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(Hypertension. 2001;37:478.)
© 2001 American Heart Association, Inc.

Scientific Contributions

Src and Rac Mediate Endothelin-1 and Lysophosphatidic Acid Stimulation of the Human Brain Natriuretic Peptide Promoter

Quan He; Margot C. LaPointe

From the Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, Mich.

Correspondence to Dr Margot C. LaPointe, Hypertension and Vascular Research Division, Henry Ford Hospital, 2799 W Grand Blvd, Detroit, MI 48202-2689. E-mail mclapointe{at}aol.com

Brain natriuretic peptide (BNP) gene expression accompanies cardiac hypertrophy and heart failure. The vasoconstrictor endothelin-1 (ET) may be involved in the development of these diseases. ET has also been shown to activate phospholipase A₂ (PLA₂), and the resulting metabolites are important second messengers. We studied how ET and PLA₂ metabolites regulate BNP gene expression. The human BNP (hBNP) promoter (from -1818 to +100) coupled to a luciferase reporter gene was transferred into neonatal ventricular myocytes (NVMs), and luciferase activity was measured as an index of promoter activity. ET induced BNP mRNA in NVMs as assessed by Northern blot. It also stimulated the hBNP promoter, an effect completely inhibited by actinomycin D. To test the involvement of different PLA₂ isoforms, transfected cells were treated with various PLA₂ inhibitors before stimulation with ET. Only Ca²⁺-independent PLA₂ blockade prevented ET-stimulated hBNP promoter activity. The PLA₂ metabolite lysophosphatidic acid (LPA) also activated the hBNP promoter, but arachidonic acid itself did not. ET regulation of the hBNP promoter is pertussis toxin–sensitive. The nonreceptor tyrosine kinase Src and the small GTPase Rac mediate the effects of both ET and LPA in stimulation of the hBNP promoter. We studied the involvement of cis elements in ET-stimulated hBNP promoter activity. Deletion of BNP promoter sequences from -1818 to -408 and from -408 to -40 reduced the effect of ET by 60% and 80%, respectively. Moreover, ET-stimulated luciferase activity was reduced by 50% when the proximal GATA element was mutated. These data suggest that (1) ET activates the hBNP promoter through a transcriptional mechanism; (2) LPA, perhaps generated by iPLA₂, is involved in the effect of ET; (3) Src and Rac mediate ET and LPA stimulation of the hBNP promoter; and (4) ET regulation of the hBNP promoter targets both distal and proximal cis elements.

Key Words: cardiomyocytes • genes • brain natriuretic peptide • endothelin • phospholipases

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