University of Adelaide (Australia) research has uncovered how the metal cadmium,
which is accumulating in the food chain, causes toxicity in living
cells. Published in the journal Nature Communications, this research has shown how cadmium disrupts the transport of the essential metals manganese and zinc into and out of cells.
“Cadmium
is a very important industrial metal, but exposure to it results in
accumulation in the food chain, leading to toxicity in animals and
humans,” says project leader Dr Christopher McDevitt, Senior Research Fellow and Deputy Director of the University’s Research Centre for Infectious Diseases.
“Exposure
to cadmium can occur due to poor disposal of industrial or electronics
waste, and also through cigarette smoke and ingestion of contaminated
food. While the toxicity of cadmium has been known for a long time, how
it causes toxicity and damages cells hasn't been understood.”
“We've
shown, in a model bacterial system, that the chemistry of cadmium
allows it to bypass the mechanisms that prevent other metals, such as
iron and zinc, from freely entering cells.
“Once inside the cell,
cadmium inserts itself into the cell's metal sensing machinery causing
it to malfunction and pump out the wrong metal ions while still bringing
in more cadmium. This ultimately leads to death of the cell.
“This
understanding of how cadmium causes toxicity, at a molecular level, is
crucial for developing new strategies for preventing cadmium poisoning.”
Dr
McDevitt and the team of researchers including PhD student Stephanie
Begg, who conducted the research, are investigating how the
disease-causing bacteria Streptococcus pneumoniae is able to scavenge
essential metals during infection, and how this might be blocked to
prevent disease.
Cadmium is an important metal for a range of
electronics industries and is used widely in nickel-cadmium batteries.
Cadmium from industrial waste can leach back into soil and water and
isn’t degraded. Global cadmium production has risen by more than one
thousand-fold since the beginning of the 20th century to approximately
20,000 tons per year. It is estimated that humans ingest up to 30
micrograms every day.
“Cadmium isn’t used in biological systems
(with one rare exception) which means that cells haven’t evolved ways to
deal with this metal when they encounter it,” says Dr McDevitt. “Our
findings here open the way for developing new therapies for preventing
cadmium toxicity.”
This research was in collaboration with
University of Queensland and La Trobe University, and has been funded by
the National Health and Medical Research Council.