Comparative anti-inflammatory effect of curcumin at air-liquid interface and submerged conditions using lipopolysaccharide stimulated human lung epithelial A549 cells

Acute exposure to seasonal PM2.5 induces toxicological responses in A549 cells cultured at the air-liquid interface mediated by oxidative stress and endoplasmic reticulum stress

Atmospheric fine particulate matter (PM2.5) enters the human body through respiration and poses a threat to human health. This is not only dependent on its mass concentration in the atmosphere, but also related to seasonal variations in its chemical components, which makes it important to study the cytotoxicity of PM2.5 in different seasons. Traditional immersion exposure cannot simulate the living environment of human epithelial cells in the human body, making this method unsuitable for evaluating the inhalation toxicity of PM2.5. In this study, a novel air-liquid interface (ALI) particulate matter exposure device (VITROCELL Cloud 12 system) was used to evaluate the toxic effects and potential mechanisms of human lung epithelial cells (A549) after exposure to seasonal PM2.5. PM2.5 samples from four seasons were collected and analyzed for chemical components. After 6 h of exposure to seasonal PM2.5, winter PM2.5 exhibited the highest cytotoxicity among most toxicity indicators, especially apoptosis rate, reactive oxygen species (ROS), inflammatory responses and DNA damage (γ-H2AX). The effect of autumn PM2.5 on apoptosis rate was significantly higher than that in spring, and there was no significant difference in other toxicity indicators between spring and autumn. The cytotoxicity of summer PM2.5 was the lowest among the four seasons. It should be noted that even exposure to low doses of summer PM2.5 leads to significant DNA damage in A459 cells. Correlation analysis results showed that water-soluble ions, metallic elements, and polycyclic aromatic hydrocarbons (PAHs) were associated with most toxicological endpoints. Inhibitors of oxidative stress and endoplasmic reticulum (ER) stress significantly inhibited cellular damage, indicating that PM2.5-induced cytotoxicity may be related to the generation of ROS and ER stress. In addition, PM2.5 can induce ER stress through oxidative stress, which ultimately leads to apoptosis.

How to use an in vitro approach to characterize the toxicity of airborne compounds

As part of the development of new approach methodologies (NAMs), numerous in vitro methods are being developed to characterize the potential toxicity of inhalable xenobiotics (gases, volatile organic compounds, polycyclic aromatic hydrocarbons, particulate matter, nanoparticles). However, the materials and methods employed are extremely diverse, and no single method is currently in use. Method standardization and validation would raise trust in the results and enable them to be compared. This four-part review lists and compares biological models and exposure methodologies before describing measurable biomarkers of exposure or effect. The first section emphasizes the importance of developing alternative methods to reduce, if not replace, animal testing (3R principle). The biological models presented are mostly to cultures of epithelial cells from the respiratory system, as the lungs are the first organ to come into contact with air pollutants. Monocultures or cocultures of primary cells or cell lines, as well as 3D organotypic cultures such as organoids, spheroids and reconstituted tissues, but also the organ(s) model on a chip are examples. The exposure methods for these biological models applicable to airborne compounds are submerged, intermittent, continuous either static or dynamic. Finally, within the restrictions of these models (i.e. relative tiny quantities, adhering cells), the mechanisms of toxicity and the phenotypic markers most commonly examined in models exposed at the air-liquid interface (ALI) are outlined.

An integrated new approach methodology for inhalation risk assessment of safe and sustainable by design nanomaterials

The production and use of nanomaterials (NMs) has increased over the last decades posing relevant questions on their risk after release and exposure of the population or sub-populations. In this context, the safe and sustainable by design (SSbD) approach framework requires to assess the potential hazard connected with intrinsic properties of the material along the whole life cycle of the NM and/or of the nano enabled products. Moreover, in the last years, the use of new advanced methodologies (NAMs) has increasingly gained attention for the use of alternative methods in obtaining relevant information on NMs hazard and risk. Considering the SSbD and the NAMs frameworks, within the ASINA H2020 project, we developed new NAMs devoted at improving the hazard and risk definition of different Ag and TiO2 NPs. The NAMs are developed considering two air liquid interface exposure systems, the Vitrocell Cloud-α and the Cultex Compact module and the relevant steps to obtain reproducible exposures are described. The new NAMs build on the integration of environmental monitoring campaigns at nano-coating production sites, allowing the quantification by the multiple-path particle dosimetry (MPPD) model of the expected lung deposited dose in occupational settings. Starting from this information, laboratory exposures to the aerosolized NPs are performed by using air liquid interface exposure equipment and human alveolar cells (epithelial cells and macrophages), replicating the doses of exposure estimated in workers by MPPD. Preliminary results on cell viability and inflammatory responses are reported. The proposed NAMs may represent possible future reference procedures for assessing the NPs inhalation toxicology, supporting risk assessment at real exposure doses.

Rethinking of TEER measurement reporting for epithelial cells grown on permeable inserts

Transepithelial electrical resistance (TEER) measures electrical resistance across epithelial tissue barriers involving confluent layer(s) of cells. TEER values act as a prerequisite for determining the barrier integrity of cells, which play a key role in evaluating the transport of drugs, materials or chemicals of interest across an epithelial barrier. The measurements can be performed non-invasively by measuring ohmic resistance across a defined area. Thus, the TEER values are reported in Ω·cm2. In vitro epithelial models are typically assembled on semi-permeable inserts providing two-chamber compartments, and the majority of the studies use inserts with polyethylene terephthalate (PET) membranes. Recently, new inserts with different membrane types and properties have been introduced. However, the TEER values presented so far did not allow a direct comparison. This study presents the characterization of selected epithelial tissues, i.e., lung, retina, and intestine, grown on an ultra-thin ceramic microporous permeable insert (SiMPLI) and PET membranes with different properties, i.e., thickness, material, and pore numbers. We verified the epithelial cell growth on both inserts via phase-contrast and confocal laser scanning microscope imaging. Barrier characteristics were assessed by TEER measurements and also by evaluating the permeability of fluorescein isothiocyanate through cell layers. The findings indicated that background TEER value calculations and the available surface area for cell growth must be thoroughly assessed when new inserts are introduced, as the values cannot be directly compared without re-calculations. Finally, we proposed electrical circuit models highlighting the contributors to TEER recordings on PET and SiMPLI insert membranes. This study paves the way for making the ohmic-based evaluation of epithelial tissues' permeability independent of the material and geometry of the insert membrane used for cell growth.

Bovine Airway Models: Approaches for Investigating Bovine Respiratory Disease

Bovine respiratory disease (BRD) is a multifactorial condition where different genera of bacteria, such as Mannheimia haemolytica, Histophilus somni, Pasteurella multocida, and Mycoplasma bovis, and viruses, like bovine respiratory syncytial virus, bovine viral diarrhea virus, and bovine herpes virus-1, infect the lower respiratory tract of cattle. These pathogens can co-infect cells in the respiratory system, thereby making specific treatment very difficult. Currently, the most common models for studying BRD include a submerged tissue culture (STC), where monolayers of epithelial cells are typically covered either in cellular or spent biofilm culture medium. Another model is an air-liquid interface (ALI), where epithelial cells are exposed on their apical side and allowed to differentiate. However, limited work has been reported on the study of three-dimensional (3D) bovine models that incorporate multiple cell types to represent the architecture of the respiratory tract. The roles of different defense mechanisms in an infected bovine respiratory system, such as mucin production, tight junction barriers, and the production of antimicrobial peptides in in vitro cultures require further investigation in order to provide a comprehensive understanding of the disease pathogenesis. In this report, we describe the different aspects of BRD, including the most implicated pathogens and the respiratory tract, which are important to incorporate in disease models assembled in vitro. Although current advancements of bovine respiratory cultures have led to knowledge of the disease, 3D multicellular organoids that better recapitulate the in vivo environment exhibit potential for future investigations.

Therapeutic potential and limitations of curcumin as antimetastatic agent

Treatment of metastatic cancer is one of the biggest challenges in anticancer therapy. Curcumin is interesting nature polyphenolic compound with unique biological and medicinal effects, including repression of metastases. High impact studies imply that curcumin can modulate the immune system, independently target various metastatic signalling pathways, and repress migration and invasiveness of cancer cells. This review discusses the potential of curcumin as an antimetastatic agent and describes potential mechanisms of its antimetastatic activity. In addition, possible strategies (curcumin formulation, optimization of the method of administration and modification of its structure motif) to overcome its limitation such as low solubility and bioactivity are also presented. These strategies are discussed in the context of clinical trials and relevant biological studies.

Micellar Curcumin: Pharmacokinetics and Effects on Inflammation Markers and PCSK-9 Concentrations in Healthy Subjects in a Double-Blind, Randomized, Active-Controlled, Crossover Trial

SCOPE

Preclinical models have demonstrated the anti-inflammatory and lipid-lowering effects of curcumin. Innovative formulations have been developed to overcome the poor bioavailability of native curcumin. The study hypothesizes that the bioavailability of micellar curcumin is superior to native curcumin and investigates the potential anti-inflammatory and proprotein convertase subtilisin/kexin type 9 (PCSK9) concentration lowering effects.

METHODS AND RESULTS

In this double-blind, randomized, crossover trial, 15 healthy volunteers receive micellar or native curcumin (105 mg day^-1 ) for 7 days with a ≥7 days washout period. Curcumin and metabolite concentrations are quantified by high-performance liquid chromatography with fluorescence detection (HPLC-FD), and pharmacokinetics are calculated. To analyze anti-inflammatory effects, blood samples (baseline, 2 h, 7 days) are stimulated with 50 ng mL^-1 lipopolysaccharides (LPS). Interleukin (IL)-6, tumor-necrosis factor (TNF-α), and PCSK9 concentrations are quantified. Micellar curcumin demonstrates improved bioavailability (≈39-fold higher maximum concentrations, ≈14-fold higher area-under-the-time-concentration curve, p < 0.001) but does not reduce pro-inflammatory cytokines in the chosen model. Subjects receiving micellar curcumin have significantly lower PCSK9 concentrations (≈10% reduction) after 7 days compared to baseline (p = 0.038).

CONCLUSION

Micellar curcumin demonstrates an improved oral bioavailability but does not show anti-inflammatory effects in this model. Potential effects on PCSK9 concentrations warrant further investigation.

Pharmacologic therapies of ARDS: From natural herb to nanomedicine

Acute respiratory distress syndrome (ARDS) is a common critical illness in respiratory care units with a huge public health burden. Despite tremendous advances in the prevention and treatment of ARDS, it remains the main cause of intensive care unit (ICU) management, and the mortality rate of ARDS remains unacceptably high. The poor performance of ARDS is closely related to its heterogeneous clinical syndrome caused by complicated pathophysiology. Based on the different pathophysiology phases, drugs, protective mechanical ventilation, conservative fluid therapy, and other treatment have been developed to serve as the ARDS therapeutic methods. In recent years, there has been a rapid development in nanomedicine, in which nanoparticles as drug delivery vehicles have been extensively studied in the treatment of ARDS. This study provides an overview of pharmacologic therapies for ARDS, including conventional drugs, natural medicine therapy, and nanomedicine. Particularly, we discuss the unique mechanism and strength of nanomedicine which may provide great promises in treating ARDS in the future.

A Barrier to Defend - Models of Pulmonary Barrier to Study Acute Inflammatory Diseases

Pulmonary diseases represent four out of ten most common causes for worldwide mortality. Thus, pulmonary infections with subsequent inflammatory responses represent a major public health concern. The pulmonary barrier is a vulnerable entry site for several stress factors, including pathogens such as viruses, and bacteria, but also environmental factors e.g. toxins, air pollutants, as well as allergens. These pathogens or pathogen-associated molecular pattern and inflammatory agents e.g. damage-associated molecular pattern cause significant disturbances in the pulmonary barrier. The physiological and biological functions, as well as the architecture and homeostatic maintenance of the pulmonary barrier are highly complex. The airway epithelium, denoting the first pulmonary barrier, encompasses cells releasing a plethora of chemokines and cytokines, and is further covered with a mucus layer containing antimicrobial peptides, which are responsible for the pathogen clearance. Submucosal antigen-presenting cells and neutrophilic granulocytes are also involved in the defense mechanisms and counterregulation of pulmonary infections, and thus may directly affect the pulmonary barrier function. The detailed understanding of the pulmonary barrier including its architecture and functions is crucial for the diagnosis, prognosis, and therapeutic treatment strategies of pulmonary diseases. Thus, considering multiple side effects and limited efficacy of current therapeutic treatment strategies in patients with inflammatory diseases make experimental in vitro and in vivo models necessary to improving clinical therapy options. This review describes existing models for studyying the pulmonary barrier function under acute inflammatory conditions, which are meant to improve the translational approaches for outcome predictions, patient monitoring, and treatment decision-making.

Reparation of an Inflamed Air-Liquid Interface Cultured A549 Cells with Nebulized Nanocurcumin

The anti-inflammatory, antifibrotic and antimicrobial activities of curcumin (CUR) are missed because of its low solubility in aqueous media, low bioavailability, and structural lability upon oral intake. Soft nanoparticles such as nanoliposomes are not efficient as CUR carriers, since crystalline CUR is expelled from them to physiological media. Nanostructures to efficiently trap and increase the aqueous solubility of CUR are needed to improve both oral or nebulized delivery of CUR. Here we showed that SRA1 targeted nanoarchaeosomes (nATC) [1:0.4 w:w:0.04] archaeolipids, tween 80 and CUR, 155 ± 16 nm sized of −20.7 ± 3.3 z potential, retained 0.22 mg CUR ± 0.09 per 12.9 mg lipids ± 4.0 (~600 μM CUR) in front to dilution, storage, and nebulization. Raman and fluorescence spectra and SAXS patterns were compatible with a mixture of enol and keto CUR tautomers trapped within the depths of nATC bilayer. Between 20 and 5 µg CUR/mL, nATC was endocytosed by THP1 and A549 liquid–liquid monolayers without noticeable cytotoxicity. Five micrograms of CUR/mL nATC nebulized on an inflamed air–liquid interface of A549 cells increased TEER, normalized the permeation of LY, and decreased il6, tnfα, and il8 levels. Overall, these results suggest the modified pharmacodynamics of CUR in nATC is useful for epithelia repair upon inflammatory damage, deserving further deeper exploration, particularly related to its targeting ability.

Toxicological effects of zinc oxide nanoparticle exposure: an in vitro comparison between dry aerosol air-liquid interface and submerged exposure systems

Engineered nanomaterials (ENMs) are increasingly produced and used today, but health risks due to their occupational airborne exposure are incompletely understood. Traditionally, nanoparticle (NP) toxicity is tested by introducing NPs to cells through suspension in the growth media, but this does not mimic respiratory exposures. Different methods to introduce aerosolized NPs to cells cultured at the air-liquid-interface (ALI) have been developed, but require specialized equipment and are associated with higher cost and time. Therefore, it is important to determine whether aerosolized setups induce different cellular responses to NPs than traditional ones, which could provide new insights into toxicological responses of NP exposure. This study evaluates the response of human alveolar epithelial cells (A549) to zinc oxide (ZnO) NPs after dry aerosol exposure in the Nano Aerosol Chamber for In Vitro Toxicity (NACIVT) system as compared to conventional, suspension-based exposure: cells at ALI or submerged. Similar to other studies using nebulization of ZnO NPs, we found that dry aerosol exposure of ZnO NPs via the NACIVT system induced different cellular responses as compared to conventional methods. ZnO NPs delivered at 1.0 µg/cm² in the NACIVT system, mimicking occupational exposure, induced significant increases in metabolic activity and release of the cytokines IL-8 and MCP-1, but no differences were observed using traditional exposures. While factors associated with the method of exposure, such as differing NP aggregation, may contribute toward the different cellular responses observed, our results further encourage the use of more physiologically realistic exposure systems for evaluating airborne ENM toxicity.