A team of researchers from the U.S., France and Japan found that people with rosacea have high levels of the anti microbial peptide cathelicidin in their skin, which produces proteins that are different from those found in people who do not have the disease. Another important contributor to the development of the condition is an enzyme called stratum corneum tryptic enzyme (SCTE).



The triplet of factors are like ?lots of gasoline and a match,? said the leader of the team, Dr Richard L. Gallo, professor of medicine and chief of the Division of Dermatology at the University of California, San Diego (UCSD) School of Medicine and the Dermatology section of the Veterans Affairs San Diego Healthcare System.

He and his team found that over-production of two inflammatory proteins leads to high levels of a third protein that causes rosacea symptoms.

Rosacea is characterized by facial redness (erythema), bumps and pimples (papulopustules), and spider veins (telangiectasia). The condition is chronic and gets worse over time. It is cyclical and flares up for weeks or months and then subsides. There is no effective cure although antibiotics are sometimes prescribed with mixed results.

In some cases, the eyes may also be affected by rosacea, resulting in a gritty feeling and bloodshot appearance. As the severity advances, the symptoms may include swollen blood vessels in the eyes, and in rare cases small hard bumps may develop on the eyelids and vision may be affected.

Rosacea flare-ups can be triggered by an astonishing array of factors, almost anything that causes the face to become flushed such as demanding exercise, sunburn, stress, anxiety, and sudden changes in temperature like moving from a cold to a hot environment. Certain foods and drinks such as alcohol, hot caffeinated drinks (tea, coffee), and spicy foods are also triggers. Rosacea can even be triggered by blushing with embarrassment.

Dr. Gallo and the team first noticed in the laboratory that anti-microbial peptides, small proteins of the immune system, caused the same skin redness, bumps, pimples and spider veins seen in rosacea patients. And these peptides were triggered by the same things as rosacea. When they looked at patients with rosacea they found that everyone in the sample had more of these peptides than normal.

What makes the discovery more interesting is that the precursor to the peptides they found is another peptide, cathelicidin, which has been thought to protect the skin from infection. A range of other diseases with skin inflammation is linked to a shortage of cathelicidin. But in rosacea patients the scientists found too much of a different type of cathelicidin not found in people who do not have the disease.

The researchers also found that patients with rosacea had too much of the enzyme called stratum corneum tryptic enzyme (SCTE), which converts cathelicidin into the immune system peptides that lead to rosacea.

As a follow-up, the researchers tested the effect of the two substances by injecting laboratory mice with the cathelicidin peptides found in rosacea, adding SCTE, and increasing their protease activity by switching off a gene (Spink5, the protease inhibitor). Each of these increased inflammation of the skin.

They also tested the role that cathelicidin plays in helping inflammation caused by SCTE by deleting the gene that codes for it in mice, the Camp gene.

Gallo explained that: "Too much SCTE and too much cathelicidin lead to the abnormal peptides that cause the symptoms of this disease."

He went on to explain that "antibiotics tend to alleviate the symptoms of rosacea in patients because some of them work to inhibit these enzymes. Our findings may modify the therapeutic approach to treating rosacea, since bacteria aren't the right target."

Reference: Kenshi Yamasaki, Anna Di Nardo, Antonella Bardan, Masamoto Murakami, Takaaki Ohtake, Alvin Coda, Robert A Dorschner, Chrystelle Bonnart, Pascal Descargues, Alain Hovnanian, Vera B Morhenn and Richard L Gallo. Nature Medicine, published online August 05, 2007