Interleukin-36 in hidradenitis suppurativa: evidence for a distinctive proinflammatory role and a key factor in the development of an inflammatory loop

A state-of-the-art systematic review of cancer in hidradenitis suppurativa

PURPOSE

Hidradenitis suppurativa (HS) is a chronic inflammatory disease associated with an increased risk of malignancy. The aim of this systematic review was to investigate the prevalence of different malignancies in HS.

METHODS

This review meets the PRISMA criteria. A data-driven approach was used to conduct the research, which involved a detailed keyword search. The study considered meta-analyses, experimental studies, case-control studies, cross-sectional studies, cohort studies, and recently published cases, published in English or German. Excluded were reviews, summaries, and letters to the editor, as well as studies, which are not based on the human population.

RESULTS

Out of the initial 443 publications found, 25 met the inclusion criteria for this systematic review. Patients with HS have a significantly increased risk of cancer, up to 50%. Additionally, the risk of oropharyngeal, central nervous system, colorectal, prostate, vulvar and non-melanocytic skin cancers increase with the severity of HS. The likelihood of comorbid lymphoma in patients with HS is significantly higher compared to healthy controls. In severe cases of HS, malignant degeneration of lesions in the groin, perianal, perineal, and gluteal region can occur in up to 4.6% of cases. This leads to the development of cSCC, which often have a complicated course, are more refractory to treatment and associated with a poorer outcome. The pathogenic mechanisms responsible for the malignant transformation of HS are currently unknown.

CONCLUSIONS

Patients with HS have a higher risk of cancer compared to the general population. Untreated, long-standing HS lesions can lead to complicated malignant degeneration resulting in cutaneous squamous cell carcinoma. The mechanisms underlying this malignant degeneration are not fully understood. HS patients also have an increased risk of developing other cancers, including prostate, oral, pharyngeal and colorectal cancers of the central nervous system and lymphomas.

Hidradenitis Suppurativa: New Targets and Emerging Treatments

Hidradenitis suppurativa (HS) is a chronic inflammatory skin condition that can be challenging to treat. Biologics and targeted small molecules have become an increasingly popular area of investigation for therapeutic development for moderate-to-severe HS, though only three biologics-adalimumab, secukinumab, and bimekizumab-have received US Food and Drug Administration (FDA) or European Medicines Evaluation Agency approval for treating HS. Promising agents under investigation are targeting interleukin 17A/F, JAK/STAT pathway, interleukin 36, interleukin 1, and more.

Activated and Naïve Allogenic Human Placental Mesenchymal Stromal Cells Exert an Immunomodulatory Effect on Hidradenitis Suppurativa Patient Peripheral Blood Mononuclear Cells

This pilot study aimed to evaluate the immunomodulatory effect of placental mesenchymal stem/stromal cells (MSCs) on peripheral blood mononuclear cells (PBMCs) from patients with hidradenitis suppurativa (HS). Blood samples were collected from 3 healthy and 3 patients with HS. Isolated PBMCs were stained with carboxyfluorescein succinimidyl ester (CFSE) and stimulated with phorbol 12-myristate 13-acetate (PMA)/Ionomycin solution. The PBMCs of patients with HS were co-cultured with naïve MSCs (n-MSCs), activated with tumor necrosis factor (TNF)-α (10 ng/mL) and interferon (IFN)-γ (10 ng/mL) MSCs (a-MSCs), or adalimumab (30 μg/mL). The division index (proliferation inhibition) of PBMCs was analyzed by flow cytometry using the Proliferation Modeling tool after 5 days of coculture. The relative inflammatory gene expression dynamics and cytokine secretion were quantified in triplicate using real-time polymerase chain reaction (PCR) and Luminex assays. PBMCs from the HS control group showed statistically significant increases in interleukin (IL)-6 and IFN-γ cytokine concentrations and IL-17A gene expression when compared with healthy subjects. Statistically significant reduction of the division index was found in the a-MSCs group (P = 0.04). Also, the Luminex assay revealed significantly reduced proinflammatory cytokine concentrations of IL-9 (P = 0.022) and IL-17A (P = 0.022) in the a-MSCs group with the same trend of numerical lowering in n-MSCs group when compared to HS control. The results of real-time PCR revealed a numerical increase in the expression of the IL-1β, IL-36α, and TNF-α genes in both the a-MSCs and n-MSCs groups compared with the HS control. In conclusion, our findings suggest that MSCs can effectively curb PBMCs proliferation and suppress the production of inflammatory cytokines. Moreover, the preactivation of MSCs with IFN-γ and TNF-α before use can enhance their therapeutic effectiveness. Nevertheless, a larger sample size is imperative to validate these results.

Inflammatory loop involving Staphylococcus aureus, IL-36γ, and cathepsin S drives immunity disorders in familial acne inversa keratinocytes

Acne inversa (AI) is an inflammatory skin disease associated with nicastrin (NCSTN) mutations. Despite the dysregulated bacterial-host immune interactions being an essential event in AI, the interaction between bacteria and keratinocytes in AI pathophysiology remains unclear. In this study, the NCSTN gene was suppressed using short hairpin RNA in HaCaT cells. Using RNA sequencing, real-time polymerase chain reaction, and western blotting, the expression of IL-36 cytokines was analyzed. The impact of Staphylococcus aureus on AI keratinocyte inflammation and underlying regulatory molecules was investigated by exposing the HaCaT cells to S. aureus. By stimulating NCSTN knockdown HaCaT cells with IFN-γ, the expression and regulatory mechanism of Cathepsin S (Cat S), an IL-36γ cleavage and activating protease, were investigated. After NCSTN knockdown, the IL-36α expression increased, and the IL-36Ra expression was downregulated. NCSTN/MEK/ERK impairment-induced Krüppel-like factor 4 (KLF4) up-regulation in concert with S. aureus-induced nuclear factor kappa B elevation acts synergistically to promote IL-36γ production with the subsequent IL-8 activation in HaCaT cells. NCSTN/MEK/ERK impairment was also observed in familial AI lesions. IFN-γ-induced Cat S in keratinocytes was enhanced after NCSTN knockdown. The expression of IFN-II pathway molecules was significantly upregulated in both NCSTN knockdown HaCaT cells and familial AI lesions. The Cat S expression was significantly elevated in the patient's AI lesions. Our findings suggested a synergistic relationship between S. aureus and NCSTN/MAPK/KLF4 axis in IL-36γ-induced familial AI keratinocytes.

[Hidradenitis suppurativa]

Hidradenitis suppurativa (HS) is a chronic inflammatory skin and systemic disease that is associated with considerable discomfort and a significant reduction in the quality of life. Despite a significantly increased understanding of the disease, the diagnosis is still delayed for many years. Delayed patient access to suitable treatment often leads to disease progression with increased surgical interventions and the occurrence of possible comorbidities. In recent years, there has been an improved understanding of the pathophysiology and, as a result the authorization of modern therapeutic agents for HS. The treatment of HS is based on three treatment pillars: surgery, antibiotics and biologics. Additionally, risk factors, such as smoking and obesity should be positively influenced. Knowledge of comorbidities and their interdisciplinary treatment is important for the individualized care of patients.

The role of interleukin-36 in health and disease states

The interleukin (IL)-1 superfamily upregulates immune responses and maintains homeostasis between the innate and adaptive immune systems. Within the IL-1 superfamily, IL-36 plays a pivotal role in both innate and adaptive immune responses. Of the four IL-36 isoforms, three have agonist activity (IL-36α, IL-36β, IL-36γ) and the fourth has antagonist activity (IL-36 receptor antagonist [IL-36Ra]). All IL-36 isoforms bind to the IL-36 receptor (IL-36R). Binding of IL-36α/β/γ to the IL-36R recruits the IL-1 receptor accessory protein (IL-1RAcP) and activates downstream signalling pathways mediated by nuclear transcription factor kappa B and mitogen-activated protein kinase signalling pathways. Antagonist binding of IL-36Ra to IL-36R inhibits recruitment of IL-1RAcP, blocking downstream signalling pathways. Changes in the balance within the IL-36 cytokine family can lead to uncontrolled inflammatory responses throughout the body. As such, IL-36 has been implicated in numerous inflammatory diseases, notably a type of pustular psoriasis called generalized pustular psoriasis (GPP), a chronic, rare, potentially life-threatening, multisystemic skin disease characterised by recurrent fever and extensive sterile pustules. In GPP, IL-36 is central to disease pathogenesis, and the prevention of IL-36-mediated signalling can improve clinical outcomes. In this review, we summarize the literature describing the biological functions of the IL-36 pathway. We also consider the evidence for uncontrolled activation of the IL-36 pathway in a wide range of skin (e.g., plaque psoriasis, pustular psoriasis, hidradenitis suppurativa, acne, Netherton syndrome, atopic dermatitis and pyoderma gangrenosum), lung (e.g., idiopathic pulmonary fibrosis), gut (e.g., intestinal fibrosis, inflammatory bowel disease and Hirschsprung's disease), kidney (e.g., renal tubulointerstitial lesions) and infectious diseases caused by a variety of pathogens (e.g., COVID-19; Mycobacterium tuberculosis, Pseudomonas aeruginosa, Streptococcus pneumoniae infections), as well as in cancer. We also consider how targeting the IL-36 signalling pathway could be used in treating inflammatory disease states.

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 Clinical Significance of Serum Interleukin-36α Levels in Patients with Gout

BACKGROUND

Gout is a chronic inflammatory diseases caused by monosodium urate crystal deposition. However, the role of interleukin (IL)-36 in gout has not dbeen elucidated.

METHODS

We enrolled 75 subjects, including 20 healthy controls (HC), 30 patients with acute gout attack and 25 patients in remission. Baseline data were obtained through clinical interrogation and laboratory data were obtained through tests of blood samples. Serum levels of IL-36α were detected using enzyme-linked immunosorbent assay. Spearman correlation analysis was used to investigate the correlation of IL-36α with other parameters. The diagnostic value of IL-36α was demonstrated using a receiver operating characteristic curve.

RESULTS

The serum IL-36α level of gout patients in acute attack and remission stage was significantly higher than that of HC. Serum IL-36α was positively correlated with alanine transaminase (ALT) and aspartate transaminase (AST). Serum amyloid A (SAA) levels positively correlated with C-reactive protein levels and erythrocyte sedimentation rates. Glutamyl transpeptidase levels positively correlated with AST and ALT levels.

CONCLUSION

In conclusion, serum IL-36α levels were elevated in patients with gout and correlated with the clinical markers of inflammation. Our findings suggest that IL-36α may be a novel inflammatory indicator for gout.

The Pathophysiology and Treatment of Pyoderma Gangrenosum-Current Options and New Perspectives

Pyoderma gangrenosum (PG) is an uncommon inflammatory dermatological disorder characterized by painful ulcers that quickly spread peripherally. The pathophysiology of PG is not fully understood; however, it is most commonly considered a disease in the spectrum of neutrophilic dermatoses. The treatment of PG remains challenging due to the lack of generally accepted therapeutic guidelines. Existing therapeutic methods focus on limiting inflammation through the use of immunosuppressive and immunomodulatory therapies. Recently, several reports have indicated the successful use of biologic drugs and small molecules administered for coexisting diseases, resulting in ulcer healing. In this review, we summarize the discoveries regarding the pathophysiology of PG and present treatment options to raise awareness and improve the management of this rare entity.

Therapeutic Potential of IL-1 Antagonism in Hidradenitis Suppurativa

The immunopathogenesis of HS is partially understood and exhibits features of an autoinflammatory disease; it is associated with the potential involvement of B cells and the contribution of Th1 or Th17 cell subsets. Recently, the pathogenic role of both innate immunity and IL-1 family cytokines in HS has been deeply investigated. Several agents targeting the IL-1 family pathway at different levels are currently available and under investigation for the treatment of HS. HS is still characterized by unmet clinical needs and represents an expanding field in the current scientific research. The aim of this narrative review is to describe the pathological dysregulation of IL-1 family members in HS and to provide an update on therapeutic strategies targeting IL-1 family cytokine signaling. Further clinical and preclinical data may likely lead to the enrichment of the therapeutic armamentarium of HS with IL-1 family cytokine antagonists.

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.

Hidradenitis suppurativa: new insights into disease mechanisms and an evolving treatment landscape

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic disabling and debilitating inflammatory disease with a high unmet medical need. The prevalence of HS reported in most studies is 1-2%, although it is likely to be under-reported and estimates vary globally owing to variance in data collection methods, ethnicity, geographical location and under-diagnosis. HS is characterized by persistent, painful cutaneous nodules, abscesses and draining tunnels commonly affecting the axillary, anogenital, inguinal and perianal/gluteal areas. Over time, chronic uncontrolled inflammation results in irreversible tissue destruction and scarring. Although the pathophysiology of HS has not been fully elucidated, the tumour necrosis factor (TNF)-α and interleukin (IL)-17 pathways have an important role, involving multiple cytokines. Currently, treatment options include topical medications; systemic therapies, including repeated and/or rotational courses of systemic antibiotics, retinoids and hormonal therapies; and various surgical procedures. The anti-TNF-α antibody adalimumab is currently the only biologic approved by both the US Food and Drug Administration and the European Medicines Agency for HS; however, its efficacy varies, with a clinical response reported in approximately 50% of patients in phase III trials. HS is a rapidly evolving field of discovery, with a diverse range of agents with distinct mechanisms of action currently being explored in clinical trials. Several other promising therapeutic targets have recently emerged, and agents targeting the IL-17 and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways are the most advanced in ongoing or completed phase III clinical trials. Alongside limited therapeutic options, significant challenges remain in terms of diagnosis and disease management, with a need for better treatment outcomes. Other unmet needs include significant diagnostic delays, thus missing the therapeutic 'window of opportunity'; the lack of standardized outcome measures in clinical trials; and the lack of established, well-defined disease phenotypes and biomarkers.

Spesolimab: a comprehensive review on the anti-IL-36 receptor antibody in dermatology

Interleukin-36 (IL-36) cytokines contribute to the pathogenesis of various inflammatory skin conditions and are potential therapeutic targets. Spesolimab is a monoclonal antibody that inhibits IL-36 signaling recently approved by the Food and Drug Administration for the management of generalized pustular psoriasis flares in adults. Clinical trials are evaluating the efficacy of this monoclonal antibody in a few other dermatological conditions. Here, this review comprehensively summarizes the safety and efficacy of spesolimab treatment in various dermatological conditions.

Genetic Variants Associated With Hidradenitis Suppurativa

Importance

Hidradenitis suppurativa (HS) is a common and severely morbid chronic inflammatory skin disease that is reported to be highly heritable. However, the genetic understanding of HS is insufficient, and limited genome-wide association studies (GWASs) have been performed for HS, which have not identified significant risk loci.

Objective

To identify genetic variants associated with HS and to shed light on the underlying genes and genetic mechanisms.

Design, Setting, and Participants

This genetic association study recruited 753 patients with HS in the HS Program for Research and Care Excellence (HS ProCARE) at the University of North Carolina Department of Dermatology from August 2018 to July 2021. A GWAS was performed for 720 patients (after quality control) with controls from the Add Health study and then meta-analyzed with 2 large biobanks, UK Biobank (247 cases) and FinnGen (673 cases). Variants at 3 loci were tested for replication in the BioVU biobank (290 cases). Data analysis was performed from September 2021 to December 2022.

Main Outcomes and Measures

Main outcome measures are loci identified, with association of P < 1 × 10-8 considered significant.

Results

A total of 753 patients were recruited, with 720 included in the analysis. Mean (SD) age at symptom onset was 20.3 (10.57) years and at enrollment was 35.3 (13.52) years; 360 (50.0%) patients were Black, and 575 (79.7%) were female. In a meta-analysis of the 4 studies, 2 HS-associated loci were identified and replicated, with lead variants rs10512572 (P = 2.3 × 10-11) and rs17090189 (P = 2.1 × 10-8) near the SOX9 and KLF5 genes, respectively. Variants at these loci are located in enhancer regulatory elements detected in skin tissue.

Conclusions and Relevance

In this genetic association study, common variants associated with HS located near the SOX9 and KLF5 genes were associated with risk of HS. These or other nearby genes may be associated with genetic risk of disease and the development of clinical features, such as cysts, comedones, and inflammatory tunnels, that are unique to HS. New insights into disease pathogenesis related to these genes may help predict disease progression and novel treatment approaches in the future.

Emerging Treatments and the Clinical Trial Landscape for Hidradenitis Suppurativa Part I: Topical and Systemic Medical Therapies

Hidradenitis suppurativa (HS) is an oftentimes debilitating condition that presents with painful nodules, abscesses, and sinus tracts. This condition is challenging to treat, in part because the pathogenesis of the condition is incompletely understood but also because there are limited therapeutic options. HS research is undergoing explosive growth with multiple new molecular pathways under study, which will hopefully lead to improved disease control for patients. Part I of this review will provide an overview of the emerging topical and systemic therapies under investigation for HS.

Blood T Helper Memory Cells: A Tool for Studying Skin Inflammation in HS?

Hidradenitis suppurativa (HS) is an inflammatory skin disease characterized by painful lesions on intertriginous body areas such as the axillary, inguinal, and perianal sites. Given the limited treatment options for HS, expanding our knowledge of its pathogenetic mechanisms is a prerequisite for novel therapeutic developments. T cells are assumed to play a crucial role in HS pathogenesis. However, it is currently unknown whether blood T cells show specific molecular alterations in HS. To address this, we studied the molecular profile of CD4⁺ memory T (Th_mem) cells purified from the blood of patients with HS and matched healthy participants. About 2.0% and 1.9% of protein-coding transcripts were found to be up- and down-regulated in blood HS Th_mem cells, respectively. These differentially expressed transcripts (DETs) are known to be involved in nucleoside triphosphate/nucleotide metabolic processes, mitochondrion organization, and oxidative phosphorylation. The detected down-regulation of transcripts involved in oxidative phosphorylation suggest a metabolic shift of HS Th_mem cells towards glycolysis. The inclusion of transcriptome data from skin from HS patients and healthy participants in the analyses revealed that in HS skin lesions, the expression pattern of transcripts identified as DETs in blood HS Th_mem cells was very similar to the expression pattern of the totality of protein-coding transcripts. Furthermore, there was no significant association between the extent of the expressional changes in the DETs of blood HS Th_mem cells and the extent of the expressional changes in these transcripts in HS skin lesions compared to healthy donor skin. Additionally, a gene ontology enrichment analysis did not demonstrate any association of the DETs of blood HS Th_mem cells with skin disorders. Instead, there were associations with different neurological diseases, non-alcoholic fatty liver disease, and thermogenesis. The levels of most DETs linked to neurological diseases showed a positive correlation to each other, suggesting common regulatory mechanisms. In summary, the transcriptomic changes in blood Th_mem cells observed in patients with manifest cutaneous HS lesions do not appear to be characteristic of the molecular changes in the skin. Instead, they could be useful for studying comorbidities and identifying corresponding blood biomarkers in these patients.

New Insight into the Molecular Pathomechanism and Immunomodulatory Treatments of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is an immune-mediated inflammatory disorder characterized by deep-seated nodules, abscesses, sinus tracts and scars localized in the intertriginous areas. It is accompanied by pain, malodourous secretion and a dramatically decreased quality of life. Although the pathogenesis has not been entirely elucidated, the primary event is follicular hyperkeratosis of the pilosebaceous apocrine unit. Since the registration of the tumor necrosis factor-alpha inhibitor Adalimumab in 2015, several cytokines have been implicated in the pathomechanism of HS and the research of novel therapeutic targets has been intensified. We provide an update on the inflammatory cytokines with a central role in HS pathogenesis and the most promising target molecules of future HS management.

Impact of Pretreatment Systemic Inflammatory Markers on Treatment Persistence with Biologics and Conventional Systemic Therapy: A Retrospective Study of Patients with Psoriasis Vulgaris and Psoriatic Arthritis

Systemic inflammation plays a central role in the pathophysiology of psoriasis. This study examined accessible systemic inflammatory markers in patients with psoriasis vulgaris and psoriatic arthritis. We aimed to evaluate their association with psoriasis severity, the presence of arthritis, and drug continuation rates. The findings revealed that neutrophil, monocyte, and platelet count, neutrophil/lymphocyte ratio, monocyte/lymphocyte ratio, systemic inflammation response index, systemic immune/inflammation index (SII), and CRP were positively correlated with Psoriasis Area and Severity Index scores. Patients presenting with higher platelet/lymphocyte ratio (PLR) or CRP values were more likely to be diagnosed with psoriatic arthritis than with psoriasis vulgaris in the multivariate regression analysis. Importantly, patients with higher pretreatment neutrophil or platelet count, PLR, and SII were associated with lower treatment continuation rates of conventional systemic agents. Higher pretreatment scores of systemic inflammatory markers did not affect treatment retention rates of biologics. These findings suggest that several accessible systemic inflammatory markers may effectively assess underlying systemic inflammation and may provide an indication for a therapeutic approach in patients with psoriasis vulgaris and psoriatic arthritis.

Neutrophilic granulocyte-derived B-cell activating factor supports B cells in skin lesions in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory disease characterized by painful inflamed nodules, abscesses, and pus-draining tunnels appearing in axillary, inguinal, and perianal skin areas. HS lesions contain various types of immigrated immune cells.

OBJECTIVE

This study aimed to characterize mediators that support lesional B/plasma cell persistence in HS.

METHODS

Skin samples from several cohorts of HS patients and control cohorts were assessed by mRNA sequencing, quantitative PCR on reverse-transcribed RNA, flow cytometry, and immunohistofluorescence. Blood plasma and cultured skin biopsy samples, keratinocytes, dermal fibroblasts, neutrophilic granulocytes (neutrophils), monocytes, and B cells were analyzed. Complex systems biology approaches were used to evaluate bulk and single-cell RNA sequencing data.

RESULTS

Proportions of B/plasma cells, neutrophils, CD8+ T cells, and M0 and M1 macrophages were elevated in HS lesions compared to skin of healthy and perilesional intertriginous areas. There was an association between B/plasma cells, neutrophils, and B-cell activating factor (BAFF, aka TNFSF13B). BAFF was abundant in HS lesions, particularly in nodules and abscesses. Among the cell types present in HS lesions, myeloid cells were the main BAFF producers. Mechanistically, granulocyte colony-stimulating factor in the presence of bacterial products was the major stimulus for neutrophils' BAFF secretion. Lesional upregulation of BAFF receptors was attributed to B cells (TNFRSF13C/BAFFR and TNFRSF13B/TACI) and plasma cells (TNFRSF17/BCMA). Characterization of the lesional BAFF pathway revealed molecules involved in migration/adhesion (eg, CXCR4, CD37, CD53, SELL), proliferation/survival (eg, BST2), activation (eg, KLF2, PRKCB), and reactive oxygen species production (eg, NCF1, CYBC1) of B/plasma cells.

CONCLUSION

Neutrophil-derived BAFF supports B/plasma cell persistence and function in HS lesions.

Interleukin-36 cytokines are overexpressed in the skin and sera of patients with bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune bullous disease, characterized by autoantibodies targeting BP180 and BP230. The role of interleukin (IL)-36, a potent chemoattractant for granulocytes, in BP remains elusive.The expression of IL-36 cytokines (IL-36α, β, γ) and their antagonists (IL-36Ra and IL-38) was analysed in the skin and serum samples of patients with BP (n = 31), psoriasis (n = 10) and healthy controls (HC) (n = 14) by quantitative polymerase chain reaction and enzyme linked immunosorbent assay, respectively. Skin and serum levels of all cytokines were correlated with the Bullous Pemphigoid Disease Area Index (BPDAI) score and with the serum concentration of pathogenic antibodies.IL-36α, IL-36β, IL-36γ and IL-36Ra were significantly (p < 0.05) overexpressed in BP skin compared to HC, without remarkable differences relative to psoriasis skin. The expression of IL-38 was significantly (p < 0.05) higher in BP compared to psoriasis skin.IL-36α and γ, but not β, serum concentrations were significantly (p < 0.05) higher in BP compared to HC. IL-36γ was significantly (p < 0.05) more expressed in the serum of psoriasis patients than BP. The serum concentration of IL-36Ra and IL-38 were similar between BP and HC, while IL-38 serum levels were significantly (p < 0.05) higher in BP compared to psoriasis patients. Serum IL-36α correlated significantly with BPDAI (r = 0.5 p = 0.001).IL-36 agonists are increased in BP patients, both locally and systemically. Serum IL-36α might represent a potential biomarker for BP. An inefficient balance between IL-36 agonists and antagonists is likely to occur during BP 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.

Keratinocytes and immune cells in the epidermis are key drivers of inflammation in hidradenitis suppurativa providing a rationale for novel topical therapies

BACKGROUND

Hidradenitis suppurativa (HS) is a debilitating inflammatory skin disease characterized by painful nodules, drainage and scarring in skin folds. Injectable adalimumab is the only drug approved by the US Food and Drug Administration for the treatment of HS. Although systemic Janus kinase (JAK) inhibitors show promise, serious side-effects have been reported. There are no highly effective topical treatments for HS; furthermore, the contribution of epidermal keratinocytes to the intense inflammation has largely been unexplored.

OBJECTIVES

We investigated the role of keratinocytes and epidermal immune cells in HS inflammation at all Hurley stages of disease severity. We aimed to determine whether ruxolitinib can mitigate inflammation from keratinocytes and to develop a better understanding of how topical therapeutics might benefit patients with HS.

METHODS

We used skin samples from 87 patients with HS (Hurley stages I-III) and 39 healthy controls to compare keratinocyte- and immune cell-driven epidermal inflammation, in addition to the response of lesional HS keratinocytes to treatment with interferon (IFN)-γ and ruxolitinib. We used haematoxylin and eosin staining, immunohistochemistry, immunoblotting and quantitative reverse-transcription polymerase chain reaction assessments in whole skin, isolated epidermis, and cultured keratinocytes from healthy controls and both nonlesional and lesional HS skin to identify and define epidermal and keratinocyte-mediated inflammation in HS and how this may be targeted by therapeutics.

RESULTS

HS lesional keratinocytes autonomously secreted high levels of chemokines, such as CCL2, CCL3 and CXCL3, which recruited neutrophils, CD8 T cells, and natural killer cells to the epidermis. Keratinocytes were the dominant source of tumour necrosis factor-α and interleukin (IL)-6 in HS lesions with little to no contribution from underlying dermal immune cells. In the presence of IFN-γ, which is dependent on immune cell infiltrate in vivo, keratinocytes expressed increased levels of additional cytokines including IL-1β, IL-12, IL-23 and IL-36γ. The JAK inhibitor ruxolitinib mitigated the expression of inflammatory cytokines and chemokines in HS lesional keratinocytes, thus providing a rationale for future study as a topical treatment for HS.

CONCLUSIONS

This study demonstrates that keratinocytes actively recruit immune cells to HS epidermis and interactions between these cells drive a broad inflammatory profile in HS epidermis. Targeting epidermal inflammation in HS with novel topical formulations may be highly efficacious with reduced systemic side-effects.

Sex-disaggregated population analysis in patients with hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is a common chronic inflammatory skin disease, which affects both sexes.

OBJECTIVES

Identification of sex-specific risk factors, comorbidity, clinical manifestations, and treatments in HS patients.

METHODS

A non-interventional, cross-sectional, mono-centric study with 500 HS patients. All patients were examined by dermatologists. Prospectively collected demographic, anamnestic, clinical data, and blood parameters were evaluated.

RESULTS

There were no significant differences in age at HS onset and in disease duration between female and male patients. Furthermore, no differences regarding the family history for HS were found between sexes. Regarding further risk factors for HS, central obesity was more frequent in women while extensive cigarette smoking and acne vulgaris were more commonly found among male patients. Regarding comorbidity, lower HDL-levels were significantly more frequent in men. Female patients were found to suffer significantly more often from back pain, especially in the neck/shoulder region and lower back. Analyzing the clinical manifestation of HS, the groin was more frequently involved in women and the axillae in men. Women showed a higher number of skin sites with inflammatory nodules, whereas fistulas were observed more frequently in men. Nevertheless, there was no difference in HS treatment applied to female vs. male patients.

LIMITATIONS

Data were obtained from a mono-centric study.

CONCLUSION

Significant differences in HS risk factors, comorbidity, and clinical manifestation exist between female and male patients. Thus, sex-specific differences should be taken into account in the prevention as well as medical and surgical treatment of HS patients.

Transcriptome Meta-Analysis Confirms the Hidradenitis Suppurativa Pathogenic Triad: Upregulated Inflammation, Altered Epithelial Organization, and Dysregulated Metabolic Signaling

Hidradenitis suppurativa (HS) is an inflammatory skin condition clinically characterized by recurrent painful deep-seated nodules, abscesses, and sinus tracks in areas bearing apocrine glands, such as axillae, breasts, groins, and buttocks. Despite many recent advances, the pathophysiological landscape of HS still demands further clarification. To elucidate HS pathogenesis, we performed a meta-analysis, set analysis, and a variant calling on selected RNA-Sequencing (RNA-Seq) studies on HS skin. Our findings corroborate the HS triad composed of upregulated inflammation, altered epithelial differentiation, and dysregulated metabolism signaling. Upregulation of specific genes, such as KRT6, KRT16, serpin-family genes, and SPRR3 confirms the early involvement of hair follicles and the impairment of barrier function in HS lesioned skin. In addition, our results suggest that adipokines could be regarded as biomarkers of HS and metabolic-related disorders. Finally, the RNA-Seq variant calling identified several mutations in HS patients, suggesting potential new HS-related genes associated with the sporadic form of this disease. Overall, this study provides insights into the molecular pathways involved in HS and identifies potential HS-related biomarkers.

Immunomodulatory Drugs in the Treatment of Hidradenitis Suppurativa—Possibilities and Limitations

Hidradenitis suppurativa, also known as acne inversa, is a chronic, progressive, debilitating, recurrent inflammatory skin disease characterized by the occurrence of very severe, persistent, painful nodules, abscesses, and fistulas, most commonly found in the skin folds of the axilla, groin, gluteal, and perianal areas. Treatment is rather difficult and typically requires the use of multiple modalities. Regardless of the presence of several therapeutic options, treatment often turns out to be ineffective or poorly selected concerning the clinical picture of the disease. Thus, the search for new biologics and other target treatments of hidradenitis suppurativa is ongoing. The safety and efficacy of adalimumab, still the only U.S. Food and Drug Administration approved biologic in the hidradenitis suppurativa treatment, paved the way for new drugs to be compared with it. Several more drugs with new immunological targets are currently under investigation for the treatment of acne inversa. The aim of the article was to present the current and future targets of acne inversa treatment, simultaneously providing insights into the molecular pathomechanisms of the disease.

IL-1 Family Cytokines in Inflammatory Dermatoses: Pathogenetic Role and Potential Therapeutic Implications

The interleukin-1 (IL-1) family is involved in the correct functioning and regulation of the innate immune system, linking innate and adaptative immune responses. This complex family is composed by several cytokines, receptors, and co-receptors, all working in a balanced way to maintain homeostasis. Dysregulation of these processes results in tissue inflammation and is involved in the pathogenesis of common inflammatory dermatoses such as psoriasis, hidradenitis suppurativa, and atopic dermatitis. Therefore, therapeutic targeting of IL-1 pathways has been studied, and several monoclonal antibodies are currently being assessed in clinical trials. So far, promising results have been obtained with anti-IL-36R spesolimab and imsidolimab in pustular psoriasis, and their efficacy is being tested in other conditions.

Ex Vivo Culture Models of Hidradenitis Suppurativa for Defining Molecular Pathogenesis and Treatment Efficacy of Novel Drugs

Hidradenitis suppurativa (HS) is a complex and debilitating inflammatory skin disease for which no effective treatment is available currently. This is partly because of the lack of adequate human or animal models for defining the pathobiology of the disease. Here, we describe the development of air-liquid (A-L) interface, liquid-submersion (L-S), and bioreactor (Bio) ex vivo skin culture models. All three ex vivo platforms were effective for culturing skin samples for up to 14 days. Tissue architecture and integrity remained intact for at least 3 days for healthy skin and 14 days for HS skin. Up to day 3, no significant differences were observed in % early apoptotic cells among all three platforms. However, late apoptotic/necrotic cell death was increased in HS skin at day 3 in A-L and Bio culture. These cultures efficiently support the growth of various cells populations, including keratinocytes and immune cells. Profiling inflammatory gene signatures in HS skin from these ex vivo cultures showed dynamic changes in expression at day 3 and day 14. All three culture platforms were necessary to represent the inflammatory gene status of HS skin at day 0, suggesting that not all gene clusters were identically altered in each culture method. Similarly, cytokine/chemokine profiling of the supernatants from vehicle- and drug-treated ex vivo HS cultures again showed a better prediction of drug efficacy against HS. Overall, development of these three culture systems collectively provides a powerful tool to uncover the pathobiology of HS progression and screen various drugs against HS.

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.

Insights into hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic, debilitating, inflammatory skin disorder with a prevalence of around 1% and a profound impact on patients' quality of life. Characteristic lesions such as inflammatory nodules, abscesses, and sinus tracts develop in the axillae, inguinal, and gluteal areas, typically during or after puberty. A complex interplay of genetic predisposition, hormonal factors, obesity, and smoking contributes to development and maintenance of the disease. HS is considered to arise from an intrinsic defect within the hair follicle, leading to follicular plugging, cyst formation, and subsequent rupture that in turn induce an acute inflammatory response characterized by elevated levels of IL-1β, IL-17, and TNF. Over time, acute lesions transition into chronic disease, with active draining sinus tracts accompanied by extensive fibrosis. HS is associated with other immune-mediated inflammatory diseases, metabolic and cardiovascular disorders, and psychiatric comorbidities. Treatment of HS often requires a combination of antibiotic or immunosuppressing therapies and surgical intervention. Nonetheless, the currently available treatments are not universally effective, and many drugs, which are often repurposed from other inflammatory diseases, are under investigation. Studies into the early stages of HS may yield treatments to prevent disease progression; yet, they are hampered by a lack of appropriate in vitro and animal models.

The Immunological Impact of IL-1 Family Cytokines on the Epidermal Barrier

The skin barrier would not function without IL-1 family members, but their physiological role in the immunological aspects of skin barrier function are often overlooked. This review summarises the role of IL-1 family cytokines (IL-1α, IL-1β, IL-1Ra, IL-18, IL-33, IL-36α, IL-36β, IL-36γ, IL-36Ra, IL-37 and IL-38) in the skin. We focus on novel aspects of their interaction with commensals and pathogens, the important impact of proteases on cytokine activity, on healing responses and inflammation limiting mechanisms. We discuss IL-1 family cytokines in the context of IL-4/IL-13 and IL-23/IL-17 axis-driven diseases and highlight consequences of human loss/gain of function mutations in activating or inhibitory pathway molecules. This review highlights recent findings that emphasize the importance of IL-1 family cytokines in both physiological and pathological cutaneous inflammation and emergent translational therapeutics that are helping further elucidate these cytokines.

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

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

Assessment of the Pharmacokinetics and Safety of Spesolimab, a Humanised Anti-interleukin-36 Receptor Monoclonal Antibody, in Healthy Non-Japanese and Japanese Subjects: Results from Phase I Clinical Studies

BACKGROUND AND OBJECTIVE

The interleukin-36 signalling pathway is associated with pathogenesis of a number of inflammatory diseases. Spesolimab is a selective, humanised, IgG1 antibody that targets the interleukin-36 receptor. We aimed to evaluate the pharmacokinetics, safety and tolerability of single and multiple doses of spesolimab in healthy non-Japanese and Japanese subjects.

METHODS

Five phase I clinical studies (three placebo-controlled dose-escalation, two open-label) were conducted in healthy volunteers; single or multiple doses of spesolimab were administered by intravenous infusion or subcutaneous injection. Plasma samples were collected to investigate the pharmacokinetics of spesolimab and evaluate changes with respect to dose, frequency of dosing, formulation and injection site. Immunogenicity, safety and tolerability were also assessed.

RESULTS

Intravenous spesolimab exhibited target-mediated drug disposition at low doses (0.01-0.3 mg/kg) and linear kinetics at doses ≥ 0.3 mg/kg. Steady state was not attained after the fourth weekly dose because of the long half-life (3-5 weeks). Bioavailability of subcutaneous spesolimab increased with increasing dose over the range of 150-600 mg and was higher when administered to the thigh than to the abdomen. The pharmacokinetic profile was consistent between Japanese and non-Japanese subjects. Positive anti-drug antibody responses occurred during the terminal phase of the spesolimab concentration-time profile in 26.7-33.3% and 16.7-37.5% of subjects receiving intravenous and subcutaneous spesolimab, respectively. The impact of anti-drug antibodies on spesolimab pharmacokinetics was low in healthy volunteers, with the impact on spesolimab plasma concentrations only observed in a few subjects at higher titres (≥ 11,400). No serious adverse events were reported; intravenous doses up to 1200 mg were well tolerated in healthy volunteers.

CONCLUSIONS

The pharmacokinetic profile and safety data obtained from these phase I clinical studies have been used to guide spesolimab dosing in clinical studies of patients with interleukin-36-mediated diseases.

CLINICAL TRIAL REGISTRATION

For Studies 1-5, NCT02525679, NCT02852824, NCT03100903, NCT03123094, NCT03617835.

Hidradenitis Suppurativa: Host-Microbe and Immune Pathogenesis Underlie Important Future Directions

Hidradenitis suppurativa (HS) is an inflammatory disease of the skin with a chronic, relapsing-remitting course. The pathogenesis of the disease is poorly understood and involves multiple factors, including genetics, environment, host-microbe interactions, and immune dysregulation. In particular, the composition of the cutaneous microbiome shifts as the disease progresses, although it is unclear whether this is a primary or secondary process. Trials with immunomodulatory therapy elucidate the role of specific immune pathways and cytokine signaling in disease mechanism, such as TNF-α, IL-1β, IL-12, IL-17, IL-23, and complement. Future studies should continue examining the causes of and contributing factors to microbial changes and immune dysregulation in HS pathogenesis.

Immunobiological Properties and Clinical Applications of Interleukin-38 for Immune-Mediated Disorders: A Systematic Review Study

Exponential growth in the usage of "cytokines" (as seroimmunobiomarkers) has facilitated more accurate prognosis, early diagnosis, novel, and efficient immunotherapeutics. Numerous studies have reported immunopathophysiological and immunopathological processes of interleukin-38 (IL-38). Therefore, in this systematic review article, the authors aimed to present an updated comprehensive overview on the immunobiological mechanisms, diagnostic, and immune gene-based therapeutic potentials of IL-38. According to our inclusion and exclusion criteria, a total of 216 articles were collected from several search engines and databases from the January 2012 to July 2021 time interval by using six main keywords. Physiologic or pathologic microenvironments, optimal dosage, and involved receptors affect the functionalities of IL-38. Alterations in serum levels of IL-38 play a major role in the immunopathogenesis of a wide array of immune-mediated disorders. IL-38 shows anti-inflammatory activities by reduction or inhibition of pro-inflammatory cytokines, supporting the therapeutic aspects of IL-38 in inflammatory autoimmune diseases. According to the importance of pre-clinical studies, it seems that manipulation of the immune system by immunomodulatory properties of IL-38 can increase the accuracy of diagnosis, and decipher optimal clinical outcomes. To promote our knowledge, more collaboration is highly recommended among laboratory scientists, internal/infectious diseases specialists, oncologists, immunologists, diseases-specific biomarkers scientists, and basic medical researchers.

Insights into the Pathogenesis of HS and Therapeutical Approaches

Hidradenitis suppurativa (HS) is a debilitating, chronic, (auto)inflammatory disease primarily affecting apocrine gland-rich areas of the body. Although pathogenic mechanisms responsible for HS have not yet been fully elucidated, it is a multifactorial process whose main target is the terminal follicle. The role of the inflammatory process (and consequently of cytokine milieu) and of several other factors (genetics, lifestyle, hormonal status, microbiome, innate and adaptive immune systems) involved in HS pathogenesis has been investigated (and often defined) over the years with a view to transferring research results from bench to bedside and describing a unique and universally accepted pathogenetic model. This review will update readers on recent advances in our understanding of HS pathogenesis and novel (potential) medical therapies for patients with moderate-to-severe HS.

Hidradenitis suppurativa: A folliculotropic disease of innate immune barrier dysfunction?

The innate immune system of human skin consists of a multi-layered barrier consisting of cells and soluble effector molecules charged with maintaining homeostasis and responding to insults and infections. It has become increasingly clear that these barrier layers become compromised in skin diseases, especially in disorders of an (auto)inflammatory nature. In the case of hidradenitis suppurativa, great strides have been made in recent years in characterizing the underlying breakdown in homeostatic innate immunity, including an increasing understanding of the central role of the hair follicle in this process. This breakdown appears to occur at multiple levels: the pilosebaceous unit, associated epithelium, the cutaneous microbiome, alteration of immune cell function and local molecular events such as complement activation. This review seeks to summarize, contextualize and analyse critically our current understanding of how these innate immune barriers become dysregulated in the early stage(s) of hidradenitis suppurativa, and to speculate on where potential hidradenitis suppurativa research could be most fruitful.

Clinical Implementation of Biologics and Small Molecules in the Treatment of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic, recurrent, auto-inflammatory skin disease originating from the hair follicles. The typical inflammatory nodules, abscesses, and draining sinus tracts (tunnels) are characterized by a massive influx of neutrophils, macrophages, B-cells, plasma cells, T helper (Th)1, Th17 cells and upregulation of pro-inflammatory cytokines such as IL-1, IL-17, IL-12/23, and TNF-α. Over the last decades, several clinical trials evaluated the clinical efficacy of different biologics targeting these pro-inflammatory cytokines, in particular TNF-α and IL-1. However, adalimumab is still the only registered drug for HS. This review discusses biologics and small molecules with high level of evidence for their clinical application, provides guidance on when and how to use these biologics and small molecules in clinical practice, and elaborates on the combination with medical and surgical treatment options beyond the current guidelines. Furthermore this review provides an overview of potential biologics and small molecules currently under investigation for novel targets in HS such as IL-36, C5a, Janus kinase family members, CD-40, LTA4 and CXCR1/2.

IL-38 Exerts Anti-Inflammatory and Antifibrotic Effects in Thyroid-Associated Ophthalmopathy

CONTEXT

Thyroid-associated ophthalmopathy (TAO) is an organ-specific autoimmune disease closely associated with Graves' disease. IL-38, a novel cytokine in the IL-1 superfamily, has been reported to be involved in the pathogenesis of various autoimmune diseases.

OBJECTIVE

We aimed to evaluate the relationship between IL-38 and TAO disease activity and its role in inflammation and fibrosis in TAO.

METHODS

Blood samples and orbital connective tissues were collected from TAO patients and controls. Orbital fibroblasts were isolated from patients with TAO. Enzyme-linked immunosorbent assay, immunohistochemistry, flow cytometry, immunofluorescence, quantitative real-time PCR and Western blot analysis were performed.

RESULTS

Here, we demonstrated that IL-38 levels decreased in the circulation and orbital connective tissues of patients with TAO compared with the controls, and levels were negatively correlated with the clinical activity score. In vitro, potent anti-inflammatory and antifibrotic effects of IL-38 were observed. Furthermore, we revealed that IL-38 can counteract the phosphorylation of star molecules in multiple classical pathways.

CONCLUSION

IL-38 plays a protective role in TAO and is associated with its pathogenesis. Our data suggest that IL-38 may be a promising marker of TAO disease activity and a potential target for TAO therapy.

NOD2 signalling in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is associated with dysregulated immune responses including altered expression of cytokines, chemokines, and antimicrobial peptides and proteins (AMPs).

AIMS

To evaluate the expression of nucleotide-binding oligomerization domain-containing (NOD)2 and related factors in HS skin samples and keratinocyte cultures.

METHODS

We performed real-time PCR for NOD2, receptor-interacting serine/threonine-protein kinase (RIP)2, cyclic amine resistance locus (CARL), skin-derived antileukoproteinase (SKALP)/elafin, human β-defensin (hBD)2, LL37, psoriasin and RNAse7 in lesional and nonlesional skin of 19 patients with HS and in keratinocyte cultures [unstimulated, muramyl dipeptide (MDP)-stimulated or Pam2CSK4 (Pam2)-stimulated] from and nonlesional skin.

RESULTS

We observed significantly elevated mRNA expression for NOD2 (P < 0.01), hBD2 (P = 0.02), RNase7 (P < 0.001), psoriasin (P < 0.01) and SKALP/elafin (P = 0.02) in lesional compared with nonlesional skin. We found a significant correlation between NOD2 mRNA and hBD2 (r = 46; P = 0.04), psoriasin (r = 0.67; P < 0.01) and SKALP/elafin (r = 0.65; P < 0.01). In unstimulated, Pam2-stimulated and MDP-stimulated normal keratinocytes, NOD2, RIP2, CARL and SKALP/elafin expression significantly (P < 0.05) increased from 6 to 48 h, whereas in unstimulated, Pam2-stimulated and MDP-stimulated HS keratinocytes, RIP2, CARL and SKALP/elafin expression significantly (P < 0.05) declined from 6 to 48 h. mRNA expression of NOD2 (unstimulated, Pam2-stimulated, MDP-stimulated), CARL (unstimulated, Pam2-stimulated, MDP-stimulated) and SKALP/elafin (unstimulated, Pam2-stimulated) at 6 h was significantly increased in HS compared with normal keratinocytes.

CONCLUSION

We have shown for the first time that NOD2 signalling is activated in HS and might contribute to the pathogenesis via induction of AMPs and activation of other pathways such as nuclear factor κB signalling.

Features Associated With Quality of Life Impairment in Hidradenitis Suppurativa Patients

Background: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease with an adverse impact on patients' quality of life (QoL).

Objectives: To quantify QoL impairment in patients in Germany suffering from HS and to identify the parameters associated with QoL impairment.

Methods: A non-interventional, cross-sectional, mono-centric study with 500 HS patients. QoL data (measured using the Dermatology Life Quality Index; DLQI) and demographic, anamnestic, clinical, and blood parameters were collected. All patients were examined by dermatologists that documented the skin alterations. QoL data from 462 HS patients were available and evaluated.

Results: The mean (± standard deviation) DLQI score of HS patients was 13.18 ± 7.99. Approximately 40% and 20% of HS patients declared very large and extremely large QoL impairment, respectively. The degree of QoL disturbance correlated with the severity of skin alterations, blood leucocyte count and, in particular, with anogenital localization and the presence of nodules and fistulas. Furthermore, QoL impairment was associated with specific comorbidities, such as adiposity and back pain, but not with HS family history. QoL impairment was not influenced by whether or not the patients had undergone resection surgery or antibiotic treatment but was more severe in HS patients that had undergone abscess lancing compared to patients without such treatment in the past.

Limitations: It was a mono-centric study and most data were obtained from self-administered patient questionnaires. The association of QoL with type of treatment was analyzed for abscess lancing, resection surgery, and antibiotic treatment. Further therapeutic modalities recommended in the guidelines were not investigated.

Conclusion: A profound impairment in QoL was present in patients with HS, and this was higher than that observed in other studied dermatoses. The degree of impairment correlated with the extent of cutaneous and some extra-cutaneous alterations. Surgical and conventional medicamentous therapies of HS were not associated with long-lasting reduction of QoL impairment. Our data support the implementation of patient-reported outcome measures for the assessment of therapy responses.

IL-1 Family Antagonists in Mouse and Human Skin Inflammation

Interleukin (IL)-1 family cytokines initiate inflammatory responses, and shape innate and adaptive immunity. They play important roles in host defense, but excessive immune activation can also lead to the development of chronic inflammatory diseases. Dysregulated IL-1 family signaling is observed in a variety of skin disorders. In particular, IL-1 family cytokines have been linked to the pathogenesis of psoriasis and atopic dermatitis. The biological activity of pro-inflammatory IL-1 family agonists is controlled by the natural receptor antagonists IL-1Ra and IL-36Ra, as well as by the regulatory cytokines IL-37 and IL-38. These four anti-inflammatory IL-1 family members are constitutively and highly expressed at steady state in the epidermis, where keratinocytes are a major producing cell type. In this review, we provide an overview of the current knowledge concerning their regulatory roles in skin biology and inflammation and their therapeutic potential in human inflammatory skin diseases. We further highlight some common misunderstandings and less well-known observations, which persist in the field despite recent extensive interest for these cytokines.

Identifying key components and therapeutic targets of the immune system in hidradenitis suppurativa with an emphasis on neutrophils

Hidradenitis suppurativa (HS) is a chronic, inflammatory, recurrent and debilitating skin disease of the hair follicle unit that typically develops after puberty. The disorder is characterized by comedones, painful inflammatory nodules, abscesses, dermal tunnels and scarring, with a predilection for intertriginous areas of the body (axillae, inguinal and anogenital regions). Recruitment of neutrophils to HS lesion sites may play an essential role in the development of the painful inflammatory nodules and abscesses that characterize the disease. This is a review of the major mediators involved in the recruitment of neutrophils to sites of active inflammation, including bacterial components (endotoxins, exotoxins, capsule fragments, etc.), the complement pathway anaphylatoxins C3a and C5a, tumour necrosis factor-alpha, interleukin (IL)-17, IL-8 (CXCL8), IL-36, IL-1, lipocalin-2, leukotriene B4, platelet-activating factor, kallikreins, matrix metalloproteinases, and myeloperoxidase inhibitors. Pharmacological manipulation of the various pathways involved in the process of neutrophil recruitment and activation could allow for successful control and stabilization of HS lesions and the remission of active, severe flares.

A Systematic Review of Promising Therapeutic Targets in Hidradenitis Suppurativa: A Critical Evaluation of Mechanistic and Clinical Relevance

This systematic review identifies and critically evaluates the mechanistic and clinical evidence of new promising therapeutic targets in hidradenitis suppurativa (HS). Evidence for these targets is largely based on observational data with limited ex vivo and translational data from clinical trials. A number of placebo-controlled studies have been completed or are underway utilizing IL-1, IL-23, IL-17, complement, and Jak inhibition, although there is concern regarding elevated placebo response rates and the questionable validity of clinical scores in some participant subsets. Knowledge gaps are identified suggesting a direction for future mechanistic studies in HS, including more comprehensive inflammatory endotype profiling of disease.

Enhanced IL-36R signaling promotes barrier impairment and inflammation in skin and intestine

Deficiency in interleukin-36R (IL-36R) antagonist caused by loss-of-function mutations in IL-36RN leads to DITRA (deficiency of IL-36 receptor antagonist), a rare inflammatory human disease that belongs to a subgroup of generalized pustular psoriasis (GPP). We report a functional genetic mouse model of DITRA with enhanced IL-36R signaling analogous to that observed in patients with DITRA, which provides new insight into our understanding of the IL-36 family of molecules in regulating barrier integrity across multiple tissues. Humanized DITRA-like mice displayed increased skin inflammation in a preclinical model of psoriasis, and in vivo blockade of IL-36R pathway using anti-human IL-36R antibody ameliorated imiquimod-induced skin pathology as both prophylactic and therapeutic treatments. Deeper characterization of the humanized DITRA-like mice revealed that deregulated IL-36R signaling promoted tissue pathology during intestinal injury and led to impairment in mucosal restoration in the repair phase of chronic dextran sulfate sodium (DSS)-induced colitis. Blockade of IL-36R pathway significantly ameliorated DSS-induced intestinal inflammation and rescued the inability of DITRA-like mice to recover from mucosal damage in vivo. Our results indicate a central role for IL-36 in regulating proinflammatory responses in the skin and epithelial barrier function in the intestine, suggesting a new therapeutic potential for targeting the IL-36R axis in psoriasis and at the later stages of intestinal pathology in inflammatory bowel disease.

The Proinflammatory Cytokine IL-36γ Is a Global Discriminator of Harmless Microbes and Invasive Pathogens within Epithelial Tissues

Epithelial tissues represent vital interfaces between organisms and their environment. As they are constantly exposed to harmful pathogens, innocuous commensals, and environmental microbes, it is essential they sense and elicit appropriate responses toward these different types of microbes. Here, we demonstrate that the epithelial cytokine interleukin-36γ (IL-36γ) acts as a global discriminator of pathogenic and harmless microbes via cell damage and proteolytic activation. We show that intracellular pro-IL-36γ is upregulated by both fungal and bacterial epithelial microbes; yet, it is only liberated from cells, and subsequently processed to its mature, potent, proinflammatory form, by pathogen-mediated cell damage and pathogen-derived proteases. This work demonstrates that IL-36γ senses pathogen-induced cell damage and proteolytic activity and is a key initiator of immune responses and pathological inflammation within epithelial tissues. As an apically located epithelial proinflammatory cytokine, we therefore propose that IL-36γ is critical as the initial discriminator of harmless microbes and invasive pathogens within epithelial tissues.

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Epithelial pathogens induce expression and release of IL-36γ

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Proteases secreted by several epithelial pathogens activate IL-36γ

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The A. fumigatus and S. pyogenes virulence factors Asp F13 and SpeB activate IL-36γ

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IL-36γ is a global sensor of pathogen-derived proteases during epithelial infection

Reduced concentrations of the B cell cytokine interleukin 38 are associated with cardiovascular disease risk in overweight subjects

The IL‐1 family member IL‐38 (IL1F10) suppresses inflammatory and autoimmune conditions. Here, we report that plasma concentrations of IL‐38 in 288 healthy Europeans correlate positively with circulating memory B cells and plasmablasts. IL‐38 correlated negatively with age (p = 0.02) and was stable in 48 subjects for 1 year. In comparison with primary keratinocytes, IL1F10 expression in CD19⁺ B cells from PBMC was lower, whereas cell‐associated IL‐38 expression was comparable. In vitro, IL‐38 is released from CD19⁺ B cells after stimulation with rituximab. Intravenous LPS in humans failed to induce circulating IL‐38, compared to 100‐fold induction of IL‐6 and IL‐1 receptor antagonist. In a cohort of 296 subjects with body mass index > 27 at high risk for cardiovascular disease, IL‐38 plasma concentrations were significantly lower than in healthy subjects (p < 0.0001), and lowest in those with metabolic syndrome (p < 0.05). IL‐38 also correlated inversely with high sensitivity C‐reactive protein (p < 0.01), IL‐6, IL‐1Ra, and leptin (p < 0.05). We conclude that a relative deficiency of the B cell product IL‐38 is associated with increased systemic inflammation in aging, cardiovascular and metabolic disease, and is consistent with IL‐38 as an anti‐inflammatory cytokine.