ABSTRACT
Histone deacetylase (HDAC) inhibitors have been demonstrated to regulate myeloid cell differentiation. In the present study the effects of the HDAC inhibitor trichostatin A (TSA) on the tetraspanin cell surface antigen CD9 were determined in primary murine macrophages. TSA inhibited CD9 protein and message expression and was optimal by 48 h. TSA did not induce similar effects on other surface markers and resulted in a modest increase or no effect on CD54 and CD11b, respectively. These effects were concentration dependent and concomitant with increased histone H4 acetylation. While interferon-gamma (IFN-gamma) and TSA had similar effects on CD9 expression, transcriptional profiling demonstrated significant differences in the genes activated by these stimuli. Notably CD14 message was down-regulated by IFN-gamma while increased by TSA. These results demonstrate that HDAC inhibition may modulate macrophage function in part through changes in the expression of membrane proteins associated with matrix interactions.
Subject(s)
Antigens, CD/biosynthesis , Enzyme Inhibitors/pharmacology , Histone Deacetylase Inhibitors , Hydroxamic Acids/pharmacology , Macrophages, Peritoneal/metabolism , Acetylation , Animals , Cell Differentiation , Cells, Cultured , Down-Regulation , Histone Deacetylases/metabolism , Membrane Glycoproteins/metabolism , Mice , Mice, Inbred BALB C , Signal Transduction , Tetraspanin 29ABSTRACT
The pathological role of interferon-gamma (IFN-gamma) in atherosclerosis is mediated through effects on macrophages, foam cells, and other vascular cells. Recently, we reported that ATP-binding cassette transporter 1(ABC1) message and protein levels were decreased 3- to 4-fold in foam cells by IFN-gamma. In the present study, the pathway by which IFN-gamma inhibited ABC1 expression was investigated with signal transducers and activators of transcription (Stat1) knockout mice. IFN-gamma-stimulated, wild-type, macrophage-derived foam cells, as previously reported, exhibited a decrease in cholesterol efflux and ABC1 expression as well as an increase in acyl coenzyme A:cholesterol-O-acyltransferase activity. However, IFN-gamma treatment of foam cells from Stat1 knockout mice failed to demonstrate reductions in efflux or ABC1 expression at the message or protein levels, nor were there any increases in acyl coenzyme A:cholesterol-O-acyltransferase activity. However, ABC1 mRNA expression in macrophages from Stat1 knockout mice could still be demonstrated to be increased by lipid loading with acetylated low density lipoprotein. Finally, Stat1-independent gene activation by IFN-gamma was intact in the Stat1 KO macrophages, inasmuch as IFN-gamma was shown to stimulate increases in interleukin-6 production in the Stat1 KO macrophages that were comparable to those observed in the wild-type macrophages. Therefore, Stat1 signaling is necessary and sufficient for the inhibitory effects of IFN-gamma on cholesterol efflux and ABC1 expression.
Subject(s)
ATP-Binding Cassette Transporters/biosynthesis , Anticholesteremic Agents/pharmacology , Cholesterol/metabolism , DNA-Binding Proteins/physiology , Down-Regulation/physiology , Glycoproteins/biosynthesis , Interferon-gamma/physiology , Signal Transduction , Trans-Activators/physiology , ATP Binding Cassette Transporter 1 , ATP-Binding Cassette Transporters/antagonists & inhibitors , Animals , Arteriosclerosis/physiopathology , Cells, Cultured , DNA-Binding Proteins/deficiency , Foam Cells/metabolism , Glycoproteins/antagonists & inhibitors , Macrophages, Peritoneal/metabolism , Mice , Mice, Knockout , STAT1 Transcription Factor , Signal Transduction/genetics , Trans-Activators/deficiencyABSTRACT
CD9, a member of the tetraspanin family is a cell surface marker expressed on myeloid and nonmyeloid as well as on neoplastic cells. The present study has focused on the role of inflammation and macrophage activation in the regulation of CD9 expression. We report that the expression of CD9 on primary cultures of murine peritoneal macrophages was down regulated by Interferon-gamma, IFN-gamma. This down regulation was concentration-dependent and maximal by 48 h. The changes in surface expression were consistent with similar reductions in CD9 protein and message levels by Western and Northern blot analyses. The mechanism by which IFN-gamma decreases CD9 expression appears to be through the Stat1 signaling pathway as Stat1 knockout mice did not demonstrate any reduction in CD9 expression by IFN-gamma treatment. These results represent the first evidence for the down regulation of CD9 expression with macrophage activation.
