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During the past two decades, there has been increasing interest in understanding and characterizing the role of inflammation in major depressive disorder (MDD). Indeed, several are the evidences linking alterations in the inflammatory system to Major Depression, including the presence of elevated levels of pro-inflammatory cytokines, together with other mediators of inflammation. However, it is still not clear whether inflammation represents a cause or whether other factors related to depression result in these immunological effects. Regardless, exposure to early life stressful events, which represent a vulnerability factor for the development of psychiatric disorders, act through the modulation of inflammatory responses, but also of neuroplastic mechanisms over the entire life span. Indeed, early life stressful events can cause, possibly through epigenetic changes that persist over time, up to adulthood. Such alterations may concur to increase the vulnerability to develop psychopathologies. In this review we will discuss the role of inflammation and neuronal plasticity as relevant processes underlying depression development. Moreover, we will discuss the role of epigenetics in inducing alterations in inflammation-immune systems as well as dysfunction in neuronal plasticity, thus contributing to the long-lasting negative effects of stressful life events early in life and the consequent enhanced risk for depression. Finally we will provide an overview on the potential role of inflammatory system to aid diagnosis, predict treatment response, enhance treatment matching, and prevent the onset or relapse of Major Depression.

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Background:Major depression is associated with several alterations, including reduced neuronal plasticity and impaired synaptic function, which represent an important target of pharmacological intervention.Methods:In the present study, we have investigated the ability of the antipsychotic drug lurasidone to modulate behavioral and neuroplastic alterations in the chronic mild stress model of depression.Results:Rats that show reduced sucrose consumption after 2 weeks of chronic mild stress have reduced expression of the pool of Bdnf transcripts with the long 3′ untranslated region (3′-UTR) that may be targeted to the synaptic compartment, suggesting the contribution of the neurotrophin to the behavioral dysfunction produced by chronic mild stress. The downregulation of Bdnf expression persisted also after 7 weeks of chronic mild stress, whereas chronic lurasidone treatment improved anhedonia in chronic mild stress rats and restored Bdnf mRNA levels in the prefrontal cortex. Moreover, chronic lurasidone treatment was able to normalize chronic mild stress-induced defects of Psd95 and Gfap as well as changes in molecular regulators of protein translation at the synapse, including mTOR and eEF2.Conclusions:These results demonstrate that lurasidone shows antidepressant properties in the chronic mild stress model through the modulation of synaptic and neuroplastic proteins. Such changes may contribute to the amelioration of functional capacities, which are deteriorated in patients with major depression and stress-related disorders.