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 cyclin A gene expression by APOE. (a) Cyclin A promoter ac...
Inhibition of cyclin A gene expression by APOE. (a) Cyclin A promoter activity in early-passage aortic SMCs was determined as described in Methods. Results show mean ± SEM, n = 3, *P < 0.001 as compared with cells stimulated with 10% FBS. C, control. (b) Quiescent SMCs were incubated for 48 hours with 10% FBS in the absence or presence of 2 μM APOA-I or APOE prior to analysis of cyclin A expression by immunofluorescence microscopy. DAPI staining shows cell nuclei. (c) Quiescent murine aortic SMCs treated with 10% FBS in the absence or presence of 2 μM APOE were collected, lysed, and analyzed by immunoblotting using Ab’s to cyclin D1, cyclin E, cyclin A, and cdk4 (loading control). (d) Aortic SMCs were transiently cotransfected with an eGFP expression vector and either a control (vector) or cyclin A expression vector. The effect of cyclin A expression on S-phase entry was determined in the absence or presence of 2 μM APOE or 2 μM APOA-I as described in Methods. Results show mean ± SEM, n = 2, *P < 0.001 as compared with cells stimulated with 10% FBS (vector). (e) A10 SMCs were treated as in c, collected at 20 hours, lysed, and analyzed by immunoblotting for cyclin A and actin (loading control). Cell lysates were incubated with anti-cyclin A, and the immunoprecipitates were used to assess in vitro kinase activity or analyzed by immunoblotting for associated cdk2.