Stress increases vulnerability to inflammation in the rat prefrontal cortex
ABSTRACT Inflammation could be involved in some neurodegenerative disorders that accompany signs of inflammation. However, because sensitivity to inflammation is not equal in all brain structures, a direct relationship is not clear. Our aim was to test whether some physiological circumstances, such as stress, could enhance susceptibility to inflammation in the prefrontal cortex (PFC), which shows a relative resistance to inflammation. PFC is important in many brain functions and is a target for some neurodegenerative diseases. We induced an inflammatory process by a single intracortical injection of 2 microg of lipopolysaccharide (LPS), a potent proinflammogen, in nonstressed and stressed rats. We evaluated the effect of our treatment on inflammatory markers, neuronal populations, BDNF expression, and behavior of several mitogen-activated protein (MAP) kinases and the transcription factor cAMP response element-binding protein. Stress strengthens the changes induced by LPS injection: microglial activation and proliferation with an increase in the levels of the proinflammatory cytokine tumor necrosis factor-alpha; loss of cells such as astroglia, seen as loss of glial fibrillary acidic protein immunoreactivity, and neurons, studied by neuronal-specific nuclear protein immunohistochemistry and GAD67 and NMDA receptor 1A mRNAs expression by in situ hybridization. A significant increase in the BDNF mRNA expression and modifications in the levels of MAP kinase phosphorylation were also found. In addition, we observed a protective effect from RU486 [mifepristone (11beta-[p-(dimethylamino)phenyl]-17beta-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one)], a potent inhibitor of the glucocorticoid receptor activation. All of these data show a synergistic effect between inflammation and stress, which could explain the relationship described between stress and some neurodegenerative pathologies.
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ABSTRACT: Animal models of chronic stress represent valuable tools for investigation of the neurobiological changes underlying the stress-related psychopathologies in which neuroinflammation also plays an important role. The aim of the present study was to estimate the influence of antidepressants given chronically on brain-derived neurotrophic factor (BDNF) alterations induced by lipopolysaccharide (LPS) in the amygdala and hippocampus of female rats subjected to chronic social instability stress (CSIS) for 29-30 days. This stress paradigm known to be more stressful for females was applied because stress induces affective disorders more frequently in women than men. The model was based on alternating stressful situations, including phases of isolation and crowding, in an unpredictable manner. An increased relative adrenal weight and a tendency towards the enhanced plasma corticosterone concentration were found in the stressed rats. CSIS did not change sucrose preference. Desipramine (10mg/kg), fluoxetine (5mg/kg), tianeptine (10mg/kg) or saline was administered ip once daily. On the last day of the experiment, the rats in the estrus phase were injected ip with LPS (1mg/kg) or saline. In the stressed rats, LPS administration decreased BDNF mRNA levels in both limbic structures. The studied antidepressants reversed the effect of the combined stress and LPS, and tianeptine induced the strongest effects. These results indicate that chronic stress enhances vulnerability of BDNF response to deleterious influence of neuroinflammation in the examined limbic structures, what may account for its role in triggering neuropsychiatric diseases. The observed effect of antidepressants may be of significance for their therapeutic effects in the stress-induced affective disorders in females.Neuroscience Research 08/2014; 88. DOI:10.1016/j.neures.2014.08.008 · 2.15 Impact Factor
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ABSTRACT: Chronic stress as well as chronic treatment with glucocorticoids (GCs) primes the neuroinflammatory response to a subsequent pro-inflammatory challenge. However, it remains unclear whether chronic GCs sensitize the response of key CNS immune substrates (i.e. microglia) to pro-inflammatory stimuli. In the present set of studies, male Sprague-Dawley rats underwent sham surgery or were adrenalectomized and then treated with varying concentrations of corticosterone (CORT; 0, 25, 50, and 75 μg/ml) administered in their drinking water. After 10 days of CORT exposure, whole hippocampus was collected and expression of glial activation markers measured or hippocampal microglia were isolated and challenged with LPS to probe for CORT-induced sensitization of pro-inflammatory responses. Chronic CORT exposure increased the gene expression of NLRP3, Iba-1, MHCII, and NF-κBIα in a concentration dependent manner. Chronic CORT (75 μg/ml) exposure potentiated the microglial proinflammatory response (TNFα, IL-1β, IL-6 and NLRP3) to LPS compared to the microglial response of sham surgery animals treated with vehicle. The present set of results demonstrate that chronic exposure to GCs primes microglia to pro-inflammatory stimuli and add to a growing body of evidence suggesting that a permissive function of GCs is that of an endogenous danger signal or alarmin.Psychoneuroendocrinology 02/2014; 40:191-200. DOI:10.1016/j.psyneuen.2013.11.006 · 5.59 Impact Factor
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ABSTRACT: Low socioeconomic status is consistently associated with reduced physical and mental health, but the mechanisms remain unclear. Increased levels of urban air pollutants interacting with parental stress have been proposed to explain health disparities in respiratory disease, but the impact of such interactions on mental health is unknown. We aimed to determine whether combined prenatal air pollution exposure and stress during pregnancy act synergistically on offspring to induce a neuroinflammatory response and subsequent neurocognitive disorders in adulthood. Mouse dams were intermittently exposed via oropharyngeal aspiration to diesel exhaust particles (DEP; 50 μg x 6 doses) or vehicle throughout gestation, combined with standard housing or nest material restriction (NR; a novel model of maternal stress) during the last third of gestation. Adult [postnatal day (P)60] offspring of dams that experienced both stressors (DEP/NR) displayed increased anxiety, but only male offspring of this group had impaired cognition. Furthermore, maternal DEP exposure increased proinflammatory IL-1β levels within the brains of adult males but not females, and maternal DEP and NR both decreased anti-inflammatory IL-10 in male, but not female, brains. Similarly, only DEP/NR males showed increased expression of the innate immune recognition gene, toll-like receptor (TLR)4, and its downstream effector, caspase-1. These results show that maternal stress during late gestation increases the susceptibility of offspring-particularly males-to the deleterious effects of prenatal air pollutant exposure, which may be due to a synergism of these factors acting on innate immune recognition genes and downstream neuroinflammatory cascades within the developing brain.Environmental Health Perspectives 07/2013; 121(9). DOI:10.1289/ehp.1306560 · 7.03 Impact Factor