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

Review on the role of autophagy in the toxicity of nanoparticles and the signaling pathways involved

As the development of nanotechnology, the application of nanoproducts and the advancement of nanomedicine, the contact of nanoparticles (NPs) with human body is becoming increasingly prevalent. This escalation elevates the risk of NPs exposure for workers, consumers, researchers, and both aquatic and terrestrial organisms throughout the production, usage, and disposal stages. Consequently, evaluating nanotoxicity remains critically important, though standardized assessment criteria are still lacking. The diverse and complex properties of NPs further complicate the understanding of their toxicological mechanisms. Autophagy, a fundamental cellular process, exhibits dual functions-both pro-survival and pro-death. This review offers an updated perspective on the dual roles of autophagy in nanotoxicity and examines the factors influencing autophagic responses. However, no definitive framework exists for predicting NPs-induced autophagy. Beyond the conventional autophagy pathways, the review highlights specific transcription factors activated by NPs and explores metabolic reprogramming. Particular attention is given to NPs-induced selective autophagy, including mitophagy, ER-phagy, ferritinophagy, lysophagy, and lipophagy. Additionally, the review investigates autophagy's involvement in NPs-mediated biological processes such as ferroptosis, inflammation, macrophage polarization, epithelial-mesenchymal transition, tumor cell proliferation and drug resistance, as well as liver and kidney injury, neurotoxicity, and other diseases. In summary, this review presents a novel update on selective autophagy-mediated nanotoxicity and elucidates the broader interactions of autophagy in NPs-induced biological processes. Collectively, these insights offer valuable strategies for mitigating nanotoxicity through autophagy modulation and advancing the development of NPs in biomedical applications.

Microneedle patches incorporating zinc-doped mesoporous silica nanoparticles loaded with betamethasone dipropionate for psoriasis treatment

Treating psoriasis presents a major clinical challenge because of the limitations associated with traditional topical glucocorticoid therapy. This study introduced a drug delivery system utilizing zinc-doped mesoporous silica nanoparticle (Zn-MSN) and microneedle (MN), designed to enhance drug utilization for prolonged anti-inflammatory and anti-itch effects. The MN system facilitated the transdermal delivery of betamethasone dipropionate (BD), allowing its slow release. The BD@Zn-MSN-MN system promoted the polarization of macrophages towards the anti-inflammatory M2 phenotype, achieving superior anti-inflammatory effects compared to the clinically used BD cream. Additionally, this study demonstrated that BD@Zn-MSN-MN could further alleviate itching in psoriasis-afflicted mice by decreasing the excitability of the transient receptor potential vanilloid V1 (TRPV1) ion channel positive neurons and reducing the release of calcitonin gene-related peptide (CGRP) in the dorsal root ganglion (DRG). These findings offer new insights and effective therapeutic options for the future design of transdermal drug delivery for psoriasis.

All Roads Lead to Rome: Comparing Nanoparticle- and Small Molecule-Driven Cell Autophagy

Autophagy, vital for removing cellular waste, is triggered differently by small molecules and nanoparticles. Small molecules, like rapamycin, non-selectively activate autophagy by inhibiting the mTOR pathway, which is essential for cell regulation. This can clear damaged components but may cause cytotoxicity with prolonged use. Nanoparticles, however, induce autophagy, often causing oxidative stress, through broader cellular interactions and can lead to a targeted form known as "xenophagy." Their impact varies with their properties but can be harnessed therapeutically. In this review, the autophagy induced by nanoparticles is explored and small molecules across four dimensions: the mechanisms behind autophagy induction, the outcomes of such induction, the toxicological effects on cellular autophagy, and the therapeutic potential of employing autophagy triggered by nanoparticles or small molecules. Although small molecules and nanoparticles each induce autophagy through different pathways and lead to diverse effects, both represent invaluable tools in cell biology, nanomedicine, and drug discovery, offering unique insights and therapeutic opportunities.

The impact of nanomaterials on autophagy across health and disease conditions

Autophagy, a catabolic process integral to cellular homeostasis, is constitutively active under physiological and stress conditions. The role of autophagy as a cellular defense response becomes particularly evident upon exposure to nanomaterials (NMs), especially environmental nanoparticles (NPs) and nanoplastics (nPs). This has positioned autophagy modulation at the forefront of nanotechnology-based therapeutic interventions. While NMs can exploit autophagy to enhance therapeutic outcomes, they can also trigger it as a pro-survival response against NP-induced toxicity. Conversely, a heightened autophagy response may also lead to regulated cell death (RCD), in particular autophagic cell death, upon NP exposure. Thus, the relationship between NMs and autophagy exhibits a dual nature with therapeutic and environmental interventions. Recognizing and decoding these intricate patterns are essential for pioneering next-generation autophagy-regulating NMs. This review delves into the present-day therapeutic potential of autophagy-modulating NMs, shedding light on their status in clinical trials, intervention of autophagy in the therapeutic applications of NMs, discusses the potency of autophagy for application as early indicator of NM toxicity.

Prospects and hazards of silica nanoparticles: Biological impacts and implicated mechanisms

With the thrive of nanotechnology, silica nanoparticles (SiNPs) have been extensively adopted in the agriculture, food, cosmetic, and even biomedical industries. Due to the mass production and use, SiNPs inevitably entered the environment, resulting in ecological toxicity and even posing a threat to human health. Although considerable investigations have been conducted to assess the toxicity of SiNPs, the correlation between SiNPs exposure and consequent health risks remains ambiguous. Since the biological impacts of SiNPs can differ from their design and application, the toxicity assessment for SiNPs may be extremely difficult. This review discussed the application of SiNPs in different fields, especially their biomedical use, and documented their potential release pathways into the environment. Meanwhile, the current process of assessing SiNPs-related toxicity on various model organisms and cell lines was also detailed, thus estimating the health threats posed by SiNPs exposure. Finally, the potential toxic mechanisms of SiNPs were also elaborated based on results obtained from both in vivo and in vitro trials. This review generally summarizes the biological effects of SiNPs, which will build up a comprehensive perspective of the application and toxicity of SiNPs.

Autophagy regulation by inorganic, organic, and organic/inorganic hybrid nanoparticles: Organelle damage, regulation factors, and potential pathways

The rapid development of nanotechnology requires a more thorough understanding of the potential health effects caused by nanoparticles (NPs). As a programmed cell death, autophagy is one of the biological effects induced by NPs, which maintain intracellular homeostasis by degrading damaged organelles and removing aggregates of defective proteins through lysosomes. Currently, autophagy has been shown to be associated with the development of several diseases. A significant number of research have demonstrated that most NPs can regulate autophagy, and their regulation of autophagy is divided into induction and blockade. Studying the autophagy regulation by NPs will facilitate a more comprehensive understanding of the toxicity of NPs. In this review, we will illustrate the effects of different types of NPs on autophagy, including inorganic NPs, organic NPs, and organic/inorganic hybrid NPs. The potential mechanisms by which NPs regulate autophagy are highlighted, including organelle damage, oxidative stress, inducible factors, and multiple signaling pathways. In addition, we list the factors influencing NPs-regulated autophagy. This review may provide basic information for the safety assessment of NPs.

Mesoporous Core-Cone Silica Nanoparticles Can Deliver miRNA-26a to Macrophages to Exert Immunomodulatory Effects on Osteogenesis In Vitro

Nanoparticles can play valuable roles in delivering nucleic acids, including microRNAs (miRNA), which are small, non-coding RNA segments. In this way, nanoparticles may exert post-transcriptional regulatory influences on various inflammatory conditions and bone disorders. This study used biocompatible, core-cone-structured, mesoporous silica nanoparticles (MSN-CC) to deliver miRNA-26a to macrophages in order to influence osteogenesis in vitro. The loaded nanoparticles (MSN-CC-miRNA-26) showed low-level toxicity towards macrophages (RAW 264.7 cells) and were internalized efficiently, causing the reduced expression of pro-inflammatory cytokines, as seen via real-time PCR and cytokine immunoassays. The conditioned macrophages created a favorable osteoimmune environment for MC3T3-E1 preosteoblasts, driving osteogenic differentiation with enhanced osteogenic marker expression, alkaline phosphatase (ALP) production, extracellular matrix formation, and calcium deposition. An indirect co-culture system revealed that direct osteogenic induction and immunomodulation by MSN-CC-miRNA-26a synergistically increased bone production due to the crosstalk between MSN-CC-miRNA-26a-conditioned macrophages and MSN-CC-miRNA-26a-treated preosteoblasts. These findings demonstrate the value of nanoparticle delivery of miR-NA-26a using MSN-CC for suppressing the production of pro-inflammatory cytokines with macrophages and for driving osteogenic differentiation in preosteoblasts via osteoimmune modulation.

Toxicity mechanism of nanomaterials: Focus on endoplasmic reticulum stress

Over the years, although the broad application of nanomaterials has not brought convenience to people's life, growing concern surrounds their safety. Recently, much emphasis has been placed on exploring the toxicity mechanism of nanoparticles. Currently established toxic mechanisms include oxidative stress, inflammatory response, autophagy, and DNA damage. In recent years, endoplasmic reticulum stress (ERS) has gained widespread attention as another toxic mechanism of nanomaterials. It is widely acknowledged that the endoplasmic reticulum (ER) is an important site for protein synthesis, and lipids and Ca⁺ storage, playing an esseential role in the normal operation of the body functions. When the body's internal environment is damaged, the structure and function of the endoplasmic reticulum are destroyed, leading to a series of biological reactions called endoplasmic reticulum stress (ERS.) This paper reviews the mechanism of ERS in nanomaterial-associated toxicity. The process of ERS and its related unfolded protein response were briefly introduced, summarizing the factors affecting the nanoparticle ability to induce ERS and expounding on the changes of ER morphology after exposure to nanoparticles. Finally, the specific role and molecular mechanism of ERS under the action of different nanoparticles were comprehensively analyzed, including the relationship between ERS and inflammation, oxidative stress, lipid metabolism and apoptosis. This review provides a foothold for future studies on the toxic mechanism of nanoparticles, and provides novel insights into the safe application of nanoparticles and the treatment of diseases.

BECLIN-1-Mediated Autophagy Suppresses Silica Nanoparticle-Induced Testicular Toxicity via the Inhibition of Caspase 8-Mediated Cell Apoptosis in Leydig Cells

Accumulation of silica nanoparticles (SNPs) in the testes leads to male reproductive toxicity. However, little is known about the effect and mechanistic insights of SNP-induced autophagy on apoptosis in Leydig cells. In this study, we aimed to verify the role of SNP-induced autophagy in apoptosis and explore the possible underlying mechanism in mouse primary Leydig cells (PLCs). H&E staining showed that SNPs changed the histological structures of the testes, including a reduction in the Leydig cell populations in vivo. CCK-8 assay showed that SNPs decreased cell viability, and flow cytometry showed that SNPs increased cell apoptosis, both in a dose-dependent manner in vitro. Additionally, Western blotting further found that SNPs activated autophagy by an increase in BECLIN-1, ATG16L, and LC3-II levels and promoted the intrinsic pathway of apoptosis by an increase in the BAX/BCL-2 ratio, cleaved the caspase 8 and caspase 3 levels. Furthermore, autophagy decreased SNP-induced apoptosis via regulation of the caspase 8 level combined with rapamycin, 3-methyladenine, and chloroquine. BECLIN-1 depletion increased the caspase 8 level, leading to an increase in SNP-induced cell apoptosis. Collectively, this evidence demonstrates that SNPs activated BECLIN-1-mediated autophagy, which prevented SNP-induced testicular toxicity via the inhibition of caspase 8-mediated cell apoptosis in Leydig cells.

Apigenin Attenuates Mesoporous Silica Nanoparticles-Induced Nephrotoxicity by Activating FOXO3a

Mesoporous silica nanoparticles (MSNs) are widely used in many biomedical applications and clinical fields. However, the applications of MSNs are limited by their severe toxicity. Apigenin (AG) has demonstrated pharmacological effects with low toxicity. The aim of this study was to clarify the role of AG in the progression of MSNs-induced renal injury. BALB/c mice and NRK-52E cells were exposed to MSNs with or without AG. AG protected mice and NRK-52E cells from the MSNs-induced pathological variations in renal tissues and decreased cell viability. AG significantly reduced the levels of serum blood urea nitrogen (BUN) and serum creatinine (Scr), upregulated the levels of superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT), and improved the pathological changes of the kidney in MSNs-treated mice. The protective effects of AG were associated with its ability to increase the levels of antioxidants, reduce the accumulation of ROS, and inhibit the expression of the inflammatory mediators (TNF-α, IL-6). In addition, AG treatment upregulated the activity of FOXO3a, increased the level of IkBα, and reduced the nuclear translocation of NF-κB, which ultimately alleviated MSNs-induced inflammation. Nuclear FOXO3a translocation also triggered antioxidant gene transcription and protected nephrocyte from oxidative damage. However, knockdown of FOXO3a significantly blocked the protective effects of AG. These findings suggested that AG could be a promising therapeutic strategy for MSNs-induced nephrotoxicity, and this protective effect might be related to the suppression of oxidative stress and inflammation via the FOXO3a/NF-κB pathway.

Activation of Autophagy by Low-Dose Silica Nanoparticles Enhances Testosterone Secretion in Leydig Cells

Silica nanoparticles (SNPs) can cause abnormal spermatogenesis in male reproductive toxicity. However, the toxicity and toxicological mechanisms of SNPs in testosterone synthesis and secretion in Leydig cells are not well known. Therefore, this study aimed to determine the effect and molecular mechanism of low doses of SNPs in testosterone production in Leydig cells. For this, mouse primary Leydig cells (PLCs) were exposed to 100 nm Stöber nonporous spherical SNPs. We observed significant accumulation of SNPs in the cytoplasm of PLCs via transmission electron microscopy (TEM). CCK-8 and flow cytometry assays confirmed that low doses (50 and 100 μg/mL) of SNPs had no significant effect on cell viability and apoptosis, whereas high doses (more than 200 μg/mL) decreased cell viability and increased cell apoptosis in PLCs. Monodansylcadaverine (MDC) staining showed that SNPs caused the significant accumulation of autophagosomes in the cytoplasm of PLCs. SNPs activated autophagy by upregulating microtubule-associated protein light chain 3 (LC3-II) and BCL-2-interacting protein (BECLIN-1) levels, in addition to downregulating sequestosome 1 (SQSTM1/P62) level at low doses. In addition, low doses of SNPs enhanced testosterone secretion and increased steroidogenic acute regulatory protein (StAR) expression. SNPs combined with rapamycin (RAP), an autophagy activator, enhanced testosterone production and increased StAR expression, whereas SNPs combined with 3-methyladenine (3-MA) and chloroquine (CQ), autophagy inhibitors, had an opposite effect. Furthermore, BECLIN-1 depletion inhibited testosterone production and StAR expression. Altogether, our results demonstrate that low doses of SNPs enhanced testosterone secretion via the activation of autophagy in PLCs.

Exploring the role of mesoporous silica nanoparticle in the development of novel drug delivery systems

The biocompatible nature of mesoporous silica nanoparticles (MSN) attracted researchers' attention to deliver therapeutic agents in the treatment of various diseases, where their porous nature, high drug loading efficiency, and suitability to functionalize with a specific ligand of MSN helped to obtain the desired outcome. The application of MSN has been extended to deliver small chemicals to large-sized peptides or proteins to fight against complex diseases. Recently, formulation researches with MSN have been progressed for various non-conventional drug delivery systems, including liposome, microsphere, oro-dispersible film, 3D-printed formulation, and microneedle. Low bulk density, retaining mesoporous structure during downstream processing, and lack of sufficient in vivo studies are some of the important issues towards the success of mesoporous silica-based advanced drug delivery systems. The present review has aimed to evaluate the application of MSN in advanced drug delivery systems to critically analyze the role of MSN in the respective formulation over other functionalized polymers. Finally, an outlook on the future direction of MSN-based advanced drug delivery systems has been drawn against the existing challenges with this platform.

Mechanisms of immune response to inorganic nanoparticles and their degradation products

Careful assessment of the biological fate and immune response of inorganic nanoparticles is crucial for use of such carriers in drug delivery and other biomedical applications. Many studies have elucidated the cellular and molecular mechanisms of the interaction of inorganic nanoparticles with the components of the immune system. The biodegradation and dissolution of inorganic nanoparticles can influence their ensuing immune response. While the immunological properties of inorganic nanoparticles as a function of their physicochemical properties have been investigated in detail, little attention has been paid to the immune adverse effects towards the degradation products of these nanoparticles. To fill this gap, we herein summarize the cellular mechanisms of immune response to inorganic nanoparticles and their degradation products with specific focus on immune cells. We also accentuate the importance of designing new methods and instruments for the in situ characterization of inorganic nanoparticles in order to assess their safety as a result of degradation. This review further sheds light on factors that need to be considered in the design of safe and effective inorganic nanoparticles for use in delivery of bioactive and imaging agents.

Modulating Osteoimmune Responses by Mesoporous Silica Nanoparticles

The immune response plays an important role in biomaterial-mediated osteogenesis. Nanomaterials may influence immune responses and thereby alter bone regeneration. Mesoporous silica nanoparticles (MSNs) have received much attention for drug delivery and bone regeneration. Recently, immunomodulatory effects of MSNs on osteogenesis have been reported. In this Review, we summarize the osteoimmunomodulation of MSNs, including the effects of MSN characteristics on immune cells and osteogenesis. Impacts of MSNs on immune cells vary according to nanoparticle properties, including surface topography and charge, particle size, and ion release. MSNs with suitable doses can inhibit inflammation and create an immune microenvironment beneficial for bone regeneration by activating immune cells and stimulating cytokine release. Further work is needed to explore and clarify the underlying mechanisms, including crosstalk between various types of immune cells and how to design MSNs to create a suitable immune environment for osteogenesis.

Biosafety of mesoporous silica nanoparticles: a combined experimental and literature study

Mesoporous silica (MS) particles have been explored for various healthcare applications, but universal data about their safety and/or toxicity are yet to be well-established for clinical purposes. Information about general toxicity of hollow MS (HMS) particles and about immunotoxicity of MS particles are significantly lacked. Therefore, acute toxicity and immunotoxicity of HMS particles were experimentally evaluated. A systematic and objective literature study was parallelly performed to analyze the published in vivo toxicity of MS particles. Lethal acute toxicity of MS particles is likely to arise from their physical action after intravenous and intraperitoneal administrations, and only rarely observed after subcutaneous administration. No clear relationship was identified between physicochemical properties of MS particles and lethality as well as maximum tolerated dose with some exceptions. At sub-lethal doses, MS particles tend to accumulate mainly in lung, liver, and spleen. The HMS particles showed lower inflammation-inducing ability than polyinosinic-polycytidylic acid and almost the same allergy-inducing ability as Alum. Finally, the universal lowest observed adverse effect levels were determined as 0.45, 0.81, and 4.1 mg/kg (human equivalent dose) for intravenous, intraperitoneal, and subcutaneous administration of MS particles, respectively. These results could be helpful for determining an appropriate MS particle dose in clinical study.

High Surface Area Mesoporous Silica Nanoparticles with Tunable Size in the Sub-Micrometer Regime: Insights on the Size and Porosity Control Mechanisms

Mesoporous silica nanostructures (MSNs) attract high interest due to their unique and tunable physical chemical features, including high specific surface area and large pore volume, that hold a great potential in a variety of fields, i.e., adsorption, catalysis, and biomedicine. An essential feature for biomedical application of MSNs is limiting MSN size in the sub-micrometer regime to control uptake and cell viability. However, careful size tuning in such a regime remains still challenging. We aim to tackling this issue by developing two synthetic procedures for MSN size modulation, performed in homogenous aqueous/ethanol solution or two-phase aqueous/ethyl acetate system. Both approaches make use of tetraethyl orthosilicate as precursor, in the presence of cetyltrimethylammonium bromide, as structure-directing agent, and NaOH, as base-catalyst. NaOH catalyzed syntheses usually require high temperature (>80 °C) and large reaction medium volume to trigger MSN formation and limit aggregation. Here, a successful modulation of MSNs size from 40 up to 150 nm is demonstrated to be achieved by purposely balancing synthesis conditions, being able, in addition, to keep reaction temperature not higher than 50 °C (30 °C and 50 °C, respectively) and reaction mixture volume low. Through a comprehensive and in-depth systematic morphological and structural investigation, the mechanism and kinetics that sustain the control of MSNs size in such low dimensional regime are defined, highlighting that modulation of size and pores of the structures are mainly mediated by base concentration, reaction time and temperature and ageing, for the homogenous phase approach, and by temperature for the two-phase synthesis. Finally, an in vitro study is performed on bEnd.3 cells to investigate on the cytotoxicity of the MNSs.

Biomedical application of mesoporous silica nanoparticles as delivery systems: a biological safety perspective

The application of mesoporous silica nanoparticles (MSNs) as drug delivery systems to deliver drugs, proteins, and genes has expanded considerably in recent years, using in vitro and animal studies. For future translation to clinical applications, the biological safety aspects of MSNs must be considered carefully. This paper reviews the biosafety of MSNs, examining key issues such as biocompatibility, effects on immune cells and erythrocytes, biodistribution, biodegradation and clearance, and how these vary depending on the effects of the physical and chemical properties of MSNs such as particle size, porosity, morphology, surface charge, and chemical modifications. The future use of MSNs as a delivery system must extend beyond what has been learnt thus far using rodent animal models to encompass larger animals.

Nanomaterial-mediated autophagy: coexisting hazard and health benefits in biomedicine

BACKGROUND

Widespread biomedical applications of nanomaterials (NMs) bring about increased human exposure risk due to their unique physicochemical properties. Autophagy, which is of great importance for regulating the physiological or pathological activities of the body, has been reported to play a key role in NM-driven biological effects both in vivo and in vitro. The coexisting hazard and health benefits of NM-mediated autophagy in biomedicine are nonnegligible and require our particular concerns.

MAIN BODY

We collected research on the toxic effects related to NM-mediated autophagy both in vivo and in vitro. Generally, NMs can be delivered into animal models through different administration routes, or internalized by cells through different uptake pathways, exerting varying degrees of damage in tissues, organs, cells, and organelles, eventually being deposited in or excreted from the body. In addition, other biological effects of NMs, such as oxidative stress, inflammation, necroptosis, pyroptosis, and ferroptosis, have been associated with autophagy and cooperate to regulate body activities. We therefore highlight that NM-mediated autophagy serves as a double-edged sword, which could be utilized in the treatment of certain diseases related to autophagy dysfunction, such as cancer, neurodegenerative disease, and cardiovascular disease. Challenges and suggestions for further investigations of NM-mediated autophagy are proposed with the purpose to improve their biosafety evaluation and facilitate their wide application. Databases such as PubMed and Web of Science were utilized to search for relevant literature, which included all published, Epub ahead of print, in-process, and non-indexed citations.

CONCLUSION

In this review, we focus on the dual effect of NM-mediated autophagy in the biomedical field. It has become a trend to use the benefits of NM-mediated autophagy to treat clinical diseases such as cancer and neurodegenerative diseases. Understanding the regulatory mechanism of NM-mediated autophagy in biomedicine is also helpful for reducing the toxic effects of NMs as much as possible.

Pyrogenic and Precipitated Amorphous Silica Nanoparticles Differentially Affect Cell Responses to LPS in Human Macrophages

Previous work has demonstrated that precipitated (NM-200) and pyrogenic (NM-203) Amorphous Silica Nanoparticles (ASNPs) elicit the inflammatory activation of murine macrophages, with more pronounced effects observed with NM-203. Here, we compare the effects of low doses of NM-200 and NM-203 on human macrophage-like THP-1 cells, assessing how the pre-exposure to these nanomaterials affects the cell response to lipopolysaccharide (LPS). Cell viability was affected by NM-203, but not by NM-200, and only in the presence of LPS. While NM-203 stimulated mTORC1, neither ASNPs activated NFκB or the transcription of its target genes PTGS2 and IL1B. NM-200 and NM-203 caused a block of the autophagic flux and inhibited the LPS-dependent increase of Glutamine Synthetase (GS) expression. Both ASNPs suppressed the activation of caspase-1, delaying the LPS-dependent secretion of IL-1β. Thus, ASNPs modulate several important pathways in human macrophages, altering their response to LPS. NM-203 had larger effects on autophagy, mTORC1 activity and GS expression than NM-200, confirming the higher biological activity of pyrogenic ASNPs when compared with precipitated ASNPs.

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.

Enhanced efficacy of propranolol therapy for infantile hemangiomas based on a mesoporous silica nanoplatform through mediating autophagy dysfunction

Infantile hemangioma is one of the most common vascular tumors, which might result in morbidity and mortality without timely intervention. Propranolol is currently the first-line therapy for hemangiomas, but its potential side effects and high frequency of administration make it urgent to develop a suitable drug delivery system for propranolol. In the present study, we formulated a propranolol delivery system based on mesoporous silica nanoparticles (PRN@MSN) and investigated the interplay between autophagic activities mediated by nanoparticles and improved therapeutic efficacy of PRN@MSN. The results showed that PRN@MSN nanoparticles exhibited higher cytotoxicity compared with free propranolol in vitro and in vivo, which could induce excessive autophagosome accumulation through increased autophagosome formation and impaired autophagic degradation. Inhibition of autophagy in the early stage could attenuate the cytotoxicity of PRN@MSN. ROS generation was essential for nanoparticle-mediated autophagy and cytotoxicity, and PRN@MSN-induced autophagy dysfunction could enhance endoplasmic reticulum (ER) stress in hemangioma stem cells. Our study revealed a promising PRN delivery system based on a mesoporous silica nanoplatform that could induce autophagy dysfunction with excessive autophagosome accumulation to promote the therapeutic efficacy of PRN therapy. PRN@MSN drug delivery system combined with autophagy modulation may act as a promising treatment pattern in the treatment of hemangiomas.

Microarray-assisted size-effect study of amorphous silica nanoparticles on human bronchial epithelial cells

Amorphous silica nanoparticles (SiNPs) are not only abundant in nature, but also the second largest engineering nanomaterials in terms of annual output. Respiratory exposure is the main route for SiNPs to enter the human body. A large number of studies have focused on the respiratory toxicity of SiNPs and demonstrated that SiNPs could induce pulmonary tissue damage, inflammation, fibrosis, and even the malignant transformation of bronchial epithelial cells, while the size-dependent toxicity of SiNPs and their underlying biological mechanisms remain unclear. In this regard, a transcriptomics study would be conductive to gaining a better understanding of the toxic mechanism. In the present study, microarray analysis was performed to investigate the genome-wide transcriptional alteration induced by different sizes of SiNPs in human primary bronchial epithelial cells (BEAS-2B). To determine the effect of the particle size on the toxicity, nanoparticles of two sizes (41 nm and 61 nm) and submicron particles of one size (206 nm) were introduced. The bioinformatics analysis results indicated that: (1) the number of differentially expressed genes in the three SiNP-treated groups increased with the particle size decreasing; (2) the genes involved in the immune and inflammatory response, gene expression, signal transduction, endoplasmic reticulum stress, oxidative stress, cell metabolism, and cell proliferation were gradually upregulated with the particle size decreasing, while the genes related to the morphological development of the respiratory system were gradually downregulated with the particle size decreasing; (3) the modes of action of the two nanoparticles overlapped with each other to some degree, and there existed many different modes compared to those from the submicron particles; (4) both the silica nanoparticles affected the pathways associated with the cell entry of silica nanoparticles, autophagy and lysosomal dysfunction, endoplasmic reticulum stress, inflammatory response, DNA damage, and gene expression, as well as apoptotic resistance and cancer. To the best of our knowledge, this is the first study that has reported the alteration trend of gene expression profiles with the change in silica particle size. Our study provides a great deal of information on the toxic mechanisms underlying the respiratory toxicity induced by SiNPs, and can also serve as an experimental basis for the toxicity and safety evaluation of silica nanoparticles.

Polymer-Coated Gold Nanospheres Do Not Impair the Innate Immune Function of Human B Lymphocytes in Vitro

Gold nanoparticles (GNPs) are intended for use within a variety of biomedical applications due to their physicochemical properties. Although, in general, biocompatibility of GNPs with immune cells such as macrophages and dendritic cells is well established, the impact of GNPs on B lymphocyte immune function remains to be determined. Since B lymphocytes play an important role in health and disease, the suitability of GNPs as a B cell-targeting tool is of high relevance. Thus, we provide information on the interactions of GNPs with B lymphocytes. Herein, we exposed freshly isolated human B lymphocytes to a set of well-characterized and biomedically relevant GNPs with distinct surface (polyethylene glycol (PEG), PEG/poly(vinyl alcohol) (PEG/PVA)) and shape (spheres, rods) characteristics. Polymer-coated GNPs poorly interacted with B lymphocytes, in contrast to uncoated GNPs. Importantly, none of the GNPs significantly affected cell viability, even at the highest concentration of 20 μg/mL over a 24 h suspension exposure period. Furthermore, none of the nanosphere formulations affected the expression of activation markers (CD69, CD86, MHC II) of the naive B lymphocytes, nor did they cause an increase in the secretion of pro-inflammatory cytokines ( i.e. , IL-6, IL-1β). However, the absence of polymer coating on the sphere GNPs and the rod shape caused a decrease in IL-6 cytokine production by activated B lymphocytes, suggesting a functional impairment. With these findings, the present study contributes imperative knowledge toward the safe-by-design approaches being conducted to benefit the development of nanomaterials, specifically those as theranostic tools.

Particle toxicology and health - where are we?

BACKGROUND

Particles and fibres affect human health as a function of their properties such as chemical composition, size and shape but also depending on complex interactions in an organism that occur at various levels between particle uptake and target organ responses. While particulate pollution is one of the leading contributors to the global burden of disease, particles are also increasingly used for medical purposes. Over the past decades we have gained considerable experience in how particle properties and particle-bio interactions are linked to human health. This insight is useful for improved risk management in the case of unwanted health effects but also for developing novel medical therapies. The concepts that help us better understand particles' and fibres' risks include the fate of particles in the body; exposure, dosimetry and dose-metrics and the 5 Bs: bioavailability, biopersistence, bioprocessing, biomodification and bioclearance of (nano)particles. This includes the role of the biomolecule corona, immunity and systemic responses, non-specific effects in the lungs and other body parts, particle effects and the developing body, and the link from the natural environment to human health. The importance of these different concepts for the human health risk depends not only on the properties of the particles and fibres, but is also strongly influenced by production, use and disposal scenarios.

CONCLUSIONS

Lessons learned from the past can prove helpful for the future of the field, notably for understanding novel particles and fibres and for defining appropriate risk management and governance approaches.

Rapamycin Alleviates Hormone Imbalance-Induced Chronic Nonbacterial Inflammation in Rat Prostate Through Activating Autophagy via the mTOR/ULK1/ATG13 Signaling Pathway

Chronic prostatitis (CP) is a clinically common disease with high morbidity. It affects the patients' quality of life (QoL) as well as physical and mental health seriously due to the recurring symptoms of lower urinary tract and genitalia. As the opinions about the etiology of CP are still not uniform, it is very difficult to be treated or even cured. Autophagy is a highly conserved physiological function which is widely found in eukaryotic cells. In general, cells maintain a certain level of autophagy under physiological conditions, and the basal level of autophagy can be regulated by a variety of autophagy-related genes under stress such as hunger, infection, trauma, and other circumstances. Therefore, the main purpose of this study is to investigate the role of autophagy in chronic nonbacterial prostatitis (CNP, also called CP). In this paper, we established the CNP model via hypodermic injection of 17β-estradiol and subsequently abdominal rapamycin (a common autophagy inducer) treatment based on castrated rats. Then, the expression of nuclear factor-κB (NF-κB), interleukin-1β (IL-1β), and autophagy-related markers as well as autophagosome formation in prostate tissues, peripheral blood mononuclear cells (PBMCs), and serum of rats were evaluated respectively. In addition to some histological changes in the prostate tissues, we found the levels of NF-κB and IL-1β were significantly increased in the model group, along with significantly suppressed autophagy, whereas rapamycin could reverse these effects which involved in the mTOR/ULK1/ATG13 signaling pathway. In conclusion, our results suggested that rapamycin could ameliorate hormone imbalance-induced CNP by activating autophagy.

Crosstalk between Autophagy and Nanomaterials: Internalization, Activation, Termination

Nanomaterials (NMs) are comprehensively applied in biomedicine due to their unique physical and chemical properties. Autophagy, as an evolutionarily conserved cellular quality control process, is closely associated with the effect of NMs on cells. In this review, the recent advances in NM-induced/inhibited autophagy (NM-phagy) are summarized, with an aim to present a comprehensive description of the mechanisms of NM-phagy from the perspective of internalization, activation, and termination, thereby bridging autophagy and nanomaterials. Several possible mechanisms are extensively reviewed including the endocytosis pathway of NMs and the related cross components (clathrin and adaptor protein 2 (AP-2), adenosine diphosphate (ADP)-ribosylation factor 6 (Arf6), Rab, UV radiation resistance associated gene (UVRAG)), three main stress mechanisms (oxidative stress, damaged organelles stress, and toxicity stress), and several signal pathway-related molecules. The mechanistic insight is beneficial to understand the autophagic response to NMs or NMs' regulation of autophagy. The challenges currently encountered and research trend in the field of NM-phagy are also highlighted. It is hoped that the NM-phagy discussion in this review with the focus on the mechanistic aspects may serve as a guideline for future research in this field.

The toxicity of silica nanoparticles to the immune system

Silicon-based materials and their oxides are widely used in drug delivery, dietary supplements, implants and dental fillers. Silica nanoparticles (SiNPs) interact with immunocompetent cells and induce immunotoxicity. However, the toxic effects of SiNPs on the immune system have been inadequately reviewed. The toxicity of SiNPs to the immune system depends on their physicochemical properties and the cell type. Assessments of immunotoxicity include determining cell dysfunctions, cytotoxicity and genotoxicity. This review focuses on the immunotoxicity of SiNPs and investigates the underlying mechanisms. The main mechanisms were proinflammatory responses, oxidative stress and autophagy. Considering the toxicity of SiNPs, surface and shape modifications may mitigate the toxic effects of SiNPs, providing a new way to produce these nanomaterials with less toxic impaction.

Silica nanoparticles induce autophagosome accumulation via activation of the EIF2AK3 and ATF6 UPR pathways in hepatocytes

Autophagy dysfunction is a potential toxic effect of nanoparticles. Previous studies have indicated that silica nanoparticles (SiNPs) induce macroautophagy/autophagy dysfunction, while the precise mechanisms remain uncertain. Hence, the present study investigated the molecular mechanisms by which SiNPs enhanced autophagosome synthesis, which then contributed to autophagy dysfunction. First, the effects of SiNPs on autophagy and autophagic flux were verified using transmission electron microscopy, laser scanning confocal microscopy, and western blot assays. Then, the activation of endoplasmic reticular (ER) stress was validated to be through the EIF2AK3 and ATF6 UPR pathways but not the ERN1-XBP1 pathway, along with the upregulation of downstream ATF4 and DDIT3. Thereafter, the ER stress inhibitor 4-phenylbutyrate (4-PBA) was used to verify that SiNP-induced autophagy could be influenced by ER stress. Furthermore, specialized lentiviral shRNA were employed to determine that autophagy was induced via specific activation of the EIF2AK3 and ATF6 UPR pathways. Finally, the 2 autophagic genes LC3B and ATG12 were found to be transcriptionally upregulated by downstream ATF4 and DDIT3 in ER stress, which contributed to the SiNP-enhanced autophagosome synthesis. Taken together, these data suggest that SiNPs induced autophagosome accumulation via the activation of the EIF2AK3 and ATF6 UPR pathways in hepatocytes, which offers a new insight into detailed molecular mechanisms underlying SiNP-induced autophagy dysfunction, and specifically how UPR pathways regulate key autophagic genes. This work provides novel evidence for the study of toxic effects and risk assessment of SiNPs.

Modulation of Macrophage Phenotype by Biodegradable Polyurethane Nanoparticles: Possible Relation between Macrophage Polarization and Immune Response of Nanoparticles

Nanomaterials with surface functionalized by different chemical groups can either provoke or attenuate the immune responses of the nanomaterials, which is critical to their biomedical efficacies. In this study, we demonstrate that synthetic waterborne polyurethane nanoparticles (PU NPs) can inhibit the macrophage polarization toward the M1 phenotype but not M2 phenotype. The surface-functionalized PU NPs decrease the secretion levels of proinflammatory cytokines (TNF-α and IL-1β) for M1 macrophages. Specifically, PU NPs with carboxyl groups on the surface exhibit a greater extent of inhibition on M1 polarization than those with amine groups. These water-suspended PU NPs reduce the nuclear factor-κB (NF-κB) activation and suppress the subsequent NLR family pyrin domain containing 3 (NLRP3) inflammasome signals. Furthermore, the dried PU films assembled from PU NPs have a similar effect on macrophage polarization and present a smaller shifting foreign body reaction (FBR) in vivo than the conventional poly(l-lactic acid). Taken together, the biodegradable waterborne PU NPs demonstrate surface-dependent immunosuppressive properties and macrophage polarization effects. The findings suggest potential therapeutic applications of PU NPs in anti-inflammation and macrophage-related disorders and propose a mechanism for the low FBR observed for biodegradable PU materials.

Combining autophagy-inducing peptides and brefeldin A delivered by perinuclear-localized mesoporous silica nanoparticles: a manipulation strategy for ER-phagy

Autophagic degradation of the endoplasmic reticulum (ER-phagy) has been found to play a critical role in human sensory neuropathy. So far, however, specific and efficient intervention means for ER-phagy remain unexplored. Herein, brefeldin A (BFA), a blocking agent on protein transport between the ER and Golgi, was screened from ER stress inducers. BFA was then delivered to the perinuclear area co-localized with the ER by a mesoporous silica nanoparticle-based drug-carrier functionalized with autophagy-inducing peptides of TAT-beclin 1 (MSNs-BFA), to evoke a perturbation of ER-phagy. The molecular mechanism of ER-phagy regulated by BFA was explored by biochemical evaluation including time-lapse live-cell fluorescence imaging. We found that MSNs-BFA treatment caused a lower mRNA/protein expression level of FAM134b even under a compensation of autophagic flux in U2OS cells, and resulted in ER-expansion. The fragmentation of the ER was blocked as a response to ER stress mediated by inactivation of the AKT/TSC/mTOR pathway. Our work developed an efficient external manipulation strategy to regulate ER-phagy and may contribute to the therapeutic application of autophagy-related major human diseases.

MicroRNA-143 Targets ATG2B to Inhibit Autophagy and Increase Inflammatory Responses in Crohn's Disease

BACKGROUND

Dysfunctional autophagy is recognized as a contributing factor in many chronic inflammatory diseases, including Crohn's disease (CD). Genetic analyses have found that microRNA (miRNA) levels are altered in the intestinal tissues of CD patients.

METHODS

The Sequencing Alternative Poly-Adenylation Sites (SAPAS) method was used to compare the 3' end of the total mRNA sequence of 3 surgical specimens of CD patients (including inflamed tissues and corresponding noninflamed tissues in each case). The levels of autophagy-related 2B (ATG2B), LC3, and miR-143 were compared between inflamed tissues and noninflamed tissues using immunoblot and quantitative reverse transcription polymerase chain reaction. Luciferase assays were used to verify the interactions between miR-143 and ATG2B. Autophagy was measured by immunoblot analyses of LC3 and transmission electron microscopy. Inflammatory cytokines and IκBα were analyzed to evaluate the effect of miR-143 on inflammatory response.

RESULTS

The tandem repeat 3'-UTR of ATG2B was longer in inflamed tissues than in corresponding noninflamed tissues and contained an miR-143 target site. miR-143 expression was elevated, whereas ATG2B and LC3-II were downregulated in inflamed tissues. The direct interaction between miR-143 and ATG2B was verified by a 3'-UTR dual-luciferase reporter assay. Constitutive expression of miR-143 or depletion of ATG2B in cultured intestinal epithelial cells inhibited autophagy, reduced IκBα levels, and increased inflammatory responses.

CONCLUSIONS

miR-143 may induce bowel inflammation by regulating ATG2B and autophagy, suggesting that miR-143 might play a critical role in the development of CD. Therefore, miR-143 could be a promising novel target for gene therapy in CD patients.

Differential proteomics highlights macrophage-specific responses to amorphous silica nanoparticles

The technological and economic benefits of engineered nanomaterials may be offset by their adverse effects on living organisms. One of the highly produced nanomaterials under such scrutiny is amorphous silica nanoparticles, which are known to have an appreciable, although reversible, inflammatory potential. This is due to their selective toxicity toward macrophages, and it is thus important to study the cellular responses of this cell type to silica nanoparticles to better understand the direct or indirect adverse effects of nanosilica. We have here studied the responses of the RAW264.7 murine macrophage cells and of the control MPC11 plasma cells to subtoxic concentrations of nanosilica, using a combination of proteomic and targeted approaches. This allowed us to document alterations in the cellular cytoskeleton, in the phagocytic capacity of the cells as well as their ability to respond to bacterial stimuli. More surprisingly, silica nanoparticles also induce a greater sensitivity of macrophages to DNA alkylating agents, such as styrene oxide, even at doses which do not induce any appreciable cell death.

Molecular Elucidation of Biological Response to Mesoporous Silica Nanoparticles in Vitro and in Vivo

Biomedical applications of mesoporous silica nanoparticles (MSNs) require efficient cellular uptake and low toxicity. The purpose of this study is to investigate the cellular uptake and toxicity of MSNs with different sizes and charges (50, 100, and 250 nm with a positive surface charge and 100 nm with a negative surface charge) exposed to human monocyte-derived macrophages, lung epithelium BEAS-2B cells, and mice using genome-wide gene expression analysis and cellular/animal-level end point tests. We found that MSNs can be taken up into cells through endocytosis in a charge- and size-dependent manner, with positively charged and larger MSNs being more easily taken up into the cells by recruiting more types of endocytotic pathways for more cellular uptake. Moreover, the cytotoxicity of MSNs could be correlated with the amount of MSNs taken up by cells, which positively correlates to the particle size and dosage. Therefore, only positively charged and larger MSNs (≥100 nm) during higher treatment doses (≥500 μg mL^-1) resulted in a sufficient accumulation of internalized MSNs in cells to induce significant release of reactive oxygen species (ROS) and oxidative stress, inflammatory gene upregulation through NF-κB and AP-1, and eventually autophagy-mediated necrotic cell death. Furthermore, genome-wide gene expression analysis could reflect the above in vitro cellular damages and corresponding in vivo injuries in mice, indicating that specific gene expression footprints may be used for assessing the safety of nanoparticles. The present finding provides some insights into the rational design of effective MSN-based drug/gene delivery systems and biomedical applications.

New findings of silica nanoparticles induced ER autophagy in human colon cancer cell

Nanoparticle-induced autophagy has been extensively studied, however, real time information about the endoplasmic reticulum involved autophagic process (ER autophagy) induced by nanomaterials remains unknown. In this work, silica nanoparticles (SNPs) were synthesized with characteristics of low toxicity, good biocompatibility and excellent water dispersibility to treat cells. Results show that either low concentration (10 μg/mL) or high concentration (200 μg/mL) of SNPs could increase the quantity of processing from microtubule-associated protein 1-light chain 3-I (LC3-I) to the other variant of LC3 (LC3-II). Interestingly, the level of autophagy induced by the SNPs is associated with the treated time but not the concentrations of SNPs. Importantly, for the first time, SNP accumulation in ER was discovered through co-localization analysis, which incurs ER autophagy. These new findings about SNPs-induced ER autophagy could open an effective way for securely designing silica-based nanoparticles and enable us to know more about ER autophagy.

Silica nanoparticles induce autophagy dysfunction via lysosomal impairment and inhibition of autophagosome degradation in hepatocytes

Autophagy dysfunction is considered as a potential toxic mechanism of nanomaterials. Silica nanoparticles (SiNPs) can induce autophagy, but the specific mechanism involved remains unclear. Therefore, the aim of this study was to confirm the effects of SiNPs on autophagy dysfunction and explore the possible underlying mechanism. In this article, we reported that cell-internalized SiNPs exhibited dose- and time-dependent cytotoxicity in both L-02 and HepG2 cells. Multiple methods verified that SiNPs induced autophagy even at the noncytotoxic level and blocked the autophagic flux at the high-dose level. Notably, SiNPs impaired the lysosomal function through damaging lysosomal ultrastructures, increasing membrane permeability, and downregulating the expression of lysosomal proteases, cathepsin B, as evidenced by transmission electron microscopy, acridine orange staining, quantitative reverse transcription-polymerase chain reaction, and Western blot assays. Collectively, these data concluded that SiNPs inhibited autophagosome degradation via lysosomal impairment in hepatocytes, resulting in autophagy dysfunction. The current study not only discloses a potential mechanism of autophagy dysfunction induced by SiNPs but also provides novel evidence for the study of toxic effect and safety evaluation of SiNPs.

LncRNAs expression in adjuvant-induced arthritis rats reveals the potential role of LncRNAs contributing to rheumatoid arthritis pathogenesis

BACKGROUND

Long non-coding RNAs (LncRNAs) are an important class of widespread molecules involved in diverse biological functions, which are exceptionally expressed in numerous types of diseases. Currently, limited study on LncRNA in rheumatoid arthritis (RA) is available. In this study, we aimed to identify the specifically expressed LncRNA that are relevant to adjuvant-induced arthritis (AA) in rats, and to explore the possible molecular mechanisms of RA pathogenesis.

METHODS

To identify LncRNAs specifically expressed in rheumatoid arthritis, the expression of LncRNAs in synoviums of rats from the model group (n=3) was compared with that in the control group (n=3) using Arraystar Rat LncRNA/mRNA microarray and real-time polymerase chain reaction (RT-PCR).

RESULTS

Up to 260 LncRNAs were found to be differentially expressed (≥1.5-fold-change) in the synoviums between AA model and the normal rats (170 up-regulated and 90 down-regulated LncRNAs in AA rats compared with normal rats). Coding-non-coding gene co-expression networks (CNC network) were drawn based on the correlation analysis between the differentially expressed LncRNAs and mRNAs. Six LncRNAs, XR_008357, U75927, MRAK046251, XR_006457, DQ266363 and MRAK003448, were selected to analyze the relationship between LncRNAs and RA via the CNC network and GO analysis. Real-time PCR result confirmed that the six LncRNAs were specifically expressed in the AA rats.

CONCLUSIONS

These results revealed that clusters of LncRNAs were uniquely expressed in AA rats compared with controls, which manifests that these differentially expressed LncRNAs in AA rats might play a vital role in RA development. Up-regulation or down-regulation of the six LncRNAs might contribute to the molecular mechanism underlying RA. To sum up, our study provides potential targets for treatment of RA and novel profound understanding of the pathogenesis of RA.