Inadvertently swallowing modest levels of the heavy metal cadmium is known to irritate the stomach and lungs or induce renal illness, but recent study relates another health risk to the pollutant: excessive activation of the antibodies that produce an allergic reaction.
Researchers linked this relationship in mice to gut bacteria that overproduced an enzyme that destroys vitamin D after being exposed to ingested cadmium, thus simulating vitamin D deprivation. In terms of clinical impacts, mice that were sensitized to a particular allergen and ate cadmium developed significant amounts of antibodies against the allergen as well as immune cells that exacerbated their respiratory symptoms.
Separate epidemiological studies have shown a link between vitamin D deficiency and increased susceptibility to asthma and other allergy symptoms in children. And, on Sept. 29, a Congressional study revealed an unexpected source of cadmium in children, revealing that unsafe quantities of harmful heavy metals, including cadmium, had been identified in numerous types of baby food.
“The problem is that because cadmium does not degrade easily in the body — it has a half-life of at least 15 years — if you are chronically exposed to low doses, it accumulates over time,” said Prosper Boyaka, professor and chair of veterinary biosciences at The Ohio State University and study senior author. “We can’t readily avoid being exposed to it since it may persist in the air, soil, and water.”
The natural element cadmium, a heavy metal used in batteries and pigments, is ingested by most humans via eating polluted plant and animal foods or drinking contaminated water. Cadmium is one of eight metals listed by the Environmental Protection Agency as being particularly hazardous at low quantities.
In mice that had consumed cadmium, Boyaka and colleagues discovered that an experimental drug that inhibited the activated enzymes lessened the allergic reaction.
“In the study, we offered two alternative techniques,” Boyaka said. “One option is vitamin D supplementation, but this must be done before cadmium exposure has resulted in an increased allergic response, so the issue is when to take it. We also advise preventing the heightened allergic reaction by blocking those enzymes.”
The findings were recently published in the journal Mucosal Immunology.
Environmental contaminants like cadmium and lead, as well as genetic predisposition and antibiotic misuse, are thought to have a role in the rising number of individuals with allergies, but the mechanics underlying this link aren’t fully known, according to Boyaka.
Researchers introduced a “subtoxic” dosage of cadmium to drinking water ingested by groups of mice for 28 days in this investigation. The researchers used a mouse model that mimicked human genetic propensity to egg allergy to assess the mice’s allergic reaction to an egg protein.
Mice that drank water containing subtoxic amounts of cadmium and subsequently were exposed to the allergen had a higher allergic reaction than control mice, which manifested itself as internal inflammatory responses and allergy symptoms.
“Because we know that dysbiosis, or a shift in the microbiota, may trigger allergy reactions, we hypothesized that cadmium would alter the bacterial population in the gut. Yes, putting such little, tiny quantities of cadmium in the water changed allergy sensitivity “Boyaka said.
The impact was known to occur in the gut, as predicted, since germ-free mice, who lack intestinal bacteria, did not over-produce the antibody that triggers an allergic reaction when given cadmium orally. The cadmium, however, was neither harming cells or making the intestines leaky, according to the researchers. Cadmium in the stomach has been connected to the creation of inflammatory chemicals as well as the activation of two enzymes that breakdown vitamin D.
“The most important discovery is that heavy metals persist in soft tissue, including the stomach, following exposure to subtoxic amounts. And what they do is increase the reactivity of cells. Bacteria in the intestines will cause particular cells to create more of the enzyme that destroys vitamin D “Boyaka remarked. “That’s a link we weren’t aware of previously.”
Boyaka’s team is currently looking at other chemicals that may be utilized to stop the enzymes from degrading vitamin D.
The National Institutes of Health and the National Center for Advancing Translational Sciences provided funding for this research. The researchers used the Mass Spectrometry and Proteomics Core at the Ohio State Center for Clinical and Translational Science to perform their investigations.
Eunsoo Kim, Astrid Bonnegarde-Bernard, Stephen Opiyo, Marisa Joldrichsen, Zayed Attia, Brian Ahmer, and Estelle Cormet-Boyaka are all co-authors from Ohio State.