Effects of Ce3+ on conformation and activity of superoxide dismutase

A review of research on the impact of E171/TiO2 NPs on the digestive tract

Nanotechnology utilises particles of between 1 and 100 nm in size. In recent years, it has enjoyed widespread application in a variety of areas. However, this has also raised increasing concerns regarding the effects that the use of nanoparticles may have on human health. The nanoparticles of titanium dioxide (TiO₂ NPs) are among the most promising nanomaterials and have already found wide use in cosmetics, medicine and, the food industry. A nano-sized (diameter < 100 nm) fraction of TiO₂ is present, at a certain percentage, in the E171 ( in the EU) pigment commonly used as an additive in food, whose presence raises particular concerns in terms of its potential negative health impact. The consumption of E171 food additive is increasingly associated with disorders of the intestinal barrier, including intestinal dysbiosis. It may disrupt the normal functions of the gastrointestinal tract (GIT) including: enzymatic digestion of primary nutrients (lipids, proteins, or carbohydrates). The aim of this review is to provide a comprehensive and reliable overview of studies conducted in recent years in terms of the substance's potentially negative impact on human and animal alimentary systems.

DNA damage and oxidative stress induced by CeO2 nanoparticles in human dermal fibroblasts: Evidence of a clastogenic effect as a mechanism of genotoxicity

The broad range of applications of cerium oxide (CeO2) nanoparticles (nano-CeO2) has attracted industrial interest, resulting in greater exposures to humans and environmental systems in the coming years. Their health effects and potential biological impacts need to be determined for risk assessment. The aims of this study were to gain insights into the molecular mechanisms underlying the genotoxic effects of nano-CeO2 in relation with their physicochemical properties. Primary human dermal fibroblasts were exposed to environmentally relevant doses of nano-CeO2 (mean diameter, 7 nm; dose range, 6 × 10(-5)-6 × 10(-3) g/l corresponding to a concentration range of 0.22-22 µM) and DNA damages at the chromosome level were evaluated by genetic toxicology tests and compared to that induced in cells exposed to micro-CeO2 particles (mean diameter, 320 nm) under the same conditions. For this purpose, cytokinesis-blocked micronucleus assay in association with immunofluorescence staining of centromere protein A in micronuclei were used to distinguish between induction of structural or numerical chromosome changes (i.e. clastogenicity or aneuploidy). The results provide the first evidence of a genotoxic effect of nano-CeO2, (while not significant with micro-CeO2) by a clastogenic mechanism. The implication of oxidative mechanisms in this genotoxic effect was investigated by (i) assessing the impact of catalase, a hydrogen peroxide inhibitor, and (ii) by measuring lipid peroxidation and glutathione status and their reversal by application of N-acetylcysteine, a precusor of glutathione synthesis in cells. The data are consistent with the implication of free radical-related mechanisms in the nano-CeO2-induced clastogenic effect, that can be modulated by inhibition of cellular hydrogen peroxide release.

Antioxidative role of cerium against the toxicity of lead in the liver of silver crucian carp

The antioxidative role of cerium was investigated in the liver of silver crucian carp injected with lead. The fish were intraperitoneally injected with 10, 20, or 30 mg/kg wet weight PbCl(2). After a 14-day period of incubation, 35 animals were injected with a solution of 1.5 mg/kg wet weight CeCl(3). After 42 days, the wet weight and the liver weight of the fish were weighed, and the oxidative stress of the fish liver was estimated by assaying lipid peroxide, superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione, ascorbic acid, and reactive oxygen species (ROS). The results show that Ce(3+) could decrease ROS accumulation, relieve the inhibition of the activities of the antioxidant enzyme and the reduction of antioxidants in fish liver caused by Pb(2+), and decrease the enhancement of hepatosomatic index of fish under various Pb(2+) dosages.

The mechanism of CeCl3 on the activiation of alanine aminotransferase from mice

The activity of alanine aminotransferase (ALT; E.C. 2.6.1.2) is often changed upon inflammatory responses in animals. Rare earths was shown to provoke various inflammatory responses both in rats and mice; however, the molecular mechanism by which rare earths exert its toxicity has not been completely understood, especially, we know little about the mechanism of the interaction between CeCl(3) and ALT. In this report, we investigated the mechanisms of CeCl(3) on ALT activity in vivo and in vitro. Our results showed that Ce(3+) could significantly activate ALT in vivo and in vitro; the kinetics constant (Km) and Vmax were 0.018 microM and 1,380 unit mg(-1) protein min(-1), respectively, at a low concentration of Ce(3+), and 0.027 microM and 624 unit mg(-1) protein min(-1), respectively, at a high concentration of Ce(3+). By UV absorption and fluorescence spectroscopy assays, the Ce(3+) was determined to be directly bound to ALT; the binding site of Ce(3+) to ALT was 1.72, and the binding constants of the binding site were 4.82 x 10(8) and 9.05 x 10(7) L mol(-1). Based on the analysis of the circular dichroism spectra, it was concluded that the binding of Ce(3+) altered the secondary structure of ALT, suggesting that the observed enhancement of ALT activity was caused by a subtle structural change in the active site through the formation of the complex with Ce(3+).

The effects of lanthanoid on the structure–function of lactate dehydrogenase from mice heart

The activity of lactate dehydrogenase (LDH, EC1.1.1.27) is often changed upon inflammatory responses in animals. Lanthanoid (Ln) was shown to provoke various inflammatory responses both in rats and mice; however, the molecular mechanism by which Ln3+ exert its toxicity has not been completely understood, especially that we know little about the mechanism of the interaction between Ln with 4f electron shell and alternation valence and LDH. In this report, we investigated the mechanisms of LaCl3, CeCl3, and NdCl3 on LDH activity in vivo and in vitro. Our results showed that La3+, Ce3+, and Nd3+ could significantly activate LDH in vivo and in vitro; the order of activation was Ce3+>Nd3+> La3+>control. The affinity of LDH for Ce3+ was higher than Nd3+ and La3+; the saturated binding sites for Ce3+ on the LDH protein were 1.2 and for La3+ and Nd3+ 1.55. Ln3+ caused the reduction of exposure degree of cysteine or tryptophan/tyrosine of LDH, the increase of space resistance, and the enhancement of α-helix in secondary structure of LDH, which was greatest in Ce3+ treatment, medium in Nd3+ treatment, and least in La3+ treatment. It implied that the changes of structure-function on LDH caused by Ln3+ were closely related to the characteristics of 4f electron shell and alternation valence in Ln.