Department of Medicine, Division of Gastroenterology; Department of Medicine, Division of Infectious Diseases and Immunology
Alcoholism; Animals; Cerebellum; Chemokine CCL2; Chronic Disease; Ethanol; Female; Gene Expression Regulation; Inflammation; Interleukin-1beta; Mice; Mice, Knockout; MicroRNAs; Microglia; Primary Cell Culture; Signal Transduction; Toll-Like Receptor 4; Tumor Necrosis Factor-alpha
Digestive System Diseases | Gastroenterology | Genetics | Hepatology | Immunopathology
INTRODUCTION: Alcohol-induced neuroinflammation is mediated by pro-inflammatory cytokines and chemokines including tumor necrosis factor-alpha (TNFalpha), monocyte chemotactic protein-1 (MCP1) and interleukin-1-beta (IL-1beta). Toll-like receptor-4 (TLR4) pathway induced nuclear factor-kappaB (NF-kappaB) activation is involved in the pathogenesis of alcohol-induced neuroinflammation. Inflammation is a highly regulated process. Recent studies suggest that microRNAs (miRNAs) play crucial role in fine tuning gene expression and miR-155 is a major regulator of inflammation in immune cells after TLR stimulation.
AIM: To evaluate the role of miR-155 in the pathogenesis of alcohol-induced neuroinflammation.
METHODS: Wild type (WT), miR-155- and TLR4-knockout (KO) mice received 5% ethanol-containing or isocaloric control diet for 5 weeks. Microglia markers were measured by q-RTPCR; inflammasome activation was measured by enzyme activity; TNFalpha, MCP1, IL-1beta mRNA and protein were measured by q-RTPCR and ELISA; phospho-p65 protein and NF-kappaB were measured by Western-blotting and EMSA; miRNAs were measured by q-PCR in the cerebellum. MiR-155 was measured in immortalized and primary mouse microglia after lipopolysaccharide and ethanol stimulation.
RESULTS: Chronic ethanol feeding up-regulated miR-155 and miR-132 expression in mouse cerebellum. Deficiency in miR-155 protected mice from alcohol-induced increase in inflammatory cytokines; TNFalpha, MCP1 protein and TNFalpha, MCP1, pro-IL-1beta and pro-caspase-1 mRNA levels were reduced in miR-155 KO alcohol-fed mice. NF-kappaB was activated in WT but not in miR-155 KO alcohol-fed mice. However increases in cerebellar caspase-1 activity and IL-1beta levels were similar in alcohol-fed miR-155-KO and WT mice. Alcohol-fed TLR4-KO mice were protected from the induction of miR-155. NF-kappaB activation measured by phosphorylation of p65 and neuroinflammation were reduced in alcohol-fed TLR4-KO compared to control mice. TLR4 stimulation with lipopolysaccharide in primary or immortalized mouse microglia resulted in increased miR-155.
CONCLUSION: Chronic alcohol induces miR-155 in the cerebellum in a TLR4-dependent manner. Alcohol-induced miR-155 regulates TNFalpha and MCP1 expression but not caspase-dependent IL-1beta increase in neuroinflammation.
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Copyright 2013 Lippai et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
DOI of Published Version
PLoS One. 2013 Aug 9;8(8):e70945. doi: 10.1371/journal.pone.0070945 Link to article on publisher's site
Lippai, Dora; Bala, Shashi; Csak, Timea; Kurt-Jones, Evelyn A.; and Szabo, Gyongyi, "Chronic alcohol-induced microRNA-155 contributes to neuroinflammation in a TLR4-dependent manner in mice" (2013). Gastroenterology Publications and Presentations. 142.