Toxicity of Two Different Sized Lanthanum Oxides in Cultured Cells and Sprague-Dawley Rats

Abstract

In recent years, the use of both nano- and micro-sized lanthanum has been increasing in the production of optical glasses, batteries, alloys, etc. However, a hazard assessment has not been performed to determine the degree of toxicity of lanthanum. Therefore, the purpose of this study was to identify the toxicity of both nano- and micro-sized lanthanum oxide in cultured cells and rats. After identifying the size and the morphology of lanthanum oxides, the toxicity of two different sized lanthanum oxides was compared in cultured RAW264.7 cells and A549 cells. The toxicity of the lanthanum oxides was also analyzed using rats. The half maximal inhibitory concentrations of micro-La2O3 in the RAW264.7 cells, with and without sonication, were 17.3 and 12.7 times higher than those of nano-La2O3, respectively. Similar to the RAW264.7 cells, the toxicity of nano-La2O3 was stronger than that of micro-La2O3 in the A549 cells. We found that nano-La2O3 was absorbed in the lungs more and was eliminated more slowly than micro-La2O3. At a dosage that did not affect the body weight, numbers of leukocytes, and concentrations of lactate dehydrogenase and albumin in the bronchoalveolar lavage (BAL) fluids, the weight of the lungs increased. Inflammatory effects on BAL decreased over time, but lung weight increased and the proteinosis of the lung became severe over time. The effects of particle size on the toxicity of lanthanum oxides in rats were less than in the cultured cells. In conclusion, smaller lanthanum oxides were more toxic in the cultured cells, and sonication decreased their size and increased their toxicity. The smaller-sized lanthanum was absorbed more into the lungs and caused more toxicity in the lungs. The histopathological symptoms caused by lanthanum oxide in the lungs did not go away and continued to worsen until 13 weeks after the initial exposure.

Twenty‐eight‐day repeated inhalation toxicity study of nano‐sized lanthanum oxide in male sprague‐dawley rats

“…Although it decreased by 30, 33, and 54% in the 0.5, 2.5, and 10 mg/m 3 groups after 28‐day recovery, respectively, it was still at high levels. In a previous study, the lung concentration of lanthanum on day 3 decreased by 29% after 13 weeks when nano‐sized La 2 O 3 was given by intratracheal instillation at 5 mg/kg in rats (Lim, ); moreover, the elimination rate was slower than that of our study, possibly because a deeper part of the lung was exposed to the particles after intratracheal instillation. Keller et al () reported that the CeO 2 nanoparticles half‐life in the lung was 40 days in rats were exposed to 0.5 mg/m 3 for 4 weeks.…”

“…The purpose of the present study was to provide toxicological data required for risk/hazard assessment of lanthanum in order to prevent possible adverse impacts to human health and the environment. In a previous La 2 O 3 toxicity study, high toxicity was observed both in vivo and in vitro , as the particle size decreased and the surface area increased (Lim, ). Several toxicity studies using ultrafine particles reported that a smaller particle size induced higher toxicity (Duffin et al, ; Sager and Castranova, ; Toya et al, ; Keller et al, ; Lim et al, ; Peng et al, ).…”

“…Lanthanum (III) oxide (manufacturer number: Aldrich‐634271) was purchased from Sigma‐Aldrich (St. Louis, Mo, USA). The surface area of nano‐sized La 2 O 3 used in the present study was 7.66 m 2 /g as measured by the Brunauer–Emmett–Teller (BET) method, and the particle size was calculated as 103.6 nm (Lim, ). Nano‐sized La 2 O 3 was suspended in distilled water at a concentration of 0.1 to 3.0% under constant agitation, and was subsequently sonicated with a 5 s sonication/3 s rest cycle using a probe‐type ultrasonicator (VC750, Sonics & Materials, Newtown, CT, USA) to avoid heat generation.…”

“…However, it is difficult to compare different toxicity results, as the experimental conditions were heterogeneous. Particularly, in previous in vivo and in vitro studies, the toxicity of La 2 O 3 was reported to increase with time and with decreasing particle size (Lim, ).…”

Toxicological Assessment of CoO and La2O3Metal Oxide Nanoparticles in Human Small Airway Epithelial Cells

“…A gene expression study showed that CoO nanoparticles have the ability to induce inflammation and cytotoxicity in alveolar A549 and bronchial BEAS-2B epithelial cells (Verstraelen et al , 2014); however, the gene expression profile is different between the two in vitro lung epithelial cell lines suggesting the signaling cascades to cause an inflammatory response and cytotoxicity could be slightly different. Others have looked at the cytotoxicity of La 2 O 3 nanoparticles within RAW264.7 cells and A549 cells and determined that with increasing amounts of La 2 O 3 nanoparticles and increased incubation time, La 2 O 3 nanoparticles become more cytotoxic and that the size of the La 2 O 3 particles plays a large role in cytotoxicity (Lim, 2015). …”