Persistency of Enlarged Autolysosomes Underscores Nanoparticle-Induced Autophagy in Hepatocytes

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.

Identification of Potent siRNA Delivery Peptides Using Computer Modeling

Peptides with suitable aggregation behavior and electrical properties are potential siRNA delivery vectors. However, identifying suitable peptides with ideal delivery and safety features is difficult owing to the variations in amino acid sequences. Here, a holistic program based on computer modeling and single-cell RNA sequencing (scRNA-seq) is used to identify ideal siRNA delivery peptides. Stage one of this program consists of a sequential screening process for candidates with ideal assembly and delivery ability; stage two is a cell subtype-level analysis program that screens for high in vivo tissue safety. The leading candidate peptide selected from a library containing 12 amino acids showed strong lung-targeted siRNA delivery capacity after hydrophobic modification. Systemic administration of these compounds caused the least damage to liver and lung tissues and has little impact on macrophage and neutrophil numbers. By loading STAT3 siRNA, strong anticancer effects are achieved in multiple models, including patient-derived xenografts (PDX). This screening procedure may facilitate the development of peptide-based RNA interference (RNAi) therapeutics.

Enhanced Sensitivity of A549 Cells to Doxorubicin with WS2 and WSe2 Nanosheets via the Induction of Autophagy

The excellent physicochemical properties of two-dimensional transition-metal dichalcogenides (2D TMDCs) such as WS2 and WSe2 provide potential benefits for biomedical applications, such as drug delivery, photothermal therapy, and bioimaging. WS2 and WSe2 have recently been used as chemosensitizers; however, the detailed molecular basis underlying WS2- and WSe2-induced sensitization remains elusive. Our recent findings showed that 2D TMDCs with different thicknesses and different element compositions induced autophagy in normal human bronchial epithelial cells and mouse alveolar macrophages at sublethal concentrations. Here, we explored the mechanism by which WS2 and WSe2 act as sensitizers to increase lung cancer cell susceptibility to chemotherapeutic agents. The results showed that WS2 and WSe2 enhanced autophagy flux in A549 lung cancer cells at sublethal concentrations without causing significant cell death. Through the autophagy-specific RT2 Profiler PCR Array, we identified the genes significantly affected by WS2 and WSe2 treatment. Furthermore, the key genes that play central roles in regulating autophagy were identified by constructing a molecular interaction network. A mechanism investigation uncovered that WS2 and WSe2 activated autophagy-related signaling pathways by interacting with different cell surface proteins or cytoplasmic proteins. By utilizing this mechanism, the efficacy of the chemotherapeutic agent doxorubicin was enhanced by WS2 and WSe2 pre-treatment in A549 lung cancer cells. This study revealed a feature of WS2 and WSe2 in cancer therapy, in which they eliminate the resistance of A549 lung cancer cells against doxorubicin, at least partially, by inducing autophagy.

Autophagy inhibitors for cancer therapy: Small molecules and nanomedicines

Autophagy is a conserved process in which the cytosolic materials are degraded and eventually recycled for cellular metabolism to maintain homeostasis. The dichotomous role of autophagy in pathogenesis is complicated. Accumulating reports have suggested that cytoprotective autophagy is responsible for tumor growth and progression. Autophagy inhibitors, such as chloroquine (CQ) and hydroxychloroquine (HCQ), are promising for treating malignancies or overcoming drug resistance in chemotherapy. With the rapid development of nanotechnology, nanomaterials also show autophagy-inhibitory effects or are reported as the carriers delivering autophagy inhibitors. In this review, we summarize the small-molecule compounds and nanomaterials inhibiting autophagic flux as well as the mechanisms involved. The nanocarrier-based drug delivery systems for autophagy inhibitors and their distinct advantages are also described. The progress of autophagy inhibitors for clinical applications is finally introduced, and their future perspectives are discussed.

Combined surface functionalization of MSC membrane and PDA inhibits neurotoxicity induced by Fe3O4 in mice based on apoptosis and autophagy through the ASK1/JNK signaling pathway

The extensive utilization of iron oxide nanoparticles in medical and life science domains has led to a substantial rise in both occupational and public exposure to these particles. The potential toxicity of nanoparticles to living organisms, their impact on the environment, and the associated risks to human health have garnered significant attention and come to be a prominent area in contemporary research. The comprehension of the potential toxicity of nanoparticles has emerged as a crucial concern to safeguard human health and facilitate the secure advancement of nanotechnology. As nanocarriers and targeting agents, the biocompatibility of them determines the use scope and application prospects, meanwhile surface modification becomes an important measure to improve the biocompatibility. Three different types of iron oxide nanoparticles (Fe3O4, Fe3O4@PDA and MSCM-Fe3O4@PDA) were injected into mice through the tail veins. The acute neurotoxicity of them in mice was evaluated by measuring the levels of autophagy and apoptosis in the brain tissues. Our data revealed that iron oxide nanoparticles could cause nervous system damage by regulating the ASK1/JNK signaling pathway. Apoptosis and autophagy may play potential roles in this process. Exposure to combined surface functionalization of mesenchymal stem cell membrane and polydopamine showed the neuroprotective effect and may alleviate brain nervous system disorders.

Silicon dioxide nanoparticles compromise decidualization via autophagy impairment to possibly cause embryo resorption

The wide application of silicon dioxide nanoparticles (SiO₂NPs) has raised concerns about their harmful effects on reproduction. The purpose of this research was to investigate the toxic effects and the possible mechanisms by which SiO₂NPs affect decidualization and pregnancy progression. We found that SiO₂NPs could inhibit decidualization, both in mice and in human endometrial stromal cells (HESCs). Embryo resorption was also evident in mice treated with SiO₂NPs. When HESCs were treated with SiO₂NPs, decidualization was inhibited and there was an increase in intracellular lysosomes and autophagosomes as well as the blockage of autophagic flux. Interestingly, a reduction of autophagosome accumulation via 3-methyladenine (3MA) significantly restored the decidualization of HESCs. In summary, our results indicate that SiO₂NPs can affect embryo survival by impairing decidualization through a dysfunctional autophagic process.

Long-lasting postoperative analgesia with local anesthetic-loaded hydrogels prevent tumor recurrence via enhancing CD8+T cell infiltration

Postoperative pain (POP) can promote tumor recurrence and reduce the cancer patient's quality of life. However, POP management has always been separated from tumor treatment in clinical practice, and traditional postoperative analgesia using opioids is still unsatisfactory for patients, which is not conducive to tumor treatment. Here, ropivacaine, a popular amide-type LA, was introduced into a Pluronic F127 hydrogel. Postoperative analgesia with ropivacaine-loaded hydrogels reduced the incidence of high-dose ropivacaine-induced convulsions and prolonged pain relief for more than 16 h. More interestingly, ropivacaine-loaded hydrogel was found to upregulate major histocompatibility complex class I (MHC-I) in tumor cells by impairing autophagy. Therefore, a hydrogel co-dopped with ropivacaine and TLR7 agonist imiquimod (PFRM) was rationally synthesized. After postoperative analgesia with PFRM, imiquimod primes tumor-specific CD8⁺T cells through promoting DCs maturation, and ropivacaine facilitates tumor cells recognition by primed CD8⁺T cells through upregulating MHC-I. Consequently, postoperative analgesia with PFRM maximumly increases CD8⁺T cells infiltration into residual tumor tissue and prevents tumor recurrence. Overall, this study for the first time provides an LA-based approach for simultaneous long-lasting postoperative analgesia and prevention of tumor recurrence.

Inhibition of Pro-Survival Autophagy Induced by Rare-Earth Nanocomposites for Promoting Photothermal Therapy of Visualized Tumors

Manipulation of autophagic processes has emerged as a promising strategy for synergizing nanoagent-mediated photothermal therapy (PTT). Most of the current studies focus on improving PTT efficacy by inhibiting pro-survival autophagy induced by the heat generated from the photothermal process. However, autophagy induced by the nanoagents is usually ignored, which may weaken the effect of autophagy-mediated efficacy improvement in PTT if induced autophagy is pro-death. Therefore, this work aims at developing a nanoagent that is able to induce heat-synergetic pro-survival autophagy to optimize the efficacy of PTT. An approach is developed to coat carbon layer, polyethylenimine (PEI), and folic acid (FA) on NaYF₄ :Er,Yb,Nd@NaNdF₄ (DCNPs@C@PEI@FA, DCPF) nanoparticles successively, giving access to the nanoagent to induce pro-survival autophagy. The synthetic imaging-guided photothermal nanoagent displays outstanding targeting ability and biocompatibility based on the surface modification of PEI and FA. By using an autophagy inhibitor chloroquine, a conspicuously synergistic effect on DCPF-mediated PTT in vitro and in vivo tumor models (HeLa) is achieved. A promising strategy is presented here to enhance the efficacy of imaging-guided PTT by modulating the autophagy induced by the nanoagent.

Nano-drug delivery system for pancreatic cancer: A visualization and bibliometric analysis

Background: Nano drug delivery system (NDDS) can significantly improve the delivery and efficacy of drugs against pancreatic cancer (PC) in many ways. The purpose of this study is to explore the related research fields of NDDS for PC from the perspective of bibliometrics.

Methods: Articles and reviews on NDDS for PC published between 2003 and 2022 were obtained from the Web of Science Core Collection. CiteSpace, VOSviewer, R-bibliometrix, and Microsoft Excel were comprehensively used for bibliometric and visual analysis.

Results: A total of 1329 papers on NDDS for PC were included. The number of papers showed an upward trend over the past 20 years. The United States contributed the most papers, followed by China, and India. Also, the United States had the highest number of total citations and H-index. The institution with the most papers was Chinese Acad Sci, which was also the most important in international institutional cooperation. Professors Couvreur P and Kazuoka K made great achievements in this field. JOURNAL OF CONTROLLED RELEASE published the most papers and was cited the most. The topics related to the tumor microenvironment such as “tumor microenvironment”, “tumor penetration”, “hypoxia”, “exosome”, and “autophagy”, PC treatment-related topics such as “immunotherapy”, “combination therapy”, “alternating magnetic field/magnetic hyperthermia”, and “ultrasound”, and gene therapy dominated by “siRNA” and “miRNA” were the research hotspots in the field of NDDS for PC.

Conclusion: This study systematically uncovered a holistic picture of the performance of NDDS for PC-related literature over the past 20 years. We provided scholars to understand key information in this field with the perspective of bibliometrics, which we believe may greatly facilitate future research in this field.

H(+)/Cl(‑) exchange transporter 7 promotes lysosomal acidification‑mediated autophagy in mouse cardiomyocytes

Autophagy protects cardiomyocytes in various pathological and physiological conditions; however, the molecular mechanisms underlying its influence and the promotion of autophagic clearance are not completely understood. The present study aimed to explore the role of H(+)/Cl(−) exchange transporter 7 (CLC-7) in cardiomyocyte autophagy. In this study, rapamycin was used to induce autophagy in mouse cardiomyocytes, and the changes in CLC-7 were investigated. The expression levels of CLC-7 and autophagy-related proteins, such as microtubule associated protein 1 light chain 3, autophagy related 5 and Beclin 1, were detected using western blotting or immunofluorescence. Autolysosomes were observed and analyzed using transmission electron microscopy and immunofluorescence following CLC-7 silencing with small interfering RNAs. Cellular viability was assessed using Cell Counting Kit-8 and lactate dehydrogenase assays. Lysosomal acidification was measured using an acidification indicator. Increased CLC-7 co-localization with lysosomes was identified during autophagy. CLC-7 knockdown weakened the acidification of lysosomes, which are the terminal compartments of autophagy flux, and consequently impaired autophagy flux, ultimately resulting in cell injury. Collectively, the present study demonstrated that in cardiomyocytes, CLC-7 may contribute to autophagy via regulation of lysosomal acidification. These findings provide novel insights into the role of CLC-7 in autophagy and cytoprotection.

Protein corona formation of human serum albumin with carbon quantum dots from roast salmon

When food-borne nanoparticles enter biological systems, they can interact with various proteins to form protein coronas, which can affect their physicochemical properties and biological identity. In this study, the protein corona formation of carbon quantum dots (CQDs) from roast salmon with human serum albumin (HSA) was explored. Furthermore, the biological identity of the HSA-CQD coronas, in relation to cell apoptosis, energy, glucose and lipid metabolism and acute toxicity in mice, was also investigated. The HSA-CQD coronas were formed between HSA and CQDs via a static binding mechanism, and the binding site of CQDs on HSA was located at both Sudlow's site I and site II. After entering the cytoplasm, the HSA-CQD coronas became localized in the lysosomes and autolysosomes. Importantly, the HSA coronas reduced the cytotoxicity of the CQDs from 18.65% to 9.26%, and the energy metabolism was rectified by changing from glycolytic to aerobic metabolism. The glucose and lipid metabolite profile of cells exposed to the HSA-CQD coronas differed from that of those treated with CQDs, indicating that the HSA-CQD coronas rectified metabolic disturbances caused by CQDs. Histopathological and blood biochemical analysis revealed no statistically significant differences between the treated and control mice after a single CQDs dose of 2000 mg per kg body weight. Overall, the results confirmed the formation of protein coronas between HSA and food-borne fluorescent CQDs, and could be helpful for evaluating the safety of fluorescent CQDs in cooked food items.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

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.

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.

Rationally designed rapamycin-encapsulated ZIF-8 nanosystem for overcoming chemotherapy resistance

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles are widely reported as a pH-sensitive drug delivery carrier with high loading capacity for tumor therapy. However, the mechanism of intracellular corrosion of ZIF-8 and the corresponding biological effects especially for autophagy response have been rarely reported. Herein, the as-synthesized ZIF-8 was demonstrated to induce mTOR independent and pro-death autophagy. Interestingly, the autophagic process participated in the corrosion of ZIF-8. Subsequently, zinc ion release and the generation of reactive oxygen species due to its corrosion in the acidic compartments were directly responsible for tumor cell killing. In addition, ZIF-8 could sensitize tumor cells to chemotherapy by switching cytoprotective to death promoting autophagy induced by doxorubicin. The mTOR signaling pathway activation was demonstrated to restrict tumor chemotherapy efficiency. Hence, a combined platform rapamycin encapsulated zeolitic imidazolate frameworks (Rapa@ZIF-8) was constructed and demonstrated a more significant chemo-sensitized effect relative to ZIF-8 nanoparticles or rapamycin treatment alone. Lastly, the combined administration of Rapa@ZIF-8 and doxorubicin exhibited an outstanding synergistic antitumor effect without any obvious toxicity to the major organs of mice. Collectively, the optimized nanoplatform, Rapa@ZIF-8, provides a proof of concept for intentionally interfering mTOR pathway and utilizing the switch of survival-to death-promoting autophagy for adjunct chemotherapy.

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.

Combination therapy with ropivacaine-loaded liposomes and nutrient deprivation for simultaneous cancer therapy and cancer pain relief

Autophagy allows cancer cells to respond changes in nutrient status by degrading and recycling non-essential intracellular contents. Inhibition of autophagy combined with nutrient deprivation is an effective strategy to treat cancer. Pain is a primary determinant of poor quality of life in advanced cancer patients, but there is currently no satisfactory treatment. In addition, effective treatment of cancer does not efficiently relieve cancer pain, but may increase pain in many cases. Hence, few studies focus on simultaneous cancer therapy and pain relief, and made this situation even worse.

Method: Ropivacaine was loaded into tumor-active targeted liposomes. The cytotoxicity of ropivacaine-based combination therapy in B16 and HeLa cells were tested. Moreover, a mice model of cancer pain which was induced by inoculation of melanoma near the sciatic nerve was constructed to assess the cancer suppression and pain relief effects of ropivacaine-based combination therapy.

Results: Ropivacaine and ropivacaine-loaded liposomes (Rop-DPRL) were novelly found to damage autophagic degradation. Replicated administration of Rop-DPRL and calorie restriction (CR) could efficiently repress the development of tumor. In addition, administration of Rop-DPRL could relieve cancer pain with its own analgestic ability in a short duration, while repeated administration of Rop-DPRL and CR resulted in continuous alleviation of cancer pain through reduction of VEGF-A levels in advanced cancer mice. Further, dual inhibition of phosphorylation of STAT3 at Tyr705 and Ser727 by Rop-DPRL and CR contribute to the reduction of VEGF-A.

Conclusion: Combination therapy with Rop-DPRL and nutrient deprivation simultaneously suppresses cancer growth and relieves cancer pain.

Autophagy Modulated by Inorganic Nanomaterials

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

Pro-Death or Pro-Survival: Contrasting Paradigms on Nanomaterial-Induced Autophagy and Exploitations for Cancer Therapy

Autophagy is a critical lysosome-mediated cellular degradation process for the clearance of damaged organelles, obsolete proteins, and invading pathogens and plays important roles in the pathogenesis and treatment of human diseases including cancer. While not a cell death process per se, autophagy is nevertheless intimately linked to a cell's live/die decision. Basal autophagy, operating constitutively at low levels in essentially every mammalian cell, is vital for maintaining cellular homeostasis and promotes cell survival. On the other hand, elevated level of autophagy is frequently observed in cells responding to a physical, chemical, or biological stress. This "induced" autophagy, a hallmark under a variety of pathological and pathophysiological conditions, may be either pro-death or pro-survival, two contrasting paradigms for cell fate determination. Research in our laboratory and other groups around the world over the last 15 years has revealed nanomaterials as a unique class of autophagy inducers, with the capability of elevating the cellular autophagy to extremely high levels. In this Account we focus on the contrasting cell fate decision impacted by nanomaterial-induced autophagy. First, we give a brief introduction to nanomaterial-induced autophagy and summarize our current understanding on how it affects a cell's live/die decision. Autophagy induced by nanomaterials, in most cases, promotes cell death, but a significant number of nanomaterials are also able to elicit pro-survival autophagy. Although not a common feature, some nanomaterials may induce pro-death autophagy in one cell type while eliciting pro-survival autophagy in a different cell type. The ability to control the level of the induced autophagy, and furthermore its pro-death/pro-survival nature, is critically important for nanomedicine. Second, we discuss several possible mechanistic insights on the pro-death/pro-survival decision for nanomaterial-induced autophagy. "Disrupted" autophagic processes, with a "block" or perhaps "diversion" at the various stages, may be a characteristic hallmark for nanomaterial-induced autophagy, rendering it intrinsically pro-death in nature. On the other hand, autophagy-mediated upregulation and activation of pro-survival factors or signaling pathways, overriding the intrinsic pro-death nature, may be a common mechanism for nanomaterial-induced pro-survival autophagy. In addition, cargo degradation and reactive oxygen species may also play important roles in the pro-death/pro-survival decision impacted by nanomaterial-induced autophagy. Finally, we focus on the situation where nanomaterials induce autophagy in cancer cells and summarize the different strategies in exploiting the pro-death or pro-survival nature of nanomaterial-induced autophagy to enhance the various modalities of cancer therapy, including direct cancer cell killing, chemotherapy and radiotherapy, photothermal therapy, and integrated diagnosis and therapy. While the details vary, the basic principle is simple and straightforward. If the induced autophagy is pro-death, maximize it. Otherwise, inhibit it. Effective exploitation of nanomaterial-induced autophagy has the potential to become a new weapon in our ever-increasing arsenal to fight cancer, particularly difficult-to-treat and drug-resistant cancer.

Aggregation Behavior of Nanoparticle-Peptide Systems Affects Autophagy

The aggregation of nanoparticle colloidal dispersions in complex biological environments changes the nanoparticle properties, such as size and surface area, thus affecting the interaction of nanoparticles at the interface with cellular components and systems. We investigated the effect of nanoparticle aggregation on autophagy, the main catabolic pathway that mediates degradation of nanosized materials and that is activated in response to internalization of foreign nanosized materials. We used carboxylated polystyrene nanoparticles (100 nm) and altered the nanoparticle aggregation behavior through addition of a multidomain peptide, thus generating a set of nanoparticle-peptide mixtures with variable aggregation properties. Specifically, modulating the peptide concentration resulted in nanoparticle-peptide mixtures that are well dispersed extracellularly but aggregate upon cellular internalization. We monitored the effect of internalization of nanoparticle-peptide mixtures on a comprehensive set of markers of the autophagy pathway, ranging from transcriptional regulation to clearance of autophagic substrates. The nanoparticle-peptide mixtures were found to activate the transcription factor EB, a master regulator of autophagy and lysosomal biogenesis. We also found that intracellular aggregation of nanoparticle colloidal dispersions causes blockage of autophagic flux. This study provides important insights on the effect of the aggregation properties of nanoparticles on cells and, particularly, on the main homeostatic pathway activated in response to nanoparticle internalization. These results also point to the need to control the colloidal stability of nanoparticle systems for a variety of biomedical applications.

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.

Autophagic Degradation Deficit Involved in Sevoflurane-Induced Amyloid Pathology and Spatial Learning Impairment in APP/PS1 Transgenic Mice

The adverse effects of anesthetics on elderly people, especially those with brain diseases are very concerning. Whether inhaled anesthetics have adverse effects on Alzheimer’s disease (AD), which is the most common form of dementia with brain degenerative changes, remains controversial. Autophagy, a crucial biological degradation process, is extremely important for the pathogenesis of AD. In this study, the inhaled anesthetic sevoflurane elicited many enlarged autolysosomes and impaired the overall autophagic degradation in the hippocampus of an AD mouse model, which is involved in the accumulation of amyloid-β (Aβ) and spatial learning deficits. However, rapamycin treatment counteracted all these effects. The results suggested that inhaled anesthetics may accelerate the pathological process of AD, and enlarged autolysosomes may be a new marker for prediction and diagnosis of the neurotoxicity of anesthetics in AD.

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.

Development of Research into Autophagic Lysosome Reformation

Autophagy is a lysosome-dependent degradation process that is essential for maintaining cellular homeostasis. In recent years, more studies have focused on the late stages of autophagy. Our group discovered and studied the terminal step of autophagy, namely autophagic lysosome reformation (ALR). ALR is the process that regenerates functional lysosomes from autolysosomes, thus maintaining lysosome homeostasis. ALR involves clathrin-mediated membrane budding from autolysosomes, elongation of membrane tubules along microtubules with the pulling force provided by the motor protein KIF5B, proto-lysosome scission by dynamin 2, and finally maturation of proto-lysosomes to functional lysosomes. In this review, we will summarize progress in unveiling the molecular mechanisms underlying ALR and its potential pathophysiological roles.