Titanium dioxide nanoparticles induce mitochondria-associated apoptosis in HepG2 cells

Hepatotoxicity of titanium dioxide nanoparticles

The food additive E171 (titanium dioxide, TiO2), is widely used in foods, pharmaceuticals and cosmetics. It is a fine white powder, with at least one third of its particles sized in the nanoparticulate (˂100 nm range, TiO2 NPs). The use of E171 is controversial as its relevant risk assessment has never been satisfactorily accomplished. In vitro and in vivo studies have shown dose-dependent toxicity in various organs including the liver. TiO2 NPs have been shown to induce inflammation, cell death and structural and functional changes within the liver. The toxicity of TiO2 NPs in experimental models varies between organs and according to their physiochemical characteristics and parameters such as dosage and route of administration. Among these factors, ingestion is the most significant exposure route, and the liver is a key target organ. The aim of this review is to highlight the reported adverse effects of orally administered TiO2 NPs on the liver and to discuss the controversial state of its toxicity.

Facile sonochemically-assisted bioengineering of titanium dioxide nanoparticles and deciphering their potential in treating breast and lung cancers: biological, molecular, and computational-based investigations

Combining sonochemistry with phytochemistry is a modern trend in the biosynthesis of metallic nanoparticles (NPs), which contributes to the sustainability of chemical processes and minimizes hazardous effects. Herein, titanium dioxide (TiO2) NPs were bioengineered using a novel and facile ultrasound-assisted approach utilizing the greenly extracted essential oil of Ocimum basilicum. FTIR and UV-Vis spectrophotometry were used to confirm the formation of TiO2 NPs. The X-ray diffraction (XRD) analysis showed the crystalline nature of TiO2 NPs. TEM analysis revealed the spherical morphology of the NPs with sizes ranging from 5.55 to 13.89 nm. Energy-dispersive X-ray (EDX) confirmed the purity of the greenly synthesized NPs. TiO2 NPs demonstrated outstanding antitumor activity against breast (MCF-7) and lung (A-549) cancer cells with estimated IC50 values of 1.73 and 4.79 μg mL-1. The TiO2 NPs were cytocompatible to normal cells (MCF-10A) with a selectivity index (SI) of 8.77 for breast and 3.17 for lung cancer. Biological assays revealed a promising potential for TiO2 NPs to induce apoptosis and arrest cells at the sub-G1 phase of the cell cycle phase in both cancer cell lines. Molecular investigations showed the ability of TiO2 NPs to increase apoptotic genes' expression (Bak and Bax) and their profound ability to elevate the expression of apoptotic proteins (caspases 3 and 7). Molecular docking demonstrated strong binding interactions for TiO2 NPs with caspase 3 and EGFR-TK targets. In conclusion, the greenly synthesized TiO2 NPs exhibited potent antitumor activity and mitochondrion-based cell death against breast and lung cancer cell lines while maintaining cytocompatibility against normal cells.

Prospects of nanoparticle-based radioenhancement for radiotherapy

Radiotherapy is a key pillar of solid cancer treatment. Despite a high level of conformal dose deposition, radiotherapy is limited due to co-irradiation of organs at risk and subsequent normal tissue toxicities. Nanotechnology offers an attractive opportunity for increasing the efficacy and safety of cancer radiotherapy. Leveraging the freedom of design and the growing synthetic capabilities of the nanomaterial-community, a variety of engineered nanomaterials have been designed and investigated as radiosensitizers or radioenhancers. While research so far has been primarily focused on gold nanoparticles and other high atomic number materials to increase the absorption cross section of tumor tissue, recent studies are challenging the traditional concept of high-Z nanoparticle radioenhancers and highlight the importance of catalytic activity. This review provides a concise overview on the knowledge of nanoparticle radioenhancement mechanisms and their quantification. It critically discusses potential radioenhancer candidate materials and general design criteria for different radiation therapy modalities, and concludes with research priorities in order to advance the development of nanomaterials, to enhance the efficacy of radiotherapy and to increase at the same time the therapeutic window.

Role of melatonin and quercetin as countermeasures to the mitochondrial dysfunction induced by titanium dioxide nanoparticles

AIM

Due to the growing commercialization of titanium dioxide nanoparticles (TNPs), it is necessary to use these particles in a manner that is safe, healthy and environmental friendly. Through reactive oxygen species (ROS) generation, it has been discovered that TNPs have a harmful effect on the brain. The aim of this study is to provide valuable insights into the possible mechanisms of TNPs induced mitochondrial dysfunction in brain and its amelioration by nutraceuticals, quercetin (QR) and melatonin (Mel) in in vitro and in vivo conditions.

MATERIALS AND METHODS

Whole brain mitochondrial sample was used for in-vitro evaluation. Pre-treatment of QR (30 μM) and Mel (100 μM) at 25 °C for 1 h was given prior to TNPs (50 μg/ml) exposure. For in-vivo study, male Wistar rats were divided into four groups. Group I was control and group II was exposed to TNPs (5 mg/kg b.wt., i.v.). QR (5 mg/kg b.wt.) and Mel (5 mg/kg b.wt.) were given orally as pre-treatment in groups III and IV, respectively. Biochemical parameters, neurobehavioural paradigms, mitochondrial respiration, neuronal architecture assessment were assessed.

KEY FINDINGS

QR and Mel restored the mitochondrial oxidative stress biomarkers in both the studies. Additionally, these nutraceuticals resuscitated the neurobehavioural alterations and restored the neuronal architecture alterations in TNPs exposed rats. The mitochondrial dysfunction induced by TNPs was also ameliorated by QR and Mel by protecting the mitochondrial complex activity and mitochondrial respiration rate.

SIGNIFICANCE

Results of the study demonstrated that QR and Mel ameliorated mitochondrial mediated neurotoxic effects induced by TNPs exposure.

Protective effects of lycopene on TiO2 nanoparticle-induced damage in the liver of mice

Titanium dioxide nanoparticles (nano-TiO₂ ) is one of the most widely used and produced nanomaterials. Studies have demonstrated that nano-TiO₂ could induce hepatotoxicity through oxidative stress, and lycopene has strong antioxidant capacity. The present study aimed to explore if lycopene protects the liver of mice from nano-TiO₂ damage. Ninety-six ICR mice were randomly divided into eight groups. They were control group, nano-TiO₂ -treated group (50 mg/kg BW), lycopene-treated groups (5, 20, and 40 mg/kg BW), and 50 mg/kg BW nano-TiO₂ - and lycopene-co-treated groups (nano-TiO₂  + 5 mg/kg BW of lycopene, nano-TiO₂  + 20 mg/kg BW of lycopene, nano-TiO₂  + 40 mg/kg BW of lycopene). After treated by gavage for 30 days, the histopathology of the liver was observed. Liver function was evaluated using changes in serum biochemical indicators of the liver (AST, ALT, ALP); and the level of ROS was indirectly reflected by the level of SOD, GSH-Px, MDA, GSH, and T-AOC. TUNEL assay was performed to examine the apoptosis of hepatocytes. Proteins of p53, cleaved-caspase 9, cleaved-caspase 3, Bcl-2, and Bax as well as p38 were detected. Results showed that lycopene alleviated the liver pathological damage and reduced the injury to liver function induced by nano-TiO₂ , as well as decreased nano-TiO₂ -induced ROS. Meanwhile, lycopene mitigated apoptosis resulting from nano-TiO₂ , accompanied by the reversed expression of apoptosis-related proteins. Furthermore, lycopene significantly reversed the upregulation of p-p38 induced by nano-TiO₂ . In conclusion, this study demonstrated that nano-TiO₂ resulted in hepatocyte apoptosis through ROS/ROS-p38 MAPK pathway and led to liver function injury. Lycopene protected mice liver against the hepatotoxicity of nano-TiO₂ through antioxidant property.

Antioxidant thymoquinone and eugenol alleviate TiO2 nanoparticle-induced toxicity in human blood cells in vitro

Titanium dioxide (TiO₂) nanoparticles (NPs) are used extensively in a variety of commercial, industrial, and medical products, due to which human exposure is inevitable. This study aimed to explore the potential of eugenol and thymoquinone (TQ), two well-known antioxidants, in counteracting the NP-induced toxicity in human blood cells in vitro. Fresh lymphocytes and erythrocytes were isolated from volunteer human blood donors and incubated with 50 μg/mL of TiO₂ NPs in the presence and absence of 50 μM of TQ and 20 μg/mL of eugenol for 3 h. Results showed that NP-treatment-induced hemolysis, oxidative stress, lactate dehydrogenase (LDH) leakage, and reduced ATPase activity in the erythrocytes. In the lymphocytes treated with NPs alone (50 μg/mL), cytotoxicity in MTT assay and DNA damage in comet assay were observed; in addition, mitochondrial membrane potential collapsed and ADP/ATP ratio increased indicating mitochondrial function impairment. However, in the presence of antioxidants, all these NP-induced changes were mitigated significantly. The results were more significant when both antioxidants eugenol and TQ were given together. Thus, it seems that antioxidants eugenol and TQ can be used as a protective agent against TiO₂ NP-induced toxicity.

Coenzyme Q10 protects isolated human blood cells from TiO2 nanoparticles induced oxidative/antioxidative imbalance, hemolysis, cytotoxicity, DNA damage and mitochondrial impairment

TiO₂ NPs have been investigated for their toxic potential and studies have reported their toxicity is due to generation of oxidative stress. In the present study, we investigated the toxicity of TiO₂ NPs and explored the potential of well-known antioxidant coenzyme Q10 (CoQ10) in counteracting the NP-induced toxicity in isolated human blood cells. When the isolated blood cells were treated with varying concentrations of TiO₂ NPs (25-100 μg/ml), only 50 μg/ml dose induced statistically significant hemolysis in erythrocytes and cytotoxicity in lymphocytes (p < 0.05). None of the concentrations induced any significant increase in platelet aggregation. To investigate the protective effect of CoQ10, we incubated the isolated blood cells with 50 μg/ml of TiO₂ NPs in the presence and absence of 25 μM of CoQ10 for 3 h. Hemolysis, oxidative stress, LDH leakage and ATPase enzyme activity were studied in erythrocytes; cytotoxic and DNA damaging potential of NPs were determined in lymphocytes, along with mitochondrial membrane potential (MMP) and ADP/ATP ratio. Hemolysis, generation of oxidative stress, LDH leakage and reduced ATPase activity were observed in the erythrocytes treated with NPs alone (50 μg/ml), the results were statistically significant at p < 0.05. Oxidative stress was evident by increased levels of malonaldehyde, indicating lipid peroxidation and generation of reactive oxygen species including hydrogen peroxide, together with statistically significant decrease in the activities of catalase and superoxide dismutase and reduced glutathione levels. In the lymphocytes treated with NPs alone (50 μg/ml), cytotoxicity in MTT assay and DNA damage in comet assay were observed; in addition, mitochondrial membrane potential collapsed and ADP/ATP ratio increased indicating mitochondrial function impairment. However, in the presence of CoQ10, hemolysis, oxidative stress and LDH leakage in the erythrocytes and lymphocyte cytotoxicity and DNA damage were drastically reduced, enzyme activities, MMP and ADP/ATP ratio were restored towards normal levels. TiO₂ NPs induce cytotoxicity, damage DNA in lymphocytes, and induce oxidative/anti-oxidative imbalance in erythrocytes. Antioxidant CoQ10 protects erythrocytes and lymphocytes from toxicity induced by TiO₂ NPs.

Effect of fenofibrate on proliferation of SMMC-7721 cells via regulating cell cycle

Liver cancer is a malignant cancer with great harmfulness. Fenofibrate is a peroxisome proliferation activated receptor (PPARα) agonist widely used in the treatment of dyslipidemia. Previous studies have shown that fenofibrate may promote cell proliferation, but the underlying mechanism has not been fully characterized. The aim of this study was to investigate the role of PPARα agonist fenofibrate in cell proliferation of SMMC-7721 cells compared with that of THLE-2 cells. SMMC-7721 and THLE-2 cells were treated with different concentrations of fenofibrate. Cell proliferation was analyzed by MTT, using flow cytometry for cell cycle analysis, and CyclinD1, Cyclin-dependent kinases2 (CDK2) and Proliferating Cell Nuclear Antigen (PCNA) were analyzed by Western blotting. RT-qPCR method was used to assess CDK2, CyclinD1 and PCNA mRNA levels. The results showed that 10^-9-10^-4 mol/L fenofibrate could induce cell growth and 10^-4, 10^-5, 10^-6 mol/L fenofibrate could reduce the number of G0/G1 phase cells and increased in the number of cells in S and G2/M phase of cell cycle in SMMC-7721 cells. Furthermore, fenofibrate could significantly increase the expression of cell cycle related protein (CyclinD1, CDK2)and cell proliferation related proteins (PCNA). The use of PPARα inhibitor MT886 inhibited cell cycle progression and promote tumor cell apoptosis. But fenofibrate had no obvious effect on THLE-2 cells. These results revealed the effect of fenofibrate on the cell cycle of liver cancer cells, and provided a reasonable explanation for studying how fenofibrate promotes cell proliferation.

Aging-independent and size-dependent genotoxic response induced by titanium dioxide nanoparticles in mammalian cells

Titanium dioxide nanoparticles (TiO₂ NPs) are subjected to various transformation processes (chemical, physical and biological processes) in the environment, potentially affecting their bioavailability and toxic properties. However, the size variation of TiO₂ NPs during aging process and subsequent effects in mammalian cells are largely unknown. The aim of this study was to illustrate the adverse effects of TiO₂ NPs in different sizes (5, 15 and <100 nm) during aging process on human-hamster hybrid (A_L) cells. There was an aging-time dependent enhancement of average hydrodynamic size in TiO₂ NPs stock suspensions. The cytotoxicity of fresh TiO₂ NPs increased in a size-dependent manner; in contrast, their genotoxicity decreased with the increasing sizes of NPs. No significant toxicity difference was observed in cells exposed to either fresh or 60 day-aged TiO₂ NPs. Both Fresh and aged TiO₂ NPs efficiently induced mitochondrial dysfunction and activated Caspase-3/7 in a size-dependent manner. Using mitochondrial-DNA deficient (ρ⁰) A_L cells, we further discovered that mitochondrial dysfunction made significant contribution to the size-dependent toxicity induced by TiO₂ NPs during the aging process. Taken together, our data indicated that TiO₂ NPs could significantly induced the cytotoxicity and genotoxicity in an aging time-independent and size-dependent manner, which were triggered by mitochondrial dysfunction. Our study suggested the necessity to include size as an additional parameter for the cautious monitoring of TiO₂ NPs disposal before entering the environment.

Study of mitochondrial swelling, membrane fluidity and ROS production induced by nano-TiO2 and prevented by Fe incorporation

The potential impact of TiO2 and Fe incorporated TiO2 nanoparticles at the organelle level has been reported. The toxicity of the samples on mitochondria isolated from chicken liver tissue has been examined through mitochondrial swelling, membrane fluidity, ROS generation capacity, and activity of complex II. The toxic effect of TiO2 was prevented by incorporating Fe into the TiO2 matrix at different concentrations. The activity of the succinate dehydrogenase enzyme complex was affected and permeabilization of the mitochondrial inner membrane to H+ and K+ and its alteration in membrane fluidity at 100 μg mL-1 of nano-TiO2 dosage were investigated, which showed significant changes in the anisotropy of DPH-labeled mitochondria. Fe incorporation into the TiO2 matrix makes it more biocompatible by changing its structure and morphology.