Abstract
Lipopolysaccharide (LPS)/toll-like receptor 4 (TLR4) signaling pathway is demonstrated to be involved in the hepatic fibrosis. MicroRNA (miR)-146a-5p is a key regulator of the innate immune response. The functional significance of miR-146a-5p during the LPS/TLR4 mediated hepatic fibrosis process remains unclear. In this study, we found that TLR4 and α-smooth muscle actin (α-SMA) were up-regulated and miR-146a-5p was down-regulated in human hepatic stellate cell (HSC) line LX2 after LPS stimulation. Overexpression of miR-146a-5p inhibited LPS induced pro-inflammatory cytokines secretion through down-regulating the expression levels of TLR-4, IL-1 receptor-associated kinase 1 (IRAK1), TNF receptor associated factor-6 (TRAF6) and phosphorylation of nuclear factor-kappa B (NF-κB). Knockdown of IRAK1 and TRAF6 also suppressed pro-inflammatory cytokine production by inhibiting NF-κB phosphorylation. In addition, miR-146a-5p mimic blocked LPS induced TRAF6 dependent c-Jun N-terminal kinase (JNK) and Smad2 activation as well as α-SMA production. Taken together, these results suggest that miR-146a-5p suppresses pro-inflammatory cytokine secretion and cell activation of HSC through inhibition of TLR4/NF-κB and TLR4/TRAF6/JNK pathway.
Keywords:
hepatic fibrosis; inflammation; microRNA-146a; toll like receptor 4.
MeSH terms
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Actins / genetics
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Actins / metabolism
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Antagomirs / metabolism
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Cells, Cultured
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Cytokines / analysis
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Cytokines / genetics
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Cytokines / metabolism*
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Down-Regulation / drug effects
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Enzyme-Linked Immunosorbent Assay
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Hepatic Stellate Cells / cytology
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Hepatic Stellate Cells / drug effects
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Hepatic Stellate Cells / metabolism
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Humans
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Interleukin-1 Receptor-Associated Kinases / antagonists & inhibitors
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Interleukin-1 Receptor-Associated Kinases / genetics
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Interleukin-1 Receptor-Associated Kinases / metabolism
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JNK Mitogen-Activated Protein Kinases / metabolism
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Lipopolysaccharides / toxicity*
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MicroRNAs / antagonists & inhibitors
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MicroRNAs / genetics
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MicroRNAs / metabolism*
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NF-kappa B / genetics
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NF-kappa B / metabolism
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Phosphorylation / drug effects
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RNA Interference
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RNA, Small Interfering / metabolism
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Signal Transduction / drug effects*
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Smad2 Protein / genetics
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Smad2 Protein / metabolism
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TNF Receptor-Associated Factor 6 / antagonists & inhibitors
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TNF Receptor-Associated Factor 6 / genetics
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TNF Receptor-Associated Factor 6 / metabolism
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Toll-Like Receptor 4 / antagonists & inhibitors
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Toll-Like Receptor 4 / metabolism*
Substances
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ACTA2 protein, human
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Actins
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Antagomirs
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Cytokines
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Lipopolysaccharides
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MicroRNAs
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NF-kappa B
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RNA, Small Interfering
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Smad2 Protein
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TNF Receptor-Associated Factor 6
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Toll-Like Receptor 4
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Interleukin-1 Receptor-Associated Kinases
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JNK Mitogen-Activated Protein Kinases