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Treatment of organ donors with catecholamines reduces acute rejection episodes and improves long-term graft survival after renal transplantation. The aim of this study was to investigate the effect of catecholamine pre-treatment on ischemia/reperfusion (I/R)- and cold preservation injury in rat kidneys. I/R-injury was induced by clamping the left kidney vessels for 60 min along with a contralateral nephrectomy. Cold preservation injury was induced by storage of the kidneys for 24 h at +4 degrees Celsius in University of Wisconsin solution, followed by syngeneic transplantation. Rats were pre-treated with either dopamine (DA), dobutamine (DB), or norepinephrine (2, 5, and 10 microg/kg/min, each group) intravenously via an osmotic minipump for 24 h before I/R- and cold preservation injury. Pre-treatment with DA (2 or 5 microg/kg/min) and DB (5 microg/kg/min) improved recovery of renal function after I/R-injury and dose dependently reduced mononuclear and major histocompatibility complex class II-positive cells infiltrating the kidney after I/R-injury. One day after I/R-injury, upregulation of transforming growth factor (TGF)-beta 1 and 2 and phosphorylation of p42/p44 mitogen-activated protein kinases was observed in kidneys of animals treated with DA or DB. DA (5 microg/kg/min) and DB (5 microg/kg/min) pre-treatment reduced endothelial cell damage after 24 h of cold preservation. Only DA pre-treatment improved renal function and reduced renal inflammation after 24 h of cold preservation and syngeneic transplantation. Our results demonstrate a protective effect of pre-treatment with catecholamines on renal inflammation and function after I/R- or cold preservation injury. This could help to explain the potent organoprotective effects of catecholamine pre-treatment observed in human kidney transplantation.

Background: Brain death has been identified as an independent risk factor for chronic allograft dysfunction. In two independent retrospective clinical studies, we showed that dopamine treatment of brain-dead donors improves long-term kidney graft survival. The mechanisms underlying the protective effects of dopamine treatment in vivo have not been identified. To elucidate the mechanisms underlying the protective effect of dopamine on kidneys of brain-dead donors, we studied a model for brain death in rats., Methods: In F344 rats, brain death was induced by epidural inflation of a 3F Fogarty catheter. Apneic animals were mechanically ventilated, and clinically relevant dosages of dopamine (2, 6, 10, or 14 microg/kg/min) were given for 6 hr from the onset of brain death. Ventilated, non-brain-dead animals served as controls., Results: Dopamine significantly reduced renal monocyte infiltration and major histocompatibility class II and P-selectin expression in brain-dead animals. It also prevented further up-regulation of the inflammatory markers tumor necrosis factor-alpha and monocyte chemoattractant peptide-1. Concomitantly, the presence of inducible anti-oxidant heme oxygenase-1, known for its cytoprotective effects, was strongly increased by dopamine., Conclusion: We identified several mechanisms underlying the protective effects of dopamine treatment on kidney grafts. The identification of these mechanisms may help to design more effective future strategies for treatment of cadaveric kidney donors.

Optimizing medical donor management may have a considerable impact on transplantation outcome. This study investigated the effect of donor dopamine on initial graft function in renal allograft recipients, involving 254 consecutive recipients of a cadaver kidney, aged 18-74 years, transplanted between 1990 and 2003. Immunosuppression was based on cyclosporine. Patients were grouped according to donor use of dopamine during intensive care. Delayed graft function (DGF), and serial creatinine concentrations were compared between the groups. Dopamine-treated and -untreated donors were very similar regarding hemodynamics and renal function. Delayed graft function occurred in 47/158 treated and 48/96 untreated kidneys (p = 0.001). Donor dopamine was associated with a more rapid decrease of s-creatinine, which became obvious on the first postoperative day. Of patients in the treated and untreated group, respectively, 81.9% and 65.8% reached a s-creatinine level less than 2 mg/dL during the first month (p = 0.005). Donor dopamine remained predictive of a normalized s-creatinine level [HR 1.71; 95% CI 1.22-2.41] after controlling for confounding factors by multivariate Cox regression. Donor dopamine is associated with improvements of initial graft function after kidney transplantation. The beneficial effect of dopamine is achievable without side-effects for the recipients, and correlates with superior long-term graft survival.

Oxidative stress is markedly increased after kidney transplantation and may participate in the development and/or progression of chronic renal allograft nephropathy. In the present study we sought to assess the nephroprotective potential of antioxidative treatment in renal allograft recipients. Experiments were performed in the Fisher-Lewis rat model of chronic renal allograft nephropathy, with isografted Lewis rats serving as controls. Allografted rats were orally treated with carvedilol, an antihypertensive drug with antioxidative properties (25 mg/kg/d), its purely antioxidative derivative BM 91.0228 (5 mg/kg/d), alpha-tocopherol (100 mg/kg/d), a combination of propranolol/doxazosine (10/5 mg/kg/d), or vehicle for 24 weeks. At the end of the study, oxidative status and influence of antioxidative treatment were assessed in transplanted animals. Chronic allograft nephropathy was characterized by a marked increase of markers for oxidative stress (increased plasma and kidney levels of malondialdehyde, reduced glutathione, and tocopherol levels in renal allografts). Treatment with carvedilol, BM 91.0228, and tocopherol significantly improved antioxidative status of allograft kidney recipients. In addition, carvedilol reduced elevated blood pressure in allografted rats. However none of the drugs had a beneficial influence on functional and morphologic renal changes. Our data thus demonstrate that long-term treatment with the antioxidants carvedilol, BM 91.0228, or alpha-tocopherol does not prevent development of chronic transplant nephropathy, despite an improvement of antioxidative status.

We have recently demonstrated up-regulation of renal endothelin (ET) synthesis in a rat model of chronic renal allograft rejection. Treatment with a selective ET-A receptor antagonist improved survival and reduced functional and morphological kidney damage. However, the underlying mechanisms have not yet been elucidated, as ET exhibits both hemodynamic and inflammatory properties. Therefore, in the present study we investigated acute hemodynamic effects of the selective ET-A receptor antagonist LU 302146 (LU) on chronic renal allograft rejection in rats. Experiments were performed in the Fisher-to-Lewis model of chronic renal allograft rejection. Lewis-to-Lewis isografts served as controls. After 2, 12, and 24 weeks, hemodynamic measurements were performed on anesthetized animals. Measurement of mean arterial pressure (MAP) was performed via a catheter in the femoral artery. Renal blood flow (RBF) was measured by an ultrasonic flow probe placed around the renal transplant artery. Medulla blood flow (MBF) and cortex blood flow (CBF) were determined with laser Doppler probes. Hemodynamic response upon intravenous bolus injection of LU (50 mg/kg) was investigated. The application of LU was followed by a decline in MAP that reached statistical significance only in isografts (ISOs) after 12 weeks and allografts (ALLOs) after 24 weeks. RBF slightly decreased in all groups; however, without reaching statistical significance. MBF showed a small increase in ALLO12 and ALLO24 whereas CBF slightly decreased in all groups. Acute ET-A receptor blockade does not induce important hemodynamic effects in kidneys undergoing chronic rejection. The lack of response to ET-A receptor blockade suggests that the beneficial effect of ET receptor antagonists in this model is likely to be due to improvement of renal morphology.

Background: Low-molecular-weight heparin (LMWH) has been shown to prolong survival of rat cardiac allografts independently from immunosuppressive treatment. Furthermore, long-term treatment reduces the development of chronic graft vascular disease after experimental heart transplantation. The aim of the present study was to determine whether treatment with the LMWH reviparin has a beneficial effect on chronic rejection in a rat renal allograft model., Methods: Kidneys of Fisher (F344) rats were transplanted into unilaterally nephrectomized Lewis (LEW) recipients. LEW-->LEW isografts served as controls. Animals were treated with cyclosporine (5 mg/kg/d) for the first 10 days. Nephrectomy of the remaining kidney was performed after 10 days. Allografted animals were treated either with reviparin (2 mg/kg/d subcutaneously) for 24 weeks (Allo-24), from week 12 to 24 (Allo-12), or with vehicle for 24 weeks. Proteinuria was determined at regular intervals. Kidneys were harvested after 24 weeks for histomorphological and immunohistochemical evaluation., Results: No major bleeding complications were observed in reviparin-treated animals. Proteinuria was significantly reduced in allografted animals both by early as well as by late-onset treatment with reviparin. Transplant glomerulopathy was diminished in Allo-24 and in Allo-12 groups compared to vehicle-treated animals, whereas tubulointerstitial inflammation was influenced only in animals immediately treated with reviparin. Immunohistochemical studies demonstrated a marked reduction of renal monocyte and T-cell infiltration as well as expression of MHC II by treatment with reviparin., Conclusions: Treatment with the LMWH reviparin significantly improved chronic renal allograft rejection in the F344-to-LEW rat model, both after early and late start of therapy. Although the exact mechanisms of this beneficial effect remain unclear, our data offer a potential new therapeutical approach for prevention of chronic allograft nephropathy.

A markedly increased expression of endothelin (ET)-1 has been observed in renal allografts with chronic rejection, one of the most common causes of kidney graft loss. In this study we investigated the effect of treatment with a combined ET-A/B-receptor antagonist on the course of chronic renal allograft rejection. Experiments were performed in the Fisher-to-Lewis rat model of chronic rejection. Lewis-to-Lewis isografts and uninephrectomized Lewis rats served as controls. Animals were treated with either the oral combined ET-A/B-receptor antagonist LU224332 (20 mg/kg/day) or vehicle. Animal survival, blood pressure, creatinine clearance, proteinuria, and urinary ET excretion were investigated for 24 weeks. Kidneys were removed for light-microscopic evaluation and immunohistochemical assessment of cell-surface markers. Treatment with LU224332 did not improve survival after 24 weeks (0.47 vs. 0.38; p > 0.05 by log-rank test), nor did it have an influence on blood pressure, creatinine clearance, or proteinuria. Combined ET-A/B-receptor blockade was associated with a reduction of expression of cell-surface markers for macrophages (EDI), T-cells (R73), and major histocompatibility complex (MHC) II (F17-23-2), but did not lead to an improvement of histologic changes of chronic allograft rejection. Our data show that blocking both ET-A- and -B receptors, in opposition to a previously published beneficial effect of selective ET-A blockade, does not prevent the progression of chronic renal allograft rejection and does not prolong survival in this model. Functional integrity of the ET-B receptor therefore seems to play an important role in the nephroprotection provided by selective ET-A-receptor antagonists in chronic renal allograft nephropathy.

Background: Delayed renal function after transplantation is a strong predictor of long-term graft survival. As an increased expression of endothelin (ET) has been demonstrated during ischemia/reperfusion injury, we hypothesized that ET-A receptor blockade could improve the recovery of acute renal failure in a rat model of isogeneic kidney transplantation., Methods: Kidneys of Fisher (F344, RT1(1v1)) rat donors flushed with cooled University of Wisconsin solution were transplanted into bilaterally nephrectomized Fisher rats. Recipient animals were treated orally either with vehicle or the selective ET-A receptor antagonist LU135252 (30 mg/kg/day p.o.) for 14 days. Unilaterally nephrectomized Fisher rats not subjected to ischemia served as controls. No immunosuppression was given. On days 2, 6 and 14, metabolic studies were performed to evaluate endogenous creatinine clearance, fractional sodium excretion, and urinary endothelin excretion. Kidneys were harvested at the end of the experiment for determination of renal ET content and immunohistochemical assessment., Results: Urinary ET excretion was increased in vehicle-treated isografts compared to uninephrectomized controls after 14 days. Treatment with LU135252 resulted in a significant improvement in creatinine clearance and fractional sodium excretion to the level of uninephrectomized rats after 14 days. Isografts treated with selective ET-A receptor blockade demonstrated a marked reduction in cell surface markers for macrophages/monocytes, T cells, MHC-II, and ICAM-1., Conclusion: Treatment with the selective ET-A receptor antagonist LU135252 accelerates recovery of renal function after isogeneic renal transplantation and attenuates cellular graft infiltration. This effect could have major implications for the treatment of patients undergoing renal transplantation, as an improved initial renal function may delay the onset of chronic allograft rejection., (Copyright 2000 S. Karger AG, Basel)

Background: Chronic rejection is the most common cause of graft loss in renal transplantation. The pathomechanisms underlying chronic rejection are poorly understood, and no treatment has yet successfully been established. We hypothesized that, in analogy to models of reduced renal mass, the administration of a selective endothelin (ET) A receptor antagonist could improve the course of chronic rejection in renal allografts., Methods: Experiments were performed in the Fisher-to-Lewis rat model of chronic rejection. Lewis-->Lewis isografts served as controls. Animals were treated with either the oral selective ET-A receptor antagonist LU135252 (50 mg/kg/day) or vehicle. Animal survival, blood pressure, creatinine clearance, proteinuria, and urinary ET excretion were investigated for 24 weeks. Kidneys were removed for light microscopical evaluation, determination of ET mRNA expression and tissue protein concentration, and immunohistochemical assessment of cell surface markers., Results: Rats with chronic rejection showed an increase in renal ET mRNA synthesis and ET protein content. Treatment with LU135252 resulted in a significant improvement in survival after 24 weeks (0.92 vs. 0.38, P<0.01 by log-rank test). Creatinine clearance was higher in animals treated with the selective ET-A receptor antagonist (P<0.05). LU135252 had no influence on blood pressure and proteinuria. Selective ET-A blockade was associated with significantly less morphological changes and a significant reduction of expression of cell surface markers for macrophages (ED1), T cells (R73), and MHC II (F17-23-2)., Conclusion: The renal ET-A system plays an important role in the pathomechanisms underlying chronic renal allograft rejection, because the treatment with a selective ET-A receptor antagonist dramatically improves the course of chronic renal failure after allograft transplantation. These results offer a novel therapeutical option for treatment of chronic renal allograft rejection, for which so far no therapy is known.

Blocking CD28-B7 T cell costimulatory activation by the fusion protein CTLA4Ig prevents rejection and induces long-term graft acceptance in various experimental transplant models. There are reported differences in the efficacy of CTLA4Ig in renal and cardiac rodent allograft models, but it is not clear whether these are due to the strain or species differences investigated in the different studies reported. This study investigates the effect of blocking CD28-B7 T cell costimulation with murine CTLA4Ig in rat models of acute renal and cardiac allograft rejection models, using the same complete major histocompatibility complex-incompatible strain combination. A single injection of murine CTLA4Ig 2 d after engraftment was able to induce long-term graft acceptance (> 100 d) in 54% of Lewis rat recipients of Wistar-Furth kidneys. Transferring this protocol into the acute Wistar-Furth to Lewis heart allograft model resulted in a mean graft survival time of 24.7+/-16.9 d, and all grafts were ultimately rejected. Only concomitant injection of donor cells (4 x 10(7) splenocytes) plus a single injection of CTLA4Ig on the day of transplant could induce long-term graft acceptance in 50% of animals. In both the cardiac and renal transplant models, the thymus and spleen were required for induction of tolerance. The maintenance phase of tolerance, however, did not require an intact thymus but did require the presence of a spleen. These data have important clinical applicability because human studies with T cell costimulatory blockade are being planned.