A Novel Mechanism of BAM8-22 Inhibiting Microglia Activation: Represses CX3CR1 Expression via Upregulating miR-184

J Mol Neurosci. 2020 Apr;70(4):550-558. doi: 10.1007/s12031-019-01455-0. Epub 2019 Dec 12.

Abstract

Bone cancer pain (BCP) is the most common type of pain in cancer patients, during which microglia cells were activated. A previous study showed BAM8-22 had the ability to alleviate BCP via inhibiting microglia activation while the mechanism was not clear. This study aims to investigate the specific mechanism of BAM8-22 inhibiting microglia activation. This study was mainly investigated in BCP mice or LPS-treated microglia BV-2 cells. The behavior tests of mice were performed at 0, 1, 2, 12, and 24 h after BAM8-22 treatment. The expression of miR-184 and CX3CR1 mRNAs was detected by quantitative RT-PCR. The expression of CX3CR1 protein and microglia activation marker, Iba-1, was measured by western blot analysis. The levels of TNF-α and IL-1β were detected by ELISA. Dual-luciferase assay was performed to verify the combination between miR-184 and CX3CR1. After BAM8-22 treatment, increased miR-184 level was observed in both BCP mice and LPS-treated BV-2 cells, with the downregulated expression of Iba-1 and inflammatory cytokines, namely the inhibition of microglia activation. The inhibition of miR-184 reversed the inhibitory effect of BAM8-22 on microglia activation. Further, in vitro studies showed that miR-184 bound to the 3'UTR of CX3CR1 and inhibited microglia activation via repressing CX3CR1 expression. What's more, the suppression of CX3CR1 expression eliminated the reversal effect of the miR-184 inhibitor on BAM8-22-induced microglia activation and decreased Iba-1 expression and pro-inflammatory cytokine secretion. In BCP models, miR-184 was upregulated by BAM8-22 and the elevated level of miR-184 bound to the 3'UTR region of CX3CR1 and repressed CX3CR1 expression, thus inhibiting the microglia activation, suggesting the potential application of miR-184/CX3CR1 for BCP treatment.

Keywords: BAM8-22; Bone cancer pain; CX3CR1; MiR-184; Microglia activation.

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology*
  • CX3C Chemokine Receptor 1 / genetics*
  • CX3C Chemokine Receptor 1 / metabolism
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism
  • Cell Line
  • Cell Line, Tumor
  • Cells, Cultured
  • Interleukin-1beta / genetics
  • Interleukin-1beta / metabolism
  • Lipopolysaccharides / toxicity
  • Male
  • Mice
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Microglia / drug effects*
  • Microglia / metabolism
  • Peptide Fragments / pharmacology*
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Aif1 protein, mouse
  • Anti-Inflammatory Agents
  • CX3C Chemokine Receptor 1
  • Calcium-Binding Proteins
  • Cx3cr1 protein, mouse
  • Interleukin-1beta
  • Lipopolysaccharides
  • MIRN184 microRNA, mouse
  • MicroRNAs
  • Microfilament Proteins
  • Peptide Fragments
  • Tumor Necrosis Factor-alpha
  • bovine adrenal medulla 8-22