Methyl 5-Chloro-4,5-didehydrojasmonate (J7) Inhibits Macrophage-Derived Chemokine Production via Down-Regulation of the Signal Transducers and Activators of Transcription 1 Pathway in HaCaT Human Keratinocytes

Jasmonates are lipid-based stress hormones that are critical for the defense of plants against insects. Two naturally occurring jasmonates, jasmonic acid and methyl jasmonate, have recently been explored for their efficacy as anti-cancer agents. Furthermore, certain synthetic jasmonates (e.g., the cyclopentenone isoprostane J2) exert anti-inflammatory actions in lipopolysaccharide (LPS)-challenged murine macrophages via down-regulation of chemokines and other inflammatory mediators. Chemokines participate in the development and progression of many inflammatory disorders, such as atopic dermatitis (AD) and Crohn's disease, as exemplified by the role of macrophage-derived chemokine (MDC/CCL22) in the pathology of AD. The current study therefore investigated the impact of jasmonate derivatives (jasmonic acid and methyl jasmonate) and their synthetic analogues (J2 and J7) on the expression of MDC in interferon (IFN)-gamma- and tumor necrosis factor (TNF)-alpha-stimulated HaCaT human keratinocytes, as well as the attendant mechanism of action. Jasmonic acid, methyl jasmonate, and J2 failed to inhibit the cytokine-stimulated production of MDC. By contrast, J7 suppressed the mRNA and protein expression levels of MDC in a dose-dependent manner. Moreover, J7 diminished the activation of signal transducers and activators of transcription 1 (STAT1), but had no inhibitory effect on the nuclear factor kappa B (NF-kappa B) or mitogen-activated protein kinase (MAPK) pathways. These results demonstrate that J7 impairs IFN-gamma- and TNF-alpha-induced inflammatory chemokine production by targeting the STAT1 pathway.