Assessment of oxygen radicals during kidney transplantation — effect of radical scavenger

Combating Ischemia-Reperfusion Injury with Micronutrients and Natural Compounds during Solid Organ Transplantation: Data of Clinical Trials and Lessons of Preclinical Findings

Although extended donor criteria grafts bear a higher risk of complications such as graft dysfunction, the exceeding demand requires to extent the pool of potential donors. The risk of complications is highly associated with ischemia-reperfusion injury, a condition characterized by high loads of oxidative stress exceeding antioxidative defense mechanisms. The antioxidative properties, along with other beneficial effects like anti-inflammatory, antiapoptotic or antiarrhythmic effects of several micronutrients and natural compounds, have recently emerged increasing research interest resulting in various preclinical and clinical studies. Preclinical studies reported about ameliorated oxidative stress and inflammatory status, resulting in improved graft survival. Although the majority of clinical studies confirmed these results, reporting about improved recovery and superior organ function, others failed to do so. Yet, only a limited number of micronutrients and natural compounds have been investigated in a (large) clinical trial. Despite some ambiguous clinical results and modest clinical data availability, the vast majority of convincing animal and in vitro data, along with low cost and easy availability, encourage the conductance of future clinical trials. These should implement insights gained from animal data.

Tubular epithelial injury and inflammation after ischemia and reperfusion in human kidney transplantation

OBJECTIVE

To provide an integrated insight into the kinetics of tubular injury, inflammation, and oxidative stress after human kidney transplantation.

BACKGROUND

Tissue injury due to ischemia and reperfusion is an inevitable consequence of kidney transplantation. Tubular epithelial injury, inflammation, and oxidative stress play major roles in the pathophysiology of acute kidney injury in small animals, but it remains to be established whether this paradigm holds true for human kidney transplantation.

METHODS

Markers of tubular injury, inflammation, and oxidative stress were compared between recipients of kidneys from donors after cardiac death (DCD; N = 8) with prolonged ischemia and recipients of living donor kidneys with minimal ischemia (N = 8).

RESULTS

In the early postoperative period, creatinine clearance and tubular sodium reabsorption were profoundly reduced in DCD kidneys, coinciding with significantly increased urinary concentrations of tubular injury markers (neutrophil gelatinase-associated lipocalin, N-acetyl-β--glucosaminidase, and cystatin C) and an 18-fold increase in renal production of cytokeratin-18, indicating extensive necrotic cell death. Tubular injury in DCD kidneys was followed by greater systemic inflammatory activity and oxidative stress in the postoperative period (measured with 17-plex cytokine arrays and as plasma F2-isoprostanes, respectively). In contrast, no evidence of oxidative damage to either of the 2 kidney types was found in the early reperfusion period.

CONCLUSIONS

These findings establish the relevance of observations in animal models for human kidney transplantation and form the basis for development of novel therapies to improve early graft function and expand the use of donor kidneys with prolonged ischemia.

Biological modulation of renal ischemia-reperfusion injury

PURPOSE OF REVIEW

Biological modulation of renal ischemia-reperfusion injury holds the potential to reduce the incidence of early graft dysfunction and to safely expand the donor pool with kidneys that have suffered prolonged ischemic injury before organ recovery.

RECENT FINDINGS

In the current review, we will discuss clinical studies that compare kidney transplant recipients with and without early graft dysfunction in order to elucidate the pathophysiology of ischemic acute allograft injury. We will specifically review the mechanisms leading to depression of the glomerular filtration rate and activation of the innate immune system in response to tissue injury.

SUMMARY

We conclude that the pathophysiology of delayed graft function after kidney transplantation is complex and shares broad similarity with rodent models of ischemic acute kidney injury. Given the lack of specific therapies to prevent delayed graft function in transplant recipients, comprehensive efforts should be initiated to translate the promising findings obtained in small animal models into clinical interventions that attenuate ischemic acute kidney injury after transplantation.

Lack of association of polymorphisms 239+34A/C in the SOD1 gene and 47C/T in the SOD2 gene with delayed graft function and acute and chronic rejection of kidney allografts

The superoxide dismutases (SODs) seem to be the most important enzymes involved in defense against reactive oxygen species, in particular against superoxide anion radicals. We hypothesized that genetic variability of antioxidant enzymes may have a role in development of these complications. The objective of the present study was to examine the association between polymorphisms 239+34A/C in the SOD1 gene or 47C/T in the SOD2 gene and development of delayed graft function (DGF) and acute or chronic rejection. The study included 187 recipients of first renal transplants. Patient history was analyzed taking into account DGF, acute rejection episodes, and chronic rejection. The polymorphisms were analyzed using the polymerase chain reaction-restriction fragment length polymorphism method. There were no significant associations between the polymorphisms and DGF or acute or chronic rejection. Our findings suggest that polymorphisms in SOD1 and SOD2 are not associated with development of either DGF or acute or chronic rejection.

Purine and Cytokine Concentrations in the Renal Vein of the Allograft During Reperfusion

The impairment of organ function derived from ischemia-reperfusion injury is still an important problem in solid organ transplantation. Cell alterations induced by ischemia prime the tissue for subsequent damage during the reperfusion phase. The aim of present study was to examine the association between changes in cytokine and purine metabolite concentrations in graft renal vein during reperfusion. The study included 17 recipients of cadaveric renal grafts: 10 men and seven women of overall mean age of 49 +/- 7 years and cold ischemia time 25 +/- 3 hour. The levels of interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-10, interferon (INF)-gamma, tumor necrosis factor (TNF)-beta, and TNF-alpha in renal graft vein plasma during 5 first minutes of reperfusion were quantified by flow cytometry. Increased concentrations of IL-6, TNF-alpha, and IL-1beta were observed during reperfusion. The IFN-gamma concentrations correlated negatively with xanthine (Xan) concentrations in renal vein blood during reperfusion, whereas there was a positive correlation between IL-2 and Xan concentrations. Moreover, the concentrations of IL-6 and IL-10 correlated negatively with hypoxanthine concentrations, and the concentrations of IL-4 also correlated negatively with Xan concentrations. The results of this study indicated the enhanced release of some cytokines during kidney graft reperfusion. It occurred in association with release of purine metabolites-the markers of energy status of renal tissue. Therefore, the enhanced cytokine production during reperfusion might influence ischemia-reperfusion injury and the early graft function.

Correlation between oxidative stress and immunosuppressive therapy in renal transplant recipients with an uneventful postoperative course and stable renal function

BACKGROUND

Reactive oxygen species (ROS) are important mediators of cellular damage and lipid peroxidation is the most important expression of ROS-induced oxidative stress. Recent studies have suggested that increased plasma malondialdehyde (MDA) levels are a consequence of specific immunosuppressive therapies. This study aims at investigating the relation between oxidative stress and immunosuppressive therapies in renal transplant patients with stable renal function and uneventful postoperative course.

METHODS

The study group included 26 renal patients. Two groups of renal transplant recipients, treated with a different combination of immunosuppressive agents were studied (Group A: CyA, MMF, Steroids and Basiliximab, Group B: Tacrolimus, MMF, Steroids and Daclizumab). All patients had an uneventful postoperative course. Plasma MDA levels were measured before transplantation, 1 and 6 months after. Plasma concentration of endogenous creatinine (Cr) was used as a measure of stable renal function.

RESULTS

Levels of MDA were increased before the transplantation in all renal patients (MDA: 7.81 +/- 4.81, normal levels: 2.23-4.08 nmol/ml, P < 0.05). Combined therapy with CyA was associated with high values of MDA at 6 months measurement after transplantation. However this tendency of increased MDA levels did not achieve a statistical significance (Group A: 6.97 vs. 9.06 nmol/ml, P>0.05). On the contrary, statistically significant diminution of MDA levels was observed in Group B patients (Tacrolimus-MMF-steroids) at 6 months measurement after transplantation. (Group B: 8.61 vs. 4.11 nmol/ml, P<0.02<0.05).

CONCLUSIONS

Immunosuppressive combined therapy with CyA was associated with the high values of MDA that were measured posttransplantly. Our study provides strong evidence that Tacrolimus is significantly associated with improved free radical metabolism.

Oxypurine and nucleoside concentrations in renal veins during reperfusion are predictors of early graft function

OBJECTIVE

To examine whether purine and pyrimidine nucleoside concentrations as well as oxypurine concentrations in renal and peripheral veins during reperfusion correlate with graft function parameters.

MATERIAL AND METHODS

The study population comprised 25 recipients of cadaver kidney transplant. A first blood sample was taken from the recipient's peripheral vein before anastomosing the kidney allograft vessels with the recipient's iliac vessels. Subsequent samples were taken from the allograft renal vein and the recipient's peripheral vein 5 min after beginning reperfusion. High-performance liquid chromatography was done to measure plasma concentrations of the oxypurines hypoxanthine (Hyp), xanthine (Xan) and uric acid and the nucleosides guanosine, inosine (Ino) and uridine (Urd).

RESULTS

Concentrations of Hyp, Xan and Ino were significantly higher in the renal than the peripheral vein. The differences between the Xan, Hyp, Ino and Urd plasma concentrations in the renal and peripheral veins before and 5 min after reperfusion correlated positively and significantly with serum creatinine concentrations 24 and 72 h after graft transplantation. Moreover, the concentrations of Hyp were significantly increased in renal transplant recipients with delayed graft function.

CONCLUSION

The results of this study suggest that the concentration of Hyp in the kidney allograft vein can be a useful predictor of early graft function.

Hypoxanthine as a graft ischemia marker stimulates catalase activity in the renal vein during reperfusion in humans

BACKGROUND

The impairment of organ function derived from ischemia-reperfusion injury is still an important problem in solid organ transplantation. Cell alterations induced by ischemia prime the tissue for subsequent damage occurring during the reperfusion phase. Purine nucleotides and oxypurines are products of adenine nucleotide degradation. Reperfusion and reoxygenation are characterized by great production of reactive oxygen species and free radicals. On the contrary, superoxide dismutase, catalase, glutathione, and glutathione peroxidase are involved in protecting against free radicals. The aim of the study was to examine the correlation between concentrations of ischemia markers (hypoxanthine or inosine) and the activity of erythrocyte superoxide dismutase, catalase, or glutathione peroxidase.

PATIENTS AND METHODS

The study included 40 renal transplant recipients. Before anastomosis of the kidney vessels with the recipient's iliac vessels, a "0" blood sample was taken from the iliac vein. Then, after anastomosis, the renal vein of the graft was cannulated and blood samples I, II, and III were obtained. The reperfusion of the transplanted kidney was measured with a thermovision camera ThermaCAM SC500.

RESULTS

The plasma concentrations of hypoxanthine and inosine increased in statistically significant fashion immediately after total tissue reperfusion (P < .0001). Catalase activity at 4 minutes after total tissue reperfusion correlated positively with hypoxanthine concentrations immediately after total tissue reperfusion (Rs = +0.49), 2 minutes after total tissue reperfusion (Rs = +0.47), and 4 minutes after total tissue reperfusion (Rs = +0.46). There were no statistically significant correlations between hypoxanthine or inosine concentrations or superoxide dismutase or glutathione peroxidase activities.

CONCLUSIONS

The results of the present study suggest that catalase activity may correlate with the concentration of hypoxanthine in the graft renal vein and other mediators of oxidative stress.

Effect of trimetazidine on the nucleotide profile in rat kidney with ischemia-reperfusion injury

Ischemia-reperfusion injury is often responsible for delayed graft function after transplantation. Trimetazidine (TMZ) is an antioxidant agent used to protect grafts from ischemia-reperfusion injury. The aim of the study was to examine the effect of TMZ on nucleotide profile in rat kidney with ischemia-reperfusion injury. The study was carried out on Wistar rats divided into two groups: animals treated with TMZ and control group receiving placebo. TMZ 10mg/kg/day was administrated for 30 days. Concentrations of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), adenosine (Ado), guanosine triphosphate (GTP), guanosine diphosphate (GDP), guanosine monophosphate (GMP), guanosine (Guo), inosine monophosphate (IMP), inosine (Ino), hypoxanthine (Hyp), xanthine (Xan), uric acid (UA), uridine (Urd), nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) were determined in kidney tissues after ischemia-reperfusion using HPLC. The total adenine nucleotide concentration (TAN) and adenylate energy charge (AEC) were also determined. Moreover the kidneys were evaluated histologically. Tissue concentrations of ATP, ADP, AMP, TAN and AEC were significantly increased in kidneys from rats treated with TMZ in comparison with rats receiving placebo. Concentrations of products of nucleotide degradation: inosine (Ino), guanosine (Guo) and uridine (Urd), as well as oxypurines: Hyp and Xan, were significantly decreased in rats treated with trimetazidine. Moreover, significantly less pronounced acute tubular necrosis was observed in kidneys of rats treated with TMZ. These results suggest that trimetazidine protects against dephosphorylation of nucleotides and ischemic damage.

Activity of CuZn-superoxide dismutase, catalase and glutathione peroxidase in erythrocytes in kidney allografts during reperfusion in patients with and without delayed graft function

BACKGROUND

Generation of reactive oxygen species (ROS) is the main mechanism involved in the ischemic/reperfusion damage of the transplanted organ. Oxygen burst is a trigger for complex biochemical events leading to generation of oxygenated lipids and changes in microcirculation. Many markers have been researched to prove the presence of ROS in the transplanted tissue. Some of them, like superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) are considered to play a major role in graft protection against oxygen stress during reperfusion.

METHODS

The aim of this study was to examine the changes of SOD1, CAT and GPx activity in erythrocytes during the first minutes after total graft reperfusion. Forty patients undergoing kidney transplantation at our center were assigned to two groups: with or without delayed graft function (DGF). Before anastomosing kidney vessels with recipient's iliac vessels, the '0' blood sample was taken from the iliac vein. Next blood samples I, II and III were taken from the graft's renal vein. The reperfusion of the transplanted kidney was evaluated precisely with the thermovision camera. Erythrocyte SOD1, CAT and GPx activity was measured with a spectrophotometric method.

RESULTS

We did not observe statistically significant changes in SOD1, CAT and GPx activity in erythrocytes during the early phase of reperfusion in patients with and without DGF.

CONCLUSIONS

Erythrocyte-antioxidative system in graft's vein remain stable during the early phase of reperfusion. The results of the study suggest that further studies on extracellular enzymes are required for the assessment of antioxidant system in the conditions of ischemia/reperfusion.

Hydrogen peroxide production by monoamine oxidase during ischemia/reperfusion

Reactive oxygen species have been postulated to play a crucial role in the pathogenesis of renal ischemia-reperfusion injury. However, the intracellular sources of reactive oxygen species during ischemia-reperfusion are still unclear. In the present study, we examined whether catecholamine-degrading enzymes monoamine oxidases contribute to hydrogen peroxide (H(2)O(2)) generation during ischemia-reperfusion using an in vivo rat model of unilateral renal ischemia. The monoamine oxidases were characterized in homogenates of renal cortex by enzyme assay and by Western blot analysis. The monoamine oxidase-dependent H(2)O(2) production was measured by luminol-amplified chemiluminescence assay. Renal monoamine oxidase activity and H(2)O(2) generation by monoamine oxidases were suppressed during ischemia. The monoamine oxidase-dependent H(2)O(2) production was observed during the first 15 min of reperfusion. In addition, enzyme assays showed that monoamine oxidase is also activated in this period. Rat pre-treatment with the irreversible inhibitor of monoamine oxidase, pargyline, prevented H(2)O(2) production. These data suggest that monoamine oxidases are a potential source of H(2)O(2) generation in the early reperfusion following ischemia, which could be involved in renal ischemia-reperfusion injury.

Phagocyte-induced oxidative stress in patients with haemodialysis treatment and organ transplantation

The aim of the study was to examine the phagocyte-derived production of reactive oxygen species (ROS), lipoperoxidation and the total radical-trapping antioxidant parameter (TRAP) in patients undergoing regular haemodialysis (HD) followed by kidney transplantation (n = 13). A significant increase in both spontaneous and activated ROS generation was found during the post-transplantation period in days 1-3. This effect was caused mainly by an increased number of neutrophils. On the other hand, the TRAP parameter was decreased in HD patients. After kidney transplantation, the TRAP parameter increased, reaching the level of healthy controls at the end of the first week after surgery. Increase in MDA level was determined after HD and kidney transplantation. It can be concluded from the results obtained that phagocyte mobilisation and increased oxidative stress after HD and kidney transplantation were associated with the insufficient activity of extracellular antioxidant mechanisms resulting in increased lipid peroxidation.