Vinh Q Chau

Adrenergic Receptor Blockade Reverses Right Heart Remodeling and Dysfunction in Pulmonary Hypertensive Rats

RATIONALE Most patients with pulmonary arterial hypertension (PAH) die from right heart failure. Beta-adrenergic receptor blockade reduces mortality by about 30% in patients with left-sided systolic heart failure, but is not used in PAH. OBJECTIVES To assess the effect of the adrenergic receptor blocker carvedilol on the pulmonary circulation and right heart in experimental pulmonary hypertension in rats. METHODS Angioproliferative pulmonary hypertension was induced in rats by combined exposure to the vascular endothelial growth factor-receptor antagonist SU5416 and hypoxia. Carvedilol treatment was started after establishment of pulmonary hypertension and right heart dysfunction. MEASUREMENTS AND MAIN RESULTS Compared with vehicle-treated animals, treatment with carvedilol resulted in increased exercise endurance; improved right ventricular (RV) function (increased tricuspid annular plane systolic excursion and decreased RV dilatation); and an increased cardiac output. The morphology of the pulmonary vessels and the RV afterload were not affected by carvedilol. Carvedilol treatment was associated with enhancement of RV fetal gene reactivation, increased protein kinase G (PKG) activity, and a reduction in capillary rarefaction and fibrosis. Metoprolol had similar but less pronounced effects in the SU5416 and hypoxia model. Cardioprotective effects were noted of both carvedilol and metoprolol in the monocrotaline model. In the case of carvedilol, but not metoprolol, part of these effects resulted from a prevention of monocrotaline-induced lung remodeling. CONCLUSIONS Adrenergic receptor blockade reverses RV remodeling and improves RV function in experimental pulmonary hypertension. Beta-adrenergic receptor blockers are not recommended in humans with PAH before their safety and efficacy are assessed in well-designed clinical trials.

Phosphodiesterase-5 Inhibitor, Tadalafil, Protects Against Myocardial Ischemia/Reperfusion Through Protein-Kinase G–Dependent Generation of Hydrogen Sulfide

Background— Tadalafil is a novel long-acting inhibitor of phosphodiesterase-5. Because cGMP-dependent protein kinase (PKG) signaling plays a key role in cardioprotection, we hypothesized that PKG activation with tadalafil would limit myocardial ischemia/reperfusion (I/R) injury and dysfunction. Additionally, we contemplated that cardioprotection with tadalafil is mediated by hydrogen sulfide (H2S) signaling in a PKG-dependent fashion. Methods and Results— After baseline transthoracic echocardiography (TTE), adult ICR mice were injected i.p. with vehicle (10% DMSO) or tadalafil (1 mg/kg) with or without KT5823 (KT, PKG blocker, 1 mg/kg) or dl-propargylglycine (PAG, Cystathionine-γ-lyase [CSE, H2S-producing enzyme] blocker; 50 mg/kg) 1 hour before coronary artery ligation for 30 minutes and reperfusion for 24 hours, whereas C57BL wild-type and CSE-knockout mice were treated with either vehicle or tadalafil. After reperfusion, TTE was performed and hearts were collected for infarct size (IS) measurement using TTC staining. Survival was increased with tadalafil (95%) compared with control (65%, P<0.05). Infarct size was reduced with tadalafil (13.2±1.7%) compared to vehicle (40.6±2.5%; P<0.05). KT and PAG abolished tadalafil-induced protection (IS: 39.2±1% and 51.2±2.4%, respectively) similar to genetic deletion of CSE (47.2±5.1%). Moreover, tadalafil preserved fractional shortening (FS: 31±1.5%) compared to control (FS: 22±4.8%, P<0.05). Baseline FS was 44±1.7%. KT and PAG abrogated the preservation of LV function with tadalafil by decline in FS to 17±1% and 23±3%, respectively. Compared to vehicle, myocardial H2S production was significantly increased with tadalafil and was abolished with KT. Conclusion— PKG activation with tadalafil limits myocardial infarction and preserves LV function through H2S signaling.

Cinaciguat, a novel activator of soluble guanylate cyclase, protects against ischemia/reperfusion injury: role of hydrogen sulfide

Cinaciguat (BAY 58-2667) is a novel nitric oxide (NO)-independent activator of soluble guanylate cyclase (sGC), which induces cGMP-generation and vasodilation in diseased vessels. We tested the hypothesis that cinaciguat might trigger protection against ischemia/reperfusion (I/R) in the heart and adult cardiomyocytes through cGMP/protein kinase G (PKG)-dependent generation of hydrogen sulfide (H(2)S). Adult New Zealand White rabbits were pretreated with 1 or 10 μg/kg cinaciguat (iv) or 10% DMSO (vehicle) 15 min before I/R or with 10 μg/kg cinaciguat (iv) at reperfusion. Additionally, adult male ICR mice were treated with either cinaciguat (10 μg/kg ip) or vehicle 30 min before I/R or at the onset of reperfusion (10 μg/kg iv). The PKG inhibitor KT5283 (KT; 1 mg/kg ip) or dl-propargylglycine (PAG; 50 mg/kg ip) the inhibitor of the H(2)S-producing enzyme cystathionine-γ-lyase (CSE) were given 10 and 30 min before cinaciguat. Cardiac function and infarct size were assessed by echocardiography and tetrazolium staining, respectively. Primary adult mouse cardiomyocytes were isolated and treated with cinaciguat before simulated ischemia/reoxygenation. Cinaciguat caused 63 and 41% reduction of infarct size when given before I/R and at reperfusion in rabbits, respectively. In mice, cinaciguat pretreatment caused a more robust 80% reduction in infarct size vs. 63% reduction when given at reperfusion and preserved cardiac function following I/R, which were blocked by KT and PAG. Cinaciguat also caused an increase in myocardial PKG activity and CSE expression. In cardiomyocytes, cinaciguat (50 nM) reduced necrosis and apoptosis and increased H(2)S levels, which was abrogated by KT. Cinaciguat is a novel molecule to induce H(2)S generation and a powerful protection against I/R injury in heart.

Mitigation of the progression of heart failure with sildenafil involves inhibition of RhoA/Rho-kinase pathway

Chronic inhibition of phosphodiesterase-5 with sildenafil immediately after permanent occlusion of the left anterior descending coronary artery was shown to limit ischemic heart failure (HF) in mice. To mimic a more clinical scenario, we postulated that treatment with sildenafil beginning at 3 days post-myocardial infarction (MI) would also reduce HF progression through the inhibition of the RhoA/Rho-kinase pathway. Adult male ICR mice with fractional shortening < 25% at day 3 following permanent left anterior descending coronary artery ligation were continuously treated with either saline (volume matched, ip, 2 times/day) or sildenafil (21 mg/kg, ip, 2 times/day) for 25 days. Echocardiography showed fractional shortening preservation and less left ventricular end-diastolic dilatation with sildenafil treatment compared with saline treatment at 7 and 28 days post-MI (P < 0.05). Both fibrosis and apoptosis, determined by Massons trichrome and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL), respectively, were attenuated in the sildenafil-treated mice (P < 0.05 vs. saline). Western blot analysis showed enchanced Bcl-2-to-Bax ratio with sildenafil treatment (P < 0.05 vs. saline). Activity assay showed sildenafil-mediated PKG activation 1 day after treatment (P < 0.05 vs. sham and saline). PKG activation was associated with sildenafil-mediated inhibition of Rho kinase (P < 0.05) compared with saline treatment, whereas PKG inhibition with KT-5823 abolished this inhibitory effect of sildenafil. In conclusion, for the first time, our findings show that chronic sildenafil treatment, initiated at 3 days post-MI, attenuates left ventricular dysfunction independent of its infarct-sparing effect, and this cardioprotection involves the inhibition of the RhoA/Rho-kinase pathway. Sildenafil may be a promising therapeutic tool for advanced HF in patients.

Interleukin-1 Trap Attenuates Cardiac Remodeling After Experimental Acute Myocardial Infarction in Mice

Background: Interleukin-1 (IL-1) is an inflammatory cytokine that responds as an acute phase reactant during acute myocardial infarction. Conflicting data describe the role of anti-IL-1 interventions to reduce cardiac remodeling after AMI. IL-1 Trap is a modified recombinant fusion protein that binds circulating IL-1. Our study evaluated the effects of murine IL-1 Trap on cardiac remodeling after AMI resulting from permanent surgical coronary artery ligation. Methods: Mice received treatment with intraperitoneal injection of murine IL-1 Trap (1 mg/kg [n = 5], 5 mg/kg [n = 5], or 30 mg/kg [n = 5]) or NaCl 0.9% (saline; n = 10) every 48 hours after surgery. Transthoracic echocardiography was performed at baseline and 7 days after surgery. Inhibition of IL-1 signaling was determined by measurement of IL-6 plasma levels (enzyme-linked immunosorbent assay) after IL-1β injection. Apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) was measured in murine heart samples and in a primary culture of murine cardiomyocytes. Results: Mice treated with 5 mg/kg or 30 mg/kg IL-1 Trap had more favorable cardiac remodeling and echocardiographic assessment of infarct size at 7 days compared with saline (P < 0.05 for each comparison). Treatment with IL-1 Trap also reduced apoptosis and IL-6 levels compared with saline treatment. Conclusions: IL-1 Trap ameliorates cardiac remodeling and reduces cardiomyocyte apoptosis after experimental acute myocardial infarction in the mouse.

Induction of MicroRNA-21 With Exogenous Hydrogen Sulfide Attenuates Myocardial Ischemic and Inflammatory Injury in Mice

Background—Maintaining physiological levels of hydrogen sulfide during ischemia is necessary to limit injury to the heart. Because of the anti-inflammatory effects of hydrogen sulfide, we proposed that the hydrogen sulfide donor, sodium sulfide (Na2S), would attenuate myocardial injury through upregulation of protective microRNA-21 (miR-21) and suppression of the inflammasome, a macromolecular structure that amplifies inflammation and mediates further injury. Methods and Results—Na2S-induced miR-21 expression was measured by quantitative polymerase chain reaction in adult primary rat cardiomyocytes and in the mouse heart. We measured inflammasome formation and activity in cardiomyocytes challenged with lipopolysaccharide and ATP or simulated ischemia/reoxygenation and in the heart after regional myocardial ischemia/reperfusion, in the presence or absence of Na2S. To assess the direct anti-inflammatory effects of hydrogen sulfide in vivo, we used a peritonitis model by way of intraperitoneal injection of zymosan A. Na2S attenuated inflammasome formation and activity, measured by counting cytoplasmic aggregates of the scaffold protein apoptosis speck-like protein containing a caspase-recruitment domain (−57%) and caspase-1 activity (−50%) in isolated cardiomyocytes and in the mouse heart (all P<0.05). Na2S also inhibited apoptosis (−38%) and necrosis (−43%) in cardiomyocytes in vitro and reduced myocardial infarct size (−63%) after ischemia/reperfusion injury in vivo (all P<0.05). These protective effects were absent in cells treated with the miR-21 eraser, antagomiR-21, and in miR-21 knockout mice. Na2S also limited the severity of inflammasome-dependent inflammation in the model of peritonitis (P<0.05) in wild-type but not in miR-21 knockout mice. Conclusions—Na2S induces cardioprotective effects through miR-21–dependent attenuation of ischemic and inflammatory injury in cardiomyocytes.

Pharmacologic inhibition of myeloid differentiation factor 88 (MyD88) prevents left ventricular dilation and hypertrophy after experimental acute myocardial infarction in the mouse.

Background: Myeloid differentiation factor 88 (MyD88) is an endogenous adaptor protein that coordinates the inflammatory response to agonists of the Toll-like receptor and interleukin-1 receptor families. This particular response is activated following myocardial ischemia and infarction and may represent a viable target for pharmacologic inhibition. The current study tested MyD88 inhibitors in a murine model of nonreperfused acute myocardial infarction (AMI). Methods: AMI was induced by permanent ligation of the left coronary artery. Adult, male, Imprinting Control Region mice were randomized to daily injections with 1 of 2 MyD88 pharmacologic inhibitors (ST2825 25 mg/kg or IMG2005 1 mg/kg), saline, or pretreatment with MyD88-targeted silencing small interfering RNA (siRNA) or scrambled nontargeted siRNA (n = 6 for each group). Echocardiography was performed at baseline and 7 days after surgery to evaluate pathologic cardiac enlargement. Results: Pharmacologic inhibition of MyD88 with ST2825 or IMG2005) and MyD88-targeted siRNA protected against left ventricular (LV) dilatation (reduced LV end-systolic and LV end-diastolic diameter) and hypertrophy. This protection occurred despite no measurable reduction in infarct size. Conclusions: Pharmacologic MyD88 inhibition protects against pathologic LV remodeling without altering infarct scar formation. MyD88 may be a viable target for pharmacologic inhibition in AMI.

Outcomes in patients with chronicity of left bundle- branch block with possible acute myocardial infarction

INTRODUCTION Guidelines derived from patients in clinical trials indicate that emergency department patients with likely myocardial infarction (MI) who have new left bundle-branch block (LBBB) should undergo rapid reperfusion therapy. Whether this pertains to lower risk emergency department patients with LBBB is unclear. METHODS A total of 401 consecutive patients with LBBB undergoing an MI rule-out protocol were included. Left bundle-branch blocks were classified as chronic; new; or, if no prior electrocardiogram (ECG) was available, as presumably new. Left bundle-branch blocks were considered concordant if there was ≥1 mm concordant ST elevation or depression. Rates of MI, peak MB values in MI patients, and 30-day mortality were compared across groups. RESULTS A majority of patients (64%) had new (37%) or presumably new LBBB (27%). A total of 116 patients (29%) had MI, with no significant difference in prevalence or size of MI among the 3 ECG groups. Myocardial infarction was diagnosed in 86% of patients with concordant ECG changes versus 27% of patients without concordant ECG changes (P < .01). Peak MB was >5× normal in 50% who had concordant ST changes compared to none of those who did not. Concordant ST changes were the most important predictor of MI (odds ratio 17, 95% CI 3.4-81, P < .001) and an independent predictor of mortality (odds ratio 4.3, 95% CI 1.3-15, P < .001); new or presumably new LBBB was neither. CONCLUSIONS Most patients with possible MI with new or presumably new LBBB do not have MI. Concordant ECG changes were an important predictor of MI and death. Current guidelines regarding early reperfusion therapy for patients with LBBB should be reconsidered.

Phosphodiesterase-5 inhibition and cardioprotection: potential role of hydrogen sulfide

Background Our laboratory has shown that phosphodiesterase-5 (PDE-5) inhibitors including sildenafil, vardenafil and tadalafil induce powerful protection against myocardial ischemia-reperfusion injury. We have shown that sildenafil protects through activation PKC, expression of eNOS/ iNOS, protein kinase G (PKG) and opening of mitochondrial KATP (mitoKATP) channels [1]. Hydrogen sulfide (H2S) is a gaseous molecule that is produced enzymatically and exerts physiological actions in the cardiovascular system. Similar to PKG, H2S has been shown to protect the heart via opening of mitoKATP channel [2]. In the current study, we hypothesized that tadalafil, the long acting inhibitor of PDE-5 mediates cardioprotection through H2S signaling in a PKG-dependent fashion.