Search

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is upregulated in congestive heart failure (CHF), contributing to electrical, structural, and functional remodeling. CaMKII inhibition is known to improve CHF, but its direct cardiac effects in CHF remain unclear. We hypothesized that CaMKII inhibition improves cardiomyocyte function, [Ca2+]i regulation, and β-adrenergic reserve, thus improving advanced CHF. In a 16-week study, we compared plasma neurohormonal levels and left ventricular (LV)- and myocyte-functional and calcium transient ([Ca2+]iT) responses in male Sprague-Dawley rats (10/group) with CHF induced by isoproterenol (170 mg/kg sq for 2 days). In rats with CHF, we studied the effects of the CaMKII inhibitor KN-93 or its inactive analog KN-92 (n = 4) (70 µg/kg per day, mini-pump) for 4 weeks. Compared with controls, isoproterenol-treated rats had severe CHF with 5-fold–increased plasma norepinephrine and about 50% decreases in ejection fraction (EF) and LV contractility [slope of LV end-systolic pressure–LV end-systolic volume relation (EES)] but increased time constant of LV relaxation (τ). They also showed significantly reduced myocyte contraction [maximum rate of myocyte shortening (dL/dtmax)], relaxation (dL/dtmax), and [Ca2+]iT. Isoproterenol superfusion caused significantly fewer increases in dL/dtmax and [Ca2+]iT. KN-93 treatment prevented plasma norepinephrine elevation, with increased basal and acute isoproterenol-stimulated increases in EF and EES and decreased τ in CHF. KN-93 treatment preserved normal myocyte contraction, relaxation, [Ca2+]iT, and β-adrenergic reserve, whereas KN-92 treatment failed to improve LV and myocyte function, and plasma norepinephrine remained high in CHF. Thus, chronic CaMKII inhibition prevented CHF-induced activation of the sympathetic nervous system, restoring normal LV and cardiomyocyte basal and β-adrenergic–stimulated contraction, relaxation, and [Ca2+]iT, thereby playing a rescue role in advanced CHF. SIGNIFICANCE STATEMENT We investigated the therapeutic efficacy of late initiation of chronic Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibition on progression of advanced congestive heart failure (CHF). Chronic CaMKII inhibition prevented CHF-induced activation of the sympathetic nervous system and restored normal intrinsic cardiomyocyte basal and β-adrenergic receptor–stimulated relaxation, contraction, and [Ca2+]i regulation, leading to reversal of CHF progression. These data provide new evidence that CaMKII inhibition is able and sufficient to rescue a failing heart, and thus cardiac CaMKII inhibition is a promising target for improving CHF treatment.

Background Angiotensin-(1–12) [Ang-(1–12)] is a renin-independent precursor for direct angiotensin-II production by chymase. Substantial evidence suggests that heart failure (HF) may alter cardiac Ang-(1–12) expression and activity; this novel Ang-(1–12)/chymase axis may be the main source for angiotensin-II deleterious actions in HF. We hypothesized that HF alters cardiac response to Ang-(1–12). Its stimulation may produce cardiac negative modulation and exacerbate left ventricle (LV) systolic and diastolic dysfunction. Methods and results We assessed the effects of Ang-(1–12) (2 nmol/kg/min, iv, 10 min) on LV contractility, LV diastolic filling, and LV-arterial coupling (AVC) in 16 SD male rats with HF-induced by isoproterenol (3 mo after 170 mg/kg sq. for 2 consecutive days) and 10 age-matched male controls. In normal controls, versus baseline, Ang-(1–12) increased LV end-systolic pressure, without altering heart rate, arterial elastance (EA), LV end-diastolic pressure (PED), the time constant of LV relaxation (τ) and ejection fraction (EF). Ang-(1–12) significantly increased the slopes (EES) of LV end-systolic pressure (P)-volume (V) relations and the slopes (MSW) of LV stroke wok-end-diastolic V relations, indicating increased LV contractility. AVC (quantified as EES/EA) improved. In contrast, in HF, versus HF baseline, Ang-(1–12) produced a similar increase in PES, but significantly increased τ, EA, and PED. The early diastolic portion of LV P V loop was shifted upward with reduced in EF. Moreover, Ang-(1–12) significantly decreased EES and MSW, demonstrating decreased LV contractility. AVC was decreased by 43%. Conclusions In both normal and HF rats, Ang-(1–12) causes similar vasoconstriction. In normal, Ang-(1–12) increases LV contractile function. In HF, Ang-(1–12) has adverse effects and depresses LV systolic and diastolic functional performance.

Acute myocardial infarction (AMI) is myocardial necrosis caused by the persistent interruption of myocardial blood supply, which has high incidence rate and high mortality in middle-aged and elderly people in the worldwide. Biomarkers play an important role in the early diagnosis and treatment of AMI. Recently, more and more researches confirmed that circRNA may be a potential diagnostic biomarker and therapeutic target for cardiovascular diseases. In this paper, a series of biological analyses were performed to find new effective circRNA biomarkers for AMI. Firstly, the expression levels of circRNAs in blood samples of patients with AMI and those with mild coronary stenosis were compared to reveal circRNAs which were involved in AMI. Then, circRNAs which were significant expressed abnormally in the blood samples of patients with AMI were selected from those circRNAs. Next, a ceRNA network was constructed based on interactions of circRNA, miRNA and mRNA through biological analyses to detect crucial circRNA associated with AMI. Finally, one circRNA was selected as candidate biomarker for AMI. To validate effectivity and efficiency of the candidate biomarker, fluorescence in situ hybridization, hypoxia model of human cardiomyocytes, and knockdown and overexpression analyses were performed on candidate circRNA biomarker. In conclusion, experimental results demonstrated that the candidate circRNA was an effective biomarker for diagnosis and therapy of AMI.

Background: Transgenic rats expressing the human angiotensinogen gene [TGR (hAogen) 1623] (hAogen) exhibit sustained hypertension and systolic dysfunction associated with altered cardiac renin-angiotensin system and β- adrenergic receptor (AR) signal transduction systems. We have shown previously, in contrast to β 1 - and β 2 -ARs, β 3 -ARs are linked to G i proteins, and stimulation of β 3 -ARs inhibits cardiac contraction and relaxation. Hypertension is associated with increased cardiac expression of G i proteins. This may alter β 3 -AR stimulation and play an important role in the cardiac functional impairment of this humanized model of hypertension. However, the alteration and functional effect of β 3 -AR activation in this model are unknown. We tested the hypothesis that high cardiac tissue Ang II content in hAogen may cause an up-regulation of cardiac β 3 -AR, which exacerbates myocyte dysfunction and impairs calcium regulation, thereby directly contributing to the cardiac dysfunction. Methods: We compared LV myocyte β 3 -AR expression and myocyte functional and [Ca 2+ ] i transient ([Ca 2+ ] iT ) responses to β- and β 3 -AR stimulation in myocytes obtained from 8 Sprague Dawley (SD) control and 8 hAogen male adult rats. Results: Versus SD, in hAGT rats, basal myocyte contraction (dL/dt max , 107.1 vs 138.8 μm/s), relaxation (dR/dt max , 94.0 vs 103.9 μm/s) and [Ca 2+ ] iT (0.15 vs 0.21) were depressed. A non-selective β-AR agonist, isoproterenol (ISO) (10 -8 M) produced significantly smaller increases in dL/dt max , (42% vs. 61%), dR / dtmax (35% vs. 51%), and [Ca 2+ ] iT (20% vs. 30%). Moreover, versus SD, in hAogen rats, LV myocyte β 3 -AR protein level increased by 32% (0.29 vs 0.22) with resulted significantly altered myocyte functional response to β 3 -AR stimulation. Compared with the changes in SD myocytes, in hAogen myocytes, BRL (10 -8 M) produced a significantly greater decreases in dL/dt max , (27% vs 12%), dR/dt max (28% vs 11%), and [Ca 2+ ] iT (17% vs 10%). Conclusions: TGR (hAogen) 1623, this humanized model of hypertension is associated with an up-regulation of LV myocyte β 3 -AR, which enhances β 3 -AR-caused inhibition of myocyte contractile, relaxation and [Ca 2+ ] iT and exacerbates β-AR desensitization, thereby directly contributing to the cardiac dysfunction.

Background: The negative inotrope and up-regulation of β 3 -adrenergic receptors (AR) in human and animal failing hearts suggest a direct and contributing role of cardiac β 3 -AR activation on the progression of congestive heart failure (CHF). However, its precise role is still being debated. We hypothesize that up-regulation of cardiac β 3 -AR is detrimental and chronic β 3 -AR blockade may prevent CHF-caused intrinsic defects of left ventricular (LV) myocyte force-generating capacity and relaxation and improve β-AR regulation, thereby limiting the progression of CHF. Methods: We compared the alterations of LV and myocyte functional responses and [Ca 2+ ] i transient ([Ca 2+ ] iT ) in SD rats divided into 3 groups (8/group): 1) CHF 3 months after isoproterenol (ISO) (170 mg/kg, sq, for 2 days); 2) ISO/β 3 -ANT , 2 months after receiving ISO, a selective β 3 -AR antagonist (ANT), L-748,337, was initiated (10 -7 M/kg/day, sq. by mini-pump) and was given for 1 month; and 3) Sham controls . Results: Compared with controls, the animals that received ISO treatment had CHF onset at 1 month and progressed to severe HF at 3 months after ISO. Plasma norepinephrine (NE) (1295 vs 259 pg/ml) increased 5-fold; whereas, stroke volume (SV) (39 vs 91 μl) and ejection fraction (EF) (39 vs 62%) significantly decreased, and LV end-diastolic pressure (P ED ) (13.9 vs 6.0 mmHg) was doubled. These changes were paralleled with about 50% reductions in cell contraction (dL/dt max , 93 vs 186 μm/s) and relaxation (dR/dt max , 96 vs 159 μm/s) associated with a significant decrease in the peak systolic [Ca 2+ ] iT , (0.17 vs 0.26). In addition, superfusion of ISO (10 -8 M) caused much less increases in dL/dt max (39 vs 68%), dR/dt max (23 vs 54%), and [Ca 2+ ] IT (14 vs 28%). Treatment with β 3 -ANT increased SV (89 μl) and EF (60%), decreased P ED more than 90% from ISO-treated values, and corrected the elevation of plasma NE (301 pg/ml), dL/dt max (184 μm/s), dR/dt max (152 μm/s), and [Ca 2+ ] iT (0.24). ISO-induced increase in dL/dt max and [Ca 2+ ] iT also returned close to control levels. Conclusion: Chronic β 3 -ANT treatment after CHF significantly improves LV and myocyte contractile function and [Ca 2+ ] i regulation and limits the development of CHF. Thus, β 3 -AR blocker may provide a new therapeutic strategy for the treatment of CHF.

Background: Natriuretic peptides (NPs) play a crucial role in maintaining cardiovascular homeostasis. NPs stimulate the production and release of cGMP, leading to the vasodilating and natriuretic actions. In heart failure (HF), circulating and cardiac ANP, BNP, and CNP are increased and exhibit a range of actions. However, although they serve as therapeutic agents, their direct cardiac effects in HF are uncertain due to the confounding influence of NPs-produced changes in loading condition on conventional measures of LV function. We test the hypothesis that equal hypotensive 3 NPs may have different inotropic effects on LV contractility and relaxation in HF. Methods: We assessed the cardiac effects of intravenous infusion (20 min) of ANP (2 μg/kg plus 0.5 μg/kg/min), BNP (2 μg/kg plus 0.04 μg/kg/min) and CNP (2 μg/kg plus 0.4 μg/kg/min) on different days in 6 instrumented conscious dogs with pacing-induced HF by using pressure (P)-volume (V) analysis, a load-independent measure of LV contractility. Results: Versus baselines, 3 NPs produced arterial vasodilation with similar and significant decreases in LV end-systolic pressure (10 to 12 mmHg) with relatively unchanged heart rate. ANP caused significant reductions (13%) of E ES (4.2 vs 4.8 mmHg/ml) and M SW (54.6 vs 62.8 mmHg). The time constant of LV relaxation (τ, 45.1 vs 37.6 ms) was lengthened. The LV-arterial coupling, E ES / E A (arterial elastance) (0.57 vs 0.58) was unaltered. The peak mitral flow, dV/dt max was only increased by 7% (178 vs 166 ml/s). With BNP, there were no significant changes in E ES (5.1 vs 4.9 mmHg/ml) and M SW, but E ES /E A was improved 30% (0.74 vs 0.57) due to decreased E A . τ (33.4 vs 37.9 ms) was significantly shortened and dV/dt max increased 15% (189 vs 165 ml/s). In contrast, CNP produced significant increases (~30%) in E ES (6.3 vs 4.8 mmHg/ml) and M SW (80.5 vs 62.4 mmHg) with enhanced increase in E ES /E A (50%, 0.87vs 0.58), but decrease in τ (25%, 28.4 vs 38.1 ms) and significantly greater augmented dV/dt max (25%, 205 vs 164 ml/s). Similar observations of NPs were made at constant heart rate, or after autonomic blockade. Conclusion: In conscious dogs with HF, equal hypotensive ANP, BNP and CNP have negative, no effect, and positive inotropic effects on LV contractility and relaxation, respectively.

AIMS: G protein-coupled estrogen receptor 30 (GPR30) activation by its agonist, G1, exhibits beneficial actions in female with heart failure (HF). Recent evidence indicates its cardiovascular benefits may also include male as well. However, whether and how GPR30 activation may limit HF progression and have a salutary role in males is unknown. We hypothesized that chronic G1 treatment improves LV and cardiomyocyte function, [Ca(2+)](i) regulation and β-adrenergic reserve, thus reversing HF progression in male. MAIN METHODS: We compared left ventricle (LV) and myocyte function, [Ca(2+)](i) transient ([Ca(2+)](iT)) and β-AR modulation in control male mice (12/group) and isoproterenol-induced HF (150 mg/kg s.c. for 2 days). Two weeks after isoproterenol injection, HF mice received placebo, or G1 (150 μg/kg/day s.c. mini-pump) for 2 weeks. KEY FINDINGS: Isoproterenol-treated mice exhibited HF with preserved ejection fraction (HFpEF) at 2-weeks and progressed to HF with reduced EF (HFrEF) at 4-weeks, manifested by significantly increased LV time constant of relaxation (τ), decreased EF and mitral flow (dV/dt(max)), which were accompanied by reduced myocyte contraction (dL/dt(max)), relaxation (dR/dt(max)) and [Ca(2+)](iT). Acute isoproterenol-superfusion caused significantly smaller increases in dL/dt(max), dR/dt(max) and [Ca(2+)](iT). G1 treatment in HF increased basal and isoproterenol-stimulated increases in EF and LV contractility of E(ES). Importantly, G1 improved basal and isoproterenol-stimulated dL/dt(max), dR/dt(max) and [Ca(2+)](iT) to control levels and restored normal cardiac β-AR subtypes modulation. SIGNIFICANCE: Chronic G1 treatment restores normal myocyte basal and β-AR-stimulated contraction, relaxation, and [Ca(2+)](iT), thereby reversing LV dysfunction and playing a rescue role in a male mouse model of HF.

Atrial structural and electrical remodelling play important roles in atrial fibrillation (AF). Sacubitril/valsartan attenuates cardiac remodelling in heart failure. However, the effect of sacubitril/valsartan on AF is unclear. The aim of this study was to evaluate the effect of sacubitril/valsartan on atrial electrical and structural remodelling in AF and investigate the underlying mechanism of action. Thirty-three rabbits were randomized into sham, RAP, and sac/val groups. HL-1 cells were subjected to control treatment or rapid pacing with or without LBQ657 and valsartan. Echocardiography, atrial electrophysiology, and histological examination were performed. The concentration of Ca2+ and expression levels of calcineurin, NFAT, p-NFAT, Cav1.2, collagen Ⅰ and Ⅲ, ANP, BNP, CNP, NT-proBNP, and ST2 in HL-1 cells, and IcaL in left atrial cells, were determined. We observed that compared to that in the sham group, the atrium and right ventricle were enlarged, myocardial fibrosis was markedly higher, AF inducibility was significantly elevated, and atrial effective refractory periods were shortened in the RAP group. These effects were significantly reversed by sacubitril/valsartan. Compared to that in the sham group, collagen Ⅰ and Ⅲ, NT-proBNP, ST2, calcineurin, and NFAT were significantly up-regulated, while p-NFAT and Cav1.2 were down-regulated in the RAP group, and sacubitril/valsartan inhibited these changes. Ca2+ concentration increased and ICaL density decreased in in vivo and in vitro AF models, reversed by sacubitril/valsartan. Sacubitril/valsartan attenuates atrial electrical remodelling and ameliorates structure remodelling in AF. This study paves the way for the possibility of clinical use of sacubitril/valsartan in AF patients.

3-Bromopyruvate (3-BrPA) is a promising agent that has been widely studied in the treatment of cancer and pulmonary hypertension. Rotenone is a pesticide commonly used on farms and was shown to have anti-cancer activity and delay fibrosis progression in chronic kidney disease in a recent study. However, there are few studies showing the toxicity of rotenone and 3-BrPA in the myocardium. To support further medical exploration, it is necessary to clarify the side effects of these compounds on the heart. This study was designed to examine the cardiotoxicity of 3-BrPA and rotenone by investigating electrical and structural cardiac remodeling in rats. Forty male rats were divided into 4 groups (n = 10 in each group) and injected intraperitoneally with 3-BrPA, rotenone or a combination of 3-BrPA and rotenone. The ventricular effective refractory period (VERP), corrected QT interval (QTc), and ventricular tachycardia/ventricular fibrillation (VT/VF) inducibility were measured. The expression of Cx43, Kir2.1, Kir6.2, DHPRα1, KCNH2, caspase3, caspase9, Bax, Bcl2, and P53 was detected. Masson's trichrome, TUNEL, HE, and PAS staining and transmission electron microscopy were used to detect pathological and ultrastructural changes. Our results showed that rotenone alone and rotenone combined with 3-BrPA significantly increased the risk of ventricular arrhythmias. Rotenone combined with 3-BrPA caused myocardial apoptosis, and rotenone alone and rotenone combined with 3-BrPA caused electrical and structural cardiac remodeling in rats.

Background: Atrial fibrillation (AF) is an important and growing clinical problem. Current pharmacological treatments are unsatisfactory. Electrical remodeling has been identified as one of the principal pathophysiological mechanisms that promote AF, but there are no effective therapies to prevent or correct electrical remodeling in patients with AF. In AF, cardiac production and circulating levels of B-type natriuretic peptide (BNP) are increased. However, its functional significance in AF remains to be determined. We assessed the hypotheses that chronic BNP treatment may prevent the altered electrophysiology in AF, and preventing AF-induced activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) may play a role. Methods and Results: Forty-four rabbits were randomly divided into sham, rapid atrial pacing (RAP at 600 beats/min for 3 weeks), RAP/BNP, and sham/BNP groups. Rabbits in the RAP/BNP and sham/BNP groups received subcutaneous BNP (20 μg/kg twice daily) during the 3-week study period. HL-1 cells were subjected to rapid field stimulation for 24 hours in the presence or absence of BNP, KN-93 (a CaMKII inhibitor), or KN-92 (a nonactive analog of KN-93). We compared atrial electrical remodeling-related alterations in the ion channel/function/expression of these animals. We found that only in the RAP group, AF inducibility was significantly increased, atrial effective refractory periods and action potential duration were reduced, and the density of I Ca, L and I to decreased, while I K1 increased. The changes in the expressions of Cav1.2, Kv4.3, and Kir2.1 and currents showed a similar trend. In addition, in the RAP group, the activation of CaMKIIδ and phosphorylation of ryanodine receptor 2 and phospholamban significantly increased. Importantly, these changes were prevented in the RAP/BNP group, which were further validated by in vitro studies. Conclusions: Chronic BNP therapy prevents atrial electrical remodeling in AF. Inhibition of CaMKII activation plays an important role to its anti-AF efficacy in this model.

Background Whether chronic obstructive sleep apnea ( OSA ) could promote epicardial adipose tissue ( EAT ) secretion of profibrotic adipokines, and thereby contribute to atrial fibrosis, and the potential therapeutic effects of metoprolol remain unknown. Methods and Results A chronic OSA canine model was established by repeatedly clamping the endotracheal tube for and then reopening it for 4 hours every other day for 12 weeks. In a metoprolol treatment group, metoprolol succinate was administered daily for 12 weeks. The EAT infiltration and left atrial fibrosis were examined. The expressions of adipokines secreted by EAT and hypoxic 3T3‐L1 adipocytes were detected. The changes in collagen synthesis, transforming growth factor‐β1 expression, and cell differentiation and proliferation in cardiac fibroblasts induced by hypoxic 3T3‐L1 adipocyte‐derived conditioned medium were further analyzed. Chronic OSA induced infiltration of EAT into the left atrium. OSA enhanced the profibrotic effect of EAT on the adjacent atrial myocardium. Moreover, OSA induced profibrotic cytokine secretion from EAT . We also found that hypoxia induced adipokine secretion in cultured adipocytes, and the medium conditioned by the hypoxic adipocytes increased collagen and transforming growth factor‐β1 protein expression and cell proliferation of cardiac fibroblasts. More importantly, metoprolol attenuated infiltration of EAT and alleviated the profibrotic effect of EAT by inhibiting adipokine secretion. Metoprolol also inhibited hypoxia‐induced adipokine secretion in adipocytes and thereby blocked the hypoxic adipocyte–derived conditioned medium–induced fibrotic response of cardiac fibroblasts. Conclusions Chronic OSA enhanced the profibrotic effect of EAT on the neighboring atrial myocardium by stimulating the secretion of profibrotic adipokines from EAT , which was significantly attenuated by metoprolol. This study gives insights into mechanisms underlying OSA ‐induced atrial fibrillation and also provides experimental evidence for the protective effects of metoprolol.

An increase in oxidative stress is an important pathological mechanism of heart injury induced by doxorubicin (DOX). Tranilast is an anti-allergy drug that has been shown to possess good antioxidant activity in previous studies. The overexpression and secretion of chymase by mast cells (MCs) increase the pathological overexpression of angiotensin II (Ang II), which plays a crucial role in myocardial hypertrophy and the deterioration of heart disease. The MC stabilizer tranilast (N-(3,4-dimethoxycinnamoyl) anthranilic acid; tran) prevents mast cells from degranulating, which may reduce DOX-induced Ang II synthesis. Therefore, in the present study, we hypothesized that tranilast will protect rats from DOX-induced myocardial damage via its antioxidant activity, thereby inhibiting Ang II expression. Thirty male Wistar rats were divided into three groups (n = 10 in each group) that received DOX, a combination of DOX and tranilast or saline (the control group) to test this hypothesis. Tranilast suppressed chymase expression, reduced Ang II levels and prevented the myocardial hypertrophy and the deterioration of heart function induced by DOX. Based on the findings of the present study, the suppression of chymase-dependent Ang-II production and the direct effect of tranilast on the inhibition of apoptosis and fibrosis because of its antioxidant stress capacity may contribute to the protective effect of tranilast against DOX-induced myocardial hypertrophy.

In heart failure (HF), the impaired left ventricular (LV) arterial coupling and diastolic dysfunction present at rest are exacerbated during exercise. C-type natriuretic peptide (CNP) is elevated in HF; however, its functional effects are unclear. We tested the hypotheses that CNP with vasodilating, natriuretic, and positive inotropic and lusitropic actions may prevent this abnormal exercise response after HF. We determined the effects of CNP (2 μg/kg plus 0.4 μg/kg per minute, i.v., 20 minutes) on plasma levels of cGMP before and after HF and assessed LV dynamics during exercise in 10 chronically instrumented dogs with pacing-induced HF. Compared with the levels before HF, CNP infusion caused significantly greater increases in cGMP levels after HF. After HF, at rest, CNP administration significantly reduced LV end-systolic pressure (PES), arterial elastance (EA), and end-diastolic pressure. The peak mitral flow (dV/dtmax) was also increased owing to decreased minimum LVP (LVPmin) and the time constant of LV relaxation (τ) (P < 0.05). In addition, LV contractility (EES) was increased. The LV-arterial coupling (EES/EA) was improved. The beneficial effects persisted during exercise. Compared with exercise in HF preparation, treatment with CNP caused significantly less important increases in PES but significantly decreased τ (34.2 vs. 42.6 ms) and minimum left ventricular pressure with further augmented dV/dtmax. Both EES, EES/EA (0.87 vs. 0.32) were increased. LV mechanical efficiency improved from 0.38 to 0.57 (P < 0.05). After HF, exogenous CNP produces arterial vasodilatation and augments LV contraction, relaxation, diastolic filling, and LV arterial coupling, thus improving LV performance at rest and restoring normal exercise responses after HF.

Background Angiotensin-(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 [Ca 2+ ] i regulation and alter cardiomyocyte contractility in normal and HF rats. Methods and results We compared left ventricle (LV) myocyte contractile and calcium transient ([Ca 2+ ] 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/dt max : 40%) and [Ca 2+ ] iT (29%). Ang-(1–12) (4 × 10 −6 M) caused similar increases in dL/dt max (34%) and [Ca 2+ ] 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/dt max and [Ca 2+ ] 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. Conclusions Ang-(1–12) stimulates cardiomyocyte contractile function and [Ca 2+ ] 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.

Objective: Recent evidence has shown that, in heart failure (HF), clinically relevant concentrations of angiotensin-(1-7) [Ang-(1-7)] counteracts angiotensin II induced cardiac depression and produces positive inotropic effects in both left ventricle (LV) and myocytes. However, the underlying electrophysiological mechanism is unclear. We investigated the role and mechanism of Ang-(1-7) on LV myocyte L-type calcium current (ICa,L) responses in normal state and in HF. Method: We compared the effect of Ang-(1-7) (10−5 M) on ICa,L responses in isolated LV myocytes obtained from 11 rats with isoproterenol (ISO) induced HF (3 months after 170 mg/kg subcutaneous for 2 days) and from 8 age-matched normal control rats by patch clamp technique. Results: In normal myocytes, compared with baseline, superfusion of Ang-(1-7) caused no significant changes in ICa,L (8.2 ± 0.2 versus 8.0 ± 0.3 pA/pF, p= not significant). In HF myocytes, the baseline ICa,L was significantly reduced (5.3 ± 0.1 versus 8.0 ± 0.3 pA/pF, p < 0.01). Ang-(1-7) produced a 21% increase in ICa,L (6.4±0.1 versus 5.3±0.1 pA/pF, p < 0.01). Pretreatment of HF myocytes with a nitric oxide (NO) synthase inhibitor (L-NAME, 10−5 M) resulted in a significantly greater increase in ICa,L (28%, 8.4 ± 0.1 versus 6.5 ± 0.1 pA/pF, p < 0.01) during Ang-(1-7) superfusion. In contrast, during incubation with the bradykinin (BK) inhibitor HOE 140 (10−6 M), Ang-(1-7) induced increase in ICa,L was significantly decreased. The Ang-(1-7) induced increase in ICa,L was abolished by [D-Ala7]-Ang-(1-7) (A-779, 10−5 M). Conclusions: HF alters the response of ICa,L to Ang-(1-7). In normal myocytes, Ang-(1-7) has no significant effect on ICa,L. However, in HF myocytes, Ang-(1-7) increases ICa,L. These effects are mediated by the Ang-(1-7) Mas receptors and involve activation of NO/BK pathways.

Background: In addition to its well-known vasodilating and natriuretic actions, C-type natriuretic peptide (CNP), has been viewed as an endogenous inhibitor of the renin-angiotensin system, but its...

Angiotensin-(1-12) [Ang-(1-12)] functions in rodents and humans as a tissue substrate for the direct generation of Ang II via chymase. Since its direct cardiac effect have not been studied, the importance of this renin-independent mechanism for Ang II paracrine/intracrine actions in modulating cardiac contractility were determined in freshly isolated myocytes from 11 normal SD rats. Systolic amplitude (SA), peak velocity of shortening (dL/dtmax), the peak velocity of relengthening (dR/dtmax), and changes in the peak calcium transient ([Ca2+]i) were evaluated before and following exposure to Ang II (10-6 M), Ang-(1-12) delivered alone (range: 2x10-6 to 4x10-6 M) or after 1 h incubation with human recombinant chymase (10 μg protein/mL at 37°C). Both Ang II and the mixture of Ang-(1-12) with chymase elicited positive inotropic responses in freshly isolated cardiac myocytes associated with significant increases in peak systolic [Ca2+]i (Figure) while superfusion of Ang-(1-12) alone elicited an increase in dL/dtmax without significant changes in [Ca2+]i. The increases in contractility elicited by Ang II or the Ang-(1-12)/chymase mixture were abolished by prior exposure of the myocytes to losartan (10-5 M) or the chymase inhibitor chymostatin (8x10-5 M). We conclude that in single adult rat myocytes Ang-(1-12) stimulates contractile function through a chymase mediated action and by mechanisms that implicate a paracrine/intracrine activation of intracellular calcium.

Background: Accumulating evidence suggests that Angiotensin (A)-(1-7) exhibits cardiovascular effects that are in opposition to that of AII, thus providing protection against heart diseases. However, the exact means by which A-(1-7) affords cardioprotection are unclear. Its direct cardiac effect is not well understood. We previously showed that in heart failure (HF), AII decreases left ventricle (LV) contractility. Whether A-(1-7) may antagonize AII-induced cardiac depression, thereby contributing to its beneficial actions in HF remains to be determined. We assessed the hypothesis that A-(1-7) may produce positive modulation on [Ca 2+ ] i regulation and LV and myocyte contraction via A-(1-7) receptors, coupled with nitric oxide (NO)/bradykinin (BK)-mediated mechanism. Methods: We measured LV contractility changes after A-(1-7) (650 ng/kg, iv), which produced a 20-fold increase in plasma A-(1-7) levels, mimicking the elevations caused by angiotensin-converting enzyme inhibitor therapy in HF, and compared myocyte contractile, [Ca 2+ ] i transient ([Ca 2+ ] iT ) and I Ca,L responses to A-(1-7) (10 -5 M) in 14 rats with isoproterenol induced HF (3 months after 170 mg/kg sq for 2 days). In the subsets of cell contractile study, myocytes were pretreated to inhibit NO synthase (L-NAME, 10 -5 M), BK (HOE 140, 10 -6 M) or A-(1-7) receptor [D-Ala 7 ]-A-(1-7), 10 -5 M) followed with A-(1-7) exposure. Results: Compared with baseline, after A-(1-7), E ES (47%, 1.0 vs 0.68 mmHg/μl) and M SW (49%, 94.3 vs 62.8 mmHg) were increased, indicating enhanced LV contractility. In HF myocytes, A-(1-7) increased myocyte percent shortening (28%, 6.8% vs 5.3%), the velocity of contraction (31%, 106.4 vs 74.5 μm/sec) and relengthening (41%, 74.7vs 50.1 μm/sec) accompanied by significantly-increased [Ca 2+ ] iT (27%, 0.19 vs 0.15 pA/pF) and I Ca,L (24%, 6.3 vs 5.1pA/pF). L-NAME increased, HOE 140 decreased, and A-(1-7) receptor blockade prevented myocyte contractile responses to A-(1-7). Conclusion: In HF, clinically-relevant concentrations of A-(1-7) counteracted AII-induced cardiac depression, increased [Ca 2+ ] iT and I Ca,L , and produced positive inotropic effects in both LV and myocytes. These effects are coupled with A-(1-7) receptors and involve activation of NO/BK pathways.

Background: Sildenafil (SIL), a selective inhibitor of PDE5 has been shown to exert profound beneficial effects in heart failure (HF). Recently we further found that SIL caused regression of cardiac dysfunction in a rat model with isoproterenol (ISO)-induced progressive HF. However, the molecular basis is unclear. We hypothesized that reversal of HF-induced detrimental alterations on the expressions of cardiac SR Ca 2+ -ATPase (SERCA2a), β-adrenergic receptors (AR) and nitric oxide synthase (NOS) isoforms by SIL may play a key role for its salutary role in HF. Methods: Left ventricular (LV) and myocyte function and the protein levels of myocyte β 1 - and β 3 - AR, SERCA2a, phospholamban (PLB) and three NOS were simultaneously evaluated in 3 groups of male rats (6/group): HF , 3 months (M) after receiving ISO (170 mg/kg sq for 2 days); HF/SIL , 2 M after receiving ISO, SIL (70 μg/kg/day sq via mini pump) was initiated and given for 1 M; and Controls (C). Results: Compared with controls, ISO-treated rats progressed to severe HF at 3 M after ISO followed by significantly decreased LV contractility (E ES , HF: 0.7 vs C: 1.2 mmHg/μl) and slowed LV relaxation, reductions in the peak velocity of myocyte shortening (77 vs 136 μm/sec), relengthening (62 vs 104 μm/sec) and [Ca 2+ ] iT (0.15 vs 0.24) accompanied by a diminished myocyte inotropic response to β-AR agonist, ISO (10 -8 M). These abnormalities were associated with concomitant significant decreases in myocyte protein levels of β 1 -AR (0.23 vs 0.64), SERCA2a (0.46 vs 0.80), PLB Ser16 /PLB ratio (0.24 vs 0.40) and eNOS (0.28 vs 0.46), but significantly increases in protein levels of β 3 -AR (0.29 vs 0.10) and iNOS (0.18 vs 0.08) with relatively unchanged nNOS. Chronic SIL prevented the HF-induced decreases in LV and myocyte contraction, relaxation, peak [Ca 2+ ] iT , and restored normal myocyte contractile response to ISO stimulation. With SIL, protein levels of myocyte β 1 - and β 3 -AR, SERCA2a were restored close to control values, but eNOS was significantly elevated than controls (0.77). Conclusions: Chronic SIL prevents HF-caused downregulation of cardiac β 1 -AR and reverse contrast changes between iNOS and β 3 -AR with SERCA 2a and eNOS expression, leading to the preservation of LV and myocyte function, [Ca 2+ ] iT , and β-adrenergic reserve.

Three europium complexes 1-methyl-4-octadecylpyridinium tetrakis(α-thenoyl trifluoroacetonato) europium(III), tris(α-thenoyl trifluoroacetonato) mono-(9-(4-hexadecylanilino)-4,5-diazafluorene) europium(III), and tris(α-thenoyltrifluoro acetonato) mono(2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline) europium(III) have been newly synthesized. They were capable of forming stable Langmuir films on pure water subphase(pH 5.6, 18 °C) with collapse pressures of 39.0, 50.0 and 20.5 mN/m, respectively. Langmuir-Blodgett films of these complexes have been prepared and studied by surface pressure-area isotherms, ultraviolet, fluorescent spectroscopy, fluorescent lifetime measurements and second-harmonic generation.

A series of lanthanoid complexes (E)-1-ferrocenyl-2-(N-hexadecylpyridinium-4-yl)ethylene tetrakis(dibenzoylmethanato)lanthanoides(III) (La, Nd, Dy and Yb) have been newly synthesized for second-order nonlinear optical LB materials. The monolayer behaviors at the air-water interface, ultraviolet spectra and second-harmonic generation (SHG) of the films have been reported. The values of second-order molecular hyperpolarizability β of the complexes were estimated to be (1.37–1.58) × 10−28 esu.