Attenuation of inflammatory mediator production by the NF-κB member RelB is mediated by microRNA-146a in lung fibroblasts

Abstract

Lung inflammation can result from exposure to multiple types of inflammatory stimuli. Fibroblasts, key structural cells in the lung that are integral to inflammation and wound healing, produce inflammatory mediators after exposure to stimuli such as IL-1β. We and others have shown that the NF-κB member RelB has anti-inflammatory properties in mice. Little is known, however, about the anti-inflammatory role of RelB in human cells and how it functions. MicroRNAs (miRNAs), a novel class of small, noncoding RNAs, can mediate inflammatory signaling pathways, including NF-κB, through regulation of target gene expression. Our goal was to analyze the anti-inflammatory properties of RelB in human lung fibroblasts. We hypothesized that RelB regulates inflammatory mediator production in lung fibroblasts in part through a mechanism involving miRNAs. To accomplish this, we transfected human lung fibroblasts with a plasmid encoding RelB and small interfering (si)RNA targeting RelB mRNA to overexpress and downregulate RelB, respectively. IL-1β, a powerful proinflammatory stimulus, was used to induce NF-κB-driven inflammatory responses. RelB overexpression reduced IL-1β-induced cyclooxygenase (Cox)-2, PGE₂, and cytokine production, and RelB downregulation increased Cox-2 expression and PGE₂ production. Furthermore, RelB overexpression increased IL-1β-induced expression of miRNA-146a, an NF-κB-dependent miRNA with anti-inflammatory properties, whereas RelB downregulation reduced miRNA-146a. miR-146a overexpression ablated the effects of RelB downregulation on IL-1β-induced Cox-2, PGE₂, and IL-6 production, suggesting that RelB mediates IL-1β-induced inflammatory mediator production in lung fibroblasts through miRNA-146a. RelB and miRNA-146a may therefore be new therapeutic targets in the treatment of lung inflammation caused by various agents and conditions.

Inhibition of miR-146a prevents enterovirus-induced death by restoring the production of type I interferon

“…This data indicated that AP1 is the key transcription factor contributing to EV71-induced upregulation of miR-146a. Previous studies have reported that RelA, RelB and p50 could regulate miR-146a expression and suggested that miR-146a expression was NF-kB-dependent 32,[39][40][41][42] . To verify whether NF-kB is involved in EV71-induced miR-146a upregulation, NF-kB translocation and NF-kB activity were examined in EV71-infected RD cells and assayed by NF-kB immunoblot and NF-kB regulatory element assays.…”

Resolvin D2 decreases TLR4 expression to mediate resolution in human monocytes

“…miR27 is primarily linked to adipocyte differentiation, with increased miR27a decreasing adipogenesis, but has additionally been shown to be downregulated by TLR4 induction, resulting in reduced IL-10, an anti-inflammatory cytokine important in M2 macrophage activation (58). miR-146a is both regulated by and negatively regulates TLR4, MyD88, NF-kB, other TLRs, and a range of proinflammatory proteins, as well positively regulating RelB (37,(59)(60)(61)(62)(63)(64). The effects of regulation have been specifically identified in macrophages; THP-1 cells that are exogenously transfected with a miR-146a mimic had decreased production of TNF-a, IL-6, and IL-1b (62).…”

Mapracorat, a selective glucocorticoid receptor agonist, upregulates RelB, an anti-inflammatory nuclear factor-kappaB protein, in human ocular cells

“…We and others have shown that RelB expression is increased by IL-1b stimulation (data not shown and (Vardar-Sengul et al, 2009;McMillan et al, 2013)). McMillan et al demonstrated that RelB reduces inflammatory mediator production, in part, via a miRNA dependent mechanism, and showed that RelB and miR-146a may coordinately regulate this anti-inflammatory pathway (McMillan et al, 2013). In human lung fibroblasts depleted of RelB, overexpression of miR-146a reversed the RelB downregulation-induced increase in IL-1b inflammatory mediator production (IL-6, IL-8 and MCP-1).…”

“…Another possible explanation for how mapracorat could regulate RelB involves a recently reported novel feedback control mechanism in human lung fibroblasts that functions to reduce and reverse the prolonged effects of inflammation (McMillan et al, 2013). We and others have shown that RelB expression is increased by IL-1b stimulation (data not shown and (Vardar-Sengul et al, 2009;McMillan et al, 2013)).…”