Piceatannol exhibits anti-inflammatory effects on macrophages interacting with adipocytes

Piceatannol (PIC), a natural analog of resveratrol (RES), is a phytochemical found in passion fruit seeds. To clarify the effects of PIC on obesity-induced inflammation in adipose tissue, we investigated the anti-inflammatory activity of PIC-related compounds (PIC, RES, and metabolites from PIC) in culture models of obese adipose tissue. Lipopolysaccharide (LPS) and conditioned medium from 3T3-L1 adipocytes (3T3-L1-CM) enhanced proinflammatory gene expression and synthesis of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) in RAW264.7 macrophages. Although each compound inhibited the mRNA expression of iNOS (inducible NO synthase), TNF-alpha, and IL-6, PIC potently inhibited them, and 30 mu mol/L PIC suppressed the LPS- and 3T3-L1-CM-induced mRNA expression of iNOS (70.4% and 69.2% suppression, respectively), TNF-alpha (42.6% and 47.0% suppression), and IL-6 (27.3% and 42.1% suppression). PIC also significantly suppressed production of NO (80.3% suppression) and inflammatory cytokines (TNF-alpha; 33.7% suppression, IL-6; 66.5% suppression). Furthermore, PIC was found to rescue the uncoupling protein 1 mRNA expression induced by isoproterenol in 10T1/2 adipocytes, which was suppressed by LPS-activated macrophages. These results suggest that PIC may attenuate the pathologic inflammation triggered by adipose tissues.