Oral administration of β‐carotene or lycopene prevents atopic dermatitis‐like dermatitis in HR‐1 mice

Atopic dermatitis (AD) is a chronic relapsing eczematous skin disease. Certain populations of patients are resistant to standard therapies with topical steroids and/or calcineurin inhibitors, and require systemic medication, such as immunosuppressants. Recently, several reports have shed light on the anti‐allergic effects of carotenoids. Therefore, we investigated the effect of p.o. administration of β‐carotene or lycopene on AD‐like symptoms of HR‐1 hairless mice fed with a low zinc/magnesium diet. Mice were divided into four groups: (i) fed with a standard diet (Co group); (ii) low zinc/magnesium diet (HR group); (iii) low zinc/magnesium and β‐carotene diet (HR‐C group); and (iv) low zinc/magnesium and lycopene diet (HR‐L group). They were then fed these diets for 8 weeks. Severities of dermatitis were assessed by their appearance, and histopathological and hematological observations. Mice in the HR group developed AD‐like dermatitis both clinically and histologically. HR‐C and HR‐L group mice also developed xerosis and wrinkle‐like skin changes, but they were milder than those of HR group mice. Histological analysis revealed that epidermis thickening and inflammatory cell infiltration in the skin of the HR‐C and HR‐L groups were both statistically less than those of the HR group. The concentration of thymus and activation regulated chemokine in the skin of the HR‐L group and the concentration of CCL27 in the skin of the HR‐C group were significantly lower than those of the HR group, respectively. In conclusion, p.o. administration of β‐carotene or lycopene prevents AD‐like symptoms in association with a suppression of T‐helper 2 chemokines in a murine model. Ingestion of carotenoids may be beneficial for patients with AD.     

Heparinoid suppresses Der p‐induced IL‐1β production by inhibiting ERK and p38 MAPK pathways in keratinocytes

Epidermal keratinocytes initiate skin inflammation by activating immune cells. The skin barrier is disrupted in atopic dermatitis (AD) and epidermal keratinocytes can be exposed to environmental stimuli, such as house dust mite (HDM) allergens. We showed previously that HDM allergens activate the NLRP3 inflammasome of keratinocytes, thereby releasing pro‐inflammatory cytokines. Heparinoid is an effective moisturizer for atopic dry skin. However, a recent report showed that heparinoid treatment can improve inflammation of lichen planus. Therefore, we hypothesized that it acts on epidermal keratinocytes not only as a moisturizer, but also as a suppressant of the triggers of skin inflammation. We found that HDM allergen‐induced interleukin (IL)‐1β release from keratinocytes was inhibited significantly by heparinoid pretreatment without affecting cell viability. However, heparinoid did not affect caspase‐1 release, suggesting that heparinoid did not affect HDM allergen‐induced inflammasome activation. Heparinoid treatment not only decreased intracellular levels of pro‐IL‐1β, but also suppressed IL‐1β messenger RNA (mRNA) expression in keratinocytes. Among the intracellular signalling pathways, the activation of extracellular signal‐regulated kinase and p38 pathways, which are required for IL‐1β expression in keratinocytes, was inhibited by heparinoid treatment. The inhibitory effect of heparinoid on IL‐1β mRNA expression was also confirmed with living skin equivalents. Our results demonstrated that heparinoid suppresses the initiation of keratinocyte‐mediated skin inflammation.     

Effects of a ceramide‐containing water‐in‐oil ointment on skin barrier function and allergen penetration in an IL‐31 treated 3D model of the disrupted skin barrier

Atopic dermatitis (AD) is a chronically relapsing, pruritic inflammation of the skin with dryness and disturbed skin barrier function. Recently, we established that IL‐31 treatment of human 3D skin models resulted in a disrupted skin barrier phenotype resembling AD. In this model, we found that IL‐31 interferes with the differentiation of keratinocytes and inhibits the expression of terminal differentiation markers. In the present study, we investigated the effects of a ceramide‐containing water‐in‐oil skin care ointment on the physical skin barrier structure and function in disrupted skin barrier models, generated either by using primary normal human epidermal keratinocytes (NHEK) or HaCaT cells. We observed that the physical skin barrier of the models recovered after daily topical treatment with the ceramide‐containing ointment. Topical application of the ointment prevented downregulation of filaggrin and disorganization of other differentiation markers, such as keratin 10 and β4‐integrin, as demonstrated by immunohistological analysis. The expression of Ki67 was also upregulated in response to the ointment. Furthermore, functional studies revealed that local application of the ointment diminished the increased uptake of fluorescently labelled recombinant allergens of timothy grass (phl p1) in our model. In conclusion, our data revealed that topical application of a ceramide‐containing skin care ointment reduced IL‐31 induced impairments of the physical skin barrier and skin barrier function in an in vitro model of the disrupted skin barrier. This standardized model can be utilized in the future to monitor ex vivo effects of various topical therapies on skin morphology, physiology, and gene expression.     

Topical acidic cream prevents the development of atopic dermatitis‐ and asthma‐like lesions in murine model

Long‐standing or repeated skin barrier damage followed by atopic dermatitis (AD) is the initial step of the atopic march that eventually progresses to respiratory allergies. Maintenance of an acidic pH in the stratum corneum (SC) is an important factor for normal skin barrier function. We performed this study to determine whether an oxazolone (Ox)‐induced AD murine model can develop airway inflammation by topical application and nasal inhalation of a house dust mite, Dermatofagoides pteronyssinus (Dp), which is a novel ‘atopic march animal model’, and whether an acidic SC environment, made by repeated application of acidic cream, can interrupt this atopic march. During repeated treatment with Ox and Dp to make an atopic march murine model, acidic cream (pH 2.8) and neutral cream (pH 7.4) adjusted by citric acid and sodium hydroxide mixed with vehicle were applied twice daily. Repeated treatment with Ox and Dp to hairless mice induced AD‐like skin lesions followed by respiratory allergy, defining it as an atopic march model. Acidic cream inhibited the occurrence of respiratory allergic inflammation as well as AD‐like skin lesions. These results indicate that a novel atopic march animal model can be developed by repeated topical and nasal treatments with house dust mite on Ox‐induced AD mice and that the acidification of SC could be a novel intervention method to block the atopic march.     

Various peroxisome proliferator‐activated receptor (PPAR)‐γ agonists differently induce differentiation of cultured human keratinocytes

Peroxisome proliferator‐activated receptors (PPARs) are potentially useful for the treatment of skin diseases, because they stimulate keratinocyte differentiation, exert anti‐inflammatory effects and improve barrier function. We examined five PPAR‐γ agonists, including four thiazolidinediones (ciglitazone, troglitazone, rosiglitazone and pioglitazone) and an angiotensin‐II receptor blocker (telmisartan), for their ability to upregulate filaggrin and loricrin expression at both mRNA and protein levels in cultured normal human keratinocytes (NHKs). Troglitazone, rosiglitazone, pioglitazone and telmisartan significantly increased filaggrin expression at both mRNA and protein levels in calcium‐induced differentiated NHKs. Rosiglitazone and pioglitazone, but not troglitazone nor telmisartan, also significantly increased loricrin expression at both mRNA and protein levels in differentiated NHKs. These effects were not found in undifferentiated NHKs nor differentiated NHKs treated with ciglitazone. This study revealed differential effects of various PPAR‐γ agonists on epidermal differentiation, and the most potent of those are rosiglitazone and pioglitazone.     

Therapeutic potential of topically administered γ‐AlOOH on 2,4‐dinitrochlorobenzene‐induced atopic dermatitis‐like lesions in Balb/c mice

Boehmite (γ‐AlOOH) has a wide range of applications in a variety of industrial and biological fields. However, little is known about its potential roles in skin diseases. The current study investigated its effect on atopic dermatitis (AD). Following characterization, cytotoxicity, pro‐inflammatory response and oxidative stress associated with boehmite were assessed, using TNF‐α‐induced keratinocytes and mast cells. In addition, therapeutic effects of boehmite, topically administered to Balb/c mice induced by 2,4‐dinitrochlorobenzene (DNCB), were evaluated. Expression of cytokines (TLSP, IL‐25 and IL‐33) and the generation of ROS from keratinocytes induced by TNF‐α were significantly inhibited by boehmite without affecting cell viability. MAPKs (ERK, JNK and p38) required for cytokine expression were suppressed by boehmite treatment. Up‐regulation of cytokines (TSLP, IL‐4, IL‐5, IL‐13, RANTES) in human mast cells treated with phorbol 12‐myristate 13‐acetate and calcium ionophore was also suppressed by boehmite. Boehmite improved the AD severity score, epidermal hyperplasia and transepidermal water loss in DNCB‐induced AD‐like lesions. Moreover, Th2‐mediated cytokine expression, mast cell hyperplasia and destruction of the skin barrier were improved by boehmite treatment. Overall, we demonstrated that boehmite may potentially protect against AD.     

Characterization of a hapten-induced, murine model with multiple features of atopic dermatitis: structural, immunologic, and biochemical changes following single versus multiple oxazolone challenges

Atopic dermatitis (AD) is a chronic dermatosis bearing clinical, histological, and immunologic similarities to chronic allergic contact dermatitis (ACD). AD shows a Th2 cell-dominant inflammatory infiltrate, elevated serum IgE levels, a permeability barrier abnormality, and Staphylococcus aureus colonization. Repeated hapten challenges reportedly produce a Th2-like hypersensitivity reaction (Th2-like HR). Here, 9-10 challenges with oxazolone (Ox) to hairless mice also produced a chronic Th2-like HR. Permeability barrier function and expression of differentiation proteins, filaggrin, loricrin, and involucrin, became abnormal. CRTH-positive Th2-dominant inflammatory infiltrate, with increased IL-4 expression, and a large increase in serum IgE levels were observed. The barrier abnormality was associated with decreased stratum corneum (SC) ceramide content and impaired lamellar body secretion, resulting in abnormal lamellar membranes, as in human AD. Furthermore, as in human AD, epidermal serine protease activity in SC increased and expression of two lamellar body-derived antimicrobial peptides, CRAMP and mBD3, declined after Ox challenges, paralleling the decrease of their human homologues in AD. Thus, multiple Ox challenges to normal murine skin produce a chronic Th2-like HR, with multiple features of human AD. Because of its reproducibility, predictability, and low cost, this model could prove useful for evaluating both pathogenic mechanisms and potential therapies for AD.     

Increased interleukin‐36γ expression in skin and sera of patients with atopic dermatitis and mycosis fungoides/Sézary syndrome

Interleukin (IL)‐36γ is expressed by keratinocytes and functions as a key initiator of inflammation in the skin. IL‐36γ expression is enhanced by tumor necrosis factor‐α and IL‐17A, having a strong association with psoriasis. In this study, we examined the role of IL‐36γ in atopic dermatitis (AD) and mycosis fungoides (MF)/Sézary syndrome (SS). Serum levels of IL‐36γ in AD patients and MF/SS patients were elevated compared with those of healthy controls. Importantly, serum IL‐36γ levels in AD patients positively correlated with Eczema Area and Severity Index and those of MF/SS patients positively correlated with serum soluble IL‐2 receptor levels. IL‐36γ mRNA levels in AD skin and MF/SS skin were significantly higher than those of normal skin. IL‐36γ mRNA levels in MF/SS skin positively correlated with IL‐17A mRNA levels. Immunohistochemical staining revealed that IL‐36γ was highly expressed in keratinocytes in lesional skin of AD and MF/SS. Taken together, our study demonstrated that IL‐36γ expression was increased in sera and skin of patients with AD and MF/SS as was reported in psoriatic patients.     

High‐fat diet exacerbates imiquimod‐induced psoriasis‐like dermatitis in mice

Psoriasis, a chronic inflammatory skin disease, is closely related to systemic metabolism. An elevated body mass index (BMI) is a risk factor for psoriasis; inflammasomes are activated by adipose tissue macrophages in obese subjects. We hypothesized that hyperlipidaemia is involved in the pathogenesis of psoriasis and examined the role of a high‐fat diet (HFD) in the development of psoriasis in imiquimod (IMQ)‐treated mice. The body weight and serum level of cholesterol were significantly higher in mice fed an HFD than in a regular diet (RD). HFD mice had higher psoriasis skin scores, and the number of neutrophils infiltrating into the lesional skin was elevated. IL‐17A mRNA expression was significantly increased in the skin of IMQ‐treated HFD mice; the expression of IL‐22, IL‐23 and TNF‐α mRNA was not enhanced. Caspase‐1 and IL‐1β were activated in the skin of IMQ‐treated HFD mice, and their serum level of IL‐17A, TNF‐α and IL‐1β was significantly upregulated. Our findings strongly suggest that hyperlipidaemia is involved in the development and progression of psoriasis via systemic inflammation and inflammasome activation.     

Mild electrical stimulation with heat shock reduces inflammatory symptoms in the imiquimod‐induced psoriasis mouse model

Psoriasis is a chronic skin disease caused by immune disorder. The chronic skin inflammation involves inflammatory molecules that are released from T lymphocytes and keratinocytes. Therefore, developing an anti‐inflammatory therapy that is suitable for long‐term treatment is needed. Electrical stimulation induces biological responses by modulating intracellular signaling pathways. Our previous studies showed that the optimized combination treatment of mild electrical stimulation (MES, 0.1‐millisecond; ms, 55‐pulses per second; pps) and heat shock (HS, 42°C) modulates inflammatory symptoms of metabolic disorders and chronic kidney disease in mice models and clinical trials. Here, we investigated the effect of MES+HS treatment on imiquimod‐induced psoriasis mouse model. Topical application of imiquimod cream (15 mg) to mice ear induced keratinocyte hyperproliferation and psoriasis‐like inflammation. In MES+HS‐treated mice, imiquimod‐induced skin hyperplasia was significantly decreased. MES+HS treatment reduced the protein expression of IL‐17A and the infiltration of CD3‐positive cells in lesioned skin. In addition, MES+HS‐treated mice had decreased mRNA expression level of antimicrobial molecules (S100A8 and Reg3γ) which aggravate psoriasis. In IL‐17A‐stimulated HaCaT cells, MES+HS treatment significantly lowered the mRNA expression of aggravation markers (S100A8, S100A9 and β‐defensin2). Taken together, our study suggested that MES+HS treatment improves the pathology of psoriasis via decreasing the expression of inflammatory molecules.     

Evidence for a regulatory loop between IFN‐γ and IL‐33 in skin inflammation

Interleukin‐33 has recently gained much attention due to its role in allergic responses. It has been shown to amplify Th2 responses and to act as a damage‐associated molecular pattern. IL‐33 acts on a broad range of cells and has been proposed to link innate and adaptive features of allergic responses. It was the aim of this study to investigate this property of IL‐33 in the inflammatory response characterising atopic dermatitis (AD). We have analysed the response of skin‐resident cells derived from patients with AD and healthy donors with regard to the expression of IL‐33 and its receptor ST2. The functional impact of IL‐33 on CD4+ T cells was investigated. Keratinocytes and dermal fibroblasts clearly differ in their regulation of IL‐33. In fibroblasts, the concerted action of TNF‐α and IL‐1β was the strongest inducer, whereas IFN‐γ is clearly the key molecule that upregulates IL‐33 in keratinocytes with a more pronounced response of cells derived from patients with AD. Keratinocytes from patients with AD showed a markedly higher constitutive expression level of surface ST2. CD4+ T cells respond to IL‐33. Unexpectedly, IL‐33 failed to induce a significant secretion of IL‐5 or IL‐13. By contrast, high amounts of IFN‐γ were detectable if IL‐33 was added to the T‐cell receptor‐stimulated cells or in combination with IL‐12. These results suggest that IL‐33 and IFN‐γ are closely interlinked in epidermal AD inflammation. IFN‐γ induces IL‐33 in keratinocytes and IL‐33 acts on activated T cells to further increase the release of IFN‐γ, therefore contributing to drive skin inflammation towards chronic responses.     

Ustekinumab improves psoriasis‐related gene expression in noninvolved psoriatic skin without inhibition of the antimicrobial response

Background Ustekinumab is a fully human anti‐p40 monoclonal antibody which neutralizes interleukin (IL)‐12 and IL‐23, thereby interfering with T‐helper (Th)1/Th17 pathways and keratinocyte activation, and is highly effective in the treatment of psoriasis. During ustekinumab treatment, some of our patients noticed reduced koebnerization of noninvolved skin and less new plaque formation. Objectives To determine whether ustekinumab improves psoriasis‐related gene expression and tape‐strip responses in noninvolved skin. Methods Before and 4 weeks after ustekinumab treatment, noninvolved skin was tape‐stripped. After 5 h, biopsies were taken from untouched and tape‐stripped skin. The mRNA expression of psoriasis‐related markers such as NGF, GATA3 and IL‐22RA1, and several antimicrobial peptides (AMP) was quantified. Leucocyte counts and a broad range of inflammatory serum proteins were analysed to gain insight into the systemic alterations. Results Four weeks following a single ustekinumab injection, NGF showed a significant decrease, whereas GATA3 and IL‐22RA1 expression increased, indicative of reduced responsiveness to epidermal triggering. This was accompanied by an increase of the inflammation‐related serum proteins GPNMB, MST1 and TRADD. The baseline and tape‐strip‐induced mRNA expression of the AMP human β‐defensin‐2 (hBD‐2), S100A7 and LL‐37 remained unaltered. Clinically, after 4 weeks, eight out of 11 patients showed a 50% psoriasis area and severity index (PASI) improvement, which was accompanied by a significant reduction in serum hBD‐2 levels. No changes were noted in total leucocytes, C‐reactive protein and erythrocyte sedimentation rate. Conclusions These findings indicate that ustekinumab reduces psoriasis‐related gene expression in noninvolved psoriatic skin, making it more resistant to exogenous triggering, without disturbing its antimicrobial response. In parallel, ustekinumab modulates important circulating inflammation‐related proteins.     

Time‐dependent progression from the acute to chronic phases in atopic dermatitis induced by epicutaneous allergen stimulation in NC/Nga mice

Atopic dermatitis (AD) is a complicated skin condition influenced by genetic background and environmental factors. In this study, we applied Dermatophagoides farinae body extract (DfE) to the barrier‐disrupted skin of NC/Nga mice twice a week for 8 weeks to identify the clinical and immunological factors in AD progression. Repeated application of the DfE to the skin of NC/Nga mice showed the similar consequences for the natural course of progression in human AD, histologically and immunologically. We confirmed that the AD‐like skin lesions in NC/Nga mice did not last for the whole period of our experiment in spite of repeated topical applications of DfE twice a week. Topical DfE stimulation increased the skin mRNA expressions of Th1‐, Th2‐ and Th17‐related cytokines in the acute phase. The expression patterns of IL‐4 and IL‐13 in splenic T cells and skin lesions were consistent with the time course alterations of clinical features of AD‐like skin symptoms. We also showed that there was a remission phase either just before or right after the chronic phase in this experimental model. Interestingly, splenic T‐cell‐derived IL‐5 expression began to increase in the chronic phase, while skin‐derived IL‐5 mRNA expression increased in the acute phase. In conclusion, our results suggest that we should pay attention to the characteristics of each stage of AD progression and choose a suitable corresponding stage of animal model not only to elucidate the pathogenesis of AD but also to develop and evaluate therapeutic drugs for AD.     

Toll‐like receptor 4 attenuates a murine model of atopic dermatitis through inhibition of langerin‐positive DCs migration

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that is often associated with skin barrier dysfunction leading to a higher frequency of bacterial and viral skin infections. Toll‐like receptor (TLR) 4 on resident skin cells was involved in sensing pathogens and eliciting pathogen‐specific innate and adaptive immune responses. Previous studies have demonstrated that TLR4 was linked to AD severity in context of pathogen infection. However, the immune regulatory role of TLR4 in AD remains to be defined. We here investigated the immune regulatory function of TLR4 in AD induced by repeated epicutaneous application of a hapten, 2,4‐dinitrochlorobenzene (DNCB). Our results showed that TLR4‐deficient (TLR4^?/?) mice exhibited more severe AD symptoms than WT mice after DNCB challenge. The DNCB‐treated TLR4^?/? mice also displayed higher expression levels of inflammatory cytokines and stronger Th2 response than WT counterparts. Moreover, the skin expression of thymic stromal lymphopoietin (TSLP), an important potential contributor to allergic inflammation, was significantly elevated in TLR4^?/? mice compared with that in WT mice upon DNCB administration. Furthermore, we demonstrated that the migration of langerin‐positive dendritic cells (DCs) into draining lymph nodes was enhanced in TLR4^?/? mice following DNCB challenge, which is partially dependent on the production of pro‐inflammatory cytokine TNF‐α. Together, these results determined that TLR4 affected the hapten‐induced skin inflammation in the absence of exogenous pathogen infection, suggesting that TLR4 not only regulates infection but also may serve as a modulator of the immune response during AD development.     

Aggravation of atopic dermatitis‐like symptoms by consecutive low concentration of formaldehyde exposure in NC/Nga mice

Formaldehyde (FA) has been known to be associated with development of asthma (AS) and atopic dermatitis (AD). In this study, we investigated whether FA inhalation would affect the provocation or exacerbation of AD‐like symptoms. Atopic‐prone NC/Nga mice were exposed to low (0.2 ppm) and high (1.0 ppm) concentration of FA by inhalation. Combined exposure to low concentration of FA inhalation and topical house dust mite (HDM) stimulation significantly upregulated HDM‐induced total plasma IgE and IgG2a production, Th1‐, Th2‐, Th17‐related cytokine as well as COX‐2 mRNA expressions in the skin. Interestingly, independent FA inhalation, especially at low concentration (0.2 ppm), increased the skin mRNA expressions of IL‐13, IL‐17E/IL‐25 and COX‐2, even though it failed to induce AD‐like skin inflammation. In conclusion, we suggest that increased skin mRNA expressions of IL‐13, IL‐25/IL‐17E and COX‐2 by independent low concentration of FA exposure might be a key factor to exacerbate HDM‐mediated AD‐like skin inflammation.     

Increased expression of IL‐33 in rosacea skin and UVB‐irradiated and LL‐37‐treated HaCaT cells

Rosacea is one of the most common dermatoses of adults. Although the detailed pathophysiology remains unknown, it is thought that rosacea is caused by a consistently aberrant, innate immune response, and that LL‐37 plays an important role. However, involvement of the inflammatory cytokine IL‐33 has not yet been studied. We explored the role played by IL‐33 in the pathophysiology of rosacea. First, we immunohistochemically evaluated the expression of IL‐33 and its receptor (ST2) in rosacea skin. Second, we exposed HaCaT cells to ultraviolet B (UVB) irradiation in the presence or absence of LL‐37 and measured the expression of proinflammatory cytokines including IL‐33. We also analysed VEGF (vascular endothelial growth factor) mRNA expression and protein release after costimulation of HaCaT cells by LL‐37 and IL‐33. Immunohistochemically, IL‐33 expression was enhanced in the skin of rosacea patients, especially with erythematotelangiectatic subtype. In vitro, UVB and LL‐37 synergistically increased mRNAs expression of proinflammatory cytokines, especially IL‐33 and IL‐1β. IL‐33 protein release was also synergistically increased by LL‐37 and UVB treatment. LL‐37 and IL‐33 stimulated VEGF mRNA expression and VEGF release from HaCaT cells. Our findings suggest that rosacea skin with abundant LL‐37 may robustly produce and release IL‐33 when exposed to UV radiation. IL‐33 may participate in the angiogenesis and vasodilation of rosacea skin by enhancing VEGF release.     

Osteopontin deficiency affects imiquimod‐induced psoriasis‐like murine skin inflammation and lymphocyte distribution in skin,draining lymph nodes and spleen

Osteopontin (OPN) that enhances autoimmunity is expressed in psoriasis lesions; however, its functions in psoriatic inflammation are unknown. We investigated the role of OPN in OPN deficient mice (OPN?/?) by inducing psoriasis‐like inflammation through skin application of imiquimod (IMQ). OPN?/? mice treated with IMQ showed delayed onset ear swelling and attracted less inflammatory cells to the skin. IMQ‐induced lymph node swelling was reduced in the absence of OPN, and IMQ‐mediated expansion of B cells was inhibited. Further, reduction of CD4⁺ T‐cell numbers by IMQ in lymph nodes was suppressed in OPN?/? mice, with an increase in the CD4/CD8 ratio. A comparable pattern was found in spleen. Importantly, IMQ‐induced IL‐17 and IL‐4 expression by CD4⁺ lymph node T cells was reduced in OPN?/? mice. In conclusion, OPN may modulate psoriasis‐like inflammation through altering lymphocyte distribution in skin and draining lymph nodes and by inducing IL‐17 expression of inflammatory T cells.     

Analyses of FLG mutation frequency and filaggrin expression in isolated ichthyosis vulgaris (IV) and atopic dermatitis‐associated IV

Background Ichthyosis vulgaris (IV; OMIM 146700) is a very common inherited skin disorder. Loss‐of‐function mutations in the filaggrin gene (FLG) have been identified as the cause of IV. In a previous study, we found that the percentage of FLG null mutations was lower in IV associated with atopic dermatitis (AD) than in IV not associated with AD (isolated IV). We speculated that some clinical manifestations of IV in patients with AD are not induced by FLG mutations. Objectives In order to clarify this issue, we collected 21 IV pedigrees, 33 patients with sporadic isolated IV and 116 patients with AD‐associated IV to analyse FLG mutation frequency and filaggrin expression in isolated IV and AD‐associated IV. Methods A comprehensive sequencing of the FLG gene in all patients was performed using an overlapping polymerase chain reaction (PCR) strategy. We also studied the immunohistochemistry of profilaggrin/filaggrin protein expression in the skin and measured the mRNA expression using real‐time PCR in seven patients, including one patient with IV harbouring the mutation c.3321delA, two patients with AD‐associated IV harbouring c.3321delA and c.6834del5, and four patients with AD‐associated IV without FLG mutations. Results The percentage of mutations in the FLG gene was 74% and 43% in patients with isolated IV and patients with AD‐associated IV, respectively. Immunohistochemical staining revealed that profilaggrin/filaggrin peptides were remarkably reduced in the epidermis of all the patients. All the patients with either AD or IV showed lower FLG mRNA expression compared with the normal control. Conclusions These results indicate that factors other than FLG gene mutations can downregulate profilaggrin/filaggrin expression, leading to the ichthyosiform phenotype in the context of AD.     

Lipocalin‐2 exacerbates psoriasiform skin inflammation by augmenting T‐helper 17 response

Lipocalin‐2 (LCN2) is an antimicrobial protein and adipokine associated with insulin resistance, obesity and atherosclerotic disease. Psoriasis is a T‐helper (Th)1/Th17‐mediated, chronic inflammatory dermatosis related to metabolic syndromes and serum LCN2 levels are elevated in psoriatic patients. We examined the in vivo effects of LCN2 on topical imiquimod (IMQ)‐induced psoriasiform skin in BALB/c mice and in vitro on human keratinocytes (KC). Clinically, i.p. injected LCN2 exacerbated erythema and scaling in IMQ‐treated murine skin compared with phosphate‐buffered saline injection alone, and it augmented interleukin (IL)‐17A, IL‐17F, IL‐22, IL‐23p19, IL‐12p40, CCL20, tumor necrosis factor‐α, chemokine (C‐X‐C motif) ligand (CXCL)1, CXCL2, DEFB4, DEFB14, LCN2 and S100A7 mRNA levels of IMQ‐treated murine skin while it did not increase the mRNA levels of interferon‐γ, IL‐12p35 or CXCL10. LCN2 in synergy with IL‐17 increased mRNA levels of CCL20, LCN2 and DEFB4A but not of CXCL10 in human KC in vitro. These results suggest that LCN2 enhances the expression of Th17 cytokines/chemokines and antimicrobial peptides in murine IMQ‐treated psoriatic skin and KC. LCN2 may potentiate the development of psoriasis via the enhancement of Th17‐ and antimicrobial peptide‐mediated inflammation.