Copper complexes as a source of redox active MRI contrast agents

The study reports an advance in designing copper-based redox sensing MRI contrast agents. Although the data demonstrate that copper(II) complexes are not able to compete with lanthanoids species in terms of contrast, the redox-dependent switch between diamagnetic copper(I) and paramagnetic copper(II) yields a novel redox-sensitive contrast moiety with potential for reversibility.

Role of reactive oxygen species-mediated endoplasmic reticulum stress in contrast-induced renal tubular cell apoptosis

BACKGROUND

Renal tubular cell apoptosis is a key mechanism of contrast-induced acute kidney injury. It has been reported that endoplasmic reticulum (ER) stress is the underlying mechanism of high osmolar contrast-induced renal tubular cell apoptosis. Whether ER stress is involved in low osmolar contrast-induced renal tubular cell injury remains unclear. In the present study, the roles of ER stress in iopromide-induced (a low osmolar contrast) renal tubular cell apoptosis and the effects of N-acetylcysteine (NAC) on ER stress were investigated.

METHODS

NRK-52E cells were exposed to different concentrations of iopromide [50, 100 and 150 mg iodine (I)/ml] for 4 h. In a separate experiment, NRK-52E cells were exposed to iopromide (100 mg I/ml, 4 h) with or without NAC (10 mmol/l). NAC was added 1 h before incubation with iopromide. Apoptosis was determined by Hoechst staining and flow cytometry. The intracellular formation of reactive oxygen species (ROS) was detected by confocal microscopy with fluorescent probe CM-H2DCFDA. The expression of glucose-regulated protein 78 (GRP78) and CAAT/enhancer-binding protein homologous protein (CHOP) was determined by Western blot.

RESULTS

Iopromide induced NRK-52E cell apoptosis in a concentration-dependent manner. The intracellular ROS production increased significantly following iopromide exposure in the NRK-52E cells. Significantly increased expressions of GRP78 and CHOP were observed in the NRK-52E cells exposed to iopromide for 4 h; NAC attenuated iopromide-induced NRK-52E cell apoptosis by inhibiting the overproduction of intracellular ROS and subsequently suppressing the overexpression of GRP78 and CHOP.

CONCLUSION

ROS-mediated ER stress is involved in contrast-induced renal tubular cell apoptosis.

Determination of location, size, and transmurality of chronic myocardial infarction without exogenous contrast media by using cardiac magnetic resonance imaging at 3 T

BACKGROUND

Late-gadolinium-enhanced (LGE) cardiac MRI (CMR) is a powerful method for characterizing myocardial infarction (MI), but the requisite gadolinium infusion is estimated to be contraindicated in ≈20% of patients with MI because of end-stage chronic kidney disease. The purpose of this study is to investigate whether T1 CMR obtained without contrast agents at 3 T could be an alternative to LGE CMR for characterizing chronic MIs using a canine model of MI.

METHODS AND RESULTS

Canines (n=29) underwent CMR at 7 days (acute MI [AMI]) and 4 months (chronic MI [CMI]) after MI. Infarct location, size, and transmurality measured by using native T1 maps and LGE images at 1.5 T and 3 T were compared. Resolution of edema between AMI and CMI was examined with T2 maps. T1 maps overestimated infarct size and transmurality relative to LGE images in AMI (P=0.016 and P=0.007, respectively), which was not observed in CMI (P=0.49 and P=0.81, respectively) at 3 T. T1 maps underestimated infarct size and transmurality relative to LGE images in AMI and CMI (P<0.001) at 1.5 T. Relative to the remote territories, T1 of the infarcted myocardium was increased in CMI and AMI (P<0.05), and T2 of the infarcted myocardium was increased in AMI (P<0.001) but not in CMI (P>0.20) at both field strengths. Histology showed extensive replacement fibrosis within the CMI territories. CMI detection sensitivity and specificity of T1 CMR at 3 T were 95% and 97%, respectively.

CONCLUSIONS

Native T1 maps at 3 T can determine the location, size, and transmurality of CMI with high diagnostic accuracy. Patient studies are necessary for clinical translation.

Application of fullerenes in nanomedicine: an update

Fullerenes are carbon spheres presently being pursued globally for a wide range of applications in nanomedicine. These molecules have unique electronic properties that make them attractive candidates for diagnostic, therapeutic and theranostic applications. Herein, the latest research is discussed on developing fullerene-based therapeutics as antioxidants for inflammatory diseases, their potential as antiviral/bacterial agents, utility as a drug delivery device and the promise of endohedral fullerenes as new MRI contrast agents. The recent discovery that certain fullerene derivatives can stabilize immune effector cells to prevent or inhibit the release of proinflammatory mediators makes them potential candidates for several diseases such as asthma, arthritis and multiple sclerosis. Gadolinium-containing endohedral fullerenes are being pursued as diagnostic MRI contrast agents for several diseases. Finally, a new class of fullerene-based theranostics has been developed, which combine therapeutic and diagnostic capabilities to specifically detect and kill cancer cells.

Role of intracellular Ca2+ and Na+/Ca2+ exchanger in the pathogenesis of contrast-induced acute kidney injury

The precise mechanisms underlying contrast-induced acute kidney injury (CI-AKI) are not well understood. Intracellular Ca²⁺ overload is considered to be a key factor in CI-AKI. Voltage-dependent Ca²⁺ channel (VDC) and Na⁺/Ca²⁺ exchanger (NCX) system are the main pathways of intracellular Ca²⁺ overload in pathological conditions. Here, we review the potential underlying mechanisms involved in CI-AKI and discuss the role of NCX-mediated intracellular Ca²⁺ overload in the contrast media-induced renal tubular cell injury and renal hemodynamic disorder.

Bio-inspired, melanin-like nanoparticles as a highly efficient contrast agent for T1-weighted magnetic resonance imaging

The development of nontoxic and biocompatible imaging agents will create new opportunities for potential applications in clinical MRI diagnosis. Synthetic melanin-like nanoparticles (MelNPs), analogous to natural sepia melanin (a major component of the cuttlefish ink), can be used as contrast agent for MRI. MelNPs complexed with paramagnetic Fe(3+) ions show much higher relaxivity values than existing MRI T1 contrast agents based on gadolinium (Gd) or manganese (Mn); MelNP values at 3T were r1 = 17 and r2 = 18 mM(-1) s(-1) (r2/r1 value of 1.1). With significant enhancement to MRI contrast, this biomimetic approach using MelNPs functionalized with paramagnetic Fe(3+) ions and surface-modified with biocompatible poly(ethylene glycol) units, could provide new insight into how melanin-based bioresponsive and therapeutic imaging probes integrate with their various biological functions.

Safety of meglumine gadoterate (Gd-DOTA)-enhanced MRI compared to unenhanced MRI in patients with chronic kidney disease (RESCUE study)

Objective

To prospectively compare the renal safety of meglumine gadoterate (Gd-DOTA)-enhanced magnetic resonance imaging (MRI) to a control group (unenhanced MRI) in high-risk patients.

Methods

Patients with chronic kidney disease (CKD) scheduled for MRI procedures were screened. The primary endpoint was the percentage of patients with an elevation of serum creatinine levels, measured 72 ± 24 h after the MRI procedure, by at least 25 % or 44.2 μmol/l (0.5 mg/dl) from baseline. A non-inferiority margin of the between-group difference was set at −15 % for statistical analysis of the primary endpoint. Main secondary endpoints were the variation in serum creatinine and eGFR values between baseline and 72 ± 24 h after MRI and the percentage of patients with a decrease in eGFR of at least 25 % from baseline. Patients were screened for signs of nephrogenic systemic fibrosis (NSF) at 3-month follow-up.

Results

Among the 114 evaluable patients, one (1.4 %) in the Gd-DOTA-MRI group and none in the control group met the criteria of the primary endpoint [Δ = −1.4 %, 95%CI = (−7.9 %; 6.7 %)]. Non-inferiority was therefore demonstrated (P = 0.001). No clinically significant differences were observed between groups for the secondary endpoints. No serious safety events (including NSF) were noted.

Conclusion

Meglumine gadoterate did not affect renal function and was a safe contrast agent in patients with CKD.

Key points

• Contrast-induced nephropathy (CIN) is a potential problem following gadolinium administration for MRI.

• Meglumine gadoterate (Gd-DOTA) appears safe, even in patients with chronic kidney disease.

• Gd-DOTA only caused a temporary creatinine level increase in 1/70 such patients.

• No case or sign of NSF was detected at 3-month follow-up.

Involvement of caspase-12-dependent apoptotic pathway in ionic radiocontrast urografin-induced renal tubular cell injury

Contrast medium (CM) induces a direct toxic effect on renal tubular cells. This toxic effect subjects in the disorder of CM-induced nephropathy. Our previous work has demonstrated that CM shows to activate the endoplasmic reticulum (ER)-related adaptive unfolding protein response (UPR) activators. Glucose-regulated protein 78 (GRP78)/eukaryotic initiation factor 2α (eIF2α)-related pathways play a protective role during the urografin (an ionic CM)-induced renal tubular injury. However, the involvement of ER stress-related apoptotic signals in the urografin-induced renal tubular cell injury remains unclear. Here, we examined by the in vivo and in vitro experiments to explore whether ER stress-regulated pro-apoptotic activators participate in urografin-induced renal injury. Urografin induced renal tubular dilation, tubular cells detachment, and necrosis in the kidneys of rats. The tubular apoptosis, ER stress-related pro-apoptotic transcriptional factors, and kidney injury marker-1 (kim-1) were also conspicuously up-regulated in urografin-treated rats. Furthermore, treatment of normal rat kidney (NRK)-52E tubular cells with urografin augmented the expressions of activating transcription factor-6 (ATF-6), C/EBP homologous protein (CHOP), Bax, caspase-12, JNK, and inositol-requiring enzyme (IRE) 1 signals. Urografin-induced renal tubular cell apoptosis was not reversed by the inhibitors of ATF-6, JNK signals or CHOP siRNA transfection, but it could be partially reversed by the inhibitor of caspase-12. Taken together, the present results and our previous findings suggest that exposure of CM/urografin activates the ER stress-regulated survival- and apoptosis-related signaling pathways in renal tubular cells. Caspase-12-dependent apoptotic pathway may be partially involved in the urografin-induced nephropathy.

N-acetylcysteine protects rats with chronic renal failure from gadolinium-chelate nephrotoxicity

The aim of this study was to evaluate the effect of Gd-chelate on renal function, iron parameters and oxidative stress in rats with CRF and a possible protective effect of the antioxidant N-Acetylcysteine (NAC). Male Wistar rats were submitted to 5/6 nephrectomy (Nx) to induced CRF. An ionic-cyclic Gd (Gadoterate Meglumine) was administrated (1.5 mM/KgBW, intravenously) 21 days after Nx. Clearance studies were performed in 4 groups of anesthetized animals 48 hours following Gd- chelate administration: 1--Nx (n = 7); 2--Nx+NAC (n = 6); 3--Nx+Gd (n = 7); 4--Nx+NAC+Gd (4.8 g/L in drinking water), initiated 2 days before Gd-chelate administration and maintained during 4 days (n = 6). This group was compared with a control. We measured glomerular filtration rate, GFR (inulin clearance, ml/min/kg BW), proteinuria (mg/24 hs), serum iron (µg/dL); serum ferritin (ng/mL); transferrin saturation (%), TIBC (µg/dL) and TBARS (nmles/ml). Normal rats treated with the same dose of Gd-chelate presented similar GFR and proteinuria when compared with normal controls, indicating that at this dose Gd-chelate is not nephrotoxic to normal rats. Gd-chelate administration to Nx-rats results in a decrease of GFR and increased proteinuria associated with a decrease in TIBC, elevation of ferritin serum levels, transferrin oversaturation and plasmatic TBARS compared with Nx-rats. The prophylactic treatment with NAC reversed the decrease in GFR and the increase in proteinuria and all alterations in iron parameters and TBARS induced by Gd-chelate. NAC administration to Nx rat did not modify the inulin clearance and iron kinetics, indicating that the ameliorating effect of NAC was specific to Gd-chelate. These results suggest that NAC can prevent Gd-chelate nephrotoxicity in patients with chronic renal failure.

Prophylactic 0.9% saline hydration inhibited high-dose gadodiamide-induced nephropathy in rats

High doses of gadolinium-based contrast media are reported to induce deterioration of renal function. We assessed whether prophylactic 0.9% saline hydration inhibits high-dose gadodiamide-induced renal damage in rats. Twelve Sprague-Dawley rats were randomly divided into two groups, which are given gadodiamide (5 mmol/kg) with (hydration group) or without (control group) 0.9% saline hydration. The saline (4 mL/kg) was infused as a bolus into the peritoneum every 4 h, starting 12 h before and continuing for 12 h after the gadodiamide injection. Urine was collected to calculate creatinine clearance (Ccr) 24 h before and 48 h after the gadodiamide injection. The kidneys were harvested and stained for pathologic analysis. High-dose gadodiamide induced acute kidney injury as shown by decreased Ccr and renal histology with tubular cell injuries 48 h postinjection in both the groups. However, the extent of Ccr reduction was significantly (p = 0.02) less in the hydrated rats (-15% in the hydration group vs. -39% in the control group). Renal tubular cell injuries characterized by vacuolization, loss of brush borders, sloughing of tubular cells into the lumen, and flattening of the tubular epithelium were less frequently seen in the hydration group; only vacuolization (p = 0.01) and epithelial sloughing (p = 0.02) of the proximal tubules differed significantly between the two groups. We conclude that prophylactic 0.9% saline hydration significantly inhibited high-dose gadodiamide-induced nephropathy.

[Renal toxicity of contrast agents in oncologic patients]

Cancer patients frequently undergo imaging examinations to diagnosis but also to evaluate their responses to treatment. These patients are also at high risk of kidney impairment before considering the possible nephrotoxicity of their chemotherapy. In this context, it is overriding to know contrast agents induced risks and what are the good practices to avoid them. Renal function evaluation takes a major part in there. The X-ray radiology using iodinated contrast agent (ICA) exposes patients to acute renal failure. This induced nephropathy is prevented by adequate hydration prior to injection when the glomerular filtration rate (GFR) of the patient is less than 60 ml/min/1.73 m(2). For hardly nephrotoxic, gadolinium-based contrast agents (GBCA) injected in magnetic resonance imaging, were considered for a long as a safe alternative to ICA. Yet they may induce nephrogenic systemic fibrosis (NSF). The recommendations of European and U.S. drugs safety agencies have recently converged defining groups at risk of NSF based on the level of patients GFR and the type of GBCA used. How to assess the risk-benefit balance of the cancer patient for whom you should choose an informative, effective and safe imaging examination?

Residual Flow After Cerebral Aneurysm Coil Occlusion

Background and Purpose—

The purpose of this study was to estimate the performance measures of MR angiography (MRA) in the diagnosis of aneurysm residual flow after coil occlusion.

Methods—

Patients having at least 1 cerebral aneurysm treated with coil occlusion were prospectively and consecutively enrolled. Time of flight and contrast-enhanced MRA were performed the same day of the DSA follow-up. The degree of aneurysm occlusion and dimensions of the residual flow were evaluated by independent readers at MRA and digital subtraction angiogram. MRA performance measures were estimated in a cross-sectional analysis and repeated in subgroups of aneurysm sizes and locations. MRA predictive values for recurrence were also estimated using a longitudinal design.

Results—

We obtained 167 aneurysm evaluations for each imaging modality. Class 3 residual flow was seen on digital subtraction angiogram follow-up in 27%. The sensitivity and specificity of MRA was 88% (95% CI, 80–94) and 79% (95% CI, 67–88), respectively. The positive predictive value for a Class 3 recurrence was 67% (95% CI, 51–80) and the negative predictive value was 93% (95% CI, 86–97). Time-of-flight MRA underestimated the length of the residual flow ( P =0.039), whereas contrast-enhanced MRA overestimated its width ( P <0.0001). MRA sensitivity for a Class 3 residual flow was lower for aneurysms <6 mm ( P =0.01).

Conclusions—

MRA has sufficient accuracy for screening of aneurysm residual flow after coil occlusion. Due to its lower negative predictive value, recurrent aneurysms should be confirmed with digital subtraction angiogram before planning a retreatment. Routine use of MRA to follow small aneurysms should wait better estimation of its performance in this particular subgroup.

Applications of molecular MRI and optical imaging in cancer

Some of the most exciting advances in molecular-functional imaging of cancer are occurring at the interface between chemistry and imaging. Several of these advances have occurred through the development of novel imaging probes that report on molecular pathways, the tumor micro-environment and the response of tumors to treatment; as well as through novel image-guided platforms such as nanoparticles and nanovesicles that deliver therapeutic agents against specific targets and pathways. Cancer cells have a remarkable ability to evade destruction despite the armamentarium of drugs currently available. While these drugs can destroy cancer cells, normal tissue toxicity is a major limiting factor, a problem further compounded by poor drug delivery. One major challenge for chemistry continues to be to eliminate cancer cells without damaging normal tissues. Here we have selected examples of MRI and optical imaging, to demonstrate how integrating imaging with novel probes can facilitate the successful treatment of this multifaceted disease.

Nephrogenic systemic fibrosis and gadolinium-based contrast agents

The strong association between nephrogenic systemic fibrosis (NSF) and exposure to gadolinium-based contrast agents (GBCAs) has greatly affected the care of patients with kidney disease. NSF has been reported in patients with ESRD, CKD, and acute kidney injury (AKI). The majority of cases have occurred in patients with ESRD, but about 20% have been reported in patients with AKI or CKD stages 4 and 5. There is also a risk difference among GBCAs, with the Food and Drug Administration contraindicating 3 linear agents in patients at risk. Given the significant morbidity and mortality of NSF, it is imperative to identify individuals at risk. Although there are no data to support a role for hemodialysis (HD) in reducing the risk for NSF after administration of GBCAs, immediate HD is still recommended within 2 hours. Patients maintained on peritoneal dialysis seem to be at high risk and immediate HD is also recommended. However, this is not the current recommendation for CKD stages 4 and 5, especially with suspected lower risk of noncontraindicated agents. Individualized assessment is important and especially in those patients close to dialysis initiation. Instituting policies is important to address the imaging needs of patients with CKD and AKI while ensuring a balance between benefits and risks.

Signal quality of single dose gadobenate dimeglumine pulmonary MRA examinations exceeds quality of MRA performed with double dose gadopentetate dimeglumine

During a recent multi-center trial assessing gadolinium (Gd)-enhanced magnetic resonance angiography (MRA) for diagnosis of acute pulmonary embolism (PE), the Food and Drug Administration announced a risk of nephrogenic sclerosing fibrosis in patients with renal insufficiency who had received intravenous Gd-based MR contrast agents. Although no patients in this trial had renal insufficiency, in cautious response to this announcement, the trial protocol was changed from an intravenous administration of 0.2 mmol/Kg of a conventional Gd-based MR contrast agent to 0.1 mmol/Kg of gadobenate dimeglumine. The study described herein compares the signal quality of pulmonary MRA performed with double dose conventional agent to single dose gadobenate dimeglumine. This study is a retrospective analysis of data from a prospective, multicenter study in men and women ≥18 years with documented presence or absence of PE. The study was approved by the Institutional Review Board at all participating centers, and all patients provided written indication of informed consent. We performed both objective and subjective analysis of pulmonary artery image quality. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in the main pulmonary artery were assessed in single and double dose protocols and compared. SNR and CNR of the main PA were correlated with subjective quality assessment of main/lobar, segmental and subsegmental pulmonary arteries. Although there were individual outliers, both SNR (P = 0.01) and CNR (P = 0.008) were higher in all quartiles for examinations using gadobenate dimeglumine than with gadopentetate dimeglumine. Subjective quality of vascular signal intensity at each vessel order was significantly better for gadobenate dimeglumine (P < 0.0001), and correlated well with SNR and CNR at each order (<0.001). Because of agent high relaxivity, a single dose of gadobenate dimeglumine provides better pulmonary MRA signal quality than double dose of a conventional Gd-based MR contrast agent.

Pharmacokinetics and magnetic resonance imaging of biodegradable macromolecular blood-pool contrast agent PG-Gd in non-human primates: a pilot study

The purpose of this study was to evaluate poly(L-glutamic acid)-benzyl-DTPA-Gd (PG-Gd), a new biodegradable macromolecular magnetic resonance imaging contrast agent, for its pharmacokinetics and MRI enhancement in nonhuman primates. Studies were performed in rhesus monkeys at intravenous doses of 0.01, 0.02 and 0.08 mmol Gd/kg. T(1)-weighted MR images were acquired at 1.5 T using fast spoiled gradient recalled echo and fast spin echo imaging protocols. The small-molecule contrast agent Magnevist was used as a control. PG-Gd in the monkey showed a bi-exponential disposition. The initial blood concentrations within 2 h of PG-Gd administration were much higher than those for Magnevist. The high blood concentration of PG-Gd was consistent with the MR imaging data, which showed prolonged circulation of PG-Gd in the blood pool. Enhancement of blood vessels and organs with a high blood perfusion (heart, liver, and kidney) was clearly visualized at 2 h after contrast injection at the three doses used. A greater than proportional increase of the area under the blood concentration-time curve was observed when the administered single dose was increased from 0.01 to 0.08 mmol/kg. By 2 days after PG-Gd injection, the contrast agent was mostly cleared from all major organs, including kidney. The mean residence time was 15 h at the 0.08 mmol/kg dose. A similar pharmacokinetic profile was observed in mice, with a mean residence time of 5.4 h and a volume of distribution at steady-state of 85.5 ml/kg, indicating that the drug was mainly distributed in the blood compartment. Based on this pilot study, further investigations on the potential systemic toxicity of PG-Gd in both rodents and large animals are warranted before testing this agent in humans.

Evaluation and management of the renal mass

The evaluation and management of renal cell carcinoma (RCC) has evolved in recent decades in response to the changing clinical presentation of the disease. Traditional teaching suggested that RCC usually presents with signs or symptoms. However, RCC discovered this way was usually locally advanced and often metastatic, requiring radical nephrectomy in most cases but often having a poor prognosis. As contemporary general medical practice began routinely using axial body imaging in the evaluation of many nonspecific abdominal complaints, today more than 70% of RCC cases identified are "screen-detected" as incidental findings having no attributable symptoms. This change has prompted a significant RCC stage migration over the past 20 years, with most kidney tumors seen in 2010 being smaller, organ-confined, and appropriate for nephron-sparing approaches with the anticipation of a favorable outcome. The approach to addressing patients with these incidentally detected, often localized, small renal masses raises different concerns than those for traditional patients presenting with symptomatic RCC. This article reviews the modern epidemiology of RCC, outlines the components of the evaluation of the incidental renal mass, details the current options of management, and discusses the long-term expectations for these patients.

Endovascular Intervention for Central Venous Cannulation in Patients with Vascular Occlusion after Previous Catheterization

Objectives

This study was designed to assess endovascular intervention for central venous cannulation in patients with vascular occlusion after previous catheterization.

Methods

Patients referred for endovascular management of central venous occlusion during a 42-month period were identified from a regional endovascular database, providing prospective information on techniques and clinical outcome. Corresponding patient records, angiograms, and radiographic reports were analyzed retrospectively.

Results

Sixteen patients aged 48 years (range 0.5–76), including 11 females, were included. All patients but 1 had had multiple central venous catheters with a median total indwelling time of 37 months. Eleven patients cannulated for hemodialysis had had significantly fewer individual catheters inserted compared with 5 patients cannulated for nutritional support (mean 3.6 vs. 10.2, p<0.001) before endovascular intervention. Preoperative imaging by magnetic resonance tomography (MRT) in 8 patients, computed tomography (CT) venography in 3, conventional angiography in 6, and/or ultrasonography in 8, verified 15 brachiocephalic, 13 internal jugular, 3 superior caval, and/or 3 subclavian venous occlusions. Patients were subjected to recanalization (n=2), recanalization and percutaneous transluminal angioplasty (n=5), or stenting for vena cava superior syndrome (n=1) prior to catheter insertion. The remaining 8 patients were cannulated by avoiding the occluded route.

Conclusions

Central venous occlusion occurs particularly in patients under hemodialysis and with a history of multiple central venous catheterizations with large-diameter catheters and/or long total indwelling time periods. Patients with central venous occlusion verified by CT or MRT venography and need for central venous access should be referred for endovascular intervention.

Imaging chronic renal disease and renal transplant in children

At Great Ormond Street Hospital we have the highest number of paediatric renal transplant patients in Europe, taking cases from across the United Kingdom and abroad. Our caseload includes many children with rare complicating medical problems and chronic renal failure related morbidity. This review aims to provide an overview of our experience of imaging children with chronic renal failure and transplants.

The role of endoplasmic reticulum stress-related unfolded protein response in the radiocontrast medium-induced renal tubular cell injury

Contrast medium (CM) induces a direct toxic effect on renal tubular cells. This toxic effect may have a role in the pathophysiology of CM-induced nephropathy. CM has been shown to affect the endoplasmic reticulum (ER)-related capacity. Unfolded protein response (UPR) is known as a prosurvival response to reduce the accumulation of unfolded proteins and restore normal ER function. However, the role of ER stress-related UPR in the CM-induced renal cell injury still remains unclear. In this study, we examined whether UPR participates in urografin (an ionic CM)-induced renal tubular cells apoptosis. Treatment with urografin in normal rat renal tubular cell line (NRK52E) markedly increased cell apoptosis and decreased cell viability with a dose- and time-dependent manner. The cell necrosis was not increased in urografin-treated cells. Urografin also enhance the induction of ER stress-related markers in NRK52E cells, including glucose-regulated protein (GRP)78 and GRP94 expressions, procaspase-12 cleavage, phosphorylation of PERK (PKR [double-stranded RNA-activated protein kinase]-like ER kinase), and eukaryotic initiation factor 2alpha (eIF2alpha). Salubrinal, a selective inhibitor of eIF2alpha dephosphorylation, effectively decreased urografin-induced cell apoptosis. Furthermore, transfection of GRP78-small interfering RNA in NRK52E cells significantly enhanced urografin-induced cell apoptosis. These results suggest that GRP78/eIF2alpha-related signals play a protective role during UPR, and the activation of ER stress-related UPR may play an important regulative role in urografin-induced renal tubular injury.

Involvement of gadolinium chelates in the mechanism of nephrogenic systemic fibrosis: an update

Nephrogenic systemic fibrosis (NSF) is a highly debilitating scleroderma-like disease occurring exclusively in patients with severe or end-stage renal failure. Since the recognition of a link between gadolinium chelates (GCs) used as contrast agents for MR imaging and NSF by two independent European teams in 2006, numerous studies have described the clinical issues and investigated the mechanism of this disease. So far the most commonly reported hypothesis is based on the in vivo dechelation of GCs. The physicochemical properties of GCs, especially their thermodynamic and kinetic stabilities, are described in the present article. High kinetic stability provided by the macrocyclic structure, combined with high thermodynamic stability, minimizes the amount of free gadolinium released in the body. The current hypotheses regarding the pathophysiologic mechanism are critically discussed.