Reduced microvascular coverage links a hypoxia-associated niche to microglial autophagic dysfunction in Parkinson’s disease

Abstract

Microglial hyperactivation contributes to Parkinson’s disease (PD) progression, yet the upstream microenvironmental cues that sustain this state remain incompletely understood. While α-synuclein (α-Syn) aggregation is a primary trigger, aging and PD are also associated with microvascular and perfusion abnormalities. However, how vascular-associated hypoxic stress interacts with protein toxicity in microglial fate determination remains unclear. We integrated human single-nucleus RNA sequencing (snRNA-seq) data, a chronic progressive transgenic mouse model (9-month-old A53T), and an in vitro “double-hit” model. Neuropathological and immunofluorescence analyses were employed to assess the neurovascular unit and microglial phenotypes. The snRNA-seq analysis of human PD brains revealed a Disease-Associated Microglia (DAM) subset characterized by enrichment of hypoxia and glycolysis pathways, with HIF1A acting as a central node. In vivo, 9-month-old A53T mice exhibited motor deficits and dopaminergic degeneration, accompanied by reduced CD31+ microvascular coverage in the substantia nigra. This reduction in CD31+ vascular coverage was associated with microglial HIF1A accumulation and increased IBA1-defined soma area. In vitro, physical hypoxia amplified α-Syn preformed fibril (PFF)-induced microglial reactivity, intracellular accumulation of phosphorylated α-Syn (p-αSyn). Our study supports a “double-hit” model in which hypoxia-associated stress may amplify α-Syn-induced microglial dysfunction through HIF1A-linked metabolic remodeling and impaired autophagy-related protein handling. Targeting neurovascular-immune interactions may offer therapeutic opportunities for advanced PD.