Functional Genomics and Insights into the Pathogenesis and Treatment of Psoriasis.

Psoriasis is a lifelong, systemic, immune mediated inflammatory skin condition, affecting 1-3% of the world's population, with an impact on quality of life similar to diseases like cancer or diabetes. Genetics are the single largest risk factor in psoriasis, with Genome-Wide Association (GWAS) studies showing that many psoriasis risk genes lie along the IL-23/Th17 axis. Potential psoriasis risk genes determined through GWAS can be annotated and characterised using functional genomics, allowing the identification of novel drug targets and the repurposing of existing drugs. This review is focused on the IL-23/Th17 axis, providing an insight into key cell types, cytokines, and intracellular signaling pathways involved. This includes examination of currently available biological treatments, time to relapse post drug withdrawal, and rates of primary/secondary drug failure, showing the need for greater understanding of the underlying genetic mechanisms of psoriasis and how they can impact treatment. This could allow for patient stratification towards the treatment most likely to reduce the burden of disease for the longest period possible.

Effects on peripheral and central nervous system of key inflammatory intercellular signalling peptides and proteins in psoriasis.

Psoriasis is a chronic systemic inflammatory cutaneous disease. Where the immune system plays an important role in its pathogenesis, with key inflammatory intercellular signalling peptides and proteins including IL-17 and IL-23. The psychoneurological system also figures prominently in development of psoriasis. There is a high prevalence of comorbidity between psoriasis and mental health disorders such as depression, anxiety and mania. Patients with psoriasis often suffer from pathological pain in the lesions, and their neurological accidents could improve the lesions in innervated areas. The immune system and the psychoneurological system interact closely in the pathogenesis of psoriasis. Patients with psoriasis exhibit abnormal levels of neuropeptides both in circulating and localized lesion, acting as immunomodulators involved in the inflammatory response. Moreover, receptors for inflammatory factors are expressed in both peripheral and central nervous systems (CNSs), suggesting that nervous system can receive and be influenced by signals from immune system. Key inflammatory intercellular signalling peptides and proteins in psoriasis, such as IL-17 and IL-23, can be involved in sensory signalling and may affect synaptic plasticity and the blood-brain barrier of CNS through the circulation. This review provides an overview of the multiple effects on the peripheral and CNS under conditions of systemic inflammation in psoriasis, providing a framework and inspiration for in-depth studies of neuroimmunomodulation in psoriasis.

CHOP-mediated IL-23 overexpression does not drive colitis in experimental spondyloarthritis.

HLA-B27 is a major risk factor for spondyloarthritis (SpA), yet the underlying mechanisms remain unclear. HLA-B27 misfolding-induced IL-23, which is mediated by endoplasmic reticulum (ER) stress has been hypothesized to drive SpA pathogenesis. Expression of HLA-B27 and human ß2m (hß2m) in rats (HLA-B27-Tg) recapitulates key SpA features including gut inflammation. Here we determined whether deleting the transcription factor CHOP (Ddit3-/-), which mediates ER-stress induced IL-23, affects gut inflammation in HLA-B27-Tg animals. ER stress-mediated Il23a overexpression was abolished in CHOP-deficient macrophages. Although CHOP-deficiency also reduced Il23a expression in immune cells isolated from the colon of B27+ rats, Il17a levels were not affected, and gut inflammation was not reduced. Rather, transcriptome analysis revealed increased expression of pro-inflammatory genes, including Il1a, Ifng and Tnf in HLA-B27-Tg colon tissue in the absence of CHOP, which was accompanied by higher histological Z-scores. RNAScope localized Il17a mRNA to the lamina propria of the HLA-B27-Tg rats and revealed similar co-localization with Cd3e (CD3) in the presence and absence of CHOP. This demonstrates that CHOP-deficiency does not improve, but rather exacerbates gut inflammation in HLA-B27-Tg rats, indicating that HLA-B27 is not promoting gut disease through ER stress-induced IL-23. Hence, CHOP may protect rats from more severe HLA-B27-induced gut inflammation.

Decreased HMGCS1 inhibits proliferation and inflammatory response of keratinocytes and ameliorates imiquimod-induced psoriasis via the STAT3/IL-23 axis.

Psoriasis is an immuno-inflammatory disease characterized by excessive keratinocyte proliferation, requiring extensive lipids. 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1 (HMGCS1) is an essential enzyme in the mevalonate pathway, involved in cholesterol synthesis and the inflammatory response. However, the role of HMGCS1 in psoriasis has remained elusive. This study aims to elucidate the mechanism by which HMGCS1 controls psoriasiform inflammation. We discovered an increased abundance of HMGCS1 in psoriatic lesions when analyzing two Gene Expression Omnibus (GEO) datasets and confirmed this in psoriatic animal models and psoriatic patients by immunohistochemistry. In a TNF-α stimulated psoriatic HaCaT cell line, HMGCS1 was found to be overexpressed. Knockdown of HMGCS1 using siRNA suppressed the migration and proliferation of HaCaT cells. Mechanistically, HMGCS1 downregulation also reduced the expression of IL-23 and the STAT3 phosphorylation level. In imiquimod-induced psoriatic mice, intradermal injection of HMGCS1 siRNA significantly decreased the expression of HMGCS1 in the epidermis, which in turn led to an improvement in the Psoriasis Area and Severity Index score, epidermal thickening, and pathological Baker score. Additionally, expression levels of inflammatory cytokines IL-23, IL1-ß, chemokine CXCL1, and innate immune mediator S100A7-9 were downregulated in the epidermis. In conclusion, HMGCS1 downregulation improved psoriasis in vitro and in vivo through the STAT3/IL-23 axis.

IL-23 past, present, and future: a roadmap to advancing IL-23 science and therapy.

Interleukin (IL)-23, an IL-12 cytokine family member, is a hierarchically dominant regulatory cytokine in a cluster of immune-mediated inflammatory diseases (IMIDs), including psoriasis, psoriatic arthritis, and inflammatory bowel disease. We review IL-23 biology, IL-23 signaling in IMIDs, and the effect of IL-23 inhibition in treating these diseases. We propose studies to advance IL-23 biology and unravel differences in response to anti-IL-23 therapy. Experimental evidence generated from these investigations could establish a novel molecular ontology centered around IL-23-driven diseases, improve upon current approaches to treating IMIDs with IL-23 inhibition, and ultimately facilitate optimal identification of patients and, thereby, outcomes.

Effects of silencing NLRP3 gene on proliferation of psoriasis-like HaCaT cells and expressions of cytokines.

We aimed to explore the effects of silencing NOD-like receptor protein 3 (NLRP3) on proliferation of psoriasis-like HaCaT cells and expressions of cytokines. HaCaT cells were treated with human keratinocyte growth factor (KGF) and were divided into KGF group, negative control group, NLRP3-RNAi group and control group. Cells proliferation was detected by CCK8, cell clone formation rate was detected by clone formation assay, distribution of cells cycle was detected by flow cytometry, expressions of cyclin B1 (Cyclin B1), cyclin-dependent kinase 2 (CDK2), Ki67 and proliferating cell nuclear antigen (PCNA) proteins were detected by Western blot, and levels of interleukin (IL)-17, IL-23, IL-6 and tumor necrosis factor α (TNF-α) were detected by enzyme-linked immunosorbent assay. Compared with control group, expressions of NLRP3 mRNA and protein, proliferation rate and clonal formation rate were increased in KGF group, percentage of cells in G0/G1 phase was decreased, percentage of cells in S phase was increased, expressions of Cyclin B1, CDK2, Ki67 and PCNA proteins were increased, and levels of IL-17, IL-23, IL-6 and TNF-α were increased. Compared with negative control group, expressions of NLRP3 mRNA and protein, proliferation rate and clonal formation rate were decreased in NLRP3-RNAi group, percentage of cells in G0/G1 phase was increased, percentage of cells in S phase was decreased, expressions of Cyclin B1, CDK2, Ki67 and PCNA proteins were decreased, and levels of IL-17, IL-23, IL-6 and TNF-α were decreased. Silencing NLRP3 gene can inhibit the proliferation of psoriasis-like HaCaT cells, arrest cell cycle, inhibit the expressions of cell proliferation-related proteins and reduce levels of pro-inflammatory factors.

IL-23 regulation of myeloid cell biology during inflammation.

Interleukin (IL)-23 is implicated in the pathogenesis of several inflammatory diseases and is usually linked with helper T cell (Th17) biology. However, there is some data linking IL-23 with innate immune biology in such diseases. We therefore examined the effects of IL-23p19 genetic deletion and/or neutralization on in vitro macrophage activation and in an innate immune-driven peritonitis model. We report that endogenous IL-23 was required for maximal macrophage activation by zymosan as determined by pro-inflammatory cytokine production, including a dramatic upregulation of granulocyte-colony stimulating factor (G-CSF). Furthermore, both IL-23p19 genetic deletion and neutralization in zymosan-induced peritonitis (ZIP) led to a specific reduction in the neutrophil numbers, as well as a reduction in the G-CSF levels in exudate fluids. We conclude that endogenous IL-23 can contribute significantly to macrophage activation during an inflammatory response, mostly likely via an autocrine/paracrine mechanism; of note, endogenous IL-23 can directly up-regulate macrophage G-CSF expression, which in turn is likely to contribute to the regulation of IL-23-dependent neutrophil number and function during an inflammatory response, with potential significance for IL-23 targeting particularly in neutrophil-associated inflammatory diseases.

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.

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.

Structural cell heterogeneity underlies the differential contribution of IL-17A, IL-17F and IL-23 to joint versus skin chronic inflammation.

The current therapeutic strategy used in immune-mediated inflammatory diseases (IMIDs) primarily targets immune cells or associated-pathways. However, recent evidence suggests that the microenvironment modulates immune cell development and responses. During inflammation, structural cells acquire a pathogenetic phenotype and the interactions with immune cells are often greatly modified. Understanding the importance of these tissue-specific interactions may allow to explain why some biologics are effective in some IMIDs but not in others. The differential effects of interleukin (IL)-17 A, IL-17F and IL-23 in joint versus skin inflammation depends on structural cell heterogeneity. In addition, the sometimes opposite effects of immune/structural cell interactions on the production of these cytokines illustrate the importance of these cells in chronic inflammation, using the examples of rheumatoid arthritis, psoriasis and spondyloarthritis. This review describes these concepts, shows their interests through clinical observations, and finally discusses strategies to optimize therapeutic strategies.

ANKRD22 promotes resolution of psoriasiform skin inflammation by antagonizing NIK-mediated IL-23 production.

Inflammation resolution is an essential process for preventing the development of chronic inflammatory diseases. However, the mechanisms that regulate inflammation resolution in psoriasis are not well understood. Here, we report that ANKRD22 is an endogenous negative orchestrator of psoriasiform inflammation because ANKRD22-deficient mice are more susceptible to IMQ-induced psoriasiform inflammation. Mechanistically, ANKRD22 deficiency leads to excessive activation of the TNFRII-NIK-mediated noncanonical NF-κB signaling pathway, resulting in the hyperproduction of IL-23 in DCs. This is due to ANKRD22 being a negative feedback regulator for NIK because it physically binds to and assists in the degradation of accumulated NIK. Clinically, ANKRD22 is negatively associated with IL-23A expression and psoriasis severity. Of greater significance, subcutaneous administration of an AAV carrying ANKRD22-overexpression vector effectively hastens the resolution of psoriasiform skin inflammation. Our findings suggest ANKRD22, an endogenous supervisor of NIK, is responsible for inflammation resolution in psoriasis, and may be explored in the context of psoriasis therapy.

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.

Differential requirement for IL-2 and IL-23 in the differentiation and effector functions of Th17/ILC3-like cells in a human T cell line.

A well-documented Achilles heel of current cancer immunotherapy approaches is T cell exhaustion within solid tumor tissues. The proinflammatory cytokine interleukin (IL)-23 has been utilized to augment chimeric antigen receptor (CAR) T cell survival and tumor immunity. However, in-depth interrogation of molecular events downstream of IL-23/IL-23 receptor signaling is hampered by a paucity of suitable cell models. The current study investigates the differential contribution of IL-2 and IL-23 to the maintenance and differentiation of the IL-23 responsive Kit225 T-cell line. We observed that IL-23 enhanced cellular fitness and survival but was insufficient to drive proliferation. IL-23 rapidly induced phosphorylation of STAT1, STAT3, and STAT4, and messenger RNA expression of IL17A, the archetypal effector cytokine of T helper 17 (Th17) cells, but not their lineage markers RORC and NCR1. These observations suggest that IL-23 endowed Th17/ILC3-like effector function but did not promote their differentiation. In contrast, spontaneous differentiation of Kit225 cells toward a Th17/ILC3-like phenotype was induced by prolonged IL-2 withdrawal. This was marked by strongly elevated basal IL17A and IL17F expression and the secretion of IL-17. Together, our data present Kit225 cells as a valuable model for studying the interplay between cytokines and their contribution to T cell survival, proliferation, and differentiation.

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.

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.

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.

D-alanine Inhibits Murine Intestinal Inflammation by Suppressing IL-12 and IL-23 Production in Macrophages.

BACKGROUND AND AIMS: Free D-amino acids, which have different functions from L-amino acids, have recently been discovered in various tissues. However, studies on the potential interactions between intestinal inflammation and D-amino acids are limited. We examined the inhibitory effects of D-alanine on the pathogenesis of intestinal inflammation. METHODS: We investigated serum D-amino acid levels in 40 patients with ulcerative colitis and 34 healthy volunteers. For 7 days [d], acute colitis was induced using dextran sulphate sodium in C57BL/6J mice. Plasma D-amino acid levels were quantified in mice with dextran sulphate sodium-induced colitis, and these animals were administered D-alanine via intraperitoneal injection. IFN-γ, IL-12p35, IL-17A, and IL-23p19 mRNA expression in the colonic mucosa was measured using real-time polymerase chain reaction [PCR]. In vitro proliferation assays were performed to assess naïve CD4+ T cell activation under Th-skewing conditions. Bone marrow cells were stimulated with mouse macrophage-colony stimulating factor to generate mouse bone marrow-derived macrophages. RESULTS: Serum D-alanine levels were significantly lower in patients with ulcerative colitis than in healthy volunteers. Dextran sulphate sodium-treated mice had significantly lower plasma D-alanine levels than control mice. D-alanine-treated mice had significantly lower disease activity index than control mice. IFN-γ, IL-12p35, IL-17A, and IL-23p19 mRNA expression levels were significantly lower in D-alanine-administered mice than in control mice. D-alanine suppressed naïve T cell differentiation into Th1 cells in vitro, and inhibited the production of IL-12p35 and IL-23p19 in bone marrow-derived macrophages. CONCLUSIONS: Our results suggest that D-alanine prevents dextran sulphate sodium-induced colitis in mice and suppresses IL-12p35 and IL-23p19 production in macrophages.