Arctoscopus japonicus lipids inhibit anti-inflammatory efficacy via eicosanoid synthesis pathways in activated macrophages

Abstract

The most effective lipid mediators in inflammation are eicosanoids, which involve numerous enzymes such as cyclooxygenases (COX), lipoxygenases (LOX), and cytochrome P450 (CYP). Arctoscopus japonicus lipids (AJL) have been shown to inhibit inflammation, but their effects on cellular mechanisms via lipid mediators remain unclear. In this study, we examined the eicosanoid synthesis pathways for the anti-inflammatory effects of AJL in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. AJL significantly reduced LPS-activated macrophages the production of pro-inflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α), as well as the expression of interferon-γ (IFN-γ) and IL-12. It also increased the expression of anti-inflammatory cytokines transforming growth factor-β (TGF-β) and IL-10. AJL inhibited LPS-activated COX, LOX, and CYP metabolites from producing thromboxane A₂ (TXA₂), prostaglandins (PG) H₂, PGI₂, PGE₂, and PGF_2α, leukotriene B₄ (LTB₄), as well as epoxyeicosatrienoic acids (EETs). Furthermore, AJL decreased LPS-induced the expression of both of COXs (COX-1 and COX-2) and 5-LOX mRNAs and proteins in the COX and LOX pathways, respectively. AJL also suppressed the expression of CYP4A11 proteins in the CYP pathway. Furthermore, CD86 expression was down regulated by AJL in LPS-stimulated cells. These findings conclusively reveal that AJL modulates eicosanoid synthesis pathways, contributing to its anti-inflammatory properties.