Neutrophil Extracellular Traps in Systemic Lupus Erythematosus Stimulate IgG2 Production From B Lymphocytes

A variety of death modes of neutrophils and their role in the etiology of autoimmune diseases

Neutrophils are important in the context of innate immunity and actively contribute to the progression of diverse autoimmune disorders. Distinct death mechanisms of neutrophils may exhibit specific and pivotal roles in autoimmune diseases and disease pathogenesis through the orchestration of immune homeostasis, the facilitation of autoantibody production, the induction of tissue and organ damage, and the incitement of pathological alterations. In recent years, more studies have provided in-depth examination of various neutrophil death modes, revealing nuances that challenge conventional understanding and underscoring their potential clinical utility in diagnosis and treatment. This review explores the multifaceted processes and characteristics of neutrophil death, with a focus on tailored investigations within various autoimmune diseases. It also highlights the potential interplay between neutrophil death and the landscape of autoimmune disorders. The review encapsulates the pertinent pathways implicated in various neutrophil death mechanisms across diverse autoimmune diseases while also charts possible avenues for future research.

Neutrophil extracellular traps drive lupus flares with acute skin and kidney inflammation triggered by ultraviolet irradiation

Sunlight triggers lupus flares causing both local skin and systemic inflammation, including lupus nephritis, through poorly understood mechanisms. To address this knowledge gap, we found that UVB irradiation of asymptomatic, young female lupus-prone mice induced skin and kidney inflammation with proteinuria, accompanied by neutrophil infiltration and neutrophil extracellular trap (NET) formation. Furthermore, UVB irradiation induced co-expression of CXCR4 and cytokines/C3 by neutrophils in vitro and in vivo, in the skin and kidneys of lupus-prone mice, indicating their transmigratory and pro-inflammatory potentials. A causality study demonstrated that inhibiting CXCR4 attenuated renal neutrophil infiltration, accumulation of NETs, NET-associated cytokines/C3, and proteinuria in UVB-irradiated lupus-prone mice. Remarkably, inhibiting NETosis through a novel strategy targeting nuclear envelope integrity reduced deposition of NET-associated cytokines/C3 in skin and kidneys, attenuating proteinuria in UVB-irradiated MRL/lpr·lmnB1 Tg mice. Our investigation unveils a new mechanism by which neutrophil NETs drive the early onset of lupus flares triggered by UVB-irradiation. Targeting neutrophil transmigration and NETosis could be promising therapeutic strategies.

Systemic lupus erythematosus: latest insight into etiopathogenesis

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder of unknown etiology. Multifactorial interaction among various susceptible factors such as environmental, hormonal, and genetic factors makes it more heterogeneous and complex. Genetic and epigenetic modifications have been realized to regulate the immunobiology of lupus through environmental modifications such as diet and nutrition. Although these interactions may vary from population to population, the understanding of these risk factors can enhance the perception of the mechanistic basis of lupus etiology. To recognize the recent advances in lupus, an electronic search was conducted among search engines such as Google Scholar and PubMed, where we found about 30.4% publications of total studies related to genetics and epigenetics, 33.5% publications related to immunobiology and 34% related to environmental factors. These outcomes suggested that management of diet and lifestyle have a direct relationship with the severity of lupus that influence via modulating the complex interaction among genetics and immunobiology. The present review emphasizes the knowledge about the multifactorial interactions between various susceptible factors based on recent advances that will further update the understanding of mechanisms involved in disease pathoetiology. Knowledge of these mechanisms will further assist in the creation of novel diagnostic and therapeutic options.

Neutrophil extracellular traps primed intercellular communication in cancer progression as a promising therapeutic target

In addition to the anti-infection response, neutrophils are linked to tumor progression through the secretion of inflammation components and neutrophil extracellular traps (NETs) formation. NET is a web-like structure constituted by a chromatin scaffold coated with specific nuclear and cytoplasmic proteins, such as histone and granule peptides. Increasing evidence has demonstrated that NETs are favorable factors to promote tumor growth, invasion, migration, and immunosuppression. However, the cell-cell interaction between NETs and other cells (tumor cells and immune cells) is complicated and poorly studied. This work is the first review to focus on the intercellular communication mediated by NETs in cancer. We summarized the complex cell-cell interaction between NETs and other cells in the tumor microenvironment. We also address the significance of NETs as both prognostic/predictive biomarkers and molecular targets for cancer therapy. Moreover, we presented a comprehensive landscape of cancer immunity, improving the therapeutic efficacy for advanced cancer in the future.

Insights into the pathogenic role of neutrophils in systemic lupus erythematosus

PURPOSE OF REVIEW

Although dysregulated adaptive immune response has been considered as the main culprit for systemic lupus erythematosus (SLE), emerging studies have indicated that innate immunity, functioning upstream of adaptive immunity, acts as an important trigger of autoimmune diseases and promotes SLE development. Here, we have reviewed the most recent findings to highlight the influence of neutrophils on SLE pathogenesis.

RECENT FINDINGS

Neutrophils participate in SLE development mainly via promoting self-antigen exposure and autoantibody production, advocating the release of type I interferons (IFNs) and other pro-inflammatory cytokines, and mediating systemic tissue injury. A recent study revealed that neutrophil ferroptosis exerts a strong pathogenic effect in SLE, and that dysregulated innate immunity is adequate to disrupt the homeostasis of immune tolerance.

SUMMARY

Insights into the pathogenic role of neutrophils in SLE will contribute to a more comprehensive understanding of this disease and may propose novel clinical targets for accurate diagnosis and precision medicine.

Increased formation of neutrophil extracellular traps in patients with anti-N-methyl-d-aspartate receptor encephalitis

Background

Neutrophil extracellular traps (NETs) have been found to play an important role in several nervous system diseases. However, their role in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis remains unclear. The purpose of this study was to examine the possible role of NETs in anti-NMDAR encephalitis.

Materials and methods

Eleven patients with anti-NMDAR encephalitis and ten healthy participants were enrolled. Plasma NETs levels were detected using an immunofluorescence assay and enzyme-linked immunosorbent assay. Additionally, we examined 10 plasma cytokines in patients with anti-NMDAR encephalitis and analyzed the correlation between citrullinated histone 3 levels and cytokine release.

Results

Peripheral blood neutrophils from patients with anti-NMDAR encephalitis were more susceptible to NET generation. When compared with controls, cases of anti-NMDAR encephalitis showed elevated levels of IL-1 α, IL-6, IL-8, IL-13, MCP-1, and TNF-α (p < 0.05). Moreover, IL-6, IL-8, and TNF-α levels were positively correlated with H3Cit levels.

Conclusion

We provide evidence that NETs may play a role in anti-NMDAR encephalitis, providing clues for elucidation of the pathogenesis of this disease.

NET Formation in Systemic Lupus Erythematosus: Changes during the COVID-19 Pandemic

The severity of the coronavirus disease in 2019 (COVID-19) is strongly linked to a dysregulated immune response. This fuels the fear of severe disease in patients with autoimmune disorders continuously using immunosuppressive/immunomodulating medications. One complication of COVID-19 is thromboembolism caused by intravascular aggregates of neutrophil extracellular traps (NETs) occluding the affected vessels. Like COVID-19, systemic lupus erythematosus (SLE) is characterized by, amongst others, an increased risk of thromboembolism. An imbalance between NET formation and clearance is suggested to play a prominent role in exacerbating autoimmunity and disease severity. Serologic evidence of exposure to SARS-CoV-2 has a minor impact on the SLE course in a Swedish cohort reportedly. Herein, we assessed NET formation in patients from this cohort by neutrophil elastase (NE) activity and the presence of cell-free DNA, MPO-DNA, and NE-DNA complexes and correlated the findings to the clinical parameters. The presence of NE-DNA complexes and NE activity differed significantly in pre-pandemic versus pandemic serum samples. The latter correlated significantly with the hemoglobin concentration, blood cell counts, and complement protein 3 and 4 levels in the pre-pandemic but only with the leukocyte count and neutrophil levels in the pandemic serum samples. Taken together, our data suggest a change, especially in the NE activity independent of exposure to SARS-CoV-2.

Pathological mechanisms and crosstalk among different forms of cell death in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by a profound immune dysregulation and the presence of a variety of autoantibodies. Aberrant activation of programmed cell death (PCD) signaling and accelerated cell death is critical in the immunopathogenesis of SLE. Accumulating cellular components from the dead cells and ineffective clearance of the dead cell debris, in particular the nucleic acids and nucleic acids-protein complexes, provide a stable source of self-antigens, which potently activate auto-reactive B cells and promote IFN-I responses in SLE. Different cell types display distinct susceptibility and characteristics to a certain type of cell death, while different PCDs in various cells have mutual and intricate connections to promote immune dysregulation and contribute to the development of SLE. In this review, we discuss the role of various cell death pathways and their interactions in the pathogenesis of SLE. An in depth understanding of the interconnections among various forms cell death in SLE will lead to a better understanding of disease pathogenesis, shedding light on the development of novel therapeutic targets.

Anti-alpha enolase multi-antibody specificity in human diseases. Clinical significance and molecular mechanisms

Alpha-enolase (Eno) is an ubiquitary glycolytic enzyme playing multiple functions that go well beyond its principal metabolic role of energy supplier during glycolysis. Eno is localized in the cytoplasm, but also expressed on the cell membrane, where it binds plasminogen allowing its activation. Its shorter form, in the nucleus, acts as transcription factor. In inflammatory conditions, Eno undergoes post-translational modifications, such as citrullination, oxidation and phosphorylation. Eno is also an autoantigen in different disorders. In fact, autoantibodies to Eno have been detected in rheumatoid arthritis, lupus nephritis, primary glomerulonephritis, cancer, infections and other disorders, and in many cases they represent specific markers to be utilized in clinical practice. Anti-Eno antibodies in the different clinical conditions are not equal: they differ in isotype and often recognize different epitopes on the enzyme. IgG1 and IgG3 are prevalent in Rheumatoid Arthritis, IgG2 in Lupus nephritis and IgG4 in primary autoimmune glomerulopathy. This review analyzes the characteristics of anti-Eno autoantibodies in autoimmune disorders and cancer, describing their fine specificity and isotype restriction. The post-translational modifications that are target of autoantibodies are also discussed, as they represent the basis for elucidating the molecular mechanisms responsible for epitope generation. Despite an impressive amount of experimental work on anti-Eno antibodies, it is still necessary to validate the use of anti-Eno antibodies as biomarkers of selected diseases and extend the knowledge on the mechanisms of anti-Eno autoantibody production. Strategies that downmodulate the immune response to Eno may represent in the future novel approaches in the treatment of autoimmune disorders.