Date of Award

January 2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

First Advisor

Thad A. Rosenberger

Abstract

Acetate supplementation increases brain acetyl-CoA and attenuates lipopolysaccharide (LPS)-induced neuroinflammation in vivo. To explain the anti-inflammatory effect of acetate treatment, we proposed that acetate treatment disrupts inflammatory signaling in microglia and astrocytes, and induces histone hyperacetylation known to be correlated with anti-inflammatory properties. To test this hypothesis, we measured the effects that LPS and acetate treatment had on histone acetylation, mitogen-activated protein kinase (MAPK), nuclear factor-kappa B (NF-κB), and eicosanoid signaling. A single oral dose of acetate treatment (6 g/kg) in normal animals induced a time- and site-specific pattern of histone hyperacetylation, associated with reduction of histone deacetylase (HDAC) activity and expression. Long-term acetate treatment over 28 days induced the same site-specific pattern of histone hyperacetylation, and reversed LPS-induced histone H3 at lysine 9 (H3K9) hypoacetylation and interleukin (IL)-1β expression. In LPS-stimulated BV-2 microglia, acetate treatment reversed LPS-induced H3K9 hypoacetylation, IL-1β, IL-6, tumor necrosis factor (TNF)-α, cyclooxygenase (Cox)-1 and 2 protein levels, and NF-κB p65 protein level and phosphorylation at serine 468. Further, acetate treatment increased IL-4 and transforming growth factor (TGF)-β1 expression, and NF-κB p65 acetylation at lysine 310. Conversely, acetate treatment did not alter LPS-induced

cytosolic (c) phospholipase A2 (PLA2), transiently reduced MAPK p38 and JNK phosphorylation, and increased MAPK ERK1/2 phosphorylation. In LPS-stimulated astrocyte, acetate treatment induced H3K9 hyperacetylation, reversed LPS-induced increases in IL-1β, TNF-α, NF-κB p65, and Cox-1 protein levels, MAPK p38 and cPLA2 phosphorylation and PGE2 release, and reversed LPS-induced decreases in TGF-β1 and IL-4. Moreover, acetate treatment reduced basal levels of IL-6, phosphorylated ERK1/2 and NF-κB p65 at serine 536, sPLA2 IIA and PLCβ1. Acetate treatment also increased acetylated H3K9 bound to the promoters of the genes of Cox-1, Cox-2, IL-1β and NF-κB p65, but not IL-4 in BV-2 microglia, which suggests that acetate treatment-induced H3K9 hyperacetylation can potentially be involved in the alteration of the expression of these genes. These data suggest that acetate treatment has net anti-inflammatory effects in vivo and in vitro both in LPS-stimulated microglia and astrocyte cultures through neuroglial cell type-distinct mechanisms.

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