Early Lead Exposure Greatly Hampers Recovery from Brain Injury

Scientists at the Jefferson Medical College of Thomas Jefferson University in Philadelphia, under the lead of Jay Schneider, Ph.D., professor of Pathology, Anatomy and Cell Biology and Neurology at Jefferson Medical College, and postdoctoral fellow Emmanuel Decamp, Ph.D., discovered that a patient's recovery from brain injury can be impeded, if the patient had been exposed to lead earlier on in life. The brain's ability to compensate for the injury it suffered can be greatly reduced in such cases.

Lead exposure is known to have negative effects on the human body like a higher risk for cancer, renal disease, hypertension, and cardiovascular disease. As a consequence lead exposure can also lead to an increased risk for stroke and brain damage. The new study demonstrated that lead exposure also changes the brain's capacity to compensate for the injury (plasticity).

The scientists had already discovered through earlier studies that short exposure to lead could have a negative impact on neurotrophic factors, which are needed for brain neuron maintenance, growth, and connection. For purposes of their newest study, the scientists added lead to the diet of young rats. They compared these rats to a group, which did not receive lead additives to their diet.

Each group of rats was put through simple behavioral tests. Then a stroke was artificially induced in a part of the rats' brain, which had an impact on a hind limb. The group on the non-lead diet was observed to recover quickly from the brain injury. Although the rats did not completely re-acquire all functions in the affected hind limb, the brain's compensatory forces clearly had worked quickly. However, the rats in the lead diet group experienced a different result. The brain had been much less able to compensate for the injury caused by the stroke.

The scientists caution that further research is necessary to completely discover the effects of early lead exposure on brain injury recovery. Their study had been brief. Therefore it is unknown whether a longer timeframe might have allowed for the lead diet group to catch up with the control group in terms of functional recovery. While the non-lead diet group continued to improve during the study time frame, the lead diet showed only a little bit of functional recovery, which later on let up. Thus, it is clear from the study that lead exposure early in life will result in a greatly slowed down recovery process after brain injury. However, the question remains whether lead exposure only delays recovery or if it also has an effect on overall recovery.

Furthermore, the group would like to study, if the results of the study would be the same for other types of brain injuries, such a trauma. They want to gather further data that proves lead poisoning impairs brain plasticity, the ability of the brain to compensate for injuries, to learn, and to be molded. Ultimately, the scientists would like to pinpoint the biological process involved in causing the impairment due to the lead exposure.