Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unexpected findings of lead exposure may lead to treating blindness

26.10.2010
Research team at UH sees novel changes in retinal anatomy, results published in high-impact journal

Some unexpected effects of lead exposure that may one day help prevent and reverse blindness have been uncovered by a University of Houston (UH) professor and his team.

Donald A. Fox, a professor of vision sciences in UH's College of Optometry (UHCO), described his team's findings in a paper titled "Low-Level Gestational Lead Exposure Increases Retinal Progenitor Cell Proliferation and Rod Photoreceptor and Bipolar Cell Neurogenesis in Mice," published recently online in Environmental Health Perspectives and soon to be published in the print edition of the prestigious peer-reviewed journal.

The study suggests that lead, or a new drug that acts like lead, could transform human embryonic retinal stem cells into neurons that would be transplanted into patients to treat retinal degenerations.

"We saw a novel change in the cellular composition of the retina in mice exposed to low levels of lead during gestation. The retina contained more cells in the rod vision pathway than normal or than we expected," said Fox, who also is a professor of biology and biochemistry, pharmacology and health and human performance. "The rod photoreceptors and bipolar cells in this pathway are responsible for contrast and light/dark detection. These new findings directly relate to the supernormal retinal electrophysiological changes seen in children, monkeys and rats with low-level gestational lead exposure."

Fox said these effects occur at blood lead levels at or below 10 micrograms per deciliter, the current low-level of concern by the Centers for Disease Control and Prevention. Because the effects occur below the "safe level," Fox says it raises more questions about what should be considered the threshold level for an adverse effect of lead on the brain and retina.

Fox has studied lead toxicity for 35 years, specifically as it relates to its effects on the brain and retina of children. His interest in gestational lead exposure started in 1999, when he and colleague Stephen Rothenberg studied a group of children in Mexico City whose mothers had lead exposure throughout their pregnancies. The study was funded to measure the adverse effects of lead poisoning on the nervous system of children born in Mexico City – a city that has elevated levels of lead in the air due to the use of leaded gasoline, as well as continued use of lead-containing pottery and glassware for food preparation. The study was funded by the U.S. Environmental Protection Agency and the Mexican government and was published in 2002 in the journal Investigative Ophthalmology and Visual Sciences.

Supported by a $1.7 million National Institutes of Health (NIH) grant, Fox and his group set out to find possible reasons for this supernormal retinal response in children. The researchers employed rat and mice models that covered the three levels of lead found in the blood of the Mexico City mothers – some below, some right at and some higher than the CDC "safe level." The researchers exposed rodents to lead throughout pregnancy and the first 10 days of life, which is a time period equivalent to human gestation.

Fox said that the early-born retinal progenitor cells give rise to four neuron types, which were not affected by lead exposure. The later-born retinal progenitor cells, he said, give rise to two types of neurons and a glial cell. Surprisingly, only the late-born neurons increased in number. The glial cells, which nurture neurons and sometimes protect them from disease, were not changed at all. The rats and mice both had "bigger, fatter retinas," according to Fox. Interestingly, the lower and moderate doses of lead produced a larger increase in cell number than the high lead dose.

"This is really a novel and highly unexpected result, because lead exposure after birth or during adulthood kills retinal and brain cells, but our study showed that low-level lead exposure during gestation caused cells to proliferate, increased neurons and did not affect glia," Fox said. "So, gestational exposure produces an exact opposite to what was previously shown by our lab and others. It also shows that the timing of chemical exposure during development is just as important as the amount of exposure."

This brought the researchers to a crossroads. On the one hand, the retina is not built to have all these extra cells and, according to unpublished data from Fox's mouse studies, the retinas will start to degenerate as the mice age. This suggests that the retinas of the children from the original Mexico City study should be examined as they might start to degenerate when they are 40 years of age.

"This work has long-term implications in retinal degeneration and diseases where photoreceptors die. If we can figure out how low-level lead increases the number of retinal progenitor cells and selectively produces photoreceptors and bipolar cells, then perhaps a drug can be created to help those with degenerative retinal diseases that eventually cause blindness," Fox said. "Researchers may be able to use lead as tool in transforming embryonic retinal stem cells into rods and bipolar cells that could be transplanted into diseased retinas, ultimately saving sight and reversing blindness."

Fox said that more research is needed before such a potential drug could be developed to mimic the effects of lead. Ideally, this drug would induce human embryonic retinal stem cells to form rods and bipolars that could be transplanted into patients to treat early stages of retinal degeneration.

In addition to Fox and research assistant professor Dr. Weimin Xiao in the UHCO, the research team consisted of a number of Fox's current and former students, including Anand Giddabasappa, a former Ph.D. student and now UHCO alumnus; Jerry E. Johnson, a UH alumnus from the department of biology and biochemistry, former post-doctoral fellow in Fox's lab and now an assistant professor at UH-Downtown; and current Ph.D. students W. Ryan Hamilton, Shawntay Chaney and Shradha Mukherjee.

Supplementing the NIH research project grant, this study also was funded by National Eye Institute training and core grants and a National Institute for Occupational Safety and Health educational resource grant.

A copy of the article can be found at http://ehp03.niehs.nih.gov/article/info:doi/10.1289/ehp.1002524.

NOTE TO JOURNALISTS: High-resolution photos of Donald Fox and his research team are available to media by contacting Lisa Merkl.

About the University of Houston

The University of Houston is a comprehensive national research institution serving the globally competitive Houston and Gulf Coast Region by providing world-class faculty, experiential learning and strategic industry partnerships. UH serves more than 38,500 students in the nation's fourth-largest city, located in the most ethnically and culturally diverse region of the country.

About the UH College of Optometry

Since 1952, the University of Houston College of Optometry (UHCO) has educated and trained optometrists to provide the highest quality vision care. One of only 20 optometry schools in the country, UHCO offers a variety of degree programs, including Doctor of Optometry (O.D.), a combined Doctor of Optometry/Doctor of Philosophy (O.D./Ph.D.), Master of Science (M.S.) and Doctor of Philosophy (Ph.D.). UHCO serves an average of 36,000 patients a year through The University Eye Institute and its satellite clinics.

For more information about UH, visit the university's Newsroom at http://www.uh.edu/news-events/.

To receive UH science news via e-mail, visit http://www.uh.edu/news-events/mailing-lists/sciencelistserv/index.php.

For additional news alerts about UH, follow us on Facebook at http://www.facebook.com/UHNewsEvents and Twitter at http://twitter.com/UH_News.

Lisa Merkl | EurekAlert!
Further information:
http://www.uh.edu

More articles from Health and Medicine:

nachricht Cystic fibrosis alters the structure of mucus in airways
29.06.2017 | University of Iowa Health Care

nachricht Mice provide insight into genetics of autism spectrum disorders
28.06.2017 | University of California - Davis

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making Waves

Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.

Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Nanostructures taste the rainbow

29.06.2017 | Physics and Astronomy

New technique unveils 'matrix' inside tissues and tumors

29.06.2017 | Life Sciences

Cystic fibrosis alters the structure of mucus in airways

29.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>