The multifactorial role of neutrophils in rheumatoid arthritis

Functional and dynamic profiling of transcript isoforms reveals essential roles of alternative splicing in interferon response

Type I interferon (IFN-I) plays an important role in the innate immune response through inducing IFN-I-stimulated genes (ISGs). However, how alternative splicing (AS) events, especially over time, affect their function remains poorly understood. We generated an annotation (113,843 transcripts) for IFN-I-stimulated human B cells called isoISG using high-accuracy long-read sequencing data from PacBio Sequel II/IIe. Transcript isoform profiling using isoISG revealed that isoform switching occurred in the early response to IFN-I so that ISGs would gain functional domains (e.g., C4B) or higher protein production (e.g., IRF3). Conversely, isoforms lacking functional domains increased during the late phase of IFN-I response, mainly due to intron retention events. This suggests that isoform switching both triggers and terminates IFN-I responses at the translation and protein levels. Furthermore, genetic variants influencing the isoform ratio of ISGs were associated with immunological and infectious diseases. AS has essential roles in regulating innate immune response and associated diseases.

Citrullination modulation stabilizes HIF-1α to promote tumour progression

Citrullination plays an essential role in various physiological or pathological processes, however, whether citrullination is involved in regulating tumour progression and the potential therapeutic significance have not been well explored. Here, we find that peptidyl arginine deiminase 4 (PADI4) directly interacts with and citrullinates hypoxia-inducible factor 1α (HIF-1α) at R698, promoting HIF-1α stabilization. Mechanistically, PADI4-mediated HIF-1αR698 citrullination blocks von Hippel-Lindau (VHL) binding, thereby antagonizing HIF-1α ubiquitination and subsequent proteasome degradation. We also show that citrullinated HIF-1αR698, HIF-1α and PADI4 are highly expressed in hepatocellular carcinoma (HCC) tumour tissues, suggesting a potential correlation between PADI4-mediated HIF-1αR698 citrullination and cancer development. Furthermore, we identify that dihydroergotamine mesylate (DHE) acts as an antagonist of PADI4, which ultimately suppresses tumour progression. Collectively, our results reveal citrullination as a posttranslational modification related to HIF-1α stability, and suggest that targeting PADI4-mediated HIF-1α citrullination is a promising therapeutic strategy for cancers with aberrant HIF-1α expression.

Dietary omega-3 fatty acids modulate the production of platelet-derived microvesicles in an in vivo inflammatory arthritis model

PURPOSE

The aim of this study was to investigate the effects of different ω-3 polyunsaturated fatty acid (PUFA) enriched diets, including a novel renewable plant source of ω-3 fatty acids (Buglossoides arvensis), on the development and progression of rheumatoid arthritis (RA).

METHODS

RA was induced in mice consuming experimental diets using the K/BxN model. The experimental diets consisted of either a western control diet (control), diets containing B. arvensis oil or fish oil. The effects of the diets on platelets, platelet microvesicles (PMVs), and inflammatory markers such as clinical index, ankle thickness and cytokine/chemokine release were measured.

RESULTS

While ω-3 PUFA-enriched diets did not prevent the development of arthritis in the K/BxN model, a significant decrease in ankle swelling was observed compared to the control group. Platelets isolated from mice consuming either low content of B. arvensis oil or fish oil diets exhibited significantly decreased PMVs production compared to mice consuming the control diet.

CONCLUSION

Our study provides insight into the contribution of ω-3 PUFA supplementation in modulating the pro-inflammatory phenotype of platelets in RA pathology. Furthermore, our study suggests that low concentrations of dietary B. arvensis oil may have similar anti-inflammatory potential seen with dietary fish oil supplementation.

The Phenotypes and Functions of Neutrophils in Systemic Sclerosis

Systemic sclerosis (SSc) is a chronic disease of the connective tissue characterized by its multifaceted impact on various bodily systems, yet its precise cause remains elusive. Central to its pathology are abnormal immune activation, vasculopathy, and consequent fibrosis affecting both the skin and internal organs. The intricate interplay between the innate and adaptive immune systems significantly influences the pathogenesis of SSc. Despite substantial research, the role of neutrophils, key players in innate immunity, in the context of SSc has remained enigmatic. Emerging evidence suggests that neutrophils not only contribute to the initiation and perpetuation of SSc but also inflict damage on organs and promote fibrosis-a hallmark of the disease in many patients. This review aims to investigate the nuanced involvement of neutrophils in the development of SSc. By shedding light on the intricate mechanisms through which neutrophils influence the pathogenesis of SSc, we can gain deeper insights into the disease process and potentially identify novel therapeutic targets. Understanding the precise role of neutrophils may pave the way for more targeted and effective interventions to alleviate the burden of SSc on affected individuals.

The emerging role of neutrophil extracellular traps in the progression of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease with a complex etiology. Neutrophil extracellular traps (NETs are NETwork protein structures activated by neutrophils to induce the cleavage and release of DNA-protein complexes). Current studies have shown the critical involvement of NETs in the progression of autoimmune diseases, Neutrophils mostly gather in the inflammatory sites of patients and participate in the pathogenesis of autoimmune diseases in various ways. NETs, as the activated state of neutrophils, have attracted much attention in immune diseases. Many molecules released in NETs are targeted autoantigens in autoimmune diseases, such as histones, citrulline peptides, and myeloperoxidase. All of these suggest that NETs have a direct causal relationship between the production of autoantigens and autoimmune diseases. For RA in particular, as a disorder of the innate and adaptive immune response, the pathogenesis of RA is inseparable from the generation of RA. In this article, we investigate the emerging role of NETs in the pathogenesis of RA and suggest that NETs may be an important target for the treatment of inflammatory autoimmune diseases.

Advancements in rheumatoid arthritis therapy: a journey from conventional therapy to precision medicine via nanoparticles targeting immune cells

Rheumatoid arthritis (RA) is a progressive autoimmune disease that mainly affects the inner lining of the synovial joints and leads to chronic inflammation. While RA is not known as lethal, recent research indicates that it may be a silent killer because of its strong association with an increased risk of chronic lung and heart diseases. Patients develop these systemic consequences due to the regular uptake of heavy drugs such as disease-modifying antirheumatic medications (DMARDs), glucocorticoids (GCs), nonsteroidal anti-inflammatory medicines (NSAIDs), etc. Nevertheless, a number of these medications have off-target effects, which might cause adverse toxicity, and have started to become resistant in patients as well. Therefore, alternative and promising therapeutic techniques must be explored and adopted, such as post-translational modification inhibitors (like protein arginine deiminase inhibitors), RNA interference by siRNA, epigenetic drugs, peptide therapy, etc., specifically in macrophages, neutrophils, Treg cells and dendritic cells (DCs). As the target cells are specific, ensuring targeted delivery is also equally important, which can be achieved with the advent of nanotechnology. Furthermore, these nanocarriers have fewer off-site side effects, enable drug combinations, and allow for lower drug dosages. Among the nanoparticles that can be used for targeting, there are both inorganic and organic nanomaterials such as solid-lipid nanoparticles, liposomes, hydrogels, dendrimers, and biomimetics that have been discussed. This review highlights contemporary therapy options targeting macrophages, neutrophils, Treg cells, and DCs and explores the application of diverse nanotechnological techniques to enhance precision RA therapies.

Altered neutrophil responses to dengue virus serotype three: delayed apoptosis is regulated by stabilisation of Mcl-1

Dengue is a global health concern, and the host-viral interactions that regulate disease severity are largely unknown. Detrimental effects of neutrophils in this disease have been reported, but the precise mechanisms and functional properties of dengue-activated neutrophils are not fully characterised. Here, we measured the effects of dengue virus serotype 3 (DV3) on neutrophil lifespan and functions. We show that DV3 extends neutrophil survival with a significant proportion of cells surviving for 72 h post-incubation. These effects on neutrophil survival were greater than those observed by adding GM-CSF and TNF-α alone, but these cytokines enhanced survival induced by the virus. Enhanced reactive oxygen species (ROS) generation was observed following incubation with DV3 activation and this ROS production was enhanced by co-incubation with priming agents. In addition, DV triggered the enhanced IL-8 expression by the majority of neutrophils and a low percentage of cells were activated to express MCP-1 (CCL2). A low number of neutrophils showed increased co-expression of the migratory markers, CCR7 and CXCR4 which could promote their migration towards lymph nodes. DV3 significantly upregulated the BCL-XL gene at 3, 12, and 24 h, and the Mcl-1 gene at 12 h, following treatment. We also show that DV3 induces the Mcl-1 protein stabilization similar to GM-CSF. This report sheds new light on the mechanisms by which neutrophils may contribute to the pathology of dengue disease via delayed apoptosis and generation of pro-inflammatory molecules, and raises the possibility that dengue-activated neutrophils may play a role in activating cells of adaptive immunity.

Neutrophil extracellular traps: Potential targets for the treatment of rheumatoid arthritis with traditional Chinese medicine and natural products

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease. Abnormal formation of neutrophil extracellular traps (NETs) at the synovial membrane leads to the release of many inflammatory cytokines, including IL-1β, IL-6, and TNF-α. Elastase, histone H3, and myeloperoxidase, which are carried by NETs, damage the soft tissues of the joints and aggravate the progression of RA. The balance of NET formation coordinates the pro-inflammatory and anti-inflammatory effects and plays a key role in the development of RA. Therefore, when NETs are used as effector targets, highly targeted drugs with fewer side effects can be developed to treat RA without damaging the host immune system. Currently, an increasing number of studies have shown that traditional Chinese medicines and natural products can regulate the formation of NETs through multiple pathways to counteract RA, which shows great potential for the treatment of RA and has a promising future for clinical application. In this article, we review the latest biological progress in understanding NET formation, the mechanism of NETs in RA, and the potential targets or pathways related to the modulation of NET formation by Chinese medicines and natural products. This review provides a relevant basis for the use of Chinese medicines and natural products as natural adjuvants in the treatment of RA.

Systemic inflammation response index is associated with increased all-cause and cardiovascular mortality in US adults with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) stands as a persistent systemic inflammatory autoimmune condition. Despite this understanding, the precise impact of the systemic inflammation response index (SIRI) on the prognosis of RA patients remains elusive. This study aims to elucidate the correlation between the inflammatory biomarker SIRI and both all-cause mortality and cardiovascular mortality among RA patients.

METHODS

Utilizing data from the National Health and Nutrition Examination Survey (NHANES) spanning from 1999 to 2020, a retrospective analysis was conducted. Survival data were depicted through Kaplan-Meier survival curves, while the relationship between SIRI and all-cause or cardiovascular mortality in RA patients was scrutinized via multivariable Cox proportional hazards regression analysis and restricted cubic spline plots. Furthermore, subgroup analysis and mediation analysis were also performed.

RESULTS

This study encompassed 2656 RA patients with a comprehensive 20-year follow-up, during which 935 all-cause deaths and 273 deaths attributed to cardiovascular disease were recorded. We observed a nonlinear positive correlation between SIRI with both all-cause and cardiovascular mortality in RA patients. Notably, at a SIRI level of 1.12, the hazard ratio reached 1, indicating a shift from low to high mortality risk. Furthermore, mediation analysis revealed that 12.6% of the association between RA and mortality risk was mediated through SIRI. Subgroup analysis indicated a more pronounced association between SIRI and mortality in female patients or those with a high BMI.

CONCLUSION

This study underscores a non-linear positive correlation between the biomarker SIRI and both all-cause mortality and cardiovascular mortality in RA patients.

Nonlinear associations of systemic immune-inflammation index with all-cause and cardiovascular mortality in US adults with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory autoimmune disease. However, the relationship between the systemic immune-inflammation index (SII) and the prognosis of RA patients remains unclear. This study aimed to investigate the association between inflammatory biomarker SII and all-cause and cardiovascular mortality in RA patients. A retrospective analysis was conducted using data from the National Health and Nutrition Examination Survey database spanning from 1999 to March 2020. We assessed the association between the SII and all-cause as well as cardiovascular mortality in RA patients employing multivariable Cox proportional hazards regression analysis and restricted cubic spline plots. Receiver operating characteristic curves were employed to evaluate the prognostic capacity of SII in predicting outcomes in both the RA patients and the general population, alongside its predictive performance compared to other markers. This study comprised 2247 RA patients and a control cohort of 29,177 individuals from the general population. Over a 20-year follow-up period, 738 all-cause deaths and 215 deaths attributable to cardiovascular disease were documented in RA patients. We observed a nonlinear positive correlation between the SII and both all-cause and cardiovascular mortality in RA patients. Of significance, at an SII level of 529.7, the hazard ratio reached 1, signifying a transition from low to high mortality risk. Moreover, subgroup analysis did not reveal any potential interactions. Our study findings indicate a nonlinear positive correlation between the inflammatory biomarker SII and both all-cause and cardiovascular mortality in patients with RA.

Biomimetic NO Scavenging Hyaluronic Acid Nanoparticles Enable Targeted Delivery of MTX and Integrated Management of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a complicated chronic disorder of the immune system, featured with severe inflammatory joints, synovium hyperplasia, articular cartilage, and bone damage. In the RA microenvironment, RA-involved cells, overproduced nitric oxide (NO), and pro-inflammatory cytokines are highly interplayed and mutually reinforced, which form a vicious circle and play crucial roles in the formation and progression of RA. To comprehensively break the vicious circle and obtain the maximum benefits, we have developed neutrophil membrane-camouflaged NO scavenging nanoparticles based on an NO-responsive hyaluronic acid derivative for delivery of MTX. These multifunctional nanoparticles (NNO-NPs/MTX), by inheriting the membrane functions of the source cells, possess prolonged circulation and specific localization at the inflamed sites when administrated in the body. Remarkably, NNO-NPs/MTX can neutralize the pro-inflammatory cytokines via the outer membrane receptors, scavenge NO, and be responsively disassociated to release MTX for RA-involved cell regulation and HA for lubrication in the RA sites. In a collagen-induced arthritis mouse model, NNO-NPs/MTX exhibits a significant anti-inflammation effect and effectively alleviates the characteristic RA symptoms such as synovial hyperplasia and cartilage destruction, realizing the synergistic and boosted therapeutic outcome against intractable RA. Thus, NNO-NPs/MTX provides a promising and potent platform to integrately treat RA.

Nanomedicines targeting activated immune cells and effector cells for rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovial inflammation and inflammatory cellular infiltration. Functional cells in the RA microenvironment (RAM) are composed of activated immune cells and effector cells. Activated immune cells, including macrophages, neutrophils, and T cells, can induce RA. Effector cells, including synoviocytes, osteoclasts, and chondrocytes, receiving inflammatory stimuli, exacerbate RA. These functional cells, often associated with the upregulation of surface-specific receptor proteins and significant homing effects, can secrete pro-inflammatory factors and interfere with each other, thereby jointly promoting the progression of RA. Recently, some nanomedicines have alleviated RA by targeting and modulating functional cells with ligand modifications, while other nanoparticles whose surfaces are camouflaged by membranes or extracellular vesicles (EVs) of these functional cells target and attack the lesion site for RA treatment. When ligand-modified nanomaterials target specific functional cells to treat RA, the functional cells are subjected to attack, much like the intended targets. When functional cell membranes or EVs are modified onto nanomaterials to deliver drugs for RA treatment, functional cells become the attackers, similar to arrows. This study summarized how diversified functional cells serve as targets or arrows by engineered nanoparticles to treat RA. Moreover, the key challenges in preparing nanomaterials and their stability, long-term efficacy, safety, and future clinical patient compliance have been discussed here.

Triptolide regulates neutrophil function through the Hippo signaling pathway to alleviate rheumatoid arthritis disease progression

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammatory changes in the joints, the etiology of which is unclear. It is now well established that regulated cell death (RCD) and migration of neutrophils play an important role in the pathogenesis of RA. Tripterygium wilfordii Hook.f (TwHF) is a total saponin extracted from the root of Tripterygium wilfordii Hook.f, a plant of the family Wesleyanaceae, which has strong anti-inflammatory and immunomodulatory effects and has been used as a basic drug in the clinical treatment of RA. Despite the good efficacy of TwHF treatment, the mechanism of action of TwHF remains unclear. Several studies have demonstrated that the drug tripterygium glycosides, in which TwHF is the main ingredient, has achieved excellent efficacy in the clinical treatment of RA. Investigations have also found that TwHF can affect cellular RCD, cell migration, cell proliferation, and the apoptosis-related Hippo signaling pathway. In this study, we first analyzed the RCD and migration differences of neutrophils in patients with RA through network pharmacology and transcriptome analysis. Subsequently, we used electron microscopy, immunofluorescence, and other methods to identify the RCD phenotype of neutrophils. In collagen-induced arthritis (CIA) model, we demonstrated that Triptolide (the main active ingredient in TwHF) could alleviate the progression of arthritis by reducing the bone destruction and the infiltration of neutrophils. Furthermore, in vitro experiments showed that Triptolide induced neutrophil apoptosis, inhibited the formation of neutrophil extracellular traps (NETs), and impeded the neutrophil migration process in a Hippo pathway-dependent manner. Taken together, these findings indicate that Triptolide has potential for treating RA and provide theoretical support for the clinical application of TwHF, as a traditional Chinese medicine, in RA.

Nanoparticle-neutrophils interactions for autoimmune regulation

Neutrophils play an essential role as 'first responders' in the immune response, necessitating many immune-modulating capabilities. Chronic, unresolved inflammation is heavily implicated in the progression and tissue-degrading effects of autoimmune disease. Neutrophils modulate disease pathogenesis by interacting with the inflammatory and autoreactive cells through effector functions, including signaling, degranulation, and neutrophil extracellular traps (NETs) release. Since the current gold standard systemic glucocorticoid administration has many drawbacks and side effects, targeting neutrophils in autoimmunity provides a new approach to developing therapeutics. Nanoparticles enable targeting of specific cell types and controlled release of a loaded drug cargo. Thus, leveraging nanoparticle properties and interactions with neutrophils provides an exciting new direction toward novel therapies for autoimmune diseases. Additionally, recent work has utilized neutrophil properties to design novel targeted particles for delivery into previously inaccessible areas. Here, we outline nanoparticle-based strategies to modulate neutrophil activity in autoimmunity, including various nanoparticle formulations and neutrophil-derived targeting.

Relationship of immature granulocytes with disease activity in rheumatoid arthritis

AIM

To determine whether the IG count (#) and IG percentage (%) are associated with disease activity in rheumatoid arthritis (RA).

METHODS

This retrospective study included 65 RA patients and 65 healthy controls. Clinical and demographic characteristics of controls and RA patients (at active period and when the patients achieved remission) were obtained from medical records. Disease activity was defined by disease activity score 28 (DAS28). Furthermore, the clinical disease activity index (CDAI), and simple disease activity index (SDAI) were calculated. For the differential diagnosis of RA patients from healthy controls, the cut-off value was estimated by making receiver-operator curves (ROC).

RESULTS

In active RA patients, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), IG#, and IG% levels were significantly higher compared to the healthy controls (p < .001, for all). When the patients achieved remission, DAS28, CDAI, SDAI, ESR, CRP, IG#, and IG% values were significantly decreased (p < .001, for all). IG# and IG% were significantly positively correlated with DAS28, CDAI, SDAI, ESR, and CRP (p = .024, p = .008, p = .003, p < .001, p < .001, respectively). According to ROC curve analysis, IG% and IG# were the biomarkers to have a significant diagnostic value for RA with the area under the curve of 0.853 and 0.865 (p < .001, for all).

CONCLUSION

The present study demonstrated that two novel inflammatory markers, IG# and IG%, can be useful for monitoring RA patients' disease activity. Furthermore, IG# and IG% can also be used as fast, inexpensive, and easily available complementary diagnostic markers to diagnose RA patients.

Co-administration of L-Ascorbic Acid and α-Tocopherol Alleviates Arsenic-Induced Immunotoxicities in the Thymus and Spleen by Dwindling Oxidative Stress-Induced Inflammation

Herein, we investigated whether L-ascorbic acid (L-AA) and α-tocopherol (α-T) co-administration has the potential to alleviate arsenic-induced immunotoxicities in the thymus, spleen, and circulating leukocytes. Forty-eight adult male Wistar rats were randomly divided into four groups before the treatment: group I (control); group II (sodium arsenite, 3 mg/kg/day/rat); group III (sodium arsenite + L-AA (200 mg/kg/day/rat) and α-T (400 mg/kg/day/rat)); group IV (L-AA and α-T). The result showed that sodium arsenite exposure (consecutive 30 days) caused weight reduction, structural alterations in the thymus and spleen, accompanied by a decrease in thymocyte and splenocyte count. Decreased superoxide dismutase and catalase activity, increased malondialdehyde and protein-carbonyl content, reduced Nrf2 and Bcl2 expression, and increased p-ERK, NF-kβ, Bax, and cleaved-caspase-3 expression were also observed in the thymus and spleen of arsenic-exposed rats. Enhanced plasma ACTH and corticosterone, ROS-induced apoptosis of lymphocytes were also observed. L-AA and α-T co-administration has the potential to abrogate the deleterious impact of arsenic on the thymus, spleen, and circulating lymphocytes. Whole transcriptome analysis of leukocytes revealed that arsenic treatment augmented the expression of Itga4, Itgam, and MMP9 genes, which might help in transient migration of the leukocytes through the endothelial cell layer. Co-administration with L-AA and α-T maintained Itga4, Itgam, and MMP9 gene expression within leukocytes at a lower level.

The ouroboros of autoimmunity

Human autoimmunity against elements conferring protective immunity can be symbolized by the 'ouroboros', a snake eating its own tail. Underlying infection is autoimmunity against three immunological targets: neutrophils, complement and cytokines. Autoantibodies against neutrophils can cause peripheral neutropenia underlying mild pyogenic bacterial infections. The pathogenic contribution of autoantibodies against molecules of the complement system is often unclear, but autoantibodies specific for C3 convertase can enhance its activity, lowering complement levels and underlying severe bacterial infections. Autoantibodies neutralizing granulocyte-macrophage colony-stimulating factor impair alveolar macrophages, thereby underlying pulmonary proteinosis and airborne infections, type I interferon viral diseases, type II interferon intra-macrophagic infections, interleukin-6 pyogenic bacterial diseases and interleukin-17A/F mucocutaneous candidiasis. Each of these five cytokine autoantibodies underlies a specific range of infectious diseases, phenocopying infections that occur in patients with the corresponding inborn errors. In this Review, we analyze this ouroboros of immunity against immunity and posit that it should be considered as a factor in patients with unexplained infection.

Neutrophil-Mimetic, ROS Responsive, and Oxygen Generating Nanovesicles for Targeted Interventions of Refractory Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most prevalent inflammatory joint disease worldwide, leading to irreversible disability and even mortality. Unfortunately, current treatment regimens fail to cure RA due to low therapeutic responses and off-target side effects. Herein, a neutrophil membrane-cloaked, natural anti-arthritic agent leonurine (Leo), and catalase (CAT) co-loaded nanoliposomal system (Leo@CAT@NM-Lipo) is constructed to remodel the hostile microenvironment for RA remission. Due to the inflammation tropism inherited from neutrophils, Leo@CAT@NM-Lipo can target and accumulate in the inflamed joint cavity where high-level ROS can be catalyzed into oxygen by CAT to simultaneously accelerate the drug release and alleviate hypoxia at the lesion site. Besides, the neutrophil membrane camouflaging also enhances the anti-inflammatory potentials of Leo@CAT@NM-Lipo by robustly absorbing pro-arthritogenic cytokines and chemokines. Consequently, Leo@CAT@NM-Lipo successfully alleviated paw swelling, reduced arthritis score, mitigated bone and cartilage damage, and reversed multiple organ dysfunctions in adjuvant-induced arthritis rats (AIA) rats by synergistic effects of macrophage polarization, inflammation resolution, ROS scavenging, and hypoxia relief. Furthermore, Leo@CAT@NM-Lipo manifested excellent biocompatibility both at the cellular and animal levels. Taken together, the study provided a neutrophil-mimetic and ROS responsive nanoplatform for targeted RA therapy and represented a promising paradigm for the treatment of a variety of inflammation-dominated diseases.

Infusion of GMSCs relieves autoimmune arthritis by suppressing the externalization of neutrophil extracellular traps via PGE2-PKA-ERK axis

INTRODUCTION

Rheumatoid arthritis (RA) is a systemic autoimmune disease with limited treatment success, characterized by chronic inflammation and progressive cartilage and bone destruction. Accumulating evidence has shown that neutrophil extracellular traps (NETs) released by activated neutrophils are important for initiating and perpetuating synovial inflammation and thereby could be a promising therapeutic target for RA. K/B × N serum transfer-induced arthritis (STIA) is a rapidly developed joint inflammatory model that somehow mimics the inflammatory response in patients with RA. Human gingival-derived mesenchymal stem cells (GMSCs) have been previously shown to possess immunosuppressive effects in arthritis and humanized animal models. However, it is unknown whether GMSCs can manage neutrophils in autoimmune arthritis.

OBJECTIVES

To evaluate whether infusion of GMSCs can alleviate RA by regulating neutrophils and NETs formation. If this is so, we will explore the underlying mechanism(s) in an animal model of inflammatory arthritis.

METHODS

The effects of GMSCs on RA were assessed by comparing the symptoms of the K/B × N serum transfer-induced arthritis (STIA) model administered either with GMSCs or with control cells. Phenotypes examined included clinical scores, rear ankle thickness, paw swelling, inflammation, synovial cell proliferation, and immune cell frequency. The regulation of GMSCs on NETs was examined through immunofluorescence and immunoblotting in GMSCs-infused STIA mice and in an in vitro co-culture system of neutrophils with GMSCs. The molecular mechanism(s) by which GMSCs regulate NETs was explored both in vitro and in vivo by silencing experiments.

RESULTS

We found in this study that adoptive transfer of GMSCs into STIA mice significantly ameliorated experimental arthritis and reduced neutrophil infiltration and NET formation. In vitro studies also showed that GMSCs inhibited the generation of NETs in neutrophils. Subsequent investigations revealed that GMSCs secreted prostaglandin E2 (PGE2) to activate protein kinase A (PKA), which ultimately inhibited the downstream extracellular signal-regulated kinase (ERK) pathway that is essential for NET formation.

CONCLUSION

Our results demonstrate that infusion of GMSCs can ameliorate inflammatory arthritis mainly by suppressing NET formation via the PGE2-PKA-ERK signaling pathway. These findings further support the notion that the manipulation of GMSCs is a promising stem cell-based therapy for patients with RA and other autoimmune and inflammatory diseases.

Peptide targeting improves the delivery and therapeutic index of glucocorticoids to treat rheumatoid arthritis

Rheumatoid arthritis (RA) is a prevalent autoimmune disease characterized by excessive inflammation in the joints. Glucocorticoid drugs are used clinically to manage RA symptoms, while their dosage and duration need to be tightly controlled due to severe adverse effects. Using dexamethasone (DEX) as a model drug, we explored here whether peptide-guided delivery could increase the safety and therapeutic index of glucocorticoids for RA treatment. Using multiple murine RA models such as collagen-induced arthritis (CIA), we found that CRV, a macrophage-targeting peptide, can selectively home to the inflammatory synovium of RA joints upon intravenous injection. The expression of the CRV receptor, retinoid X receptor beta (RXRB), was also elevated in the inflammatory synovium, likely being the basis of CRV targeting. CRV-conjugated DEX increased the accumulation of DEX in the inflamed synovium but not in healthy organs of CIA mice. Therefore, CRV-DEX demonstrated a stronger efficacy to suppress synovial inflammation and alleviate cartilage/bone destruction. Meanwhile, CRV conjugation reduced immune-related adverse effects of DEX even after a long-term use. Last, we found that RXRB expression was significantly elevated in human patient samples, demonstrating the potential of clinical translation. Taken together, we provide a novel, peptide-targeted strategy to improve the therapeutic efficacy and safety of glucocorticoids for RA treatment.

Neutrophils in Inflammatory Bone Diseases

PURPOSE OF REVIEW

In this review, we summarize the current evidence that suggests that neutrophils play a key role in facilitating damage to local bone structures.

RECENT FINDINGS

Neutrophil infiltration is a hallmark of inflammatory bone diseases such as rheumatoid arthritis (RA) and periodontitis disease (PD). Both of these human diseases are marked by an imbalance in bone homeostasis, favoring the degradation of local bone which ultimately leads to erosions. Osteoclasts, a multinucleated resident bone cell, are responsible for facilitating the turnover of bone and the bone damage observed in these diseases. The involvement of neutrophils and neutrophil extracellular trap formation have recently been implicated in exacerbating osteoclast function through direct and indirect mechanisms. We highlight a recent finding that NET proteins such as histones and elastase can generate non-canonical, inflammatory osteoclasts, and this process is mediated by post-translational modifications such as citrullination and carbamylation, both of which act as autoantigens in RA. It appears that NETs, autoantibodies, modified proteins, cytokines, and osteoclasts all ultimately contribute to local and permanent bone damage in RA and PD. However, more studies are needed to fully understand the role of neutrophils in inflammatory bone diseases.

Neutrophils-mediated bioinspired nanoagents for noninvasive monitoring of inflammatory recruitment dynamics and navigating phototherapy in rheumatoid arthritis

Neutrophils play a crucial role in inflammatory immune responses, but their in vivo homing to inflammatory lesions remains unclear, hampering precise treatment options. In this study, we employed a biomineralization-inspired multimodal nanoagent to label neutrophils, enabling noninvasive monitoring of the dynamic process of inflammatory recruitment and guiding photothermal therapy in rheumatoid arthritis. Our nanoagents allowed visualization of neutrophil fate through magnetic resonance imaging, photoacoustic imaging, and fluorescence imaging in the first and second near-infrared windows. Histopathology and immunofluorescence analysis revealed pronounced inflammatory cell infiltration in rheumatoid arthritis compared to the normal limb. Furthermore, the recruitment quantity of neutrophils positively correlated with the inflammatory stage. Additionally, the inherent photothermal effect of the nanoagents efficiently ablated inflammatory cells during the optimal homing time and inflammatory phase. This neutrophil imaging-guided photothermal therapy precisely targeted inflammatory nuclei in rheumatoid arthritis and downregulated pro-inflammatory cytokines in serum. These results demonstrate that in vivo tracking of inflammatory immune response cells can significantly optimize the treatment of inflammatory diseases, including rheumatoid arthritis.

Inflammation-Targeting Mesenchymal Stem Cells Combined with Photothermal Treatment Attenuate Severe Joint Inflammation

Current clinical therapeutic efficacy for the treatment of osteo- and rheumatoid-arthritis is obviously limited. Although mesenchymal stem cells (MSCs) are considered as a source of promising regenerative therapy, un-modified or genetically engineered MSCs injected in vivo restrict their clinical utility because of the low drug efficacy and unpredicted side effect, respectively. Herein, a strategy to enhance the migration efficacy of MSCs to inflamed joints via an inflammation-mediated education process is demonstrated. To reinforce the limited anti-inflammatory activity of MSCs, gold nanostar loaded with triamcinolone is conjugated to MSC. Furthermore, near-infrared laser-assisted photothermal therapy (PTT) induced by gold nanostar significantly elevates the anti-inflammatory efficacy of the developed drugs, even in advanced stage arthritis model. An immunological regulation mechanism study of PTT is first suggested in this study; the expression of the interleukin 22 receptor, implicated in the pathogenesis of arthritis, is downregulated in T lymphocytes by PTT, and Th17 differentiation from naïve CD4 T cell is inhibited. Collectively, inflammation-targeting MSCs conjugated with triamcinolone-loaded gold nanostar (Edu-MSCs-AuS-TA) promote the repolarization of macrophages and decrease neutrophil recruitment in joints. In addition, Edu-MSCs-AuS-TA significantly alleviate arthritis-associated pain, improve general locomotor activity, and more importantly, induce cartilage regeneration even for severe stages of arthritis model.

Neutrophil-like cells derived from the HL-60 cell-line as a genetically-tractable model for neutrophil degranulation

Research on neutrophil biology has been limited by the short life span and limited genetic manipulability of these cells, driving the need for representative and efficient model cell lines. The promyelocytic cell line HL-60 and its subline PLB-985 can be differentiated into neutrophil-like cells (NLCs) and have been used to study neutrophil functions including chemotaxis, phagocytosis, endocytosis, and degranulation. Compared to neutrophils derived from hematopoietic stem cells, NLCs serve as a cost-effective neutrophil model. NLCs derived from both HL-60 and PLB-985 cells have been shown to perform degranulation, an important neutrophil function. However, no study has directly compared the two lines as models for degranulation including their release of different types of mobilizable organelles. Furthermore, Nutridoma, a commercially available supplement, has recently been shown to improve the chemotaxis, phagocytosis, and oxidative burst abilities of NLCs derived from promyelocytic cells, however it is unknown whether this reagent also improves the degranulation ability of NLCs. Here, we show that NLCs derived from both HL-60 and PLB-985 cells are capable of degranulating, with each showing markers for the release of multiple types of secretory organelles, including primary granules. We also show that differentiating HL-60 cells using Nutridoma does not enhance their degranulation activity over NLCs differentiated using Dimethyl Sulfoxide (DMSO) plus Granulocyte-colony stimulating factor (G-CSF). Finally, we show that promyelocytic cells can be genetically engineered and differentiated using these methods, to yield NLCs with a defect in degranulation. Our results indicate that both cell lines serve as effective models for investigating the mechanisms of neutrophil degranulation, which can advance our understanding of the roles of neutrophils in inflammation and immunity.

Network-based cytokine inference implicates Oncostatin M as a driver of an inflammation phenotype in knee osteoarthritis

Inflammatory cytokines released by synovium after trauma disturb the gene regulatory network and have been implicated in the pathophysiology of osteoarthritis. A mechanistic understanding of how aging perturbs this process can help identify novel interventions. Here, we introduced network paradigms to simulate cytokine-mediated pathological communication between the synovium and cartilage. Cartilage-specific network analysis of injured young and aged murine knees revealed aberrant matrix remodeling as a transcriptomic response unique to aged knees displaying accelerated cartilage degradation. Next, network-based cytokine inference with pharmacological manipulation uncovered IL6 family member, Oncostatin M (OSM), as a driver of the aberrant matrix remodeling. By implementing a phenotypic drug discovery approach, we identified that the activation of OSM recapitulated an "inflammatory" phenotype of knee osteoarthritis and highlighted high-value targets for drug development and repurposing. These findings offer translational opportunities targeting the inflammation-driven osteoarthritis phenotype.

Card9/neutrophil signalling axis promotes IL-17A-mediated ankylosing spondylitis

OBJECTIVE

Polymorphisms in the antifungal signalling molecule CARD9 are associated with ankylosing spondylitis (AS). Here, we investigated the cellular mechanism by which CARD9 controls pathogenic Th17 responses and the onset of disease in both experimental murine AS and patients.

METHODS

Experiments in SKG, Card9-/-SKG, neutrophil-deplete SKG mice along with in vitro murine, neutrophil and CD4+ T cell cocultures examined Card9 function in neutrophil activation, Th17 induction and arthritis in experimental AS. In AS patients the neutrophil: Bath Ankylosing Spondylitis Functional Index relationship was analysed. In vitro studies with autologous neutrophil: T cell cocultures examined endogenous CARD9 versus the AS-associated variant (rs4075515) of CARD9 in T cellular production of IL-17A.

RESULTS

Card9 functioned downstream of Dectin-1 and was essential for induction of Th17 cells, arthritis and spondylitis in SKG mice. Card9 expression within T cells was dispensable for arthritis onset in SKG mice. Rather, Card9 expression controlled neutrophil function; and neutrophils in turn, were responsible for triggering Th17 expansion and disease in SKG mice. Mechanistically, cocultures of zymosan prestimulated neutrophils and SKG T cells revealed a direct cellular function for Card9 within neutrophils in the potentiation of IL-17 production by CD4+ T cells on TCR-ligation. The clinical relevance of the neutrophil-Card9-coupled mechanism in Th17-mediated disease is supported by a similar observation in AS patients. Neutrophils from HLA-B27+ AS patients expanded autologous Th17 cells in vitro, and the AS-associated CARD9S12N variant increased IL-17A.

CONCLUSIONS

These data reveal a novel neutrophil-intrinsic role for Card9 in arthritogenic Th17 responses and AS pathogenesis. These data provide valuable utility in our future understanding of CARD9-specific mechanisms in spondyloarthritis .

Association Between Human Metabolomics and Rheumatoid Arthritis: A Systematic Review and Meta-analysis

OBJECTIVE

The underdiagnosis and inadequate treatment of rheumatoid arthritis (RA) can be attributed to the various clinical manifestations presented by patients. To address this concern, we conducted an extensive review and meta-analysis, focusing on RA-related metabolites.

METHODS

A comprehensive literature search was conducted in PubMed, the Cochrane Library, Web of Science, and Embase to identify relevant studies published up to October 5, 2022. The quality of the included articles was evaluated and, subsequently, a meta-analysis was conducted using Review Manager software to analyze the association between metabolites and RA.

RESULTS

Forty nine studies met the inclusion criteria for the systematic review, and six of these studies were meta-analyzed to evaluate the association between 28 reproducible metabolites and RA. The results indicated that, compared to controls, the levels of histidine (RoM = 0.83, 95% CI = 0.79-0.88, I2 = 0%), asparagine (RoM = 0.83, 95% CI = 0.75-0.91, I2 = 0%), methionine (RoM = 0.82, 95% CI = 0.69-0.98, I2 = 85%), and glycine (RoM = 0.81, 95% CI = 0.67-0.97, I2 = 68%) were significantly lower in RA patients, while hypoxanthine levels (RoM = 1.14, 95% CI = 1.09-1.19, I2 = 0%) were significantly higher.

CONCLUSION

This study identified histidine, methionine, asparagine, hypoxanthine, and glycine as significantly correlated with RA, thus offering the potential for the advancement of biomarker discovery and the elucidation of disease mechanisms in RA.

Dehydroandrographolide alleviates rheumatoid arthritis by inhibiting neutrophil activation via LMIR3 in collagen induced arthritis rats

Rheumatoid arthritis (RA) is an inflammatory disease which causes severe pain and disability. Neutrophils play essential roles in the onset and progression of RA; thus, inhibition of neutrophil activation is becoming a popular therapeutic strategy. Dehydroandrographolide has provided satisfactory outcomes in inflammatory diseases; however, its therapeutic effects and mechanism in RA are not fully understood. Leukocyte mono-immunoglobulin-like receptor 3 (LMIR3) is a negative regulator highly expressed in neutrophils. To determine whether dehydroandrographolide negatively regulated neutrophils activation via LMIR3, cytokines release and collagen-induced arthritis (CIA) rats were used in vitro and in vivo. Biacore, molecular docking analysis and molecular dynamics simulation were performed to prove the target of dehydroandrographolide. Moreover, the downstream signaling pathways of LMIR3 activation were analyzed by western blotting. Results showed that oral dehydroandrographolide administration of 2 mg/kg/day to CIA rats attenuated synovitis and bone and cartilage damage after the 28-day intervention, revealed using HE sections and micro-CT. Dehydroandrographolide significantly inhibited cytokine release and chemotaxis of LPS/TNF-α-activated neutrophils in vitro. Dehydroandrographolide inhibited neutrophils activation via binding to LMIR3. Moreover, dehydroandrographolide up-regulated the phosphorylation of SHP-1 and SHP-2, which are the essential kinases in the LMIR3 signaling pathways. This study revealed that dehydroandrographolide attenuated collagen-induced arthritis by suppressing neutrophil activation via LMIR3.

How Neutrophils Shape the Immune Response: Reassessing Their Multifaceted Role in Health and Disease

Neutrophils are the most abundant of the circulating immune cells and are the first to be recruited to sites of inflammation. Neutrophils are a heterogeneous group of immune cells from which are derived extracellular traps (NETs), reactive oxygen species, cytokines, chemokines, immunomodulatory factors, and alarmins that regulate the recruitment and phenotypes of neutrophils, macrophages, dendritic cells, T cells, and B cells. In addition, cytokine-stimulated neutrophils can express class II major histocompatibility complex and the internal machinery necessary for successful antigen presentation to memory CD4+ T cells. This may be relevant in the context of vaccine memory. Neutrophils thus emerge as orchestrators of immune responses that play a key role in determining the outcome of infections, vaccine efficacy, and chronic diseases like autoimmunity and cancer. This review aims to provide a synthesis of current evidence as regards the role of these functions of neutrophils in homeostasis and disease.

Relationship of Complete Blood Count Derived Biomarkers With Methotrexate Resistance

Background Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and joint damage. Among the therapeutic agents, methotrexate remains a cornerstone of initial treatment. Complete blood count (CBC)-derived biomarkers such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), and systemic immune response index (SIRI) have been extensively studied in various diseases. Still, their specific role in RA patients undergoing methotrexate treatment has not been investigated. Objective This study aimed to investigate the relationship of CBC-derived biomarkers with methotrexate resistance in newly diagnosed rheumatoid arthritis patients. Methods We performed a comprehensive analysis of 54 RA patients, divided into methotrexate-resistant (MTXR) and methotrexate-sensitive (MTXS) groups. Analysis of variance (ANOVA) was used to assess differences in hematological biomarkers between groups. Standard t-tests were used to compare specific biomarkers between the MTXR and MTXS groups. The chi-squared test was used to compare categorical variables between groups. Pearson's correlation test was also used to examine correlations between these biomarkers and Disease Activity Score 28 (DAS28) in both groups. Receiver operating characteristic (ROC) curve analysis was performed for each biomarker to determine predictive ability. Results A statistically increased PLR ratio was observed in the MTXR group compared to the MTXS group. Significant correlations between DAS28 and NLR, PLR, SII, and SIRI were observed in the MTXR group. In contrast, these correlations were absent in the MTXS group. In addition to PLR, DAS28 and ESR were significantly higher in the MTXR group than in the MTXS group. None of these biomarkers showed prognostic value for methotrexate treatment outcomes. Conclusion PLR could be used as a biomarker for resistance to methotrexate treatment in a specific RA patient population. Increased PLR and ESR, together with higher DAS28, might be associated with a more pronounced inflammatory state in MTXR patients.

An injectable hydrogel to disrupt neutrophil extracellular traps for treating rheumatoid arthritis

Rheumatoid arthritis (RA), an autoimmune disease, is characterized by inflammatory cell infiltration that damages cartilage, disrupts bone, and impairs joint function. The therapeutic efficacy of RA treatments with the severely affected side remains unsatisfactory despite current treatment methods that primarily focus on anti-inflammatory activity, largely because of the complicatedly pathological mechanisms. A recently identified mechanism for RA development involves the interaction of RA autoantibodies with various proinflammatory cytokines to facilitate the formation of neutrophil extracellular traps (NETs), which increased inflammatory responses to express inflammatory cytokines and chemokines. Therefore, NETs architecture digestion may inhibit the positive-feedback inflammatory signal pathway and lessen joint damage in RA. In this work, deoxyribonuclease I (DNase) is connected to oxidized hyaluronic acid (OHA) via Schiff base reaction to extend the half-life of DNase. The modification does not influence the DNase activity for plasmid deoxyribonucleic acid hydrolysis and NETs' architecture disruption. Carboxymethyl chitosan is crosslinked with DNase-functionalised OHA (DHA) to form an injectable, degradable, and biocompatible hydrogel (DHY) to further strengthen the adhesive capability of DHA. Importantly, the collagen-induced arthritis model demonstrates that intra-articular injection of DHY can significantly reduce inflammatory cytokine expression and alleviate RA symptoms, which can be significantly improved by combining methotrexate. Here, a DNase-functionalised hydrogel has been developed for RA treatment by constantly degrading the novel drug target of NETs to decrease inflammatory response in RA.

Helicobacter pylori extract induces purified neutrophils to produce reactive oxygen species only in the presence of plasma

H. pylori is a bacterial pathogen infecting over half of the world's population and induces several gastric and extra-gastric diseases through its various virulence factors, especially cagA. These factors may be released from the bacteria during interactions with host immune cells. Neutrophils play key roles in innate immunity, and their activity is regulated by plasma factors, which can alter how these cells may interact with pathogens. The aim of the present study was to determine whether purified neutrophils could produce reactive oxygen species (ROS), one of the key functions of their anti-microbial functions, in response to extracts of cagA+ and cagA- H. pylori. Extracts from either cagA+ or cagA- H. pylori were co-cultured with human neutrophils in the presence or absence of plasma, and the neutrophil ROS production was measured. In the absence of plasma, extracts from cagA+ and cagA- H. pylori did not induce neutrophil ROS production, whereas in the presence of plasma, extracts from both cagA+ and cagA- H. pylori-induced ROS production. Furthermore, when peripheral blood mononuclear cells (PBMCs) were added to the purified neutrophils in the absence of plasma, there was no neutrophil ROS production after challenging with extracts from either cagA+ or cagA- H. pylori. Thus, it is suggested that plasma contains immunological components that change the responsiveness of neutrophils, such that when neutrophils encounter the bacterial antigens in H. pylori extracts, they become activated and produce ROS. This study also revealed a potential novel immunopathogenic pathway by which cagA activation of neutrophils contributed to inflammatory damage.

Single-cell transcriptomics reveals peripheral immune responses in non-segmental vitiligo

Background

Vitiligo is a common autoimmune depigmented dermatology due to destruction of melanocytes. Much evidence suggests that vitiligo is associated with systemic immune activation. Previous studies have focused on immune cell infiltration in and around lesion areas, but few studies have investigated the cell types and function of circulating immune cells in peripheral blood. Here, single cell RNA-sequencing (scRNA-seq) was used to investigate the mechanisms of peripheral immune responses in vitiligo patients.

Methods

Peripheral blood was collected from five patients with progressive non-segmental vitiligo and three healthy controls. Peripheral blood mononuclear cells (PBMCs) were obtained by Ficoll-Paque density gradient centrifugation, and scRNA-seq was performed on isolated cell populations to obtain single cell transcriptomes and characterize important genes and intracellular signaling pathways. The key findings were validated with qPCR and flow cytometry assays.

Results

We identified 10 major cell types by scRNA-seq. Among these cell types, neutrophils were specifically observed in our scRNA-seq data from PBMCs. Peripheral blood effector CD8+ T cells from vitiligo patients did not show significant differences at the transcriptome level compared with healthy controls, whereas regulatory T cells showed pro-inflammatory TH1-like properties. Innate immune cells, including natural killer cells and dendritic cells, showed increased antigen processing and presentation as well as upregulated interferon responses. B cells, monocytes, and neutrophils all showed activation. B cells, especially memory B cells, had upregulated expression of genes related to humoral immunity. Monocytes showed production of proinflammatory cytokines and chemokines. Neutrophils showed strong chemokine ligand-receptor (L-R) pair (CXCR8-CXCR2) autocrine signaling pathway.

Conclusion

This study revealed the genetic profile and signaling pathway characteristics of peripheral blood immune cells in vitiligo patients, providing new insights into its pathogenesis, which may facilitate identification of potential therapeutic targets.

Neutrophils in Inflammatory Diseases: Unraveling the Impact of Their Derived Molecules and Heterogeneity

Inflammatory diseases involve numerous disorders and medical conditions defined by an insufficient level of self-tolerance. These diseases evolve over the course of a multi-step process through which environmental variables play a crucial role in the emergence of aberrant innate and adaptive immunological responses. According to experimental data accumulated over the past decade, neutrophils play a significant role as effector cells in innate immunity. However, neutrophils are also involved in the progression of numerous diseases through participation in the onset and maintenance of immune-mediated dysregulation by releasing neutrophil-derived molecules and forming neutrophil extracellular traps, ultimately causing destruction of tissues. Additionally, neutrophils have a wide variety of functional heterogeneity with adverse effects on inflammatory diseases. However, the complicated role of neutrophil biology and its heterogeneity in inflammatory diseases remains unclear. Moreover, neutrophils are considered an intriguing target of interventional therapies due to their multifaceted role in a number of diseases. Several approaches have been developed to therapeutically target neutrophils, involving strategies to improve neutrophil function, with various compounds and inhibitors currently undergoing clinical trials, although challenges and contradictions in the field persist. This review outlines the current literature on roles of neutrophils, neutrophil-derived molecules, and neutrophil heterogeneity in the pathogenesis of autoimmune and inflammatory diseases with potential future therapeutic strategies.

Neutrophils, neutrophil extracellular traps, and rheumatoid arthritis: An updated review for clinicians

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by the presence of autoantibodies. Research on the pathogenic mechanisms involved in systemic autoimmune diseases has largely focused on the involvement of the adaptive immune system with dysregulated responses of T and B cells. However, in recent years, there is increasing evidence of the significant role played by the innate immune system, particularly neutrophils, in these diseases, particularly in RA. Neutrophil extracellular traps (NETs) are extracellular structures composed of remodeled and concentrated chromatin with DNA, histones, and neutrophil proteins, and were first described in 2004. It has been studied that NETs may play a pathogenic role in RA and could be a source of autoantigens, increasing the immune response in the form of autoantibodies in this disease. The possible role of NETs and other markers of neutrophil activation as biomarkers of activity in RA and other immune-mediated diseases has also been studied. This article reviews the role of NETs in RA. It discusses the role of neutrophils and the latest advances in NETs, especially their involvement in autoimmune phenomena in RA. Finally, a literature review is conducted on the determination of NETs in peripheral blood and their relationship as a biomarker of RA activity, as well as their potential role in disease monitoring.

Early Depletion of Neutrophils Reduces Retinal Inflammation and Neovascularization in Mice with Oxygen-Induced Retinopathy

Retinal inflammation is a central feature of ocular neovascular diseases such as diabetic retinopathy and retinopathy of prematurity, but the contribution of neutrophils to this process is not fully understood. We studied oxygen-induced retinopathy (OIR) which develops in two phases, featuring hyperoxia-induced retinal vaso-obliteration in phase I, followed by retinal neovascularization in phase II. As neutrophils are acute responders to tissue damage, we evaluated whether neutrophil depletion with an anti-Ly6G mAb administered in phase I OIR influenced retinal inflammation and vascular injury. Neutrophils were measured in blood and spleen via flow cytometry, and myeloperoxidase, an indicator of neutrophil activity, was evaluated in the retina using Western blotting. Retinal vasculopathy was assessed by quantitating vaso-obliteration, neovascularization, vascular leakage, and VEGF levels. The inflammatory factors, TNF, MCP-1, and ICAM-1 were measured in retina. In the OIR controls, neutrophils were increased in the blood and spleen in phase I but not phase II OIR. In OIR, the anti-Ly6G mAb reduced neutrophils in the blood and spleen, and myeloperoxidase, inflammation, and vasculopathy in the retina. Our findings revealed that the early rise in neutrophils in OIR primes the retina for an inflammatory and angiogenic response that promotes severe damage to the retinal vasculature.

Sialylation: An alternative to designing long-acting and targeted drug delivery system

Long-acting and specific targeting are two important properties of excellent drug delivery systems. Currently, the long-acting strategies based on polyethylene glycol (PEG) are controversial, and PEGylation is incapable of simultaneously possessing targeting ability. Thus, it is crucial to identify and develop approaches to produce long-acting and targeted drug delivery systems. Sialic acid (SA) is an endogenous, negatively charged, nine-carbon monosaccharide. SA not only mediates immune escape in the body but also binds to numerous disease related targets. This suggests a potential strategy, namely "sialylation," for preparing long-acting and targeted drug delivery systems. This review focuses on the application status of SA-based long-acting and targeted agents as a reference for subsequent research.

The association between neutrophil-to-lymphocyte ratio and disease activity in rheumatoid arthritis

The inflammatory response is responsible for the promotion of pannus development over the joint, which is the primary factor in joint injury in rheumatoid arthritis (RA). More in-depth investigations have been conducted in recent years leading to a greater understanding of RA. Yet, it's difficult to gauge inflammation levels in RA patients. Some people who have RA do not exhibit normal symptoms, which makes it more challenging to make a diagnosis. Typical RA evaluations are subject to a few restrictions. Earlier research demonstrated that some patients continued to experience the progression of bone and joint degeneration even while in clinical remission. This progression was attributed to ongoing synovial inflammation. As a result, performing a precise evaluation of the level of inflammation is of the utmost importance. The neutrophil-to-lymphocyte ratio (NLR) has consistently been one of the most interesting novel non-specific inflammatory indicators. It is a reflection of the equilibrium between lymphocytes and neutrophils, which are inflammatory regulators and inflammatory activators, respectively. A higher NLR is linked to more severe levels of imbalance and inflammation. The aim of this study was to depict the role of NLR in RA progression and to show if NLR could predict the response to disease-modifying antirheumatic drugs (DMARDs) therapy in RA.

Cystic fibrosis autoantibody signatures associate with Staphylococcus aureus lung infection or cystic fibrosis-related diabetes

Introduction

While cystic fibrosis (CF) lung disease is characterized by persistent inflammation and infections and chronic inflammatory diseases are often accompanied by autoimmunity, autoimmune reactivity in CF has not been studied in depth.

Methods

In this work we undertook an unbiased approach to explore the systemic autoantibody repertoire in CF using autoantibody microarrays.

Results and discussion

Our results show higher levels of several new autoantibodies in the blood of people with CF (PwCF) compared to control subjects. Some of these are IgA autoantibodies targeting neutrophil components or autoantigens linked to neutrophil-mediated tissue damage in CF. We also found that people with CF with higher systemic IgM autoantibody levels have lower prevalence of S. aureus infection. On the other hand, IgM autoantibody levels in S. aureus-infected PwCF correlate with lung disease severity. Diabetic PwCF have significantly higher levels of IgA autoantibodies in their circulation compared to nondiabetic PwCF and several of their IgM autoantibodies associate with worse lung disease. In contrast, in nondiabetic PwCF blood levels of IgA autoantibodies correlate with lung disease. We have also identified other autoantibodies in CF that associate with P. aeruginosa airway infection. In summary, we have identified several new autoantibodies and associations of autoantibody signatures with specific clinical features in CF.

Neutrophil extracellular traps and extracellular histones potentiate IL-17 inflammation in periodontitis

Neutrophil infiltration is a hallmark of periodontitis, a prevalent oral inflammatory condition in which Th17-driven mucosal inflammation leads to destruction of tooth-supporting bone. Herein, we document that neutrophil extracellular traps (NETs) are early triggers of pathogenic inflammation in periodontitis. In an established animal model, we demonstrate that neutrophils infiltrate the gingival oral mucosa at early time points after disease induction and expel NETs to trigger mucosal inflammation and bone destruction in vivo. Investigating mechanisms by which NETs drive inflammatory bone loss, we find that extracellular histones, a major component of NETs, trigger upregulation of IL-17/Th17 responses, and bone destruction. Importantly, human findings corroborate our experimental work. We document significantly increased levels of NET complexes and extracellular histones bearing classic NET-associated posttranslational modifications, in blood and local lesions of severe periodontitis patients, in the absence of confounding disease. Our findings suggest a feed-forward loop in which NETs trigger IL-17 immunity to promote immunopathology in a prevalent human inflammatory disease.

Global research trends and focus on the link between rheumatoid arthritis and neutrophil extracellular traps: a bibliometric analysis from 1985 to 2023

Rheumatoid arthritis (RA) is an autoimmune disease that currently has an unknown cause and pathogenesis, and is associated with many complications and a high disability rate. The neutrophil extracellular trap network (NETs) is a newly discovered mechanism that allows neutrophils to capture and kill pathogens. Multiple studies in recent years have highlighted its relevance to the progression of rheumatoid arthritis. Despite the growing number of studies indicating the crucial role of NETs in RA, there has been no bibliometric review of research hotspots and trends in this area. In this study, we retrieved articles related to NETs in RA from the Web of Science Core Collection (WoSCC) database from 1985 to 2023 and used visualization tools such as Citespace, VOSviewer, Tableau Public, and Microsoft Office Excel 2021 to analyze the data. After screening, we included a total of 416 publications involving 2,334 researchers from 1,357 institutions in 167 countries/regions, with relevant articles published in 219 journals. The U.S., China, and Germany are the top 3 countries/regions with 124, 57, and 37 publications respectively. Mariana J. Kaplan is the most published author, and journals such as Frontiers in Immunology and International Journal of Molecular Sciences have had a significant impact on research in this field. The clinical application of PAD enzymes and their inhibitors, and the drug development of NETs as therapeutic targets for RA is a trend for future research. Our study provides a comprehensive bibliometric analysis and summary of NETs in RA publications, which will aid researchers in conducting further scientific research.

Brensocatib (an oral, reversible inhibitor of dipeptidyl peptidase-1) attenuates disease progression in two animal models of rheumatoid arthritis

Rheumatoid arthritis (RA) is a painful and incurable disease characterized by chronic joint inflammation and a progressive destruction of cartilage and bone. Although current treatments have improved clinical outcomes for some patients, the high relapse rates and sizeable proportion of non-responders emphasize the need for further research. Arthritic joints are massively infiltrated by neutrophils, which influence inflammatory and immune processes by releasing cytokines, chemokines, eicosanoids, and neutrophil serine proteases (NSPs) - all of which are known to contribute to RA initiation and progression. Active NSPs are generated from zymogens at the promyelocytic stage of neutrophil differentiation under the action of dipeptidyl peptidase 1 (DPP-1) and DPP-1 knockout mice are resistant to the development of arthritis. Thus, DPP-1 inhibition represents a promising therapeutic approach in RA. In this study, we assessed the efficacy of a potent and highly selective DPP-1 inhibitor, brensocatib, in two well established RA models - rat collagen-induced arthritis (CIA) and mouse collagen antibody-induced arthritis (CAIA). In both models, brensocatib at 3 and 30 mg/kg/day significantly reduced bone marrow NSP levels, in keeping with prior pharmacodynamic studies in rodents. More importantly, brensocatib treatment significantly improved disease score at both dosages in both rodent models. In the mouse CAIA model, brensocatib even proved at least as potent as anti-TNF antibodies in diminishing both the histopathological score and neutrophil infiltration into arthritic joints. Together, these results show that brensocatib alters RA disease progression in rodents and supports the need for its further evaluation as a potential therapeutic option, or to complement existing RA treatments.

Research Progress of Neutrophil-Mediated Drug Delivery Strategies for Inflammation-Related Disease

As the most abundant white blood cells in humans, neutrophils play a key role in acute and chronic inflammation, suggesting that these cells are a key component of targeted therapies for various inflammation-related diseases. Specific enzyme-responsive or specific ligand-modified polymer nanoparticles are beneficial for improving drug efficacy, reducing toxicity, and enhancing focal site retention. However, there remain significant challenges in biomedical applications of these synthetic polymer nanoparticles, mainly due to their rapid clearance by the reticuloendothelial system. In recent years, biomimetic drug delivery systems such as neutrophils acting directly as drug carriers or neutrophil-membrane-coated nanoparticles have received increasing attention due to the natural advantages of neutrophils. Thus, neutrophil-targeted, neutrophil-assisted, or neutrophil-coated nanoparticles exhibit a prolonged blood circulation time and improved accumulation at the site of inflammation. Despite recent advancements, further clinical research must be performed to evaluate neutrophil-based delivery systems for future biomedical application in the diagnosis and treatment of related inflammatory diseases. In this review, we have summarized new exciting developments and challenges in neutrophil-mediated drug delivery strategies for treating inflammation-related diseases.

Mass spectrometric investigations of the action of hypochlorous acid on monomeric and oligomeric components of glycosaminoglycans

Hypochlorous acid (HOCl) is a strong non-radical oxidant, which is generated during inflammatory processes under the catalysis of the enzyme myeloperoxidase (MPO). HOCl reacts particularly with sulfhydryl and amino acid residues but affects also many other biomolecules. For instance, the glycosaminoglycans of articular cartilage and synovial fluids (such as hyaluronan) undergo degradation in the presence of HOCl at which the native polysaccharide is fragmented into oligosaccharides in a complex reaction. This is an initial mass spectrometry (MS)-based investigation dealing with the HOCl-induced degradation of glycosaminoglycans and the conversion of the related monosaccharides into chlorinated products. In particular, it will be shown that the reaction between HOCl and hyaluronan is slower than originally assumed and results in the generation of different products (particularly the hyaluronan monosaccharides) by the cleavage of the β-1,3/1,4-glycosidic linkages. The MS detection of chlorinated products is, however, only possible in the case of the monosaccharides. Potential reasons will be discussed.

Targeting cyclin-dependent kinases in rheumatoid arthritis and psoriasis - a review of current evidence

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with synovial proliferation and bone erosion, which leads to the structural and functional impairment of the joints. Immune cells, together with synoviocytes, induce a pro-inflammatory environment and novel treatment agents target inflammatory cytokines. Psoriasis is a chronic immune-mediated skin disease, and several cytokines are considered as typical mediators in the progression of the disease, including IL-23, IL-22, and IL-17, among others.

AREA COVERED

In this review, we try to evaluate whether cyclin-dependent kinases (CDK), enzymes that regulate cell cycle and transcription of various genes, could become novel therapeutic targets in RA and psoriasis. We present the main results of in vitro and in vivo studies, as well as scarce clinical reports.

EXPERT OPINION

CDK inhibitors seem promising for treating RA and psoriasis because of their multidirectional effects. CDK inhibitors may affect not only the process of osteoclastogenesis, thereby reducing joint destruction in RA, but also the process of apoptosis of neutrophils and macrophages responsible for the development of inflammation in both RA and psoriasis. However, assessing the efficacy of these drugs in clinical practice requires multi-center, long-term clinical trials evaluating the effectiveness and safety of CDK-blocking therapy in RA and psoriasis.

Neutrophil extracellular trap-associated carbamylation and histones trigger osteoclast formation in rheumatoid arthritis

OBJECTIVE

Neutrophil infiltration into the synovial joint is a hallmark of rheumatoid arthritis (RA), a disease characterised by progressive bone erosion. However, the mechanisms by which neutrophils participate in bone destruction remain unclear. Carbamylation is a posttranslational modification linked to increased bone erosion in RA and we previously showed that carbamylation is present in RA neutrophil extracellular traps (NETs). However, it remains unclear whether NETs and their carbamylated protein cargo directly promote bone destruction and alter osteoclast biology.

METHODS

NETs and carbamylated NETs (cNETs) were assessed for their capacity to induce osteoclast formation in CD14+ monocytes. Chemical inhibitors and neutralising antibodies were used to elucidate the pathway by which NETs induce osteoclastogenesis. HLA-DRB1*04:01 mice received intra-articular injection of cNETs for 4 weeks. Joints were isolated and assessed for osteoclast formation. Plasma and synovial fluid samples from patients with RA (n=32) were assessed for the presence of carbamylated histone, and correlations to disease specific outcomes were performed.

RESULTS

We found that NETs, when cNETs, instruct monocytes to undergo rapid osteoclast formation. NET-mediated osteoclastogenesis appears to depend on Toll-like receptor 4 signalling and NET-associated proteins including histones and neutrophil elastase. In vivo, we identified that the number of osteoclasts increased following immunisation with cNETs in HLA-DRB1*04:01 transgenic mice. Furthermore, carbamylated histones are increased in plasma and synovial fluid from patients with RA and correlate with active bone resorption and inflammatory markers.

CONCLUSIONS

Our results suggest that NETs have a direct role in RA-associated bone erosion by promoting osteoclast formation.

Glutathione peroxidase 3 is a novel clinical diagnostic biomarker and potential therapeutic target for neutrophils in rheumatoid arthritis

BACKGROUND

Neutrophils have a critical role in the pathogenesis of rheumatoid arthritis (RA) with immune system dysfunction. However, the molecular mechanisms of this process mediated by neutrophils still remain elusive. The purpose of the present study is to identify hub genes in neutrophils for diagnosis and treatment of RA utilizing publicly available datasets.

METHODS

Gene expression profiles were downloaded from the Gene Expression Omnibus, and batch-corrected and normalized expression data were obtained using the ComBat package. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were used to conduct significantly functional analysis and crucial pathways. The resulting co-expression genes modules and hub genes were generated based on the weighted gene co-expression network analysis and visualization by Cytoscape. Flow cytometry was conducted to detect reactive oxygen species (ROS) levels in neutrophils.

RESULTS

Neutrophils underwent transcriptional changes in synovial fluid (SF) of RA patients, different from peripheral blood of healthy controls or patients with RA. Especially, glycolysis, HIF-1 signaling, NADH metabolism, and oxidative stress were affected. These hub genes were strongly linked with classical glycolysis-related genes (ENO1, GAPDH, and PKM) responsible for ROS production. The antioxidant enzyme glutathione peroxidase 3 (GPX3), a ROS scavenger, was first identified as a hub gene in RA neutrophils. Neutrophils from patients with autoinflammatory and autoimmune diseases had markedly enhanced ROS levels, most notably in RA SF.

CONCLUSION

This research recognized hub genes and explored the characteristics of neutrophils in RA. Our findings suggest that the novel hub gene GPX3 is involved in the neutrophil-driven oxidative stress-mediated pathogenesis of RA. It has the potency to be a target for neutrophil-directed RA therapy.

Design Strategies for Cellular Nanosponges as Medical Countermeasures

The interest in using therapeutic nanoparticles to bind with harmful molecules or pathogens and subsequently neutralize their bioactivity has grown tremendously. Among various nanomedicine platforms, cell membrane-coated nanoparticles, namely, "cellular nanosponges," stand out for their broad-spectrum neutralization capability challenging to achieve in traditional countermeasure technologies. Such ability is attributable to their cellular function-based rather than target structure-based working principle. Integrating cellular nanosponges with various synthetic substrates further makes their applications exceptionally versatile and adaptive. This review discusses the latest cellular nanosponge technology focusing on how the structure-function relationship in different designs has led to versatile and potent medical countermeasures. Four design strategies are discussed, including harnessing native cell membrane functions for biological neutralization, functionalizing cell membrane coatings to enhance neutralization capabilities, combining cell membranes and functional cores for multimodal neutralization, and integrating cellular nanosponges with hydrogels for localized applications. Examples in each design strategy are selected, and the discussion is to highlight their structure-function relationships in complex disease settings. The review may inspire additional design strategies for cellular nanosponges and fulfill even broader medical applications.

Genetic susceptibility for autoimmune diseases and white blood cell count

Some autoimmune (AI) conditions affect white blood cell (WBC) counts. Whether a genetic predisposition to AI disease associates with WBC counts in populations expected to have low numbers of AI cases is not known. We developed genetic instruments for 7 AI diseases using genome-wide association study summary statistics. Two-sample inverse variance weighted regression (IVWR) was used to determine associations between each instrument and WBC counts. Effect size represents change in transformed WBC counts per change in log odds-ratio of the disease. For AI diseases with significant associations by IVWR, polygenic risk scores (PRS) were used to test for associations with measured WBC counts in individuals of European ancestry in a community-based (ARIC, n = 8926), and a medical-center derived cohort (BioVU, n = 40,461). The IVWR analyses revealed significant associations between 3 AI diseases and WBC counts: systemic lupus erythematous (Beta = - 0.05 [95% CI, - 0.06, - 0.03]), multiple sclerosis (Beta =  - 0.06 [- 0.10, - 0.03]), and rheumatoid arthritis (Beta = 0.02 [0.01, 0.03]). PRS for these diseases showed associations with measured WBC counts in ARIC and BioVU. Effect sizes tended to be larger among females, consistent with the known higher prevalence of these diseases among this group. This study shows that genetic predisposition to systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis was associated with WBC counts, even in populations expected to have very low numbers of disease cases.

Simiao Yong'an decoction ameliorates murine collagen-induced arthritis by modulating neutrophil activities: An in vitro and in vivo study

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a common systemic autoimmune disease with high morbidity and disability rate. Currently, there is no effective allopathic treatment for RA, and most of the drugs provoke many adverse effects. Simiao Yong'an decoction (SMYAD) is a traditional Chinese prescription for the treatment of sore and gangrene caused by hot poison. With the development of pharmacology and clinical research, SMYAD has remarkable anti-inflammatory properties and has been used for RA treatments for years.

AIM OF THE STUDY

This study aimed to investigate the anti-arthritic effect of SMYAD and further explore the immunopharmacological mechanisms.

MATERIALS AND METHODS

Arthritis was induced in DBA/1 mice by two-time immunizations. Collagen-induced rheumatoid arthritis (CIA) mice were divided into 4 groups: control, model, methotrexate (MTX), and SMYAD group (n = 6). The administration groups were given MTX (0.5 mg/kg/3 d) and SMYAD (4.5 g/kg/d) by gavage from day 14. The arthritis index (AI) score was evaluated every 3 days after the second immunization. Hematoxylin and eosin (H&E) staining, Safranin-O fast green staining, Trap staining, and Micro-CT were used to measure the histopathology injuries and bone destruction of joints. Granulocyte changes in the spleen, bone marrow, and period blood were analyzed by flow cytometry. The expression of inflammatory cytokines and chemokines in joints were detected by qRT-PCR. SMYAD-containing serum was obtained from SD rats gavaged with SMYAD. Neutrophils were isolated from peripheral blood and bone marrow for the in vitro experiments of transwell cell assay, apoptosis assay, reactive oxygen species (ROS) generation and neutrophil extracellular traps (NETs) formation.

RESULTS

SMYAD significantly relieved arthritis severity in CIA mice. The AI score was significantly decreased in the SMYAD group compared with the model group. Additionally, SMYAD alleviated inflammatory infiltration, cartilage damage, osteoclast formation, and bone damage in the ankle joints. In the flow cytometry assay, SMYAD significantly reduced granulocytes number in the spleen and bone marrow, while increased in peripheral blood. Furthermore, compared with the CIA group, SMYAD suppressed the mRNA levels of inflammatory factors including TNF-α, IL-1β, IL-6 and chemokines CXCL1, CXCL2, and IL-8 in the inflamed joints. In the in vitro studies, 20% SMYAD-containing serum effectively inhibited the migration of neutrophils, promoted neutrophils apoptosis, reduced ROS production and NETs formation.

CONCLUSION

Collectively, our results demonstrated that SMYAD effectively restrained arthritis in CIA mice by modulating neutrophil activities.