Clearance of peripheral nerve misfolded mutant protein by infiltrated macrophages correlates with motor neuron disease progression

Assessment of Rab geranylgeranyltransferase subunit beta in amyotrophic lateral sclerosis

Introduction

Geranylgeranyltransferase Subunit Beta (RABGGTB) was expressed at higher levels in patients with Amyotrophic lateral sclerosis (ALS) compared with healthy controls. This study aims to observe the expression of RABGGTB in different cells from patients with ALS and different diseases.

Methods

In this case-control study, we collected peripheral blood from patients with ALS and healthy controls, and compared the expression of RABGGTB in natural killer cells (NK), T cells and B cells between patients with ALS and healthy controls by flow cytometry. And compared the expression of RABGGTB in monocytes and monocyte-derived macrophages from patients with ALS, Parkinson's disease (PD), acute cerebrovascular disease (ACVD), and healthy controls by flow cytometry and immunofluorescence. Then flow cytometry was used to detect the expression of RABGGTB in monocytes from SOD1G93A mice and WT mice.

Results

The expression of RABGGTB was not significantly changed in NK cells, cytotoxic T cells (CTL), helper T cells (Th), regulatory T cells (Treg), and B cells from patients with ALS compared to healthy controls. And the expression of RABGGTB in monocytes and monocyte-derived macrophages was higher in the ALS group than in the PD, ACVD and control group. The expression of RABGGTB was significantly higher in monocytes of SOD1G93A mice compared to WT mice.

Conclusion

These findings suggest that RABGGTB expression was increased in monocytes and monocyte-derived macrophages from patients with ALS, not in NK, CTL, Th, Treg, and B cells. Future studies are needed to find the clinical implication of RABGGTB in ALS.

Rab Geranylgeranyltransferase Subunit Beta as a Potential Indicator to Assess the Progression of Amyotrophic Lateral Sclerosis

BACKGROUND

Currently, there is no effective treatment for amyotrophic lateral sclerosis (ALS), a devastating neurodegenerative disorder. Many biomarkers have been proposed, but because ALS is a clinically heterogeneous disease with an unclear etiology, biomarker discovery for ALS has been challenging due to the lack of specificity of these biomarkers. In recent years, the role of autophagy in the development and treatment of ALS has become a research hotspot. In our previous studies, we found that the expression of RabGGTase (low RABGGTB expression and no change in RABGGTA) is lower in the lumbar and thoracic regions of spinal cord motoneurons in SOD1G93A mice compared with WT (wild-type) mice groups, and upregulation of RABGGTB promoted prenylation modification of Rab7, which promoted autophagy to protect neurons by degrading SOD1. Given that RabGGTase is associated with autophagy and autophagy is associated with inflammation, and based on the above findings, since peripheral blood mononuclear cells are readily available from patients with ALS, we proposed to investigate the expression of RabGGTase in peripheral inflammatory cells.

METHODS

Information and venous blood were collected from 86 patients diagnosed with ALS between January 2021 and August 2023. Flow cytometry was used to detect the expression of RABGGTB in monocytes from peripheral blood samples collected from patients with ALS and healthy controls. Extracted peripheral blood mononuclear cells (PBMCs) were differentiated in vitro into macrophages, and then the expression of RABGGTB was detected by immunofluorescence. RABGGTB levels in patients with ALS were analyzed to determine their impact on disease progression.

RESULTS

Using flow cytometry in monocytes and immunofluorescence in macrophages, we found that RABGGTB expression in the ALS group was significantly higher than in the control group. Age, sex, original location, disease course, C-reactive protein (CRP), and interleukin-6 (IL-6) did not correlate with the ALS functional rating scale-revised (ALSFRS-R), whereas the RABGGTB level was significantly correlated with the ALSFRS-R. In addition, multivariate analysis revealed a significant correlation between RABGGTB and ALSFRS-R score. Further analysis revealed a significant correlation between RABGGTB expression levels and disease progression levels (ΔFS).

CONCLUSIONS

The RABGGTB level was significantly increased in patients with ALS compared with healthy controls. An elevated RABGGTB level in patients with ALS is associated with the rate of progression in ALS, suggesting that elevated RABGGTB levels in patients with ALS may serve as an indicator for tracking ALS progression.

Regulation of the Innate Immune System as a Therapeutic Approach to Supporting Respiratory Function in ALS

Amyotrophic lateral sclerosis (ALS) is a clinical diagnosis used to define a neurodegenerative process that involves progressive loss of voluntary muscle function and leads to death within 2–5 years after diagnosis, in most cases because of respiratory function failure. Respiratory vital capacity (VC) measurements are reproducible and strong predictors of survival. To understand the role of the innate immune response in progressive VC loss we evaluated ALS clinical trial and biomarker results from a 6-month phase 2 study of NP001, a regulator of innate immune function. All ALS baseline values were similar between treated and controls except for those > 65 years old who were excluded from analysis. Treated patients with plasma CRP ≥ 1.13 mg/L (high CRP) showed a 64% slower rate of VC decline compared with placebo and those with plasma CRP < 1.13 mg/L (low CRP) who showed no response. High CRP patients showed no age associated loss of VC whereas low CRP patients showed an age dependent loss of VC function. Plasma levels of serum amyloid A (SAA) were similarly elevated in high CRP patients consistent with ongoing innate immune activation. Plasma TGFB1 in high CRP treated patients was 95% higher than placebo at 6-months, confirming the activation and release of this anti-inflammatory factor by the innate immune alpha 2 macroglobulin (A2M) system. This report is the first to link a biomarker confirmed regulation of the innate immune system with a therapeutic approach for controlling VC loss in ALS patients.

Intramuscular IL-10 Administration Enhances the Activity of Myogenic Precursor Cells and Improves Motor Function in ALS Mouse Model

Amyotrophic Lateral Sclerosis (ALS) is the most common adult motor neuron disease, with a poor prognosis, a highly unmet therapeutic need, and a burden on health care costs. Hitherto, strategies aimed at protecting motor neurons have missed or modestly delayed ALS due to a failure in countering the irreversible muscular atrophy. We recently provided direct evidence underlying the pivotal role of macrophages in preserving skeletal muscle mass. Based on these results, we explored whether the modulation of macrophage muscle response and the enhancement of satellite cell differentiation could effectively promote the generation of new myofibers and counteract muscle dysfunction in ALS mice. For this purpose, disease progression and the survival of SOD1G93A mice were evaluated following IL-10 injections in the hindlimb skeletal muscles. Thereafter, we used ex vivo methodologies and in vitro approaches on primary cells to assess the effect of the treatment on the main pathological signatures. We found that IL-10 improved the motor performance of ALS mice by enhancing satellite cells and the muscle pro-regenerative activity of macrophages. This resulted in delayed muscle atrophy and motor neuron loss. Our findings provide the basis for a suitable adjunct multisystem therapeutic approach that pinpoints a primary role of muscle pathology in ALS.

Connexin 30 Deficiency Ameliorates Disease Progression at the Early Phase in a Mouse Model of Amyotrophic Lateral Sclerosis by Suppressing Glial Inflammation

Connexin 30 (Cx30), which forms gap junctions between astrocytes, regulates cell adhesion and migration, and modulates glutamate transport. Cx30 is upregulated on activated astroglia in central nervous system inflammatory lesions, including spinal cord lesions in mutant superoxide dismutase 1 (mSOD1) transgenic amyotrophic lateral sclerosis (ALS) model mice. Here, we investigated the role of Cx30 in mSOD1 mice. Cx30 was highly expressed in the pre-onset stage in mSOD1 mice. mSOD1 mice with knockout (KO) of the Cx30 gene (Cx30KO-mSOD1 mice) showed delayed disease onset and tended to have an extended survival period (log-rank, p = 0.09). At the progressive and end stages of the disease, anterior horn cells were significantly preserved in Cx30KO-mSOD1 mice. In lesions of these mice, glial fibrillary acidic protein/C3-positive inflammatory astroglia were decreased. Additionally, the activation of astrocytes in Cx30KO-mSOD1 mice was reduced compared with mSOD1 mice by gene expression microarray. Furthermore, expression of connexin 43 at the pre-onset stage was downregulated in Cx30KO-mSOD1 mice. These findings suggest that reduced expression of astroglial Cx30 at the early disease stage in ALS model mice protects neurons by attenuating astroglial inflammation.

Macrophage-Targeted Sodium Chlorite (NP001) Slows Progression of Amyotrophic Lateral Sclerosis (ALS) through Regulation of Microbial Translocation

Amyotrophic lateral sclerosis (ALS) is a heterogeneous, progressive, and universally fatal neurodegenerative disease. A subset of ALS patients has measurable plasma levels of lipopolysaccharide (LPS) and C-reactive protein (CRP) consistent with low-grade microbial translocation (MT). Unless interrupted, MT sets up a self-perpetuating loop of inflammation associated with systemic macrophage activation. To test whether MT contributed to ALS progression, blood specimens from a phase 2 study of NP001 in ALS patients were evaluated for changes in activity in treated patients as compared to controls over the 6-month study. In this post hoc analysis, plasma specimens from baseline and six-month timepoints were analyzed. Compared with baseline values, biomarkers related to MT were significantly decreased (LPS, LPS binding protein (LBP), IL-18, Hepatocyte growth factor (HGF), soluble CD163 (sCD163)) in NP001-treated patients as compared to controls, whereas wound healing and immunoregulatory factors were increased (IL-10, Epidermal growth factor (EGF), neopterin) by the end of study. These biomarker results linked to the positive clinical trial outcome confirm that regulation of macrophage activation may be an effective approach for the treatment of ALS and, potentially, other neuroinflammatory diseases related to MT.

Misfolding at the synapse: A role in amyotrophic lateral sclerosis pathogenesis?

A growing wave of evidence has placed the concept of protein homeostasis at the center of the pathogenesis of amyotrophic lateral sclerosis (ALS). This is due primarily to the presence of pathological transactive response DNA-binding protein (TDP-43), fused in sarcoma (FUS) or superoxide dismutase-1 (SOD1) inclusions within motor neurons of ALS postmortem tissue. However, the earliest pathological alterations associated with ALS occur to the structure and function of the synapse, prior to motor neuron loss. Recent evidence demonstrates the pathological accumulation of ALS-associated proteins (TDP-43, FUS, C9orf72-associated di-peptide repeats and SOD1) within the axo-synaptic compartment of motor neurons. In this review, we discuss this recent evidence and how axo-synaptic proteome dyshomeostasis may contribute to synaptic dysfunction in ALS.

Neuroimmune Crosstalk Between the Peripheral and the Central Immune System in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease characterized by the degeneration and death of motor neurons. Systemic neuroinflammation contributes to the pathogenesis of ALS. The proinflammatory milieu depends on the continuous crosstalk between the peripheral immune system (PIS) and central immune system (CIS). Central nervous system (CNS) resident immune cells interact with the peripheral immune cells via immune substances. Dysfunctional CNS barriers, including the blood–brain barrier, and blood–spinal cord barrier, accelerate the inflammatory process, leading to a systemic self-destructive cycle. This review focuses on the crosstalk between PIS and CIS in ALS. Firstly, we briefly introduce the cellular compartments of CIS and PIS, respectively, and update some new understanding of changes specifically occurring in ALS. Then, we will review previous studies on the alterations of the CNS barriers, and discuss their crucial role in the crosstalk in ALS. Finally, we will review the moveable compartments of the crosstalk, including cytokines, chemokines, and peripheral immune cells which were found to infiltrate the CNS, highlighting the interaction between PIS and CIS. This review aims to provide new insights into pathogenic mechanisms and innovative therapeutic approaches for ALS.

Boosting the peripheral immune response in the skeletal muscles improved motor function in ALS transgenic mice

Monocyte chemoattractant protein-1 (MCP1) is one of the most powerful pro-inflammatory chemokines. However, its signalling is pivotal in driving injured axon and muscle regeneration.