Effects of CSE on Phase I cytochrome P450s detoxification genes. As mentioned earlier, hCMEC/D3 cell monolayers were exposed to nicotine (100 ng/mL) or CSE derived from 3R4F or ULN cigarettes. Following exposure for 24 h, expression of CYPs-CYP2S1 and CYP51A1 was analyzed by a DNA microarray, b real time PCR for mRNA; and c protein expression was analyzed by western blotting. Representative western blots were shown with actin as a loading control; data were expressed as mean ± SEM (fold change over control). *p < 0.05, **p < 0.01, ***p < 0.001 vs. control. n = 6 biological replicates/condition.