Exposure to lead can hinder the brain's ability to recover from injury, a recent study in laboratory animals shows.
The results have implications for the effects of environmental lead exposure on brain injuries such as stroke, say researchers at Jefferson Medical College, who led the work.
Lead exposure early in life is known to increase the risk for cancer, renal disease, hypertension and cardiovascular disease later in life, and as a result, also increases the risk for stroke and brain damage. Jay Schneider, Ph.D., professor of Pathology, Anatomy and Cell Biology and Neurology at Jefferson Medical College of Thomas Jefferson University in Philadelphia and postdoctoral fellow Emmanuel Decamp, Ph.D., wanted to know if it was possible that lead might alter the potential for plasticity, the ability of the brain to compensate for an injury. They studied young rats that were fed a diet supplemented with lead and compared them to others on a diet without lead. In earlier work in the lab, they found that even brief exposures to lead affected neurotrophic factors in the brain important for growth and maintenance of neurons and their connections.
They ran each group through some simple behavioral tests before causing a small stroke in a specific part of the brain that affected a hind limb. Reporting in the journal NeuroToxicology, Dr. Schneider, who is director of the Parkinson's Disease Research Unit at Thomas Jefferson University, and his group saw significant recovery after a brief period of time in the control group, “as compensatory processes take over,” though the limb function was not completely back to normal.
“In contrast, those animals that were exposed to lead earlier in life had worse outcomes in the same period after the stroke,” he says. “There was significant difference in the brain's ability to compensate for that injury.”
Because the study was brief, he says, they don't know if in a longer period of time the lead-exposed animals would catch up in their recovery to the controls. There was some recovery in the lead group, but then it leveled off. The control group continued to get better.
“That's one of the questions we would like to pursue in further studies – whether lead exposure slows or attenuates the recovery process after a brain injury,” Dr. Schneider notes. “Have they recovered as much as they will recover or given more time, would they recover to the same extent" Is lead exposure affecting the rate of recovery or the recovery potential"”