Toll-like receptor 4 is involved in the mechanism of early alcohol-induced liver injury in mice

Authors

  • Takehiko Uesugi,

    Corresponding author
    1. Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina, Chapel Hill, NC.
    • Department of Pharmacology, Laboratory of Hepatobiology and Toxicology, CB# 7365, Mary Ellen Jones Building, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365. fax: 919-966-1893
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  • Matthias Froh,

    1. Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina, Chapel Hill, NC.
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  • Gavin E. Arteel,

    1. Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina, Chapel Hill, NC.
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  • Blair U. Bradford,

    1. Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina, Chapel Hill, NC.
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  • Ronald G. Thurman

    1. Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina, Chapel Hill, NC.
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Abstract

Chronic alcohol administration increases gut-derived endotoxin in the portal blood, which activates Kupffer cells and causes liver injury. Mice (C3H/HeJ) with mutations in toll-like receptor 4 (TLR4) are hyporesponsive to endotoxin. To test the hypothesis that TLR4 is involved in early alcohol-induced liver injury, the long-term intragastric ethanol feeding protocol developed by Tsukamoto and French for rats was adapted to mice. Animals with nonfunctional TLR4 and wild-type mice (C3H/HeOuJ) were compared. Two-month-old female mice were fed a high-fat liquid diet with either ethanol or isocaloric maltose-dextrin as control continuously for 4 weeks. There was no difference in mean urine alcohol concentrations between the groups. Dietary alcohol significantly increased liver-to-body weight ratios and serum alanine transaminase (ALT) levels in wild-type mice (109 ± 18 U/L) over high-fat controls (40 ± 3 U/L), effects that were blunted significantly in mice with a mutation of TLR4 (55 ± 9 U/L). While no significant pathologic changes were observed in high-fat controls, dietary ethanol caused steatosis, mild inflammation, and focal necrosis in wild-type animals (pathology score = 5.2 ± 1.2). These pathologic changes were significantly lower in TLR4-deficient mice fed ethanol (score = 2.0 ± 1.3). Endotoxin levels in the portal vein were increased significantly after 4 weeks in both groups fed ethanol. Moreover, ethanol increased tumor necrosis factor α (TNF-α) mRNA expression in wild-type, but not in TLR4-deficient, mice. These data are consistent with the hypothesis that Kupffer cell activation by endotoxin via TLR4 is involved in early alcohol-induced liver injury.

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