Srinivas Indu Kumari

Toxicity assessment of manganese oxide micro and nanoparticles in Wistar rats after 28 days of repeated oral exposure

In the near future, nanotechnology is envisaged for large‐scale use. Hence health and safety issues of nanoparticles (NPs) should be promptly addressed. Twenty‐eight‐day oral toxicity, genotoxicity, biochemical alterations, histopathological changes and tissue distribution of nano and microparticles (MPs) of manganese oxide (MnO2) in Wistar rats was studied. Genotoxicity was assessed using comet, micronucleus and chromosomal aberration assays. The results demonstrated a significant increase in DNA damage in leukocytes, micronuclei and chromosomal aberrations in bone marrow cells after exposure of MnO2‐NPs at 1000, 300 mg kg–1 bw per day and MnO2‐MPs at the dose of 1000 mg kg–1 bw per day. Our findings showed acetylcholinestrase inhibition at 1000 as well as at 300 mg kg–1 bw per day in blood and with all the doses in the brain indicating the toxicity of MnO2‐NPs. Further, the doses significantly inhibited different ATPases in the brain P2 fraction. Significant changes were observed in aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) in the liver, kidney and serum in a dose‐dependent manner. MnO2‐MPs at 1000 mg kg–1 bw per day were found to induce significant alterations in biochemical enzymes. A significant distribution was found in all the tissues in a dose‐dependent manner. MnO2‐NPs showed a much higher absorptivity and tissue distribution as compared with MnO2‐MPs. A large fraction of MnO2‐NPs and MnO2‐MPs was cleared by urine and feces. Histopathological analysis revealed that MnO2‐NPs caused alterations in liver, spleen, kidney and brain. The MnO2‐NPs induced toxicity at lower doses compared with MnO2‐MPs. Further, this study did not display gender differences after exposure to MnO2‐NPs and MnO2‐MPs. Therefore, the results suggested that prolonged exposure to MnO2 has the potential to cause genetic damage, biochemical alterations and histological changes. Copyright

Genotoxicity assessment of cerium oxide nanoparticles in female Wistar rats after acute oral exposure.

Cerium oxide nanoparticles (CeO2 NPs; nanoceria) have demonstrated excellent potential for commercial use in various arenas, such as in biomedical industry in cosmetics and as a fuel additive. However, limited knowledge exists regarding their potential toxicity. In this study, acute oral toxicity of CeO2 NPs and their microparticles (MPs; bulk) was carried out in female albino Wistar rats. The CeO2 NPs and CeO2 MPs were characterized utilizing transmission electron microscopy (TEM), dynamic light scattering (DLS) and laser Doppler velocimetry (LDV) for the size, distribution and surface charge respectively. The genotoxicity studies were conducted using micronucleus test (MNT), comet and chromosomal aberration (CA) assays. Results revealed that at high dose (1000mg/kg bw) CeO2 NPs induced significant DNA damage in peripheral blood leukocytes (PBL) and liver cells, micronucleus formation in bone marrow and blood cells and total cytogenetic changes in bone marrow. However, significant genotoxicity was not observed at 500 and 100mg/kg bw of CeO2 NPs. The findings from biochemical assays depicted significant alterations in ALP and LDH activity in serum and GSH content in liver, kidneys and brain only at the high dose of CeO2 NPs. Tissue biodistribution of both particles was analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES). Bioaccumulation of nanoceria in all tissues was significant and dose-, time- and organ-dependent. Moreover, CeO2 NPs exhibited higher tissue distribution along with greater clearance in large fractions through urine and feces than CeO2 bulk, whereas, maximum amount of micro-sized CeO2 got excreted in feces. The histopathological examination documented alterations in the liver due to exposure with CeO2 NPs only. Hence, the results suggest that bioaccumulation of CeO2 NPs may induce genotoxic effects. However, further research on long term fate and adverse effects of CeO2 NPs is warranted.

Genotoxicity analysis of cerium oxide micro and nanoparticles in Wistar rats after 28 days of repeated oral administration

The applications of cerium oxide nanoparticles (CeO2 NPs; nanoceria) extend to polishing agents, diesel fuel additives and as a putative antioxidant in therapeutics. Therefore, understanding the long-term toxic effects of CeO2 NPs is of particular importance. This study investigated the 28 days of repeated toxicity of 30, 300 and 600 mg/kg body weight (bw)/day of nanoceria and CeO2 microparticles (MPs) in Wistar rats after oral exposure. Genotoxicity was analysed using comet, micronucleus (MN) and chromosomal aberration (CA) assays. The results demonstrated a significant increase in DNA damage in peripheral blood leukocytes and liver, MN and CA in bone marrow as well as MN in peripheral blood after exposure to CeO2 NPs at 300 and 600 mg/kg bw/day. Significant alterations were observed in alkaline phosphatase and lactate dehydrogenase activity in serum and reduced glutathione content in the liver, kidneys and brain at 300 and 600 mg/kg bw/day in a dose-dependent manner. Conversely, CeO2 MPs did not induce any significant toxicological changes. A much higher absorptivity and significant tissue distribution of CeO2 NPs was perceived in comparison to CeO2 MPs in a dose-dependent manner. A substantial fraction of CeO2 NPs was cleared by urine and faeces. Histopathological analysis revealed that CeO2 NPs caused alterations in liver, spleen and brain. Further, distinct difference in the data among genders was not obvious. In general, the results suggested that prolonged oral exposure to nanoceria has the potential to cause genetic damage, biochemical alterations and histological changes after retention in vital organs of rats at high concentrations.

Genotoxicity of nano- and micron-sized manganese oxide in rats after acute oral treatment.

The use of nanotechnology has led to rapid growth in various areas. Manganese oxide (MnO2) nanomaterials (NMs) are typically used for biomedical applications. However, characterizing the potential human health effects of MnO2 NMs is required before fully exploiting these materials. The aim of this study was to investigate the acute oral toxicity of MnO2 NMs and MnO2-bulk particles in female albino Wistar rats. The genotoxic effects were examined using comet, micronucleus and chromosomal aberration assays. Nanosized MnO2 (45nm) significantly (p<0.01) increased DNA damage in peripheral blood leukocytes and micronuclei and enhanced chromosomal aberrations in the bone marrow cells at 1000mg/kg bw. These findings showed that the neurotoxicity of MnO2-45nm in the brain and red blood cells, as determined through acetylcholinesterase activity, was significantly (p<0.01) inhibited at 1000 and 500mg/kg bw doses. MnO2-45nm disrupted the physicochemical state and neurological system of the animals through alterations in ATPases via the total Na(+)-K(+), Mg(2+) and Ca(2+) levels in the brain P2 fraction. In addition, 500 and 1000mg/kg bw doses of MnO2-45nm caused significant changes in AST, ALT and LDH levels in the liver, kidney and serum of treated rats. Significant tissue distribution was found in all tissues in a dose- and time-dependent manner. MnO2-45nm exhibited much higher absorptivity and tissue distribution compared with MnO2-bulk. A large fraction of MnO2-45nm was cleared in the urine and feces. The histopathological analysis revealed that MnO2-45nm caused alterations in the liver, spleen and brain. These findings will provide fundamental information regarding the potential toxicities and biodistribution of nano and bulk MnO2 generated through acute oral treatment.

Assessment of genotoxic effects of lead in occupationally exposed workers

The genotoxicological effects in 200 lead acid storage battery recycling and manufacturing industry workers in Hyderabad along with matched 200 controls were studied. The genetic damage was determined by comet, micronucleus (MN), and chromosomal aberration (CA) test in peripheral blood lymphocytes (PBL). The MN test was also carried out in buccal epithelial cells (BECs). Pb in ambient air, blood Pb (B-Pb) concentrations, and hematological parameters were measured. The superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GPx), and malondialdehyde (MDA) formed were also studied. The results of the present study showed that there was a statistically significant (P < 0.01) increase in mean percent tail DNA, frequency of CA, and MN in PBL as well as in BEC as compared to controls. Pb in ambient air and B-Pb concentrations were found to be significantly higher (P < 0.01). The hematocrit, hemoglobin, and red blood cell values were significantly lowered in Pb-exposed workers in comparison to controls. SOD, GPx, and CAT levels were significantly decreased while GSH and MDA levels increased in exposed group when compared to control group. The present study suggests that environmental health standards should be enforced to control Pb contamination from battery industries to reduce human health risk.

Genotoxicity study of nickel oxide nanoparticles in female Wistar rats after acute oral exposure

Nanoparticles (NPs) apart from their widespread advantages and increased utilisation, have aroused concerns over their safe use. Nickel (II) oxides (NiO) NPs are used as catalysts, biosensors and in many of the consumer products. The increasing use of NiO NPs necessitates an improved understanding of their potential impact on the environment and human health. In this study, we investigated the acute genotoxic effects of NiO NPs by oral route administration with three different doses (125, 250 and 500 mg/kg bw). Before the in vivo toxicological evaluation, characterisation of particles by Transmission Electron Microscopy, X-ray diffraction, Dynamic Light Scattering (DLS) and Laser Doppler Velocimetry analysis was performed. Genotoxicity biomarkers such as comet, micronucleus and chromosomal aberrations (CAs) assays were utilised in this study. To document the uptake, retention and elimination of the NPs, biodistribution studies were also performed. The particle size obtained from Transmission Electron Microscopy analysis for NiO NPs was 15.62 ± 2.59 nm. The mean hydrodynamic diameter and PdI of NiO NPs in Milli-Q water suspension obtained by DLS was 168.9 ± 17.13 nm and 0.375, respectively. Comet assay revealed significant (P < 0.001) DNA damage at 500 mg/kg bw dose in the PBL, liver and kidney cells of rats at the 24-h sampling time. The result of micronucleus and CAs tests was in agreement with the comet assay data. Biodistribution of NiO NPs revealed a maximum accumulation of Ni in the liver tissue at the 24-h sampling time. Our study showed significant DNA damage at the high dose level and the effect was more prominent at 24-h sampling time, providing preliminary evidence that the NiO NPs are capable of inducing genotoxicity when administered through the oral route. However, mechanistic investigations are needed before drawing any firm conclusion regarding the toxicology of NiO NPs.

Comparative study of cyto- and genotoxic potential with mechanistic insights of tungsten oxide nano- and microparticles in lung carcinoma cells: Genotoxic potential of tungsten oxide nanoparticles in A549 cells

The exigency of semiconductor and super capacitor tungsten oxide nanoparticles (WO3 NPs) is increasing in various sectors. However, limited information on their toxicity and biological interactions are available. Hence, we explored the underlying mechanisms of toxicity induced by WO3 NPs and their microparticles (MPs) using different concentrations (0–300 μg ml–1) in human lung carcinoma (A549) cells. The mean size of WO3 NPs and MPs by transmission electron microscopy was 53.84 nm and 3.88 μm, respectively. WO3 NPs induced reduction in cell viability, membrane damage and the degree of induction was size‐ and dose‐dependent. There was a significant increase in the percentage tail DNA and micronuclei formation at 200 and 300 μg ml–1 after 24 hours of exposure. The DNA damage induced by WO3 NPs could be attributed to increased oxidative stress and inflammation through reactive oxygen species generation, which correlated with the depletion of reduced glutathione content, catalase and an increase in malondialdehyde levels. Cellular uptake studies unveiled that both the particles were attached/surrounded to the cell membrane according to their size. In addition, NP inhibited the progression of the cell cycle in the G2/M phase. Other studies such as caspase‐9 and ‐3 and Annexin‐V‐fluorescein isothiocyanate revealed that NPs induced intrinsic apoptotic cell death at 200 and 300 μg ml–1 concentrations. However, in comparison to NPs, WO3 MPs did not incite any toxic effects at the tested concentrations. Under these experimental conditions, the no‐observed‐significant‐effect level of WO3 NPs was determined to be ≤200 μg ml–1 in A549 cells.

Assessment of genotoxicity and biodistribution of nano‐ and micron‐sized yttrium oxide in rats after acute oral treatment

The increasing use of yttrium oxide (Y2O3) nanoparticles (NPs) entails an improved understanding of their potential impact on the environmental and human health. In the present study, the acute oral toxicity of Y2O3 NPs and their microparticles (MPs) was carried out in female albino Wistar rats with 250, 500 and 1000 mg kg−1 body weight doses. Before the genotoxicity evaluation, characterization of the particles by transmission electron microscopy, dynamic light scattering and laser Doppler velocimetry was performed. The genotoxicity studies were conducted using micronucleus and comet assays. Results showed that Y2O3 NP‐induced significant DNA damage at higher dose (1000 mg kg−1 body weight) in peripheral blood leukocytes and liver cells, micronucleus formation in bone marrow and peripheral blood cells. The findings from biochemical assays depicted significant alterations in aspartate transaminase, alanine transaminase, alkaline phosphatase, malondialdehyde, superoxide dismutase, reduced glutathione, catalase and lactate dehydrogenase levels in serum, liver and kidneys at the higher dose only. Furthermore, tissue biodistribution of both particles was analyzed by inductively coupled plasma optical emission spectrometry. Bioaccumulation of yttrium (Y) in all tissues was significant and dose‐, time‐ and organ‐dependent. Moreover, Y2O3 NP‐treated rats exhibited higher tissue distribution along with greater clearance through urine whereas Y2O3 MP‐dosed animals depicted the maximum amount of Y in the feces. Hence, the results indicated that bioaccumulation of Y2O3 NPs via its Y ions may induce genotoxic effects.