2.4 Allergic Rhinitis
Allergic rhinitis (AR) has a similar inflammatory process to that of
asthma. In allergic individuals, many Th2 cells infiltrate the nasal
mucosa and release cytokines (e.g. IL-4, IL-5 and IL-13) that promote
IgE production by plasma cells. Avoiding contact with allergens is the
safest treatment, but it does not usually achieve satisfactory
results.4444 Although anti-histamines and
corticosteroids can significantly relieve related symptoms, such
treatments must be taken repeatedly throughout the lives of allergic
individuals.44,45 Immunotherapy administered through
subcutaneous injection or sublingual administration of allergens induces
immune tolerance, but continuous treatment is again required, which is
expensive and can potentially lead to allergic
reactions.46
Generally, large-scale production and release of inflammatory cells,
including eosinophils and ROS and their metabolites, plays a vital role
in the pathogenesis of allergic inflammatory airway
diseases.47,48 As an endogenous anti-oxidant protein,
Trx1 has strong anti-oxidative stress effects. Thus, administration of
exogenous Trx1 can inhibit airway hyper responsiveness induced by
specific allergens via the inhibition of eosinophil accumulation in the
airway of mouse models with asthma.22,23 Quercetin has
been suggested as a dietary supplement for improving the clinical
symptoms of allergic diseases such as AR, but its precise mechanisms of
action remain unclear. Nevertheless, Trx1 levels in the nasal mucosa are
known to significantly increase after oral administration of quercetin;
moreover, the frequency of nasal allergy-like symptoms, such as sneezing
and nasal rubbing, are significantly reduced.49 These
changes provide insights into the possible mechanism through which
quercetin has favourable effects on AR.