Neurological implications of heavy metals toxicity in relation to exposure source and explicated mechanisms

Abstract

Heavy metal toxicity is world-wide alarming problem now-a-days. Some metals play important roles in the body like neurotransmission, gene expression and other mechanisms of the body. These are required in traces and excess amount leads to toxicity in the body. Most toxic heavy metals lead to toxicity in different body organs and may cause neurological disorders. Human beings are mostly exposed to heavy metals through food, water and environment. Heavy metal sources include both natural and by human activities i.e. industrialization, mining etc. Heavy metals are mostly non-biodegradable and remain in the environment for years, concentrated in the environment and enter into biological cycle to cause toxic effects. Toxicity of these metals leads to reduced cerebral activity, low IQ levels, sluggish learning and infections like Parkinson’s disease, Amyotrophic lateral sclerosis, Autism disease and Wilson disease. Like some studies shows that aluminum has role in causing Autism disease and Parkinson’s disease. Mostly heavy metals induce their toxic effect, through oxidative stress by enhancing the production of ROS, impaired mitochondrial function, inhibition of enzyme activity while few others like aluminum can cause disturbances in metal homeostasis. Most of the heavy metals can cross the blood brain barrier (BBB) without difficulty and prompt their toxic effects in brain. The consequences of heavy metals differ depending upon age, development and other physiological factors. This review addresses brief introduction of heavy metals, their neurotoxic effects and their possible mechanism of action associated with toxicity.