Interleukin (IL)-19, IL-20 and IL-24 are produced by and act on keratinocytes and are distinct from classical ILs

The Role of Interleukin-24 and Downstream Pathways in Inflammatory and Autoimmune Diseases

Inflammatory and autoimmune diseases are pathological immune disorders and pose significant public health challenges due to their impact on individuals and society. Cytokine dysregulation plays a critical role in the development of these disorders. Interleukin (IL)-24, a member of the IL-10 cytokine family, can be secreted by various cell types, including immune and non-immune cells. The downstream effects of IL-24 upon binding to its receptors can occur in dependence on, or independently of, the Janus kinase (JAK)/signal transducer and the activator of transcription (STAT) signaling pathway. IL-24 and its downstream pathways influence crucial processes such as cell differentiation, proliferation, apoptosis, and inflammation, with its role varying across different diseases. On the one hand, IL-24 can inhibit the activation of pathogenic cells and autoimmune responses in autoimmune ocular diseases; on the other hand, IL-24 has been also implicated in promoting tissue damage by fostering immune cell activation and infiltration in psoriasis and allergic diseases. It suggests that IL-24, as a multifunctional cytokine, has complex regulatory functions in immune cells and related diseases. In this paper, we summarize the current knowledge on IL-24's immunomodulatory actions and its involvement in inflammatory and autoimmune disorders. Such insights may pave the way for novel therapeutic strategies for these diseases.

Enhancement of keratinocyte survival and migration elicited by interleukin 24 upregulation in dermal microvascular endothelium upon welding-fume exposure

Occupational exposure to welding fumes constitutes a serious health concern. Although the effects of fumes on the respiratory tract have been investigated, few apparent reports were published on their effects on the skin. The purpose of this study was to investigate the effects of exposure to welding fumes on skin cells, focusing on interleukin-24 (IL-24), a cytokine involved in the pathophysiology of skin conditions, such as atopic dermatitis and psoriasis. Treatment with welding fumes increased IL-24 expression and production levels in human dermal microvascular endothelial cells (HDMEC) which were higher than that in normal human epidermal keratinocytes. IL-24 levels in Trolox and deferoxamine markedly suppressed welding fume-induced IL-24 expression in HDMEC, indicating that oxidative stress may be involved in this cytokine expression. IL-24 released from HDMEC protected keratinocytes from welding fume-induced damage and enhanced keratinocyte migration. Serum IL-24 was higher in welding workers than in general subjects and was positively correlated with elevated serum levels of 8-hydroxy-2'-deoxyguanosine, an oxidative stress marker. In summary, welding fumes enhanced IL-24 expression in HDMEC, stimulating keratinocyte survival and migration. IL-24 expression in endothelial cells may act as an adaptive response to welding-fume exposure in the skin.

Interleukin-24: A molecular mediator of particulate matter's impact on skin aging

Air pollution, a global health concern, has been associated with adverse effects on human health. In particular, particulate matter (PM), which is a major contributor to air pollution, impacts various organ systems including the skins. In fact, PM has been suggested as a culprit for accelerating skin aging and pigmentation. In this study, using single-cell RNA sequencing, IL-24 was found to be highly upregulated among the differentially expressed genes commonly altered in keratinocytes and fibroblasts of ex vivo skins exposed to PM. It was verified that PM exposure triggered the expression of IL-24 in keratinocytes, which subsequently led to a decrease in type I procollagen expression and an increase in MMP1 expression in fibroblasts. Furthermore, long-term treatment of IL-24 induced cellular senescence in fibroblasts. Through high-throughput screening, we identified chemical compounds that inhibit the IL-24-STAT3 signaling pathway, with lovastatin being the chosen candidate. Lovastatin not only effectively reduced the expression of IL24 induced by PM in keratinocytes but also exhibited a capacity to restore the decrease in type I procollagen and the increase in MMP1 caused by IL-24 in fibroblasts. This study provides insights into the significance of IL-24, illuminating mechanisms behind PM-induced skin aging, and proposes IL-24 as a promising target to mitigate PM-associated skin aging.

Novel insight into MDA-7/IL-24: A potent therapeutic target for autoimmune and inflammatory diseases

Melanoma differentiation-associated gene-7 (MDA-7)/interleukin-24 (IL-24) is a pleiotropic member of the IL-10 family of cytokines, and is involved in multiple biological processes, including cell proliferation, cell differentiation, tissue fibrosis, the inflammatory response, and antitumor activity. MDA-7/IL-24 can regulate epithelial integrity, homeostasis, mucosal immunity and host resistance to various pathogens by enhancing immune and inflammatory responses. Our recent study revealed the mechanism of MDA-7/IL-24 in promoting airway inflammation and airway remodeling through activating the JAK/STAT3 and ERK signaling pathways in bronchial epithelial cells. Herein, we summarize the cellular sources, inducers, target cells, signaling pathways, and biological effects of MDA-7/IL-24 in several allergic and autoimmune diseases. This review also synopsizes recent advances in clinical research targeting MDA-7/IL-24 or its receptors. Based on these advancements, we emphasize its potential as a target for immunotherapy and discuss the challenges of developing immunotherapeutic drugs targeting MDA-7/IL-24 or its receptors in autoimmune and inflammatory disorders.

Serum level of interleukin-24 and its polymorphism in eczematic Iraqi patients

Eczema is a common skin disease associated with inflammation. Interleukin (IL)-24 is crucial in the pathogenesis of inflammatory diseases like eczema. The study objective was the assessment of IL-24 serum levels and its gene polymorphisms in eczematic Iraqi patients. This retrospective case-control study involved 145 participants, divided into 82 patients with eczema and 63 healthy controls. An enzyme-linked immunosorbent assay measured serum IL-24, while polymerase chain reaction and Sanger DNA sequencing were used for genotype analysis. Serum IL-24 level was significantly higher (P value < .001) in patients compared to controls (41.6 [interquartile range (IQR): 28.9-53.6] vs 9.8 [IQR: 0.8-19.6] pg/mL, respectively). DNA sequence illustrated 2 SNPs with polymorphic frequencies (rs1150256 G/A and rs3093425 del/ins). The first SNP (rs1150256 G/A) showed 3 genotypes (GG, AA, and G/A), while the second SNP (rs3093425) showed 3 genotypes (-/G del/Ins, G Ins/Ins, and - del/del). The subsequent investigation revealed the presence of the following findings within the DNA sequence of the PCR amplified region (329bp). In the control group, all participants had GG/G (wild type) genotype/allele for the rs1150256 SNP, while in eczematic patients, 24.4% GG, 50% GA, and 25.6% AA. For the second SNP genotype (rs3093425 del/ins), the genotype frequencies in patients vs control were (24.4% vs 84.1%, 50.0% vs 11.1%, and 25.6% vs 4.8; Del/Del, Del/Ins, and Ins/Ins, respectively). The presence of Ins compared to Del increased the risk of eczema by 8.91 (4.66-17.03); OR (95% CI). In conclusion, IL-24 is a good predictor of eczema and A-allele carrier for rs1150256 SNP, and insertion-allele carrier for rs3093425 SNP is associated with elevated serum IL-24 and higher risk of eczema.

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.

Serum Interleukin-19 Levels in Acne Vulgaris Patients of Varying Clinical Severity in Erbil City

Background Acne vulgaris (AV) is a common multifactorial disorder affecting the pilosebaceous units. Research has shown that inflammation plays a crucial role in the pathogenesis of AV, including both inflammatory and non-inflammatory acne. Several studies have linked proinflammatory cytokines to AV; however, only a few have explored the correlation between interleukin-19 (IL-19) and AV. Our aim is to estimate the level of IL-19 in patients with AV compared to matched controls and to investigate the role of IL-19 in the pathogenesis of acne.  Materials and methods This prospective cross-sectional case and control study includes 80 patients and 40 matched controls. Patients were divided into mild (20), moderate (40), and severe (20) groups based on their global acne score severity index. Detailed history and complete general and dermatological examinations were taken from each patient. Furthermore, 5 ml of blood was taken from all participants to assess the level of IL-19. Results IL-19 levels were significantly higher in patients with AV compared to matched controls. Furthermore, IL-19 concentrations were found to be proportional to the severity of acne, with the highest levels detected in patients with severe AV (p-value <0.005). Conclusion IL-19 levels in AV were significantly higher than in matched control. The difference was proportional to its severity. This might indicate IL-19 as an inflammatory marker and could potentially be related to AV.

Inhibition of IL-17 ameliorates keratinocyte-borne cytokine responses in an in vitro model for house-dust-mite triggered atopic dermatitis

A subgroup of patients suffering from atopic dermatitis (AD) does not respond to biologics therapy targeting the key players of type-2 inflammation, and it is an ongoing discussion whether skin-infiltrating Th17 cells may underlie this phenomenon. This study aimed to investigate the potential of allergen-induced, immune-cell derived IL-17 on the induction of inflammatory processes in keratinocytes. Peripheral blood mononuclear cells derived from respectively sensitized AD patients were stimulated with house dust mite (HDM) extract and cell culture supernatants were applied subsequently in absence or presence of secukinumab to primary human keratinocytes. Hereby we confirm that the immune response of sensitized AD patients to HDM contains aside from type-2 cytokines significant amounts of IL-17. Blocking IL-17 efficiently reduced the stimulation-induced changes in keratinocyte gene expression. IL-17-dependent transcriptional changes included increased expression of the cytokines IL-20 and IL-24 as well as Suppressor of Cytokine Siganling 3 (SOCS3), a negative feedback-regulator of the STAT3/IL-17/IL-24 immune response. We conclude that the immune response to HDM can induce pro-inflammatory cytokines from keratinocytes in AD, which in part is mediated via IL-17. Targeting IL-17 may turn out to be a reasonable alternative therapy in a subgroup of patients with moderate to severe AD and HDM sensitization.

Interleukin-19 Gene-Deficient Mice Promote Liver Fibrosis via Enhanced TGF-β Signaling, and the Interleukin-19-CCL2 Axis Is Important in the Direction of Liver Fibrosis

IL-19 is a cytokine discovered by homologous searching with IL-10 and is produced by non-immune cells, such as keratinocytes, in addition to immune cells, such as macrophages. Liver fibrosis results from the inflammation and activation of hepatic stellate cells via chronic liver injury. However, the participation of IL-19 in liver fibrosis remains to be sufficiently elucidated. Our group studied the immunological function of IL-19 in a mouse model of carbon tetrachloride (CCl₄)-induced liver fibrosis. IL-19 gene-deficient (KO) mice and body weight-matched wild-type (WT) mice were used. A liver fibrosis mouse model was created via CCl₄ administration (two times per week) for 8 weeks. In CCl₄-induced liver fibrosis, serum analysis revealed that IL-19 KO mice had higher ALT levels compared to WT mice. IL-19 KO mice had worse fibrosis, as assessed by morphological evaluation of total area stained positive with Azan and Masson trichrome. In addition, the expression of α-SMA was increased in liver tissues of IL-19 KO mice compared to WT mice. Furthermore, mRNA expression levels of TGF-β and α-SMA were enhanced in IL-19 KO mice compared to WT mice. In vitro assays revealed that IL-19-high expressing RAW264.7 cells inhibited the migration of NIH3T3 cells via the inhibited expression of CCL2 in the presence of CCl₄ and IL-4. These findings indicate that IL-19 plays a critical role in liver fibrosis by affecting TGF-β signaling and the migration of hepatic stellate cells during liver injury. Enhancement of the IL-19 signaling pathway is a potential treatment for liver fibrosis.

Interleukin-19 Levels Are Increased in Palmoplantar Pustulosis and Reduced following Apremilast Treatment

Palmoplantar pustulosis (PPP) is a chronic inflammatory skin disease characterised by neutrophilic granulocyte (neutrophil)-filled pustules on the palms and soles. The pathogenesis of PPP is poorly understood. This study conducted an identification of the immune mediators associated with PPP and an exploration of apremilast treatment effects on them. We screened for immune mediators elevated in blood taken from 68 patients with PPP versus control participants and included the most promising parameters in the protocol of phase the 2, multicentre study of apremilast (PDE4 inhibitor) in 21 patients with moderate-to-severe PPP (APLANTUS; EudraCT 2016-005122-11) for respective analysis of blood and skin samples of study patients. We investigated stimulated neutrophils and three-dimensional reconstituted epidermis cultures. Interleukin (IL)-19 was found to be the most upregulated immune mediator in the blood of PPP patients. IL-19 serum levels were independent of patients' age, gender, and BMI but were associated with strongly upregulated cutaneous IL-19 expression and correlated with the number of palmoplantar pustules. In patients participating in the APLANTUS study, apremilast reduced pustules more effectively than erythema and scaling. Moreover, this treatment significantly reduced IL-19 blood and skin levels. The reduction in IL-19 blood levels at week 4 correlated with the reduction in pustule counts at week 20 (end of treatment). IL-19 was expressed by neutrophils activated in vitro and induced CXCL6, a neutrophil-attracting chemokine, in epidermis models. This work demonstrates elevated IL-19 levels in the blood and skin of PPP patients and suggests a relevant role of this cytokine in the appearance of pustules in this disorder. It also suggests the suitability of IL-19 blood levels as a predictive biomarker for the treatment response of PPP patients, which should be validated in further studies.

The Monocyte, a Maestro in the Tumor Microenvironment (TME) of Breast Cancer

Simple Summary

Breast cancer is one of the most prevalent cancers worldwide, surpassing lung cancer as the leading cause of overall cancer incidence. Available possible treatments nowadays include chemotherapy, hormonal therapy, and HER2-targeted therapy. Chemotherapy is notorious for its severe adverse effects. On the other hand, hormonal and HER2-targeted therapies only cover a narrow range of breast cancer subtypes. Accordingly, it is important to shed light on other therapy options. For this reason, immunotherapy nowadays is one of the most important research topics. It can be accomplished either by enhancing the pro-inflammatory immunity or suppressing the anti-inflammatory immunity. This review article aims to shed light on the importance of monocytes in the TME of breast cancer. The review also aims to highlight the behavior of the monocyte-derived populations, especially the anti-inflammatory populations. Thus, suppressing this anti-inflammatory activity might have a remarkable impact on future immunotherapy research.

Abstract

Breast cancer (BC) is well-known for being a leading cause of death worldwide. It is classified molecularly into luminal A, luminal B HER2−, luminal B HER2+, HER2+, and triple-negative breast cancer (TNBC). These subtypes differ in their prognosis; thus, understanding the tumor microenvironment (TME) makes new treatment strategies possible. The TME contains populations that exhibit anti-tumorigenic actions such as tumor-associated eosinophils. Moreover, it contains pro-tumorigenic populations such as tumor-associated neutrophils (TANs), or monocyte-derived populations. The monocyte-derived populations are tumor-associated macrophages (TAMs) and MDSCs. Thus, a monocyte can be considered a maestro within the TME. Moreover, the expansion of monocytes in the TME depends on many factors such as the BC stage, the presence of macrophage colony-stimulating factor (M-CSF), and the presence of some chemoattractants. After expansion, monocytes can differentiate into pro-inflammatory populations such as M1 macrophages or anti-inflammatory populations such as M2 macrophages according to the nature of cytokines present in the TME. Differentiation to TAMs depends on various factors such as the BC subtype, the presence of anti-inflammatory cytokines, and epigenetic factors. Furthermore, TAMs and MDSCs not only have a role in tumor progression but also are key players in metastasis. Thus, understanding the monocytes further can introduce new target therapies.

The IL-20RB receptor and the IL-20 signaling pathway in regulating host defense in oral mucosal candidiasis

Pseudomembranous candidiasis (thrush), erythematous candidiasis, and fungal esophagitis are infections of the barrier mucosa of the upper gastrointestinal tract. The majority of these infections are caused by Candida albicans, an opportunistic fungal pathogen that frequently exists as a harmless commensal on mucosal surfaces lining the gastrointestinal tract. Oral infections are initiated in the superficial stratified squamous epithelium, in which keratinocytes are the most abundant host cells and are the initial points of contact with C. albicans present in saliva. Intrinsic features of oral keratinocytes are likely to play important roles in host defense and tissue homeostasis in oral candidiasis. One understudied pathway that may be important for modulating oral candidiasis is the IL-20 cytokine signaling pathway that employs keratinocyte IL-20RB receptors as ligands for IL-19, IL-20, and IL-24. We report that production of human oral keratinocyte il24 mRNA and protein are stimulated during co-culture with C. albicans. To test the role of the IL-20 family signaling pathway in oral candidiasis, Il20rb^-/- mice (lacking the IL-20RB receptor) were compared to wild-type mice in a murine model of oropharyngeal candidiasis. Fungal burdens and percent loss in body weight were determined. Despite comparable fungal burdens, the Il20rb^-/- mice exhibited less weight loss over the course of their infection compared to the B6 mice, suggestive of reduced overall disease consequences in the mutant mice. Interference with IL-20 family cytokine signaling may be useful for augmenting the ability of the host to defend itself against pathogens.

IL-20 subfamily cytokines impair the oesophageal epithelial barrier by diminishing filaggrin in eosinophilic oesophagitis

OBJECTIVE

Disruption of the epithelial barrier plays an essential role in developing eosinophilic oesophagitis (EoE), a disease defined by type 2 helper T cell (Th2)-mediated food-associated and aeroallergen-associated chronic inflammation. Although an increased expression of interleukin (IL)-20 subfamily members, IL-19, IL-20 and IL-24, in Th2-mediated diseases has been reported, their function in EoE remains unknown.

DESIGN

Combining transcriptomic, proteomic and functional analyses, we studied the importance of the IL-20 subfamily for EoE using patient-derived oesophageal three-dimensional models and an EoE mouse model.

RESULTS

Patients with active EoE have increased expression of IL-20 subfamily cytokines in the oesophagus and serum. In patient-derived oesophageal organoids stimulated with IL-20 cytokines, RNA sequencing and mass spectrometry revealed a downregulation of genes and proteins forming the cornified envelope, including filaggrins. On the contrary, abrogation of IL-20 subfamily signalling in Il20R2 ^-/- animals resulted in attenuated experimental EoE reflected by reduced eosinophil infiltration, lower Th2 cytokine expression and preserved expression of filaggrins in the oesophagus. Mechanistically, these observations were mediated by the mitogen-activated protein kinase (MAPK); extracellular-signal regulated kinases (ERK)1/2) pathway. Its blockade prevented epithelial barrier impairment in patient-derived air-liquid interface cultures stimulated with IL-20 cytokines and attenuated experimental EoE in mice.

CONCLUSION

Our findings reveal a previously unknown regulatory role of the IL-20 subfamily for oesophageal barrier function in the context of EoE. We propose that aberrant IL-20 subfamily signalling disturbs the oesophageal epithelial barrier integrity and promotes EoE development. Our study suggests that specific targeting of the IL-20 subfamily signalling pathway may present a novel strategy for the treatment of EoE.

IL-20 promotes cutaneous inflammation and peripheral itch sensation in atopic dermatitis

Atopic dermatitis (AD) is a chronic skin disease, which is associated with intense itch, skin barrier dysfunction and eczematous lesions. Aberrant IL‐20 expression has been implicated in numerous inflammatory diseases, including psoriasis. However, the role of IL‐20 in AD remains unknown. Here, RNA‐seq, Q‐PCR, and immunocytochemistry were utilized to examine disease‐driven changes of IL‐20 and its cognate receptor subunits in skin from healthy human subjects, AD patients and murine AD‐models. Calcium imaging, knockdown and cytokine array were used to investigate IL‐20‐evoked responses in keratinocytes and sensory neurons. The murine cheek model and behavioral scoring were employed to evaluate IL‐20‐elicited sensations in vivo. We found that transcripts and protein of IL‐20 were upregulated in skin from human AD and murine AD‐like models. Topical MC903 treatment in mice ear enhanced IL‐20R1 expression in the trigeminal sensory ganglia, suggesting a lesion‐associated and epidermal‐driven mechanism for sensitization of sensory IL‐20 signaling. IL‐20 triggered calcium influx in both keratinocytes and sensory neurons, and promoted their AD‐related molecule release and transcription of itch‐related genes. In sensory neurons, IL‐20 application increased TLR2 transcripts, implicating a link between innate immune response and IL‐20. In a murine cheek model of acute itch, intradermal injection IL‐20 and IL‐13 elicited significant itch‐like behavior, though only when co‐injected. Our findings provide novel insights into IL‐20 function in peripheral (skin‐derived) itch and clinically relevant intercellular neuron‐epidermal communication, highlighting a role of IL‐20 signaling in the pathophysiology of AD, thus forming a new basis for the development of a novel antipruritic strategy via interrupting IL‐20 epidermal pathways.

Identification of IL20RB as a Novel Prognostic and Therapeutic Biomarker in Clear Cell Renal Cell Carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is a type of life-threatening malignant tumor of the urinary system. IL20RB, interleukin 20 receptor subunit beta, is a cytokine receptor subunit coding gene and was initially found to play a vital role in human cancers, while its role in ccRCC still remains unclear.

Methods

In this work, we explored the prognostic value and therapeutic potential of IL20RB in ccRCC mainly by online tools. Firstly, we used UALCAN and GEPIA to explore the expression profile and prognostic value of IL20RB in various cancers; the expression profile in tumor cell lines was also analysed with CCLE and Expression Atlas. Then, we decided to focus on ccRCC for further analysis; we further demonstrated the significant correlation between expression and clinical features by GEPIA and UALCAN. In order to reveal the potential intrinsic mechanism responsible for the upregulation of IL20RB in ccRCC, we made genetic alternation analysis and methylation analysis. cBioPortal was used for genetic alternation analysis. UALCAN, MethSurv, and Xena were used for methylation analysis. To learn details of how IL20RB might function in ccRCC, we further conducted functional analysis and immune infiltration analysis. STRING and GSEA were used to do functional analysis. TIMER was used for immune infiltration analysis; KM plotter was used for survival analysis.

Results

Results show that IL20RB is upregulated in ccRCC, and low methylation may be responsible for its upregulation. Both high expression and low methylation of IL20RB predict worse survival, and both have a strong positive correlation with clinical characteristics. In addition, results indicate that there exists a crosstalk between IL20RB and neutrophils. Furthermore, the immune microenvironment could influence the prognosis predicting ability of IL20RB.

Conclusions

In conclusion, IL20RB plays an important role in ccRCC and is identified as a novel prognostic and potential therapeutic biomarker in ccRCC.

The Role of Interleukins in the Pathogenesis of Dermatological Immune-Mediated Diseases

Autoimmune inflammatory diseases are primarily characterized by deregulated expression of cytokines, which drive pathogenesis of these diseases. A number of approved and experimental therapies utilize monoclonal antibodies against cytokine proteins. Cytokines can be classified into different families including the interleukins, which are secreted and act on leukocytes, the tumor necrosis factor (TNF) family, as well as chemokine proteins. In this review article, we focus on the interleukin family of cytokines, of which 39 members have been identified to this date. We outline the role of each of these interleukins in the immune system, and various dermatological inflammatory diseases with a focused discussion on the pathogenesis of psoriasis and atopic dermatitis. In addition, we describe the roles of various interleukins in psychiatric, cardiovascular, and gastrointestinal comorbidities. Finally, we review clinical efficacy and safety data from emerging late-phase anti-interleukin therapies under development for psoriasis and atopic dermatitis. Collectively, additional fundamental and clinical research remains necessary to fully elucidate the roles of various interleukin proteins in the pathogenesis of inflammatory dermatologic diseases, and treatment outcomes in patients.

IL-22 Binding Protein (IL-22BP) in the Regulation of IL-22 Biology

Cytokines are powerful mediators of inflammation. Consequently, their potency is regulated in many ways to protect the host. Several cytokines, including IL-22, have coordinating binding proteins or soluble receptors that bind to the cytokine, block the interaction with the cellular receptor, and thus prevent cellular signaling. IL-22 is a critical cytokine in the modulation of tissue responses during inflammation and is highly upregulated in many chronic inflammatory disease patients, including those with psoriasis, rheumatoid arthritis, and inflammatory bowel disease (IBD). In healthy individuals, low levels of IL-22 are secreted by immune cells, mainly in the gastrointestinal (GI) tract. However, much of this IL-22 is likely not biologically active due to the high levels of IL-22 binding protein (IL-22BP) produced by intestinal dendritic cells (DCs). IL-22BP is a soluble receptor homolog that binds to IL-22 with greater affinity than the membrane spanning receptor. Much is known regarding the regulation and function of IL-22 in health and disease. However, less is known about IL-22BP. In this review, we will focus on IL-22BP, including its regulation, role in IL-22 biology and inflammation, and promise as a therapeutic. IL-22 can be protective or pathogenic, depending on the context of inflammation. IL-22BP also has divergent roles. Ongoing and forthcoming studies will expand our knowledge of IL-22BP and IL-22 biology, and suggest that IL-22BP holds promise as a way to regulate IL-22 biology in patients with chronic inflammatory disease.

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

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

Transcriptomic analysis revealed increased expression of genes involved in keratinization in the tears of COVID-19 patients

Recent studies have focused their attention on conjunctivitis as one of the symptoms of coronavirus disease 2019 (COVID-19). Therefore, tear samples were taken from COVID-19 patients and the presence of SARS-CoV-2 was evidenced using Real Time reverse transcription polymerase chain reaction. The main aim of this study was to analyze mRNA expression in the tears of patients with COVID-19 compared with healthy subjects using Next Generation Sequencing (NGS). The functional evaluation of the transcriptome highlighted 25 genes that differ statistically between healthy individuals and patients affected by COVID-19. In particular, the NGS analysis identified the presence of several genes involved in B cell signaling and keratinization. In particular, the genes involved in B cell signaling were downregulated in the tears of COVID-19 patients, while those involved in keratinization were upregulated. The results indicated that SARS-CoV-2 may induce a process of ocular keratinization and a defective B cell response.

Upregulation of interleukin-19 in severe asthma: a potential saliva biomarker for asthma severity

Interleukin (IL)-19, a designated IL-20 subfamily cytokine, has been implicated in inflammatory disorders including rheumatoid arthritis, psoriasis and, lately, asthma. Here, through the analysis of transcriptomic datasets of lung tissue of large asthma cohorts, we report that IL-19 expression is upregulated in asthma and correlates with disease severity. The gene expression of IL-19 was significantly higher in lung tissue from patients with severe and mild/moderate asthma compared to healthy controls. IL-19 protein level, however, was significantly higher in the blood and saliva of patients with severe asthma compared to mild/moderate subgroups as measured by ELISA assay. IL-19 protein level was not affected by corticosteroid treatment in plasma. Our data provide insights into the potential use of IL-19 as a saliva marker for asthma severity and a potential therapeutic target.

Plasma and saliva IL-19 are significantly upregulated in asthma and correlate with disease severity. Plasma IL-19 is not affected by steroid treatment. This suggests that IL-19 can be used as a biomarker of asthma severity.https://bit.ly/2QfYwpc

Potential of Point-of-Care and At-Home Assessment of Immune Status via Rapid Cytokine Detection and Questionnaire-Based Anamnesis

Monitoring the immune system's status has emerged as an urgent demand in critical health conditions. The circulating cytokine levels in the blood reflect a thorough insight into the immune system status. Indeed, measuring one cytokine may deliver more information equivalent to detecting multiple diseases at a time. However, if the reported cytokine levels are interpreted with considering lifestyle and any comorbid health conditions for the individual, this will promote a more precise assessment of the immune status. Therefore, this study addresses the most recent advanced assays that deliver rapid, accurate measuring of the cytokine levels in human blood, focusing on add-on potentials for point-of-care (PoC) or personal at-home usage, and investigates existing health questionnaires as supportive assessment tools that collect all necessary information for the concrete analysis of the measured cytokine levels. We introduced a ten-dimensional featuring of cytokine measurement assays. We found 15 rapid cytokine assays with assay time less than 1 h; some could operate on unprocessed blood samples, while others are mature commercial products available in the market. In addition, we retrieved several health questionnaires that addressed various health conditions such as chronic diseases and psychological issues. Then, we present a machine learning-based solution to determine what makes the immune system fit. To this end, we discuss how to employ topic modeling for deriving the definition of immune fitness automatically from literature. Finally, we propose a prototype model to assess the fitness of the immune system through leveraging the derived definition of the immune fitness, the cytokine measurements delivered by a rapid PoC immunoassay, and the complementary information collected by the health questionnaire about other health factors. In conclusion, we discovered various advanced rapid cytokine detection technologies that are promising candidates for point-of-care or at-home usage; if paired with a health status questionnaire, the assessment of the immune system status becomes solid and we demonstrated potentials for promoting the assessment tool with data mining techniques.

MicroRNA 452 regulates IL20RA-mediated JAK1/STAT3 pathway in inflammatory colitis and colorectal cancer

OBJECTIVE

MicroRNAs are a class of small, non-coding RNAs that play a key role in several biological and molecular processes, including tumorigenesis. We previously identified that MIR452 is upregulated in both colorectal cancer (CRC) and colitis. However, the functional mechanisms of MIR452 and its target genes in CRC and colitis are not well understood. So, we hypothesize that MIR452 can influence CRC and DSS-induced colitis model through the regulation of IL20RA and its downstream JAK-STATs signaling pathway.

METHODS

We used a luciferase reporter assay to confirm the effect of MIR452 on IL20RA expression. The protein and mRNA expression of a target gene and its associated molecules were measured by western blot, quantitative RT-PCR, and immunohistochemistry.

RESULTS

We found that the IL20RA was a direct target gene of MIR452. Overexpression of MIR452 in CRC cell lines significantly decreased IL20RA and its downstream Janus kinase 1 (JAK1), Signal transducer and activator of transcription 1 (STAT1) and STAT3. Knockdown of IL20RA in CRC cell lines by IL20RA gene silencing also decreased the expression of IL20RA, JAK1, and STAT3, but not of STAT1.

CONCLUSION

Our results suggest that MIR452 regulates STAT3 through the IL20RA-mediated JAK1 pathway, but not STAT1. Overall, MIR452 acts as tumor suppressor in human CRC and in a mouse colitis model. These findings suggest that MIR452 is a promising therapeutic target in the treatment of cancer and colitis.

High IL-22RA1 gene expression is associated with poor outcome in muscle invasive bladder cancer

BACKGROUND

The cell surface interleukin 22 (IL-22) receptor complex is mainly expressed in epithelial and tissue cells like pancreatitis cells. Recent studies described that IL-22R was overexpressed in malignant diseases and was associated with a poor overall survival (OS). The role of IL-22RA1 gene expression in muscle invasive bladder cancer (MIBC) has not been investigated, yet.

OBJECTIVES

The aim of this study was to analyze the role of IL-22RA1 gene expression in patients with MIBC.

METHODS

In a cohort of 114 patients with MIBC who underwent radical cystectomy, IL-22RA1 gene expression was analyzed with qRT-PCR and correlated with clinical parameters. Furthermore, Kaplan-Meier and Cox regression analysis were performed. For validation, an in silico dataset (TCGA 2017, n=407) was reanalyzed.

RESULTS

IL-22RA1 gene expression was independent of clinicopathological parameters like age (P=0.2681), T stage (P=0.2130), nodal status (P=0.3238) and lymph vascular invasion (LVI, P=0.5860) in patients with MIBC. A high expression of IL-22RA1 was associated with a shorter OS (P=0.0040) and disease-specific survival (P=0.0385). Furthermore, a shorter disease-free survival (DFS) was also associated with a high expression of IL-22RA1 (P=0.0102). In the multivariable analysis, IL-22RA1 expression was an independent prognostic predictors regarding OS (P=0.0096, HR=0.48). In the TCGA cohort, IL-22RA1 expression was independent regarding to OS and DFS.

CONCLUSION

A high IL-22RA1 gene expression was associated with worse outcome. Furthermore, IL-22RA1 represented an independent predictor regarding OS in our cohort and therefore might be used for risk stratification in patients with MIBC.

HMGB1-mediated chromatin remodeling attenuates Il24 gene expression for the protection from allergic contact dermatitis

Dysregulation of inflammatory cytokines in keratinocytes promote the pathogenesis of the skin inflammation, such as allergic contact dermatitis (ACD). High-mobility group box 1 protein (HMGB1) has been implicated in the promotion of skin inflammation upon its extracellular release as a damage-associated molecular pattern molecule. However, whether and how HMGB1 in keratinocytes contributes to ACD and other skin disorders remain elusive. In this study, we generated conditional knockout mice in which the Hmgb1 gene is specifically deleted in keratinocytes, and examined its role in ACD models. Interestingly, the mutant mice showed exacerbated skin inflammation, accompanied by increased ear thickening in 2,4-dinitrofluorobenezene-induced ACDs. The mRNA expression of interleukin-24 (IL-24), a cytokine known to critically contribute to ACD pathogenesis, was elevated in skin lesions of the mutant mice. As with constitutively expressed, IL-4-induced Il24 mRNA, expression was also augmented in the Hmgb1-deficient keratinocytes, which would account for the exacerbation of ACD in the mutant mice. Mechanistically, we observed an increased binding of trimethyl histone H3 (lys4) (H3K4me3), a hallmark of transcriptionally active genes, to the promoter region of the Il24 gene in the hmgb1-deficient cells. Thus, the nuclear HMGB1 is a critical "gate keeper" in that the dermal homeostasis is contingent to its function in chromatin remodeling. Our study revealed a facet of nuclear HMGB1, namely its antiinflammatory function in keratinocytes for the skin homeostasis.

Interleukin-20 inhibits the osteogenic differentiation of MC3T3-E1 cells via the GSK3β/β-catenin signalling pathway

OBJECTIVE

To investigate the effects of interleukin-20 (IL-20) on the osteogenic differentiation of MC3T3-E1 cells.

METHODS

The pre-osteoblast line MC3T3-E1 was treated with different concentrations of IL-20 (0, 2, 20 and 100 ng/mL), and the cell viability was detected by the CCK8 assay. To assess the influence of IL-20 on osteogenic differentiation, alkaline phosphatase (ALP) activity and Alizarin red staining were performed at predetermined times. The expression levels of Runt-related transcription factor 2 (RUNX2), Osterix (Osx), glycogen synthase kinase-3β (GSK-3β) and β-catenin were detected by qRT-PCR and Western blotting analyses. 5 nmol/L lithium chloride (LiCl) was used as GSK-3β inhibitor.

RESULTS

IL-20 promoted cell proliferation but decreased ALP activity and mineralization. Moreover, IL-20 downregulated the expression of RUNX2, Osx and β-catenin but upregulated the level of GSK-3β.

CONCLUSIONS

The results suggest that IL-20 could inhibit the osteogenic differentiation of MC3T3-E1 cells via the GSK3β/β-catenin signalling pathway.

Interleukin-19 Abrogates Experimental Autoimmune Encephalomyelitis by Attenuating Antigen-Presenting Cell Activation

Interleukin-19 (IL-19) acts as a negative-feedback regulator to limit proinflammatory response of macrophages and microglia in autocrine/paracrine manners in various inflammatory diseases. Multiple sclerosis (MS) is a major neuroinflammatory disease in the central nervous system (CNS), but it remains uncertain how IL-19 contributes to MS pathogenesis. Here, we demonstrate that IL-19 deficiency aggravates experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, by promoting IL-17-producing helper T cell (Th17 cell) infiltration into the CNS. In addition, IL-19-deficient splenic macrophages expressed elevated levels of major histocompatibility complex (MHC) class II, co-stimulatory molecules, and Th17 cell differentiation-associated cytokines such as IL-1β, IL-6, IL-23, TGF-β1, and TNF-α. These observations indicated that IL-19 plays a critical role in suppression of MS pathogenesis by inhibiting macrophage antigen presentation, Th17 cell expansion, and subsequent inflammatory responses. Furthermore, treatment with IL-19 significantly abrogated EAE. Our data suggest that IL-19 could provide significant therapeutic benefits in patients with MS.

I-Kappa-B-Zeta Regulates Interleukin-17A/Tumor Necrosis Factor-Alpha Mediated Synergistic Induction of Interleukin-19 and Interleukin-20 in Humane Keratinocytes

Background

Interleukin (IL)-19 and IL-20 are important members of the IL-10 cytokine family, which are known to play a role in inflammatory processes. Both anti-IL-19 and -IL-20 targeting drugs have been suggested in the treatment of inflammatory diseases such as psoriasis and rheumatoid arthritis. Recently, we presented I-kappa-B-zeta (IκBζ) as a key player in psoriasis by identifying IκBζ as a regulator of IL-17/tumor necrosis factor (TNF)α-inducible psoriasis-associated genes and proteins. Some of these genes were synergistically regulated by IL-17/TNFα.

Objective

The purpose of this study was to explore the role of IκBζ in the regulation of IL-17A/TNFα-mediated induction of IL-19 and IL-20 expression in human keratinocytes.

Methods

In vitro experiments with cultured primary humane keratinocytes were conducted and investigated by quantitative polymerase chain reaction (qPCR), Western blotting, ELISA and EMSA. For statistics, a one- or two- way repeated-measures analysis of variance (RM ANOVA) or the Friedman test (a nonparametric equivalent to the RM ANOVA) were conducted.

Results

We demonstrated that IL-19 and IL-20 mRNA and protein expressions were synergistically induced by IL-17A and TNFα, whereas IL-17A and TNFα alone had only a minor effect on the IL-19 and IL-20 expression. Moreover, we demonstrated IκBζ to be a regulator of this synergistic induction of IL-19 and IL-20. Finally, the IL-17A/TNFα-induced synergistic induction of IL-19 and IL-20 expression was found to be mediated by a p38 MAPK-, NF-κB- and JNK1/2-dependent mechanism.

Conclusion

This study demonstrates that IκBζ plays a role in the IL-17A/TNFα-mediated synergistic induction of IL-19 and IL-20 in humane keratinocytes.

Therapeutics targeting the IL-23 and IL-17 pathway in psoriasis

Psoriasis is a chronic inflammatory disease characterised by sharply demarcated erythematous and scaly skin lesions accompanied by systemic manifestations. Classified by WHO as one of the most serious non-infectious diseases, psoriasis affects 2-3% of the global population. Mechanistically, psoriatic lesions result from hyperproliferation and disturbed differentiation of epidermal keratinocytes that are provoked by immune mediators of the IL-23 and IL-17 pathway. Translational immunology has had impressive success in understanding and controlling psoriasis. Psoriasis is the first disease to have been successfully treated with therapeutics that directly block the action of the cytokines of this pathway; in fact, therapeutics that specifically target IL-23, IL-17, and IL-17RA are approved for clinical use and show excellent efficacy. Furthermore, inhibitors of IL-23 and IL-17 intracellular signalling, such as TYK2 or RORγt, are in clinical development. Although therapies that target the IL-23 and IL-17 pathway also improve psoriatic arthritis symptoms, their effects on long-term disease modification and psoriasis-associated comorbidities still need to be explored.

Assessment of serum interleukin-19 in acne vulgaris patients of different clinical severities

BACKGROUND

Acne vulgaris (AV) is a common chronic inflammatory disorder of the pilosebaceous unit among adolescents and young adults. Inflammation does have a central role in formation of both inflammatory and noninflammatory acne lesions with production of proinflammatory cytokines.

AIMS

To measure serum levels of interleukin 19 (IL-19) in acne vulgaris patients with different severities, and compare it with healthy controls, to evaluate its role in pathogenesis of acne vulgaris and correlate it with acne severity.

MATERIALS AND METHODS

This study included 120 subjects, aged 18-30 years, divided into four groups, 30 in each; mild, moderate, and severe AV patients groups according to acne severity as well as apparently healthy controls group of matched age and sex with no previous history of acne or active acne. Each patient was subjected to history taking, general and dermatological examination with assessment of acne severity. Serum IL-19 levels of both patients and controls were also measured using quantitative enzyme-linked immunosorbent assay (ELISA).

RESULTS

Results revealed significant difference in serum IL-19 levels between acne patients and controls, being higher in the former group (P value is < 0.001). Moreover, the rise in serum IL-19 levels was significantly proportional to the increased acne severity (P value < 0.001).

CONCLUSION

IL-19 is related to the etiopathological inflammatory process of acne vulgaris and correlates with acne severity. It could be proposed as a prognostic inflammatory marker for acne vulgaris.

Trial Watch: Immunostimulatory cytokines

During the last two decades, a number of approaches for the activation of the immune system against cancer has been developed. These include highly specific interventions, such as monoclonal antibodies, vaccines and cell-based therapies, as well as relatively unselective strategies, such as the systemic administration of adjuvants and immunomodulatory cytokines. Cytokines constitute a huge group of proteins that, taken together, regulate not only virtually all the aspects of innate and cognate immunity, but also several other cellular and organismal functions. Cytokines operate via specific transmembrane receptors that are expressed on the plasma membrane of target cells and, depending on multiple variables, can engage autocrine, paracrine or endocrine signaling pathways. The most appropriate term for defining the cytokine network is “pleiotropic”: cytokines are produced by - and operate on - multiple, often overlapping, cell types, triggering context-depend biological outcomes as diverse as cell proliferation, chemotaxis, differentiation, inflammation, elimination of pathogens and cell death. Moreover, cytokines often induce the release of additional cytokines, thereby engaging self-amplificatory or self-inhibitory signaling cascades. In this Trial Watch, we will summarize the biological properties of cytokines and discuss the progress of ongoing clinical studies evaluating their safety and efficacy as immunomodulatory agents against cancer.

Role of IL-24 in NK cell activation and its clinical implication in systemic lupus erythematosus

OBJECTIVES

Interleukin (IL)-24 has been considered as an inflammatory cytokine in autoimmune diseases. However, conflicting data exist and its biological function remains controversial. Additionally, little is known about its functional impact on natural killer (NK) cells. The aim of this study was to investigate the role of IL-24 in NK cell activation and its clinical implication in systemic lupus erythematosus (SLE).

METHODS

Serum cohort consisting of 299 SLE patients, 214 RA patients, and 159 healthy controls (HCs) and plasma cohort consisting of 70 SLE patients, 82 RA patients, and 123 HCs were included in evaluating IL-24 concentrations. Impact of IL-24 on NK cell activation was assessed in two NK cell subsets, i.e., CD56^dimCD16⁺ and CD56^brightCD16^- NK cells. Human NK-92 cell line was applied to evaluate functional potential of IL-24 on NK cell migration and invasion.

RESULTS

Serum and plasma levels of IL-24 were comparable between patients with SLE or RA and HCs. While recombinant human (rh) IL-2 consistently induced an increased expression of CD69 on both CD56^dimCD16⁺ and CD56^brightCD16^- cells derived from both healthy subjects and patients with SLE, IL-24 alone was insufficient to activate the CD56^dim and CD56^bright NK cells. Similarly, while the migratory NK-92 cell numbers were significantly increased with rhIL-2 stimulation, IL-24 alone was unable to enhance NK-92 cell migratory and invasive capacity.

CONCLUSION

Our data indicate that there were no significant differences in serum and plasma concentrations of IL-24 between SLE patients and healthy controls. Recombinant IL-24 has no effect on NK cell activation and migration. Key points • This is the first study to investigate functional potential of IL-24 on NK cell activation. • Recombinant IL-24 lacks functional capacity on NK cell activation in either CD56^dimCD16⁺ or CD56^brightCD16^- NK cell subsets derived from both healthy subjects and patients with SLE. • No significant differences in serum and plasma levels of IL-24 between SLE patients and healthy controls.

Aetiology and pathogenesis of hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory disorder. Patients develop inflamed nodules and abscesses and, at later stages of disease, epithelialized tunnels and scars in skinfolds of axillary, inguinal, gluteal and perianal areas. Quality of life is affected due to severe pain, purulent secretion, restricted mobility and systemic involvement. Genetics and lifestyle factors including smoking and obesity contribute to the development of HS. These factors lead to microbiome alteration, subclinical inflammation around the terminal hair follicles, and infundibular hyperkeratosis, resulting in plugging and rupture of the follicles. Cell-damage-associated molecules and propagating bacteria trigger inflammation and lead to massive immune cell infiltration that clinically manifests as inflamed nodules and abscesses. The immune system plays a key role also in the progression and chronification of skin alterations. Innate proinflammatory cytokines (e.g. interleukin-1β and tumour necrosis factor-α), mediators of activated T helper (Th)1 and Th17 cells (e.g. interleukin-17 and interferon-γ), and effector mechanisms of neutrophilic granulocytes, macrophages and plasma cells are involved. Simultaneously, skin lesions contain anti-inflammatory mediators (e.g. interleukin-10) and show limited activity of Th22 and regulatory T cells. The inflammatory vicious circle finally results in pain, purulence, tissue destruction and scarring. Chronic inflammation in patients with HS is also frequently detected in organs other than the skin, as indicated by their comorbidities. All these aspects represent a challenge for the development of therapeutic approaches, which are urgently needed for this debilitating disease. This scholarly review focuses on the causes and pathogenetic mechanisms of HS and the potential therapeutic value of this knowledge.

Resolution of inflammation in immune and nonimmune cells by interleukin-19

The inflammatory response is a complex, tightly regulated process activated by tissue wounding, foreign body invasion, and sterile inflammation. Over the decades, great progress has been made to advance our understanding of this process. One often overlooked aspect of inflammation is its sequel: resolution. We know that dysregulated resolution often results in numerous chronic degenerative diseases such as arthritis, cancer, and asthma. However, identification of components and mechanisms of resolving pathways lags behind those of proinflammatory processes, yet represents overlooked therapeutic opportunities. One approach is identification of endogenous, negative compensatory mechanisms, which are activated in response to inflammation for the purpose of resolution of that inflammatory stimuli. This review will focus on literature that describes expression and function of interleukin-19, a proposed anti-inflammatory cytokine, in numerous inflammatory diseases. The literature concerning IL-19 is complex, context-dependent, and often contradictory. The expression and function of IL-19 in the inflammatory response are in no way settled. We will attempt to clarify the role that this interesting and understudied cytokine plays in resolution of inflammation and discuss its mechanisms of action in different cell types. We will present a hypothesis that endogenous IL-19 expression in response to inflammatory stimuli is a cellular compensatory mechanism to dampen inflammation. We further present studies suggesting that while endogenously expressed IL-19 may be a response to inflammation, pharmacological levels may be necessary to effectively resolve the inflammatory cascade.

TgROP18 targets IL20RB for host-defense-related-STAT3 activation during Toxoplasma gondii infection

Background

Toxoplasma gondii is an opportunistic protozoan infecting almost one-third of the world’s population. Toxoplasma gondii rhoptry protein 18 (TgROP18) is a key virulence factor determining the parasite’s acute virulence and is secreted into host cells during infection. We previously identified the interaction of TgROP18 and host cell immune-related receptor protein IL20RB, and observed the activation of STAT3 in human keratinocytes (HaCaT) cells infected by the rop16 knockout RH strain, though TgROP16 is regarded as being responsible for host STAT3 activation during T. gondii invasion. Therefore, we hypothesize TgROP18 can activate host STAT3 through binding to IL20RB.

Methods

CRISPR-CAS9 technology was used to generate the ROP16 and ROP18 double knockout RH strain, RH-∆rop16∆rop18. SDS-PAGE and western blot were used to detect STAT3 activation in different HaCaT cells with high endogenous IL20RB expression treated with T. gondii tachyzoites infection, recombinant ROP18, or IL-20. FRET and co-immunoprecipitation (Co-IP) was used to detect the protein-protein interaction.

Results

We observed that TgROP18 was involved in a synergic activation of the host JAK/STAT3 pathway together with TgROP16 in human HaCaT cells infected with T. gondii or treated with recombinant TgROP18 protein, stimulating host proinflammatory immune responses such as expression of TNF-α. The effect of recombinant ROP18 on STAT3 phosphorylation was presented in a dose-dependent manner. Additionally, TgROP18 was identified to target IL20RB on its extracellular domain. When we treated different cell lines with the recombinant ROP18, STAT3 phosphorylation could only be observed in the cells with endogenous IL20RB expression, such as HaCaT cells.

Conclusions

These findings indicate that TgROP18-IL20RB interaction upon T. gondii invasion was involved in STAT3 activation, which is associated with host cell defense.

IL-24: A new player in the pathogenesis of pro-inflammatory and allergic skin diseases

Interleukin (IL)-24 is a member of the IL-20 family of cytokines and is produced by various types of cells, such as CD4⁺ T cells, NK cells, mast cells, keratinocytes, bronchial epithelial cells, and myofibroblasts. Previous studies suggest that IL-24 plays an essential role in the pathogenesis of pro-inflammatory autoimmune disorders such as psoriasis, arthritis, and inflammatory bowel diseases. However, the role of IL-24 in the pathogenesis of allergic diseases has been elusive. It has already been reported that IL-24 is involved in the pathogenesis of allergic lung and skin diseases. Moreover, we have recently revealed for the first time the pivotal functions of IL-24 in IL-13-mediated skin barrier dysfunction in atopic dermatitis (AD), which is known to be a characteristic of AD caused by Th2 cytokines such as IL-4 or IL-13. In this review, we show recent advances in the basic characteristics of IL-24 and its novel functions in the pathogenesis of allergic skin inflammation, focusing on AD. A better understanding of the role of IL-24 in allergic diseases can lead to the development of new therapeutic options.

Interleukin-19 enhances cytokine production induced by lipopolysaccharide and inhibits cytokine production induced by polyI:C in BALB/c mice

Interleukin (IL)-19 is a cytokine of the IL-10 family. There are many reports on the involvement of IL-19 in several human diseases. There also are many reports elucidating the role of IL-19 using mouse disease models. Most reports use C57BL/6 mice, whereas few reports use BALB/c mice, in terms of the mouse disease model that the researchers used in the present study. To date, research on the role of IL-19 is diversified, yet some basic mechanisms are still unclear. In this study, we administered lipopolysaccharide (LPS), polyI:C, and CpG to BALB/c mice, measured more than 20 cytokines in the blood and compared them with that of the wild-type and IL-19-deficient (IL-19 KO) mice. LPS is associated with bacterial infection, polyI:C is associated with viral infection, and CpG is associated with both bacterial and viral infections. Among the cytokines measured, the results of experiments using LPS revealed that the production of some cytokines was suppressed in IL-19 KO mice. Interestingly, the experiments using polyI:C revealed that production of some cytokines was enhanced in IL-19 KO mice. However, the experiments using CpG have shown that the production of only one cytokine was enhanced in IL-19 KO mice. These results revealed that cytokine production in the blood was regulated by IL-19, and the type of regulation was dependent on the administered stimulant.

Characterization of IL-19, -20, and -24 in acute and chronic kidney diseases reveals a pro-fibrotic role of IL-24

BACKGROUND

Recently, the role of IL-19, IL-20 and IL-24 has been reported in renal disorders. However, still little is known about their biological role.

METHODS

Localization of IL-20RB was determined in human biopsies and in the kidneys of mice that underwent unilateral ureteral obstruction (UUO). Renal Il19, Il20 and Il24 expression was determined in ischemia/reperfusion, lipopolysaccharide, streptozotocin, or UUO induced animal models of kidney diseases. The effects of H₂O₂, LPS, TGF-β1, PDGF-B and IL-1β on IL19, IL20 and IL24 expression was determined in peripheral blood mononuclear cells (PBMCs). The extents of extracellular matrix (ECM) and α-SMA, Tgfb1, Pdgfb, and Ctgf expression were determined in the kidneys of Il20rb knockout (KO) and wild type (WT) mice following UUO. The effect of IL-24 was also examined on HK-2 tubular epithelial cells and NRK49F renal fibroblasts.

RESULTS

IL-20RB was present in the renal biopsies of patients with lupus nephritis, IgA and diabetic nephropathy. Amount of IL-20RB increased in the kidneys of mice underwent UUO. The expression of Il19, Il20 and Il24 increased in the animal models of various kidney diseases. IL-1β, H₂O₂ and LPS induced the IL19, IL20 and IL24 expression of PBMCs. The extent of ECM, α-SMA, fibronectin, Tgfb1, Pdgfb, and Ctgf expression was lower in the kidney of Il20rb KO compared to WT mice following UUO. IL-24 treatment induced the apoptosis and TGF-β1, PDGF-B, CTGF expression of HK-2 cells.

CONCLUSIONS

Our data confirmed the significance of IL-19, IL-20 and IL-24 in the pathomechanism of renal diseases. Furthermore, we were the first to demonstrate the pro-fibrotic effect of IL-24.

Eavesdropping on the conversation between immune cells and the skin epithelium

The skin epithelium covers our body and serves as a vital interface with the external environment. Here, we review the context-specific interactions between immune cells and the epithelium that underlie barrier fitness and function. We highlight the mechanisms by which these two systems engage each other and how immune-epithelial interactions are tuned by microbial and inflammatory stimuli. Epithelial homeostasis relies on a delicate balance of immune surveillance and tolerance, breakdown of which results in disease. In addition to their canonical immune functions, resident and recruited immune cells also supply the epithelium with instructive signals to promote repair. Decoding the dialogue between immunity and the epithelium therefore has great potential for boosting barrier function or mitigating inflammatory epithelial diseases.

Targeting the STING pathway in tumor-associated macrophages regulates innate immune sensing of gastric cancer cells

Rationale:STING is a critical player in the innate and adaptive immune system, sensing cytosolic DNA to activate the expression of interferon genes and regulate T lymphocytes, which drives immunogenic responses to cancer cells. Tumor-associated macrophages (TAMs), abundantly present in the tumor microenvironment, play a key role in cancer development. Gastric cancer is one of the most common and leading causes in cancer-related death worldwide. However, studies on the function and regulation of STING in TAMs and their roles in gastric cancer progression are still limited.

Methods: We analyzed STING and CD68 expression of 200 pairs of gastric cancer and adjacent normal tissues by immunohistochemistry to identify the prognostic values of STING, as well as the correlations between STING and CD68 in gastric cancer. The characteristics of STING-altered macrophages, as well as their effects on cancer cell apoptosis and T cell differentiation were examined by flow cytometry. Cytokines secreted by STING-altered macrophages were identified by the Human Inflammation Array3 kit. Concentrations of soluble IL24 and IFN-β were measured by ELISA. In vivo models, including spontaneous gastric cancer in p53^+/- mice and cell line-based xenografts, were established, and clinical benefits of STING-altered macrophages were examined.

Results: Our study identifies STING as a prognostic factor for gastric cancer, and for the first time demonstrated that knocking-down STING and STING activation by 2'3'-c-GAMP both promote TAMs polarizing into pro-inflammatory subtype and induce apoptosis of gastric cancer cells, mechanistically through IL6R-JAK-IL24 pathway.

Conclusions: This study evaluated effects of targeting STING in TAMs in anti-gastric-cancer therapies. Moreover, we unveil a novel function of STING to activate the IL6R-JAK-IL24 pathway in macrophages.

Increased IL-26 Expression Promotes T Helper Type 17- and T Helper Type 2-Associated Cytokine Production by Keratinocytes in Atopic Dermatitis

Whereas atopic dermatitis (AD) is considered as a T helper 2 (Th2)-centered disease, IL-17-producing Th (Th17) cells are also activated in AD lesional skin. However, the relationship between Th17 responses and Th2 responses in AD is still to be elucidated. Although Th17 cells are increased in AD skin, the expression and function of IL-26, which is also produced by Th17 cells, in AD are still unknown. In this report, we demonstrated that IL-26 mRNA expression levels were elevated in AD lesional skin compared with healthy controls and that IL-26-producing cells were increased in AD lesional skin by immunohistochemistry. Furthermore, IL-26 promoted IL-8, IL-1β, chemokine (C-C motif) ligand 20, IL-33, and β-defensin 2 production in keratinocytes through phosphorylation of signal transducer and activator of transcription 1 and signal transducer and activator of transcription 3. Selective JAK inhibitors for JAK1, JAK2, and tyrosine kinase 2 blocked IL-26-induced cytokine production in keratinocytes. We also showed that injection of IL-26 exacerbated an oxazolone-induced AD mouse model and upregulated Th2 and Th17 cytokine expression in vivo. Because previous studies indicate that the above molecules induced by IL-26 can promote Th17 and/or Th2 immune responses, IL-26 may play an important role for bridging between Th17 and Th2 responses, resulting in the development of AD.

[Recent progress in the pathophysiological role of interleukin-19]

Cytokine signal is essential for the biological function including development, maintenance of homeostasis and progression of disease. There are growing evidences that signaling via pro-inflammatory cytokines underlie a variety of immunological diseases such as psoriasis, atopic dermatitis, inflammatory bowel disease, and metabolic syndromes, in which cytokine signals are known as a potential therapeutic target of antibody drugs. In contrast, anti-inflammatory cytokines, which is represented by IL-10, largely contribute to suppression of inflammation and restoration of injured tissues. IL-19 is a member of IL-10 cytokine family, which comprises IL-20 cytokine subfamily with IL-20, IL-22, IL-24, and IL-26. IL-19 is produced by myeloid and epithelial cells with stimulation of bacterial components and cytokines. Although IL-19 has been originally recognized as a potential Th2-related cytokine, in recent researches, it has been reported that this cytokine upregulates Th17 response to reflect and promote progression of Th17-related disease including psoriasis. On the other hand, IL-19 has anti-inflammatory effects on inflammatory diseases such as infectious skin disease, inflammatory bowel disease, and cardiovascular disease. Therefore, IL-19 may exert pleiotropic effects dependent on the pathological mechanism of inflammatory diseases. In this review, we summarize recent studies about IL-19 and introduce the pathophysiological and therapeutic role of IL-19 in inflammatory diseases.

Expression of interleukin (IL)-10 family cytokines in aqueous humour of patients with specific endogenous uveitic entities: elevated levels of IL-19 in human leucocyte antigen-B27-associated uveitis

PURPOSE

Evidence exists that the interleukin (IL)-10 family of cytokines is involved in autoimmune diseases. The aim of this study was to analyse the levels of the IL-10 family cytokines IL-10, IL-19, IL-20, IL-22, IL-26, IL-28A and IL-29 in aqueous humour (AH) samples from patients with specific uveitic entities. In addition, we correlated their levels with the levels of the proinflammatory cytokines tumour necrosis factor-α (TNF-α) and IL-1β.

METHODS

Aqueous humour (AH) samples from patients with active uveitis associated with Behçet's disease (BD; n = 13), sarcoidosis (n = 8), human leucocyte antigen (HLA)-B27-related inflammation (n = 12), Vogt-Koyanagi-Harada (VKH) disease (n = 12) and control subjects (n = 9) were assayed with the use of a multiplex assay.

RESULTS

Of all the IL-10 family cytokines studied, only IL-19 levels were significantly higher in AH samples of patients (n = 45) than in controls (p = 0.022). When comparing the four individual disease groups to controls, IL-19 levels were only significantly higher in HLA-B27-associated uveitis (p < 0.001). IL-19 levels were significantly higher in patients with HLA-B27-associated uveitis than in patients with BD, sarcoidosis and VKH disease (p < 0.001; p = 0.002; p < 0.001, respectively). Significant correlations were found between AH levels of IL-19 and AH levels of TNF-α, (r = 0.3; p = 0.03) and IL-1β (r = 0.56; p < 0.001).

CONCLUSIONS

Among the IL-10 family cytokines analysed, IL-19 demonstrated the highest expression in endogenous uveitis, particularly in HLA-B27-associated uveitis. IL-19 thus might assist in the regulation of inflammation in HLA-B27-associated uveitis.

Recent insights into apoptosis and toxic autophagy: The roles of MDA-7/IL-24, a multidimensional anti-cancer therapeutic

Apoptosis and autophagy play seminal roles in maintaining organ homeostasis. Apoptosis represents canonical type I programmed cell death. Autophagy is viewed as pro-survival, however, excessive autophagy can promote type II cell death. Defective regulation of these two obligatory cellular pathways is linked to various diseases, including cancer. Biologic or chemotherapeutic agents, which can reprogram cancer cells to undergo apoptosis- or toxic autophagy-mediated cell death, are considered effective tools for treating cancer. Melanoma differentiation associated gene-7 (mda-7) selectively promotes these effects in cancer cells. mda-7 was identified more than two decades ago by subtraction hybridization showing elevated expression during induction of terminal differentiation of metastatic melanoma cells following treatment with recombinant fibroblast interferon and mezerein (a PKC activating agent). MDA-7 was classified as a member of the IL-10 gene family based on its chromosomal location, and the presence of an IL-10 signature motif and a secretory sequence, and re-named interleukin-24 (MDA-7/IL-24). Multiple studies have established MDA-7/IL-24 as a potent anti-cancer agent, which when administered at supra-physiological levels induces growth arrest and cell death through apoptosis and toxic autophagy in a wide variety of tumor cell types, but not in corresponding normal/non-transformed cells. Furthermore, in a phase I/II clinical trial, MDA-7/IL-24 administered by means of a non-replicating adenovirus was well tolerated and displayed significant clinical activity in patients with multiple advanced cancers. This review examines our current comprehension of the role of MDA-7/IL-24 in mediating cancer-specific cell death via apoptosis and toxic autophagy.

IL-19 Up-Regulates Mucin 5AC Production in Patients With Chronic Rhinosinusitis via STAT3 Pathway

The mucin gene, MUC5AC, is highly expressed both in chronic respiratory inflammatory diseases and inflammatory bowel disease where mucin secretion is regulated by members of the interleukin IL-20 subfamily. This study was conducted to determine the roles and mechanisms of IL-19, a member of the IL-20 subfamily, in regulating MUC5AC production in chronic rhinosinusitis (CRS). We analyzed the expression of mucin and MUC5AC in the nasal mucosa of patients with CRS through periodic acid Schiff (PAS) staining and immunohistochemical examination. Real-time quantitative PCR, ELISA, confocal microscopy and western blotting were used to measure MUC5AC expression in primary human nasal epithelium cells (PHNECs) stimulated with recombinant human IL-19 (rhIL-19), IL-19 receptor siRNA transfection or a control. The involvement of the STAT3 signaling pathway was examined using cryptotanshinone (CRY, an inhibitor of STAT3). Mucin and MUC5AC were significantly increased in mucosa of CRS patients with/without nasal polyps compared to mucosa isolated from controls who had no CRS, but there were no significant differences between these two groups. Pretreatment with rhIL-19 up-regulated the expression of MUC5AC levels in PHNECs. Knockdown of IL-20R2 and pretreatment with CRY attenuated MUC5AC production induced by rhIL-19. We propose that IL-19 up-regulates MUC5AC-induced mucin production via the STAT3 pathway in CRS, highlighting the important role IL-19 may play in mucin production in chronic respiratory diseases.

IL-24 contributes to skin inflammation in Para-Phenylenediamine-induced contact hypersensitivity

Para-Phenylenediamine (PPD) is an aromatic amine used in hair dyes and in temporary black henna tattoos, which is a frequent cause of allergic contact dermatitis (ACD). ACD is a skin inflammatory reaction characterized by modifications such as spongiosis, exocytosis and acanthosis. The aim of this study is to characterize the expression and the role of IL-20-related cytokines, including IL-19, IL-20, IL-22 and IL-24, in ACD. The expression of IL19, IL20, IL22 and IL24 is increased in affected skin from PPD allergic patients compared with uninvolved skin. In addition, the expression of these cytokines positively correlates with clinical symptoms. To assess their role in ACD, we set up a mouse model of PPD-induced allergic contact dermatitis and we showed that, in contrast to Il22-deficient mice, Il22ra1-, Il20rb- and Il24-deficient mice are partially protected against development of PPD-induced contact hypersensitivity. These mice have decreased ear thickening and less acanthosis compared with WT mice after PPD treatment. In addition, the absence of IL-22R, IL-20R2 or IL-24 affects the recruitment of neutrophils into the skin but not the total IgE production. Taken together, these results demonstrate the implication of IL-24 via the IL-20R type II receptor in the inflammatory process of ACD.

The Interleukin-10 Family of Cytokines and Their Role in the CNS

Resident cells of the central nervous system (CNS) play an important role in detecting insults and initiating protective or sometimes detrimental host immunity. At peripheral sites, immune responses follow a biphasic course with the rapid, but transient, production of inflammatory mediators giving way to the delayed release of factors that promote resolution and repair. Within the CNS, it is well known that glial cells contribute to the onset and progression of neuroinflammation, but it is only now becoming apparent that microglia and astrocytes also play an important role in producing and responding to immunosuppressive factors that serve to limit the detrimental effects of such responses. Interleukin-10 (IL-10) is generally considered to be the quintessential immunosuppressive cytokine, and its ability to resolve inflammation and promote wound repair at peripheral sites is well documented. In the present review article, we discuss the evidence for the production of IL-10 by glia, and describe the ability of CNS cells, including microglia and astrocytes, to respond to this suppressive factor. Furthermore, we review the literature for the expression of other members of the IL-10 cytokine family, IL-19, IL-20, IL-22 and IL-24, within the brain, and discuss the evidence of a role for these poorly understood cytokines in the regulation of infectious and sterile neuroinflammation. In concert, the available data indicate that glia can produce IL-10 and the related cytokines IL-19 and IL-24 in a delayed manner, and these cytokines can limit glial inflammatory responses and/or provide protection against CNS insult. However, the roles of other IL-10 family members within the CNS remain unclear, with IL-20 appearing to act as a pro-inflammatory factor, while IL-22 may play a protective role in some instances and a detrimental role in others, perhaps reflecting the pleiotropic nature of this cytokine family. What is clear is that our current understanding of the role of IL-10 and related cytokines within the CNS is limited at best, and further research is required to define the actions of this understudied family in inflammatory brain disorders.