FoxO1 Alleviates the Mitochondrial ROS Levels Induced by α-Synuclein Preformed Fibrils in BV-2 Microglial Cells

Parkinson's disease (PD) is a complex neurodegenerative disorder marked by the gradual deterioration of dopaminergic neurons, especially in the substantia nigra pars compacta (SNc). Dysregulation of the transcription factor FoxO1 is associated with various neurodegenerative conditions, including Alzheimer's disease and PD, though the specific mechanisms involved are not fully understood. This study explores the effects of α-Synuclein preformed fibrils (PFF) on BV-2 microglial cells, focusing on changes in molecular characteristics and their impact on neuronal degeneration. Our results demonstrate that PFF treatment significantly increases FoxO1 mRNA (p = 0.0443) and protein (p = 0.0216) levels, leading to its nuclear translocation (p = 0.0142) and enhanced expression of genes involved in the detoxification of reactive oxygen species (ROS), such as Catalase (Cat, p = 0.0249) and superoxide dismutase 2 (Sod2, p = 0.0313). Furthermore, we observed that PFF treatment elevates mitochondrial ROS levels. However, cells lacking FoxO1 or treated with FoxO1 inhibitors showed increased vulnerability to PFF-induced ROS, attributed to reduced expression of ROS detoxifying enzymes Cat and Sod2 (p < 0.0001). Besides enhancing ROS production, inhibiting FoxO1 also heightens neurotoxicity induced by PFF treatment in microglia-conditioned medium (p < 0.0001). Conversely, treatment with N-acetylcysteine or bacterial superoxide dismutase A mitigated the ROS increase induced by PFF (p < 0.0001). These findings suggest the essential role of FoxO1 in regulating ROS levels, which helps alleviate pathology in PFF-induced PD models. Our study provides insights into the genetic mechanisms of PD and suggests potential pathways for developing novel therapeutic strategies.