IL-1F5, -F6, -F8, and -F9: a novel IL-1 family signaling system that is active in psoriasis and promotes keratinocyte antimicrobial peptide expression

Association of Obesity and Innate Immune Markers With Resistance to Biologic Therapy in Psoriasis

Importance

Currently available biologics specifically target dermal adaptive immune molecules, such as interleukin (IL)-17 and IL-23, which are crucial in the pathogenesis of psoriasis. Despite their remarkably enhanced therapeutic effects compared with those of traditional anti-inflammatory systemic medications, 25% to 50% of patients are still resistant to biologic therapy.

Objective

To delineate the inflammatory microenvironmental factors that affect sustained treatment response in patients with severe psoriasis.

Design, Setting, and Participants

A cross-sectional study was carried out including patients aged 18 years or older who visited the Gachon University Gil Medical Center dermatology clinic between January 2012 and December 2022 with plaque-type severe psoriasis with a Psoriasis Area and Severity Index score greater than 10 and body surface area larger than 10 despite conventional treatment with cyclosporine, methotrexate, acitretin, and phototherapy for longer than 3 months, and treatment with biologics for at least 24 months. Analysis was carried out from December 2023 to September 2024.

Main Outcome and Measure

Clinical and inflammatory factors associated with sustained response to biologics therapy.

Results

Among the 87 patients (mean [SD] age, 42.2 [12.5] years; 24 female patients and 63 male patients) included in the study, 16 (18.4%) had to switch to other biologics because of an early loss of therapeutic efficacy. Having overweight (body mass index, >25) was the only clinically relevant factor (odds ratio, 17.3; 95% CI, 3.2-434.6; P = .009). Other factors, including initial disease severity before biologics or disease duration until the first use of biologics, were not different between patients with treatment-resistant disease and those with a sustained treatment response. Spatial transcriptomics pathway analyses revealed enriched innate immune signaling and T-helper 17 cells (Th17)/IL-17 signaling pathways, with upregulated expression of innate immune- or neutrophil-related genes, such as TNFSF10, CXCL8, LCN2, S100A8, and S100A9, mainly in the epidermis. Enriched ligand-receptor interactions were observed in the IL-36 family of cytokines, antimicrobial peptides, and tumor necrosis factor (TNF) signaling. Immunofluorescence analysis showed enhanced protein expression of lipocalin 2, S100A8/A9, IL-36α, IL-36γ, IL-1RA, and TNF-related apoptosis-inducing ligand (TRAIL) in the epidermis.

Conclusions and Relevance

This cross-sectional study found that dysregulated innate immune responses in the epidermis and heightened neutrophil activity may be responsible for decreased sustainability of therapeutic responses to biologics. Given that current biologics mainly target dermal adaptive immune-related mediators, the development of novel therapeutic strategies to target the epidermal innate immune response, including neutrophils, is warranted.

A translational approach to improve therapeutics in atopic dermatitis and beyond

Atopic dermatitis (AD) and alopecia areata are highly prevalent inflammatory skin/hair conditions. While previously not fully understood and limited in treatment options, AD is currently undergoing a therapeutic revolution. Our increased understanding of the underlying immunologic and barrier dysregulations and disease heterogeneity across its spectrum is facilitating hypothesis-driven therapeutic development. Early transcriptomic analyses in AD skin and blood have identified disease-specific biomarkers and uncovered immune and barrier abnormalities that may contribute to disease pathogenesis. From these findings, various therapeutic targets were then proposed and investigated in clinical trials, leading to the Food and Drug Administration approval of several biologics and small molecule drugs that are now widely used in the clinical setting. Molecular phenotyping of patient samples before and after treatment has further elucidated the specific immunomodulatory effect of each therapeutic, as well as the relative contributions of various immune pathways to disease pathogenesis. This bench-to-bedside cyclical approach has rapidly broadened our understanding of AD and enabled the rapid expansion of the AD therapeutic pipeline. In this brief review, we detail how molecular and blood profiling studies in AD laid the foundation for a therapeutic revolution, discuss currently approved and potential therapeutics for AD resulting from this bench-to-bedside approach, and highlight how this translational approach is being applied to advancing the therapeutic pipeline of alopecia areata.

Increased IL- 36γ in visceral adipose tissue as a key mediator of obesity-driven inflammation in colon cancer

Dysfunctional adipose tissue (AT) in the context of obesity promotes a chronic inflammatory state, associated with worse cancer progression and prognosis. Interleukin (IL)-36γ is a proinflammatory factor increased in obesity. The aim was to analyse the role of IL-36γ in colon cancer (CC) development in patients with obesity. Samples obtained from 74 volunteers (27 with normal weight (NW) and 47 with obesity (OB)) were used in a case-control study. Participants were also subclassified according to the presence of CC (45 without and 29 with CC). HT-29 cells were treated with pro-inflammatory factors, adipocyte conditioned media (ACM) and IL-36γ to evaluate the expression levels of inflammation- and extracellular matrix (ECM) remodelling-related molecules. Increased gene expression levels of IL36G and IL36R in visceral AT from patients with OB and CC were found. Moreover, mRNA levels of IL36G were significantly associated with the gene expression levels of its receptor and relevant genes involved in AT inflammation (ASC, IL1B and NLRP6). Consistently, IL36G expression was upregulated by hypoxia, inflammation-related factors (LPS, TNF-α and leptin) and by the adipocyte secretome from patients with obesity in HT-29 cancer cells. Furthermore, we revealed that IL-36γ increased the gene expression levels of inflammation-related genes (IL36G, IL1 A, IL1B, IL6, IL8 and NGAL) as well as ECM markers (MMP9, SPP1 and TNC) in HT-29 cells. Increased gene expression levels of IL36G in VAT from patients with OB and CC may promote a pro-inflammatory microenvironment favourable for tumour progression and migration. KEY MESSAGES: Obesity and colon cancer increase gene expression levels of IL36G and IL36R in visceral adipose tissue. Hypoxia, inflammation-related factors and the adipocyte secretome from patients with obesity upregulate mRNA levels of IL36G in HT-29 cancer cells. IL-36γ increase the gene expression levels of inflammation-related genes (IL36G, IL1A, IL1B, IL6, IL8 and NGAL) as well as ECM markers (MMP9, SPP1 and TNC) in HT-29 cells.

Future Directions and Pipeline Therapies for Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a painful, autoinflammatory condition with dramaticimpact on quality of life. As of January 1, 2024, there are 25 phase I-III clinical trials for topical and systematic medications in the management of HS. Only three medications, adalimumab, secukinumab and bemikizumab, are currently approved by the United States Food and Drug Administration for the treatment of moderate to severe HS. In addition, 15 nonmedication-based studies are ongoing, including those for various surgical techniques, botulinum toxin, laser and light-based therapies, differing wound care methods, and a variety of complementary and alternative medicine practices for HS.

LL37 complexed to double-stranded RNA induces RIG-I-like receptor signalling and Gasdermin E activation facilitating IL-36γ release from keratinocytes

The Interleukin-36 (IL-36) cytokine family have emerged as important players in mounting an inflammatory response at epithelial barriers and tailoring appropriate adaptive immune responses. As members of the Interleukin-1 superfamily, IL-36 cytokines lack a signal peptide for conventional secretion and require extracellular proteolysis to generate bioactive cytokines. Although the IL-36 family plays an important role in the pathogenesis of plaque and pustular psoriasis, little is known about the release mechanisms of these cytokines from keratinocytes and the physiological stimuli involved. Nucleic acid released from damaged or dying keratinocytes initiates early inflammatory signals that result in the breaking of tolerance associated with psoriasis pathogenesis onset. Cathelicidin peptide, LL37 binds to DNA or double-stranded RNA (dsRNA) and activates a type I Interferon responses in plasmacytoid dendritic cells and keratinocytes. Here, we demonstrate that LL37 binds to dsRNA and induces IL-36γ release from human primary keratinocytes. LL37/dsRNA complexes activate RIG-I-like Receptor signalling, resulting in Caspase-3 and Gasdermin E (GSDME) cleavage. Subsequent GSDME pore formation facilitates IL-36γ release. This response is magnified by priming with psoriasis-associated cytokines, IL-17A and IFNγ. IL-36γ release in this manner is largely independent of cell death in primary keratinocytes and lacked extracellular proteolysis of IL-36γ. Conversely, transfection of keratinocytes directly with dsRNA synthetic analogue, Poly(I:C) induces NLRP1 inflammasome activation, which facilitates IL-36γ expression and release in a GSDMD-dependent manner. Inflammasome-associated cell death also enables extracellular processing of IL-36γ by the release of keratinocyte-derived proteases. These data highlight the distinct responses triggered by dsRNA sensors in keratinocytes. Depending on the inflammatory context and magnitude of the exogenous threat, keratinocytes will release IL-36γ coupled with cell death and extracellular cleavage or release the inactive pro-form, which requires subsequent processing by neutrophil proteases to unleash full biological activity, as occurring in psoriatic skin. Cytoplasmic sensing of dsRNA in keratinocytes mediates IL-36γ release via caspase activity and GSDM pore formation Keratinocytes release IL-36γ upon stimulation with intracellular dsRNA alone or complexed to the psoriasis-associated cathelicidin anti-microbial peptide LL37. Left: Transfected dsRNA triggers NLRP1 inflammasome assembly and IL-1β release, which can enhance IL-36γ expression, resulting in IL-36γ release and extracellular cleavage by released proteases. Right: LL37/dsRNA complexes activate a MDA5-MAVS pathway facilitating the release of IL-36γ through Caspase-3 activation and GSDME pore formation.

Unveiling the role of resident memory T cells in psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by periods of remission and relapse. In this pathology, keratinocytes, dendritic cells, and different subpopulations of T cells are critical to developing psoriatic lesions. Although current treatments can reduce symptoms, they reappear in previously injured areas months after stopping treatment. Evidence has pointed out that besides T-helper 17 cells, other T-cell subsets may be involved in relapses. This review focuses on the leading evidence linking resident memory T cells and P2X7 receptor to psoriasis' pathogenesis and their role in this pathology. Finally, we discuss some of the most widely used experimental murine models and novel strategies to investigate further the role of resident memory T cells in psoriasis.

Circulating CD31 and resistin levels reflect different stages of coronary atherosclerosis in patients with psoriasis

Psoriasis is a skin disease with a complicated pathophysiology that includes an extensive inflammatory cytokine network. Nevertheless, the relationship between psoriasis severity, cytokine levels, and coronary artery atherosclerosis remains poorly understood. Our aim was to find serum markers as potential candidates for cardiovascular disease (CVD) risk monitoring in patients with psoriasis. Therefore, we examined coronary artery atherosclerosis via coronary computed tomography angiography (CCTA), serum cytokine levels via multiple immunoassays, and the patients' psoriasis state. Our findings reveal for the first time that the mainstream psoriasis cytokines interleukin 17A (IL-17A), IL-19, and IL-36 in the sera of Japanese patients with psoriasis showed a linear regression association with the Psoriasis Area and Severity Index score. Furthermore, the serum level of IL-19 was remarkably correlated to Th2-related serum cytokines such as IL-4 and IL-17E. When we investigated potential markers to monitor CVD in patients with psoriasis, circulating cluster of differentiation 31 (CD31) and resistin, but not psoriasis-related cytokines, were expressed differently at each stage of coronary atherosclerosis by CCTA. CD31 and resistin levels rose dramatically in individuals with psoriasis vulgaris (PV) and noncalcified atherosclerosis. In contrast, CD31 was negatively correlated with the coronary artery calcification score (CACS) in patients with PV, whereas resistin was inversely correlated with CACS in patients with psoriatic arthritis. In conclusion, the axis of IL-17A, IL-19, and IL-36 remains associated with the severity of psoriasis during the chronic phase of the disease, regardless of the application of topical or systemic treatment. Monitoring the levels of these cytokines can accurately determine the severity of skin inflammation. Resistin and CD31 are linked to coronary artery lesions and might be good candidates for tracking the progression of coronary atherosclerosis in patients with psoriasis.

Psoriasis: Immunological and genetic blueprints driving pathogenesis and potential for personalized therapies

Psoriasis is a long-lasting inflammatory skin condition that impacts millions globally. The occurrence of this disorder differs significantly across various areas, resulting from a complex interplay of genetic and environmental influences. In psoriasis, the pathogenesis represents a complex interaction of innate and adaptive immunity that plays a significant role in the disease manifestation process. Many genetic factors predispose to psoriasis, which is considered a polygenic disease. Several genes concerning pathways like NF-κB and PI3K/Akt that modulate the amplification of inflammatory response and keratinocyte dysregulation have been elaborated in the light of their differential expression, susceptibility loci, and polymorphisms. Such genetic insights could open a whole new avenue for precision medicine in which biomarkers and gene-targeting therapies are promising options for personalized treatment. This review emphasizes the need for complex investigations into psoriasis, from molecular mechanisms to clinical manifestations, to bridge the gap between basic research and therapeutic development by furthering the understanding of psoriasis and paving the way for innovative treatments addressing skin lesions and systemic effects.

The Central Roles of Keratinocytes in Coordinating Skin Immunity

The function of keratinocytes (KCs) to form a barrier and produce cytokines is well-known, but recent progress has revealed many different roles for KCs in regulation of skin immunity. In this review, we provide an update on the current understanding of how KCs communicate with microbes, immunocytes, neurons, and other cells to form an effective immune barrier. We catalog the large list of genes and metabolites of KCs that participate in host defense and discuss the mechanisms of immune crosstalk, addressing how KCs simultaneously form a physical barrier, communicate with fibroblasts, and control immune signals. Overall, the signals sent and received by KCs are an exciting group of therapeutic targets to explore in the treatment of dermatologic disorders.

Recent advances in mRNA-based cancer vaccines encoding immunostimulants and their delivery strategies

The high prevalence of drug resistance, relapse, and unfavorable response rate of conventional cancer therapies necessitate the development of more efficient treatment modalities. Immunotherapy represents a novel therapeutic approach to cancer treatment in which the immune system's potential is harnessed to recognize and eliminate tumor cells. mRNA cancer vaccines, as a burgeoning field of immunotherapy, have recently drawn particular attention, and among mRNAs encoding tumor-associated antigens, tumor-specific antigens, and immune stimulatory factors, the latter has been relatively less explored. These immunostimulatory mRNAs encode a range of proteins, including stimulatory ligands, receptors, enzymes, pro-inflammatory cytokines, and inhibitory binding proteins, which collectively augment the host immune system's ability against cancerous cells. In this review, we aimed to provide a comprehensive account of mRNA-based cancer vaccines encoding immune stimulants, encompassing their current status, mechanisms of action, delivery strategies employed, as well as recent advances in preclinical and clinical studies. The potential challenges, strategies and future perspectives have also been discussed.

The Contribution of the Skin Microbiome to Psoriasis Pathogenesis and Its Implications for Therapeutic Strategies

Psoriasis is a common chronic inflammatory skin disease, associated with significant morbidity and a considerable negative impact on the patients' quality of life. The complex pathogenesis of psoriasis is still incompletely understood. Genetic predisposition, environmental factors like smoking, alcohol consumption, psychological stress, consumption of certain drugs, and mechanical trauma, as well as specific immune dysfunctions, contribute to the onset of the disease. Mounting evidence indicate that skin dysbiosis plays a significant role in the development and exacerbation of psoriasis through loss of immune tolerance to commensal skin flora, an altered balance between Tregs and effector cells, and an excessive Th1 and Th17 polarization. While the implications of skin dysbiosis in psoriasis pathogenesis are only starting to be revealed, the progress in the characterization of the skin microbiome changes in psoriasis patients has opened a whole new avenue of research focusing on the modulation of the skin microbiome as an adjuvant treatment for psoriasis and as part of a long-term plan to prevent disease flares. The skin microbiome may also represent a valuable predictive marker of treatment response and may aid in the selection of the optimal personalized treatment. We present the current knowledge on the skin microbiome changes in psoriasis and the results of the studies that investigated the efficacy of the different skin microbiome modulation strategies in the management of psoriasis, and discuss the complex interaction between the host and skin commensal flora.

Molecular aspects of Interleukin-36 cytokine activation and regulation

Interleukin-36 (IL-36) cytokines are structurally similar to other Interleukin-1 superfamily members and are essential to convey inflammatory responses at epithelial barriers including the skin, lung, and gut. Due to their potent effects on immune cells, IL-36 cytokine activation is regulated on multiple levels, from expression and activation to receptor binding. Different IL-36 isoforms convey specific responses as a consequence of particular danger- or pathogen-associated molecular patterns. IL-36 expression and activation are regulated by exogenous pathogens, including fungi, viruses and bacteria but also by endogenous factors such as antimicrobial peptides or cytokines. Processing of IL-36 into potent bioactive forms is necessary for host protection but can elevate tissue damage. Indeed, exacerbated IL-36 signalling and hyperactivation are linked to the pathogenesis of diseases such as plaque and pustular psoriasis, emphasising the importance of understanding the molecular aspects regulating IL-36 activation. Here, we summarise facets of the electrochemical properties, regulation of extracellular cleavage by various proteases and receptor signalling of the pro-inflammatory and anti-inflammatory IL-36 family members. Additionally, this intriguing cytokine subfamily displays many characteristics that are unique from prototypical members of the IL-1 family and these key distinctions are outlined here.

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.

Interleukin-1 family cytokines at the crossroads of microbiome regulation in barrier health and disease

Recent advances in understanding how the microbiome can influence both the physiology and the pathogenesis of disease in humans have highlighted the importance of gaining a deeper insight into the complexities of the host-microbial dialogue. In tandem with this progress, has been a greater understanding of the biological pathways which regulate both homeostasis and inflammation at barrier tissue sites, such as the skin and the gut. In this regard, the Interleukin-1 family of cytokines, which can be segregated into IL-1, IL-18 and IL-36 subfamilies, have emerged as important custodians of barrier health and immunity. With established roles as orchestrators of various inflammatory diseases in both the skin and intestine, it is now becoming clear that IL-1 family cytokine activity is not only directly influenced by external microbes, but can also play important roles in shaping the composition of the microbiome at barrier sites. This review explores the current knowledge surrounding the evidence that places these cytokines as key mediators at the interface between the microbiome and human health and disease at the skin and intestinal barrier tissues.

The Immunology of Psoriasis-Current Concepts in Pathogenesis

Psoriasis is one of the most common inflammatory skin diseases with a chronic, relapsing-remitting course. The last decades of intense research uncovered a pathological network of interactions between immune cells and other types of cells in the pathogenesis of psoriasis. Emerging evidence indicates that dendritic cells, TH17 cells, and keratinocytes constitute a pathogenic triad in psoriasis. Dendritic cells produce TNF-α and IL-23 to promote T cell differentiation toward TH17 cells that produce key psoriatic cytokines IL-17, IFN-γ, and IL-22. Their activity results in skin inflammation and activation and hyperproliferation of keratinocytes. In addition, other cells and signaling pathways are implicated in the pathogenesis of psoriasis, including TH9 cells, TH22 cells, CD8+ cytotoxic cells, neutrophils, γδ T cells, and cytokines and chemokines secreted by them. New insights from high-throughput analysis of lesional skin identified novel signaling pathways and cell populations involved in the pathogenesis. These studies not only expanded our knowledge about the mechanisms of immune response and the pathogenesis of psoriasis but also resulted in a revolution in the clinical management of patients with psoriasis. Thus, understanding the mechanisms of immune response in psoriatic inflammation is crucial for further studies, the development of novel therapeutic strategies, and the clinical management of psoriasis patients. The aim of the review was to comprehensively present the dysregulation of immune response in psoriasis with an emphasis on recent findings. Here, we described the role of immune cells, including T cells, B cells, dendritic cells, neutrophils, monocytes, mast cells, and innate lymphoid cells (ILCs), as well as non-immune cells, including keratinocytes, fibroblasts, endothelial cells, and platelets in the initiation, development, and progression of psoriasis.

Mature IL-36γ Induces Stratum Corneum Exfoliation in Generalized Pustular Psoriasis by Suppressing Corneodesmosin

Loss-of-function sequence variations in the IL36RN gene encoding IL-36 receptor antagonist cause familial generalized pustular psoriasis, which begins shortly after birth and is difficult to treat, and its effects on the epidermis are unclear. This study investigated the involvement of IL-36 receptor agonists in the epidermal formation of generalized pustular psoriasis. We found that the IL-36 receptor agonists, especially mature IL-36γ, stimulated IL-8 and pro-IL-36γ production in the epidermis while downregulating the genes encoding epidermal cornified envelope-related proteins, for example, corneodesmosin. IL-36 receptor antagonist and monoclonal anti-IL-36γ antibodies counteracted the effect of mature IL-36γ on corneodesmosin in keratinocytes in a dose-dependent manner. In the epidermis of patients with generalized pustular psoriasis with IL36RN loss-of-function sequence variations, pro-IL-36γ was overproduced in the epidermis, and corneodesmosin protein expression was markedly decreased in the region of giant subcorneal pustules (Kogoj's spongiform pustules), with high neutrophil infiltration. IL-8 induced by mature IL-36γ stimulated the infiltration of several neutrophils in the epidermis. The newly produced pro-IL-36γ is cleaved to the mature form by neutrophil proteases. This newly produced mature IL-36γ was predicted to further suppress the gene expression of corneodesmosin, leading to significant stratum corneum exfoliation and formation of the pustules. Overall, our results elucidate the mechanism underlying the formation of Kogoj's spongiform pustules in generalized pustular psoriasis.

Human interleukin-36γ plays a crucial role in cytokine induction during Sporothrix brasiliensis and S. schenckii infection in keratinocytes and PBMCs

Cytokines of the interleukin (IL)-1 superfamily including the different IL-36 isoforms, have been reported as mediators of acute and chronic inflammation in human skin diseases, such as psoriasis. Here, we demonstrated for the first time that Sporothrix schenckii and S. brasiliensis, the fungi that cause subcutaneous infection sporotrichosis, can induce the expression of IL-36α, IL-36γ and IL-36Ra in human keratinocytes and primary peripheral blood mononuclear cells (PBMCs). Specifically, IL-36γ was differentially expressed by keratinocytes stimulated with Sporothrix yeasts when compared to the commensal microorganism Staphylococcus epidermidis. The exposure of keratinocytes to 24 h or 7-days culture supernatant of PBMCs stimulated with Sporothrix induced higher IL-36γ production compared to direct stimulation of keratinocytes with the live fungus. We identified that IL-36γ mRNA expression in keratinocytes is increased in the presence of IL-17, TNF, IL-1β and IL-1α and these cytokines may act synergistically to maintain IL-36γ production. Lastly, using a cohort of 164 healthy individuals, we showed that individuals carrying variants of the IL36G gene (rs11690399 and rs11683399) exhibit increased IL-36γ production as well as increased innate cytokine production after Sporothrix exposure. Importantly, stimulation of PBMCs with recombinant IL-36γ increased the production of IL-1β and IL-6, while IL-36Ra were able to decrease the concentration of these cytokines. Our findings contribute to the understanding of the pathogenesis of sporotrichosis and suggest that IL-36γ may be involved in maintaining the cytokine loop that leads to tissue destruction by exacerbating the immune response in sporotrichosis. Of high interest, we present the IL-36 signalling pathway as a potential new therapeutic target.

Fucosylation deficiency enhances imiquimod-induced psoriasis-like skin inflammation by promoting CXCL1 expression

Psoriasis is a multifaceted chronic inflammatory skin disease; however, its underlying molecular mechanisms remain unclear. In this study, we explored the role of fucosylation in psoriasis using an imiquimod-induced psoriasis-like mouse model. ABH antigen and fucosyltransferase 1 (Fut1) expression was reduced in the granular layer of lesional skin of patients with psoriasis. In particular, the blood group H antigen type 2 (H2 antigen)-a precursor of blood group A and B antigens-and FUT1 were highly expressed throughout the spinous layer in both patients with psoriasis and the skin of imiquimod-treated mice. Upon the application of imiquimod, Fut1-deficient mice, which lacked the H2 antigen, exhibited higher clinical scores based on erythema, induration, and scaling than those of wild-type mice. Imiquimod-treated Fut1-deficient mice displayed increased skin thickness, trans-epidermal water loss, and Gr-1+ cell infiltration compared with wild-type mice. Notably, the levels of CXCL1 protein and mRNA were significantly higher in Fut1-deficient mice than those in wild-type mice; however, there were no significant differences in other psoriasis-related markers, such as IL-1β, IL-6, IL-17A, and IL-23. Fut1-deficient primary keratinocytes treated with IL-17A also showed a significant increase in both mRNA and protein levels of CXCL1 compared with IL-17A-treated wild-type primary keratinocytes. Further mechanistic studies revealed that this increased Cxcl1 mRNA in Fut1-deficient keratinocytes was caused by enhanced Cxcl1 mRNA stabilization. In summary, our findings indicated that fucosylation, which is essential for ABH antigen synthesis in humans, plays a protective role in psoriasis-like skin inflammation and is a potential therapeutic target for psoriasis.

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.

Signaling pathways and targeted therapies for psoriasis

Psoriasis is a common, chronic, and inflammatory skin disease with a high burden on individuals, health systems, and society worldwide. With the immunological pathologies and pathogenesis of psoriasis becoming gradually revealed, the therapeutic approaches for this disease have gained revolutionary progress. Nevertheless, the mechanisms of less common forms of psoriasis remain elusive. Furthermore, severe adverse effects and the recurrence of disease upon treatment cessation should be noted and addressed during the treatment, which, however, has been rarely explored with the integration of preliminary findings. Therefore, it is crucial to have a comprehensive understanding of the mechanisms behind psoriasis pathogenesis, which might offer new insights for research and lead to more substantive progress in therapeutic approaches and expand clinical options for psoriasis treatment. In this review, we looked to briefly introduce the epidemiology, clinical subtypes, pathophysiology, and comorbidities of psoriasis and systematically discuss the signaling pathways involving extracellular cytokines and intracellular transmission, as well as the cross-talk between them. In the discussion, we also paid more attention to the potential metabolic and epigenetic mechanisms of psoriasis and the molecular mechanistic cascades related to its comorbidities. This review also outlined current treatment for psoriasis, especially targeted therapies and novel therapeutic strategies, as well as the potential mechanism of disease recurrence.

Immunosuppression causes dynamic changes in expression QTLs in psoriatic skin

Psoriasis is a chronic, systemic inflammatory condition primarily affecting skin. While the role of the immune compartment (e.g., T cells) is well established, the changes in the skin compartment are more poorly understood. Using longitudinal skin biopsies (n = 375) from the "Psoriasis Treatment with Abatacept and Ustekinumab: A Study of Efficacy"(PAUSE) clinical trial (n = 101), we report 953 expression quantitative trait loci (eQTLs). Of those, 116 eQTLs have effect sizes that were modulated by local skin inflammation (eQTL interactions). By examining these eQTL genes (eGenes), we find that most are expressed in the skin tissue compartment, and a subset overlap with the NRF2 pathway. Indeed, the strongest eQTL interaction signal - rs1491377616-LCE3C - links a psoriasis risk locus with a gene specifically expressed in the epidermis. This eQTL study highlights the potential to use biospecimens from clinical trials to discover in vivo eQTL interactions with therapeutically relevant environmental variables.

Regulatory Mechanism of the IL-33-IL-37 Axis via Aryl Hydrocarbon Receptor in Atopic Dermatitis and Psoriasis

Interleukin (IL)-33 and IL-37 have been identified as novel cytokines involved in various inflammatory diseases. However, their specific roles remain largely unknown. Recent studies have shown that IL-33, which triggers inflammation, and IL-37, which suppresses it, cooperatively regulate the balance between inflammation and anti-inflammation. IL-33 and IL-37 are also deeply involved in the pathogenesis of inflammatory skin diseases such as atopic dermatitis (AD) and psoriasis. Furthermore, a signaling pathway by which aryl hydrocarbon receptor (AHR), a receptor for dioxins, regulates the expression of IL-33 and IL-37 has been revealed. Here, we outline recent findings on the mechanisms regulating IL-33 and IL-37 expression in AD and psoriasis. IL-33 expression is partially dependent on mitogen-activated protein kinase (MAPK) activation, and IL-37 has a role in suppressing MAPK in human keratinocytes. Furthermore, IL-33 downregulates skin barrier function proteins including filaggrin and loricrin, thereby downregulating the expression of IL-37, which colocalizes with these proteins. This leads to an imbalance of the IL-33-IL-37 axis, involving increased IL-33 and decreased IL-37, which may be associated with the pathogenesis of AD and psoriasis. Therefore, AHR-mediated regulation of the IL-33-IL-37 axis may lead to new therapeutic strategies for the treatment of AD and psoriasis.

The emerging role of IL-38 in diseases: A comprehensive review

INTRODUCTION

Interleukin-38 (IL-38) is a new type of anti-inflammatory cytokine, which is mainly expressed in the immunity-related organs and is involved in various diseases including cardiovascular and cerebrovascular diseases, lung diseases, viral infectious diseases and autoimmune diseases.

AIM

This review aims to detail the biological function, receptors and signaling of IL-38, which highlights its therapeutic potential in related diseases.

CONCLUSION

This article provides a comprehensive review of the association between interleukin-38 and related diseases, using interleukin-38 as a keyword and searching the relevant literature through Pubmed and Web of science up to July 2023.

Increased Interleukin-36β Expression Promotes Angiogenesis in Japanese Atopic Dermatitis

While atopic dermatitis (AD) is considered as a T helper 2 (Th2)-centered disease, an increase in other types of inflammatory cytokines is also noted in AD and they may also contribute to the development of the disease. Recently, the efficacy of an anti-IL-36 receptor antibody in AD was demonstrated in a clinical trial. Although there have been several reports on IL-36α and IL-36γ expression and function in AD, IL-36β has been barely studied. In this report, we examined IL-36β expression and function using clinical samples of AD and the epidermal keratinocyte cell line, HaCaT cells. We demonstrated that IL-36β expression in epidermal keratinocytes was increased in AD lesional skin compared to healthy skin. IL-36β promoted vascular endothelial growth factor A production in HaCaT keratinocytes through phosphorylation of extracellular signal-regulated kinases 1 and 2. In addition, IL-36β up-regulated placental growth factor mRNA expression in HaCaT keratinocytes. IL-36β expression levels in epidermal keratinocytes were correlated with the number of dermal vessels in AD skin. These results suggest that IL-36β may play an important role for angiogenesis in lesional skin of AD and that IL-36β can be a therapeutic target in AD.

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.

Psoriasis and Leprosy: An Arcane Relationship

Purpose

Psoriasis (Ps) and leprosy are chronic inflammatory skin disorders, characterised by enhanced innate and adaptive immunity. Ps and leprosy rarely coexist. The molecular immune mechanism of the Ps and leprosy rarely coexistence is unclear.

Patients and Methods

RNA-sequencing (RNA-seq) was performed on 20 patients with Ps, 5 adults with lepromatous leprosy (L-lep), and 5 patients with tuberculoid leprosy (T-lep) to analyse the differentially expressed genes (DEGs) between them. Moreover, the biological mechanism of Ps and leprosy was explored by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, Gene Ontology (GO) analysis, Gene Set Enrichment Analysis analysis, and protein-protein interaction (PPI) analyses. Finally, 13 DEGs of 10 skin biopsies of Ps patients, 6 samples of L-lep patients, 6 samples of T-lep patients and 5 healthy controls were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

The PPI network was constructed and primarily associated with immune response, IL-17 signalling, and Toll-like receptor pathway between Ps and leprosy. Th17 markers (interleukin (IL)-19, IL-20, IL-36A, IL-36G, IL-22, IL-17A, and lipocalin-2 (LCN2) had higher expression in Ps than in L-lep and T-lep, whereas macrophage biomarkers (CLEC4E and TREM2), SPP1, and dendritic cell (DC)-related hallmarks (ITGAX) and TNF-a had significantly lower expression across Ps and T-lep than in L-lep.

Conclusion

To put it simply, Ps patients with IL-17A, IL-19, IL-20, IL-36A, IL-36G, and IL-22 in conjunction with LCN2 with up-graduated expression might be not susceptible to L-lep. However, high levels of CLEC4E, TREM2, and SPP1 in L-lep patients indicated that they unlikely suffered from Ps.

Single cell and spatial sequencing define processes by which keratinocytes and fibroblasts amplify inflammatory responses in psoriasis

The immunopathogenesis of psoriasis, a common chronic inflammatory disease of the skin, is incompletely understood. Here we demonstrate, using a combination of single cell and spatial RNA sequencing, IL-36 dependent amplification of IL-17A and TNF inflammatory responses in the absence of neutrophil proteases, which primarily occur within the supraspinous layer of the psoriatic epidermis. We further show that a subset of SFRP2+ fibroblasts in psoriasis contribute to amplification of the immune network through transition to a pro-inflammatory state. The SFRP2+ fibroblast communication network involves production of CCL13, CCL19 and CXCL12, connected by ligand-receptor interactions to other spatially proximate cell types: CCR2+ myeloid cells, CCR7+ LAMP3+ dendritic cells, and CXCR4 expressed on both CD8+ Tc17 cells and keratinocytes, respectively. The SFRP2+ fibroblasts also express cathepsin S, further amplifying inflammatory responses by activating IL-36G in keratinocytes. These data provide an in-depth view of psoriasis pathogenesis, which expands our understanding of the critical cellular participants to include inflammatory fibroblasts and their cellular interactions.

Potential skin health promoting benefits of costunolide: a therapeutic strategy to improve skin inflammation in imiquimod-induced psoriasis

Psoriasis is a recurrent inflammatory skin disease. IL-36-related cytokines are overexpressed in psoriasis, but the mechanism is not yet clear. Costunolide (Cos) is a sesquiterpenoid compound derived from the root of the traditional Chinese medicine Aucklandia lappa Decne. This study aimed to explore the mechanism of Cos on improving psoriasis-like skin inflammation. An in vivo model was established by applying imiquimod treatment to the back skin of mice, and an in vitro model was established by using polyinosinic-polycytidylic acid (Poly(I:C)) stimulated-mouse primary dermal fibroblasts to induce inflammation. The results showed that Cos improved the pathological changes of psoriasis-like skin inflammation. In addition, Cos could inhibit epidermal damage and inflammation-related expression and improve the occurrence of skin-related inflammation in both in vivo and in vitro experiments. The improvement of psoriasis-like skin inflammatory response might be through the P2X7R/IL-36 signaling pathway. Collectively, Cos has an inhibitory effect on the expression of psoriasis-like skin inflammation. This showed that Cos has potential skin health promoting benefits by preventing psoriasis-like skin inflammation.

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.

Management of Infections in Psoriatic Patients Treated with Systemic Therapies: A Lesson from the Immunopathogenesis of Psoriasis

Modern treatments continue to be developed based on identifying targets within the innate and adaptive immune pathways associated with psoriasis. Whilst there is a sound biologic rationale for increased risk of infection following treatment with immunomodulators, the clinical evidence is confounded by these agents being used in patients affected with several comorbidities. In an era characterized by an ever greater and growing risk of infections, it is necessary to always be updated on this risk. In this mini-review, we will discuss recent updates in psoriasis immunopathogenesis as a rationale for systemic therapy, outline the risk of infections linked to the disease itself and systemic therapy as well, and provide an overview of the prevention and management of infections.

Dermal fibroblasts are the key sensors of aseptic skin inflammation through interleukin 1 release by lesioned keratinocytes

IL-1 plays a crucial role in triggering sterile inflammation following tissue injury. Although most studies associate IL-1 release by injured cells to the recruitment of neutrophils for tissue repair, the inflammatory cascade involves several molecular and cellular actors whose role remains to be specified. In the present study, we identified dermal fibroblasts among the IL-1R1-expressing skin cells as key sensors of IL-1 released by injured keratinocytes. After in vitro stimulation by recombinant cytokines or protein extracts of lysed keratinocytes containing high concentrations of IL-1, we show that dermal fibroblasts are by far the most IL-1-responsive cells compared to keratinocytes, melanocytes and endothelial cells. Fibroblasts have the property to respond to very low concentrations of IL-1 (from 10 fg/ml), even in the presence of 100-fold higher concentrations of IL-1RA, by increasing their expression of chemokines such as IL-8 for neutrophil recruitment. The capacity of IL-1-stimulated fibroblasts to attract neutrophils has been demonstrated both in vitro using cell migration assay and in vivo using a model of superficial epidermal lesion in IL-1R1-deficient mice which harbored reduced expression of inflammatory mediators and neutrophil skin infiltration. Together, our results shed a light on dermal fibroblasts as key relay cells in the chain of sterile inflammation induced after epidermal lesion.

Regulation of Interleukin-36γ/IL-36R Signaling Axis by PIN1 in Epithelial Cell Transformation and Breast Tumorigenesis

Simple Summary

Members of the interleukin (IL)-1 cytokine family exhibit dual functions in the regulation of inflammation and cancer. Recent studies have shown the critical role of IL-36γ, the newly identified IL-1 family member, in the regulation of cellular processes implicated in the progression of cancer. Therefore, the underlying mechanism of IL-36γ in tumor development is of considerable interest. Here, we identified the pivotal role of IL-36γ in the proliferation of breast cancer cells. Consistently, IL-36γ was found to promote epithelial cell transformation via the activation of c-Fos, c-Jun, and AP-1 transcription factors, followed by the IL36R-mediated MEK/ERK and JNK/c-Jun cascades. Furthermore, our findings demonstrate the critical role of PIN1 in the regulation of IL-36γ-induced mammary gland tumorigenesis.

Abstract

Given the increasing recognition of the relationship between IL-1 cytokines, inflammation, and cancer, the significance of distinct members of the IL-1 cytokine family in the etiology of cancer has been widely researched. In the present study, we investigated the underlying mechanism of the IL-36γ/IL-36R axis during breast cancer progression, which has not yet been elucidated. Initially, we determined the effects of IL-36γ on the proliferation and epithelial cell transformation of JB6 Cl41 mouse epidermal and MCF7 human breast cancer cells using BrdU incorporation and anchorage-independent growth assays. We found that treatment with IL-36γ increased the proliferation and colony formation of JB6 Cl41 and MCF7 cells. Analysis of the mechanism underlying the neoplastic cell transformation revealed that IL-36γ induced IL-36R-mediated phosphorylation of MEK1/2, ERK1/2, JNK1/2, and c-Jun, resulting in increased c-Fos, c-Jun, and AP-1 activities in JB6 Cl41 and MCF7 cells. Furthermore, the IL-36γ-induced tumorigenic capacity of MCF7 cells was considerably enhanced by PIN1, following MEK/ERK and JNK/c-Jun signaling. Interestingly, blocking PIN1 activity using juglone suppressed the IL-36γ-induced increase in the anchorage-independent growth of 4T1 metastatic mouse breast cancer cells. Finally, in a syngeneic mouse model, IL-36γ-induced tumor growth in the breast mammary gland was significantly inhibited following PIN1 knockout.

Diverse Control Mechanisms of the Interleukin-1 Cytokine Family

The majority of interleukin-1 (IL-1) family cytokines lack amino terminal secretion signals or transmembrane domains for secretion along the conventional biosynthetic pathway. Yet, these factors must be translocated from the cytoplasm across the plasma membrane into the extracellular space in order to regulate inflammation. Recent work has identified an array of mechanisms by which IL-1 family cytokines can be released into the extracellular space, with supramolecular organizing centers known as inflammasomes serving as dominant drivers of this process. In this review, we discuss current knowledge of the mechanisms of IL-1 family cytokine synthesis, processing, and release from cells. Using this knowledge, we propose a model whereby host metabolic state dictates the route of IL-1β secretion, with implications for microbial infection and sterile inflammation.

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.

Therapeutic potential of MCC950, a specific inhibitor of NLRP3 inflammasome

NOD-like receptor protein 3 (NLRP3), an important intracellular pattern recognition receptor, is a component of the NLRP3 inflammasome along with apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) and pro-caspase-1. Previous studies have shown that dysregulation of NLRP3 inflammasome may be associated with several human diseases, and therefore blocking NLRP3 inflammasome activation may represent a therapeutic strategy for various diseases. MCC950 is a specific small-molecule inhibitor that selectively blocks activation of the NLRP3 inflammasome. In recent years, research on MCC950 has expanded; its targets are gradually being elucidated, and its metabolism and toxicity have been a focus of study. Preclinical research of MCC950 has yielded promising findings, and MCC950 has shown good efficacy in the treatment of autoimmune diseases, cardiovascular diseases, metabolic diseases and other diseases. Furthermore, clinical trials of MCC950 and other inhibitors of NLRP3 inflammasome have also been conducted. In this review, we discuss the drug targets, metabolism, toxicity and preclinical and clinical research advances of MCC950. We further discuss the clinical therapeutic potential of MCC950 to provide insights for the further study and application of MCC950.

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.

Transcriptomic Profiling of Peripheral Edge of Lesions to Elucidate the Pathogenesis of Psoriasis Vulgaris

Elucidating transcriptome in the peripheral edge of the lesional (PE) skin could provide a better understanding of the molecules or signalings that intensify inflammation in the PE skin. Full-thickness biopsies of PE skin and uninvolved (UN) skin were obtained from psoriasis patients for RNA-seq. Several potential differentially expressed genes (DEGs) in the PE skin compared to those in the UN skin were identified. These DEGs enhanced functions such as angiogenesis, growth of epithelial tissue, chemotaxis and homing of cells, growth of connective tissues, and degranulation of myeloid cells beneath the PE skin. Moreover, the canonical pathways of IL-17A, IL-6, and IL-22 signaling were enriched by the DEGs. Finally, we proposed that inflammation in the PE skin might be driven by the IL-36/TLR9 axis or IL-6/Th17 axis and potentiated by IL-36α, IL-36γ, IL-17C, IL-8, S100A7, S100A8, S100A9, S100A15, SERPINB4, and hBD-2. Along with IL-36α, IL-17C, and IκBζ, ROCK2 could be an equally important factor in the pathogenesis of psoriasis, which may involve self-sustaining circuits between innate and adaptive immune responses via regulation of IL-36α and IL-36γ expression. Our finding provides new insight into signaling pathways in PE skin, which could lead to the discovery of new psoriasis targets.

A review of IL-36: an emerging therapeutic target for inflammatory dermatoses

BACKGROUND

IL-36 cytokines are members of the IL-1 superfamily. Increasing evidence in the IL-36 pathway demonstrates their potential as a therapeutic target for treating inflammatory skin diseases, such as generalized pustular psoriasis (GPP).

OBJECTIVE

A narrative review was written to further study preclinical and clinical evidence for the role of IL-36 in psoriasis, atopic dermatitis (AD), hidradenitis suppurativa (HS), acne, autoimmune blistering diseases, and neutrophilic dermatoses.

RESULTS

IL-36 has important downstream effects such as inducing expression of inflammatory cytokines, antimicrobial peptides, and growth factors. Increased expression of IL-36 cytokines has been observed in the lesional skin of patients with psoriasis. Studies of other inflammatory skin diseases have also noted similar findings, albeit to a lesser extent. IL-36 inhibition has been shown to be effective in GPP and is currently being studied for other inflammatory skin diseases.

CONCLUSIONS

The IL-36 pathway contributes to pathogenesis of many inflammatory skin diseases and is a promising therapeutic target.

Orchestrated Cytokines Mediated by Biologics in Psoriasis and Its Mechanisms of Action

Psoriasis is an autoimmune disease mediated by disturbed T cells and other immune cells, and is defined by deep-red, well-demarcated skin lesions. Due to its varied etiologies and indefinite standard pathogenesis, it is challenging to consider the right treatment exclusively for each psoriasis patient; thus, researchers yearn to seek even more precise treatments other than topical treatment and systemic therapy. Using biologics to target specific immune components, such as upregulated cytokines secreted by activated immune cells, is the most advanced therapy for psoriasis to date. By inhibiting the appropriate pro-inflammatory cytokines, cellular signaling can be altered and, thus, can inhibit further downstream inflammatory pathways. Herein, the roles of cytokines with their mechanisms of action in progressing psoriasis and how the usage of biologics alleviates cellular inflammation are discussed. In addition, other potential pro-inflammatory cytokines, with their mechanism of action, are presented herein. The authors hope that this gathered information may benefit future research in expanding the discovery of targeted psoriasis therapy.

Interleukin-1 Receptor-Like 2: One Receptor, Three Agonists, and Many Implications

The interleukin (IL)-1 superfamily of cytokines comprises 11 pro- and anti-inflammatory cytokines, which play essential roles during the immune response. Several pathogenic pathways are initiated by IL-1RL2 (interleukin 1 receptor-like 2) signaling, also known as IL-36R, in the skin, lungs, and gut. IL-36 cytokines promote the secretion of proinflammatory cytokines and chemokines, upregulation of antimicrobial peptides, proliferation mediators, and adhesion molecules on endothelial cells. In addition, the IL-36-IL-1RL2 axis has an essential role against viral infections, including a potential role in COVID-19 pathology. The evidence presented in this review highlights the importance of the axis IL-36-IL-1RL2 in the development of several inflammation-related diseases and the healing process. It suggests that IL-1RL2 ligands have specific roles depending on the tissue or cell source. However, there is still much to discover about this cytokine family, their functions in other organs, and how they accomplish a dual effect in inflammation and healing.

The Protective Role of IL-36/IL-36R Signal in Con A-Induced Acute Hepatitis

The IL-36 family, including IL-36α, IL-36β, IL-36γ, and IL-36R antagonist, belong to the IL-1 superfamily. It was reported that IL-36 plays a role in immune diseases. However, it remains unclear how IL-36 regulates inflammation. To determine the role of IL-36/IL-36R signaling pathways, we established an acute hepatitis mouse model (C57BL/6) by i.v. injection of the plant lectin Con A. We found that the levels of IL-36 were increased in the liver after Con A injection. Our results demonstrated the infiltrated neutrophils, but not the hepatocytes, were the main source of IL-36 in the liver. Using the IL-36R-/- mouse model (H-2b), we surprisingly found that the absence of IL-36 signals led to aggravated liver injury, as evidenced by increased mortality, elevated serum alanine aminotransferase and aspartate aminotransferase levels, and severe liver pathological changes. Further investigations demonstrated that a lack of IL-36 signaling induced intrahepatic activation of CD4+ and CD8+ T lymphocytes and increased the production of inflammatory cytokines. In addition, IL-36R-/- mice had reduced T regulatory cell numbers and chemokines in the liver. Together, our results from the mouse model suggested a vital role of IL-36 in regulating T cell function and homeostasis during liver inflammation.

The role of IL-36 subfamily in intestinal disease

Interleukin (IL)-36 is a subfamily, of the IL-1 super-family and includes IL-36α, IL-36β, IL-36γ, IL-38 and IL-36Ra. IL-36 cytokines are involved in the pathology of multiple tissues, including skin, lung, oral cavity, intestine, kidneys and joints. Recent studies suggest that IL-36 signaling regulates autoimmune disease in addition to antibacterial and antiviral responses. Most research has focused on IL-36 in skin diseases such as psoriasis, however, studies on intestinal diseases are also underway. This review outlines what is known about the bioactivity of the IL-36 subfamily and its role in the pathogenesis of intestinal diseases such as inflammatory bowel disease, colorectal cancer, gut dysbacteriosis and infection, and proposes that IL-36 may be a target for novel therapeutic strategies to prevent or treat intestinal diseases.

Increased Levels of Interleukin-36 in Obesity and Type 2 Diabetes Fuel Adipose Tissue Inflammation by Inducing Its Own Expression and Release by Adipocytes and Macrophages

Interleukin (IL)-36 is a recently described cytokine with well-known functions in the regulation of multiple inflammatory diseases. Since no data exists on how this cytokine regulates adipose tissue (AT) homeostasis, we aimed to explore the function of a specific isoform, IL-36γ, an agonist, in human obesity and obesity-associated type 2 diabetes as well as in AT inflammation and fibrosis. Plasma IL-36γ was measured in 91 participants in a case-control study and the effect of weight loss was evaluated in 31 patients with severe obesity undergoing bariatric surgery. Gene expression levels of IL36G and its receptor were analyzed in relevant human metabolic tissues. The effect of inflammatory factors and IL-36γ was determined in vitro in human adipocytes and macrophages. We found, for the first time, that the increased (P<0.05) circulating levels of IL-36γ in patients with obesity decreased (P<0.001) after weight and fat loss achieved by Roux-en-Y gastric bypass and that gene expression levels of IL36G were upregulated in the visceral AT (P<0.05) and in the peripheral blood mononuclear cells (P<0.01) from patients with obesity. We also demonstrated increased (P<0.05) expression levels of Il36g in the epididymal AT from diet-induced obese mice. IL36G was significantly enhanced (P<0.001) by LPS in human adipocytes and monocyte-derived macrophages, while no changes were found after the incubation with anti-inflammatory cytokines. The addition of IL-36γ for 24 h strongly induced (P<0.01) its own expression as well as key inflammatory and chemoattractant factors with no changes in genes associated with fibrosis. Furthermore, adipocyte-conditioned media obtained from patients with obesity increased (P<0.01) the release of IL-36γ and the expression (P<0.05) of cathepsin G (CTSG) in monocyte-derived macrophages. These findings provide, for the first time, evidence about the properties of IL-36γ in the regulation of AT-chronic inflammation, emerging as a link between AT biology and the obesity-associated comorbidities.

Cytokine alterations in psoriasis: an updated review

INTRODUCTION

Psoriasis is a chronic immune-mediated disease affecting 125 million people globally. It is characterized by erythematous plaques in the skin, covered by silvery scales. However, non-cutaneous manifestations (e.g., joint symptoms in psoriatic arthritis) and a high prevalence of other immune-mediated diseases such as inflammatory bowel diseases reflect its systemic nature. So far, research on psoriasis pathogenesis has improved our knowledge of the roles of the immune system, and cytokines play significant roles in immune responses.

AREAS COVERED

Herein, we review cytokine changes in psoriasis patients. Moreover, we will investigate the possible relationships between disease severity and cytokines alongside describing cytokine alterations in psoriasis patients with other comorbidities. Lastly, we will discuss the biologics and their effects on cytokines in psoriasis patients.

EXPERT OPINION

Psoriasis could develop various clinical types and clinical manifestations in people. It is an immune-mediated disease, and these manifestations are associated with different impaired cytokines. Imbalanced cytokines could lead to abnormal keratinocytes, neovascularization, and inflammation in psoriasis patients. So, a better understanding of the cytokine roles can help one choose a specific cytokine-targeting biologic to treat psoriasis. Moreover, these cytokines may be used as a severity marker for following up with these patients.