Differential Cell Sensitivity between OTA and LPS upon Releasing TNF-α

The release of tumor necrosis factor a (TNF-alpha) by ochratoxin A (OTA) was studied in various macrophage and non-macrophage cell lines and compared with E. coli lipopolysaccharide (LPS) as a standard TNF-alpha release agent. Cells were exposed either to 0, 2.5 or 12.5 mu mol/L OTA, or to 0.1 mu g/mL LPS, for up to 24 h. OTA at 2.5 mu mol/L and LPS at 0.1 mu g/mL were not toxic to the tested cells as indicated by viability markers. TNF-alpha was detected in the incubated cell medium of rat Kupffer cells, peritoneal rat macrophages, and the mouse monocyte macrophage cell line J774A. 1: TNF-alpha concentrations were 1,000 pg/mL, 1,560 pg/mL, and 650 pg/mL, respectively, for 2.5 mu mol/L OTA exposure and 3,000 pg/mL, 2,600 pg/mL, and 2,115 pg/mL, respectively, for LPS exposure. Rat liver sinusoidal endothelial cells, rat hepatocytes, human HepG2 cells, and mouse L929 cells lacked any cytokine response to OTA, but showed a significant release of TNF-alpha after LPS exposure, with the exception of HepG2 cells. In non-responsive cell lines, OTA lacked both any activation of NF-kappa B or the translocation of activated NF-kappa B to the cell nucleus, i.e., in mouse L929 cells. In J774A. 1 cells, OTA mediated TNF-alpha release via the pRaf/MEK 1/2-NF-kappa B and p38-NF-kappa B pathways, whereas LPS used pRaf/MEK 1/2-NF-kappa B, but not p38-NF-kappa B pathways. In contrast, in L929 cells, LPS used other pathways to activate NF-kappa B. Our data indicate that only macrophages and macrophage derived cells respond to OTA and are considered as sources for TNF-alpha release upon OTA exposure.