Quantitative real-time Polymerase Chain Reaction (qPCR) was performed using TaqMan® Probe-Based Gene Expression Assays supplied by Applied Biosystems, Life Technologies (Carlsbad, CA). Individual TaqMan gene expression assays were selected for nuclear factor erythroid-derived 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Briefly, total RNA was isolated from lung tissue of mice fed 0% FS, 10% FS, 10% FLC or 20% FLC for 3 weeks using a commercially available kit: RNeasy Plus Mini Kit, supplied by Qiagen (Valencia, CA). Total RNA was quantified using a NanoDrop 2000 (ThermoFisher Scientific, Waltham, MA). Reverse transcription of RNA to cDNA was then performed on a Veriti® Thermal Cycler using the high capacity RNA to cDNA kit supplied by Applied Biosystems, Life Technologies. qPCR was performed using 25 ng of cDNA per reaction well on a StepOnePlus™ Real-Time PCR System (Applied Biosystems). Gene expression data was normalized to 18S ribosomal RNA and was calibrated to untreated control samples according to the ΔΔCT method.