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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Inhibition of S-phase entry by APOE is dependent on Cox-2 and IP. (a and...
Inhibition of S-phase entry by APOE is dependent on Cox-2 and IP. (a and b) Aortic SMCs isolated from WT (black bars) and IP-null (white bars) mice were cultured, serum starved for 48 hours, and treated with 10% FBS in the absence (control) or presence of HDL (50 0g/ml), LDL (50 μg/ml), APOE (2 μM),or APOA-I (2 μM). Cells were also treated with 0.1–1 μM nimesulide or 200 nM cicaprost, a prostacyclin mimetic (13). All the cells were incubated for 48 hours in the presence of BrdU. BrdU incorporation into nuclei was determined by immunofluorescence microscopy. Results show the mean ± SEM, n = 3, *P < 0.001 as compared with cells treated with 10% FBS (control). (c) Aortic SMCs from WT and IP-null mice were serum starved and treated with 10% FBS for 24 hours in the absence (control) or presence of 2 μM APOE. Conditioned media was then collected and assayed for 6-keto-PGF1α, while the cell lysates were analyzed by immunoblotting using anti–cyclin A, anti–Cox-2, and anti-cdk4 (loading control). The bar graph in c shows mean ± SEM, n = 2, *P < 0.001 as compared with cells treated with 10% FBS (control).