Retinal Ganglion Cell Loss and Microglial Activation in a SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

The neurodegenerative disease amyotrophic lateral sclerosis (ALS) affects the spinal cord, brain stem, and cerebral cortex. In this pathology, both neurons and glial cells are affected. However, few studies have analyzed retinal microglia in ALS models. In this study, we quantified the signs of microglial activation and the number of retinal ganglion cells (RGCs) in an SOD1G93A transgenic mouse model at 120 days (advanced stage of the disease) in retinal whole-mounts. For SOD1G93A animals (compared to the wild-type), we found, in microglial cells, (i) a significant increase in the area occupied by each microglial cell in the total area of the retina; (ii) a significant increase in the arbor area in the outer plexiform layer (OPL) inferior sector; (iii) the presence of cells with retracted processes; (iv) areas of cell groupings in some sectors; (v) no significant increase in the number of microglial cells; (vi) the expression of IFN-γ and IL-1β; and (vii) the non-expression of IL-10 and arginase-I. For the RGCs, we found a decrease in their number. In conclusion, in the SOD1G93A model (at 120 days), retinal microglial activation occurred, taking a pro-inflammatory phenotype M1, which affected the OPL and inner retinal layers and could be related to RGC loss.

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Evidence for a protective role of the CX3CL1/CX3CR1 axis in a model of amyotrophic lateral sclerosis

Biological Chemistry ◽

10.1515/hsz-2018-0204 ◽

2019 ◽

Vol 400 (5) ◽

pp. 651-661 ◽

Cited By ~ 9

Author(s):

Chang Liu ◽

Kun Hong ◽

Huifang Chen ◽

Yanping Niu ◽

Weisong Duan ◽

...

Keyword(s):

Amyotrophic Lateral Sclerosis ◽

Communication System ◽

Microglial Activation ◽

Neuronal Cell ◽

Cell Loss ◽

Degradation Pathway ◽

Neuroprotective Effects ◽

End Stage ◽

Lateral Sclerosis

Abstract Aberrant microglial activation and neuroinflammation is a pathological hallmark of amyotrophic lateral sclerosis (ALS). Fractalkine (CX3CL1) is mostly expressed on neuronal cells. The fractalkine receptor (CX3CR1) is predominantly expressed on microglia. Many progressive neuroinflammatory disorders show disruption of the CX3CL1/CX3CR1 communication system. But the exact role of the CX3CL1/CX3CR1 in ALS pathology remains unknown. F1 nontransgenic/CX3CR1+/− females were bred with SOD1G93A/CX3CR1+/− males to produce F2 SOD1G93A/CX3CR1−/−, SOD1G93A/CX3CR1+/+. We analyzed end-stage (ES) SOD1G93A/CX3CR1−/− mice and progression-matched SOD1G93A/CX3CR1+/+ mice. Our study showed that the male SOD1G93A/CX3CR1−/− mice died sooner than male SOD1G93A/CX3CR1+/+ mice. In SOD1G93A/CX3CR1−/− mice demonstrated more neuronal cell loss, more microglial activation and exacerbated SOD1 aggregation at the end-stage of ALS. The NF-κB pathway was activated; the autophagy-lysosome degradation pathway and the autophagosome maturation were impaired. Our results indicated that the absence of CX3CR1/CX3CL1 signaling in the central nervous system (CNS) may worsen neurodegeneration. The CX3CL1/CX3CR1 communication system has anti-inflammatory and neuroprotective effects and plays an important role in maintaining autophagy activity. This effort may lead to new therapeutic strategies for neuroprotection and provide a therapeutic target for ALS patients.

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