Background Barrier disruption and the resulting continuous exposure to allergens are presumed to be responsible for the development of atopic dermatitis (AD). However, the mechanism through which ...skin barrier function is disrupted in patients with AD remains unclear. Objectives Taking into account the fact that the TH 2 milieu impairs keratinocyte terminal differentiation, we sought to clarify our hypothesis that the Janus kinase (JAK)–signal transducer and activator of transcription (STAT) pathway plays a critical role in skin barrier function and can be a therapeutic target for AD. Methods We analyzed the mechanism of keratinocyte differentiation using a microarray and small interfering RNA targeting STATs. We studied the effect of the JAK inhibitor JTE-052 on keratinocyte differentiation using the human skin equivalent model and normal human epidermal keratinocytes. We applied topical JAK inhibitor onto NC/Nga mice, dry skin model mice, and human skin grafted to immunocompromised mice. Results IL-4 and IL-13 downregulated genes involved in keratinocyte differentiation. STAT3 and STAT6 are involved in keratinocyte differentiation and chemokine production by keratinocytes, respectively. Topical application of the JAK inhibitor suppressed STAT3 activation and improved skin barrier function, permitting increases in levels of terminal differentiation proteins, such as filaggrin, and natural moisturizing factors in models of AD and dry skin and in human skin. Conclusion STAT3 signaling is a key element that regulates keratinocyte differentiation. The JAK inhibitor can be a new therapeutic tool for the treatment of disrupted barrier function in patients with AD.
Background Atopic dermatitis (AD) is caused by a complex interplay between immune and barrier abnormalities. Murine models of AD are essential for preclinical assessments of new treatments. Although ...many models have been used to simulate AD, their transcriptomic profiles are not fully understood, and a comparison of these models with the human AD transcriptomic fingerprint is lacking. Objective We sought to evaluate the transcriptomic profiles of 6 common murine models and determine how they relate to human AD skin. Methods Transcriptomic profiling was performed by using microarrays and quantitative RT-PCR on biopsy specimens from NC/Nga, flaky tail, Flg -mutated, ovalbumin-challenged, oxazolone-challenged, and IL-23–injected mice. Gene expression data of patients with AD, psoriasis, and contact dermatitis were obtained from previous patient cohorts. Criteria of a fold change of 2 or greater and a false discovery rate of 0.05 or less were used for gene arrays. Results IL-23–injected, NC/Nga, and oxazolone-challenged mice show the largest homology with our human meta-analysis–derived AD transcriptome (37%, 18%, 17%, respectively). Similar to human AD, robust TH 1, TH 2, and also TH 17 activation are seen in IL-23–injected and NC/Nga mice, with similar but weaker inflammation in ovalbumin-challenged mice. Oxazolone-challenged mice show a TH 1-centered reaction, and flaky tail mice demonstrate a strong TH 17 polarization. Flg -mutated mice display filaggrin downregulation without significant inflammation. Conclusion No single murine model fully captures all aspects of the AD profile; instead, each model reflects different immune or barrier disease aspects. Overall, among the 6 murine models, IL-23–injected mice best simulate human AD; still, the translational focus of the investigation should determine which model is most applicable.
Background The clarification of cutaneous dendritic cell subset and the role of thymic stromal lymphopoietin (TSLP) signaling in epicutaneous sensitization with protein antigens, as in the ...development of atopic dermatitis, is a crucial issue. Objectives Because TSLP is highly expressed in the vicinity of Langerhans cells (LCs), we sought to clarify our hypothesis that LCs play an essential role in epicutaneous sensitization with protein antigens through TSLP signaling. Methods By using Langerin-diphtheria toxin receptor knock-in mice and human Langerin-diphtheria toxin A transgenic mice, we prepared mice deficient in LCs. We also prepared mice deficient in TSLP receptors in LCs by using TSLP receptor–deficient mice with bone marrow chimeric technique. We applied these mice to an ovalbumin (OVA)-induced epicutaneous sensitization model. Results Upon the epicutaneous application of OVA, conditional LC depletion attenuated the development of clinical manifestations as well as serum OVA-specific IgE increase, OVA-specific T-cell proliferation, and IL-4 mRNA expression in the draining lymph nodes. Consistently, even in the steady state, permanent LC depletion resulted in decreased serum IgE levels, suggesting that LCs mediate the TH 2 local environment. In addition, mice deficient in TSLP receptors on LCs abrogated the induction of OVA-specific IgE levels upon epicutaneous OVA sensitization. Conclusion LCs initiate epicutaneous sensitization with protein antigens and induce TH 2-type immune responses via TSLP signaling.
Background Nonsense mutations in filaggrin (FLG) represent a significant genetic factor in the cause of atopic dermatitis (AD). Objective It is of great importance to find drug candidates that ...upregulate FLG expression and to determine whether increased FLG expression controls the development of AD. Methods We screened a library of bioactives by using an FLG reporter assay to find candidates that promoted FLG mRNA expression using a human immortalized keratinocyte cell line (HaCaT). We studied the effect of the compound on keratinocytes using the human skin equivalent model. We examined the effect of the compound on AD-like skin inflammation in NC/Nga mice. Results JTC801 promoted FLG mRNA and protein expression in both HaCaT and normal human epidermal keratinocytes. Intriguingly, JTC801 promoted the mRNA and protein expression levels of FLG but not the mRNA levels of other makers for keratinocyte differentiation, including loricrin, keratin 10, and transglutaminase 1, in a human skin equivalent model. In addition, oral administration of JTC801 promoted the protein level of Flg and suppressed the development of AD-like skin inflammation in NC/Nga mice. Conclusion This is the first observation that the compound, which increased FLG expression in human and murine keratinocytes, attenuated the development of AD-like skin inflammation in mice. Our findings provide evidence that modulation of FLG expression can be a novel therapeutic target for AD.
Background Although eosinophils have been detected in several human skin diseases in the vicinity of basophils, how eosinophils infiltrate the skin and the role of eosinophils in the development of ...skin inflammation have yet to be examined. Objective Using murine irritant contact dermatitis (ICD) as a model, we sought to clarify the roles of eosinophils in ICD and the underlying mechanism of eosinophil infiltration of the skin. Methods We induced croton oil–induced ICD in eosinophil-deficient ΔdblGATA mice with or without a reactive oxygen species (ROS) inhibitor. We performed cocultivation with fibroblasts and bone marrow–derived basophils and evaluated eosinophil migration using a chemotaxis assay. Results ICD responses were significantly attenuated in the absence of eosinophils or by treatment with the ROS inhibitor. ROS was produced abundantly by eosinophils, and both basophils and eosinophils were detected in human and murine ICD skin lesions. In coculture experiments, basophils attracted eosinophils, especially in the presence of fibroblasts. Moreover, basophils produced IL-4 and TNF-α in contact with fibroblasts and promoted the expression of eotaxin/CCL11 from fibroblasts in vitro. Conclusion Eosinophils mediated the development of murine ICD, possibly through ROS production. Recruitment of eosinophils into the skin was induced by basophils in cooperation with fibroblasts. Our findings introduce the novel concept that basophils promote the recruitment of eosinophils into the skin through fibroblasts in the development of skin inflammation.
RIPK3 in keratinocytes facilitates psoriatic inflammation by promoting cytokine and chemokine production, independent of the induction of necroptosis. Control of RIPK3 activation may be a novel ...therapeutic target for psoriasis.
Pemphigus is one of such autoantibody-mediated disorders, which is caused by pathogenic autoantibodies against epidermal desmosomal cadherins, desmoglein (Dsg) 1 and Dsg3. Because these ...autoantibodies can directly disrupt epidermal cell-cell adhesion,1 their concentration in the epidermis would be linked to the disease severity. ...we irradiated mouse ears with ultraviolet B and demonstrated a positive correlation of IgG1-MFI with the ultraviolet B irradiation dose (r = 1.00) (Fig 2, C) and with the intensity of skin inflammation as evaluated by ear swelling (r = 0.90) (Fig 2, D). ...to confirm that local inflammation predisposes to the development of the pemphigus phenotype, we used a pathogenic antimouse Dsg3 antibody, AK23. In summary, our results in mice suggest that local inflammation might also enhance anti-Dsg3 antibody deposition in the skin in patients with pemphigus. ...taking skin biopsies from perilesional erythematous (presumably inflammable) areas in autoimmune blistering diseases might be beneficial to increase the DIF sensitivity. NS indicates not significant. 1 M. Amagai, S. Karpati, R. Prussick, V. Klaus-Kovtun, J.R. Stanley, Autoantibodies against the amino-terminal cadherin-like binding domain of pemphigus vulgaris antigen are pathogenic, J Clin Invest, Vol. 90, 1992, 919-926 2 Y. Kano, M. Shimosegawa, Y. Mizukawa, T. Shiohara, Pemphigus foliaceus induced by exposure to sunlight: report of a case and analysis of photochallenge-induced lesions, Dermatology, Vol. 201, 2000, 132-138 3 D.R. Mehregan, R.K. Roenigk, L.E. Gibson, Postsurgical pemphigus, Arch Dermatol, Vol. 128, 1992, 414-415 4 G. Egawa, S. Nakamizo, Y. Natsuaki, H. Doi, Y. Miyachi, K. Kabashima, Intravital analysis of vascular permeability...
Because it has been reported that CHS response was impaired in DT-treated langerin-eGFP-DTR mice sensitized with low-dose dinitrofluorobenzene (DNFB),3 we followed the same protocol: we sensitized ...mice with 25 μL of 0.3% (wt/vol) DNFB (Nacalai Tesque, Kyoto, Japan) in acetone/olive oil (4:1) on shaved abdominal skin and challenged the mice with 20 μL of 0.\n The numbers of CD4+ CD44+ and CD8+ CD44+ memory T cells in draining lymph nodes 6 days after sensitization were significantly reduced in DT-treated langerin-eGFP-DTR mice (Fig 2, B, left). ...our results suggest that neither langerin-positive dDCs alone nor LCs alone are essential in sensitization; rather, both types play compensatory roles in the sensitization phase of CHS in a low-dose DNFB sensitization protocol, although not in a standard-dose DNFB sensitization protocol.
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