Network pharmacology for antiepileptogenesis: Tolerability and neuroprotective effects of novel multitargeted combination treatments in nonepileptic vs. post-status epilepticus mice

MiR-324-5p inhibition after intrahippocampal kainic acid-induced status epilepticus does not prevent epileptogenesis in mice

Background

Acquired epilepsies are caused by an initial brain insult that is followed by epileptogenesis and finally the development of spontaneous recurrent seizures. The mechanisms underlying epileptogenesis are not fully understood. MicroRNAs regulate mRNA translation and stability and are frequently implicated in epilepsy. For example, antagonism of a specific microRNA, miR-324-5p, before brain insult and in a model of chronic epilepsy decreases seizure susceptibility and frequency, respectively. Here, we tested whether antagonism of miR-324-5p during epileptogenesis inhibits the development of epilepsy.

Methods

We used the intrahippocampal kainic acid (IHpKa) model to initiate epileptogenesis in male wild type C57BL/6 J mice aged 6-8 weeks. Twenty-four hours after IHpKa, we administered a miR-324-5p or scrambled control antagomir intracerebroventricularly and implanted cortical surface electrodes for EEG monitoring. EEG data was collected for 28 days and analyzed for seizure frequency and duration, interictal spike activity, and EEG power. Brains were collected for histological analysis.

Results

Histological analysis of brain tissue showed that IHpKa caused characteristic hippocampal damage in most mice regardless of treatment. Antagomir treatment did not affect latency to, frequency, or duration of spontaneous recurrent seizures or interictal spike activity but did alter the temporal development of frequency band-specific EEG power.

Conclusion

These results suggest that miR-324-5p inhibition during epileptogenesis induced by status epilepticus does not convey anti-epileptogenic effects despite having subtle effects on EEG frequency bands. Our results highlight the importance of timing of intervention across epilepsy development and suggest that miR-324-5p may act primarily as a proconvulsant rather than a pro-epileptogenic regulator.

Bumetanide potentiates the anti-seizure and disease-modifying effects of midazolam in a noninvasive rat model of term birth asphyxia

Birth asphyxia and the resulting hypoxic-ischemic encephalopathy (HIE) are highly associated with perinatal and neonatal death, neonatal seizures, and an adverse later-life outcome. Currently used drugs, including phenobarbital and midazolam, have limited efficacy to suppress neonatal seizures. There is a medical need to develop new therapies that not only suppress neonatal seizures but also prevent later-life consequences. We have previously shown that the loop diuretic bumetanide does not potentiate the effects of phenobarbital in a rat model of birth asphyxia. Here we compared the effects of bumetanide (0.3 or 10 mg/kg i.p.), midazolam (1 mg/kg i.p.), and a combination of bumetanide and midazolam on neonatal seizures and later-life outcomes in this model. While bumetanide at either dose was ineffective when administered alone, the higher dose of bumetanide markedly potentiated midazolam's effect on neonatal seizures. Median bumetanide brain levels (0.47-0.53 µM) obtained with the higher dose were in the range known to inhibit the Na-K-Cl-cotransporter NKCC1 but it remains to be determined whether brain NKCC1 inhibition was underlying the potentiation of midazolam. When behavioral and cognitive alterations were examined over three months after asphyxia, treatment with the bumetanide/midazolam combination, but not with bumetanide or midazolam alone, prevented impairment of learning and memory. Furthermore, the combination prevented the loss of neurons in the dentate hilus and aberrant mossy fiber sprouting in the CA3a area of the hippocampus. The molecular mechanisms that explain that bumetanide potentiates midazolam but not phenobarbital in the rat model of birth asphyxia remain to be determined.

The metabolic basis of epilepsy

The brain is a highly energy-demanding organ and requires bioenergetic adaptability to balance normal activity with pathophysiological fuelling of spontaneous recurrent seizures, the hallmark feature of the epilepsies. Recurrent or prolonged seizures have long been known to permanently alter neuronal circuitry and to cause excitotoxic injury and aberrant inflammation. Furthermore, pathological changes in bioenergetics and metabolism are considered downstream consequences of epileptic seizures that begin at the synaptic level. However, as we highlight in this Review, evidence is also emerging that primary derangements in cellular or mitochondrial metabolism can result in seizure genesis and lead to spontaneous recurrent seizures. Basic and translational research indicates that the relationships between brain metabolism and epileptic seizures are complex and bidirectional, producing a vicious cycle that compounds the deleterious consequences of seizures. Metabolism-based treatments such as the high-fat, antiseizure ketogenic diet have become mainstream, and metabolic substrates and enzymes have become attractive molecular targets for seizure prevention and recovery. Moreover, given that metabolism is crucial for epigenetic as well as inflammatory changes, the idea that epileptogenesis can be both negatively and positively influenced by metabolic changes is rapidly gaining ground. Here, we review evidence that supports both pathophysiological and therapeutic roles for brain metabolism in epilepsy.

Pericardial Injection of Kainic Acid Induces a Chronic Epileptic State in Larval Zebrafish

Epilepsy is a common disorder of the brain characterized by spontaneous recurrent seizures, which develop gradually during a process called epileptogenesis. The mechanistic processes underlying the changes of brain tissue and networks toward increased seizure susceptibility are not fully understood. In rodents, injection of kainic acid (KA) ultimately leads to the development of spontaneous epileptic seizures, reflecting similar neuropathological characteristics as seen in patients with temporal lobe epilepsy (TLE). Although this model has significantly contributed to increased knowledge of epileptogenesis, it is technically demanding, costly to operate and hence not suitable for high-throughput screening of anti-epileptic drugs (AEDs). Zebrafish, a vertebrate with complementary advantages to rodents, is an established animal model for epilepsy research. Here, we generated a novel KA-induced epilepsy model in zebrafish larvae that we functionally and pharmacologically validated. KA was administered by pericardial injection at an early zebrafish larval stage. The epileptic phenotype induced was examined by quantification of seizure-like behavior using automated video recording, and of epileptiform brain activity measured via local field potential (LFP) recordings. We also assessed GFP-labeled GABAergic and RFP-labeled glutamatergic neurons in double transgenic KA-injected zebrafish larvae, and examined the GABA and glutamate levels in the larval heads by liquid chromatography with tandem mass spectrometry detection (LC-MS/MS). Finally, KA-injected larvae were exposed to five commonly used AEDs by immersion for pharmacological characterization of the model. Shortly after injection, KA induced a massive damage and inflammation in the zebrafish brain and seizure-like locomotor behavior. An abnormal reorganization of brain circuits was observed, a decrease in both GABAergic and glutamatergic neuronal population and their associated neurotransmitters. Importantly, these changes were accompanied by spontaneous and continuous epileptiform brain discharges starting after a short latency period, as seen in KA rodent models and reminiscent of human pathology. Three out of five AEDs tested rescued LFP abnormalities but did not affect the seizure-like behavior. Taken together, for the first time we describe a chemically-induced larval zebrafish epilepsy model offering unique insights into studying epileptogenic processes in vivo and suitable for high-throughput AED screening purposes and rapid genetic investigations.

Single-Target Versus Multi-Target Drugs Versus Combinations of Drugs With Multiple Targets: Preclinical and Clinical Evidence for the Treatment or Prevention of Epilepsy

Rationally designed multi-target drugs (also termed multimodal drugs, network therapeutics, or designed multiple ligands) have emerged as an attractive drug discovery paradigm in the last 10-20 years, as potential therapeutic solutions for diseases of complex etiology and diseases with significant drug-resistance problems. Such agents that modulate multiple targets simultaneously are developed with the aim of enhancing efficacy or improving safety relative to drugs that address only a single target or to combinations of single-target drugs. Although this strategy has been proposed for epilepsy therapy >25 years ago, to my knowledge, only one antiseizure medication (ASM), padsevonil, has been intentionally developed as a single molecular entity that could target two different mechanisms. This novel drug exhibited promising effects in numerous preclinical models of difficult-to-treat seizures. However, in a recent randomized placebo-controlled phase IIb add-on trial in treatment-resistant focal epilepsy patients, padsevonil did not separate from placebo in its primary endpoints. At about the same time, a novel ASM, cenobamate, exhibited efficacy in several randomized controlled trials in such patients that far surpassed the efficacy of any other of the newer ASMs. Yet, cenobamate was discovered purely by phenotype-based screening and its presumed dual mechanism of action was only described recently. In this review, I will survey the efficacy of single-target vs. multi-target drugs vs. combinations of drugs with multiple targets in the treatment and prevention of epilepsy. Most clinically approved ASMs already act at multiple targets, but it will be important to identify and validate new target combinations that are more effective in drug-resistant epilepsy and eventually may prevent the development or progression of epilepsy.

Mechanism of Huoxue Tongluo Decoction in treatment of erectile dysfunction caused by ischemic stroke based on network pharmacology

Objective

To study the therapeutic effect of Huoxue Tongluo Decoction (HXTLD) on erectile dysfunction caused by ischemic stroke and identify the mechanisms involved.

Methods

Network pharmacology was used to predict the key active ingredients and targets of HXTLD. Surgical methods were used to create a rat model of ischemic stroke. The rats were then given a suspension of HXTLD by ig administration. Erectile function was evaluated by Apomorphine (APO) induction. Real-time fluorescence quantitative reverse transcription-polymerase chain reaction (Real-time PCR) and Western blotting were used to detect the expression of related mRNAs and proteins in rat penile corpus cavernous tissue and brain tissue. Hematoxylin & Eosin (HE) staining was used to investigate structural changes in the penile cavernous tissue.

Results

Network pharmacology showed that tumor necrosis factor (TNF), nitric oxide synthase 3 (eNOS), and vascular endothelial growth factor (VEGF) were the key targets of HXTLD in the treatment of erectile dysfunction caused by ischemic stroke. Experimental studies showed that HXTLD improved erectile dysfunction caused by ischemic stroke. HE results showed that HXTLD improved the structure of the corpus cavernosa. HXTLD also inhibited the expression of TNF and VEGF proteins in penile tissue (P < 0.05) and enhanced the expression of eNOS protein in penile tissue (P < 0.05).

Conclusion

HXTLD improved the erectile function of rats with erectile dysfunction caused by ischemic stroke by regulating the mRNA and protein levels of TNF, eNOS and VEGF.

New approaches for developing multi-targeted drug combinations for disease modification of complex brain disorders. Does epilepsy prevention become a realistic goal?

Over decades, the prevailing standard in drug discovery was the concept of designing highly selective compounds that act on individual drug targets. However, more recently, multi-target and combinatorial drug therapies have become an important treatment modality in complex diseases, including neurodegenerative diseases such as Alzheimer's and Parkinson's disease. The development of such network-based approaches is facilitated by the significant advance in our understanding of the pathophysiological processes in these and other complex brain diseases and the adoption of modern computational approaches in drug discovery and repurposing. However, although drug combination therapy has become an effective means for the symptomatic treatment of many complex diseases, the holy grail of identifying clinically effective disease-modifying treatments for neurodegenerative and other brain diseases remains elusive. Thus, despite extensive research, there remains an urgent need for novel treatments that will modify the progression of the disease or prevent its development in patients at risk. Here we discuss recent approaches with a focus on multi-targeted drug combinations for prevention or modification of epilepsy. Over the last ~10 years, several novel promising multi-targeted therapeutic approaches have been identified in animal models. We envision that synergistic combinations of repurposed drugs as presented in this review will be demonstrated to prevent epilepsy in patients at risk within the next 5-10 years.

How to Find Candidate Drug-targets for Antiepileptogenic Therapy?

Although over 25 antiepileptic drugs (AEDs) have become currently available for clinical use, the incidence of epilepsy worldwide and the proportions of drug-resistant epilepsy among them are not significantly reduced during the past decades. Traditional screens for AEDs have been mainly focused on their anti-ictogenic roles, and their efficacies primarily depend on suppressing neuronal excitability or enhancing inhibitory neuronal activity, almost without the influence on the epileptogenesis or with inconsistent results from different studies. Epileptogenesis refers to the pathological process of a brain from its normal status to the alterations with the continuous prone of unprovoked spontaneous seizures after brain insults, such as stroke, traumatic brain injury, CNS infectious, and autoimmune disorders, and even some specific inherited conditions. Recently growing experimental and clinical studies have discovered the underlying mechanisms for epileptogenesis, which are multi-aspect and multistep. These findings provide us a number of interesting sites for antiepileptogenic drugs (AEGDs). AEGDs have been evidenced as significantly roles of postponing or completely blocking the development of epilepsy in experimental models. The present review will introduce potential novel candidate drug-targets for AEGDs based on the published studies.

Systematic evaluation of rationally chosen multitargeted drug combinations: a combination of low doses of levetiracetam, atorvastatin and ceftriaxone exerts antiepileptogenic effects in a mouse model of acquired epilepsy

Epileptogenesis, the gradual process that leads to epilepsy after brain injury or genetic mutations, is a complex network phenomenon, involving a variety of morphological, biochemical and functional brain alterations. Although risk factors for developing epilepsy are known, there is currently no treatment available to prevent epilepsy. We recently proposed a multitargeted, network-based approach to prevent epileptogenesis by rationally combining clinically available drugs and provided first proof-of-concept that this strategy is effective. Here we evaluated eight novel rationally chosen combinations of 14 drugs with mechanisms that target different epileptogenic processes. The combinations consisted of 2-4 different drugs per combination and were administered systemically over 5 days during the latent epileptogenic period in the intrahippocampal kainate mouse model of acquired temporal lobe epilepsy, starting 6 h after kainate. Doses and dosing intervals were based on previous pharmacokinetic and tolerability studies in mice. The incidence and frequency of spontaneous electrographic and electroclinical seizures were recorded by continuous (24/7) video linked EEG monitoring done for seven days at 4 and 12 weeks post-kainate, i.e., long after termination of drug treatment. Compared to vehicle controls, the most effective drug combination consisted of low doses of levetiracetam, atorvastatin and ceftriaxone, which markedly reduced the incidence of electrographic seizures (by 60%; p<0.05) and electroclinical seizures (by 100%; p<0.05) recorded at 12 weeks after kainate. This effect was lost when higher doses of the three drugs were administered, indicating a synergistic drug-drug interaction at the low doses. The potential mechanisms underlying this interaction are discussed. We have discovered a promising novel multitargeted combination treatment for modifying the development of acquired epilepsy.

Role of Adenosine in Epilepsy and Seizures

Adenosine is an endogenous anticonvulsant and neuroprotectant of the brain. Seizure activity produces large quantities of adenosine, and it is this seizure-induced adenosine surge that normally stops a seizure. However, within the context of epilepsy, adenosine plays a wide spectrum of different roles. It not only controls seizures (ictogenesis), but also plays a major role in processes that turn a normal brain into an epileptic brain (epileptogenesis). It is involved in the control of abnormal synaptic plasticity and neurodegeneration and plays a major role in the expression of comorbid symptoms and complications of epilepsy, such as sudden unexpected death in epilepsy (SUDEP). Given the important role of adenosine in epilepsy, therapeutic strategies are in development with the goal to utilize adenosine augmentation not only for the suppression of seizures but also for disease modification and epilepsy prevention, as well as strategies to block adenosine A_2A receptor overfunction associated with neurodegeneration. This review provides a comprehensive overview of the role of adenosine in epilepsy.

Epigenetics and epilepsy prevention: The therapeutic potential of adenosine and metabolic therapies

Prevention of epilepsy and its progression remains the most urgent need for epilepsy research and therapy development. Novel conceptual advances are required to meaningfully address this fundamental challenge. Maladaptive epigenetic changes, which include methylation of DNA and acetylation of histones - among other mechanisms, are now well recognized to play a functional role in the development of epilepsy and its progression. The methylation hypothesis of epileptogenesis suggests that changes in DNA methylation are implicated in the progression of the disease. In this context, global DNA hypermethylation is particularly associated with chronic epilepsy. Likewise, acetylation changes of histones have been linked to epilepsy development. Clinical as well as experimental evidence demonstrate that epilepsy and its progression can be prevented by metabolic and biochemical manipulations that target previously unrecognized epigenetic functions contributing to epilepsy development and maintenance of the epileptic state. This review will discuss epigenetic mechanisms implicated in epilepsy development as well as metabolic and biochemical interactions thought to drive epileptogenesis. Therefore, metabolic and biochemical mechanisms are identified as novel targets for epilepsy prevention. We will specifically discuss adenosine biochemistry as a novel therapeutic strategy to reconstruct the DNA methylome as antiepileptogenic strategy as well as metabolic mediators, such as beta-hydroxybutyrate, which affect histone acetylation. Finally, metabolic dietary interventions (such as the ketogenic diet) which have the unique potential to prevent epileptogenesis through recently identified epigenetic mechanisms will be reviewed. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Epilepsy Benchmarks Area II: Prevent Epilepsy and Its Progression

Area II of the 2014 Epilepsy Research Benchmarks aims to establish goals for preventing the development and progression of epilepsy. In this review, we will highlight key advances in Area II since the last summary of research progress and opportunities was published in 2016. We also highlight areas of investigation that began to develop before 2016 and in which additional progress has been made more recently.

Proof-of-concept that network pharmacology is effective to modify development of acquired temporal lobe epilepsy

Epilepsy is a complex network phenomenon that, as yet, cannot be prevented or cured. We recently proposed network-based approaches to prevent epileptogenesis. For proof of concept we combined two drugs (levetiracetam and topiramate) for which in silico analysis of drug-protein interaction networks indicated a synergistic effect on a large functional network of epilepsy-relevant proteins. Using the intrahippocampal kainate mouse model of temporal lobe epilepsy, the drug combination was administered during the latent period before onset of spontaneous recurrent seizures (SRS). When SRS were periodically recorded by video-EEG monitoring after termination of treatment, a significant decrease in incidence and frequency of SRS was determined, indicating antiepileptogenic efficacy. Such efficacy was not observed following single drug treatment. Furthermore, a combination of levetiracetam and phenobarbital, for which in silico analysis of drug-protein interaction networks did not indicate any significant drug-drug interaction, was not effective to modify development of epilepsy. Surprisingly, the promising antiepileptogenic effect of the levetiracetam/topiramate combination was obtained in the absence of any significant neuroprotective or anti-inflammatory effects as indicated by multimodal brain imaging and histopathology. High throughput RNA-sequencing (RNA-seq) of the ipsilateral hippocampus of mice treated with the levetiracetam/topiramate combination showed that several genes that have been linked previously to epileptogenesis, were significantly differentially expressed, providing interesting entry points for future mechanistic studies. Overall, we have discovered a novel combination treatment with promise for prevention of epilepsy.

The holy grail of epilepsy prevention: Preclinical approaches to antiepileptogenic treatments

A variety of acute brain insults can induce epileptogenesis, a complex process that results in acquired epilepsy. Despite advances in understanding mechanisms of epileptogenesis, there is currently no approved treatment that prevents the development or progression of epilepsy in patients at risk. The current concept of epileptogenesis assumes a window of opportunity following acute brain insults that allows intervention with preventive treatment. Recent results suggest that injury-induced epileptogenesis can be a much more rapid process than previously thought, suggesting that the 'therapeutic window' may only be open for a brief period, as in stroke therapy. However, experimental data also suggest a second, possibly delayed process ("secondary epileptogenesis") that influences the progression and refractoriness of the epileptic state over time, allowing interfering with this process even after onset of epilepsy. In this review, both methodological issues in preclinical drug development and novel targets for antiepileptogenesis will be discussed. Several promising drugs that either prevent epilepsy (antiepileptogenesis) or slow epilepsy progression and alleviate cognitive or behavioral comorbidities of epilepsy (disease modification) have been described in recent years, using diverse animal models of acquired epilepsy. Promising agents include TrkB inhibitors, losartan, statins, isoflurane, anti-inflammatory and anti-oxidative drugs, the SV2A modulator levetiracetam, and epigenetic interventions. Research on translational target validity and on prognostic biomarkers that can be used to stratify patients (or experimental animals) at high risk of developing epilepsy will hopefully soon lead to proof-of-concept clinical trials with the most promising drugs, which will be essential to make prevention of epilepsy a reality. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.