Inflammation and immunomodulation in central nervous system injury - B cells as a novel therapeutic opportunity

Causal Association Between Inflammatory Proteins, Inflammatory Cells, and Cauda Equina Syndrome: A Two-Sample Mendelian Randomization

BACKGROUND

Recent studies have shown that inflammation plays a crucial role in the progression of cauda equina syndrome (CES). However, the exact cause-and-effect relationship between them is still unclear.

METHODS

We used CES data from the FinnGen genome-wide association study (GWAS), containing 329 cases and 408,351 control patients. Inflammatory proteins data were obtained from a large scale GWAS of 14,828 European ancestry participants, and inflammatory cells data were obtained from a GWAS summary of 3757 Sardinians. We chose inverse variance weighted as the main method and the Cochrane Q test to assess heterogeneity in the results. The MR-Egger intercept test and MR pleiotropy residual sum and outliers test were used to evaluate the horizontal pleiotropy, and sensitivity analysis was performed by leave-one-out analysis.

RESULTS

We examined robust associations between inflammatory proteins, inflammatory cells, and CES using Mendelian randomization. Two inflammatory proteins and 12 inflammatory cells were found as risk factors for CES: IL-8 and PD-L1; and basophil plasmacytoid dendritic cell, CD86+plasmacytoid dendritic cell, CD62L-plasmacytoid dendritic cell, CD39+secreting Treg, IgD+CD38-B cell, switched memory B cell, IgD+CD24+B cell, CD62L+dendritic cell, CD4+T cell, γδ T cell, and CD33dim HLA DR-myeloid cell. Two inflammatory proteins and 7 inflammatory cells were found as protective factors for CES: IL-10RA and CCL25; and transitional B cell, terminal differentiation double negative T cell, CD28-CD127-CD25++CD8br T cell, IgD+CD38br B cell, CD28+CD45RA-CD8br Treg, IgD+CD38-naive B cell, and granulocyte. Heterogeneity and pleiotropy analysis confirmed the reliability of the results. Our study reveals the causal relationship between inflammatory proteins, inflammatory cells, and CES, offering new insights for the development of future therapeutic drugs and early warning indicators.

CONCLUSIONS

Our findings extend genetic research to causal analysis between inflammatory proteins, cells, and CES. We found 2 proteins and 12 cells as risk factors and 2 proteins and 7 cells as protective factors. Further investigations are needed to verify whether these inflammation markers can be used to prevent or treat CES.

Immune Cells and Intracerebral Hemorrhage: A Causal Investigation Through Mendelian Randomization

BACKGROUND

The involvement of immune cells in the pathophysiology of intracerebral hemorrhage (ICH) is becoming increasingly recognized, yet their specific causal contributions remain uncertain. The objective of this research is to uncover the potential causal interactions between diverse immune cells and ICH using Mendelian randomization (MR) analysis.

METHODS

Genetic variants associated with 731 immune cell traits were sourced from a comprehensive genome-wide association study (GWAS) involving 3757 participants. Summary statistics data for ICH were acquired from FinnGen, comprising 4056 ICH cases and 371,717 controls. The principal analytical tool utilized in our study was the inverse-variance weighted (IVW) method, incorporated as a key component of a two-sample MR approach. To mitigate potential biases and verify the stability of the conclusions drawn from the primary analytical methods, a series of sensitivity analyses were performed.

RESULTS

MR analysis elucidated 33 immune cell traits with causal associations, comprising B cells (eight traits), conventional dendritic cells (cDC, two traits), maturation stages of T cells (two traits), monocytes (two traits), myeloid cells (five traits), TBNK cells (six traits), and regulatory T cells (Treg, eight traits). DP (CD4+CD8+) %T cell (OR = 0.83, CI = 0.72-0.96, p = 0.013) exhibited the strongest protective effect. In contrast, transitional AC (OR = 1.09, CI = 1.02-1.16, p = 0.006) and IgD- CD27- %lymphocyte (OR = 1.08, CI = 1.00-1.17, p = 0.045) showed a higher tendency to increase the ICH risk. The sensitivity analyses validated the robustness and consistency of these results.

CONCLUSION

Our research provides robust evidence substantiating the causal relationship between specific immunophenotypes and ICH risk. The identification of these findings significantly enhances our understanding of the pathogenic mechanisms underlying ICH, particularly pertaining to the immune system. This breakthrough paves the way for innovative clinical and pharmaceutical research opportunities, potentially promoting the development of targeted therapies and enhanced strategies for managing and preventing ICH.

Traumatic brain injury alters the effects of class II invariant peptide (CLIP) antagonism on chronic meningeal CLIP + B cells, neuropathology, and neurobehavioral impairment in 5xFAD mice

BACKGROUND

Traumatic brain injury (TBI) is a significant risk factor for Alzheimer's disease (AD), and accumulating evidence supports a role for adaptive immune B and T cells in both TBI and AD pathogenesis. We previously identified B cell and major histocompatibility complex class II (MHCII)-associated invariant chain peptide (CLIP)-positive B cell expansion after TBI. We also showed that antagonizing CLIP binding to the antigen presenting groove of MHCII after TBI acutely reduced CLIP + splenic B cells and was neuroprotective. The current study investigated the chronic effects of antagonizing CLIP in the 5xFAD Alzheimer's mouse model, with and without TBI.

METHODS

12-week-old male wild type (WT) and 5xFAD mice were administered either CLIP antagonist peptide (CAP) or vehicle, once at 30 min after either sham or a lateral fluid percussion injury (FPI). Analyses included flow cytometric analysis of immune cells in dural meninges and spleen, histopathological analysis of the brain, magnetic resonance diffusion tensor imaging, cerebrovascular analysis, and assessment of motor and neurobehavioral function over the ensuing 6 months.

RESULTS

9-month-old 5xFAD mice had significantly more CLIP + B cells in the meninges compared to age-matched WT mice. A one-time treatment with CAP significantly reduced this population in 5xFAD mice. Importantly, CAP also improved some of the immune, histopathological, and neurobehavioral impairments in 5xFAD mice over the ensuing six months. Although FPI did not further elevate meningeal CLIP + B cells, it did negate the ability of CAP to reduce meningeal CLIP + B cells in the 5xFAD mice. FPI at 3 months of age exacerbated some aspects of AD pathology in 5xFAD mice, including further reducing hippocampal neurogenesis, increasing plaque deposition in CA3, altering microgliosis, and disrupting the cerebrovascular structure. CAP treatment after injury ameliorated some but not all of these FPI effects.

Genetically supported causality between gut microbiota, immune cells, and ischemic stroke: a two-sample Mendelian randomization study

Background

Previous studies have highlighted a robust correlation between gut microbiota/immune cells and ischemic stroke (IS). However, the precise nature of their causal relationship remains uncertain. To address this gap, our study aims to meticulously investigate the causal association between gut microbiota/immune cells and the likelihood of developing IS, employing a two-sample Mendelian randomization (MR) analysis.

Methods

Our comprehensive analysis utilized summary statistics from genome-wide association studies (GWAS) on gut microbiota, immune cells, and IS. The primary MR method employed was the inverse variance-weighted (IVW) approach. To address potential pleiotropy and identify outlier genetic variants, we incorporated the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) technique, along with MR-Egger regression. Heterogeneity was assessed using Cochran's Q-test. Additionally, leave-one-out analysis was conducted to pinpoint any individual genetic variant influencing the observed causal associations. Finally, a reverse MR analysis was performed to explore the potential of reverse causation.

Results

Our investigation revealed four gut microbial taxa and 16 immune cells with a significant causal relationship with IS (p < 0.05). Notably, two bacterial features and five immunophenotypes were strongly associated with a lower IS risk: genus.Barnesiella.id.944 (OR: 0.907, 95% CI: 0.836-0.983, p = 0.018), genus.LachnospiraceaeNK4A136group.id.11319 (OR: 0.918, 95% CI: 0.853-0.983, p = 0.988), Activated & resting Treg % CD4++ (OR: 0.977, 95% CI: 0.956-0.998, p = 0.028). Additionally, significant associations between IS risk and two bacterial features along with eleven immunophenotypes were observed: genus.Paraprevotella.id.962 (OR: 1.106, 95% CI: 1.043-1.172, p < 0.001), genus.Streptococcus.id.1853 (OR: 1.119, 95% CI: 1.034-1.210, p = 0.005), CD127 on granulocyte (OR: 1.039, 95% CI: 1.009-1.070, p = 0.011). Our analyses did not reveal heterogeneity based on the Cochrane's Q-test (p > 0.05) nor indicate instances of horizontal pleiotropy according to MR-Egger and MR-PRESSO analyses (p > 0.05). Furthermore, the robustness of our MR results was confirmed through leave-one-out analysis.

Conclusion

Our study provides further evidence supporting the potential association between gut microbiota and immune cells in relation to IS, shedding light on the underlying mechanisms that may contribute to this condition. These findings lay a solid foundation for future investigations into targeted prevention strategies.

Adiponectin in spinal cord injury: What is the role of nutrition in serum adiponectin concentration?

Objectives: The study aimed to analyze the relationship between serum adiponectin concentration, Mediterranean diet (MD) adherence, and Dietary Approaches to Stop Hypertension (DASH) diet adherence in patients with spinal cord injury (SCI). Patients and methods: Thirty-three SCI patients (21 males, 12 females; median age: 33 years; range, 18 to 65 years) and 33 age-, sex-, and body mass index-matched healthy controls (21 males, 12 females; median age: 33 years; range, 18 to 64 years) were included in this cross-sectional study between March 2021 and March 2022. Serum adiponectin concentrations of all participants were measured. Body weight, height, and neck, hip, waist, and mid-upper arm circumferences were measured. Twenty-four-hour dietary records were obtained by the researchers for evaluation of the nutritional status. The DASH diet score and MD score were measured for each participant. Results: Most of the cases of SCI were due to motor vehicle collisions (n=12, 36.4%) and complete paraplegic. Mid-upper arm circumference, waist circumference, hip circumference, and neck circumference of the patient group were significantly higher than the control group (p=0.020, p=0.002, p=0.042, and p<0.001, respectively). Mediterranean diet scores and DASH diet scores of the patient group were significantly higher than the control group (p<0.001 and p=0.031, respectively). Serum adiponectin concentration of patients was significantly higher than the control group (p=0.049). No correlation was detected between adiponectin concentration, MD score, and DASH diet score in both groups. Conclusion: Although correlation analysis in the current research did not show significant relation between nutrition and adiponectin concentrations, nutrition of patients with SCI, as demonstrated by higher adherence to MD and DASH, may have provided positive effects on adiponectin concentrations. Future studies focused on the effect of a healthy diet intervention on serum adiponectin concentration is warranted.

Genetic insights into the relationship between immune cell characteristics and ischemic stroke: A bidirectional Mendelian randomization study

BACKGROUND AND PURPOSE

Ischemic stroke, a major contributor to global disability and mortality, is underpinned by intricate pathophysiological mechanisms, notably neuroinflammation and immune cell dynamics. Prior research has identified a nuanced and often paradoxical link between immune cell phenotypes and ischemic stroke susceptibility. The aim of this study was to elucidate the potential causal links between the median fluorescence intensity (MFI) and morphological parameters (MP) of 731 immune cell types and ischemic stroke risk.

METHODS

By analyzing extensive genetic datasets, we conducted comprehensive Mendelian randomization (MR) analyses to discern the genetic correlations between diverse immune cell attributes (MFI and MP) and ischemic stroke risk.

RESULTS

Our study identified key immune cell signatures linked to ischemic stroke risk. Both B cells and T cells, among other immune cell types, have a bidirectional influence on stroke risk. Notably, the regulatory T-cell phenotype demonstrates significant neuroprotective properties, with all odds ratio (OR) values and confidence intervals (CIs) being less than 1. Furthermore, CD39 phenotype immune cells, particularly CD39+ CD8+ T cells (inverse variance weighting [IVW] OR 0.92, 95% CI 0.87-0.97; p = 0.002) and CD39+ activated CD4 regulatory T cells (IVW OR 0.93, 95% CI 0.90-0.97; p < 0.001), show notable neuroprotection against ischemic stroke.

CONCLUSION

This investigation provides new genetic insights into the interplay between various immune cells and ischemic stroke, underscoring the complex role of immune processes in stroke pathogenesis. These findings lay a foundation for future research, which may confirm and expand upon these links, potentially leading to innovative immune-targeted therapies for stroke prevention and management.

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

Neutrophil-to-lymphocyte ratio at admission for early diagnosis, severity assessment, and prognosis of acute traumatic spinal cord injury

STUDY DESIGN

A retrospective study.

OBJECTIVE

This study examined the value of neutrophil-to-lymphocyte ratio at admission for early diagnosis, severity assessment, and prognosis of acute traumatic SCI.

SETTING

The First People's Hospital of Neijiang, China.

METHODS

This was a single-center, retrospective, cohort study of patients treated within 12 h of acute SCI between January 2018 and October 2022. Ninety-four SCI patients were selected as the Observation group, including 26 with complete injury (AIS grade A) and 68 with incomplete injury (AIS grade B-D), while 94 patients with simple spinal fracture were randomly selected as the Control group. Eighty-one observation group patients underwent surgical treatment, of which 33 had a higher AIS grade (Good prognosis subgroup) and 48 a lower or equal grade post-surgery (Poor prognosis subgroup). Univariate and multivariate analyses were performed to assess predictors of early diagnosis, severity, and 6-month outcome.

RESULTS

Initial white blood cell count, neutrophil count, monocyte count, and NLR were higher in the Observation group than the Control group, while lymphocyte count was lower in the Observation group. Multivariate logistic regression analysis identified NLR as an independent predictor of early diagnosis. Spinal canal encroachment ≥50%, neutrophil count, and NLR were higher in the complete injury subgroup, and spinal canal encroachment ≥50% was an independent predictor of complete injury, while NLR was not. The NLR was higher in the poor prognosis subgroup and was an independent risk factor.

CONCLUSIONS

Peripheral blood NLR is useful for early diagnosis of acute SCI and is predictive of clinical outcome.

Intruders or protectors - the multifaceted role of B cells in CNS disorders

B lymphocytes are immune cells studied predominantly in the context of peripheral humoral immune responses against pathogens. Evidence has been accumulating in recent years on the diversity of immunomodulatory functions that B cells undertake, with particular relevance for pathologies of the central nervous system (CNS). This review summarizes current knowledge on B cell populations, localization, infiltration mechanisms, and function in the CNS and associated tissues. Acute and chronic neurodegenerative pathologies are examined in order to explore the complex, and sometimes conflicting, effects that B cells can have in each context, with implications for disease progression and treatment outcomes. Additional factors such as aging modulate the proportions and function of B cell subpopulations over time and are also discussed in the context of neuroinflammatory response and disease susceptibility. A better understanding of the multifactorial role of B cell populations in the CNS may ultimately lead to innovative therapeutic strategies for a variety of neurological conditions.

Spinal cord tethering and syringomyelia after trauma: impact of age and surgical outcome

Posttraumatic spinal cord tethering and syringomyelia frequently lead to progressive neurological loss. Although several studies demonstrated favourable outcome following spinal cord detethering with/without shunting, additional research is required as no clear consensus exists over the ideal treatment strategy and knowledge about prognostic demographic determinants is currently limited. In this investigation, we retrospectively investigated 67 patients (56 men, 11 women) who were surgically treated and followed for symptomatic spinal cord tethering and syringomyelia from 2012 to 2022 at our center. Age (B-coefficient 0.396) and severity of trauma to the spinal cord (B-coefficient - 0.462) have been identified as independent predictors for the rate of development of symptomatic spinal cord tethering and syringomyelia (p < 0.001). Following untethering surgery including expansion duraplasty with/without shunting, 65.9% of patients demonstrated an improvement of neurological loss (p < 0.001) whereas 50.0% of patients displayed amelioration of spasticity and/or neuropathic pain (p < 0.001). Conclusively, active screening for symptomatic spinal cord tethering and syringomyelia, particularly in younger patients with severe spinal trauma, is crucial as surgical untethering with/without shunting is able to achieve favourable clinical outcomes. This knowledge may enable clinicians to tailor treatment strategies in spinal cord injury patients suffering from progressive neurological loss towards a more optimal and personalized patient care.

B cell treatment promotes a neuroprotective microenvironment after traumatic brain injury through reciprocal immunomodulation with infiltrating peripheral myeloid cells

Traumatic brain injury (TBI) remains a major cause of death and severe disability worldwide. We found previously that treatment with exogenous naïve B cells was associated with structural and functional neuroprotection after TBI. Here, we used a mouse model of unilateral controlled cortical contusion TBI to investigate cellular mechanisms of immunomodulation associated with intraparenchymal delivery of mature naïve B lymphocytes at the time of injury. Exogenous B cells showed a complex time-dependent response in the injury microenvironment, including significantly increased expression of IL-10, IL-35, and TGFβ, but also IL-2, IL-6, and TNFα. After 10 days in situ, B cell subsets expressing IL-10 or TGFβ dominated. Immune infiltration into the injury predominantly comprised myeloid cells, and B cell treatment did not alter overall numbers of infiltrating cells. In the presence of B cells, significantly more infiltrating myeloid cells produced IL-10, TGFβ, and IL-35, and fewer produced TNFα, interferon-γ and IL-6 as compared to controls, up to 2 months post-TBI. B cell treatment significantly increased the proportion of CD206+ infiltrating monocytes/macrophages and reduced the relative proportion of activated microglia starting at 4 days and up to 2 months post-injury. Ablation of peripheral monocytes with clodronate liposomes showed that infiltrating peripheral monocytes/macrophages are required for inducing the regulatory phenotype in exogenous B cells. Reciprocally, B cells specifically reduced the expression of inflammatory cytokines in infiltrating Ly6C+ monocytes/macrophages. These data support the hypothesis that peripheral myeloid cells, particularly infiltrating monocyte/macrophages, are key mediators of the neuroprotective immunomodulatory effects observed after B cell treatment.