ETHNOPHARMACOLOGICAL RELEVANCE: Ligusticum chuanxiong Hort. (Chuanxiong) is a traditional Chinese medicinal herb whose rhizome has been historically and clinically used to treat conditions such as headache, dizziness, and depression. These traditional application broadly correlate with modern diagnoses of cerebrovascular dysfunction, impaired cerebral blood flow, and neuroinflammation. As a characteristic phthalide dimer and major bioactive constituent of Chuanxiong, levistilide A (LA) has shown significant therapeutic potential. However, its specific antidepressant and anxiolytic properties require further clarification.
AIM OF THE STUDY: This study aimed to assess the efficacy of LA against depression and anxiety, with the further goal of elucidating its underlying molecular mechanisms.
MATERIALS AND METHODS: A depression- and anxiety-like state was induced in C57BL/6 mice by LPS challenge after which they received therapeutic intervention with different doses of LA. The therapeutic efficacy was assessed by behavioral tests, histopathological analyses, and enzyme-linked immunosorbent assays (ELISA). Concurrently, we assessed microglial activation via immunofluorescence, along with mitochondrial status by measuring reactive oxygen species (ROS) levels with flow cytometry and examining ultrastructure with transmission electron microscopy (TEM). To investigate the cellular mechanisms, LPS-stimulated BV2 cells was established. In this model, autophagic flux was quantitatively measured using Bafilomycin A1 (Baf A1) inhibition assays combined with western blot analysis of LC3B-II. And mitophagy was evaluated by co-immunofluorescence LC3B with the mitochondrial marker Tomm40 in both BV2 cells and mouse hippocampal CA3. Building on this, computational approaches, along with experimental methodologies including immunofluorescence and western blotting, were utilized to elucidate the underlying molecular mechanisms. Furthermore, SIRT3-specific siRNA (siRNA-SIRT3) was used for further validation.
RESULTS: The LA treatment demonstrated a notable protective role against LPS-induced depression and anxiety through ameliorating behaviors accompanied by depression- and anxiety-like behaviors, attenuating neuronal damage, downregulating pro-inflammatory cytokine expression levels, and suppressing microglial overactivation. Mechanistically, LA alleviated oxidative stress and mitochondrial dysfunction by reducing ROS accumulation and mitigating mitochondrial damage. In the LPS-induced BV2 cells, LA treatment significantly enhanced autophagic flux, as evidenced by the further accumulation of LC3B-II upon Baf A1 inhibition, which confirmed the promotion of functional autophagy. Concurrently, the increased co-localization of Tomm40 with LC3B upon LA treatment provided direct evidence for mitophagy activation. Molecular docking combined with molecular dynamics simulation analyses revealed robust binding interactions between LA and SIRT3, as well as between SIRT3 and PINK1. Further investigation into the downstream pathway revealed that LA effectively activated the SIRT3/PINK1/Parkin pathway. This was supported by the western blot analyses. Specifically, LA treatment increased the SIRT3, PINK1, Parkin, and LC3B-II expression levels, while it decreased p62 levels. This result suggested mitophagy activation. An immunofluorescence analysis corroborated this result and revealed increased cytoplasmic colocalization of Tomm40 with LC3B following the LA treatment. Consistent with these findings, LA significantly suppressed neuroinflammation in LPS-stimulated BV2 microglial cells by inhibiting both NO production and the release of pro-inflammatory cytokines.. Importantly, LA recapitulated its favorable impacts on mitochondrial function and the SIRT3/PINK1/Parkin signaling cascade in this cellular model. The functional necessity of this pathway was demonstrated by the findings that SIRT3 knockdown with siRNA-SIRT3 in BV2 cells abolished regulatory impact of LA on PINK1/Parkin pathway proteins.
CONCLUSIONS: LA serves as a potential therapeutic agent for depression and anxiety through activating mitophagy mediated by the SIRT3/PINK1/Parkin pathway. The results of this study provide scientific evidence for the clinical application of LA in treating depression and anxiety.
