Neuronal alpha-synuclein-mediated autophagy drives lipid droplets accumulation in astrocytes and microglia and aggravates ischemic stroke.

Abstract

BACKGROUND: Lipid droplets (LDs) agglomeration in glial cells after stroke contributes to cellular dysfunction and neuronal injury. Alpha-synuclein has been identified as a critical regulator in the uptake and metabolism of fatty acids across various neurological disorders. Moreover, alterations in autophagic function can impact the agglomeration of LDs following a stroke. It is also well-established that alpha-synuclein is directly involved in neuronal autophagy. Although substantial research has been conducted on the relationship between alpha-synuclein and lipid metabolism, the precise mechanisms by which alpha-synuclein modulates lipid metabolism in glial cells post-stroke are not yet fully understood. METHODS: Primary neurons and glial cells from neonatal mice were used to establish in vitro oxygen-glucose deprivation/reoxygenation and neuron-glia co-culture models. In vivo studies employed alpha-synuclein knockdown mice subjected to middle cerebral artery occlusion. Analysis of readout parameters using various techniques, including qRT-PCR, immunofluorescence, western blot assays, phagocytosis and behavioral tests. Utilizing both in vitro and in vivo stroke models, we investigated how alpha-synuclein modulates the interactions between neurons and microglia/astrocytes. RESULTS: We found that ischemic stroke induces LD agglomeration, triggers autophagy, and increases alpha-synuclein levels. Knockdown of alpha-synuclein reduced LD formation, restored autophagic balance, and improved neurological outcomes. In co-culture, silencing neuronal alpha-synuclein or enhancing neuronal autophagy decreased LD accumulation and modified LD-associated protein expression in microglia and astrocytes. Moreover, neuronal alpha-synuclein and autophagy regulation modulated glial phagocytic activity without directly altering glial autophagy. Additionally, changes in LD accumulation appear to play a pivotal role in mediating interactions between glial cells and neurons, thereby influencing cell viability and autophagy. Consistent with these findings, treatment with alpha-synuclein siRNA alleviates stroke-induced neurological deficits. CONCLUSION: Alpha-synuclein regulates lipid metabolism and phagocytic activity in glial cells through autophagy mechanisms under ischemic conditions, providing new insight into therapeutic strategies for stroke.