Molecular role of GATA binding protein 4 GATA-4 in hyperglycemia-induced reduction of cardiac contractilityReport as inadecuate




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Cardiovascular Diabetology

, 10:57

First Online: 24 June 2011Received: 31 May 2011Accepted: 24 June 2011

Abstract

BackgroundDiabetic cardiomyopathy, a diabetes-specific complication, refers to a disorder that eventually leads to left ventricular hypertrophy in addition to diastolic and systolic dysfunction. In recent studies, hyperglycemia-induced reactive oxygen species ROS in cardiomyocytes have been linked to diabetic cardiomyopathy. GATA binding protein 4 GATA-4 regulates the expression of many cardio-structural genes including cardiac troponin-I cTnI.

MethodsStreptozotocin-induced diabetic rats and H9c2 embryonic rat cardiomyocytes treated with a high concentration of glucose a D-glucose concentration of 30 mM was used and cells were cultured for 24 hr were used to examine the effect of hyperglycemia on GATA-4 accumulation in the nucleus. cTnI expression was found to be linked to cardiac tonic dysfunction, and we evaluated the expression levels of cTnI and GATA-4 by Western blot analysis.

ResultsCardiac output was lowered in STZ-induced diabetic rats. In addition, higher expressions of cardiac troponin I cTnI and phosphorylated GATA-4 were identified in these rats by Western blotting. The changes were reversed by treatment with insulin or phlorizin after correction of the blood sugar level. In H9c2 cells, ROS production owing to the high glucose concentration increased the expression of cTnI and GATA-4 phosphorylation. However, hyperglycemia failed to increase the expression of cTnI when GATA-4 was silenced by small interfering RNA siRNA in H9c2 cells. Otherwise, activation of ERK is known to be a signal for phosphorylation of serine105 in GATA-4 to increase the DNA binding ability of this transcription factor. Moreover, GSK3β could directly interact with GATA-4 to cause GATA-4 to be exported from the nucleus. GATA-4 nuclear translocation and GSK3β ser9 phosphorylation were both elevated by a high glucose concentration in H9c2 cells. These changes were reversed by tiron ROS scavenger, PD98059 MEK-ERK inhibitor, or siRNA of GATA-4. Cell contractility measurement also indicated that the high glucose concentration decreased the contractility of H9c2 cells, and this was reduced by siRNA of GATA-4.

ConclusionsHyperglycemia can cause systolic dysfunction and a higher expression of cTnI in cardiomyocytes through ROS, enhancing MEK-ERK-induced GATA-4 phosphorylation and accumulation in the cell nucleus.

List of abbreviationsROSreactive oxygen species

GATA-4GATA binding protein 4

cTnIcardiac troponin-I

siRNAsmall interfering RNA

GSK3βglycogen synthase kinase 3 beta

CHFcongestive heart failure

ERK1-2activate extracellular signal-regulated kinases

MAPmean arterial pressure

HRheart rate

STZstreptozotoxin

COcardiac output

i.p.intraperitoneal

DHEdihydroethidium

HGhigh glucose

PBSphosphate-buffered saline

BSAbovine serum albumin

DAPI4-, 6-diamidino-2-phenylindole

RIPAradioimmunoprecipitation assay

SDS-PAGEsodium dodecyl sulfate polyacry lamide gel electrophoresis

ECLenzymatic chemiluminescence

PEphenylephrine

MAPKmitogen-activated protein kinases

ANFatrial natriuretic factor

BNPbeta-type natriuretic peptide

MHCmyosin heavy chain

SDstandard deviation

SEMstandard error of mean.

Electronic supplementary materialThe online version of this article doi:10.1186-1475-2840-10-57 contains supplementary material, which is available to authorized users.

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Author: Po-Ming Ku - Li-Jen Chen - Jia-ru Liang - Kai-Chun Cheng - Yin-Xiao Li - Juei-Tang Cheng

Source: https://link.springer.com/article/10.1186/1475-2840-10-57







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