Tranilast, an orally active anti-allergic drug, up-regulates the anti-inflammatory heme oxygenase-1 expression but down-regulates the pro-inflammatory cyclooxygenase-2 and inducible nitric oxide synthase expression in RAW264.7 macrophages

Tranilast (N-[3',4'-dimethoxycinnamonyl] anthranilic acid), an orally active anti-allergic drug, is reported to exert the anti-inflammatory effects, but the underlying mechanisms that could explain the antiinflammatory actions of tranilast remain largely unknown. Here, we found that tranilast induces heme oxygenase-1 (HO-1) expression through the extracellular signal-regulated kinase-1/2 (ERK1/2) pathway in RAW264.7 macrophages. Tranilast suppressed cyclooxygenase-2 (COX-2) and inducible nitric oxide (NO) synthase (iNOS) expression and thereby reduced COX-2-derived prostaglandin E-2 (PGE(2)) and iNOS-derived NO production in lipopolysaccharide (LPS)-stimulated macrophages. Similarly, tranilast diminished tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 P (IL-1 beta) production. Interestingly, the effects of tranilast on LPS-incluced PGE(2), NO, TNF-alpha, and IL-1 beta production were partially reversed by the HO-1 inhibitor tin protoporpoyrin, suggesting that tranilast-induced HO-1 expression is at least partly responsible for the resulting anti-inflammatory effects of the drug. Thus, HO-I expression via ERK1/2 activation may be at least one of the possible mechanisms explaining the anti-inflammatory actions of tranilast. (C) 2008 Published by Elsevier Inc.