UC researchers have identified the gene
responsible for spreading the toxic effects of cadmium--a finding that
may one day lead to the prevention of cadmium toxicity in humans.
Cadmium--a heavy metal suspected of
causing human birth defects, lung cancer and testicular cancer--is
found in cigarette smoke, some shellfish and seafood, soil and some
plants. It is known to damage the human central nervous system, the
kidneys, lungs and developing embryos.
The researchers, studying low doses of
cadmium in mice, found that the gene Slc39a8 works to transport cadmium
to the testes, causing tissue to die.
The study appears in the March 1 edition of the Proceedings of the National Academy of Sciences (PNAS).
"We suspect that cadmium at higher doses
could be transported to other regions of the body via the Slc39a8 gene
or another gene in this family," says Daniel Nebert, MD, lead author
and professor in the Department of Environmental Health and the Center
for Environmental Genetics. "We know humans carry the same gene and
gene family. Thus, we've identified a target that could be used to
prevent cadmium's toxic effects in humans."
This is especially important, says Dr.
Nebert, for many Third World countries. When populations are
malnourished or have iron-deficient anemia, the damaging effects of
cadmium increase dramatically.
Humans need certain essential
metals--including zinc, calcium, magnesium, iron, copper, cobalt and
manganese--for normal metabolism and biological processes.
Industrialization, however, has introduced many nonessential heavy
metals, such as cadmium, lead, silver, mercury, nickel, arsenic and
chromium into the environment.
There have been many studies on heavy
metal toxicity, but until now no study has determined how nonessential
heavy metals cause toxicity in humans or other vertebrates.
"We believe that the Slc39a8 gene could
be responsible for the transportation not only of cadmium, but also of
other nonessential heavy metals such as lead, nickel and mercury," says
Dr. Nebert. "Identification and characterization of this gene in mice
is a significant breakthrough that will improve our understanding of
how heavy metals actually cause toxicity and cancer in humans."
Co-authors include Timothy Dalton, PhD,
Lei He, Bin Wang, Marian Miller, PhD, Li Jin, PhD, Xiaoqing Chang and
C. Stuart Baxter, PhD, all in the Department of Environmental Health,
and Keith Stringer, PhD, Department of Pathology and Laboratory