Nephrogenic systemic fibrosis: An epidemic of gadolinium toxicity

Oxidative stress modulating nanomaterials and their biochemical roles in nanomedicine

Many pathological conditions are predominantly associated with oxidative stress, arising from reactive oxygen species (ROS); therefore, the modulation of redox activities has been a key strategy to restore normal tissue functions. Current approaches involve establishing a favorable cellular redox environment through the administration of therapeutic drugs and redox-active nanomaterials (RANs). In particular, RANs not only provide a stable and reliable means of therapeutic delivery but also possess the capacity to finely tune various interconnected components, including radicals, enzymes, proteins, transcription factors, and metabolites. Here, we discuss the roles that engineered RANs play in a spectrum of pathological conditions, such as cancer, neurodegenerative diseases, infections, and inflammation. We visualize the dual functions of RANs as both generator and scavenger of ROS, emphasizing their profound impact on diverse cellular functions. The focus of this review is solely on inorganic redox-active nanomaterials (inorganic RANs). Additionally, we deliberate on the challenges associated with current RANs-based approaches and propose potential research directions for their future clinical translation.

Gadolinium Doping Modulates the Enzyme-like Activity and Radical-Scavenging Properties of CeO2 Nanoparticles

Their unique physicochemical properties and multi-enzymatic activity make CeO2 nanoparticles (CeO2 NPs) the most promising active component of the next generation of theranostic drugs. When doped with gadolinium ions, CeO2 NPs constitute a new type of contrast agent for magnetic resonance imaging, possessing improved biocatalytic properties and a high level of biocompatibility. The present study is focused on an in-depth analysis of the enzyme-like properties of gadolinium-doped CeO2 NPs (CeO2:Gd NPs) and their antioxidant activity against superoxide anion radicals, hydrogen peroxide, and alkylperoxyl radicals. Using an anion-exchange method, CeO2:Gd NPs (~5 nm) with various Gd-doping levels (10 mol.% or 20 mol.%) were synthesized. The radical-scavenging properties and biomimetic activities (namely SOD- and peroxidase-like activities) of CeO2:Gd NPs were assessed using a chemiluminescent method with selective chemical probes: luminol, lucigenin, and L-012 (a highly sensitive luminol analogue). In particular, gadolinium doping has been shown to enhance the radical-scavenging properties of CeO2 NPs. Unexpectedly, both bare CeO2 NPs and CeO2:Gd NPs did not exhibit SOD-like activity, acting as pro-oxidants and contributing to the generation of reactive oxygen species. Gadolinium doping caused an increase in the pro-oxidant properties of nanoscale CeO2. At the same time, CeO2:Gd NPs did not significantly inhibit the intrinsic activity of the natural enzyme superoxide dismutase, and CeO2:Gd NPs conjugated with SOD demonstrated SOD-like activity. In contrast to SOD-like properties, peroxidase-like activity was observed for both bare CeO2 NPs and CeO2:Gd NPs. This type of enzyme-like activity was found to be pH-dependent. In a neutral medium (pH = 7.4), nanoscale CeO2 acted as a prooxidant enzyme (peroxidase), while in an alkaline medium (pH = 8.6), it lost its catalytic properties; thus, it cannot be regarded as a nanozyme. Both gadolinium doping and conjugation with a natural enzyme were shown to modulate the interaction of CeO2 NPs with the key components of redox homeostasis.

Advances of nanomedicine in treatment of atherosclerosis and thrombosis

Atherosclerosis (AS) is a chronic inflammatory vascular disease. Myocardial ischemia originated from AS is the main cause of cardiovascular diseases, one of the major factors contributing to the global disease burden. AS is typically quiescent until occurrence of plaque rupture and thrombosis, leading to acute coronary syndrome and sudden death. Currently, clinical diagnostic techniques suffer from major pitfalls including lack of accuracy and specificity, which makes it rather difficult for drugs to directly target plaques to achieve therapeutic effect. Therefore, how to accurately diagnose and effectively intervene vulnerable AS plaques to achieve accurate delivery of drugs has become an urgent and evolving clinical problem. With the rapid development of nanomedicine and nanomaterials, nanotechnology has shown unique advantages in monitoring vulnerable plaques and thrombus and improving drug efficacy. Recent studies have shown that application of nanoparticle drug delivery system can booster the safety and effectiveness of drug therapy, and molecular imaging technology and nanomedicine also exhibit high clinical application potentials in disease diagnosis. Therefore, nanotechnology provides another promising avenue for diagnosis and treatment of AS and thrombosis, and has shown excellent performance in the development of targeted drug therapy and biomaterials. In this review, the research progress, challenges and prospects of nanotechnology in AS and thrombosis are discussed, expecting to provide new ideas for the prevention, diagnosis and treatment of AS and thrombosis.

Yeast Deletomics to Uncover Gadolinium Toxicity Targets and Resistance Mechanisms

Among the rare earth elements (REEs), a crucial group of metals for high-technologies. Gadolinium (Gd) is the only REE intentionally injected to human patients. The use of Gd-based contrasting agents for magnetic resonance imaging (MRI) is the primary route for Gd direct exposure and accumulation in humans. Consequently, aquatic environments are increasingly exposed to Gd due to its excretion through the urinary tract of patients following an MRI examination. The increasing number of reports mentioning Gd toxicity, notably originating from medical applications of Gd, necessitates an improved risk-benefit assessment of Gd utilizations. To go beyond toxicological studies, unravelling the mechanistic impact of Gd on humans and the ecosystem requires the use of genome-wide approaches. We used functional deletomics, a robust method relying on the screening of a knock-out mutant library of Saccharomyces cerevisiae exposed to toxic concentrations of Gd. The analysis of Gd-resistant and -sensitive mutants highlighted the cell wall, endosomes and the vacuolar compartment as cellular hotspots involved in the Gd response. Furthermore, we identified endocytosis and vesicular trafficking pathways (ESCRT) as well as sphingolipids homeostasis as playing pivotal roles mediating Gd toxicity. Finally, tens of yeast genes with human orthologs linked to renal dysfunction were identified as Gd-responsive. Therefore, the molecular and cellular pathways involved in Gd toxicity and detoxification uncovered in this study underline the pleotropic consequences of the increasing exposure to this strategic metal.

Nephrogenic systemic fibrosis-related pulmonary restriction: An under-appreciated manifestation potentially reversible with imatinib therapy

Nephrogenic systemic fibrosis typically occurs in patients with renal failure and is strongly associated with gadolinium exposure through stimulation of macrophage-activated fibrosis. Patients present with prominent fibrosis of the skin and internal organs. Quality of life is significantly diminished due to impairment from restrictive mobility of large and small joint contractures, pain, and ensuing psychological stress. Nephrogenic systemic fibrosis can be severe and life-threatening. Nephrogenic systemic fibrosis patients reliant on hemodialysis with cutaneous symptoms, defined as hyperpigmentation, hardening, and tethering of skin on the extremities, experience rates of mortality as high as 48%. Physician awareness and preventive strategies coincided with a reduction in the incidence of nephrogenic systemic fibrosis. Several treatments, of which physical therapy may be a key adjuvant, have been used to treat nephrogenic systemic fibrosis, with variable and inconsistent results, lacking wide consensus. Improvement of renal function may improve nephrogenic systemic fibrosis, with some patients demonstrating stabilization or improvement after renal transplantation or resolution of acute renal failure. Imatinib, a tyrosine kinase inhibitor, demonstrates antifibrotic effects in the skin and recently was used to successfully treat nephrogenic systemic fibrosis. We report a case of severe nephrogenic systemic fibrosis with extensive skin fibrosis causing extrapulmonary restriction who demonstrated improved lung function following treatment with imatinib.

Molecular imaging nanoprobes for theranostic applications

As a non-invasive imaging monitoring method, molecular imaging can provide the location and expression level of disease signature biomolecules in vivo, leading to early diagnosis of relevant diseases, improved treatment strategies, and accurate assessment of treating efficacy. In recent years, a variety of nanosized imaging probes have been developed and intensively investigated in fundamental/translational research and clinical practice. Meanwhile, as an interdisciplinary discipline, this field combines many subjects of chemistry, medicine, biology, radiology, and material science, etc. The successful molecular imaging not only requires advanced imaging equipment, but also the synthesis of efficient imaging probes. However, limited summary has been reported for recent advances of nanoprobes. In this paper, we summarized the recent progress of three common and main types of nanosized molecular imaging probes, including ultrasound (US) imaging nanoprobes, magnetic resonance imaging (MRI) nanoprobes, and computed tomography (CT) imaging nanoprobes. The applications of molecular imaging nanoprobes were discussed in details. Finally, we provided an outlook on the development of next generation molecular imaging nanoprobes.

Cerium Oxide Nanoparticles with Entrapped Gadolinium for High T 1 Relaxivity and ROS-Scavenging Purposes

Gadolinium chelates are employed worldwide today as clinical contrast agents for magnetic resonance imaging. Until now, the commonly used linear contrast agents based on the rare-earth element gadolinium have been considered safe and well-tolerated. Recently, concerns regarding this type of contrast agent have been reported, which is why there is an urgent need to develop the next generation of stable contrast agents with enhanced spin-lattice relaxation, as measured by improved T ₁ relaxivity at lower doses. Here, we show that by the integration of gadolinium ions in cerium oxide nanoparticles, a stable crystalline 5 nm sized nanoparticulate system with a homogeneous gadolinium ion distribution is obtained. These cerium oxide nanoparticles with entrapped gadolinium deliver strong T ₁ relaxivity per gadolinium ion (T ₁ relaxivity, r ₁ = 12.0 mM^-1 s^-1) with the potential to act as scavengers of reactive oxygen species (ROS). The presence of Ce³⁺ sites and oxygen vacancies at the surface plays a critical role in providing the antioxidant properties. The characterization of radial distribution of Ce³⁺ and Ce⁴⁺ oxidation states indicated a higher concentration of Ce³⁺ at the nanoparticle surfaces. Additionally, we investigated the ROS-scavenging capabilities of pure gadolinium-containing cerium oxide nanoparticles by bioluminescent imaging in vivo, where inhibitory effects on ROS activity are shown.

Synthesis of Ce/Gd@HA/PLGA Scaffolds Contributing to Bone Repair and MRI Enhancement

It is important for future clinical applications to design and synthesize multipurpose scaffolding materials for bone tissue engineering with high osteogenic induction and MRI capability. In the present study, we synthesized Ce/Gd@HA by co-doping Ce3+ and Gd3+ into hydroxyapatite (HA) using a hydrothermal synthesis method, and then Ce/Gd@HA composites were synthesized by combining Ce/Gd@HA nanoparticles with polylactic-co-glycolic acid (PLGA) to investigate whether implanted Ce/Gd@HA/PLGA composites could promote osteoblast viability, leading to tibia repair of the rats and enhance MRI. The measurement results contain X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and environmental scanning electron microscopy (ESEM) showing that HA doped with Ce3+ and Gd3+ was still a hexagonal crystal with high crystallinity. The synthesized Ce/Gd@HA/PLGA composites have a structure and obvious magnetic resonance imaging (MRI) capability. The in vitro experimental results indicated that Ce/Gd@HA/PLGA composites significantly promoted the performance of MC3T3-E1 cells, containing proliferation, adhesion, and osteogenic differentiation capacities. These include the improvement of alkaline phosphatase activity, enhancement of mineral deposition, and upregulation of OCN and COL-1 gene expression. The in vivo experimental results demonstrated that the Ce/Gd@HA/PLGA composites significantly improved the healing rate of rat bone defects. The MRI images indicated that the Ga-doped composites were observed in the MRI T1 sequence in rats. The aforementioned results suggested that Ce/Gd@HA/PLGA composites not only effectively promoted bone formation but also enhanced MRI capability. The composites synthesized in this study have great potential in bone regeneration with an extensive application in bone tissue engineering.

Nanoparticles for Detection and Treatment of Peripheral Arterial Disease

Peripheral arterial disease (PAD) is defined as a slow, progressive disorder of the lower extremity arterial vessels characterized by chronic narrowing that often results in occlusion and is associated with loss of functional capacity. Although the PAD occurrence rate is increasing in the elderly population, outcomes with current treatment strategies are suboptimal. Hence, there is an urgent need to develop new technologies that overcome limitations of traditional modalities for PAD detection and therapy. In this Review, the application of nanotechnology as a tool that bridges the gap in PAD diagnosis and therapy is in focus. Several materials including synthetic, natural, biodegradable, and biocompatible materials are used to develop nanoparticles for PAD diagnostic and/or therapeutic applications. Moreover, various recent research approaches are being explored to diagnose PAD through multimodality imaging with different nanoplatforms. Further efforts include targeted delivery of various therapeutic agents using nanostructures as carriers to treat PAD. Last, but not least, despite being a fairly new field, researchers are exploring the use of nanotheranostics for PAD detection and therapy.

Cerium oxide nanoparticles with antioxidant capabilities and gadolinium integration for MRI contrast enhancement

The chelating gadolinium-complex is routinely used as magnetic resonance imaging (MRI) -contrast enhancer. However, several safety issues have recently been reported by FDA and PRAC. There is an urgent need for the next generation of safer MRI-contrast enhancers, with improved local contrast and targeting capabilities. Cerium oxide nanoparticles (CeNPs) are designed with fractions of up to 50% gadolinium to utilize the superior MRI-contrast properties of gadolinium. CeNPs are well-tolerated in vivo and have redox properties making them suitable for biomedical applications, for example scavenging purposes on the tissue- and cellular level and during tumor treatment to reduce in vivo inflammatory processes. Our near edge X-ray absorption fine structure (NEXAFS) studies show that implementation of gadolinium changes the initial co-existence of oxidation states Ce3+ and Ce4+ of cerium, thereby affecting the scavenging properties of the nanoparticles. Based on ab initio electronic structure calculations, we describe the most prominent spectral features for the respective oxidation states. The as-prepared gadolinium-implemented CeNPs are 3-5 nm in size, have r1-relaxivities between 7-13 mM-1 s-1 and show clear antioxidative properties, all of which means they are promising theranostic agents for use in future biomedical applications.

Gadolinium accumulation after contrast-enhanced magnetic resonance imaging: Which implications in patients with Crohn's disease?

Crohn's disease (CD) is a chronic inflammatory condition of the bowel, characterized by an alternation of remission and relapse phases, leading to a progressive intestinal damage with loss of function. Magnetic resonance enterography has been widely used in the past for the evaluation of fistulizing disease, but its use increased over time, being considered helpful in different moments of disease course. Intravenous injection of Gadolinium-based contrast agents has been demonstrated to be crucial to assess mucosal inflammation, transmural involvement, and extraintestinal disease. Recently, Gadolinium accumulation in human tissues has been increasingly reported, although clinical implications of this event are still unclear. In the present paper, we review the main evidence on the topic, focusing on the potential implications for gastroenterological practice.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.

A colloidally stable water dispersion of Ni nanowires as an efficient T2-MRI contrast agent

A colloidally stable dispersion of anisotropic Ni nanowires in water has been achieved showing good performance as a T₂-contrast agent in MRI.

Development of silica-encapsulated silver nanoparticles as contrast agents intended for dual-energy mammography

OBJECTIVE

Dual-energy (DE) mammography has recently entered the clinic. Previous theoretical and phantom studies demonstrated that silver provides greater contrast than iodine for this technique. Our objective was to characterize and evaluate in vivo a prototype silver contrast agent ultimately intended for DE mammography.

METHODS

The prototype silver contrast agent was synthesized using a three-step process: synthesis of a silver core, silica encapsulation and PEG coating. The nanoparticles were then injected into mice to determine their accumulation in various organs, blood half-life and dual-energy contrast. All animal procedures were approved by the institutional animal care and use committee.

RESULTS

The final diameter of the nanoparticles was measured to be 102 (±9) nm. The particles were removed from the vascular circulation with a half-life of 15 min, and accumulated in macrophage-rich organs such as the liver, spleen and lymph nodes. Dual-energy subtraction techniques increased the signal difference-to-noise ratio of the particles by as much as a factor of 15.2 compared to the single-energy images. These nanoparticles produced no adverse effects in mice.

CONCLUSION

Silver nanoparticles are an effective contrast agent for dual-energy x-ray imaging. With further design improvements, silver nanoparticles may prove valuable in breast cancer screening and diagnosis.

KEY POINTS

• Silver has potential as a contrast agent for DE mammography. • Silica-coated silver nanoparticles are biocompatible and suited for in vivo use. • Silver nanoparticles produce strong contrast in vivo using DE mammography imaging systems.

Strategies for the preparation of bifunctional gadolinium(III) chelators

The development of gadolinium chelators that can be easily and readily linked to various substrates is of primary importance for the development high relaxation efficiency and/or targeted magnetic resonance imaging (MRI) contrast agents. Over the last 25 years a large number of bifunctional chelators have been prepared. For the most part, these compounds are based on ligands that are already used in clinically approved contrast agents. More recently, new bifunctional chelators have been reported based on complexes that show a more potent relaxation effect, faster complexation kinetics and in some cases simpler synthetic procedures. This review provides an overview of the synthetic strategies used for the preparation of bifunctional chelators for MRI applications.

Zinc transmetallation and gadolinium retention after MR imaging: case report

A patient with chronic zinc poisoning from denture cream retained gadolinium after a magnetic resonance imaging procedure, likely due to transmetallation. During chelation therapy, high levels of gadolinium in excreted urine (up to 89 μg/d, 29 days after gadolinium administration) were present, indicating that gadolinium had been retained. Almost 2½ years after gadolinium exposure, a 24-hour urine collection indicated that the gadolinium level remained in the elevated range (0.6 μg/d). This single case report suggests that patients with elevated zinc exposure may be at increased risk of gadolinium retention.

The accuracy of multidetector computerized tomography for evaluating tumor thrombus in patients with renal cell carcinoma

PURPOSE

New advances in computerized tomography, including multidetector computerized tomography with 3-dimensional reformatting has recently called into question the absolute need for magnetic resonance imaging for evaluating renal cell carcinoma with suspected venous involvement. We assessed the accuracy of multidetector computerized tomography for predicting tumor thrombus and the level of venous involvement in patients with renal cell carcinoma.

MATERIALS AND METHODS

We retrospectively reviewed clinical and pathological features in 41 patients with renal cell carcinoma who underwent staging multidetector computerized tomography before surgery. Multidetector computerized tomography findings regarding the presence and level of tumor thrombus were compared to findings at surgery and at final pathological evaluation. All multidetector computerized tomography studies were read by a single radiologist (EKF) before surgery.

RESULTS

When excluding patients with segmental venous involvement only, the concordance rate between multidetector computerized tomography and pathological findings was 84%. Multidetector computerized tomography accurately predicted the level of tumor thrombus in 26 of 27 patients (96%). Four cases of negative multidetector computerized tomography findings were up staged to renal vein involvement based on pathological findings. All 4 patients had early distal thrombi that did not change operative management.

CONCLUSIONS

Multidetector computerized tomography with 3-dimensional mapping is an effective imaging modality for accurately characterizing the level of venous thrombus in patients with renal cell carcinoma. This modality effectively identified patients with clinically significant venous thrombus. Patients with renal cell carcinoma in whom multidetector computerized tomography fails to detect tumor thrombus are unlikely to have a tumor thrombus found at surgery that would change the surgical approach.

Non-crystalline and crystalline rheumatic disorders in chronic kidney disease

Rheumatic syndromes are cause for morbidity in patients with end-stage renal disease. Recent advances in understanding the role of tissue remodeling have provided insight into the pathogenic mechanisms responsible for some of these manifestations. Here, we survey recent and clinically relevant advances in translational research that impact our understanding of rheumatic syndromes seen in patients with significant renal disease. The management of acute and chronic crystalline arthropathies in chronic kidney disease and hemodialysis patients is discussed.