The influence of stress on neuroinflammation and alterations in brain structure and function in major depressive disorder

• Published in: Behavioural brain research Vol. 329; pp. 6 - 11
• Main Authors: Kim, Yong-Ku, Won, Eunsoo
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.06.2017
• Subjects: Animals; Brain - pathology; Brain - physiopathology; Brain structure and function; Depressive Disorder, Major - complications; Depressive Disorder, Major - pathology; Encephalitis - etiology; Humans; Kynurenic Acid - metabolism; Kynurenine pathway metabolites; Major depressive disorder; Neuroinflammation; Neurotransmitter Agents - metabolism; Pro-inflammatory cytokines; Signal Transduction - physiology; Stress; Stress, Psychological - etiology; Pro-inflammatory cytokines; Kynurenine pathway metabolites; Neuroinflammation; Brain structure and function; Stress; Major depressive disorder
• ISSN: 0166-4328; 1872-7549; 1872-7549
• DOI: 10.1016/j.bbr.2017.04.020

•Chronic stress can lead to increases in pro-inflammatory cytokine levels.•Inflammation leads to alterations in the ratio of kynurenine pathway metabolites.•Pro-inflammatory cytokines and kynurenine pathway metabolites can be neurotoxic.•Neurotoxicity causes changes in the hippocampus, amygdala, and cingulate cortex.•Alterations in brain regions are associated with the pathophysiology of depression. Major depressive disorder (MDD) is a condition which has often been associated with chronic stress. The sympathetic nervous system is continuously activated without the normal counteraction of the parasympathetic nervous system under the influence of chronic stress. As a result, epinephrine and norepinephrine levels are increased, and acetylcholine levels are decreased, which in turn can increase the levels of pro-inflammatory cytokines. Peripheral inflammatory responses can access the brain, with neuroinflammation contributing to the increase in neurotoxic kynurenine pathway metabolites such as 3-hydroxykynurenine, 3-hydroxyanthranilic acid and quinolinic acid, and decrease in neuroprotective metabolites such as kynurenic acid. Pro-inflammatory cytokines can also exert direct neurotoxic effects on specific brain regions. Previous imaging studies have reported associations between pro-inflammatory states and alterations in brain regions involved in emotional regulation, including the hippocampus, amygdala and anterior cingulate cortex. Alterations in structure and function of such brain areas due to the neurotoxic effects of increased inflammation may be associated with the pathophysiology of depression. This review focuses the influence of stress on neuroinflammation which may cause alterations in brain structure and function in MDD.