Figure 4: Tolerance of Atg5 Tg MEFs to oxidative stress via autophagy activity.

(a) Comparison of Atg12-Atg5 conjugate levels in WT and Atg5 Tg MEFs by western blot analysis. MEFs from WT and Atg5 Tg mice were cultured at embryonic day 13, after which cell extracts were examined by western blot analysis using anti-Atg5 and anti-β-actin antibodies. (b) Increased conversion of LC3 and reduced expression of p62 in Atg5 Tg MEFs no. 6 by rapamycin and/or Baf.A1. WT MEFs no. 1 and Atg5 Tg MEFs no. 6 in passage number 3 were incubated for 48 h with 10 μM rapamycin in the absence or presence of Baf.A1, and cell extracts were then analysed by western blotting. The signals on the blot were quantified by densitometric analysis and represented as the ratio of p62 to β-actin. (c,d) Increased resistance of Atg5 Tg MEFs to oxidative stress. WT MEFs no. 1 and Atg5 Tg MEFs no. 6 were treated for 24 h with 50, 100, 200 and 300 μM H₂O₂ (c) or 300 μM H₂O₂ in the absence or presence of 5 mM 3-MA or 20 nM Baf.A1 (Baf.A1) (d). Cell viability was assessed by propidium iodide staining. The values are the mean±s.e.m. (n=3). **P<0.001, ***P<0.0001 versus control; Student’s t-test. (e) Representative photographs showing the resistance of Atg5 Tg MEFs to oxidative stress. Primary cultured WT and Atg5 Tg MEFs were treated with 300 μM H₂O₂ for 24 h and then observed under a light microscope. Scale bars, 50 μm. (f) Effect of oxidative stress on the autophagy activity in Atg5 Tg MEFs. WT MEFs no. 1 and Atg5 Tg MEFs no. 6 were treated with 100 μM H₂O₂ for 24 h in the presence or absence of 20 nM Baf.A1, and cell extracts were analysed by western blotting. About 10 and 30 μg of proteins were used for LC3 (upper panel) and p62 (bottom panel) detection, respectively. β-Actin served as a control.