Alexander Disease Modeling in Zebrafish: An In Vivo System Suitable to Perform Drug Screening.

Alexander disease (AxD) is a rare astrogliopathy caused by heterozygous mutations, either inherited or arising de novo, on the glial fibrillary acid protein (GFAP) gene (17q21). Mutations in the GFAP gene make the protein prone to forming aggregates which, together with heat-shock protein 27 (HSP27), αB-crystallin, ubiquitin, and proteasome, contribute to form Rosenthal fibers causing a toxic effect on the cell. Unfortunately, no pharmacological treatment is available yet, except for symptom reduction therapies, and patients undergo a progressive worsening of the disease. The aim of this study was the production of a zebrafish model for AxD, to have a system suitable for drug screening more complex than cell cultures. To this aim, embryos expressing the human GFAP gene carrying the most severe p.R239C under the control of the zebrafish gfap gene promoter underwent functional validation to assess several features already observed in in vitro and other in vivo models of AxD, such as the localization of mutant GFAP inclusions, the ultrastructural analysis of cells expressing mutant GFAP, the effects of treatments with ceftriaxone, and the heat shock response. Our results confirm that zebrafish is a suitable model both to study the molecular pathogenesis of GFAP mutations and to perform pharmacological screenings, likely useful for the search of therapies for AxD.

[Clinical characteristics and diagnostic criteria on Alexander disease].

Alexander disease (ALXDRD) is a primary astrocyte disease caused by glial fibrillary acidic protein (GFAP) gene mutation. ALXDRD had been clinically regarded as a cerebral white matter disease that affects only children for about 50 years since the initial report in 1949; however, in the early part of the 21st century, case reports of adult-onset ALXDRD with medulla and spinal cord lesions increased. Basic research on therapies to reduce abnormal GFAP accumulation, such as drug-repositioning and antisense oligonucleotide suppression, has recently been published. The accumulation of clinical data to advance understanding of natural history is essential for clinical trials expected in the future. In this review, I classified ALXDRD into two subtypes: early-onset and late-onset, and detail the clinical symptoms, imaging findings, and genetic characteristics as well as the epidemiology and historical changes in the clinical classification described in the literature. The diagnostic criteria based on Japanese ALXDRD patients that are useful in daily clinical practice are also mentioned.

Inflammatory neuropathology of infantile Alexander disease: A case report.

BACKGROUND: Alexander disease (AxD) is a rare fatal leukodystrophy caused by a dominant missense mutation in the glial fibrillary acidic protein. In a mouse model of AxD, the pathological astrocyte causes a pronounced immune response. The inflammatory environment in the brain might play an important role in the neuronal dysfunction of AxD. CASE: A 3-month-old girl diagnosed with infantile AxD presented with severe intractable seizures and a deteriorated neurological state. Steroid pulse therapy was effective at preventing the epileptic activity and progressive white matter abnormalities on magnetic resonance images, but the effect was temporary. Levels of interleukin (IL)-6, IL-8, and macrophage chemotactic protein 1 (MCP-1) in the cerebrospinal fluid were high at onset and reduced transiently after steroid pulse therapy. DISCUSSION: These results suggest that inflammatory responses of astrocyte and microglia can contribute to the neuropathology of AxD. Robust immunomodulation that targets activated astrocytes and microglia may be a novel therapeutic strategy to improve neurological prognosis in AxD.

Antisense suppression of glial fibrillary acidic protein as a treatment for Alexander disease.

OBJECTIVE: Alexander disease is a fatal leukodystrophy caused by autosomal dominant gain-of-function mutations in the gene for glial fibrillary acidic protein (GFAP), an intermediate filament protein primarily expressed in astrocytes of the central nervous system. A key feature of pathogenesis is overexpression and accumulation of GFAP, with formation of characteristic cytoplasmic aggregates known as Rosenthal fibers. Here we investigate whether suppressing GFAP with antisense oligonucleotides could provide a therapeutic strategy for treating Alexander disease. METHODS: In this study, we use GFAP mutant mouse models of Alexander disease to test the efficacy of antisense suppression and evaluate the effects on molecular and cellular phenotypes and non-cell-autonomous toxicity. Antisense oligonucleotides were designed to target the murine Gfap transcript, and screened using primary mouse cortical cultures. Lead oligonucleotides were then tested for their ability to reduce GFAP transcripts and protein, first in wild-type mice with normal levels of GFAP, and then in adult mutant mice with established pathology and elevated levels of GFAP. RESULTS: Nearly complete and long-lasting elimination of GFAP occurred in brain and spinal cord following single bolus intracerebroventricular injections, with a striking reversal of Rosenthal fibers and downstream markers of microglial and other stress-related responses. GFAP protein was also cleared from cerebrospinal fluid, demonstrating its potential utility as a biomarker in future clinical applications. Finally, treatment led to improved body condition and rescue of hippocampal neurogenesis. INTERPRETATION: These results demonstrate the efficacy of antisense suppression for an astrocyte target, and provide a compelling therapeutic approach for Alexander disease. Ann Neurol 2018;83:27-39.

Alexander Disease.

Alexander disease is a leukodystrophy caused by dominant missense mutations in the gene encoding the glial fibrillary acidic protein. Individuals with this disorder often present with a typical neuroradiologic pattern including white matter abnormalities with brainstem involvement, selective contrast enhancement, and structural changes to the basal ganglia/thalamus. In rare cases, focal lesions have been seen and cause concern for primary malignancies. Here the authors present an infant initially diagnosed with a chiasmatic astrocytoma that was later identified as having glial fibrillary acidic protein mutation-confirmed Alexander disease. Pathologic and radiologic considerations that were helpful in arriving at the correct diagnosis are discussed.

Interactions of GFAP with ceftriaxone and phenytoin: SRCD and molecular docking and dynamic simulation.

BACKGROUND: GFAP is the major intermediate filament protein in mature astrocytes. Its increased expression and aggregation was firstly associated to Alexander's disease, and successively in different neurological diseases including scrapie, Alzheimer's and Creutzfeld-Jacob diseases. Recently, ceftriaxone a multi-potent ß-lactam antibiotic able to overcome the blood-brain barrier, successfully eliminated the cellular toxic effects of misfolded mutated GFAP, similarly to phenytoin sodium, in a cellular model of Alexander's disease and inhibited α-synuclein aggregation protecting PC12 cells from the exposure to 6-hydroxydopamine. METHODS: In this study, synchrotron radiation circular dichroism spectroscopy has been used to obtain structural information about the GFAP-ceftriaxone (phenytoin) interactions, while computational methods allowed the identification of the relevant putative binding site of either ceftriaxone or phenytoin on the dimer structure of GFAP, permitting to rationalize the spectroscopic experimental results. RESULTS: We found that GFAP exhibited enhanced stability upon the addition of two equivalents of each ligands with ceftriaxone imparting a more spontaneous interactions and a more ordered complex system than phenytoin. CONCLUSIONS: SRCD data and MD models indicate a stronger protective effect of ceftriaxone in neurological disorders characterized by an increased production and polymerization of GFAP. GENERAL SIGNIFICANCE: This result, in addition to our previous works in which we documented that ceftriaxone interacts with α-synuclein inhibiting its pathological aggregation and that a cyclical treatment with this molecule in a patient with adult-onset Alexander's disease halted, and partly reversed, the progression of neurodegeneration, suggests the possibility of a chaperone-like effect of ceftriaxone on protein involved in specific neurodegenerative diseases.

An In Vivo Pharmacological Screen Identifies Cholinergic Signaling as a Therapeutic Target in Glial-Based Nervous System Disease.

The role that glia play in neurological disease is poorly understood but increasingly acknowledged to be critical in a diverse group of disorders. Here we use a simple genetic model of Alexander disease, a progressive and severe human degenerative nervous system disease caused by a primary astroglial abnormality, to perform an in vivo screen of 1987 compounds, including many FDA-approved drugs and natural products. We identify four compounds capable of dose-dependent inhibition of nervous system toxicity. Focusing on one of these hits, glycopyrrolate, we confirm the role for muscarinic cholinergic signaling in pathogenesis using additional pharmacologic reagents and genetic approaches. We further demonstrate that muscarinic cholinergic signaling works through downstream Gαq to control oxidative stress and death of neurons and glia. Importantly, we document increased muscarinic cholinergic receptor expression in Alexander disease model mice and in postmortem brain tissue from Alexander disease patients, and that blocking muscarinic receptors in Alexander disease model mice reduces oxidative stress, emphasizing the translational significance of our findings. We have therefore identified glial muscarinic signaling as a potential therapeutic target in Alexander disease, and possibly in other gliopathic disorders as well. SIGNIFICANCE STATEMENT: Despite the urgent need for better treatments for neurological diseases, drug development for these devastating disorders has been challenging. The effectiveness of traditional large-scale in vitro screens may be limited by the lack of the appropriate molecular, cellular, and structural environment. Using a simple Drosophila model of Alexander disease, we performed a moderate throughput chemical screen of FDA-approved drugs and natural compounds, and found that reducing muscarinic cholinergic signaling ameliorated clinical symptoms and oxidative stress in Alexander disease model flies and mice. Our work demonstrates that small animal models are valuable screening tools for therapeutic compound identification in complex human diseases and that existing drugs can be a valuable resource for drug discovery given their known pharmacological and safety profiles.

Lithium Decreases Glial Fibrillary Acidic Protein in a Mouse Model of Alexander Disease.

Alexander disease is a fatal neurodegenerative disease caused by mutations in the astrocyte intermediate filament glial fibrillary acidic protein (GFAP). The disease is characterized by elevated levels of GFAP and the formation of protein aggregates, known as Rosenthal fibers, within astrocytes. Lithium has previously been shown to decrease protein aggregates by increasing the autophagy pathway for protein degradation. In addition, lithium has also been reported to decrease activation of the transcription factor STAT3, which is a regulator of GFAP transcription and astrogliogenesis. Here we tested whether lithium treatment would decrease levels of GFAP in a mouse model of Alexander disease. Mice with the Gfap-R236H point mutation were fed lithium food pellets for 4 to 8 weeks. Four weeks of treatment with LiCl at 0.5% in food pellets decreased GFAP protein and transcripts in several brain regions, although with mild side effects and some mortality. Extending the duration of treatment to 8 weeks resulted in higher mortality, and again with a decrease in GFAP in the surviving animals. Indicators of autophagy, such as LC3, were not increased, suggesting that lithium may decrease levels of GFAP through other pathways. Lithium reduced the levels of phosphorylated STAT3, suggesting this as one pathway mediating the effects on GFAP. In conclusion, lithium has the potential to decrease GFAP levels in Alexander disease, but with a narrow therapeutic window separating efficacy and toxicity.

Alexander disease with mild dorsal brainstem atrophy and infantile spasms.

We present the case of a Japanese male infant with Alexander disease who developed infantile spasms at 8 months of age. The patient had a cluster of partial seizures at 4 months of age. He presented with mild general hypotonia and developmental delay. Macrocephaly was not observed. Brain magnetic resonance imaging (MRI) findings fulfilled all MRI-based criteria for the diagnosis of Alexander disease and revealed mild atrophy of the dorsal pons and medulla oblongata with abnormal intensities. DNA analysis disclosed a novel heterozygous missense mutation (c.1154 C>T, p.S385F) in the glial fibrillary acidic protein gene. At 8 months of age, tonic spasms occurred, and electroencephalography (EEG) revealed hypsarrhythmia. Lamotrigine effectively controlled the infantile spasms and improved the abnormal EEG findings. Although most patients with infantile Alexander disease have epilepsy, infantile spasms are rare. This comorbid condition may be associated with the distribution of the brain lesions and the age at onset of Alexander disease.

Beneficial effects of curcumin on GFAP filament organization and down-regulation of GFAP expression in an in vitro model of Alexander disease.

Heterozygous mutations of the GFAP gene are responsible for Alexander disease, a neurodegenerative disorder characterized by intracytoplasmic Rosenthal fibers (RFs) in dystrophic astrocytes. In vivo and in vitro models have shown co-localization of mutant GFAP proteins with the small heat shock proteins (sHSPs) HSP27 and alphaB-crystallin, ubiquitin and proteasome components. Results reported by several recent studies agree on ascribing an altered cytoskeletal pattern to mutant GFAP proteins, an effect which induces mutant proteins accumulation, leading to impaired proteasome function and autophagy induction. On the basis of the protective role shown by both these small heat shock proteins (sHSPs), and on the already well established neuroprotective effects of curcumin in several diseases, we have investigated the effects of this compound in an in vitro model of Alexander disease, consisting in U251-MG astrocytoma cells transiently transfected with a construct encoding for GFAP carrying the p.R239C mutation in frame with the reporter green fluorescent protein (GFP). In particular, depending on the dose used, we have observed that curcumin is able to induce both HSP27 and alphaB-crystallin, to reduce expression of both RNA and protein of endogenous GFAP, to induce autophagy and, finally, to rescue the filamentous organization of the GFAP mutant protein, thus suggesting a role of this spice in counteracting the pathogenic effects of GFAP mutations.

TRH therapy in a patient with juvenile Alexander disease.

Alexander disease is a rare disorder of the central nervous system caused by a de novo mutation in the glial fibrillary acidic protein (GFAP) gene. Unlike the much more common infantile form, the juvenile form is slowly progressive with bulbar, pyramidal and cerebellar signs. Herein, we report a 9-year old Japanese girl suffering from frequent vomiting, slurred speech and truncal ataxia. Juvenile Alexander disease was diagnosed by genetic analysis, which detected a novel GFAP mutation, D360V. We also describe our clinical success in treating this patient with thyrotropin releasing hormone (TRH).