Liver X receptor-dependent inhibition of microglial nitric oxide synthase 2

Journal of Neuroinflammation

Unsong Oh¹  Hanadi Ajam Oughli¹  Julie R Secor McVoy¹ 

[1] Department of Neurology, Virginia Commonwealth University School of Medicine, Richmond, 23298, VA, USA

关键词: Experimental allergic encephalomyelitis;    Central nervous system;    NF-kappaB;    HDAC;    Inflammation;    Microglia;    Liver X receptor;   

Others  :  1137614
DOI  :  10.1186/s12974-015-0247-2

 received in 2014-06-16, accepted in 2015-01-14,  发布年份 2015

【 摘 要 】

Background

The nuclear receptor liver X receptor (LXR) exerts transcriptional control over lipid metabolism and inflammatory response in cells of the myeloid lineage, suggesting that LXR may be a potential target in a number of chronic neuroinflammatory and neurodegenerative diseases where persistent microglial activation has been implicated in the pathogenesis.

Methods

The effect of LXR activation on microglia and central nervous system (CNS) inflammation was studied using a synthetic LXR agonist in cultured microglia, a microglial cell line and experimental allergic encephalomyelitis (EAE), an animal model of CNS inflammation.

Results

LXR activation inhibited nitric oxide synthase 2, inducible (Nos2) expression and nitric oxide production in lipopolysaccharide (LPS)-stimulated microglia. Inhibition of microglial activation in response to interferon-γ was less reliable. In LPS-stimulated cells, LXR activation did not inhibit nuclear translocation of NF-kappaB1 p50. Instead, LXR-dependent Nos2 repression was associated with inhibition of histone 4 acetylation and inhibition of NF-kappaB1 p50 binding at the Nos2 promoter. Histone acetylation and NF-kappaB1 p50 binding were mechanistically linked, and histone deacetylase (HDAC) activity appeared to be important for LXR-dependent transcriptional repression of Nos2. Analysis of CNS gene expression in animals undergoing EAE showed that the expressions of Lxr and LXR-dependent genes were downregulated during CNS inflammation. Nevertheless, administration of LXR agonist GW3965 during the effector phase of EAE delayed the onset of clinical disease and reversed the diminished expression of LXR-dependent reverse cholesterol transport genes. However, the CNS expressions of Nos2 and other inflammatory genes were not significantly inhibited by LXR activation in EAE, and clinical disease severity was comparable to vehicle controls at later time points in LXR agonist treated animals.

Conclusions

LXR can be targeted to modulate microglial activation. LXR-dependent repression of inflammatory genes may be stimulus-dependent and impaired by HDAC inhibition. Endogenous LXR activity does not appear to modulate CNS inflammation, but LXR activity can be partially restored in the CNS by administration of exogenous LXR agonist with an impact on clinical disease severity at early, but not late, time points in EAE.

【 授权许可】

   
2015 Secor McVoy et al.; licensee BioMed Central.

【 图 表 】

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