STAT1-Dependent Signal Integration between IFNγ and TLR4 in Vascular Cells Reflect Pro-Atherogenic Responses in Human Atherosclerosis

Abstract

Signal integration between IFNγ and TLRs in immune cells has been associated with the host defense against pathogens and injury, with a predominant role of STAT1. We hypothesize that STAT1-dependent transcriptional changes in vascular cells involved in cross-talk between IFNγ and TLR4, reflect pro-atherogenic responses in human atherosclerosis. Genome-wide investigation identified a set of STAT1-dependent genes that were synergistically affected by interactions between IFNγ and TLR4 in VSMCs. These included the chemokines Cxcl9, Ccl12, Ccl8, Ccrl2, Cxcl10 and Ccl5, adhesion molecules Cd40, Cd74, and antiviral and antibacterial genes Rsad2, Mx1, Oasl1, Gbp5, Nos2, Batf2 and Tnfrsf11a. Among the amplified genes was also Irf8, of which Ccl5 was subsequently identified as a new pro-inflammatory target in VSMCs and ECs. Promoter analysis predicted transcriptional cooperation between STAT1, IRF1, IRF8 and NFκB, with the novel role of IRF8 providing an additional layer to the overall complexity. The synergistic interactions between IFNγ and TLR4 also resulted in increased T-cell migration and impaired aortic contractility in a STAT1-dependent manner. Expression of the chemokines CXCL9 and CXCL10 correlated with STAT1 phosphorylation in vascular cells in plaques from human carotid arteries. Moreover, using data mining of human plaque transcriptomes, expression of a selection of these STAT1-dependent pro-atherogenic genes was found to be increased in coronary artery disease (CAD) and carotid atherosclerosis. Our study provides evidence to suggest that in ECs and VSMCs STAT1 orchestrates a platform for cross-talk between IFNγ and TLR4, and identifies a STAT1-dependent gene signature that reflects a pro-atherogenic state in human atherosclerosis.

Pre-infection transcript levels of FAM26F in peripheral blood mononuclear cells inform about overall plasma viral load in acute and post-acute phase after simian immunodeficiency virus infection

“…Its expression is upregulated by numerous signalling pathways that are likely to act synergistically (Chmielewski et al , 2014). FAM26F expression on dendritic cells increases after TLR3 via polyI : C or TLR4 stimulation (Chmielewski et al , 2014; Ebihara et al , 2010; Lee et al , 2014), upon IFN-β exposure (Lee et al , 2014), by stimulating the dectin-1 pathway (Chiba et al , 2014) and after murine cytomegalovirus (MCMV) infection (Manh et al , 2013). Furthermore, deletion of IFNRA1 (IFN-α and IFN-β receptor) in mice resulted in abrogation of FAM26F induction by polyI : C (Kasamatsu et al , 2014).…”

“…Depending on the initial signal, IRF-3 and TICAM-1/TRIF (Ebihara et al , 2010) or IRF-5 (Chiba et al , 2014) are required, since their deletion results in loss of or markedly reduced FAM26F expression in dendritic cells/macrophages and impaired activation and cytolytic function of NK cells. These pathways can merge in STAT1 activation, which probably switches on FAM26F transcription (Chmielewski et al , 2014; Lee et al , 2014). …”

“…However, its effect was moderate and is likely to depend on the pre-activation status of the lymphocytes. In other species, IFN-γ alone (Brown et al , 2010; Chmielewski et al , 2014) or IFN-γ in combination with lipopolysaccharide or IFN-β (Chmielewski et al , 2014; Zhang et al , 2010) also leads to an increase of FAM26F RNA in different immune cells. Depletion of IFN-γ with a monoclonal antibody in human patients resulted in downregulation of FAM26F in blood cells (Welcher et al , 2015).…”

“…Activation of dendritic cells/macrophages via IFN- α / β receptor (IFNAR), TLR3, TLR4 and/or dectin-1 and pathogens results in increased FAM26F expression probably through activation of STAT1 (Chiba et al , 2014; Chmielewski et al , 2014; Ebihara et al , 2010; Kasamatsu et al , 2014; Lee et al , 2014; Zhang et al , 2010). Deletion of IRF-3 or IRF-5 reduces FAM26F expression in mice (Chiba et al , 2014; Ebihara et al , 2010).…”

Targeted inhibition of STATs and IRFs as a potential treatment strategy in cardiovascular disease

“…Together, this coordinates the antimicrobial and inflammatory synergism between IFNγ and TLRs in immune cells [70–73]. Recently, we characterized the role of STAT1 in the transcriptional response pathways involved in the interaction between IFNγ and TLR4 signaling in ECs and VSMCs [74]. Promoter analysis of the genes encoding multiple chemokines, adhesion molecules and antiviral and antibacterial response proteins followed by chromatin immunoprecipitation followed by qPCR (ChIP-qPCR), predicted that cooperation between NF-κB, STAT1 and/or IRFs is involved in the transcriptional regulation of transcriptional responses to IFNγ and LPS [74].…”