Differences in inflammatory responses and cytotoxicity in RAW264.7 macrophages induced by Streptomyces anulatus grown on different building materials

Streptomyces anulatus, an indicator microbe of mold in buildings, was grown on different building materials in order to study the impact of growth con ditions on the ability of the spores of this microbe to induce toxicity and inflammatory responses. The microbes were grown for 2 months on sterilized and unsterilized wood, chipboard, concrete, plaster board and mineral wool in tight glass vessels under humid conditions. The highest microbial spore concentration was detected on the sterilized mineral wool followed by the sterilized plaster board and the unsterilized mineral wool. Mouse RAW264.7 macrophages were exposed in vitro for 24 h to the spores of S, anulatus and the production of the inflammatory mediators, nitric oxide (NO), tumor nec rosis factor alpha (TNF alpha), interleukin-6 (IL-6), interleukin-10 (IL-10 ) and cytotoxicity, were measured. The dose equivalent to 5x10(5) spores/ml of medium was used to compare the different materials. The most intense pr oduction of NO (11.6 muM), TNF alpha (560 pg/ml) and IL-6 (2800 pg/ml) in m acrophages was induced by the spores grown on sterilized plaster board. The y also caused the greatest loss of cell viability (39%). The spores grown o n sterilized concrete induced significant production of NO (1.5 muM) and de creased cell viability (22%), and the spores grown on unsterilized and ster ilized mineral wool increased production of NO (4.1 muM and 0.8 muM, respec tively). The spores did not stimulate production of the anti-inflammatory c ytokine IL-10. These results indicate that the ability of S. anulatus to in duce inflammatory responses and cytotoxicity in macrophages is dependent on the growth conditions provided by different building materials.