Effect of pharmacologic inhibitors on MEK and iNOS on the induction of COX-2 in RAW264.7 cells exposed to MWCNTs. A) Western blot analysis showing inhibition of COX-2 expression and phosphorylated ERK1,2 (p-ERK1,2) by the MEK inhibitor U0126 relative to vehicle (Veh) in cells treated with 50 μg/ml MWCNTs. Controls (C) were treated with serum-free medium alone. Levels of iNOS were not affected by U0126 (10 μM) at 24 hr post-treatment with MWCNTs, nor were constitutive levels of total ERK1,2 or β-actin. B) Western blot showing inhibition of MWCNT-induced iNOS at 24 hr by L-NAME (250 μM) with no significant effect on MWCNT-induced COX-2 or p-ERK. Numeric values above the Western blot represent the fold-increase in relative densitometric intensity of each band relative to control (zero) nanoparticle treatment which was normalized to 1.0. Data for all three experiments were from duplicate studies which yielded similar results. C) Results of PGE2 ELISA showing that production of PGE2 and release into cell supernatants after 24 hr treatment with MWCNTs (50 μg/ml) is blocked by 10 μM U0126 co-treatment.