Pathogenesis of renal ischemia/reperfusion injury: lessons from knockout mice

Pathophysiological aspects of transferrin-A potential nano-based drug delivery signaling molecule in therapeutic target for varied diseases

Transferrin (Tf), widely known for its role as an iron-binding protein, exemplifies multitasking in biological processes. The role of Tf in iron metabolism involves both the uptake of iron from Tf by various cells, as well as the endocytosis mediated by the complex of Tf and the transferrin receptor (TfR). The direct conjugation of the therapeutic compound and immunotoxin studies using Tf peptide or anti-Tf receptor antibodies as targeting moieties aims to prolong drug circulation time and augment efficient cellular drug uptake, diminish systemic toxicity, traverse the blood-brain barrier, restrict systemic exposure, overcome multidrug resistance, and enhance therapeutic efficacy with disease specificity. This review primarily discusses the various biological actions of Tf, as well as the development of Tf-targeted nano-based drug delivery systems. The goal is to establish the use of Tf as a disease-targeting component, accentuating the potential therapeutic applications of this protein.

Complement Inhibition in Kidney Transplantation: Where Are We Now?

Kidney transplantation is a life-saving strategy for patients with end-stage renal disease. Although progress has been made in the field of transplantation medicine in recent decades in terms of surgical techniques and immunosuppression, long-term organ survival remains a challenge. Also, for reasons of organ shortage, there is an unmet need for new therapeutic approaches to improve the long-term survival of transplants. There is increasing evidence that the complement system plays a crucial role in various pathological events after transplantation, including ischemia/reperfusion injury as well as rejection episodes. The complement system is part of the innate immune system and plays a crucial role in the defense against pathogens but is also involved in tissue homeostasis. However, the tightly regulated complement system can become dysregulated or activated by non-infectious stimuli, then targeting the organism's own cells and leading to inflammatory tissue damage that exacerbates injury. In this review, we will highlight the role of the complement system after transplantation and discuss ongoing and potential therapeutic approaches.

Sevoflurane activates MEF2D-mediated Wnt/β-catenin signaling pathway via microRNA-374b-5p to affect renal ischemia/reperfusion injury

BACKGROUND

The inhaled sevoflurane (Sev) has been demonstrated to protect multiple organs against ischemia/reperfusion injury (IRI). However, the mechanisms of Sev in renal IRI remain largely unknown. This study intends to explore the effect of Sev on renal IRI and the molecular mechanism behind.

METHODS

Following Sev preconditioning, a mouse model with renal IRI was established. The effects of Sev on IRI in mice were assessed by BUN, Scr, MDA and SOD kits, Western blot, HE staining, and TUNEL. Subsequently, we performed microarray analysis on renal tissues from mice with Sev to identify differentially expressed microRNAs (miRNAs). Then, the mice were treated with agomiR-374b-5p combined with Sev to observe the renal histopathology after IRI. The targeting mRNA of miR-374b-5p was verified using bioinformatics analysis and dual-luciferase assay, followed by KEGG enrichment analysis. Rescue experiments were implemented with simultaneous miR-374b-5p and MEF2D overexpression to detect renal histopathology and Wnt/β-catenin pathway activity in the mice.

RESULTS

Sev significantly reduced the levels of BUN and Scr in mouse serum, prevented cell apoptosis, decreased MDA content and increased SOD levels in renal tissues. Moreover, Sev downregulated the miR-374b-5p expression in the renal tissues. Overexpression of miR-374b-5p attenuated the protective effects of Sev on mouse renal tissues. miR-374b-5p targeted MEF2D and blocked the Wnt/β-catenin pathway. Overexpression of MEF2D activated the Wnt/β-catenin pathway and attenuated the supporting effects of miR-374b-5p on renal IRI.

CONCLUSION

Sev promotes MEF2D and activates the Wnt/β-catenin pathway through inhibition of miR-374b-5p expression to affect renal IRI.

Renoprotective effect of vinpocetine against ischemia/reperfusion injury: Modulation of NADPH oxidase/Nrf2, IKKβ/NF-κB p65, and cleaved caspase-3 expressions

Ischemia/reperfusion injury (IRI) during kidney transplantation is a serious clinical problem with a high mortality rate and a lack of therapy. Therefore, there is a need to improve the ability of the kidney to tolerate IRI during transplantation. This study aimed to investigate the possible protective effect of vinpocetine; a derivative of vincamine alkaloid; against renal IRI in rats with the elucidation of the involved mechanisms. Vinpocetine (25 mg/kg; i.p.) was administered for 10 successive days before the induction of ischemia by bilateral clamping of both renal pedicles for 45 min followed by 24 h of reperfusion. Blood and renal tissue samples were then collected for biochemical, molecular, and histopathological investigations. Vinpocetine significantly reduced serum creatinine and blood urea nitrogen levels in rats subjected to IRI. It also reduced mRNA expression of NADPH oxidase and renal content of malondialdehyde, while enhanced Nrf2 protein expression and renal content of reduced glutathione. The suppression of the provoked inflammatory response was evident by the downregulation of IKKβ and NF-κB p65 protein expressions, as well as their downstream inflammatory markers; tumor necrosis factor-α, interleukin-6, and myeloperoxidase. In addition, vinpocetine reduced protein expression of the apoptotic executioner cleaved caspase-3. These nephroprotective effects were confirmed by the improvement in histopathological features. Collectively, the protective effect of vinpocetine against IRI could be attributed to modulation of NADPH oxidase/Nrf2, IKKβ/NF-κB p65, and cleaved caspase-3 expressions. Thus, vinpocetine could improve oxidant/antioxidant balance, suppress triggered inflammatory response, and promote renal cell survival after IRI.

Blood and urinary cytokine balance and renal outcomes at cardiac surgery

BACKGROUND

Increased perioperative pro-inflammatory biomarkers, renal hypoperfusion and ischemia reperfusion injury (IRI) heighten cardiac surgery acute kidney injury (CS-AKI) risk. Increased urinary anti-inflammatory cytokines attenuate risk. We evaluated whether blood and urinary anti-inflammatory biomarkers, when expressed as ratios with biomarkers of inflammation, hypoperfusion and IRI are increased in CS-AKI patients.

METHODS

Preoperative and 24-h postoperative blood and urinary pro-inflammatory and anti-inflammatory cytokines, blood VEGF and H-FABP (hypoperfusion biomarkers), and MK, a biomarker for IRI, were measured in 401 cardiac surgery patients. Pre- and postoperative concentrations of biomarkers and selected ratios thereof, were compared between non-CS-AKI and CS-AKI patients.

RESULTS

Compared with non-CS-AKI, blood pro-inflammatory (pre- and post-op TNFα, IP-10, IL-12p40, MIP-1α, NGAL; pre-op IL-6; post-op IL-8, MK) and anti-inflammatory (pre- and post-op sTNFsr1, sTNFsr2, IL-1RA) biomarkers together with urinary pro-inflammatory (pre- and post-op uIL-12p40; post-op uIP-10, uNGAL) and anti-inflammatory (pre- and post-op usTNFsr1, usTNFsr2, uIL-1RA) biomarkers, were significantly higher in CS-AKI patients. Urinary anti-inflammatory biomarkers, when expressed as ratios with biomarkers of inflammation (blood and urine), hypoperfusion (blood H-FABP and VEGF) and IRI (blood MK) were decreased in CS-AKI. In contrast, blood anti-inflammatory biomarkers expressed as similar ratios with blood biomarkers were increased in CS-AKI.

CONCLUSIONS

The urinary anti-inflammatory response may protect against the injurious effects of perioperative inflammation, hypoperfusion and IRI. These finding may have clinical utility in bioprediction and earlier diagnosis of CS-AKI and informing future therapeutic strategies for CS-AKI patients.

Urinary biomarkers to predict severe fluid overload after cardiac surgery: a pilot study

Aim: To assess the predictive ability of urinary and plasma biomarkers and clinical routine parameters for subsequent severe fluid overload. Patients & methods: In a pilot study, we studied 100 adult patients after cardiac surgery. On intensive care unit admission, we measured biomarkers in urine (midkine, IL-6, neutrophil gelatinase-associated lipocalin [NGAL], hepcidin-25) and plasma (creatinine, urea, B-type natriuretic peptide, lactate, C-reactive protein, leukocytes, IL-6, NGAL, hepcidin-25) to predict postoperative severe fluid overload. Results: Urinary midkine, IL-6, NGAL and hepcidin-25 (all AUCs ≥0.79) predicted postoperative severe fluid overload (n = 5 patients). Urinary NGAL/hepcidin-25 ratio (AUC 0.867) predicted postoperative severe fluid overload after adjustment to EuroScore and need for norepinephrine on surgery day (odds ratio: 2.4). Conclusion: Urinary biomarkers on intensive care unit admission might be helpful to predict subsequent severe fluid overload after cardiac surgery.

Akt1 is involved in tubular apoptosis and inflammatory response during renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) is one of the major causes of acute kidney injury (AKI). Although Akt is involved in renal IRI, it is unclear as to which Akt isoform plays an important role in renal IRI. In this study, we investigated the role of Akt1 in renal IRI. We subjected the C57BL/6 male mice to unilateral IRI with contralateral nephrectomy. Two days after IRI, IRI-kidneys were harvested. The mice were divided into four groups: wild type (WT) IRI, Akt1^-/- IRI, WT sham, and Akt1^-/- sham. We found that Akt1, not Akt2 or Akt3, was markedly activated in WT IRI than in WT sham mice. The histologic damage score and serum creatinine level significantly increased in WT IRI mice, the increase being the highest in Akt1^-/- IRI mice. The number of TdT-mediated dUTP nick-end labeling (TUNEL)-positive tubular cells and expression of cleaved caspase-3/Bax were higher in Akt1^-/- IRI mice than in WT IRI mice. The expression of Bcl-2 was lower in Akt1^-/- IRI mice than in WT IRI mice. The expression of tumor necrosis factor-α/interleukin-6/interleukin-1β and number of F4/80-positive macrophages were markedly higher in Akt1^-/- IRI than in WT IRI mice. The expression of phosphorylated nuclear factor-κB p65 was also higher in Akt1^-/- IRI mice than in WT IRI mice. Our results show that Akt1 deletion exacerbates kidney damage as it increases tubular apoptosis and inflammatory response during renal IRI. Akt1 could be a potential therapeutic target for developing treatments against IRI-induced AKI.

"Adenosine an old player with new possibilities in kidney diseases": Preclinical evidences and clinical perspectives

Renal injury might originate from multiple factors like ischemia reperfusion (I/R), drug toxicity, cystic fibrosis, radio contrast agent etc. The four adenosine receptor subtypes have been identified and found to show diverse physiological and pathological roles in kidney diseases. The activation of A₁ adenosine receptor (A₁) protects against acute kidney injury by improving renal hemodynamic alterations, decreasing tubular necrosis and its inhibition might facilitate removal of toxin or drug metabolite in chronic kidney disease models. Furthermore, recent findings revealed that A_2A receptor subtype activation regulates macrophage phenotype in experimental models of nephritis. Interestingly the emerging role of adenosine kinase inhibitors in kidney diseases has been discussed which act by increasing adenosine availability at target sites and thereby promote A_2A receptor stimulation. In addition, the least explored adenosine receptor subtype A₃ inhibition was observed to exert anti- oxidant, immunosuppressive and anti-fibrotic effects, but more studies are required to confirm its benefits in other renal injury models. The clinical studies targeting A₁ receptor in patients with pre-existing kidney disease have yielded disappointing results, perhaps owing to the origin of unexpected neurological complications during the course of trial. Importantly, conducting well designed clinical trials and testing adenosine modulators with lesser brain penetrability could clear the way for clinical approval of these agents for patients with renal functional impairments.

Total Glucosides of Paeony Alleviate Cell Apoptosis and Inflammation by Targeting the Long Noncoding RNA XIST/MicroRNA-124-3p/ITGB1 Axis in Renal Ischemia/Reperfusion Injury

OBJECTIVE

Renal ischemia/reperfusion injury (RI/RI) is the main cause of acute kidney injury. Total glucosides of paeony (TGP) are a traditional Chinese medicine. This study was aimed at exploring the role of TGP in RI/RI and its underlying mechanism of action.

METHODS

Rat RI/RI models were constructed by surgical operation. Serum creatinine (Scr) and blood urea nitrogen (BUN) were used to evaluate renal function. The levels of proinflammatory cytokines were detected by ELISA. RI/RI was simulated by hypoxia/reoxygenation (H/R) treatment in renal cells in vitro. The lncRNA XIST (XIST) expression was analyzed by qRT-PCR. Then, the viability and apoptosis of renal cells were detected by MTT and flow cytometry assay. Additionally, dual-luciferase reporter assay was used to determine the interactions among XIST, microRNA-124-3p (miR-124-3p), and ITGB1.

RESULTS

TGP improved renal function and inhibited inflammatory responses after RI/RI. XIST expression was highly expressed in rat RI/RI models and H/R-treated renal cells, whereas treatment with TGP downregulated the XIST expression. Additionally, TGP increased viability and attenuated apoptosis and inflammation of H/R-treated renal cells via inhibiting XIST. Moreover, XIST was competitively bound to miR-124-3p, and ITGB1 was a target of miR-124-3p. miR-124-3p overexpression or ITGB1 inhibition rescued the reduction effect on viability and mitigated the promoting effects on cell apoptosis and inflammation caused by XIST overexpression in H/R-treated renal cells.

CONCLUSIONS

In vivo, TGP attenuated renal dysfunction and inflammation in RI/RI rats. In vitro, TGP inhibited XIST expression to modulate the miR-124-3p/ITGB1 axis, alleviating the apoptosis and inflammation of H/R-treated renal cells.

Nobiletin Protects from Renal Ischemia-Reperfusion Injury in Rats by Suppressing Inflammatory Cytokines and Regulating iNOS-eNOS Expressions

Ischemia-reperfusion injury is an organ failure caused by hypoxia and reperfusion, which is closely associated with oxidative stress and inflammation. In this study, we investigated whether nobiletin had protective effects on inflammatory parameters, oxidative damage, iNOS-eNOS expressions, and histopathological structure of renal tissue in rats with renal ischemia-reperfusion injury. For this purpose, 24 rats were divided into 4 groups: group 1 (Control), group 2 (Ischemia-Reperfusion-IR), group 3 (Nobiletin-10 mg/kg p.o.), group 4 (Nobiletin + IR). The study was continued for 7 days. At the end of the study, urea (p < 0.05), creatine (p < 0.05), MDA (p < 0.001), TNF-alpha (p < 0.001), IL-1 beta (p < 0.05), and IL-6 (p < 0.001) levels increased in the IR group; however, a significant decrease occurred in group 4 (Nobiletin + IR) and it reached the control group levels. In the IR group, GSH (p < 0.01) levels, and GSH.Px (p < 0.01) and CAT (p < 0.05) activities decreased whereas they increased significantly in group 4 (Nobiletin + IR) and reached the same levels as the control group. In histopathological analyses, destruction and increased iNOS-eNOS expressions in the IR group showed a significant decrease in group 4 (Nobiletin + IR). As a result, the application of nobiletin has shown that it has protective effects by reducing kidney damage caused by IR injury.

NOX1 Inhibition Attenuates Kidney Ischemia-Reperfusion Injury via Inhibition of ROS-Mediated ERK Signaling

The protective effects of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) 1 inhibition against kidney ischemia-reperfusion injury (IRI) remain uncertain. The bilateral kidney pedicles of C57BL/6 mice were clamped for 30 min to induce IRI. Madin–Darby Canine Kidney (MDCK) cells were incubated with H₂O₂ (1.4 mM) for 1 h to induce oxidative stress. ML171, a selective NOX1 inhibitor, and siRNA against NOX1 were treated to inhibit NOX1. NOX expression, oxidative stress, apoptosis assay, and mitogen-activated protein kinase (MAPK) pathway were evaluated. The kidney function deteriorated and the production of reactive oxygen species (ROS), including intracellular H₂O₂ production, increased due to IRI, whereas IRI-mediated kidney dysfunction and ROS generation were significantly attenuated by ML171. H₂O₂ evoked the changes in oxidative stress enzymes such as SOD2 and GPX in MDCK cells, which was mitigated by ML171. Treatment with ML171 and transfection with siRNA against NOX1 decreased the upregulation of NOX1 and NOX4 induced by H₂O₂ in MDCK cells. ML171 decreased caspase-3 activity, the Bcl-2/Bax ratio, and TUNEL-positive tubule cells in IRI mice and H₂O₂-treated MDCK cells. Among the MAPK pathways, ML171 affected ERK signaling by ERK phosphorylation in kidney tissues and tubular cells. NOX1-selective inhibition attenuated kidney IRI via inhibition of ROS-mediated ERK signaling.

Renal ischemia/reperfusion injury: An insight on in vitro and in vivo models

Optimal tissue oxygenation is essential for its normal function. Suboptimal oxygenation or ischemia contributes to increased mortalities during various pathological conditions such as stroke, acute kidney injury (AKI), cardiac failure. Despite the rapid progression of renal tissue injury, the mechanism underlying renal ischemia/reperfusion injury (IRI) remains highly unclear. Experimental in vitro and in vivo models epitomizing the fundamental process is critical to the research of the pathogenesis of IRI and the development of plausible therapeutics. In this review, we describe the in vitro and in vivo models of IRI, ranges from proximal tubular cell lines to surgery-based animal models like clamping of both renal pedicles (bilateral IRI), clamping of one renal pedicle (unilateral IRI), clamping of one/or both renal arteries/or vein, or unilateral IRI with contralateral nephrectomy (uIRIx). Also, advanced technologies like three-dimensional kidney organoids, kidney-on-a-chip are explained. This review provides thoughtful information for establishing reliable and pertinent models for studying IRI-associated acute renal pathologies.

Effect of anti-C5 antibody on recuperation from ischemia/reperfusion-induced acute kidney injury

Aim: The complement system is activated in acute kidney injury (AKI). Anti-C5 antibody targets the common terminal portion of the complement cascade that generate the terminal complex C5b-9 and has a renal-protective effect in paroxysmal nocturnal hemoglobinuria. However, the anti-C5 antibody’s role in ischemia/reperfusion (I/R)-induced AKI has not been fully investigated. We therefore evaluated its effect on the pathophysiological cascade of I/R-induced AKI.

Methods: Sprague–Dawley rats underwent unilateral right kidney nephrectomies with simultaneous clamping of the contralateral hilum for 60 min (ischemia), followed by reperfusion. In addition to a placebo, two treatment groups received either high or low doses of anti-C5 monoclonal antibody. After 48 h, the rats were euthanized, blood was drawn to evaluate systemic inflammation and to estimate glomerular filtration rate (GFR). The remaining kidney was removed for pathological evaluation and intra-renal complement activation.

Results: I/R induced significant intra-renal complement activation and systemic inflammation compared with unilateral nephrectomy group. The anti-C5 antibody ameliorated the intra-renal complement activation (intra-renal C3 and C6), reduced systemic inflammation (C-reactive protein, and systemic C3), decreased intra-renal acute tubular necrosis damage and improved GFR (seen by the sensitive marker, serum cystatin C; 1.63 mg/L (I/R + placebo), 1.36 mg/L (I/R + low dose) and 1.21 mg/L (I/R + high dose), p = .08 and .03 compared with I/R + placebo).

Conclusion: In I/R-induced AKI, the monoclonal anti-C5 complement factor ameliorates intra renal complement activation, decreases local and systemic inflammation and may improve GFR.

The effects of acute sumatriptan treatment on renal ischemia/reperfusion injury in rat and the possible involvement of nitric oxide

Renal ischemia/reperfusion (I/R) injury is a common pathological condition. Studies reported renal toxicity following administration of triptans, which are commonly used for treating migraine headaches. To investigate the effects of sumatriptan and the molecular mechanisms involved in renal I/R injury in rats, ischemia was induced by bilateral clamping of renal pedicles followed by 24 h of reperfusion. Sumatriptan was administered in three different doses (5, 10, and 20 mg/kg) before I/R injury induction. Biochemical and histopathological changes were evaluated. The contribution of nitric oxide in modulating the effects of sumatriptan was determined by administrating aminoguanidine at 50 mg/kg 60 min before I/R injury. The tissue level of nitrite, superoxide dismutase (SOD), and malondialdehyde (MDA) were measured. Sumatriptan at 10 and 20 mg/kg increased the serum level of creatinine (Cr) and blood urea nitrogen (BUN) significantly. There was also a significant increase in nitrite level of animals that received 10 mg/kg sumatriptan. Co-administration of sumatriptan with aminoguanidine significantly decreased the BUN and Cr. Depletion of SOD level (P < 0.05) and elevation of serum levels of MDA (P < 0.001) indicated the involvement of oxidative stress in sumatriptan adverse effects. Overall, the administration of sumatriptan intensified renal I/R injury through activation of inducible nitric oxide synthase and oxidative responses in rats.

Schisantherin A protects renal tubular epithelial cells from hypoxia/reoxygenation injury through the activation of PI3K/Akt signaling pathway

Schisantherin A (SchA), a dibenzocyclooctadiene lignan isolated from the fruit of Schisandra sphenanthera, was reported to possess anti-inflammatory and antioxidant activities. However, its protective effect against renal ischemia-reperfusion (I/R) injury in human renal tubular epithelial cells subjected to hypoxia/reoxygenation (H/R) has never been studied. Thus, herein, we investigated the effect of SchA on renal I/R injury in vitro. Our results demonstrated that SchA pretreatment significantly improved HK-2 cell viability exposed to H/R. Pretreatment with SchA markedly inhibited the levels of reactive oxygen species and malondialdehyde, as well as suppressed the production of tumor necrosis factor-α (TNF-α), interleukin-1β, and interleukin-6 in H/R-stimulated HK-2 cells. In addition, SchA also suppressed H/R-induced HK-2 cell apoptosis. Furthermore, this protective effect of SchA was mediated through the PI3K/Akt signaling pathway in HK-2 cells. These findings showed that SchA may exert a protective effect on renal tubular epithelial cells against H/R injury through the activation of PI3K/Akt signaling pathway.

Extracellular vesicles as immune mediators in response to kidney injury

Important progress has been made on cytokine signaling in response to kidney injury in the past decade, especially cytokine signaling mediated by extracellular vesicles (EVs). For example, EVs released by injured renal tubular epithelial cells (TECs) can regulate intercellular communications and influence tissue recovery via both regulating the expression and transferring cytokines, growth factors, as well as other bioactive molecules at the site of injury. The effects of EVs on kidney tissue seem to vary depending on the sources of EVs; however, the literature data are often inconsistent. For example, in rodents EVs derived from mesenchymal stem cells (MSC-EVs) and endothelial progenitor cells (EPC-EVs) can have both beneficial and harmful effects on injured renal tissue. Caution is thus needed in the interpretation of these data as contradictory findings on EVs may not only be related to the origin of EVs, they can also be caused by the different methods used for EV isolation and the physiological and pathological states of the tissues/cells under which they were obtained. Here, we review and discuss our current understanding related to the immunomodulatory function of EVs in renal tubular repair in the hope of encouraging further investigations on mechanisms related to their antiinflammatory and reparative role to better define the therapeutic potential of EVs in renal diseases.

The effects of glomerular and tubular renal progenitors and derived extracellular vesicles on recovery from acute kidney injury

Background

Mesenchymal stromal cells (MSCs) and renal stem/progenitors improve the recovery of acute kidney injury (AKI) mainly through the release of paracrine mediators including the extracellular vesicles (EVs). Several studies have reported the existence of a resident population of MSCs within the glomeruli (Gl-MSCs). However, their contribution towards kidney repair still remains to be elucidated. The aim of the present study was to evaluate whether Gl-MSCs and Gl-MSC-EVs promote the recovery of AKI induced by ischemia-reperfusion injury (IRI) in SCID mice. Moreover, the effects of Gl-MSCs and Gl-MSC-EVs were compared with those of CD133⁺ progenitor cells isolated from human tubules of the renal cortical tissue (T-CD133⁺ cells) and their EVs (T-CD133⁺-EVs).

Methods

IRI was performed in mice by clamping the left renal pedicle for 35 minutes together with a right nephrectomy. Immediately after reperfusion, the animals were divided in different groups to be treated with: Gl-MSCs, T-CD133⁺ cells, Gl-MSC-EVs, T-CD133⁺-EVs or vehicle. To assess the role of vesicular RNA, EVs were either isolated by floating to avoid contamination of non-vesicles-associated RNA or treated with a high dose of RNase. Mice were sacrificed 48 hours after surgery.

Results

Gl-MSCs, and Gl-MSC-EVs both ameliorate kidney function and reduce the ischemic damage post IRI by activating tubular epithelial cell proliferation. Furthermore, T-CD133⁺ cells, but not their EVs, also significantly contributed to the renal recovery after IRI compared to the controls. Floating EVs were effective while RNase-inactivated EVs were ineffective. Analysis of the EV miRnome revealed that Gl-MSC-EVs selectively expressed a group of miRNAs, compared to EVs derived from fibroblasts, which were biologically ineffective in IRI.

Conclusions

In this study, we demonstrate that Gl-MSCs may contribute in the recovery of mice with AKI induced by IRI primarily through the release of EVs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0478-5) contains supplementary material, which is available to authorized users.

Renoprotective effects of ursolic acid on ischemia/reperfusion‑induced acute kidney injury through oxidative stress, inflammation and the inhibition of STAT3 and NF‑κB activities

Ursolic acid, a pentacyclic triterpene compound with low toxicity and easy availability, has a variety of biological activities, including antitumor, antioxidant, antihepatitis, anti‑inflammatory and antibacterial effects. The present study aimed to investigate the renoprotective effects of ursolic acid on ischemia/reperfusion‑induced acute kidney injury (I/R‑IAKI) in rats associated with its antioxidant and anti‑inflammatory effects, as well as interference with the signal transducer and activator of transcription (STAT)3/nuclear factor (NF)‑κB signaling pathway. The present study demonstrated that pre‑treatment with ursolic acid significantly increased renal functioning and attenuated increases of serum angiotensin II levels in rats subjected to I/R‑IAKI. In addition, I/R‑IAKI‑induced inflammation and oxidative stress were significantly reduced by pre‑treatment with ursolic acid. Furthermore, ursolic acid significantly suppressed the upregulation of STAT3, NF‑κB and caspase‑3 activities in rats following I/R‑IAKI. These results indicated that ursolic acid may be a potential drug for reducing I/R‑IAKI through suppression of inflammation and oxidative stress damage, as well as modulation of STAT3 and NF‑κB activities.

Prediction of Nephrotoxicant Action and Identification of Candidate Toxicity-Related Biomarkers

A vast majority of pharmacological compounds and their metabolites are excreted via the urine, and within the complex structure of the kidney, the proximal tubules are a main target site of nephrotoxic compounds. We used the model nephrotoxicants mercuric chloride, 2-bromoethylamine hydrobromide, hexachlorobutadiene, mitomycin, amphotericin, and puromycin to elucidate time- and dose-dependent global gene expression changes associated with proximal tubular toxicity. Male Sprague–Dawley rats were dosed via intraperitoneal injection once daily for mercuric chloride and amphotericin (up to 7 doses), while a single dose was given for all other compounds. Animals were exposed to 2 different doses of these compounds and kidney tissues were collected on day 1, 3, and 7 postdosing. Gene expression profiles were generated from kidney RNA using 17K rat cDNA dual dye microarray and analyzed in conjunction with histopathology. Analysis of gene expression profiles showed that the profiles clustered based on similarities in the severity and type of pathology of individual animals. Further, the expression changes were indicative of tubular toxicity showing hallmarks of tubular degeneration/regeneration and necrosis. Use of gene expression data in predicting the type of nephrotoxicity was then tested with a support vector machine (SVM)-based approach. A SVM prediction module was trained using 120 profiles of total profiles divided into four classes based on the severity of pathology and clustering. Although mitomycin C and amphotericin B treatments did not cause toxicity, their expression profiles were included in the SVM prediction module to increase the sample size. Using this classifier, the SVM predicted the type of pathology of 28 test profiles with 100% selectivity and 82% sensitivity. These data indicate that valid predictions could be made based on gene expression changes from a small set of expression profiles. A set of potential biomarkers showing a time- and dose-response with respect to the progression of proximal tubular toxicity were identified. These include several transporters ( Slc21a2, Slc15, Slc34a2), Kim 1, IGFbp-1, osteopontin, α -fibrinogen, and Gstα.

Global miRNA expression is temporally correlated with acute kidney injury in mice

MicroRNAs (miRNAs) are negative regulators of gene expression and protein abundance. Current evidence shows an association of miRNAs with acute kidney injury (AKI) leading to substantially increased morbidity and mortality. Here, we investigated whether miRNAs are inductive regulators responsible for the pathological development of AKI. Microarray analysis was used to detect temporal changes in global miRNA expression within 48 h after AKI in mice. Results indicated that global miRNA expression gradually increased over 24 h from ischemia reperfusion injury after 24 h, and then decreased from 24 h to 48 h. A similar trend was observed for the index of tubulointerstitial injury and the level of serum creatinine, and there was a significant correlation between the level of total miRNA expression and the level of serum creatinine (p < 0.05). This expression-phenotype correlation was validated by quantitative reverse transcription PCR on individual miRNAs, including miR-18a, -134, -182, -210 and -214. Increased global miRNA expression may lead to widespread translational repression and reduced cellular activity. Furthermore, significant inflammatory cytokine release and peritubular capillary loss were observed, suggesting that the initiation of systematic destruction programs was due to AKI. Our findings provide new understanding of the dominant role of miRNAs in promoting the pathological development of AKI.

Overexpression of Heme Oxygenase-1 Prevents Renal Interstitial Inflammation and Fibrosis Induced by Unilateral Ureter Obstruction

Renal fibrosis plays an important role in the onset and progression of chronic kidney diseases. Many studies have demonstrated that heme oxygenase-1 (HO-1) is involved in diverse biological processes as a cytoprotective molecule, including anti-inflammatory, anti-oxidant, anti-apoptotic, antiproliferative, and immunomodulatory effects. However, the mechanisms of HO-1 prevention in renal interstitial fibrosis remain unknown. In this study, HO-1 transgenic (TG) mice were employed to investigate the effect of HO-1 on renal fibrosis using a unilateral ureter obstruction (UUO) model and to explore the potential mechanisms. We found that HO-1 was adaptively upregulated in kidneys of both TG and wild type (WT) mice after UUO. The levels of HO-1 mRNA and protein were increased in TG mice compared with WT mice under normal conditions. HO-1 expression was further enhanced after UUO and remained high during the entire experimental process. Renal interstitial fibrosis in the TG group was significantly attenuated compared with that in the WT group after UUO. Moreover, overexpression of HO-1 inhibited the loss of peritubular capillaries. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by HO-1 overexpression. Furthermore, HO-1 restrained tubulointerstitial infiltration of macrophages and regulated the secretion of inflammatory cytokines in UUO mice. We also found that high expression of HO-1 inhibited reactivation of Wnt/β-catenin signaling, which could play a crucial role in attenuating renal fibrosis. In conclusion, these data suggest that HO-1 prevents renal tubulointerstitial fibrosis possibly by regulating the inflammatory response and Wnt/β-catenin signaling. This study provides evidence that augmentation of HO-1 levels may be a therapeutic strategy against renal interstitial fibrosis.

Dipyridamole attenuates ischemia reperfusion induced acute kidney injury through adenosinergic A1 and A2A receptor agonism in rats

Dipyridamole (DYP) is an anti-platelet agent with marked vasodilator, anti-oxidant, and anti-inflammatory activity. The present study investigated the role of adenosine receptors in DYP-mediated protection against ischemia reperfusion-induced acute kidney injury (AKI) in rats. The rats were subjected to bilateral renal ischemia for 40 min followed by reperfusion for 24 h. The renal damage induced by ischemia reperfusion injury (IRI) was assessed by measuring creatinine clearance, blood urea nitrogen, uric acid, plasma potassium, fractional excretion of sodium, and microproteinuria in rats. The oxidative stress in renal tissues was assessed by quantification of thiobarbituric acid-reactive substances, superoxide anion generation, and reduced glutathione level. The hematoxylin-eosin staining was carried out to observe histopathological changes in renal tissues. DYP (10 and 30 mg/kg, intraperitoneal, i.p.) was administered 30 min before subjecting the rats to renal IRI. In separate groups, caffeine (50 mg/kg, i.p.), an adenosinergic A1 and A2A receptor antagonist was administered with and without DYP treatment before subjecting the rats to renal IRI. The ischemia reperfusion-induced AKI was demonstrated by significant changes in serum as well as urinary parameters, enhanced oxidative stress, and histopathological changes in renal tissues. The administration of DYP demonstrated protection against AKI. The prior treatment with caffeine abolished DYP-mediated reno-protection suggesting role of A1 and A2A adenosine receptors in DYP-mediated reno-protection in rats. It is concluded that adenosine receptors find their definite involvement in DYP-mediated anti-oxidative and reno-protective effect against ischemia reperfusion-induced AKI.

Erythropoietin pretreatment ameliorates renal ischaemia-reperfusion injury by activating PI3K/Akt signalling

AIM

Renal ischaemia-reperfusion (I/R) injury, a primary cause of acute renal failure, can induce high morbidity and mortality. This study aimed to explore the effect of erythropoietin on renal I/R injury and its underlying mechanism.

METHODS

Fifty male Sprague-Dawley rats were randomly allocated to three groups (n = 10): the sham group, the renal ischaemia-reperfusion-saline (IRI) group, and the IRI+-Erythropoietin (EPO) group. Erythropoietin (250, 500, 1000 U/kg) was intraperitoneally injected 30 min before inducing I/R. Renal I/R injury were induced by clamping the left renal artery for 30 min followed by reperfusion, along with a contralateral nephrectomy. Renal function and histological damage were determined after 24 h reperfusion. The expression of pro-inflammatory cytokines interleukin-6 (IL-6), interleukin-1 β (IL-1β), and tumour necrosis factor-α (TNF-α) in the serum and renal tissue were evaluated by enzyme linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR), respectively. Further, the effects of erythropoietin on PI3K/Akt signalling, erythropoietin receptor (EPOR) and nuclear factor (NF)-κB activation were measured by Western blotting.

RESULTS

Erythropoietin pretreatment can significantly decrease the level of renal dysfunction in a dose-dependent manner, attenuated the renal histological changes, the expression of TNF-α, IL-1β, and IL-6, the levels of reactive oxygen species (ROS) production and NF-κB p65 phosphorylation in renal tissue upon IRI. Moreover, erythropoietin pretreatment could further activate the PI3K/Akt signalling and induced EPOR activity.

CONCLUSIONS

Erythropoietin pretreatment could attenuate renal I/R injury by suppressing inflammation, which was associated with activating PI3K/Akt signalling though EPOR activation. Our findings suggest that erythropoietin may be a novel practical strategy to prevent renal I/R injury.

Clinical applications of remote ischaemic preconditioning in native and transplant acute kidney injury

Ischaemia-reperfusion (IR) injury is a composite of the injury sustained during a period of reduced or absent blood flow to a tissue or organ and the additional insult sustained upon reperfusion that limits the amount of tissue that can be salvaged. IR injury plays a central role in both native and transplant acute kidney injury (AKI). Native AKI is associated with increased morbidity and mortality in hospital inpatients, and transplant AKI contributes to graft dysfunction, ultimately limiting graft longevity. In this review, we discuss the potential therapeutic benefits of a cost-effective and low-risk intervention, remote ischaemic preconditioning (RIPC), and its applicability in the prevention and reduction of AKI.

Effect of Γ-aminobutyric acid on kidney injury induced by renal ischemia-reperfusion in male and female rats: Gender-related difference

Background:

The most important cause of kidney injury is renal ischemia/reperfusion injury (IRI), which is gender-related. This study was designed to investigate the protective role of Γ-aminobutyric acid (GABA (against IRI in male and female rats.

Materials and Methods:

Thirty-six female and male wistar rats were assigned to six experimental groups. The IRI was induced by clamping renal vessels for 45 min then was performed reperfusion for 24 h. The group sex posed to IRI were pretreated with GABA and were compared with the control groups.

Results:

Serum levels of creatinine and blood urea nitrogen, kidney weight, and kidney tissue damage score increased in the IRI alone groups, (P < 0.05), while GABA decreased these parameters in female significantly (P < 0.05), but not in male rats. Uterus weight decreased significantly in female rats treated with GABA. Testis weight did not alter in male rats. Serum level of nitrite and kidney level of malondialdehyde (MDA) had no significant change in both female and male rats. Kidney level of nitrite increased significantly in female rats experienced IRI and serum level of MDA increased significantly in males that were exposed to IRI (P < 0.05).

Conclusion:

GABA could ameliorate kidney injury induced by renal IRI in a gender dependent manner.

The administration of erythropoietin attenuates kidney injury induced by ischemia/reperfusion with increased activation of Wnt/β-catenin signaling

BACKGROUND/PURPOSE

Understanding the mechanisms of protecting the kidneys from injury is of great importance because there are no effective therapies that promote repair and the kidneys frequently do not repair adequately. Evidence has shown that erythropoietin (EPO) has a vital renoprotective role, independent of its erythropoietic effect. However, whether EPO can contribute to kidney repair after injury and the potential mechanisms are not fully understood.

METHODS

To investigate the renoprotective mechanism of EPO, a kidney ischemia/reperfusion injury (IRI) model was induced in adult male Sprague-Dawley rats. The rats were subsequently randomly treated with EPO or a vehicle 6 hours after the kidney IRI. The rats were sacrificed on Day 3, Day 5, and Day 7 post kidney IRI. Renal function and histological alterations were examined. Renal interstitial macrophage infiltration, cell proliferation, apoptosis, and angiogenesis were evaluated by immunostaining. Furthermore, the effects of EPO on the Wnt/β-catenin pathway and IRI-related micro-RNAs were investigated.

RESULTS

The administration of EPO significantly improved renal function and reduced tubular injury. Furthermore, EPO treatment significantly prevented tubular cell apoptosis and promoted cell proliferation after IRI. Erythropoietin significantly suppressed macrophage infiltration, compared to the vehicle. In addition, treatment with EPO markedly prevented the loss of microvasculature. We have also demonstrated that, compared to the vehicle, EPO administration enhanced the expression of Wnt7b and β-catenin, and downregulated miR-21, -214, -210, and -199a.

CONCLUSION

Erythropoietin protects the kidneys against IRI by attenuating injury of the renal microvasculature and tubule epithelial cells, by promoting Wnt/β-catenin pathway activation, and by regulating miRNA expression.

Subnormothermic machine perfusion for preservation of porcine kidneys in a donation after circulatory death model

Machine perfusion for preservation led to compelling success for the outcome of renal transplantation. Further refinements of methods to decrease preservation injury remain an issue of high interest. This study investigates functional and morphological aspects of kidneys preserved by subnormothermic (20 °C) machine perfusion (SNTM) compared with oxygenated hypothermic machine perfusion (HMPox) and cold storage (CS) in a donation after circulatory death (DCD) model. After 30 min of warm ischaemia, porcine kidneys were randomly assigned to preservation for 7 h by CS, HMPox or SNTM. Afterwards, kidneys were reperfused for 2 h with autologous blood in vitro for assessment of function and integrity. Application of SNTM for preservation led to significantly higher blood flow and urine output compared with both other groups. SNTM led to a twofold increased creatinine clearance compared with HMPox and 10-fold increased creatinine clearance compared with CS. Structural integrity was best preserved by SNTM. In conclusion, this is the first study on SNTM for kidneys from DCD donors. SNTM seems to be a promising preservation method with the potential to improve functional parameters of kidneys during reperfusion.

Tissue-specific deletion of Crry from mouse proximal tubular epithelial cells increases susceptibility to renal ischemia-reperfusion injury

The murine cell surface protein Crry (complement receptor 1-related protein/gene y) is a key complement regulator with similar activities to human membrane cofactor protein (MCP) and decay-accelerating factor. MCP has a critical role in preventing complement-mediated tissue injury and its mutation has been implicated in several human kidney diseases. The study of Crry in mice has relevance to understanding MCP activity in human diseases; however, such efforts have been hampered by the embryonic lethality phenotype of Crry gene knockout. Here we used a conditional gene-targeting approach and deleted Crry from the mouse proximal tubular epithelial cells where Crry is prominently expressed. Absence of Crry from proximal tubular epithelial cells resulted in spontaneous C3 deposition on the basolateral surface but no apparent renal disease in unchallenged mice. However, mice deficient in Crry on proximal tubular epithelial cells developed exacerbated renal injury when subjected to renal ischemia-reperfusion, showing increased blood urea nitrogen levels, higher tubular injury scores, more tubular epithelial cell apoptosis, and inflammatory infiltrates. Renal ischemia-reperfusion injury in the Crry conditional knockout mice was prevented by blocking C3 and C5 activation using an anti-properdin or anti-C5 monoclonal antibody (mAb), respectively. Thus, Crry has a critical role in protecting proximal tubular epithelial cells during ischemia-reperfusion challenge. Our results highlight the latent risk for inflammatory kidney injury associated with defects in membrane complement regulators.

Effects of compound Shenhua tablet on renal tubular Na+-K+-ATPase in rats with acute ischemic reperfusion injury

OBJECTIVE

To observe the effect of Compound Shenhua Tablet (, SHT) on the sodium-potassium- exchanging adenosinetriphosphatase (Na(+)-K(+)-ATPase) in the renal tubular epithelial cells of rats with acute ischemic reperfusion and to investigate the mechanisms underlying the effects of SHT on renal ischemic reperfusion injury (RIRI).

METHODS

Fifty male Wistar rats were randomly divided into the sham surgery group, model group, astragaloside group [150 mg/(kg·d)], SHT low-dose group [1.5 g/(kg·d)] and SHT high-dose group [3.0 g/(kg·d)], with 10 rats in each group. After 1 week of continuous intragastric drug administration, surgery was performed to establish the model. At either 24 or 72 h after the surgery, 5 rats in each group were sacrificed, blood biochemistry, renal pathology, immunoblot and immunohistochemical examinations were performed, and double immunofluorescence staining was observed under a laser confocal microscope.

RESULTS

Compared with the sham surgery group, the serum creatinine (SCr) and blood urea nitrogen (BUN) levels were significantly increased, Na(+)-K(+)-ATPase protein level was decreased, and kidney injury molecule-1 (KIM-1) protein level was increased in the model group after the surgery (P<0.01 or P<0.05). Compared with the model group, the SCr, BUN, pathological scores, Na(+)-K(+)-ATPase, and the KIM-1 protein level of the three treatment groups were significantly improved at 72 h after the surgery (P<0.05 or P<0.01). And the SCr, BUN of the SHT low- and high-dose groups, and the pathological scores of the SHT high-dose group were significantly lower than those of the astragaloside group (P<0.05). The localizations of Na(+)-K(+)-ATPase and megalin of the model group were disrupted, with the distribution areas overlapping with each other and alternately arranged. The severity of the disruption was slightly milder in three treatment groups compared with that of the model group. The results of immunofluorescence staining showed that the SHT high-dose group had a superior effect as compared with the astragaloside group and the SHT low-dose group.

CONCLUSIONS

The SHT effectively alleviated RIRI caused by ischemic reperfusion, promoted the recovery of the polarity of renal tubular epithelial cells, and protected the renal tubules. The therapeutic effects of SHT were superior to those of astragaloside as a single agent.

The effect of melatonin on acetylsalicylic acid-induced kidney and testis damage

The aim of this study was to evaluate the acute effect of high-dose acetylsalicylic acid (ASA) on kidney and testis, and the potential protective and therapeutic effects of melatonin on ASA-related pathology. A total of 40 rats were randomly divided into the following 5 groups ( n = 8): group 1: control, not given any drug; group 2: only 200 mg/kg ASA was given; group 3: 5 mg/kg melatonin was given 45 min before administering 200 mg/kg ASA; group 4: 5 mg/kg melatonin was given 45 min after administering 200 mg/kg ASA; and group 5: only 5 mg/kg melatonin was given. The histopathological changes and the biochemical findings; such as malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), reduced glutathione (GSH), and blood urea nitrogen (BUN) as well as serum creatinine (Cr) levels were evaluated. ASA significantly increased MDA levels in both kidney and testis, whereas it significantly decreased the values of SOD, CAT, GPX, and GSH in kidney and CAT levels in testis. Melatonin significantly decreased MDA levels in kidney and ameliorated it in testis, whereas it caused elevation in the levels of antioxidants. BUN and Cr levels were higher after ASA, whereas these levels were diminished after melatonin administration. The improvement obtained by melatonin on ASA-induced histological alterations was more prominent when it was used after ASA in kidney and before ASA in testis. In this study, we demonstrated the beneficial effect of melatonin on high-dose ASA-related pathology of kidney and testis for the first time.

Localized expression of human BMP-7 by BM-MSCs enhances renal repair in an in vivo model of ischemia-reperfusion injury

Ischemia and subsequent reperfusion (I/R) damage kidney tubular cells and consequently impair renal function. Rabbit bone marrow mesenchymal stem cells (BM-MSCs) expressing human bone morphogenic protein-7 (hBMP-7) regenerated tubular cells and improved renal function in a kidney I/R model. Rabbits were injected immediately after I/R with one of the following: (i) hBMP-7-transduced BM-MSCs (BM-MSCshBMP-7); (ii) enhanced green fluorescent protein-transduced BM-MSCs (BM-MSCsEGFP); or (iii) PBS. The activity of superoxide dismutase (SOD) was higher, and the amount of malondialdehyde (MDA) was lower in the BM-MSCshBMP-7 group than in the BM-MSCsEGFP group. Both the BM-MSCshBMP-7 group and the BM-MSCsEGFP group had higher SOD activity and lower amounts of MDA than the PBS group. Bcl-2- and Bcl-2-associated X protein levels, and other variables, indicated the regeneration of the kidney in both experimental groups. However, the BM-MSCs (hBMP-7) group showed higher activity than the BM-MSCsEGFP group, indicating that the combined strategy of BM-MSC transplantation with hBMP-7 gene therapy could be a useful approach for the treatment of renal IRI.

The protective effects of apocynin on kidney damage caused by renal ischemia/reperfusion

PURPOSE

This experimental study was designed to explore the protective effect of apocynin, the NADPH-oxidase inhibitor, on kidney damage induced by ischemia/reperfusion (I/R) in a rat model.

METHODS

Thirty-two rats were randomly divided into a control group and three I/R groups (1-hour ischemia followed by 23-hour reperfusion). Three I/R groups were treated by apocynin (20 mg/kg, i.p.) at two different time points (before ischemia and during ischemia). The histopathological findings, including apoptotic changes, and also tissue malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathion peroxidase (GPX), reduced glutathione (GSH), myeloperoxidase (MPO), blood urea nitrogen (BUN), and serum creatinine (Cr) levels, were determined.

RESULTS

Kidney tissue MDA and MPO, and serum BUN and Cr levels were found to be significantly higher in the I/R group, but there was no statistically significant difference in the levels of SOD, CAT, GPX, and GSH between the I/R and the control groups. Although apocynin significantly reduced MDA and MPO in group 3 and increased GPX in both treatment groups when compared to the I/R group, the elevated BUN and Cr levels were significantly reduced in treatment groups. Renal I/R injury also induced extensive tubular necrosis, glomerular damage, and apoptosis in the histological evaluation. Apocynin, especially when used during ischemia, ameliorated these histological damages in different amounts in treatment groups.

CONCLUSION

The beneficial effects of apocynin on renal I/R injury were evaluated for the first time.

Lessons from the heart and ischemic limbs: midkine as anti-inflammatory mediator for kidney diseases?

Inflammatory responses ensuing ischemia involve the release of numerous mediators. Among these the heparin-binding growth factor midkine has been recognized as a potent inducer of neoangiogenesis. In a recent publication, the release of midkine has been studied in different in vitro models, and effects of abrogated midkine expression by means of genetic knockout has been analyzed in ischemia models of the limbs. The observed effects indicate a profound effect exerted by midkine under ischemia in the coordination of the inflammatory response and neoangiogenesis.

The effects of tadalafil on renal ischemia reperfusion injury: an experimental study

Many pharmacological agents were investigated for the prevention of renal ischemic reperfusion (I/R) injury as well as the phosphodiesterase (PDE) inhibitors. The aim of the study was to examine the possible renoprotective effect of a member in this family, tadalafil (Td) on I/R injury. Thirty-six Spraque Dawley rats were allocated to six groups as; control, sham, ischemia (I), ischemia/reperfusion (I/R), Td pretreatment ischemia (Td/I) and Td pretreatment ischemia/reperfusion (Td/IR) groups. Right nephrectomy was performed in all groups. Td was dissolved in saline solution and given as a single dose (1mg/kg) through an orogastrictube 60 min before the operation in the Td pretreatment groups. In ischemia group the left renal pedicle was occluded for 45 minutes and after than underwent left nephrectomy. In I/R group left renal pedicle was occluded for 45 minutes, reperfused for 1hour and after then underwent nephrectomy. The left kidneys were evaluated after standard laboratory procedures with regard to tubular morphology, and leukocyte infiltration. The data were analyzed by using Kruskal-Wallis test to determine differences among the groups. A p value of < 0.05 was considered significant. Renal tubular damage was significant increased in the ischemia and I/R group (Groups III and IV) when compared to those in the sham group (Group II), (p = 0.004, 0.004, respectively). Tubular damage, in the Td pretreatment ischemia (Td/I) (Group V) and Td pretreatment ischemia/reperfusion (Td/IR) (Group VI) were less than that in the ischemia group (Group III) (p= 0.010, p= 0.025, respectively). Td administration prior to the renal I/R injury attenuated these morphological disarrangements, which were observed in renal I/R. Tubular necrosis, which may be considered as an important issue of the developing renal injury, was also completely prevented with Td administration.

Immunopathogenesis of ischemia/reperfusion-associated tissue damage

Ischemia/reperfusion (IR) instigates a complex array of inflammatory events which result in damage to the local tissue. IR-related organ damage occurs invariably in several clinical conditions including trauma, organ transplantation, autoimmune diseases and revascularization procedures. We critically review available pre-clinical experimental information on the role of immune response in the expression of tissue damage following IR. Distinct elements of the innate and adaptive immune response are involved in the expression of tissue injury. Interventions such as prevention of binding of natural antibody to antigen expressed on the surface of ischemia-conditioned cells, inhibition of the ensuing complement activation, modulation of Toll-like receptors, B or T cell depletion and blockade of inflammatory cytokines and chemokines limit IR injury in preclinical studies. Clinical trials that will determine the therapeutic value of each approach is needed.

Segment-specific overexpression of redoxins after renal ischemia and reperfusion: protective roles of glutaredoxin 2, peroxiredoxin 3, and peroxiredoxin 6

The disruption of redox control, i.e., oxidative stress, is one of the most destructive causes of ischemia-reperfusion (IR) injury. Thioredoxin (Trx) family proteins play a major role in the cellular response to oxidative stress. Here, we systematically investigated the levels and tissue distribution of 15 members of this family (Trx and TrxR 1 and 2, Nrx, Prx 1-6, and Grx 1-3 and 5) in mouse kidneys after induction of IR by comparing control, clamped, and contralateral organs. After IR, levels of various redoxins were quantified. Immunohistochemical analysis revealed segment-specific alterations induced by the ischemic insult. Grx2, Prx3, and Prx6 were highly expressed in proximal tubule cells. Overexpression of these proteins in HEK293 and HeLa cells subjected to hypoxia and reoxygenation revealed higher survival and proliferation rates and lower oxidative damage compared to controls. Furthermore, we report for the first time the accumulation of Grx1 at the apical side of distal convoluted cells and the specific secretion of Grx1 into the urine after IR. The differences in both the basal equipment and the segment-specific responses of the antioxidant proteins may contribute to the distinct susceptibilities and regeneration processes of the various segments of the nephron to the IR insult.

Preservation strategies to reduce ischemic injury in kidney transplantation: pharmacological and genetic approaches

PURPOSE OF REVIEW

In the current graft shortage, it is paramount to improve the quality of transplanted organs. Organ preservation represents an underused therapeutic window with great potential to reduce ischaemia-reperfusion injury (IRI) and improve graft quality. Herein, we review strategies using this window as well as other promising work targeting IRI pathways using pharmacological treatments and gene therapy.

RECENT FINDINGS

We highlight studies using molecules administered during kidney preservation to target key components of IRI such as inflammation, oxidative stress, mitochondrial activity and the coagulation pathway. We further expose recent studies of gene therapy directed against inflammation or apoptosis during cold storage. Other pathways with potential therapeutic molecules are cited.

SUMMARY

The use of cold preservation as a therapeutic window to deliver pharmacological or gene therapy treatments can significantly improve both short-term and long-term graft outcomes. Even if human gene therapy remains hampered by the quantity of agent needed and the potential harmfulness of the vector, it clearly offers a wide array of possibilities for the future. Although gene therapy is still too immature, we expose pharmacological strategies which can readily be applied to the clinic and improve both transplantation success rates and the patients' quality of life.

Glutamine contributes to ameliorate inflammation after renal ischemia/reperfusion injury in rats

The aim of this study was to investigate the effects of glutamine in an in vivo rat model of renal ischemia/reperfusion (I/R) injury. Male Wistar rats underwent bilateral renal pedicle clamping for 45 min followed by reperfusion for 6 h. Glutamine (1.5 mg/kg) was administered intraperitoneally (i.p.) 15 min prior to reperfusion. Plasma concentrations of urea, creatinine, γ-glutamyl transferase (γ-GT), and aspartate aminotransferase (AST) were measured for the assessment of renal function and reperfusion injury. Markers of oxidative stress, expression of the pro-inflammatory mediators inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), AT-1 expression, and changes in the oxidative stress-sensitive nuclear factor kappa B (NF-κB) signaling pathway were measured to investigate whether glutamine can reduce the renal dysfunction. Kidney myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured for assessment of polymorphonuclear (PMN) cell infiltration and lipid peroxidation, respectively. Renal sections were used for histologic grading of renal injury and for immunohistochemical localization of nitrotyrosine and poly(ADP-ribose) synthetase (PARS). In vivo, glutamine significantly reduced the increase in urea, creatinine, γ-GT, AST, produced by renal ischemia/reperfusion (I/R), suggesting an improvement in both renal function and injury. Glutamine significantly reduced iNOS and NF-κB, kidney MPO activity and MDA levels, indicating a reduction in PMN infiltration and lipid peroxidation, respectively. Glutamine reduced the histological evidence of renal damage associated with I/R and caused a substantial reduction in the staining for nitrotyrosine and PARS, suggesting reduced nitrosative and oxidative stress. Moreover, glutamine attenuated the reduction of COX-2 expression and prevented the increased AT-1 expression after I/R. Our results suggest that glutamine reduces the renal dysfunction and injury associated with I/R of the kidney.

The beneficial effects of tadalafil on renal ischemia-reperfusion injury in rats

Acute renal failure due to ischemia-reperfusion (I/R) injury is a common complication in cardiovascular surgery. We determined the influence of tadalafil on renal injury in a renal I/R model in rats. For this purpose, 21 male Wistar albino rats were separated into 3 groups: sham, placebo and tadalafil. A right nephrectomy was performed, and the left renal pedicles were occluded for 60 min and reperfused for 60 min in the placebo and tadalafil groups. A single dose of tadalafil (10 mg/kg) through an orogastric tube was administered to the tadalafil group. Tubular atrophy with acute inflammation in renal histology, total oxidant status (TOS) and total antioxidant status (TAS) were determined in tissue homogenates. Compared to the tadalafil group, tubular atrophy and acute inflammation was significant in the placebo group. TAS levels were significantly higher in the tadalafil group compared to the placebo (p = 0.01) and sham groups (p = 0.04). While TOS levels were significantly higher in the placebo group (p = 0.03), tadalafil did not significantly alter the TOS levels. The beneficial effects of tadalafil can be attributed to its protective effects on renal tubular cells and inhibition of leukocyte infiltration in renal tissue. We think that tadalafil treatment has an important role in reducing renal injury resulting from renal I/R.

Sildenafil attenuates renal ischemia reperfusion injury by decreasing leukocyte infiltration

The aim of the study was to investigate the effects of sildenafil citrate (SC) on renal ischemia reperfusion (I/R) injury in a rat model. Forty eight male Wistar albino rats were randomly assigned into six groups: sham, ischemia, I/R, SC+sham, SC+ischemia and SC+I/R. In the I/R groups, the right kidney was removed and the artery and vein of the left kidney were clamped for 45 min followed by reperfusion for 1 h. In the SC-treated groups, SC dissolved in saline solution was given as a single dose (1 mg/kg) 60 min before the operation. Renal histology was analyzed by scoring the tubular damage and neutrophil infiltration. Tissue myeloperoxidase activity and lipid peroxidation were analyzed. The histological damage and the neutrophil infiltration induced by I/R were significantly less in the SC+I/R group (p = 0.004 and p = 0.003, respectively). Pretreatment with SC significantly diminished the tissue myeloperoxidase activity, indicating the prevention of the neutrophil sequestration into the kidney in the SC+I/R group (p = 0.004); however, it did not result in any changes in lipid peroxidation. Our results in a rat model of ischemia-reperfusion indicate that pre-ischemic treatment with sildenafil citrate can significantly attenuate ischemia/reperfusion-induced renal injury by decreasing leukocyte infiltration.

Comparison of two models for evaluation histopathology of experimental renal ischemia

Renal ischemia/reperfusion (I/R) injury is one of the frequent causes of acute renal failure (ARF) due to the complex, interrelated sequence of events, that result in damage to and death of kidney cells. Cells of the proximal tubular epithelium are especially susceptible to I/R injury, leading to acute tubular necrosis, which plays a pivotal role in the pathogenesis of ARF. Several models have been explicated to assess morphological changes, including those of Jabonski et al. and Goujon et al. We compared the 2 models for histopathological evaluation of 30- or 120-minute periods of renal ischemia followed by 24-hour reperfusion in rats. Several changes were observed after application of the 2 models: proximal tubular cell necrosis, loss of brush border, vacuolization, denudation of tubular basement membrane as a consequence of flattening of basal cells, and presence of intratubular exfoliated cells in the lumen of proximal convoluted tubules at various stages of degeneration (karyorexis, kariopyknosis and karyolysis). Evaluating tubular lesions after 2 periods of experimental ischemia with light microscopy allowed us to conclude that the Goujon classification better characterized the main changes in cortical renal tubules after ischemia.