Vol. 302, Issue 1, 296-303, July 2002

4-Hydroxynonenal Decreases Interleukin-6 Expression and Protein Production in Primary Rat Kupffer Cells by Inhibiting Nuclear Factor-B Activation

Stephen W. Luckey, Melinda Taylor, Brante P. Sampey, Robert I. Scheinman and Dennis R. Petersen

Molecular Toxicology and Environmental Health Sciences Program, University of Colorado Health Sciences Center, Denver, Colorado

Kupffer cells have been documented to play an important role in the early events of liver injury and regeneration by releasing biologically active mediators such as interleukin-6 (IL-6). 4-Hydroxy-trans-2-nonenal (4-HNE), a major end product of lipid peroxidation, has multiple cytotoxic effects and is implicated in chemical-induced liver injury. Consequently, the purpose of this study was to evaluate the ability of 4-HNE to modulate IL-6 production in isolated primary rat Kupffer cells. 4-HNE (0.1-10 µM) reduced both lipopolysaccharide (LPS)-induced IL-6 protein production and mRNA levels. The role of nuclear factor-B (NF-B) in IL-6 induction was elucidated using Kupffer cells transduced in vitro with a recombinant adenovirus containing a IB super-repressor resistant to phosphorylation and degradation (Ad5IB). Using this system, LPS-induced IL-6 protein production was inhibited by 65% in Ad5IB-infected cells. The treatment of Kupffer cells for 1 h with 4-HNE followed by stimulation for 1 h with LPS (500 ng/ml) resulted in a concentration-dependent decrease in NF-B activation. Similarly, decreased NF-B activity in these cells paralleled a reduction in IB mRNA levels. Furthermore, upon LPS stimulation, 4-HNE stabilized IB, which corresponded to a decrease in phosphorylated IB. At lower 4-HNE concentrations (0-5 µM), interactions between p65 and IB proteins were maintained as detected by immunoprecipitation-immunoblot analyses. In conclusion, these data suggest that 4-HNE inhibits IL-6 production in rat Kupffer cells by preventing activation of the NF-B pathway and suppressing IB phosphorylation. These results have functional implications in that 4-HNE may interfere with the ability of Kupffer cells to produce cytokines proposed to play an important role in liver regeneration.