With the widespread use of plastics and nanotechnology products, nanoplastics (NPs) have become a potential threat to human health. It is of great practical significance to study and evaluate the distribution of NPs in mice as mammal models and their entry, transport, and cytotoxicity in human cell lines. In this study, we detected the tissue distribution of fluorescent polystyrene nanoplastics (PS-NPs) in mice and assessed their endocytosis, transport pathways, and cytotoxic effects in GES-1 cells. We found that PS-NPs were clearly visible in gastric, intestine, and liver tissues of mice and in GES-1 cells treated with PS-NPs. Entry of PS-NPs into GES-1 cells decreased with the inhibition of caveolae-mediated endocytosis (nystatin), clathrin-mediated endocytosis (chlorpromazine HCl), micropinocytosis (ethyl-isopropyl amiloride), RhoA (CCG-1423), and F-actin polymerization (lantrunculin A). Rac1 inhibitors (NSC 23766) had no significant effect on PS-NPs entering GES-1 cells. F-actin levels significantly decreased in CCG-1423-pretreated GES-1 cells exposed to PS-NPs. GES-1 cell ultrastructural features indicated that internalized PS-NPs can be encapsulated in vesicles, autophagosomes, lysosomes, and lysosomal residues. RhoA, F-actin, RAB7, and LAMP1 levels in PS-NPs-treated GES-1 cells were remarkably up-regulated and the Rab5 level was significantly down-regulated compared to levels in untreated cells. PS-NPs treatment decreased cell proliferation rates and increased cell apoptosis. The formation of autophagosomes and autolysosomes and levels of LC3II increased with the length of PS-NPs treatment. The results indicated that cells regulated endocytosis in response to PS-NPs through the RhoA/F-actin signaling pathway and internalized PS-NPs in the cytoplasm, autophagosomes, or lysosomes produced cytotoxicity. These results illustrate the potential threat of NPs pollution to human health.

It is very important to explore the potential harm and underlying mechanism of fluoride due to the extensive distribution and the significant health risks of fluoride in environment. The objective of this study to investigate whether fluoride can induce mitochondrial impairment and mitophagy in testicular cells. For this, 40 male mice were randomly divided into four groups treated with 0, 0.6, 1.2, 2.4 mM NaF deionized water, respectively, for 90 days continuously. The results showed that mitophagy was triggered by F in testicular tissues, especially in the Leydig cells by transmission electron microscopy and mitophagy receptor PHB2 locations by immunofluorescence. Furthermore, TM3 Leydig cells line was employed and treated with 0, 0.125, 0.25, and 0.5 mM NaF for 24 h. The mitochondrial function indicators and mitophagy maker PHB2, COX IV and regulator PINK1 in transcript and protein levels in Leydig cells were examined by the methods of qRT-PCR, western blotting, and immunofluorescence co-localization. The results showed that fluoride decreased the mitochondrial membrane potential with a concomitant increase in the number of lysosomes. Meanwhile, fluoride exposure also increased the expressions of PINK1 and PHB2 in TM3 Leydig cells. These results revealed that fluoride could induce mitochondrial impairment and excessive PINK1/Parkin-mediated mitophagy in testicular cells, especially in Leydig cells, which could contribute to the elucidation of the mechanisms of F-induced male reproductive toxicity.

Ambient ultrafine black carbon (uBC) can potentially cross blood-brain barrier, however, very little is currently known about the effects they may have on central nervous system. This study aimed to explore the roles of autophagy in Alzheimer-like pathogenic changes promoted by uBC in SH-SY5Y cells. We firstly found uBC could cause cytotoxicity and oxidative stress in SH-SY5Y cells. Additionally we found uBC initiated progressive development of Alzheimer's disease (AD) associated features, mainly including neuro-inflammation and phosphorylation of tau protein (p-Tau) accumulation. Meanwhile, autophagy process was activated by uBC probably through phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway. RNA interference and autophagosome-lysosome fusion inhibitor were applied to block autophagy process at different stages. Autophagy dysfunction at the initial membrane expansion stage could aggravate p-Tau accumulation and other Alzheimer-like changes in SH-SY5Y cells promoted by uBC. However, autophagy inhibition at the final stage could alleviate p-Tau accumulation caused by uBC. This suggested that inhibition of the infusion of autophagosome and lysosome could possibly activate ubiquitination degradation pathway to regulate p-Tau equilibrium in SH-SY5Y cells. Our findings further raise the concerns about the effects of uBC on the risk of AD and indicate potential roles of autophagy in early Alzheimer-like pathogenic changes caused by ambient uBC.

The contamination of the aquatic environment by plastic nanoparticles is becoming a major concern due to their potential adverse effects in aquatic biota. Therefore, in-depth knowledge of their uptake, trafficking and effects at cellular and systemic levels is essential to understand their potential impacts for aquatic species. In this work, zebrafish (Danio rerio) was used as a model and our aims were: i) to determine the distribution, uptake, trafficking, degradation and genotoxicity of polystyrene (PS) NPs of different sizes in a zebrafish cell line; ii) to study PS NPs accumulation, migration of immune cells and genotoxicity in larvae exposed to PS NPs; and iii) to assess how PS NPs condition the survival of zebrafish larvae exposed to a pathogen and/or how they impact the resistance of an immunodeficient zebrafish. Our results revealed that the cellular distribution differed depending on the particle size: the 50 nm PS NPs were more homogeneously distributed in the cytoplasm and the 1 μM PS NPs more agglomerated. The main endocytic mechanisms for the uptake of NPs were dynamin-dependent internalization for the 50 nm NPs and phagocytosis for the 1 μm nanoparticles. In both cases, degradation in lysosomes was the main fate of the PS NPs, which generated alkalinisation and modified cathepsin genes expression. These effects at cellular level agree with the results in vivo, since lysosomal alkalization increases oxidative stress and vice versa. Nanoparticles mainly accumulated in the gut, where they triggered reactive oxygen species, decreased expression of the antioxidant gene catalase and induced migration of immune cells. Finally, although PS NPs did not induce mortality in wild-type larvae, immunodeficient and infected larvae had decreased survival upon exposure to PS NPs. This fact could be explained by the mechanical disruption and/or the oxidative damage caused by these NPs that increase their susceptibility to pathogens.

Epidemiological studies have demonstrated that the general population’s exposure to bisphenol A (BPA) substitutes is ubiquitous. Bisphenol F (BPF), one of the main BPA substitutes, is increasingly replacing BPA in plastics for food and beverage applications. Accumulating evidence suggests that BPA exposure is associated with nonalcoholic fatty liver disease (NAFLD)-like changes. However, the potential effects of BPF on lipid homeostasis remain poorly understood. In the present study, an epidemiological analysis with LC-MS-MS revealed that the BPF concentrations in the serum of NAFLD patients were significantly higher than those in a control group. Supporting this result, using Oil Red O, BODIPY 493/503, LipidTox Deep Red staining and gas chromatography-time-of-flight mass spectrometry (TOF-MS) assays, we found that BPF exposure induced NAFLD-like changes, with obvious lipid droplet deposition, triglyceride (TG) and fatty acids increase in mouse livers. Meanwhile, lipid droplet deposition and TG increase induced by BPF were also observed in HepG2 cells, accompanied by autophagic flux blockade, including autophagosome accumulation and the decreased degradation of SQSTM1/p62. Using adenoviruses dual-reporter plasmid RFP-GFP-LC3, RFP-GFP-PLIN2 transfection, AO staining, and EGFR degradation assays, we demonstrated that BPF treatment impaired lysosomal degradative capacity, since BPF treatment obviously impaired lysosomal acidification, manifested as decreased lysosomal hydrolase cathepsin L (CTSL) and mature cathepsin D (CTSD) in HepG2 and mouse liver issues. Additionally, v-ATPase D, a multi-subunit enzyme that mediates acidification of eukaryotic intracellular organelles, significantly decreased after BPF exposure in both the vitro and in vivo studies.This study ascertained a novel mechanism involving dysfunctional of lysosomal degradative capacity induced by BPF, which contributes to lipophagic disorders and causes lipid droplet deposition. This work provides evidence that lysosomes may be a target organelle where BPF exerts its potential toxicity; therefore, novel intervention strategies targeting lysosome are promising for BPF-induced NAFLD-like changes.

Attention has been paid to the environmental distribution and fate of nanomedicines. However, their effects on the toxicity of environmental pollutants are lack of knowledge. In this study, the negatively charged poly (ethylene glycol)-b-poly (L-lactide-co-glycolide) (mPEG-PLA) and positively charged polyethyleneimine-palmitate (PEI-PA) nanomicelles were synthesized and served as model drug carriers to study the interaction and combined toxicity with dichlorodiphenyltrichloroethane (DDT). DDT exerted limited effect on the biointerfacial behavior of mPEG-PLA nanomicelles, whereas it significantly mitigated the attachment of PEI-PA nanomicelles on the model cell membrane as monitored by quartz crystal microbalance with dissipation (QCM-D). The cytotoxicity of DDT towards NIH 3T3 cells was greatly decreased by either co-treatment or pre-treatment with the nanomicelles according to the results of real-time cell analysis (RTCA). The cell viability of NIH 3T3 exposed to DDT was increased up to 90% by the co-treatment with mPEG-PLA nanomicelles. Three possible reasons were proposed: (1) decreased amount of free DDT in the cell culture medium due to the partitioning of DDT into nanomicelles; (2) mitigated cellular uptake of nanomicelle-DDT complexes due to the complex agglomeration or electrostatic repulsion between complexes and cell membrane; (3) detoxification effect in the lysosome upon endocytosis of nanomicelle-DDT complexes.

The mechanisms underlying cobalt toxicity in aquatic species in general and cnidarians in particular remain poorly understood. Herein we investigated cobalt toxicity in a Hydra model from morphological, histological, developmental, and molecular biological perspectives. Hydra, exposed to cobalt (0–60 mg/L), were altered in morphology, histology, and regeneration. Exposure to standardized sublethal doses of cobalt impaired feeding by affecting nematocytes, which in turn affected reproduction. At the cellular level, excessive ROS generation, as the principal mechanism of action, primarily occurred in the lysosomes, which was accompanied by the upregulation of expression of the antioxidant genes SOD, GST, GPx, and G6PD. The number of Hsp70 and FoxO transcripts also increased. Interestingly, the upregulations were higher in the 24-h than in the 48-h time-point group, indicating that ROS overwhelmed the cellular defense mechanisms at the latter time-point. Comet assay revealed DNA damage. Cell cycle analysis indicated the induction of apoptosis accompanied or not by cell cycle arrest. Immunoblot analyses revealed that cobalt treatment triggered mitochondria-mediated apoptosis as inferred from the modulation of the key proteins Bax, Bcl-2, and caspase-3. From this data, we suggest the use of Hydra as a model organism for the risk assessment of heavy metal pollution in aquatic ecosystems.

Cocaine and its metabolites are the prevalent psychotropic substances in aquatic environment. However, to date the knowledge on their adverse effects to non-target organisms is inadequate. The aims of this study were to investigate sub-lethal effects induced by the ecgonine methyl ester (EME) to the freshwater bivalve Dreissena polymorpha and to compare its toxicity to that by benzoylecgonine (BE), the other main cocaine metabolite. EME sub-lethal effects were investigated by 14 days in-vivo exposures and a multi-biomarker approach. Slight variations in biomarker responses were found at 0.15 μg/L treatment. 0.5 μg/L EME treatment induced destabilization of lysosome membranes, an overall inactivation of defense enzymes, increases in lipid peroxidation, protein carbonylation and DNA fragmentation, but no variations in fixed genetic damage. The use of a biomarker response index (BRI) showed that at 0.5 μg/L both cocaine metabolites had the same toxicity to zebra mussels specimens.

Hemocytes are the main immune cells in bivalve mollusks and one of the sensitive targets for nanoparticle toxicity. Bivalve hemocytes consist of multiple functional heterogeneous cell types, but their different roles in immune system against foreign particles remain largely unknown. In order to clarify the different immune responses of hemocyte subpopulations to silver nanoparticles (AgNPs) and Ag ions, in this study, the Hong Kong oyster (Crassostrea hongkongensis) hemocytes were employed and separated into three subpopulations based on their cell size and granularity, including agranulocytes (R1), semigranulocytes (R2), and granulocytes (R3). We first demonstrated that AgNPs could rapidly enter into the oyster hemocytes within 3 h by phagocytosis process and resulted in different immune responses in hemocyte subpopulations. The most affected cell subtype by AgNPs was the granulocytes, followed by semigranulocytes, whereas agranulocytes were not affected following exposure to AgNPs. Interestingly, AgNPs induced the granule formation in semigranulocytes and further increased the proportion of granulocytes, whereas their ionic counterparts had no such effects on hemocyte composition, indicating the different detoxification mechanisms for nanoparticulate and ionic form. Following AgNP exposure, the dissolved Ag ions were accumulated in lysosomes and caused lysosomal dysfunction, indicating that lysosomes were the main targets for AgNP toxicity and the dissolved Ag ions were the main contributor of AgNP toxicity. Furthermore, AgNP exposure induced reactive oxygen production and impeded the lysosome function and phagocytosis in granulocytes, with impaired immunity system in oysters. Our study identified the different immune responses of oyster hemocyte subpopulations to AgNPs based on the in vitro short-term exposure assays, which may be applied to rapidly evaluate the ecotoxicological risks of different nanoparticles in aquatic systems.

Zn and Cu are two of the essential trace elements and it is important to understand the regulation of their distribution on cellular functions. Herein, we for the first time investigated the subcellular fate and behavior of Zn and Cu in zebrafish cells through bioimaging, and demonstrated the completely different behaviors of Zn and Cu. The distribution of Zn²⁺ was concentration-dependent, and Zn²⁺ at low concentration was predominantly located in the lysosomes (76.5%). A further increase of cellular Zn²⁺ resulted in a spillover and more diffusive distribution, with partitioning to mitochondria and other regions. In contrast, the subcellular distribution of Cu⁺ was time-dependent. Upon entering the cells, Cu²⁺ was reduced to Cu⁺, which was first concentrated in the mitochondria (71.4%) followed by transportation to lysosomes (58.6%), and finally removal from the cell. With such differential transportation, Cu²⁺ instead of Zn²⁺ had a negative effect on the mitochondrial membrane potential and glutathione. Correspondingly, the pH of lysosomes was more sensitive to Zn²⁺ exposure and decreased with increasing internalized Zn²⁺, whereas it increased upon Cu²⁺ exposure. The responses of cellular pH showed an opposite pattern from the lysosomal pH. Lysosome was the most critical organelle in response to incoming Zn²⁺ by increasing its number and size, whereas Cu²⁺ reduced the lysosome size. Our study showed that Zn²⁺ and Cu²⁺ had completely different cellular handlings and fates with important implications for understanding of their toxicity.