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Liu X, Lei Z, Gilhooly D, He J, Li Y, Ritzel RM, Li H, Wu LJ, Liu S, Wu J. Traumatic brain injury-induced inflammatory changes in the olfactory bulb disrupt neuronal networks leading to olfactory dysfunction. Brain Behav Immun 2023; 114:22-45. [PMID: 37557959 PMCID: PMC10910858 DOI: 10.1016/j.bbi.2023.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 06/14/2023] [Accepted: 08/06/2023] [Indexed: 08/11/2023] Open
Abstract
Approximately 20-68% of traumatic brain injury (TBI) patients exhibit trauma-associated olfactory deficits (OD) which can compromise not only the quality of life but also cognitive and neuropsychiatric functions. However, few studies to date have examined the impact of experimental TBI on OD. The present study examined inflammation and neuronal dysfunction in the olfactory bulb (OB) and the underlying mechanisms associated with OD in male mice using a controlled cortical impact (CCI) model. TBI caused a rapid inflammatory response in the OB as early as 24 h post-injury, including elevated mRNA levels of proinflammatory cytokines, increased numbers of microglia and infiltrating myeloid cells, and increased IL1β and IL6 production in these cells. These changes were sustained for up to 90 days after TBI. Moreover, we observed significant upregulation of the voltage-gated proton channel Hv1 and NOX2 expression levels, which were predominantly localized in microglia/macrophages and accompanied by increased reactive oxygen species production. In vivo OB neuronal firing activities showed early neuronal hyperexcitation and later hypo-neuronal activity in both glomerular layer and mitral cell layer after TBI, which were improved in the absence of Hv1. In a battery of olfactory behavioral tests, WT/TBI mice displayed significant OD. In contrast, neither Hv1 KO/TBI nor NOX2 KO/TBI mice showed robust OD. Finally, seven days of intranasal delivery of a NOX2 inhibitor (NOX2ds-tat) ameliorated post-traumatic OD. Collectively, these findings highlight the importance of OB neuronal networks and its role in TBI-mediated OD. Thus, targeting Hv1/NOX2 may be a potential intervention for improving post-traumatic anosmia.
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Affiliation(s)
- Xiang Liu
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Zhuofan Lei
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Dylan Gilhooly
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059 USA
| | - Junyun He
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Yun Li
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Rodney M Ritzel
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Hui Li
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Long-Jun Wu
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA
| | - Shaolin Liu
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059 USA; Center for Neurological Disease Research, Department of Physiology and Pharmacology, Department of Biomedical Sciences, University of Georgia College of Veterinary Medicine, Athens, GA 30602, USA.
| | - Junfang Wu
- Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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De Luca R, Bonanno M, Rifici C, Quartarone A, Calabrò RS. Post-traumatic olfactory dysfunction: a scoping review of assessment and rehabilitation approaches. Front Neurol 2023; 14:1193406. [PMID: 37521284 PMCID: PMC10374209 DOI: 10.3389/fneur.2023.1193406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 06/27/2023] [Indexed: 08/01/2023] Open
Abstract
Post-traumatic Olfactory Dysfunction (PTOD) consists of a complete or partial loss of olfactory function that may occur after a traumatic brain injury (TBI). PTOD may be linked to some neuropsychiatric features, such as social, cognitive and executive dysfunction, as well as behavioral symptoms, especially when TBI involves the orbito-frontal cortex. The diagnosis of PTOD is based on medical history and clinical data and it is supported by psychometric tests (i.e., subjective tools) as well as electrophysiological and neuroimaging measures (i.e., objective methods). The assessment methods allow monitoring the changes in olfactory function over time and help to establish the right therapeutic and rehabilitative approach. In this context, the use of the olfactory training (OT), which is a non-pharmacological and non-invasive treatment option, could promote olfactory function through top-down (central) and bottom-up (peripheral) processes. To better manage patients with TBI, PTOD should be detected early and properly treated using the various therapeutic rehabilitative possibilities, both conventional and advanced, also taking into consideration the emerging neuromodulation approach.
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Konstantinidis I. Managing Post-traumatic Olfactory Disorders. CURRENT OTORHINOLARYNGOLOGY REPORTS 2022. [DOI: 10.1007/s40136-022-00431-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Abstract
Purpose of Review
This study aims to summarize and critically review recent literature on management of post-traumatic olfactory dysfunction (PTOD) with emphasis on the diagnostic procedure and treatment options.
Recent Findings
Magnetic resonance imaging and olfactory testing are the basis of the diagnostic procedure. Time of diagnosis is critical as the most improvement occurs within the first year after trauma. Olfactory training and oral steroids seem to be a relatively evidence-based therapeutic option but with non-optimal results. Surgery has a limited place in the management of PTOD. Promising future options could be the development of olfactory implants and transplantation of olfactory epithelium or stem cells.
Summary
PTOD management is challenging as it has several pathogenetic mechanisms and relatively poor prognosis. Patients with olfactory impairment and head trauma have diminished quality of life, and increased risk for harmful events and development of depression. Thus, clinicians should not only focus to therapeutic options but equally to appropriate counseling to their patients in order to decrease risks of personal injury and improve their daily life.
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