Antimitogenic effects of HDL and APOE mediated by Cox-2–dependent IP activation
Devashish Kothapalli, … , Daniel J. Rader, Richard K. Assoian
Devashish Kothapalli, … , Daniel J. Rader, Richard K. Assoian
Published February 15, 2004
Citation Information: J Clin Invest. 2004;113(4):609-618. https://doi.org/10.1172/JCI19097.
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Article Cardiology

Antimitogenic effects of HDL and APOE mediated by Cox-2–dependent IP activation

Abstract

HDL and its associated apo, APOE, inhibit S-phase entry of murine aortic smooth muscle cells. We report here that the antimitogenic effect of APOE maps to the N-terminal receptor–binding domain, that APOE and its N-terminal domain inhibit activation of the cyclin A promoter, and that these effects involve both pocket protein–dependent and independent pathways. These antimitogenic effects closely resemble those seen in response to activation of the prostacyclin receptor IP. Indeed, we found that HDL and APOE suppress aortic smooth muscle cell cycle progression by stimulating Cox-2 expression, leading to prostacyclin synthesis and an IP-dependent inhibition of the cyclin A gene. Similar results were detected in human aortic smooth muscle cells and in vivo using mice overexpressing APOE. Our results identify the Cox-2 gene as a target of APOE signaling, link HDL and APOE to IP action, and describe a potential new basis for the cardioprotective effect of HDL and APOE.

Authors

Devashish Kothapalli, Ilia Fuki, Kamilah Ali, Sheryl A. Stewart, Liang Zhao, Ron Yahil, David Kwiatkowski, Elizabeth A. Hawthorne, Garret A. FitzGerald, Michael C. Phillips, Sissel Lund-Katz, Ellen Puré, Daniel J. Rader, Richard K. Assoian

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CRE-dependent effects of APOE on cyclin A gene transcription. (a) EMSAs ...
CRE-dependent effects of APOE on cyclin A gene transcription. (a) EMSAs were performed with 32P-labeled CCAAT or CRE oligonucleotides and nuclear lysates from serum-starved SMCs before (G0) or after stimulation with 10% FBS for 18 hours in the absence or presence of APOE or APOA-I. Competitor, 100-fold molar excess unlabeled oligonucleotide. (b) Nuclear extracts were prepared from serum-starved SMCs after 18-hour incubation with 10% FBS. The extracts were preincubated with the indicated Ab’s before addition of the 32P-labeled CRE oligonucleotide. *Supershifted complex. (c) Serum-starved murine aortic SMCs were incubated with 10% FBS in the absence or presence of APOE. Cells were collected, lysed, and analyzed by immunoblotting using anti-phosphoCREB, anti-CREB, and anti–ATF-1. Note that the anti-phosphoCREB Ab detects both phosphoCREB (pCREB) and phosphoATF-1 (pATF-1). (d) Activity of the +CRE or –CRE cyclin A promoters was determined in the absence (–E7) or presence (+E7) of E7 and the absence (control) or presence of 2 μM APOE. Promoter activity is plotted as fold stimulation relative to the FBS-treated cells in the absence of E7. Results show the mean ± SEM, n = 3, *P < 0.001 as compared with vector-transfected cells (–E7) stimulated with FBS (+CRE and –CRE). Normalized luciferase activities of the cyclin A promoters containing and lacking the CRE in control (FBS-stimulated) cells were 0.05 and 0.02, respectively.