Influence of Donor Pretreatment with Dopamine on Allogeneic Kidney Transplantation after Prolonged Cold Storage in Rats

Electroacupuncture alleviates intestinal inflammation and barrier dysfunction by activating dopamine in a rat model of intestinal ischaemia

BACKGROUND

To investigate whether the mechanism underlying the anti-inflammatory effects of electroacupuncture (EA) at ST36 involves dopamine (DA) and its receptor and whether it is mediated by the vagus nerve in a rat model of intestinal ischaemia-reperfusion (I/R) injury.

METHODS

Rats were subjected to gut ischaemia for 30 min and then received EA for 30 min with or without abdominal vagotomy or intraperitoneal administration of butaclamol (D1 receptor antagonist) or spiperone (D2 receptor antagonist). Plasma levels of DA and tumour necrosis factor (TNF)-α were assessed 1 or 4 h after reperfusion. Myeloperoxidase (MPO) activity and malondialdehyde (MDA) content in intestinal tissues were assessed using enzyme-linked immunosorbent assay (ELISA) kits. Intestinal tissue injury was assessed by observation of the pathological lesions and permeability to 4 kDa fluorescein isothiocyanate (FITC)-dextran.

RESULTS

EA significantly increased levels of DA and lowered levels of TNF-α. EA also inhibited intestinal levels of MPO and MDA and intestinal tissue injury and decreased intestinal permeability to FITC-dextran. Abdominal vagotomy and intraperitoneal administration of butaclamol (but not spiperone) inhibited the effects of EA.

CONCLUSION

These findings suggest that EA at ST36 could attenuate intestinal I/R-induced inflammatory injury and that the underlying mechanism may involve EA-induced increases in levels of DA, mediated by the vagus nerve and D1 receptors.

Renal temperature reduction progressively favors mitochondrial ROS production over respiration in hypothermic kidney preservation

BACKGROUND

Hypothermia, leading to mitochondrial inhibition, is widely used to reduce ischemic injury during kidney preservation. However, the exact effect of hypothermic kidney preservation on mitochondrial function remains unclear.

METHODS

We evaluated mitochondrial function [i.e. oxygen consumption and production of reactive oxygen species (ROS)] in different models (porcine kidney perfusion, isolated kidney mitochondria, and HEK293 cells) at temperatures ranging 7-37 °C.

RESULTS

Lowering temperature in perfused kidneys and isolated mitochondria resulted in a rapid decrease in oxygen consumption (65% at 27 °C versus 20% at 7 °C compared to normothermic). Decreased oxygen consumption at lower temperatures was accompanied by a reduction in mitochondrial ROS production, albeit markedly less pronounced and amounting only 50% of normothermic values at 7 °C. Consequently, malondialdehyde (a marker of ROS-induced lipid peroxidation) accumulated in cold stored kidneys. Similarly, low temperature incubation of kidney cells increased lipid peroxidation, which is due to a loss of ROS scavenging in the cold.

CONCLUSIONS

Lowering of temperature highly affects mitochondrial function, resulting in a progressive discrepancy between the lowering of mitochondrial respiration and their production of ROS, explaining the deleterious effects of hypothermia in transplantation procedures. These results highlight the necessity to develop novel strategies to decrease the formation of ROS during hypothermic organ preservation.

Contribution of alloantigens to hepatic ischemia/reperfusion injury: Roles of natural killer cells and innate immune recognition of nonself

Hepatic ischemia/reperfusion injury (IRI) remains a major clinical problem and involves the innate immune system's recognition of "nonself." Considering the efficient nonself recognition by natural killer (NK) cells, we hypothesize in this study that hepatic IRI associated with liver transplantation (LT) could be augmented in allogeneic rather than in syngeneic (Syn) grafts due to alloantigen recognition by innate immune cells, especially by NK cells. Using green fluorescent protein (GFP)/Sprague-Dawley rats, we tested our hypothesis in a rat LT model with 18 hours of cold storage in University of Wisconsin solution. Hepatic IRI was significantly augmented in allografts with higher alanine transaminase levels, increased necrosis, and vigorous proinflammatory mediator up-regulation compared to Syn grafts. Injury increased in allografts associated with augmented GFP+ host leukocyte infiltration due to significantly increased host CD11b/c+ and RP-1(+) neutrophil recruitment. A large number of liver-resident (donor) mature CD11b/c+ NK cells quickly diminished from allografts, but not from Syn grafts. Depletion of mature NK cells from liver grafts with anti-asialo monosialotetrahexosylganglioside significantly improved hepatic IRI and reduced neutrophil infiltration and proinflammatory mediators. In conclusion, early innate immune responses were more significantly enhanced in allografts than in Syn grafts during hepatic IRI, in part through NK cell recognition of "missing self."

N-octanoyl-dopamine is a potent inhibitor of platelet function

Dopamine (DA) is a co-agonist for platelet activation; yet, donor DA treatment is associated with improved transplantation outcome in renal and heart recipients. Recently, N-octanoyl-dopamine (NOD) was developed which displays superior effects compared to DA in terms of graft protecting properties. Whereas DA is a known platelet co-agonist, the effect of NOD on platelet function is unknown. This is a hypothesis generating study with the aim to assess the effects and molecular mechanisms of NOD and NOD-like compounds on platelet function. The influence of DA, NOD, and NOD-like compounds on platelet responses to classical agonists (adenosine 5'-diphosphate (ADP), U46619) was investigated in six healthy donors by applying whole blood aggregometry (Multiplate®) and flow cytometry for Pac-1, CD62P, and CD63 expression. Changes in platelet cAMP concentrations were assessed by ELISA. While DA showed synergy in platelet activation by ADP and U46619, NOD caused significant inhibition of platelet function both in whole blood aggregometry and flow cytometry. The inhibitory effect of NOD was not mediated via cAMP levels. The nonredox-active NOD-analog N-octanoyl-tyramine had no effects on platelet function. Acetylated NOD conferred to NOD by intracellular esterases showed similar inhibitory effects as NOD. In contrast to DA, NOD is a potent inhibitor of platelet function most likely through intracellular redox-active processes. This adds to the overall protective effect of NOD on pre-transplantation injury and makes NOD an attractive candidate compound for donor or organ conditioning prior to transplantation.

Innate pathways of immune activation in transplantation

Studies of the immune mechanisms of allograft rejection have predominantly focused on the adaptive immune system that includes T cells and B cells. Recent investigations into the innate immune system, which recognizes foreign antigens through more evolutionarily primitive pathways, have demonstrated a critical role of the innate immune system in the regulation of the adaptive immune system. Innate immunity has been extensively studied in its role as the host's first-line defense against microbial pathogens; however, it is becoming increasingly recognized for its ability to also recognize host-derived molecules that result from tissue damage. The capacity of endogenous damage signals acting through the innate immune system to lower immune thresholds and promote immune recognition and rejection of transplant grafts is only beginning to be appreciated. An improved understanding of these pathways may reveal novel therapeutic targets to decrease graft alloreactivity and increase graft longevity.

N-octanoyl dopamine, a non-hemodyanic dopamine derivative, for cell protection during hypothermic organ preservation

Background

Although donor dopamine treatment reduces the requirement for post transplantation dialysis in renal transplant recipients, implementation of dopamine in donor management is hampered by its hemodynamic side-effects. Therefore novel dopamine derivatives lacking any hemodynamic actions and yet are more efficacious in protecting tissue from cold preservation injury are warranted. We hypothesized that variation of the molecular structure would yield more efficacious compounds avoid of any hemodynamic effects.

Methodology/Principal Findings

To this end, we assessed protection against cold preservation injury in HUVEC by the attenuation of lactate dehydrogenase (LDH) release. Modification of dopamine by an alkanoyl group increased cellular uptake and significantly improved efficacy of protection. Further variation revealed that only compounds bearing two hydroxy groups in ortho or para position at the benzene nucleus, i.e. strong reductants, were protective. However, other reducing agents like N-acetyl cysteine and ascorbate, or NADPH oxidase inhibition did not prevent cellular injury following cold storage. Unlike dopamine, a prototypic novel compound caused no hemodynamic side-effects.

Conclusions/Significance

In conclusion, we demonstrate that protection against cold preservation injury by catecholamines is exclusively governed by strong reducing capacity and sufficient lipophilicity. The novel dopamine derivatives might be of clinical relevance in donor pre-conditioning as they are completely devoid of hemodynamic action, their increased cellular uptake would reduce time of treatment and therefore also may have a potential use for non-heart beating donors.

Dopamine as additive to cold preservation solution improves postischemic integrity of the liver

Dopamine pretreatment has been used to confer protection against cellular injury following hypothermia or anoxia, especially in vascular endothelial cells. Ischemia/reperfusion-associated tissue alterations still represent a major drawback in liver transplantation. The present study was aimed to investigate the effect of dopamine as an ex vivo adjunct, added to the cold storage solution, on cold preservation of the liver. Rat livers were excised 30 min after cardiac arrest, flushed with preservation solution and cold stored for 18 h. Dopamine (10, 50 or 100 microM) was added to the preservation solution in other livers. Organ viability was evaluated by 120 min of warm reperfusion in vitro (n = 6, resp.). Dopamine induced a dose related up to fourfold (at 50 mum) reduction in parenchymal (ALT, LDH) and mitochondrial (GLDH) enzyme release and significantly reduced histologic signs of tissue injury. Bile production and tissue ATP was doubled by dopamine. On the molecular level, dopamine enhanced postischemic phosphorylation of protein kinase A and p42/44 MAP kinase. Inhibition of cAMP-PKA pathway by simultaneous application of RP-cAMPs had no effect on P42/44 phosphorylation, or functional recovery of dopamine-treated grafts. Dopamine supplementation of the flush-out solution appears as a simple way for ex vivo augmentation of liver viability during preservation, not mediated via the catecholamine-cAMP signal cascade.

Donor dopamine treatment limits pulmonary oedema and inflammation in lung allografts subjected to prolonged hypothermia

BACKGROUND

Endothelial barrier dysfunction severely compromises organ function after reperfusion. Because dopamine pretreatment improves hypothermia mediated barrier dysfunction, we tested the hypothesis that dopamine treatment of lung allografts positively affects tissue damage associated with hypothermic preservation and reperfusion.

METHODS

Rats were treated for 1 hr with dopamine (5 microg/min/kg) or vehicle (NaCl). Thereafter lungs were explanted, flushed with Perfadex solution and stored at 4 degrees C for different time periods. Peak inspiratory pressure (PIP), pulmonary arterial pressure (PAP), and lung weight were measured online during reperfusion. Inflammatory mediators in the perfusate and the expression of adhesion molecules in situ were measured after perfusion.

RESULTS

Lungs could tolerate a cold ischemia time of up to 6 hr with stable PIP, PAP, and no edema formation upon reperfusion. Cold ischemia time above 6 hr significantly increased PIP, PAP, and pulmonary edema in untreated but not in dopamine treated lungs (P< or =0.001 dopamine treated vs. untreated). Perfusion and ventilation alone induced a strong up-regulation of cytokine-induced neutrophil chemoattractant-1 and adhesion molecules in untreated lungs, whereas in dopamine treated lungs significantly lower levels were found. Dopamine treatment also inhibited tissue damage associated with hypothermic preservation as measured by nicotinamide adenine dinucleotide staining.

CONCLUSION

Our study suggests that donor dopamine treatment is a highly effective modality to maintain organ quality of lung allograft. These findings are of high clinical relevance because prevention of tissue damage might reduce complications associated with lung transplantation and hence improve graft survival in lung transplant recipients.

Activation and modulation of cardiac poly-adenosine diphosphate ribose polymerase activity in a rat model of brain death

DNA damage during transplantation can activate poly-adenosine diphosphate ribose polymerase (PARP) resulting in the generation of polymers of adenosine diphosphate-ribose (PAR). Excessive linkage of PAR to nuclear proteins can induce cell death, thereby limiting the function of transplanted organs. This study uses a rat model of brain death to determine the profile of PARP activation and whether mechanisms that lead to cell death can be ameliorated by appropriate donor resuscitation. The expression of PAR-linked nuclear proteins within cardiac myocytes was greatly increased after the induction of donor brain death. Importantly, infusion of noradrenaline or vasopressin to normalize the chronic hypotension produced by brain death reduced the expression of PAR to a level below baseline. These data suggest that chronic hypotension after donor brain death has the potential to limit cardiac function through the activation of PARP; however, this early cause of graft damage can be mitigated by appropriate donor resuscitation.

Gene expression profiling on acute rejected transplant kidneys with microarray

To investigate the gene expression profiles in acute allograft rejection of renal transplantation, and identify the markers for the early diagnosis of acute rejection, heterotopic kidney transplantation was performed by using F344 or Lewis donors and Lewis recipients. No immunosuppressant was used. Renal grafts were harvested on days 3, 7, and 14. A commercial microarray was used to measure gene expression levels in day-7 grafts. The expression levels of 48 genes were up-regulated in the allograft in comparison with the isograft control, and interferon-gamma-induced GTPase gene was most significantly up-regulated in allografts. It is concluded that a variety of pathways are involved in organ transplant rejection which is dynamic and non-balanced. IFN-inducible genes, such as IGTP, may play an important role in the rejection. A lot of important factors involved in acute rejection are unnecessary but sufficient conditions for the rejection. We are led to conclude that it is virtually impossible to make an early diagnosis based on a single gene marker, but it could be achieved on the basis of a set of markers.

Atorvastatin Donor Pretreatment Prevents Ischemia/Reperfusion Injury in Renal Transplantation in Rats: Possible Role for Aldose-Reductase Inhibition

BACKGROUND

The aim of the present study was to evaluate the effect of donor pretreatment with atorvastatin on ischemia/reperfusion (I/R) injury in renal transplantation in rats.

METHODS

Donor rats were pretreated orally with atorvastatin or vehicle 2 days prior to explantation. Kidneys were stored for 24 hr at 4 degrees C in University of Wisconsin solution and transplanted into isogeneic or allogeneic recipients.

RESULTS

Donor treatment with atorvastatin improved initial graft function, reduced renal inflammation, and the number of TUNEL-positive cells in renal tissue after prolonged cold storage and isogeneic transplantation. In the allogeneic transplantation model, donor treatment with atorvastatin reduced renal inflammation in grafts harvested after 5 days, but no improvement of long-term graft survival (24 weeks) could be observed. A genome wide gene expression profile of donor kidneys from atorvastatin treated or vehicle treated rats revealed a fivefold downregulation of aldose reductase in all atorvastatin treated animals (P<0.01). Donor treatment with an aldose-reductase inhibitor improved kidney function and reduced renal inflammation after prolonged cold storage and isogeneic transplantation.

CONCLUSION

Our data suggest that downregulation of aldose reductase in renal tissue might underlie the protective effect of donor atorvastatin treatment. Donor pretreatment with a statin or an aldose reductase inhibitor could offer a new treatment strategy to prevent transplantation associated tissue injury.

Kidney grafts from brain dead donors: Inferior quality or opportunity for improvement?

Major improvements in immunosuppressive treatment, surgical techniques, and treatment of post-transplant complications have contributed considerably to improved outcome in renal transplantation over the past decades. Yet, these accomplishments have not led to similar improvements in transplant outcome when the results of living and deceased donors are compared. The enormous demand for donor kidneys has allowed for the increase in acceptance of suboptimal donors. The use of brain dead patients as organ donors has had a tremendous positive influence on the number of renal transplants. Unfortunately, the physiologically abnormal state of brain death has a negative effect on transplant outcome. The fact that transplanted kidneys derived from brain dead donors have a decreased viability indicates that potential grafts are already damaged before retrieval and preservation. In this review, we present an overview of the current knowledge of (patho)-physiological effects of brain death and its relevance for renal transplant outcome. In addition, several options for therapeutic intervention during brain death in the donor with the goal to improve organ viability and transplant outcome are discussed.

Donor Dopamine Pretreatment Inhibits Tubulitis in Renal Allografts Subjected to Prolonged Cold Preservation

BACKGROUND

In the present study, we used the Brown-Norway (BN) to Lewis model as a model for acute rejection, to test the hypothesis that dopamine (DA) treatment of BN donors significantly reduces the inflammatory response after renal transplantation.

METHODS

BN and Lewis rats (isograft controls) were treated for 24 hr with DA (5 microg/kg/min) or NaCl (0.9%), respectively. After 24 hr of cold storage in University of Wisconsin (UW) solution, renal allografts were orthotopically transplanted into Lewis recipients. All recipients received immunosuppression until they were sacrificed. Allografts were harvested one, three, five, and 10 days after transplantation and analyzed by light microscopy, immunohistochemistry (CD3, major histocompatibility complex [MHC] class II, ED1, P-selectin and intercellular adhesion molecule [ICAM]-1) and by RNase protection assay for cytokine mRNA.

RESULTS

Ten days after transplantation Banff tubulitis scores were significantly lower in DA-treated than in NaCl-treated allografts. No significant differences were found in Banff interstitial infiltration scores. The numbers of MHC class II+ and CD3+ cells were significantly decreased in DA-treated animals as assessed by immunohistochemistry. No differences were found in the number of ED1+, P-selectin+, and ICAM-1+ cells. The expression of Ltalpha, tumor necrosis factor, interleukin-1beta, and interleukin-2 mRNA was significantly reduced in DA-treated animals.

CONCLUSION

Our data indicate that donor DA treatment significantly inhibits tubulitis in renal allografts subjected to prolonged cold preservation. A reduced number of infiltrating MHC class II+ and CD3+ cells together with decreased cytokine expression could diminish renal scarring, reduce allograft immunogenicity, and hence improve transplantation outcome.

Effect of pre-treatment with catecholamines on cold preservation and ischemia/reperfusion-injury in rats

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.