Gaku Tsuji

An environmental contaminant, benzo(a)pyrene, induces oxidative stress-mediated interleukin-8 production in human keratinocytes via the aryl hydrocarbon receptor signaling pathway

BACKGROUND Benzo(a)pyrene (BaP) is an environmental contaminant found in cigarette smoke. It is well known that cigarette smoking exacerbates interleukin-8 (IL-8)-related inflammatory skin diseases such as psoriasis, palmoplantar pustulosis and acne. Although BaP has been shown to exert its biological effects via the aryl hydrocarbon receptor (AhR) signaling pathway, the mechanism of its inflammatory effects on skin remains unanswered. OBJECTIVE To elucidate whether or not BaP cause AhR activation and subsequent oxidative stress leading to IL-8 production in normal human epidermal keratinocytes (NHEKs). METHODS NHEKs exposed to BaP were analyzed. Immunofluorescence, real-time PCR, Western blotting, ELISA, reactive oxygen species (ROS) detection using H2DCFDA and RNA interference using si (small interfering) RNA were employed. RESULTS Immunofluorescence analysis clearly demonstrated that BaP induced nuclear translocation of AhR from cytoplasm. The AhR activation subsequently induced CYP1A1 mRNA and protein expression in a dose-dependent manner. In addition, ROS and IL-8 production were coordinately augmented by BaP, whereas this was not the case in IL-1α, IL-6, TNF-α or GM-CSF production. Knockdown of AhR expression using siRNA transfection inhibited BaP-induced-ROS and IL-8 production, suggesting that these responses are strongly dependent on the AhR signaling pathway. Furthermore, the addition of N-acetyl cystein or catalase cancelled the IL-8 production by BaP, indicating that ROS production is essential for IL-8 production. RESULTS This data highlights AhR-ROS-dependent regulation of IL-8 in NHEKs by BaP, providing a plausible explanation, at least in part, for why cigarette smoking exacerbates IL-8-related skin diseases such as psoriasis, palmoplantar pustulosis and acne.

Identification of Ketoconazole as an AhR-Nrf2 Activator in Cultured Human Keratinocytes: The Basis of Its Anti-Inflammatory Effect

Ketoconazole (KCZ) has been shown to exhibit anti-inflammatory effects in addition to its inhibitory effects against fungi; however, the underlying molecular mechanism remains poorly understood. Aryl hydrocarbon receptor (AhR), a receptor that is activated by polycyclic aromatic hydrocarbons (PAHs) and halogenated aromatic hydrocarbons such as dioxin, is a sensor of the redox system against oxidative stress and regulates nuclear factor-erythroid 2-related factor-2 (Nrf2), a master switch of the redox machinery. To clarify whether KCZ modulates AhR-Nrf2 function leading to redox system activation, cultured human keratinocytes were treated with KCZ. Confocal microscopic analysis revealed that KCZ induced AhR nuclear translocation, resulting in the upregulation of CYP1A1 mRNA and protein expression. Furthermore, KCZ actively switched on Nrf2 nuclear translocation and quinone oxidoreductase 1 expression. Tumor necrosis factor-α- and benzo(a)pyrene (BaP)-induced reactive oxidative species (ROS) and IL-8 production were effectively inhibited by KCZ. Knockdown of either AhR or Nrf2 abolished the inhibitory capacity of KCZ on ROS and IL-8 production. In addition, KCZ-induced Nrf2 activation was canceled by AhR knockdown. Moreover, KCZ inhibited BaP-induced 8-hydroxydeoxyguanosine and IL-8 production. In conclusion, the engagement of AhR by KCZ exhibits the cytoprotective effect mediated by the Nrf2 redox system, which potently downregulates either cytokine-induced (AhR-independent) or PAH-induced (AhR-dependent) oxidative stress.

Arylhydrocarbon receptor (AhR) activation in airway epithelial cells induces MUC5AC via reactive oxygen species (ROS) production.

The dioxins and dioxin-like compounds in cigarette smoke regulate various immunological responses via the arylhydrocarbon receptor (AhR). These environmental toxicants are known to cause bronchitis, asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. Recent studies have demonstrated that AhR activation upregulates the expression of mucin 5AC, oligomeric mucus/gel-forming (MUC5AC) in the airway epithelial cell line. However, the mechanism for the production of mucin has not been clarified. In this study, we investigated the role and pathway of AhR in airway epithelial cells by using selective agonists and antagonists. After stimulation with or without benzopyrene (B[a]P), an AhR agonist, MUC5AC expression was measured by real-time RT-PCR. The mechanism of AhR-induced MUC5AC expression in airway epithelial cells was studied in terms of the production of cytokine and reactive oxygen species (ROS). Treatment with B[a]P increased ROS generation in NCI-H₂₉₂ cells. Furthermore, B[a]P-induced MUC5AC upregulation and mucin production were inhibited by AhR siRNA or the use of an antioxidative agent. These results suggest that the AhR-induced increase of mucin production is partially mediated by ROS generation. An antioxidant therapy approach may help to cure AhR-induced mucus hypersecretory diseases.

Are lifetime prevalence of impetigo, molluscum and herpes infection really increased in children having atopic dermatitis?

BACKGROUND Cutaneous infections such as impetigo contagiosum (IC), molluscum contagiosum (MC) and herpes virus infection (HI) appear to be associated with atopic dermatitis (AD), but there are no reports of concrete epidemiological evidence. OBJECTIVE We evaluated the association of childhood AD with these infections by conducting a population-based cross-sectional study. METHODS Enrolled in this study were 1117 children aged 0-6 years old attending nursery schools in Ishigaki City, Okinawa Prefecture, Japan. Physical examination was performed by dermatologists, and a questionnaire was completed on each childs history of allergic diseases including AD, asthma, allergic rhinitis and egg allergy, and that of skin infections including IC, MC and HI, as well as familial history of AD. RESULTS In 913 children (AD; 132), a history of IC, MC or HI was observed in 45.1%, 19.7%, and 2.5%, respectively. Multiple logistic regression analysis revealed that the odds of having a history of IC were 1.8 times higher in AD children than in non-AD children. Meanwhile, a history of MC was significantly correlated to the male gender, but not to a personal history of AD. As for HI, we found no correlated factors in this study. CONCLUSIONS The lifetime prevalence of IC was indeed higher in young children with a history of AD.

Gene regulation of filaggrin and other skin barrier proteins via aryl hydrocarbon receptor.

Aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor that binds to structurally diverse chemicals including dioxins, coal tar, flavonoids and tryptophan photoproducts. Upon ligation, cytoplasmic AHR translocates to the nucleus, heterodimerizes with aryl hydrocarbon receptor nuclear translocator and mediates numerous biological effects by inducing the transcription of various AHR-responsive genes such as epidermal barrier proteins. The activation of AHR usually generates oxidative stress. However, AHR also mediates antioxidant signaling by a plethora of ligands via nuclear factor-erythroid 2-related factor-2. Both oxidative and antioxidant ligands upregulate the expression of the filaggrin gene. We review the role of AHR signaling in the gene regulation of epidermal barrier proteins.

Cutaneous Scedosporium apiospermum infection in an immunocompromised patient and a review of the literature.

Scedosporium apiospermum (also known as Pseudallescheria boydii) is a ubiquitous filamentous fungus. This fungus is known as a cause of mycetoma, which may occur in a normally immune host following trauma. However, in an immunocompromised host, S. apiospermum may cause a life-threatening infection. We describe a case of S. apiospermum infection of the right hand in a patient who was receiving long-term immunosuppressants for adult Stills disease. We also review the cases of S. apiospermum infection with cutaneous manifestations reported between 1998 and 2003.

Atopic dermatitis: immune deviation, barrier dysfunction, IgE autoreactivity and new therapies

Atopic dermatitis (AD) is a chronic or chronically relapsing, eczematous, severely pruritic skin disorder mostly associated with IgE elevation and skin barrier dysfunction due to decreased filaggrin expression. The lesional skin of AD exhibits Th2- and Th22-deviated immune reactions that are progressive during disease chronicity. Th2 and Th22 cytokines further deteriorate the skin barrier by inhibiting filaggrin expression. Some IgEs are reactive to self-antigens. The IgE autoreactivity may precipitate the chronicity of AD. Upon activation of the ORAI1 calcium channel, atopic epidermis releases large amounts of thymic stromal lymphopoietin (TSLP), which initiates the Th2 and Th22 immune response. Th2-derived interleukin-31 and TSLP induce an itch sensation. Taken together, TSLP/Th2/Th22 pathway is a promising target for developing new therapeutics for AD. Enhancing filaggrin expression using ligands for the aryl hydrocarbon receptor may also be an adjunctive measure to restore the disrupted barrier function specifically for AD.

Cynaropicrin attenuates UVB-induced oxidative stress via the AhR-Nrf2-Nqo1 pathway

UNLABELLED Due to its antioxidant and anti-inflammatory activities, artichoke (Cynara scolymus) has been used as folk medicine to treat various diseases. Cynaropicrin (Cyn), a sesquiterpene lactone, is the major bioactive phytochemical in the artichoke; however, its pharmacological mechanism remains unknown. Because some phytochemicals exert their antioxidant activity by activating aryl hydrocarbon receptor (AhR), leading to subsequent induction of the antioxidant pathway including nuclear factor E2-related factor 2 (Nrf2) and NAD(P)H quinone oxidoreductase 1 (Nqo1), we investigated whether Cyn also activates the AhR-Nrf2-Nqo1 pathway. Cyn indeed induced the activation (nuclear translocation) of AhR, leading to nuclear translocation of Nrf2 and dose-dependent upregulation of Nrf2 and Nqo1 mRNAs in human keratinocytes. The Cyn-induced AhR-Nrf2-Nqo1 activation was AhR- and Nrf2-dependent, as demonstrated by the observation that it was absent in keratinocytes transfected by siRNA against either AhR or Nrf2. In accordance with these findings, Cyn actively inhibited generation of reactive oxygen species from keratinocytes irradiated with ultraviolet B (UVB) in a Nrf2-dependent manner. Cyn also inhibited the production of proinflammatory cytokines such as interleukin 6 and tumor necrosis factor-α from UVB-treated keratinocytes. Our findings demonstrate that Cyn is a potent activator of the AhR-Nrf2-Nqo1 pathway, and could therefore be applied to prevention of UVB-induced photo aging.

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.

Cathepsin K-upregulation in fibroblasts promotes matrigel invasive ability of squamous cell carcinoma cells via tumor-derived IL-1α

BACKGROUND Cathepsin K (CTSK), a cysteine protease with strong collagenolytic properties, is involved in extracellular matrix turnover. In the previous studies, CTSK expression was detected in peritumoral fibroblasts (Fbs) around squamous cell carcinoma (SCC), but not in those surrounding benign epidermal tumors. However, the mechanism governing CTSK expression in epidermal tumors remains unclear. OBJECTIVE To study the regulatory mechanisms of fibroblastic CTSK expression in the SCC-stromal interaction. METHODS We examined dynamic interactions of Fbs with tumorigenic SCC cells (A431 and A253) or normal human keratinocytes. RESULTS SCC cells and normal keratinocytes did not synthesize CTSK, while Fbs constitutively expressed CTSK. When cocultured, SCC cells upregulated fibroblastic CTSK expression more potently than did normal keratinocytes, which was mainly attributable to SCC-derived IL-1α. Coculturing Fbs with SCC cells significantly augmented the matrigel invasive ability of SCC cells, which was downregulated when cocultured with CTSK knockdown Fbs or in the presence of neutralizing anti-IL-1α antibody. CONCLUSION The CTSK-upregulated Fbs generated by SCC-derived IL-1α may play a crucial role in the progression and invasion of SCC.