Ligand-activated RXFP1 gene therapy ameliorates pressure overload-induced cardiac dysfunction.

Recurrent episodes of decompensated heart failure (HF) represent an emerging cause of hospitalizations in developed countries with an urgent need for effective therapies. Recently, the pregnancy-related hormone relaxin (RLN) was found to mediate cardio-protective effects and act as a positive inotrope in the cardiovascular system. RLN binds to the RLN family peptide receptor 1 (RXFP1), which is predominantly expressed in atrial cardiomyocytes. We therefore hypothesized that ventricular RXFP1 expression might exert potential therapeutic effects in an in vivo model of cardiac dysfunction. Thus, mice were exposed to pressure overload by transverse aortic constriction and treated with AAV9 to ectopically express RXFP1. To activate RXFP1 signaling, RLN was supplemented subcutaneously. Ventricular RXFP1 expression was well tolerated. Additional RLN administration not only abrogated HF progression but restored left ventricular systolic function. In accordance, upregulation of fetal genes and pathological remodeling markers were significantly reduced. In vitro, RLN stimulation of RXFP1-expressing cardiomyocytes induced downstream signaling, resulting in protein kinase A (PKA)-specific phosphorylation of phospholamban (PLB), which was distinguishable from ß-adrenergic activation. PLB phosphorylation corresponded to increased calcium amplitude and contractility. In conclusion, our results demonstrate that ligand-activated cardiac RXFP1 gene therapy represents a therapeutic approach to attenuate HF with the potential to adjust therapy by exogenous RLN supplementation.

Pharmacologic TWIK-Related Acid-Sensitive K+ Channel (TASK-1) Potassium Channel Inhibitor A293 Facilitates Acute Cardioversion of Paroxysmal Atrial Fibrillation in a Porcine Large Animal Model.

Background The tandem of P domains in a weak inward rectifying K+ channel (TWIK)-related acid-sensitive K+ channel (TASK-1; hK2P3.1) two-pore-domain potassium channel was recently shown to regulate the atrial action potential duration. In the human heart, TASK-1 channels are specifically expressed in the atria. Furthermore, upregulation of atrial TASK-1 currents was described in patients suffering from atrial fibrillation (AF). We therefore hypothesized that TASK-1 channels represent an ideal target for antiarrhythmic therapy of AF. In the present study, we tested the antiarrhythmic effects of the high-affinity TASK-1 inhibitor A293 on cardioversion in a porcine model of paroxysmal AF. Methods and Results Heterologously expressed human and porcine TASK-1 channels are blocked by A293 to a similar extent. Patch clamp measurements from isolated human and porcine atrial cardiomyocytes showed comparable TASK-1 currents. Computational modeling was used to investigate the conditions under which A293 would be antiarrhythmic. German landrace pigs underwent electrophysiological studies under general anesthesia. Paroxysmal AF was induced by right atrial burst stimulation. After induction of AF episodes, intravenous administration of A293 restored sinus rhythm within cardioversion times of 177±63 seconds. Intravenous administration of A293 resulted in significant prolongation of the atrial effective refractory period, measured at cycle lengths of 300, 400 and 500 ms, whereas the surface ECG parameters and the ventricular effective refractory period lengths remained unchanged. Conclusions Pharmacological inhibition of atrial TASK-1 currents exerts antiarrhythmic effects in vivo as well as in silico, resulting in acute cardioversion of paroxysmal AF. Taken together, these experiments indicate the therapeutic potential of A293 for AF treatment.

Functional characterization of zebrafish K2P18.1 (TRESK) two-pore-domain K+ channels.

The human KCNK18 gene is predominantly expressed in brain, spinal cord, and dorsal root ganglion neurons. Encoded K2P18.1K(+) channels are functionally implicated in migraine, pain and anesthesia. Data delineating the in vivo significance of K2P18.1 are still limited owing to a lack of model systems allowing for rapid, whole organism phenotypic analyses. We hypothesized that zebrafish (Danio rerio) might close this scientific gap. This work was designed to characterize the zebrafish ortholog of K2P18.1 in comparison to human K2P18.1 channels. The complete coding sequence of zKCNK18 was amplified from zebrafish cDNA. Zebrafish KCNK18 expression was assessed by in situ hybridization. Human and zebrafish K2P18.1 currents were functionally analyzed using two-electrode voltage clamp electrophysiology and the Xenopus oocyte expression system. KCNK18 mRNA is expressed in zebrafish brain and eyes. Human and zebrafish K2P18.1 proteins share 32 % identity. Zebrafish K2P18.1 channels mediate K(+)-selective background currents that stabilize the negative resting membrane potential. Functional similarities between human and zK2P18.1 currents include open rectification properties, inhibition by barium, and regulation by signaling molecules protein kinase (PK)C, PKA, and phospholipase C. In contrast to the human ortholog, zK2P18.1 exhibited reduced sensitivity to elevation of intracellular calcium levels by ionomycin and was virtually insensitive to inhibition by quinidine. Zebrafish and human K2P18.1 channels share functional and regulatory properties, indicating that the zebrafish may serve as model to assess K2P18.1 function in vivo. However, distinct differences in K2P18.1 current regulation require careful consideration when zebrafish data are extrapolated to human physiology.

[Shutter-glasses haploscope with eye-tracking control for fusion therapy]. / Shutter-Brillen-Haploskop mit Eye-Tracker-Regelung zum Zweck der Fusionstherapie.

BACKGROUND: Common haploscopes require a manual input of the presented disparity and particularly prepared images; moreover, they can be used predominantly by orthoptists. We developed a device that makes possible a haploscope on the basis of a computer monitor with shutter-glasses. The presented disparity is determined with help of an eye-tracker. MATERIALS AND METHODS: A patient looks at a monitor through shutter-glasses, the eyes being recorded by a camera. An eye-tracking software determines the fixation points and the angle of strabismus. Images are presented at the monitor with a disparity that is regulated according to these measurements. This is controlled by means of a software so that the disparity is gradually decreased according to the patients abilities. Diagnostic data are recorded permanently. RESULTS: Any monitor contents, such as videos, TV or computer applications, can be used for fusion training or diagnostic purposes with the new apparatus. Initial investigations of patients with heterophoria or intermittent exophoria indicate a decrease of the subjective angle of strabismus by compensation and an increase of the fusional range. CONCLUSIONS: The developed shutter-glass-haploscope with eye-tracking control provides several methods for diagnosis. The appliance provides automated fusion training adapted to the patient that can be done at the working place or at home.