Renal ischaemia-reperfusion injury

Pharmacological functions of salidroside in renal diseases: facts and perspectives

Rhodiola rosea is a valuable functional medicinal plant widely utilized in China and other Asian countries for its anti-fatigue, anti-aging, and altitude sickness prevention properties. Salidroside, a most active constituent derived from Rhodiola rosea, exhibits potent antioxidative, hypoxia-resistant, anti-inflammatory, anticancer, and anti-aging effects that have garnered significant attention. The appreciation of the pharmacological role of salidroside has burgeoned over the last decade, making it a beneficial option for the prevention and treatment of multiple diseases, including atherosclerosis, Alzheimer's disease, Parkinson's disease, cardiovascular disease, and more. With its anti-aging and renoprotective effects, in parallel with the inhibition of oxidative stress and inflammation, salidroside holds promise as a potential therapeutic agent for kidney damage. This article provides an overview of the microinflammatory state in kidney disease and discuss the current therapeutic strategies, with a particular focus on highlighting the recent advancements in utilizing salidroside for renal disease. The potential mechanisms of action of salidroside are primarily associated with the regulation of gene and protein expression in glomerular endothelial cells, podocytes, renal tubule cells, renal mesangial cells and renal cell carcinoma cell, including TNF-α, TGF-β, IL-1β, IL-17A, IL-6, MCP-1, Bcl-2, VEGF, ECM protein, caspase-3, HIF-1α, BIM, as well as the modulation of AMPK/SIRT1, Nrf2/HO-1, Sirt1/PGC-1α, ROS/Src/Cav-1, Akt/GSK-3β, TXNIP-NLRP3, ERK1/2, TGF-β1/Smad2/3, PI3K/Akt, Wnt1/Wnt3a β-catenin, TLR4/NF-κB, MAPK, JAK2/STAT3, SIRT1/Nrf2 pathways. To the best of our knowledge, this review is the first to comprehensively cover the protective effects of salidroside on diverse renal diseases, and suggests that salidroside has great potential to be developed as a drug for the prevention and treatment of metabolic syndrome, cardiovascular and cerebrovascular diseases and renal complications.

Long-Term Effects of Hypoxia-Reoxygenation on Thioredoxins in Rat Central Nervous System

BACKGROUND

Oxidative stress induced by the oxidative pathway dysregulation following ischemia/ reperfusion has been proposed as an important cause of neuronal death and brain damage. The proteins of the thioredoxin (Trx) family are crucial mediators of protein function regulating the intracellular hydrogen peroxide levels and redox-sensitive post-translational protein changes.

AIM

To analyze the expression and distribution of fourteen members of the Trx family, potentially essential for the regeneration upon long-term brain damage, in a perinatal hypoxia-ischemia rat model induced by common carotid artery ligation.

METHODS

The right common carotid artery (CCA) was exposed by an incision on the right side of the neck, isolated from nerve and vein, and permanently ligated. Sham-surgery rats underwent right CCA surgical exposure but no ligation. Euthanasia was administered to all rats at 30, 60, and 90 days of age. Protein expression and distribution of fourteen members of the Trx family and related proteins (Grx1, Grx2, Grx3, Grx5, Prx1, Prx2, Prx3, Prx4, Prx5, Prx6, Trx1, Trx2, TrxR1, TrxR2) was examined in the most hypoxia susceptible rat brain areas, namely, cerebellum, corpus striatum, and the hippocampus.

RESULTS

The thioredoxin proteins displayed a complex, cell-type, and tissue-specific expression pattern following ischemia/reperfusion. Even 60 days after ischemia/reperfusion, Western blot analysis showed a persistent expression of Trx1 and Grx2 in several brain areas.

CONCLUSION

The Trx family of proteins might contribute to long-term survival and recovery supporting their therapeutic use to curtail ischemic brain oxidative damage following an ischemia/reperfusion insult. Characterization of ischemia/reperfusion oxidative brain damage and analysis of the involved mechanisms are required to understand the underneath processes triggered by ischemia/reperfusion and to what extent and in what way thioredoxins contribute to recovery from brain hypoxic stress.

miR-195-5p alleviates acute kidney injury through repression of inflammation and oxidative stress by targeting vascular endothelial growth factor A

Acute kidney injury (AKI) is a common renal dysfunction. Renal ischemia-reperfusion (I/R) injury contributes to AKI progression. The microRNA miR-195-5p can act as a crucial tumor inhibitor in various cancers. However, the potential biological effects of miR-195-5p on AKI are not well-understood. We found that miR-195-5p levels were decreased in the serum samples of patients with AKI. Next, we determined miR-195-5p expression in the renal tissues of the rats and found that it was downregulated. Renal function was evaluated and confirmed using blood urea nitrogen and serum Cr levels. In parallel, the hypoxia-induced NRK-52E cell model was employed, and miR-195-5p was found to be markedly reduced under hypoxic conditions. Furthermore, miR-195-5p was modulated in NRK-52E cells. miR-195-5p induced NRK-52E cell proliferation and protected NRK-52E cells against hypoxia-triggered apoptosis. In an I/R mouse model, miR-195-5p alleviated renal injury triggered by I/R. In addition, oxidative stress and inflammatory factor concentrations were assessed using ELISA. The results showed that miR-195-5p mimicked attenuated oxidative stress induced by I/R injury and downregulated the protein expression of inflammatory factors. Moreover, we identified that vascular endothelial growth factor A (VEGFA) was a target gene of miR-195-5p, which could negatively regulate VEGFA expression in vitro. Inhibitors of miR-195-5p subsequently contributed to renal injury, which was reversed by VEGFA loss. In conclusion, miR-195-5p may repress AKI by targeting VEGFA.

C1q/TNF-related protein 6 (CTRP6) attenuates renal ischaemia-reperfusion injury through the activation of PI3K/Akt signalling pathway

C1q/TNF-related protein 6 (CTRP6) is a member of the CTRP family that has been reported to exhibit a nephroprotective effect. However, the role of CTRP6 in renal ischaemia/reperfusion (I/R) injury (IRI) remains unclear. In the present study, we aimed to explore the protective effect of CTRP6 in renal IRI and the potential mechanism. We found that CTRP6 expression was markedly decreased in the kidneys of mice subjected to I/R and HK-2 cells in response to hypoxia/reoxygenation (H/R) stimulation. Recombinant CTRP6 protein protected against renal I/R injury by the reduction of blood urea nitrogen (BUN) and creatinine levels. The increased production of ROS and malondialdehyde (MDA), as well the decreased activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) caused by H/R induction were mitigated by CTRP6 in HK-2 cells. The caspase-3 activity and apoptotic rate were both decreased in CTRP6-overexpressing HK-2 cells. In addition, we also found that knockdown of CTRP6 aggravated H/R-caused oxidative stress and cell apoptosis in HK-2 cells. Moreover, CTRP6 overexpression enhanced the H/R-stimulated activation of PI3K/Akt pathway in HK-2 cells. Inhibition of PI3K reversed the nephroprotective effects of CTRP6 in HK-2 cells. Taken together, CTRP6 exerted protective effects against H/R-caused oxidative injury in HK-2 cells via activating the PI3K/Akt pathway.

MicroRNA-214 promotes chronic kidney disease by disrupting mitochondrial oxidative phosphorylation

Mitochondria are critical in determining a cell's energy homeostasis and fate, and mitochondrial dysfunction has been implicated in the pathogenesis of chronic kidney disease (CKD). We sought to identify causative mitochondrial microRNAs. A microarray screen of kidney tissue from healthy mice identified 97 microRNAs that were enriched in the mitochondrial fraction. We focused on microRNA-214-3p (miR-214) because of a very high ratio of mitochondrial to cytoplasmic expression in the kidney compared to other organs. Tubular expression of miR-214 was more abundant in kidney tissue from patients with CKD than from healthy controls, and was positively correlated with the degree of proteinuria and kidney fibrosis. Expression of miR-214 was also increased in the kidney of mouse models of CKD induced by obstruction, ischemia/reperfusion, and albumin overload. Proximal tubule-specific deletion of miR-214 attenuated apoptosis, inflammation, fibrosis, and mitochondrial damage in these CKD models. Pharmacologic inhibition of miR-214 had a similar effect in the albumin overload model of CKD. In vitro, overexpressing miR-214 in proximal tubular cell lines induced apoptosis and disrupted mitochondrial oxidative phosphorylation, while miR-214 expression was upregulated in response to a variety of insults. The mitochondrial genes mt-Nd6 and mt-Nd4l were identified as the specific targets of miR-214 in the kidney. Together, these results demonstrate a pathogenic role of miR-214 in CKD through the disruption of mitochondrial oxidative phosphorylation, and suggest the potential for miR-214 to serve as a therapeutic target and diagnostic biomarker for CKD.

Fimasartan attenuates renal ischemia-reperfusion injury by modulating inflammation-related apoptosis

Fimasartan, a new angiotensin II receptor antagonist, reduces myocyte damage and stabilizes atherosclerotic plaque through its anti-inflammatory effect in animal studies. We investigated the protective effects of pretreatment with fimasartan on ischemia-reperfusion injury (IRI) in a mouse model of ischemic renal damage. C57BL/6 mice were pretreated with or without 5 (IR-F5) or 10 (IR-F10) mg/kg/day fimasartan for 3 days. Renal ischemia was induced by clamping bilateral renal vascular pedicles for 30 min. Histology, pro-inflammatory cytokines, and apoptosis assays were evaluated 24 h after IRI. Compared to the untreated group, blood urea nitrogen and serum creatinine levels were significantly lower in the IR-F10 group. IR-F10 kidneys showed less tubular necrosis and interstitial fibrosis than untreated kidneys. The expression of F4/80, a macrophage infiltration marker, and tumor necrosis factor (TNF)-α, decreased in the IR-F10 group. High-dose fimasartan treatment attenuated the upregulation of TNF-α, interleukin (IL)-1β, and IL-6 in ischemic kidneys. Fewer TUNEL positive cells were observed in IR-F10 compared to control mice. Fimasartan caused a significant decrease in caspase-3 activity and the level of Bax, and increased the Bcl-2 level. Fimasartan preserved renal function and tubular architecture from IRI in a mouse ischemic renal injury model. Fimasartan also attenuated upregulation of inflammatory cytokines and decreased apoptosis of renal tubular cells. Our results suggest that fimasartan inhibited the process of tubular injury by preventing apoptosis induced by the inflammatory pathway.

Alda-1, an aldehyde dehydrogenase-2 agonist, causes deterioration in renal functions following ischemia-reperfusion injury due to crystalline nephropathy

Renal ischemia-reperfusion injury (IRI) induces the production of aldehydes which are detoxified by aldehyde dehydrogenases (ALDHs). Alda-1 is a selective ALDH2 agonist and its protective effect was demonstrated in several conditions. The effect of Alda-1 on the kidney or on renal IRI was not investigated. We investigated the effect of Alda-1 on the renal dysfunction following IRI. Wistar rats underwent left IRI for 40 min. Group-Alda (n = 11) received Alda-1 starting 24 h before IRI and continued for 7 days thereafter when renal functions were measured. Group-Vx (n = 11) underwent similar protocol but received the dissolvent. Alda-1 did not affect renal blood flow or glomerular filtration rate in the left ischemic kidney in Group-Alda compared to Group-Vx (3.05 ± 0.50 vs. 3.53 ± 0.70, and 0.40 ± 0.06 vs. 0.51 ± 0.08, respectively, p > .05 for both). However, left renal fractional sodium excretion was higher in Group-Alda (2.80 ± 0.43 vs. 1.37 ± 0.36, p = .02). Alda-1 also adversely affected the gene expressions of kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin (217 ± 38 vs. 99 ± 13 and 49 ± 13 vs. 20 ± 5, respectively, p < .05 for both) and the alterations in tumor necrosis factor-α, transforming growth factor-β1, plasminogen activator inhibitor-1, fibronectin 1 and p53 (4.4 ± 0.9 vs. 2.1 ± 0.3, 1.5 ± 0.1 vs. 1.1 ± 0.1, 30.0 ± 2.7 vs. 11.7 ± 2.3, 3.6 ± 0.4 vs. 2.1 ± 0.2 and 1.3 ± 0.1 vs. 0.9 ± 0.07, respectively, p ≤ .05 for all). This was associated with intratubular crystal deposition suggestive of crystalline nephropathy. Alda-1 exacerbated the IRI-induced renal tubular dysfunction and alterations in markers of acute kidney injury, biomarkers of inflammation, fibrosis and apoptosis and this was associated with intratubular crystal deposition suggestive of crystalline nephropathy.

A Si-rhodamine-based near-infrared fluorescent probe for visualizing endogenous peroxynitrite in living cells, tissues, and animals

An aromatic tertiary amine-functionalized Si-rhodamine dye has been exploited as a near-infrared fluorescent probe for visualizing endogenous peroxynitrite in living cells, tissues, and mice.

Berberine protects HK-2 cells from hypoxia/reoxygenation induced apoptosis via inhibiting SPHK1 expression

Renal ischemia reperfusion injury (RIRI) refers to the irreversible damage for renal function when blood perfusion is recovered after ischemia for an extended period, which is common in clinical surgeries and has been regarded as a major risk for acute renal failures (ARF) that is accompanied with unimaginably high morbidity and mortality. Hypoxia during ischemia followed by reoxygenation via reperfusion serves as a major event contributing to cell apoptosis, which has been widely accepted as the vital pathogenesis in RIRI. Preventing apoptosis in renal tubular epithelial cell has been considered as effective method for blocking RIRI. In this paper, we established a hypoxia/reoxygenation (H/R) injury model in human proximal tubular epithelial HK-2 cells. Here, we found increased SPHK1 levels in H/R injured HK-2 cells, which could be significantly down regulated after berberine treatment. Berberine has been reported to exert a protective effect on H/R-induced apoptosis of HK-2 cells. So, in our present study, we planned to investigate whether SPHK1 participated in the anti-apoptosis process of berberine in H/R injured HK-2 cells. Our study confirmed the protective effect of berberine against H/R-induced apoptosis in HK-2 cells through promoting cells viability, inhibiting cells apoptosis, and down-regulating p-P38, caspase-3, caspase-9 as well as SPHK1, while up regulating the ratio of Bcl-2/Bax. However, SPHK1 overexpression in HK-2 cells induced severe apoptosis, which can be significantly ameliorated with additional berberine treatment. We concluded that berberine could remarkably prevent H/R-induced apoptosis in HK-2 cells through down-regulating SPHK1 expression levels, and the mechanisms included the suppression of p38 MAPK activation and mitochondrial stress pathways.

The protective effects of carboxyhemoglobin during the resuscitation from hemorrhagic shock in rats

Aim

This study was aimed to explore the effects of carboxyhemoglobin on reperfusion injury in hemorrhagic shock, as well as its action time and related mechanisms.

Results

CO-RBC group showed milder oxidative injury than O2-RBC group. CO reperfusion did not show advantages in functions of kidney and lung during resuscitation. The level of Bax was decreased in CO-RBC group, especially in early CO-RBC group. Moreover, the autophay-related gene Beclin-1 was down-regulated in CO-RBC and early CO-RBC groups. The inflammation was severer in CO-RBC resuscitation group.

Materials and Methods

The hemorrhagic shock model rats were randomly divided into: the hemorrhagic shock group (n = 6); the O2-red blood cells (O₂-RBC) group (n = 6), perfused with O₂-RBC 1 h after ischemia; CO-RBC group (n = 12), perfused with CO-RBC 1 h after ischemia; and early CO-RBC group (n = 12), perfused with CO-RBC 30 min after ischemia. The reperfusion injuries were evaluated through anti-reactive oxygen species (ROS), inflammatory action, organ function, cell apoptosis and autophagy.

Conclusions

Carboxyhemoglobin not only relieves the oxidative injury and inhibites apoptosis and autophagy, but also aggravates inflammatory reactions during reperfusion. The action time of carboxyhemoglobin may be an influencing factor for reperfusion outcomes.

Optimising renal cancer patients for nephron-sparing surgery: a review of pre-operative considerations and peri-operative techniques for partial nephrectomy

Nonmodifiable factors including pre-operative renal function and amount of healthy renal tissue preserved are the most important predictive factors that determine renal function after partial nephrectomy. Ischaemia time is an important modifiable risk factor and cold ischaemia time should be used if longer ischaemia time is anticipated. New techniques may have a role in maximising postoperative kidney function, but more robust studies are required to understand their potential benefits and risks.

CCR2 Positive Exosome Released by Mesenchymal Stem Cells Suppresses Macrophage Functions and Alleviates Ischemia/Reperfusion-Induced Renal Injury

Mesenchymal stem cells (MSCs) derived exosomes have been shown to have protective effects on the kidney in ischemia/reperfusion-induced renal injury. However, the key components in the exosomes and their potential mechanisms for the kidney protective effects are not well understood. In our current study, we focused on the abundant proteins in exosomes derived from MSCs (MSC-exo) and found that the C-C motif chemokine receptor-2 (CCR2) was expressed on MSC-exo with a high ability to bind to its ligand CCL2. We also proved that CCR2 high-expressed MSC-exo could reduce the concentration of free CCL2 and suppress its functions to recruit or activate macrophage. Further, knockdown of CCR2 expression on the MSC-exo greatly abolished these effects. Finally, we also found that CCR2 knockdown impaired the protective effects of MSC-exo for the renal ischemia/reperfusion injury in mouse. The results indicate that CCR2 expressed on MSC-exo may play a key role in inflammation regulation and renal injury repair by acting as a decoy to suppress CCL2 activity. Our study may cast new light on understanding the functions of the MSC-exo and these receptor proteins expressed on exosomes.

Organ protection during aortic cross-clamping

Open surgical repair of an aortic aneurysm requires aortic cross-clamping, resulting in temporary ischemia of all organs and tissues supplied by the aorta distal to the clamp. Major complications of open aneurysm repair due to aortic cross-clamping include renal ischemia-reperfusion injury and postoperative colonic ischemia in case of supra- and infrarenal aortic aneurysm repair. Ischemia-reperfusion injury results in excessive production of reactive oxygen species and in oxidative stress, which can lead to multiple organ failure. Several perioperative protective strategies have been suggested to preserve renal function during aortic cross-clamping, such as pharmacotherapy and therapeutic hypothermia of the kidneys. In this chapter, we will briefly discuss the pathophysiology of ischemia-reperfusion injury and the preventative measures that can be taken to avoid abdominal organ injury. Finally, techniques to minimize the risk of complications during and after open aneurysm repair will be presented.

Upregulation of miR-21 by Ghrelin Ameliorates Ischemia/Reperfusion-Induced Acute Kidney Injury by Inhibiting Inflammation and Cell Apoptosis

Renal ischemia-reperfusion (I/R) injury can be caused by cardiac surgery, renal vascular obstruction, and kidney transplantation, mainly leading to acute kidney injury (AKI), which is complicated by lack of effective preventative and therapeutic strategies. Ghrelin has recently been reported to possess anti-inflammatory properties in several types of cells; however, little attention has been given to the role of ghrelin in I/R-induced AKI. The aim of this study is to explore the role of ghrelin in I/R-induced AKI. In this study, an I/R-induced rat AKI model and a hypoxia-induced NRK-52E cell I/R model were successfully constructed. Ghrelin expression was increased significantly in these rat and cell models. After enhancing ghrelin level by injecting exogenous ghrelin into rats or transfecting a ghrelin-pcDNA3.1 vector into renal tubular epithelial cells, we observed that I/R-induced AKI can be ameliorated by ghrelin, as shown by alterations in histology, as well as changes in serum creatinine (SCr) level, cell apoptosis, and the levels of inflammatory factors. Based on the importance of microRNA-21 (miR-21) in renal disease and the modulation effect of ghrelin on miR-21 in gastric epithelial cells, we tested whether miR-21 participates in the protective effect of ghrelin on I/R-induced AKI. Ghrelin could upregulate the PI3K/AKT signaling pathway by increasing the miR-21 level, which led to the protective effect of ghrelin on I/R-induced AKI by inhibiting the inflammatory response and renal tubular epithelial cell apoptosis. Our research identifies that ghrelin can ameliorate I/R-induced AKI by upregulating miR-21, which advances the understanding of mechanisms by which ghrelin ameliorates I/R-induced AKI.

Hyperbaric Oxygen Therapy Suppresses Apoptosis and Promotes Renal Tubular Regeneration After Renal Ischemia/Reperfusion Injury in Rats

BACKGROUND

Renal ischemia/reperfusion (I/R) injury remains a major cause of acute kidney injury (AKI), in addition to I/R injury-induced tissue inflammation, necrosis and apoptosis. Hyperbaric oxygen therapy (HBO) is defined as a treatment in which a patient is intermittently exposed to 100% oxygen pressurized to a pressure above sea level (> 2.0 atmospheres absolute (ATA), 1.0 ATA = 760 mmHg). It has been used in a number of medical conditions with a proven efficacy in a limited number of disorders. However, the effects of HBO therapy on apoptosis and proliferative activity after I/R injury have not been fully understood.

OBJECTIVES

We studied the possible beneficial effects of HBO therapy on apoptosis and tubular cell regeneration after renal I/R injury in rats.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were randomized into three groups: Sham (Sham-operated rats); I/R (animals submitted to I/R); and I/R + HBO (I/R rats exposed to HBO). Tubular cell apoptosis was confirmed by DNA laddering and the terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick end labeling (TUNEL) assay. Cellular proliferation activity was determined using the anti-Ki-67 antibody.

RESULTS

A significant decrease in apoptotic cells and increase in proliferative reaction were observed in the I/R + HBO group compared to the I/R group.

CONCLUSIONS

We demonstrated that HBO suppressed apoptosis, which caused inflammation after renal I/R, and promoted tubular cell regeneration. HBO has protective effects against AKI caused by renal I/R through the inhibition of apoptosis.

Protective effect of truncated Na+/K+-ATPase β on ischemia/reperfusion-induced renal injury in rats

Renal ischemia/reperfusion(I/R) is an important injury part of ischemic acute renal failure, and it is also the main factor that affects the early functional recovery and the long-term survival of transplanted kidney in renal transplantation. In this study, we cloned and expressed truncated Na+/K+-ATPase β(tNKAβ) and demonstrated that tNKAβ could activate NKA α subunit and induce protective effect on human kidney-2(HK-2) cells via PKCɛ signal pathway. The half maximum effective concentrations (EC₅₀) of tNKAβ were 0.24 µM. Furthermore, the application of EAVSLKPT (PKCɛ inhibitor) could abolish the protective effect of tNKAβ in HK-2 cells subjected to ischemia/reperfusion. To identify the protective effect of tNKAβ against the I/R injury in the kidney, Sprague-Dawley rats were treated with tNKAβ (75 mg/kg) for 2 h before ischemia. The tNKAβ-treated group demonstrated a significant improvement in renal function with a lower serum creatinine and blood urea nitrogen (BUN) levels on postoperative days 1-6. Renal sections obtained from rats of the I/R group showed serious renal injury which included degeneration of tubular structure, tubular dilation, swelling and necrosis, luminal congestion, and muddy brown casts formed by sloughing of severely damaged tubular epithelial cells. However, sections of rats that were administered with tNKAβ 2 h before reperfusion showed marked reduction of the histological features of renal injury compared with kidneys that were subjected to I/R only. In conclusion, the protective effects of tNKAβ against renal I/R injury have been evaluated for the first time, and these protective effects may occur via stimulation of PKCɛ pathways.

Vascular and circulating microRNAs in renal ischaemia-reperfusion injury

Ischaemia-reperfusion (I/R) injury of the kidney is a major cause of acute kidney injury. It may result in worsening or even loss of organ function. Transient occlusion of the renal vessel is followed by a reperfusion period, which induces further tissue damage by release of reactive oxygen and nitrogen species. Ischaemia-reperfusion injury of the kidney may be associated with surgical interventions in native kidneys and is also a common and unavoidable phenomenon in kidney transplantation. MicroRNAs are fascinating modulators of gene expression. They are capable of post-transcriptional silencing of genetic information by targeting the 3'-untranslated region of mRNAs, culminating in a suppression of protein synthesis or an increase in mRNA degradation. They might therefore be useful diagnostic and therapeutic entities during renal I/R injury; for instance, miR-21 has been shown to be enriched in kidney tissue in mice and humans with acute kidney injury. Interestingly, most recent literature suggests that modulation of vascular microRNAs might result in the amelioration of kidney function during renal I/R injury. To that end, miR-126 and miR-24, which have been demonstrated to be highly enriched in endothelial cells, were therapeutically modulated and shown to ameliorate renal I/R injury in mice. MicroRNAs in plasma, urine or enriched in microvesicles have been shown to serve as non-invasive tools for disease monitoring and to have potential impact on downstream mechanisms in recipient cells. This review highlights the latest developments regarding the role of microRNAs in renal I/R injury.

Expression of Bcl-2 and NF-κB in brain tissue after acute renal ischemia-reperfusion in rats

OBJECTIVE

To investigate the effect of acute renal ischemia reperfusion on brain tissue.

METHODS

Fourty eight rats were randomly divided into four groups (n=12): sham operation group, 30 min ischemia 60 min reperfusion group, 60 min ischemia 60 min reperfusion group, and 120 min ischemia 60 min reperfusion group. The brain tissues were taken after the experiment. TUNEL assay was used to detect the brain cell apoptosis, and western blot was used to detect the expression of apoptosis-related proteins and inflammatory factors.

RESULTS

Renal ischemia-reperfusion induced apoptosis of brain tissues, and the apoptosis increased with prolongation of ischemia time. The detection at the molecular level showed decreased Bcl-2 expression, increased Bax expression, upregulated expression of NF-κB and its downstream factor COX-2/PGE2.

CONCLUSIONS

Acute renal ischemia-reperfusion can cause brain tissue damage, manifested as induced brain tissues apoptosis and inflammation activation.

Thioredoxin 1 and glutaredoxin 2 contribute to maintain the phenotype and integrity of neurons following perinatal asphyxia

BACKGROUND

Thioredoxin (Trx) family proteins are crucial mediators of cell functions via regulation of the thiol redox state of various key proteins and the levels of the intracellular second messenger hydrogen peroxide. Their expression, localization and functions are altered in various pathologies. Here, we have analyzed the impact of Trx family proteins in neuronal development and recovery, following hypoxia/ischemia and reperfusion.

METHODS

We have analyzed the regulation and potential functions of Trx family proteins during hypoxia/ischemia and reoxygenation of the developing brain in both an animal and a cellular model of perinatal asphyxia. We have analyzed the distribution of 14 Trx family and related proteins in the cerebellum, striatum, and hippocampus, three areas of the rat brain that are especially susceptible to hypoxia. Using SH-SY5Y cells subjected to hypoxia and reoxygenation, we have analyzed the functions of some redoxins suggested by the animal experiment.

RESULTS AND CONCLUSIONS

We have described/discovered a complex, cell-type and tissue-specific expression pattern following the hypoxia/ischemia and reoxygenation. Particularly, Grx2 and Trx1 showed distinct changes during tissue recovery following hypoxia/ischemia and reoxygenation. Silencing of these proteins in SH-SY5Y cells subjected to hypoxia-reoxygenation confirmed that these proteins are required to maintain the normal neuronal phenotype.

GENERAL SIGNIFICANCE

These findings demonstrate the significance of redox signaling in cellular pathways. Grx2 and Trx1 contribute significantly to neuronal integrity and could be clinically relevant in neuronal damage following perinatal asphyxia and other neuronal disorders.

Bis maltolato oxovanadium (BMOV) and ischemia/reperfusion-induced acute kidney injury in rats

Background

The aim of the present study was to test the potential protective effects of the organic vanadium salt bis (maltolato) oxovanadium (BMOV; 15 mg/kg) in the context of renal ischemia/reperfusion (30 min of ischemia) and its effects on renal oxygenation and renal function in the acute phase of reperfusion (up to 90 min post-ischemia).

Methods

Ischemia was established in anesthetized and mechanically ventilated male Wistar rats by renal artery clamping. Renal microvascular and venous oxygenation were measured using phosphorimetry. Creatinine clearance rate, sodium reabsorption, and renal oxygen handling efficiency were considered markers for renal function.

Results

The main findings were that BMOV did not affect the systemic and renal hemodynamic and oxygenation variables and partially protected renal sodium reabsorption.

Conclusions

Pretreatment with the organic vanadium compound BMOV did not protect the kidney from I/R injury.

Lutein protects against ischemia/reperfusion injury in rat kidneys

Ischemia‑reperfusion (I/R) injury has a major impact on renal dysfunction during transplantation. The present study investigated the role of lutein against I/R injury‑induced oxidative stress in rat kidneys. Biochemical analysis and oxidative stress parameters demonstrated that lutein protected the rat kidney significantly from I/R injury. Pretreatment with lutein significantly increased the total antioxidant capacity with a concomitant decline in the total oxidant status. Rats with I/R injury showed a significant increase in oxidative stress. The results revealed significant increases in the levels of lipid peroxidation and protein carbonyl content with concomitant decreases in enzymic and non‑enzymic antioxidants. The activity of these enzymes was reversed and demonstrated a significant increase following lutein pre‑treatment compared with the rats subjected to I/R injury alone. Furthermore, lutein protected the renal tissue from I/R injury by maintaining normal kidney architecture and led to a reduction in the levels of the renal markers urea and creatinine in the serum. These results demonstrated clear evidence that lutein offered a significant protective effect against I/R injury by enhancing antioxidant defense mechanisms.

Curcumin attenuates renal ischemia and reperfusion injury-induced restrictive respiratory insufficiency

OBJECTIVE

Pulmonary failure, instead of kidney failure, is one of the leading causes of acute kidney injury (AKI)-related death. Volume overload was previously regarded as the primary cause of lung injury, presumably by impaired renal fluid clearance. Recent evidence suggested that proinflammatory cytokines, chemokines, and free radicals released during AKI are playing a crucial role in the lung injury. We aimed to examine the protective efficacy of lung function with curcumin pretreatment.

METHODS

AKI was induced by 45 minutes of kidney ischemia (bilateral occlusion of renal pedicles) followed by 3 hours of reperfusion. Rats were divided into 3 groups: sham-operated, kidney ischemia and reperfusion (I/R), and a group with 2 days of oral pretreatment with curcumin (12.5 mg/kg/d) before I/R injury. The pulmonary function test (PFT) was conducted at baseline and after 3 hours of reperfusion, yielding parameters of lung volumes, chord compliance (Cchord), inspiratory resistance (RI), and forced expiratory volume at the first 200 millisecond (FEV200). We also examined levels of protein concentration (PC), methylguanidine (MG), tumor necrosis factor-α (TNF-α), and malondialdehyde (MDA) in the bronchoalveolar lavage (BAL).

RESULTS

Ischemic AKI-induced restrictive lung disease was demonstrated by the decreased Cchord, total lung capacitance (TLC), and FEV200, in addition to the increased lavage PCBAL, MG, TNF-α, and MDA level. Curcumin pretreatment ameliorated lung function impairment and alveolar vascular protein leak and attenuated lung inflammation.

CONCLUSIONS

The protective effect of curcumin pretreatment against restrictive lung disease is most likely associated with decreasing hydroxyl radical, lipid peroxidation, and inflammation in the lungs and improving alveolar vascular permeability.

Transforming growth factor-β1 in the microenvironment of ischemia reperfusion-injured kidney enhances the chemotaxis of mesenchymal stem cells to stromal cell-derived factor-1 through upregulation of surface chemokine (C-X-C motif) receptor 4

Acute renal failure is one of the most common complications observed in hospitals. Although extensive studies have been carried out to search for therapeutic treatments, no effective cure has been established. In recent years, stem cell therapy for tissue engineering and repair has become a key area of study. Bone marrow mesenchymal stem cells (MSCs) have been demonstrated to exhibit a reparative role in ischemia reperfusion-injured kidney tissue, and the stromal cell-derived factor-1 (SDF-1)/chemokine (C-X-C motif) receptor 4 (CXCR4) axis has been found to play an important role in the migration and homing of MSCs. In the present study, transforming growth factor-β1 (TGF-β1) in the homogenate of the acute ischemia reperfusion-injured renal tissue was found to markedly increase the CXCR4 surface expression of MSCs, which contributes to the migration of MSCs to SDF-1. Neutralization of TGF-β1 inhibited the migration in an antibody concentration-dependent manner, through downregulation of CXCR4 localized to the membrane. These observations suggest a potential mechanism for MSC migration to the kidney which may provide a possible therapeutic target for curing acute renal failure.

Sildenafil ameliorates oxidative stress and DNA damage in the stenotic kidneys in mice with renovascular hypertension

Background

Oxidative stress and DNA damage have been implicated in the pathogenesis of renovascular hypertension induced by renal artery stenosis in the two-kidney, one-clip (2K1C) Goldblatt model. Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra®) has marked beneficial effects on oxidative stress and DNA damage, we tested the hypothesis that sildenafil could also protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and genotoxicity.

Methods

The experiments were performed with C57BL6 mice subjected to renovascular hypertension by left renal artery clipping. Two weeks after clipping, the mice were treated with sildenafil (40 mg/kg/day for 2 weeks, 2K1C-sildenafil group) or the vehicle (2K1C). These mice were compared with control mice not subjected to renal artery clipping (Sham). After hemodynamic measurements, the stenotic kidneys were assessed using flow cytometry to evaluate cell viability and the comet assay to evaluate DNA damage. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained.

Results

Sildenafil treatment significantly reduced mean arterial pressure (15%), heart rate (8%), intrarenal angiotensin II (50%) and renal atrophy (36%). In addition, it caused a remarkable decrease of reactive oxygen species production. On the other hand, sildenafil increased nitric oxide levels relative to those in the nontreated 2K1C mice. Sildenafil treatment also significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice.

Conclusions

Our data reveal that sildenafil has a protective effect on the stenotic kidneys of 2K1C mice, suggesting a new use of phosphodiesterase 5 inhibitors for protection against the DNA damage observed in the hypoperfused kidneys of individuals with renovascular hypertension. Further translational research is necessary to delineate the mechanisms involved in the prevention of renal stenosis in the clinical setting.

Renal protective effects of resveratrol

Resveratrol (3,5,4′-trihydroxystilbene), a natural polyphenolic compound found in grapes and red wine, is reported to have beneficial effects on cardiovascular diseases, including renal diseases. These beneficial effects are thought to be due to this compound's antioxidative properties: resveratrol is known to be a robust scavenger of reactive oxygen species (ROS). In addition to scavenging ROS, resveratrol may have numerous protective effects against age-related disorders, including renal diseases, through the activation of SIRT1. SIRT1, an NAD⁺-dependent deacetylase, was identified as one of the molecules through which calorie restriction extends the lifespan or delays age-related diseases, and this protein may regulate multiple cellular functions, including apoptosis, mitochondrial biogenesis, inflammation, glucose/lipid metabolism, autophagy, and adaptations to cellular stress, through the deacetylation of target proteins. Previous reports have shown that resveratrol can ameliorate several types of renal injury, such as diabetic nephropathy, drug-induced injury, aldosterone-induced injury, ischemia-reperfusion injury, sepsis-related injury, and unilateral ureteral obstruction, in animal models through its antioxidant effect or SIRT1 activation. Therefore, resveratrol may be a useful supplemental treatment for preventing renal injury.

The effects of alpha-lipoic acid on MMP-2 and MMP-9 activities in a rat renal ischemia and re-perfusion model

Matrix metalloproteinases (MMPs) are enzymes that are responsible for degradation of extracellular matrix (ECM); they are involved in the pathogenesis of ischemia-re-perfusion (I-R) injury. We investigated the possible preventive effect of alpha-lipoic acid (LA) in a renal I-R injury model in rats by assessing its reducing effect on the expression and activation of MMP-2 and MMP-9 induced by I-R. Rats were assigned to four groups: control, sham-operated, I-R (saline, i.p.) and I-R+ LA (100 mg/kg, i.p.). After a right nephrectomy, I-R was induced by clamping the left renal pedicle for 1 h, followed by 6 h re-perfusion. In the sham group, a right nephrectomy was performed and left renal pedicles were dissected without clamping and the entire left kidney was excised after 6 h. LA pretreatment was started 30 min prior to induction of ischemia. Injury to tubules was evaluated using light and electron microscopy. The expressions of MMP-2 and MMP-9 were determined by immunohistochemistry and their activities were analyzed by gelatin zymography. Serum creatinine was measured using a quantitative kit based on the Jaffe colorimetric technique. Malondialdehyde (MDA) and glutathione (GSH) were analyzed using high performance liquid chromatography. Tissue inhibitor of metalloproteinase (TIMP)-2 and TIMP-1 were assessed using enzyme-linked immunosorbent assay (ELISA). I-R caused tubular dilatation and brush border loss. LA decreased both renal dysfunction and abnormal levels of MDA and GSH during I-R. Moreover, LA decreased significantly both MMP-2 and MMP-9 expressions and activations during I-R. TIMP-1 and TIMP-2 levels were increased significantly by LA administration. LA modulated increased MMP-2 and MMP-9 activities and decreased TIMP-1 and TIMP-2 levels during renal I-R.

Influence of oxidative stress on inducing micturition dysfunction following chronic infravesical obstruction and the protective role of an antioxidant diet - association of in vivo and in vitro studies in rats

OBJECTIVE

This study was developed to determine whether the generation of free radicals, induced by ischemia followed by reperfusion in a model of chronic intravesical obstruction in rats, would lead to damage in the detrusor. It also investigates the possible protective action of the flavonoid galangin on the tissue lesion induced by lipid peroxidation.

MATERIALS AND METHODS

Twenty-one male rats were divided into three groups of seven animals each. Group A was subjected to a sham procedure; group B to partial obstruction of the bladder neck; and group C to partial obstruction of the bladder neck, but also received a diet rich in the flavonoid galangin. All the animals were subjected to urodynamic evaluation and then sacrificed. The bladders were sent for enzymatic tests.

RESULTS

The urodynamic showed that group B developed significantly greater numbers of involuntary contractions of the detrusor, greater post-micturition residue and lower compliance. The group A presented TEAC levels greater than to the group B. Comparative analysis of group A, B and C demonstrated significantly greater malondialdehyde levels in group B in relation to groups A and C. The group B presented smaller contraction amplitudes than did groups A and C, in electrically stimulated contractions.

CONCLUSIONS

That oxidative stress is implicated in the damage to the detrusor musculature following a period of chronic intravesical obstruction. We show, for the first time, that administration of an antioxidant prior to and following the start of chronic obstruction makes it possible to avoid the cellular lesions that cause detrusor dysfunction.

Nephrogenic diabetes insipidus: essential insights into the molecular background and potential therapies for treatment

The water channel aquaporin-2 (AQP2), expressed in the kidney collecting ducts, plays a pivotal role in maintaining body water balance. The channel is regulated by the peptide hormone arginine vasopressin (AVP), which exerts its effects through the type 2 vasopressin receptor (AVPR2). Disrupted function or regulation of AQP2 or the AVPR2 results in nephrogenic diabetes insipidus (NDI), a common clinical condition of renal origin characterized by polydipsia and polyuria. Over several years, major research efforts have advanced our understanding of NDI at the genetic, cellular, molecular, and biological levels. NDI is commonly characterized as hereditary (congenital) NDI, arising from genetic mutations in the AVPR2 or AQP2; or acquired NDI, due to for exmple medical treatment or electrolyte disturbances. In this article, we provide a comprehensive overview of the genetic, cell biological, and pathophysiological causes of NDI, with emphasis on the congenital forms and the acquired forms arising from lithium and other drug therapies, acute and chronic renal failure, and disturbed levels of calcium and potassium. Additionally, we provide an overview of the exciting new treatment strategies that have been recently proposed for alleviating the symptoms of some forms of the disease and for bypassing G protein-coupled receptor signaling.

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.

Role of reduced manganese superoxide dismutase in ischemia-reperfusion injury: a possible trigger for autophagy and mitochondrial biogenesis?

Excessive generation of superoxide and mitochondrial dysfunction has been described as being important events during ischemia-reperfusion (I/R) injury. Our laboratory has demonstrated that manganese superoxide dismutase (MnSOD), a major mitochondrial antioxidant that eliminates superoxide, is inactivated during renal transplantation and renal I/R and precedes development of renal failure. We hypothesized that MnSOD knockdown in the kidney augments renal damage during renal I/R. Using newly characterized kidney-specific MnSOD knockout (KO) mice the extent of renal damage and oxidant production after I/R was evaluated. These KO mice (without I/R) exhibited low expression and activity of MnSOD in the distal nephrons, had altered renal morphology, increased oxidant production, but surprisingly showed no alteration in renal function. After I/R the MnSOD KO mice showed similar levels of injury to the distal nephrons when compared with wild-type mice. Moreover, renal function, MnSOD activity, and tubular cell death were not significantly altered between the two genotypes after I/R. Interestingly, MnSOD KO alone increased autophagosome formation, mitochondrial biogenesis, and DNA replication/repair within the distal nephrons. These findings suggest that the chronic oxidative stress as a result of MnSOD knockdown induced multiple coordinated cell survival signals including autophagy and mitochondrial biogenesis, which protected the kidney against the acute oxidative stress following I/R.

Flow-dependent endothelial function and kidney dysfunction

The vascular endothelium constantly integrates biomechanical and humoral signals and responds by secreting or metabolizing multiple factors that act in an autocrine or paracrine manner on the vasculature and adjacent tissues. Several studies have documented the effects of blood flow on renal endothelial cells and its effects on the pathophysiology of the kidney. In contrast, less is known about the effects of acute flow cessation on renal endothelium and kidney function. Here we review our current knowledge on flow cessation, endothelial function, and kidney dysfunction in the context of two clinically relevant settings, namely, the no-reflow phenomenon, observed during periods of renal warm ischemia, and the cold storage of kidney transplants.

Grape seed proanthocyanidin extract reduces renal ischemia/reperfusion injuries in rats

Activation of reactive oxygen species and inflammation are implicated in renal ischemia/reperfusion (I/R) injuries. This study investigated whether grape seed proanthocyanidin extract (GSPE) protects against renal I/R injury by its effect on reactive oxygen species and the inflammation pathway. Wistar rats were administered GSPE before renal ischemia, followed by reperfusion for 24 hours. Plasma concentrations of urea, creatinine and cystatin C were measured for renal dysfunction. Serum and tissue superoxide dismutase activity and glutathione peroxidase and malondialdehyde levels were measured. Renal sections were analyzed for histological grading of renal injury, and nuclear factor-ĸB activity was determined. GSPE significantly reduced increases in urea, creatinine and cystatin C; increased kidney superoxide dismutase activity and glutathione peroxidase levels and reduced malondialdehyde levels. GSPE reduced histological renal damage and nuclear factor-ĸB activity. These results suggest that GSPE reduces renal dysfunction and injury caused by renal I/R.

Curcumin provides incomplete protection of the kidney in ischemia reperfusion injury

Curcumin, a component of the spice turmeric, was shown to have a protective effect on acute kidney injury markers following ischemia-reperfusion injury (IRI). However, its effect on glomerular and tubular renal functions following IRI is not known and this data is probably of more clinical relevance. In this study, curcumin was tested for its effect on renal functional parameters following two different periods of warm IRI in the rat. Groups V-30 (n=10) and C-30 (n=10) underwent ischemia for 30 minutes whereas groups V-45 (n=8) and C-45 (n=8) underwent ischemia for 45 minutes. C-30 and C-45 received oral curcumin (200 mg/kg/day) whereas V-30 and V-45 received a vehicle. The left renal artery blood flow was measured by a flowmeter before and 15 minutes after reperfusion. Serum TNF-alpha was measured before and 2 days after ischemia. The function of both kidneys was measured 2 days following ischemia using clearance technique. IRI caused significant increase in TNF-alpha in all groups. Curcumin significantly ameliorated the ischemia-induced alterations in serum TNF-alpha and associated histological changes but did not affect the alterations in renal artery blood flow, glomerular (glomerular filtration rate, renal blood flow) or tubular (urinary volume, urinary sodium and fractional excretion of sodium) functions following 30 or 45 min of IRI.

Stimulation of carnitine palmitoyltransferase 1 improves renal function and attenuates tissue damage after ischemia/reperfusion

BACKGROUND

Renal injury as a result of ischemia/reperfusion (I/R) is a major clinical problem with a high mortality rate and a lack of therapeutic treatment. During I/R, cellular homeostasis is disrupted owing to energy depletion, leading to cell death. Fatty acid β-oxidation is the major metabolic pathway for generating adenosine triphosphate (ATP) in the kidneys, which is governed by carnitine palmitoyltransferase 1 (CPT1). C75 is a synthetic compound that up-regulates CPT1 activity. Thus, we hypothesized that C75 treatment could increase energy production and alleviate renal I/R injury.

METHODS

We subjected male adult rats to renal I/R by bilateral renal pedicle clamping with microvascular clips for 60 min, followed by administration of 8% dimethyl sulfoxide (vehicle) or C75 (3 mg/kg body weight), with 5 animals/group. We collected blood and renal tissues 24 h after reperfusion and subjected them to various measurements and histological examination.

RESULTS

C75 treatment restored the loss of CPT1 activity and intracellular ATP levels in the kidneys after I/R. Administration of C75 significantly lowered serum creatinine, blood urea nitrogen, aspartate aminotransferase, and lactate dehydrogenase levels elevated by I/R. C75 treatment preserved morphological features of the kidneys with a significant improvement in the damage score. In addition, C75 treatment inhibited the increase of TNF-α levels in serum and kidneys, and lowered myeloperoxidase activity in the kidneys after I/R.

CONCLUSIONS

Stimulation of CPT1 activity by C75 recovered ATP depletion, improved renal function, attenuated tissue injury, and inhibited proinflammatory cytokine production and neutrophil infiltration after renal I/R injury. Therefore, enhancing the metabolism pathways for energy production may provide a novel modality to treat renal I/R injury.

Induced pluripotent stem cells without c-Myc attenuate acute kidney injury via downregulating the signaling of oxidative stress and inflammation in ischemia-reperfusion rats

Induced pluripotent stem (iPS) cells have potential for multilineage differentiation and provide a resource for stem cell-based treatment. However, the therapeutic effect of iPS cells on acute kidney injury (AKI) remains uncertain. Given that the oncogene c-Myc may contribute to tumorigenesis by causing genomic instability, herein we evaluated the therapeutic effect of iPS cells without exogenously introduced c-Myc on ischemia-reperfusion (I/R)-induced AKI. As compared with phosphate-buffered saline (PBS)-treated group, administration of iPS cells via intrarenal arterial route into kidneys improved the renal function and attenuated tubular injury score at 48 h after ischemia particularly at the dose of 5 × 10(5) iPS cells. However, a larger number of iPS cells (5 × 10(7) per rat) diminished the therapeutic effects for AKI and profoundly reduced renal perfusion detected by laser Doppler imaging in the reperfusion phase. In addition, the green fluorescence protein-positive iPS cells mobilized to the peritubular area at 48 h following ischemia, accompanied by a significant reduction in infiltration of macrophages and apoptosis of tubular cells, and a remarkable enhancement in endogenous tubular cell proliferation. Importantly, transplantation of iPS cells reduced the expression of oxidative substances, proinflammatory cytokines, and apoptotic factors in I/R kidney tissues and eventually improved survival in rats of ischemic AKI. Six months after transplantation in I/R rats, engrafted iPS cells did not result in tumor formation in kidney and other organs. In summary, considering the antioxidant, anti-inflammatory, and antiapoptotic properties of iPS cells without c-Myc, transplantation of such cells may be a treatment option for ischemic AKI.

Renal tubular fluid shear stress facilitates monocyte activation toward inflammatory macrophages

Modified urinary fluid shear stress (FSS) induced by variations of urinary fluid flow and composition is observed in early phases of most kidney diseases. Recently, we reported that renal tubular FSS promotes endothelial cell activation and subsequent adhesion of human monocytes, thereby suggesting that changes in urinary FSS can induce the development of inflammation (Miravète M, Klein J, Besse-Patin A, Gonzalez J, Pecher C, Bascands JL, Mercier-Bonin M, Schanstra JP, Buffin-Meyer B, BBRC 407: 813-817, 2011). Here, we evaluated the influence of tubular FSS on monocytes as they play an important role in the progression of inflammation in nephropathies. Human renal tubular cells (HK-2) were exposed to FSS 0.01 Pa for 30 min or 5 h. Treatment of human THP-1 monocytes with the resulting conditioned medium (FSS-CM) modified the expression of macrophage differentiation markers, suggesting differentiation toward the inflammatory M1-type macrophage. The effect was confirmed in freshly isolated human monocytes. In contrast to endothelial cells, the activation of monocytes by FSS-CM did not require TNF-α. Cytokine array analysis of FSS-CM showed that FSS modified secretion of cytokines by HK-2 cells, particularly by increasing secretion of TGF-β and by decreasing secretion of C-C chemokine ligand 2 (CCL2). Neutralization of TGF-β or CCL2 supplementation attenuated the effect of FSS-CM on macrophage differentiation. Finally, FSS-injured HK-2 cells expressed and secreted early biomarkers of tubular damage such as kidney injury molecule 1 and neutrophil gelatinase-associated lipocalin. In conclusion, changes in urinary FSS should now also be considered as potential insults for tubular cells that initiate/perpetuate interstitial inflammation.

Affirmative effects of iloprost on apoptosis during ischemia-reperfusion injury in kidney as a distant organ

OBJECTIVE

Apoptosis and its regulatory mechanisms take part in renal ischemia-reperfusion (I/R) injury which can result in acute renal failure and the inhibition of the caspase is considered as a new therapeutic strategy. In this context, we investigated the antiapoptotic and cytoprotective effects of iloprost, a prostacyclin analog, in kidney as a distant organ.

METHODS

Wistar albino rats were randomized into five groups (n = 12 in each) as sham, ischemia, I/R, iloprost (10 μg kg(-1)), and I/R + iloprost (10 μg kg(-1)). A 4 h reperfusion procedure was carried out after 4 h of ischemia. Caspase-8 was evaluated for death receptor-induced pathways, whereas caspase-9 was evaluated for mitochondria-dependent pathways and caspase-3 was investigated for overall apoptosis. Superoxide dismutase (SOD) enzyme activity and nitrite content as an indicator of nitric oxide (NO) production were also analyzed in kidney tissues.

RESULTS

Caspases-3, -8, and -9 were all significantly elevated in both ischemia and I/R groups compared to the sham group; however, treatment with iloprost reduced caspases-3, -8, and -9. SOD enzyme activity was attenuated by iloprost when compared to ischemic rats. The different effects of NO were found which change according to the present situation in ischemia, I/R, and treatment with iloprost.

CONCLUSIONS

These findings suggested that iloprost prevents apoptosis in both receptor-induced and mitochondria-dependent pathways in renal I/R injury and it may be considered as a cytoprotective agent for apoptosis. Understanding the efficiency of iloprost on the pathways for cell death may lead to an opportunity in the therapeutic approach for renal I/R injury.

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.