Isoproterenol-induced Heart Failure Research Articles

Changes in Gut Microbiome Structure and Function of Rats with Isoproterenol-Induced Heart Failure.

Recently, the potential role of gut microbiome (GM) in cardiovascular diseases has been revealed. Heart failure (HF) is one of the most prevalent cardiovascular diseases worldwide; however, whether GM dysbiosis participates in the development of HF remains largely unknown. This study aimed to investigate the specific changes in GM composition and function in isoproterenol (ISO)-induced HF in rats.The rats were divided into C (control), 4w-HF (ISO, 2.5 mg/kg/day for 4 weeks, intraperitoneally), and 2w-HF (ISO, 2.5 mg/kg/day for 2 weeks, intraperitoneally) groups. The cardiac structure and function in rats were assessed, and metagenomic analyses were then performed. Compared with the healthy control group, we found that the Shannon diversity index and microbial gene count in the 4w-HF and 2w-HF groups was drastically decreased. High-throughput sequencing showed that the three groups differed in intestinal bacterial community composition. Overgrowth of bacteria, such as Prevotella, was observed in the 4w-HF group, with reduced growth of bacteria, such as Roseburia, Lactobacillus, and Butyrivibrio, associated with healthy status compared with the C group on the genus level. Concomitant with the alteration of GM composition, underrepresentation of health-linked microbial function was observed in both the 4w-HF and 2w-HF groups compared with the C group.Iso-induced HF rats showed a significant decrease in the diversity and richness of the intestinal microbiome, with a downregulation of the key intestinal bacterial groups and overgrowth of bacteria considered to be involved in inflammatory responses as well as a decrease in health-linked microbial function. Our data indicated that altered GM may be a potential player in the pathogenesis and progression of HF.

Cardioprotective Efficacy of Hispidulin on Isoproterenol-induced Heart Failure in Wistar Rats

Cardioprotective Efficacy of Hispidulin on Isoproterenol-induced Heart Failure in Wistar Rats

Probiotics Mitigates Skeletal Muscle Atrophy in Isoproterenol-Induced Heart Failure Adult Rats; by Increasing IGF-I Gene Expression and Improving Insulin Sensitivity

AbstractBackground: Skeletal muscle atrophy is a common com-plication of heart failure that may result from the accompanying neuro-hormonal disturbances. Altered gut microbiome can mediate these neuro-hormonal disturbances. Growing evidenc-es pointed to the health benefits of probiotics.Aim of Study: To evaluate the effects of probiotics on skeletal muscle state in ISO-induced HF and the underlying mechanisms.Material and Methods: 21 male adult rats were divided into: Control group (C), ISO-HF group; rats were injected with isoproterenol (ISO) 5mg/kg/d IP for 7 days and Pro-T group which were given probiotics by oral gavage for 6 weeks after ISO injection. Plasma Ang II, insulin, glucose, skeletal muscle atrogin and cardiac BNP levels were measured. Also relative gene expression of skeletal muscle IGF-1, IRS-1, NADPH oxidase was assessed. Cardiac and skeletal muscle tissues were weighed and histopathologically assessed.Results: In pro T group, cardiac BNP, plasma Ag II, left ventricular weight and LV/BW ratio were significant reduced. Also, skeletal muscle atrogin and NADPH oxidase were significantly decreased with a significant increase in skeletal muscle weight, IGF-1 and IRS-1 relative gene expression. In addition, probiotics decreased insulin resistance, plasma glucose, insulin levels and HOMA-IR score. This was accom-panied by the restoration of normal collagen distribution and cardiac muscle distinct cell borders and skeletal muscle distinct cell borders.Conclusion: Probiotics mitigates muscle atrophy in ISO-HF by lowering Ang II and by their anti-oxidant, anti-fibrotic, anti-hypertrophic and anti-hyperglycemic effects.

CXCR4 Cardiac Specific Knockout Mice Develop a Progressive Cardiomyopathy.

Activation of multiple pathways is associated with cardiac hypertrophy and heart failure. We previously published that CXCR4 negatively regulates β-adrenergic receptor (β-AR) signaling and ultimately limits β-adrenergic diastolic (Ca2+) accumulation in cardiac myocytes. In isolated adult rat cardiac myocytes; CXCL12 treatment prevented isoproterenol-induced hypertrophy and interrupted the calcineurin/NFAT pathway. Moreover; cardiac specific CXCR4 knockout mice show significant hypertrophy and develop cardiac dysfunction in response to chronic catecholamine exposure in an isoproterenol-induced (ISO) heart failure model. We set this study to determine the structural and functional consequences of CXCR4 myocardial knockout in the absence of exogenous stress. Cardiac phenotype and function were examined using (1) gated cardiac magnetic resonance imaging (MRI); (2) terminal cardiac catheterization with in vivo hemodynamics; (3) histological analysis of left ventricular (LV) cardiomyocyte dimension; fibrosis; and; (4) transition electron microscopy at 2-; 6- and 12-months of age to determine the regulatory role of CXCR4 in cardiomyopathy. Cardiomyocyte specific-CXCR4 knockout (CXCR4 cKO) mice demonstrate a progressive cardiac dysfunction leading to cardiac failure by 12-months of age. Histological assessments of CXCR4 cKO at 6-months of age revealed significant tissue fibrosis in knockout mice versus wild-type. The expression of atrial naturietic factor (ANF); a marker of cardiac hypertrophy; was also increased with a subsequent increase in gross heart weights. Furthermore, there were derangements in both the number and the size of the mitochondria within CXCR4 cKO hearts. Moreover, CXCR4 cKO mice were more sensitive to catocholamines, their response to β-AR agonist challenge via acute isoproterenol (ISO) infusion demonstrated a greater increase in ejection fraction, dp/dtmax, and contractility index. Interestingly, prior to ISO infusion, there were significant differences in baseline hemodynamics between the CXCR4 cKO compared to littermate controls. However, upon administering ISO, the CXCR4 cKO responded in a robust manner overcoming the baseline hemodynamic deficits reaching WT values supporting our previous data that CXCR4 negatively regulates β-AR signaling. This further supports that, in the absence of the physiologic negative modulation, there is an overactivation of down-stream pathways, which contribute to the development and progression of contractile dysfunction. Our results demonstrated that CXCR4 plays a non-developmental role in regulating cardiac function and that CXCR4 cKO mice develop a progressive cardiomyopathy leading to clinical heart failure.

Relations between markers of cardiac remodelling and left ventricular collagen in an isoproterenol-induced heart damage model.

There is a great urgency of detecting and monitoring myocardial fibrosis in clinical practice with the aim to improve and personalize therapy against cardiac remodelling. Hence, the aim of this study was to describe alterations in and show potential correlations between the structural characteristics and the molecular and biochemical markers of cardiac remodelling on a model of isoproterenol-induced heart failure. Two groups of 3-month-old male Wistar rats (n = 8 per group) were sacrificed after four weeks of treatment: control (placebo), ISO (5 mg/kg/day intraperitoneally). Chronic ISO treatment led to heart failure (HF) characterized by significant reduction of systolic blood pressure (SBP) accompanied by an increase in left ventricular weight (LVW) along with increased collagen content in the LV. The collagen content correlated negatively with SBP (R = -0.776, P < 0.001) and positively with LVW (R = 0.796, P < 0.001), with Col1a1 (0.83; P < 0.001) and Acta2 (0.73; P < 0.01). Moreover, the mRNA expression of fibrotic remodelling indicator, i.e. TGF-β1 tended to increase, while the level of fibrinolysis markers (MCP-1, TIMP-2, MMP) were unchanged. The plasma markers of collagen, procollagen I C-terminal propeptide (PICP) was 37.34 ± 7.10 pg/mL in control and was reduced by 42% (P < 0.05) in the ISO group and procollagen III N-terminal propeptide (PIIINP) was 1216.7 ± 191.0 pg/mL in control and was decreased by 66% (P < 0.05) in the ISO group. Surprisingly, there was no positive correlation between plasma markers of collagen, i.e. PICP and PIIINP and collagen content or molecular markers of collagen. However, both PICP and PIIINP correlated with BW (R = 0.712, resp. 0.803, P < 0.001), which was significantly reduced (by 25%, P < 0.05) in the ISO group. In conclusion, we assume that the collagen content of the left ventricle does not need unavoidably correlate with plasma markers of collagen, which might be affected by confounding factors in heart failure, such as loss of body weight, presumably associated with a catabolic condition.

Isoproterenol-induced heart failure in rat heart: Evaluation and cardioprotective strategy

It is well established that cardiac remodelling plays a pivotal role in the development of heart failure (HF), a leading cause of death worldwide. Meanwhile, a preclinical rat model of isoproterenol (Iso)-induced HF causes sympathetic hyperactivity, an important factor of cardiac remodelling, hemodynamic changes and cardiac fibrosis development. Several studies showed that metoprolol, a β1-adrenergic receptor (β1-AR) blocker prevents cardiac dysfunction following prolonged β-AR stimulation in different preclinical models. We evaluated the cardioprotective effects of metoprolol on cardiac remodelling and diastolic function in a severe Iso-induced HF model using echocardiography and cardiac pressure measurement. Rats received Iso injections (Iso; 5 mg/kg/day, N = 5), metoprolol (Meto; 24 mg/kg/day) + Iso 5 (Iso + Meto, N = 6), or vehicle ( N = 9) for 7 days. Left ventricular (LV) dimensions and function were followed-up by echocardiography before and after the treatment to assess LV hypertrophy. After echocardiography, LV end-diastolic pressure (LVEDP) was recorded to assess ventricular compliance and rat hearts were used for cardiac remodelling analysis. One week of Iso injections significantly increased LVEDP (+ 48%) and was associated with a major LV hypertrophy, characterised by a significant increase in LV mass (+ 33%) and a thickening of the LV walls observed by echocardiography. Simultaneous treatment with metoprolol prevented diastolic dysfunction and LV remodelling. Hypertrophy and fibrosis will be analysed in each group by histology (on-going experiments). Metoprolol afforded a cardioprotective effect on cardiac remodelling and diastolic dysfunction in Iso-induced HF model. Echocardiography and LVEDP measurements validate the reversibility of hypertrophic HF, and Iso-induced HF developed in rat could represent an effective and predictive preclinical model for evaluating antihypertrophic and antifibrotic agents.

MiR-1a-3p mitigates isoproterenol-induced heart failure by enhancing the expression of mitochondrial ND1 and COX1

MicroRNAs (miRNAs) have become potential targets for the treatment of heart failure (HF). It has been shown that miR-1 can reverse cardiac hypertrophy during the compensatory phase of HF development, but it is unknown whether miR-1 can still reverse cardiac dysfunction and improve cardiac remodeling after HF progresses to the decompensation stage. We established a mouse model of isoproterenol-induced HF and then injected miR-1a-3p agomir (agomir-1) into the tail vein. Echocardiography showed that the mice treated with agomir-1 had significantly increased ejection fraction and fractional shortening. These mice also showed a decrease in the N-terminal pro-B type natriuretic peptide (NT-proBNP) levels, but this remained higher than in controls. Cardiac hypertrophy, myocardial fibrosis, apoptosis, and glycogen deposition were reduced in mice treated with agomir-1. Furthermore, we found that supplementation of agomir-1 increased the expression of two mitochondrial DNA-encoded proteins, mitochondrially encoded NADH dehydrogenase 1 (ND1) and mitochondrially encoded cytochrome c oxidase I (COX1). In conclusion, our study found that miR-1a-3p alleviated the symptoms of ISO-induced HF in mice by enhancing mitochondrial ND1 and COX1. The results of this work may provide new therapeutic strategies for the treatment of HF patients.

Oltipraz attenuates the progression of heart failure in rats through inhibiting oxidative stress and inflammatory response.

To evaluate the effect of oltipraz (OPZ) on isoproterenol-induced heart failure (HF) and heart function. We also explore the underlying molecular mechanism of OPZ. The rats were randomly divided into four groups, including normal control group, isoproterenol (ISO) group, ISO +100 mg/kg OPZ group, and OPZ group. Hemodynamic parameters, such as left-ventricular systolic pressure, were statistically analyzed. Besides, plasma levels of brain natriuretic peptide (BNP), pro-inflammatory cytokines and antioxidant markers were assessed by using enzyme-linked immunosorbent assay (ELISA). Moreover, histopathological examination was applied to assess the degree of cardiac interstitial fibrosis. OPZ could statistically improve the hemodynamic parameters of the heart function, and could also obviously attenuate cardiac interstitial fibrosis in ISO-induced HF rats when compared with the ISO group. Besides, plasma level of BNP in ISO +100 mg/kg OPZ group dramatically decreased in comparison with that of ISO group. Moreover, compared with ISO group, OPZ treatment significantly reduced the levels of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). Moreover, OPZ treatment remarkably increased the levels of antioxidant markers such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) in ISO-induced HF rats. OPZ administration may provide experimental evidence for the possible effect of OPZ on isoproterenol-induced heart failure in rats. Moreover, OPZ administration may have potential utility for the treatment of heart failure.

Cardioprotective Efficacy of Coriandrum sativum (L.) Seed Extract in Heart Failure Rats Through Modulation of Endothelin Receptors and Antioxidant Potential

The present study aimed to evaluate the therapeutic and prophylactic potential of Coriandrum sativum extract in isoproterenol-induced heart failure (HF) in Wistar rats. Two weeks after the isoproterenol administration, rats developed severe impairment in left ventricular functions, reduced baroreflex sensitivity, and significant alteration in hemodynamic parameters and lipid profile. HF rats also exhibited enhanced lipid peroxidation and increased expression of endothelin receptors (ETA and ETB). Therapeutic and prophylactic treatment with C. sativum extract significantly (p < .05) improved the left ventricular functions and hemodynamic parameters and increased baroreflex sensitivity. It also inhibited lipid peroxidation, improved lipid profile, and downregulated the expression of endothelin receptors. Simvastatin treatment showed a similar cardioprotective effect. Our results suggest that C. sativum extract provides significant protection from heart failure possibly due to its ability to improve left ventricular functions and baroreflex sensitivity, attenuate lipid peroxidation, and modulate the expression of endothelin receptors.

Effects of Coriandrum Sativum Extract and Simvastatin in Isopreterenol Induced Heart Failure in Rats

Abstract Heart failure is a syndrome, caused due to structural and functional cardiac abnormalities, characterized by changes in the hemodynamic and neurohumoral mechanisms. It is becoming a major health burden worldwide. More effective therapies are desperately needed. Coriandrum sativum (C. sativum), a traditional spice crop has been known to possess many biological and medicinal properties. The present study was designed to investigate the cardioprotective efficacy of C. sativum in rat model of isoproterenol induced heart failure. Heart failure was produced by injecting isoproterenol subcutaneously (85 mg/kg twice at an interval of 24 h). Oral efficacy of seed extract was assessed on hemodynamic profile, antioxidant enzyme activities, lipid peroxidation, lipid profile, atherogenic indices, mRNA and protein expression of endothelin receptors (ETA and ETB) and histopathology. Treatment of heart failure rats with C. sativum orally (1g/kg b.wt) improved the altered hemodynamics, restored the cardiac antioxidant enzymes armory, attenuated oxidative stress, improved lipid profile, lowered atherogenic indices, decreased the levels of ETA and ETB receptor mRNA and protein, and restored the cardiac morphology. In conclusion, our results suggest C. sativum to be a cardioprotective agent in heart failure, possibly by the virtue of its ability to alleviate oxidative stress, improve lipid profile and endothelial dysfunction.

Critical role of the chymase/angiotensin-(1–12) axis in modulating cardiomyocyte contractility

BackgroundAngiotensin-(1–12) [Ang-(1–12)] is a chymase-dependent source for angiotensin II (Ang II) cardiac activity. The direct contractile effects of Ang-(1–12) in normal and heart failure (HF) remain to be demonstrated. We assessed the hypothesis that Ang-(1–12) may modulate [Ca2+]i regulation and alter cardiomyocyte contractility in normal and HF rats. Methods and resultsWe compared left ventricle (LV) myocyte contractile and calcium transient ([Ca2+]iT) responses to angiotensin peptides in 16 SD rats with isoproterenol-induced HF and 16 age-matched controls. In normal myocytes, versus baseline, Ang II (10−6 M) superfusion significantly increased myocyte contractility (dL/dtmax: 40%) and [Ca2+]iT (29%). Ang-(1–12) (4 × 10−6 M) caused similar increases in dL/dtmax (34%) and [Ca2+]iT (25%). Compared with normal myocytes, superfusion of Ang II and Ang-(1–12) in myocytes obtained from rats with isoproterenol-induced HF caused similar but significantly attenuated positive inotropic actions with about 42% to 50% less increases in dL/dtmax and [Ca2+]iT. Chymostatin abolished Ang-(1–12)-mediated effects in normal and HF myocytes. The presence of an inhibitory cAMP analog, Rp-cAMPS prevented Ang-(1–12)-induced inotropic effects in both normal and HF myocytes. Incubation of HF myocytes with pertussis toxin (PTX) further augmented Ang II-mediated contractility. ConclusionsAng-(1–12) stimulates cardiomyocyte contractile function and [Ca2+]iT in both normal and HF rats through a chymase mediated action. Altered inotropic responses to Ang-(1–12) and Ang II in HF myocytes are mediated through a cAMP-dependent mechanism that is coupled to both stimulatory G and inhibitory PTX-sensitive G proteins.

Cardioprotective Role of Myeloid-Derived Suppressor Cells in Heart Failure.

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that expand in cancer, inflammation, and infection and negatively regulate inflammation and the immune response. Heart failure (HF) is a complex clinical syndrome wherein inflammation induction and incomplete resolution can potentially contribute to HF development and progression. However, the role of MDSCs in HF remains unclear. The percentage of MDSCs in patients with HF and in mice with pressure overload-induced HF using isoproterenol infusion or transverse aortic constriction (TAC) was detected by flow cytometry. The effects of MDSCs on isoproterenol- or TAC-induced HF were observed on depleting MDSCs with 5-fluorouracil (50 mg/kg) or gemcitabine (120 mg/kg), transferring purified MDSCs, or enhancing endogenous MDSCs with rapamycin (2 mg·kg-1·d-1). Hypertrophic markers and inflammatory factors were detected by ELISA, real-time polymerase chain reaction, or Western blot. Cardiac functions were determined by echocardiography and hemodynamic analysis. The percentage of human leukocyte antigen-D-related (HLA-DR)-CD33+CD11b+ MDSCs in the blood of patients with HF was significantly increased and positively correlated with disease severity and increased plasma levels of cytokines, including interleukin-6, interleukin-10, and transforming growth factor-β. Furthermore, MDSCs derived from patients with HF inhibited T-cell proliferation and interferon-γ secretion. Similar results were observed in TAC- and isoproterenol-induced HF in mice. Pharmaceutical depletion of MDSCs significantly exacerbated isoproterenol- and TAC-induced pathological cardiac remodeling and inflammation, whereas adoptive transfer of MDSCs prominently rescued isoproterenol- and TAC-induced HF. Consistently, administration of rapamycin significantly increased endogenous MDSCs by suppressing their differentiation and improved isoproterenol- and TAC-induced HF, but MDSC depletion mostly blocked beneficial rapamycin-mediated effects. Mechanistically, MDSC-secreted molecules suppressed isoproterenol-induced hypertrophy and proinflammatory gene expression in cardiomyocytes in a coculture system. Neutralization of interleukin-10 blunted both monocytic MDSC- and granulocytic MDSC-mediated anti-inflammatory and antihypertrophic effects, but treatment with a nitric oxide inhibitor only partially blocked the antihypertrophic effect of monocytic MDSCs. Our findings revealed a cardioprotective role of MDSCs in HF by their antihypertrophic effects on cardiomyocytes and anti-inflammatory effects through interleukin-10 and nitric oxide. Pharmacological targeting of MDSCs by rapamycin constitutes a promising therapeutic strategy for HF.

178 Application of cardiac mri to quantitatively assess myocardial damage in isoproterenol-induced heart failure

IntroductionCardiovascular disease is the Number-1 cause-of-death globally with an estimation of 17.5 million deaths annually. Being one of the most active organs of the body, the heart is vulnerable to...

Protective effects of low-dose rosuvastatin on isoproterenol-induced chronic heart failure in rats by regulation of DDAH-ADMA-NO pathway.

Cardiovascular disease is the leading cause of death with high morbidity and mortality, and chronic heart failure is the terminal phase of it. This study aimed to investigate the protective effects of the low-dose rosuvastatin on isoproterenol-induced chronic heart failure and to explore the possible related mechanisms. Male Sprague Dawley rats were given isoproterenol 5mg/kg once a day for 7days to establish heart failure model by subcutaneous injection. Simultaneously, low-dose rosuvastatin (5mg/kg) was orally administrated from day 1 to day 14. Protective effects were evaluated by hemodynamic parameter, histopathological variables, serum asymmetric dimethylarginine (ADMA), cardiac troponin I (cTnI), brain natriuretic peptide (BNP) and myocardial nitric oxide (NO), and the levels of dimethylarginine dimethylaminohydrolase 2 (DDAH2), arginine methyltransferases 1 (PRMT1) and endothelial nitric oxide synthase (eNOS) expression were analyzed. Therapeutic rosuvastatin (5mg/kg) significantly attenuated isoproterenol-induced hypertrophy, remodeling and dysfunction of ventricle, reduced the increased serum content of ADMA, cTnI, and BNP, and elevated myocardial NO in rats (P<.05). Besides, rosuvastatin also significantly inhibited fibrosis of myocardium, normalized the increased PRMT1 and decreased DDAH2 expression. Low-dose rosuvastatin exerted cardioprotective effects on isoproterenol-induced heart failure in rats by modulating DDAH-ADMA-NO pathway, and it may present the new therapeutic value in ameliorating chronic heart failure.

A systems genetics approach identifies Trp53inp2 as a link between cardiomyocyte glucose utilization and hypertrophic response.

Cardiac failure has been widely associated with an increase in glucose utilization. The aim of our study was to identify factors that mechanistically bridge this link between hyperglycemia and heart failure. Here, we screened the Hybrid Mouse Diversity Panel (HMDP) for substrate-specific cardiomyocyte candidates based on heart transcriptional profile and circulating nutrients. Next, we utilized an in vitro model of rat cardiomyocytes to demonstrate that the gene expression changes were in direct response to substrate abundance. After overlaying candidates of interest with a separate HMDP study evaluating isoproterenol-induced heart failure, we chose to focus on the gene Trp53inp2 as a cardiomyocyte glucose utilization-specific factor. Trp53inp2 gene knockdown in rat cardiomyocytes reduced expression and protein abundance of key glycolytic enzymes. This resulted in reduction of both glucose uptake and glycogen content in cardiomyocytes stimulated with isoproterenol. Furthermore, this reduction effectively blunted the capacity of glucose and isoprotereonol to synergistically induce hypertrophic gene expression and cell size expansion. We conclude that Trp53inp2 serves as regulator of cardiomyocyte glycolytic activity and can consequently regulate hypertrophic response in the context of elevated glucose content.NEW & NOTEWORTHY Here, we apply a novel method for screening transcripts based on a substrate-specific expression pattern to identify Trp53inp2 as an induced cardiomyocyte glucose utilization factor. We further show that reducing expression of the gene could effectively blunt hypertrophic response in the context of elevated glucose content.

Cellular basis of angiotensin-(1-7)-induced augmentation of left ventricular functional performance in heart failure

BackgroundAngiotensin-(1-7) [Ang-(1-7)] exhibits cardiovascular effects opposite those of angiotensin II (Ang II), thus providing protection against heart disease. However, how Ang-(1-7) imparts cardioprotection is unclear, and its direct cardiac effects are controversial. Whether heart failure (HF) alters cardiac contractile responses to Ang-(1-7) remains undetermined. We tested the hypothesis that in HF, Ang-(1-7) may produce positive modulation on [Ca2+]i regulation, enhancing left ventricular (LV) and myocyte contraction and relaxation via Ang-(1-7) Mas receptor coupled with nitric oxide (NO)/bradykinin (BK)-mediated mechanism. Methods and resultsWe measured LV contractility changes after Ang-(1-7) (650ng/kg, iv) and compared myocyte functional and [Ca2+]i transient ([Ca2+]iT) responses to Ang-(1-7) superfusion in 24 normal rats and 34 rats with isoproterenol-induced HF (3months after 170mg/kg, s.q. for 2days). To assess the mechanisms of altered HF responses to Ang-(1-7), subsets of HF myocytes were pretreated to inhibit NO synthase (L-NAME), BK (HOE-140), and Mas receptor (A-779) followed with Ang-(1-7). In normal rats, Ang-(1-7) produced no significant changes in LV and myocyte function. In HF rats, Ang-(1-7) significantly augmented LV contractility and relaxation with increased EES (51%), but decreased τ compared to baseline. Ang-(1-7) also significantly increased myocyte contraction (dL/dtmax, 30%), relaxation (dR/dtmax, 41%), and [Ca2+]iT. L-NAME increased, HOE-140 decreased, and A-779 prevented HF myocyte contractile responses to Ang-(1-7). ConclusionsIn a rat model of HF, Ang-(1-7) increases [Ca2+]iT, and produces positive inotropic and lusitropic effects in the LV and myocytes. These effects are mediated by the Mas receptor and involve activation of NO/BK pathways.

Relaxin Ameliorates Renal Fibrosis and Expression of Endothelial Cell Transition Markers in Rats of Isoproterenol-Induced Heart Failure.

There may be cardio-renal interactions in rats of isoproterenol-induced heart failure, which may be associated with renal fibrosis and endothelial-to-mesenchymal transition (EndMT). Since its discovery, relaxin (RLX) which was regarded as a reproductive hormone for a long time, is recently considered an effective antifibrotic hormone in cardiac and renal fibrosis. We studied whether RLX diminished renal fibrosis in rats of isoproterenol (Iso)-induced heart failure and investigated the mechanism. Fifty male Sprague-Dawley rats were separated into five groups for treatment: control; Iso subcutaneously injection to induce heart failure, which led to renal fibrosis; RLX subcutaneously injection at low, medium and high dose (0.2, 2, 20 µg·kg-1·d-1 for 21 d). Indices of cardiac function and organ fibrosis were examined. Expression and changes in levels of collagen, cluster of differentiation 31 (CD31), α-smooth muscle actin (SMA), and transforming growth factor β (TGF-β) were measured in renal tissues. In rats with heart failure induced by Iso, treatment with RLX significantly ameliorated cardiac function and inhibited cardiac and renal fibrosis. RLX decreased renal collagen types I and III deposition, increased CD31 expression, and decreased the expression of α-SMA and TGF-β, thereby possibly indicating inhibited renal EndMT in kidneys. Iso-induced heart and renal fibrosis was inhibited even greater with high-dose RLX, so the antifibrotic effect of RLX may be dose-related. In conclusion, RLX may ameliorate renal fibrosis in rats of Iso-induced heart failure, and it is infered that prevention of the EndMT may be one of the possible potential signaling pathways.

Oxymatrine attenuated isoproterenol-induced heart failure in rats via regulation of COX-2/PGI2 pathway.

Oxymatrine (OMT) is an active constituent of traditional Chinese herb Sophora japonica Ait which has been shown to exert potent anti-inflammatory,anti-oxidant and anti-fibrosis properties. Our previous studies have demonstrated that OMT has protective effects on isoproterenol-induced heart failure in rats through regulation of DDAH/ADMA metabolism pathway.In this study,we further investigated whether OMT could attenuate isoproterenol-induced heart failure through the regulation of COX-2/PGI2 pathway. Heart failure was induced in Sprague-Dawley rats by 5mg/kg isoproterenol subcutaneous injection for 7days. The rats were maintained on normal diet and randomly divided into five groups: control, isoproterenol, isoproterenol with OMT (50, 100mg/kg), and OMT alone groups (n=12 in each group). Serum brain natruretic peptide (BNP, a heart failure biomarker), histopathological variables, expression of Cytosolic phospholipase A2 (cPLA2), cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2) and Prostacyclin synthase (PGIS) were analysed. Administration of OMT significantly reduced the increased BNP in plasm of isoproterenol-induced rats, attenuated cardiac fibrosis,suppressed overexpression of myocardial COX-1 expression, up-regulated COX-2 and PGIS expression, but had no effects on isoproterenol-induced elevated protein cPLA2. And compared with control group, any indexes in sham rats treated with OMT (100mg/kg) alone were unaltered. These results demonstrated that OMT has cardioprotective effects on isoproterenol-induced heart failure in rats by regulating COX-2/PGI2 pathway.

Genetic Dissection of Cardiac Remodeling in an Isoproterenol-Induced Heart Failure Mouse Model.

We aimed to understand the genetic control of cardiac remodeling using an isoproterenol-induced heart failure model in mice, which allowed control of confounding factors in an experimental setting. We characterized the changes in cardiac structure and function in response to chronic isoproterenol infusion using echocardiography in a panel of 104 inbred mouse strains. We showed that cardiac structure and function, whether under normal or stress conditions, has a strong genetic component, with heritability estimates of left ventricular mass between 61% and 81%. Association analyses of cardiac remodeling traits, corrected for population structure, body size and heart rate, revealed 17 genome-wide significant loci, including several loci containing previously implicated genes. Cardiac tissue gene expression profiling, expression quantitative trait loci, expression-phenotype correlation, and coding sequence variation analyses were performed to prioritize candidate genes and to generate hypotheses for downstream mechanistic studies. Using this approach, we have validated a novel gene, Myh14, as a negative regulator of ISO-induced left ventricular mass hypertrophy in an in vivo mouse model and demonstrated the up-regulation of immediate early gene Myc, fetal gene Nppb, and fibrosis gene Lgals3 in ISO-treated Myh14 deficient hearts compared to controls.

Disruption of Gravin's Scaffolding Protects against Isoproterenol Induced Heart Failure

β‐adrenergic receptor (β‐AR) signaling is the primary mechanism to increase cardiac contractility. However, chronic β‐AR stimulation, which occurs in HF, results in impairment of the β‐adrenergic pathway, leading to reduced contractility due in part by desensitization of these receptors. To induce contractility, β‐ARs signal through protein kinase A (PKA)‐dependent phosphorylation, which affects calcium homeostasis. PKA binds to A‐kinase anchoring proteins (AKAPs), which localize PKA and its substrates to defined intracellular locations. Gravin, an AKAP that targets PKA, protein kinase C (PKC) and protein phosphatase 2B (PP2B) to β2‐ARs, is involved in the modulation of the desensitization / resensitization cycle of β2‐ARs by facilitating PKA‐dependent phosphorylation and scaffolding of the β2‐AR complex. Thus, disruption of gravin's scaffolding action might prove beneficial to restore cardiac contractility during heart failure. In our studies, we used isoproterenol to chronically stimulate the β‐ARs to induce heart failure. We found that gravin‐t/t mice, harboring the truncated non‐functional gravin, leads to restriction of receptor desensitization during chronic β‐AR stimulation, due to loss in the assembly of the desensitization complex mediated by gravin's scaffolding. The β‐AR density is significantly higher in gravin‐t/t mice than wild‐type animals after 2 weeks of isoproterenol treatment. This decrease in the desensitization leads to the availability of more receptors on the heart to mediate chronotropy, ionotropy and lusitropy. Together, gravin‐t/t mice exhibited enhanced cardiac function in the presence of chronic β‐AR stimulation. PKA‐dependent substrates including cardiac troponin I (cTnI), phospholamban (PLB), and cardiac myosin binding protein C (cMyBPC), which show aberration activation patterns during heart failure, had normal phosphorylation levels in the gravin‐t/t mice, compared to the wild‐type mice. Gravin‐t/t mice also displayed enhanced myofilaments sensitivity to calcium compared to the wild‐type mice. Our results indicate that gravin plays an important role in regulating the β‐ AR pathway and disruption of its scaffolding augments cardiac function. Thus, blocking of gravin's scaffolding can be further explored as a potential therapeutic target for heart failure.Support or Funding InformationResearch reported in this poster was supported by the NHLBI institute of NIH under Award Number R01HL085487 (to B.K.M.) and R15HL124458 (to B.K.M.). This project was also supported by the Mouse Phenotyping Core at Baylor College of Medicine with funding from the NIH (U54 HG006348).