Tubular cell damage in acute renal failure-apoptosis, necrosis, or both

Enhanced apoptotic index in hepatocytes, Kupffer cells, and inflammatory infiltrate showed positive correlation with hepatic lesion intensity, parasite load, and clinical status in naturally Leishmania-infected dogs

It is unknown if Leishmania amastigote infections affect hepatocytes and Kupffer cell apoptosis, and the role played by apoptosis in liver lesions in leishmaniasis is still unclear. Clinically affected and subclinically infected dogs with leishmaniosis and uninfected controls were assessed. Parasite load, biochemical markers for evaluation of liver damage, morphometry (area, perimeter, number of inflammatory focus, major and minor diameters), apoptosis in hepatic tissue (hepatocytes, Kupffer cells, and inflammatory infiltrates) and cellularity in inflammatory foci were quantified. The parasite load in clinically affected dogs proved to be higher than in the other groups. All morphometric parameters (area, perimeter, number of inflammatory focus, major and minor diameters) from clinically affected were higher than the values found in the subclinically infected and uninfected control dogs. Only clinically affected dogs presented high levels of ALT, FA, GGT and cholesterol in serum. Strong positive correlation was observed between biochemical markers for evaluation of liver damage (ALT, FA, GGT and cholesterol) and hepatic apoptosis (hepatocytes, Kupffer cells, and inflammation). Clinically affected dogs showed a more intense hepatic lesion. Hepatocytes showed a higher rate of apoptosis in Leishmania-infected dogs than in uninfected control dogs. The Kupffer cell apoptotic index and apoptosis within the inflammatory infiltrates were higher in clinically affected dogs. The apoptotic index evaluated in hepatocytes, Kupffer cells, and inflammatory infiltrates showed a positive correlation with the intensity of the hepatic lesion, parasite load, and clinical status. Apoptotic cells also showed positive immunostaining for TUNEL, Bcl2, and Bax. Our data showed that hepatic apoptosis was related to the severity of liver damage, the progression of infection, and the parasite load in leishmaniasis. Apoptotic regulated cell recruitment modulated the inflammatory response and favored the survival and dissemination of parasites, depending on the clinical status of the Leishmania-infected dogs.

Renal Papillary Necrosis (RPN) in an African Population: Disease Patterns, Relevant Pathways, and Management

Renal papillary necrosis (RPN) is characterized by coagulative necrosis of the renal medullary pyramids and papillae. Multiple conditions and toxins are associated with RPN. Several RPN risk factors, or POSTCARDS, have been identified, with most patients presenting with RPN having at least two contributing risk factors. Currently, there is no specific test to diagnose and confirm RPN; however, several imaging tools can be used to diagnose the condition. RPN is currently underdiagnosed in African populations, often with fatal outcomes. In African clinical settings, there is a lack of consensus on how to define and describe RPN in terms of kidney anatomy, pathology, endourology, epidemiology, the identification of African-specific risk factors, the contribution of oxidative stress, and lastly an algorithm for managing the condition. Several risk factors are unique to African populations including population-specific genetic factors, iatrogenic factors, viral infections, antimicrobial therapy, schistosomiasis, substance abuse, and hypertension (GIVASSH). Oxidative stress is central to both GIVASSH and POSTCARDS-associated risk factors. In this review, we present information specific to African populations that can be used to establish an updated consensual definition and practical grading system for radiologists, urologists, nephrologists, nuclear physicians, and pathologists in African clinical settings.

Effect of Fc-Elabela-21 on renal ischemia/reperfusion injury in mice: Mediation of anti-apoptotic effect via Akt phosphorylation

INTRODUCTION

Renal ischemia/reperfusion injury (IRI) is the most common cause of acute kidney injury (AKI), and patients with AKI have a high rate of mortality. Apelin is a therapeutic candidate for treatment of IRI and Elabela (ELA) is a recently discovered hormone that also activates the apelin receptor (APJ). We examined the use of ELA as a preventive treatment for IRI using in vitro and in vivo models.

METHODS

Male mice were subjected to renal IRI, with or without administration of a stabilized form of ELA (Fc-ELA-21) for 4 days. Renal tubular lesions were measured using H&E staining, reactive oxygen species (ROS) were measured using a dihydroethidium stain assay, and renal cell apoptosis was measured using the TUNEL assay and flow cytometry. Immortalized human proximal tubular epithelial (HK-2) cells were pretreated with or without LY294002 and/or ELA-32, maintained at normoxic or hypoxic conditions, and then returned to normal culture conditions to mimic IRI. Cell apoptosis was determined using the TUNEL assay and cell proliferation was determined using the MTT assay. The levels of Akt, p-Akt, ERK1/2, p- ERK1/2, Bcl-2, Bax, caspase-3 and cleaved caspase-3 were measured using western blotting.

RESULTS

Fc-ELA-21 administration reduced renal tissue damage, ROS production, and apoptosis in mice that had renal IRI. ELA-32 reduced HK-2 cell apoptosis and restored the proliferation of cells subjected to IRI. Akt phosphorylation had a role in the anti-apoptotic effect of ELA.

CONCLUSION

This study of in vitro and in vivo models of IRI indicated that the preventive and anti-apoptotic effects of ELA were mediated via the PI3K/Akt signaling pathway.

Discovery of novel Ketamine-inspired derivatives as a protective agent against renal ischemic/reperfusion injury in Wistar rats

Renal ischemia-reperfusion (I/R) injury is a limiting factor for the success of renal grafts and is deemed greatly responsible for the mortality. A novel series of Ketamine inspired compounds were synthesized and subjected to NF-ĸB transcriptional inhibitory activity in LPS-stimulated RAW264.7 cells, where entire set of compounds showed mild to significant NF-ĸB transcriptional inhibitory activity (IC₅₀ 6.53 - 67.52 µM). Compound 6d showed highest inhibitory activity among the tested series (IC₅₀ 2.62 µM), and found more potent as compared to Ketamine as standard. The effect of compound 6d was further quantified in I/R injury in Wistar rats, where it dose-dependently improves kidney function of rats with significant amelioration of kidney injury as suggested by histopathological examination of renal tissues. It further showed reduction in the generation of pro-inflammatory cytokines and improves the anti-oxidant status of experimental rats. Compound 6d inhibited apoptosis and increases the expression of Bcl2 and decreases Bax, and cleaved caspase-3 level. It further reduces TLR-4 and NF-κB expression in renal cells of rats, with increases in IκB-α level in western blot analysis as compared to I/R group. In summary, our current study showed the development of a novel class of Ketamine-inspired derivatives against renal ischemia/reperfusion injury.

Enhanced apoptotic index, chemokines and inflammatory recruitment in renal tissues shows relationship with the clinical signs in Leishmania-infected dogs

Apoptosis is associated with resolution of inflammation. However, apoptosis may also occur in active inflammation, balancing inflammatory recruitment instead of a resolution event. To test that hypothesis, we measured apoptosis and chemokines expression, involved in recruitment of inflammatory cells. Clinical affected and subclinically infected dogs with canine leishmaniosis (CanL) and uninfected controls were assessed. Apoptosis in renal tissue (glomeruli, tubules, and inflammatory infiltrate) and cellularity in inflammatory foci were quantified. Messenger RNA of CCL5, CCL4, MCP-1, MCP-2, Caspase (Casp) 3, Casp 8, Casp 9, Bax, Bcl₂ and Fas were quantified by qRT PCR. Clinical affected dogs showed more intense inflammation and higher cellularity in the inflammatory infiltrates than subclinically infected ones, which were higher than controls. Glomerular and tubular cells showed higher apoptotic index in clinical affected dogs when compared to controls. Apoptosis within the inflammatory infiltrates was higher in clinical affected dogs. Bax/Bcl₂ ratio and CCL4 showed higher expression in kidney from clinical affected when compared to subclinically infected dogs. Casp 3/CCL4 ratio expression were higher in subclinically infected dogs than in the clinical affected group. Additionally, results suggest that Casp 3/CCL4 ratio is balancing towards an inflammatory recruitment and CCL4 and Bax/Bcl₂ ratio expression is associated with active inflammation in clinical affected CanL. Data demonstrate that apoptosis was not always correlated with resolution of inflammation, when a morphometric and a molecular evaluation were performed concomitantly. In kidneys of Leishmania infected dogs, apoptosis and chemokines may be balancing inflammatory recruitment. In conclusion, Bax/Bcl₂ ratio, chemokines, Casp 8, Casp 3 and Fas were associated with renal apoptosis, active inflammation and increased inflammatory recruitment observed in clinical affected animals, influencing the clinical presentation of leishmaniosis.

Protein disulfide isomerase inhibition impairs Keap1/Nrf2 signaling and mitochondrial function and induces apoptosis in renal proximal tubular cells

Renal proximal tubular apoptosis plays a critical role in kidney health and disease. However, cellular molecules that trigger renal apoptosis remain elusive. Here, we evaluated the effect of inhibiting protein disulfide isomerase (PDI), a critical thioredoxin chaperone protein, on apoptosis as well as the underlying mechanisms in human renal proximal tubular (HK2) cells. HK2 cells were transfected with PDI-specific siRNA in the absence and presence of an antioxidant, tempol. PDI siRNA transfection resulted in a decrease of ~70% in PDI protein expression and enzyme activity. PDI inhibition increased caspase-3 activity and induced profound cell apoptosis. Mitochondrial function, as assessed by mitochondrial cytochrome c levels, mitochondrial membrane potential, oxygen consumption, and ATP levels, was significantly reduced in PDI-inhibited cells. Also, PDI inhibition caused nuclear factor erythroid 2-related factor 2 (Nrf2; a redox-sensitive transcription factor) cytoplasmic sequestration, decreased superoxide dismutase and glutathione-S-transferase activities, and increased oxidative stress. In PDI-inhibited cells, tempol reduced apoptosis, caspase-3 activity, and oxidative stress and also restored Nrf2 nuclear translocation and mitochondrial function. Silencing Nrf2 in the cells abrogated the beneficial effect of tempol, whereas Kelch-like ECH-associated protein 1 (an Nrf2 regulatory protein) silencing protected cells from PDI inhibitory effects. Collectively, our data indicate that PDI inhibition diminishes Nrf2 nuclear translocation, causing oxidative stress that further triggers mitochondrial dysfunction and renal cell apoptosis. This study suggests an important role for PDI in renal cell apoptosis involving Nrf2 and mitochondrial dysfunction.

Incidence, Risk Factors, and Outcomes of Transition of Acute Kidney Injury to Chronic Kidney Disease in Cirrhosis: A Prospective Cohort Study

Transition to chronic kidney disease (CKD) after an episode of acute kidney injury (AKI) is known in patients without cirrhosis. We studied the incidence and risk factors for development of CKD in patients with cirrhosis. Competing risk analysis was performed to identify risk factors for CKD development. Of 818 patients with cirrhosis (age, 50.4 ± 11.8 years; 84% males; Model for End-Stage Liver Disease [MELD], 19.9 ± 9.9), 36% had AKI at enrollment, 27% had previous AKI, and 61% developed new episodes of AKI during the follow-up period. CKD developed in 269 (33%) patients. Serum cystatin C (CysC; subdistribution hazard ratio [SHR], 1.58; 1.07-2.33), episodes of previous AKI (SHR, 1.26; 1.02-1.56), and AKI stage at enrollment (no AKI [SHR, 1] vs. stage 1 [SHR, 3.28; 1.30-8.25] vs. stage 2 [SHR, 4.33; 1.76-10.66] vs. stage 3 [SHR, 4.5; 1.59-12.73]) were identified as baseline risk factors for CKD development. On time-varying competing risk analysis, MELD (SHR, 1.01; 1.00-1.03), number of AKI episodes (SHR, 1.25; 1.15-1.37), and CysC (SHR, 1.38; 1.01-1.89) predicted CKD development. Development of CKD was associated with higher risk of death. Reduction in glomerular filtration rate (GFR) not meeting CKD criteria was observed in 66% of patients with cirrhosis, more so in those with previous AKI episodes and a high CysC level and MELD score. Renal histology, available in 55 patients, showed tubulointerstitial injury in 86%, cholemic nephrosis in 29%, and glomerular changes in 38%. Conclusion: Almost two-thirds of patients with cirrhosis develop episodes of AKI and reduction in GFR; one-third progress to CKD, resulting in adverse outcomes. Higher MELD and CysC levels and number of AKI episodes predict development of CKD in patients with cirrhosis.

Dual roles of hydrogen peroxide in promoting zebrafish renal repair and regeneration

Acute renal injury (AKI) is a serious disorder of renal failure or renal damage that occurs within hours or days. At present, there is no approved pharmaceutical treatment for AKI. Zebrafish is an excellent model for studying the repair of AKI because of its remarkable ability to repair kidney injury. Using zebrafish AKI model inducing by gentamicin, we found that hydrogen peroxide (H₂O₂) plays dual roles during the period of AKI recovery including renal repair and kidney regeneration. In the repair stage of AKI, H₂O₂ was produced in proximal and distal segments of renal tubules. By inhibiting H₂O₂ generation using Duox Vivo-Morpholino or chemical inhibitor, it was observed of severe damage of renal tubules, and extensive cell apoptosis. In the stage of regeneration, we found that H₂O₂ was highly generated in renal interstitium. Inhibiting production of H₂O₂ could significantly down-regulate the ability of kidney regeneration, which was associated with the failure of proliferation of renal progenitor cells. Therefore, H₂O₂ acts as a protective factor in renal repair and an initial signal of kidney regeneration, indicating the key roles of H₂O₂ in promoting recovery of AKI in zebrafish.

AICAR, an AMPK activator, protects against cisplatin-induced acute kidney injury through the JAK/STAT/SOCS pathway

Cisplatin causes acute kidney injury (AKI) through proximal tubular injury. We investigated the protective effect of the adenosine monophosphate protein kinase (AMPK) activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) against cisplatin-induced AKI. We investigated whether the AMP-kinase activator AICAR ameliorates cisplatin-induced AKI through the JAK/STAT/SOCS pathway. Male Sprague-Dawley (SD) rats were randomly divided into four groups: control, AICAR, cisplatin, and cisplatin + AICAR. As appropriate to their treatment group, the rats were injected with a single dose of cisplatin (7 mg/kg, i.p.). AICAR was administered to the rats at 100 mg/kg i.p. daily. Blood urea nitrogen (BUN) and serum creatinine were measured. Renal damage was analyzed in sections stained with hematoxylin and eosin (H&E). Renal tissues were also examined by immunohistochemistry and western blot for p-AMPK, Kim-1, cleaved caspase 3, and JAK/STAT/SOCS. For in vitro studies, NRK-52E normal rat kidney cells were treated with cisplatin and/or AICAR. By western blot, we confirmed the expression of p-AMPK and the JAK/STAT/SOCS pathway in NRK-52E cells. AICAR was protective against cisplatin-induced acute tubular injury by up-regulating p-AMPK expression in NRK-52E cells. Protein expression levels of JAK2/STAT1 were markedly ameliorated in NRK-52E cells by AICAR. The protective mechanism of AICAR may be associated with suppression of the JAK2/STAT1 pathway and up-regulation of SOCS1, an inhibitor of the JAK2/STAT1 pathway. The present study demonstrates the protective effects of AICAR against cisplatin-induced AKI and shows a new renoprotective mechanism through the JAK2/STAT1/SOCS1 pathway and apoptosis inhibition. This study suggests that activation of the AMPK activator AICAR might ameliorate cisplatin-induced AKI.

Epoxide metabolites of arachidonate and docosahexaenoate function conversely in acute kidney injury involved in GSK3β signaling

Acute kidney injury (AKI) causes severe morbidity and mortality for which new therapeutic strategies are needed. Docosahexaenoic acid (DHA), arachidonic acid (ARA), and their metabolites have various effects in kidney injury, but their molecular mechanisms are largely unknown. Here, we report that 14 (15)-epoxyeicosatrienoic acid [14 (15)-EET] and 19 (20)-epoxydocosapentaenoic acid [19 (20)-EDP], the major epoxide metabolites of ARA and DHA, respectively, have contradictory effects on kidney injury in a murine model of ischemia/reperfusion (I/R)-caused AKI. Specifically, 14 (15)-EET mitigated while 19 (20)-EDP exacerbated I/R kidney injury. Manipulation of the endogenous 19 (20)-EDP or 14 (15)-EET by alteration of their degradation or biosynthesis with selective inhibitors resulted in anticipated effects. These observations are supported by renal histological analysis, plasma levels of creatinine and urea nitrogen, and renal NGAL. The 14 (15)-EET significantly reversed the I/R-caused reduction in glycogen synthase kinase 3β (GSK3β) phosphorylation in murine kidney, dose-dependently inhibited the hypoxia/reoxygenation (H/R)-caused apoptosis of murine renal tubular epithelial cells (mRTECs), and reversed the H/R-caused reduction in GSK3β phosphorylation in mRTECs. In contrast, 19 (20)-EDP dose-dependently promoted H/R-caused apoptosis and worsened the reduction in GSK3β phosphorylation in mRTECs. In addition, 19 (20)-EDP was more metabolically stable than 14 (15)-EET in vivo and in vitro. Overall, these epoxide metabolites of ARA and DHA function conversely in I/R-AKI, possibly through their largely different metabolic stability and their opposite effects in modulation of H/R-caused RTEC apoptosis and GSK3β phosphorylation. This study provides AKI patients with promising therapeutic strategies and clinical cautions.

In vivo nephroprotective efficacy of propolis against contrast-induced nephropathy

PURPOSE

Contrast agents administered in diagnostic imaging or interventional procedures of clinical radiology may cause contrast-induced nephropathy (CIN). Preventive measures against CIN involve pharmaceutical pretreatments, such as N-acetylcystein (NAC) or calpain, but alternative medicines can also be helpful. This study aims to assess the prospects of a natural compound, propolis, as a potential nephroprotector against a specific contrast agent, diatrizoate.

METHODS

In vivo experiments were performed on 35 male rats in five groups: control, diatrizoate alone, and pretreatments with propolis, NAC, or calpain one hour before diatrizoate administration. Three days later, blood and renal tissue samples were collected and quantitatively processed for determining induced changes in critical biomarkers malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT), as well as serum creatinine and plasma urea.

RESULTS

Diatrizoate increased creatinine (113%), urea (400%), and MDA (162%) levels and decreased GSH (-71%), SOD (-69%), GSH-Px (-77%), and CAT (-73%) levels. Evaluating the response of each pretreatment provided sufficient evidence that propolis was as effective as either NAC or calpain, but consistently more prominent in restoring the MDA, GSH, SOD, and GSH-Px levels close to their normal range. This outcome demonstrated the nephroprotective effect of propolis against CIN.

CONCLUSION

Propolis protects renal tissue against toxicity, free radicals, and other adverse effects induced by diatrizoate. This function is most likely exerted through the antioxidant and antitoxic activities of propolis.

Dietary unsaponifiable fraction of extra virgin olive oil supplementation attenuates lung injury and DNA damage of rats co-exposed to aluminum and acrylamide

Aluminum chloride (AlCl3) and acrylamide (ACR) are well known as environmental pollutants inducing oxidative stress. Our study investigated the effects of these contaminants and if the hydrophilic fraction of extra virgin olive oil was able to prevent lung oxidative stress and DNA damage. Animals were divided into four groups of six each: group 1, serving as controls, received distilled water; group 2 received in drinking water aluminum chloride (50 mg/ kg body weight) and by gavage acrylamide (20 mg/kg body weight); group 3 received both aluminum and acrylamide in the same way and the same dose as group 2 and hydrophilic fraction from olive oil (OOHF) (1 ml) by gavage; group 4 received only OOHF by gavage. Exposure of rats to both aluminum and acrylamide provoked oxidative stress in lung tissue based on biochemical parameters and histopathological alterations. In fact, we have observed an increase in malondialdehyde (MDA), H2O2, and advanced oxidation protein product (AOPP) and a decrease in reduced glutathione (GSH), non-protein thiols (NPSH), and vitamin C levels. Activities of catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were also decreased. Histopathological changes in lung tissue were noted like emphysema, vascular congestion, and infiltration of inflammatory cells. A random DNA degradation was observed on agarose gel in the lung of AlCl3 and acrylamide (ACR)-treated rats. Co-administration of OOHF to treated rats improved biochemical parameters to near control values and lung histoarchitecture. The smear formation of genomic DNA was reduced. The hydrophilic fraction of extra virgin olive oil might provide a basis for developing a new dietary supplementation strategy in order to prevent lung tissue damage.

p38-MAPK inhibition and endotoxin induced tubular dysfunction in men

Background: To evaluate the possibility of preventing endotoxin induced renal damage by p38-MAPK inhibition in a human model.

Design and Methods: Twenty-one healthy young male volunteers received 4 ng/kg Escherichia coli endotoxin as a single dose. Four groups of volunteers received an oral dose of placebo or 350, 700 or 1400 mg RWJ-67657, a p38-MAPK inhibitor, 20 min before endotoxin infusion. Urine samples were collected at set time intervals. The urinary excretion rate of β2-microglobulin and N-acetyl-β-D-glucosaminidase, as indicators of tubular dysfunction was determined.

Results: There was a significant increase of β2-microglobulin and N-acetyl-β-D-glucosaminidase urine excretion rate after endotoxin infusion in the placebo group. p38-MAPK inhibition prevented the increase of markers for tubulopathy.

Conclusions: Endotoxin infusion induces measurable tubular damage. Blocking the p38-MAPK may prevent this damage. The mechanism is unclear, but blocking TNF-α release is a possible explanation.

Renal-Dose Dopamine: From Hypothesis to Paradigm to Dogma to Myth and, Finally, Superstition?

Acute renal failure (ARF) is common in the critically ill and is associated with a high mortality rate. Its pathogenesis is not understood. Because animal models use ischemia to induce experimental ARF, there is the widespread belief that lack of blood flow is responsible for ARF. Low-dose dopamine (LDD) has been shown to increase renal blood flow in animal and in human volunteers. Thus, it has been administered to humans for almost 3 decades in the belief that it would lead to renal arterial vasodilation and increase renal blood flow (RBF). However, the etiology of ARF in critical illness is likely multifactorial, and the contribution of hypovolemia and reduced renal perfusion is unknown. Furthermore, interindividual variation in the pharmacokinetics of dopamine typically results in poor correlation between blood levels and administered dose, making accurate and reliable delivery of LDD difficult. Finally, dopamine is a proximal tubular diuretic that increases Na+ delivery to tubular cells, thus increasing their oxygen demands. Accordingly, even if LDD were able to preferentially increase RBF, there is no guarantee that it would restore renal parenchymal oxygen homeostasis. More important, 2 meta-analyses and a large double-blind, prospective, multiple-center, randomized controlled trial have failed to demonstrate that dopamine protects the kidney in critically ill patients with ARF. Currently, there is insufficient evidence to support the use of renal-dose dopamine in the intensive care unit.

Solute carrier transporter and drug-related nephrotoxicity: the impact of proximal tubule cell models for preclinical research

INTRODUCTION

The final excretion step of several drugs is facilitated by membrane transporters of the Solute carrier (SLC) family expressed in the proximal tubules of the kidney. Membrane transporters contribute substantially to the pharmacokinetic profile of drugs and play important roles in drug-induced nephrotoxicity. Different cell models have been applied as tools for the assessment of nephrotoxic effects caused by drugs.

AREAS COVERED

This review gives an overview over clinically relevant SLC transporters involved in the renal elimination of drug agents and their specific role in drug-induced nephrotoxicity. Most widely applied cell models are described and their advantages and limitations are outlined.

EXPERT OPINION

In vitro cell culture models (e.g., continuous and primary renal cell lines, polarized cell monolayers) represent valuable tools for early assessment of the nephrotoxic potential of drugs. Since SLC transporters contribute to drug excretion in a large part, in vitro cell culture models might be very helpful to study transport pathways and/or potential drug-drug interactions at an early stage of the drug development process to predict nephrotoxic effects.

Cisplatin : an old drug with a newfound efficacy -- from mechanisms of action to cytotoxicity

INTRODUCTION

Cisplatin is a highly effective antineoplastic drug with an extremely current mechanism of action. Cisplatin-induced side effects are dose-dependent and limit the administration of increased dosages, thus compromising its therapeutic efficacy.

AREAS COVERED

This review aims to describe the emerging knowledge about the biochemical mechanisms that mediate cisplatin cytotoxicity and side effects. A specific section is devoted to discuss the pathogenesis of cisplatin-related toxicities and the potential measures to counteract them.

EXPERT OPINION

Although cisplatin has been used for a long time, only recently its exact mechanism of action has been better defined. The cytotoxic activity of cisplatin is largely dependent on the glycolytic metabolism of tumor cells: cisplatin redirects cancer cells to oxidative phosphorylation from the 'Warburg effect', which is considered one of the most important mechanisms of tumor cell survival. The interference of cisplatin with glucose metabolism is also a cause of its relevant toxicities. The emerging knowledge on the complex mechanisms, which mediate cisplatin cytotoxicity and side effect, may lead to a more appropriate and safe use of this drug. Further studies are warranted to define and implement its effectiveness in combination with targeted drugs able to interfere with cellular energy metabolism, such as mTOR inhibitors.

Protective effect of plaunotol against doxorubicin-induced renal cell death

In searching for a safe and effective compound to be used as a chemoprotective agent to prevent toxicity of the anthracyclin doxorubicin to renal cells, the present study demonstrated that plaunotol, a purified acyclic diterpene from Croton stellatopilosus Ohba, showed potential protection against doxorubicin-induced cell death in human proximal tubule cells. Treatment of renal cells with doxorubicin resulted in a significant decrease in viability of the cells, and we next proved that such toxicity was mainly due to apoptotic cell death. Pretreatment of the cells with plaunotol for at least 9 h prior to doxorubicin exposure improved the cells' survival. Plaunotol was shown to up-regulate the anti-apoptotic myeloid cell leukemia-1 (Mcl-1) level whereas it had no effect on the Bcl-2 level. The reduction in Mcl-1 after doxorubicin treatment was shown to be closely associated with the toxic action of the drug, and the increase in Mcl-1 induced by plaunotol pretreatment was able to prevent cell death induced by doxorubicin. Furthermore, the protective effect of plaunotol was evaluated in human lung and melanoma cells. Results indicated that plaunotol had no significantly protective effect in human lung carcinoma cells, whereas it sensitized melanoma cells to drug-induced cell death.

Carbon tetrachloride-induced nephrotoxicity and DNA damage in rats

In this study, the protective effects of vanillin were evaluated against carbon tetrachloride (CCl4)-induced kidney damages in Wistar albino rats. CCl4 (1 ml/kg, intraperitoneally [i.p.]) caused a significant induction of renal disorder, oxidative damage and DNA fragmentation as evidenced by increased plasma creatinine, urea and uric acid levels, increased lipid peroxidation (malondialdehyde [MDA]) and protein carbonyl. Furthermore, glutathione levels, catalase, superoxide dismutase, glutathione transferase and glutathione peroxidase activities were significantly decreased. A smear without ladder formation on agarose gel was also shown, indicating random DNA degradation. Pretreatment of rats with vanillin (150 mg/kg/day, i.p.), for 3 consecutive days before CCl4 injection, protected kidney against the increase of MDA and degradation of membrane proteins compared to CCl4-treated rats and exhibited marked prevention against CCl4-induced nephropathology, oxidative stress and DNA damage. Kidney histological sections showed glomerular hypertrophy and tubular dilatation in CCl4-treated rats, however, in vanillin pretreated rats, these histopathological changes were less important and present a similar structure to that of control rats. These data indicated the protective role of vanillin against CCl4-induced nephrotoxicity and suggested its significant contribution of these beneficial effects.

Pathophysiology of acute kidney injury

Acute kidney injury (AKI) is the leading cause of nephrology consultation and is associated with high mortality rates. The primary causes of AKI include ischemia, hypoxia, or nephrotoxicity. An underlying feature is a rapid decline in glomerular filtration rate (GFR) usually associated with decreases in renal blood flow. Inflammation represents an important additional component of AKI leading to the extension phase of injury, which may be associated with insensitivity to vasodilator therapy. It is suggested that targeting the extension phase represents an area potential of treatment with the greatest possible impact. The underlying basis of renal injury appears to be impaired energetics of the highly metabolically active nephron segments (i.e., proximal tubules and thick ascending limb) in the renal outer medulla, which can trigger conversion from transient hypoxia to intrinsic renal failure. Injury to kidney cells can be lethal or sublethal. Sublethal injury represents an important component in AKI, as it may profoundly influence GFR and renal blood flow. The nature of the recovery response is mediated by the degree to which sublethal cells can restore normal function and promote regeneration. The successful recovery from AKI depends on the degree to which these repair processes ensue and these may be compromised in elderly or chronic kidney disease (CKD) patients. Recent data suggest that AKI represents a potential link to CKD in surviving patients. Finally, earlier diagnosis of AKI represents an important area in treating patients with AKI that has spawned increased awareness of the potential that biomarkers of AKI may play in the future.

Augmenter of liver regeneration attenuates tubular cell apoptosis in acute kidney injury in rats: the possible mechanisms

Augmenter of liver regeneration (ALR), the expression of which increased in rat kidneys after renal ischemia/reperfusion (I/R) injury, enhances renal tubular cell regeneration in vivo and in vitro. We aimed to investigate the effects of ALR on apoptosis of renal tubular cells after renal I/R injury in vivo and consider the possible mechanisms. Rats that were subjected to bilateral renal ischemia for 60 min followed by reperfusion were administered with either vehicle or recombinant human ALR (rhALR). Renal dysfunction and histologic injury were assessed by the measurement of serum biochemical markers and histological grading. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). Caspase-3 activity was measured using a colorimetric protease assay. Expression of Bcl-2, Bax Fas, phosphorylated-Akt (p-Akt), and phosphorylated-p53 (p-p53) was determined by western blotting. Compared with vehicle-treated rats, renal dysfunction and histologic injury were significantly attenuated by administration of rhALR. The number of TUNEL-positive tubular cells and caspase-3 activity were decreased, Bcl-2 and p-Akt expression was up-regulated, and Bax and p-p53 expression was down-regulated by administration of rhALR. However, administration of rhALR had no effect on Fas protein expression. These results indicate that the protective effect of rhALR on renal I/R injury is associated with its anti-apoptotic action in renal tubular cells. RhALR inhibits apoptosis by increasing the ratio of Bcl-2 to Bax and by decreasing the activity of caspase-3. The activation of Akt and inactivation of p53 are involved in the rhALR anti-apoptosis process.

Nec-1 protects against nonapoptotic cell death in cisplatin-induced kidney injury

BACKGROUND/AIMS

Necrostatin-1 (Nec-1) inhibits necroptosis, a nonapoptotic cell death pathway. Acute kidney injury (AKI) is a clinical problem of high incidence and mortality. It involves several mechanisms of cell death. We aim to evaluate the effect of Nec-1 in the toxic kidney injury model by cisplatin.

METHODS

We analyzed the effect of Nec-1 in AKI by cisplatin in human proximal tubule cells by flow cytometry.

RESULTS

Our results show that Nec-1 has no effect on apoptosis in renal tubular epithelial cells (Nec-1 + Cis group 13.4 ± 1.7% vs. Cis group 14.6 ± 1.4%) (p > 0.05). But, in conditions in which apoptosis was blocked by benzyloxy-carbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD-fmk) the use of Nec-1 completely reversed cell viability (Nec-1 + Cis + z-VAD group 72.9 ± 6.3% vs. Cis group 35.5 ± 2.2%) (p < 0.05) suggesting that Nec-1 has effect on nonapoptotic cell death (necroptosis).

CONCLUSION

Our findings suggest that the combined use of apoptosis and necroptosis inhibitors can provide additional cytoprotection in AKI. Furthermore, this is the first study to demonstrate that Nec-1 inhibits tubular kidney cell death and restores cell viability via a nonapoptotic mechanism.

Deleterious effects of cypermethrin on rat liver and kidney: protective role of sesame oil

The involvement of reactive oxygen species (ROS) has been implicated in the toxicity of various pesticides. Our study was designed to investigate the induction of oxidative stress by cypermethrin; a Type II pyrethroid in rat liver and kidney. In addition, the protective role of sesame oil against the toxicity of cypermethrin was investigated. Animals were divided into four equal groups; the first group used as control while groups 2, 3 and 4 were treated with sesame oil (5 mL/kg b.w), cypermethrin (12 mg/kg b.w) and the combination of both sesame oil (5 mL/kg b.w) plus cypermethrin (12 mg/kg b.w), respectively. Rats were daily administered with their respective doses for 30 days by gavage. Repeated oral administration of cypermethrin was found to reduce the level of glutathione (GSH) and the activities of the antioxidant enzymes. While, the level of TBARS was elevated indicating the presence of oxidative stress. The activities of LDH, AST and ALT were decreased in the liver extract while increased in the plasma of the cypermethrin-treated group. Also, the levels of urea and creatinine were significantly increased after treatment with cypermethrin. Liver and kidney injury was confirmed by the histological changes. In conclusion, the administration of sesame oil provided significant protection against cypermethrin-induced oxidative stress, biochemical changes, histopathological damage and genomic DNA fragmentation.

Intravital Two-Photon Microscopy Assessment of Renal Protection Efficacy of siRNA for p53 in Experimental Rat Kidney Transplantation Models

Renal ischemia-reperfusion (I/R) injury, which is unavoidable in renal transplantation, frequently influences both short- and long-term allograft survival. Despite decades of laboratory and clinical investigations, and the advent of renal replacement therapy, the overall mortality rate due to acute tubular injury has changed little. I/R-induced DNA damage results in p53 activation in proximal tubule cells (PTC), leading to their apoptosis. Therefore, we examined the therapeutic effect of temporary p53 inhibition in two rat renal transplantation models on structural and functional aspects of injury using intravital two-photon microscopy. Nephrectomized Sprague-Dawley rats received syngeneic left kidney transplantation either after 40 min of intentional warm ischemia or after combined 5-h cold and 30-min warm ischemia of the graft. Intravenously administrated siRNA for p53 (siP53) has previously been shown to be filtered and reabsorbed by proximal tubular epithelial cells following the warm ischemia/reperfusion injury in a renal clamp model. Here, we showed that it was also taken up by PTC following 5 h of cold ischemia. Compared to saline-treated recipients, treatment with siP53 resulted in conservation of renal function and significantly suppressed the I/R-induced increase in serum creatinine in both kidney transplantation models. Intravital two-photon microscopy revealed that siP53 significantly ameliorated structural and functional damage to the kidney assessed by quantification of tubular cast formation and the number of apoptotic and necrotic tubular cells and by evaluation of blood flow rate. In conclusion, systemic administration of siRNA for p53 is a promising new approach to protect kidneys from I/R injury in renal transplantation.

The effect of cyanide compounds, fluorides, aluminum, and inorganic oxides present in spent pot liner on germination and root tip cells of Lactuca sativa

SPL (spent pot liner) is a solid waste produced by the aluminum industry. This waste has a highly variable composition, consisting of cyanides, fluorides, organics, and metals. The aim of this work was to study the effect of SPL on root tips of Lactuca sativa using current plant bioassays. We observed a decrease in the germination rate with increasing concentrations of SPL. In addition, SPL was found to reduce root growth, which is correlated with a decrease in the mitotic index. Nevertheless, we noticed a significant enhancement in the percentage of stickiness, c-metaphase, anaphase bridges, and laggard chromosomes in dividing cells and also an increase in the number of cells with condensed nuclei. Moreover, SPL was found to alter the root tip surface, resulting in a reduction in the amount of root hair. These results demonstrate that SPL is a toxic agent that leads to cell damage and disturbance.

GSK3beta promotes apoptosis after renal ischemic injury

The mechanism by which the serine-threonine kinase glycogen synthase kinase-3beta (GSK3beta) affects survival of renal epithelial cells after acute stress is unknown. Using in vitro and in vivo models, we tested the hypothesis that GSK3beta promotes Bax-mediated apoptosis, contributing to tubular injury and organ dysfunction after acute renal ischemia. Exposure of renal epithelial cells to metabolic stress activated GSK3beta, Bax, and caspase 3 and induced apoptosis. Expression of a constitutively active GSK3beta mutant activated Bax and decreased cell survival after metabolic stress. In contrast, pharmacologic inhibition (4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione [TDZD-8]) or RNA interference-mediated knockdown of GSK3beta promoted cell survival. Furthermore, RNA interference-mediated knockdown of Bax abrogated the cell death induced by constitutively active GSK3beta. In a cell-free assay, TDZD-8 inhibited the phosphorylation of a peptide containing the Bax serine(163) site targeted by stress-activated GSK3beta. In rats, TDZD-8 inhibited ischemia-induced activation of GSK3beta, Bax, and caspase 3; ameliorated tubular and epithelial cell damage; and significantly protected renal function. Taken together, GSK3beta-mediated Bax activation induces apoptosis and tubular damage that contribute to acute ischemic kidney injury.

Protective effect of ginger extract against bromobenzene-induced hepatotoxicity in male rats

The bromobenzene (BB)-induced hepatotoxicity comes from its reactive metabolites. The efficacy of different doses of ginger (Zingiber officinalesRose) extract in alleviating hepatotoxicity was investigated in male albino rats. Oxidative stress parameters were monitored. The drugs metabolizing enzymes; cytochrome P450 and GST, pro-inflammatory marker; COX-2 and the apoptotic marker; caspase-3 were assessed. Animals were assigned to 1 of 5 groups: control group; bromobenzene (460 mg/kg BW) alone, three animal groups 3-5 treated with different doses of ethanolic ginger extract (100, 200, 300 mg/kg BW, respectively) 2 weeks prior bromobenzene (460 mg/kg BW) treatment. Rats received orally ginger extract daily for 21 days whereas bromobenzene treatment for 7 days starting from 15th day of treatment. Oral treatment of BB was found to elicit a significant decrease in the activities of the antioxidant enzymes; SOD, GPx and the GSH level, while the activities of GR and drug metabolizing enzymes; GSTs and Cyt P450 were enhanced. Also, BB-treatment resulted in a great enhanced production of nitric oxide products and activation of COX-2 and caspase-3. Pre-treatment with different doses of ginger extract prior to BB-treatment alleviated its toxic effects on the tested parameters in the three animal groups.

Adverse effects of nicotine and immunosuppression on proximal tubular epithelial cell viability, tissue repair and oxidative stress gene expression

BACKGROUND

Renal dysfunction in non-renal transplantation is a major arbiter of poor late allograft outcomes. Tobacco recidivism is an important modifiable risk marker for cardiac allograft loss, but its effects on renal dysfunction remain poorly studied.

METHODS

In a 96-well plate, 10(-5) proximal tubular epithelial (PTE) cells (HK-2, American Type Culture Collection) were cultured overnight and treated with sirolimus (SRL; 100 nmol/liter), nicotine (N; 10(-7) mol/liter) and mycophenolate mofetil (MMF; 10 micromol/liter), alone or in combination for 24 hours. Cell viability was quantified by treatment with tetrazolium salt WST-1 and calculated as the difference in percent inhibition with respect to the optical densitometry (OD) of treated and untreated cells. Gene and protein expression was analyzed using real-time polymerase chain reaction and Western blot techniques.

RESULTS

OD decreased with SRL (-52.7 +/- 2.85%), N (-47.3 +/- 3.84%) and MMF (-53.3 +/- 2.4%) in isolation. Further reduction in OD occurred when N was combined with SRL (-63 +/- 2.3%, p < 0.04), MMF (-64.3 +/- 1.45%, p < 0.02) or the combination of SRL and MMF (-78.2%, p < 0.007). Compared with control, treatment of PTE cells with N increased mRNA expression of transforming growth factor-beta (TGF-beta; 10-fold), connective tissue growth factor (CTGF; 25-fold), osteopontin (OPN; 10-fold) and NADPH oxidase components (p22(phox), NOX-1 and Rac-1 at 18-, 16- and 12-fold, respectively). The pre-treatment of cells with inhibitor of superoxide generator diphenylene iodonium (DPI) reversed these effects.

CONCLUSIONS

Nicotine adversely amplified the effects of SRL and MMF on tissue repair and oxidative stress markers, subsequently modulating PTE viability. However, caution is advised in extrapolating these in vitro findings to the human model.

Investigating the role of ischemia vs. elevated hydrostatic pressure associated with acute obstructive uropathy

Obstructive uropathy can cause irreversible renal damage. It has been hypothesized that elevated hydrostatic pressure within renal tubules and/or renal ischemia contributes to cellular injury following obstruction. However, these assaults are essentially impossible to isolate in vivo. Therefore, we developed a novel pressure system to evaluate the isolated and coordinated effects of elevated hydrostatic pressure and ischemic insults on renal cells in vitro. Cells were subjected to: (1) elevated hydrostatic pressure (80 cm H(2)O); (2) ischemic insults (hypoxia (0% O(2)), hypercapnia (20% CO(2)), and 0 mM glucose media); and (3) elevated pressure + ischemic insults. Cellular responses including cell density, lactate dehydrogenase (LDH) release, and intracellular LDH (LDH(i)), were recorded after 24 h of insult and following recovery. Data were analyzed to assess the primary effects of ischemic insults and elevated pressure. Unlike pressure, ischemic insults exerted a primary effect on nearly all response measurements. We also evaluated the data for insult interactions and identified significant interactions between ischemic insults and pressure. Altogether, findings indicate that pressure may sub-lethally effect cells and alter cellular metabolism (LDH(i)) and membrane properties. Results suggest that renal ischemia may be the primary, but not the sole, cause of cellular injury induced by obstructive uropathy.

Experimental strategies to improve in vitro models of renal ischemia

Ischemia has elicited a great deal of interest among the scientific community due to its role in life-threatening pathologies such as cancer, stroke, acute renal failure, and myocardial infarction. Oxygen deprivation (hypoxia) associated with ischemia has recently become a subject of intense scrutiny. New investigators may find it challenging to induce hypoxic injury in vitro. Researchers may not always be aware of the experimental barriers that contribute to this phenomenon. Furthermore, ischemia is associated with other major insults, such as excess carbon dioxide (hypercapnia), nutrient deprivation, and accumulation of cellular wastes. Ideally, these conditions should also be incorporated into in vitro models. Therefore, the motivation behind this review is to: i. delineate major in vivo ischemic insults; ii. identify and explain critical in vitro parameters that need to be considered when simulating ischemic pathologies; iii. provide recommendations to improve experiments; and as a result, iv. enhance the validity of in vitro results for understanding clinical ischemic pathologies. Undoubtedly, it is not possible to completely replicate the in vivo environment in an ex vivo model system. In fact, the primary goal of many in vitro studies is to elucidate the role of specific stimuli during in vivo pathological events. This review will present methodologies that may be implemented to improve the applicability of in vitro models for understanding the complex pathological mechanisms of ischemia. Finally, although these topics will be discussed within the context of renal ischemia, many are pertinent for cellular models of other organ systems and pathologies.

Apoptosis antagonizing transcription factor protects renal tubule cells against oxidative damage and apoptosis induced by ischemia-reperfusion

Apoptosis antagonizing transcription factor (AATF) is a leucine zipper domain-containing protein that has antiapoptotic properties. AATF is expressed in several organs and tissues, including the kidney. AATF may participate in inhibition of proapoptotic pathways and/or activation of antiapoptotic pathways. Ischemia/reperfusion-induced renal injury (IRI) is clinically important because it typically damages renal tubular epithelial cells and glomerular cells and is the most common cause of acute renal failure. It now is reported that AATF is expressed in human kidney proximal tubule (HK-2) cells and in mouse primary renal tubule epithelial cells. Levels of AATF expression were altered significantly in these cells in a well-established in vitro model of renal IRI. In transfected HK-2 cells, RNA interference-mediated silencing of AATF exacerbated whereas overexpression of the full-length AATF ameliorated mitochondrial dysfunction, accumulation of superoxide and peroxynitrite, lipid peroxidation, caspase-3 activation, and apoptotic death that were induced by IRI. In primary renal tubule epithelial cells, overexpression of AATF mediated by recombinant adeno-associated virus (AAV) vectors resulted in significant antiapoptotic activity, whereas knockdown of AATF by small interference RNA led to exacerbated cell death after IRI. These results identify AATF as a novel cytoprotective factor against oxidative and apoptotic damage in renal tubular cells. AATF may represent a potential candidate for therapeutic application in IRI.

Par-4 is a novel mediator of renal tubule cell death in models of ischemia-reperfusion injury

Prostate apoptosis response-4 (Par-4) is a leucine zipper protein linked to apoptotic cell death in prostate cancer and neuronal tissues. The leucine zipper domain of Par-4 (Leu.zip) mediates protein-protein interactions that are essential for sensitization of cells to apoptosis, and overexpression of Leu.zip blocks Par-4 activity in a dominant negative fashion. Ischemia-reperfusion-induced renal injury (IRI) is clinically important because it typically damages renal tubular epithelial cells and glomerular cells, and it is the most common cause of acute renal failure (ARF). We now report that Par-4 is expressed in renal tubule cells and that aberrant expression of Par-4 activity plays a crucial role in activating apoptotic pathways in well-characterized models of renal IRI. Increased levels of Par-4 were observed following chemical ischemia-reperfusion in HK-2 cells in vitro and in mouse renal tubular cells following bilateral clamping of renal pedicles in vivo. Inhibition of Par-4 expression by specific par-4 antisense oligonucleotides largely prevented HK-2 cell apoptosis induced by IRI. Overexpression of Par-4 in these cells exacerbated mitochondrial dysfunction and caspase activation and conferred increased sensitivity to IRI-induced apoptosis. Expression of Leu.zip, a dominant negative regulator of Par-4, largely prevented mitochondrial dysfunction and caspase activation and significantly inhibited IRI-induced apoptosis in HK-2 cells. In addition, transfection of Par-4 increased while transfection of Leu.zip decreased necrosis in HK-2 cells following prolonged IRI. These results identify Par-4 as a novel and early mediator of renal tubule cell injury following IRI and provide a potential target for developing new therapeutic strategies for renal IRI and ARF.

Administered mesenchymal stem cells enhance recovery from ischemia/reperfusion-induced acute renal failure in rats

BACKGROUND

Adult stem cells are promising for the development of novel therapies in regenerative medicine. Acute renal failure (ARF) remains a frequent clinical complication, associated with an unacceptably high mortality rate, in large part due to the ineffectiveness of currently available therapies. The aim of this study was, therefore, to evaluate the therapeutic effectiveness of bone marrow-derived mesenchymal stem cells in a rat model of ischemia/reperfusion (I/R) ARF.

METHODS

We used a common I/R model in rats to induce ARF by clamping both renal pedicles for 40 minutes. Mesenchymal stem cells were iron-dextran-labeled for in vivo tracking studies by magnetic resonance imaging (MRI) and kidneys were imaged for mesenchymal stem cells immediately after infusion and at day 3 after ARF. Renal injury was scored on day 3 and cells were additionally tracked by Prussian blue staining.

RESULTS

We show in I/R-induced ARF in rats, modeling the most common form of clinical ARF, that infusion of mesenchymal stem cells enhances recovery of renal function. Mesenchymal stem cells were found to be located in the kidney cortex after injection, as demonstrated by MRI. Mesenchymal stem cells-treated animals had both significantly better renal function on days 2 and 3 and better injury scores at day 3 after ARF. Histologically, mesenchymal stem cells were predominantly located in glomerular capillaries, while tubules showed no iron labeling, indicating absent tubular transdifferentiation.

CONCLUSION

We conclude that the highly renoprotective capacity of mesenchymal stem cells opens the possibility for a cell-based paradigm shift in the treatment of I/R ARF.

Protection of HIF-1-deficient primary renal tubular epithelial cells from hypoxia-induced cell death is glucose dependent

Ischemic acute renal failure is a frequent clinical problem in hospitalized patients and is associated with significant mortality. Hypoxia-inducible factor 1 (HIF-1) mediates cellular adaptation to hypoxia by regulating biological processes important for cell survival, which include glycolysis, angiogenesis, erythropoiesis, apoptosis, and proliferation. To investigate the role of HIF-1 in hypoxia-induced renal epithelial cell death, we generated mice that allow inactivation of HIF-1α by tetracycline-inducible Cre-loxP-mediated recombination in primary renal proximal tubule cells (PRPTC), resulting in a suppression of HIF-1-mediated gene transcription during oxygen deprivation. In the absence of glucose, the onset and the degree of hypoxia-induced cell death in HIF-1-deficient PRPTC were comparable to wild-type cells. However, when glucose availability was limited, the onset of cell death was delayed in either PRPTC that were HIF-1 deficient or in wild-type PRPTC when glycolysis or glucose uptake was partially inhibited. Our findings suggest in an in vitro genetic model that 1) the generation of adequate energy levels for the maintenance of PRPTC viability under hypoxia does not require HIF-1 and 2) that HIF-1 regulates the timing of hypoxia-induced cell death and apoptosis onset through its effects on glucose consumption.

ApoSense: a novel technology for functional molecular imaging of cell death in models of acute renal tubular necrosis

Purpose

Acute renal tubular necrosis (ATN), a common cause of acute renal failure, is a dynamic, rapidly evolving clinical condition associated with apoptotic and necrotic tubular cell death. Its early identification is critical, but current detection methods relying upon clinical assessment, such as kidney biopsy and functional assays, are insufficient. We have developed a family of small molecule compounds, ApoSense, that is capable, upon systemic administration, of selectively targeting and accumulating within apoptotic/necrotic cells and is suitable for attachment of different markers for clinical imaging. The purpose of this study was to test the applicability of these molecules as a diagnostic imaging agent for the detection of renal tubular cell injury following renal ischemia.

Methods

Using both fluorescent and radiolabeled derivatives of one of the ApoSense compounds, didansyl cystine, we evaluated cell death in three experimental, clinically relevant animal models of ATN: renal ischemia/reperfusion, radiocontrast-induced distal tubular necrosis, and cecal ligature and perforation-induced sepsis.

Results

ApoSense showed high sensitivity and specificity in targeting injured renal tubular epithelial cells in vivo in all three models used. Uptake of ApoSense in the ischemic kidney was higher than in the non-ischemic one, and the specificity of ApoSense targeting was demonstrated by its localization to regions of apoptotic/necrotic cell death, detected morphologically and by TUNEL staining.

Conclusion

ApoSense technology should have significant clinical utility for real-time, noninvasive detection of renal parenchymal damage of various types and evaluation of its distribution and magnitude; it may facilitate the assessment of efficacy of therapeutic interventions in a broad spectrum of disease states.

Omi/HtrA2 protease mediates cisplatin-induced cell death in renal cells

Omi/HtrA2 is a mitochondrial proapoptotic serine protease that is able to induce both caspase-dependent and caspase-independent cell death. After apoptotic stimuli, Omi is released to the cytoplasm where it binds and cleaves inhibitor of apoptosis proteins. In this report, we investigated the role of Omi in renal cell death following cisplatin treatment. Using primary mouse proximal tubule cells, as well as established renal cell lines, we show that the level of Omi protein is upregulated after treatment with cisplatin. This upregulation is followed by the release of Omi from mitochondria to the cytoplasm and degradation of XIAP. Reducing the endogenous level of Omi protein using RNA interference renders renal cells resistant to cisplatin-induced cell death. Furthermore, we show that the proteolytic activity of Omi is necessary and essential for cisplatin-induced cell death in this system. When renal cells are treated with Omi's specific inhibitor, ucf-101, they become significantly resistant to cisplatin-induced cell death. Ucf-101 was also able to minimize cisplatin-induced nephrotoxic injury in animals. Our results demonstrate that Omi is a major mediator of cisplatin-induced cell death in renal cells and suggest a way to limit renal injury by specifically inhibiting its proteolytic activity.

Cephaloridine Induces Translocation of Protein Kinase C δ Into Mitochondria and Enhances Mitochondrial Generation of Free Radicals in the Kidney Cortex of Rats Causing Renal Dysfunction

We have previously reported that the enhancement of free radical generation in mitochondria isolated from the kidney cortex of rats exposed to cephaloridine (CER) is probably mediated by the activation of protein kinase C (PKC). We examined which isoenzymes of PKC might be involved in the development of nephrotoxicity induced by CER in rats. The CER-induced renal dysfunction observed 24 h after its injection was prevented by a potent antioxidant DPPD and well-known PKC inhibitors like H-7 and rottlerin. At 1.5 and 3.5 h after the CER injection, the free radical generation was increased markedly and this was associated with translocation of PKCdelta into the mitochondria of renal cortex tissue. Pretreatment of rats with H-7, a PKC inhibitor, significantly inhibited the CER-derived increase in mitochondrial generation of free radicals, suggesting that H-7 probably gets into the mitochondria and inhibits the activity of translocated PKC within the mitochondria. It was also shown that pretreatment of rats with rottlerin, a specific inhibitor of PKCdelta, suppressed the early translocation of PKCdelta into mitochondria and inhibited the CER-derived development of renal dysfunction. These results suggest that the CER-derived early translocation of PKCdelta into mitochondria probably leads to the enhanced production of free radicals through the mitochondrial respiratory chain during the development of the nephrotoxicity caused by CER. Understanding the role of PKCdelta in mitochondria may provide an important clue to the molecular mechanisms of mitochondrial production of reactive oxygen species and the free radical-induced renal failure in rats treated with CER.

L-Arginine Does Not Affect Renal Morphology and Cell Survival in Ischemic Acute Renal Failure in Rats

BACKGROUND

L-Arginine (L-Arg), a substrate of nitric oxide synthases, improves renal function in ischemic acute renal failure (iARF). We evaluated whether L-Arg improves renal morphology and cell survival in the course of iARF.

METHODS AND RESULTS

iARF was induced in rats by bilateral clamping of renal arteries for 45 min. L-Arg was applied intraperitoneally during clamping, and orally during 14 days of follow-up. Morphology and cell survival of renal cortical and medullar tissue was analyzed on days 1, 3, 7, and 14 of follow-up, using toluidine blue staining and immunohistochemistry of perfusion-fixated tissue, and Western blot analysis of tissue homogenate. Renal tubular injury showed typical features of necrosis and was most severe on days 1 and 3 after clamping, predominantly in S3 segments, with almost complete recovery by day 14. Enhanced medullar monocyte infiltration, determined by ED-1 expression as well as by immunohistochemistry, and enhanced expression of proliferating cell nuclear antigen (PCNA), indicative of proliferation and regeneration, accompanied these morphological changes. Compared to controls, L-Arg had no impact on renal morphology, ED-1, and PCNA expression. Furthermore, expression of markers of apoptosis Bcl-2, Bax, and cleaved caspase-3 was only slightly increased in iARF rats, compared to sham-operated animals, and was also not influenced by L-Arg.

CONCLUSION

Despite its repeatedly reported positive impact on renal function as also shown in our model, L-Arg does not alter cell death and proliferation in the course of iARF in our model. Thus, different mechanisms have to be considered, in particular improved intrarenal hemodynamics.

Differential effects of caspase inhibitors on the renal dysfunction and injury caused by ischemia–reperfusion of the rat kidney

Caspase activation has been implicated in the development of ischemia-reperfusion injury. Here, we investigate the effects of different caspase inhibitors on the renal dysfunction and injury caused by ischemia-reperfusion of the rat kidney. Bilateral clamping of renal pedicles (45 min) followed by reperfusion (6 h) caused significant renal dysfunction and marked renal injury. Caspase-1 inhibitor II (N-acetyl-L-tyrosyl-L-valyl-N-[(1S)-1-(carboxymethyl)-3-chloro-2-oxo-propyl]-L-alaninamide, Ac-YVAD-CMK, 3 mg/kg, administered i.p.) significantly reduced biochemical and histological evidence of renal dysfunction and injury. However, although caspase-3 inhibitor I (N-acetyl-L-aspartyl-L-glutamyl-N-(2-carboxyl-1-formylethyl]-L-valinamide, Ac-DEVD-CHO, 3 mg/kg, administered i.p.) produced a significant improvement of renal (glomerular) dysfunction (reduction of serum creatinine levels), it was not able to reduce tubular dysfunction and injury. Furthermore, the pan-caspase inhibitor caspase inhibitor III (N-tert-butoxycarbonyl-aspartyl(OMe)-fluoromethylketone, Boc-D-FMK, 3 mg/kg, administered i.p.) did not reduce renal dysfunction and injury. Both caspase-1 and -3 inhibitors markedly reduced the evidence of oxidative and nitrosative stress in rat kidneys subjected to ischemia-reperfusion. Overall, these results demonstrate that inhibition of caspase-1 reduces renal ischemia-reperfusion injury to a greater extent than caspase-3 inhibition, supporting the notion that the mode of acute cell death in our model of renal ischemia-reperfusion is primarily via necrosis. Furthermore, our finding that a pan-caspase inhibitor did not reduce the renal dysfunction and injury suggests that activation of some caspases during ischemia-reperfusion could provide protection against acute ischemic renal injury. Overall, these results demonstrate that inhibition of caspase-1 activity reduces renal ischemia-reperfusion injury and that this therapeutic strategy may be of benefit against ischemic acute renal failure.

Calpain is activated in experimental uremia: is calpain a mediator of uremia-induced myocardial injury?

BACKGROUND

The cysteine proteases calpain and caspase-3 are known mediators of cell death. The aim of this study was to assess their contribution to the tissue damage found in experimental uremia.

METHODS

Calpain and caspase-3 activities were measured in the hearts of rats that were sham-operated (control), sham-operated and spontaneously hypertensive (SHR), and those rendered uremic by 5/6 nephrectomy (uremic). In an in vitro study, heart myoblasts (Girardi) were incubated with human serum from healthy subjects (control serum conditioned media, CSCM) or uremic patients (uremic serum conditioned media, USCM), in the presence and absence of calpain and caspase-3 inhibitors. After 48 hours the activity of calpain and caspase-3 was measured, and cell injury determined by DNA fragmentation (ELISA) and lactate dehydrogenase (LDH) release. An in situ assay was designed to study how USCM affects calpain activity over time.

RESULTS

In the in vivo study, mean calpain activities were almost identical in the control and SHR groups, but calpain and caspase-3 activities were much elevated in the uremic group (P < 0.01 and 0.001 respectively vs. control). The SHR group had significantly higher mean arterial blood pressure (P < 0.001 vs. control, 0.01 vs. uremic). In the in vitro study calpain activity and DNA fragmentation were markedly higher in USCM treated cells compared to CSCM (both P<0.05). Both were reduced in USCM cells containing calpain inhibitors (E64d, calpastatin, or PD 150606). LDH release was raised also in USCM treated cultures (P < 0.05), which only the E64d treatment could significantly reduce (P < 0.02). Caspase-3 activities were similar in USCM and CSCM groups. The in situ assay showed significant increases in calpain activity in USCM treated cells compared to CSCM after just 3.5 hours (P<0.01).

CONCLUSIONS

In vivo results suggest that the increases in calpain and caspase-3 activity in uremic rat hearts were primarily due to uremia and not to hypertension. In vitro data demonstrate that uremia-induced cell injury can be attenuated by calpain inhibition. Therefore, it is likely that calpain is a mediator of uremia-induced myocardial injury.

P53 mediates the apoptotic response to GTP depletion after renal ischemia-reperfusion: protective role of a p53 inhibitor

Ischemic injury to the kidney is characterized in part by nucleotide depletion and tubular cell death in the form of necrosis or apoptosis. GTP depletion was recently identified as an important inducer of apoptosis during chemical anoxia in vitro and ischemic injury in vivo. It has also been shown that GTP salvage with guanosine prevented apoptosis and protected function. This study investigates the role of p53 in mediating the apoptotic response to GTP depletion. Male Sprague-Dawley rats underwent bilateral renal artery clamp for 30 min followed by reperfusion. p53 protein levels increased significantly in the medulla over 24 h post-ischemia. The provision of guanosine inhibited the increase in p53. Pifithrin-alpha, a specific inhibitor of p53, mimicked the effects of guanosine. It had no effect on necrosis, yet it prevented apoptosis and protected renal function. Pifithrin-alpha was protective when given up to 14 h after the ischemic insult. The effects of pifithrin-alpha on p53 included inhibition of transcriptional activation of downstream p53 targets like p21 and Bax and inhibition of p53 translocation to the mitochondria. Similar results were obtained in cultured renal tubular cells. It is concluded that p53 is an important mediator of apoptosis during states of GTP depletion. Inhibitors of p53 should be considered in the treatment of ischemic renal injury.

Meprin, a brush-border enzyme, plays an important role in hypoxic/ischemic acute renal tubular injury in rats

BACKGROUND

It has been shown that non-congenic mice strains with lower levels of renal meprin develop less renal injury following renal ischemia and reperfusion. We have demonstrated that following ischemia-reperfusion renal injury, there is a rapid shift of meprin localization and intensity from the brush border to the cytoplasmic compartment, tubular lumens and the tubular basement membranes. Radical shifts in the localization of an activated enzyme to potentially sensitive areas of the tubule suggest a toxic role for meprin in ischemia-reperfusion injury. Though meprin degrades extracellular matrix components and other substrates, to our knowledge meprin cytotoxicity has never been examined. Therefore, the first objective of this study was to determine if meprin is directly cytotoxic to renal cells in vitro. The second objective was to determine if inhibition of meprin is protective against hypoxia-reoxygenation injury in vitro and ischemia-reperfusion injury in vivo.

METHODS

The immortalized porcine epithelial cell line (LLC-PK1) and Madin-Darby canine kidney (MDCK) cells in culture were exposed to meprin in various concentrations and for various times. Cell death was determined by Trypan Blue exclusion, lactate dehydrogenase (LDH) release and the 3-[4,5] dimethylthiazol-2,5-diphenyltetrazolium bromide (MTT) assay. Renal slices were used to examine the effect of the meprin inhibitor, actinonin, on hypoxic injury in vitro. Male Sprague-Dawley rats were used in ischemia-reperfusion injury studies to determine the effect of actinonin on renal function as measured by plasma urea nitrogen, creatinine and renal histology.

RESULTS

Meprin is cytotoxic to LLC-PK1 and MDCK cells in a concentration and time dependent manner. The meprin inhibitor 1,10-phenanthroline completely abolished the cytotoxic effect. Renal slices exposed to hypoxia and hypoxia followed by reoxygenation showed marked cell death. Pre-treatment with the actinonin was markedly protective while not interfering with the hypoxia-induced fall in adenosine 5'-triphosphate (ATP) levels. In in vivo studies, rats exposed to ischemia/reperfusion injury were markedly protected against acute renal failure by IP treatment with actinonin.

CONCLUSIONS

Meprin is cytotoxic to cultured renal tubular epithelial cells in vitro. Renal slices are protected from hypoxia-reoxygenation injury in vitro by the meprin inhibitor actinonin. Meprin inhibition is protective against rat renal hypoxia-reoxygenation injury. These data strongly support the concept that meprin is cytotoxic and may play a key role in renal ischemia-reperfusion induced renal injury.

Apoptosis versus necrosis during cold storage and rewarming of human renal proximal tubular cells

BACKGROUND

A recent clinical study demonstrated that in renal allografts preserved in the cold apoptosis occurred soon after reperfusion. The mode of cell death during cold storage is generally considered necrotic. Whether apoptosis occurs as a part of cold storage is uncertain. The objective was to determine in human renal tubular cells whether apoptosis is specific for rewarming or it also occurs during cold storage and whether it could be modified.

METHODS AND RESULTS

Cold storage (4 degrees C) of primary human renal proximal tubular epithelial (RPTE) in University of Wisconsin (UW) solution up to 48 hr caused a time-dependent increase in cell death measured by lactic dehydrogenase (LDH) release and vital dye exclusion methods. Transmission electron microscopy (TEM) demonstrated that cell death in the cold was necrotic, involving considerable mitochondrial disruption, and was not apoptotic. The TUNEL assay that provides a specific, quantitative measure for apoptosis showed no increase in TUNEL-positivity during flow cytometry of cells stored in cold: 37 degrees C, 0.23+/-0.14%; 24 hr cold, 0.23+/-0.1%; 48 hr cold, 1.79+/-0.58%. Annexin-V staining, a sensitive method for detecting early apoptosis, similarly showed no increase in positively stained cells during cold storage. Addition of antioxidants 2-methyl aminochroman and deferoxamine to UW solution inhibited necrotic cell death and preserved mitochondrial structure. In contrast to cold storage alone, rewarming (37 degrees C for 24 hr) of cold stored cells, however, resulted in significant apoptosis (TUNEL positive: 48 hr cold: 2+/-0.6%, 48 hr cold and 24 hr rewarming: 54+/-17%), which was confirmed by the TEM based on typical apoptotic features. Addition of 2-MAC and DFO significantly inhibited rewarming-induced apoptotic cell death (plus 2-MAC: 3+/-1%, plus DFO: 3+/-2%).

CONCLUSION

Our study in human tubular cells provides evidence that cold storage per se does not result in apoptosis, but is primarily necrotic. However, rewarming is associated with significant apoptosis in the presence of ongoing necrosis, speculatively due to the activation of the apoptotic enzymic process of sublethally injured cells. Inclusion of antioxidants in the storage solution confers protection against both cold storage and rewarming-induced necrosis and apoptosis.