NF-κB Activation In Keratinocytes Research Articles

Periostin activates distinct modules of inflammation and itching downstream of the type 2 inflammation pathway

Atopic dermatitis (AD) is a chronic relapsing skin disease accompanied by recurrent itching. Although type 2 inflammation is dominant in allergic skin inflammation, it is not fully understood how non-type 2 inflammation co-exists with type 2 inflammation or how type 2 inflammation causes itching. We have recently established the FADS mouse, a mouse model of AD. In FADS mice, either genetic disruption or pharmacological inhibition of periostin, a downstream molecule of type 2 inflammation, inhibits NF-κB activation in keratinocytes, leading to downregulating eczema, epidermal hyperplasia, and infiltration of neutrophils, without regulating the enhanced type 2 inflammation. Moreover, inhibition of periostin blocks spontaneous firing of superficial dorsal horn neurons followed by a decrease in scratching behaviors due to itching. Taken together, periostin links NF-κB-mediated inflammation with type 2 inflammation and promotes itching in allergic skin inflammation, suggesting that periostin is a promising therapeutic target for AD.

Gain-of-Function Mutation of Card14 Leads to Spontaneous Psoriasis-like Skin Inflammation through Enhanced Keratinocyte Response to IL-17A

Genetic mutations of CARD14 (encoding CARMA2) are observed in psoriasis patients. Here we showed that Card14E138A/+ and Card14ΔQ136/+ mice developed spontaneous psoriasis-like skin inflammation, which resulted from constitutively activated CARMA2 via self-aggregation leading to the enhanced activation of the IL-23-IL-17A cytokine axis. Card14-/- mice displayed attenuated skin inflammation in theimiquimod-induced psoriasis model due to impaired IL-17A signaling in keratinocytes. CARMA2, mainly expressed in keratinocytes, associates with the ACT1-TRAF6 signaling complex and mediates IL-17A-induced NF-κB and MAPK signaling pathwayactivation, which leads to expression of pro-inflammatory factors. Thus, CARMA2 serves as a key mediator of IL-17A signaling and its constitutive activation in keratinocytes leads to the onset of psoriasis, which indicates an important role of NF-κB activation in keratinocytes in psoriatic initiation.

Potentiation of skin TSLP production by a cosmetic colorant leads to aggravation of dermatitis symptoms

Certain cosmetic colorants are irritant to skin or aggravate dermatitis. Thymic stromal lymphopoietin (TSLP) plays an important role in the initiation and progress of skin inflammation and atopic dermatitis by triggering Th2 immune responses. However, the effects of cosmetic colorants on TSLP production are unknown yet. Therefore, we investigated whether cosmetic colorants regulated TSLP production and dermatitis. Lithol Rubine B (LR-B, Pigment Red 57) and its calcium salt (LR-BCA), commonly used cosmetic colorants, potentiated phorbol-12-myristate-13-acetate-induced TSLP production in keratinocytes. In addition, the topical exposure to LR-B or LR-BCA on mouse ear upregulated a TSLP inducer (MC903)-induced TSLP production and Th2 cytokine expression. Dermatitis symptoms and serum IgE and histamine levels were also aggravated by LR-B or LR-BCA, implicating the role of increased TSLP expression in acute dermatitis. LR-B or LR-BCA induced IκBα degradation and NF-κB activation in keratinocytes, leading to TSLP expression. Collectively, our results demonstrate that LR-B and LR-BCA increase TSLP expression and Th2 immune responses, thereby aggravating acute dermatitis in the compromised skin. The results further suggest that certain cosmetic colorants such as LR-B may aggravate dermatitis under pro-inflammatory conditions by upregulating TSLP production.

Requirement of aquaporin-3-mediated hydrogen peroxide for NF-κB cell signaling and psoriasis pathogenesis

Aquaporin 3 (AQP3), a water/glycerol channel protein, has been recently shown to transport hydrogen peroxide (H2O2). Here we show that AQP3-mediated H2O2 is involved in nuclear factor-κB (NF-κB) cell signaling in keratinocytes and in the pathogenesis of psoriasis. In in vitro studies with primary keratinocytes from wild-type and AQP3 knockout (AQP3−/−) mice, the extracellular H2O2 generated by membrane NADPH oxidase 2 (Nox2) activation in response to TNF-α was intracellularly transported via AQP3, which was indispensable for the activation of NF-κB. We found the association of AQP3 with Nox2 in membrane fraction that might facilitate the transient increase in intracellular H2O2 levels around membranes after TNF-α stimulation. Coincidentally, AQP3−/− mice was impaired in the development of psoriasis in vivo mouse model which was partially dependent on TNF-α-mediated cell signaling, in which continuous NF-κB activation and a higher H2O2 level in keratinocytes were found to be suppressed by AQP3 deficiency. These data reveal that AQP3-mediated H2O2 is required for NF-κB activation in keratinocytes during psoriasis development. Our findings provide novel insights into the pathogenesis of psoriasis and may provide a basis for new therapies.

Aquaporin-3-mediated hydrogen peroxide transport is required for NF-κB signalling in keratinocytes and development of psoriasis.

Aquaporin 3 (AQP3), a water/glycerol channel protein, has been found to transport hydrogen peroxide (H2O2). Here, we show that H2O2, imported via AQP3, is involved in nuclear factor-κB (NF-κB) signalling in keratinocytes and in the pathogenesis of psoriasis. IL-23-mediated induction of psoriasis is reduced in AQP3 knockout mice (AQP3(-/-)), and is accompanied by impaired NF-κB activation and intracellular H2O2 accumulation. In primary keratinocyte cultures, cellular import of H2O2 produced by membrane NADPH oxidase 2 (Nox2) in response to TNF-α is facilitated by AQP3 and required for NF-κB activation by regulation of protein phosphatase 2A. As AQP3 associates with Nox2, we propose that this interplay constitutes H2O2-mediated signalling in response to TNF-α stimulation. Collectively, these data indicate that AQP3-facilitated H2O2 transport is required for NF-κB activation in keratinocytes in the development of psoriasis.

Pyrrolidine dithiocarbamate inhibits UVB-induced skin inflammation and oxidative stress in hairless mice and exhibits antioxidant activity in vitro

Ultraviolet B (UVB) irradiation may cause oxidative stress- and inflammation-dependent skin cancer and premature aging. Pyrrolidine dithiocarbamate (PDTC) is an antioxidant and inhibits nuclear factor-κB (NF-κB) activation. In the present study, the mechanisms of PDTC were investigated in cell free oxidant/antioxidant assays, in vivo UVB irradiation in hairless mice and UVB-induced NFκB activation in keratinocytes. PDTC presented the ability to scavenge 2,2′-azinobis-(3-ethyl benzothiazoline-6-sulfonic acid) radical (ABTS), 2,2-diphenyl-1-picryl-hydrazyl radical (DPPH) and hydroxyl radical (OH); and also efficiently inhibited iron-dependent and -independent lipid peroxidation as well as chelated iron. In vivo, PDTC treatment significantly decreased UVB-induced skin edema, myeloperoxidase (MPO) activity, production of the proinflammatory cytokine interleukin-1β (IL-1β), matrix metalloproteinase-9 (MMP-9), increase of reduced glutathione (GSH) levels and antioxidant capacity of the skin tested by the ferric reducing antioxidant power (FRAP) and ABTS assays. PDTC also reduced UVB-induced IκB degradation in keratinocytes. These results demonstrate that PDTC presents antioxidant and anti-inflammatory effects in vitro, which line up well with the PDTC inhibition of UVB irradiation-induced skin inflammation and oxidative stress in mice. These data suggest that treatment with PDTC may be a promising approach to reduce UVB irradiation-induced skin damages and merits further pre-clinical and clinical studies.

Cultivated ginseng inhibits 2,4-dinitrochlorobenzene-induced atopic dermatitis-like skin lesions in NC/Nga mice and TNF-α/IFN-γ-induced TARC activation in HaCaT cells

Ginseng contains many bioactive constituents, including various ginsenosides that are believed to have anti-allergic, anti-oxidant, and immunostimulatory activities; however, its effects on atopic dermatitis (AD) remain unclear. In the current study, we hypothesized that cultivated ginseng (CG) would inhibit 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin lesions in NC/Nga mice by regulating the T helper (Th)1/Th2 balance. Also, CG inhibits TNF-α/IFN-γ-induced thymus- and activation-regulated chemokine (TARC) expression through nuclear factor-kappa B (NF-κB)-dependent signaling in HaCaT cells. CG ameliorated DNCB-induced dermatitis severity, serum levels of IgE and TARC, and mRNA expression of TARC, TNF-α, IFN-γ, IL-4, IL-5, and IL-13 in mice. Histopathological examination showed reduced thickness of the epidermis/dermis and dermal infiltration of inflammatory cells in the ears. Furthermore, CG suppressed the TNF-α/IFN-γ-induced mRNA expression of TARC in HaCaT cells. CG inhibited TNF-α/IFN-γ-induced NF-κB activation. These results suggest that CG inhibited the development of the AD-like skin symptoms by modulating Th1 and Th2 responses in the skin lesions in mice and TARC expression by suppressing TNF-α/IFN-γ-induced NF-κB activation in keratinocytes, and so may be a useful tool in the therapy of AD-like skin symptoms.

Inhibitory effects of curcuminoids from Curcuma longa on matrix metalloproteinase-1 expression in keratinocytes and fibroblasts

Because aging and inflammation mechanisms share common signaling pathways and mediators, natural products with anti-inflammatory effects are also good candidates as anti-aging agents. Bismethoxycurcumin, demethoxycurcumin, and curcumin are three curcuminoids that can be isolated from Curcuma longa and are well known for their anti-inflammatory and anti-cancer activities. In this study, we examined the anti-wrinkle effects of three curcuminoids from Curcuma longa in keratinocytes and fibroblasts to determine whether an anti-inflammatory agent could also be developed as an anti-aging treatment. The inhibitory effects of UV-B-induced upregulation of nuclear factor-kappaB (NF-κB) activity were detected by a reporter gene assay. Tumor necrosis factor (TNF-α) release was detected by reverse transcriptase-polymer chain reaction (RT-PCR), and matrix metalloprotease-1 (MMP-1) expression was determined by western blot and enzyme-linked immunosorbent assay (ELISA). UV-B induced TNF-α release through NF-κB activation in keratinocytes. Three curcuminoids inhibited the UV-B-induced TNF-α mRNA expression. Specifically, demethoxycurcumin and bisdemethoxycurcunim inhibited UV-B-induced NF-κB activation in HaCaT keratinocytes and reduced the expression of MMP-1 in both keratinocytes and fibroblasts. We found that curcuminoids have anti-wrinkle activity through the inhibition of UV-B induction in keratinocytes and TNF-α induction in fibroblasts. Our results suggest that wrinkle formation and inflammation have common signaling pathways.