A modern cause of Alzheimer’s disease may lie in the ancient poisons of arsenic, lead, and cadmium. Indian researchers recently reported that young rats exposed to water contaminated with these toxic metals developed symptoms of Alzheimer’s disease, a form of dementia affecting more than 25 million people worldwide. Disturbingly, rats which drank water contaminated with all three metals–water similar to that drank by many Indian people–developed much worse symptoms than rats which drank water with fewer metals. The researchers cautioned that people who drink contaminated water during childhood may develop symptoms of Alzheimer’s disease decades earlier than normal.
How do three ancient poisons work together to create such a potent brew? To tease out the answer, the researchers examined the toxic effects of each metal alone, and the effects of different combinations. Compared to arsenic and cadmium, lead provoked the rats’ brains to make more amyloid-beta–the sticky protein which congeals into plaques in the brains of Alzheimer’s patients. Rats which consumed lead with arsenic had even more amyloid-beta. But when rats consumed lead with arsenic and cadmium, the three metals acted synergistically–the toxic equivalent of shouting into a bullhorn hooked up to an amplifier. The metals amplified each other’s damage to the rats’ brains, and even caused the brains to become inflamed.
With their damaged brains, the rats were worse at figuring out a maze. They were losing their ability to learn and remember–just like humans with Alzheimer’s disease.
Ashok A, Rai NK, Tripathi S, & Bandyopadhyay S (2014). Exposure to As-, Cd-, and Pb-Mixture Induces Aβ, Amyloidogenic APP Processing and Cognitive Impairments via Oxidative Stress-Dependent Neuroinflammation in Young Rats. Toxicological sciences : an official journal of the Society of Toxicology PMID: 25288670