Figure 2. Effects of different HSP70-inducing agents.

(A) Cells were treated with or without each HSP70-inducing agent: geldanamycin (GA), alkannin (A), oxymatrine (Oxy), osthole (Ost), shikonin (S) and palmatine chloride (P), at a dose of 1 µM for 24 h. Western blot analysis was performed with HSP70 protein (30 µg protein in each group). (B) Cells were exposed to UVB light (40 mJ/cm²) after the pretreatment with: geldanamycin (GA), alkannin (A), oxymatrine (Oxy), osthole (Ost), shikonin (S) and palmatine chloride (P), at a dose of 1 µM for 24 h. (C) DNA fragmentation assay was carried out after 6 h incubation at 37°C. Data are presented as mean ± S.D (n = 5). *p<0.001, **p<0.01. (D) Early apoptosis (cells positive for annexin V-FITC and negative for PI), and secondary necrosis (cells positive for both annexin V-FITC and PI). The percentages of early apoptosis and secondary necrosis were analyzed 6 h after UVB radiation by flow cytometry. Data are presented as mean ± S.D (n = 5). *p<0.001, **p<0.01.