Exploring why some COVID-19 patients lose their sense of smell

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The new coronavirus still holds many secrets, one of which is how it can cause loss of smell -- even in infected people who have no other COVID-19 symptoms. Image is in the public domain.

Summary: ACE2 and TMPRSS2, two proteins required for SARS-CoV-2 entry, are produced in cells in the nasal cavity that contribute to odor detection. The findings may explain why people with coronavirus often describe the loss of the sense of smell as a symptom of the virus.

Source: ACS

Doctors have reported that partial or total loss of the sense of smell is often an early symptom of infection with SARS-CoV-2, the virus that causes COVID-19. Now, researchers reporting in ACS Chemical Neuroscience have shown that in mice, two proteins required for SARS-CoV-2 entry are produced by cells of the nasal cavity that contribute to odor detection. Moreover, larger amounts of the proteins are made in older animals than in younger ones.

The new coronavirus still holds many secrets, one of which is how it can cause loss of smell — even in infected people who have no other COVID-19 symptoms. SARS-CoV-2 hijacks two proteins to invade human cells: the cell surface receptor ACE2 and the protease TMPRSS2. However, scientists still aren’t sure which cells in the olfactory epithelium (the tissue lining the nasal cavity) express these proteins and could potentially be infected by the virus. Finding out could help explain symptoms and aid in the development of more accurate diagnostic tests. So Rafal Butowt and colleagues studied the proteins’ expression in mice and how their levels change with age.

Using several methods, the researchers found that ACE2 and TMPRSS2 are expressed in sustentacular cells — cells of the nose that help transfer odors from the air to neurons. Older mice made more of the two proteins in nasal cells than younger mice. If also true in humans, this result could explain why older people are more susceptible to SARS-CoV-2, the researchers say. They also note that future studies should examine whether sustentacular cells can pass the virus to neurons, which could provide SARS-CoV-2 a route to infect the brain.

Funding: The authors acknowledge funding from the National Science Centre of Poland and the National Institute of General Medical Sciences of the National Institutes of Health.

About this coronavirus research article

Media Contacts:
Katie Cottingham – ACS
Image Source:
The image is in the public domain.

Original Research: Closed access
“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”. by Katarzyna Bilinska, Patrycja Jakubowska, CHRISTOPHER S. VON BARTHELD, Rafal Butowt.
ACS Chemical Neuroscience doi:10.1021/acschemneuro.0c00210


Thalamic, cortical, and amygdala involvement in the processing of a natural sound cue of danger

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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    The following expert-competent reports in the U.S. and The Netherlands are significant leading to corroboration of implications of this Vedic astrology writer’s a lot prior predictive alerts on record :-
    (1) Report published on 4 May , 2020 in a newspaper has highlighted significant finding of a team of scientists from University Medical Center Groningen in the Netherlands relating to the Coronavirus infection. It has been indicated by the team that two types of cells found in the nose are a mechanism that the SARS-CoV-2 virus uses as a means to enter the body and trigger an infection. Significantly , nasal swabs have yield higher viral loads than throat swabs. The lead researcher , Dr. Martijn Nawijn has reportedly stated :- “ This is the first time these particular cells in the nose have been associated with COVID-19………..Our findings are consistent with the rapid infection rates of the virus seen so far. The location of these cells on the surface of the inside of nose make them highly accessible to the virus , and also may assist with transmission to other people”. It has also been opined that such knowledge can provide the basis for developing potential treatments to reduce spread of the virus. The news report can be found at digitaljournal.com/tech-and-science/science/essential-sience-coronavirus-is-the-nos-a-route-of-infection/article/571145.
    (2). That nose has precise role to play in providing some indication about potential of Covid-19 infection in the person , was earlier brought out by Roni Caryn Robin as early as on 22 March 2020 ( 26 March , 2020) through news report titled – “ Lost sense of smell may be peculiar clue to Coronavirus infection” – published at nytimes.com. It was mentioned in the report that doctor groups in the US were recommending testing and isolation for people who had lost their ability to smell and taste , even if they had no other symptoms.
    (3). There is a report from Ahmad Sedachat , Associate Professor in the University of Cincinnati , the U.S. , — “ Your nose may know more when it comes to COVID-19. University Cincinnati expert says loss of smell could be an early indication of infection”. The said report has been published at eurekalert.org on 14 April , 2020. It reads like this :- “ A University of Cincinnati ear , nose and throat specialist says your nose may hold a clue in identifying COVID-19. Physicians are increasingly recognizing the importance of the nasal cavity in determining the physiology of COVID-19. COVID-19 is associated with a fairly unique combination of nasal symptoms : a sudden loss of one’s sense of smell , also known as ‘ anosmia’ , without nasal obstruction”.
    (4). In this context , a lot prior to all these reports , this Vedic astrology writer’s 11 November , 2019 predictive alerts through article – “ Astrological probable alert for 2020” – published at wisdom-magazine.com/Article.aspx/5176/ on 1 January 2020 can be read to imply the same conclusion. The text related to the theme aforesaid reads like this in the 11 November 2019 predictive article :-
    “ Predictive Conclusions
    4. The months of April to June , particularly May-June 2020 look to be trending into the scene some serious worrisome landscapes. There could be war or war-like conditions across the world , which the US may be called upon to address…………………………….More care and appropriate strategy may be taken during April to June , particularly May-June in 2020 , against loss of such stuff as are known for repugnant and repulsive smell through air passage”. It implies that smell ability to sense repugnancy and repulsive nature of stuff could be impaired , due to some deficiency ( loss ) caused by infection. In other words , during the effective period of April-June , 2020 , smell ability of the cells in the nose could be affected , which doctors have found as additional symptom for sending people for testing. An inference of nose or smell playing a vital role in worrisome concern calling for more care and appropriate strategy can be drawn from this writer’s following alert in other predictive articles as well:-
    “ Some substances or industries having repugnant or repulsive smell may call for more care and appropriate strategy during twenty days from 20 March to 10 April 2020”. This predictive alert was indicated by this writer through article – “ Vedic astrology highlights for Japan in coming year 2020” – brought to public domain widely on 23 October , 2019.
    A clear indication for more care and appropriate strategy in relation to respiratory system in the body was also recorded in article – “ Potential of stars for Italy in soon coming year 2020” – published last year 2019 on 15 December at http://www.astralis.it/Kumar02.htm. The alert reads like this :-
    “ 7…………………..This scenario can also mean worrisome ailments involving respiratory system in the body or venereal disease or increase in ailments relating to nerves”.
    In conclusion , this writer’s predictive alerts of last year 2019 can be said to be substantially on the same page with those of competent –expert scientists briefly brought out herebefore.

  2. according to what I comprehend it sounds like it shuts off the receptors in the brain that are responsible for smell? Do peripheral nerves play a function?

    So many reasons to explore, gle1

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