Modulation of TLR2 Protein Expression by miR-105 in Human Oral Keratinocytes

Abstract

Mammalian biological processes such as inflammation, involve regulation of hundreds of genes controlling onset and termination. MicroRNAs (miRNAs) can translationally repress target mRNAs and regulate innate immune responses. Our model system comprised primary human keratinocytes, which exhibited robust differences in inflammatory cytokine production (interleukin-6 and tumor necrosis factor-␣) following specific Toll-like receptor 2 and 4 (TLR-2/TLR-4) agonist challenge. We challenged these primary cells with Porphyromonas gingivalis (a Gram-negative bacterium that triggers TLR-2 and TLR-4) and performed miRNA expression profiling. We identified miRNA (miR)-105 as a modulator of TLR-2 protein translation in human gingival keratinocytes. There was a strong inverse correlation between cells that had high cytokine responses following TLR-2 agonist challenge and miR-105 levels. Knock-in and knock-down of miR-105 confirmed this inverse relationship. In silico analysis predicted that miR-105 had complementarity for TLR-2 mRNA, and the luciferase reporter assay verified this. Further understanding of the role of miRNA in host responses may elucidate disease susceptibility and suggest new anti-inflammatory therapeutics.

Epigenetic Mechanisms in Inflammation

“…Furthermore, miR-147 attenuates the TLR-induced inflammatory response in macrophages . In another study, miR-105 was shown to modulate TLR-2 translation in human gingival keratinocytes (Benakanakere et al, 2009). It was recently suggested that the TLR4-dependent reprogramming of inflammatory genes is mediated by two distinct levels of regulation .…”

MicroRNAs in the regulation of TLR and RIG-I pathways

“…A reciprocal relationship between TLR2 signaling and miR-105 was found in primary human oral keratinocytes, and TLR2 mRNA was shown to be regulated by miR-105. 75 However, in fibroblast-like synoviocytes from rheumatoid arthritis patients, miR-19a/b was decreased in response to TLR2 ligands and was responsible for the upregulated TLR2 expression in these cells. 76 miR-19a/b mimics reduced TLR2 level and thus inhibited TLR2-triggered cytokine production.…”

MicroRNAs in inflammation and immune responses

“…64 In oral keratinocytes, miR-105 regulates TLR2. 65 In mouse peritoneal macrophages, Let-7 family miRNAs target TLR4. 50 Downstream of the TLRs, miR-145 and miR-146a target the TLR adapter proteins TRAF6 and IRAK1.…”