Allopurinol in Renal Ischemia

Metabolomic and lipidomic landscape of porcine kidney associated with kidney perfusion in heart beating donors and donors after cardiac death

Transplant centers are currently facing a lack of tools to ensure adequate evaluation of the quality of the available organs, as well as a significant shortage of kidney donors. Therefore, efforts are being made to facilitate the effective use of available organs and expand the donor pool, particularly with expanded criteria donors. Fulfilling a need, we aim to present an innovative analytical method based on solid-phase microextraction (SPME) - chemical biopsy. In order to track changes affecting the organ throughout the entire transplant procedure, porcine kidneys were subjected to multiple samplings at various time points. The application of small-diameter SPME probes assured the minimal invasiveness of the procedure. Porcine model kidney autotransplantation was executed for the purpose of simulating two types of donor scenarios: donors with a beating heart (HBD) and donors after cardiac death (DCD). All renal grafts were exposed to continuous normothermic ex vivo perfusion. Following metabolomic and lipidomic profiling using high-performance liquid chromatography coupled to a mass spectrometer, we observed differences in the profiles of HBD and DCD kidneys. The alterations were predominantly related to energy and glucose metabolism, and differences in the levels of essential amino acids, purine nucleosides, lysophosphocholines, phosphoethanolamines, and triacylglycerols were noticed. Our results indicate the potential of implementing chemical biopsy in the evaluation of graft quality and monitoring of renal function during perfusion.

Neutrophils and NADPH Oxidases Are Major Contributors to Mild but Not Severe Ischemic Acute Kidney Injury in Mice

Upregulation of free radical-generating NADPH oxidases (NOX), xanthine oxidoreductase (XOR), and neutrophil infiltration-induced, NOX2-mediated respiratory burst contribute to renal ischemia-reperfusion injury (IRI), but their roles may depend on the severity of IRI. We investigated the role of NOX, XOR, and neutrophils in developing IRI of various severities. C57BL/6 and Mcl-1ΔMyelo neutrophil-deficient mice were used. Oxidases were silenced by RNA interference (RNAi) or pharmacologically inhibited. Kidney function, morphology, immunohistochemistry and mRNA expression were assessed. After reperfusion, the expression of NOX enzymes and XOR increased until 6 h and from 15 h, respectively, while neutrophil infiltration was prominent from 3 h. NOX4 and XOR silencing or pharmacological XOR inhibition did not protect the kidney from IRI. Attenuation of NOX enzyme-induced oxidative stress by apocynin and neutrophil deficiency improved kidney function and ameliorated morphological damage after mild but not moderate/severe IRI. The IR-induced postischemic renal functional impairment (BUN, Lcn-2), tubular necrosis score, inflammation (TNF-α, F4/80), and decreases in the antioxidant enzyme (GPx3) mRNA expression were attenuated by both apocynin and neutrophil deficiency. Inhibition of NOX enzyme-induced oxidative stress or the lack of infiltration by NOX2-expressing neutrophils can attenuate reperfusion injury after mild but not moderate/severe renal IR.

Reno- and hepato-protective effect of allopurinol after renal ischemia/reperfusion injury: Crosstalk between xanthine oxidase and peroxisome proliferator-activated receptor gamma signaling

Renal ischemia/reperfusion (I/R) is a common cause of acute kidney injury and remote liver damage is an ultimate negative outcome. Current treatments for I/R typically involve the use of antioxidants and anti-inflammatory to protect against oxidative stress and inflammation. Xanthine oxidase (XO) and PPAR-γ contribute to renal I/R-induced oxidative stress; however, the crosstalk between the two pathways remains unexplored. In the present study, we report that XO inhibitor, allopurinol (ALP), protects kidney and liver after renal I/R by PPAR-γ activation. Rats with renal I/R showed reduced kidney and liver functions, increased XO, and decreased PPAR-γ. ALP increased PPAR-γ expression and improved liver and kidney functions. ALP also reduced inflammation and nitrosative stress indicated by reduction in TNF-α, iNOS, nitric oxide (NO), and peroxynitrite formation. Interestingly, rats co-treated with PPAR-γ inhibitor, BADGE, and ALP showed diminished beneficial effect on renal and kidney functions, inflammation, and nitrosative stress. This data suggests that downregulation of PPAR-γ contributes to nitrosative stress and inflammation in renal I/R and the use of ALP reverses this effect by increasing PPAR-γ expression. In conclusion, this study highlights the potential therapeutic value of ALP and suggests targeting XO-PPAR-γ pathway as a promising strategy for preventing I/R injury.

Transdermal delivery of allopurinol-loaded nanostructured lipid carrier in the treatment of gout

BACKGROUND

Allopurinol (ALP), a xanthine oxidase inhibitor, is a first line drug for the treatment of gout and hyperuricemia. Being the member of BCS class II drugs, ALP has solubility problem, which affects its bioavailability. Also, ALP has shorter half-life and showed GI related problems. In present study, ALP was encapsulated in nanostructured lipid carriers (NLCs) to ensure enhanced bioavailability, improved efficacy and safety in vivo.

METHODOLOGY

ALP-loaded NLCs were fabricated by micro-emulsion technique. The prepared NLCs were optimized via design expert in term of particle size, zeta potential and entrapment efficiency. FTIR, PXRD and TEM analysis were carried out to check chemical interaction, polymorphic form and surface morphology of the optimized formulation. ALP-loaded NLCs were then loaded into HPMC based poloxamer-407 gel and were characterized. In vitro and ex vivo analysis were carried out via dialysis membrane method and franz diffusion cell, respectively. Uric acid was used for induction of gout and the anti-gout activity of ALP-loaded NLCs gel was performed and compared with ALP suspension.

RESULTS

The optimized formulation had particles in nano-range (238.13 nm) with suitable zeta potential (-31.5 mV), poly-dispersity index (0.115) and entrapment of 87.24%. FTIR results confirmed absence of chemical interaction among formulation ingredients. XRD indicated amorphous nature of ALP-loaded NLCs, whereas TEM analysis confirmed spherical morphology of nanoparticles. The optimized formulation was successfully loaded in to gel and characterized accordingly. The in vitro release and drug release kinetics models showed sustained release of the drug from ALP-loaded NLCs gel. Furthermore, about 28 fold enhanced permeation was observed from ALP-loaded NLCs gel as compared to conventional gel. Skin irritation study disclosed safety of ALP-loaded NLCs gel for transdermal application. Furthermore, ALP-loaded NLCs gel showed significantly enhanced anti-gout activity in Sprague-Dawley rats after transdermal administration as compared to oral ALP suspension.

CONCLUSION

ALP-loaded NLCs gel after transdermal administration sustained the drug release, avoid gastrointestinal side effects and enhance the anti-gout performance of ALP. It can be concluded, that NLCs have the potential to deliver drugs via transdermal route as indicated in case of allopurinol.

Efficacy and safety of urate-lowering agents in asymptomatic hyperuricemia: systematic review and network meta-analysis of randomized controlled trials

BACKGROUND

Asymptomatic hyperuricemia was found to be associated with increased cardiovascular disease risk but the potential benefits of urate-lowering therapy (ULT) remain controversial. We conducted a systematic review and network meta-analysis (NMA) with frequentist model to estimate the efficacy and safety of ULT in asymptomatic hyperuricemia.

METHODS

MEDLINE, Embase, and Scopus were searched without language restrictions. Randomized controlled trials (RCT) of adults with asymptomatic hyperuricemia were eligible if they compared any pair of ULTs (i.e., allopurinol, febuxostat, probenecid, benzbromarone, sulfinpyrazone, rasburicase, lesinurad, and topiroxostat) and placebo or no ULT, and had outcomes of interest, including composite renal events, major adverse cardiovascular events, serum urate levels, estimated glomerular filtration rate (eGFR), systolic blood pressure, and adverse events.

RESULTS

NMA with frequentist approach was applied to estimate relative treatment effects, i.e., risk ratio (RR) and mean difference (MD). A total of 23 RCTs were eligible. NMA identified beneficial effects of ULT on composite renal events and eGFR but not for other outcomes. Allopurinol and febuxostat had significantly lower composite renal events than placebo (RR 0.39, 95% confidence interval [CI] 0.23 to 0.66, and RR 0.68, 95% CI 0.46 to 0.99, respectively). Both treatments also resulted in significantly higher eGFR than placebo (MD 3.69 ml/min/1.73 m², 95% CI 1.31 to 6.08, and MD 2.89 ml/min/1.73 m², 95% CI 0.69 to 5.09, respectively). No evidence of inconsistency was identified.

CONCLUSIONS

Evidence suggests that allopurinol and febuxostat are the ULTs of choice in reducing composite renal events and improving renal function.

TRIAL REGISTRATION

This study was registered with PROSPERO: CRD42019145908. The date of the first registration was 12^th November 2019.

The Possible Role of Nitric Oxide signaling and NMDA Receptors in Allopurinol effect on Maximal Electroshock- and Pentylenetetrazol-Induced Seizures in Mice

Allopurinol, a uric-acid-lowering medication, has shown its efficacy in several studies suggesting that allopurinol can be prescribed as adjunctive cure meant for intractable epilepsy. The exact mechanism of allopurinol is still unknown. This study evaluates allopurinol's effect on seizure threshold, seizure incidence, and mortality rate in mice models. Moreover, the possible involvement of nitric oxide (NO) pathway and N-methyl-D-aspartate (NMDA) receptors are investigated. To evaluate the effect of allopurinol on seizure, we used the pentylenetetrazole (PTZ)-induced seizure along with maximal electroshock (MES)-induced seizure. To assess the underlying mechanism behind the allopurinol activity, we used nitric oxide synthase (NOS) substrate (L-arginine), NOS inhibitors (L-NAME, aminoguanidine, 7-nitroindazole), and NMDA receptor antagonist (MK-801). Intraperitoneal allopurinol administration at a dose of 50 mg/kg in mice showed a significant (p<0.001) anti-convulsant activity in the PTZ-induced seizure. Even though pre-treatment with L-Arginine (60 mg/kg) potentiates allopurinol's anti-convulsant effect in the PTZ-induced seizure, pre-treatment with L-NAME (10 mg/kg), aminoguanidine (100 mg/kg), and 7-nitroindazole (30 mg/kg) reversed the anti-convulsant effect of allopurinol in the PTZ-induced seizure. In addition, pre-treatment with MK-801 also decreased the anti-convulsant effect of allopurinol in the PTZ-induced seizure. While allopurinol at a dose of 50 mg/kg and 100 mg/kg did not induce protection against seizure incidence in the MES-induced seizure, it revealed a remarkable effect in reducing the mortality rate in the MES-induced seizure. Allopurinol increases the seizure threshold in PTZ-induced seizure and enhances the survival rate in MES-induced seizure. Allopurinol exerts its anti-convulsant effect, possibly through targeting NO pathway and NMDA receptors.

Ellagic acid and allopurinol decrease H2O2 concentrations, epileptiform activity and astrogliosis after status epilepticus in the hippocampus of adult rats

Status epilepticus (SE) can result in an overproduction of hydrogen peroxide (H₂O₂), which contributes to oxidative stress and brain injury during different phases of epileptogenesis and seizures. The purpose of this study was to evaluate the effects of ellagic acid and allopurinol administered after SE on H₂O₂ concentrations, electrical activity and GFAP immunoreactivity in the hippocampus of rats evaluated on Day 18 after SE. H₂O₂ levels were measured using an online technique with high temporal resolution and simultaneous electrical activity recording. For this purpose, the lateral ventricles of male Wistar rats (200-250 g) were injected with pilocarpine (2.4 mg/2 µl) to induce SE. After SE, rats were injected with ellagic acid (50 mg/kg i.p., and two additional doses at 24 and 48 h) or allopurinol (50 mg/kg i.p., single dose). Administration of ellagic acid or allopurinol after SE significantly reduced the H₂O₂ concentrations and decreased the presence of epileptiform activity and GFAP immunoreactivity in the hippocampus 18 days after SE. In conclusion, the administration of antioxidants potentially reduces oxidative stress, which indicates the possible attenuation of the neurobiological consequences after SE.

Targeting oxidative stress, a crucial challenge in renal transplantation outcome

Disorders characterized by ischemia/reperfusion (I/R) are the most common causes of debilitating diseases and death in stroke, cardiovascular ischemia, acute kidney injury or organ transplantation. In the latter example the I/R step defines both the amplitude of the damages to the graft and the functional recovery outcome. During transplantation the kidney is subjected to blood flow arrest followed by a sudden increase in oxygen supply at the time of reperfusion. This essential clinical protocol causes massive oxidative stress which is at the basis of cell death and tissue damage. The involvement of both reactive oxygen species (ROS) and nitric oxides (NO) has been shown to be a major cause of these cellular damages. In fact, in non-physiological situations, these species escape endogenous antioxidant control and dangerously accumulate in cells. In recent years, the objective has been to find clinical and pharmacological treatments to reduce or prevent the appearance of oxidative stress in ischemic pathologies. This is very relevant because, due to the increasing success of organ transplantation, clinicians are required to use limit organs, the preservation of which against oxidative stress is crucial for a better outcome. This review highlights the key actors in oxidative stress which could represent new pharmacological targets.

Xanthine oxidase inhibition in SARS-CoV-2 infection: the mechanism and potency of allopurinol and febuxostat in COVID-19 management

The number of coronavirus disease 2019 (COVID-19) infection cases has been increasing globally, including in Indonesia. Definitive therapy for COVID-19 has not yet been found; hence, repurposed drugs for COVID-19 have been considered and have been practiced by several researchers in the world. This literature review investigates the action of xanthine oxidase as a component of the biomolecular pathway against severe acute respiratory syndrome-related coronavirus-2, the cause of COVID-19, and describes the mechanism and potential of uric acid drugs (allopurinol and febuxostat) as prophylaxis and curative therapy for COVID-19. 

Combination Therapy of Allopurinol and Dantrolene and Its Role In The Prevention of Experimental Ischemia Reperfusion Injury Of The Small Intestine

BACKGROUND

The effect of different drugs on ischemia and reperfusion (I/R; induced oxygen free radical damage) was examined in small bowel tissue because the intestine is extremely sensitive to this pathology. Different drugs (allopurinol and dantrolene) can remove oxygen free radicals or inhibit the mechanisms leading to their generation, thus reducing mucosal lesions. We investigated the protective potential of combination therapy in the intestine against I/R damage.

METHODS

Forty-eight male Wistar rats were separated into 8 groups: one sham (control), one I/R (ischemia 60 min + reperfusion at 24 h), and 6 groups treated with allopurinol, dantrolene, or combination therapy. The grade of injury in the small bowel was established by the lipid peroxidation (MDA) and antioxidant enzymatic activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in tissue samples. Moreover, the collected samples were subjected to histological study.

RESULTS

Combination therapy preserved normal enzymatic levels compared to the I/R groups (p < 0.05) for all parameters studied. The animals treated with combination therapy showed less severe small bowel damage than I/R group in accordance with the histological results.

CONCLUSIONS

Results obtained in the experimental process indicate that the administration of antioxidants protects against intestinal damage by I/R. Overall, combination therapy may protect intestinal tissue from I/R injury.

Comparative effectiveness of allopurinol, febuxostat and benzbromarone on renal function in chronic kidney disease patients with hyperuricemia: a 13-year inception cohort study

Background

Direct comparisons of the effectiveness of allopurinol with that of other urate-lowering agents in chronic kidney disease (CKD) populations, as well as guideline recommendations for clinical practice, are lacking.

Methods

We constructed a pharmacoepidemiology cohort study by including patients from Taiwan's long-term integrated CKD care program to compare the effectiveness among allopurinol, febuxostat and benzbromarone in reducing the risk of progression to dialysis. A total of 874 patients with hyperuricemia who were newly treated with allopurinol, febuxostat or benzbromarone were included. The primary and secondary outcomes were incident end-stage renal disease (ESRD) and the serum uric acid (SUA) changes from baseline, respectively. The results were analyzed using multiple Cox proportional models adjusted for multinomial propensity scores. For subgroup analyses, we further stratified patients according to whether their latest SUA level reached the therapeutic target.

Results

Compared with allopurinol, benzbromarone therapy was associated with a reduced risk of progression to dialysis, the adjusted hazard ratio was 0.50 (95% confidence interval, 0.25-0.99). Patients who received allopurinol or febuxostat exhibited a comparable risk of ESRD [adjusted hazard ratio, 0.99 (0.40-2.44)]. Febuxostat was significantly more potent than allopurinol or benzbromarone in lowering SUA levels in the fully adjusted model. Among patients who reached the therapeutic target, those with febuxostat and benzbromarone initiation had a significantly lower risk of ESRD.

Conclusions

In conclusion, compared with conventional allopurinol, febuxostat and benzbromarone may be more effective in reducing the risk of progression to dialysis and in lowering SUA levels in CKD populations.

Meta-analysis on allopurinol preventive intervention on contrast-induced acute kidney injury with random controlled trials: PRISMA

OBJECTIVES

The objective of this meta-analysis on randomized controlled trials is to evaluate whether the administration of allopurinol with or without hydration will reduce contrast-induced acute kidney injury (CI-AKI) in patients undergoing contrast exposure.

BACKGROUND

The efficacy of allopurinol in the prevention of CI-AKI after cardiac catheterization and percutaneous coronary intervention (PCI) is significantly related to the heterogeneous results.

METHODS

Two investigators independently searched MEDLINE, EMBASE, the Cochrane Controlled Trials Registry, the China Wanfang Data, the China Biological Medicine Database and the China National Knowledge Infrastructure (CNKI) databases for randomized controlled trials (RCTs) comparing allopurinol with placebo or no allopurinol for the prevention of CI-AKI in patients from their inception to July 31, 2018. The primary outcome was the incidence of CI-AKI, and the secondary outcomes were the differences of serum creatinine (Scr), blood urea nitrogen (BUN), uric acid (UA), and estimated glomerular filtration rate (eGFR) levels between groups after contrast media exposure. We used fixed-effects or random-effects models according to I statistics. The meta-analytic procedures were completed by Review Manager, version 5.3.

ACHIEVEMENTS

Eight random controlled trials with 1141 patients were included for this analysis. Compared with the control, allopurinol was associated with a reduced risk of CI-AKI (Relatives Risk (RR) 0.39, 95% confidence interval [CI] 0.20,0.74, P = .004) and only a intend for decrease a post-procedure uric acid levels compared with the controlled ones at 48 hours (standardized mean difference (SMD) -0.72, 95% CI -1.44, 0.01, P = .05). But the difference of post-procedure uric acid levels was not statistically significant in allopurinol groups compared with controlled groups. There were lower post-procedure Scr and BUN levels in allopurinol groups than those in controlled groups (SMD -0.50, 95% CI -0.79,-0.21, P = .0009; SMD -0.40, 95% CI -0.60,-0.20, P < .0001;respectively). There were higher post-procedure eGFR levels in allopurinol groups than those in controlled groups (SMD 0.65, 95% CI 0.48, 0.83, P < .0001).

CONCLUSION

The main findings of this meta-analysis are focus on allopurinol may cause reduces in the incidence of CI-AKI in patients undergoing interventional coronary procedures. Further researches are still required for confirmation.

Antioxidants as Renoprotective Agents for Ischemia during Partial Nephrectomy

Small renal masses have been diagnosed increasingly in recent decades, allowing surgical treatment by partial nephrectomy. This treatment option is associated with better renal function preservation, in comparison with radical nephrectomy. However, for obtaining a bloodless field during surgery, occlusion of renal artery and veins is often required, which results in transitory ischemia. The renal ischemia-reperfusion injury is associated with increased reactive oxygen species production leading to renal tissue damage. Thus, the use of antioxidants has been advocated in the partial nephrectomy perioperative period. Several antioxidants were investigated in regard to renal ischemia-reperfusion injury. The present manuscript aims to present the literature on the most commonly studied antioxidants used during partial nephrectomy. The results of experimental and clinical studies using antioxidants during partial nephrectomy are reported. Further, alimentary sources of some antioxidants are presented, stimulating future studies focusing on perioperative antioxidant-rich diets.

Lung Ischaemia-Reperfusion Injury: The Role of Reactive Oxygen Species

Lung ischaemia-reperfusion injury (LIRI) occurs in many lung diseases and during surgical procedures such as lung transplantation. The re-establishment of blood flow and oxygen delivery into the previously ischaemic lung exacerbates the ischaemic injury and leads to increased microvascular permeability and pulmonary vascular resistance as well as to vigorous activation of the immune response. These events initiate the irreversible damage of the lung with subsequent oedema formation that can result in systemic hypoxaemia and multi-organ failure. Alterations in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been suggested as crucial mediators of such responses during ischaemia-reperfusion in the lung. Among numerous potential sources of ROS/RNS within cells, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, nitric oxide synthases and mitochondria have been investigated during LIRI. Against this background, we aim to review here the extensive literature about the ROS-mediated cellular signalling during LIRI, as well as the effectiveness of antioxidants as treatment option for LIRI.

Inhibition of Oxidative Stress in Renal Ischemia-Reperfusion Injury

BACKGROUND

Superoxide, nitric oxide (NO), and peroxynitrite are important mediators in the pathogenesis of ischemia-reperfusion (I/R) injury. We tested the renoprotective effects of allopurinol (ALP), a xanthine oxidase inhibitor, N-nitro-L-arginine methyl ester (L-NAME), and 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinato iron (III) (FeTMPyP) by selective inhibition of superoxide, NO, and peroxynitrite, respectively.

METHODS

Male Sprague-Dawley rats were randomly assigned to 5 groups (n = 6 per group). Group 1 was a sham-operated group. Group 2 was the renal I/R group (30-minute ischemia followed by 24-hour reperfusion). Rats in groups 3, 4, and 5 received ALP, L-NAME, or FeTMPyP, respectively, at 5 minutes before the reperfusion. Serum creatinine (Cr), blood urea nitrogen (BUN), renal tissue malondialdehyde, superoxide dismutase, histological changes, apoptosis, and monocyte infiltration were evaluated. In addition, the combined treatment with ALP and L-NAME was compared with FeTMPyP in a second independent experiment.

RESULTS

The administration of ALP, L-NAME, and FeTMPyP diminished the increase in Cr (P = .0066 for all) and BUN (P = .0066 for ALP; and P = .013 for L-NAME) induced by I/R injury and decreased the histological damage (P = .0066 for all). In addition, ALP, L-NAME, and FeTMPyP attenuated the oxidative stress response as determined by a decrease in malondialdehyde level (P = .0066 for all), apoptotic renal tubular cells (P = .0066 for all), and monocyte infiltration (P = .0066 for all). The combined treatment of ALP and L-NAME decreased Cr and BUN levels to a greater degree than FeTMPyP (P = .016 for Cr; P = .0079 for BUN).

CONCLUSIONS

Superoxide, NO, and peroxynitrite are involved in renal I/R injury. The reduction of peroxynitrite formation, via inhibition of superoxide or NO, or the induction of peroxynitrite decomposition may be beneficial in renal I/R injury.

Disruption of xanthine oxidoreductase gene attenuates renal ischemia reperfusion injury in mice

AIMS

We examined the roles of xanthine oxidoreductase (XOR) in renal ischemia reperfusion (IR) injury.

MAIN METHODS

XOR+/+ and XOR+/- mice were subjected to 24-h reperfusion after a 45-min bilateral renal artery occlusion or sham operation. We evaluated the renal damage based on the concentrations of blood urea nitrogen (BUN) and serum creatinine (Cr), and histological changes were detected by PAS staining. Xanthine dehydrogenase, oxidase (XO) and XOR activities, amounts of blood and urine 8-OHdG, and expressions of TNF-α and MCP-1 mRNA were examined. F4/80 and nitrotyrosine-positive cells were assessed by immunohistochemical staining.

KEY FINDINGS

The BUN and Cr concentrations in the XOR+/+IR mice were increased significantly compared to those in XOR+/-IR and allopurinol-treated XOR+/+IR mice. XO and XOR activity, which were increased in IR mice, were reduced in the allopurinol-treated XOR+/+IR and XOR+/-IR mice compared to the XOR+/+IR mice. The concentrations of blood and urine 8-OHdG, and the expressions of MCP-1 and TNF-α mRNA were increased significantly in the XOR+/+IR mice compared to those in the XOR+/-IR mice. The histological analysis revealed that the XOR+/-IR and allopurinol-treated XOR+/+IR mice showed less tubular injury than the XOR+/+IR mice in the cortex regions, with the reduction of inflammation and oxidative stress assessed by the immunohistological staining for F4/80 and nitrotyrosine.

SIGNIFICANCE

Both the disruption of XOR gene in XOR+/- mice and the reduction of XOR activity in allopurinol-treated XOR+/+IR mice attenuated renal tissue injury in this IR model. Reduced XOR activity during renal IR could be a beneficial treatment target.

The hypoxanthine-xanthine oxidase axis is not involved in the initial phase of clinical transplantation-related ischemia-reperfusion injury

The hypoxanthine-xanthine oxidase (XO) axis is considered to be a key driver of transplantation-related ischemia-reperfusion (I/R) injury. Whereas interference with this axis effectively quenches I/R injury in preclinical models, there is limited efficacy of XO inhibitors in clinical trials. In this context, we considered clinical evaluation of a role for the hypoxanthine-XO axis in human I/R to be relevant. Patients undergoing renal allograft transplantation were included (n = 40) and classified based on duration of ischemia (short, intermediate, and prolonged). Purine metabolites excreted by the reperfused kidney (arteriovenous differences) were analyzed by the ultra performance liquid chromatography-tandem mass spectrometer (UPLCMS/MS) method and tissue XO activity was assessed by in situ enzymography. We confirmed progressive hypoxanthine accumulation (P < 0.006) during ischemia, using kidney transplantation as a clinical model of I/R. Yet, arteriovenous concentration differences of uric acid and in situ enzymography of XO did not indicate significant XO activity in ischemic and reperfused kidney grafts. Furthermore, we tested a putative association between hypoxanthine accumulation and renal oxidative stress by assessing renal malondialdehyde and isoprostane levels and allantoin formation during the reperfusion period. Absent release of these markers is not consistent with an association between ischemic hypoxanthine accumulation and postreperfusion oxidative stress. On basis of these data for the human kidney we hypothesize that the role for the hypoxanthine-XO axis in clinical I/R injury is less than commonly thought, and as such the data provide an explanation for the apparent limited clinical efficacy of XO inhibitors.

Allopurinol preconditioning attenuates renal ischemia/reperfusion injury by inhibiting HMGB1 expression in a rat model

PURPOSE

To investigate the potential effects of pretreatment with allopurinol on renal ischemia/reperfusion injury (IRI) in a rat model.

METHODS

Twenty four rats were subjected to right kidney uninephrectomy were randomly distributed into the following three groups (n=8): Group A (sham-operated group); Group B (ischemic group) with 30 min of renal ischemia after surgery; and Group C (allopurinol + ischemia group) pretreated with allopurinol at 50 mg/kg for 14 days. At 72 h after renal reperfusion, the kidney was harvested to assess inflammation and apoptosis.

RESULTS

Pretreatment with allopurinol significantly improved renal functional and histological grade scores following I/R injury (p<0.05). Compared with Group B, the expression levels of caspase-3 and Bax were markedly reduced in Group C, meanwhile, whereas expression of bcl-2 was clearly increased (p<0.05). A newly described marker of inflammation, High Mobility Group Box 1(HMGB1), showed reduced expression in Group C (p<0.05).

CONCLUSION

Pretreatment with allopurinol had a protective effect on kidney ischemia/reperfusion injury, which might be related to the inhibition of HMGB1 expression.

Allopurinol Protective Effect of Renal Ischemia by Downregulating TNF-α, IL-1β, and IL-6 Response

Allopurinol is a well-known antioxidant that protects tissue against ischemia and reperfusion injury, blocking purine catabolism, and possibly reducing TNF-α and other cytokines. It also plays a significant role in reducing the inflammatory processes by inhibiting chemotaxis and other inflammatory mediators. The objective of this study was to define the role of allopurinol regarding kidney ischemic injury particularly as to its effect on inflammatory molecules such as TNF-α, IL-1β, and IL-6 response. One hundred and twenty five rats were subjected to warm renal ischemia. Five more animals were included as sham. Animal survival and plasma levels of lipid peroxidation, myeloperoxidase, lactate dehydrogenase, glutathione, urea, creatinine, and cytokines were determined. Inflammatory parameters (TNF-α, IL-1β, and IL-6) were measured in all groups by quantitative immunosorbent assay. Further, immunohistological and histopathological studies were carried out on animals treated prior to, or following reperfusion with 10 and 50 mg/kg of Allopurinol. The statistical analysis included ANOVA and Fisher test as well as χ² test. Significance was reached at a p < 0.05. The results of this study indicated that Allopurinol protected against kidney ischemia-reperfusion injury since significantly better results of survival, biochemical analysis, and histopathological testing were observed in treated animals as compared to ischemic controls. In conclusion, Allopurinol protected ischemic kidneys through a mechanism associated with downregulation of TNF-α, IL-1 β, and IL-6, in addition to other well-known effects such as decreased lipid peroxidation and neutrophil activity. It also increased antioxidant capacity and diminished endogenous peroxidase stain in renal ischemic tissue. Therefore, this experiment showed an effectiveness of allopurinol protection against proteomic and morphological damage.

Are allopurinol dose and duration of use nephroprotective in the elderly? A Medicare claims study of allopurinol use and incident renal failure

OBJECTIVE

To assess the effect of allopurinol dose/duration on the risk of renal failure in the elderly with allopurinol use.

METHODS

We used the 5% random Medicare claims data from 2006 to 2012. Multivariable-adjusted Cox regression analyses assessed the association of allopurinol dose/duration with subsequent risk of developing incident renal failure or end-stage renal disease (ESRD) (no prior diagnosis in last 183 days) in allopurinol users, controlling for age, sex, race and Charlson-Romano comorbidity index. HRs with 95% CIs were calculated. Sensitivity analyses considered a longer baseline period (365 days), controlled for gout or used more specific codes.

RESULTS

Among the 30 022 allopurinol treatment episodes, 8314 incident renal failure episodes occurred. Compared with 1-199 mg/day, allopurinol dose of 200-299 mg/day (HR 0.81; 95% CI 0.75 to 0.87) and ≥300 mg/day, 0.71 (0.67 to 0.76), had significantly lower hazard of renal failure in multivariable-adjustment model, confirmed in multiple sensitivity analyses. Longer allopurinol use duration was significantly associated with lower hazards in sensitivity analyses (365-day look-back; reference, <0.5 year): 0.5-1 year, 1.00 (0.88, 1.15); >1-2 years, 0.85 (0.73 to 0.99); and >2 years, 0.81 (0.67 to 0.98). Allopurinol ≥300 mg/day was also associated with significantly lower risk of acute renal failure and ESRD with HR of 0.89 (0.83 to 0.94) and 0.57 (0.46 to 0.71), respectively.

CONCLUSIONS

Higher allopurinol dose is independently protective against incident renal failure in the elderly allopurinol users. A longer duration of allopurinol use may be associated with lower risk of incident renal failure. Potential mechanisms of these effects need to be examined.

Pharmacology of Ischemia-Reperfusion. Translational Research Considerations

Ischemia-reperfusion (IRI) is a complex physiopathological mechanism involving a large number of metabolic processes that can eventually lead to cell apoptosis and ultimately tissue necrosis. Treatment approaches intended to reduce or palliate the effects of IRI are varied, and are aimed basically at: inhibiting cell apoptosis and the complement system in the inflammatory process deriving from IRI, modulating calcium levels, maintaining mitochondrial membrane integrity, reducing the oxidative effects of IRI and levels of inflammatory cytokines, or minimizing the action of macrophages, neutrophils, and other cell types. This study involved an extensive, up-to-date review of the bibliography on the currently most widely used active products in the treatment and prevention of IRI, and their mechanisms of action, in an aim to obtain an overview of current and potential future treatments for this pathological process. The importance of IRI is clearly reflected by the large number of studies published year after year, and by the variety of pathophysiological processes involved in this major vascular problem. A quick study of the evolution of IRI-related publications in PubMed shows that in a single month in 2014, 263 articles were published, compared to 806 articles in the entire 1990.

Effects of Allopurinol and Apocynin on Renal Ischemia-Reperfusion Injury in Rats

BACKGROUND

This study evaluated the effects of allopurinol (ALP), a xanthine oxidase inhibitor, and apocynin (APC), a NADPH oxidase inhibitor, administered alone or together, on kidney damage caused by renal ischemia-reperfusion (IR) in rats.

METHODS

Thirty rats were randomly assigned to 5 groups. Group 1 was a sham group. Group 2 was the renal IR control group (30-min ischemia followed by 24-h reperfusion). In groups 3 and 4, ALP or APC, respectively, was administered 1 h before the ischemia. In group 5, ALP and APC were co-administered. Blood urea nitrogen (BUN) and serum creatinine (Cr), renal tissue malondialdehyde (MDA) and superoxide dismutase (SOD), and histological changes were evaluated.

RESULTS

A significant increase in BUN and Cr level, and histological damage was seen in the IR control group, indicating renal injury. Elevated MDA and decreased SOD levels in the IR control group demonstrated that renal damage occurred through oxidative stress. Pretreatment with ALP or APC alone or together prevented IR-induced renal damage. However, there was no significant difference between treatment with a single drug and co-administration of ALP and APC.

CONCLUSIONS

The use of ALP and/or APC before ischemia may be beneficial to ameliorate renal IR injury.

Effect of amlodipine, lisinopril and allopurinol on acetaminophen-induced hepatotoxicity in rats

Background

Exposure to chemotherapeutic agents such as acetaminophen may lead to serious liver injury. Calcium deregulation, angiotensin II production and xanthine oxidase activity are suggested to play mechanistic roles in such injury.

Objective

This study evaluates the possible protective effects of the calcium channel blocker amlodipine, the angiotensin converting enzyme inhibitor lisinopril, and the xanthine oxidase inhibitor allopurinol against experimental acetaminophen-induced hepatotoxicity, aiming to understand its underlying hepatotoxic mechanisms.

Material and methods

Animals were allocated into a normal control group, a acetaminophen hepatotoxicity control group (receiving a single oral dose of acetaminophen; 750 mg/kg/day), and four treatment groups receive N-acetylcysteine (300 mg/kg/day; a reference standard), amlodipine (10 mg/kg/day), lisinopril (20 mg/kg/day) and allopurinol (50 mg/kg/day) orally for 14 consecutive days prior to acetaminophen administration. Evaluation of hepatotoxicity was performed by the assessment of hepatocyte integrity markers (serum transaminases), oxidative stress markers (hepatic malondialdehyde, glutathione and catalase), and inflammatory markers (hepatic myeloperoxidase and nitrate/nitrite), in addition to a histopathological study.

Results

Rats pre-treated with amlodipine, lisinopril or allopurinol showed significantly lower serum transaminases, significantly lower hepatic malondialdehyde, myeloperoxidase and nitrate/nitrite, as well as significantly higher hepatic glutathione and catalase levels, compared with acetaminophen control rats. Serum transaminases were normalized in the lisinopril treatment group, while hepatic myeloperoxidase was normalized in the all treatment groups. Histopathological evaluation strongly supported the results of biochemical estimations.

Conclusion

Amlodipine, lisinopril or allopurinol can protect against acetaminophen-induced hepatotoxicity, showing mechanistic roles of calcium channels, angiotensin converting enzyme and xanthine oxidase enzyme in the pathogenesis of hepatotoxicity induced by acetaminophen.