Mouse strain background can influence vulnerability to excitotoxic neuronal cell death and potentially modulate phenotypes in transgenic mouse models of human disease. Evidence supports a ...contribution of excitotoxicity to the selective death of medium spiny neurons in Huntington's disease (HD). Here, we assess whether strain differences in excitotoxic vulnerability influence striatal cell death in a knock-in mouse model of HD. Previous studies that evaluated resistance to excitotoxic lesions in several mouse models of HD had variable outcomes. In the present study, we directly compare one model on two different background strains to test the contribution of strain to excitotoxicity-mediated neurodegeneration. Mice of the FVB/N strain, which are highly vulnerable to excitotoxicity, become extremely resistant to quinolinic acid-induced striatal neurodegeneration with age, when carrying a huntingtin (Htt) allele expressing a HD transgene (CAG140). The resistance is much greater than the age-dependent resistance that has been previously reported in YAC128 mice. By 12 months of age, both heterozygous and homozygous FVB.CAG140 mice displayed virtually complete resistance to quinolinic acid-induced striatal neurodegeneration. A similar resistance develops in CAG140 mice on a C57BL/6N background although the effect size is smaller because C57BL/6N mice are already resistant due to genetic background. In a direct comparison with the YAC128 mice, FVB.CAG140 mice have greater resistance. FVB.CAG140 mice are also resistant to neurodegeneration following kainic acid-induced status epilepticus suggesting the existence of a common cellular mechanism that provides protection against multiple types of excitotoxic insult. These findings establish FVB.CAG140 mice as a useful model to investigate the cellular and molecular mechanisms that confer neuroprotection against excitotoxicity.
BackgroundPridopidine is a safe, well-tolerated oral drug candidate, that potently activates the Sigma-1 Receptor (S1R). The S1R regulates many cellular processes.. Human brain PET studies show that ...pridopidine 45 mg bid, the dose evaluated in PROOF, selectively and robustly occupies the S1R.Total Functional Capacity (TFC) is a validated, regulatory-accepted measure of disease stage and functional decline.To date, no therapeutic agent has shown benefit on the rate of decline in TFC. Analysis of the pre-specified endpoint TFC in the PRIDE-HD trial shows a beneficial effect of pridopidine 45 mg bid vs. placebo on maintenance of TFC at wk52 (Δ 0.87, p=0.0032). Post-hoc analysis revealed that this effect is driven by early HD patients (TFC 7-13) (Δ 1.16, p=0.0003). The effect remains significant using a more conservative analysis (nominal p=0.016). Responder analysis shows that 45 mg bid reduces the probability of worsening in TFC by 80% (p=0.002,). Exploratory analysis also shows improvements in total motor score, TFC, and the symbol digit modality test vs. placebo (Δ0.6, p=0.04) when assessed in combination. Q-motor, a quantitative motor test, demonstrated improvement in the finger inter-tap interval vs. placebo at wk26 (Δ-0.034 sec, p=0.035) and 52 (Δ-0.044, p=0.03). P-values are nominal.AimEvaluate the efficacy and safety of pridopidine 45 mg bid on TFC in early HD.DesignPROOF-HD is a 65-week, double-blind, placebo-controlled, global Ph 3 trial.PROOF assesses the effect of pridopidine 45 mg bid vs placebo on TFC in early HD patients. Primary endpoint is mean ΔTFC from baseline to Wk 65. Secondary endpoints are the proportion of patients with no TFC decline (TFC≥ 0) at Wk65 and changes from baseline to Wk65 in Q-motor, Total Motor Score (TMS) and cUHDRS.StatusAs of July 4, 2021, 58/60 (97%) of sites have been activated and 235 patients have been randomized (48% of the total). There have been no dropouts from the trial, supporting the tolerability and safety of the drug.
BackgroundHuntington’s disease (HD) is a hereditary neurodegenerative disorder caused by expansion of cytosine-adenine-guanine (CAG) trinucleotide repeats in the huntingtin gene (HTT). Consequently, ...the mutant protein is ubiquitously expressed and drives HD pathogenesis via a toxic gain-of-function mechanism.1–3 HD animal models demonstrate that reducing huntingtin protein (HTT) levels alleviates motor and neuropathological abnormalities, supporting HTT lowering as a therapeutic approach2. Clinical and preclinical stage modalities including antisense oligonucleotides, virally delivered microRNAs, and zinc finger transcription factors, reduce HTT levels by repressing HTT transcription, stability and/or translation.1 2 Such modalities require invasive procedures to reach the central nervous system (CNS) and are not evenly distributed. These compounds act via a novel mechanism promoting the inclusion of a pseudoexon containing a premature termination codon, leading to HTT messenger RNA (mRNA) degradation and reduction of HTT levels.AimsWe aimed to develop a class of small molecule splicing modifiers specifically synthesised to promote selective splicing and ultimately reduction in huntingtin mRNA and protein levels.Methods/TechniquesHere, we describe the identification of small molecule splicing modifiers lowering HTT expression by selective modulation of the critical recognition step of pre-mRNA splicing.Results/OutcomeThese data demonstrate the potential of small molecules that effectively lower HTT consistently throughout the CNS and periphery to be a non-invasive effective treatment option for patients.ConclusionsThis work represents the first example of the identification and optimisation of orally bioavailable splicing modifiers that penetrate all tissues and lower HTT evenly throughout the body.ReferencesWild EJ, Tabrizi SJ. Therapies targeting DNA and RNA in huntington’s disease. Lancet Neurol 2017;16:837–847.Tabrizi SJ, Ghosh R, Leavitt BR. Huntingtin lowering strategies for disease modification in huntington’s disease. Neuron 2019;101:801–819.Nopoulos PC. Huntington disease: a single-gene degenerative disorder of the striatum. Dialogues Clin Neurosci 2016;18:91–98.
Huntington’s disease (HD) is a hereditary neurodegenerative disorder characterized by changes in personality, cognition and motor control. The cardinal neuropathological hallmark of this disease is ...the massive atrophy of the striatum resulting from neuronal dysfunction and loss, but which extends to other areas of the brain as well as peripheral organs. The genetic mutation underlying HD originates in Exon1 of the huntingtin gene gives rise to a toxic/mutated form of the huntingtin protein (mtHTT). The mtHTT protein is ubiquitously expressed but also exhibits the ability to propagate from cell-to-cell to disseminate pathology, a property which may serve as a new therapeutic focus. We have developed a monoclonal antibody C6-17 targeting a particularly exposed region close to the aa586 Caspase 6 cleavage site of the huntingtin protein and, as recently published, mAB C6-17 is able to block cell-to-cell propagation of mutated HTT in vitro. In order to reduce the burden of the mutant protein in vivo, we queried whether the freely accessible and extracellular mtHTT can be targeted by an antibody. In POC experiments, using the transgenic animal model YAC128, we found that after 3 months mAB C6-17 treatment the circulating mtHTT in the peripheral as well as in the CNS tissues was reduced. Further, we could demonstrate the presence of active mAB C6-17 in PBS/heparin perfused peripheral and CNS tissues. The mAB C6-17 treated YAC128 animals showed benefits in body wight and motor behaviors and we could observe a delay in the HD disease progression. The obtained in vivo results provide the first POC data for the feasibility and efficacy of an antibody-based anti-mtHTT approach and suggest this therapeutic strategy as a potential new HD treatment possibility.
Abstract A striking failure of modern medicine is the debilitating and lethal consequences of adverse drug reactions (ADRs) which rank as one of the top ten leading causes of death and illness in the ...developed world with direct medical costs of US$137–177 billion annually in the USA. Although many factors influence the effect of medications (i.e. age, organ function, drug interactions), genetic factors account for 20–95% of drug response variability and play a significant role in the incidence and severity of ADRs. The field of pharmacogenomics seeks to identify genetic factors responsible for individual differences in drug efficacy and adverse drug reactions. Pharmacogenomics has led to several genetic tests that provide clinical dosing recommendations. For autoimmune disease, pharmacogenomics has led to several DNA-based tests to improve drug selection, optimize dosing, and minimize the risk of toxicity. The ‘GATC’ project is a nation-wide project established in Canada to identify novel predictive genomic markers of severe ADRs in children. An ADR surveillance network has been established in all of Canada's major children's hospitals, serving up to 75% of all Canadian children. The goal of the project is to identify patients experiencing specific ADRs, collect DNA samples, and apply genomics-based technologies to identify ADR-associated genetic markers.
The epsin N-terminal homology (ENTH) domain is a protein module of ∼150 amino acids found at the N terminus of a variety of proteins identified in yeast, plants, nematode, frog, and mammals. ENTH ...domains comprise multiple α-helices folded upon each other to form a compact globular structure that has been implicated in interactions with lipids and proteins. In characterizing this evolutionarily conserved domain, we isolated and identified tubulin as an ENTH domain-binding partner. The interaction, which is direct and has a dissociation constant of ∼1 μm, was observed with ENTH domains of proteins present in various species. Tubulin is co-immunoprecipitated from rat brain extracts with the ENTH domain-containing proteins, epsins 1 and 2, and punctate epsin staining is observed along the microtubule cytoskeleton of dissociated cortical neurons. Consistent with a role in microtubule processes, the over-expression of epsin ENTH domain in PC12 cells stimulates neurite outgrowth. These data demonstrate an evolutionarily conserved property of ENTH domains to interact with tubulin and microtubules.
Defects in the gene encoding for the ATP binding cassette (ABC) transporter A1 (ABCA1) were shown to be one of the genetic causes for familial hypoalphalipoproteinemia (FHA). We investigated the role ...of ABCA1-mediated cholesterol efflux in Dutch subjects suffering from FHA. Eighty-eight subjects (mean HDL cholesterol levels 0.63 +/- 0.21 mmol/l) were enrolled. Fibroblasts were cultured and loaded with 3Hcholesterol. ABCA1 and non-ABCA1-mediated efflux was studied by using apolipoprotein A-I (apoA-I), HDL, and methyl-beta-cyclodextrin as acceptors. Efflux to apoA-I was decreased in four patients (4/88, 4.5%), and in all cases, a mutation in the ABCA1 gene was found. In the remaining 84 subjects, no correlation between efflux and apoA-I or HDL cholesterol was found. Efflux to both HDL and cyclodextrin, in contrast, did correlate with HDL cholesterol plasma levels (r = 0.34, P = 0.01; and r = 0.27, P = 0.008, respectively). The prevalence of defects in ABCA1-dependent cholesterol efflux in Dutch FHA patients is low. The significant correlation between plasma HDL cholesterol levels and methyl-beta-cyclodextrin-mediated efflux in the FHA patients with normal ABCA1 function suggests that non-ABCA1-mediated efflux might also be important for plasma HDL cholesterol levels in these individuals.
Lipoprotein lipase (LPL) is crucial in the hydrolysis of triglycerides (TG) in TG-rich lipoproteins in the formation of HDL particles. As both these lipoproteins play an important role in the ...pathogenesis of atherosclerotic vascular disease, we sought to assess the relationship between post-heparin LPL (PH-LPL) activity and lipids and lipoproteins in a large, well-defined cohort of Dutch males with coronary artery disease (CAD). These subjects were drawn from the REGRESS study, totaled 730 in number and were evaluated against 75 healthy, normolipidemic male controls. Fasting mean PH-LPL activity in the CAD subjects was 108 (46) mU/ml, compared to 138 (44) mU/ml in controls (P < 0.0001). When these patients were divided into activity quartiles, those in the lowest versus the highest quartile had higher levels of TG (P < 0.001), VLDLc and VLDL-TG (P = 0.001). Conversely, levels of TC, LDL, and HDLc were lower in these patients (P = 0.001, P = 0.02, and P = 0.001, respectively). Also, in this cohort PH-LPL relationships with lipids and lipoproteins were not altered by apoE genotypes. The frequency of common mutations in the LPL gene associated with partial LPL deficiency (N291S and D9N carriers) in the lowest quartile for LPL activity was more than double the frequency in the highest quartile (12.0% vs. 5.0%; P = 0.006). By contrast, the frequency of the S447X LPL variant rose from 11.5% in the lowest to 18.3% (P = 0.006) in the highest quartile. This study, in a large cohort of CAD patients, has shown that PH-LPL activity is decreased (22%; P = 0.001) when compared to controls; that the D9N and N291S, and S447X LPL variants are genetic determinants, respectively, in CAD patients of low and high LPL PH-LPL activities; and that PH-LPL activity is strongly associated with changes in lipids and lipoproteins.—Henderson, H. E., J. J. P. Kastelein, A. H. Zwinderman, E. Gagne, J. W. Jukema, P. W. A. Reymer, B. E. Groenemeyer, K. I. Lie, A. V. G. Bruschke, M. R. Hayden, and H. Jansen. Lipoprotein lipase activity is decreased in a large cohort of patients with coronary artery disease and is associated with changes in lipids and lipoproteins. J. Lipid Res. 1999. 40: 735–743.
The Wisconsin hypoalpha mutant (WHAM) chicken has a >90% reduction in plasma HDL due to hypercatabolism by the kidney of lipid-poor apoA-I. The WHAM chickens have a recessive white skin phenotype ...caused by a single-gene mutation that maps to the chicken Z-chromosome. This corresponds to human 9q31.1, a chromosomal segment that contains the ATP-binding cassette protein-1 (ABCA1) gene, which is mutated in Tangier Disease and familial hypoalphalipoproteinemia. Complete sequencing of the WHAM ABCA1 cDNA identified a missense mutation near the N-terminus of the protein (E89K). The substitution of this evolutionary conserved glutamate residue for lysine in the mouse ABCA1 transporter leads to complete loss of function, resulting principally from defective intracellular trafficking and very little ABCA1 reaching the plasma membrane. The WHAM chicken is a naturally occurring animal model for Tangier Disease.
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