Dysregulation of arginase and arginine pathways in neurodegenerative diseases: Metabolic and cellular dysfunction and therapeutic implications.

Neurodegenerative diseases are increasingly recognized as disorders associated with metabolic dysfunction with arginine metabolism emerging as a significant contributor. Arginase, by regulating the balance between arginine and ornithine, is positioned at the crossroads of multiple arginine metabolic pathways, thereby controlling a variety of cellular processes essential for proper brain homeostasis. Chronic disruption of these pathways may lead to dysfunction of neurons and glia ultimately resulting in the induction of neurodegenerative processes. In this review, based on data from patients and experimental models, we synthesize and critically evaluate evidence demonstrating alterations in arginase isoenzymes and associated metabolic pathways in Alzheimer's Parkinson's and Huntington's diseases, and amyotrophic lateral sclerosis. We discuss mechanisms through which dysregulation of arginase and arginine metabolism may contribute to neurodegeneration, including disturbances in nitrogen metabolism, oxidative and nitrosative stress, mitochondrial dysfunction, and neuroinflammation. Based on this body of evidence, we propose therapeutic strategies targeting arginase-related pathways, with the aim of preserving cellular metabolic homeostasis to ameliorate disease progression. Finally, we outline directions for future research, emphasizing that a proper understanding of the physiological roles of arginase isoenzymes and their disease-, stage-, and cell-specific dysregulation will be essential for the development of effective metabolically targeted therapies against neurodegenerative diseases.