title: Elevated myocardial Na+/H+ exchanger isoform 1 activity elicits gene expression that leads to cardiac hypertrophy.
abstract: In myocardial disease, elevated expression and activity of Na(+)/H(+) exchanger isoform 1 (NHE1) are detrimental. To better understand the involvement of NHE1, transgenic mice with elevated heart-specific NHE1 expression were studied. N-line mice expressed wild-type NHE1, and K-line mice expressed activated NHE1. Cardiac morphology, interstitial fibrosis, and cardiac function were examined by histological staining and echocardiography. Differences in gene expression between the N-line or K-line and nontransgenic littermates were probed with genechip analysis. We found that NHE1 K-line (but not N-line) hearts developed hypertrophy, including elevated heart weight-to-body weight ratio and increased cross-sectional area of the cardiomyocytes, interstitial fibrosis, as well as depressed cardiac function. N-line hearts had modest changes in gene expression (50 upregulations and 99 downregulations, P < 0.05), whereas K-line hearts had a very strong transcriptional response (640 upregulations and 677 downregulations, P < 0.05). In addition, the magnitude of expression alterations was much higher in K-line than N-line mice. The most significant changes in gene expression were involved in cardiac hypertrophy, cardiac necrosis/cell death, and cardiac infarction. Secreted phosphoprotein 1 and its signaling pathways were upregulated while peroxisome proliferator-activated receptor gamma signaling was downregulated in K-line mice. Our study shows that expression of activated NHE1 elicits specific pathways of gene activation in the myocardium that lead to cardiac hypertrophy, cell death, and infarction.
authors.affiliation: Department of Pediatrics, University of California San Diego, La Jolla, California 92093-0735, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Xue
authors.forename: Fatima
authors.initials: F
authors.lastname: Mraiche
authors.forename: Dan
authors.initials: D
authors.lastname: Zhou
authors.forename: Morris
authors.initials: M
authors.lastname: Karmazyn
authors.forename: Tatsujiro
authors.initials: T
authors.lastname: Oka
authors.forename: Larry
authors.initials: L
authors.lastname: Fliegel
authors.forename: Gabriel G
authors.initials: GG
authors.lastname: Haddad
mesh_terms: D000818:Animals; D006332:Cardiomegaly / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D016923:Cell Death / Q000235:genetics; D004719:Endomyocardial Fibrosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000502:physiology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009203:Myocardial Infarction / Q000235:genetics / Q000473:pathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology / Q000502:physiology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D027682:Cation Transport Proteins; D020033:Protein Isoforms; C490997:Slc9a1 protein, mouse; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers
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