Impairment of ovarian follicular development caused by titanium dioxide nanoparticles exposure involved in the TGF-ß/BMP/Smad pathway.

Titanium dioxide nanoparticles (TiO2 NPs) have been shown to induce reproductive system damages in animals. To better underline how TiO2 NPs act in reproductive system, female mice were exposed to 2.5, 5, or 10 mg/kg TiO2 NPs by gavage administration for 60 days, the ovary injuries, follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels as well as ovarian follicular development-related molecule expression were investigated. The results showed that TiO2 NPs exposure resulted in reduction of ovary weight and inhibition of ovarian follicular development. Furthermore, the suppression of follicular development was demonstrated to be closely related to higher FSH and LH levels, and higher expression of activin, follistatin, BMP2, BMP4, TGF-ß1, Smad2, Smad3, and Smad4 as well as decreased inhibin-α expression in mouse ovary in a dose-dependent manner. It implies that the impairment of ovarian follicular development caused by TiO2 NPs exposure may be mediated by TGF-ß signal pathway.

Damage to the Blood Brain Barrier Structure and Function from Nano Titanium Dioxide Exposure Involves the Destruction of Key Tight Junction Proteins in the Mouse Brain.

Numerous studies have proven that nano titanium dioxide (nano TiO2) can accumulate in animal brains, where it damages the blood brain barrier (BBB); however, whether this process involves destruction of tight junction proteins in the mouse brain has not been adequately investigated. In this study, mice were exposed to nano TiO2 for 30 consecutive days, and then we used transmission electron microscopy to observe the BBB ultrastructure and the Evans blue assay to evaluate the permeability of the BBB. Our data suggested that nano TiO2 damaged the BBB ultrastructure and increased BBB permeability. Furthermore, we used immunofluorescence and Western blotting to examine the expression of key tight junction proteins, including Occludin, ZO-1, and Claudin-5 in the mouse brain. Our data showed that nano TiO2 reduced Occludin, ZO-1 and Claudin-5 expression. Taken together, nano TiO2-induced damage to the BBB structure and function may involve the destruction of key tight junction proteins.

Nano-TiO2 Reduces Testosterone Production in Primary Cultured Leydig Cells from Rat Testis Through the Cyclic Adenosine Phosphate/Cyclic Guanosine Phosphate/Epidermal Growth Factor Receptor/Matrix Metalloproteinase Signaling Pathway.

Nano-titanium dioxide (nano-TiO2) has been shown to inhibit testosterone synthesis in male mice or rats; however, the mechanisms underlying these effects have yet to be elucidated. In this study, we investigated whether the inhibition of testosterone synthesis by nano-TiO2 on Leydig cells (LCs) was related to the dysfunction of the cAMP/CGMP/EGFR/MMP signaling pathway in primary cultures of LCs prepared from rat testis exposed to nano-TiO2. We found that the early apoptotic rate of LCs increased by 4.34 and 4.94 times, respectively, after exposure to 20 g/mL and 40 g/mL nano-TiO2 ; we also found that NO increased by 1.1 and 2.86 times, respectively. ROS increased by times of 0.71, 3.15 and 3.43; RNS increased by 0.62, 1.34 and 1.14 times; and SOD activity decreased by 18.3%, 28.16%, and 67.6%, respectively, when the concentration of nano-TiO2 was 10, 20 and 40 g/mL. These results indicated that nano-TiO2 treatment resulted caused damage to the LCs, including an imbalance of oxidation and antioxidation. Following nano-TiO2 treatment, the cAMP content had decreased by 48%, 48% and 47.6%; cGMP content had decreased by 18.7%, 52.2% and 56.7%; the levels of ATP in the LCs had decreased by 15.15%, 45.75% and 66.67%; the expression of HCGR protein had decreased by 26.7%, 45.07% and 74.64%; the expression of LHR protein had decreased by 18.3%, 28.16% and 67.6%; and the levels of T had decreased by 34.48%, 46.62% and 44.12%. Collectively, our results indicated that the inhibition of testosterone production by nano-TiO2 is related to the dysfunction of the cAMP/CGMP/EGFR/MMP signaling pathway.

Titanium Dioxide Inhibits Hippocampal Neuronal Synapse Growth Through the Brain-Derived Neurotrophic Factor-Tyrosine Kinase Receptor B Signaling Pathway.

Nanoparticulate titanium dioxide (nano-TiO2) is a commonly used nanoparticle material and has been widely used in the fields of medicine, cosmetics, construction, and environmental protection. Numerous studies have demonstrated that nano-TiO2 has toxic effects on neuronal development, which lead to defects in learning and memory functions. However, it is still unclear whether nano-TiO2 inhibits the development of synapse and the underlying molecular mechanism is still unknown. In this study, nano-TiO2 was administered to rat primary hippocampal neurons for 24 h to investigate the underlying molecular mechanisms behind the inhibition of neuronal synaptic development by nano-TiO2. We used hippocampal neurons as a model to study the effect of nano-TiO2 on synaptic development. Our results demonstrated that dendritic development that represented synaptic plasticity in hippocampal neurons was significantly inhibited in a concentration-dependent manner after exposure to nano-TiO2 for 24 h. Experiments with varying concentrations of nano-TiO2 (5, 15, and 30 g/mL) indicated that the apoptotic rate of hippocampal neurons increased, development of neuronal synapses were inhibited, and synaptic densities decreased by 24.29%, 54.29%, and 72.86%, respectively, in post-treatment with nano-TiO2. Furthermore, the results indicated that the expressions of Synapsin I (SYN I) and postsynaptic density 95 (PSD95) in neuron synapse were also significantly inhibited, particularly SYN I decreased by 18.43%, 37.2%, and 51.6%, and PSD95 decreased by 16.02%, 24.06%, and 38.74% after treatment with varying concentrations of nano-TiO2, respectively. In addition, experiments to assess the BDNF-TrkB signaling pathway indicated that nano-TiO2 inhibited the expressions of key proteins in the downstream MEK/ERK and PI3K/Akt signaling pathways by inhibiting the expression of BDNF. With concentrations of nano-TiO2 at 5, 15, and 30 µg/mL, the expression of BDNF decreased by 22.64%, 33.3%, and 53.58% compared with the control group. Further, the expression ratios of downstream key proteins p-CREB/CREB decreased by 3.03%, 18.11%, and 30.57%; p-ERK1/2/ERK1/2 ratios decreased by 19.11%, 28.82%, and 58.09%, and p-Akt1/Akt1 ratios decreased by 1.92%, 27.79%, and 41.33%, respectively. These results demonstrated that nano-TiO2 inhibited the normal function of the BDNF-TrkB signaling pathway, which is closely related to neuronal synapse. Thus, it can be hypothesized that the inhibition of neuronal synaptic growth by nano-TiO2 may be related to the inhibition of BDNF-TrkB signaling pathway.

Molecular mechanism of mice gastric oxidative damage induced by nanoparticulate titanium dioxide.

BACKGROUND: Nanoparticulate titanium dioxide (Nano-TiO2) has been widely used in food industry, and it has been demonstrated to have adverse effects on mice and human stomach, but its mechanism is rarely concerned. The aim of this study is to determine the effects of nano-TiO2 on the stomach and confirm the role of oxidative stress and apoptosis in the mice gastric damage caused by nano-TiO2, as well as its molecular mechanisms. METHODS: Mice were continuously exposed to nano-TiO2 with 1.25, 2.5 and 5 mg/kg bw by intragastric administration for 9 months in the present study. The ultrastructure, levels of reactive oxygen species (ROS) and peroxides, activities of antioxidant enzymes and mitochondria-related enzymes, ATP contents as well as apoptosis-related factors expression in mice stomach were examined. RESULTS: Oxidative stress, apoptosis and nano-TiO2 aggregation were found in gastric mucosal smooth muscle cells after nano-TiO2 exposure. Nano-TiO2 exposure also resulted in the over-production of ROS and peroxides, decrease of ATP production and activities of antioxidant enzymes and mitochondria-related ATPases, upregulation of apoptosis-related factors including γH2AX, Cyt c, caspase 3, and p-JNK expression, and down-regulation of Bcl-2 expression in mice stomach. CONCLUSIONS: The gastric toxicity of mice induced by chronic exposure to low dose nano-TiO2 may be associated with oxidative stress and mitochondria-mediated apoptosis in mice.

Molecular mechanisms associated with oxidative damage in the mouse testis induced by LaCl3.

China is the world's largest rare earth producer and exporter, previous studies have shown that rare earth elements can cause oxidative damage in animal testis. However, the molecular mechanisms underlying these observations have yet to be elucidated. In this paper, male mice were fed with different doses (10, 20, and 40 mg/kg BW) of LaCl3 for 90 consecutive days, regulatory role of nuclear factor erythroid-2 related factor 2 (Nrf-2)/antioxidant response element (ARE) pathway in testicular oxidative stress induced by LaCl3 were investigated. Analysis showed that LaCl3 exposure could lead to severe testicular pathological changes and apoptosis in spermatogenic cells, it up-regulated the peroxidation of lipids, proteins and DNA, and induced the excessive levels of reactive oxygen species (ROS) production in mouse testis, reduced the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione S epoxide transferase (GST) as well as the glutathione (GSH) content. Furthermore, exposure to LaCl3 also downregulated the expression of Nrf2 and its target gene products, including heme oxygenase 1 (HO-1), glutamate-cysteine ligase catalytic subunit (GCLC), NAD(P)H dehydrogenase [quinine] 1(NQO1), protein kinase C (PKC), and phosphatidylinositol 3-kinase (PI3K), but upregulated the expression of Kelch-like ECH-related protein 1 (Keap1) in damaged mouse testes. Collectively, our data imply that the oxidative damage induced by LaCl3 in testis was related to inhibition of the Nrf-2/AREs pathway activation.

BDE-47 induced apoptosis in zebrafish embryos through mitochondrial ROS-mediated JNK signaling.

2,2,4,4-tetrabromodiphenyl ether (BDE-47) has received considerable attention because of its high detection level in biological samples and potential developmental toxicity. Here, using zebrafish (Danio rerio) as the experimental animal, we investigated developmental effects of BDE-47 and explored the potential mechanism. Zebrafish embryos at 4 h post-fertilization (hpf) were exposed to 0.312, 0.625 and 1.25 mg/L BDE-47 to 74-120 hpf. We found that BDE-47 instigated a dose-related developmental toxicity, evidenced by reduced embryonic survival and hatching rate, shortened body length and increased aberration rate. Meanwhile, higher doses of BDE-47 reduced mitochondrial membrane potential and ATP production but increased apoptosis in zebrafish embryos. Expression of genes involved in mitochondrial oxidative phosphorylation (OXPHOS) (ndufb8, sdha, uqcrc1, cox5ab and atp5fal) were negatively related to BDE-47 doses in zebrafish embryos. Moreover, exposure to BDE-47 at 0.625 or 1.25 mg/L impaired mitochondrial biogenesis and mitochondrial dynamics. Our data further showed that BDE- 47 exposure induced excessive reactive oxygen species (ROS) and oxidative stress, which was accompanied by the activation of c-Jun N-terminal Kinase (JNK). Antioxidant NAC and JNK inhibition could mitigate apoptosis in embryos and improve embryonic development in BDE-47-treated zebrafish, suggesting the involvement of ROS/JNK pathway in embryonic developmental changes induced by BDE-47. Altogether, our data suggest here that developmental toxicity of BDE-47 may be associated with mitochondrial ROS-mediated JNK signaling in zebrafish embryo.

Liver Inflammation and Fibrosis Induced by Long-Term Exposure to Nano Titanium Dioxide (TiO2) Nanoparticles in Mice and Its Molecular Mechanism.

Titanium dioxide (TiO2) and nano-sized titanium dioxide (nano-TiO2), which are used in food production, may be harmful to the body. Long-term exposure to nano-TiO2 can lead to hepatic injury; however, the effect of nano-TiO2 on liver fibrosis and the underlying mechanism remain unclear. The TGF-ß/Smad/MAPK/Wnt signaling pathway is important for tissue fibrosis. In this study, mice were fed nano-TiO2 (2.5, 5, and 10 mg/kg body weight) for nine consecutive months to investigate its effect on liver fibrosis. Nano-TiO2 induced hepatic inflammatory cell infiltration and hepatic fibrosis and upregulated the expression of HIF-1α (+75-fold to +2.38-fold), Wnt3 (+12% to +135%), Wnt4 (1.33-fold to 6-fold), NF-κB (+3.13% to +34.38%), TGF-ß1 (+1307-fold to +1.85-fold), TGF-ß1R (+0.8-fold to 1.33-fold), Smad-2 (+0.58-fold to +1.58-fold), ILK (+0.43-fold to +1.19-fold), ECM (+1.82-fold to 2.36-fold), calpain 2 (+0.11-fold to +0.78-fold), α-SMA (+0.63-fold to +1.56-fold), c-Myc (+0.27-fold to +0.46-fold), and collagen I (+8% to +36%), and increased the phosphorylation level of p38MAPK (+66.67% to +153.33%) in inflammatory and fibrotic liver tissues, whereas it downregulated cyclin D (-6.25% to -43.75%) and decreased the phosphorylation levels of GSK-3ß (-3.12% to -46.88%) and ß-catenin (-19.57% to -45.65%). These results indicate that hepatic fibrosis induced by nano-TiO2 is mediated by the TGF-ß/Smads/MAPK/Wnt signaling pathway. This study provides insight into the mechanism underlying hepatic toxicity induced by nano-TiO2 .

Nanostructured Titanium Dioxide (TiO2) Reduces Sperm Concentration Involving Disorder of Meiosis and Signal Pathway.

Nano-titanium dioxide (nano-TiO2) has been widely used in food and cosmetic industries, and the medical sector. However, nano-TiO2 is potentially toxic to the reproductive system. Previous research has shown that nano-TiO2 can reduce sperm concentration but do not yet known whether this effect occurs because of dysfunctional meiosis in spermatogenic cells. In the present paper, we demonstrate that Nano-TiO2 can penetrate through the blood-testis barrier of a mouse model and enter the testicular tissue, thus causing damage to the testis and epididymis. This reduced the number of developing sperm; we demonstrated that the mechanism underlying this effect was the inhibition or destruction of meiosis in spermatogenic cells, particularly during meiosis I. We also found that the inhibition of meiosis I caused by nano-TiO2 exposure was related to dysfunctional meiosis and that the abnormal expression of meiosis-related factors. Therefore, our data demonstrate that nano-TiO2 reduces sperm concentration by disrupting meiosis and related signaling pathways.

Spermatogenic Apoptosis and the Involvement of the Nrf2 Pathway in Male Mice Following Exposure to Nano Titanium Dioxide.

Titanium dioxide nanoparticles (TiO2 NPs) are largely manufactured and extensively applied for the treatment of environmental pollution. Studies have proved that exposure to TiO2 NPs leads to toxicity of the reproductive system. However, very few studies have highlighted the involvement of nuclear factor erythroid-2 related factor 2 (Nrf2) under TiO2 NPinduced spermatogenic apoptosis. Our findings suggested that TiO2 NPs could cross the blood-testis barrier and were aggregated or deposed in spermatogenic cells, which resulted in spermatogenic apoptosis. Furthermore, exposure to TiO2 NPs caused an overproduction of reactive oxygen species and the peroxidation of lipids, proteins, and DNA. Such exposure also caused significant decreases in the activities of SOD, GSH-PX, GST, and GSH content in the testis. Importantly, exposure to TiO2 NPs resulted in an up-regulation of Keap1 expression and a down-regulation of Nrf2 and its target gene products, NQO1, HO-1, GCLC, PKC, and PI3K. The present study implies that TiO2 NPs could lead to spermatogenic apoptosis, and Nrf2 is the initial factor that responded to such reproductive toxicity by regulating the expression of antioxidative proteins.

Molecular mechanism of nanoparticulate TiO2 induction of axonal development inhibition in rat primary cultured hippocampal neurons.

Numerous studies have demonstrated the in vitro and in vivo neurotoxicity of nanoparticulate titanium dioxide (nano-TiO2 ), a mass-produced material for a large number of commercial and industrial applications. The mechanism of nano-TiO2 -induced inhibition of axonal development, however, is still unclear. In our study, primary cultured hippocampal neurons of 24-hour-old fetal Sprague-Dawley rats were exposed to 5, 15, or 30 µg/mL nano-TiO2 for 6, 12, and 24 hours, and the toxic effects of nano-TiO2 exposure on the axons development were detected and its molecular mechanism investigated. Nano-TiO2 accumulated in hippocampal neurons and inhibited the development of axons as nano-TiO2 concentrations increased. Increasing time in culture resulted in decreasing axon length by 32.5%, 36.6%, and 53.8% at 6 hours, by 49.4%, 53.8%, and 69.5% at 12 hours, and by 44.5%, 58.2%, and 63.6% at 24 hours, for 5, 15, and 30 µg/mL nano-TiO2 , respectively. Furthermore, nano-TiO2 downregulated expression of Netrin-1, growth-associated protein-43, and Neuropilin-1, and promoted an increase of semaphorin type 3A and Nogo-A. These studies suggest that nano-TiO2 inhibited axonal development in rat primary cultured hippocampal neurons and this phenomenon is related to changes in the expression of axon growth-related factors.

Respiratory exposure to nano-TiO2 induces pulmonary toxicity in mice involving reactive free radical-activated TGF-ß/Smad/p38MAPK/Wnt pathways.

Numerous studies have shown that lung injury can be caused by respiratory exposure to nanoparticulate titanium dioxide (nano-TiO2 ), but whether pulmonary inflammation and fibrosis are related to the activation of the TGF-ß/Smad/p38MAPK/Wnt pathways remains unclear. In this study, mice were administrated nano-TiO2 by nasal instillation for nine consecutive months, and the molecular mechanisms of nano-TiO2 on the pulmonary toxicity of mice were examined. The findings suggested that nano-TiO2 caused pneumonia and pulmonary fibrosis. Furthermore, the results also showed that an overproduction of reactive free radicals occurred in mouse lungs, and that the expression of TGF-ß/p38MAPK/Wnt pathway-related factors, including hypoxia-inducible factor 1α (HIF-1α), transforming growth factor-ß1 (TGF-ß1), phosphorylated p38 mitogen activated protein kinases (p-p38MAPK), small mothers against decapentaplegic homolog 2 (Smad2), extracellular matrix (ECM), Wingless/Integrated 3 (Wnt3), Wingless/Integrated 4 (Wnt4), integrin-linked kinase (ILK), ß-catenin, nuclear factor-κB (NF-κB), α-smooth muscle actin (α-SMA), c-Myc, Type I collage (collagen I), and Type collage III (collagen III) were remarkably elevated, while phosphorylated glycogen synthase kinase-3ß (p-GSK-3ß) expression was decreased. Those data implied that the pulmonary inflammation and fibrosis caused by nano-TiO2 exposure may be involved in reactive free radical-mediated activation of the TGF-ß/Smad/p38MAPK/Wnt pathways.

Nanoparticulate TiO2 Induced Suppression of Spermatogenesis is Involved in Regulatory Dysfunction of the cAMP-CREB/CREM Signaling Pathway in Mice.

Long-term exposure to nanoparticulate titanium dioxide (nano-TiO2) is known to cause reductions of sperm numbers and quality in animals, and the cAMP-dependent signaling pathway has been demonstrated to play a key role in regulating spermatogenesis. However, whether the suppression of spermatogenesis induced by nano-TiO2 is related to regulatory disturbances of the cAMP-CREB/CREM signaling pathway is not well investigated. In the current study, male mice were exposed to nano-TiO2 at doses of 1.25, 2.5, or 5 mg/kgbw via gavage instillation for 90 consecutive days and the molecular mechanisms underlying suppression of spermatogenesis caused by nano-TiO2 were investigated. Our findings showed that nano-TiO2 could cross the blood-testis barrier, and accumulated in mouse testes, thus inducing obvious pathological changes and decreasing sperm concentrations and motility, as well as increasing rate of sperm malformation. Furthermore, nano-TiO2 also induced significant reductions in protein expression including cyclic adenosine monophosphate content, protein kinase A, cAMP-responsive element modulator, p-cAMP-response element binding protein, lactate dehydrogenase-C, testis-specific protein kinase 1, and testicular specific CREM activator, and upregulation of protein expression including protein phosphatase, and transducer of regulated CREB 1, which may be associated with reductions of follicle stimulating hormone and luteinizing hormone levels. Together, the present study indicates that the reductions of FSH and LH concentrations and suppression of spermatogenesis in mice caused by nano-TiO2 may be associated with the dysfunctions of the cAMP-CREB/CREM signaling pathway.

Maternal Exposure to Nanoparticulate Titanium Dioxide Causes Inhibition of Hippocampal Development Involving Dysfunction of the Rho/NMDAR Signaling Pathway in Offspring.

Numerous studies have suggested that nano-TiO2 can be translocated to the brain via the placental barrier and blood brain barrier, leading to brain damage and cognitive impairment in both mice and rat offspring. The mechanism of nanoTiO2-induced neurotoxicity is still unclear, as is its role in the inhibition of hippocampal development. In this experiment, nano-TiO2 was employed to investigate whether the inhibition of the hippocampal development of mice offspring involved the alterations in the Rho signaling pathway following consecutive gavage of female mice between 7-21 days postpartum. The results showed that nano-TiO2 particles were concentrated in the hippocampus of offspring, resulting in reduced hippocampal indices and in inhibited axonal and dendritic growth. Furthermore, nano-TiO2 downregulated expression of N-methyl-D-aspartate receptor (NR)1, NR2A, NR2B, RhoGTPase, Ras-related C1 botulinum toxin substrate (Rac1), cell division cycle42 (Cdc42), phosphorylated cAMP response element binding protein (p-CREB), p21-activated kinase (PAK) 3, and PAK1, LIMK (LIM kinase) 1, p-LIMK1, activated Cdc42 kinase (ACK), and myotonic dystrophic kinaseassociated Cdc42-binding kinase (MRCK) and increased expression of RhoA, Rho kinase (ROCK) 1 and cyclin dependent kinase (Cdk) 5 in offspring. In addition, nano-TiO2 disrupted the balance of RhoA/Rac1, RhoA/Cdc42, and Rac1/Cdc42 ratios in the hippocampus of mice offspring. Taken together, these data imply that maternal exposure to nano-TiO2 inhibited development of hippocampal axons and dendrites of offspring may be correlated with the dysfunction of the Rho pathway and that N-methyl-D-aspartate receptors (NMDAR) may also mediate nano-TiO2-Rho pathway interactions.

Retardation of Axonal and Dendritic Outgrowth Is Associated with the MAPK Signaling Pathway in Offspring Mice Following Maternal Exposure to Nanosized Titanium Dioxide.

Exposure to nanosized titanium oxide (nano-TiO2) has been proven to suppress brain growth in mouse offspring; however, whether retardation of axonal or dendritic outgrowth is associated with activation of the mitogen-activated protein kinase (MAPK) pathway remains unclear. In the present study, pregnant mice were exposed to nano-TiO2 at 1.25, 2.5, and 5 mg/kg body weight, and the molecular mechanism of axonal or dendritic outgrowth retardation was investigated. The results suggested that nano-TiO2 crossed the blood-fetal barrier and blood-brain barrier and deposited in the brain of offspring, which retarded axonal and dendritic outgrowth, including the absence of axonal outgrowth, and decreased dendritic filament length, dendritic branching number, and dendritic spine density. Importantly, maternal exposure to nano-TiO2 increased phosphorylated (p)-extracellular signal-regulated kinase1/2 (ERK1/2, +24.35% to +59.4%), p-p38 (+60.82% to 181.85%), and p-c-jun N-terminal kinase (JNK, +28.28% to 97.28%) expression in the hippocampus of the offspring. These findings suggested that retardation of axonal and dendritic outgrowth in mouse offspring caused by maternal exposure to nano-TiO2 may be related to excessive activation of the ERK1/2/MAPK signaling pathway. Therefore, the potential toxicity of nano-TiO2 is a concern, especially in pregnant woman or children who are exposed to nano-TiO2.

Purple sweet potato color protects against high-fat diet-induced cognitive deficits through AMPK-mediated autophagy in mouse hippocampus.

Prevention of obesity-induced cognitive decline is an important public health goal. Purple sweet potato color (PSPC), a class of naturally occurring anthocyanins, has beneficial potentials including antioxidant and neuroprotective activity. Evidence shows that anthocyanins can activate AMP-activated protein kinase (AMPK), a critical mediator of autophagy induction. This study investigated whether PSPC could improve cognitive function through regulating AMPK/autophagy signaling in HFD-fed obese mice. Our results showed that PSPC significantly ameliorated obesity, peripheral insulin resistance and memory impairment in HFD-fed mice. Moreover, enhanced autophagy was observed, along with the decreased levels of protein carbonyls, malondialdehyde and reactive oxygen species (ROS) in the hippocampus of HFD-fed mice due to PSPC administration. PSPC also promoted hippocampal brain-derived neurotrophic factor (BDNF) expression and neuron survival in HFD-fed mouse. These improvements were mediated, at least in part, by the activation of AMPK, which was confirmed by metformin treatment. It is concluded that PSPC has great potential to improve cognitive function in HFD-fed mice via AMPK activation that restores autophagy and protects against hippocampal apoptosis.

Suppression of ovarian follicle development by nano TiO2 is associated with TGF-ß-mediated signaling pathways.

Nanoparticulate titanium dioxide (nano TiO2 ) is extensively applied in biological tissue engineering materials, food additives, cosmetics, and sunscreens. Numerous studies to date have demonstrated that nano TiO2 penetrates through the digestive system and possibly the blood circulation, leading to accumulation in the ovary and consequent reproductive toxicity. However, the mechanisms underlying the toxic effects of nano TiO2 on the female reproductive system remain to be established. In this study, female mice were exposed to different doses of nano TiO2 (1.25, 2.5, or 5 mg/kg body weight) via intragastric administration for 60 consecutive days, followed by investigation of follicular development, regulation of TGF-ß-mediated signaling pathways, and expression of the pathway components. Subchronic exposure to nano TiO2 induced a decrease in the number of primordial, secondary, and antral follicles and corpus luteum and concomitant increase in atretic follicles. Furthermore, follicular development disorder induced by nano TiO2 was associated with upregulation of TGF-ß1, TGF-ßR1, PTEN, and Foxo3a involved in cell growth and apoptosis and downregulation of several growth factors (PI3K, AKT, p-mTOR, p70S6K, p-p70S6K1, rpS6, p-rpS6, TSC1, and TSC2) in mouse ovaries. Our data collectively implied that suppression of ovarian follicle development by nano TiO2 was triggered by dysfunction of the TGF-ß, PI3K/AKT/mTOR, and AKT/p70S6K-rpS6/TSC/mTOR pathways. The adverse effects of nano TiO2 on follicular development highlights the necessity for caution in the use of nanomaterials in the food industry. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 414-422, 2019.

Wnt Pathway-Mediated Nano TiO2-Induced Toxic Effects on Rat Primary Cultured Sertoli Cells.

Nanosized titanium dioxide (Nano TiO2) has been widely used in daily lives, medicine, industry, and caused the potential reproduction toxicity for animals and human, however, the underlying molecular mechanisms for the reproductive toxicity of nano TiO2 are still largely unclear. In the present study, when primary cultured rat Sertoli cells (SCs) were exposed to nano TiO2, cell injury and alterations in wingless related MMTV integration site (Wnt) pathway-related factors including Wnt1, Wnt3a, Wnt5a, Wnt11, ß-catenin, and p-GSK-3ß expression were investigated. The results suggested that nano TiO2 could be translocated to cytoplasm or nucleus, and decreased cell viability, and impaired morphological structures of SCs, induced apoptosis and dead of primary cultured rat SCs. Furthermore, nano TiO2-induced the toxicity of primary cultured rat SCs was associated with increased expression of Wnt1, Wnt3a, Wnt5a, Wnt11, and ß-catenin and involved with reduced p-GSK-3ß expression. Therefore, this implies that nano TiO2-induced toxic effects on SCs may be associated with Wnt signaling pathways.

Suppression of testosterone production by nanoparticulate TiO2 is associated with ERK1/2-PKA-PKC signaling pathways in rat primary cultured Leydig cells.

BACKGROUND: Nanoparticulate titanium dioxide (nano-TiO2) enters the body through various routes and causes organ damage. Exposure to nano-TiO2 is reported to cause testicular injury in mice or rats and decrease testosterone synthesis, sperm number, and motility. Importantly, nano-TiO2 suppresses testosterone production by Leydig cells (LCs) and impairs the reproductive capacity of animals. METHODS: In an attempt to establish the molecular mechanisms underlying the inhibitory effect of nano-TiO2 on testosterone synthesis, primary cultured rat LCs were exposed to varying concentrations of nano-TiO2 (0, 10, 20, and 40 µg/mL) for 24 hours, and alterations in cell viability, cell injury, testosterone production, testosterone-related factors (StAR, 3ßHSD, P450scc, SR-BI, and DAX1), and signaling molecules (ERK1/2, PKA, and PKC) were investigated. RESULTS: The data show that nano-TiO2 crosses the membrane into the cytoplasm or nucleus, triggering cellular vacuolization and nuclear condensation. LC viability decreased in a time-dependent manner at the same nano-TiO2 concentration, nano-TiO2 treatment (10, 20, and 40 µg/mL) decreased MMP (36.13%, 45.26%, and 79.63%), testosterone levels (11.40% and 44.93%), StAR (14.7%, 44.11%, and 72.05%), 3ßHSD (26.56%, 50%, and 79.69%), pERK1/2 (27.83%, 63.61%, and 78.89%), PKA (47.26%, 70.54%, and 85.61%), PKC (30%, 50%, and 71%), SR-BI (16.41%, 41.79%, and 67.16%), and P450scc (39.41%, 55.26%, and 86.84%), and upregulated DAX1 (1.31-, 1.63-, and 3.18-fold) in primary cultured rat LCs. CONCLUSION: Our collective findings indicated that nano-TiO2-mediated suppression of testosterone in LCs was associated with regulation of ERK1/2-PKA-PKC signaling pathways.

Nano-TiO2 Inhibits Development of the Central Nervous System and Its Mechanism in Offspring Mice.

Nano titanium dioxide (Nano-TiO2) has been applied in food packaging systems and food additives, but it may cause potential neurotoxicity for human and animals. In our study, the effects of nano-TiO2 exposure during pregnancy/lactation on the development of the central nervous system in offspring mice were examined and its molecular mechanism involving Rho family was investigated. Our findings showed that pregnancy/lactation exposure to nano-TiO2 resulted in thinning of cerebral and cerebellar cortex, decrease in number of neurons per unit area of cerebrum, edema and nuclear condensation, dysplasia of neurites in hippocampal pyramidal cells, thinning in pyramidal cell layer in hippocampus, and decrease in learning and memory of offspring mice. Furthermore, expressions of Rac1 and Cdc42 involved in axon and dendritic development were decreased, whereas RhoA expression and ratio of RhoA/Rac1 were increased in offspring brain. It implies that exposure to nano-TiO2 during pregnancy/lactation could result in brain retardation and cognitive impairment in offspring mice, which was closely related to alterations in the expression of Rho protein family. Therefore, application of nano-TiO2 in daily life should be performed with caution.