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Modifying macrophages at the periphery has the capacity to change microglial reactivity and increase ALS survival

ABSTRACT: Microglia and peripheral macrophages, combined, have been implicated in the motor neuron disease Amyotrophic Lateral Sclerosis (ALS), but without discriminating their respective roles. We now show that macrophages along peripheral motor neuron axons of ALS mice and patients react to neurodegeneration. In ALS mice, peripheral myeloid cell infiltration into the spinal cord was limited and disease duration dependent. Targeted gene modulation of the reactive oxygen species pathway in peripheral myeloid cells of ALS mice, using cell replacement, reduced both peripheral macrophage and microglial activation, delayed symptoms and increased ALS mouse survival. Transcriptomics revealed that sciatic nerve macrophages and microglia reacted very different to neurodegeneration, with abrupt temporal changes in macrophages and progressive, unidirectional activation in microglia. Modifying peripheral macrophages suppressed proinflammatory microglial responses, with a strong shift towards neuronal support. Thus, modifying macrophages at the periphery has the capacity to influence disease progression and is of therapeutic value for ALS.

ORGANISM(S): Mus musculus

PROVIDER: GSE156202 | GEO | 2020/10/19

REPOSITORIES: GEO

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Project description:Abnormal accumulation of aggregated proteins and sustained microglial activation are important contributors of neurodegenerative process in neurological diseases. Recent studies have shown that aggregation-prone proteins, such as a-synuclein, the protein implicated in Parkinson’s disease (PD), are released from neuronal cells and thus present in the extracellular fluid, pointing to the possible paracrine effects of these proteins on microglial immune responses. However, the mechanism underlying the disease-associated microglial activation and the role of neuronal proteins in this process remain unknown. Here, we show that extracellular a-synuclein released from neuronal cells is an endogenous ligand of toll-like receptor 2 (TLR2) and activates microglia, which in turn induces neurodegeneration. Interaction between neuron-released a-synuclein and TLR2 and subsequent activation of the TLR2 signaling were demonstrated comprehensively by using computational modeling of signaling network and by the experimental validation in TLR2-deficient microglia both in vitro and in vivo. In contrast to the neuron-released a-synuclein, recombinant a-synuclein proteins, including monomer, oligomer, fibril, or nitrated forms, were not able to interact or activate TLR2, suggesting that neuronal cells have a mechanism of enriching specific forms of a-synuclein capable of activating TLR2 during the process of releasing this protein. Taken together, the results suggest that both neuron-released extracellular a-synuclein and TLR2 might be novel therapeutic targets for modifying neuroinflammation in PD and related neurodegenerative diseases. We collected culture media from differentiated SH-SY5Y cells overexpressing either human a-synuclein (alpha-SCM) or beta-galactosidase (LZCM) and treat these media to primary rat microglia at the concentration of a-synuclein of 1.1M. Transcriptome analyses with microglial cells treated with either aSCM or LZCM at two different time points, 6 h and 24 h.

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Modifying macrophages at the periphery has the capacity to change microglial reactivity and increase ALS survival

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