Macrophage heterogeneity in the context of rheumatoid arthritis

The mannose receptor (CD206) identifies a population of colonic macrophages in health and inflammatory bowel disease

To understand the contribution of mononuclear phagocytes (MNP), which include monocyte-derived intestinal macrophages, to the pathogenesis of inflammatory bowel disease (IBD), it is necessary to identify functionally-different MNP populations. We aimed to characterise intestinal macrophage populations in patients with IBD. We developed 12-parameter flow cytometry protocols to identify and human intestinal MNPs. We used these protocols to purify and characterize colonic macrophages from colonic tissue from patients with Crohn’s disease (CD), ulcerative colitis (UC), or non-inflamed controls, in a cross-sectional study. We identify macrophage populations (CD45⁺CD64⁺ HLA-DR⁺) and describe two distinct subsets, differentiated by their expression of the mannose receptor, CD206. CD206⁺ macrophages expressed markers consistent with a mature phenotype: high levels of CD68 and CD163, higher transcription of IL-10 and lower expression of TREM1. CD206⁻ macrophages appear to be less mature, with features more similar to their monocytic precursors. We identified and purified macrophage populations from human colon. These appear to be derived from a monocytic precursor with high CCR2 and low CD206 expression. As these cells mature, they acquire expression of IL-10, CD206, CD63, and CD168. Targeting the newly recruited monocyte-derived cells may represent a fruitful avenue to ameliorate chronic inflammation in IBD.

ROS-Responsive Boronate-Stabilized Polyphenol-Poloxamer 188 Assembled Dexamethasone Nanodrug for Macrophage Repolarization in Osteoarthritis Treatment

Osteoarthritis (OA) is a disabling joint disease associated with chronic inflammation. The polarization of macrophages plays the key role in inflammatory microenvironment of joint which is a therapeutic target for OA treatment. Herein, a boronate-stabilized polyphenol-poloxamer assembled dexamethasone nanodrug with reactive oxygen species (ROS)-responsive drug release behavior and ROS scavenging ability is prepared. Thanks to that, the nanodrug can efficiently inhibit the ROS and nitric oxide production in lipopolysaccharide-activated RAW264.7 macrophages and modulate macrophages M2 polarization at a much lower concentration than free drug dexamethasone. Furthermore, the monosodium iodoacetate-induced OA mice treated with this nanodrug is very similar with the normal mice with the evaluation of body weight and scores including clinical arthritis scores, claw circumference, and kinematics score. The inflammation associated angiogenesis is also reduced which revealed by ⁶⁸ Ga-labeled arginine-glycine-aspartic acid peptide micro-positron emission tomography imaging. Cartilage degradation and bone erosion in the joints are also inhibited by the nanodrug, along with the inhibition of proinflammatory cytokines. In addition, the biosafety of this nanodrug is also verified. This nanodrug with excellent immunomodulation properties can be used not only for OA therapy but also for other inflammatory diseases associated with excess oxidative stress and macrophage polarization.

Stromal cell-derived DEL-1 inhibits Tfh cell activation and inflammatory arthritis

The secreted protein developmental endothelial locus 1 (DEL-1) regulates inflammatory cell recruitment and protects against inflammatory pathologies in animal models. Here, we investigated DEL-1 in inflammatory arthritis using collagen-induced arthritis (CIA) and collagen Ab-induced arthritis (CAIA) models. In both models, mice with endothelium-specific overexpression of DEL-1 were protected from arthritis relative to WT controls, whereas arthritis was exacerbated in DEL-1-deficient mice. Compared with WT controls, mice with collagen VI promoter-driven overexpression of DEL-1 in mesenchymal cells were protected against CIA but not CAIA, suggesting a role for DEL-1 in the induction of the arthritogenic Ab response. Indeed, DEL-1 was expressed in perivascular stromal cells of the lymph nodes and inhibited Tfh and germinal center B cell responses. Mechanistically, DEL-1 inhibited DC-dependent induction of Tfh cells by targeting the LFA-1 integrin on T cells. Overall, DEL-1 restrained arthritis through a dual mechanism, one acting locally in the joints and associated with the anti-recruitment function of endothelial cell-derived DEL-1; the other mechanism acting systemically in the lymph nodes and associated with the ability of stromal cell-derived DEL-1 to restrain Tfh responses. DEL-1 may therefore be a promising therapeutic for the treatment of inflammatory arthritis.

The monomer derivative of paeoniflorin inhibits macrophage pyroptosis via regulating TLR4/ NLRP3/ GSDMD signaling pathway in adjuvant arthritis rats

OBJECTIVE

This study was aimed to investigate the effect of monomer derivative of paeoniflorin (MDP) on macrophage pyroptosis mediated by TLR4/NLRP3/GSDMD signaling pathway in adjuvant arthritis (AA) rats.

METHOD

Wistar rats were divided into normal group, AA model group, MDP (50 mg/kg) group and MTX (0.5 mg/kg) group. The expression of TLR4, NLRP3 and GSDMD in macrophage were detected by immunofluorescence assay. The expression of TLR4 and the ratio of macrophage pyroptosis were analyzed by flow cytometry. Cell morphology was observed by scanning electron microscopy. The cytokine levels of IL-18 and IL-1β were detected by ELISA. The expressions of proteins related to macrophage pyroptosis were detected by western blot.

RESULTS

MDP has a therapeutic effect on rats AA by reducing the secondary inflammation and improving pathological changes. The results of X-ray imaging and ultrasound images showed that MDP could inhibit bone erosion, soft tissue swelling, and joint space narrowing. Macrophage pyroptosis was found in secondary inflammation of AA rats. The expressions of TLR4, MyD88, NLRP3, Caspase-1, ASC, and GSDMD-N in macrophage were increased, the levels of IL-18 and IL-1β were enhanced, and the morphology of pyroptosis could be observed. MDP could inhibit macrophage polarization and macrophage pyroptosis, and down-regulated the cytokine levels of IL-18 and IL-1β in AA rats. MDP could regulate the M1/M2 ratio, decreased the ratio of macrophage pyroptosis and down-regulated the expressions of TLR4, MyD88, NLRP3, Caspase-1, ASC, and GSDMD-N in vivo and in vitro.

CONCLUSION

Abnormal activation of TLR4/NLRP3/GSDMD signaling pathway may be involved in macrophage pyroptosis in AA rats. The therapeutic effect of MDP on AA rats is related to the inhibition of macrophage pyroptosis by regulating the TLR4/NLRP3/GSDMD signaling pathway.

A Peptide Derived from IKK-Interacting Protein Attenuates NF-κB Activation and Inflammation

The IκB kinase (IKK) complex plays a vital role in regulating the NF-κB activation. Aberrant NF-κB activation is involved in various inflammatory diseases. Thus, targeting IKK activation is an ideal therapeutic strategy to cure and prevent inflammatory diseases related to NF-κB activation. In a previous study, we demonstrated that IKK-interacting protein (IKIP) inhibits the phosphorylation of IKKα/β and the activation of NF-κB through disruption of the formation of IKK complex. In this study, we identified a 15-aa peptide derived from mouse IKIP (46-60 aa of IKIP), which specifically suppressed IKK activation and NF-κB targeted gene expression via disrupting the association of IKKβ and NEMO. Importantly, administration of the peptide reduced LPS-induced acute inflammation and attenuated Zymosan-induced acute arthritis in mice. These findings suggest that this IKIP peptide may be a promising therapeutic reagent in the prevention and treatment of inflammatory diseases.

Targeting thymidine phosphorylase as a potential therapy for bone loss associated with periprosthetic osteolysis

Macrophages are generally thought to play a key role in the pathogenesis of aseptic loosening through initiating periprosthetic inflammation and pathological bone resorption. The aim of this study was to identify macrophage-derived factors that promote osteoclast differentiation and periprosthetic bone destruction. To achieve this, we examined the effects of 12 macrophage-derived factors that were identified by RNA-seq analysis of stimulated macrophages on osteoclast differentiation. Surprisingly, thymidine phosphorylase (TYMP) was found to trigger significant number of osteoclasts that exhibited resorbing activities on dentine slices. Functionally, TYMP knockdown reduced the number of osteoclasts in macrophages that had been stimulated with polyethylene debris. TYMP were detected in serum and synovial tissues of patients that had been diagnosed with aseptic loosening. Moreover, the administration of TYMP onto calvariae of mice induced pathological bone resorption that was accompanied by an excessive infiltration of inflammatory cells and osteoclasts. The RNA-seq for TYMP-induced-osteoclasts was then performed in an effort to understand action mode of TYMP. TYMP stimulation appeared to activate the tyrosine kinase FYN signaling associated with osteoclast formation. Oral administration of saracatinib, a FYN kinase inhibitor, significantly suppressed formation of bone osteolytic lesions in a polyethylene debris-induced osteolysis model. Our findings highlight a novel molecular target for therapeutic intervention in periprosthetic osteolysis.

KP-10/Gpr54 attenuates rheumatic arthritis through inactivating NF-κB and MAPK signaling in macrophages

Rheumatoid arthritis (RA) is an autoimmune disease mainly characterized as chronic inflammation of joint. Both genetic and environmental factors play important roles in RA progression. G protein-coupled receptor 54 (GPR54) and Kisspeptins (KPs), the natural GRP54 ligands encoded by Kiss-1 gene are known to play important roles in immune regulation but the precise role of KP-10/GPR54 in RA remains elusive. Kiss1/Gpr54 expression was determined by immunohistochemistry on protein and real-time PCR on RNA from isolated RA-patient synovial tissue and PBMC. Collagen-induced arthritis (CIA) mouse models were used to investigate the effect of KP-10/Gpr54 on the rheumatic arthritis severity in the mice. The signaling pathway involved in KP-10/GPR54 was assessed by western blot and immunofluorescence.In the present study, we demonstrated that GPR54 upregulation in bone marrow-derived macrophages (BMDM) was associated with the severity of RA. In addition, Gpr54-/- increased the inflammatory cytokines induced by lipopolysaccharide (LPS) in BMDM and diseased severity of CIA (n = 10), while KP-10 reduced the LPS-induced inflammatory cytokines in vitro and ameliorated the CIA symptoms in vivo. Furthermore, we demonstrated that KP-10/GPR54 binds to PP2A-C to suppressed LPS induced NF-κB and MAPK signaling in BMDM. All these findings suggest that KP-10/GPR54 may be a novel therapeutic target for the diagnosis and treatment of RA.

Inflammatory macrophages exacerbate neutrophil-driven joint damage through ADP/P2Y1 signaling in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that primarily affects the joints and is associated with excessive immune cell infiltration. However, the complex interactions between the immune cell populations in the RA synovium remain unknown. Here, we demonstrate that inflammatory macrophages in the synovium exacerbate neutrophil-driven joint damage in RA through ADP/P2Y₁ signaling. We show that extracellular ADP (eADP) and its receptors are obviously increased in synovial tissues of RA patients as well as collagen-induced arthritis (CIA) mice, and eADP enhances neutrophil infiltration into joints through macrophages producing the chemokine CXCL2, aggravating disease development. Accordingly, the arthritis mouse model had more neutrophils in inflamed joints following ADP injection, whereas P2Y₁ deficiency and pharmacologic inhibition restored arthritis severity to basal levels, suggesting a dominant role of ADP/P2Y₁ signaling in RA pathology. Moreover, cellular activity of ADP/P2Y₁-mediated CXCL2 production was dependent on the G_αq/Ca²⁺-NF-κB/NFAT pathway in macrophages. Overall, this study reveals a non-redundant role of eADP as a trigger in the pathogenesis of RA through neutrophil recruitment and disrupted tissue homeostasis and function.

Macrophages: The Good, the Bad, and the Gluttony

Macrophages are dynamic cells that play critical roles in the induction and resolution of sterile inflammation. In this review, we will compile and interpret recent findings on the plasticity of macrophages and how these cells contribute to the development of non-infectious inflammatory diseases, with a particular focus on allergic and autoimmune disorders. The critical roles of macrophages in the resolution of inflammation will then be examined, emphasizing the ability of macrophages to clear apoptotic immune cells. Rheumatoid arthritis (RA) is a chronic autoimmune-driven spectrum of diseases where persistent inflammation results in synovial hyperplasia and excessive immune cell accumulation, leading to remodeling and reduced function in affected joints. Macrophages are central to the pathophysiology of RA, driving episodic cycles of chronic inflammation and tissue destruction. RA patients have increased numbers of active M1 polarized pro-inflammatory macrophages and few or inactive M2 type cells. This imbalance in macrophage homeostasis is a main contributor to pro-inflammatory mediators in RA, resulting in continual activation of immune and stromal populations and accelerated tissue remodeling. Modulation of macrophage phenotype and function remains a key therapeutic goal for the treatment of this disease. Intriguingly, therapeutic intervention with glucocorticoids or other DMARDs promotes the re-polarization of M1 macrophages to an anti-inflammatory M2 phenotype; this reprogramming is dependent on metabolic changes to promote phenotypic switching. Allergic asthma is associated with Th2-polarised airway inflammation, structural remodeling of the large airways, and airway hyperresponsiveness. Macrophage polarization has a profound impact on asthma pathogenesis, as the response to allergen exposure is regulated by an intricate interplay between local immune factors including cytokines, chemokines and danger signals from neighboring cells. In the Th2-polarized environment characteristic of allergic asthma, high levels of IL-4 produced by locally infiltrating innate lymphoid cells and helper T cells promote the acquisition of an alternatively activated M2a phenotype in macrophages, with myriad effects on the local immune response and airway structure. Targeting regulators of macrophage plasticity is currently being pursued in the treatment of allergic asthma and other allergic diseases. Macrophages promote the re-balancing of pro-inflammatory responses towards pro-resolution responses and are thus central to the success of an inflammatory response. It has long been established that apoptosis supports monocyte and macrophage recruitment to sites of inflammation, facilitating subsequent corpse clearance. This drives resolution responses and mediates a phenotypic switch in the polarity of macrophages. However, the role of apoptotic cell-derived extracellular vesicles (ACdEV) in the recruitment and control of macrophage phenotype has received remarkably little attention. ACdEV are powerful mediators of intercellular communication, carrying a wealth of lipid and protein mediators that may modulate macrophage phenotype, including a cargo of active immune-modulating enzymes. The impact of such interactions may result in repair or disease in different contexts. In this review, we will discuss the origin, characterization, and activity of macrophages in sterile inflammatory diseases and the underlying mechanisms of macrophage polarization via ACdEV and apoptotic cell clearance, in order to provide new insights into therapeutic strategies that could exploit the capabilities of these agile and responsive cells.

Eucommia ulmoides Polysaccharides Attenuate Rabbit Osteoarthritis by Regulating the Function of Macrophages

Background and purpose:Eucommia ulmoides polysaccharides (EUP) can regulate the immunity of macrophages, but the functional status of macrophages is related to osteoarthritis and synovial inflammation. The purpose of this study is to explore whether EUP has the effect of inhibiting osteoarthritis and its possible mechanism.

Methods: MTT test was used to evaluate the appropriate concentration of EUP and real-time quantitative polymerase chain reaction (RT-qPCR) was conducted to detect the effect of EUP on gene expression in RAW 264.7 cells. The osteoarthritis model was constructed by the anterior cruciate ligament transection (ACLT) in the rabbits. These rabbits were divided into three groups, sham operation group, OA group, and EUP group. The changes in articular cartilage were detected by gross observation and histological staining, and Micro-CT tested subchondral bone. Finally, the changes of macrophages in synovial tissue were studied by immunohistochemistry.

Results: The results showed that EUP at the concentration of 50ug/mL and 100ug/mL were beneficial to the proliferation of macrophages. The qPCR results indicated that EUP inhibited the expression of inflammation-related genes IL-6, IL-18 and IL-1β, and promoted the expression of osteogenic and cartilage-related genes BMP-6, Arg-1 and transforming growth factor beta (TGF-β). The results of in vivo experiments suggested that the degree of destruction of articular cartilage in the EUP group was significantly reduced, and the Osteoarthritis Research Society International (OARSI) score was significantly reduced. Compared with the OA group, the subchondral cancellous bone density of the EUP group increased, the number and thickness of trabecular bone increased, and the separation of trabecular bone decreased. Synovial macrophage immunohistochemistry results manifested that EUP, on the one hand, reduced M1 polarized macrophages, on the other hand, accumulated M2 polarized macrophages.

Conclusion: EUP can promote articular cartilage repair and subchondral bone reconstruction. The regulation of the polarization state of macrophages may be one of its mechanisms to delay the progression of osteoarthritis.

TNFR2/14-3-3ε signaling complex instructs macrophage plasticity in inflammation and autoimmunity

TNFR1 and TNFR2 have received prominent attention because of their dominance in the pathogenesis of inflammation and autoimmunity. TNFR1 has been extensively studied and primarily mediates inflammation. TNFR2 remains far less studied, although emerging evidence demonstrates that TNFR2 plays an antiinflammatory and immunoregulatory role in various conditions and diseases. Herein, we report that TNFR2 regulates macrophage polarization, a highly dynamic process controlled by largely unidentified intracellular regulators. Using biochemical copurification and mass spectrometry approaches, we isolated the signaling molecule 14-3-3ε as a component of TNFR2 complexes in response to progranulin stimulation in macrophages. In addition, 14-3-3ε was essential for TNFR2 signaling-mediated regulation of macrophage polarization and switch. Both global and myeloid-specific deletion of 14-3-3ε resulted in exacerbated inflammatory arthritis and counteracted the protective effects of progranulin-mediated TNFR2 activation against inflammation and autoimmunity. TNFR2/14-3-3ε signaled through PI3K/Akt/mTOR to restrict NF-κB activation while simultaneously stimulating C/EBPβ activation, thereby instructing macrophage plasticity. Collectively, this study identifies 14-3-3ε as a previously unrecognized vital component of the TNFR2 receptor complex and provides new insights into the TNFR2 signaling, particularly its role in macrophage polarization with therapeutic implications for various inflammatory and autoimmune diseases with activation of the TNFR2/14-3-3ε antiinflammatory pathway.

Identifying Immune Cell Infiltration and Effective Diagnostic Biomarkers in Rheumatoid Arthritis by Bioinformatics Analysis

Background

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disorder characterized by inflammatory cell infiltration, leading to persistent synovitis and joint destruction. The pathogenesis of RA remains unclear. This study aims to explore the immune molecular mechanism of RA through bioinformatics analysis.

Methods

Five microarray datasets and a high throughput sequencing dataset were downloaded. CIBERSORT algorithm was performed to evaluate immune cell infiltration in synovial tissues between RA and healthy control (HC). Wilcoxon test and Least Absolute Shrinkage and Selection Operator (LASSO) regression were conducted to identify the significantly different infiltrates of immune cells. Differentially expressed genes (DEGs) were screened by "Batch correction" and "RobustRankAggreg" methods. Functional correlation of DEGs were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Candidate biomarkers were identified by cytoHubba of Cytoscape, and their diagnostic effectiveness was predicted by Receiver Operator Characteristic Curve (ROC) analysis. The association of the identified biomarkers with infiltrating immune cells was explored using Spearman's rank correlation analysis in R software.

Results

Ten significantly different types of immune cells between RA and HC were identified. A total of 202 DEGs were obtained by intersection of DEGs screened by two methods. The function of DEGs were significantly associated with immune cells. Five hub genes (CXCR4, CCL5, CD8A, CD247, and GZMA) were screened by R package "UpSet". CCL5+CXCR4 and GZMA+CD8A were verified to have the capability to diagnose RA and early RA with the most excellent specificity and sensitivity, respectively. The correlation between immune cells and biomarkers showed that CCL5 was positively correlated with M1 macrophages, CXCR4 was positively correlated with memory activated CD4+ T cells and follicular helper T (Tfh) cells, and GZMA was positively correlated with Tfh cells.

Conclusions

CCL5, CXCR4, GZMA, and CD8A can be used as diagnostic biomarker for RA. GZMA-Tfh cells, CCL5-M1 macrophages, and CXCR4- memory activated CD4+ T cells/Tfh cells may participate in the occurrence and development of RA, especially GZMA-Tfh cells for the early pathogenesis of RA.

Macrophage as a Peripheral Pain Regulator

A neuroimmune crosstalk is involved in somatic and visceral pathological pain including inflammatory and neuropathic components. Apart from microglia essential for spinal and supraspinal pain processing, the interaction of bone marrow-derived infiltrating macrophages and/or tissue-resident macrophages with the primary afferent neurons regulates pain signals in the peripheral tissue. Recent studies have uncovered previously unknown characteristics of tissue-resident macrophages, such as their origins and association with regulation of pain signals. Peripheral nerve macrophages and intestinal resident macrophages, in addition to adult monocyte-derived infiltrating macrophages, secrete a variety of mediators, such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6, high mobility group box 1 and bone morphogenic protein 2 (BMP2), that regulate the excitability of the primary afferents. Neuron-derived mediators including neuropeptides, ATP and macrophage-colony stimulating factor regulate the activity or polarization of diverse macrophages. Thus, macrophages have multitasks in homeostatic conditions and participate in somatic and visceral pathological pain by interacting with neurons.

Tuning Monocytes and Macrophages for Personalized Therapy and Diagnostic Challenge in Rheumatoid Arthritis

Monocytes/macrophages play a central role in chronic inflammatory disorders, including rheumatoid arthritis (RA). Activation of these cells results in the production of various mediators responsible for inflammation and RA pathogenesis. On the other hand, the depletion of macrophages using specific antibodies or chemical agents can prevent their synovial tissue infiltration and subsequently attenuates inflammation. Their plasticity is a major feature that helps the switch from a pro-inflammatory phenotype (M1) to an anti-inflammatory state (M2). Therefore, understanding the precise strategy targeting pro-inflammatory monocytes/macrophages should be a powerful way of inhibiting chronic inflammation and bone erosion. In this review, we demonstrate potential consequences of different epigenetic regulations on inflammatory cytokines production by monocytes. In addition, we present unique profiles of monocytes/macrophages contributing to identification of new biomarkers of disease activity or predicting treatment response in RA. We also outline novel approaches of tuning monocytes/macrophages by biologic drugs, small molecules or by other therapeutic modalities to reduce arthritis. Finally, the importance of cellular heterogeneity of monocytes/macrophages is highlighted by single-cell technologies, which leads to the design of cell-specific therapeutic protocols for personalized medicine in RA in the future.

New Insights From Single-Cell Sequencing Data: Synovial Fibroblasts and Synovial Macrophages in Rheumatoid Arthritis

Single-cell RNA sequencing (scRNA-seq) technology can analyze the transcriptome expression level of cells with high-throughput from the single cell level, fully show the heterogeneity of cells, and provide a new way for the study of multicellular biological heterogeneity. Synovitis is the pathological basis of rheumatoid arthritis (RA). Synovial fibroblasts (SFs) and synovial macrophages are the core target cells of RA, which results in the destruction of articular cartilage, as well as bone. Recent scRNA-seq technology has made breakthroughs in the differentiation and development of two types of synovial cells, identification of subsets, functional analysis, and new therapeutic targets, which will bring remarkable changes in RA treatment.

Cinnamaldehyde Attenuates the Progression of Rheumatoid Arthritis through Down-Regulation of PI3K/AKT Signaling Pathway

Cinnamaldehyde (CA), as an active compound isolated from the bark of Cinnamomum cassia, has been reported to possess the anti-fungal, anti-bacterial, anti-inflammatory, anti-mutagenic, and anti-oxidant properties. However, the possible effects and underlying mechanisms of CA on rheumatoid arthritis (RA) have not been revealed yet. In the present study, we found that CA obviously improved the type II collagen-induced RA in rats, accompanied with decreasing pro-inflammatory factors, proliferation and metastasis. In addition, CA decreased the expression levels of TNF-α, IL-1β, and IL-6 in RA-FLSs. Besides, CA remarkably inhibited the proliferation, downregulated the EdU-positive cells, and promoted apoptosis of RA-FLSs by CCK-8, EdU and flow cytometry analysis. Moreover, the results of wound healing, transwell migration and invasion assays showed that CA inhibited the migration and invasion of RA-FLSs. Further, western blot experiment showed CA inhibited the activation of PI3K/AKT signaling pathway in RA-FLSs. Finally, 740Y-P, the PI3K/AKT signaling pathway activator, could reverse the effects of CA on the proliferation and metastasis in RA-FLSs. In conclusion, we confirmed that CA exhibited potential therapeutic properties against RA via suppressing proliferation and metastasis of RA-FLSs by blockage of PI3K/AKT signaling pathway. Therefore, our study provides evidence that CA may emerge as a therapeutic option for RA treatment.

IFN-γ Drives Human Monocyte Differentiation into Highly Proinflammatory Macrophages That Resemble a Phenotype Relevant to Psoriasis

As key cells of the immune system, macrophages coordinate the activation and regulation of the immune response. Macrophages present a complex phenotype that can vary from homeostatic, proinflammatory, and profibrotic to anti-inflammatory phenotypes. The factors that drive the differentiation from monocyte to macrophage largely define the resultant phenotype, as has been shown by the differences found in M-CSF- and GM-CSF-derived macrophages. We explored alternative inflammatory mediators that could be used for in vitro differentiation of human monocytes into macrophages. IFN-γ is a potent inflammatory mediator produced by lymphocytes in disease and infections. We used IFN-γ to differentiate human monocytes into macrophages and characterized the cells at a functional and proteomic level. IFN-γ alone was sufficient to generate macrophages (IFN-γ Mϕ) that were phagocytic and responsive to polarization. We demonstrate that IFN-γ Mϕ are potent activators of T lymphocytes that produce IL-17 and IFN-γ. We identified potential markers (GBP-1, IP-10, IL-12p70, and IL-23) of IFN-γ Mϕ and demonstrate that these markers are enriched in the skin of patients with inflamed psoriasis. Collectively, we show that IFN-γ can drive human monocyte to macrophage differentiation, leading to bona fide macrophages with inflammatory characteristics.

Lipidated Methotrexate Microbubbles: A Promising Rheumatoid Arthritis Theranostic Medicine Manipulated via Ultrasonic Irradiation

De novo designed lipidated methotrexate was synthesized and self-assembled into microbubbles for targeted rheumatoid arthritis theranostic treatment. Controlled lipidatedmethotrexate delivery was achieved by ultrasound-targetedmicrobubble destruction technique. Methotrexate was dissociated inflammatory microenvironment of synovial cavity, owing to representive low pH and enriched leucocyte esterase. We first manipulated methotrexate controlled release with RAW 264.7 cell line in vitro and further verified with rheumatoid arthritis rabbits in vivo. Results showed that lipidated methotrexate microbubbles precisely affected infection focus and significantly enhanced rheumatoid arthritis curative effect comparing with dissociative methotrexate. This study indicates that lipidated methotrexate microbubbles might be considered as a promising rheumatoid arthritis theranostics medicine.

Liver X receptors conserve the therapeutic target potential for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic multi-system autoimmune disease with extremely complex pathogenesis. Significantly altered lipid paradox related to the inflammatory burden is reported in RA patients, inducing 50% higher cardiovascular risks. Recent studies have also demonstrated that lipid metabolism can regulate many functions of immune cells in which metabolic pathways have altered. The nuclear liver X receptors (LXRs), including LXRα and LXRβ, play a central role in regulating lipid homeostasis and inflammatory responses. Undoubtedly, LXRs have been considered as an attractive therapeutic target for the treatment of RA. However, there are some contradictory effects of LXRs agonists observed in previous animal studies where both pro-inflammatory role and anti-inflammatory role were revealed for LXRs activation in RA. Therefore, in addition to updating the knowledge of LXRs as the prominent regulators of lipid homeostasis, the purpose of this review is to summarize the effects of LXRs agonists in RA-associated immune cells, to explore the underlying reasons for the contradictory therapeutic effects of LXRs agonists observed in RA animal models, and to discuss future strategy for the treatment of RA with LXRs modulators.

A Tale of Two Immune Cells in Rheumatoid Arthritis: The Crosstalk Between Macrophages and T Cells in the Synovium

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease. Joint inflammation of RA is closely related to infiltration of immune cells, synovium hyperplasia, and superfluous secretion of proinflammatory cytokines, which lead to cartilage degradation and bone erosion. The joint synovium of RA patients contains a variety of immune cellular types, among which monocytes/macrophages and T cells are two essential cellular components. Monocytes/macrophages can recruit and promote the differentiation of T cells into inflammatory phenotypes in RA synovium. Similarly, different subtypes of T cells can recruit monocytes/macrophages and promote osteoblast differentiation and production of inflammatory cytokines. In this review, we will discuss how T cell-monocyte/macrophage interactions promote the development of RA, which will provide new perspectives on RA pathogenesis and the development of targeted therapy.

MS-Based HLA-II Peptidomics Combined With Multiomics Will Aid the Development of Future Immunotherapies

Immunotherapies have emerged to treat diseases by selectively modulating a patient's immune response. Although the roles of T and B cells in adaptive immunity have been well studied, it remains difficult to select targets for immunotherapeutic strategies. Because human leukocyte antigen class II (HLA-II) peptides activate CD4+ T cells and regulate B cell activation, proliferation, and differentiation, these peptide antigens represent a class of potential immunotherapy targets and biomarkers. To better understand the molecular basis of how HLA-II antigen presentation is involved in disease progression and treatment, systematic HLA-II peptidomics combined with multiomic analyses of diverse cell types in healthy and diseased states is required. For this reason, MS-based innovations that facilitate investigations into the interplay between disease pathologies and the presentation of HLA-II peptides to CD4+ T cells will aid in the development of patient-focused immunotherapies.

Metabolically engineered stem cell–derived exosomes to regulate macrophage heterogeneity in rheumatoid arthritis

Despite the remarkable advances in therapeutics for rheumatoid arthritis (RA), a large number of patients still lack effective countermeasures. Recently, the reprogramming of macrophages to an immunoregulatory phenotype has emerged as a promising therapeutic strategy for RA. Here, we report metabolically engineered exosomes that have been surface-modified for the targeted reprogramming of macrophages. Qualified exosomes were readily harvested from metabolically engineered stem cells by tangential flow filtration at a high yield while maintaining their innate immunomodulatory components. When systemically administered into mice with collagen-induced arthritis, these exosomes effectively accumulated in the inflamed joints, inducing a cascade of anti-inflammatory events via macrophage phenotype regulation. The level of therapeutic efficacy obtained with bare exosomes was achievable with the engineered exosomes of 10 times less dose. On the basis of the boosted nature to reprogram the synovial microenvironment, the engineered exosomes display considerable potential to be developed as a next-generation drug for RA.

Tumor Necrosis Factor-α Blockade Corrects Monocyte/Macrophage Imbalance in Primary Immune Thrombocytopenia

Primary immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder. Monocytes and macrophages are the major cells involved in autoantibody-mediated platelet clearance in ITP. In the present study, we found increased percentages of peripheral blood proinflammatory CD16+ monocytes and elevated frequencies of splenic tumor necrosis factor-α (TNF-α)-expressing macrophages in ITP patients compared with healthy controls. Concurrently, we observed elevated TNF-α secretion in plasma as well as higher TNF-α mRNA expression in total peripheral blood mononuclear cells and CD14+ monocytes of ITP patients. Of note, in vitro TNF-α blockade with neutralizing antibody remarkably reduced polarization to M1 macrophages by inhibiting the nuclear factor kappa B (NF-κB) signaling pathway. Moreover, TNF-α blockade dampened macrophage phagocytosis and T cell stimulatory capacity. Finally, in passive and active murine models of ITP, anti-TNF-α therapy reduced the number of nonclassical monocytes and M1 macrophages, ameliorated the retention of platelets in spleen and liver, and increased the platelet count of ITP mice. Taken together, TNF-α blockade decreased the number and function of proinflammatory subsets of monocytes and macrophages by inhibiting the NF-κB signaling pathway, leading to remarkable attenuation of antibody-mediated platelet destruction. Thus, TNF-α blockade may be a promising therapeutic strategy for the management of ITP.

Integration of Immunome With Disease-Gene Network Reveals Common Cellular Mechanisms Between IMIDs and Drug Repurposing Strategies

Objective

Development and progression of immune-mediated inflammatory diseases (IMIDs) involve intricate dysregulation of the disease-associated genes (DAGs) and their expressing immune cells. Identifying the crucial disease-associated cells (DACs) in IMIDs has been challenging due to the underlying complex molecular mechanism.

Methods

Using transcriptome profiles of 40 different immune cells, unsupervised machine learning, and disease-gene networks, we constructed the Disease-gene IMmune cell Expression (DIME) network and identified top DACs and DAGs of 12 phenotypically different IMIDs. We compared the DIME networks of IMIDs to identify common pathways between them. We used the common pathways and publicly available drug-gene network to identify promising drug repurposing targets.

Results

We found CD4+Treg, CD4+Th1, and NK cells as top DACs in inflammatory arthritis such as ankylosing spondylitis (AS), psoriatic arthritis, and rheumatoid arthritis (RA); neutrophils, granulocytes, and BDCA1+CD14+ cells in systemic lupus erythematosus and systemic scleroderma; ILC2, CD4+Th1, CD4+Treg, and NK cells in the inflammatory bowel diseases (IBDs). We identified lymphoid cells (CD4+Th1, CD4+Treg, and NK) and their associated pathways to be important in HLA-B27 type diseases (psoriasis, AS, and IBDs) and in primary-joint-inflammation-based inflammatory arthritis (AS and RA). Based on the common cellular mechanisms, we identified lifitegrast as a potential drug repurposing candidate for Crohn's disease and other IMIDs.

Conclusions

Existing methods are inadequate in capturing the intricate involvement of the crucial genes and cell types essential to IMIDs. Our approach identified the key DACs, DAGs, common mechanisms between IMIDs, and proposed potential drug repurposing targets using the DIME network. To extend our method to other diseases, we built the DIME tool (https://bitbucket.org/systemsimmunology/dime/) to help scientists uncover the etiology of complex and rare diseases to further drug development by better-determining drug targets, thereby mitigating the risk of failure in late clinical development.

G protein-coupled receptor kinase 5 deletion suppresses synovial inflammation in a murine model of collagen antibody-induced arthritis

G protein-coupled receptor kinase 5 (GRK5) regulates inflammatory responses via the nuclear factor-kappa B (NF-κB) pathway. This study investigated the functional involvement of GRK5 in the pathogenesis of inflammatory arthritis. Immunohistochemically, rheumatoid arthritis (RA) synovium had a significantly higher proportion of GRK5-positive cells in the synovial lining layer than healthy control synovium. Gene expression and NF-κB activation in lipopolysaccharide-stimulated human SW982 synovial cells were significantly suppressed by silencing of the GRK5 gene. Similarly, GRK5 kinase activity inhibition in human primary RA synovial cells attenuated gene expressions of inflammatory factors. In a murine model of collagen antibody-induced arthritis, arthritis scores and serum IL6 production of GRK5 knockout (GRK5^-/-) mice were significantly lower than those of wild-type mice. Histologically, the degree of synovitis and cartilage degeneration in GRK5^-/- mice was significantly lower than in wild-type mice. In in vitro analyses using activated murine macrophages and fibroblast-like synoviocytes, gene expression of inflammatory factors and p65 nuclear translocation were significantly lower in GRK5^-/- mice compared to wild-type mice. In conclusion, our results suggested that GRK5 is deeply involved in the pathogenesis of inflammatory arthritis, therefore, GRK5 inhibition could be a potential therapeutic target for types of inflammatory arthritis such as RA.

Comparative Analysis on Abnormal Methylome of Differentially Expressed Genes and Disease Pathways in the Immune Cells of RA and SLE

We identified abnormally methylated, differentially expressed genes (DEGs) and pathogenic mechanisms in different immune cells of RA and SLE by comprehensive bioinformatics analysis. Six microarray data sets of each immune cell (CD19⁺ B cells, CD4⁺ T cells and CD14⁺ monocytes) were integrated to screen DEGs and differentially methylated genes by using R package “limma.” Gene ontology annotations and KEGG analysis of aberrant methylome of DEGs were done using DAVID online database. Protein-protein interaction (PPI) network was generated to detect the hub genes and their methylation levels were compared using DiseaseMeth 2.0 database. Aberrantly methylated DEGs in CD19⁺ B cells (173 and 180), CD4⁺ T cells (184 and 417) and CD14⁺ monocytes (193 and 392) of RA and SLE patients were identified. We detected 30 hub genes in different immune cells of RA and SLE and confirmed their expression using FACS sorted immune cells by qPCR. Among them, 12 genes (BPTF, PHC2, JUN, KRAS, PTEN, FGFR2, ALB, SERB-1, SKP2, TUBA1A, IMP3, and SMAD4) of RA and 12 genes (OAS1, RSAD2, OASL, IFIT3, OAS2, IFIH1, CENPE, TOP2A, PBK, KIF11, IFIT1, and ISG15) of SLE are proposed as potential biomarker genes based on receiver operating curve analysis. Our study suggests that MAPK signaling pathway could potentially differentiate the mechanisms affecting T- and B- cells in RA, whereas PI3K pathway may be used for exploring common disease pathways between RA and SLE. Compared to individual data analyses, more dependable and precise filtering of results can be achieved by integrating several relevant data sets.

Macrophage Plasticity and Atherosclerosis Therapy

Atherosclerosis is a chronic disease starting with the entry of monocytes into the subendothelium and the subsequent differentiation into macrophages. Macrophages are the major immune cells in atherosclerotic plaques and are involved in the dynamic progression of atherosclerotic plaques. The biological properties of atherosclerotic plaque macrophages determine lesion size, composition, and stability. The heterogenicity and plasticity of atherosclerotic macrophages have been a hotspot in recent years. Studies demonstrated that lipids, cytokines, chemokines, and other molecules in the atherosclerotic plaque microenvironment regulate macrophage phenotype, contributing to the switch of macrophages toward a pro- or anti-atherosclerosis state. Of note, M1/M2 classification is oversimplified and only represent two extreme states of macrophages. Moreover, M2 macrophages in atherosclerosis are not always protective. Understanding the phenotypic diversity and functions of macrophages can disclose their roles in atherosclerotic plaques. Given that lipid-lowering therapy cannot completely retard the progression of atherosclerosis, macrophages with high heterogeneity and plasticity raise the hope for atherosclerosis regression. This review will focus on the macrophage phenotypic diversity, its role in the progression of the dynamic atherosclerotic plaque, and finally discuss the possibility of treating atherosclerosis by targeting macrophage microenvironment.

PAQR11 modulates monocyte-to-macrophage differentiation and pathogenesis of rheumatoid arthritis

During inflammation or tissue injury, pro-inflammatory mediators attract migratory monocytes to inflammatory sites and monocyte-to-macrophage differentiation occurs to activate macrophages. We report here that PAQR11, a member of the progesterone and AdipoQ receptor family, regulates monocyte-to-macrophage differentiation in vitro and in vivo. Paqr11 gene was highly induced during monocyte-to-macrophage differentiation. Knockdown or deletion of Paqr11 inhibited monocyte differentiation but had little effect on macrophage polarization. Mechanistically, PAQR11 promoted cell survival as apoptosis was increased by Paqr11 knockdown or deletion. Activation of the MAPK signalling pathway was involved in the regulatory role of PAQR11 on monocyte differentiation and cell survival. C/EBPβ regulated the expression of Paqr11 at the transcriptional level. In mice, deletion of Paqr11 gene alleviated progression of collagen-induced rheumatoid arthritis. Thus, these results provide strong evidence that PAQR11 has a function in monocyte-to-macrophage differentiation and such function is related to autoimmune disease in vivo.

Novel approaches to develop biomarkers predicting treatment responses to TNF-blockers

Introduction: Chronic inflammatory diseases (CIDs) cause significant morbidity and are a considerable burden for the patients in terms of pain, impaired function, and diminished quality of life. Important progress in CID treatment has been obtained with biological therapies, such as tumor-necrosis-factor blockers. However, more than a third of the patients fail to respond to these inhibitors and are exposed to the side effects of treatment, without the benefits. Therefore, there is a strong interest in developing tools to predict response of patients to biologics. Areas covered: The authors searched PubMed for recent studies on biomarkers for disease assessment and prediction of therapeutic responses, focusing on the effect of TNF blockers on immune responses in spondyloarthritis (SpA), and other CID, in particular rheumatoid arthritis and inflammatory bowel disease. Conclusions will be drawn about the possible development of predictive biomarkers for response to treatment. Expert opinion: No validated biomarker is currently available to predict treatment response in CID. New insight could be generated through the development of new bioinformatic modeling approaches to combine multidimensional biomarkers that explain the different genetic, immunological and environmental determinants of therapeutic responses.

Chromatin accessibility landscapes of immune cells in rheumatoid arthritis nominate monocytes in disease pathogenesis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that involves a variety of cell types. However, how the epigenetic dysregulations of peripheral immune cells contribute to the pathogenesis of RA still remains largely unclear.

RESULTS

Here, we analysed the genome-wide active DNA regulatory elements of four major immune cells, namely monocytes, B cells, CD4⁺ T cells and CD8⁺ T cells, in peripheral blood of RA patients, osteoarthritis (OA) patients and healthy donors using Assay of Transposase Accessible Chromatin with sequencing (ATAC-seq). We found a strong RA-associated chromatin dysregulation signature in monocytes, but no other examined cell types. Moreover, we found that serum C-reactive protein (CRP) can induce the RA-associated chromatin dysregulation in monocytes via in vitro experiments. And the extent of this dysregulation was regulated through the transcription factor FRA2.

CONCLUSIONS

Together, our study revealed a CRP-induced pathogenic chromatin dysregulation signature in monocytes from RA patients and predicted the responsible signalling pathway as potential therapeutic targets for the disease.

Immune response profiling of patients with spondyloarthritis reveals signalling networks mediating TNF-blocker function in vivo

OBJECTIVES

Antitumour necrosis factor (TNF) therapy has revolutionised treatment of several chronic inflammatory diseases, including spondyloarthritis (SpA). However, TNF inhibitors (TNFi) are not effective in all patients and the biological basis for treatment failure remains unknown. We have analysed induced immune responses to define the mechanism of action of TNF blockers in SpA and to identify immunological correlates of responsiveness to TNFi.

METHODS

Immune responses to microbial and pathway-specific stimuli were analysed in peripheral blood samples from 80 patients with axial SpA before and after TNFi treatment, using highly standardised whole-blood stimulation assays. Cytokines and chemokines were measured in a Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory, and gene expression was monitored using nCounter assays.

RESULTS

Anti-TNF therapy induced profound changes in patients' innate immune responses. TNFi action was selective, and had only minor effects on Th1/Th17 immunity. Modular transcriptional repertoire analysis identified prostaglandin E2 synthesis and signalling, leucocyte recirculation, macrophage polarisation, dectin and interleukin (IL)-1 signalling, as well as the nuclear factor kappa B (NF-kB) transcription factor family as key pathways targeted by TNF blockers in vivo. Analysis of induced immune responses before treatment initiation revealed that expression of molecules associated with leucocyte adhesion and invasion, chemotaxis and IL-1 signalling are correlated with therapeutic responses to anti-TNF.

CONCLUSIONS

We show that TNFi target multiple immune cell pathways that cooperate to resolve inflammation. We propose that immune response profiling provides new insight into the biology of TNF-blocker action in patients and can identify signalling pathways associated with therapeutic responses to biological therapies.

Current Status of Functional Studies on Circular RNAs in Rheumatoid Arthritis and Their Potential Role as Diagnostic Biomarkers

Circular RNAs (circRNAs), a new class of endogenous non-coding RNAs (ncRNAs), are highly stable and exhibit tissue-specific expression. Accumulating evidence has indicated that circRNAs play crucial roles in the development and progression of multiple diseases. Notably, circRNAs, important epigenetic modulators of gene expression in inflammation and autoimmune regulation, have a close association with the pathogenesis of rheumatoid arthritis (RA). RA, one of the most common systemic autoimmune diseases, is characterized by synovial hyperplasia and inflammation, and cartilage and bone destruction. Here, we focus on the roles of circRNAs in macrophage, synovial tissues, fibroblast-like synoviocytes (FLSs), and cartilage tissues in pathogenesis and progression of RA, highlighting the potential of circRNAs in the blood as diagnostic biomarkers, and aiming at providing new insights into the diagnosis and therapy of this disease.

Intermediate monocytes correlate with CXCR3+ Th17 cells but not with bone characteristics in untreated early rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is associated with development of generalized osteoporosis. Bone-degrading osteoclasts are derived from circulating precursor cells of monocytic lineage, and the intermediate monocyte population is important as osteoclast precursors in inflammatory conditions. T cells of various subsets are critical in the pathogenesis of both RA and associated osteoporosis, but so far, no studies have examined associations between circulating intermediate monocytes, T cell subsets and bone characteristics in patients with RA. The aim of this study was to investigate the frequency of intermediate monocytes in patients with untreated early rheumatoid arthritis (ueRA) compared to healthy controls (HC), and to explore the correlation between intermediate monocytes and a comprehensive panel of T helper cell subsets, bone density and bone microarchitecture in ueRA patients.

METHODS

78 patients with ueRA fulfilling the ACR/EULAR 2010 criteria were included and compared to 29 age- and sex-matched HC. Peripheral blood samples were obtained before start of treatment and proportions of monocyte subsets and CD4+ helper and regulatory T cell subsets were analyzed by flow cytometry. Bone densitometry was performed on 46 of the ueRA patients at inclusion using DXA and HR-pQCT.

RESULTS

Flow cytometric analyses showed that the majority of ueRA patients had frequencies of intermediate monocytes comparable to HC. The intermediate monocyte population correlated positively with CXCR3+ Th17 cells in ueRA patients but not in HC. However, neither the proportions of intermediate monocytes nor CXCR3+ Th17 cells were associated with bone density or bone microarchitecture measurements.

CONCLUSIONS

Our findings suggest that in early RA, the intermediate monocytes do not correlate with bone characteristics, despite positive correlation with circulating CXCR3+ Th17 cells. Future longitudinal studies in patients with longer disease duration are required to fully explore the potential of intermediate monocytes to drive bone loss in RA.

Neuroimmune interactions and osteoarthritis pain: focus on macrophages

Bidirectional interactions between the immune system and the nervous system are increasingly appreciated as playing a pathogenic role in chronic pain. Unraveling the mechanisms by which inflammatory pain is mediated through communication between nerves and immune cells may lead to exciting new strategies for therapeutic intervention. In this narrative review, we focus on the role of macrophages in the pathogenesis of osteoarthritis (OA) pain. From regulating homeostasis to conducting phagocytosis, and from inducing inflammation to resolving it, macrophages are plastic cells that are highly adaptable to their environment. They rely on communicating with the environment through cytokines, growth factors, neuropeptides, and other signals to respond to inflammation or injury. The contribution of macrophages to OA joint damage has garnered much attention in recent years. Here, we discuss how macrophages may participate in the initiation and maintenance of pain in OA. We aim to summarize what is currently known about macrophages in OA pain and identify important gaps in the field to fuel future investigations.

Proteinase-Mediated Macrophage Signaling in Psoriatic Arthritis

Objective

Multiple proteinases are present in the synovial fluid (SF) of an arthritic joint. We aimed to identify inflammatory cell populations present in psoriatic arthritis (PsA) SF compared to osteoarthritis (OA) and rheumatoid arthritis (RA), identify their proteinase-activated receptor 2 (PAR2) signaling function and characterize potentially active SF serine proteinases that may be PAR2 activators.

Methods

Flow cytometry was used to characterize SF cells from PsA, RA, OA patients; PsA SF cells were further characterized by single cell 3’-RNA-sequencing. Active serine proteinases were identified through cleavage of fluorogenic trypsin- and chymotrypsin-like substrates, activity-based probe analysis and proteomics. Fluo-4 AM was used to monitor intracellular calcium cell signaling. Cytokine expression was evaluated using a multiplex Luminex panel.

Results

PsA SF cells were dominated by monocytes/macrophages, which consisted of three populations representing classical, non-classical and intermediate cells. The classical monocytes/macrophages were reduced in PsA compared to OA/RA, whilst the intermediate population was increased. PAR2 was elevated in OA vs. PsA/RA SF monocytes/macrophages, particularly in the intermediate population. PAR2 expression and signaling in primary PsA monocytes/macrophages significantly impacted the production of monocyte chemoattractant protein-1 (MCP-1). Trypsin-like serine proteinase activity was elevated in PsA and RA SF compared to OA, while chymotrypsin-like activity was elevated in RA compared to PsA. Tryptase-6 was identified as an active serine proteinase in SF that could trigger calcium signaling partially via PAR2.

Conclusion

PAR2 and its activating proteinases, including tryptase-6, can be important mediators of inflammation in PsA. Components within this proteinase-receptor axis may represent novel therapeutic targets.

Rheumatoid cachexia: the underappreciated role of myoblast, macrophage and fibroblast interplay in the skeletal muscle niche

Although rheumatoid arthritis affects 1% of the global population, the role of rheumatoid cachexia, which occurs in up to a third of patients, is relatively neglected as research focus, despite its significant contribution to decreased quality of life in patients. A better understanding of the cellular and molecular processes involved in rheumatoid cachexia, as well as its potential treatment, is dependent on elucidation of the intricate interactions of the cells involved, such as myoblasts, fibroblasts and macrophages. Persistent RA-associated inflammation results in a relative depletion of the capacity for regeneration and repair in the satellite cell niche. The repair that does proceed is suboptimal due to dysregulated communication from the other cellular role players in this multi-cellular environment. This includes the incomplete switch in macrophage phenotype resulting in a lingering pro-inflammatory state within the tissues, as well as fibroblast-associated dysregulation of the dynamic control of the extracellular matrix. Additional to this endogenous dysregulation, some treatment strategies for RA may exacerbate muscle wasting and no multi-cell investigation has been done in this context. This review summarizes the most recent literature characterising clinical RA cachexia and links these features to the roles of and complex communication between multiple cellular contributors in the muscle niche, highlighting the importance of a targeted approach to therapeutic intervention.

Gold Nanomaterial Engineering for Macrophage-Mediated Inflammation and Tumor Treatment

Macrophages play an important role in the body's immune defense process. Phenotype imbalance between M1 and M2 macrophages induced by inflammation-related disorders and tumor can also be reversibly converted to treat these diseases. As exogenous substances, a large part of gold-based nanomaterials interact with macrophages once they enter the body, which provides gold nanomaterials a huge advantage to act as imaging contrasts, active substance carriers, and therapeutic agents for macrophage modulation. By cutting off macrophage recruitment, inhibiting macrophage activities, and modulating M1/M2 polarization, gold nanomaterial engineering exerts therapeutic effects on inflammation-related diseases at target sites. In this review, biological functions of macrophages in inflammation-related diseases are introduced, the effect of physicochemical factors of gold nanomaterials including size, shape, and surface chemistry is focused on the interaction between macrophages and gold nanomaterials, and the applications of gold nanomaterials are elaborated for tracking and treating these diseases by macrophages. The rational and smart engineering of gold nanomaterials allows a promising platform for macrophage-mediated inflammation and tumor imaging and treatment.

Novel insights into macrophage diversity in rheumatoid arthritis synovium

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease affecting joints and causing progressive damage and disability. Macrophages are of critical importance in the initiation and perpetuation of synovitis in RA, they can function as antigen presenting cells leading to T-cell dependent B-cell activation, assume a variety of inflammatory cell states with the production of destructive cytokines, but also contribute to tissue homeostasis/repair. The recent development of high-throughput technologies, including bulk and single cells RNA-sequencing, has broadened our understanding of synovial cell diversity, and opened novel perspectives to the discovery of new potential therapeutic targets in RA. In this review, we will focus on the relationship between the synovial macrophage infiltration and clinical disease severity and response to treatment. We will then provide a state-of-the-art picture of the biological roles of synovial macrophages and distinct macrophage subsets described in RA. Finally, we will review the effects of approved conventional and biologic drugs on the synovial macrophage component and highlight the therapeutic potential of future strategies to re-program macrophage phenotypes in RA.

Suppression of macrophage migration by down-regulating Src/FAK/P130Cas activation contributed to the anti-inflammatory activity of sinomenine

A large number of macrophages in inflamed sites not only amplify the severity of inflammatory responses but also contribute to the deleterious progression of many chronic inflammatory diseases, autoimmune diseases and cancers. Macrophage migration is a prerequisite for their entry into inflammatory sites and their participation of macrophages in the pathologic processes. Inhibition of macrophage migration is therefore a potential anti-inflammatory mechanism. Moreover, alleviation of inflammation also prevents the macrophages infiltration. Sinomenine (SIN) is an alkaloid derived from the Chinese medicinal plant Sinomenium acutum. It has multiple pharmacological effects, including anti-inflammation, immunosuppression, and anti-arthritis. However, its anti-inflammatory molecular mechanisms and effect on macrophage migration are not fully understood. The purpose of this research was to investigate the pharmacological effects and the molecular mechanism of SIN on macrophage migration in vivo and in vitro as well as to elucidate its anti-inflammatory mechanisms associated with macrophage migration. Our results showed that SIN reduced the number of RAW264.7 cells migrating into inflammatory paws and blocked lipopolysaccharide (LPS)-induced RAW264.7 cells and bone marrow-derived macrophages (BMDMs) migration in vitro. Furthermore, SIN attenuated the 3D mesenchymal migration of BMDMs. The absence of macrophage migration after circulatory and periphery macrophages depletion led to a reduction in the severity of inflammatory response. In macrophages depleted (macrophages^-/-) mice, as inflammatory severity decreased, RAW264.7 cells migration was suppressed. A non-obvious effect of SIN on the inflammatory response was found in macrophages^-/- mice, while the inhibitory effect of SIN on RAW264.7 cells migration was still observed. Furthermore, the migration of RAW264.7 cells pre-treated with SIN was suppressed in normal mice. Finally, Src/focal adhesion kinase (FAK)/P130Cas axis activation, which supports macrophages mesenchymal migration, and iNOS expression, NO production, integrin αV and in integrin β3 expressions, which promote Src/FAK/P130Cas activation, were down-regulated by SIN. However, SIN had no obvious effect on the expression of the monocyte chemoattractant protein-1 (MCP-1), which is an important chemokine for macrophage migration. These results indicated that SIN significantly inhibited macrophage mesenchymal migration by down-regulating on Src/FAK/P130Cas axis activation. There was a mutual regulatory correlation between the inflammatory response and macrophage migration, and the effects of SIN on macrophage migration were involved in its anti-inflammatory activity.

The therapeutic applications of mesenchymal stromal cells from human perinatal tissues in autoimmune diseases

The autoimmune diseases are characterized by overactivation of immune cells, chronic inflammation, and immune response to self-antigens, leading to the damage and dysfunction of multiple organs. Patients still do not receive desired clinical outcomes while suffer from various adverse effects imparted by current therapies. The therapeutic strategies based on mesenchymal stromal cell (MSC) transplantation have become the promising approach for the treatment of autoimmune diseases due to the immunomodulation property of MSCs. MSCs derived from perinatal tissues are collectively known as perinatal MSCs (PMSCs), which can be obtained via painless procedures from donors with lower risk of being contaminated by viruses than those MSCs from adult tissue sources. Therefore, PMSCs may be the ideal cell source for the treatment of autoimmune diseases. This article summarizes recent progress and possible mechanisms of PMSCs in treating autoimmune diseases in animal experiments and clinical studies. This review also presents existing challenges and proposes solutions, which may provide new hints on PMSC transplantation as a therapeutic strategy for the treatment of autoimmune diseases.

LncRNA H19 regulates macrophage polarization and promotes Freund's complete adjuvant-induced arthritis by upregulating KDM6A

Aberrant expression of long non-coding RNA (lncRNA) H19 is tightly linked to multiple steps of tumorigenesis via the modulation of cell proliferation and apoptosis; however, the pathological significance and regulatory mechanisms of lncRNA H19 in macrophages remain obscure. To investigate whether lncRNA H19 modulates macrophage activation in rheumatoid arthritis (RA), lncRNA H19 levels in PMA-induced PBMC from patients with RA and healthy volunteers were assessed. In addition, the distribution of macrophage subsets, macrophage phenotypic characteristics, and pro-inflammatory gene expression were examined in lncRNA H19 smart silencer- or pcDNA 3.1- H19-transfected macrophages and AAV8-mediated H19 overexpression in a Freund' s complete adjuvant-induced arthritis mouse model. The level of lncRNA H19 was higher in RA patients than in healthy volunteers. Silencing of lncRNA H19 altered lipopolysaccharide plus interferon-induced M1 macrophage polarization and decreased IL-6, CD80, CCL8, and CXCL10 expression in macrophages of RA patients. LncRNA H19 overexpression markedly induced IL-6, CD80, HLA-DR, KDM6A, STAT1, IRF5, CCL8, CXCL9, CXCL10, and CXCL11 expression in macrophages and promoted macrophage migration. AAV8-mediated H19 overexpression aggravated arthritis in mice by promoting M1 macrophage polarization along with iNOS, IL-6, CCL8, CXCL9, CXCL10, CXCL11, MMP3, MMP13 and COX-2 expression in mononuclear cells isolated from the swollen ankle. GSK-J4, an inhibitor of KDM6A, suppressed the activity of lncRNA H19 in macrophages and ameliorated lncRNA H19-aggravated arthritis. In summary, the current study demonstrated that lncRNA H19 is upregulated in RA patients and arthritic mice. LncRNA H19 promotes M1 macrophage polarization and aggravates arthritis by upregulating KDM6A expression.

Substance P blocks β-aminopropionitrile-induced aortic injury through modulation of M2 monocyte-skewed monocytopoiesis

Aortic injuries, including aortic aneurysms and dissections, are fatal vascular diseases with distinct histopathological features in the aortic tissue such as inflammation-induced endothelial dysfunction, infiltration of immune cells, and breakdown of the extracellular matrix. Few treatments are available for treating aortic aneurysms and dissections; thus, basic and clinical studies worldwide have been attempted to inhibit disease progression. Substance P (SP) exerts anti-inflammatory effects and promotes restoration of the damaged endothelium, leading to vasculature protection and facilitation of tissue repair. This study was conducted to explore the protective effects of systemically injected SP on thoracic aortic injury (TAI). A TAI animal model was induced by orally administering β-aminopropionitrile to rats for 6 weeks. β-aminopropionitrile blocked crosslinking ECM in aorta to cause structural alteration with inflammation within 1 week and then, induced aortic dissection within 4 weeks of initiating treatment, leading to mortality within 6 weeks. Treatment of TAI rats with SP-induced anti-inflammatory responses systemically and locally, possibly by enriching anti-inflammatory M2 monocytes in the spleen and peripheral blood at early phase of aortic injury due to β-aminopropionitrile. SP-induced immune suppression finally prevented the development of aortic dissection by limiting inflammation-mediated aortic destruction. Taken together, these results suggest that SP treatment can block aortic injury by controlling the immune-cell profile and suppressing proinflammatory responses during the initial stage of vascular disease progression.

HLA-DRB1 allelic epitopes that associate with autoimmune disease risk or protection activate reciprocal macrophage polarization

Associations between particular human leukocyte antigen (HLA) alleles and susceptibility to-or protection from-autoimmune diseases have been long observed. Allele-specific antigen presentation (AP) has been widely proposed as a culprit, but it is unclear whether HLA molecules might also have non-AP, disease-modulating effects. Here we demonstrate differential macrophage activation by HLA-DRB1 alleles known to associate with autoimmune disease risk or protection with resultant polarization of pro-inflammatory ("M1") versus anti-inflammatory ("M2") macrophages, respectively. RNA-sequencing analyses of in vitro-polarized macrophages in the presence of AP-incompetent short synthetic peptides corresponding to the third allelic hypervariable regions coded by those two HLA-DRB1 alleles showed reciprocal activation of pro- versus anti-inflammatory transcriptomes, with implication of corresponding gene ontologies and upstream regulators. These results identify a previously unrecognized mechanism of differential immune modulation by short HLA-DRB1-coded allelic epitopes independent of AP, and could shed new light on the mechanistic basis of HLA-disease association.

Macrophage reprogramming for therapy

Dysfunction of the immune system underlies a plethora of human diseases, requiring the development of immunomodulatory therapeutic intervention. To date, most strategies employed have been focusing on the modification of T lymphocytes, and although remarkable improvement has been obtained, results often fall short of the intended outcome. Recent cutting-edge technologies have highlighted macrophages as potential targets for disease control. Macrophages play central roles in development, homeostasis and host defence, and their dysfunction and dysregulation have been implicated in the onset and pathogenesis of multiple disorders including cancer, neurodegeneration, autoimmunity and metabolic diseases. Recent advancements have led to a greater understanding of macrophage origin, diversity and function, in both health and disease. Over the last few years, a variety of strategies targeting macrophages have been developed and these open new therapeutic opportunities. Here, we review the progress in macrophage reprogramming in various disorders and discuss the potential implications and challenges for macrophage-targeted approaches in human disease.

Artocarpus tonkinensis Extract Inhibits LPS-Triggered Inflammation Markers and Suppresses RANKL-Induced Osteoclastogenesis in RAW264.7

Artocarpus tonkinensis (At) leaf decoction, a traditional remedy prepared in North Vietnam by the Hmong ethnic group, is a tea extract rich in bioactive compounds that may have therapeutic effects in arthritis and backache. Indeed, it has been demonstrated that At is able to inhibit Th17 lymphocytes development and to protect mice in an experimental model of collagen-induced arthritis. By resorting to macrophage in vitro models of inflammation and osteoclastogenesis, we showed that At extract significantly reduced nitric oxide synthase 2 (NOS2) activity and IL-6 production by RAW 264.7 murine cells. Moreover, At demonstrated an anti-osteoclastogenic effect, as revealed by complete inhibition of TRAP-positive osteoclast formation and decreased expression of key osteoclast-related genes. This At activity likely relies on the inhibition of RANK downstream signaling pathway, as the activation of non-receptor tyrosine kinase Src is reduced upon RANKL-At exposure. Protective effect of At against bone loss was also enlightened in vivo by collagen-induced arthritis (CIA) experiment demonstrating that, although paw edema was only weakly opposed by drinking At decoction, bone and cartilage were well preserved in CIA+At mice and joint tissue expressed decreased levels of osteoclast marker genes respect to CIA control group. Maesopsin 4-O-β-D-glucoside (i.e., TAT-2, one of the main decoction bioactive components) was capable to contrast NOS2 activity, IL-6 expression and osteoclast formation, too, albeit to a lesser extent when compared to At decoction. Overall, this study enlightens another At cell target, macrophages, beside Th17 lymphocytes, and suggests that the anti-arthritic beneficial effects of At decoction largely derives from its ability to counteract not only inflammation, but also osteoclastogenesis.

Low levels of PCSK9 are associated with remission in patients with rheumatoid arthritis treated with anti-TNF-α: potential underlying mechanisms

Background

Proprotein convertase subtilisin kexin 9 (PCSK9) targets the LDL-receptor (LDLR) which raises LDL-levels. In addition, PCSK9 has proinflammatory immunological effects. Here, we investigate the role of PCSK9 in relation to the inflammatory activity in patients with rheumatoid arthritis (RA).

Methods

PCSK9-levels were determined at baseline by ELISA in 160 patients with RA not previously treated with biologics. The patients started anti-TNF-α (adalimumab, infliximab, or etanercept) treatment and were followed-up for 1 year. Disease activity was determined by DAS28.

Effects of PCSK9 on cytokine production from macrophages of healthy individuals and synoviocytes from RA patients and inhibition by anti-PCSK9 antibodies were studied in supernatants by ELISA.

Results

A significantly lower level of PCSK9 at baseline, p = 0.035, was observed in patients who reached remission within 1 year, defined as DAS28 < 2.6, compared to those not in remission. At 12 months of TNF-α antagonist treatment, the mean DAS28 was reduced but was significantly greater in patients with highest quartile PCSK9 (Q4) compared to those at lowest PCSK9 (Q1) in both crude (p = 0.01) and adjusted analysis (p = 0.004).

In vitro, PCSK9 induced TNF-alpha and IL-1beta in macrophages and monocyte chemoattractant protein-1 (MCP1) in synoviocytes. These effects were inhibited by anti-PCSK9 antibodies.

Conclusions

Low levels of PCSK9 at baseline are associated with being DAS28-responder to anti-TNF-α treatment in RA. An underlying cause could be that PCSK9 stimulates the production of proinflammatory cytokines from macrophages and synoviocytes, effects inhibited by anti-PCSK9 antibodies. PCSK9 could thus play an immunological role in RA.

Rheumatoid arthritis CD14+ monocytes display metabolic and inflammatory dysfunction, a phenotype that precedes clinical manifestation of disease

Introduction

This study investigates the metabolic activity of circulating monocytes and their impact on pro‐inflammatory responses in RA and explores whether this phenotype is already primed for inflammation before clinical manifestations of disease.

Methods

Blood was collected and CD14⁺ monocytes isolated from healthy control donors (HC), individuals at‐risk (IAR) and RA patients. Monocyte frequency in blood and synovial tissue was assessed by flow cytometry. Inflammatory responses and metabolic analysis ± specific inhibitors were quantified by RT‐PCR, Western blot, migration assays, Seahorse‐XFe‐technology, mitotracker assays and transmission electron microscopy. Transcriptomic analysis was performed on HC, IAR and RA synovial tissue.

Results

CD14⁺ monocytes from RA patients are hyper‐inflammatory following stimulation, with significantly higher expression of cytokines/chemokines than those from HC. LPS‐induced RA monocyte migratory capacity is consistent with increased monocyte frequency in RA synovial tissue. RA CD14⁺ monocytes show enhanced mitochondrial respiration, biogenesis and alterations in mitochondrial morphology. Furthermore, RA monocytes display increased levels of key glycolytic enzymes HIF1α, HK2 and PFKFB3 and demonstrate a reliance on glucose consumption, blockade of which abrogates pro‐inflammatory mediator responses. Blockade of STAT3 activation inhibits this forced glycolytic flux resulting in metabolic reprogramming and resolution of inflammation. Interestingly, this highly activated monocytic phenotype is evident in IAR of developing disease, in addition to an enhanced monocyte gene signature observed in synovial tissue from IAR.

Conclusion

RA CD14⁺ monocytes are metabolically re‐programmed for sustained induction of pro‐inflammatory responses, with STAT3 identified as a molecular regulator of metabolic dysfunction. This phenotype precedes clinical disease onset and may represent a potential pathway for therapeutic targeting early in disease.

LncRNA MIAT downregulates IL-1β, TNF-ɑ to suppress macrophage inflammation but is suppressed by ATP-induced NLRP3 inflammasome activation

Cardiovascular disease (CVD) has been identified as the leading cause of premature deaths in rheumatoid arthritis (RA), accounting for about 40 to 50% of all deaths. Macrophage inflammation is regarded as a key point to link to the two diseases. Recently, long non-coding RNAs (lncRNAs) have acknowledged as a regulator of inflammation significantly. Here, we firstly found that lncRNA myocardial infarction associated transcript (lncRNA MIAT), a crucial lncRNA to regulate CVD, expressed increasingly in synovium and myocardial tissues of collagen-induced arthritis (CIA) mice. Besides, we also verified that the increased infiltration of macrophage occurred in those tissues of the CIA. In vitro, we found that macrophage inflammation induced by LPS could up-regulate lncRNA MIAT expression. LncRNA MIAT seemed to inhibit the expression of IL-1β, TNF-ɑ and be suppressed by ATP-induced NLRP3 inflammasome activation pathway. Therefore, these data indicated an anti-inflammatory effect of lncRNA MIAT in macrophage and an original research direction for high cardiovascular risk in RA.