What Does Lead Do to the Brain?

  • By Anna Rothschild
  • Posted 05.31.17
  • NOVA

How does lead poisoning damage the brain—and can we stop it? Gross Science investigates. 

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Running Time: 05:21

Transcript

What Does Lead Do to the Brain?

Published May 31, 2017

Lead is a sneaky little element. It’s malleable and durable, so it’s no wonder that for years we used it in piping and added it to paint. But it’s also extremely poisonous. It can create problems all over the body—from rashes, to abdominal pain, to anemia. But the most serious effects occur in the brain—and especially in the brains of children. It can cause headaches, memory loss, learning disabilities, behavioral issues, and seizures. And kids don’t even have to be exposed directly. Women who wind up ingesting lead can store it in their bones. And if they get pregnant, that lead can be passed on and damage the brains of their children.

Lead poisoning is still a big problem in the US today—and not just in communities you may have heard of, like Flint, Michigan. So, what’s actually happening to the brain when you have lead poisoning? And is there anything we can do to stop it?

I’m Anna and this is Gross Science.

Lead messes with our brains in a few different ways. But to understand what they are, let’s look really quickly at how brain cells—or neurons—communicate: and I promise, this will be short, sweet, and hopefully deeply enlightening.

Ok, so neurons have a long tail called an “axon” at one end, and branch-like structures called “dendrites” at the other. They talk to one another when the axon from one cell sends chemical signals to another cell’s dendrites. The receiving cell can then pass the message on to yet another neuron. And all that communicating happens in this tiny gap between the cells called the “synapse.”

One thing lead can do is block those chemical signals from being sent, which sounds bad enough. But, lead does another thing that can have even more long-term effects. It can make the synapse—that connection between your neurons—become weaker over time.

You see, in order for neurons to maintain a strong connection, the axon needs to know that the dendrite is receiving its messages. So the dendrite produces a molecule that lets the axon know it’s being heard loud and clear. That molecule is called BDNF, and you can kind of think of it like the best-friends molecule. It makes the axon and dendrite’s relationship even stronger.

But, in order for the cell to produce BDNF, it needs calcium. Calcium usually enters the dendrite through channels, which act like a door that opens for a little while when a signal is received. When the door’s unlocked by the right set of molecules, calcium flows through freely. But when lead’s present, it jams the door, preventing calcium from entering and keeping BDNF from being made. That means that the connections between brain cells start to wither.

In adults, having poor connections between your neurons is harmful enough. But in children, with their fast growing brains, it’s especially dangerous—not to mention that the amount of lead needed to cause brain damage in kids is much smaller, in part because their brains are making (and removing) new connections at much faster rates.

Sadly, in the past there haven’t been great treatments for lead poisoning—and especially not for its effects on the brain. But recently, scientists have shown that simply by adding a BDNF substitute, neurons may be able to bounce back.

Here’s a video showing this process in action. On the left are normal cells, in the middle are cells exposed to lead, and on the right are cells exposed to lead that have been given BDNF. When the green dye disappears, it means that the neurons are able to send their chemical signals—so when the video turns black you know everything’s working properly. You can see that the green starts to disappear in the cells with additional BDNF, even though they’ve been exposed to lead.

Now, we’re still far from using BDNF as a cure for lead poisoning—this isn’t even being tested on humans yet. Certainly, preventing the exposure to lead in the first place should be the primary goal. But this research offers hope that one day, lead poisoning may be much more treatable. And that’s a great thing, since today, at least 4 million American households with kids are exposed to high levels of lead. And that’s gross.

Ew.

Credits

PRODUCTION CREDITS

Host, Writer, Producer, Editor
Anna Rothschild
Camera, Sound
Ana Aceves
Culture Shock
Music provided by APM
Special Thanks to:
Dr. Tomás Guilarte, Dean of Robert Stempel College of Public Health and Social Work at Florida International University
Dr. Patric K. Stanton, New York Medical College

FOOTAGE AND STILLS

Original Footage
©WGBH Educational Foundation 2017
Footage of brain cells with and without BDNF
Courtesy Dr. Tomás Guilarte
Neuronsfiring-loop
Pond5/kitchendon
Lead electrolytic and 1cm3 cube
Wikimedia Commons/Alchemist-hp
Lead Pipe - Bath Roman Baths
Wikimedia commons/Andrew Dunn
LeadPaint1
Wikimedia Commons/Thester11
Peinture Plomb écailles 3
Wikimedia Commons/Lamiot
PSM V01 D357 Human encelphalon
Wikimedia Commons/Popular Science Monthly Volume 1
Skelett-Mensch-drawing
Wikimedia Commons/Hubert Ludwig
31 Weeks Pregnant
Flickr/Jerry Lai
New baby
Flickr/Jeremy Tarling

SFX

Cockroaches
Freesound/StateAardvark­
(used with permission from author)
Squeak Pack/squeak_10
Freesound/Corsica_S
Bubbles Popping
Freesound/ch0cchi
Nord analog howling wind storm
Freesound/medialint
Wink
Freesound/Bennychico11
Lock Unlock
Freesound/cemagar
Produced by WGBH for PBS Digital Studios

POSTER IMAGE

LeadPaint1
Wikimedia Commons/Thester11

Sources

Want More Info?

Dysregulation of BDNF-TrkB Signaling in Developing Hippocampal Neurons by Pb2þ: Implications for an Environmental Basis of Neurodevelopmental Disorders:
https://www.ncbi.nlm.nih.gov/pubmed/22345308

CDC on Lead Poisoning:
https://www.cdc.gov/nceh/lead/

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