Endothelin-1 is an autocrine/paracrine factor in the mechanism of angiotensin II-induced hypertrophy in cultured rat cardiomyocytes.
To elucidate the cellular mechanism by which angiotensin II (ANG II) induces cardiac hypertrophy, we investigated the possible autocrine/paracrine role of endogenous endothelin-1 (ET-1) in ANG II-induced hypertrophy of neonatal rat cardiomyocytes by use of synthetic ET-1 receptor antagonist and antisense oligonucleotides to preproET-1 (ppET-1) mRNA. Northern blot analysis and in situ hybridization revealed that ppET-1 mRNA was expressed in cardiomyocytes, but, to a lesser extent, in nonmyocytes as well. ANG II upregulated ppET-1 mRNA level by threefold over control level as early as 30 min, and it stimulated release of immunoreactive ET-1 from cardiomyocytes in a dose- and time-dependent manner. ET-1 stimulated ppET-1 mRNA levels after 30 min in a similar fashion as ANG II. Tetradecanoylphorbol-acetate (10(-7) M) mimicked the effects of ANG II and ET-1 on induction of ppET-1 mRNA. ANG II-induced ppET-1 gene expression was completely blocked by protein kinase C inhibitor H-7 or by down-regulation of endogenous protein kinase C by pretreatment with phorbol ester. ET-1 and ANG II stimulated twofold increase [3H]leucine incorporation into cardiomyocytes, whose effects were similarly and dose dependently inhibited by endothelin A receptor antagonist (BQ123). Introduction of antisense sequence against coding region of ppET-1 mRNA into cardiomyocytes resulted in complete blockade with ppET-1 mRNA levels and [3H]leucine incorporation stimulated by ANG II. These results suggest that endogenous ET-1 locally generated and secreted by cardiomyocytes may contribute to ANG II-induced cardiac hypertrophy via an autocrine/paracrine fashion.
Ito
H
H
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
Hirata
Y
Y
Adachi
S
S
Tanaka
M
M
Tsujino
M
M
Koike
A
A
Nogami
A
A
Murumo
F
F
Hiroe
M
M
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D001713:Biphenyl Compounds / Q000494:pharmacology; D006332:Cardiomegaly / Q000209:etiology*; D002478:Cells, Cultured; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D019808:Losartan; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000096:biosynthesis; D009206:Myocardium / Q000166:cytology*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013777:Tetrazoles / Q000494:pharmacology
D001713:Biphenyl Compounds; D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D007093:Imidazoles; D009124:Muscle Proteins; D009838:Oligodeoxyribonucleotides; D016376:Oligonucleotides, Antisense; D010456:Peptides, Cyclic; D012333:RNA, Messenger; D013777:Tetrazoles; D000804:Angiotensin II; D019808:Losartan; C072247:cyclo(Trp-Asp-Pro-Val-Leu)