The outer membrane protein I of Pseudomonas aeruginosa PAO1, a possible pollutant of dialysate in hemodialysis, induces cytokines in mouse bone marrow cells

The finding of outer membrane protein I (Oprl) of Pseudomonas aeruginosa in hemodialyzers used by patients with end-stage renal failure led us to stud y the possible role of Oprl as cytokine inducer. However, there are few rep orts on the biological activity of Oprl, because it is difficult to obtain highly purified Oprl. In this study, we attempt to establish a procedure fo r the efficient purification of Oprl, which does not include lipopolysaccha ride, from the bacterial culture broth, not hemodialyzers, to demonstrate t hat Oprl is a potent cytokine inducer. From bacterial culture broth (1 lite r), P. aeruginosa PAO1, which was confirmed previously by the sequence codi ng, was separated by centrifugation, high-performance liquid chromatography , and disk electrophoresis. Mouse bone marrow cells were stimulated by puri fied Oprl, and the supernatants of the culture were analyzed by several enz yme-linked immunosorbent assay kits. The tumor necrosis factor alpha produc tion stimulated by purified Oprl was confirmed and degraded within 24 h. Fu rthermore, interleukin (IL) 1 alpha, IL-1 beta, IL-6, and granulocyte-macro phage colony-stimulating factor were also induced by Oprl despite the absen ce of lipopolysaccharide. We conclude that Oprl has the potential to induce tumor necrosis factor alpha production in mouse bone marrow cells and that tumor necrosis factor alpha contributes to the induction of inflammatory c ytokines, namely IL-1 alpha, IL-1 beta, IL-6, and granulocyte/macrophage co lony-stimulating factor, while lipopolysaccharide has little effect on thes e cells. These results suggest the presence of a pathway of inflammatory si gnal transduction triggered by Oprl. In addition, Oprl is possibly one of t he harmful dialysate pollutants in hemodialysis patients besides the well-k nown lipopolysaccharide.