Drug Candidate BGP-15 Prevents Isoproterenol-Induced Arrhythmias and Alters Heart Rate Variability (HRV) in Telemetry-Implanted Rats

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  Figure 1. Effects of BGP-15 dose-escalation on ECG parameters of telemetry-implanted rats. (a) BGP-15 (20 mg/kg) decreased mean heart rate. (b) BGP-15 treatment (40–160 mg) decreased heart rate but failed to prevent the isoproterenol-induced tachycardia. (c) ISO-induced ST segment depression was counteracted by all BGP-15 doses. (d) Representative ECG recording of unrestrained rats under baseline conditions (left panels), and under the influence of isoproterenol (1 mg/kg, upper right) and BGP-15 (40 mg/kg, bottom right) + isoproterenol (1 mg/kg). Arrows indicate depressed ST segments. (e) The effects of ISO and BGP-15 on corrected QT intervals (Bazett’s formula, modified for rats). QT-prolongation was observed after the wear-off of isoproterenol-induced tachycardia, which was counteracted by BGP-15 treatment. (f) Representative telemetric recordings. Upper panel: 2 mg isoproterenol-induced torsade de pointes (after, exitus); bottom panel: co-administration of 2 mg/kg ISO and 160 mg/kg BGP-15 caused AV block. Normal distribution was assessed by the Shapiro–Wilk normality test. Asterisks (*) denote the level of significance compared to BASE (*: p < 0.05; **: p < 0.01; ***: p < 0.001;…

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  Figure 2. Effects of 40 mg/kg, 80 mg/kg, and 160 mg/kg cumulative doses of BGP-15 on echocardiographic parameters of ISO-treated rats. (a) HR increased after ISO administration but decreased after all doses of BGP-15. (b) BGP-15 failed to counteract the positive effect of ISO on LV ejection fraction. (c) Transmittal E/A decreased after ISO but increased under the influence of BGP-15. (d) Left ventricle end-systolic volume decreased after ISO but tended to increase after BGP-15 injections. (e) Left ventricle end-diastolic volume increased after BGP-15 dosing. (f) Changes in E/e′ ratios (indicative for LV filling pressure) were only tendentious. (g) Representative echocardiographic traces of treatment groups. Upper panels: transmitral PW Doppler images; bottom panels: M-mode traces of the LV (PSLAX view). (h) Tissue Doppler e′/a′ ratio decreased after ISO injection. (i) Transmitral atrial wave (A) velocity decreased after BGP-15 administration (j) Septal atrial (a′) velocity decreased under the influence of BGP-15. Normal distribution was assessed by the Shapiro–Wilk normality test. Asterisks (*) denote significance compared to the Baseline group, and hashmarks (#) denote significance…

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  Figure 3. Effects of 2-week BGP-15 and ISO treatment on resting HRV parameters of conscious rats. (a) Two-week-long administration of BGP-15 (40 mg/kg) slightly, but BGP-15+ISO significantly decreased mean HR (in resting conditions, after wear-off of acute ISO-induced tachycardia). (b) BGP-15 treatment increased total variability (described by SDNN: standard deviation of the NN (R-R) intervals). (c) RMSSD (root mean square of the successive differences, indicative of increased parasympathetic tone) increased in all treated groups. (d) pNN10% (proportion of the number of pairs of successive NNs that differ by more than 10 ms) increased significantly in the BGP-15+ISO group. (e) SD1 (standard deviation of the width of the Poincaré plot ellipse, indicative of short-term variability in the parasympathetic tone) significantly elevated in the BGP-15-treated groups of rats. (f) Representative images of HRV analyses: filtered tachogram. (g) the R-R spectrum (Fast Fourier Transformation) showing VLF (grey), LF (orange), and HF (blue) bands. (h) representative non-linear analysis (Poincaré plot). Normal distribution was assessed by the Shapiro–Wilk normality test. Asterisks (*) denote significance…

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  Figure 4. Arrhythmic events (interpolated to a 10 min period) recorded on the last day of Protocol II. (a) Number of premature ventricular complexes (PVCs). (b) The incidence of salvos. (c) Duration of monomorphic ventricular tachycardia. (d) Duration of polymorphic ventricular tachycardia. (e) The number of ventricular fibrillation events significantly decreased in the BGP-15-treated rats. (f) The duration of ventricular fibrillation was shorter in the BGP-15+ISO group. (g) The total number of arrhythmic events was decreased in the BGP-15-treated animals. Data distribution was assessed by the Shapiro–Wilk normality test. Groups were compared by the Mann–Whitney test; *: p < 0.05. (h) Telemetric lead II ECG recording of ventricular premature complexes. (i) ECG recording of a monomorphic ventricular tachycardia (j) ECG trace of a ventricular fibrillation episode (all representative recordings were obtained from the experiments).

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  Figure 5. Effects of BGP-15 and ISO treatment in isolated cardiomyocytes. (a) After vehicle pre-treatment, the application of 100 nM ISO evoked aftercontractions and increased Ca2+-transient amplitudes (green line shows the sarcomere length, red line indicates Ca2+-transients, and the yellow arrow shows the 3rd aftercontraction with a spontaneous Ca2+ peak). (b) Representative magnified image illustrates sarcomere length changes during ISO treatment (black arrows for electrical stimulation, yellow arrow for the last aftercontraction). (c) Pre-treatment with 100 µM BGP-15 increased diastolic sarcomere length and prevented ISO-induced aftercontractions. (d) Magnified image for sarcomere length shows the combined effects of BGP-15 and ISO treatments (black arrows for electrical stimulation). Note the absence of aftercontractions. (e) 100 µM BGP-15 increased diastolic sarcomere length, but ISO treatment blunted this effect. (f) The number of ISO-induced aftercontractions (ACs) during 10 field stimulations in BGP-15 or saline pre-treated cardiomyocytes. Data distribution was assessed by the Shapiro–Wilk normality test. Groups were compared by the Mann–Whitney test, p < 0.05. (g) Magnitude of…