Inhibition of lipopolysaccharide activation of Kupffer cells by transition metals.
BACKGROUND
Bacterial endotoxins are the principal agents causing sepsis and septic shock. Cytokine cascades produced by cellular interactions to endotoxins can cause cardiovascular failure followed by multi-organ failure and death. Endotoxin intravenously administered to mice can have fatal consequences. Previous studies have shown that the transition metals Mn2+ and Cr3+ can be protective.


METHODS
The effects of Mn2+, Cr3+, Zn2+, and Cu2+ on lipopolysaccharide (LPS) binding to rat Kupffer cell extracts were analyzed using dot-blots, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western transfer. Kupffer cells were isolated from rat livers by collagenase perfusion, differential centrifugation, and adhesion to plastic.


RESULTS
Five millimolar of Mn2+, Zn2+, Cr3+, and Cu2+ completely inhibited LPS binding. Isolated Kupffer cells were also exposed to Mn2+ and to LPS and tumor necrosis factor-alpha release measured. The presence of Mn2+ significantly (P < 0.05) reduced tumor necrosis factor-alpha production by Kupffer cells in response to LPS. Experiments to determine if these effects were mediated by binding to LPS-binding proteins showed this was not the case. More likely a complex occurs between the metal and LPS. We also showed significantly enhanced uptake of LPS into Kupffer cells in the presence of Mn2+.


CONCLUSIONS
The data are consistent with the metals binding to LPS via its two phosphate groups and neutralizing their charge. These data also support the hypothesis that there is enhanced cellular uptake by non-receptor-mediated methods such as absorptive pinocytocis. At the same time receptor binding and activation of the cells is inhibited. This can explain the effects of transition metals on LPS toxicity.
Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA. peterthomas@creighton.edu
Peter
P
Thomas
Hiroshi
H
Hayashi
Donald
D
Lazure
Peter A
PA
Burke
Olga
O
Bajenova
Aniruddha
A
Ganguly
R Armour
RA
Forse
D000818:Animals; D002857:Chromium / Q000494:pharmacology*; D003300:Copper / Q000494:pharmacology*; D007728:Kupffer Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D008345:Manganese / Q000494:pharmacology*; D010873:Pinocytosis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D002857:Chromium; D008345:Manganese; D003300:Copper; D015032:Zinc