NAO facilitating opto-activated apoptosis in a CL-dependent manner. (a) Cells were treated with NAO (100 nM) for 30 min and light exposure (5.7 W/cm2) for 30 min, and PS externalization by Annexin V binding was analyzed at different time points (0.5, 6, 24, 48, and 72 h) after treatments. (b) Cells were treated with NAO for 30 min and exposed to light at different intensities (W/cm2) for 30 min. At 24 h after treatment, cells were collected for analysis of PS externalization. (c) NAO-loaded cells were exposed to light as described in a, and caspase activity was measured at 24 h. (d) WT and CL-deficient (induced by CLS knockdown) HeLa cells were treated with NAO and light as described in a. Cells were collected at different time points (0.5, 24, 48, and 72 h) for analysis of PS externalization. CLS KD: cardiolipin synthase knockdown. Mean ± SD (N = 3). #p < 0.05 vs nontreated controls. *p < 0.05 vs light only treated controls; $p < 0.05 vs WT cells under the same conditions.