Increased expression of the aryl hydrocarbon receptor in patients with chronic inflammatory skin diseases

Polychlorinated biphenyls (PCBs) and 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) are major environmental pollutants, and their effects on the human body critically depend on the aryl hydrocarbon receptor (AhR). The aim of this study was to evaluate the significance of the AhR and its ligands in chronic inflammatory skin diseases such as atopic dermatitis (AD) and psoriasis. Expression of AhR‐related mRNA was increased in lesional skin from patients with AD and psoriasis compared to those of normal skin from healthy controls. The AhR and aryl hydrocarbon receptor nuclear translocator were colocalized in the nuclei of keratinocytes at the lower epidermis of psoriatic lesions, which suggested activation of the AhR pathway. After treatment of normal human epidermal keratinocytes with TCDD or PCBs, IL‐6 and IL‐8 production were increased. The results of this study suggest that AhR is highly expressed in the acute lesional skin of patients with AD and psoriasis, and the AhR pathway is activated especially in psoriasis.     

Environment‐induced lentigines: formation of solar lentigines beyond ultraviolet radiation

There is no doubt that ultraviolet radiation (UVR) contributes to the generation of acquired lentigines in human skin, as indicated by the term solar lentigo. A growing number of recent epidemiological and mechanistic studies, however, strongly suggest that in addition to UVR, other environmental factors contribute to lentigines’ formation as well. We therefore here introduce the term ‘environment‐induced lentigo’ (EIL) to refer to acquired pigment spots of human skin. In this view point, we (i) summarize the existing evidence to support a role of environmental toxicants other than UVR in the pathogenesis of EILs, (ii) we argue that activation of aryl hydrocarbon receptor (AHR) signalling by UVR and environmental toxicants is critically involved in triggering and sustaining a crosstalk between melanocytes, keratinocytes and fibroblasts, which then causes the development and persistence of EILs in human skin, and (iii) we discuss clinical implications for the prevention and treatment of EILs resulting from this concept.     

Curcumin inhibits UVB‐induced matrix metalloproteinase‐1/3 expression by suppressing the MAPK‐p38/JNK pathways in human dermal fibroblasts

Curcumin (diferuloylmethane) is a polyphenol derived from turmeric (Curcuma longa), which is commonly used as a spice. Recent studies have shown that curcumin has a wide range of pharmacological activities, including anticarcinogenic, antioxidant, anti‐inflammatory and antiangiogenic activities. However, the antiphotoageing effects of curcumin have yet to be characterized. In this study, we investigated the inhibitory effects of curcumin on matrix metalloproteinase (MMP)‐1 and MMP‐3 expression in human dermal fibroblast cells. Western blot analysis revealed that curcumin inhibited ultraviolet (UV) B‐induced MMP‐1 and MMP‐3 expression. Furthermore, curcumin significantly blocked UVB‐induced reactive oxygen species generation in fibroblasts. Curcumin treatment significantly blocked the UVB‐induced activation of nuclear factor (NF)‐κB and activator protein (AP)‐1. Additionally, curcumin strongly repressed the UVB‐induced phosphorylation of p38 and c‐Jun N‐terminal kinase. Curcumin prevented UVB‐induced MMP expression through mitogen‐activated protein kinase/NF‐κB inhibition and AP‐1 activation. In conclusion, curcumin may be useful for preventing and treating skin photoageing.     

Antioxidant soybean tar Glyteer rescues T‐helper‐mediated downregulation of filaggrin expression via aryl hydrocarbon receptor

Soybean tar Glyteer (Gly) has been widely used for the treatment of various inflammatory skin diseases in Japan since 1924 as an alternative to coal tar remedy. Recently, coal tar has been shown to induce barrier repair in atopic dermatitis via aryl hydrocarbon receptor (AhR). In this study, we demonstrated that Gly activated AhR by inducing its cytoplasmic to nuclear translocation in keratinocytes. The AhR ligation by Gly was biologically active, with significant and dose‐dependent upregulation of CYP1A1 expression, which is a specific marker for AhR activation. Gly upregulated the expression of filaggrin in an AhR‐dependent manner because its enhancing effect was completely abrogated in AhR‐knockdown keratinocytes. T‐helper (Th)2 cytokines inhibited the expression of filaggrin; however, Gly completely restored the Th2‐mediated inhibition of filaggrin expression. Furthermore, Gly coordinately upregulated a series of epidermal differentiation complex genes, including involucrin, loricrin and hornerin. In addition, Gly exhibited potent antioxidant activity through the activation of nuclear factor‐erythroid 2‐related factor‐2 (Nrf2) and downstream antioxidant enzymes such as NAD(P)H:quinone oxidoreductase 1 (Nqo1), which actually inhibited the generation of reactive oxygen species in keratinocytes treated with tumor necrosis factor‐α or benzo[α]pyrene. In conclusion, antioxidant Gly rescues the downregulated expression of filaggrin (and plausibly other barrier proteins) in a Th2‐skewed milieu via AhR activation, which may partly explain its empirical anti‐inflammatory therapeutic effects.     

Serum amyloid A1 secreted from UV‐irradiated keratinocytes induces matrix metalloproteinase‐1 in fibroblasts through toll‐like receptor 4

Ultraviolet (UV) irradiation on skin triggers photoageing‐related phenotypes such as formation of wrinkles. UV ray upregulates matrix metalloproteinase‐1 (MMP‐1), which in turn degrades extracellular matrix proteins, mostly collagens. Serum amyloid A1 (SAA1) is an acute‐phase protein of which plasma concentration increases in response to inflammation. Although the expression of SAA1 in the skin was reported, its function in the skin is yet to be studied. In this research, we found that the expression of SAA1 was increased in acute UV‐irradiated buttock skin and photoaged forearm skin in vivo. UV irradiation also increased SAA1 in normal human epidermal keratinocytes (NHEK), and treatment of recombinant human SAA1 (rhSAA1) induced MMP‐1 in normal human dermal fibroblasts (NHDF) but not in NHEK. Next, we demonstrated that NHDF treated with UV‐irradiated keratinocyte‐conditioned media showed the increased MMP‐1 expression; however, this increase of MMP‐1 in NHDF was inhibited by knockdown of SAA1 in NHEK. In addition, knockdown of Toll‐like receptor 4 (TLR4) inhibited rhSAA1‐induced MMP‐1 expression in NHDF. Taken together, our data showed that UV‐induced SAA1 production in NHEK, and this secreted SAA1 induced MMP‐1 expression in NHDF in a paracrine manner through TLR4 signalling pathway. Therefore, our results suggest that SAA1 can be a potential mediator for UV‐induced MMP‐1 expression in human skin.     

Z‐Ligustilide inhibits benzo(a)pyrene‐induced CYP1A1 upregulation in cultured human keratinocytes via ROS‐dependent Nrf2 activation

Benzo(a)pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH), is an environmental contaminant that can induce cytochrome P4501A1 (CYP1A1) upregulation via aryl hydrocarbon receptor (AhR) activation and provoke inflammation. Here, we investigated the effect of Z‐Ligustilide, an active ingredient isolated from the medicinal plants Cnidium officinale and Angelica acutiloba, on BaP‐induced CYP1A1 upregulation in normal human epidermal keratinocytes (NHEKs) as well as its underlying mechanisms. Z‐Ligustilide significantly inhibited BaP‐induced CYP1A1 upregulation in NHEKs. Treatment of NHEKs with Z‐Ligustilide induced Nuclear factor‐E2‐related factor 2 (Nrf2) nuclear translocation and expression of the Nrf2‐regulated genes for haeme oxygenase‐1 (HO‐1) and NAD(P)H:quinine oxidoreductase‐1 (NQO1). AhR silencing, SB203580 (a p38 inhibitor), SP600125 (a JNK inhibitor), U0126 (a MEK inhibitor) and LY294002 (a PI3K inhibitor) did not suppress Z‐Ligustilide‐induced Nrf2 activation. Moreover, treatment of NHEKs with Z‐Ligustilide increased reactive oxygen species (ROS) and L‐N‐acetylcysteine (L‐NAC, an antioxidant) attenuated Z‐ligustilide‐induced Nrf2 nuclear translocation and HO‐1 expression. L‐NAC or knock‐down of Nrf2 significantly attenuated the inhibitory effects of Z‐Ligustilide on BaP‐induced CYP1A1 upregulation in NHEKs. Taken together, these findings suggest that Z‐Ligustilide can suppress BaP‐induced CYP1A1 upregulation through ROS‐dependent Nrf2 pathway activation and may be beneficial in preventing or treating BaP‐induced skin damage.     

Malassezia‐derived aryl hydrocarbon receptor ligands enhance the CCL20/Th17/soluble CD163 pathogenic axis in extra‐mammary Paget's disease

Malassezia yeast play a role in the pathogenesis of chronic dermatitis, especially in apocrine areas, by polarizing the local immunologic background to a Th2/Th17 state through aryl hydrocarbon receptor (AhR)‐dependent pathways. Extra‐mammary Paget's disease (EMPD) is an adenocarcinoma of apocrine origin, and except for cases associated with Malassezia yeast and their metabolites, the lesions typically develop in areas not exposed to environmental material. The purpose of this study was to investigate (a) the immunomodulatory effects of Malassezia metabolites on normal human keratinocytes (NHKCs), focusing on interleukin (IL)‐17 and related cytokines/chemokines (IL‐23, IL‐36γ, CCL20), (b) the expression of these factors in lesion‐affected skin in EMPD and (c) the activation of tumor‐associated macrophages (TAMs) by these factors. Malassezia metabolites augmented the expression of cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1), CCL20 and IL‐36γ mRNA in NHKCs in vitro. In lesion‐affected skin of patients with EMPD, epidermal keratinocytes expressed CYP1A1 and CCL20. In addition, Paget cells expressed CCL20 and IL‐23. IL‐17–producing cells were distributed adjacent to Paget cells. Compared to healthy donors, patients with EMPD exhibited significantly increased serum levels of soluble (s)CD163, CXCL5, CXCL10 and CCL20. In addition, serum levels of sCD163 decreased significantly following tumor resection. Our study demonstrates a possible mechanism for the development of EMPD involving AhR‐mediated signalling by epidermal keratinocytes and RANKL‐induced recruitment of Th17 cells and TAMs.     

Activation of toll‐like receptors 2, 3 or 5 induces matrix metalloproteinase‐1 and ‐9 expression with the involvement of MAPKs and NF‐κB in human epidermal keratinocytes

Please cite this paper as: Activation of toll‐like receptors 2, 3 or 5 induces matrix metalloproteinase‐1 and ‐9 expression with the involvement of MAPKs and NF‐κB in human epidermal keratinocytes. Experimental Dermatology 2010; 19 : e44–e49. Abstract: Toll‐like receptors (TLRs) on epidermal keratinocytes are the first line of defense against microbe invasion, and matrix metalloproteases (MMPs) regulate inflammation, cell migration and wound healing. In this study, we demonstrate that the mRNA and protein expressions of MMP‐1 and MMP‐9 in human epidermal keratinocytes are induced by ligands for TLR2, TLR3 and TLR5 [Pam3CSK4, Poly(I:C) and flagellin, respectively] in a dose‐dependent manner. We also found that the ligands for TLR2, TLR3 and TLR5 activate the MAP kinases, JNK and p38 MAPK, but not ERK1/2. Furthermore, treatment with the ligands for TLR2, TLR3 and TLR5 also induced the degradation of IκB‐α and activated the nuclear translocation of NF‐κB. MMP‐1 induction by the ligands for TLR2, TLR3 and TLR5 was inhibited by pretreatment with BAY11‐7082 (NF‐κB inhibitor) or SP600125 (JNK inhibitor), whereas MMP‐9 expression was inhibited by pretreatment with BAY11‐7082, SP600125 or SB203580. These findings demonstrate that the activation of TLR2, TLR3 or TLR5 induces the expression of MMP‐1 and MMP‐9 in human epidermal keratinocytes. In addition, NF‐κB or JNK mediated the MMP‐1 expression induced by TLR2, TLR3 and TLR5, whereas NF‐κB, JNK or p38 MAPK mediated the MMP‐9 expression induced by TLR2, TLR3 and TLR5.     

Serum levels of matrix metalloproteinase‐13 in patients with eosinophilic fasciitis

Matrix metalloproteinase‐13 (MMP‐13), a member of the collagenase family, has been implicated in the pathogenesis of connective tissue diseases characterized by extracellular matrix remodeling. Since serum MMP‐13 levels reflect disease severity of systemic sclerosis and localized scleroderma, we evaluated the clinical significance of serum MMP‐13 levels in eosinophilic fasciitis (EF). All the EF patients had serum MMP‐13 levels lower than the mean – 2SD of healthy controls. Serum MMP‐13 levels were also significantly decreased in EF patients compared with diffuse cutaneous systemic sclerosis, limited cutaneous systemic sclerosis, and generalized morphea patients. Although serum MMP‐13 levels did not reflect any clinical and serological features of EF, these results indicate that MMP‐13 may be involved in the development of this disease.     

Induction of a chloracne phenotype in an epidermal equivalent model by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is dependent on aryl hydrocarbon receptor activation and is not reproduced by aryl hydrocarbon receptor knock down

Background2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent activator of the aryl hydrocarbon receptor (AhR) and causes chloracne in humans. The pathogenesis and role of AhR in chloracne remains incompletely understood.ObjectiveTo elucidate the mechanisms contributing to the development of the chloracne-like phenotype in a human epidermal equivalent model and identify potential biomarkers.MethodsUsing primary normal human epidermal keratinocytes (NHEK), we studied AhR activation by XRE-luciferase, AhR degradation and CYP1A1 induction. We treated epidermal equivalents with high affinity TCDD or two non-chloracnegens: β-naphthoflavone (β-NF) and 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Using Western blotting and immunochemistry for filaggrin (FLG), involucrin (INV) and transglutaminase-1 (TGM-1), we compared the effects of the ligands on keratinocyte differentiation and development of the chloracne-like phenotype by H&E.ResultsIn NHEKs, activation of an XRE-luciferase and CYP1A1 protein induction correlated with ligand binding affinity: TCDD > β-NF > ITE. AhR degradation was induced by all ligands. In epidermal equivalents, TCDD induced a chloracne-like phenotype, whereas β-NF or ITE did not. All three ligands induced involucrin and TGM-1 protein expression in epidermal equivalents whereas FLG protein expression decreased following treatment with TCDD and β-NF. Inhibition of AhR by α-NF blocked TCDD-induced AhR activation in NHEKs and blocked phenotypic changes in epidermal equivalents; however, AhR knock down did not reproduce the phenotype.ConclusionLigand-induced CYP1A1 and AhR degradation did not correlate with their chloracnegenic potential, indicating that neither CYP1A1 nor AhR are suitable biomarkers. Mechanistic studies showed that the TCDD-induced chloracne-like phenotype depends on AhR activation whereas AhR knock down did not appear sufficient to induce the phenotype.     

芳香烃受体在特应性皮炎患者外周血及皮损组织中的表达及意义

目的 检测特应性皮炎（AD）患者外周血单个核细胞（PBMC）及血清中芳香烃受体（AhR）及其下游分子的表达水平,并分析其表达与AD患者疾病严重程度与血清中细胞因子的相关性。方法 采用实时PCR检测29例AD患者及17例健康对照PBMC中AhR、细胞色素P4501A （CYP1A1）、芳香烃受体抑制因子（AHRR）和芳香烃受体核转位蛋白（ARNT）mRNA表达水平,酶联免疫吸附试验（ELISA）检测AD患者血清中白细胞介素（IL）-1β、IL-6、肿瘤坏死因子（TNF）-α、IL-4、IL-22和AhR的表达水平,免疫组化检测AD患者皮损和色素痣患者（21例）的正常皮肤中AhR的表达水平。计量资料比较采用非配对Student′s t检验,计数资料采用χ2检验比较,Pearson检验分析各指标间的相关性。结果 AD组血清AhR水平（41.26 ± 4.52） pmol/L高于健康对照组［（33.73 ± 2.49） pmol/L,t = 6.507,P＜0.001］。AD患者PBMC中AhR mRNA（1.572 ± 0.392比1.000 ± 0.173,t = 6.819,P = 0.007）、AHRR mRNA（2.402 ± 1.716比1.000 ± 0.788,t = 3.722,P = 0.039）、CYP1A1 mRNA（2.258 ± 1.598比1.000 ± 0.796,t = 3.400,P = 0.002）和ARNT mRNA（1.383 ± 0.842比1.000 ± 0.586,t = 1.653,P = 0.105）相对表达量均显著高于健康对照组。AD组皮损组织中AhR的表达量高于正常皮肤对照组（0.191 ± 0.041比0.087 ± 0.017,t = 10.036,P＜0.001）。AD组PBMC中AhR mRNA表达与湿疹面积及严重程度指数呈正相关（r = 0.448,P = 0.019）,与血清IL-6水平呈正相关（r = 0.377,P = 0.046）,AHRR mRNA与血清IL-1β水平呈正相关（r = 0.467,P = 0.021）。结论 AD患者AhR及其下游分子的表达高于健康对照组, 且AhR表达与血清IL-6水平和严重程度呈正相关,推测AhR信号通路在AD发病机制中发挥一定作用,AhR可作为评价疾病严重程度的有效指标。     

Mineralocorticoid receptor blockade improves glucocorticoid‐induced skin atrophy but partially ameliorates anti‐inflammatory actions in an irritative model in human skin explants

We recently demonstrated that blockade of the mineralocorticoid receptor (MR) effectively ameliorated GC‐induced skin atrophy in healthy human skin explants and epidermal MR knockout mice. However, whether MR blockade improves the therapeutic index of glucocorticoids (GCs) in skin pathology was not investigated. We assessed the effects of GCs, MR antagonists (MRA) or both, in SDS‐treated human skin explants. All treatments restored SDS‐augmented epidermal thickness but only GC plus MRA restored the expression of COL1A1. However, MRA alone or in combination with GCs may exert a dual role in regulating inflammatory cytokines. Thus, although combined treatment may be beneficial to improve irritative skin, extensive in vivo testing is required to establish whether the anti‐inflammatory effects of GCs are maintained in the presence of MRA.     

Induction of matrix metalloproteinase‐1 by small interfering RNA targeting connective tissue growth factor in dermal fibroblasts from patients with systemic sclerosis

Please cite this paper as: Induction of matrix metalloproteinase‐1 by small interfering RNA targeting connective tissue growth factor in dermal fibroblasts from patients with systemic sclerosis. Experimental Dermatology 2010; 19 : e111–e116. Abstract: We aimed to evaluate the effect of small interfering RNA (siRNA) targeting CTGF on extracellular matrices (ECMs) metabolism in normal and SSc fibroblasts. Normal and SSc fibroblasts were transfected with CTGF‐specific siRNAs to silence CTGF synthesis. After silencing CTGF, production of type I collagen and matrix metalloproteinase (MMP)‐1 by fibroblasts stimulated with TGF‐β was examined. Then quantitative analyses of protein production or mRNA expression of type I collagen, MMP‐1,‐2,‐9 and tissue inhibitor of metalloproteinase (TIMP)‐1 with TGF‐β stimulation were carried out. Furthermore, after silencing CTGF, proliferations of normal and SSc fibroblasts were investigated. CTGF‐specific siRNA significantly reduced CTGF production. The production of type I collagen was significantly reduced by CTGF silencing in normal fibroblasts. The CTGF silencing significantly increased the production of MMP‐1 and decreased the production of TIMP‐1 in SSc fibroblasts. The mRNA expression of MMP‐1 was increased in CTGF‐silenced SSc fibroblasts, but not in normal fibroblasts. There were no significant changes in the production or mRNA expression of other ECM‐related genes in normal and SSc fibroblasts. Fibroblast proliferations were suppressed by CTGF silencing in normal and SSc fibroblasts. Our data showed that MMP‐1 was increased by CTGF‐specific siRNA transfection only in SSc fibroblasts. RNAi targeting CTGF could be a novel therapeutic strategy for SSc.     

Topical retinol attenuates stress‐induced ageing signs in human skin ex vivo,throughEGFR activation viaEGF,but notERK andAP‐1 activation

Stress‐induced oxidative damage and the inflammatory response lead to degradation of collagen and elastic fibres and wrinkle formation. Topical retinol (or vitamin A) can be a strategy to attenuate the effects of stress in skin as it promotes collagen and elastic fibre production and reduces protease synthesis. This study investigated the effect of topical retinol in stressed human skin using in vitro and ex vivo models. Human skin explants were treated with high levels of epinephrine (as observed in stressed patients) and topically with retinol for 13 days. Human dermal fibroblasts were treated with conditioned medium of ex vivo retinol‐treated and non‐stressed (without epinephrine) human skin for 24 hours. In ex vivo human skin, retinol reversed the epinephrine‐induced reduction in epidermal proliferation and differentiation, normalizing epidermal thickness. Retinol also inhibited the epinephrine‐induced reduction in elastic fibre deposition and organization, restoring dermal thickness. In addition, retinol reversed the epinephrine‐induced increase in c‐JUN protein expression, but it did not alter extracellular signal‐regulated kinase 1/2 (ERK) phosphorylation in ex vivo human skin. Conditioned medium of ex vivo retinol‐treated and non‐stressed human skin presented an increased protein expression of epidermal growth factor (EGF). In human dermal fibroblasts, conditioned medium of ex vivo retinol‐treated and non‐stressed human skin increased protein and gene expression of fibrillin‐1 and protein expression of EGF receptor (EGFR). In conclusion, topical retinol attenuates stress‐induced skin ageing signs in human skin ex vivo, probably through EGFR activation via EGF, but not by the stress‐activated ERK 1/2 and c‐JUN pathways.