Investigating acupuncture therapy in depression: mechanisms of synaptic plasticity regulation

Depression is a severe heterogeneous mental illness that is highly co-morbid with other mental and somatic disorders. It poses a significant healthcare burden on both individuals and society. Currently, the use of single-target antidepressants exhibits suboptimal efficacy with significant adverse effects. Acupuncture has been advocated as a practical and effective treatment for depression, due to its low adverse effects rate compared to antidepressant medication. Currently, several studies have shown that acupuncture treatment for depression primarily involves multiple therapeutic mechanisms, including the regulation of specific gene expression, neuropeptide and neurotransmitter release, increasing the expression of neurotrophic factors, suppressing hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, attenuating inflammatory responses, and restoring gut microbiota balance. These therapeutic effects involve the regulation of critical signaling pathways, including the cAMP-responsive element binding protein (CREB) signaling pathway, mitogen-activated protein kinases (MAPK) signaling pathway, mechanistic target of rapamycin (mTOR) signaling pathway, and toll-like receptors (TLR) signaling pathway. Notably, depression-associated molecular mechanisms and signaling pathway dysregulations are closely linked to impaired neural and synaptic plasticity. Acupuncture synergistically modulates the neuro-immune-microbiome multidimensional network and integrates crosstalk among key pathways such as CREB, thereby systemically restoring synaptic plasticity. This multi-dimensional integrative mechanism likely underlies its therapeutic superiority over single-target antidepressants. This review aims to elucidate how acupuncture restores cerebral synaptic plasticity by rectifying depression-related systemic dysfunctions and signaling pathway abnormalities, which will advance our understanding of its regulatory potential in depression treatment and inform the development of precision therapeutic strategies.