Quercetin suppress microglial neuroinflammatory response and induce antidepressent-like effect in olfactory bulbectomized rats
ABSTRACT In rodents, olfactory bulbectomy (OBX) results in several behavioral and biochemical changes, useful as a screening model for antidepressants. Recent evidences suggest that quercetin; a bioflavonoid exhibits a variety of behavioral effects including anxiolytic, antidepressant, etc. Since microglia are commonly implicated in the neuroinflammation cascade of depression, we hypothesized that quercetin might involve microglial inhibition pathway in its antidepressant-like effects. To support such a possibility, we investigated the interaction of quercetin with a known microglial inhibitor (minocycline) against olfactory bulbectomy induced depression in male Wistar rats. In our study, ablation of olfactory bulbs caused hyperactivity in open field arena and increased immobility time in forced swim test which was coupled with enhanced serum corticosterone levels. Additionally, there were increased oxidative-nitrosative stress markers, inflammatory mediators (TNF-α and IL-6) along with enhanced apoptotic factor (caspase-3) in both cerebral cortex and hippocampal brain regions of OBX animals. These results were further supported by reports from histopathological analysis. After a surgical recovery period of two weeks, treatment with quercetin (40, 80 mg/kg; p.o., 14 days) significantly prevented OBX-induced behavioral, biochemical, molecular and histopathological alterations. Further, combination of sub effective doses of quercetin (20, 40 mg/kg; p.o.) with minocycline (25 mg/kg; p.o.) significantly potentiated their protective effects as compared to their effects alone. Based on our results, we propose that microglial inhibitory pathway might be involved in the neuroprotective effects of quercetin and suppression of oxidative-nitrosative stress mediated neuroinflammation- apoptotic cascade associated with olfactory bulbectomy rat model of depression.
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ABSTRACT: There is a paucity of data on the role of microglia and neuroinflammatory processes in the association between chronic pain and depression. The current study examined the effect of the microglial inhibitor minocycline on depressive-like behaviour, spinal nerve ligation (SNL)-induced mechanical and cold allodynia and associated changes in the expression of genes encoding microglial markers (M1 vs. M2 polarisation) and inflammatory mediators in the prefrontal cortex in the olfactory bulbectomised (OB) rat model of depression. Acute minocycline administration did not alter OB-induced depressive-like behaviour but prevented SNL-induced mechanical allodynia in both OB and sham rats. In comparison, chronic minocycline attenuated OB-induced depressive-like behaviour and prevented the development of SNL-induced mechanical allodynia in OB, but not sham, rats. Further analysis revealed that SNL-induced mechanical allodynia in OB rats was attenuated by chronic minocycline at almost all time-points over a 2 week testing period, an effect observed only from day 10 post-SNL in sham rats. Chronic administration of minocycline reduced the expression of CD11b, a marker of microglial activation, and the M1 pro-inflammatory cytokine IL-1β, in the prefrontal cortex of sham-SNL animals. In comparison, the expression of the M2 microglia marker (MRC2) and anti-inflammatory cytokine IL-10 was increased, as were IL-1β, IL-6 and SOCS3, in the prefrontal cortex of OB-SNL animals following chronic minocycline. Thus, chronic minocycline attenuates neuropathic pain behaviour and modulates microglial activation and the central expression of inflammatory mediators in a manner dependent on the presence or absence of a depressive-like phenotype.Brain Behavior and Immunity 06/2014; 42. DOI:10.1016/j.bbi.2014.06.015 · 6.13 Impact Factor
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ABSTRACT: Salidroside (SA) is the primary bioactive marker compound in the standardized extracts from Rhodiola rosea. Although it has potential antidepressant activity in a rat behavioral despair model, the mechanisms of antidepressant effect for SA remain unclear. The objective of this study was to evaluate the antidepressant effects of SA and to discuss the potential mechanisms in olfactory bulbectomized (OBX) rats. SA of 20, 40 mg/kg (p.o.) for 2 weeks notably alleviated OBX-induced hyperactivity in open field test, decreased immobility time in TST and FST. Chronic treatment with SA could remarkably reduce TNF-α and IL-1β levels in hippocampus. Western blot showed that SA could markedly increase glucocorticoid receptor (GR) and brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Besides, SA could also attenuate corticotropin-releasing hormone (CRH) expression in hypothalamus, as well as reducing significantly the levels of serum corticosterone. In conclusion, this study demonstrated that OBX rats treated with SA could significantly improve the depressive-like behaviors. The antidepressant mechanisms of SA might be associated with its anti-inflammatory effects and the regulation of HPA axis activity. Reversal of abnormalities of GR may be partly responsible for those effects. These findings suggested that SA might become a beneficial agent to prevent and treat the depression.Pharmacology Biochemistry and Behavior 08/2014; DOI:10.1016/j.pbb.2014.07.015 · 2.82 Impact Factor