An Innate Neuroprotective Reflex Activates NRF2 via Phosphorylation of p62 at Ser351 to Mitigate Traumatic Brain Injury

Rationale: The oxidative crisis in traumatic brain injury (TBI) has remained therapeutically intractable to direct antioxidant therapies. Activating nuclear factor erythroid 2-related factor 2 (NRF2) offers a promising strategy, but its translation is hindered by a key question: whether TBI's depleted antioxidant reserves can accommodate canonical electrophilic activation. The diving reflex (DR) is a potential non-electrophilic alternative, but its efficacy in TBI is unknown and its natural induction is clinically impractical. This study tests whether artificial DR, induced by trigeminal nerve stimulation (TNS), can safely engage this non-electrophilic NRF2 pathway and exert a protective role in the acutely injured brain. Methods: In a rat model of severe TBI, we compared TNS-induced DR, natural DR, and exogenous calcitonin gene-related peptide (CGRP) against the electrophilic NRF2 activator dimethyl fumarate (DMF). To define the mechanism of action, we quantified p62 phosphorylation at Ser351 (NRF2-activating) versus Ser403 (autophagy-related), alongside redox homeostasis, lesion volume, and multi-domain functional outcomes. Results: TNS-induced DR fully recapitulated the neuroprotection of natural DR, an effect mimicked by exogenous CGRP, and prevented by CGRP inhibition, confirming a shared, neuropeptide-driven mechanism. This non-electrophilic pathway operated by selectively phosphorylating p62 at Ser351, which preserved glutathione reserves, halted lipid peroxidation, and reduced chronic lesion volume. In contrast, while DMF activated NRF2, its electrophilic mechanism was associated with a further reduction in the brain's already compromised glutathione pools and increased lipid peroxidation. This mechanistic difference was functionally significant, as only the non-electrophilic approaches delivered multi-domain recovery. Conclusion: The TNS-evoked artificial DR is a mechanistically tailored strategy for activating NRF2 in acute TBI. By engaging the endogenous CGRP-p62-KEAP1 pathway, it circumvents the fundamental limitations of both passively consumed direct antioxidants and redox-costly electrophilic activators. Our findings establish a clear translational roadmap for harnessing an innate reflex as a clinically deployable therapy for hyper-oxidative states.