[The formation of a mediator of inflammation]

Tumor necrosis factor-alpha (TNF-alpha) represents a central distal mediator of inflammation. It is a protein released upon infections, traumatic, lesions or autoimmune disorders from immunocompetent cells and thus maintains or enhances the inflammatory reaction. The determination of such mediators in experimentally challenged animals is a mean for testing the efficacy of putative drugs. Alternative attempts for the assessment of mediator release from cell cultures are limited by profound differences in the time course of mediator release in vitro. We checked the hypothesis that these kinetic differences are due to the lack of elimination of mediators formed and released in vitro. We used the release of TNF-alpha from liver macrophage cultures stimulated with the bacterial cell wall component endotoxin as a model. The discrepancy between the in vivo release of the cytokines during endotoxic shock in the rat and the in vitro release from Kupffer cells was confirmed. By using a continuous open perfusion system instead of a static culture, the simulation of an elimination resulted in a mediator release that closely resembled the kinetics seen in vivo. Perfusion cultures appear to be suitable for relevant in vitro screening models in drug development and testing.