Impulse conduction and gap junctional remodelling by endothelin‐1 in cultured neonatal rat ventricular myocytes

Abstract

Endothelin-1 (ET-1) is an important contributor to ventricular hypertrophy and failure, which are associated with arrhythmogenesis and sudden death. To elucidate the mechanism(s) underlying the arrhythmogenic effects of ET-1 we tested the hypothesis that long-term (24 hrs) exposure to ET-1 impairs impulse conduction in cultures of neonatal rat ventricular myocytes (NRVM). NRVM were seeded on micro-electrode-arrays (MEAs, Multi Channel Systems, Reutlingen, Germany) and exposed to 50 nM ET-1 for 24 hrs. Hypertrophy was assessed by morphological and molecular methods. Consecutive recordings of paced activation times from the same cultures were conducted at baseline and after 3, 6 and 24 hrs, and activation maps for each time period constructed. Gap junctional Cx43 expression was assessed using Western blot and confocal microscopy of immunofluorescence staining using anti-Cx43 antibodies. ET-1 caused hypertrophy as indicated by a 70% increase in mRNA for atrial natriuretic peptide (P < 0.05), and increased cell areas (P < 0.05) compared to control. ET-1 also caused a time-dependent decrease in conduction velocity that was evident after 3 hrs of exposure to ET-1, and was augmented at 24 hrs, compared to controls (P < 0.01). ET-1 increased total Cx43 protein by ∼40% (P < 0.05) without affecting non- phosphorylated Cx43 (NP-Cx43) protein expression. Quantitative confocal microscopy showed a ∼30% decrease in the Cx43 immunofluorescence per field in the ET-1 group (P < 0.05) and a reduced field stain intensity (P < 0.05), compared to controls. ET-1-induced hypertrophy was accompanied by reduction in conduction velocity and gap junctional remodelling. The reduction in conduction velocity may play a role in ET-1 induced susceptibility to arrhythmogenesis.

Molecular characterization and functional properties of cardiomyocytes derived from human inducible pluripotent stem cells

“…Unipolar electrograms were recorded from iPS-CM plated on MEAs as previously described [17, 18]. In order to generate meaningful activation maps, for these experiments we selected large and flat spontaneously contracting EBs which covered most of the recording electrodes.…”

“…The local activation times (LAT) at each electrode, defined as the time of occurrence of the first derivative plot minimum of the fast activation phase, was used to construct activation maps and calculate conduction velocity. The scalar value of local conduction velocity was calculated at each of the array electrodes as previously described [17, 18]. Finally, the conduction velocity shown for each measurement is the average of all the local velocities calculated at each of the 60 recording electrodes.…”

New Trends and Challenges in the Development of Microfabricated Probes for Recording and Stimulating of Excitable Cells

“…Neuronal electrophysiological research with microelectrode arrays is conducted in various domains of neuroscience, for example long term potentiation from acute slice preparations (Dimoka, Courellis, Gholmieh, Marmarelis & Berger (2008); ) or organotypic slice cultures (Cater et al (2007); Haustein et al (2008)), electroretinograms (Wilms & Eckhorn (2005)) and microERGs (Rosolen et al (2008;2002)) and recordings from cortical, hippocampal or striatal primary cell cultures for various studies including network plasticity ; Wagenaar et al (2006)) and memory processing and network activity (Baruchi & Ben-Jacob (2007); Pasquale et al (2008)). Micro-electrode arrays are also widely used to study electrophysiological properties of the heart, such as gap junction functionality and impulse conduction (Reisner et al (2008)), arrhythmias (Ocorr et al (2007)) and experimental stem-cell derived cardiac research (Gepstein (2008); Mauritz et al (2008)). …”

The Remodeling of Connexins Localized at Pulmonary Vein – Left Atria in Triggering and Maintenance of Atrial Fibrillation

“…These channels form a low-resistance pathway between adjacent myocytes and consist of connexin proteins. The connexin family is a large multigene family, and the channels formed by different members of this family have distinct electrical and regulatory properties (Reisner et al, 2009;Gros & Jongsma, 1996;Verheijck et al, 2001;Valiunas et al, 2002). Voltage sensitivity is particularly important in regulating the intercellular coupling between excitable cells.…”