Ashwagandha ( Withania somnifera (L.) dunal) root extract containing withanolide a alleviates depression-like behavior in mice by enhancing the brain-derived neurotrophic factor pathway under unexpected chronic mild stress

Ethnopharmacological relevance: Ashwagandha ( Withania somnifera (L.) Dunal) root or whole-plant extracts are used to treat anxiety, insomnia, and other nervous system disturbances. Aim of the study: We evaluated the neuroprotective and antidepressant effects of ashwagandha root extract (ARE) on corticosterone-exposed HT-22 cells and unpredictable chronic mild stress (UCMS)-challenged mice. Materials and methods: The neuroprotective properties of ARE containing withanolide A were assessed in HT-22 cells subjected to corticosterone-induced oxidative stress. Additionally, the effects of ARE on depression-like behavior, stress-related hormones, and inflammatory cytokine levels were evaluated in a mouse model of UCMS. Results: In HT-22 cells, ARE (100 and 200 mu g/mL) and its constituent, withanolide A (1.56 and 3.12 mu g/mL), mitigated corticosterone-induced increases in MAO activity, ROS, and MDA levels. Treatment also reversed corticosterone-induced reductions in BDNF, TrkB, p-AKT, p-ERK, and p-CREB and normalized Nrf2 and Keap1 levels, thereby elevating HO-1 expression. In UCMS mice, ARE improved behavioral outcomes, increased sucrose preference, and reduced immobility in the forced swimming test while enhancing activity in the open field test and elevated plus maze. ARE decreased the levels of stress hormones (corticotropin-releasing hormone, adrenocorticotropic hormone, and corticosterone) and increased the levels of neurotransmitters (L-DOPA, 5-HTP, and serotonin). Histological analysis revealed that ARE reduced hippocampal cell loss. Additionally, ARE (60 and 100 mg/kg) restored decreased levels of p-AKT, p-ERK, and p-CREB and lowered inflammation-related proteins (Cox2, iNOS, IL-6, IL-1 beta, TNF-alpha). Conclusion: These results indicate that ARE containing withanolide A exhibits notable neuroprotective and antidepressant properties.