Early renal ischemia-reperfusion injury in humans is dominated by IL-6 release from the allograft

GC-MS and GC-MS/MS measurement of malondialdehyde (MDA) in clinical studies: Pre-analytical and clinical considerations

Malondialdehyde (MDA; 1,3-propanedial, OHC-CH2-CHO) is one of the most frequently measured biomarkers of oxidative stress in plasma and serum. L-Arginine (Arg) is the substrate of nitric oxide synthases (NOS), which convert L-arginine to nitric oxide (NO) and L-citrulline. The Arg/NO pathway comprises several members, including the endogenous NOS-activity inhibitor asymmetric dimethylarginine (ADMA) and its major metabolite dimethyl amine (DMA), and nitrite and nitrate, the major NO metabolites. Reliable measurement of MDA and members of the Arg/NO pathway in plasma, serum, urine and in other biological samples, such as saliva and cerebrospinal fluid, is highly challenging both for analytical and pre-analytical reasons. In our group, we use validated gas chromatography-mass spectrometry (GC-MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) methods for the quantitative determination in clinical studies of MDA as a biomarker of oxidative stress, and various Arg/NO metabolites that describe the status of this pathway. Here, the importance of pre-analytical issues, which has emerged from the use of GC-MS and GC-MS/MS in clinico-pharmacological studies, is discussed. Paradigmatically, two studies on the long-term oral administration of L-arginine dihydrochloride to patients suffering from peripheral arterial occlusive disease (PAOD) or coronary artery disease (CAD) were considered. Pre-analytical issues that were addressed include blood sampling, plasma or serum storage, study design (notably in long-term studies), and the alternative of measuring MDA in human urine.

Taurine as Antioxidant in a Novel Cell- and Oxygen Carrier-Free Perfusate for Normothermic Machine Perfusion of Porcine Kidneys

Donor organ-shortage has resulted in the increased use of marginal grafts; however, normothermic machine perfusion (NMP) holds the potential for organ viability assessment and restoration of marginal grafts prior to transplantation. Additionally, cell-, oxygen carrier-free and antioxidants-supplemented solutions could potentially prevent adverse effects (transfusion reactions, inflammation, hemolysis), associated with the use of autologous packed red blood cell (pRBC)-based perfusates. This study compared 6 h NMP of porcine kidneys, using an established pRBC-based perfusate (pRBC, n = 7), with the novel cell- and oxygen carrier-free organ preservation solution Ecosol, containing taurine (Ecosol, n = 7). Despite the enhanced tissue edema and tubular injury in the Ecosol group, related to a suboptimal molecular mass of polyethylene glycol as colloid present in the solution, functional parameters (renal blood flow, intrarenal resistance, urinary flow, pH) and oxygenation (arterial pO₂, absence of hypoxia-inducible factor 1-alpha) were similar to the pRBC group. Furthermore, taurine significantly improved the antioxidant capacity in the Ecosol group, reflected in decreased lactate dehydrogenase, urine protein and tubular vacuolization compared to pRBC. This study demonstrates the feasibility of 6 h NMP using a taurine containing, cell- and oxygen carrier-free perfusate, achieving a comparable organ quality to pRBC perfused porcine kidneys.

A biocompatible nanoparticle-based approach to inhibiting renal ischemia reperfusion injury in mice by blocking thrombospondin-1 activity

Thrombospondin-1 (TSP-1) is a key mediator of renal ischemia-reperfusion injury (IRI), a major cause of kidney dysfunction under various disease conditions and a risk factor of renal allograft rejection. In this study, we developed a nanotechnology-based therapy targeting TSP-1 to prevent renal IRI. A biocompatible nanoparticle (NP) capable of specific binding to TSP-1 was prepared by conjugating NPs with TSP-1-binding (LSKL) peptides. LSKL/NPs not only effectively adsorbed recombinant TSP-1 proteins in vitro, but also efficiently neutralized TSP-1 in mice undergoing renal IRI. IRI-induced elevation of TSP-1 in the kidney was significantly inhibited by post-IR treatment with LSKL/NPs, but not free LSKL or NPs. Furthermore, TSP-1 proteins adsorbed on LSKL/NPs were functionally inactive and unable to induce apoptosis in renal tubular epithelial cells. Importantly, LSKL/NPs induced strong protection against renal IRI, as shown by markedly diminished serum creatinine levels and improved histological lesions of the kidney. Thus, LSKL/NPs provide a useful means of depleting and inactivating TSP-1 and a potential therapy for renal IRI.

Kidney Normothermic Machine Perfusion Can Be Used as a Preservation Technique and a Model of Reperfusion to Deliver Novel Therapies and Assess Inflammation and Immune Activation

Ischaemia-reperfusion injury (IRI) is an inevitable process in transplantation and results in inflammation and immune system activation. Alpha-1 antitrypsin (AAT) has anti-inflammatory properties. Normothermic machine perfusion (NMP) can be used to deliver therapies and may help in assessing the effects of IRI and immunity. This study investigated the effects of AAT on IRI and inflammation in pig kidneys when administered during preservation, followed by normothermic reperfusion (NR) with autologous whole blood, as a surrogate for transplant. Two different models were used to deliver AAT or placebo to paired slaughterhouse pig kidneys: Model 1: 7-h static cold storage (SCS) + 3-h NR (n = 5 pairs), where either AAT (10 mg/ml) or placebo was delivered in the flush following retrieval; Model 2: 4-h SCS + 3-h NMP + 3-h NR (n = 5 pairs), where either AAT or placebo was delivered during NMP. Injury markers and cytokines levels were analysed in the perfusate, and heat shock protein 70 KDa (HSP-70) was analysed in biopsies. AAT delivered to kidneys showed no adverse effects on perfusion parameters. HSP-70 fold changes were significantly lower in the AAT group during NMP (P < 0.01, paired t-test) but not during NR. Interleukin-1 receptor antagonist (IL-1ra) fold changes were significantly higher in the AAT group during NR model 1 (p < 0.05, two-way ANOVA). In contrast to the AAT group, significant upregulation of interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) between t = 90 min and t = 180 min and interleukin-8 (IL-8) between baseline and t = 90 min was observed in the control group in NR model 2 (p < 0.05, Tukey's multiple comparison test). However, overall inflammatory cytokines and injury markers showed similar levels between groups. Delivery of AAT to pig kidneys was safe without any detrimental effects. NMP and NR provided excellent methods for comparison of inflammation and immune activation in the delivery of a novel therapy.

Fimasartan ameliorates renal ischemia reperfusion injury via modulation of oxidative stress, inflammatory and apoptotic cascades in a rat model

Ischemia-reperfusion injury (IRI) can be defined as changes in the functions and structures of the tissues resulting from the restoration of blood after a period of ischemia. This study aimed to assess the potential protective effect of Fimasartan (angiotensin receptor antagonist) in the bilateral renal IRI in male rats through its potential effect on renal functions, modulation of the inflammatory cascade, oxidative stress, and apoptotic effect. The animals were equally assigned into four groups. The sham (negative control) group was exposed to surgical conditions without induction of IRI. The control group was exposed to ischemia by occluding the renal pedicles by clamps for 30 min, followed by restoration of blood for 2h. The vehicle-treated group received dimethyl sulfoxide (DMSO) by intraperitoneal injection (IP) 30 minutes before clamping. Fimasartan-treated group: rats pretreated with Fimasartan a dose of 3 mg/kg IP; this was half hour before occluding the renal pedicles. Animals were then exposed to 30 min ischemia (clamping the renal pedicles) followed by 2h reperfusion by releasing the clamps. Blood samples were collected to examine the levels of serum urea and creatinine. Renal tissue was used to measure the levels of cytokines (TNFα, IL-6) and total antioxidant capacity (TAC). Immunohistochemistry was used to assess the levels of Bax, caspase 3, and Bcl-2. Histopathological analyses were performed to detect the parenchymal injury. The present study shows that pretreatment with Fimasartan improves kidney function through its effects on oxidative stress, cytokines, and apoptotic markers.

Complement Blockade in Recipients Prevents Delayed Graft Function and Delays Antibody-mediated Rejection in a Nonhuman Primate Model of Kidney Transplantation

BACKGROUND

Complement activation in kidney transplantation is implicated in the pathogenesis of delayed graft function (DGF). This study evaluated the therapeutic efficacy of high-dose recombinant human C1 esterase inhibitor (rhC1INH) to prevent DGF in a nonhuman primate model of kidney transplantation after brain death and prolonged cold ischemia.

METHODS

Brain death donors underwent 20 h of conventional management. Procured kidneys were stored on ice for 44-48 h, then transplanted into ABO-compatible major histocompatibility complex-mismatched recipients. Recipients were treated with vehicle (n = 5) or rhC1INH 500 U/kg plus heparin 40 U/kg (n = 8) before reperfusion, 12 h, and 24 h posttransplant. Recipients were followed up for 120 d.

RESULTS

Of vehicle-treated recipients, 80% (4 of 5) developed DGF versus 12.5% (1 of 8) rhC1INH-treated recipients (P = 0.015). rhC1INH-treated recipients had faster creatinine recovery, superior urinary output, and reduced urinary neutrophil gelatinase-associated lipocalin and tissue inhibitor of metalloproteinases 2-insulin-like growth factor-binding protein 7 throughout the first week, indicating reduced allograft injury. Treated recipients presented lower postreperfusion plasma interleukin (IL)-6, IL-8, tumor necrosis factor-alpha, and IL-18, lower day 4 monocyte chemoattractant protein 1, and trended toward lower C5. Treated recipients exhibited less C3b/C5b-9 deposition on day 7 biopsies. rhC1INH-treated animals also trended toward prolonged mediated rejection-free survival.

CONCLUSIONS

Our results recommend high-dose C1INH complement blockade in transplant recipients as an effective strategy to reduce kidney injury and inflammation, prevent DGF, delay antibody-mediated rejection development, and improve transplant outcomes.

Rational selection of a biomarker panel targeting unmet clinical needs in kidney injury

The pipeline of biomarker translation from bench to bedside is challenging and limited biomarkers have been adopted to routine clinical care. Ideally, biomarker research and development should be driven by unmet clinical needs in health care. To guide researchers, clinical chemists and clinicians in their biomarker research, the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) has developed a structured questionnaire in which the clinical gaps in current clinical pathways are identified and desirable performance specifications are predefined. In kidney injury, the high prevalence of the syndrome acute kidney injury (AKI) in the hospital setting has a significant impact on morbidity, patient survival and health care costs, but the use of biomarkers indicating early kidney injury in daily patient care remains limited. Routinely, medical labs measure serum creatinine, which is a functional biomarker, insensitive for detecting early kidney damage and cannot distinguish between renal and prerenal AKI. The perceived unmet clinical needs in kidney injury were identified through the EFLM questionnaire. Nephrologists within our tertiary care hospital emphasized that biomarkers are needed for (1) early diagnosis of in-hospital AKI after a medical insult and in critically ill patients, (2) risk stratification for kidney injury prior to a scheduled (elective) intervention, (3) kidney injury monitoring in patients scheduled to receive nephrotoxic medication and after kidney transplantation and (4) differentiation between prerenal AKI and structural kidney damage. The biomarker search and selection strategy resulted in a rational selection of an eleven-protein urinary panel for kidney injury that target these clinical needs. To assess the clinical utility of the proposed biomarker panel in kidney injury, a multiplexed LC-MS test is now in development for the intended translational research.

Transplanted Kidney Increases Nitric Oxide Formation With Metabolic Acidosis Reduction

OBJECTIVES

As a vasodilator, nitric oxide is considered to play a significant role in the homeostatic regulation of renal hemodynamics. To test the hypothesis that a kidney graft is capable of producing nitric oxide immediately after renal transplant surgery, we examined the possibility that it positively affects local metabolic acidosis.

MATERIALS AND METHODS

In kidney transplant recipients, we analyzed renal vein and central vein blood samples, which reflect local and systemic metabolic alterations, respectively. Samples were taken immediately after kidney recirculation (that is, the first blood passing through after clamps are released) and at 5, 15, and 30 minutes thereafter. Levels of nitric oxide metabolites (nitrites, nitrates, and their sum), malondialdehyde (an indicator of oxidative damages), and parameters of acid-base balance (pH level, actual excess base, hemoglobin, actual bicarbonate, partial pressure of carbon dioxide, partial pressure of oxygen) were analyzed. Living kidney donors (the recipients' parents) were controls.

RESULTS

In renal vein samples, nitrates and the sum of nitrites and nitrates were significantly higher than that shown in control (P < .001) and central vein (P < .05) samples, suggesting an immediate increase in nitric oxide production in the transplanted organ. Metabolic acidosis occurred in both the renal and central vein, indicated by decreased pH and actual bicarbonate level as well as by negative actual base excess level. Only in the renal vein was an increased nitrite and nitrate associated with a reduction of negative actual excess base, thereby suggesting a decrease in anion formation.

CONCLUSIONS

Transplanted kidneys increase nitric oxide production immediately after organ transplant surgery, which positively affects local metabolic acidosis. The mechanism for this effect is likely local circulation improvement.

Results of an explorative clinical evaluation suggest immediate and persistent post-reperfusion metabolic paralysis drives kidney ischemia reperfusion injury

Delayed graft function is the manifestation of ischemia reperfusion injury in the context of kidney transplantation. While hundreds of interventions successfully reduce ischemia reperfusion injury in experimental models, all clinical interventions have failed. This explorative clinical evaluation examined possible metabolic origins of clinical ischemia reperfusion injury combining data from 18 pre- and post-reperfusion tissue biopsies with 36 sequential arteriovenous blood samplings over the graft in three study groups. These groups included living and deceased donor grafts with and without delayed graft function. Group allocation was based on clinical outcome. Magic angle NMR was used for tissue analysis and mass spectrometry-based platforms were used for plasma analysis. All kidneys were functional at one-year. Integration of metabolomic data identified a discriminatory profile to recognize future delayed graft function. This profile was characterized by post-reperfusion ATP/GTP catabolism (significantly impaired phosphocreatine recovery and significant persistent (hypo)xanthine production) and significant ongoing tissue damage. Failing high-energy phosphate recovery occurred despite activated glycolysis, fatty-acid oxidation, glutaminolysis and autophagia, and related to a defect at the level of the oxoglutarate dehydrogenase complex in the Krebs cycle. Clinical delayed graft function due to ischemia reperfusion injury associated with a post-reperfusion metabolic collapse. Thus, efforts to quench delayed graft function due to ischemia reperfusion injury should focus on conserving metabolic competence, either by preserving the integrity of the Krebs cycle and/or by recruiting metabolic salvage pathways.

Association of Impaired Reactive Aldehyde Metabolism with Delayed Graft Function in Human Kidney Transplantation

Delayed graft function is an early complication following kidney transplantation with an unclear molecular mechanism. Here we determined whether impaired reactive aldehyde metabolism is associated with delayed graft function. Human kidney biopsies from grafts with delayed graft function were compared with grafts that did not develop delayed graft function by Ingenuity gene pathway analysis. A second series of grafts with delayed graft function (n = 10) were compared to grafts that did not develop delayed graft function (n = 10) by measuring reactive aldehyde metabolism, reactive aldehyde-induced protein adduct formation, and aldehyde dehydrogenase (ALDH) gene and protein expression. In the first series of kidney biopsies, several gene families known for metabolizing reactive aldehydes, such as aldehyde dehydrogenase (ALDH), aldo-keto reductase (AKR), and glutathione-S transferase (GSTA), were upregulated in kidneys that did not develop delayed graft function versus those that did. In the second series of kidney grafts, we focused on measuring aldehyde-induced protein adducts and ALDH enzymatic activity. The reactive aldehyde metabolism by ALDH enzymes was reduced in kidneys with delayed graft function compared to those that did not (37 ± 12^∗ vs. 79 ± 5 μg/min/mg tissue, ^∗P < 0.005, respectively). ALDH enzymatic activity was also negatively correlated with length of hospital stay after a kidney transplant. Together, our study identifies a reduced ALDH enzymatic activity with kidneys developing delayed graft function compared to those that did not. Measuring ALDH enzymatic activity and reactive aldehyde-induced protein adducts can potentially be further developed as a biomarker to assess for delayed graft function and recovery from a kidney transplant.

Protective action of Crateva nurvala Buch. Ham extracts against renal ischaemia reperfusion injury in rats via antioxidant and anti-inflammatory activities

ETHNOPHARMACOLOGICAL RELEVANCE

Crateva nurvala stem bark is commonly used in Ayruveda in treatment of many renal injuries, e.g., urinary lithiasis, diuretic and nephroprotective. However, its protective effect against renal ischaemia/reperfusion, the major cause of acute kidney injury, has never been studied. Moreover, no comprehensive chemical profiling of its extracts was recorded.

AIM OF THE STUDY

Assessment of the protective effect of the plant extracts against renal ischaemia/reperfusion and elucidation of the possible mechanism of action. Then, to determine its bioactive constituents using modern UPLC-HRMS technique.

MATERIAL AND METHODS

Unilateral ischaemia was induced by clamping the left renal artery for 1h then reperfusion for 24h. Rats were divided in 4 groups: i) sham-operated group, ii) ischaemia/reperfusion, I/R group, iii) I/R protected by previous administration of Crateva leaves extract, CLE group and iv) I/R protected by previous administration of Crateva bark extract, CBE group. At the end of reperfusion, blood samples were analyzed for renal function biomarkers. Kidneys were examined histopathologically and their homogenates were used in determining the intracellular levels of oxidative stress, inflammatory, and apoptosis markers.

RESULTS

Leaves and bark extracts attenuated the deleterious effects of I/R apparent in reducing LDH, creatinine and blood urea nitrogen levels. The extracts reduced the oxidative stress by replenishing the glutathione levels and Nrf2 factor levels. Moreover, extracts decreased levels of pro-inflammatory TNF-α, NF-κβ and IL-6; which ultimately resulted in reducing the pro-apoptotic caspase-3. Bark and leave extracts have quite similar chemical profile where 42 compounds of various chemical classes were identified. Flavonoids are the major class of the bioactive phytochemicals CONCLUSION: C. nurvala extracts had effectively ameliorated the deleterious effects of renal I/R by mainly counteracting oxidative stress and presumably inflammation. Consequently, it can be used as a complementary treatment with other agents. In this aspect, leaves stand as a sustainable alternative to bark. The presented chemical profiling can be used in future standardization and quality control of the drug.

Novel Application of Localized Nanodelivery of Anti-Interleukin-6 Protects Organ Transplant From Ischemia-Reperfusion Injuries

Ischemia-reperfusion injury (IRI) evokes intragraft inflammatory responses, which markedly augment alloimmune responses against the graft. Understanding the mechanisms underlying these responses is fundamental to develop therapeutic regimens to prevent/ameliorate organ IRI. Here, we demonstrate that IRI results in a marked increase in mitochondrial damage and autophagy in dendritic cells (DCs). While autophagy is a survival mechanism for ischemic DCs, it also augments their production of interleukin (IL)-6. Allograft-derived dendritic cells (ADDCs) lacking autophagy-related gene 5 (Atg5) showed higher death rates posttransplantation. Transplanted ischemic hearts from CD11cCre/Atg5 conditional knockout mice showed marked reduction in intragraft expression of IL-6 compared with controls. To antagonize the effect of IL-6 locally in the heart, we synthesized novel anti-IL-6 nanoparticles with capacity for controlled release of anti-IL-6 over time. Compared with systemic delivery of anti-IL-6, localized delivery of anti-IL-6 significantly reduced chronic rejection with a markedly lower amount administered. Despite improved allograft histology, there were no changes to splenic T cell populations, illustrating the importance of local IL-6 in driving chronic rejection after IRI. These data carry potential clinical significance by identifying an innovative, targeted strategy to manipulate organs before transplantation to diminish inflammation, leading to improved long-term outcomes.

The hypoxanthine-xanthine oxidase axis is not involved in the initial phase of clinical transplantation-related ischemia-reperfusion injury

The hypoxanthine-xanthine oxidase (XO) axis is considered to be a key driver of transplantation-related ischemia-reperfusion (I/R) injury. Whereas interference with this axis effectively quenches I/R injury in preclinical models, there is limited efficacy of XO inhibitors in clinical trials. In this context, we considered clinical evaluation of a role for the hypoxanthine-XO axis in human I/R to be relevant. Patients undergoing renal allograft transplantation were included (n = 40) and classified based on duration of ischemia (short, intermediate, and prolonged). Purine metabolites excreted by the reperfused kidney (arteriovenous differences) were analyzed by the ultra performance liquid chromatography-tandem mass spectrometer (UPLCMS/MS) method and tissue XO activity was assessed by in situ enzymography. We confirmed progressive hypoxanthine accumulation (P < 0.006) during ischemia, using kidney transplantation as a clinical model of I/R. Yet, arteriovenous concentration differences of uric acid and in situ enzymography of XO did not indicate significant XO activity in ischemic and reperfused kidney grafts. Furthermore, we tested a putative association between hypoxanthine accumulation and renal oxidative stress by assessing renal malondialdehyde and isoprostane levels and allantoin formation during the reperfusion period. Absent release of these markers is not consistent with an association between ischemic hypoxanthine accumulation and postreperfusion oxidative stress. On basis of these data for the human kidney we hypothesize that the role for the hypoxanthine-XO axis in clinical I/R injury is less than commonly thought, and as such the data provide an explanation for the apparent limited clinical efficacy of XO inhibitors.

The influence of warm ischemia elimination on kidney injury during transplantation - clinical and molecular study

Kidney surface cooling was used during implantation to assess the effect of warm ischemia elimination on allograft function, histological changes and immune-related gene expression. 23 recipients were randomly assigned to a group operated on with kidney surface cooling during implantation (ice bag technique, IBT group), and the other 23 recipients receiving the contralateral kidney from the same donor were operated on with a standard technique. Three consecutive kidney core biopsies were obtained during the transplantation procedure: after organ recovery, after cold ischemia and after reperfusion. Gene expression levels were determined using low-density arrays (Format 32, TaqMan). The IBT group showed a significantly lower rate of detrimental events (delayed graft function and/or acute rejection, p = 0.015) as well as higher glomerular filtration rate on day 14 (p = 0.026). A greater decrease of MMP9 and LCN2 gene expression was seen in the IBT group during total ischemia (p = 0.003 and p = 0.018). Elimination of second warm ischemia reduced the number of detrimental events after kidney transplantation, and thus had influence on the short-term but not long-term allograft function. Surface cooling of the kidney during vascular anastomosis may reduce some detrimental effects of immune activation resulting from both brain death and ischemia-reperfusion injury.

IL-6: A Janus-like factor in abdominal aortic aneurysm disease

BACKGROUND AND AIMS

An abdominal aortic aneurysm (AAA) is part of the atherosclerotic spectrum of diseases. The disease is hallmarked by a comprehensive localized inflammatory response with striking IL-6 hyperexpression. IL-6 is a multifaceted cytokine that, depending on the context, acts as a pro- or anti-inflammatory factor. In this study, we explore a putative role for IL-6 in AAA disease.

METHODS

ELISA's, Western blot analysis, real time PCR and array analysis were used to investigate IL-6 expression and signaling in aneurysm wall samples from patients undergoing elective AAA repair. A role for IL-6 in AAA disease was tested through IL-6 neutralization experiments (neutralizing antibody) in the elastase model of AAA disease.

RESULTS

We confirmed an extreme disparity in aortic wall IL-6 content between AAA and atherosclerotic disease (median [5th-95th percentile] aortic wall IL-6 content: 281.6 [0.0-1820.8] (AAA) vs. 1.9 [0.0-37.8] μg/g protein (atherosclerotic aorta), (p < 0.001). Array analysis followed by pathway analysis showed that IL-6 hyper-expression is followed by increased IL-6 signaling (p < 0.000039), an observation confirmed by higher aneurysm wall pSTAT3 levels, and SOCS1 and SOCS3 mRNA expression, (p < 0.018). Remarkably, preventive IL-6 neutralization i.e. treatment started one day prior to the elastase-induction resulted in >40% 7-day mortality due to aortic rupture. In contrast, delayed IL-6 neutralization (i.e. neutralization started at day 4 after elastase induction) did not result in ruptures, and quenched AAA growth (p < 0.021).

CONCLUSIONS

AAA disease is characterized by increased IL-6 signaling. In the context of the elastase model of AAA disease, IL-6 appears a multi-faceted factor, protective upon acute injury, but negatively involved in the perpetuation of the disease process.

Reduction in Renal Ischemia-Reperfusion Injury in Mice by a Phosphoinositide 3-Kinase p110gamma-Specific Inhibitor

BACKGROUND

Although renal ischemia-reperfusion injury (IRI) can cause delayed graft function, a targeted therapy is not yet available. Because phosphoinositide 3-kinases (PI3K) p110γ and p110δ play important roles in immune cell migration and function, we investigated the effects of PI3K p110γ- and p110δ-specific inhibitors in a murine renal IRI model.

METHODS

Renal function was assessed by serum creatine and hematoxylin-eosin staining. Immune cell migration was assessed by flow cytometry and an in vitro cell migration assay using Transwell plates. Gene expression analysis and a multiplex cytokine/chemokine assay were performed to find cytokines/chemokines whose expression was upregulated in renal IRI and affected by p110γ-specific inhibitor.

RESULTS

The PI3K p110γ-specific inhibitor, but not p110δ-specific inhibitor, significantly reduced serum creatine levels and acute tubular necrosis. These were accompanied by reduced infiltration of B cells and reduced expression of CXCL9, a CXCR3 ligand, suggesting that p110γ plays an important role in B-cell migration toward injured kidneys. An in vitro cell migration assay revealed for the first time that B-cell migration to injured kidney cells and to CXCL9 requires p110γ.

CONCLUSIONS

p110γ-specific inhibitor ameliorates renal IRI by reducing necrosis and immune cell migration. This inhibitor may have the potential to reduce renal graft failure caused by renal IRI.

Hypoxia/Reoxygenation Inhibits P2Y11 Receptor Expression and Its Immunosuppressive Activity in Human Dendritic Cells

High concentrations of extracellular ATP (eATP) resulting from cell damage may be found during an ischemia/reperfusion (I/R) episode at the site of injury. eATP activates purinergic receptors in dendritic cells (DCs) and may inhibit inflammation. This immunosuppressive activity could be of interest in the field of I/R, which is an inflammatory condition involved in myocardial infarction, stroke, and solid organ transplantation. However, the specific purinergic receptor responsible for this effect remains to be identified. In this study, we report that eATP induced maturation of human monocyte-derived DCs. Additionally, eATP inhibited IL-12 production whereas IL-10 levels remained unchanged in activated DCs. These effects were prevented by the P2Y11R antagonist NF340. Interestingly, a 5-h hypoxia prevented the effects of eATP on cytokine production whereas a 1-h hypoxia did not affect the eATP-mediated decrease of IL-12 and IL-6. We showed a time-dependent downregulation of P2Y11R at both mRNA and protein levels that was prevented by knocking down hypoxia-inducible factor-1α. In this study, we showed an immunosuppressive role of P2Y11R in human DCs. Additionally, we demonstrated that the time-dependent downregulation of P2Y11R by hypoxia orientates DCs toward a proinflammatory phenotype that may be involved in post-I/R injuries as observed after organ transplantation.

Advances and challenges in immunotherapy for solid organ and hematopoietic stem cell transplantation

Although major advances have been made in solid organ and hematopoietic stem cell transplantation in the last 50 years, big challenges remain. This review outlines the current immunological limitations for hematopoietic stem cell and solid organ transplantation and discusses new immune-modulating therapies in preclinical development and in clinical trials that may allow these obstacles to be overcome.

1400W reduces ischemia reperfusion injury in an ex-vivo porcine model of the donation after circulatory death kidney donor

AIM: To investigate the effects of 1400W-a selective inducible nitric oxide synthase (iNOS) inhibitor in a model of donation after circulatory death (DCD) kidneys.

METHODS: Porcine kidneys were retrieved after 25 min warm ischemia. They were then stored on ice for 18 h before being reperfused ex vivo with oxygenated autologous blood on an isolated organ perfusion system. The selective iNOS inhibitor 1400W (10 mg/kg) was administered before reperfusion (n = 6) vs control group (n = 7). Creatinine (1000 μmol/L) was added to the system, renal and tubular cell function and the level of ischemia reperfusion injury were assessed over 3 h of reperfusion using plasma, urine and tissue samples.

RESULTS: Kidneys treated with 1400W had a higher level of creatinine clearance (CrCl) [area under the curve (AUC) CrCl: 2.37 ± 0.97 mL/min per 100 g vs 0.96 ± 0.32 mL/min per 100 g, P = 0.004] and urine output [Total: 320 ± 96 mL vs 156 ± 82 mL, P = 0.008]. There was no significant difference in levels of fractional excretion of sodium (AUC, Fr ex Na+: Control, 186.3% ± 81.7%.h vs 1400W, 153.4% ± 12.1%.h, P = 0.429). Levels of total protein creatinine ratio were significantly lower in the 1400W group after 1 h of reperfusion (1h Pr/Cr: 1400W 9068 ± 6910 mg/L/mmol/L vs Control 21586 ± 5464 mg/L/mmol/L, P = 0.026). Levels of 8-isoprostane were significantly lower in the 1400W group [8-iso/creatinine ratio: Control 239 ± 136 pg/L/mmol/L vs 1400W 139 ± 47 pg/L/mmol/L, P = 0.041].

CONCLUSION: This study demonstrated that 1400W reduced ischaemia reperfusion injury in this porcine kidney model of DCD donor. Kidneys had improved renal function and reduced oxidative stress.

Renal ischemia-reperfusion induces release of angiopoietin-2 from human grafts of living and deceased donors

BACKGROUND

Recent insights suggest that endothelial cell (EC) activation plays a major role in renal ischemia-reperfusion (I/R) injury. Interactions between ECs and pericytes via signaling molecules, including angiopoietins, are involved in maintenance of the vascular integrity. Experimental data have shown that enhancement of Angiopoietin (Ang)-1 signaling might be beneficial in renal I/R injury. However, little is known about the role of angiopoietins in human renal I/R injury.

METHODS

In this study, EC activation and changes in angiopoeitins are assessed in human living-donor (LD) and deceased-donor (DD) kidney transplantation. Local release of angiopoietins was measured by unique, dynamic arteriovenous measurements over the reperfused kidney.

RESULTS

Renal I/R is associated with acute EC activation shown by a vast Ang-2 release from both LD and DD shortly after reperfusion. Its counterpart Ang-1 was not released. Histologic analysis of kidney biopsies showed EC loss after reperfusion. Baseline protein and mRNA Ang-1 expression was significantly reduced in DD compared with LD and declined further after reperfusion.

CONCLUSIONS

Human renal I/R injury induces EC activation after reperfusion reflected by Ang-2 release from the kidney. Interventions aimed at maintenance of vascular integrity by modulating angiopoietin signaling may be promising in human clinical kidney transplantation.

Hematopoietic microRNA-126 protects against renal ischemia/reperfusion injury by promoting vascular integrity

Ischemia/reperfusion injury (IRI) is a central phenomenon in kidney transplantation and AKI. Integrity of the renal peritubular capillary network is an important limiting factor in the recovery from IRI. MicroRNA-126 (miR-126) facilitates vascular regeneration by functioning as an angiomiR and by modulating mobilization of hematopoietic stem/progenitor cells. We hypothesized that overexpression of miR-126 in the hematopoietic compartment could protect the kidney against IRI via preservation of microvascular integrity. Here, we demonstrate that hematopoietic overexpression of miR-126 increases neovascularization of subcutaneously implanted Matrigel plugs in mice. After renal IRI, mice overexpressing miR-126 displayed a marked decrease in urea levels, weight loss, fibrotic markers, and injury markers (such as kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin). This protective effect was associated with a higher density of the peritubular capillary network in the corticomedullary junction and increased numbers of bone marrow-derived endothelial cells. Hematopoietic overexpression of miR-126 increased the number of circulating Lin(-)/Sca-1(+)/cKit(+) hematopoietic stem and progenitor cells. Additionally, miR-126 overexpression attenuated expression of the chemokine receptor CXCR4 on Lin(-)/Sca-1(+)/cKit(+) cells in the bone marrow and increased renal expression of its ligand stromal cell-derived factor 1, thus favoring mobilization of Lin(-)/Sca-1(+)/cKit(+) cells toward the kidney. Taken together, these results suggest overexpression of miR-126 in the hematopoietic compartment is associated with stromal cell-derived factor 1/CXCR4-dependent vasculogenic progenitor cell mobilization and promotes vascular integrity and supports recovery of the kidney after IRI.

Oxidative damage in clinical ischemia/reperfusion injury: a reappraisal

AIMS

Ischemia/reperfusion (I/R) injury is a common clinical problem. Although the pathophysiological mechanisms underlying I/R injury are unclear, oxidative damage is considered a key factor in the initiation of I/R injury. Findings from preclinical studies consistently show that quenching reactive oxygen and nitrogen species (RONS), thus limiting oxidative damage, alleviates I/R injury. Results from clinical intervention studies on the other hand are largely inconclusive. In this study, we systematically evaluated the release of established biomarkers of oxidative and nitrosative damage during planned I/R of the kidney and heart in a wide range of clinical conditions.

RESULTS

Sequential arteriovenous concentration differences allowed specific measurements over the reperfused organ in time. None of the biomarkers of oxidative and nitrosative damage (i.e., malondialdehyde, 15(S)-8-iso-prostaglandin F2α, nitrite, nitrate, and nitrotyrosine) were released upon reperfusion. Cumulative urinary measurements confirmed plasma findings. As of these negative findings, we tested for oxidative stress during I/R and found activation of the nuclear factor erythroid 2-related factor 2 (Nrf2), the master regulator of oxidative stress signaling.

INNOVATION

This comprehensive, clinical study evaluates the role of RONS in I/R injury in two different human organs (kidney and heart). Results show oxidative stress, but do not provide evidence for oxidative damage during early reperfusion, thereby challenging the prevailing paradigm on RONS-mediated I/R injury.

CONCLUSION

Findings from this study suggest that the contribution of oxidative damage to human I/R may be less than commonly thought and propose a re-evaluation of the mechanism of I/R.

Acute but transient release of terminal complement complex after reperfusion in clinical kidney transplantation

BACKGROUND

Ischemia/reperfusion (I/R) injury has a major impact on kidney graft function and survival. Animal studies have suggested a role for complement activation in mediating I/R injury; however, results are not unambiguous. Whether complement activation is involved in clinical I/R injury in humans is still unclear.

METHODS

In the present study, we assessed the formation and release of C5b-9 during early reperfusion in clinical kidney transplantation in living donor, brain-dead donor, and cardiac dead donor kidney transplantation. By arteriovenous measurements and histologic studies, local terminal complement activation in the reperfused kidney was assessed.

RESULTS

There was no release of soluble C5b-9 (sC5b-9) from living donor kidneys, nor was there a release of C5a. In contrast, instantly after reperfusion, there was a significant but transient venous release of sC5b-9 from the reperfused kidney graft in brain-dead donor and cardiac dead donor kidney transplantation. This short-term activation of the terminal complement cascade in deceased-donor kidney transplantation was not reflected by renal tissue deposition of C5b-9 in biopsies taken 45 min after reperfusion.

CONCLUSIONS

This systematic study in human kidney transplantation shows an acute but nonsustained sC5b-9 release on reperfusion in deceased-donor kidney transplantation. This instantaneous, intravascular terminal complement activation may be induced by intravascular cellular debris and hypoxic or injured endothelium.

The functional polymorphism Ala258Ser in the innate receptor gene ficolin-2 in the donor predicts improved renal transplant outcome

BACKGROUND

Innate immunity plays a role in controlling adaptive immune responses.

METHODS

We investigated the clinical relevance of single nucleotide polymorphisms in 22 genes encoding innate, secreted, and signaling pattern recognition receptors in a total of 520 donor-recipient pairs of postmortem, human leukocyte antigen-DR-compatible kidney transplantations. Associations with rejection incidence were tested in an a priori randomized training set and validation set.

RESULTS

Polymorphisms in TLR-3 (rs3775296) in the recipients and in ficolin-2 (rs7851696; Ala258Ser) and C1qR1 (rs7492) in the donors showed the strongest association with severe rejection. In multivariate analysis, presence of the ficolin-2 Ala258Ser variant in the donor predicted lower incidence of severe rejection (odds ratio=0.3; 95% confidence interval, 0.1-0.9; P=0.024) and of graft loss (hazard ratio=0.5; 95% confidence interval, 0.2-1.0; P=0.046) independently of clinical risk factors. Ficolin-2 messenger RNA expression was detected in pretransplantation biopsies from 69 donor grafts. Serum and tissue ficolin-2 levels were unaffected by genotype. Ficolin-2 protein, which bound to dying cells, was detected in donor kidneys in a passenger leukocyte-like pattern. Indeed, monocytes, monocyte-derived macrophages, and peripheral blood mononuclear cells expressed ficolin-2. Donor grafts with the ficolin-2 Ala258Ser variant contained significantly elevated expression of interleukin 6, having ascribed cytoprotective effects. It has been described that Ala258Ser leads to increased binding capacity of ficolin-2 to N-acetylglucosamine.

CONCLUSIONS

Presence of the ficolin-2 Ala258Ser polymorphism in the donor independently predicts improved graft outcome. Based on mechanistic data, we propose that this functional polymorphism leads to more efficient handling of injured cells by phagocytozing cells, resulting in decreased intragraft exposure to danger signals and dampened alloimmune responses.

Interleukin-9 release from human kidney grafts and its potential protective role in renal ischemia/reperfusion injury

OBJECTIVE AND DESIGN

The pathophysiology of ischemia/reperfusion (I/R) injury is dominated by an inflammatory response. In the identification of new therapeutic agents, the role of individual cytokines may be essential. Interleukin (IL)-9 is a pleiotropic cytokine recently identified to be involved in various immune responses. In this study, the role of IL-9 in renal I/R injury was assessed.

METHODS

We performed repeated direct measurements of arteriovenous IL-9 concentration differences over the reperfused graft in human kidney transplantation.

RESULTS

Substantial renal IL-9 release was observed from deceased donor kidneys (P = 0.006). In contrast, living donor kidneys, which have a more favourable clinical outcome, did not release IL-9 during early reperfusion (P = 0.78). Tissue expression of IL-9 did not change upon reperfusion in both living and deceased human donor kidneys. To assess the role of IL-9 in I/R injury, an experimental study comprising IL-9 inhibition in mice undergoing renal I/R was performed. Although there was no difference in kidney function, structural damage was significantly aggravated in anti-IL-9 treated mice.

CONCLUSIONS

Deceased donor grafts show a substantial IL-9 release upon reperfusion in clinical kidney transplantation. However, inhibition of IL-9 aggravated kidney damage, suggesting a regulating or minor role of IL-9 in clinical I/R injury.

The conditioning effect of ex vivo normothermic perfusion in an experimental kidney model

BACKGROUND

A short period of isolated normothermic perfusion (NP) can be used to improve the condition of the kidney after periods of warm and cold ischemic injury. However, the mechanisms underlying this beneficial effect have not been determined.

MATERIALS AND METHODS

Porcine kidneys were retrieved after 10 min of warm ischemic injury and stored by either static cold storage (CS) for 24 h (control) or CS for 23 h followed by 1 h of NP at 38°C with leukocyte-depleted autologous blood (NP). After preservation, kidneys in both groups underwent 3 h of ex vivo reperfusion to assess the injury (n = 6).

RESULTS

NP kidneys had significantly lower levels of intrarenal resistance (NP 2.28 ± 1.1 versus control 3.86 ± 1.2 mm Hg/mL/h; P = 0.040), maintained their acid base homeostasis (P = 0.080), and had higher levels of oxygen consumption (NP 42.6 ± 19.5 versus control 20.8 ± 5.7 mL/min/g; P = 0.026) and reduced tubular injury (P = 0.008) compared with kidneys in the control group during reperfusion. There were no significant differences in the levels of inflammatory cytokines (interleukin [IL]-1β, IL-8, or tumor necrosis factor-α; P > 0.05) or in renal function (creatinine clearance NP 2.6 ± 1.3 versus control 3.0 ± 1.5 mL/min/100 g; P = 0.070). However, levels of IL-6 were significantly raised in the NP group after reperfusion (P = 0.016). Levels of heat shock protein 70 were upregulated after 1 h of NP and expression increased during reperfusion to a significantly higher level than in the control group (P = 0.045).

CONCLUSION

Kidneys undergoing a short period of NP had improved metabolic function and less tubular injury compared with static cold-stored kidneys. The increased expression of heat shock protein 70 and IL-6 suggests that NP may upregulate mechanisms that condition the kidney.

Clinical analysis of perioperative complement activity during ischemia/reperfusion injury following renal transplantation

BACKGROUND AND OBJECTIVES

The complement cascade seems to be an important mediator modulating renal ischemia/reperfusion injury. This study analyzed whether significant changes occur in the levels of a terminal panel of complement molecules (C3a, C5a, and C5b-9/membrane attack complex) during the early phase of human kidney allograft reperfusion and evaluated the potential association of these changes with clinical post-transplant graft function in kidney transplant recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Seventy-five renal transplant recipients undergoing transplantation between 2004 and 2006 were enrolled in the study and divided into early, slow, and delayed graft function groups. Blood samples were collected perioperatively during consecutive minutes of allograft reperfusion from the renal vein. Levels of complement molecules were measured using ELISA.

RESULTS

Analysis revealed no significant changes in C3a and C5a levels throughout reperfusion. The main complement molecule that was significantly associated with post-transplant graft function was C5b-9/membrane attack complex; throughout the reperfusion period, perioperative levels of C5b-9/membrane attack complex were around two to three times higher in delayed graft function patients than early and slow graft function individuals (P<0.005). In addition, C5b-9/membrane attack complex levels had a relatively high clinical sensitivity and specificity (70%-87.5%) for the prediction of early and long-term (1 year) post-transplant allograft function.

CONCLUSIONS

This clinical study supports a role for the complement cascade in delayed graft function development. However, additional studies are needed to elucidate the exact mechanisms responsible for this phenomenon. In addition, perioperative measurements of C5b-9/membrane attack complex are highlighted as promising potential clinical markers of post-transplant renal allograft function.

Mesenchymal stromal cells in renal ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is an inevitable consequence of organ transplantation and a major determinant of patient and graft survival in kidney transplantation. Renal I/R injury can lead to fibrosis and graft failure. Although the exact sequence of events in the pathophysiology of I/R injury remains unknown, the role of inflammation has become increasingly clear. In this perspective, mesenchymal stromal cells (MSCs) are under extensive investigation as potential therapy for I/R injury, since MSCs are able to exert immune regulatory and reparative effects. Various preclinical studies indicate the beneficial effects of MSCs in ameliorating renal injury and accelerating tissue repair. These versatile cells have been shown to migrate to sites of injury and to enhance repair by paracrine mechanisms instead of by differentiating and replacing the injured cells. The first phase I studies of MSCs in human renal I/R injury and kidney transplantation have been started, and results are awaited soon. In this review, preliminary results and opportunities of MSCs in human renal I/R injury are summarized. We might be heading towards a cell-based paradigm shift in the treatment of renal I/R injury.

Oxidative stress indices in rats under immunosuppression

Immunosuppressants lead to generation of reactive oxygen species (ROS). Oxidative stress (OxS) can initiate chronic allograft nephropathy (CAN). The most active antioxidant enzymes, superoxide dysmutase (SOD) and catalase (CAT), are present in erythrocytes. Glutathione peroxidase (GPx) is produced in the proximal tubules of nephrons. Malonyldialdehyde (MDA) concentrations are a marker of OxS intensity in plasma. In vitro and animal model studies have shown increased or decreased OxS during treatment with tacrolimus (Tac) or cyclosporine (CyA). Results obtained in humans after solid organ transplantation have been contradictory, because of confounding factors such as ischemia-reperfusion injury, donor and recipient ages, endothelial injury, and comorbidity. The aim of this study was to assess the intensity of OxS among rats under chronic immunosuppression (IS) without a transplantation. We examined 49 male Wistar rats. IS started at 12 weeks of age was continued for 6 months: group I were controls (n=7); group II, Tac+sirolimus (Rapamycin [Rapa])+corticosteroids (CS; n=6); group III, CyA+Rapa+CS (n=4 of which 2 died); group IV, Rapa+mycophenolate mofetil (MMF)+CS (n=6); group V, CyA+MMF+CS (n=6); group VI, CsA+MMF+CS for 3 months followed by conversion to Rapa (n=6); group VII, Tac+MMF+CS (n=6 rats); and group VIII, Tac+MMF+CS for 3 months followed by conversion to Rapa (n=6). The drug doses were as follows: Tac 4 mg/kg/d; MMF 20 mg/kg/d; CyA 5mg/kg/d; Rapa 0.5 mg/kg/d; and CS 4 mg/kg/d. Multiple regression analysis revealed that all IS drugs decreased GPx activity (P<.001) except CS, which increased it (P<.0001). Multiple regression analysis showed that CsA and Tac decreased plasma MDA concentrations (P<.01), whereas CS increased them (P<.05). In conclusion, all IS drugs except CS damage proximal tubules of nephrons.

Distinct roles of trauma and transfusion in induction of immune modulation after injury

BACKGROUND

Trauma and transfusion can both alter immunity, and while transfusions are common among traumatically injured patients, few studies have examined their combined effects on immunity.

STUDY DESIGN AND METHODS

We tracked the plasma levels of 41 immunomodulatory proteins in 56 trauma patients from time of injury up to 1 year later. In addition, a murine model was developed to distinguish between the effects of transfusion and underlying injury and blood loss.

RESULTS

Thirty-one of the proteins had a significant change over time after traumatic injury, with a mixed early response that was predominantly anti-inflammatory followed by a later increase in proteins involved in wound healing and homeostasis. Results from the murine model revealed similar cytokine responses to humans. In mice, trauma and hemorrhage caused early perturbations in a number of the pro- and anti-inflammatory mediators measured, and transfusion blunted early elevations in interleukin (IL)-6, IL-10, matrix metalloproteinase-9, and interferon-γ. Transfusion caused or exacerbated changes in monocyte chemotactic protein-1, IL-1α, IL-5, IL-15, and soluble E-selectin. Finally, trauma and hemorrhage alone increased CXCL1 and IL-13.

CONCLUSIONS

This work provides a detailed characterization of the major shift in the immunologic environment in response to trauma and transfusion and clarifies which immune mediators are affected by trauma and hemorrhage and which by transfusion.

Use of monoclonal antibodies in renal transplantation

Monoclonal antibodies are applied in various settings in renal transplantation. Depleting T-cell antibodies are used for treatment of steroid-resistant acute rejection and as induction therapy to reduce the intensity of concomitant immunosuppressive drug therapy. Induction therapy with the nondepleting IL-2 receptor antagonists basiliximab and daclizumab, added to cyclosporine-based regimens, reduces the incidence of acute rejection without side effects. However, an increase in long-term graft and patient survival has not been demonstrated yet. The B-cell-targeting antibody rituximab is used in blood group ABO-incompatible transplantation, in desensitization protocols, and for treatment of antibody-mediated rejection. Eculizumab interrupts the complement pathway and is a promising tool for the treatment of antibody-mediated rejection and post-transplant hemolytic-uremic syndrome. Future options are monoclonal antibodies with new molecular targets and antibodies that can be used for maintenance immunosuppression in order to avoid the toxicity of existing drugs. However, in several cases, the development of new monoclonal antibodies has been hampered by safety issues.

Preservation strategies to reduce ischemic injury in kidney transplantation: pharmacological and genetic approaches

PURPOSE OF REVIEW

In the current graft shortage, it is paramount to improve the quality of transplanted organs. Organ preservation represents an underused therapeutic window with great potential to reduce ischaemia-reperfusion injury (IRI) and improve graft quality. Herein, we review strategies using this window as well as other promising work targeting IRI pathways using pharmacological treatments and gene therapy.

RECENT FINDINGS

We highlight studies using molecules administered during kidney preservation to target key components of IRI such as inflammation, oxidative stress, mitochondrial activity and the coagulation pathway. We further expose recent studies of gene therapy directed against inflammation or apoptosis during cold storage. Other pathways with potential therapeutic molecules are cited.

SUMMARY

The use of cold preservation as a therapeutic window to deliver pharmacological or gene therapy treatments can significantly improve both short-term and long-term graft outcomes. Even if human gene therapy remains hampered by the quantity of agent needed and the potential harmfulness of the vector, it clearly offers a wide array of possibilities for the future. Although gene therapy is still too immature, we expose pharmacological strategies which can readily be applied to the clinic and improve both transplantation success rates and the patients' quality of life.

Donor brain death predisposes human kidney grafts to a proinflammatory reaction after transplantation

Donor brain death has profound effects on post-transplantation graft function and survival. We hypothesized that changes initiated in the donor influence the graft's response to ischemia and reperfusion. In this study, human brain dead donor kidney grafts were compared to living and cardiac dead donor kidney grafts. Pretransplant biopsies of brain dead donor kidneys contained notably more infiltrating T lymphocytes and macrophages. To assess whether the different donor conditions result in a different response to reperfusion, local cytokine release from the reperfused kidney was studied by measurement of paired arterial and renal venous blood samples. Reperfusion of kidneys from brain dead donors was associated with the instantaneous release of inflammatory cytokines, such as G-CSF, IL-6, IL-9, IL-16 and MCP-1. In contrast, kidneys from living and cardiac dead donors showed a more modest cytokine response with release of IL-6 and small amounts of MCP-1. In conclusion, this study shows that donor brain death initiates an inflammatory state of the graft with T lymphocyte and macrophage infiltration and massive inflammatory cytokine release upon reperfusion. These observations suggest that brain dead donors require a novel approach for donor pretreatment aimed at preventing this inflammatory response to increase graft survival.

Inflammation-associated graft loss in renal transplant recipients

BACKGROUND

Although short-term graft survival has improved substantially in renal transplant recipients, long-term graft survival has not improved over the last decades. The lack of knowledge of specific causes and risk factors has hampered improvements in long-term allograft survival. There is an uncertainty if inflammation is associated with late graft loss.

METHODS

We examined, in a large prospective trial, the inflammation markers high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) and their association with chronic graft dysfunction. We collected data from the Assessment of Lescol in Renal Transplant trial, which recruited 2102 maintenance renal transplant recipients.

RESULTS

Baseline values were hsCRP 3.8 ± 6.7 mg/L and IL-6 2.9 ± 1.9 pg/mL. Adjusted for traditional risk factors, hsCRP and IL-6 were independently associated with death-censored graft loss, the composite end points graft loss or death and doubling of serum creatinine, graft loss or death.

CONCLUSION

The inflammation markers hsCRP and IL-6 are associated with long-term graft outcomes in renal transplant recipients.

Minimising cold ischaemic injury in an experimental model of kidney transplantation

BACKGROUND

Cold ischaemic (CI) injury is associated with reduced renal graft function and survival. However, there is little evidence on the benefits of reducing CI injury within a 24 h period in donation after cardiac death (DCD) kidney transplantation.

METHODS

Porcine kidneys subjected to 10-min warm ischaemia were retrieved and flushed with hyperosmolar citrate (HOC) preservation solution at 4 °C. They were stored on ice for periods of 2, 6, 18 or 24 h (n = 6). Renal function and injury were assessed during 3 h of ex-vivo reperfusion with oxygenated autologous blood.

RESULTS

Area under the curve (AUC) serum creatinine (Cr) levels were significantly higher in the 18- and 24-h groups and creatinine clearance (CrCl) lower compared to the 2-h group (P = 0·001, 0·003). Urinary biomarkers of ischaemic damage (Endothelin-1, Total nitric oxide) and renal and tubular cell function significantly correlated with the duration of CI time (r = 0·726, 0·642; P ≤ 0·001).

CONCLUSIONS

This study demonstrated the progressive effects of CI injury in DCD porcine kidneys over a 24 h hypothermic storage period. This highlights the need to minimise the cold storage period to improve graft function in DCD kidney transplantation.

Ischemic injury enhances dendritic cell immunogenicity via TLR4 and NF-kappa B activation

Ischemic (isc) injury during the course of transplantation enhances the immunogenicity of allografts and thus results in poorer graft outcome. Given the central role of dendritic cells (DCs) in mounting alloimmune responses, activation of donor DCs by ischemia may have a primary function in the increased immunogenicity of isc allografts. In this study, we sought to investigate the effect of ischemia on DC activity in vitro. Following induction of ischemia, bone marrow-derived DCs were shown to augment allogeneic T cell proliferation as well as the IFN-gamma response. Isc DCs produced greater levels of IL-6, and isc insult was concurrent with NF-kappaB activation. TLR4 ligation was also shown to occur in isc DCs, most likely in response to the endogenous ligand heat shock protein 70, which was found to be elevated in DCs following isc injury, and lack of TLR4 abrogated the observed effects of isc DCs. As compared with control DCs, isc DCs injected into the footpads of mice demonstrated enhanced migration, which was concomitant with increased recipient T cell activity. Moreover, isc DCs underwent a greater degree of apoptosis in the lymph nodes of injected mice, which may further demonstrate enhanced immunogenicity of isc DCs. We thus show that isc injury of DCs enhances DC function, augments the allogeneic T cell response, and occurs via ligation of TLR4, followed by activation of NF-kappaB. These data may serve to identify novel therapeutic targets to attenuate graft immunogenicity following ischemia.