In allergic airways, as in
asthma,
inflammation and impaired functioning of
toll-like receptor 7 (TLR7) has been found. The augmentation of this receptor with agonist compounds resulted in bronchodilation and a switch of the T(H)2 inflammatory pattern, specific for allergic conditions, to T(H)1
inflammation, characterised by an increased production of
interferon-γ. This was a preclinical study evaluating the effects of two TLR7 agonists,
imiquimod and
resiquimod, on the isolated guinea pig trachea. The TLR7-related downstream signalling pathways were also assessed. Both TLR7 agonists were shown to reduce
serotonin-induced bronchoconstriction, which is possibly exerted via the p38MAPK and NF-κB pathways. Therapeutic targeting of TLR7 with specific agonists might represent a promising immunomodulatory approach in
asthma, especially if systemic exposure is minimised with inhaled formulations.