Microglial forkhead box O3a deficiency attenuates LPS-induced neuro-inflammation and depressive-like behaviour through regulating the expression of peroxisome proliferator-activated receptor-γ.

BACKGROUND AND PURPOSE: Depression is closely linked with microglial activation and neuro-inflammation. Peroxisome proliferator-activated receptor-γ (PPAR-γ) plays an important role in M2 activation of microglia. Forkhead box (FOX) O3a has been implicated in the regulation of mood-relevant behaviour. However, little is known about the inflammatory mechanisms of in the microglia of the brain. Here, we have investigated the role of microglial FOXO3a/PPAR-γ in the development of depression. EXPERIMENTAL APPROACH: The effect of FOXO3a on microglia inflammation was analysed in vitro and in lipopolysaccharide (LPS)-induced depression-like behaviours in vivo. ChIP-seq and Dual-luciferase reporter assays were used to confirm the interaction between FOXO3a and PPAR-γ. Behavioural changes were measured, while inflammatory cytokines, microglial phenotype and morphological properties were determined by ELISA, qRT-PCR, western blotting and immunostaining. KEY RESULTS: Overexpression of FOXO3a significantly attenuated expression of PPAR-γ and enhanced the microglial polarization towards the M1 phenotype, while knockdown of FOXO3a had the opposite effect. FOXO3a binds to the promoters of PPAR-γ and decreases its transcription activity. Importantly, deacetylation and activation of FOXO3a regulate LPS-induced neuro-inflammation by inhibiting the expression of PPAR-γ in microglia cells, supporting the antidepressant potential of histone deacetylase inhibitors. Microglial FOXO3a deficiency in mice alleviated LPS-induced neuro-inflammation and depression-like behaviours but failed to reduce anxiety behaviour, whereas pharmacological inhibition of PPAR-γ by GW9662 restored LPS-induced microglial activation and depressive-like behaviours in microglial FOXO3a-deficient mice. CONCLUSION AND IMPLICATIONS: FOXO3a/PPAR-γ axis plays an important role in microglial activation and depression, identifying a new therapeutic avenue for the treatment of major depression.

Microglial FoxO3a deficiency ameliorates ferroptosis-induced brain injury of intracerebral haemorrhage via regulating autophagy and heme oxygenase-1.

Microglial HO-1 regulates iron metabolism in the brain. Intracerebral haemorrhage (ICH) shares features of ferroptosis and necroptosis; hemin is an oxidized product of haemoglobin from lysed red blood cells, leading to secondary injury. However, little is known about the underlying molecular mechanisms attributable to secondary injury by hemin or ICH. In this study, we first show that FoxO3a was highly co-located with neurons and microglia but not astrocytes area of ICH model mice. Hemin activated FoxO3a/ATG-mediated autophagy and HO-1 signalling resulting in ferroptosis in vitro and in a mice model of brain haemorrhage. Accordingly, autophagy inhibitor Baf-A1 or HO-1 inhibitor ZnPP protected against hemin-induced ferroptosis. Hemin promoted ferroptosis of neuronal cells via FoxO3a/ATG-mediated autophagy and HO-1 signalling pathway. Knock-down of FoxO3a inhibited autophagy and prevented hemin-induced ferroptosis dependent of HO-1 signalling. We first showed that hemin stimulated microglial FoxO3a/HO-1 expression and enhanced the microglial polarisation towards the M1 phenotype, while knockdown of microglial FoxO3a inhibited pro-inflammatory cytokine production in microglia. Furthermore, the microglia activation in the striatum showed significant along with a high expression level of FoxO3a in the ICH mice. We found that conditional knockout of FoxO3a in microglia in mice alleviated neurological deficits and microglia activation as well as ferroptosis-induced striatum injury in the autologous blood-induced ICH model. We demonstrate, for the first time, that FoxO3a/ATG-mediated autophagy and HO-1 play an important role in microglial activation and ferroptosis-induced striatum injury of ICH, identifying a new therapeutic avenue for the treatment of ICH.

A Mechanism Study of NMDAR1 in A Rat Alzheimer Disease (AD) Model

ABSTRACT This study aimed to investigate the expression and mechanism of N- methyl -D- aspartate receptor 1 (NMDAR1) in the pathogenesis of Alzheimer disease (AD). Eighty adult Wistar rats were randomly divided into 4 groups (n=20 each) to receive an injection of 0, 5, 7 and 10 μl of 1 μg/μl amyloid-β 42 (Aβ1-42) in the hippocampus. Twenty rats in normal control group were injected with equal volume of saline. After 10 days, the hippocampus was isolated from 5 randomly selected rats in each group. The NMDAR1 protein and mRNA expression was determined by immunohistochemical staining and qRT-PCR. The aquaporin-1 (AQP-1) mRNA expression was also measured by qRT-PCR. We found that both NMDAR1 and AQP-1 expression in Aβ1-42 groups was increased in a dose-dependent manner. NMDAR1 and AQP-1 expression in 7 and 10 μl Aβ1-42 groups was significantly higher compared with 0 μl Aβ1-42 group (P <0.01). Further, the 10 μl Aβ1-42 group was randomly divided into 3 subgroups: AD-NMDA, AD-MK-801, and AD-Ctrl subgroup, which was given an intraperitoneal injection of NMDAR agonist NMDA, NMDAR antagonist MK-801 and saline, respectively. The relative APQ-1 expression in each subgroup was determined by qRT-PCR and Western blot analysis after 24 h. The AQP-1 expression was significantly decreased in AD-MK-801 group (P < 0.05), but was markedly increased in AD-NMDA group when compared with AD-Ctrl group (P <0.01). Our study suggested that expression abnormity of NMDAR1 is involved in the pathogenesis of AD. NMDAR1 might regulate the pathogenic process through stimulating the expression of AQP-1.