Mitochondrial dysfunction, autophagy stimulation and non-apoptotic cell death caused by nitric oxide-inducing Pt-coated Au nanoparticle in human lung carcinoma cells

Autophagy and Biomaterials: A Brief Overview of the Impact of Autophagy in Biomaterial Applications

Macroautophagy (hereafter autophagy), a tightly regulated physiological process that obliterates dysfunctional and damaged organelles and proteins, has a crucial role when biomaterials are applied for various purposes, including diagnosis, treatment, tissue engineering, and targeted drug delivery. The unparalleled physiochemical properties of nanomaterials make them a key component of medical strategies in different areas, such as osteogenesis, angiogenesis, neurodegenerative disease treatment, and cancer therapy. The application of implants and their modulatory effects on autophagy have been known in recent years. However, more studies are necessary to clarify the interactions and all the involved mechanisms. The advantages and disadvantages of nanomaterial-mediated autophagy need serious attention in both the biological and bioengineering fields. In this mini-review, the role of autophagy after biomaterial exploitation and the possible related mechanisms are explored.

Bismuth Oxide (Bi2O3) Nanoparticles Cause Selective Toxicity in a Human Endothelial (HUVE) Cell Line Compared to Epithelial Cells

A review of recent literature suggests that bismuth oxide (Bi₂O₃, referred to as B in this article) nanoparticles (NPs) elicit an appreciable response only after a concentration above 40-50 µg/mL in different cells all having an epithelial origin, to the best of our knowledge. Here, we report the toxicological profile of Bi₂O₃ NPs (or BNPs) (71 ± 20 nm) in a human endothelial cell (HUVE cell line) in which BNPs exerted much steeper cytotoxicity. In contrast to a high concentration of BNPs (40-50 µg/mL) required to stimulate an appreciable toxicity in epithelial cells, BNPs induced 50% cytotoxicity in HUVE cells at a very low concentration (6.7 µg/mL) when treated for 24 h. BNPs induced reactive oxygen species (ROS), lipid peroxidation (LPO), and depletion of the intracellular antioxidant glutathione (GSH). BNPs also induced nitric oxide (NO,) which can result in the formation of more harmful species in a fast reaction that occurs with superoxide (O₂^•-). Exogenously applied antioxidants revealed that NAC (intracellular GSH precursor) was more effective than Tiron (a preferential scavenger of mitochondrial O₂^•-) in preventing the toxicity, indicating ROS production is extra-mitochondrial. Mitochondrial membrane potential (MMP) loss mediated by BNPs was significantly less than that of exogenously applied oxidant H₂O₂, and MMP loss was not as intensely reduced by either of the antioxidants (NAC and Tiron), again suggesting BNP-mediated toxicity in HUVE cells is extra-mitochondrial. When we compared the inhibitory capacities of the two antioxidants on different parameters of this study, ROS, LPO, and GSH were among the strongly inhibited biomarkers, whereas MMP and NO were the least inhibited group. This study warrants further research regarding BNPs, which may have promising potential in cancer therapy, especially via angiogenesis modulation.

Nanoplastics induces oxidative stress and triggers lysosome-associated immune-defensive cell death in the earthworm Eisenia fetida

Nanoplastics (NPs) are increasingly perceived as an emerging threat to terrestrial environments, but the adverse impacts of NPs on soil fauna and the mechanisms behind these negative outcomes remain elusive. Here, a risk assessment of NPs was conducted on model organism (earthworm) from tissue to cell. Using palladium-doped polystyrene NPs, we quantitatively measured nanoplastic accumulation in earthworm and investigated its toxic effects by combining physiological assessment with RNA-Seq transcriptomic analyses. After a 42-day exposure, earthworm accumulated up to 15.9 and 143.3 mg kg-1 of NPs for the low (0.3 mg kg-1) and high (3 mg kg-1) dose groups, respectively. NPs retention led to the decrease of antioxidant enzyme activity and the accumulation of reactive oxygen species (O2- and H2O2), which reduced growth rate by 21.3 %-50.8 % and caused pathological abnormalities. These adverse effects were enhanced by the positively charged NPs. Furthermore, we observed that irrespective of surface charge, after 2 h of exposure, NPs were gradually internalized by earthworm coelomocytes (∼0.12 μg per cell) and mainly amassed at lysosomes. Those agglomerations stimulated lysosomal membranes to lose stability and even rupture, resulting in impeded autophagy process and cellular clearance, and eventually coelomocyte death. In comparison with negatively charged nanoplastics, the positively charged NPs exerted 83 % higher cytotoxicity. Our findings provide a better understanding of how NPs posed harmful effects on soil fauna and have important implications for evaluating the ecological risk of NPs.

Evaluation of Human Spermatozoa Mitochondrial Membrane Potential Using the JC-1 Dye

Mitochondria are fundamental for human spermatozoa motility and fertilizing ability. Mitochondria participate not only in ATP production, but also in reactive oxygen species production, redox equilibrium, and calcium regulation, all of which are central for human spermatozoa motility, capacitation, acrosome reaction, and ultimately, oocyte fertilization. Mitochondrial membrane potential is a key indicator of mitochondrial health and activity. Most commonly used methods for the study of mitochondrial membrane potential, however, cannot be applied to human spermatozoa due to their unique characteristics, including high motility and time-dependent decay of quality, limiting the study of this important parameter in these cells. Here, we describe an easy, fast, and cheap protocol for the quantitative evaluation of human spermatozoa mitochondrial membrane potential, using the fluorescent cationic dye 5,5,6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimi-dazoylcarbocyanine iodide (JC-1). JC-1 is a sensitive marker for mitochondrial membrane potential, exhibiting a potential-dependent accumulation in the mitochondria. At high mitochondrial membrane potential, JC-1 forms J-aggregates, which emit red fluorescence, whereas at low mitochondrial membrane potential, JC-1 remains at its monomer state, which emits green fluorescence. We first describe how to evaluate human spermatozoa mitochondrial membrane potential using JC-1 and a fluorescence plate reader, for high-throughput studies. The calculation of the JC-1 ratio (indicative of the J-aggregates/monomers ratio) is then used to quantitatively evaluate mitochondrial health and activity. In addition, we describe an imaging protocol for the qualitative evaluation of human spermatozoa mitochondrial membrane potential using a fluorescence microscope. This allows for a visual analysis of the results that can complement the quantitative data. These protocols can be used to study the effects of spermatozoa exposure to compounds of interest, and alterations due to diseases or different conditions. While these protocols are illustrated with human spermatozoa, they can be adapted and used on spermatozoa of different species. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Quantitative evaluation of human spermatozoa mitochondrial membrane potential using the JC-1 dye and a fluorescence plate reader Basic Protocol 2: Qualitative evaluation of human spermatozoa mitochondrial membrane potential using the JC-1 dye and fluorescence microscopy Support Protocol: Preparation of the JC-1 working solution.

Perturbation of autophagy: An intrinsic toxicity mechanism of nanoparticles

Nanoparticles (NPs) have been widely used for various purposes due to their unique physicochemical properties. Such widespread applications greatly increase the possibility of human exposure to NPs in various ways. Once entering the human body, NPs may interfere with cellular homeostasis and thus affect the physiological system. As a result, it is necessary to evaluate the potential disturbance of NPs to multiple cell functions, including autophagy. Autophagy is an important cell function to maintain cellular homeostasis, and minimizing the disturbance caused by NP exposures to autophagy is critical to nanosafety. Herein, we summarized the recent research progress in nanotoxicity with particular focuses on the perturbation of NPs to cell autophagy. The basic processes of autophagy and complex relationships between autophagy and major human diseases were further discussed to emphasize the importance of keeping autophagy under control. Moreover, the most recent advances on perturbation of different types of NPs to autophagy were also reviewed. Last but not least, we also discussed major research challenges and potential coping strategies and proposed a safe-by-design strategy towards safer applications of NPs.

CeO2-Zn Nanocomposite Induced Superoxide, Autophagy and a Non-Apoptotic Mode of Cell Death in Human Umbilical-Vein-Derived Endothelial (HUVE) Cells

In this study, a nanocomposite of cerium oxide-zinc (CeO₂-Zn; 26 ± 11 nm) based on the antioxidant rare-earth cerium oxide (CeO₂) nanoparticles (NPs) with the modifier zinc (Zn) was synthesized by sintering method and characterized. Its bio-response was examined in human umbilical-vein-derived endothelial (HUVE) cells to get insight into the components of vascular system. While NPs of CeO₂ did not significantly alter cell viability up to a concentration of 200 µg/mL for a 24 h exposure, 154 ± 6 µg/mL of nanocomposite CeO₂-Zn induced 50% cytotoxicity. Mechanism of cytotoxicity occurring due to nanocomposite by its Zn content was compared by choosing NPs of ZnO, possibly the closest nanoparticulate form of Zn. ZnO NPs lead to the induction of higher reactive oxygen species (ROS) (DCF-fluorescence), steeper depletion in antioxidant glutathione (GSH) and a greater loss of mitochondrial membrane potential (MMP) as compared to that induced by CeO₂-Zn nanocomposite. Nanocomposite of CeO₂-Zn, on the other hand, lead to significant higher induction of superoxide radical (O₂^•−, DHE fluorescence), nitric oxide (NO, determined by DAR-2 imaging and Griess reagent) and autophagic vesicles (determined by Lysotracker and monodansylcadeverine probes) as compared to that caused by ZnO NP treatment. Moreover, analysis after triple staining (by annexin V-FITC, PI, and Hoechst) conducted at their respective IC50s revealed an apoptosis mode of cell death due to ZnO NPs, whereas CeO₂-Zn nanocomposite induced a mechanism of cell death that was significantly different from apoptosis. Our findings on advanced biomarkers such as autophagy and mode of cell death suggested the CeO₂-Zn nanocomposite might behave as independent nanostructure from its constituent ones. Since nanocomposites can behave independently of their constituent NPs/elements, by creating nanocomposites, NP versatility can be increased manifold by just manipulating existing NPs. Moreover, data in this study can furnish early mechanistic insight about the potential damage that could occur in the integrity of vascular systems.

Combination of starvation therapy and Pt-NP based chemotherapy for synergistic cancer treatment

Platinum nanoparticles (Pt-NPs) have been developed for enhanced toxicity against tumor cells. However, the therapeutic effect of Pt-NPs was severely limited by the lack of cellular uptake of Pt-NPs and an oxidative environment. The combination of starvation therapy with Pt-NP based chemotherapy in a well-designed nano-system is expected to eliminate tumors. Therefore, GOx and Pt-NPs were coated with PLGA to obtain a functional nano-system (GOx-Pt-NS), which increased the cellular uptake of Pt-NPs. The accumulation of GOx-Pt-NS in tumors increased significantly via the enhanced permeability and retention (EPR) effect of nanoparticles. In addition, protection of the GOx-Pt-NS overcame several drawbacks of GOx such as poor stability, short in vivo half-life, immunogenicity, and systemic toxicity. Glucose oxidase (GOx) elevated the gluconic acid ROS levels in tumor cells, resulting in an acidic and oxidative environment. The acidic and oxidative environment enhanced the conversion of Pt²⁺via Pt NPs as well as DNA-binding ability. Finally, combining GOx based starvation therapy with Pt-NP based chemotherapy was expected to eliminate tumors more efficiently through a synergistic strategy.

Pt-Coated Au Nanoparticle Toxicity Is Preferentially Triggered Via Mitochondrial Nitric Oxide/Reactive Oxygen Species in Human Liver Cancer (HepG2) Cells

Reactive nitrogen species (RNS) that are formed from the reaction of versatile nitric oxide (NO) with reactive oxygen species (ROS) have been less explored in potential cancer therapy. This may be partly due to the fewer available agents that could induce NO in cells. Here, we report platinum-coated gold nanoparticles (Pt-coated Au NPs; 27 ± 20 nm) as a strong inducer of NO (assessed by live-cell imaging under NO-specific DAR-1 probe labeling and indirectly using a Griess reagent) in human liver carcinoma (HepG2) cells. In addition to NO, this study found a critical role of ROS from mitochondrial sources in the mechanism of toxicity caused by Pt-coated Au NPs. Cotreatment with a thiol-replenishing general antioxidant NAC (N-acetyl cysteine) led to significant amelioration of oxidative stress against NP-induced toxicity. However, NAC did not exhibit as much ameliorative potential against NP-induced oxidative stress as the superoxide radical (O2•-)-scavenging mitochondrial specific antioxidant mito-TEMPO did. The higher protective potential of mito-TEMPO in comparison to NAC reveals mitochondrial ROS as an active mediator of NP-induced toxicity in HepG2 cells. Moreover, the relatively unaltered NP-induced NO concentration under cotreatment of GSH modulators NAC and buthionine sulfoximine (BSO) suggested that NO production due to NP treatment is rather independent of the cellular thiols at least in HepG2 cells. Moreover, toxicity potentiation by exogenous H2O2 again suggested a more direct involvement of ROS/RNS in comparison to the less potentiation of toxicity due to GSH-exhausting BSO. A steeper amelioration in NP-induced NO and ROS and, consequently, cytotoxicity by mito-TEMPO in comparison to NAC reveal a pronounced role of NO and ROS via the mitochondrial pathway in the toxicity of Pt-coated Au NPs in HepG2 cells.

Au@Pt Core-Shell Nanoparticle Bioconjugates for the Therapy of HER2+ Breast Cancer and Hepatocellular Carcinoma. Model Studies on the Applicability of 193mPt and 195mPt Radionuclides in Auger Electron Therapy

^193mPt and ^195mPt radionuclides are therapeutically attractive Auger electron emitters with notably high Auger electron yield per decay. The present paper summarizes the first step of research on the applications of core-shell (Au@Pt) nanoparticles for electron Auger therapy of HER2+ (human epidermal growth factor receptor 2) breast cancer and hepatocellular carcinoma. Gold nanoparticles (30 nm) were synthesized covered with a platinum shell at high efficiency (>80%) and were further evaluated for in vitro studies such as binding affinity, internalization and cytotoxicity. To find the mechanism(s) responsible for platinum cytotoxicity in HepG2 cells, the platinum concentration in isolated cell nuclei and cytoplasm was determined using ICP-MS (inductively coupled plasma mass spectrometry). Lack of platinum in cell nuclei suggests that the cytotoxic effect is associated with the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Studies carried out on the SKOV-3 cell line with the use of a synthesized targeting bioconjugate (Au@Pt-PEG-trastuzumab) revealed a high affinity of this preparation to HER2+ cells, its internalization, its placement in the perinuclear area and partial intranuclear location. The specific binding for HER2 negative cells, MDA-MB-231, was negligible and Au@Pt-PEG-trastuzumab did not enter these cells. The results obtained are promising and warrant future investigation of Auger electron therapy using ^193mPt and ^195mPt based radiopharmaceuticals.

Co-exposure of Bi2O3 nanoparticles and bezo[a]pyrene-enhanced in vitro cytotoxicity of mouse spermatogonia cells

Recent attention has been focused on reproductive toxicity of nanoscale materials in combination with pre-existing environmental pollutants. Due to its unique characteristics, bismuth (III) oxide (Bi₂O₃) nanoparticles (BONPs) are being used in diverse fields including cosmetics and biomedicine. Benzo[a]pyrene (BaP) is a known endocrine disruptor that most common sources of BaP exposure to humans are cigarette smoke and well-cooked barbecued meat. Hence, joint exposure of BONPs and BaP in humans is common. There is scarcity of information on toxicity of BONPs in combination with BaP in human reproductive system. In this work, combined effects of BONPs and BaP in mouse spermatogonia (GC-1 spg) cells were assessed. Results showed that combined exposure of BONPs and BaP synergistically induced cell viability reduction, lactate dehydrogenase leakage, induction of caspases (-3 and -9) and mitochondrial membrane potential loss in GC-1 spg cells. Co-exposure of BONPs and BaP also synergistically induced production of pro-oxidants (reactive oxygen species and hydrogen peroxide) and reduction of antioxidants (glutathione and several antioxidant enzymes). Experiments with N-acetyl-cysteine (NAC, a reactive oxygen species scavenger) indicated that oxidative stress was a plausible mechanism of synergistic toxicity of BONPs and BaP in GC-1 spg cells. Present data could be helpful for future in vivo research and risk assessment of human reproductive system co-exposed to BONPs and BaP.

Cascaded amplification of intracellular oxidative stress and reversion of multidrug resistance by nitric oxide prodrug based-supramolecular hydrogel for synergistic cancer chemotherapy

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Supramolecular hydrogel was facilely developed by self-assembly of NO prodrug conjugated hydrogelator sequence.

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The locoregionally sustained NO release from the hydrogel could be triggered by intracellular over-expressed GSH/GST.

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NO could effectively reverse the P-gp mediated MDR effect and facilitate the intracellular accumulation of DOX.

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This type of stimuli-sensitive NO delivery platform holds great potential for combating drug-resistance cancer.

Gadolinium Oxide Nanoparticles Induce Toxicity in Human Endothelial HUVECs via Lipid Peroxidation, Mitochondrial Dysfunction and Autophagy Modulation

In spite of the potential preclinical advantage of Gd₂O₃ nanoparticles (designated here as GO NPs) over gadolinium-based compounds in MRI, recent concerns of gadolinium deposits in various tissues undergoing MRI demands a mechanistic investigation. Hence, we chose human to measure umbilical vein endothelial cells (HUVECs) that line the vasculature and relevant biomarkers due to GO NPs exposure in parallel with the NPs of ZnO as a positive control of toxicity. GO NPs, as measured by TEM, had an average length of 54.8 ± 29 nm and a diameter of 13.7 ± 6 nm suggesting a fiber-like appearance. With not as pronounced toxicity associated with a 24-h exposure, GO NPs induced a concentration-dependent cytotoxicity (IC₅₀ = 304 ± 17 µg/mL) in HUVECs when exposed for 48 h. GO NPs emerged as significant inducer of lipid peroxidation (LPO), reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and autophagic vesicles in comparison to that caused by ZnO NPs at its IC₅₀ for the same exposure time (48 h). While ZnO NPs clearly appeared to induce apoptosis, GO NPs revealed both apoptotic as well as necrotic potentials in HUVECs. Intriguingly, the exogenous antioxidant NAC (N-acetylcysteine) co-treatment significantly attenuated the oxidative imbalance due to NPs preventing cytotoxicity significantly.

High Surface Reactivity and Biocompatibility of Y2O3 NPs in Human MCF-7 Epithelial and HT-1080 FibroBlast Cells

This study aimed to generate a comparative data on biological response of yttrium oxide nanoparticles (Y₂O₃ NPs) with the antioxidant CeO₂ NPs and pro-oxidant ZnO NPs. Sizes of Y₂O₃ NPs were found to be in the range of 35±10 nm as measured by TEM and were larger from its hydrodynamic sizes in water (1004 ± 134 nm), PBS (3373 ± 249 nm), serum free culture media (1735 ± 305 nm) and complete culture media (542 ± 108 nm). Surface reactivity of Y₂O₃ NPs with bovine serum albumin (BSA) was found significantly higher than for CeO₂ and ZnO NPs. The displacement studies clearly suggested that adsorption to either BSA, filtered serum or serum free media was quite stable, and was dependent on whichever component interacted first with the Y₂O₃ NPs. Enzyme mimetic activity, like that of CeO₂ NPs, was not detected for the NPs of Y₂O₃ or ZnO. Cell viability measured by MTT and neutral red uptake (NRU) assays suggested Y₂O₃ NPs were not toxic in human breast carcinoma MCF-7 and fibroblast HT-1080 cells up to the concentration of 200 μg/mL for a 24 h treatment period. Oxidative stress markers suggested Y₂O₃ NPs to be tolerably non-oxidative and biocompatible. Moreover, mitochondrial potential determined by JC-1 as well as lysosomal activity determined by lysotracker (LTR) remained un-affected and intact due to Y₂O₃ and CeO₂ NPs whereas, as expected, were significantly induced by ZnO NPs. Hoechst-PI dual staining clearly suggested apoptotic potential of only ZnO NPs. With high surface reactivity and biocompatibility, NPs of Y₂O₃ could be a promising agent in the field of nanomedicine.