Filaggrin Expression In Keratinocytes Research Articles

Transient receptor potential vanilloid 1 plays a major role in low temperature–mediated skin barrier dysfunction

Children born in the fall and winter are at increased risk for developing atopic dermatitis and food allergy. Because these seasons are associated with low temperatures, we hypothesized that exposure to low temperatures may compromise keratinocyte differentiation and contribute to skin barrier dysfunction. We examined whether low temperature causes skin barrier dysfunction. Primary human epidermal keratinocytes (HEK) were differentiated in 1.3 mmol CaCl2 media and cultured at different temperatures. The cells were transfected with transient receptor potential cation channel subfamily V member 1 (TRPV1) or STAT3 small interfering RNA (siRNA) to examine the effects of these gene targets in HEK exposed to low temperature. Gene expression of TRPV1, epidermal barrier proteins, and keratinocyte-derived cytokines were evaluated. Organotypic skin equivalents were generated using HEK transfected with control or TRPV1 siRNA and grown at 25°C or 37°C. Transepidermal water loss (TEWL) and levels of epidermal barrier proteins were evaluated. Filaggrin (FLG) and loricrin (LOR) expression, but not keratin (KRT)-1 and KRT-10 expression, was downregulated in HEK incubated at 25°C, while TRPV1 silencing increased intracellular Ca2+ influx (keratinocyte differentiation signal) and enhanced the expression of epidermal differentiation proteins. IL-1β and thymic stromal lymphopoietin induced by low temperature inhibited FLG expression in keratinocytes through the TRPV1/STAT3 pathway. Moreover, low temperature-mediated inhibition of FLG and LOR was recovered, and TEWL was decreased in organotypic skin transfected with TRPV1 siRNA. TRPV1 is critical in low temperature-mediated skin barrier dysfunction. Low temperature exposure induced thymic stromal lymphopoietin, an alarmin implicated in epicutaneous allergen sensitization.

Basics and recent advances in the pathophysiology of atopic dermatitis.

Atopic dermatitis is a common, chronic inflammatory skin disease that is characterized by skin barrier dysfunction, inflammation and intense itch. Although the exact mechanisms behind its pathogenesis remain unclear, it is evident that the complex interplay among barrier dysfunction, inflammation and itch are critical in its development, progression and chronicity. Abnormalities in filaggrin, intercellular lipids and tight junctions induce barrier-disrupted skin, which produces thymic stromal lymphopoietin, interleukin (IL)-25 and IL-33; these in turn promote skin inflammation characterized by type 2 immune deviation. This inflammation then downregulates the expression of filaggrin in keratinocytes and exacerbates epidermal barrier dysfunction. Furthermore, various itch mediators/pruritogens produced during this inflammatory process can act directly on sensory nerves and cause itch. In this review, we summarize the basics and recent advances in our understanding of the pathophysiology of atopic dermatitis focusing on three aspects: barrier dysfunction, skin inflammation and itch.

The Potential Application of Ecklonia cava Extract in Scalp Protection

The scalp is exposed to environmental hazards including airborne pollutants, which exert adverse effects on skin health. Therefore, compounds for defending skin from pollutants have attracted interest in the cosmeceutical community. We investigated whether Ecklonia cava exhibited prophylactic effects against urban pollutants by measuring cell viability and cell cycle distribution in human follicle dermal papilla cells (HFDPC). The effect of E. cava on pollutant-induced damage to skin barrier was determined by measuring filaggrin and MMP-1 expression in both keratinocytes and in a skin explant model. In a clinical trial, the effect of E. cava on scalp skin of patients with scalp scale was observed by evaluating hydration and redness after 4 weeks of daily treatment with a shampoo containing E. cava extract. E. cava extract recovered the loss of cell viability and abnormal cell cycle distribution induced by urban pollutants in HFDPCs. It also attenuated pollutant-induced damage to skin barrier by decreasing MMP-1 and increasing filaggrin expression in keratinocytes and the epidermis of skin explants. Moreover, E. cava showed soothing effects on human scalp by increasing hydration and decreasing redness in a clinical trial. Collectively, E. cava extract may be a good candidate for therapeutic applications designed to repair or protect hair scalp.

Pathogenesis of Atopic Dermatitis: Current Paradigm.

Atopic dermatitis (AD) is characterized by skin inflammation, barrier dysfunction and chronic pruritus. In this review, recent advances in the pathogenesis of AD are summarized. Clinical efficacy of the anti-IL-4 receptor antibody dupilumab implies that type 2 cytokines IL-4 and IL-13 have pivotal roles in atopic inflammation. The expression of IL-4 and IL-13 as well as type 2 chemokines such as CCL17, CCL22 and CCL26 is increased in the lesional skin of AD. In addition, IL-4 and IL-13 down-regulate the expression of filaggrin in keratinocytes and exacerbate epidermal barrier dysfunction. Keratinocytes in barrier-disrupted epidermis produce large amounts of thymic stromal lymphopoietin, IL-25 and IL-33, conducing to type 2 immune deviation via OX40L/OX40 signaling. IL-31, produced by type 2 T cells, is a cardinal pruritogenic cytokine. IL-4 and IL-13 also amplify the IL-31-mediated sensory nerve signal. These molecules are particularly important targets for future drug development for AD.

Aryl hydrocarbon receptor activation restores filaggrin expression via OVOL1 in atopic dermatitis

Filaggrin (FLG) mutation is a well-confirmed genetic aberration in atopic dermatitis (AD). Genome-wide association studies on AD have revealed other susceptibility genes, for example, Ovo-like 1 (OVOL1). Nonetheless, the relation between FLG and OVOL1 is unclear. Because aryl hydrocarbon receptor (AHR; a ligand-activated transcription factor), plays a role in FLG expression in keratinocytes, we hypothesized that AHR regulates FLG expression via OVOL1. To demonstrate this mechanism, we analyzed FLG expression in OVOL1-overexpressing or OVOL1-knockdown normal human epidermal keratinocytes (NHEKs). Furthermore, we tested whether AHR activation by 6-formylindolo(3,2-b)carbazole (FICZ), an endogenous AHR ligand, or Glyteer, clinically used soybean tar, upregulates FLG and OVOL1 expression in NHEKs. We found that (1) OVOL1 regulates FLG expression; (2) AHR activation upregulates OVOL1; and (3) AHR activation upregulates FLG via OVOL1. Moreover, nuclear translocation of OVOL1 was less pronounced in AD skin compared with normal skin. IL-4-treated NHEKs, an in vitro AD skin model, also showed inhibition of the OVOL1 nuclear translocation, which was restored by FICZ and Glyteer. Thus, targeting the AHR–OVOL1–FLG axis may provide new therapeutics for AD.

T Helper 1 and T Helper 2 Cytokines Differentially Modulate Expression of Filaggrin and its Processing Proteases in Human Keratinocytes.

Background:Atopic dermatitis (AD) is characterized by defective skin barrier and imbalance in T helper 1/T helper 2 (Th1/Th2) cytokine expression. Filaggrin (FLG) is the key protein to maintaining skin barrier function. Recent studies indicated that Th1/Th2 cytokines influence FLG expression in keratinocytes. However, the role of Th1/Th2 cytokines on FLG processing is not substantially documented. Our aim was to investigate the impact of Th1/Th2 cytokines on FLG processing.Methods:HaCaT cells and normal human keratinocytes were cultured in low and high calcium media and stimulated by either interleukin (IL)-4, 13 or interferon-γ (IFN-γ). FLG, its major processing proteases and key protease inhibitor lymphoepithelial Kazal-type-related inhibitor (LEKTI) were measured by both real-time quantitative polymerase chain reaction and Western blotting. Their expression was also evaluated in acute and chronic AD lesions by immunohistochemistry.Results:IL-4/13 significantly reduced, while IFN-γ significantly up-regulated FLG expression. IL-4/13 significantly increased, whereas IFN-γ significantly decreased the expression of kallikreins 5 and 7, matriptase and channel-activating serine protease 1. On the contrary, IL-4/13 significantly decreased, while IFN-γ increased the expression of LEKTI and caspase-14. Similar trends were observed in AD lesions.Conclusions:Our results suggested that Th1/Th2 cytokines differentially regulated the expression of major FLG processing enzymes. The imbalance between Th1 and Th2 polarized immune response seems to extend to FLG homeostasis, through the network of FLG processing enzymes.

Chronic exposure to cigarette smoke increases matrix metalloproteinases and Filaggrin mRNA expression in oral keratinocytes: Role of nicotine stimulation

The vegetal alkaloid nicotine has been proved to modify the expression of many keratinocyte markers. In this study, the basal expression of MMP-2, MMP-9, MMP-28, and Filaggrin has been evaluated in oral keratinocytes, in order to collect information about the ability of cigarette smoke to modify the basal expression pattern of these key enzymes in the absence of evident clinical signs in the oral epithelium. MMP-2, MMP-9, MMP-28, and Filaggrin basal expression was investigated by RT-PCR in oral keratinocytes derived from smokers (n=11), non-smokers (n=11), and ex-smokers (n=6) healthy volunteers. Moreover keratinocytes from non-smokers volunteers were stimulated in vitro by a single dose administration of nicotine (10 μM) in order to estimate the effect of nicotinic receptors activation on the basal expression of the studied markers. RT-PCR analysis showed that all the markers studied were overexpressed in keratinocytes from smoker donors compared to control keratinocytes, while a single dose of nicotine was able to induce only Filaggrin expression in keratinocytes from non-smoking donors. Markers expression in ex-smoker donors was similar to that observed in normal non-smoker donors. These data indicate for the first time that cigarette smoking affects basal expression of some important markers in oral mucosa keratinocytes in vivo in the absence of clinical signs and that smoke quitting restores basal expression levels of these markers.