Contrast medium- and mannitol-induced apoptosis in heart and kidney of SHR rats

Effects of intratesticular injection of hypertonic mannitol and saline on the quality of donkey sperm, indicators of oxidative stress and testicular tissue pathology

OBJECTIVES

The aim of the present study was to examine donkey sperm quality after intratesticular injection of hypertonic mannitol (HM) and saline (HS).

METHODS

Randomly assigned to five treatment groups were 15 adult male donkeys: (1) Control group (no treatment), (2) Surgery group (surgical castration for testosterone control), (3) NS group (normal saline intratesticular injection), (4) HS group (hypertonic saline), and (5) HM group. We injected 20 mL per testicle. We took 5 mL blood from all donkeys before injection. Castration was performed under general anesthesia 60 days later. Samples included blood and testicular tissue. Total motility (TM), progressive motility (PM), movementy features, DNA damage, morphology, viability, and plasma membrane functionality were evaluated. Hormone analyses, histomorphometric studies and oxidative stress indices including total antioxidant capacity (TAC), glutathione peroxidase (GPx), glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), and NADP+/NADPH were evaluated. Apoptosis, pyroptosis-related Bax, Caspase-1, GSDMD, and Bcl-2 expression were also assessed.

RESULTS

In HS and HM groups, testosterone, epididymal sperm count, motility, viability, and plasma membrane functionality dropped while sperm DNA damage increased. HS and HM groups had significantly lower histomorphometric parameters, TAC, GPx, SOD, GSH, and Bcl-2 gene expression. MDA, NADP+/NADPH, Bax, Caspase-1, and GSDMD gene expression were substantially higher in the HS and HM groups than in the control group.

CONCLUSIONS

Toxic effects of hypertonic saline and mannitol on reproductive parameters were seen following, hence, they might be considered as a good chemical sterilizing treatment in donkeys.

The Potential Biotherapeutic Targets of Contrast-Induced Acute Kidney Injury

Contrast-induced acute kidney injury (CI-AKI) is manifested by an abrupt decline in kidney function as a consequence of intravascular exposure to contrast media. With the increased applicability of medical imaging and interventional procedures that utilize contrast media for clinical diagnosis, CI-AKI is becoming the leading cause of renal dysfunction. The pathophysiological mechanism associated with CI-AKI involves renal medullary hypoxia, the direct toxicity of contrast agents, oxidative stress, apoptosis, inflammation, and epigenetic regulation. To date, there is no effective therapy for CI-AKI, except for the development of strategies that could reduce the toxicity profiles of contrast media. While most of these strategies have failed, evidence has shown that the proper use of personalized hydration, contrast medium, and high-dose statins may reduce the occurrence of CI-AKI. However, adequate risk predication and attempts to develop preventive strategies can be considered as the key determinants that can help eliminate CI-AKI. Additionally, a deeper understanding of the pathophysiological mechanism of CI-AKI is crucial to uncover molecular targets for the prevention of CI-AKI. This review has taken a step further to solidify the current known molecular mechanisms of CI-AKI and elaborate the biomarkers that are used to detect early-stage CI-AKI. On this foundation, this review will analyze the molecular targets relating to apoptosis, inflammation, oxidative stress, and epigenetics, and, thus, provide a strong rationale for therapeutic intervention in the prevention of CI-AKI.

A nephroprotective iodinated contrast agent with cardioprotective properties: A pilot study

BACKGROUND AND PURPOSE

Evaluation and treatment of acute ischemic syndromes, in the heart and brain, require vessel visualization by iodinated X-ray contrast agents. However, these contrast agents can induce injury, in both the kidneys and target organs themselves. Sulfobutylether beta cyclodextrin (SBECD) added to iohexol (SBECD-iohexol) (Captisol Enabled-iohexol, Ligand Pharmaceuticals, Inc, San Diego, CA) is currently in clinical trials in cardiovascular procedures, to determine its relative renal safety in high-risk patients. Preclinical studies showed that SBECD-iohexol reduced contrast-induced acute kidney injury in rodent models by blocking apoptosis. The current study was undertaken to determine whether SBECD-iohexol is also cardioprotective, in the male rat ischemia-reperfusion model, compared to iohexol alone.

METHODS

After anesthesia, the left coronary artery was ligated for 30 min and the ligation released and reperfusion followed for 2 h prior to sacrifice. Groups 1-4 were injected in the tail vein 10 min prior to ischemia with: (1) vehicle; (2) iohexol; (3) SBECD; and (4) SBECD-iohexol. Infarct size, hemodynamics, and serum markers were measured.

RESULTS

An eight-fold increase in serum creatine kinase in the iohexol-alone group was observed, compared with no increase in the SBECD-iohexol group. The mean arterial pressure and rate pressure product were depressed in the iohexol-alone group, but not in the SBECD-iohexol group, or controls. No difference in infarct size or serum creatinine among the groups was observed.

CONCLUSION

The results of this study suggest that SBECD-iohexol is superior to iohexol alone, for both the preservation of cardiomyocyte integrity and preservation of myocardial function in myocardial ischemia.

The use of mannitol in cardiopulmonary bypass prime solution-Prospective randomized double-blind clinical trial

BACKGROUND

The optimal prime solution for the cardiopulmonary bypass (CPB) circuit in adult cardiac surgery has not yet been defined. Mannitol is widely used in the priming solution for CPB despite the fact that there is no clear consensus on the role of mannitol in cardiac surgery. The aim of this study was to investigate the effect of mannitol in the CPB prime solution.

METHODS

This prospective, randomized, double-blind study included 40 patients with normal cardiac and renal functions, who underwent coronary artery bypass grafting. One group received a prime based on Ringer's acetate (n = 20), and the other a prime consisting of Ringer's acetate with 200 mL mannitol (n = 20). Changes in osmolality, acid-base status, electrolytes, and renal-related parameters were monitored.

RESULTS

No significant differences were found in osmolality between the Ringer's acetate group and the mannitol group at any time. The mannitol group showed a pronounced decrease in sodium, from 138.7 ± 2.8 mmol/L at anaesthesia onset, to 133.9 ± 2.6 mmol/L after the start of CPB (P < .001). No differences were seen in the renal parameters between the groups, apart from a short-term effect of mannitol on peroperative urine production (P = .003).

CONCLUSION

We observed no effects on osmolality of a prime solution containing mannitol compared to Ringer's acetate-based prime in patients with normal cardiac and renal function. The use of mannitol in the prime resulted in a short-term, significant decrease in sodium level.

Hydrogen sulfide inhibits Ca2+-induced mitochondrial permeability transition pore opening in type-1 diabetes

Hydrogen sulfide (H2S) attenuates N-methyl-d-aspartate receptor-R1 (NMDA-R1) and mitigates diabetic renal damage; however, the molecular mechanism is not well known. Whereas NMDA-R1 facilitates Ca2+ permeability, H2S is known to inhibit L-type Ca2+ channel. High Ca2+ activates cyclophilin D (CypD), a gatekeeper protein of mitochondrial permeability transition pore (MPTP), thus facilitating molecular exchange between matrix and cytoplasm causing oxidative outburst and cell death. We tested the hypothesis of whether NMDA-R1 mediates Ca2+ influx causing CypD activation and MPTP opening leading to oxidative stress and renal injury in diabetes. We also tested whether H2S treatment blocks Ca2+ channel and thus inhibits CypD and MPTP opening to prevent renal damage. C57BL/6J and Akita (C57BL/6J-Ins2Akita) mice were treated without or with H2S donor GYY4137 (0.25 mg·kg-1·day-1 ip) for 8 wk. In vitro studies were performed using mouse glomerular endothelial cells. Results indicated that low levels of H2S and increased expression of NMDA-R1 in diabetes induced Ca2+ permeability, which was ameliorated by H2S treatment. We observed cytosolic Ca2+ influx in hyperglycemic (HG) condition along with mitochondrial-CypD activation, increased MPTP opening, and oxidative outburst, which were mitigated with H2S treatment. Renal injury biomarker KIM-1 was upregulated in HG conditions and normalized following H2S treatment. Inhibition of NMDA-R1 by pharmacological blocker MK-801 revealed similar results. We conclude that NMDA-R1-mediated Ca2+ influx in diabetes induces MPTP opening via CypD activation leading to increased oxidative stress and renal injury, and H2S protects diabetic kidney from injury by blocking mitochondrial Ca2+ permeability through NMDA-R1 pathway.

Renal tubular epithelial cells injury induced by mannitol and its potential mechanism

Administration of mannitol with high dose could induce extensive isometric renal proximal tubular vacuolization and acute renal failure in clinic. We previously demonstrated that mannitol-induced human kidney tubular epithelial cell (HK-2) injury. The objective of our present work was to further study the cytotoxicity of mannitol in HK-2 cells and its potential mechanism. Cell viability was assessed by an MTT method. Cell morphological changes were observed. Furthermore, levels of malondialdehyde (MDA) and glutathione (GSH) were measured. Flow cytometry was performed to determine cell apoptosis by using Annexin V-FITC and PI. In addition, the F-actin of cells was labeled by FITC-Phalloidin for observation of cytoskeleton. The MTT assay displayed that the cell viability decreased significantly in a dose- and time-dependent manner. The morphological changes were observed, including cell membrane rapture and cell detachment. The GSH concentration in HK-2 cells decreased dramatically in mannitol treatment group, while MDA content increased significantly. The results of flow cytometry indicated that apoptotic percentages of HK-2 cells increased in 250 mmol/L mannitol treatment group. After treatment with 250 mmol/L mannitol for 48 h, HK-2 cells showed disorganization of cytoskeleton and even exhibited a totally destroyed cytoskeleton. Therefore, high dose of mannitol has a toxic effect on renal tubular epithelial cells, which might be attributed to oxidative stress, destroyed cellular cytoskeleton and subsequent cell apoptosis.

miR‑21 attenuates contrast‑induced renal cell apoptosis by targeting PDCD4

Contrast medium (CM) is widely used in cardiac catheterization; however, it may induce acute kidney injury or renal failure, although the underlying mechanism remains to be elucidated. MicroRNA‑21 (miR‑21) is involved in renal disease and has been indicated to regulate cellular apoptosis and fibrosis, although its role in CM‑induced renal cell injury is unknown. The present study examined the expression and potential targets of miR‑21 in human renal proximal tubular epithelial (HK‑2) cells following CM treatment. CM induced renal cell apoptosis and decreased miR‑21 expression. The expression level of the apoptosis regulator protein, B‑cell lymphoma 2 (Bcl‑2) was upregulated, whereas that of the apoptosis regulator, Bcl‑2‑associated X protein (Bax) was downregulated upon transfection of miR‑21 mimics; miR‑21 overexpression additionally directly inhibited the expression of programmed cell death protein 4 (PDCD4), as determined by a dual luciferase reporter assay, and PDCD4 silencing reduced the rate of HK‑2 cell apoptosis. The results of the present study indicated that miR‑21 protected renal cells against CM‑induced apoptosis by regulating PDCD4 expression.

Meta-Analysis of Individual Patient Data of Sodium Bicarbonate and Sodium Chloride for All-Cause Mortality After Coronary Angiography

We sought to examine the relation between sodium bicarbonate prophylaxis for contrast-associated nephropathy (CAN) and mortality. We conducted an individual patient data meta-analysis from multiple randomized controlled trials. We obtained individual patient data sets for 7 of 10 eligible trials (2,292 of 2,764 participants). For the remaining 3 trials, time-to-event data were imputed based on follow-up periods described in their original reports. We included all trials that compared periprocedural intravenous sodium bicarbonate to periprocedural intravenous sodium chloride in patients undergoing coronary angiography or other intra-arterial interventions. Included trials were determined by consensus according to predefined eligibility criteria. The primary outcome was all-cause mortality hazard, defined as time from randomization to death. In 10 trials with a total of 2,764 participants, sodium bicarbonate was associated with lower mortality hazard than sodium chloride at 1 year (hazard ratio 0.61, 95% confidence interval [CI] 0.41 to 0.89, p = 0.011). Although periprocedural sodium bicarbonate was associated with a reduction in the incidence of CAN (relative risk 0.75, 95% CI 0.62 to 0.91, p = 0.003), there exists a statistically significant interaction between the effect on mortality and the occurrence of CAN (hazard ratio 5.65, 95% CI 3.58 to 8.92, p <0.001) for up to 1-year mortality. Periprocedural intravenous sodium bicarbonate seems to be associated with a reduction in long-term mortality in patients undergoing coronary angiography or other intra-arterial interventions.

Preclinical Studies of a Kidney Safe Iodinated Contrast Agent

BACKGROUND AND PURPOSE

Contrast-induced acute kidney injury (CI-AKI) is a serious complication of the use of iodinated contrast agents. This problem is particularly acute in interventional neurology and interventional cardiology, probably due to the intra-arterial route of injection, high contrast volumes, and preexisting risk factors of these patients. In an attempt to develop a contrast agent that is less damaging to the kidneys, we have studied the effects of adding a small amount of the substituted cyclodextrin, sulfobutyl-ether-β-cyclodextrin (SBECD), to iohexol in rodent models of renal toxicity.

METHODS

Renally compromised mice and rats were injected with iohexol and iohexol-SBECD via the tail vein. The renal pathology, creatinine clearance, and survival benefits of iohexol-SBECD were studied. The safety of direct intra-arterial injection of the iohexol-SBECD formulation was studied in a dog heart model system. Mechanism of action studies in cell culture model using a human kidney cell line was performed using flow cytometry.

RESULTS

Nephrotoxicity was significantly reduced using iohexol-SBECD compared to iohexol alone, at mole ratios of iohexol:SBECD of 1:0.025. SBECD increased survival from 50% to 88% in a rat survival study. In the dog heart model, iohexol-SBECD was safe. Cell culture studies suggest that SBECD interferes with the early stages of contrast-induced apoptosis in a human renal cell line.

CONCLUSION

We have shown that the addition of a small amount of SBECD (one molecule of SBECD per 40 iohexol molecules) significantly protects rodent kidneys from CI-AKI. Further development of this new formulation of iodinated contrast is warranted.

Aging Male Spontaneously Hypertensive Rat as an Animal Model for the Evaluation of the Interplay between Contrast-Induced Acute Kidney Injury and Cardiorenal Syndrome in Humans

BACKGROUND

Although there are some animal models for biomarkers of contrast-induced acute kidney injury (CI-AKI), for cardiorenal syndrome (CRS) and for acute renal failure, the interplay between CI-AKI and CRS has yet to be evaluated. Insight into the pathogenesis of CRS is urgently needed from animal models in order to foster the discovery and implementation of novel biomarkers for this disease. Specially designed animal models for type 1 and 3 CRS, particularly CI-AKI, have not yet emerged.

SUMMARY

We hypothesize that the aging male spontaneously hypertensive rat (SHR) is likely to be a suitable model. The SHR model is able to mimic risk factors for preclinical CRS that appears in the clinical setting, specifically hypertension, age, preexisting damage and dysfunction of the heart and kidney, endothelial dysfunction, increased level of reactive oxygen species, decreased level and bioavailability of nitric oxide (NO), impairment of the L-arginine-NO pathway, and insulin resistance. In the SHR, CI-AKI results in a different profile of AKI biomarkers than is seen with preexisting chronic kidney injury.

KEY MESSAGES

The SHR model can be used to evaluate the interaction between CI-AKI and CRS type 1 and 3 and to verify neutrophil gelatinase-associated lipocalin (NGAL) as a reliable CI-AKI biomarker for clinical application. Further research is warranted with a large number of aging male SHRs to prove NGAL as a sensitive, specific, highly predictive, early biomarker for CI-AKI.

Extended exenatide administration enhances lipid metabolism and exacerbates pancreatic injury in mice on a high fat, high carbohydrate diet

This study expanded upon a previous study in mice reporting a link between exenatide treatment and exocrine pancreatic injury by demonstrating temporal and dose responses and providing an initial mechanistic hypothesis. The design of the present study included varying lengths of exenatide exposure (3, 6 weeks to 12 weeks) at multiple concentrations (3, 10, or 30 µg/kg) with multiple endpoints (histopathology evaluations, immunoassay for cytokines, immunostaining of the pancreas, serum chemistries and measurement of trypsin, amylase, and, lipase, and gene expression profiles). Time- and dose-dependent exocrine pancreatic injury was observed in mice on a high fat diet treated with exenatide. The morphological changes identified in the pancreas involved acinar cell injury and death (autophagy, apoptosis, necrosis, and atrophy), cell adaptations (hypertrophy and hyperplasia), and cell survival (proliferation/regeneration) accompanied by varying degrees of inflammatory response leading to secondary injury in pancreatic blood vessels, ducts, and adipose tissues. Gene expression profiles indicated increased signaling for cell survival and altered lipid metabolism in exenatide treated mice. Immunohistochemistry supported gene expression findings that exenatide caused and/or exacerbated pancreatic injury in a high fat diet environment potentially by further increasing high fat diet exacerbated lipid metabolism and resulting oxidative stress. Further investigation is required to confirm these findings and determine their relevance to human disease.

Differential activation of signaling pathways by low-osmolar and iso-osmolar radiocontrast agents in human renal tubular cells

Radiocontrast media (RCM)-induced nephrotoxicity (CIN) is a major clinical problem accounting for 12% of all hospital-acquired cases of acute kidney injury (AKI). The pathophysiology of AKI due to RCM is not well understood, but direct toxic effects on renal cells have been postulated as contributing to CIN. It is believed that iso-osmolar RCM (IOCM) are less nephrotoxic than low-osmolar RCM (LOCM) but clinical data have been controversial. We have investigated the intracellular signaling pathways that may be affected by the LOCM iomeprol (IOM) and the IOCM iodixanol (IOD). Both IOM and IOD caused a dramatic decrease in phosphorylation of the kinase Akt at Ser473 and Thr308 in human renal tubular (HK-2) cells, with IOM having a greater effect; IOM also caused a greater decrease in cell viability. IOM also had a greater effect on phosphorylation of p38 MAP kinases, JNKs, and NF-kB (Ser276), and caused a marked decrease in the phosphorylation of forkhead box O3a (FOXO3a) and signal transducer and activator of transcription 3 (STAT3). However, IOD caused a greater decrease in the phosphorylation of mTOR (Ser2448) and phospho-ERK 1/2 while both RCM caused a similar decrease in the phosphorylation of phospho-p70S6 kinase (Ser371). In vivo studies showed that both IOM and IOD caused a significant decrease in both pAkt (Ser473) and pERK 1/2 in rat kidneys. Our study gives an insight into the possible mechanism of toxicity of RCM via their action on intracellular signaling pathways and may help in developing pharmacological interventions for their side-effects.

Kidney Injury Biomarkers in Hypertensive, Diabetic, and Nephropathy Rat Models Treated with Contrast Media

Contrast-induced nephropathy (CIN) refers to a decline in renal function following exposure to iodinated contrast media (CM). The present study was initiated to explore the role of known human risk factors (spontaneous hypertension, diabetes, protein-losing nephropathy) on CIN development in rodent models and to determine the effect of CM administration on kidney injury biomarkers in the face of preexisting kidney injury. Spontaneously hypertensive rats (hypertension), streptozotocin-treated Sprague Dawley rats (diabetes), and Dahl salt-sensitive rats (protein-losing nephropathy) were given single intravenous injections of the nonionic, low osmolar contrast medium, iohexol. Blood urea nitrogen (BUN), serum creatinine (sCr), and urinary biomarkers; albumin, lipocalin 2 (Lcn-2), osteopontin (Opn), kidney injury molecule 1 (Kim-1), renal papillary antigen 1 (Rpa-1), α-glutathione S-transferase (α-Gst), µ-glutathione S-transferase (µ-Gst), and beta-2 microglobulin (β2m) were measured in disease models and appropriate controls to determine the response of these biomarkers to CM administration. Each disease model produced elevated biomarkers of kidney injury without CM. Preexisting histopathology was exacerbated by CM but little or no significant increases in biomarkers were observed. When 1.5-fold or greater sCr increases from pre-CM were used to define true positives, receiver–operating characteristic curve analysis of biomarker performance showed sCr was the best predictor of CIN across disease models. β2m, Lcn-2, and BUN were the best predictors of histopathology defined kidney injury.

Toxic effects of a high dose of non-ionic iodinated contrast media on renal glomerular and aortic endothelial cells in aged rats in vivo

Iodinated contrast media (CM) can induce apoptosis and necrosis of renal tubular cells. The injuries of endothelial cells induced by CM on the systemic condition have not been fully understood. To assess the toxic effects of non-ionic CM on the glomerular and aortic endothelial cells, iopromide and iodixanol, two kinds of representative non-ionic CM, were used for the in vivo study. Sixty aged rats were respectively received the agents or normal sodium intravascularly. No obvious apoptosis and morphological change was detected in the glomerular and aortic endothelial cells apart from renal tubules after CM administration. However, expressions of the nitric oxide synthase (eNOS) in glomerular endothelium were decreased at 12h after CM injection. Furthermore, plasma creatinine and endothelin-1 were increased and plasma nitric oxide (NO) was decreased significantly after CM administration. However, we failed to observe the significant increase of plasma von Willebrand Factor. These results suggest that non-ionic iodinated CM do not induce apoptosis and necrosis of glomerular and aortic endothelial cells in vivo. Decreased eNOS expression and increased plasma endothelin-1 may be involved in non-ionic iodinated CM-induced endothelial dysfunction and kidney injury.

Differential activation of signaling pathways involved in cell death, survival and inflammation by radiocontrast media in human renal proximal tubular cells

Radiocontrast media (RCM) are widely used in clinical medicine but may lead to radiocontrast-induced nephropathy (RCIN). The pathogenesis of acute renal failure secondary to RCM is not fully understood, but direct toxic effects are believed to be a major cause of RCIN. We have investigated the effect of different types of RCM on signaling pathways known to play a role in cell death, survival, and inflammation. HK-2 cells were incubated with sodium diatrizoate and iomeprol (IOM) at a concentration of 75 mg I/ml for 2 h. Both RCM caused an increase in phosphorylation of p38 mitogen-activated protein kinase (MAPK) (p38) and c-Jun N-terminal kinases (JNKs) and NF-κB (at Ser 276), with sodium diatrizoate having a more drastic effect. Although cell viability was reduced significantly by both RCM, in cells pretreated with IOM the cell viability recovered over a 22-h time period after removal of the RCM. However, viability of diatrizoate-treated cells rose at 5 h but then fell at 22 h after removal of the RCM. The decrease in cell viability in diatrizoate-treated cells corresponded with an increase in phosphorylation of JNKs, p38, and NF-κB and a decrease in phosphorylation of Akt, signal transducer and activator of transcription 3, and forkhead box O3a, as well as poly (ADP-ribose) polymerase and caspase-3 cleavage. The recovery in viability of IOM-treated cells corresponded most notably with an increase in STAT3 phosphorylation and induction of Pim-1 kinase. There was also an increase in interleukin-8 release by diatrizoate-treated cells indicating the possibility of proinflammatory effects of RCM. A knowledge of the signaling pathways by which RCM exert their cytotoxic actions may help in finding future therapies for RCIN.

Differences in immunolocalization of Kim-1, RPA-1, and RPA-2 in kidneys of gentamicin-, cisplatin-, and valproic acid-treated rats: potential role of iNOS and nitrotyrosine

The present study compared the immunolocalization of Kim-1, renal papillary antigen (RPA)-1, and RPA-2 with that of inducible nitric oxide synthase (iNOS) and nitrotyrosine in kidneys of gentamicin sulfate (Gen)- and cisplatin (Cis)-treated rats. The specificity of acute kidney injury (AKI) biomarkers, iNOS, and nitrotyrosine was evaluated by dosing rats with valproic acid (VPA). Sprague-Dawley (SD) rats were injected subcutaneously (sc) with 100 mg/kg/day of Gen for six or fourteen days; a single intraperitoneal (ip) dose of 1, 3, or 6 mg/kg of Cis; or 650 mg/kg/day of VPA (ip) for four days. In Gen-treated rats, Kim-1 was expressed in the epithelial cells, mainly in the S1/S2 segments but less so in the S3 segment, and RPA-1 was increased in the epithelial cells of collecting ducts (CD) in the cortex. Spatial expression of iNOS or nitrotyrosine with Kim-1 or RPA-1 was detected. In Cis-treated rats, Kim-1 was expressed only in the S3 segment cells, and RPA-1 and RPA-2 were increased in the epithelial cells of medullary CD or medullary loop of Henle (LH), respectively. Spatial expression of iNOS or nitrotyrosine with RPA-1 or RPA-2 was also identified. These findings suggest that peroxynitrite formation may be involved in the pathogenesis of Gen and Cis nephrotoxicity and that Kim-1, RPA-1, and RPA-2 have the potential to serve as site-specific biomarkers for Gen or Cis AKI.

Renal cell apoptosis induced by nephrotoxic drugs: cellular and molecular mechanisms and potential approaches to modulation

Apoptosis plays a central role not only in the physiological processes of kidney growth and remodeling, but also in various human renal diseases and drug-induced nephrotoxicity. We present in a synthetic fashion the main molecular and cellular pathways leading to drug-induced apoptosis in kidney and the mechanisms regulating it. We illustrate them using three main nephrotoxic drugs (cisplatin, gentamicin, and cyclosporine A). We discuss the main regulators and effectors that have emerged as key targets for the design of therapeutic strategies. Novel approaches using gene therapy, antisense strategies, recombinant proteins, or compounds obtained from both classical organic and combinatorial chemistry are examined. Finally, key issues that need to be addressed for the success of apoptosis-based therapies are underlined.

Radiocontrast media cause dephosphorylation of Akt and downstream signaling targets in human renal proximal tubular cells

Radiocontrast medium induced nephrotoxicity is a major clinical problem. There is considerable interest in reducing the incidence of acute renal failure due to the use of radiocontrast media (RCM). Reduction of renal blood flow and direct toxic effect on renal tubular epithelial cells have been postulated as major causes of RCM nephropathy. Understanding the molecular mechanisms by which RCM cause cell damage may allow the development of pharmacological therapy to prevent their nephrotoxicity. In this work we have investigated the signaling pathways that may be affected by RCM. The incubation of human renal tubular proximal cells with sodium diatrizoate, iopromide and iomeprol caused a marked dephosphorylation of the kinase Akt on Ser473 within 5min of incubation. RCM also caused a decrease in cell viability, which was substantially alleviated by transfecting the cells with a constitutively active form of Akt. Further downstream targets of Akt, including the Forkhead family of transcription factors FKHR and FKHRL1, were also dephosphorylated by RCM at Thr24 and Thr32, respectively. The P70S6 kinase was also dephosphorylated at Thr389 and Ser371 by RCM. However there was a more dramatic decrease in phosphorylation of the phosphorylated form of mammalian target of rapamycin (mTOR) and of the extracellular-signal regulated kinases (ERK) 1/2 caused by sodium diatrizoate than by iopromide. These results demonstrate the effect of RCM on some intracellular signaling pathways that may allow understanding of the mechanism of their toxicity and may allow the development of strategies to overcome their adverse effects.

Mechanisms and biomarkers of cardiovascular injury induced by phosphodiesterase inhibitor III SK&F 95654 in the spontaneously hypertensive rat

The cardiovascular injury of the type III selective PDE inhibitor SK&F 95654 was investigated in SHR. Twenty-four hours after a single sc injection of 100 or 200 mg/kg of the drug, rats exhibited cardiomyocyte necrosis and apoptosis, interstitial inflammation, hemorrhage and edema, as well as mesenteric arterial hemorrhage and necrosis, periarteritis, EC and VSMC apoptosis, EC activation, and MC activation and degranulation. Elevated serum levels of cTnT and decreased cTnT immunoperoxidase staining on cardiomyocytes were detected in the drug-treated rats. Serum levels of alpha2-macroglobulin and IL-6 were significantly elevated following drug treatment. NMR spectral patterns of urine samples are significantly different between the drug-treated and control rats. These results indicate that measurement of serum cTnT, acute phase proteins, and cytokines as well as metabonomic urine profiles may serve as potential biomarkers for drug-induced cardiovascular injury in rats. Increased expression of CD63 on MC (tissue biomarker of MC), of nitrotyrosine on MC and EC (an indirect indicator of NO in vivo), and of iNOS on MC and EC (source of NO) suggest that NO produced by activated and degranulated MC as well as activated EC play an important role in SK&F 95654-induced mesenteric vascular injury.

Low hematocrit predicts contrast-induced nephropathy after percutaneous coronary interventions

BACKGROUND

The relationship between low hematocrit and contrast-induced nephropathy has not been investigated.

METHODS

Of 6,773 consecutive patients treated with percutaneous coronary intervention, contrast-induced nephropathy (an increase of >/=25% or >/=0.5 mg/dL in preprocedure serum creatinine, at 48 hours postprocedure) occurred in 942 (13.9%) patients.

RESULTS

Rates of contrast-induced nephropathy steadily increased as baseline hematocrit quintile decreased (from 10.3% in the highest quintile to 23.3% in the lowest quintile) (chi(2) for trend, P < 0.0001). Stratification by baseline estimated glomerular filtration rate (eGFR) and baseline hematocrit showed that the rates of contrast-induced nephropathy were the highest (28.8%) in patients who had the lowest level for both baseline eGFR and hematocrit. Patients with the lowest eGFR but relatively high baseline hematocrit values had remarkably lower rates of contrast-induced nephropathy (15.8%, 12.3%, 17.1%, and 15.4% in 2nd, 3rd, 4th, and 5th quintiles of baseline hematocrit, respectively) (P < 0.0001). The rates of contrast-induced nephropathy increased with increment in change in hematocrit. Patients in the lowest quintile of baseline hematocrit with absolute hematocrit drop >5.9% had almost doubled rates of contrast-induced nephropathy compared with patients with hematocrit change <3.4% (38.1% vs. 18.8%, respectively) (P < 0.0001). By multivariate analysis, lower baseline hematocrit was an independent predictor of contrast-induced nephropathy; each 3% decrease in baseline hematocrit resulted in a significant increase in the odds of contrast-induced nephropathy in patients with and without chronic kidney disease (11% and 23%, respectively). When introduced into the multivariate model instead of baseline hematocrit, change in hematocrit also showed a significant association with contrast-induced nephropathy.

CONCLUSION

Lower hematocrit is an important risk factor for contrast-induced nephropathy. Whether correcting the hematocrit prepercutaneous coronary intervention might decrease the rates of contrast-induced nephropathy should be addressed in a prospectively designed trial.

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.

Effects of contrast media on porcine bone marrow-derived mononuclear cells and calf myoblast viability and secretion of VEGF and MCP-1

We investigated the effect of contrast media on bone marrow-derived cell viability, growth factor secretion, and myoblast viability. Bone marrow was exposed to contrast media, mononuclear cells were isolated, viability was assessed by Trypan blue exclusion or cultured for 4 weeks, and conditioned medium was assayed for vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1). Skeletal myoblasts viability was assessed after exposing them to contrast media. In separate experiments, bone marrow or bone marrow-derived mononuclear cells were exposed to contrast media, cultured for 40 hr, then assessed for viability. None of the contrast media tested had any effect on bone marrow-derived cell viability. Hypaque or Hexabrix increased myoblasts viability by 8-10%. VEGF and MCP-1 concentrations in the conditioned medium increased in a time-related manner. These findings support the concept that for cell therapy, bone marrow cells or myoblasts may be mixed with contrast media and injected into ischemic myocardium without compromise in viability or function.

Cyclic AMP reverses radiocontrast media-induced apoptosis in LLC-PK1 cells by activating A kinase/PI3 kinase

BACKGROUND

Radiographic contrast material is one of agents that are prone to cause nephropathy, although little is known about cellular mechanisms underlying contrast media-induced renal failure. The present study was designed to determine the role of caspase in contrast media-induced renal injury. The modulation by cyclic adenosine monophosphate (cAMP) of cell injury was subsequently examined.

METHODS

LLC-PK1 cells (a proximal renal tubular cell line of porcine origin) were exposed to diverse contrast media for 30 minutes followed by incubation for 24 hours in normal medium. Cell viability was assessed by mitochondrial enzyme activity and propidium iodide stain. Apoptosis was determined by DNA electrophoresis and annexin V stain. Caspase activity was measured fluorometrically. The mRNA for bax and bcl-2 was determined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Iodinated and magnetic resonance contrast media reduced cell viability due to apoptosis. The cell damage induced by a non-ionic contrast medium ioversol was inhibited by specific inhibitors for caspase-3 and -9 but not caspase-8. Ioversol enhanced the activities of caspase-3 and -9, but to a lesser extent, caspase-8. The bax mRNA was enhanced, while bcl-2 mRNA was reduced, after exposure to ioversol. All of these actions of ioversol were reversed by dibutyl cAMP in the manner sensitive to a protein kinase A inhibitor H89 and a phosphatidylinositol 3 (PI3) kinase inhibitor wortmannin.

CONCLUSION

We demonstrated for the first time that cAMP reversed caspase-dependent apoptotic renal cell damage caused by contrast media. Both protein kinase A and PI3 kinase might be involved in protective effect of cAMP.

Should we use diuretics in acute renal failure?

Because oliguria is a bad prognostic sign in patients with acute renal failure (ARF), diuretics are often used to increase urine output in patients with or at risk of ARF. From a pathophysiological point of view there are several reasons to expect that loop diuretics also could have a beneficial effect on renal function. However, clinical trials on the prophylactic use of loop diuretics rather point to a deleterious effect on parameters of kidney function. In patients with established ARF loop diuretics have been shown to increase urine output, which may facilitate patient management. A beneficial effect on renal function has, however, not been demonstrated. On the other hand, such an effect cannot be excluded because the available trials lack statistical power. Possible explanations for the absence of a renoprotective effect are discussed. The evidence for a renoprotective effect of mannitol is restricted to the setting of renal transplantation.

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.

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.

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.

Cardiomyocyte apoptotic cell death in arterial hypertension: mechanisms and potential management

Hypertensive heart disease is a progressive condition in which the compensatory left ventricular hypertrophy that maintains cardiac output leads to myocardial remodeling, characterized by fibrosis, insufficient vascularization, and alterations in cardiomyocytes, including contractile disturbances, changes in gene expression, and decrease in the number of cells. Structural abnormalities in the myocardial wall accelerate the development of diastolic and systolic dysfunction, resulting in heart failure. Many observations point to the apoptotic cell death of cardiomyocytes as a relevant factor in the transition from compensatory hypertrophy to pump failure in experimental and human hypertension. Potential inducers of cardiomyocyte apoptosis in overloaded hearts include extrinsic factors, such as mechanical forces, neurohormonal activation, oxidative stress, hypoxia, and cytokines. Some lines of evidence indicate that angiotensin II and the overstretching of cardiomyocytes are originally involved in the triggering of apoptosis in hypertension, whereas other factors are being investigated. Furthermore, intracellular changes, such as downregulation of survival proteins or activation of death proteins, seem to play an important role. The assumption that the apoptosis of cardiomyocytes worsens hypertensive heart disease prognosis brings forth new approaches to avoid or slow the transition to pump failure. In this respect, experimental data indicate that currently used antihypertensive drugs interfere with cardiomyocyte apoptosis. Moreover, the knowledge of intracellular apoptotic processes in cardiomyocytes provides novel therapeutic strategies to be added to the multimodal approach in the prevention of heart failure.

Review of studies establishing the aging male spontaneously hypertensive rat as a detector and quantifier of the kidney toxicity of radiocontrast media and other chemicals

RATIONALE AND OBJECTIVES

There is a need for practical and sensitive preclinical tests for detecting the kidney toxicity of chemicals. The spontaneously hypertensive rat (SHR), as it ages, develops renal and cardiovascular changes similar to those considered as human risk factors for radiocontrast-induced renal damage. Age, male gender, and uncontrolled hypertension make these animals susceptible to the volume and osmolality of the administered contrast agent and the effect of repeated contrast administration after a brief interval. This article reviews studies in which the role of these and other factors were evaluated to validate the male SHR as a small animal model for renal damage induced by contrast and other agents.

METHODS

Systolic blood pressure was measured with a tail cuff before and after the administration of the experimental substances, and the left kidney and heart were studied histologically to determine the influence of age, dose of contrast repeated at a short interval, gender and strain, the role of the sympathetic adrenergic nervous system, osmolality, and apoptosis.

RESULTS

As the animals aged and the systolic blood pressure remained elevated, the animals developed progressive renal lesions that worsened after the administration of contrast. The most advanced renal lesions occurred in adult male SHRs that received two doses of contrast 6 hours apart. Female SHR rats and male Wistar Kyoto rats showed no effect or only minimal changes in heart and kidneys after the administration of contrast compared with age-matched male SHRs. Adrenergic blockade allowed only a small elevation in systolic blood pressure after contrast administration but did not protect the kidneys against renal damage by contrast. Hypaque, Omnipaque, and mannitol caused renal damage in proportion to their osmolality. Apoptosis with Hypaque, Omnipaque, and mannitol was observed in the kidney and heart.

CONCLUSION

The results indicate that the aging male SHR develops spontaneous renal lesions that progress with age, increasing the susceptibility to the renal-damaging effects of contrast. Thus, the aging male SHR provides a laboratory tool for detecting the risk of renal damage of new contrast media as well as other pharmaceuticals and assessing methods to protect the kidneys and possible mechanisms of renal damage.

Effects of radiographic contrast media on proliferation and apoptosis of human vascular endothelial cells

The aim of the study was to determine the effects of radiographic contrast media (RCM) on proliferation and apoptosis of human vascular endothelial cells. Human umbilical vein endothelial cells (HUVECs) were exposed for either 1 min or 15 min to RCM (diatrizoate, ioxaglate, iopromide, iotrolan) at an iodine concentration of 250 mgl ml-1. Controls were complete growth medium (CGM) and saturated mannitol (osmotic control). [3H]thymidine incorporation was used to determine cell proliferation 24 h after exposure. Apoptosis was determined at 1 h and 6 h by terminal uridine nick end labelling (TUNEL), time lapse video microscopy (TLVM) and DNA electrophoresis. Mean proliferation rates (%) (+/- SEM) (p-values compared with the CGM control) at 1 min and 15 min, respectively, were: diatrizoate: 31.9 (10.6), 5.8 (1.5) (p < 0.001); ioxaglate: 48.4 (10.9), 20.4 (4.5) (p < 0.001); iopromide: 63.4 (8.7), 58.2 (10.2) (p < 0.05); iotrolan: 84.7 (7.3), 72.8 (12.4) (p = ns); saturated mannitol 50.5 (9.6), 45.9 (10.0) (p < 0.001). Mean apoptotic indices (%) (+/- SEM) at 1 h and 6 h following 1 min exposure, respectively, were: CGM: 0.25 (0.13), 0.23 (0.08); diatrizoate: 2.18 (0.19), 2.69 (0.34) (p < 0.001); ioxaglate: 1.90 (0.23), 1.69 (0.02) (p < 0.05); iopromide: 0.59 (0.04), 0.33 (0.02) (p = ns); iotrolan: 0.30 (0.07), 0.27 (0.1) (p = ns); saturated mannitol 2.11 (0.24), 1.4 (0.1) (p < 0.05). After 15 min exposure, apoptosis rates at both 1 h and 6 h, respectively, were: iotrolan: 0.29 (0.17), 0.51 (0.16) (p = ns); diatrizoate: 3.19 (0.81), 11.66 (1.75) (p < 0.001); ioxaglate: 1.88 (0.14), 2.87 (0.20) (p < 0.05); iopromide: 1.06 (0.11), 1.52 (0.15) (p < 0.05); saturated mannitol 1.62 (0.09), 4.63 (0.74) (p < 0.05). TLVM and DNA electrophoresis confirmed the occurence of apoptosis after exposure to RCM. In conclusion, saturated mannitol and all tested RCM, with the exception of iotrolan, (diatrizoate > ioxaglate > iopromide) reduced proliferation and increased apoptosis of HUVECs. The effects were more pronounced with ionic RCM and seem to depend on osmolality as well as the chemical structure of these agents. Endothelial injury and apoptosis may be responsible for some of the side effects associated with intravascular use of RCM.

Pharmaceutical excipient development: the need for preclinical guidance

Pharmaceutical excipients have a vital role in drug formulations, a role that has tended to be neglected as evidenced by the lack of mechanisms to assess excipient safety outside a new drug application process. Currently, it is assumed that an excipient is "approved" when the new drug formulation, of which it is a constituent, receives regulatory acceptance. Existing regulations and guidelines indicate that new (novel) excipients should be treated as new chemical entities with full toxicological evaluation. No guidance is available for potentially useful materials (essentially new excipients) available from other industries, e.g., food additives or for established excipients with a new application, e.g., dose route change. However, despite this situation, drug companies are actively evaluating new materials or applying new uses to established excipients. Recently developed excipients (e.g., materials giving "sugar-free" status to medical preparations, the cyclodextrins, and the hydrofluoroalkane inhalation propellants) and excipients undergoing development (e.g., chitosan, various enteric coating substances, liposomes, polymers derived from glycolic and lactic acids, and vaccine adjuvants) are all discussed. In light of many other areas of drug development having recently benefited from new or updated regulatory guidance, specific guidance to assist companies in the development of their excipients is urgently needed. Also, an excipient testing strategy would be an excellent topic for inclusion for International Conference on Harmonisation (ICH) consideration. Such guidance/discussion would complement the current advances in pharmacopoeial standardization of excipient quality. As a consequence, it may be possible to have excipients reviewed by a committee of an international pharmacopoeia with the safety data assessed by elected experts and published.