During the prenatal period, the fetus begins to form one of the most complex structures in nature, the human brain. This process is called neural embryogenesis and it represents one of the most complicated processes in prenatal life. The process relies on the tight regulation of behavior of the cells that will make up the brain. Neuronal stem cells (NSC) play a key role in embryonic brain development.
NSCs need a special environment in order to be able to carry out their function in neural embryogenesis, the creation of new cells to populate the nervous system. However, in some cases, harmful environmental exposure can result in abnormal NSC behavior. Prenatal exposure to lead is one of these harmful influences that may overwhelm the NSCs’ mechanisms of coping with cellular damage. As a result, NSC-regulated processes in neural embryogenesis may become affected, often leading to neurodevelopmental disorders.
Upon fertilization, from a single cell, a mass of cells is formed and later this mass divides into several layers from which all structures of the human body originate. This is also the case for the central nervous system. It derives from one of the layers that forms the neural tube, the precursor to the brain, brainstem, and the spinal cord. Initially, the neural tube is rather small, but due to the creation of new cells from NSCs it gradually enlarges. Later, the cells in the neural tube get specialized to different functions by changing their cellular and biochemical characteristics. Evidently, if something goes wrong at any of these steps, developmental brain abnormalities may occur.
Lead has been a part of human civilization for a long period of time. However, only recently has the mechanisms by which lead causes negative health effects began to emerge. Lead is particularly harmful to NSCs, even when the exposure is minimal. Very minimal prenatal exposure to lead has been linked to lower IQ, aggressiveness, and other problems. Research studies have also shown that prenatal exposure to lead produces more harm than exposure during the postnatal period. These findings have been linked to the mechanisms behind cellular injury of NSCs by lead. The proposed mechanisms affect essential cellular functions that result in an increase in reactive oxygen species (ROS) and alterations in DNA methylation.
Source: Brain Blogger