Evaluation of biomarker discovery approaches to detect protein biomarkers of acute renal allograft rejection

Management of host responses to allografts by immunosuppressive therapy is the cornerstone of transplantation medicine, but it is still deficient in one important element: biomarkers that are readily accessible and predict the fate of the transplant early, specifically, and reliably. Using a Brown Norway (BN)-to-Lewis rat renal allograft model of kidney transplantation, this study aims at evaluating two proteomic approaches to discover biomarkers for acute rejection: SELDI-MS technology and 2D gel electrophoresis combined with mass spectrometry. Several novel potential serum biomarkers have been identified for follow up. Overall, the conclusion is that apparently at the serum protein level, dramatic changes only occur at a stage where kidney function is already severely affected. Multivariate analysis of serum profiles suggests that there is an ensemble of subtle changes, comprising a proteomic signature of acute rejection at an early stage, a more detailed evaluation of which might provide novel opportunities for the diagnosis of acute rejection. Profiling of the excreted proteins indicates that urine might even present the earliest signs of the rejection process.     

大鼠肾移植慢性排斥反应模型的建立

目的建立一种稳定的大鼠原位肾移植慢性排斥反应模型。方法供体为近交系F344大鼠,受体为Lewis大鼠,供肾采用左肾,在体修整,原位灌注。肾静脉用硬膜外导管做为临时内支架管端-端、六针法吻合,腹主动脉端-侧连续缝合,输尿管带膀胱瓣与膀胱吻合。受体术前3 d开始环孢素A灌胃至术后30 d（5 mg/kg·d）,以预防急性排斥反应。结果手术时间120～180 min;手术成功率90.9%（40P44）;受体均存活60 d。并发症有吻合口出血、静脉血栓形成、急性排斥反应等。结论供肾原位灌注,在体修整是简单可靠的方法。静脉內支架管端端吻合,腹主动脉端侧吻合能够达到稳定的成功率,值得推广。熟练的外科操作技能和血管吻合技术是手术成功的关键。     

Metabolic markers for differentiation between renal allograft rejection and immunosuppressant toxicity in rat urine

Introduction

Although current immunosuppressive protocols have dramatically improved 1-year survival of kidney transplants, there has been less progress in terms of long-term graft survival over the last two decades. The key to avoiding late graft loss is early diagnosis and differentiation between anti-allograft immune processes and immunosuppressant toxicity (IS-Tox). Modern bioanalytical technologies have opened new opportunities for the development of sensitive and specific diagnostic tools. There is an immediate need for biomarkers that are able to differentiate between renal allograft rejection and immunosuppressant toxicity.

Objective

To test our hypothesis that changes of metabolite patterns in urine have the potential to serve as a non-invasive combinatorial biomarker that can differentiate between allograft immune reactions and IS-Tox.

Methods

We used ¹H-NMR spectroscopy and Luminex multiplexing for metabolic profiling of rat urine and the analysis of protein biomarkers in urine and plasma, respectively, to compare the effects of chronic allograft rejection in a Fisher-to-Lewis rat transplant model with IS-Tox induced by cyclosporine, tacrolimus and/or sirolimus in Lewis rats.

Results

Our results showed that, while IS-Tox caused changes in metabolite patterns that are typically associated with proximal tubule damage, rejection caused more profuse changes not specifically focused on a particular kidney region. Moreover, metabolite pattern changes were more sensitive than changes in protein markers that were evident only during the later stages of rejection.

Conclusion

The present study provides first proof-of-concept that longitudinal monitoring of urine metabolite markers has the potential to differentiate between early renal allograft rejection and immunosuppressant nephrotoxicity.

     

Urinary Peptidomic Analysis Identifies Potential Biomarkers for Acute Rejection of Renal Transplantation

Introduction  Human urine is a complex matrix of proteins, endogenous peptides, lipids, and metabolites. The level of any or all of these components can reflect the pathophysiological status of an individual especially of the kidney at the time of urine collection. The naturally occurring endogenous urinary peptides which are thought to be the product of several proteolytic and degradation processes may provide clinically useful biomarkers for different renal and systemic diseases. Materials and Methods  To examine if specific differences in the urinary peptidome (<10 kDa) occur at the time of acute renal transplant rejection (AR), we undertook a study of urine samples collected from biopsy-proven AR (n = 10), stable graft function (n = 10), and healthy normal control (n = 10). The peptides (<10 kDa) were extracted and fractionated with high-performance liquid chromatography followed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometric (MS) analysis. Results  We identified 54 endogenous peptides, including multiple peptides for Tamm–Horsfall protein (UMOD). A panel of peptides are identified which discriminate renal transplant patients with AR from stable graft. We have shown that liquid chromatography followed by MALDI is a useful tool to identify potential biomarkers, which after verification with larger patient cohort can be used as a non-invasive monitoring tool for renal transplant rejection.     

PDIA3 mRNA expression and IL-2, IL-4, IL-6, and CRP levels of acute kidney allograft rejection in rat

Kidney transplantation to treat end-stage renal disease has evolved rapidly from the first successful transplantations to the current widespread use of grafts from both cadaveric and living donors. But acute rejection is still a strong risk factor for chronic rejection in recipients of renal grafts. To investigate possible mechanisms, we describe a comparison between differentially proteins expression and immune markers profile (IL-2, IL-4, IL-6, and CRP) of acute rejection and the controls. Through quantitative real-time RT-PCR confirmation, PDIA3 mRNA and protein expression levels in serum and transplanted kidney in experiment group was significantly (P < 0.05) higher than that in control group. Immunity analysis showed that plasma IL-2, IL-4, IL-6, and CRP levels were higher in experimental rats than those in control rats. Our data thus indicate that PDIA3 might be potentially involve into the occurence and development of acute rejection response in renal transplantation and increased plasma IL-2, IL-4, IL-6, and CRP levels play an important role to prevent acute kidney allograft rejection in rats.     

Expression of the Integrin-Linked Kinase in a Rat Kidney Model of Chronic Allograft Nephropathy

The purpose of this study was to investigate the expression and significance of integrin-linked kinase (ILK) in the pathogenesis of chronic allograft nephropathy (CAN) in rats. For this, kidneys of Fisher (F344) rats were orthotopically transplanted into Lewis (LEW) rats. The animals were evaluated at 4, 8, 12, 16, and 24 weeks post-transplantation for renal function and histopathology. ILK protein expression was determined by Western-blot and immunohistological assays, and mRNA by RT-PCR. Our data show that 24-h urinary protein excretion in CAN rats increased significantly at week 16 as compared with F344/LEW controls. Allografts showed markedly increased mononuclear cells infiltration and presented with severe interstitial fibrosis and tubular atrophy at 16 and 24 weeks. ILK expression (protein/mRNA) was upregulated in rat kidneys with CAN, and the increase became more significant over time after transplantation. ILK expression correlated significantly with 24-h urinary protein excretion, serum creatinine levels, tubulointerstitial mononuclear cells infiltration, smooth muscle cells (SMCs) migration in vascular wall, and interstitial fibrosis. Therefore, it was concluded that ILK overexpression was the key event that involved mononuclear cells infiltration and vascular SMCs migration at early stage, and interstitial fibrosis and allograft nephroangiosclerosis at later stage of CAN pathogenesis in rats.     

A study of the impact of cytokine gene polymorphism in acute rejection of renal transplant recipients

Acute rejection is a common phenomenon in transplantation. Inflammatory and anti-inflammatory mediators affect the graft microenvironment. Th1 responses cause acute rejection while Th2 immune responses help the survival of the graft. In this study, we evaluated gene polymorphisms of IL-6 G-174C, TGF-β T+869C, IL-4 C-590T, and IFN-γ T+874A cytokines in renal transplant patients. ARMS-PCR method was used to characterize IL-6 G-174C (rs76144090), TGF-β T+869C (rs1800471), and IFN-γ T+874A (rs2430561) polymorphisms and PCR-RFLP, for characterization of IL-4 C-590T (rs2243250) in 100 renal transplant patients. Acute rejection episodes were diagnosed according to the standard criteria. Analysis of the results showed that IL-6-174 GG genotype (P = 0.018, OR = 3.023, 95% CI = 1.183–7.726) and IL-6-174G allele (P = 0.046, OR = 2.114, 95% CI = 1.005–4.447) were more frequent, but IL-6-174GC genotype was less frequent in acute rejection of kidney transplantation in comparison with control group (P = 0.024, OR = 0.302, 95% CI = 0.103–0.883). IFN-γ+874 T allele was associated with a higher risk of acute rejection (P = 0.019, OR = 2.088, 95% CI = 1.124–3.880) while IFN-γ+874 AA genotype was associated with a lower risk of rejection (P = 0.023, OR = 0.318, 95% CI = 0.115–0.875). Frequencies of TGF-β T+869C and IL-4 C-590T were not significantly different (P > 0.05). Consequently, our results show that IL-6 G-174C and IFN-γ T+874A gene polymorphisms have predictive values for acute rejection after renal transplantation in Iranian patients.     

Influence of recipient and donor IL-10, TNFA and INFG genotypes on the incidence of acute renal allograft rejection

Objective Transplantation of renal grafts is an established treatment for renal failure in a variety of medical conditions. Acute allograft rejection remains an important cause of morbidity after kidney transplantation, and has been shown to be a crucial determinant of long-term graft function. Although rejection is mediated by recipient lymphocytes, both donor and recipient factors contribute to the local environment that influences the severity of rejection response. Because cytokines are the main components of immune responses, we evaluate single nucleotide polymorphisms (SNP) of several cytokine genes that may influence the production of a given cytokine and therefore the features of immune reactions. Material and Methods The aim of this study was to determine the impact of the cytokine gene polymorphism of pro and anti-inflammatory cytokines on the development of acute allograft rejection, which could be used in pretransplant patient assessment. Three SNPs including IL-10 (−1082 G/A), TNFA (−308 G/A), and INFG (+874 T/A) were analyzed in 46 patients with acute allograft rejection, 54 patients with stable graft function and their kidney donors by PCR-ARMS method. Results We are unable to find statistically significant association between any of the studies polymorphisms and clinical outcomes. Conclusion We have found no evidence to suggest that either recipient or donor cytokines polymorphisms determine the incidence of acute rejection after renal transplantation. Our observation, however, is based on few cases, and this may mask a possible favorable effect. It is recommended that several functionally related genes should be tested in similar studies, since this approach has a higher chance to detect genetic risk factors than the screening of single genetic variants.     

In vivo microscopic assessment of cremasteric microcirculation during hindlimb allograft rejection in rats.

Experimental and clinical studies of vascular allogenic extremity transplantation have yielded disappointing results and have not been clinically useful. With recent advances in transplantation immunology, considerable interest has focused on the understanding of leukocyte-endothelial interaction at the microcirculatory level. The objective of this study was to characterize the alterations in leukocyte-endothelial interaction in the early stages of rat hindlimb allograft rejection. To study the changes at the microcirculatory level, a new microsurgical model was developed; the cremaster muscle was incorporated into the transplanted hindlimb. The purpose of this study was to report on the microcirculatory changes during rat hindlimb allograft rejection. A total of 24 transplantations were performed among the four experimental groups. In a control group, 12 rat hindlimb-cremaster grafts were transplanted between genetically identical animals, Lewis to Lewis. Microcirculatory measurements of graft survival were taken at 24 hours (group 1A, n = 6) and at 72 hours (group 1B, n = 6). In the rejection control group, 12 transplantations were performed across a major histocompatibility barrier between Lewis-Brown Norway and Lewis rats. Microcirculatory measurements were taken at 24 (group 2A, n = 6) and 72 hours (group 2A, n = 6) as above. The following parameters were evaluated to discover the leukocyte-endothelial interaction: endothelial edema index and the number of rolling, adherent, and transmigrating leukocytes and lymphocytes in the postcapillary venule. Physical signs of limb rejection, such as edema, erythema, scaling, plaque formation on the skin, hair loss, and skin surface temperature, were monitored. Microcirculatory signs of rejection included the following. There was a significant increase in the number of adherent leukocytes in allograft transplants at both 24 hours (205 percent; 2.05 +/- 0.38) and 72 hours (431 percent; 9.11 +/- 3.41) when compared with isograft controls (1.00 +/- 0.89 at 24 hours; 2.11 +/- 0.34 at 72 hours) (p < 0.05). The activation of leukocyte transmigration increased more than 7-fold in muscle allografts at 24 hours (0.55 +/- 0.25 versus 4.16 +/- 1.89) and more than 6-fold at 72 hours (0.72 +/- 0.38 versus 4.38 +/- 1.28) after transplantation (p < 0.05). Endothelial edema index, a measure of endothelial swelling and cellular deposit accumulation, increased more than 119 percent in the allograft group 72 hours after transplantation (1.23 +/- 0.07 versus 1.46 +/- 0.09) (p < 0.05). The first clinical signs of limb rejection were scaling of the skin or hair loss; they were observed between the seventh and ninth postoperative days. The composite rat hindlimb-cremaster model presented in this study introduces a new in vivo approach to monitor acute graft rejection using the intravital microscopy system. This is a valuable model for defining the timing, sequence, and correlation between immunologic events and clinical signs during the acute phase of allograft rejection.     

Effects of propolis,caffeic acid phenethyl ester,and pollen on renal injury in hypertensive rat: An experimental and theoretical approach

The objective of this study was to evaluate the antioxidant effects of propolis, caffeic acid phenethyl ester (CAPE; active compound in propolis), and pollen on biochemical oxidative stress biomarkers in rat kidney tissue inhibited by N^ω‐nitro‐L‐arginine methyl ester (L‐NAME). The biomarkers evaluated were paraoxonase (PON1), oxidative stress index (OSI), total antioxidant status (TAS), total oxidant status (TOS), asymmetric dimethylarginine (ADMA), and nuclear factor kappa B (NF‐κB). TAS levels and PON1 activity were significantly decreased in kidney tissue samples in the L‐NAME‐treated group (P < 0.05). The levels of TAS and PONI were higher in the L‐NAME plus propolis, CAPE, and pollen groups compared with the L‐NAME‐treated group. TOS, ADMA, and NF‐κB levels were significantly increased in the kidney tissue samples of the L‐NAME‐treated group (P < 0.05). However, these parameters were significantly lower in the L‐NAME plus propolis, CAPE, and pollen groups (P < 0.05) compared with rats administered L‐NAME alone (P < 0.05). Furthermore, the binding energy of CAPE within catalytic domain of glutathione reductase (GR) enzyme as well as its inhibitory mechanism was determined using molecular modeling approaches. In conclusion, experimental and theoretical data suggested that oxidative alterations occurring in the kidney tissue of chronic hypertensive rats may be prevented via active compound of propolis, CAPE administration.     

Developing a tool for noninvasive monitoring of renal allografts

Renal transplantation has emerged as the therapy of choice for many patients with end-stage renal disease. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient at every time point post transplant, balancing the risk for rejection and over-immunosuppression. Such individualized treatment will require assays that can detect harmful processes in the allograft early and that can be measured repeatedly. In this review, advantages and disadvantages of current assays to monitor renal allografts noninvasively and how proteomic technology might contribute to the development of novel biomarkers to improve patient management will be discussed.     

Developing a tool for noninvasive monitoring of renal allografts

Renal transplantation has emerged as the therapy of choice for many patients with end-stage renal disease. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient at every time point post transplant, balancing the risk for rejection and over-immunosuppression. Such individualized treatment will require assays that can detect harmful processes in the allograft early and that can be measured repeatedly. In this review, advantages and disadvantages of current assays to monitor renal allografts noninvasively and how proteomic technology might contribute to the development of novel biomarkers to improve patient management will be discussed.     

Trophic factor supplemented UW solution reduces intimal hyperplasia in the rat aortic transplant model

BACKGROUND: Chronic allograft nephropathy (CAN) is associated with delayed graft function, cold ischemic injury, and is an important cause of premature graft loss. A characteristic vascular lesion of CAN is intimal hyperplasia (IH). The goal of this study was to evaluate the effect of cold storage in University of Wisconsin solution supplemented with trophic factors (UW-TF) on IH in rat aortic isograft (IG) and allograft (AG) models. METHODS: F344 --> F344 and Lewis --> F344 orthotopic abdominal aortic transplants were performed after 48 h of cold storage in either UW or UW-TF solution with and without immunosuppression. RESULTS: Significant reduction in IH was observed when IG were stored in UW-TF solution compared to UW solution. A significant reduction in intimal inflammation was observed in UW-TF stored, nonimmunosuppressed AG. In immunosuppressed recipients, AG stored in UW-TF solution evidenced significantly less IH compared to those stored in UW alone. CONCLUSIONS: UW-TF solution decreased IH in both alloindependent and dependent models.     

Enzyme-Linked Immunosorbent Spot (ELISpot) monitoring of cytokine-producing cells for the prediction of acute rejection in renal transplant patients

The purpose of this study was to evaluate T-cell immunity markers using serial post-transplantation monitoring of cytokine-producing cells during the first post-transplant months for the prediction of acute rejection and potentially chronic rejection of kidney allograft. We followed 57 kidney allograft recipients for meanly 3 years post-transplantation. Blood samples were collected pre-transplant, 2, 4 and 12 weeks post-transplant. The frequencies of IL-10-, IL-17- and IFN-γ-producing cells were determined in all time-points using ELISPOT assay. The results of ELISpot monitoring and levels of IL-23 and TGF-β were compared between recipients with acute (n = 12) or chronic rejection episodes and patients with stable graft function (n = 45). In all post-transplant time-points, significantly high frequencies of IFN-γ- and IL-17-producing cells and low frequency of IL-10-producing cells were observed in rejection group versus patients with stable graft function (P<0.0001). TheROCcurve analysis for determining the reliability of cytokine-producing cells for the prediction of acute rejection revealed that AUC was 0.046 for IL-10 (P<0.001), 0.927 for IL-17 (P<0.001) and 0.929 for INF-γ-producing cells (P<0.001). Our results indicate that analyzing the frequencies of INF-γ/IL-10/IL-17-producing cells may define a reliable panel for the prediction of acute rejection within the first post-transplant year which could also be applicable for the prediction of chronic rejection episodes.     

Significant decrease in plasma midregional proadrenomedullin level in patients with end-stage renal disease after living kidney transplantation

Impaired renal function has been suggested to significantly impact plasma midregional proADM (MR-proADM) level. The aim of this study was to assess whether improvement of renal function after living kidney transplantation has an impact on plasma MR-proADM-like immunoreactive substance (IS) level. Eleven patients with end-stage renal disease (ESRD) who were scheduled to undergo the first living kidney allograft transplantation were enrolled. Plasma MR-proADM-IS levels were measured before and 3, 7, 10, 14, 21, 30, 60 and 90 days after kidney transplantation. Plasma MR-proADM-IS level decreased significantly from day 3 after kidney transplantation compared to before kidney transplantation. A significant negative correlation was observed between creatinine clearance and plasma MR-proADM-IS level from before to 90 days after kidney transplantation (r_s = −0.70, p < 0.0001). These results suggest that recovery of kidney function after kidney transplantation may lead to decrease in plasma MR-proADM level in patients with ESRD, and that plasma MR-proADM level may depend largely on renal function.