By Rich Maloof for MSN Health & Fitness
A group of researchers at the University of California, San Francisco, may be making headway in the fight against asthma.
Dr. Richard Locksley leads a small team at UCSF considering new approaches to asthma research. His program is funded by Marion and Herb Sandler, a philanthropist couple who have underwritten research on many diseases. But Marion Sandler herself has suffered from asthma most of her life. After 40 years of spraying steroids down her throat, she wondered why there have been so few advances in preventing or treating asthma. We can recognize asthma-and we diagnose it in more and more children every year-but we don't even understand what causes the condition. Locksley and his team may be on the heels of some answers.
A new suspect, found everywhere
Asthmatics can have great difficulty breathing when confronted with
allergens, the organisms that provoke an allergic response. Locksley
and his colleagues were struck by the idea that a wide range of
organisms known to be highly allergenic-from various fungi and molds,
to dust mites and cockroaches, to shrimp and other shellfish-all have a
common compound called chitin (pronounced KI-tin). They wondered, could
the body's inflammatory response to chitin be a root cause of asthma?
The team's recent study, performed on mice, showed that chitin triggered an allergic response in the lungs. Their observations may explain why there is higher incidence of asthma where there's a known problem with mold or insects, and why reactions to shellfish are so common. The shells, cell walls and exoskeletons of these critters are made of chitin. Moreover, they may leave chitin behind as they molt.
The hygiene hypothesis
A popular theory of why we've seen dramatic increases in allergies is
known as "the hygiene hypothesis." As the theory goes, developed
countries have cleaned up so much bacteria and vaccinated against so
many microbes that our immune systems overreact when faced with
allergens. If we still grew up in "dirty" environments, it's been
suggested, we wouldn't have so much allergy and asthma.
The hygiene hypothesis and the chitin hypothesis cross paths in an interesting way. Though we often think of bacteria causing health problems, chitin may be naturally broken down by bacteria.
"There are all these funky ideas about asthma, such as if you grow up with a dog under the bed before you're 6 months old, or if you grow up in a farm environment, you almost never get asthma," Locksley further explains. "Because bacteria has an enzyme that breaks down chitin, one possibility is that there will be low chitin where there is a lot of bacteria."
Clean house?
So what are we to do-live knee-deep in bacteria to prevent allergies and asthma?
"That's a big question, and a loaded question since it's tough to say,
'Go out and get dirty!' " Locksley says with a laugh. "If there really
is an association with chitin, maybe the response is not so much to
worry about the bacteria in a household, but to worry about the chitin.
One approach might be to develop ways to break down chitin in the
environment." Amplifying his point, Locksley cites a compelling example
of bacteria and chitin at play. "The snow-crab industry is a big part
of a seasonal industry up in Alaska and Canada," he begins, emphasizing
that the shells of crabs are a rich source of chitin. "College kids
come in and they work in these crab processing plants. It's the food
industry, so the first thing they do is get all the bacteria out of the
environment by using microbicides. Then you've got these kids in there
pulverizing chitin shells for hours on end. "The attack rate for new
onset asthma in that industry is something like
25 to 28 percent per year," he says. "It's now a major cause of disability in Canada."
Fightin' chitin
The UCSF team also saw that their lab mice increased production of an
anti-chitin enzyme known as chitinase to fight off the chitin. Humans
likewise produce extra chitinase in response to allergies. But Locksley
and his fellow researchers are now trying to determine if people with
asthma may have a variant of chitinase that lessens their ability to
ward off the allergen.
"It turns out that a disproportionate number of people who have asthma have this [variant of chitinase]. So another potential issue is whether kids with a variant are at particularly high risk when they go into these environments, such as a home that might be moldy or have a lot of dust mites."
Wondering what's next
"It's early days, and first we'd want to confirm that there's an
association between chitin and risk in a household or an industrial
setting," says Locksley. "Second is whether there's any relation to
genes that people carry around and their ability to manage these
responses."
Pressed to consider what related asthma treatments may be down the road, Locksley offered a few thoughts.
"People have asked me if you could just spray a chitinase down people's
lungs during an attack to prevent a reaction. I think that's unlikely.
And gene therapy is not going to happen any time soon," he says. "It's
possible that if we could find the major receptor for chitin in the
body, we could make a drug to block that receptor. But until we
identify that receptor and understand how it works, we're a long way
from a drug therapy."
In the meantime, asthmatics should always pay close attention to known triggers. Though these new findings suggest you may not want to scrub your house down with antibacterial cleansers, it's clearly worthwhile to reduce fungi, mold, dust mites and cockroaches in your home. Not that they were welcome houseguests in the first place.
Dr. Richard Locksley is a Sandler Distinguished Professor at UCSF in the departments of Medicine, Microbiology and Immunology, and Investigator at the Howard Hughes Medical Institute.
Comments