Dual Effects of Bilirubin on the Proliferation of Rat Renal NRK52E Cells and ITS Association with Gap Junctions.
OBJECTIVE
The effect of bilirubin on renal pathophysiology is controversial. This study aimed to observe the effects of bilirubin on the proliferation of normal rat renal tubular epithelial cell line (NRK52E) and its potential interplay with gap junction function.


METHODS
Cultured NRK52E cells, seeded respectively at high- or low- densities, were treated with varying concentrations of bilirubin for 24 hours. Cell injury was assessed by measuring cell viability and proliferation, and gap junction function was assessed by Parachute dye-coupling assay. Connexin 43 protein was assessed by Western blotting.


RESULTS
At doses from 17.1 to 513μmol/L, bilirubin dose-dependently enhanced cell viability and colony-formation rates when cells were seeded at either high- or low- densities (all p<0.05 vs. solvent group) accompanied with enhanced intercellular fluorescence transmission and increased Cx43 protein expression in high-density cells. However, the above effects of BR were gradually reversed when its concentration increased from 684 to 1026μmol/L. In high-density cells, gap junction inhibitor 12-O-tetradecanoylphorbol 13-acetate attenuated bilirubin-induced enhancement of colony-formation and fluorescence transmission. However, in the presence of high concentration bilirubin (1026μmol/L), activation of gap junction with retinoid acid decreased colony-formation rates.


CONCLUSIONS
Bilirubin can confer biphasic effects on renal NRK52E cell proliferation potentially by differentially affecting gap junction functions.
Department of anesthesiology, the third affiliated hospital of Sun Yat-sen university. NO.600 Tianhe Road, Tianhe district, Guangzhou, China, 510630.
Yanling
Y
Wang
Qiongfang
Q
Zhu
Chenfang
C
Luo
Ailan
A
Zhang
Ziqing
Z
Hei
Guangjie
G
Su
Zhengyuan
Z
Xia
Michael G
MG
Irwin
Bilirubin; NRK52E cells; cell proliferation; connexin; gap junction; kidney injury