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

Silica nanoparticles induce lung inflammation in mice via ROS/PARP/TRPM2 signaling-mediated lysosome impairment and autophagy dysfunction

Background

Wide applications of nanoparticles (NPs) have raised increasing concerns about safety to humans. Oxidative stress and inflammation are extensively investigated as mechanisms for NPs-induced toxicity. Autophagy and lysosomal dysfunction are emerging molecular mechanisms. Inhalation is one of the main pathways of exposing humans to NPs, which has been reported to induce severe pulmonary inflammation. However, the underlying mechanisms and, more specifically, the interplays of above-mentioned mechanisms in NPs-induced pulmonary inflammation are still largely obscure. Considered that NPs exposure in modern society is often unavoidable, it is highly desirable to develop effective strategies that could help to prevent nanomaterials-induced pulmonary inflammation.

Results

Pulmonary inflammation induced by intratracheal instillation of silica nanoparticles (SiNPs) in C57BL/6 mice was prevented by PJ34, a poly (ADP-ribose) polymerase (PARP) inhibitor. In human lung bronchial epithelial (BEAS-2B) cells, exposure to SiNPs reduced cell viability, and induced ROS generation, impairment in lysosome function and autophagic flux. Inhibition of ROS generation, PARP and TRPM2 channel suppressed SiNPs-induced lysosome impairment and autophagy dysfunction and consequent inflammatory responses. Consistently, SiNPs-induced pulmonary inflammation was prevented in TRPM2 deficient mice.

Conclusion

The ROS/PARP/TRPM2 signaling is critical in SiNPs-induced pulmonary inflammation, providing novel mechanistic insights into NPs-induced lung injury. Our study identifies TRPM2 channel as a new target for the development of preventive and therapeutic strategies to mitigate nanomaterials-induced lung inflammation.

Graphical abstract

Dual role of oxidative stress-JNK activation in autophagy and apoptosis induced by nickel oxide nanoparticles in human cancer cells

Nickel oxide nanoparticles (NiO-NPs) are an important group of nanoparticles with increasing applications in many aspects of industry. At present, there is evidence demonstrating the cytotoxic characteristics of NiO-NPs, while the involvement of autophagy in the cytotoxicity of NiO-NPs has not been reported. In this study, we aimed to study the role of autophagy in the cytotoxicity of NiO-NPs and the underlying regulatory mechanisms. First, we provided evidence that NiO-NPs induce autophagy in human cancer cells. Second, we found that the enhanced autophagic flux by NiO-NPs via the generation of intracellular reactive oxygen species (ROS) from mitochondria and the subsequent activation of the JNK pathway. Third, we demonstrated that the activation of JNK is a main force in mediating NiO-NPs-induced apoptosis. Finally, we demonstrated that the autophagic response plays an important protective role against the cytotoxic effect of NiO-NPs. Therefore, this study identifies the dual role of oxidative stress-JNK activation in the biological effects of NiO-NPs via promoting autophagy and mediating apoptosis. Understanding the protective role of autophagy and the underlying mechanism is important for the potential application of NiO-NPs in the biomedical industry.

p62/SQSTM1 accumulation due to degradation inhibition and transcriptional activation plays a critical role in silica nanoparticle-induced airway inflammation via NF-κB activation

BACKGROUND

Most nanoparticles (NPs) reportedly block autophagic flux, thereby upregulating p62/SQSTM1 through degradation inhibition. p62 also acts as a multifunctional scaffold protein with multiple domains, and is involved in various cellular processes. However, the autophagy substrate-independent role of p62 and its regulation at the transcriptional level upon NPs exposure remain unclear.

RESULTS

In this work, we exposed BEAS-2b cells and mice to silica nanoparticles (SiNPs), and found that SiNPs increased p62 protein levels in vivo and vitro. Then, we further explored the role and mechanism of SiNPs-stimulated p62 in vitro, and found that p62 degradation was inhibited due to autophagic flux blockade. Mechanistically, SiNPs blocked autophagic flux through impairment of lysosomal capacity rather than defective autophagosome fusion with lysosomes. Moreover, SiNPs stimulated translocation of NF-E2-related factor 2 (Nrf2) to the nucleus from the cytoplasm, which upregulated p62 transcriptional activation through direct binding of Nrf2 to the p62 promoter. Nrf2 siRNA dramatically reduced both the mRNA and protein levels of p62. These two mechanisms led to p62 protein accumulation, thus increasing interleukin (IL)-1 and IL-6 expression. SiNPs activated nuclear factor kappa B (NF-κB), and this effect could be alleviated by p62 knockdown.

CONCLUSION

SiNPs caused accumulation of p62 through both pre- and post-translational mechanisms, resulting in airway inflammation. These findings improve our understanding of SiNP-induced pulmonary damage and the molecular targets available to mitigate it.

Synthesis, Characterization, and Investigation of the Antimicrobial Activity of Cetylpyridinium Tetrachlorozincate

Cetylpyridinium tetrachlorozincate (referred to herein as (CP)₂ZnCl₄) was synthesized and its solid-state structure was elucidated via single-crystal X-ray diffraction (SC-XRD), revealing a stoichiometry of C₄₂H₇₆Cl₄N₂Zn with two cetylpyridinium (CP) cations per [ZnCl₄]^2- tetrahedra. Crystal structures at 100 and 298 K exhibited a zig-zag pattern with alternating alkyl chains and zinc units. The material showed potential for application as a broad-spectrum antimicrobial agent, to reduce volatile sulfur compounds (VSCs) generated by bacteria, and in the fabrication of advanced functional materials. Minimum inhibitory concentration (MIC) of (CP)₂ZnCl₄ was 60, 6, and 6 μg mL^-1 for Salmonella enterica, Staphylococcus aureus, and Streptococcus mutans, respectively. The MIC values of (CP)₂ZnCl₄ were comparable to that of pure cetylpyridinium chloride (CPC), despite the fact that approximately 16% of the bactericidal CPC is replaced with bacteriostatic ZnCl₂ in the structure. A modified layer-by-layer deposition technique was implemented to synthesize mesoporous silica (i.e., SBA-15) loaded with approximately 9.0 wt % CPC and 8.9 wt % Zn.

Copper Oxide Nanoparticles Induce Oxidative DNA Damage and Cell Death via Copper Ion-Mediated P38 MAPK Activation in Vascular Endothelial Cells

Background

Inhaled nanoparticles can cross pulmonary air–blood barrier into circulation and cause vascular endothelial injury and progression of cardiovascular disease. However, the molecular mechanism underlying the vascular toxicity of copper oxide nanoparticles (CuONPs) remains unclear. We have recently demonstrated that the release of copper ions and the accumulation of superoxide anions contributed to CuONPs-induced cell death in human umbilical vein endothelial cells (HUVECs). Herein, we further demonstrate the mechanism underlying copper ions-induced cell death in HUVECs.

Methods and Results

CuONPs were suspended in culture medium and vigorously vortexed for several seconds before exposure. After treatment with CuONPs, HUVECs were collected, and cell function assays were conducted to elucidate cellular processes including cell viability, oxidative stress, DNA damage and cell signaling pathways. We demonstrated that CuONPs uptake induced DNA damage in HUVECs as evidenced by γH2AX foci formation and increased phosphorylation levels of ATR, ATM, p53 and H2AX. Meanwhile, we showed that CuONPs exposure induced oxidative stress, indicated by the increase of cellular levels of superoxide anions, the upregulation of protein levels of heme oxygenase-1 (HO-1) and glutamate-cysteine ligase modifier subunit (GCLM), the elevation of the levels of malondialdehyde (MDA), but the reduction of glutathione to glutathione disulfide ratio. We also found that antioxidant N-acetyl-L-cysteine (NAC) could ameliorate CuONPs-induced oxidative stress and cell death. Interestingly, we demonstrated that p38 mitogen-activated protein kinase (MAPK) signaling pathway was activated in CuONPs-treated HUVECs, while p38α MAPK knockdown by siRNA significantly rescued HUVECs from CuONPs-induced DNA damage and cell death. Importantly, we showed that copper ions chelator tetrathiomolybdate (TTM) could alleviate CuONPs-induced oxidative stress, DNA damage, p38 MAPK pathway activation and cell death in HUVECs.

Conclusion

We demonstrated that CuONPs induced oxidative DNA damage and cell death via copper ions-mediated p38 MAPK activation in HUVECs, suggesting that the release of copper ions was the upstream activator for CuONPs-induced vascular endothelial toxicity, and the copper ions chelator TTM can alleviate CuONPs-associated cardiovascular disease.

Effects of titanium dioxide and zinc oxide nano-materials on lipid order in model membranes

Engineered nano-materials (ENM) have been reported to affect lipid membrane permeability in cell models, but a mechanistic understanding of how these materials interact with biological membranes has not been described. To assess mechanisms of permeability, liposomes composed of DOPC, DOPS, or POPC, with or without cholesterol, were used as model membranes for measuring ENM-induced changes to lipid order to improve our understanding of ENM effects on membrane permeability. Liposomes were treated with either titanium dioxide (TiO₂) or zinc oxide (ZnO) ENM, and changes to lipid order were measured by time-resolved fluorescence anisotropy of a lipophilic probe, Di-4-ANEPPDHQ. Both ENM increased lipid order in two lipid models differing in headgroup charge. TiO₂ increased lipid order of POPC liposomes (neutral charge), while ZnO acted primarily on DOPS liposomes (negative charge). Addition of cholesterol to these models significantly increased lipid order while in some cases attenuated ENM-induced changes to lipid order. To assess the ability of ENM to induce membrane permeability, liposomes composed of the above lipids were assayed for membrane permeability by calcein leakage in response to ENM. Both ENM caused a dose-dependent increase in permeability in all liposome models tested, and the addition of cholesterol to the liposome models neither blocked nor reduced calcein leakage. Together, these experiments show that ENM increased permeability of small molecules (calcein) from model liposomes, and that the magnitude of the effect of ENM on lipid order depended on ENM surface charge, lipid head group charge and the presence of cholesterol in the membrane.

Subchronic continuous inhalation exposure to zinc oxide nanoparticles induces pulmonary cell response in mice

OBJECTIVES

We used mice as an animal model to investigate the entry of ZnO nanoparticles from the ambient air into the lungs and other organs, subsequent changes in Zn levels and the impact on the transcription of Zn homeostasis-related genes in the lungs.

METHODS

The mice were exposed to two concentrations of ZnO nanoparticles; lower (6.46 × 104 particles/cm3) and higher (1.93 × 106 particles/cm3), allowed to breathe the nanoparticles in the air for 12 weeks and subjected to necropsy. Characterization of the ZnO nanoparticles was done using transmission electron microscopy (TEM). Energy-dispersive X-ray (EDX) spectroscopy was used to quantify ZnO nanoparticles in the lungs, brain, liver and kidney. The total zinc content in the lungs, brain, liver, kidney, red blood cells and plasma was estimated by inductively coupled plasma mass spectroscopy (ICP-MS). Transcription rate of the genes was evaluated by RealTime PCR.

RESULTS

The two concentration of ZnO nanoparticles in the ambient air produced two different outcomes. The lower concentration resulted in significant increases in Zn content of the liver while the higher concentration significantly increased Zn in the lungs (p < 0.05). Additionally, at the lower concentration, Zn content was found to be lower in brain tissue (p < 0.05). Using TEM/EDX we detected ZnO nanoparticles inside the cells in the lungs, kidney and liver. Inhaling ZnO NP at the higher concentration increased the levels of mRNA of the following genes in the lungs: Mt2 (2.56 fold), Slc30a1 (1.52 fold) and Slc30a5 (2.34 fold). At the lower ZnO nanoparticle concentration, only Slc30a7 mRNA levels in the lungs were up (1.74 fold). Thus the two air concentrations of ZnO nanoparticles produced distinct effects on the expression of the Zn-homeostasis related genes.

CONCLUSION

Until adverse health effects of ZnO nanoparticles deposited in organs such as lungs are further investigated and/or ruled out, the exposure to ZnO nanoparticles in aerosols should be avoided or minimised.

Toxicity assessment of metal oxide nanomaterials using in vitro screening and murine acute inhalation studies

Characterizations and in vitro toxicity screening were performed on metal oxide engineered nanomaterials (ENMs) independently comprising ZnO, CuO, CeO₂, Fe₂O₃, WO₃, V₂O₅, TiO₂, Al₂O₃ and MgO. Nanomaterials that exhibited the highest toxicity responses in the in vitro screening assays (ZnO, CuO, and V₂O₅) and the lesser explored material WO₃ were tested for acute pulmonary toxicity in vivo. Female and male mice (C57Bl/6J) were exposed to aerosolized metal oxide ENMs in a nose-only exposure system and toxicity outcomes (biomarkers of cytotoxicity, immunotoxicity, inflammation, and lung histopathology) at 4 and 24 h after the start of exposure were assessed. The studies were performed as part of the NIEHS Nanomaterials Health Implications Research consortium with the purpose of investigating the effects of ENMs on various biological systems. ENMs were supplied by the Engineered Nanomaterials Resource and Coordination Core. Among the ENMs studied, the highest toxicity was observed for CuO and ZnO NPs in both in vitro and in vivo acute models. Compared to sham-exposed controls, there was a significant increase in bronchoalveolar lavage neutrophils and proinflammatory cytokines and a loss of macrophage viability at both 4 h and 24 h for ZnO and CuO but not seen for V₂O₅ or WO₃. These effects were observed in both female and male mice. The cell viability performed after in vitro exposure to ENMs and assessment of lung inflammation after acute inhalation exposure in vivo were shown to be sensitive endpoints to predict ENM acute toxicity.

The Effects of 50 nm Unmodified Nano-ZnO on Lipid Metabolism and Semen Quality in Male Mice

Fifty male mice were exposed to 50 nm unmodified nano-ZnO through intragastric administration for 90 days to detect the long-term effects of unmodified nano-ZnO in mice. Results showed that the blood glucose, serum follicle stimulating hormone, luteinizing hormone, testosterone, and estradiol were significantly decreased (p < 0.05). The serum triglyceride, total cholesterol, and low-density lipoprotein were significantly increased (p < 0.05). The semen quality of the 160 mg/kg·bw group were significantly lowered (p < 0.05). The liver and testis catalase and CuZn-SOD activities were significantly elevated (p < 0.05). The abilities of •OH inhibition in the livers and testes of the 160 mg/kg·bw group were significantly lowered (p < 0.05). The liver and testis MDA levels of the 160 mg/kg·bw group were significantly elevated (p < 0.05). Results indicate that exposure of nano-ZnO could induce lipid metabolism disorder, hyperlipidemia, and reproductive toxicity to male mice through oxidative injury.

The NADPH oxidase 4 protects vascular endothelial cells from copper oxide nanoparticles-induced oxidative stress and cell death

AIMS

Nanoparticles (NPs) exposure is associated with increased risk of cardiovascular diseases, but the underlying mechanism is still obscure. In this study, we investigated the role of NADPH oxidase 4 (NOX4) in copper oxide nanoparticles (CuONPs)-induced cytotoxicity in human umbilical vein endothelial cells (HUVECs).

MATERIALS AND METHODS

Morphology changes were examined under the microscope. Cell viability was determined by MTS assay and Calcein AM assay. Apoptosis and the levels of superoxide anion (O₂^-) and hydrogen peroxide (H₂O₂) were measured by fluorescence activated cell sorting (FACS). Oxidative stress was detected by assaying the levels of glutathione/glutathione disulfide (GSH/GSSG) and malondialdehyde (MDA). Protein expression levels were determined by western blotting.

KEY FINDINGS

We revealed that O₂^- rather than H₂O₂ was the major component of reactive oxygen species (ROS) in CuONPs-treated HUVECs. Meanwhile, CuONPs downregulated expression of O₂^--eliminating enzyme NOX4 both at mRNA and protein levels, but did not affect the expression of SOD2 and catalase. NOX4 knockdown caused more accumulation of O₂^-, and a further decrease of H₂O₂ in CuONPs-treated HUVECs, suggesting that NOX4 regulates the conversion of O₂^- to H₂O₂ in CuONPs-treated HUVECs. Furthermore, we revealed that NOX4 knockdown aggravated CuONPs-induced oxidative stress, characterized by a decrease of GSH/GSSG ratio, an increase of MDA level, and upregulation of HSPA5 and γH2AX. Finally, we showed that NOX4 knockdown exacerbated CuONPs-induced apoptotic cell death in HUVECs, indicating that NOX4 could protect ECs from CuONPs-induced cell death.

SIGNIFICANCE

Our study provides the evidence that NOX4 protects vascular endothelial cells from CuONPs-induced oxidative stress and cell death.

Autophagy Modulated by Inorganic Nanomaterials

With the rapid development of nanotechnology, inorganic nanomaterials (NMs) have been widely applied in modern society. As human exposure to inorganic NMs is inevitable, comprehensive assessment of the safety of inorganic NMs is required. It is well known that autophagy plays dual roles in cell survival and cell death. Moreover, inorganic NMs have been proven to induce autophagy perturbation in cells. Therefore, an in-depth understanding of inorganic NMs-modulated autophagy is required for the safety assessment of inorganic NMs. This review presents an overview of a set of inorganic NMs, consisting of iron oxide NMs, silver NMs, gold NMs, carbon-based NMs, silica NMs, quantum dots, rare earth oxide NMs, zinc oxide NMs, alumina NMs, and titanium dioxide NMs, as well as how each modulates autophagy. This review emphasizes the potential mechanisms underlying NMs-induced autophagy perturbation, as well as the role of autophagy perturbation in cell fate determination. Furthermore, we also briefly review the potential roles of inorganic NMs-modulated autophagy in diagnosis and treatment of disease.

Potential risks and benefits of zinc oxide nanoparticles: a systematic review

Zinc oxide nanoparticles are well-known metal oxide nanoparticles having numbers of applications in the field of cosmetology, medicine, and chemistry. However, the number of reports has indicated its toxicity also such as hepatotoxicity, pulmonary toxicity, neurotoxicity, and immunotoxicity. Thus, in this article, we have analyzed the potential risks and benefits of zinc oxide nanoparticles. The data related to risks and benefits of zinc oxide nanoparticles have been extracted from PubMed (from January 2007 to August 2019). A total of 3,892 studies have been published during this period regarding zinc oxide nanoparticles. On the basis of inclusion and exclusion criteria, 277 studies have been included for the analysis of risks and benefits. Emerging reports have indicated both risks and benefits of zinc oxide nanoparticles in concentration- and time-dependent manner under in vitro and in vivo conditions through different mechanism of action. In conclusion, zinc oxide nanoparticles could play a beneficial role in the treatment of various diseases but safety of these particles at particular effective concentration should be thoroughly evaluated.

Lysosomal dysfunction is associated with persistent lung injury in dams caused by pregnancy exposure to carbon black nanoparticles

AIMS

Carbon black nanoparticles (CBNPs) are widely used in industrial field. Sensitive stages such as pregnancy are assumed to be more susceptible to stimulus, however whether pregnancy exposure to CBNPs (PrE-to-CBNPs) would cause long-term toxic effects in dams and the underlying mechanisms remain poorly addressed. The present study is aimed to determine the long-term toxic effects of PrE-to-CBNPs in dams.

MATERIALS AND METHODS

The pregnant mice were randomly divided into control group, low (21 μg/animal), medium (103 μg/animal) and high (515 μg/animal) CBNPs-treated groups. From gestational day (GD) 9 to GD18, the pregnant mice were intranasal exposed. At 49 days after parturition, lung tissues and bronchoalveolar lavage fluid (BALF) were obtained. Weight change, lung histopathology, lung ultrastructural pathology, cell count in BALF, oxidative stress/inflammatory maker and autophagy/lysosome-related protein expression were determined.

KEY FINDINGS

PrE-to-CBNPs caused a dose-dependent persistent lung injury in mice even 49 days after parturition, including the deteriorative lung histopathological changes, elevation of oxidative stress marker Nrf-2, HO-1 and CHOP, infiltration of macrophage and increased mRNA expression of inflammatory cytokines in the lung tissues and elevation of cells in BALF. However, PrE-to-CBNPs did not induce significant neutrophil infiltration and fibrosis. Moreover, we found that CBNPs could deposit in the lysosomes and decrease cathepsin D (an important hydrolase in lysosome), which might be associated with the dysfunction of lysosome and autophagy.

SIGNIFICANCE

Our study demonstrated that PrE-to-CBNPs could result in long-term lung injury in dams, and lysosomal dysfunction was probably linked to this process.

Nano-bio interactions: a neutrophil-centric view

Neutrophils are key components of the innate arm of the immune system and represent the frontline of host defense against intruding pathogens. However, neutrophils can also cause damage to the host. Nanomaterials are being developed for a multitude of different purposes and these minute materials may find their way into the body through deliberate or inadvertent exposure; understanding nanomaterial interactions with the immune system is therefore of critical importance. However, whereas numerous studies have focused on macrophages, less attention is devoted to nanomaterial interactions with neutrophils, the most abundant leukocytes in the blood. We discuss the impact of engineered nanomaterials on neutrophils and how neutrophils, in turn, may digest certain carbon-based materials such as carbon nanotubes and graphene oxide. We also discuss the role of the corona of proteins adsorbed onto the surface of nanomaterials and whether nanomaterials are sensed as pathogens by cells of the immune system.

Long-Term Effects of Unmodified 50 nm ZnO in Mice

Nanometer zinc oxide (nano-ZnO) is widely used in many kinds of fields. However, information about the toxicity and toxic mechanism of nano-ZnO is limited. The aims of this study were to investigate the long-term toxic effects of unmodified 50 nm ZnO administered by gavage in mice. After 90 days, hematological parameters, hepatic and renal functions, and oxidative and anti-oxidative status were measured. Pathological damages in livers, kidneys, and other tissues were also examined by hematoxylin and eosin (H&E) staining. The results showed that oral nano-ZnO exposure induced anemia and damages to liver and kidney, influenced the antioxidant system, and impacted functions of liver and kidney in mice after a 90-day exposure. The main cause for oxidative stress in vivo induced by nano-ZnO might be hydroxyl free radical. The lowest observed adverse effect level (LOAEL) was 40 mg/kg·bw, and the livers, kidneys, lungs, pancreas, and gastrointestinal tracts are the target organs.

Cationic gold nanoparticles elicit mitochondrial dysfunction: a multi-omics study

Systems biology is increasingly being applied in nanosafety research for observing and predicting the biological perturbations inflicted by exposure to nanoparticles (NPs). In the present study, we used a combined transcriptomics and proteomics approach to assess the responses of human monocytic cells to Au-NPs of two different sizes with three different surface functional groups, i.e., alkyl ammonium bromide, alkyl sodium carboxylate, or poly(ethylene glycol) (PEG)-terminated Au-NPs. Cytotoxicity screening using THP-1 cells revealed a pronounced cytotoxicity for the ammonium-terminated Au-NPs, while no cell death was seen after exposure to the carboxylated or PEG-modified Au-NPs. Moreover, Au-NR3+ NPs, but not the Au-COOH NPs, were found to trigger dose-dependent lethality in vivo in the model organism, Caenorhabditis elegans. RNA sequencing combined with mass spectrometry-based proteomics predicted that the ammonium-modified Au-NPs elicited mitochondrial dysfunction. The latter results were validated by using an array of assays to monitor mitochondrial function. Au-NR3+ NPs were localized in mitochondria of THP-1 cells. Moreover, the cationic Au-NPs triggered autophagy in macrophage-like RFP-GFP-LC3 reporter cells, and cell death was aggravated upon inhibition of autophagy. Taken together, these studies have disclosed mitochondria-dependent effects of cationic Au-NPs resulting in the rapid demise of the cells.

Necrotic, apoptotic and autophagic cell fates triggered by nanoparticles

Nanomaterials have gained a rapid increase in use in a variety of applications that pertain to many aspects of human life. The majority of these innovations are centered on medical applications and a range of industrial and environmental uses ranging from electronics to environmental remediation. Despite the advantages of NPs, the knowledge of their toxicological behavior and their interactions with the cellular machinery that determines cell fate is extremely limited. This review is an attempt to summarize and increase our understanding of the mechanistic basis of nanomaterial interactions with the cellular machinery that governs cell fate and activity. We review the mechanisms of NP-induced necrosis, apoptosis and autophagy and potential implications of these pathways in nanomaterial-induced outcomes. Abbreviations: Ag, silver; CdTe, cadmium telluride; CNTs, carbon nanotubes; EC, endothelial cell; GFP, green fluorescent protein; GO, graphene oxide; GSH, glutathione; HUVECs, human umbilical vein endothelial cells; NP, nanoparticle; PEI, polyethylenimine; PVP, polyvinylpyrrolidone; QD, quantum dot; ROS, reactive oxygen species; SiO2, silicon dioxide; SPIONs, superparamagnetic iron oxide nanoparticles; SWCNT, single-walled carbon nanotubes; TiO2, titanium dioxide; USPION, ultra-small super paramagnetic iron oxide; ZnO, zinc oxide.

Biosynthesis of zinc oxide nanoparticles using Albizia lebbeck stem bark, and evaluation of its antimicrobial, antioxidant, and cytotoxic activities on human breast cancer cell lines

Background

Biocompatibility and stability of zinc oxide nanoparticles (ZnO NPs) synthesized using plants is an interesting research area of study in nanotechnology, due to its wide applications in biomedical, industrial, cell imaging, and biosensor fields. The present study reports the novel green synthesis of stable ZnO NPs using various concentrations of zinc nitrate (0.01M, 0.05M, 0.1M) and Albizia lebbeck stem bark extracts as an efficient chelating agent. Antimicrobial, antioxidant, cytotoxic, and antiproliferative activities of the synthesized NPs on human breast cancer cell lines were evaluated using different assays.

Methods

Characterization of the synthesized ZnO NPs were carried out using various spectroscopic and microscopic techniques. Antimicrobial activity evaluation using disc diffusion method, antioxidant activity using hydrogen peroxide (H₂O₂) free radical scavenging assay and cytotoxic activity on MDA-MB 231 and MCF-7 using tryphan blue dye exclusion and MTT assay.

Results

The UV–vis spectroscopy result revealed an absorption peak in the range of 370 nm. The involvements of A. lebbeck bioactive compounds in the stabilization of the ZnO NPs were confirmed by X-ray diffraction and Fourier transform infrared analysis. Zeta sizer studies showed an average size of 66.25 nm with a polydisparity index of 0.262. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses results revealed irregular spherical morphology and the presence of primarily Zn, C, O, Na, P, and K, respectively. The biosynthesized ZnO NPs revealed strong antimicrobial potentials against various gram-negative and gram-positive bacterial pathogens. Antioxidant activities carried out using H₂O₂ free radical scavenging assay revealed higher IC50 values of 48.5, 48.7, and 60.2 µg/mL for 0.1M, 0.05M, and 0.01M ZnO NPs, respectively. Moreover, the biosynthesized ZnO NPs showed significant cytotoxic effects on MDA-MB 231 and MCF-7 breast cancer cell lines (P< 0.001, n≥3) in a concentration-dependent manner.

Conclusion

Overall, various concentrations of ZnO NPs were synthesized through a stable, simple, and eco-friendly green route via the use of A. lebbeck stem bark extract. The biosynthesized ZnO NPs showed strong antimicrobial, antioxidant and cytotoxic activity against strongly and weakly metastatic breast cancer cell lines.

Disruption of the superoxide anions-mitophagy regulation axis mediates copper oxide nanoparticles-induced vascular endothelial cell death

Copper oxide nanoparticles (CuONPs) have been widely used in the industrial and pharmaceutical fields; however, their toxicity profile is deeply concerning. Currently, nanomaterials-induced toxicity in the cardiovascular system is receiving increased attention. Our previous toxicological study found that lysosomal deposition of CuONPs triggered vascular endothelial cell death, indicating that the involvement of autophagic dysfunction was crucial for CuONPs-induced toxicity in human umbilical vein endothelial cells (HUVECs). In the current study, we investigated the detailed mechanism underlying the autophagic dysfunction induced by CuONPs. We demonstrated that CuONPs exposure caused accumulation of superoxide anions, which likely resulted from mitochondrial dysfunctions. MnTBAP, a superoxide anions scavenger, alleviated CuONPs-induced HUVECs death, indicating that excessive superoxide anions were directly related to the CuONPs cytotoxicity in HUVECs. Interestingly, we found that mitophagy (a protective mechanism for clearance of damaged mitochondria and excessive superoxide anions) was initiated but failed to be cleared in CuONPs-treated cells, resulting in the accumulation of damaged mitochondria. Inhibition of mitophagy through Atg5 knockout or blocking of mitochondria fission with Mdivi-1 significantly aggravated CuONPs-induced superoxide anions accumulation and cell death, suggesting that mitophagy is a protective mechanism against CuONPs cytotoxicity in HUVECs. In summary, we demonstrate that superoxide anions (originating from damaged mitochondria) are involved in CuONPs-associated toxicity and that impaired mitophagic flux aggravates the accumulation of excessive superoxide anions, which leads to HUVECs death. Our findings indicate that there are crucial roles for superoxide anions and mitophagy in CuONPs-induced toxicity in vascular endothelial cells.

A 3D human lung-on-a-chip model for nanotoxicity testing

The prevalent application of nanoparticles (NPs) has drawn intense concerns about their impact on the environment and human health. Inhalation of NPs is the major route of NP exposure and has led to adverse effects on the lung. It is of great concern to evaluate the potential hazards of nanoparticles for human health during pulmonary exposure. Here, we proposed a novel 3D human lung-on-a-chip model to recreate the organ-level structure and functions of the human lung that allow to us evaluate the pulmonary toxicity of nanoparticles. The lung-on-a-chip consists of three parallel channels for the co-culture of human vascular endothelial cells and human alveolar epithelial cells sandwiching a layer of Matrigel membrane, which recapitulate the key features of the alveolar capillary barrier in the human lung. Cell-cell interaction, cell-matrix interaction and vascular mechanical cues work synergistically to promote the barrier function of the lung-on-a-chip model. TiO2 nanoparticles and ZnO nanoparticles were applied on the lung-on-a-chip to assay their nanotoxicity on both epithelial cells and endothelial cells. Junction protein expression, increased permeability to macromolecules, dose dependent cytotoxicity, ROS production and apoptosis were assayed and compared on the chip. This lung-on-a-chip model indicated its versatile application in human pulmonary health and safety assessment for nanoparticles, environment, food and drugs.

Graphene oxide induces p62/SQSTM-dependent apoptosis through the impairment of autophagic flux and lysosomal dysfunction in PC12 cells

Graphene oxide (GO), as a two-dimensional carbon nanosheet, has been extensively studied for potential biomedical applications due to its notable properties. Although a growing number of studies have investigated the adverse effects of GO nanosheets, the available toxicity data concerning GO's effect on the neuronal cells remain highly limited. In this work, we systematically investigated the toxic responses of commercially available GO on a rat pheochromocytoma-derived PC12 cell line, which was an ideal in vitro model to study the neurotoxicity of GO. GO exerted a significant toxic effect on PC12 cells in a dose- and time-dependent manner. GO treatments under doses of 40, 50, and 60 μg/mL triggered an autophagic response and the blockade of autophagic flux via disrupting lysosome degradation capability. Caspase 9-mediated apoptosis was also observed in GO-treated cells. Moreover, GO-induced apoptosis was relevant to the aberrant accumulation of autophagy substrate p62/SQSTM. Inhibitionofthe accumulation of autophagic substrate alleviated GO-caused apoptotic cell death. Our findings raise a concern for the putative biomedical applications of GO in the form of diagnostic and therapeutic tools, where its systematic biocompatibility should be thoroughly explored. STATEMENT OF SIGNIFICANCE: Graphene oxide (GO) has attracted considerable interests in biomedical fields, which also resulted in numerous safety risks to human bodies. It is urgently required to establish a paradigm for accurately evaluating their adverse effects in biological systems. This study thoroughly explored the neurotoxicity of GO in PC12 cells. We found GO triggered an increased autophagic response and the impairment of autophagic flux, which was functionally involved in cell apoptosis. Inhibitionofexcessive accumulation of autophagic cargo attenuated apoptotic cell death. Our findings highlight deep considerations on the regulation mechanism of autophagy-lysosomes-apotosis-axis, which will contribute to a better understanding of the neurotoxicity of graphene-family nanomaterials, and provide a new insight in the treatment of cancer cells at nanoscale levels.

Autophagy-dependent release of zinc ions is critical for acute lung injury triggered by zinc oxide nanoparticles

Pulmonary exposure to zinc oxide nanoparticles (ZnONPs) could cause acute lung injury (ALI), but the underlying molecular mechanism remains unclear. Herein, we established a ZnONPs-induced ALI mouse model, characterized by the histopathological changes (edema and infiltration of inflammatory cells in lung tissues), and the elevation of total protein and cytokine interleukin-6 in bronchoalveolar lavage fluid in time- and dose-dependent manners. This model also exhibited features like the disturbance of redox-state (reduced of glutathione to glutathione disulfide ratio, elevation of heme oxygenase-1 and superoxide dismutase 2), the decrease of adenosine triphosphate synthesis and the release of zinc ions in the lung tissues. Interestingly, we found that ZnONPs exposure caused the accumulation of autophagic vacuoles and the elevation of microtubule-associated proteins 1A/1B light chain (LC)3B-II and p62, indicating the impairment of autophagic flux. Our data indicated that the above process might be regulated by the activation of AMP-activated protein kinase but not the mammalian target of rapamycin pathway. The association between ZnONPs-induced ALI and autophagy was further verified by a classical autophagy inhibitor, 3-methyladenine (3-MA). 3-MA administration reduced the accumulation of autophagic vacuoles, the expression of LC3B-II and p62, followed by a significant attenuation of histopathological changes, inflammation, and oxidative stress. More importantly, 3-MA could directly decrease the release of zinc ions in lung tissues. Taken together, our study provides the evidence that ZnONPs-induced pulmonary toxicity is autophagy-dependent, suggests that limiting the release of zinc ions by inhibiting autophagy could be a feasible strategy for the prevention of ZnONPs-associated pulmonary toxicity.

Cross Talk Between Autophagy and Apoptosis Contributes to ZnO Nanoparticle-Induced Human Osteosarcoma Cell Death

Killing osteosarcoma cells by zinc oxide nanoparticles (NPs) and its underlying subcellular mechanism are never studied. Here, it is found that the NPs induce cross talk between apoptosis and autophagy, which leads to osteosarcoma cell death. Specifically, the NP uptake promotes autophagy by inducing accumulation of autophagosomes along with impairment of lysosomal functions. The autophagy further causes the uptaken NPs to release zinc ions by promoting their dissolution. These intracellular zinc ions, together with those that are originally released from the extracellular NPs and flowed into the cells, collectively target and damage mitochondria to produce reactive oxygen species (ROS). Then the ROS inhibit cell proliferation by arresting S phase and trigger apoptosis by extrinsic and intrinsic pathways, ultimately leading to cell death. More importantly, suppression of the early stage autophagy restores cell viability by abolishing apoptosis whereas blockade of the late stage autophagy inversely enhances apoptosis. In contrast, inhibition of apoptosis shows a limited ability to restore cell viability but obviously enhance autophagy. Notably, cell viability is strongly ameliorated by the combination of inhibitors for both the late stage autophagy and the apoptosis. These findings provide a mechanistic understanding of the NP-directed autophagy and apoptosis in osteosarcoma cells.

The Advancing of Zinc Oxide Nanoparticles for Biomedical Applications

Zinc oxide nanoparticles (ZnO NPs) are used in an increasing number of industrial products such as rubber, paint, coating, and cosmetics. In the past two decades, ZnO NPs have become one of the most popular metal oxide nanoparticles in biological applications due to their excellent biocompatibility, economic, and low toxicity. ZnO NPs have emerged a promising potential in biomedicine, especially in the fields of anticancer and antibacterial fields, which are involved with their potent ability to trigger excess reactive oxygen species (ROS) production, release zinc ions, and induce cell apoptosis. In addition, zinc is well known to keep the structural integrity of insulin. So, ZnO NPs also have been effectively developed for antidiabetic treatment. Moreover, ZnO NPs show excellent luminescent properties and have turned them into one of the main candidates for bioimaging. Here, we summarize the synthesis and recent advances of ZnO NPs in the biomedical fields, which will be helpful for facilitating their future research progress and focusing on biomedical fields.

Alveolar epithelial cell processing of nanoparticles activates autophagy and lysosomal exocytosis

Using confocal microscopy, we quantitatively assessed uptake, processing, and egress of near-infrared (NIR)-labeled carboxylated polystyrene nanoparticles (PNP) in live alveolar epithelial cells (AEC) during interactions with primary rat AEC monolayers (RAECM). PNP fluorescence intensity (content) and colocalization with intracellular vesicles in a cell were determined over the entire cell volume via z stacking. Isotropic cuvette-based microfluorimetry was used to determine PNP concentration ([PNP]) from anisotropic measurements of PNP content assessed by confocal microscopy. Results showed that PNP uptake kinetics and steady-state intracellular content decreased as diameter increased from 20 to 200 nm. For 20-nm PNP, uptake rate and steady-state intracellular content increased with increased apical [PNP] but were unaffected by inhibition of endocytic pathways. Intracellular PNP increasingly colocalized with autophagosomes and/or lysosomes over time. PNP egress exhibited fast Ca²⁺ concentration-dependent release and a slower diffusion-like process. Inhibition of microtubule polymerization curtailed rapid PNP egress, resulting in elevated vesicular and intracellular PNP content. Interference with autophagosome formation led to slower PNP uptake and markedly decreased steady-state intracellular content. At steady state, cytosolic [PNP] was higher than apical [PNP], and vesicular [PNP] (~80% of intracellular PNP content) exceeded both cytosolic and intracellular [PNP]. These data are consistent with the following hypotheses: 1) autophagic processing of nanoparticles is essential for maintenance of AEC integrity; 2) altered autophagy and/or lysosomal exocytosis may lead to AEC injury; and 3) intracellular [PNP] in AEC can be regulated, suggesting strategies for enhancement of nanoparticle-driven AEC gene/drug delivery and/or amelioration of AEC nanoparticle-related cellular toxicity.

Iron(III)-Tannic Molecular Nanoparticles Enhance Autophagy effect and T1 MRI Contrast in Liver Cell Lines

Herein, a new molecular nanoparticle based on iron(III)-tannic complexes (Fe–TA NPs) is presented. The Fe–TA NPs were simply obtained by mixing the precursors in a buffered solution at room temperature, and they exhibited good physicochemical properties with capability of inducing autophagy in both hepatocellular carcinoma cells (HepG2.2.15) and normal rat hepatocytes (AML12). The Fe–TA NPs were found to induce HepG2.2.15 cell death via autophagic cell death but have no effect on cell viability in AML12 cells. This is possibly due to the much higher uptake of the Fe–TA NPs by the HepG2.2.15 cells via the receptor-mediated endocytosis pathway. As a consequence, enhancement of the T₁ MRI contrast was clearly observed in the HepG2.2.15 cells. The results demonstrate that the Fe–TA NPs could provide a new strategy combining diagnostic and therapeutic functions for hepatocellular carcinoma. Additionally, because of their autophagy-inducing properties, they can be applied as autophagy enhancers for prevention and treatment of other diseases.

Zinc oxide nanoparticles induce murine photoreceptor cell death via mitochondria-related signaling pathway

Zinc oxide (ZnO) nanoparticles can exhibit toxic effect on cells and tissues, which may be involved in the excessive generation of reactive oxygen species (ROS) and the consequent mitochondria-mediated apoptotic pathway. Nevertheless, the detailed mechanism remains unclear. In this study, we explored the effects of ZnO nanoparticles on the expressions of cytochrome c, ATP level, mitochondrial membrane potential, ROS, apoptosis, total antioxidant enzyme activities and apoptotic-related protein levels in murine photoreceptor cells as well as the changes of proteomic profiling. Moreover, we also performed the bioinformatics analysis for the differentially expressed proteins. Our results show that ZnO nanoparticles induce the release of cytochorme c, decrease the intracellular ATP level, collapse the mitochondrial membrane potential, elevate the ROS level, inhibit total antioxidant enzyme activities and increase the Bax and Caspase 3 levels whereas it decrease the Bcl-2 expression, leading to cell death. Proteomic analysis reveals the differentially expressed proteins are involved in cytochrome c oxidase activity and oxidative phosphorylation. Protein-protein interaction analysis confirms the differentially expressed proteins are closely associated with the clusters related to apoptotic signaling pathway and oxidative phosphorylation-associated proteins. Our results indicate that mitochondria play a central role in ZnO nanoparticle-induced murine photoreceptor cell death.

In vitro comparative cytotoxicity study of aminated polystyrene, zinc oxide and silver nanoparticles on a cervical cancer cell line

Nanoparticles use in nano-biotechnology applications have increased significantly with Aminated polystyrene amine (AmPs NP), Zinc oxide (ZnO NP), and Silver (Ag NP) nanoparticles utilized in wide variety of consumer products. This has presented a number of concerns due to their increased exposure risks and associated toxicity on living systems. Changes in the structural and physicochemical properties of nanoparticles can lead to changes in biological activities. This study investigates, compares, and contrasts the potential toxicity of AmPs, ZnO and Ag NPs on an in vitro model (HeLa cells) and assesses the associated mechanism for their corresponding cytotoxicity relative to the surface material. It was noted that NPs exposure attributed to the reduction in cell viability and high-level induction of oxidative stress. All three test particles were noted to induce ROS to varying degrees which is irrespective of the attached surface group. Cell cycle analysis indicated a G2/M phase cell arrest, with the corresponding reduction in G0/G1 and S phase cells resulting in caspase-mediated apoptotic cell death. These findings suggest that all three NPs resulted in the decrease in cell viability, increase intracellular ROS production, induce cell cycle arrest at the G2/M phase and finally result in cell death by caspase-mediated apoptosis, which is irrespective of their differences in physiochemical properties and attached surface groups.

The size of zinc oxide nanoparticles controls its toxicity through impairing autophagic flux in A549 lung epithelial cells

Zinc oxide nanoparticles (ZnONPs) widely used in various products, have been concerned with its impact on human health, in particular, on the risk of pulmonary toxicity. Our previous study indicated that ZnONPs could harness autophagy and impair the autophagic flux, which was positively linked to ZnONPs-induced toxicity. The objective of this study was to investigate whether ZnONPs-induced impairment of autophagic flux and cell death in lung epithelial cells is related to the size of ZnONPs. We demonstrate that ZnONPs with the average size of 50 nm could induce toxic effects in A549 lung epithelial cells, including accumulation of autophagosomes (the elevation of LC3B-II/LC3B-I ratio), impaired autophagic flux (the increase of p62 expression), the release of intracellular zinc ions (the increase of FluoZin-3 signal and ZnT1 mRNA expression), mitochondrial damage (the decrease of TMRE signal), lysosomal dysfunction (the aberrant expression of LAMP-2), oxidative stress (the increase of DCFH-DA signal and HO-1 expression) and cell death. Interestingly, ZnONPs with the average size of 200 nm failed to induce autophagy-mediated toxicity. Taken together, our results indicate that the size of ZnONPs is closely correlated with its toxicity, which is probably mediated by induction of impaired autophagic flux. This finding provides an insight into better understating of ZnONPs-associated toxicity, and mitigating the risk to humans and allowing the safer application.

Mechanically induced autophagy is associated with ATP metabolism and cellular viability in osteocytes in vitro

Both mechanical loading and intracellular autophagy play important roles in bone homeostasis; however, their relationship remains largely unexplored. The objectives of this study were to determine whether osteocytes undergo autophagy upon fluid shear stress (FSS) loading and to determine the correlation between mechanically induced autophagy and ATP metabolism. Autophagic vacuoles were observed by transmission electron microscopy (TEM) in osteocyte-like MLO-Y4 cells subjected to FSS. Increased autophagic flux was further confirmed by the increased amount of the LC3-II isoform and the degradation of p62. Fluorescent puncta distributed in the cytoplasm were observed in the GFP-LC3 transformed cells subjected to FSS. Furthermore, FSS-induced ATP release and synthesis in osteocytes were attenuated by inhibiting autophagy with 3-MA. After FSS exposure, a high ratio of cell death was observed in cultures pretreated with 3-MA, an autophagy inhibitor, with no significantly different Caspase 3/7 activity. Our results indicated that FSS induces protective autophagy in osteocytes and that mechanically induced autophagy is associated with ATP metabolism and osteocyte survival. From the clinical perspective, it may be possible to enhance skeletal cell survival with drugs that modulate the autophagic state, and the autophagy-related pathway could be a potential target for the prevention of ageing-related bone disorders.

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Fluid flow shear stress (FSS) induces activation of autophagic flux in MLO-Y4 osteocytes.

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FSS-induced autophagy promoted ATP metabolism in MLO-Y4 osteocytes.

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Inhibited autophagy decreased FSS-induced ATP release.

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FSS-induced autophagy was beneficial to the osteocyte survival after FSS exposure.

TRIM25 is associated with cisplatin resistance in non-small-cell lung carcinoma A549 cell line via downregulation of 14-3-3σ

Lung cancer, in particular, non-small cell lung cancer (NSCLC), is the leading cause of cancer-related mortality. Cis-Diamminedichloroplatinum (cisplatin, CDDP) as first-line chemotherapy for NSCLC, but resistance occurs frequently. We previously reported that Tripartite motif protein 25 (TRIM25) was highly expressed in cisplatin-resistant human lung adenocarcinoma A549 cells (A549/CDDP) in comparison with its parental A549 cells. Herein, we take a further step to demonstrate the association of TRIM25 and cisplatin resistance and also the underlying mechanisms. Knockdown of TRIM25 by RNA interference in A549/CDDP cells decreased half maximal inhibitory concentration (IC₅₀) values and promoted apoptosis in response to cisplatin, whereas overexpression of TRIM25 had opposite effects. More importantly, we found that concomitant knockdown of 14-3-3σ and TRIM25 absolutely reversed the decreased MDM2, increased p53, increased cleaved-Capsese3 and decreased IC₅₀ value induced by knockdown of TRIM25 individually, suggesting that TRIM25 mediated cisplatin resistance primarily through downregulation of 14-3-3σ. Our results indicate that TRIM25 is associated with cisplatin resistance and 14-3-3σ-MDM2-p53 signaling pathway is involved in this process, suggesting targeting TRIM25 may be a potential strategy for the reversal of cisplatin resistance.