Identification of dehydroxytrichostatin A as a novel up-regulator of the ATP-binding cassette transporter A1 (ABCA1)

Abstract

The ATP-binding cassette transporter A1 (ABCA1) mediates the cellular efflux of excess cholesterol and phospholipids to lipid-poor apolipoprotein A-I (apoA-I). ABCA1 plays an important role in high-density lipoprotein (HDL) biogenesis and reverse cholesterol transport. By using a cell-based screening model for the ABCA1 up-regulator and column chromatography, an active compound, 9179B, was isolated. Through analysis of its NMR data, 9179B was identified as dehydroxytrichostatin A. We found that 9179B increased the transcription of ABCA1 in a cell-based reporter assay, with an EC(50) value of 2.65 μM. 9179B up-regulated ABCA1 expression at both mRNA and protein levels in HepG2 and RAW264.7 cells. It also up-regulated the expression of scavenger receptor class B type I (SR-BI) as well as the uptake of DiI-HDL in RAW264.7 cells. This compound stimulated ApoA-I-mediated cellular cholesterol efflux from RAW 264.7 cells. We further found that 9179B was a potent histone deacetylase (HDAC) inhibitor with an IC(50) value of 0.08 μM. Reporter gene assays showed that the regulation of ABCA1 transcription by 9179B was mainly mediated by the -171/-75 bp promoter region. Together, our results indicate that 9179B is an ABCA1 up-regulator and dehydroxytrichostatin A may be a novel anti-atherogenic compound.

Figure 1

The chemical structure of 9179B.

Figure 2

The effect of 9179B and other HDAC inhibitors on ABCA1 promoter activity.

Figure 3

The effects of 9179B on the expression of ABCA1 in HepG2 and RAW 264.7 cells andon cholesterol efflux in RAW 264.7 Cells.

Figure 4

The effect of 9179B on the expression of SR-BI in RAW 264.7 cells and flow cytometry analysis of the uptake of DiI-HDL by RAW 264.7 cells.

Figure 5

Characterization of the DNA motifs mediating 9179B up-regulation of ABCA1 promoter activity.