Researchers funded in part by the National Institute of Arthritis and Musculoskeletal and Skin Diseases have uncovered clues related to the cause of rosacea, a common inflammatory skin condition that causes redness of the face, bumps, and visible blood vessels. Their discovery could trigger the development of novel therapies for prevention or treatment, offering new hope for individuals affected by the disease.

In the absence of solid evidence, rosacea has been believed to be caused by the bacteria responsible for causing acne. However, research conducted by Richard L. Gallo, M.D., Ph.D., of the University of California, San Diego, and the VA San Diego Healthcare System, along with an international team of investigators, has uncovered a possible flaw in the immune system that contributes to the disease. Their findings were reported in Nature Medicine.

Through skin biopsies, Gallo and his team found that people with rosacea had high levels of cathelicidins, peptides with antimicrobial and pro-inflammatory properties that protect the skin against infection. (Cathelicidins are secreted in an inactive form and undergo a cleaving process to take on their active form.) Investigators also discovered that levels of stratum corneum tryptic enzyme or SCTE — the enzyme responsible for cleaving the inactive cathelicidins into their active form — were also elevated in people with the disease.

In separate experiments, Gallo's team then injected mice with cathelicidins found in rosacea, added SCTE, and increased SCTE by turning off the gene that inhibits its activity. Each of these actions produced the inflammatory characteristics of rosacea in the skin of the mice. However, these responses were absent in mice with a deleted cathelicidin gene. Says Gallo, "Our findings help to show that antimicrobial peptides such as the cathelicidins, which are evolutionarily ancient elements of immune defense, play a critical role in inflammation."

Rosacea is a chronic ailment that affects around 14 million people in the United States. Along with redness and visible blood vessels, people with rosacea frequently have papules (pink bumps) and pustules (pink bumps with pus). Many people experience facial burning and swelling. The disease is more common in people between the ages of 30 and 60, and in those with fair skin.

Other support for this research came from the National Rosacea Society, the Veterans Administration and the Association for Preventive Medicine of Japan.

The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases, a part of the Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov.

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Yamasaki, K, et al. Increased serine protease activity and cathelicidin promotes skin inflammation in rosacea. Nature Medicine, 2007:13(8):975-980.