Myocardial expression of endothelin-2 is altered reciprocally to that of endothelin-1 during ischemia of cardiomyocytes in vitro and during heart failure in vivo.
We and other groups have reported that endothelin (ET)-1 expression in the heart is altered in the setting of heart diseases. We have also reported that myocardial ET-1 is involved in the progression of heart failure, and that an ET receptor antagonist improves long-term survival in heart failure (Nature 384: 353-355, 1996). However, the role of myocardial ET-2 in disease states are not known. To characterize the role of ET-2, we used a) the failing hearts of rats with heart failure caused by myocardial infarction, and b) primary cultured cardiomyocytes subjected to hypoxia. In the failing heart in vivo, ET-1 mRNA increased by 390% compared with that in the non-failing heart, while ET-2 mRNA drastically decreased by 88%. Thus, gene expression of ET-1 and ET-2 was reciprocally altered in the failing heart in vivo. In in vitro studies, reciprocal alterations in ET-1 and ET-2 gene expression were also observed in isolated primary cultured cardiomyocytes, subjected to hypoxia. Specifically, acute hypoxic stress induced a significant increase (360% of the basal level) in ET-2 mRNA expression compared with that in normoxic cells, whereas it decreased ET-1 mRNA expression by 62% in primary cultured cardiomyocytes. Although these two crucial conditions, i.e., heart failure in vivo and acute hypoxic stress in vitro, are pathophysiologically distinct from each other, reciprocal alteration of ET-1 and ET-2 gene expression was observed in both cases. To further investigate the regulatory mechanism of the altered gene expression, luciferase analysis was performed using primary cultured cardiomyocytes. ET-2 promoter, which is the 5'-flanking region of preproET-2 gene (5'ET-2), showed a marked increase in luciferase activity during acute hypoxia. In contrast, the luciferase activity of 5'ET-1 (ET-1 promoter) did not change in response to hypoxic stress. The present study suggests that there are transcriptionally distinct regulatory mechanisms for ET-1 and ET-2 expression in cardiomyocytes, and therefore this study may provide a new aspect of cardiac ET system that not only ET-1 but also ET-2 can be participated in the pathophysiological conditions.
Kakinuma
Y
Y
Department of Internal Medicine, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
Miyauchi
T
T
Kobayashi
T
T
Yuki
K
K
Maeda
S
S
Sakai
S
S
Goto
K
K
Yamaguchi
I
I
D000818:Animals; D015687:Cell Hypoxia / Q000235:genetics; D002478:Cells, Cultured; D004195:Disease Models, Animal; D019332:Endothelin-1 / Q000096:biosynthesis* / Q000235:genetics; D019333:Endothelin-2 / Q000096:biosynthesis* / Q000235:genetics; D016232:Endothelins / Q000096:biosynthesis / Q000235:genetics; D005786:Gene Expression Regulation; D006333:Heart Failure / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D006439:Hemodynamics; D008297:Male; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology*; D011498:Protein Precursors / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley
D019332:Endothelin-1; D019333:Endothelin-2; D016232:Endothelins; D011498:Protein Precursors; D012333:RNA, Messenger; C099648:preproendothelin 2