Reducing neuroinflammation through PKCγ/p38/NF-κB signaling pathway: the mechanism of Danzhi Xiaoyaosan in improving post-stroke depression

Ethnopharmacological relevance

Post-stroke depression (PSD) is a common sequela of stroke, causing tremendous mental burden to patients. Danzhi Xiaoyao San (DZX) is a widely used traditional Chinese medicine formula for the clinical treatment of PSD and has favorable therapeutic effects. However, its mechanism of action in treating PSD is still unclear.

Aim of study

This study aimed to assess the therapeutic effects of DZX on rats with PSD and further investigate its underlying mechanism.

Materials and methods

The active ingredients of DZX aqueous extract were quantified by the high-performance liquid chromatography (HPLC). Neurological function and depression-like behavioral tests were performed to evaluate the therapeutic effects of DZX on PSD after establishing a rat model of PSD by the MCAO + CUMS protocol. Laser speckle is used to evaluate brain tissue blood flow, TTC staining is used to evaluate cerebral infarction volume, and transmission electron microscopy (TEM) is used to observe the ultrastructure of the hippocampus. ELISA was conducted to detect the levels of inflammatory factors in serum and cortical tissues, combined with HE staining to assess the neuroinflammatory response in the cortex of PSD rats. Then, network pharmacology combined with untargeted metabolomics of hippocampus tissue predicted the possible targets and pathways of DZX. In addition, flow cytometry was performed to detect Ca²⁺ content in cortical tissues, Western blot was used to detect the expression levels of key proteins of the PKCγ/p38/NF-κB signaling pathway, and immunofluorescence staining was performed to assess the M1/M2 polarization of hippocampal microglia. Moreover, specific inhibitors of PKCγ were used to validate the critical role of the PKCγ/p38/NF-κB signaling pathway in the treatment of PSD with DZX.

Results

DZX was found to increase cerebral blood flow, reduce infarct volume, and enhance the sucrose preference rate in the sucrose preference test (SPT), grooming time in the splash test (ST), and time spent in the central zone in the open field test (OFT) in PSD rats. Additionally, it significantly decreased immobility time in the forced swim test (FST). Furthermore, DZX ameliorated neuronal damage and ultrastructural abnormalities in the hippocampal region of PSD rats. In addition, DZX treatment effectively reduced Ca²⁺ and inflammatory factor levels, inhibited the phosphorylation of PLCγ, and activated PKCγ to suppress the p38/NF-κB pathway, thereby balancing the M1/M2 polarization phenotype of hippocampal microglia. More importantly, the specific PKCγ inhibitor reversed the neuroprotective effects of DZX and its inhibition of hippocampal neuroinflammation in PSD rats.

Conclusion

The findings demonstrated that DZX exhibits the ability to ameliorate PSD symptoms by activating PKCγ-mediated suppression of the p38/NF-κB signaling pathway. These results highlight the importance of the PKCγ/p38/NF-κB signaling pathway in improving PSD symptoms and provide additional pharmacological evidence for the therapeutic use of DZX in treating PSD.