Induced Skin Inflammation Research Articles

The Skin Microbiome in Inflammatory Skin Diseases

Ongoing investigations of the human skin microbiome strongly suggest a connection to skin diseases and skin health. This review provides an overview of recent literature on the skin microbiome in relation to skin diseases, with a specific focus on common inflammatory skin conditions, such as atopic dermatitis, psoriasis, hidradenitis suppurativa, acne, and rosacea. In healthy subjects, the skin microbiome mediates fundamental processes involving the immune response and epidermal development and differentiation. Microbiome characteristics in inflammatory skin diseases differ depending on disease, as both topography and disease severity and even host genetics seem to influence the microbiome composition. Not only the bacterial species are important but also different strains within the same species can act differently, where some can be commensal and protect against microbial dysbiosis, whereas others can induce skin inflammation and immune reactions in humans. The interplay between skin microbes, host genetics, and the immune system is anticipated to be of importance for both the development and severity of many skin diseases. However, the causality of specific pathogens and the effect on the pathogenesis in relation to inflammatory skin diseases is yet to be understood.

Interplay of Staphylococcal and Host Proteases Promotes Skin Barrier Disruption in Netherton Syndrome

SUMMARYNetherton syndrome (NS) is a monogenic skin disease resulting from loss of function of lymphoepithelial Kazal-type-related protease inhibitor (LEKTI-1). In this study we examine if bacteria residing on the skin are influenced by the loss of LEKTI-1 and if interaction between this human gene and resident bacteria contributes to skin disease. Shotgun sequencing of the skin microbiome demonstrates that lesional skin of NS subjects is dominated by Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Isolates of either species from NS subjects are able to induce skin inflammation and barrier damage on mice. These microbes promote skin inflammation in the setting of LEKTI-1 deficiency due to excess proteolytic activity promoted by S. aureus phenol-soluble modulin α as well as increased bacterial proteases staphopain A and B from S. aureus or EcpA from S. epidermidis. These findings demonstrate the critical need for maintaining homeostasis of host and microbial proteases to prevent a human skin disease.

Preclinical study of the topical anti-inflammatory activity of Cyperus rotundus L. extract (Cyperaceae) in models of skin inflammation

Ethnopharmacological relevanceCyperus rotundus L. (Cyperaceae) is considered one of the most widely distributed plant species in the world, especially in tropical and subtropical regions. In addition, it is commonly used in India, China and Japan in traditional medicine to treat different diseases, including dermatitis and other skin disorders. Aim of the studyTo investigate the topical anti-inflammatory activity of C. rotundus rhizome ethanolic extract in models of acute and chronic dermatitis. Materials and methodsPhytochemical analysis was carried out using High-performance liquid chromatography-ultraviolet detection (HPLC/UV) to determine the presence of quercetin and chlorogenic acid in C. rotundus extract. Topical anti-inflammmatory effects of C. rotundus extract were evaluated on arachidonic acid (AA) and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation in mice. Skin biopsies were collected and submitted to histological and enzymatic analysis to evaluate the C. rotundus effect in leukocyte migration into inflamed tissue. Antiproliferative activity of C. rotundus was confirmed by PCNA immunostained cell analysis. Systemic and possible adverse effects of topical treatment with C. rotundus were evaluated by the skin atrophy and same organ weights. In addition, the glucocorticoid receptor (GR) antagonist mifepristone was used to investigate possible GR-mediated mechanisms of action. ResultsThe phytochemical analysis show that C. rotundus ethanol extract contains 45 μg/g of chlorogenic acid. Topical treatment with C. rotundus extract reduced ear edema and cellular infiltrate in acute and chronic skin inflammation models. Moreover, mice topically treated with C. rotundus exhibited decrease in TPA-induced keratinocyte hyperproliferation. Relevantly, topical treatment with C. rotundus did not caused skin atrophy or changes in lymphoid organ weight. The anti-inflammatory effect of C. rotundus was not influenced by the GR antagonist. ConclusionThe results here demonstrate for the first time the topical anti-inflammatory and antiproliferative efficacy of C. rotundus extract, suggesting that the extract could be a potential new therapeutic tool for the treatment of inflammatory skin disorders.

The anti-IgE mAb omalizumab induces adverse reactions by engaging Fcγ receptors.

Omalizumab is an anti-IgE monoclonal antibody (mAb) approved for the treatment of severe asthma and chronic spontaneous urticaria. Use of omalizumab is associated with reported side effects ranging from local skin inflammation at the injection site to systemic anaphylaxis. To date, the mechanisms through which omalizumab induces adverse reactions are still unknown. Here, we demonstrated that immune complexes formed between omalizumab and IgE can induce both skin inflammation and anaphylaxis through engagement of IgG receptors (FcγRs) in FcγR-humanized mice. We further developed an Fc-engineered mutant version of omalizumab, and demonstrated that this mAb is equally potent as omalizumab at blocking IgE-mediated allergic reactions, but does not induce FcγR-dependent adverse reactions. Overall, our data indicate that omalizumab can induce skin inflammation and anaphylaxis by engaging FcγRs, and demonstrate that Fc-engineered versions of the mAb could be used to reduce such adverse reactions.

Phospholipase A2 from bee venom increases poly(I:C)-induced activation in human keratinocytes.

Bee venom (BV) induces skin inflammation, characterized by erythema, blisters, edemas, pain and itching. Although BV has been found to have an inhibitory effect on toll-like receptors (TLRs), we here show that BV enhances keratinocyte responses to polyinosinic-polycytidylic acid [poly(I:C)], a ligand for TLR3. Our results revealed that the enhanced TLR activity was primarily induced by secretory phospholipase A2 (sPLA2), a component of BV (BV-sPLA2). PLA2 mediates the hydrolysis of membrane phospholipids into lysophospholipids and free fatty acids. We demonstrated that BV-sPLA2 increased the intracellular uptake of poly(I:C), phosphorylation of the nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs), and poly(I:C)-mediated interleukin 8 production in human keratinocytes. We further showed that the enzymatic activity of BV-sPLA2 was essential for the increased uptake of poly(I:C). These findings suggest that BV-sPLA2 may induce a modification of the cell membrane structure, leading to enhanced poly(I:C) uptake in keratinocytes. BV-sPLA2 might be able to promote wound healing by enhancing TLR3 responses.

Intrauterine growth restriction induces skin inflammation, increases TSLP and impairs epidermal barrier function.

Intrauterine growth restriction (IUGR) and low birth weight are risk factors for childhood asthma. Atopic march describes the progression from early dermatitis to asthma during life. Since inflammatory signaling is linked to increased airway resistance and lung remodeling in rats after IUGR, we queried if these findings are related to skin inflammatory response. Firstly, we induced IUGR in Wistar rats by isocaloric protein restriction during gestation. IUGR rats showed lower body weight at postnatal day 1 (P1), catch-up growth at P21, and similar body weight like controls at P90. At P1 and P90, mRNA of inflammatory as well as fibrotic markers and number of skin immune cells (macrophages) were increased after IUGR. Skin thymic stromal lymphopoietin (TSLP) mRNA at P1 and serum TSLP at P1 and P21 were elevated in IUGR. Moreover, IUGR impaired transepidermal water loss at P21 and P90. IUGR induced higher. Secondly, the increase of TEWL after Oxazolone treatment as a model of atopic dermatitis (AD) was greater in IUGR than in Co. Our data demonstrate an early inflammatory skin response, which is linked to persistent macrophage infiltration in the skin and impaired epidermal barrier function after IUGR. These findings coupled with elevated TSLP could underlie atopic diseases in rats after IUGR. KEY MESSAGES: • The present study shows that IUGR increases macrophage infiltration and induces an inflammatory and fibrotic gene expression pattern in the skin of newborn rats. • Early postnatal inflammatory response in the skin after IUGR is followed by impaired epidermal barrier function later in life. • IUGR aggravates transepidermal water loss in an experimental atopic dermatitis model, possibly through elevated TSLP in skin and serum. • Early anti-inflammatory treatment and targeting TSLP signaling could offer novel avenues for early prevention of atopic disorders and late asthma in high-risk infants.

Effect of LG Herbal Medicine Complex (LG-HMC) on Diesel Particulate Matter (DPM) Induced Skin Inflammation and Xenobiotic Response Activity In Vitro

Effect of LG Herbal Medicine Complex (LG-HMC) on Diesel Particulate Matter (DPM) Induced Skin Inflammation and Xenobiotic Response Activity In Vitro

Topical Anti-Inflammatory Activity of Essential Oils of Alpinia calcarata Rosc., Its Main Constituents, and Possible Mechanism of Action.

This study aimed at investigating the anti-inflammatory potential of essential oil from rhizome and leaf of Alpinia calcarata Rosc. (ACEO) with the focus of its topical anti-inflammatory activity along with its dominant compounds 1,8-cineole and α-terpineol using mouse ear edema model. ACEOs were analyzed by GC-MS. The anti-inflammatory activity was determined by studying the inhibition of overproduction of proinflammatory mediators—nitric oxide, reactive oxygen species, prostaglandins, cyclooxygenases, and cytokines induced by lipopolysaccharides in murine macrophages. Topical anti-inflammatory and antinociceptive activity was studied by 12-O-tetradecanoylphorbol-13-acetate (TPA) induced skin inflammation and formalin-induced pain model in mice, respectively. Rhizome oil has 1,8-cineole (31.08%), α-terpineol (10.31%), and fenchyl acetate (10.73%) as major compounds whereas the ACEO from leaves has 1,8-cineole (38.45%), a-terpineol (11.62%), and camphor (10%). ACEOs reduced the production of inflammatory mediators in vitro in a concentration-dependent manner. Further, ACEO and its major compounds reduced ear thickness, weight, myeloperoxidase, and cytokines significantly (p < 0.01) in mouse ear. Dose-dependent reduction in flinching and licking in both the phases of pain sensation concludes the topical analgesic effect. Our findings suggest the potency of topical use of ACEOs for inflammatory disease conditions.

Interleukin-36: Structure, Signaling and Function.

The IL-36 family belongs to a larger IL-1 superfamily and consists of three agonists (IL-36α/β/γ), one antagonist (IL-36Ra), one cognate receptor (IL-36R) and one accessory protein (IL-1RAcP). The receptor activation follows a two-step mechanism in that the agonist first binds to IL-36R and the resulting binary complex recruits IL-1RAcP. Assembled ternary complex brings together intracellular TIR domains of receptors which activate downstream NF-κB and MAPK signaling. Antagonist IL-36Ra inhibits the signaling by binding to IL-36R and preventing recruitment of IL-1RAcP. Members of IL-36 are normally expressed at low levels. Upon stimulation, they are inducted and act on a variety of cells including epithelial and immune cells. Protease mediated N-terminal processing is needed for cytokine activation. In the skin, the functional role of IL-36 is to contribute to host defense through inflammatory response. However, when dysregulated, IL-36 stimulates keratinocyte and immune cells to enhance the Th17/Th23 axis and induces psoriatic-like skin disorder. Genetic mutations of the antagonist IL-36Ra are associated with occurrence of generalized pustular psoriasis, a rare but life-threatening skin disease. Anti-IL-36 antibodies attenuate IMQ or IL-23 induced skin inflammation in mice, illustrating IL-36's involvement in mouse model of psoriasis. Other organs such as the lungs, the intestine, the joints and the brain also express IL-36 family members upon stimulation. The physiological and pathological roles of IL-36 are less well defined in these organs than in the skin. In this chapter, current progress on IL-36 protein and biology is reviewed with a discussion on investigative tools for this novel target.

NEUROIMMUNOENDOCRINE REGULATION OF THE SKIN FUNCTIONING

The review deals with modern ideas of neuroimmunoendocrine regulation of physiological and pathophysiological processes in skin. The present data are provided which indicate to composite mechanisms of intercellular interactions in complex regulating systems (nervous, immune, endocrine) acting at the level of skin in normal conditions, as well during the posttraumatic period. We describe different modes for participation of endocrine and nervous systems in immunologically induced skin inflammation. The data are provided confirming localization of adrenergic receptors on membranes of immunocompetent cells and leukocytes, on regulatory effects of hypothalamus upon immune functions, about multidirectional actions upon inflammation of sympathetic and parasympathetic nervous system etc.There are sufficient data on promotion of pathophysiological changes and reconstitution processes in the skin due to effects of local immune cells and bioactive substances expressed by them. The course of skin wound regeneration depend on the type of damage, degree and a phase of healing process. Posttraumatic reparative potential of skin is often limited by the infectious processes initiated by local microflora, products of cell disintegration and necrotic tissues. The cause-effect relationship is proven by arising inflammation which is implemented by inclusion of immune protection responses. The increased necrotic area and suppuration of the wound occurs die to inhibition of system of the phagocytizing macrophages. However, activation of this system brings about formation of the connective tissue capsule around the inflammation focus within early terms.We also discuss the issues of reparative skin regeneration which of great medico-social value, in connection with considerable prevalence of traumatic events and their social consequences, followed by expressed cosmetic defects. Evolving neurocognitive problems lead to decreased quality of the patient’s life, development of social disadaptation and further deprivation. The role of nervous system and psychological frustration in genesis of skin manifestations requires future development of the modern scientific direction, i.e., psychodermatology.Understanding of molecular mechanisms regulating the neuroimmunocutaneous interactions offers new prospectives in treatment of some skin diseases, as well as activation of the damaged skin recovery. According to the data presented in the review article, one may conclude on relevance of further studies on reparative potential of skin under interactions of homeostatic regulatory systems.

NLRP inflammasomes and induced skin inflammation, barrier recovery and extended skin hydration.

In vitro assays were designed to examine the release of active Caspase-1 (ACasp-1) from NLRP inflammasome-activated Normal Human Epidermal Keratinocytes (NHEK) employing a bioluminescent assay specific for measuring inflammasome-induced ACasp-1 expression. Four anticipated exogenous activators of the NLRP inflammasome including: UVB, ATP, Nigericin and Urban Dust were examined. Follow-up studies examined the influence of extracellular application of three different natural blends of known anti-inflammatories, one a polysaccharide blend and the other two antioxidant blends, one oil-soluble the other water-soluble, to examine ACasp-1 inhibition. Clinical work using the same blend of polysaccharides employed at 3% in a moisturizing formulation was examined for skin barrier recovery, measured with TEWL over a 60-h time frame after tape stripping on 10 individuals, and extended moisturization, measured using corneometer conductance after a single product application out through a 48-h regression on 10 individuals. In vitro results indicated that two exogenous activators, 60mJcm-2 UVB and 5mM ATP, worked to upregulate expression of ACasp-1 within a 20-h timeframe. Additional studies were conducted to examine the influence of three extracellularly applied active ingredient blends. A blend of polysaccharides demonstrated potential to inhibit ACasp-1 expression in both UVB- and ATP-activated skin cells. Oil-soluble and water-soluble antioxidant blends inhibited ACasp-1 expression in UVB-activated keratinocytes but not ATP-activated keratinocytes. Barrier disruption studies indicated that 3% of the polysaccharide blend accelerated barrier recovery in a 60-h time frame as measured by TEWL. Skin hydration studies showed an ability for the polysaccharide blend to show significant improvements in skin hydration out to 48h after a single application vs. a moisturizing placebo. The role of the skin's innate immune response, controlled by NLRP inflammasomes, is beginning to be linked to numerous skin conditions including inflammaging. In this work, it was found that: (i) an in vitro assay could activate NHEKs to express NLRP inflammasome-induced ACasp-1 expression, (ii) Ingredient blends inhibited UVB and ATP-induced NLRP inflammasome-induced ACasp-1 expression, and (iii) skin barrier disruption improvements and extended skin hydration could be achieved with 3% of the polysaccharide blend.

The Influence of Ketogenic Diets on Psoriasiform-Like Skin Inflammation

The Influence of Ketogenic Diets on Psoriasiform-Like Skin Inflammation

Superoxide Dismutase 3 Inhibits LL-37/KLK-5–Mediated Skin Inflammation through Modulation of EGFR and Associated Inflammatory Cascades

The expressions of LL-37 and KLK-5 were found to be altered in various dermatoses, including atopic dermatitis, psoriasis, and rosacea. However, the downstream inflammatory effect of LL-37 and KLK-5 is not as well studied. In addition, there is little high-quality evidence for the treatment of LL-37- and KLK-5-mediated inflammation. In this study, we investigated the effect of superoxide dismutase 3 (SOD3) on LL-37- or KLK-5-induced skin inflammation invitro and invivo and its underlying anti-inflammatory mechanisms. Our data showed that SOD3 significantly reduced both LL-37- and KLK-5-induced expression of pro-inflammatory mediators and suppressed the activation of EGFR, protease-activated receptor 2, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3, and p38/extracellular signal-regulated kinase signaling pathways in human keratinocytes. Moreover, SOD3 suppressed LL-37-induced expression of inflammatory mediators, reactive oxygen species production, and p38/extracellular signal-regulated kinase activation in mast cells. In addition, subcutaneous injection of KLK-5 in SOD3 knockout mice exhibited erythema with increased epidermal thickness, mast cell and neutrophil infiltration, expression of inflammatory mediators, and activation of EGFR, protease-activated receptor 2, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3, and downstream mitogen-activated protein kinase pathways. However, treatment with SOD3 in SOD3 knockout mice rescued KLK-5-induced inflammatory cascades. Similarly, KLK-5-induced inflammation in wild-type mice was also ameliorated when treated with SOD3. Taken together, our data suggest that SOD3 is a potentially effective therapy for both LL-37-and KLK-5-induced skin inflammation.

Comparative Histological Study on the Preventive Role of Acarbose and Calcipotriol/Betamethasone in Mouse Model of Psoriasis-Like Skin Inflammation Induced by Imiquimod

Introduction: Psoriasis is an autoimmune skin disorder that is symptomized by erythema and scaling. Recently, imiquimod (IMQ) has been used to induce skin inflammation in mice to create a psoriasis model.Aim of the Work: To assess the possible preventive potential of acarbose on psoriasis-like skin inflammation induced by IMQ in adult male mice, and to compare it to calcipotriol/betamethasone applied on the same psoriasis mouse model.Materials and Methods: Thirty four BALB/c mice were classified as the following groups: I(Control), II(IMQ): IMQ-model with topically applied Aldara cream, ІII(Acarbose): IMQ-model treated with Glucobay orally, ІV(Calcipotriol/Betamethasone): IMQ-model treated with Calcipoheal-Cort ointment and V(Acarbose+Calcipotriol/Betamethasone): IMQ-model treated with both Glucobay and Calcipoheal-Cort combined. Haematoxylin & Eosin stain and S100 immunohistochemical staining were performed along with electron microscopic study of skin sections. Mean epidermal thickness and mean number of S100 immuno-positive keratinocytes were measured and measurements were statistically analyzed.Results: Group II mice showed psoriasis-like signs of skin inflammation. Groups III and IV mice showed less signs of inflammation which were markedly attenuated by combination of both of the treatments. Group II demonstrated significant acanthosis and abundant infiltrates of inflammatory cells in the dermis and significantly numerous S100 immuno-positive keratinocytes. Groups III and IV showed significant improvement of these changes which were markedly diminished in group V as it showed almost normal histological structure.Conclusion: Acarbose had an overall beneficial effect on psoriasis-mimicking mouse model triggered by IMQ, almost comparable to that demonstrated by calcipotriol/betamethasone. However, combination of both treatments exerted a more powerful therapeutic effect.

The Unique Immunoregulatory Function of Staphylococcus Aureus Lipoteichoic Acid in Dendritic Cells

Background and objectives: Lipoteichoic acid (LTA) is a structural component of Staphylococcus aureus (S. aureus) that induces severe infection disease and skin inflammation such as atopic dermatitis (AD); the biological function of LTA is still unclear. Dendritic cells (DC) are important regulators in the immune system, and the cells ectopically recognize agents that have an influence on the host immune response. We aimed to reveal the DC-based immune response against LTA to understand the novel mechanism in S. aureus related acute skin inflammation. Materials and Methods: Different doses of LTA were applied on the epidermal barrier dysfunction mice in order to evaluate the epidermal thickness, DC activation, and subsequent immunological response such as effector T-cell (Teff) activation. In addition, bone marrow-derived dendritic cells (BMDCs) were also treated with LTA, and the immunoregulatory mechanism was investigated. Results: A low dose of LTA did not induce skin inflammation at all; however, a high dose of LTA induced severe skin inflammation on epidermalba rrier dysfunction mice. Those symptoms were correlated with the DC and Teff activation status. The low-dose treatment of LTA showed a suppressive effect in pro-inflammatory cytokine production via a Toll-like receptor 2 (TLR2)-dominant manner, and the effect was significant regarding the co-treatment with another stimulatory signal such as TLR4 by lipopolysaccharide (LPS). Meanwhile, a high-dose treatment of LTA completely abolished the suppressive effect of a low-dose treatment. This phenomenon was based on C-type lectin receptors (CLRs), because the high dose of LTA greatly enhanced the expression of CLRs in the activated DCs. Conclusions: DCs sensed the dose difference of LTA, and the mechanism contributed to regulating immune responses such as effector T-cell activation, which was directly correlated with inflammatory response. This finding might provide an understanding for the novel immunological effect of LTA and S. aureus pathogenesis under inflammation, as well as the mechanism of symbiosis.

A novel approach for dermal controlled release of salicylic acid for improved anti-inflammatory action: Combination of hydrophilic-lipophilic balance and response surface methodology

The present investigation was aimed to develop SA loaded nanoemulsion by implementing response surface methodology (RSM) and hydrophilic-lipophilic balance (HLB) approach, in amalgamation. The concentration of oil phase (Lemongrass oil containing SA, corresponding to HLB from 13.43 to 14.88) and the ratio of surfactants were taken as independent factors while particle size and polydispersibility index as dependent variables in RSM. The droplet size and polydispersibility index of the optimized nanoemulsion (SANE 14) were 134.70 ± 4.51 nm and 0.168 ± 0.011 respectively, corresponding to the HLB value of 14.8. The retention of SA from SANE 14 in skin layers was found to be 97.23% after 24 h study period. Moreover, a 2.8 and 4.13 folds amount of SA from SANE 14 was retained in epidermis and dermis, respectively, when compared with the drug solution. Therefore, the SANE 14 was capable of delivering the SA into the deeper skin layers with notable retention which was further verified by the confocal microscopy images. The TPA induced skin inflammation in mice ear was significantly reduced (80.25%) in terms of ear thickness. Significant inhibition of pro-inflammatory cytokines proved the efficacy of SANE 14. Conclusively, the controlled dermal release of salicylic acid for improved anti-inflammatory action was successfully achieved.

Transcription factor Blimp-1 regulates sebocyte homeostasis and cytokine production

Abstract Blimp-1, encoded by Prdm1, is a master transcriptional factor that governs the differentiation fate of many cell types, including epidermal keratinocytes. Previous results from our laboratory showed that inducible deletion of Prdm1 in mouse epidermis spontaneously induces skin inflammation. Epidermis composes of not only epidermal keratinocytes, but also epidermal appendages, including hair follicles, sebaceous glands and sweat glands. Sebaceous glands release the “oil” contents that lubricate the skin. Our previous results also showed that Blimp-1 is required for the maintenance of the homeostasis of terminally differentiated sebocytes. Here, we aim to investigate the potential function of Blimp-1 in inflammation and lipid metabolism in sebocytes. We depleted Blimp-1 by siRNA in SZ95, the immortalized human sebocyte cells. We found accumulated and enlarged lipid droplets in Blimp-1 depleted cells. Consistently, gas chromatography–mass spectrometry (GC-MS) analyses showed that the levels of several long-chain fatty acids, including 1,3-dipalmitoyl-2oleoylglycerol, 1-palmitoyl-2oleoyl-3-lineoleoyl-rac-glycerol, and triolein, were accumulated in Blimp-1-depleted SZ95 cells, linking with the significant increases in the production of pro-inflammatory cytokines, including IL-1β, IL-6, IL-8 and IL-18. Thus, Blimp-1 served as a pivotal mediator in the regulation of the inflammatory responses in epidermis, likely also through affecting the lipid metabolism and cytokine production in sebocytes.

Imiquimod enhances DNFB mediated contact hypersensitivity in mice

Imiquimod (Imiq) is a synthetic imizoquinoline compound which can act on Toll-like receptor (TLR)7 and transduce signals involved in cell activation. We investigated the role of Imiq on contact hypersensitivity (CHS) and explored the potential mechanisms of mast cells involved in the process. Topical application of Imiq cream augmented DNFB mediated CHS in C57BL/6 mice. Imiq application induced skin inflammation and increased the number of dendritic cells (DCs) in the draining lymph nodes (DLNs). The splenic cell proliferation to DNBS in DNFB and Imiq treated mice was greater than that in mice of DNFB treatment alone. Peritoneal cell-derived mast cells (PCMCs) expressed TLR7 mRNA. The results from toluidine blue staining for mast cells and histamine detection indicated that Imiq alone did not induce mast cell degranulation while Imiq plus DNFB significantly induced mast cell degranulation. Cromolyn, pyrilamine and cimetidine attenuated CHS reaction induced by Imiq. Our findings suggest that Imiq could augment the intensity of CHS reaction. The mechanisms underlying the effect may relate to histamine release by mast cells and induction of DC homing to DLNs. Blocking histamine action in early time of allergen contact is beneficial to the alleviation of CHS.

Methodological refinement of Aldara-induced psoriasiform dermatitis model in mice

Imiquimod (IMQ)-induced skin inflammation is currently the most widely accepted psoriasis animal model, however, it features several limitations. We have modified the IMQ-model to minimize its systemic effects towards effectively maintaining the characteristic skin reactions. The original protocol (OP) uses 62.5 mg Aldara cream (or vaseline) on the shaved back skin of mice for 4 days. In contrast, in our modified protocol (MP) 25 mg Aldara and vaseline are applied simultaneously in separate Finn chambers over the dorsal skin of mice. In both the OP and MP groups, histology showed unequivocal hallmarks of psoriasiform dermatitis. Additionally, skin scaling and blood perfusion values were similar. While Aldara elicited significantly increased skin thickness in the MP group, significant weight loss, spleen enlargement, increased inflammatory cytokine levels in plasma, and treatment related death were only observed in the OP group. Our new method reproduces psoriatic skin alterations highlighting considerably reduced systemic inflammatory reactions. Possessing psoriasiform and control skin areas on the same mouse also reduces inter-individual differences. Additionally, the new method permits prolonged IMQ treatment studies to mimic the chronic nature of psoriasis. Finally, our experimental approach may also be used in other mouse models, to prevent the undesired systemic effects of topically applied drugs.

IL-17E (IL-25) Enhances Innate Immune Responses during Skin Inflammation

IL-17E (IL-25) is a member of the IL-17 cytokine family involved in the promotion of type 2 immune responses. Recently, IL-17E has been reported to be up-regulated in distinct skin inflammatory diseases such as psoriasis and atopic and contact dermatitis. We assessed the role played by IL-17E in skin inflammation. Here, we show that IL-17E induces skin inflammation invivo, characterized by the expression of innate immune response genes and the recruitment of innate immune cells, particularly neutrophils. Genetic deletion or IL-17E neutralization ameliorated skin inflammation induced by imiquimod application or tape stripping, with reductions in neutrophil and macrophage infiltration as assessed by t-distributed stochastic neighbor embedding-guided multiparameter flow cytometry analysis, in mice. In humans, IL-17E promotes the recruitment of neutrophils via activation of macrophages in a p38-dependent mechanism. In addition, IL-17E is up-regulated in neutrophil-rich inflammatory skin diseases, such as pyoderma gangrenosum and acute generalized exanthematous pustulosis. Our data show a role for IL-17E in skin inflammation that is unrelated to the development of type 2 immune reactions. We propose that IL-17E is an important common denominator of chronic skin inflammation, promoting innate immune cell recruitment and activation.