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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Conserved effects of APOE on Cox-2 expression in human and mouse SMCs an...
Conserved effects of APOE on Cox-2 expression in human and mouse SMCs and mice. (a) Quiescent mouse aortic SMCs were treated with 10% FBS in the absence or presence of 50 μg/ml HDL, 50 μg/ml LDL, 2 μM APOE or 2 μM APOA-I. Changes in the levels of Cox-1, Cox-2, and GAPDH (loading control) mRNAs were determined by RT-PCR and analyzed using NIH Image 1.63 software. (b) Cell lysates made from serum-starved aortic SMCs stimulated with 10% FBS in the absence and presence of 2 μM APOA-I or APOE were immunoblotted using anti–Cox-2 and anti-cdk4 (loading control). Human aortic SMCs (HSMC) were grown to near confluence in 150-mm dishes, serum starved for 48 hours in defined medium, and then directly stimulated with 10% FBS in the absence or presence of 2 μM APOE or 2 μM APOA-I. Changes in the levels of Cox-2 mRNA (c) and protein (d) were determined as in a and b, respectively. Cell lysates were also made from serum-starved human aortic endothelial cells (HAEC) stimulated with 2 μM APOA-I or APOE, and the levels of Cox-2 protein were determined by immunoblotting (d). (e) C57BL/6 mice were injected with adenoviral constructs expressing APOA-I, APOE, or null vector. Total RNA was isolated from the aortae and reverse transcribed into cDNA. Changes in the levels of Cox-1, Cox-2, and GAPDH mRNA were determined as outlined in Methods.