Systemic adrenocorticotropic hormone administration down-regulates the expression of corticotropin-releasing hormone (CRH) and CRH-binding protein in infant rat hippocampus

Mechanisms of infantile epileptic spasms syndrome: What have we learned from animal models?

The devastating developmental and epileptic encephalopathy of infantile epileptic spasms syndrome (IESS) has numerous causes, including, but not limited to, brain injury, metabolic, and genetic conditions. Given the stereotyped electrophysiologic, age-dependent, and clinical findings, there likely exists one or more final common pathways in the development of IESS. The identity of this final common pathway is unknown, but it may represent a novel therapeutic target for infantile spasms. Previous research on IESS has focused largely on identifying the neuroanatomic substrate using specialized neuroimaging techniques and cerebrospinal fluid analysis in human patients. Over the past three decades, several animal models of IESS were created with an aim to interrogate the underlying pathogenesis of IESS, to identify novel therapeutic targets, and to test various treatments. Each of these models have been successful at recapitulating multiple aspects of the human IESS condition. These animal models have implicated several different molecular pathways in the development of infantile spasms. In this review we outline the progress that has been made thus far using these animal models and discuss future directions to help researchers identify novel treatments for drug-resistant IESS.

Animal Models in Epileptic Spasms and the Development of Novel Treatment Options

SUMMARY

The infantile spasms (IS) syndrome is a catastrophic developmental epileptic encephalopathy syndrome characterized by an age-specific expression of epileptic spasms that are associated with extremely abnormal, oftentimes described as chaotic, interictal EEG pattern known as hypsarrhythmia. Patients with IS generally have poor neurodevelopmental outcomes, in large part because of the frequent epileptic spasms and interictal EEG abnormalities. Current first-line treatments such as adrenocorticotropic hormone or vigabatrin are often ineffective and are associated with major toxic side effects. There is therefore a need for better and safer treatments for patients with IS, especially for the intractable population. Hope is on the horizon as, over the past 10 years, there has been robust progress in the development of etiology-specific animal models of IS. These models have been used to identify potential new treatments for IS and are beginning to provide some important insights into the pathophysiological substrates for this disease. In this review, we will highlight strengths and weaknesses of the currently available animal models of IS in addition to new insights into the pathophysiology and treatment options derived from these models.

A variant in the 3'-untranslated region of the MC2R gene decreases the risk of schizophrenia in a female Han Chinese population

Objective

Schizophrenia is a complex mental disorder with high heritability. The hypothalamic–pituitary–adrenal (HPA) axis, which is the stress system of the neuroendocrine system, is considered to impact psychotic disorders. We hypothesized that polymorphisms of HPA axis genes might be involved in the development of schizophrenia.

Methods

A case–control study comprising 234 patients with schizophrenia and 399 matched healthy controls was conducted to investigate the association between the human melanocortin 2 receptor (MC2R) gene and schizophrenia risk. Seven tag single nucleotide polymorphisms (SNPs) (rs16941303, rs16941314, rs2186944, rs28926188, rs7230126, rs948322, and rs948331) of MC2R were genotyped by direct sequencing.

Results

No significant associations were observed between any of the alleles, genotypes, or haplotypes examined within the MC2R gene and the risk of schizophrenia in the total group or in subgroups stratified by smoking or alcoholism. However, a subgroup analysis stratified by sex revealed that under the additive model, the C allele of the MC2R rs948331 SNP significantly decreased the risk of schizophrenia in females (odds ratio=0.18).

Conclusion

The C allele of the MC2R rs948331 locus may be a protective factor, reducing the risk of schizophrenia in the female Han Chinese population.

Hyperactive mTOR signals in the proopiomelanocortin-expressing hippocampal neurons cause age-dependent epilepsy and premature death in mice

Epilepsy is a frequent comorbidity in patients with focal cortical dysplasia (FCD). Recent studies utilizing massive sequencing data identified subsets of genes that are associated with epilepsy and FCD. AKT and mTOR-related signals have been recently implicated in the pathogenic processes of epilepsy and FCD. To clarify the functional roles of the AKT-mTOR pathway in the hippocampal neurons, we generated conditional knockout mice harboring the deletion of Pten (Pten-cKO) in Proopiomelanocortin-expressing neurons. The Pten-cKO mice developed normally until 8 weeks of age, then presented generalized seizures at 8–10 weeks of age. Video-monitored electroencephalograms detected paroxysmal discharges emerging from the cerebral cortex and hippocampus. These mice showed progressive hypertrophy of the dentate gyrus (DG) with increased expressions of excitatory synaptic markers (Psd95, Shank3 and Homer). In contrast, the expression of inhibitory neurons (Gad67) was decreased at 6–8 weeks of age. Immunofluorescence studies revealed the abnormal sprouting of mossy fibers in the DG of the Pten-cKO mice prior to the onset of seizures. The treatment of these mice with an mTOR inhibitor rapamycin successfully prevented the development of seizures and reversed these molecular phenotypes. These data indicate that the mTOR pathway regulates hippocampal excitability in the postnatal brain.

Neuropeptides as targets for the development of anticonvulsant drugs

Epilepsy is a common neurological disorder characterized by recurrent seizures. These seizures are due to abnormal excessive and synchronous neuronal activity in the brain caused by a disruption of the delicate balance between excitation and inhibition. Neuropeptides can contribute to such misbalance by modulating the effect of classical excitatory and inhibitory neurotransmitters. In this review, we discuss 21 different neuropeptides that have been linked to seizure disorders. These neuropeptides show an aberrant expression and/or release in animal seizure models and/or epilepsy patients. Many of these endogenous peptides, like adrenocorticotropic hormone, angiotensin, cholecystokinin, cortistatin, dynorphin, galanin, ghrelin, neuropeptide Y, neurotensin, somatostatin, and thyrotropin-releasing hormone, are able to suppress seizures in the brain. Other neuropeptides, such as arginine-vasopressine peptide, corticotropin-releasing hormone, enkephalin, β-endorphin, pituitary adenylate cyclase-activating polypeptide, and tachykinins have proconvulsive properties. For oxytocin and melanin-concentrating hormone both pro- and anticonvulsive effects have been reported, and this seems to be dose or time dependent. All these neuropeptides and their receptors are interesting targets for the development of new antiepileptic drugs. Other neuropeptides such as nesfatin-1 and vasoactive intestinal peptide have been less studied in this field; however, as nesfatin-1 levels change over the course of epilepsy, this can be considered as an interesting marker to diagnose patients who have suffered a recent epileptic seizure.

NR3C1 gene polymorphism for genetic susceptibility to infantile spasms in a Chinese population

AIMS

To test the genetic association of NR3C1 gene which encodes the glucocorticoid receptor with infantile spasms (IS).

MAIN METHODS

Nine single nucleotide polymorphisms (SNPs) within the NR3C1 gene were genotyped in a sample set of 128 cases and 131 controls. Association analysis was performed on the genotyped data.

KEY FINDINGS

Two SNPs, rs10482672 and rs2963155, showed nominal associations with IS (P=0.018, OR=1.89, 95% CI=1.11-3.22, for rs10482672; P=0.04, OR=1.70, 95% CI=1.03-2.81 for rs2963155) under the assumption of a dominant model. The haplotype TG of two SNPs (rs6877893 and rs4912905) was associated with a decreased risk of IS (P=0.038, OR=0.66, 95% CI=0.45-0.98), whereas haplotype TC being homozygous was associated with an increased risk of IS (P=0.015, OR=2.60, 95% CI=1.20-5.60). The rs6866893 was also associated with the responsiveness of adrenocorticotropic hormone.

SIGNIFICANCE

The current experimental results suggest the importance of the NR3C1 gene polymorphism for genetic susceptibility to IS in a Chinese population.

Effects of adrenal dysfunction and high-dose adrenocorticotropic hormone on NMDA-induced spasm seizures in young Wistar rats

Infantile spasms (IS) is a devastating epilepsy syndrome treated with adrenocorticotropic hormone (ACTH). To demonstrate the effects of adrenal dysfunction, adrenalectomy (ADX) and N-methyl-d-aspartate (NMDA)-induced rat model studies of IS were performed. The latency of the seizure in the ADX group decreased and the severity of seizures increased significantly. Hippocampal corticotropin-releasing hormone (CRH) mRNA was overexpressed in ADX rats. After ACTH administration, the latency increased and the severity of seizures decreased significantly. ADX increased seizure susceptibility of the rats to NMDA. Pretreatment with a single high dose of ACTH caused an obvious reduction in susceptibility to NMDA-induced seizures and suppressed CRH mRNA expression. These findings are especially useful for IS patients with adrenal diseases and worthy of further clinical study.

ACTH receptor (MC2R) promoter variants associated with infantile spasms modulate MC2R expression and responsiveness to ACTH

OBJECTIVE

Adrenocorticotropin hormone (ACTH) has been the standard treatment to infantile spasms (IS). However, the mechanism of ACTH therapy is still unclear. ACTH exerts the function via melanocortin 2 receptor (MC2R). Our previous study showed a common 4-single nucleotide polymorphism (SNP) haplotype TCCT at the MC2R promoter was strongly associated with responsiveness to ACTH therapy, where these 4 SNPs [rs1893219, rs1893220, rs2186944, and a novel SNP (T>C)] were mapped at position -853, -759, -7, and -2 bp based on the transcription start site of the MC2R gene. In this study, we further elucidated functional significances of the TCCT haplotype.

METHODS

To evaluate whether the TCCT haplotype influences MC2R transcription levels, the luciferase reporter vector was used by a transient transfection. Expression of rat MC2R cDNA driven by the TCCT-carrying or TCCC-carrying promoter was detected by the real-time quantitative reverse transcription-PCR. These assays were performed on cell lines cultured in absence or presence of ACTH.

RESULTS

In the baseline, the light intensity of the luciferase reporter assay driven by the TCCT promoter was four times higher than that by the TCCC promoter. The intensity was dramatically increased in the pGL3-TCCT after ACTH stimulation, compared to that in the pGL3-TCCC. MC2R expression assay showed a 5-fold increase in the TCCT promoter in presence of ACTH, compared with that in absence of ACTH.

CONCLUSION

The results showed that the haplotype TCCT in MC2R promoter significantly led to increased MC2R expression and strong responses to ACTH, providing evidence of the molecular mechanism of ACTH therapy in IS.

Justification of vigabatrin administration in West syndrome patients? Warranting a re-consideration for improvement in their quality of life

West syndrome (WS) or infantile spasms (IS) is a severe epileptic syndrome associated with poor prognosis and increased morbidity. The exact etio-pathogenesis of the disorder still remains elusive ant therefore the management continues to pose a challenge to the clinicians. Currently, adreno-corticotrophic hormone (ACTH), steroids and vigabatrin (VGB) form the mainstay of its treatment. However, the recent detection of an irreversible visual field defect observed in as high as 30-50% of children treated with vigabatrin has raised concern over the drug's usage. This brief paper is intended to highlight the significance of the irreversible visual toxicity in an already existent mentally challenged state in WS patients, which can lead to a worsening in the disability status of such patients. Therefore, based on the enhancement of handicap by VGB administration it is recommended that a comprehensive review be performed on its continuation in WS patients in order to prevent further deterioration of their quality of life (QOL).

Cardiac Vagal Activation by Adrenocorticotropic Hormone Treatment in Infants with West Syndrome

West syndrome (WS) is a generalized epileptic syndrome of infancy and early childhood with various etiologies, and consists of a triad of infantile spasm, arrest or regress of psychomotor development and specific electroencephalogram (EEG) pattern of hypsarrhythmia. WS had been believed to be refractory, but recent evidence supports effectiveness of adrenocorticotropic hormone (ACTH) treatment. The ACTH treatment, however, has a problem that it is often accompanied by adverse autonomic symptoms. We therefore examined heart rate variability (HRV) for assessing cardiac autonomic functions in WS and prospectively observed the changes during ACTH treatment. We studied 15 patients with WS and 9 age-matched controls during sleep (EEG stage 2). Compared with controls, the patients with WS were greater in the low-frequency component (LF) of HRV, an index reflecting sympatho-vagal interaction (p = 0.02), but were comparable for high-frequency component (HF) and LF-to-HF ratio (LF/HF), indices reflecting cardiac vagal activity and sympathetic predominance, respectively. During ACTH treatment, heart rate decreased (p < 0.01), LF and HF increased (p < 0.01), and LF/HF did not differ significantly. These results indicate that WS might be accompanied by autonomic changes and that ACTH treatment enhances parasympathetic function and causes bradycardia.

A nutrition odyssey: knowledge discovery, translation, and outreach. 2006 Ryley-Jeffs Memorial Lecture

BACKGROUND

The 21st-century model of health research is founded on a broad base of multidisciplinary research that is expeditiously and effectively translated into evidence-based practice, education, policy, and advocacy. The key objective is to improve the health of populations. DIETITIANS' ROLES: Dietitians, whether they are working in clinical or public health nutrition or food science, have a vital role to play in this paradigm of health research. As dietitians' roles have evolved beyond the traditional ones into subspecialties including epidemiology, nutrigenomics, functional foods, nutraceuticals, toxicology, natural health products, and multidisciplinary research, the need for advanced training in subspecialty fields has become essential.

OPPORTUNITIES

A dietetics background is an excellent foundation upon which to develop a research career in one of these new areas of nutrition. Opportunities for personnel awards and research funding targeted at nutrition clinician-scientists and other nutrition subspecialists have grown tremendously in recent years.

CONCLUSION

The information in this paper is intended to inspire dietitians seeking advanced academic training in one of the new exciting avenues for a career in nutrition. These avenues will permit dietitians to contribute to knowledge discovery, translation, and outreach to improve the nutritional status and health of populations in Canada and globally.

Expression of AgRP, NPY, POMC and CART in human fetal and adult hippocampus

The Agouti-Related Protein (AgRP), Neuropeptide Y (NPY), Proopiomelanocortin (POMC) and the Cocaine and Amphetamine-Regulated Transcript (CART) are four neuropeptides that play essential roles in the regulation of food intake and energy homeostasis in mammals. CART, POMC and NPY have also been suggested to play a role in the development of the hippocampus. We therefore employed quantitative real-time RT-PCR (qPCR) to analyze the expression levels of these genes in the fetal and adult human hippocampus to examine whether the four neuropeptides are differentially regulated in the hippocampus during development. CART (6.5-fold) and POMC (8.3-fold) mRNAs were significantly higher in the adult hippocampus. NPY on the other hand, was significantly reduced (2.1-fold) in the adult hippocampus, while AgRP mRNA was comparatively unchanged between fetal and adult hippocampus. In relative terms, CART mRNA was the highest and AgRP the lowest in both the fetal and adult hippocampus. CART, POMC and NPY are, therefore, differentially expressed in the human fetal and adult hippocampus and could play a role in its development or could be regulated by various stimuli involved in the development of this brain structure.

The latest on infantile spasms

PURPOSE OF REVIEW

This article reviews the most significant advances in the field of infantile spasm during the past year, with emphasis on best practise for treatment, and on some new etiological genetic and metabolic causes for the spasms, and new advances in the knowledge of tuberous sclerosis.

RECENT FINDINGS

Up-to-date information comparing corticotrophin, oral steroids and vigabatrin shows that hormonal treatment is the most effective therapy in the short term. In a recent randomized trial, large doses of prednisolone were as effective as corticotrophin. There are insufficient data to recommend any treatment schedule for infantile spasms. Vigabatrin is the choice for infants with tuberous sclerosis. Visual field defects in (older) children seem to be as common as in adults. In animals, vigabatrin can induce apoptosis of the neurons in the developing brain. New rare factors associated with infantile spasms are mitochondrial diseases, mutations of the Aristales-related homeobax gene and posterior quadrantic dysplasia syndrome. The outcome in children with tuberous sclerosis and infantile spasms is better understood.

SUMMARY

The accurate determination of etiology is now becoming increasingly possible. There is still a lack of consensus about the treatment of first choice for infantile spasms. However, recent data show that hormonal treatment is the most effective therapy in the short term. Frequency of visual field defects in children treated with vigabatrin should be studied in addition to the long-term outcome in general. Advances in our understanding of brain maturation, etiologies, mechanisms and genetics underlying catastrophic epilepsy may facilitate more effective pharmacologic interventions.