Particle-dependent impact on the mRNA regulation of HO-1 and iNOS. NR8383 cells were treated with 10 or 40 μg/cm2 of the indicated particles for 4 h in complete culture medium (A and C) or HBSS (B and D). In medium (A), ufTiO2 and DQ12 trigger mRNA upregulation of the stress-response gene HO-1 in a concentration-dependent manner, whereas in HBSS (B) a significant induction was only observed with DQ12. The synthesis of the inflammatory marker iNOS is induced on the mRNA level by both ufTiO2 and DQ12 at a concentration of 40 μg/cm2 in medium (C) as well as in HBSS (D). In HBSS, DQ12 also elicited significant induction of iNOS at the lower treatment concentration. All data are corrected for GAPDH. Figures represent mean ± SEM of seven (A, C) or three (B, D) independent experiments, with * p < 0.05, ** p < 0.01 and *** p < 0.001 vs. medium control (ANOVA with LSD post-hoc comparison).