Research Techniques Made Simple: Murine Models of Human Psoriasis

Sensory neurons increase keratinocyte proliferation through CGRP release in a tissue engineered in vitro model of innervation in psoriasis

Skin denervation has been shown to cause remission of psoriatic lesions in patients, which can reappear if reinnervation occurs. This effect can be induced by the activation of dendritic cells through sensory innervation. However, a direct effect of nerves on the proliferation of keratinocytes involved in the formation of psoriatic plaques has not been investigated. We developed, by tissue engineering, a model of psoriatic skin made of patient skin cells that showed increased keratinocyte proliferation and epidermal thickness compared to healthy controls. When this model was treated with CGRP, a neuropeptide released by sensory neurons, an increased keratinocyte proliferation was observed in the psoriatic skin model, but not in the control. When a sensory nerve network was incorporated in the psoriatic model and treated with capsaicin to induce neuropeptide release, an increase of keratinocyte proliferation was confirmed, which was blocked by a CGRP antagonist while no difference was noticed in the innervated healthy control. We showed that sensory neurons can participate directly to keratinocyte hyperproliferation in the formation of psoriatic lesions through the release of CGRP, independently of the immune system. Our unique tissue-engineered innervated psoriatic skin model could be a valuable tool to better understand the mechanism by which nerves may modulate psoriatic lesion formation in humans. STATEMENT OF SIGNIFICANCE: This study shows that keratinocytes extracted from patients' psoriatic skin retain, at least in part, the disease phenotype. Indeed, when combined in a 3D model of tissue-engineered psoriatic skin, keratinocytes exhibited a higher proliferation rate, and produced a thicker epidermis than a healthy skin control. In addition, their hyperproliferation was aggravated by a treatment with CGRP, a neuropeptide released by sensory nerves. In a innervated model of tissue-engineered psoriatic skin, an increase in keratinocyte hyperproliferation was also observed after inducing neurons to release neuropeptides. This effect was prevented by concomitant treatment with an antagonist to CGRP. Thus, this study shows that sensory nerves can directly participate to affect keratinocyte hyperproliferation in psoriasis through CGRP release.

Challenges in Psoriasis Research: A Systematic Review of Preclinical Models

INTRODUCTION

Psoriasis is a chronic inflammatory skin disease with variable clinical presentation, multifactorial etiology and an immunogenetic basis. Several studies demonstrate that it results from a dysregulated interaction between skin keratinocytes, immune cells, and the environment that leads to a persistent inflammatory process modulated by cytokines and T cells. The development of new treatment options requires increased understanding of pathogenesis. However, the successful implementation of effective drugs requires well-characterized and highly available preclinical models that allow researchers to quickly and reproducibly determine their safety and efficacy.

METHODS

A systematic search on PubMed and Scopus databases was performed and assessed to find appropriate articles about psoriasis models applying the key words previously defined. The PRISMA guidelines were employed.

RESULTS

A total of 45 original articles were selected that met the selection criteria. Among these, there are articles on in vivo, in vitro, and ex vivo models, with the in vitro model being the majority due to its ease of use. Within animal models, the most widely used in recent years are chemically induced models using a compound known as imiquimod. However, the rest of the animal models used throughout the disease's research were also discussed. On the other hand, in vitro models were divided into two and three dimensions. The latter were the most used due to their similarity to human skin. Lastly, the ex vivo models were discussed, although they were the least used due to their difficulty in obtaining them.

CONCLUSIONS

Therefore, this review summarizes the current preclinical models (in vivo, in vitro, and ex vivo), discussing how to develop them, their advantages, limitations, and applications. There are many challenges to improve the development of the different models. However, research in these in vitro model studies could reduce the use of animals. This is favored with the use of future technologies such as 3D bioprinting or organ-on-a-chip technologies.

Adenosine A2B receptor agonist improves epidermal barrier integrity in a murine model of epidermal hyperplasia

Adenosine regulates multiple physiological processes through the activation of four receptor subtypes, of which the A2B adenosine receptor (A2BAR) has the lowest affinity for adenosine. Being the adenosine receptor subtype most prominently expressed in epidermis, we recently described the antiproliferative and anti-inflammatory effect of the selective A2BAR agonist BAY60-6583 (BAY) in human keratinocytes stimulated with 12-O-tetradecanoylphorbol-13-acetate (TPA), so we sought to establish the effect of topical application of BAY in a model of murine epidermal hyperplasia. Topical application of BAY (1 or 10 μg/site) prevented the inflammatory reaction and skin lesions induced by TPA, minimizing hyperproliferation and acanthosis, as well as the expression of specific markers of proliferative keratinocytes. On the other hand, pre-treatment with the selective A2BAR antagonist, PSB-1115 (PSB, 5 or 50 μg/site) reversed these beneficial effects. Additionally, BAY application normalized the expression of epidermal barrier proteins, whose integrity is altered in inflammatory skin diseases, while treatment with the antagonist alone worsened it. Our results, besides confirming the anti-inflammatory and antiproliferative effects of the A2BAR agonist, further demonstrate a role of A2BAR activation to preserve the epidermal barrier. Therefore, the activation of A2BAR may constitute a possible new pharmacological target for the treatment of skin inflammatory diseases such as psoriasis.

Small-molecule agents for treating skin diseases

Skin diseases are a class of common and frequently occurring diseases that significantly impact daily lives. Currently, the limited effective therapeutic drugs are far from meeting the clinical needs; most drugs typically only provide symptomatic relief rather than a cure. Developing small-molecule drugs with improved efficacy holds paramount importance for treating skin diseases. This review aimed to systematically introduce the pathogenesis of common skin diseases in daily life, list related drugs applied in the clinic, and summarize the clinical research status of candidate drugs and the latest research progress of candidate compounds in the drug discovery stage. Also, it statistically analyzed the number of publications and global attention trends for the involved skin diseases. This review might provide practical information for researchers engaged in dermatological drugs and further increase research attention to this disease area.

The role of the interleukin-36 axis in generalized pustular psoriasis: a review of the mechanism of action of spesolimab

Generalized pustular psoriasis (GPP) is a rare, chronic, inflammatory skin disorder characterized by recurrent flares associated with skin erythema, desquamation, and widespread superficial sterile pustules, which may be severe ("lakes of pus"). Systemic symptoms are often present, including malaise, fever, and skin pain. In GPP, innate immune responses are driven by abnormal activation of the interleukin (IL)-36-chemokine-neutrophil axis and excessive neutrophil infiltration. This review highlights the IL-36 pathway in the context of the IL-1 superfamily and describes how unopposed IL-36 signaling can lead to the development of GPP. Targeted inhibition of the IL-36 receptor (IL-36R) is an attractive therapeutic strategy in the treatment of GPP, including flare prevention and sustained disease control. Spesolimab is a first-in-class, humanized, monoclonal antibody that binds specifically to the IL-36R and antagonizes IL-36 signaling. Spesolimab was approved by the US Food and Drug Administration in September 2022 to treat GPP flares in adults and was subsequently approved for GPP flare treatment in other countries across the world. Anti-IL-36R therapy, such as spesolimab, can mitigate flares and address flare prevention in GPP, presumably through rebalancing IL-36 signaling and modulating the pro-inflammatory response of the downstream effectors.

IL-22RA2 Is a SMAD7 Target Mediating the Alleviation of Dermatitis and Psoriatic Phenotypes in Mice

Long-term management of inflammatory skin diseases is challenging because of side effects from repeated use of systemic treatments or topical corticosteroids. This study sought to identify the mechanisms and developmental therapeutics for these diseases using genetic models and pharmacological approaches. We found that mice overexpressing SMAD7 in keratinocytes but not mice overexpressing the N-terminal domain of SMAD7 (i.e., N-SMAD7) were resistant to imiquimod-induced T helper 1/17- and T helper 2-type inflammation. We generated a Tat-PYC-SMAD7 (truncated SMAD7 protein encompassing C-terminal SMAD7 and PY motif fused with cell-penetrating Tat peptide). Topically applied Tat-PYC-SMAD7 to inflamed skin entered cells upon contact and attenuated imiquimod-, 2,4-dinitrofluorobenzene-, and tape-stripping-induced inflammation. RNA-sequencing analyses of mouse skin exposed to these insults showed that in addition to inhibiting TGFβ/NF-κB, SMAD7 blunted IL-22/signal transducer and activator of transcription 3 activation and associated pathogenesis, which is due to SMAD7 transcriptionally upregulating IL-22 antagonist IL-22RA2. Mechanistically, SMAD7 facilitated nuclear translocation and DNA binding of C/EBPβ to IL22RA2 promoter for IL22RA2 transactivation. Consistent with the observations in mice mentioned earlier, transcript levels of IL22RA2 were increased in human atopic dermatitis and psoriasis lesions with clinical remission. Our study identified the anti-inflammation functional domain of SMAD7 and suggests the mechanism and feasibility for developing SMAD7-based biologics as a topical therapy for skin inflammatory disorders.

Potential roles of inflammasomes in the pathophysiology of Psoriasis: A comprehensive review

Psoriasis is an inflammatory skin disease whose pathophysiology is attributed to both innate and adaptive immune cells and molecules. Despite the crucial roles of the immune system in psoriasis, it cannot be categorized as an autoimmune disease because of the lack of main signs of autoimmunity, such as specific antibodies, well-defined antigens, and autoimmune genetic risk factors. The presence of some cellular and molecular properties, such as the presence of neutrophils in skin lesions and the activation of the innate immune system, attributes psoriasis to a group of diseases called autoinflammatory disorders. Autoinflammatory diseases refer to a group of inherited disorders whose main manifestations are recurrent fever, a high level of acute-phase reactant, and a tendency for inflammation of the skin, joints, and other organs like the nervous system. In most autoinflammatory disorders, it has been seen that complexes of the high-molecular-weight protein named inflammasomes have significant roles. The inflammasome complex usually is formed and activated in the stimulated immune cell cytoplasm, and its activation consequently leads to inflammatory events such as producing of active caspase-1, mature interleukin-1β (IL-1β), and IL-18 and can cause an inflammatory programmed cell death called pyroptosis. Since the identification of inflammasomes, it has been shown that there are close links between them and hereditary and acquired autoinflammatory diseases like psoriasis. In this review, we aim to focus on well-defined inflammasome and their role in the pathophysiology of psoriasis.

Fufang Shengdi mixture alleviates psoriasis-like skin inflammation via promoting Annexin-A proteins expression

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine believes that "blood fever" is an important cause of psoriasis. Fufang Shengdi mixture (FFSD), based on the Hongban Decoction, is composed of Rehmannia glutinosa (Gaertn.) DC., Raw gypsum (Chinese: Sheng Shi Gao), and Lonicera japonica Thunb (Caprifoliaceae). FFSD has effects on nourishing Yin, clearing heat, connecting collaterals, and cooling blood. In modern medical explanation, FFSD has the effects of anti-inflammatory and immunosuppression. Our study proved that FFSD can suppress immunity and ameliorate the symptoms of imiquimod-induced psoriasis in mice.

AIM OF THE STUDY

This study evaluated the efficacy and possible mechanism of FFSD in psoriasis mice.

METHODS AND MATERIALS

First, the main components of FFSD were analyzed using high-performance liquid chromatography-tandem high-resolution mass spectrometry (HPLC-HRMS). An imiquimod (IMQ)-induced psoriasis mouse model was used to evaluate the efficacy of FFSD orally. Psoriasis area and severity index (PASI) scores were recorded throughout the course of the mice to reflect the severity of psoriasis. Hematoxylin-eosin staining was used to observe the pathological changes in skin lesions. Enzyme-linked immunosorbent assay (ELISA) was performed to test the level of IFN-γ and TNF-α in plasma. To further investigate the immunopharmacological effect of FFSD, we used chicken ovalbumin (OVA) to induce immunoreaction in mice. ELISA was used to detect the levels of anti-OVA antibody, IFN-γ and TNF-α in mice. Flow cytometry was performed to quantify the ratio of cell types in peripheral blood mononuclear cells (PBMCs) to evaluate the effect of FFSD on immunosuppression. Proteomics and bioinformatics analyzes were performed to find the regulation pathway of the immunosuppressive effect of FFSD. Finally, quantitative PCR (qPCR) and immunohistochemistry were used to measure the upregulation of Annexin-A proteins (ANXAs) in the skin lesion tissue of IMQ-induced mouse.

RESULTS

On the basis of knowing the composition of FFSD, we first proved the efficacy of FFSD in alleviating IMQ-induced psoriasis in mice. Second, we further clarified the pharmacological effect of FFSD on immunosuppression via OVA-induced mice. Subsequently, it was found that the significant up-regulation of ANXAs was caused by FFSD through proteomics analysis, and the finding was proved in the IMQ-induced psoriasis mouse model.

CONCLUSIONS

This study elucidates the immunosuppressive pharmacological effect of FFSD on improving psoriasis through up-regulating ANXAs.

The Experimental Animal Models in Psoriasis Research: A Comprehensive Review

Psoriasis is an autoimmune, chronic, inflammatory skin condition mediated by T cells. It differs from other inflammatory conditions by causing significant alterations in epidermal cell proliferation and differentiation that are both complicated and prominent. The lack of an appropriate animal model has significantly hindered studies into the pathogenic mechanisms of psoriasis since animals other than humans typically do not exhibit the complex phenotypic features of human psoriasis. A variety of methods, including spontaneous mutations, drug-induced mutations, genetically engineered animals, xenotransplantation models, and immunological reconstitution approaches, have all been employed to study specific characteristics in the pathogenesis of psoriasis. Although some of these approaches have been used for more than 50 years and far more models have been introduced recently, they have surprisingly not yet undergone detailed validation. Despite their limitations, these models have shown a connection between keratinocyte hyperplasia, vascular hyperplasia, and a cell-mediated immune response in the skin. The xenotransplantation of diseased or unaffected human skin onto immune-compromised recipients has also significantly aided psoriasis research. This technique has been used in a variety of ways to investigate the function of T lymphocytes and other cells, including preclinical therapeutic studies. The design of pertinent in vivo and in vitro psoriasis models is currently of utmost concern and a crucial step toward its cure. This article outlines the general approach in the development of psoriasis-related animal models, aspects of some specific models, along with their strengths and limitations.

A Novel Murine Model of Endothelial Keratoplasty

PURPOSE

The purpose of this study was to establish a murine model of endothelial keratoplasty.

METHODS

Endothelial keratoplasty (EK) was performed using C57BL/6 donor and BALB/c recipient mice. The central endothelium and Descemet membrane were removed from the recipient cornea, and a 1.5-mm posterior lamellar donor graft was made adherent to the recipient cornea with a small amount of viscoelastic. Mice were followed through slitlamp microscopy postoperatively, and OCT was used to assess the cornea and anterior chamber and measure central corneal thickness. Histology and immunohistochemistry were performed to confirm graft adherence and endothelial cell morphology.

RESULTS

Successfully attached EK grafts were visualized in all transplanted animals. Histology and immunostaining confirmed proper graft orientation and adherence, as well as the presence of donor endothelium on transplanted grafts. We observed maximal corneal edema in all animals at day 1 postoperatively which gradually subsided. EK graft survival was 97% at 8 weeks.

CONCLUSIONS

In this study, we describe a novel murine model for EK which we anticipate will enable detailed investigation into the cellular and molecular mechanisms involved in EK pathobiology.

Dual targeting of mTOR/IL-17A and autophagy by fisetin alleviates psoriasis-like skin inflammation

Psoriasis is a chronic autoimmune inflammatory skin disorder characterized by epidermal hyperplasia and aberrant immune response. In addition to aberrant cytokine production, psoriasis is associated with activation of the Akt/mTOR pathway. mTOR/S6K1 regulates T-lymphocyte activation and migration, keratinocytes proliferation and is upregulated in psoriatic lesions. Several drugs that target Th1/Th17 cytokines or their receptors have been approved for treating psoriasis in humans with variable results necessitating improved therapies. Fisetin, a natural dietary polyphenol with anti-oxidant and anti-proliferative properties, covalently binds mTOR/S6K1. The effects of fisetin on psoriasis and its underlying mechanisms have not been clearly defined. Here, we evaluated the immunomodulatory effects of fisetin on Th1/Th17-cytokine-activated adult human epidermal keratinocytes (HEKa) and anti-CD3/CD28-stimulated inflammatory CD4+ T cells and compared these activities with those of rapamycin (an mTOR inhibitor). Transcriptomic analysis of HEKa revealed 12,713 differentially expressed genes (DEGs) in the fisetin-treated group compared to 7,374 DEGs in the rapamycin-treated group, both individually compared to a cytokine treated group. Gene ontology analysis revealed enriched functional groups related to PI3K/Akt/mTOR signaling pathways, psoriasis, and epidermal development. Using in silico molecular modeling, we observed a high binding affinity of fisetin to IL-17A. In vitro, fisetin significantly inhibited mTOR activity, increased the expression of autophagy markers LC3A/B and Atg5 in HEKa cells and suppressed the secretion of IL-17A by activated CD4+ T lymphocytes or T lymphocytes co-cultured with HEKa. Topical administration of fisetin in an imiquimod (IMQ)-induced mouse psoriasis model exhibited a better effect than rapamycin in reducing psoriasis-like inflammation and Akt/mTOR phosphorylation and promoting keratinocyte differentiation and autophagy in mice skin lesions. Fisetin also significantly inhibited T-lymphocytes and F4/80+ macrophage infiltration into skin. We conclude that fisetin potently inhibits IL-17A and the Akt/mTOR pathway and promotes keratinocyte differentiation and autophagy to alleviate IMQ-induced psoriasis-like disease in mice. Altogether, our findings suggest fisetin as a potential treatment for psoriasis and possibly other inflammatory skin diseases.

Immunoproteasome inhibition attenuates experimental psoriasis

Introduction

Psoriasis is an autoimmune skin disease associated with multiple comorbidities. The immunoproteasome is a special form of the proteasome expressed in cells of hematopoietic origin.

Methods

The therapeutic use of ONX 0914, a selective inhibitor of the immunoproteasome, was investigated in Card14ΔE138+/- mice, which spontaneously develop psoriasis-like symptoms, and in the imiquimod murine model.

Results

In both models, treatment with ONX 0914 significantly reduced skin thickness, inflammation scores, and pathological lesions in the analyzed skin tissue. Furthermore, immunoproteasome inhibition normalized the expression of several pro-inflammatory genes in the ear and significantly reduced the inflammatory infiltrate, accompanied by a significant alteration in the αβ+ and γδ+ T cell subsets.

Discussion

ONX 0914 ameliorated psoriasis-like symptoms in two different murine psoriasis models, which supports the use of immunoproteasome inhibitors as a therapeutic treatment in psoriasis.

Phosphodiesterase-4 Inhibition Reduces Cutaneous Inflammation and IL-1β Expression in a Psoriasiform Mouse Model but Does Not Inhibit Inflammasome Activation

Apremilast (Otezla^®) is an oral small molecule phosphodiesterase 4 (PDE4) inhibitor approved for the treatment of psoriasis, psoriatic arthritis, and oral ulcers associated with Behçet’s disease. While PDE4 inhibition overall is mechanistically understood, the effect of apremilast on the innate immune response, particularly inflammasome activation, remains unknown. Here, we assessed the effect of apremilast in a psoriasis mouse model and primary human cells. Psoriatic lesion development in vivo was studied in K5.Stat3C transgenic mice treated with apremilast for 2 weeks, resulting in a moderate (2 mg/kg/day) to significant (6 mg/kg/day) resolution of inflamed plaques after 2-week treatment. Concomitantly, epidermal thickness dramatically decreased, the cutaneous immune cell infiltrate was reduced, and proinflammatory cytokines were significantly downregulated. Additionally, apremilast significantly inhibited lipopolysaccharide- or anti-CD3-induced expression of proinflammatory cytokines in peripheral mononuclear cells (PBMCs). Notably, inflammasome activation and secretion of IL-1β were not inhibited by apremilast in PBMCs and in human primary keratinocytes. Collectively, apremilast effectively alleviated the psoriatic phenotype of K5.Stat3 transgenic mice, further substantiating PDE4 inhibitor-efficiency in targeting key clinical, histopathological and inflammatory features of psoriasis. Despite lacking direct effect on inflammasome activation, reduced priming of inflammasome components upon apremilast treatment reflected the indirect benefit of PDE4 inhibition in reducing inflammation.

Pyruvate Kinase M2 Mediates Glycolysis Contributes to Psoriasis by Promoting Keratinocyte Proliferation

Psoriasis is characterized by keratinocyte proliferation and immune cell infiltration. M2 isoform of pyruvate kinase (PKM2) was reported to have an important role in cell proliferation, which is a rate-limiting enzyme that regulates the final step of glycolysis. However, how PKM2 regulates cell metabolism and proliferation in psoriatic keratinocytes is still poorly understood. Interestingly, we found that PKM2 was highly expressed in psoriatic epidermis from patients and mouse models. PKM2 overexpression promoted keratinocyte glycolytic metabolism while knockdown inhibited keratinocyte proliferation and glycolysis. Mice lacking PKM2 specifically in keratinocytes, pharmacological inhibition of PKM2 or glycolysis inhibited keratinocyte proliferation and showed obvious remission in an imiquimod-induced psoriatic mouse model. Moreover, the inhibitor of the EGF-receptor blocked EGF-stimulated PKM2 expression and glycolysis in keratinocytes. We identify PKM2 as an upregulated gene in psoriasis. PKM2 is essential in keratinocyte over-proliferation and may represent a therapeutic target for psoriasis.

Unconventional Therapy with IgY in a Psoriatic Mouse Model Targeting Gut Microbiome

Psoriasis has a multifactorial pathogenesis and recently it was shown that alterations in the skin and intestinal microbiome are involved in the pathogenesis of psoriasis. Therefore, microbiome restoration becomes a promising preventive/therapy strategy in psoriasis. In our pre-clinical study design using a mice model of induced psoriatic dermatitis (Ps) we have tested the proof-of-concept that IgY raised against pathological human bacteria resistant to antibiotics can alleviate psoriatic lesions and restore deregulated immune cell parameters. Besides clinical evaluation of the mice and histology of the developed psoriatic lesions, cellular immune parameters were monitored. Immune cells populations/subpopulations from peripheral blood and spleen cell suspensions that follow the clinical improvement were assessed using flow cytometry. We have quantified T lymphocytes (CD3ε⁺) with T-helper (CD4⁺CD8^-) and T-suppressor/cytotoxic (CD8a⁺CD4^-) subsets, B lymphocytes (CD3ε^-CD19⁺) and NK cells (CD3ε^-NK1.1⁺). Improved clinical evolution of the induced Ps along with the restoration of immune cells parameters were obtained when orally IgY was administered. We pin-point that IgY specific compound can be used as a possible pre-biotic-like alternative adjuvant in psoriasis.

Hidradenitis Suppurativa: Where We Are and Where We Are Going

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease primarily affecting apocrine gland-rich areas of the body. It is a multifactorial disease in which genetic and environmental factors play a key role. The primary defect in HS pathophysiology involves follicular occlusion of the folliculopilosebaceous unit, followed by follicular rupture and immune responses. Innate pro-inflammatory cytokines (e.g., IL-1β, and TNF-α); mediators of activated T helper (Th)1 and Th17 cells (e.g., IFN-γ, and IL-17); and effector mechanisms of neutrophilic granulocytes, macrophages, and plasma cells are involved. On the other hand, HS lesions contain anti-inflammatory mediators (e.g., IL-10) and show limited activity of Th22 cells. The inflammatory vicious circle finally results in pain, purulence, tissue destruction, and scarring. HS pathogenesis is still enigmatic, and a valid animal model for HS is currently not available. All these aspects represent a challenge for the development of therapeutic approaches, which are urgently needed for this debilitating disease. Available treatments are limited, mostly off-label, and surgical interventions are often required to achieve remission. In this paper, we provide an overview of the current knowledge surrounding HS, including the diagnosis, pathogenesis, treatments, and existing translational studies.

Systematic Optimization of Potent and Orally Bioavailable Purine Scaffold as a Dual Inhibitor of Toll-Like Receptors 7 and 9

Several toll-like receptors (TLRs) reside inside endosomes of specific immune cells-among them, aberrant activation of TLR7 and TLR9 is implicated in myriad contexts of autoimmune diseases, making them promising therapeutic targets. However, small-molecule TLR7 and TLR9 antagonists are not yet available for clinical use. We illustrate here the importance of C2, C6, and N9 substitutions in the purine scaffold for antagonism to TLR7 and TLR9 through structure-activity relationship studies using cellular reporter assays and functional studies on primary human immune cells. Further in vitro and in vivo pharmacokinetic studies identified an orally bioavailable lead compound 29, with IC₅₀ values of 0.08 and 2.66 μM against TLR9 and TLR7, respectively. Isothermal titration calorimetry excluded direct TLR ligand-antagonist interactions. In vivo antagonism efficacy against mouse TLR9 and therapeutic efficacy in a preclinical murine model of psoriasis highlighted the potential of compound 29 as a therapeutic candidate in relevant autoimmune contexts.

Molecular and histopathological profiling of imiquimod induced dermatosis in Swiss Wistar rats: contribution to the rat model for novel anti-psoriasis treatments

Imiquimod (IMQ) induced human-like psoriasis in mice has been shown to be effective in testing and development of novel treatments. The IMQ psoriasis model has become widely used animal model, however, it is not completely characterized in different rat strains. We aimed to evaluate IMQ and betamethasone treatment for induction and reversal of psoriatic lesions on macroscopic, histological, genetic as well as cytokines and chemokines activation levels. Wistar rats were treated topically with IMQ. Adopted Psoriasis Area Severity Index (PASI) was calculated at the baseline, after the IMQ-symptoms induction and after betamethasone-symptoms reversal. Systematic effects were studied on cytokines and chemokines levels in plasma. Skin biopsy was taken to assess histological symptoms and selected inflammatory cytokines and receptors genes expression levels. Reversal of skin lesions, after betamethasone treatment, was significant (p = 0.03). Histological differences between untreated and IMQ-treated skin were significant for some markers (p < 0.05) though not significantly decreased by betamethasone treatment. Fourteen genes were significantly up-regulated after the IMQ and four genes were down-regulated after skin lesions reversal by betamethasone. This work provides new insights on biological effects of imiquimod induced psoriasis and its reversal by betamethasone treatment in Wistar rats. It also contributes to general knowledge of the rat model usage for testing of novel anti-psoriasis drugs.

Murine models of rosacea: a review

Rosacea is a chronic inflammatory disease characterized by facial flushing, erythema, telangiectasia, papules, and pustules. Its pathogenesis has not been fully understood. In 2017, the global ROSacea COnsensus (ROSCO) panel updated the diagnosis, classification, and assessment of rosacea. Phenotype-based treatments and long-term managements have also been recommended. Murine models are a powerful tool in unveiling and dissecting the mechanisms of human diseases. Here, we summarized murine models of rosacea developed or used in previous research, including LL-37 intradermal injection model, KLK-5-induced inflammation model, croton oil inflammation model, 12-O-Tetradecanoylphorbol-13-acetate inflammation model, arachidonic acid inflammation model, RTX-induced vasodilation model, and UVB-induced model. LL-37 injection model has become the most intensively used model in rosacea research. Each model could show the pathophysiological and clinical features of rosacea to some extent. However, no model can show the full picture of the characteristics of rosacea. Improving existed murine models, developing new murine models, and applying them to pathogenesis and treatment research on rosacea are highly warranted in the future.

Rapamycin Alleviates 2,3,7,8-Tetrachlorodibenzo-p-dioxin-Induced Aggravated Dermatitis in Mice with Imiquimod-Induced Psoriasis-Like Dermatitis by Inducing Autophagy

Recently, the mTOR signaling has emerged as an important player in the pathogenesis of psoriasis. We previously found that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced psoriatic skin inflammation was related to the inhibition of autophagy in keratinocytes. However, the effects and detailed molecular mechanisms of the mTOR inhibitor rapamycin and TCDD on psoriasis in vivo remain to be elucidated. In this study, we aimed to evaluate the effects of rapamycin and TCDD on skin lesions in imiquimod (IMQ)-induced psoriasis using a mouse model. TCDD aggravated skin inflammation in an IMQ-induced psoriatic mouse model. Furthermore, TCDD increased the expression of aryl hydrocarbon receptor (AHR), CYP1A1, proinflammatory cytokines, oxidative stress markers (NADPH oxidase (Nox) 2, Nox4), and phosphorylated P65NF-ĸB, whereas the expression of autophagy-related factors and the antioxidant marker nuclear factor-erythroid 2-related factor 2 (NRF2) decreased. Rapamycin reduced the aggravated skin inflammation induced by TCDD and restored TCDD-induced autophagy suppression and the increase of AHR expression, oxidative stress, and inflammatory response in the skin lesions of a psoriatic mouse model. In conclusion, we demonstrated that rapamycin alleviates TCDD-induced aggravated dermatitis in mice with imiquimod-induced psoriasis-like dermatitis through AHR and autophagy modulation.

Optimization of psoriasis mouse models

INTRODUCTION

Psoriasis, is a common, chronic, autoimmune, inflammatory, relapsing disease, which would benefit from reliable and human-relevant animal models to test drugs pre-clinically and to understand their mechanism of action. Because of its ease of use, convenience and low cost, the imiquimod (IMQ)-induced psoriasis-like model is widely utilized; however, it is not known whether all mouse strains are equivalent and if the hairless mouse is appropriate, so that the imiquimod model can be further optimized.

METHODS

Under similar experimental conditions, common mouse strains (BALB/c, C57BL/6J, and ApoE) and a new hairless strain (ApoE/SKH-hr2) as well as several inducers (IMQ, IMQ + acetic acid (AcOH) topical and IMQ + AcOH systemic) were compared by clinical, histopathological, biophysical and locomotor activity assessments.

RESULTS AND DISCUSSION

The BALB/c mice yielded an optimal psoriasis-like phenotype with IMQ + AcOH topical treatment, and the corresponding phenotypes for the other mouse strains were C57BL/6J moderate and ApoE mild. In contrast, the ApoE/SKH-hr2 mice, as a result of the absence of a Munro abscess in the histopathology analysis, left doubt about the psoriasis-like acquisition. Locomotor activity of BALB/c mice treated with IMQ, IMQ + AcOH topically and IMQ + AcOH systemically showed decreased distance and rearing coverage and increased immobility with all treatments. Hence, the BALB/c mouse strain appears to be an optimal psoriasis-like model when utilizing IMQ + AcOH topical application.

Strain specific response of mice to IMQ-induced psoriasis

OBJECTIVES

Psoriasis is an autoimmune, inflammatory disease that needs a reliable animal model. Imiquimod (IMQ)-induced psoriasis is a widely used preclinical tool for psoriasis research. However, this model is sensitive to the genetic variation of mice. The present study explores mice's genetic background on disease stability and severity induced by IMQ.

METHODS

Three distinct strains of mice (Balb/c, C57BL/6, and Swiss albino) were divided into four groups (Vaseline, IMQ, IMQ+Clobetasol, and IMQ+Curcumin). Psoriasis area severity index (PASI) score, ear/back skin thickness, body weight alterations, and histopathological examination were employed to analyze disease severity. The spleen index studied the systemic effect. Strain effect on oxidative stress induced by IMQ was evaluated by estimating antioxidant factors, superoxide dismutase (SOD), catalase, and glutathione (GSH).

RESULTS

IMQ application resulted in increased PASI score, thickness, and alterations in body weight, confirming disease development in all the mice. However, the disease stability/severity between these strains was not identical. Although IMQ application caused splenomegaly, IMQ+curcumin treated C57BL/6 mice demonstrated a synergistic effect of IMQ and curcumin on the spleen resulting in increased splenomegaly. Decreased cellular enzyme activity in SOD, Catalase, and levels of GSH was observed in IMQ challenged mice, indicating the participation of the redox system in the genesis of the disease that was comparable among the strains.

CONCLUSIONS

These results indicate the existence of strain-dependent development of the disease. The Swiss model was found to be better in terms of disease severity and stability than other models. Further, a detailed mechanistic study might help to explain the pathological difference between these strains.

Polysaccharide mycophenolate-based nanoparticles for enhanced immunosuppression and treatment of immune-mediated inflammatory diseases

Immune-mediated inflammatory diseases (IMIDs) are characterized by immune dysregulation and severe inflammation caused by the aberrant and overactive host immunological response. Mycophenolic acid (MPA)-based immunosuppressive drugs are potential treatments for IMIDs because of their mild side-effect profile; however, their therapeutic effects are limited by the high albumin binding rate, unsatisfactory pharmacokinetics, and undefined cellular uptake selectivity.

Methods: Polysaccharide mycophenolate was synthesized by conjugating MPA molecules to dextran (a typical polysaccharide widely used in drug delivery) and encapsulated extra free MPA molecules to fabricate MPA@Dex-MPA nanoparticles (NPs). The efficacy of these NPs for mediating immunosuppression and treatment of IMIDs was evaluated in imiquimod-induced psoriasis-like skin inflammation in Balb/c mice, a representative IMID model.

Results: The MPA@Dex-MPA NPs exhibited high MPA loading efficiency, low albumin binding rates, and sustained MPA release, resulting in improved pharmacokinetics in vivo. Compared to free MPA, MPA@Dex-MPA NPs induced more robust therapeutic effects on IMIDs. Mechanistic studies indicated that MPA@Dex-MPA NPs were primarily distributed in dendritic cells (DCs) and significantly suppressed the overactivated DCs in vivo and in vitro. Furthermore, the recovered DCs rehabilitated the IL-23/Th17 axis function and significantly ameliorated imiquimod-induced psoriasis-like skin inflammation. Importantly, MPA@Dex-MPA NPs showed favorable safety and biocompatibility in vivo.

Conclusion: Our results indicated the polysaccharide mycophenolate-based NPs to be highly promising for IMID treatment.

Differential Requirement for CCR6 in IL-23-Mediated Skin and Joint Inflammation

CCR6 is important for the trafficking of IL-17A-producing γδ T cells and required for the development of psoriasiform dermatitis in an IL-23 intradermal injection model. The role of CCR6, however, in IL-23-mediated joint inflammation is unclear. We herein hydrodynamically delivered IL-23 minicircle DNA into wild-type and CCR6-deficient (CCR6-knockout) mice to induce overexpression of IL-23 systemically. After IL-23 gene transfer, wild-type mice exhibited concurrent skin and joint changes that recapitulate some features found in human psoriatic skin and joints. CCR6-knockout mice were resistant to IL-23-induced skin inflammation but exhibited no changes in joint inflammation compared with wild-type mice. Depletion of neutrophils protected wild-type mice from skin and joint disease without suppressing T helper type 17 cytokine expression. In contrast, mice lacking γδ T cells showed a partial reduction in neutrophilic recruitment and a significant decrease in IL-17A expression in skin and paw tissue. Thus, in an IL-23-mediated model that allows concurrent assessment of both skin and joint disease, we showed that CCR6 is critical for inflammation in the skin but not in the joint. Furthermore, our data suggest that neutrophils and γδ T cells are key effector cells in IL-23-mediated skin and joint inflammation in mice.

Meeting Report: 68th Montagna Symposium on the Biology of Skin "Decoding Complex Skin Diseases: Integrating Genetics, Genomics, and Disease Biology"

The 68^th Montagna Symposium on the Biology of the Skin was held from 10 to 14 October 2019 at Salishan Lodge in Gleneden Beach, Oregon. The theme of the meeting was "Decoding Complex Skin Diseases: Integrating Genetics, Genomics, and Disease Biology." The meeting emphasized the integration of multiple themes and disciplines to better understand some of the most common skin diseases, ranging from psoriasis to alopecia areata to vitiligo to lupus erythematosus to atopic dermatitis and food allergy. Promising therapeutic strategies are emerging for all of these diseases, providing clues for ways to connect the bench to the bedside. A common thread was the success of GWASs, which have highlighted the importance of regulatory signals versus coding variation. These diseases also share an environmental component linked to immune system function. Hence, beyond GWASs, this meeting focused on gene regulatory mechanisms, the single-cell revolution, in vivo systems for dissection of disease pathogenesis, and the relationship between genetics and environment in the context of host defense. We concluded with a translational roundtable designed to explore how these interrelated fields can best be directed toward long-term disease control and, ultimately, a cure.

Small Extracellular Vesicles Containing miR-381-3p from Keratinocytes Promote T Helper Type 1 and T Helper Type 17 Polarization in Psoriasis

T helper cells are crucial for psoriasis pathogenesis. Communication between T cells and psoriatic keratinocytes (KCs) helps drive the Th1 and Th17 response, but the underlying mechanism is not well-understood. Small extracellular vesicles (sEVs) are emerging mediators of intercellular communication. Here, we investigated the role of KC-derived sEVs in the Th1 and Th17 response in psoriasis. We isolated and characterized sEVs from KCs under normal (untreated) and psoriatic (cytokine-treated) conditions. sEVs under both conditions exhibited a cup-shaped morphology and expressed markers CD63 and CD81. sEVs from cytokine-treated KCs can be taken up by CD4⁺T cells, leading to the induction of Th1 and Th17 polarization. Small RNA sequencing revealed that miR-381-3p was significantly increased in sEVs from cytokine-treated KCs and in CD4⁺T cells from patients with psoriasis. Moreover, sEVs-containing miR-381-3p was responsible for sEVs-induced Th1 and Th17 polarization. We further found that the miR-381-3p targeted to the 3' untranslated region of E3 ubiquitin-ligase UBR5 and stabilized RORγt protein expression. It also targeted to the 3' untranslated region of FOXO1, associated with activated T-bet and RORγt transcription. Taken together, we propose that psoriatic KCs transfer miR-381-3p to CD4⁺T cells through sEVs, inducing Th1 and Th17 polarization and promoting psoriasis development. Our findings motivate future studies of KC-derived sEVs or their specific cargoes as therapeutic candidates for psoriasis.

Interleukin-17 cytokines: Effectors and targets in psoriasis-A breakthrough in understanding and treatment

This review summarizes the steps from basic research on IL-17 family cytokines to understanding their role in psoriasis pathogenesis to the approval of a number of monoclonal antibodies targeting IL-17 pathways as first line treatment of psoriasis and psoriatic arthritis.

The IL-17 cytokine family comprising IL-17A to IL-17F and receptor subunits IL-17RA to IL-17RE represents a genetically ancient intercellular network regulating local tissue homeostasis. Its pivotal role in antifungal defense and its central position in the pathogenesis of inflammatory diseases including psoriasis were discovered only relatively late in the early 2000s. Since the connection of dysregulated IL-17 and psoriasis pathogenesis turned out to be particularly evident, a number of monoclonal antibodies targeting IL-17 pathways have been approved and are used as first line treatment of moderate-to-severe plaque psoriasis and psoriatic arthritis, and further agents are currently in clinical development.

Inflammasomes in Common Immune-Related Skin Diseases

The inflammasome is an important protein complex that cleaves the proinflammatory cytokines pro-IL-1β and pro-IL-18 into their active forms. Owing to its critical role in eliciting innate immune responses, IL-1β has been suggested to contribute to various skin diseases, including psoriasis, vitiligo, systemic lupus erythematosus (SLE), and atopic dermatitis (AD). Recently, several types of activators and inhibitors of different inflammasomes, as well as inflammasome-related genes and genetic susceptibility loci, have been identified in these immune-related common skin diseases. In particular, inflammasome activators and inhibitors presented highly cell-type-specific activity, suggesting that the inflammasome might perform different functions in different cell types. Moreover, most of these findings were based on experimental disease models, and the clinical features of the models partly resemble the typical symptoms of the diseases. In this review, from the perspective of activators and inhibitors, we collected evidence from the widely-studied inflammasomes, NLRP3, AIM2, and NLRP1, in psoriasis, vitiligo, SLE, and AD. Importantly, some small-molecule inhibitors hold therapeutic promise for the treatment of these diseases.

A Chemical Switch for Transforming a Purine Agonist for Toll-like Receptor 7 to a Clinically Relevant Antagonist

Toll-like receptor 7 (TLR7) is an established therapeutic target in myriad autoimmune disorders, but no TLR7 antagonist is available for clinical use to date. Herein, we report a purine scaffold TLR7 antagonist, first-of-its-kind to our knowledge, which was developed by rationally dissecting the structural requirements for TLR7-targeted activity for a purine scaffold. Specifically, we identified a singular chemical switch at C-2 that could make a potent purine scaffold TLR7 agonist to lose agonism and acquire antagonist activity, which could further be potentiated by the introduction of an additional basic center at C-6. We ended up developing a clinically relevant TLR7 antagonist with favorable pharmacokinetics and 70.8% oral bioavailability in mice. Moreover, the TLR7 antagonists depicted excellent selectivity against TLR8. To further validate the in vivo applicability of this novel TLR7 antagonist, we demonstrated its excellent efficacy in preventing TLR7-induced pathology in a preclinical murine model of psoriasis.

Inhibition of keratinocyte necroptosis mediated by RIPK1/RIPK3/MLKL provides a protective effect against psoriatic inflammation

Psoriasis is a common autoimmune and chronic inflammatory skin disorder globally affecting 0.51–11.43% of adults. Inflammation-associated cell death in keratinocytes plays a key role in the process of integrate inflammatory cascade in psoriasis. Necroptosis is a regulated necrotic cell death mediated by receptor interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like pseudokinase (MLKL), which participates in many human inflammatory diseases. However, the mechanism and function of programmed necrosis in psoriasis is not well-illustrated. In the current study, we provide evidence for the involvement of necroptosis in psoriasis. RIPK1 and MLKL were significantly upregulated and localized in all layers of the epidermis in human psoriatic lesions, while RIPK3 and phosphorylated MLKL were mainly expressed in keratinocytes, which located in the upper layers. Increased tendency of necroptosis was also found in IMQ-induced psoriasiform skin of mice. Further, we discovered that both the inhibitor of RIPK1 R-7-Cl-O-Necrostatin-1 (Nec-1s) and MLKL-inhibitor necrosulfonamide (NSA) suppressed necroptosis in HaCaT cells and IMQ mouse models, powerfully blocked IMQ-induced inflammatory responses in vivo, and significantly downregulated the production of inflammatory factors like IL-1β, IL-6, IL-17A, IL-23a, CXCL1, and CCL20. These findings promote the development of new therapies for the treatment of necroptosis-activated pathologies for psoriasis.

Aryl Hydrocarbon Receptor in Cutaneous Vascular Endothelial Cells Restricts Psoriasis Development by Negatively Regulating Neutrophil Recruitment

Vascular endothelial cells (VECs) that line the interiors of blood vessels participate in physiological and inflammatory processes. All skin cell types express the aryl hydrocarbon receptor (AhR), which is involved in the pathogenesis of psoriasis. However, the role of the cutaneous VEC AhR in the pathogenesis of psoriasis remains elusive. In the present study, we found that AhR protein expression and activation were downregulated in psoriatic VECs. Furthermore, cutaneous VEC-specific AhR-knockout (AhR^cVECs-KO) mice were established. Using imiquimod and IL-23-induced psoriasis models, we found that skin inflammation was exacerbated with excessive neutrophil recruitment in AhR^cVECs-KO mice. Furthermore, neutrophil neutralization alleviates exacerbated inflammation in imiquimod-treated AhR^cVECs-KO mice. In addition, cutaneous VECs in AhR^cVECs-KO mice exhibited increased dilation and activation compared with those in control mice. Finally, AhR-deficient microvascular endothelial cells stimulated by proinflammatory cytokines showed increased ICAM-1 expression in vivo and in vitro, which may have facilitated neutrophil recruitment. In summary, our study demonstrates that AhR in dermal VECs restricts psoriasis development by negatively regulating neutrophil recruitment, thereby providing insight into the pathogenesis of psoriasis.

Ex vivo culture of lesional psoriasis skin for pharmacological testing

BACKGROUND

Psoriasis is a chronic, inflammatory skin disorder resulting from a complex interplay between immune and skin cells via release of soluble mediators. While a lot is known about the molecular mechanisms behind psoriasis pathogenesis, there is still a need for preclinical research models that accuratelyreplicate the disease.

OBJECTIVE

This study aimed to develop and characterize ex vivo culture of psoriasis skin as a model for pharmacological testing, where the immunological events of psoriasis can be followed.

METHODS

Full thickness punch biopsies of lesional psoriasis skin were cultured in submerged conditions up to 144 h followingin situ T cell stimulation with rhIL-23 and anti-CD3 and anti-CD28 antibodies. The T cell mediated skin inflammation was assessed by gene and protein l analysis for a panel of inflammatory mediators. Tissue integrity and morphology were evaluated by histological analysis.

RESULTS

T cell stimulation resulted in functional and psoriasis specificin situ activation of T cells. The expression levels of most of the proinflammatory mediators related to both immune and skin cells were comparable to these in freshly isolated tissue at 48 and 96 h of culture. Tissue integrity and morphology were sustained up to 96 h. Treatment with a corticosteroid reduced the expression of several pro-inflammatory cytokines and chemokines, whereas anti-IL-17A antibody treatment reduced the expression of the IL-17A downstream markers IL-8 and DEFB4.

CONCLUSION

By preserving keyimmunopathological mechanisms of psoriasis, ex vivo culture of psoriasis skin can be used for the investigation of inflammatory processes of psoriasis and for preclinical drug discovery research.

Research Techniques Made Simple: Forward Genetic Screening to Uncover Genes Involved in Skin Biology

The primary goals of modern genetics are to identify disease-causing mutations and to define the functions of genes in biological processes. Two complementary approaches, reverse and forward genetics, can be used to achieve this goal. Reverse genetics is a gene-driven approach that comprises specific gene targeting followed by phenotypic assessment. Conversely, forward genetics is a phenotype-driven approach that involves the phenotypic screening of organisms with randomly induced mutations followed by subsequent identification of the causative mutations (i.e., those responsible for phenotype). In this article, we focus on how forward genetics in mice can be used to explore dermatologic disease. We outline mouse mutagenesis with the chemical N-ethyl-N-nitrosourea and the strategy used to instantaneously identify mutations that are causative of specific phenotypes. Furthermore, we summarize the types of phenotypic screens that can be performed to explore various aspects of dermatologic disease.

Models of human psoriasis: Zebrafish the newly appointed player

Psoriasis is a human chronic, immune disease with severe cutaneous and systemic manifestations. Its prevalence, among the world population, highly varies with ethnicity and geography, but not sex from remarkable low levels in Asia to 2.3% in Spain, or an impressive 11.5% in Norway. The pathogenesis of psoriasis derives from complex genetic and environmental interactions, which creates aberrant crosstalk between keratinocytes and variated immune cell, resulting in open amplified inflammatory and pro-proliferative circuits. Both, innate and adaptive immune systems are known to be involved in the response at the cellular and humoral levels. Nevertheless, the exact molecular mechanisms are still under debate. Therefore, discovering useful therapeutic targets to stretch the molecular gaps in psoriasis pathogenesis and its associated comorbidities is still mandatory. So far, some mutagenic or pharmacological studies in vitro or using comparative vertebrate models have provided critical molecular insights and directed the human research. Although highly feasible in rodents, the versatile physiology, genetic similarity to humans and outstanding molecular toolbox available, suggest that elaborate forward genetic screenings are far easier to be conducted using the zebrafish model. Thus, in this review, we intend to briefly overview psoriasis and revise in a digested fashion the preclinical research models available, emphasizing the zebrafish as a powerful tool in the study of immune effectors on the same, and how it supports the discovering of new therapies that may help in controlling this widespread disease around the globe.

Lessons learned from the development of a hidradenitis suppurativa xenograft mouse model

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease originating from the pilosebaceous unit, in which patients develop painful abscesses, sinus tracts, nodules and scarring, typically in intertriginous areas. Major gaps in our understanding of HS exist, and these may be partially due to the lack of an animal model for experimental studies. We developed an HS xenograft mouse model using human HS lesions grafted onto immunocompromised mice. Although the model had its limitations, several informative lessons were learned, which may contribute to future attempts at an HS animal model.

Gain of function p.E138A alteration in Card14 leads to psoriasiform skin inflammation and implicates genetic modifiers in disease severity

Psoriasis (PS) is a common inflammatory and incurable skin disease affecting 2-3% of the human population. Although genome-wide association studies implicate more than 60 loci, the full complement of genetic factors leading to disease is not known. Rare, highly penetrant, gain-of-function, dominantly acting mutations within the human caspase recruitment domain family, member 14 (CARD14) gene lead to the development of PS and psoriatic arthritis (PSA) (a familial p.G117S and de-novo p.E138A alteration). These residues are conserved in mouse and orthologous Knock-In (KI) mutations within Card14 were created. The Card14^tm.1.1Sun allele (G117S) resulted in no clinically or histologically evident phenotype of the skin or joints in young adult or old mice. However, mice carrying the Card14^tm2.1Sun mutant allele (E138A) were runted and developed thick, white, scaly skin soon after birth, dying within two weeks or less. The skin hyperplasia and inflammation was remarkable similarity to human PS at the clinical, histological, and transcriptomic levels. For example, the skin was markedly acanthotic and exhibited orthokeratotic hyperkeratosis with minimal inflammation and no pustules and transcripts affecting critical pathways of epidermal differentiation and components of the IL17 axis (IL23, IL17A, IL17C, TNF and IL22) were altered. Similar changes were seen in a set of orthologous microRNAs previously associated with PS suggesting conservation across species. Crossing the Card14^tm2.1Sun/WT mice to C57BL/6NJ, FVB/NJ, CBA/J, C3H/HeJ, and 129S1/SvImJ generated progeny with epidermal acanthosis and marked orthokeratotic hyperkeratosis regardless of the hybrid strain. Of these hybrid lines, only the FVB;B6N(129S4) mice survived to 250 days of age or older and has led to recombinant inbred lines homozygous for Card14^E138A that are fecund and have scaly skin disease. This implicates that modifiers of PS severity exist in mice, as in the familial forms of the disease in humans.

Discovery of the IL-23/IL-17 Signaling Pathway and the Treatment of Psoriasis

Psoriasis vulgaris is a common, heterogeneous, chronic inflammatory skin disease characterized by thickened, red, scaly plaques and systemic inflammation. Psoriasis is also associated with multiple comorbid conditions, such as joint destruction, cardiovascular disease, stroke, hypertension, metabolic syndrome, and chronic kidney disease. The discovery of IL-17-producing T cells in a mouse model of autoimmunity transformed our understanding of inflammation driven by T lymphocytes and associations with human inflammatory diseases, such as psoriasis. Under the regulation of IL-23, T cells that produce high levels of IL-17 create a self-amplifying, feed-forward inflammatory response in keratinocytes that drives the development of thickened skin lesions infiltrated with a mixture of inflammatory cell populations. Recently, the Food and Drug Administration approved multiple highly effective psoriasis therapies that disrupt IL-17 (secukinumab, ixekizumab, and brodalumab) and IL-23 (guselkumab and tildrakizumab) signaling in the skin, thus leading to a major paradigm shift in the way that psoriatic disease is managed.

Ferulic acid altered IL-17A/IL-17RA interaction and protected against imiquimod-induced psoriasis-like skin injury in mice

Ferulic acid (FA), a phenolic phytochemical, is commonly found in grains, vegetables, and fruits. Interleukin-17A (IL-17A) and IL-17 receptor A (IL-17RA) interaction is one of important therapeutic targets for psoriasis. Here we analyzed the FA effects on IL-17A/IL-17RA interaction and psoriasis-like skin injury induced by imiquimod (IMQ). IL-17A-blocking assay and docking analysis showed that FA interacted with Trp-67, Gln-94, and Glu-95 residues of IL-17A via hydrogen bonds and consequently abolished the binding of IL-17RA to IL-17A. Mice were topically given with IMQ and orally given with various amounts of FA for 14 consecutive days. FA attenuated IMQ-induced psoriasis-like skin lesions in a dose-dependent manner, and the epidermal thickness of mice treated with 100 mg/kg FA was reduced by 53.48 ± 4.44% in comparison with sham. Global analysis of differentially expressed genes showed that IMQ and FA significantly affected immune response, metabolism, and mitogen-activated protein kinase signaling pathways. Immunohistochemical staining showed that FA inhibited the infiltration and the cytokine secretion of Th17 cell, dendritic cell, and granulocyte subsets in psoriatic skin tissues. In conclusion, we newly identified that oral administration of FA protected against IMQ-induced psoriatic skin injury in mice. Moreover, its protection was associated with the interference of IL-17A/IL-17RA interaction.

AS2762900-00, a potent anti-human IL-23 receptor monoclonal antibody, prevents epidermal hyperplasia in a psoriatic human skin xenograft model

Interleukin (IL)-23 is thought to be critical in the pathogenesis of psoriasis, and anti-IL-23 monoclonal antibodies (mAbs) have been approved for the treatment of psoriasis. We speculated that an anti-IL-23 receptor mAb might have greater efficacy than an anti-IL-23 mAb in the treatment of local inflamed lesions with high IL-23 levels. We previously generated an anti-human IL-23 receptor mAb, AS2762900-00, which potently blocked IL-23-induced cell proliferation, regardless of the concentration of IL-23. Here, we evaluated the therapeutic potential of AS2762900-00 in the treatment of psoriasis. Compared with untreated control, AS2762900-00 significantly reduced the epidermal thickness of lesions in a clinically relevant psoriatic human skin xenograft model. The expression of inflammatory genes including genes downstream of IL-23 signaling in the lesion tended to be lower in the AS2762900-00 group than the untreated group, suggesting that the inhibitory effects of AS2762900-00 in the psoriatic human skin xenograft model might occur via blockade of IL-23 signaling pathways. Further, AS2762900-00 showed an inhibitory effect on signal transducer and activator of transcription 3 (STAT3) phosphorylation as a downstream signal of IL-23 receptor activation in whole blood from patients with psoriasis. We also confirmed that AS2762900-00 inhibited IL-23-induced STAT3 phosphorylation in a concentration-dependent manner using whole blood from healthy donors. These data suggest that AS2762900-00 is a promising drug candidate for the treatment of psoriasis. In addition, STAT3 phosphorylation in whole blood may be a useful biomarker for the evaluation of the pharmacodynamic effects of AS2762900-00 in healthy volunteers in clinical development.