Effects of cerium oxide nanoparticles on adenine-induced chronic kidney disease model rats.

AIM: Cerium oxide, particularly in nanoparticle form (nanoceria), has been investigated for biomedical applications as a promising new agent for treating several pathologies. The aim of the present study was to characterize the pharmacologic effects of nanoceria in an animal model of chronic kidney disease. METHODS: We created the chronic kidney disease animal model by feeding rats a 0.25% adenine diet. Male Wistar rats were divided into five groups: normal diet, 0.25% adenine diet, or adenine diet containing three different doses or durations of nanoceria treatment. Blood was collected weekly from the tail veins of each rat and analyzed for renal function markers. After 5 weeks, various biochemical markers in serum, plasma, and urine were also analyzed. RESULTS: In the adenine-treated group, body weight was significantly decreased, and the kidneys lost much of their healthy reddish color and became lumpy and white in appearance. In addition, levels of serum creatinine, blood urea nitrogen, and plasma uremic toxins were significantly increased in adenine-treated rats compared with controls. Renal functional and structural damage in adenine diet model rats tended to be ameliorated by nanoceria ingestion. The high-dose cerium-treated group maintained reddish areas in the kidneys, and the increases in biomarker levels of creatinine, blood urea nitrogen, and inorganic phosphorus were markedly reduced, regardless of treatment duration. CONCLUSIONS: Ingestion of nanoceria may be effective for improving or preventing renal damage caused by adenine. Geriatr Gerontol Int 2024; 24: 88-95.

Quenching effect of cerium oxide nanoparticles on singlet oxygen: validation of the potential for reaction with multiple reactive oxygen species.

Here we studied cerium oxide nanoparticles (nanoceria) as an agent for the future treatment of oxidative damage by validating and evaluating its scavenging activity towards reactive oxygen species (ROS) in vitro. Nanoceria has been shown to mimic the activities of superoxide dismutase and catalase, degrading superoxide (O2•-) and hydrogen peroxide (H2O2). We examined the antioxidative activity of nanoceria, focusing on its ability to quench singlet oxygen (1O2) in an aqueous solution. Electron paramagnetic resonance (EPR) was used to determine the rates of second-order reactions between nanoceria and three ROS (1O2, O2•-, and H2O2) in aqueous solution, and its antioxidative abilities were demonstrated. Nanoceria shows a wide range of ultraviolet-light absorption bands and thus 1O2 was produced directly in a nanoceria suspension using high-frequency ultrasound. The quenching or scavenging abilities of nanoceria for 1O2 and hypoxanthine-xanthine oxidase reaction-derived O2•- were examined by EPR spin-trapping methods, and the consumption of H2O2 was estimated by the EPR oximetry method. Our results indicated that nanoceria interact not only with two previously reported ROS but also with 1O2. Nanoceria were shown to degrade O2•- and H2O2, and their ability to quench 1O2 may be one mechanism by which they protect against oxidative damage such as inflammation.

Evaluation of cerium oxide as a phosphate binder using 5/6 nephrectomy model rat.

BACKGROUND: The number of chronic kidney disease (CKD) patients continues to increase worldwide. CKD patients need to take phosphate binders to manage serum phosphorus concentrations. Currently, several types of phosphate binder, including lanthanum carbonate, are used. However, they each have disadvantages. METHODS: In this study, we evaluated cerium oxide as a new phosphate binder in vitro and in vivo. First, cerium oxide was mixed with phosphoric acid at pH 2.5 or 7.0, and residual phosphoric acid was measured by absorption photometry using colorimetric reagent. Second, cerium oxide was fed to 5/6 nephrectomy model rats (5/6Nx), a well-known renal damage model. All rats were measured food intake, water intake, feces volume, and urine volume, and collected serum and urine were analyzed for biochemical markers. RESULTS: Cerium oxide can adsorb phosphate at acidic and neutral pH, while lanthanum carbonate, which is a one of popular phosphate binder, does not dissolve at neutral pH. Cerium oxide-treatment reduced serum phosphate concentrations of 5/6Nx rats without an increase in serum alanine transaminase levels that would indicate hepatotoxicity, and cerium oxide-treatment maintained serum creatinine and blood urea nitrogen levels, while those of normal 5/6Nx rats increased slightly. CONCLUSIONS: These results suggest that cerium oxide can be a potential phosphate binder. Decreased body weight gain and increased water intake and urine volume in 5/6Nx rats were thought to be an effect of nephrectomy because these changes did not occur in sham operation rats. Additional investigations are needed to evaluate the longer-term safety and possible accumulation of cerium oxide in the body.

Deep learning-based and hybrid-type iterative reconstructions for CT: comparison of capability for quantitative and qualitative image quality improvements and small vessel evaluation at dynamic CE-abdominal CT with ultra-high and standard resolutions.

PURPOSE: To determine the image quality improvement including vascular structures using deep learning reconstruction (DLR) for ultra-high-resolution CT (UHR-CT) and area-detector CT (ADCT) compared to a commercially available hybrid-iterative reconstruction (IR) method. MATERIALS AND METHOD: Thirty-two patients suspected of renal cell carcinoma underwent dynamic contrast-enhanced (CE) CT using UHR-CT or ADCT systems. CT value and contrast-to-noise ratio (CNR) on each CT dataset were assessed with region of interest (ROI) measurements. For qualitative assessment of improvement for vascular structure visualization, each artery was assessed using a 5-point scale. To determine the utility of DLR, CT values and CNRs were compared among all UHR-CT data by means of ANOVA followed by Bonferroni post hoc test, and same values on ADCT data were also compared between hybrid IR and DLR methods by paired t test. RESULTS: For all arteries except the aorta, the CT value and CNR of the DLR method were significantly higher compared to those of the hybrid-type IR method in both CT systems reconstructed as 512 or 1024 matrixes (p < 0.05). CONCLUSION: DLR has a higher potential to improve the image quality resulting in a more accurate evaluation for vascular structures than hybrid IR for both UHR-CT and ADCT.

Potential Mechanisms for Protective Effect of D-Methionine on Plasmid DNA Damage Induced by Therapeutic Carbon Ions.

D-methionine (D-met), a dextrorotatory isoform of the amino acid L-methionine (L-met), can prevent oral mucositis and salivary hypofunction in mice exposed to radiation. However, the mechanism of its radioprotection is unclear, especially with regard to the stereospecific functions of D-met. Radiation is known to cause injury to normal tissue by triggering DNA damage in cells. Thus, in this study we sought to determine whether the chirality of D-/L-met affects radiation-induced events at the DNA level. We selected plasmid DNA assays to examine this effect in vitro, since these assays are highly sensitive and allow easy detection of DNA damage. Samples of supercoiled pBR322 plasmid DNA mixed with D-met, L-met or dimethylsulfoxide (DMSO) were prepared and irradiated with a Bragg peak beam of carbon ions (∼290 MeV/u) with a 6-cm spread. DNA strand breaks were indicated by the change in the form of the plasmid and were subsequently quantified using agarose gel electrophoresis. We found that D-met yielded approximately equivalent protection from carbon-ion-induced DNA damage as DMSO. Thus, we propose that the protective functions of methionine against plasmid DNA damage could be explained by the same mechanism as that for DMSO, namely, hydroxyl radical scavenging. This stereospecific radioprotective mechanism occurred at a level other than the DNA level. There was no significant difference between the radioprotective effect of D-met and L-met on DNA.

A quantitative analysis of carbon-ion beam-induced reactive oxygen species and redox reactions.

The amounts of reactive oxygen species generated in aqueous samples by irradiation with X-ray or clinical carbon-ion beams were quantified. Hydroxyl radical (•OH), hydrogen peroxide (H2O2), and the total amount of oxidation reactions, which occurred mainly because of •OH and/or hydroperoxy radicals (HO2 •), were measured by electron paramagnetic resonance-based methods. •OH generation was expected to be localized on the track/range of the carbon-ion beam/X-ray, and mM and M levels of •OH generation were observed. Total •OH generation levels were identical at the same dose irrespective of whether X-ray or carbon-ion beam irradiation was used, and were around 0.28-0.35 µmol/L/Gy. However, sparse •OH generation levels decreased with increasing linear energy transfer, and were 0.17, 0.15, and 0.09 µmol/L/Gy for X-ray, 20 keV/µm carbon-ion beam, and >100 keV/µm carbon-ion beam sources, respectively. H2O2 generation was estimated as 0.26, 0.20, and 0.17 µmol/L/Gy, for X-ray, 20 keV/µm carbon-ion beam, and >100 keV/µm carbon-ion beam sources, respectively, whereas the ratios of H2O2 generation per oxygen consumption were 0.63, 0.51, and 3.40, respectively. The amounts of total oxidation reactions were 2.74, 1.17, and 0.66 µmol/L/Gy, respectively. The generation of reactive oxygen species was not uniform at the molecular level.

Localized hydroxyl radical generation at mmol/L and mol/L levels in water by photon irradiation.

The generation of localized hydroxyl radical (•OH) in aqueous samples by low linear energy transfer irradiation was investigated. Several concentrations of 5,5-dimethyl-1-pyrroline-N-oxid solution (from 0.5 to 1,680 mmol/L) were prepared and irradiated with an identical dose of X-ray or γ-ray. The density of •OH generation in aqueous solution was evaluated by the electron paramagnetic resonance spin-trapping technique using 5,5-dimethyl-1-pyrroline-N-oxid as an electron paramagnetic resonance spin-trapping agent. The relationship between the molecular density of 5,5-dimethyl-1-pyrroline-N-oxid in the samples and the concentration of 5,5-dimethyl-1-pyrroline-N-oxid-OH generated in the irradiated samples was analyzed. Two different characteristic linear trends were observed in the 5,5-dimethyl-1-pyrroline-N-oxid-OH/5,5-dimethyl-1-pyrroline-N-oxid plots, which suggested •OH generation in two fashions, i.e., mmol/L- and mol/L-level local concentrations. The dose, dose rate, and/or the energy of photon irradiation did not affect the shapes of the 5,5-dimethyl-1-pyrroline-N-oxid-OH/5,5-dimethyl-1-pyrroline-N-oxid plots. Moreover, the addition of 5 mmol/L caffeine could cancel the contribution of mmol/L-level •OH generation, leaving a trace of mol/L-level •OH generation. Thus, the localized mmol/L- and mol/L-level generations of •OH, which were independent of experimental parameters such as dose, dose rate, and/or the energy of photon of low linear energy transfer radiation, were established.

EPR-based oximetric imaging: a combination of single point-based spatial encoding and T1 weighting.

PURPOSE: Spin-lattice relaxation rate (R1 )-based time-domain EPR oximetry is reported for in vivo applications using a paramagnetic probe, a trityl-based Oxo71. METHODS: The R1 dependence of the trityl probe Oxo71 on partial oxygen pressure (pO2 ) was assessed using single-point imaging mode of spatial encoding combined with rapid repetition, similar to T1 -weighted MRI, for which R1 was determined from 22 repetition times ranging from 2.1 to 40.0 µs at 300 MHz. The pO2 maps of a phantom with 3 tubes containing 2 mM Oxo71 solutions equilibrated at 0%, 2%, and 5% oxygen were determined by R1 and apparent spin-spin relaxation rate ( R2*) simultaneously. RESULTS: The pO2 maps derived from R1 and R2* agreed with the known pO2 levels in the tubes of Oxo71. However, the histograms of pO2 revealed that R1 offers better pO2 resolution than R2* in low pO2 regions. The SDs of pixels at 2% pO2 (15.2 mmHg) were about 5 times lower in R1 -based estimation than R2*-based estimation (mean ± SD: 13.9 ± 1.77 mmHg and 18.3 ± 8.70 mmHg, respectively). The in vivo pO2 map obtained from R1 -based assessment displayed a homogeneous profile in low pO2 regions in tumor xenografts, consistent with previous reports on R2*-based oximetric imaging. The scan time to obtain the R1 map can be significantly reduced using 3 repetition times ranging from 4.0 to 12.0 µs. CONCLUSION: Using the single-point imaging modality, R1 -based oximetry imaging with useful spatial and oxygen resolutions for small animals was demonstrated.

Analysis of redox states of protic and aprotic solutions irradiated by low linear energy transfer carbon-ion beams using a 2,2-diphenyl-1-picrylhydrazyl radical.

The quantitative evaluation of changes in the redox state induced by low linear energy transfer (LET) radiations such as the plateau region of heavy-ion beams via formation of reactive oxygen species is of considerable importance to eliminate the adverse effects of radiation therapy on normal tissues adjacent to a tumour. In this study, a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙) was used as a redox probe to estimate the redox states of protic and aprotic solutions irradiated by low LET carbon-ion (C-ion) beams. The dose dependence of the decrease in the absorption band due to DPPH˙ (which was solubilised by ß-cyclodextrin (ß-CD) in water) after irradiation with low LET C-ion beams (13 keV µm-1) was similar to that after X-irradiation. Similar results were obtained when H2O was replaced with methanol or acetonitrile although the slope values of the plots of the absorbance changes vs. radiation doses were twice larger as compared to the case in ß-CD-containing H2O. Moreover, DPPH˙ was more susceptible to the C-ion beam than to X-rays in isopropyl myristate (IPM), which is one of the saturated fatty acid esters.

Suppression of phenotype of Escherichia coli mutant defective in farnesyl diphosphate synthase by overexpression of gene for octaprenyl diphosphate synthase.

We investigated suppression of the slow growth of an Escherichia coli ispA null mutant lacking farnesyl diphosphate (FPP) synthase (i.e. IspA) by plasmids carrying prenyl diphosphate synthase genes. The growth rates of ispA mutant-transformants harboring a medium-copy number plasmid that carries ispA or ispB were almost the same as that of the wild-type strain. Although the level of FPP in the transformant with the ispA plasmid was almost the same as that in the wild-type strain, the level in the transformant with the ispB plasmid was as low as that in the ispA mutant. Purified octaprenyl diphosphate synthase (IspB) could condense isopentenyl diphosphate (IPP) with dimethylallyl diphosphate (DMAPP) to form octaprenyl diphosphate and nonaprenyl diphosphate. It is possible that suppression of the slow growth of the ispA mutant by ispB was due to condensation of IPP not only with FPP but also with DMAPP by octaprenyl diphosphate synthase.

Non-invasive measurement of melanin-derived radicals in living mouse tail using X-band EPR.

The aim of this experiment is to measure in vivo generation of melanin-derived radicals non-invasively, as a quantifiable index of radio-biological effect. Melanin-derived radicals in a living intact mouse tail tip were non-invasively measured in very simple way using an X-band electron paramagnetic resonance spectrometer. Colored mouse strains, C57BL/6NCr, BDF1, and C3H/He, have clear EPR signal corresponding to melanin-derived radicals in the tail tip; however, albino mouse strains, BALB/cCr, ddY, ICR, have no EPR signals. An X-ray fraction of 2 Gy/day (1 Gy/min) was repeatedly irradiated to a C3H/He mouse tail skin every Monday to Friday for 4 weeks. In comparison to before starting irradiation, the C3H/He mouse tail skin became darker, like a suntan. The melanin-derived radicals in C3H/He mouse tail skin were increased in association with X-ray fractions. Melanin-derived radicals in mouse tail skin can be readily and chronologically measurable by using X-band EPR spectrometer, and can be a marker for a radiobiological effect in the skin.

Aluminium ion-promoted radical-scavenging reaction of methylated hydroquinone derivatives.

The effect of the aluminium ion (Al(3+)) on the scavenging reaction of a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙), as a reactivity model of reactive oxygen species, with hydroquinone (QH2) and its methylated derivatives (MenQH2, n = 1-4) was investigated using stopped-flow and electrochemical techniques in a hydroalcoholic medium. The second-order rate constants (k) for the DPPH˙-scavenging reaction of the hydroquinones increased with the increasing number of methyl substituents. Upon addition of Al(3+), the k values significantly increased depending on the concentration of Al(3+). Such an accelerating effect of Al(3+) on the DPPH˙-scavenging rates of the hydroquinones results from the remarkable positive shift of the one-electron reduction potential (Ered) of DPPH˙ in the presence of Al(3+). These results demonstrate that Al(3+), a strong Lewis acid, can act as a radical-scavenging promoter by stabilising the one-electron reduced species of the radical, although Al(3+) is reported not only to act as a pro-oxidant but also to strongly interact with biomolecules, showing toxicities.