The mammalian inflammatory response to infection involves the induction of several hundred genes, a process that must be carefully regulated to achieve pathogen clearance and prevent the consequences of unregulated expression, such as cancer. Recently, microRNAs (miRNAs) have emerged as a class of gene expression regulators that has also been linked to cancer. However, the relationship between inflammation, innate immunity, and miRNA expression is just beginning to be explored. In the present study, we use microarray technology to identify miRNAs induced in primary murine macrophages after exposure to polyriboinosinic:polyribocytidylic acid or the cytokine IFN-β. miR-155 was the only miRNA of those tested that was substantially up-regulated by both stimuli. It also was induced by several Toll-like receptor ligands through myeloid differentiation factor 88- or TRIF-dependent pathways, whereas up-regulation by IFNs was shown to involve TNF-α autocrine signaling. Pharmacological inhibition of the kinase JNK blocked induction of miR-155 in response to either polyriboinosinic:polyribocytidylic acid or TNF-α, suggesting that miR-155-inducing signals use the JNK pathway. Together, these findings characterize miR-155 as a common target of a broad range of inflammatory mediators. Importantly, because miR-155 is known to function as an oncogene, these observations identify a potential link between inflammation and cancer.

https://www.pnas.org/content/pnas/104/5/1604.full.pdf

MicroRNA-155 is induced during the macrophage inflammatory response

The presence of single nucleotide polymorphisms in microRNA genes, their processing machinery and target binding sites might affect cancer risk, treatment efficacy and patient prognosis. This evolving field of cancer biology is discussed in this Review.

Genetic variation in microRNA networks: the implications for cancer research

The integrity of the endothelial monolayer is fundamental for the homoeostasis of the vascular system. Functional endothelial cells are also required for the growth of new blood vessels during neovascularization. Although multiple growth factors have been shown to regulate angiogenesis and vascular development, little is known about the complex upstream regulation of gene expression and translation. MicroRNAs (miRNAs) are an emerging class of highly conserved, non-coding small RNAs that regulate gene expression on the post-transcriptional level by inhibiting the translation of protein from mRNA or by promoting the degradation of mRNA. More than 500 human miRNAs have been identified so far, and increasing evidence indicates that miRNAs have distinct expression profiles and play crucial roles in various physiological and pathological processes such as cardiogenesis, haematopoietic lineage differentiation, and oncogenesis. Meanwhile, a few specific miRNAs that regulate endothelial cell functions and angiogenesis have been described. Let7-f, miR-27b, and mir-130a were identified as pro-angiogenic miRNAs. In contrast, miR-221 and miR-222 inhibit endothelial cell migration, proliferation, and angiogenesis in vitro by targeting the stem cell factor receptor c-kit and indirectly regulating endothelial nitric oxide synthase expression. Moreover, some miRNAs are involved in tumour angiogenesis such as the miR-17-92 cluster and miR-378. Early studies also indicate the contribution of specific miRNAs (e.g. miR-155, miR-21, and miR-126) to vascular inflammation and diseases. Thus, the identification of miRNAs and their respective targets may offer new therapeutic strategies to treat vascular diseases such as atherosclerosis, to improve neovascularization after ischaemia, or to prevent tumour progression.

Role of microRNAs in vascular diseases, inflammation, and angiogenesis

Objective
MicroRNAs (miRNA) have recently emerged as a new class of modulators of gene expression. In this study we investigated the expression, regulation, and function of miR-155 and miR-146a in rheumatoid arthritis (RA) synovial fibroblasts (RASFs) and RA synovial tissue.

Methods
Locked nucleic acid microarray was used to screen for differentially expressed miRNA in RASFs treated with tumor necrosis factor α (TNFα). TaqMan-based real-time polymerase chain reaction was applied to measure the levels of miR-155 and miR-146a. Enforced overexpression of miR-155 was used to investigate the function of miR-155 in RASFs.

Results
Microarray analysis of miRNA expressed in RASFs treated with TNFα revealed a prominent up-regulation of miR-155. Constitutive expression of both miR-155 and miR-146a was higher in RASFs than in those from patients with osteoarthritis (OA), and expression of miR-155 could be further induced by TNFα, interleukin-1β, lipopolysaccharide, poly(I-C), and bacterial lipoprotein. The expression of miR-155 in RA synovial tissue was higher than in OA synovial tissue. Enforced expression of miR-155 in RASFs was found to repress the levels of matrix metalloproteinase 3 (MMP-3) and reduce the induction of MMPs 3 and 1 by Toll-like receptor ligands and cytokines. Moreover, compared with monocytes from RA peripheral blood, RA synovial fluid monocytes displayed higher levels of miR-155.

Conclusion
This study provides the first description of increased expression of miRNA miR-155 and miR-146a in RA. Based on these findings, we postulate that the inflammatory milieu may alter miRNA expression profiles in resident cells of the rheumatoid joints. Considering the repressive effect of miR-155 on the expression of MMPs 3 and 1 in RASFs, we hypothesize that miR-155 may be involved in modulation of the destructive properties of RASFs.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/art.23386

Altered expression of MicroRNA in synovial fibroblasts and synovial tissue in rheumatoid arthritis.

https://hal.archives-ouvertes.fr/hal-00488806/document

miR-155 gene: a typical multifunctional microRNA.

The Human Angiotensin II Type 1 Receptor +1166 A/C Polymorphism Attenuates MicroRNA-155 Binding

MicroRNA-155 Regulates Human Angiotensin II Type 1 Receptor Expression in Fibroblasts

Both angiotensin II (ANG II) and transforming growth factor-β1 (TGF-β1) are thought to be involved in mediating pulmonary fibrosis. Interactions between the renin-angiotensin system (RAS) and TGF-β1 have been well documented, with most studies describing the effect of ANG II on TGF-β1 expression. However, recent gene expression profiling experiments demonstrated that the angiotensin II type 1 receptor (AT1R) gene was a novel TGF-β1 target in human adult lung fibroblasts. In this report, we show that TGF-β1 augments human AT1R (hAT1R) steady-state mRNA and protein levels in a dose- and time-dependent manner in primary human fetal pulmonary fibroblasts (hPFBs). Nuclear run-on experiments demonstrate that TGF-β1 transcriptionally activates the hAT1R gene and does not influence hAT1R mRNA stability. Pharmacological inhibitors and specific siRNA knockdown experiments demonstrate that the TGF-β1 type 1 receptor (TβRI/ALK5), Smad2/3, and Smad4 are essential for TGF-β1-stimulated hAT1R expression. Additional pharmacological inhibitor and small interference RNA experiments also demonstrated that p38 MAPK, JNK, and phosphatidylinositol 3-kinase (PI3K) signaling pathways are also involved in the TGF-β1-stimulated increase in hAT1R density. Together, our results suggest an important role for cross talk among Smad, p38 MAPK, JNK, and PI3K pathways in mediating the augmented expression of hAT1R following TGF-β1 treatment in hPFB. This study supports the hypothesis that a self-potentiating loop exists between the RAS and the TGF-β1 signaling pathways and suggests that ANG II and TGF-β1 may cooperate in the pathogenesis of pulmonary fibrosis. The synergy between these systems may require that both pathways be simultaneously inhibited to treat fibrotic lung disease.

/pdf/tgf-b1-stimulates-human-at1-receptor-expression-in-lung-2hsr7jqt3l.pdf

Jessica A. Buckenberger

Papers

The Human Angiotensin II Type 1 Receptor +1166 A/C Polymorphism Attenuates MicroRNA-155 Binding

MicroRNA-155 Regulates Human Angiotensin II Type 1 Receptor Expression in Fibroblasts

TGF-β1 stimulates human at1 receptor expression in lung fibroblasts by cross talk between the Smad, p38 MAPK, JNK, and PI3K signaling pathways

TGF-β1 regulation of human AT1 receptor mRNA splice variants harboring exon 2.