Effects of Zeneca ZD7288 in Comparison with Alinidine and UL-FS 49 on Guinea Pig Sinoatrial Node and Ventricular Action Potentials

Briggs, Ian; BoSmith, R. E.; Heapy, Chris G.

doi:10.1097/00005344-199409000-00005

Cited by 18 publications

(11 citation statements)

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“…ZD7288 at 1 μM is a specifi c HCN channel blocker and was therefore used to inhibit the HCN-mediated current (I f ) and automaticity [ 24 ]. Immunostaining with the HCN4 antibody revealed substantial presence of membrane HCN4 channels in most hESC-CMs at early and 60D differentiation (>99% of cells, Fig.…”

Section: Quantitative Rt-pcr and Immunostaining Of Frozen Sectionsmentioning

confidence: 99%

Non-Cardiomyocytes Influence the Electrophysiological Maturation of Human Embryonic Stem Cell-Derived Cardiomyocytes During Differentiation

Kim

Majdi

Xia

et al. 2010

Stem Cells and Development

163

153

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Various types of cardiomyocytes undergo changes in automaticity and electrical properties during fetal heart development. Human embryonic stem cell-derived cardiomyocytes (hESC-CMs), like fetal cardiomyocytes, are electrophysiologically immature and exhibit automaticity. We used hESC-CMs to investigate developmental changes in mechanisms of automaticity and to determine whether electrophysiological maturation is driven by an intrinsic developmental clock and/or is regulated by interactions with non-cardiomyocytes in embryoid bodies (EBs). We isolated pure populations of hESC-CMs from EBs by lentivirus-engineered Puromycin resistance at various stages of differentiation. Using pharmacological agents, calcium (Ca 2+ ) imaging, and intracellular recording techniques, we found that intracellular Ca 2+ -cycling mechanisms developed early and contributed to dominant automaticity throughout hESC-CM differentiation. Sarcolemmal ion channels evolved later upon further differentiation within EBs and played an increasing role in controlling automaticity and electrophysiological properties of hESC-CMs. In contrast to the development of intracellular Ca 2+ -handling proteins, ion channel development and electrophysiological maturation of hESC-CMs did not occur when hESC-CMs were isolated from EBs early and maintained in culture without further interaction with non-cardiomyocytes. Adding back non-cardiomyocytes to early-isolated hESC-CMs rescued the arrest of electrophysiological maturation, indicating that non-cardiomyocytes in EBs drive electrophysiological maturation of early hESC-CMs. Non-cardiomyocytes in EBs contain most cell types present in the embryonic heart that are known to infl uence early cardiac development. Our study is the fi rst to demonstrate that non-cardiomyocytes infl uence electrophysiological maturation of early hESC-CMs in cultures. Defi ning the nature of these extrinsic signals will aid in the directed maturation of immature hESC-CMs to mitigate arrhythmogenic risks of cell-based therapies.

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Section: Quantitative Rt-pcr and Immunostaining Of Frozen Sectionsmentioning

confidence: 99%

Non-Cardiomyocytes Influence the Electrophysiological Maturation of Human Embryonic Stem Cell-Derived Cardiomyocytes During Differentiation

Kim

Majdi

Xia

et al. 2010

Stem Cells and Development

163

153

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“…This compound potently reduces I f in sinoatrial node cells but is a less potent blocker of I h in neurons or heterologously expressed HCN channels. In sinoatrial node cells isolated from the guinea pig heart, ZD7288 slowed pacemaker activity at low concentrations (10 nM-1 M) (Briggs et al, 1994) and blocked I f with an IC 50 of about 0.3 M (BoSmith et al, 1993). In contrast, the IC 50 for block of I h was reported to be 2 M in substantia nigra neurons of the guinea pig (Harris and Constanti, 1995), 41 M for mouse HCN1 channels expressed in Xenopus oocytes (Shin et al, 2001), and 20 to 41 M in transfected HEK293 cells expressing human HCN1, HCN2, HCN3, or HCN4 channels.…”

mentioning

confidence: 96%

“…1b, inset) with bradycardic and antianginal activity in experimental animals (BoSmith et al, 1993;Briggs et al, 1994). This compound potently reduces I f in sinoatrial node cells but is a less potent blocker of I h in neurons or heterologously expressed HCN channels.…”

mentioning

confidence: 99%

Molecular Mapping of the Binding Site for a Blocker of Hyperpolarization-Activated, Cyclic Nucleotide-Modulated Pacemaker Channels

Cheng¹,

Kinard²,

Rajamani³

et al. 2007

J Pharmacol Exp Ther

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Hyperpolarization-activated, cyclic nucleotide-modulated (HCN) channels mediate rhythmic electrical activity of neural and cardiac pacemaker cells. Drugs that block these channels slow the beating rate of the heart and are used to treat angina. Here, we characterized the effect of the HCN channel blocker, ZD7288 [4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyrimidinium chloride] on HCN2 channels that were heterologously expressed in Xenopus oocytes. A site-directed mutagenesis approach was used to identify specific residues of the mouse HCN2 channel pore that interact with ZD7288. Two residues (Ala425 and Ile432) located in the S6 transmembrane domain were found to be the primary determinants for block of HCN2 channels by ZD7288. I432A mutant HCN2 channels were ϳ100-fold less sensitive to block by ZD7288. Substitution of Ile432 with more hydrophobic residues (Phe, Leu, or Val) caused only modest shifts in the IC 50 for the drug. HCN1 channels have a Val (Val390) in the equivalent position of Ile432 and are less sensitive to block by ZD7288. Accordingly, mutation of this Val390 to Ile in HCN1 increased the sensitivity of these channels to drug block. Mutation of Ala425 and Ile432 also attenuated the block of HCN2 by the more potent blocker cilobradine. An HCN2 homology model based on the bacterial KcsA K ϩ channel predicts that the phenyl ring of ZD7288 occupies a hydrophobic cavity formed by Ala425 and Ile432 and that the charged ring aligns with the axis of the inner pore closely corresponding to the localization of K ϩ ions observed in the KcsA crystal structure.Pacemaker channels are activated by membrane hyperpolarization and conduct an inward cation current that contributes to spontaneous activity of specialized pacemaker cells in the heart (Baruscotti et al., 2005) and synaptic integration and network rhythmicity of central neurons (Biel et al

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“…Typically, most studies concerning the specificity of ZD7288 have focused on inwardly rectifying currents in the voltage range hyperpolarized to the resting membrane potential. In these experiments, ZD7288 clearly blocks I h while having little to no effect on the instantaneous inward rectifier (I Kir ) (BoSmith et al, 1993;Briggs et al, 1994;Harris and Constanti, 1995;Maccaferri and McBain, 1996;Gasparini and DiFrancsco, 1997). However, a recent study has shown that ZD7288 blocks both native and reconstituted low-threshold (T type) Ca 2þ currents in sperm cells (Felix et al, 2003).…”

Section: Zd7288 Nonspecific Blockmentioning

confidence: 76%

“…A candidate current for this putatively independent effect is the hyperpolarization activated delayed inward rectifier (I h ), which is also a substantive component of the total membrane current of mEC Layer II cells, especially stellates (Alonso and Llinás, 1989;Alonso and Klink, 1993;Dickson et al, 2000b). To test this hypothesis, we utilized the bradycardic agent ZD7288, reported to be a selective and specific blocker of I h (BoSmith et al, 1993;Briggs et al, 1994;Harris and Constanti, 1995;Maccaferri and McBain, 1996;Gasparini and DiFrancsco, 1997;Dickson et al, 2000b). A measure of 10-lM ZD7288 was found to block I h in EC Layer II neurons adequately, although slowly, usually requiring $20-25 min to reach maximal blockade in our experimental conditions (Fig.…”

Section: -Ht-induced Inward Current: Partial Dependence Upon I Hmentioning

confidence: 99%

Effects of serotonin on the intrinsic membrane properties of layer II medial entorhinal cortex neurons

Shalinsky

Alonso

et al. 2006

Hippocampus

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Although serotonin (5-HT) is an important neuromodulator in the superficial layers of the medial entorhinal cortex (mEC), there is some disagreement concerning its influences upon the membrane properties of neurons within this region. We performed whole cell recordings of mEC Layer II projection neurons in rat brain slices in order to characterize the intrinsic influences of 5-HT. In current clamp, 5-HT evoked a biphasic response consisting of a moderately short latency and large amplitude hyperpolarization followed by a slowly developing, long lasting, and small amplitude depolarization. Correspondingly, in voltage clamp, 5-HT evoked a robust outward followed by a smaller inward shift of holding current. The outward current evoked by 5-HT showed a consistent current/voltage (I/V) relationship across cells with inward rectification, and demonstrating a reversal potential that was systematically dependent upon the extracellular concentration of K(+), suggesting that it was predominantly carried by potassium ions. However, the inward current showed a less consistent I/V relationship across different cells, suggesting multiple independent ionic mechanisms. The outward current was mediated through activation of 5-HT(1A) receptors via a G-protein dependent mechanism while inward currents were evoked in a 5-HT(1A)-independent fashion. A significant proportion of the inward current was blocked by the I(h) inhibitor ZD7288 and appeared to be due to 5-HT modulation of I(h) as 5-HT shifted the activation curve of I(h) in a depolarizing fashion. Serotonin is thus likely to influence, in a composite fashion, the information processing of Layer II neurons in the mEC and thus, the passage of neocortical information via the perforant pathway to the hippocampus.

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Effects of Zeneca ZD7288 in Comparison with Alinidine and UL-FS 49 on Guinea Pig Sinoatrial Node and Ventricular Action Potentials

Cited by 18 publications

References 0 publications

Non-Cardiomyocytes Influence the Electrophysiological Maturation of Human Embryonic Stem Cell-Derived Cardiomyocytes During Differentiation

Non-Cardiomyocytes Influence the Electrophysiological Maturation of Human Embryonic Stem Cell-Derived Cardiomyocytes During Differentiation

Molecular Mapping of the Binding Site for a Blocker of Hyperpolarization-Activated, Cyclic Nucleotide-Modulated Pacemaker Channels

Effects of serotonin on the intrinsic membrane properties of layer II medial entorhinal cortex neurons

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