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Brenda Goodman, MA
Laura J. Martin, MD
April 27, 2012 -- Doctors have been scratching their heads over how to treat bad cases of dandruff for more than century.
Over-the-counter shampoos and scalp treatments can help when dandruff is mild, says Thomas L. Dawson, PhD, a scientist at Procter & Gamble who works on Head & Shoulders shampoo. But they may not always benefit people with badly flaking and irritated scalps.
Now, a raft of new research, including a new study published in the Journal of Medicinal Chemistry, suggests that scientists may be close to heading off the fungus that causes the problem in the first place.
Malassezia globosa is a fungus present on the skin of many newborns. Often, it lives harmlessly in the top layer of skin without causing any problems.
But for an estimated 50% of the population, it burrows into a hair follicle and sets up shop. And for reasons doctors don't fully understand, the body reacts. Skin cells can become irritated and shed roughly four times faster than normal, dropping off in days instead of once a month. The scalp can become irritated and itchy.
Scientists have long known that malassezia was the culprit behind dandruff, but because it is difficult to grow in a laboratory, it was tough to study.
In 2007, Dawson and a team of researchers at Procter & Gamble sequenced the Malassezia genome. That discovery gave scientists a new way to study the organism, and it sparked a resurgence of interest in finding ways to stop the problematic fungus.
"That was really the key in the lock that opened the door to all this work," Dawson says.
In the latest study, researchers in Italy and the U.K. were able to use the genome to look for proteins that might be critical to malassezia's growth.
They found an enzyme that helps the fungus break down carbon dioxide.
"When you inhibit this enzyme, the organism cannot grow well, so the organism dies," says Claudiu T. Supuran, a chemistry professor at the University of Florence.
What's more, the enzyme can be stopped by antibacterial drugs called sulfonamides or sulfas, which have been around since the 1930s.
Supuran and his colleagues tested that idea by giving six mice bad cases of dandruff and then treating them with a sulfa drug. Four out of the six mice showed improvement, suggesting that sulfa drugs may be a new weapon against dandruff.
That may be good news for people who aren't helped by existing treatments.
Dawson says doctors score dandruff on a scale from zero to 80. Most people with dandruff have scores that fall in the range of 15 to 30. Fifteen is the point where it starts to become visible to the naked eye.
He says over-the-counter products can be helpful for people in the 15 to 30 range.
But for "people that have a particularly severe case, there is a lot of room for improvement in being able to push that closer to zero."
In Dawson's lab, they've zeroed in on another set of enzymes that help the fungus break down and digest fats produced by the skin. Stopping those enzymes essentially cuts off the fungus' food supply.
He's trying to use zinc in shampoo to inhibit those enzymes. The key, he says, is finding zinc particles that are the right size. If they're too big, they don't make it to the fungus, which likes to live inside hair follicles. If they're too small, they get rinsed down the drain with the shampoo and don't do any good.
"You have to get to the scalp, which is really hard," he says, but notes that much of the molecular work has improved how well products deliver their active ingredients.
"We've been trying to figure this out for 50-plus years," Dawson says, "Now we finally have the tools to be able to really understand this organism and manage how we treat it."
SOURCES:Hewitson, K. Journal of Medicinal Chemistry, April 2012.News release, American Chemical Society.Dawson, T. Journal of Investigative Dermatology, Symposium Proceedings, December 2007.Claudiu T. Supuran, professor, department of biochemistry, University of Florence, Italy.Thomas L. Dawson, PhD, principle scientist, Procter & Gamble, Oxford, Ohio.
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