Methyl Dehydro-Jasmonate Has Anti-Inflammatory Effect Cells and Its Molecular Targets Mir-155 and NF-Kb Pathway against LPS Stimulation On RAW264.7.

Abstract 1357

Poster Board I-380

Jasmonic acid and methyl jasmonate are fatty acid-derived cyclopentanones, found in the plants, and play major roles in a defense against insects and disease. Methyl jasmonate suppresses cellular proliferation and induces apoptosis in human and mouse cancer cell lines. Methyl jasmonate increased the life span of EL-4 lymphoma-bearing mice with selective cytotoxicity against lymphoma cells while sparing normal blood lymphocytes.

Inflammation is one of the defence mechanisms against pathogens, caused by diverse microbial products. Microbial products are detected by the Toll-like receptors (TLRs) that are expressed at high levels on macrophages and dendritic cells. The complex of the TLRs and their ligand initiates a wide spectrum of responses from phagocytosis to production of a variety of cytokines, which enhance the inflammatory and adaptive immune responses. Of these TLRs, TLR4 recognizes the product of gram-negative bacteria, LPS. LPS stimulated-cells produce inflammatory cytokines (TNF-α and IL-6), and inducible enzymes of iNOS and COX-2. Recent evidence reveal that some microRNAs (miRNAs) play important roles in inflammation; miRNA-146a plays central roles in the negative feedback regulation of IL-1b-induced inflammation and miR-155 enhances the release of inflammatory mediators during the innate immune responses. Our structural analysis shows that methyl jasmonate contains enone group which is a common functional moiety in anti-inflammatory drugs. Our previous works found that methyl jasmonate has anti-inflammatory effects and the related compound methyl dehydro-jasmonate (J2) had the highest anti-inflammatory effect in lipopolysaccharide (LPS)-activated RAW264.7 murine macrophage cells of all synthesized methyl jasmonate analogues. In this study, we wanted to elucidate molecular targets of J2 action in its anti-inflammatory properties. We observed that a LPS stimulation of RAW264.7 cell line also induced known inflammatory markers; TNF-α, IL-6, iNOS and COX-2. Our analysis of miRNAs changes revealed an increase of miR-155 (>8 fold) and miR-146a (>3 fold), but not miR-125b. In a J2 toxicity test on the LPS stimulated RAW264.7 cells, the J2 treatment protected LPS treated RAW264.7 cells starting at 6.25 μM. We then tested J2 effects on various mediators of inflammation. We found that J2 suppressed inductions of TNF-α, IL-6, iNOS and COX-2 at a transcript level in a dose-dependent manner (IC50 = 18∼25 μM) and confirmed it also at a protein level for iNOS and COX-2. We then found that miR-155 induction was inhibited by J2 dose-dependent manner, J2 suppressed miR-146a only at 50 μM. The NF-kB pathway and MAPK pathway are thought to be important mediators of LPS induced inflammation and we show that J2 had significant effects on NF-kB, p65, and IkB while no or minimal effect on JNK, p38, and ERK.

In conclusion, the present study demonstrates that J2 supressed LPS stimulation in RAW264.7 cells and it targets miR-155, and NF-kB pathway. In addition, our results also suggest that MAPK pathway may not contribute to the induction of inflammatory markers (i.e. TNF-α, IL-6, iNOS, and COX-2).