Airway inflammation in employees involved in cultivating Japanese mushrooms (bunashimeji)

Abstract

Chronic inhalation of spores may cause respiratory symptoms such as productive cough and sputum. The purpose of this study was to determine the clinical pathophysiology of airway inflammation caused by bunashimeji spores and to investigate whether the spores have direct toxic inflammatory effects. Sensitized employees with respiratory symptoms and a stimulation index (SI) > 200%, and non-sensitized employees with a SI < 200% were enrolled. They underwent sputum induction and chest high-resolution computed tomography (HRCT). The in vitro effect of bunashimeji spore solutions on normal human bronchial epithelial (NHBE) cell cultures was investigated using the air-liquid interface method. Bunashimeji spore solution was added at 10(4) or 10(6) spores per 20 microL/well. The interleukin (IL)-8 and epithelial neutrophil-activating peptide-78 (ENA-78) concentrations in the medium and IL-8 mRNA expression of NHBE cells were assessed after each stimulation. Sensitized employees were divided into 14 with normal HRCT and 9 with abnormal HRCT. Fifteen of the sensitized group and five of the non-sensitized group had a productive cough and sputum. The neutrophil counts in induced sputum were significantly higher in subjects with abnormal HRCT than in those with normal HRCT. IL-8 and ENA-78 concentrations following stimulation with 10(4) and 10(6) spores were significantly increased compared with PBS only on day 9. IL-8 mRNA expression due to spore stimulation was significantly increased compared with control. IL-8 mRNA expression with 10(6) spore stimulation was significantly increased on days 6 and 12 compared with 10(4) spores. The inhalation of spores directly produces toxic inflammatory effects in the airways, independent of the degree of sensitization.