The nature of renal cell injury

Transcriptome analysis of renal ischemia/reperfusion (I/R) injury in BAFF and BAFF-R deficient mice

Acute kidney injury (AKI) accompanies with high morbidity and mortality. Incomplete renal recovery can lead to chronic and finally end-stage kidney disease, which results in the requirement of lifelong dialysis or kidney transplantation. Consequently, finding predictive biomarker and therefore developing preventive therapeutic approaches is an urgent need. For this purpose, a better understanding of the mechanism underlying AKI is necessary. The cytokine BAFF (B cell activating factor) is related to AKI by supporting B cells, which in turn play an important role in inflammatory processes and the production of antibodies. In our study, we investigated the role of BAFF and its receptor BAFF-R in the early phase of AKI. Therefore, we performed the well-established ischemia/reperfusion (I/R) model in BAFF (B6.129S2-Tnfsf13btm1Msc/J) and BAFF-R (B6(Cg)-Tnfrsf13ctm1Mass/J) deficient mice. Transcriptome of ischemic and contralateral control kidneys was analyzed and compared to wildtype littermates. We detected the upregulation of Lcn2, Lyz2, Cd44, Fn1 and Il1rn in ischemic kidneys as well as the downregulation of Kl. Furthermore, we revealed different expression patterns in BAFF and BAFF-R knockout mice. Compared to wildtype littermates, up- and downregulation of each investigated gene were higher in BAFF-R knockout and lower in BAFF knockout. Our findings indicate a positive impact of BAFF knockout in early phase of AKI, while BAFF-R knockout seems to worsen I/R injury. In addition, our study shows for the first time a remarkable renal upregulation of Lyz2 in a murine I/R model. Therefore, we consider Lyz2 as conceivable predictive or early biomarker in case of I/R and AKI.

Carbon monoxide mechanism of protection against renal ischemia and reperfusion injury

Carbon monoxide is quickly moving past its historic label as a molecule once feared, to a therapeutic drug that modulates inflammation. The development of carbon monoxide releasing molecules and utilization of heme oxygenase-1 inducers have shown carbon monoxide to be a promising therapy in reducing renal ischemia and reperfusion injury and other inflammatory diseases. In this review, we will discuss the developments and application of carbon monoxide releasing molecules in renal ischemia and reperfusion injury, and transplantation. We will review the anti-inflammatory mechanisms of carbon monoxide in respect to mitigating apoptosis, suppressing dendritic cell maturation and signalling, inhibiting toll-like receptor activation, promoting anti-inflammatory responses, and the effects on renal vasculature.

When the Renal (Function) Begins to Fall: A Mini-Review of Acute Kidney Injury Related to Acute Respiratory Distress Syndrome in Critically Ill Patients

Acute kidney injury (AKI) is one of the most frequent causes of organ failure encountered in patients in the intensive care unit (ICU). Because of its predisposition to occur in the most critically ill patients, it is not surprising to observe a high frequency of AKI in patients with acute respiratory distress syndrome (ARDS). However, few studies have been carried out to assess the epidemiology of AKI in subgroups of ARDS patients using recommended KDIGO criteria. Moreover, the mechanisms involved in the physio-pathogenesis of AKI are still poorly understood, in particular the impact of mechanical ventilation on the kidneys. We carried out a review of the literature, focusing on the epidemiology and physiopathology of AKI in patients with ARDS admitted to the ICU. We addressed the importance of clinical management, focusing on mechanical ventilation for improving outcomes, on AKI. Finally, we also propose candidate treatment strategies and management perspectives. Our literature search showed that AKI is particularly common in ICU patients with ARDS. In association with the classic risk factors for AKI, such as comorbidities and iatrogeny, changes in mechanical ventilation parameters, which have been exclusively evaluated for their outcomes on respiratory function and death, must be considered carefully in terms of their impact on the short-term renal prognosis.

Histological and biochemical studies on effect of Sofosbuvir (Sovaldi) on adult male albino rat kidney

Sofosbuvir (sovaldi) is the backbone of many anti-HCV drugs. We aimed to demonstrate the effect of sofosbuvir on the adult male albino rat kidney. Sixty adult male albino rats were used. The animals were divided equally into 2 main groups (I and II), and each group was divided equally into 3 subgroups (A, B, and C). In group I (control group), each rat was gavaged 0.5 ml distilled water daily for 4 weeks. In group II (sofosbuvir treated group), each albino rat was gavaged 0.5 ml distilled water containing 7.2 mg sofosbuvir daily for 4 weeks. The rats were sacrificed at the end of the 4th week (subgroups IA and IIA), 6th week (subgroups IB and IIB), and 8th week (subgroups IC and IIC) from the start of the treatment. The kidneys were used for histological study while blood samples were used for biochemical study. The obtained data were statistically analyzed. Sofosbuvir (sovaldi) induced pathological changes that gave the criteria of acute Kidney injury in the adult male albino rats. The pathological changes were confirmed by elevation of serum level of urea and creatinine. After 2 and 4 weeks of drug withdrawal, the kidney incompletely recovered. We concluded that sofosbuvir induced criteria of acute tubular injury in the kidney of the adult male albino rats. This renal injury was proved by histological and biochemical studies. These insults were incompletely reversible after the end the treatment.

Novel Insights into the Molecular Mechanisms of Ischemia/Reperfusion Injury in Kidney Transplantation

Ischemia reperfusion injury (IRI) is one of the most important mechanisms involved in delayed or reduced graft function after kidney transplantation. It is a complex pathophysiological process, followed by a pro-inflammatory response that enhances the immunogenicity of the graft and the risk of acute rejection. Many biologic processes are involved in its development, such as transcriptional reprogramming, the activation of apoptosis and cell death, endothelial dysfunction and the activation of the innate and adaptive immune response. Recent evidence has highlighted the importance of complement activation in IRI cascade, which expresses a pleiotropic action on tubular cells, on vascular cells (pericytes and endothelial cells) and on immune system cells. The effects of IRI in the long term lead to interstitial fibrosis and tubular atrophy, which contribute to chronic graft dysfunction and subsequently graft failure. Furthermore, several metabolic alterations occur upon IRI. Metabolomic analyses of IRI detected a “metabolic profile” of this process, in order to identify novel biomarkers that may potentially be useful for both early diagnosis and monitoring the therapeutic response. The aim of this review is to update the most relevant molecular mechanisms underlying IRI, and also to discuss potential therapeutic targets in future clinical practice.

Protective effect of genistein in a rat model of ischemic acute kidney injury

BACKGROUND

This study determined the possible anti-inflammatory and antioxidant renal protective effect of genistein, a soy isoflavone, against kidney damage and functional disorders following renal ischemia/reperfusion (I/R) in male rats.

MATERIALS AND METHODS

The animals were dedicated to five groups (n = 7 per group): Sham, Sham + Geni (genistein, 15 mg/kg in 1 ml 1% DMSO, i.p.), Sham + DMSO (1 ml 1% DMSO, i.p.), I/R (bilateral renal ischemia for 45 min followed by 24 h reperfusion), I/R + Geni (genistein, 15 mg/kg). 24-h urine samples, blood and tissue samples of the kidney were collected at the end of 24 h reperfusion period.

RESULTS

Compared to sham, sham + Geni and sham + DMSO groups, IR injury (IRI) ended in kidney dysfunction (decreased creatinine clearance, and increased fractional excretion of sodium), increased levels of malondialdehyde, decreased activities of antioxidant enzymes (superoxide dismutase, gluthatione peroxidase, and catalase), increased gene expression levels of TLR4 (Toll-like receptor 4) and TNF-α (tumor necrosis factor-alpha), as well as histological damages in kidney tissue. Genistein administration decreased all the changes. Therefore, genistein apparently protects the kidney against IRI by mitigating both oxidative stress and inflammation. The antioxidant and anti-inflammatory properties of genistein probably exert important roles in improving functional disorders and offer renal protection against IRI.

Dexmedetomidine-Mediated Prevention of Renal Ischemia-Reperfusion Injury Depends in Part on Cholinergic Anti-Inflammatory Mechanisms

BACKGROUND

Organ ischemia-reperfusion injury often induces local and systemic inflammatory responses, which in turn worsen organ injury. These inflammatory responses can be regulated by the central nervous system, particularly by the vagal nerve and nicotinic acetylcholine receptors, which are the key components of cholinergic anti-inflammatory pathway. Activation of the cholinergic anti-inflammatory pathway can suppress excessive inflammatory responses and be a potential strategy for prevention of ischemia-reperfusion injury of organs including the kidney.

METHODS

Vagal nerve activity, plasma acetylcholine, catecholamine and inflammatory mediators, renal tissue injury, and cell death were measured in mice with bilateral renal ischemia/reperfusion with or without treatment with dexmedetomidine (Dex), an α2-adrenergic receptor agonist.

RESULTS

Dex significantly increased the discharge frequency of the cervical vagal nerve by up to 142 Hz (mean) (P < .001), and preserved kidney gross morphology and structure and attenuated cell apoptosis after ischemia-reperfusion. Furthermore, Dex also significantly increased acetylcholine release to 135.8 pmol/L (median) when compared to that (84.7 pmol/L) in the sham group (P < .001) and reduced the levels of several inflammatory mediators induced by renal ischemia/reperfusion. All the effects were abolished by vagotomy, splenectomy, or combinative administration of atipamezole, an α2-adrenergic receptor antagonist.

CONCLUSIONS

Our findings suggest that Dex provides renoprotection, at least in part, through anti-inflammatory effects of the parasympathetic nervous system activation in addition to its direct actions on α2-adrenergic receptors.

Ischemia and Reperfusion Injury in Kidney Transplantation: Relevant Mechanisms in Injury and Repair

Ischemia and reperfusion injury (IRI) is a complex pathophysiological phenomenon, inevitable in kidney transplantation and one of the most important mechanisms for non- or delayed function immediately after transplantation. Long term, it is associated with acute rejection and chronic graft dysfunction due to interstitial fibrosis and tubular atrophy. Recently, more insight has been gained in the underlying molecular pathways and signalling cascades involved, which opens the door to new therapeutic opportunities aiming to reduce IRI and improve graft survival. This review systemically discusses the specific molecular pathways involved in the pathophysiology of IRI and highlights new therapeutic strategies targeting these pathways.

Metabolomics Analysis of the Renal Cortex in Rats With Acute Kidney Injury Induced by Sepsis

Sepsis-induced acute kidney injury (AKI) can increase the mortality of critically ill patients and the incidence of chronic kidney disease in critically ill survivors. The main goal was to investigate the possible link between metabolic changes and sepsis-induced AKI development. The experimental animal model of sepsis-induced AKI was established by intraperitoneal injection of lipopolysaccharide in rats. Non-targeted metabolic screening of the renal cortex in the control and sepsis-induced AKI groups was carried out based on gas chromatography coupled with quadrupole time-of-flight mass spectrometry (GC-TOFMS) technology. The data between the two groups were analyzed by combining univariate and multivariate statistical methods, and the metabolites associated with AKI in rats with sepsis were screened. By examining the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, altered metabolic pathways associated with acute renal injury in sepsis were identified. The cross validated scores plot of orthogonal partial least squares discriminant analysis (OPLS-DA) showed a distinct separation trend between the model and control groups in the profile of renal cortex metabolites, indicating a significant change in endogenous metabolites in the rat renal cortex. Further analysis and screening showed that 26 different metabolites were identified in the renal cortex between the two groups, mainly involving taurine and hypotaurine metabolism, pantothenic acid and CoA biosynthesis, phenylalanine metabolism, and other metabolic pathways. The metabolic disorders of taurine, pantothenic acid, and phenylalanine in the renal cortex are related to the development of acute renal injury in sepsis. Correcting these metabolic disorders is expected to prevent and treat sepsis-induced AKI.

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.

L-Carnitine and Potential Protective Effects Against Ischemia-Reperfusion Injury in Noncardiac Organs: From Experimental Data to Potential Clinical Applications

The mechanism of ischemia-reperfusion (I/R) injury is complex and multifactorial. In this condition, systemic event results in morbidity and mortality in several pathologies, including myocardial infarction, ischemic stroke, acute kidney injury, trauma, and circulatory arrest. Hypoxia over ischemia phase leads to energy imbalance and changes of cellular homeostasis and functional or structural alterations. In addition, during the reperfusion period, some events, including calcium influx, release of intracellular enzymes, and cell membrane integrity breakdown, cause cell death. L-carnitine (LC) and its derivatives have been suggested to improve tolerance against I/R injury in various tissues. The favorable effects of LC are possibly mediated by its antioxidant and anti-inflammatory effects or by other capability due to increase in the intracellular carnitine content. In this article, anti-ischemic properties of LC and its derivative in noncardiac organs are reviewed using relative animal and human research. Although most of the studies on noncardiac internal organs have shown protective effects of LC administration against I/R injury, more clinical trials are needed to clarify the clinical importance of LC as a treatment option for I/R-induced injury.

Dietary nitrate attenuates renal ischemia-reperfusion injuries by modulation of immune responses and reduction of oxidative stress

Ischemia-reperfusion (IR) injury involves complex pathological processes in which reduction of nitric oxide (NO) bioavailability is suggested as a key factor. Inorganic nitrate can form NO in vivo via NO synthase-independent pathways and may thus provide beneficial effects during IR. Herein we evaluated the effects of dietary nitrate supplementation in a renal IR model. Male mice (C57BL/6J) were fed nitrate-supplemented chow (1.0mmol/kg/day) or standard chow for two weeks prior to 30min ischemia and during the reperfusion period. Unilateral renal IR caused profound tubular and glomerular damage in the ischemic kidney. Renal function, assessed by plasma creatinine levels, glomerular filtration rate and renal plasma flow, was also impaired after IR. All these pathologies were significantly improved by nitrate. Mechanistically, nitrate treatment reduced renal superoxide generation, pro-inflammatory cytokines (IL-1β, IL-6 and IL-12 p70) and macrophage infiltration in the kidney. Moreover, nitrate reduced mRNA expression of pro-inflammatory cytokines and chemo attractors, while increasing anti-inflammatory cytokines in the injured kidney. In another cohort of mice, two weeks of nitrate supplementation lowered superoxide generation and IL-6 expression in bone marrow-derived macrophages. Our study demonstrates protective effect of dietary nitrate in renal IR injury that may be mediated via modulation of oxidative stress and inflammatory responses. These novel findings suggest that nitrate supplementation deserve further exploration as a potential treatment in patients at high risk of renal IR injury.

Effect of ozone oxidative preconditioning on oxidative stress injury in a rat model of kidney transplantation

The aim of the present study was to investigate the protective effect of ozone oxidative preconditioning (OOP) on renal oxidative stress injury in a rat model of kidney transplantation. Thirty-six male Sprague Dawley (SD) rats were randomly divided into three groups: A sham (S) group, a kidney transplantation (KT) group and an OOP and kidney transplantation (OOP+KT) group. In the S group, the rats' abdomens were opened and closed without transplantation. In the KT group, the rats received a left kidney from donor SD rats. In the OOP+KT group, donor SD rats received 15 OOP treatments by transrectal insufflations (1 mg/kg), once a day, at an ozone concentration of 50 µg/ml, before the kidney transplantation. Twenty-four hours after transplantation, the parameters of renal function of the recipients were measured. The morphology and pathological effects of renal allograft were examined using hematoxylin and eosin staining, periodic acid-Schiff staining, a terminal deoxynucleotidyl transferase dUTP nick end labeling assay and immunohistochemistry. Markers of oxidative stress were also detected using the thiobarbituric acid method, and expression levels of Nrf-2 and HO-1 were determined by western blot analysis. Blood urea nitrogen and creatinine levels were significantly decreased in the OOP+KT group compared with the KT group, and the morphology and pathological changes of renal allograft were also less severe. Meanwhile, the renal allograft cell apoptosis index was significantly higher in the KT group compared to the OOP+KT group (P<0.05). Levels of superoxide dismutase, glutathione and catalase in the renal allografts were significantly higher in the OOP+KT group compared to those in the KT group (P<0.05), while malondialdehyde levels were significantly lower in the OOP+KT group compared to those in the KT group (P<0.05). Western blot analysis indicated that the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf-2) and heme oxygenase 1 (HO-1) were significantly higher in the OOP+KT compared to the KT group (P<0.05). In conclusion, the mechanism by which OOP alleviates oxidative stress injury in renal transplantation may be related to the activation of the signaling pathways of Nrf-2/HO-1 and inhibition of renal tubular epithelial cell apoptosis.

Sodium Pentosan Polysulfate Reduced Renal Ischemia-Reperfusion-Induced Oxidative Stress and Inflammatory Responses in an Experimental Animal Model

Acute kidney injury (AKI) remains an independent risk factor for mortality and morbidity after vascular surgery (affecting the renal arteries) or aortic surgery (requiring suprarenal aortic clamping). These types of vascular surgery produce renal ischemia/reperfusion (I/R) injury, a common cause of AKI. The present studies aimed at monitoring the course of renal I/R injury at the cellular level and investigating the efficacy of long-term preoperative and single-shot intraoperative administration of sodium pentosan polysulfate (PPS) to protect renal tissue from acute I/R injury both in native and diabetic kidneys in rats. Western blot analyses of the proapoptotic (bax) and antiapoptotic (bcl-2) signaling pathways, as well as the extent of DNA damage (phospho-p53), were performed. Oxidative stress followed upon the termination of malondialdehyde, reduced glutathione, thiol group, and superoxide dismutase plasma levels. Inflammatory changes were measured by the determination of serum tumor necrosis factor-α and interleukin-1 levels. Morphological changes were detected by histological examinations. Our results showed that the long-term administration of PPS has an advantage in reducing I/R kidney injury in diabetic rats, while high-dose, single-shot parenteral administration of PPS prior to revascularization might be useful in nondiabetic rats.

Renal pathology in patients with occupational exposure to carbon disulphide: A case series

AIM

Carbon disulphide (CS₂ ) is widely used as an organic solvent. However, there is little information available regarding the clinical manifestations and the pathological features of kidney injury caused by CS₂ . The current study aimed to describe the renal manifestations of a group of patients with long-term occupational exposure to CS₂ .

METHODS

Ten patients with long-term exposure to CS₂ and visiting a single centre were enrolled, with their clinical features recorded. Renal biopsies were taken from all patients, and their pathological findings were documented.

RESULTS

All patients came from the same chemical fibre factory. Their mean age at enrollment was 36.9 ± 2.4 years, and each patient had a CS₂ exposure duration exceeding 10 years. Eight patients (80%) presented with proteinuria and none had hematuria. Two patients (20%) had underlying hypertension and five (50%) had increased serum creatinine levels. Light microscopic examination of their renal biopsy specimens revealed diffuse mesangial cell proliferation and mesangial hyperplasia in all patients. Moreover, three patients (30%) had nodular hyperplasia, resembling the lesions of diabetic nephropathy. Variable degrees of tubular atrophy and interstitial infiltrations of lymphocytes and monocytes were observed in all patients. Similarly, lectron microscopic examination showed glomerular mesangial cell proliferation and mesangial hyperplasia. Immunopathological staining for IgA and IgG, complements or hepatitis B markers (hepatitis B surface antigen and e antigen-antibody) are negative in all patients.

CONCLUSION

Long-term occupational exposure to CS₂ may be associated with renal injury, although the renal pathological features are often non-specific.

Major comorbid disease processes associated with increased incidence of acute kidney injury

Acute kidney injury (AKI) is commonly seen amongst critically ill and hospitalized patients. Individuals with certain co-morbid diseases have an increased risk of developing AKI. Thus, recognizing the co-morbidities that predispose patients to AKI is important in AKI prevention and treatment. Some of the most common co-morbid disease processes that increase the risk of AKI are diabetes, cancer, cardiac surgery and human immunodeficiency virus (HIV) acquired immune deficiency syndrome (AIDS). This review article identifies the increased risk of acquiring AKI with given co-morbid diseases. Furthermore, the pathophysiological mechanisms underlying AKI in relation to co-morbid diseases are discussed to understand how the risk of acquiring AKI is increased. This paper reviews the effects of various co-morbid diseases including: Diabetes, cancer, cardiovascular disease and HIV AIDS, which all exhibit a significant increased risk of developing AKI. Amongst these co-morbid diseases, inflammation, the use of nephrotoxic agents, and hypoperfusion to the kidneys have been shown to be major pathological processes that predisposes individuals to AKI. The pathogenesis of kidney injury is complex, however, effective treatment of the co-morbid disease processes may reduce its risk. Therefore, improved management of co-morbid diseases may prevent some of the underlying pathology that contributes to the increased risk of developing AKI.

Early lipid changes in acute kidney injury using SWATH lipidomics coupled with MALDI tissue imaging

Acute kidney injury (AKI) is one of the leading causes of in-hospital morbidity and mortality, particularly in critically ill patients. Although our understanding of AKI at the molecular level remains limited due to its complex pathophysiology, recent advances in both quantitative and spatial mass spectrometric approaches offer new opportunities to assess the significance of renal metabolomic changes in AKI models. In this study, we evaluated lipid changes in early ischemia-reperfusion (IR)-related AKI in mice by using sequential window acquisition of all theoretical spectra (SWATH)-mass spectrometry (MS) lipidomics. We found a significant increase in two abundant ether-linked phospholipids following IR at 6 h postinjury, a plasmanyl choline, phosphatidylcholine (PC) O-38:1 (O-18:0, 20:1), and a plasmalogen, phosphatidylethanolamine (PE) O-42:3 (O-20:1, 22:2). Both of these lipids correlated with the severity of AKI as measured by plasma creatinine. In addition to many more renal lipid changes associated with more severe AKI, PC O-38:1 elevations were maintained at 24 h post-IR, while renal PE O-42:3 levels decreased, as were all ether PEs detected by SWATH-MS at this later time point. To further assess the significance of this early increase in PC O-38:1, we used matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) to determine that it occurred in proximal tubules, a region of the kidney that is most prone to IR injury and also rich in the rate-limiting enzymes involved in ether-linked phospholipid biosynthesis. Use of SWATH-MS lipidomics in conjunction with MALDI-IMS for lipid localization will help in elucidating the role of lipids in the pathobiology of AKI.

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

Background:

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

Materials and Methods:

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

Results:

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

Conclusion:

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

The effect of endocannabinoid system in ischemia-reperfusion injury: a friend or a foe?

INTRODUCTION

In recent years, the endocannabinoid system has emerged as a new therapeutic target in variety of disorders associated with inflammation and tissue injury, including those of the neuronal, liver, renal and cardiovascular system. The aim of the present review is to elucidate the effect of endocannabinoid system on ischemia reperfusion injury (IRI) in different organs and systems.

AREAS COVERED

The MEDLINE/PubMed database was searched for publications with the medical subject heading Cannabinoids* (CBs), CB receptors*, organ*, ischemia/reperfusion injury*, endocannabinoid* and system*. The initial relevant studies retrieved from the literature were 91 from PubMed. This number was initially limited to 35, after excluding the reviews and studies reporting data for receptors other than cannabinoid.

EXPERT OPINION

CB2 receptors may play an important compensatory role in controlling tissue inflammation and injury in cells of the neuronal, cardiovascular, liver and renal systems, as well as in infiltrating monocytes/macrophages and leukocytes during various pathological conditions of the systems (atherosclerosis, restenosis, stroke, myocardial infarction, heart, liver and renal failure). These receptors limit inflammation and associated tissue injury. On the basis of preclinical results, pharmacological modulation of CB2 receptors may hold a unique therapeutic potential in stroke, myocardial infarction, atherosclerosis, IRI and liver disease.

Noradrenaline enhances angiotensin II responses via p38 MAPK activation after hypoxia/re-oxygenation in renal interlobar arteries

AIM

Hypoxia and sympathetic activation are main factors in the pathogenesis of acute kidney injury (AKI). We tested the hypothesis that noradrenaline (NE) in combination with hypoxia aggravates the vasoreactivity of renal arteries after hypoxia/re-oxygenation (H/R). We tested the role of adrenergic receptors and p38 MAPK using an in vitro H/R protocol.

METHODS

Mouse interlobar arteries (ILA) and afferent arterioles (AA) were investigated under isometric and isotonic conditions respectively. The in vitro protocol consisted of 60-min hypoxia and control condition, respectively, 10-min re-oxygenation followed by concentration-response curves for Ang II or endothelin.

RESULTS

Hypoxia reduced the response to Ang II. Hypoxia and NE (10(-9)  mol L(-1) ) together increased it in ILA and AA. In ILA, NE alone influenced neither Ang II responses under control conditions nor endothelin responses after hypoxia. Prazosin or yohimbine treatment did not significantly influence the NE+hypoxia effect. The combination of prazosin and yohimbine or propranolol alone inhibited the effect of NE+hypoxia. BRL37344 (β3 receptor agonist) mimicked the NE effect. In contrast, the incubation with β3 receptor blocker did not influence the mentioned effect. Phosphorylation of p38 MAPK and MLC(20) was increased after H/R with NE and Ang II treatment. The selective p38 MAPK inhibitor SB202190 blocked the NE+hypoxia effect on the Ang II response.

CONCLUSION

The results suggest an interaction of NE and hypoxia in enhancing vasoreactivity, which may be important for the pathogenesis of AKI. The effect of NE+hypoxia in ILA is mediated by several adrenergic receptors and requires the p38 MAPK activation.

A nitric oxide-donor furoxan moiety improves the efficacy of edaravone against early renal dysfunction and injury evoked by ischemia/reperfusion

Edaravone (5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one, EDV) is a free-radical scavenger reduces organ ischemic injury. Here we investigated whether the protective effects of EDV in renal ischemia/reperfusion (I/R) injury may be enhanced by an EDV derivative bearing a nitric oxide- (NO-) donor furoxan moiety (NO-EDV). Male Wistar rats were subjected to renal ischemia (45 minutes), followed by reperfusion (6 hours). Administration of either EDV (1.2–6–30 µmol/kg, i.v.) or NO-EDV (0.3–1.2–6 µmol/kg, i.v.) dose-dependently attenuated markers of renal dysfunction (serum urea and creatinine, creatinine clearance, urine flow, urinary N-acetyl-β-D-glucosaminidase, and neutrophil gelatinase-associated lipocalin/lipocalin-2). NO-EDV exerted protective effects in the dose-range 1.2–6 µmol/kg, while a higher dose (30 µmol/kg) was needed to obtain protection by EDV. Both EDV and NO-EDV modulated tissue markers of oxidative stress and lipid peroxidation. NO-EDV, but not EDV, activated endothelial NO synthase (NOS) and blunted I/R-induced upregulation of inducible NOS, secondary to modulation of Akt and NF-κB activation, respectively. Besides NO-EDV administration inhibited I/R-induced IL-1β, IL-18, IL-6, and TNF-α overproduction. Overall, these findings demonstrate that the NO-donor moiety contributes to the protection against early renal I/R injury and suggest that NO-donor EDV codrugs are worthy of additional study as innovative pharmacological tools.

Karyopherins: potential biological elements involved in the delayed graft function in renal transplant recipients

Background

Immediately after renal transplantation, patients experience rapid and significant improvement of their clinical conditions and undergo considerable systemic and cellular modifications. However, some patients present a slow recovery of the renal function commonly defined as delayed graft function (DGF). Although clinically well characterized, the molecular mechanisms underlying this condition are not totally defined, thus, we are currently missing specific clinical markers to predict and to make early diagnosis of this event.

Methods

We investigated, using a pathway analysis approach, the transcriptomic profile of peripheral blood mononuclear cells (PBMC) from renal transplant recipients with DGF and with early graft function (EGF), before (T0) and 24 hours (T24) after transplantation.

Results

Bioinformatics/statistical analysis showed that 15 pathways (8 up-regulated and 7 down-regulated) and 11 pathways (5 up-regulated and 6 down-regulated) were able to identify DGF patients at T0 and T24, respectively. Interestingly, the most up-regulated pathway at both time points was NLS-bearing substrate import into nucleus, which includes genes encoding for several subtypes of karyopherins, a group of proteins involved in nucleocytoplasmic transport. Signal transducers and activators of transcription (STAT) utilize karyopherins-alpha (KPNA) for their passage from cytoplasm into the nucleus. In vitro functional analysis demonstrated that in PBMCs of DGF patients, there was a significant KPNA-mediated nuclear translocation of the phosphorylated form of STAT3 (pSTAT3) after short-time stimulation (2 and 5 minutes) with interleukin-6.

Conclusions

Our study suggests the involvement, immediately before transplantation, of karyopherin-mediated nuclear transport in the onset and development of DGF. Additionally, it reveals that karyopherins could be good candidates as potential DGF predictive clinical biomarkers and targets for pharmacological interventions in renal transplantation. However, because of the low number of patients analyzed and some methodological limitations, additional studies are needed to validate and to better address these points.

Protective effect of tea polyphenols on renal ischemia/reperfusion injury via suppressing the activation of TLR4/NF-κB p65 signal pathway

Tea polyphenols (TP) was investigated in rats for its protective effect on renal ischemia/reperfusion injury (RIRI). Rats were randomized into groups as follows: (I) sham group (n=10); (II) RIRI group (n=10); (III) RIRI+TP (100mg/kg) group (n=5); (IV) RIRI+TP (200mg/kg) group (n=5); (V) RIRI+TP+ Astragalus mongholicus aqueous extract (AMAE) (300 mg/kg+100mg/kg) group (n=5). For the IRI+TP groups, rats were orally given with tea polyphenols (100, 200 and 300 mg/kg body weight) once daily 10 days before induction of ischemia, followed by renal IRI. For the sham group and RIRI group, rats were orally given with equal volume of saline once daily 10 days before induction of ischemia, followed by renal IRI. Results showed that tea polyphenol pretreatment significantly suppressed ROS level and MDA release. On the other hand, in rats subjected to ischemia-reperfusion, the activities of endogenous antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GSH-Px) showed recovery, whereas the levels of urea nitrogen and serum creatinine were reduced by administration of tea polyphenols orally for 10 days prior to ischemia-reperfusion. Moreover, tea polyphenol pretreatment significantly decreased TLR4 and NF-κB p65 protein expression levels in RIRI rats. At the same time, tea polyphenol pretreatment attenuated the increased level of serum IL-1β, IL-6, ICAM-1 and TNF-α, and enhanced IL-10 production in RIRI rats. Furthermore, tea polyphenol pretreatment significantly decreased renal epithelial tubular cell apoptosis induced by renal ischemia/reperfusion, alleviating renal ischemia/reperfusion injury. These results cumulatively indicate that tea polyphenol pretreatment could suppress the TLR4/NF-κB p65 signaling pathway, protecting renal tubular epithelial cells against ischemia/reperfusion-induced apoptosis, which implies that antioxidants may be a potential and effective agent for prevention of the ischemic/reperfusion injury through the suppression extrinsic apoptotic signal pathway induced by TLR4/NF-κB p65 signal pathway. Moreover, supplement of AMAE can increased renal protection effect of TP.

The anti-inflammatory effect of erythropoietin and melatonin on renal ischemia reperfusion injury in male rats

PURPOSE

Renal ischemia reperfusion (IR) is an important cause of renal dysfunction. It contributes to the development of acute renal failure (ARF). The purpose of this study was to investigate the anti-inflammatory effect of erythropoietin (EPO) and melatonin (MEL), which are known anti-inflammatory and antioxidant agents, in IR-induced renal injury in rats.

METHODS

Male Wistar Albino rats were unilaterally nephrectomized and subjected to 45 min of renal pedicle occlusion followed by 24 h reperfusion. MEL (10mg/kg, i.p) and EPO (5000U/kg, i.p) were administered prior to ischemia. After 24 h reperfusion, blood samples were collected for the determination of total antioxidant capacity (TAC), malondialdehyde (MDA) and serum creatinine levels. Also, renal samples were taken for Immunohistochemical evaluation of Bcl2 and TNF-α (tumor necrosis factor-α) expression.

RESULTS

Ischemia reperfusion increased creatinine, TAC, MDA levels and TNF-α expression, also, IR decreased Bcl2 expression. Treatment with EPO or MEL decreased creatinine, MDA levels, and increased TAC level. Also, MEL up-regulated Bcl2 expression and down-regulated TNF-α expression compared with EPO.

CONCLUSION

Treatment with EPO and MEL had a curative effect on renal IR injury. These results may indicate that MEL protects against inflammation and apoptosis better than EPO in renal IR injury.

Oligomycin, an F1Fo-ATPase inhibitor, protects against ischemic acute kidney injury in male but not in female rats

We investigated the effects of oligomycin, an F1Fo-ATPase inhibitor, on ischemic acute kidney injury in male and female rats. Ischemic acute kidney injury was induced by clamping the left renal artery and vein for 45 or 60 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal dysfunction and histological renal damage were observed 1 day after reperfusion in both male and female rats, although these renal injuries were more marked in male rats than in female rats. Intravenous bolus injection of oligomycin (0.5 mg/kg) 5 min before ischemia markedly attenuated the ischemia/reperfusion-induced renal injury in male rats. However, oligomycin did not show the protective effect in female rats subjected to ischemia/reperfusion-induced renal injury. Pre-ischemic treatment with oligomycin suppressed partly but significantly ischemia-induced renal ATP depletion only in male rats. These results indicate that oligomycin prevents the onset of ischemic acute kidney injury in male but not in female rats, and the effect is accompanied by suppression of the ATP depletion only in the male rat kidney during ischemia, thereby suggesting that the ATP hydrolysis pathway by mitochondrial F1Fo-ATPase induces a sex difference in ischemic acute kidney injury.

Tight junction proteins and oxidative stress in heavy metals-induced nephrotoxicity

Kidney is a target organ for heavy metals. They accumulate in several segments of the nephron and cause profound alterations in morphology and function. Acute intoxication frequently causes acute renal failure. The effects of chronic exposure have not been fully disclosed. In recent years increasing awareness of the consequences of their presence in the kidney has evolved. In this review we focus on the alterations induced by heavy metals on the intercellular junctions of the kidney. We describe that in addition to the proximal tubule, which has been recognized as the main site of accumulation and injury, other segments of the nephron, such as glomeruli, vessels, and distal nephron, show also deleterious effects. We also emphasize the participation of oxidative stress as a relevant component of the renal damage induced by heavy metals and the beneficial effect that some antioxidant drugs, such as vitamin A (all-trans-retinoic acid) and vitamin E (α-tocopherol), depict on the morphological and functional alterations induced by heavy metals.

Effect of naloxone on ischemic acute kidney injury in the mouse

Renal ischemia produces sympathoexcitation, which is responsible for the development of ischemic acute kidney injury. Stimulation of central opioid receptors activates the renal sympathetic nerve. The present study examined the effect of an opioid receptor antagonist naloxone on the ischemia/reperfusion-induced renal dysfunction in mice. Blood urea nitrogen (BUN) and plasma creatinine increased 24 h after the renal ischemia/reperfusion. Intraperitoneal or intracerebroventricular, but not intrathecal, pretreatment with naloxone suppressed the renal ischemia/reperfusion-induced increases in BUN and plasma creatinine. This effect of naloxone was reversed by subcutaneous pretreatment with morphine. Selective MOP receptor antagonist β-funaltrexamine (FNA) also suppressed the renal ischemia/reperfusion-induced increases in BUN and plasma creatinine. Moreover, tyrosine hydroxylase expression in the renal tissue increased 24 h after renal ischemia/reperfusion, which was abolished by intraperitoneal or intracerebroventricular pretreatment with naloxone and FNA. Immunohistochemical experiments revealed a significant increase in the number of the Fos family proteins (c-Fos, FosB, Fra-1, and Fra-2) positive cells in the paraventricular nucleus of hypothalamus and supraoptic nucleus 24 h after the renal ischemia/reperfusion. Intracerebroventricular pretreatment with naloxone attenuated the renal ischemia/reperfusion-induced increase in the number of the Fos family proteins positive cells in these areas. Finally, we observed that i.c.v. pretreatment with antiserum against β-endorphin also suppressed the increased blood urea and plasma creatinine. These results suggest that the blockade of central opioid receptors can attenuate the ischemic acute kidney injury through the inhibition of renal sympathoexcitation. The central opioid receptors may thus be a new target for the treatment of ischemic organ failures.

Efficiency of endovenous versus arterial administration of mesenchymal stem cells for ischemia-reperfusion-induced renal dysfunction in rats

BACKGROUND

Ischemia followed by reperfusion leads to acute renal failure in both native kidneys and a renal allograft. Our previous study found that transplantation of mesenchymal stem cells (MSCs) ameliorated ischemia-reperfusion (I/R)-induced kidney dysfunction by increasing the activities of antioxidant enzymes. The purpose of this study was to evaluate whether intra-arterial versus intravenous administration was more effective.

METHODS

Renal ischemia was induced by clamping the right renal vessels for 60 minutes after removal of the left kidney. MSCs (1 × 10(6)) were administered through either the tail vein (TV) or the renal arter (RA), followed by reperfusion. We evaluated kidney function as well as tissue activities of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Histopathologic and immunohistochemical examinations were performed. To tracking MSCs in vivo, they were transfected with firefly luciferase and monomeric red fluorescent protein reporter genes (fluc-mrfp). MSC retention and survival were assessed using bioluminescence imaging. We observed the effects of MSCs (1 × 10(6), 2 × 10(6), and 5 × 10(6)) on IR injury.

RESULTS

MSC infusion via either the tail vein or the renal artery significantly improved kidney function at days 1, 3, and 5 as indicated by lower urea and creatinine levels compared with vehicle controls (P < .05). I/R induced a reduction in renal tissue SOD activity but GSH-PX was significantly improved by MSCs (P < .05) on day 1. Treatment with MSCs also significantly reduced renal tissue MDA levels that had been otherwise increased by renal I/R injury (P < .05). The above parameters were similar between the TV and the RA groups. Histological examination revealed kidneys from MSC-treated rats to show fairly normal morphology. The percentages of proliferating cell nuclear antigen (PCNA)-positive cells were higher in the MSC groups: 16.83 ± 4.62%, 19.17 ± 6.21%, and 2.17 ± 1.16% for the TV, RA, and control groups, respectively. There was no significant dose-related difference among MSC groups. Bioluminescence imaging demonstrated most MSCs to be lost within 7 days after either intravenous or intra-arterial infusion.

CONCLUSIONS

MSCs ameliorated I/R-induced acute renal failure in rats with similar efficiency whether infused either through the TV or the RA. There was no dose-dependent responses.

Protective effects of captopril in diabetic rats exposed to ischemia/reperfusion renal injury

Objectives

To investigate the potential protective effects of captopril, the angiotensin-converting enzyme inhibitor, in diabetic rats exposed to ischaemia/reperfusion (I/R) renal injury.

Methods

Following successful induction of diabetes, captopril treatment (50 mg/kg/day, p.o.) was applied for 4 weeks, after which bilateral renal ischaemia was induced for 30 min followed by reperfusion for 24 h.

Results

Captopril significantly attenuated hyperglycaemia and hypoinsulinaemia in diabetic rats, and significantly reduced the elevations of serum creatinine and aldosterone levels, and renal malondialdehyde, tumour necrosis factor-α and nitric oxide (NO), and prevented the depletion of reduced glutathione caused by I/R in diabetic rats. Histopathological renal tissue damage induced by I/R in diabetic rats was ameliorated by captopril treatment. Immunohistochemical analysis revealed that captopril significantly attenuated the reduction of insulin content in pancreatic islet β-cells, and decreased the I/R-induced expression of inducible NO synthase, nuclear factor-κB, Fas ligand and caspase-3, and increased the expression of survivin and heme oxygenase-1 in the kidney tissue of diabetic rats.

Conclusions

Captopril represents a potential candidate to reduce the risk of renal injury induced by ischaemia/reperfusion in type 2 diabetes.

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.

Cannabidiol treatment ameliorates ischemia/reperfusion renal injury in rats

AIMS

To investigate the protective effect of cannabidiol, the major non-psychotropic Cannabis constituent, against renal ischemia/reperfusion injury in rats.

MAIN METHODS

Bilateral renal ischemia was induced for 30 min followed by reperfusion for 24h. Cannabidiol (5mg/kg, i.v.) was given 1h before and 12h following the procedure.

KEY FINDINGS

Ischemia/reperfusion caused significant elevations of serum creatinine and renal malondialdehyde and nitric oxide levels, associated with a significant decrease in renal reduced glutathione. Cannabidiol significantly attenuated the deterioration in the measured biochemical parameters induced by ischemia/reperfusion. Histopathological examination showed that cannabidiol ameliorated ischemia/reperfusion-induced kidney damage. Immunohistochemical analysis revealed that cannabidiol significantly reduced the expression of inducible nitric oxide synthase, tumor necrosis factor-α, cyclooxygenase-2, nuclear factor-κB, Fas ligand and caspase-3, and increased the expression of survivin in ischemic/reperfused kidney tissue.

SIGNIFICANCE

Cannabidiol, via its antioxidant and anti-inflammatory properties, may represent a potential therapeutic option to protect against ischemia/reperfusion renal injury.

Protective effect of 17β-estradiol on ischemic acute kidney injury through the renal sympathetic nervous system

Enhanced renal sympathetic nerve activity during an ischemic period and renal venous norepinephrine overflow after reperfusion play important roles in the development of ischemic acute kidney injury. In this study, we examined the effect of 17β-estradiol on the renal sympathetic nervous system and kidney function in ischemia/reperfusion-induced acute kidney injury in anesthetized rats. Ischemic acute kidney injury was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after a contralateral nephrectomy. Intravenous injection of 17β-estradiol (100 μg/kg) 15 min before reperfusion suppressed enhanced renal sympathetic nerve activity during renal ischemia, also suppressed renal venous norepinephrine overflow after reperfusion, and attenuated ischemia/reperfusion-induced renal dysfunction with histological damage. The above renoprotective effects of 17β-estradiol were reversed by pretreatment with tamoxifen (5 mg/kg), an estrogen receptor antagonist, or N(G)-nitro-L-arginine methyl ester (0.3 mg/kg), a non-selective nitric oxide synthase inhibitor. These results indicate that 17β-estradiol can suppress enhanced renal sympathetic nerve activity during renal ischemia, and its consequent effect on norepinephrine overflow from nerve endings, by nitric oxide production via estrogen receptors. These effects appear to contribute to renoprotection against ischemia/reperfusion-induced renal injury.

Profiling of fatty acids released during calcium-induced mitochondrial permeability transition in isolated rabbit kidney cortex mitochondria

Increases in intracellular Ca(2+) during cellular stress often lead to the mitochondrial permeability transition (MPT). We examined changes in fatty acids (FAs) released from isolated renal cortical mitochondria subjected to Ca(2+)-induced MPT. Exposing mitochondria to Ca(2+) stimulated mitochondrial swelling and release of FAs such as arachidonic (20:4) and docosahexenoic acids which increased 71% and 32%, respectively, and linoleic (18:2) which decreased 23% compared to controls. Stearic (18:0), oleic (18:1), and linoleic (18:3) acids were unchanged. To elucidate a mechanism for FA release, mitochondria were pre-treated with bromoenolactone (BEL) to inhibit Ca(2+)-independent phospholipase A(2) gamma activity (iPLA(2)γ). BEL blocked Ca(2+)-induced release of arachidonic and behenic (22:0) acids. Finally, four FAs were released in the absence of Ca(2+) in a BEL-sensitive manner, including arachidonic and docosatrienoic acids. Thus, extensive FA release occurs during Ca(2+)-induced MPT, and that mitochondrial iPLA(2)γ maintains mitochondrial arachidonic acid homeostasis under both basal and Ca(2+)-induced stress conditions.

Intracellular calcium signaling pathways during liver ischemia and reperfusion

Calcium plays a major role in intracellular signaling mechanisms during ischemia reperfusion (I/R) injury of a liver cell. Under ischemic conditions, the absence of oxygen arrests oxidative phosphorylation, thereby eliminating the energy source by which hepatocellular mechanisms maintain homeostasis of calcium. This, in turn, leaves nonselective plasma membrane influx pores unopposed and results in a net increase in intracellular calcium concentrations. Subsequent reperfusion marks the onset and progression of apoptosis and necrosis, as it involves inflammatory responses as well as free-radical formation due to re-oxygenation of cells. These processes destroy the structural integrity of organelles, leading to disruptive redistribution of calcium between cellular and subcellular compartments. This initial elevation and later imbalance of intracellular calcium concentrations associated with I/R induce various molecular responses within each organelle. In the cytoplasm, a series of pro-apoptotic pathways involving various calcium sensitive enzymes are activated. The injury is further exacerbated in the endoplasmic reticulum (ER) due to the malfunction of mechanisms responsible for intracellular calcium sequestration. Both the mitochondria and the nucleus are also adversely affected, as their structural integrity and physiologic functions are disrupted. To date, however, the precise pathophysiology of these calcium-mediated signaling pathways is not fully understood due to its complex nature. This review aims to systematically examine the current literature about individual molecular signaling pathways in the cytoplasm, ER, mitochondria, and the nucleus prior to causing time-sensitive progression of permanent tissue injury.

Inhibitory action of Wnt target gene osteopontin on mitochondrial cytochrome c release determines renal ischemic resistance

Certain determinants of ischemic resistance in the Brown Norway rat strain have been proposed, but no studies to date have focused on the role of the Wnt pathway in the ischemic resistance mechanism. We performed a comparative genomic study in Brown Norway vs. Sprague-Dawley rats. Selective manipulations of the Wnt pathway in vivo and in vitro allowed us to study whether the action of the Wnt pathway on apoptosis through the regulation of osteopontin was critical to the maintenance of inherent ischemic resistance mechanisms. The results revealed a major gene upregulation of the Wnt family in Brown Norway rats after renal ischemia-reperfusion. Manipulation of the Wnt signaling cascade by selective antibodies increased mitochondrial cytochrome c release and caspase 3 activity. The antiapoptotic role of Wnt was mediated by osteopontin, a direct Wnt target gene. Osteopontin was reduced by Wnt antibody administration in vivo, and osteopontin gene silencing in vitro significantly increased mitochondrial cytochrome c release. The overexpression of Wnt pathway genes detected in Brown Norway rats is critical in the maintenance of their inherent ischemic resistance. Activation of the Wnt signaling cascade reduces mitochondrial cytochrome c release and caspase 3 activity through the action of osteopontin.

Tetrahydrobiopterin protects the kidney from ischemia-reperfusion injury

Tetrahydrobiopterin (BH4) is an essential cofactor for the nitric oxide (NO) synthases and represents a critical determinant of NO production. BH4 depletion during ischemia leads to the uncoupling of the synthases, thus contributing to reperfusion injury due to increased superoxide formation. To examine whether BH4 supplementation attenuates ischemia-reperfusion injury, we clamped the left renal arteries of male Lewis rats immediately following right-side nephrectomy. BH4 tissue levels significantly decreased after 45 min of warm ischemia compared with levels in non-ischemic controls. Histopathology demonstrated significant tubular damage and increased peroxynitrite formation. Intravital fluorescent microscopy found perfusion deficits in the microvasculature and leakage of the capillary mesh. Supplemental BH4 treatment before ischemia significantly reduced ischemia-induced renal dysfunction, and decreased tubular histologic injury scores and peroxynitrite generation. BH4 also significantly improved microcirculatory parameters such as functional capillary density and diameter. These protective effects of BH4 on microvasculature were significantly correlated with its ability to abolish peroxynitrite formation. We suggest that BH4 significantly protects against acute renal failure following ischemia reperfusion. Whether BH4 has a therapeutic potential will require more direct testing in humans.