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Objective: About one third of all patients with epilepsy have pharmacoresistant seizures. Thus there is a need for better pharmacological treatments. The human voltage-gated potassium (hK V ) channel hK V 7.2/7.3 is a validated antiseizure target for compounds that activate this channel. In a previous study we have shown that resin acid derivatives can activate the hK V 7.2/7.3 channel. In this study we investigated if these channel activators have the potential to be developed into a new type of antiseizure drug. Thus we examined their structure-activity relationships and the site of action on the hK V 7.2/7.3 channel, if they have unwanted cardiac and cardiovascular effects, and their potential antiseizure effect., Methods: Ion channels were expressed in Xenopus oocytes or mammalian cell lines and explored with two-electrode voltage-clamp or automated patch-clamp techniques. Unwanted vascular side effects were investigated with isometric tension recordings. Antiseizure activity was studied in an electrophysiological zebrafish-larvae model., Results: Fourteen resin acid derivatives were tested on hK V 7.2/7.3. The most efficient channel activators were halogenated and had a permanently negatively charged sulfonyl group. The compounds did not bind to the sites of other hK V 7.2/7.3 channel activators, retigabine, or ICA-069673. Instead, they interacted with the most extracellular gating charge of the S4 voltage-sensing helix, and the effects are consistent with an electrostatic mechanism. The compounds altered the voltage dependence of hK V 7.4, but in contrast to retigabine, there were no effects on the maximum conductance. Consistent with these data, the compounds had less smooth muscle-relaxing effect than retigabine. The compounds had almost no effect on the voltage dependence of hK V 11.1, hNa V 1.5, or hCa V 1.2, or on the amplitude of hK V 11.1. Finally, several resin acid derivatives had clear antiseizure effects in a zebrafish-larvae model., Significance: The described resin acid derivatives hold promise for new antiseizure medications, with reduced risk for adverse effects compared with retigabine., (© 2021 The Authors. Epilepsia published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.)

Alcohol use disorders (AUDs) are a major public health issue and produce enormous societal and economic burdens. Current Food and Drug Administration (FDA)-approved pharmacotherapies for treating AUDs suffer from deleterious side effects and are only effective in a subset of individuals. It is therefore essential to find improved medications for the management of AUDs. Emerging evidence suggests that anticonvulsants are a promising class of drugs for treating individuals with AUDs. In these studies, we used integrative functional genomics to demonstrate that genes that encode Kv7 channels (i.e. Kcnq2/3) are related to alcohol (ethanol) consumption, preference and acceptance in rodents. We then tested the ability of the FDA-approved anticonvulsant retigabine, a Kv7 channel opener, to reduce voluntary ethanol consumption of Wistar rats in a two-bottle choice intermittent alcohol access paradigm. Systemic administration and microinjections of retigabine into the nucleus accumbens significantly reduced alcohol drinking, and retigabine was more effective at reducing intake in high- versus low-drinking populations of Wistar rats. Prolonged voluntary drinking increased the sensitivity to the proconvulsant effects of pharmacological blockade of Kv7 channels and altered surface trafficking and SUMOylation patterns of Kv7.2 channels in the nucleus accumbens. These data implicate Kcnq2/3 in the regulation of ethanol drinking and demonstrate that long-term drinking produces neuroadaptations in Kv7 channels. In addition, these results have identified retigabine as a potential pharmacotherapy for treating AUDs and Kv7 channels as a novel therapeutic target for reducing heavy drinking., (© 2015 Society for the Study of Addiction.)

Objectives: Accumulating evidence implicates the potassium voltage-gated channel, KQT-like subfamily, member 2 and 3 (KCNQ2 and KCNQ3) genes in the etiology of bipolar disorder (BPD). Reduced KCNQ2 or KCNQ3 gene expression might lead to a loss of inhibitory M-current and an increase in neuronal hyperexcitability in disease. The goal of the present study was to evaluate epigenetic and gene expression associations of the KCNQ2 and KCNQ3 genes with BPD., Methods: DNA methylation and gene expression levels of alternative transcripts of KCNQ2 and KCNQ3 capable of binding the ankyrin G (ANK3) gene were evaluated using bisulfite pyrosequencing and the quantitative real-time polymerase chain reaction in the postmortem prefrontal cortex of subjects with BPD and matched controls from the McLean Hospital. Replication analyses of DNA methylation findings were performed using prefrontal cortical DNA obtained from the Stanley Medical Research Institute., Results: Significantly lower expression was observed in KCNQ3, but not KCNQ2. DNA methylation analysis of CpGs within an alternative exonic region of KCNQ3 exon 11 demonstrated significantly lower methylation in BPD, and correlated significantly with KCNQ3 mRNA levels. Lower KCNQ3 exon 11 DNA methylation was observed in the Stanley Medical Research Institute replication cohort, although only after correcting for mood stabilizer status. Mood stabilizer treatment in rats resulted in a slight DNA methylation increase at the syntenic KCNQ3 exon 11 region, which subsequent analyses suggested could be the result of alterations in neuronal proportion., Conclusion: The results of the present study suggest that epigenetic alterations in the KCNQ3 gene may be important in the etiopathogenesis of BPD and highlight the importance of controlling for medication and cellular composition-induced heterogeneity in psychiatric studies of the brain., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Chloroprocaine is a local ester anesthetic, producing excellent sensory block in clinical use. The Kv7/M potassium channel plays an important role in the control of neuronal excitability. In this study, we investigated the effects of the local anesthetic chloroprocaine on Kv7/M channels as well as the effect of retigabine on chloroprocaine-induced seizures., Methods: A perforated whole-cell patch technique was used to record Kv7 currents from HEK293 cells and M-type currents from rat dorsal root ganglion (DRG) neurons., Results: Chloroprocaine produced a number of effects on Kv7.2/Kv7.3 currents, including a lowering of current amplitudes, a rightward shift in the voltage-dependent activation curves, and a slowing of channel activation. Chloroprocaine had a more selective inhibitory effect on the homomeric Kv7.3 and heteromeric Kv7.2/Kv7.3 channels than on the homomeric Kv7.2 channel. Chloroprocaine also inhibited native M channel currents and induced a depolarization of the DRG neuron membrane potential., Conclusion: Taken together, the findings indicate that chloroprocaine concentration dependently inhibited Kv7/M channel currents., (© 2015 S. Karger AG, Basel.)

KCNQ2 (Kv7.2) and KCNQ3 (Kv7.3) are voltage-gated K(+) channel subunits that underlie the neuronal M current. In humans, mutations in these genes lead to a rare form of neonatal epilepsy (Biervert et al., 1998; Singh et al., 1998), suggesting that KCNQ2/Q3 channels may be attractive targets for novel antiepileptic drugs. In the present study, we have identified the compound N-(6-chloro-pyridin-3-yl)-3,4-difluoro-benzamide (ICA-27243) as a selective activator of the neuronal M current and KCNQ2/Q3 channels. In SH-SY5Y human neuroblastoma cells, ICA-27243 produced membrane potential hyperpolarization that could be prevented by coadministration with the M-current inhibitors 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride (XE-991) and linopirdine. ICA-27243 enhanced both (86)Rb(+) efflux (EC(50) = 0.2 microM) and whole-cell currents in Chinese hamster ovary cells stably expressing heteromultimeric KCNQ2/Q3 channels (EC(50) = 0.4 microM). Activation of KCNQ2/Q3 channels was associated with a hyperpolarizing shift of the voltage dependence of channel activation (V((1/2)) shift of -19 mV at 10 microM). In contrast, ICA-27243 was less effective at activating KCNQ4 and KCNQ3/Q5 and was selective over a wide range of neurotransmitter receptors and ion channels such as voltage-dependent sodium channels and GABA-gated chloride channels. ICA-27243 (1-10 microM) was found to reversibly suppress seizure-like activity in an ex vivo hippocampal slice model of epilepsy and demonstrated in vivo anticonvulsant activity (ED(50) = 8.4 mg/kg) in the mouse maximal electroshock epilepsy model. In conclusion, ICA-27243 represents the first member of a novel chemical class of selective KCNQ2/Q3 activators with anticonvulsant-like activity in experimental models of epilepsy.

The Kv7 potassium channel family encompasses five members (from Kv7.1 to Kv7.5) having distinct expression pattern and functional role. Although Kv7.1 is prevalently expressed in the cardiac muscle, Kv7.2, Kv7.3, Kv7.4, and Kv7.5 are expressed in neural tissue. Mutations in Kv7.2 and/or Kv7.3 genes are responsible for an autosomal-dominant epilepsy of the newborn defined as benign familial neonatal seizures (BFNS), whereas defects in the Kv7.4 gene have been found in families affected by a rare form of nonsyndromic autosomal-dominant hearing loss (DFNA2). Compounds acting as direct activators of neuronal channels formed by Kv7 subunits have been approved for clinical use as analgesics or are in advanced stages of clinical evaluation as anticonvulsants; in addition to these indications, solid preclinical studies reveal their potential usefulness in other diseases characterized by neuronal hyperexcitability. In the present work, we will summarize the available evidence providing proof-of-principles that neuronal Kv7 channels are highly attractive pharmacological targets, review the molecular basis of their peculiar pharmacological sensitivity, introduce some newly synthesized I(KM) openers showing improved pharmacokinetic or pharmacodynamic properties compared to older congeners, and discuss the potential novel therapeutic application of neuronal Kv7 channels in diseases additional to epilepsy.

Activity of KCNQ (Kv7) channels requires binding of phosphatidylinositol 4,5-bisphosphate (PIP(2)) from the plasma membrane. We give evidence that Mg(2+) and polyamines weaken the KCNQ channel-phospholipid interaction. Lowering internal Mg(2+) augmented inward and outward KCNQ currents symmetrically, and raising Mg(2+) reduced currents symmetrically. Polyvalent organic cations added to the pipette solution had similar effects. Their potency sequence followed the number of positive charges: putrescine (+2) < spermidine (+3) < spermine (+4) < neomycin (+6) < polylysine (>>+6). The inhibitory effects of Mg(2+) were reversible with sequential whole-cell patching. Internal tetraethylammonium ion (TEA) gave classical voltage-dependent block of the pore with changes of the time course of K(+) currents. The effect of polyvalent cations was simpler, symmetric, and without changes of current time course. Overexpression of phosphatidylinositol 4-phosphate 5-kinase Igamma to accelerate synthesis of PIP(2) attenuated the sensitivity to polyvalent cations. We suggest that Mg(2+) and other polycations reduce the currents by electrostatic binding to the negative charges of PIP(2), competitively reducing the amount of free PIP(2) available for interaction with channels. The dose-response curves could be modeled by a competition model that reduces the pool of free PIP(2). This mechanism is likely to modulate many other PIP(2)-dependent ion channels and cellular processes.

The M-current is a slowly activating, non-inactivating potassium current that has been shown to be present in numerous cell types. In this study, KCNQ2, Q3 and Q5, the molecular correlates of M-current in neurons, were identified in the visceral sensory neurons of the nodose ganglia from rats through immunocytochemical studies. All neurons showed expression of each of the three proteins. In voltage clamp studies, the cognition-enhancing drug linopirdine (1-50 microM) and its analogue, XE991 (10 microM), quickly and irreversibly blocked a small, slowly activating current that had kinetic properties similar to KCNQ/M-currents. This current activated between -60 and -55 mV, had a voltage-dependent activation time constant of 208 +/- 12 ms at -20 mV, a deactivation time constant of 165 +/- 24 ms at -50 mV and V1/2 of -24 +/- 2 mV, values which are consistent with previous reports for endogenous M-currents. In current clamp studies, these drugs also led to a depolarization of the resting membrane potential at values as negative as -60 mV. Flupirtine (10-20 microM), an M-current activator, caused a 3-14 mV leftward shift in the current-voltage relationship and also led to a hyperpolarization of resting membrane potential. These data indicate that the M-current is present in nodose neurons, is activated at resting membrane potential and that it is physiologically important in regulating excitability by maintaining cells at negative voltages.