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The role of Ch25h in the macrophage response to poly(I:C) (bone-marrow-derived macrophages)

ABSTRACT: Cross-talk between sterol regulatory pathways and inflammatory pathways has been demonstrated to play an important role in the response to viral infections. 25-Hydroxycholesterol (25HC) is an oxysterol that plays multiple roles in lipid biosynthesis and immunity, and has recently been shown to have anti-viral activity. Surprisingly, we found that deletion of Ch25h, the gene encoding the enzyme responsible for 25HC production, is protective in a mouse model of influenza infection as a result of decreased inflammatory-induced pathology. Anti-viral responses involve complex gene regulatory circuits with multiple feedback loops and we demonstrated that 25HC acts as an amplifier of TLR3 signaling in macrophages and airway epithelial cells. We determined that 25HC amplifies TLR3 signaling, at least in part, by mediating the up-regulation and recruitment of the AP1 components Fos and Jun to the promoters of a subset of TLR3 responsive genes. Thus, our study demonstrates for the first time that in addition to its direct anti-viral role, 25HC also regulates transcriptional responses and acts as an amplifier of TLR3-induced inflammation via AP1.

ORGANISM(S): Mus musculus

PROVIDER: GSE54062 | GEO | 2014/06/20

SECONDARY ACCESSION(S): PRJNA234506

REPOSITORIES: GEO

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Project description:We previously demonstrated that 25HC (25-hydroxycholesterol, a derivative of cholesterol) blocks KSHV (Kaposi Sarcoma-associated Herpesvirus/ Human Herpesvirus-8) de novo infection of primary endothelial cells at a post-entry step and decreases viral gene expression. Herein we sought to determine transcriptomic changes associated with 25HC treatment of primary endothelial cells and primary B cells using RNA sequencing. To understand how 25HC inhibits KSHV infection, we examined global gene expression changes induced by 25HC in HUVECs, with or without KSHV infection. We pre-treated HUVEC with 25HC or vehicle control, then infected with KSHV (four conditions: -/+ 25HC, -/+ infection). At 2 days post-infection (dpi), we harvested RNA and performed RNA-seq to determine differentially expressed genes. We found that 25HC treatment inhibited KSHV gene expression globally and induced several inflammatory cytokines (CXCL8, IL1?), AP-1 components, and innate immunity receptors (RIG-I, TLR2) . Likewise, we also observed 25HC to block EBV de novo infection by inducing apoptosis and blocking transformation into lymphoblastoid cell lines. To determine transcriptomic changes that contributes to this, we purified B cells from healthy donors and infected them with EBV after 25HC pre-treatment with 4 similar conditions mentioned above. Samples were sent for RNA-Seq at 10-12 dpi. In contrast to KSHV infection, we found that only a subset of EBV viral transcripts are downregulated in the 25HC-treated samples. LMP1, which is the primary oncogenic factor, was suppressed and several downstream host targets that would prevent apoptosis during infection were likewise dysregulated. Additionally, several viral noncoding RNAs were also highly downregulated. Further analyses revealed that some 25HC-induced genes in our KSHV data set overlap with antiviral genes that were previously identified in various published screens involving other viruses, demonstrating the broad activity of 25HC. Together, these results answer some important questions about a widely acting antiviral (25HC), with implications for multiple viral and bacterial infections.

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The role of Ch25h in the macrophage response to poly(I:C) (bone-marrow-derived macrophages)

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