Ischemia-reperfusion injury in renal transplantation is independent of the immunologic background

Effect of PERLA®, a new cold-storage solution, on oxidative stress injury and early graft function in rat kidney transplantation model

BACKGROUND

The composition of organ preservation solutions is crucial for maintaining graft integrity and early graft function after transplantation. The aim of this study is to compare new organ preservation solution PERLA® with the gold standard preservation solution University of Wisconsin (UW) regarding oxidative stress and early graft injury.

METHODS

In order to assess oxidative stress after cold storage, kidney grafts have been preserved for 18 h at 4° C in either UW solution or PERLA® solution and then assessed for oxidative stress injury (protocol 1). To assess kidney injuries and oxidative stress after reperfusion, rat kidneys were harvested, stored in cold UW or in PERLA® solutions for 18 h at 4 °C and then transplanted heterotopically for 6 h (protocol 2). PERLA® is a high Na+/low K+ solution including PEG-35 (1 g/L), trimetazidine (1 µM), carvedilol (10 µM) and tacrolimus (5 µM).

RESULTS

Our results showed that preservation of kidneys in PERLA® solution significantly attenuates oxidative stress parameters after cold storage and reperfusion. We found a significant decrease in oxidative damage indicators (MDA, CD and CP) and a significant increase in antioxidant indicators (GPx, GSH, CAT, SOD and PSH). Moreover, PERLA® solution decreased kidney injury after reperfusion (creatinine, LDH and uric acid).

CONCLUSION

PERLA® solution was more effective than UW storage solution in preserving rat's kidney grafts.

Updated Views on Neutrophil Responses in Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is an inevitable event during organ transplantation and represents a primary risk factor for the development of early graft dysfunction in lung, heart, liver, and kidney transplant recipients. Recent studies have implicated recipient neutrophils as key mediators of this process and also have found that early innate immune responses after transplantation can ultimately augment adaptive alloimmunity and affect late graft outcomes. Here, we discuss signaling pathways involved in neutrophil recruitment and activation after ischemia-mediated graft injury in solid organ transplantation with an emphasis on lung allografts, which have been the focus of recent studies. These findings suggest novel therapeutic interventions that target ischemia-reperfusion injury-mediated graft dysfunction in transplant recipients.

Targeting vascular inflammation through emerging methods and drug carriers

Acute inflammation is a common dangerous component of pathogenesis of many prevalent conditions with high morbidity and mortality including sepsis, thrombosis, acute respiratory distress syndrome (ARDS), COVID-19, myocardial and cerebral ischemia-reperfusion, infection, and trauma. Inflammatory changes of the vasculature and blood mediate the course and outcome of the pathology in the tissue site of insult, remote organs and systemically. Endothelial cells lining the luminal surface of the vasculature play the key regulatory functions in the body, distinct under normal vs. pathological conditions. In theory, pharmacological interventions in the endothelial cells might enable therapeutic correction of the overzealous damaging pro-inflammatory and pro-thrombotic changes in the vasculature. However, current agents and drug delivery systems (DDS) have inadequate pharmacokinetics and lack the spatiotemporal precision of vascular delivery in the context of acute inflammation. To attain this level of precision, many groups design DDS targeted to specific endothelial surface determinants. These DDS are able to provide specificity for desired tissues, organs, cells, and sub-cellular compartments needed for a particular intervention. We provide a brief overview of endothelial determinants, design of DDS targeted to these molecules, their performance in experimental models with focus on animal studies and appraisal of emerging new approaches. Particular attention is paid to challenges and perspectives of targeted therapeutics and nanomedicine for advanced management of acute inflammation.

The mTOR inhibitor Rapamycin protects from premature cellular senescence early after experimental kidney transplantation

Interstitial fibrosis and tubular atrophy, a major cause of kidney allograft dysfunction, has been linked to premature cellular senescence. The mTOR inhibitor Rapamycin protects from senescence in experimental models, but its antiproliferative properties have raised concern early after transplantation particularly at higher doses. Its effect on senescence has not been studied in kidney transplantation, yet. Rapamycin was applied to a rat kidney transplantation model (3 mg/kg bodyweight loading dose, 1.5 mg/kg bodyweight daily dose) for 7 days. Low Rapamycin trough levels (2.1-6.8 ng/mL) prevented the accumulation of p16INK4a positive cells in tubules, interstitium, and glomerula. Expression of the cytokines MCP-1, IL-1β, and TNF-α, defining the proinflammatory senescence-associated secretory phenotype, was abrogated. Infiltration with monocytes/macrophages and CD8+ T-lymphocytes was reduced and tubular function was preserved by Rapamycin. Inhibition of mTOR was not associated with impaired structural recovery, higher glucose levels, or weight loss. mTOR inhibition with low-dose Rapamycin in the immediate posttransplant period protected from premature cellular senescence without negative effects on structural and functional recovery from preservation/reperfusion damage, glucose homeostasis, and growth in a rat kidney transplantation model. Reduced senescence might maintain the renal regenerative capacity rendering resilience to future injuries resulting in protection from interstitial fibrosis and tubular atrophy.

The Pathological and Clinical Diversity of Acute Vascular Rejection in Kidney Transplantation

BACKGROUND

Vascular rejection (VR) is characterized by arteritis, steroid resistance, and increased graft loss but is poorly described using modern diagnostics.

METHODS

We screened 3715 consecutive biopsies and retrospectively evaluated clinical and histological phenotypes of VR (n = 100) against rejection without arteritis (v0REJ, n = 540) and normal controls (n = 1108).

RESULTS

Biopsy sample size affected the likelihood of arterial sampling, VR diagnosis, and final Banff v scores (P < 0.001). Local v and cv scores were greatest in larger arteries (n = 258). VR comprised 15.6% of all rejection episodes, presented earlier (median 1.0 mo, interquartile range, 0.4-8 mo) with higher serum creatinine levels and inferior graft survival, versus v0REJ (P < 0.001). Early VR (≤1 mo) was common (54%) and predicted by sensitization, delayed function, and prior corticosteroid use, with associated acute dysfunction and optimal therapeutic response, independent of Banff v score. Late VR followed under-immunosuppression in 71.4% (noncompliance 38.8%, iatrogenic 32.6%), and was associated with chronic interstitial fibrosis, incomplete renal functional recovery and persistent inflammation using sequential histopathology. The etiology was "pure" antibody-mediated VR (n = 21), mixed VR (n = 36), and "pure" T cell-mediated VR (n = 43). Isolated VR (n = 34, Banff i < 1 without tubulitis) comprised 24 T cell-mediated VR and 10 antibody-mediated VR, presenting with mild renal dysfunction, minimal Banff acute scores, and better graft survival compared with inflamed VR. Interstitial inflammation influenced acute renal dysfunction and early treatment response, whereas chronic tubulointerstitial damage determined long-term graft loss.

CONCLUSIONS

VR is a heterogenous entity influenced by time-of-onset, pathophysiology, accompanying interstitial inflammation and fibrosis. Adequate histological sampling is essential for its accurate diagnostic classification and treatment.

Role of Fractalkine-CX3CR1 Axis in Acute Rejection of Mouse Heart Allografts Subjected to Ischemia Reperfusion Injury

Transplantation outcomes are affected by the increase in rejection associated with ischemia reperfusion injury (IRI). Fractalkine (FKN), a chemokine for recruitment of CX3CR1⁺ leukocytes, contributes to the pathogenesis of various inflammatory diseases. Herein, we evaluated the importance of the FKN-CX3CR1 axis during IRI-related rejections using a mouse heterotopic heart transplantation model. FKN expression and graft survival was compared between wild-type C57BL/6 recipients transplanted with BALB/c hearts preserved for 8 (WT-IRI) and 0.5 h (WT-control) at 4°C. Graft survival of WT-IRI was shorter than that of WT-control. FKN was expressed on the vascular endothelium in WT-IRI allografts, but minimally in WT-control. The role of the FKN-CX3CR1 axis in IRI-related rejection was directly investigated using the transplant model with CX3CR1-deficient recipients (CX3CR1 KO-IRI) or treatment with anti-mouse FKN monoclonal antibodies. Graft survival of CX3CR1 KO-IRI was longer than that of WT-IRI; antibody treatment prolonged graft survival. The contribution of CX3CR1⁺ monocytes to IRI-related rejection was evaluated by adoptive transfer to CX3CR1 KO-IRI. Adoptive transfer of CX3CR1⁺ monocytes attenuated the effect of prolonged graft survival in CX3CR1 KO-IRI. Overall, the FKN-CX3CR1 axis plays a major role during IRI-related rejection; its blockade has the potential to improve the outcomes of deceased donor transplantation.

Low-dose rapamycin does not impair vascular integrity and tubular regeneration after kidney transplantation in rats

mTOR inhibitors offer advantages after kidney transplantation including antiviral and antitumor activity besides facilitating low calcineurin inhibitor exposure to reduce nephrotoxicity. Concerns about adverse effects due to antiproliferative and antiangiogenic properties have limited their clinical use particularly early after transplantation. Interference with vascular endothelial growth factor (VEGF)-A, important for physiologic functioning of renal endothelial cells and tubular epithelium, has been implicated in detrimental renal effects of mTOR inhibitors. Low doses of Rapamycin (loading dose 3 mg/kg bodyweight, daily doses 1.5 mg/kg bodyweight) were administered in an allogenic rat kidney transplantation model resulting in a mean through concentration of 4.30 ng/mL. Glomerular and peritubular capillaries, tubular cell proliferation, or functional recovery from preservation/reperfusion injury were not compromised in comparison to vehicle treated animals. VEGF-A, VEGF receptor 2, and the co-receptor Neuropilin-1 were upregulated by Rapamycin within 7 days. Rat proximal tubular cells (RPTC) responded in vitro to hypoxia with increased VEGF-A and VEGF-R1 expression that was not suppressed by Rapamycin at therapeutic concentrations. Rapamycin did not impair proliferation of RPTC under hypoxic conditions. Low-dose Rapamycin early posttransplant does not negatively influence the VEGF network crucial for recovery from preservation/reperfusion injury. Enhancement of VEGF signaling peritransplant holds potential to further improve outcomes.

Proteomics and Metabolomics for AKI Diagnosis

Acute kidney injury (AKI) is a severe and frequent condition in hospitalized patients. Currently, no efficient therapy of AKI is available. Therefore, efforts focus on early prevention and potentially early initiation of renal replacement therapy to improve the outcome in AKI. The detection of AKI in hospitalized patients implies the need for early, accurate, robust, and easily accessible biomarkers of AKI evolution and outcome prediction because only a narrow window exists to implement the earlier-described measures. Even more challenging is the multifactorial origin of AKI and the fact that the changes of molecular expression induced by AKI are difficult to distinguish from those of the diseases associated or causing AKI as shock or sepsis. During the past decade, a considerable number of protein biomarkers for AKI have been described and we expect from recent advances in the field of omics technologies that this number will increase further in the future and be extended to other sorts of biomolecules, such as RNAs, lipids, and metabolites. However, most of these biomarkers are poorly defined by their AKI-associated molecular context. In this review, we describe the state-of-the-art tissue and biofluid proteomic and metabolomic technologies and new bioinformatics approaches for proteomic and metabolomic pathway and molecular interaction analysis. In the second part of the review, we focus on AKI-associated proteomic and metabolomic biomarkers and briefly outline their pathophysiological context in AKI.

Direct peritoneal resuscitation reduces inflammation in the kidney after acute brain death

Brain death is associated with significant inflammation within the kidneys, which may contribute to reduced graft survival. Direct peritoneal resuscitation (DPR) has been shown to reduce systemic inflammation after brain death. To determine its effects, brain dead rats were resuscitated with normal saline (targeted intravenous fluid) to maintain a mean arterial pressure of 80 mmHg; DPR animals also received 30 cc of intraperitoneal peritoneal dialysis solution. Rats were euthanized at 0, 2, 4, and 6 h after brain death. Pro-inflammatory cytokines were measured using ELISA. Levels of IL-1β, TNF-α, and IL-6 in the kidney were significantly increased as early as 2 h after brain death and significantly decreased with DPR. Levels of leukocyte adhesion molecules ICAM and VCAM increased after brain death and were decreased with DPR (ICAM 2.33 ± 0.14 vs. 0.42 ± 0.04, P = 0.002; VCAM 82.6 ± 5.8 vs. 37.3 ± 1.9, P = 0.002 at 4 h) as were E-selectin and P-selectin (E-selectin 25,605 vs. 16,144, P = 0.005; P-selectin 82.5 ± 3.3 vs. 71.0 ± 2.3, P = 0.009 at 4 h). Use of DPR reduces inflammation and adhesion molecule expression in the kidneys, and is associated with reduced macrophages and neutrophils on immunohistochemistry. Using DPR in brain dead donors has the potential to reduce the immunologic activity of transplanted kidneys and could improve graft survival.

Amniotic fluid cells: current progress and emerging challenges in renal regeneration

Amniotic fluid (AF) contains a heterogeneous population of cells that have been identified to possess pluripotent and progenitor-like characteristics. These cells have been applied in various regenerative medicine applications ranging from in vitro cell differentiation to tissue engineering to cellular therapies for different organs including the heart, the liver, the lung, and the kidneys. In this review, we examine the different methodologies used for the derivation of amniotic fluid stem cells and renal progenitors, and their application in renal repair and regeneration. Moreover, we discuss the recent achievements and newly emerging challenges in our understanding of their biology, their immunoregulatory characteristics, and their paracrine-mediated therapeutic potential for the treatment of acute and chronic kidney diseases.

Mechanisms of antibody-mediated acute and chronic rejection of kidney allografts

PURPOSE OF REVIEW

Antibody-mediated rejection is responsible for up to half of acute rejection episodes in kidney transplant patients and more than half of late graft failures. Antibodies cause acute graft abnormalities that are distinct from T cell-mediated rejection and at later times posttransplant, a distinct pathologic lesion is associated with capillary basement membrane multilayering and glomerulopathy. Despite the importance of donor-reactive antibodies as the leading cause of kidney graft failure, mechanisms underlying antibody-mediated acute and chronic kidney graft injury are poorly understood. Here, we review recent insights provided from clinical studies as well as from animal models that may help to identify new targets for therapy.

RECENT FINDINGS

Studies of biopsies from kidney grafts in patients with donor-specific antibody versus those without have utilized analysis of pathologic lesions and gene expression to identify the distinct characteristics of antibody-mediated rejection. These analyses have indicated the presence of natural killer cells and their activation during antibody-mediated rejection. The impact of studies of antibody-mediated allograft injury in animal models have lagged behind these clinical studies, but have been useful in testing the activation of innate immune components within allografts in the presence of donor-specific antibodies.

SUMMARY

Most insights into processes of antibody-mediated rejection of kidney grafts have come from carefully designed clinical studies. However, several new mouse models of antibody-mediated kidney allograft rejection may replicate the abnormalities observed in clinical kidney grafts and may be useful in directly testing mechanisms that underlie acute and chronic antibody-mediated graft injury.

Hypoxia: The Force that Drives Chronic Kidney Disease

In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy.

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."

Role of innate immunity in primary graft dysfunction after lung transplantation

PURPOSE OF REVIEW

Primary graft dysfunction (PGD), a form of acute lung injury after lung transplantation, has a significant impact on clinical outcomes after lung transplantation. This potentially reversible graft impairment occurs after ischemia-reperfusion injury. This review describes the expanding body of literature evaluating the central role of innate immune activation, nonadaptive responses and dysregulation in the development of PGD after lung transplant.

RECENT FINDINGS

The innate immune system, highlighted by Toll-like receptor pathways and neutrophil migration and influx, plays an important role in the initiation and propagation of ischemia-reperfusion injury. Recent plasma biomarker and gene association studies have identified several genes and proteins composing innate immune pathways to be associated with PGDs. Long pentraxin-3 and Toll-like receptors, as well as inflammasomes and Toll-interacting protein, are associated with the development of PGD after lung transplantation.

SUMMARY

Innate immune pathways are involved in the development of PGD and may provide attractive targets for therapies. It may be possible to prevent or treat PGD, as well as to allow pre-transplant PGD risk stratification. To improve understanding of the mechanisms behind clinical risk factors for PGD will require further in-depth correlation of donor-specific and recipient-related triggers of nonadaptive immune responses.

CD154-CD40 T-cell co-stimulation pathway is a key mechanism in kidney ischemia-reperfusion injury

Ischemia-reperfusion occurs in a great many clinical settings and contributes to organ failure or dysfunction. CD154-CD40 signaling in leukocyte–endothelial cell interactions or T-cell activation facilitates tissue inflammation and injury. Here we tested a siRNA anti-CD40 in rodent warm and cold ischemia models to check the therapeutic efficacy and anti-inflammatory outcome of in vivo gene silencing. In the warm ischemia model different doses were used, resulting in clear renal function improvement and a structural renoprotective effect. Renal ischemia activated the CD40 gene and protein expression, which was inhibited by intravenous siRNA administration. CD40 gene silencing improved renal inflammatory status, as seen by the reduction of CD68 and CD3 T-cell infiltrates, attenuated pro-inflammatory, and enhanced anti-inflammatory mediators. Furthermore, siRNA administration decreased a spleen pro-inflammatory monocyte subset and reduced TNFα secretion by splenic T cells. In the cold ischemia model with syngeneic and allogeneic renal transplantation, the most effective dose induced similar functional and structural renoprotective effects. Our data show the efficacy of our siRNA in modulating both the local and the systemic inflammatory milieu after an ischemic insult. Thus, CD40 silencing could emerge as a novel therapeutic strategy in solid organ transplantation.

Renal PKC-ε deficiency attenuates acute kidney injury and ischemic allograft injury via TNF-α-dependent inhibition of apoptosis and inflammation

Acute kidney injury (AKI) increases the risk of morbidity and mortality after major surgery and transplantation. We investigated the effect of PKC-ε deficiency on AKI and ischemic allograft damage after kidney transplantation. PKC-ε-deficient and wild type (WT) control mice were subjected to 35 min of renal pedicle clamping to induce AKI. PKC-ε deficiency was associated with a marked improvement in survival and an attenuated loss of kidney function. Furthermore, functional MRI experiments revealed better renal perfusion in PKC-ε-deficient mice than in WT mice one day after IRI. Acute tubular necrosis and neutrophil infiltration were markedly reduced in PKC-ε-deficient mice. To determine whether this resistance to ischemia-reperfusion injury resulted from changes in local renal cells or infiltrating leukocytes, we studied a life-supporting renal transplant model of ischemic graft injury. We transplanted kidneys from H2b PKC-ε-deficient mice (129/SV) and their corresponding WT littermates into major histocompatibility complex-incompatible H2d recipients (BALB/c) and induced ischemic graft injury by prolonged cold ischemia time. Recipients of WT allografts developed severe renal failure and died within 10 days of transplantation. Recipients of PKC-ε-deficient allografts had better renal function and survival; they had less generation of ROS and upregulation of proinflammatory proteins (i.e., ICAM-1, inducible nitric oxide synthase, and TNF-α) and showed less tubular epithelial cell apoptosis and inflammation in their allografts. These data suggest that local renal PKC-ε expression mediates proapoptotic and proinflammatory signaling and that an inhibitor of PKC-ε signaling could be used to prevent hypoxia-induced AKI.

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.

Amniotic fluid-derived mesenchymal stem cells prevent fibrosis and preserve renal function in a preclinical porcine model of kidney transplantation

It is well known that ischemia/reperfusion injuries strongly affect the success of human organ transplantation. Development of interstitial fibrosis and tubular atrophy is the main deleterious phenomenon involved. Stem cells are a promising therapeutic tool already validated in various ischemic diseases. Amniotic fluid-derived mesenchymal stem cells (af-MSCs), a subpopulation of multipotent cells identified in amniotic fluid, are known to secrete growth factors and anti-inflammatory cytokines. In addition, these cells are easy to collect, present higher proliferation and self-renewal rates compared with other adult stem cells (ASCs), and are suitable for banking. Consequently, af-MSCs represent a promising source of stem cells for regenerative therapies in humans. To determine the efficiency and the safety of af-MSC infusion in a preclinical porcine model of renal autotransplantation, we injected autologous af-MSCs in the renal artery 6 days after transplantation. The af-MSC injection improved glomerular and tubular functions, leading to full renal function recovery and abrogated fibrosis development at 3 months. The strong proof of concept generated by this translational porcine model is a first step toward evaluation of af-MSC-based therapies in human kidney transplantation.

Endothelial HIF-2 mediates protection and recovery from ischemic kidney injury

The hypoxia-inducible transcription factors HIF-1 and HIF-2 mediate key cellular adaptions to hypoxia and contribute to renal homeostasis and pathophysiology; however, little is known about the cell type-specific functions of HIF-1 and HIF-2 in response to ischemic kidney injury. Here, we used a genetic approach to specifically dissect the roles of endothelial HIF-1 and HIF-2 in murine models of hypoxic kidney injury induced by ischemia reperfusion or ureteral obstruction. In both models, inactivation of endothelial HIF increased injury-associated renal inflammation and fibrosis. Specifically, inactivation of endothelial HIF-2α, but not endothelial HIF-1α, resulted in increased expression of renal injury markers and inflammatory cell infiltration in the postischemic kidney, which was reversed by blockade of vascular cell adhesion molecule-1 (VCAM1) and very late antigen-4 (VLA4) using monoclonal antibodies. In contrast, pharmacologic or genetic activation of HIF via HIF prolyl-hydroxylase inhibition protected wild-type animals from ischemic kidney injury and inflammation; however, these same protective effects were not observed in HIF prolyl-hydroxylase inhibitor-treated animals lacking endothelial HIF-2. Taken together, our data indicate that endothelial HIF-2 protects from hypoxia-induced renal damage and represents a potential therapeutic target for renoprotection and prevention of fibrosis following acute ischemic injury.

The regulation of inflammatory mediators in acute kidney injury via exogenous mesenchymal stem cells

Acute kidney injury (AKI) remains to be an independent risk factor for mortality and morbidity. Inflammation is believed to play a major role in the pathophysiology of AKI. Exogenous mesenchymal stem cells (MSCs) are now under extensive investigation as a potential therapy for AKI. Various preclinical studies indicated the beneficial effects of MSCs in alleviating renal injury and accelerating tissue repair. However the mechanisms responsible for these effects are incompletely understood. In the recent years, anti-inflammatory/immunoregulatory properties of MSCs have become one of the important issues in the treatment of AKI. This review will summarize the current literature on the regulation of inflammatory mediators via exogenous MSCs contributing to the recovery from AKI.

Effect of PACAP treatment on kidney morphology and cytokine expression in rat diabetic nephropathy

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide, exerting diverse effects. One of its frequently examined functions is cell protection, which is achieved mainly via inhibiting apoptotic, inflammatory and oxidative processes. All its three receptors (PAC1, VPAC1, VPAC2) are expressed in the kidney and PACAP has been shown to have protective effects against different renal pathologies. Diabetic nephropathy is the leading cause of end stage renal disease. The aim of the present study was to investigate the possible ameliorative effect of PACAP in streptozotocin-induced diabetic nephropathy and to evaluate its anti-inflammatory effect in this model. Diabetes was induced by a single intravenous injection of streptozotocin (65 mg/kg) in male Wistar rats. PACAP-treated animals were administered ip. 20 μg PACAP every second day, while untreated animals were given vehicle. Kidneys were removed after 8-weeks survival. Besides the complex histological analysis (glomerular PAS positive area/glomerulus area, tubular damage, arteriolar hyalinosis), expression of several cytokines was evaluated by cytokine array and Luminex assay. Histological analysis revealed severe diabetic changes in kidneys of control diabetic animals (glomerular PAS-positive area expansion, tubular damage, Armanni-Ebstein phenomenon). PACAP treatment significantly diminished the damage. Diabetic kidneys showed significant cytokine activation compared to their healthy controls. PACAP was effective in downregulation of several cytokines including CINC-1, TIMP-1, LIX, MIG, s-ICAM. To conclude, PACAP is effective in ameliorating diabetic nephropathy at least partly through its well-known anti-inflammatory effect. These results raise the opportunity for the use of PACAP as a possible therapeutic or preventive method in treating the complications of diabetes.

Therapeutic potential of human elafin

Elafin is an endogenous human protein composed of an N-terminal transglutaminase substrate motif and a C-terminal WAP (whey acidic protein)-domain with antiproteolytic properties. Elafin is expressed predominantly in epithelial tissue and potently inhibits the neutrophil-derived serine proteases elastase and proteinase-3 by a competitive tight-binding mechanism. Furthermore, it inhibits EVE (endogenous vascular elastase). Studies on several animal models show that antiprotease augmentation with human elafin is an effective strategy in the treatment of inflammatory vascular, systemic and pulmonary diseases and of inflammation triggered by reperfusion injury. This raises the possibility that elafin might be effective in the treatment of a variety of human inflammatory diseases. In a Phase I clinical trial, elafin was well tolerated. Phase II trials are underway to investigate the therapeutic effects of elafin on post-operative inflammation and the clinical consequences of major surgery. Of particular interest is the reduction of post-operative morbidity after oesophagus cancer surgery, coronary artery bypass surgery and kidney transplantation.

Supplementation with a new therapeutic oxygen carrier reduces chronic fibrosis and organ dysfunction in kidney static preservation

Static preservation is currently the most widely used organ preservation strategy; however, decreased donor organ quality is impacting outcome negatively. M101 is an O₂ carrier with high-oxygen affinity and the capacity to function at low temperatures. We tested the benefits of M101 both in vitro, on cold preserved LLC-PK1, as well as in vivo, in a large white pig kidney autotransplantation model. In vitro, M101 supplementation reduced cold storage-induced cell death. In vivo, early follow-up demonstrated superiority of M101-supplemented solutions, lowering the peak of serum creatinine and increasing the speed of function recovery. On the longer term, supplementation with M101 reduced kidney inflammation levels and maintained structural integrity, particularly with University of Wisconsin (UW). At the end of the 3-month follow-up, M101 supplementation proved beneficial in terms of survival and function, as well as slowing the advance of interstitial fibrosis. We show that addition of M101 to classic organ preservation protocols with UW and Histidine-Tryptophane-Ketoglutarate, the two most widely used solutions worldwide in kidney preservation, provides significant benefits to grafts, both on early function recovery and outcome. Simple supplementation of the solution with M101 is easily translatable to the clinic and shows promises in terms of outcome.

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.

Contribution of large pig for renal ischemia-reperfusion and transplantation studies: the preclinical model

Animal experimentation is necessary to characterize human diseases and design adequate therapeutic interventions. In renal transplantation research, the limited number of in vitro models involves a crucial role for in vivo models and particularly for the porcine model. Pig and human kidneys are anatomically similar (characterized by multilobular structure in contrast to rodent and dog kidneys unilobular). The human proximity of porcine physiology and immune systems provides a basic knowledge of graft recovery and inflammatory physiopathology through in vivo studies. In addition, pig large body size allows surgical procedures similar to humans, repeated collections of peripheral blood or renal biopsies making pigs ideal for medical training and for the assessment of preclinical technologies. However, its size is also its main drawback implying expensive housing. Nevertheless, pig models are relevant alternatives to primate models, offering promising perspectives with developments of transgenic modulation and marginal donor models facilitating data extrapolation to human conditions.

Notoginsenoside R1 attenuates renal ischemia-reperfusion injury in rats

Ischemia-reperfusion (I/R) injury of the kidney is a complex pathophysiological process and a major cause of acute renal failure. It has been shown that I/R injury is related to inflammatory responses and activation of apoptotic pathways. Inhibition of certain elements of inflammatory responses and apoptotic pathway seemed to ameliorate renal I/R injury. As an effective element of Panax notoginseng, NR1 has antioxidant, anti-inflammatory, antiapoptotic, and immune-stimulatory activities. Therefore, we speculate that NR1 can attenuate renal I/R injury. Ischemia-reperfusion injury was induced by renal pedicle ligation followed by reperfusion along with a contralateral nephrectomy. Male Sprague-Dawley rats were randomized to four groups: sham group, I/R control group, NR1-1 group (rats treated with NR1, 20 mg.kg.d) and NR1-2 group (rats treated with NR1, 40 mg.kg.d). All animals were killed 72 h after I/R induction. Blood and renal tissues were collected. Renal dysfunction was observed by the level of serum creatinine and histological evaluation. Apoptosis and inflammatory response in the tissue of kidney were detected mainly with molecular biological methods. NR1 attenuated I/R-induced renal dysfunction as indicated by the level of serum creatinine and histological evaluation. It prevented the I/R-induced increases in the levels of proinflammatory cytokine TNF-alpha, myeloperoxidase activity, phosphorylation of p38, and activation of nuclear factor kappaB with cell apoptosis in the kidney and enhanced expression of antiapoptosis cytokine bcl-2. Treatment with NR1 improves renal function after I/R associated with a significant reduction in cell apoptosis and inflammatory responses, which may be related to p38 and nuclear factor kappaB inhibition.

Effect of polyethylene glycol-based preservation solutions on graft injury in experimental kidney transplantation

Background

New preservation solutions are emerging, of various ionic compositions and with hydroxyethyl starch replaced by polymers such as polyethylene glycols (PEGs), offering the potential for ‘immunocamouflage’. This experimental study investigated which of three clinically available preservation protocols offered the best graft protection, based on epithelial-to-mesenchymal transition (EMT) and fibrosis.

Methods

Kidneys were preserved for 24 h at 4 °C with University of Wisconsin solution (UW) as standard, compared with solutions containing either 1 g/l PEG 35 kDa (Institute Georges Lopez solution, IGL) or 30g/l PEG 20 kDa (solution de conservation des organes et des tissus, SCOT). Animals were followed for up to 3 months and development of EMT, tubular atrophy and fibrosis was evaluated in comparison with sham-operated animals.

Results

Functional recovery was better in the SCOT group compared with the other groups. Chronic fibrosis, EMT and inflammation were observed in the UW and IGL groups, but limited in the SCOT group. Levels of profibrosis markers such as transforming growth factor β1, plasminogen activator inhibitor 1 and connective tissue growth factor were increased in IGL and UW groups compared with the SCOT group. Hypoxia-inducible factor (HIF) 1α and 2α expression was increased at 3 months in grafts preserved in UW and IGL, but detected transiently on day 14 when SCOT was used. Expression of HIF-regulated genes vascular endothelial growth factor and erythropoietin was increased in UW and IGL groups.

Conclusion

The choice of colloid and ionic content is paramount in providing long-term protection against chronic graft injury after renal transplantation. Preservation solutions based on PEGs may optimize graft quality.

A pair analysis of the delayed graft function in kidney recipient: the critical role of the donor

PURPOSE

The aim of this study was to analyze the importance of donor factors and especially the potential role of hemodynamic management in regard to delayed graft function in paired kidney recipient patients after renal transplantation and to analyze the urine of organ donors by proton-nuclear magnetic resonance spectroscopy to identify urine markers potentially correlated with delayed graft function in recipient patients.

METHODS

A prospective multicenter epidemiologic study was conducted. A logistic regression model taking into account paired data was used.

RESULTS

Data from 72 donors and the 144 corresponding paired recipients were analyzed. Univariate analysis showed that age of donor, previous history of tobacco, ischemic cause of brain death, norepinephrine infusion, and recipient age were the risk factors for delayed graft function. After adjusting for correlated outcome data and controlling for other potential prognostic factors, 3 variables remained significantly associated with outcome: donor age (odds ratio [OR], 10.7), hemodynamic status (OR, 0.167), and hydroxyl-ethyl starch infusion (OR, 0.135). Proton-nuclear magnetic resonance analysis evidenced 3 metabolites of interest in donors (trimethylamine-N-oxide, citrate, and lactate). However, these peaks were not correlated the clinical parameters in donors.

CONCLUSIONS

Paired analysis of kidney transplantation emphasizes the important role of factor donor associated with delayed graft function in recipient. Thus, a particular attention should be paid to the hemodynamic management of donor.

Prevenção do estresse oxidativo na síndrome de isquemia e reperfusão renal em ratos com suplementação nutricional com antioxidantes

OBJETIVO: Verificar o potencial efeito protetor de suplementação com vitaminas antioxidantes em um modelo de síndrome de isquemia-reperfusão renal em ratos. MÉTODOS: Foram utilizados 29 ratos Wistar, divididos em três grupos: Grupo I e II (n=10 cada), submetidos a indução do estresse oxidativo pela aplicação de 60 minutos de isquemia renal, seguidos de 10 minutos de reperfusão; adicionalmente, os animais do Grupo II foram pré-tratados por doze dias com vitaminas antioxidantes (vitamina C 11,43mg/kg e vitamina E 28,57mg/kg) antes da submissão à isquemia; Grupo III (n=9), correspondendo aos animais Sham, que foram manipulados de forma equivalente aos outros grupos, porém sem indução do estresse oxidativo e sem suplementação antioxidante. Findo isso, as amostras de sangue e os rins foram colhidos para avaliação dos níveis do malondialdeído, do ácido úrico e da capacidade antioxidante total. RESULTADOS: Para o malondialdeído e ácido úrico do Grupo I foi observado um aumento estatisticamente significante (p<0,01) em relação ao Grupo III, o qual não apresentou diferença em relação ao Grupo II. Para os níveis de capacidade antioxidante total, foi encontrada uma diminuição nos animais do Grupo I em relação aos Grupos II e III (p<0,01). CONCLUSÃO: Esses dados confirmam não apenas a efetiva participação do estresse oxidativo neste modelo de síndrome de isquemia e reperfusão renal em ratos, como também que o uso de vitaminas antioxidantes, associadas à dieta, pode proteger os animais das alterações oxidativas.

Mediators of inflammation in acute kidney injury

Acute kidney injury (AKI) remains to be an independent risk factor for mortality and morbidity. Inflammation is now believed to play a major role in the pathopathophysiology of AKI. It is hypothesized that in ischemia, sepsis and nephrotoxic models that the initial insult results in morphological and/or functional changes in vascular endothelial cells and/or in tubular epithelium. Then, leukocytes including neutrophils, macrophages, natural killer cells, and lymphocytes infiltrate into the injured kidneys. The injury induces the generation of inflammatory mediators like cytokines and chemokines by tubular and endothelial cells which contribute to the recruiting of leukocytes into the kidneys. Thus, inflammation has an important role in the initiation and extension phases of AKI. This review will focus on the mediators of inflammation contributing to the pathogenesis of AKI.

Direct thrombin inhibitor prevents delayed graft function in a porcine model of renal transplantation

BACKGROUND

Kidney transplantations from donors after cardiac arrest (DCA) are characterized by an increase in the occurrence of delayed graft function and primary nonfunction. In this study, Melagatran, a selective reversible direct thrombin inhibitor was used to limit renal injury in a DCA pig kidney transplantation model.

METHODS

We used a porcine model of DCA to study the effects of treatment with Melagatran in the peri-conservation period. Thromboelastography was used to check Melagatran antithrombin effect on in vitro clot formation. Reverse-transcriptase polymerase chain reaction was used to analyze the peripheral immune cells activation status. Renal function and morphologic study were performed at days 1 and 7. Finally, we analyzed the mechanisms of Melagatran protection on kidney microvasculature primary endothelial cells.

RESULTS

Prolongation of coagulation time (Ex-Tem) was observed 10 min after injection; however, Melagatran did not modulate increases of thrombin-antithrombin complexes following reperfusion. Melagatran significant treatment lowered the proinflammatory status of circulating immune cells. Animal's survival was increased in Melagatran-treated groups (9 of 10 in Melagatran groups vs. 4 of 10 in controls at day 7). Renal injury and inflammation were also significantly reduced in treated groups. We also demonstrated a direct protective effect of Melagatran against endothelial cell activation and inflammation in vitro.

CONCLUSION

Direct thrombin inhibitor administration in the periconservation period improved graft outcome and reduced renal injury in a model of DCA.

Ischemia/reperfusion injury in kidney transplantation: mechanisms and prevention

Ischemia has been an inevitable event accompanying kidney transplantation. Ischemic changes start with brain death, which is associated with severe hemodynamic disturbances: increasing intracranial pressure results in bradycardia and decreased cardiac output; the Cushing reflex causes tachycardia and increased blood pressure; and after a short period of stabilization, systemic vascular resistance declines with hypotension leading to cardiac arrest. Free radical-mediated injury releases proinflammatory cytokines and activates innate immunity. It has been suggested that all of these changes-the early innate response and the ischemic tissue damage-play roles in the development of adaptive responses, which in turn may lead to an acute font of kidney rejection. Hypothermic kidney storage of various durations before transplantation add to ischemic tissue damage. The final stage of ischemic injury occurs during reperfusion. Reperfusion injury, the effector phase of ischemic injury, develops hours or days after the initial insult. Repair and regeneration processes occur together with cellular apoptosis, autophagy, and necrosis; the fate of the organ depends on whether cell death or regeneration prevails. The whole process has been described as the ischemia-reperfusion (I-R) injury. It has a profound influence on not only the early but also the late function of a transplanted kidney. Prevention of I-R injury should be started before organ recovery by donor pretreatment. The organ shortage has become one of the most important factors limiting extension of deceased donor kidney transplantation worldwide. It has caused increasing use of suboptimal deceased donors (high risk, extended criteria [ECD], marginal donors) and uncontrolled non-heart-beating (NHBD) donors. Kidneys from such donors are exposed to much greater ischemic damage before recovery and show reduced chances for proper early as well as long-term function. Storage of kidneys, especially those recovered from ECD (or NHBD) donors, should use machine perfusion.

NK cells induce apoptosis in tubular epithelial cells and contribute to renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) can result in acute renal failure with mortality rates of 50% in severe cases. NK cells are important participants in early-stage innate immune responses. However, their role in renal tubular epithelial cell (TEC) injury in IRI is currently unknown. Our data indicate that NK cells can kill syngeneic TEC in vitro. Apoptotic death of TEC in vitro is associated with TEC expression of the NK cell ligand Rae-1, as well as NKG2D on NK cells. In vivo following IRI, there was increased expression of Rae-1 on TEC. FACS analyses of kidney cell preparations indicated a quantitative increase in NKG2D-bearing NK cells within the kidney following IRI. NK cell depletion in wild-type C57BL/6 mice was protective, while adoptive transfer of NK cells worsened injury in NK, T, and B cell-null Rag2(-/-)gamma(c)(-/-) mice with IRI. NK cell-mediated kidney injury was perforin (PFN)-dependent as PFN(-/-) NK cells had minimal capacity to kill TEC in vitro compared with NK cells from wild-type, FasL-deficient (gld), or IFN-gamma(-/-) mice. Taken together, these results demonstrate for the first time that NK cells can directly kill TEC and that NK cells contribute substantially to kidney IRI. NK cell killing may represent an important underrecognized mechanism of kidney injury in diverse forms of inflammation, including transplantation.

Peroxisome proliferator-activated receptor-alpha contributes to the resolution of inflammation after renal ischemia/reperfusion injury

This study was designed to elucidate the role of peroxisome proliferator-activated receptor (PPAR)-alpha in the development of inflammation after ischemia/reperfusion injury of the kidney. We have evaluated the effects of ischemia/reperfusion on renal dysfunction, injury, and inflammation in wild-type mice or mice in which the gene for PPAR-alpha has been deleted [PPAR-alpha(-/-)] and then treated with the PPAR-alpha agonist fenofibrate. Mice were subjected to bilateral renal ischemia (30 min) and reperfusion (24 h) and received fenofibrate (3 mg/kg i.p.) before reperfusion. Plasma creatinine, urea, and aspartate aminotransferase were all used as indicators of renal dysfunction and injury. Kidneys were used for histological and immunohistochemical analysis and markers of inflammation. Fenofibrate significantly attenuated the degree of renal dysfunction, injury, and inflammation caused by ischemia/reperfusion injury. The degree of renal dysfunction, injury, and inflammation caused by ischemia/reperfusion was also significantly augmented in PPAR-alpha(-/-) mice compared with their wild-type littermates. It is interesting that fenofibrate did not protect PPAR-alpha(-/-) mice against ischemia/reperfusion injury. Therefore, we propose that ligands of PPAR-alpha may be useful in the treatment of renal ischemia/reperfusion injury and that endogenous PPAR-alpha limits the degree of renal dysfunction, injury, and inflammation associated with ischemia/reperfusion injury.

A functional folate receptor is induced during macrophage activation and can be used to target drugs to activated macrophages

Previous work has demonstrated that a subset of macrophages expresses a folate receptor (FR) that can mediate internalization of folate-linked molecules, including imaging and therapeutic agents. To characterize this subset, macrophages were collected from peritoneal cavities of mice injected with saline, thioglycolate, zymosan, heat-killed or live bacteria, and cell-surface markers that coexpress with FR were identified. Virtually no F4/80(+) peritoneal macrophages from saline-injected mice expressed FR, whereas numerous macrophages from mice injected with each inflammatory stimulus expressed FR. Examination of cell differentiation antigens that are up-regulated in FR(+) macrophages revealed markers characteristic of an activated state (CD80, CD86, Ly-6C/G), whereas macrophages lacking these activation markers expressed few or no FR. FR(+) macrophages also produced tumor necrosis factor-alpha (TNF-alpha) and reactive oxygen species, and production of reactive oxygen species correlated linearly with expression of FR. Synovial macrophages collected from arthritic patients were found to bind and internalize folate-linked dyes. Moreover, a folate-linked radioimaging agent was shown to image inflamed joints of rheumatoid arthritic patients. These results suggest that FR constitutes a marker for macrophage activation and that FR(+) macrophages can be targeted with folate-linked drugs without promoting drug uptake by nonactivated macrophages. This trial was registered at www.clinicaltrials.gov as #NCT00588393.

FK506: An Immunosuppressive Agent Preserving HIF-1 Activity

During transplantation, donor organs or cells are subjected to hypoxia. Hypoxia-inducible factor-1 (HIF-1) is essential for cellular adaptation to hypoxia. Immunosuppressive agents should be used for preventing graft rejection, but of these, rapamycin and cyclosporine A have been reported to inhibit HIF-1. We examined whether or not another important immunosuppressant, FK506, inhibits HIF-1. In contrast to cyclosporine A, FK506 neither inhibits HIF-1alpha expression in 8 different cell lines, nor represses the transcriptional activity of HIF-1. Compared with cyclosporine A, FK506 significantly reduced the apoptotic cell death by hypoxia. FK506 could preserve HIF-1 activity in donor organs subjected to hypoxia.

Cytokine gene expression in kidney allograft biopsies after donor brain death and ischemia-reperfusion injury using in situ reverse-transcription polymerase chain reaction analysis

BACKGROUND

This study focuses on the cytokine genes expression after brain-death, ischemia-reperfusion injury, and during allograft rejection.

METHODS

A total of 49 needle core biopsies from kidney transplant recipients, performed before and during transplantation procedures were studied. The first biopsy was taken during procurement of the organ, the second after cold ischemia, and the third after approximately 30 min of reperfusion. We also assessed 34 allograft biopsies obtained during acute rejection. Tubular and glomerular expression of interferon (IFN)-gamma, transforming growth factor (TGF)-beta1, platelet-desired growth factor-B (PDGF-B), interleukin (IL)-2, IL-6, IL-10 mRNA was analyzed with reverse-transcription polymerase chain reaction (RT-PCR) in situ technique, which allows to detect a few copies of the target gene without destruction of the tissue architecture.

RESULTS

Compared with normal kidney tissue from living donor, high gene expression of IFN-gamma, TGF-beta1, PDGF-B, IL-2, IL-6, and IL-10 was detected in all procurement specimens. After reperfusion gene expressions of IL-2, IL-6, and IL-10 were significantly upregulated in renal tubules compared to biopsies taken after cold ischemia. The gene expression of IFN-gamma, TGF-beta1, and PDGF-B remained stable after organ procurement, during cold ischemia, and after reperfusion. Gene expression of IFN-gamma, IL-2, IL-6, IL-10, and PDGF-B in procurement biopsies, as well as in those taken after cold ischemia and reperfusion, were significantly higher than during the period of acute rejection.

CONCLUSION

The data presented herein strongly point out the importance of the immunological and morphological injury that occurs before and during transplantation. The increase of inflammatory response after brain death is important for further stimulation of the immune response and long-term kidney survival.

Fractalkine receptor (CX3CR1) inhibition is protective against ischemic acute renal failure in mice

Fractalkine (CX3CL1) is expressed on injured endothelial cells and is a potent chemoattractant and adhesion molecule for macrophages carrying the fractalkine receptor (CX3CR1). The aim of this study was to investigate the role of CX3CL1, and its ligand CX3CR1, in ischemic acute renal failure (ARF) in mice. On immunoblotting, CX3CL1 protein expression in the kidney increased markedly in ischemic ARF. On immunofluorescence staining, the intensity of CX3CL1 staining in blood vessels was significantly more prominent in ischemic ARF compared with controls. A specific anti-CX3CR1 antibody (25 microg i.p. 1 h before induction of ischemia) was functionally and histologically protective against ischemic ARF. CX3CR1 is predominantly expressed on macrophages. Macrophage infiltration in the kidney in ischemic ARF was significantly decreased after anti-CX3CR1 antibody treatment. To determine the role of macrophages in ischemic ARF, macrophages in the kidney were depleted using liposomal-encapsulated clodronate (LEC). LEC resulted in significant functional and histological protection against ischemic ARF. In summary, in ischemic ARF, 1) there is upregulation of CX3CL1 protein in the kidney, specifically in blood vessels; 2) CX3CR1 inhibition using a specific antibody is partially protective and is associated with reduced macrophage infiltration in the kidney; and 3) macrophage depletion in the kidney is protective.

Allopurinol and enalapril failed to conserve urinary NOx and sodium in ischemic acute renal failure in spontaneously hypertensive rats

BACKGROUND

Ischemia-reperfusion-induced acute renal failure (ARF) is associated with a high mortality in patients with hypertension and with an unfavorable outcome of kidney transplants from marginal donors.

AIM

The influence of allopurinol and enalapril on urinary nitrate/nitrite (UNOx), glomerular filtration rate, plasma and urinary sodium, and hemodynamic parameters was examined in spontaneously hypertensive rats (SHR) with ARF.

METHODS

ARF was induced by right-kidney removal and clamping the left renal artery for 40 min in 50 male 26-week-old SHR weighing 300 +/- 23 g. The rats were randomly allocated to five groups: (1) sham operated; (2) ARF; (3) ARF after pretreatment with 40 mg/kg allopurinol; (4) ARF after pretreatment with 40 mg/kg enalapril, and (5) ARF after pretreatment with 40 mg/kg allopurinol and 40 mg/kg enalapril. Creatinine clearance, UNOx (Griess reaction), cardiac output (dye dilution technique), mean arterial blood pressure, and renal blood flow were measured 24 h after reperfusion. Total vascular resistance and renal vascular resistance were calculated and compared between the groups.

RESULTS

A nonsignificant decrease was found in both daily UNOx excretion and creatinine clearance when pretreated ARF groups and the ARF group without pretreatment were compared (p > 0.05). Significantly lower plasma sodium values (139.5 +/- 4.86 mmol/l) in the allopurinol-pretreated ARF group were found than in the ARF group without pretreatment, in the ARF group pretreated with enalapril, and in the sham SHR group (p = 0.029). The urinary sodium loss was greater in the enalapril-pretreated than in the allopurinol-pretreated ARF group (p = 0.047). Allopurinol and/or enalapril pretreatment decreased total vascular resistance (p = 0.003) in comparison with the sham SHR group.

CONCLUSION

Neither allopurinol nor enalapril nor both were protective against ischemia-reperfusion injury in SHR, nor altered glomerular filtration rate and UNOx in a favorable direction.

Effect of mycophenolate mofetil on rat kidney grafts with prolonged cold preservation

The impact of mycophenolate mofetil (MMF) on initial renal transplant function is not well characterized. We tested how MMF may modulate graft function and survival in a syngeneic rat kidney transplantation model after prolonged cold preservation. Donor kidneys were preserved in University of Wisconsin for either 24 or 39 h prior to transplantation into nephrectomized rats. Recipients received MMF (20 mg/kg/day) or vehicle. Mycophenolic acid (MPA) blood concentrations were measured by high-performance liquid chromatography. The inflammatory response, tubular epithelial proliferation, and histologic damage 3 days post-transplantation were assessed microscopically. In the 24 h cold storage (c.s.) group serum-creatinine was measured. In the 39 h c.s. group 1-week recipient survival was determined. After 24 h of c.s., recipient survival was 100%. The number of T-cell infiltrates was low and not influenced by MMF, whereas renal ED1+ cell infiltration was significantly suppressed by MMF. Tubular cell proliferation was enhanced by MMF. Serum-creatinine levels and renal histology were comparable between MMF and vehicle-treated animals. In the 39 h c.s. group, recipient survival was 20% in MMF-treated vs 90% in vehicle-treated animals (P=0.001). MMF effectively suppressed inflammatory cell infiltration and inhibited tubular cell proliferation. MMF-induced structural damage was most striking in the renal papilla. In rat kidney grafts with moderate preservation injury (24 h c.s.), MMF, given at an immunosuppressive dose, showed predominantly antiinflammatory effects without compromising graft function. In grafts with severe preservation injury (39 h c.s.), MMF caused irreversible structural damage and inhibited tubular cell regeneration resulting in renal failure.

Mammalian Target of Rapamycin Pathway Blockade Slows Progression of Diabetic Kidney Disease in Rats

Recent data suggest that the phosphatidylinositol 3-kinase (PI3-K)/Akt/mammalian target of rapamycin (mTOR) pathway is important in diabetic nephropathy. The effect of mTOR blockade by sirolimus (SRL) in diabetic kidney disease in rats was investigated. Diabetes was induced by streptozotocin in male Sprague-Dawley rats. Sixteen weeks later, diabetic animals were divided into the following groups: diabetes (D; n = 8), diabetes + SRL at 1 mg/kg per d, SRL trough level 2.3 +/- 0.25 ng/ml (D+SRL; n = 7); and diabetes + normoglycemia maintained by insulin implants (D+NG; n = 5). There was an age-matched nondiabetic group (ND; n = 6). All animals were followed for 4 wk. The D group showed glomerular hypertrophy (mean glomerular volume 5.0 +/- 0.4 in D versus 3.3 +/- 0.2 10(6) mu(3) in ND; P < 0.05) without renal hyperplasia (calculated by reverse transcription-PCR of proliferative cell nuclear antigen) and albuminuria (29 +/- 4 in D versus 1.4 +/- 1.5 mg/24 h in ND; P < 0.05). Both D+NG and D+SRL groups had a significant reduction of albuminuria, although glomerular hypertrophy was still present. SRL treatment did not modify the number of infiltrating renal ED1(+) cells. Diabetic animals had greater expression of p-Akt and mTOR, unlike ND rats. NG and SRL treatment reduced p-Akt and normalized mTOR. It is interesting that D+SRL was associated with a significant reduction of renal TGF-beta1 and glomerular connective tissue growth factor. SRL treatment reduced glomerular alpha-smooth muscle actin overexpression and reduced significantly the mesangial matrix accumulation that is characteristic of diabetic nephropathy. In conclusion, mTOR blockade by low-dose SRL has a beneficial effect in diabetic kidney disease, suggesting that the mTOR pathway has an important pathogenic role in diabetic nephropathy.

Theophylline Improves Early Allograft Function in Rat Kidney Transplantation

Several previous studies have demonstrated a beneficial effect of the adenosine receptor (AdoR) antagonist theophylline in different forms of acute renal failure in laboratory animals and in humans. Therefore, we wanted to test whether theophylline can also improve impaired allograft function following ischemia reperfusion injury in experimental kidney transplantation (KT). Orthotopic transplantation of the left kidney was performed from Fisher 344 into Lewis rats. All transplanted rats received daily cyclosporine (5 mg/kg). The effect of theophylline treatment (10 mg/kg) on graft function was compared with appropriate controls on day 5 after KT by assessment of glomerular filtration rate (GFR) (inulin clearance). On day 5, GFR of allografts in control rats was 0.23 +/- 0.05 ml/min/g kidney weight (n = 10) compared with 0.50 +/- 0.09 ml/min/g in rats receiving theophylline (n = 9, p < 0.01), representing a 2-fold increase in GFR. Renal AdoR A(1) mRNA content was significantly increased in both KT groups compared with their respective control groups, whereas mRNA of AdoR A(2a), A(2b), and A(3) were found to be unchanged. Theophylline did not affect significantly interstitial infiltration of the graft by monocytes/macrophages and T-cells. Likewise, serum cytokines [interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor-alpha] and erythropoietin plasma levels were not different among the allograft groups. The present study demonstrates that theophylline remarkably improved early renal allograft function in rats undergoing KT without influencing cytokine serum patterns or tissue inflammation. Since theophylline is a commonly used medication in humans, clinical studies in patients undergoing KT are warranted.