9-cis-canthaxanthin exhibits higher pro-apoptotic activity than all-trans-canthaxanthin isomer in THP-1 macrophage cells

All-trans-canthaxanthin (4, 4'-diketo beta-carotene) but not 9-cis-canthaxanthin has been shown to induce Apoptosis in some cell lines. In this study apoptotic activity of 9-cis-canthaxanthin on THP-1 macrophage is reported. Comparison of apoptotic activities of the two canthaxanthin isomers on this cell line by annexin V-cy3 and TUNEL assays indicated the higher pro-apoptotic activity of 9-cis-isomer than the all-trans-isomer. Canthaxanthin-induced Apoptosis in this cell line was found to be accompanied by increased Caspase-3 and Caspase-8 activities, indicating its progression via Caspase cascade. Induction of both Caspase activities was higher by 9-cis-canthaxanthin than that by trans-canthaxanthin. All these results suggest that canthaxanthin stereoisomers differentially induce Apoptosis of THP-1 monocyte/macrophage.