Potential Role of Cytosolic RNA Sensor MDA5 as an Inhibitor for Keratinocyte Differentiation in the Pathogenesis of Psoriasis.

BACKGROUND: Psoriasis is a chronic inflammatory skin disease. The etiology of psoriasis is not fully understood, but the genetic background is considered to be the most important factor. To date, many psoriasis-related genes have been discovered, but the role of many important genes has not been well understood. OBJECTIVE: The purpose of this study is to uncover possible roles of MDA5 in psoriasis. METHODS: Expression of MDA5 was investigated using immunohistochemistry. Then, MDA5 was overexpressed in keratinocytes using a recombinant adenovirus. RESULTS: As a result of immunohistochemical staining, the expression of MDA5 was significantly increased in the epidermis of psoriasis compared to normal skin. Similarly, the expression of MDA5 was increased in imiquimod-induced psoriasiform dermatitis model. In cultured keratinocytes, toll-like receptor 3 agonist poly(I:C) induced expression of MDA5 at both mRNA and protein levels. When MDA5 was overexpressed using a recombinant adenovirus, poly(I:C)-induced cytokine expression was significantly increased. Finally, MDA5 overexpression significantly inhibited calcium-induced differentiation of keratinocytes. CONCLUSION: These results suggest that MDA5 increases in psoriasis and negatively regulates keratinocyte differentiation.

Inhibition of Insulin-Like Growth Factor-1-Induced Sebum Production by Bilobetin in Cultured Human Sebocytes.

BACKGROUND: Sebocytes are the major cells of sebaceous gland. The essential role of sebocytes is the production of sebum, a specific lipid mixture, that covers the body surface and provides the barrier function. At puberty, sebum production increases under the effects of various stimuli including androgens and insulin-like growth factor-1 (IGF-1). Excessive sebum production changes the microenvironment surrounding hair follicle, often leading to the onset of acne. OBJECTIVE: We previously performed screening test using cultured human sebocytes, and found that bilobetin had a potential for inhibiting lipid production. The aim of this study is to demonstrate the effects of bilobetin on IGF-1-induced lipogenesis in sebocytes. METHODS: We pretreated simian virus 40 T (SV40T)-transformed sebocytes with bilobetin then stimulated with IGF-1. Effects of bilobetin on lipogenesis of sebocytes were examined by thin layer chromatography and Western blot. RESULTS: Bilobetin markedly inhibited IGF-1-induced lipid production in sebocytes, especially in terms of production of squalene and wax ester. Supporting these results, bilobetin showed significant inhibitory effect on squalene synthase promoter activity. In addition, bilobetin significantly down-regulated lipogenic transcription factors such as sterol response element binding protein (SREBP)-1 and SREBP-2. To delineate the possible action mechanism, we investigated the effect of bilobetin on intracellular signaling. As a result, bilobetin inhibited IGF-1-induced phosphorylation of AKT. CONCLUSION: Together, these results suggest that bilobetin has an inhibitory potential on sebum production in sebocytes, being applicable for acne treatment.

Tropomyosin-receptor kinase fused gene (TFG) regulates lipid production in human sebocytes.

The endoplasmic reticulum (ER) is an organelle in which important cellular events such as protein synthesis and lipid production occur. Although many lipid molecules are produced in the ER, the effect of ER-organizing proteins on lipid synthesis in sebocytes has not been completely elucidated. Tropomyosin-receptor kinase fused gene (TFG) is located in ER exit sites and participates in COPII-coated vesicle formation along with many scaffold proteins, such as Sec. 13 and Sec. 16. In this study, we investigated the putative role of TFG in lipid production in sebocytes using an immortalized human sebocyte line. During IGF-1-induced lipogenesis, the level of the TFG protein was increased in a time- and dose-dependent manner. When TFG was over-expressed using recombinant adenovirus, lipid production in sebocytes was increased along with an up-regulation of the expression of lipogenic regulators, such as PPAR-γ, SREBP-1 and SCD. Conversely, down-regulation of TFG using a microRNA (miR) decreased lipid production and the expression of lipogenic regulators. Based on these data, TFG is a novel regulator of lipid synthesis in sebocytes.

Inhibitory effect of imperatorin on insulin-like growth factor-1-induced sebum production in human sebocytes cultured in vitro.

AIMS: Acne is a common skin disease that originates in the sebaceous gland. The pathogenesis of acne is very complex, involving the increase of sebum production and perifollicular inflammation. In this study, we screened the anti-lipogenic material and demonstrated its effect using cultured human sebocytes. MAIN METHODS: Normal human sebocytes were cultured by explanting the sebaceous glands. To evaluate the anti-lipogenic effect, sebocytes were treated with test materials and (14)C-acetate incorporation assay was performed. KEY FINDINGS: To screen the anti-lipogenic materials, we tested the effect of many herbal plant extracts. We found that Angelica dahurica extract inhibited the insulin-like growth factor-1 (IGF-1)-induced sebum production in terms of squalene synthesis in sebocytes. Furthermore, imperatorin isolated from A. dahurica showed remarkable inhibitory effect on squalene production as well as squalene synthase promoter activity. To investigate the putative action mechanism, we tested the effect of imperatorin on intracellular signaling. The results showed that imperatorin inhibited IGF-1-induced phosphorylation of Akt. In addition, imperatorin significantly down-regulated PPAR-γ and SREBP-1, the important transcription factors for lipid synthesis. SIGNIFICANCE: These results suggest that imperatorin has a potential for reducing sebum production in sebocytes, and can be applicable for acne treatment.

A Novel Compound Rasatiol Isolated from Raphanus sativus Has a Potential to Enhance Extracellular Matrix Synthesis in Dermal Fibroblasts.

BACKGROUND: The fibrous proteins of extracellular matrix (ECM) produced by dermal fibroblast contributes to the maintenance of connective tissue integrity. OBJECTIVE: This study is carried out to identify the bioactive ingredient from natural products that enhances ECM production in dermal fibroblasts. METHODS: Bioassay-directed fractionation was used to isolate the active ingredient from natural extracts. The effects of rasatiol (isolated from Raphanus sativus) on ECM production in primary cultured human dermal fibroblasts was investigated by enzyme linked immunosorbent assay and western blot analysis. RESULTS: Rasatiol accelerated fibroblast growth in a dose-dependent manner and increased the production of type 1 collagen, fibronectin and elastin. Phosphorylation of p42/44 extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, and Akt was remarkably increased by rasatiol, indicating that enhanced ECM production is linked to the activation of intracellular signaling cascades. CONCLUSION: These results indicate that rasatiol stimulates the fibrous components of ECM production, and may be applied to the maintenance of skin texture.

Cedrol Enhances Extracellular Matrix Production in Dermal Fibroblasts in a MAPK-Dependent Manner.

BACKGROUND: The extracellular matrix (ECM) produced by dermal fibroblasts supports skin structure, and degradation and/or reduced production of ECM are the main causes of wrinkle formation. OBJECTIVE: The aim of this study was to identify the active ingredient that enhances ECM production in dermal fibroblasts. METHODS: Polarity-based fractionation was used to isolate the active ingredient from natural extracts, and the effects of cedrol (isolated from Pterocarpus indicusirginia) on ECM production in cultured human dermal fibroblasts was investigated by reverse transcription-polymerase chain reaction, enzyme linked immunosorbent assay, and Western blot analysis. RESULTS: Cedrol accelerated fibroblast growth in a dose-dependent manner and increased the production of type 1 collagen and elastin. Phosphorylation of p42/44 extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, and Akt was markedly increased by cedrol, indicating that enhanced ECM production is linked to activation of intracellular signaling cascades. CONCLUSION: These results indicate that cedrol stimulates ECM production, with possible applications to the maintenance of skin texture.

Adenosine stimulates growth of dermal papilla and lengthens the anagen phase by increasing the cysteine level via fibroblast growth factors 2 and 7 in an organ culture of mouse vibrissae hair follicles.

Hair regression and balding are distressing concerns for an increasing number of people due to changes in lifestyle and serious nutritional imbalances. Therapies for treatment of hair loss are needed. Among potential therapeutics, adenosine has been suggested as a potent regulator of hair growth. In this study, we investigated the effects of adenosine on hair follicles and dermal papilla (DP) cells, and the mechanism underlying the action of adenosine. Hair follicles are organs, including DP cells, that are responsible for the production of hair fibers by inducing and maintaining the hair growth phase (anagen). In a culture of DP cells in vitro, adenosine stimulated proliferation of DP cells by increasing thymidine uptake. Subsequently, adenosine activated and elongated the anagen phase by increasing the uptake of radiolabeled cysteine in an organ culture of mouse vibrissae hair follicles. We also confirmed that adenosine promoted the expression of several growth factors that are responsible for hair growth, including fibroblast growth factors (FGF)-7, FGF-2, insulin-like growth factor (IGF)-1, and vascular endothelial growth factor (VEGF) in a cDNA microarray with semi-quantitative RT-PCR. Transcriptional activation of ß-catenin in DP cells was increased by adenosine in a luciferase assay. ß-catenin is a co-activator of Wnt/ß-catenin signaling that induces morphogenesis and differentiation of hair follicles and also acts to transactivate downstream signaling pathways, including the ERK pathway. Using Western blotting, we found that adenosine stimulated phosphorylation of ERK, CREB and AKT. These results suggest that adenosine stimulates growth of hair follicles by triggering the expression of growth factors and ß-catenin, and by inducing their downstream target signaling pathways.

Stimulation of the extracellular matrix production in dermal fibroblasts by velvet antler extract.

BACKGROUND: Fibroblasts produce many components of the extracellular matrix (ECM) and so they contribute to the maintenance of connective tissue integrity. OBJECTIVE: The aim of this study is to evaluate the effect of velvet antler extract (VAE) on the ECM production of dermal fibroblasts cultured in vitro. METHODS: Primary cultured human dermal fibroblasts were treated with VAE, and then the ECM production was determined by RT-PCR, ELISA and Western blot analysis. Furthermore, the change of gene expression according to VAE treatment was evaluated by cDNA microarray. RESULTS: VAE accelerated the growth of fibroblasts in a dose-dependent manner. VAE increased the production of several ECM components, including type 1 collagen, fibronectin and elastin. In line with these results, the phosphorylations of p42/44 ERK and p38 mitogen-activated protein kinase were markedly increased by VAE, suggesting that the enhancement of ECM production may be linked to the activation of intracellular signaling cascades. VAE also significantly increased cell migration on an in vitro scratch wound test. In cDNA microarray, many genes related with connective tissue integrity were identified to be up-regulated by VAE. CONCLUSION: These results suggest that VAE has a potential to stimulate ECM production, and VAE may be applicable for maintaining the skin's texture.