Abstract
BackgroundQuercetin, a dietary flavonoid found in many fruits, red wine and onion, among others, has been reported to have potent anti-oxidant, anti-viral and anti-cancer effects. Although quercetin is also reported to have anti-inflammatory and anti-allergic effects, the precise mechanisms by which quercetin favorably modify the clinical conditions of allergic diseases such as allergic rhinitis (AR). The present study was designed to examine the influence of quercetin on the development of AR by using AR model rats.MethodsSprague-Dawley (SD) rats were sensitized with toluene 2,4-diisocyanate (TDI) by intranasal instillation of a 10 % TDI in ethyl acetate in a volume of 5 μl once a day for 5 consecutive days. This sensitization procedure was repeated after a 2-day interval. After 5 days of the second sensitization, rats were treated with various doses of quercetin once a day for 2 to 7 days. Nasal allergy-like symptoms, which were induced by bilateral application of 5 μl of 10 % TDI in ethyl acetate, were assessed by counting sneezing and nasal rubbing behaviors for 10 min just after TDI nasal challenge. The levels of substance P (SP), calcitonin gene-related peptide (CGRP) and nerve growth factor (NGF) in nasal lavage fluids obtained 6 h after TDI nasal challenge was examined by ELISA.ResultsOral administration of quercetin for 5 and 7 days, but not 2 and 3 days, could inhibit sneezing and nasal rubbing movements, which were increased by TDI nasal challenge. The minimum dose that caused significant inhibition was 25 mg/kg. Oral administration of quercetin at more than 25 mg/kg for 5 days significantly inhibited the increase in SP, CGRP and NGF contents in nasal lavage fluids induced by TDI nasal challenge.ConclusionThe present results strongly suggested that quercetin will be a good candidate for the supplement on the management and treatment of allergic diseases, especially AR.
Highlights
Quercetin, a dietary flavonoid found in many fruits, red wine and onion, among others, has been reported to have potent anti-oxidant, anti-viral and anti-cancer effects
Influence of quercetin on the development of TDIinduced nasal allergy-like symptoms The first set of experiments was undertaken to examine whether oral administration of quercetin into TDI-sensitized rats could inhibit the development of nasal allergy-like symptoms, which was induced by nasal antigenic challenge
Oral administration of quercetin at more than 25 mg/kg, but not 10 mg/kg and 20 mg/kg, for 5 and 7 consecutive days inhibited the development of sneezing: the numbers of sneezing observed in rats treated with 10 and 20 mg/kg quercetin are nearly identical to that in TDI-sensitized, not treated rats but the sneezing observed in TDI-sensitized rats treated with quercetin at 25 mg/kg and more is significantly lower than control rats (Fig. 1)
Summary
A dietary flavonoid found in many fruits, red wine and onion, among others, has been reported to have potent anti-oxidant, anti-viral and anti-cancer effects. AR is not life-threatening disease, it can deteriorate the quality of life and an economic burden through the clinical symptoms such as sneezing, rhinorrhea, itching and nasal congestion [1, 2]. It is reported that quercetin could effectively block the development of anaphylactic responses against peanuts in the experimental mouse model and in vitro cell lines [15, 16]. These reports strongly suggest that quercetin will be a good candidate as a potential drug to allergic diseases, the influence of quercetin on neuropeptide productions is poorly understood. We examined the influence of quercetin on neuropeptide production by using AR model rat
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