Characterization of the K+ channel opening effect of the anticonvulsant retigabine in PC12 cells
Introduction
Epilepsy is a chronic disease which is characterized by a condition of recurrent paroxysmal seizures of cerebral origin. The prevalence of epilepsy is found to be 0.5–1% of the world’s population (over 50 million people) which makes it one of the most common neurological disorders (Porter, 1993).
A large percentage (20–30%) of patients diagnosed as having epilepsy are not adequately controlled by presently available medications (Dam, 1986, Loiseau, 1988, Schmidt et al., 1992). In many cases, seizure control is limited by occurrence of severe side effects directly related to the antiepileptic drug treatment. There is therefore a need to develop novel, more effective and less toxic pharmacological agents rather than variations based on currently available but inadequate therapeutic regimes to increase control of seizures in currently drug resistant patients and to reduce side effects in patients which are only seizure free at the expense of chronic side effects.
Retigabine (D-23129) is a new anticonvulsant currently undergoing phase 2 clinical trials. The drug is chemically unrelated to currently marketed anticonvulsants. It exhibited pronounced anticonvulsant activity in a broad range of in vivo and in vitro seizure models and in genetic models of epileptic syndromes (Dailey et al., 1995, Kapetanovic and Rundfeldt, 1996, Rostock et al., 1996). In a model discussed to be the most predictive for complex partial seizures, retigabine was particularly effective in increasing the threshold (Tober et al., 1996). While in previous studies direct and indirect facilitating effects on GABAergic neurotransmission and weak blocking effects on neuronal sodium channels were reported (Kapetanovic et al., 1995, Rundfeldt et al., 1995, Kapetanovic and Rundfeldt, 1996), we recently found that retigabine acts as a potent opener of K+ channels in neuronal cells (Rundfeldt, 1997). Several lines of evidence can be found that the opening of K+ channels may be promising strategy for new anticonvulsant drug therapy (Doupnik et al., 1995, Sah, 1996, Meldrum, 1997). Opening K+ channels tends to hyperpolarize cells and decreases the effect of excitatory input. In both animal models of epilepsy and epileptic patients, mutations of K+ channels were reported as possible cause (Patil et al., 1995, Beck et al., 1996, Janigro et al., 1997, Charlier et al., 1998); an in vivo virus mediated transfection of CNS neurones with a voltage gated K+ channel resulted in a reduction in seizure susceptibility (Kirkby et al., 1996) and K+ channel openers of ATP sensitive K+ channels (given intracerebroventricularly) provide anticonvulsant action in some models (Gandolfo et al., 1989, Popoli et al., 1991). However, currently known K+ channel openers are hampered by their pronounced effects on blood pressure and other peripheral organ systems (Weston and Edwards, 1992).
The present work was aimed at characterizing the K+ channel opening effect of retigabine. Part of the work was already published in abstract form (Rundfeldt and Dost, 1997).
Section snippets
Cell culture
Experiments were performed in PC12 cells and in cultured cortical neurons.
The pheochromocytoma cell line PC12 was obtained from the European Collection of Cell Cultures (ECACC, Porton Down, UK) and cultivated as described elsewhere (Grene et al., 1982). Cells were grown at 37°C and 5% CO2 in RPMI medium containing 5% heat inactivated fetal calf serum (FCS) and 10% heat inactivated horse serum, 4 mM glutamine, penicillin (10 000 U/ml) and streptomycin (10 000 μg/ml), (Gibco Life Technologies,
Effects of nerve growth factor on current activation in PC12 cells
PC12 cells were treated with NGF to induce the neuronal like differentiation (Grene et al., 1982). If these cells were clamped at −40 mV to shift the membrane potential away from the K+ reversal potential, application of retigabine using a fast application system induced an outward K+ current which is comparable to the current induced in the cell line NG 108-15 (Rundfeldt, 1997).
As has been shown in this cell line, a rise in extracellular K+ concentration and hyperpolarization, respectively,
Selectivity of the K+ channel opening effect for neuronal cells
Some K+ channel openers were reported to exert anticonvulsant activity (Gandolfo et al., 1989, Popoli et al., 1991). However, these openers of ATP sensitive K+ channels are hampered by their pronounced effects on blood pressure and other peripheral organ systems (Weston and Edwards, 1992). The results obtained in PC12 and neuronal cells indicate, that retigabine selectively activates a K+ channel in neurones. While the data are not sufficient to exclude the possibility that retigabine may also
References (48)
- et al.
Anticonvulsant properties of D-20443 in genetically epilepsy-prone rats: prediction of clinical response
Neurosci. Lett.
(1995) - et al.
The inward rectifier potassium channel family
Curr. Opin. Neurobiol.
(1995) - et al.
K+ channel openers decrease seizures in genetically epileptic rats
Eur. J. Pharmacol.
(1989) - et al.
The effects of D-23129, a new experimental anticonvulsant drug, on neurotransmitter amino acids in the rat hippocampus in vitro
Epilepsy Res.
(1995) Structural basis of voltage-gated K+ channel pharmacology
Trends Pharmacol. Sci.
(1992)- et al.
D-23129: a new anticonvulsant with a broad spectrum activity in animal models of epileptic seizures
Epilepsy Res.
(1996) Diversity and ubiquity of potassium channels
Neuroscience
(1988)The new anticonvulsant retigabine (D-23129) acts as an opener of K+ channels in neuronal cells
Eur. J. Pharmacol.
(1997)Ca2+-activated K+ currents in neurones: types, physiological roles and modulation
Trends Neurosci.
(1996)- et al.
D-23129: a potent anticonvulsant in the amygdala kindling model of complex partial seizures
Eur. J. Pharmacol.
(1996)
Eight potassium channel families revealed by the C. elegans genome project
Neuropharmacology
Recent progress in potassium channel opener pharmacology
Biochem. Pharmacol.
Properties of a delayed rectifier potassium current in dentate granule cells isolated from the hippocampus of patients with chronic temporal lobe epilepsy
Epilepsia
Voltage-gated potassium channel genes
A pore mutation in a novel KQT-like potassium channel gene in an idiopathic epilepsy family
Nat. Genet.
Selective inhibition of a slow-inactivating voltage-dependent K+ channel in rat PC12 cells by hypoxia
J. Physiol. Lond.
Intractable epilepsy: introduction
Regulation of ionic currents in pheochromocytoma cells by nerve growth factor and dexamethasone
J. Neurosci.
ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae
Proc. Natl. Acad. Sci. USA
PC12 pheochromocytoma cultures in neurobiological reseach
Adv. Cell Neurobiol.
Improved patch clamp techniques for high-resolution current recording from cells and cell-free membrane patches
Pflügers Arch.
Characterization of an inward-rectifying potassium current in NG108-15 neuroblastoma x glioma cells
Pflügers Arch.
Cited by (46)
A medium-throughput functional assay of KCNQ2 potassium channels using rubidium efflux and atomic absorption spectrometry
2003, Analytical BiochemistryCitation Excerpt :Thus, the known pharmacological profile of KCNQ2 defined by electrophysiological studies is faithfully reproduced in the Rb+ efflux assay. Retigabine is an anticonvulsant compound, capable of increasing potassium conductance in numerous cell types of neuronal origin [26,27]. It has been shown to enhance currents through heterologously expressed monomeric and heteromeric channels of the KCNQ family including KCNQ2 and KCNQ2/3 [28–31].
Retigabine
2007, NeurotherapeuticsCitation Excerpt :Because neuronal potassium channels, including Kv7 channels, are discussed as potential targets for neuroprotection, retigabine was evaluated in three models of neurodegeneration. It was found to reduce infarct size in a model of permanent medial cerebral artery occlusion; it reversed functional deficits induced by unilateral carotid artery occlusion24; and in a model of kainic acid-induced status epilepticus, retigabine partially prevented the severe neurodegeneration resulting from the prolonged status.31 Kv7.3 and Kv7.5 subunits are expressed in bladder and in intestinal smooth muscle.
Identifying the mechanism of action of the Kv7 channel opener, retigabine in the treatment of epilepsy
2023, Neurological SciencesM-channel activation contributes to the anticonvulsant action of the ketone body b-hydroxybutyrate
2020, Journal of Pharmacology and Experimental TherapeuticsDirect neurotransmitter activation of voltage-gated potassium channels
2018, Nature Communications