MD-2 expression is up-regulated by IL-6 but not IL-1β. (A) MD-2 mRNA and IL-8 mRNA levels in HepG2, HepaRG, and THP-1 cells stimulated for 6 hours with 10 ng/mL IL-6 and 1 ng/mL IL-1β. Messenger RNA levels were measured by quantitative RT-PCR. Mean plus or minus SD MD-2 mRNA levels were normalized with the expression of GAPDH mRNA and expressed as arbitrary units. This experiment was performed in triplicates and representative of 3 different experiments. (B) Western blot of MD-2 protein (17 kDa) in whole cell lysates from HepG2 cells stimulated with IL-6 and IL-1β. This experiment is representative of 3 different experiments.