Neutrophils in the Pathogenesis of Rheumatic Diseases

Neutrophils with low production of reactive oxygen species are activated during immune priming and promote development of arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease mediated by immune cell dysfunction for which there is no universally effective prevention and treatment strategy. As primary effector cells, neutrophils are important in the inflammatory joint attack during the development of RA. Here, we used single-cell sequencing technology to thoroughly analyze the phenotypic characteristics of bone marrow-derived neutrophils in type II collagen (COL2)-induced arthritis (CIA) models, including mice primed and boosted with COL2. We identified a subpopulation of neutrophils with high expression of neutrophil cytoplasmic factor 1 (NCF1) in primed mice, accompanied by a characteristic reactive oxygen species (ROS) response, and a decrease in Ncf1 expression in boosted mice with the onset of arthritis. Furthermore, we found that after ROS reduction, arthritis occurred in primed mice but was attenuated in boosted mice. This bidirectional effect of ROS suggested a protective role of ROS during immune priming. Mechanistically, we combined functional assays and metabolomics identifying Ncf1-deficient neutrophils with enhanced migration, chemotactic receptor CXCR2 expression, inflammatory cytokine secretion, and Th1/Th17 differentiation. This alteration was mainly due to the metabolic reprogramming of Ncf1-deficient neutrophils from an energy supply pathway dominated by gluconeogenesis to an inflammatory immune pathway associated with the metabolism of histidine, glycine, serine, and threonine signaling, which in turn induced arthritis. In conclusion, we have systematically identified the functional and inflammatory phenotypic characteristics of neutrophils under ROS regulation, which provides a theoretical basis for understanding the pathogenesis of RA, to further improve prevention strategies and identify novel therapeutic targets.

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.

Lipidome profiling of neutrophil-derived extracellular vesicles unveils their contribution to the ensemble of synovial fluid-derived extracellular vesicles during joint inflammation

The molecular signature of cell-derived extracellular vesicles (EVs) from synovial fluid (SF) offers insights into the cells and molecular processes associated with joint disorders and can be exploited to define biomarkers. The EV-signature is determined by cargo molecules and the lesser-studied lipid bilayer. We here investigated the lipidome of SF-EVs in inflamed joints derived from Rheumatoid Arthritis (RA) and Spondyloarthritis (SpA) patients, two autoimmune-driven joint diseases, and compared these signatures to the lipid profile of equine SF-EVs obtained during induced acute synovitis. Since neutrophils are primary SF-infiltrating cells during these inflammatory joint diseases, we also analyzed how inflammatory stimuli alter the lipidomic profile of human and equine neutrophil-derived EVs (nEVs) in vitro and how these signatures relate to the lipidome signatures of SF-EVs from inflamed joints. We identified neutrophil stimulation intensity-dependent changes in the lipidomic profile of nEVs with elevated presence of dihexosylceramide (lactosylceramide), phosphatidylserine, and phosphatidylethanolamine ether-linked lipid classes in human nEVs upon full neutrophil activation. In horses, levels of monohexosylceramide (glucosylceramide) increased instead of dihexosylceramide, indicating species-specific differences. The lipid profiles of RA and SpA SF-EVs were relatively similar and showed a relative resemblance with stimulated human nEVs. Similarly, the lipidome of equine synovitis-derived SF-EVs closer resembled the one of stimulated equine nEVs. Hence, lipidome profiling can provide insights into the contribution of nEVs to the heterogeneous pool of SF-EVs, deepening our understanding of inflammatory joint diseases and revealing molecular changes in joint homeostasis, which can lead to the development of more precise disease diagnosis and treatment strategies.

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.

CAR T cell therapy for refractory pediatric systemic lupus erythematosus: a new era of hope?

Systemic lupus erythematosus (SLE) is a chronic autoimmune condition that can affect multiple organ systems and is heterogenous in its presentation and response to therapy. When diagnosed in childhood, SLE is associated with increased morbidity and mortality compared to adult SLE, often requiring substantial immunosuppression with the risk of significant side effects. There remains a significant unmet need for new therapies that can improve disease control and reduce glucocorticoid and other toxic medication exposure for patients with severe or refractory disease. The pathogenesis of SLE involves B cell dysregulation and autoantibody production, which are a hallmark of the disease. Currently approved B cell directed therapies often result in incomplete B cell depletion and may not target long-lived plasma cells responsible for SLE autoantibodies. It is hypothesized that by persistently eliminating both B cells and plasmablasts, CAR T therapy can halt autoimmunity and prevent organ damage in patient's refractory to current B cell-depleting treatments. Herein we summarize the current preclinical and clinical data utilizing CAR T cells for SLE and discuss the future of this treatment modality for lupus.

(Chemical) Roles of HOCl in Rheumatic Diseases

Chronic rheumatic diseases such as rheumatoid arthritis (RA) are characterized by a dysregulated immune response and persistent inflammation. The large number of neutrophilic granulocytes in the synovial fluid (SF) from RA patients leads to elevated enzyme activities, for example, from myeloperoxidase (MPO) and elastase. Hypochlorous acid (HOCl), as the most important MPO-derived product, is a strong reactive oxygen species (ROS) and known to be involved in the processes of cartilage destruction (particularly regarding the glycosaminoglycans). This review will discuss open questions about the contribution of HOCl in RA in order to improve the understanding of oxidative tissue damaging. First, the (chemical) composition of articular cartilage and SF and the mechanisms of cartilage degradation will be discussed. Afterwards, the products released by neutrophils during inflammation will be summarized and their effects towards the individual, most abundant cartilage compounds (collagen, proteoglycans) and selected cellular components (lipids, DNA) discussed. New developments about neutrophil extracellular traps (NETs) and the use of antioxidants as drugs will be outlined, too. Finally, we will try to estimate the effects induced by these different agents and their contributions in RA.

Synovial fluid extracellular vesicles as arthritis biomarkers: the added value of lipid-profiling and integrated omics

Arthritis, a diverse group of inflammatory joint disorders, poses great challenges in early diagnosis and targeted treatment. Timely intervention is imperative, yet conventional diagnostic methods are not able to detect subtle early symptoms. Hence, there is an urgent need for specific biomarkers that discriminate between different arthritis forms and for early diagnosis. The pursuit of such precise diagnostic tools has prompted a growing interest in extracellular vesicles (EVs). EVs, released by cells in a regulated fashion, are detectable in body fluids, including synovial fluid (SF), which fills the joint space. They provide insights into the intricate molecular landscapes of arthritis, and this has stimulated the search for minimally invasive EV-based diagnostics. As such, the analysis of EVs in SF has become a focus for identifying EV-based biomarkers for joint disease endotyping, prognosis, and progression. EVs are composed of a lipid bilayer and a wide variety of different cargo types, of which proteins and RNAs are widely investigated. In contrast, membrane lipids of EVs, especially the abundance, presence, or absence of specific lipids and their contribution to the biological activity of EVs, are largely overlooked in EV research. Furthermore, the identification of specific combinations of different EV components acting in concert in EVs can fuel the definition of composite biomarkers. We here provide a state-of-the-art overview of the knowledge on SF-derived EVs with emphasis on lipid analysis and we give an example of the added value of integrated proteomics and lipidomics analysis in the search for composite EV-associated biomarkers.

Personalized cardiovascular risk assessment in Rheumatoid Arthritis patients using circulating molecular profiles and their modulation by TNFi, IL6Ri, and JAKinibs

BACKGROUND & OBJECTIVES

This study aimed to: 1) analyze the inflammatory profile of Rheumatoid Arthritis (RA) patients, identifying clinical phenotypes associated with cardiovascular (CV) risk; 2) evaluate biologic and targeted-synthetic disease-modifying antirheumatic drugs (b-DMARDs and ts-DMARDs': TNFi, IL6Ri, JAKinibs) effects; and 3) characterize molecular mechanisms in immune-cell activation and endothelial dysfunction.

PATIENTS & METHODS

A total of 387 RA patients and 45 healthy donors were recruited, forming three cohorts: i) 208 RA patients with established disease but without previous CV events; ii) RA-CVD: 96 RA patients with CV events, and iii) 83 RA patients treated with b-DMARDs/ts-DMARDs for 6 months. Serum inflammatory profiles (cytokines/chemokines/growth factors) and NETosis/oxidative stress-linked biomolecules were evaluated. Mechanistic in vitro studies were performed on monocytes, neutrophils and endothelial cells (EC).

RESULTS

In the first RA-cohort, unsupervised clustering unveiled three distinct groups: cluster 3 (C3) displayed the highest inflammatory profile, significant CV-risk score, and greater atheroma plaques prevalence. In contrast, cluster 1 (C1) exhibited the lowest inflammatory profile and CV risk score, while cluster 2 (C2) displayed an intermediate phenotype. Notably, 2nd cohort RA-CVD patients mirrored C3's inflammation. Treatment with b-DMARDs or ts-DMARDs effectively reduced disease-activity scores (DAS28) and restored normal biomolecules levels, controlling CV risk. In vitro, serum from C3-RA or RA-CVD patients increased neutrophils activity and CV-related protein levels in cultured monocytes and EC, which were partially prevented by pre-incubation with TNFi, IL6Ri, and JAKinibs.

CONCLUSIONS

Overall, analyzing circulating molecular profiles in RA patients holds potential for personalized clinical management, addressing CV risk and assisting healthcare professionals in tailoring treatment, ultimately improving outcomes.

TLR7 activation by imiquimod worsens glycemic control in female FVB/N mice consuming a high-fat diet

Toll-like receptor-7 (TLR7) activation promotes autoimmunity, and metabolic syndrome (MetS) is a common comorbidity in patients with autoimmune disease. We previously demonstrated hyperinsulinemia in TLR7 agonist imiquimod (IMQ)-treated, high-fat diet (HFD)-fed female C57BL/6 mice. Since mouse strains differ in susceptibility to MetS and target organ damage, this study investigated whether 12 weeks of exposure to HFD and IMQ promoted MetS, autoimmunity, and target organ damage in female FVB/N mice. Supporting early-stage autoimmunity, spleen-to-tibia ratio, and anti-nuclear antibodies (ANA) were significantly increased by IMQ. No significant effect of IMQ on urinary albumin excretion or left ventricular hypertrophy was observed. HFD increased liver-to-tibia ratio, which was further exacerbated by IMQ. HFD increased fasting blood glucose levels at the end of 12 weeks, but there was no significant effect of IMQ treatment on fasting blood glucose levels at 6 or 12 weeks of treatment. However, oral glucose tolerance testing at 12 weeks revealed impaired glucose tolerance in HFD-fed mice compared to control diet mice together with IMQ treatment exacerbating the impairment. Accordingly, these data suggest TLR7 activation also exacerbates HFD-induced dysregulation of glucose handling FVB/N mice, supporting the possibility that endogenous TLR7 activation may contribute to dysglycemia in patients with autoimmune disease.

Chronic abdominal aortic occlusive disease related to antiphospholipid syndrome: a rare presentation

OBJECTIVE

Chronic abdominal aortic occlusive disease (CAAOD) is an uncommon manifestation of antiphospholipid syndrome (APS), impacting cardiovascular health and peripheral arterial circulation. We investigated CAAOD in antiphospholipid antibodies (aPL)-positive patients, aimed to offer comprehensive clinical and radiological insights.

METHODS

aPL-positive patients with arterial thrombotic events were categorised into CAAOD and non-CAAOD. Extensive data, including clinical features, radiological images and outcomes, were analysed.

RESULTS

This case-control study involved 114 patients who experienced arterial events from 2013 to 2021, revealing 12 patients with abdominal aortic stenosis or occlusion. The CAAOD group, predominantly young (36.67±11.83) males (75.00%), exhibited significantly higher rates of critical smoking habits (66.67% vs 25.49%, p=0.006) and hyperhomocysteinaemia (66.67% vs 31.37%, p=0.026). Radiological findings showed long-segment infrarenal aorta stenosis in CAAOD, occasionally involving renal and common iliac arteries. The lesions presented varying degrees of stenosis, including smooth lumen narrow and total vascular occlusion. Treatment modalities typically involved interventions or surgery, complementing anticoagulation therapy.

CONCLUSION

The study shed light on the rare occurrence of CAAOD in APS, highlighting the roles of smoking and hyperhomocysteinaemia as notable risk factors. These findings emphasised the significance of early diagnosis and management of CAAOD.

Modulatory immune responses in fungal infection associated with organ transplant - advancements, management, and challenges

Organ transplantation stands as a pivotal achievement in modern medicine, offering hope to individuals with end-stage organ diseases. Advancements in immunology led to improved organ transplant survival through the development of immunosuppressants, but this heightened susceptibility to fungal infections with nonspecific symptoms in recipients. This review aims to establish an intricate balance between immune responses and fungal infections in organ transplant recipients. It explores the fundamental immune mechanisms, recent advances in immune response dynamics, and strategies for immune modulation, encompassing responses to fungal infections, immunomodulatory approaches, diagnostics, treatment challenges, and management. Early diagnosis of fungal infections in transplant patients is emphasized with the understanding that innate immune responses could potentially reduce immunosuppression and promise efficient and safe immuno-modulating treatments. Advances in fungal research and genetic influences on immune-fungal interactions are underscored, as well as the potential of single-cell technologies integrated with machine learning for biomarker discovery. This review provides a snapshot of the complex interplay between immune responses and fungal infections in organ transplantation and underscores key research directions.