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Lazzeri G, Biagioni F, Ferrucci M, Puglisi-Allegra S, Lenzi P, Busceti CL, Giannessi F, Fornai F. The Relevance of Autophagy within Inner Ear in Baseline Conditions and Tinnitus-Related Syndromes. Int J Mol Sci 2023; 24:16664. [PMID: 38068993 PMCID: PMC10706730 DOI: 10.3390/ijms242316664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/07/2023] [Accepted: 11/21/2023] [Indexed: 12/18/2023] Open
Abstract
Tinnitus is the perception of noise in the absence of acoustic stimulation (phantom noise). In most patients suffering from chronic peripheral tinnitus, an alteration of outer hair cells (OHC) starting from the stereocilia (SC) occurs. This is common following ototoxic drugs, sound-induced ototoxicity, and acoustic degeneration. In all these conditions, altered coupling between the tectorial membrane (TM) and OHC SC is described. The present review analyzes the complex interactions involving OHC and TM. These need to be clarified to understand which mechanisms may underlie the onset of tinnitus and why the neuropathology of chronic degenerative tinnitus is similar, independent of early triggers. In fact, the fine neuropathology of tinnitus features altered mechanisms of mechanic-electrical transduction (MET) at the level of OHC SC. The appropriate coupling between OHC SC and TM strongly depends on autophagy. The involvement of autophagy may encompass degenerative and genetic tinnitus, as well as ototoxic drugs and acoustic trauma. Defective autophagy explains mitochondrial alterations and altered protein handling within OHC and TM. This is relevant for developing novel treatments that stimulate autophagy without carrying the burden of severe side effects. Specific phytochemicals, such as curcumin and berberin, acting as autophagy activators, may mitigate the neuropathology of tinnitus.
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Affiliation(s)
- Gloria Lazzeri
- Human Anatomy, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, PI, Italy; (G.L.); (M.F.); (P.L.); (F.G.)
| | - Francesca Biagioni
- IRCCS, Istituto di Ricovero e Cura a Carattere Scientifico, Neuromed, 86077 Pozzilli, IS, Italy; (F.B.); (S.P.-A.); (C.L.B.)
| | - Michela Ferrucci
- Human Anatomy, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, PI, Italy; (G.L.); (M.F.); (P.L.); (F.G.)
| | - Stefano Puglisi-Allegra
- IRCCS, Istituto di Ricovero e Cura a Carattere Scientifico, Neuromed, 86077 Pozzilli, IS, Italy; (F.B.); (S.P.-A.); (C.L.B.)
| | - Paola Lenzi
- Human Anatomy, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, PI, Italy; (G.L.); (M.F.); (P.L.); (F.G.)
| | - Carla Letizia Busceti
- IRCCS, Istituto di Ricovero e Cura a Carattere Scientifico, Neuromed, 86077 Pozzilli, IS, Italy; (F.B.); (S.P.-A.); (C.L.B.)
| | - Francesco Giannessi
- Human Anatomy, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, PI, Italy; (G.L.); (M.F.); (P.L.); (F.G.)
| | - Francesco Fornai
- Human Anatomy, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, PI, Italy; (G.L.); (M.F.); (P.L.); (F.G.)
- IRCCS, Istituto di Ricovero e Cura a Carattere Scientifico, Neuromed, 86077 Pozzilli, IS, Italy; (F.B.); (S.P.-A.); (C.L.B.)
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Dewey JB. Cubic and quadratic distortion products in vibrations of the mouse cochlear apex. JASA EXPRESS LETTERS 2022; 2:114402. [PMID: 36456371 PMCID: PMC9704500 DOI: 10.1121/10.0015244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 11/03/2022] [Indexed: 06/17/2023]
Abstract
When the ear is stimulated by two tones presented at frequencies f1 and f2, nonlinearity in the cochlea's vibratory response leads to the generation of distortion products (DPs), with the cubic 2f1-f2 DP commonly viewed as the most prominent. While the quadratic f2-f1 DP is also evident in numerous physiological and perceptual studies, its presence in the cochlea's mechanical response has been less well documented. Here, examination of vibratory DPs within the mouse cochlea confirmed that f2-f1 was a significant and sometimes dominant component, whether DPs were measured near their generation site, or after having propagated from more basal locations.
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Affiliation(s)
- James B Dewey
- Caruso Department of Otolaryngology-Head & Neck Surgery, University of Southern California, Los Angeles, California 90033, USA
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