Decoding crosstalk between neurotransmitters and α-synuclein in Parkinson's disease: pathogenesis and therapeutic implications.

Parkinson's disease (PD) is the second most common neurodegenerative disease, characterized by progressive worsening of motor symptoms. The primary pathological hallmark of PD is the degeneration of dopaminergic neurons in the substantia nigra and the presence of Lewy bodies, which are primarily composed of α-synuclein (α-syn) aggregates. Both α-syn and various neurotransmitters, including catecholamines (catechols), play crucial roles in the pathogenesis of PD, although the precise pathogenic mechanisms remain incompletely understood. The crosstalk between neurotransmitters and α-syn is intricate and multifaceted. Pathological α-syn disrupted neurotransmitters' homeostasis by impairing release and reuptake of neurotransmitters, with specific modulation of catecholaminergic and glutamatergic systems. Conversely, neurotransmitters, especially catechols, covalently modify α-syn. Such modifications significantly influence α-syn aggregation dynamics and alter its neurotoxic properties. However, determining whether these interactions induce synergistic toxicity or confer neuroprotection remains controversial. Emerging evidence suggests other neurotransmitters like serotonin and γ-aminobutyric acid may also modulate α-syn aggregation and PD progression, though their roles require further investigation. Understanding these interactions is crucial for developing novel diagnostic and multi-target therapeutic strategies.