CDK7 inhibition suppresses super-enhancer-linked oncogenic transcription in MYCN-driven cancer

The MYC oncoproteins are thought to stimulate tumor cell growth and proliferation through amplification of gene transcription, a mechanism that has thwarted most efforts to inhibit MYC function as potential cancer therapy. Using a covalent inhibitor of cyclin-dependent kinase 7 (CDK7) to disrupt the transcription of amplified MYCN in neuroblastoma cells, we demonstrate downregulation of the oncoprotein with consequent massive suppression of MYCN-driven global transcriptional amplification. This response translated to significant tumor regression in a mouse model of high-risk neuroblastoma, without the introduction of systemic toxicity. The striking treatment selectivity of MYCN-overexpressing cells correlated with preferential downregulation of super-enhancer-associated genes, including MYCN and other known oncogenic drivers in neuroblastoma. These results indicate that CDK7 inhibition, by selectively targeting the mechanisms that promote global transcriptional amplification in tumor cells, may be useful therapy for cancers that are driven by MYC family oncoproteins.

Small molecule modulators of copper-induced Abeta aggregation

Our design of bifunctional metal chelators as chemical probes and potential therapeutics for Alzheimer's disease (AD) is based on the incorporation of a metal binding moiety into structural frameworks of Abeta aggregate-imaging agents. Using this strategy, two compounds 2-[4-(dimethylamino)phenyl]imidazo[1,2-a]pyridine-8-ol (1) and N(1),N(1)-dimethyl-N(4)-(pyridin-2-ylmethylene)benzene-1,4-diamine (2) were prepared and characterized. The bifunctionality for metal chelation and Abeta interaction of 1 and 2 was verified by spectroscopic methods. Furthermore, the reactivity of 1 and 2 with Cu(II)-associated Abeta aggregates was investigated. The modulation of Cu(II)-triggered Abeta aggregation by 1 and 2 was found to be more effective than that by the known metal chelating agents CQ, EDTA, and phen. These studies suggest a new class of multifunctional molecules for the development of chemical tools to unravel metal-associated events in AD and potential therapeutic agents for metal-ion chelation therapy.

Molecular pharmacology and therapeutic potential of neuronal Kv7-modulating drugs

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.

Nervous system KV7 disorders: breakdown of a subthreshold brake

Voltage-gated K+channels of the K(V)7 (KCNQ) family have been identified in the last 10-15 years by discovering the causative genes for three autosomal dominant diseases: cardiac arrhythmia (long QT syndrome) with or without congenital deafness (KCNQ1), a neonatal epilepsy (KCNQ2 and KCNQ3) and progressive deafness alone (KCNQ4). A fifth member of this gene family (KCNQ5) is not affected in a disease so far. Four genes (KCNQ2-5) are expressed in the nervous system. This review is focused on recent findings on the neuronal K(V)7 channelopathies, in particular on benign familial neonatal seizures (BFNS) and peripheral nerve hyperexcitability (PNH, neuromyotonia, myokymia) caused by KCNQ2 mutations. The phenotypic spectrum associated with KCNQ2 mutations is probably broader than initially thought, as patients with severe epilepsies and developmental delay, or with Rolando epilepsy have been described. With regard to the underlying molecular pathophysiology, it has been shown that mutations with very subtle changes restricted to subthreshold voltages can cause BFNS thereby proving in a human disease model that this is the relevant voltage range for these channels to modulate neuronal firing. The two mutations associated with PNH induce much more severe channel dysfunction with a dominant negative effect on wild type (WT) channels. Finally, K(V)7 channels present interesting targets for new therapeutic approaches to diseases caused by neuronal hyperexcitability, such as epilepsy, neuropathic pain, and migraine. The molecular mechanism of K(V)7 activation by retigabine, which is in phase III clinical testing to treat pharmacoresistant focal epilepsies, has been recently elucidated as a stabilization of the open conformation by binding to the pore region.

Tribendimidine: a promising, safe and broad-spectrum anthelmintic agent from China

We review, for the first time, a 20-year Chinese story of research and development pertaining to tribendimidine, a promising anthelmintic agent that is safe and exhibits a broad spectrum of activity. Tribendimidine was first synthesized at the National Institute of Parasitic Diseases in Shanghai in the mid 1980s. In laboratory studies, tribendimidine showed high efficacy against Nippostrongylus braziliensis in rats, Necator americanus in hamsters, Ancylostoma caninum and Toxocara canis in dogs, and Syphacia mesocriceti in mice. Activity was also found against several species of cestodes in chicken. In clinical trials, a single oral dose of 400 mg tribendimidine, administered to patients infected only with N. americanus, or with N. americanus and Ancylostoma duodenalis, resulted in cure rates of 85.7% (132/154) and 89.8% (53/59), respectively. In comparison, a single oral dose of 400 mg albendazole resulted in significantly lower cure rates, namely 65.5% (91/139; chi(2) = 16.47, P < 0.001) and 71.7% (43/60; chi(2) = 6.29, P = 0.012), respectively. Single oral doses of tribendimidine (300 mg) and albendazole (400mg) were equally effective against Ascaris lumbricoides infections; cure rates were 96.0% (97/101) and 98.1% (101/103), respectively. In 5-14-year-old children with an Enterobius vermicularis infection, treated with a single oral dose of 200 mg tribendimidine, a cure rate of 81.6% (93/114) was observed. Tribendimidine was well-tolerated as only mild and transient side effects were observed. It would be of great public health significance if these findings are confirmed in other epidemiological settings, as more than one-quarter of the world population is currently affected by intestinal nematodes, with only very few drugs currently available on the market.

Retigabine: chemical synthesis to clinical application

Retigabine [D23129; N-(2-amino-4-(4-fluorobenzylamino)-phenyl)carbamic acid ethyl ester] is an antiepileptic drug with a recently described novel mechanism of action that involves opening of neuronal K(V)7.2-7.5 (formerly KCNQ2-5) voltage-activated K(+) channels. These channels (primarily K(V)7.2/7.3) enable generation of the M-current, a subthreshold K(+) current that serves to stabilize the membrane potential and control neuronal excitability. In this regard, retigabine has been shown to have a broad-spectrum of activity in animal models of electrically-induced (amygdala-kindling, maximal electroshock) and chemically-induced (pentylenetetrazole, picrotoxin, NMDA) epileptic seizures. These encouraging results suggest that retigabine may also prove useful in the treatment of other diseases associated with neuronal hyperexcitability. Neuropathic pain conditions are characterized by pathological changes in sensory pathways, which favor action potential generation and enhanced pain transmission. Although sometimes difficult to treat with conventional analgesics, antiepileptics can relieve some symptoms of neuropathic pain. A number of recent studies have reported that retigabine can relieve pain-like behaviors (hyperalgesia and allodynia) in animal models of neuropathic pain. Neuronal activation within several key structures within the CNS can also be observed in various animal models of anxiety. Moreover, amygdala-kindled rats, which have a lowered threshold for neuronal activation, also display enhanced anxiety-like responses. Retigabine dose-dependently reduces unconditioned anxiety-like behaviors when assessed in the mouse marble burying test and zero maze. Early clinical studies have indicated that retigabine is rapidly absorbed and distributed, and is resistant to first pass metabolism. Tolerability is good in humans when titrated up to its therapeutic dose range (600-1200 mg/day). No tolerance, dependence or withdrawal potential has been reported, although adverse effects can include mild dizziness, headache, nausea and somnolence. Thus, retigabine may prove to be useful in the treatment of a diverse range of disease states in which neuronal hyperexcitability is a common underlying factor.

Inhibition of HDAC3 prevents diabetic cardiomyopathy in OVE26 mice via epigenetic regulation of DUSP5-ERK1/2 pathway

Inhibition of total histone deacetylases (HDACs) was phenomenally associated with the prevention of diabetic cardiomyopathy (DCM). However, which specific HDAC plays the key role in DCM remains unclear. The present study was designed to determine whether DCM can be prevented by specific inhibition of HDAC3 and to elucidate the mechanisms by which inhibition of HDAC3 prevents DCM. Type 1 diabetes OVE26 and age-matched wild-type (WT) mice were given the selective HDAC3 inhibitor RGFP966 or vehicle for 3 months. These mice were then killed immediately or 3 months later for cardiac function and pathological examination. HDAC3 activity was significantly increased in the heart of diabetic mice. Administration of RGFP966 significantly prevented DCM, as evidenced by improved diabetes-induced cardiac dysfunction, hypertrophy, and fibrosis, along with diminished cardiac oxidative stress, inflammation, and insulin resistance, not only in the mice killed immediately or 3 months later following the 3-month treatment. Furthermore, phosphorylated extracellular signal-regulated kinases (ERK) 1/2, a well-known initiator of cardiac hypertrophy, was significantly increased, while dual specificity phosphatase 5 (DUSP5), an ERK1/2 nuclear phosphatase, was substantially decreased in diabetic hearts. Both of these changes were prevented by RGFP966. Chromatin immunoprecipitation (ChIP) assay showed that HDAC3 inhibition elevated histone H3 acetylation on the DUSP5 gene promoter at both two time points. These findings suggest that diabetes-activated HDAC3 inhibits DUSP5 expression through deacetylating histone H3 on the primer region of DUSP5 gene, leading to the derepression of ERK1/2 and the initiation of DCM. The present study indicates the potential application of HDAC3 inhibitor for the prevention of DCM.

Suppression of KCNQ/M (Kv7) potassium channels in dorsal root ganglion neurons contributes to the development of bone cancer pain in a rat model

Bone cancer pain has a strong impact on the quality of life of patients, but is difficult to treat. Better understanding of the pathogenic mechanisms underlying bone cancer pain will likely lead to the development of more effective treatments. In the present study, we investigated whether inhibition of KCNQ/M channels contributed to the hyperexcitability of primary sensory neurons and to the pathogenesis of bone cancer pain. By using a rat model of bone cancer pain based on intratibial injection of MRMT-1 tumour cells, we documented a prominent decrease in expression of KCNQ2 and KCNQ3 proteins and a reduction of M-current density in small-sized dorsal root ganglia (DRG) neurons, which were associated with enhanced excitability of these DRG neurons and the hyperalgesic behaviours in bone cancer rats. Coincidently, we found that inhibition of KCNQ/M channels with XE-991 caused a robust increase in the excitability of small-sized DRG neurons and produced an obvious mechanical allodynia in normal rats. On the contrary, activation of the KCNQ/M channels with retigabine not only inhibited the hyperexcitability of these small DRG neurons, but also alleviated mechanical allodynia and thermal hyperalgesia in bone cancer rats, and all of these effects of retigabine could be blocked by KCNQ/M-channel antagonist XE-991. These results suggest that repression of KCNQ/M channels leads to the hyperexcitability of primary sensory neurons, which in turn causes bone cancer pain. Thus, suppression of KCNQ/M channels in primary DRG neurons plays a crucial role in the development of bone cancer pain.

Retigabine, a Kv7.2/Kv7.3-Channel Opener, Attenuates Drug-Induced Seizures in Knock-In Mice Harboring Kcnq2 Mutations

The hetero-tetrameric voltage-gated potassium channel K_v7.2/K_v7.3, which is encoded by KCNQ2 and KCNQ3, plays an important role in limiting network excitability in the neonatal brain. K_v7.2/K_v7.3 dysfunction resulting from KCNQ2 mutations predominantly causes self-limited or benign epilepsy in neonates, but also causes early onset epileptic encephalopathy. Retigabine (RTG), a K_v7.2/ K_v7.3-channel opener, seems to be a rational antiepileptic drug for epilepsies caused by KCNQ2 mutations. We therefore evaluated the effects of RTG on seizures in two strains of knock-in mice harboring different Kcnq2 mutations, in comparison to the effects of phenobarbital (PB), which is the first-line antiepileptic drug for seizures in neonates. The subjects were heterozygous knock-in mice (Kcnq2^Y284C/+ and Kcnq2^A306T/+) bearing the Y284C or A306T Kcnq2 mutation, respectively, and their wild-type (WT) littermates, at 63–100 days of age. Seizures induced by intraperitoneal injection of kainic acid (KA, 12mg/kg) were recorded using a video-electroencephalography (EEG) monitoring system. Effects of RTG on KA-induced seizures of both strains of knock-in mice were assessed using seizure scores from a modified Racine’s scale and compared with those of PB. The number and total duration of spike bursts on EEG and behaviors monitored by video recording were also used to evaluate the effects of RTG and PB. Both Kcnq2^Y284C/+ and Kcnq2^A306T/+ mice showed significantly more KA-induced seizures than WT mice. RTG significantly attenuated KA-induced seizure activities in both Kcnq2^Y284C/+ and Kcnq2^A306T/+ mice, and more markedly than PB. This is the first reported evidence of RTG ameliorating KA-induced seizures in knock-in mice bearing mutations of Kcnq2, with more marked effects than those observed with PB. RTG or other K_v7.2-channel openers may be considered as first-line antiepileptic treatments for epilepsies resulting from KCNQ2 mutations.

The anti-hyperalgesic activity of retigabine is mediated by KCNQ potassium channel activation

Retigabine (N-(2-amino-4-(4-fluorobenzylamino)-phenyl) carbamic acid ethyl ester) has a broad anticonvulsant spectrum and is currently in clinical development for epilepsy. The compound has an opening effect on neuronal KCNQ channels. At higher concentrations an augmentation of gamma-aminobutyric acid (GABA) induced currents as well as a weak blocking effect on sodium and calcium currents were observed. The goal of this study was to characterise the activity of retigabine in models of acute and neuropathic pain and to investigate if the potassium channel opening effect of retigabine contributes to its activity. Retigabine was tested in mice and rats in the tail flick model of acute pain and in the nerve ligation model with tight ligation of the 5th spinal nerve (L5) using both thermal and tactile stimulation. While retigabine like gabapentin had almost no analgesic effect in mice it showed some analgesic effects in rats in the tail flick model. These effects could not be antagonised with linopirdine, a selective KCNQ potassium channel blocker, indicating a different mode of action for this activity. In L5-ligated rats retigabine significantly and dose-dependently elevated the pain threshold and prolonged the withdrawal latency after tactile and thermal stimulation, respectively. In the L5 ligation model with thermal stimulation retigabine 10 mg/kg p.o. was as effective as 100 mg/kg gabapentin or 10 mg/kg tramadol. The L5 model with tactile stimulation was used to test the role of the KCNQ potassium channel opening effect of retigabine. If retigabine 10 mg/kg p.o. was administered alone it was as effective as tramadol 10 mg/kg p.o. in elevating the pain threshold. Linopirdine (1 and 3 mg/kg i.p.) had nearly no influence on neuropathic pain response. If we administered both retigabine and linopirdine the effect of retigabine was abolished or diminished depending on the dose of linopirdine used.In summary, retigabine is effective in predictive models for neuropathic pain. The activity is comparable to tramadol and is present at lower doses compared with gabapentin. Since the anti-allodynic effect can be inhibited by linopirdine we can conclude that the potassium channel opening properties of retigabine are critically involved in its ability to reduce neuropathic pain response.

Evaluation of the in vivo activity of tribendimidine against Schistosoma mansoni, Fasciola hepatica, Clonorchis sinensis, and Opisthorchis viverrini

We examined the in vivo activity of tribendimidine against selected trematodes. A single 150-mg/kg dose of tribendimidine achieved a 99.1% reduction of Clonorchis sinensis in rats. A 400-mg/kg dose of tribendimidine reduced Opisthorchis viverrini in hamsters by 95.7%. High doses of tribendimidine showed no activity against Schistosoma mansoni and Fasciola hepatica.

Ferroptosis Promotes Cyst Growth in Autosomal Dominant Polycystic Kidney Disease Mouse Models

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD), the most common inherited kidney disease, is regulated by different forms of cell death, including apoptosis and autophagy. However, the role in ADPKD of ferroptosis, a recently discovered form of cell death mediated by iron and lipid metabolism, remains elusive.

METHODS

To determine a pathophysiologic role of ferroptosis in ADPKD, we investigated whether the absence of Pkd1 (encoding polycystin-1) affected the expression of key factors involved in the process of ferroptosis, using Western blot and qRT-PCR analysis in Pkd1 mutant renal cells and tissues. We also examined whether treatment with erastin, a ferroptosis inducer, and ferrostain-1, a ferroptosis inhibitor, affected cyst growth in Pkd1 mutant mouse models.

RESULTS

We found that kidney cells and tissues lacking Pkd1 exhibit extensive metabolic abnormalities, including reduced expression of the system Xc- amino acid antiporter (critical for import of cystine), of iron exporter (ferroportin), and of GPX4 (a key and negative regulator of ferroptosis). The abnormalities also include increased expression of iron importers (TfR1, DMT1) and HO-1, which in turn result in high iron levels, low GSH and GPX4 activity, increased lipid peroxidation, and propensity to ferroptosis. We further found that erastin increased, and ferrostatin-1 inhibited ferroptotic cell death and proliferation of Pkd1-deficient cells in kidneys from Pkd1 mutant mice. A lipid peroxidation product increased in Pkd1-deficient cells, 4HNE, promoted the proliferation of survived Pkd1 mutant cells via activation of Akt, S6, Stat3, and Rb during the ferroptotic process, contributing to cyst growth.

CONCLUSION

These findings indicate that ferroptosis contributes to ADPKD progression and management of ferroptosis may be a novel strategy for ADPKD treatment.

High MITF Expression Is Associated with Super-Enhancers and Suppressed by CDK7 Inhibition in Melanoma

Cutaneous melanoma is an aggressive tumor that accounts for most skin cancer deaths. Among the physiological barriers against therapeutic success is a strong survival program driven by genes such as MITF that specify melanocyte identity, a phenomenon known in melanoma biology as lineage dependency. MITF overexpression is occasionally explained by gene amplification, but here we show that super-enhancers are also important determinants of MITF overexpression in some melanoma cell lines and tumors. Although compounds that directly inhibit MITF are unavailable, a covalent CDK7 inhibitor, THZ1, has recently been shown to potently suppress the growth of various cancers through the depletion of master transcription-regulating oncogenes and the disruption of their attendant super-enhancers. We also show that melanoma cells are highly sensitive to CDK7 inhibition both in vitro and in vivo and that THZ1 can dismantle the super-enhancer apparatus at MITF and SOX10 in some cell lines, thereby extinguishing their intracellular levels. Our results show a dimension to MITF regulation in melanoma cells and point to CDK7 inhibition as a potential strategy to deprive oncogenic transcription and suppress tumor growth in melanoma.

Kv7.2-7.5 voltage-gated potassium channel (KCNQ2-5) opener, retigabine, reduces capsaicin-induced visceral pain in mice

K(v)7.2-7.5 voltage-gated potassium channels (KCNQ2-5) are associated with M-current and known to distribute in the nociceptive sensory pathway (e.g., dorsal root ganglia and spinal cord). Opening of these channels leads to cell membrane hyperpolarization that results in decreased neuronal action potentials. Since, KCNQ/M-current is located in the visceral sensory system, we examined the anti-nociceptive effect of the KCNQ opener, retigabine, on visceral pain induced by an intracolonic injection of capsaicin in mice. Intraperitoneal administration of retigabine (1, 3 and 10 mg/kg) dose-dependently suppressed visceral pain behavior (i.e., the number of licking) induced by the capsaicin treatment and prolonged the latency to first licking. These data provide the first evidence that increased KCNQ channel conductance plays an inhibitory role in the visceral pain pathway.

HDAC3 inhibitor suppresses endothelial-to-mesenchymal transition via modulating inflammatory response in atherosclerosis

A total number of 18 different isoforms of histone deacetylases (HDACs) which were categorized into 4 classes have been identified in human. HDAC3 is categorized as class I HDACs and is closely related to the occurrence and development of atherosclerosis. Recent evidence has pointed to endothelial-to-mesenchymal transition (EndMT) as a key process in vascular inflammation in atherosclerosis. However, little is known about the effect of HDAC3 on EndMT in atherosclerosis. Therefore, we aimed to investigate the effect of HDAC3 specific inhibitor on EndMT in ApoE^-/- mice fed a Western diet and human umbilical vein endothelial cells (HUVECs) induced by inflammatory cytokines. Firstly, we found that HDAC3 expression was up-regulated and EndMT occurred in the aortas of ApoE^-/- mice compared with C57BL/6J mice. However, HDAC3 specific inhibitor RGFP966 alleviated atherosclerotic lesions and inhibited EndMT of the atherosclerotic plaque in ApoE^-/- mice. Then, in vitro study showed that inflammatory cytokines TNF-α and IL-1β co-treatment increased the expression of HDAC3 and induced EndMT in HUVECs. HDAC3 inhibition by siRNA or specific inhibitor RGFP966 suppressed EndMT in HUVECs stimulated with TNF-α and IL-1β. By contrast, HDAC3 overexpression by adenovirus further promoted EndMT of HUVECs. In addition, we found that HDAC3 also regulated the inflammatory response of HUVECs by modulating the expression of inflammatory cytokines and the number of monocytes attached to HUVECs. These above results suggest that HDAC3 inhibitor suppresses EndMT via modulating inflammatory response in ApoE^-/- mice and HUVECs.

Effect of the new antiepileptic drug retigabine in a rodent model of mania

Bipolar spectrum disorders are severe chronic mood disorders that are characterized by episodes of mania or hypomania and depression. Because patients with manic symptoms often experience clinical benefit from treatment with anticonvulsant drugs, it was hypothesized that retigabine, a novel compound with anticonvulsant efficacy, may also possess antimanic activity. The amphetamine (AMPH)+chlordiazepoxide (CDP)-induced hyperactivity model has been proposed as a suitable model for studying antimanic-like activity of novel compounds in mice and rats. The aims of the present study in rats were therefore (1) to confirm previous findings with lithium and lamotrigine, and (2) to evaluate the effect of the novel compound retigabine on AMPH+CDP-induced hyperactivity in rats. In all experiments, co-administration of AMPH and CDP induced a significant increase (191-295%) in locomotor activity. Lithium chloride (0.9 mg/kg) and lamotrigine (20 mg/kg), which are known to effectively stabilize mood in humans, both significantly decreased AMPH+CDP-induced locomotor activity without affecting basal locomotor activity. The results furthermore indicate that retigabine, like lithium and lamotrigine, significantly and dose-dependently attenuates the induced hyperactivity at a lowest effective dose of 1.0 mg/kg, whereas basal locomotor activity is reduced only at doses 4.0 mg/kg. In conclusion, retigabine was found to have an antimanic-like effect in the AMPH+CDP-induced hyperactivity model, suggesting a potential role for retigabine in the treatment of mania and possibly in the management of bipolar disorder.

The anticonvulsant retigabine is a subtype selective modulator of GABAA receptors

OBJECTIVE

Within its range of therapeutic plasma concentrations, the anticonvulsant retigabine (ezogabine) is believed to selectively act on Kv7 channels. Here, the contribution of specific γ-aminobutyric acid (GABA)A receptor subtypes to the antiseizure effects of retigabine was investigated.

METHODS

Using patch-clamp recordings, seizure-like activity, tonic currents, and GABA-induced currents in hippocampal neurons were tested for their sensitivity toward retigabine, as were recombinant GABAA receptors expressed in tsA 201 cells.

RESULTS

Retigabine reduced seizure-like activity elicited by low Mg(2+) in a concentration-dependent manner with half maximal inhibition at 1 μm. Seizure-like activity triggered by blocking either Kv7 channels or GABAA receptors was equally reduced by retigabine, but when these channels/receptors were blocked simultaneously, the inhibition was lost. Retigabine (10 μm) enhanced bicuculline-sensitive tonic currents in hippocampal neurons, but failed to affect GABA-evoked currents. However, when receptors involved in phasic GABAergic inhibition were blocked by penicillin, retigabine did enhance GABA-evoked currents. In tsA 201 cells expressing various combinations of GABAA receptor subunits, 10 μm retigabine enhanced currents through α1β2δ, α4β2δ, α4β3δ, and α6β2δ receptors, but left currents through α1β2γ2S, α4β3γ2S, α5β3γ2S, and α6β2γ2S receptors unaltered. With αβ receptors, retigabine diminished currents through α1β2 and α4β3, but increased currents through α6β2 receptors. The enhancement of currents through α1β2δ receptors by retigabine was concentration dependent and became significant at 1 μm.

SIGNIFICANCE

These results demonstrate that retigabine is a subtype selective modulator of GABAA receptors with preference for extrasynaptic δ-containing receptors; this property may contribute to its broad antiepileptic effectiveness and explain its lack of effect on absence seizures.

Antiepileptogenic and antiictogenic effects of retigabine under conditions of rapid kindling: an ontogenic study

PURPOSE

To examine antiepileptogenic and antiictogenic potential of retigabine (RTG) under conditions of rapid kindling epileptogenesis during different stages of development.

METHODS

The experiments were performed in postnatal day 14 (P14), P21, and P35 male Wistar rats. After stereotaxic implantation of hippocampal stimulating and recording electrodes, the effects of RTG on baseline afterdischarge (AD) properties were studied. Next, the animals underwent rapid kindling (sixty 10 s trains, bipolar 20 Hz square wave pulses delivered every 5 min). The progression of seizures (kindling acquisition), and responses to test stimulations after kindling (retention) were compared between RTG and vehicle-treated rats. Additionally, the effects of RTG on the severity of seizures in previously kindled animals were examined.

RESULTS

When administered intraperitoneally in doses that induced only mild, or no motor deficits, RTG significantly dampened brain excitability, evident as the increase of AD threshold and shortening of AD duration. During kindling, RTG delayed the development of focal seizures in P14 rats, and prevented the occurrence of full limbic seizures at all three ages. At P14 and P21, but not at P35, pretreatment with RTG prevented the establishment of kindling-induced enhanced seizure susceptibility. Administration of RTG to kindled animals decreased the severity of seizures induced by test stimulation. The effect was most prominent at P14.

DISCUSSION

RTG exerted both antiepileptogenic and antiictogenic effects under conditions of rapid kindling model. These effects were apparent during postneonatal, early childhood, and adolescent stages of development.

Neuropathic pain and Kv7 voltage-gated potassium channels: The potential role of Kv7 activators in the treatment of neuropathic pain

Neuropathic pain conditions severely and chronically affect the quality of life in a large human population, but the pain conditions are not adequately managed due to poor understanding of their underlying mechanisms. There is a pressing need for further research into this field to help develop effective and nonaddictive medications to treat neuropathic pain. This article first describes general clinical classification of pain, types and symptoms of neuropathic pain, and current practices of clinical management for neuropathic pain. This is followed by a discussion of various cellular and molecular mechanisms responsible for the development and maintenance of neuropathic pain. In this review, we highlight the loss of function of Kv7 voltage-gated potassium as a mechanism of neuropathic pain and the potential use of Kv7 channel activator as subsequent treatment.

Ferrostatin-1 attenuates ferroptosis and protects the retina against light-induced retinal degeneration

Degenerative retinal diseases, including age-related macular degeneration, are serious diseases that may lead to irreversible retinal neuron damage and permanent vision impairment. There are currently no effective treatments for these diseases due to our incomplete understanding of the underlying pathological mechanisms. Ferroptosis, a newly identified iron-dependent mode of cell death, is implicated in various diseases. However, it is unknown whether ferroptosis is involved in light-induced retinal degeneration. In this study, we found that light exposure significantly reduced the viability of photoreceptor cells in vitro and induced pro-ferroptotic changes, including iron accumulation, mitochondrial shrinkage, glutathione depletion, increased malondialdehyde (MDA), and decreased protein expression of SLC7A11 and GPX4. The effects of light exposure on ferroptosis were attenuated by ferrostatin-1. Consistently, the results of in vivo studies demonstrated that ferrostatin-1 protected against light-induced ferroptosis. And it exerted therapeutic effects by inhibiting neuroinflammation and prevented the effects of light exposure on the structure and function of the retina. The findings reveal an important role of ferroptosis in the pathogenesis of light-induced retinal degeneration and suggest that ferroptosis may be a novel treatment target for preventing retinal degeneration.

Is there a role for potassium channel openers in neuronal ion channel disorders?

Malfunction in ion channels, due to mutations in genes encoding channel proteins or the presence of autoantibodies, are increasing being implicated in causing disease conditions, termed channelopathies. Dysfunction of potassium (K(+)) channels has been associated with the pathophysiology of a number of neurological, as well as peripheral, disorders (e.g., episodic ataxia, epilepsy, neuromyotonia, Parkinson's disease, congenital deafness, long QT syndrome). K(+) channels, which demonstrate a high degree of diversity and ubiquity, are fundamental in the control of membrane depolarisation and cell excitability. A common feature of K(+) channelopathies is a reduction or loss of membrane potential repolarisation. The identification of K(+) channel subtype specific openers will allow the recovery of the mechanism(s) responsible for counteraction of uncontrolled cellular depolarisation. Synthetic agents that demonstrate K(+) channel opening properties are available for a variety of K(+) channel subtypes (e.g., K(ATP), BK(Ca), GIRK and M-channel). This study reviews the realistic therapeutic potential that may be gained in a broad spectrum of clinical conditions by K(+) channel openers. K(+) channel openers would therefore identify dysfunctional K(+) channel as therapeutic targets for clinical benefit, in addition being able to modulate normally functioning K(+) channels to gain clinical management of pathophysiological events irrespective of the cause.