Clinical evidence of the association between serum perioperative changes in xanthine metabolizing enzymes activity and early post-transplant kidney allograft function

Xanthine oxidoreductase activity in platelet-poor and rich plasma as a oxidative stress indicator in patients required renal replacement therapy

Background

Xanthine oxidoreductase (XOR) is a hydroxylase enzyme involved in the metabolism of purines. XOR activity can vary: the homodimer protein can be converted into two different isoforms XD (antioxidant) and XO (prooxidant). Oxidative stress and inflammation that accompanying chronic kidney disease (CKD), dialysis, and kidney transplantation, resulted in platelet activation. Present study aimed to determine the influence of applied renal replacement therapy on xanthine oxidoreductase and its isoforms activity.

Materials and Methods

The study group consisted of 117 patients, divided into 4 groups: hemodialysis - 30 patients, peritoneal dialysis - 30 patients, kidney transplant patients - 27 and conservative treatment - 30 patients. The control group consisted of 30 healthy volunteers.

Results

Significant differences were found in XOR activity in platelet-poor plasma (PPP) within the groups studied (p = 0.001). There was a relationship between the type of renal replacement therapy of all oxidoreductase isoforms in PPP (p < 0.001 all isoforms) and XD (p = 0.008), XO (p < 0.001) in platelet rich-plasma (PRP). A relationship was observed between the activity of all oxidoreductase isoforms in PPP and PRP, and the type of renal replacement therapy and the duration of dialysis and the age of patients. The cause of chronic kidney disease was also reflected differences in XD and XO activity in PPP.

Conclusions

The type of renal replacement therapy used in CKD patients, age of patients, duration of dialysis, CKD causes, and stage of progression significantly affect the activity of XOR and its isoforms.

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.

Plasma xanthine oxidoreductase is associated with carotid atherosclerosis in stable kidney transplant recipients

AIM

Xanthine oxidoreductase (XOR) is known as an enzyme related to purine metabolism, catalysing the oxidation of hypoxanthine to xanthine and of xanthine to uric acid. We investigated the relationship between plasma XOR activity in stable kidney transplantation (KT) recipients and carotid artery lesions.

METHODS

A total of 42 KT patients visiting our outpatient clinic on regular basis were recruited. Associations between plasma XOR activity and the existence of plaque in the common carotid artery (CCA) or internal carotid artery (ICA) and maximum intima-medial thickness (IMT) of CCA (max-CIMT) > 0.9 mm were examined using univariate and multivariate analyses.

RESULTS

At blood sampling, the mean and SD patient age was 52.7 ± 13.8 years old. Plasma XOR(pmol/h/ml) activity was significantly higher in patients with CCA/ICA plaque or max-CIMT >0.9 mm than those without. [23.9 (11.8, 38.3) vs. 8.29 (6.67, 17.5), p < .01, 23.9 (16.9, 71.2) vs. 9.16 (6.67, 28.2), p = .01] Univariate and multivariate logistic regression analyses revealed age and plasma XOR activity as independent predictors of CCA/ICA plaque or max-CIMT >0.9 mm. Receiver operator characteristic curve analyses revealed that the cutoff value of plasma XOR activity for the diagnosis of CCA/ICA plaque or CCA-IMT > 0.9 mm was 16.3 pmol/h/ml.

CONCLUSION

Plasma XOR activity is associated independently with atherosclerotic changes in the carotid artery of stable post-KT patients.

Perirenal Adipose Tissue Displays an Age-Dependent Inflammatory Signature Associated With Early Graft Dysfunction of Marginal Kidney Transplants

Background: Better understanding of the contribution of donor aging and comorbidity factors of expanded criteria donors (ECD) to the clinical outcome of a transplant is a challenge in kidney transplantation. We investigated whether the features of donor-derived stromal vascular fraction of perirenal adipose tissue (PRAT-SVF) could be indicative of the deleterious impact of the ECD microenvironment on a renal transplant.

Methods: A comparative analysis of cellular components, transcriptomic and vasculogenic profiles was performed in PRAT-SVF obtained from 22 optimal donors and 31 ECD deceased donors. We then investigated whether these parameters could be associated with donor aging and early allograft dysfunction.

Results: When compared with the PRAT-SVF of non-ECD donors, ECD PRAT-SVF displayed a lower proportion of stromal cells, a higher proportion of inflammatory NK cells. The global RNA sequencing approach indicated a differential molecular signature in the PRAT-SVF of ECD donors characterized by the over-expression of CXCL1 and IL1-β inflammatory transcripts. The vasculogenic activity of PRAT-SVF was highly variable but was not significantly affected in marginal donors. Periorgan recruitment of monocytes/macrophages and NK cells in PRAT-SVF was associated with donor aging. The presence of NK cell infiltrates was associated with lower PRAT-SVF angiogenic activity and with early allograft dysfunction evaluated on day 7 and at 1 month post-transplant.

Conclusions: Our results indicate that human NK cell subsets are differentially recruited in the periorgan environment of aging kidney transplants. We provide novel evidence that PRAT-SVF represents a non-invasive and timely source of donor material with potential value to assess inflammatory features that impact organ quality and function.

Hydrogen Sulfide in Renal Physiology and Disease

SIGNIFICANCE

Hydrogen sulfide (H2S) has only recently gained recognition for its physiological effects. It is synthesized widely in the mammalian tissues and regulates several biologic processes ranging from development, angiogenesis, neurotransmission to protein synthesis. Recent Advances: The aim of this review is to critically evaluate the evidence for a role for H2S in kidney function and disease.

CRITICAL ISSUES

H2S regulates fundamental kidney physiologic processes such as glomerular filtration and sodium reabsorption. In kidney disease states H2S appears to play a complex role in a context-dependent manner. In some disease states such as ischemia-reperfusion and diabetic kidney disease it can serve as an agent that ameliorates kidney injury. In other diseases such as cis-platinum-induced kidney disease it may mediate kidney injury although more investigation is needed. Recent studies have revealed that the actions of nitric oxide and H2S may be integrated in kidney cells.

FUTURE DIRECTIONS

Further studies are needed to understand the full impact of H2S on kidney physiology. As it is endowed with the properties of regulating blood flow, oxidative stress, and inflammation, H2S should be investigated for its role in inflammatory and toxic diseases of the kidney. Such in-depth exploration may identify specific kidney diseases in which H2S may constitute a unique target for therapeutic intervention. Antioxid. Redox Signal. 25, 720-731.

Xanthine oxidoreductase reference values in platelet-poor plasma and platelets in healthy volunteers

Introduction. Xanthine oxidoreductase (XOR) is an enzyme belonging to the class of hydroxylases. XOR is stated, inter alia, in the kidneys, liver, and small intestine as well as in leukocytes and platelets and endothelial cells of capillaries. Its main role is to participate in the conversion of hypoxanthine to xanthine and the uric acid. It occurs in two isoforms: dehydrogenase (XD) and oxidase (XO), which is considered one of the sources of reactive oxygen species. Aim of the Study. Determination of reference values of xanthine oxidoreductase activity in PPP and platelets. Materials and Methods. Study group consisted of 70 healthy volunteers. The isoform activities of xanthine oxidoreductase were determined by kinetic spectrophotometry. Results. A statistically significant difference between the activity of the XOR in PPP and platelets (P < 0.001). The highest activity of XO was found in both PPP and blood platelets. Significant differences between the activity of the various isoforms in PPP (P = 0.0032) and platelets (P < 0.001) were also found. Conclusions. The healthy volunteers showed the highest activity XO (prooxidant) and the lowest XD (antioxidant), which indicates a slight oxidative stress and confirmed physiological effects of XOR.

Classical and remote post-conditioning effects on ischemia/reperfusion-induced acute oxidant kidney injury

The present study aimed to analyze and compare the effects of classical and remote ischemic postconditioning (POC) on rat renal ischemia/reperfusion (IR)-induced acute kidney injury. After right nephrectomy, male rats were randomly assigned into four groups (n = 8). In the IR group, 45 min of left renal artery occlusion was induced followed by 24 h of reperfusion. In the classical POC group, after induction of 45 min ischemia, 4 cycles of 10 s of intermittent ischemia and reperfusion were applied to the kidney before complete restoring of renal blood. In the remote POC group, 4 cycles of 5 min ischemia and reperfusion of left femoral artery were applied after 45 min renal ischemia and right at the time of renal reperfusion. There was a reduction in renal function (increase in blood urea and creatinine) in the IR group. Application of both forms of POC prevented the IR-induced reduction in renal function and histology. There were also significant improvements in kidney oxidative stress status in both POC groups demonstrated by a reduction in malondialdehyde (MDA) formation and preservation of antioxidant levels comparing to the IR group. We concluded that both methods of POC have protective effects on renal function and histology possibly by a reduction in IR-induced oxidative stress.

Selected cytokines in patients with pancreatic cancer: a preliminary report

BACKGROUND/AIMS

Recent experimental studies have suggested that various cytokines may be important players in the development and progression of pancreatic cancer. However, these findings have not yet been verified in a clinical setting.

METHODS

In this study, we examined the levels of a broad panel of cytokines, including interleukin (IL)-1, IL-6, IL-8, IL-10, IL-12, IL-17, and IL-23, as well as tumor necrosis factor alpha (TNFα) and granulocyte-colony stimulating factor (G-CSF) in patients with pancreatic adenocarcinoma (n=43), other pancreatic malignancies (neuroendocrine [n=10] and solid pseudopapillary tumors [n=3]), and healthy individuals (n=41).

RESULTS

We found that there were higher levels of IL-6, IL-8, IL-10 and TNFα in patients with pancreatic cancer compared to healthy controls (for all, at least p<0.03). Cancer patients had lower IL-23 concentrations than healthy individuals and patients diagnosed with other types of malignancies (for both, p=0.002). Levels of IL-6, IL-8, IL-10, and IL-23 were significantly associated with the direct number of circulating bone marrow (BM)-derived mesenchymal or very small embryonic/epiblast-like stem cells (SCs) in patients with pancreatic cancer. Moreover, our study identified a potential ability of IL-6, IL-8, IL-10, IL-23, and TNFα levels to enable discrimination of pancreatic cancer from other pancreatic tumors and diseases, including acute and chronic pancreatitis and post-pancreatitis cysts (with sensitivity and specificity ranging between 70%-82%).

CONCLUSIONS

Our study i) supports the significance of selected cytokines in the clinical presentation of pancreatic cancer, ii) highlights numerous associations between selected interleukins and intensified BMSCs trafficking in patients with pancreatic cancer, and iii) preliminarily characterizes the diagnostic potential of several cytokines as potential novel clinical markers of pancreatic cancer in humans.

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

BACKGROUND AND OBJECTIVES

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

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

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

RESULTS

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

CONCLUSIONS

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

Oxidative stress indices in rats under immunosuppression

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

Association between the perioperative antioxidative ability of platelets and early post-transplant function of kidney allografts: a pilot study

BACKGROUND

Recent studies have demonstrated that the actions of platelets may unfavorably influence post-transplant function of organ allografts. In this study, the association between post-transplant graft function and the perioperative activity of platelet antioxidants was examined among kidney recipients divided into early (EGF), slow (SGF), and delayed graft function (DGF) groups.

METHODOLOGY/PRINCIPAL FINDINGS

Activities of superoxide dismutase, catalase, glutathione transferase (GST), glutathione peroxidase, and glucose-6-phosphate dehydrogenase (G6P) were determined and levels of glutathione, oxidized glutathione, and isoprostane were measured in blood samples collected immediately before and during the first and fifth minutes of renal allograft reperfusion. Our results demonstrated a significant increase in isoprostane levels in all groups. Interestingly, in DGF patients, significantly lower levels of perioperative activity of catalase (p<0.02) and GST (p<0.02) were observed. Moreover, in our study, the activity of platelet antioxidants was associated with intensity of perioperative oxidative stress. For discriminating SGF/DGF from EGF, sensitivity, specificity, and positive and negative predictive values of platelet antioxidants were 81-91%, 50-58%, 32-37%, and 90-90.5%, respectively.

CONCLUSIONS

During renal transplantation, significant changes occur in the activity of platelet antioxidants. These changes seem to be associated with post-transplant graft function and can be potentially used to differentiate between EGF and SGF/DGF. To the best of our knowledge, this is the first study to reveal the potential protective role of platelets in the human transplantation setting.

Presence of glucose in dialyzing fluid and synthesis of selected lipoxygenase-derived eicosanoids during hemodialysis

PURPOSE

Active metabolites of arachidonic acid (AA), eicosanoids, are exerting a significant influence on renal homeostasis. In our recent paper, we demonstrated that high levels of lipoxygenase (LOX)-derived AA metabolites, hydroxyeicosatetraenoic acids (HETEs), unfavorably influence post-transplant function of kidney allografts. Hence, in this study, we wanted (1) to analyze 5-, 12- and 15-HETE levels in non-diabetic chronic kidney disease (CKD) patients, already undergoing regular hemodialysis treatment, and determine factors that may influence these eicosanoids' generation, as well as, (2) to verify whether application of glucose-containing, instead of glucose-free, dialyzing fluids may be beneficial for the limitation of 5-, 12- and 15-HETE synthesis during a single hemodialysis session.

METHODS

Twenty-four healthy individuals and 50 CKD patients undergoing regular hemodialysis treatment were included in the study. CKD patients were divided into two subgroups depending on presence/absence of glucose in dialyzing fluid. LOX-derived HETEs were measured using liquid chromatography.

RESULTS

Results demonstrated higher levels of examined eicosanoids in CKD patients (P<0.05 for all). Older age and higher C-reactive protein levels were associated with HETEs concentrations. Presence of glucose in dialyzing fluid significantly diminished the increase in 5- and 12-HETE synthesis (411.24% vs. 107.29%, P<0.006; 301.70% vs. 98.21%, P<0.0008, respectively), however, it did not influence 15-HETE generation (156.98% vs. 135.24%, P=0.26).

CONCLUSIONS

Non-diabetic CKD patients have higher levels of LOX-derived HETEs, which are associated mainly with age and intensified inflammatory process. The presence of glucose in the dialysate is associated with a reduced synthesis of selected LOX-derived HETEs in these patients; hence, we speculate that the application of such a simple hemodialysis fluid modification may have a favorable influence on post-transplant outcomes.

Delayed graft function in the kidney transplant

Acute kidney injury occurs with kidney transplantation and too frequently progresses to the clinical diagnosis of delayed graft function (DGF). Poor kidney function in the first week of graft life is detrimental to the longevity of the allograft. Challenges to understand the root cause of DGF include several pathologic contributors derived from the donor (ischemic injury, inflammatory signaling) and recipient (reperfusion injury, the innate immune response and the adaptive immune response). Progressive demand for renal allografts has generated new organ categories that continue to carry high risk for DGF for deceased donor organ transplantation. New therapies seek to subdue the inflammatory response in organs with high likelihood to benefit from intervention. Future success in suppressing the development of DGF will require a concerted effort to anticipate and treat tissue injury throughout the arc of the transplantation process.