Accumulating evidence has accrued demonstrating that inflammatory processes in the central nervous system (CNS) are associated with various neurological disorders including depression. However, whether inflammation-mediated neuronal damage is involved in depression-like behaviors induced by chronic stress and, in particular, whether suppression of inflammation could then serve as a potential strategy in depression therapy remains largely unknown. The present study aimed to investigate the neuronal mechanisms and signaling pathways through which inflammation results in neuronal deterioration in a rat model of depression and thus identify agents with potential roles as antidepressant treatments. Our results showed that chronic unpredictable mild stress (CUMS) exposure induced microglia activation and overexpression of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-a (TNF-α) within the medial prefrontal cortex (mPFC), effects which were paralleled with neuronal structural changes. In contrast, chronic administration of either IL-1β or nuclear factor κB (NF-κB) antagonists significantly ameliorated this dysregulation of neuronal structure and biochemical parameters such as SSH1 and phospho-cofilin within the mPFC, as well as the display of depression-like behaviors induced by CUMS exposure. More importantly, pretreatment with curcumin (40 mg/kg, i.p., 5 weeks), produced antidepressant-like actions and repressed the inflammatory responses and neuronal structural abnormalities. These findings reveal some of the molecular neuroinflammation pathways associated with depression and suggest new avenues of investigation for the development of potential antidepressant therapies in the treatment of inflammation-related neuronal deterioration in this disorder.
Keywords: IL-1β; cofilin; curcumin; depression; neuroinflammation; neuroplasticity.
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