Inhibitory effect of paeoniflorin on the inflammatory vicious cycle between adipocytes and macrophages.

Obesity is associated with a state of chronic, low-grade inflammation. It is considered that the paracrine loop involving free fatty acid (FFA) and tumor necrosis factor (TNF)α between adipocytes and macrophages establishes an inflammatory vicious cycle that augments the inflammatory changes and insulin resistance in obese adipose tissue. Paeoniflorin (PF), one of the major components of Paeony root, has been shown to have anti-inflammatory effects in vivo. We investigated the effect of PF on the production of FFA and TNFα in the interaction between adipocytes and macrophages. Coculture of 3T3-L1 adipocytes and RAW 264.7 macrophages markedly enhanced the production of TNFα and FFA compared with the control cultures, however, treatment with PF dose-dependently inhibited the production. We further examined the effects of PF on TNFα-stimulated adipocyte lipolysis and on FFA-induced macrophage TNFα expression. PF inhibited TNFα-stimulated adipocyte lipolysis in a dose-dependent manner, which was compatible with suppressed phosphorylation of TNFα-activated ERK1/2 and preserved downregulation of perilipin. Palmitate, one of the most important saturated FFAs, induced macrophage TNFα upexpression, but PF partially attenuated the effect. These results indicate that PF exhibits anti-inflammatory properties by inhibiting the vicious cycle between adipocytes and macrophages. PF may be useful for ameliorating the inflammatory changes in obese adipose tissue.