Fig. 2
Hypoxia leads to dependence on unsaturated FA whereas saturated FA exert toxic effects. To analyze the influence of serum deprivation and lipid supplementation on the survival of oxic and anoxia-tolerant NCI-H460 cells, cells were cultured for 72 h in standard medium (10 %FCS) or serum-deprived medium (0.5%FCS) without or with additional supplementation of saturated (50 μM palmitic acid, PA) or unsaturated FA (50 μM oleic acid, OA). a Schematic representation of the experimental timeline. b Representative light microscopic pictures of NCI-H460 cells 72 h after treatment under the indicated conditions in normoxia (20 % O2) or severe hypoxia (0.2 % O2). Scale bar = 10 μM. c Representation of the increase in apoptosis as heat map (fold changes; FC). Apoptosis induction was quantified 72 h after treatment by measuring DNA fragmentation upon staining of the cells with PI in a hypotonic citrate buffer (subG1 fraction). d, e Cell death was quantified 72 h after treatment by flow cytometry upon staining the cells with PI under normoxic (d) or severely hypoxic (e) conditions. The increase in cell death levels by a particular treatment is visualized in a heat map representing fold changes (d lower panel, e lower panel). Almost no effect on apoptosis induction (c) or cell death levels (d) was observed in both cell lines under indicated treatment conditions in normoxia. Serum deprivation and supplementation of palmitic acid induced apoptosis and increased cell death levels in both cell lines in severe hypoxia, particularly in anoxia-tolerant NCI-H460 cells (c, e). Supplementation of oleic acid abolished the increase in apoptosis and cell death induced by serum-deprivation without or with PA-supplementation in both cell lines under severe hypoxia (c, e). Mean values ± SD are shown, n = 3. (* p ≤ 0.05, *** p ≤ 0.001; two- way ANOVA with Bonferroni post-test)