Anti-inflammatory Effect of a Limonin Derivative In Vivo and Its Mechanisms in RAW264.7 Cells

A potential new limonoid derivative, (12S,12aS)-6,6,8a,12a-tetramethyl-12-(5-(4-(piperidin-1-yl)butanoyl)furan-3-yl)decahydro-1H,3H-oxireno[2,3-d]pyrano[4',3':3,3a]isobenzofuro[5,4-f]isochromene-3,8,10(6H,9aH)-trione (I-C-1), has been screened for its anti-inflammatory activity. This study aimed to demonstrate the anti-inflammatory activities of I-C-1 and to further explore the underlying mechanisms of these activities in RAW264.7 macrophages. We verified the anti-inflammatory activity of I-C-1 in vivo by a carrageenan-induced paw edema model in rats and cotton pellet-induced granuloma in mice. Further, we found that I-C-1 significantly inhibited levels of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in lipopolysaccharide (LPS)-induced RAW264.7 cells. I-C-1 demonstrated strong inhibition of the NF-κB activation through repression of the IKKα and IKKβ phosphorylations, as well as a significant suppression of the phosphatidylinositol 3-kinase (PI3K)/serine-threonine kinase (Akt) pathway, an upstream of the NF-κB pathway. Additionally, we verified the inhibitory effect of I-C-1 on PI3K phosphorylation by immunofluorescence assay and compared the effects of I-C-1 with the PI3K inhibitor LY294002 in IL-1β, IL-6, and TNF-α levels. The data indicated that I-C-1 likely acts as an inhibitor of PI3K, exerting anti-inflammatory effects by inhibiting the PI3K/AKT/NF-κB signaling pathway. Based on these findings, we believe that I-C-1 has the potential to be further developed as a potential therapeutic agent for inflammatory-related diseases.