Neuroscience
Abstract
Deposition of amyloid-β protein (Aβ) to form neuritic plaques is the characteristic neuropathology of Alzheimer’s disease (AD). Aβ is generated from amyloid precursor protein (APP) by β- and γ-secretase cleavages. BACE1 is the β-secretase and its inhibition induces severe side effects, whereas its homolog BACE2 normally suppresses Aβ by cleaving APP/Aβ at the θ-site (Phe20) within the Aβ domain. Here, we report that BACE2 also processes APP at the β site, and the juxtamembrane helix (JH) of APP inhibits its β-secretase activity, enabling BACE2 to cleave nascent APP and aggravate AD symptoms. JH-disrupting mutations and clusterin binding to JH triggered BACE2-mediated β-cleavage. Both BACE2 and clusterin were elevated in aged mouse brains, and enhanced β-cleavage during aging. Therefore, BACE2 contributes to AD pathogenesis as a conditional β-secretase and could be a preventive and therapeutic target for AD without the side effects of BACE1 inhibition.
Authors
Zhe Wang, Qin Xu, Fang Cai, Xi Liu, Yili Wu, Weihong Song
Abstract
To address challenges in the diagnosis of cognitive dysfunction (CD) related to systemic lupus erythematosus–associated (SLE-associated) autoimmune mechanisms rather than confounding factors, we employed an integrated approach, using resting-state functional (FDG-PET) and structural (diffusion tensor imaging [DTI]) neuroimaging techniques and cognitive testing, in adult SLE patients with quiescent disease and no history of neuropsychiatric illness. We identified resting hypermetabolism in the sensorimotor cortex, occipital lobe, and temporal lobe of SLE subjects, in addition to validation of previously published resting hypermetabolism in the hippocampus, orbitofrontal cortex, and putamen/GP/thalamus. Regional hypermetabolism demonstrated abnormal interregional metabolic correlations, associated with impaired cognitive performance, and was stable over 15 months. DTI analyses demonstrated 4 clusters of decreased microstructural integrity in white matter tracts adjacent to hypermetabolic regions and significantly diminished connecting tracts in SLE subjects. Decreased microstructural integrity in the parahippocampal gyrus correlated with impaired spatial memory and increased serum titers of DNRAb, a neurotoxic autoantibody associated with neuropsychiatric lupus. These findings of regional hypermetabolism, associated with decreased microstructural integrity and poor cognitive performance and not associated with disease duration, disease activity, medications, or comorbid disease, suggest that this is a reproducible, stable marker for SLE-associated CD that may be may be used for early disease detection and to discriminate between groups, evaluate response to treatment strategies, or assess disease progression.
Authors
Meggan Mackay, An Vo, Chris C. Tang, Michael Small, Erik W. Anderson, Elisabeth J. Ploran, Justin Storbeck, Brittany Bascetta, Simran Kang, Cynthia Aranow, Carl Sartori, Philip Watson, Bruce T. Volpe, Betty Diamond, David Eidelberg
Abstract
OXTR modulates a variety of behaviors in mammals, including social memory and recognition. Genetic and epigenetic dysregulation of OXTR has been suggested to be implicated in neuropsychiatric disorders, including autism spectrum disorder (ASD). While the involvement of DNA methylation is suggested, the mechanism underlying epigenetic regulation of OXTR is largely unknown. This has hampered the experimental design and interpretation of the results of epigenetic studies of OXTR in neuropsychiatric disorders. From the generation and characterization of a new line of Tet1 mutant mice — by deleting the largest coding exon 4 (Tet1Δe4) — we discovered for the first time to our knowledge that Oxtr has an array of mRNA isoforms and a complex transcriptional regulation. Select isoforms of Oxtr are significantly reduced in the brain of Tet1Δe4–/– mice. Accordingly, CpG islands of Oxtr are hypermethylated during early development and persist into adulthood. Consistent with the reduced express of OXTR, Tet1Δe4–/– mice display impaired maternal care, social behavior, and synaptic responses to oxytocin stimulation. Our findings elucidate a mechanism mediated by TET1 protein in regulating Oxtr expression by preventing DNA hypermethylation of Oxtr. The discovery of epigenetic dysregulation of Oxtr in TET1-deficient mouse brain supports the necessity of a reassessment of existing findings and a value of future studies of OXTR in neuropsychiatric disorders.
Authors
Aaron J. Towers, Martine W. Tremblay, Leeyup Chung, Xin-lei Li, Alexandra L. Bey, Wenhao Zhang, Xinyu Cao, Xiaoming Wang, Ping Wang, Lara J. Duffney, Stephen K. Siecinski, Sonia Xu, Yuna Kim, Xiangyin Kong, Simon Gregory, Wei Xie, Yong-hui Jiang
HIV-associated sensory polyneuropathy and neuronal injury are associated with miRNA–455-3p induction
Abstract
Symptomatic distal sensory polyneuropathy (sDSP) is common and debilitating in people with HIV/AIDS, leading to neuropathic pain, although the condition’s cause is unknown. To investigate biomarkers and associated pathogenic mechanisms for sDSP, we examined plasma miRNA profiles in HIV/AIDS patients with sDSP or without sDSP in 2 independent cohorts together with assessing related pathogenic effects. Several miRNAs were found to be increased in the Discovery Cohort (sDSP, n = 29; non-DSP, n = 40) by array analyses and were increased in patients with sDSP compared with patients without sDSP. miR–455-3p displayed a 12-fold median increase in the sDSP group, which was confirmed by machine learning analyses and verified by reverse transcription PCR. In the Validation Cohort (sDSP n = 16, non-DSP n = 20, healthy controls n = 15), significant upregulation of miR–455-3p was also observed in the sDSP group. Bioinformatics revealed that miR–455-3p targeted multiple host genes implicated in peripheral nerve maintenance, including nerve growth factor (NGF) and related genes. Transfection of cultured human dorsal root ganglia with miR–455-3p showed a concentration-dependent reduction in neuronal β-III tubulin expression. Human neurons transfected with miR–455-3p demonstrated reduced neurite outgrowth and NGF expression that was reversed by anti–miR–455-3p antagomir cotreatment. miR–455-3p represents a potential biomarker for HIV-associated sDSP and might also exert pathogenic effects leading to sDSP.
Authors
Eugene L. Asahchop, William G. Branton, Anand Krishnan, Patricia A. Chen, Dong Yang, Linglong Kong, Douglas W. Zochodne, Bruce J. Brew, M. John Gill, Christopher Power
Abstract
BACKGROUND. Increasing evidence indicates a role for EBV in the pathogenesis of multiple sclerosis (MS). EBV-infected autoreactive B cells might accumulate in the CNS because of defective cytotoxic CD8+ T cell immunity. We sought to determine the feasibility and safety of treating progressive MS patients with autologous EBV-specific T cell therapy. METHODS. An open-label phase I trial was designed to treat 5 patients with secondary progressive MS and 5 patients with primary progressive MS with 4 escalating doses of in vitro–expanded autologous EBV-specific T cells targeting EBV nuclear antigen 1, latent membrane protein 1 (LMP1), and LMP2A. Following adoptive immunotherapy, we monitored the patients for safety and clinical responses. RESULTS. Of the 13 recruited participants, 10 received the full course of T cell therapy. There were no serious adverse events. Seven patients showed improvement, with 6 experiencing both symptomatic and objective neurological improvement, together with a reduction in fatigue, improved quality of life, and, in 3 patients, reduced intrathecal IgG production. All 6 patients receiving T cells with strong EBV reactivity showed clinical improvement, whereas only 1 of the 4 patients receiving T cells with weak EBV reactivity showed improvement (P = 0.033, Fisher’s exact test). CONCLUSION. EBV-specific adoptive T cell therapy was well tolerated. Clinical improvement following treatment was associated with the potency of EBV-specific reactivity of the administered T cells. Further clinical trials are warranted to determine the efficacy of EBV-specific T cell therapy in MS. TRIAL REGISTRATION. Australian New Zealand Clinical Trials Registry, ACTRN12615000422527. FUNDING. MS Queensland, MS Research Australia, Perpetual Trustee Company Ltd., and donations from private individuals who wish to remain anonymous.
Authors
Michael P. Pender, Peter A. Csurhes, Corey Smith, Nanette L. Douglas, Michelle A. Neller, Katherine K. Matthews, Leone Beagley, Sweera Rehan, Pauline Crooks, Tracey J. Hopkins, Stefan Blum, Kerryn A. Green, Zara A. Ioannides, Andrew Swayne, Blake T. Aftab, Kaye D. Hooper, Scott R. Burrows, Kate M. Thompson, Alan Coulthard, Rajiv Khanna
Abstract
Glycine encephalopathy (GE), or nonketotic hyperglycinemia (NKH), is a rare recessive genetic disease caused by defective glycine cleavage and characterized by increased accumulation of glycine in all tissues. Here, based on new case reports of GLDC loss-of-function mutations in GE patients, we aimed to generate a zebrafish model of severe GE in order to unravel the molecular mechanism of the disease. Using CRISPR/Cas9, we knocked out the gldc gene and showed that gldc–/– fish recapitulate GE on a molecular level and present a motor phenotype reminiscent of severe GE symptoms. The molecular characterization of gldc–/– mutants showed a broad metabolic disturbance affecting amino acids and neurotransmitters other than glycine, with lactic acidosis at stages preceding death. Although a transient imbalance was found in cell proliferation in the brain of gldc–/– zebrafish, the main brain networks were not affected, thus suggesting that GE pathogenicity is mainly due to metabolic defects. We confirmed that the gldc–/– hypotonic phenotype is due to NMDA and glycine receptor overactivation, and demonstrated that gldc–/– larvae depict exacerbated hyperglycinemia at these synapses. Remarkably, we were able to rescue the motor dysfunction of gldc–/– larvae by counterbalancing pharmacologically or genetically the level of glycine at the synapse.
Authors
Raphaëlle Riché, Meijiang Liao, Izabella A. Pena, Kit-Yi Leung, Nathalie Lepage, Nicolas D.E. Greene, Kyriakie Sarafoglou, Lisa A. Schimmenti, Pierre Drapeau, Éric Samarut
Abstract
Noninvasive tools that target tumor cells could improve the management of glioma. Cancer generally has a high demand for Fe(III), an essential nutrient for a variety of biochemical processes. We tested whether 68Ga-citrate, an Fe(III) biomimetic that binds to apo-transferrin in blood, detects glioma in preclinical models and patients using hybrid PET/MRI. Mouse PET/CT studies showed that 68Ga-citrate accumulates in subcutaneous U87MG xenografts in a transferrin receptor–dependent fashion within 4 hours after injection. Seventeen patients with WHO grade III or IV glioma received 3.7–10.2 mCi 68Ga-citrate and were imaged with PET/MR 123–307 minutes after injection to establish that the radiotracer can localize to human tumors. Multiple contrast-enhancing lesions were PET avid, and tumor to adjacent normal white matter ratios were consistently greater than 10:1. Several contrast-enhancing lesions were not PET avid. One minimally enhancing lesion and another tumor with significantly reduced enhancement following bevacizumab therapy were PET avid. Advanced MR imaging analysis of one patient with contrast-enhancing glioblastoma showed that metabolic hallmarks of viable tumor spatially overlaid with 68Ga-citrate accumulation. These early data underscore that high-grade glioma may be detectable with a radiotracer that targets Fe(III) transport.
Authors
Spencer C. Behr, Javier E. Villanueva-Meyer, Yan Li, Yung-Hua Wang, Junnian Wei, Anna Moroz, Julia K.L. Lee, Jeffrey C. Hsiao, Kenneth T. Gao, Wendy Ma, Soonmee Cha, David M. Wilson, Youngho Seo, Sarah J. Nelson, Susan M. Chang, Michael J. Evans
Abstract
Mechanical injury to the brain triggers multiple biochemical events whose specific contributions to the pathogenesis define clinical manifestations and the overall outcome. Among many factors, mitochondrial injury has recently attracted much attention due to the importance of the organelle for bioenergetics as well as intra- and extracellular signaling and cell death. Assuming the essentiality of a mitochondria-unique phospholipid, cardiolipin (CL), for the structural and functional organization of mitochondria, here we applied global (phospho) lipidomics and redox lipidomics to reveal and identify CL modifications during controlled cortical impact (CCI). We revealed 2 major pathways activated in the CCI-injured brain as time-specific responses: early accumulation of oxidized CL (CLox) products was followed by hydrolytic reactions yielding monolyso-CLs (mCLs) and free fatty acids. To quantitatively assess possible specific roles of peroxidation and hydrolysis of mitochondrial CL, we performed comparative studies of CL modifications using an animal model of Barth syndrome where deficiency of CL reacylation (Tafazzin [Taz] deficiency) was associated exclusively with the accumulation of mCLs (but not CLox). By comparing the in vitro and in vivo results with genetic manipulation of major CL-, CLox-, and mCL-metabolizing enzymes, calcium-independent phospholipase A2γ and Taz, we concluded that the 2 processes — CL oxidation and CL hydrolysis — act as mutually synergistically enhancing components of the pathogenic mechanism of mitochondrial injury in traumatic brain injury. This emphasizes the need for combined therapeutic approaches preventing the formation of both CLox and mCL.
Authors
Honglu Chao, Tamil S. Anthonymuthu, Elizabeth M. Kenny, Andrew A. Amoscato, Laura K. Cole, Grant M. Hatch, Jing Ji, Valerian E. Kagan, Hülya Bayır
Abstract
Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited ataxia caused by expansion of a translated CAG repeat encoding a glutamine tract in the ataxin-1 (ATXN1) protein. Despite advances in understanding the pathogenesis of SCA1, there are still no therapies to alter its progressive fatal course. RNA-targeting approaches have improved disease symptoms in preclinical rodent models of several neurological diseases. Here, we investigated the therapeutic capability of an antisense oligonucleotide (ASO) targeting mouse Atxn1 in Atxn1154Q/2Q-knockin mice that manifest motor deficits and premature lethality. Following a single ASO treatment at 5 weeks of age, mice demonstrated rescue of these disease-associated phenotypes. RNA-sequencing analysis of genes with expression restored to WT levels in ASO-treated Atxn1154Q/2Q mice was used to demonstrate molecular differences between SCA1 pathogenesis in the cerebellum and disease in the medulla. Finally, select neurochemical abnormalities detected by magnetic resonance spectroscopy in vehicle-treated Atxn1154Q/2Q mice were reversed in the cerebellum and brainstem (a region containing the pons and the medulla) of ASO-treated Atxn1154Q/2Q mice. Together, these findings support the efficacy and therapeutic importance of directly targeting ATXN1 RNA expression as a strategy for treating both motor deficits and lethality in SCA1.
Authors
Jillian Friedrich, Holly B. Kordasiewicz, Brennon O’Callaghan, Hillary P. Handler, Carmen Wagener, Lisa Duvick, Eric E. Swayze, Orion Rainwater, Bente Hofstra, Michael Benneyworth, Tessa Nichols-Meade, Praseuth Yang, Zhao Chen, Judit Perez Ortiz, H. Brent Clark, Gülin Öz, Sarah Larson, Huda Y. Zoghbi, Christine Henzler, Harry T. Orr
Abstract
Despite the initial promise of immunotherapy for CNS disease, multiple recent clinical trials have failed. This may be due in part to characteristically low penetration of antibodies to cerebrospinal fluid (CSF) and brain parenchyma, resulting in poor target engagement. We here utilized transcranial macroscopic imaging to noninvasively evaluate in vivo delivery pathways of CSF fluorescent tracers. Tracers in CSF proved to be distributed through a brain-wide network of periarterial spaces, previously denoted as the glymphatic system. CSF tracer entry was enhanced approximately 3-fold by increasing plasma osmolality without disruption of the blood-brain barrier. Further, plasma hyperosmolality overrode the inhibition of glymphatic transport that characterizes the awake state and reversed glymphatic suppression in a mouse model of Alzheimer’s disease. Plasma hyperosmolality enhanced the delivery of an amyloid-β (Aβ) antibody, obtaining a 5-fold increase in antibody binding to Aβ plaques. Thus, manipulation of glymphatic activity may represent a novel strategy for improving penetration of therapeutic antibodies to the CNS.
Authors
Benjamin A. Plog, Humberto Mestre, Genaro E. Olveda, Amanda M. Sweeney, H. Mark Kenney, Alexander Cove, Kosha Y. Dholakia, Jeffrey Tithof, Thomas D. Nevins, Iben Lundgaard, Ting Du, Douglas H. Kelley, Maiken Nedergaard
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