Abstract
Lignin is a heterogenous natural plant substance composed of phenylpropenoid. We previously reported that lignified materials displayed diverse biological action such as stimulation of macrophage, antimicrobial, antiviral and antitumor activity. Here, we report that both lignin and synthetic dehydrogenation polymer of phenylpropenoids (so-called synthetic lignin) significantly induce tumor necrosis factor (TNF) production by the mouse macrophagelike cell line, J774.1, and by mouse residual peritoneal macrophages. The amount of TNF was measured by ELISA, using a specific monoclonal antibody against mouse TNF. The dehydrogenation polymer of calfeic acid (DHP-CA), among the synthetic lignins, most strongly induced TNF production. Recently, TNF has been revealed to have diverse biological activities in addition to antitumor activity. The results of our study suggest that part of the diverse biological action stimulated by lignin is due to the biological activity of TNF. The expression of TNF mRNA was also studied to investigate the mechanism of TNF induction by lignin. Northern blot hybridization was performed with total RNA obtained from the J774.1 cells and from mouse residual peritoneal macrophages after induction by treatment with DHP-CA. Bacterial lipopolysaccharides (LPS), one of the most potent inducers of TNF production by monocytes/macrophages, is well chararterized by its mechanism and induces TNF mRNA mainly at the level of transcription. We conclude, from the fact of Northern blot analysis that DHPCA did not show induction of TNF mRNA, that DHP-CA acts mainly at the level of translation, or posttranslational processing.
