Oxidative stress in kidney transplantation: malondialdehyde is an early predictive marker of graft dysfunction

The Clinical Utility and Plausibility of Oxidative and Antioxidant Variables in Chronic and End-Stage Kidney Disease: A Review of the Literature

Oxidative stress (OS) is caused by an imbalance between the production of reactive oxygen species (ROS) in cells and tissues and the ability of the biological system to detoxify these products. In chronic kidney disease (CKD), OS contributes to deterioration of kidney function and disease progression. In patients with end-stage kidney disease undergoing hemodialysis or peritoneal dialysis, OS is further increased and associated with adverse clinical outcomes, including deterioration and subsequent loss of residual renal function, atherosclerosis, hypertension, cardiovascular disease and death. However, currently, there is no consensus or guidelines for the diagnosis and treatment of OS in these patients. Herein, we aim to present the existing data regarding biomarkers of OS, pro-oxidants (oxidized albumin, advanced oxidation protein products, xanthine oxidase/dehydrogenase, nitrite/nitrate, malondialdehyde) and antioxidants (superoxide dismutase, catalase, vitamin E, total antioxidant capacity, N-acetylcysteine) that are most clinically relevant and have been more extensively studied in patients with chronic kidney disease, aiming to provide a clearer understanding of this complex area.

Living donors kidney transplantation and oxidative stress: Nitric oxide as a predictive marker of graft function

BACKGROUND

Glomerular filtration rate is the best indicator of renal function and a predictor of graft and patient survival after kidney transplantation.

METHODS

In a single-centre prospective analysis, we assessed the predictive performances of 4 oxidative stress biomarkers in estimating graft function at 6 months and 1 year after kidney transplantation from living donors. Blood samples were achieved on days (D-1, D1, D2, D3, D6 and D8), months (M1, M3 and M6) and after one year (1Y). For donors, a blood sample was collected on D-1. Malondialdehyde (MDA), nitric oxide (NO), glutathione s-transferase (GST), myeloperoxydase (MPO), and creatinine (Cr) were measured by spectrophotometric essays. The estimated glomerular filtration rate by the modification of diet in renal disease equation (MDRD-eGFR) was used to assess renal function in 32 consecutive donor-recipient pairs. Pearson's and Spearman's correlations have been applied to filter out variables and covariables that can be used to build predictive models of graft function at six months and one year. The predictive performances of NO and MPO were tested by multivariable stepwise linear regression to estimate glomerular filtration rate at six months.

RESULTS

Three models with the highest coefficients of determination stand out, combining the two variables nitric oxide at day 6 and an MDRD-eGFR variable at day 6 or MDRD-eGFR at day 21 or MDRD-eGFR at 3 months, associated for the first two models or not for the third model with donor age as a covariable (P = 0.000, r2 = 0.599, r2adj = 0.549; P = 0.000, r2 = 0.548, r2adj = 0.497; P = 0.000, r2 = 0.553, r2adj = 0.517 respectively).

CONCLUSION

Quantification of nitric oxide at day six could be useful in predicting graft function at six months in association with donor age and the estimated glomerular filtration rate in recipient at day 6, day 21 and 3 months after transplantation.

Vitamin C deficiency after kidney transplantation: a cohort and cross-sectional study of the TransplantLines biobank

PURPOSE

Vitamin C deficiency is associated with excess mortality in kidney transplant recipients (KTR). We aim to evaluate plasma vitamin C status at different post-transplantation moments and assess the main characteristics associated with vitamin C deficiency in KTR.

METHODS

Plasma vitamin C was assessed in 598 KTR at 3-, 6-, 12-, 24-, and 60-months post-transplantation, 374 late KTR with a functioning graft ≥ 1 year, and 395 potential donors. Vitamin C deficiency was defined as plasma vitamin C ≤ 28 µmol/L. Diet was assessed by a 177-item food frequency questionnaire. Data on vitamin C-containing supplements use were extracted from patient records and verified with the patients.

RESULTS

Vitamin C deficiency ranged from 46% (6-months post-transplantation) to 30% (≥ 1 year post-transplantation). At all time points, KTR had lower plasma vitamin C than potential donors (30-41 µmol/L vs 58 µmol/L). In cross-sectional analyses of the 953 KTR at their first visit ≥ 12 months after transplantation (55 ± 14 years, 62% male, eGFR 55 ± 19 mL/min/1.73 m2), the characteristics with the strongest association with vitamin C deficiency were diabetes and smoking (OR 2.67 [95% CI 1.84-3.87] and OR 1.84 [95% CI 1.16-2.91], respectively). Dietary vitamin C intake and vitamin C supplementation were associated with lower odds (OR per 100 mg/day 0.38, 95% CI 0.24-0.61 and OR 0.21, 95% CI 0.09-0.44, respectively).

CONCLUSION

Vitamin C deficiency is frequent among KTR regardless of the time after transplantation, especially among those with diabetes and active smokers. The prevalence of vitamin C deficiency was lower among KTR with higher vitamin C intake, both dietary and supplemented. Further research is warranted to assess whether correcting this modifiable risk factor could improve survival in KTR.

Donor-Dependent Variations in Systemic Oxidative Stress and Their Association with One-Year Graft Outcomes in Kidney Transplantation

INTRODUCTION

Oxidative stress has been implicated in complications after kidney transplantation (KT), including delayed graft function (DGF) and rejection. However, its role in long-term posttransplant outcomes remains unclear.

METHODS

We investigated oxidative damage and antioxidant defense dynamics, and their impact on the graft outcomes, in 41 KT recipients categorized by type of donation over 12 months. Oxidative status was determined using OxyScore and AntioxyScore indexes, which comprise several circulating biomarkers of oxidative damage and antioxidant defense. Donor types included donation after brain death (DBD [61.0%]), donation after circulatory death (DCD [26.8%]), and living donation (LD [12.1%]).

RESULTS

There was an overall increase in oxidative damage early after transplantation, which was significantly higher in DCD as compared to DBD and LD recipients. The multivariate adjustment confirmed the independent association of OxyScore and type of deceased donation with DGF, donor kidney function, and induction therapy with antithymocyte globulin. There were no differences in terms of antioxidant defense. Lower oxidative damage at day 7 predicted better graft function at 1-year posttransplant only in DBD recipients.

CONCLUSION

DCD induced greater short-term oxidative damage after KT, whereas the early levels of oxidative damage were predictive of the graft function 1 year after KT among DBD recipients.

Effect of resuscitation of cryopreserved porcine adrenal glands at 26 °C on their recovery and functioning under xenotransplantation

The study is devoted to the effect of lowered resuscitation temperature (26 °C) on cryopreserved porcine adrenal glands functional activity in vitro and in vivo under xenotransplantation. The adrenals were collected from newborn pigs, cryopreserved with 5 % DMSO at a rate of 1 °C/min, resuscitated at 26 or 37 °C for 48 h (5 % CO2, DMEM), embedded into small intestinal submucosa, and transplanted to bilaterally adrenalectomized rats. It has been shown that the glands resuscitated at 26 °C have suppressed free-radical processes and can produce cortisol and aldosterone in vitro, and may lead to elevated blood levels of these hormones. Moreover, the adrenal grafts maintain blood glucose levels and promote the formation of glycogen stores. Thus, the resuscitation at 26 °C can improve the quality of grafts and favor the introduction and application of the cryopreserved organs and tissues for transplantation in clinical and experimental practice.

Nephroprotective Effect of Hibiscus Sabdariffa Leaf Flavonoid Extracts via KIM-1 and TGF-1β Signaling Pathways in Streptozotocin-Induced Rats

Diabetes-induced kidney damage represents a substantial health hazard, emphasizing the imperative to explore potential therapeutic interventions. This study investigates the nephroprotective activity of flavonoid-rich extracts from Hibiscus sabdariffa leaves in streptozotocin-induced diabetic rats. The flavonoid-rich extracts of H. sabdariffa leaves was obtained using a standard procedure. The animals were induced with streptozotocin and thereafter treated with both low (LDHSFL) and high doses (HDHSFL) of flavonoid-rich extracts from H. sabdariffa leaves and metformin (MET), and other groups are diabetic control (DC) and normal control (NC). The study assesses diverse renal parameters, encompassing kidney redox stress biomarkers, serum electrolyte levels, kidney inflammatory biomarkers, serum concentrations of creatinine, urea, and uric acid, kidney phosphatase activities, renal histopathology, and relative gene expressions of kidney injury molecule-1 (KIM-1) and transforming growth factor beta-1 (TGF-1β), comparing these measurements with normal and diabetic control groups (NC and DC). The findings indicate that the use of extracts from H. sabdariffa leaves markedly (p < 0.05) enhanced renal well-being by mitigating nephropathy, as demonstrated through the adjustment of various biochemical and gene expression biomarkers, indicating a pronounced antioxidative and anti-inflammatory effect, improved kidney morphology, and mitigation of renal dysfunction. These findings suggest that H. sabdariffa leaf flavonoid extracts exhibit nephroprotective properties, presenting a potential natural therapeutic approach for the treatment of diabetic nephropathy.

The potential role of upregulated PARP-1/RIPK1 expressions in amikacin-induced oxidative damage and nephrotoxicity in Wistar rats

This study aimed to investigate the gene expression levels associated with nephrotoxic action of amikacin, as well as the post-treatment effect of diuretics on its nephrotoxic effects. Sixty male rats were divided equally into six groups, including the control group receiving saline intra-peritoneally (ip), and the five treated groups including therapeutic and double therapeutic dose groups, injected ip (15 and 30 mg/kg b.wt./day) respectively for seven days, and another two rat groups treated as therapeutic and double therapeutic dose groups then administered the diuretic orally for seven days and the last group received amikacin ip at a rate of 15 mg/kg/day for seven days, then given free access to water without diuretics for another seven days and was kept as a self-recovery group. Amikacin caused kidney injury, which was exacerbated by the double therapeutic dose, as evidenced by abnormal serum renal injury biomarkers, elevated renal MDA levels, inhibition of renal catalase and SOD enzyme activities, with renal degenerative and necrotic changes. Moreover, comet assays also revealed renal DNA damage. Interestingly, amikacin administration markedly elevated expression levels of the PARP-1, RIP1, TNF-α, IL-1β, and iNOS genes as compared to the control group. However, compared to the self-recovery group, post-amikacin diuretic treatment modulates amikacin-induced altered findings and alleviates amikacin nephrotoxic effects more efficiently. Our findings suggested the potential role of PARP-1 and RIPK1 expressions that influence the expression of proinflammatory cytokines such as IL-1β and TNF-α by exaggerating oxidative stress which may contribute to the pathogenesis of amikacin-induced nephrotoxicity.

Circulating "Neutrophils extra-cellular traps" during the early post-renal transplant period and correlation with graft dysfunction and rejection

BACKGROUND

Neutrophil extracellular traps (NETs) have a role in infection, autoimmunity, autoinflammation, thrombosis, ischemia-reperfusion injury (IRI), epithelial-mesenchymal transition, vasculitis, and metabolic diseases. However, its role in early graft injury and graft outcome has not been elucidated till now. We evaluated the circulating NETs during early post-transplant periods and their correlation with graft outcome and IRI.

METHODS

Prospectively, thirty kidney transplants recipient (KTR) were recruited and grouped into non-dysfunction (Group-A) and dysfunction groups (Group-B). Serum levels of circulating NETs were estimated by measuring myeloperoxidase-DNA complex at three-time points: pre-transplant, 8 h post-transplant, and 18 h post-transplant; and correlated with early graft outcome. Malondialdehyde (MDA), a marker of oxidative stress or IRI, was also measured to assess its relation with NETs and early graft outcome.

RESULTS

Circulating NETs were significantly increased in both non-dysfunctional [Median OD: 0.11 (0.01-0.19) to 0.51 (0.22-0.91); p = 0.001] and dysfunctional [Median OD: 0.16 (0.12-0.27) to 0.38 (0.19-0.68); p = 0.047] KTR during first 8 h of transplant followed by fall at 18 h post-transplant [0.25 (0.18-0.72) and 0.35 (0.26-0.36) respectively]; however, no significant difference were observed between two groups at any time points. Isolated biopsy-proven graft rejection KTR also had higher circulating NETs during the early post-transplant period [Median OD: 0.16 (0.13-0.31) to 0.38 (0.28-1.5); p > 0.05] but no significant difference compared to non-dysfunctional KTR. MDA also displayed similar trends with an early significant rise [9.30 (7.74-12.56) μM to 17.37 (9.11-22.25) μM; p = 0.03 in group-A, and 8.7 (6.04-10.30) μM to 14.66 (13.39-21.63) μM; p = 0.01in group-B] followed by fall at 18 h in both groups [10.21 (7.64-13.90) μM and 11.11 (9.15-17.54) μM respectively]. Despite similar trends of both NETs and MDA, there was no significant correlation between these; however, creatinine exhibits a significant inverse correlation with NETs and MDA both.

CONCLUSION

Circulating NETs are significantly increased during the early post-transplant period in KTR irrespective of early graft outcome. Similar dynamics of MDA indicate that the early rise of NETs might be a part of IRI. However, molecular studies with large sample sizes and longer follow up are required to reach more defined conclusions.

Mitoquinone Alleviates Donation after Cardiac Death Kidney Injury during Hypothermic Machine Perfusion in Rat Model

Transplanted organs are subjected to harmful conditions through stopping blood flow, hypothermic storage of the graft, and subsequent reperfusion. In particular, kidneys donated from patients after cardiac arrest (DCD) are classified as more vulnerable to ischemia-reperfusion injury (IRI). Hypothermic machine perfusion is proposed as a solution for better kidney storage before transplantation, and it is a good platform for additional graft treatment. Antioxidants have gained interest in regenerative medicine due to their ability to scavenge reactive oxygen species (ROS), which play a key role in IRI. We evaluated the effect of Mitoquinone (MitoQ), a strong mitochondria-targeted antioxidant, administered directly to the perfusing buffer. Rat kidneys were isolated, randomly classified into one of the following groups, donation after brainstem death (DBD), DCD, and DCD with MitoQ, and perfused for 22 hours with a hypothermic machine perfusion system. Subsequently, we detected levels of kidney injury (KIM-1) and oxidative stress (ROS/RNS, cytochrome C oxidase, and mitochondrial integrity) markers. We compared the activation of the apoptosis pathway (caspase 3 and 9), the concentration of phosphorylated Akt (pAkt), and the pAkt/total Akt ratio. MitoQ reduces KIM-1 concentration, total ROS/RNS, and the level of caspases. We observed a decrease in pAkt and the pAkt/total Akt ratio after drug administration. The length of warm ischemia time negatively impacts the graft condition. However, MitoQ added to the perfusing system as an 'on pump' therapy mitigates injury to the kidney before transplantation by inhibiting apoptosis and reducing ROS/RNS levels. We propose MitoQ as a potential drug for DCD graft preconditioning.

Plasma Copper Concentration Is Associated with Cardiovascular Mortality in Male Kidney Transplant Recipients

Kidney transplant recipients (KTR) are at increased risk of cardiovascular mortality. We investigated whether, in KTR, post-transplantation copper status is associated with the risk of cardiovascular mortality and potential effect modification by sex. In this cohort study, plasma copper was measured using mass spectrometry in extensively-phenotyped KTR with a functioning allograft >1-year. Cox regression analyses with the inclusion of multiplicative interaction terms were performed. In 660 KTR (53 ± 13 years old, 56% male), the median baseline plasma copper was 15.42 (IQR 13.53-17.63) µmol/L. During a median follow-up of 5 years, 141 KTR died, 53 (38%) due to cardiovascular causes. Higher plasma copper was associated with an increased risk of cardiovascular mortality in the overall KTR population (HR 1.37; 95% CI, 1.07-1.77 per 1-SD, p = 0.01). Sex was a significant effect modifier of this association (Pinteraction = 0.01). Among male KTR, higher plasma copper concentration was independently associated with a two-fold higher risk of cardiovascular mortality (HR 2.09; 95% CI, 1.42-3.07 per 1-SD, p < 0.001). Among female KTR, this association was absent. This evidence offers a rationale for considering a sex-specific assessment of copper's role in cardiovascular risk evaluation. Further studies are warranted to elucidate whether copper-targeted interventions may decrease cardiovascular mortality in male KTR.

Evaluation of Oxidative Stress and Metabolic Profile in a Preclinical Kidney Transplantation Model According to Different Preservation Modalities

This study addresses a joint nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy approach to provide a platform for dynamic assessment of kidney viability and metabolism. On porcine kidney models, ROS production, oxidative damage kinetics, and metabolic changes occurring both during the period between organ retrieval and implantation and after kidney graft were examined. The 1H-NMR metabolic profile—valine, alanine, acetate, trimetylamine-N-oxide, glutathione, lactate, and the EPR oxidative stress—resulting from ischemia/reperfusion injury after preservation (8 h) by static cold storage (SCS) and ex vivo machine perfusion (HMP) methods were monitored. The functional recovery after transplantation (14 days) was evaluated by serum creatinine (SCr), oxidative stress (ROS), and damage (thiobarbituric-acid-reactive substances and protein carbonyl enzymatic) assessments. At 8 h of preservation storage, a significantly (p < 0.0001) higher ROS production was measured in the SCS vs. HMP group. Significantly higher concentration data (p < 0.05−0.0001) in HMP vs. SCS for all the monitored metabolites were found as well. The HMP group showed a better function recovery. The comparison of the areas under the SCr curves (AUC) returned a significantly smaller (−12.5 %) AUC in the HMP vs. SCS. EPR-ROS concentration (μmol·g−1) from bioptic kidney tissue samples were significantly lower in HMP vs. SCS. The same result was found for the NMR monitored metabolites: lactate: −59.76%, alanine: −43.17%; valine: −58.56%; and TMAO: −77.96%. No changes were observed in either group under light microscopy. In conclusion, a better and more rapid normalization of oxidative stress and functional recovery after transplantation were observed by HMP utilization.

Experimental Static Cold Storage of the Rat Uterus: Protective Effects of Relaxin- or Erythropoietin-Supplemented HTK-N Solutions

Uterus transplantation (UTx) is the only treatment method for women with absolute uterine infertility. Currently, the number of grafts retrieved from deceased donors is increasing; hence, prolonged cold ischemia time is inevitable. Thus, this study was designed to assess the effect of the novel relaxin (RLN)- or erythropoietin (EPO)-supplemented Custodiol-N (HTK-N) solutions in an experimental uterus static cold storage (SCS) model. A total of 15 Sprague Dawley rats were used. Uterus horns were randomly assigned into three groups (n = 10/group). SCS was performed by keeping samples at 4 °C in HTK-N solution without or with different additives: 10 IU/mL EPO or 20 nM RLN. Tissue samples were taken after 8 and 24 h of preservation. Uterine tissue histology, and biochemical and immunohistochemical markers were analyzed. No significant differences in SCS-induced tissue damage were observed between groups after 8 h of preservation. Uterine tissue histology, MDA, SOD levels and the TUNEL-positive cell number showed severe damage in HTK-N without additives after 24 h of preservation. This damage was significantly attenuated by adding RLN to the preservation solution. EPO showed no favorable effect. Our study shows that RLN as an additive to an HTK-N solution can serve as an effective uterine tissue preservative in the uterus SCS setting.

Protective effect of hydroxysafflor yellow A on cyclosporin A-induced renal oxidative stress in vitro and in vivo

PURPOSE

To explore the mechanism and investigate the protective effect of hydroxysafflor yellow A (HSYA) on renal oxidative stress, which cyclosporine A (CsA) induces.

METHODS

HK-2 cells were treated with CsA to get CsA-induced oxidative stress. The effects on oxidative stress and apoptosis of HK-2 cells were detected. The contents of SOD, MDA, GSH-Px, ROS, and CAT in serum were measured, and the expression of apoptosis-related proteins was detected by western blot. Then, established the renal oxidative stress injury rats to verify the efficacy of HSYA.

RESULTS

HSYA could reduce the ROS and MDA contents induced by CsA. Compared with the CsA group, the activities of SOD, CAT, and GSH-Px increased significantly when treated with HSYA. HSYA could inhibit CsA-induced apoptosis in HK-2 cells, and promote the protein of Bcl-2 and inhibit the expression of Bax. Animal experiments showed that HSYA could reduce CsA-induced renal cell injury by reducing glomerular cell vacuoles and inflammatory factors in tissues. It also decreased serum creatinine (Crea) and blood urea nitrogen, increased Crea clearance significantly.

CONCLUSIONS

HSYA could significantly improve the antioxidant capacity of the kidney cells and inhibit cell apoptosis, thereby effectively ameliorating CsA-induced oxidative stress in vitro and in vivo.

Renal Normothermic Machine Perfusion: The Road Toward Clinical Implementation of a Promising Pretransplant Organ Assessment Tool

The increased utilization of high-risk renal grafts for transplantation requires optimization of pretransplant organ assessment strategies. Current decision-making methods to accept an organ for transplantation lack overall predictive power and always contain an element of subjectivity. Normothermic machine perfusion (NMP) creates near-physiological conditions, which might facilitate a more objective assessment of organ quality before transplantation. NMP is rapidly gaining popularity, with various transplant centers developing their own NMP protocols and renal viability criteria. However, to date, no validated sets of on-pump viability markers exist nor are there unified NMP protocols. This review provides a critical overview of the fundamentals of current renal NMP protocols and proposes a framework to approach further development of ex vivo organ evaluation. We also comment on the potential logistical implications of routine clinical use of NMP, which is a more complex procedure compared with static cold storage or even hypothermic machine perfusion.

Novel pharmacological effects of lecithinized superoxide dismutase on ischemia/reperfusion injury in the kidneys of mice

Renal ischemia/reperfusion (I/R) injury is a major clinical problem because it can cause acute kidney injury (AKI) or lead to the transition from AKI to chronic kidney disease (CKD). Oxidative stress, which involves the production of reactive oxygen species (ROS), plays an important role in the development and exacerbation of I/R-induced kidney injury. However, we have previously reported that lecithinized superoxide dismutase (PC-SOD), a SOD derivative with high tissue affinity and high stability in plasma, has beneficial effects in various disease models because of its inhibitory effect on ROS production. Therefore, we aimed to determine the effects of intravenous PC-SOD administration in a mouse model of renal injury induced by I/R. PC-SOD markedly ameliorated the I/R-induced increases in markers of renal damage (urea nitrogen, creatinine, neutrophil gelatinase-associated lipocalin, and interleukin-6) and tubular necrosis 48 h after the intervention. We also found that PC-SOD significantly ameliorated the I/R-induced increase in ROS production, using an ex vivo imaging system. Furthermore, PC-SOD inhibited the increases in expression of markers of fibrosis (α-smooth muscle actin and collagen 1A1) 96 h after, and renal fibrosis 25 days after I/R was induced. Finally, we found that PC-SOD ameliorated the I/R-induced AKI in mice with high-fat diet-induced prediabetes. These results suggest that PC-SOD inhibits AKI and the transition from AKI to CKD through the inhibition of ROS production. Therefore, we believe that PC-SOD may represent an effective therapeutic agent for I/R-induced renal injury.

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.

Natural Antibodies and Alloreactive T Cells Long after Kidney Transplantation

Background

The relationship between circulating effector memory T and B cells long after transplantation and their susceptibility to immunosuppression are unknown. To investigate the impact of antirejection therapy on T cell-B cell coordinated immune responses, we assessed IFN-γ-producing memory cells and natural antibodies (nAbs) that potentially bind to autoantigens on the graft.

Methods

Plasma levels of IgG nAbs to malondialdehyde (MDA) were measured in 145 kidney transplant recipients at 5-7 years after transplantation. In 54 of these patients, the number of donor-reactive IFN-γ-producing cells was determined. 35/145 patients experienced rejection, 18 of which occurred within 1 year after transplantation.

Results

The number of donor-reactive IFN-γ-producing cells and the levels of nAbs were comparable between rejectors and nonrejectors. The nAbs levels were positively correlated with the number of donor-reactive IFN-γ-producing cells (r _s = 0.39, p=0.004). The positive correlation was only observed in rejectors (r _s = 0.53, p=0.003; nonrejectors: r _s = 0.24, p=0.23). Moreover, we observed that intravenous immune globulin treatment affected the level of nAbs and this effect was found in patients who experienced a late ca-ABMR compared to nonrejectors (p=0.008).

Conclusion

The positive correlation found between alloreactive T cells and nAbs in rejectors suggests an intricate role for both components of the immune response in the rejection process. Treatment with intravenous immune globulin impacted nAbs.

Biomarkers as diagnostic tests for delayed graft function in kidney transplantation

Delayed graft function (DGF) after kidney transplantation is associated with inferior outcomes and higher healthcare costs. DGF is currently defined as the requirement for dialysis within seven days post-transplant; however, this definition is subjective and nonspecific. Novel biomarkers have potential to improve objectivity and enable earlier diagnosis of DGF. We reviewed the literature to describe the range of novel biomarkers previously studied to predict DGF. We identified marked heterogeneity and low reporting quality of published studies. Among the novel biomarkers, serum NGAL had the greatest potential as a biomarker to predict DGF, but requires further assessment and validation through larger scale studies of diagnostic test performance. Given inadequacies in the dialysis-based definition, coupled with the high incidence and impact of DGF, such studies should be pursued.

Elevated plasma free thiols are associated with early and one-year graft function in renal transplant recipients

Background

Reduced free thiols in plasma are indicative of oxidative stress, which is an important contributor to ischaemia-reperfusion injury (IRI) in kidney transplantation leading to kidney damage and possibly delayed graft function (DGF). In a post-hoc, exploratory analysis of the randomised controlled CONTEXT trial, we investigated whether higher (i.e. less oxidised) plasma levels of free thiols as a biomarker of reduced oxidative stress are associated with a better initial graft function or a higher GFR.

Methods

Free thiol levels were measured in plasma at baseline, 30 and 90 minutes after reperfusion of the kidney as well as at Day 1, Day 5 and twelve months after kidney transplantation in 217 patients from the CONTEXT study. Free thiol levels were compared to the kidney graft function measured as the estimated time to a 50% reduction in plasma creatinine (tCr50), the risk of DGF and measured GFR (mGFR) at Day 5 and twelve months after transplantation.

Results

Higher levels of free thiols at Day 1 and Day 5 are associated with higher mGFR at Day 5 (p<0.001, r²_adj. = 0.16; p<0.001, r²_adj. = 0.25), as well as with mGFR at twelve months (p<0.001, r²_adj. = 0.20; p<0.001, r²_adj. = 0.16). However, plasma levels of free thiols at 30 minutes and 90 minutes, but not Day 1, were significantly higher among patients experiencing DGF.

Conclusion

Higher levels of plasma free thiols at Day 1 and Day 5, which are reflective of lower levels of oxidative stress, are associated with better early and late graft function in recipients of a kidney graft from deceased donors.

Trial registration

ClinicalTrials.gov Identifier:NCT01395719.

Assessment of Oxidative Stress Markers in Hypothermic Preservation of Transplanted Kidneys

Ischemia-reperfusion injury (IRI) after renal transplantation is a complex biochemical process. The first component is an ischemic phase during kidney storage. The second is reperfusion, the main source of oxidative stress. This study aimed to analyze the activity of enzymes and concentrations of non-enzymatic compounds involved in the antioxidant defense mechanisms: glutathione (GSH), glutathione peroxidase (GPX), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione transferase (GST), thiobarbituric acid reactive substances (TBARS), malondialdehyde (MDA), measured in preservation fluid before transplantation of human kidneys (KTx) grafted from brain dead donors. The study group (N = 66) was divided according to the method of kidney storage: Group 1—hypothermic machine perfusion (HMP) in LifePort perfusion pump, n1 = 26, and Group 2—static cold storage (SCS), n2 = 40. The measurements of kidney function parameters, blood count, and adverse events were performed at constant time points during 7-day hospitalization and 3-month follow-up. Kidney perfusate in Group 2 was characterized by significantly more acidic pH (p < 0.0001), higher activity of GPX [U/mgHb] (p < 0.05) and higher concentration of MDA [μmol/L] (p < 0.05). There was a statistically significant improvement of kidney function and specific blood count alterations concerning storage method in repeated measures. There were aggregations of significant correlations (p < 0.05) between kidney function parameters after KTx and oxidative stress markers: diuresis & CAT, Na⁺ & CAT, K⁺ & GPX, urea & GR. There were aggregations of significant correlations (p < 0.05) between recipient blood count and oxidative stress markers: CAT & MON, SOD & WBC, SOD & MON. Study groups demonstrated differences concerning the method of kidney storage. A significant role of recipient’s gender, gender matching, preservation solution, and perfusate pH was not confirmed, however, basing on analyzed data, the well-established long-term beneficial impact of HMP on the outcome of transplanted kidneys might partially depend on the intensity of IRI ischemic phase and oxidative stress, reflected by the examined biomarkers.

Urinary Carnosinase-1 Excretion is Associated with Urinary Carnosine Depletion and Risk of Graft Failure in Kidney Transplant Recipients: Results of the TransplantLines Cohort Study

Carnosine affords protection against oxidative and carbonyl stress, yet high concentrations of the carnosinase-1 enzyme may limit this. We recently reported that high urinary carnosinase-1 is associated with kidney function decline and albuminuria in patients with chronic kidney disease. We prospectively investigated whether urinary carnosinase-1 is associated with a high risk for development of late graft failure in kidney transplant recipients (KTRs). Carnosine and carnosinase-1 were measured in 24 h urine in a longitudinal cohort of 703 stable KTRs and 257 healthy controls. Cox regression was used to analyze the prospective data. Urinary carnosine excretions were significantly decreased in KTRs (26.5 [IQR 21.4–33.3] µmol/24 h versus 34.8 [IQR 25.6–46.8] µmol/24 h; p < 0.001). In KTRs, high urinary carnosinase-1 concentrations were associated with increased risk of undetectable urinary carnosine (OR 1.24, 95%CI [1.06–1.45]; p = 0.007). During median follow-up for 5.3 [4.5–6.0] years, 84 (12%) KTRs developed graft failure. In Cox regression analyses, high urinary carnosinase-1 excretions were associated with increased risk of graft failure (HR 1.73, 95%CI [1.44–2.08]; p < 0.001) independent of potential confounders. Since urinary carnosine is depleted and urinary carnosinase-1 imparts a higher risk for graft failure in KTRs, future studies determining the potential of carnosine supplementation in these patients are warranted.

Mitochondrial Reactive Oxygen Species and Their Contribution in Chronic Kidney Disease Progression Through Oxidative Stress

Mitochondria are known to generate approximately 90% of cellular reactive oxygen species (ROS). The imbalance between mitochondrial reactive oxygen species (mtROS) production and removal due to overproduction of ROS and/or decreased antioxidants defense activity results in oxidative stress (OS), which leads to oxidative damage that affects several cellular components such as lipids, DNA, and proteins. Since the kidney is a highly energetic organ, it is more vulnerable to damage caused by OS and thus its contribution to the development and progression of chronic kidney disease (CKD). This article aims to review the contribution of mtROS and OS to CKD progression and kidney function deterioration.

Oxidative stress increases 1-deoxysphingolipid levels in chronic kidney disease

Chronic kidney disease (CKD) leads to deep changes in lipid metabolism and obvious dyslipidemia. The dysregulation of lipid metabolism in turn results in CKD progression and the complications of cardiovascular diseases. To obtain a profound insight into the associated dyslipidemia in CKD, we performed lipidomic analysis to measure lipid metabolites in the serum from a rat 5/6 nephrectomy (5/6 Nx) model of CKD as well as in the serum from CKD patients. HK-2 cells were also used to examine oxidative stress-induced sphingolipid changes. Totally 182 lipid species were identified in 5/6 Nx rats. We found glycerolipids, total free fatty acids, and sphingolipids levels were significantly upregulated in 5/6 Nx rats. The atypical sphingolipids, 1-deoxysphingolipids, were significantly altered in both CKD animals and human CKD patients. The levels of 1-deoxysphingolipids directly relevant to the level of oxidative stress in vivo and in vitro. These results demonstrate that 1-deoxysphingolipid levels are increased in CKD and this increase directly correlates with increased kidney oxidative stress.

Effects of the fermented Zizyphus jujuba in the amyloid β25-35-induced Alzheimer's disease mouse model

BACKGROUD/OBJECTIVES

Alzheimer's disease (AD) is the most common cause of dementia in the elderly. Due to the increased incidence of dementia, there is a corresponding increase concerning the importance of AD. In this study, we investigated the protective effects conferred by Zizyphus jujuba (Zj) and Zizyphus jujuba fermented by yeast (Zj-Y), on cognitive impairment in an AD mouse model.

MATERIALS/METHODS

AD was induced by injecting amyloid beta_25-35 (Aβ_25-35) in ICR mice, and subsequently 200 mg/kg Zj or Zj-Y was administered daily for 14 days. The cognitive ability of AD mice was observed through behavioral experiments in T-maze, novel object recognition, and Morris water maze tests. We subsequently measured the levels of malondialdehyde (MDA), nitric oxide (NO), aspartate aminotransferase, and alanine aminotransferase in either tissues or serum.

RESULTS

In behavioral tests, deterioration was revealed in the short- and long-term learning and memory functions in the Aβ_25-35-injected control group compared to the normal group, indicating that Aβ_25-35 injection impairs cognitive functions. However, administration of Zj and Zj-Y improved cognitive function in mice, as compared to the Aβ_25-35-injected control mice. In addition, the Aβ_25-35 induced elevations of MDA and NO in the brain, kidney, and liver were suppressed after exposure to Zj and Zj-Y. Especially, Zj-Y showed stronger scavenging effect against MDA and NO, as compared to Zj.

CONCLUSIONS

Results of the present study indicate that Zj-Y exerts a protective effect on cognitive impairment and memory dysfunction, which is exerted by attenuating the oxidative stress induced by Aβ_25-35.

Changes in redox state of albumin before and after kidney transplantation in patients with end-stage renal disease

OBJECTIVES

Cardiovascular disease is one of the major causes of death in patients with end-stage kidney disease who have undergone kidney transplantation. Since the complication of cardiovascular disease in patients with chronic kidney disease is strongly linked to oxidative stress, understanding the oxidative stress condition after kidney transplantation would be of great importance for the prevention of cardiovascular disease. This study examined whether improvement of renal function after kidney transplantation has an impact on the redox state of the Cys34 residue of albumin that reflects the level of oxidative stress in blood.

DESIGN & METHODS

We enrolled 23 patients with end-stage renal failure who received kidney transplantation. All patients were followed for 180 days after transplantation. The fractions of albumin isoforms were determined by the electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) method.

RESULTS

Serum creatinine decreased significantly immediately after kidney transplantation, suggesting successful transplantations. The ESI-TOFMS method identified three albumin isoforms cysteinylated at the Cys34 residue (Cys-Cys34-albumin) and the three corresponding albumin isoforms without Cys34 cysteinylation. The fraction of total Cys-Cys34-albumin decreased transiently after kidney transplantation, and was followed by an elevation at day 7 and gradual decrease thereafter until day 180. Meanwhile, reduced albumin concentration did not change until day 14 after kidney transplantation, then showed a significant increase compared to pre-transplant level at day 30 and remained stably elevated until day 180.

CONCLUSIONS

Actual reduced albumin levels were found to exceed pre-transplant levels on or after day 30 following kidney transplantation unlike immediate restoration of renal function. Renal function was recovered immediately following kidney transplantation, but reduced albumen concentration increased above the pre-transplant levels only from day 30 after transplantation.

Post-transplantation plasma malondialdehyde is associated with cardiovascular mortality in renal transplant recipients: a prospective cohort study

BACKGROUND

In renal transplant recipients (RTRs), cardiovascular mortality is the most common cause of long-term renal graft loss. Oxidative stress (OS) has been associated with cardiovascular disease and is known to be enhanced in RTRs. We aimed to prospectively investigate whether the concentration of the OS biomarker malondialdehyde (MDA) is associated with long-term risk of cardiovascular mortality in a large cohort of RTRs.

METHODS

The plasma MDA concentration was measured using the thiobarbituric acid reaction assay in 604 extensively phenotyped RTRs with a functioning allograft for ≥1 year. The association between MDA and cardiovascular mortality was assessed using Cox proportional hazard regression analyses in the overall cohort and within subgroups according to significant effect modifiers.

RESULTS

Median circulating MDA concentration at baseline was 5.38 [interquartile range (IQR) 4.31-6.45] μmol/L. During a follow-up period of 6.4 (IQR 5.6-6.8) years, 110 (18%) RTRs died, with 40% of deaths due to cardiovascular causes. MDA concentration was significantly associated with the risk for cardiovascular mortality {hazard ratio [HR] 1.31 [95% confidence interval (CI) 1.03-1.67] per 1-SD increment}, independent of adjustment for potential confounders, including renal function, immunosuppressive therapy, smoking status and blood pressure. The association between MDA concentration and the risk for cardiovascular mortality was stronger in RTRs with relatively lower plasma ascorbic acid concentrations [≤42.5 µmol/L; HR 1.79 (95% CI 1.30-2.48) per 1-SD increment] or relatively lower estimated glomerular filtration rates [≤45 mL/min/1.73 m2; HR 2.09 (95% CI 1.45-3.00) per 1-SD increment].

CONCLUSIONS

Circulating MDA concentration is independently associated with long-term risk for cardiovascular mortality, particularly in RTRs with relatively lower ascorbic acid concentrations or renal function. Further studies are warranted to elucidate whether OS-targeted interventions could decrease cardiovascular mortality in RTRs.

The role of oxidative stress and hypoxia in renal disease

Oxygen is required to sustain aerobic organisms. Reactive oxygen species (ROS) are constantly released during mitochondrial oxygen consumption for energy production. Any imbalance between ROS production and its scavenger system induces oxidative stress. Oxidative stress, a critical contributor to tissue damage, is well-known to be associated with various diseases. The kidney is susceptible to hypoxia, and renal hypoxia is a common final pathway to end stage kidney disease, regardless of the underlying cause. Renal hypoxia aggravates oxidative stress, and elevated oxidative stress, in turn, exacerbates renal hypoxia. Oxidative stress is also enhanced in chronic kidney disease, especially diabetic kidney disease, through various mechanisms. Thus, the vicious cycle between oxidative stress and renal hypoxia critically contributes to the progression of renal injury. This review examines recent evidence connecting chronic hypoxia and oxidative stress in renal disease and subsequently describes several promising therapeutic approaches against oxidative stress.

Urinary Taurine Excretion and Risk of Late Graft Failure in Renal Transplant Recipients

Taurine is a sulfur containing nutrient that has been shown to protect against oxidative stress, which has been implicated in the pathophysiology leading to late graft failure after renal transplantation. We prospectively investigated whether high urinary taurine excretion, reflecting high taurine intake, is associated with low risk for development of late graft failure in renal transplant recipients (RTR). Urinary taurine excretion was measured in a longitudinal cohort of 678 stable RTR. Prospective associations were assessed using Cox regression analyses. Graft failure was defined as the start of dialysis or re-transplantation. In RTR (58% male, 53 ± 13 years old, estimated glomerular filtration rate (eGFR) 45 ± 19 mL/min/1.73 m²), urinary taurine excretion (533 (210–946) µmol/24 h) was significantly associated with serum free sulfhydryl groups (β = 0.126; P = 0.001). During median follow-up for 5.3 (4.5–6.0) years, 83 (12%) patients developed graft failure. In Cox regression analyses, urinary taurine excretion was inversely associated with graft failure (hazard ratio: 0.74 (0.67–0.82); P < 0.001). This association remained significant independent of potential confounders. High urinary taurine excretion is associated with low risk of late graft failure in RTR. Therefore, increasing taurine intake may potentially support graft survival in RTR. Further studies are warranted to determine the underlying mechanisms and the potential of taurine supplementation.

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.

Unveiling the Role of DNA Methylation in Kidney Transplantation: Novel Perspectives toward Biomarker Identification

The burden of chronic kidney disease is dramatically rising, making it a major public health concern worldwide. Kidney transplantation is now the best treatment for patients with end-stage renal disease. Although kidney transplantation may improve survival and quality of life, its long-term results are hampered by immune- and/or non-immune-mediated complications. Thus, the identification of transplanted patients with a higher risk of posttransplant complications has become a big challenge for public health. However, current biomarkers of posttransplant complications have a poor predictive value, rising the need to explore novel approaches for the management of transplant patient. In this review we summarize the emerging literature about DNA methylation in kidney transplant complications, in order to highlight its perspectives toward biomarker identification. In the forthcoming future the monitoring of DNA methylation in kidney transplant patients could become a plausible strategy toward the prevention and/or treatment of kidney transplant complications.

Bilirubin, a new therapeutic for kidney transplant?

In patients with end-stage renal disease, kidney transplantation has been associated with numerous benefits, including increased daily activity, and better survival rates. However, over 20% of kidney transplants result in rejection within five years. Rejection is primarily due to a hypersensitive immune system and ischemia/reperfusion injury. Bilirubin has been shown to be a potent antioxidant that is capable of potentially reversing or preventing damage from reactive oxygen species generated from ischemia and reperfusion. Additionally, bilirubin has several immunomodulatory effects that can dampen the immune system to promote organ acceptance. Increased bilirubin has also been shown to have a positive impact on renal hemodynamics, which is critical post-transplantation. Lastly, bilirubin levels have been correlated with biomarkers of successful transplantation. In this review, we discuss a multitude of potentially beneficial effects that bilirubin has on kidney acceptance of transplantation based on numerous clinical trials and animal models. Exogenous bilirubin delivery or increasing endogenous levels pre- or post-transplantation may have therapeutic benefits.

Methods for the evaluation of biomarkers in patients with kidney and liver diseases: multicentre research programme including ELUCIDATE RCT

Background

Protein biomarkers with associations with the activity and outcomes of diseases are being identified by modern proteomic technologies. They may be simple, accessible, cheap and safe tests that can inform diagnosis, prognosis, treatment selection, monitoring of disease activity and therapy and may substitute for complex, invasive and expensive tests. However, their potential is not yet being realised.

Design and methods

The study consisted of three workstreams to create a framework for research: workstream 1, methodology – to define current practice and explore methodology innovations for biomarkers for monitoring disease; workstream 2, clinical translation – to create a framework of research practice, high-quality samples and related clinical data to evaluate the validity and clinical utility of protein biomarkers; and workstream 3, the ELF to Uncover Cirrhosis as an Indication for Diagnosis and Action for Treatable Event (ELUCIDATE) randomised controlled trial (RCT) – an exemplar RCT of an established test, the ADVIA Centaur® Enhanced Liver Fibrosis (ELF) test (Siemens Healthcare Diagnostics Ltd, Camberley, UK) [consisting of a panel of three markers – (1) serum hyaluronic acid, (2) amino-terminal propeptide of type III procollagen and (3) tissue inhibitor of metalloproteinase 1], for liver cirrhosis to determine its impact on diagnostic timing and the management of cirrhosis and the process of care and improving outcomes.

Results

The methodology workstream evaluated the quality of recommendations for using prostate-specific antigen to monitor patients, systematically reviewed RCTs of monitoring strategies and reviewed the monitoring biomarker literature and how monitoring can have an impact on outcomes. Simulation studies were conducted to evaluate monitoring and improve the merits of health care. The monitoring biomarker literature is modest and robust conclusions are infrequent. We recommend improvements in research practice. Patients strongly endorsed the need for robust and conclusive research in this area. The clinical translation workstream focused on analytical and clinical validity. Cohorts were established for renal cell carcinoma (RCC) and renal transplantation (RT), with samples and patient data from multiple centres, as a rapid-access resource to evaluate the validity of biomarkers. Candidate biomarkers for RCC and RT were identified from the literature and their quality was evaluated and selected biomarkers were prioritised. The duration of follow-up was a limitation but biomarkers were identified that may be taken forward for clinical utility. In the third workstream, the ELUCIDATE trial registered 1303 patients and randomised 878 patients out of a target of 1000. The trial started late and recruited slowly initially but ultimately recruited with good statistical power to answer the key questions. ELF monitoring altered the patient process of care and may show benefits from the early introduction of interventions with further follow-up. The ELUCIDATE trial was an ‘exemplar’ trial that has demonstrated the challenges of evaluating biomarker strategies in ‘end-to-end’ RCTs and will inform future study designs.

Conclusions

The limitations in the programme were principally that, during the collection and curation of the cohorts of patients with RCC and RT, the pace of discovery of new biomarkers in commercial and non-commercial research was slower than anticipated and so conclusive evaluations using the cohorts are few; however, access to the cohorts will be sustained for future new biomarkers. The ELUCIDATE trial was slow to start and recruit to, with a late surge of recruitment, and so final conclusions about the impact of the ELF test on long-term outcomes await further follow-up. The findings from the three workstreams were used to synthesise a strategy and framework for future biomarker evaluations incorporating innovations in study design, health economics and health informatics.

Trial registration

Current Controlled Trials ISRCTN74815110, UKCRN ID 9954 and UKCRN ID 11930.

Funding

This project was funded by the NIHR Programme Grants for Applied Research programme and will be published in full inProgramme Grants for Applied Research; Vol. 6, No. 3. See the NIHR Journals Library website for further project information.

N-acetylcysteine decreases urinary level of neutrophil gelatinase-associated lipocalin in deceased-donor renal transplant recipients: a randomized clinical trial

CONTEXT

Acute kidney injury (AKI) is a common complication after kidney transplantation (KT), especially in recipients from deceased donors. Urinary neutrophil gelatinase-associated lipocalin (u-NGAL) is an early and sensitive marker of AKI after transplantation.

OBJECTIVES

We assessed the renoprotective effect of N-acetylcysteine (NAC) on u-NGAL levels as an early prognostic marker of graft function immediately after transplantation.

MATERIALS AND METHODS

A double-blind, randomized, placebo-controlled trial was conducted on 70 deceased-donor KT recipients ( www.irct.ir , trial registration number: IRCT2014090214693N4). Patients received 600 mg oral NAC or placebo twice daily from day 0 to 5 and urine samples were taken before, and on the first and fifth days after transplantation. U-NGAL and early graft function were compared between the two groups.

RESULTS

NAC significantly reduced u-NGAL levels compared to placebo (p value = 0.02), while improvement in early graft function with NAC did not reach statistical significance.

CONCLUSIONS

This study showed that NAC administration in deceased-donor KT recipients can reduce tubular kidney injury, evidenced by u-NGAL measurements. Improvement in early graft function needs a larger sample size to reach a statistical conclusion.

Post-Transplant Natural Antibodies Associate with Kidney Allograft Injury and Reduced Long-Term Survival

Background The development of antibodies specific to HLA expressed on donor tissue (donor-specific antibodies [DSAs]) is a prominent risk factor for kidney graft loss. Non-HLA antibodies with pathogenic potential have also been described, including natural antibodies (Nabs). These IgG Nabs bind to immunogenic self-determinants, including oxidation-related antigens.Methods To examine the relationship of Nabs with graft outcomes, we assessed Nabs in blinded serum specimens collected from a retrospective cohort of 635 patients who received a transplant between 2005 and 2010 at Necker Hospital in Paris, France. Serum samples were obtained immediately before transplant and at the time of biopsy-proven rejection within the first year or 1 year after transplant. Nabs were detected by ELISA through reactivity to the generic oxidized epitope malondialdehyde.Results Univariate Cox regression analysis identified the development of post-transplant Nabs (defined as 50% increase in reactivity to malondialdehyde) as a significant risk factor for graft loss (hazard ratio, 2.68; 95% confidence interval, 1.49 to 4.82; P=0.001). Post-transplant Nabs also correlated with increased mean Banff scores for histologic signs of graft injury in post-transplant biopsy specimens. Multivariable Cox analyses confirmed Nabs development as a risk factor independent from anti-HLA DSAs (hazard ratio, 2.07; 95% confidence interval, 1.03 to 4.17; P=0.04). Moreover, patients with Nabs and DSAs had a further increased risk of kidney graft loss.Conclusions These findings reveal an association between Nabs, kidney graft injury, and eventual graft failure, suggesting the involvement of Nabs in immune mechanisms of rejection.

Organ-specific responses during brain death: increased aerobic metabolism in the liver and anaerobic metabolism with decreased perfusion in the kidneys

Hepatic and renal energy status prior to transplantation correlates with graft survival. However, effects of brain death (BD) on organ-specific energy status are largely unknown. We studied metabolism, perfusion, oxygen consumption, and mitochondrial function in the liver and kidneys following BD. BD was induced in mechanically-ventilated rats, inflating an epidurally-placed Fogarty-catheter, with sham-operated rats as controls. A 9.4T-preclinical MRI system measured hourly oxygen availability (BOLD-related R2*) and perfusion (T1-weighted). After 4 hrs, tissue was collected, mitochondria isolated and assessed with high-resolution respirometry. Quantitative proteomics, qPCR, and biochemistry was performed on stored tissue/plasma. Following BD, the liver increased glycolytic gene expression (Pfk-1) with decreased glycogen stores, while the kidneys increased anaerobic- (Ldha) and decreased gluconeogenic-related gene expression (Pck-1). Hepatic oxygen consumption increased, while renal perfusion decreased. ATP levels dropped in both organs while mitochondrial respiration and complex I/ATP synthase activity were unaffected. In conclusion, the liver responds to increased metabolic demands during BD, enhancing aerobic metabolism with functional mitochondria. The kidneys shift towards anaerobic energy production while renal perfusion decreases. Our findings highlight the need for an organ-specific approach to assess and optimise graft quality prior to transplantation, to optimise hepatic metabolic conditions and improve renal perfusion while supporting cellular detoxification.

Decreased expression of sirtuin 3 protein correlates with early stage chronic renal allograft dysfunction in a rat kidney model

Chronic renal allograft dysfunction (CRAD) is the primary factor affecting the long-term survival of patients who have undergone renal transplantation. Oxidative stress and inflammation serve an important role in the pathological damage caused by CRAD in the early post-transplantation phase. Previous studies have demonstrated that sirtuin 3 (sirt3) protects cells from oxidative stress and inflammation. A model of renal orthotopic transplantation was established in the current study and kidney samples were harvested from the rats 12 weeks following surgery. Compared with the control groups, there were significantly increased levels of serum creatinine, blood urea nitrogen and 24 h urinary protein in the allograft group (P<0.05). Pathological examinations indicated mononuclear cell infiltration and intimal proliferation in the allograft group, which had a higher Banff score compared with the control groups. There were increased levels of malondialdehyde, decreased sirt3 protein expression and decreased superoxide dismutase enzyme activity in the allograft group compared with the control groups (P<0.05). In addition, there was a negative correlation between the expression of sirt3 and 24 h urinary protein excretion, serum creatinine levels, tubulointerstitial mononuclear cell infiltration, smooth muscle cell migration in the vascular wall and Banff scores. Thus, sirt3 may serve an important protective role in the early stage of CRAD.

Protective effect of curcumin against cyclosporine A‑induced rat nephrotoxicity

This study explored the potential value of curcumin, a natural product, in the protection of CsA‑induced nephrotoxicity. The aim of the present study was to investigate the effects of curcumin on Cyclosporine A (CsA)‑induced renal oxidative stress and determine the potential underlying molecular mechanisms of the renal protective effects of Cur. HK‑2 human renal cells were co‑treated with CsA and various doses of Cur. Cell survival rate was determined by an MTT assay, total cellular protein was collected and oxidative stress in cell homogenates was evaluated by determining the activity of superoxide dismutase (SOD), glutathione peroxidase (GSH‑Px) and catalase (CAT), the levels of malondialdehyde (MDA) and reactive oxygen species (ROS), and total antioxidant capacity. Furthermore, Bcl‑2 and Bcl‑2‑associated X (Bax) protein expression was measured by western blot analysis. In addition, a CsA‑induced nephrotoxicity (CAN) rat model was also established. Renal function was analyzed by measuring creatinine (Crea) and blood urea nitrogen (BUN) in the serum of rats, and histopathological examination was performed on renal tissues using hematoxylin and eosin staining, periodic acid‑Schiff staining and nuclear factor‑κB (NF‑κB) immunostaining. The results demonstrated that treatment of HK‑2 cells with CsA significantly increased ROS and MDA levels, and decreased the activities of SOD, GSH‑Px and CAT, compared with the control group. However, these effects of CsA were dose‑dependently improved by treatment with Cur. In addition, Cur treatment increased Bcl‑2 and decreased Bax protein in HK‑2 cells, compared with cells treated with CsA alone. In the CAN rat model CsA (30 mg/kg) treatment significantly elevated serum Crea levels and BUN, but lowered endogenous Crea clearance rate, compared with the control group. Co‑administration of Cur with CsA significantly reversed the effects of CsA on serum Crea levels, BUN and Crea clearance rate (Ccr). Additionally, Cur alleviated CsA‑induced renal cell injury, as less vacuolar degeneration of glomerular cells was observed compared with the CsA alone group. In conclusion, Cur may increase renal antioxidant capacity and reduce the Bax/Bcl‑2 ratio, subsequently improving CsA‑induced renal failure and renal tubular deformation and cell vacuolization.

Chronic kidney disease, kidney transplantation and oxidative stress: a new look to successful kidney transplantation

Oxidative stress plays a key role in the pathophysiological process of uremia and its complications, particularly in cardiovascular disease. The level of oxidative stress markers is known to increase as chronic kidney disease progresses and correlates significantly with the level of renal function. Hemodialysis and peritoneal dialysis are major modes of renal replacement therapy for end-stage renal disease patients, but unfortunately they are also accompanied by increased oxidative stress. Successful kidney transplantation, however, results in near normalization of the antioxidant status and lipid metabolism by eliminating free radicals despite the surge of oxidative stress caused by the surgical procedure and ischemic injury to the organ during the operation. This success is associated with both improved renal function, reduced cardiovascular complications and overall improved morbidity and mortality. Measuring oxidative stress markers such as malondialdehyde is promising in predicting allograft survival and delayed graft function.

Effects of DNA Methylation on Progression to Interstitial Fibrosis and Tubular Atrophy in Renal Allograft Biopsies: A Multi-Omics Approach

Progressive fibrosis of the interstitium is the dominant final pathway in renal destruction in native and transplanted kidneys. Over time, the continuum of molecular events following immunological and nonimmunological insults lead to interstitial fibrosis and tubular atrophy and culminate in kidney failure. We hypothesize that these insults trigger changes in DNA methylation (DNAm) patterns, which in turn could exacerbate injury and slow down the regeneration processes, leading to fibrosis development and graft dysfunction. Herein, we analyzed biopsy samples from kidney allografts collected 24 months posttransplantation and used an integrative multi-omics approach to understand the underlying molecular mechanisms. The role of DNAm and microRNAs on the graft gene expression was evaluated. Enrichment analyses of differentially methylated CpG sites were performed using GenomeRunner. CpGs were strongly enriched in regions that were variably methylated among tissues, implying high tissue specificity in their regulatory impact. Corresponding to this methylation pattern, gene expression data were related to immune response (activated state) and nephrogenesis (inhibited state). Preimplantation biopsies showed similar DNAm patterns to normal allograft biopsies at 2 years posttransplantation. Our findings demonstrate for the first time a relationship among epigenetic modifications and development of interstitial fibrosis, graft function, and inter-individual variation on long-term outcomes.

Metabolomics for clinical use and research in chronic kidney disease

Chronic kidney disease (CKD) has a high prevalence in the general population and is associated with high mortality; a need therefore exists for better biomarkers for diagnosis, monitoring of disease progression and therapy stratification. Moreover, very sensitive biomarkers are needed in drug development and clinical research to increase understanding of the efficacy and safety of potential and existing therapies. Metabolomics analyses can identify and quantify all metabolites present in a given sample, covering hundreds to thousands of metabolites. Sample preparation for metabolomics requires a very fast arrest of biochemical processes. Present key technologies for metabolomics are mass spectrometry and proton nuclear magnetic resonance spectroscopy, which require sophisticated biostatistic and bioinformatic data analyses. The use of metabolomics has been instrumental in identifying new biomarkers of CKD such as acylcarnitines, glycerolipids, dimethylarginines and metabolites of tryptophan, the citric acid cycle and the urea cycle. Biomarkers such as c-mannosyl tryptophan and pseudouridine have better performance in CKD stratification than does creatinine. Future challenges in metabolomics analyses are prospective studies and deconvolution of CKD biomarkers from those of other diseases such as metabolic syndrome, diabetes mellitus, inflammatory conditions, stress and cancer.

Conjugated linoleic acid rat pretreatment reduces renal damage in ischemia/reperfusion injury: Unraveling antiapoptotic mechanisms and regulation of phosphorylated mammalian target of rapamycin

SCOPE

Conjugated linoleic acids (CLAs) are dietary components with beneficial effects on human health. The aim of this study was to evaluate the potential benefits of CLA pretreatment in a rat model of renal ischemia/reperfusion injury (IRI).

METHODS AND RESULTS

Animals were treated with CLAs (200 mg/kg/day) or water for two weeks prior to sham surgery or to surgery to induce IRI. Renal function, oxidative stress, apoptosis, and cell proliferation markers, were evaluated. Moreover, kidney sections were submitted to histological evaluation. IRI induced increased serum creatinine, blood urea nitrogen, fractional sodium excretion, malondialdehyde, Bax, and phosphorylated mammalian target of rapamycin (P-mTOR), and decreased clearance of creatine, superoxide dismutase and catalase activities, and Bax in comparison with control groups. CLA prefeeding restored, at least in part, the above reported markers to normal levels, increased the anti-apoptotic protein, B-cell lymphoma 2 (Bcl-2), and reduce the histological damage.

CONCLUSION

The results suggest that the decreased renal tissue damage and improved renal function and oxidative stress, in rats pretreated with CLAs before renal IRI induction, could be associated with downregulation of Bax and P-mTOR, and upregulation of Bcl-2. CLAs pretreatment resulted to protect against IRI through the regulation of signaling pathways involved in apoptosis.

Erythrocyte superoxide dismutase as a biomarker of septic acute kidney injury

Background

Oxidative stress is a key feature of sepsis and could be a common pathophysiological pathway between septic shock and acute kidney injury (AKI) Our objective was to evaluate the erythrocyte superoxide dismutase (SOD1) activity as predictor of AKI in patients with septic shock.

Methods

This is a prospective observational study that evaluated 175 consecutive patients over the age of 18 years with septic shock upon intensive care unit (ICU) admission. However, 43 patients were excluded (27 due to AKI at ICU admission). Thus, 132 patients were enrolled in the study. At the time of the patients’ enrollment, demographic information was recorded. Blood samples were taken within the first 24 h of the patient’s admission to determine the erythrocyte SOD1 activity. All patients were followed throughout the ICU stay, and the development of AKI was evaluated. In addition, we also evaluated 17 control subjects.

Results

The mean age of patients with septic shock was 63.2 ± 15.7 years, 53 % were male and the median ICU stay was 8 days (4–16). Approximately 50.7 % developed AKI during the ICU stay. The median erythrocyte SOD1 activity was 2.92 (2.19–3.92) U/mg Hb. When compared to control subjects, septic shock patients had a higher serum malondialdehyde concentration and lower erythrocyte SOD1 activity. In univariate analysis, erythrocyte SOD1 activity was lower in patients who developed AKI. The ROC curve analysis revealed that lower erythrocyte SOD1 activity was associated with AKI development (AUC 0.686; CI 95 % 0.595–0.777; p < 0.001) at the cutoff of <3.32 U/mg Hb. In the logistic regression models, SOD1 activity higher than 3.32 U/mg Hb was associated with protection of AKI development when adjusted by hemoglobin, phosphorus and APACHE II score (OR 0.309; CI 95 % 0.137–0.695; p = 0.005) and when adjusted by age, gender, chronic kidney disease, admission category (medical or surgery) and APACHE II score (OR 0.129; CI 95 % 0.033–0.508; p = 0.003).

Conclusions

In conclusion, our data suggest that erythrocyte SOD1 activity could play a role as an early marker of septic AKI and could be seen as a new research avenue in the field of biomarker in AKI. However, our study did not show a strong correlation between SOD activity and AKI. Nevertheless, these original data do warrant further research in order to confirm or not this hypothesis.

Senescence in chronic allograft nephropathy

Despite increasing numbers of patients on dialysis, the numbers of renal transplants performed yearly have remained relatively static. During the last 50 years, there have been many advances in the pharmacology of prevention of organ rejection. However, most patients will suffer from a slow but steady decline in renal function leading to graft loss. The most common cause of long-term graft loss is chronic allograft nephropathy (CAN). Therefore, elucidating and understanding the mechanisms involved in CAN is crucial for achieving better posttransplant outcomes. It is thought that the development of epithelial to mesenchymal transition (EMT) in proximal tubules is one of the first steps towards CAN, and has been shown to be a result of cellular senescence. Cells undergoing senescence acquire a senescence associated secretory phenotype (SASP) leading to the production of interleukin-1 alpha (IL-1α), which has been implicated in several degenerative and inflammatory processes including renal disease. A central mediator in SASP activation is the production of reactive oxygen species (ROS), which are produced in response to numerous physiological and pathological stimuli. This review explores the connection between SASP and the development of EMT/CAN in an effort to suggest future directions for research leading to improved long-term graft outcomes.

Association of interleukin 18-607A/C and -137C/G polymorphisms with oxidative stress in renal transplant recipients

Objectives IL-18 mediates various inflammatory and oxidative responses including renal injury, fibrosis, and graft rejection. It has been reported that the promoter -607 and -137 polymorphisms of IL-18 influence the level of IL-18. This prospective observational study investigated the association between oxidative stress with IL-18-607 and -137 polymorphisms in renal transplant recipients. Patients and methods This study included 75 renal transplant recipients (28 female, 47 male) from living-related donors. Blood samples were collected immediately before and after transplantation at day 7 and month 1. Serum IL-18, creatinine, cystatin C, CRP, and oxidative stress markers (TOS, TAC) were measured. The Oxidative Stress Index (OSI) was calculated. Polymorphisms of the promoter region of the IL-18 gene, IL18-607A/C, and -137C/G were determined by analysis of a "real-time PCR/Melting curve". Results Serum creatinine, cystatin C, CRP, IL-18, TOS, and OSI levels significantly decreased after transplantation. Post-transplant levels of serum TAC and estimated GFR demonstrated consistent significant increases. Serum IL-18 levels were significantly higher in patients with IL-18-137 GG and IL-18-607 CC genotypes before transplantation. Conclusion Our results indicate that the IL-18-137 GG and -607 CC genotypes contribute to higher IL-18 levels; however, the influence of these polymorphisms on oxidative stress has not been observed.

Predicting delayed kidney graft function with gene expression in preimplantation biopsies and first-day posttransplant blood

The purpose of this study was to investigate possible markers for predicting delayed graft function (DGF). To this end we analyzed, in pre-implantation biopsies (PIB) and in first-day post-Tx peripheral blood mononuclear cells (PBMC), the expression of five genes (ACSL4, CUBN, DEFB1, FABP3, GK) through real-time TaqMan PCR assays. These genes were selected from a large scale gene expression study in PIB. DEFB1, FABP3 and GK expression levels in PIB were lower in cases with DGF and, in a multivariate analysis which included these genes and clinical variables, only FABP3 expression remained independently associated with DGF. FABP3 expression lower than -1.32 units of relative expression conferred an odds ratio for DGF of 41.1. Compared to the PBMC of recipients without DGF, recipients with prolonged DGF (pDGF) had lower ACSL4 and higher DEFB1 expression levels. In a multivariate analysis, including PBMC gene expression levels of ACSL4, DEFB1 and TLR4 (data from a previous study with the same patients) and clinical variables, only TLR4 remained independently associated with pDGF. In summary, this study revealed FABP3 expression in PIB as a marker for DGF and disclosed new genes possibly involved in the pathogenesis of DGF.

Kinetic Estimation of GFR Improves Prediction of Dialysis and Recovery after Kidney Transplantation

BACKGROUND

The early prediction of delayed graft function (DGF) would facilitate patient management after kidney transplantation.

METHODS

In a single-centre retrospective analysis, we investigated kinetic estimated GFR under non-steady-state conditions, KeGFR, in prediction of DGF. KeGFR(sCr) was calculated at 4h, 8h and 12h in 56 recipients of deceased donor kidneys from initial serum creatinine (sCr) concentrations, estimated creatinine production rate, volume of distribution, and the difference between consecutive sCr values. The utility of KeGFR(sCr) for DGF prediction was compared with, sCr, plasma cystatin C (pCysC), and KeGFR(pCysC) similarly derived from pCysC concentrations.

RESULTS

At 4h, the KeGFR(sCr) area under the receiver operator characteristic curve (AUC) for DGF prediction was 0.69 (95% CI: 0.56-0.83), while sCr was not useful (AUC 0.56, (CI: 0.41-0.72). Integrated discrimination improvement analysis showed that the KeGFR(sCr) improved a validated clinical prediction model at 4h, 8h, and 12h, increasing the AUC from 0.68 (0.52-0.83) to 0.88 (0.78-0.99) at 12h (p = 0.01). KeGFR(pCysC) also improved DGF prediction. In contrast, sCr provided no improvement at any time point.

CONCLUSIONS

Calculation of KeGFR from sCr facilitates early prediction of DGF within 4 hours of renal transplantation.

Infectious episodes lead to the oxidative stress response after lung transplantation

Case series

Patient: Male, 30 • Female, 44

Final Diagnosis: Post-transplant respiratory infection

Symptoms: Oxidative stress

Medication: —

Clinical Procedure: —

Specialty: Transplantology

Recent advances in renal interstitial fibrosis and tubular atrophy after kidney transplantation

Although kidney transplantation has been an important means for the treatment of patients with end stage of renal disease, the long-term survival rate of the renal allograft remains a challenge. The cause of late renal allograft loss, once known as chronic allograft nephropathy, has been renamed “interstitial fibrosis and tubular atrophy” (IF/TA) to reflect the histologic pattern seen on biopsy. The mechanisms leading to IF/TA in the transplanted kidney include inflammation, activation of renal fibroblasts, and deposition of extracellular matrix proteins. Identifying the mediators and factors that trigger IF/TA may be useful in early diagnosis and development of novel therapeutic strategies for improving long-term renal allograft survival and patient outcomes. In this review, we highlight the recent advances in our understanding of IF/TA from three aspects: pathogenesis, diagnosis, and treatment.