Kwangmi Kim

CXCR7 mediates SDF1-induced melanocyte migration.

Melanoblasts are derived from the neural crest and migrate to the dermal/epidermal border of skin and hair bulges. Although melanoblast migration during embryogenesis has been well investigated, there are only a few reports regarding the migration of mature melanocytes. Here, we demonstrate that a chemokine, stromal‐derived factor‐1 (SDF1, also known as CXCL12), and one of its receptor CXCR7 regulate normal human epidermal melanocyte (NHEM) migration. We found that SDF1 induces the directional migration of NHEMs. Interestingly, although both CXCR4 and CXCR7 are expressed in NHEMs, blockade of CXCR4 using a CXCR4‐specific neutralizing antibody did not exert any influence on the SDF1‐induced migration of NHEMs, whereas blockade of CXCR7 using a CXCR7‐specific neutralizing antibody did influence migration. Furthermore, SDF1‐induced NHEMs migration exhibited the early hallmark events of CXCR7 signaling associated with MAP kinase activation. It is known that the phosphorylation of ERK through CXCR7 signaling is mediated by β‐arrestins. The treatment of NHEMs with SDF1 resulted in the phosphorylation of ERK in a β‐arrestin 2‐dependent manner. These results suggest that melanocytes may have a unique mechanism of migration via SDF1/CXCR7 signaling that is different from that of other cell types.

IL-4 inhibits the melanogenesis of normal human melanocytes through the JAK2-STAT6 signaling pathway.

Skin diseases can be characterized by their predominant CD4-positive T-helper (Th) cell profiles. Chronic dermatological conditions often give rise to abnormal skin pigmentation. To understand the role of Th cells in pigmentation, the effects of the major Th cell cytokines, IFNγ, IL-4, and IL-17A, on melanogenesis were evaluated using cultured normal human melanocytes (NHMs) instead of relying on transformed melanoma cell lines. IL-4 directly inhibited melanogenesis in NHMs and downregulated both transcription and translation of melanogenesis-associated genes, such as microphthalmia-associated transcription factor (MITF) and dopachrome tautomerase. Despite the lack of a direct inhibition of melanin pigment synthesis, IFNγ and IL-17A increased the synthesis of an antimelanogenic cytokine IL-6 in NHMs. IFNγ activated signal transducers and activators of transcription 1 (STAT1) and STAT3 phosphorylation in NHMs, and IL-4 increased the STAT3 and STAT6 phosphorylation. The differential phosphorylation profile of STAT proteins between IFNγ and IL-4 may explain the difference in their effect on melanogenesis in NHMs. The IL-4-induced downregulation of melanogenesis was inhibited by treating NHMs with a JAK2 inhibitor AG490 or STAT6 siRNA. In conclusion, the involvement of the IL-4-induced JAK2-STAT6 signaling and the IFNγ- or IL-17A-dependent antimelanogenic IL-6 production should be considered as one of the mechanisms explaining the association with hypopigmention in skin diseases.

Characterizations of sphingosylphosphorylcholine-induced scratching responses in ICR mice using naltrexon, capsaicin, ketotifen and Y-27632

Sphingosylphosphorylcholine (SPC) is upregulated in the stratum corneum of atopic dermatitis patients by sphingomyelin deacylase. We conducted an investigation, both to confirm that intradermal injection of SPC elicits scratching in mice, and to elucidate the detailed mechanism of the SPC-induced itch-scratch response. Intradermal administration of SPC increased the incidence of scratching behavior in a dose-dependent manner. SPC-induced scratching could be suppressed, significantly, by the mu-opoid receptor antagonist, naltrexon, the vaniloid receptor agonist, capsaicin, and the histamine H1 receptor antagonist ketotifen. d-erythro SPC, one of the SPC stereotypes, could elicit the scratch response, but not l-threo SPC. Y-27632 (1 mg/kg, an inhibitor of Rho-associated protein kinase (ROCK)), was found to suppress SPC-induced scratching. Both the stereospecificity of SPC and the involvement of the Rho/ROCK pathway suggested that SPC-induced scratching is related to the receptor.

Sphingosylphosphorylcholine down-regulates filaggrin gene transcription through NOX5-based NADPH oxidase and cyclooxygenase-2 in human keratinocytes

Sphingosylphosphorylcholine (SPC) mediates various inflammatory and behavioral responses in atopic dermatitis. Recent studies have shown that dysfunction of the epidermal permeability barrier itself plays a primary role in the etiology of atopic dermatitis. However, the effects of SPC on major proteins essential to the development of the epidermal permeability barrier such as filaggrin, loricrin, involucrin, keratin 1, keratin 10 and small proline-rich proteins are still unclear. In this study, we demonstrated that SPC significantly reduces filaggrin gene transcription, implying that SPC plays a pivotal role in impairment of the epidermal permeability barrier in atopic dermatitis lesional skin. In cultured normal human keratinocytes (NHKs), SPC increases the intracellular level of reactive oxygen species (ROS) and up-regulates NADPH oxidase 5 (NOX5) gene transcription. SPC also stimulates prostaglandin (PG) E(2) production by increasing cyclooxygenase (COX)-2 expression in NHK. The effects of the prostanoid EP receptor agonists, limaprost, butaprost, and sulprostone on filaggrin gene expression in NHK suggest that the prostanoid EP2 receptor plays a significant role in the PGE(2)-mediated filaggrin down-regulation. In contrast, limaprost and butaprost do not affect NOX5 expression in NHK, implying that the NOX5-regulated ROS pathway stimulated by SPC may be upstream of the COX-2 pathway. We propose that the increase in SPC levels further aggravates dermatological symptoms of atopic dermatitis through SPC-induced down-regulation of filaggrin in NHK.

Kojic acid-induced IL-6 production in human keratinocytes plays a role in its anti-melanogenic activity in skin

BACKGROUND Kojic acid is a fungal metabolite widely used in medicinal and cosmetic formulations as a skin-lightening agent based on its de-pigmenting activity. Although in human clinical studies kojic acid has been shown to be effective in the treatment of hyper-pigmentation disorders such as melasma, the reasons for its apparent lack of anti-melanogenic activity in cultured mammalian melanocytes are unclear. OBJECTIVES This study was aimed to elucidate pharmacological mechanisms of the in vivo anti-melanogenic activity of kojic acid in human skin. METHODS A primary human melanocyte and keratinocyte co-culture system was used to evaluate whether kojic-acid-induced changes in keratinocytes were associated with anti-melanogenic activities in melanocytes. The cytokine secretion profiles in response to kojic acid were analyzed. RESULTS Kojic acid increased interleukin (IL)-6 and IL-8 production in melanocyte/keratinocyte co-cultures; however, IL-6 directly inhibited melanogenesis whereas IL-8 did not. In melanocyte monocultures, kojic acid did not increase IL-6 production whereas in keratinocyte monocultures it significantly up-regulated IL-6 gene and protein expression. Therefore, the up-regulation of IL-6 in melanocyte/keratinocyte co-cultures seems to be originated from kojic acid-induced changes in keratinocytes. Anti-IL-6 antibody treatment antagonized the anti-melanogenic effect of kojic acid on the co-cultures. CONCLUSIONS The pharmacological mechanism of kojic acid to explain clinically effective anti-melanogenic activity on hyper-pigmented skin is associated with the kojic acid-induced IL-6 production in keratinocytes. The cross-talk between melanocytes and keratinocytes should be determined in future studies on the pharmacological mechanisms of clinically effective dermatological drugs acting on the epidermis.

Role of epidermal γδ T‐cell‐derived interleukin 13 in the skin‐whitening effect of Ginsenoside F1

Ginsenoside F1 (GF1) is a metabolite of ginsenoside Rg1. Although GF1 has several benefits for skin physiology, the effect of GF1 on skin pigmentation has not been reported. We found that a cream containing 0.1% GF1 showed a significant whitening effect on artificially tanned human skin after 8 weeks of application. However, GF1 did not inhibit mRNA expression of tyrosinase or dopachrome tautomerase (DCT) in normal human epidermal melanocytes (NHEMs) or cocultured NHEMs/normal human epidermal keratinocytes. Interestingly, GF1 enhanced production of interleukin 13 (IL‐13) from human epidermal γδ T cells. IL‐13 significantly reduced the mRNA expression and protein amount of both tyrosinase and DCT and reduced melanin synthesis activities in NHEMs, resulting in visible brightening of NHEM pellet. These results suggest that enhancement of IL‐13 production by GF1 from epidermal γδ T cells might play a role in the skin‐whitening effect of GF1 via the suppression of tyrosinase and DCT.

Comparative Analysis of Human Epidermal and Peripheral Blood γδ T Cell Cytokine Profiles

Background Human epidermal γδ T cells are known to play crucial roles in the defense and homeostasis of the skin. However, their precise mechanism of action in skin inflammation remains less clear. Objective In this study, we analyzed the cytokine expression profile of human epidermal γδ T cells and compared it to that of peripheral blood γδ T cells to investigate the specific activity of epidermal γδ T cells in modulating skin inflammation. Methods We isolated γδ T cells from epidermal tissue or peripheral blood obtained from healthy volunteers. Isolated γδ T cells were stimulated using immobilized anti-CD3 antibody and interleukin-2 plus phytohaemagglutinin, and were then analyzed using a cytokine array kit. Results Both epidermal and peripheral blood γδ T cells produced comparable levels of granulocyte-macrophage colony-stimulating factor, I-309, interferon-γ, macrophage migration inhibitory factor, macrophage inflammatory protein-1α, and chemokine (C-C) ligand 5. The epidermal γδ T cells produced significantly higher levels of interleukin-4, -8, -13, and macrophage inflammatory protein-1β than the peripheral blood γδ T cells did. Notably, the epidermal γδ T cells produced several hundred-fold higher levels of interleukin-13 than interleukin-4. Conclusion These results suggest that the epidermal γδ T cells have a stronger potential to participate in the Th2-type response than the peripheral blood γδ T cells do. Furthermore, epidermal γδ T cells might play an important role in the pathogenesis of Th2-dominant skin diseases because of their active production of interleukin-13.

Immunohistological comparison of cutaneous pathology of three representative murine atopic dermatitis models

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ITAC induces the melanocytic migration and hypopigmentation through destabilizing p53 via HDAC5: A possible role of ITAC in pigment-related disorders

Cell migration plays a major role in the immune response and in tumorigenesis. Interferon‐inducible T‐cell alpha chemoattractant (ITAC) elicits a strong chemotactic response from immune cells.