Effects of gadolinium-based MRI contrast agents on liver tissue

Association between concentrations of rare earth elements in chorionic villus and risk for unexplained spontaneous abortion

Rare earth elements (REEs) exposure during pregnancy may increase the risk of unexplained spontaneous abortion. However, the association between REEs intrauterine exposure and unexplained spontaneous abortion had yet to be studied. In order to conduct this large case-control study, we thus collected chorionic villus from 641 unexplained spontaneous abortion and 299 control pregnant women and detected the concentrations of 15 REEs by inductively coupled plasma mass spectrometer (ICP-MS). Because the detection rates of 10 REEs were less than 80%, the remaining 5 REEs, which were lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd) and yttrium (Y), underwent to further analysis. The association between 5 REEs and unexplained spontaneous abortion was assessed by using the logistic regression, bayesian kernel regression (BKMR) and weighted quantile sum regression (WQS) models. In the adjusted logistic regression model, Pr, Nd and Y enhanced the incidence of unexplained spontaneous abortion in a dose-dependent way and Ce increased the risk only at high concentration group. The result of BKMR model demonstrated that the risk of unexplained spontaneous abortion increased as the percentile of five mixed REEs increased. Y and Nd were both significantly associated with an increased incidence of unexplained spontaneous abortion, but La was correlated with a decrease in the risk of unexplained spontaneous abortion. Pr was substantially associated with an increase in the risk of unexplained spontaneous abortion when other REEs concentrations were fixed at the 25th and 50th percentiles. According to WQS regression analysis, the WQS index was significantly associated with unexplained spontaneous abortion (OR = 3.75, 95% CI:2.40-5.86). Y had the highest weight, followed by Nd and Pr, which was consistent with the analysis results of our other two models. In short, intrauterine exposure to REEs was associated with an increased risk of unexplained spontaneous abortion, with Y, Nd and Pr perhaps playing an essential role.

Toxicity Mechanisms of Gadolinium and Gadolinium-Based Contrast Agents-A Review

Gadolinium-based contrast agents (GBCAs) have been used for more than 30 years to improve magnetic resonance imaging, a crucial tool for medical diagnosis and treatment monitoring across multiple clinical settings. Studies have shown that exposure to GBCAs is associated with gadolinium release and tissue deposition that may cause short- and long-term toxicity in several organs, including the kidney, the main excretion organ of most GBCAs. Considering the increasing prevalence of chronic kidney disease worldwide and that most of the complications following GBCA exposure are associated with renal dysfunction, the mechanisms underlying GBCA toxicity, especially renal toxicity, are particularly important. A better understanding of the gadolinium mechanisms of toxicity may contribute to clarify the safety and/or potential risks associated with the use of GBCAs. In this work, a review of the recent literature concerning gadolinium and GBCA mechanisms of toxicity was performed.

Expression of GRP78 and its copartners in HEK293 and pancreatic cancer cell lines (BxPC-3/PANC-1) exposed to MRI and CT contrast agents

Endoplasmic reticulum (ER) stress-associated chaperones trigger a defense mechanism called as unfolded protein response (UPR) which can manage apoptosis and be determinative in cell fate. Both anticancer drug effects and potential toxicity effects of magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents were aimed to be evaluated. For this purpose, we investigated expression profiles of endoplasmic reticulum stress-associated chaperone molecules in human pancreatic tumor lines BxPC-3 and PANC-1 and control human embryonic kidney cells 293 (HEK293) induced with a variety of gadolinium and iohexol contrast agents. Protein expression levels of ER stress-associated chaperones (master regulator: GRP78/Bip and its copartners: Calnexin, Ero1, PDI, CHOP, IRE1α and PERK) were evaluated with Western blotting. Expression levels at mRNA level were also assessed for GRP78/Bip and CHOP with real-time PCR. Induction of cells was carried out with four different Gd-based contrast agents (GBCAs): (Dotarem, Optimark, Primovist and Gadovist) and two different iohexol agents (Omnipol, Omnipaque). CT contrast agents tested in the study did not result in significant ER stress in HEK293 cells. However, they do not seem to have theranostic potential in pancreas cancer through ER pathway. The potential efficiency of macrocyclic MRI contrast agents to provoke apoptosis via ER stress-associated chaperones in BxPC-3 cells lends credibility for their future theranostic use in pancreas cancer as long as undesired toxicity effects were carefully considered. ER stress markers and/or contrast agents seem to have promising potential to be translated into the clinical practice to manage pancreas cancer progression.

In Vivo and In Vitro Analysis of Toxicity of a Prospective Magnetic Resonance Contrast Agent Based on Arabinogalactan and Gadolinium Nanocomposite

We studied the cytotoxic effect of gadolinium nanocomposite on cultured mouse fibroblasts 3T3-SV40 and histological changes in the liver tissue of albino rats after its administration. For in vitro experiment, gadolinium nanocomposite on the natural matrix of arabinogalactan (nGd-AG) was dissolved in DMEM nutrient medium to concentrations of 0.005, 0.02, 0.5, 2, and 5 mM. In in vivo experiment, a nGd-AG solution was orally administered to rats through a tube in a dose of 500 μg Gd/kg in 1 ml of 0.9% NaCl for 10 days. The pattern and degree of influence of the gadolinium nanocomposite on the studied cell culture depended on the concentration and duration of exposure. IC50 of nGd-AG determined after cell incubation for 24, 48, and 72 h were 616 μg/kg (3.9 mM), 302 μg/kg (1.9 mM), and 222 μg/kg (1.4 mM), respectively. Histological changes in the liver of white rats induced by exposure to nanocomposite attested to the development of a compensatory reaction of the organ.

Effects of gadodiamide and gadoteric acid on lung tissue: A comparative study

We set out to investigate the effects of gadodiamide and gadoteric acid, used for magnetic resonance imaging, on the lungs. In this study, 32 male Sprague Dawley rats were used. These were allocated into four groups; The first group (control) was untreated. The second group received isotonic saline on the first and fourth days of the week for 5 weeks. Following the same schedule, the third and fourth groups received a total of 2 mg/kg gadodiamide and gadoteric acid, respectively, in place of saline. The alveolar Wall thickness was evaluated. Gadodiamide and gadoteric acid significantly increased the numbers of collagen-3 and caspase-3 positive cells in the lung tissue (p < 0.05). In addition, these two substances increased the alveolar Wall thickness (p < 0.05). Furthermore, they increased the levels of malondialdehyde and glutathione (p < 0.05). This study demonstrates that both linear and macrocyclic contrast agents are toxic for the lungs in rats.

Cellular and molecular pathways underlying the nephrotoxicity of gadolinium

Mounting evidence on the short- and long-term adverse effects associated with gadolinium [Gd (III)]-based contrast agents used in magnetic resonance imaging have emerged in the past three decades. Safety issues arise from the release of Gd (III) from chelates and its deposition in tissues, which is exacerbated in patients with renal disease, since the kidney is the major excretion organ of most of these agents. This study aimed at unveiling the cellular and molecular mechanisms of nephrotoxicity of Gd (III), using an in vitro model of human proximal tubular cells (HK-2 cell line). Cell viability declined in a concentration- and time-dependent manner after exposure to GdCl3·6H2O. The estimated inhibitory concentrations (ICs) eliciting 1 to 50% of cell death, after 24 h of exposure, ranged from 3.4 to 340.5 µM. At toxic concentrations, exposure to Gd (III) led to disruption of the oxidative status, mitochondrial dysfunction, cell death by apoptosis, switching to necrosis at higher levels, and autophagic activation. Disturbance of the lipid metabolism was already observed at low-toxicity ICs, with accumulation of lipid droplets, and upregulation of genes related to both lipogenesis and lipolysis. Gd (III)-exposure, even at the subtoxic IC01, increased the expression of modulators of various signaling pathways involved in the development and progression of renal disease, including inflammation, hypoxia and fibrosis. Our results give new insights into the mechanisms underlying the nephrotoxic potential of Gd (III) and highlight the need to further clarify the risks versus benefits of the Gd (III)-based contrast agents currently in use.

2D Gadolinium Oxide Nanoplates as T1 Magnetic Resonance Imaging Contrast Agents

Millions of people a year receive magnetic resonance imaging (MRI) contrast agents for the diagnosis of conditions as diverse as fatty liver disease and cancer. Gadolinium chelates, which provide preferred T₁ contrast, are the current standard but face an uncertain future due to increasing concerns about their nephrogenic toxicity as well as poor performance in high-field MRI scanners. Gadolinium-containing nanocrystals are interesting alternatives as they bypass the kidneys and can offer the possibility of both intracellular accumulation and active targeting. Nanocrystal contrast performance is notably limited, however, as their organic coatings block water from close interactions with surface Gadoliniums. Here, these steric barriers to water exchange are minimized through shape engineering of plate-like nanocrystals that possess accessible Gadoliniums at their edges. Sulfonated surface polymers promote second-sphere relaxation processes that contribute remarkable contrast even at the highest fields (r₁ = 32.6 × 10^-3 m Gd^-1 s^-1 at 9.4 T). These noncytotoxic materials release no detectable free Gadolinium even under mild acidic conditions. They preferentially accumulate in the liver of mice with a circulation half-life 50% longer than commercial agents. These features allow these T₁ MRI contrast agents to be applied for the first time to the ex vivo detection of nonalcoholic fatty liver disease in mice.

Albumin-based nanoparticles as contrast medium for MRI: vascular imaging, tissue and cell interactions, and pharmacokinetics of second-generation nanoparticles

This multidisciplinary study examined the pharmacokinetics of nanoparticles based on albumin-DTPA-gadolinium chelates, testing the hypothesis that these nanoparticles create a stronger vessel signal than conventional gadolinium-based contrast agents and exploring if they are safe for clinical use. Nanoparticles based on human serum albumin, bearing gadolinium and designed for use in magnetic resonance imaging, were used to generate magnet resonance images (MRI) of the vascular system in rats ("blood pool imaging"). At the low nanoparticle doses used for radionuclide imaging, nanoparticle-associated metals were cleared from the blood into the liver during the first 4 h after nanoparticle application. At the higher doses required for MRI, the liver became saturated and kidney and spleen acted as additional sinks for the metals, and accounted for most processing of the nanoparticles. The multiple components of the nanoparticles were cleared independently of one another. Albumin was detected in liver, spleen, and kidneys for up to 2 days after intravenous injection. Gadolinium was retained in the liver, kidneys, and spleen in significant concentrations for much longer. Gadolinium was present as significant fractions of initial dose for longer than 2 weeks after application, and gadolinium clearance was only complete after 6 weeks. Our analysis could not account quantitatively for the full dose of gadolinium that was applied, but numerous organs were found to contain gadolinium in the collagen of their connective tissues. Multiple lines of evidence indicated intracellular processing opening the DTPA chelates and leading to gadolinium long-term storage, in particular inside lysosomes. Turnover of the stored gadolinium was found to occur in soluble form in the kidneys, the liver, and the colon for up to 3 weeks after application. Gadolinium overload poses a significant hazard due to the high toxicity of free gadolinium ions. We discuss the relevance of our findings to gadolinium-deposition diseases.

Gadolinium labelled nanoliposomes as the platform for MRI theranostics: in vitro safety study in liver cells and macrophages

Gadolinium (Gd)-based contrast agents are extensively used for magnetic resonance imaging (MRI). Liposomes are potential nanocarrier-based biocompatible platforms for development of new generations of MRI diagnostics. Liposomes with Gd-complexes (Gd-lip) co-encapsulated with thrombolytic agents can serve both for imaging and treatment of various pathological states including stroke. In this study, we evaluated nanosafety of Gd-lip containing PE-DTPA chelating Gd+3 prepared by lipid film hydration method. We detected no cytotoxicity of Gd-lip in human liver cells including cancer HepG2, progenitor (non-differentiated) HepaRG, and differentiated HepaRG cells. Furthermore, no potential side effects of Gd-lip were found using a complex system including general biomarkers of toxicity, such as induction of early response genes, oxidative, heat shock and endoplasmic reticulum stress, DNA damage responses, induction of xenobiotic metabolizing enzymes, and changes in sphingolipid metabolism in differentiated HepaRG. Moreover, Gd-lip did not show pro-inflammatory effects, as assessed in an assay based on activation of inflammasome NLRP3 in a model of human macrophages, and release of eicosanoids from HepaRG cells. In conclusion, this in vitro study indicates potential in vivo safety of Gd-lip with respect to hepatotoxicity and immunopathology caused by inflammation.

Prenatal Effects of a 1,800-MHz Electromagnetic Field on Rat Livers

The use of devices, including mobile phones, generating electromagnetic fields (EMF) is widespread and is progressively increasing. It has also been shown that EMF may have detrimental effects. This is the first study to investigate the postnatal biochemical and histological effects of prenatal exposure of rat livers to 1,800-MHz EMF at different time intervals in uteroplacental life. The 3 EMF groups of rats were exposed to 1,800-MHz EMF for 6, 12, or 24 h daily for 20 days. Unexposed rats served as control group. All rats were subjected to anesthesia, and on postnatal day 60, the livers were excised, and blood was collected for histological and biochemical analyses. Malondialdehyde levels were significantly higher in the exposed groups than the unexposed controls (p < 0.05). In contrast, EMF-exposed groups had lower liver tissue glutathione levels than controls (p < 0.05). Serum Ca2+, alanine transaminase, and aspartate aminotransferase levels were higher in EMF-exposed groups than controls (p < 0.05). In addition, liver tissue total oxidant status levels were increased (p < 0.05), and liver tissue total antioxidant status levels were decreased (p < 0.05) compared to the control group. Furthermore, in the EMF groups, extensive vacuolation and degeneration of the hepatocytes in the portal area, as well as those surrounding the sinusoids, were evident. Affected hepatocytes had polygonally shaped nuclei and vacuolic cytoplasm imparting eosinophilic staining. Loss of cellular membrane integrity and invaginations, as well as picnotic nuclei, was prominent. This study has shown that intrauterine liver damage caused by 1,800-MHz EMF exposure persists into puberty in rats.

Malus micromalus Makino phenolic extract preserves hepatorenal function by regulating PKC-α signaling pathway and attenuating endoplasmic reticulum stress in lead (II) exposure mice

Lead (Pb), which widely recognized as a nonessential heavy metal and a major environmental contamination, is a growing threat to the ecosystem and human body. In the present study, Malus micromalus Makino cv. 'Dong Hong' phenolic extract (MMPE) has been used to antagonise Pb-induced erythrocyte injury, hepatic and renal dysfunction in mice. Six-week-old male Kunming mice were gavaged with PbCl₂ (20 mg/kg mouse/day) and/or MMPE (100 mg/kg mouse/day) by gavage administration for 10 days. We evaluated erythrocyte fragility, relative organ mass, biochemical parameters and histopathological changes to evaluate the protection effect of MMPE on the injury of liver and kidney in Pb-treated mice. MMPE significantly inhibited the increase of protein kinase C-α, B-cell lymphoma-2-associated X, cytochrome C and Caspase-3 protein levels and decreased calreticulin protein expression level in Pb-exposed mice. MMPE supplementation could maintain the integrity of erythrocyte membranes and ameliorate the endoplasmic reticulum stress in Pb-treated mice. It suggested MMPE as a natural nutritional supplement to alleviate Pb-induced hazardous effects in Pb-exposed humans.

The radioprotective effect of N-acetylcysteine against x-radiation-induced renal injury in rats

The purpose of this study was therefore to investigate the effects of radiotherapy on the kidney and the potential use of agents such as N-acetylcysteine (NAC) in developing a future therapeutic protocol for radiation-induced nephrotoxicity at the histopathological and biochemical levels. Our study consisted of three groups: control (oral saline solution only; group 1), irradiation (IR; group 2), and NAC + IR (group 3). The irradiation groups received a single dose of whole-body 6-Gy x-irradiation. The NAC group received 300 mg/kg by the oral route for 7 days, from 5 days before irradiation to 2 days after. All subjects were sacrificed under anesthesia 2 days after irradiation. IR increased tubular necrosis scores (TNS), MDA, and caspase-3 expression, while reducing renal tissue GSH levels. We also observed dilation in renal corpuscles and tubules. Capillary congestion was present in the intertubular spaces. NAC reduced the levels of TNS, MDA, and caspase-3 expression, but increased the levels of renal tissue GSH. ROS-scavenging antioxidants may represent a promising means of preventing renal injury in patients undergoing radiotherapy.