Kolaviron Reduces Cadmium-induced Cytotoxicity and Production of Reactive Oxygen Species by Suppressing Inflammatory Response

The effect of kolaviron (a bi-flavonoid complex extracted from Garcinia kola) on cadmium (Cd)-induced cell death/ production of reactive oxygen species (ROS) in monocyte U937 cells and production of inflammatory markers/ antioxidant enzymes in U937-derived macrophages was investigated. In the first experiment, U937 cells were incubated with or without kolaviron for 24 h before exposed to Cd (10 µM). Cell viability and ROS production were later assessed via MTT reduction and DCHF assays respectively. In the other experiment, U937 cells were transformed to the macrophage form using phorbol 12-myristate 13-acetate and incubated with or without kolaviron for 24 h before exposed to Cd. Subsequently, production of TNF-a, IL-6 were analysed via cytokine ELISA and the expression of NF-κB, iNOS, SOD and catalase were assessed using RT-PCR. The results revealed that Cd caused significant cell death and production of ROS in U937 cells which were reduced by kolaviron in a dose-dependent manner (p < 0.05). Kolaviron also reduced Cd-mediated secretion of TNF-a and IL-6 in U937-derived macrophages which was concentration-dependent for the reduction of TNF-a (p < 0.05). The bi-flavonoid complex also reduced Cd-mediated expression of the transcription factors (NF-κB and iNOS) and the antioxidant enzymes (SOD and catalase) but the observation was only concentration-dependent for the reduction of catalase (p < 0.05). These shows that kolaviron reduced Cd-mediated alterations in monocyte U937 cells and macrophages. Implications are discussed.