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Articles by D. R Pimentel
Total Records ( 6 ) for D. R Pimentel
  D. S De Silva , R. M Wilson , C Hutchinson , P. C Ip , A. G Garcia , S Lancel , M Ito , D. R Pimentel and F. Sam
 

Aldosterone induces extracellular signal-regulated kinase (ERK)-dependent cardiac remodeling. Fenofibrate improves cardiac remodeling in adult rat ventricular myocytes (ARVM) partly via inhibition of aldosterone-induced ERK1/2 phosphorylation and inhibition of matrix metalloproteinases. We sought to determine whether aldosterone caused apoptosis in cultured ARVM and whether fenofibrate ameliorated the apoptosis. Aldosterone (1 µM) induced apoptosis by increasing terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive nuclei in ARVM. Spironolactone (100 nM), an aldosterone receptor antagonist, but not RU-486, a glucocorticoid receptor, inhibited aldosterone-mediated apoptosis, indicating that the mineralocorticoid receptor (MR) plays a role. SP-600125 (3 µM)—a selective inhibitor of c-Jun NH2-terminal kinase (JNK)—inhibited aldosterone-induced apoptosis in ARVM. Although aldosterone increased the expression of both stress-activated protein kinases, pretreatment with fenofibrate (10 µM) decreased aldosterone-mediated apoptosis by inhibiting only JNK phosphorylation and the aldosterone-induced increases in Bax, p53, and cleaved caspase-3 and decreases in Bcl-2 protein expression in ARVM. In vivo studies demonstrated that chronic fenofibrate (100 mg·kg body wt–1·day–1) inhibited myocardial Bax and increased Bcl-2 expression in aldosterone-induced cardiac hypertrophy. Similarly, eplerenone, a selective MR inhibitor, used in chronic pressure-overload ascending aortic constriction inhibited myocardial Bax expression but had no effect on Bcl-2 expression. Therefore, involvement of JNK MAPK-dependent mitochondrial death pathway mediates ARVM aldosterone-induced apoptosis and is inhibited by fenofibrate, a peroxisome proliferator-activated receptor (PPAR) ligand. Fenofibrate mediates beneficial effects in cardiac remodeling by inhibiting programmed cell death and the stress-activated kinases.

  Y Oshima , N Ouchi , M Shimano , D. R Pimentel , K. N Papanicolaou , K. D Panse , K Tsuchida , E Lara Pezzi , S. J Lee and K. Walsh
 

Background— Transforming growth factor-β family cytokines have diverse actions in the maintenance of cardiac homeostasis. Activin A is a member of this family whose regulation and function in heart are not well understood at a molecular level. Follistatin-like 3 (Fstl3) is an extracellular regulator of activin A protein, and its function in the heart is also unknown.

Methods and Results— We analyzed the expression of various transforming growth factor-β superfamily cytokines and their binding partners in mouse heart. Activin βA and Fstl3 were upregulated in models of myocardial injury. Overexpression of activin A with an adenoviral vector (Ad-actβA) or treatment with recombinant activin A protein protected cultured myocytes from hypoxia/reoxygenation-induced apoptosis. Systemic overexpression of activin A in mice by intravenous injection of Ad-actβA protected hearts from ischemia/reperfusion injury. Activin A induced the expression of Bcl-2, and ablation of Bcl-2 by small interfering RNA abrogated its protective action in myocytes. The protective effect of activin A on cultured myocytes was abolished by treatment with Fstl3 or by a pharmacological activin receptor-like kinase inhibitor. Cardiac-specific Fstl3 knockout mice showed significantly smaller infarcts after ischemia/reperfusion injury that was accompanied by reduced apoptosis.

Conclusions— Activin A and Fstl3 are induced in heart by myocardial stress. Activin A protects myocytes from death, and this activity is antagonized by Fstl3. Thus, the relative expression levels of these factors after injury is a determinant of cell survival in the heart.

  F Qin , S Lennon Edwards , S Lancel , A Biolo , D. A Siwik , D. R Pimentel , G. W Dorn , Y. J Kang and W. S. Colucci
 

Background— Although it seems that reactive oxygen species contribute to chronic myocardial remodeling, questions remain about (1) the specific types of reactive oxygen species involved, (2) the role of reactive oxygen species in mediating specific cellular events, and (3) the cause-and-effect relationship between myocardial reactive oxygen species and the progression to heart failure. Transgenic mice with myocyte-specific overexpression of Gq develop a dilated cardiomyopathy that progresses to heart failure. We used this model to examine the role of H2O2 in mediating myocardial remodeling and the progression to failure.

Methods and Results— In Gq myocardium, markers of oxidative stress were increased at 4 weeks and increased further at 20 weeks. Gq mice were crossbred with transgenic mice having myocyte-specific overexpression of catalase. At 4 weeks of age, left ventricular end-diastolic dimension was increased and left ventricular fractional shortening decreased in Gq mice and deteriorated further through 20 weeks. In Gq mice, myocardial catalase overexpression had no effect on left ventricular end-diastolic dimension or fractional shortening at 4 weeks but prevented the subsequent deterioration in both. In Gq mice, myocyte hypertrophy; myocyte apoptosis; interstitial fibrosis; and the progression to overt heart failure, as reflected by lung congestion and exercise intolerance, were prevented by catalase overexpression.

Conclusion— In Gq mice, myocyte-specific overexpression of catalase had no effect on the initial phenotype of left ventricular dilation and contractile dysfunction but prevented the subsequent progressive remodeling phase leading to heart failure. Catalase prevented the cellular hallmarks of adverse remodeling (myocyte hypertrophy, myocyte apoptosis, and interstitial fibrosis) and the progression to overt heart failure. Thus, H2O2, associated oxidant pathways, or both play a critical role in adverse myocardial remodeling and the progression to failure.

 
 
 
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