Full Length Research Paper

Garcinia kola extract reduced lipopolysaccharide activation of macrophages using U937 cells as a model

Tebekeme Okoko¹* and Ibiba F. Oruambo²

¹Biochemistry Division, Department of Chemical Sciences, Niger Delta University, PMB 71, Yenagoa, Bayelsa State, Nigeria.

²Department of Chemistry, River State University of Science and Technology, Port Harcourt, Rivers State, Nigeria.

*Corresponding author. E-mail: tebebuddy@yahoo.com. Tel. +2348051069342.

Former address: Biomedical Division, School of Applied Sciences, University of Northumbria at Newcastle, United Kingdom.

Accepted 4 December, 2007

The effect of Garcinia kola heckel seed extract on the promonocytic cell line U937 activated by lipopolysaccharide (LPS) was investigated. 200 μl of U937 cells maintained in culture at 5 x 10⁵ cells per ml was delivered into wells of a culture plate according to groups. Cells were pre-treated with 20 μl of 100 ng/ml phorbol myristate acetate (PMA) for 24, 48, or 72 h in order to transform them to the macrophage form. Following the PMA treatment, some cells were incubated with 100 μg/ml LPS (group C), while others (group D) were treated with 100 μg/ml LPS and 100 µl of 100 μg/ml of the G. kola methanolic extract. Other cells (groups A, and B) were incubated with neither LPS nor extract. 24 h later, the supernatants were analysed for the production of TNF-α and IL6 as indices for the activation of macrophages. The results show that the G. kola extract reduced the tendency of LPS to activate the cells. However, highest activation of LPS was observed when the cells were incubated with PMA for 48 h prior to the addition of LPS. This suggests that stimulation of U937 cells with PMA is necessary for the production of cytokines and that G. kola possesses considerable immunomodulatory activity.

Key words: Garcinia kola, lipopolysaccharide, phorbol myristate acetate, macrophage, cytokines.