Rapid DNA fragmentation from hypoxia along the thick ascending limb of rat kidneys

Differential Incidence of Contrast-Associated Acute Kidney Injury: Comparing Intravenous and Intraarterial Contrast Administration

PURPOSE OF THE REVIEW

Contrast-associated acute kidney injury (CA-AKI) remains a significant concern in diagnostic and invasive procedures, particularly in the context of iodinated contrast material administration. The traditional definition of CA-AKI, based on serum creatinine elevation following contrast exposure, may not accurately capture its multifactorial nature.

RECENT FINDINGS

Studies have provided new insights into the differential incidence of CA-AKI between intravenous and intraarterial contrast administration, emphasizing the importance of tailored preventative strategies for high-risk procedures. This higher risk may arise from two proposed mechanisms: one implicating free radical formation leading to cytotoxicity and apoptosis in renal cells and another suggesting that contrast media alter renal hemodynamics, particularly in the outer medulla, by constricting the vasa recta and reducing medullary flow. Advances in technology and patient care, including contemporary use of low-osmolar contrast agents and hydration protocols, mitigate CA-AKI risk. Diagnostic and invasive procedures should not be avoided solely due to concerns about renal dysfunction if the patient is likely to benefit clinically.

Neutrophil gelatinase–associated lipocalin as a marker for contrast-induced nephropathy in patients undergoing percutaneous coronary intervention: A prospective observational analysis

Introduction:

Incidence of contrast-induced nephropathy (CIN) post percutaneous coronary intervention (PCI) varies between 5% and 20%. Neutrophil gelatinase–associated lipocalin (NGAL) is a sensitive marker for acute kidney injury. Data regarding the predictive accuracy of NGAL in Indian patients undergoing PCI is sparse.

Methods:

A total of 212 consecutive “all-comer” patients, undergoing PCI from March 2015 to April 2016 were recruited in this single-center observational study. Plasma NGAL levels were measured at 4 hours post PCI using commercially available enzyme-linked immunosorbent assay (Triage® Alere™, San Diego, CA, USA).

Results:

Twenty-five (11.8%) patients developed CIN. The 4-hour post-PCI plasma NGAL levels were significantly higher in patients with CIN than without (400.6 ± 269.3 ng/mL vs. 109.8 ± 68.0 ng/mL, P < 0.0001). Patients developing CIN had higher age, low estimated glomerular filtration rate (eGFR), and higher contrast volume usage during PCI. After adjusting for confounding factors, diabetes mellitus (adjusted odds ratio [AOR] 3.04; P = 0.039; 95% confidence interval [CI]: 1.06–8.73), hypotension at presentation (AOR 24.84; P < 0.0001; 95% CI: 4.65–132.83), and multi-staged PCI (AOR 13.45; P < 0.0001; 95% CI: 4.54–39.79) were found to independently predict the development of CIN. NGAL levels significantly correlated with age (r = 0.149, P = 0.031), eGFR (r = −0.385, P < 0.0001), hemoglobin (r = −0.214, P = 0.002), contrast volume (r = 0.185, P = 0.007), and 48-hour post-PCI serum creatinine levels (r = 0.334, P < 0.0001). At a cutoff of 256.5 ng/mL, plasma NGAL had a sensitivity of 68% and a specificity of 95.2% (area under the curve = 0.878; P < 0.0001; 95% CI: 0.801–0.955) to predict the occurrence of CIN.

Conclusions:

Plasma NGAL is an early and highly predictive biomarker of CIN in patients undergoing PCI. Patients having diabetes, hypotension at presentation and those undergoing second-stage procedures are at a high risk of developing CIN after PCI.

Treprostinil reduces mitochondrial injury during rat renal ischemia-reperfusion injury

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is a major factor contributing to acute kidney injury and it is associated with a high morbidity and mortality if untreated. Renal IRI depletes cellular and tissue adenosine triphosphate (ATP), which compromises mitochondrial function, further exacerbating renal tubular injury. Currently, no treatment for IRI is available. This study investigates the protective role of treprostinil in improving mitochondria biogenesis and recovery during rat renal IRI.

METHODS

Male Sprague Dawley rats were randomly assigned to groups: control, sham, IRI-placebo or IRI-treprostinil and subjected to 45 min of bilateral renal ischemia followed by 1-72 h reperfusion. Placebo or treprostinil (100 ng/kg/min) was administered subcutaneously via an osmotic minipump.

RESULTS

Treprostinil significantly reduced peak elevated serum creatinine (SCr) levels and accelerated normalization relative to IRI-placebo (p < 0.0001). Treatment with treprostinil also inhibited IRI-mediated renal apoptosis, mitochondrial oxidative injury (p < 0.05), and the release of cytochrome c (p < 0.01) vs. IRI-placebo. In addition, treprostinil preserved renal mitochondrial DNA copy number (p < 0.0001) and renal ATP levels (p < 0.05) to nearly those of sham-operated animals. Non-targeted semi-quantitative proteomics showed reduced levels of ATP synthase subunits in the IRI-placebo group which were restored to sham levels by treprostinil treatment (p < 0.05). Furthermore, treprostinil reduced renal IRI-induced upregulated Drp1 and pErk protein levels, and restored Sirt3 and Pgc-1α levels to baseline (p < 0.05).

CONCLUSIONS

Treprostinil reduces mitochondrial-mediated renal apoptosis, inhibits mitochondria fission, and promotes mitochondria fusion, thereby accelerating mitochondrial recovery and protecting renal proximal tubules from renal IRI. These results support the clinical investigation of treprostinil as a viable therapy to reduce renal IRI.

Caspase-(8/3) activation and organ inflammation in a rat model of resuscitated hemorrhagic shock: A role for uric acid

BACKGROUND

Multiple organ failure can develop after hemorrhagic shock (HS). Uric acid (UA) is released from dying cells and can be proinflammatory. We hypothesized that UA could be an alternative mediator of organ apoptosis and inflammation after HS.

METHODS

Ventilated male Wistar rats were used for the HS model. Two durations of shock (5 minutes vs. 60 minutes) were compared, and shams were instrumented only; animals were resuscitated and observed for 24 hours/72 hours. Caspases-(8/3), myeloperoxidase (MPO), TNF-α were measured in lungs and kidneys. Plasma UA and cytokine (IL-1β, IL-18, TNF-α) were measured. A second set of animals were randomized to vehicle versus Rasburicase intraperitoneal intervention (to degrade UA) during resuscitation. Another group received exogenous UA intraperitoneally without HS. Measures mentioned above, in addition to organs UA, were performed at 24 hours. In vitro, caspases-(8/3) activity was tested in epithelial cells exposed to UA.

RESULTS

Hemorrhagic shock increased organ (kidney and lung) TNF-α, MPO, and caspases activity in various patterns while caspase-8 remained elevated over time. Hemorrhagic shock led to increased plasma UA at 2 hours, which remained high until 72 hours; TNF-α and IL-18 were elevated at 24 hours. The exogenous UA administration in sham animals reproduced the activation of caspase-8 and MPO in organs, and TNF-α in the lung. The increased plasma and organ UA levels, plasma and lung TNF-α, as well as organ caspase-(8/3) and MPO, observed at 24 hours after HS, were prevented by the administration of Rasburicase during resuscitation. In vitro, soluble UA induced caspases-(3/8) activity in epithelial cells.

CONCLUSION

Uric acid is persistently high after HS and leads to the activation of caspases-8 and organ inflammation; these can be prevented by an intervention to degrade UA. Therefore, UA is an important biomarker and mediator that could be considered a therapeutic target during HS resuscitation in human.

Contrast-Induced Acute Kidney Injury: An Update

Contrast-induced acute kidney injury (CI-AKI) is defined as an abrupt deterioration in renal function associated with the administration of iodinated contrast media. This type of acute kidney injury is frequently encountered as a complication of percutaneous coronary intervention (PCI) and is associated with adverse short- and long-term outcomes including mainly mortality, cardiovascular morbidity and prolongation of hospitalization. The incidence of CI-AKI after PCI ranges from 2 to 20 % according to baseline kidney function. It may also range according to the clinical setting, being higher after emergency PCI. The primary manifestation is a small decline in kidney function, occurring 1 to 3 days after the procedure. Kidney function usually returns to preexisting levels within 7 days. Incidence of acute renal failure requiring dialysis following PCI is rare (<1 %). The present article aims to review up-to-date published data concerning diagnosis, definition, epidemiology and prognosis of this novel in-hospital epidemic.

Acute kidney function and morphology following topload administration of recombinant hemoglobin solution

There is a 0.138% incidence of adverse reactions related to blood transfusion. Transfusion-related acute lung injury, immunosuppression, fever, pathogen transmission, and hemolytic transfusion reactions are the most common ones. Synthetic oxygen carriers have been developed to deal with blood shortages and for use in the field where stored blood was not available. They were also designed to be pathogen free, including unknown viruses. In this study, we used Male Golden Syrian Hamsters implemented with a dorsal window chamber to determine how infusion of three different, genetically crosslinked recombinant acellular hemoglobin (rHb) solutions with different oxygen affinities and nitric oxide kinetics affect mean arterial pressure (MAP), heart rate (HR), kidney function, and kidney structure. We found that the administration of all three rHb solutions caused mild hypertension and bradycardia 30 minutes after infusion. However, acute changes in glomerular filtration rate (GFR) were not detected, even though histological analysis was performed 72 hours after treatment revealed some structural changes. All the rHb solutions resulted in hypertension 30 minutes after a 10% topload administration. Regardless of their properties, the presence of acellular Hb causes significant alterations to kidney tissue.

Intermedin/adrenomedullin 2 protects against tubular cell hypoxia-reoxygenation injury in vitro by promoting cell proliferation and upregulating cyclin D1 expression

AIM

Intermedin/adrenomedullin 2 (IMD/ADM2) is a newly discovered peptide closely related to adrenomedullin. We recently reported that IMD/ADM2 gene transfer could significantly reduce renal ischaemia/reperfusion injury. In this study, we evaluated the effect of IMD/ADM2 on cell proliferation and regeneration in a cultured rat renal tubular epithelial cell line (NRK-52E) of hypoxia-reoxygenation (H/R) injury.

METHODS

The H/R model in NRK-52E cells consisted of hypoxia for 1 h and reoxygenation for 2 h. IMD/ADM2 was overexpressed in NRK-52E cells using the vector pcDNA3.1-IMD. Enzyme-linked immunosorbent assays were used to measure the concentration of IMD/ADM2 in the culture medium, and real-time PCR and Western blotting were used to determine mRNA and protein levels. In addition, luciferase reporter assays and electrophoretic mobility-shift assays were performed to measure cyclin D1 promoter activity and transcription factor activity.

RESULTS

We found that IMD/ADM2 gene transfer markedly promoted cell viability and decreased lactate dehydrogenase (LDH) activity and cell apoptosis compared with that of H/R. IMD/ADM2 increased the phosphorylation of ERK and decreased the phosphorylation of JNK and P38. Furthermore, IMD/ADM2 promoted cell cycle progression with concomitant increases in the levels of cyclin D1 and cyclin E, and these effects were blocked by the inhibition of ERK, or the agonist JNK and P38. IMD/ADM2 also increased cyclin D1 promoter activity and AP-1 DNA-binding activity.

CONCLUSIONS

We demonstrated that IMD/ADM2 promotes renal cell proliferation and regeneration after renal H/R injury by upregulating cyclin D1 and that this upregulation seems to be mediated by the ERK, JNK, and P38 MAPK signalling pathways.

Proximal tubule proliferation is insufficient to induce rapid cyst formation after cilia disruption

Disrupting the function of cilia in mouse kidneys results in rapid or slow progression of cystic disease depending on whether the animals are juveniles or adults, respectively. Renal injury can also markedly accelerate the renal cyst formation that occurs after disruption of cilia in adult mice. Rates of cell proliferation are markedly higher in juvenile than adult kidneys and increase after renal injury, suggesting that cell proliferation may enhance the development of cysts. Here, we induced cilia loss in the kidneys of adult mice in the presence or absence of a Cux-1 transgene, which maintains cell proliferation. By using this model, we were able to avoid additional factors such as inflammation and dedifferentiation, which associate with renal injury and may also influence the rate of cystogenesis. After induction of cilia loss, cystic disease was not more pronounced in adult mice with the Cux-1 transgene compared with those without the transgene. In conclusion, these data suggest that proliferation is unlikely to be the sole mechanism underlying the rapid cystogenesis observed after injury in mice that lose cilia function in adulthood.

Prevention of acute kidney injury by tauroursodeoxycholic acid in rat and cell culture models

BACKGROUND

Acute kidney injury (AKI) has grave short- and long-term consequences. Often the onset of AKI is predictable, such as following surgery that compromises blood flow to the kidney. Even in such situations, present therapies cannot prevent AKI. As apoptosis is a major form of cell death following AKI, we determined the efficacy and mechanisms of action of tauroursodeoxycholic acid (TUDCA), a molecule with potent anti-apoptotic and pro-survival properties, in prevention of AKI in rat and cell culture models. TUDCA is particularly attractive from a translational standpoint, as it has a proven safety record in animals and humans.

METHODOLOGY/PRINCIPAL FINDINGS

We chose an ischemia-reperfusion model in rats to simulate AKI in native kidneys, and a human kidney cell culture model to simulate AKI associated with cryopreservation in transplanted kidneys. TUDCA significantly ameliorated AKI in the test models due to inhibition of the mitochondrial pathway of apoptosis and upregulation of survival pathways.

CONCLUSIONS

This study sets the stage for testing TUDCA in future clinical trials for prevention of AKI, an area that needs urgent attention due to lack of effective therapies.

Role of contrast media on oxidative stress, Ca(2+) signaling and apoptosis in kidney

Contrast media (CM)-induced nephropathy is a common cause of iatrogenic acute renal failure. The aim of the present review was to discuss the mechanisms and risk factors of CM, to summarize the controlled studies evaluating measures for prevention and to conclude with evidence-based strategies for prevention. A review of the relevant literature and results from recent clinical studies as well as critical analyses of published systematic reviews used MEDLINE and the Science Citation Index. The cytotoxicity induced by CM leads to apoptosis and death of endothelial and tubular cells and may be initiated by cell membrane damage together with reactive oxygen species (ROS) and inflammation. Cell damage may be aggravated by factors such as tissue hypoxia, properties of individual CM such as ionic strength, high osmolarity and/or viscosity. Clinical studies indeed support this possibility, suggesting a protective effect of ROS scavenging with the administration of N-acetylcysteine, ascorbic acid erdosteine, glutathione and bicarbonate infusion. The interaction between extracellular Ca(2+), which plays a central role in intercellular contacts and production of ROS, and the in vitro toxicity of CM was also reviewed. The current review addresses the role of oxidative stress in the pathogenesis of CM in the kidney as well as current and potential novel treatment modalities for the prevention of neutrophil activation and CM-induced kidney degeneration in patients. ROS production through CM-induced renal hypoxia may exert direct tubular and vascular endothelial injury. Preventive strategies via antioxidant supplementation include inhibition of ROS generation or scavenging.

Simvastatin attenuates contrast-induced nephropathy through modulation of oxidative stress, proinflammatory myeloperoxidase, and nitric oxide

Contrast media- (CM-) induced nephropathy is a serious complication of radiodiagnostic procedures. Available data suggests that the development of prophylaxis strategies is limited by poor understanding of pathophysiology of CM-induced nephropathy. Present study was designed to determine the role of oxidative stress, myeloperoxidase, and nitric oxide in the pathogenesis of iohexol model of nephropathy and its modification with simvastatin (SSTN). Adult Sprague Dawley rats were divided into seven groups. After 24 h of water deprivation, all the rats except in control and SSTN-only groups were injected (10 ml/kg) with 25% glycerol. After 30 min, SSTN (15, 30, and 60 mg/kg) was administered orally, daily for 4 days. Twenty-four hours after the glycerol injection, iohexol was infused (8 ml/kg) through femoral vein over a period of 2 min. All the animals were sacrificed on day 5 and blood and kidneys were collected for biochemical and histological studies. The results showed that SSTN dose dependently attenuated CM-induced rise of creatinine, urea, and structural abnormalities suggesting its nephroprotective effect. A significant increase in oxidative stress (increased lipid hydroperoxides and reduced glutathione levels) and myeloperoxidase (MPO) and decreased nitric oxide in CM group were reversed by SSTN. These findings support the use of SSTN to combat CM-induced nephrotoxicity.

Oxidants as important determinants of renal apoptosis during pneumoperitoneum: a study in an isolated perfused rat kidney model

INTRODUCTION

Pneumoperitoneum-associated ischemia-reperfusion (IR) may initiate renal dysfunction. Whether oxidants are responsible for renal structural damage, such as cell apoptosis, has not yet been evaluated. We investigated such eventuality in an isolated rat kidney model.

METHODS

Thirty-five rat kidneys with their vessels and ureter were harvested and perfused within a closed environment at flow of 15 ml min(-1). After stabilization, kidneys were assigned to one of five groups (n = 7 per group): CO(2)-induced intrachamber pressure of 8, 12, or 0 mmHg (control), and 8 or 12 mmHg pressure applied to kidneys from rats treated pre-experimentally with tungsten for 14 days. Pressurization lasted 60 min.

RESULTS

Organ perfusion pressure raised as intrachamber pressure increased. Urinary output decreased in the two pressurized nonpretreated groups. Intrachamber pressure was directly associated with an increase in postexperimental xanthine oxidase tissue levels. Twofold apoptosis was documented (p < 0.05) in cortex of nonpretreated kidney in the 12 mmHg group compared with the 8 or 0 mmHg groups. Tungsten pretreatment significantly (p < 0.05) attenuated the abnormalities documented in the 12 mmHg group, but less so in the 8 mmHg pressurized nontreated counterparts.

CONCLUSIONS

Pneumoperitoneal pressure applied to isolated perfused kidney is associated with renal apoptosis. This rapidly induced structural renal damage is oxidant dependent and can be attenuated by antioxidants. Further studies may shed more light on the role of antioxidants in preventing pneumoperitoneum-induced kidney dysfunction.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Contrast-induced nephropathy in interventional cardiology

Development of contrast-induced nephropathy (CIN), ie, a rise in serum creatinine by either ≥0.5 mg/dL or by ≥25% from baseline within the first 2-3 days after contrast administration, is strongly associated with both increased inhospital and late morbidity and mortality after invasive cardiac procedures. The prevention of CIN is critical if long-term outcomes are to be optimized after percutaneous coronary intervention. The prevalence of CIN in patients receiving contrast varies markedly (from <1% to 50%), depending on the presence of well characterized risk factors, the most important of which are baseline chronic renal insufficiency and diabetes mellitus. Other risk factors include advanced age, anemia, left ventricular dysfunction, dehydration, hypotension, renal transplant, low serum albumin, concomitant use of nephrotoxins, and the volume of contrast agent. The pathophysiology of CIN is likely to be multifactorial, including direct cytotoxicity, apoptosis, disturbances in intrarenal hemodynamics, and immune mechanisms. Few strategies have been shown to be effective to prevent CIN beyond hydration, the goal of which is to establish brisk diuresis prior to contrast administration, and to avoid hypotension. New strategies of controlled hydration and diuresis are promising. Studies are mixed on whether prophylactic oral N-acetylcysteine reduces the incidence of CIN, although its use is generally recommended, given its low cost and favorable side effect profile. Agents which have been shown to be ineffective or harmful, or for which data supporting routine use do not exist, include fenoldopam, theophylline, dopamine, calcium channel blockers, prostaglandin E(1), atrial natriuretic peptide, statins, and angiotensin-converting enzyme inhibitors.

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.

Apoptosis in the osteonecrosis of the femoral head

Background

Osteonecrosis of the femoral head is classified into idiopathic and secondary forms. A number of etiological factors in the development of osteonecrosis have been suggested but the biological mechanisms are still unclear. Recently, some reports suggested that the apoptosis is closely related to osteonecrosis of the femoral head. Therefore, this study examined the expression of apoptosis in osteonecrosis of the femoral head.

Methods

Of the patients diagnosed preoperatively with osteonecrosis and underwent total hip replacement arthroplasty between August 2004 and July 2005, 58 patients (58 hips) were available for this study. Their diagnoses were confirmed by the postoperative pathology findings. Tissue samples of the femoral head sections were terminal deoxynucleotydyl transferase mediated dUTP nick-end labeling (TUNEL) stained using an in situ cell death detection POD kit. The number of total and TUNEL-positive osteocytes, and the average ratio of TUNEL-positive cells were calculated and analyzed according to the cause.

Results

Osteonecrosis was steroid-induced in 8 cases (13.8%), alcohol-induced in 29 cases (50%), post-traumatic in 6 cases (10.3%) and idiopathic in 15 cases (25.9%). The percentage of TUNEL-positive osteocytes was high in patients with steroid- and alcohol-induced osteonecrosis of the femoral head but low in patients with post-traumatic and idiopathic osteonecrosis. The difference in the percentage of TUNEL-positive osteocytes between these groups was significant (p < 0.05).

Conclusions

Apoptosis might play an important role in the pathogenesis of osteonecrosis of the femoral head induced by steroid and alcohol. These findings highlight a need for further research into the role of apoptosis in the development of osteonecrosis of the femoral head.

A Role for Erythropoietin in the Attenuation of Radiocontrast-Induced Acute Renal Failure in Rats

BACKGROUND

Radiocontrast-induced nephropathy (CIN) remains an important iatrogenic cause of acute renal failure in high-risk patients, despite the development of safer contrast media, the improvement of hydration protocols, and the introduction of additional preventive strategies. Erythropoietin (EPO) pretreatment may confer protection against acute renal failure through the induction of stress response genes.

METHODS

The effect of EPO has been evaluated in a rat model of CIN, induced by iothalamate, following the inhibition of nitric oxide- and prostaglandin-synthesis with indomethacin and N(omega) nitro-L-arginine methyl ester (L-NAME). Twenty-two male Sprague-Dawley rats were subjected to saline (CTR) or EPO injections (3000 U/kg and 600 U/kg, 24 and 2 h before the induction of CIN, respectively).

RESULTS

The decline in creatinine clearance in CTR animals from 0.38 +/- 0.03 to 0.28 +/- 0.03 mL/min/100 g (p < 0.005), was prevented by EPO pretreatment (from 0.34 +/- 0.02 to 0.32 +/- 0.03 mL/min/100 g, NS). The extent of medullary thick ascending limb- and S3-tubular damage in the outer medulla, however, was comparable in the two experimental groups.

CONCLUSIONS

EPO pretreatment prevents renal dysfunction in a rat model of CIN. Further experimental and clinical studies are required to confirm these preliminary conclusions regarding a potential protective potency of EPO against CIN.

Bcl-2 protects tubular epithelial cells from ischemia reperfusion injury by inhibiting apoptosis

Ischemia followed by reperfusion leads to severe organ injury and dysfunction. Inflammation is considered to be the most important cause of graft dysfunction in kidney transplantation subjected to ischemia. The mechanism that triggers inflammation and renal injury after ischemia remains to be elucidated; however, cellular stress may induce apoptosis during the first hours and days after transplantation, which might play a crucial role in early graft dysfunction. Bcl-2 is known to inhibit apoptosis induced by the etiological factors promoting ischemia and reperfusion injury. Accordingly, we hypothesized that an augmentation of the antiapoptotic factor Bcl-2 may thus protect tubular epithelial cells by inhibiting apoptosis, thereby ameliorating the subsequent tubulointerstitial injury. We examined the effects of Bcl-2 overexpression on ischemia-reperfusion (I/R) injury using Bcl-2 transgenic mice (Bcl-2 TG) and their wild-type littermates (WT). To investigate the effects of I/R injury, the left renal artery and vein were clamped for 45 min, followed by reperfusion for 0-96 h. Bcl-2 TG exhibited decreased active caspase protein in the tubular cells, which led to a reduction in TUNEL-positive apoptotic cells. Consequently, interstitial fibrosis and phenotypic changes were ameliorated in Bcl-2 TG. In conclusion, Bcl-2 augmentation protected renal tubular epithelial cells from I/R, and subsequent interstitial injury by inhibiting tubular apoptosis.

Renal apoptosis following carbon dioxide pneumoperitoneum in a rat model

PURPOSE

Laparoscopically recruited kidneys regain normal function more slowly than laparotomy harvested organs for several possible reasons. We investigated the effects of CO(2) induced pneumoperitoneum on kidney function, as reflected by blood and urine creatinine levels, and its relation with renal cell apoptosis.

MATERIALS AND METHODS

CO(2) pneumoperitoneum was established in anesthetized Wistar male rats that were randomly allocated at 6 per group into 1 of 6 groups with an intraperitoneal pressure of 0 (control), 5, 8, 12, 15 or 18 mm Hg. Pressure was maintained for 60 minutes in all groups. Three additional groups were subjected to 30-minute pneumoperitoneum at 0, 12 and 18 mm Hg, respectively. The rats were kept alive for the ensuing 24 hours, after which blood and urine creatinine were analyzed and the abdominal organs were harvested. Various areas of the organs were analyzed for apoptotic cells using the TUNEL method. Cells were randomly counted in 10 eyeshots in 3 sections each using an ocular micrometer.

RESULTS

Creatinine levels in blood and urine changed as pressure and pneumoperitoneum duration progressed. Isolated TUNEL positive nuclei were detected in the outer medulla and the cortex of control kidneys. There was a significantly higher number of TUNEL positive nuclei in the cortex and the medulla of all pressurized kidneys (p <0.05), which increased in parallel with increasing intraperitoneal pressure and pneumoperitoneum exposure time.

CONCLUSIONS

The CO(2) pneumoperitoneum gradient and its duration affect renal function and induce apoptosis. This could be a mechanism involved in renal delayed graft dysfunction in recipients of laparoscopically harvested kidneys.

Contrast agents and renal cell apoptosis

AIMS

Contrast media (CM) induce a direct toxic effect on renal tubular cells. This toxic effect may have a role in the pathophysiology of contrast nephropathy.

METHODS AND RESULTS

We evaluated (i) the cytotoxicity of CM [both low-osmolality (LOCM) and iso-osmolality (IOCM)], of iodine alone, and of an hyperosmolar solution (mannitol 8%) on human embryonic kidney (HEK 293), porcine proximal renal tubular (LLC-PK1), and canine Madin-Darby distal tubular renal (MDCK) cells; and (ii) the effectiveness of various antioxidant compounds [n-acetylcysteine (NAC), ascorbic acid and sodium bicarbonate] in preventing CM cytotoxicity. The cytotoxicity of CM was assessed at different time points, with different methods: cell viability, DNA laddering, flow cytometry, and caspase activation. Both LOCM and IOCM produced a concentration- and time-dependent increase in cell death as assessed by the different methods. On the contrary, iodine alone and hyperosmolar solution did not induce any significant cytotoxic effect. There was not any significant difference in the cytotoxic effect between LOCM and IOCM. Furthermore, both LOCM and IOCM caused a marked increase in caspase-3 and -9 activities and poly(ADP-ribose) fragmentation, while no effect on caspase-8/-10 was observed, thus indicating that the CM activated apoptosis mainly through the intrinsic pathway. Both CM induced an increase in protein expression levels of pro-apoptotic members of the Bcl2 family (Bim and Bad). NAC and ascorbic acid but not sodium bicarbonate had a dose-dependent protective effect on renal cells after 3 h incubation with high dose (200 mg iodine/mL) of both LOCM and IOCM.

CONCLUSION

Both LOCM and IOCM induce a dose-dependent renal cell apoptosis. NAC and ascorbic acid but not sodium bicarbonate prevent this contrast-induced apoptosis.

Renal parenchymal hypoxia, hypoxia adaptation, and the pathogenesis of radiocontrast nephropathy

BACKGROUND AND OBJECTIVES

Renal parenchymal Po(2) declines after the administration of iodinated radiocontrast agents, reaching critically low levels of approximately 10 mmHg in medullary structures.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this review, the causes of renal parenchymal hypoxia and its potential role in the pathogenesis of contrast nephropathy are appraised.

RESULTS

Commonly associated predisposing factors are associated with a propensity to enhance renal hypoxia. Indeed, animal models of radiocontrast nephropathy require the induction of such predisposing factors, mimicking clinical scenarios that lead to contrast nephropathy in high-risk individuals. In these models, in association with medullary hypoxic damage, a transient local cellular hypoxia response is noted, initiated at least in part by hypoxia-inducible factors. Some predisposing conditions that are distinguished by chronically aggravated medullary hypoxia, such as tubulointerstitial disease and diabetes, are characterized by a priori upregulation of hypoxia-inducible factors, which seems to confer tolerance against radiocontrast-related hypoxic tubular damage. Renal dysfunction under such circumstances likely reflects to some extent altered intrarenal hemodynamics, rather than acute tubular injury.

CONCLUSIONS

Real-time, noninvasive novel methods may help to differentiate between evolving tubular damage and altered hemodynamics and in the design of appropriate preventive interventions.

N-acetylcysteine in the prevention of contrast-induced nephropathy

BACKGROUND AND OBJECTIVES

Contrast-induced nephropathy (CIN) is a common clinical problem that is growing in importance as an increasing number of tests and procedures that utilize contrast media are performed.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

The biological and pharmacological properties of n-acetylcysteine (NAC) are reviewed, as well as the current literature relevant to the ability of NAC to prevent CIN.

RESULTS

After publication of a seminal study by Tepel et al. in 2000, there has been a surge in interest regarding the ability of NAC to reduce the risk for CIN. Since then a large number of studies, mostly with relatively small sample sizes, have been published.

CONCLUSIONS

The results have been remarkably varied with some studies finding great efficacy with NAC but most finding no significant benefit.

Contrast-induced nephropathy

Interventional radiological procedures involving anaesthesia are generally increasing. Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 44 micromol litre(-1) (0.5 mg dl(-1)) or a 25% increase from the baseline value 48 h after intravascular injection of contrast media, is a common and potentially serious complication of the use of iodinated contrast media in patients at risk of acute renal injury. It is an important cause of hospital-acquired renal failure, may be a difficult differential diagnosis and the incidence does not appear to have changed over the last few decades. In the general population, the incidence of CIN is estimated to be 1-2%. However, the risk for developing CIN may be as high as 50% in some patient subgroups, such as those with diabetes mellitus and pre-existing renal impairment. The impact of CIN on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention where it is associated with increased mortality both in hospital and at 1 yr. As treatment is limited to supportive measures while awaiting the resolution of the renal impairment, emphasis needs to be directed at prevention.

A novel method for the evaluation of proximal tubule epithelial cellular necrosis in the intact rat kidney using ethidium homodimer

BACKGROUND

Ethidium homodimer is a cell-membrane impermeant nuclear fluorochrome that has been widely used to identify necrotic cells in culture. Here, we describe a novel technique for evaluating necrosis of epithelial cells in the proximal tubule that involves perfusing ethidium homodimer through the intact rat kidney. As a positive control for inducing necrosis, rats were treated with 3.5, 1.75, 0.87 and 0.43 mg/kg mercuric chloride (Hg2+, intraperitoneal), treatments which have previously been shown to rapidly cause dose-dependent necrosis of the proximal tubule. Twenty-four h after the administration of Hg2+, ethidium homodimer (5 microM) was perfused through the intact left kidney while the animal was anesthetized. The kidney was then removed, placed in embedding medium, frozen and cryosectioned at a thickness of 5 microm. Sections were permeabilized with -20 degrees C methanol and then stained with 4',6-diamidino-2-phenylindole (DAPI) to label total nuclei. Total cell number was determined from the DAPI staining in random microscopic fields and the number of necrotic cells in the same field was determined by ethidium homodimer labeling.

RESULTS

The Hg2+-treated animals showed a dose-dependent increase in the number of ethidium labeled cells in the proximal tubule, but not in other segments of the nephron. Other results showed that a nephrotoxic dose of gentamicin also caused a significant increase in the number of ethidium labeled cells in the proximal tubule.

CONCLUSION

These results indicate that this simple and sensitive perfusion technique can be used to evaluate cellular necrosis in the proximal tubule with the three-dimensional cyto-architecture intact.

Role of anemia in progression of chronic kidney disease

Anemia is a well-known consequence of chronic kidney disease (CKD), and its prevalence progressively increases when the estimated glomerular filtration rate decreases to less than 60 mL/min/1.73 m2. However, analyses of the consequences of anemia and of the mechanisms of progression of CKD suggest that anemia also could contribute to the deterioration of kidney function. This hypothesis is based mostly on experimental data that imply that hypoxia of tubular cells plays an important role in tubulointerstitial damage associated with CKD and, thus, in the progression of renal failure. It also is supported by the fact that red blood cells represent a major antioxidant component of blood and that oxidative stress appears to contribute to glomerulosclerosis and tubulointerstitial damage. In humans, post hoc analysis of the Reduction of End points in non insulin-dependent diabetes mellitus (NIDDM) with the Angiotensin II Antagonist Losartan study and analyses of smaller prospective cohorts of CKD patients have shown that anemia is an independent risk factor for progression of CKD. In addition, 3 small randomized studies have suggested that anemia correction could slow the progression of CKD. Thus, the existence of a relationship between anemia and progression of CKD is not only plausible biologically, but also is supported by observational studies and by small intervention studies. However, only a large, randomized, prospective trial will be able to establish if anemia correction can slow the progression of CKD effectively.

RENAL PARENCHYMAL OXYGENATION AND HYPOXIA ADAPTATION IN ACUTE KIDNEY INJURY

The pathogenesis of acute kidney injury (AKI), formally termed acute tubular necrosis, is complex and, phenotypically, may range from functional dysregulation without overt morphological features to literal tubular destruction. Hypoxia results from imbalanced oxygen supply and consumption. Increasing evidence supports the view that regional renal hypoxia occurs in AKI irrespective of the underlying condition, even under circumstances basically believed to reflect 'direct' tubulotoxicity. However, at present, it is remains unclear whether hypoxia per se or, rather, re-oxygenation (possibly through reactive oxygen species) causes AKI. Data regarding renal hypoxia in the clinical situation of AKI are lacking and our current concepts regarding renal oxygenation during acute renal failure are presumptive and largely derived from experimental studies. There is robust experimental evidence that AKI is often associated with altered intrarenal microcirculation and oxygenation. Furthermore, renal parenchymal oxygen deprivation seems to participate in the pathogenesis of experimental AKI, induced by exogenous nephrotoxins (such as contrast media, non-steroidal anti-inflammatory drugs or amphotericin), sepsis, pigment and obstructive nephropathies. Sub-lethal cellular hypoxia engenders adaptational responses through hypoxia-inducible factors (HIF). Forthcoming technologies to modulate the HIF system form a novel potential therapeutic approach for AKI.

Detection of evolving acute tubular necrosis with renal 23Na MRI: studies in rats

The clinical detection of evolving acute tubular necrosis (ATN) and differentiating it from other causes of renal failure are currently limited. The maintenance of the corticomedullary sodium gradient, an indicator of normal kidney function, is presumably lost early in the course of ATN. Herein, sodium magnetic resonance imaging (23Na MRI) was applied to study the early alteration in renal sodium distribution in rat kidneys 6 h after the induction of ATN. Three-dimensional gradient echo sodium images were recorded at 4.7 T with high spatial resolution. ATN was produced by the administration of radiologic contrast medium, combined with inhibition of nitric oxide and prostaglandin synthesis. The sodium images revealed that the sham-controlled kidney exhibited a linear increase in sodium concentration along the corticomedullary axis of 30+/-2 mmol/l/mm, resulting in an inner medulla to cortex sodium ratio of 4.3+/-0.3 (n=5). In the ATN kidney, however, the cortico-outer medullary sodium gradient was reduced by 21% (P<0.01, n=7) and the inner medulla to cortex sodium ratio was decreased by 40% (P<0.001, n=7). Small, though significant, increments in plasma creatinine at this time inversely correlated with the decline in the corticomedullary sodium gradient. Histological findings demonstrated outer medullary ATN involving 4% of medullary thick ascending limbs. Hence, 23Na MRI non-invasively quantified changes in the corticomedullary sodium gradient in the ATN kidney when morphologic tubular injury was still focal and very limited. MRI detection of corticomedullary sodium gradient abnormalities may serve to identify evolving ATN at its early phases.

Contrast medium-induced nephropathy: The pathophysiology

A widespread, rather general, definition of contrast-induced nephropathy (CIN) is an impairment in renal function occurring within 3 days following the intravascular administration of contrast media (CM) and the absence of an alternative aetiology. In spite of the vast clinical importance of CIN, its understanding and the pathophysiology behind CIN remain incomplete. Many studies have been performed; however, they have provided no widely accepted conclusion so far. Here the possible mechanisms underlying CIN are outlined, which span from altered rheological properties, perturbation of renal haemodynamics, regional hypoxia, auto-, and paracrine factors (adenosine, endothelin, reactive oxygen species) to direct cytotoxic effects. Although these potential mediators of CIN will be discussed separately, several factors may act in concert to perturb kidney function after exposure to contrast media. From the current knowledge of the mechanisms causing CIN, it is not possible to recommend a certain class of contrast media, except to avoid large doses of CM of the first generation. From a pathophysiological perspective, volume expansion is effective in avoiding CIN, since water permeability of the collecting ducts will decrease and enhance fluid excretion. Hence, CM in the distal portions of the tubular system is diluted, which implies reduced fluid viscosity and a lower risk of obstruction.

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.

Uroangiographic Contrast Media-Induced Nephropathy: Correlations between Their Physicochemical Properties and Renal Damage

Contrast media-induced nephropathy (CN) is an important cause of hospital-acquired acute renal failure. Patients with both diabetes mellitus and renal impairment are at high risk. CN pathophysiology involves activation of the tubulo-glomerular feedback and vasoactive mediators such as renin-angiotensin 2, endothelin, adenosine, ADH, etc. The risk of CN can be minimized by the use of non-ionic, low or isoosmolar, contrast material, adequate hydration and prophylactic pharmacological measures. In patients with chronic renal failure who are undergoing arteriography (e.g. coronary angiography and angioplasty), periprocedural hemofiltration appears effective in preventing further renal damage due to contrast agents.

Pathophysiology of contrast medium-induced nephropathy

BACKGROUND

Contrast medium-induced nephropathy (CIN) is a well-known cause of acute renal failure, but the development of CIN remains poorly understood. A number of studies have been performed with the one aim, to shed some light onto the pathophysiology of CIN. These have led to manifold interpretations and sometimes contradicting conclusions.

METHODS

This review critically surveys mechanisms believed to mediate CIN by highlighting the complex pathophysiologic entity, including altered rheologic properties, perturbation of renal hemodynamics, regional hypoxia, auto- and paracrine factors [adenosine, endothelin, and reactive oxygen species (ROS)], and direct cytotoxic effects. Moreover, the importance of physicochemical properties of contrast media are made clear.

RESULTS

The more recently developed iso-osmolar contrast media are dimers, not monomers as the widely used nonionic low osmolar contrast media. The dimers have physicochemical features different from other contrast media which may be of clinical importance, not only with respect to osmolality. The viscosity of the commercially available dimers is considerably higher than blood.

CONCLUSION

Many experimental studies provide evidence for a greater perturbation in renal functions by dimeric contrast media in comparison to nonionic monomeric contrast media. Clinical trials have yielded conflicting results.

The diagnosis of acute renal failure in intensive care: mongrel or pedigree?

Acute renal failure is common in the intensive care unit; it is well recognised that patients who develop acute renal failure have a high mortality rate. While there have been improvements in the management of acute renal failure, the mortality remains high. Acute renal failure is easily diagnosed biochemically and clinically but it is not a single disease entity. It is a syndrome that affects a very heterogeneous population. Studies of acute renal failure and of the impact of renal replacement therapy in intensive care are usually inconclusive, which may be the natural consequence of studying a syndrome. This article focuses on the more uncertain features of acute renal failure, the problems of investigating acute renal failure as a disease and the difficulties of applying the results of a study of a heterogeneous population to the management of individuals.

Expression of human heme oxygenase-1 in the thick ascending limb attenuates angiotensin II-mediated increase in oxidative injury

BACKGROUND

Heme oxygenase-1 (HO-1) catalyzes the conversion of heme to bilirubin, carbon monoxide (CO), and free iron, thus controlling the level of cellular heme. The medullary thick ascending limb of the loop of Henle (TALH) is situated in a site of markedly diminished oxygen tension and, as such, is highly vulnerable to ischemic insult. We hypothesize that selective upregulation of HO-1 in TALH by gene transfer attenuates oxidative stress caused by angiotensin II (Ang II).

METHODS

An adenoviral vector expressing the human HO-1 under the control of the TALH-specific promoter [Na(+)-K(+)-Cl(-) cotransporter (NKCC2 promoter)] was constructed and the cell specific expression of the recombinant adenovirus was examined using several types of cells, including endothelial, vascular smooth muscle, and TALH cells. The effects of HO-1 transduction on HO-1 expression, HO activity and the response to Ang II with respect to cyclooxygenase-2 (COX-2) up-regulation and oxidative injury [growth-stimulating hormone (GSH) levels and cell death] were determined.

RESULTS

Western blot and reverse transcription-polymerase chain reaction (RT-PCR) revealed that human HO-1 was selectively expressed in primary cultured TALH cells following infection with Ad-NKCC2-HO-1. In TALH cells infected with Ad-NKCC2-HO-1, Ang II-stimulated prostaglandin E(2) (PGE(2)) levels were reduced by 40%. Ang II caused a marked decrease in GSH levels and this decrease was greatly attenuated in TALH cells transduced with Ad-NKCC2-HO-1. Moreover, Ang II-mediated DNA degradation was completely blocked by the site-specific expression of human HO-1 gene.

CONCLUSION

These results indicate that TALH cell survival after exposure to oxidative stress injury may be facilitated by selective upregulation of HO-1, thusly blocking inflammation and apoptosis.

The cytotoxicity of iodinated radiocontrast agents on renal cells in vitro

A deterioration of renal function is one preoccupying complication of iodinated radiocontrast agents in clinical practice. These compounds have direct toxic effects on renal cells, which are only in part related to their physicochemical properties. The hyperosmolal monomeric ionic radiocontrast agents, like diatrizoate, have the highest toxicity, whereas renal cells are less affected by (nonionic) compounds with reduced osmolality. The toxic effects include cellular energy failure, a disruption of calcium homeostasis, a disturbance of tubular cell polarity and programmed cell death (apoptosis). The molecular mechanisms of the direct cytotoxicity are still unclear, although oxidative stress has been implicated. Radiocontrast cytotoxicity has been demonstrated in glomerular mesangial cells and in renal epithelial cells in vitro. In vivo, the direct cellular toxicity of radiocontrast agents is compounded with alterations in blood flow and/or viscosity, ultimately resulting in renal medullary hypoxia, which is a hallmark feature of the complex clinical syndrome of radiocontrast nephropathy.

Apoptotic pathways in ischemic acute renal failure

The study of cell death has emerged as an important and exciting area of research in cell biology. Although two kinds of cell death, apoptosis and necrosis, are recognized, one of the major advances in our understanding of cell death has been the recognition that the pathways traditionally associated with apoptosis may be very critical in the form of cell injury associated with necrosis. Renal tubular epithelial cell injury from ischemia has been generally regarded as a result of necrotic form of cell death. We briefly describe recent evidence indicating that pathways generally associated with apoptosis, including endonuclease activation, role of mitochondria and caspases, are important in renal tubular injury. It is likely that the cascades that lead to apoptotic or necrotic mode of cell death are activated almost simultaneously and may share some common pathways.

Detection of apoptotic cells in intestines from horses with and without gastrointestinal tract disease

OBJECTIVE

To identify apoptosis in equine intestines and determine whether apoptosis is associated with gastrointestinal tract disease or a specific tissue layer of intestine.

ANIMALS

38 horses that underwent surgery or were euthanatized for small or large intestine obstruction, strangulation, or distension and 9 control horses euthanatized for reasons other than gastrointestinal tract disease or systemic disease.

PROCEDURE

Specimens were collected at surgery from intestine involved in the primary lesion and distant to the primary lesion site or at necropsy from several sites including the primary lesion site. Histologic tissue sections were stained with H&E, and apoptosis was detected by use of the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling technique. The number of apoptotic cells per hpf was counted in the mucosa, circular muscle, longitudinal muscle, and serosa.

RESULTS

Apoptotic nuclei were seen in all layers of intestine. An increased number of apoptotic cells was found in the circular muscle of the intestine from horses with simple obstruction, compared with strangulating obstruction or healthy intestine. Intestine distant from a primary strangulating lesion had higher numbers of apoptotic cells than did intestine distant from a simple obstructive lesion or intestine taken at the site of a strangulating or simple obstructive lesion.

CONCLUSIONS AND CLINICAL RELEVANCE

Intestine from horses with obstructing or strangulating lesions in the small intestine and large colon had high numbers of apoptotic cells possibly because of ischemic cell injury and subsequent inflammation. Whether substantial apoptosis affects intestinal function is not yet known.

Radiographic contrast media-induced tubular injury: evaluation of oxidant stress and plasma membrane integrity

BACKGROUND

Experimental and clinical investigations suggest that oxidant stress is a critical determinant of radiocontrast nephropathy (RCN), and that N acetyl cysteine (NAC) can prevent this damage. This study addresses these issues directly at the tubular cell level. Potential alternative mechanisms for RCN have also been sought.

METHODS

Isolated mouse proximal tubule segments (PTS), or cultured proximal tubule (HK-2) cells, were subjected to radiocontrast media (RCM) (Ioversol, Optiray 320) exposure, followed by assessments of cellular viability [% lactate dehydrogenase (LDH) release, tetrazolium dye (MTT), uptake] and lipid peroxidation. These experiments were conducted in the absence or presence of a variety of antioxidants [NAC, glutathione (GSH), superoxide dismutase, catalase] or pro-oxidant (GSH depletion, heme oxygenase inhibition) strategies. RCM effects on mitochondrial and plasma membrane integrity were also assessed.

RESULTS

RCM exposure did not induce PTS lipid peroxidation. Neither antioxidant nor pro-oxidant interventions mitigated or exacerbated RCM-induced tubular cell injury, respectively. RCM impaired mitochondrial integrity, as assessed by ouabain-resistant ATP reductions, and by cytochrome c release (before cell death). RCM also induced plasma membrane damage, as indicated by loss of key resident proteins (NaK-ATPase, caveolin) and by increased susceptibility to phospholipase A2 (PLA2) attack (increase of >/=2 times in free fatty acid and NaK-ATPase release). Hyperosmolality could not account for RCM's toxic effects.

CONCLUSION

RCM toxicity can be dissociated from tubular cell oxidant stress. Alternative mechanisms may include mitochondrial injury/cytochrome c release and plasma membrane damage. The latter results in critical protein loss, as well as a marked increase in plasma membrane susceptibility to exogenous/endogenous PLA2 attack.

Cell death induced by acute renal injury: a perspective on the contributions of apoptosis and necrosis

In humans and experimental models of renal ischemia, tubular cells in various nephron segments undergo necrotic and/or apoptotic cell death. Various factors, including nucleotide depletion, electrolyte imbalance, reactive oxygen species, endonucleases, disruption of mitochondrial integrity, and activation of various components of the apoptotic machinery, have been implicated in renal cell vulnerability. Several approaches to limit the injury and augment the regeneration process, including nucleotide repletion, administration of growth factors, reactive oxygen species scavengers, and inhibition of inducers and executioners of cell death, proved to be effective in animal models. Nevertheless, an effective approach to limit or prevent ischemic renal injury in humans remains elusive, primarily because of an incomplete understanding of the mechanisms of cellular injury. Elucidation of cell death pathways in animal models in the setting of renal injury and extrapolation of the findings to humans will aid in the design of potential therapeutic strategies. This review evaluates our understanding of the molecular signaling events in apoptotic and necrotic cell death and the contribution of various molecular components of these pathways to renal injury.

Contrast media augmented apoptosis of cultured renal mesangial, tubular, epithelial, endothelial, and hepatic cells

RATIONALE AND OBJECTIVE

Nephrotoxicity of contrast media, resulting in apoptosis and acute necrosis of tubular cells, is well documented. No studies concerning mesangial cells apoptosis have been published yet.

AIM

Apoptosis of cultured mesangial, tubular, and hepatic cell lines was investigated following exposure to different contrast media.

METHODS

Apoptosis was assessed by TUNEL assay and verified by Mayer Hematoxylin staining.

RESULTS

Iopromide, Ioxaglate, and Ioxatalamate induced apoptosis in all cell cultures at final concentrations ranged from 0.1% to 10.0%. However, only 1% to 10% Iomeprol elicited a significant apoptosis. Moreover, at 10% concentration, Iomeprol induced significantly less apoptosis than Iopromide, Ioxaglate, or Ioxatalamate.

CONCLUSIONS

First, Iomeprol, which has a different physico-chemical properties, proved to be less proapoptotic compared with other contrast compounds. Second, all types of cells similarly respond by apoptosis to contrast media induced injury. However, apoptosis of mesangial cells might generate additional deleterious effects in vivo.

Apoptotic pathways of oxidative damage to renal tubular epithelial cells

Toxic renal failure induced by gentamicin, glycerol, or cisplatin, as well as ischemic renal failure in vivo and hypoxia/reoxygenation of tubular epithelial cells in vitro, induces the production of reactive oxygen metabolites (ROM). Generation of ROM is responsible for the induction of tubular epithelial cell death, which is mediated by caspases and/or endonucleases. Scavenging of ROM protects tubular epithelium from caspase and endonuclease activation and from cell death. Thus, the inhibition of ROM production combined with the pharmacological control of caspase and endonuclease pathways may provide future modalities in the prevention or treatment of acute renal failure in humans.

Iodinated contrast media induce neutrophil apoptosis through a mitochondrial and caspase mediated pathway

Iodinated contrast media (ICM) can induce apoptosis (programmed cell death) in renal, myocardial and endothelial cells. Following intravascular injection, circulating immune cells are exposed to high concentrations of ICM. As neutrophils constitutively undergo apoptosis we hypothesized that ICM may adversely affect neutrophil survival. Our aim was to investigate the effect of ICM on neutrophil apoptosis. Neutrophils were isolated from healthy subjects and cultured in vitro with ionic (diatrizoate and ioxaglate) and non-ionic (iohexol and iotrolan) ICM. The effect of ICM on neutrophil apoptosis in both unstimulated and lipopolysaccharide-stimulated neutrophils was determined by annexin V flow cytometry. The influence of physicochemical properties of the different ICM on apoptosis of neutrophils was also studied. We further investigated the effects of ICM on key intracellular signal pathways, including p38 mitogen-activated protein kinase (MAPK) by Western blotting, and mitochondrial depolarization and caspase activity by flow cytometry. Isoiodine concentrations (20 mg ml(-1)) of ionic (diatrizoate 69.6+/-2.9%; ioxaglate 58.9+/-2.0%) and non-ionic (iohexol 57.3+/-2.9%; iotrolan 57.1+/-2.6%) ICM significantly induced neutrophil apoptosis over control levels (47.7+/-1.4%). The apoptotic effect of ICM was influenced by their chemical structure, with ionic ICM having a more significant (p<0.01) apoptotic effect than non-ionic ICM (p<0.05). Furthermore, ICM reversed the anti-apoptotic effect of lipopolysaccharide (1000 ng ml(-1)) treated neutrophils to control levels (23.0+/-3.5% to 61.2+/-5.3%; n=4; p<0.05). These agents induce apoptosis through a p38 MAPK independent pathway that results in mitochondrial depolarization, and is dependent on caspase activation. As neutrophils play a central role in host response to infection and injury, ICM, through induction of neutrophil apoptosis, could have a significant deleterious effect on host immune defence and resolution of an inflammatory response.