Chromium 6: A killer compound with an improbable
trigger
Even miniscule amounts of chromium 6 can cause
cancer. Blame that do-gooder nutrient, vitamin C.
Brown University researchers have discovered that
naturally occurring vitamin C reacts inside human lung cells with
chromium 6, or hexavalent chromium, and causes massive DNA damage. Low
doses of chromium 6, combined with vitamin C, produce up to 15 times
as many chromosomal breaks and up to 10 times more mutations – forms
of genetic damage that lead to cancer – compared with cells that
lacked vitamin C altogether.
This finding is startling, said Anatoly Zhitkovich,
an associate professor of medical science at Brown who oversaw the
experiments. Outside cells, Zhitkovich said, vitamin C actually
protects against the cellular damage caused by hexavalent chromium,
the toxic chemical that starred as the villain in the true-to-life
Hollywood drama, Erin Brockovich. In fact, vitamin C has been used as
an antidote in industrial accidents and other instances when large
amounts of chromium are ingested.
Vitamin C works protective wonders because it is a
powerful antioxidant, blocking cellular damage from free radicals.
Specifically, the vitamin rapidly "reduces," or adds electrons, to
free radicals, converting them into harmless molecules. This electron
transfer from vitamin C to chromium 6 produces chromium 3, a form of
the compound that is unable to enter cells.
But what happens when chromium and vitamin C come
together inside cells? Because vitamin C isn't found in cells grown in
a lab, Zhitkovich and his team conducted experiments using human lung
cells supplemented with vitamin C. They learned that when vitamin C is
present, chromium reduction has a very different effect. Cellular
vitamin C acted as a potent toxic amplifier, sparking significantly
more chromosomal breaks and cellular mutations.
"When we increased the concentration of vitamin C
inside cells, we saw progressively more mutations and DNA breaks,
showing how seemingly innocuous amounts of chromium can become toxic,"
Zhitkovich said. "For years, scientists have wondered why exposure to
small amounts of hexavalent chromium can cause such high rates of
cancer. Now we know. It's vitamin C."
Hexavalent chromium is used to plate metals and to
make paints, dyes, plastics and inks. As an anticorrosive agent, it is
also added to stainless steel, which releases hexavalent chromium
during welding. Hexavalent chromium causes lung cancer and is found in
40 percent of Superfund sites nationwide. This is the toxic metal,
found in drinking water in a small California town, that Erin
Brockovich campaigned against, successfully winning residents a record
settlement of $333 million in 1996.
Zhitkovich said his team's research, published in
Nucleic Acids Research, might have policy implications. When combined
with vitamin C, chromium 6 caused genetic damage in cells in doses
four times lower than current federal standards, Zhitkovich said. If
additional research backs these findings, he said federal regulators
might want to lower exposure standards.
Zhitkovich is part of a major Brown research
initiative, the Superfund Basic Research Program, which addresses
the health and environmental concerns created by hazardous waste
contamination. As part of this program, funded by the National
Institute of Environmental Health Sciences, Zhitkovich is
conducting basic research that may result in a medical test that
assesses DNA damage from hexavalent chromium.
-
Former Brown graduate student Mindy Reynolds
was lead author of the journal article. Brown research assistant
Lauren Stoddard and postdoctoral research associate Ivan Bespalov
also took part in the research.
-
The National Institutes of Health funded the
work.
ChemLin offers different
instruments with which you can publish or refer to the appropriate web
pages, press releases, product news, appointments etc.
For your personal publication please use this form.
