Nanoparticle size-specific actin rearrangement and barrier dysfunction of endothelial cells

Differential effect of gold nanoparticles on cerebrovascular function and biomechanical properties

Human stroke serum (HSS) has been shown to impair cerebrovascular function, likely by factors released into the circulation after ischemia. 20 nm gold nanoparticles (GNPs) have demonstrated anti-inflammatory properties, with evidence that they decrease pathologic markers of ischemic severity. Whether GNPs affect cerebrovascular function, and potentially protect against the damaging effects of HSS on the cerebral circulation remains unclear. HSS obtained 24 h poststroke was perfused through the lumen of isolated and pressurized third-order posterior cerebral arteries (PCAs) from male Wistar rats with and without GNPs (~2 × 109 GNP/ml), or GNPs in vehicle, in an arteriograph chamber (n = 8/group). All vessels were myogenically reactive ≥60 mmHg intravascular pressure; however, vessels containing GNPs had significantly less myogenic tone. GNPs increased vasoreactivity to small and intermediate conductance calcium activated potassium channel activation via NS309; however, reduced vasoconstriction to nitric oxide synthase inhibition. Hydraulic conductivity and transvascular filtration, were decreased by GNPs, suggesting a protective effect on the blood-brain barrier. The stress-strain curves of PCAs exposed to GNPs were shifted leftward, indicating increased vessel stiffness. This study provides the first evidence that GNPs affect the structure and function of the cerebrovasculature, which may be important for their development and use in biomedical applications.

Overview of mechanism and consequences of endothelial leakiness caused by metal and polymeric nanoparticles

Nanoparticles (NPs) exhibit unique physicochemical properties that enable them to overcome biological barriers and to be considered one of the best materials with anticancer properties. Most of the administered NPs that end up in the bloodstream interact with the endothelial layer. The interaction of the NPs with the endothelium widens the existing gaps or induces new ones in the monolayer of vascular endothelial cells, thus increasing the access to the target sites in the organism. This type of interaction can lead to NP-modulated endothelial leakiness (NanoEL). The most important factors determining NanoEL are the physicochemical properties of the NPs. NP-modulated endothelial leakiness can lead to the discovery of new therapeutic targets and strategies to improve drug delivery through controlling and regulating NanoEL. Nevertheless, the NanoEL mechanism also carries some limitations that result from an incomplete understanding of NP metabolism and toxicity, and the possibility of their participation in the unintended bidirectional vascular permeability, which may contribute to the formation of cancer metastases. In this review we are focusing on the effect of metal and polymeric NPs on mechanism and degree of induction of NanoEL, as well as on the benefits and risks of using NPs that induce endothelial leakiness.

Impaired barrier integrity of endothelial cells induced by PEGylated black phosphorus nanosheets

PEGylated black phosphorus nanosheets (PEG-BPNSs) have shown promising applications in biomedicine and potentially interact with the vasculature following iatrogenic exposures. Whether the exposure to PEG-BPNSs could induce toxic effects on endothelial cells that line the blood vessels remains largely unknown. Herein, we investigate the cellular response and transcriptional profiling of human umbilical vein endothelial cells (HUVECs) after the exposure to BPNSs and PEG-BPNSs. BPNSs and PEG-BPNSs induce cellular elongation and cause significant cytotoxicity to HUVECs at 0.8 μg/mL, with viabilities of 87.8% and 87.7% respectively. The transcriptome analysis indicates that BPNSs and PEG-BPNSs at 0.4 μg/mL cause marked alterations in the expression of genes associated with detection of stimulus, ion transmembrane transport and components of plasma membrane. BPNSs and PEG-BPNSs at 0.4 μg/mL decrease the transendothelial electrical resistance (TEER) across monolayers of HUVECs by 22.8% and 20.3% compared to the control, respectively. The disturbance of tight junctions (TJs) after 24 h exposure to 0.4 μg/mL BPNSs and PEG-BPNSs is indicated with the downregulated mRNA expression of zona occluden-1 (ZO-1) by respective 16.5% and 29.9%, which may be involved in the impairment of endothelial barrier integrity. Overall, the response of HUVECs to PEG-BPNSs and BPNSs has no statistical difference, suggesting that PEGylation does not attenuate the BPNSs-induced endothelial injury. This study demonstrates the detrimental effects of BPNSs and PEG-BPNSs on barrier integrity of HUVECs, contributing to our understanding on the potential toxicological mechanisms.

How Nanoparticles Open the Paracellular Route of Biological Barriers: Mechanisms, Applications, and Prospects

Biological barriers are essential physiological protective systems and obstacles to drug delivery. Nanoparticles (NPs) can access the paracellular route of biological barriers, either causing adverse health impacts on humans or producing therapeutic opportunities. This Review introduces the structural and functional influences of NPs on the key components that govern the paracellular route, mainly tight junctions, adherens junctions, and cytoskeletons. Furthermore, we evaluate their interaction mechanisms and address the influencing factors that determine the ability of NPs to open the paracellular route, which provides a better knowledge of how NPs can open the paracellular route in a safer and more controllable way. Finally, we summarize limitations in the research models and methodologies of the existing research in the field and provide future research direction. This Review demonstrates the in-depth causes for the reversible opening or destruction of the integrity of barriers generated by NPs; more importantly, it contributes insights into the design of NP-based medications to boost paracellular drug delivery efficiency.

Inducible endothelial leakiness in nanotherapeutic applications

All intravenous delivered nanomedicine needs to escape from the blood vessel to exert their therapeutic efficacy at their designated site of action. Failure to do so increases the possibility of detrimental side effects and negates their therapeutic intent. Many powerful anticancer nanomedicine strategies rely solely on the tumor derived enhanced permeability and retention (EPR) effect for the only mode of escaping from the tumor vasculature. However, not all tumors have the EPR effect nor can the EPR effect be induced or controlled for its location and timeliness. In recent years, there have been exciting developments along the lines of inducing endothelial leakiness at the tumor to decrease the dependence of EPR. Physical disruption of the endothelial-endothelial cell junctions with coordinated biological intrinsic pathways have been proposed that includes various modalities like ultrasound, radiotherapy, heat and even nanoparticles, appear to show good progress towards the goal of inducing endothelial leakiness. This review explains the intricate and complex biological background behind the endothelial cells with linkages on how updated reported nanomedicine strategies managed to induce endothelial leakiness. This review will also end off with fresh insights on where the future of inducible endothelial leakiness holds.

Impact of surface chemistry of ultrasmall superparamagnetic iron oxide nanoparticles on protein corona formation and endothelial cell uptake, toxicity, and barrier function

Ultrasmall superparamagnetic iron oxide nanoparticles (USPION) have been investigated for biomedical applications, including novel contrast agents, magnetic tracers for tumor imaging, targeted drug delivery vehicles, and magneto-mechanical actuators for hyperthermia and thrombolysis. Despite significant progress, recent clinical reports have raised concerns regarding USPION safety related to endothelial cell dysfunction; however, there is limited information on factors contributing to these clinical responses. The influence of USPION surface chemistry on nanoparticle interactions with proteins may impact endothelial cell function leading to adverse responses. Therefore, the goal of this study was to assess the effects of carboxyl-functionalized USPION (CU) or amine-functionalized USPION (AU) (∼30 nm diameter) on biological responses in human coronary artery endothelial cells. Increased protein adsorption was observed for AU compared to CU after exposure to serum proteins. Exposure to CU, but not AU, resulted in a concentration-dependent decrease in cell viability and perinuclear accumulation inside cytoplasmic vesicles. Internalization of CU was correlated with endothelial cell functional changes under non-cytotoxic conditions, as evidenced by a marked decreased expression of endothelial-specific adhesion proteins (e.g., VE-cadherin and PECAM-1) and increased endothelial permeability. Evaluation of downstream signaling indicated endothelial permeability is associated with actin cytoskeleton remodeling, possibly elicited by intracellular events involving reactive oxygen species, calcium ions, and the nanoparticle cellular uptake pathway. This study demonstrated that USPION surface chemistry significantly impacts protein adsorption and endothelial cell uptake, viability, and barrier function. This information will advance the current toxicological profile of USPION and improve development, safety assessment, and clinical outcomes of USPION-enabled medical products.

Engineered nanomaterials induce alterations in biological barriers: focus on paracellular permeability

Engineered nanoparticles (ENPs) are widely used in medical diagnosis and treatment, as food additives and as energy materials. ENPs may exert adverse or beneficial effects on the human body, which may be linked to interactions with biological barriers. In this review, the authors summarize the influences of four typical metal/metal oxide nanomaterials (Ag, TiO₂, Au, ZnO nanoparticles) on the paracellular permeability of biological barriers. Disruptions on tight junctions, adhesion junctions, gap junctions and desmosomes via complex signaling pathways, such as the MAPK, PKC and ROCK signaling pathways, affect paracellular permeability. Reactive oxygen species and cytokines underlie the mechanism of ENP-triggered alterations in paracellular permeability. This review provides the information necessary for the cautious application of nanoparticles in medicine and life sciences in the future.

Cancer-Nano-Interaction: From Cellular Uptake to Mechanobiological Responses

With the advancement of nanotechnology, the nano-bio-interaction field has emerged. It is essential to enhance our understanding of nano-bio-interaction in different aspects to design nanomedicines and improve their efficacy for therapeutic and diagnostic applications. Many researchers have extensively studied the toxicological responses of cancer cells to nano-bio-interaction, while their mechanobiological responses have been less investigated. The mechanobiological properties of cells such as elasticity and adhesion play vital roles in cellular functions and cancer progression. Many studies have noticed the impacts of cellular uptake on the structural organization of cells and, in return, the mechanobiology of human cells. Mechanobiological changes induced by the interactions of nanomaterials and cells could alter cellular functions and influence cancer progression. Hence, in addition to biological responses, the possible mechanobiological responses of treated cells should be monitored as a standard methodology to evaluate the efficiency of nanomedicines. Studying the cancer-nano-interaction in the context of cell mechanics takes our knowledge one step closer to designing safe and intelligent nanomedicines. In this review, we briefly discuss how the characteristic properties of nanoparticles influence cellular uptake. Then, we provide insight into the mechanobiological responses that may occur during the nano-bio-interactions, and finally, the important measurement techniques for the mechanobiological characterizations of cells are summarized and compared. Understanding the unknown mechanobiological responses to nano-bio-interaction will help with developing the application of nanoparticles to modulate cell mechanics for controlling cancer progression.

Adult Primary Capillary Hemangioma of the Sclera: A Previously Undescribed Entity With a Review of Epibulbar Vascular Lesions

PURPOSE

The objective of this article is to document a unique case of a primary hemangioma and review epibulbar vascular tumors of the conjunctiva and episclera.

METHODS

A case report with detailed histopathologic, histochemical, and immunohistochemical studies coupled with a comprehensive review of the relevant literature with a tabulation of previously reported epibulbar vascular lesions was performed.

RESULTS

A vascular tumor developed in a 46-year-old woman over 2-3 months that histopathologically was located in the superficial third of the normally avascular sclera and was composed of capillary caliber vessels. CD31 and CD34 positivity established the vascular nature of the lesion. Despite its adult onset, the tumor was also glut-1 positive, a vascular characteristic of childhood capillary hemangiomas that will ultimately involute. Smooth muscle actin was positive in the endothelial cells and associated pericytes. An ectatic muscular vessel identified in the midst of the lesion was interpreted as an anomalous intrascleral branch of an epibulbar anterior ciliary artery, where it perforated the sclera in the vicinity of the insertion of an extraocular rectus muscle. It was deduced to be the source of the capillary proliferation. A literature review failed to identify any previously reported epibulbar vascular tumor that originated primarily in the sclera or secondarily infiltrated this ocular tunic.

CONCLUSION

An adult primary capillary intrascleral neoplasm is described as the rarest of all epibulbar vascular tumors and in keeping with the exceptional status of the ocular endothelium was glut-1 positive. This lesion must be distinguished from an array of other common and esoteric epibulbar vascular conditions.

Gold nanoparticles disrupt actin organization and pulmonary endothelial barriers

This study explored the impact of gold nanoparticles on the metabolic activity and morphology of human pulmonary endothelial cell monolayers. We developed a gold nanoparticle library of three different sizes and two surface chemistries that include anionic citrate and the cationic polyelectrolyte poly(allylamine hydrochloride). The nanoparticles were characterized in cell culture medium to assess how their physical properties are altered after exposure to biological fluids. A bovine serum albumin pretreatment protocol was developed to stabilize the nanoparticles in cell culture medium. Results of this study show that an 18 h exposure of human pulmonary artery endothelial cells to the different nanoparticles modestly affects cellular metabolic activity. However, nanoparticle exposure perturbs the cortical actin networks and induces the formation of intercellular gaps. In particular, exposure to the poly(allylamine hydrochloride)-coated particles reduces the area of cell-cell junctions-a change that correlates with increased leakiness of endothelial barriers. The presence of excess polyelectrolyte capping agents in the supernatant of poly(allylamine hydrochloride)-coated nanoparticles significantly impacts endothelial morphology. Pretreatment of the particle supernatant with bovine serum albumin mitigates the negative effects of free or bound polyelectrolytes on endothelial cell monolayers.

Human brain microvascular endothelial cell pairs model tissue-level blood-brain barrier function

The blood-brain barrier plays a critical role in delivering oxygen and nutrients to the brain while preventing the transport of neurotoxins. Predicting the ability of potential therapeutics and neurotoxicants to modulate brain barrier function remains a challenge due to limited spatial resolution and geometric constraints offered by existing in vitro models. Using soft lithography to control the shape of microvascular tissues, we predicted blood-brain barrier permeability states based on structural changes in human brain endothelial cells. We quantified morphological differences in nuclear, junction, and cytoskeletal proteins that influence, or indicate, barrier permeability. We established a correlation between brain endothelial cell pair structure and permeability by treating cell pairs and tissues with known cytoskeleton-modulating agents, including a Rho activator, a Rho inhibitor, and a cyclic adenosine monophosphate analog. Using this approach, we found that high-permeability cell pairs showed nuclear elongation, loss of junction proteins, and increased actin stress fiber formation, which were indicative of increased contractility. We measured traction forces generated by high- and low-permeability pairs, finding that higher stress at the intercellular junction contributes to barrier leakiness. We further tested the applicability of this platform to predict modulations in brain endothelial permeability by exposing cell pairs to engineered nanomaterials, including gold, silver-silica, and cerium oxide nanoparticles, thereby uncovering new insights into the mechanism of nanoparticle-mediated barrier disruption. Overall, we confirm the utility of this platform to assess the multiscale impact of pharmacological agents or environmental toxicants on blood-brain barrier integrity.

Near Infrared-Activated Dye-Linked ZnO Nanoparticles Release Reactive Oxygen Species for Potential Use in Photodynamic Therapy

Novel dye-linked zinc oxide nanoparticles (NPs) hold potential as photosensitizers for biomedical applications due to their excellent thermal- and photo-stability. The particles produced reactive oxygen species (ROS) upon irradiation with 850 nm near infrared (NIR) light in a concentration- and time-dependent manner. Upon irradiation, ROS detected in vitro in human umbilical vein endothelial cells (HUVEC) and human carcinoma MCF7 cells positively correlated with particle concentration and interestingly, ROS detected in MCF7 was higher than in HUVEC. Preferential cytotoxicity was also exhibited by the NPs as cell killing was higher in MCF7 than in HUVEC. In the absence of irradiation, dye-linked ZnO particles minimally affected the viability of cell (HUVEC) at low concentrations (<30 μg/mL), but viability significantly decreased at higher particle concentrations, suggesting a need for particle surface modification with poly (ethylene glycol) (PEG) for improved biocompatibility. The presence of PEG on particles after dialysis was indicated by an increase in size, an increase in zeta potential towards neutral, and spectroscopy results. Cell viability was improved in the absence of irradiation when cells were exposed to PEG-coated, dye-linked ZnO particles compared to non-surface modified particles. The present study shows that there is potential for biological application of dye-linked ZnO particles in photodynamic therapy.

Nanoparticles' interactions with vasculature in diseases

The ever-growing use of inorganic nanoparticles (NPs) in biomedicine provides an exciting approach to develop novel imaging and drug delivery systems, owing to the ease with which these NPs can be functionalized to cater to various applications. In cancer therapeutics, nanomedicine generally relies on the enhanced permeability and retention (EPR) effect observed in tumour vasculature to deliver anti-cancer drugs across the endothelium. However, such a phenomenon is dependent on the tumour microenvironment and is not consistently observed in all tumour types, thereby limiting drug transport to the tumour site. On the other hand, there is a rise in utilizing inorganic NPs to intentionally induce endothelial leakiness, creating a window of opportunity to control drug delivery across the endothelium. While this active targeting approach creates a similar phenomenon compared to the EPR effect arising from tumour tissues, its drug delivery applications extend beyond cancer therapeutics and into other vascular-related diseases. In this review, we summarize the current findings of the EPR effect and assess its limitations in the context of anti-cancer drug delivery systems. While the EPR effect offers a possible route for drug passage, we further explore alternative uses of NPs to create controllable endothelial leakiness within short exposures, a phenomenon we coined as nanomaterial-induced endothelial leakiness (NanoEL). Furthermore, we discuss the main mechanistic features of the NanoEL effect that make it unique from conventionally established endothelial leakiness in homeostatic and pathologic conditions, as well as examine its potential applicability in vascular-related diseases, particularly cancer. Therefore, this new paradigm changes the way inorganic NPs are currently being used for biomedical applications.

Quantifying the effects of engineered nanomaterials on endothelial cell architecture and vascular barrier integrity using a cell pair model

Engineered nanomaterials (ENMs) are increasingly used in consumer products due to their unique physicochemical properties, but the specific hazards they pose to the structural and functional integrity of endothelial barriers remain elusive. When assessing the effects of ENMs on vascular barrier function, endothelial cell monolayers are commonly used as in vitro models. Monolayer models, however, do not offer a granular understanding of how the structure-function relationships between endothelial cells and tissues are disrupted due to ENM exposure. To address this issue, we developed a micropatterned endothelial cell pair model to quantitatively evaluate the effects of 10 ENMs (8 metal/metal oxides and 2 organic ENMs) on multiple cellular parameters and determine how these parameters correlate to changes in vascular barrier function. This minimalistic approach showed concerted changes in endothelial cell morphology, intercellular junction formation, and cytoskeletal organization due to ENM exposure, which were then quantified and compared to unexposed pairs using a "similarity scoring" method. Using the cell pair model, this study revealed dose-dependent changes in actin organization and adherens junction formation following exposure to representative ENMs (Ag, TiO2 and cellulose nanocrystals), which exhibited trends that correlate with changes in tissue permeability measured using an endothelial monolayer assay. Together, these results demonstrate that we can quantitatively evaluate changes in endothelial architecture emergent from nucleo-cytoskeletal network remodeling using micropatterned cell pairs. The endothelial pair model therefore presents potential applicability as a standardized assay for systematically screening ENMs and other test agents for their cellular-level structural effects on vascular barriers.

PEGylated gold nanorods are not cytotoxic to human endothelial cells but affect kruppel-like factor signaling pathway

Gold (Au) nanomaterials (NMs), particularly those with PEG surface functionalization, are generally considered to be biocompatible for biomedical applications due to relatively low cytotoxicity. Herein, we investigated the toxicity of PEGylated Au nanorods (NRs) to human umbilical vein endothelial cells (HUVECs), a commonly used in vitro model for human endothelium. We found a previously unknown effect that up to 10 μg/mL Au NRs, albeit not cytotoxic, decreased the mRNA and protein levels of kruppel-like factor 2 (KLF2), a transcription factor with well-documented vasoprotective effects. The results from PCR array showed that a number of genes associated with risk of cardiovascular diseases were altered by Au NRs, and several genes are downstream genes of KLF2 according to ingenuity pathway analysis (IPA). These effects could be observed with or without the presence of inflammatory stimuli lipopolysaccharide (LPS), which suggests a pre-existing inflammatory state is not required for Au NRs to alter KLF2 signaling pathway. We further identified that Au NRs significantly decreased eNOS mRNA/p-eNOS proteins as well as increased MCP-1 mRNA/sMCP-1 release, which are targets of KLF2. Combined, our data revealed a novel pathway that PEGylated Au NPs at non-cytotoxic concentrations might alter KLF leading to the increase of risk of cardiovascular diseases in human endothelial cells. Given the importance of KLF in vascular homeostasis, our data indicate that it is necessary to evaluate the influence of engineered NPs to KLF signaling pathways, especially for NPs with biomedical uses.

A multiparametric study of gold nanoparticles cytotoxicity, internalization and permeability using an in vitro model of blood-brain barrier. Influence of size, shape and capping agent

Gold nanoparticles (AuNPs) have biomedical application on imaging and due to increased optical performance, star-shaped AuNPs are of special interest. Because shape, size and capping greatly influence their toxicokinetics and toxicodynamics, a systematic multiparametric comparative study of the influence of these parameters on the cytotoxicity, internalization, and in vitro permeability was conducted in human Cerebral Microvascular Endothelial Cell line (hCMEC/D3), an in vitro model of the human blood-brain barrier (BBB). AuNPs of different size (14 nm and ∼50 nm), shape (spheres and stars), and coating (11-mercaptoundecanoic acid or MUA and sodium citrate) were synthesized and fully characterized. The time- and concentration-dependent cytotoxic profile of the tested AuNPs differed for the different AuNPs. Generally, toxicity was greater for stars relative to sphere-shaped AuNPs, and citrate coating was more toxic than MUA. Regarding the influence of size, smaller-sized AuNPs were more cytotoxic when compared at the same Au concentration. However, when the concentration of AuNPs was expressed as the number of AuNPs/mL, a higher degree of cytotoxicity was noted for the larger ̴50 nm AuNPs. To understand the influence of size, shape and capping, a systematic study design, in which only one of the variables changes, is determinant for correct data interpretation. Considering the results herein presented, for the sake of comparison of differently-sized AuNPs, it is preferable to design the study based upon the number of nanoparticles, since at a fixed Au concentration the number of particles available to promote effect is higher for smaller-sized AuNPs. Cellular internalization also differed among the tested AuNPs; although all were unable to cross the in vitro BBB, the intracellularly accumulated AuNPs can induce cell damage and later compromise BBB integrity and permeability.

Disturbance of adhesomes by gold nanoparticles reveals a size- and cell type-bias

Gold nanoparticles (AuNP) have been thoroughly studied as multifunctional theranosis agents for cell imaging and cancer therapy as well as sensors due to their tunable physical and chemical properties. Although AuNP have proved to be safe in a wide concentration range, yet other important biological effects can arise in the sublethal window of treatment. This is especially pivotal to understand how AuNP can affect cell biology when labeling steps are needed for cell tracking in vivo, as nanoparticle loading can affect cell migratory/invasion ability, a function mediated by filamentous actin-rich nanometric structures collectively called adhesomes. It is noteworthy that, although numerous research studies have addressed the cell response to AuNP loading, yet none of them focuses on adhesome dynamics as a target of intracellular pathways affected by AuNP. We intend to study the collective dynamics of adhesive F-actin rich structures upon AuNP treatment as an approach to understand the complex AuNP-triggered modulation of migration/invasion related cellular functions. We demonstrated that citrate-coated spherical AuNP of different sizes (3, 11, 16, 30 and 40 nm) disturbed podosome-forming rosettes and the resulting extracellular matrix (ECM) degradation in a murine macrophage model depending on core size. This phenomenon was accompanied by a reduction in metalloproteinase MMP2 and an increment in metalloproteinase inhibitors, TIMP-1/2 and SerpinE1. We also found that AuNP treatment has opposite effects on focal adhesions (FA) in endothelial and mesenchymal stem cells. While endothelial cells reduced their mature FA number and ECM degradation rate upon AuNP treatment, mouse mesenchymal stem cells increased the number and size of mature FA and, therefore, the ECM degradation rate. Overall, AuNP appear to disturb adhesive structures and therefore migratory/invasive cell functions measured as ECM degradation ability, providing new insights into AuNP-cell interaction depending on cell type.

Size-dependent cellular uptake and TLR4 attenuation by gold nanoparticles in lung adenocarcinoma cells

AIM

To elucidate uptake mechanisms and immunomodulatory potential of differently sized gold nanoparticles (GNPs) in lung adenocarcinoma cells (A549) to enable their use as an adjunct therapy for treating inflammation-linked lung cancer.

METHODS

Internalization of the synthesized (5, 15 and 30 nm) GNPs by various endocytosis pathways was determined. Immunomodulatory mechanisms induced by differently sized GNPs in A549 cells in the presence of TLR4 and TLR9 ligands were evaluated.

RESULTS

GNPs were size-dependently internalized efficiently by A549 cells. Various sized GNPs downregulated the expression of proinflammatory signaling molecules (5 nm most potent). Mechanistically, 5-nm GNPs attenuated TLR4 signaling by downregulating TLR4 expression in A549 cells.

CONCLUSION

Our study suggests the use of immunomodulatory GNPs as an adjunct therapy against inflammation-linked lung cancer.

Titanium Dioxide Nanoparticles Enhance Leakiness and Drug Permeability in Primary Human Hepatic Sinusoidal Endothelial Cells

Liver sinusoidal endothelial cells (LSECs) represent the permeable interface that segregates the blood compartment from the hepatic cells, regulating hepatic vascular tone and portal pressure amidst changes in the blood flow. In the presence of pathological conditions, phenotypic changes in LSECs contribute to the progression of chronic liver diseases, including the loss of endothelial permeability. Therefore, modulating LSECs offers a possible way to restore sinusoidal permeability and thereby improve hepatic recovery. Herein, we showed that titanium dioxide nanoparticles (TiO₂ NPs) could induce transient leakiness in primary human hepatic sinusoidal endothelial cells (HHSECs). Interestingly, HHSECs exposed to these NPs exhibited reduced protein kinase B (Akt) phosphorylation, an important protein kinase which regulates cell attachment. Using a 3D co-culture system, we demonstrated that TiO₂ NPs diminished the attachment of HHSECs onto normal human hepatic cell LO2. To further illustrate the significance of leakiness in liver sinusoids, we showed that NP-induced leakiness promoted Sunitinib transport across the HHSEC layer, resulting in increased drug uptake and efficacy. Hence, TiO₂ NPs have the potential to modulate endothelial permeability within the specialized sinusoidal endothelium, especially during events of fibrosis and occlusion. This study highlighted the possible use of inorganic NPs as a novel strategy to promote drug delivery targeting the diseased liver.

Effect of the development of a cell barrier on nanoparticle uptake in endothelial cells

In order to improve the current success of nanomedicine, a better understanding of how nano-sized materials interact with and are processed by cells is required. Typical in vitro nanoparticle-cell interaction studies often make use of cells cultured at different cell densities. However, in vivo, for their successful delivery to the target tissue, nanomedicines need to overcome several barriers, such as endothelial and epithelial cell barriers. Unlike sub-confluent or confluent cell cultures, cell barriers are tight cell monolayers, expressing a series of specialized tight junction proteins between adjacent cells to limit paracellular transport and ensure close cell-to-cell interactions. A clear understanding on how the development of cells into a cell barrier may affect the uptake of nano-sized drug carriers is still missing. To this aim, here, human primary umbilical vein endothelial cells (HUVEC) are used as a model cell line to form endothelial cell barriers. Then, nanoparticle uptake is assessed in the developed endothelial barriers and compared to the uptake in sub-confluent or confluent HUVEC cultures. The results clearly show that the organization of cells into a cell barrier leads to a differential gene expression of endocytic markers, and - interestingly - this is accompanied by reduced nanoparticle uptake levels. Transport inhibitors are used to characterise the mechanisms involved in the uptake. However, we show that some of them can strongly compromise barrier integrity, thus impairing the interpretation of the outcomes, and overall, only a partial inhibition of nanoparticle uptake could be obtained.

Endothelial barrier dysfunction induced by nanoparticle exposure through actin remodeling via caveolae/raft-regulated calcium signalling

The rapid development of modern nanotechnology has resulted in nanomaterial being use in nearly all applications of life, raising the potential risk of nanomaterial exposure alongside the need to design safe and effective materials. Previous work has demonstrated a specific effect of gold nanoparticles (GNPs) of approximately 20 nm on endothelial barrier function in vitro. To expand our understanding of this size-specific effect, titanium dioxide, silicon dioxide, and polystyrene nanoparticles (NPs) in this similar size range were studied. All tested nanoparticles were found to have minimal effects on cell viability, but exhibited a significant detrimental effect on endothelial barrier function. Nanoparticles in the size range of 20 to 30 nm were internalized by endothelial cells through caveolae/raft-mediated endocytosis, causing intracellular calcium elevation by approximately 30% at 2 hours after administration, and triggering myosin light chain kinase (MLCK)-regulated actomyosin contraction. These effects culminated in an increase in endothelial monolayer permeability across all particle types within the 20-30 nm range. This nanoparticle exposure-induced endothelial barrier dysfunction may provide valuable information for designing safer nanomaterials or potential applications of this nanoparticle exposure-induced permeability effect in biomedicine.

Silicon dioxide nanoparticle exposure affects small intestine function in an in vitro model

The use of nanomaterials to enhance properties of food and improve delivery of orally administered drugs has become common, but the potential health effects of these ingested nanomaterials remain unknown. The goal of this study is to characterize the properties of silicon dioxide (SiO₂) nanoparticles (NP) that are commonly used in food and food packaging, and to investigate the effects of physiologically realistic doses of SiO₂ NP on gastrointestinal (GI) health and function. In this work, an in vitro model composed of Caco-2 and HT29-MTX co-cultures, which represent absorptive and goblet cells, was used. The model was exposed to well-characterized SiO₂ NP for acute (4 h) and chronic (5 d) time periods. SiO₂ NP exposure significantly affected iron (Fe), zinc (Zn), glucose, and lipid nutrient absorption. Brush border membrane intestinal alkaline phosphatase (IAP) activity was increased in response to nano-SiO₂. The barrier function of the intestinal epithelium, as measured by transepithelial electrical resistance, was significantly decreased in response to chronic exposure. Gene expression and oxidative stress formation analysis showed NP altered the expression levels of nutrient transport proteins, generated reactive oxygen species, and initiated pro-inflammatory signaling. SiO₂ NP exposure damaged the brush border membrane by decreasing the number of intestinal microvilli, which decreased the surface area available for nutrient absorption. SiO₂ NP exposure at physiologically relevant doses ultimately caused adverse outcomes in an in vitro model.