8 research outputs found
Increased Cellular Free Cholesterol in Macrophage-specific Abca1 Knock-out Mice Enhances Pro-inflammatory Response of Macrophages*S⃞
Macrophage-specific Abca1 knock-out
(Abca1–M/–M)
mice were generated to determine the role of macrophage ABCA1 expression in
plasma lipoprotein concentrations and the innate immune response of
macrophages. Plasma lipid and lipoprotein concentrations in chow-fed
Abca1–M/–M
and wild-type (WT) mice were indistinguishable. Compared with WT macrophages,
Abca1–M/–M
macrophages had a >95% reduction in ABCA1 protein, failed to efflux lipid
to apoA-I, and had a significant increase in free cholesterol (FC) and
membrane lipid rafts without induction of endoplasmic reticulum stress.
Lipopolysaccharide (LPS)-treated
Abca1–M/–M
macrophages exhibited enhanced expression of pro-inflammatory cytokines and
increased activation of the NF-κB and MAPK pathways, which could be
diminished by silencing MyD88 or by chemical inhibition of NF-κB or
MAPK. In vivo LPS injection also resulted in a higher
pro-inflammatory response in
Abca1–M/–M
mice compared with WT mice. Furthermore, cholesterol depletion of macrophages
with methyl-β-cyclodextrin normalized FC content between the two
genotypes and their response to LPS; cholesterol repletion of macrophages
resulted in increased cellular FC accumulation and enhanced cellular response
to LPS. Our results suggest that macrophage ABCA1 expression may protect
against atherosclerosis by facilitating the net removal of excess lipid from
macrophages and dampening pro-inflammatory MyD88-dependent signaling pathways
by reduction of cell membrane FC and lipid raft content