Donor Preconditioning With Fenoldopam Reduces Graft Injury Through HIF-1α And HO-1Expressions In Rat Kidney Transplantation

Kidney transplantation is booming in the last half century. There areapproximately10,000cases of kidney transplantation surgery every year;However, the number of patients waiting for kidney transplantation is up to1.5million. Kidney transplantation is unavailable without donor kidney. In contrastto the large patient pool of end-stage kidney disease, the source of donor kidneyremains in short supply. With the establishment of criteria on donation aftercardiac death (DCD), donor kidney from DCD will be an important source forkidney transplantation, whereas organ quality from DCD is inferior to that fromliving donation.Fenoldopam is a dopamine1-like receptor (DA1R) agonist that canincrease renal blood flow and glomerular infiltration rate besides anti-hypertension. Low-dose fenoldopam increases renal blood flow withoutaffecting systemic blood pressure; a higher dose will decrease the bloodpressure but maintain renal perfusion. Donor pretreatment with dopaminergicdrugs, including fenoldopam, reduces graft loss. These drugs can also preventcultured cells and grafts from cold ischemic injury. Furthermore, strongerprotection is in accordance with longer-time cold preservation. It is confirmedthat fenoldopam avoids or reduces acute kidney injury induced by experimentalhypotension and contrast. In previous studies, dopaminergic drugs weredemonstrated to induce heme oxygenase1(HO-1) in tubular cells inconsequence to reduce graft injury, exerting a reno-protective role. HO-1is arate-limiting enzyme of heme degrading into carbon monoxide, ferri ion andbiliverdin, which is also a sensitive marker reflecting cell stress. HO-1expression prolongs graft survival, reduces interstitial fibrosis, and inhibitsapoptosis of endothelial cells. Hypoxia-inducible factor (HIF-1), a heterogenicdimer composed by HIF-1α and HIF-1β, can enhance HO-1expression. HIF-1protein, depending on HIF-1α stability, involves in the regulation of a series ofphysiological function, as energy metabolism, revascularization, cellproliferation and angiogenesis, through recognizing and binding to a consensussequence5’-RCGTG-3’ of target genes. HIF-1α up-regulation can reduce renalcold-ischemic injury. Hence we consider that fenoldopam exerts areno-protective role through HIF-1α and HO-1expressions.Objective: The effect of donor pretreatment with fenoldopam on graftfunction was investigated through fenoldopam with or without DA1R inhibitorinfusion in donor rats. Whether HIF-1α and HO-1were implicated in thereno-protection of fenoldopam or not was evaluated by Western Blot andreverse transcriptase Polymerase Chain Reaction. Unraveling the reno-protective mechanism of fenoldopam is beneficial for the followingclinical investigation.Method: The effect of donor preconditioning with fenoldopam on grafts,and whether DA1R inhibitor reversed this effect were investigated. Whether ornot fenoldopam exerts reno-protection through HIF-1α and HO-1expressionswas evaluated.48SD rats were equally randomly divided into FD group，Sch group，FD+Sch group and Control group each containing6pairs of donor andrecipient. The procedure of donor preconditioning was as follows: FD group,fenoldopam was intravenously infused through tail vein at5μg/kg·min for60min; Sch group, Sch23390infusion at10μg/kg·min for60min; FD+Sch group,combined infusion of FD (5μg/kg·min) and Sch23390(10μg/kg·min) for60min; Control group, no pretreatment was given.18h later left kidney washarvested and preserved in HC-A solution at4℃for24h, then orthotopicallygrafted into SD recipients by modified technique of end to end anastomosisdeveloped in our laboratory. Right kidney in recipient was excised7days aftersurgery. Blood sample and graft were obtained at day10. Serum concentrationsof creatinine, blood urea nitrogen, IL-8and TNF-α were determined.Histological changes of graft were observed. Meanwhile apoptotic indexcalculated by TUNEL assay, oxidative stress and HIF-1α and HO-1expressionsin graft were assessed.Results:1. We excised the normal right kidney of recipient through dorsal approach.The in situ rat kidney transplantation model we established was suitable forexperimental study.2. Serum concentrations of creatinine, blood urea nitrogen, IL-8and TNF-α, and the level of oxidative stress in FD group were remarkably lowerwhen compared with other groups, suggesting minor graft injury and bettergraft function in FD group. Fenoldopam preconditioning reduced cold-ischemicinjury of graft, indicating a reno-protective role.3. WB and rt-PCR results revealed that HIF-1α and HO-1expressions inFD group were higher than in other groups, while DA1R inhibitor partlyreversed the reno-protection and HIF-1α and HO-1inductions of fenoldopam,indicating HIF-1α and HO-1were implicated in the reno-protection offenoldopam.Conclusion:Donor preconditioning with fenoldopam reduces long-time cold-ischemicinjury of transplant. HIF-1α and HO-1expressions are implicated in thereno-protection of fenoldopam. DA1R inhibitor partly reverses this effect,which is related to decreased expressions of HIF-1α and HO-1proteins.