Risk assessment of silica nanoparticles on liver injury in metabolic syndrome mice induced by fructose

Quercetin Protects against Silicon dioxide Particles-induced spleen ZBP1-Mediated PANoptosis by regulating the Nrf2/Drp1/mtDNA axis

Silicon dioxide particles (SiO2) are a widely used novel material, and SiO2 that enter the body can accumulate in the spleen and cause spleen injury. Quercetin (Que) has a strong antioxidant activity and can also regulate and improve immune function, but whether Que can improve SiO2-induced spleen injury and its underlying mechanism remain to be explored. Herein, we established a C57BL/6 mice model with SiO2 exposure (10 mg/kg) and treated with Que (25 mg/kg). We also cultured CTLL-2 cells for in vitro experiments. Studies in vivo and in vitro showed that SiO2 exposure caused oxidative stress and mitochondrial dynamics disorder, which led to decrease of mitochondrial membrane potential (ΔΨm) and mitochondrial DNA (mtDNA) leakage. mtDNA was recognized by Z-DNA binding protein 1 (ZBP1) in the cytoplasm and increased the expression of ZBP1. This process further promoted the assembly of the ZBP1-mediated PANoptosome, which subsequently induced PANoptosis. Interestingly, supplementation with Que significantly reversed these changes. Specifically, Que mitigated spleen ZBP-1 mediated PANoptosis through preventing mtDNA leakage via regulating nuclear factor erythroid 2-related factor 2/reactive oxygen species/dynamin-related protein 1 (Nrf2/ROS/Drp1) axis. This study enriches the understanding of the toxicological mechanisms of SiO2 and provides evidence for the protective effects of Que against SiO2-induced splenic toxicity.

Silica nanoparticles induce liver lipid metabolism disorder via ACSL4-mediated ferroptosis

The disease burden of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide. Emerging evidence has revealed that silica nanoparticles (SiNPs) could disorder the liver lipid metabolism and cause hepatotoxicity, but the underlying mechanism remains unknown. The purpose of this study is to elucidate the molecular mechanism of hepatic lipid metabolism disorder caused by SiNPs, and to reveal the role of ferroptosis in SiNPs-induced hepatotoxicity. To explore the phenotypic changes in liver, the wild-type C57BL/6J mice were exposed to different doses of SiNPs (5, 10, 20 mg/kg·bw) with or without melatonin (20 mg/kg·bw). SiNPs accelerated hepatic oxidative stress and promoted pathological injury and lipid accumulation, resulting in NAFLD development. Melatonin significantly inhibited the oxidative damage caused by SiNPs. Then, the hepatocytes were treated with SiNPs, the ferroptosis inducer and inhibitor, respectively. In vitro, SiNPs (25 μg/mL) generated mitochondrial and intracellular Fe2+ accumulation and lipid peroxidation repair ability impairment, decreased the activity of GPX4 through ACSL4/p38 MAPK signaling pathway, resulting in ferroptosis of hepatocytes. Notably, Erastin (the ferroptosis activator, 5 μM) increased the sensitivity of hepatocytes to ferroptosis. Ferrostatin-1 (Fer-1, the ferroptosis inhibitor, 5 μM) restored GPX4 activity and protected against deterioration of lipid hydroperoxides (LOOHs) to salvage SiNPs-induced cytotoxicity. Finally, the liver tissue conditional ACSL4 knockout (cKO) mice and ACSL4-KO hepatocytes were adopted to further identify the role of the ACSL4-mediated ferroptosis on SiNPs-induced NAFLD development. The results displayed ACSL4 knockout could down-regulate the lipid peroxidation and ferroptosis, ultimately rescuing the progression of NAFLD. In summary, our data indicated that ACSL4/p38 MAPK/GPX4-mediated ferroptosis was a novel and critical mechanism of SiNPs-induced NAFLD.

Re-evaluation of silicon dioxide (E 551) as a food additive in foods for infants below 16 weeks of age and follow-up of its re-evaluation as a food additive for uses in foods for all population groups

The present opinion is the follow-up of the conclusions and recommendations of the Scientific Opinion on the re-evaluation of silicon dioxide (E 551) as a food additive relevant to the safety assessment for all age groups. In addition, the risk assessment of silicon dioxide (E 551) for its use in food for infants below 16 weeks of age is performed. Based on the newly available information on the characterisation of the SAS used as E 551 and following the principles of the 2021 EFSA Guidance on Particle-TR, the conventional safety assessment has been complemented with nano-specific considerations. Given the uncertainties resulting from the limitations of the database and in the absence of genotoxicity concern, the Panel considered that it is not appropriate to derive an acceptable daily intake (ADI) but applied the margin of exposure (MOE) approach for the risk assessment. The Panel concluded that the MOE should be at least 36 for not raising a safety concern. The calculated MOEs considering the dietary exposure estimates for all population groups using the refined non-brand loyal scenario, estimated at the time of the 2018 re-evaluation, were all above 36. The Panel concluded that E 551 does not raise a safety concern in all population groups at the reported uses and use levels. The use of E 551 in food for infants below 16 weeks of age in FC 13.1.1 and FC 13.1.5.1 does not raise a safety concern at the current exposure levels. The Panel also concluded that the technical data provided support an amendment of the specifications for E 551 laid down in Commission Regulation (EU) No 231/2012. The paucity of toxicological studies with proper dispersion protocol (with the exception of the genotoxicity studies) creates uncertainty in the present assessment of the potential toxicological effects related to the exposure to E 551 nanosize aggregates.

Molecular mechanism of nanomaterials induced liver injury: A review

The unique physicochemical properties inherent to nanoscale materials have unveiled numerous potential applications, spanning beyond the pharmaceutical and medical sectors into various consumer industries like food and cosmetics. Consequently, humans encounter nanomaterials through diverse exposure routes, giving rise to potential health considerations. Noteworthy among these materials are silica and specific metallic nanoparticles, extensively utilized in consumer products, which have garnered substantial attention due to their propensity to accumulate and induce adverse effects in the liver. This review paper aims to provide an exhaustive examination of the molecular mechanisms underpinning nanomaterial-induced hepatotoxicity, drawing insights from both in vitro and in vivo studies. Primarily, the most frequently observed manifestations of toxicity following the exposure of cells or animal models to various nanomaterials involve the initiation of oxidative stress and inflammation. Additionally, we delve into the existing in vitro models employed for evaluating the hepatotoxic effects of nanomaterials, emphasizing the persistent endeavors to advance and bolster the reliability of these models for nanotoxicology research.

Evaluating the Effects of Chronic Oral Exposure to the Food Additive Silicon Dioxide on Oral Tolerance Induction and Food Sensitivities in Mice

BACKGROUND

The increasing prevalence of food sensitivities has been attributed to changes in gut microenvironment; however, ubiquitous environmental triggers such as inorganic nanoparticles (NPs) used as food additives have not been thoroughly investigated.

OBJECTIVES

We explored the impact of the NP-structured food-grade silicon dioxide (f g - SiO 2 ) on intestinal immune response involved in oral tolerance (OT) induction and evaluated the consequences of oral chronic exposure to this food-additive using a mouse model of OT to ovalbumin (OVA) and on gluten immunopathology in mice expressing the celiac disease risk gene, HLA-DQ8.

METHODS

Viability, proliferation, and cytokine production of mesenteric lymph node (MLN) cells were evaluated after exposure to f g - SiO 2 . C57BL/6J mice and a mouse model of OT to OVA were orally exposed to f g - SiO 2 or vehicle for 60 d. Fecal lipocalin-2 (Lcn-2), anti-OVA IgG, cytokine production, and immune cell populations were analyzed. Nonobese diabetic (NOD) mice expressing HLA-DQ8 (NOD/DQ8), exposed to f g - SiO 2 or vehicle, were immunized with gluten and immunopathology was investigated.

RESULTS

MLN cells exposed to f g - SiO 2 presented less proliferative T cells and lower secretion of interleukin 10 (IL-10) and transforming growth factor beta (TGF- β ) by T regulatory and CD 45 + CD 11 b + CD 103 + cells compared to control, two factors mediating OT. Mice given f g - SiO 2 exhibited intestinal Lcn-2 level and interferon gamma (IFN- γ ) secretion, showing inflammation and less production of IL-10 and TGF- β . These effects were also observed in OVA-tolerized mice exposed to f g - SiO 2 , in addition to a breakdown of OT and a lower intestinal frequency of T cells. In NOD/DQ8 mice immunized with gluten, the villus-to-crypt ratio was decreased while the CD 3 + intraepithelial lymphocyte counts and the Th1 inflammatory response were aggravated after f g - SiO 2 treatment.

DISCUSSION

Our results suggest that chronic oral exposure to f g - SiO 2 blocked oral tolerance induction to OVA, and worsened gluten-induced immunopathology in NOD/DQ8 mice. The results should prompt investigation on the link between SiO 2 exposure and food sensitivities in humans. https://doi.org/10.1289/EHP12758.

Amorphous silica nanoparticles and the human gut microbiota: a relationship with multiple implications

Amorphous silica nanoparticles (ASNP) are among the nanomaterials that are produced in large quantities. ASNP have been present for a long time in several fast-moving consumer products, several of which imply exposure of the gastrointestinal tract, such as toothpastes, food additives, drug excipients, and carriers. Consolidated use and experimental evidence have consistently pointed to the very low acute toxicity and limited absorption of ASNP. However, slow absorption implies prolonged exposure of the intestinal epithelium to ASNP, with documented effects on intestinal permeability and immune gut homeostasis. These effects could explain the hepatic toxicity observed after oral administration of ASNP in animals. More recently, the role of microbiota in these and other ASNP effects has attracted increasing interest in parallel with the recognition of the role of microbiota in a variety of conditions. Although evidence for nanomaterial effects on microbiota is particularly abundant for materials endowed with bactericidal activities, a growing body of recent experimental data indicates that ASNPs also modify microbiota. The implications of these effects are recounted in this contribution, along with a discussion of the more important open issues and recommendations for future research.

Hexafluoropropylene oxide trimer acid exposure triggers necroptosis and inflammation through the Wnt/β-catenin/NF-κB axis in the liver

Hexafluoropropylene oxide trimer acid (HFPO-TA), an emerging alternative to perfluorooctanoic acid (PFOA), has recently been identified as a significant environmental pollutant. Nevertheless, there is a scarcity of studies regarding the hepatotoxic effects of HFPO-TA. Here, we investigated the types and potential mechanisms of liver damage caused by HFPO-TA. Initially, we validated that the introduction of HFPO-TA resulted in the Wnt/β-catenin signaling (W/β signaling) activation, as well as the induction of necroptosis and inflammation, both in the liver of mice and in HepG2 cells. Subsequently, we established that the W/β signaling mediated the necroptosis and inflammation observed in the liver and HepG2 cells exposed to HFPO-TA. Finally, we demonstrated that the phosphorylated form of NF-κB p65 (p-NF-κB p65) played a role in mediating the necroptosis and inflammation, and its activity could be regulated by the W/β signaling pathway in the liver of mice and HepG2 cells exposed to HFPO-TA. In conclusion, our investigation elucidates the role of HFPO-TA in inducing necroptosis and inflammation in the liver, which is facilitated through the activation of the W/β/NF-κB axis.

Silica Nanoparticles Promote the Megakaryocyte Maturation and Differentiation: Potential Implications for Hematological Homeostasis

Silica nanoparticles (SiO₂ NPs) have been widely applied in diverse areas, thus causing the extensive release through multiple routes. Their toxicological effects, especially for the disturbance in hematological homeostasis, have raised public concern. Considering the detrimental role of excessive platelets in many cardiovascular diseases, the regulation of platelet formation offers a unique aspect for studying the blood compatibility of nanomaterials. In this study, the effects of SiO₂ NPs with four sizes (80, 120, 200, and 400 nm) were investigated on the maturation and differentiation of the megakaryocytes into platelets. The results showed that SiO₂ NPs promoted megakaryocyte development as manifested by the occurrence of irregular cell morphology, enlargement of cell size, increases in DNA content and DNA ploidy, and formation of spore-like protrusions. The expression of megakaryocyte-specific antigen (CD41a) was up-regulated, due to SiO₂ NP treatments. The correlation analysis of SiO₂ NP size with the above test bioindicators showed that the smaller the SiO₂ NPs were, the stronger effects they induced. Moreover, exposure to SiO₂ NPs induced the up-regulation of both GATA-1 and FLI-1, while the transcriptional expressions of aNF-E2 and fNF-E2 remained unchanged. The significant positive correlation of GATA-1 and FLI-1 with megakaryocytic maturation and differentiation suggested their crucial roles in the SiO₂ NP-promoted effect. The finding herein provided new insight into the potential health risk of SiO₂ NPs by perturbing the platelet-involved hematological homeostasis.

Adverse effects and underlying mechanism of amorphous silica nanoparticles in liver

Amorphous silica nanoparticles (SiNPs) have been widely used and mass-producted due to its unique properties. With the life cycle of SiNPs-based products, SiNPs are further released into the air, soil, surface water and sediment, resulting in an increasing risk to humans. SiNPs could enter into the human body through vein, respiratory tract, digestive tract or skin. Moreover, recent evidences have showed that, regardless of exposure pathways, SiNPs could even be traced in liver, which is gradually considered as one of the main organs that SiNPs accumulate. Increasing evidences supported the link between SiNPs exposure and adverse liver effects. However, the research models are diverse and the molecular mechanisms have not been well integrated. In this review, the liver-related studies of SiNPs in vivo and in vitro were screened from the PubMed database by systematic retrieval method. We explored the interaction between SiNPs and the liver, and especially proposed a framework of SiNPs-caused liver toxicity, considering AOP Wiki and existing studies. We identified increased reactive oxygen species (ROS) as a molecular initiating event (MIE), oxidative stress, endoplasmic reticulum stress, lysosome disruption and mitochondrial dysfunction as subsequent key events (KEs), which gradually led to adverse outcomes (AOs) containing liver dysfunction and liver fibrosis through a series of key events about cell inflammation and death such as hepatocyte apoptosis/pyroptosis, hepatocyte autophagy dysfuncton and hepatic macrophages pyroptosis. To our best knowledge, this is the first AOP proposed on SiNPs-related liver toxicity. In the future, more epidemiological studies need to be performed and more biomarkers need to be explored to improve the AOP framework for SiNPs-associated liver toxicity.

Silica nanoparticles aggravated the metabolic associated fatty liver disease through disturbed amino acid and lipid metabolisms-mediated oxidative stress

The metabolic associated fatty liver disease (MAFLD) is a public health challenge, leading to a global increase in chronic liver disease. The respiratory exposure of silica nanoparticles (SiNPs) has revealed to induce hepatotoxicity. However, its role in the pathogenesis and progression of MAFLD was severely under-studied. In this context, the hepatic impacts of SiNPs were investigated in vivo and in vitro through using ApoE^-/- mice and free fatty acid (FFA)-treated L02 hepatocytes. Histopathological examinations and biochemical analysis showed SiNPs exposure via intratracheal instillation aggravated hepatic steatosis, lipid vacuolation, inflammatory infiltration and even collagen deposition in ApoE^-/- mice, companied with increased hepatic ALT, AST and LDH levels. The enhanced fatty acid synthesis and inhibited fatty acid β-oxidation and lipid efflux may account for the increased hepatic TC/TG by SiNPs. Consistently, SiNPs induced lipid deposition and elevated TC in FFA-treated L02 cells. Further, the activation of hepatic oxidative stress was detected in vivo and in vitro, as evidenced by ROS accumulation, elevated MDA, declined GSH/GSSG and down-regulated Nrf2 signaling. Endoplasmic reticulum (ER) stress was also triggered in response to SiNPs-induced lipid accumulation, as reflecting by the remarkable ER expansion and increased BIP expression. More importantly, an UPLC-MS-based metabolomics analysis revealed that SiNPs disturbed the hepatic metabolic profile in ApoE^-/- mice, prominently on amino acids and lipid metabolisms. In particular, the identified differential metabolites were strongly correlated to the activation of oxidative stress and ensuing hepatic TC/TG accumulation and liver injuries, contributing to the progression of liver diseases. Taken together, our study showed SiNPs promoted hepatic steatosis and liver damage, resulting in the aggravation of MAFLD progression. More importantly, the disturbed amino acids and lipid metabolisms-mediated oxidative stress was a key contributor to this phenomenon from a metabolic perspective.

Silica Nanoparticles Induce Hepatotoxicity by Triggering Oxidative Damage, Apoptosis, and Bax-Bcl2 Signaling Pathway

The increase in the usage of silica nanoparticles (SiNPs) in the industrial and medical fields has raised concerns about their possible adverse effects on human health. The present study aimed to investigate the potential adverse effects of SiNPs at daily doses of 25 and 100 mg/kg body weight intraperitoneally (i.p.) for 28 consecutive days on markers of liver damage in adult male rats. Results revealed that SiNPs induced a marked increase in serum markers of liver damage, including lactate dehydrogenase (LDH), alanine aminotransferase (ALAT), and aspartate aminotransferase (ASAT). SiNPs also induced an elevation of reactive oxygen species (ROS) production in liver, along with an increase in oxidative stress markers (NO, MDA, PCO, and H₂O₂), and a decrease in antioxidant enzyme activities (CAT, SOD, and GPx). Quantitative real-time PCR showed that SiNPs also induced upregulation of pro-apoptotic gene expression (including Bax, p53, Caspase-9/3) and downregulation of anti-apoptotic factors Bcl-2. Moreover, histopathological analysis revealed that SiNPs induced hepatocyte alterations, which was accompanied by sinusoidal dilatation, Kupffer cell hyperplasia, and the presence of inflammatory cells in the liver. Taken together, these data showed that SiNPs trigger hepatic damage through ROS-activated caspase signaling pathway, which plays a fundamental role in SiNP-induced apoptosis in the liver.

Integrative Metabolomics, Proteomics and Transcriptomics Analysis Reveals Liver Toxicity of Mesoporous Silica Nanoparticles

As pharmaceutical excipients, mesoporous silica nanoparticles (MSNs) have attracted considerable concern based on potential risks to the public. The impact of MSNs on biochemical metabolism is poorly understood, and few studies have compared the effects of MSNs administered via different routes. To evaluate the hepatotoxicity of MSNs, metabolomics, proteomics and transcriptomic analyses were performed in mice after intravenous (20 mg/kg/d) or oral ad-ministration (200 mg/kg/d) of MSNs for 10 days. Intravenous injection induced significant hepatic injury based on pathological inspection and increased the levels of AST/ALT and the inflammatory factors IL-6, IL-1β and TNF-a. Omics data suggested intravenous administration of MSNs perturbed the following metabolites: succinate, hypoxanthine, GSSG, NADP+, NADPH and 6-phosphogluconic acid. In addition, increases in GPX, SOD3, G6PD, HK, and PFK at proteomic and transcriptomic levels suggested elevation of glycolysis and pentose phosphate pathway, synthesis of glutathione and nucleotides, and antioxidative pathway activity, whereas oxidative phosphorylation, TCA and mitochondrial energy metabolism were reduced. On the other hand, oral administration of MSNs disturbed inflammatory factors and metabolites of ribose-5-phosphate, 6-phosphogluconate, GSSG, and NADP+ associated with the pentose phosphate pathway, glutathione synthesis and oxidative stress albeit to a lesser extent than intravenous injection despite the administration of a ten-fold greater dose. Overall, systematic biological data suggested that intravenous injection of nanoparticles of pharmaceutical excipients substantially affected hepatic metabolism function and induced oxidative stress and inflammation, whereas oral administration exhibited milder effects compared with intravenous injection.

Nanotechnology in Drug Delivery for Liver Fibrosis

Liver fibrosis is a reversible disease course caused by various liver injury etiologies, and it can lead to severe complications, such as liver cirrhosis, liver failure, and even liver cancer. Traditional pharmacotherapy has several limitations, such as inadequate therapeutic effect and side effects. Nanotechnology in drug delivery for liver fibrosis has exhibited great potential. Nanomedicine improves the internalization and penetration, which facilitates targeted drug delivery, combination therapy, and theranostics. Here, we focus on new targets and new mechanisms in liver fibrosis, as well as recent designs and development work of nanotechnology in delivery systems for liver fibrosis treatment.

Doxorubicin Loaded Gold Nanoparticles Mitigate Liver Fibrosis and Inflammatory Cytokines Gene Expression in Rat

BACKGROUND

Gold nanoparticles have the potential to be used as a carrier in drug delivery systems due to their small size, large surface area and short circulation time in blood.

OBJECTIVE

This study demonstrates that doxorubicin conjugation with gold nanoparticles (AuNPs) may reduce its toxicity as well as improve therapeutic efficacy.

METHODS

Five groups of Albino rats were used; 1: healthy control, 2: injured, 3: injured and treated with Dox, 4: injured and treated with AuNPs, 5: injured and treated with AuNPs: Dox. At the end of the experiment, blood and liver tissues were processed for biochemical and histopathological analysis. The expression of collagen, HO-1, IL-6 and TNF-α genes involved in liver fibrosis was observed through real-time PCR.

RESULTS

At the end of the experiment, it was observed that the body weights of DOX-treated rats decreased by 0.72%, however, AuNPs and Au: DOX-treated rats were 15.3% and 29.13% respectively. The percentage of liver protection determined through alanine aminotransferase and aspartate aminotransferase levels in DOX, AuNPs and AuNPs: DOX treated groups were 39.21%, 79.26%, 98.17% and 47.77%, 84.17%, 97.92%, respectively, representing better recovering liver in Dox-AuNPs treated rats compared to others. Histopathological and gene expression studies further support the findings. The mRNA expression levels of inflammatory and oxidative stress-related genes HO-1, IL-6 and TNF- α were upregulated in the injured group but downregulated in the treated group.

CONCLUSION

As depicted through biochemical, histopathological and gene expression studies, Au: DOX conjugate group seems to be protective against liver fibrosis.

Nanosafety vs. nanotoxicology: adequate animal models for testing in vivo toxicity of nanoparticles

Nanotoxicological studies using existing models of normal cells and animals often encounter a paradox: retention of nanoparticles in intracellular compartments for a long time is not accompanied by any significant toxicological effects. Can we expect that the revealed changes will be not harmful after translation to practice, outside of a sterile laboratory and ideally healthy organisms? Age-associated and pathological processes can affect target organs, metabolism, and detoxification in the mononuclear phagocyte system organs and change biodistribution routes, thus making the use of nanomaterial not safe. The potential solution to this issue can be testing the toxic properties of nanoparticles in animal models with chronic diseases. However, current studies of nanotoxicity in animal models with a brain, cardiovascular system, liver, digestive tract, reproductive system, and skin diseases are unsystematic. Even though these studies demonstrate the emergence of new toxic effects that are not present in healthy animals. In this regard, we set the goal of this review as the formulation of the requirements for an animal model capable of assessing the potential toxicity of nanoparticles based on the nanosafety approach.

Lactobacillus rhamnosus GG Ameliorated Long-Term Exposure to TiO2 Nanoparticles Induced Microbiota-Mediated Liver and Colon Inflammation and Fructose-Caused Metabolic Abnormality in Metabolism Syndrome Mice

A huge number of titanium dioxide nanoparticles (TiO₂ NPs) exist in confectionery foods, which is a high-risk factor for development of diet-induced metabolism syndrome (MetS). In this study, we built a high fructose drinking-induced MetS mouse model, and oral intake of 20 mg/kg TiO₂ NPs was administered for 8 weeks. Significant pathological changes and inflammatory factors of overproduction were detected in the liver and colon. The 16S rDNA sequencing analysis results indicated that TiO₂ NPs evidently and further perturbed the gut microbiota diversity, compositions, and KEGG pathways in MetS mice. Fecal microbiota transplant experiment proved that TiO₂ NPs-altered gut microbiota drives liver and colon inflammation damage. More importantly, oral supplementation of Lactobacillus rhamnosus GG (LGG) ameliorated not only the TiO₂ NPs-induced inflammation but also the fructose-caused metabolic abnormality. LGG recovered the gut dysbiosis and decreased the abundance of inflammation-related bacteria (Desulfovibrionaceae, Clostridia, and Proteobacteria), thereby protecting against TiO₂ NPs-induced severe inflammation damage. Our study suggests the necessity of assessing the toxic effects of foodborne nanoparticles on the chronic disease population and potential usefulness of probiotics as prophylactic and therapeutic.

Genotoxicity evaluation of silica nanoparticles in murine: a systematic review and meta-analysis

Silica nanoparticles (SiNPs) have been widely used in nanotechnology, and more attention has been paid to their safety evaluation. However, there are still inconsistent conclusions about the genotoxicity of SiNPs. A systematic review was conducted to explore whether SiNPs have genotoxicity followed by a meta-analysis of in vivo and in vitro murine genotoxicity tests. A total of 26 eligible studies were identified in this meta-analysis through a detailed process of inclusion and exclusion, which included 9 in vivo studies, 15 in vitro studies, and 2 in both. The results of in vitro studies showed that SiNPs exposure significantly increased the indicators of the comet assay, such as tail DNA content (T DNA%), tail length (TL), and olive tail moment (OTM). Indicators of mutagenicity had not been affected in vitro studies, such as mutation frequency (MF) and micronucleus (MN) frequency. There was a significant increase in MN frequency, but there was no influence on T DNA% in vivo. Results of subgroup analysis indicated that size and treatment time of SiNPs were the associated factors in vitro genotoxicity. The size of SiNPs, <21 nm, induced more DNA damage than larger sized SiNPs. It could induce MN formation when the treatment time of SiNPs was <12 h, and even more DNA damage when the exposure time over 12 h. SiNPs can induce genotoxicity both in vivo and in vitro. Comet assay may be more sensitive to detect in vitro genotoxicity, and MN frequency may be more suitable to detect in vivo genotoxicity.

Stearoyl CoA Desaturase 1 and Inositol-Requiring Protein 1α Determine the Efficiency of Oleic Acid in Alleviating Silica Nanoparticle-Induced Insulin Resistance

Despite the widespread use of silica nanoparticles (SiNPs), their metabolic impact and mechanisms of action have not been well studied. Exposure to SiNPs induces insulin resistance (IR) in hepatocytes by endoplasmic reticulum (ER) stress via inositol-requiring protein 1α (IRE1α) activation of c-Jun N-terminal kinases (JNK). It has been well established that stearoyl CoA desaturase (SCD1) and its major product oleic acid elicited beneficial effects in restoring ER homeostasis. However, the potential coordination of SCD1 and IRE1α in determining SiNP regulation of insulin signaling is unclear. Herein, we investigated the effects of SCD1 and oleic acid on IR induced by SiNPs or thapsigargin in hepatocytes. SCD1 overexpression or oleic acid efficiently reversed SiNP-induced ER stress and IR, whereas the effects of thapsigargin treatment could not be restored. Thapsigargin diminished SCD1 protein levels, leading to the accumulation of IRE1α and sustained activation of the IRE1α/JNK pathway. Moreover, knockdown of activating transcription factor 4 (ATF4) upstream of SCD1 suppressed SiNP-induced SCD1 expression, rescued the activated IRE1α, and inhibited insulin signaling but was not able to restore the effects of thapsigargin. Collectively, downregulation of SCD1 and excess accumulation of IRE1α protein prevented the beneficial effects of exogenous oleic acid on IR induced by ER stress. Our results provide valuable mechanistic insights into the synergic regulation of IR by SiNPs and ER stress and suggest a combinational strategy to restore ER homeostasis by targeting SCD1 and IRE1α proteins, as well as supplementation of unsaturated fatty acids.

Issues currently complicating the risk assessment of synthetic amorphous silica (SAS) nanoparticles after oral exposure

Synthetic amorphous silica (SAS) is applied in food products as food additive E 551. It consists of constituent amorphous silicon dioxide (SiO₂) nanoparticles that form aggregates and agglomerates. We reviewed recent oral toxicity studies with SAS. Some of those report tissue concentrations of silicon (Si). The results of those studies were compared with recently determined tissue concentrations of Si (and Si-particles) in human postmortem tissues. We noticed inconsistent results of the various toxicity studies regarding toxicity and reported tissue concentrations, which hamper the risk assessment of SAS. A broad range of Si concentrations is reported in control animals in toxicity studies. The Si concentrations found in human postmortem tissues fall within this range. On the other hand, the mean concentration found in human liver is higher than the reported concentrations causing liver effects in some animal toxicity studies after oral exposure to SAS. Also higher liver concentrations are observed in other, negative animal studies. Those inconsistencies could be caused by the presence of other Si-containing chemical substances or particles (which potentially also includes background SAS) and/or different sample preparation and analytical techniques that were used. Other factors which could explain the inconsistencies in outcome between the toxicity studies are the distinct SAS used and different dosing regimes, such as way of administration (dietary, via drinking water, oral gavage), dispersion of SAS and dose. More research is needed to address these issues and to perform a proper risk assessment for SAS in food. The current review will help to progress research on the toxicity of SAS and the associated risk assessment.

Hepatotoxicity induced by nanomaterials: mechanisms and in vitro models

The unique physicochemical properties of materials at nanoscale have opened a plethora of opportunities for applications in the pharmaceutical and medical field, but also in consumer products from food and cosmetics industries. As a consequence, daily human exposure to nanomaterials through distinct routes is considerable and, therefore, may raise health concerns. Many nanomaterials have been described to accumulate and induce adversity in the liver. Among these, silica and some types of metallic nanoparticles are the most broadly used in consumer products and, therefore, the most studied and reported. The reviewed literature was collected from PubMed.gov during the month of March 2020 using the search words "nanomaterials induced hepatotoxicity", which yielded 181 papers. This present paper reviews the hepatotoxic effects of nanomaterials described in in vitro and in vivo studies, with emphasis on the underlying mechanisms. The induction of oxidative stress and inflammation are the manifestations of toxicity most frequently reported following exposure of cells or animal models to different nanomaterials. Furthermore, the available in vitro models for the evaluation of the hepatotoxic effects of nanomaterials are discussed, highlighting the continuous interest in the development of more advanced and reliable in vitro models for nanotoxicology.

Recent Advances in Nanomedicine for the Diagnosis and Therapy of Liver Fibrosis

Liver fibrosis, a reversible pathological process of inflammation and fiber deposition caused by chronic liver injury and can cause severe health complications, including liver failure, liver cirrhosis, and liver cancer. Traditional diagnostic methods and drug-based therapy have several limitations, such as lack of precision and inadequate therapeutic efficiency. As a medical application of nanotechnology, nanomedicine exhibits great potential for liver fibrosis diagnosis and therapy. Nanomedicine enhances imaging contrast and improves tissue penetration and cellular internalization; it simultaneously achieves targeted drug delivery, combined therapy, as well as diagnosis and therapy (i.e., theranostics). In this review, recent designs and development efforts of nanomedicine systems for the diagnosis, therapy, and theranostics of liver fibrosis are introduced. Relative to traditional methods, these nanomedicine systems generally demonstrate significant improvement in liver fibrosis treatment. Perspectives and challenges related to these nanomedicine systems translated from laboratory to clinical use are also discussed.

A review of hepatic nanotoxicology - summation of recent findings and considerations for the next generation of study designs

The liver is one of the most important multi-functional organs in the human body. Amongst various crucial functions, it is the main detoxification center and predominantly implicated in the clearance of xenobiotics potentially including particulates that reach this organ. It is now well established that a significant quantity of injected, ingested or inhaled nanomaterials (NMs) translocate from primary exposure sites and accumulate in liver. This review aimed to summarize and discuss the progress made in the field of hepatic nanotoxicology, and crucially highlight knowledge gaps that still exist.Key considerations include In vivo studies clearly demonstrate that low-solubility NMs predominantly accumulate in the liver macrophages the Kupffer cells (KC), rather than hepatocytes.KCs lining the liver sinusoids are the first cell type that comes in contact with NMs in vivo. Further, these macrophages govern overall inflammatory responses in a healthy liver. Therefore, interaction with of NM with KCs in vitro appears to be very important.Many acute in vivo studies demonstrated signs of toxicity induced by a variety of NMs. However, acute studies may not be that meaningful due to liver's unique and unparalleled ability to regenerate. In almost all investigations where a recovery period was included, the healthy liver was able to recover from NM challenge. This organ's ability to regenerate cannot be reproduced in vitro. However, recommendations and evidence is offered for the design of more physiologically relevant in vitro models.Models of hepatic disease enhance the NM-induced hepatotoxicity.The review offers a number of important suggestions for the future of hepatic nanotoxicology study design. This is of great significance as its findings are highly relevant due to the development of more advanced in vitro, and in silico models aiming to improve physiologically relevant toxicological testing strategies and bridging the gap between in vitro and in vivo experimentation.

Endoplasmic Reticulum Stress Cooperates in Silica Nanoparticles-Induced Macrophage Apoptosis via Activation of CHOP-Mediated Apoptotic Signaling Pathway

While silica nanoparticles (SiNPs) have wide applications, they inevitably increase atmospheric particulate matter and human exposure to this nanomaterial. Numerous studies have focused on how to disclose SiNP toxicity and on understanding its toxic mechanisms. However, there are few studies in the literature reporting the interaction between endoplasmic reticulum (ER) stress and SiNP exposure, and the corresponding detailed mechanisms have not been clearly determined. In this study, CCK-8 and flow cytometry assays demonstrated that SiNPs gradually decreased cell viability and increased cell apoptosis in RAW 264.7 macrophage cells in dose- and time-dependent manners. Western blot analysis showed that SiNPs significantly activated ER stress by upregulating GRP78, CHOP, and ERO1α expression. Meanwhile, western blot analysis also showed that SiNPs activated the mitochondrial-mediated apoptotic signaling pathway by upregulating BAD and Caspase-3, and downregulating the BCL-2/BAX ratio. Moreover, 4-phenylbutyrate (4-PBA), an ER stress inhibitor, significantly decreased GRP78, CHOP, and ERO1α expression, and inhibited cell apoptosis in RAW 264.7 macrophage cells. Furthermore, overexpression of CHOP significantly enhanced cell apoptosis, while knockdown of CHOP significantly protected RAW 264.7 macrophage cells from apoptosis induced by SiNPs. We found that the CHOP-ERO1α-caspase-dependent apoptotic signaling pathway was activated by upregulating the downstream target protein ERO1α and caspase-dependent mitochondrial-mediated apoptotic signaling pathway by upregulating Caspase-3 and downregulating the ratio of BCL-2/BAX. In summary, ER stress participated in cell apoptosis induced by SiNPs and CHOP regulated SiNP-induced cell apoptosis, at least partly, via activation of the CHOP-ERO1α-caspase apoptotic signaling pathway in RAW 264.7 macrophage cells.