Assessing teratogenic risks of gadolinium in freshwater environments: Implications for environmental health

Gadolinium (Gd) is among the rare earth elements extensively utilized in both industrial and medical applications. The latter application appears to contribute to the rise in Gd levels in aquatic ecosystems, as it is excreted via urine from patients undergoing MRI scans and often not captured by wastewater treatment systems. The potential environmental and biological hazards posed by gadolinium exposure are still under investigation. This study aimed to assess the teratogenic risk posed by a gadolinium chelate on the freshwater cnidarian Hydra vulgaris. The experimental design evaluated the impact of pure Gadodiamide (25 μg/l, 50 μg/l, 100 μg/l, 500 μg/l) and its commercial counterpart compound (Omniscan®; 100 μg/l, 500 μg/l, 782.7 mg/l) at varying concentrations using the Teratogenic Risk Index (TRI). Here we showed a moderate risk (Class III of TRI) following exposure to both tested formulations at concentrations ≥ 100 μg/l. Given the potential for similar concentrations in aquatic environments, particularly near wastewater discharge points, a teratogenic risk assessment using the Hydra regeneration assay was conducted on environmental samples collected from three rivers (Tiber, Almone, and Sacco) in Central Italy. Additionally, chemical analysis of field samples was performed using ICP-MS. Analysis of freshwater samples revealed low Gd concentrations (≤ 0.1 μg/l), despite localized increases near domestic and/or industrial wastewater discharge sites. Although teratogenic risk in environmental samples ranged from high (Class IV of TRI) to negligible (Class I of TRI), the low Gd concentrations, particularly when compared to higher levels of other contaminants like arsenic and heavy metals, preclude establishing a direct cause-effect relationship between Gd and observed teratogenic risks in environmental samples. Nevertheless, the teratogenic risks observed in laboratory tests warrant further investigation.

Gadolinium-based contrast agents aggravate mechanical and thermal hyperalgesia in a nitroglycerine-induced migraine model in male mice

In the diagnosis of migraine, which is a neurovascular disease, gadolinium-based contrast agents (GBCAs) are used to rule out more serious conditions. On the other hand, it remains unclear as a scientific gap whether GBCAs may trigger migraine-related pain. The aim of this study was to investigate the effect of GBCAs on mechanical and thermal pain behaviour in a nitroglycerin (NTG)-induced migraine model in mice. NTG (10 mg/kg) was administered intraperitoneally to adult (6-8weeks old) BALB/c mice 2 h before behavioral tests 5 times every other day on days 1st, 3rd, 5th and 9th to induce migraine model (N = 50). As GBCAs, gadobenate dimeglumine (linear-ionic), Gadodiamide (linear-nonionic), and gadobutrol (macrocyclic-nonionic) were delivered intravenously through the tail vein of mice for 5 days on test days. Mechanical pain threshold (plantar and facial withdrawal threshold) was evaluated by plantar von Frey and periorbital von Frey tests on days 1st, 5th, and 9th, and thermal pain threshold (latency) was evaluated by hot plate and cold plate tests on days 3rd and 7th. There was a statistically significant increase in mechanical and thermal hyperalgesia in NTG administered groups compared to the control group. Gadodiamide, gadobutrol and gadobenate dimeglumine administration significantly decreased latency, paw and facial withdrawal threshold (0.18 ± 0.05, 0.17 ± 0.07, 0.16 ± 0.09; 9th day values respectively) compared to NTG group (0.27 ± 0.05). The results of this in vivo study show that GBCAs produce effects that may trigger migraine attacks in migraine. It is recommended that these effects be further investigated and supported by further clinical studies.

Analysis of the Gadolinium retention in the Experimental Autoimmune Encephalomyelitis (EAE) murine model of Multiple Sclerosis

OBJECTIVES

The aim of this study is to quantitatively investigate, at the preclinical level, the extent of Gd retention in the CNS, and peripheral organs, of immune-mediated murine models (Experimental Autoimmune Encephalomyelitis -EAE) of Multiple Sclerosis, compared to control animals, upon the injection of gadodiamide. The influence of the Gadolinium Based Contrast Agent administration timing during the course of EAE development is also monitored.

METHODS

EAE mice were injected with three doses (1.2 mmol/kg each) of gadodiamide at three different time points during the EAE development and sacrificed after 21 or 39 days. Organs were collected and the amount of Gd was quantified through Inductively Coupled Plasma-Mass Spectrometry. Transmission electron microscopy (TEM) and MRI techniques were applied to add spatial and qualitative information to the obtained results.

RESULTS

In the spinal cord of EAE group, 21 days after gadodiamide administration, a significantly higher accumulation of Gd occurred. Conversely, in the encephalon, a lower amount of Gd retention was reached, even if differences emerged between EAE and controls mice. After 39 days, the amounts of retained Gd markedly decreased. TEM validated the presence of Gd in CNS. MRI of the encephalon at 7.1T did not highlight any hyper intense region.

CONCLUSION

In the spinal cord of EAE mice, which is the mostly damaged region in this specific animal model, a preferential but transient accumulation of Gd is observed. In the encephalon, the Gd retention could be mostly related to inflammation occurring upon immunization rather than to demyelination.

Within-network brain connectivity in Crohn's disease patients with gadolinium deposition in the cerebellum

PURPOSE

Patients with Crohn's disease (CD) undergo multiple gadolinium-based contrast agent injections across their lifespan to enhance signal intensity of the intestinal wall and differentiate active from quiescent inflammatory disease. Thus, CD patients are prone to gadolinium accumulation in the brain and represent a non-neurological population to explore gadolinium-related brain toxicity. Possible effects are expected to be greater on the cerebellar network due to the high propensity of the dentate nucleus to accumulate gadolinium. Herein, we provide a whole-brain network analysis of resting-state fMRI dynamics in long-term quiescent CD patients with normal renal function and MRI evidence of gadolinium deposition in the brain.

METHODS

Fifteen patients with CD and 16 healthy age- and gender-matched controls were enrolled in this study. Relevant resting-state networks (RSNs) were identified using independent component analysis (ICA) from functional magnetic resonance imaging data. An unpaired two-sample t test (with age and sex as nuisance variables) was used to investigate between different RSNs. Clusters were determined by using threshold-free cluster enhancement and a family-wise error corrected cluster significance threshold of p < 0.05.

RESULTS

Patients showed significantly decreased resting-state functional connectivity (p < 0.05, FWE corrected) of several regions of the right frontoparietal (FPR) and the dorsal attention (DAN) RSNs. No differences between the two groups were found in the functional connectivity maps of all the other RSNs, including the cerebellar network.

CONCLUSION

Our findings suggest a non-significant impact of gadolinium deposition on within-network cerebellar functional connectivity of long-term quiescent CD patients.

A new type of gadodiamide-conjugated amphiphilic chitosan nanoparticle and its use for MR imaging with significantly enhanced contrastability

Magnetic resonance imaging (MRI) has been one of the most frequently-used diagnostic tools with high dimensional precision and positioning accuracy in clinical practices. To achieve contrast enhancement, utilization of high-efficient MR imaging contrast agents becomes a prime consideration and is indispensably reinforced the diagnosis precision, especially for the emerging precision medicine. Gadolinium (Gd)-based complexes has been widely used in current clinical MRI operations, however, numerous side effects were reported and highlighted in clinic. Those drawbacks render specific unmet needs to be clinically and technically improved with a new version of Gd-based compound. Here we report a newly-synthesized amphiphilic Gadodiamide-conjugated carboxymethyl-hexanoyl chitosan (termed as CHC-Gd) hybrid. The gadodiamide was selected is due to its smallest molecular size among other Gd-based complexes reported in literature, which assumed to give least influence on the resulting physicochemical properties such as colloidal stability, nanostructural evolution, and cytocompability, particularly self-assembly capability, of the resulting hybrid upon practical uses. Experimental outcomes showed a successful synthesis of the CHC-Gd hybrid using a one-pot synthesis protocol, where the gadodiamide complexes were covalently attached to the carboxyl groups along the CHC backbone. Self-assembly behavior can be observed to form a sphere-like nanoparticle of 100-200 nm in size as of amphiphilic native CHC macromolecule. Experimental outcomes indicated a largely improved cytocompatibility of the hybrid, compared with free Gd, suggesting the Gd⁺³ ions were well stabilized in the CHC nanostructure. Excellent contrastability in-vitro and in particular in vivo were measured, where for in-vivo test, a 10-40-folded reduction in dosage, compared with clinical Gd dose, was used and demonstrated a comparative-to-better imaging resolution and brightness. Therefore, from this preliminary investigation, a potential translation to clinical practice through the use of newly-synthesized amphiphilic CHC-Gd hybrid appears to be relatively promising.

Spatially resolved quantification of gadolinium deposited in the brain of a patient treated with gadolinium-based contrast agents

Due to its paramagnetic properties resulting from seven unpaired f-electrons, Gd is frequently applied in magnetic resonance imaging examinations. Due to the acute toxicity of free Gd³⁺, ligand ions based on polyaminocarboxylic acids are used to create thermodynamically stable linear or macrocyclic complexes. The highly water soluble Gd-based contrast agents (GBCAs) are known to be excreted fast and unmetabolized, mostly via the kidneys. Nevertheless, recent studies showed that Gd traces persists not only in animal but also in human brain. Aim of this study was the development and application of an analytical method for the spatially resolved quantification of gadolinium traces in human brain thin sections of a patient treated with GBCAs. For this retrospective study different human brain regions were selected to analyze the distribution of gadolinium. An additional patient served as control sample, as no GBCA was administered. Deep-frozen brain thin sections were analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and matrix-matched gelatin standards were prepared to quantify the gadolinium deposits via an external calibration. LA-ICP-MS analyses with high spatial resolution showed gadolinium deposits in different brain regions with highest concentrations above 800ngg^-1 more than two years after the last application of a GBCA. An excellent limit of quantification of 7ngg^-1, which is far below the limits of detection of MRI methods, could be achieved. The found concentrations confirm recent reports on gadolinium depositions in human brain, which were obtained without high spatial resolution. LA-ICP-MS provides limits of quantification, which are well suited to detect ultratrace amounts of gadolinium in human brain. Therefore, it provides valuable information on the distribution of gadolinium traces in the human brain even after single administration of GBCAs.

Comparison of nephrotoxicity between two gadolinium-contrasts, gadodiamide and gadopentetate in patients with mildly diminished renal failure

Although gadolinium (Gd)-based contrast media have been found to be nephrotoxic, their nephrotoxicity, and the dependence of nephrotoxicity on chelate types, have not been assessed in patients with normal or mildly diminished renal failure. This prospective, randomized study compared the nephrotoxicity of low doses of the nonionic Gd-based contrast medium gadodiamide (Omniscan®) and the ionic Gd-based contrast medium gadopentetate (Magnevist®) in patients with serum creatinine < 1.6 mg/dL. Patients aged 20 to 80 years, weighing 45 to 70 kg and with normal or < 1.6 mg/dL Serum-creatinine in the 3 months prior to undergoing magnetic resonance imaging (MRI) of brain, were enrolled. Patients were randomized to receive 0.1 mol/kg gadodiamide or gadopentetate. Serum-creatinine, serum cystatin-C, estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease (MDRD) formula, and estimated creatinine clearance rate (eCCr) using the Cockcroft-Gault formula were measured just before and 16-80 hr after MRI. Groups were compared statistically by Mann-Whitney U-tests and Wilcoxon signed-rank tests. There were no significant differences in clinical characteristics between the gadodiamide (n = 43) and gadopentetate (n = 59) groups. Serum-creatinine, eGFR and eCCr before and 16-80 hr after MRI did not differ significantly within either group or between the two groups. Serum cystatin-C was significantly higher 16-80 hr after than before MRI only in the gadodiamide group (0.79 ± 0.21 vs. 0.74 ± 0.14 mg/L, p = 0.028). The ionic contrast medium, gadopentetate, did not affect renal function during MRI, whereas the nonionic contrast medium, gadodiamide, affected renal function transiently.

The Impact of Excess Ligand on the Retention of Nonionic, Linear Gadolinium-Based Contrast Agents in Patients With Various Levels of Renal Dysfunction: A Review and Simulation Analysis

The role of gadolinium (Gd)-based contrast agents (GBCAs) in the pathophysiology of nephrogenic systemic fibrosis (NSF) is now uncontested. Although the definitive mechanism has not been established, the association with weaker GBCA ligands and with reduced renal clearance supports a hypothesis that Gd release from the GBCAs is a key process in precipitating the disease. Prevention strategies often include the use of more stable GBCA ligands in patients with reduced kidney function, but animal models and some clinical data suggest that better patient outcomes can be achieved when excess ligand is administered with weaker GBCAs; this is particularly significant for OptiMARK, which contains a nonionic, linear ligand similar to gadodiamide, the active ingredient in Omniscan, but contains twice the amount of excess ligand. Here we review evidence regarding the use of OptiMARK over Omniscan for prevention of NSF and perform a pharmacokinetic-based simulation to determine if the presented evidence is consistent with the established kinetics of GBCAs and Gd.

Diffusion characteristics of human annulus fibrosus-a study documenting the dependence of annulus fibrosus on end plate for diffusion

BACKGROUND

Intervertebral disc being avascular depends on nutrition from either the end plate or the annulus fibrosus (AF). The role of the end plate on disc diffusion had been extensively studied. However, diffusion of human AF remains poorly understood because of the lack of reliable techniques to study AF in vivo and non-invasively. The present study for the first time evaluates the 24-hour diffusion characteristics of AF in radial, axial, and circumferential directions.

PURPOSE

The study aimed to document the 24-hour diffusion characteristics of human AF.

STUDY DESIGN

This is an in vivo human serial post-contrast magnetic resonance image study.

METHODS

Twenty-five discs from five healthy volunteers (age <20 years) were studied. Diffusion over 24 hours following intravenous gadodiamide injection (0.3 mmol/kg) was studied at 10 minutes, and at 2, 4, 6, 12, and 24 hours. Axial images of the cranial, middle, and caudal zones of the discs were obtained. The vertebral body and end plate signal intensities were measured in sagittal sections. Thirty-nine regions of interest (24 in AF, 15 in nucleus pulposus) in each disc were analyzed. The peak enhancement percentage (EPmax) and the time to attain EPmax (Tmax) were calculated. Radial (outer vs. inner AF), axial (cranial vs. caudal vs. middle zone), and circumferential diffusions were analyzed. (The study received research grant from AOSpine India for US$6,000).

RESULTS

Annulus fibrosus showed a biphasic pattern of diffusion with a characteristic "double peak." Early peak was seen at 10 minutes (coinciding with Tmax of the vertebral body) and delayed peak was seen at 6 hours (coinciding with Tmax of the nucleus pulposus), and characteristically noted after Tmax of the end plate (2 hours). The inner AF showed significant regional differences both at the early and delayed peaks, but the outer AF had no regional differences in the early peak. In axial direction, both outer and inner AF showed maximum enhancement percentage in the middle zone, followed by the caudal zone and least in the cranial zone.

CONCLUSIONS

Annulus fibrosus characteristically showed a "double-peak" pattern of diffusion. Both the peaks had different characteristics, confirming two different sources of nutrition. The initial peak was contributed by periannular vascularity and the delayed one via the end plate from the vertebral body. The fact that even AF depends on the end plate for nutrition helps us better understand the complex nutritional pathways of intervertebral discs.

Interference of gadolinium-based contrast agents on colorimetric calcium assays

OBJECTIVE

The aim of this study was to evaluate the potential interference of five gadolinium-based contrast agents (GBCAs), gadodiamide (Omniscan®), gadobenate dimeglumine (Multihance®), gadoxetate disodium (Primovist®), gadobutrol (Gadovist®), and gadoteridol (Prohance®), on three clinical laboratory widely used colorimetric calcium assays including the newly developed 5-nitro-5'methyl-l,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (NM-BAPTA) method.

METHODS

Plasma was collected from healthy volunteers aged 23-52, and spiked with varying concentrations of the five GBCAs. Calcium determinations were performed in duplicates using the o-cresolphthalein complexone (OCP), arsenazo-III dye, and NM-BAPTA methods on the Roche Integra 400, Abbott Architect 16000, and Roche Modular P automated analyzers respectively.

RESULTS

Gadobenate dimeglumine, gadobutrol, and gadoteridol did not interfere with any of the assays. There was a small positive bias (8%, p<0.01) at a very high concentration (25mmol/L) of gadoxetate disodium when calcium was assayed using the arsenazo-III method. Gadodiamide at a very high concentration (50mmol/L) induced a significant positive bias (16%, p<0.01) on calcium when measured using the NM-BAPTA method; however a much larger bias (90%, p≪0.01) was observed when calcium was measured using the arsenazo-III method. Significant interferences in calcium measurements using the OCP method began at gadodiamide concentrations as low as 0.5mmol/L (-9%, p<0.01). This negative bias was more pronounced at higher gadodiamide concentrations.

CONCLUSIONS

Of all 5 GBCAs tested, only gadodiamide showed significant interference on the OCP calcium assay at clinically relevant concentrations. The NM-BAPTA assay showed minimum interference with the five GBCAs and demonstrated equal or better performance than the OCP and the arsenazo-III methods in terms of interference with GBCAs.