Apoptosis in the left ventricle of chronic volume overload causes endocardial endothelial dysfunction in rats

The hypothesis is that chronic increases in left ventricular (LV) load induce oxidative stress and latent matrix metalloproteinase (MMP) is activated, allowing the heart to dilate in the absence of endothelial nitric oxide (NO) and thereby reduce filling pressure. To create volume overload, an arteriovenous (A-V) fistula was placed in male Sprague-Dawley rats. To decrease oxidative stress and apoptosis, 0.08 mg/ml nicotinamide (Nic) was administered in drinking water 2 days before surgery. The rats were divided into the following groups: 1) A-V fistula, 2) A-V fistula + Nic, 3) sham operated, 4) sham + Nic, and 5) control (unoperated); n = 6 rats/group. After 4 wk, hemodynamic parameters were measured in anesthetized rats. The heart was removed and weighed, and LV tissue homogeneates were prepared. A-V fistula caused an increase in heart weight, lung weight, and end-diastolic pressure compared with the sham group. The levels of malondialdehyde (MDA; a marker of oxidative stress) was 6.60 ± 0.23 ng/mg protein and NO was 6.87 ± 1.21 nmol/l in the LV of A-V fistula rats by spectrophometry. Nic treatment increased NO to 13.88 ± 2.5 nmol/l and decreased MDA to 3.54 ± 0.34 ng/mg protein ( P= 0.005). Zymographic levels of MMP-2 were increased, as were protein levels of nitrotyrosine and collagen fragments by Western blot analysis. The inhibition of oxidative stress by Nic decreased nitrotyrosine content and MMP activity. The levels of tissue inhibitor of metalloproteinase-4 mRNA were decreased in A-V fistula rats and increased in A-V fistula rats treated with Nic by Northern blot analysis. TdT-mediated dUTP nick-end labeling-positive cells were increased in A-V fistula rats and decreased in fistula rats treated with Nic. Acetylcholine and nitroprusside responses in cardiac rings prepared from the above groups of rats suggest impaired endothelial-dependent cardiac relaxation. Treatment with Nic improves cardiac relaxation. The results suggest that an increase in the oxidative stress and generation of nitrotyrosine are, in part, responsible for the activation of metalloproteinase and decreased endocardial endothelial function in chronic LV volume overload.

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Abstract 867: The Longevity Factor Sirt1 Exacerbates LV Dysfunction and Energy Depletion in Response to Pressure Overload

Circulation ◽

10.1161/circ.116.suppl_16.ii_169-b ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Ralph Alcendor ◽

Chull Hong ◽

Peiyong Zhai ◽

Shumin Gao ◽

Junichi Sadoshima

Keyword(s):

Oxidative Stress ◽

Stress Resistance ◽

Diastolic Pressure ◽

Pressure Overload ◽

Left Ventricular ◽

Class Iii ◽

Lung Weight ◽

Energy Depletion ◽

Lv Dysfunction ◽

And Oxidative Stress

Sirt1, a class III histone deacetylase, extends the lifespan of many organisms. Longevity mechanisms usually confer stress resistance to organisms, and accumulation of stress resistance leads to lifespan extension. We have shown previously that Sirt1 is upregulated by stress up to 10 fold in the heart, and heart specific overexpression (up to 7.5 fold) of Sirt1 in mice not only suppresses histological/biochemical markers of aging, but also induces resistance to oxidative stress in the heart. We examined whether Sirt1 is protective against another pathologically relevant stimulus, namely pressure overload. Cardiac specific Sirt1 transgenic mice (Tg-Sirt1) from line #40, the line which has been shown to be protected against aging and oxidative stress, were subjected to transverse aortic constriction (TAC). Unexpectedly, at 10 days, the left ventricular (LV) ejection fraction (EF) in Tg-Sirt1 was significantly reduced (46 vs 71%, p<0.01), the LV end diastolic dimension was significantly increased (4.1 vs 3.4 mm, p<0.05), and the pressure gradient was reduced (92 vs 57 mmHg, p<0.05), possibly due to reduced LV contractility, in Tg-Sirt1 compared with non-transgenic (NTg) controls. At 4 weeks, LV weight/body weight (BW) (6.4 vs 4.7, p<0.05) and lung weight/BW (18.8 vs 7.0, p<0.05) were significantly increased in Tg-Sirt1, LV +dP/dt was significantly reduced (4617 vs 7513, p<0.05), and the LV end diastolic pressure was significantly elevated (13.6 vs 1.4 mmHg, p<0.05) in Tg-Sirt1 compared with NTg. These results suggest that Tg-Sirt1 mice develop more severe LV dysfunction than NTg in response to TAC. Tg-Sirt1 mice exhibited significantly less apoptosis (−50%, p<0.05) than NTg however, despite the development of LV dysfunction, suggesting that the LV dysfunction may be caused by apoptosis-independent mechanisms. The myocardial ATP content in Tg-Sirt1 was significantly less (−41%, p<0.05) than that in NTg after TAC. These results suggest that the cardioprotective effect of Sirt1 depends on the type of stress: although modest expression of Sirt1 confers resistance to aging and oxidative stress, it exacerbates heart failure in response to TAC through apoptosis-independent mechanisms possibly involving energy depletion.

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Xanthine oxidase inhibition preserves left ventricular systolic but not diastolic function in cardiac volume overload

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00007.2013 ◽

2013 ◽

Vol 305 (10) ◽

pp. H1440-H1450 ◽

Cited By ~ 17

Author(s):

James D. Gladden ◽

Blake R. Zelickson ◽

Jason L. Guichard ◽

Mustafa I. Ahmed ◽

Danielle M. Yancey ◽

...

Keyword(s):

Xanthine Oxidase ◽

Diastolic Pressure ◽

Contractile Function ◽

Severe Heart Failure ◽

Volume Overload ◽

Wall Stress ◽

Left Ventricular ◽

Lv Function ◽

Lung Weight ◽

Twofold Increase

Xanthine oxidase (XO) is increased in human and rat left ventricular (LV) myocytes with volume overload (VO) of mitral regurgitation and aortocaval fistula (ACF). In the setting of increased ATP demand, XO-mediated ROS can decrease mitochondrial respiration and contractile function. Thus, we tested the hypothesis that XO inhibition improves cardiomyocyte bioenergetics and LV function in chronic ACF in the rat. Sprague-Dawley rats were randomized to either sham or ACF ± allopurinol (100 mg·kg−1·day−1, n ≥7 rats/group). Echocardiography at 8 wk demonstrated a similar 37% increase in LV end-diastolic dimension ( P < 0.001), a twofold increase in LV end-diastolic pressure/wall stress ( P < 0.05), and a twofold increase in lung weight ( P < 0.05) in treated and untreated ACF groups versus the sham group. LV ejection fraction, velocity of circumferential shortening, maximal systolic elastance, and contractile efficiency were significantly depressed in ACF and significantly improved in ACF + allopurinol rats, all of which occurred in the absence of changes in the maximum O2 consumption rate measured in isolated cardiomyocytes using the extracellular flux analyzer. However, the improvement in contractile function is not paralleled by any attenuation in LV dilatation, LV end-diastolic pressure/wall stress, and lung weight. In conclusion, allopurinol improves LV contractile function and efficiency possibly by diminishing the known XO-mediated ROS effects on myofilament Ca2+ sensitivity. However, LV remodeling and diastolic properties are not improved, which may explain the failure of XO inhibition to improve symptoms and hospitalizations in patients with severe heart failure.

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d-Propranolol protects against oxidative stress and progressive cardiac dysfunction in iron overloaded rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y2012-091 ◽

2012 ◽

Vol 90 (9) ◽

pp. 1257-1268 ◽

Cited By ~ 15

Author(s):

Jay H. Kramer ◽

Christopher F. Spurney ◽

Micaela Iantorno ◽

Constantine Tziros ◽

Joanna J. Chmielinska ◽

...

Keyword(s):

Oxidative Stress ◽

Body Mass ◽

Cardiac Dysfunction ◽

Diastolic Pressure ◽

Heart Function ◽

Treated Group ◽

Aortic Pressure ◽

Left Ventricular ◽

Sprague Dawley ◽

Cardiac Inflammation

d-Propranolol (d-Pro: 2–8 mg·(kg body mass)–1·day–1) protected against cardiac dysfunction and oxidative stress during 3–5 weeks of iron overload (2 mg Fe–dextran·(g body mass)–1·week–1) in Sprague–Dawley rats. At 3 weeks, hearts were perfused in working mode to obtain baseline function; red blood cell glutathione, plasma 8-isoprostane, neutrophil basal superoxide production, lysosomal-derived plasma N-acetyl-β-galactosaminidase (NAGA) activity, ventricular iron content, and cardiac iron deposition were assessed. Hearts from the Fe-treated group of rats exhibited lower cardiac work (26%) and output (CO, 24%); end-diastolic pressure rose 1.8-fold. Further, glutathione levels increased 2-fold, isoprostane levels increased 2.5-fold, neutrophil superoxide increased 3-fold, NAGA increased 4-fold, ventricular Fe increased 4.9-fold; and substantial atrial and ventricular Fe-deposition occurred. d-Pro (8 mg) restored heart function to the control levels, protected against oxidative stress, and decreased cardiac Fe levels. After 5 weeks of Fe treatment, echocardiography revealed that the following were depressed: percent fractional shortening (%FS, 31% lower); left ventricular (LV) ejection fraction (LVEF, 17%), CO (25%); and aortic pressure maximum (Pmax, 24%). Mitral valve E/A declined by 18%, indicating diastolic dysfunction. Cardiac CD11b+ infiltrates were elevated. Low d-Pro (2 mg) provided modest protection, whereas 4–8 mg greatly improved LVEF (54%–75%), %FS (51%–81%), CO (43%–78%), Pmax (56%–100%), and E/A >100%; 8 mg decreased cardiac inflammation. Since d-Pro is an antioxidant and reduces cardiac Fe uptake as well as inflammation, these properties may preserve cardiac function during Fe overload.

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The aging-induced hyperexcretion of glucose-dependent insulinotropic peptide is essential for the healthy cardiac remodeling by prevention of cardiac ceramide accumulation

European Heart Journal ◽

10.1093/ehjci/ehaa946.3615 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

Y Kureishi Bando ◽

Y.R Remina ◽

T.K Kamihara ◽

K.N Nishimura ◽

T.M Murohara

Keyword(s):

Oxidative Stress ◽

Ketone Bodies ◽

Left Ventricular ◽

Heart Weight ◽

Lv Function ◽

Cardiac Aging ◽

Normal Left Ventricular ◽

Insulinotropic Peptide ◽

Ceramide Accumulation ◽

And Oxidative Stress

Abstract Background Glucose-dependent insulinotropic peptide (GIP) is incretin hormone that is emerged as an important regulator of lipid metabolism. Fat intake induces hypersecretion of GIP that is involved in obesity and ectopic fat accumulation. Aging is another stimulant of GIP hypersecretion, which is suggested as a cause of “sarcopenic obesity in elderly”. In heart, aging is the known risk factor of HFpEF, of which typical characteristics is pathological cardiac hypertrophy induced by unknown cause(s). It remained uncertain whether any ectopic fat accumulation, such as cardiac steatosis may cause the aging-induced cardiac hypertrophy. Ceramide is one of the lipid metabolites that involves in apoptosis, inflammation, and stress responses, which are among the pathogenic components of heart failure. However, it remained unclear whether the ceramide may play any pathophysiological role in cardiac aging. Purpose We thus hypothesized whether cardiac aging may alter cardiac lipid metabolism and the GIP may play a regulatory role in the cardiac aging via modulating cardiac steatosis, particularly ceramide. Methods Mouse model of GIPR deficiency (GIPR-KO) was employed and cardiac evaluation of GIPR-KO and the age-matched wild type mice were performed. Results Aging (50w/o) induced GIP hypersecretion in control mice and their body and heart weight were 50% increased as compared to younger counterpart (10w/o). In contrast, the aging-induced increase rate in body and heart weight of GIPR-KO was significantly lower (22%). Aging also increased the circulating ketone bodies with increase in FGF21 expression in heart and, notably, there was no pathological increase in cardiac ceremide and oxidative stress with normal left-ventricular (LV) function (LVEF=82.2±1.8). In contrast, GIPR-KO exhibited pathological increase in cardiac ceramide without the elevation of the circulating ketone bodies. The younger GIPR-KO (10 w/o) exhibited normal left-ventricular (LV) function, however, the older mice (50 w/o) exhibited systolic LV dysfunction (LVEF=55.8±8.5) with increase in cardiac apoptosis and oxidative stress. Cardiac ceramide accumulation was increased in the aged normal mice, which was significantly higher in the aged GIPR-KO. Furthermore, GIPR-KO exhibited increase in cardiac fibrosis and oxidative stress, which were absent in the aged normal counterpart. Conclusion Aging increased circulating GIP level the leads to compensatory rise in the circulating ketone bodies without pathological increase in cardiac ceremide and related oxidative stress in heart. Loss of GIP signaling caused pathological increase in cardiac ceramide, leading to the aging-induced progression of systolic left-ventricular dysfunction. Collectively, we conclude that the aging-induced GIP hyperexcretion is essential for the aging-induced healthy cardiac remodeling by augmenting compensatory ketone body elevation. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): KAKEN-HI

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Importance of antioxidant and antiapoptotic effects of β-receptor blockers in heart failure therapy

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00797.2003 ◽

2004 ◽

Vol 287 (3) ◽

pp. H1003-H1012 ◽

Cited By ~ 55

Author(s):

Keisuke Kawai ◽

Fuzhong Qin ◽

Junya Shite ◽

Weike Mao ◽

Shuji Fukuoka ◽

...

Keyword(s):

Oxidative Stress ◽

Heart Failure ◽

Ventricular Remodeling ◽

Diastolic Pressure ◽

Cardiac Pacing ◽

Left Ventricular ◽

Beneficial Effects ◽

Myocyte Apoptosis ◽

Adrenergic Blocking ◽

Fractional Shortening

The present study was carried out to determine whether beneficial effects of carvedilol in congestive heart failure (CHF) are mediated via its β-adrenergic blocking, antioxidant, and/or α-adrenergic blocking action. Rabbits with heart failure induced by rapid cardiac pacing were randomized to receive subcutaneous carvedilol, metoprolol, propranolol plus doxazosin, or placebo pellets for 8 wk and compared with sham-operated rabbits without pacing. We found rapid cardiac pacing produced clinical heart failure, left ventricular dilation, and decline of left ventricular fractional shortening. This was associated with an increase in left ventricular end-diastolic pressure, decrease in left ventricular first derivative of left ventricular pressure, and myocyte hypertrophy. Tissue oxidative stress measured by GSH/GSSG was increased in the heart with increased oxidation product of mitochondrial DNA, 8-oxo-7,8-dihydro-2′-deoxyguanosine, increase of Bax, decrease of Bcl-2, and increase of apoptotic myocytes as measured by anti-single-stranded DNA monoclonal antibody. Administration of carvedilol and metoprolol, which had no effect in sham animals, attenuated cardiac ventricular remodeling, cardiac hypertrophy, oxidative stress, and myocyte apoptosis in CHF. In contrast, propranolol plus doxazosin, which has less antioxidant effects, produced smaller effects on left ventricular function and myocyte apoptosis. In all animals, GSH/GSSG correlated significantly with changes of left ventricular end-diastolic dimension ( r = −0.678, P < 0.0001), fractional shortening ( r = 0.706, P < 0.0001), and apoptotic myocytes ( r = −0.473, P = 0.0001). Thus our findings suggest antioxidant and antiapoptotic actions of carvedilol and metoprolol are important determinants of clinical beneficial effects of β-receptors in the treatment of CHF.

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DNA enzyme targeting TNF-α mRNA improves hemodynamic performance in rats with postinfarction heart failure

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.281.5.h2211 ◽

2001 ◽

Vol 281 (5) ◽

pp. H2211-H2217 ◽

Cited By ~ 26

Author(s):

Per Ole Iversen ◽

Gunnar Nicolaysen ◽

Mouldy Sioud

Keyword(s):

Heart Failure ◽

Therapeutic Potential ◽

Diastolic Pressure ◽

Substantial Reduction ◽

Left Ventricular ◽

Lung Weight ◽

Cleavage Activity ◽

Arterial Blood ◽

Modified Dna ◽

Tnf Α

Tumor necrosis factor-α (TNF-α) probably affects the pathogenesis of heart failure. Here we have investigated the therapeutic potential of a nuclease-resistant DNA enzyme that specifically cleaves TNF-α mRNA. A phosphorothioate-modified DNA enzyme was designed to retain similar cleavage activity as its unmodified version, and that inhibited the expression of TNF-α in vitro. To test its efficacy in vivo, postinfarction congestive heart failure was induced in anesthetized rats by ligation of the left coronary artery. A 4-wk treatment with the DNA enzyme induced a substantial reduction in left ventricular end-diastolic pressure and lung weight concomitant with an increase in arterial blood pressure and myocardial blood flow compared with controls. The concentration of TNF-α in coronary sinus blood was markedly lowered on treatment, and myocardial TNF-α mRNA was substantially reduced. Recovery studies showed that the DNA enzyme cleavage activity was present within the myocardium throughout the observation period and had no apparent toxic effects. Our findings indicate that DNA enzyme-based therapy may hold promise in the treatment of this debilitating disease.

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The Effect of Gypenosides on Cardiac Function and Expression of Cytoskeletal Genes of Myocardium in Diabetic Cardiomyopathy Rats

The American Journal of Chinese Medicine ◽

10.1142/s0192415x09007491 ◽

2009 ◽

Vol 37 (06) ◽

pp. 1059-1068 ◽

Cited By ~ 4

Author(s):

Min Ge ◽

Shanfeng Ma ◽

Liang Tao ◽

Sudong Guan

Keyword(s):

Cardiac Function ◽

Diabetic Cardiomyopathy ◽

Diastolic Pressure ◽

Pure Water ◽

Systolic Pressure ◽

Left Ventricular ◽

Control Group ◽

Sprague Dawley ◽

Gene Expressions ◽

Ventricular Systolic Pressure

The relationship between changes of cardiac function and the gene expressions of two major myocardial skeleton proteins, titin and nebulin, and the effect of gypenosides on these gene expressions in diabetic cardiomyopathy rat were explored in the present study. Forty Sprague-Dawley rats were randomly divided into three groups: control group, diabetic cardiomyopathy group and gypenosides-treated diabetic cardiomyopathy group. The diabetic cardiomyopathy was induced in rats by injecting streptozotocin (STZ, 55 mg/kg) intraperitoneally. Seven weeks after the rats suffered from diabetes, the rats were treated with gypenosides 100 mg/kg per day orally for six weeks in gypenosides-treated group. In the meanwhile, the pure water was given to diabetic cardiomyopathy and the control groups. Subsequently, the cardiac functions, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), ± dP/dtmax and t–dP/dmaxt, as well as the mRNA content and proteins of titin and nebulin in myocardium were determined. The results indicated that (1) the diabetic cardiomyopathy rats had decreased LVSP and ± dP/dtmax, increased LVEDP, and prolonged t–dP/dtmax than normal rats; (2) LVSP and ± dP/dtmax in diabetic cardiomyopathy rats treated with gypenosides were significantly higher and LVEDP and t–dP/dtmax were significantly lower than those without giving gypenosides; (3) the mRNA contents and proteins of titin and nebulin in diabetic cardiomyopathy rats were remarkably lower than those in the control rats and gypenosides had no effect on mRNA and protein expression levels of titin and nebulin in diabetic cardiomyopathy rats. We conclude that (1) the cardiac function as well as the mRNA expressions of titin and nebulin decreased in diabetic cardiomyopathy rats; (2) gypenosides secure cardiac muscles and their function from diabetic impairment and these beneficial effects of gypenosides are not by changing the expressions of titin and nebulin.

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Comparative and Combinatorial Effects of Resveratrol and Sacubitril/Valsartan alongside Valsartan on Cardiac Remodeling and Dysfunction in MI-Induced Rats

Molecules ◽

10.3390/molecules26165006 ◽

2021 ◽

Vol 26 (16) ◽

pp. 5006

Author(s):

Pema Raj ◽

Karen Sayfee ◽

Mihir Parikh ◽

Liping Yu ◽

Jeffrey Wigle ◽

...

Keyword(s):

Oxidative Stress ◽

Cardiac Remodeling ◽

Left Ventricular ◽

Myocardial Tissue ◽

Additive Effects ◽

Sprague Dawley ◽

Neutrophil Gelatinase Associated Lipocalin ◽

Sprague Dawley Rats ◽

And Function ◽

Neutrophil Gelatinase

The development and progression of heart failure (HF) due to myocardial infarction (MI) is a major concern even with current optimal therapy. Resveratrol is a plant polyphenol with cardioprotective properties. Sacubitril/valsartan is known to be beneficial in chronic HF patients. In this study, we investigated the comparative and combinatorial benefits of resveratrol with sacubitril/valsartan alongside an active comparator valsartan in MI-induced male Sprague Dawley rats. MI-induced and sham-operated animals received vehicle, resveratrol, sacubitril/valsartan, valsartan alone or sacubitril/valsartan + resveratrol for 8 weeks. Echocardiography was performed at the endpoint to assess cardiac structure and function. Cardiac oxidative stress, inflammation, fibrosis, brain natriuretic peptide (BNP), creatinine and neutrophil gelatinase associated lipocalin were measured. Treatment with resveratrol, sacubitril/valsartan, valsartan and sacubitril/valsartan + resveratrol significantly prevented left ventricular (LV) dilatation and improved LV ejection fraction in MI-induced rats. All treatments also significantly reduced myocardial tissue oxidative stress, inflammation and fibrosis, as well as BNP. Treatment with the combination of sacubitril/valsartan and resveratrol did not show additive effects. In conclusion, resveratrol, sacubitril/valsartan, and valsartan significantly prevented cardiac remodeling and dysfunction in MI-induced rats. The reduction in cardiac remodeling and dysfunction in MI-induced rats was mediated by a reduction in cardiac oxidative stress, inflammation and fibrosis.

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Abstract 370: Type 2 Diabetes Is Associated with the Exacerbation of Heart Failure via Increasing Myocardial NAD(P)H Oxidase-Derived Superoxide Production

Circulation ◽

10.1161/circ.118.suppl_18.s_292-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Shintaro Kinugawa ◽

Shouji Matsushima ◽

Takashi Yokota ◽

Yukihiro Ohta ◽

Naoki Inoue ◽

...

Keyword(s):

Heart Failure ◽

Type 2 Diabetes ◽

Diastolic Pressure ◽

Interstitial Fibrosis ◽

Left Ventricular ◽

Lung Weight ◽

Tissue Mass ◽

Tibial Length ◽

Lv Remodeling

Type 2 diabetes mellitus (DM) adversely affects the outcomes in patients with myocardial infarction (MI), which is associated with the development of left ventricular (LV) remodeling and failure. NAD(P)H oxidase-derived superoxide (O 2 − ) production is increased in DM. However, its pathophysiological significance in advanced post-MI LV failure associated with DM remains unestablished. We thus determined whether an inhibitor of NAD(P)H oxidase activation, apocynin, could attenuate the exacerbated LV remodeling and heart failure after MI in high-fat diet (HFD)-induced obese mice with DM. Male C57BL/6J mice were fed on either HFD or normal diet (ND) for 8 weeks. At 4 weeks of feeding, MI was created in all mice by ligating left coronary artery. MI mice were treated with either apocynin (10 mmol/l in drinking water; n = 10 for ND and n = 11 for HFD) or vehicle (n = 15 for ND and n = 13 for HFD). HFD significantly increased body weight (BW), adipose tissue mass, fasting plasma glucose and insulin levels compared to ND after 4 and 8 weeks. HFD + MI had significantly greater LV end-diastolic diameter (LVEDD; 5.7 ± 0.1 vs. 5.3 ± 0.2 mm) by echocardiography, end-diastolic pressure (EDP; 12 ± 2 vs. 8 ± 1 mmHg) and lung weight/tibial length (10.1 ± 0.3 vs. 8.7 ± 0.7 mg/mm) than ND + MI, which was accompanied by an increased interstitial fibrosis of non-infarcted LV. Treatment of HFD + MI with apocynin significantly decreased LVEDD (5.4 ± 0.1 mm), LVEDP (9.7 ± 0.8 mmHg), lung weight/tibial length (9.0 ± 0.3 mg/mm), and concomitantly interstitial fibrosis of non-infarcted LV to ND + MI level without affecting BW, glucose metabolism, infarct size and aortic pressure. On the other hand, treatment of ND + MI with apocynin did not affect LV remodeling and failure. NAD(P)H oxidase activity, O 2 − production measured by lucigenin chemiluminescence, and thiobarbituric acid-reactive substances were increased in non-infarcted LV tissues from HFD + MI, all of which were also attenuated by apocynin to ND + MI level. Type 2 DM was associated with the exacerbation of LV remodeling and failure after MI via increasing NAD(P)H oxidase derived O 2 − production, which may be a novel important therapeutic target in advanced heart failure with DM.

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Abstract 13469: Drp1 Accumulates in Mitochondria and Plays a Protective Role in the Heart in Response to Pressure Overload

Circulation ◽

10.1161/circ.130.suppl_2.13469 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Akihiro Shirakabe ◽

Yoshiyuki Ikeda ◽

Peiyong Zai ◽

Junichi Sadoshima

Keyword(s):

Diastolic Pressure ◽

Pressure Overload ◽

Protective Role ◽

Left Ventricular ◽

Multiple Time ◽

Lung Weight ◽

Knock Out ◽

Multiple Time Points ◽

Increased Activity ◽

Adaptive Role

Dynamin-related protein 1 (Drp1) plays an essential role in maintaining the quality control of mitochondria through mitochondrial (Mt) fission and mitophagy. We investigated how Mt function, autophagy and Drp1 are regulated in the heart during pressure overload (PO) and whether endogenous Drp1 plays an important role in regulating cardiac function. Mice were subjected to transverse aortic constriction (TAC) at multiple time points between 6 hours and 30 days. Left ventricular (LV) weight/tibial length (LVW/TL) was significantly elevated at Day 7 (TAC vs sham; 5.92 ± 0.27 vs 4.22 ± 0.12, p<0.05). Ejection fraction (EF) was maintained at Day 7, but gradually decreased thereafter (at 30 days; 65±9 vs 83±9 %, p<0.05). LC3-II was decreased (-45.7%, p<0.05) while p62 accumulated (1.17 fold, p<0.05) significantly at Day 7. Both Mt ATP content (-65.6%, p<0.05) and production (-90.3%, p<0.05) were reduced significantly at Days 7 and 14, respectively, and thereafter. Mt mass, evaluated by electron microscopy, was also reduced (-19.9%, p<0.05) at Day 7. Drp1 accumulated in mitochondria at Day 7, and S616 phosphorylation of Drp1, associated with increased activity, was increased at Day 7. Thus, PO suppresses autophagy and induces Mt dysfunction by Day 7, at which time Drp1 accumulates in mitochondria and Mt mass is decreased. To examine the functional significance of endogenous Drp1 during PO, cardiac-specific heterozygous Drp1 knock out (Drp-hetCKO) mice were subjected to TAC. At Day 7, decreases in EF (61± 2 vs 84 ± 7%, p<0.05) and increases in LVW/TL (7.22 ± 0.26 vs 5.86 ± 0.65, p<0.05) and lung weight/TL (12.01 ± 1.10 vs 6.31 ± 1.19, p<0.05) were exacerbated in Drp-hetCKO compared to in control mice. LV end diastolic pressure was significantly higher (22.0 ± 2.8 vs 5.7 ± 2.9 mmHg, p<0.05) and myocardial fibrosis (14.1 ± 2.5 vs 6.2 ± 4.3 %, p<0.05) was greater in Drp-hetCKO than in control mice. Mt mass was also significantly greater in Drp-hetCKO than in control mice (relative Mt mass, 1.21 ± 0.46 vs 1.00 ± 0.02, p<0.05). These results suggest that PO inhibits autophagy and induces mitochondrial dysfunction by Day7, which coincides with Mt accumulation of Drp1. Drp1 plays an adaptive role in this condition, mediating decreases in Mt mass and protecting the heart from dysfunction.

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