Reversible Kupffer cell suppression in biliary obstruction is caused by hydrophobic bile acids

Background/Aim: Biliary obstruction is associated with suppressed Kupffer cell clearance of bacteria and intracellular bactericidal activity of the phagocytes. We studied the superoxide generation of Kupffer cell in biliary obstruction and after incubation with bile acids to elucidate the mechanism of impaired intracellular killing of these phagocytes. Methods: Kupffer cells were extracted from rats with common bile duct ligation or sham-operation. The extracted cells were tested for superoxide production immediately after extraction, 2 h and 24 h post-extraction. Superoxide generation from Kupffer cells after incubation with five bile acids (cholic acid, taurocholic acid, deoxycholic acid, chenodeoxycholic acid and ursodeoxycholic acid) at two different concentrations (0.1 mM and 1.0 mM) were also studied. Cell viability was monitored by trypan blue exclusion. Results: Kupffer cells extracted from common ductligated animals had significantly lower superoxide production (−1.37±0.24 nmol O2−/106 cells) compared to that from sham-operated rats (2.54±0.58 nmol O2−/106 cells) and non-operated rats (2.15±0.76 nmol O2−/106 cells) (p<0.05). After 2 h of resting in culture medium, these cells recovered significantly in superoxide production to 2.72±0.63 nmol O2−/106 cells (p<0.01). A dose-related reduction in superoxide production was demonstrated when Kupffer cells were incubated with bile acids. Hydrophobic bile acids (deoxycholic acid and chenodeoxycholic acid) caused more significant suppression than with hydrophilic bile acids (cholic acid, taurocholic acid, ursodeoxycholic acid). The drop in superoxide production after bile acid treatment was not due to cell death. Washing in Hankʹs balanced salt solution resulted in partial recovery of Kupffer cell superoxide production. Conclusion: High blood levels of hydrophobic bile acids are likely to be the cause of impaired intracellular bactericidal activity of Kupffer cells in biliary obstruction.