Pharmacological inhibition of O-GlcNAcase reduces pS129-α-synuclein positive aggregates in the substantia nigra of mThy1-hSNCA mice

Background The aggregation and spread of α-synuclein within brain are associated with the loss of dopaminergic neurons and the formation of Lewy bodies as seen in Parkinson's disease. Blocking the initiation of α-synuclein aggregation, or the spread of such aggregates, may offer disease-modifying approaches to slow disease progression. Previous studies have demonstrated that modification of aggregation prone proteins, including α-synuclein, with O-linked β- N -acetylglucosamine (O-GlcNAc) reduces their aggregation. Small molecule inhibitors of the enzyme O-GlcNAcase (OGA), which removes O-GlcNAc from proteins, confers neuroprotective benefits in various preclinical disease models of Alzheimer's and Parkinson's diseases. Objective This study investigates the effects of long-term pharmacological enhancement of O-GlcNAcylation in a transgenic mouse model of Parkinson's disease overexpressing human α-synuclein. Methods Thiamet-G was orally administered to mThy1-hSNCA and wild-type (WT) mice for ten months. Behavioral assessments were conducted to examine changes in locomotion and cognition. Histological analyses were performed to analyze α-synuclein aggregates and dopaminergic neurons in brain sections. Immunoblot and ELISA analyses were performed to analyze O-GlcNAc and soluble α-synuclein using brain lysates, respectively. Results Thiamet-G increased the level of O-GlcNAc in the brain of both mThy1-hSNCA and WT mice. The levels of total α-synuclein in the brain were unaltered. However, Thiamet-G strongly attenuated the deposition of pS129-immunoreactive α-synuclein aggregates within the substantia nigra, prior to observable neurodegeneration. Thiamet-G also protected against locomotor decline. Conclusions These results support OGA inhibition as a therapeutic approach to block the pathological formation of toxic α-synuclein as a disease-modifying treatment against Parkinson's disease.