Genome-wide Analysis of Acute Inflammatory and Anti-Inflammatory Responses in RAW264 Cells Suggests cis-Elements Associated with Translational Regulation

Abstract

Translational regulation plays pivotal roles in mediating inflammatory responses. Glucocorticoids, represented in this study by dexamethasone (DEX), are widely recognized anti-inflammatory agents that exert significant inhibitory effects on the translation of diverse gene groups, including inflammatory genes. However, their regulation is highly complex and diverse, involving transcriptional and translational regulation. Although transcriptional regulation has been investigated by genome-wide transcriptome analyses, translational regulation has been studied by only a few specific gene targets (e.g., Tumor necrosis factor) and the global impact of glucocorticoids on translation levels has scarcely been studied, mainly due to its technical difficulty. Here, using ribosome profiling coupled with high-throughput mRNA sequencing (mRNA-Seq) in which footprints of translating ribosomes can be captured, we conducted a genomewide transcriptional and translational analysis of the acute inflammatory or anti-inflammatory responses of RAW264 cells stimulated by lipopolysaccharide (LPS) or LPS coupled with DEX (LPS + DEX). We showed that the majority of the differential regulation between LPS alone and LPS + DEX were predominated by translation levels rather than transcription levels. Further analysis on the up- and down-regulated gene clusters revealed putative cis regulatory elements exclusively enriched in the 3'-UTR of either up- or down-regulated genes induced by LPS + DEX. The results imply an alternative to the currently recognized mechanisms of glucocorticoid-induced translational regulation in the acute inflammatory response of RAW264 cells.