Redox regulation of 7-ketocholesterol-induced apoptosis by β-carotene in human macrophages

The aim of this study was to verify the hypothesis that β-carotene may prevent 7-ketocholesterol (7-KC)-induced apoptosis in human macrophages. Therefore, THP-1 macrophages were exposed to 7-KC (5–50 μM) alone and in combination with β-carotene (0.25–1 μM). 7-KC inhibited the growth of macrophages in a dose- and a time-dependent manner by inducing an arrest of cell cycle progression in the G0/G1 phase and apoptosis. Concomitantly, p53, p21, and Bax expressions were increased by 7-KC, whereas the levels of AKT, Bcl-2, and Bcl-xL were decreased. β-Carotene prevented the growth-inhibitory effects of 7-KC in a dose- and time-dependent manner as well as the effects of 7-KC on the expression of cell cycle- and apoptosis-related proteins. 7-KC also enhanced reactive oxygen species (ROS) production through an increased expression of NAD(P)H oxidase (NOX-4). The effects of 7-KC were counteracted by the addition of the NAD(P)H oxidase inhibitor DPI or by cotransfection of siNOX-4 mRNA. β-Carotene prevented 7-KC-induced increase in ROS production and in NOX-4 expression, as well as the phosphorylation of p38, JNK, and ERK1/2 induced by 7-KC. These data suggest a possible antiatherogenic role of β-carotene through the prevention of 7-KC toxicity in human macrophages.