Regulation of keratinocyte differentiation by O-GlcNAcylation.

BACKGROUND: O-linked ß-N-acetylglucosamine (O-GlcNAc) modification is one of the posttranslational modification, emerging as an important regulatory mechanism in various cellular events. OBJECTIVE: We attempted to investigate whether O-GlcNAcylation is involved in keratinocyte differentiation. METHODS: Immunohistochemistry and Western blot were performed to demonstrate O-GlcNAcylation in keratinocyte differentiation. RESULTS: During calcium-induced keratinocyte differentiation, overall O-GlcNAcylation was decreased in a temporal manner. We focused our attention on transcription factor Sp-1, which is implicated in keratinocyte differentiation. Total Sp-1 level did not change during keratinocyte differentiation. However, O-GlcNAcylated Sp-1 was decreased in a keratinocyte differentiation-dependent manner. Interestingly, transcriptional activity of Sp-1, in terms of involucrin and loricrin promoter activities, was markedly increased by overexpression of O-GlcNAcase (OGA). In addition, membrane permeable non-O-GlcNAcylated Sp-1 did show transcriptional activity, while membrane permeable O-GlcNAcylated Sp-1 did not, suggesting O-GlcNAcylated Sp-1 is an inactive form in keratinocyte differentiation. CONCLUSION: Our results reveal that O-GlcNAcylation is a dynamic regulatory mechanism for keratinocyte differentiation.

Toenail onychomycosis treated with a fractional carbon-dioxide laser and topical antifungal cream.

BACKGROUND: Traditional pharmacotherapy for onychomycosis has low to moderate efficacy and may be associated with adverse reactions and medication interactions limiting its use in many patients. OBJECTIVE: We evaluated the clinical efficacy and safety of a fractional carbon-dioxide laser with topical antifungal therapy in the treatment of onychomycosis. METHODS: In all, 24 patients were treated with fractional carbon-dioxide laser therapy and a topical antifungal cream. The laser treatment consisted of 3 sessions at 4-week intervals. Efficacy was assessed based on the response rate from standardized photographs, a microscopic examination of subungual debris, and subjective evaluations. RESULTS: Among the patients, 92% showed a clinical response and 50% showed a complete response with a negative microscopic result. The factors that influenced a successful outcome were the type of onychomycosis and the thickness of the nail plate before treatment. The treatment regimen was well tolerated and there was no recurrence 3 months after the last treatment episode. LIMITATIONS: The study followed up only 24 patients and there were no relevant treatment controls. CONCLUSIONS: Fractional carbon-dioxide laser therapy, combined with a topical antifungal agent, was effective in the treatment of onychomycosis. It should be considered an alternative therapeutic option in patients for whom systemic antifungal agents are contraindicated.

Glucocorticoid receptor enhances involucrin expression of keratinocyte in a ligand-independent manner.

In this study, we investigated the role of glucocorticoid receptor (GR) in epidermal keratinocytes. In adult normal human skin, GR was highly expressed in the upper layers of the epidermis. Consistent with normal skin, GR expression was increased after calcium treatment of HaCaT keratinocytes cultured in vitro, suggesting that GR is involved in keratinocyte differentiation process. Overexpression of GR using an adenovirus showed that expression of involucrin, an early differentiation marker of keratinocytes, was markedly increased due to GR overexpression. However, treatment with dexamethasone, a GR agonist, did not increase involucrin expression. Overexpression of GR led to phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinases (ERK) in the absence of glucocorticoid, suggesting that the GR effect on involucrin expression is related to activation of intracellular signaling cascades. This idea was supported by the fact that GR-mediated involucrin induction was abolished after treatment with JNK and ERK inhibitors. In addition, GR mutants lacking the ligand-binding domain increased involucrin expression concomitantly with increase of ERK phosphorylation. Together, these results suggest that GR modulates involucrin expression of keratinocytes by regulating the intracellular signaling network in a ligand-independent manner.