Leonurine Exerts Antidepressant-Like Effects in the Chronic Mild Stress-Induced Depression Model in Mice by Inhibiting Neuroinflammation

Background: Leonurine is an active alkaloid that is extracted from Traditional Chinese Medicine Herba leonuri. Emerging evidence indicates that leonurine produces neuroprotective effects in ischemic stroke, Parkinson's disease, and Alzheimer's disease. However, the effect of leonurine in neuropsychiatric disorders, especially in major depression, remains unknown. Methods: We used the chronic mild stress mouse model to explore the antidepressant effects of leonurine and the potential mechanisms. Behavioral tests including sucrose preference test, forced swimming test, and tail suspension test were taken to evaluate depression symptoms. Moreover, the contents of monoamine neurotransmitters in hippocampus and prefrontal cortex were measured by high-performance liquid chromatography. Neuronal morphology was detected by transmission electron microscopy. Results: Administration of leonurine (60 mg/kg) for 4 weeks significantly alleviated depression-like behaviors of chronic mild stress mice, including increased sucrose preference and reduced immobility time in forced swimming test and tail suspension test. We further found that leonurine (60 mg/kg) effectively restored the levels of 5-hydroxytryptamine, noradrenaline, and dopamine in the hippocampus and prefrontal cortex of chronic mild stress mice, accompanied by amelioration of hippocampal neuronal damage. Furthermore, leonurine (60 mg/kg) significantly inhibited the production of proinflammatory cytokine interleukin- 1 beta, interleukin-6 and TNF-alpha, and suppressed the nuclear factor kappaB signaling pathway. Conclusions: These findings demonstrate that leonurine exerts antidepressant-like effects, which may be mediated, at least in part, by improving monoamine neurotransmitters and inhibiting neuroinflammation. Our study provides insight into the potential of leonurine in depression therapy.