Simvastatin prevents and ameliorates depressive behaviors via neuroinflammatory regulation in mice.

BACKGROUND: Statins play a beneficial role in the treatment of coronary artery disease and are widely prescribed to prevent hypercholesterolemia. Previous studies have demonstrated that statins also have anti-inflammatory and immunomodulatory properties, and these are being explored for potential benefits in depression. However, the role of statins in the treatment of depression has not been well examined. METHODS: We investigated the effects of simvastatin on depressive behaviors and neuroinflammation in lipopolysaccharide (LPS) and chronic mild stress (CMS) induced depression model in mice. Sucrose preference test (SPT), forced swimming test (FST), novelty-suppressed feeding test (NSFT) were used to detect the depressive behaviors. The microglial activation was detected by immunohistochemistry analysis and the pro-inflammatory cytokines expressions including IL-1ß, TNF-α and IL-6 were examined by Western blot analysis. RESULTS: Our data indicated that oral administration of simvastatin at 20 mg/kg significantly prevented and ameliorated depressive behaviors reflected by better performance in the SPT, FST and NSFT. Moreover, simvastatin markedly prevented and ameliorated LPS and CMS-induced neuroinflammation, as shown by the suppressed activation of microglia in hippocampus and decreased hippocampal pro-inflammatory cytokines expressions including IL-1ß, TNF-α, IL-6, which might be mediated via the inhibition of NF-κB pathway, as shown by the decreased nuclear NF-κB p65 expression. LIMITATIONS: The interpretation of the evidence of a positive treatment effect of simvastatin on the depressive manifestations, multifaceted etiology of depression, and confirmation of this finding from animal models to humans is needed. CONCLUSION: These results suggest that simvastatin has the potential to be employed as a therapy for depression associated with neuroinflammation.

PPARδ agonist GW0742 ameliorates Aß1-42-induced hippocampal neurotoxicity in mice.

Amyloid-ß deposition is thought to be associated with memory deficits, neuroinflammation, apoptotic responses, and progressive neuronal death manifested in Alzheimer's disease. Peroxisome proliferator-activated receptor δ (PPARδ) is a transcription factor with potent anti-inflammatory effect. In the current study, the effect of GW0742, a selective PPARδ agonist, on Aß1-42-induced neurotoxicity was investigated in the hippocampus of mice. Intra-hippocampal infusion of aggregated Aß1-42 oligomer (410pmol/mouse) remarkably damaged learning and memory in the Morris water maze (MWM) and Y-maze tests, accompanied by decreased expression of PPARδ in the hippocampus as confirmed by Western blot. Intra-hippocampal infusion of GW0742 (1.06 mM/mouse) significantly improved Aß1-42-induced memory deficits in mice, reversed Aß1-42-induced hippocampal PPARδ down-regulation and repressed Aß1-42-triggered neuroinflammatory and apoptotic responses, indicated by decreased nuclear NF-κB p65, TNF-α, IL-1ß as well as a decrease in cleaved caspase-3 and increased ratio of Bcl-2/Bax in the hippocampus. These results suggest that PPARδ activation ameliorates Aß1-42-induced hippocampal neurotoxicity, and it might play a crucial role in Alzheimer's disease.

Knockdown of hippocampal cysteinyl leukotriene receptor 1 prevents depressive behavior and neuroinflammation induced by chronic mild stress in mice.

RATIONALE: Numerous studies have demonstrated that neuroinflammation is associated with depression-like symptoms and neuropsychological disturbances, and cysteinyl leukotriene receptor 1 (CysLT1R) was reported to be involved in neuroinflammation. The pathophysiological role of CysLT1R has been reported in several types of brain damage. However, the role of CysLT1R in depression remains to be elucidated. OBJECTIVES: We aimed to investigate the effect of hippocampal CysLT1R downregulation on depressive behaviors and neuroinflammatory responses in mice exposed to chronic mild stress (CMS). RESULTS: We firstly found that expression of hippocampal CysLT1R was gradually increased over CMS exposure, while 3 weeks treatment with fluoxetine reversed the increment of hippocampal CysLT1R expression. Hippocampal CysLT1R knockdown suppressed CMS-induced depressive-like behaviors as evidenced by decreases in immobility time in tail suspension test (TST), decreased latency to feed in novelty-suppressed feeding (NSF) test, and by increase in the number of entries and decrease in time spent in the open arm in elevated plus maze (EPM) test. Increments of hippocampal NF-κB p65, IL-1ß, and TNF-α induced by CMS were also prevented by hippocampal CysLT1R knockdown beforehand. CONCLUSIONS: Hippocampal CysLT1R participates in depression, and knockdown of hippocampal CysLT1R prevents CMS-induced depressive-like behaviors and neuroinflammation, suggesting that suppression of CysLT1R could prevent the development of depression.

Hippocampal PPARδ Overexpression or Activation Represses Stress-Induced Depressive Behaviors and Enhances Neurogenesis.

BACKGROUND: Emerging data have demonstrated that peroxisome proliferator-activated receptor δ (PPARδ) activation confers a potentially neuroprotective role in some neurodegenerative diseases. However, whether PPARδ is involved in depression is unknown. METHODS: In this study, PPARδ was firstly investigated in the chronic mild stress (CMS) and learned helplessness (LH) models of depression. The changes in depressive behaviors and hippocampal neurogenesis were investigated after PPARδ overexpression by microinfusion of the lentiviral vector, containing the coding sequence of mouse PPARδ (LV-PPARδ), into the bilateral dentate gyri of the hippocampus or PPARδ activation by repeated systemic administration of PPARδ agonist GW0742 (5 or 10mg/kg.d, i.p., for 21 d). RESULTS: We found that both CMS and LH resulted in a significant decrease in the PPARδ expression in the hippocampi of mice, and this change was reversed by treatment with the antidepressant fluoxetine. PPARδ overexpression and PPARδ activation each suppressed the CMS- and LH-induced depressive-like behavior and produced an antidepressive effect. In vivo or in vitro studies also showed that both overexpression and activation of PPARδ enhanced proliferation or differentiation of neural stem cells in the hippocampi of mice. CONCLUSIONS: These results suggest that hippocampal PPARδ upregulation represses stress-induced depressive behaviors, accompanied by enhancement of neurogenesis.