Unraveling the Metabolic Derangements Occurring in Non-infarcted Areas of Pig Hearts With Chronic Heart Failure.

Objective: After myocardial infarction (MI), the non-infarcted left ventricle (LV) ensures appropriate contractile function of the heart. Metabolic disturbance in this region greatly exacerbates post-MI heart failure (HF) pathology. This study aimed to provide a comprehensive understanding of the metabolic derangements occurring in the non-infarcted LV that could trigger cardiovascular deterioration. Methods and Results: We used a pig model that progressed into chronic HF over 3 months following MI induction. Integrated gene and metabolite signatures revealed region-specific perturbations in amino acid- and lipid metabolism, insulin signaling and, oxidative stress response. Remote LV, in particular, showed impaired glutamine and arginine metabolism, altered synthesis of lipids, glucose metabolism disorder, and increased insulin resistance. LPIN1, PPP1R3C, PTPN1, CREM, and NR0B2 were identified as the main effectors in metabolism dysregulation in the remote zone and were found differentially expressed also in the myocardium of patients with ischemic and/or dilated cardiomyopathy. In addition, a simultaneous significant decrease in arginine levels and altered PRCP, PTPN1, and ARF6 expression suggest alterations in vascular function in remote area. Conclusions: This study unravels an array of dysregulated genes and metabolites putatively involved in maladaptive metabolic and vascular remodeling in the non-infarcted myocardium and may contribute to the development of more precise therapies to mitigate progression of chronic HF post-MI.

Rapid Production of Human VEGF-A following Intradermal Injection of Modified VEGF-A mRNA Demonstrated by Cutaneous Microdialysis in the Rabbit and Pig In Vivo.

Chemically modified mRNA is a novel, highly efficient, biocompatible modality for therapeutic protein expression that may overcome the challenges and safety concerns with current gene therapy strategies. We explored the efficiency of intradermally injected modified VEGF-A165 mRNA (VEGF-A mRNA) formulated in a biocompatible citrate/saline buffer to locally produce human VEGF-A165 protein. Rabbits (n=4) and minipigs (n=3) were implanted with subcutaneous microdialysis probes close to the injection sites and interstitial-fluid samples and skin biopsies were analysed for production of VEGF-A protein over time for up to 8 hours. Three to 4 hours after the intradermal injection of VEGF-A mRNA, detectable levels of human VEGF-A protein were seen in the microdialysis eluates in both species. In the pig, the VEGF-A concentrations increased dose-dependently reaching a maximum 6 hours after dosing (62.7±28.4, 357.6±240.6, and 746.3±210.2 pg/mL following injection of 24, 120, and 600 µg VEGF-A mRNA, respectively). Likewise, in tissue biopsies harvested at study end (8 hours after VEGF-A mRNA injection), the content of VEGF-A protein increased dose-dependently. In contrast, VEGF-A protein was not detected in eluates originating from sites injected with citrate/saline vehicle. It is concluded that intradermal injection of VEGF-A mRNA is associated with a rapid and local production of VEGF-A protein. Considering the pro-angiogenic effect of VEGF-A, VEGF-A mRNA may hold promise for regenerative treatment of patients with diabetic wounds and ischemic cardiovascular disease.

Biocompatible, Purified VEGF-A mRNA Improves Cardiac Function after Intracardiac Injection 1 Week Post-myocardial Infarction in Swine.

mRNA can direct dose-dependent protein expression in cardiac muscle without genome integration, but to date has not been shown to improve cardiac function in a safe, clinically applicable way. Herein, we report that a purified and optimized mRNA in a biocompatible citrate-saline formulation is tissue specific, long acting, and does not stimulate an immune response. In small- and large-animal, permanent occlusion myocardial infarction models, VEGF-A 165 mRNA improves systolic ventricular function and limits myocardial damage. Following a single administration a week post-infarction in mini pigs, left ventricular ejection fraction, inotropy, and ventricular compliance improved, border zone arteriolar and capillary density increased, and myocardial fibrosis decreased at 2 months post-treatment. Purified VEGF-A mRNA establishes the feasibility of improving cardiac function in the sub-acute therapeutic window and may represent a new class of therapies for ischemic injury.

Is the acetylcholine-regulated inwardly rectifying potassium current a viable antiarrhythmic target? Translational discrepancies of AZD2927 and A7071 in dogs and humans.

AIMS: We aimed at examining the acetylcholine-dependent inward-rectifier current (IKAch) as a target for the management of atrial fibrillation (AF). METHODS AND RESULTS: The investigative agents AZD2927 and A7071 concentration-dependently blocked IKACh in vitro with minimal off-target activity. In anaesthetized dogs (n = 17) subjected to 8 weeks of rapid atrial pacing (RAP), the left atrial effective refractory period (LAERP) was maximally increased by 50 ± 7.4 and 50 ± 4.8 ms following infusion of AZD2927 and A7071. Ventricular refractoriness and the QT interval were unaltered. During sustained AF, both drugs significantly reduced AF frequency and effectively restored sinus rhythm. AZD2927 successfully restored sinus rhythm at 10/10 conversion attempts and A7071 at 14/14 attempts, whereas saline converted 4/17 episodes only (P<0.001 vs. AZD2927 and A7071). In atrial flutter patients (n = 18) undergoing an invasive investigation, AZD2927 did not change LAERP, the paced QT interval, or ventricular refractoriness when compared with placebo. To address the discrepancy on LAERP by IKACh blockade in man and dog and the hypothesis that atrial electrical remodelling is a prerequisite for IKACh blockade being efficient, six dogs were studied after 8 weeks of RAP followed by sinus rhythm for 4 weeks to reverse electrical remodelling. In these dogs, both AZD2927 and A7071 were as effective in increasing LAERP as in the dogs studied immediately after the 8-week RAP period. CONCLUSION: Based on the present series of experiments, an important role of IKACh in human atrial electrophysiology, as well as its potential as a viable target for effective management of AF, may be questioned.

Lactam sulfonamides as potent inhibitors of the Kv1.5 potassium ion channel.

A series of lactam sulfonamides has been discovered and optimized as inhibitors of the Kv1.5 potassium ion channel for treatment of atrial fibrillation. In vitro structure-activity relationships from lead structure C to optimized structure 3y are described. Compound 3y was evaluated in a rabbit PD-model and was found to selectively prolong the atrial effective refractory period at submicromolar concentrations.

Electrophysiological characterization and antiarrhythmic efficacy of the mixed potassium channel-blocking antiarrhythmic agent AZ13395438 in vitro and in vivo.

OBJECTIVE: To examine the electrophysiological, hemodynamic, and antiarrhythmic effects of the novel antiarrhythmic agent AZ13395438. METHODS: The ion channel-blocking potency of AZ13395438 was assessed in Chinese hamster ovary cells stably expressing various human cardiac ion channels and in human atrial myocytes. The in vivo electrophysiological, hemodynamic, and antiarrhythmic effects of intravenously administered AZ13395438 were examined in anesthetized rabbits, in anesthetized naive dogs, and in dogs subjected to rapid atrial pacing (RAP) for 8 weeks. Pharmacokinetic/pharmacodynamic (PKPD) modeling was applied to predict the potency of AZ13395438 in increasing atrial and ventricular refractoriness. RESULTS: AZ13395438 potently and predominantly blocked the atrial repolarizing potassium currents I(Kur), I(Ach), and I(to) in vitro. In vivo, AZ13395438 caused a concentration-dependent and selective increase in atrial refractoriness with no or small effects on ventricular refractoriness and repolarization and on hemodynamics in both rabbits and dogs. The PKPD modeling predicted unbound plasma concentrations of AZ13395438 of 0.20 ± 0.039, 0.38 ± 0.084, and 0.34 ± 0.057 µmol/L to increase the right atrial effective refractory period by 20 milliseconds in the rabbit and in the naive and the RAP dogs, respectively. In the RAP dog with atrial fibrillation (AF), AZ13395438 significantly increased AF cycle length and successfully converted AF to sinus rhythm in 12 of the 12 occasions at an unbound plasma concentration of 0.48 ± 0.076 µmol/L. During saline infusion, conversion was seen only in 4 of the 10 occasions (P = .003 vs AZ13395438). Furthermore, AZ13395438 reduced AF inducibility by burst pacing from 100% to 25% (P < .001). CONCLUSION: AZ13395438 can be characterized as a mixed potassium ion channel-blocking agent that selectively prolongs atrial versus ventricular refractoriness and shows promising antiarrhythmic efficacy in a clinically relevant animal model of AF.

Synthesis and evaluation of diphenylphosphinic amides and diphenylphosphine oxides as inhibitors of Kv1.5.

Diphenylphosphinic amides and diphenylphosphine oxides have been synthesized and tested as inhibitors of the Kv1.5 potassium ion channel as a possible treatment for atrial fibrillation. In vitro structure-activity relationships are discussed and several compounds with Kv1.5 IC(50) values of <0.5 µM were discovered. Selectivity over the ventricular IKs current was monitored and selective compounds were found. Results from a rabbit PD-model are included.

AZD1305 exerts atrial predominant electrophysiological actions and is effective in suppressing atrial fibrillation and preventing its reinduction in the dog.

Recent development of drugs for the treatment of atrial fibrillation (AF) has focused on atrial selective agents. We examined the atrioventricular differences in sodium channel block of the antiarrhythmic agent AZD1305 in atria and ventricles of anesthetized dogs in vivo, canine isolated arterially perfused preparations in vitro, and isolated myocytes using whole-cell patch-clamp techniques. AZD1305 did not change heart rate or blood pressure in vivo but prolonged action potential duration and increased effective refractory period, diastolic threshold of excitation, and conduction time preferentially in atria both in vitro and in vivo. AZD1305 reduced the maximum rate of rise of the action potential upstroke (V(max)) predominantly in atria (-51% +/- 10% in atria vs. -31% +/- 23% in ventricles; 3 microM; cycle length = 500 milliseconds). Fast sodium current (I(Na)) was blocked by AZD1305 to a greater degree in atrial versus ventricular myocytes (particularly tonic inhibition). In coronary-perfused right atria, AZD1305 very effectively prevented induction of persistent acetylcholine-mediated AF and, in a different set of atria, terminated persistent AF (in 5 of 5 and 7 of 8 atria, respectively). In conclusion, AZD1305 exerts atrial predominant sodium channel-blocking effects in vitro and in vivo and effectively suppresses AF.

Assessment of the ion channel-blocking profile of the novel combined ion channel blocker AZD1305 and its proarrhythmic potential versus dofetilide in the methoxamine-sensitized rabbit in vivo.

AZD1305 is a novel antiarrhythmic agent under clinical evaluation for management of atrial fibrillation. This study assessed its ion channel-blocking potency by the whole cell patch-clamp technique in vitro and its proarrhythmic liability in anesthetized methoxamine-sensitized rabbits in comparison with dofetilide. AZD1305 predominantly blocked the hERG, the L-type calcium and the hNav1.5 currents in a concentration-dependent manner. In vivo AZD1305 increased the QT interval (from 145 +/- 8 to 196 +/- 18 ms, P < 0.01) without inducing ventricular extrasystoles or torsades de pointes (TdP). In contrast, dofetilide prolonged the QT interval from 161 +/- 3 to 256 +/- 15 ms (P < 0.001) and caused TdP in 12/17 rabbits (P < 0.01 vs. AZD1305). During AZD1305 and dofetilide infusion, the QTend-peak interval maximally increased by 14 +/- 4 and 30 +/- 6 ms (P < 0.05 vs. AZD1305) and the beat-by-beat QT interval variability (quantified as the short-term variability, STV) changed from 2 +/- 0.8 to 2 +/- 0.3 ms (NS) and from 2 +/- 0.2 to 12 +/- 1.1 ms (P < 0.001), respectively. Following dofetilide-induced TdP, 6 rabbits each were injected with saline or AZD1305. In contrast to saline, AZD1305 abbreviated the QT interval (from 275 +/- 25 to 216 +/- 9 ms, P < 0.05), reduced the STV to 1 +/- 0.1 ms (P < 0.001) and suppressed TdP in all 6 rabbits (P < 0.01 vs. saline). In conclusion, AZD1305 can be characterised as a combined ion channel blocker that delays repolarization without increasing beat-by-beat variability of repolarization (BVR) or inducing TdP whereas selective IKr blockade by dofetilide prolongs the QT interval and eventually increases BVR resulting in TdP.