Figure 3.

Quercetin increased the susceptibility to FasL-induced apoptosis in senescent human lung fibroblasts. Caspase-3 activity, cell viability, and lactate dehydrogenase (LDH) release by senescent lung fibroblasts from normal patients (NL) (A–C) and patients with stable (D–F) or rapidly progressing IPF (G–I) (stable IPF and rapid IPF, respectively) after 24-hour treatment with vehicle (DMSO 0.05%), quercetin (50 μM), FasL (75 ng/ml), or quercetin + FasL. Caspase-3 activity was expressed as relative fluorescence units (RFU) normalized to β-actin concentrations, cell viability as optical density (OD) values at 450 nm, and LDH release as the difference in the absorbance values at 490 and 680 nm. Data are presented as mean ± SEM (n = 3 or 4 per group). *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; and ****P ≤ 0.0001 as indicated by the bars.