Fig. 5

DQ12 quartz dust and Saharan dust did not induce oxidative stress marker gene expression. Air-liquid interface co-cultures were exposed to DQ12 and Saharan dust (SD) at doses in the range of 0–31 µg/cm² for 24 h or 250 ± 60 ng/cm² LPS for 21 h. The relative gene expression of HMOX1 (A), APE1/REF1 (B), GGCS (C), and NQO1 (D) was assessed by qRT-PCR. The results were normalized to control ALI cultures as well as to the reference genes ACTB and GAPDH. The depicted fold changes with standard deviations were derived from the means of the ΔΔC_T values and standard deviations of the ΔC_T values of N = 4 independent experiments (Controls and LPS: one or two biological replicates; DQ12 and SD: duplicates per concentration). A mixed-effects model with Šidák’s post hoc test was calculated based on the ΔC_T values (no significant differences obtained)