Cytokines link osteoblasts and inflammation: microarray analysis of interleukin-17- and TNF-alpha-induced genes in bone cells

Unveiling a novel pyrazolopyrimidine scaffold as a dual COX-2/5-LOX inhibitor with immunomodulatory potential: Design, synthesis, target prediction, anti-inflammatory activity, and ADME-T with docking simulation

Dual-target COX-2/5-LOX inhibitors are regarded as a rational strategy for the design of potent anti-inflammatory agents with favorable safety profiles. In this study, novel pyrazolo[1,5-a]pyrimidine derivatives were synthesized, developed, and screened for their ability to inhibit the cyclooxygenase-2 enzyme in vitro, with comparisons made to the established inhibitors Celecoxib and Meloxicam. Spectroscopic analyses confirmed the structure of the designed derivatives. The target prediction using AI was performed to identify potential targets that could be engaged through Swiss target prediction database. The SAR study was established by incorporating various substituents and nuclei into the pyrazolopyrimidine pharmacophore. The synthesized pyrazolopyrimidines exhibited IC50 values ranging from 53.32 ± 4.43 to 254.90 ± 6.45 nM, in comparison to Celecoxib (IC50 = 6.73 ± 5.69 nM) and Meloxicam (IC50 = 52.35 ± 6.66 nM). Notably, compound 5a was identified as the most active derivative, demonstrating an IC50 of 53.32 ± 4.43 nM. The three most prominent pyrazolopyrimidine derivatives, 3a, 5a, and 6a, were subsequently evaluated for their ability to inhibit the COX-1 and 5-LOX enzymes. Compounds 3a, 5a, and 6a demonstrated inhibitory activity against COX-1, with IC50 values of 476.45 ± 16.56, 757.51 ± 2.61, and 169.13 ± 5.77 nM, respectively. These derivatives 3a, 5a, and 6a showed significant selectivity index values of 7.91, 14.20, and 2.80, respectively, toward COX-2 rather than COX-1 in comparison to Meloxicam (SI = 0.75) and Celecoxib (SI = 2.35). Moreover, compound 5a exhibited 86 % inhibition compared to Zileuton's 88 %, while compounds 3a and 6a displayed inhibition rates of 84 % and 80 %, respectively, at a concentration of 100 μM. The most potent compound 5a, demonstrated the highest 5-LOX inhibitory activity, with IC50 of 2.292 ± 0.14 μM. The most promising pyrazolopyrimidine derivative 5a demonstrated a down-regulation of TNF-α and IL-6 gene expression by approximately 0.3826-fold and 0.2732-fold, respectively, when compared to Celecoxib, which induced reductions of 0.2320-fold and 0.2730-fold in these cytokines to promote apoptosis in RAW264.7 cells. Finally, in-silico ADME-T and docking simulations were conducted to predict the oral bioavailability, toxicity, and binding interactions with binding affinity.

JAK inhibition and axial spondyloarthritis: new steps on the path to understanding pathophysiology

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease that predominantly affects the sacroiliac joints and spine. Tumor necrosis factor (TNF) and interleukin (IL)-17A are key cytokines in disease pathogenesis and are established axSpA treatment targets. Recently, axSpA treatment options have been complemented by Janus kinase inhibitors (JAKi), which inhibit various cytokines without directly impacting TNF or IL-17 signaling. The effect of JAKi on axSpA remains under investigation: besides a JAK2-mediated (and potentially tyrosine kinase 2 [TYK2]-mediated) effect on the IL-23/IL-17 axis, emerging evidence suggests γδ T cells, type 3 innate lymphoid cells, and mucosa-associated invariant T cells, which are dependent on IL-7 and/or IL-15 and thus on JAK1, are strongly inhibited by JAKi used to treat axSpA. This review summarizes potential effects of JAKi on axSpA and shows evidence from pre-clinical/clinical studies. Greater understanding of the mechanisms of action of available treatments may improve knowledge of axSpA and pave the road for future therapies.

The role of immunity in insulin resistance in patients with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a prevalent disorder of the endocrine system with significant clinical implications, often leading to health complications related to adipose tissue accumulation, including obesity, insulin resistance (IR), metabolic syndrome, and type 2 diabetes mellitus. While the precise pathogenesis of PCOS remains unclear, it is now recognized that genetic, endocrine, and metabolic dysregulations all contribute significantly to its onset. The immunopathogenesis of PCOS has not been extensively explored, but there is growing speculation that immune system abnormalities may play a pivotal role. This chronic inflammatory state is exacerbated by factors such as obesity and hyperinsulinemia. Therefore, this review aims to elucidate the interplay between IR in PCOS patients, the controlled immune response orchestrated by immune cells and immunomodulatory molecules, and their interactions with adipocytes, hyperandrogenemia, chronic inflammation, and metabolic homeostasis.

Identification and analysis of pancreatic intraepithelial neoplasia: opportunities and challenges

Pancreatic intraepithelial neoplasia (PanIN) is the most common precursor lesion of pancreatic ductal adenocarcinoma (PDAC), which has poor prognosis with a short median overall survival of 6-12 months and a low 5-year survival rate of approximately 3%. It is crucial to remove PanIN lesions to prevent the development of invasive PDAC, as PDAC spreads rapidly outside the pancreas. This review aims to provide the latest knowledge on PanIN risk, pathology, cellular origin, genetic susceptibility, and diagnosis, while identifying research gaps that require further investigation in this understudied area of precancerous lesions. PanINs are classified into PanIN 1, PanIN 2, and PanIN 3, with PanIN 3 having the highest likelihood of developing into invasive PDAC. Differentiating between PanIN 2 and PanIN 3 is clinically significant. Genetic alterations found in PDAC are also present in PanIN and increase with the grade of PanIN. Imaging methods alone are insufficient for distinguishing PanIN, necessitating the use of genetic and molecular tests for identification. In addition, metabolomics technologies and miRNAs are playing an increasingly important role in the field of cancer diagnosis, offering more possibilities for efficient identification of PanIN. Although detecting and stratifying the risk of PanIN poses challenges, the combined utilization of imaging, genetics, and metabolomics holds promise for improving patient survival in this field.

Sleep loss-induced oncogenic pathways are mediated via the neuron-specific interleukin-1 receptor accessory protein (AcPb)

Interleukin-1β (IL1), a pleiotropic cytokine, is involved in sleep regulation, tumor ontogeny, and immune responses. IL1 receptor adaptor proteins, including the IL1 receptor accessory protein (AcP), and its neuron-specific isoform, AcPb, are required for IL1 signaling. The AcPb isoform is resultant from alternate splicing of the AcP transcript. Our previous studies using AcPb null (AcPb-/-) mice characterized its participation in sleep regulation and emergent neuronal/glial network properties. Here, we investigated the impact of acute sleep disruption (SD) on brain cancer-related pathways in wild-type (WT) and AcPb-/- mice, employing RNA sequencing methods. In WT mice, SD increased AcPb mRNA levels, but not AcP mRNA, confirming prior similar work in rats. Transcriptome and pathway enrichment analyses demonstrated significant alterations in cancer, immune, and viral disease-related pathways in WT mice after SD, which were attenuated in AcPb-/- mice including multiple upregulated Src phosphorylation-signaling-dependent genes associated with cancer progression and metastasis. Our RNAseq findings, were analyzed within the context of The Cancer Genome Atlas Program (TCGA) data base; revealing an upregulation of sleep- and cancer-linked genes (e.g., IL-17B, IL-17RA, LCN2) across various tumors, including brain tumors, compared to normal tissues. Sleep-linked factors, identified through TCGA analyses, significantly impact patient prognosis and survival, particularly in low-grade glioma (LGG) and glioblastoma multiforme (GBM) patients. Overall, our findings suggest that SD promotes a pro-tumor environment through AcPb-modulated pathways.

IL-17A/CEBPβ/OPN/LYVE-1 axis inhibits anti-tumor immunity by promoting tumor-associated tissue-resident macrophages

Tumor-associated macrophages (TAMs) are a critical component of the immunosuppressive tumor microenvironment, comprising monocyte-derived macrophages (MDM-TAMs) and tissue-resident macrophages (TRM-TAMs). Here, we discovered that TRM-TAMs mediate the pro-tumor effects of interleukin (IL)-17A and that IL-17A-driven tumor progression requires tumor cell production of osteopontin (OPN). Mechanistically, we identified CEBPβ as a transcription factor downstream of IL-17A in tumor cells and LYVE-1 as an OPN receptor on TRM-TAMs. IL-17A stimulates tumor cell production of OPN, and OPN/LYVE-1 signaling activates the JNK/c-Jun pathway, leading to the proliferation of immunosuppressive LYVE-1+ TRM-TAMs. Unlike its effect on LYVE-1+ TRM-TAMs, OPN interacts with α4β1 to promote the chemotaxis of LYVE-1- MDM-TAMs toward tumors. IL-17A neutralization, OPN inactivation in tumor cells, or LYVE-1 deletion in macrophages inhibited TAMs and enhanced anti-tumor immune responses and anti-PDL1 therapy. Thus, the IL-17A/CEBPβ/OPN/LYVE-1 axis offers a mechanism suppressing anti-tumor immune responses and, hence, an effective therapeutic target for cancer.

C/EBPδ Mediates Immunity to Renal Autoinflammatory Disorders in a Stage-specific Manner

Kidney disease represents a major medical and economic burden for which improved treatments are urgently needed. Emerging data have implicated Th17 cells and IL-17 signaling in the underlying pathogenesis of autoantibody-induced glomerulonephritis (AGN). However, the downstream transduction pathways mediated by IL-17 in autoimmunity are not well defined. In this article, we show that CCAAT/enhancer-binding protein (C/EBP) δ is elevated in kidney biopsies from multiple manifestations of human AGN. C/EBPδ is similarly upregulated in a mouse model of anti-glomerular basement membrane protein-mediated kidney disease, and Cebpd-/- mice were fully refractory to disease. Although C/EBPδ is expressed in a variety of cell types, C/EBPδ was required only in the radioresistant compartment to drive GN pathology. C/EBPδ induced expression of several IL-17-induced kidney injury markers and cytokines implicated in disease, including Il6 and Lcn2. Because mouse AGN models do not progress to fibrosis, we employed a nephrotoxic injury model using aristolochic acid I to assess the contribution of the IL-17-C/EBPδ pathway to renal fibrotic events. Surprisingly, deficiency of either C/EBPδ or the IL-17 receptor caused kidney fibrosis to be enhanced. Thus, C/EBPδ and IL-17 play divergent and apparently stage-specific roles in the pathogenesis of kidney disease.

The RNA binding protein Arid5a drives IL-17-dependent autoantibody-induced glomerulonephritis

Autoantibody-mediated glomerulonephritis (AGN) arises from dysregulated renal inflammation, with urgent need for improved treatments. IL-17 is implicated in AGN and drives pathology in a kidney-intrinsic manner via renal tubular epithelial cells (RTECs). Nonetheless, downstream signaling mechanisms provoking kidney pathology are poorly understood. A noncanonical RNA binding protein (RBP), Arid5a, was upregulated in human and mouse AGN. Arid5a-/- mice were refractory to AGN, with attenuated myeloid infiltration and impaired expression of IL-17-dependent cytokines and transcription factors (C/EBPβ, C/EBPδ). Transcriptome-wide RIP-Seq revealed that Arid5a inducibly interacts with conventional IL-17 target mRNAs, including CEBPB and CEBPD. Unexpectedly, many Arid5a RNA targets corresponded to translational regulation and RNA processing pathways, including rRNAs. Indeed, global protein synthesis was repressed in Arid5a-deficient cells, and C/EBPs were controlled at the level of protein rather than RNA accumulation. IL-17 prompted Arid5a nuclear export and association with 18S rRNA, a 40S ribosome constituent. Accordingly, IL-17-dependent renal autoimmunity is driven by Arid5a at the level of ribosome interactions and translation.

The Nuclear NF-κB Regulator IκBζ: Updates on Its Molecular Functions and Pathophysiological Roles

More than a decade after the discovery of the classical cytoplasmic IκB proteins, IκBζ was identified as an additional member of the IκB family. Unlike cytoplasmic IκB proteins, IκBζ has distinct features, including its nuclear localization, preferential binding to NF-κB subunits, unique expression properties, and specialized role in NF-κB regulation. While the activation of NF-κB is primarily controlled by cytoplasmic IκB members at the level of nuclear entry, IκBζ provides an additional layer of NF-κB regulation in the nucleus, enabling selective gene activation. Human genome-wide association studies (GWAS) and gene knockout experiments in mice have elucidated the physiological and pathological roles of IκBζ. Despite the initial focus to its role in activated macrophages, IκBζ has since been recognized as a key player in the IL-17-triggered production of immune molecules in epithelial cells, which has garnered significant clinical interest. Recent research has also unveiled a novel molecular function of IκBζ, linking NF-κB and the POU transcription factors through its N-terminal region, whose role had remained elusive for many years.

Distinct inflammatory markers in primary and secondary dengue infection: can cytokines CXCL5, CXCL9, and CCL17 act as surrogate markers?

Dengue fever poses a significant global health threat, with symptoms including dengue hemorrhagic fever and dengue shock syndrome. Each year, India experiences fatal dengue outbreaks with severe manifestations. The primary cause of severe inflammatory responses in dengue is a cytokine storm. Individuals with a secondary dengue infection of a different serotype face an increased risk of complications due to antibody-dependent enhancement. Therefore, it is crucial to identify potential risk factors and biomarkers for effective disease management. In the current study, we assessed the prevalence of dengue infection in and around Aligarh, India, and explored the role of cytokines, including CXCL5, CXCL9, and CCL17, in primary and secondary dengue infections, correlating them with various clinical indices. Among 1,500 suspected cases, 367 tested positive for dengue using Real-Time PCR and ELISA. In secondary dengue infections, the serum levels of CXCL5, CXCL9, and CCL17 were significantly higher than in primary infections (P < 0.05). Dengue virus (DENV)-2 showed the highest concentrations of CXCL5 and CCL17, whereas DENV-1 showed the highest concentrations of CXCL9. Early detection of these cytokines could serve as potential biomarkers for diagnosing severe dengue, and downregulation of these cytokines may prove beneficial for the treatment of severe dengue infections.

Potential causal associations of PM2.5 and osteoporosis: a two-sample mendelian randomization study

Background: Observational studies suggest a potential association between atmospheric particulate matter 2.5 (PM2.5) and osteoporosis, but a causal association is unclear due to the presence of confounding factors. Methods: We utilized bone mineral density indices at four specific sites to represent osteoporosis: femoral neck (FN-BMD), lumbar spine (LS-BMD), forearm (FA-BMD), and heel (HE-BMD). The PM2.5 data was obtained from the UK Biobank database, while the datasets for FN-BMD, LS-BMD, and FA-BMD were obtained from the GEFOS database, and the dataset for HE-BMD was obtained from the EBI database. A two-sample Mendelian randomization analysis was conducted using mainly the inverse variance weighted method, horizontal pleiotropy and heterogeneity were also assessed. Results: The results indicated that PM2.5 was not correlated with a decrease in FN-BMD (β: -0.305, 95%CI: -0.762, 0.153), LS-BMD (β: 0.134, 95%CI: -0.396, 0.666), FA-BMD (β: -0.056, 95%CI: -1.172,1.060), and HE-BMD (β: -0.084, 95%CI: -0.261,0.093). Additionally, acceptable levels of horizontal pleiotropy and heterogeneity were observed. Conclusion: In contrast to most observational studies, our research did not discover a potential causal relationship between PM2.5 and the development of osteoporosis.

Physiological roles of human interleukin-17 family

Interleukin-17 s (IL-17s) are well-known proinflammatory cytokines, and their antagonists perform excellently in the treatment of inflammatory skin diseases such as psoriasis. However, their physiological functions have not been given sufficient attention by clinicians. IL-17s can protect the host from extracellular pathogens, maintain epithelial integrity, regulate cognitive processes and modulate adipocyte activity through distinct mechanisms. Here, we present a systematic review concerning the physiological functions of IL-17s. Our goal is not to negate the therapeutic effect of IL-17 antagonists, but to ensure their safe use and reasonably explain the possible adverse events that may occur in their application.

The IL-17 family in diseases: from bench to bedside

The interleukin-17 (IL-17) family comprises six members (IL-17A-17F), and recently, all of its related receptors have been discovered. IL-17 was first discovered approximately 30 years ago. Members of this family have various biological functions, including driving an inflammatory cascade during infections and autoimmune diseases, as well as boosting protective immunity against various pathogens. IL-17 is a highly versatile proinflammatory cytokine necessary for vital processes including host immune defenses, tissue repair, inflammatory disease pathogenesis, and cancer progression. However, how IL-17 performs these functions remains controversial. The multifunctional properties of IL-17 have attracted research interest, and emerging data have gradually improved our understanding of the IL-17 signaling pathway. However, a comprehensive review is required to understand its role in both host defense functions and pathogenesis in the body. This review can aid researchers in better understanding the mechanisms underlying IL-17's roles in vivo and provide a theoretical basis for future studies aiming to regulate IL-17 expression and function. This review discusses recent progress in understanding the IL-17 signaling pathway and its physiological roles. In addition, we present the mechanism underlying IL-17's role in various pathologies, particularly, in IL-17-induced systemic lupus erythematosus and IL-17-related tumor cell transformation and metastasis. In addition, we have briefly discussed promising developments in the diagnosis and treatment of autoimmune diseases and tumors.

Obesity, Metabolic Syndrome, and Osteoarthritis-An Updated Review

PURPOSE OF REVIEW

Metabolic syndrome (MetS), also called the 'deadly quartet' comprising obesity, diabetes, dyslipidemia, and hypertension, has been ascertained to have a causal role in the pathogenesis of osteoarthritis (OA). This review is aimed at discussing the current knowledge on the contribution of metabolic syndrome and its various components to OA pathogenesis and progression.

RECENT FINDINGS

Lately, an increased association identified between the various components of metabolic syndrome (obesity, diabetes, dyslipidemia, and hypertension) with OA has led to the identification of the 'metabolic phenotype' of OA. These metabolic perturbations alongside low-grade systemic inflammation have been identified to inflict detrimental effects upon multiple tissues of the joint including cartilage, bone, and synovium leading to complete joint failure in OA. Recent epidemiological and clinical findings affirm that adipokines significantly contribute to inflammation, tissue degradation, and OA pathogenesis mediated through multiple signaling pathways. OA is no longer perceived as just a 'wear and tear' disease and the involvement of the metabolic components in OA pathogenesis adds up to the complexity of the disease. Given the global surge in obesity and its allied metabolic perturbations, this review aims to throw light on the current knowledge on the pathophysiology of MetS-associated OA and the need to address MetS in the context of metabolic OA management. Better regulation of the constituent factors of MetS could be profitable in preventing MetS-associated OA. The identification of key roles for several metabolic regulators in OA pathogenesis has also opened up newer avenues in the recognition and development of novel therapeutic agents.

Bone Metabolite Profile Differs between Normal and Femur Head Necrosis (FHN/BCO)-Affected Broilers: Implications for Dysregulated Metabolic Cascades in FHN Pathophysiology

Femur head necrosis (FHN), also known as bacterial chondronecrosis with osteomyelitis (BCO), has remained an animal welfare and production concern for modern broilers regardless of efforts to select against it in primary breeder flocks. Characterized by the bacterial infection of weak bone, FHN has been found in birds without clinical lameness and remains only detectable via necropsy. This presents an opportunity to utilize untargeted metabolomics to elucidate potential non-invasive biomarkers and key causative pathways involved in FHN pathology. The current study used ultra-performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS) and identified a total of 152 metabolites. Mean intensity differences at p < 0.05 were found in 44 metabolites, with 3 significantly down-regulated and 41 up-regulated in FHN-affected bone. Multivariate analysis and a partial least squares discriminant analysis (PLS-DA) scores plot showed the distinct clustering of metabolite profiles from FHN-affected vs. normal bone. Biologically related molecular networks were predicted using an ingenuity pathway analysis (IPA) knowledge base. Using a fold-change cut off of -1.5 and 1.5, top canonical pathways, networks, diseases, molecular functions, and upstream regulators were generated using the 44 differentially abundant metabolites. The results showed the metabolites NAD+, NADP+, and NADH to be downregulated, while 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) and histamine were significantly increased in FHN. Ascorbate recycling and purine nucleotides degradation were the top canonical pathways, indicating the potential dysregulation of redox homeostasis and osteogenesis. Lipid metabolism and cellular growth and proliferation were some of the top molecular functions predicted based on the metabolite profile in FHN-affected bone. Network analysis showed significant overlap across metabolites and predicted upstream and downstream complexes, including AMP-activated protein kinase (AMPK), insulin, collagen type IV, mitochondrial complex, c-Jun N-terminal kinase (Jnk), extracellular signal-regulated kinase (ERK), and 3β-hydroxysteroid dehydrogenase (3β HSD). The qPCR analysis of relevant factors showed a significant decrease in AMPKα2 mRNA expression in FHN-affected bone, supporting the predicted downregulation found in the IPA network analysis. Taken as a whole, these results demonstrate a shift in energy production, bone homeostasis, and bone cell differentiation that is distinct in FHN-affected bone, with implications for how metabolites drive the pathology of FHN.

Commensal gut bacterium critically regulates alveolar bone homeostasis

The alveolar bone is a unique osseous tissue due to the presence of the teeth and the proximity of commensal oral microbes. Commensal microbe effects on alveolar bone homeostasis have been attributed to the oral microbiota, yet the impact of commensal gut microbes is unknown. Study purpose was to elucidate whether commensal gut microbes regulate osteoimmune mechanisms and skeletal homeostasis in alveolar bone. Male C57BL/6T germfree (GF) littermate mice were maintained as GF or monoassociated with segmented filamentous bacteria (SFB), a commensal gut bacterium. SFB has been shown to elicit broad immune response effects, including the induction of T_H17/IL17A immunity, which impacts the development and homeostasis of host tissues. SFB colonized the gut, but not oral cavity, and increased IL17A levels in the ileum and serum. SFB had catabolic effects on alveolar bone and non-oral skeletal sites, which was attributed to enhanced osteoclastogenesis. The alveolar bone marrow of SFB vs. GF mice had increased dendritic cells, activated helper T-cells, T_H1 cells, T_H17 cells, and upregulated Tnf. Primary osteoblast cultures from SFB and GF mice were stimulated with vehicle-control, IL17A, or TNF to elucidate osteoblast-derived signaling factors contributing to the pro-osteoclastic phenotype in SFB mice. Treatment of RAW264.7 osteoclastic cells with supernatants from vehicle-stimulated SFB vs. GF osteoblasts recapitulated the osteoclast phenotype found in vivo. Supernatants from TNF-stimulated osteoblasts normalized RAW264.7 osteoclast endpoints across SFB and GF cultures, which was dependent on the induction of CXCL1 and CCL2. This report reveals that commensal gut microbes have the capacity to regulate osteoimmune processes in alveolar bone. Outcomes from this investigation challenge the current paradigm that alveolar bone health and homeostasis is strictly regulated by oral microbes.

Local delivery and controlled release of miR-34a loaded in hydroxyapatite/mesoporous organosilica nanoparticles composite-coated implant wire to accelerate bone fracture healing

Immediate mechanical stability is a prerequisite for fracture healing. In addition to bringing immediate mechanical stability in fracture site, implants with bioactive coating can release active substance to accelerate bone-fracture healing. However, limited drug-loading capacity of established coatings weakens their biological functions, which urges the engineering of more effective coating biomaterials for accelerating fracture healing. Herein, mesoporous organosilica nanoparticles (MONs), as miR-34a delivers, are loaded onto hydroxyapatite (HA)-coated Kirschner wire to engineer a HA/MONs@miR-34a composite coating. The composite coating can effectively deliver miR-34a into osteoclasts, generate gene dose-dependent inhibiting effect on differentiation and resorptive activity of osteoclasts by regulating multiple downstream gene expression at the early stage of fracture healing, which additionally exhibits decent bone regeneration potentials as evidenced in rat tibial fracture model. In particular, differentially expressed genes regulated by miR-34a are identified using RNA-seq followed by bioinformatics analysis. Functional enrichment analysis reveals that genes with altered expression mainly distribute in mainly distribute in DNA replication and cell cycle, which are associated with the development of osteoclasts. This work not only demonstrates the high clinical translation potential of HA/MONs@miR-34a to accelerate fracture healing, but also reveals the underlying molecular mechanism of regulating physiological functions of osteoclasts based on analysis of singlecell RNA sequencing.

Exploring the Diverse Immune and Genetic Landscape of Psoriatic Arthritis

Psoriatic arthritis (PsA) is characterized by delays in diagnosis and modest effect of treatment in terms of joint response. An understanding of molecular pathomechanisms may aid in developing diagnostic and prognostic models. Genetic susceptibility (e.g., HLA class I genes, IL-23-related genes) can be responsible for the pattern of psoriatic manifestations and affinity for tissue involvement. Gene expression analysis indicates an inflammatory profile that is distinct for PsA, but disparate across tissues. This has clinical implications, as for example, dual blockade of IL-17A and IL-17F can lead to superior clinical effects if there is differential expression of IL-17 receptors in tissues. Structural and functional impairment of barrier tissue, including host-microbiome interactions, may be the source of immune activation. Interplay between different cell populations of innate and adaptive immunity is emerging, potentially providing a link between the transition of skin-to-joint disease. Th17 subsets, IL-17A, IL-17F and IL-23 are crucial in PsA pathogenesis, with both clinical and experimental evidence suggesting a differential molecular landscape in cutaneous and articular compartments.

Intestinal Intervention Strategy Targeting Myeloid Cells to Improve Hepatic Immunity during Hepatocarcinoma Development

Innate immunity in the tumor microenvironment plays a pivotal role in hepatocarcinoma (HCC) progression. Plant seeds provide serine-type protease inhibitors (SETIs), which can have a significant influence on liver inflammation and macrophage function. To elucidate the influence of SETIs to counter pro-tumorigenic conditions, at the early stages of HCC development, it was used as an established model of diethylnitrosamine/thioacetamide-injured liver fed with a standard diet (STD) or high-fat diet (42%) (HFD). The administration of SETIs improved survival and ameliorated tumor burden via modulation of monocyte-derived macrophages as key effectors involved in diet-induced HCC development. RT-qPCR analyses of hepatic tissue evidenced a diet-independent downregulatory effect of SETIs on the transcripts of CD36, FASN, ALOX15, and SREBP1c; however, animals fed with an STD showed opposing effects for PPAR and NRLP3 levels. These effects were accompanied by a decreased production of IL-6 and IL-17 but increased that of TNF in animals receiving SETIs. Moreover, only animals fed an HFD displayed increased concentrations of the stem cell factor. Overall, SETIs administration decreased the hepatic contents of lysophosphatydilcholine, phosphatidylinositol, phosphatidylcholine, and phosphatidyl ethanolamine. Notably, animals that received SETIs exhibited increased hepatic proportions of CD68⁺CX3CR1⁺CD74⁺ cells and at a higher rate in those animals fed an HFD. Altogether, the data evidence that oral administration of SETIs modulates the tumor microenvironment, improving hepatic innate immune response(s) and favoring a better antitumoral environment. It represents a path forward in developing coadjutant strategies to pharmacological therapies, with either a preventive or therapeutic character, to counter physiopathological conditions at early stages of HCC development.

Association between particulate matter containing EPFRs and neutrophilic asthma through AhR and Th17

BACKGROUND

Epidemiological data associate high levels of combustion-derived particulate matter (PM) with deleterious respiratory outcomes, but the mechanism underlying those outcomes remains elusive. It has been acknowledged by the World Health Organization that PM exposure contributes to more than 4.2 million all-cause mortalities worldwide each year. Current literature demonstrates that PM exacerbates respiratory diseases, impairs lung function, results in chronic respiratory illnesses, and is associated with increased mortality. The proposed mechanisms revolve around oxidative stress and inflammation promoting pulmonary physiological remodeling. However, our previous data found that PM is capable of inducing T helper cell 17 (Th17) immune responses via aryl hydrocarbon receptor (Ahr) activation, which was associated with neutrophilic invasion characteristic of steroid insensitive asthma.

METHODS

In the present study, we utilized a combination of microarray and single cell RNA sequencing data to analyze the immunological landscape in mouse lungs following acute exposure to combustion derived particulate matter.

RESULTS

We present data that suggest epithelial cells produce specific cytokines in the aryl hydrocarbon receptor (Ahr) pathway that inform dendritic cells to initiate the production of pathogenic T helper (eTh17) cells. Using single-cell RNA sequencing analysis, we observed that upon exposure epithelial cells acquire a transcriptomic profile indicative of increased Il-17 signaling, Ahr activation, Egfr signaling, and T cell receptor and co-stimulatory signaling pathways. Epithelial cells further showed, Ahr activation is brought on by Ahr/ARNT nuclear translocation and activation of tyrosine kinase c-src, Egfr, and subsequently Erk1/2 pathways.

CONCLUSIONS

Collectively, our data corroborates that PM initiates an eTh17 specific inflammatory response causing neutrophilic asthma through pathways in epithelial, dendritic, and T cells that promote eTh17 differentiation during initial PM exposure.

Targeting the Interleukin-23/Interleukin-17 Inflammatory Pathway: Successes and Failures in the Treatment of Axial Spondyloarthritis

The IL-23/IL-17 pathway has been implicated in the etiopathogenesis of axial spondyloarthritis through studies of genetic polymorphisms associated with disease, an animal model with over-expression of IL-23 that resembles human disease, and observations that cytokines in this pathway can be found at the site of disease in both humans and animal models. However, the most direct evidence has emerged from clinical trials of agents targeting cytokines in this pathway. Monoclonal antibodies targeting IL-17A have been shown to ameliorate signs and symptoms, as well as MRI inflammation in the spine and sacroiliac joints, in patients with radiographic and non-radiographic axial spondyloarthritis. This was evident in patients refractory to non-steroidal anti-inflammatory agents as well as patients failing treatment with tumor necrosis factor inhibitor therapies. Treatment with a bispecific antibody targeting both IL-17A and IL-17F was also effective in a phase II study. Post-hoc analyses have even suggested a potential disease-modifying effect in reducing development of spinal ankylosis. However, benefits for extra-articular manifestations were limited to psoriasis and did not extend to colitis and uveitis. Conversely, trials of therapies targeting IL-23 did not demonstrate any significant impact on signs, symptoms, and MRI inflammation in axial spondyloarthritis. These developments coincide with recent observations that expression of these cytokines is evident in many different cell types with roles in innate as well as adaptive immunity. Moreover, evidence has emerged for the existence of both IL-23-dependent and IL-23-independent pathways regulating expression of IL-17, potentially associated with different roles in intestinal and axial skeletal inflammation.

The m6A reader IMP2 directs autoimmune inflammation through an IL-17- and TNFα-dependent C/EBP transcription factor axis

Excessive cytokine activity underlies many autoimmune conditions, particularly through the interleukin-17 (IL-17) and tumor necrosis factor-α (TNFα) signaling axis. Both cytokines activate nuclear factor κB, but appropriate induction of downstream effector genes requires coordinated activation of other transcription factors, notably, CCAAT/enhancer binding proteins (C/EBPs). Here, we demonstrate the unexpected involvement of a posttranscriptional "epitranscriptomic" mRNA modification [N6-methyladenosine (m6A)] in regulating C/EBPβ and C/EBPδ in response to IL-17A, as well as IL-17F and TNFα. Prompted by the observation that C/EBPβ/δ-encoding transcripts contain m6A consensus sites, we show that Cebpd and Cebpb mRNAs are subject to m6A modification. Induction of C/EBPs is enhanced by an m6A methylase "writer" and suppressed by a demethylase "eraser." The only m6A "reader" found to be involved in this pathway was IGF2BP2 (IMP2), and IMP2 occupancy of Cebpd and Cebpb mRNA was enhanced by m6A modification. IMP2 facilitated IL-17-mediated Cebpd mRNA stabilization and promoted translation of C/EBPβ/δ in response to IL-17A, IL-17F, and TNFα. RNA sequencing revealed transcriptome-wide IL-17-induced transcripts that are IMP2 influenced, and RNA immunoprecipitation sequencing identified the subset of mRNAs that are directly occupied by IMP2, which included Cebpb and Cebpd Lipocalin-2 (Lcn2), a hallmark of autoimmune kidney injury, was strongly dependent on IL-17, IMP2, and C/EBPβ/δ. Imp2-/- mice were resistant to autoantibody-induced glomerulonephritis (AGN), showing impaired renal expression of C/EBPs and Lcn2 Moreover, IMP2 deletion initiated only after AGN onset ameliorated disease. Thus, posttranscriptional regulation of C/EBPs through m6A/IMP2 represents a previously unidentified paradigm of cytokine-driven autoimmune inflammation.

Expression and Function Analysis of Interleukin-17A/F1, 2, and 3 Genes in Yellow Catfish (Pelteobagrus fulvidraco): Distinct Bioactivity of Recombinant IL-17A/F1, 2, and 3

In mammals, Interleukin-17 cytokine family plays critical roles in both acute and chronic inflammatory responses. In fish species, three Interleukin-17A/F (IL-17A/F) genes have been identified to be homologous to mammalian IL-17A and IL-17F, but little is known about their functional activity. In this study, Pf_IL-17A/F1, 2 and 3 genes were cloned from yellow catfish (Pelteobagrus fulvidraco) and they differed in protein structure and exon length, implying that they may have divergent bioactivity. Real-time quantitative PCR analyses revealed that three Pf_IL-17A/F genes were highly expressed in blood and mucosal tissues (skin+mucus and gill) from healthy adult fish. The mRNA expressions of Pf_IL-17A/F1, 2 and 3 genes were significantly up-regulated in the gill, skin+mucus, head kidney and spleen after challenge with Edwardsiella ictaluri and in the isolated peripheral blood leucocytes (PBLs) of yellow catfish after stimulation with phytohaemagglutinin (PHA), lipopolysaccharides (LPS), peptidoglycan (PGN) and polyinosinic-polycytidylic acid (Poly I:C). These results indicate that Pf_IL-17A/F1, 2 and 3 genes may play a vital role in the regulation of immune against pathogens. Additionally, the recombinant (r) Pf_IL-17A/F1, 2 and 3 proteins significantly induced the mRNA expressions of proinflammatory cytokines, chemokines and antibacterial peptides genes, and the rPf_IL-17A/F 2 and 3 proteins promoted phagocytosis of PBLs more powerfully than the rPf_IL-17A/F1. Furthermore, the rPf_IL-17A/F1, 2 and 3 proteins might activate the NF-κB and MAPK signal pathways by IL-17RA, ACT1, TRAF6, TRAF2, TRAF5 and TAK1, indicating that the three Pf_IL-17A/F proteins may play different roles in promoting inflammatory response.

T cell transgressions: Tales of T cell form and function in diverse disease states

Insights into T cell form, function, and dysfunction are rapidly evolving. T cells have remarkably varied effector functions including protecting the host from infection, activating cells of the innate immune system, releasing cytokines and chemokines, and heavily contributing to immunological memory. Under healthy conditions, T cells orchestrate a finely tuned attack on invading pathogens while minimizing damage to the host. The dark side of T cells is that they also exhibit autoreactivity and inflict harm to host cells, creating autoimmunity. The mechanisms of T cell autoreactivity are complex and dynamic. Emerging research is elucidating the mechanisms leading T cells to become autoreactive and how such responses cause or contribute to diverse disease states, both peripherally and within the central nervous system. This review provides foundational information on T cell development, differentiation, and functions. Key T cell subtypes, cytokines that create their effector roles, and sex differences are highlighted. Pathological T cell contributions to diverse peripheral and central disease states, arising from errors in reactivity, are highlighted, with a focus on multiple sclerosis, rheumatoid arthritis, osteoarthritis, neuropathic pain, and type 1 diabetes.

Serial Lipocalin 2 and Oncostatin M levels reflect inflammation status and treatment response in axial spondyloarthritis

Background

Informative serum biomarkers for monitoring inflammatory activity and treatment responses in axial spondyloarthritis (axSpA) are lacking. We assessed whether Lipocalin 2 (LCN2) and Oncostatin M (OSM), both having roles in inflammation and bone remodeling, may accurately reflect chronic joint inflammation and treatment response in axSpA. Previous reports in animal models showed involvement of LCN2 and OSM in joint/gut inflammation. We asked whether they also play a role in human axSpA.

Methods

We analyzed a longitudinal observational axSpA cohort (286 patients) with yearly clinical assessments and concurrent measurements of serum LCN2 and OSM (1204 serum samples) for a mean of 4 years. Biomarker levels were correlated with MRI scoring and treatment response.

Results

Persistent and transient elevation of LCN2 and OSM were observed in axSpA patients. Persistent elevation of LCN2 or OSM, but not CRP, correlated with sacroiliac joint (SIJ) MRI SPARCC scores (Pearson’s correlation p = 0.0005 and 0.005 for LCN2 and OSM respectively), suggesting that LCN2/OSM outperforms CRP as reflective of SIJ inflammation. We observed both concordant and discordant patterns of LCN2 and OSM in relationship to back pain, the cardinal clinical symptom in axSpA. Twenty-six percent (73/286) of the patients remained both clinically and serologically active (CASA). Sixty percent (173/286) of the patients became clinically quiescent, with back pain resolved, but 53% (92/173) of them were serologically active (CQSA), indicating that pain control may not indicate control of joint inflammation, as reflected by positive MRI imaging of SIJ. With respect to treatment responses, transient elevation of LCN2 or OSM over time was predictive of better response to all treatments.

Conclusion

In axSpA, persistent LCN2 and/or OSM elevation reflects chronic SIJ inflammation and suboptimal treatment response. In our cohort, half of the currently deemed clinically quiescent patients with back pain resolved continued to demonstrate chronic joint inflammation. LCN2 and OSM profiling outperforms CRP as a predictive measure and provides an objective assessment of chronic local inflammation in axSpA patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02521-y.

IL-17 in the Pathogenesis of Disease: Good Intentions Gone Awry

The IL-17 family is an evolutionarily old cytokine family consisting of six members (IL-17A through IL-17F). IL-17 family cytokines signal through heterodimeric receptors that include the shared IL-17RA subunit, which is widely expressed throughout the body on both hematopoietic and nonhematopoietic cells. The founding family member, IL-17A, is usually referred to as IL-17 and has received the most attention for proinflammatory roles in autoimmune diseases like psoriasis. However, IL-17 is associated with a wide array of diseases with perhaps surprisingly variable pathologies. This review focuses on recent advances in the roles of IL-17 during health and in disease pathogenesis. To decipher the functions of IL-17 in diverse disease processes it is useful to first consider the physiological functions that IL-17 contributes to health. We then discuss how these beneficial functions can be diverted toward pathogenic amplification of deleterious pathways driving chronic disease.

Outlining cell interaction and inflammatory cytokines on UV-photofunctionalized mixed-phase TiO2 thin film

Photofunctionalization mediated by ultraviolet (UV) light seems to be a promising approach to improve the physico-chemical characteristics and the biological response of titanium (Ti) dental implants. Seeing that photofunctionalization is able to remove carbon from the surface, besides to promote reactions on the titanium dioxide (TiO₂) layer, coating the Ti with a stable TiO₂ film could potentialize the UV effect. Thus, here we determined the impact of UV-photofunctionalized mixed-phase (anatase and rutile) TiO₂ films on the physico-chemical properties of Ti substrate and cell biology. Mixed-phase TiO₂ films were grown by radiofrequency magnetron sputtering on commercially pure titanium (cpTi) discs, and samples were divided as follow: cpTi (negative control), TiO₂ (positive control), cpTi UV, TiO₂ UV (experimental). Photofunctionalization was performed using UVA (360 nm - 40 W) and UVC (250 nm - 40 W) lamps for 48 h. Surfaces were analyzed in terms of morphology, topography, chemical composition, crystalline phase, wettability and surface free energy. Pre-osteoblastic cells (MC3T3E1) were used to assess cell morphology and adhesion, metabolism, mineralization potential and cytokine secretion (IFN-γ, TNF-α, IL-4, IL-6 and IL-17). TiO₂-coated surfaces exhibited granular surface morphology and greater roughness. Photofunctionalization increased wettability (p < 0.05) and surface free energy (p < 0.001) on both surface conditions. TiO₂-treated groups featured normal cell morphology and spreading, and greater cellular metabolic activity at 2 and 4 days (p < 0.05), whereas UV-photofunctionalized surfaces enhanced cell metabolism, cell adhered area, and calcium deposition (day 14) (p < 0.05). In general, assessed proteins were found slightly affected by either UV or TiO₂ treatments. Altogether, our findings suggest that UV-photofunctionalized TiO₂ surface has the potential to improve pre-osteoblastic cell differentiation and the ability of cells to form mineral nodules by modifying Ti physico-chemical properties towards a more stable context. UV-modified surfaces modulate the secretion of key inflammatory markers.

Interleukin-17A Facilitates Chikungunya Virus Infection by Inhibiting IFN-α2 Expression

Interferons (IFNs) are the key components of innate immunity and are crucial for host defense against viral infections. Here, we report a novel role of interleukin-17A (IL-17A) in inhibiting IFN-α2 expression thus promoting chikungunya virus (CHIKV) infection. CHIKV infected IL-17A deficient (Il17a^-/- ) mice expressed a higher level of IFN-α2 and developed diminished viremia and milder footpad swelling in comparison to wild-type (WT) control mice, which was also recapitulated in IL-17A receptor-deficient (Il17ra^-/- ) mice. Interestingly, IL-17A selectively blocked IFN-α2 production during CHIKV, but not West Nile virus (WNV) or Zika virus (ZIKV), infections. Recombinant IL-17A treatment inhibited CHIKV-induced IFN-α2 expression and enhanced CHIKV replication in both human and mouse cells. We further found that IL-17A inhibited IFN-α2 production by modulating the expression of Interferon Regulatory Factor-5 (IRF-5), IRF-7, IFN-stimulated gene 49 (ISG-49), and Mx1 expression during CHIKV infection. Neutralization of IL-17A in vitro leads to the increase of the expression of these antiviral molecules and decrease of CHIKV replication. Collectively, these results suggest a novel function of IL-17A in inhibiting IFN-α2-mediated antiviral responses during CHIKV infection, which may have broad implications in viral infections and other inflammatory diseases.

Multitasking by the OC Lineage during Bone Infection: Bone Resorption, Immune Modulation, and Microbial Niche

Bone infections, also known as infectious osteomyelitis, are accompanied by significant inflammation, osteolysis, and necrosis. Osteoclasts (OCs) are the bone-resorbing cells that work in concert with osteoblasts and osteocytes to properly maintain skeletal health and are well known to respond to inflammation by increasing their resorptive activity. OCs have typically been viewed merely as effectors of pathologic bone resorption, but recent evidence suggests they may play an active role in the progression of infections through direct effects on pathogens and via the immune system. This review discusses the host- and pathogen-derived factors involved in the in generation of OCs during infection, the crosstalk between OCs and immune cells, and the role of OC lineage cells in the growth and survival of pathogens, and highlights unanswered questions in the field.

Targeting interleukin-17 in chronic inflammatory disease: A clinical perspective

Although many chronic inflammatory diseases share the feature of elevated IL-17 production, therapeutic targeting of IL-17 has vastly different clinical outcomes. Here the authors summarize the recent progress in understanding the protective and pathogenic role of the IL-23/IL-17 axis in preclinical models and human inflammatory diseases.

Chronic inflammatory diseases like psoriasis, Crohn’s disease (CD), multiple sclerosis (MS), rheumatoid arthritis (RA), and others are increasingly recognized as disease entities, where dysregulated cytokines contribute substantially to tissue-specific inflammation. A dysregulation in the IL-23/IL-17 axis can lead to inflammation of barrier tissues, whereas its role in internal organ inflammation remains less clear. Here we discuss the most recent developments in targeting IL-17 for the treatment of chronic inflammation in preclinical models and in patients afflicted with chronic inflammatory diseases.

Tumor Necrosis Factor Receptor Associated Factor 3 Modulates Cartilage Degradation through Suppression of Interleukin 17 Signaling

Interleukin 17A (IL-17A) is critical in the pathogenesis of autoimmune diseases through driving inflammatory cascades. However, the role of IL-17 in osteoarthritis (OA) is not well understood. Tumor necrosis factor-receptor-associated factor 3 (TRAF3) is a receptor proximal negative regulator of IL-17 signaling. It remains unclear whether TRAF3 exerts regulatory effects on cartilage degradation and contributes to the pathogenesis of OA. In this study, we found that TRAF3 notably suppressed IL-17-induced NF-κB and mitogen-activated protein kinase activation and, subsequently, the production of matrix-degrading enzymes. TRAF3 depletion enhanced IL-17 signaling, along with increased matrix-degrading enzyme production. In vivo, cartilage destruction caused by surgery-induced OA was alleviated markedly both in 1l17a-deficient mice and in TRAF3 transgenic mice. In contrast, silencing TRAF3 through adenoviruses worsened cartilage degradation in experimental OA. Moreover, the destructive effect of IL-17 on cartilage was abolished in TRAF3 transgenic mice in an IL-17 intra-articular injection animal model. Similarly, genetic deletion of IL-17 blocked TRAF3 knockdown-mediated promotion of cartilage destruction, suggesting that the protective effect of TRAF3 on cartilage is mediated by its suppression of IL-17 signaling. Collectively, our results suggest that TRAF3 negatively regulates IL-17-mediated cartilage degradation and pathogenesis of OA, and may serve as a potential new therapy target for OA.

Lipocalin 2 links inflammation and ankylosis in the clinical overlap of inflammatory bowel disease (IBD) and ankylosing spondylitis (AS)

Background

Little is known about the mechanisms underlying the clinical overlap between gut inflammation and joint ankylosis, as exemplified by the concurrence of inflammatory bowel diseases (IBD) and ankylosing spondylitis (AS). As dysbiosis may serve as a common contributor, the anti-microbial pleiotropic factor lipocalin 2 could be a potential mediator due to its roles in inflammation and bone homeostasis.

Methods

Baseline colonic pathology was conducted in the ank/ank mouse model. Serum lipocalin 2 was analyzed by ELISA, in ank/ank mutants versus C3FeB6-A/A^w-jwt/wt, in patients with concurrent AS-IBD, AS alone, IBD alone, or mechanical back pain, and in healthy controls. In the ank/ank mouse model, the expression of nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) was examined by real-time PCR. Intraperitoneal injection was done with the PPARγ agonist rosiglitazone or antagonist bisphenol A diglycidyl ether for four consecutive days. Serum levels of lipocalin 2 were examined on the sixth day.

Results

This study showed that the ank/ank mice with fully fused spines had concurrent colonic inflammation. By first using the ank/ank mouse model with progressive ankylosis and subclinical colonic inflammation, confirmed in patients with concurrent AS and IBD, elevated circulating lipocalin 2 levels were associated with the coexisting ankylosis and gut inflammation. The intracellular pathway of lipocalin 2 was further investigated with the ank/ank mouse model involving PPARγ. Colonic expression of PPARγ was negatively associated with the degree of gut inflammation. The PPARγ agonist rosiglitazone treatment significantly upregulated the serum levels of lipocalin 2, suggesting a potential regulatory role of PPARγ in the aberrant expression of lipocalin 2.

Conclusions

In summary, lipocalin 2 modulated by PPARγ could be a potential pathway involved in concurrent inflammation and ankylosis in AS and IBD.

Hidradenitis suppurativa

Hidradenitis suppurativa (HS; also designated as acne inversa) is a chronic inflammatory disorder, which affects the intertriginous skin and is associated with numerous systemic comorbidities. The estimated prevalence of HS is ~1% in most studied countries. Typically starting in early adulthood, cutaneous inflamed nodules, abscesses and pus-discharging tunnels develop in axillary, inguinal, gluteal and perianal body sites. The comorbidities of HS include metabolic and cardiovascular disorders, which contribute to reduced life expectancy. A genetic predisposition, smoking, obesity and hormonal factors are established aetiological factors for HS. Cutaneous changes seem to start around hair follicles and involve activation of cells of the innate and adaptive immune systems, with pivotal roles for pro-inflammatory cytokines such as tumour necrosis factor, IL-1β and IL-17. The unrestricted and chronic immune response eventually leads to severe pain, pus discharge, irreversible tissue destruction and scar development. HS has profound negative effects on patients' quality of life, which often culminate in social withdrawal, unemployment, depression and suicidal thoughts. The therapeutic options for HS comprise antibiotic treatment, neutralization of tumour necrosis factor and surgical intervention together with lifestyle modification. Nevertheless, there is an enormous need for awareness of HS, understanding of its pathogenesis and novel treatments.

Lung CD4+ resident memory T cells remodel epithelial responses to accelerate neutrophil recruitment during pneumonia

Previous pneumococcal experience establishes lung-resident IL-17A-producing CD4⁺ memory T_RM cells that accelerate neutrophil recruitment against heterotypic pneumococci. Herein, we unravel a novel crosstalk between CD4⁺ T_RM cells and lung epithelial cells underlying this protective immunity. Depletion of CD4⁺ cells in pneumococcus-experienced mice diminished CXCL5 (but not CXCL1 or CXCL2) and downstream neutrophil accumulation in the lungs. Epithelial cells from experienced lungs exhibited elevated mRNA for CXCL5 but not other epithelial products such as GM-CSF or CCL20, suggesting a skewing by CD4⁺ T_RM cells. Genome-wide expression analyses revealed a significant remodeling of the epithelial transcriptome of infected lungs due to infection history, ~80% of which was CD4⁺ cell-dependent. The CD4⁺ T_RM cell product IL-17A stabilized CXCL5 but not GM-CSF or CCL20 mRNA in cultured lung epithelial cells, implicating posttranscriptional regulation as a mechanism for altered epithelial responses. These results suggest that epithelial cells in experienced lungs are effectively different, owing to their communication with T_RM cells. Our study highlights the role of tissue-resident adaptive immune cells in fine-tuning epithelial functions to hasten innate immune responses and optimize defense in experienced lungs, a concept that may apply broadly to mucosal immunology.

CUX1 and IκBζ (NFKBIZ) mediate the synergistic inflammatory response to TNF and IL-17A in stromal fibroblasts

The role of stromal fibroblasts in chronic inflammation is unfolding. In rheumatoid arthritis, leukocyte-derived cytokines TNF and IL-17A work together, activating fibroblasts to become a dominant source of the hallmark cytokine IL-6. However, IL-17A alone has minimal effect on fibroblasts. To identify key mediators of the synergistic response to TNF and IL-17A in human synovial fibroblasts, we performed time series, dose-response, and gene-silencing transcriptomics experiments. Here we show that in combination with TNF, IL-17A selectively induces a specific set of genes mediated by factors including cut-like homeobox 1 (CUX1) and IκBζ (NFKBIZ). In the promoters of CXCL1, CXCL2, and CXCL3, we found a putative CUX1-NF-κB binding motif not found elsewhere in the genome. CUX1 and NF-κB p65 mediate transcription of these genes independent of LIFR, STAT3, STAT4, and ELF3. Transcription of NFKBIZ, encoding the atypical IκB factor IκBζ, is IL-17A dose-dependent, and IκBζ only mediates the transcriptional response to TNF and IL-17A, but not to TNF alone. In fibroblasts, IL-17A response depends on CUX1 and IκBζ to engage the NF-κB complex to produce chemoattractants for neutrophil and monocyte recruitment.

Specific Commensal Bacterium Critically Regulates Gut Microbiota Osteoimmunomodulatory Actions During Normal Postpubertal Skeletal Growth and Maturation

The commensal gut microbiota critically regulates immunomodulatory processes that influence normal skeletal growth and maturation. However, the influence of specific microbes on commensal gut microbiota osteoimmunoregulatory actions is unknown. We have shown previously that the commensal gut microbiota enhances T_H17/IL17A immune response effects in marrow and liver that have procatabolic/antianabolic actions in the skeleton. Segmented filamentous bacteria (SFB), a specific commensal gut bacterium within phylum Firmicutes, potently induces T_H17/IL17A‐mediated immunity. The study purpose was to delineate the influence of SFB on commensal gut microbiota immunomodulatory actions regulating normal postpubertal skeletal development. Two murine models were utilized: SFB‐monoassociated mice versus germ‐free (GF) mice and specific‐pathogen‐free (SPF) mice +/− SFB. SFB colonization was validated by 16S rDNA analysis, and SFB‐induced T_H17/IL17A immunity was confirmed by upregulation of Il17a in ileum and IL17A in serum. SFB‐colonized mice had an osteopenic trabecular bone phenotype, which was attributed to SFB actions suppressing osteoblastogenesis and enhancing osteoclastogenesis. Intriguingly, SFB‐colonized mice had increased expression of proinflammatory chemokines and acute‐phase reactants in the liver. Lipocalin‐2 (LCN2), an acute‐phase reactant and antimicrobial peptide, was substantially elevated in the liver and serum of SFB‐colonized mice, which supports the notion that SFB regulation of commensal gut microbiota osteoimmunomodulatory actions are mediated in part through a gut–liver–bone axis. Proinflammatory T_H17 and T_H1 cells were increased in liver‐draining lymph nodes of SFB‐colonized mice, which further substantiates that SFB osteoimmune‐response effects may be mediated through the liver. SFB‐induction of Il17a in the gut and Lcn2 in the liver resulted in increased circulating levels of IL17A and LCN2. Recognizing that IL17A and LCN2 support osteoclastogenesis/suppress osteoblastogenesis, SFB actions impairing postpubertal skeletal development appear to be mediated through immunomodulatory effects in both the gut and liver. This research reveals that specific microbes critically impact commensal gut microbiota immunomodulatory actions regulating normal postpubertal skeletal growth and maturation. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Targeting interleukin-17 in chronic inflammatory disease: A clinical perspective

Chronic inflammatory diseases like psoriasis, Crohn's disease (CD), multiple sclerosis (MS), rheumatoid arthritis (RA), and others are increasingly recognized as disease entities, where dysregulated cytokines contribute substantially to tissue-specific inflammation. A dysregulation in the IL-23/IL-17 axis can lead to inflammation of barrier tissues, whereas its role in internal organ inflammation remains less clear. Here we discuss the most recent developments in targeting IL-17 for the treatment of chronic inflammation in preclinical models and in patients afflicted with chronic inflammatory diseases.

CD4+ T Cell-Derived NGAL Modifies the Outcome of Ischemic Acute Kidney Injury

CD4⁺ T cells mediate the pathogenesis of ischemic and nephrotoxic acute kidney injury (AKI). However, the underlying mechanisms of CD4⁺ T cell-mediated pathogenesis are largely unknown. We therefore conducted unbiased RNA-sequencing to discover novel mechanistic pathways of kidney CD4⁺ T cells after ischemia compared with normal mouse kidney. Unexpectedly, the lipocalin-2 (Lcn2) gene, which encodes neutrophil gelatinase-associated lipocalin (NGAL) had the highest fold increase (∼60). The NGAL increase in CD4⁺ T cells during AKI was confirmed at the mRNA level with quantitative real-time PCR and at the protein level with ELISA. NGAL is a potential biomarker for the early detection of AKI and has multiple potential biological functions. However, the role of NGAL produced by CD4⁺ T cells is not known. We found that ischemic AKI in NGAL knockout (KO) mice had worse renal outcomes compared with wild-type (WT) mice. Adoptive transfer of NGAL-deficient CD4⁺ T cells from NGAL KO mice into CD4 KO or WT mice led to worse renal function than transfer of WT CD4⁺ T cells. In vitro-simulated ischemia/reperfusion showed that NGAL-deficient CD4⁺ T cells express higher levels of IFN-γ mRNA compared with WT CD4⁺ T cells. In vitro differentiation of naive CD4⁺ T cells to Th17, Th1, and Th2 cells led to significant increase in Lcn2 expression. Human kidney CD4⁺ T cell NGAL also increased significantly after ischemia. These results demonstrate an important role for CD4⁺ T cell NGAL as a mechanism by which CD4⁺ T cells mediate AKI and extend the importance of NGAL in AKI beyond diagnostics.

IL-17 receptor-based signaling and implications for disease

IL-17 is a highly versatile pro-inflammatory cytokine crucial for a variety of processes, including host defense, tissue repair, the pathogenesis of inflammatory disease and the progression of cancer. In contrast to its profound impact in vivo, IL-17 exhibits surprisingly moderate activity in cell-culture models, which presents a major knowledge gap about the molecular mechanisms of IL-17 signaling. Emerging studies are revealing a new dimension of complexity in the IL-17 pathway that may help explain its potent and diverse in vivo functions. Discoveries of new mRNA stabilizers and receptor-directed mRNA metabolism have provided insights into the means by which IL-17 cooperates functionally with other stimuli in driving inflammation, whether beneficial or destructive. The integration of IL-17 with growth-receptor signaling in specific cell types offers new understanding of the mitogenic effect of IL-17 on tissue repair and cancer. This Review summarizes new developments in IL-17 signaling and their pathophysiological implications.

Interleukin-17: Potential Target for Chronic Wounds

Chronic wounds exhibit persistent inflammation with markedly delayed healing. The significant burden of chronic wounds, which are often resistant to standard therapy, prompts further research on novel therapies. Since the interleukin-17 family has been implicated as a group of proinflammatory cytokines in immune-mediated diseases in the gut and connective tissue, as well as inflammatory skin conditions, we consider here if it may contribute to the pathogenesis of chronic wounds. In this review, we discuss the interleukin-17 family's signaling pathways and role in tissue repair. A PubMed review of the English literature on interleukin-17, wound healing, chronic wounds, and inflammatory skin conditions was conducted. Interleukin-17 family signaling is reviewed in the context of tissue repair, and preclinical and clinical studies examining its role in the skin and other organ systems are critically reviewed. The published work supports a pathologic role for interleukin-17 family members in chronic wounds, though this needs to be more conclusively proven. Clinical studies using monoclonal interleukin-17 antibodies to improve healing of chronic skin wounds have not yet been performed, and only a few studies have examined interleukin-17 family expression in chronic skin wounds. Furthermore, different interleukin-17 family members could be playing selective roles in the repair process. These studies suggest a therapeutic role for targeting interleukin-17A to promote wound healing; therefore, interleukin-17A may be a target worthy of pursuing in the near future.

The IL-17 Family of Cytokines in Health and Disease

The interleukin 17 (IL-17) family of cytokines contains 6 structurally related cytokines, IL-17A through IL-17F. IL-17A, the prototypical member of this family, just passed the 25^th anniversary of its discovery. Although less is known about IL-17B-F, IL-17A (commonly known as IL-17) has received much attention for its pro-inflammatory role in autoimmune disease. Over the past decade, however, it has become clear that the functions of IL-17 are far more nuanced than simply turning on inflammation. Accumulating evidence indicates that IL-17 has important context- and tissue-dependent roles in maintaining health during response to injury, physiological stress, and infection. Here, we discuss the functions of the IL-17 family, with a focus on the balance between the pathogenic and protective roles of IL-17 in cancer and autoimmune disease, including results of therapeutic blockade and novel aspects of IL-17 signal transduction regulation.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

Silencing of LncRNA-ANCR Promotes the Osteogenesis of Osteoblast Cells in Postmenopausal Osteoporosis via Targeting EZH2 and RUNX2

PURPOSE

This study aimed to explore the effects and mechanisms of long non-coding RNA (lncRNA) anti-differentiation non-coding RNA (ANCR) on the osteogenesis of osteoblast cells in postmenopausal osteoporosis (PMOP).

MATERIALS AND METHODS

Mice models of PMOP were established. ANCR expression and intracellular calcium ions were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and laser confocal microscopy, respectively. ANCR was silenced in osteoblast cells from PMOP mice by the transfection of siRNA-ANCR (si-ANCR). The proliferation and apoptosis of osteoblast cells was analyzed by MTT and flow cytometry, respectively. Alkaline phosphatase (ALP) activity and calcium nodules were examined by ALP and alizarin red staining assay, respectively. The expression of enhancer of zeste homolog 2 (EZH2), runt related transcription factor 2 (RUNX2), and OSTERIX was detected by qRT-PCR and Western blot. Furthermore, an osteogenesis model was constructed in mice, and osteoid formation was observed by hematoxylin-eosin (HE) staining. The interaction between lncRNA-ANCR and EZH2 was further identified by RNA pull-down assay.

RESULTS

ANCR expression and intracellular calcium ions were increased in PMOP mice. Si-ANCR significantly increased the proliferation, ALP activity, calcium deposition of osteoblast cells and decreased apoptosis. ANCR and EZH2 were down-regulated by si-ANCR, while RUNX2 and OSTERIX were upregulated. Si-ANCR also promoted osteoid formation in mice treated with hydroxyapatite-tricalcium phosphate. In addition, ANCR specifically bound to EZH2.

CONCLUSION

Silencing ANCR promotes the osteogenesis of PMOP osteoblast cells. The specific binding of ANCR with EZH2 suppressed RUNX2, thereby inhibiting osteogenesis.

Interleukin-17: The Role for Pathological Angiogenesis in Ocular Neovascular Diseases

Ocular neovascular diseases are featured by abnormal angiogenesis in the eye, and they seriously threaten the human visual health. These diseases include proliferative diabetic retinopathy (PDR), age-related macular degeneration (AMD), retinopathy of prematurity (ROP), and retinal vein occlusion (RVO). In fact, ocular neovascular diseases represent the leading causes of vision impairment and blindness worldwide. Ocular neovascularization, the process of pathological vessel formation in eye, underlies ocular neovascular diseases. Cytokines have important regulatory roles in neovascularization through immunological networks. Interleukin (IL)-17, the signature cytokine produced by T helper 17 (Th17) cells, has proven to be involved in ocular neovascularization. However, roles of IL-17 in ocular neovascular diseases still remain controversial. This review provides an overview of the functional roles of IL-17 in ocular neovascular diseases from basic research to clinical evidence by focusing on PDR, AMD, ROP, and RVO. The possible roles of IL-17 in neovascularization are achieved through a regulatory network of cytoskeleton remodeling, vascular endothelial growth factor (VEGF), VEGF-related cytokines, and complement components. Current applications as well as potential therapies targeting IL-17 with genome editing systems are also outlined and discussed. Targeting IL-17 might be a promising therapeutic strategy against ocular neovascular diseases.

Osteoblastic PLEKHO1 contributes to joint inflammation in rheumatoid arthritis

Background

Osteoblasts participating in the inflammation regulation gradually obtain concerns. However, its role in joint inflammation of rheumatoid arthritis (RA) is largely unknown. Here, we investigated the role of osteoblastic pleckstrin homology domain-containing family O member 1 (PLEKHO1), a negative regulator of osteogenic lineage activity, in regulating joint inflammation in RA.

Methods

The level of osteoblastic PLEKHO1 in RA patients and collagen-induced arthritis (CIA) mice was examined. The role of osteoblastic PLEKHO1 in joint inflammation was evaluated by a CIA model and a K/BxN serum-transfer arthritis (STA) model which were induced in osteoblast-specific Plekho1 conditional knockout mice and mice expressing high Plekho1 exclusively in osteoblasts, respectively. The effect of osteoblastic PLEKHO1 inhibition was explored in a CIA mice model and a non-human primate arthritis model. The mechanism of osteoblastic PLEKHO1 in regulating joint inflammation were performed by a series of in vitro studies.

Results

PLEKHO1 was highly expressed in osteoblasts from RA patients and CIA mice. Osteoblastic Plekho1 deletion ameliorated joint inflammation, whereas overexpressing Plekho1 only within osteoblasts exacerbated local inflammation in CIA mice and STA mice. PLEKHO1 was required for TRAF2-mediated RIP1 ubiquitination to activate NF-κB for inducing inflammatory cytokines production in osteoblasts. Moreover, osteoblastic PLEKHO1 inhibition diminished joint inflammation and promoted bone formation in CIA mice and non-human primate arthritis model.

Conclusions

These data strongly suggest that the highly expressed PLEKHO1 in osteoblasts contributes to joint inflammation in RA. Targeting osteoblastic PLEKHO1 may exert dual therapeutic action of alleviating joint inflammation and promoting bone formation in RA.

Combined Blockade of TNF-α and IL-17A Alleviates Progression of Collagen-Induced Arthritis without Causing Serious Infections in Mice

The cytokines TNF-α and IL-17A are elevated in a variety of autoimmune diseases, including rheumatoid arthritis. Both cytokines are targets of several biologic drugs used in the clinic, but unfortunately many patients are refractory to these therapies. IL-17A and TNF-α are known to mediate signaling synergistically to drive expression of inflammatory genes. Hence, combined blockade of TNF-α and IL-17A represents an attractive treatment strategy in autoimmune settings where monotherapy is not fully effective. However, a major concern with this approach is the potential predisposition to opportunistic infections that might outweigh any clinical benefits. Accordingly, we examined the impact of individual versus combined neutralization of TNF-α and IL-17A in a mouse model of rheumatoid arthritis (collagen-induced arthritis) and the concomitant susceptibility to infections that are likely to manifest as side effects of blocking these cytokines (oral candidiasis or tuberculosis). Our findings indicate that combined neutralization of TNF-α and IL-17A was considerably more effective than monotherapy in improving collagen-induced arthritis disease even when administered at a minimally efficacious dose. Encouragingly, however, dual cytokine blockade did not cooperatively impair antimicrobial host defenses, as mice given combined IL-17A and TNF-α neutralization displayed infectious profiles and humoral responses comparable to mice given high doses of individual anti-TNF-α or anti-IL-17A mAbs. These data support the idea that combined neutralization of TNF-α and IL-17A for refractory autoimmunity is likely to be associated with acceptable and manageable risks of opportunistic infections associated with these cytokines.

Association of CCL2 with systemic inflammation in Schnitzler syndrome

BACKGROUND

Schnitzler syndrome (SchS) is a rare autoinflammatory disease characterized by urticarial exanthema, bone and joint alterations, fever and monoclonal gammopathy, which manifest mostly in the second half of life. It involves overactivation of the interleukin (IL)-1 system, but the exact pathophysiological pathways remain largely unknown.

OBJECTIVES

To identify and characterize the pathogenetic players in SchS.

METHODS

Blood parameters were quantified in patients with SchS compared with healthy controls and patients with psoriasis and hidradenitis suppurativa using enzyme-linked immunosorbent assay (ELISA). CCL2 expression in cultured primary cells was analysed by quantitative reverse-transcriptase polymerase chain reaction and ELISA.

RESULTS

CCL2, a chemoattractant for monocytic and further mononuclear immune cells, was found to be significantly elevated in patients with SchS. CCL2 levels showed a positive association with global disease activity, especially with bone pain, but not disease duration, gammopathy, neutrophilia or skin disease. In vitro stimulation assays demonstrated a strong CCL2 production capacity of mononuclear immune cells and fibroblasts, but not epithelial or endothelial cells. Among a range of inflammatory mediators, only IL-1β (immune cells, fibroblasts) and tumour necrosis factor (TNF)-α (fibroblasts) were important CCL2 inducers. TNF-α, but not IL-17, strengthened the CCL2-inducing effect of IL-1β in fibroblasts. Accordingly, CCL2 levels positively correlated with both TNF-α and IL-1β serum levels in patients with SchS. Therapeutic IL-1β blockade decreased CCL2 blood levels in these patients as early as 1 week after the initiation of treatment.

CONCLUSIONS

CCL2 may be an important component of the pathogenetic cascade leading to bone alterations, and a suitable marker of disease activity in patients with SchS.

Interleukin 12 and interleukin 23 play key pathogenic roles in inflammatory and proliferative pathways in giant cell arteritis

OBJECTIVES

The pathogenesis of giant cell arteritis (GCA) remains unclear. TH1 and TH17 pathways are implicated, but the proximal initiators and effector cytokines are unknown. Our aim was to assess the role of interleukin 12 (IL-12) and interleukin 23 (IL-23) in GCA pathogenesis.

METHODS

IL-12 and IL-23 expression were quantified by immunohistochemistry in temporal artery biopsies (TABs). Temporal artery (TA) explant, peripheral blood mononuclear cell (PBMC) and myofibroblast outgrowth culture models were established. PBMCs and TA explants were cultured for 24 hours in the presence or absence of IL-12 (50 ng/mL) or IL-23 (10 ng/mL). Gene expression in TA was quantified by real-time PCR and cytokine secretion by ELISA. Myofibroblast outgrowths were quantified following 28-day culture.

RESULTS

Immunohistochemistry demonstrated increased expression of interleukin 12p35 (IL-12p35) and interleukin 23p19 (IL-23p19) in biopsy-positive TAs, localised to inflammatory cells. IL-12p35 TA expression was significantly increased in those with cranial ischaemic complications (p=0.026) and large vessel vasculitis (p=0.006). IL-23p19 TA expression was increased in those with two or more relapses (p=0.007). In PBMC cultures, exogenous IL-12 significantly increased interleukin 6 (IL-6) (p=0.009), interleukin 22 (IL-22) (p=0.003) and interferon γ (IFN-γ) (p=0.0001) and decreased interleukin 8 (IL-8) (p=0.0006) secretion, while exogenous IL-23 significantly increased IL-6 (p=0.029), IL-22 (p=0.001), interleukin 17A (IL-17A) (p=0.0003) and interleukin 17F (IL-17F) (p=0.012) secretion. In ex vivo TA explants, IL-23 significantly increased gene expression of IL-8 (p=0.0001) and CCL-20 (p=0.027) and protein expression of IL-6 (p=0.002) and IL-8 (p=0.004). IL-12 (p=0.0005) and IL-23 (p<0.0001) stimulation increased the quantity of myofibroblast outgrowths from TABs.

CONCLUSION

IL-12 and IL-23 play central and distinct roles in stimulating inflammatory and proliferative pathways relevant to GCA pathogenesis.

IL-17 integrates multiple self-reinforcing, feed-forward mechanisms through the RNA binding protein Arid5a

Interleukin-17A (IL-17A) not only stimulates immunity to fungal pathogens but also contributes to autoimmune pathology. IL-17 is only a modest activator of transcription in experimental tissue culture settings. However, IL-17 controls posttranscriptional events that enhance the expression of target mRNAs. Here, we showed that the RNA binding protein (RBP) Arid5a (AT-rich interactive domain-containing protein 5a) integrated multiple IL-17-driven signaling pathways through posttranscriptional control of mRNA. IL-17 induced expression of Arid5a, which was recruited to the adaptor TRAF2. Arid5a stabilized IL-17-induced cytokine transcripts by binding to their 3' untranslated regions and also counteracted mRNA degradation mediated by the endoribonuclease MCPIP1 (Regnase-1). Arid5a inducibly associated with the eukaryotic translation initiation complex and facilitated the translation of the transcription factors (TFs) IκBζ (Nfkbiz ) and C/EBPβ (Cebpb). These TFs in turn transactivated IL-17-dependent promoters. Together, these data indicated that Arid5a orchestrates a feed-forward amplification loop, which promoted IL-17 signaling by controlling mRNA stability and translation.