results indicate that MT-induction in the epidermis effectively up-regulates tolerance against oxidative stress and inhibits the secretion of melanocyte growth and activating factors from keratinocytes. Thus, Zn(II)(Gly)(2) is a good candidate as a new skin-lightening active.     

Independent self-assembly of cadmium-binding {alpha}-fragment of metallothionein in Escherichia coli without participation of {beta}-fragment

We examined the independent self-assembly of the - and ß-fragmentsof human metallothionein (MT) into cadmiumbinding conformationin an Escherichia coli expression system, in addition to wild-typeMT expression. The expressed -fragment formed independentlythe structure of a metal-binding cluster without the aid ofthe ß-fragment. The -fragment and wild-type MT expressedin E.coli were purified and analyzed for their biochemical andspectroscopic properties. The apparent cadmium binding of the-fragment was approximately 12-fold greater than that for thewild-type MT, whereas in other respects the studied biochemicalproperties were similar. In contrast, we were unable to obtainany independently expressed ß-fragment as the cadmium-bindingform in this study. Possible explanations for this phenomenonare discussed.     

转金属硫蛋白基因平菇对受辐照、衰老和铅中毒小鼠抗氧化能力的影响

研究了转金属硫蛋白基因平菇对不同模型小鼠抗氧化能力的影响。结果表明:在小鼠饲料中掺入1%和3.16%的转金属硫蛋白基因平菇干粉(前者相当于50～60kg体重的人每日摄食鲜菇1kg),可明显增强受辐照小鼠血清SOD活性,降低其血清MDA含量;明显增强铅中毒小鼠血清SOD活性和抗活性氧能力;对衰老小鼠血清SOD活性的降低、MDA含量的升高无明显改善作用。结论:转金属硫蛋白基因平菇可提高受辐照和铅中毒小鼠的抗氧化能力,对增强D-半乳糖致衰老模型小鼠抗氧化能力无明显效果。     

金属硫蛋白对鲤鱼不同组织重金属蓄积影响的研究

金属硫蛋白(Metallothionein,简MT)能有效地表征水体中重金属对生物的影响,故以MT作为生物标志物,采用ELISA法测定鲤鱼组织中MT的含量,以鲤鱼各组织中MT的含量动态变化来评价在其受重金属胁迫下不同组织对重金属的蓄积规律。探讨鱼体内MT与水环境和体内组织中重金属之间的相关性。对深入研究鱼体自身对重金属的蓄积和净化机制、对不同重金属耐受力、确定污染源及污染程度等具有重要意义。