Abstract
Purpose :
neuroinflammation is a prominent feature in common neurodegenerative diseases. Increasing evidence suggest that chemokines and their receptors are involved in regulating proinflammatory responses in neurological disorders. Previous studies reported that the chemokine fractalkine (CX3CL1), which is expressed on neuronal cells, and its receptor (CX3CR1), which is predominantly expressed on microglia, serve as an important communication link between neurons and microglia. However, the signalings by which CX3CR1 regulates microglial neurotoxicity are not fully understood. Here, we investigated the role of CX3CR1 signalling in the neurotoxic effects of microglia in the retina.
Methods :
We made use of the CX3CR1GFP/GFP receptor knockout mouse to study the role of CX3CR1 in microglia in the retina using immunocytochemistry, qPCR, western bot and electroretinography (ERG) approaches. To explore the downstream molecules of CX3CR1 signalling in regulating microglial neurotoxicity in the retina, we performed label-free LC-MS/MS-based proteomics and bioinformatics analysis.
Results :
We found that CX3CR1-deficient microglia induced microglia activation with increased CD68 immunoreactivity, and the activated microglia migrated to the outer nuclear layer (ONL) from their normal strata within the outer and inner plexiform layers (OPL and IPL). Meanwhile, we found that CX3CR1 deficiency triggered astrocytes activation, and reactive astrocytes extended hypertrophic dendritic processes well beyond their normal strata within the nerve fiber layer (NFL) into the IPL. Most importantly, we found that microglial activity mediated by CX3CR1 deficiency promoted cone photoreceptor cell loss and visual function decline in the retina. Moreover, we performed LC-MS/MS-based proteomics and bioinformatics analysis and identified that signal transducer and activator of transcription 3 (STAT3), a transcription factor, could be a potential downstream effector of CX3CR1 signalling in regulating microglial neurotoxicity in the retina.
Conclusions :
We demonstrated that CX3CR1 deficiency induced retinal glial cell reactivity and cone photoreceptor loss by regulating Stat3 signal. Targeting CX3CR1/Stat3 signal could be a new therapeutic strategy for controlling microglia activation and providing neuroprotection in neurological disorders featuring neuroinflammation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.