T-type channel blocking properties and antiabsence activity of two imidazo[1,2-b]pyridazine derivatives structurally related to indomethacin

Anesthesia and analgesia for experimental craniotomy in mice and rats: a systematic scoping review comparing the years 2009 and 2019

Experimental craniotomies are a common surgical procedure in neuroscience. Because inadequate analgesia appears to be a problem in animal-based research, we conducted this review and collected information on management of craniotomy-associated pain in laboratory mice and rats. A comprehensive search and screening resulted in the identification of 2235 studies, published in 2009 and 2019, describing craniotomy in mice and/or rats. While key features were extracted from all studies, detailed information was extracted from a random subset of 100 studies/year. Reporting of perioperative analgesia increased from 2009 to 2019. However, the majority of studies from both years did not report pharmacologic pain management. Moreover, reporting of multimodal treatments remained at a low level, and monotherapeutic approaches were more common. Among drug groups, reporting of pre- and postoperative administration of non-steroidal anti-inflammatory drugs, opioids, and local anesthetics in 2019 exceeded that of 2009. In summary, these results suggest that inadequate analgesia and oligoanalgesia are persistent issues associated with experimental intracranial surgery. This underscores the need for intensified training of those working with laboratory rodents subjected to craniotomies.

Systematic review registration

https://osf.io/7d4qe.

mGlu3 Metabotropic Glutamate Receptors as a Target for the Treatment of Absence Epilepsy: Preclinical and Human Genetics Data

BACKGROUND

Previous studies suggest that different metabotropic glutamate (mGlu) receptor subtypes are potential drug targets for treating absence epilepsy. However, no information is available on mGlu3 receptors.

OBJECTIVE

To examine whether (i) changes of mGlu3 receptor expression/signaling are found in the somatosensory cortex and thalamus of WAG/Rij rats developing spontaneous absence seizures; (ii) selective activation of mGlu3 receptors with LY2794193 affects the number and duration of spikewave discharges (SWDs) in WAG/Rij rats; and (iii) a genetic variant of GRM3 (encoding the mGlu3 receptor) is associated with absence epilepsy.

METHODS

Animals: immunoblot analysis of mGlu3 receptors, GAT-1, GLAST, and GLT-1; realtime PCR analysis of mGlu3 mRNA levels; assessment of mGlu3 receptor signaling; EEG analysis of SWDs; assessment of depressive-like behavior. Humans: search for GRM3 and GRM5 missense variants in 196 patients with absence epilepsy or other Idiopathic Generalized Epilepsy (IGE)/ Genetic Generalized Epilepsy (GGE) and 125,748 controls.

RESULTS

mGlu3 protein levels and mGlu3-mediated inhibition of cAMP formation were reduced in the thalamus and somatosensory cortex of pre-symptomatic (25-27 days old) and symptomatic (6-7 months old) WAG/Rij rats compared to age-matched controls. Treatment with LY2794193 (1 or 10 mg/kg, i.p.) reduced absence seizures and depressive-like behavior in WAG/Rij rats. LY2794193 also enhanced GAT1, GLAST, and GLT-1 protein levels in the thalamus and somatosensory cortex. GRM3 and GRM5 gene variants did not differ between epileptic patients and controls.

CONCLUSION

We suggest that mGlu3 receptors modulate the activity of the cortico-thalamo-cortical circuit underlying SWDs and that selective mGlu3 receptor agonists are promising candidate drugs for absence epilepsy treatment.

Imidazopyridazine Acetylcholinesterase Inhibitors Display Potent Anti-Proliferative Effects in the Human Neuroblastoma Cell-Line, IMR-32

Imidazo[1,2-b]pyridazine compounds are a new class of promising lead molecules to which we have incorporated polar nitro and amino moieties to increase the scope of their biological activity. Two of these substituted 3-nitro-6-amino-imidazo[1,2-b]pyridazine compounds (5c and 5h) showed potent acetylcholinesterase (AChE) inhibitory activity (IC₅₀ 40–50 nM), which we have previously reported. In this study, we wanted to test the biological efficacy of these compounds. Cytotoxicity assays showed that compound 5h mediated greater cell death with over 43% of cells dead at 100 μM and activation of caspase 3-mediated apoptosis. On the other hand, compound 5c mediated a dose-dependent decrease in cell proliferation. Both compounds showed cell cycle arrest in the G₀/G₁ phase and reduced cellular ATP levels leading to activation of adenosine monophosphate-activated protein kinase (AMPK) and enhanced mitochondrial oxidative stress. It has to be noted that all these effects were observed at doses beyond 10 μM, 200-fold above the IC₅₀ for AChE inhibition. Both compounds also inhibited bacterial lipopolysaccharide-mediated cyclooxygenase-2 and nitric oxide release in primary rat microglial cells. These results suggested that the substituted imidazo (1,2-b) pyridazine compounds, which have potent AChE inhibitory activity, were also capable of antiproliferative, anti-migratory, and anti-inflammatory effects at higher doses.

The effect of dexketoprofen trometamol on WAG/Rij rats with absence epilepsy (dexketoprofen in absence epilepsy)

AIM

Epilepsy is one of the most common neurological diseases. Dexketoprofen (DEX) is a nonselective nonsteroidal anti-inflammatory drug that is used as an analgesic. The present study aimed to assess the efficiency of DEX on WAG/Rij rats by electrophysiologically and behaviorally.

MATERIAL AND METHODS

Twenty-eight male WAG/Rij rats were used. The effects of acute treatment with DEX (5, 25, and 50 mg/kg, i.p) on absence-like seizures, and related psychiatric comorbidity were assessed. The ECoG recording was taken for 180 min before and after drug injection. After drug injection and EcoG recording, anxiety-depression-like behavior was tested with the open field test for 5 min.

RESULTS

The 5 mg/kg DEX significantly reduced the number and duration of SWDs percentage (p < 0.05) between 120 and 180 min, but 25 and 50 mg/kg DEX significantly increased the number and duration of SWDs percentage between 0 and 30 min (p < 0.05), and after 30 min the increase stopped (p > 0.05). And also, the 5 mg/kg DEX decreased the number and duration of SWDs percentage (p < 0.05) for 180 min (p < 0.05), but 25 and 50 mg/kg DEX administration did not alter (p > 0.05). The 5, 25, and 50 mg/kg doses of DEX significantly increased the duration of grooming (p < 0.05) but did not change the number of squares crossed (p > 0.05).

CONCLUSION

Low dose DEX reduced absence-like seizures, but care should be taken when using high doses in absence epilepsy. Also, it may be beneficial for painful diseases accompanied by anxiety-depression.

Etanercept rescues cognitive deficits, depression-like symptoms, and spike-wave discharge incidence in WAG/Rij rat model of absence epilepsy

Pro-inflammatory cytokines have been shown to be associated with the development of seizures in the WAG/Rij rat model of absence epilepsy. Importantly, WAG/Rij rats also exhibit cognitive deficits and depression-like behaviors. It is possible that pro-inflammatory cytokines mediate these comorbid conditions of absence epilepsy given their well-established effects on cognition and affective responses. The current study investigated the potential therapeutic effect of etanercept (tumor necrosis factor inhibitor) on cognitive impairment, depression-like behavior, and spike-wave discharges (SWDs) typically observed in the WAG/Rij rats. Eight-month-old male WAG/Rij rats and Wistar controls were tested in Morris water maze (MWM), passive avoidance (PA), forced swimming, sucrose preference, and locomotor activity tests, and electroencephalogram (EEG) recordings were taken from a separate group of WAG/Rij rats after 8 weeks of etanercept or vehicle treatment. Consistent with earlier work, WAG/Rij rats exhibited cognitive deficits and depression-like behavior. From these, the cognitive deficits and despair-like behavior were rescued by etanercept administration, which also reduced the frequency of SWDs without affecting their duration. Our results support the hypothesis that pro-inflammatory cytokines mediate the absence seizures and comorbid symptoms of absence epilepsy.

IL-6 Receptor Blockade by Tocilizumab Has Anti-absence and Anti-epileptogenic Effects in the WAG/Rij Rat Model of Absence Epilepsy

Increased expression of interleukin-6 (IL-6) both in cerebrospinal fluid (CSF) and plasma is closely associated with convulsive epilepsy and symptom severity of depression. By comparison, at present, little is known about the role of this cytokine in childhood (non-convulsive) absence epilepsy. The aim of this work was to investigate the potential effects of acute and chronic treatment with tocilizumab (TCZ, 10 and 30 mg/kg/day), on absence seizures, their development, and related psychiatric comorbidity in WAG/Rij rats. It is known that lipopolysaccharide (LPS)-induced changes in inflammatory processes increase absence epileptic activity. In order to study the central effects of TCZ, we investigated whether administration of this anti-IL-6R antibody could modulate the lipopolysaccharide (LPS) or IL-6-evoked changes in absence epileptic activity in WAG/Rij rats. Our results demonstrate that TCZ, at both doses, significantly reduced the development of absence seizures in adult WAG/Rij rats at 6 months of age (1 month after treatment suspension) compared with untreated controls, thus showing disease-modifying effects. Decreased absence seizure development at 6 months of age was also accompanied by reduced comorbid depressive-like behavior, whereas no effects were observed on anxiety-related behavior. Acute treatment with TCZ, at 30 mg/kg, had anti-absence properties lasting ~25 h. The co-administration TCZ with i.c.v. LPS or IL-6 showed that TCZ inhibited the worsening of absence seizures induced by both proinflammatory agents in the WAG/Rij rats, supporting a central anti-inflammatory-like protective action. These results suggest the possible role of IL-6 and consequent neuroinflammation in the epileptogenic process underlying the development and maintenance of absence seizures in WAG/Rij rats. Accordingly, IL-6 signaling could be a promising pharmacological target in absence epilepsy and depressive-like comorbidity.

An update of cyclooxygenase (COX)-inhibitors in epilepsy disorders

INTRODUCTION

Neuroinflammation has a critical role in brain disorders. Cyclooxygenase (COX) is one of the principal drug targets for the reduction of neuroinflammation; however, studies have yielded mixed results for COX-inhibitors in the treatment of diverse acute and chronic models of epilepsy.

AREAS COVERED

The article covers the effects of COX-inhibitors in epilepsy disorders. A considerable emphasis has been placed on the antiepileptic and 'disease-modifying' properties of COX-1 and COX-2 inhibitors in various preclinical epilepsy models.

EXPERT OPINION

The effect of COX-inhibitors on epilepsy is inconclusive. Studies have indicated beneficial effects in preclinical models; however, proconvulsant or no effects have also been observed. These molecules may have a bidirectional role with early neuroprotective and delayed neurotoxic effects. Further systematic preclinical studies to establish the use of COX-inhibitors in epilepsy are necessary.

Uric acid and allopurinol aggravate absence epileptic activity in Wistar Albino Glaxo Rijswijk rats

Uric acid has a role in several physiological and pathophysiological processes. For example, uric acid may facilitate seizure generalization while reducing uric acid level may evoke anticonvulsant/antiepileptic effects. Allopurinol blocks the activity of xanthine oxidase, by which allopurinol inhibits catabolism of hypoxanthine to xanthine and uric acid and, as a consequence, decreases the level of uric acid. Although the modulation of serum uric acid level is a widely used strategy in the treatment of certain diseases, our knowledge regarding the effects of uric acid on epileptic activity is far from complete. Thus, the main aim of this study was the investigation of the effect of uric acid on absence epileptic seizures (spike-wave discharges: SWDs) in a model of human absence epilepsy, the Wistar Albino Glaxo/Rijswijk (WAG/Rij) rat. We investigated the influence of intraperitoneally (i.p.) injected uric acid (100 mg/kg and 200 mg/kg), allopurinol (50 mg/kg and 100 mg/kg), a cyclooxygenase 1 and 2 (COX-1 and COX-2) inhibitor indomethacin (10 mg/kg) and inosine (500 mg/kg) alone and the combined application of allopurinol (50 mg/kg) with uric acid (100 mg/kg) or inosine (500 mg/kg) as well as indomethacin (10 mg/kg) with uric acid (100 mg/kg) and inosine (500 mg/kg) with uric acid (100 mg/kg) on absence epileptic activity. We demonstrated that both uric acid and allopurinol alone significantly increased the number of SWDs whereas indomethacin abolished the uric acid-evoked increase in SWD number. Our results suggest that uric acid and allopurinol have proepileptic effects in WAG/Rij rats.

Fingolimod Exerts only Temporary Antiepileptogenic Effects but Longer-Lasting Positive Effects on Behavior in the WAG/Rij Rat Absence Epilepsy Model

One of the major challenges in the epilepsy field is identifying disease-modifying drugs in order to prevent or delay spontaneous recurrent seizure onset or to cure already established epilepsy. It has been recently reported that fingolimod, currently approved for the treatment of relapsing-remitting multiple sclerosis, has demonstrated antiepileptogenic effects in 2 different preclinical models of acquired epilepsy. However, to date, no data exist regarding the role of fingolimod against genetic epilepsy. Therefore, we have addressed this issue by studying the effects of fingolimod in Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats, a well-established genetic model of absence epilepsy, epileptogenesis, and neuropsychiatric comorbidity. Our results have demonstrated that an early long-term treatment with fingolimod (1 mg/kg/day), started before absence seizure onset, has both antiepileptogenic and antidepressant-like effects in WAG/Rij rats. However, these effects were transitory, as 5 months after treatment discontinuation, both absence seizure and depressive like-behavior returned to control levels. Furthermore, a temporary reduction of mTOR signaling pathway activity, indicated by reduced phosphorylated mammalian target of rapamycin and phosphorylated p70S6k levels, and by increased phosphorylated Akt in WAG/Rij rats of 6 months of age accompanied the transitory antiepileptogenic effects of fingolimod. Surprisingly, fingolimod has demonstrated longer-lasting positive effects on cognitive decline in this strain. This effect was accompanied by an increased acetylation of lysine 8 of histone H4 (at both 6 and 10 months of age). In conclusion, our results support the antiepileptogenic effects of fingolimod. However, the antiepileptogenic effects were transitory. Moreover, fingolimod might also have a positive impact on animal behavior and particularly in protecting the development of memory decline.

Guanosine may increase absence epileptic activity by means of A2A adenosine receptors in Wistar Albino Glaxo Rijswijk rats

The non-adenosine nucleoside guanosine (Guo) was demonstrated to decrease quinolinic acid(QA)-induced seizures, spontaneously emerged absence epileptic seizures and lipopolysaccharide(LPS)-evoked induction of absence epileptic seizures suggesting its antiepileptic potential. It was also described previously that intraperitoneal (i.p.) injection of 20 and 50mg/kg Guo decreased the number of spike-wave discharges (SWDs) in a well investigated model of human absence epilepsy, the Wistar Albino Glaxo Rijswijk (WAG/Rij) rats during 4th (20mg/kg Guo) and 3rd as well as 4th (50mg/kg Guo) measuring hours. Guanosine can potentially decrease SWD number by means of its putative receptors but absence epileptic activity changing effects of Guo by means of increased extracellular adenosine (Ado) cannot be excluded. An increase in the dose of i.p. injected Guo is limited by its low solubility in saline, therefore, we addressed in the present study whether higher doses of Guo, diluted in sodium hydroxide (NaOH) solution, have more potent antiepileptic effect in WAG/Rij rats. We confirmed that i.p. 50mg/kg Guo decreased but, surprisingly, i.p. 100mg/kg Guo enhanced the number of SWDs in WAG/Rij rats. Combined i.p. injection of a non-selective Ado receptor antagonist theophylline (5mg/kg) or a selective Ado A2A receptor (A2AR) antagonist SCH 58261 (7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine) (1mg/kg) and a cyclooxygenase 1 and 2/COX-1 and COX-2 inhibitor indomethacin (10mg/kg) with 100mg/kg Guo decreased the SWD number compared to i.p. 100mg/kg Guo alone. The results suggest that i.p. 100mg/kg Guo can increase SWD number by means of the adenosinergic system.

The Role of Calcium Channels in Epilepsy

A central theme in the quest to unravel the genetic basis of epilepsy has been the effort to elucidate the roles played by inherited defects in ion channels. The ubiquitous expression of voltage-gated calcium channels (VGCCs) throughout the central nervous system (CNS), along with their involvement in fundamental processes, such as neuronal excitability and synaptic transmission, has made them attractive candidates. Recent insights provided by the identification of mutations in the P/Q-type calcium channel in humans and rodents with epilepsy and the finding of thalamic T-type calcium channel dysfunction in the absence of seizures have raised expectations of a causal role of calcium channels in the polygenic inheritance of idiopathic epilepsy. In this review, we consider how genetic variation in neuronal VGCCs may influence the development of epilepsy.

Early molecular and behavioral response to lipopolysaccharide in the WAG/Rij rat model of absence epilepsy and depressive-like behavior, involves interplay between AMPK, AKT/mTOR pathways and neuroinflammatory cytokine release

The mammalian target of rapamycin (mTOR) pathway has been recently indicated as a suitable drug target for the prevention of epileptogenesis. The mTOR pathway is known for its involvement in the control of the immune system. Since neuroinflammation is recognized as a major contributor to epileptogenesis, we wished to examine whether the neuroprotective effects of mTOR modulation could involve a suppression of the neuroinflammatory process in epileptic brain. We have investigated the early molecular mechanisms involved in the effects of intracerebral administration of the lipopolysaccharide (LPS) in the WAG/Rij rat model of absence epilepsy, in relation to seizure generation and depressive-like behavior; we also tested whether the effects of LPS could be modulated by treatment with rapamycin (RAP), a specific mTOR inhibitor. We determined, in specific rat brain areas, levels of p-mTOR/p-p70S6K and also p-AKT/p-AMPK as downstream or upstream indicators of mTOR activity and tested the effects of LPS and RAP co-administration. Changes in the brain levels of pro-inflammatory cytokines IL-1β and TNF-α and their relative mRNA expression levels were measured, and the involvement of nuclear factor-κB (NF-κB) was also examined in vitro. We confirmed that RAP inhibits the aggravation of absence seizures and depressive-like/sickness behavior induced by LPS in the WAG/Rij rats through the activation of mTOR and show that this effect is correlated with the ability of RAP to dampen and delay LPS increases in neuroinflammatory cytokines IL-1β and TNF-α, most likely through inhibition of the activation of NF-κB. Our results suggest that such a mechanism could contribute to the antiseizure, antiepileptogenic and behavioral effects of RAP and further highlight the potential therapeutic usefulness of mTOR inhibition in the management of human epilepsy and other neurological disorders. Furthermore, we show that LPS-dependent neuroinflammatory effects are also mediated by a complex interplay between AKT, AMPK and mTOR with specificity to selective brain areas. In conclusion, neuroinflammation appears to be a highly coordinated phenomenon, where timing of intervention may be carefully evaluated in order to identify the best suitable target.

Comparative proteomic approach in rat model of absence epilepsy

The aim of this study was to investigate cellular proteins in the pathogenesis of the genetic rat model of absence epilepsy. Protein spots were identified with peptide mass fingerprinting analysis using matrix-assisted laser desorption ionization time of flight mass spectrometry. Data were gathered from the frontoparietal cortex and thalamus of Wistar Albino Glaxo/Rij (WAG/Rij) and Wistar by using two-dimensional gel electrophoresis (2D-PAGE). Six proteins (Clathrin light chain-A protein, Transmembrane EMP24 Domain-Containing Protein, Stathmin-4, Myosin Light Chain4, Rheb, phosphoserine phosphatase) were found to be differentially expressed in the frontoparietal cortex of WAG/Rij and Wistar rats in both age groups. Another set of six proteins (Protein FAM89A and Oasl1, Gemin2, NuDEL1, Pur-beta, 3-alpha HSD) were found to be differentially expressed in the thalamus of WAG/Rij and Wistar rats. Findings from the frontoparietal cortex suggest the presence of altered serine metabolism and increased vesicular trafficking in the frontoparietal cortex of WAG/Rij rats compared with Wistar rats. These differences in the protein levels might reflect the crucial role of these proteins and related pathways in the generation of absence seizures. In the thalamic specimens, age-dependent changes in protein expression were remarkable, suggesting that this phenomenon may be a precursor or a consequence of absence seizures. Our findings further highlight the potential role of the mTOR signaling pathway in absence epilepsy.

T-type calcium channels inhibitors: a patent review

IMPORTANCE OF THE FIELD

T-type calcium channels are transmembrane proteins that regulate calcium entry in the cell in a voltage-dependent manner. Intracellular calcium levels are the key to many physiological processes, ranging from neuron firing to cardiac pacemaking. Inhibition of T-type calcium channels is heralded as a potential treatment to peripheral and CNS disorders, including hypertension, heart failure, sleep, epilepsy, drug addiction and neuropathic pain.

AREAS COVERED IN THIS REVIEW

A comprehensive summary of patent literature disclosing T-type calcium channels inhibitors is provided.

WHAT THE READER WILL GAIN

In all, 46 patent applications including 15 chemical structure classes are reviewed. Available in vitro, in vivo and clinical results are also discussed.

TAKE HOME MESSAGE

Several selective T-type calcium channels inhibitors with demonstrated in vitro and in vivo effects, including one Phase I clinical candidate, are now available. While future clinical results will be paramount to assess target validity in patients, these novel inhibitors represent excellent tools to further investigate the role of T-type channels in pathophysiological conditions.