Triggers for rosacea (a chronic inflammatory skin disease affecting fair skinned people of European or Celtic descent which causes facial redness, bumps and pimples and spider veins and for which there is no effective treatment) usually involve anything that causes the face to become flushed – exercise, sunburn, stress, anxiety and sudden changes in temperature. Other triggers are food and drink that cause flushing (alcohol, hot caffeine drinks and certain spicy foods) and blusing with embarrassment.
Research by by 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, found that people with rosacea have high levels of the anti microbial peptide cathelicidin in their skin and the proteins this produces are different to those found in people who do not have the disease. Another important contributor is an enzyme called stratum corneum tryptic enzyme (SCTE). Over-production of two inflammatory proteins leads to high levels of a third protein that causes rosacea symptoms, "A trifecta of unfortunate factors in people with rosacea," said Gallo.
They first noticed in the laboratory that anti-microbial peptides, small proteins of the immune system, caused the same redness of skin, 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 every one of them had more of these peptides than normal.
The surprising thing about the discovery is that the precursor to the peptides they found is another peptide, cathelicidin, which is 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 the opposite: too much cathelicidin, altough it was a different type to that found in people who do not have the disease.They also found that patients with rosacea had too much SCTE, which converts cathelicidin into the immune system peptides that lead to rosacea.
They 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.
Dr Gallo explained that antibiotics sometimes work in treating rosaceaeven though no bacterial infection is involved because some antibiotics work to inhibit the action of the enzymes.
"Increased serine protease activity and cathelicidin promotes skin inflammation in rosacea."
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: 05 August 2007. doi:10.1038/nm1616
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