DNA damage-independent apoptosis induced by curcumin in normal resting human T cells and leukaemic Jurkat cells

Curcumin, a phytochemical derived from the rhizome of Curcuma longa, is a very potent inducer of cancer cell death. It is believed that cancer cells are more sensitive to curcumin treatment than normal cells. Curcumin has been shown to act as a prooxidant and induce DNA lesions in normal cells. We were interested in whether curcumin induces DNA damage and the DNA damage response (DDR) signalling pathway leading to apoptosis in normal resting human T cells. To this end, we analysed DNA damage after curcumin treatment of resting human T cells (CD3) and of proliferating leukaemic Jurkat cells by the fluorimetric detection of alkaline DNA unwinding (FADU) assay and immunocytochemical detection of -H2AX foci. We showed that curcumin-treated Jurkat cells and resting T cells showed neither DNA lesions nor did they activate key proteins in the DDR signalling pathway, such as phospho-ATM and phospho-p53. However, both types of cell were equally sensitive to curcumin-induced apoptosis and displayed activation of caspase-8 but not of DNA damage-dependent caspase-2. Altogether, our results revealed that curcumin can induce apoptosis of normal resting human T cells that is not connected with DNA damage.