Stabilization of microtubules restores barrier function after cytokine-induced defects in reconstructed human epidermis.

BACKGROUND: A variety of human skin disorders is characterized by defects in the epidermal barrier, leading to dehydration, itchiness, and rashes. Previously published literature suggests that microtubule stabilization at the cortex of differentiating keratinocytes is necessary for the formation of the epidermal barrier. OBJECTIVES: We tested whether stabilization of microtubules with paclitaxel or epothilone B can repair barrier defects that were experimentally induced in three-dimensional culture models of epidermis. METHODS: We established two models of defective epidermis in vitro, using three-dimensional cultures of primary human keratinocytes on filter supports: immature reconstructed human epidermis (RHE), and RHE that was compromised by treatment with inflammatory cytokines, the latter mimicking defects seen in atopic dermatitis. RESULTS: Both paclitaxel and epothilone B promoted keratinocyte differentiation, accumulation of junctional proteins at the cell cortex, and the early appearance of lamellar bodies in immature RHE, whereas destabilization of microtubules by nocodazole had the reverse effect. Moreover, stabilization of microtubules rescued the barrier after cytokine treatment. The rescued barrier function correlated with the restoration of filaggrin and loricrin protein levels, the cortical accumulation of junctional proteins (E-cadherin, ß-catenin, and claudin-1), and with the secretion of lamellar bodies. CONCLUSIONS: Our data suggest that the microtubule network is important for the formation of the epidermis, and that stabilization of microtubules promotes barrier formation. Microtubule stabilization may support regeneration of damaged skin, by restoring or improving the barrier.

Cathepsin S, a new pruritus biomarker in clinical dandruff/seborrhoeic dermatitis evaluation.

Dandruff/seborrhoeic dermatitis (D/SD) is characterized by Malassezia colonization, impaired barrier function with subsequent inflammation, resulting in dandruff and itching. Histamine is one of the biomarkers of pruritus now widely used in treatment efficacy trials. The exact mechanism leading to histamine release and pruritus is not yet clear. However, it could involve cathepsin S, an activator of proteinase-activated receptor 2 (PAR2). The purpose of this study was to evaluate the levels of cathepsin S, PAR2 and histamine in patients with D/SD compared with healthy subjects through non-invasive sampling of the scalp and to correlate those markers with D/SD clinical parameters. A significant increase in the three biological markers was observed in the D/SD group versus healthy subjects, and those markers were correlated with clinical parameters. In conclusion, cathepsin S could be a potential marker of pruritus in D/SD and could help assessing the effect of treatments.

Clinical and biochemical assessment of maintenance treatment in chronic recurrent seborrheic dermatitis: randomized controlled study.

INTRODUCTION: Few studies have investigated the long-term effects of a maintenance regimen in the prevention of relapses in scalp seborrheic dermatitis (SD), in particular following biomarker changes. MATERIALS AND METHODS: A new shampoo containing beta-glycyrrhetinic acid (18ßGA) in addition to cyclopiroxolamine (CPO) and zinc pyrithione (ZP) was tested in 67 subjects suffering from SD with moderate to severe erythema and itching in a biphasic study. After a first common intensive treatment phase (investigational product thrice a week × 2 weeks), subjects randomly received the investigational product once a week × 8 weeks (maintenance) or a neutral shampoo (discontinuation) in a comparative, parallel group maintenance phase. Efficacy was assessed clinically (overall clinical dandruff score, erythema, overall efficacy, self-evaluation), biochemically and microbiologically by quantitative polymerase chain reaction (qPCR), high performance liquid chromatography (HPLC) or enzyme-linked immunoabsorbent assay (ELISA) analysis of scale samples (Malassezia species (restricta and globosa), cohesion proteins (plakoglobins), inflammation (Interleukin (IL)-8, IL-1RA/IL-1α) and pruritus (histamine, cathepsin S) markers). RESULTS: During the intensive treatment phase, SD improved significantly (p < 0.0001) with a decrease in clinical signs as well as Malassezia species, cohesion proteins, inflammation and pruritus markers. During the maintenance phase, the improvement persisted in the 'maintenance' group only, with a significant intergroup difference. A consistently positive relationship was found between dandruff, itching, erythema and Malassezia populations, histamine levels and IL-1RA/IL-1α ratio. CONCLUSION: The effectiveness of this maintenance regimen was objectively demonstrated at the clinical, biochemical and microbiological level. Correlations between clinical signs and biomarkers could provide clues to explain the resolution of SD and confirm the interest of biomarkers for SD treatment assessment.

Slow internal release of bioactive compounds under the effect of skin enzymes.

A new strategy for the skin delivery of bioactive compounds has been developed, using enzymes involved in the maintenance of the epidermal barrier function and the enzymatic transformation of corresponding precursors. This new strategy has been tested with regard to two enzymatic activities of the skin barrier: extracellular glucosidase and esterase/lipase. An analysis of the requirements for the glycosidic bond hydrolysis of any glycoconjugate by beta-glucocerebrosidase indicates that the release of the moiety linked to the glucose unit is obtained as long as the glycosidic bond being broken is not hindered, and as long as the leaving group property of the released moiety is good enough. This strategy was first applied to the release of the antioxidant delta-tocopherol. It was then extended to retinoic acid by introducing a spacer between the glucose unit and the bioactive moiety. This spacer was either a good leaving group such as hydroquinone, or a structure akin to a ceramide, namely glycerol. In these conditions, beta-glucocerebrosidase releases the complex spacer-active compound that is cleaved by an esterase. One of the advantages of this strategy lies in the slow release of the bioactive compound, extending in time its effect and most likely its tolerance, as is the case for retinoic acid.

Selective inhibition of Fe- versus Cu/Zn-superoxide dismutases by 2,3-dihydroxybenzoic acid derivatives.

A series of catechol derivatives were synthesised and tested for their ability to inactivate the iron-containing superoxide dismutase (Fe-SOD) from Escherichia coli and the bovine erythrocytes Cu/Zn-SOD. Incubation of catechols with Fe- or Cu/Zn SODs resulted in a time-dependent loss of enzyme activity with highly selective inhibition for the iron-dependent enzyme. Catechol-induced inactivation of SODs was correlated with the auto-oxidation of the catechol compounds to their corresponding ortho-quinone derivatives, which was found to be non-dependent on the presence of enzymes. Mass electrospray experiments on catechol-incubated Fe-SOD provided evidence for the irreversible nature of the inhibition process, yielding to a complex mixture of modified proteins.