Modulation of Expression of Endothelial Nitric Oxide Synthase by Nordihydroguaiaretic Acid, a Phenolic Antioxidant in Cultured Endothelial Cells
- Santhini Ramasamy1,
- Grant R. Drummond1,
- Joon Ahn1,
- Michal Storek3,
- Jan Pohl3,
- Sampath Parthasarathy2 and
- David G. Harrison1
- 1Division of Cardiology (S.R., G.R.D., J.A., D.G.H.), 2Department of Gynecology and Obstetrics (S.P.), and 3Microchemical Facility (M.S., J.P.), Emory University, Atlanta, Georgia
Abstract
Retrospective epidemiological studies have suggested that antioxidant therapy may decrease cardiovascular morbidity and mortality rates, although the mechanisms for this effect remain unclear. In the present study, we demonstrate that selective antioxidants can enhance expression of endothelial nitric oxide synthase (eNOS). We found that the antioxidants nordihydroguaiaretic acid (NDGA), catechol, glutaryl probucol, and N-acetylcysteine increased eNOS expression in cultured bovine aortic endothelial cells (BAECs). NDGA seemed to be the most potent of the phenolic antioxidants, producing a 3-fold increase in eNOS mRNA. This effect of NDGA was enhanced by nonphenolic antioxidants such as N-acetylcysteine and ascorbic acid. Nuclear run-on studies indicated that NDGA increased eNOS transcription. A similar increase in eNOS protein content was observed with Western blot analysis after treating BAECs or human aortic endothelial cells with NDGA. Exposure of BAECs to NDGA enhanced NO production, as measured by electron paramagnetic resonance spin trapping and eNOS activity, as measured by [14C]arginine-to-[14C]citrulline assay. Methylation of the phenolic hydroxyl groups completely inhibited the NDGA effect on eNOS mRNA levels. This effect of NDGA was not due to inhibition of lipoxygenase becausecis-5,8,11,14-eicosatetraynoic acid did not alter eNOS expression. We conclude that antioxidants may not only increase the bioactivity of nitric oxide but also enhance expression of the eNOS enzyme. Such an effect may prove useful in conditions such as hypertension and atherosclerosis, in which nitric oxide production and/or biological activity is impaired.
Footnotes
-
Send reprint requests to: Santhini Ramasamy, Ph.D., Division of Cardiology, Emory University, 1639 Pierce Drive, Atlanta, GA 30322. E-mail: sramasa{at}emory.edu
-
This work was supported by National Institutes of Health Grants HL390006 and HL48667m as well as American Heart Association Scientist Development Grant Award 9630119N (to S.R.). Portions of this work were presented at the American Heart Association 70th Meeting, November 1997, Orlando, FL; Society of Toxicology 37th Meeting, Seattle, WA, March 1998; and Vascular Biology, 1998, San Francisco, CA, April 1998.
- Abbreviations:
- NO
- nitric oxide
- NDGA
- nordihydroguaiaretic acid
- BHT
- butylated hydroxy toluene
- M199
- Medium 199
- EPR
- electron paramagnetic resonance
- MGD
- N-methyl-d-glucamine dithiocarbamate
- eNOS
- endothelial nitric oxide synthase
- HAEC
- human aortic endothelial cell
- NAC
- N-acetylcysteine
- l-NAME
- NG-nitro-l-arginine methyl ester
- BAEC
- bovine aortic endothelial cell
- SOD
- superoxide dismutase
- Sp1
- simian virus 40 promoter factor 1
- AP-1
- activator protein 1
- EGM
- endothelial cell growth media
- ARE
- antioxidant response element
- ETYA
- cis-5,8,11,14-eicosatetraynoic acid
-
- Received March 30, 1999.
- Accepted April 5, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
