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Austin TT, Thomas CL, Lewis C, Blockley A, Warren B. Metabolic decline in an insect ear: correlative or causative for age-related auditory decline? Front Cell Dev Biol 2023; 11:1138392. [PMID: 37274746 PMCID: PMC10233746 DOI: 10.3389/fcell.2023.1138392] [Citation(s) in RCA: 2] [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] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 04/25/2023] [Indexed: 06/06/2023] Open
Abstract
One leading hypothesis for why we lose our hearing as we age is a decrease in ear metabolism. However, direct measurements of metabolism across a lifespan in any auditory system are lacking. Even if metabolism does decrease with age, a question remains: is a metabolic decrease a cause of age-related auditory decline or simply correlative? We use an insect, the desert locust Schistocerca gregaria, as a physiologically versatile model to understand how cellular metabolism correlates with age and impacts on age-related auditory decline. We found that auditory organ metabolism decreases with age as measured fluorometrically. Next, we measured the individual auditory organ's metabolic rate and its sound-evoked nerve activity and found no correlation. We found no age-related change in auditory nerve activity, using hook electrode recordings, and in the electrophysiological properties of auditory neurons, using patch-clamp electrophysiology, but transduction channel activity decreased. To further test for a causative role of the metabolic rate in auditory decline, we manipulated metabolism of the auditory organ through diet and cold-rearing but found no difference in sound-evoked nerve activity. We found that although metabolism correlates with age-related auditory decline, it is not causative. Finally, we performed RNA-Seq on the auditory organs of young and old locusts, and whilst we found enrichment for Gene Ontology terms associated with metabolism, we also found enrichment for a number of additional aging GO terms. We hypothesize that age-related hearing loss is dominated by accumulative damage in multiple cell types and multiple processes which outweighs its metabolic decline.
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Blockley A, Ogle D, Woodrow C, Montealegre-Z F, Warren B. Physiological changes throughout an insect ear due to age and noise - a longitudinal study. iScience 2022; 25:104746. [PMID: 36034233 PMCID: PMC9400085 DOI: 10.1016/j.isci.2022.104746] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 06/06/2022] [Accepted: 06/07/2022] [Indexed: 11/20/2022] Open
Abstract
Hearing loss is not unique to humans and is experienced by all animals in the face of wild and eclectic differences in ear morphology. Here, we exploited the high throughput and accessible tympanal ear of the desert locust, Schistocerca gregaria to rigorously quantify changes in the auditory system due to noise exposure and age. In this exploratory study, we analyzed tympanal displacements, morphology of the auditory Müller’s organ and measured activity of the auditory nerve, the transduction current, and electrophysiological properties of individual auditory receptors. This work shows that hearing loss manifests as a complex disorder due to differential effects of age and noise on several processes and cell types within the ear. The “middle-aged deafness” pattern of hearing loss found in locusts mirrors that found for humans exposed to noise early in their life suggesting a fundamental interaction of the use of an auditory system (noise) and its aging. Locusts routinely exposed to noise follow same pattern of hearing loss as humans Parts of the auditory system are affected by noise, age, or both noise and age Hearing loss is a multifaceted disorder caused by defects in distinct ear processes
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Smith LJ, Bochkareva A, Rolfe MD, Hunt DM, Kahramanoglou C, Braun Y, Rodgers A, Blockley A, Coade S, Lougheed KEA, Hafneh NA, Glenn SM, Crack JC, Le Brun NE, Saldanha JW, Makarov V, Nobeli I, Arnvig K, Mukamolova GV, Buxton RS, Green J. Cmr is a redox-responsive regulator of DosR that contributes to M. tuberculosis virulence. Nucleic Acids Res 2017; 45:6600-6612. [PMID: 28482027 PMCID: PMC5499769 DOI: 10.1093/nar/gkx406] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [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: 09/12/2016] [Accepted: 04/28/2017] [Indexed: 12/05/2022] Open
Abstract
Mycobacterium tuberculosis (MTb) is the causative agent of pulmonary tuberculosis (TB). MTb colonizes the human lung, often entering a non-replicating state before progressing to life-threatening active infections. Transcriptional reprogramming is essential for TB pathogenesis. In vitro, Cmr (a member of the CRP/FNR super-family of transcription regulators) bound at a single DNA site to act as a dual regulator of cmr transcription and an activator of the divergent rv1676 gene. Transcriptional profiling and DNA-binding assays suggested that Cmr directly represses dosR expression. The DosR regulon is thought to be involved in establishing latent tuberculosis infections in response to hypoxia and nitric oxide. Accordingly, DNA-binding by Cmr was severely impaired by nitrosation. A cmr mutant was better able to survive a nitrosative stress challenge but was attenuated in a mouse aerosol infection model. The complemented mutant exhibited a ∼2-fold increase in cmr expression, which led to increased sensitivity to nitrosative stress. This, and the inability to restore wild-type behaviour in the infection model, suggests that precise regulation of the cmr locus, which is associated with Region of Difference 150 in hypervirulent Beijing strains of Mtb, is important for TB pathogenesis.
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Affiliation(s)
- Laura J Smith
- Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.,School of Pharmacy, De Montfort University, Leicester LE1 9BH, UK
| | | | - Matthew D Rolfe
- Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Debbie M Hunt
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Christina Kahramanoglou
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Yvonne Braun
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Angela Rodgers
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Alix Blockley
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Stephen Coade
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Kathryn E A Lougheed
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Nor Azian Hafneh
- Department of Infection, Immunity and Inflammation, University of Leicester, University Road, Leicester LE1 9HN, UK
| | - Sarah M Glenn
- Department of Infection, Immunity and Inflammation, University of Leicester, University Road, Leicester LE1 9HN, UK
| | - Jason C Crack
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
| | - José W Saldanha
- Division of Mathematical Biology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Vadim Makarov
- A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia
| | - Irene Nobeli
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
| | - Kristine Arnvig
- Institute for Structural and Molecular Biology, University College London, London WC1E 6BT, UK
| | - Galina V Mukamolova
- Department of Infection, Immunity and Inflammation, University of Leicester, University Road, Leicester LE1 9HN, UK
| | - Roger S Buxton
- Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Jeffrey Green
- Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
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Boonham N, Pérez LG, Mendez MS, Peralta EL, Blockley A, Walsh K, Barker I, Mumford RA. Development of a real-time RT-PCR assay for the detection of potato spindle tuber viroid. J Virol Methods 2004; 116:139-46. [PMID: 14738980 DOI: 10.1016/j.jviromet.2003.11.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Potato spindle tuber viroid (PSTVd) is a quarantine pathogen in the European Union and causes damaging diseases of solanaceous crops. Under the EU Plant Health directive 2000/29/EC, countries must have the ability to detect and identify accurately and rapidly the introduction of harmful organisms in plants or plant products; furthermore, if the quarantine pathogen is found, be able to survey extensively for it. In this respect, PSTVd poses an interesting technical problem, since its RNA does not code for any proteins and thus any diagnostic method must be based on the detection of the RNA and be suitable for scaling up to testing large sample numbers. With this in mind a one-tube real-time RT-PCR assay based on TaqMan chemistry was developed. Investigations were carried out into various aspects of the assay relevant to the efficient amplification of targets that have a significant amount of secondary structure such as viroids. Thus comparisons were made of reverse transcription temperature, concentration and type of reverse transcriptase, RNA denaturation, sample purity and single versus two-tube reaction format. The assay developed was shown to be able to detect a wide range of isolates of PSTVd and in comparison with a chemi-luminescent hybridisation system was shown to be 1000-fold more sensitive. A further significant advantage of this assay format compared with hybridisation is that it is suitable for scaling up to large sample numbers using robotic liquid handling systems.
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Affiliation(s)
- N Boonham
- Central Science Laboratory, Sand Hutton, York YO41 1LZ, UK.
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