Carvacrol mitigates chronic social isolation stress–induced depressive-like phenotypes via Nrf2-dependent antioxidant defense and downregulation of NF-κB proinflammatory pathway

Chronic social isolation stress (CSIS) disrupts redox homeostasis and promotes neuroinflammation, contributing to depressive-like behavior. Carvacrol (CV), a monoterpenoid phenol with antioxidants and anti-inflammatory properties, has been studied merely in stress-induced depression. Adult male NMRI mice underwent 6 weeks of CSIS and received CV (10 or 20 mg/kg, i.p.) or a positive control during the final 2 weeks. Depressive-like behavior was evaluated using open-field, splash, and forced-swim tests. Medial prefrontal cortex (mPFC) and hippocampal dentate gyrus tissues were assayed for catalase (CAT) and glutathione-S-transferase (GST) activities, reduced glutathione (GSH), and lipid peroxidation (LPO; TBARS), together with selected proinflammatory cytokines. Hematoxylin-eosin staining assessed cytoarchitecture, and molecular docking examined putative interactions of CV with the Nrf2/Keap1 complex and NF-κB. CSIS increased behavioral despair and reduced exploration and grooming, accompanied by decreased CAT, GST, and GSH, elevated TBARS, and higher inflammatory mediators, with neuronal alterations in mPFC and dentate gyrus. CV dose-dependently improved locomotor and grooming behavior, restored antioxidant defenses, reduced TBARS, and lowered inflammatory markers while preserving neuronal structure. Docking supported plausible binding (≈ -5.8 kcal/mol for Nrf2/Keap1; ≈ -5.1 kcal/mol for NF-κB), consistent with the observed molecular changes. These findings indicate that CV produces antidepressant-like effects in CSIS by reinforcing redox balance and attenuating neuroinflammation in stress-sensitive brain regions, supporting its therapeutic potential for stress-related mood disorder.