Bear Bile Powder Alleviates Corticosterone-induced Depression-like Behavior in Female Mice by Protecting Hippocampal Neurons via the BDNF/TrkB/ CREB Pathway.

Introduction: Bear bile powder (BBP) has been traditionally used in Chinese medicine for calming the liver, pacifying the mind, and relieving convulsions, as recorded in Ben Jing Feng Yuan and Yu Qiu Yao Jie. Although the antidepressant effects of BBP have been previously reported, the underlying neurological mechanisms have yet to be fully elucidated. This study aimed to investigate the antidepressant effects of BBP on corticosterone (CORT)-induced depression-like behaviors in female mice and to explore the involvement of the BDNF/TrkB/CREB signaling pathway.

Methods: Female mice received subcutaneous CORT injections to induce depression-like behaviors, followed by oral administration of BBP at doses of 50, 100, and 200 mg/kg. Behavioral assessments, biochemical analyses, UPLC-MS/MS, immunohistochemistry, and Western blotting were conducted to evaluate antidepressant effects. Additionally, a CORT-induced HT22 cell injury model was established to assess the neuroprotective mechanisms of BBP, with or without the TrkB antagonist K252a, focusing on the BDNF/TrkB/CREB pathway.

Results: BBP significantly alleviated depression-like behaviors in CORT-treated female mice. It restored neurotransmitter levels, reduced neuronal necrosis in the hippocampal CA3 region, increased DCX-positive cells in the dentate gyrus, and activated hippocampal BDNF/TrkB/CREB signaling. In vitro, BBP attenuated CORT-induced apoptosis and promoted proliferation in HT22 cells. Applying K252a confirmed that BBP's neuroprotective and antidepressant effects were mediated via the BDNF/TrkB/CREB pathway.

Discussion: These findings suggest that BBP exerts notable antidepressant and neuroprotective effects in female depression models by modulating neurotransmitters and enhancing neurogenesis through the BDNF/Trk- B/CREB pathway. Using both in vivo and in vitro models strengthens the evidence for BBP's mechanism of action. However, further studies involving additional brain regions and upstream regulatory mechanisms are warranted.

Conclusion: BBP effectively alleviates CORT-induced depressive-like behaviors in female mice by restoring neurotransmitter balance, protecting hippocampal neurons, and promoting neurogenesis via the BDNF/Trk- B/CREB pathway. These results provide a theoretical basis for the potential application of BBP in managing female depression.