Effect of viability of actinomycete spores on their ability to stimulate production of nitric oxide and reactive oxygen species in RAW264.7 macrophages.

Spores of actinomycetes, mesophilic gram-positive bacteria, isolated from moldy houses, induced the expression of inducible NO-synthase (iNOS) with a subsequent NO-production in RAW264.7 macrophages. No differences were detected between production of nitric oxide (NO) by alive or irradiated spores of different strains of Actinomycetes sp. or Streptomyces sp. Moreover, a significant production of reactive oxygen species (ROS) occurred in the macrophages after their stimulation both by alive and irradiation killed spores of actinomycetes. However, ROS-responses in macrophage induced by dead spores were significantly lower compared to those induced by alive spores. The cytotoxicity of the spores of different actinomycetes differed widely. The production of NO and ROS did not depend directly on the viability of the spores, suggesting an important role for cell wall components in the activation of the cells.