Zinc oxide nanoparticles induce apoptosis by enhancement of autophagy via PI3K/Akt/mTOR inhibition

Ameliorative effects of selenium on arsenic-induced cytotoxicity in PC12 cells via modulating autophagy/apoptosis

Arsenic is well known toxicant responsible for human diseases including cancers. On the other hand, selenium is an essential trace element with significant chemopreventive effects, anticancer potentials and antioxidant properties. Although previous studies have reported antagonism/synergism between arsenic and selenium in biological systems, the biomolecular mechanism/s is still inconclusive. Therefore, to elucidate the molecular phenomena in cellular level, we hypothesized that co-exposure of selenium with arsenic may have suppressive effects on arsenic-induced cytotoxicity. We found that selenium in co-exposure with arsenic increases cell viability, and suppresses oxidative stress induced by arsenic in PC12 cells. Consequently, DNA fragmentation due to arsenic exposure was also reduced by arsenic and selenium co-exposure. Furthermore, western blot analyses revealed that simultaneous exposure of both metals significantly inhibited autophagy which further suppressed apoptosis through positively regulation of key proteins; p-mTOR, p-Akt, p-Foxo1A, p62, and expression of ubiquitin, Bax, Bcl2, NFкB, and caspases 3 and 9, although those are negatively regulated by arsenic. In addition, reverse transcriptase PCR analysis confirmed the involvement of caspase cascade in cell death process induced by arsenic and subsequent inhibition by co-exposure of selenium with arsenic. The cellular accumulation study of arsenic in presence/absence of selenium via inductively coupled plasma mass spectrometry confirmed that selenium effectively retarded the uptake of arsenic in PC12 cells. Finally, these findings imply that selenium is capable to modulate arsenic-induced intrinsic apoptosis pathway via enhancement of mTOR/Akt autophagy signaling pathway through employing antioxidant potentials and through inhibiting the cellular accumulation of arsenic in PC12 cells.

Identification of Exosomal miRNAs in Rats With Pulmonary Neutrophilic Inflammation Induced by Zinc Oxide Nanoparticles

It has been previously shown that inhaled zinc oxide nanoparticles (ZnO-NPs) can modulate inflammation. MicroRNAs (miRNAs) enclosed in exosomes have been identified as an important signature for inflammatory responses. However, the role of exosomal miRNAs during pathogenic inflammation has not been investigated. Healthy rats were exposed to ZnO-NPs (41.7 nm; 2, 4, and 8 mg/kg) or saline (control) via oropharyngeal aspiration. ZnO-NPs induced significant increases in the serum levels of interleukin 8 (IL-8), interleukin-1 beta (IL-1β), and tumor necrosis factor α (TNF-α), and elevated the number of cells and the percentage of neutrophils in the blood. Moreover, exposure to ZnO-NPs increased the levels of lactate dehydrogenase (LDH) activity and total protein in bronchoalveolar lavage fluid (BALF). Differential profiling of miRNAs in isolated serum exosomes revealed that 16 miRNAs were up-regulated and 7 down-regulated in ZnO-NP-treated rats compared with the controls. Functional and pathway analysis indicated that miRNAs may participate in inflammation directly and indirectly through protein and vesicle-mediated transport or regulation of IL-1, oxidative stress, apoptosis, and autophagy. These results suggest that miRNAs in serum exosomes are involved in pulmonary neutrophilic inflammation induced by ZnO-NPs.

MicroRNA-383 upregulation protects against propofol-induced hippocampal neuron apoptosis and cognitive impairment

Anesthesia-induced cognitive impairment is a recognized clinical phenomenon. The present study aimed to investigate the effect of microRNA-383 (miR-383) expression on propofol-induced learning and memory impairment. In total, 48 male Sprague-Dawley rats (weight, 250±10 g) were randomly divided into four groups (n=12 each): Control group, and three groups of rats that were anesthetized with propofol for 6 h and untreated (propofol model group), treated with a constructed lentivirus vector expressing miR-383 mimics (mimic + propofol group), or treated with miR-383 scramble (scramble + propofol group). The learning memory ability, hippocampal neuron apoptosis and expression of apoptosis-associated factors were detected using reverse transcription-quantitiative polymerase chain reaction and western blot analysis. Propofol treatment significantly reduced the relative mRNA and protein expression of miR-383, induced neuron apoptosis, upregulated the Bax/Bcl-2 ratio, downregulated the relative mRNA and protein expression levels of postsynaptic density protein 95 and cAMP-response element binding protein, and inactivated the phosphoinositide 3-kinase/protein kinase B signaling pathway. By contrast, miR-383 mimics significantly altered the propofol-induced dysregulation of the aforementioned factors. In conclusion, miR-383 mimic was able to repair propofol-induced cognitive impairment via protecting against hippocampal neuron apoptosis and dysregulation of related factors. The present study suggested that miR-383 may be used as a potential therapeutic target for the clinical treatment of cognitive impairment induced by propofol anesthesia.

Molecular Mechanisms of Zinc Oxide Nanoparticle-Induced Genotoxicity Short Running Title: Genotoxicity of ZnO NPs

Background: Zinc oxide nanoparticles (ZnO NPs) are among the most frequently applied nanomaterials in consumer products. Evidence exists regarding the cytotoxic effects of ZnO NPs in mammalian cells; however, knowledge about the potential genotoxicity of ZnO NPs is rare, and results presented in the current literature are inconsistent. Objectives: The aim of this review is to summarize the existing data regarding the DNA damage that ZnO NPs induce, and focus on the possible molecular mechanisms underlying genotoxic events. Methods: Electronic literature databases were systematically searched for studies that report on the genotoxicity of ZnO NPs. Results: Several methods and different endpoints demonstrate the genotoxic potential of ZnO NPs. Most publications describe in vitro assessments of the oxidative DNA damage triggered by dissoluted Zn²⁺ ions. Most genotoxicological investigations of ZnO NPs address acute exposure situations. Conclusion: Existing evidence indicates that ZnO NPs possibly have the potential to damage DNA. However, there is a lack of long-term exposure experiments that clarify the intracellular bioaccumulation of ZnO NPs and the possible mechanisms of DNA repair and cell survival.

Nitration of TRPM2 as a Molecular Switch Induces Autophagy During Brain Pericyte Injury

AIMS

Dysfunction of neurovascular pericytes underlies breakdown of the blood-brain barrier, but the molecular mechanisms are largely unknown. In this study, we evaluated the role of the transient receptor potential melastatin-related 2 (TRPM2) channel and autophagy during brain pericyte injury both in vitro and in vivo.

RESULTS

A rapid induction in autophagy in human brain vascular pericytes, in the zinc oxide nanoparticles (ZnO-NP)-induced cell stress model, was paralleled with an increase in the expression of the TRPM2-S truncated isoform, which was abolished by treatment with a nitric oxide synthase inhibitor and a peroxynitrite scavenger. Furthermore, Y1485 in the C-terminus of the TRPM2 protein was identified as the tyrosine nitration substrate by mass spectrometry. Overexpression of the Y1485S TRPM2 mutant reduced LC3-II accumulation and pericyte injury induced by ZnO-NP. Consistently, LC3-II accumulation was reduced and pericytes were better preserved in intact brain microvessels of the TRPM2 knockout mice after ZnO-NP-induced vascular injury. Innovation and Conclusions: Our present study has revealed a novel mechanism of autophagy disturbance secondary to nitrosative stress-induced tyrosine nitration of TRPM2 during pericyte injury. Antioxid. Redox Signal. 27, 1297-1316.

Honokiol induces autophagy and apoptosis of osteosarcoma through PI3K/Akt/mTOR signaling pathway

Honokiol is the main active constituent of Magnolia officinalis. With effective and long‑term pharmacological functions of being antibacterial, anti‑oxidative, anti‑inflammatory, antitumor, anti‑spasmic, anti‑anxiety and anti‑viral, Honokiol is clinically used in the treatment of acute enteritis and chronic gastritis. The aim of the present study was to observe the possible anti‑effects of honokiol on autophagy and apoptosis of osteosarcoma, and to investigate the role of the PI3K/Akt/mTOR signaling pathway in its anticancer effects. MTT assay was used to evaluate cell proliferation and Annexin V‑fluorescein isothiocyanate/propidium iodide staining flow cytometry was used to analyze the apoptotic rate. The authors identified that honokiol could inhibit cell proliferation and induce the apoptotic rate of osteosarcoma cells. The expression level of Bcl‑2‑like protein 4, caspase‑3 and p53 protein expression were induced and cyclin D1 protein expression was suppressed in osteosarcoma cells by honokiol. Autophagy‑associated LC3II protein expression level was promoted, and PI3K, p‑Akt and p‑mTOR protein expression level was suppressed in osteosarcoma cells by honokiol. The present study demonstrated, to the best of the authors' knowledge, for the first time that honokiol induces autophagy and apoptosis of osteosarcoma cells through the PI3K/Akt/mTOR signaling pathway.

ZnO Nanoparticles Protect RNA from Degradation Better than DNA

Gene therapy and RNA delivery require a nanoparticle (NP) to stabilize these nucleic acids when administered in vivo. The presence of degradative hydrolytic enzymes within these environments limits the nucleic acids' pharmacologic activity. This study compared the effects of nanoscale ZnO and MgO in the protection afforded to DNA and RNA from degradation by DNase, serum or tumor homogenate. For double-stranded plasmid DNA degradation by DNase, our results suggest that the presence of MgO NP can protect DNA from DNase digestion at an elevated temperature (65 °C), a biochemical activity not present in ZnO NP-containing samples at any temperature. In this case, intact DNA was remarkably present for MgO NP after ethidium bromide staining and agarose gel electrophoresis where these same stained DNA bands were notably absent for ZnO NP. Anticancer RNA, polyinosinic-polycytidylic acid (poly I:C) is now considered an anti-metastatic RNA targeting agent and as such there is great interest in its delivery by NP. For it to function, the NP must protect it from degradation in serum and the tumor environment. Surprisingly, ZnO NP protected the RNA from degradation in either serum-containing media or melanoma tumor homogenate after gel electrophoretic analysis, whereas the band was much more diminished in the presence of MgO. For both MgO and ZnO NP, buffer-dependent rescue from degradation occurred. These data suggest a fundamental difference in the ability of MgO and ZnO NP to stabilize nucleic acids with implications for DNA and RNA delivery and therapy.

Zinc oxide nanoparticles induce toxic responses in human neuroblastoma SHSY5Y cells in a size-dependent manner

Due to the widespread applications of zinc oxide nanoparticles (ZnO NPs), the potential exposure of workers, consumers, and scientists to these particles has increased. This potential for exposure has attracted extensive attention in the science community. Many studies have examined the toxicological profile of ZnO NPs in the immune system, digestive system, however, information regarding the toxicity of ZnO NPs in the nervous system is scarce. In this study, we detected the cytotoxicity of two types of ZnO NPs of various sizes - ZnOa NPs and ZnOb NPs - and we characterized the shedding ability of zinc ions within culture medium and the cytoplasm. We found that reactive oxygen species played a crucial role in ZnO NP-induced cytotoxicity, likely because zinc ions were leached from ZnO NPs. Apoptosis and cytoskeleton changes were also toxic responses induced by the ZnO NPs, and ZnOb NPs induced more significant toxic responses than ZnOa NPs in SHSY5Y cells. In conclusion, ZnO NPs induced toxic responses in SHSY5Y cells in a size-dependent manner, which can probably be attributed to their ion-shedding ability.

Role of autophagy in cell-penetrating peptide transfection model

Cell-penetrating peptides (CPPs) uptake mechanism is still in need of more clarification to have a better understanding of their action in the mediation of oligonucleotide transfection. In this study, the effect on early events (1 h treatment) in transfection by PepFect14 (PF14), with or without oligonucleotide cargo on gene expression, in HeLa cells, have been investigated. The RNA expression profile was characterized by RNA sequencing and confirmed by qPCR analysis. The gene regulations were then related to the biological processes by the study of signaling pathways that showed the induction of autophagy-related genes in early transfection. A ligand library interfering with the detected intracellular pathways showed concentration-dependent effects on the transfection efficiency of splice correction oligonucleotide complexed with PepFect14, proving that the autophagy process is induced upon the uptake of complexes. Finally, the autophagy induction and colocalization with autophagosomes have been confirmed by confocal microscopy and transmission electron microscopy. We conclude that autophagy, an inherent cellular response process, is triggered by the cellular uptake of CPP-based transfection system. This finding opens novel possibilities to use autophagy modifiers in future gene therapy.

Zinc oxide nanoparticles harness autophagy to induce cell death in lung epithelial cells

Although zinc oxide nanoparticles (ZnONPs) are widely used, they have raised concerns of toxicity in humans. Previous studies have indicated that reactive oxygen species (ROS) and autophagy are involved in the cytotoxicity of ZnONPs, but the regulatory mechanisms between autophagy and ROS remain to be elucidated. Herein, we comprehensively investigated the regulatory mechanism of autophagy and the link between autophagy and ROS in ZnONPs-treated lung epithelial cells. We demonstrated that ZnONPs could induce autophagy, and this process could enhance the dissolution of ZnONPs in lysosomes to release zinc ions. Sequentially, zinc ions released from ZnONPs were able to damage not only lysosomes, leading to impaired autophagic flux, but also mitochondria. Impaired autophagic flux resulted in the accumulation of damaged mitochondria, which could generate excessive ROS to cause cell death. We further demonstrated that the inhibition of autophagy by either pharmacological inhibitors or small interfering RNA (siRNA)-mediated knockdown of Beclin-1 and AMP-activated protein kinase could ameliorate ZnONPs-induced cell death. Moreover, we found that lysosomal-associated membrane protein 1/2 (LAMP-1/2), which were the most abundant highly glycosylated protein in late endosomes/lysosomes, exhibited aberrant expression pattern upon treatment with ZnONPs. Intriguingly, LAMP-2 knockdown, but not LAMP-1 knockdown, could exacerbate the ROS generation and cell death induced by ZnONPs treatment. Meanwhile, LAMP-2 overexpression alleviated ZnONPs-induced cell death, suggesting that LAMP-2 was linked to this toxic phenotype induced by ZnONPs. Our results indicate that autophagic dysfunction could contribute to excessive ROS generation upon treatment with ZnONPs in lung epithelial cells, suggesting that modulating the autophagy process would minimize ZnONPs-associated toxicity.

Aloe-emodin (AE) nanoparticles suppresses proliferation and induces apoptosis in human lung squamous carcinoma via ROS generation in vitro and in vivo

Human lung squamous cell carcinoma is a deadly cancer for which present therapeutic strategies are inadequate. And traditional chemotherapy results in severe systemic toxicity. Compounds from living organisms often exert a biological activity, triggering several targets, which may be useful for the improvement of novel pharmaceuticals. Aloe-emodin (AE), a well-known natural compound, is a primary component of anthraquinones in Aloe vera and exhibits anti-proliferative and apoptotic effects on various tumor cells. However, the translational and clinical use of AE has been limited owing to its rapid degradation and poor bioavailability. To improve its efficacy, a poly (lactic-co-glycolic acid) based AE nanoparticle formulation (NanoAE) was prepared. Our study indicated that compared to the free AE, nanoAE significantly suppressed cancer cell proliferation, induced cell cycle arrest and apoptosis, evidenced by high cleavage of Caspase-3, poly (ADP-ribose) polymerase (PARP), Caspase-8 and Caspase-9. NanoAE enhanced reactive oxygen species (ROS) production, along with Mitogen-activated protein kinases (MAPKs) activation and PI3K/AKT inactivation. Cell proliferation, apoptosis and MAPKs and PI3K/AKT were dependent on ROS production in nanoAE-treated groups. In vivo, nanoAE exhibited inhibitory effects on the tumor growth with little toxicity. Together, our results indicated that nanoAE might be an effective treatment for human lung squamous cell carcinoma.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Prenatal exposure to nanosized zinc oxide in rats: neurotoxicity and postnatal impaired learning and memory ability

AIM

To examine the neurotoxicity of prenatal exposure to ZnO nanoparticles on rat offspring.

MATERIALS & METHODS

Pregnant Sprague-Dawley rats were exposed to ZnO nanoparticles (NPs) by gavage. Toxicity was assessed including zinc biodistribution, cerebral histopathology, antioxidant status and learning and memory capability.

RESULTS

A significantly elevated concentration of zinc was detected in offspring brains. Transmission electron microscope observations showed abnormal neuron ultrastructures. Histopathologic changes such as decreased proliferation and higher apoptotic death were observed. An obvious imbalanced antioxidant status occurred in brains. Adult experimental offspring exhibited impaired learning and memory behavior in the Morris water maze test compared with control groups.

CONCLUSION

These adverse effects on offspring brain may cause impaired learning and memory capabilities in adulthood, particularly in female rats.

Zinc Oxide Nanoparticle-Poly I:C RNA Complexes: Implication as Therapeutics against Experimental Melanoma

There is current interest in harnessing the combined anticancer and immunological effect of nanoparticles (NPs) and RNA. Here, we evaluate the bioactivity of poly I:C (pIC) RNA, bound to anticancer zinc oxide NP (ZnO-NP) against melanoma. Direct RNA association to unfunctionalized ZnO-NP is shown by observing change in size, zeta potential, and absorption/fluorescence spectra upon complexation. RNA corona was visualized by transmission electron microscopy (TEM) for the first time. Binding constant (K_b = 1.6-2.8 g^-1 L) was determined by modified Stern-Volmer, absorption, and biological surface activity index analysis. The pIC-ZnO-NP complex increased cell death for both human (A375) and mouse (B16F10) cell lines and suppressed tumor cell growth in BALB/C-B16F10 mouse melanoma model. Ex vivo tumor analysis indicated significant molecular activity such as changes in the level of phosphoproteins JNK, Akt, and inflammation markers IL-6 and IFN-γ. High throughput proteomics analysis revealed zinc oxide and poly I:C-specific and combinational patterns that suggested possible utility as an anticancer and immunotherapeutic strategy against melanoma.

Inhaled Pollutants: The Molecular Scene behind Respiratory and Systemic Diseases Associated with Ultrafine Particulate Matter

Air pollution of anthropogenic origin is largely from the combustion of biomass (e.g., wood), fossil fuels (e.g., cars and trucks), incinerators, landfills, agricultural activities and tobacco smoke. Air pollution is a complex mixture that varies in space and time, and contains hundreds of compounds including volatile organic compounds (e.g., benzene), metals, sulphur and nitrogen oxides, ozone and particulate matter (PM). PM_0.1 (ultrafine particles (UFP)), those particles with a diameter less than 100 nm (includes nanoparticles (NP)) are considered especially dangerous to human health and may contribute significantly to the development of numerous respiratory and cardiovascular diseases such as chronic obstructive pulmonary disease (COPD) and atherosclerosis. Some of the pathogenic mechanisms through which PM_0.1 may contribute to chronic disease is their ability to induce inflammation, oxidative stress and cell death by molecular mechanisms that include transcription factors such as nuclear factor κB (NF-κB) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Epigenetic mechanisms including non-coding RNA (ncRNA) may also contribute towards the development of chronic disease associated with exposure to PM_0.1. This paper highlights emerging molecular concepts associated with inhalational exposure to PM_0.1 and their ability to contribute to chronic respiratory and systemic disease.

iTRAQ proteomics analysis reveals that PI3K is highly associated with bupivacaine-induced neurotoxicity pathways

Bupivacaine, a commonly used local anesthetic, has potential neurotoxicity through diverse signaling pathways. However, the key mechanism of bupivacaine-induced neurotoxicity remains unclear. Cultured human SH-SY5Y neuroblastoma cells were treated (bupivacaine) or untreated (control) with bupivacaine for 24 h. Compared to the control group, bupivacaine significantly increased cyto-inhibition, cellular reactive oxygen species, DNA damage, mitochondrial injury, apoptosis (increased TUNEL-positive cells, cleaved caspase 3, and Bcl-2/Bax), and activated autophagy (enhanced LC3II/LC3I ratio). To explore changes in protein expression and intercommunication among the pathways involved in bupivacaine-induced neurotoxicity, an 8-plex iTRAQ proteomic technique and bioinformatics analysis were performed. Compared to the control group, 241 differentially expressed proteins were identified, of which, 145 were up-regulated and 96 were down-regulated. Bioinformatics analysis of the cross-talk between the significant proteins with altered expression in bupivacaine-induced neurotoxicity indicated that phosphatidyl-3-kinase (PI3K) was the most frequently targeted protein in each of the interactions. We further confirmed these results by determining the downstream targets of the identified signaling pathways (PI3K, Akt, FoxO1, Erk, and JNK). In conclusion, our study demonstrated that PI3K may play a central role in contacting and regulating the signaling pathways that contribute to bupivacaine-induced neurotoxicity.

Metal homeostasis disruption and mitochondrial dysfunction in hepatocytes exposed to sub-toxic doses of zinc oxide nanoparticles

Increased production and use of zinc oxide nanoparticles (ZnO-NPs) in consumer products has prompted the scientific community to investigate their potential toxicity, and understand their impact on the environment and organisms. Molecular mechanisms involved in ZnO-NP toxicity are still under debate and focus essentially on high dose expositions. In our study, we chose to evaluate the effect of sub-toxic doses of ZnO-NPs on human hepatocytes (HepG2) with a focus on metal homeostasis and redox balance disruptions. We showed massive dissolution of ZnO-NPs outside the cell, transport and accumulation of zinc ions inside the cell but no evidence of nanoparticle entry, even when analysed by high resolution TEM microscopy coupled with EDX. Gene expression analysis highlighted zinc homeostasis disruptions as shown by metallothionein 1X and zinc transporter 1 and 2 (ZnT1, ZnT2) over-expression. Major oxidative stress response genes, such as superoxide dismutase 1, 2 and catalase were not induced. Phase 2 enzymes in term of antioxidant response, such as heme oxygenase 1 (HMOX1) and the regulating subunit of the glutamate-cysteine ligase (GCLM) were slightly upregulated, but these observations may be linked solely to metal homeostasis disruptions, as these actors are involved in both metal and ROS responses. Finally, we observed abnormal mitochondria morphologies and autophagy vesicles in response to ZnO-NPs, indicating a potential role of mitochondria in storing and protecting cells from zinc excess but ultimately causing cell death at higher doses.

Hydroxylated-graphene quantum dots induce cells senescence in both p53-dependent and -independent manner

The numerous particular chemical/physical properties make graphene quantum dots (GQDs) attractive for various biomedical applications such as drug delivery, bioimaging and tumor photodynamic therapy (PDT). In the present study, the critical roles of hydroxyl-modified GQDs (OH-GQDs) on lung carcinoma A549 (wild type p53) and H1299 (p53-null) cells were investigated. Our data showed that a medium concentration (50 μg mL-1) of OH-GQDs significantly decreased the viability of A549 and H1299 cells. OH-GQDs treatment enhanced intracellular reactive oxygen species (ROS) generation. Furthermore, we found that treatment with ROS scavenger N-acetylcysteine (NAC) at least partially abolished the cytotoxic effect of OH-GQDs on A549 and H1299 cells. Hydroxylated GQDs lead to G0-G1 arrest and cells senescence. Signal pathway analysis revealed that OH-GQDs activated the expression of p21 in both a p53-dependent and -independent manner. Consistent with this, OH-GQDs could also inhibit the phosphorylation of Rb in both A549 and H1299 cells. These findings provide valuable information for the consideration of biomedical application of GQDs in the future.

Amorphous silica nanoparticles trigger vascular endothelial cell injury through apoptosis and autophagy via reactive oxygen species-mediated MAPK/Bcl-2 and PI3K/Akt/mTOR signaling

Environmental exposure to silica nanoparticles (SiNPs) is inevitable due to their widespread application in industrial, commercial, and biomedical fields. In recent years, most investigators focus on the evaluation of cardiovascular effects of SiNPs in vivo and in vitro. Endothelial injury and dysfunction is now hypothesized to be a dominant mechanism in the development of cardiovascular diseases. This study aimed to explore interaction of SiNPs with endothelial cells, and extensively investigate the exact effects of reactive oxygen species (ROS) on the signaling molecules and cytotoxicity involved in SiNPs-induced endothelial injury. Significant induction of cytotoxicity as well as oxidative stress, apoptosis, and autophagy was observed in human umbilical vein endothelial cells following the SiNPs exposure (P<0.05). The oxidative stress was induced by ROS generation, leading to redox imbalance and lipid peroxidation. SiNPs induced mitochondrial dysfunction, characterized by membrane potential collapse, and elevated Bax and declined bcl-2 expression, ultimately leading to apoptosis, and also increased number of autophagosomes and autophagy marker proteins, such as LC3 and p62. Phosphorylated ERK, PI3K, Akt, and mTOR were significantly decreased, but phosphorylated JNK and p38 MAPK were increased in SiNPs-exposed endothelial cells. In contrast, all of these stimulation phenomena were effectively inhibited by N-acetylcysteine. The N-acetylcysteine supplement attenuated SiNPs-induced endothelial toxicity through inhibition of apoptosis and autophagy via MAPK/Bcl-2 and PI3K/Akt/mTOR signaling, as well as suppression of intracellular ROS property via activating antioxidant enzyme and Nrf2 signaling. In summary, the results demonstrated that SiNPs triggered autophagy and apoptosis via ROS-mediated MAPK/Bcl-2 and PI3K/Akt/mTOR signaling in endothelial cells, and subsequently disturbed the endothelial homeostasis and impaired endothelium. Our findings may provide experimental evidence and explanation for cardiovascular diseases triggered by SiNPs. Furthermore, results hint that the application of antioxidant may provide a novel way for safer use of nanomaterials.

Molecular Mechanism of Silver Nanoparticles-Induced Human Osteoblast Cell Death: Protective Effect of Inducible Nitric Oxide Synthase Inhibitor

BACKGROUND

Silver nanoparticles (AgNPs) show strong antibacterial properties, making them excellent candidates to be used in orthopaedic repair and regeneration. However, there are concerns regarding the cytotoxicity of AgNPs and molecular mechanisms underlying AgNPs-induced bone cells toxicity have not been elucidated. Therefore, the aim of our study was to explore mechanisms of AgNPs-induced osteoblast cell death with particular emphasis on the role of nitric oxide (NO) generated by inducible nitric oxide synthase (iNOS).

METHODS AND RESULT

Silver nanoparticles used in this study were 18.3±2.6 nm in size, uncoated, spherical, regular shape and their zeta potential was -29.1±2.4 mV as measured by transmission electron microscopy (TEM) and zetasizer. The release of silver (Ag) from AgNPs was measured in cell culture medium by atomic absorption spectroscopy (AAS). The exposure of human osteoblast cells (hFOB 1.19) to AgNPs at concentration of 30 or 60 μg/mL for 24 or 48 hours, respectively resulted in cellular uptake of AgNPs and changes in cell ultrastructure. These changes were associated with apoptosis and necrosis as shown by flow cytometry and lactate dehydrogenase (LDH) assay as well as increased levels of pro-apoptotic Bax and decreased levels of anti-apoptotic Bcl-2 mRNA and protein. Importantly, we have found that AgNPs elevated the levels of nitric oxide (NO) with concomitant upregulation of inducible nitric oxide synthase (iNOS) mRNA and protein. A significant positive correlation was observed between the concentration of AgNPs and iNOS at protein and mRNA level (r = 0.837, r = 0.721, respectively; p<0.001). Finally, preincubation of osteoblast cells with N-iminoethyl-l-lysine (L-NIL), a selective iNOS inhibitor, as well as treating cells with iNOS small interfering RNAs (siRNA) significantly attenuated AgNPs-induced apoptosis and necrosis. Moreover, we have found that AgNPs-induced cells death is not related to Ag dissolution is cell culture medium.

CONCLUSION

These results unambiguously demonstrate that increased expression of iNOS and generation of NO as well as NO-derived reactive species is involved in AgNPs-induced osteoblast cell death. Our findings may help in development of new strategies to protect bone from AgNPs-induced cytotoxicity and increase the safety of orthopaedic tissue repair.

The role of hypoxia-inducible factor-1α in zinc oxide nanoparticle-induced nephrotoxicity in vitro and in vivo

Background

Zinc oxide nanoparticles (ZnO NPs) are used in an increasing number of products, including rubber manufacture, cosmetics, pigments, food additives, medicine, chemical fibers and electronics. However, the molecular mechanisms underlying ZnO NP nephrotoxicity remain unclear. In this study, we evaluated the potential toxicity of ZnO NPs in kidney cells in vitro and in vivo.

Results

We found that ZnO NPs were apparently engulfed by the HEK-293 human embryonic kidney cells and then induced reactive oxygen species (ROS) generation. Furthermore, exposure to ZnO NPs led to a reduction in cell viability and induction of apoptosis and autophagy. Interestingly, the ROS-induced hypoxia-inducible factor-1α (HIF-1α) signaling pathway was significantly increased following ZnO NPs exposure. Additionally, connective tissue growth factor (CTGF) and plasminogen activator inhibitor-1 (PAI-1), which are directly regulated by HIF-1 and are involved in the pathogenesis of kidney diseases, displayed significantly increased levels following ZnO NPs exposure in HEK-293 cells. HIF-1α knockdown resulted in significantly decreased levels of autophagy and increased cytotoxicity. Therefore, our results suggest that HIF-1α may have a protective role in adaptation to the toxicity of ZnO NPs in kidney cells. In an animal study, fluorescent ZnO NPs were clearly observed in the liver, lungs, kidneys, spleen and heart. ZnO NPs caused histopathological lesions in the kidney and increase in serum creatinine and blood urea nitrogen (BUN) which indicate possible renal possible damage. Moreover, ZnO NPs enhanced the HIF-1α signaling pathway, apoptosis and autophagy in mouse kidney tissues.

Conclusions

ZnO NPs may cause nephrotoxicity, and the results demonstrate the importance of considering the toxicological hazards of ZnO NP production and application, especially for medicinal use.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0163-3) contains supplementary material, which is available to authorized users.

Hydrogen-Rich Saline Attenuates Acute Kidney Injury After Liver Transplantation via Activating p53-Mediated Autophagy

BACKGROUND

Acute kidney injury (AKI) impacts the survival of liver transplant recipients severely. To date, the related mechanism and effective therapy have not been rigorously explored. The present study aimed to explore the role of p53-mediated autophagy in the protective effect of hydrogen-rich saline (HRS) on AKI after orthotropic liver transplantation (OLT).

METHODS

Adult male Sprague-Dawley rats were randomly allocated into four groups: sham, OLT, OLT with HRS (6 ml/kg) pretreatment (HS), OLT with HRS and chloroquine pretreatment (60 mg/kg) group (CQ). All the samples were collected 6 hours after reperfusion. The renal function and oxidative stress level were measured by biochemical and histopathologic examinations. The formation of autophagosome was observed by transmission electron microscopy. The apoptotic rate was determined by terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick-end labeling analysis. The expression of caspase-3, cytochrome c, p53, damage-regulated autophagy modulator, Becline-1, microtubule-associated protein light 3-II, p62, lysosome-associated membrane protein-2, and the phosphorylation of p53 were assayed by western blot assay.

RESULTS

Compared with the OLT group, HRS dramatically attenuated the histopathologic damage, restored the renal function, and decreased the oxidative stress level. Simultaneously, HRS significantly ameliorated apoptosis by decreasing the apoptotic rate and inhibiting the expression of caspase-3 and cytochrome c in rats subjected to OLT. The expression of Becline-1 and microtubule-associated protein light 3-II were upregulated with the inhibition of p62 and lysosome-associated membrane protein-2. The inhibition of autophagy by chloroquine counteracted the renoprotective effects of HRS.

CONCLUSIONS

HRS is able to protect against AKI after liver transplantation partly by reducing apoptosis, which is possibly involved in the modulation of p53-mediated autophagy.

High glucose induces autophagy of MC3T3-E1 cells via ROS-AKT-mTOR axis

In the present study, we investigate the function of ROS-AKT-mTOR axis on the apoptosis, proliferation and autophagy of MC3T3-E1 cells, and the proliferation of MC3T3-E1 cells after autophagy inhibition under high glucose conditions. MC3T3-E1 cells cultured in vitro were divided into the following groups: normal control group, N-acetylcysteine (NAC) group, 11.0 mM high glucose group, 11.0 mM high glucose + NAC group, 22.0 mM high glucose group, 22.0 mM high glucose + NAC group, CQ group, 22.0 mM high glucose + CQ group, 3-MA group and 3-MA + 22.0 mM high glucose group. ROS production was measured by DCFH-DA fluorescent probe. Cell proliferation was measured by MTT assay. Cells in different groups were stained with Annexin V-FITC/PI, and then apoptosis rate was detected by flow cytometry. Nucleus morphology was observed under fluorescence microscope after being incubated with Honchest33258. Protein expression was measured using Western blotting and immunofluorescence. Cell apoptosis and proliferation in high glucose group were increased and decreased, respectively, in a dose-dependent manner. Autophagy was significantly induced in high glucose group, even though different concentration of glucose induced autophagy in different stages of autophagy. ROS production in MC3T3-E1 cells was remarkably increased in high glucose group, but not in a dose-dependent manner. NAC, as an antioxidant, reduced ROS production and ameliorated cell apoptosis, proliferation abnormity and autophagy caused by high glucose. Expression of p-AKT and p-mTOR proteins were dramatically decreased in high glucose group, and NAC reversed their expression. In addition, 3-MA, an inhibitor of autophagy, significantly decreased the proliferation of MC3T3-E1 cells. When cocultured with 22.0 mM glucose that induced autophagy, proliferation of MC3T3-E1 cells was not affected compared to 22.0 mM high glucose group. Our present findings reveal that high glucose affects apoptosis, proliferation and autophagy of MC3T3-E1 cells through ROS-AKT-mTOR axis. In addition, autophagy inhibition does not affect the proliferation of MC3T3-E1 cells under high glucose conditions.

Cytotoxicity and autophagy dysfunction induced by different sizes of silica particles in human bronchial epithelial BEAS-2B cells

The adverse effects of silica nanoparticles are gaining attention due to their wide application in biomedicine. However, information about size-dependent toxicity induced by silica nanoparticles is insufficient. In this study, two size of nano-scale (40 nm, 60 nm) and one size of micro-scale (200 nm) silica particles were studied to investigate the possible mechanism of cytotoxicity and autophagy dysfunction in human bronchial epithelial BEAS-2B cells. The cell viability was decreased in a size- and dose-dependent manner, while the LDH activity, oxidative stress and mitochondrial damage significantly increased, induced by both nano- and micro-scale silica particles. Ultrastructural analysis showed that nano-scale silica particles could induce mitochondrial damage and autophagy, but not micro-scale particles. Verified by the autophagy inhibitor 3-MA, the expression of LC3 and SQSTM1/p62 was upregulated in nano-scale silica particles in a size- and dose-dependent manner, while the micro-scale particles had an inhibitory effect. In addition, autophagy activation and autophagy blockage were triggered by nano-scale silica particles via the PI3K/Akt/mTOR pathway. Our findings first demonstrated that exposure to nano-scale silica particles rather than micro-scale particles could lead to autophagy dysfunction and impair cellular homeostasis.

Nano-ZnO leads to tubulin macrotube assembly and actin bundling, triggering cytoskeletal catastrophe and cell necrosis

Zinc is a crucial element in biology that plays chief catalytic, structural and protein regulatory roles. Excess cytoplasmic zinc is toxic to cells so there are cell-entry and intracellular buffering mechanisms that control intracellular zinc availability. Tubulin and actin are two zinc-scavenging proteins that are essential components of the cellular cytoskeleton implicated in cell division, migration and cellular architecture maintenance. Here we demonstrate how exposure to different ZnO nanostructures, namely ZnO commercial nanoparticles and custom-made ZnO nanowires, produce acute cytotoxic effects in human keratinocytes (HaCat) and epithelial cells (HeLa) triggering a dose-dependent cell retraction and collapse. We show how engulfed ZnO nanoparticles dissolve intracellularly, triggering actin filament bundling and structural changes in microtubules, transforming these highly dynamic 25 nm diameter polymers into rigid macrotubes of tubulin, severely affecting cell proliferation and survival. Our results demonstrate that nano-ZnO causes acute cytoskeletal collapse that triggers necrosis, followed by a late reactive oxygen species (ROS)-dependent apoptotic process.

Hydrogen sulfide decreases high glucose/palmitate-induced autophagy in endothelial cells by the Nrf2-ROS-AMPK signaling pathway

Background

Excessive autophagy induced by extravagant oxidative stress is the main reason for diabetes-induced vascular endothelial cells dysfunction. Hydrogen sulfide (H₂S) has anti-oxidative effects but its regulation on excessive autophagy of vascular endothelial cells is unclear.

Methods

In this study, aorta of db/db mice (28 weeks old) and rat aortic endothelial cells (RAECs) treated with 40 mM glucose and 500 μM palmitate acted as type II diabetic animal and cellular models, respectively, and 100 μMNaHS was used as an exogenous H₂S donor. The apoptosis level was measured by terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL) staining and Hoechst 33342/PI staining. The activities of SOD, CAT and respiratory complexes were also measured. The mRNA levels of SOD and CAT were detected by real-time PCR. AMPK-siRNA was used to detect the effect of AMPK on autophagy. Western blotting was used to detected the protein level.

Results

H₂S production was decreased (p < 0.05, p < 0.01) both in vitro and in vivo; NaHS treatment rescued this impairment (p < 0.05, p < 0.01). The expression of adhesive proteins was increased (p < 0.05, p < 0.01) both in vitro and in vivo; NaHS attenuated (p < 0.05, p < 0.01) these alterations. NaHS could protect endothelial cells against apoptosis induced by type II diabetes (p < 0.05, p < 0.01). Furthermore, the expressions and activities of SOD and CAT were impaired (p < 0.05, p < 0.01) in endothelial cells of diabetes II; NaHS treatment attenuated (p < 0.05) this impairment. NaHS also increased ATP production (p < 0.05) and activities of respiratory complexes (p < 0.05), and the ratio of p-AMPK to AMPK was also decreased by NaHS (p < 0.01). The level of autophagy in endothelial cells was also decreased (p < 0.05, p < 0.01) by NaHS treatment and AMPK-siRNA treatment. The expression of Nrf2 in the nuclei was increased (p < 0.05) by NaHS treatment.

Conclusion

Exogenous H₂S might protect arterial endothelial cells by suppressing excessive autophagy induced by oxidative stress through the Nrf2-ROS-AMPK signaling pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s13578-016-0099-1) contains supplementary material, which is available to authorized users.

Nanomaterial-modulated autophagy: underlying mechanisms and functional consequences

Autophagy is an essential lysosome-dependent process that controls the quality of the cytoplasm and maintains cellular homeostasis, and dysfunction of this protein degradation system is correlated with various disorders. A growing body of evidence suggests that nanomaterials (NMs) have autophagy-modulating effects, thus predicting a valuable and promising application potential of NMs in the diagnosis and treatment of autophagy-related diseases. NMs exhibit unique physical, chemical and biofunctional properties, which may endow NMs with capabilities to modulate autophagy via various mechanisms. The present review highlights the impacts of various NMs on autophagy and their functional consequences. The possible underlying mechanisms for NM-modulated autophagy are also discussed.

Autophagy and autophagy dysfunction contribute to apoptosis in HepG2 cells exposed to nanosilica

Great concerns have led to the evaluation of the potential hazards of nanosilica to human health and the environment. However, there still exists persistent debates on the biological effects and toxic consequences induced by nanosilica. The present study investigated both autophagy and apoptosis in ICR mice and Human hepatocellular carcinoma cells (HepG2), and then explored the interactive mechanism between these two distinct cell death modalities in HepG2 cells. Mice liver injuries seen by hematoxylin and eosin (HE) staining indicated the hepatotoxic effects of nanosilica. The TUNEL assay and immunohistochemistry results confirmed that nanosilica could induce both apoptosis and autophagy in vivo. Flow cytometry analysis demonstrated apoptosis induction in vitro, while autophagic ultrastructures, LC3-II expression and immunofluorescence clarified autophagy activation by nanosilica. Apoptosis suppression by the autophagy inhibitor of 3-methyladenine (3-MA) implied that autophagy was involved in apoptotic cell death. A mechanistic study verified that nanosilica induced autophagy via negative regulation of mammalian target of rapamycin (mTOR) signaling but not the Beclin-1 associated pathway. The enhancement of p62 accumulation and mTOR down-regulation might account for the molecular mechanism in contribution of autophagy to apoptosis. As an emerging new mechanism of nanomaterial toxicity, autophagy might be a more susceptive indicator for toxicological consequence evaluation in nanoparticle toxicity. The present study provides novel evidence to elucidate the toxicity mechanisms and may be beneficial to more rational applications of nanosilica in the future.

Biomedical Potential of mTOR Modulation by Nanoparticles

Modulation of the mammalian target of rapamycin (mTOR), the principal regulator of cellular homeostasis, underlies the biological effects of engineered nanoparticles, including regulation of cell death/survival and metabolic responses. Understanding the mechanisms and biological actions of nanoparticle-mediated mTOR modulation may help in developing safe and efficient nanotherapeutics to fight human disease.

Autophagy upregulation promotes macrophages to escape mesoporous silica nanoparticle (MSN)-induced NF-κB-dependent inflammation

BACKGROUND

Our previous studies (Int J Nanomed 10:22, 2015) have indicated that a single large dose of mesoporous silica nanoparticles (MSNs) can induce severe and selective nephrotoxicity, which is closely related to inflammation mediated by the NF-κB pathway. However, the effect of MSNs on other organs and the interactions of nanomaterials with biological systems remain rudimentary.

OBJECTIVE

This study aimed to clarify the biological behaviour and influence of MSNs on macrophages.

METHODS

The mice received a single intraperitoneal injection of a suspension of 150, 300 of 600 mg/kg MSNs, and RAW 264.7 cells were treated with MSNs at various concentrations and times. Cell viability was determined by MTT assay and LDH release assay. The NF-κB pathway and the target proinflammatory cytokines IL-1β and TNF-α were determined by western blotting or ELISA. Autophagy is considered as an emerging mechanism of nanomaterials. So the autophagic ultrastructural analysis, the determination of Beclin-1 and LC3 expression, and the calculation of LC3II dots were employed to verify autophagy activation. In addition, RNA interference, autophagy agonist and inhibitor were used to explore the role of autophagy in inflammation.

RESULTS

The results indicated that MSNs are internalized into macrophages and induce cytotoxicity in a dose- and time-dependent manner. The NF-κB pathway, IL-1β and TNF-α were induced and released by MSNs. The levels of Beclin-1 and LC3II dots were obviously up-regulated by MSNs, which indicated that autophagy was induced in the MSN-treated cells. Moreover, the enhanced autophagy can attenuate the inflammation mediated by the NF-κB pathway, whereas the inhibition of autophagy can contribute to inflammation.

CONCLUSIONS

In summary, our results suggest that autophagy may be a possible protective factor in inflammation induced by MSNs in macrophages.

Zinc-Oxide Nanoparticles Exhibit Genotoxic, Clastogenic, Cytotoxic and Actin Depolymerization Effects by Inducing Oxidative Stress Responses in Macrophages and Adult Mice

Zinc oxide nanoparticles (ZnO-NPs) have wide biological applications, which have raised serious concerns about their impact on the health and environment. Although, various studies have shown ZnO-NP toxicity on different cells underin vitroconditions, sufficient information is lacking regarding toxicity and underlying mechanisms underin vivoconditions. In this work, we investigated genotoxic, clastogenic, and cytotoxic effects of ZnO-NPs on macrophages and in adult mice. ZnO-NP-treated mice showed signs of toxicity such as loss in body weight, passive behavior and reduced survival. Further mechanistic studies revealed that administration of higher dose caused severe DNA damage in peripheral blood and bone marrow cells as evident by the formation of COMET tail, micronuclei, chromosomal fragmentation, and phosphorylation of H2A histone family member X. Moreover, ZnO-NPs inhibited DNA repair mechanism by downregulating the expression offen-1andpolBproteins. Histopathological examinations showed severe inflammation and damage to liver, lungs, and kidneys. Cell viability and wound healing assays revealed that ZnO-NPs killed macrophages in a dose-dependent manner, caused severe wounds and inhibited cellular migration by irreversible actin depolymerization and degradation. Reduction in the viability of macrophages was due to the arrest of the cell cycle at the G0/G1 phase, inhibition of superoxide dismutase and catalase and eventually reactive oxygen species. Furthermore, treatment with an antioxidant drug N-acetyl cysteine significantly reduced the ZnO-NP induced genotoxicity bothin vitroandin vivo Altogether, this study gives detailed pathological insights of ZnO-NP that impair cellular functions, thus will enable to arbitrate their biological applications.

Interplay of Oxidative Stress and Autophagy in PAMAM Dendrimers-Induced Neuronal Cell Death

Poly-amidoamine (PAMAM) dendrimers are proposed to be one of the most promising drug-delivery nanomaterials. However, the toxicity of PAMAM dendrimers on the central nervous system seriously hinders their medical applications. The relationship between oxidative stress and autophagy induced by PAMAM dendrimers, and its underlying mechanism remain confusing. In this study, we reported that PAMAM dendrimers induced both reactive oxygen species and autophagy flux in neuronal cells. Interestingly, autophagy might be triggered by the formation of reactive oxygen species induced by PAMAM dendrimers. Suppression of reactive oxygen species could not only impair PAMAM dendrimers-induced autophagic effects, but also reduce PAMAM dendrimers-induced neuronal cell death. Moreover, inhibition of autophagy could protect against PAMAM dendrimers-induced neuronal cell death. These findings systematically elucidated the interplay between oxidative stress and autophagy in the neurotoxicity of PAMAM dendrimers, which might encourage the application of antioxidants and autophagy inhibitors to ameliorate the neurotoxicity of PAMAM dendrimers in clinic.

Engineered metal based nanoparticles and innate immunity

Almost all people in developed countries are exposed to metal nanoparticles (MeNPs) that are used in a large number of applications including medical (for diagnostic and therapeutic purposes). Once inside the body, absorbed by inhalation, contact, ingestion and injection, MeNPs can translocate to tissues and, as any foreign substance, are likely to encounter the innate immunity system that represent a non-specific first line of defense against potential threats to the host. In this review, we will discuss the possible effects of MeNPs on various components of the innate immunity (both specific cells and barriers). Most important is that there are no reports of immune diseases induced by MeNPs exposure: we are operating in a safe area. However, in vitro assays show that MeNPs have some effects on innate immunity, the main being toxicity (both cyto- and genotoxicity) and interference with the activity of various cells through modification of membrane receptors, gene expression and cytokine production. Such effects can have both negative and positive relevant impacts on humans. On the one hand, people exposed to high levels of MeNPs, as workers of industries producing or applying MeNPs, should be monitored for possible health effects. On the other hand, understanding the modality of the effects on immune responses is essential to develop medical applications for MeNPs. Indeed, those MeNPs that are able to stimulate immune cells could be used to develop of new vaccines, promote immunity against tumors and suppress autoimmunity.

Central nervous system toxicity of metallic nanoparticles

Nanomaterials (NMs) are increasingly used for the therapy, diagnosis, and monitoring of disease- or drug-induced mechanisms in the human biological system. In view of their small size, after certain modifications, NMs have the capacity to bypass or cross the blood–brain barrier. Nanotechnology is particularly advantageous in the field of neurology. Examples may include the utilization of nanoparticle (NP)-based drug carriers to readily cross the blood–brain barrier to treat central nervous system (CNS) diseases, nanoscaffolds for axonal regeneration, nanoelectromechanical systems in neurological operations, and NPs in molecular imaging and CNS imaging. However, NPs can also be potentially hazardous to the CNS in terms of nano-neurotoxicity via several possible mechanisms, such as oxidative stress, autophagy, and lysosome dysfunction, and the activation of certain signaling pathways. In this review, we discuss the dual effect of NMs on the CNS and the mechanisms involved. The limitations of the current research are also discussed.

The critical molecular interconnections in regulating apoptosis and autophagy

Apoptosis and autophagy are both highly regulated biological processes that have important roles in development, differentiation, homeostasis, and disease. These processes may take place independently, with autophagy being cytoprotective for preventing cells from apoptosis and apoptosis blocking autophagy. But in most circumstances, both may be induced sequentially with autophagy preceding apoptosis. The simultaneous activation of both processes has been observed not only in experimental settings but also in pathophysiological conditions. In fact, these two pathways are tightly connected with each other by substantial interplays between them, enabling the coordinated regulation of cell fates by these two pathways. They share some common upstream signaling components, and some components of one pathway may play important roles in the other, and vice versa. Such proteins represent the critical interconnections of the two pathways, which seem to determine the cell for survival or death. Here several critical molecular interconnections between apoptosis and autophagy pathways are reviewed, with their action mechanisms being highlighted.

Zn(II) released from zinc oxide nano/micro particles suppresses vasculogenesis in human endothelial colony-forming cells

Zinc oxide (ZnO) nanoparticles have been widely used in industry, cosmetics, and biomedicine. Recent studies suggested that these nanoparticles could have a major impact on the cardiovascular system. Endothelial progenitor cells (EPCs) contribute to postnatal endothelial repair and regeneration. The present study dissected the effects of ZnO nanoparticles on vasculogenesis using human endothelial colony forming cells (ECFCs), which participate in post-natal vasculogenesis. Two types of ZnO particles were used (nano and micro), in addition to zinc chloride solutions with zinc ion concentrations equal to those in ZnO nanoparticles. Twenty-four-hour exposure induced cytotoxicity in a dose-dependent manner and increased ECFCs apoptosis in all groups. The exposure also reduced the functional capacity of ECFCs on Matrix gel to form tubules, compared with the control cells. These effects were associated with downregulation of expression of vascular endothelial growth factor receptor, VEGFR2 and CXC chemokine receptor, CXCR4. The results suggest that ZnO nanoparticles suppress vasculogenesis from ECFCs through downregulation of the expression of receptors related to vasculogenesis. These effects are based the concentration of released Zn(II).

Genotoxicity and cytotoxicity of ZnO and Al2O3 nanoparticles

OBJECTIVES

Metal oxide nanoparticles (ZnO-NPs and Al2O3-NPs) are used in many fields, including consumer products and biomedical applications. As a result, exposure to these NPs is highly frequent, however, no conclusive information on their potential cytotoxicity and genotoxicity mechanisms are available. For this reason, we studied cytotoxic and genotoxic effects of ZnO-NPs and Al2O3-NPs on human peripheral blood lymphocytes.

MATERIALS AND METHODS

We obtained our goals by using MTT assay, Annexin V-FITC flow cytometry, and alkaline, neural and pH 12.1 versions of comet assay.

RESULTS

Exposure of lymphocytes to both NPs for 24 h slightly decreased viability of lymphocytes at ≥ 0.5 mM. For the first time, we revealed using the comet assays that both ZnO-NPs and Al2O3-NPs caused a concentration-dependent increase of DNA single-strand breaks, but not alkali-labile sites. Treatment with DNA glycosylases showed that the NPs induced oxidative DNA damage. DNA damage caused by both nanoparticles at 0.05 mM was removed within 120 min, however lymphocytes did not repair DNA damage induced by 0.5 mM NPs. Studied nanoparticles did not induce apoptosis in lymphocytes.

CONCLUSION

Our results suggest that ZnO-NPs and Al2O3-NPs at concentration up to 0.5 mM did not exhibit cytotoxic effect but may exert genotoxic effect on lymphocytes, at least partially by the generation of oxidative DNA damage and strand breaks.

Autophagy as the effector and player in DNA damage response of cells to genotoxicants

In this review, we provide an overview and discuss the molecular mechanism of DNA damage induced autophagy, and their mutual regulation and its role in cell fate determination in response to genotoxic effects of environmental toxicants.

Ceria nanoparticles stabilized by organic surface coatings activate the lysosome-autophagy system and enhance autophagic clearance

Cerium oxide nanoparticles (nanoceria) are widely used in a variety of industrial applications including UV filters and catalysts. The expanding commercial scale production and use of ceria nanoparticles have inevitably increased the risk of release of nanoceria into the environment as well as the risk of human exposure. The use of nanoceria in biomedical applications is also being currently investigated because of its recently characterized antioxidative properties. In this study, we investigated the impact of ceria nanoparticles on the lysosome-autophagy system, the main catabolic pathway that is activated in mammalian cells upon internalization of exogenous material. We tested a battery of ceria nanoparticles functionalized with different types of biocompatible coatings (N-acetylglucosamine, polyethylene glycol and polyvinylpyrrolidone) expected to have minimal effect on lysosomal integrity and function. We found that ceria nanoparticles promote activation of the transcription factor EB, a master regulator of lysosomal function and autophagy, and induce upregulation of genes of the lysosome-autophagy system. We further show that the array of differently functionalized ceria nanoparticles tested in this study enhance autophagic clearance of proteolipid aggregates that accumulate as a result of inefficient function of the lysosome-autophagy system. This study provides a mechanistic understanding of the interaction of ceria nanoparticles with the lysosome-autophagy system and demonstrates that ceria nanoparticles are activators of autophagy and promote clearance of autophagic cargo. These results provide insights for the use of nanoceria in biomedical applications, including drug delivery. These findings will also inform the design of engineered nanoparticles with safe and precisely controlled impact on the environment and the design of nanotherapeutics for the treatment of diseases with defective autophagic function and accumulation of lysosomal storage material.