Genetic polymorphism directs IL-6 expression in fibroblasts but not selected other cell types

Abstract

Interleukin (IL)-6 blockade is an effective treatment for rheumatoid arthritis (RA), and synovial fibroblasts are a major IL-6 producer in the inflamed joint. We found that human RA and osteoarthritis (OA) synovial fibroblasts derived from independent donors reproducibly segregated into low, medium, and high IL-6 producers, independent of stimulus, cell passage, or disease state. IL-6 expression pattern correlated strongly with total mRNA expression, not mRNA stability, suggesting transcriptional rather than posttranscriptional regulation. High-fibroblast IL-6 expression was significantly associated with the IL-6 proximal promoter single nucleotide polymorphism (SNP) rs1800795 minor allele (CC) genotype. In contrast, no association between this SNP and IL-6 production was detected in CD14+ monocytes, another major producer of synovial IL-6. Luciferase expression assays confirmed that this SNP was associated with differential IL-6 expression in fibroblasts. To date, several association studies examining rs1800795 allele frequency and disease risk have reported seemingly conflicting results ranging from no association to association with either the major or minor allele across a spectrum of conditions, including cancer and autoimmune, cardiovascular, infectious, and metabolic diseases. This study points to a prominent contribution from promoter genetic variation in fibroblast IL-6 regulation, but not in other IL-6–producing cell types. We propose that some of the heterogeneity in these clinical studies likely reflects the cellular source of IL-6 in specific diseases, much of which may be produced by nonhematopoietic cells. These results highlight that functional analysis of disease-associated SNPs on gene expression and pathologic processes must consider variation in diverse cell types.

Autocrine Loop Involving IL-6 Family Member LIF, LIF Receptor, and STAT4 Drives Sustained Fibroblast Production of Inflammatory Mediators

“…To partially model the inflammatory milieu in RA, we examined the in vitro responses of primary cultured human fibroblasts, including those from synovial, skin and lung tissues after stimulation with TNF or the combination of TNF and IL-17 (Noss et al, 2015; Zrioual et al, 2009). Fibroblasts responded dramatically to the combined stimulation of TNF and IL-17 compared to TNF or IL-17 alone by producing substantial amounts of IL-6 (Figure 1A) that were sustained even after 72 hours (Figure 1B).…”

Stromal Fibroblasts in Tertiary Lymphoid Structures: A Novel Target in Chronic Inflammation

“…In support of this hypothesis, Th17 cells isolated from TLS of EAE affected mice display features of T fh , including the upregulation of expression of CXCR5, ICOS and Bcl6 (109). Within TLS the activated fibroblast compartment may provide key signals for T cell differentiation, such as IL-6, required for the induction and maintenance of the T fh phenotype (207, 208), thus suggesting an additional role for stromal cells in the context of TLS development.…”

Enterococcus faecalisAHG0090 is a genetically tractable bacterium and produces a secreted peptidic bioactive that suppresses NF-kB activation in human gut epithelial cells

“…Cells were also treated with I3C and BHI medium alone. Total RNA was isolated and the expression of the NF-КB dependent genes IL-6, IL-8 and CXCL10 was assessed as previously described (Ó Cuív et al, 2017), except that different primers were used for IL-6 (Pf5’ CCA CTC ACC TCT TCA GAA CG; Pr5’ CAT CTT TGG AAG GTT CAG GTT G) (Noss et al, 2015).…”