ABSTRACT
We report about the release of a soluble mediator(s) from cultured human monocytes/macrophages after exposure to quartz dust DQ12 or coal mine dust TF-1. This mediator(s) activates isolated human polymorphonuclear granulocytes (PMN) to generation of free oxygen radicals. The strong and long-lasting production of reactive oxygen species (ROS), especially of superoxide anion, was measured as lucigenin dependent chemiluminescence (CL). Studies of mediator exposed PMN with the NBT-test (nitroblue-tetrazolium test) also demonstrated the strong activation of PMN. Electromicroscopical studies of mediator exposed PMN showed strong chemotactic changes in a time dependent manner and suggested the release of lysosomal products. According to these properties we called the mediator(s) "granulocyte activating mediator(s)" (GRAM). Biochemical characterisation indicated a protein nature of GRAM. High pressure liquid chromatography (HPLC) gel-filtration suggested that two molecules or two fragments of one molecule with a m.w. of about 20 kda and just below 10 kda resp. were responsible for the observed effects. PMN are potent inflammatory cells, which are known to immigrate in the lung tissue, especially in the early phases of silicosis. ROS released by activated PMN can act tissue destroying, mutagenic and are probably involved in collagene synthesis by regulation of activity of prolylhydroxylase. Mediator induced release of ROS seems to be an important event in development of lung fibrosis and presents a new mechanism of quartz dust and coal mine dust fibrogenicity.
