Abstract:

This study focused on the regulatory relationship between inflammatory signaling pathways and microglial polarization, aiming to clarify the antidepressant effect and immunological mechanism of volatile oil of Acorus tatarinowii (VOA). In in vivo experiments, male ICR mice were randomly divided into control group, model group, fluoxetine hydrochloride positive control group, and VOA low-, medium-, and high-dose groups. VOA was administered by intranasal inhalation, and lipopolysaccharide (LPS) was intraperitoneal injected to establish the depression model. Transcriptome sequencing was used to screen key differentially expressed genes related to the antidepressant effect of VOA and perform pathway enrichment analysis. Meanwhile, Western blot was employed to detect the expression levels of proteins related to the tumor necrosis factor/nuclear factor kappa B/NOD-like receptor protein 3 (TNF/NF-κB/NLRP3) pathway and microglial M1/M2 phenotypic markers CD16/32 and CD206 in mouse hippocampus. In vitro experiments were performed using LPS-activated BV‑2 microglia. The cell survival rate was detected by CCK‑8 assay and the optimal drug concentration was screened, nitric oxide (NO) release in the cell supernatant was detected by the Griess method, and the protein expression ratio of p‑NF‑κB p65/NF‑κB p65 was determined by Western blot. The results showed that differentially expressed genes regulated by VOA were mainly enriched in inflammation‑related targets such as TNF, interleukin‑1β (IL-1β), chemokine (C‑C motif) ligand 2 (CCL2), prostaglandin endoperoxide synthase 2 (PTGS2), and NLRP3, and the antidepressant effect of VOA was closely related to the TNF-mediated inflammatory signaling pathway. Compared with the model group, the expression levels of M1-type microglial marker CD16/32 protein and proteins related to the TNF/NF-κB/NLRP3 pathway in the hippocampal tissue of mice in each VOA dose group were significantly decreased, while the expression level of M2-type marker CD206 protein was significantly increased (P<0.05). In vitro experiments confirmed that VOA could dose-dependently protect BV-2 cell against LPS-induced injury, inhibit LPS-induced activation of BV-2 microglia, reduce NO release (P<0.05), and significantly downregulate the expression ratio of p-NF-κB p65/NF-κB p65 protein (P<0.05). In conclusion, VOA can inhibit microglial M1 polarization, promote M2 transformation, and alleviate central nervous inflammation by downregulating the TNF/NF‑κB/NLRP3 signaling pathway, thereby exerting an antidepressant effect.

Key words:  Acorus tatarinowii volatile oil, depression, TNF/NF-κB/NLRP3 signaling pathway, microglia, neuroinflammation