CNN：研究表明空气污染中的超细颗粒可以进入大脑组织

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近期CNN报道了一个研究报告，表明雾霾中的部分解超细颗粒物可以进入人的大脑对人体造成伤害。
WHO报告说全球每年因空气污染有130万人死亡，但研究者相信空气污染造成的伤害不仅如此，他们认为部分老年痴呆症也与空气污染相关。
Air pollution particles found inside human brains

Story highlights

• Magnetite particles are commonly found within air pollution
• A new study has found magnetite particles inside human brain samples
  

(CNN)Another new concern could be on the horizon for city dwellers, particularly those living in the more polluted cities of the world, as a new study has found that certain particles found within pollution could enter the human brain -- by people breathing them in.
The particles discovered, known as magnetite, are less than 150 nanometers in size -- smaller than the width of a human hair -- and commonly form inside engines and open fires. But researchers at Lancaster University in the UK found them inside the frontal cortex of the human brain during their recent studypublished Monday.
Brain samples from 37 people who lived in either Mexico City or Manchester in the UK were analyzed for levels of magnetism, to see if any particles were present, and the six most magnetic were then visualized using spectroscopy to decipher which particles were present and what they were made of. The answer was this harmful pollutant.
"Magnetite is toxic to the human brain," said Barbara Maher, a professor of environmental science at the University of Lancaster who led the study. "And magnetite particulates are always present in pollution."
Magnetite is a mineral form of iron and is believed to be toxic due to its ability to easily react and release other particles, known as free radicals, which cause oxidative stress within brain cells, damaging and killing them in the process.
A tale of two particles
Maher discovered two forms of magnetite particle inside the brain samples, with each having a different story behind how they got there.
One form of the particle was angular or jagged in shape and is known to form naturally inside the human brain. The other was more spherical in shape, resulting from them being formed in high temperatures, such as inside a car engine, and associated with various other metals, such as platinum and nickel. As a result, the latter also had a unique size, texture and composition as well as their distinct shape, which indicates coming from pollution.
"These, altogether, are a total match with atmospheric pollution particles," said Maher. To verify this, the team compared the particles with those obtained from atmospheric pollution that was pumped from various roadsides. "It's pretty convincing," she said.

The two forms of magnetite can be distinguished based on shape, with the natural forms more angular and jagged while the pollutant forms are more spherical.




There were also many more of the rounded particles, with 100 of them for every angular one found inside the brain samples.
The more angular version, thought to occur naturally within the brain, may also have natural measures in place to protect the brain. "If the brain has produced them itself, they may be safely encased within some kind of membrane or cellular envelope in order to reduce their [in-cell] reactivity," said Maher.
More research is needed to determine whether this is true.
Entry into the brain
The team studied the frontal cortex region of the brain samples they obtained, which can be accessed from someone's olfactory bulb located at the top of their nose. The team believe this is the entry point of the particles into the brain.
"There's no blood-brain barrier there," said Maher, adding that the particles could then be transported to other regions of the brain. "That's a real vulnerability."
The miniscule size of the particles also reduces the chances of them being trapped by hairs and mucus that line your nose -- your body's natural barrier -- further aiding them getting into your bloodstream and then your brain.
Outdoor air pollution is estimated to cause 1.3 million deaths worldwide per year, according to the World Health Organization. It is considered a risk factor for acute and chronic respiratory disease.
But Maher's team believes this particular pollutant could increase someone's risk of developing Alzheimer's disease.
A risk of Alzheimer's?
Previous studies have been linked to the presence of magnetite in the brain to the occurrence of Alzheimer's disease and Maher believes this could be caused by the development of these free radicals, which in turn cause damage inside the brain. The particles could also cause other brain conditions.
"For now, these are potential environmental risk factors for Alzheimer's [disease]," said Maher. But evidence of this is limited and other experts stress the need to look into this further.
"I think any correlation with this and Alzheimer's disease is weak," said Dr. Jennifer Pocock from the University College London Institute of Neurology. "The authors admit that these particles would enter by the olfactory unit, but a damaged one is needed. How likely is this in the general population and does this correlate with the cases of Alzheimer's disease linked to magnetite in the brain?"




Pocock added that more needs to be done to correlate the magnetite concentrations among patients who lived primarily in a city against patients living in relatively unpolluted area to see if "analyses of their Alzheimer's disease brain pathology correlate with magnetite concentrations."
Maher's team are planning to gain more insight from larger epidemiological studies as well as further studies exploring the true toxicity of these particles.
"If these particles are having an impact, then as a society we need to do something about it," said Maher. "That's what we now need to go and investigate."



http://www.cnn.com/2016/09/06/health/air-pollution-inside-the-brain/

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早前研究及类似新闻

新证据：空气污染与自闭症相关
　　一项发表于《环境与健康展望》的研究显示，早年所经历的空气污染可能导致小鼠大脑发生多种有害变化，而这些现象也可见于自闭症及精神分裂症患者。
　　对于人类自闭症及精神分裂症患者，上述改变主要发生在男性中。另外，在短期记忆、学习能力及冲动控制方面，暴露于污染空气的小鼠同样表现欠佳。
　　该项研究结果与先前数项研究结果一致，即空气污染与儿童自闭症相关。尤其值得关注的是2013年发表于《美国医学会杂志?精神病学》的一项研究，该研究显示，0-1岁之间生活在交通相关空气污染较严重地区的儿童,罹患自闭症的风险为其他儿童的3倍。
　　“我们的研究为以下观点进一步增加了证据，即空气污染可能在自闭症及其他神经发育障碍的发病中扮演了某种角色。”主要研究者、罗彻斯特大学环境医学系教授Deborah Cory-Slechta指出。
　　研究者采用了三种研究设计。Cory-Slechta教授及其同事将小鼠暴露于污染空气中，其主要成分为高浓度大气超细颗粒物，研究者在暴露完成后24小时检查了第一组小鼠的大脑。结果显示，该组所有小鼠脑内均存在广泛分布的严重炎症，且双侧的侧脑室体积扩大至正常的2-3倍。
　　另外两组小鼠大脑也存在同样的问题，研究者分别在暴露后40天及270天对其进行了检查。这一结果证明，污染空气对大脑的损害是永久性的。研究还显示，三组小鼠大脑中谷氨酸盐水平均有所升高，这一现象同样见于自闭症及精神分裂症患者。
　　数十年来，针对空气污染损害身体的研究多聚焦于受累最为明显的器官——肺。研究显示，直径不同的污染物颗粒对身体的影响也有所不同。事实上，直径最大的颗粒危害反而最小，因为人们可通过咳嗽将其排出；直径更小的颗粒，也就是所谓超细颗粒的危害更大，因为这种污染物小到可以深入肺部并被吸收入血，导致全身性的毒性反应。
　　这一观点促使Cory-Slechta教授设计了上述试验。该研究同时也是首项同时探讨超细颗粒对大脑的影响及其作用机制的研究。
　　“我认为，本项研究将一个新问题摆上了台面：现行针对空气质量的管理标准是否足够保护我们的孩子。”Cory-Slechta教授称。
　　--自然整体医学

http://health.sohu.com/20160808/n463136434.shtml

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自闭症的证据？吸入超细颗粒物与小鼠大脑变化
http://ehp.niehs.nih.gov/ehpce/?p=3451

流行病学证据表明， 空气污染物暴露可能是自闭症谱系障碍（autism spectrum disorders, ASDs）和精神分裂症的危险因素。例如，近期的一项研究显示， 居住在加利福尼亚州的那些在孕期及出生后第一年暴露于交通来源空气污染的孩子中， 最高暴露水平的孩子发展为自闭症的风险是最低暴露水平的2倍。在一篇发表在EHP [(122(9):939-945 (2014)]的论文中，研究者们提出的实验室研究结果可能能够解释这些现象。

出生后14 天对照小鼠（A）和暴露组小鼠（B）侧脑室图片，显示颗粒物暴露致侧脑室增大（此处标注为“浓缩颗粒物”或CAPs）。
Allen at al. (2014)

由罗切斯特大学医学中心（University of Rochester Medical Center, URMC）的Deborah Cory-Slechta率领的团队发现，生命早期暴露于超细颗粒物会引起小鼠大脑变化，与ASDs和精神分裂症病人的大脑变化相类似。值得注意的是，暴露于超细颗粒物的雄性小鼠的侧脑室明显扩大，人脑的这种现象被称为脑室扩张。“这种变化是惊人的，因为人类的脑室扩张可引起一系列行为的改变，”包括ASDs和精神分裂症， Cory-Slechta说道。

研究者们将出生后4~7天和11~13天的小鼠暴露于超细颗粒物（直径＜100纳米）中，每天染毒4小时，颗粒物浓度与大城市交通高峰期的浓度相仿。小鼠出生后2个星期相当于人类妊娠的第三期，是脑部发育的一个关键时期，Cory- Slechta说。

染毒后24小时后检查发现，暴露组雌性小鼠的大脑出现炎症改变，而雄性的侧脑室较正常大2~3倍。雌性小鼠在出生后55天（小鼠的青春期）仍能检测到脑部的炎症变化，而雄性小鼠脑室扩张则持续至出生后270天（成年后期），提示永久性脑损伤。

“我们以前从不认为超细颗粒物对大脑具有明显的毒性。现在是时候考虑这种可能性了，”文章的第一作者、URMC的研究助理教授Joshua Allen说道。在其他的小鼠研究中，URMC的研究团队还报道了吸入超细颗粒物与行为和记忆改变间的关联，说明超细颗粒物可损伤神经发育。

在美国，8岁男孩的ASDs发病率估计为1/42，女孩为1/189。作者的说法是，儿童早期暴露于超细颗粒物可能是ASDs发生的一个危险因素。然而，更重要的是，尽管研究结果提示了这些关联，但从这些结果推论出空气污染导致自闭症的结论还为时过早。

并未参与该项研究的华盛顿大学西雅图分校的毒理学教授Lucio Costa认为，新的研究结果提供了超细颗粒物对神经系统发育的潜在影响的新信息。这些结果也为空气污染暴露与神经发育异常的因果关系添加了证据。“这一研究领域值得进一步研究探讨这些关联和潜在的机制，”Costa说道。

senwater

另一篇文章，讨论了纳米颗粒物的中枢神经毒性效应，研究表明 纳米颗粒可跨越血脑屏障进入大脑, 并不损伤血脑屏障完整性。

也就是说在污染情况下，纳米级的细微颗粒物对人体的伤害更大。

纳米颗粒物的中枢神经毒性效应.pdf (1.27 MB, 下载次数: 2879)

2016-9-20 18:17 上传

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