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Butowt R, Bilinska K, von Bartheld CS. Olfactory dysfunction in COVID-19: new insights into the underlying mechanisms. Trends Neurosci 2023; 46:75-90. [PMID: 36470705 PMCID: PMC9666374 DOI: 10.1016/j.tins.2022.11.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [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: 08/25/2022] [Revised: 11/06/2022] [Accepted: 11/14/2022] [Indexed: 11/17/2022]
Abstract
The mechanisms of olfactory dysfunction in COVID-19 are still unclear. In this review, we examine potential mechanisms that may explain why the sense of smell is lost or altered. Among the current hypotheses, the most plausible is that death of infected support cells in the olfactory epithelium causes, besides altered composition of the mucus, retraction of the cilia on olfactory receptor neurons, possibly because of the lack of support cell-derived glucose in the mucus, which powers olfactory signal transduction within the cilia. This mechanism is consistent with the rapid loss of smell with COVID-19, and its rapid recovery after the regeneration of support cells. Host immune responses that cause downregulation of genes involved in olfactory signal transduction occur too late to trigger anosmia, but may contribute to the duration of the olfactory dysfunction.
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Affiliation(s)
- Rafal Butowt
- Global Consortium of Chemosensory Research - Poland, Przybory Str 3/2, 85-791 Bydgoszcz, Poland
| | - Katarzyna Bilinska
- Department of Molecular Cell Genetics, L. Rydygier Collegium Medicum, Nicolaus Copernicus University, uI. Curie Sklodowskiej 9, 85-94, Bydgoszcz, Poland.
| | - Christopher S. von Bartheld
- Center of Biomedical Research Excellence in Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV 89557-0352, USA,Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV 89557-0352, USA,Correspondence:
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Bilinska K, von Bartheld CS, Butowt R. Expression of the ACE2 Virus Entry Protein in the Nervus Terminalis Reveals the Potential for an Alternative Route to Brain Infection in COVID-19. Front Cell Neurosci 2021; 15:674123. [PMID: 34290590 PMCID: PMC8287262 DOI: 10.3389/fncel.2021.674123] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 06/09/2021] [Indexed: 12/11/2022] Open
Abstract
Previous studies suggested that the SARS-CoV-2 virus may gain access to the brain by using a route along the olfactory nerve. However, there is a general consensus that the obligatory virus entry receptor, angiotensin converting enzyme 2 (ACE2), is not expressed in olfactory receptor neurons, and the timing of arrival of the virus in brain targets is inconsistent with a neuronal transfer along olfactory projections. We determined whether nervus terminalis neurons and their peripheral and central projections should be considered as a potential alternative route from the nose to the brain. Nervus terminalis neurons in postnatal mice were double-labeled with antibodies against ACE2 and two nervus terminalis markers, gonadotropin-releasing hormone (GnRH) and choline acetyltransferase (CHAT). We show that a small fraction of CHAT-labeled nervus terminalis neurons, and the large majority of GnRH-labeled nervus terminalis neurons with cell bodies in the region between the olfactory epithelium and the olfactory bulb express ACE2 and cathepsins B and L. Nervus terminalis neurons therefore may provide a direct route for the virus from the nasal epithelium, possibly via innervation of Bowman's glands, to brain targets, including the telencephalon and diencephalon. This possibility needs to be examined in suitable animal models and in human tissues.
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Affiliation(s)
- Katarzyna Bilinska
- L. Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
| | - Christopher S. von Bartheld
- Department of Physiology and Cell Biology, Reno School of Medicine, University of Nevada, Reno, NV, United States
| | - Rafal Butowt
- L. Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
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Bilinska K, von Bartheld CS, Butowt R. Expression of the ACE2 virus entry protein in the nervus terminalis reveals the potential for an alternative route to brain infection in COVID-19. bioRxiv 2021:2021.04.11.439398. [PMID: 33880469 PMCID: PMC8057234 DOI: 10.1101/2021.04.11.439398] [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] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Previous studies suggested that the SARS-CoV-2 virus may gain access to the brain by using a route along the olfactory nerve. However, there is a general consensus that the obligatory virus entry receptor, angiotensin converting enzyme 2 (ACE2), is not expressed in olfactory receptor neurons, and the timing of arrival of the virus in brain targets is inconsistent with a neuronal transfer along olfactory projections. We determined whether nervus terminalis neurons and their peripheral and central projections should be considered as a potential alternative route from the nose to the brain. Nervus terminalis neurons in postnatal mice were double-labeled with antibodies against ACE2 and two nervus terminalis markers, gonadotropin-releasing hormone (GnRH) and choline acetyltransferase (CHAT). We show that a small fraction of CHAT-labeled nervus terminalis neurons, and the large majority of GnRH-labeled nervus terminalis neurons with cell bodies in the region between the olfactory epithelium and the olfactory bulb express ACE2 and cathepsins B and L. Nervus terminalis neurons therefore may provide a direct route for the virus from the nasal epithelium, possibly via innervation of Bowman's glands, to brain targets, including the telencephalon and diencephalon. This possibility needs to be examined in suitable animal models and in human tissues.
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Affiliation(s)
- Katarzyna Bilinska
- L. Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
| | - Christopher S. von Bartheld
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, United States
| | - Rafal Butowt
- L. Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
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Butowt R, Bilinska K, Von Bartheld CS. Chemosensory Dysfunction in COVID-19: Integration of Genetic and Epidemiological Data Points to D614G Spike Protein Variant as a Contributing Factor. ACS Chem Neurosci 2020; 11:3180-3184. [PMID: 32997488 PMCID: PMC7581292 DOI: 10.1021/acschemneuro.0c00596] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 09/16/2020] [Indexed: 12/25/2022] Open
Abstract
After several months of rapid pandemic expansion, it is now apparent that the SARS-CoV-2 coronavirus interferes with smell and taste sensation in a substantial proportion of COVID-19 patients. Recent epidemiological data documented intriguing differences in prevalence of chemosensory dysfunctions between different world regions. Viral genetic factors as well as host genetic factors appear to be relevant; however, it is not yet known which mutations or polymorphisms actually contribute to such phenotypic differences between populations. Here, we discuss recent genetic and epidemiological data on the D614G spike protein variant and assess whether current evidence is consistent with the notion that this single nucleotide polymorphism augments chemosensory impairments in COVID-19 patients. We hypothesize that this spike variant is an important viral genetic factor that facilitates infection of chemosensory epithelia, possibly acting together with yet to be identified host factors, and thereby increases smell and taste impairment. We suggest that the prevalence of chemosensory deficits may reflect the pandemic potential for transmissibility and spread which differs between populations.
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Affiliation(s)
- Rafal Butowt
- Department
of Molecular Cell Genetics and Department of Anatomy, L. Rydygier
Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz 85-094, Poland
| | - Katarzyna Bilinska
- Department
of Molecular Cell Genetics and Department of Anatomy, L. Rydygier
Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz 85-094, Poland
| | - Christopher S. Von Bartheld
- Department
of Physiology and Cell Biology, University
of Nevada, Reno School of Medicine, Reno, Nevada 89557, United States
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Abstract
It has become clear since the pandemic broke out that SARS-CoV-2 virus causes reduction of smell and taste in a significant fraction of COVID-19 patients. The olfactory dysfunction often occurs early in the course of the disease, and sometimes it is the only symptom in otherwise asymptomatic carriers. The cellular mechanisms for these specific olfactory disturbances in COVID-19 are now beginning to be elucidated. Several very recent papers contributed to explaining the key cellular steps occurring in the olfactory epithelium leading to anosmia/hyposmia (collectively known as dysosmia) initiated by SARS-CoV-2 infection. In this Viewpoint, we discuss current progress in research on olfactory dysfunction in COVID-19 and we also propose an updated model of the SARS-CoV-2-induced dysosmia. The emerging central role of sustentacular cells and inflammatory processes in the olfactory epithelium are particularly considered. The proposed model of anosmia in COVID-19 does not answer unequivocally whether the new coronavirus exploits the olfactory route to rapidly or slowly reach the brain in COVID-19 patients. To answer this question, new systematic studies using an infectious virus and appropriate animal models are needed.
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Affiliation(s)
- Katarzyna Bilinska
- Department of Molecular Cell
Genetics, L. Rydygier Collegium Medicum, Nicolaus Copernicus University, uI. Curie Sklodowskiej 9, 85-094 Bydgoszcz, Poland
- Department of Anatomy,
L.
Rydygier Collegium Medicum, Nicolaus Copernicus
University, ul. Lukasiewicza 1, 85-821 Bydgoszcz, Poland
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Bilinska K, Jakubowska P, von Bartheld CS, Butowt R. Expression of the SARS-CoV-2 Entry Proteins, ACE2 and TMPRSS2, in Cells of the Olfactory Epithelium: Identification of Cell Types and Trends with Age. ACS Chem Neurosci 2020; 11:1555-1562. [PMID: 32379417 PMCID: PMC7241737 DOI: 10.1021/acschemneuro.0c00210] [Citation(s) in RCA: 279] [Impact Index Per Article: 69.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Accepted: 05/07/2020] [Indexed: 12/24/2022] Open
Abstract
The COVID-19 pandemic revealed that there is a loss of smell in many patients, including in infected but otherwise asymptomatic individuals. The underlying mechanisms for the olfactory symptoms are unclear. Using a mouse model, we determined whether cells in the olfactory epithelium express the obligatory receptors for entry of the SARS-CoV-2 virus by using RNAseq, RT-PCR, in situ hybridization, Western blot, and immunocytochemistry. We show that the cell surface protein ACE2 and the protease TMPRSS2 are expressed in sustentacular cells of the olfactory epithelium but not, or much less, in most olfactory receptor neurons. These data suggest that sustentacular cells are involved in SARS-CoV-2 virus entry and impairment of the sense of smell in COVID-19 patients. We also show that expression of the entry proteins increases in animals of old age. This may explain, if true also in humans, why individuals of older age are more susceptible to the SARS-CoV-2 infection.
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Affiliation(s)
- Katarzyna Bilinska
- Department of Molecular Cell Genetics, L. Rydygier Collegium Medicum, Nicolaus Copernicus University, uI. Curie Sklodowskiej 9, 85-94, Bydgoszcz, Poland
| | - Patrycja Jakubowska
- Department of Molecular Cell Genetics, L. Rydygier Collegium Medicum, Nicolaus Copernicus University, uI. Curie Sklodowskiej 9, 85-94, Bydgoszcz, Poland
| | - Christopher S. von Bartheld
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV 89557, USA
| | - Rafal Butowt
- Department of Molecular Cell Genetics, L. Rydygier Collegium Medicum, Nicolaus Copernicus University, uI. Curie Sklodowskiej 9, 85-94, Bydgoszcz, Poland
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Butowt R, Bilinska K. SARS-CoV-2: Olfaction, Brain Infection, and the Urgent Need for Clinical Samples Allowing Earlier Virus Detection. ACS Chem Neurosci 2020; 11:1200-1203. [PMID: 32283006 PMCID: PMC7160911 DOI: 10.1021/acschemneuro.0c00172] [Citation(s) in RCA: 244] [Impact Index Per Article: 61.0] [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: 03/31/2020] [Accepted: 04/03/2020] [Indexed: 12/11/2022] Open
Abstract
The novel SARS-CoV-2 virus has very high infectivity, which allows it to spread rapidly around the world. Attempts at slowing the pandemic at this stage depend on the number and quality of diagnostic tests performed. We propose that the olfactory epithelium from the nasal cavity may be a more appropriate tissue for detection of SARS-CoV-2 virus at the earliest stages, prior to onset of symptoms or even in asymptomatic people, as compared to commonly used sputum or nasopharyngeal swabs. Here we emphasize that the nasal cavity olfactory epithelium is the likely site of enhanced binding of SARS-CoV-2. Multiple non-neuronal cell types present in the olfactory epithelium express two host receptors, ACE2 and TMPRSS2 proteases, that facilitate SARS-CoV-2 binding, replication, and accumulation. This may be the underlying mechanism for the recently reported cases of smell dysfunction in patients with COVID-19. Moreover, the possibility of subsequent brain infection should be considered which begins in olfactory neurons. In addition, we discuss the possibility that olfactory receptor neurons may initiate rapid immune responses at early stages of the disease. We emphasize the need to undertake research focused on additional aspects of SARS-CoV-2 actions in the nervous system, especially in the olfactory pathway.
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Affiliation(s)
- Rafal Butowt
- L. Rydygier Collegium Medicum,
Nicolaus Copernicus University, Ul.
CurieSklodowskiej 9, 85-94 Bydgoszcz, Poland
| | - Katarzyna Bilinska
- L. Rydygier Collegium Medicum,
Nicolaus Copernicus University, Ul.
CurieSklodowskiej 9, 85-94 Bydgoszcz, Poland
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Jazurek M, Ciesiolka A, Starega-Roslan J, Bilinska K, Krzyzosiak WJ. Identifying proteins that bind to specific RNAs - focus on simple repeat expansion diseases. Nucleic Acids Res 2016; 44:9050-9070. [PMID: 27625393 PMCID: PMC5100574 DOI: 10.1093/nar/gkw803] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 09/01/2016] [Indexed: 12/11/2022] Open
Abstract
RNA–protein complexes play a central role in the regulation of fundamental cellular processes, such as mRNA splicing, localization, translation and degradation. The misregulation of these interactions can cause a variety of human diseases, including cancer and neurodegenerative disorders. Recently, many strategies have been developed to comprehensively analyze these complex and highly dynamic RNA–protein networks. Extensive efforts have been made to purify in vivo-assembled RNA–protein complexes. In this review, we focused on commonly used RNA-centric approaches that involve mass spectrometry, which are powerful tools for identifying proteins bound to a given RNA. We present various RNA capture strategies that primarily depend on whether the RNA of interest is modified. Moreover, we briefly discuss the advantages and limitations of in vitro and in vivo approaches. Furthermore, we describe recent advances in quantitative proteomics as well as the methods that are most commonly used to validate robust mass spectrometry data. Finally, we present approaches that have successfully identified expanded repeat-binding proteins, which present abnormal RNA–protein interactions that result in the development of many neurological diseases.
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Affiliation(s)
- Magdalena Jazurek
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Adam Ciesiolka
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Julia Starega-Roslan
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Katarzyna Bilinska
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Wlodzimierz J Krzyzosiak
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
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Palczak R, Obara L, Bilinska K. [Clinical aspects of granulosa cell tumor]. Ginekol Pol 1981; 52:349-55. [PMID: 7262598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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