rotigaptide and antiarrhythmic-peptide

The gap junction modifier Rotigaptide (ZP123), which promotes cellular coupling, was hypothesized to decrease defibrillation thresholds during prolonged ventricular fibrillation (VF). Thirty-two New Zealand white rabbits were randomized to receive saline (control, n = 16) or Rotigaptide (n = 16). Following 4 min of untreated VF, biphasic defibrillation shocks were applied through chest wall patches, starting either at 300 volts (V) (n = 16) or 500 V (n = 16), with 200 V increasing steps to 900 V in case of shock failure. Rotigaptide significantly decreased defibrillation voltage requirements (average cumulative voltage of all shocks: 1206 +/- 709 V in control group vs. 844 +/- 546 V in treated group, P = .002). Rotigaptide had no effect on heart rate, QRS duration, QT interval, ventricular effective refractory period, monophasic action potential duration or on connexin 43 density using immunofluorescence. Rotigaptide improves the ability to defibrillate after untreated VF.

Topics: Action Potentials; Animals; Blood Pressure; Connexin 43; Disease Models, Animal; Electric Countershock; Electric Stimulation; Electrocardiography; Fluorescent Antibody Technique; Gap Junctions; Heart Arrest; Heart Rate; Injections, Intravenous; Male; Myocytes, Cardiac; Oligopeptides; Rabbits; Random Allocation; Resuscitation; Ventricular Fibrillation

Previous studies suggest that dephosphorylation of connexin43 (Cx43) is related to uncoupling of gap junction communication, which plays an important role in the genesis of ischemia-induced ventricular tachycardia. We studied changes in Cx43 phosphorylation during global ischemia in the absence and presence of the antiarrhythmic peptide analogue rotigaptide (formerly known as ZP123). Phosphorylation analysis was performed on Cx43 purified from isolated perfused rat hearts using matrix-assisted laser desorption/ionization mass spectrometry and liquid chromatography electrospray ionization tandem mass spectrometry. Thirteen different serine phosphorylation sites were identified in Cx43 during non-ischemic conditions, three of which had not previously been described. Within the first 7 min of ischemia, Ser306 became fully dephosphorylated whereas Ser330 became phosphorylated. Between 15 and 30 min of ischemia, the critical time interval where gap junction uncoupling occurs, Ser297 and Ser368 also became fully dephosphorylated. During the same time period, all untreated hearts developed asystole. Treatment with rotigaptide significantly increased the time to ischemia-induced asystole and suppressed dephosphorylation of Ser297 and Ser368 at 30 min of ischemia. Our results suggest that phosphorylation of Ser297 and Ser368 may be involved in functional gating of Cx43 during ischemia and may be possible downstream targets for rotigaptide signaling.

Topics: Amino Acid Sequence; Animals; Connexin 43; Heart Arrest; Male; Molecular Sequence Data; Myocardial Ischemia; Oligopeptides; Phosphorylation; Phosphotransferases; Rats; Rats, Sprague-Dawley; Serine

As atrial conduction slowing is important in the pathogenesis of atrial reentry arrhythmias, a drug that increases atrial conduction or prevents atrial conduction slowing could serve to prevent atrial reentry arrhythmias. In this study, we investigated whether the novel stable antiarrhythmic peptide analog, ZP123, was able to prevent atrial conduction slowing.. We examined the effect of ZP123 on metabolic stress-induced changes in conduction velocity (CV) and on dynamic CV restitution in isolated left atria from male Sprague-Dawley rats. We performed binding of ZP123 to a broad panel of 80 different cardiac and noncardiac ion channels and receptors and examined the effect of ZP123 on HERG channel conductance.. ZP123 dose-dependently prevented metabolic stress-induced atrial CV slowing at doses ranging from 1 nM to 10 microM. ZP123 did not affect CV during physiological conditions nor did it affect dynamic CV restitution. ZP123 had no effect on atrial contractility. ZP123 showed no or low affinity binding to all ion channels and receptors examined. ZP123 had no effects on HERG channel activity in concentrations that affected atrial conduction. The concentration of ZP123 giving maximal effect on atrial conduction (100 nM) inhibited the outward K(+)-current by 2.7 +/- 0.1%.. ZP123 has no effects on atrial conduction during physiological conditions, but it selectively prevents atrial conduction slowing during metabolic stress.

Topics: Animals; Dose-Response Relationship, Drug; Electrophysiologic Techniques, Cardiac; Heart Atria; Heart Conduction System; In Vitro Techniques; Ion Channels; Male; Myocardial Contraction; Oligopeptides; Rats; Rats, Sprague-Dawley

The aim of this study was to determine if the stable antiarrhythmic peptide (AAP) analogue ZP123 increases gap junctional intercellular conductance and prevents reentrant ventricular tachycardia (VT) during coronary artery occlusion.. Voltage clamp experiments demonstrated that 10 nM ZP123 improved gap junctional intercellular conductance by 69% +/- 20% in pairs of guinea pig ventricular myocytes. VT was induced by programmed stimulation in alpha-chloralose anaesthetized open chest dogs 1 to 4 hours after coronary artery occlusion. Three-dimensional activation mapping was done using six bipolar electrograms on each of 23 multipolar needles in the risk zone. When VT was reproducibly induced, dogs were randomly assigned to receive either saline or ZP123 cumulatively at three dose levels (intravenous bolus followed by 30-min infusion per dose). Attempts to induce VT were repeated in each infusion period. Mass spectrometry was used to measure ZP123 plasma concentrations. Twenty-six dogs with reentrant VT were included. ZP123 significantly prevented reentrant VT at all plasma concentrations vs saline: 1.0 +/- 0.2 nM: 6/12 vs 0/12; 7.7 +/- 0.6 nM: 7/13 vs 1/12; and 69.2 +/- 5.4 nM: 9/13 vs 1/13. The preventive effect of ZP123 on reentrant VT was closely correlated to reversal of functional, unidirectional conduction block. ZP123 did not affect effective refractory period, surface ECG parameters, mean arterial pressure, or infarct size.. The stable AAP analogue ZP123 increased gap junctional intercellular conductance and specifically prevented the induction of reentrant VT during ischemia in a broad dose range without proarrhythmic or hemodynamic side effects. ZP123 is a promising candidate for use in preventing ischemia-induced VT.

Topics: Animals; Blood Pressure; Cell Membrane; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Electrocardiography; Female; Gap Junctions; Heart Block; Heart Conduction System; Incidence; Infusions, Intravenous; Male; Models, Cardiovascular; Myocardial Ischemia; Myocytes, Cardiac; Oligopeptides; Reproducibility of Results; Statistics as Topic; Tachycardia, Ventricular