Figure 2

ZnO NP mediated pro-inflammation in A549 cells exposed to the sub-cytotoxic dose (20 μg/mL) over 24 hr. (A) ZnO NP induced up-regulation of HO-1 mRNA indicative of a strong antioxidant response in A549 cells. Highest HO-1 expression was seen at 6hr which was a 30-fold increase in gene expression compared to untreated cells at 6hr (p<0.001). Block bars compare the statistical significance between pristine or surfactant-dispersed solutions for each ZnO NP size. (B) mRNA over expression of the pro-inflammatory cytokine IL-8 in A549 cells stimulated with 20 μg/mL of ZnO NPs at 1, 2, 4, 6 or 24hr. Maximum expression of IL-8 gene was recorded at 4hr. (C) Release of pro-inflammatory cytokine IL-8 by ZnO NP-exposed A549 cells at 1, 2, 4, 6 or 24 hr. Statistical significance is shown in (B) and (C) compared to untreated cells at each time point. *p<0.05,**<0.01,***p<0.001, ****p<0.0001. Data are expressed as mean ±SEM of the fold levels compared to untreated controls at each time point (n=3) separate experiments, each performed with triplicates).