Immediate and extended effects of abrasion on stratum corneum natural moisturizing factor.

BACKGROUND: Natural moisturizing factor (NMF), principally comprised of hygroscopic amino acids and derivatives that absorb moisture from the surrounding environment, serves as the primary humectant of the stratum corneum (SC). Acute barrier disruption has been shown to differentially affect the concentration of NMF in the SC. This study measured the recovery kinetics of NMF after mechanical damage of the SC, which is not well understood. METHODS: The study population included 20 healthy female volunteers (18-72-year old) with no history of dermatological disorders. Transepidermal water loss (TEWL), erythema, and SC water and NMF were measured at all sites before abrasion, 30 min following abrasion, and 1-3, 6, 8, and 10 days following abrasion. Measurements obtained from the abraded site were compared with those obtained from an untreated site. RESULTS: As expected, both TEWL and erythema increased significantly with abrasion. Erythema and TEWL values remained higher at the abraded site for 2 and 6 days, respectively, after abrasion. No changes in NMF component levels in the SC were observed at 30 min after abrasion. One day following abrasion, reduced levels of glycine, histidine pH4, trans-urocanic acid (tUca) pH4, and tUca pH8 were observed. In addition, a significantly lower level of serine was observed at the abraded site 2 and 6 days following abrasion. Within 8 days after abrasion, these components returned to levels comparable to those observed in untreated skin. Throughout the study, no differences were observed in the level of water in the SC. CONCLUSION: These results demonstrate that acute barrier disruption induced by mechanical abrasion has relatively little impact on biochemical events responsible for NMF generation. Though reductions in certain NMF components were observed, abrasion had no measureable effect on SC water content over the duration of the study. This implies that the reduced NMF components may not contribute substantially to water retention in the SC. The reduced components belong to a group of NMF molecules thought to be principally derived through degradation of S-100 proteins in the epidermis. NMF components measured in this study that are derived from sweat and/or urea cycling were not impacted. These data imply that while abrasion elicits clinical signs of barrier disruption within the SC, effects on its biochemical constituents and ability to retain water are relatively minor.

Immediate and extended effects of sodium lauryl sulphate exposure on stratum corneum natural moisturizing factor.

OBJECTIVES: Natural moisturizing factor (NMF) serves as the primary humectant of the stratum corneum (SC), principally comprised of hygroscopic amino acids and derivatives that absorb moisture. Barrier disruption has been shown to differentially affect the levels of specific NMF components, though the kinetics of NMF component restoration following disruption have not been examined. Here, we investigated the impact of barrier disruption caused by surfactant exposure on a subset of NMF components immediately following exposure and out to 10 days post-exposure. METHODS: Volunteers wore patches containing either 1% w/v sodium lauryl sulphate (SLS) or distilled water on their forearms for 24 h. Measurements of transepidermal water loss, erythema, SC water content and a subset of SC NMF and lipid components were obtained at both sites before treatment, the day of patch removal, and 1, 2, 3, 6, and 10 days following treatment. RESULTS: Most measured NMF components decreased in response to SLS exposure. Exceptions were increases in lactate, ornithine and urea, and no difference in proline levels. In the days following exposure, reduced levels of several NMF components continued at the SLS site; however, all measured NMF components demonstrated equivalence to the vehicle control within 10 days. Histidine pH 7, lactate, ornithine and urea were the first to achieve levels equivalent to the vehicle control site, normalizing within 1 day after patch removal. CONCLUSION: Results imply that NMF components derived from sweat and urea cycling are least impacted by SLS exposure whereas NMF components derived from degradation of filaggrin and/or other S-100 proteins are most impacted. This implies the restoration of the processes responsible for S-100 protein processing into free amino acids takes several days to return to normal. Further examination of the enzymes involved in S-100 protein processing following barrier disruption would provide insight into the pathway(s) for NMF restoration during SC recovery.