Protein content of comedones from patients with acne vulgaris.

Characteristic early lesions in acne vulgaris are the open and closed comedones (blackheads and whiteheads) which are well known to contain a "plug" of cornified material. Histological analysis of these lesions has indicated that their protein content, presumed in part to be keratin, may be degraded, possibly by bacterial action, though this has never been adequately demonstrated biochemically. We have analysed the keratin content in a pool of material taken from a number of open comedones (approximately 200-500 mg by weight). Using a highly sensitive silver stain technique which can detect minute quantities of protein we have also been able to analyse individual lesions. In normal keratin extracted from human stratum corneum using a Tris-urea-mercaptoethanol buffer, SDS/polyacrylamide gel electrophoresis reveals the presence of a group of polypeptides with molecular weights in the range 66 000-44 000. Comedonal material contained bands of the same molecular weight but in addition to these undegraded keratin polypeptides, showed bands corresponding to molecular weights in the region of 15 000-10 000 and 30 000-25 000 indicating that the keratins in this material are partially degraded. Similar groups of low molecular weight polypeptides were observed when keratin was digested with purified V8 protease from Staphylococcus aureus. It is possible that inflammation around the follicle could involve the leakage of keratin digestion products into the dermis.