Translational regulation of specific mRNAs controls feedback inhibition and survival during macrophage activation [array]

When macrophages encounter pathogens, they transiently induce an orchestrated cascade of pro- and anti-inflammatory genes. We systematically analyzed the contribution of translational regulation to the early phase of macrophage activation. While the expression of most cytokines is regulated by changes in mRNA levels, de-repression of translation was found to permit expression of many feedback inhibitors of the inflammatory response. This includes NF-kB inhibitors (IkBd, IkBz, Nr4a1, Ier3), a p38 MAPK antagonist (Dusp1) and post-transcriptional suppressors of cytokine expression (TTP and Zc3h12a). Ier3 is tightly co-regulated with TNF at the level of mRNA abundance and translation. Macrophages lacking Ier3 show reduced survival upon activation, indicating that induction of Ier3 is required to protect macrophages from lipopolysaccharide-induced cell death. Our analysis reveals an important role of translational regulation in the resolution of inflammation and macrophage survival. RNA was purified from cytoplasmic lysate or polysome fractionation before and 1 h after stimulation of RAW264.7 macrophages with LPS. Fractions were pooled into four samples per condition: Free RNA (F), 40S-associated RNA (S), light (L) and heavy polysomes (H). The experiment was performed in three biological replicates, and RNA was quantified with GeneChip Mouse Gene 1.0 ST Arrays (Affymetrix).