Induction of acyl-coenzyme A:cholesterol acyltransferase-1 by 1,25-dihydroxyvitamin D3 or 9-cis-retinoic acid in undifferentiated THP-1 cells

Abstract

We have previously shown that acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1) protein content increases significantly during the human monocyte-macrophage differentiation process. To gain further insight, we used undifferentiated human monocytic THP-1 cells as a model system with which to examine whether ACAT-1 mRNA and protein content can be increased by treating cells with 1,25-dihydroxyvitamin D 3 [1,25-(OH) 2 D 3 ] or with 9-cis -retinoic acid (9-cis -RA), two agents known to upregulate the expression of various genes during the monocyte-macrophage differentiation process. Immunoblot analysis with anti-human ACAT-1 antibodies revealed that ACAT-1 protein was increased by 2.6-fold, using 1,25-(OH) 2 D 3 at a physiological concentration (100 pM). ACAT-1 protein was also increased when using 9-cis -RA, but only at relatively high concentrations (0.1-1 M). Northern blot analysis revealed that among the four ACAT-1 mRNA transcripts (2.8, 3.6, 4.2, and 7.0 kb) examined, only the 2.8-and 3.6-kb transcripts were selectively increased. On the basis of enzyme assays in vitro, ACAT activity was increased 3.0-fold by using 100 nM 1,25-(OH) 2 D 3 , and 1.8-fold by using 1 M 9-cis -RA.Together, our results suggest that 1,25-(OH) 3 participates in ACAT-1 gene expression during the monocyte-macrophage differentiation process. -Maung, K. K., A. Miyazaki, H. Nomiyama, C. C. Y. Chang, T-Y. Chang, and S. Horiuchi. Induction of acyl-coenzyme A:cholesterol acyltransferase-1 by 1,25-dihydroxyvitamin D 3 or 9-cis -retinoic acid in undifferentiated THP-1 cells.

Differential Modulation of ACAT1 and ACAT2 Transcription and Activity by Long Chain Free Fatty Acids in Cultured Cells

“…Changes in ACAT1 mRNA expression, either by differentiation of THP1 cells into macrophages or OA, AA, or EPA incubation in HepG2 cells, were observed only in the major 3.8 and 4.3 kb bands. Similarly, only these two transcripts are modulated in THP1 cells by vitamin D 3 or 9-cis-retinoic acid (11). Presumably, FFAs might only affect transcription from sequences proximal to ACAT1 gene (9).…”

“…[1,2-3 H(N)]Cholesterol, [4- 14 C]cholesterol, [9,10-3 H(N)]oleic acid, and [R-32 P]deoxycytidine 5′-triphosphate (3000 Ci/mmol) were purchased from Dupont NEM, Wilmington, DE. [5,6,8,9,11,12,14,15,17, Cells. HepG2 human hepatocytes (15) and THP1 human monocyte/macrophages were grown as described previously (16).…”

“…This indicates that these ACAT transcripts may be regulated differently at the transcriptional level. In keeping with this, ACAT1 mRNA levels are increased in macrophages compared to monocytes (10,11) and in mouse liver in response to a high fat, high cholesterol diet (12). There is no data available to indicate transcriptional regulation of ACAT2.…”

Stealth Liposomes Encapsulating a Potent ACAT1/SOAT1 Inhibitor F12511: Pharmacokinetic, Biodistribution, and Toxicity Studies in Wild-Type Mice and Efficacy Studies in Triple Transgenic Alzheimer’s Disease Mice

“…This finding implicates that once the inhibitor binds to the ACAT enzyme, it stays firmly bound for a few hours before dissociating from the enzyme. Based on this finding, we treated the animals with the inhibitor by IV injection, perfused the mice after the animals were treated (to remove blood contamination from the tissues), then prepared the tissue homogenates, and monitored the ACAT enzyme activity in these tissues by using the mixed micelles enzyme assay described previously [ 24 , 39 , 49 , 50 ] (the mixed micelles assay measures the ACAT enzyme activity independent of endogenous lipid composition because it reconstitutes the ACAT protein in mixed micelles with a defined lipid composition). We injected nanoparticles with F12511 (nanoparticle F) at 5.8 mg/kg or with K604 at 40 mg/kg by IV.…”

Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis

“…In vivo, ACAT1 detected by immunohistochemical staining is abundantly present in lipid-rich atherosclerotic lesions (27). Additional cell culture work showed that in the human monocytic cell line THP-1, ACAT1 gene expression is upregulated by 1,25-dihydroxyvitamin D 3 (28). In human macrophages and macrophage-like cells, the ACAT1 gene is upregulated by the cytokine interferon ␥ (29).…”