Workers engaged in the growing of mushrooms develop respiratory problems including asthma and hypersensitity pneumonitis. We recently studied the effect of Oyster mushroom, (Pleurotus ostreatus) extract on isolated guinea pig trachea (GPT). In the current study, we investigate the potential role of agents in the growing medium, the compost used to cultivate these mushrooms. An extract of mushroom compost (MCE) was prepared as a 1:10 w/v solution. The extract was added to GPT in a series of 12 organ baths, in parallel, in 1/2 log dose increments. Dose related contractions of GPT were demonstrated using MCE. Tissue response was measured as a percent of the tissue's maximal contraction to carbachol. The effects of mediator modifying drugs including atropine, indomethacin, pyrilamine, acivicin, NDGA, BPB (blocks part of the arachidonic acid cascade), TMB8 (blocks intracellular calcium mobilization), capsaicin and captopril (ACE inhibitor) were tested by pre-treating the tissues with these agents. Endotoxin content of the extract was 10,619 EU/mg. Protein analysis revealed 708 mcg/mg of extract. The histamine content was <2mg/l00mg of compost. Atropine completely blocked the contractile response of MCE. Pyrilamine, and to a lesser extent, indomethacin partially blocked the constrictor effect of MCE. Acivicin, BPB, NDGA, capsaicin, captopril and TMB8 significantly reduced the contractile effects of MCE (p<0.05). As previously studied organic dusts, MCE causes a non-immunologically mediated constriction of airway smooth muscle modulated by inflammatory mediators. These extracts exhibited high contents of endotoxin. Cholinergic receptors appear to be prominently involved in this effect. These findings may be related to respiratory symptoms in workers cultivating mushrooms.
Proceedings of the American Thoracic Society. 2005 ATS International Conference, May 20-25, 2005, San Diego, California