Control or shATG5 HEK293 cells stably expressing mito-Keima. Control cells were treated with DMSO, 200 µM H2O2, or 4 mM 3-NPA for 2 h, and shATG5 cells were treated with 200 µM H2O2 as a negative control. Cells were then imaged with 458 nm (measuring mitochondria with a neutral pH) and 561 nm (measuring mitochondria with an acidic pH) laser excitation for mito-Keima by confocal microscopy. Right panels show the pixel intensity of red (mitochondria within lysosomes) and green (mitochondria in the cytoplasm) from a line. Scale bar, 10 µm. Quantification of the relative ratio of red to green fluorescence intensity (561 nm/458 nm) of the cells described in (E). Data are presented as mean ± SD (n = 3 independent experiments, 20 cells per experiment), statistical significance was assessed by a two-way ANOVA, N.S., not significant, **p < 0.01. 