Dr. Hao Wang (right) has a new paper published in Toxicological Sciences that describes the effects of chronic cadmium exposure on the formation of neurons in adult mice.
For adults, learning and memory formation depend on the production of new neurons in the part of the brain known as the hippocampus. New work by Dr. Hao Wang, a trainee in the lab of Dr. Zhengui Xia, shows that cadmium exposure not only impairs new neurons in the hippocampus from forming and maturing, but it also causes the death of the stem cells that produce them.
Previously Wang and Xia used behavioral experiments to find that cadmium exposure impaired learning and memory-formation in adult mice, but the mechanism by which cadmium was having this effect remained unclear. Very little work had been done on the role that cadmium plays as a neurotoxin.
In the current study, Wang applied cadmium directly to petri dishes full of the stem cells responsible for forming new neurons in the hippocampus and found that it caused cell death and interfered with the production and maturation of new neurons. The concentration of cadmium used was close to the U.S. Environmental Protection Agency's maximum allowable contaminant level of cadmium in drinking water.
Wang also exposed adult male mice to low levels of cadmium in their drinking water for 13 weeks which created blood levels of cadmium in the treated mice that resemble those found in human cigarette smokers and lower than OSHA's standard trigger level of cadmium for medical surveillance. He compared the brains of these treated mice to those of controls. What he found was that cadmium exposure decreased the number of new neurons in the hippocampus and impaired their maturation.
These two complementary sets of results provide the first strong evidence of the mechanism by which cadmium impairs learning and memory-formation in adults and has implications for the role of environmentally-relevant cadmium exposure in neurogenerative diseases like Alzheimer's in humans.
In July, Dr. Wang and his collaborators published these results in Toxicological Studies as a paper titled "Cadmium exposure impairs adult hippocampal neurogenesis." The full text of the paper can be found here.