TI-I-174, a Synthetic Chalcone Derivative, Suppresses Nitric Oxide Production in Murine Macrophages via Heme Oxygenase- 1 Induction and Inhibition of AP-1

Chalcones (1,3-diaryl-2-propen-1-ones), a flavonoid subfamily, are widely known for their anti-inflammatory properties. Propenonemoiety in chalcones is known to play an important role in generating biological responses by chalcones. In the present study, wesynthesized chalcone derivatives structurally modified in propenone moiety and examined inhibitory effect on nitric oxide (NO)production and its potential mechanisms. Among the chalcone derivatives used for this study, TI-I-174 (3-(2-Hydroxyphenyl)-1-(thiophen-3-yl)prop-2-en-1-one) most potently inhibited lipopolysaccharide (LPS)-stimulated nitrite production in RAW 264.7macrophages. TI-I-174 treatment also markedly inhibited inducible nitric oxide synthase (iNOS) expression. However, TI-I-174 didnot significantly affect production of IL-6, cyclooxygenase-2 (COX-2) and tumor necrosis factor-a (TNF-a), implying that TI-I-174inhibits production of inflammatory mediators in a selective manner. Treatment of macrophages with TI-I-174 significantly inhibitedtranscriptional activity of activator protein-1 (AP-1) as determined by luciferase reporter gene assay, whereas nuclear factor-kB(NF-kB) activity was not affected by TI-I-1744. In addition, TI-I-174 significantly inhibited activation of c-Jun-N-Terminal kinase(JNK) without affecting ERK1/2 and p38MAPK, indicating that down-regulation of iNOS gene expression by TI-I-174 is mainlyattributed by blockade of JNK/AP-1 activation. We also demonstrated that TI-I-174 treatment led to an increase in heme oxygenase-1 (HO-1) expression both at mRNA and protein level. Transfection of siRNA targeting HO-1 reversed TI-I-174-mediatedinhibition of nitrite production. Taken together, these results indicate that TI-I-174 suppresses NO production in LPS-stimulatedRAW 264.7 macrophages via induction of HO-1 and blockade of AP-1 activation.