[Possibility of formation of the S100A8/A9-proinflammatory cytokine complexes in vivo in acute inflammation and their functional roles].

We previously hypothesized that S100A8/A9 binds with several kinds of proinflammatory cytokines, such as TNF-alpha, IL-6 and IL-1beta, to form the S100A8/A9-proinflammatory cytokine complexes in vivo in acute inflammation, leading to subsidence of inflammatory responses. Our goal was to verify the presence of these complexes in liver tissues of rats with lipopolysaccharide (LPS) induced damage. We firstly prepared two kinds of the full-length cDNA encoding amino acid sequences of human S100A8 and S100A9 proteins, and constructed their pCold-I expression vectors. The recombinant S100A8 and S100A9 were successfully expressed in E. coli, and then purified by Ni-agarose columns, respectively. The S100A8/A9 was noncovalently synthesized in 2.0 mol/1 Tris-NaOH solution (pH 12) using the purified S100A8 and S100A9. After purification, this heterodimer (1 mg) was intraperitoneally injected into a rat 1h after injection of LPS. Two kinds of ELISA systems were used to detect the S100A8/A9-inflammatory cytokine complexes in the rat liver tissue. As determined by the ELISA-A and B, the reaction was apparently positive and quantitative. Immunohistochemistry provided such complexes-positive cells in the liver with damage. The S100A8/A9-positive cells almost corresponded to the cytokines-positive ones morphologically, strongly suggested the presence of the S100A8/A9-proinflammatory cytokine complexes. In conclusion, the possibility that these complexes were formed in vivo and accumulated to the immunological cells, such as macrophages and/or activated neutrophils, was indicated. Our effort is currently addressed to isolate the S100A8/A9-proinflammatory cytokine complexes using biochemical techniques, and to comprehensively resolute their clinical significance in the differential diagnosis of inflammatory diseases.