Induction of heart failure by minimally invasive aortic constriction in mice: Reduced peroxisome proliferator-activated receptor gamma coactivator levels and mitochondrial dysfunction
ABSTRACT Mitochondrial dysfunction has been suggested as a potential cause for heart failure. Pressure overload is a common cause for heart failure. However, implementing pressure overload in mice is considered a model for compensated hypertrophy but not for heart failure. We assessed the suitability of minimally invasive transverse aortic constriction to induce heart failure in C57BL/6 mice and assessed mitochondrial biogenesis and function.
Minimally invasive transverse aortic constriction was performed through a ministernotomy without intubation (minimally invasive transverse aortic constriction, n = 68; sham operation, n = 43). Hypertrophy was assessed based on heart weight/body weight ratios and histologic analyses, and contractile function was assessed based on intracardiac Millar pressure measurements. Expression of selected metabolic genes was assessed with reverse transcription-polymerase chain reaction and Western blotting. Maximal respiratory capacity (state 3) of isolated mitochondria was measured with a Clark-type electrode.
Survival was 62%. Within 7 weeks, minimally invasive transverse aortic constriction induced significant hypertrophy (heart weight/body weight ratio: 10.08±0.28 mg/g for minimally invasive transverse aortic constriction vs 4.66±0.07 mg/g for sham operation; n=68; P<.01). Fifty-seven percent of mice undergoing minimally invasive transverse aortic constriction displayed signs of heart failure (pleural effusions, dyspnea, weight loss, and dp/dtmax of 3114±422 mm Hg/s, P<.05). All of them had heart weight/body weight ratios of greater than 10. Mice undergoing minimally invasive transverse aortic constriction with heart weight/body weight ratios of less than 10 had normal contractile function (dp/dtmax of 6471±292 mm Hg/s vs dp/dtmax of 6933±205 mmHg/s in sham mice) and no clinical signs of heart failure. The mitochondrial coactivator peroxisome proliferator-activated receptor γ coactivator alpha (PGC-1α) was downregulated in failing hearts only. PGC-1α and fatty acid oxidation gene expression were also decreased in failing hearts. State 3 respiration of isolated mitochondria was significantly reduced in all hearts subjected to pressure overload.
Contractile dysfunction and heart failure can be induced in wild-type mice by means of minimally invasive aortic constriction. Pressure overload-induced heart failure in mice is associated with mitochondrial dysfunction, as characterized by downregulation of PGC-1α and reduced oxidative capacity.
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ABSTRACT: Mitochondrial dysfunction is frequently observed in vascular diseases. Cilostazol is a drug approved by the US Food and Drug Administration for the treatment of intermittent claudication. Cilostazol increases intracellular cyclic adenosine monophosphate (cAMP) levels through inhibition of type III phosphodiesterase. The effects of cilostazol in mitochondrial biogenesis in human umbilical vein endothelial cells (HUVECs) were investigated in this study. Cilostazol treated HUVECs displayed increased levels of ATP, mitochondrial DNA/nuclear DNA ratio, expressions of cytochrome B, and mitochondrial mass, suggesting an enhanced mitochondrial biogenesis induced by cilostazol. The promoted mitochondrial biogenesis could be abolished by Protein Kinase A (PKA) specific inhibitor H-89, implying that PKA pathway played a critical role in increased mitochondrial biogenesis after cilostazol treatment. Indeed, expression levels of peroxisome proliferator activator receptor gamma-coactivator 1α (PGC-1α), NRF 1 and mitochondrial transcription factor A (TFAM) were significantly increased in HUVECs after incubation with cilostazol at both mRNA levels and protein levels. Importantly, knockdown of PGC-1α could abolish cilostazol- induced mitochondrial biogenesis. Enhanced expression of p-CREB and PGC-1α induced by cilostazol could be inhibited by H-89. Moreover, the increased expression of PGC-1α induced by cilostazol could be inhibited by downregulation of CREB using CREB siRNA at both mRNA and protein levels. All the results indicated that cilostazol promoted mitochondrial biogenesis through activating the expression of PGC-1α in HUVECs, which was mediated by PKA/CREB pathway.Biochemical and Biophysical Research Communications 02/2013; DOI:10.1016/j.bbrc.2013.02.068 · 2.28 Impact Factor
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ABSTRACT: Supplementation with the n3 polyunsaturated fatty acid docosahexaenoic acid (DHA) is beneficial in heart failure patients, however the mechanisms are unclear. DHA is incorporated into membrane phospholipids, which may prevent mitochondrial dysfunction. Thus we assessed the effects of DHA supplementation on cardiac mitochondria and the development of heart failure caused by aortic pressure overload. Pathological cardiac hypertrophy was generated in rats by thoracic aortic constriction. Animals were fed either a standard diet or were supplemented with DHA (2.3 % of energy intake). After 14 weeks, heart failure was evident by left ventricular hypertrophy and chamber enlargement compared to shams. Left ventricle fractional shortening was unaffected by DHA treatment in sham animals (44.1 ± 1.6 % vs. 43.5 ± 2.2 % for standard diet and DHA, respectively), and decreased with heart failure in both treatment groups, but to a lesser extent in DHA treated animals (34.9 ± 1.7 %) than with the standard diet (29.7 ± 1.5 %, P < 0.03). DHA supplementation increased DHA content in mitochondrial phospholipids and decreased membrane viscosity. Myocardial mitochondrial oxidative capacity was decreased by heart failure and unaffected by DHA. DHA treatment enhanced Ca(2+) uptake by subsarcolemmal mitochondria in both sham and heart failure groups. Further, DHA lessened Ca(2+)-induced mitochondria swelling, an index of permeability transition, in heart failure animals. Heart failure increased hydrogen peroxide-induced mitochondrial permeability transition compared to sham, which was partially attenuated in interfibrillar mitochondria by treatment with DHA. DHA decreased mitochondrial membrane viscosity and accelerated Ca(2+) uptake, and attenuated susceptibility to mitochondrial permeability transition and development of left ventricular dysfunction.Cardiovascular Drugs and Therapy 09/2013; DOI:10.1007/s10557-013-6487-4 · 2.67 Impact Factor