miRNA­21 promotes the progression of acute liver failure via the KLF6/autophagy/IL­23 signaling pathway.

Acute liver failure (ALF) is a complex syndrome characterized by overactivation of innate immunity, and the recruitment and differentiation of immune cells at inflammatory sites. The present study aimed to explore the role of microRNA (miRNA/miR)­21 and its potential mechanisms underlying inflammatory responses in ALF. Baseline serum miR­21 was analyzed in patients with ALF and healthy controls. In addition, miR­21 antagomir was injected via the tail vein into C57BL/6 mice, and lipopolysaccharide/D­galactosamine (LPS/GalN) was injected into mice after 48 h. The expression levels of miR­21, Krüppel­like­factor­6 (KLF6), autophagy­related proteins and interleukin (IL)­23, and hepatic pathology were then assessed in the liver tissue. Furthermore, THP­1­derived macrophages were transfected with a miRNA negative control, miR­21 inhibitor, miR­21 mimics or KLF6 overexpression plasmid, followed by treatment with or without rapamycin, and the expression levels of miR­21, KLF6, autophagy­related proteins and IL­23 were evaluated. The results revealed that baseline serum miR­21 levels were significantly upregulated in patients with ALF. In addition, LPS/GalN­induced ALF was attenuated in the antagomir­21 mouse group. KLF6 was identified as a target of miR­21­5p with one putative seed match site identified by TargetScan. A subsequent luciferase activity assay demonstrated a direct interaction between miR­21­5p and the 3'­UTR of KLF6 mRNA. Further experiments suggested that miR­21 promoted the expression of IL­23 via inhibiting KLF6, which regulated autophagy. In conclusion, in the present study, baseline serum miR­21 levels were highly upregulated in patients with ALF, antagomir­21 attenuated LPS/GalN­induced ALF in a mouse model, and miR­21 could promote the expression of IL­23 via inhibiting KLF6.

The Dysregulated IL-23/TH17 Axis in Endometriosis Pathophysiology.

Endometriosis is a chronic inflammatory disease in which endometrial-like tissue grows ectopically, resulting in pelvic pain and infertility. IL-23 is a key contributor in the development and differentiation of TH17 cells, driving TH17 cells toward a pathogenic profile. In a variety of inflammatory and autoimmune disorders, TH17 cells secrete proinflammatory cytokines, including IL-17, contributing to disease pathophysiology. Our studies and others have implicated IL-17 and TH17 cell dysregulation in endometriosis, which is associated with disease severity. In this article, we address whether IL-23-driven TH17 cells contribute to cardinal features of lesion proliferation, vascularization, and inflammation in endometriosis using patient samples, representative cell lines, and our established mouse model of endometriosis. The results indicated dysregulated expression of key genes in the IL-23/TH17 axis in patient ectopic and eutopic endometrial samples and increased IL-23 protein in patient plasma compared with controls. In vitro studies using primary human TH cells determined that rIL-23 mixture treatment increased pathogenic TH17 cell frequency. Similarly, rIL-23 treatment of cell lines (12Z cells, EECCs, HUVECs, and hESCs) representative of the endometriotic lesion microenvironment increased cytokines and growth factors, which play a role in lesion establishment and maintenance. In a syngeneic mouse model of endometriosis, rIL-23 treatment altered numbers of myeloid and T cell subsets in peritoneal fluid and increased giant cells within the lesion. Lesions from rIL-23-treated mice did not reveal significant alterations in proliferation/vascularization, although trends of increased proliferation and vascularization were observed. Collectively, these findings provide insights into the impact of the IL-23/TH17 axis on local immune dysfunction and broadly on endometriosis pathophysiology.

IL-6 Up-Regulates Expression of LIM-Domain Only Protein 4 in Psoriatic Keratinocytes through Activation of the MEK/ERK/NF-κB Pathway.

Psoriasis is a chronic inflammatory skin disease characterized by the activation of keratinocytes and the infiltration of immune cells. Overexpression of the transcription factor LIM-domain only protein 4 (LMO4) promoted by IL-23 has critical roles in regulating the proliferation and differentiation of psoriatic keratinocytes. IL-6, an autocrine cytokine in psoriatic epidermis, is a key mediator of IL-23/T helper 17-driven cutaneous inflammation. However, little is known about how IL-6 regulates the up-regulation of LMO4 expression in psoriatic lesions. In this study, human immortalized keratinocyte cells, clinical biopsy specimens, and an animal model of psoriasis induced by imiquimod cream were used to investigate the role of IL-6 in the regulation of keratinocyte proliferation and differentiation. Psoriatic epidermis showed abnormal expression of IL-6 and LMO4. IL-6 up-regulated the expression of LMO4 and promoted keratinocyte proliferation and differentiation. Furthermore, in vitro and in vivo studies showed that IL-6 up-regulates LMO4 expression by activating the mitogen-activated extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK)/NF-κB signaling pathway. These results suggest that IL-6 can activate the NF-κB signaling pathway, up-regulate the expression of LMO4, lead to abnormal proliferation and differentiation of keratinocytes, and promote the occurrence and development of psoriasis.

IL-23 induces CLEC5A+ IL-17A+ neutrophils and elicit skin inflammation associated with psoriatic arthritis.

IL-23-activation of IL-17 producing T cells is involved in many rheumatic diseases. Herein, we investigate the role of IL-23 in the activation of myeloid cell subsets that contribute to skin inflammation in mice and man. IL-23 gene transfer in WT, IL-23RGFP reporter mice and subsequent analysis with spectral cytometry show that IL-23 regulates early innate immune events by inducing the expansion of a myeloid MDL1+CD11b+Ly6G+ population that dictates epidermal hyperplasia, acanthosis, and parakeratosis; hallmark pathologic features of psoriasis. Genetic ablation of MDL-1, a major PU.1 transcriptional target during myeloid differentiation exclusively expressed in myeloid cells, completely prevents IL-23-pathology. Moreover, we show that IL-23-induced myeloid subsets are also capable of producing IL-17A and IL-23R+MDL1+ cells are present in the involved skin of psoriasis patients and gene expression correlations between IL-23 and MDL-1 have been validated in multiple patient cohorts. Collectively, our data demonstrate a novel role of IL-23 in MDL-1-myelopoiesis that is responsible for skin inflammation and related pathologies. Our data open a new avenue of investigations regarding the role of IL-23 in the activation of myeloid immunoreceptors and their role in autoimmunity.

HMGB1 regulates Th17 cell differentiation and function in patients with psoriasis.

BACKGROUND: Psoriasis is an immune-mediated chronic inflammatory skin disease, in which T helper 17 (Th17) cells and its effective cytokine interleukin (IL)-17A play a pivotal pathogenic role. High mobility group box 1 (HMGB1) is an important proinflammatory cytokine, which has been confirmed to be highly expressed in the peripheral circulation and epidermis tissues of psoriasis patients. The regulatory effect of HMGB1 on IL-17A expression and function has been reported in some inflammatory and autoimmune diseases by the HMGB1-Toll-like receptor 4 (TLR4)-interleukin (IL)-23-IL-17A pathway. While, in the pathological environment of psoriasis, whether HMGB1 can exert the regulatory effect on IL-17A is not clear. OBJECTIVE: We aimed to evaluate the role of HMGB1-TLR4-IL-23-IL-17A pathway in the pathogenesis of psoriasis and explore the possible regulatory mechanism of HMGB1 on Th17 cell differentiation. METHODS: Serum levels of HMGB1, TLR4, IL-23, and IL-17A were quantified in 50 patients with moderate-to-severe plaque psoriasis and 30 healthy controls. Peripheral blood mononuclear cells  were acquired from 10 severe psoriasis patients and administrated by different concentrations of recombinant-HMGB1 (rHMGB1) to detect the Th17 cell percentage, mRNA and protein levels of TLR4, IL-23, IL-17A and retinoid-related orphan receptor γt (RORγt). RESULTS: The serum levels of HMGB1, TLR4, IL-23, and IL-17A in psoriasis patients were significantly higher than healthy controls, especially in severe patients, and positively correlated with the severity index. There were also positive correlations between every two detected indicators of HMGB1, TLR4, IL-23, and IL-17A. In vitro study, rHMGB1 can promote the elevated expression of Th17 cell percentage as well as TLR4, IL-23, IL-17A, and RORγt in a dose-dependent manner. CONCLUSION: HMGB1 can contribute to the pathogenesis of psoriasis by regulating Th17 cell differentiation through HMGB1-TLR4-IL-23-RORγt pathway, then promotes IL-17A production and aggravates inflammation process. Targeting HMGB1 may be a possible potential candidate for the immunotherapy of psoriasis.

Cang-ai volatile oil ameliorates imiquimod-induced psoriatic skin lesions by suppressing the ILC3s.

ETHNOPHARMACOLOGICAL RELEVANCE: Cang-ai volatile oil (CAVO) is an aromatic Chinese medicine with potent antibacterial and immune regulatory properties. While CAVO has been used to treat upper respiratory tract infections, depression, otomycosis, and bacterial infections in the skin, its effect on psoriasis is unknown. AIM OF THE STUDY: This study explores the effect and mechanism of CAVO in psoriasis intervention. MATERIAL AND METHODS: The effect of CAVO on the expression of IL-6 and IL-1ß was assessed in TNF-α-induced HaCaT cells using enzyme-linked immunosorbent assay (ELISA). Mice were given imiquimod (IMQ) and administered orally with different CAVO doses (0.03 and 0.06 g/kg) for 5 days. The levels of inflammatory cytokines related to group-3 innate lymphoid cells (ILC3s) in the skin were assessed using hematoxylin and eosin (H&E) staining, ELISA, and western blotting (WB). The frequency of ILC3s in mice splenocytes and skin cells was evaluated using flow cytometry. RESULTS: The results demonstrated that CAVO decreased the expression of IL-6 and IL-1ß in TNF-α- induced HaCaT cells. CAVO significantly reduced the severity of psoriatic symptoms in IMQ-induced mice. The expression of inflammatory cytokines in the skin, such as IL-1ß, IL-6, IL-8, IL-22, IL-23, and IL-17 A were decreased, whereas IL-10 levels were increased. The mRNA expressions of TNF-α, IL-23 A, IL-23 R, IL-22, IL-17 A, and RORγt were down-regulated in skin tissues. CAVO also decreased the levels of NF-κB, STAT3, and JAK2 proteins. CONCLUSIONS: CAVO potentially inhibits ILC3s activation to relieve IMQ-induced psoriasis in mice. These effects might be attributed to inhibiting the activation of NF-κB, STAT3, and JAK2 signaling pathways.

Th17 cell promotes apoptosis of IL-23R+ neurons in experimental autoimmune encephalomyelitis.

Myelin antigen-reactive Th1 and Th17 cells are critical drivers of central nervous system (CNS) autoimmune inflammation. Transcription factors T-bet and RORγt play a crucial role in the differentiation and function of Th1 and Th17 cells, and impart them a pathogenic role in CNS autoimmune inflammation. Mice deficient in these two factors do not develop experimental autoimmune encephalomyelitis (EAE). While T-bet and RORγt are known to regulate the expression of several cell adhesion and migratory molecules in T cells, their role in supporting Th1 and Th17 trafficking to the CNS is not completely understood. More importantly, once Th1 and Th17 cells reach the CNS, how the function of these transcription factors modulates the local inflammatory response during EAE is unclear. In the present study, we showed that myelin oligodendrocyte glycoprotein 35-55 peptide (MOG35-55)-specific Th1 cells deficient in RORγt could cross the blood-brain barrier (BBB) but failed to induce demyelination, apoptosis of neurons, and EAE. Pathogenic Th17 cell-derived cytokines GM-CSF, TNF-α, IL-17A, and IL-21 significantly increased the surface expression of IL-23R on neuronal cells. Furthermore, we showed that, in EAE, neurons in the brain and spinal cord express IL-23R. IL-23-IL-23R signaling in neuronal cells caused phosphorylation of STAT3 (Ser727 and Tyr705) and induced cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase-1 (PARP-1) molecules in an IL-23R-dependent manner and caused apoptosis. Thus, we provided a mechanism showing that T-bet is required to recruit pathogenic Th17 cells to the CNS and RORγt-mediated inflammatory response to drive the apoptosis of IL-23R+ neurons in the CNS and cause EAE. Understanding detailed molecular mechanisms will help to design better strategies to control neuroinflammation and autoimmunity. ONE SENTENCE SUMMARY: IL-23-IL-23R signaling promotes apoptosis of CNS neurons.

SGLT2 knockdown restores the Th17/Treg balance and suppresses diabetic nephropathy in db/db mice by regulating SGK1 via Na.

The imbalance between T helper 17 (Th17) and regulatory T (Treg) cells is an important mechanism in the pathogenesis of diabetic nephropathy (DN). Serum/glucocorticoid regulated kinase 1 (SGK1) is a serine-threonine kinase critical for stabilizing the Th17 cell phenotype. Sodium-glucose cotransporter 2 (SGLT2) is a glucose transporter that serves as a treatment target for diabetes. Our study investigated the regulatory role of SGLT2 in the development of DN. The results revealed that SGLT2 knockdown suppressed high glucose-induced excessive secretion of sodium (Na+) and inflammatory cytokines in mouse renal tubular epithelial TCMK-1 cells. High Na+ content induced Th17 differentiation and upregulated SGK1, phosphorylated forkhead box protein O1 (p-FoxO1), and the interleukin 23 receptor (IL-23 R) in primary mouse CD4+ T cells. Co-culture of CD4+ T cells with the culture medium of TCMK-1 cells with insufficient SGLT2 expression significantly suppressed cell migration ability, reduced the production of pro-inflammatory cytokines, and inhibited Th17 differentiation possibly by downregulating SGK1, p-FoxO1, and IL-23 R. In addition, in vivo data demonstrated that SGLT2 knockdown markedly downregulated SGK1 in db/db mice. Insufficient SGLT2 or SGK1 expression also ameliorated the Th17/Treg imbalance, suppressed the development of DN, and regulated the expression of IL-23 R and p-FoxO1. In conclusion, this study showed that SGLT2 knockdown restored the Th17/Treg balance and suppressed DN possibly by regulating the SGK1/p-FoxO1/IL-23 R axis by altering Na+ content in the local environment. These findings highlight the potential use of SGLT2 and SGK1 for the management of DN.

Elevated levels of peripheral Th17 cells and Th17-related cytokines in patients with periampullary adenocarcinoma.

AIM: Periampullary adenocarcinoma (PAC) is a malignant tumor originating at the ampulla of Vater, distal common bile duct, head of the pancreas, ampulla and duodenum. The levels of circulating Th17 cells and Th17-related cytokines in patients with PAC remain unreported. Therefore, the aim of this study was to determine the levels of circulating Th17 cells and Th17-related cytokines in patients with PAC. MATERIALS AND METHODS: Flow cytometry was used to measure Th17 cell proportions in PBMCs from 60 PAC patients and 30 healthy controls. Enzyme-linked immunosorbent assay (ELISA) was used to quantify IL-17A and IL-23 levels in serum samples, while quantitative reverse transcription polymerase chain reaction (qRT-PCR) assessed IL-17A mRNA expression and Th17-related transcription factors (RORγt and STAT3) in tissue samples. RESULTS: The findings showed a substantial increase in Th17 cell percentages, elevated concentrations of IL-17A and IL-23, and higher mRNA expression levels of IL-17A, RORγt, and STAT3 in patients with PAC when compared to healthy controls (HCs). CONCLUSION: Th17 cells play an important role in the pathogenesis of PAC and may represent potential therapeutic targets.

Tanshinone IIA, a component of the self-made Xiao-Yin decoction, ameliorates psoriasis by inhibiting IL-17/IL-23 and PTGS2/NF-κB/AP-1 pathways.

BACKGROUND: Psoriasis is a persistent inflammatory dermatological disorder. Tanshinone IIA (tan-IIA) is a biologically active compound in the self-made Xiao-Yin decoction (SMXYD) and exhibits diverse biological properties, such as anti-proliferative and anti-inflammatory effects. The objective of this investigation was to assess the potential of tan-IIA as a therapeutic agent against psoriasis. METHODS: Network pharmacology was employed to ascertain the active constituents and potential pathways associated with SMXYD and psoriasis. We conducted CCK-8, qRT-PCR, and western blotting to assess the proliferation of HaCaT keratinocytes and the expression of IL-17/IL-23 and PTGS2/NF-κB/AP-1 pathways. Additionally, we used H&E staining, western blotting, and ELISA to evaluate the therapeutic effects and signaling pathways of tan-IIA in psoriasis-like mice induced by imiquimod (IMQ). RESULTS: Network pharmacology analysis identified eight hub compounds. The Th17/IL-17 signaling was found to be a potential therapeutic pathway of SMXYD against psoriasis, with JUN (AP-1) as the core molecule. Next, PTGS2 was selected as the target of tan-IIA against psoriasis using network pharmacology analysis. Molecular docking showed a high affinity between PTGS2 and tan-IIA. Tan-IIA treatment attenuated M-5-induced hyperproliferation and inflammation in HaCaT keratinocytes. Additionally, Tan-IIA downregulated the PTGS2/NF-κB/AP-1 pathway in HaCaT keratinocytes. In the IMQ-induced psoriasis-like mouse, tan-IIA significantly reduced the severity of skin lesions and downregulated the PTGS2/NF-κB/AP-1 pathway. Moreover, the combination of methotrexate (MTX) and tan-IIA further inhibited the IL-17/IL-23 and PTGS2/NF-κB/AP-1 pathways. CONCLUSION: The administration of tan-IIA has shown a positive effect on psoriasis by inhibiting the IL-17/IL-23 and PTGS2/NF-κB/AP-1 pathways. The findings suggest that it has promising qualities that make it a potential candidate for the development of future anti-psoriatic agents.

Single-cell analysis of psoriasis resolution demonstrates an inflammatory fibroblast state targeted by IL-23 blockade.

Biologic therapies targeting the IL-23/IL-17 axis have transformed the treatment of psoriasis. However, the early mechanisms of action of these drugs remain poorly understood. Here, we perform longitudinal single-cell RNA-sequencing in affected individuals receiving IL-23 inhibitor therapy. By profiling skin at baseline, day 3 and day 14 of treatment, we demonstrate that IL-23 blockade causes marked gene expression shifts, with fibroblast and myeloid populations displaying the most extensive changes at day 3. We also identify a transient WNT5A+/IL24+ fibroblast state, which is only detectable in lesional skin. In-silico and in-vitro studies indicate that signals stemming from these WNT5A+/IL24+ fibroblasts upregulate multiple inflammatory genes in keratinocytes. Importantly, the abundance of WNT5A+/IL24+ fibroblasts is significantly reduced after treatment. This observation is validated in-silico, by deconvolution of multiple transcriptomic datasets, and experimentally, by RNA in-situ hybridization. These findings demonstrate that the evolution of inflammatory fibroblast states is a key feature of resolving psoriasis skin.

IL-23 contributes to Particulate Matter induced allergic asthma in the early life of mice and promotes asthma susceptibility.

Air pollutant exposure leads to and exacerbates respiratory diseases. Particulate Matter (PM) is a major deleterious factor in the pathophysiology of asthma. Nonetheless, studies on the effects and mechanisms of exposure in the early life of mice remain unresolved. This study aimed to investigate changes in allergic phenotypes and effects on allergen-specific memory T cells resulting from co-exposure of mice in the early life to PM and house dust mites (HDM) and to explore the role of interleukin-23 (IL-23) in this process. PM and low-dose HDM were administered intranasally in 4-day-old C57BL/6 mice. After confirming an increase in IL-23 expression in mouse lung tissues, changes in the asthma phenotype and lung effector/memory Th2 or Th17 cells were evaluated after intranasal administration of anti-IL-23 antibody (Ab) during co-exposure to PM and HDM. Evaluation was performed up to 7 weeks after the last administration. Co-exposure to PM and low-dose HDM resulted in increases in airway hyperresponsiveness (AHR), eosinophils, neutrophils, and persistent Th2/Th17 effector/memory cells, which were all inhibited by anti-IL-23 Ab administration. When low-dose HDM was administered twice after a 7-week rest, mice exposed to PM and HDM during the previous early life period exhibited re-increases AHR, eosinophil count, HDM-specific IgG1, and effector/memory Th2 and Th17 cell populations. However, anti-IL-23 Ab administration during the early life period resulted in inhibition. Co-exposure to PM and low-dose HDM reinforced the allergic phenotypes and allergen-specific memory responses in early life of mice. During this process, IL-23 contributes to the enhancement of effector/memory Th2/Th17 cells and allergic phenotypes. KEY MESSAGES: PM-induced IL-23 expression, allergic responses in HDMinstilled mice of early life period. PM-induced effector/memory Th2/Th17 cells in HDMinstilled mice of early life period. Inhibition of IL-23 reduced the increase in allergic responses. Inhibition of IL-23 reduced the increase in allergic responses. After the resting period, HDM administration showed re-increase in allergic responses. Inhibition of IL-23 reduced the HDM-recall allergic responses.

Interleukin 23 receptor: Expression and regulation in immune cells.

The importance of IL-23 and its specific receptor, IL-23R, in the pathogenesis of several chronic inflammatory diseases has been established, but the underlying pathological mechanisms are not fully understood. This review focuses on IL-23R expression and regulation in immune cells.

Dexamethasone alleviates pulmonary sarcoidosis by regulating the TGF-ß/Smad3 signaling to promote Th17/Treg cell rebalance.

Pulmonary sarcoidosis is an immune-mediated disorder closely related to Th17/Treg cell imbalance. Dexamethasone has been shown to regulate inflammation and immune responses in sarcoidosis patients. However, the underlying mechanisms of dexamethasone regulating Th17/Treg balance in sarcoidosis remain elusive. Herein, we elucidated the function role of TGF-ß/Smad3 signaling in pulmonary sarcoidosis development and explored the underlying mechanism of dexamethasone in treating pulmonary sarcoidosis. We found that the TGF-ß/Smad3 pathway was inactivated in pulmonary sarcoidosis patients. Propionibacterium acnes (PA) induced mouse model was generated to investigate the function of TGF-ß/Smad3 signaling in vivo. Data indicated that IL17A inhibition with neutralizing antibody and activation of TGF-ß/Smad3 signaling with SRI-011381 alleviated granuloma formation in the sarcoidosis mouse model. Moreover, we revealed that the Th17/Treg cell ratio was increased with PA treatment in mouse bronchoalveolar lavage fluid (BALF) and peripheral blood. The concentration of cytokines produced by Th17 cells (IL-17A, IL-23) was up-regulated in the BALF of PA-treated mice, while those produced by Tregs (IL-10, TGF-ß1) presented significant reduction. The treatment of IL-17A neutralizing antibody or SRI-011381 was demonstrated to rescue the PA-induced changes in the concentration of IL-17A, IL-23, IL-10, and TGF-ß1. Additionally, we demonstrated that dexamethasone treatment activated the TGF-ß/Smad3 signaling in the lung tissues of pulmonary sarcoidosis mice. Dexamethasone was also revealed to promote the rebalancing of the Th17/Treg ratio and attenuated the granuloma formation in pulmonary sarcoidosis. In conclusion, dexamethasone activates the TGF-ß/Smad3 signaling and induces Th17/Treg rebalance, alleviating pulmonary sarcoidosis, which suggests the potential of dexamethasone in treating pulmonary sarcoidosis.

Risankizumab to treat moderately to severely active Crohn's disease in adults: an evaluation of trials and data.

INTRODUCTION: Risankizumab is a humanized monoclonal antibody that selectively inhibits interleukin (IL)-23. It is approved for the treatment of moderate-to-severe plaque psoriasis, psoriatic arthritis, and more recently moderate-to-severe Crohn's disease (CD). AREAS COVERED: After examining the current landscape of CD management including therapies which are currently approved and those in late stages of development, we will review the interleukin pathway and discuss the specific mechanism of targeted IL-23 inhibition, summarize available clinical trial data on efficacy and safety of Risankizumab, consider future positioning of Risankizumab in the therapeutic armamentarium, and ultimately discuss future needs for the field. EXPERT OPINION: Risankizumab represents the first and only targeted IL-23 inhibitor approved for the treatment of CD, providing a promising addition to the therapeutic armamentarium for CD, with a favorable safety profile and demonstrated efficacy in both biologic-naïve and exposed populations. It is possible that the targeted nature of Risankizumab may enhance efficacy and safety over combined IL-12/23 inhibition, with trials underway attempting to shed light on that hypothesis.

Th17-associated cytokines IL-17 and IL-23 in inflamed skin of Darier disease patients as potential therapeutic targets.

Darier disease (DD) is a rare, inherited multi-organ disorder associated with mutations in the ATP2A2 gene. DD patients often have skin involvement characterized by malodorous, inflamed skin and recurrent, severe infections. Therapeutic options are limited and inadequate for the long-term management of this chronic disease. The aim of this study was to characterize the cutaneous immune infiltrate in DD skin lesions in detail and to identify new therapeutic targets. Using gene and protein expression profiling assays including scRNA sequencing, we demonstrate enhanced expression of Th17-related genes and cytokines and increased numbers of Th17 cells in six DD patients. We provide evidence that targeting the IL-17/IL-23 axis in a case series of three DD patients with monoclonal antibodies is efficacious with significant clinical improvement. As DD is a chronic, relapsing disease, our findings might pave the way toward additional options for the long-term management of skin inflammation in patients with DD.

Differential effects of interleukin-17A and 17F on cell interactions between immune cells and stromal cells from synovium or skin.

We compared the contribution of IL-17A and IL-17F in co-culture systems mimicking cell interactions as found in inflamed synovium and skin. Synoviocytes or skin fibroblasts were co-cultured with activated PBMC, with IL-17A, IL-17 A/F, IL-17F, IL-23, anti-IL-17A, anti-IL-17A/F or anti-IL-17F antibodies. IL-17A, IL-17F, IL-6 and IL-10 production was measured at 48 h. mRNA expression of receptor subunits for IL-23, IL-12 and IL-17 was assessed at 24 h. Both cell activation and interactions were needed for a high IL-17A secretion while IL-17F was stimulated by PHA activation alone and further increased in co-cultures. IL-17F levels were higher than IL-17A in both co-cultures (p < 0.05). IL-17F addition decreased IL-17A secretion (p < 0.05) but IL-17A addition had no effect on IL-17F secretion. Interestingly, IL-17A and IL-17F upregulated IL-17RA and IL-17RC mRNA expression in PBMC/skin fibroblast co-cultures (p < 0.05) while only IL-17F exerted this effect in synoviocytes (p < 0.05). Monocyte exclusion in both co-cultures increased IL-17A and IL-17F (twofold, p < 0.05) while decreasing IL-10 and IL-6 secretion (twofold, p < 0.05). IL-17A and F had differential effects on their receptor expression with a higher sensitivity for skin fibroblasts highlighting the differential contribution of IL-17A and F in joint vs. skin diseases.

Assembly-dependent Structure Formation Shapes Human Interleukin-23 versus Interleukin-12 Secretion.

Interleukin 12 (IL-12) family cytokines connect the innate and adaptive branches of the immune system and regulate immune responses. A unique characteristic of this family is that each member is anα:ßheterodimer. For human αsubunits it has been shown that they depend on theirßsubunit for structure formation and secretion from cells. Since subunits are shared within the family and IL-12 as well as IL-23 use the same ßsubunit, subunit competition may influence cytokine secretion and thus downstream immunological functions. Here, we rationally design a folding-competent human IL-23α subunit that does not depend on itsßsubunit for structure formation. This engineered variant still forms a functional heterodimeric cytokine but shows less chaperone dependency and stronger affinity in assembly with its ßsubunit. It forms IL-23 more efficiently than its natural counterpart, skewing the balance of IL-12 and IL-23 towards more IL-23 formation. Together, our study shows that folding-competent human IL-12 familyαsubunits are obtainable by only few mutations and compatible with assembly and function of the cytokine. These findings might suggest that human α subunits have evolved for assembly-dependent folding to maintain and regulate correct IL-12 family member ratios in the light of subunit competition.

Protein Concentration Affects the Food Allergen γ-Conglutin Uptake and Bacteria-Induced Cytokine Production in Dendritic Cells.

γ-Conglutin (γ-C) from lupin seeds has been identified as a potent allergen with cross reactivity to peanuts. Here, we investigated how γ-C affected the response in bone marrow-derived dendritic cells (DCs) to bacterial stimuli. γ-C enhanced L. acidophilus NCFM (LaNCFM)-induced IL-12, IL-10, and IL-23 dose-dependently. In contrast, together with E. coli Nissle or LPS, γ-C reduced the production of IL-12 but not of IL-23 and IL-10. Enzyme-hydrolyzed γ-C also enhanced LaNCFM-induced IL-12 and IL-23 production. All preparations induced ROS production in the DCs. The mannose receptor ligands mannan and dextran and the clathrin inhibitor monodansylcadaverine partly inhibited the endocytosis of γ-C. Kunitz trypsin inhibitor and the scavenger receptor ligand polyG also enhanced LaNCFM-induced IL-12, indicating the involvement of receptors other than C-type lectin receptors. The endocytosis of labeled γ-C increased dose-dependently by addition of unlabeled γ-C, which coincided with γ-C's tendency to aggregate. Taken together, γ-C aggregation affects endocytosis and affects the cytokine production induced by gram-positive and gram-negative bacteria differently. We suggest that γ-C is taken up by the same mechanism as other food proteins but due to aggregation is present in higher concentration in the DCs. This could influence the resulting T-cell response in a microbial stimuli-dependent way.

Epigenetic Regulation of IL-23 by E3 Ligase FBXW7 in Dendritic Cells Is Critical for Psoriasis-like Inflammation.

Dendritic cells (DCs), a driver of psoriasis pathogenesis, produce IL-23 and trigger IL-23/IL-17 cytokine axis activation. However, the mechanisms regulating IL-23 induction remain unclear. In the current study, we found that mice with E3 ligase FBXW7 deficiency in DCs show reduced skin inflammation correlated with the reduction of IL-23/IL-17 axis cytokines in the imiquimod-induced psoriasis model. Fbxw7 deficiency results in decreased production of IL-23 in DCs. FBXW7 interacts with the lysine N-methyltransferase suppressor of variegation 39 homolog 2 (SUV39H2), which catalyzes the trimethylation of histone H3 Lys9 (H3K9) during transcription regulation. FBXW7 mediates the ubiquitination and degradation of SUV39H2, thus decreasing H3K9m3 deposition on the Il23a promoter. The Suv39h2 knockout mice displayed exacerbated skin inflammation with the IL-23/IL-17 axis overactivating in the psoriasis model. Taken together, our results indicate that FBXW7 increases IL-23 expression in DCs by degrading SUV39H2, thereby aggravating psoriasis-like inflammation. Inhibition of FBXW7 or the FBXW7/SUV39H2/IL-23 axis may represent a novel therapeutic approach to psoriasis.