Intragastric exposure to titanium dioxide nanoparticles induced nephrotoxicity in mice, assessed by physiological and gene expression modifications

Chronic exposure to TiO2 micro- and nano particles: A biochemical and histopathological experimental study

The aim of this work was to analyze the effects of long-term exposure to titanium dioxide (TiO2) micro- (MPs) and nanoparticles (NPs) (six and 12 months) on the biochemical and histopathological response of target organs using a murine model. Male Wistar rats were intraperitoneally injected with a suspension of TiO2 NPs (5 nm; TiO2-NP5 group) or MPs (45 μm; TiO2-NP5 group); the control group was injected with saline solution. Six and 12 months post-injection, titanium (Ti) concentration in plasma and target organs was determined spectrometrically (ICP-MS). Blood smears and organ tissue samples were evaluated by light microscopy. Liver and kidney function was evaluated using serum biochemical parameters. Oxidative metabolism was assessed 6 months post-injection (determination of superoxide anion by nitroblue tetrazolium (NBT) test, superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation, and paraoxonase 1). Titanium (Ti) concentration in target organs and plasma was significantly higher in the TiO2-exposed groups than in the control group. Histological evaluation showed the presence of titanium-based particles in the target organs, which displayed no structural alterations, and in blood monocytes. Oxidative metabolism analysis showed that TiO2 NPs were more reactive over time than MPs (p < .05) and mobilization of antioxidant enzymes and membrane damage varied among the studied organs. Clearance of TiO2 micro and nanoparticles differed among the target organs, and lung clearance was more rapid than clearance from the lungs and kidneys (p < .05). Conversely, Ti concentration in plasma increased with time (p < .05). In conclusion, neither serum biochemical parameters nor oxidative metabolism markers appear to be useful as biomarkers of tissue damage in response to TiO2 micro- and nanoparticle deposits at chronic time points.

The DaNa projects: public communication of (nano)material safety data-from conspiracy theories to study quality

In this perspective, the authors give their view on the developments and experiences on communicating on (nano)materials safety. We would like to share our experiences with the scientific community in order to make them useful for future communication activities. We present the long-term work of the science communication projects DaNa, DaNa2.0 and DaNa4.0, running from 2009 to 2023. Starting in the early 2000s with the beginnings of nanotechnology research, communication on the safety of nanomaterials with the public was still very new and faced the projects with many challenges. Today, science communication is indispensable for the dissemination of scientific findings and a fact-based approach like the DaNa "Knowledge Base Materials" creates a trustworthy dialogue with the public. This long-term project series has made a significant contribution to communication on the safety of nanomaterials, perhaps even the largest among publicly funded project series worldwide.

Renal tubular response to titanium dioxide nanoparticles exposure

Titatinum dioxide nanoparticles (TiO2-NPs) are frequently used in several areas. Titanium alloys are employed in orthopedic and odontological surgery (such as hip, knee, and teeth implants). To evaluate the potential acute toxic effects of titanium pieces implantations and in other sources that allow the systemic delivery of titanium, parenteral routes of TiO2-NPs administration should be taken into account. The present study evaluated the impact of subcutaneous administration of TiO2-NPs on renal function and structure in rats. Animals were exposed to a dose of 50 mg/kg b.w., s.c. and sacrificed after 48 h. Titanium levels were detected in urine (135 ± 6 ηg/mL) and in renal tissue (502 ± 40 ηg/g) employing inductively coupled plasma mass spectrometry. An increase in alkaline phosphatase activity, total protein levels, and glucose concentrations was observed in urine from treated rats suggesting injury in proximal tubule cells. In parallel, histopathological studies showed tubular dilatation and cellular desquamation in these nephron segments. In summary, this study demonstrates that subcutaneous administration of TiO2-NPs causes acute nephrotoxicity evidenced by functional and histological alterations in proximal tubule cells. This fact deserves to be mainly considered when humans are exposed directly or indirectly to TiO2-NPs sources that cause the systemic delivery of titanium.

Effects of Nano-titanium Dioxide on Calcium Homeostasis in Vivo and in Vitro: a Systematic Review and Meta-analysis

With the extensive application of titanium dioxide nanoparticles (TiO₂ NPs), their impacts on calcium homeostasis have aroused extensive attention from scholars. However, there are still some controversies in relevant reports. Therefore, a systematic review was performed followed by a meta-analysis to explore whether TiO₂ NPs could induce the imbalance in calcium homeostasis in vivo and in vitro through Revman5.4 and Stata15.0 in this research. 14 studies were included through detailed database retrieval and literature screening. Results indicated that the calcium levels were significantly increased and the activity of Ca²⁺-ATPase was significantly decreased by TiO₂ NPs in vivo and in vitro. Subgroup analysis of the studies in vivo showed that TiO₂ NPs exposure caused a significant increase in calcium levels in rats, exposure to large-sized TiO₂ NPs (> 10 nm) and long-term (> 30 d) exposure could significantly increase calcium levels, and the activity of Ca²⁺-ATPase showed a concentration-dependent downward trend. Subgroup analysis of the studies in vitro revealed that intracellular calcium levels increased significantly in animal cells, exposure to small-sized TiO₂ NPs (≤ 10 nm) and high concentration (> 10 μg/mL) exposure could induce a significant increase in Ca²⁺ concentration, and the activity of Ca²⁺-ATPase also showed a concentration-dependent downward trend. This research showed that the physicochemical properties of TiO₂ NPs and the experimental scheme could affect calcium homeostasis.

Review on Metal-Based Nanoparticles: Role of Reactive Oxygen Species in Renal Toxicity

The rapidly emerging field of nanotechnology has offered innovative discoveries. Due to a wide variety of nanotechnology applications in the industrial, medical, and consumptive products, the application of nanotechnology has received considerable attention in the past decades. Metal-based nanoparticles including metal and metal oxide nanoparticles are now widely utilized in different areas of nanotechnology, leading to an increase in human exposure to nonmaterial. Since the kidney is one of the major organs to remove a variety of potentially harmful substances, including nanoparticles (NPs), from living organisms and a large proportion of cardiac output reaches the kidney, this organ is susceptible to the toxin-induced renal injury. However, despite the extensive use of NPs, there is still a limited understanding of NP-mediated toxicity. The unique physicochemical properties of metal-based NPs not only make them highly desirable in a variety of applications but also enable them to induce changes at biological levels of cellular activities, including reactive oxygen species (ROS) generation. Since oxidative stress is a key factor of NP-induced injury, it is urgent to characterize the ROS response resulting from metal-based NPs. This review summarizes an assessment of the signaling pathways that are involved in the metal-based NP-induced nephrotoxicity, with a particular focus on ROS production along with the potential oxidative stress-dependent mechanism. However, available data show that metal-based NPs may have a severe impact on the renal system, but the exact molecular mechanism of nephrotoxicity is not fully understood. A highly effective strategy for a better understanding of the mechanism would be to collect an increasing volume of information about the exposure time, physicochemical characteristics of the engineered NPs, and the cellular effects. In order to achieve a thorough knowledge of ROS-dependent renal toxicity, both in vitro and in vivo studies should be considered.

Charge-switchable magnetic separation and characterization of food additive titanium dioxide nanoparticles from commercial food

Growing concerns about the potential health effects of nanoscale titanium dioxide (TiO₂) have necessitated the need for monitoring the size distribution and physicochemical properties of food additive TiO₂ that are present in commercial food. Acid digestion is by far the most widely used method to remove interfering food matrices, but the highly corrosive nature of the reaction could alter the physicochemical properties of the TiO₂, which may give a skewed information about the materials. Here, we report an effective approach to extract intact form of food additive TiO₂ nanoparticles from processed food through charge-charge interaction between TiO₂ particles and charge-switchable starch magnetic beads (PL@SMBs), of which the captured TiO₂ is readily harvested by switching the surface charge of PL@SMBs to neutral. The size and surface property of extracted TiO₂ were shown to be well maintained due to the mild nature of the reaction. The extracted TiO₂ particles from 10 commercial processed food showed a size distribution from 40 to 250 nm with a mean diameter of 115 nm, of which 22 % of them were less than 100 nm. The extracted TiO₂ did not exhibit short-term cytotoxicity, but induced cellular oxidative stress at high concentration.

Relative Expression of Mouse Udp-glucuronosyl Transferase 2b1 Gene in the Livers, Kidneys, and Hearts: The Influence of Nonsteroidal Anti-inflammatory Drug Treatment

BACKGROUND

Mouse Udp-glucuronosyl Transferase (UGT) 2b1 is equivalent to the human UGT2B7 enzyme, which is a phase II drug-metabolising enzyme and plays a major role in the metabolism of xenobiotic and endogenous compounds. This study aimed to find the relative expression of the mouse ugt2b1 gene in the liver, kidney, and heart organs and the influence of Nonsteroidal Anti-inflammatory Drug (NSAID) administration.

METHODS

Thirty-five Blab/c mice were divided into 5 groups and treated with different commonly-used NSAIDs; diclofenac, ibuprofen, meloxicam, and mefenamic acid for 14 days. The livers, kidneys, and hearts were isolated, while the expression of ugt2b1 gene was analysed with a quantitative real-time polymerase chain reaction technique.

RESULTS

It was found that the ugt2b1 gene is highly expressed in the liver, and then in the heart and the kidneys. NSAIDs significantly upregulated (ANOVA, p < 0.05) the expression of ugt2b1 in the heart, while they downregulated its expression (ANOVA, p < 0.05) in the liver and kidneys. The level of NSAIDs' effect on ugt2b1 gene expression was strongly correlated (Spearman's Rho correlation, p < 0.05) with NSAID's lipophilicity in the liver and its elimination half-life in the heart.

CONCLUSION

This study concluded that the mouse ugt2b1 gene was mainly expressed in the liver, as 14-day administration of different NSAIDs caused alterations in the expression of this gene, which may influence the metabolism of xenobiotic and endogenous compounds.

In vitro genotoxic effects of titanium dioxide nanoparticles (n-TiO2 ) in human sperm cells

Titanium dioxide nanoparticles (TiO₂ -NPs) are one of the most widely engineered nanoparticles used. The study has been focused on TiO ₂ -NPs genotoxic effects on human spermatozoa in vitro. TiO ₂ -NPs are able to cross the blood-testis barrier induced inflammation, cytotoxicity, and gene expression changes that lead to impairment of the male reproductive system. This study presents new data about DNA damage in human sperms exposed in vitro to two n-TiO ₂ concentrations (1 µg/L and 10 µg/L) for different times and the putative role of reactive oxygen species (ROS) as mediators of n-TiO ₂ genotoxicity. Primary n-TiO ₂ characterization was performed by transmission electron microscopy. The dispersed state of the n-TiO ₂ in media was spectrophotometrically determined at 0, 24, 48, and 72 hr from the initial exposure. The genotoxicity has been highlighted by different experimental approaches (comet assay, terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL] test, DCF assay, random amplification of polymorphic DNA polymerase chain reaction [RAPD-PCR]). The comet assay showed a statistically significant loss of sperm DNA integrity after 30 min of exposure. Increased threshold of sperm DNA fragmentation was highlighted after 30 min of exposure by the TUNEL Test. Also, the RAPD-PCR analysis showed a variation in the polymorphic profiles of the sperm DNA exposed to n-TiO ₂ . The evidence from the DCF assay showed a statistically significant increase in intracellular ROS linked to n-TiO ₂ exposure. This research provides the evaluation of n-TiO ₂ potential genotoxicity on human sperm that probably occurs through the production of intracellular ROS.

The flavonoid quercetin inhibits titanium dioxide (TiO2)-induced chronic arthritis in mice

Titanium dioxide (TiO₂) is a common component of orthopedic prosthesis. However, prosthesis wear releases TiO₂, which induces inflammation and osteolysis in peri-prosthetic tissues. Quercetin is a flavonoid widely present in human diet, which presents biological activities such as antinociceptive, anti-inflammatory and antioxidant effects. Therefore, the effect of intraperitoneal treatment with quercetin in TiO₂-induced arthritis model was evaluated. In the first set of experiments, mice received injection of TiO₂ (0.1-3 mg/knee joint) and articular mechanical hyperalgesia, edema and histopathology analysis were performed in a 30 days protocol. The dose of 3 mg of TiO₂ showed the most harmful effect, and was chosen to the following experiments. Subsequently, mice received 3 mg of TiO₂ followed by post-treatment with quercetin during 30 days. Quercetin (10-100 mg/kg) inhibited in a dose-dependent manner TiO₂-induced knee joint mechanical hyperalgesia, edema and leukocyte recruitment and did not induce damage in major organs such as liver, kidney and stomach. The dose of 30 mg/kg was chosen for the subsequent analysis, and reduced histopathological changes such as leukocyte infiltration, vascular proliferation and synovial hyperplasia (pannus formation) on day 30 after TiO₂ challenge. The protective analgesic and anti-inflammatory mechanisms of quercetin included the inhibition of TiO₂-induced neutrophil and macrophage recruitment, proteoglycan degradation, oxidative stress, cytokine production (TNF-α, IL-1β, IL-6, and IL-10), COX-2 mRNA expression, and bone resorption as well as activation of Nrf2/HO-1 signaling pathway. These results demonstrate the potential therapeutic applicability of the dietary flavonoid quercetin to reduce pain and inflammatory damages associated with prosthesis wear process-induced arthritis.

Many si/shRNAs can kill cancer cells by targeting multiple survival genes through an off-target mechanism

Over 80% of multiple-tested siRNAs and shRNAs targeting CD95 or CD95 ligand (CD95L) induce a form of cell death characterized by simultaneous activation of multiple cell death pathways preferentially killing transformed and cancer stem cells. We now show these si/shRNAs kill cancer cells through canonical RNAi by targeting the 3’UTR of critical survival genes in a unique form of off-target effect we call DISE (death induced by survival gene elimination). Drosha and Dicer-deficient cells, devoid of most miRNAs, are hypersensitive to DISE, suggesting cellular miRNAs protect cells from this form of cell death. By testing 4666 shRNAs derived from the CD95 and CD95L mRNA sequences and an unrelated control gene, Venus, we have identified many toxic sequences - most of them located in the open reading frame of CD95L. We propose that specific toxic RNAi-active sequences present in the genome can kill cancer cells.

Cells store their genetic code within molecules of DNA. Some of this information will be copied into chemically similar molecules called RNAs, from which the sequence of letters in the genetic code can be translated to build proteins. However, these messenger RNAs are not the only RNA molecules that cells can make. MicroRNAs are other short pieces of RNA that closely match sequences in parts of certain messenger RNAs. The messenger RNAs targeted by microRNAs are broken down inside the cell, which reduces how much protein can be produced from them. Since its discovery, scientists have exploited this process – called RNA interference (or RNAi for short) – and designed microRNA-like small interfering RNAs (siRNAs) to target particular messenger RNAs and decrease the levels of the corresponding proteins in countless experiments.

Two proteins that have been studied in RNAi experiments are CD95 and its interaction partner CD95L. Both of these proteins are important in human cancer cells, and targeting them via RNAi killed cancer cells in an unknown mechanism that the cancer cells were unable to resist.

RNAi experiments are designed to be specific, but sometimes they can accidently target other non-target messenger RNAs. Putzbach, Gao, Patel et al. have now analyzed all of the siRNAs that can be made from the messenger RNAs for CD95 and CD95L to mediate RNAi in cancer cells. This revealed that several messenger RNAs, other than those for CD95 and CD95L, were unintentionally being targeted, including many that code for proteins that cells need to survive. Further examination of the messenger RNA for CD95 and CD95L showed that they contain short sequences that are similar to those in the messenger RNAs of the genes that encode these survival proteins. Putzbach et al. were able to study and then predict which siRNA sequences would be toxic to cancer cells.

These findings indicate that an RNAi off-target effect may actually be used to kill cancer cells. Future studies will determine whether this effect could be exploited to shrink tumors in animal models of cancer. If successful, this in turn could lead to new treatments for cancer patients.

Tiron ameliorates oxidative stress and inflammation in titanium dioxide nanoparticles induced nephrotoxicity of male rats

Although the widespread use of titanium dioxide nanoparticles (TiO₂ NPs), few studies were conducted on its hazard influence on human health. Tiron a synthetic vitamin E analog was proven to be a mitochondrial targeting antioxidant. The current investigation was performed to assess the efficacy of tiron against TiO₂ NPs induced nephrotoxicity. Eighty adult male rats divided into four different groups were used: group I was the control, group II received TiO2 NPs (100mg\Kg BW), group III received TiO2 NPs plus tiron (470mg\kg BW), and group IV received tiron alone. Urea, creatinine and total protein concentrations were measured in serum to assess the renal function. Antioxidant status was estimated by determining the activities of glutathione peroxidase, superoxide dismutase, malondialdehyde (MDA) level and glutathione concentration in renal tissue. As well as Renal fibrosis was evaluated though measuring of transforming growth factor-β1 (TGFβ1) and matrix metalloproteinase 9 (MMP9) expression levels and histopathological examination. TiO₂ NPs treated rats showed marked elevation of renal indices, depletion of renal antioxidant enzymes with marked increase in MDA concentration as well as significant up-regulation in fibrotic biomarkers TGFβ1 and MMP9. Oral administration of tiron to TiO₂ NPs treated rats significantly attenuate the renal dysfunction through decreasing of renal indices, increasing of antioxidant enzymes activities, down-regulate the expression of fibrotic genes and improving the histopathological picture for renal tissue. In conclusion, tiron was proved to attenuate the nephrotoxicity induced by TiO₂ NPs through its radical scavenging and metal chelating potency.

Transcriptome analysis of the effects of chitosan on the hyperlipidemia and oxidative stress in high-fat diet fed mice

Transcriptome analysis was performed to investigate the alterations in gene expression after chitosan (CS) treatment on the liver of mice fed with high-fat diet (HFD). The results showed that the body weight, the liver weight and the epididymal fat mass of HFD mice, which were 62.98%, 46.51% and 239.37%, respectively, higher than those of control mice, could be significantly decreased by chitosan supplementation. Also, high-fat diet increased both plasma lipid and liver lipid as compared with the control mice. Chitosan supplementation decreased the plasma lipid and liver lipid, increased the lipoprotein lipase (LPL) and hepatic lipase (HL) activity, increased T-AOC and decreased MDA in the liver and the epididymis adipose as compared with the HFD mice. Transcriptome analysis indicated that increased Mups, Lcn2, Gstm3 and CYP2E1 expressions clearly indicated HFD induced lipid metabolism disorder and oxidative damage. Especially, chitosan treatment decreased the Mup17 and Lcn2 expressions by 64.32% and 82.43% respectively as compared with those of HFD mice. These results indicated that chitosan possess the ability to improve the impairment of lipid metabolism as strongly associated with increased Mups expressions and gene expressions related to oxidative stress.

Toxic Effects of Titanium Dioxide Nanoparticles and Titanium Dioxide Bulk Salt in the Liver and Blood of Male Sprague-Dawley Rats Assessed by Different Assays

This study evaluated the toxic effects of titanium dioxide (TiO2) bulk salt as well as its nanoparticles (NPs) in anatase phase with mean crystallite size of 36.15 nm in male Sprague-Dawley rats by subcutaneous injections at four different dose levels of either control (0), 50, 100 or 150 mg/kg of body weight (BW) of rat for 28 days on alternate days. Animal mortality, haematology, micronucleus assay, liver histology and activities of liver tissue damage markers like, alkaline phosphate (ALP), alanine transaminase (ALT), aspartate transaminase (AST), as well as oxidative stress indicators like superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO) were investigated. The study revealed significant differences (P < 0.05) among control and experimental groups in all the haematological parameters at the end of experiment. Significantly elevated levels (P < 0.05) of ALT, AST and ALP were found for the group treated with TiO2 NPs at the dose of 150 mg/kg of body weight as compared to control. TiO2 and TiO2 NPs caused dose-dependent genotoxicity in the blood cells of the treated rat as revealed by micronuclei test. The highest frequency of micronuclei was observed in rats treated with NPs at the dose of 150 mg/kg BW which was significantly different (P < 0.001) from all other experimental groups after 28 days of exposure. Similarly, all the treatments showed dose-dependent oxidative stress in the treated rats. However, the significantly high decline in the activities of CAT, SOD, and GST as well as elevation in malondialdehyde and GSH was observed in the group receiving NPs at the rate of 150 mg/kg BW. TiO2 also caused histological alterations in the liver. The study revealed that higher dose of TiO2 NPs exerted significantly harmful effects on liver and blood as compared to its lower doses as well as from all other doses of their bulk counterparts.

Toxicity of Nano-Titanium Dioxide (TiO2-NP) Through Various Routes of Exposure: a Review

Nano-titanium dioxide (TiO2) is one of the most commonly used materials being synthesized for use as one of the top five nanoparticles. Due to the extensive application of TiO2 nanoparticles and their inclusion in many commercial products, the increased exposure of human beings to nanoparticles is possible. This exposure could be routed via dermal penetration, inhalation and oral ingestion or intravenous injection. Therefore, regular evaluation of their potential toxicity and distribution in the bodies of exposed individuals is essential. Keeping in view the potential health hazards of TiO2 nanoparticles for humans, we reviewed the research articles about studies performed on rats or other mammals as animal models. Most of these studies utilized the dermal or skin and the pulmonary exposures as the primary routes of toxicity. It was interesting that only very few studies revealed that the TiO2 nanoparticles could penetrate through the skin and translocate to other tissues, while many other studies demonstrated that no penetration or translocation could happen through the skin. Conversely, the TiO2 nanoparticles that entered through the pulmonary route were translocated to the brain or the systemic circulation from where these reached other organs like the kidney, liver, etc. In most studies, TiO2 nanoparticles appeared to have caused oxidative stress, histopathological alterations, carcinogenesis, genotoxicity and immune disruption. Therefore, the use of such materials in humans must be either avoided or strictly managed to minimise risks for human health in various situations.

Decreased spermatogenesis led to alterations of testis-specific gene expression in male mice following nano-TiO2 exposure

Although TiO2 nanoparticles (NPs) exposure has been demonstrated to cross blood-testis barrier and accumulate in the testis resulting in the reduction of sperm numbers, limited data with respect to the molecular mechanism of decreased spermatogenesis caused by TiO2 NP exposure. In this research, testicular damage, sperm number and alterations in testis-specific gene expressions in male mice induced by intragastric administration with TiO2 NPs for six months were investigated. It was found out that TiO2 NPs could migrate to cells, deposit in the testis and epididymis and thus cause damages to relevant organs, which are, to be more specific, the reductions of total sperm concentrations and sperm motility and an enhancement in the number of abnormal sperms in the cauda epididymis. Furthermore, the individual expression regarding to the mRNAs and proteins of testis-specific genes, including Cdc2, Cyclin B1, Dmcl, TERT, Tesmin, TESP-1, XPD and XRCCI, were significantly declined, whereas Gsk3-β and PGAM4 expressions were greatly elevated in mouse testis due to the exposures, which in fact implied that the reduced spermatogenesis may be involved in the alternated testis-specific gene expressions in those exposed male mice.

Causes of genome instability: the effect of low dose chemical exposures in modern society

Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome's integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus, genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling, telomere length), acrylamide (DNA repair, chromosome segregation), bisphenol A (epigenetic modification, DNA damage signaling, mitochondrial function, chromosome segregation), benomyl (chromosome segregation), quinones (epigenetic modification) and nano-sized particles (epigenetic pathways, mitochondrial function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make scientists aware of the increasing need to unravel the underlying mechanisms via which chemicals at low doses can induce genome instability and thus promote carcinogenesis.

Cross talk between poly(ADP-ribose) polymerase 1 methylation and oxidative stress involved in the toxic effect of anatase titanium dioxide nanoparticles

Given the tremendous growth in the application of titanium dioxide nanoparticles (TNPs), concerns about the potential health hazards of TNPs to humans have been raised. Poly(ADP-ribose) polymerase 1 (PARP-1), a highly conserved DNA-binding protein, is involved in many molecular and cellular processes. Limited data demonstrated that certain nanomaterials induced the aberrant hypermethylation of PARP-1. However, the mechanism involved in TNP-induced PARP-1 abnormal methylation has not been studied. A549 cells were incubated with anatase TNPs (22.1 nm) for 24 hours pretreatment with or without methyltransferase inhibitor 5-aza-2′-deoxycytidine and the reactive oxygen species (ROS) scavenger α-lipoic acid to assess the possible role of methylation and ROS in the toxic effect of TNPs. After TNPs characterization, a battery of assays was performed to evaluate the toxic effect of TNPs, PARP-1 methylation status, and oxidative damage. Results showed that TNPs decreased the cell viability in a dose-dependent manner, in accordance with the increase of lactate dehydrogenase activity, which indicated membrane damage of cells. Similar to the high level of PARP-1 methylation, the generation of ROS was significantly increased after exposure to TNPs for 24 hours. Furthermore, α-lipoic acid decreased TNP-induced ROS generation and then attenuated TNP-triggered PARP-1 hypermethylation. Meanwhile, 5-aza-2′-deoxycytidine simultaneously decreased the ROS generation induced by TNPs, resulting in the decline of PARP-1 methylation. In summary, TNPs triggered the aberrant hypermethylation of the PARP-1 promoter and there was a cross talk between oxidative stress and PARP-1 methylation in the toxic effect of TNPs.

TiO2 Nanoparticle Exposure Decreases Spermatogenesis via Biochemical Dysfunctions in the Testis of Male Mice

TiO2 nanoparticles (NPs) have been demonstrated to suppress spermatogenesis in animals, while there is little data related to the biochemical dysfunctions during spermatogenesis due to exposure to TiO2 NPs. In this study, male mice have been exposed to TiO2 NPs via intragastric administration for 60 consecutive days. The findings showed that TiO2 NP exposure resulted in lesions of testis and epididymis, deductions in sperm concentration and sperm motility, and an increase of the number of abnormal sperm in mice. Furthermore, TiO2 NP exposure with 2.5, 5, or 10 mg/kgbw decreased activities of lactate dehydrogenase (-11.59% to -39.84%), sorbitol dehydrogenase (-23.56% to -57.33%), succinate dehydrogenase (-27.04% to -57.85%), glucose-6-phosphate dehydrogenase (-28.3% to -56.42%), Na(+)/K(+)-ATPase (-15.59% to -53.11%), Ca(2+)-ATPase (-12.44% to -55.41%), and Ca(2+)/Mg(2+)-ATPase (-28.25% to -65.72%), and elevated activities of acid phosphatase (+10.48% to +40.0%), alkaline phosphatase (+20.65% to +64.07%), and total nitric oxide synthase (+0.68- to +2.3-fold) in the testes of mice, respectively. In addition, TiO2 NP exposure caused excessive production of reactive oxygen species (+16.15% to +110.62%), and increased malondialdehyde of lipid peroxidation product (+38.96% to +118.07%), carbonyl of protein oxidative product (+20.98% to +108.1%), and 8-hydroxydeoxyguanosine of DNA oxidative product (+0.9- to +1.83-fold) in the testes, respectively. It implied that spermatogenesis suppression caused by TiO2 NP exposure may be associated with alterations of testicular marked enzymes and oxidative stress in the testes.

Measurement of oxidative damage to DNA in nanomaterial exposed cells and animals

Increased levels of oxidatively damaged DNA have been documented in studies of metal, metal oxide, carbon-based and ceramic engineered nanomaterials (ENMs). In particular, 8-oxo-7,8-dihydroguanine-2'-deoxyguanosine (8-oxodG) is widely assessed as a DNA nucleobase oxidation product, measured by chromatographic assays, antibody-based methods or the comet assay with DNA repair enzymes. However, spurious oxidation of DNA has been a problem in certain studies applying chromatographic assays, yielding high baseline levels of 8-oxodG. Antibody-based assays detect high 8-oxodG baseline levels, related to cross-reactivity with other molecules in cells. This review provides an overview of efforts to reliably detect oxidatively damaged DNA and a critical assessment of the published studies on DNA damage levels. Animal studies with high baseline levels of oxidatively damaged DNA are more likely to show positive associations between exposure to ENMs and oxidized DNA in tissue than studies showing acceptable baseline levels (odds ratio = 12.1, 95% confidence interval: 1.2-124). Nevertheless, reliable studies indicate that intratracheal instillation of nanosized carbon black is associated with increased levels of oxidatively damaged DNA in lung tissue. Oral exposure to nanosized carbon black, TiO2 , carbon nanotubes and ZnO is associated with elevated levels of oxidatively damaged DNA in tissues. These observations are supported by cell culture studies showing concentration-dependent associations between ENM exposure and oxidatively damaged DNA measured by the comet assay. Cell culture studies show relatively high variation in the ability of ENMs to oxidatively damage DNA; hence, it is currently impossible to group ENMs according to their DNA damaging potential.

Cell cycle synchronization reveals greater G2/M-phase accumulation of lung epithelial cells exposed to titanium dioxide nanoparticles

Titanium dioxide has been classified in the 2B group as a possible human carcinogen by the International Agency for Research on Cancer, and amid concerns of its exposure, cell cycle alterations are an important one. However, several studies show inconclusive effects, mainly because it is difficult to compare cell cycle effects caused by TiO2 nanoparticle (NP) exposure between different shapes and sizes of NP, cell culture types, and time of exposure. In addition, cell cycle is frequently analyzed without cell cycle synchronization, which may also mask some effects. We hypothesized that synchronization after TiO2 NP exposure could reveal dissimilar cell cycle progression when compared with unsynchronized cell population. To test our hypothesis, we exposed lung epithelial cells to 1 and 10 μg/cm(2) TiO2 NPs for 7 days and one population was synchronized by serum starvation and inhibition of ribonucleotide reductase using hydroxyurea. Another cell population was exposed to TiO2 NPs under the same experimental conditions, but after treatments, cell cycle was analyzed without synchronization. Our results showed that TiO2 NP-exposed cells without synchronization had no changes in cell cycle distribution; however, cell population synchronized after 1 and 10 μg/cm(2) TiO2 NP treatment showed a 1.5-fold and 1.66-fold increase, respectively, in proliferation. Synchronized cells also reveal a faster capability of TiO2 NP-exposed cells to increase cell population in the G2/M phase in the following 9 h after synchronization. We conclude that synchronization discloses a greater percentage of cells in the G2/M phase and higher proliferation than TiO2 NP-synchronized cells.

Critical review of public health regulations of titanium dioxide, a human food additive

From 1916 to 2011, an estimated total of 165050000 metric tons of titanium dioxide (TiO2 ) pigment were produced worldwide. Current safety regulations on the usage of the TiO2 pigment as an inactive ingredient additive in human food are based on legislation from 1969 and are arguably outdated. This article compiles new research results to provide fresh data for potential risk reassessment. However, even after 45 years, few scientific research reports have provided truly reliable data. For example, administration of very high doses of TiO2 is not relevant to daily human uptake. Nevertheless, because dose makes the poison, the literature provides a valuable source for understanding potential TiO2 toxicity after oral ingestion. Numerous scientific articles have observed that TiO2 can pass and be absorbed by the mammalian gastrointestinal tract; can bioconcentrate, bioaccumulate, and biomagnify in the tissues of mammals and other vertebrates; has a very limited elimination rate; and can cause histopathological and physiological changes in various organs of animals. Such action is contrary to the 1969 decision to approve the use of TiO2 as an inactive ingredient in human food without an established acceptable daily intake, stating that neither significant absorption nor tissue storage following ingestion of TiO2 was possible. Thus, relevant governmental agencies should reassess the safety of TiO2 as an additive in human food and consider establishing an acceptable maximum daily intake as a precautionary measure.

Titanium nanoparticle inhalation induces renal fibrosis in mice via an oxidative stress upregulated transforming growth factor-β pathway

Titanium dioxide nanoparticles (Nano-TiO2) are gradually being used extensively in clinical settings, industry, and daily life. Accumulation studies showed that Nano-TiO2 exposure is able to cause injuries in various animal organs, including the lung, liver, spleen, and kidney. However, it remains unclear whether exposure of Nano-TiO2 by inhalation causes renal fibrosis. Here, we investigated the role of reactive oxygen species (ROS)/reactive nitrogen species (RNS) related signaling molecules in chronic renal damage after Nano-TiO2 inhalation in mice. Mice were treated with Nano-TiO2 (0.1, 0.25, and 0.5 mg/week) or microparticle-TiO2 (0.5 mg/week) by nonsurgical intratracheal instillation for 4 weeks. The results showed that Nano-TiO2 inhalation increased renal pathological changes in a dose-dependent manner. No renal pathological changes were observed in microparticle-TiO2-instilled mice. Nano-TiO2 (0.5 mg/week) possessed the ability to precipitate in the kidneys, determined by transmission electron microscopy and increased serum levels of blood urea nitrogen. The expressions of markers of ROS/RNS and renal fibrosis markers, including nitrotyrosine, inducible nitric oxide synthase, hypoxia inducible factor-1α (HIF-1α), heme oxygenase 1, transforming growth factor-β (TGFβ), and collagen I, determined by immunohistochemical staining were increased in the kidneys. Furthermore, Nano-TiO2-induced renal injury could be mitigated by iNOS inhibitor aminoguanidine and ROS scavenger N-acetylcysteine treatment in transcription level. The in vitro experiments showed that Nano-TiO2 significantly and dose-dependently increased the ROS production and the expressions of HIF-1α and TGFβ in human renal proximal tubular cells, which could be reversed by N-acetylcysteine treatment. Taken together, these results suggest Nano-TiO2 inhalation might induce renal fibrosis through a ROS/RNS-related HIF-1α-upregulated TGF-β signaling pathway.

Changes of serum parameters of TiO₂ nanoparticle-induced atherosclerosis in mice

The evaluation of toxicological effects of nanoparticulate matter is increasingly important due to their growing occupational use and presence as compounds in consumer products. Numerous studies have shown that exposure to nanosized particles lead to systemic inflammation in experimental animals, but whether long-term exposure to nanosized particles induces atherogenesis is rarely evaluated. In the current study, mice were continuously exposed to TiO2 nanoparticles (NPs) at 1.25, 2.5, or 5mg/kg body weight, administered by nasal instillation for nine consecutive months, and the association between serum parameter changes and atherosclerosis in mice were investigated. The present findings suggested that chronic exposure to TiO2 NPs resulted in atherogenesis coupling with pulmonary inflammation, increased levels of serum triglycerides, glucose, total cholesterol, low-density lipoprotein cholesterol, advanced glycation end products, reactive oxygen species, NAD(P)H oxidases 4, C-reaction protein, E-selectin, endothelin-1, tissue factor, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, and reduced levels of serum high-density lipoprotein cholesterol, nitric oxide and tissue plasminogen activator. Our study suggests an association of long-term exposure to TiO2 NPs with atherosclerosis and pulmonary inflammation. This finding demonstrates the hypothesized role of TiO2 NPs as a risk factor for atherogenesis.

Mechanisms of nanosized titanium dioxide-induced testicular oxidative stress and apoptosis in male mice

Background

Due to the increased application of titanium dioxide nanoparticles (TiO₂ NPs) in the food industry and daily life, their potential toxic effects in humans and animals have been investigated. However, very few studies have focused on testicular oxidative stress and/or apoptosis.

Methods

In order to understand the possible molecular mechanisms of testicular lesions following exposure to TiO₂ NPs, male mice were exposed to 2.5, 5, or 10 mg/kg body weight TiO₂ NPs for 90 consecutive days. Testicular oxidative stress and apoptosis were then evaluated, and the testicular mRNA expression of several genes and their proteins involved in oxidative stress and/or apoptosis was investigated.

Results

TiO₂ NPs entered Sertoli cells and caused severe testicular oxidative damage and/or apoptosis, accompanied by excessive production of reactive oxygen species and peroxidation of lipids, proteins and DNA as well as a significant reduction in antioxidant capacity. Furthermore, exposure to TiO₂ NPs resulted in the up-regulation of caspase-3, Nrbp2, and cytochrome c expression, and caused down-regulation of SOD, CAT, GPx, GST, GR, Cyp1b1, Car3, Bcl-2, Acaa2, and Axud1 expression in mouse testis.

Conclusions

TiO₂ NPs entered Sertoli cells via the blood-testis barrier and were deposited in mouse seminiferous cord and/or Sertoli cells, causing oxidative damage and apoptosis.

Nano-sized titanium dioxide-induced splenic toxicity: a biological pathway explored using microarray technology

Titanium dioxide nanoparticles (TiO2 NPs) have been widely used in various areas, and its potential toxicity has gained wide attention. However, the molecular mechanisms of multiple genes working together in the TiO2 NP-induced splenic injury are not well understood. In the present study, 2.5, 5, or 10mg/kg body weight TiO2 NPs were administered to the mice by intragastric administration for 90 consecutive days, their immune capacity in the spleen as well as the gene-expressed characteristics in the mouse damaged spleen were investigated using microarray assay. The findings showed that with increased dose, TiO2 NP exposure resulted in the increases of spleen indices, immune dysfunction, and severe macrophage infiltration as well as apoptosis in the spleen. Importantly, microarray data showed significant alterations in the expressions of 1041 genes involved in immune/inflammatory responses, apoptosis, oxidative stress, stress responses, metabolic processes, ion transport, signal transduction, cell proliferation/division, cytoskeleton and translation in the 10 mg/kg TiO2 NP-exposed spleen. Specifically, Cyp2e1, Sod3, Mt1, Mt2, Atf4, Chac1, H2-k1, Cxcl13, Ccl24, Cd14, Lbp, Cd80, Cd86, Cd28, Il7r, Il12a, Cfd, and Fcnb may be potential biomarkers of spleen toxicity following exposure to TiO2 NPs.

Sheet-type titania, but not P25, induced paraptosis accompanying apoptosis in murine alveolar macrophage cells

In this study, we identified the toxic effects of sheet-type titania (TNS), which are being developed as a material for UV-blocking glass, comparing with P25, a benchmark control for titania, in MH-S cells, a mouse alveolar macrophage cell line. After 24 h exposure, the TNS-exposed cells formed large vacuoles while the P25-exposed ones did not. The decreased levels of cell viability were similar between the P25 and TNS groups, but ATP production was clearly lower in cells exposed to the TNS. P25 decreased the expression of calnexin protein, an endoplasmic reticulum (ER) membrane marker, and increased the number of cells generating ROS in a dose dependent manner. Meanwhile, TNS dilated the ER and mitochondria and increased the secretion of NO and pro-inflammatory cytokines, but not of ROS. Subsequently, we studied the molecular response following TNS-induced vacuolization. TNS started to form vacuoles in the cytosol since 20 min after exposure, and the expression of the mitochondria function-related genes were down-regulated the most in the cells exposed for 1 h. After 24 h exposure, the number of apoptotic cells and the relative levels of BAX to Bcl-2 increased. The expression of SOD1 protein, but not of SOD2, also dose-dependently increased with an increase in caspase-8 activity. Additionally, the MAPK pathway was significantly activated, even though the expression of p-EGFR did not change significantly. Furthermore, the number of apoptotic cells increased rapidly with time and with the inhibition of vacuole formation. Taken together, we suggest that P25 and TNS may target different organelles. In addition, TNS, but not P25, induced paraptosis accompanied by apoptosis in MH-S cells, and the formation of the cytoplasmic vacuoles allowed delay apoptosis following TNS exposure.

Use of whole genome expression analysis in the toxicity screening of nanoparticles

The use of nanoparticles (NPs) offers exciting new options in technical and medical applications provided they do not cause adverse cellular effects. Cellular effects of NPs depend on particle parameters and exposure conditions. In this study, whole genome expression arrays were employed to identify the influence of particle size, cytotoxicity, protein coating, and surface functionalization of polystyrene particles as model particles and for short carbon nanotubes (CNTs) as particles with potential interest in medical treatment. Another aim of the study was to find out whether screening by microarray would identify other or additional targets than commonly used cell-based assays for NP action. Whole genome expression analysis and assays for cell viability, interleukin secretion, oxidative stress, and apoptosis were employed. Similar to conventional assays, microarray data identified inflammation, oxidative stress, and apoptosis as affected by NP treatment. Application of lower particle doses and presence of protein decreased the total number of regulated genes but did not markedly influence the top regulated genes. Cellular effects of CNTs were small; only carboxyl-functionalized single-walled CNTs caused appreciable regulation of genes. It can be concluded that regulated functions correlated well with results in cell-based assays. Presence of protein mitigated cytotoxicity but did not cause a different pattern of regulated processes.

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Regulated functions were screened using whole genome expression assays.

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Polystyrene particles regulated more genes than short carbon nanotubes.

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Protein coating of polystyrene particles did not change regulation pattern.

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Functions regulated by microarray were confirmed by cell-based assay.

Th2 factors may be involved in TiO₂ NP-induced hepatic inflammation

TiO2 nanoparticles (NPs) are used in the food industry but have potential toxic effects in humans and animals. The resulting immune response is driven by the production of Th2 cytokines IL-4 and IL-5, which contribute to the development of hepatic inflammation. However, TiO2 NPs have been demonstrated to impair liver function and cause liver inflammation in animal models, which may be associated with activation of Th2 factor-mediated pathways. Mice were administered a gavage instillation of 2.5, 5, or 10 mg/kg body weight TiO2 NPs for six consecutive months. We investigated whether TiO2 NPs activate the Th2 factor-mediated signaling pathway under TiO2 NP-induced hepatic toxicity. The results showed that mice exhibited an accumulation of titanium in the liver, which in turn led to reductions in body weight, increases in liver indices, liver dysfunction, infiltration of inflammatory cells, and hepatocyte apoptosis or necrosis. Furthermore, hepatic inflammation was accompanied by increased (0.67 ± 0.09- to 2.14 ± 0.19-fold) IL-4 expression and up-regulation of its target genes including IL-5 (0.1 ± 0.06- to 0.69 ± 0.12-fold), IL-12 (0.08 ± 0.03- to 0.83 ± 0.21-fold), IFN-γ (0.17 ± 0.09- to 0.87 ± 0.15-fold), GATA3 (0.05 ± 0.02- to 1.29 ± 0.18-fold), GATA4 (0.04 ± 0.01- to 0.87 ± 0.13-fold), T-bet (0.3 ± 0.06- to 0.93 ± 0.15-fold), RORγt (0.32 ± 0.11- to 1.67 ± 0.17-fold), STAt3 (0.16 ± 0.06- to 2.14 ± 0.23-fold), STAT6 (0.2 ± 0.05- to 0.63 ± 0.12-fold), eotaxin (0.53 ± 0.13- to 1.49 ± 0.21-fold), MCP-1 (0.5 ± 0.11- to 0.74 ± 0.18-fold), and MIP-2 (0.27 ± 0.07- to 0.71 ± 0.18-fold) and significant down-regulation of its target gene STAT1 (-0.15 ± 0.05 to -0.81 ± 0.11-fold). Taken together, the alteration of Th2 factor expression may be involved in the control of hepatic inflammation induced by chronic TiO2 NP toxicity.

Characterization of titanium dioxide nanoparticles in food products: analytical methods to define nanoparticles

Titanium dioxide (TiO2) is a common food additive used to enhance the white color, brightness, and sometimes flavor of a variety of food products. In this study 7 food grade TiO2 materials (E171), 24 food products, and 3 personal care products were investigated for their TiO2 content and the number-based size distribution of TiO2 particles present in these products. Three principally different methods have been used to determine the number-based size distribution of TiO2 particles: electron microscopy, asymmetric flow field-flow fractionation combined with inductively coupled mass spectrometry, and single-particle inductively coupled mass spectrometry. The results show that all E171 materials have similar size distributions with primary particle sizes in the range of 60-300 nm. Depending on the analytical method used, 10-15% of the particles in these materials had sizes below 100 nm. In 24 of the 27 foods and personal care products detectable amounts of titanium were found ranging from 0.02 to 9.0 mg TiO2/g product. The number-based size distributions for TiO2 particles in the food and personal care products showed that 5-10% of the particles in these products had sizes below 100 nm, comparable to that found in the E171 materials. Comparable size distributions were found using the three principally different analytical methods. Although the applied methods are considered state of the art, they showed practical size limits for TiO2 particles in the range of 20-50 nm, which may introduce a significant bias in the size distribution because particles <20 nm are excluded. This shows the inability of current state of the art methods to support the European Union recommendation for the definition of nanomaterials.

Molecular interactions of nanomaterials and organisms: defining biomarkers for toxicity and high-throughput screening using traditional and next-generation sequencing approaches

The expression of molecular pathways in an organism provides a clue as to the potential impacts of exposure to nanomaterials.

Immunomodulatory effects in the spleen-injured mice following exposure to titanium dioxide nanoparticles

Immune injuries following the exposure of titanium dioxide nanoparticles (TiO₂ NPs) have been greatly concerned along with the TiO₂ NPs are widely used in pharmacology and daily life. However, very little is known about the immunomodulatory mechanisms in the spleen-injured mice due to TiO₂ NPs exposure. In this study, mice were continuously exposed to 2.5, 5, or 10 TiO₂ NPs mg kg(-1) body weight for 90 days with intragastric administration to investigate the immunomodulatory mechanisms in the spleen. The findings showed that TiO₂ NPs exposure resulted in significant increases in spleen and thymus indices, and titanium accumulation, in turn led to histopathological changes and splenocyte apoptosis. Furthermore, the exposure of TiO₂ NPs could significantly increase the levels of macrophage inflammatory protein (MIP)-1α, MIP-2, Eotaxin, monocyte chemotactic protein-1, interferon-γ, vascular cell adhesion molecule-1, interleukin-13, interferon-γ-inducible protein-10, migration inhibitory factor, CD69, major histocompatibility complex, protein tyrosine phosphatase, protein tyrosine kinase 1, basic fibroblast growth factor, Fasl, and GzmB expression, whereas markedly decrease the levels of NKG2D, NKp46, 2B4 expression involved in immune responses, lymphocyte healing and apoptosis. These findings would better understand toxicological effects induced by TiO₂ NPs exposure.

Renal injury and Nrf2 modulation in mouse kidney following chronic exposure to TiO₂ nanoparticles

TiO₂ nanoparticles (NPs) are used in the food industry but have potential toxic effects in humans and animals. TiO₂ NPs impair renal function and cause oxidative stress and renal inflammation in mice, associated with inhibition of nuclear factor erythroid-2-related factor 2 (Nrf2), which regulates genes encoding many antioxidants and detoxifying enzymes. This study determined whether TiO₂ NPs activated the Nrf2 signaling pathway. Mice exhibited accumulation of reactive oxygen species and peroxidation of lipid, protein, and DNA in the kidney, coupled with renal dysfunction, glutathione depletion, inflammatory cell infiltration, fatty degeneration, and apoptosis. These were associated with increased expression of NOX4, cyclooxygenase-2, and nuclear factor-κB. Oxidative stress and inflammation were accompanied by decreased expression of Nrf2 and down-regulation of its target gene products including heme oxygenase 1, glutamate-cysteine ligase catalytic subunit, and glutathione S-transferase. Chronic TiO₂ NP exposure is associated with suppression of Nrf2, which contributes to the pathogenesis of oxidative stress and inflammation.

Titanium dioxide nanoparticle-induced testicular damage, spermatogenesis suppression, and gene expression alterations in male mice

Although titanium dioxide nanoparticles (TiO2 NPs) have been demonstrated to accumulate in organs resulting in toxicity, there is currently only limited data regarding male reproductive toxicity by TiO2 NPs. In this study, testicular damage and alterations in gene expression profiles in male mice induced by intragastric administration of 2.5, 5, and 10mg/kg body weight of TiO2 NPs for 90 consecutive days were examined. Our findings showed that TiO2 NPs can cross the blood-testis barrier to reach the testis and accumulate therein, which, in turn, results in testicular lesions, sperm malformations, and alterations in serum sex hormone levels. Furthermore, microarray analysis showed that 70 genes with known functions were up-regulated, while 72 were down-regulated in TiO2 NPs-exposed testes. Of the altered gene expressions, Ly6e, Adam3, Tdrd6, Spata19, Tnp2, and Prm1 are involved in spermatogenesis, whereas Sc4mol, Psmc3ip, Mvd, Srd5a2, Lep, and Cyp2e1 are associated with steroid and hormone metabolism. Hence, the production and application of TiO2 NPs should be carried out cautiously, especially by humans of reproductive age.

Comparison of cellular uptake and inflammatory response via toll-like receptor 4 to lipopolysaccharide and titanium dioxide nanoparticles

The innate immune response is the earliest cellular response to infectious agents and mediates the interactions between microbes and cells. Toll-like receptors (TLRs) play an important role in these interactions. We have already shown that TLRs are involved with the uptake of titanium dioxide nanoparticles (TiO₂ NPs) and promote inflammatory responses. In this paper, we compared role of cellular uptake and inflammatory response via TLR 4 to lipopolysaccharide (LPS) and TiO₂ NPs. In the case of LPS, LPS binds to LPS binding protein (LBP) and CD 14, and then this complex binds to TLR 4. In the case of TiO₂ NPs, the necessity of LBP and CD 14 to induce the inflammatory response and for uptake by cells was investigated using over-expression, antibody blocking, and siRNA knockdown experiments. Our results suggested that for cellular uptake of TiO₂ NPs, TLR 4 did not form a complex with LBP and CD 14. In the TiO₂ NP-mediated inflammatory response, TLR 4 acted as the signaling receptor without protein complex of LPS, LBP and CD 14. The results suggested that character of TiO₂ NPs might be similar to the complex of LPS, LBP and CD 14. These results are important for development of safer nanomaterials.