Anti-inflammatory effects and molecular mechanisms of 8-prenyl quercetin

Scope: 8-prenyl quercetin (PQ) is a typical prenylflavonoid distributed in plant foods. It shows higher potential bioactivity than its parent quercetin (Q) although the mechanisms are not fully understood. This study aims to clarify the anti-inflammatory effects and molecular mechanisms of PQ in cell and animal models, compared to Q. Methods and results: RAW264.7 cells were treated with PQ or Q to investigate the influence on the production of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and protein kinases by Western blotting. Nitric oxide (NO) and prostaglandin E-2 (PGE(2)) were measured by the Griess method and ELISA, respectively. Cytokines were assayed by the multiplex technology. Mouse paw edema was induced by LPS. The results revealed that PQ had stronger inhibition on the production of iNOS, COX-2, NO, PGE(2), and 12 kinds of cytokines, than Q. PQ also showed in vivo anti-inflammatory effect by attenuating mouse paw edema. Molecular data revealed that PQ had no competitive binding to Toll-like receptor 4 with LPS, but directly targeted SEK1-JNK1/2 (where SEK is stress-activated protein kinase and JNK1/2 is Jun-N-terminal kinase 1/2) and MEK1-ERK1/2 (where ERK is extracellular signal regulated kinase). Conclusion: PQ as a potential inhibitor revealed anti-inflammatory effect in both cell and animal models at least by targeting SEK1-JNK1/2 and MEK1-ERK1/2.