Nrf2/Keap1 Signaling Axis in the Brain: Master Regulator of Oxidative Stress in Neurodegenerative and Psychiatric Disorders.

Oxidative stress is a crucial factor in the development of CNS disorders, including neurodegenerative and psychiatric conditions. The Nrf2/Keap1 signaling axis plays a central role in defending against oxidative damage by regulating antioxidant and cytoprotective gene expression. Beyond its antioxidant function, Nrf2 influences neurogenesis, synaptic plasticity, mitochondrial bioenergetics, and glial neuronal interactions, all of which are vital for maintaining neural integrity and cognitive performance. Dysregulation of this pathway through altered dimerization, post-translational modifications, or impaired regulation contributes to the pathophysiology of Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, leading to protein aggregation, mitochondrial dysfunction, and neuroinflammation. Emerging evidence also implicates aberrant Nrf2 activity in psychiatric disorders such as depression, schizophrenia, and bipolar disorder, where redox imbalance and neuroimmune activation disrupt neural function. This review summarizes the molecular structure and regulation of the Nrf2/Keap1 pathway, including basal and stress-induced activation, post-translational modifications, and cross-talk with PI3K/Akt, MAPK, and NF-κB signaling. We highlight cell-type-specific roles of Nrf2 in neurons, astrocytes, and microglia, and the gene expression networks that drive CNS antioxidant and detoxification responses. Recent therapeutic strategies include natural and synthetic Nrf2 activators, gene therapy approaches, and nanotechnology-based delivery systems. While the translational potential of Nrf2-targeted interventions is considerable, challenges remain, including risks of overactivation and oncogenicity, lack of reliable biomarkers, and barriers related to blood-brain barrier permeability, dose, timing, and bioavailability. By integrating advances in neuroscience, pharmacology, and molecular medicine, this review emphasizes the promise of Nrf2 as a unifying therapeutic target across diverse CNS pathologies. Future directions include precision modulation through epigenetic regulation and circRNAs, as well as personalized pharmacotherapy. The Nrf2/Keap1 axis represents a multidisciplinary platform for developing multimodal interventions to preserve brain health in neurodegenerative and psychiatric disorders.