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Achanta LB, Thomas DS, Housley GD, Rae CD. AMP-activated protein kinase activators have compound and concentration-specific effects on brain metabolism. J Neurochem 2024; 168:677-692. [PMID: 36977628 DOI: 10.1111/jnc.15815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/18/2023] [Accepted: 03/20/2023] [Indexed: 03/30/2023]
Abstract
AMP-activated protein kinase (AMPK) is a key sensor of energy balance playing important roles in the balancing of anabolic and catabolic activities. The high energy demands of the brain and its limited capacity to store energy indicate that AMPK may play a significant role in brain metabolism. Here, we activated AMPK in guinea pig cortical tissue slices, both directly with A769662 and PF 06409577 and indirectly with AICAR and metformin. We studied the resultant metabolism of [1-13C]glucose and [1,2-13C]acetate using NMR spectroscopy. We found distinct activator concentration-dependent effects on metabolism, which ranged from decreased metabolic pool sizes at EC50 activator concentrations with no expected stimulation in glycolytic flux to increased aerobic glycolysis and decreased pyruvate metabolism with certain activators. Further, activation with direct versus indirect activators produced distinct metabolic outcomes at both low (EC50) and higher (EC50 × 10) concentrations. Specific direct activation of β1-containing AMPK isoforms with PF 06409577 resulted in increased Krebs cycle activity, restoring pyruvate metabolism while A769662 increased lactate and alanine production, as well as labelling of citrate and glutamine. These results reveal a complex metabolic response to AMPK activators in brain beyond increased aerobic glycolysis and indicate that further research is warranted into their concentration- and mechanism-dependent impact.
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Affiliation(s)
- Lavanya B Achanta
- Neuroscience Research Australia, Barker St, Randwick, New South Wales, 2031, Australia
- Translational Neuroscience Facility, School of Biomedical Sciences, UNSW, Sydney, New South Wales, 2052, Australia
| | - Donald S Thomas
- Mark Wainwright Analytical Centre, UNSW, Sydney, New South Wales, 2052, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, School of Biomedical Sciences, UNSW, Sydney, New South Wales, 2052, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Barker St, Randwick, New South Wales, 2031, Australia
- School of Psychology, UNSW, Sydney, New South Wales, 2052, Australia
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Kalotay E, Klugmann M, Housley GD, Fröhlich D. Dominant aminoacyl-tRNA synthetase disorders: lessons learned from in vivo disease models. Front Neurosci 2023; 17:1182845. [PMID: 37274211 PMCID: PMC10234151 DOI: 10.3389/fnins.2023.1182845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 04/05/2023] [Indexed: 06/06/2023] Open
Abstract
Aminoacyl-tRNA synthetases (ARSs) play an essential role in protein synthesis, being responsible for ligating tRNA molecules to their corresponding amino acids in a reaction known as 'tRNA aminoacylation'. Separate ARSs carry out the aminoacylation reaction in the cytosol and in mitochondria, and mutations in almost all ARS genes cause pathophysiology most evident in the nervous system. Dominant mutations in multiple cytosolic ARSs have been linked to forms of peripheral neuropathy including Charcot-Marie-Tooth disease, distal hereditary motor neuropathy, and spinal muscular atrophy. This review provides an overview of approaches that have been employed to model each of these diseases in vivo, followed by a discussion of the existing animal models of dominant ARS disorders and key mechanistic insights that they have provided. In summary, ARS disease models have demonstrated that loss of canonical ARS function alone cannot fully account for the observed disease phenotypes, and that pathogenic ARS variants cause developmental defects within the peripheral nervous system, despite a typically later onset of disease in humans. In addition, aberrant interactions between mutant ARSs and other proteins have been shown to contribute to the disease phenotypes. These findings provide a strong foundation for future research into this group of diseases, providing methodological guidance for studies on ARS disorders that currently lack in vivo models, as well as identifying candidate therapeutic targets.
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Affiliation(s)
- Elizabeth Kalotay
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
- Research Beyond Borders, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Dominik Fröhlich
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
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Kalotay E, Klugmann M, Housley GD, Fröhlich D. Recessive aminoacyl-tRNA synthetase disorders: lessons learned from in vivo disease models. Front Neurosci 2023; 17:1182874. [PMID: 37274208 PMCID: PMC10234152 DOI: 10.3389/fnins.2023.1182874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 04/17/2023] [Indexed: 06/06/2023] Open
Abstract
Protein synthesis is a fundamental process that underpins almost every aspect of cellular functioning. Intriguingly, despite their common function, recessive mutations in aminoacyl-tRNA synthetases (ARSs), the family of enzymes that pair tRNA molecules with amino acids prior to translation on the ribosome, cause a diverse range of multi-system disorders that affect specific groups of tissues. Neurological development is impaired in most ARS-associated disorders. In addition to central nervous system defects, diseases caused by recessive mutations in cytosolic ARSs commonly affect the liver and lungs. Patients with biallelic mutations in mitochondrial ARSs often present with encephalopathies, with variable involvement of peripheral systems. Many of these disorders cause severe disability, and as understanding of their pathogenesis is currently limited, there are no effective treatments available. To address this, accurate in vivo models for most of the recessive ARS diseases are urgently needed. Here, we discuss approaches that have been taken to model recessive ARS diseases in vivo, highlighting some of the challenges that have arisen in this process, as well as key results obtained from these models. Further development and refinement of animal models is essential to facilitate a better understanding of the pathophysiology underlying recessive ARS diseases, and ultimately to enable development and testing of effective therapies.
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Affiliation(s)
- Elizabeth Kalotay
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
- Research Beyond Borders, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Dominik Fröhlich
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
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Fröhlich D, Kalotay E, von Jonquieres G, Bongers A, Lee B, Suchowerska AK, Housley GD, Klugmann M. Dual-function AAV gene therapy reverses late-stage Canavan disease pathology in mice. Front Mol Neurosci 2022; 15:1061257. [PMID: 36568275 PMCID: PMC9772617 DOI: 10.3389/fnmol.2022.1061257] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 11/18/2022] [Indexed: 12/13/2022] Open
Abstract
The leukodystrophy Canavan disease is a fatal white matter disorder caused by loss-of-function mutations of the aspartoacylase-encoding ASPA gene. There are no effective treatments available and experimental gene therapy trials have failed to provide sufficient amelioration from Canavan disease symptoms. Preclinical studies suggest that Canavan disease-like pathology can be addressed by either ASPA gene replacement therapy or by lowering the expression of the N-acetyl-L-aspartate synthesizing enzyme NAT8L. Both approaches individually prevent or even reverse pathological aspects in Canavan disease mice. Here, we combined both strategies and assessed whether intracranial adeno-associated virus-mediated gene delivery to a Canavan disease mouse model at 12 weeks allows for reversal of existing pathology. This was enabled by a single vector dual-function approach. In vitro and in vivo biopotency assessment revealed significant knockdown of neuronal Nat8l paired with robust ectopic aspartoacylase expression. Following nomination of the most efficient cassette designs, we performed proof-of-concept studies in post-symptomatic Aspa-null mice. Late-stage gene therapy resulted in a decrease of brain vacuoles and long-term reversal of all pathological hallmarks, including loss of body weight, locomotor impairments, elevated N-acetyl-L-aspartate levels, astrogliosis, and demyelination. These data suggest feasibility of a dual-function vector combination therapy, directed at replacing aspartoacylase with concomitantly suppressing N-acetyl-L-aspartate production, which holds potential to permanently alleviate Canavan disease symptoms and expands the therapeutic window towards a treatment option for adult subjects.
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Affiliation(s)
- Dominik Fröhlich
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia,*Correspondence: Dominik Fröhlich,
| | - Elizabeth Kalotay
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Georg von Jonquieres
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Andre Bongers
- Biological Resources Imaging Laboratory, University of New South Wales, Sydney, NSW, Australia
| | - Brendan Lee
- Biological Resources Imaging Laboratory, University of New South Wales, Sydney, NSW, Australia
| | - Alexandra K. Suchowerska
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia,Research Beyond Borders, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany,Matthias Klugmann,
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Cederholm JME, Parley KE, Perera CJ, von Jonquieres G, Pinyon JL, Julien JP, Ryugo DK, Ryan AF, Housley GD. Noise-induced hearing loss vulnerability in type III intermediate filament peripherin gene knockout mice. Front Neurol 2022; 13:962227. [PMID: 36226085 PMCID: PMC9549866 DOI: 10.3389/fneur.2022.962227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 08/24/2022] [Indexed: 11/13/2022] Open
Abstract
In the post-natal mouse cochlea, type II spiral ganglion neurons (SGNs) innervating the electromotile outer hair cells (OHCs) of the ‘cochlear amplifier' selectively express the type III intermediate filament peripherin gene (Prph). Immunolabeling showed that Prph knockout (KO) mice exhibited disruption of this (outer spiral bundle) afferent innervation, while the radial fiber (type I SGN) innervation of the inner hair cells (~95% of the SGN population) was retained. Functionality of the medial olivocochlear (MOC) efferent innervation of the OHCs was confirmed in the PrphKO, based on suppression of distortion product otoacoustic emissions (DPOAEs) via direct electrical stimulation. However, “contralateral suppression” of the MOC reflex neural circuit, evident as a rapid reduction in cubic DPOAE when noise is presented to the opposite ear in wildtype mice, was substantially disrupted in the PrphKO. Auditory brainstem response (ABR) measurements demonstrated that hearing sensitivity (thresholds and growth-functions) were indistinguishable between wildtype and PrphKO mice. Despite this comparability in sound transduction and strength of the afferent signal to the central auditory pathways, high-intensity, broadband noise exposure (108 dB SPL, 1 h) produced permanent high frequency hearing loss (24–32 kHz) in PrphKO mice but not the wildtype mice, consistent with the attenuated contralateral suppression of the PrphKO. These data support the postulate that auditory neurons expressing Prph contribute to the sensory arm of the otoprotective MOC feedback circuit.
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Affiliation(s)
- Jennie M. E. Cederholm
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Kristina E. Parley
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Chamini J. Perera
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Georg von Jonquieres
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Jeremy L. Pinyon
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Jean-Pierre Julien
- Department of Psychiatry and Neuroscience, CERVO Brain Research Centre, Laval University, Quebec, QC, Canada
| | - David K. Ryugo
- Garvan Institute of Medical Research, Sydney, NSW, Australia
- School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, Australia
- Department of Otolaryngology, Head, Neck & Skull Base Surgery, St Vincent's Hospital, Sydney, NSW, Australia
| | - Allen F. Ryan
- Departments of Surgery and Neurosciences, University of California, San Diego, La Jolla, CA, United States
- Veterans Administration Medical Center, La Jolla, CA, United States
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, Australia
- *Correspondence: Gary D. Housley
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Murphy TV, Perry MA, Ulman LG, Marden NA, Daniel B, Hanna G, Housley GD. Microvascular anatomy and physiology laboratory class using the Australian cane toad. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.0r828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Housley DM, Irani D, Housley GD, Ten Cate WJF. Audiological and Surgical Correlates of Myringoplasty Associated with Ethnography in the Bay of Plenty, New Zealand. Audiol Neurootol 2022; 27:406-417. [PMID: 35477110 DOI: 10.1159/000524312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 03/23/2022] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION This retrospective cohort study of myringoplasty performed at Tauranga Hospital, Bay of Plenty, New Zealand from 2010 to 2020 sought to identify predictive factors for successful myringoplasty with particular consideration given to the known high prevalence of middle ear conditions in New Zealand Māori. METHODS Outcomes were surgical success (perforation closure at 1 month) and hearing improvement, which were correlated against demographic, pathological, and surgical variables. RESULTS 174 patients underwent 221 procedures (139 in children under 18 years old), with 66.1% of patients being New Zealand Māori and 24.7% New Zealand European ethnicity. Normalized by population demographics, New Zealand Māori were 2.3 times overrepresented, whereas New Zealand Europeans were underrepresented by 0.34 times (a 6.8 times relative treatment differential). The rate of surgical success was 84.6%, independent of patient age, gender, and ethnicity. A postauricular approach and the use of temporalis fascia grafts were both correlated with optimal success rates, whereas early postoperative infection (<1 month) was correlated with ∼3 times increased failure. Myringoplasty improved hearing in 83.1% of patients (average air-bone gap reduction of 10.7 dB). New Zealand Māori patients had ∼4 times greater preoperative conductive hearing loss compared to New Zealand Europeans, but benefited the most from myringoplasty. DISCUSSION/CONCLUSION New Zealand Māori and pediatric populations required greater access to myringoplasty, achieving good surgical and audiological outcomes. Myringoplasty is highly effective and significantly improves hearing, particularly for New Zealand Māori. Pediatric success rates were equivalent to adults, supporting timely myringoplasty to minimize morbidity from untreated perforations.
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Affiliation(s)
- David M Housley
- Department of Otolaryngology, Tauranga Hospital, Bay of Plenty District Health Board, Tauranga, New Zealand
| | - Dinaz Irani
- Department of Otolaryngology, Tauranga Hospital, Bay of Plenty District Health Board, Tauranga, New Zealand
| | - Gary D Housley
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Wouter-J F Ten Cate
- Department of Otolaryngology, Tauranga Hospital, Bay of Plenty District Health Board, Tauranga, New Zealand.,School of Medicine, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
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Klugmann M, Kalotay E, Delerue F, Ittner LM, Bongers A, Yu J, Morris MJ, Housley GD, Fröhlich D. Developmental delay and late onset HBSL pathology in hypomorphic Dars1 M256L mice. Neurochem Res 2022; 47:1972-1984. [PMID: 35357600 PMCID: PMC9217827 DOI: 10.1007/s11064-022-03582-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 10/05/2021] [Accepted: 03/15/2022] [Indexed: 12/03/2022]
Abstract
The leukodystrophy Hypomyelination with Brainstem and Spinal cord involvement and Leg spasticity (HBSL) is caused by recessive mutations of the DARS1 gene, which encodes the cytoplasmic aspartyl-tRNA synthetase. HBSL is a spectrum disorder with disease onset usually during early childhood and no available treatment options. Patients display regression of previously acquired motor milestones, spasticity, ataxia, seizures, nystagmus, and intellectual disabilities. Gene-function studies in mice revealed that homozygous Dars1 deletion is embryonically lethal, suggesting that successful modelling of HBSL requires the generation of disease-causing genocopies in mice. In this study, we introduced the pathogenic DARS1M256L mutation located on exon nine of the murine Dars1 locus. Despite causing severe illness in humans, homozygous Dars1M256L mice were only mildly affected. To exacerbate HBSL symptoms, we bred Dars1M256L mice with Dars1-null ‘enhancer’ mice. The Dars1M256L/− offspring displayed increased embryonic lethality, severe developmental delay, reduced body weight and size, hydrocephalus, anophthalmia, and vacuolization of the white matter. Remarkably, the Dars1M256L/− genotype affected energy metabolism and peripheral organs more profoundly than the nervous system and resulted in reduced body fat, increased respiratory exchange ratio, reduced liver steatosis, and reduced hypocellularity of the bone marrow. In summary, homozygous Dars1M256L and compound heterozygous Dars1M256L/− mutation genotypes recapitulate some aspects of HBSL and primarily manifest in developmental delay as well as metabolic and peripheral changes. These aspects of the disease might have been overlooked in HBSL patients with severe neurological deficits but could be included in the differential diagnosis of HBSL in the future.
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Affiliation(s)
- Matthias Klugmann
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, University of New South Wales, 2052, Sydney, NSW, Australia.
| | - Elizabeth Kalotay
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, University of New South Wales, 2052, Sydney, NSW, Australia
| | - Fabien Delerue
- Dementia Research Centre, Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 2109, Sydney, NSW, Australia
| | - Lars M Ittner
- Dementia Research Centre, Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 2109, Sydney, NSW, Australia
| | - Andre Bongers
- Biomedical Resources Imaging Laboratory, University of New South Wales, 2052, Sydney, NSW, Australia
| | - Josephine Yu
- Department of Pharmacology, School of Medical Sciences, University of New South Wales, 2052, Sydney, NSW, Australia
| | - Margaret J Morris
- Department of Pharmacology, School of Medical Sciences, University of New South Wales, 2052, Sydney, NSW, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, University of New South Wales, 2052, Sydney, NSW, Australia
| | - Dominik Fröhlich
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, University of New South Wales, 2052, Sydney, NSW, Australia.
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von Jonquieres G, Rae CD, Housley GD. Emerging Concepts in Vector Development for Glial Gene Therapy: Implications for Leukodystrophies. Front Cell Neurosci 2021; 15:661857. [PMID: 34239416 PMCID: PMC8258421 DOI: 10.3389/fncel.2021.661857] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 05/12/2021] [Indexed: 12/12/2022] Open
Abstract
Central Nervous System (CNS) homeostasis and function rely on intercellular synchronization of metabolic pathways. Developmental and neurochemical imbalances arising from mutations are frequently associated with devastating and often intractable neurological dysfunction. In the absence of pharmacological treatment options, but with knowledge of the genetic cause underlying the pathophysiology, gene therapy holds promise for disease control. Consideration of leukodystrophies provide a case in point; we review cell type – specific expression pattern of the disease – causing genes and reflect on genetic and cellular treatment approaches including ex vivo hematopoietic stem cell gene therapies and in vivo approaches using adeno-associated virus (AAV) vectors. We link recent advances in vectorology to glial targeting directed towards gene therapies for specific leukodystrophies and related developmental or neurometabolic disorders affecting the CNS white matter and frame strategies for therapy development in future.
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Affiliation(s)
- Georg von Jonquieres
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Randwick, NSW, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW, Australia
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Muthiah A, Housley GD, Klugmann M, Fröhlich D. The Leukodystrophies HBSL and LBSL-Correlates and Distinctions. Front Cell Neurosci 2021; 14:626610. [PMID: 33574740 PMCID: PMC7870476 DOI: 10.3389/fncel.2020.626610] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/21/2020] [Indexed: 12/16/2022] Open
Abstract
Aminoacyl-tRNA synthetases (ARSs) accurately charge tRNAs with their respective amino acids. As such, they are vital for the initiation of cytosolic and mitochondrial protein translation. These enzymes have become increasingly scrutinized in recent years for their role in neurodegenerative disorders caused by the mutations of ARS-encoding genes. This review focuses on two such genes-DARS1 and DARS2-which encode cytosolic and mitochondrial aspartyl-tRNA synthetases, and the clinical conditions associated with mutations of these genes. We also describe attempts made at modeling these conditions in mice, which have both yielded important mechanistic insights. Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a disease caused by a range of mutations in the DARS2 gene, initially identified in 2003. Ten years later, hypomyelination with brainstem and spinal cord involvement and leg spasticity (HBSL), caused by mutations of cytosolic DARS1, was discovered. Multiple parallels have been drawn between the two conditions. The Magnetic Resonance Imaging (MRI) patterns are strikingly similar, but still set these two conditions apart from other leukodystrophies. Clinically, both conditions are characterized by lower limb spasticity, often associated with other pyramidal signs. However, perhaps due to earlier detection, a wider range of symptoms, including peripheral neuropathy, as well as visual and hearing changes have been described in LBSL patients. Both HBSL and LBSL are spectrum disorders lacking genotype to phenotype correlation. While the fatal phenotype of Dars1 or Dars2 single gene deletion mouse mutants revealed that the two enzymes lack functional redundancy, further pursuit of disease modeling are required to shed light onto the underlying disease mechanism, and enable examination of experimental treatments, including gene therapies.
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Affiliation(s)
| | | | | | - Dominik Fröhlich
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Kensington, NSW, Australia
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Fröhlich D, Mendes MI, Kueh AJ, Bongers A, Herold MJ, Salomons GS, Housley GD, Klugmann M. A Hypomorphic Dars1 D367Y Model Recapitulates Key Aspects of the Leukodystrophy HBSL. Front Cell Neurosci 2021; 14:625879. [PMID: 33551752 PMCID: PMC7855723 DOI: 10.3389/fncel.2020.625879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 12/21/2020] [Indexed: 01/18/2023] Open
Abstract
Hypomyelination with brain stem and spinal cord involvement and leg spasticity (HBSL) is a leukodystrophy caused by missense mutations of the aspartyl-tRNA synthetase-encoding gene DARS1. The clinical picture includes the regression of acquired motor milestones, spasticity, ataxia, seizures, nystagmus, and intellectual disabilities. Morphologically, HBSL is characterized by a distinct pattern of hypomyelination in the central nervous system including the anterior brainstem, the cerebellar peduncles and the supratentorial white matter as well as the dorsal columns and the lateral corticospinal tracts of the spinal cord. Adequate HBSL animal models are lacking. Dars1 knockout mice are embryonic lethal precluding examination of the etiology. To address this, we introduced the HBSL-causing Dars1 D367Y point mutation into the mouse genome. Surprisingly, mice carrying this mutation homozygously were phenotypically normal. As hypomorphic mutations are more severe in trans to a deletion, we crossed Dars1 D367Y/D367Y mice with Dars1-null carriers. The resulting Dars1 D367Y/- offspring displayed a strong developmental delay compared to control Dars1 D367Y/+ littermates, starting during embryogenesis. Only a small fraction of Dars1 D367Y/- mice were born, and half of these mice died with hydrocephalus during the first 3 weeks of life. Of the few Dars1 D367Y/- mice that were born at term, 25% displayed microphthalmia. Throughout postnatal life, Dars1 D367Y/- mice remained smaller and lighter than their Dars1 D367Y/+ littermates. Despite this early developmental deficit, once they made it through early adolescence Dars1 D367Y/- mice were phenotypically inconspicuous for most of their adult life, until they developed late onset motor deficits as well as vacuolization and demyelination of the spinal cord white matter. Expression levels of the major myelin proteins were reduced in Dars1 D367Y/- mice compared to controls. Taken together, Dars1 D367Y/- mice model aspects of the clinical picture of the corresponding missense mutation in HBSL. This model will enable studies of late onset deficits, which is precluded in Dars1 knockout mice, and can be leveraged to test potential HBSL therapeutics including DARS1 gene replacement therapy.
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Affiliation(s)
- Dominik Fröhlich
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, UNSW Sydney, Kensington, NSW, Australia
| | - Marisa I. Mendes
- Metabolic Unit/Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Amsterdam Neuroscience, Amsterdam Gastroenterology & Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Andrew J. Kueh
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
| | - Andre Bongers
- Biomedical Resources Imaging Laboratory, UNSW Sydney, Kensington, NSW, Australia
| | - Marco J. Herold
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
| | - Gajja S. Salomons
- Metabolic Unit/Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Amsterdam Neuroscience, Amsterdam Gastroenterology & Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Gary D. Housley
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, UNSW Sydney, Kensington, NSW, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, UNSW Sydney, Kensington, NSW, Australia
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12
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Przybyla M, van Eersel J, van Hummel A, van der Hoven J, Sabale M, Harasta A, Müller J, Gajwani M, Prikas E, Mueller T, Stevens CH, Power J, Housley GD, Karl T, Kassiou M, Ke YD, Ittner A, Ittner LM. Onset of hippocampal network aberration and memory deficits in P301S tau mice are associated with an early gene signature. Brain 2021; 143:1889-1904. [PMID: 32375177 DOI: 10.1093/brain/awaa133] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 02/10/2020] [Accepted: 03/04/2020] [Indexed: 01/30/2023] Open
Abstract
Hyperphosphorylation and deposition of tau in the brain characterizes frontotemporal dementia and Alzheimer's disease. Disease-associated mutations in the tau-encoding MAPT gene have enabled the generation of transgenic mouse models that recapitulate aspects of human neurodegenerative diseases, including tau hyperphosphorylation and neurofibrillary tangle formation. Here, we characterized the effects of transgenic P301S mutant human tau expression on neuronal network function in the murine hippocampus. Onset of progressive spatial learning deficits in P301S tau transgenic TAU58/2 mice were paralleled by long-term potentiation deficits and neuronal network aberrations during electrophysiological and EEG recordings. Gene-expression profiling just prior to onset of apparent deficits in TAU58/2 mice revealed a signature of immediate early genes that is consistent with neuronal network hypersynchronicity. We found that the increased immediate early gene activity was confined to neurons harbouring tau pathology, providing a cellular link between aberrant tau and network dysfunction. Taken together, our data suggest that tau pathology drives neuronal network dysfunction through hyperexcitation of individual, pathology-harbouring neurons, thereby contributing to memory deficits.
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Affiliation(s)
- Magdalena Przybyla
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Janet van Eersel
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Annika van Hummel
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Julia van der Hoven
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Miheer Sabale
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Anne Harasta
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Julius Müller
- Genome Informatics at Molecular Health GmbH, Heidelberg, Germany
| | - Mehul Gajwani
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia.,Faculty of Medicine, University of New South Wales, Sydney, Australia
| | - Emmanuel Prikas
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Thomas Mueller
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Claire H Stevens
- School of Chemistry and Molecular Bioscience, University of Wollongong and the Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia
| | - John Power
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Tim Karl
- School of Medicine, Western Sydney University, Penrith, NSW, Australia
| | - Michael Kassiou
- School of Chemistry, University of Sydney, Sydney, NSW, Australia
| | - Yazi D Ke
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Arne Ittner
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
| | - Lars M Ittner
- Dementia Research Centre and Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, 2109, NSW, Australia
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13
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Das A, Fröhlich D, Achanta LB, Rowlands BD, Housley GD, Klugmann M, Rae CD. Correction to: L-Aspartate, L-Ornithine and L-Ornithine-L-Aspartate (LOLA) and Their Impact on Brain Energy Metabolism. Neurochem Res 2020; 45:2527. [PMID: 32638216 DOI: 10.1007/s11064-020-03087-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The original version of this published article, the bottom right hand panels of Figs. 3-6 were labelled as "Isotopomers formed from [1-13C]D-glucose". This is incorrect and should read "Isotopomers formed from [1,2-13C]acetate". This has been corrected by publishing this correction article.
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Affiliation(s)
- Abhijit Das
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia.,School of Medical Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Dominik Fröhlich
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Lavanya B Achanta
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia.,Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Benjamin D Rowlands
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia.,Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia. .,School of Medical Sciences, The University of New South Wales, Sydney, NSW, Australia.
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14
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Das A, Fröhlich D, Achanta LB, Rowlands BD, Housley GD, Klugmann M, Rae CD. L-Aspartate, L-Ornithine and L-Ornithine-L-Aspartate (LOLA) and Their Impact on Brain Energy Metabolism. Neurochem Res 2020; 45:1438-1450. [PMID: 32424601 DOI: 10.1007/s11064-020-03044-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 04/25/2020] [Accepted: 04/29/2020] [Indexed: 12/11/2022]
Abstract
L-Ornithine-L-aspartate (LOLA), a crystalline salt, is used primarily in the management of hepatic encephalopathy. The degree to which it might penetrate the brain, and the effects it might have on metabolism in brain are poorly understood. Here, to investigate the effects of LOLA on brain energy metabolism we incubated brain cortical tissue slices from guinea pig (Cavea porcellus) with the constituent amino acids of LOLA, L-ornithine or L-aspartate, as well as LOLA, in the presence of [1-13C]D-glucose and [1,2-13C]acetate; these labelled substrates are useful indicators of brain metabolic activity. L-Ornithine produced significant "sedative" effects on brain slice metabolism, most likely via conversion of ornithine to GABA via the ornithine aminotransferase pathway, while L-aspartate showed concentration-dependent excitatory effects. The metabolic effects of LOLA reflected a mix of these two different processes and were concentration-dependent. We also investigated the effect of an intraperitoneal bolus injection of L-ornithine, L-aspartate or LOLA on levels of metabolites in kidney, liver and brain cortex and brain stem in mice (C57Bl6J) 1 h later. No significant changes in metabolite levels were seen following the bolus injection of L-aspartate, most likely due to rapid metabolism of aspartate before reaching the target tissue. Brain cortex glutamate was decreased by L-ornithine but no other brain effects were observed with any other compound. Kidney levels of aspartate were increased after injection of L-ornithine and LOLA which may be due to interference by ornithine with the kidney urea cycle. It is likely that without optimising chronic intravenous infusion, LOLA has minimal impact on healthy brain energy metabolism due to systemic clearance and the blood - brain barrier.
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Affiliation(s)
- Abhijit Das
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia.,School of Medical Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Dominik Fröhlich
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Lavanya B Achanta
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia.,Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Benjamin D Rowlands
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia.,Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Kensington, 2052, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia. .,School of Medical Sciences, The University of New South Wales, Sydney, NSW, Australia.
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15
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Housley DM, Pinyon JL, von Jonquieres G, Perera CJ, Smout M, Liddell MJ, Jennings EA, Wilson D, Housley GD. Australian Scorpion Hormurus waigiensis Venom Fractions Show Broad Bioactivity Through Modulation of Bio-Impedance and Cytosolic Calcium. Biomolecules 2020; 10:E617. [PMID: 32316246 PMCID: PMC7226344 DOI: 10.3390/biom10040617] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 04/06/2020] [Accepted: 04/06/2020] [Indexed: 12/13/2022] Open
Abstract
Scorpion venoms are a rich source of bioactive molecules, but characterisation of toxin peptides affecting cytosolic Ca2+, central to cell signalling and cell death, is limited. We undertook a functional screening of the venom of the Australian scorpion Hormurus waigiensis to determine the breadth of Ca2+ mobilisation. A human embryonic kidney (HEK293) cell line stably expressing the genetically encoded Ca2+ reporter GCaMP5G and the rabbit type 1 ryanodine receptor (RyR1) was developed as a biosensor. Size-exclusion Fast Protein Liquid Chromatography separated the venom into 53 fractions, constituting 12 chromatographic peaks. Liquid chromatography mass spectroscopy identified 182 distinct molecules with 3 to 63 components per peak. The molecular weights varied from 258 Da-13.6 kDa, with 53% under 1 kDa. The majority of the venom chromatographic peaks (tested as six venom pools) were found to reversibly modulate cell monolayer bioimpedance, detected using the xCELLigence platform (ACEA Biosciences). Confocal Ca2+ imaging showed 9/14 peak samples, with molecules spanning the molecular size range, increased cytosolic Ca2+ mobilization. H. waigiensis venom Ca2+ activity was correlated with changes in bio-impedance, reflecting multi-modal toxin actions on cell physiology across the venom proteome.
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Affiliation(s)
- David M. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (D.M.H.); (J.L.P.); (G.v.J.); (C.J.P.)
- Department of Otolaryngology, Sunshine Coast University Hospital, Sunshine Coast, QLD 4575, Australia
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, QLD 4878, Australia;
| | - Jeremy L. Pinyon
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (D.M.H.); (J.L.P.); (G.v.J.); (C.J.P.)
| | - Georg von Jonquieres
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (D.M.H.); (J.L.P.); (G.v.J.); (C.J.P.)
| | - Chamini J. Perera
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (D.M.H.); (J.L.P.); (G.v.J.); (C.J.P.)
| | - Michael Smout
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD 4878, Australia; (M.S.); (D.W.)
- Centre for Molecular Therapeutics, James Cook University, Cairns, QLD 4878, Australia
| | - Michael J. Liddell
- Centre for Tropical Environmental and Sustainability Science, College of Science & Engineering, Cairns Campus, James Cook University, Cairns, QLD 4878, Australia;
| | - Ernest A. Jennings
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, QLD 4878, Australia;
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD 4878, Australia; (M.S.); (D.W.)
- Centre for Molecular Therapeutics, James Cook University, Cairns, QLD 4878, Australia
| | - David Wilson
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD 4878, Australia; (M.S.); (D.W.)
- Centre for Molecular Therapeutics, James Cook University, Cairns, QLD 4878, Australia
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (D.M.H.); (J.L.P.); (G.v.J.); (C.J.P.)
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16
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Cederholm JME, Ryan AF, Housley GD. Onset kinetics of noise-induced purinergic adaptation of the 'cochlear amplifier'. Purinergic Signal 2019; 15:343-355. [PMID: 31377959 PMCID: PMC6737159 DOI: 10.1007/s11302-019-09648-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 02/06/2019] [Indexed: 12/18/2022] Open
Abstract
A major component of slowly reversible hearing loss which develops with sustained exposure to noise has been attributed to release of ATP in the cochlea activating P2X2 receptor (P2X2R) type ATP-gated ion channels. This purinergic humoral adaptation is thought to enable the highly sensitive hearing organ to maintain function with loud sound, protecting the ear from acoustic overstimulation. In the study that established this hearing adaptation mechanism as reported by Housley et al. (Proc Natl Acad Sci U S A 110:7494-7499, 2013), the activation kinetics were determined in mice from auditory brainstem response (ABR) threshold shifts with sustained noise presentation at time points beyond 10 min. The present study was designed to achieve finer resolution of the onset kinetics of purinergic hearing adaptation, and included the use of cubic (2f1-f2) distortion product otoacoustic emissions (DPOAEs) to probe whether the active mechanical outer hair cell 'cochlear amplifier' contributed to this process. We show that the ABR and DPOAE threshold shifts were largely complete within the first 7.5 min of moderate broadband noise (85 dB SPL) in wildtype C57Bl/6J mice. The ABR and DPOAE adaptation rates were both best fitted by a single exponential function with ~ 3 min time constants. ABR and DPOAE threshold shifts with this noise were minimal in mice null for the P2rx2 gene encoding the P2X2R. The findings demonstrate a considerably faster purinergic hearing adaptation to noise than previously appreciated. Moreover, they strongly implicate the outer hair cell as the site of action, as the DPOAEs stem from active cochlear electromotility.
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Affiliation(s)
- Jennie M E Cederholm
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW, Australia
| | - Allen F Ryan
- Departments of Surgery and Neurosciences, University of California San Diego, La Jolla, CA, USA
- Veterans Administration Medical Center, La Jolla, CA, USA
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Sydney, Sydney, NSW, Australia.
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17
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Pinyon JL, von Jonquieres G, Crawford EN, Duxbury M, Al Abed A, Lovell NH, Klugmann M, Wise AK, Fallon JB, Shepherd RK, Birman CS, Lai W, McAlpine D, McMahon C, Carter PM, Enke YL, Patrick JF, Schilder AG, Marie C, Scherman D, Housley GD. Neurotrophin gene augmentation by electrotransfer to improve cochlear implant hearing outcomes. Hear Res 2019; 380:137-149. [DOI: 10.1016/j.heares.2019.06.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/07/2019] [Accepted: 06/12/2019] [Indexed: 12/14/2022]
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18
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Al Abed A, Pinyon JL, Foster E, Crous F, Cowin GJ, Housley GD, Lovell NH. Computational Simulation Expands Understanding of Electrotransfer-Based Gene Augmentation for Enhancement of Neural Interfaces. Front Neurosci 2019; 13:691. [PMID: 31447624 PMCID: PMC6691069 DOI: 10.3389/fnins.2019.00691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 06/18/2019] [Indexed: 12/16/2022] Open
Abstract
The neural interface is a critical factor in governing efficient and safe charge transfer between a stimulating electrode and biological tissue. The interface plays a crucial role in the efficacy of electric stimulation in chronic implants and both electromechanical properties and biological properties shape this. In the case of cochlear implants, it has long been recognized that neurotrophins can stimulate growth of the target auditory nerve fibers into a favorable apposition with the electrode array, and recently such arrays have been re-purposed to enable electrotransfer (electroporation)-based neurotrophin gene augmentation to improve the "bionic ear." For both this acute bionic array-directed electroporation and for chronic conventional cochlear implant arrays, the electric fields generated in target tissue during pulse delivery are central to efficacy, but are challenging to map. We present a computational model for predicting electric fields generated by array-driven DNA electrotransfer in the cochlea. The anatomically realistic model geometry was reconstructed from magnetic resonance images of the guinea pig cochlea and an eight-channel electrode array embedded within this geometry. The model incorporates a description of both Faradaic and non-Faradaic mechanisms occurring at the electrode-electrolyte interface with frequency dependency optimized to match experimental impedance spectrometry measurements. Our simulations predict that a tandem electrode configuration with four ganged cathodes and four ganged anodes produces three to fourfold larger area in target tissue where the electric field is within the range for successful gene transfer compared to an alternate paired anode-cathode electrode configuration. These findings matched in vivo transfection efficacy of a green fluorescent protein (GFP) reporter following array-driven electrotransfer of the reporter-encoding plasmid DNA. This confirms utility of the developed model as a tool to optimize the safety and efficacy of electrotransfer protocols for delivery of neurotrophin growth factors, with the ultimate aim of using gene augmentation approaches to improve the characteristics of the electrode-neural interfaces in chronically implanted neurostimulation devices.
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Affiliation(s)
- Amr Al Abed
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW, Australia
| | - Jeremy L Pinyon
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Evelyn Foster
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW, Australia
| | - Frederik Crous
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW, Australia
| | - Gary J Cowin
- National Imaging Facility, Centre for Advanced Imaging, University of Queensland, Brisbane, QLD, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW, Australia
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19
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Lin SCY, Thorne PR, Housley GD, Vlajkovic SM. Purinergic Signaling and Aminoglycoside Ototoxicity: The Opposing Roles of P1 (Adenosine) and P2 (ATP) Receptors on Cochlear Hair Cell Survival. Front Cell Neurosci 2019; 13:207. [PMID: 31156393 PMCID: PMC6529511 DOI: 10.3389/fncel.2019.00207] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 04/24/2019] [Indexed: 01/12/2023] Open
Abstract
Purinergic signaling regulates important physiological processes and the homeostatic response to stress in the cochlea via extracellular nucleosides (adenosine) and nucleotides (ATP, UTP). Using a previously established organotypic culture model, the current study investigated the effect of purinergic P1 (adenosine) and P2 (ATP) receptor activation on the survival of the sensory hair cell population in the cochlea exposed to the ototoxic aminoglycoside neomycin. Organ of Corti explants were obtained from C57BL/6 mice at postnatal day 3 (P3) and maintained in normal culture medium (with or without purine receptor agonists or analogs) for 19.5 h prior to neomycin exposure (1 mM, 3 h) followed by a further incubation for 19.5 h in culture medium. The cochlear explants were then fixed in 4% paraformaldehyde (PFA) and sensory hair cells labeled with Alexa 488-phalloidin. Neomycin induced a substantial loss of the sensory hair cells, mostly in the middle segment of the cochlea. This neomycin-induced ototoxicity was unaffected by the addition of P2 receptor agonists (ATP and UTP) in the culture medium, whilst the addition of their slowly-hydrolyzable analogs (ATPγS, UTPγS) aggravated neomycin-induced sensory hair cell loss. In contrast, the activation of P1 receptors by adenosine or adenosine amine congener (ADAC) conferred partial protection from neomycin ototoxicity. This study demonstrates a pro-survival effect of P1 receptor stimulation, whilst prolonged activation of P2 receptors has an opposite effect. Based on these findings, we postulate that P1 and P2 receptors orchestrate differential responses to cochlear injury and that the balance of these receptors is important for maintaining cochlear homeostasis following ototoxic injury.
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Affiliation(s)
- Shelly C Y Lin
- Department of Physiology and The Eisdell Moore Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Peter R Thorne
- Department of Physiology and The Eisdell Moore Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Gary D Housley
- Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Srdjan M Vlajkovic
- Department of Physiology and The Eisdell Moore Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
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20
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Pinyon JL, Klugmann M, Lovell NH, Housley GD. Dual-Plasmid Bionic Array-Directed Gene Electrotransfer in HEK293 Cells and Cochlear Mesenchymal Cells Probes Transgene Expression and Cell Fate. Hum Gene Ther 2019; 30:211-224. [DOI: 10.1089/hum.2018.062] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
- Jeremy L. Pinyon
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, and UNSW Sydney, Sydney, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, and UNSW Sydney, Sydney, Australia
| | - Nigel H. Lovell
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, Australia
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, and UNSW Sydney, Sydney, Australia
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21
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Abed AA, Foster E, Pinyon JL, Li CH, Cowin GJ, Housley GD, Lovell NH. Computational Simulation of Array-based Electroporation in the Cochlea. Annu Int Conf IEEE Eng Med Biol Soc 2018; 2018:2462-2465. [PMID: 30440906 DOI: 10.1109/embc.2018.8512808] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We present a computational model for predicting electric field distributions following array-based closed-loop electroporation in the cochlea. The model geometry was reconstructed from magnetic resonance images of the guinea pig cochlea and an eight-channel electrode array embedded within this geometry. The model's electrode voltage output waveform was obtained from electric potential mapping conducted in physiological solution following constant-current stimulation using the electrode array. Our simulations predict that a tandem electrode configuration with four ganged cathodes and four ganged anodes produces a larger area in target tissue where the electric field is within the range for successful gene transfer compared to an alternate paired anode-cathode electrode configuration. These findings corroborate published in vivo evidence comparing the two configurations and support the utility of the developed model as a tool to optimize the efficacy of electroporation electrodes.
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22
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Fröhlich D, Suchowerska AK, Voss C, He R, Wolvetang E, von Jonquieres G, Simons C, Fath T, Housley GD, Klugmann M. Expression Pattern of the Aspartyl-tRNA Synthetase DARS in the Human Brain. Front Mol Neurosci 2018; 11:81. [PMID: 29615866 PMCID: PMC5869200 DOI: 10.3389/fnmol.2018.00081] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 03/01/2018] [Indexed: 12/21/2022] Open
Abstract
Translation of mRNA into protein is an evolutionarily conserved, fundamental process of life. A prerequisite for translation is the accurate charging of tRNAs with their cognate amino acids, a reaction catalyzed by specific aminoacyl-tRNA synthetases. One of these enzymes is the aspartyl-tRNA synthetase DARS, which pairs aspartate with its corresponding tRNA. Missense mutations of the gene encoding DARS result in the leukodystrophy hypomyelination with brainstem and spinal cord involvement and leg spasticity (HBSL) with a distinct pattern of hypomyelination, motor abnormalities, and cognitive impairment. A thorough understanding of the DARS expression domains in the central nervous system is essential for the development of targeted therapies to treat HBSL. Here, we analyzed endogenous DARS expression on the mRNA and protein level in different brain regions and cell types of human post mortem brain tissue as well as in human stem cell derived neurons, oligodendrocytes, and astrocytes. DARS expression is significantly enriched in the cerebellum, a region affected in HBSL patients and important for motor control. Although obligatorily expressed in all cells, DARS shows a distinct expression pattern with enrichment in neurons but only low abundance in oligodendrocytes, astrocytes, and microglia. Our results reveal little homogeneity across the different cell types, largely matching previously published data in the murine brain. This human gene expression study will significantly contribute to the understanding of DARS gene function and HBSL pathology and will be instrumental for future development of animal models and targeted therapies. In particular, we anticipate high benefit from a gene replacement approach in neurons of HBSL mouse models, given the abundant endogenous DARS expression in this lineage cell.
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Affiliation(s)
- Dominik Fröhlich
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Alexandra K Suchowerska
- Neurodegenerative and Repair Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Carola Voss
- Stem Cell Engineering Group, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, Australia
| | - Ruojie He
- Stem Cell Engineering Group, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, Australia.,Department of Neurology, First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Ernst Wolvetang
- Stem Cell Engineering Group, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, Australia
| | - Georg von Jonquieres
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Cas Simons
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Thomas Fath
- Neurodegenerative and Repair Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
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Palmer JC, Lord MS, Pinyon JL, Wise AK, Lovell NH, Carter PM, Enke YL, Housley GD, Green RA. Comparing perilymph proteomes across species. Laryngoscope 2017; 128:E47-E52. [DOI: 10.1002/lary.26885] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 08/02/2017] [Accepted: 08/07/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Jonathan C. Palmer
- Graduate School of Biomedical EngineeringUniversity of New South Wales SydneySydneyNew South WalesAustralia
| | - Megan S. Lord
- Graduate School of Biomedical EngineeringUniversity of New South Wales SydneySydneyNew South WalesAustralia
| | - Jeremy L. Pinyon
- Translational Neuroscience Facility and Department of Physiology, School of Medical SciencesUniversity of New South Wales SydneySydneyNew South WalesAustralia
| | | | - Nigel H. Lovell
- Graduate School of Biomedical EngineeringUniversity of New South Wales SydneySydneyNew South WalesAustralia
| | - Paul M. Carter
- Cochlear LtdMacquarie UniversitySydneyNew South WalesAustralia
| | - Ya Lang Enke
- Cochlear LtdMacquarie UniversitySydneyNew South WalesAustralia
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical SciencesUniversity of New South Wales SydneySydneyNew South WalesAustralia
| | - Rylie A. Green
- Graduate School of Biomedical EngineeringUniversity of New South Wales SydneySydneyNew South WalesAustralia
- Department of BioengineeringImperial College LondonLondonUnited Kingdom
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24
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Achanta LB, Rowlands BD, Thomas DS, Housley GD, Rae CD. β-Hydroxybutyrate Boosts Mitochondrial and Neuronal Metabolism but is not Preferred Over Glucose Under Activated Conditions. Neurochem Res 2017; 42:1710-1723. [DOI: 10.1007/s11064-017-2228-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/06/2017] [Accepted: 03/09/2017] [Indexed: 12/21/2022]
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25
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Palmer JC, Lord MS, Pinyon JL, Wise AK, Lovell NH, Carter PM, Enke YL, Housley GD, Green RA. Understanding the cochlear implant environment by mapping perilymph proteomes from different species. Annu Int Conf IEEE Eng Med Biol Soc 2017; 2016:5237-5240. [PMID: 28269445 DOI: 10.1109/embc.2016.7591908] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cochlear implants operate within a bony channel of the cochlea, bathed in a fluid known as the perilymph. The perilymph is a complex fluid containing ions and proteins, which are known to actively interact with metallic electrodes. To improve our understanding of how cochlear implant performance varies in preclinical in vivo studies in comparison to human trials and patient outcomes, the protein composition (or perilymph proteome) is needed. Samples of perilymph were gathered from feline and guinea pig subjects and analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS) to produce proteomes and compare against the recently published human proteome. Over 64% of the proteins in the guinea pig proteome were found to be common to the human proteome. The proportions of apolipoproteins, enzymes and immunoglobulins showed little variation between the two proteomes, with other classes showing similarity. This establishes a good basis for comparison of results. The results for the feline profile showed less similarity with the human proteome and would not provide a quality comparison. This work highlights the suitability of the guinea pig to model the biological environment of the human cochlear and the need to carefully select models of the biological environment of a cochlear implant to more adequately translate in vitro and in vivo studies to the clinic.
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26
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Vlajkovic SM, Ambepitiya K, Barclay M, Boison D, Housley GD, Thorne PR. Adenosine receptors regulate susceptibility to noise-induced neural injury in the mouse cochlea and hearing loss. Hear Res 2016; 345:43-51. [PMID: 28034618 DOI: 10.1016/j.heares.2016.12.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 11/15/2016] [Accepted: 12/20/2016] [Indexed: 12/20/2022]
Abstract
Our previous studies have shown that the stimulation of A1 adenosine receptors in the inner ear can mitigate the loss of sensory hair cells and hearing loss caused by exposure to traumatic noise. Here, we focus on the role of adenosine receptors (AR) in the development of noise-induced neural injury in the cochlea using A1AR and A2AAR null mice (A1AR-/- and A2AAR-/-). Wildtype (WT) and AR deficient mice were exposed to octave band noise (8-16 kHz, 100 dB SPL) for 2 h to induce cochlear injury and hearing loss. Auditory thresholds and input/output functions were assessed using auditory brainstem responses (ABR) before and two weeks post-exposure. The loss of outer hair cells (OHC), afferent synapses and spiral ganglion neurons (SGN) were assessed by quantitative histology. A1AR-/- mice (6-8 weeks old) displayed a high frequency hearing loss (ABR threshold shift and reduced ABR wave I and II amplitudes). This hearing loss was further aggravated by acute noise exposure and exceeded the hearing loss in the WT and A2AAR-/- mice. All mice experienced the loss of OHC, synaptic ribbons and SGN after noise exposure, but the loss of SGN was significantly higher in A1AR-/- mice than in the A2AAR-/- and WT genotypes. The A2AAR-/- demonstrated better preservation of OHC and afferent synapses and the minimal loss of SGN after noise exposure. The findings suggest that the loss of A1AR expression results in an increased susceptibility to cochlear neural injury and hearing loss, whilst absence of A2AAR increases cochlear resistance to acoustic trauma.
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Affiliation(s)
- Srdjan M Vlajkovic
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand.
| | - Kaushi Ambepitiya
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand
| | - Meagan Barclay
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand
| | - Detlev Boison
- RS Dow Neurobiology Laboratories, Legacy Research, Portland, OR, 97232, USA
| | - Gary D Housley
- Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, UNSW Australia, Sydney, NSW, 2052, Australia
| | - Peter R Thorne
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland, New Zealand
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27
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Abstract
Exposure to intense sound or noise can result in purely temporary threshold shift (TTS), or leave a residual permanent threshold shift (PTS) along with alterations in growth functions of auditory nerve output. Recent research has revealed a number of mechanisms that contribute to noise-induced hearing loss (NIHL). The principle cause of NIHL is damage to cochlear hair cells and associated synaptopathy. Contributions to TTS include reversible damage to hair cell (HC) stereocilia or synapses, while moderate TTS reflects protective purinergic hearing adaptation. PTS represents permanent damage to or loss of HCs and synapses. While the substrates of HC damage are complex, they include the accumulation of reactive oxygen species and the active stimulation of intracellular stress pathways, leading to programmed and/or necrotic cell death. Permanent damage to cochlear neurons can also contribute to the effects of NIHL, in addition to HC damage. These mechanisms have translational potential for pharmacological intervention and provide multiple opportunities to prevent HC damage or to rescue HCs and spiral ganglion neurons that have suffered injury. This paper reviews advances in our understanding of cellular mechanisms that contribute to NIHL and their potential for therapeutic manipulation.
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Affiliation(s)
- Arwa Kurabi
- Division of Otolaryngology, Department of Surgery, UCSD School of Medicine and San Diego VA Medical Center, La Jolla, CA, 92093, United States
| | - Elizabeth M Keithley
- Division of Otolaryngology, Department of Surgery, UCSD School of Medicine and San Diego VA Medical Center, La Jolla, CA, 92093, United States
| | - Gary D Housley
- Division of Otolaryngology, Department of Surgery, UCSD School of Medicine and San Diego VA Medical Center, La Jolla, CA, 92093, United States
| | - Allen F Ryan
- Division of Otolaryngology, Department of Surgery, UCSD School of Medicine and San Diego VA Medical Center, La Jolla, CA, 92093, United States.
| | - Ann C-Y Wong
- Division of Otolaryngology, Department of Surgery, UCSD School of Medicine and San Diego VA Medical Center, La Jolla, CA, 92093, United States
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28
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Housley DM, Housley GD, Liddell MJ, Jennings EA. Scorpion toxin peptide action at the ion channel subunit level. Neuropharmacology 2016; 127:46-78. [PMID: 27729239 DOI: 10.1016/j.neuropharm.2016.10.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/06/2016] [Accepted: 10/06/2016] [Indexed: 12/19/2022]
Abstract
This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of excitable tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- David M Housley
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Michael J Liddell
- Centre for Tropical Environmental and Sustainability Science and College of Science & Engineering, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia
| | - Ernest A Jennings
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Queensland 4878, Australia; Australian Institute of Tropical Health and Medicine, James Cook University, Cairns Campus, QLD, Australia
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29
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Przybyla M, Stevens CH, van der Hoven J, Harasta A, Bi M, Ittner A, van Hummel A, Hodges JR, Piguet O, Karl T, Kassiou M, Housley GD, Ke YD, Ittner LM, van Eersel J. Disinhibition-like behavior in a P301S mutant tau transgenic mouse model of frontotemporal dementia. Neurosci Lett 2016; 631:24-29. [DOI: 10.1016/j.neulet.2016.08.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/19/2016] [Accepted: 08/04/2016] [Indexed: 11/28/2022]
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30
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Craig AJ, Housley GD. Evaluation of Gene Therapy as an Intervention Strategy to Treat Brain Injury from Stroke. Front Mol Neurosci 2016; 9:34. [PMID: 27252622 PMCID: PMC4877374 DOI: 10.3389/fnmol.2016.00034] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/06/2016] [Indexed: 01/01/2023] Open
Abstract
Stroke is a leading cause of death and disability, with a lack of treatments available to prevent cell death, regenerate damaged cells and pathways, or promote neurogenesis. The extended period of hours to weeks over which tissue damage continues to occur makes this disorder a candidate for gene therapy. This review highlights the development of gene therapy in the area of stroke, with the evolution of viral administration, in experimental stroke models, from pre-injury to clinically relevant timeframes of hours to days post-stroke. The putative therapeutic proteins being examined include anti-apoptotic, pro-survival, anti-inflammatory, and guidance proteins, targeting multiple pathways within the complex pathology, with promising results. The balance of findings from animal models suggests that gene therapy provides a viable translational platform for treatment of ischemic brain injury arising from stroke.
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Affiliation(s)
- Amanda J Craig
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney NSW, Australia
| | - Gary D Housley
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney NSW, Australia
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31
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von Jonquieres G, Fröhlich D, Klugmann CB, Wen X, Harasta AE, Ramkumar R, Spencer ZHT, Housley GD, Klugmann M. Recombinant Human Myelin-Associated Glycoprotein Promoter Drives Selective AAV-Mediated Transgene Expression in Oligodendrocytes. Front Mol Neurosci 2016; 9:13. [PMID: 26941604 PMCID: PMC4763065 DOI: 10.3389/fnmol.2016.00013] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 02/05/2016] [Indexed: 11/13/2022] Open
Abstract
Leukodystrophies are hereditary central white matter disorders caused by oligodendrocyte dysfunction. Recent clinical trials for some of these devastating neurological conditions have employed an ex vivo gene therapy approach that showed improved endpoints because cross-correction of affected myelin-forming cells occurred following secretion of therapeutic proteins by transduced autologous grafts. However, direct gene transfer to oligodendrocytes is required for the majority of leukodystrophies with underlying mutations in genes encoding non-secreted oligodendroglial proteins. Recombinant adeno-associated viral (AAV) vectors are versatile tools for gene transfer to the central nervous system (CNS) and proof-of-concept studies in rodents have shown that the use of cellular promoters is sufficient to target AAV-mediated transgene expression to glia. The potential of this strategy has not been exploited. The major caveat of the AAV system is its limited packaging capacity of ~5 kb, providing the rationale for identifying small yet selective recombinant promoters. Here, we characterize the human myelin associated glycoprotein (MAG) promoter for reliable targeting of AAV-mediated transgene expression to oligodendrocytes in vivo. A homology screen revealed highly conserved genomic regions among mammalian species upstream of the transcription start site. Recombinant AAV expression cassettes carrying the cDNA encoding enhanced green fluorescent protein (GFP) driven by truncated versions of the recombinant MAG promoter (2.2, 1.5 and 0.3 kb in size) were packaged as cy5 vectors and delivered into the dorsal striatum of mice. At 3 weeks post-injection, oligodendrocytes, neurons and astrocytes expressing the reporter were quantified by immunohistochemical staining. Our results revealed that both 2.2 and 1.5 kb MAG promoters targeted more than 95% of transgene expression to oligodendrocytes. Even the short 0.3 kb fragment conveyed high oligodendroglial specific transgene expression (>90%) in vivo. Moreover, cy5-MAG2.2-GFP delivery to the neonate CNS resulted in selective GFP expression in oligodendrocytes for at least 8 months. Broadly, the characterization of the extremely short yet oligodendrocyte-specific human MAG promoter may facilitate modeling neurological diseases caused by oligodendrocyte pathology and has translational relevance for leukodystrophy gene therapy.
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Affiliation(s)
- Georg von Jonquieres
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Dominik Fröhlich
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Claudia B Klugmann
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Xin Wen
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Anne E Harasta
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Roshini Ramkumar
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Ziggy H T Spencer
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia Sydney, NSW, Australia
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32
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Morton-Jones RT, Vlajkovic SM, Thorne PR, Cockayne DA, Ryan AF, Housley GD. Properties of ATP-gated ion channels assembled from P2X2 subunits in mouse cochlear Reissner's membrane epithelial cells. Purinergic Signal 2015; 11:551-60. [PMID: 26424615 DOI: 10.1007/s11302-015-9473-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 09/16/2015] [Indexed: 12/26/2022] Open
Abstract
In the cochlea, Reissner's membrane separates the scala media endolymphatic compartment that sustains the positive endocochlear potential and ion composition necessary for sound transduction, from the scala vestibuli perilymphatic compartment. It is known that with sustained elevated sound levels, adenosine 5'-triphosphate (ATP) is released into the endolymph and ATP-gated ion channels on the epithelial cells lining the endolymphatic compartment shunt the electrochemical driving force, contributing to protective purinergic hearing adaptation. This study characterises the properties of epithelial cell P2X(2)-type ATP-activated membrane conductance in the mouse Reissner's membrane, which forms a substantial fraction of the scale media surface. The cells were found to express two isoforms (a and b) of the P2X(2) subunit arising from alternative splicing of the messenger RNA (mRNA) transcript that could contribute to the trimeric subunit assembly. The ATP-activated conductance demonstrated both immediate and delayed desensitisation consistent with incorporation of the combination of P2X(2) subunit isoforms. Activation by the ATP analogue 2meSATP had equipotency to ATP, whereas α,β-meATP and adenosine 5'-diphosphate (ADP) were ineffective. Positive allosteric modulation of the P2X(2) channels by protons was profound. This native conductance was blocked by the P2X(2)-selective blocker pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) and the conductance was absent in these cells isolated from mice null for the P2rX2 gene encoding the P2X(2) receptor subunit. The activation and desensitisation properties of the Reissner's membrane epithelial cell ATP-gated P2X(2) channels likely contribute to the sensitivity and kinetics of purinergic control of the electrochemical driving force for sound transduction invoked by noise exposure.
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Affiliation(s)
| | - Srdjan M Vlajkovic
- Department of Physiology, University of Auckland, Auckland, New Zealand.,Centre for Brain Research, School of Medical Sciences, University of Auckland, Auckland, New Zealand
| | - Peter R Thorne
- Department of Physiology, University of Auckland, Auckland, New Zealand.,Centre for Brain Research, School of Medical Sciences, University of Auckland, Auckland, New Zealand.,Section of Audiology, School of Population Health, University of Auckland, Private Bag 92019, Auckland, New Zealand
| | | | - Allen F Ryan
- Departments of Surgery and Neurosciences, VA Medical Center, University of California San Diego, La Jolla, CA, 92037, USA
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW, 2052, Australia.
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33
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Pinyon JL, Tadros SF, Froud KE, Y Wong AC, Tompson IT, Crawford EN, Ko M, Morris R, Klugmann M, Housley GD. Close-field electroporation gene delivery using the cochlear implant electrode array enhances the bionic ear. Sci Transl Med 2015; 6:233ra54. [PMID: 24760189 DOI: 10.1126/scitranslmed.3008177] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The cochlear implant is the most successful bionic prosthesis and has transformed the lives of people with profound hearing loss. However, the performance of the "bionic ear" is still largely constrained by the neural interface itself. Current spread inherent to broad monopolar stimulation of the spiral ganglion neuron somata obviates the intrinsic tonotopic mapping of the cochlear nerve. We show in the guinea pig that neurotrophin gene therapy integrated into the cochlear implant improves its performance by stimulating spiral ganglion neurite regeneration. We used the cochlear implant electrode array for novel "close-field" electroporation to transduce mesenchymal cells lining the cochlear perilymphatic canals with a naked complementary DNA gene construct driving expression of brain-derived neurotrophic factor (BDNF) and a green fluorescent protein (GFP) reporter. The focusing of electric fields by particular cochlear implant electrode configurations led to surprisingly efficient gene delivery to adjacent mesenchymal cells. The resulting BDNF expression stimulated regeneration of spiral ganglion neurites, which had atrophied 2 weeks after ototoxic treatment, in a bilateral sensorineural deafness model. In this model, delivery of a control GFP-only vector failed to restore neuron structure, with atrophied neurons indistinguishable from unimplanted cochleae. With BDNF therapy, the regenerated spiral ganglion neurites extended close to the cochlear implant electrodes, with localized ectopic branching. This neural remodeling enabled bipolar stimulation via the cochlear implant array, with low stimulus thresholds and expanded dynamic range of the cochlear nerve, determined via electrically evoked auditory brainstem responses. This development may broadly improve neural interfaces and extend molecular medicine applications.
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Affiliation(s)
- Jeremy L Pinyon
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, University of New South Wales, UNSW Australia, Sydney, New South Wales 2052, Australia
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34
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Canales CP, Wong ACY, Gunning PW, Housley GD, Hardeman EC, Palmer SJ. The role of GTF2IRD1 in the auditory pathology of Williams-Beuren Syndrome. Eur J Hum Genet 2014; 23:774-80. [PMID: 25248400 DOI: 10.1038/ejhg.2014.188] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 08/11/2014] [Accepted: 08/15/2014] [Indexed: 12/15/2022] Open
Abstract
Williams-Beuren Syndrome (WBS) is a rare genetic condition caused by a hemizygous deletion involving up to 28 genes within chromosome 7q11.23. Among the spectrum of physical and neurological defects in WBS, it is common to find a distinctive response to sound stimuli that includes extreme adverse reactions to loud, or sudden sounds and a fascination with certain sounds that may manifest as strengths in musical ability. However, hearing tests indicate that sensorineural hearing loss (SNHL) is frequently found in WBS patients. The functional and genetic basis of this unusual auditory phenotype is currently unknown. Here, we investigated the potential involvement of GTF2IRD1, a transcription factor encoded by a gene located within the WBS deletion that has been implicated as a contributor to the WBS assorted neurocognitive profile and craniofacial abnormalities. Using Gtf2ird1 knockout mice, we have analysed the expression of the gene in the inner ear and examined hearing capacity by evaluating the auditory brainstem response (ABR) and the distortion product of otoacoustic emissions (DPOAE). Our results show that Gtf2ird1 is expressed in a number of cell types within the cochlea, and Gtf2ird1 null mice showed higher auditory thresholds (hypoacusis) in both ABR and DPOAE hearing assessments. These data indicate that the principal hearing deficit in the mice can be traced to impairments in the amplification process mediated by the outer hair cells and suggests that similar mechanisms may underpin the SNHL experienced by WBS patients.
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Affiliation(s)
- Cesar P Canales
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Ann C Y Wong
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NWS, Australia
| | - Peter W Gunning
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Gary D Housley
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NWS, Australia
| | - Edna C Hardeman
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Stephen J Palmer
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
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35
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von Jonquieres G, Froud KE, Klugmann CB, Wong ACY, Housley GD, Klugmann M. Loss of central auditory processing in a mouse model of Canavan disease. PLoS One 2014; 9:e97374. [PMID: 24826990 PMCID: PMC4020830 DOI: 10.1371/journal.pone.0097374] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 04/19/2014] [Indexed: 11/18/2022] Open
Abstract
Canavan Disease (CD) is a leukodystrophy caused by homozygous null mutations in the gene encoding aspartoacylase (ASPA). ASPA-deficiency is characterized by severe psychomotor retardation, and excessive levels of the ASPA substrate N-acetylaspartate (NAA). ASPA is an oligodendrocyte marker and it is believed that CD has a central etiology. However, ASPA is also expressed by Schwann cells and ASPA-deficiency in the periphery might therefore contribute to the complex CD pathology. In this study, we assessed peripheral and central auditory function in the AspalacZ/lacZ rodent model of CD using auditory brainstem response (ABR). Increased ABR thresholds and the virtual loss of waveform peaks 4 and 5 from AspalacZ/lacZ mice, indicated altered central auditory processing in mutant mice compared with Aspawt/wt controls and altered central auditory processing. Analysis of ABR latencies recorded from AspalacZ/lacZ mice revealed that the speed of nerve conduction was unchanged in the peripheral part of the auditory pathway, and impaired in the CNS. Histological analyses confirmed that ASPA was expressed in oligodendrocytes and Schwann cells of the auditory system. In keeping with our physiological results, the cellular organization of the cochlea, including the organ of Corti, was preserved and the spiral ganglion nerve fibres were normal in ASPA-deficient mice. In contrast, we detected substantial hypomyelination in the central auditory system of AspalacZ/lacZ mice. In summary, our data suggest that the lack of ASPA in the CNS is responsible for the observed hearing deficits, while ASPA-deficiency in the cochlear nerve fibres is tolerated both morphologically and functionally.
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Affiliation(s)
- Georg von Jonquieres
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, New South Wales, Sydney, Australia
| | - Kristina E. Froud
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, New South Wales, Sydney, Australia
| | - Claudia B. Klugmann
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, New South Wales, Sydney, Australia
| | - Ann C. Y. Wong
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, New South Wales, Sydney, Australia
| | - Gary D. Housley
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, New South Wales, Sydney, Australia
| | - Matthias Klugmann
- Translational Neuroscience Facility & Department of Physiology, School of Medical Sciences, University of New South Wales, New South Wales, Sydney, Australia
- * E-mail:
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O'Keeffe MG, Thorne PR, Housley GD, Robson SC, Vlajkovic SM. Hair cell specific NTPDase6 immunolocalisation in vestibular end organs: potential role of purinergic signaling in vestibular sensory transduction. J Vestib Res 2013; 22:213-9. [PMID: 23302703 DOI: 10.3233/ves-2012-00461] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A complex extracellular nucleotide signalling system acting on P2 receptors is involved in regulation of cochlear function in the mammalian inner ear. Ectonucleoside triphosphate diphosphohydrolases (E-NTPDases) are ectonucleotidases that regulate P2 receptor signalling pathways in mammalian tissues by hydrolysing extracellular nucleotides to the respective nucleosides. All enzymes from the CD39/ENTPD family (NTPDase1-8) are expressed in the adult rat cochlea, but their expression and distribution in the vestibular end organ is unknown. This report demonstrates selective expression of NTPDase6 by rat vestibular hair cells. Hair cells transducing both angular acceleration (crista ampullaris) and static head position (maculae of the utricle and saccule) exhibited strong immunolabelling with a bias towards the sensory pole and in particular, the hair cell bundle. NTPDase6 is an intracellular enzyme that can be released in a soluble form from cell cultures and shows an enzymatic preference for nucleoside 5'-diphosphates, such as guanosine 5'-diphosphate (GDP) and uridine 5'-diphosphate (UDP). The main function of NTPDase6 may be the regulation of nucleotide levels in cellular organelles by regulating the conversion of nucleotides to nucleosides. NTPDase6 immunolocalisation in the vestibular end organ could be linked to the regulation of P2 receptor signalling and sensory transduction, including maintenance of vestibular hair bundles.
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Affiliation(s)
- Mary G O'Keeffe
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
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Brand Y, Sung M, Chavez E, Wei E, Pak KK, Housley GD, Bodmer D, Ryan AF. Neural cell adhesion molecule L1 modulates type I but not type II inner ear spiral ganglion neurite outgrowth in an in vitro alternate choice assay. J Mol Neurosci 2013; 51:663-70. [PMID: 23760987 DOI: 10.1007/s12031-013-0040-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Accepted: 05/27/2013] [Indexed: 12/17/2022]
Abstract
L1, a neural cell adhesion molecule of the immunoglobulin superfamily, is widely expressed in the nervous system and important in axonal outgrowth, guidance, synapse formation, and signaling. Gene deletion studies emphasize the significance of L1 during development of the central nervous system and L1 is crucial for the topographic targeting of retinal axons. In contrast to the brain and retina, the role of L1 in the inner ear is largely unknown. While previous studies have localized L1 in the developing inner ear of the chicken and mouse, its function during the innervation of the cochlea still remains largely unclear. We therefore investigated the functional role of L1 in the mammalian inner ear. Our aim was to determine whether or not L1 can modulate type I and/or type II spiral ganglion neuron outgrowth using an in vitro alternate choice assay. We found that L1, presented in stripe micropatterns, provide directional cues to neonatal rodent type I but not type II inner ear spiral ganglion neurites. The results suggest that L1 may play a role in axonal pathfinding of type I spiral ganglion dendrites toward their inner hair cell targets but not of type II toward the outer hair cells.
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Affiliation(s)
- Yves Brand
- Department of Surgery/Otolaryngology, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA, 92093, USA
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Wong ACY, Birnbaumer L, Housley GD. Canonical transient receptor potential channel subtype 3-mediated hair cell Ca2+entry regulates sound transduction and auditory neurotransmission. Eur J Neurosci 2013; 37:1478-86. [DOI: 10.1111/ejn.12158] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/09/2013] [Accepted: 01/16/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Ann Chi Yan Wong
- Translational Neuroscience Facility and Department of Physiology; School of Medical Sciences; University of New South Wales; Sydney; 2052; NSW; Australia
| | - Lutz Birnbaumer
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, NIH, Building 101, Room F180, 111 TW Alexander Dr; Research Triangle Park; NC 27709; USA
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology; School of Medical Sciences; University of New South Wales; Sydney; 2052; NSW; Australia
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Huang LC, Barclay M, Lee K, Peter S, Housley GD, Thorne PR, Montgomery JM. Synaptic profiles during neurite extension, refinement and retraction in the developing cochlea. Neural Dev 2012; 7:38. [PMID: 23217150 PMCID: PMC3545844 DOI: 10.1186/1749-8104-7-38] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 11/26/2012] [Indexed: 12/23/2022] Open
Abstract
Background During development, excess synapses form between the central and peripheral nervous systems that are then eliminated to achieve correct connectivity. In the peripheral auditory system, the developing type I spiral ganglion afferent fibres undergo a dramatic re-organisation, initially forming connections with both sensory inner hair cells (IHCs) and outer hair cells (OHCs). The OHC connections are then selectively eliminated, leaving sparse innervation by type II afferent fibres, whilst the type I afferent synapses with IHCs are consolidated. Results We examined the molecular makeup of the synaptic contacts formed onto the IHCs and OHCs during this period of afferent fibre remodelling. We observed that presynaptic ribbons initially form at all the afferent neurite contacts, i.e. not only at the expected developing IHC-type I fibre synapses but also at OHCs where type I fibres temporarily contact. Moreover, the transient contacts forming onto OHCs possess a broad set of pre- and postsynaptic proteins, suggesting that functional synaptic connections are formed prior to the removal of type I fibre innervation. AMPA-type glutamate receptor subunits were transiently observed at the base of the OHCs, with their downregulation occurring in parallel with the withdrawal of type I fibres, dispersal of presynaptic ribbons, and downregulation of the anchoring proteins Bassoon and Shank. Conversely, at developing type I afferent IHC synapses, the presence of pre- and postsynaptic scaffold proteins was maintained, with differential plasticity in AMPA receptor subunits observed and AMPA receptor subunit composition changing around hearing onset. Conclusions Overall our data show a differential balance in the patterns of synaptic proteins at developing afferent IHC versus OHC synapses that likely reflect their stable versus transient fates.
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Affiliation(s)
- Lin-Chien Huang
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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Cederholm JME, Froud KE, Wong ACY, Ko M, Ryan AF, Housley GD. Differential actions of isoflurane and ketamine-based anaesthetics on cochlear function in the mouse. Hear Res 2012; 292:71-9. [PMID: 22960466 DOI: 10.1016/j.heares.2012.08.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 08/13/2012] [Accepted: 08/21/2012] [Indexed: 10/28/2022]
Abstract
Isoflurane is a volatile inhaled anaesthetic widely used in animal research, with particular utility for hearing research. Isoflurane has been shown to blunt hearing sensitivity compared with the awake state, but little is known about how isoflurane compares with other anaesthetics with regard to hair cell transduction and auditory neurotransmission. The current study was undertaken in C57Bl/6J and C129/SvEv strains of mice to determine whether isoflurane anaesthesia affects hearing function relative to ketamine-based anaesthesia. Cochlear function and central auditory transmission were assessed using auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE), comparing thresholds and input/output functions over time, for isoflurane vs. ketamine/xylazine/acepromazine anaesthesia. ABR thresholds at the most sensitive region of hearing (16 kHz) were initially higher under isoflurane anaesthesia. This reduced hearing sensitivity worsened over the 1 h study period, and also became evident with broadband click stimulus. Ketamine anaesthesia provided stable ABR thresholds. Although the growth functions were unchanged over time for both anaesthetics, the slopes under isoflurane anaesthesia were significantly less. Cubic (2f(1)-f(2)) DPOAE thresholds and growth functions were initially similar for both anaesthetics. After 60 min, DPOAE thresholds increased for both groups, but this effect was significantly greater with ketamine anaesthesia. The isoflurane-mediated increase in ABR thresholds over time is attributable to action on cochlear nerve activation, evident as a right-shift in the P1-N1 input/output function compared to K/X/A. The ketamine-based anaesthetic produced stable ABR thresholds and gain over time, despite a right-shift in the outer hair cell - mediated DPOAE input/output function.
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Affiliation(s)
- Jennie M E Cederholm
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, UNSW Kensington Campus, Sydney, NSW Australia
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Senadheera S, Kim Y, Grayson TH, Toemoe S, Kochukov MY, Abramowitz J, Housley GD, Bertrand RL, Chadha PS, Bertrand PP, Murphy TV, Tare M, Birnbaumer L, Marrelli SP, Sandow SL. Transient receptor potential canonical type 3 channels facilitate endothelium-derived hyperpolarization-mediated resistance artery vasodilator activity. Cardiovasc Res 2012; 95:439-47. [PMID: 22721989 DOI: 10.1093/cvr/cvs208] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS Microdomain signalling mechanisms underlie key aspects of artery function and the modulation of intracellular calcium, with transient receptor potential (TRP) channels playing an integral role. This study determines the distribution and role of TRP canonical type 3 (C3) channels in the control of endothelium-derived hyperpolarization (EDH)-mediated vasodilator tone in rat mesenteric artery. METHODS AND RESULTS TRPC3 antibody specificity was verified using rat tissue, human embryonic kidney (HEK)-293 cells stably transfected with mouse TRPC3 cDNA, and TRPC3 knock-out (KO) mouse tissue using western blotting and confocal and ultrastructural immunohistochemistry. TRPC3-Pyr3 (ethyl-1-(4-(2,3,3-trichloroacrylamide)phenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate) specificity was verified using patch clamp of mouse mesenteric artery endothelial and TRPC3-transfected HEK cells, and TRPC3 KO and wild-type mouse aortic endothelial cell calcium imaging and mesenteric artery pressure myography. TRPC3 distribution, expression, and role in EDH-mediated function were examined in rat mesenteric artery using immunohistochemistry and western blotting, and pressure myography and endothelial cell membrane potential recordings. In rat mesenteric artery, TRPC3 was diffusely distributed in the endothelium, with approximately five-fold higher expression at potential myoendothelial microdomain contact sites, and immunoelectron microscopy confirmed TRPC3 at these sites. Western blotting and endothelial damage confirmed primary endothelial TRPC3 expression. In rat mesenteric artery endothelial cells, Pyr3 inhibited hyperpolarization generation, and with individual SK(Ca) (apamin) or IK(Ca) (TRAM-34) block, Pyr3 abolished the residual respective IK(Ca)- and SK(Ca)-dependent EDH-mediated vasodilation. CONCLUSION The spatial localization of TRPC3 and associated channels, receptors, and calcium stores are integral for myoendothelial microdomain function. TRPC3 facilitates endothelial SK(Ca) and IK(Ca) activation, as key components of EDH-mediated vasodilator activity and for regulating mesenteric artery tone.
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Affiliation(s)
- Sevvandi Senadheera
- Department of Physiology, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney 2052, Australia.
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Barclay M, Ryan AF, Housley GD. Type I vs type II spiral ganglion neurons exhibit differential survival and neuritogenesis during cochlear development. Neural Dev 2011; 6:33. [PMID: 21989106 PMCID: PMC3207869 DOI: 10.1186/1749-8104-6-33] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 10/11/2011] [Indexed: 11/10/2022] Open
Abstract
Background The mechanisms that consolidate neural circuitry are a major focus of neuroscience. In the mammalian cochlea, the refinement of spiral ganglion neuron (SGN) innervation to the inner hair cells (by type I SGNs) and the outer hair cells (by type II SGNs) is accompanied by a 25% loss of SGNs. Results We investigated the segregation of neuronal loss in the mouse cochlea using β-tubulin and peripherin antisera to immunolabel all SGNs and selectively type II SGNs, respectively, and discovered that it is the type II SGN population that is predominately lost within the first postnatal week. Developmental neuronal loss has been attributed to the decline in neurotrophin expression by the target hair cells during this period, so we next examined survival of SGN sub-populations using tissue culture of the mid apex-mid turn region of neonatal mouse cochleae. In organotypic culture for 48 hours from postnatal day 1, endogenous trophic support from the organ of Corti proved sufficient to maintain all type II SGNs; however, a large proportion of type I SGNs were lost. Culture of the spiral ganglion as an explant, with removal of the organ of Corti, led to loss of the majority of both SGN sub-types. Brain-derived neurotrophic factor (BDNF) added as a supplement to the media rescued a significant proportion of the SGNs, particularly the type II SGNs, which also showed increased neuritogenesis. The known decline in BDNF production by the rodent sensory epithelium after birth is therefore a likely mediator of type II neuron apoptosis. Conclusion Our study thus indicates that BDNF supply from the organ of Corti supports consolidation of type II innervation in the neonatal mouse cochlea. In contrast, type I SGNs likely rely on additional sources for trophic support.
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Affiliation(s)
- Meagan Barclay
- Department of Physiology, The University of Auckland, Private Bag 92019, Auckland, New Zealand
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Vlajkovic SM, Guo CX, Telang R, Wong ACY, Paramananthasivam V, Boison D, Housley GD, Thorne PR. Adenosine kinase inhibition in the cochlea delays the onset of age-related hearing loss. Exp Gerontol 2011; 46:905-14. [PMID: 21846498 DOI: 10.1016/j.exger.2011.08.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 07/07/2011] [Accepted: 08/01/2011] [Indexed: 12/12/2022]
Abstract
This study was undertaken to determine the role of adenosine signalling in the development of age-related hearing loss (ARHL). We and others have shown previously that adenosine signalling via A(1) receptors is involved in cochlear protection from noise-induced cochlear injury. Here we demonstrate that enhanced adenosine signalling in the cochlea provides partial protection from ARHL in C57BL/6J mice. We targeted adenosine kinase (ADK), the key enzyme in adenosine metabolism, using a treatment regime with the selective ADK inhibitor ABT-702 (1.5mg/kg intraperitoneally twice a week) commencing at the age of three months or six months. This treatment, intended to increase free adenosine levels in the cochlea, was maintained until the age of nine months and hearing thresholds were evaluated monthly using auditory brainstem responses (ABR). At nine months, when C57BL/6J mice normally exhibit significant ARHL, both groups treated with ABT-702 showed lower ABR threshold shifts at 10 and 16kHz compared to control animals receiving the vehicle solution. The better thresholds of the ABT-702-treated mice at these frequencies were supported by increased survival of hair cells in the apical region of the cochlea. This study provides the first evidence that ARHL can be mitigated by enhancing adenosine signalling in the cochlea.
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Affiliation(s)
- Srdjan M Vlajkovic
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, New Zealand.
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Vlajkovic SM, Guo CX, Dharmawardana N, Wong ACY, Boison D, Housley GD, Thorne PR. Role of adenosine kinase in cochlear development and response to noise. J Neurosci Res 2011; 88:2598-609. [PMID: 20648650 DOI: 10.1002/jnr.22421] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Adenosine signalling has an important role in cochlear protection from oxidative stress. In most tissues, intracellular adenosine kinase (ADK) is the primary route of adenosine metabolism and the key regulator of intracellular and extracellular adenosine levels. The present study provides the first evidence for ADK distribution in the adult and developing rat cochlea. In the adult cochlea, ADK was localized to the nuclear or perinuclear region of spiral ganglion neurons, lateral wall tissues, and epithelial cells lining scala media. In the developing cochlea, ADK was strongly expressed in multiple cell types at birth and reached its peak level of expression at postnatal day 21 (P21). Ontogenetic changes in ADK expression were evident in the spiral ganglion, organ of Corti, and stria vascularis. In the spiral ganglion, ADK showed a shift from predominantly satellite cell immunolabelling at P1 to neuronal expression from P14 onward. In contrast to the role of ADK in various aspects of cochlear development, the ADK contribution to the cochlear response to noise stress was less obvious. Transcript and protein levels of ADK were unaltered in the cochlea exposed to broadband noise (90-110 dBSPL, 24 hr), and the selective inhibition of ADK in the cochlea with ABT-702 failed to restore hearing thresholds after exposure to traumatic noise. This study indicates that ADK is involved in purine salvage pathways for nucleotide synthesis in the adult cochlea, but its role in the regulation of adenosine signalling under physiological and pathological conditions has yet to be established.
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Affiliation(s)
- Srdjan M Vlajkovic
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Aukland, New Zealand.
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Abstract
Adenosine is a signalling molecule that modulates cellular activity in the central nervous system and peripheral organs via four G protein-coupled receptors designated A1, A2A, A2B, and A3. This review surveys the literature on the role of adenosine in auditory function, particularly cochlear function and its protection from oxidative stress. The specific tissue distribution of adenosine receptors in the mammalian cochlea implicates adenosine signalling in sensory transduction and auditory neurotransmission although functional studies have demonstrated that adenosine stimulates cochlear blood flow, but does not alter the resting and sound-evoked auditory potentials. An interest in a potential otoprotective role for adenosine has recently evolved, fuelled by the capacity of A1 adenosine receptors to prevent cochlear injury caused by acoustic trauma and ototoxic drugs. The balance between A1 and A2A receptors is conceived as critical for cochlear response to oxidative stress, which is an underlying mechanism of the most common inner ear pathologies (e.g. noise-induced and age-related hearing loss, drug ototoxicity). Enzymes involved in adenosine metabolism, adenosine kinase and adenosine deaminase, are also emerging as attractive targets for controlling oxidative stress in the cochlea. Other possible targets include ectonucleotidases that generate adenosine from extracellular ATP, and nucleoside transporters, which regulate adenosine concentrations on both sides of the plasma membrane. Developments of selective adenosine receptor agonists and antagonists that can cross the blood-cochlea barrier are bolstering efforts to develop therapeutic interventions aimed at ameliorating cochlear injury. Manipulations of the adenosine signalling system thus hold significant promise in the therapeutic management of oxidative stress in the cochlea.
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Affiliation(s)
- Srdjan M Vlajkovic
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, New Zealand.
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Phan PAB, Tadros SF, Kim Y, Birnbaumer L, Housley GD. Developmental regulation of TRPC3 ion channel expression in the mouse cochlea. Histochem Cell Biol 2010; 133:437-48. [PMID: 20229053 DOI: 10.1007/s00418-010-0686-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/28/2010] [Indexed: 02/07/2023]
Abstract
Canonical transient receptor potential type 3 (TRPC3) ion channels assemble from TRPC3 subunits and exhibit multiple activation mechanisms. TRPC3 has been proposed to contribute to Ca(2+) entry supporting Ca(2+) homeostasis in cochlear hair cells and to be activated by G protein-coupled receptor (GPCR) signaling in spiral ganglion neurons. The present study was designed to determine the spatiotemporal profile of TRPC3 expression during mouse cochlear ontogeny. TRPC3 immunofluorescence of cryosectioned cochleae was performed using E16-adult tissue. We found that prior to birth, TRPC3 expression was strongest in epithelial cells that form the cochlear partition. In the early postnatal period, to the onset of hearing (~P12), immunofluorescence was strongest in the hair cells, with increased expression in stria vascularis and Reissner's membrane. Afferent neurite labeling in inner spiral plexus and outer spiral bundles developed transiently in the perinatal period, corresponding to the critical period of synaptic consolidation, while signal in the spiral ganglion soma increased from the perinatal period through to adulthood. Compared with the late embryonic/early postnatal levels, hair cell expression was relatively weaker from the third postnatal week, whereas spiral ganglion soma labeling was stronger. In the adult, TRPC3 expression was primarily in the soma of spiral ganglion neurons, the hair cells, and the inner and outer sulcus regions. This spatiotemporal profile of TRPC3 expression was consistent with this ion channel contributing to development of sensory, neural and epithelial cochlear tissues, as well as hair cell Ca(2+) homeostasis and regulation of auditory neurotransmission via GPCR signaling.
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Affiliation(s)
- Patrick A B Phan
- Translational Neuroscience Facility, Department of Physiology, School of Medical Sciences, University of New South Wales, Wallace Wurth Building, UNSW Kensington Campus, Sydney, NSW, 2052, Australia
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O'Keeffe MG, Thorne PR, Housley GD, Robson SC, Vlajkovic SM. Developmentally regulated expression of ectonucleotidases NTPDase5 and NTPDase6 and UDP-responsive P2Y receptors in the rat cochlea. Histochem Cell Biol 2010; 133:425-36. [PMID: 20217113 DOI: 10.1007/s00418-010-0682-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/15/2010] [Indexed: 12/31/2022]
Abstract
Ectonucleoside triphosphate diphosphohydrolases (E-NTPDases) regulate complex extracellular P2 receptor signalling pathways in mammalian tissues by hydrolysing extracellular nucleotides to the respective nucleosides. All enzymes from this family (NTPDase1-8) are expressed in the adult rat cochlea. This study reports the changes in expression of NTPDase5 and NTPDase6 in the developing rat cochlea. These two intracellular members of the E-NTPDase family can be released in a soluble form and show preference for nucleoside 5'-diphosphates, such as UDP and GDP. Here, we demonstrate differential spatial and temporal patterns for NTPDase5 and NTPDase6 expression during cochlear development, which are indicative of both cytosolic and extracellular action via pyrimidines. NTPDase5 is noted during the early postnatal period in developing sensory hair cells and supporting Deiters' cells of the organ of Corti, and primary auditory neurons located in the spiral ganglion. In contrast, NTPDase6 is confined to the embryonic and early postnatal hair cell bundles. NTPDase6 immunolocalisation in the developing cochlea underpins its putative role in hair cell bundle development, probably via cytosolic action, whilst NTPDase5 may have a broader extracellular role in the development of sensory and neural tissues in the rat cochlea. Both NTPDase5 and NTPDase6 colocalize with UDP-preferring P2Y(4), P2Y(6) and P2Y(14) receptors during cochlear development, but this strong association was lost in the adult cochlea. Spatiotemporal topographic expression of NTPDase5 and NTPDase6 and P2Y receptors in adult and developing cochlear tissues provide strong support for the role of pyrimidinergic signalling in cochlear development.
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Affiliation(s)
- Mary G O'Keeffe
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand
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Barclay M, Julien JP, Ryan AF, Housley GD. Type III intermediate filament peripherin inhibits neuritogenesis in type II spiral ganglion neurons in vitro. Neurosci Lett 2010; 478:51-5. [PMID: 20132868 DOI: 10.1016/j.neulet.2010.01.063] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 01/23/2010] [Accepted: 01/27/2010] [Indexed: 02/04/2023]
Abstract
Peripherin, a type III intermediate filament protein, forms part of the cytoskeleton in a subset of neurons, most of which have peripheral fibre projections. Studies suggest a role for peripherin in axon outgrowth and regeneration, but evidence for this in sensory and brain tissues is limited. The exclusive expression of peripherin in a sub-population of primary auditory neurons, the type II spiral ganglion neurons (SGN) prompted our investigation of the effect of peripherin gene deletion (pphKO) on these neurons. We used confocal immunofluorescence to examine the establishment of the innervation of the cochlear outer hair cells by the type II SGN neurites in vivo and in vitro, in wildtype (WT) and pphKO mice, in the first postnatal week. The distribution of the type II SGN nerve fibres was normal in pphKO cochleae. However, using P1 spiral ganglion explants under culture conditions where the majority of neurites were derived from type II SGN, pphKO resulted in increased numbers of neurites/explant compared to WT controls. Type II SGN neurites from pphKO explants extended approximately double the distance of WT neurites, and had reduced complexity based on greater distance between turning points. Addition of brain-derived neurotrophic factor (BDNF) to the culture media increased neurite number in WT and KO explants approximately 30-fold, but did not affect neurite length or distance between turning. These results indicate that peripherin may interact with other cytoskeletal elements to regulate outgrowth of the peripheral neurites of type II SGN, distinguishing these neurons from the type I SGN innervating the inner hair cells.
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Affiliation(s)
- Meagan Barclay
- Department of Physiology, The University of Auckland, Private Bag 92019, Auckland, New Zealand
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Wong ACY, Guo CX, Gupta R, Housley GD, Thorne PR, Vlajkovic SM. Post exposure administration of A(1) adenosine receptor agonists attenuates noise-induced hearing loss. Hear Res 2009; 260:81-8. [PMID: 19995597 DOI: 10.1016/j.heares.2009.12.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2009] [Revised: 11/04/2009] [Accepted: 12/01/2009] [Indexed: 02/09/2023]
Abstract
Adenosine is a constitutive cell metabolite with a putative role in protection and regeneration in many tissues. This study was undertaken to determine if adenosine signalling pathways are involved in protection against noise injury. A(1) adenosine receptor expression levels were altered in the cochlea exposed to loud sound, suggesting their involvement in the development of noise injury. Adenosine and selective adenosine receptor agonists (CCPA, CGS-21680 and Cl-IB-MECA) were applied to the round window membrane of the cochlea 6h after noise exposure. Auditory brainstem responses measured 48h after drug administration demonstrated partial recovery of hearing thresholds (up to 20dB) in the cochleae treated with adenosine (non-selective adenosine receptor agonist) or CCPA (selective A(1) adenosine receptor agonist). In contrast, the selective A(2A) adenosine receptor agonist CGS-21680 and A(3) adenosine receptor agonist Cl-IB-MECA did not protect the cochlea from hearing loss. Sound-evoked cochlear potentials in control rats exposed to ambient noise were minimally altered by local administration of the adenosine receptor agonists used in the noise study. Free radical generation in the cochlea exposed to noise was reduced by administration of adenosine and CCPA. This study pinpoints A(1) adenosine receptors as attractive targets for pharmacological interventions to reduce noise-induced cochlear injury after exposure.
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Affiliation(s)
- Ann Chi Yan Wong
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, New Zealand.
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