Ischemic postconditioning inhibits apoptosis after renal ischemia/reperfusion injury in rat

The role of non-protein-coding RNAs in ischemic acute kidney injury

Acute kidney injury (AKI) is a condition characterized by a rapid decline in kidney function within a span of 48 hours. It is influenced by various factors including inflammation, oxidative stress, excessive calcium levels within cells, activation of the renin-angiotensin system, and dysfunction in microcirculation. Ischemia-reperfusion injury (IRI) is recognized as a major cause of AKI; however, the precise mechanisms behind this process are not yet fully understood and effective treatments are still needed. To enhance the accuracy of diagnosing AKI during its early stages, the utilization of innovative markers is crucial. Numerous studies suggest that certain noncoding RNAs (ncRNAs), such as long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), play a central role in regulating gene expression and protein synthesis. These ncRNAs are closely associated with the development and recovery of AKI and have been detected in both kidney tissue and bodily fluids. Furthermore, specific ncRNAs may serve as diagnostic markers and potential targets for therapeutic interventions in AKI. This review aims to summarize the functional roles and changes observed in noncoding RNAs during ischemic AKI, as well as explore their therapeutic potential.

Trimetazidine an emerging paradigm in renal therapeutics: Preclinical and clinical insights

Trimetazidine (TMZ) is a well-known anti-ischemic agent used for the treatment of angina pectoris. In the past decades, the efficacy of this drug has been tested in a wide range of kidney injuries, including drug-induced nephrotoxicity (DIN), radio-contrast agent-induced nephropathy, and surgically induced renal ischemic injury. TMZhas renoprotective effects by attenuating oxidative stress, inflammatory cytokine release, maintaining oxygen and energy balance. Moreover, TMZ administration prevented kidney graft rejection in the porcine model by suppressing the infiltration of mononuclear cells, preserving mitochondrial functions, and maintaining Ca+ homeostasis. In DIN and diabetic kidney diseases,TMZ treatment prevents renal injury by inactivating immune cells, attenuating renal fibrosis, inflammation, apoptosis, and histological abnormalities. Interestingly, the clinical therapeutic efficacy of TMZ has also been documented in pre-existing kidney disease patients undergoing contrast exposure for diagnostic intervention. However, the mechanistic insights into the TMZ mediated renoprotective effects in other forms of renal injuries, including type-2 diabetes, drug-induced nephrotoxicity, and hypertension-induced chronic kidney diseases, remain uninvestigated and incomplete. Moreover, the clinical utility of TMZ as a renoprotective agent in radio-contrast-induced nephrotoxicity needs to be tested in a large patient population. Nevertheless, the available pieces of evidence suggest that TMZ is a promising and emerging renal therapy for the treatment and management of kidney diseases of variable etiologies. This review discusses the various pre-clinical and clinical findings and provides mechanistic insights into the TMZ mediated beneficial effects in various kidney diseases.

MiR-7a-5p Attenuates Hypoxia/Reoxygenation-Induced Cardiomyocyte Apoptosis by Targeting VDAC1

MicroRNA-7a-5p (miR-7a-5p) is closely related to apoptosis and plays an important role in ischemia/reperfusion (I/R) injury. Whether miR-7a-5p is involved in hypoxia/reoxygenation (H/R)-induced cardiomyocyte apoptosis is unknown. Therefore, this study aims to evaluate the role of miR-7a-5p in cardiomyocyte H9C2 cells in response to H/R stimulation. The results of RT-qPCR demonstrated that the expression level of miR-7a-5p was significantly down-regulated in H/R-treated H9C2 cells. MTT assay revealed that the cell viability was notably decreased in H/R group. Flow cytometric analysis found that the ratio of apoptotic cells was increased markedly following H/R. Enforced miR-7a-5p expression increased cell viability and decreased the apoptotic rate. Western blot analysis revealed that the expressions of pro-apoptotic proteins cleaved caspase-3 and Bax were down-regulated, while the expression of anti-apoptotic protein Bcl-2 was up-regulated in H/R-treated H9C2 cells transfected with miR-7a-5p mimic. On the contrary, miR-7a-5p downexpressing promoted apoptosis in H/R-treated H9C2 cells. Furthermore, the bioinformatics prediction manifested voltage-dependent anion channel 1 (VDAC1) was a potential target for miR-7a-5p, and dual-luciferase reporter assay confirmed that miR-7a-5p targeted VDAC1 3' untranslated regions, which leads to the repressed expressions of VDAC1 mRNA and protein. Knockdown of VDAC1 potentiated the protective effects of miR-7a-5p against H/R-induced cell injury. In conclusion, our results demonstrated that miR-7a-5p is involved in H/R-induced cardiomyocyte apoptosis through targeting VDAC1. MiR-7a-5p/VDAC1 axis might be utilized as hopeful biomarkers to reveal the potential mechanism of myocardial I/R injury.

Gastrin Attenuates Renal Ischemia/Reperfusion Injury by a PI3K/Akt/Bad-Mediated Anti-apoptosis Signaling

Ischemic/reperfusion (I/R) injury is the primary cause of acute kidney injury (AKI). Gastrin, a gastrointestinal hormone, is involved in the regulation of kidney function of sodium excretion. However, whether gastrin has an effect on kidney I/R injury is unknown. Here we show that cholecystokinin B receptor (CCKBR), the gastrin receptor, was significantly up-regulated in I/R-injured mouse kidneys. While pre-administration of gastrin ameliorated I/R-induced renal pathological damage, as reflected by the levels of serum creatinine and blood urea nitrogen, hematoxylin and eosin staining and periodic acid-Schiff staining. The protective effect could be ascribed to the reduced apoptosis for gastrin reduced tubular cell apoptosis both in vivo and in vitro. In vitro studies also showed gastrin preserved the viability of hypoxia/reoxygenation (H/R)-treated human kidney 2 (HK-2) cells and reduced the lactate dehydrogenase release, which were blocked by CI-988, a specific CCKBR antagonist. Mechanistically, the PI3K/Akt/Bad pathway participates in the pathological process, because gastrin treatment increased phosphorylation of PI3K, Akt and Bad. While in the presence of wortmannin (1 μM), a PI3K inhibitor, the gastrin-induced phosphorylation of Akt after H/R treatment was blocked. Additionally, wortmannin and Akt inhibitor VIII blocked the protective effect of gastrin on viability of HK-2 cells subjected to H/R treatment. These studies reveals that gastrin attenuates kidney I/R injury via a PI3K/Akt/Bad-mediated anti-apoptosis signaling. Thus, gastrin can be considered as a promising drug candidate to prevent AKI.

Protective effect of renal ischemic postconditioning in renal ischemic-reperfusion injury

Background

Renal ischemic postconditioning (RIPo) can protect the kidney from renal ischemia/reperfusion injury (RIRI). However, the underlying molecular mechanisms for RIPo in renal protection remained elusive. This study aimed to investigate the renoprotective effects of RIPo in an RIR rat model.

Method

The Sprague Dawley (SD) rats were randomly divided into three groups respectively: sham group, the RIRI group and the RIPo group. The levels of proteinuria, blood urea nitrogen (BUN), creatinine (Cr), malondialdehyde (MDA), superoxide dismutase (SOD), lactate dehydrogenase (LDH), reactive oxidative species (ROS), interleukins (IL)-6, IL-1β, and IL-18 were measured by ELISA. Apoptotic cells and caspase-3 positive cells were detected by TUNEL assay and immunohistochemistry, respectively. The protein expressive levels of caspase-3, caspase-9, ATG8, Beclin1, p62, LC3-II, P-P13K, P-AKT and P-mTOR were detected by western blot.

Results

Our results showed that pretreatment with RIPo significantly reduced ischemic pathological and morphological changes. The levels of proteinuria, BUN, and Cr were also significantly reduced by RIPo pretreatment. Besides, ATG8, LC3-II and Beclin-1 were upregulated in the RIPo group, but p62 was downregulated. Moreover, RIPo pretreatment resulted in higher levels of phosphorylated PI3K, Akt, and mTOR. These results showed that RIPo protects the kidneys of rats from IRI with suppressed apoptosis and activated autophagy. Mechanically, the activated PI3K/AKT/mTOR signaling pathway were activated.

Conclusions

Collectively, our data demonstrated that RIPo could suppress Inflammatory response, oxidative stress, apoptosis and induce autophagy as well as activate the PI3K/AKT/mTOR pathway, which may play an important role in renal protection against RIRI.

Remote ischemic conditioning enhances heart and brain antioxidant defense

Background

Ischemia-reperfusion injury contributes to morbidity after revascularization procedures. Along with early reperfusion, tissue conditioning by alternating intervals of brief ischemia-reperfusion episodes is considered the best approach to limit tissue damage. Remote ischemic conditioning is conducted remotely, in tissues other than those under ischemia. Despite this, remote ischemic conditioning protection mechanisms are poorly understood, which can lead to misapplication.

Objectives

To assess whether remote ischemic conditioning works in the heart and brain through enhancement of cells’ antioxidant defenses and whether the response is sustained or temporary.

Methods

Twenty-one male Wistar rats were assigned to three groups (n = 7): SHAM: same procedure as the other groups, but no remote ischemic conditioning was carried out. RIC 10: heart and brain were harvested 10 minutes after the remote ischemic conditioning protocol. RIC 60: heart and brain were harvested 60 minutes after the remote ischemic conditioning protocol. The remote ischemic conditioning protocol consisted of 3 cycles of 5 min left hindlimb ischemia followed by 5 min left hindlimb perfusion, lasting 30 min in total. Heart and brain samples were used to measure the tissue antioxidant capacity.

Results

Remote ischemic conditioning increased heart and brain antioxidant capacity after 10 minutes (0.746 ± 0.160/0.801 ± 0.227 mM/L) when compared to SHAM (0.523 ± 0.078/0.404 ± 0.124 mM/L). No enhancement of heart or brain antioxidant capacity was detected 60 minutes after remote ischemic conditioning (0.551 ± 0.073/0.455 ± 0.107 mM/L).

Conclusions

Remote ischemic conditioning temporarily enhances heart and brain antioxidant defenses in male Wistar rats.

Protective effect of dapsone against renal ischemia-reperfusion injury in rat

Background: Ischemia/reperfusion can cause injury to tissues and compromise functionality of organs due to inflammatory processes. Significantly, development of these effects in kidney tissue has been a challenging issue that leads to acute renal injury. In this study, anti-inflammatory, anti-oxidative, and protective features of dapsone on kidney ischemia/reperfusion injury were investigated.Material and methods: Renal ischemia was induced in rats by bilateral renal arteries clamping for 45 min followed by 24 h reperfusion phase. The effects of different doses of dapsone (1, 3, 10 mg/kg) on ischemia/reperfusion injury in kidney tissue were investigated by targeting BUN, Creatinine, LDH, MDA, MPO, IL-1β, TNF-α, and NFκB. In addition histopathological examination was performed by H&E staining method.Results and discussion: Comparing the findings of this study showed significant reduction in BUN and LDH in 10 mg/kg dapsone received groups, and Cr, MDA, and MPO in 3 mg/kg dapsone received groups. The serum level of TNF-α was significantly decreased with both doses of 3 and 10 mg/kg dapsone. The same results were observed in the serum level of IL-1β and NFκB. Besides, remarkable improvement in histological damages was also observed with dapsone treatment.Conclusion: These results support the hypothesis that the positive effects of dapsone on the renal ischemia/reperfusion injury are mediated by modulating inflammatory cascades.

Thymoquinone and curcumin combination protects cisplatin-induced kidney injury, nephrotoxicity by attenuating NFκB, KIM-1 and ameliorating Nrf2/HO-1 signalling

This study evaluates the protective effects of Thymoquinone (Tq) and Curcumin (Cur) in models of cisplatin-induced renal toxicity. Proliferation studies were carried out in HEK-293 cells. Cisplatin(ip) 5 mg/kg BW was used to induce renal injury in Sprague-Dawley rats. 50 mg/kg BW Tq + 100 mg/kg BW Cur, with or without cisplatin-treatment were administered for 5 days. Tq + Cur combination synergistically reduced the proliferation inhibition of HEK-293 cells resulted from cisplatin treatment and brought down cisplatin-induced apoptosis in these cells. In vitro studies revealed serum levels of BUN, creatinine, CK and pro-inflammatory cytokines like TNF-α, IL-6 and MRP-1 to be elevated in the cisplatin-treated group while reducing glomerular filtration rate. Tq + Cur treatment significantly improved these conditions. The antioxidant enzyme levels and mitochondrial ATPases were restored upon treatment, which were lessened in the cisplatin-treated group. Cisplatin induced the expression of KIM-1, which was brought down by the combination treatment. Tq + Cur treatment increased the expressions of phosphorylated Akt, Nrf2 and HO-1 proteins while decreasing the levels of cleaved caspase 3 and NFκB in kidney homogenates. In summary, Tq + Cur had protective effects on cisplatin-induced nephrotoxicity and renal injury, which could be mediated by up-regulation of survival signals like Akt, Nrf2/HO-1 and attenuation of KIM-1, NFκB.

Bone marrow mesenchymal stem cell-secreted exosomes carrying microRNA-125b protect against myocardial ischemia reperfusion injury via targeting SIRT7

MicroRNA-125b (miR-125b) reduces myocardial infarct area and restrains myocardial ischemia reperfusion injury (I/R). In this study, we aimed to investigate the effect of bone marrow mesenchymal stem cell (BMSC)-derived exosomes carrying miR-125b on I/R rats. The myocardial I/R model in rats was constructed by ligation of the left anterior descending coronary artery (LAD). Rats were randomly divided into I/R and Sham group. Lv-cel-miR-67 (control) or Lv-miR-125b was transfected into BMSCs. Exosomes were extracted from transfected BMSCs, and separately named BMSC-Exo-67, BMSC-Exo-125b, and BMSC-Exo. MTT assay and flow cytometry were used to detect the viability and apoptosis of I/R myocardium cells, respectively. The expression of cell apoptosis proteins and the levels of inflammatory factors were examined by Western blot and ELISA assay, respectively. The target relationship between miR-125b and SIRT7 was predicted by using StarBase3.0, and was confirmed by using dual-luciferase reporter gene assay. qRT-PCR, immunohistochemistry staining, and Western blot were used to evaluate the expression of SIRT7 in myocardium tissues in I/R rats. BMSC-derived exosomes were successfully isolated and identified by TEM and positive expression of CD9 and CD63. The expression of miR-125b was down-regulated in I/R myocardium tissues and cells. BMSC-Exo-125b significantly up-regulated miR-125b in I/R myocardium cells. The intervention of BMSC-Exo-125b significantly increased the cell viability, decreased the apoptotic ratio, down-regulated Bax and caspase-3, up-regulated Bcl-2, and decreased the levels of IL-1β, IL-6, and TNF-α in I/R myocardium cells. SIRT7 was a target of miR-125b, and BMSC-Exo-125b significantly down-regulated SIRT7 in myocardium cells. In addition, the injection of BMSC-Exo-125b alleviated the pathological damages and down-regulated SIRT7 in myocardium tissues of I/R rats. BMSC-derived exosomes carrying miR-125b protected against myocardial I/R by targeting SIRT7.

Protective Effects of miR-126 Specifically Regulates Nrf2 Through Ischemic Postconditioning on Renal Ischemia/Reperfusion Injury in Mice

The protective effects of ischemic postconditioning on renal ischemia/reperfusion injury in mice and the role of miR-126 and Nrf2 signaling pathway in the process were the focus of this study. Mice were classified into 5 groups: sham-operation, I/R6h, I/R24h, postconditioning (POC), and miR-126 agomir. Serum creatinine, renal histopathology changes, and oxidative stress were examined. The expression of miR-126 and Nrf2 were detected. We also treated NRK52E cells with hypoxia reoxygenation. The I/R group showed significant renal injury and increased generation of oxidative stress. However, the severity of renal injury and oxidative stress were markedly attenuated in the POC group. MiR-126 was downregulated, and Nrf2 was upregulated in NRK52E cells subjected to hypoxia/reoxygenation (H/R) and in mouse kidneys subjected to POC. Oxidative stress was higher and Nrf2 was lower in the mouse miR-126 agomir group; apoptosis were higher in H/R-treated NRK52E cells transfected with Nrf2 siRNA and lower in anti-miR-126. These findings demonstrate that after renal ischemic postconditioning, miR-126 inhibits oxidative stress by inducing Nrf2 and suppresses injury.

Costimulation Blockade in Transplantation

T cells play a pivotal role in orchestrating immune responses directed against a foreign (allogeneic) graft. For T cells to become fully activated, the T-cell receptor (TCR) must interact with the major histocompatibility complex (MHC) plus peptide complex on antigen-presenting cells (APCs), followed by a second "positive" costimulatory signal. In the absence of this second signal, T cells become anergic or undergo deletion. By blocking positive costimulatory signaling, T-cell allo-responses can be aborted, thus preventing graft rejection and promoting long-term allograft survival and possibly tolerance (Alegre ML, Najafian N, Curr Mol Med 6:843-857, 2006; Li XC, Rothstein DM, Sayegh MH, Immunol Rev 229:271-293, 2009). In addition, costimulatory molecules can provide negative "coinhibitory" signals that inhibit T-cell activation and terminate immune responses; strategies to promote these pathways can also lead to graft tolerance (Boenisch O, Sayegh MH, Najafian N, Curr Opin Organ Transplant 13:373-378, 2008). However, T-cell costimulation involves an incredibly complex array of interactions that may act simultaneously or at different times in the immune response and whose relative importance varies depending on the different T-cell subsets and activation status. In transplantation, the presence of foreign alloantigen incites not only destructive T effector cells but also protective regulatory T cells, the balance of which ultimately determines the fate of the allograft (Lechler RI, Garden OA, Turka LA, Nat Rev Immunol 3:147-158, 2003). Since the processes of alloantigen-specific rejection and regulation both require activation of T cells, costimulatory interactions may have opposing or synergistic roles depending on the cell being targeted. Such complexities present both challenges and opportunities in targeting T-cell costimulatory pathways for therapeutic purposes. In this chapter, we summarize our current knowledge of the various costimulatory pathways in transplantation and review the current state and challenges of harnessing these pathways to promote graft tolerance (summarized in Table 10.1).

Apoptosis repressor with caspase recruitment domain deficiency accelerates ischemia/reperfusion (I/R)-induced acute kidney injury by suppressing inflammation and apoptosis: The role of AKT/mTOR signaling

Acute kidney injury (AKI) is a significant medical problem worldwide. Ischemia-reperfusion (I/R) injury of the kidney is a major cause of AKI. However, the pathogenesis that contributes to renal I/R injury is still unclear. Apoptosis repressor with caspase recruitment domain (ARC) is abundantly expressed in various tissues, and has been reported to play a strong protective role during pathological processes. Our results indicated that ARC expression was decreased in the reperfused kidneys. ARC deficiency markedly accelerated renal dysfunction, promoted reperfusion-regulated tubular epithelial cell apoptosis, and enhanced the vulnerability of kidney to I/R damage. Furthermore, in the kidney samples of mice underwent renal I/R injury, ARC knockout significantly accelerated the expression levels of inflammatory factors, including interleukin (IL)-1β, IL-6, tumor necrosis factor a (TNF-α), monocyte chemoattractant protein-1 (MCP-1) and IL-2. In addition, renal I/R injury-induced apoptosis was further exacerbated in ARC-deficient mice through promoting the expression of cleaved Caspase-3 and poly (ADP-ribose) polymerase (PARP). From the molecular level, ARC deletion obviously accelerated mitochondrial injury, as evidenced by the further decreased adenosine triphosphate (ATP) levels and mitochondrial potential in hypoxia-reoxygenation (H/R)-treated cells. Moreover, ARC knockout exacerbated AKI through activating phosphorylated protein kinase B (AKT), mammalian target of Rapamycin (mTOR) and p53, whereas reducing phosphorylated glycogen synthase kinase 3β (GSK3β). Of note, blocking AKT/mTOR signaling markedly attenuated inflammation, mitochondrial damage and apoptosis stimulated by H/R in ARC knockdown cells. In summary, our results suggested that ARC played a pivotal role in the pathogenesis of AKI induced by renal I/R operation through regulating AKT/mTOR signaling.

Comprehensive circRNA expression profile during ischemic postconditioning attenuating hepatic ischemia/reperfusion injury

Ischemic postconditioning (IPO) attenuates hepatic ischemia/reperfusion (I/R) injury. The aim of this study was to explore the role of circular RNAs (circRNAs) in the protective mechanism of IPO. In this study, microarray hybridization analysis was performed to determine the circRNA expression profile. Briefly, a total of 1599 dysregulated circRNAs were detected. The competitive endogenous RNA (ceRNA) network, including 6 circRNAs, 47 miRNAs and 90 mRNAs, indicated that the potential “housekeeping” function of circRNAs is dysregulated in hepatic I/R injury. Based on the validation results of selected circRNAs, miRNAs and mRNAs following qRT-PCR amplification, the mmu_circRNA_005186-miR-124-3p-Epha2 pathway was constructed. Dual-luciferase reporter analysis showed that miR-124-3p interacted directly with mmu_circRNA_005186 and Epha2 through the predicted binding sites, which suggested that mmu_circRNA_005186, serving as a miRNA sponge for miR-124-3p, regulated the expression of Epha2. Functionally, we explored the mechanism of mmu_circRNA_005186 in LPS-treated RAW264.7 cells which simulated the inflammation in hepatic I/R injury. We found that mmu_circRNA_005186 silencing attenuated the LPS-induced inflammation and was associated with miR-124-3p upregulation and Epha2 downregulation. Our study is the first to show that circRNAs are closely related to hepatic I/R injury and IPO and suggests that targeting mmu_circRNA_005186-miR-124-3p-Epha2 pathway might attenuate hepatic I/R injury.

Gene Expression Profiling in Ischemic Postconditioning to Alleviate Mouse Liver Ischemia/Reperfusion Injury

Ischemic postconditioning (IPO) attenuates hepatic ischemia/reperfusion (I/R) injury. However, little is known about the underlying biological pathophysiology, which could be, at least in part, informed by exploring the transcriptomic changes using next-generation RNA sequencing (RNA-Seq). In this study, 18 mice (C57BL/6) were involved and randomly assigned to three groups: normal (n=6), I/R (n=6, subjected to 70% hepatic I/R), and IR+IPO (n=6, applying IPO to mice with I/R injury). We randomly selected 3 mice per group and extracted their liver tissues for next-generation RNA-Seq. We performed a bioinformatics analysis for two comparisons: normal vs. I/R and I/R vs. IR+IPO. From the analysis, 2416 differentially expressed genes (DEGs) were identified (p < 0.05 and fold change ≥ 1.5). Gene ontology (GO) analysis revealed that these genes were mainly related to cellular metabolic processes, nucleic acids and protein binding processes. The enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for the DEGs were the mitogen-activated protein kinase (MAPK), IL-17 signalling pathway, regulating pluripotency of stem cells, and insulin resistance pathway. Validation of 12 selected DEGs by qRT-PCR showed that Cyr61, Atf3, Nr4a1, Gdf15, Osgin1, Egr1, Epha2, Dusp1, Dusp6, Gadd45a and Gadd45b were significantly amplified. Finally, a protein-protein interaction (PPI) network constructed to determine interactions of these 11 DEGs. In summary, by exploring gene expression profiling in regard to hepatic I/R and IPO using next-generation RNA-Seq, we suggested a few progression-related genes and pathways, providing some clues for future experimental research.

A “self-accelerating endosomal escape” siRNA delivery nanosystem for significantly suppressing hyperplasia via blocking the ERK2 pathway

Highly efficient ERK2 silencing in VSMCs via a “self-accelerating endosomal escape” siRNA transport nanosystem.

Cystathionine γ-Lyase Is Involved in the Renoprotective Effect of Brief and Repeated Ischemic Postconditioning After Renal Ischemia/Reperfusion Injury in Diabetes Mellitus

BACKGROUND

The aim of this study was to determine whether the protective effects of brief and repeated ischemic postconditioning (IPoC) are associated with the modulation of cystathionine γ-lyase (CSE) expression after renal ischemia/reperfusion (I/R) injury in diabetes mellitus (DM).

METHODS

We subjected diabetic rats to 45 minutes of ischemia followed by reperfusion at 24 hours. Before reperfusion, diabetic rats were treated with 3 cycles of 6 seconds of reperfusion, followed by 6 seconds of ischemia. DL-Propargylglycine (PAG, a CSE inhibitor) was administered to the diabetic rats to investigate its effects on the severity of renal I/R injury in diabetes mellitus (DM). Blood samples and left kidneys were collected for the measurement of blood urea nitrogen (BUN) and serum creatinine (SCr) levels and renal pathologic changes. Western blot and immunochemistry techniques were also performed for the localization of CSE. Levels of superoxidase dismutase (SOD), malonyldialdehyde (MDA), tumor necrosis-alpha (TNF-α), and hydrogen sulfide (H₂S) were quantified using commercially available kits.

RESULTS

The results showed that BUN and SCr levels increased on renal ischemia/reperfusion injury (RI/RI) in the DM group. Diabetic rats treated with IPoC exhibited significantly less renal damage on I/R. Kit measurements showed that IPoC could markedly inhibit the levels of MDA and TNF-α and also improve SOD and H₂S levels. Western blot and immunochemistry showed that expression of CSE was downregulated on I/R in the DM group and IPoC upregulated CSE expression, whereas PAG treatment resulted in opposite effects.

CONCLUSION

Our findings show that brief and repeated IPoC increased the expression of CSE after I/R in DM, and the modulation of CSE may underlie the renoprotective effect of IPoC.

Kidney ischemia and reperfunsion syndrome: effect of lidocaine and local postconditioning

Objective:

to evaluate the effects of blocking the regulation of vascular tone on the ischemia and reperfusion syndrome in rats through the use of lidocaine in the postconditioning technique.

Methods:

we randomized 35 rats into seven groups of five animals: Group 1- Control; Group 2- Ischemia and Reperfusion; Group 3- Ischemia, Reperfusion and Saline; Group 4- Ischemic Postconditioning; Group 5- Ischemic Postconditioning and Saline; Group 6- Lidocaine; Group 7- Ischemic Postconditioning and Lidocaine. Except for the control group, all the others were submitted to renal ischemia for 30 minutes. In postconditioning groups, we performed ischemia and reperfusion cycles of five minutes each, applied right after the main ischemia. In saline and lidocaine groups, we instilled the substances at a rate of two drops per minute. To compare the groups, we measured serum levels of urea and creatinine and also held renal histopathology.

Results:

The postconditioning and postconditioning + lidocaine groups showed a decrease in urea and creatinine values. The lidocaine group showed only a reduction in creatinine values. In histopathology, only the groups submitted to ischemic postconditioning had decreased degree of tubular necrosis.

Conclusion:

Lidocaine did not block the effects of postconditioning on renal ischemia reperfusion syndrome, and conferred better glomerular protection when applied in conjunction with ischemic postconditioning.

Objetivo:

avaliar os efeitos do bloqueio da regulação do tônus vascular por meio do uso da lidocaína na técnica de pós-condicionamento isquêmico na síndrome de isquemia e reperfusão renal em ratos.

Métodos:

trinta e cinco ratos foram randomizados em sete grupos de cinco animais: Grupo 1- Controle; Grupo 2- Isquemia e Reperfusão; Grupo 3- Isquemia, Reperfusão e Solução Salina; Grupo 4- Pós-condicionamento Isquêmico; Grupo 5- Pós-condicionamento Isquêmico e Solução Salina; Grupo 6- Lidocaína; Grupo 7- Pós-condicionamento Isquêmico e lidocaína. Com exceção do grupo controle, todos os demais foram submetidos à isquemia renal de 30 minutos. Nos grupos de pós-condicionamento, foi realizado o ciclo de isquemia e reperfusão de cinco minutos cada, aplicado logo após a isquemia principal. Nos grupos salina e lidocaína foram instiladas as substâncias numa taxa de duas gotas por minuto. Para comparar os grupos, foram dosados os níveis séricos de ureia e creatinina e análise histopatológica renal.

Resultados:

os grupos pós-condicionamento e pós-condicionamento + lidocaína apresentaram uma redução nos valores de ureia e creatinina. O grupo lidocaína apresentou apenas uma redução nos valores de creatinina. Na análise histopatológica, apenas os grupos submetidos ao pós-condicionamento isquêmico apresentaram redução do grau de necrose tubular.

Conclusão:

a lidocaína não bloqueou os efeitos do pós-condicionamento na síndrome de isquemia e reperfusão renal, mas conferiu melhor na proteção glomerular quando aplicada em conjunto com o pós-condicionamento isquêmico.

Perconditioning combined with postconditioning on kidney ischemia and reperfusion

Purpose:

To evaluate if combination of perconditioning and postconditioning provides improved renal protection compared to perconditioning alone in a model of renal reperfusion injury.

Methods:

Thirty rats were assigned into 6 groups: normality; sham; ischemia and reperfusion; postconditioning; perconditioning; perconditioning + postconditioning. Animals were subjected to right nephrectomy and left renal ischemia for 30 minutes. Postconditioning consisted of 3 cycles of 5 min renal perfusion followed by 5 min of renal ischemia after major ischemic period. Perconditioning consisted of 3 cycles of 5 min hindlimb ischemia followed by 5 min of hindlimb perfusion contemporaneously to renal major ischemic period. After 24 hours, kidney was harvested and blood collected to measure urea and creatinine.

Results:

Perconditioning obtained better values for creatinine and urea level than only postconditioning (p<0.01); performing both techniques contemporaneously had no increased results (p>0.05). Regarding tissue structure, perconditioning was the only technique to protect the glomerulus and tubules (p<0.05), while postconditioning protected only the glomerulus (p<0.05). Combination of both techniques shows no effect on glomerulus or tubules (p>0.05).

Conclusions:

Perconditioning had promising results on ischemia and reperfusion induced kidney injury, enhanced kidney function and protected glomerulus and tubules. There was no additive protection when postconditioning and perconditioning were combined.

Application of ischemic postconditioning's algorithms in tissues protection: response to methodological gaps in preclinical and clinical studies

Ischaemic postconditioning (IPostC) was introduced for the first time by Zhao et al. as a feasible method for reduction of myocardial ischaemia–reperfusion (IR) injury. The cardioprotection by this protocol has been extensively evaluated in various species. Then, further research revealed that IPostC is a safe and convenient approach in limiting IR injury of non‐myocardial tissues such as lung, liver, kidney, intestine, skeletal muscle, brain and spinal cord. IPostC has been conducted with different algorithms, resulting in diverse effects. The possible important factors leading to these differences are the difference in activation levels of signalling pathways and protective mediators by any algorithm, presence or absence of IPostC effectors in each tissue, or intrinsic characteristics of the tissues as well as the methodological biases. Also, the conflicting results have been shown with the application of the same algorithm of IPostC in certain tissues or animal species. The effectiveness of IPostC may depend upon various parameters including the species and the tissues characteristics. For example, different heart rates and metabolic rates of the species and unequal amounts of perfusion and blood flow of the tissues should be considered as the important determinants of IPostC effectiveness and should be thought about in designing IPostC algorithms for future studies. Due to these discrepancies, there is still no optimal single IPostC algorithm applicable to any tissue or any species. This issue is the main topic of the present article.

The Impact of Remote Ischemic Preconditioning on Arterial Stiffness and Heart Rate Variability in Patients with Angina Pectoris

Remote ischemic preconditioning (RIPC) is the set of ischemia episodes that protects against subsequent periods of prolonged ischemia through the cascade of adaptive responses; however, the mechanisms of RIPC are not entirely clear. Here, we aimed to study the impact of RIPC in patients with stable angina pectoris and compare it with healthy individuals with respect to arterial stiffness and heart rate variability. In the randomized, sham-controlled, crossover blind design study, a group of 30 coronary heart disease (CHD) patients (63.9 ± 1.6 years) with stable angina pectoris NYHA II-III and a control group of 20 healthy individuals (58.2 ± 2.49) were both randomly allocated for remote RIPC or sham RIPC. Arterial stiffness, pulse wave velocity (Spygmacor, Australia), and heart rate variability (HRV) were recorded before and after the procedure followed by the crossover examination. In the group of healthy individuals, RIPC showed virtually no impact on the cardiovascular parameters, while, in the CHD group, the systolic and central systolic blood pressure, central pulse pressure, and augmentation decreased, and total power of HRV improved. We conclude that ischemic preconditioning reduces not only systolic blood pressure, but also reduces central systolic blood pressure and improves arterial compliance and heart rate modulation reserve, which may be associated with the antianginal effect of preconditioning.

Preclinical Evidence for the Efficacy of Ischemic Postconditioning against Renal Ischemia-Reperfusion Injury, a Systematic Review and Meta-Analysis

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is a major cause of kidney damage after e.g. renal surgery and transplantation. Ischemic postconditioning (IPoC) is a promising treatment strategy for renal IRI, but early clinical trials have not yet replicated the promising results found in animal studies.

METHOD

We present a systematic review, quality assessment and meta-analysis of the preclinical evidence for renal IPoC, and identify factors which modify its efficacy.

RESULTS

We identified 39 publications studying >250 control animals undergoing renal IRI only and >290 animals undergoing renal IRI and IPoC. Healthy, male rats undergoing warm ischemia were used in the vast majority of studies. Four studies applied remote IPoC, all others used local IPoC. Meta-analysis showed that both local and remote IPoC ameliorated renal damage after IRI for the outcome measures serum creatinine, blood urea nitrogen and renal histology. Subgroup analysis indicated that IPoC efficacy increased with the duration of index ischemia. Measures to reduce bias were insufficiently reported.

CONCLUSION

High efficacy of IPoC is observed in animal models, but factors pertaining to the internal and external validity of these studies may hamper the translation of IPoC to the clinical setting. The external validity of future animal studies should be increased by including females, comorbid animals, and transplantation models, in order to better inform clinical trial design. The severity of renal damage should be taken into account in the design and analysis of future clinical trials.

Antiapoptotic Effect of Recombinant HMGB1 A-box Protein via Regulation of microRNA-21 in Myocardial Ischemia-Reperfusion Injury Model in Rats

The ~80 amino acid A box DNA-binding domain of high mobility group box 1 (HMGB1) protein antagonizes proinflammatory responses during myocardial ischemia reperfusion (I/R) injury. The exact role of microRNA-21 (miR-21) is unknown, but its altered levels are evident in I/R injury. This study examined the roles of HMGB1 A-box and miR-21 in rat myocardial I/R injury model. Sixty Sprague-Dawley rats were randomly divided into six equal groups: (1) Sham; (2) I/R; (3) Ischemic postconditioning (IPost); (4) AntagomiR-21 post-treatment; (5) Recombinant HMGB1 A-box pretreatment; and (6) Recombinant HMGB1 A-box + antagomiR-21 post-treatment. Hemodynamic indexes, arrhythmia scores, ischemic area and infarct size, myocardial injury, and related parameters were studied. Expression of miR-21 was detected by real-time quantitative polymerase chain reaction (qRT-PCR) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was used to quantify apoptosis. Left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), maximal rate of pressure rise (+dp/dtmax), and decline (-dp/dtmax) showed clear reduction upon treatment with recombinant HMGB1 A-box. Arrhythmia was relieved and infarct area decreased in the group pretreated with recombinant HMGB1 A-box, compared with other groups. Circulating lactate dehydrogenase (LDH) and malondialdehyde (MDA) levels increased in response to irreversible cellular injury, while creatine kinase MB isoenzymes (CK-MB) and superoxide dismutase (SOD) activities were reduced in the I/R group, which was reversed following recombinant HMGB1 A-box treatment. Interestingly, pretreatment with recombinant HMGB1 A-box showed the most dramatic reductions in miR-21 levels, compared with other groups. Significantly reduced apoptotic index (AI) was seen in recombinant HMGB1 A-box pretreatment group and recombinant HMGB1 A-box + antagomiR-21 post-treatment group, with the former showing a more dramatic lowering in AI than the latter. Bax, caspase-8, and CHOP showed reduced expression, and Bcl-2 and p-AKT levels were upregulated in recombinant HMGB1 A-box pretreatment group. Thus, recombinant HMGB1 A-box treatment protects against I/R injury and the mechanisms may involve inhibition of miR-21 expression.

No Effect of Remote Ischemic Conditioning Strategies on Recovery from Renal Ischemia-Reperfusion Injury and Protective Molecular Mediators

Ischemia-reperfusion injury (IRI) is the major cause of acute kidney injury. Remote ischemic conditioning (rIC) performed as brief intermittent sub-lethal ischemia and reperfusion episodes in a distant organ may protect the kidney against IRI. Here we investigated the renal effects of rIC applied either prior to (remote ischemic preconditioning; rIPC) or during (remote ischemic perconditioning; rIPerC) sustained ischemic kidney injury in rats. The effects were evaluated as differences in creatinine clearance (CrCl) rate, tissue tubular damage marker expression, and potential kidney recovery mediators. One week after undergoing right-sided nephrectomy, rats were randomly divided into four groups: sham (n = 7), ischemia and reperfusion (IR; n = 10), IR+rIPC (n = 10), and IR+rIPerC (n = 10). The rIC was performed as four repeated episodes of 5-minute clamping of the infrarenal aorta followed by 5-minute release either before or during 37 minutes of left renal artery clamping representing the IRI. Urine and blood were sampled prior to ischemia as well as 3 and 7 days after reperfusion. The kidney was harvested for mRNA and protein isolation. Seven days after IRI, the CrCl change from baseline values was similar in the IR (δ: 0.74 mL/min/kg [-0.45 to 1.94]), IR+rIPC (δ: 0.21 mL/min/kg [-0.75 to 1.17], p > 0.9999), and IR+rIPerC (δ: 0.41 mL/min/kg [-0.43 to 1.25], p > 0.9999) groups. Kidney function recovery was associated with a significant up-regulation of phosphorylated protein kinase B (pAkt), extracellular regulated kinase 1/2 (pERK1/2), and heat shock proteins (HSPs) pHSP27, HSP32, and HSP70, but rIC was not associated with any significant differences in tubular damage, inflammatory, or fibrosis marker expression. In our study, rIC did not protect the kidney against IRI. However, on days 3-7 after IRI, all groups recovered renal function. This was associated with pAkt and pERK1/2 up-regulation and increased HSP expression at day 7.

Molecular Mechanisms of Renal Ischemic Conditioning Strategies

Ischemia-reperfusion injury is the leading cause of acute kidney injury in a variety of clinical settings such as renal transplantation and hypovolemic and/or septic shock. Strategies to reduce ischemia-reperfusion injury are obviously clinically relevant. Ischemic conditioning is an inherent part of the renal defense mechanism against ischemia and can be triggered by short periods of intermittent ischemia and reperfusion. Understanding the signaling transduction pathways of renal ischemic conditioning can promote further clinical translation and pharmacological advancements in this era. This review summarizes research on the molecular mechanisms underlying both local and remote ischemic pre-, per- and postconditioning of the kidney. The different types of conditioning strategies in the kidney recruit similar powerful pro-survival mechanisms. Likewise, renal ischemic conditioning mobilizes many of the same protective signaling pathways as in other organs, but differences are recognized.

Ischaemic conditioning reduces kidney injury in an experimental large-animal model of warm renal ischaemia

BACKGROUND

Ischaemic conditioning, using short repeated sequences of intermittent ischaemia, is a strategy that may ameliorate ischaemia-reperfusion injury. The aim of the study was to assess the effects of direct and remote ischaemic conditioning in a porcine model of renal warm ischaemia-reperfusion injury.

METHODS

Pigs (50 kg) underwent laparotomy and 60-min occlusion of the left renal pedicle followed by right nephrectomy. Animals were divided into three groups: untreated controls (n = 8); direct postconditioning involving six 15-s cycles of clamping then releasing of the left renal artery (n = 7); or remote periconditioning involving four 5-min cycles of clamping then releasing of the left common iliac artery (n = 8). After 7 days kidney tissue was harvested, and blood and urine samples were collected on postoperative days 1, 3 and 7.

RESULTS

The direct postconditioning group had a lower area under the serum creatinine curve (mean(s.d.) 1378(157) versus 2001(1022) µmol/l · day respectively; P = 0.036) and peak creatinine level (316(46) versus 501(253) µmol/l respectively; P = 0.033) compared with values in control animals. There was a significant increase in serum levels of tumour necrosis factor α on day 1 in control animals but not in the conditioning groups (P = 0.013). Urinary levels of neutrophil gelatinase-associated lipocalin increased over the study period in both the control and remote groups (P = 0.001 for both), but not in the direct group (P = 0.176). There was no mortality and no complications related to either conditioning technique.

CONCLUSION

In this in vivo large-animal model, direct renal artery ischaemic postconditioning protected kidneys against warm ischaemia injury. This straightforward technique could readily be translated into clinical practice. Surgical relevance Ischaemic conditioning has been shown to improve outcomes in both experimental studies and clinical trials in cardiac surgery. Evidence from small-animal and human studies assessing ischaemic conditioning techniques in renal transplantation have not yet established the optimal technique and timing of conditioning. In this study, a large-animal model of renal warm ischaemia was used to compare different conditioning techniques. Postconditioning applied directly to the renal artery was shown to reduce renal injury. Furthermore, new evidence is provided that shorter cycles of ischaemic postconditioning than previously described can protect against renal injury. Evidence from a large-animal model is provided for different conditioning techniques. The beneficial postconditioning technique described is straightforward to perform and provides an alternative method of conditioning following renal transplantation, with potential for application in clinical practice.

Remote ischemic conditioning temporarily improves antioxidant defense

BACKGROUND

Remote ischemic conditioning (RIC) is the most promising surgical approach to mitigate ischemia and reperfusion (IR) injury. It consists in performing brief cycles of IR in tissues other than those exposed to ischemia. The underlying mechanisms of the induced protection are barely understood, so we evaluated if RIC works enhancing the antioxidant defense of the liver and kidney before IR injury.

MATERIALS AND METHODS

Twenty-one Wistar rats were assigned into three groups as follows: sham, same surgical procedure as in the remaining groups was performed, but no RIC was carried out. RIC 10, RIC was performed, and no abdominal organ ischemia was induced. After 10 min of the end of the RIC protocol, the liver and kidney were harvested. RIC 60, similar procedure as performed in RIC 10, but the liver and the kidney were harvested 60 min. RIC consisted of three cycles of 5-min left hind limb ischemia followed by 5-min left hind limb perfusion, lasting 30 min in total. Samples were used to measure tissue total antioxidant capacity.

RESULTS

RIC protocol increased both liver (1.064 ± 0.26 mM/L) and kidney (1.310 ± 0.17 mM/L) antioxidant capacity after 10 min when compared with sham (liver, 0.759 ± 0.10 mM/L and kidney, 1.08 ± 0.15 mM/L). Sixty minutes after the RIC protocol, no enhancement on liver (0.687 ± 0.13 mM/L) or kidney (1.09 ± 0.15 mM/L) antioxidant capacity was detected.

CONCLUSIONS

RIC works through temporary and short-term enhancement of liver and kidney cells antioxidant defenses to avoid the deleterious consequences of a future IR injury.

Postconditioning is protective in renal reperfusion injury only in male rats. A gender difference study

PURPOSE

We investigated the impact of sex on the protective effect of postconditioning (POC), a series of brief ischemia-reperfusion (IR) cycles at the reperfusion onset, as a recently described novel approach to attenuate renal IR injury. In this study, the left renal pedicles of uni-nephrectomized male and female rats were clamped for 45 minutes followed by 24 hours of reperfusion as IR groups. Uni-nephrectomized, sham-operated male and female rats served as control groups. Ischemic postconditioning was performed using 4 cycles of 10 seconds of IR of renal pedicle at the end of the ischemia. Twenty-four hours later, BUN (blood urea nitrogen), plasma creatinine (Cr), and renal histological changes, as well as kidney levels of MDA (malondialdehyde) and SOD (superoxide dismutase) as oxidative stress markers were evaluated to detect the protective effect of POC against IR injury in rats.

RESULTS

Induction of IR resulted in significant reduction in renal function, demonstrated by increase in plasma Cr and BUN, histological changes and oxidative stress in both genders. Application of POC afforded significant protection against these injuries in male rats, namely decreased levels of BUN and Cr, histological improvements and less oxidative damages. However, there were no significant differences in the above-mentioned parameters in female rats.

CONCLUSION

While POC is shown to be beneficial against renal IR injury in male rats, it did not show any protective effect in female rats.

Renal ischemia/reperfusion injury; from pathophysiology to treatment

Ischemia/reperfusion injury (IRI) is caused by a sudden temporary impairment of the blood flow to the particular organ. IRI usually is associated with a robust inflammatory and oxidative stress response to hypoxia and reperfusion which disturbs the organ function. Renal IR induced acute kidney injury (AKI) contributes to high morbidity and mortality rate in a wide range of injuries. Although the pathophysiology of IRI is not completely understood, several important mechanisms resulting in kidney failure have been mentioned. In ischemic kidney and subsequent of re-oxygenation, generation of reactive oxygen species (ROS) at reperfusion phase initiates a cascade of deleterious cellular responses leading to inflammation, cell death, and acute kidney failure. Better understanding of the cellular pathophysiological mechanisms underlying kidney injury will hopefully result in the design of more targeted therapies to prevent and treatment the injury. In this review, we summarize some important potential mechanisms and therapeutic approaches in renal IRI.

Ischemic postconditioning attenuates inflammation in rats following renal ischemia and reperfusion injury

Ischemic postconditioning (IPoC) involves a series of brief rapid intermittent ischemic episodes applied at the onset of reperfusion in the previously ischemic tissue or organ. Previous studies have demonstrated that IPoC attenuates tissue damage induced by ischemia and reperfusion (I/R) injury. The aim of the present study was to investigate whether IPoC has a beneficial effect on inflammation in a rat model of renal I/R injury. Wistar rats were subjected to 45 min of ischemia followed by 24, 72 or 120 h of reperfusion (I/R group). In the IPoC group, rats subjected to I/R were treated with six cycles of 10 sec reperfusion followed by a 10-sec ischemic episode. Blood samples were collected for the determination of blood urea nitrogen (BUN) and creatinine (Cr) levels. Furthermore, histological examination and immunohistochemical staining for the localization of nuclear factor-κB (NF-κB) were performed. In addition, quantitative polymerase chain reaction (qPCR) analysis was used to determine the expression levels of intercellular adhesion molecule-1 (ICAM-1), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), while western blot analysis was used to detect the protein expression levels of NF-κB. The results indicated that the BUN and Cr levels increased significantly in the I/R group, while the IPoC rats showed evidently reduced renal damage. Immunohistochemical analysis revealed that the expression levels of NF-κB were decreased by IPoC. In addition, the qPCR results revealed that IPoC significantly inhibited the increased mRNA expression levels of ICAM-1, IL-6 and TNF-α, induced by I/R injury. Western blot analysis indicated that the expression levels of NF-κB were upregulated in the I/R group, while IPoC was shown to inhibit the expression. In conclusion, IPoC was demonstrated to exhibit potent anti-inflammatory properties against renal I/R injury.

Ischemic postconditioning inhibits apoptosis in an in vitro proximal tubular cell model

Ischemia-reperfusion is a common injury of clinical ischemic disease and surgical lesions. Ischemic postconditioning (IPO) improves the ability of organs subjected to ischemia to tolerate injury. However, renal IPO studies have been based on animal models. In order to gain insights into IPO-induced alterations at the cellular level, an in vitro model for IPO was designed using the rat proximal tubular cell line NRK-52E. This model was established by placing NRK-52E cells in ischemic conditions for 3 h, then exposing cells to three cycles of reperfusion for 10 min and finally to ischemic conditions for 10 min (postconditioning). The cells were cultured further in reperfusion conditions for 3, 6, 12 and 24 h. Flow cytometry and Hoechst were used to assess apoptosis. The protein expression of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, cleaved caspase-3 and caspase-8 were analyzed by western blotting. The results demonstrated that apoptosis occurred in cells subjected to ischemia/reperfusion (I/R) alone or with postconditioning following reperfusion for 24 h. Cells subjected to I/R demonstrated increased expression of Bax, cleaved caspase-3 and caspase-8 at the end of reperfusion. However, the levels of Bax, cleaved caspase-3 and caspase-8 were significantly attenuated in cells, which had undergone IPO. In conclusion, apoptosis was observed in cells subjected to 3 h of ischemia-reperfusion injury and IPO was able to inhibit this apoptosis. IPO inhibited apoptosis by inhibiting the caspase pathway thereby exerting protective effects.

Postconditioning with simvastatin decreases myocardial injury in rats following acute myocardial ischemia

The aim of the present study was to investigate whether postconditioning with simvastatin attenuated myocardial ischemia reperfusion injury by inhibiting the expression of high mobility group box 1 (HMGB1) in rat myocardium following acute myocardial ischemia. In total, 30 male Sprague-Dawley rats were divided into sham operation (sham; n=10), acute myocardial infarction (AMI; n=10) and simvastatin (sim; n=10) groups. The AMI and sim groups were subjected to ischemia for 30 min, followed by reperfusion for 180 min. The rats in the sim group were administered 20 mg/kg simvastatin intravenously 5 min prior to reperfusion. Subsequently, the infarct size, serum cardiac troponin (c-TnI), tumor necrosis factor (TNF)-α and myocardial malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity were measured. Western blot analysis was used to detect the protein expression of HMGB1. Postconditioning with simvastatin was shown to decrease the infarct size and HMGB1 expression levels in the myocardium following AMI (P<0.05). In addition, postconditioning with simvastatin not only decreased the serum levels of c-TnI and TNF-α (P<0.05), but also inhibited the increase in MDA levels and the reduction in SOD activity (P<0.05). Therefore, postconditioning with simvastatin was shown to attenuate myocardial injury. The underlying mechanism may be associated with the downregulation of HMGB1 expression in the ischemic myocardium.

The effect of remote ischemic postconditioning on graft function in patients undergoing living donor kidney transplantation

BACKGROUND

We evaluated whether remote ischemic postconditioning (RiPoC) could improve initial graft function in living donor kidney transplantation (KT).

METHODS

Patients undergoing living donor KT were randomly assigned to either RiPoC (n=30) or control group (n=30). Immediately after reperfusion in the RiPoC group, three cycles of ischemia and reperfusion, lasting 5 min each, were performed on one upper limb. Renal function was assessed before surgery, 2 hr after surgery, and at 12-hr intervals for 96 hr postsurgery by measuring serum creatinine (sCr) and the estimated glomerular filtration rate (eGFR). Urine output and urine creatinine were assessed until postoperative day 7, and hospital stay and complication rates were compared.

RESULTS

The time for sCr to reach 50% of its preoperative level was significantly shorter in the RiPoC group than in the control group [12 (12-24) hr for RiPoC vs. 24 (21-36) hr for the control, P=0.005]. The number of patients whose sCr was reduced by 50% within 24 hr was significantly greater in the RiPoC group than in the control group [n=26 (87%) in RiPoC vs. n=18 (60%) in control, P=0.020]. However, there were no differences in sCr and eGFR thereafter, the incidence of graft dysfunction or complication rates between groups.

CONCLUSION

In this study, RiPoC appeared to hasten the recovery of graft function within 24 hr but did not affect the graft function thereafter. However, considering most recipients had immediate graft function, further studies with deceased donors or studies powered to detect a smaller difference are needed.

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

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

Aged kidneys are refractory to ischemic postconditioning in a rat model

BACKGROUND

Ischemic postconditioning (IPoC) is defined as a series of intermittent interruptions of blood flow in the early phase of reperfusion that mechanically alters the hydrodynamics of reperfusion and it attenuates renal damage after ischemia/reperfusion (I/R) injury in vivo. But all of these data had been obtained in adult populations and whether this protection was maintained in aging kidneys was unknown. The objective of this study was to establish whether the efficacy of IPoC is maintained in aging kidneys.

MATERIALS AND METHODS

The aged (24-month-old) and young (3-month-old) Wistar rats were used. Rats were subjected to 45 min of renal ischemia, both with and without treatment with IPoC. Serum urea nitrogen and creatinine levels, histological examination and apoptosis were assessed at 24 h. Oxidative stress was evaluated and apoptosis-related molecules were studied by Western blotting.

RESULTS

In young rat kidneys, IPoC significantly attenuated the renal dysfunction and cell apoptosis induced by I/R. In contrast, IPoC failed to limit renal dysfunction, possibly a consequence of increased apoptosis in aged rat kidneys.

CONCLUSIONS

Our data indicated that IPoC was ineffective in aged rat kidneys. These findings may have major implications in that severe apoptosis in aged kidneys might be refractory to anti-apoptotic effect by IPoC.

Roles of MAPKAPK-2 and HSP27 in the reduction of renal ischemia-reperfusion injury by ischemic postconditioning in rats

PURPOSE

Ischemic postconditioning is a procedure during which intermittent reperfusions are performed in the early phase of reperfusion to protect organs from ischemia/reperfusion injury. And in this study, we mainly investigated the injury-alleviative role of mitogen-activated protein kinase-activating protein kinase-2 (MAPKAPK-2) and heat shock protein 27 (HSP27) in renal ischemic reperfusion injury during the procedure of ischemic postconditioning.

METHODS

Sprague-Dawley rats were randomly divided into four groups. The injury models were prepared by clipping the left renal pedicle of rats after ligating the right renal pedicle for 60 min. In the ischemic postconditioning group, sequential reperfusions were done for 10 s and another ischemia for 10 s for six cycles after kidney ischemia for 60 min. In addition, the specific inhibitor SB203580 was injected through caudal vein before ischemia. Serum creatinine, blood urea nitrogen and the expression of HSP27 and MAPKAPK-2 were detected 1, 3, 6 and 24 h later after reperfusion. Furthermore, phosphorylation of HSP27 and MAPKAPK-2 protein contents, histological changes and apoptosis were compared 24 h later after reperfusion.

RESULTS

Our data showed that ischemic postconditioning attenuated the renal dysfunction and cell apoptosis induced by I/R and increased phosphorylation of MAPKAPK-2 and HSP27. The results indicated that ischemic postconditioning decreased apoptosis and improved renal function.

CONCLUSIONS

Taken together, it is suggested that the renal protective effect may be related to the levels of HSP27 and MAPKAPK-2 activation.

Biomarkers for ischemic preconditioning: finding the responders

Ischemic preconditioning is emerging as an innovative and novel cytoprotective strategy to counter ischemic vascular disease. At the root of the preconditioning response is the upregulation of endogenous defense systems to achieve ischemic tolerance. Identifying suitable biomarkers to show that a preconditioning response has been induced remains a translational research priority. Preconditioning leads to a widespread genomic and proteonomic response with important effects on hemostatic, endothelial, and inflammatory systems. The present article summarizes the relevant preclinical studies defining the mechanisms of preconditioning, reviews how the human preconditioning response has been investigated, and which of these bioresponses could serve as a suitable biomarker. Human preconditioning studies have investigated the effects of preconditioning on coagulation, endothelial factors, and inflammatory mediators as well as on genetic expression and tissue blood flow imaging. A biomarker for preconditioning would significantly contribute to define the optimal preconditioning stimulus and the extent to which such a response can be elicited in humans and greatly aid in dose selection in the design of phase II trials. Given the manifold biologic effects of preconditioning a panel of multiple serum biomarkers or genomic assessments of upstream regulators may most accurately reflect the full spectrum of a preconditioning response.

Combined remote ischemic perconditioning and local postconditioning on liver ischemia-reperfusion injury

BACKGROUND

Remote ischemic perconditioning (rPER) is the newest technique described to mitigate ischemia and reperfusion (IR) injury. Local postconditioning (POS) is also an effective technique for this purpose. It is uncertain if adding local POS to rPER provides superior liver protection, so we tested this hypothesis.

MATERIALS AND METHODS

Twenty five Wistar rats were assigned into five groups: sham, IR, POS, rPER, and rPER + POS. Animals were subjected to liver ischemia for 60 min. POS consisted of four cycles of 5-min liver perfusion followed by 5-min liver ischemia (40 min total) after the major ischemic period. rPER consisted of four cycles of 5-min hindlimb ischemia followed by 5 min hindlimb perfusion contemporaneously to major liver ischemic period, during its last 40 min. After 2 h, median and left lobes were harvested for malondialdehyde and Trolox equivalent antioxidant capacity (TEAC) measurement, and blood for the measurement of serum transaminases.

RESULTS

All tissue conditioning techniques were able to reduce transaminases serum levels, having no differences among them. All tissue conditioning techniques were able to reduce hepatic tissue MDA level; however, only rPER + POS had higher values than SHAM. All tissue conditioning techniques also enhanced TEAC; however, only POS had lower TEAC than SHAM.

CONCLUSIONS

rPER appears as the most promising technique to avoid IR injury. This technique reduced oxidative stress of cell membranes and lowered transaminases serum level. There was no additive protection when POS and rPER were held together.

Protection of liver as a remote organ after renal ischemia-reperfusion injury by renal ischemic postconditioning

This study was designed to investigate the protective effects of local renal ischemic postconditioning (POC) on liver damage after renal ischemia-reperfusion (IR) injury. Male rats were divided into three groups  (n = 8). They underwent a right nephrectomy before induction of 45 minutes of left kidney ischemia or sham operation. POC was performed by four cycles of 10 seconds of ischemia and 10 seconds of reperfusion just at the beginning of 24 hours of reperfusion. Then blood and liver samples were collected to measure serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and liver oxidative stress parameters including superoxide dismutase (SOD) activity and malondialdehyde (MDA) level. Renal IR caused a significant increase in liver functional indices as demonstrated by increased serum AST and ALT compared to sham group. These parameters reduced significantly in POC group compared to IR group. Liver MDA levels increased and SOD activity decreased in IR group compared to sham group. Induction of POC reduced the elevated liver MDA levels and increased the reduced liver SOD activity. These results revealed that renal IR injury causes liver damage as a remote organ and POC protects liver from renal IR injury by a modification in the hepatic oxidative stress status.

Ischaemic conditioning strategies for the nephrologist: a promise lost in translation?

Over the last quarter of a century, a huge effort has been made to develop interventions that can minimise ischaemia reperfusion injury. The most potent of these are the ischaemic conditioning strategies, which comprise ischaemic preconditioning, remote ischaemic preconditioning and ischaemic postconditioning. While much of the focus for these interventions has been on protecting the myocardium, other organs including the kidney can be similarly protected. However, translation of these beneficial effects from animal models into routine clinical practice has been less straightforward than expected. In this review, we examine the role of ischaemic conditioning strategies in reducing tissue injury from the 'bench to the bedside' and discuss the barriers to their greater translation.

Activation of nuclear factor erythroid 2-related factor 2 (Nrf2) and Nrf-2-dependent genes by ischaemic pre-conditioning and post-conditioning: new adaptive endogenous protective responses against renal ischaemia/reperfusion injury

AIM

To investigate the impact of ischaemic pre-conditioning (Ipre) and post-conditioning (Ipost) on expression of nuclear factor erythroid 2-related factor 2 (Nrf2) gene and its dependent genes, haem oxygenase-1 (HO-1) and NADPH-quinone oxidoreductase-1 (NQO-1); inflammatory cytokines TNF-α, IL1β and ICAM-1; and apoptotic markers such as caspase-3 in renal ischaemia/reperfusion (I/R) injury.

METHODS

One hundred and fifty male Sprague Dawley rats were classified into five groups (each consisted of 30 rats): sham, control (I/R), Ipre + I/R, Ipre without I/R and Ipost + I/R. Serum creatinine and blood urea nitrogen (BUN) were measured at 2, 24 and 48 h after ischaemia. In kidney tissues, mRNA of Nrf2, HO-1, NQO-1, TNF-α, IL-1β and ICAM-1 and immunohistochemical expression of Nrf2 and caspase-3 were assessed.

RESULTS

Serum creatinine and BUN improved significantly in Pre + I/R group; however, they did not show any significant improvement in Post + I/R group. Also, Ipre-I/R group showed non-significant change in serum creatinine and BUN. The expression of Nrf2, HO-1 and NQO-1 is increased significantly in Pre + I/R and Pre - I/R groups, while the enhancement in Post + I/R group was non-significant. Moreover, the expression of proinflammatory cytokines (TNF-α, IL-1 and ICAM-1) and apoptotic (caspase-3) markers showed high significant attenuation in Pre + I/R group, but slight significant attenuation in Pre + I/R group.

CONCLUSION

The renoprotective action of Ipre might include early activation and enhanced expression of Nrf2 gene and its dependent antioxidant genes, HO-1 and NOQ1, as endogenous adaptive renoprotective genes, as well as reduction in TNF-α, IL-1β, ICAM-1 and caspase-3.

Preconditioning the human brain: practical considerations for proving cerebral protection

Ischemic preconditioning has evolved as one of the most powerful strategies for cerebral protection in laboratory models of ischemia. Translating the success of laboratory studies to human cerebral protection will necessitate an approximation of laboratory conditions. This would require a practical, easily implemented method of preconditioning and clinical settings in which cerebral ischemia is anticipated, thereby allowing cerebral preconditioning prior to ischemia onset. Remote limb ischemic preconditioning is readily instituted and used in several ongoing cardiac studies for ischemic myocardial protection. It is a potentially promising intervention for brain protection as well. Suitable clinical settings, in which a preliminary study of ischemic preconditioning in neurological disorders appears feasible, include carotid endarterectomy or stenting, cardiac surgery, and subarachnoid hemorrhage with the accompanying risk of vasospasm. These are settings, in which there is substantial risk of brain ischemia, which occurs over a short and predictable period, allowing for preconditioning to be implemented prior to ischemia onset.

Protection against renal ischemia-reperfusion injury by ischemic postconditioning

Ischemia-reperfusion injury (IRI) is inevitable during transplantation. Attempts to reduce IRI have mainly focused on ways to improve hypothermic organ preservation and reduce the nephrotoxic effects of calcineurin inhibitors. Recently, it has been shown that short, repeated sequences of intermittent ischemia and reperfusion after a prolonged ischemic episode, so-called ischemic postconditioning (IPoC), reduce myocardial infarct size by approximately 40% in animal models and in humans. The principle of IPoC could be applied to every organ after ischemic injury, including kidney transplants. In fact, IPoC has demonstrated its clinical potential by reducing IRI in different organs in several animal models. In this review, we provide an overview of animal experiments on renal IRI and IPoC, demonstrating benefits with respect to organ damage and kidney function. We propose potential mechanisms by which IPoC protects against IRI. However, thus far, no human trials investigating IPoC in transplantation have been performed. Such clinical studies are needed to establish whether a simple procedure such as IPoC can improve the outcomes of human organ transplantation.

Osthole ameliorates renal ischemia-reperfusion injury in rats

BACKGROUND

Renal ischemia-reperfusion (I/R) injury is a major cause of acute kidney injury. The pathogenetic mechanisms underlying I/R injury involve oxidative stress and apoptosis. Osthole, a natural coumarin derivative, has been reported to possess antioxidant and antiapoptotic activities. This study aimed to investigate the potential effects of osthole on renal I/R injury in an in vivo rat model.

MATERIALS AND METHODS

We induced renal I/R injury by clamping the left renal artery for 45 min followed by reperfusion, along with a contralateral nephrectomy. We randomly assigned 54 rats to three groups (18 rats/group): sham-operated, vehicle-treated I/R, and osthole-treated I/R. We treated rats intraperitoneally with osthole (40 mg/kg) or vehicle (40 mg/kg) 30 min before renal ischemia. We harvested serum and kidneys at 1, 6, and 24 h after reperfusion. Renal function and histological changes were assessed. We also determined markers of oxidative stress and cell apoptosis in kidneys.

RESULTS

Osthole treatment significantly attenuated renal dysfunction and histologic damage induced by I/R injury. The I/R-induced elevation in kidney malondialdehyde level decreased, whereas reduced kidney superoxide dismutase and catalase activities were markedly increased. Moreover, osthole-treated rats had a dramatic decrease in apoptotic tubular cells, along with a decrease in caspase-3 and an increase in the Bcl-2/Bax ratio.

CONCLUSIONS

Osthole treatment protects murine kidney from renal I/R injury by suppressing oxidative stress and cell apoptosis. Thus, osthole may represent a novel practical strategy to prevent renal I/R injury.

HuR inhibits apoptosis by amplifying Akt signaling through a positive feedback loop

Human antigen R (HuR) is a post-transcriptional regulator of gene expression that plays a key role in stabilizing mRNAs during cellular stress, leading to enhanced survival. HuR expression is tightly regulated through multiple transcription and post-transcriptional controls. Although HuR is known to stabilize a subset of mRNAs involved in cell survival, its role in the survival pathway of PI3-kinase/Akt signaling is unclear. Here, we show that in renal proximal tubule cells, HuR performs a central role in cell survival by amplifying Akt signaling in a positive feedback loop. Key to this feedback loop is HuR-mediated stabilization of mRNA encoding Grb10, an adaptor protein whose expression is critical for Akt activation. Stimulation of Akt by interaction with Grb10 then activates NF-κB, which further enhances HuR mRNA and protein expression. This feedback loop is active in unstressed cells, but its effects are increased during stress. Therefore, this study demonstrates a central role for HuR in Akt signaling and reveals a mechanism by which modest changes in HuR levels below or above normal may be amplified, potentially resulting in cell death or cellular transformation.