(P01-020-24) Anti-Inflammatory Effect of 3-Hydroxy-Beta-Ionone in Lipopolysaccharide-Stimulated Macrophages

Objectives: We recently reported that 3-hydroxy-β-ionone (HBI), an apocarotenoid, is a potential anti-inflammatory compound in Spirulina platensis, a blue-green algae. Therefore, we investigated the effects of HBI on inflammation and oxidative stress in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages (RAW macrophages) and mouse bone marrow-derived macrophages (BMMs). Also, we explored whether LPS and HBI can modulate the mitochondrial unfolded protein response (UPR^mt) pathway to exert their effect on the inflammatory pathway.

Methods: RAW macrophages and BMMs isolated from C57BL/6 mice were pretreated with DMSO vehicle or 1 μM HBI for 12 h and then stimulated with 100 ng/mL LPS for 18 h to measure mRNA and protein expression, cytokine secretion, and cellular reactive oxygen species (ROS) accumulation. Also, cells were pretreated with DMSO or HBI for 15 h, followed by 1 h LPS stimulation to analyze nuclear factor kappa B (NFκB) p65 nuclear translocation.

Results: LPS markedly increased the expression of pro-inflammatory genes, such as tumor necrosis factor (Tnf), interleukin-1 beta (Il-1β), and Il-6, and TNFα secretion concomitantly with increased nuclear translocation of NFκβ p65 in RAW macrophages and BMMs. However, HBI inhibited the LPS-induced pro-inflammatory features. Increased cellular ROS accumulation by LPS was significantly, but modestly, attenuated by HBI with no significant changes in antioxidant genes in RAW macrophages. The expression of several UPR^mt genes, including mitochondrial chaperones and proteases, was significantly induced by LPS, but HBI did not alter their expression. However, at the protein levels, UPR^mt proteins, such as heat shock protein 60, lon peptidase 1, and caseinolytic protease proteolytic subunit, were noticeably increased by LPS, which were attenuated by HBI in RAW macrophages.

Conclusions: HBI exerted potent anti-inflammatory action with a minimal antioxidant effect in LPS-stimulated macrophages. Also, LPS increased UPR^mt genes, which were attenuated by HBI at the protein level. Future study is warranted to unveil the role of the UPR^mt pathway in the inflammatory response and whether HBI can modulate this pathway to play its anti-inflammatory role in macrophages.

Funding Sources: Supported by the funds from the College of Agriculture, Health and Natural Resources at the University of Connecticut