Oxidized Low-density Lipoprotein Decreases the Expression of Endothelial Nitric Oxide Synthase

doi:10.1074/jbc.270.1.319

Oxidized Low-density Lipoprotein Decreases the Expression of Endothelial Nitric Oxide Synthase (*)

From the Cardiovascular Division, Brigham & Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115

^§ To whom correspondence should be addressed:
Cardiovascular Div., Department of Medicine, 221 Longwood Ave., LMRC-307, Boston, MA 02115
. Tel.: 617-732-6538; Fax: 617-732-6961.

Abstract

The atherogenic effects of low-density lipoprotein (LDL) may be mediated, in part, by its effect(s) on endothelial-derived nitric oxide (NO). To determine whether LDL can modulate NO production by changing NO synthase expression, we treated human saphenous vein endothelial cells with increasing concentrations of native or oxidized LDL (0-100 μg/ml) for various durations (0-72 h). Oxidized, but not native LDL caused a time-dependent decrease in steady-state NO synthase mRNA levels. This coincided with a maximal 56% decrease in NOS activity as determined by [³H]arginine to [³H]citrulline conversion. In the presence of actinomycin D, treatment with oxidized LDL reduced the half-life of NO synthase mRNA from 36 to 10 h. This decrease in NO synthase mRNA correlated with the degree of LDL oxidation and was attenuated by pretreatment with cycloheximide. Nuclear run-off studies showed a biphasic transcriptional pattern of NO synthase gene with an initial 25% decrease during the first 6 h followed by a maximal 2.2-fold increase over baseline during the subsequent 18 h. These results indicate that oxidized LDL regulates endothelial NOS expression through a combination of early transcriptional inhibition and post-transcriptional mRNA destabilization.

Footnotes

↵* This work was supported by National Institutes of Health Grant HL02508 and the American Heart Association Grant-in-Aid Award (to J. K. L.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

LDL

low density lipoprotein

PCR

polymerase chain reaction

TBARS

thiobarbituric acid reactive substances

NO

nitric oxide.
↵² J. K. Liao, unpublished observation.
- Received July 25, 1994.
- Revision received November 3, 1994.