Rhein attenuates lipopolysaccharide-primed inflammation through NF-κB inhibition in RAW264.7 cells: targeting the PPAR-γ signal pathway

Inflammation is a common inducer of numerous severe diseases such as sepsis. The NF-kappa B signaling pathway plays a key role in the inflammatory process. Its activation promotes the release of pro-inflammatory mediators like inducible nitric oxide synthase and tumor necrosis factor alpha. Peroxisome proliferator-activated receptor gamma (PPAR-gamma) inactivates nuclear factor kappa B (NF-kappa B) and subsequently attenuates inflammation. Rhein, an agent isolated from rhubarb, has been known to have anti-inflammatory effects. However, its influence on PPAR-gamma remains largely unknown. In this study, an inflammation model was constructed by stimulating RAW264.7 cells with lipopolysaccharide. Rhein was used as a therapeutic agent, while rosiglitazone (PPAR-gamma activator) and GW9662 (PPAR-gamma inhibitor) were used as disrupters for in depth studies. The results demonstrated that rhein inhibits NF-kappa B activation and inflammatory factor release. However, GW9662 significantly reduced this effect, indicating that PPAR-gamma is a critical mediator in the rhein-mediated anti-inflammatory process. Additionally, positive modulation of PPAR-gamma expression and activity by rosiglitazone correspondingly influenced the effects of rhein on inflammatory factors and NF-kappa B expression. We also found that rhein could enhance PPAR-gamma, NF-kappa B, and histone deacetylase 3 (HDAC3) binding. These results indicate that rhein exerts its anti-inflammation function by regulating the PPAR-gamma-NF-kappa B-HDAC3 axis.