The influence of royal jelly and human interferon-alpha (HuIFN-αN3) on proliferation, glutathione level and lipid peroxidation in human colorectal adenocarcinoma cells in vitro

Among royal jelly's (RJ) various biological activities, its possible antitumour activity deserves particular attention. The purpose of this study was to investigate the influence of RJ, its bioactive component 10-hydroxy-2-decenoic acid (10-HDA), and human interferon-alpha (HuIFN-alpha N3) on the proliferation of human colorectal adenocarcinoma cells (CaCo-2), and ascertain their effect on intracellular glutathione (GSH) level and lipid peroxidation. We studied the antiproliferative (AP) activity of RJ [(0.1 g/10 mL phosphate buffer saline (PBS)], HuIFN-alpha N3 (1000 I.U. mL(-1)), 10-HDA at 100.0 mu mol L-1, and their different combinations, in the ratio 1:1, 1:2, and 2:1 on CaCo-2 cells. The GSH level was measured by glutathione assay. The lipid peroxidation was measured by malondialdehyde (MDA) assay. Single RJ had a low AP activity: 2.0 (0.5 mg mL(-1)). HuIFN-alpha N3 had an AP activity of 2.5 (208.33 I.U. mL(-1)), while 10-HDA had an AP activity of 1.5 (37.5 mu mol mL(-1)). The highest AP activity of 3.8 was obtained when RJ and HuIFN-alpha N3 were applied at the ratio 2:1. In that combination the level of GSH was 24.9 +/- 2.4 nmol g(-3) of proteins (vs. 70.2 +/- 3.2 nmol g(-3) in the control) and the level of MDA was 72.3 +/- 3.1 nmol g(-3) (vs. 23.6 +/- 9.1 nmol g(-3) in the control). It is generally assumed that 10-HDA, an important constituent of RJ, together with HuIFN-alpha N3, is responsible for the inhibition of CaCo-2 cells proliferation in vitro. In our study, however, RJ and HuIFN-alpha N3 applied at 2:1 decreased the level of GSH the most and significantly increased lipid peroxidation via MDA in CaCo-2 cells. Future studies should show whether these GSH-and MDA-related activities of RJ, HuIFN-alpha N3, 10-HDA, and their combinations may decrease the tumorigenicity index and tumorigenic potential of various tumour cells in vitro.