Tiotropium inhibits increases in nerve-associated eosinophils following antigen challenge and prevents airway hyperreactivity in a guinea pig model of asthma

Parasympathetic nerves strongly regulate airway tone, and in allergic asthma, excess acetylcholine release contributes to airway hyperresponsiveness linked to nerve‑associated eosinophils. This work shows that blocking M3 muscarinic receptors with tiotropium prevents hyperresponsiveness in guinea pigs by reducing eosinophilic inflammation rather than inhibiting bronchoconstriction. Neurons can produce CCR3 chemokines in vitro, but in vivo eosinophil recruitment appears driven mainly by non‑neuronal cells. These findings suggest that M3 antagonists may reduce asthma exacerbations through anti‑inflammatory effects, particularly by limiting eosinophil interactions with airway nerves.