Rescue Allocation Modes in Eurotransplant Kidney Transplantation: Recipient Oriented Extended Allocation Versus Competitive Rescue Allocation-A Retrospective Multicenter Outcome Analysis

BACKGROUND

Whenever the kidney standard allocation (SA) algorithms according to the Eurotransplant (ET) Kidney Allocation System or the Eurotransplant Senior Program fail, rescue allocation (RA) is initiated. There are 2 procedurally different modes of RA: recipient oriented extended allocation (REAL) and competitive rescue allocation (CRA). The objective of this study was to evaluate the association of patient survival and graft failure with RA mode and whether or not it varied across the different ET countries.

METHODS

The ET database was retrospectively analyzed for donor and recipient clinical and demographic characteristics in association with graft outcomes of deceased donor renal transplantation (DDRT) across all ET countries and centers from 2014 to 2021 using Cox proportional hazards methods.

RESULTS

Seventeen thousand six hundred seventy-nine renal transplantations were included (SA 15 658 [89%], REAL 860 [4.9%], and CRA 1161 [6.6%]). In CRA, donors were older, cold ischemia times were longer, and HLA matches were worse in comparison with REAL and especially SA. Multivariable analyses showed comparable graft and recipient survival between SA and REAL; however, CRA was associated with shorter graft survival. Germany performed 76% of all DDRTs after REAL and CRA and the latter mode reduced waiting times by up to 2.9 y.

CONCLUSIONS

REAL and CRA are used differently in the ET countries according to national donor rates. Both RA schemes optimize graft utilization, lead to acceptable outcomes, and help to stabilize national DDRT programs, especially in Germany.

Acetylsalicylic Acid Resistance After Simultaneous Pancreas-Kidney Transplantation

BACKGROUND

The most common conditions leading to death after simultaneous pancreas-kidney transplantations (SPKs) are cardiovascular diseases. The aim of this study was to test the platelet aggregation inhibitor acetylsalicylic acid (ASA) resistance in patients after SPKs, including investigations into the triggering factors.

METHODS

Thirty-two patients (22 men, 10 women; overall age, 47.4 ± 8.6 years) were involved in our study and took 100 mg ASA per day. We used optical platelet aggregometry to detect resistance.

RESULTS

Resistance occurred in 40.6% of the study group. However, with the use of logistic regression analysis, the examined 24 factors did not show any significant correspondence with resistance.

CONCLUSIONS

The incidence of ASA resistance seems to be higher compared with other groups, but the triggering effect is still unproved. Clarifying this question should be important regarding the mortality- and morbidity-reducing capacity of antiplatelet drugs in the management of cardiovascular conditions.

Ischemia/reperfusion-induced Kidney Injury in Heterozygous PACAP-deficient Mice

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with very diverse distribution and functions. Among others, PACAP is a potent cytoprotective peptide due to its antiapoptotic, anti-inflammatory, and antioxidant actions. This also has been shown in different kidney pathologies, including ischemia/reperfusion-induced kidney injury. Similar protective effects of the endogenous PACAP are confirmed by the increased vulnerability of PACAP-deficient mice to different harmful stimuli. Kidneys of homozygous PACAP-deficient mice have more severe damages in renal ischemia/reperfusion and kidney cell cultures isolated from these mice show increased sensitivity to renal oxidative stress. In our present study we raised the question of whether the partial lack of the PACAP gene is also deleterious, i.e. whether heterozygous PACAP-deficient mice also display more severe damage after renal ischemia/reperfusion. Mice underwent 45 or 60 minutes of ischemia followed by 2 weeks reperfusion. Histological evaluation of the kidneys was performed and individual histopathological parameters were graded. Furthermore, we investigated apoptotic markers, cytokine expression, and the activity of superoxide dismutase (SOD) enzyme 24 hours after 60 minutes of renal ischemia/reperfusion. We found no difference between the intact kidneys of wild-type and heterozygous mice, but marked differences could be observed following ischemia/reperfusion. Heterozygous PACAP-deficient mice had more severe histological alterations, with significantly higher histopathological scores for most of the tested parameters. Higher level of the proapoptotic pp38 MAPK and of some proinflammatory cytokines, as well as lower activity of the antioxidant SOD could be found in these mice. In conclusion, the partial lack of the PACAP gene results in worse outcomes in cases of renal ischemia/reperfusion, confirming that PACAP functions as an endogenous protective factor in the kidney.

Clopidogrel resistance after renal transplantation

BACKGROUND

Leading causes of mortality and morbidity after kidney transplantation are cardiovascular diseases. One of the fundamentals of their prevention is the inhibition of platelet aggregation. Resistance to anti-platelet agents is a well-established phenomenon; however, its causes are yet to be clarified.

PATIENTS AND METHODS

Forty post-transplant patients, who received 75 mg clopidogrel q.d. as a prophylactic measure, were examined using optical aggregometry. Subsequently, logistic regression analysis was performed with 24 variables in order to expose possible causes of resistance.

RESULTS

Sixty percent of patients (24) were resistant to clopidogrel therapy; effective thrombocyte inhibition could only be shown in 40% of them (16). Significant correspondence between resistance and variables could not be found.

CONCLUSION

Clopidogrel resistance is expected to occur on a large scale in patients who underwent kidney transplant surgery. Thus, a key component of preventive therapy, which stresses the importance of discovering the cause of resistance so as to decrease mortality rates, is missing.

Acetylsalicylic acid resistance after renal transplantation

BACKGROUND

Cardiovascular diseases are a leading cause of mortality after kidney transplantation. According to guidelines, acetylsalicylic acid (ASA) must be given as preventive antiplatelet therapy, but resistance to this drug is also well-known.

PATIENTS AND METHODS

A total of 214 renal transplant patients were included in our study and took 100 mg of ASA q.d. Aggregometry was performed to determine resistance. Twenty-four variables were examined using logistic regression analysis as possible causes of resistance.

RESULTS

ASA resistance was observed in 40.18% of the patients. Resistance reduced concomitant statin therapy and significantly increased simultaneous cyclosporine therapy.

CONCLUSION

Our study assessed the post-transplant ASA resistance in a large population. Clarification of this matter is crutial, since one of the major preventive pharmacological therapies of cardiovascular mortality is not effective in a significant number of patients.

Efficacy and safety of oral oseltamivir for influenza prophylaxis in transplant recipients

BACKGROUND

Haematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients are at high risk for severe influenza and its complications, and may not be adequately protected by vaccination.

METHODS

Liver, kidney, or liver-kidney transplant or allogeneic HSCT recipients aged ≥1 year were randomized to oseltamivir (75 mg once daily for those ≥13 years or weight-based dosing for children 1-12 years) or placebo for 12 weeks during periods of local influenza circulation. Patients were assessed for influenza infection via daily diary, every-other-week culture and PCR, and baseline and end-of-treatment serology.

RESULTS

A total of 477 subjects were enrolled (239 oseltamivir and 238 placebo); most were adults (96%) and SOT recipients (81%). In the intent-to-treat population, the frequency of laboratory-confirmed clinical influenza (culture positive and/or >4-fold increase in haemagglutinin antibody inhibition [primary end point]) was similar in the oseltamivir and placebo groups (2.1% [5/237] and 2.9% [7/238]). Incidence of laboratory-confirmed influenza was significantly reduced in the oseltamivir group versus placebo when determined by reverse transcriptase-PCR (1.7% [4/237] versus 8.4% [20/238]; 95% CI 2.8, 11.1) or viral culture (<1% [1/237] versus 3.8% [9/238]; 95% CI 0.7, 6.6), giving protective efficacies of 79.9 and 88.8%, respectively. Serious adverse events (oseltamivir 8% and placebo 10%) and adverse events (oseltamivir 55% and placebo 58%) were reported in both arms with a similar frequency. One illness due to oseltamivir-resistant A/H1N1 virus was detected in each group.

CONCLUSIONS

Oseltamivir prophylaxis is generally well-tolerated and may reduce culture- or PCR-confirmed influenza incidence in transplant recipients.

Effects of pituitary adenylate cyclase activating polypeptide in the urinary system, with special emphasis on its protective effects in the kidney

Pituitary adenylate cyclase activating polypeptide (PACAP) is a widespread neuropeptide with diverse effects in the nervous system and peripheral organs. One of the most well-studied effects of PACAP is its cytoprotective action, against different harmful stimuli in a wide variety of cells and tissues. PACAP occurs in the urinary system, from the kidney to the lower urinary tract. The present review focuses on the nephroprotective effects of PACAP and summarizes data obtained regarding the protective effects of PACAP in different models of kidney pathologies. In vitro data show that PACAP protects tubular cells against oxidative stress, myeloma light chain, cisplatin, cyclosporine-A and hypoxia. In vivo data provide evidence for its protective effects in ischemia/reperfusion, cisplatin, cyclosporine-A, myeloma kidney injury, diabetic nephropathy and gentamicin-induced kidney damage. Results accumulated on the renoprotective effects of PACAP suggest that PACAP is an emerging candidate for treatment of human kidney pathologies.

Mice deficient in pituitary adenylate cyclase activating polypeptide (PACAP) show increased susceptibility to in vivo renal ischemia/reperfusion injury

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with well-known cytoprotective effects. We have reported earlier that PACAP decreases mortality and the degree of tubular atrophy in a rat model of renal ischemia/reperfusion injury. Recently, we have shown that kidney cultures isolated from PACAP deficient mice show increased susceptibility to renal oxidative stress. Based on these previous studies, we raised the question whether PACAP deficient mice display increased sensitivity to in vivo kidney ischemia/reperfusion. PACAP⁻/⁻ mice underwent 45 or 60 min of renal ischemia followed by 2 weeks reperfusion. Kidneys were processed for histological analysis. Sections stained with PAS-haematoxylin were graded for the following parameters: degree of tubular dilation, Bowmann's capsule dilation, lymphocyte and macrophage infiltration, thyroidization and the disappearance of the PAS-positive glycocalyx from under the brush border. In other sets of experiments, tissue cytokine expression and the level of the endogenous antioxidant superoxide dismutase (SOD) were also determined after 60 min ischemia/reperfusion. Our results show that while intact kidneys were not different between wild-type and PACAP deficient mice, marked differences were observed in the histological structures in groups that underwent ischemia/reperfusion. PACAP deficient mice had a worse histological outcome, with significantly higher histological scores for all tested parameters. Cytokine expression was also markedly different between wild-type and PACAP deficient mice. In addition, the level of SOD was significantly lower in PACAP⁻/⁻ animals after ischemia/reperfusion. In conclusion, the lack of endogenous PACAP leads to higher susceptibility to in vivo renal ischemia/reperfusion, suggesting that PACAP has an endogenous renoprotective effect.

Effects of PACAP on oxidative stress-induced cell death in rat kidney and human hepatocyte cells

Oxidative stress plays an important role in various renal and hepatic pathologies, and reduction of oxidative stress-induced processes is an important protective strategy in tissues of diverse origins against harmful stimuli. Pituitary adenylate cyclase activating polypeptide (PACAP) is a well-known cytotrophic and cytoprotective peptide. PACAP promotes cell survival in numerous cells and tissues exposed to various stimuli. Protective effects of PACAP have been shown in the kidney, but it is not known whether PACAP is protective against oxidative stress in renal cells. Little is known about the effects of PACAP in the liver. The aim of the present study was to investigate whether PACAP is protective against oxidative stress in primary rat kidney cell culture and whether PACAP has any effect on cell survival in human WRL-68 hepatocytes and HEP-G2 hepatocellular carcinoma cells subjected to oxidative stress. Cells were exposed to various concentrations of H(2)O(2) with or without PACAP co-treatment and cell viability was evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test (MTT). We found that oxidative stress induced a significant decrease in cell viability in both cell lines. PACAP could dose-dependently increase the percentage of living cells in kidney cells, but it failed to do so in hepatocytes. Given the survival-promoting effects of PACAP against oxidative stress in rat kidney, we conducted a further experiment to determine whether PACAP influences the markers of oxidative stress in vivo. We have proven earlier that PACAP was effective in kidney ischemia/reperfusion injury in vivo. In the present study, we determined the levels of the oxidative stress marker malondialdehyde and the activity of the scavenger molecules glutathione (GSH) and superoxide dismutase (SOD) following kidney ischemia/reperfusion in rats. We found that PACAP significantly increased the level of GSH and counteracted the marked reduction of SOD activity after ischemia/reperfusion in vivo. In summary, the present study showed that while PACAP was able to significantly increase the cell survival in primary kidney cell cultures exposed to oxidative stress, possibly involving interaction with the endogenous scavenger system, it failed to influence the viability of normal or cancerous hepatocytes.

Effects of PACAP on mitochondrial apoptotic pathways and cytokine expression in rats subjected to renal ischemia/reperfusion

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with highly efficient cytoprotective actions. Its neuroprotective effects are well-known, but PACAP is able to exert similar actions in non-neuronal cells. Recently, we have shown that PACAP prolongs renal ischemic time, decreases mortality, and attenuates tubular degeneration in a rat model of renal ischemia/reperfusion, but the mechanism of renoprotection is not yet known. Therefore, the aim of the present study was to obtain further insight into the renoprotective effects of PACAP by examining its direct effects of PACAP on mitochondrial permeability transition in vitro and on the expression of the anti-apoptotic Bcl-2 and cytokines/chemokines in kidney tissues following 45 and 60 min renal ischemia and reperfusion in vivo. We found that PACAP did not have any direct effect on mitochondrial permeability transition. Cytokine array revealed that the expression of a few cytokines/chemokines was strongly increased after ischemia/reperfusion, which was ameliorated by PACAP treatment. Furthermore, in rats subjected to renal ischemia, PACAP treatment counteracted the ischemia/reperfusion-induced decrease of the anti-apoptotic Bcl-2, both after 45 and 60 min ischemia, as analyzed by Western blot. In summary, we showed that PACAP could attenuate tissue injury involving both anti-inflammatory and anti-apoptotic effects, but not directly acting on mitochondrial permeability transition.

Mice deficient in pituitary adenylate cyclase activating polypeptide display increased sensitivity to renal oxidative stress in vitro

Pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide, showing widespread occurrence in the nervous system and also in peripheral organs. The neuroprotective effects of PACAP are well-established in different neuronal systems against noxious stimuli in vitro and in vivo. Recently, its general cytoprotective actions have been recognized, including renoprotective effects. However, the effect of endogenous PACAP in the kidneys is not known. The main aim of the present study was to investigate whether the lack of this endogenous neuropeptide influences survival of kidney cells against oxidative stress. First, we determined the presence of endogenous PACAP from mouse kidney homogenates by mass spectrometry and PACAP-like immunoreactivity by radioimmunoassay. Second, primary cultures were isolated from wild type and PACAP deficient mice and cell viability was assessed following oxidative stress induced by 0.5, 1.5 and 3mM H(2)O(2). Our mass spectrometry and radioimmunoassay results show that PACAP is endogenously present in the kidney. The main part of our study revealed that the sensitivity of cells from PACAP deficient mice was increased to oxidative stress: both after 2 or 4h of exposure, cell viability was significantly reduced compared to that from control wild type mice. This increased sensitivity of kidneys from PACAP deficient mice could be counteracted by exogenously given PACAP38. These results show, for the first time, that endogenous PACAP protects against oxidative stress in the kidney, and that PACAP may act as a stress sensor in renal cells. These findings further support the general cytoprotective nature of this neuropeptide.