No abstract

Amyotrophic lateral sclerosis (ALS) is an adult-onset fatal neurodegenerative disease characterized by muscle wasting, weakness, and spasticity due to a progressive degeneration of cortical, brainstem, and spinal motor neurons. The etiopathological causes are still largely obscure, although astrocytes definitely play a role in neuronal damage. Several mechanisms have been proposed to concur to neurodegeneration in ALS, including mitochondrial dysfunction. We have previously shown profound modifications of glutamate release and presynaptic plasticity in the spinal cord of the SOD1 mouse model of ALS. In this work, we characterized, for the first time, the aerobic metabolism in two specific compartments actively involved in neurotransmission (i.e. the presynaptic district, using purified synaptosomes, and the perisynaptic astrocyte processes, using purified gliosomes) in SOD1 mice at different stages of the disease. ATP/AMP ratio was lower in synaptosomes isolated from the spinal cord, but not from other brain areas, of SOD1 vs. control mice. The energy impairment was linked to altered oxidative phosphorylation (OxPhos) and increment of lipid peroxidation. These metabolic dysfunctions were present during disease progression, starting at the very pre-symptomatic stages, and did not depend on a different number of mitochondria or a different expression of OxPhos proteins. Conversely, gliosomes showed a reduction of the ATP/AMP ratio only at the late stages of the disease and an increment of oxidative stress also in the absence of a significant decrement in OxPhos activity. Data suggest that the presynaptic neuronal moiety plays a pivotal role for synaptic energy metabolism dysfunctions in ALS. Changes in the perisynaptic compartment seem subordinated to neuronal damage.

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Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with no effective cure. Astrocytes display a toxic phenotype in ALS and contribute to motoneuron (MN) degeneration. Modulating astrocytes’ neurotoxicity can reduce MN death. Our previous studies showed the beneficial effect of mesenchymal stem cell (MSC) administration in SOD1G93A ALS mice, but the mechanisms are still unclear. We postulated that the effects could be mediated by extracellular vesicles (EVs) secreted by MSCs. We investigated, by immunohistochemical, molecular, and in vitro functional analyses, the activity of MSC-derived EVs on the pathological phenotype and neurotoxicity of astrocytes isolated from the spinal cord of symptomatic SOD1G93A mice and human astrocytes (iAstrocytes) differentiated from inducible neural progenitor cells (iNPCs) of ALS patients. In vitro EV exposure rescued mouse and human ALS astrocytes’ neurotoxicity towards MNs. EVs significantly dampened the pathological phenotype and neuroinflammation in SOD1G93A astrocytes. In iAstrocytes, exposure to EVs increased the antioxidant factor Nrf2 and reduced reactive oxygen species. We previously found nine miRNAs upregulated in MSC-derived EVs. Here, the transfection of SOD1G93A astrocytes with single miRNA mimics reduced astrocytes’ activation and the expression of neuroinflammatory factors. Moreover, miR-466q and miR-467f mimics downregulate Mapk11, while miR-466m-5p and miR-466i-3p mimics promote the nuclear translocation of Nrf2. In iAstrocytes, transfection with miR-29b-3p mimic upregulated NQO1 antioxidant activity and reduced neurotoxicity towards MNs. MSC-derived EVs modulate astrocytes’ reactive phenotype and neurotoxicity through anti-inflammatory and antioxidant-shuttled miRNAs, thus representing a therapeutic strategy in ALS.

No abstract