Inhibition of Phosphorylated c-Jun NH(2)-terminal Kinase by 2',4'-dihydroxy-6-methoxy-3,5-dimethylchalcone Isolated from Eugenia aquea Burm f. Leaves in Jurkat T-cells

Abstract

Background: Indonesian medicinal plants have been used for their anticancer activity for decades. However, the therapeutic effects of medicinal plants have not been fully examined scientifically. As cancer is a major health problem worldwide, searching for a new anticancer compound has attracted considerable attention. Our previous study found that 2',4'-dihydroxy-6-methoxy-3,5-dimethylchalcone, an active compound isolated from leaves of Indonesian medicinal plants Eugenia aquea Burm f. (Myrtaceae), had anticancer activity in MCF-7 human breast cancer cells through induction of apoptosis.

Objective: To investigate the molecular mechanism of 2',4'-dihydroxy-6-methoxy-3,5-dimethylchalcone antiproliferative activity.

Materials and methods: Leaves of E. aquea were extracted by ethanol, fractionated by ethyl acetate, n-hexane, or water, and isolated for its active compound. Jurkat T-cells were treated with 2',4'-dihydroxy-6-methoxy-3,5-dimethylchalcone for 12 and 24 h, and a cell viability assay and real-time-reverse transcriptase polymerase chain reaction for interleukin-2 (IL-2) mRNA measurement were performed. The effects of active compound to mitogen-activated protein kinases were also examined to investigate the mechanism of its antiproliferative activity.

Results: 2',4'-dihydroxy-6-methoxy-3,5-dimethylchalcone inhibited Jurkat T-cell proliferation with a half maximal inhibitory concentration of 59.5 mM. Although IL-2 mRNA expression was slightly increased after treatment, it inhibited c-Jun N-terminal kinase expression but not p38 and extracellular signal-regulated kinase expression.

Conclusions: Our study indicated that the molecular mechanism mediating the antiproliferative activity of 2',4'-dihydroxy-6-methoxy-3,5-dimethylchalcone may be attributed to the stimulation of an immunological microenvironment in the cells.

Summary: 2',4'-dihydroxy-6-methoxy-3,5-dimethylchalcone was isolated from Eugenia aquea. The antiproliferative activity of 2',4'-dihydroxy-6- methoxy-3,5-dimethylchalcone significantly showed in Jurkat T-cells with a half maximal inhibitory concentration of 59.5 mM through inhibition of c-Jun N-terminal kinase phosphorylation. Interleukin-2 mRNA expression was also slightly increased after treatment with the compound, and this result may be indicated to the stimulation of the immunological microenvironment in T-cells. Abbreviations used:E. aquea: Eugenia aquea, IL-2: Interleukin-2, MAPK: Mitogen-activated protein kinase, ERKs: Extracellular signal-regulated kinases, JNKs: c-Jun N-terminal kinases, p38: p38 MAPK, PI3K: Phosphatidylinositol-3 kinase, IC₅₀: Half maximal inhibitory concentration.

Keywords: Indonesia; c-Jun N-terminal kinase; interleukin-2; proliferation.

Figure 1

Structure of 2’,4’-dihydroxy-6-methoxy-3,5-dimethylchalcone, the active compound isolated from Eugenia aquea

Figure 2

Inhibition of Jurkat cells proliferation after treatment with 2’,4’-dihydroxy-6-methoxy-3,5-dimethylchalcone in various concentrations for 12 or 24 h

Figure 3

The active compound of Eugenia aquea stimulated interleukin-2 mRNA expression in Jurkat cells after a 24 h treatment of vehicle, 2’,4’-dihydroxy-6-methoxy-3,5-dimethylchalcone, or ionomycin

Figure 4

The active compound of Eugenia aquea inhibited phosphorylation of c-Jun N-terminal kinase at indicated times by Western blot analysis and densitometer (a) but not extracellular signal-regulated kinase or p38 (b)