KC Ngai, CY Yeung

Clinical observations have suggested that sepsis may enhance the risk of kernicterus. Endotoxin from gram-negative bacteria has been shown to open the "blood brain barrier" thereby increasing the risk of brain damage by bilirubin. This study aims at investigating the effect on human endothelial cells by bilirubin, endotoxin and cytokines (TNFα, IL-1, IL-6) which simulate sepsis.

A modified MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) method was used to study these cytotoxic effects. The peroxidase oxidation method was applied for bilirubin-albumin titration studies to identify the effect of endotoxin and cytokines on bilirubin-albumin binding.

The results showed that bilirubin produced a dose response cytotoxicity in the cultured human umbilical cord vein endothelial cells over a range of Bilirubin/Albumin-molar ratios of 1.0, 1.4 and 1.6. This phenomenon was significantly amplified by the addition of TNFα and endotoxin. Further addition of IL- 1α, IL-1β and IL-6 made no more contribution to the damage. Cytokines or endotoxin showed no effect on the bilirubin-albumin titration curves. These results suggest that the additive cytotoxic effect to bilirubin by these inflammatory factors on human endothelial cells is a combined effect of endotoxin and cytokines. These findings provide evidence of the effect of sepsis in opening up the "blood brain barrier" which would increase the occurrence of bilirubin brain damage.