KC Ngai, CY Yeung

Aims Clinical observations have suggested that sepsis may enhance the risk of kernicterus. Endotoxin from gram-negative bacteria has been shown to increase the permeability of the 'blood brain barrier' thereby increasing the risk of brain damage by bilirubin. This study investigated the combined effects of bilirubin, endotoxin and cytokines (TNFα, IL-1, IL-6) which simulate sepsis on a mouse fibroblast cell line.

Materials and Methods A modified 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyl -tetrazolium bromide method was used to study cytotoxicity (1). The peroxidase oxidation method was applied for bilirubin-albumin titration studies to test the effect of endotoxin and cytokines on bilirubin-albumin binding (2).

Results Bilirubin caused cytotoxicity in a dose-dependent manner in the cultured mouse fibroblast cell line. This phenomenon was significantly amplified by the addition of TNFα and endotoxin. Further addition of IL- 1α, IL-1β and IL-6 caused no extra damage. Individual cytokines or endotoxin alone had no effect on the bilirubin-albumin titration curves.

Conclusions The results show TNFα and endotoxin increase the cytotoxicity of bilirubin. These findings provide good evidence that sepsis increases the risk of damage by bilirubin.

References

1. Mosmann T 1983 Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays. J Immunol Methods 1983;65:55-63.

2. Jacobsen J, Wennberg RP. Determination of unbound bilirubin in the serum of newborns. Clin Chem 1974;20(7):783.