الفهرس 
Introduction and Aim of the WorkOnly 14 pages are availabe for public view
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Abstract
Olfactory dysfunctions are quite common disorders of the nose. Anosmia is the inability to smell, either partially or completely. Anomia has big impact on mortality and quality of life. The loss of smell is considered an eminent, characteristic feature of SARS-CoV-2 associate disease (COVID-19). In 20 % of COVID-19 cases, patients can develop a Consistent form of olfactory dysfunction, lasting more than six months (or years) after the resolution of COVID-19.
Quercetin is a naturally occurring flavonoid that is known to have many health benefits.
Despite having a wide range of pharmacological actions, quercetin has poor water solubility, poor bioavailability, so Chitosan nanoparticles are widely acceptable as carriers for hydrophobic drugs to increase their therapeutic effectiveness.
This study was done to compare the effect of Quercetin and Quercetin loaded Chitosan nanoparticles on rat model of anosmia and explaining different mechanisms involved in those effects by using histological, immunohistochemical, and biochemical methods.
In this study, 40 male albino rats at the age 8-10 weeks, weighing 150-200 grams were used. The total period of the study was three weeks. Rats were divided randomly into four groups; each group included 10 rats: group I, the control group which received intranasal irrigation of 0.2ml saline solution every five days starting from the eighth day and received intravenous injection of 0.5 ml PBS via tail vein twice a week through the whole experiment period.
group II, ZnS group which irrigated intranasally with 0.2ml volume of 10% Zinc sulfate solution every five days starting from the eighth day till the end of the experiment.
group III, ZnS+ QU treated group which received intravenous injection of 25 mg /kg QU via tail vein twice a week from the beginning of the experiment one week before induction of anosmia and continued through the experiment along with ZnS.
group IV, ZnS+ QU-CSNPs treated group which received intravenous injection of 25 mg /kg QU-CSNPs via tail vein twice a week from the beginning of the experiment one week before induction of anosmia and continued through the experiment along with ZnS.
The results of the current study revealed that:
• The buried food test result: there was significant increase in the duration of finding food in both ZnS and ZnS+QU-treated groups compared to other groups while there was significant deccrease in the duration of finding food in ZnS+ QU-CSNPs -treated group compared to ZnS and ZnS+QU-treated groups.
• The biochemical study: the MDA and TNF-α levels in olfactory mucosa and bulb showed a significance decrease in their mean values in ZnS+QU and ZnS+ QU-CSNPs treated groups compared to ZnS group, comparing the treated groups, ZnS+ QU-CSNPs treated group had significant decrease compared to ZnS+QU treated group.
The GSH levels in olfactory mucosa and bulb showed a significance increase in their mean values in the treated groups compared to ZnS groups, comparing the treated group, ZnS+ QU-CSNPs treated group had significant increase compared to ZnS+QU treated group.
• Hematoxylin and eosin stained results: olfactory mucosa of ZnS group showed areas of damage and shrinking of olfactory mucosa with thinning of olfactory epithelium and degeneration of Bowman’s glands and nerve bundles, while olfactory mucosa of ZnS+QU treated group showed replacement of olfactory epithelial cells with respiratory like columner ciliated cells. Olfactory bulb showed thining of olfactory nerve layer and distorted shape of glomeruli with degeneration of mitral cells in ZnS and ZnS+QU treated groups. However some mitral cells were apparently normal in ZnS+QU treated group. QU-CSNPs had ameliorative effects on both olfactory mucosa and bulb and the histological architecture was preserved.
• Alcian blue-Periodic acid Schiff stained results: olfactory mucosa of ZnS group showed negative AB-PAS reaction of Bowman’s glands contents, while showing positive reaction in ZnS+QU and ZnS+QU-CSNPs treated groups.
• SOX2 Immunohistochemical results: showed significant decrease in the mean number of SOX2 immune -reactive cells in olfactory mucosa of ZnS group compared to other groups, comparing the treated groups, ZnS+QU-CSNPs treated group had significant increase compared to ZnS+QU treated group.
• PCNA immunohistochemical study: showed significant decrease in the mean number of PCNA immune -reactive cells in olfactory mucosa and bulb of ZnS group compared to other groups, comparing the treated groups, ZnS+QU-CSNPs treated group had significant increase compared to ZnS+QU treated group.
• COX2 immunohistochemical study: showed significant increase in the mean area fraction of COX2 immunoreactivity in olfactory mucosa and bulb of ZnS group compared to other groups, comparing the treated groups, ZnS+QU-CSNPs treated group had significant decrease compared to ZnS+QU treated group.
• The TEM results: Olfactory mucosa of ZnS group showed Bowman’s glands with vaculated cytoplasm, dilated r-ER cisternae and few secretory granules, olfactory bulb of ZnS group showed degenerative changes of mitral cells and granule cells, irregular axons with splitting of myelin sheath and areas of vacuolated neuropil. ZnS+QU-CSNPs treated group had ameliorating effects on ultrastructures of both olfactory mucosa and bulb better than ZnS+QU treated group.
It was concluded that QU-CSNPs had adequate prophylactic effects against damaging effects of ZnS and these effects were extremely superior to QU.