Airway Exposure to 1,3-Beta-d-Glucan Induces Airway Hyperresponsiveness in Guinea Pigs

1,3-Beta-d-glucan (β-glucan) is a component of mold cell walls and is frequently found in fungi and house dust mites. The studies of β-glucan are inconsistent, although it has been implicated in airway adverse responses. This study was carried out to determine whether airway hyperresponsiveness was seen 24 h after airway exposure to β-glucan in guinea pigs. Two matching guinea pigs were exposed intratracheally to either β-glucan or its vehicle. Twenty-four hours after intratracheal instillation, there was no difference between these two groups in the baseline of the total pulmonary resistance (R_L), dynamic lung compliance (C_dyn), arterial blood pressure, and heart rate. In contrast, the responses of R_L to capsaicin injection were significantly increased in β-glucan animals; capsaicin at the same dose of 3.2 μg/kg increased R_L by 184% in vehicle animals and by 400% in β-glucan animals. The effective dose 200% to capsaicin injection was lower in the β-glucan animals. Furthermore, the increases in R_L were partially reduced after transient lung hyperinflation to recruit the occluding airways; however, the R_L induced by capsaicin injection after lung hyperinflation was significantly larger than the baseline in β-glucan animals; also, the lung wet-to-dry ratio in capsaicin-injected animals was augmented in the β-glucan group. Moreover, the airway hyperresponsiveness was accompanied by increases in neutrophils in the bronchoalveolar lavage fluid in the β-glucan animals. Furthermore, the levels of substance P and the calcitonin gene-related peptide in the bronchoalveolar lavage fluid collected after capsaicin injection were increased in β-glucan animals. We provide definitive evidence that β-glucan can induce airway hyperresponsiveness in guinea pigs, and the neuropeptide releases play an important role in this airway hyperresponsiveness.