Differential toxic responses between pristine and functionalized multiwall nanotubes involve induction of autophagy accumulation in murine lung

Enhancing Therapeutic Efficacy in Cancer Treatment: Integrating Nanomedicine with Autophagy Inhibition Strategies

The complicated stepwise lysosomal degradation process known as autophagy is in charge of destroying and eliminating damaged organelles and defective cytoplasmic components. This mechanism promotes metabolic adaptability and nutrition recycling. Autophagy functions as a quality control mechanism in cells that support homeostasis and redox balance under normal circumstances. However, the role of autophagy in cancer is controversial because, mostly depending on the stage of the tumor, it may either suppress or support the disease. While autophagy delays the onset of tumors and slows the dissemination of cancer in the early stages of tumorigenesis, numerous studies demonstrate that autophagy promotes the development and spread of tumors as well as the evolution and development of resistance to several anticancer drugs in advanced cancer stages. In this Review, we primarily emphasize the therapeutic role of autophagy inhibition in improving the treatment of multiple cancers and give a broad overview of how its inhibition modulates cancer responses. There have been various attempts to inhibit autophagy, including the use of autophagy inhibitor drugs, gene silencing therapy (RNA interference), and nanoparticles. In this Review, all these topics are thoroughly covered and illustrated by recent studies and field investigations.

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.

Perturbation of autophagy: An intrinsic toxicity mechanism of nanoparticles

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

Novel Approaches of Dysregulating Lysosome Functions in Cancer Cells by Specific Drugs and Its Nanoformulations: A Smart Approach of Modern Therapeutics

The smart strategy of cancer cells to bypass the caspase-dependent apoptotic pathway has led to the discovery of novel anti-cancer approaches including the targeting of lysosomes. Recent discoveries observed that lysosomes perform far beyond just recycling of cellular waste, as these organelles are metabolically very active and mediate several signalling pathways to sense the cellular metabolic status. These organelles also play a significant role in mediating the immune system functions. Thus, direct or indirect lysosome-targeting with different drugs can be considered a novel therapeutic approach in different disease including cancer. Recently, some anticancer lysosomotropic drugs (eg, nortriptyline, siramesine, desipramine) and their nanoformulations have been engineered to specifically accumulate within these organelles. These drugs can enhance lysosome membrane permeabilization (LMP) or disrupt the activity of resident enzymes and protein complexes, like v-ATPase and mTORC1. Other anticancer drugs like doxorubicin, quinacrine, chloroquine and DQ661 have also been used which act through multi-target points. In addition, autophagy inhibitors, ferroptosis inducers and fluorescent probes have also been used as novel theranostic agents. Several lysosome-specific drug nanoformulations like mixed charge and peptide conjugated gold nanoparticles (AuNPs), Au-ZnO hybrid NPs, TPP-PEG-biotin NPs, octadecyl-rhodamine-B and cationic liposomes, etc. have been synthesized by diverse methods. These nanoformulations can target cathepsins, glucose-regulated protein 78, or other lysosome specific proteins in different cancers. The specific targeting of cancer cell lysosomes with drug nanoformulations is quite recent and faces tremendous challenges like toxicity concerns to normal tissues, which may be resolved in future research. The anticancer applications of these nanoformulations have led them up to various stages of clinical trials. Here in this review article, we present the recent updates about the lysosome ultrastructure, its cross-talk with other organelles, and the novel strategies of targeting this organelle in tumor cells as a recent innovative approach of cancer management.

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.

The Applications of Carbon Nanotubes in the Diagnosis and Treatment of Lung Cancer: A Critical Review

The importance of timely diagnosis and the complete treatment of lung cancer for many people with this deadly disease daily increases due to its high mortality. Diagnosis and treatment with helping the nanoparticles are useful, although they have reasonable harms. This article points out that the side effects of using carbon nanotube (CNT) in this disease treatment process such as inflammation, fibrosis, and carcinogenesis are very problematic. Toxicity can reduce to some extent using the techniques such as functionalizing to proper dimensions as a longer length, more width, and greater curvature. The targeted CNT sensors can be connected to various modified vapors. In this regard, with helping this method, screening makes non-invasive diagnosis possible. Researchers have also found that nanoparticles such as CNTs could be used as carriers to direct drug delivery, especially with chemotherapy drugs. Most of these carriers were multi-wall carbon nanotubes (MWCNT) used for cancerous cell targeting. The results of laboratory and animal researches in the field of diagnosis and treatment became very desirable and hopeful. The collection of researches summarized has highlighted the requirement for a detailed assessment which includes CNT dose, duration, method of induction, etc., to achieve the most controlled conditions for animal and human studies. In the discussion section, 4 contradictory issues are discussed which are invited researchers to do more research to get clearer results.

Distinct autophagy-apoptosis related pathways activated by Multi-walled (NM 400) and Single-walled carbon nanotubes (NIST-SRM2483) in human bronchial epithelial (16HBE14o-) cells

Given the recent development in the field of particle and fibre toxicology, parallels have been drawn between Carbon nanotubes (CNTs) and asbestos. It is now established that both multi-walled (MWCNTs) and single-walled (SWCNTs) carbon nanotubes might contribute to pulmonary disease. Although multiple mechanisms might be involved in CNT induced pathogenesis, systematic understanding of the relationship between different CNT exposure (MWCNT vs SWCNT) and autophagy/ apoptosis/ necrosis, in human lung epithelial cells remains limited. In this study, we demonstrate that exposure to MWCNT (NM-400), but not SWCNT (NIST-SRM2483), leads to an autophagic response after acute exposure (24 h). MWCNT exposure was characterized by an increase in anti-apoptotic BCL2, downregulation of executor Caspase-3/7 and increase in expression of genes from the autophagy machinery. For SWCNT exposure however, we observed an overexpression of executor Caspase-3/7 and upregulation of pro-apoptotic BAX; enrichment for processes like cornification, apoptotic process, cell differentiation from proteomic analysis. These results clearly indicate a major difference in the pathways initiated by the CNTs, in vitro. While the present study design provides mechanistic understanding after an acute exposure for the tested CNTs, we believe that the information obtained here would have relevance in better understanding of CNT toxicity and pathogenesis in general.

Cytotoxicity and genotoxicity of MWCNT-7 and crocidolite: assessment in alveolar epithelial cells versus their coculture with monocyte-derived macrophages

In the past years, several in vitro studies have addressed the pulmonary toxicity of multi-walled carbon nanotubes (MWCNT) and compared it with that caused by asbestos fibers, but their conclusions have been somewhat inconsistent and difficult to extrapolate to in vivo. Since cell coculture models were proposed to better represent the in vivo conditions than conventional monocultures, this work intended to compare the cytotoxicity and genotoxicity of MWCNT-7 (Mitsui-7) and crocidolite using A549 cells grown in a conventional monoculture or in coculture with THP-1 macrophages. Although a decrease in A549 viability was noted following exposure to a concentration range of MWCNT-7 and crocidolite, no viability change occurred in similarly exposed cocultures. Early events indicating epithelial to mesenchymal transition (EMT) were observed which could explain apoptosis resistance. The comet assay results were similar between the two models, being positive and negative for crocidolite and MWCNT-7, respectively. An increase in the micronucleus frequency was detected in the cocultured A549-treated cells with both materials, but not in the monoculture. On the other hand, exposure of A549 monocultures to MWCNT-7 induced a highly significant increase in nucleoplasmic bridges in which those were found embedded. Our overall results demonstrate that (i) both materials are cytotoxic and genotoxic, (ii) the presence of THP-1 macrophages upholds the viability of A549 cells and increases the aneugenic/clastogenic effects of both materials probably through EMT, and (iii) MWCNT-7 induces the formation of nucleoplasmic bridges in A549 cells.

The preparation of carbon nanofillers and their role on the performance of variable polymer nanocomposites

New synergic behavior is always inspiring scientists toward the formation of nanocomposites aiming at getting advanced materials with superior performance and/or novel properties. Carbon nanotubes (CNT), graphene, fullerene, and graphite as carbon-based are great fillers for polymeric materials. The presence of these materials in the polymeric matrix would render it several characteristics, such as electrical and thermal conductivity, magnetic, mechanical, and as sensor materials for pressure and other environmental changes. This review presents the most recent works in the use of CNT, graphene, fullerene, and graphite as filler in different polymeric matrixes. The primary emphasis of this review is on CNT preparation and its composites formation, while others carbon-based nano-fillers are also introduced. The methods of making polymer nanocomposites using these fillers and their impact on the properties obtained are also presented and discussed.

Comparison of multi-wall carbon nanotube and nitrogen-doped multi-wall carbon nanotube effects on lung function and airway reactivity in rats

Incorporation of multi-wall carbon nanotubes (MWCNT) into materials has raised concerns about their potential hazards to manufacturing workers. In animal models, airway inflammation and lung fibrosis follow aspiration, instillation, and inhalation exposures to MWCNT. However, the effects of MWCNT on pulmonary function, airway reactivity and airway epithelium function following inhalation exposure has not been studied. We investigated whether inhaled MWCNT affects lung resistance (R_L) and dynamic compliance (C_dyn), reactivity to inhaled methacholine (MCh), epithelial regulation of airway reactivity to MCh in vitro, and airway epithelial ion transport. Male rats were exposed by whole body inhalation for 6 h to air or aerosolized MWCNT (0.5, 1 or 5 mg/m³) for one or nine days. Eighteen h after 1 d exposure to 5 mg/m³ MWCNT, basal R_L was increased and basal C_dyn was decreased; changes did not persist for 7 d. Reactivity to MCh (R_L) was increased and C_dyn responses were decreased at 18 h, but not 7 d after exposure to 1 and 5 mg/m³ MWCNT. The effects of i.t.-instilled MWCNT and nitrogen-doped MWCNT (N-MWCNT) on pulmonary function and reactivity to MCh at doses comparable to deposition after inhalation of 5 mg/m³ at 1 d and 0.5, 1, and 5 mg/m³ MWCNT 9 d-exposures were compared. Both nanoparticles increased airway reactivity (R_L); N-MWCNT did not affect C_dyn responses. Lung function and airway reactivity are altered following a single MWCNT inhalation and generally subside over time. Given i.t., MWCNT's and N-MWCNT's effects were comparable, but N-MWCNT evoke smaller changes in C_dyn responses.

Carbon nanotubes, but not spherical nanoparticles, block autophagy by a shape-related targeting of lysosomes in murine macrophages

Nanoparticles (NPs) can be toxic, depending on their physico-chemical characteristics. Macroautophagy/autophagy could represent a potential underlying mechanism of this toxicity. We therefore set up a study aimed to characterize in depth the effects, on autophagy, of macrophage exposure to NPs, with a particular attention paid to the role of NP physico-chemical characteristics (specifically chemical composition, shape, size, length, crystal phase, and/or surface properties). We demonstrate that exposure to carbon nanotubes (CNT) but not to spherical NPs leads to the blockage of the autophagic flux. We further identified lysosomal dysfunction, in association with the downregulation of SNAPIN expression, as the underlying mechanism responsible for the CNT-induced autophagy blockade. These results identify for the first time the shape as a major determinant of the interaction of NPs with the autophagy pathway. Moreover, identifying the lysosomes and SNAPIN as primary targets of MWCNT toxicity opens new directions in the interpretation and understanding of nanomaterial toxicity.

The Effects of Varying Degree of MWCNT Carboxylation on Bioactivity in Various In Vivo and In Vitro Exposure Models

Functionalization has been shown to alter toxicity of multi-walled carbon nanotube (MWCNT) in several studies. This study varied the degree of functionalization (viz., amount of MWCNT surface carboxylation) to define the relationship between the extent of carboxylation and effects in a variety of in vitro cell models and short-term ex vivo/in vivo particle exposures. Studies with vitamin D₃ plus phorbol ester transformed THP-1 macrophages demonstrated that functionalization, regardless of amount, corresponded with profoundly decreased NLRP3 inflammasome activation. However, all MWCNT variants were slightly toxic in this model. Alternatively, studies with A549 epithelial cells showed some varied effects. For example, IL-33 and TNF-α release were related to varying amounts of functionalization. For in vivo particle exposures, autophagy of alveolar macrophages, measured using green fluorescent protein (GFP)- fused-LC3 transgenic mice, increased for all MWCNT tested three days after exposure, but, by Day 7, autophagy was clearly dependent on the amount of carboxylation. The instilled source MWCNT continued to produce cellular injury in alveolar macrophages over seven days. In contrast, the more functionalized MWCNT initially showed similar effects, but reduced over time. Dark-field imaging showed the more functionalized MWCNTs were distributed more uniformly throughout the lung and not isolated to macrophages. Taken together, the results indicated that in vitro and in vivo bioactivity of MWCNT decreased with increased carboxylation. Functionalization by carboxylation eliminated the bioactive potential of the MWCNT in the exposure models tested. The observation that maximally functionalized MWCNT distribute more freely throughout the lung with the absence of cellular damage, and extended deposition, may establish a practical use for these particles as a safer alternative for unmodified MWCNT.

Evaluating the mechanistic evidence and key data gaps in assessing the potential carcinogenicity of carbon nanotubes and nanofibers in humans

In an evaluation of carbon nanotubes (CNTs) for the IARC Monograph 111, the Mechanisms Subgroup was tasked with assessing the strength of evidence on the potential carcinogenicity of CNTs in humans. The mechanistic evidence was considered to be not strong enough to alter the evaluations based on the animal data. In this paper, we provide an extended, in-depth examination of the in vivo and in vitro experimental studies according to current hypotheses on the carcinogenicity of inhaled particles and fibers. We cite additional studies of CNTs that were not available at the time of the IARC meeting in October 2014, and extend our evaluation to include carbon nanofibers (CNFs). Finally, we identify key data gaps and suggest research needs to reduce uncertainty. The focus of this review is on the cancer risk to workers exposed to airborne CNT or CNF during the production and use of these materials. The findings of this review, in general, affirm those of the original evaluation on the inadequate or limited evidence of carcinogenicity for most types of CNTs and CNFs at this time, and possible carcinogenicity of one type of CNT (MWCNT-7). The key evidence gaps to be filled by research include: investigation of possible associations between in vitro and early-stage in vivo events that may be predictive of lung cancer or mesothelioma, and systematic analysis of dose-response relationships across materials, including evaluation of the influence of physico-chemical properties and experimental factors on the observation of nonmalignant and malignant endpoints.

Cytogenetic evaluation of functionalized single-walled carbon nanotube in mice bone marrow cells

With their unique structure and physicochemical properties, single\-walled carbon nanotubes (SWCNTs) have many potential new applications in medicine and industry. However, there is lack of detailed information concerning their impact on human health and the environment. The aim of this study was to assess the effects, after intraperitoneal injection of functionalized SWCNTs (f-SWCNT) on the induction of reactive oxygen species (ROS), frequency of structural chromosomal aberrations (SCA), frequency of micronuclei induction, mitotic index, and DNA damage in Swiss-Webster mice. Three doses of f-SWCNTs (0.25, 0.5, and 0.75 mg/kg) and two controls (negative and positive) were administered to mice, once a day for 5 days. Bone marrow and peripheral blood samples were collected 24 h after the last treatment following standard protocols. F-SWCNT exposure significantly enhanced ROS, increased (p < 0.05) the number of SCA and the frequency of micronucleated cells, increased DNA damage, and decreased the mitotic index in exposed groups compared to negative control. The scientific findings reported here suggest that purified f-SWCNT have the potential to induce oxidative stress mediated genotoxicity in Swiss-Webster mice at higher level of exposure. Further characterization of their systemic toxicity, genotoxicity, and carcinogenicity is also essential. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1091-1102, 2016.

Dual contribution of surface charge and protein-binding affinity to the cytotoxicity of polystyrene nanoparticles in nonphagocytic A549 cells and phagocytic THP-1 cells

Knowledge that links the physicochemical properties of nanoparticles (NP) to their toxicity is key to evaluating and understanding mechanisms underlying toxicity and developing appropriate testing methods for NP; however, this is currently limited since only a small set of NP have been used, with typically poor control of their physical properties. In this study, eight types of polystyrene NP (PLNP) were synthesized with different functional groups, but all based on an identical core. In vitro cell-based assays were performed to determine the influence of changes in physicochemical properties, such as charge, hydrodynamic size, and protein binding potential, in relation to NP-mediated toxicity. The PLNP were incubated with nonphagocytic A549 cells or phagocytic differentiated THP-1 cells for 4 h with/without fetal bovine serum (FBS), followed by incubation for 20 h in FBS-supplemented medium with/without a washing step, to assess cell-type specificity and impact of protein corona formation. The effect of surface charge on cytotoxicity differed between A549 cells and THP-1 cells. In nonphagocytic A549 cells, the zeta potential of PLNP exhibited a negative correlation with cytotoxicity, partly due to the level of coronated protein that might affect cellular uptake. In phagocytic THP-1 cells, the zeta potential of PLNP showed a positive correlation with cytotoxicity but coronated protein levels displayed no marked association with cytotoxicity, owing to the professional uptake efficacy of phagocytic cells. The consistency of our data with THP-1 cells with the surface charge paradigm in nanotoxicology suggests that phagocytic cells are the predominant targets for lung inflammatory reactions induced by PLNP.

Multiwalled carbon nanotubes intratracheally instilled into the rat lung induce development of pleural malignant mesothelioma and lung tumors

Multiwalled carbon nanotubes (MWCNT) have a fibrous structure and physical properties similar to asbestos and have been shown to induce malignant mesothelioma of the peritoneum after injection into the scrotum or peritoneal cavity in rats and mice. For human cancer risk assessment, however, data after administration of MWCNT via the airway, the exposure route that is most relevant to humans, is required. The present study was undertaken to investigate the carcinogenicity of MWCNT‐N (NIKKISO) after administration to the rat lung. MWCNT‐N was fractionated by passing it through a sieve with a pore size of 25 μm. The average lengths of the MWCNT were 4.2 μm before filtration and 2.6 μm in the flow‐through fraction; the length of the retained MWCNT could not be determined. For the present study, 10‐week‐old F344/Crj male rats were divided into five groups: no treatment, vehicle control, MWCNT‐N before filtration, MWCNT‐N flow‐through and MWCNT‐N retained groups. Administration was by the trans‐tracheal intrapulmonary spraying (TIPS) method. Rats were administered a total of 1 mg/rat during the initial 2 weeks of the experiment and then observed up to 109 weeks. The incidences of malignant mesothelioma and lung tumors (bronchiolo‐alveolar adenomas and carcinomas) were 6/38 and 14/38, respectively, in the three groups administered MWCNT and 0/28 and 0/28, respectively, in the control groups. All malignant mesotheliomas were localized in the pericardial pleural cavity. The sieve fractions did not have a significant effect on tumor incidence. In conclusion, administration of MWCNT to the lung in the rat induces malignant mesothelioma and lung tumors.

Intravenous Administration of Multiwalled Carbon Nanotubes Aggravates High-Fat Diet-Induced Nonalcoholic Steatohepatitis in Sprague Dawley Rats

Multiwalled carbon nanotubes (MWCNTs) have been explored in pharmaceutical applications such as tumor targeting and delivery of drugs, in which MWCNTs are given through intravenous injection. However, the biosafety of MWCNTs is of concern for such application. Therefore, in the current study, we used a fatty liver model to investigate the possible toxicity of MWCNTs to the liver, as MWCNTs were retained mainly in the liver of mice after intravenous injection. Male Sprague Dawley rats were used to generate the fatty liver model, and the effects of intravenous administration of MWCNTs on fatty liver were studied. Hematoxylin and eosin staining for hepatocellular anatomy and Masson trichrome staining for hepatic fibrosis were conducted. Histologically, MWCNTs aggravated steatohepatitis with higher nonalcoholic fatty liver disease scores. Analysis of liver injury markers indicated that MWCNTs administration resulted in chronic hepatitis, along with increased liver fat and altered liver oxidation, including the increase of P6 protein and the depletion of glutathione. In conclusion, our results suggest that MWCNTs can aggravate nonalcoholic steatohepatitis in Sprague Dawley rats, and oxidative injury may be involved in this process.

Modifications of carbon black nanoparticle surfaces modulate type II pneumocyte homoeostasis

Inhalation uptake of carbon black nanoparticles (CBNP) bears the risk of morphological and functional lung impairment attributed to the highly reactive particle surface area. Chemical particle surface modifications might affect particle-cell interactions; however, thus far these alterations have not been determined. This is the first in vivo study comparing particle-induced acute lung injury using Printex(®)90 (Pr90, 7 µg), Printex®90 covered by benzo[a]pyrene or 9-nitroanthracene (BaP-Pr90, NA-Pr90, 7 µg, 15% BaP or NA by weight), and acetylene carbon black (CB) with polycyclic aromatic hydrocarbons (PAH-AB, 7 µg, 20% PAH by weight). All particles were suspended in distilled water with bovine serum albumin (BSA). In addition, the influence of suspension media was tested using Printex®90 suspended without BSA (Pr90(-BSA), 7 µg). Quartz (DQ12, 7 µg), 70 µl saline (NaCl), and distilled water with or without BSA (H2O(+/-BSA)) were used as reference and controls. It was postulated that CBNP surface modifications trigger pulmonary responses. After oropharyngeal particle aspiration, lung functions were measured 2 d postexposure, followed by lung preparation for histological or bronchoalveolar lavage fluid (BALF) examinations and type II pneumocyte isolation on d 3. Head-out body plethysmography revealed reduced flow rates induced by PAH-AB. Examinations of BALF demonstrated reduced influx of macrophages after exposure to Pr90(-BSA) and decreased lymphocyte levels after Pr90(+BSA) or BaP-Pr90 treatment. Further, CBNP induced changes in mRNA expressions (surfactant proteins) in type II pneumocytes. These findings indicate that CBNP surface area and media modulate interactions between NP and lung cells in short-term experiments.

Gold nanoparticles: A critical review of therapeutic applications and toxicological aspects

Gold (Au) compounds have been utilized as effective therapeutic agents for the treatment of some inflammatory diseases such as rheumatoid arthritis. However, Au compound use has become limited due to associated high incidence of side effects. Recent development of nanomaterials for therapeutic use with Au-containing drugs is improving the beneficial actions and reducing toxic properties of these agents. Lower toxicity in conjunction with anti-inflammatory and antiangiogenic effects was reported to occur with gold nanoparticles (AuNP) treatment. However, despite this therapeutic potential, safety of AuNP remains to be determined, since the balance between therapeutic properties and development of adverse effects is not well established. Several variables that drive this benefit-risk balance, including physicochemical characteristics of nanoparticles such as size, shape, surface area, and chemistry, are poorly described in the scientific literature. Moreover, therapeutic and toxicological data were obtained employing nonstandardized or poorly described protocols with different experimental settings (animal species/cell type, route and time of exposure). In contrast, effective and safe application of AuNP may be established only after elucidation of various physicochemical properties of each specific AuNP, and determination of respective kinetics and interaction of compound with target tissue. This critical review conveys the state of the art, the therapeutic use, and adverse effects mediated by AuNP, with primary emphasis on anti-inflammatory and antiangiogenic potential, highlighting the limitations/gaps in the scientific literature concerning important points: (i) selection of experimental designs (in vitro and in vivo models) and (ii) consideration of different physicochemical properties of AuNP that are often disregarded in many scientific publications. In addition, prospects and future needs for research in this area are provided.

Inhalation Exposure to Carbon Nanotubes (CNT) and Carbon Nanofibers (CNF): Methodology and Dosimetry

Carbon nanotubes (CNT) and nanofibers (CNF) are used increasingly in a broad array of commercial products. Given current understandings, the most significant life-cycle exposures to CNT/CNF occur from inhalation when they become airborne at different stages of their life cycle, including workplace, use, and disposal. Increasing awareness of the importance of physicochemical properties as determinants of toxicity of CNT/CNF and existing difficulties in interpreting results of mostly acute rodent inhalation studies to date necessitate a reexamination of standardized inhalation testing guidelines. The current literature on pulmonary exposure to CNT/CNF and associated effects is summarized; recommendations and conclusions are provided that address test guideline modifications for rodent inhalation studies that will improve dosimetric extrapolation modeling for hazard and risk characterization based on the analysis of exposure-dose-response relationships. Several physicochemical parameters for CNT/CNF, including shape, state of agglomeration/aggregation, surface properties, impurities, and density, influence toxicity. This requires an evaluation of the correlation between structure and pulmonary responses. Inhalation, using whole-body exposures of rodents, is recommended for acute to chronic pulmonary exposure studies. Dry powder generator methods for producing CNT/CNF aerosols are preferred, and specific instrumentation to measure mass, particle size and number distribution, and morphology in the exposure chambers are identified. Methods are discussed for establishing experimental exposure concentrations that correlate with realistic human exposures, such that unrealistically high experimental concentrations need to be identified that induce effects under mechanisms that are not relevant for workplace exposures. Recommendations for anchoring data to results seen for positive and negative benchmark materials are included, as well as periods for postexposure observation. A minimum data set of specific bronchoalveolar lavage parameters is recommended. Retained lung burden data need to be gathered such that exposure-dose-response correlations may be analyzed and potency comparisons between materials and mammalian species are obtained considering dose metric parameters for interpretation of results. Finally, a list of research needs is presented to fill data gaps for further improving design, analysis, and interpretation and extrapolation of results of rodent inhalation studies to refine meaningful risk assessments for humans.

Single-walled carbon nanotubes alleviate autophagic/lysosomal defects in primary glia from a mouse model of Alzheimer's disease

Defective autophagy in Alzheimer's disease (AD) promotes disease progression in diverse ways. Here, we demonstrate impaired autophagy flux in primary glial cells derived from CRND8 mice that overexpress mutant amyloid precursor protein (APP). Functionalized single-walled carbon nanotubes (SWNT) restored normal autophagy by reversing abnormal activation of mTOR signaling and deficits in lysosomal proteolysis, thereby facilitating elimination of autophagic substrates. These findings suggest SWNT as a novel neuroprotective approach to AD therapy.

Potential toxicity of differential functionalized multiwalled carbon nanotubes (MWCNT) in human cell line (BEAS2B) and Caenorhabditis elegans

The aim of this study was to evaluate in vitro (human bronchial epithelial cells, BEAS2B cells) and in vivo (the nematode Caenorhabditis elegans, C. elegans) toxicity outcomes following exposure to pristine as well as surface-functionalized multiwalled carbon nanotubes (MWCNT) following hydroxylation-oxygenation (O(+)), amination (NH2), or carboxylation (COOH) of the carbon nanotubes (CNT). Cell viability and proliferation were measured by Ez-Cytox, trypan blue exclusion, and colony formation assays. The genotoxic potential of the MWCNT was determined by using the alkaline comet assay. In addition, survival and reproduction were used as endpoints for detection of toxicity of MWCNT in C. elegans. The carboxylated (COOH)-MWCNT was found most toxic as evidenced by cytotoxic and genotoxic among all tested compounds. The order of sensitivity was COOH > O(+) > NH2 > pristine. There were almost no marked changes in survival following exposure of C. elegans to MWCNT. It is of interest that only pristine MWCNT exerted significant reduction in reproductive capacity of C. elegans. Surface functionalization significantly influenced the bioactivity of MWCNT, which displayed species as well as target-organ specificity. The mechanisms underlying these specific modes of nano-biological interactions need to be elucidated.

Single-wall carbon nanotubes (SWCNT) induce cytotoxicity and genotoxicity produced by reactive oxygen species (ROS) generation in phytohemagglutinin (PHA)-stimulated male human peripheral blood lymphocytes

Single-wall carbon nanotubes (SWCNT) possess a small size, large surface area, and high reactivity, which enable them to permeate the cytoplasmic or nuclear membrane and attach to biological molecules. During medical applications, SWNCT are usually administered intravenously, which enhances interaction with blood components. Yet despite this exposure potential, safety evaluation studies of SWCNTs focused on human blood cells are still lacking. Therefore, this study was undertaken to examine cytotoxicity, genotoxicity, and proinflammatory responses following SWCNT treatment of phytohemagglutinin (PHA)-stimulated male human peripheral blood lymphocytes (PBL). SWCNT were found to inhibit cell growth, as well as to induce DNA breakage, and micronuclei (MN) formation via reactive oxygen species (ROS) generation. The addition of N-acetylcysteine (NAC) a cell-permeable antioxidant, decreased ROS generation, cytotoxicity, and genotoxicity produced by SWCNT treatment. In addition, SWCNT induced tumor necrosis factor (TNF)-α release after 24 h, yet this phenomenon was not related to ROS generation, as antioxidant NAC treatment did not affect increased proinflammatory cytokine levels in the phytohemagglutinin (PHA)-stimulated male human PBL.