Prophylactic Treatment of Curcumin in a Rat Model of Depression by Attenuating Hippocampal Synaptic Loss.

Curcumin is a polyphenol substance considered to be effective in the treatment of a number of neurodegenerative diseases. However, details regarding the exact mechanisms for the protective effects of curcumin in neuropsychiatric disorders, like depression, remain unknown. In the pathogenesis of major depressive disorder (MDD) it appears that dysregulation of oxidative stress and immune systems, particularly within the hippocampal region, may play a critical role. Here, we show that pre-treatment with curcumin (40 mg kg-1) alleviates depression-like behaviors in a LPS-induced rat model of depression, effects which were accompanied with suppression of oxidative stress and inflammation and an inhibition of neuronal apoptosis in the hippocampal CA1 region, and results from ultramicrostructure electrophysiological experiments revealed that the curcumin pre-treatment significantly prevented excessive synaptic loss and enhanced synaptic functioning in this LPS-induced rat model. In addition, curcumin attenuated the increases in levels of miR-146a-5p and decreases in the expression of p-ERK signaling that would normally occur within CA1 regions of these depressed rats. Taken together, these results demonstrated that curcumin exerts neuroprotective and antidepressant activities by suppressing oxidative stress, neural inflammation and their related effects upon synaptic dysregulation. One of the mechanisms for these beneficial effects of curcumin appears to involve the miR-146a-5p/ERK signaling pathway within the hippocampal CA1 region. These findings not only elucidated some of the mechanisms underlying the neuroprotective/antidepressant effects of curcumin, but also suggested a role of curcumin as a potential therapeutic strategy for depression.