Autocrine/paracrine determinants of strain-activated brain natriuretic peptide gene expression in cultured cardiac myocytes.
The application of mechanical strain leads to activation of human brain natriuretic peptide gene promoter activity, a marker of hypertrophy, in cultured neonatal rat ventricular myocytes. We have used a combination of transient transfection analysis and reverse transcriptase-polymerase chain reaction to examine the role of locally produced factors in contributing to this activation. Conditioned media from strained, but not static, cultures led to a dose-dependent increase in human brain natriuretic peptide gene promoter activity. This increase was completely blocked by losartan or BQ-123, implying a role for angiotensin and endothelin as autocrine/paracrine mediators of the response to strain. Inclusion of the same antagonists in the cultures themselves led to only partial inhibition (approximately 60%), whereas inclusion of exogenous endothelin or angiotensin II resulted in amplification of the strain response. Angiotensin II and endothelin appear to be arrayed in series in the regulatory circuitry; the angiotensin response was blocked by BQ-123, whereas the endothelin response was unaffected by losartan. Mechanical strain was also shown to stimulate expression of the endogenous angiotensinogen, angiotensin-converting enzyme, and endothelin genes in this system. Collectively, these data indicate that locally generated angiotensin II and endothelin, acting in series, play an important autocrine/paracrine role in mediating strain-dependent activation of cardiac-specific gene expression.
Liang
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Metabolic Research Unit and Department of Medicine, University of California, San Francisco, California 94143, USA.
Gardner
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DG
D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000502:physiology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D019898:Autocrine Communication / Q000502:physiology; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D019332:Endothelin-1 / Q000037:antagonists & inhibitors / Q000502:physiology; D005786:Gene Expression Regulation / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D019808:Losartan / Q000494:pharmacology; D020097:Natriuretic Peptide, Brain; D009419:Nerve Tissue Proteins / Q000235:genetics*; D019899:Paracrine Communication / Q000502:physiology; D010456:Peptides, Cyclic / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D013180:Sprains and Strains; D014162:Transfection / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000276:immunology; D016276:Ventricular Function
D000906:Antibodies; D017077:Culture Media, Conditioned; D019332:Endothelin-1; D009419:Nerve Tissue Proteins; D010456:Peptides, Cyclic; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D000804:Angiotensin II; D020097:Natriuretic Peptide, Brain; D019808:Losartan; C072247:cyclo(Trp-Asp-Pro-Val-Leu)