Background: In a retrospective study of the kidney transplantations performed at our institution, we found that the administration of dopamine (DA) to the organ donors resulted in a significant improvement of long-term organ survival of the retrieved kidneys. To study the mechanisms underlying the organ protection associated with the administration of DA prior to transplantation, we questioned whether DA induces the antioxidative enzyme heme oxygenase-1 (HO-1) in cultured endothelial cells.
Methods: Human umbilical vein endothelial cells (HUVECs) in culture were incubated with varying concentrations of DA for different time periods. Cells were subsequently assessed for the expression of HO-1 by Western blot and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR).
Results: The presence of DA resulted in a dose- and time-dependent up-regulation of HO-1 both on RNA and protein level, whereas HO-1 was barely detectable under basal conditions. RT-PCR indicated the increased presence of HO-1 messenger RNA after 2 hours of incubation with DA, which peaked after 24 hours. The induction of HO-1 antigen was detectable after eight hours, as visualized by Western blot analysis. The addition of the antioxidant agents ascorbic acid and N-acetyl-cysteine both lead to dose-dependent inhibition of DA-mediated HO-1 induction. DA-mediated up-regulation of HO-1 was not influenced by the addition of either the D2-receptor antagonist haloperidol or the D1-receptor antagonist SCH 23390.
Conclusion: We conclude that DA induces the expression of the protective enzyme HO-1 in cultured endothelial cells by an oxidative mechanism. These findings may explain the beneficial effect of DA administration to kidney donors and indicate the potential role of DA in organ preconditioning.