The IRE1α pathway participated in apoptosis promoting effect of quercetin. A. Annexin-V/PI assays were performed to assess cell apoptosis, and analyses of early and late phase apoptosis are shown. B, C. Protein expression of mitochondrial apoptosis was valuated, and quantification analysis was shown. Qu, quercetin. Data are shown as the mean ± SEM; n = 4. #P < 0.05, ##P < 0.01 compared with hypoxia-treated PASMCs, &P < 0.05, &&P < 0.01 compared with quercetin-treated PASMCs.