IL-1R1 signaling facilitates Munro's microabscess formation in psoriasiform imiquimod-induced skin inflammation

Cytokines in psoriasis: From pathogenesis to targeted therapy

Psoriasis is a multifactorial disease that affects 0.84% of the global population and it can be associated with disabling comorbidities. As patients present with thick scaly lesions, psoriasis was long believed to be a disorder of keratinocytes. Psoriasis is now understood to be the outcome of the interaction between immunological and environmental factors in individuals with genetic predisposition. While it was initially thought to be solely mediated by cytokines of type-1 immunity, namely interferon-γ, interleukin-2, and interleukin-12 because it responds very well to cyclosporine, a reversible IL-2 inhibitor; the discovery of Th-17 cells advanced the understanding of the disease and helped the development of biological therapy. This article aims to provide a comprehensive review of the role of cytokines in psoriasis, highlighting areas of controversy and identifying the connection between cytokine imbalance and disease manifestations. It also presents the approved targeted treatments for psoriasis and those currently under investigation.

Photodegradation enhances the toxic effect of anthracene on skin

Anthracene, a polycyclic aromatic hydrocarbon (PAH), is a widespread environmental pollutant that poses potential risks to human health. Exposure to anthracene can result in various adverse health effects, including skin-related disorders. Photo exposure sufficiently removes the anthracene from the environment but also generates more degradation products which can be more toxic. The goal of this study was to assess the change in anthracene dermotoxicity caused by photodegradation and understand the mechanism of this change. In the present study, over 99.99% of anthracene was degraded within 24 h of sunlight exposure, while producing many intermediate products including 9,10-anthraquinone and phthalic acid. The anthracene products with different durations of photo exposure were applied to 2D and 3D human keratinocyte cultures. Although the non-degraded anthracene significantly delayed the cell migration, the cell viability and differentiation decreased dramatically in the presence of the photodegraded anthracene. Anthracene photodegradation products also altered the expression patterns of a number of inflammation-related genes in comparison to the control cells. Among these genes, il1a, il1b, il8, cxcl2, s100a9, and mmp1 were upregulated whereas the tlr4 and mmp3 were downregulated by the photodegraded anthracene. Topical deliveries of the photodegraded and non-degraded anthracene to the dorsal skin of hairless mice showed more toxic effects by the photodegraded anthracene. The 4-hour photodegradation products of anthracene thickened the epidermal layer, increased the dermal cellularity, and induced the upregulation of inflammatory markers, il1a, il1b, s100a9, and mmp1. In addition, it also prevented the production of a gap junction protein, Connexin-43. All the evidence suggested that photodegradation enhanced the toxicities of anthracene to the skin. The 4-hour photodegradation products of anthracene led to clinical signs similar to acute inflammatory skin diseases, such as atopic and contact dermatitis, eczema, and psoriasis. Therefore, the potential risk of skin irritation by anthracene should be also considered when an individual is exposed to PAHs, especially in environments with strong sunlight.

Adenosine and Its Receptors in the Pathogenesis and Treatment of Inflammatory Skin Diseases

Inflammatory skin diseases highlight inflammation as a central driver of skin pathologies, involving a multiplicity of mediators and cell types, including immune and non-immune cells. Adenosine, a ubiquitous endogenous immune modulator, generated from adenosine triphosphate (ATP), acts via four G protein-coupled receptors (A1, A2A, A2B, and A3). Given the widespread expression of those receptors and their regulatory effects on multiple immune signaling pathways, targeting adenosine receptors emerges as a compelling strategy for anti-inflammatory intervention. Animal models of psoriasis, contact hypersensitivity (CHS), and other dermatitis have elucidated the involvement of adenosine receptors in the pathogenesis of these conditions. Targeting adenosine receptors is effective in attenuating inflammation and remodeling the epidermal structure, potentially showing synergistic effects with fewer adverse effects when combined with conventional therapies. What is noteworthy are the promising outcomes observed with A2A agonists in animal models and ongoing clinical trials investigating A3 agonists, underscoring a potential therapeutic approach for the management of inflammatory skin disorders.

Floxed Il1rl2 Locus with mCherry Reporter Element Reveals Distinct Expression Patterns of the IL-36 Receptor in Barrier Tissues

IL-36 cytokines are emerging as beneficial in immunity against pathogens and cancers but can also be detrimental when dysregulated in autoimmune and autoinflammatory conditions. Interest in targeting IL-36 activity for therapeutic purposes is rapidly growing, yet many unknowns about the functions of these cytokines remain. Thus, the availability of robust research tools is essential for both fundamental basic science and pre-clinical studies to fully access outcomes of any manipulation of the system. For this purpose, a floxed Il1rl2, the gene encoding the IL-36 receptor, mouse strain was developed to facilitate the generation of conditional knockout mice. The targeted locus was engineered to contain an inverted mCherry reporter sequence that upon Cre-mediated recombination will be flipped and expressed under the control of the endogenous Il1rl2 promoter. This feature can be used to confirm knockout in individual cells but also as a reporter to determine which cells express the IL-36 receptor IL-1RL2. The locus was confirmed to function as intended and further used to demonstrate the expression of IL-1RL2 in barrier tissues. Il1rl2 expression was detected in leukocytes in all barrier tissues. Interestingly, strong expression was observed in epithelial cells at locations in direct contact with the environment such as the skin, oral mucosa, the esophagus, and the upper airways, but almost absent from epithelial cells at more inward facing sites, including lung alveoli, the small intestine, and the colon. These findings suggest specialized functions of IL-1RL2 in outward facing epithelial tissues and cells. The generated mouse model should prove valuable in defining such functions and may also facilitate basic and translational research.

Human neutrophils drive skin autoinflammation by releasing interleukin (IL)-26

Autoinflammation is a sterile inflammatory process resulting from increased neutrophil infiltration and overexpression of IL-1 cytokines. The factors that trigger these events are, however, poorly understood. By investigating pustular forms of psoriasis, we show that human neutrophils constitutively express IL-26 and abundantly release it from granular stores upon activation. In pustular psoriasis, neutrophil-derived IL-26 drives the pathogenic autoinflammation process by inducing the expression of IL-1 cytokines and chemokines that further recruit neutrophils. This occurs via activation of IL-26R in keratinocytes and via the formation of complexes between IL-26 and microbiota DNA, which trigger TLR9 activation of neutrophils. Thus our findings identify neutrophils as an important source of IL-26 and point to IL-26 as the key link between neutrophils and a self-sustaining autoinflammation loop in pustular psoriasis.

A therapeutic strategy of parthenolide in improving imiquimod-induced psoriasis-like skin inflammation targeting IL-36/NETs through skin transdermal therapeutic system

BACKGROUND

Psoriasis is an inflammatory skin disease that occurs repeatedly over time. The natural product of sesquiterpene lactones, Parthenolide (Par), is isolated from Tanacetum parthenium L. (feverfew) which has significant effects on anti-inflammatory. The therapeutic effect of the medication itself is crucial, but different routes of administration of the same drug can also produce different effects.

PURPOSE

The aim of our research sought to investigate the ameliorating effects of Par in psoriasis-like skin inflammation and its related mechanism of action.

RESULTS

In the IMQ-induced model, intragastric administration of Par reduced the Psoriasis Area and Severity Index (PASI) score, improved skin erythema, scaling, and other symptoms. And Par decreased the expression of Ki67, keratin14, keratin16 and keratin17, and increased the expression of keratin1. Par could reduce IL-36 protein expressions, meanwhile the expression of Il1b, Cxcl1 and Cxcl2 mRNA were also decreased. Par regulated the expression levels of F4/80, MPO and NE. However, skin transdermal administration of Par was more effective. Similarly, Par attenuated IL-36γ, IL-1β and caspase-1 activated by Poly(I:C) in in vitro and ex vivo. In addition, Par also reduced NE, PR3, and Cathepsin G levels in explant skin tissues.

CONCLUSION

Par ameliorated psoriasis-like skin inflammation in both in vivo and in vitro, especially after treatment with transdermal drug delivery, possibly by inhibiting neutrophil extracellular traps and thus by interfering IL-36 signaling pathway. It indicated that Par provides a new research strategy for the treatment of psoriasis-like skin inflammation and is expected to be a promising drug.

Interleukins and Psoriasis

Psoriasis is an immune-mediated chronic inflammatory skin disease that affects 2% to 3% of the world's population. It is widely assumed that immune cells and cytokines acting together play a crucial part in the pathophysiology of psoriasis by promoting the excessive proliferation of skin keratinocytes and inflammatory infiltration. Interleukins (ILs), as a critical component of cytokines, have been closely associated with the pathogenesis and progression of psoriasis. This review summarizes the current contribution of ILs to psoriasis and describes the role each IL performs in psoriasis. Furthermore, the paper presents the therapeutic effects and application prospects of biologics developed for ILs in clinical treatment and experiments. The study aims to further the research on ILs in the treatment of psoriasis.

Tumor infiltrating neutrophil microabscess in OSCC: A poorly understood histopathologic prognosticator

OBJECTIVE

Role of neutrophils in shaping the tumor microenvironment is well known in oral squamous cell carcinoma (OSCC). However, neutrophil microabscess (NM) formation within the tumor islands is distinctive phenomenon and has never been investigated in the literature. This pilot observational study identifies the incidence of NM in OSCC and its clinicopathologic correlation as a platform for the future studies.

METHODOLOGY

A retrospective study was carried out on archival specimens of 121 cases of surgically excised OSCC specimens for identification of NM formations within the tumor islands using compound microscope. Mean NM density was calculated based on the quantification done at five randomly selected hotspots.

RESULTS

Out of total 121 cases of OSCC, thirteen (10.74%) cases showed a frank evidence of NM within tumor islands. The hotspot analysis showed that the NM density ranges from 2 to 7 with mean of 3.76 ± 1.39 per high power field. NM density was higher in moderately differentiated OSCC (3.76 ± 1.93) than well differentiated (3.76 ± 1.93) however the differences were not statistically significant (p = 0.165). Similarly, higher NM density was reported in advanced T stage, lymph node involvement, advanced TNM stage and lymphovascular invasion, however, the results were statistically insignificant.

CONCLUSION

There is evidence of NM formation in the tumor islands of OSCC, however their exact role as a prognosticator needs further exploration with large sample size and follow-up data.

Crisaborole Inhibits Itch and Pain by Preventing Neutrophil Infiltration in a Mouse Model of Atopic Dermatitis

Crisaborole, a phosphodiesterase 4 (PDE4) inhibitor, has been approved for the treatment of mild to moderate atopic dermatitis. Atopic dermatitis is often associated with increased pain. Using a mouse model, this study investigated whether crisaborole suppresses pain associated with atopic dermatitis and the potential mechanisms underlying it. The mouse model for atopic dermatitis was developed by repeatedly applying MC903. MC903-treated mice had increased spontaneous scratching (itch-related behaviour) and wiping behaviour (pain-related behaviour). Crisaborole was topically applied to the cheek skin of MC903-treated mice, and it reduced both itch- and pain-related behaviours in these mice. Immunofluorescence staining revealed that crisaborole reduced neutrophil infiltration and interaction of neutrophils with sensory neurones. Intradermal injection of S100A8/A9, proinflammatory neutrophil mediator, enhanced not only itch-related behaviours evoked by histamine or chloroquine, but also pain-related behaviours evoked by capsaicin. Calcium imaging of mouse dorsal root ganglion neurones revealed that pretreatment with S100A8/A9 significantly increased calcium responses to histamine and capsaicin, and the proportion of chloroquine-sensitive neurones. These findings suggest that the PDE4 inhibitor reduces itch and pain, in part by inhibiting infiltration of S100A8/A9-containing neutrophils in a mouse model of MC903-induced atopic dermatitis.

Hovenia dulcis Thunb. Fruit Extract Attenuates Psoriatic Skin Inflammation in Tumor Necrosis Factor-α-Stimulated Human Keratinocyte HaCaT Cells In Vitro

Hovenia dulcis Thunb. fruit (HDF) is traditionally used for treating liver diseases and alcohol poisoning. The purpose of this study was to explore the effects of HDF on hyperproliferation, levels of inflammatory cytokines, and signaling mechanisms in human psoriatic keratinocyte HaCaT cells. HDF showed a preventive effect on tumor necrosis factor-α (TNF-α)-induced abnormal proliferation of psoriatic keratinocytes. Furthermore, real-time reverse transcription-PCR analysis showed that HDF suppressed the expressions of inflammatory cytokines; interleukin (IL)-1α and IL-1β and chemokines; CCL-20 and CXCL-8 in TNF-α-induced HaCaT cells. Western blotting revealed that HDF suppressed the levels of phosphorylated IκB and STAT3 together with a decline in the levels of phosphorylated mitogen-activated protein kinases (MAPKs). These outcomes indicate that HDF prevents the abnormal proliferation of keratinocytes and modulates inflammatory responses by suppressing nuclear factor-κB (NF-κB) and STAT3 activation through downregulation of the MAPK signaling pathway in TNF-α-induced psoriatic keratinocytes. Our study demonstrates that HDF is prospective and beneficial for psoriatic skin inflammation.

Topical application of aerial portion of Acalypha indica Linn ameliorates psoriasis in rodents: Evidences from in vivo and in silico studies

ETHANOPHARMACOLOGICAL RELEVANCE

Acalypha indica Linn. is a weed, used traditionally for different skin diseases such as eczema and dermatitis in various parts of India. There are no previous in vivo studies reported on the antipsoriatic potential of this medicinal plant.

AIM

The aim of this study was to investigate antipsoriatic activity of coconut oil dispersion of aerial portion of Acalypha indica Linn. Few lipid-soluble phytoconstituents of this plantwere subjected to molecular docking studies on different targets to determine phytoconstituent responsible for antipsoriatic activity.

METHODS

Virgin coconut oil dispersion of aerial portion of the plant was prepared by mixing three parts of coconut oil and one part of powdered aerial portion. The acute dermal toxicity was determined according to OECD guidelines. Mouse tail model was used to evaluate the antipsoriatic activity. Molecular docking of phytoconstituents was carried out using Biovia Discovery Studio.

RESULTS

In acute dermal toxicity study,the coconut oil dispersion was found to be safe up to the dose of 20000 mg/kg. The dispersion exhibited significant antipsoriatic activity (p < 0.01) at the dose of 250 mg/kg; at 500 mg/kg dose, the activity was similar that of 250 mg/kg dose. In the docking study of the phytoconstituents, 2-methyl anthraquinone was found to be responsible for antipsoriatic activity.

CONCLUSION

This study provides new evidence of Acalypha indica Linn as antipsoriatic plant and justifies its traditional use. Computational studies also endorse the results obtained via acute dermal toxicity study and mouse tail model for evaluation of antipsoriatic potential.

Cordycepin-induced Keratinocyte Secretome Promotes Skin Cell Regeneration

BACKGROUND/AIM

Skin regeneration is the intrinsic ability to repair damaged skin tissues to regaining skin well-being. Processes of wound healing, a major part of skin regeneration, involve various types of cells, including keratinocytes and dermal fibroblasts, through their autocrine/paracrine signals. The releasable factors from keratinocytes were reported to influence dermal fibroblasts behavior during wound-healing processes. Here, we developed a strategy to modulate cytokine components and improve the secretome quality of HaCaT cells, a nontumorigenic immortalized keratinocyte cell line, via the treatment of cordycepin, and designated as cordycepin-induced HaCaT secretome (CHS).

MATERIALS AND METHODS

The bioactivities of CHS were investigated in vitro on human dermal fibroblasts (HDF). The effects of CHS on HDF proliferation, reactive oxygen species-scavenging, cell migration, extracellular matrix production and autophagy activation were investigated by 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide cell viability assay, dichloro-dihydro-fluorescein diacetate, the wound-healing assay, reverse transcription polymerase chain reaction and immunofluorescent microscopy. Finally, Proteome Profiler™ Array was used to determine the composition of the secretome.

RESULTS

CHS induced fibroblast proliferation/migration, reactive oxygen species-scavenging property, regulation of extracellular matrix synthesis, and autophagy activation. Such enhanced bioactivities of CHS were related to the increase of some key cytokines, including C-X-C motif chemokine ligand 1, interleukin 1 receptor A, interleukin 8, macrophage migration-inhibitory factor, and serpin family E member 1.

CONCLUSION

These findings highlight the implications of cordycepin alteration of the cytokine profile of the HaCaT secretome, which represents a novel biosubstance for the development of wound healing and skin regeneration products.

IL-1β and Allergy: Focusing on Its Role in Allergic Rhinitis

Allergic rhinitis (AR) is a chronic upper airway immune-inflammation response mediated by immunoglobulin E (IgE) to allergens and can seriously affect the quality of life and work efficiency. Previous studies have shown that interleukin-1β (IL-1β) acts as a key cytokine to participate in and promote the occurrence and development of allergic diseases. It has been proposed that IL-1β may be a potential biomarker of AR. However, its definitive role and potential mechanism in AR have not been fully elucidated, and the clinical sample collection and detection methods were inconsistent among different studies, which have limited the use of IL-1β as a clinical diagnosis and treatment marker for AR. This article systematically summarizes the research advances in the roles of IL-1β in allergic diseases, focusing on the changes of IL-1β in AR and the possible interventions. In addition, based on the findings by our team, we provided new insights into the use of IL-1β in AR diagnosis and treatment, in an attempt to further promote the clinical application of IL-1β in AR and other allergic diseases.

Genome-wide DNA methylation of Munro's microabscess reveals the epigenetic regulation in the pathogenesis of psoriasis

Introduction

Munro's microabscess is a typical pathological feature in the early psoriatic lesion, mainly characterized by the accumulation of neutrophils in the epidermis. DNA methylation microenvironment of Munro's microabscess and the crosstalk with transcription and its effect on neutrophils have not yet been revealed.

Methods

Performed genome-wide DNA methylation analysis and further differential methylation analysis of psoriatic skin lesions with and without Munro's microabscess from two batch samples consisting of 114 former samples in the discovery stage and 21 newly-collected samples in the validation stage. Utilized GO, MEME, and other tools to conduct downstream analysis on differentially methylated sites (DMSs). Correlation analysis of methylation level and transcriptome data was also conducted.

Results

We observed 647 overlapping DMSs associated with Munro's microabscess. Subsequently, GO pathway analysis revealed that DNA methylation might affect the physical properties associated with skin cells through focal adhesion and cellsubstrate junction and was likely to recruit neutrophils in the epidermis. Via the MEME tool, used to investigate the possible binding transcription factors (TFs) of 20 motifs around the 647 DMSs, it was found that DNA methylation regulated the binding of AP1 family members and the recruitment of neutrophils in the epidermis through the TGF-beta pathway and the TH17 pathway. Meanwhile, combined with our earlier transcriptome data, we found DNA methylation would regulate the expressions of CFDP, SIRT6, SMG6, TRAPPC9, HSD17B7, and KIAA0415, indicating these genes would potentially promote the process of Munro's microabscess.

Discussion

In conclusion, DNA methylation may affect the course of psoriasis by regulating the progression of Munro's microabscess in psoriatic skin lesions.

Calcium/calmodulin-dependent protein kinase IV promotes imiquimod-induced psoriatic inflammation via macrophages and keratinocytes in mice

CaMK4 has an important function in autoimmune diseases, and the contribution of CaMK4 in psoriasis remains obscure. Here, we show that CaMK4 expression is significantly increased in psoriatic lesional skin from psoriasis patients compared to healthy human skin as well as inflamed skin from an imiquimod (IMQ)-induced mouse model of psoriasis compared to healthy mouse skin. Camk4-deficient (Camk4^−/−) mice treated with IMQ exhibit reduced severity of psoriasis compared to wild-type (WT) mice. There are more macrophages and fewer IL-17A⁺γδ TCR⁺ cells in the skin of IMQ-treated Camk4^−/− mice compared to IMQ-treated WT mice. CaMK4 inhibits IL-10 production by macrophages, thus allowing excessive psoriatic inflammation. Deletion of Camk4 in macrophages alleviates IMQ-induced psoriatic inflammation in mice. In keratinocytes, CaMK4 inhibits apoptosis as well as promotes cell proliferation and the expression of pro-inflammatory genes such as S100A8 and CAMP. Taken together, these data indicate that CaMK4 regulates IMQ-induced psoriasis by sustaining inflammation and provides a potential target for psoriasis treatment.

Calcium/calmodulin-dependent protein kinase IV (CaMK4) has been shown to be involved in autoimmunity but it is not clear how it functions in psoriasis. Here the authors show that CaMK4 is increased in psoriasis and promotes inflammatory responses in mouse models of psoriasis mediated through macrophages and keratinocytes.

Chlorquinaldol inhibits the activation of nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein 3 inflammasome and ameliorates imiquimod-induced psoriasis-like dermatitis in mice

Psoriasis is a common chronic autoinflammatory/autoimmune skin disease associated with elevated pro-inflammatory cytokines. The pivotal role of interleukin (IL)-1β and nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome in the pathogenesis of psoriasis has been widely described. Accordingly, the suppression of NLRP3-dependent IL-1β release is a potential therapy for psoriasis. Repurposing marketed drugs is a strategy for identifying new inhibitors of NLRP3 inflammasome activation. Herein, chlorquinaldol (CQD), a historic antimicrobial agent used as a topical treatment for skin and vaginal infections, was found to have a distinct effect by inhibiting NLRP3 inflammasome activation at concentrations ranging from 2 to 6 μM. CQD significantly suppressed apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) oligomerization, NLRP3-ASC interaction, and pyroptosis in macrophages. The levels of cleaved IL-1β and caspase-1 were reduced by CQD in the cell lysates of macrophages, suggesting that CQD acted on upstream of pore formation in the cell membrane. Mechanistically, CQD reduced mitochondrial reactive oxygen species production but did not affect the nuclear factor-κB (NF-κB) pathway. Intraperitoneal administration of CQD (15 mg/kg) for 6 days was found to improve the skin lesions in the imiquimod-induced psoriatic mouse model (male C57BL/6 mice), while secretion of pro-inflammatory cytokines (IL-17 and IL-1β) and keratinocyte proliferation were significantly suppressed by CQD. In conclusion, CQD exerted inhibitory effects on NLRP3 inflammasome activation in macrophages and decreased the severity of psoriatic response in vivo. Such findings indicate that the repurposing of the old drug, CQD, is a potential pharmacological approach for the treatment of psoriasis and other NLRP3-driven diseases.

The Protective Role of pVHL in Imiquimod-Induced Psoriasis-like Skin Inflammation

Psoriasis is a chronic inflammatory disease distinguished by an excessive proliferation and abnormal differentiation of keratinocytes. Immune cells, such as T lymphocytes and neutrophils, and inflammatory cytokines, such as Tumor Necrosis Factor-α (TNF-α) and interleukin 17 (IL-17), are essential for maintaining psoriatic lesions. Additionally, a hypoxic milieu present in the skin promotes the expression of transcriptional factor hypoxia-inducible factor-1 alpha (HIF-1α). This protein regulates the expression of angiogenic and glycolytic factors, such as vascular endothelial grown factor and lactate dehydrogenase (LDH), both relevant in chronic inflammation. The von Hippel–Lindau protein (pVHL) is a negative regulator of HIF-1α. Previously, we found that pVHL was almost absent in the lesions of psoriasis patients; therefore, we investigated the impact of rescue pVHL expression in lesional skin. We used the imiquimod-induced psoriasis-like mouse model as an adenoviral vector that allowed us to express pVHL in the skin. Our data show that, in lesional skin, pVHL expression was reduced, whereas HIF-1α was increased. Remarkably, the retrieval of pVHL prevented psoriatic lesions, diminishing erythema, scale, and epidermal and vascular thickness. Furthermore, pVHL expression was capable of reducing HIF-1α, LDH, TNF-α and immune cell infiltration (mainly IL-17⁺ neutrophils). In conclusion, our results demonstrate that pVHL has a protective role to play in the pathophysiology of psoriasis.

Epidermis-Intrinsic Transcription Factor Ovol1 Coordinately Regulates Barrier Maintenance and Neutrophil Accumulation in Psoriasis-Like Inflammation

Skin epidermis constitutes the exterior barrier that protects the body from dehydration and environmental assaults. Barrier defects underlie common inflammatory skin diseases, but the molecular mechanisms that maintain barrier integrity and regulate epidermal-immune cell cross-talk in inflamed skin are not fully understood. In this study, we show that skin epithelia-specific deletion of Ovol1, which encodes a skin disease‒linked transcriptional repressor, impairs the epidermal barrier and aggravates psoriasis-like skin inflammation in mice in part by enhancing neutrophil accumulation and abscess formation. Through molecular studies, we identify IL-33, a cytokine with known pro-inflammatory and anti-inflammatory activities, and Cxcl1, a neutrophil-attracting chemokine, as potential weak and strong direct targets of Ovol1, respectively. Furthermore, we provide functional evidence that elevated Il33 expression reduces disease severity in imiquimod-treated Ovol1-deficient mice, whereas persistent accumulation and epidermal migration of neutrophils exacerbate it. Collectively, our study uncovers the importance of an epidermally expressed transcription factor that regulates both the integrity of the epidermal barrier and the behavior of neutrophils in psoriasis-like inflammation.

Therapeutic potential of targeting IL-1 family cytokines in chronic inflammatory skin diseases

The interleukin-1 (IL-1) family of cytokines is a central regulator of a myriad of immunological responses. It comprises several cytokines, including those belonging to the IL-1, IL-36 and IL-18 subfamilies, as well as IL-33. The IL-1 family primarily plays a role in orchestrating innate immune responses but also in adaptive immunity. Increased interest in the IL-1 family occurred following the discovery that dysregulation of IL-1 signalling underlies the pathogenesis of several monogenic auto-inflammatory diseases, characterized by sterile inflammation involving the skin and other organs. This also provided increased understanding of the role of innate immunity and the IL-1 family in polygenic auto-inflammatory skin conditions, such as neutrophilic dermatoses, as well as in some of the most common chronic inflammatory skin diseases, such as psoriasis or hidradenitis suppurativa. Several therapeutic agents have been developed to inhibit the IL-1 family members and their signalling pathways. These have shown therapeutic efficacy in several chronic inflammatory skin disorders. The aim of this review is to thoroughly describe the consequences of pathological dysregulation of IL-1, IL-33, IL-36, IL-18 pathways in dermatological conditions and to provide a forward-looking update on therapeutic strategies targeting signalling by IL-1 family cytokines.

The Extracellular Vesicles from the Commensal Staphylococcus Epidermidis ATCC12228 Strain Regulate Skin Inflammation in the Imiquimod-Induced Psoriasis Murine Model

Extracellular vesicles (EVs) are evaginations of the cytoplasmic membrane, containing nucleic acids, proteins, lipids, enzymes, and toxins. EVs participate in various bacterial physiological processes. Staphylococcus epidermidis interacts and communicates with the host skin. S. epidermidis’ EVs may have an essential role in this communication mechanism, modulating the immunological environment. This work aimed to evaluate if S. epidermidis’ EVs can modulate cytokine production by keratinocytes in vitro and in vivo using the imiquimod-induced psoriasis murine model. S. epidermidis’ EVs were obtained from a commensal strain (ATC12228EVs) and a clinical isolated strain (983EVs). EVs from both origins induced IL-6 expression in HaCaT keratinocyte cultures; nevertheless, 983EVs promoted a higher expression of the pro-inflammatory cytokines VEGF-A, LL37, IL-8, and IL-17F than ATCC12228EVs. Moreover, in vivo imiquimod-induced psoriatic skin treated with ATCC12228EVs reduced the characteristic psoriatic skin features, such as acanthosis and cellular infiltrate, as well as VEGF-A, IL-6, KC, IL-23, IL-17F, IL-36γ, and IL-36R expression in a more efficient manner than 983EVs; however, in contrast, Foxp3 expression did not significantly change, and IL-36 receptor antagonist (IL-36Ra) was found to be increased. Our findings showed a distinctive immunological profile induction that is dependent on the clinical or commensal EV origin in a mice model of skin-like psoriasis. Characteristically, proteomics analysis showed differences in the EVs protein content, dependent on origin of the isolated EVs. Specifically, in ATCC12228EVs, we found the proteins glutamate dehydrogenase, ornithine carbamoyltransferase, arginine deiminase, carbamate kinase, catalase, superoxide dismutase, phenol-soluble β1/β2 modulin, and polyglycerol phosphate α-glucosyltransferase, which could be involved in the reduction of lesions in the murine imiquimod-induced psoriasis skin. Our results show that the commensal ATCC12228EVs have a greater protective/attenuating effect on the murine imiquimod-induced psoriasis by inducing IL-36Ra expression in comparison with EVs from a clinical isolate of S. epidermidis.

Randialic acid B and tomentosolic acid block formyl peptide receptor 1 in human neutrophils and attenuate psoriasis-like inflammation in vivo

Psoriasis is a long-lasting inflammatory skin disease lacking proper cure. Dysregulated activation of neutrophils is a major pathogenic factor in psoriasis. Formyl peptide receptor 1 (FPR1) triggers neutrophil activation in response to bacteria- or mitochondria-derived N-formyl peptides, but its significance in neutrophilic psoriasis remains unknown. In this study, we discovered two derivatives of ursolic acid, 3β-hydroxyurs-12,18-dien-28-oic acid (randialic acid B, RAB) and 3β-hydroxyurs-12,19-dien-28-oic acid (tomentosolic acid, TA), as FPR1 inhibitors in human neutrophils with ability to suppress psoriatic symptoms in mice. Both RAB and TA, triterpenoids of traditional medicinal plant Ilex kaushue, selectively inhibited reactive oxygen species production, elastase release, and CD11b expression in human neutrophils activated by FPR1, but not non-FPR1 agonists. Importantly, RAB and TA inhibited the binding of N-formyl peptide to FPR1 in human neutrophils, neutrophil-like THP-1 cells, and hFPR1-transfected HEK293 cells, indicating FPR1 antagonism. Moreover, in assays induced by various concentrations of FPR1 agonist, both RAB and TA acted competitively for its binding to the FPR1 receptor. The FPR1-downstream signaling such as Ca2+ mobilisation and activation of Akt and MAPKs was also competitively inhibited. In addition, imiquimod-induced psoriasis-like symptoms, including epidermal hyperplasia, desquamation with scaling, neutrophil skin infiltration, and transepidermal water loss were significantly reduced by both RAB and TA. The results illustrate a possible role of human neutrophils FPR1 receptor in psoriasis-like inflammation. Accordingly, triterpenoids RAB and TA represent novel FPR1 antagonists and exhibit therapeutic potential for treating neutrophilic inflammatory skin diseases.

SIGIRR Negatively Regulates IL-36-Driven Psoriasiform Inflammation and Neutrophil Infiltration in the Skin

SIGIRR has been described as a negative regulator of several IL-1R/TLR family members and has been implicated in several inflammatory disease conditions. However, it is unknown whether it can suppress IL-36 family cytokines, which are members of the broader IL-1 superfamily that have emerged as critical orchestrators of psoriatic inflammation in both humans and mice. In this study, we demonstrate that SIGIRR is downregulated in psoriatic lesions in humans and mice, and this correlates with increased expression of IL-36 family cytokines. Using Sigirr ^-/- mice, we identify, for the first time (to our knowledge), SIGIRR as a negative regulator of IL-36 responses in the skin. Mechanistically, we identify dendritic cells and keratinocytes as the primary cell subsets in which IL-36 proinflammatory responses are regulated by SIGIRR. Both cell types displayed elevated IL-36 responsiveness in absence of SIGIRR activity, characterized by enhanced expression of neutrophil chemoattractants, leading to increased neutrophil infiltration to the inflamed skin. Blockade of IL-36R signaling ameliorated exacerbated psoriasiform inflammation in Sigirr^-/- mice and inhibited neutrophil infiltration. These data identify SIGIRR activity as an important regulatory node in suppressing IL-36-dependent psoriatic inflammation in humans and mice.

Potential herbal constituents for psoriasis treatment as protective and effective therapy

Psoriasis is a multifactorial and chronic skin disorder. It is a recurrent disease that requires incessant therapy. Psoriasis treatment includes topical and systemic routes using synthetic drugs that lead to severe unwanted adverse effects. Herbal therapy is widely used for thousands of years in countries like China and India. The use of herbal therapy in the developed region enhanced to a great extent and showed better efficacy towards psoriasis alone or as adjuvant to synthetic therapy. Herbal medicines have gained great attention in the treatment of psoriasis due to their lesser side effects compared to synthetic drugs. In this review, the various plant sources which have been found effective in psoriasis and can be used to develop novel therapeutics have been discussed. The mechanisms by which the phytoconstituents elicit anti-psoriatic activity and various research studies that have proven the effectiveness of these natural products have also been compiled in this review.

The Skin-Liver Axis Modulates the Psoriasiform Phenotype and Involves Leucine-Rich α-2 Glycoprotein

Leucine-rich α-2 glycoprotein (LRG), one of the acute phase proteins mainly produced by the liver, similar to C-reactive protein, has been recognized as an inflammatory biomarker for rheumatoid arthritis and inflammatory bowel diseases. We recently demonstrated that LRG was also increased in the sera of psoriasis patients and correlated well with disease activity with a sensitivity and specificity much higher than C-reactive protein; however, whether LRG mechanistically contributed to the pathogenesis of psoriasis remained unclear. In this study, we explored the role of LRG in psoriasiform inflammation using LRG-knockout (KO) mice in an imiquimod (IMQ)-mediated model. Following topical treatment with IMQ, serum levels of LRG and its expression in the liver were abruptly elevated. Similarly, an acute surge of proinflammatory cytokines was observed in the liver, including IL-1β, TNF-α, and IL-6, although LRG-KO mice showed delayed responses. LRG-KO mice showed less skin inflammation in the IMQ model than wild-type mice. K5.Stat3C mice developed psoriasis-like lesions following tape stripping, which also abruptly induced LRG expression in the liver. A deficiency of Lrg mitigated tape stripping-induced lesions, similar to the IMQ model. These results indicate that LRG modulates both feed-forward and feedback loops of cytokines in the skin-liver axis involved with psoriasiform inflammation.

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.

The interleukin-1 family cytokines in psoriasis: pathogenetic role and therapeutic perspectives

Introduction: IL-1 family cytokines play an important role in the innate immune system and their uncontrolled activation and expression can initiate a pathologic inflammatory response. Their role in psoriasis, pustular psoriasis, and psoriatic arthritis has been studied, and they offer potential interest as therapeutic targets.Areas covered: This review focuses on the role that interleukin (IL)-1 family cytokines play in psoriasis pathogenesis, with a special focus on pustular psoriasis, and how these cytokines can be used as therapeutic targets. Using PubMed, we review the literature for articles related to IL-1 family cytokines and psoriasis, focusing on pustular psoriasis, and including pathogenesis, genetics and therapeutic targets.Expert opinion: IL-1 and IL-36 cytokines act as critical drivers of the autoinflammatory responses involved in pustular psoriasis. Studies on the specific role of each IL-1 cytokine are needed, as well as of their regulatory pathways. Targeting of IL-1 family cytokines has been used in pustular psoriasis, with IL-1 and IL-36 R blockade showing promising results.

Metformin inhibits IL-1β secretion via impairment of NLRP3 inflammasome in keratinocytes: implications for preventing the development of psoriasis

Psoriasis is a systemic inflammatory disease significantly associated with comorbidities including type 2 diabetes mellitus (T2DM). Metformin is utilized as a first-line agent for treating T2DM. Although metformin reportedly inhibits mature IL-1β secretion via NLRP3 inflammasome in macrophages of T2DM patients, it remains unclear whether it affects skin inflammation in psoriasis. To test this, we analysed normal human epidermal keratinocytes (NHEKs), a major skin component, stimulated with the key mediators of psoriasis development, TNF-α and IL-17A. This stimulation induced the upregulation of pro-IL-1β mRNA and protein levels, and subsequently mature IL-1β secretion, which was inhibited by metformin treatment. To further reveal the mechanism involved, we examined how metformin treatment affected NLRP3 inflammasome activated by TNF-α and IL-17A stimulation. We found that this treatment downregulated caspase-1 expression, a key mediator of NLRP3 inflammasome. Furthermore, inhibitors of AMPK and SIRT1 abrogated the downregulation of caspase-1 induced by metformin treatment, indicating that AMPK and SIRT1 are essential for the inhibitory effect on NLRP3 inflammasome in NHEKs. As IL-1β stimulation induced upregulation of IL-36γ, CXCL1, CXCL2, CCL20, S100A7, S100A8 and S100A9 mRNA and protein levels in NHEKs, we examined whether metformin treatment affects such gene expression. Metformin treatment inhibited upregulation of IL-36γ, CXCL1, CXCL2, CCL20, S100A7, S100A8 and S100A9 mRNA and protein levels induced by TNF-α and IL-17A stimulation. Finally, we examined whether metformin administration affected psoriasis development in an imiquimod-induced mouse psoriasis model. Oral metformin treatment significantly decreased ear thickness, epidermal hyperplasia and inflammatory cell infiltration. A cytokine profile in the epidermis under metformin treatment showed that IL-1β, Cxcl1, Cxcl2, S100a7, S100a8 and S100A9 mRNA levels were downregulated compared with control levels. These results indicate that metformin administration prevented psoriasis development in vivo. Collectively, our findings suggest that metformin-mediated anti-psoriatic effects on the skin have the potential for treating psoriasis in T2DM patients.

Retinol and vitamin A metabolites accumulate through RBP4 and STRA6 changes in a psoriasis murine model

Background

Psoriasis is a common chronic inflammatory skin disease that features the abnormal proliferation of keratinocytes. This proliferation could partly result from disturbances in vitamin A metabolism. Changes in psoriasis patients of the levels of retinol-binding protein 4 (RBP4), a carrier of retinol (vitamin A); transmembrane protein stimulated by retinoic acid 6 (STRA6); and other retinol metabolic molecules have not yet been fully established. Therefore, we investigated vitamin A-related proteins in mice with imiquimod (IMQ)-induced psoriasis.

Methods

Thirty mice were divided into four study groups: two groups underwent IMQ application for 3 or 6 days (groups A and B, respectively), and two groups underwent Vaseline application for 3 or 6 days (groups C and D, respectively). Blood and skin samples from both lesional and non-lesional areas of the mice were analyzed using enzyme-linked immunosorbent assays, hematoxylin and eosin staining, immunochemistry, real-time reverse transcription polymerase chain reaction, and RNA sequencing.

Results

IMQ-treated mice developed erythema, scales, and skin thickening. Compared with the control groups, IMQ-treated groups had the following changes: 1) interleukin (IL)-17A, IL-23, and tumor necrosis factor (TNF)-α levels were raised significantly in both serum and lesional skin (all p < 0.001); 2) retinol levels in lesional skin increased slightly (p = 0.364), but no change was evident in serum retinol levels; 3) STRA6 was upregulated in both lesional skin (p = 0.021) and serum (p = 0.034); 4) RBP4 levels were elevated in serum (p = 0.042), but exhibited only an increasing trend (p = 0.273) in lesional skin; and 5) proteins and enzymes that mediate retinoic acid formation and transformation were upregulated in lesional skin.

Conclusions

As the demand for vitamin A in psoriatic mice increased, retinol underwent relocation from the circulation to target tissues. RBP4, STRA6, and the transformation from retinol to retinoic acid were upregulated, which may be part of the mechanism of psoriasis skin lesion formation. We propose that a positive feedback mechanism was formed that maintained the severity of psoriasis.

Intracellular IL-1 Receptor Antagonist Isoform 1 Released from Keratinocytes upon Cell Death Acts as an Inhibitor for the Alarmin IL-1α

The inflammatory effects of IL-1α/β are controlled by IL-1R antagonist (IL-1Ra). One IL-1Ra isoform is secreted, whereas three other isoforms (intracellular IL-1Ra [icIL-1Ra] 1, 2, and 3) are supposed to remain intracellular because of the absence of a signal peptide. In contrast to the well-characterized function of the secreted isoform, the biological role of the intracellular isoforms remains largely unclear. icIL-1Ra1 represents the major isoform in keratinocytes. We created icIL-1Ra1^-/- mice and investigated the role of icIL-1Ra1 in Aldara (5% imiquimod)-induced psoriasis-like skin inflammation. Naive icIL-1Ra1^-/- mice bred habitually and exhibited a normal phenotype. icIL-1Ra1 deficiency aggravated Aldara-induced skin inflammation, as demonstrated by increased ear thickness and increased mRNA levels of key proinflammatory cytokines. No intracellular effect of icIL-1Ra1 could be detected in isolated keratinocytes using RNA-sequencing analysis; however, Aldara treatment led to caspase 1/11-, caspase 8-, and RIPK3-independent keratinocyte cell death accompanied by the release of both icIL-1Ra1 and IL-1α. Furthermore, blocking IL-1α attenuated the clinical severity of Aldara-induced ear thickening in icIL-1Ra1^-/- mice. Our data suggest that upon keratinocyte damage icIL-1Ra1 acts extracellularly as an antagonist of the alarmin IL-1α to immediately counteract its inflammatory effects.

Interleukin-18 exacerbates skin inflammation and affects microabscesses and scale formation in a mouse model of imiquimod-induced psoriasis

Background:

As a potent pro-inflammatory cytokine of the interleukin (IL)-1 family, IL-18 was elevated in early active and progressive plaque-type psoriatic lesions and that serum or plasma levels of IL-18 correlated with the Psoriasis Area and Severity Index (PASI). Although results from previous studies have established that IL-18 may aggravate psoriatic inflammation, the mechanisms of this process remain unknown. In this study, IL-18 knock out (KO) mice and wild-type (WT) mice were used to investigate the effects of IL-18 within a mouse model of psoriasis.

Methods:

WT and IL-18 KO mice were divided into four groups, including imiquimod (IMQ)-treated IL-18 KO group (n = 11) and WT group (n = 13) as well as their respectively gene-matched control mice (receiving vaseline; n = 12). PASI scores were used to evaluate psoriatic lesions in IMQ-treated mice. Pathological features and dermal cellular infiltration were investigated by hematoxylin and eosin staining. The levels of psoriasis-related cytokines including IL-23, IL-17, IL-12, IL-1β, IFNγ, IL-15, IL-27, and IL-4 were tested by real-time polymerase chain reaction (PCR). The protein level of IL-1β, IL-27, CXCL1, and Ly6 g were investigated by immunohistochemistry (IHC).

Results:

Acanthosis (98.46 ± 14.12 vs. 222.68 ± 71.10 μm, P < 0.01) and dermal cell infiltration (572.25 ± 47.45 vs. 762.47 ± 59.59 cells/field, P < 0.01) were significantly milder in IMQ-induced IL-18 KO mice compared with that in WT mice. IMQ-induced IL-18 KO mice manifested larger areas of Munro microabscesses (11,467.83 ± 5112.09 vs. 4093.19 ± 2591.88 μm², P < 0.01) and scales (100,935.24 ± 41,167.77 vs. 41,604.41 ± 14,184.10 μm², P < 0.01) as compared with WT mice. In skin lesions of IL-18 KO mice, the expressions of IL-1β, IL-4, and IL-27 were all significantly upregulated but IL-17 was decreased. Histologically, strong positive signals of Ly6g were observed within the epidermis of IL-18 KO mice but expressions of CXCL1 were decreased.

Conclusions:

IL-18 may exacerbate prominent inflammation and influence pathological features in IMQ-induced mouse model of psoriasis. IL-18 may upregulate pro-inflammatory cytokines and reduce protective cytokines, thus aggravating psoriatic inflammation. In addition, IL-18 may be involved in the formation of Munro microabscesses and scales.

Caspase 1/11 Deficiency or Pharmacological Inhibition Mitigates Psoriasis-Like Phenotype in Mice

Inflammatory caspases, activated within the inflammasome, are responsible for the maturation and secretion of IL-1β/IL-18. Although their expression in psoriasis was shown several years ago, little is known about the role of inflammatory caspases in the context of psoriasis. Here, we confirmed that caspases 1, 4, and 5 are activated in lesional skin from psoriasis patients. We showed in three psoriasis-like models that inflammatory caspases are activated, and accordingly, caspase 1/11 invalidation or pharmacological inhibition by Ac-YVAD-CMK (i.e., Ac-Tyr-Val-Ala-Asp-chloromethylketone) injection induced a decrease in ear thickness, erythema, scaling, inflammatory cytokine expression, and immune cell infiltration in mice. We observed that keratinocytes were primed to secrete IL-1β when cultured in conditions mimicking psoriasis. Generation of chimeric mice by bone marrow transplantation was carried out to decipher the respective contribution of keratinocytes and/or immune cells in the activation of inflammatory caspases during psoriasis-like inflammatory response. Our data showed that the presence of caspase 1/11 in the immune system is sufficient for a fully inflammatory response, whereas the absence of caspase 1/11 in keratinocytes/fibroblasts had no impact. In summary, our study indicates that inflammatory caspases activated in immune cells are implicated in psoriasis pathogenesis.

Interleukin 1 receptor (IL-1R1) activation exacerbates toxin-induced acute kidney injury

Acute kidney injury (AKI) is a leading cause of morbidity and mortality. Drug-induced/toxic AKI can be caused by a number of therapeutic agents. Cisplatin is an effective chemotherapeutic agent whose administration is limited by significant nephrotoxicity. Therapies to prevent cisplatin-induced AKI are lacking. Although tumor necrosis factor-α (TNF) plays a key role in the pathogenesis of cisplatin nephrotoxicity, the innate immune signaling pathways that trigger TNF generation in this context require elucidation. In this regard, sterile injury triggers the release and activation of both isoforms of interleukin(IL)-1, IL-1α and IL-1β. In turn, stimulation of the interleukin-1 receptor (IL-1R1) by these ligands engages a proinflammatory signaling cascade that induces TNF induction. We therefore hypothesized that IL-1R1 activation exacerbates cisplatin-induced AKI by inducing TNF production, thereby augmenting inflammatory signals between kidney parenchymal cells and infiltrating myeloid cells. IL-1R1+/+ (WT) and IL-1R1-/- (KO) mice were subjected to cisplatin-induced AKI. Compared with WT mice, IL-1R1 KO mice had attenuated AKI as measured by serum creatinine and BUN, renal NGAL mRNA levels, and blinded histological analysis of kidney pathology. In the cisplatin-injured kidney, IL-1R1 KO mice had diminished levels of whole kidney TNF, and fewer Ly6G-expressing neutrophils. In addition, an unbiased machine learning analysis of intrarenal immune cells revealed a diminished number of CD11bint/CD11cint myeloid cells in IL-1R1 KO injured kidneys compared with IL-1R1 WT kidneys. Following cisplatin, IL-1R1 KO kidneys, compared with WTs, had fewer TNF-producing: macrophages, CD11bint/CD11cint cells, and neutrophils, consistent with an effect of IL-1R1 to polarize intrarenal myeloid cells toward a proinflammatory phenotype. Interruption of IL-1-dependent signaling pathways warrants further evaluation to decrease nephrotoxicity during cisplatin therapy.

A Critical Role of the IL-1β-IL-1R Signaling Pathway in Skin Inflammation and Psoriasis Pathogenesis

The IL-1 signaling pathway has been shown to play a critical role in the pathogenesis of chronic, autoinflammatory skin diseases such as psoriasis. However, the exact cellular and molecular mechanisms have not been fully understood. Here, we show that IL-1β is significantly elevated in psoriatic lesional skin and imiquimod-treated mouse skin. In addition, IL-1R signaling appears to correlate with psoriasis disease progression and treatment response. IL-1 signaling in both dermal γδ T cells and other cells such as keratinocytes is essential to an IMQ-induced skin inflammation. IL-1β induces dermal γδ T cell proliferation and IL-17 production in mice. In addition, IL-1β stimulates keratinocytes to secrete chemokines that preferentially chemoattract peripheral CD27^- CCR6⁺IL-17 capable of producing γδ T cells (γδT17). Further studies showed that endogenous IL-1β secretion is regulated by skin commensals to maintain dermal γδT17 homeostasis in mice. Mouse skin associated with Corynebacterium species, bacteria enriched in human psoriatic lesional skin, has increased IL-1β and dermal γδT17 cell expansion. Thus, the IL-1β-IL-1R signaling pathway may contribute to skin inflammation and psoriasis pathogenesis via the direct regulation of dermal IL-17-producing cells and stimulation of keratinocytes for amplifying inflammatory cascade.

Topical application of anthranilate derivatives ameliorates psoriatic inflammation in a mouse model by inhibiting keratinocyte-derived chemokine expression and neutrophil infiltration

Psoriasis is an inflammatory autoimmune skin disorder possessing a complex etiology related to genetic and environmental triggers. Keratinocytes show a potential role for the origin of psoriasis. In this study, we estimated the efficiency of 2 anthranilate derivatives-(E)-4-( N-{2-[1-(hydroxyimino)ethyl]phenyl}sulfamoyl)phenyl pivalate (HFP031) and butyl 2-[2-(2-fluorophenyl)acetamido]benzoate (HFP034)-on psoriasis amelioration in a mouse model. The results showed that topical treatment with both compounds could attenuate epidermal thickness and scaling in an imiquimod (IMQ)-induced psoriasis mouse model via decreased expression of cytokines and chemokines [C-X-C chemokine ligand (CXCL)1 and CXCL2], leading to the reduction of neutrophilic abscess in the skin. The in vivo cutaneous absorption of HFP034 was 7.6-fold greater than that of HFP031. Both compounds caused negligible irritation on healthy mouse skin. In addition, we examined the effect of the anthranilate derivatives on chemokine expression in IMQ-treated HaCaT keratinocytes. Our results elucidated a mechanism for anti-inflammatory activity of HFP034 that involved the elevation of intracellular cAMP concentration, suppression of NF-κB activity, and attenuation of neutrophil chemoattractant expression. These results suggest that HFP034 could increase the cutaneous concentration of cAMP to suppress neutrophil infiltration into the skin. Topically applied HFP034 may demonstrate a potential for future clinical application as a novel therapy for psoriasis treatment.-Lin, Z.-C., Hsieh, P.-W., Hwang, T.-L., Chen, C.-Y., Sung, C. T., Fang, J.-Y. Topical application of anthranilate derivatives ameliorates psoriatic inflammation in a mouse model by inhibiting keratinocyte-derived chemokine expression and neutrophil infiltration.

Liver kinase B1/AMP-activated protein kinase-mediated regulation by gentiopicroside ameliorates P2X7 receptor-dependent alcoholic hepatosteatosis

BACKGROUND AND PURPOSE

Regulating P2X7 receptor-mediated activation of NLRP3 inflammasomes could be a therapeutic strategy to treat alcoholic hepatosteatosis. We investigated whether this process was modulated by gentiopicroside, the main active secoiridoid glycoside from Gentiana manshurica Kitagawa.

EXPERIMENTAL APPROACH

In vivo models of acute and chronic alcoholic hepatosteatosis were established by intragastrically administered ethanol or using chronic plus binge ethanol feeding of Lieber-DeCarli liquid diet to male C57BL/6 mice. In vitro, HepG2 cells were treated with ethanol. RAW 264.7 macrophages and murine bone marrow-derived macrophages (BMDMs) were stimulated with LPS and ATP.

KEY RESULTS

In both the acute and chronic alcohol-induced mouse hepatosteatosis models, gentiopicroside decreased serum aminotransferases and triglyceride accumulation. Up-regulated SREBP1, down-regulated PPARα and phosphorylated acetyl-CoA carboxylase caused by acute and chronic alcohol feeding were modulated by gentiopicroside, through the elevation of LKB1 and AMPK. Suppression of P2X7 receptor-NLRP3 activation by gentiopicroside inhibited IL-1β production. In ethanol-exposed HepG2 cells, gentiopicroside reduced lipogenesis and promoted lipid oxidation via activation of P2X7 receptor-NLRP3 inflammasomes. Genetic or pharmacological blockade of P2X7 receptors enhanced AMPK activity and reduced SREBP1 expression in ethanol-treated HepG2 cells. Gentiopicroside down-regulated P2X7 receptor-mediated inflammatory responses in LPS/ATP-stimulated RAW 264.7 macrophages and BMDMs. IL-1β from macrophages accelerated lipid accumulation in hepatocytes. Depleting macrophages by clodronate liposomes ameliorated alcoholic hepatosteatosis, and it was further alleviated by gentiopicroside.

CONCLUSIONS AND IMPLICATIONS

Activation of LKB1/AMPK signalling by gentiopicroside was mediated by the P2X7 receptor-NLRP3 inflammasome, suggesting the therapeutic value of blocking P2X7 receptors in the treatment of alcoholic hepatosteatosis.

Contribution of In Vivo and Organotypic 3D Models to Understanding the Role of Macrophages and Neutrophils in the Pathogenesis of Psoriasis

Psoriasis, a common chronic immune-mediated skin disease, is histologically characterized by a rapid keratinocyte turnover and differentiation defects. Key insights favor the idea that T cells are not the only key actors involved in the inflammatory process. Innate immune cells, more precisely neutrophils and macrophages, provide specific signals involved in the initiation and the maintenance of the pathogenesis. Current data from animal models and, to a lesser extent, three-dimensional in vitro models have confirmed the interest in leaning towards other immune cell types as a potential new cellular target for the treatment of the disease. Although these models do not mimic the complex phenotype nor all human features of psoriasis, their development is necessary and essential to better understand reciprocal interactions between skin cells and innate immune cells and to emphasize the crucial importance of the local lesional microenvironment. In this review, through the use of in vivo and 3D organotypic models, we aim to shed light on the crosstalk between epithelial and immune components and to discuss the role of secreted inflammatory molecules in the development of this chronic skin disease.

Exacerbation and Prolongation of Psoriasiform Inflammation in Diabetic Obese Mice: A Synergistic Role of CXCL5 and Endoplasmic Reticulum Stress

Accumulating evidence suggests that psoriasis is frequently accompanied by metabolic disorders, such as obesity and diabetes. However, the mechanisms underlying the association between increased psoriasis severity and concomitant metabolic syndrome have not been fully clarified. Herein, we show that imiquimod-induced psoriasiform inflammation was exacerbated and prolonged in diabetic obese mice compared to that in control mice, accompanied by remarkably increased lesional expressions of Cxcl5 and Il-1b. Notably, a large number of CXCL5⁺ Ly6G⁺ cells infiltrated the dermis and subcutaneous fat tissue of the diabetic obese mice. Most macrophages in the subcutaneous fat tissues of the diabetic obese mice were positive for expression of IL-1β and GRP78/Bip, an endoplasmic reticulum stress marker. Depletion of Ly6G⁺ cells and macrophages diminished the imiquimod-induced psoriasiform inflammation. Further, CXCL5 potentiated the secretion of IL-1β from macrophages and palmitic acid, a fatty acid released from subcutaneous adipocytes, further enhanced IL-1β secretion via endoplasmic reticulum stress induction. Combined with the fact that the serum levels of both CXCL5 and palmitic acid are significantly elevated in patients with metabolic syndrome, our results suggest a role for CXCL5 and endoplasmic reticulum stress in the increase of psoriasis severity of patients with concomitant metabolic syndrome.

GM-CSF in murine psoriasiform dermatitis: Redundant and pathogenic roles uncovered by antibody-induced neutralization and genetic deficiency

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic, Th17-derived cytokine thought to critically contribute to the pathogenesis of diverse autoimmune diseases, including rheumatoid arthritis and psoriasis. Treatment with monoclonal antibodies that block GM-CSF activity is associated with favorable therapeutic effects in patients with rheumatoid arthritis. We evaluated the role of GM-CSF as a potential target for therapeutic interference in psoriasis using a combined pharmacologic and genetic approach and the mouse model of imiquimod-induced psoriasiform dermatitis (IMQPD). Neutralization of murine GM-CSF by an anti-GM-CSF antibody ameliorated IMQPD. In contrast, genetic deficiency in GM-CSF did not alter the course of IMQPD, suggesting the existence of mechanisms compensating for chronic, but not acute, absence of GM-CSF. Further investigation uncovered an alternative pathogenic pathway for IMQPD in the absence of GM-CSF characterized by an expanded plasmacytoid dendritic cell population and release of IFNα and IL-22. This pathway was not activated in wild-type mice during short-term anti-GM-CSF treatment. Our investigations support the potential value of GM-CSF as a therapeutic target in psoriatic disease. The discovery of an alternative pathogenic pathway for psoriasiform dermatitis in the permanent absence of GM-CSF, however, suggests the need for monitoring during therapeutic use of long-term GM-CSF blockade.

Role of MyD88 signaling in the imiquimod-induced mouse model of psoriasis: focus on innate myeloid cells

Psoriasis is a chronic skin disease associated with deregulated activation of immune cells and keratinocytes. In this study, we used the imiquimod (IMQ)-induced mouse model of psoriasis to dissect better the contribution of hematopoietic and skin-resident stromal cells to psoriasis development. The comparison of disease development in mice carrying the hematopoietic cell-specific deletion of MyD88 (Myd88^fl/flVav-cre⁺ mice) with mice carrying the total MyD88 deficiency (Myd88^-/- mice), we show that the progression of skin and systemic inflammation, as well as of epidermal thickening, was completely dependent on MyD88 expression in hematopoietic cells. However, both Myd88^-/- mouse strains developed some degree of epidermal thickening during the initial stages of IMQ-induced psoriasis, even in the absence of hematopoietic cell activation and infiltration into the skin, suggesting a contribution of MyD88-independent mechanisms in skin-resident stromal cells. With the use of conditional knockout mouse strains lacking MyD88 in distinct lineages of myeloid cells (Myd88^fl/flLysM-cre⁺ and Myd88^fl/flMRP8-cre⁺ mice), we report that MyD88 signaling in monocytes and Mϕ, but not in neutrophils, plays an important role in disease propagation and exacerbation by modulating their ability to sustain γδ T cell effector functions via IL-1β and IL-23 production. Overall, these findings add new insights into the specific contribution of skin-resident stromal vs. hematopoietic cells to disease initiation and progression in the IMQ-induced mouse model of psoriasis and uncover a potential novel pathogenic role for monocytes/Mϕ to psoriasis development.

Inhibitory Effect of Imiquimod-Induced Psoriasis-Like Skin Inflammation in Mice by Histamine H4 Receptor Agonist 4-Methylhistamine

Psoriasis is a chronic inflammatory immune-mediated autoimmune skin disorder. The histamine H4 receptor (H4R) agonist 4-methylhistamine (4-MH) plays an important role in immunomodulation of inflammatory responses associated with allergic inflammatory diseases. In this study, we investigated the effects of H4R agonist 4-MH on the development of imiquimod (IMQ)-induced psoriasis-like skin inflammation in mice and explored the immunoregulatory mechanism involved. The total clinical severity scores were significantly ameliorated by treatment with 4-MH (20 mg/kg) and 4-MH (40 mg/kg). Histological analysis of the skin revealed that 4-MH (20 mg/kg) and 4-MH (40 mg/kg) significantly attenuated the psoriatic phenotypes, including epidermal hyperplasis, hyperkeratosis and lymphocytes infiltration. Treatment with 4-MH (20 mg/kg) and 4-MH (40 mg/kg) led to reductions in the levels of Th1 cytokines (TNF-α, IFN-α, and IL-27) in the serum and dorsal skin, whereas Th17 cytokines levels (IL-17A and IL-23) did not change in response to treatment with 4-MH (20 mg/kg) and 4-MH (40 mg/kg). Furthermore, the number of CD4(+) CD25(+) FoxP3(+) regulatory T (Treg) cells was significantly increased by treatment with 4-MH (40 mg/kg). Taken together, these results imply that H4R agonist 4-MH might be an effective immunomodulatory approach for treatment of patients with psoriasis and the effects may be related to inhibited epidermal alteration, selectively reduced Th1 pro-inflammatory cytokines, and recruited CD4(+) CD25(+) FoxP3(+) Treg cells.

Monocyte-derived inflammatory Langerhans cells and dermal dendritic cells mediate psoriasis-like inflammation

Dendritic cells (DCs) have been implicated in the pathogenesis of psoriasis but the roles for specific DC subsets are not well defined. Here we show that DCs are required for psoriasis-like changes in mouse skin induced by the local injection of IL-23. However, Flt3L-dependent DCs and resident Langerhans cells are dispensable for the inflammation. In epidermis and dermis, the critical DCs are TNF-producing and IL-1β-producing monocyte-derived DCs, including a population of inflammatory Langerhans cells. Depleting Ly6C^hi blood monocytes reduces DC accumulation and the skin changes induced either by injecting IL-23 or by application of the TLR7 agonist imiquimod. Moreover, we find that IL-23-induced inflammation requires expression of CCR6 by DCs or their precursors, and that CCR6 mediates monocyte trafficking into inflamed skin. Collectively, our results imply that monocyte-derived cells are critical contributors to psoriasis through production of inflammatory cytokines that augment the activation of skin T cells.

Imiquimod exacerbates IL-23-induced skin inflammation and models psoriasis in mice. Here the authors show that this pathology is not dependent on resident dendritic cells, but on CCR6-induced immigration of monocyte-derived cells.

Imiquimod Treatment Causes Systemic Disease in Mice Resembling Generalized Pustular Psoriasis in an IL-1 and IL-36 Dependent Manner

Generalized pustular psoriasis (GPP) is a severe form of psoriasis that can be caused by missense mutations in the interleukin-36 (IL-36) receptor antagonist. In addition to neutrophil rich skin inflammation, GPP patients typically also experience anorexia, fever, malaise, and pain. The imiquimod-induced skin inflammation mouse model has rapidly become a popular way to study plaque psoriasis, which typically does not involve symptoms of systemic disease. In this model, neutrophil recruitment to the skin is dependent upon the inflammatory mediators IL-1, via its receptor IL-1R1, and IL-36α. Unexpectedly, we observed that mice also exhibited signs of anorexia (weight loss and decreased food intake), general malaise (decreased activity and loss of interest in building nests), and pain (nose bulging and hunched posture). A scoring system allowing quantitative comparisons of test groups was developed. Female mice were found to develop more severe disease than male mice. Furthermore, mice deficient in both IL-1R1 and IL-36α are nearly disease-free, while mice lacking only one of these inflammatory mediators have less severe disease than wild type mice. Hence, the imiquimod-induced skin inflammation mouse model recapitulates not only plaque psoriasis, but also the more severe symptoms, that is, anorexia, malaise, and pain, seen in GPP.

Mouse model of imiquimod-induced psoriatic itch

Itch is a major indicator of psoriasis, but the underlying mechanisms behind this symptom are largely unknown. To investigate the neuronal mechanisms of psoriatic itch, we tested whether mice subjected to the imiquimod-induced psoriasis model exhibit itch-associated behaviors. Mice received daily topical applications of imiquimod to the rostral back skin for 7 days. Imiquimod-treated mice exhibited a significant increase in spontaneous scratching behavior directed to the treated area as well as touch-evoked scratching (alloknesis). To characterize this model, we measured the mRNA expression levels of pruritogens and itch-relevant receptors/channels using real-time reverse transcription PCR. The mRNA expression of MrgprA3, MrgprC11, and MrgprD decreased gradually over time in the dorsal root ganglion (DRG) cells. There was no significant change in the mRNA expression of TRPV1 or TRPA1 in DRG cells. TRPV4 mRNA expression was transiently increased in the DRG cells, whereas TRPM8 mRNA was significantly decreased. The mRNA expression levels of histidine decarboxylase and tryptophan hydroxylase 1, as well as the intensity of histamine and serotonin immunoreactivity, were transiently increased in the skin on day 2, returning to baseline by day 7. Histamine H1-receptor antagonists, chlorpheniramine and olopatadine, significantly inhibited spontaneous scratching on day 2, but not day 7. Neither chlorpheniramine nor olopatadine affected alloknesis on day 2 or day 7. These results may reflect the limited antipruritic effects of histamine H1-receptor antagonists on human psoriasis. The imiquimod-induced psoriasis model seems to be useful for the investigation of itch and its sensitization in psoriasis.

IMQ Induced K14-VEGF Mouse: A Stable and Long-Term Mouse Model of Psoriasis-Like Inflammation

An imiquimod (IMQ) induced wild type (WT) mouse can mimic some features of psoriasis, such as thickened skin, abnormal keratinocyte-related proteins, infiltration of inflammatory cells and pro-inflammatory cytokines. This model is a prevalent model that is widely used in the study of psoriasis. However, skin inflammation decreases during the eighth day when IMQ is given to WT mice, which may result in false results when evaluating the pharmacodynamics effects of a drug. To extend the timeliness and inherit the advantages of this model, we applied IMQ to the skin of 8-week-old homozygous K14-VEGF mice to investigate whether IMQ can prolong mice ear inflammation. In our experiments, we found that, compared to the IMQ induced WT mice model, the IMQ induced K14-VEGF mice have serious skin inflammation, even on the fourteenth day. We also evaluated the stability of skin inflammation at days 8, 10, and 13, and the inflammatory situation remained stable in the skin. This research intends to improve the existing model, and we hypothesize that the IMQ induced K14-VEGF mouse will become a practical mouse model in psoriasis research.

IMQ-induced skin inflammation in mice is dependent on IL-1R1 and MyD88 signaling but independent of the NLRP3 inflammasome

The pathogenesis of inflammatory skin diseases such as psoriasis involves the release of numerous proinflammatory cytokines, including members of the IL-1 family. Here we report overexpression of IL-1α, IL-1β, and IL-1 receptor antagonist mRNA, associated to expression of IL-23p19, IL-17A, and IL-22 in skin cells, upon topical application of the TLR7 agonist imiquimod (IMQ) in C57BL/6J mice. IMQ-induced skin inflammation was partially reduced in mice deficient for both IL-1α/IL-1β or for IL-1 receptor type 1 (IL-1R1), but not in IL-1α- or IL-1β-deficient mice, demonstrating the redundant activity of IL-1α and IL-1β for skin inflammation. NLRP3 or apoptosis-associated Speck-like protein containing a Caspase recruitment domain-deficient mice had no significant reduction of skin inflammation in response to IMQ treatment, mainly due to the redundancy of IL-1α. However, IMQ-induced skin inflammation was abolished in the absence of MyD88, the adaptor protein shared by IL-1R and TLR signaling pathways. These results are consistent with the TLR7 dependence of IMQ-induced skin inflammation. Thus, IL-1R1 contributes to the IMQ-induced skin inflammation, and disruption of MyD88 signaling completely abrogates this response.

Unprocessed Interleukin-36α Regulates Psoriasis-Like Skin Inflammation in Cooperation With Interleukin-1

Generalized pustular psoriasis is a severe skin disease characterized by epidermal hyperplasia, neutrophil-rich abscesses within the epidermis, and a mixed inflammatory infiltrate in the dermis. The disease may be caused by missense mutations in the IL-36 receptor antagonist, IL-36Ra. Curiously, the related IL-1Ra has therapeutic effects in some of these latter patients. Here, using an experimental mouse model of psoriasiform skin inflammation, we demonstrate in vivo connections between IL-36 and IL-1 expression. After disease initiation, IL-36α-deficient mice exhibited dramatically diminished skin pathology, including absence of epidermal neutrophils, reduced keratinocyte acanthosis, and less dermal edema. In contrast, IL-36β and IL-36γ knockout mice developed disease indistinguishable from that of wild-type mice. The endogenous IL-36α was not processed through proteolysis. Although IL-36α expression was strongly induced in an IL-1 signaling-dependent manner during disease, expression of IL-1α was also dependent upon IL-36α. Hence, after being upregulated by IL-1α, IL-36α acts through a feedback mechanism to boost IL-1α levels. Analyses of double knockout mice further revealed that IL-36α and IL-1α cooperate to promote psoriasis-like disease. In conclusion, IL-1α and IL-36α form a self-amplifying inflammatory loop in vivo that in patients with insufficient counter regulatory mechanisms may become hyper-engaged and/or chronic.

Therapeutic and immunomodulatory effects of glucosamine in combination with low-dose cyclosporine a in a murine model of imiquimod-induced psoriasis

Although cyclosporine A (CsA) is a potent immunomodulating agent and is commonly used as a systemic agent for the management of psoriasis patients, current clinical treatments are not always effective due to the clinical inefficacy of low-doses and numerous harmful effects of higher doses. Currently, the combined use of two other systemic drugs often has better therapeutic efficacy and is safer than low or high dose of a single drug. Glucosamine (Glu) also has immunomodulatory properties for autoimmune diseases. The aims of our study were to investigate the therapeutic efficacy of Glu in combination with low-dose CsA on imiquimod (IMQ)-induced psoriasis-like dermatitis in mice and to determine its immunomodulatory mechanism. We found that combined treatment with Glu (300 mg/kg) and low-dose (10 or 20mg/kg) CsA strongly ameliorated the development of psoriasis-like skin lesions and reduced the levels of Th1 cytokine (TNF-α) and Th17 cytokines (IL-17, IL-22, and IL-23) in the serum and dorsal skin. Histological findings also showed that the thickening of epidermis, stratum corneum, and inflammatory cell infiltration. Particularly, these combined treatments increased the number of CD4(+)CD25(+) regulatory T (Treg) cells in splenic. These results suggest that use of a combination of each drug might be used as an efficacious and safe alternative therapeutic strategy, as well as may provide an immunomodulatory approach for T cell-mediated autoimmune diseases, including psoriasis.