Inhibition of reactive oxygen species down-regulates protein synthesis in RAW 264.7

In order to examine the endoplasmic reticulum responses in macrophages, we stimulate macrophage cell line RAW 264.7 by LPS. We found the phosphorylation of eukaryotic initiation factor eIF2α and the expression of ATF4, GADD34, and GADD153 in RAW 264.7 cells in late time by the relatively large amount of LPS stimulation. Unexpectedly LPS in the presence of ROS inhibitor N-acetyl-l-cysteine rapidly induced phosphorylation of eIF2α and induction of GADD34 expression. We measured intra-cytoplasmic TNFα production in LPS stimulated RAW 264.7 cells. TNFα production induced by LPS stimulation was greatly suppressed by N-acetyl-l-cysteine. This suppression occurred relatively early, which correlated with early eIF2α phosphorylation indicating ER stress mediated shutoff of protein synthesis.