Uptake and modification of 125I-lipopolysaccharide by isolated rat Kupffer cells

Authors

  • Eben S. Fox,

    1. Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts 02118
    2. Laboratory for Cancer Biology, Department of Surgery, New England Deaconess Hospital, Boston, Massachusetts 02215
    Current affiliation:
    1. Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111
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  • Peter Thomas,

    1. Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts 02118
    2. Laboratory for Cancer Biology, Department of Surgery, New England Deaconess Hospital, Boston, Massachusetts 02215
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  • Selwyn A. Broitman Ph.D.

    Corresponding author
    1. Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts 02118
    2. Laboratory for Cancer Biology, Department of Surgery, New England Deaconess Hospital, Boston, Massachusetts 02215
    • Department of Microbiology, Boston University School of Medicine, 80 E. Concord St., Boston, Massachusetts 02118
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Abstract

While it is generally believed that hepatic clearance of lipopolysaccharide involves Kupffer cells, the mechanism involved has not been fully elucidated. This study assesses this phenomenon in terms of in vitro uptake and post-uptake modification experiments with an 125I-labeled Salmonella minnesota lipopolysaccharide. 125I-Lipopolysaccharide was added to Kupffer cells in suspension cultures under a variety of conditions. In vitro uptake of 125I-Lipopolysaccharide was not saturable up to concentrations of 33.33 μg per ml. Kinetics experiments performed at 16.67 μg per ml demonstrated that Kupffer cells were unsaturable after 60 min of incubation. The kinetics of uptake could be inhibited, however, by incubation in the presence of a 10-fold excess of unlabeled lipopolysaccharide, indicating that a component of the uptake process may be limited. Energy dependence in this process was demonstrated by incubation in the presence of 1 mM 2-deoxyglucose which inhibited 125I-lipopolysaccharide uptake by approximately 30%. Pretreatment with 7.5 × 10−5M colchicine had no effect on kinetics, implying no role for the cell cytoskeleton in lipopolysaccharide uptake. These results are inconsistent with a receptor-mediated process as previously suggested. Modification of internalized label has been demonstrated by changes in buoyant density in CsCl isopyknic density gradients following overnight incubation with Kupffer cells. These results indicate that Kupffer cells clear bacterial endotoxin in vitro and post-uptake degradation occurs within 20 hr of incubation.

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