An analysis of IL-36 signature genes and individuals with IL1RL2 knockout mutations validates IL-36 as a psoriasis therapeutic target

NETs contribute to psoriasiform skin inflammation: A novel therapeutic approach targeting IL-36 cytokines by a small molecule tetrahydroxystilbene glucoside

BACKGROUND

Psoriasis, a chronic immune-mediated skin disease with pathological features such as aberrant differentiation of keratinocytes, dermal-epidermal inflammation, and angiogenesis. 2,3,5,4'-Tetrahydroxy stilbene 2-Ο-β-d-glucoside (2354Glu) is a natural small molecule polyhydrostilbenes isolated from Polygonum multiglorum Thunb. The regulation of IL-36 subfamily has led to new pharmacologic strategies to reverse psoriasiform dermatitis.

PURPOSE

Here we investigated the therapeutic potential of 2354Glu and elucidated the underlying mechanism in psoriasis.

METHODS

The effects of 2354Glu on IL-36 signaling were assessed by psoriasiform in vivo, in vitro and ex vivo model. The in vivo mice model of psoriasis-like skin inflammation was established by applying imiquimod (IMQ), and the in vitro and ex vitro models were established by stimulating mouse primary keratinocyte, human keratinocytes cells (HaCaT) and ex vivo skin tissue isolated from the mice back with Polyinosine-polycytidylic acid (Poly(I:C)), IMQ, IL-36γ and Lipopolysaccharide (LPS) respectively. Moreover, NETs formation was inhibited by Cl-amidine to evaluate the effect of NETs in psoriatic mouse model. The effects of 2354Glu on skin inflammation were assessed by western blot, H&E, immunohistochemistry, immunofluorescence, enzyme-linked immunosorbent assay and real-time quantitative PCR.

RESULTS

In Poly(I:C)-stimulated keratinocytes, the secretion of IL-36 was inhibited after treatment with 2354Glu, similar to the effects of TLR3, P2X7R and caspase-1 inhibitors. In aldara (imiquimod)-induced mice, 2354Glu (100 and 25 mg/kg) improved immune cell infiltration and hyperkeratosis in psoriasis by directly targeting IL-36 in keratinocytes through P2X7R-caspase-1. When treatment with 2354Glu (25 mg/kg) was insufficient to inhibit IL-36γ, NETs reduced pathological features and IL-36 signaling by interacting with keratinocytes to combat psoriasis like inflammation.

CONCLUSION

These results indicated that NETs had a beneficial effect on psoriasiform dermatitis. 2354Glu alleviates psoriasis by directly targeting IL-36/P2X7R axis and NET formation, providing a potential candidate for the treatment of psoriasis.

Targeting the STAT3/IL-36G signaling pathway can be a promising approach to treat rosacea

BACKGROUND

Rosacea is an inflammatory skin disorder characterized by the release of inflammatory mediators from keratinocytes, which are thought to play a crucial role in its pathogenesis. Despite an incidence of approximately 5.5%, rosacea is associated with a poor quality of life. However, as the pathogenesis of rosacea remains enigmatic, treatment options are limited.

OBJECTIVES

To investigate the pathogenesis of rosacea and explore new therapeutic strategies.

METHODS

Transcriptome data from rosacea patients combined with immunohistochemical staining were used to investigate the activation of STAT3 in rosacea. The role of STAT3 activation in rosacea was subsequently explored by inhibiting STAT3 activation both in vivo and in vitro. The key molecules downstream of STAT3 activation were identified through data analysis and experiments. Dual-luciferase assay and ChIP-qPCR analysis were used to validate the direct binding of STAT3 to the IL-36G promoter. DARTS, in combination with experimental screening, was employed to identify effective drugs targeting STAT3 for rosacea treatment.

RESULTS

STAT3 signaling was hyperactivated in rosacea and served as a promoter of the keratinocyte-driven inflammatory response. Mechanistically, activated STAT3 directly bind to the IL-36G promoter region to amplify downstream inflammatory signals by promoting IL-36G transcription, and treatment with a neutralizing antibody (α-IL36γ) could mitigate rosacea-like inflammation. Notably, a natural plant extract (pogostone), which can interact with STAT3 directly to inhibit its activation and affect the STAT3/IL36G signaling pathway, was screened as a promising topical medication for rosacea treatment.

CONCLUSIONS

Our study revealed a pivotal role for STAT3/IL36G signaling in the development of rosacea, suggesting that targeting this pathway might be a potential strategy for rosacea treatment.

Dynamics of a network mediated by IL-36 and involved in the pathogenesis of psoriasis

The pathogenesis of the inflammatory, chronic, and common skin disease psoriasis involves immune cells, skin cells (keratinocytes), and the cytokines they secrete. Hyperproliferation and abnormal differentiation of keratinocytes are hallmarks of the disease. The roles of cytokines such as TNFα, IL-15, IL-17, and IL-23 in psoriasis have been studied through mathematical/computational models as well as experiments. However, the role of proinflammatory cytokine IL-36 in the onset and progression of psoriasis is still elusive. To explore the role of IL-36, we construct a network embodying indirect cell-cell interactions of a few immune and skin cells mediated by IL-36 based on existing knowledge. We also develop a mathematical model for the network and perform a global sensitivity analysis. Our results suggest that the model is most sensitive to a parameter that represents the level of cytokine IL-36. In addition, a steady-state analysis of the model suggests that an increase in the level of IL-36 could lead to the hyperproliferation of keratinocytes and, thus, psoriasis. Our analysis also highlights that the plaque formation and progression of psoriasis could occur through either a gradual or a switch-like increase in the keratinocyte population. We propose that the switch-like increase would be due to a bistable behavior of the network toward either a psoriatic or healthy state and could be used as a novel treatment strategy.

Spesolimab in the Management of Generalized Pustular Psoriasis With Concurrent Bullous Pemphigoid and Psoriasis

Autoimmune diseases often co-occur due to shared immunological mechanisms, necessitating strategic treatment approaches to manage overlapping conditions without exacerbating each other. A 75-year-old male with a history of psoriasis vulgaris and bullous pemphigoid (BP) developed new-onset pustular psoriasis under systemic corticosteroid therapy, which is known to potentially worsen psoriasis into its pustular form. Histological examination confirmed the diagnosis, showing features typical of pustular psoriasis. The patient was successfully treated with spesolimab, an anti-IL-36 neutralizing antibody, achieving complete remission without aggravating the BP. This case highlights the necessity of cautious treatment selection in patients with multiple autoimmune disorders and underscores the potential role of IL-36 in exacerbating inflammatory responses in BP. Further research into the interaction between IL-36 and BP may provide deeper insights into managing such complex clinical scenarios.

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.

Combined inhibition of IL-1, IL-33 and IL-36 signalling by targeting IL1RAP ameliorates skin and lung fibrosis in preclinical models of systemic sclerosis

BACKGROUND

The interleukin (IL)-1 receptor accessory protein (IL1RAP) is an essential coreceptor required for signalling through the IL-1, IL-33 and IL-36 receptors. Here, we investigate the antifibrotic potential of the combined inhibition of these cytokines by an anti-IL1RAP antibody to provide a scientific background for clinical development in systemic sclerosis (SSc).

METHODS

The expression of IL1RAP-associated signalling molecules was determined by data mining of publicly available RNA sequencing (RNAseq) data as well as by imaging mass cytometry. The efficacy of therapeutic dosing of anti-IL1RAP antibodies was determined in three complementary mouse models: sclerodermatous chronic graft-versus-host disease (cGvHD), bleomycin-induced dermal fibrosis model and topoisomerase-I (topo)-induced fibrosis.

RESULTS

SSc skin showed upregulation of IL1RAP and IL1RAP-related signalling molecules on mRNA and protein level compared with normal skin. IL-1, IL-33 and IL-36 all regulate distinct gene sets related to different pathophysiological processes in SSc. The responses of human fibroblasts and endothelial cells to IL-1, IL-33 and IL-36 were completely blocked by treatment with an anti-IL1RAP antibody in vitro. Moreover, anti-IL1RAP antibody treatment reduced dermal and pulmonary fibrosis in cGvHD-induced, bleomycin-induced and topoisomerase-induced fibrosis. Importantly, RNAseq analyses revealed effects of IL1RAP inhibition on multiple processes related to inflammation and fibrosis that are also deregulated in human SSc skin.

CONCLUSION

This study provides the first evidence for the therapeutic benefits of targeting IL1RAP in SSc. Our findings have high translational potential as the anti-IL1RAP antibody CAN10 has recently entered a phase one clinical trial.

The implications of exosomes in psoriasis: disease: emerging as new diagnostic markers and therapeutic targets

As the largest human organ, the skin is continuously exposed to various external and internal triggers that affect body homeostasis. Psoriasis is a persistent inflammatory skin condition that has a major bearing on patients' physiological functioning as well as their mental well-being. It is an autoimmune disorder and has been the focus of extensive research efforts in recent years. Cells secrete exosomes into the environment surrounding them, which comprises a lipid bilayer. The movement of cellular components like microRNAs, mRNAs, DNA, lipids, metabolites, and cell-surface proteins is mediated by exosomes. Exosomes are crucial for inducing communication between cells. There has been extensive study of exosomes, both preclinical and clinical, looking at their potential role in autoimmune diseases. Besides the role that they play in the body's basic processes, exosomes are also considered an increasingly essential part as diagnostic and therapeutic agents. In the following article, we conduct a literature review of current studies related to molecular and structural aspects of exosomes. We emphasis on the function of exosomes in pathogenesis, as well as the possibility of their usage in medicinal applications and as biomarkers.

Treatment of Severe Palmoplantar Pustular Psoriasis With Bimekizumab

Importance

Palmoplantar pustulosis (PPP) and palmoplantar plaque psoriasis with pustules remain challenging to treat. Studies suggest that an interleukin 17 or interleukin 36 loop acts synergistically in these diseases to induce palmoplantar pustules.

Objective

To assess the effectiveness of bimekizumab in treating PPP and palmoplantar plaque psoriasis with pustules.

Design, Setting, and Participants

This case series involved 21 adults with PPP (11 patients) or palmoplantar plaque psoriasis with pustules (10 patients) treated at 1 of 7 tertiary dermatological centers in France from September 2022 through June 2023. All patients treated with bimekizumab for at least 3 months were included in the analyses.

Main Outcomes and Measures

The main outcome was the posttreatment Investigator Global Assessment (IGA), scored as 0 (complete clearance), 1 (almost clear), 2 (mild), 3 (moderate), or 4 (severe). When relevant, evolution of joint pain and nail involvement was reported. Tolerance and potential adverse events were noted.

Results

A total of 21 patients (mean [range] age, 46 [24-68] years; 19 females) were included. Eleven patients had isolated PPP, and 10 had palmoplantar plaque psoriasis with pustules. All of them, except 2 who received bimekizumab as first systemic therapy, had not responded to at least 1 systemic treatment (median [range], 3 [1-7] treatments), and/or had adverse events leading to the discontinuation of the treatment. Complete clearance (IGA score, 0) was achieved by 17 patients in 1 to 4 months. Three patients achieved an IGA score of 1, and 1 achieved an IGA score of 2. Three patients with PPP also presented with acrodermatitis continua of Hallopeau. Nail involvement showed 50% to 70% improvement after 4 to 6 months of bimekizumab treatment for these 3 patients. Two patients had SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome; both had complete clearance of skin lesions associated with joint pain improvement. Four patients (19%) with candidiasis were successfully treated with oral antifungal agents. None of the patients had to stop bimekizumab treatment due to adverse events.

Conclusions and Relevance

The findings of this case series suggest that bimekizumab could be an appealing approach for treating PPP, palmoplantar plaque psoriasis with pustules, and SAPHO syndrome. Prospective randomized placebo-controlled clinical trials are needed to confirm these encouraging initial results.

Emerging Role of the IL-36/IL-36R Axis in Multiple Inflammatory Skin Diseases

IL-36 is a most recent member of the IL-1 cytokine family, primarily expressed at barrier sites of the body such as the skin, lungs, and intestine. It plays a vital role in inflammation and is implicated in the development of various cutaneous; intestinal; and pulmonary disorders, including psoriasis, inflammatory bowel disease, and chronic obstructive pulmonary disease. IL-36 comprises 4 isoforms: the proinflammatory IL-36α, IL-36β, and IL-36γ and the anti-inflammatory IL-36R antagonist. An imbalance between proinflammatory and anti-inflammatory IL-36 isoforms can contribute to the inflammatory fate of cells and tissues. IL-36 cytokines signal through an IL-36R heterodimer mediating their function through canonical signaling cacade, including the NF-B pathway. Prominent for its role in psoriasis, IL-36 has recently been associated with disease mechanisms in atopic dermatitis, hidradenitis suppurativa, neutrophilic dermatoses, autoimmune blistering disease, and Netherton syndrome. The major cutaneous source of IL-36 cytokines is keratinocytes, pointing to its role in the communication between the epidermis, innate (neutrophils, dendritic cells) immune system, and adaptive (T helper [Th]1 cells, Th17) immune system. Thus, cutaneous IL-36 signaling is crucial for the immunopathological outcome of various skin diseases. Consequently, the IL-36/IL-36R axis has recently been recognized as a promising drug target for the treatment of inflammatory disorders beyond psoriasis. This review summarizes the current update on IL-36 cytokines in inflammatory skin diseases.

Microglial immunometabolism endophenotypes contribute to sex difference in Alzheimer's disease

INTRODUCTION

The molecular mechanisms that contribute to sex differences, in particular female predominance, in Alzheimer's disease (AD) prevalence, symptomology, and pathology, are incompletely understood.

METHODS

To address this problem, we investigated cellular metabolism and immune responses ("immunometabolism endophenotype") across AD individuals as a function of sex with diverse clinical diagnosis of cognitive status at death (cogdx), Braak staging, and Consortium to Establish a Registry for AD (CERAD) scores using human cortex metabolomics and transcriptomics data from the Religious Orders Study / Memory and Aging Project (ROSMAP) cohort.

RESULTS

We identified sex-specific metabolites, immune and metabolic genes, and pathways associated with the AD diagnosis and progression. We identified female-specific elevation in glycerophosphorylcholine and N-acetylglutamate, which are AD inflammatory metabolites involved in interleukin (IL)-17 signaling, C-type lectin receptor, interferon signaling, and Toll-like receptor pathways. We pinpointed distinct microglia-specific immunometabolism endophenotypes (i.e., lipid- and amino acid-specific IL-10 and IL-17 signaling pathways) between female and male AD subjects. In addition, female AD subjects showed evidence of diminished excitatory neuron and microglia communications via glutamate-mediated immunometabolism.

DISCUSSION

Our results point to new understanding of the molecular basis for female predominance in AD, and warrant future independent validations with ethnically diverse patient cohorts to establish a likely causal relationship of microglial immunometabolism in the sex differences in AD.

HIGHLIGHTS

Sex-specific immune metabolites, gene networks and pathways, are associated with Alzheimer's disease pathogenesis and disease progression. Female AD subjects exhibit microglial immunometabolism endophenotypes characterized by decreased glutamate metabolism and elevated interleukin-10 pathway activity. Female AD subjects showed a shift in glutamate-mediated cell-cell communications between excitatory neurons to microglia and astrocyte.

Spesolimab for the Treatment of Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a rare but severe skin inflammatory disorder characterized by the eruption of widespread sterile neutrophilic pustules, often accompanied by systemic inflammation. Given its life-threatening potential, GPP requires prompt accurate diagnosis and effective treatment, but its rarity and relapsing-remitting nature pose challenges in performing large-scale randomized controlled clinical trials. Established international guidelines are currently lacking and management guidance often follows that for plaque psoriasis. However, while it can co-exist with plaque psoriasis and has traditionally been classified as a most severe form of psoriasis, GPP is now recognized as a distinct entity, with its own clinicopathological, autoinflammatory, immunologic and genetic features. Research conducted over the past decade revealed that an imbalance of interleukin (IL)-36 signaling favoring the proinflammatory activity is the central driver of the pathogenesis of GPP, thereby laying the groundwork for the development of targeted therapies for the disease. This article reviews the evidence thus far on spesolimab, a selective humanized antibody against the IL-36 receptor that was recently licensed in Europe and the United States for the treatment of GPP flares in adults. In phase II, randomized controlled clinical trials, spesolimab led to rapid and effective skin clearance in patients experiencing a GPP flare and demonstrated superiority to placebo in preventing flares for up to 48 weeks with maintenance treatment, with reassuring safety and tolerability profiles. Spesolimab is considered to be a first-in-class medication establishing itself as the standard of care for the treatment of GPP flares, thus changing the paradigm of the management of GPP to a new era of scientifically- and evidence-based targeted therapy for this distinctive disease.

In Silico and In Vitro Analysis of IL36RN Alterations Reveals Critical Residues for the Function of the Interleukin-36 Receptor Complex

Generalized pustular psoriasis is a potentially life-threatening skin disease, associated with IL36RN disease alleles. IL36RN encodes the IL-36 receptor antagonist (IL-36Ra), a protein that downregulates the activity of IL-36 cytokines by blocking their receptor (IL-36R). Although generalized pustular psoriasis can be treated with IL-36R inhibitors, the structural underpinnings of the IL-36Ra/IL-36R interaction remain poorly understood. In this study, we sought to address this question by systematically investigating the effects of IL36RN sequence changes. We experimentally characterized the effects of 30 IL36RN variants on protein stability. In parallel, we used a machinelearning tool (Rhapsody) to analyze the IL-36Ra three-dimensional structure and predict the impact of all possible amino acid substitutions. This integrated approach identified 21 amino acids that are essential for IL-36Ra stability. We next investigated the effects of IL36RN changes on IL-36Ra/IL-36R binding and IL-36R signaling. Combining invitro assays and machine learning with a second program (mCSM), we identified 13 amino acids that are critical for IL-36Ra/IL36R engagement. Finally, we experimentally validated three representative predictions, further confirming the reliability of Rhapsody and mCSM. These findings shed light on the structural determinants of IL-36Ra activity, with potential to facilitate the design of new IL-36 inhibitors and aid the interpretation of IL36RN variants in diagnostic settings.

Architecture of skin inflammation in psoriasis revealed by spatial transcriptomics

Psoriasis is a chronic inflammatory skin disease, thought to be predominantly mediated by TH17 cells. Significance of other inflammatory pathways and the innate immune system is not well understood and the spatial heterogeneity of inflammation in the skin has largely been overlooked. Our aim was to create a comprehensive map of skin inflammation in psoriasis, exploring the tissue patterning of inflammation. In situ whole transcriptome sequencing (spatial sequencing) was performed on lesional psoriatic skin in four patients with moderate-to-severe disease to quantify all expressed genes within a tissue section. Transcriptional analysis revealed three major inflammatory niches in psoriasis skin, each with distinct cytokine circuits and chemokines: the hyperplastic epidermis, upper (papillary) dermis, and reticular dermis. Interestingly, key cytokines such as IL-23, IL-17 s, and TNFα were not notably present in the skin's transcriptomic signature. Unexpectedly, IL-32 showed strong expression in the dermis. Our findings underscore the complexity of psoriatic inflammation, highlighting its architectural heterogeneity and the roles of innate cytokines. Both IL-32 and IL-1 family cytokines appear to play critical roles in the dermal and epidermal inflammation, respectively, and may provide pharmacological targets to improve the control of the inflammatory process.

Efficacy and safety of biological agents to treat patients with palmoplantar pustulosis: A systematic scoping review

BACKGROUND

Palmoplantar pustulosis (PPP), a chronic, recurrent pustular dermatosis associated with erythema, scales, and sterile pustules on the palms and soles, is commonly encountered in dermatology clinics. Whether PPP is a variant of psoriasis or a distinct condition is still debated. Although biological agents have been successfully used to treat moderate-to-severe psoriasis, existing literature on PPP is limited to case reports or small case series. The lack of well-documented clinical studies makes it difficult to select the ideal treatment for this condition. This review aims to discuss the efficacy and safety of biological agents in PPP treatment based on randomized controlled trials with the hope of inspiring dermatologist clinicians to propose new therapeutic approaches.

OBJECTIVES

This review aims to obtain high-level evidence to assess the efficacy and safety of biological agents in the treatment of patients with PPP.

METHODS

We searched the PubMed, Embase, and Cochrane databases up to May 18, 2023, for high-quality randomized controlled trials that reported at least one adverse event after PPP treatment with biological agents in patients > 18 years of age. RevMan 5.3 software was used for the meta-analysis.

RESULTS

Nine trials involving 799 participants were included in the analysis. We used ppPASI 75 as the primary efficacy measure. Anti-IL-23 and anti-IL-17A agents afforded 4.14-fold and 1.95-fold better outcomes than placebo treatment at weeks 16 and 12, respectively (P-value = 0.009, RR = 4.14, 95% confidence interval [CI; 1.43-11.98]; P-value = 0.02, RR = 1.95, 95% CI [1.11-3.42]). Moreover, anti-IL-23 agents at a dose of 100 mg were more effective than at 200 mg, indicating that 100 mg may be the best dose for anti-IL-23 agents. Next, we investigated the safety of biological agents for PPP treatment. The incidence of total adverse events (AEs) was 1.25 times higher for biological agents than for controls, indicating a good safety profile (RR = 1.25, P-value ＜ 0.00001, 95% CI [1.13, 1.37]). Additionally, we divided the common AEs into 16 categories and found that anti-IL-23 agents were more likely to induce infections. In conclusion, we evaluated safety and efficacy in a comprehensive comparison and found that anti-IL-23 agents conferred good clinical efficacy with a low incidence of AEs and could be recommended with caution.

LIMITATIONS

Only a few relevant, high-quality, randomized controlled trials were included in the study.

CONCLUSION

This study showed that biological agents can be used to treat patients with PPP with good efficacy; however, AEs cannot be ignored. Multi-center, high-quality clinical studies with large sample sizes are needed to further evaluate the effects and safety of biological agents in PPP treatment.

Current management of generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is a rare subset of psoriasis involving episodes of sterile pustules accompanied by inflammation and, often, systemic involvement. The inflammatory nature of GPP has potential for severe multisystem complications including high-output cardiac failure, infections, digestive system issues, and disfiguring or lethal acute flare episodes. The disease tends to have higher prevalence in females and Asians. The IL-1/IL-36 inflammatory pathway is a critical facet of GPP's pathology. Genetic mutations that are associated with GPP include modifications of Interleukin 36 Receptor Antagonist (IL36RN), Caspase Recruitment Domain Family Member 14 (CARD14), Adaptor Related Protein Complex 1 Subunit Sigma 3 (AP1S3), Myeloperoxidase (MPO) and Serpin Peptidase Inhibitor Clade A Member 3 (SERPINA3) genes. Treatment guidelines for GPP are not well-entrenched. Currently, only one GPP-specific treatment, the interleukin-36 receptor antagonist (IL-36Ra) spesolimab, has been approved for use in the United States. Additional anti-IL-36 pathway therapies are currently being developed. Other treatment options include other biologic therapies such as IL-17 inhibitors, IL-23 inhibitors and TNFα inhibitors. Non-biologic therapeutic options include retinoids, cyclosporine and methotrexate. Treatment options differ throughout the world; most countries utilize retinoids, cyclosporine and methotrexate as first-line non-biologic options. China and United Kingdom have no GPP-specific biologic therapies approved for use, while several biologic therapies are approved for use in Japan. This review aims to serve as an update on the current global management of GPP while also including relevant aspects of disease pathogenesis, diagnosis, clinical presentation, histopathology, aetiology and epidemiology.

A viewpoint on the genetic determinants of generalised pustular psoriasis

Generalised pustular psoriasis (GPP) is a rare and severe neutrophilic skin disorder, manifesting with acute episodes of pustulation and systemic upset. The discovery of recessive IL36RN mutations associated with GPP has transformed our understanding of disease drivers, paving the way for the development of targeted anti-IL36 therapeutics. In the light of these remarkable successes, this viewpoint reviews the significance of IL36RN mutations in GPP, their functional impact and their correlation with clinical phenotypes. It then covers the discovery of further genetic determinants (recessive MPO mutations) and risk factors (AP1S3 and CARD14 low-frequency variants) for the disease. It discusses the growing evidence for genetic complexity in GPP and concludes by outlining collaborative strategies that may be adopted to overcome the challenges ahead.

IL36G genetic variant is independently associated with susceptibility, severity and joint involvement in psoriasis

Psoriasis (PsO) is a chronic, immune-mediated, inflammatory and polygenic dermatosis associated with both physical and psychological burden that can be triggered by injury, trauma, infections and medications. The etiology of PsO is not fully elucidated but genetic, epigenetic and environmental factors are all likely to play a role. A case-control study was carried out to evaluate the frequency of the IL36G C>T (rs13392494) and the IL36G A>G (rs7584409) variants and their association with susceptibility, joint involvement and severity of PsO. The study included 154 patients with PsO and 154 controls from Brazilian population. The severity of PsO was assessed by the Psoriasis Area and Severity Index (PASI). The IL36G (rs13392494 and rs7584409) variants were genotyped by allelic discrimination assay using the real-time polymerase chain reaction. The association between the IL36G genetic variants and the study variables was analyzed in allelic, dominant, codominant, overdominant, recessive, and haplotype models. The main results were that PsO patients were older (p < 0.001) and had higher body mass index (p < 0.001) than controls; 95.8% of the patients had plaque PsO, 16.1% had psoriatic arthritis (PsA), and 27.9% had PASI > 10. The IL36G rs1339294 variant showed no association with PsO in all genetic models while the IL36G rs7584409 variant showed a protective effect in PsO. However, the G allele of the IL36G rs7584409 in the dominant model was positively associated with PASI > 10 (p = 0.031). Moreover, patients with the GG genotype of the IL36G rs7584409 variant had about 5.0 times more chance of PsA than those with the AA genotype (p = 0.014). Regarding the haplotypes, the C/A in a recessive model (CACA versus C/G and T/A carriers) was associated with PsO (p = 0.035) while the C/G haplotype in a dominant model (C/A carriers versus C/G and T/A carriers) showed a protective effect for PsO (p = 0.041). In conclusion, the G allele of the IL36G rs7584409 variant was associated with protection to PsO; however, in patients with PsO, this same allele was associated with moderate to severe disease and PsA. These results suggest that the IL36G rs7584409 variant may be used as a possible genetic biomarker to predict severity and joint involvement of PsO.

Genetics of Generalized Pustular Psoriasis: Current Understanding and Implications for Future Therapeutics

Psoriasis is a chronic inflammatory skin disease characterized by the appearance of clearly demarcated erythematous and scaly plaques. It can be divided into various types, including plaque, nail, guttate, inverse, and pustular psoriasis. Plaque psoriasis is the most commonly occurring type, though there is another rare but severe pustular autoinflammatory skin disease called generalized pustular psoriasis (GPP), which manifests with acute episodes of pustulation and systemic symptoms. Though the etiopathogenesis of psoriasis is not yet fully understood, a growing body of literature has demonstrated that both genetic and environmental factors play a role. The discovery of genetic mutations associated with GPP has shed light on our comprehension of the mechanisms of the disease, promoting the development of targeted therapies. This review will summarize genetic determinants as known and provide an update on the current and potential treatments for GPP. The pathogenesis and clinical presentation of the disease are also included for a comprehensive discussion.

Autonomous IL-36R signaling in neutrophils activates potent antitumor effector functions

While the rapid advancement of immunotherapies has revolutionized cancer treatment, only a small fraction of patients derive clinical benefit. Eradication of large, established tumors appears to depend on engaging and activating both innate and adaptive immune system components to mount a rigorous and comprehensive immune response. Identifying such agents is a high unmet medical need, because they are sparse in the therapeutic landscape of cancer treatment. Here, we report that IL-36 cytokine can engage both innate and adaptive immunity to remodel an immune-suppressive tumor microenvironment (TME) and mediate potent antitumor immune responses via signaling in host hematopoietic cells. Mechanistically, IL-36 signaling modulates neutrophils in a cell-intrinsic manner to greatly enhance not only their ability to directly kill tumor cells but also promote T and NK cell responses. Thus, while poor prognostic outcomes are typically associated with neutrophil enrichment in the TME, our results highlight the pleiotropic effects of IL-36 and its therapeutic potential to modify tumor-infiltrating neutrophils into potent effector cells and engage both the innate and adaptive immune system to achieve durable antitumor responses in solid tumors.

Interleukin-36 Receptor Signaling Attenuates Epithelial Wound Healing in C57BL/6 Mouse Corneas

The IL-36 cytokines are known to play various roles in mediating the immune and inflammatory response to tissue injury in a context-dependent manner. This study investigated the role of IL-36R signaling in mediating epithelial wound healing in normal (NL) and diabetic (DM) C57BL/6 mouse corneas. The rate of epithelial wound closure was significantly accelerated in IL-36 receptor-deficient (IL-36R-/-) compared to wild-type (WT) mice. Wounding increased IL-36α and -36γ but repressed IL-36R antagonist (IL-36Ra) expression in B6 mouse corneal epithelial cells. The wound-induced proinflammatory cytokines CXCL1 and CXCL2 were dampened, while the antimicrobial peptides (AMPs) S100A8 and A9 were augmented in IL-36R-/- mouse corneas. Intriguingly, the expression of AMP LCN2 was augmented at the mRNA level. LCN2 deficiency resulted in an acceleration of epithelial wound healing. IL-36R deficiency also greatly increased the healing rate of the corneal epithelial wound in DM mice. IL-36R deficiency also suppressed IL-1β, IL-1Ra, and ICAM expression in unwounded-DM mice and wounded NL corneas. Opposing IL-1β and ICAM, the expression of IL-Ra in DM corneas of IL-36R-/- mice was augmented. The presence of recombinant IL-1Ra and IL-36Ra accelerated epithelial wound closure in T1DM corneas of B6 mice. Our study revealed an unprecedented role of IL-36R signaling in controlling corneal epithelial wound healing in normal (NL) and diabetic (DM) mice. Our data suggest that IL-36Ra, similar to IL-1Ra, might be a therapeutic reagent for improving wound healing and reducing wound-associated ulceration, particularly in the cornea and potentially in the skin of DM patients.

Treg cells require Izumo1R to regulate γδT cell-driven inflammation in the skin

Izumo1R is a pseudo-folate receptor with an essential role in mediating tight oocyte/spermatozoa contacts during fertilization. Intriguingly, it is also expressed in CD4+ T lymphocytes, in particular Treg cells under the control of Foxp3. To understand Izumo1R function in Treg cells, we analyzed mice with Treg-specific Izumo1r deficiency (Iz1rTrKO). Treg differentiation and homeostasis were largely normal, with no overt autoimmunity and only marginal increases in PD1+ and CD44hi Treg phenotypes. pTreg differentiation was also unaffected. Iz1rTrKO mice proved uniquely susceptible to imiquimod-induced, γδT cell-dependent, skin disease, contrasting with normal responses to several inflammatory or tumor challenges, including other models of skin inflammation. Analysis of Iz1rTrKO skin revealed a subclinical inflammation that presaged IMQ-induced changes, with an imbalance of Rorγ+ γδT cells. Immunostaining of normal mouse skin revealed the expression of Izumo1, the ligand for Izumo1R, electively in dermal γδT cells. We propose that Izumo1R on Tregs enables tight contacts with γδT cells, thereby controlling a particular path of skin inflammation.

Targeting IL-36 in Inflammatory Skin Diseases

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily of cytokines. IL-36 cytokines are composed of three agonists (IL-36α, IL-36β, and IL-36γ) and two antagonists (IL-36 receptor antagonist [IL36Ra] and IL-38). These work in innate and acquired immunity and are known to contribute to host defense and to the pathogenesis of autoinflammatory diseases, autoimmune diseases, and infectious diseases. In the skin, IL-36α and IL-36γ are mainly expressed by keratinocytes in the epidermis, although they are also produced by dendritic cells, macrophages, endothelial cells, and dermal fibroblasts. IL-36 cytokines participate in the first-line defense of the skin against various exogenous assaults. IL-36 cytokines play significant roles in the host defense system and in the regulation of inflammatory pathways in the skin, collaborating with other cytokines/chemokines and immune-related molecules. Thus, numerous studies have shown IL-36 cytokines to play important roles in the pathogenesis of various skin diseases. In this context, the clinical efficacy and safety profiles of anti-IL-36 agents such as spesolimab and imsidolimab have been evaluated in patients with generalized pustular psoriasis, palmoplantar pustulosis, hidradenitis suppurativa, acne/acneiform eruptions, ichthyoses, and atopic dermatitis. This article comprehensively summarizes the roles played by IL-36 cytokines in the pathogenesis and pathophysiology of various skin diseases and summarizes the current state of research on therapeutic agents that target IL-36 cytokine pathways.

CCN1 upregulates IL-36 via AKT/NF-κB and ERK/CEBP β-mediated signaling pathways in psoriasis-like models

Psoriasis is a chronic skin disorder characterized by epidermal keratinocyte hyperproliferation and inflammatory infiltration. CCN1 (also termed CYR61 or cysteine-rich angiogenic inducer 61) is an extracellular matrix-associated protein that is involved in multiple physiological functions. In psoriasis, we recently demonstrated that the overexpression of CCN1 promoted keratinocyte proliferation and activation. Furthermore, CCN1 was highly expressed in psoriatic skin lesions from psoriasis vulgaris patients. Here, we dissect the underlying molecular mechanism in imiquimod (IMQ) and interleukin (IL)-23-induced psoriasis-like models. Our results demonstrate that CCN1 can significantly upregulate IL-36 production in the murine skin of IMQ and IL-23-induced psoriasis-like models. Injection of CCN1-neutralizing antibody improved epidermal acanthosis and significantly reduced IL-36 production in vivo. These results suggest that CCN1 can be a critical upstream pro-inflammatory factor in psoriasis. In primary normal human epidermal keratinocytes, we demonstrated that CCN1 can selectively induced the production of IL-36α and IL-36γ through the activation of the protein kinase B (AKT)/nuclear factor kappa light chain enhancer of activated B cells (NF-κB) and extracellular-regulated kinase (ERK)/CCAAT/enhancer binding protein β (CEBPβ) signaling pathways via integrin receptor α6β1 in vitro. Our results suggest that targeting CCN1 can be a potential therapeutic strategy for psoriasis.

The role of interleukin 36γ in the epithelial-mesenchymal transition process of chronic rhinosinusitis: A pilot study

PURPOSE

Epithelial-mesenchymal transition (EMT) is an important characteristic in the remodelling of chronic rhinosinusitis with nasal polyps (CRSwNP). IL-36γ and fibroblast activation protein (FAP) may exacerbate remodelling in CRS. Here, we aimed to determine whether IL-36γ and FAP expression are associated with EMT and may be a predictor for CRSwNP prognosis.

METHODS

Fifty-two non-Eos CRSwNP patients and 12 control patients were obtained and were followed up for more than 1 year after surgery. IL-36γ, FAP and EMT markers expression were evaluated by real-time polymerase chain reaction and western blot. Masson trichrome staining was adopted to assess tissue fibrotic changes. Furthermore, the soluble form of IL-36γ and FAP in nasal secretions was detected by ELISA.

RESULTS

While basal expression of E-cadherin decreased, the expression of IL-36γ, vimentin and FAP increased in nasal polyps. In well-prognosis patients, the expression of IL-36γ, vimentin and FAP were significantly decreased than in poor-prognosis patients, while the protein expression of E-cadherin was increased. The protein expression of IL-36γ was notably increased in recurrent nasal polyps than in preoperation specimens. A positive relationship between IL-36γ and FAP expression, a negative relationship between IL-36γ and E-cad expression was noted. The soluble form of IL-36γ and FAP increased during the development of non-Eos CRSwNP, with the highest level in poor-prognosis patients after surgery.

CONCLUSION

Non-Eos CRSwNP have partially undergone EMT under baseline conditions. IL-36γ and FAP expression were related with EMT, the soluble form of IL-36γ and FAP in nasal secretions may predict the prognosis of patients.

IL-4/IL-13 Inhibitors for Atopic Dermatitis Induce Psoriatic Rash Transcriptionally Close to Pustular Psoriasis

Dupilumab is a therapeutic antibody targeting IL-4 and IL-13 receptor subunit alpha used for the treatment of patients with atopic dermatitis (AD). Cases of psoriasis-like reactions induced under dupilumab treatment (dupilumab-induced psoriatic eruption [DI-Pso]) for AD were recently reported. To understand the pathogenesis of DI-Pso, we performed gene expression profiling studies on skin biopsies of DI-Pso (n = 7) compared with those of plaque psoriasis, AD, and healthy controls (n = 4 each). Differential gene expression was performed using enrichment and Gene Ontology analysis. Gene expression was validated by qPCR, and protein levels were assessed by immunohistochemistry. Transcriptomic and protein analysis of DI-Pso compared with that of healthy controls, plaque psoriasis, and AD skins revealed activation of T helper 17/IL-23 pathways associated with a significant expression of IL-36, surrogate marker of pustular psoriasis. By contrast, T helper 2 representative genes' expression was strongly decreased in DI-Pso across comparison. Matching analysis with public data of pustular psoriasis skin corroborated that DI-Pso and pustular psoriasis upstream regulators overlap, greater than the overlap with plaque psoriasis. Furthermore, DI-Pso showed strongly decreased expression of many barrier skin genes compared with healthy controls, plaque psoriasis, and AD. Our data indicate that the pathogenesis of DI-Pso relied on a shift of skin immune responses from a T helper 2 to an IL-36 and T helper 17 polarization and on intensified skin barrier alterations.

Interleukin-38 suppresses abdominal aortic aneurysm formation in mice by regulating macrophages in an IL1RL2-p38 pathway-dependent manner

Macrophages play crucial roles in abdominal aortic aneurysm (AAA) formation through the inflammatory response and extracellular matrix degradation; therefore, regulating macrophages may suppress AAA formation. Interleukin-38 (IL-38) is a member of the IL-1 family, which binds to IL-36 receptor (IL1RL2) and has an anti-inflammation effect. Because macrophages express IL1RL2, we hypothesized that IL-38 suppresses AAA formation by controlling macrophages. We assessed a C57BL6/J mouse angiotensin II-induced AAA model with or without IL-38 treatment. RAW 264.7 cells were cultured with tumor necrosis factor-α and treated with or without IL-38. Because p38 has important roles in inflammation, we assessed p38 phosphorylation in vitro and in vivo. To clarify whether the IL-38 effect depends on the p38 pathway, we used SB203580 to inhibit p38 phosphorylation. IL1RL2+ macrophage accumulation along with matrix metalloproteinase (MMP)-2 and -9 expression was observed in mouse AAA. IL-38 reduced the incidence of AAA formation along with reduced M1 macrophage accumulation and MMP-2 and -9 expression in the AAA wall. Macrophage activities including inducible nitric oxide, MMP-2, and MMP-9 production and spindle-shaped changes were significantly suppressed by IL-38. Furthermore, we revealed that inhibition of p38 phosphorylation diminished the effects of IL-38 on regulating macrophages to reduce AAA incidence, indicating the protective effects of IL-38 depend on the p38 pathway. IL-38 plays protective roles against AAA formation through regulation of macrophage accumulation in the aortic wall and modulating the inflammatory phenotype. Using IL-38 may be a novel therapy for AAA patients.

Keratinocyte Regnase-1, a Downregulator of Skin Inflammation, Contributes to Protection against Tumor Promotion by Limiting Cyclooxygenase-2 Expression

We previously showed that the ribonuclease Regnase-1 (Reg1) in keratinocytes plays a role in mitigating skin inflammation by downregulating proinflammatory cytokines. In this study, we explored whether Reg1 also has a protective role against skin carcinogenesis. The chemically induced two-stage carcinogenesis protocol revealed that epidermis-specific Reg1-deficient (Reg1-knockout [Reg1-cKO]) mice developed skin tumors with shorter latency and more multiplicity than control mice. In addition, repeated UVB irradiation readily provoked solar keratosis-like lesions in Reg1-cKO mice. Increased levels of cyclooxygenase 2, whose mRNA (Ptgs2) is reportedly a target of Reg1, have been known to be associated with the development of squamous cell carcinomas. Indeed, Ptgs2 mRNA levels were upregulated in the skin of Reg1-cKO mice after treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. The level of prostaglandin E2 was higher in 12-O-tetradecanoylphorbol-13-acetate‒treated Reg1-cKO mouse skin than in control mice skin. Moreover, in vivo inhibition of cyclooxygenase 2 attenuated the 12-O-tetradecanoylphorbol-13-acetate‒induced epidermal thickening in Reg1-cKO mice. Finally, REG1 knockdown in human squamous cell carcinomas lines enhanced PTGS2 mRNA levels after 12-O-tetradecanoylphorbol-13-acetate treatment. In conclusion, epidermal Reg1 plays a regulatory role not only in skin inflammation but also in tumor promotion through the downregulation of cyclooxygenase 2. Therefore, forced expression of Reg1 under inflammatory conditions may be relevant to preventing skin cancer.

Plasma Levels of Interleukins 36α, 36β, and 37 in Patients with Psoriasis and Their Correlation with Disease Activity Parameters

Psoriasis is a chronic, proliferative, inflammatory skin disease characterised by skin lesions and systemic symptoms. Numerous cytokines are produced in psoriasis as a result of inflammation. The aim of this study was to examine the plasma concentrations of IL-36α, IL-36β, and IL-37 in psoriasis and their correlations with disease activity parameters. This study recruited 84 individuals, 53 with plaque-type psoriasis and 31 healthy controls. The plaque type of psoriasis is the most common type and is typically characterized by circular-to-oval red plaques distributed over body surfaces of the extremities and scalp. In patients with psoriasis, we observed statistically significantly decreased plasma concentrations of IL-36β and IL-37. The concentrations of IL-36α were increased in comparison with control group. The plasma concentrations of IL-36α and IL-36β were statistically significantly correlated with all tested parameters of disease activity: the Psoriasis Activity Severity Index, Dermatology Life Quality Index, and Body Surface Area Index. There were no statistically significant correlations between plasma levels of IL-37 and the tested parameters of disease activity. These results indicate a role of IL36α, IL-36β, and IL-37 in the pathogenesis of psoriasis.

Defining Patient-Level Molecular Heterogeneity in Psoriasis Vulgaris Based on Single-Cell Transcriptomics

Identifying genetic variation underlying human diseases establishes targets for therapeutic development and helps tailor treatments to individual patients. Large-scale transcriptomic profiling has extended the study of such molecular heterogeneity between patients to somatic tissues. However, the lower resolution of bulk RNA profiling, especially in a complex, composite tissue such as the skin, has limited its success. Here we demonstrate approaches to interrogate patient-level molecular variance in a chronic skin inflammatory disease, psoriasis vulgaris, leveraging single-cell RNA-sequencing of CD45⁺ cells isolated from active lesions. Highly psoriasis-specific transcriptional abnormalities display greater than average inter-individual variance, nominating them as potential sources of clinical heterogeneity. We find that one of these chemokines, CXCL13, demonstrates significant correlation with severity of lesions within our patient series. Our analyses also establish that genes elevated in psoriatic skin-resident memory T cells are enriched for programs orchestrating chromatin and CDC42-dependent cytoskeleton remodeling, specific components of which are distinctly correlated with and against Th17 identity on a single-cell level. Collectively, these analyses describe systematic means to dissect cell type- and patient-level differences in cutaneous psoriasis using high-resolution transcriptional profiles of human inflammatory disease.

IL-36 Cytokines: Their Roles in Asthma and Potential as a Therapeutic

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily, which consists of three agonists (IL-36α, IL-36β and IL-36γ) and an IL-36 receptor antagonist (IL-36Ra). IL-36 cytokines are crucial for immune and inflammatory responses. Abnormal levels of IL-36 cytokine expression are involved in the pathogenesis of inflammation, autoimmunity, allergy and cancer. The present study provides a summary of recent reports on IL-36 cytokines that participate in the pathogenesis of inflammatory diseases, and the potential mechanisms underlying their roles in asthma. Abnormal levels of IL-36 cytokines are associated with the pathogenesis of different types of asthma through the regulation of the functions of different types of cells. Considering the important role of IL-36 cytokines in asthma, these may become a potential therapeutic target for asthma treatment. However, existing evidence is insufficient to fully elucidate the specific mechanism underlying the action of IL-36 cytokines during the pathological process of asthma. The possible mechanisms and functions of IL-36 cytokines in different types of asthma require further studies.

Generalized pustular psoriasis: the new era of treatment with IL-36 receptor inhibitors

Generalized pustular psoriasis (GPP) is a rare yet severe variant of psoriasis, characterized by the eruption of superficial sterile pustules that appear suddenly and widely distributed, potentially life-threatening. It more commonly presents through recurrent acute flares triggered by stress, corticosteroid withdrawals, pregnancy, or infections. The pathogenesis of this disease is yet to be fully understood. Nevertheless, studies have suggested an important role of an IL-1 subfamily of cytokines, due to an imbalance of the IL-36 axis favoring of pro-inflammatory activity. The therapeutic intervention for this condition is still a challenge as its rarity and scarce available information contribute to the absence of specific treatment. Current options stand on small, open-label trials or follows standard treatment for plaque psoriasis. Spesolimab and imsidolimab are two IL-36 receptor inhibitors which completed phase 1 and 2 trials with a good efficacy and safety profile in the treatment of this disease, including in the fast control of its acute flares. The most common adverse events reported with spesolimab were mild to moderate infections, and imsidolimab was well tolerated. GPP clinical trials remain to have their small sample size as a major limitation, but IL-36 receptor inhibitors are promising therapeutic options currently under investigation.

IL-36γ in enthesitis-related juvenile idiopathic arthritis and its association with disease activity

IL-36 has been implicated in the pathogenesis of spondyloarthropathies (SpA) like psoriasis and inflammatory bowel disease. Enthesitis-related arthritis (ERA) category of juvenile idiopathic arthritis is a form of juvenile SpA, however, no data is available on the role of IL-36 in this disease. IL-36α, β, γ and IL-36R mRNA expression in blood and synovial fluid mononuclear cells and IL-36α, γ, IL-36Ra, IL-6, and IL-17 levels were measured in serum and synovial fluid (SF). IL-36γ production by fibroblast-like synoviocytes (FLS) upon stimulation with pro-inflammatory cytokines and its effect on FLS were also studied. mRNA levels of IL-36α, IL-36γ, and IL-36R were increased in PBMCs of ERA patients as compared to healthy controls however only IL-36γ was measurable in the serum of one-third of patients. In SFMCs, all four mRNA were detectable but were lower than RA patients. SF IL-36γ levels correlated with disease activity score (r = 0.51, P < 0.0001), SF IL-6 (r = 0.4, P = 0.0063) and IL-17 levels (r = 0.57, P = 0.0018). Pro-inflammatory cytokines increased the expression of IL-36γ and IL-6 in FLS cultures. SFs from five ERA patients also increased expressions of IL-36γ and IL-6 in FLS which could be blocked by using IL-36Ra. This suggests that pro-inflammatory cytokines aid in the upregulation of IL-36γ which in turn may upregulate the expression of IL-6. This might lead to a positive feedback loop of inflammation in ERA. Association of SF levels of IL-36γ with disease activity further supports this possibility. IL-36Ra based therapy may have a role in ERA.

Interleukin-36α is elevated in diffuse systemic sclerosis and may potentiate fibrosis

Systemic sclerosis (SSc) is an autoimmune prototypical connective tissues disease that results in alterations in vasculature, inflammation and fibrosis of the skin. Interleukin-1 family cytokines has been implicated in the disease including IL-1. IL-36α is an IL-1 family member that is clearly implicated in psoriatic skin disease but its role in systemic sclerosis disease is not clear. The aim of this work is to evaluate the levels and role of IL-36α in systemic sclerosis. Early diffuse SSc patients sera was isolated along with healthy controls and IL-36 levels quantified by ELISA. In vitro analysis was also undertaken with primary dermal fibroblasts with recombinant IL-36α and keratinocyte cells were also incubated with IL-36α. Cytokines were measured by ELISA. Serum IL-36 was significantly elevated compared to healthy controls. Elevated neutrophil elastase was also elevated in the matched sera. IL-36 was not directly pro-fibrotic in dermal fibroblasts but did induce pro-inflammatory cytokines that were dependant on the MAPK pathway for their release. IL-36α also led to release of CCL20 and CCL2 in keratinocytes which may potentiate fibrosis. IL-36α is elevated in SSc serum and whilst not directly pro-fibrotic it may through keratinocytes, potentiate fibrosis through keratinocyte-immune fibroblast cross-talk.

Generalized pustular psoriasis: overview of the status quo and results of a panel discussion

Generalized pustular psoriasis (GPP) is a rare, severe, potentially life-threatening, autoinflammatory, neutrophilic skin disease that may be accompanied by fever and leukocytosis. This paper describes the current state of knowledge on GPP in terms of classification, (differential) diagnosis and prevalence. We present a comparison of the genetics and pathoimmunology of GPP and psoriasis vulgaris with the central mechanisms of autoimmunology and autoinflammation. The currently available therapeutic options, expert recommendations for therapy, and data from early clinical trials investigating targeted therapies will be summarized. We present the results of our discussion with 13 experts for psoriasis vulgaris and GPP and give an integrated overview of indication and therapy based on our personal experience and present an outlook on further research questions. Collectively, this article highlights the high unmet need in GPP, as there exists no satisfactory method of diagnosis or treatment to date and new treatment options will be of great therapeutic benefit to those affected.

Netherton syndrome subtypes share IL-17/IL-36 signature with distinct IFN-α and allergic responses

BACKGROUND

Netherton syndrome (NS) is a rare recessive skin disorder caused by loss-of-function mutations in SPINK5 encoding the protease inhibitor LEKTI (lymphoepithelial Kazal-type-related inhibitor). NS patients experience severe skin barrier defects, display inflammatory skin lesions, and have superficial scaling with atopic manifestations. They present with typical ichthyosis linearis circumflexa (NS-ILC) or scaly erythroderma (NS-SE).

OBJECTIVE

We used a combination of several molecular profiling methods to comprehensively characterize the skin, immune cells, and allergic phenotypes of NS-ILC and NS-SE patients.

METHODS

We studied a cohort of 13 patients comprising 9 NS-ILC and 4 NS-SE.

RESULTS

Integrated multiomics revealed abnormal epidermal proliferation and differentiation and IL-17/IL-36 signatures in lesion skin and in blood in both NS endotypes. Although the molecular profiles of NS-ILC and NS-SE lesion skin were very similar, nonlesion skin of each disease subtype displayed distinctive molecular features. Nonlesion and lesion NS-SE epidermis showed activation of the type I IFN signaling pathway, while lesion NS-ILC skin differed from nonlesion NS-ILC skin by increased complement activation and neutrophil infiltration. Serum cytokine profiling and immunophenotyping of circulating lymphocytes showed a T_H2-driven allergic response in NS-ILC, whereas NS-SE patients displayed mainly a T_H9 axis with increased CCL22/MDC and CCL17/TARC serum levels.

CONCLUSIONS

This study confirms IL-17/IL-36 as the predominant signaling axes in both NS endotypes and unveils molecular features distinguishing NS-ILC and NS-SE. These results identify new therapeutic targets and could pave the way for precision medicine of NS.

Novel Therapeutic Target(s) for Psoriatic Disease

Psoriasis and psoriatic arthritis, together known as psoriatic disease, is highly prevalent chronic relapsing inflammatory disease affecting skin, joints or both and is associated with several comorbidities such as cardiovascular, metabolic, psychiatric, renal disease etc. The etiopathogenesis of psoriasis is complex and mainly driven by aberrant immune response owing to the genetic susceptibility and various environmental factors such as trauma, infections and drugs. Recent advances in understanding molecular and cellular pathways have identified tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), IL-23, IL-22 as major contributors in psoriasis pathogenesis. Advances in the knowledge of pathophysiology, the interaction of autoinflammation and clinical phenotypes have led to the development of highly effective targeted therapeutic agents which include TNF-α, IL-17, IL-23, IL-1 α/β or IL-36 inhibitors or receptor blockers, small molecule drugs like phosphodiesterase-4 inhibitors (apremilast), Janus kinase (JAK) inhibitors, retinoic acid receptor-related orphan receptor γt (RORγt) inhibitors. These novel drugs have promised the potential of improved disease control. In recent years, the transition from biologics to biosimilars especially with TNF-α inhibitors had significant impact on decreasing health care cost and increasing therapeutic options to the patients. However, selection of right treatment for an individual patient still remains challenging. Moreover, interplay between different epigenetic mechanisms such as the DNA methylation, chromatin modifications and noncoding RNA regulation has recently been started to be deciphered. Enzymes inhibitors involved in epigenetic pathways such as DNA methyltransferases and histone deacetylases demonstrated to restore normal epigenetic patterns in clinical settings and have provided the potential as novel therapeutic targets for psoriasis. In this review, we will discuss novel biologic agents and newer therapeutic approaches in treatment of psoriatic disease.

Advances in the pathogenesis of psoriasis: from keratinocyte perspective

Psoriasis is a complex long-lasting inflammatory skin disease with high prevalence and associated comorbidity. It is characterized by epidermal hyperplasia and dermal infiltration of immune cells. Here, we review the role of keratinocytes in the pathogenesis of psoriasis, focusing on factors relevant to genetics, cytokines and receptors, metabolism, cell signaling, transcription factors, non-coding RNAs, antimicrobial peptides, and proteins with other different functions. The critical role of keratinocytes in initiating and maintaining the inflammatory state suggests the great significance of targeting keratinocytes for the treatment of psoriasis.

High inflammation in hidradenitis suppurativa extends to perilesional skin and can be subdivided by lipocalin-2 expression

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease presenting with diverse manifestations ranging from nodules and abscesses to draining tunnels. Whether the underlying inflammation from lesions extends to relatively healthy-appearing adjacent perilesional and distant nonlesional skin has not been systematically evaluated.

OBJECTIVE

We sought to characterize lesional, perilesional, and nonlesional skin in patients with HS.

METHODS

Skin biopsy samples were collected under ultrasound guidance from patients with active, untreated moderate-to-severe HS. Site-matched control biopsy samples from healthy volunteers were used for comparison.

RESULTS

RNA sequencing demonstrated that HS skin clustered separately from healthy control skin, with perilesional and lesion skin clustering together and away from nonlesional skin. Immunohistochemistry analysis identified psoriasiform hyperplasia with keratin 16 positivity in both perilesional and lesional skin, with comparable levels of CD3+, CD11c+, and neutrophil elastase-positive cellular infiltration. There was a marked upregulation of IL-17 signaling in perilesional and lesional skin. HS samples clustered on the basis of expression of lipocalin-2 (LCN2), with samples characterized by high LCN2 expression in the skin exhibiting a differing transcriptomic profile with significantly higher overall inflammation than that of skin characterized by low LCN2 levels.

CONCLUSIONS

Perilesional HS skin has a transcriptomic and molecular profile comparable to that of lesional skin. HS can be grouped into 2 distinct subtypes based on molecular levels of LCN2 in the skin, with the LCN2-high subtype exhibiting an overall higher inflammatory burden and an upregulation of targetable cytokines. To our knowledge, this is the first study to characterize a unique HS subtype (and a potential endotype) that may guide future therapeutic targets.

The anti-inflammatory and protective role of interleukin-38 in inflammatory bowel disease

Interleukin (IL)-38 exerts an anti-inflammatory function by binding to several cytokine receptors, including the IL-36 receptor. In this study, we evaluated IL-38 expression in the inflamed mucosa of patients with inflammatory bowel disease (IBD) and investigated its functions. IL-38 mRNA expression in endoscopic biopsy samples was evaluated using quantitative PCR. IL-38 protein expression was analyzed using immunohistochemical technique. Dextran sulfate sodium-induced colitis was induced in C57BL/6 background IL-38KO mice. The IL-38 mRNA and protein expression were enhanced in the active mucosa of ulcerative colitis, but not in Crohn's disease. The ratio of IL-36γ to IL-38 mRNA expression was significantly elevated in the active mucosa of UC patients. Immunofluorescence staining revealed that B cells are the major cellular source of IL-38 in the colonic mucosa. IL-38 dose-dependently suppressed the IL-36γ-induced mRNA expression of CXC chemokines (CXCL1, CXCL2, and CXCL8) in HT-29 and T84 cells. IL-38 inhibited the IL-36γ-induced activation of nuclear-factor kappa B (NF-κB) and mitogen-activated protein kinases in HT-29 cells. DSS-colitis was significantly exacerbated in IL-38KO mice compared to wild type mice. In conclusion, IL-38 may play an anti-inflammatory and protective role in the pathophysiology of IBD, in particular ulcerative colitis, through the suppression of IL-36-induced inflammatory responses.

Pustular psoriasis as an autoinflammatory keratinization disease (AiKD): Genetic predisposing factors and promising therapeutic targets

Pustular psoriasis is a chronic inflammatory skin disease characterized by erythematous plaques with sterile pustules. It includes the distinct clinical entities generalized pustular psoriasis (GPP), acrodermatitis continua of Hallopeau (ACH) and palmoplantar pustular psoriasis (PPPP). Recently clarified pathomechanisms of pustular psoriasis indicate that hyperactivation of the skin innate immunity, including of the IL-1/IL-36 axis, plays an important role in the pathogenesis of pustular psoriasis. Autoinflammatory keratinization disease (AiKD) is the umbrella clinical entity for inflammatory keratinization disorders with genetic autoinflammatory pathomechanisms, and pustular psoriasis is a representative AiKD. To date, mutations/variants in five genes-IL36RN, CARD14, AP1S3, MPO and SERPINA3-have been reported to be genetic causative or predisposing factors for pustular psoriasis. The pathogenic mechanisms induced by the mutations/variants in these genes are all closely related to the excessive activation of skin innate immunity and autoinflammation. A number of biologics (e.g., tumor necrosis factor inhibitors, IL-17/IL-17 receptor inhibitors and IL-23 inhibitors) and granulocyte and monocyte adsorption apheresis are used to treat pustular psoriasis. Recently, based on novel information on the pathomechanisms of pustular psoriasis, which are mainly associated with autoinflammation, inhibitors of several pathogenic pathways, including of the IL-1, IL-36, IL-8 and granulocyte colony-stimulating factor signaling pathways, have been studied as emerging treatments.

Roles of IL-1 and IL-10 family cytokines in the progression of systemic lupus erythematosus: Friends or foes?

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology that can affect nearly every organ system in the body. Besides genetic and environmental factors, unbalanced pro-inflammatory and anti-inflammatory cytokines contribute to immune dysregulation, trigger an inflammatory response, and induce tissue and organ damage. Inflammatory responses in SLE can be promoted and/or maintained by the availability of cytokines that are overproduced systemically and/or in local tissues. Several key cytokines have been considered potential targets for the reduction of chronic inflammation in SLE. Recent studies indicated that dysregulated production of several cytokines, including those of the IL-1 family and IL-10 family, orchestrate immune activation and self-tolerance, play critical roles in the pathogenesis of SLE. Among IL-1 family cytokines, IL-1, IL-18, IL-33, IL-36, IL-37, and IL-38 had been the most thoroughly investigated in SLE. Additionally, IL-10 family cytokines, IL-10, IL-20, IL-22, IL-26, IL-28, and IL-29 are dysregulated in SLE. Therefore, a better understanding of the initiation and progression of SLE may provide suitable novel targets for therapeutic intervention. In this review, we discuss the involvement of inflammation in the pathogenesis of SLE, with a focus on IL-1 family and IL-10 family cytokines, and highlight pathophysiological approaches and therapeutic potential for treating SLE.

Pustular Psoriasis: A Narrative Review of Recent Developments in Pathophysiology and Therapeutic Options

Pustular psoriasis is an unusual form of psoriasis that frequently presents clinical challenges for dermatologists. The condition presents with pustules on an erythematous background and has two distinct subtypes: localized disease on the palms and soles, called palmoplantar pustulosis (PPP), and generalized pustular psoriasis (GPP). The involvement of the fingers, toes, and nails is defined as a separate localized variant, acrodermatitis continua of Hallopeau, and is now thought to be a subset of PPP. The rarity of pustular psoriasis frequently makes the correct diagnosis problematic. In addition, treatment is limited by a relative lack of evidence-based therapeutic options. Current management is often based on existing therapies for standard plaque psoriasis. However, there remains a need for treatments with high, sustained efficacy and a rapid onset of action in pustular psoriasis. Recent advances in understanding of the pathogenesis of pustular psoriasis have provided insights into potential therapies. Treatment of pustular psoriasis is generally determined by the extent and severity of disease, and recent years have seen an increasing use of newer agents, including biologic therapies. Current classes of biologic therapies with US Food and Drug Administration and European Medicines Agency approval for treatment of moderate-to-severe plaque psoriasis in the USA (and elsewhere) include tumor necrosis factor alpha inhibitors (adalimumab, certolizumab pegol, etanercept, infliximab), interleukin (IL)-17 inhibitors (brodalumab, ixekizumab, secukinumab), an IL-12/23 inhibitor (ustekinumab), and IL-23 inhibitors (guselkumab, risankizumab, tildrakizumab). Recently, specific inhibitors of the IL-36 pathway have been evaluated in GPP and PPP, including spesolimab, an IL-36 receptor inhibitor which has shown promising results in GPP. The emerging drugs for pustular psoriasis offer the possibility of rapid and effective treatment with lower toxicities than existing therapies. Further research into agents acting on the IL-36 pathway and other targeted therapies has the potential to transform the future treatment of patients with pustular psoriasis. This article reviews the clinical features of PPP and GPP, and current understanding of the genetics and immunopathology of these conditions; it also provides an update on emerging treatments.

Pustular psoriasis is a skin condition where people develop small pus-filled blisters on their skin. Pustular psoriasis may affect certain areas of the body, such as the palms and/or the soles. This is called palmoplantar pustulosis (PPP for short). Another type of pustular psoriasis can affect most of the body called generalized pustular psoriasis (GPP for short). Not many people have PPP or GPP. Around 5–12 in every 10,000 people worldwide develop PPP. GPP is even rarer, affecting only 2–7 out of every 1 million people. In addition to being relatively uncommon, these conditions are challenging to treat. This article aims to help doctors who treat skin conditions (dermatologists) to identify and treat people with pustular psoriasis. Currently there is no standard treatment for GPP and PPP in the USA or Europe, but several medicines are approved for treatment of GPP in Japan. Doctors often use treatments that have been shown to work in plaque psoriasis, which is the most common type of psoriasis, to treat people with GPP and PPP. Traditional treatments for PPP and GPP are often not effective. Researchers are working on developing new effective treatments for pustular psoriasis that may work more rapidly and have fewer side effects. These are expected to be available in the next few years.

Overexpression of Lin28a Aggravates Psoriasis-Like Phenotype by Regulating the Proliferation and Differentiation of Keratinocytes

Purpose

Psoriasis is a common and well-studied autoimmune skin disease, which is characterized by plaques. The formation of psoriasis plaques occurs through the hyperproliferation and abnormal differentiation of keratinocytes, infiltration of numerous immune cells into the dermis, increased subepidermal angiogenesis, and various autoimmune-associated cytokines and chemokines. According to previous research, Lin28 regulates the let-7 family, and let-7b is associated with psoriasis. However, the link between Lin28 and psoriasis is unclear. In this study, an association was identified between Lin28a and psoriasis progression, which promoted the pathological characteristic of psoriasis in epidermal keratinocytes.

Patients and Methods

This study aims to investigate the role of Lin28a and its underlying mechanism in psoriasis through in vivo and in vitro models, which include the Lin28a-overexpressing transgenic (TG) mice and Lin28a-overexpressing human keratinocyte (HaCaT) cell lines, respectively.

Results

In vivo and in vitro results revealed that overexpression of Lin28a downregulated microRNA let-7 expression levels and caused hyperproliferation and abnormal differentiation in keratinocytes. In imiquimod (IMQ)-induced psoriasis-like inflammation, Lin28a overexpressing transgenic (TG) mice exhibited more severe symptoms of psoriasis.

Conclusion

Mechanistically, Lin28a exacerbated psoriasis-like inflammation through the activation of the extracellular-signal-regulated kinase (ERK) and signal transducer and activator of transcription 3 signaling (STAT 3) by targeting proinflammatory cytokine interleukin-6 (IL-6).

Establishment of an Intradermal Ear Injection Model of IL-17A and IL-36γ as a Tool to Investigate the Psoriatic Cytokine Network

Psoriasis is a chronic skin disease affecting 2–3% of the global population. The proinflammatory IL-17A is a key cytokine in psoriasis. Accumulating evidence has revealed that IL-36γ plays also a pathogenic role. To understand more precisely the role of the IL-17A–IL-36γ cytokine network in skin pathology, we used an ear injection model. We injected IL-17A or IL-36γ alone and in combination into the ear pinnae of mice. This resulted in a significant increase in ear thickness measured over time. Histological evaluation of IL-17A + IL-36γ-treated skin showed a strong acanthosis, hyperparakeratosis and infiltration of neutrophils. The same histological features were found in mice after injection of IL-36γ alone, but to a lesser extent. IL-17A alone was not able to induce psoriasis-like changes. Genes encoding proteins of the S100 family, antimicrobial peptides and chemo-attractants for neutrophils were upregulated in the IL-17A + IL-36γ group. A much weaker expression was seen after the injection of each cytokine alone. These results strengthen the hypothesis that IL-17A and IL-36γ drive psoriatic inflammation via a synergistic interaction. Our established intradermal ear injection model can be utilized in the future to monitor effects of various inhibitors of this cytokine network.

Interleukin 36 expression in psoriasis variants and other dermatologic diseases with psoriasis-like histopathologic features

BACKGROUND

Elevated epidermal interleukin (IL)-36 expression distinguishes psoriasis from eczematous dermatitis, but other psoriasiform dermatitides (PDs) have not been thoroughly investigated for IL-36 expression. In this study, we assess the IL-36 staining pattern (IL36-SP) in psoriasis variants and other PDs including lichen simplex chronicus (LSC), prurigo nodularis (PN), lichen planus (LP), tinea, pityriasis rubra pilaris (PRP), mycosis fungoides (MF), pemphigus foliaceus (PF), acute generalized exanthematous pustulosis (AGEP), impetigo (IMP), and syphilis (SY).

METHODS

IL-36 immunostaining was performed on 307 cases of psoriasis and various PDs. IL36-SP in the upper epidermis was graded on a scale of 0-4.

RESULTS

High IL36-SP occurred in all variants of psoriasis, as well as in AGEP, PRP, PN, tinea, IMP, and LP (P > 0.05). SY, PF, LSC, and MF showed a lower IL36-SP (P ≤ 0.05) compared with psoriasis.

CONCLUSION

All variants of psoriasis exhibit high IL36-SP. IL-36 staining can assist in differentiating MF, PF, SY, and LSC from psoriasis, particularly MF and LSC, which have consistent low IL-36 expression. AGEP, PRP, tinea, IMP, PN, and LP exhibit high IL-36 expression similar to psoriasis, indicating Th17 activation in these 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.

Psoriasis: a brief overview

Psoriasis is a clinically heterogeneous lifelong skin disease that presents in multiple forms such as plaque, flexural, guttate, pustular or erythrodermic. An estimated 60 million people have psoriasis worldwide, with 1.52% of the general population affected in the UK. An immune-mediated inflammatory disease, psoriasis has a major genetic component. Its association with psoriatic arthritis and increased rates of cardiometabolic, hepatic and psychological comorbidity requires a holistic and multidisciplinary care approach. Psoriasis treatments include topical agents (vitamin D analogues and corticosteroids), phototherapy (narrowband ultraviolet B radiation (NB-UVB) and psoralen and ultraviolet A radiation (PUVA)), standard systemic (methotrexate, ciclosporin and acitretin), biologic (tumour necrosis factor (TNF), interleukin (IL)-17 and IL-23 inhibitors) or small molecule inhibitor (dimethyl fumarate and apremilast) therapies. Advances in the understanding of its pathophysiology have led to development of highly effective and targeted treatments.