Can the Risk of Gadolinium be Extrapolated to Lanthanum?

Doping gadolinium versus lanthanum into hydroxyapatite particles for better biocompatibility in bone marrow stem cells

Lanthanide ions (Ln³⁺) doped hydroxyapatite (HAP) particles are well established in biomedical areas. Although Ln elements are closely located in the periodic table and have plenty of similar characteristics, the minor differences in the effective ionic radii could cause alterations in the physicochemical and biological properties of HAP substitutes. The present study synthesized lanthanum-(La-) and gadolinium-(Gd-) doped HAP particles (La-HAP and Gd-HAP). And the effects of two types of particles on bone marrow stem cells (BMSCs) viability were also measured and compared in vitro. The results indicated that the Gd-HAP adsorbed more serum proteins from culture media and inhibited the new layer of apatite formation on its surface when comparing to La-HAP with a similar crystalline structure, particle size, and Zeta potential. These surface modifications can significantly reduce the cell adhesion of Gd-HAP, simultaneously decreasing the Gd-HAP particle uptake efficiency. Moreover, the cell viability of Gd-HAP remained higher than that of La-HAP in culture periods. We concluded that a slight variation in the effective ionic radii between Gd³⁺ and La³⁺ could alter the adsorption of serum proteins on the particles' surface, modulating subsequent cellular responses. The present work provides an interesting view that Gd-HAP is endowed with better cellular biocompatibility than La-HAP.

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.

Exposure to lanthanum compound diminishes LPS-induced inflammation-associated gene expression: involvements of PKC and NF-kappaB signaling pathways

Lanthanum chloride, a rare earth compound, possesses antibacterial and cellular immunity regulating properties. However, the underlying molecular mechanisms remain largely unknown. In this study, we examined the effects of lanthanum chloride on the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha), the expression of inducible NO synthase (iNOS) and TNF-alpha in RAW 264.7 cells, a mouse macrophage cell line. We found that the LPS-elicited excessive production of NO and TNF-alpha in RAW 264.7 cells was inhibited significantly in the presence of lanthanum chloride, and the attenuation of iNOS and TNF-alpha occurred at mRNA level. Furthermore, the possible signaling components affected by lanthanum chloride in the pathway that lead to LPS-induced iNOS and TNF-alpha expression were explored. The results indicated the involvements of PKC/Ca(2+) and NF-kappaB in the attenuation of NO and pro-inflammatory cytokine production by lanthanum chloride. Our observations suggest a possible therapeutic application of this agent for treating inflammatory diseases.

Clinical pharmacokinetics of the phosphate binder lanthanum carbonate

Lanthanum carbonate is considered to be the most potent of a new generation of noncalcium phosphate binders used to treat hyperphosphataemia in chronic kidney disease (CKD), a condition associated with progressive bone and cardiovascular pathology and a markedly elevated risk of death. Its phosphate-binding action involves ionic binding and precipitation of insoluble complexes within the lumen of the intestine, thereby preventing absorption of dietary phosphate. While pharmacokinetics have little relevance to the efficacy of lanthanum carbonate, they are of fundamental importance when it comes to evaluating safety. When administered as lanthanum carbonate, the oral bioavailability of lanthanum is low (approximately 0.001%). The small absorbed fraction is excreted predominantly in bile, with less than 2% being eliminated by the kidneys. Predictably, therefore, plasma exposure and pharmacokinetics have been shown to be similar in healthy human volunteers and CKD stage 5 patients. With almost complete plasma protein binding, free lanthanum concentrations in patients at steady state are <3 pg/mL. These properties greatly reduce systemic exposure, tissue deposition and the potential for adverse effects. While lanthanum has a variety of calcium-like actions in vitro, there is little or no evidence that these occur in vivo. This paradox is explained by the very low concentrations of circulating free lanthanum ions, which are many orders of magnitude lower than reported effect concentrations in vitro. Safety pharmacology and toxicology evaluations have failed to reveal any significant calcium-like actions in vivo, despite inclusion of high intravenous doses in some cases.Lanthanum carbonate has a low propensity to cause systemic drug interactions due to its poor absorption. However, the higher concentrations present in the gastrointestinal tract can form chelates with some drugs, such as fluoroquinolones, and reduce their absorption. The improved understanding of the pharmacokinetics of lanthanum that has emerged in recent years has helped to explain why the myriad of calcium-like effects described in vitro for lanthanum have little if any relevance in vivo. The pharmacokinetic investigations of lanthanum carbonate formed an important part of the stringent premarketing safety assessment process and have been influential in reassuring both regulators and physicians that the agent can be used safely and effectively in this vulnerable dialysis population.

MRI safety update 2008: part 1, MRI contrast agents and nephrogenic systemic fibrosis

OBJECTIVE

This article is the first part of a two-part series on MRI safety. In this article, part 1, the topic of MRI contrast agents and nephrogenic systemic fibrosis (NSF) is addressed.

CONCLUSION

To prevent incidents and accidents associated with MRI, it is necessary to regularly revisit the safety topics that directly impact patient management especially with respect to the subjects that are "new" (e.g., MRI contrast agents and NSF), those that should be reassessed because of recent changes, topics that deserve emphasis because of controversy or confusion, and information that should be considered in light of new findings.

Possible involvement of gadolinium chelates in the pathophysiology of nephrogenic systemic fibrosis: a critical review

Nephrogenic systemic fibrosis (NSF) is a recently described, highly debilitating scleroderma-like disease occurring in patients with severe or end-stage renal failure. NSF is characterized by cutaneous papules and coalescing plaques ("peau d'orange" appearance) and a wooden consistency. It may ultimately cause disabling contractures of several joints, thus making many patients wheelchair-dependent. NSF has been associated to prior administration of gadolinium chelates (GC) used as contrast agents for magnetic resonance imaging. The best available treatment option at the present time is renal transplantation. The mechanism of NSF has not been fully elucidated. Several hypotheses have been proposed so far and are critically discussed in the present review article. Gadolinium has been found in skin biopsy samples of patients. The most widely accepted hypothesis is related to dechelation of less stable GC, progressively releasing free Gd3+ which may subsequently lead to the attraction of CD34+, CD45+, pro-collagen+ circulating fibrocytes via the release of chemokines, thereby inducing systemic fibrosing disorders. Pre-existing renal failure may facilitate the process by delaying the excretion of GC. A complex interplay between gadolinium and co-factors (pro-inflammatory status, vascular injury, high dose of erythropoietin, high levels of calcium, phosphorus, etc.) may occur in patients with impaired renal function. This and other hypotheses remain to be investigated, as well as the role and independence of co-factors.