Hee-Chul Eun

Delayed ERK activation by ceramide reduces melanin synthesis in human melanocytes

Sphingolipid metabolites regulate many aspects of cell growth and differentiation. However, the effects of sphingolipids on the growth and melanogenesis of human melanocytes are not known. In the present study, we investigated the effects of sphingolipid metabolites and the possible signalling pathways involved in human melanocytes. Our data show that C(2)-ceramide inhibits cell growth in a dose-dependent manner, whereas sphingosine-1-phosphate (SPP) has no effect. Moreover, we observed that the melanin content of the cells was significantly decreased by C(2)-ceramide. The pigmentation-inhibiting effect of C(2)-ceramide at 1-10 microM was stronger than that of kojic acid, tested at 1-100 microM. The tyrosinase activity of cell extracts was reduced by C(2)-ceramide treatment. However, in the cell-free system, C(2)-ceramide could not suppress tyrosinase, whereas kojic acid directly inhibited tyrosinase. These results suggest that C(2)-ceramide decreases the pigmentation of melanocytes indirectly regulating tyrosinase. Furthermore, we found that C(2)-ceramide decreased the protein expression of microphthalmia-associated transcription factor (MITF), which is required for tyrosinase expression. To identify the signalling pathway of ceramide, we studied the ability of C(2)-ceramide to influence extracellular signal-regulated protein kinase (ERK) and Akt/protein kinase B (PKB) activation. C(2)-ceramide induced a delayed activation of ERK ( > 1 h) and a much later activation of Akt/PKB ( > 3 h) in human melanocytes. In addition, the specific inhibition of the ERK and the Akt signalling pathways by PD98059 and LY294002, respectively, increased melanin synthesis. Thus, it seems that sustained ERK and Akt activation may lead to the suppression of cell growth and melanogenesis.

A randomized, double-blind, placebo-controlled trial of vitamin C iontophoresis in melasma.

Background: Vitamin C is known to both inhibit melanin formation and reduce oxidized melanin. However, vitamin C does not easily penetrate the skin. In this study, vitamin C iontophoresis was employed in order to enhance vitamin C penetration. Objective: The purpose of this study was to evaluate the efficacy of vitamin C iontophoresis for melasma patients. Methods: Twenty-nine females with melasma were enrolled. For iontophoresis, a vitamin C solution was applied to one side of the face, while distilled water was applied to the other side as a control. The L (luminance) value was measured by a colorimeter to obtain an objective pigmentation parameter. Results: Twelve weeks after iontophoresis, the colorimeter of the treated site showed a significant decrease in the L value (from 4.60 to 2.78, p = 0.002), compared to that of the control site (from 4.45 to 3.87, p = 0.142). Conclusion: Vitamin C iontophoresis may be an effective treatment modality for melasma.

Overexpression of HSP70 prevents ultraviolet B-induced apoptosis of a human melanoma cell line

Abstract The heat shock response is a highly conserved reaction common to all cells and organisms. It has been reported that hyperthermic treatment can induce the expression of the heat shock protein (HSP) and can protect cells from ultraviolet (UV) B radiation. In this study, we evaluated the effects of induced HSP70 on resistance to UV radiation. G361 amelanotic human melanoma cells were irradiated with increasing doses of UVB. UVB irradiation caused apoptotic cell death in these cells. Following transfection with MFG.hsp70.puro plasmid, the expression of HSP70 was determined. Compared to control vector-transfected cells, hsp70-transfected cells showed significantly elevated levels of HSP70 and were highly resistant to UVB irradiation. In order to investigate the effects of HSP70 on the apoptotic pathway, the changes in caspase-3 and PARP were analyzed. Following UVB irradiation, activation of caspase-3 and cleavage of PARP were observed in control vector-transfected cells, and the changes in these molecules were inhibited in the hsp70-transfected cells. These results suggest that UVB-induced apoptosis of melanoma cells is accompanied by caspase-3 activation and PARP cleavage, which can be prevented by an overexpression of HSP70.

A comparative study of the cytotoxicity of skin irritants on cultured human oral and skin keratinocytes

Summary The cytotoxicity of irritants on human oral and skin keratinocyte culture models was compared. Keratinocytes were exposed to sodium lauryl sulphate and benzalkonium chloride at concentrations of 10–4–10–7 M for 24 h. Cytotoxicity was evaluated by changes in niitochondrial metabolic activity (MIT assay) and plasma membrane integrity (LDH leakage). Our results showed that oral and skin keratinocytes are equally sensitive to the irritants tested. There were marked similarities in susceptibility between each cell type cultured from six individuals. The immunohistochemical staining pattern of both cell types resembled that of the basal cell.

Skin problems after a tsunami.

Backgroundu2002 On December 26, 2004, the biggest earthquake for 40 years, measuring 9.0 on the Richter scale, triggered a tsunami that pounded the coastal areas of South Asia and East Africa. The effects of the tsunami on skin conditions have not been evaluated.

Multicenter study of the frequency of contact allergy to gold.

Gold sodium thiosulfate (GSTS) is reputed to be the most reliable gold antigen, but control studies are still required. Although Koreans have more varied sources of contact with gold, such as herbal medicines with gold coatings and indwelling gold acupuncture needles, no epidemiological studies have been performed. This study examined the frequency and sources of contact allergy to gold in South Korea by a multicenter study. Patch testing with 0.5% GSTS in pet. was conducted in 255 eczema patients and 58 control subjects. Results were observed at 21 days (D) to ensure there were no undetected late reactions in 54 observed patients and 47 controls. 8 (3.1%) of the 255 patients reacted positively to GSTS, including 1 with a late reaction. 1 of the 58 controls showed a positive reaction to GSTS on D4 with a negative reaction on D14. Clinical relevance was lacking in the patients with positive reactions. Unexpectedly, the above particular sources of gold contact gave rise to few allergic reactions in our patients.

Botulinum toxin treatment for a compensatory hyperhidrosis subsequent to an upper thoracic sympathectomy

BACKGROUND : Compensatory hyperhidrosis is the commonest complication of sympathectomy, but theres no known effective treatment. METHODS : Botulinum toxin type A (a total dose of 300 MU, 1.0 MU/cm 2 ) was used successfully to treat a 68-year-old male with a 5-year history of compensatory hyperhidrosis of the anterior chest following thoracic sympathectomy for palmar hyperhidrosis. RESULTS : The hyperhidrosis resolved for 8 months without systemic side effects. CONCLUSION : Intracutaneous injection of botulinum toxin is a fast, safe, effective and well-accepted approach for treatment of compensatory hyperhidrosis.

Enhanced proliferation and collagen synthesis of human dermal fibroblasts in chronically photodamaged skin.

Cutaneous aging can be divided into intrinsic aging and photoaging. We investigated the influence of aging and photoaging on the proliferation and collagen synthesis of human dermal fibroblasts cultured 3‐dimensionally in a collagen gel. We examined 11 human dermal fibroblast cell lines cultured from 3 newborn skins (1 day old), and both exposed and unexposed skin from 4 elderly volunteers (60, 60, 73, 76 years old), respectively. Newborn fibroblasts actively proliferated within the attached collagen gels compared with the elderly cell lines. Within the attached collagen gels in the presence of 10% fetal calf serum (FCS), the fibroblasts from exposed skin proliferated rapidly compared with fibroblasts from unexposed skin from the same individuals. In collagen gel and monolayer cultures with 1% FCS, the percentage of collagen synthesized by photoaged and aged fibroblasts decreased significantly compared with that by newborn fibroblasts. When the fibroblasts were cultured three dimensionally in attached collagen gels in the presence of 1% FCS, the relative levels of collagen synthesis by cultured fibroblasts from photoaged skin were increased significantly compared with those of aged skin fibroblasts from the same individuals. These results suggest that fibroblasts of exposed skin may be more active than those of unexposed skin and that the three‐dimensional culture of fibroblast can be used as a model to investigate the influence of aging and photoaging on cell functions.

Patch test responses to rockwool of different diameters evaluated by cutaneous blood flow measurement

Rockwool is a man‐made mineral fiber used mainly for insulation, which can cause mechanical skin irritation. This study was performed to evaluate the irritant potential of rockwools of different diameters and to compare the change of blood flow, measured by laser Doppler flowmetry, at different patch test occlusion times with rockwools. Rockwool A(mean diameter 4.20 ± 1.96 μ) was more irritating than rockwool B (mean diameter 3.20 ± 1.5 μ). The difference was more clearly observed in a 48‐h patch test than in an 8‐h or 24‐h test. We consluded that laser patch test responses to mechanical irritants like rockwool, and that 48 h or more of occlusion time was necessary to produce irritant patch test responses to certain types of rockwool.

Microarray analysis reveals increased expression of ΔNp63α in seborrhoeic keratosis

Backgroundu2002 Seborrhoeic keratoses (SKs) are very common benign epidermal lesions without malignant potential. Ultraviolet radiation, old age and viruses are well‐known risk factors for disease development. However, the pathomechanisms of SK are not fully understood.