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Broccoli
may help boost the Aging Immune System
Newswise — Eat your broccoli! That's the
advice from UCLA researchers who have found
that a chemical in broccoli and other
cruciferous vegetables may hold a key to
restoring the body's immunity, which
declines as we age.
Published in this week's online edition of
the Journal of Allergy and Clinical
Immunology, the study findings show that
sulforaphane, a chemical in broccoli,
switches on a set of antioxidant genes and
enzymes in specific immune cells, which then
combat the injurious effects of molecules
known as free radicals that can damage cells
and lead to disease.
Free radicals are byproducts of normal body
processes, such as the metabolic conversion
of food into energy, and can also enter the
body through small particles present in
polluted air.
A supercharged form of oxygen, these
molecules can cause oxidative tissue damage,
leading to disease — for example, triggering
the inflammation process that causes clogged
arteries.
Oxidative damage to body tissues and organs
is thought to be one of the major causes of
aging.
"The mysteries of aging have always
intrigued man," said Dr. Andre Nel, the
study's principal investigator and chief of
nanomedicine at the David Geffen School of
Medicine at UCLA.
"While we have known for some time that free
radicals are important in aging, most of the
past attention has focused on the mechanisms
that produce free radicals rather than
addressing the pathways used by the body to
suppress their production."
A dynamic equilibrium exists in the body
between the mechanisms that lead to
increased free radical production and those
antioxidant pathways that help combat free
radicals.
"Our study contributes to the growing
understanding of the importance of these
antioxidant defense pathways that the body
uses to fight free radicals," said Nel, a
practicing clinical allergist and
immunologist at the Geffen School.
"Insight
into these processes points to ways in which
we may be able to alleviate the effects of
aging."
The delicate balance between pro-oxidant and
antioxidant forces in the body could
determine the outcome of many disease
processes that are associated with aging,
including cardiovascular disease,
degenerative joint diseases and diabetes, as
well as the decline in efficiency of the
immune system's ability to protect against
infectious agents.
"As we age, the ability of the immune system
to fight disease and infections and protect
against cancer wears down as a result of the
impact of oxygen radicals on the immune
system," Nel said.
According to the UCLA study, the ability of
aged tissues to reinvigorate their
antioxidant defense can play an important
role in reversing much of the negative
impact of free radicals on the immune
system.
However, until this current study, the
extent to which antioxidant defense can
impact the aging process in the immune
system was not properly understood.
"Our defense against oxidative stress damage
may determine at what rate we age, how it
will manifest and how to interfere in those
processes," Nel said.
"In particular, our study shows that a
chemical present in broccoli is capable of
stimulating a wide range of antioxidant
defense pathways and may be able to
interfere with the age-related decline in
immune function."
The UCLA team not only found that the direct
administration of sulforaphane in broccoli
reversed the decline in cellular immune
function in old mice, but they witnessed
similar results when they took individual
immune cells from old mice, treated those
cells with the chemical outside the body and
then placed the treated cells back into a
recipient animal.
In particular, the scientists discovered
that dendritic cells, which introduce
infectious agents and foreign substances to
the immune system, were particularly
effective in restoring immune function in
aged animals when treated with sulforaphane.
"We found that treating older mice with
sulforaphane increased the immune response
to the level of younger mice," said
Hyon-Jeen Kim, first author and research
scientist at the Geffen School.
To investigate how the chemical in broccoli
increased the immune system's response, the
UCLA group confirmed that sulforaphane
interacts with a protein called Nrf2, which
serves as a master regulator of the body's
overall antioxidant response and is capable
of switching on hundreds of antioxidant and
rejuvenating genes and enzymes.
Nel said that the chemistry leading to
activation of this gene-regulation pathway
could be a platform for drug discovery and
vaccine development to boost the decline of
immune function in elderly people.
"This is a radical new way of thinking in
how to increase the immune function of
elderly people to possibly protect against
viral infections and cancer," Nel said.
"We may have uncovered a new mechanism by
which to boost vaccine responses by using a
nutrient chemical to impact oxidant stress
pathways in the immune system."
Kim said that although there is a decline in
Nrf2 activity with aging, this pathway
remains accessible to chemicals like
sulforaphane that are capable of restoring
some of the ravages of aging by boosting
antioxidant pathways.
The next step is further study to see how
these findings would translate to humans.
"Dietary antioxidants have been shown to
have important effects on immune function,
and with further study, we may be adding
broccoli and other cruciferous vegetables to
that list," Nel said.
For now, Nel suggests including these
vegetables as part of a healthy diet.
Nel said that these findings offer a window
into how the immune system ages.
"We may find that combating free radicals is
only part of the answer. It may prove to be
a more multifaceted process and interplay
between pro- and antioxidant forces," he
said.
The study was funded by the National
Institute on Aging, the UCLA Claude D.
Pepper Older Adults Independence Center, and
the National Institute of Allergy and
Infectious Diseases.
Other study authors included Berenice
Barajas and Dr. Meiying Wang.
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