Altered CSF cytokine network in amyotrophic lateral sclerosis patients: A pathway-based statistical analysis

FUS Alters circRNA Metabolism in Human Motor Neurons Carrying the ALS-Linked P525L Mutation

Deregulation of RNA metabolism has emerged as one of the key events leading to the degeneration of motor neurons (MNs) in Amyotrophic Lateral Sclerosis (ALS) disease. Indeed, mutations on RNA-binding proteins (RBPs) or on proteins involved in aspects of RNA metabolism account for the majority of familiar forms of ALS. In particular, the impact of the ALS-linked mutations of the RBP FUS on many aspects of RNA-related processes has been vastly investigated. FUS plays a pivotal role in splicing regulation and its mutations severely alter the exon composition of transcripts coding for proteins involved in neurogenesis, axon guidance, and synaptic activity. In this study, by using in vitro-derived human MNs, we investigate the effect of the P525L FUS mutation on non-canonical splicing events that leads to the formation of circular RNAs (circRNAs). We observed altered levels of circRNAs in FUS^P525L MNs and a preferential binding of the mutant protein to introns flanking downregulated circRNAs and containing inverted Alu repeats. For a subset of circRNAs, FUS^P525L also impacts their nuclear/cytoplasmic partitioning, confirming its involvement in different processes of RNA metabolism. Finally, we assess the potential of cytoplasmic circRNAs to act as miRNA sponges, with possible implications in ALS pathogenesis.

Phase 1b dose-escalation, safety, and pharmacokinetic study of IC14, a monoclonal antibody against CD14, for the treatment of amyotrophic lateral sclerosis

BACKGROUND

The primary objective was to demonstrate the safety and tolerability of monoclonal antibody against CD14 (IC14) (atibuclimab) in amyotrophic lateral sclerosis patients. The secondary objectives were pharmacokinetics, pharmacodynamics, and preliminary effects on disease status and biomarkers.

METHODS

In this open-label, dose-escalation trial, IC14 was administered at 2 mg/kg intravenous (IV) followed by 1 mg/kg/d IV × 3 (n = 3) and in subsequent patients at 4 mg/kg IV followed by 2 mg/kg/d IV × 3 (n = 7) (NCT03487263). Disease status was measured using the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale, forced vital capacity, sniff nasal pressure, Edinburgh Cognitive and Behavioural ALS Screen, and Revised ALS-Specific Quality-of-Life Score. Disease biomarkers included cerebrospinal fluid and serum levels of neurofilament light chain (NfL) and urinary p75 neurotrophin receptor.

RESULTS

IC14 was safe and well tolerated. No antidrug antibodies were detected. The drug target saturation of monocyte CD14 receptors was rapid and sustained through day 8. There was no significant change in Revised Amyotrophic Lateral Sclerosis Functional Rating Scale, forced vital capacity, sniff nasal pressure, or Revised ALS-Specific Quality-of-Life Score following a single cycle of treatment. Cerebrospinal fluid NfL levels decreased in 6 of 9 patients sampled with declines of 15% to 40% between baseline (not significant [ns]) and day 8 in 3 patients. Serum NfL modestly decreased in 5 of 10 patients (ns) at day 8 and was sustained in 4 (4%-37%, ns) over 33 days of follow up.

CONCLUSION

IC14 quickly and durably saturated its target in all patients. This study demonstrated safety and tolerability in patients with amyotrophic lateral sclerosis. Even though only a single cycle of treatment was given, there were promising beneficial trends in the neurofilament light chain, a disease biomarker. The emerging understanding of the role of systemic inflammation in neurodegenerative diseases, and the potential for IC14 to serve as a safe, potent, and broad-spectrum inhibitor of immune dysregulation merits further clinical study.

CLINICAL TRIAL REGISTRATION

NCT03487263.

Distinct responses of human peripheral blood cells to different misfolded protein oligomers

Increasing evidence indicates that peripheral immune cells play a prominent role in neurodegeneration connected to protein misfolding, which are associated with formation of aberrant aggregates, including soluble protein misfolded oligomers. The precise links, however, between the physicochemical features of diverse oligomers and their effects on the immune system, particularly on adaptive immunity, remain currently unexplored, due partly to the transient and heterogeneous nature of the oligomers themselves. To overcome these limitations, we took advantage of two stable and well‐characterized types of model oligomers (A and B), formed by HypF‐N bacterial protein, type B oligomers displaying lower solvent‐exposed hydrophobicity. Exposure to oligomers of human peripheral blood mononuclear cells (PBMCs) revealed differential effects, with type B, but not type A, oligomers leading to a reduction in CD4⁺ cells. Type A oligomers promoted enhanced differentiation towards CD4⁺CD25^HighFoxP3⁺ Tregs and displayed a higher suppressive effect on lymphocyte proliferation than Tregs treated with oligomers B or untreated cells. Moreover, our results reveal Th1 and Th17 lymphocyte differentiation mediated by type A oligomers and a differential balance of TGF‐β, IL‐6, IL‐23, IFN‐γ and IL‐10 mediators. These results indicate that type B oligomers recapitulate some of the biological responses associated with Parkinson's disease in peripheral immunocompetent cells, while type A oligomers resemble responses associated with Alzheimer's disease. We anticipate that further studies characterizing the differential effects of protein misfolded oligomers on the peripheral immune system may lead to the development of blood‐based diagnostics, which could report on the type and properties of oligomers present in patients.

Plasma Inflammatory Cytokines Are Elevated in ALS

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease which leads to death in a median time of 2–3 years. Inflammation has been claimed important to the ALS pathogenesis, but its role is still not well-characterized. In the present study, a panel of five cytokines (IL-2, IL-6, IL-10, IFN-gamma, and TNF-alpha) measured in plasma has been investigated in ALS. These biomarkers of inflammation were measured in a population-based cohort of 79 patients with ALS and 79 age- and sex-matched healthy controls using the Bio-Plex technology (Bio-Rad). All the five cytokines were significantly increased in plasma samples of patients compared with controls (p < 0.0001), with IL-6 having the highest median concentration (10.11 pg/ml) in the ALS group. Furthermore, IL-6 was the plasma cytokine with the highest discrimination ability between patients and controls according to the receiver operating characteristic analysis (area under the curve = 0.93). At a cut-off point of 5.71 pg/ml, it was able to classify patients and controls with 91% of sensitivity and 87% of specificity. In the ALS group, plasma IL-6 concentration correlated with demographic (age: rs = 0.25, p = 0.025) and clinical (revised ALS Functional Rating Scale at evaluation: rs = −0.32, p = 0.007; Manual Muscle Testing: rs = −0.33, p = 0.004; progression: rs = 0.29, p = 0.0395) parameters. In line with previous studies, our results confirm that inflammatory cytokines are elevated in ALS, supporting a possible role of inflammation in disease mechanism and progression. However, the precise role of inflammation in ALS needs to be further investigated on larger samples and with more mechanistic studies.

Are Circulating Cytokines Reliable Biomarkers for Amyotrophic Lateral Sclerosis?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that has no effective treatment. The lack of any specific biomarker that can help in the diagnosis or prognosis of ALS has made the identification of biomarkers an urgent challenge. Multiple panels have shown alterations in levels of numerous cytokines in ALS, supporting the contribution of neuroinflammation to the progressive motor neuron loss. However, none of them is fully sensitive and specific enough to become a universal biomarker for ALS. This review gathers the numerous circulating cytokines that have been found dysregulated in both ALS animal models and patients. Particularly, it highlights the opposing results found in the literature to date, and points out another potential application of inflammatory cytokines as therapeutic targets.

Increased FUS levels in astrocytes leads to astrocyte and microglia activation and neuronal death

Mutations of Fused in sarcoma (FUS), a ribonucleoprotein involved in RNA metabolism, have been found associated with both familial and sporadic cases of amyotrophic lateral sclerosis (ALS). Notably, besides mutations in the coding sequence, also mutations into the 3′ untranslated region, leading to increased levels of the wild-type protein, have been associated with neuronal death and ALS pathology, in ALS models and patients. The mechanistic link between altered FUS levels and ALS-related neurodegeneration is far to be elucidated, as well as the consequences of elevated FUS levels in the modulation of the inflammatory response sustained by glial cells, a well-recognized player in ALS progression. Here, we studied the effect of wild-type FUS overexpression on the responsiveness of mouse and human neural progenitor-derived astrocytes to a pro-inflammatory stimulus (IL1β) used to mimic an inflammatory environment. We found that astrocytes with increased FUS levels were more sensitive to IL1β, as shown by their enhanced expression of inflammatory genes, compared with control astrocytes. Moreover, astrocytes overexpressing FUS promoted neuronal cell death and pro-inflammatory microglia activation. We conclude that overexpression of wild-type FUS intrinsically affects astrocyte reactivity and drives their properties toward pro-inflammatory and neurotoxic functions, suggesting that a non-cell autonomous mechanism can support neurodegeneration in FUS-mutated animals and patients.

Adipsin, MIP-1b, and IL-8 as CSF Biomarker Panels for ALS Diagnosis

Amyotrophic lateral sclerosis (ALS) is an aggressive neurodegenerative disorder that selectively attacks motor neurons in the brain and spinal cord. Despite important advances in the knowledge of the etiology and progression of the disease, there are still no solid grounds in which a clinician could make an early objective and reliable diagnosis from which patients could benefit. Diagnosis is difficult and basically made by clinical rating scales (ALSRs and El Escorial). The possible finding of biomarkers to aid in the early diagnosis and rate of disease progression could serve for future innovative therapeutic approaches. Recently, it has been suggested that ALS has an important immune component that could represent either the cause or the consequence of the disease. In this report, we analyzed 19 different cytokines and growth factors in the cerebrospinal fluid of 77 ALS patients and 13 controls by decision tree and PanelomiX program. Results showed an increase of Adipsin, MIP-1b, and IL-6, associated with a decrease of IL-8 thresholds, related with ALS patients. This biomarker panel analysis could represent an important aid for diagnosis of ALS alongside the clinical and neurophysiological criteria.

Protective effects of Withania somnifera extract in SOD1G93A mouse model of amyotrophic lateral sclerosis

Withania somnifera (WS; commonly known as Ashwagandha or Indian ginseng) is a medicinal plant whose extracts have been in use for centuries in various regions of the world as a rejuvenator. There is now a growing body of evidence documenting neuroprotective functions of the plant extracts or its purified compounds in several models of neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Based on the extract's beneficial effect in a mouse model of ALS with TDP-43 proteinopathy, the current study was designed to test its efficacy in another model of familial ALS. Our results show that administration of WS extracts by gavage to mice expressing G93A mutant form of superoxide dismutase (SOD1) resulted in increased longevity, improved motor performance and increased number of motor neurons in lumbar spinal cord. The WS treatment caused substantial reduction in levels of misfolded SOD1whereas it enhanced expression of cellular chaperons in spinal cord of SOD1^G93A mice. WS markedly reduced glial activation and prevented phosphorylation of nuclear factor kappaB (NF-κB). The overall immunomodulatory effect of WS was further evidenced by changes in expression of multiple cytokines/chemokines. WS also served as an autophagy inducer which may be beneficial at early stages of the disease. These results suggest that WS extracts might constitute promising therapeutics for treatment of ALS with involvement of misfolded SOD1.

Microglia-mediated recovery from ALS-relevant motor neuron degeneration in a mouse model of TDP-43 proteinopathy

Though motor neurons (MNs) selectively degenerate in amyotrophic lateral sclerosis (ALS), other cell types are likely involved in this disease. We recently generated rNLS8 mice in which human TDP-43 (hTDP-43) pathology could be reversibly induced in neurons and expected microglia would contribute to neurodegeneration. However, only subtle microglial changes were detected during disease in the spinal cord, despite progressive MN loss, but microglia still reacted to inflammatory triggers in these mice. Notably, after the hTDP-43 expression was suppressed, microglia dramatically proliferated and changed their morphology and gene expression profiles. These abundant, reactive microglia selectively cleared neuronal hTDP-43. Finally, when microgliosis was blocked during the early recovery phase using PLX3397, a CSF1R/c-kit inhibitor, rNLS8 mice failed to regain full motor function, revealing an important neuroprotective role for microglia. Therefore, reactive microglia exert neuroprotective functions in this ALS model and definition of the underlying mechanism could point towards novel therapeutic strategies.

Withania somnifera Reverses Transactive Response DNA Binding Protein 43 Proteinopathy in a Mouse Model of Amyotrophic Lateral Sclerosis/Frontotemporal Lobar Degeneration

Abnormal cytoplasmic mislocalization of transactive response DNA binding protein 43 (TARDBP or TDP-43) in degenerating neurons is a hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Our previous work suggested that nuclear factor kappa B (NF-κB) may constitute a therapeutic target for TDP-43-mediated disease. Here, we investigated the effects of root extract of Withania somnifera (Ashwagandha), an herbal medicine with anti-inflammatory properties, in transgenic mice expressing a genomic fragment encoding human TDP-43A315T mutant. Ashwagandha extract was administered orally to hTDP-43A315T mice for a period of 8 weeks starting at 64 and 48 weeks of age for males and females, respectively. The treatment of hTDP-43A315T mice ameliorated their motor performance on rotarod test and cognitive function assessed by the passive avoidance test. Microscopy examination of tissue samples revealed that Ashwagandha treatment of hTDP-43A315T mice improved innervation at neuromuscular junctions, attenuated neuroinflammation, and reduced NF-κB activation. Remarkably, Ashwagandha treatment reversed the cytoplasmic mislocalization of hTDP-43 in spinal motor neurons and in brain cortical neurons of hTDP-43A315T mice and it reduced hTDP-43 aggregation. In vitro evidence is presented that the neuronal rescue of TDP-43 mislocalization may be due to the indirect effect of factors released from microglial cells exposed to Ashwagandha. These results suggest that Ashwagandha and its constituents might represent promising therapeutics for TDP-43 proteinopathies.