Insights into the role of neutrophils in neuropsychiatric systemic lupus erythematosus: Current understanding and future directions

Interaction of low-density neutrophils with other immune cells in the mechanism of inflammation

Low-density neutrophils (LDNs) are a unique subpopulation of neutrophils, play a significant role in regulating innate and adaptive immunity in various inflammation-related diseases. Emerging evidence suggests that LDNs play a significant role in the pathogenesis and progression of various diseases, including infections, autoimmune disorders, and cancer. In this review, we address the origin, development, and heterogeneity of LDNs, and the roles of LDNs in system homeostasis and diseases. We will focus on the findings of the interaction between LDNs and other immune cells. We will then discuss potential novel therapeutic strategies of intervention in diseases by targeting LDNs.

A cross-sectional study on white matter hyperitensity in patients at the initial diagnosis of neuropsychiatric SLE: Correlation with Clinical and Laboratory Findings

OBJECTIVES

This study aimed to investigate the differences between neuropsychiatric systemic lupus erythematosus (NPSLE) patients with and without white matter hyperintensity (WMH) on magnetic resonance imaging (MRI) and to identify factors independently associated with the development of WMH in NPSLE.

METHOD

A comparative analysis was conducted on 84 NPSLE patients hospitalized at Peking University People's Hospital from 2015 to 2022 at the initial diagnosis of NPSLE. Patients were categorized based on the presence of WMH on brain MRI scans. Demographic data, clinical characteristics, and laboratory parameters were reviewed and statistically analyzed.

RESULTS

The study included 84 NPSLE patients, 50% exhibiting WMH (NPSLE-WMH +). At the initial diagnosis of NPSLE, the NPSLE-WMH + group showed significantly higher levels of antinuclear antibody (ANA) titer, anti-double-stranded DNA antibody (anti-dsDNA), anti-nucleosome antibody (ANuA), and lower serum C3 levels. The proportion of patients with reduced WBC, elevated anti-dsDNA, elevated ANuA, elevated anticardiolipin antibody (ACA), positive urinary protein (UPR), and positive ANA was higher in the NPSLE-WMH + group. Univariate and multivariate analyses revealed that positive UPR (p = 0.040), positive ANA (p = 0.025), elevated anti-dsDNA (0.047), and elevated ACA (p = 0.025) were potentially independent factors associated with WMH development in NPSLE patients.

CONCLUSIONS

This study provides novel insights into the clinical and laboratory differences between NPSLE patients with and without WMH, identifying specific independently associated factors for WMH development. These findings may contribute to a better understanding of this intricate disease. Key Points • Although WMH is one of the most frequently observed lesions on MRI in patients with NPSLE, previous literature has given limited attention to it. This study focuses on the differences between NPSLE patients with and without WMH, unveiling independently associated factors for developing WMH in this disease.

Neutrophil extracellular traps as a unique target in the treatment of inflammatory pain

Pain is a widespread motivation for seeking healthcare and stands as a substantial global public health concern. Despite comprehensive investigations into the mechanisms of pain sensitization induced by inflammation, efficacious treatments options remain scarce. Neutrophil extracellular traps (NETs) have been associated with the progression and tissue damage of diverse inflammatory diseases. This study aims to explore the impact of NETs on the progression of inflammatory pain and explore potential therapeutic approaches. Initially, we observed neutrophil infiltration and the formation of NETs in the left hind paw of mice with inflammatory pain induced by complete Freund's adjuvant (CFA). Furthermore, we employed the peptidyl arginine deiminase 4 (PAD4) inhibitor Cl-amidine (diluted at 50 mg/kg in saline, administered via tail vein injection once daily for three days) to impede NETs formation and administered DNase1 (diluted at 10 mg/kg in saline, once daily for three days) to break down NETs. We investigated the pathological importance of peripheral NETs formation in inflammatory pain and its influence on the activation of spinal dorsal horn microglia. The findings indicate that neutrophils infiltrating locally generate NETs, leading to an increased release of inflammatory mediators that worsen peripheral inflammatory reactions. Consequently, this results in the transmission of more harmful peripheral stimuli to the spinal cord, triggering microglial activation and NF-κB phosphorylation, thereby escalating neuroinflammation and fostering pain sensitization. Suppression of peripheral NETs can mitigate peripheral inflammation in mice with inflammatory pain, reverse mechanical and thermal hypersensitivity by suppressing microglial activation in the spinal cord, ultimately diminishing inflammatory pain. In conclusion, these discoveries propose that obstructing or intervening with NETs introduces a novel therapeutic avenue for addressing inflammatory pain.

Differences between human male and female neutrophils in mRNA, translation efficiency, protein, and phosphoprotein profiles

Background

Human males and females show differences in the incidence of neutrophil-associated diseases such as systemic lupus erythematosus, rheumatoid arthritis, and reactive arthritis, and differences in neutrophil physiological responses such as a faster response to the chemorepellent SLIGKV. Little is known about the basis of sex-based differences in human neutrophils.

Methods

Starting with human neutrophils from healthy donors, we used RNA-seq to examine total mRNA profiles, mRNAs not associated with ribosomes and thus not being translated, mRNAs in monosomes, and mRNAs in polysomes and thus heavily translated. We used mass spectrometry systems to identify proteins and phosphoproteins.

Results

There were sex-based differences in the translation of 24 mRNAs. There were 132 proteins with higher levels in male neutrophils; these tended to be associated with RNA regulation, ribosome, and phosphoinositide signaling pathways, whereas 30 proteins with higher levels in female neutrophils were associated with metabolic processes, proteosomes, and phosphatase regulatory proteins. Male neutrophils had increased phosphorylation of 32 proteins. After exposure to SLIGKV, male neutrophils showed a faster response in terms of protein phosphorylation compared to female neutrophils.

Conclusions

Male neutrophils have higher levels of proteins and higher phosphorylation of proteins associated with RNA processing and signaling pathways, while female neutrophils have higher levels of proteins associated with metabolism and proteolytic pathways. This suggests that male neutrophils might be more ready to adapt to a new environment, and female neutrophils might be more effective at responding to pathogens. This may contribute to the observed sex-based differences in neutrophil behavior and neutrophil-associated disease incidence and severity.

Latent Class Analysis Identifies Distinct Phenotypes of Systemic Lupus Erythematosus Predictive of Flares after mRNA COVID-19 Vaccination: Results from the Coronavirus National Vaccine Registry for ImmuNe Diseases SINGapore (CONVIN-SING)

We recently reported that messenger ribonucleic acid (mRNA) coronavirus disease 2019 (COVID-19) vaccination was associated with flares in 9% of patients with systemic lupus erythematosus (SLE). Herein, we focused our analysis on patients from a multi-ethnic Southeast Asian lupus cohort with the intention of identifying distinct phenotypes associated with increased flares after mRNA COVID-19 vaccination.

METHODS

Six hundred and thirty-three SLE patients from eight public healthcare institutions were divided into test and validation cohorts based on healthcare clusters. Latent class analysis was performed based on age, ethnicity, gender, vaccine type, past COVID-19 infection, interruption of immunomodulatory/immunosuppressive treatment for vaccination, disease activity and background immunomodulatory/immunosuppressive treatment as input variables. Data from both cohorts were then combined for mixed effect Cox regression to determine which phenotypic cluster had a higher risk for time to first SLE flare, adjusted for the number of vaccine doses.

RESULTS

Two clusters were identified in the test (C1 vs. C2), validation (C1' vs. C2') and combined (C1″ vs. C2″) cohorts, with corresponding clusters sharing similar characteristics. Of 633 SLE patients, 88.6% were female and there was multi-ethnic representation with 74.9% Chinese, 14.2% Malay and 4.6% Indian. The second cluster (C2, C2' and C2″) was smaller compared to the first. SLE patients in the second cluster (C2 and C2') were more likely to be male, non-Chinese and younger, with higher baseline disease activity. The second cluster (C2″) had more incident flares (hazard ratio = 1.4, 95% confidence interval 1.1-1.9, p = 0.014) after vaccination. A higher proportion of patients in C2″ had immunomodulatory/immunosuppressive treatment interruption for vaccination as compared to patients in C1″ (6.6% vs. 0.2%) (p < 0.001).

CONCLUSION

We identified two distinct phenotypic clusters of SLE with different patterns of flares following mRNA COVID-19 vaccination. Caution has to be exercised in monitoring for post-vaccination flares in patients with risk factors for flares such as non-Chinese ethnicity, young age, male gender and suboptimal disease control at the time of vaccination.

The double-edged role of neutrophil heterogeneity in inflammatory diseases and cancers

Neutrophils are important immune cells act as the body's first line of defense against infection and respond to diverse inflammatory cues. Many studies have demonstrated that neutrophils display plasticity in inflammatory diseases and cancers. Clarifying the role of neutrophil heterogeneity in inflammatory diseases and cancers will contribute to the development of novel treatment strategies. In this review, we have presented a review on the development of the understanding on neutrophil heterogeneity from the traditional perspective and a high-resolution viewpoint. A growing body of evidence has confirmed the double-edged role of neutrophils in inflammatory diseases and tumors. This may be due to a lack of precise understanding of the role of specific neutrophil subsets in the disease. Thus, elucidating specific neutrophil subsets involved in diseases would benefit the development of precision medicine. Thusly, we have summarized the relevance and actions of neutrophil heterogeneity in inflammatory diseases and cancers comprehensively. Meanwhile, we also discussed the potential intervention strategy for neutrophils. This review is intended to deepen our understanding of neutrophil heterogeneity in inflammatory diseases and cancers, while hold promise for precise treatment of neutrophil-related diseases.

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.