Effects of xenobiotics on the blood-brain barrier and neural gene expression

The blood-brain barrier (BBB) is a selective barrier that restricts the entry of most substances from the bloodstream into the brain. It consists of three main components: endothelial cells, pericytes, and the astrocytic end-feet. The tight junctions (TJs) between endothelial cells contribute to the barrier's role in preventing many blood-derived substances from crossing into the brain. Xenobiotics refer to synthetic compounds commonly employed in domestic, agricultural, and industrial activities. They are found in the environment at both micropollutant and higher concentrations. These substances can be classified based on several factors, such as their origin, application, physical form, or effects on human health and the ecosystem. Their influence on both the environment and human health is significant. Compounds like argon (Ar), cadmium (Cd), chromium (Cr), and lead (Pb) have the ability to cross the BBB, causing alterations in the TJs and astrocytes, ultimately leading to BBB disruption. Disruption of the BBB, such as a compromised TJ seal, plays a significant role in the progression of various neurological conditions, including stroke and neuroinflammatory diseases. However, the potential of these compounds to penetrate and alter the BBB has not been widely explored.This review highlights the impact of xenobiotics on the central nervous system (CNS), particularly on the BBB. We will explore instances where their role in neurodegenerative processes is suspected. A particular attention is given to heavy metals, which pose a serious risk to human health, especially when they cross the BBB and accumulate in surrounding cells, triggering changes in the brain's environment that affect the entire body.