Dermal Exposure to Vesicating Nettle Agent Phosgene Oxime: Clinically Relevant Biomarkers and Skin Injury Progression in Murine Models.

Phosgene oxime (CX), categorized as a vesicating chemical threat agent, causes effects that resemble an urticant or nettle agent. CX is an emerging potential threat agent that can be deployed alone or with other chemical threat agents to enhance their toxic effects. Studies on CX-induced skin toxicity, injury progression, and related biomarkers are largely unknown. To study the physiologic changes, skin clinical lesions and their progression, skin exposure of SKH-1 and C57BL/6 mice was carried out with vapor from 10 µl CX for 0.5-minute or 1.0-minute durations using a designed exposure system for consistent CX vapor exposure. One-minute exposure caused sharp (SKH-1) or sustained (C57BL/6) decrease in respiratory and heart rate, leading to mortality in both mouse strains. Both exposures caused immediate blanching, erythema with erythematous ring (wheel) and edema, and an increase in skin bifold thickness. Necrosis was also observed in the 0.5-minute CX exposure group. Both mouse strains showed comparative skin clinical lesions upon CX exposure; however, skin bifold thickness and erythema remained elevated up to 14 days postexposure in SKH-1 mice but not in C57BL/6 mice. Our data suggest that CX causes immediate changes in the physiologic parameters and gross skin lesions resembling urticaria, which could involve mast cell activation and intense systemic toxicity. This novel study recorded and compared the progression of skin injury to establish clinical biomarkers of CX dermal exposure in both the sexes of two murine strains relevant for skin and systemic injury studies and therapeutic target identification. SIGNIFICANCE STATEMENT: Phosgene oxime (CX), categorized as a vesicating agent, is considered as a potent chemical weapon and is of high military and terrorist threat interest since it produces rapid onset of severe injury as an urticant. However, biomarkers of clinical relevance related to its toxicity and injury progression are not studied. Data from this study provide useful clinical markers of CX skin toxicity in mouse models using a reliable CX exposure system for future mechanistic and efficacy studies.

Establishing short-term occupational exposure limits (STELs) for sensory irritants using predictive and in silico respiratory rate depression (RD50) models.

Sensory irritation is a health endpoint that serves as the critical effect basis for many occupational exposure limits (OELs). Schaper 1993 described a significant relationship with high correlation between the measured exposure concentration producing a 50% respiratory rate decrease (RD50) in a standard rodent assay and the American Conference of Governmental Industrial Hygienists (ACGIH®) Threshold Limit Values (TLVs®) as time-weighted averages (TWAs) for airborne chemical irritants. The results demonstrated the potential use of the RD50 values for deriving full-shift TWA OELs protective of irritant responses. However, there remains a need to develop a similar predictive model for deriving workplace short-term exposure limits (STELs) for sensory irritants. The aim of our study was to establish a model capable of correlating the relationship between RD50 values and published STELs to prospectively derive short-term exposure OELs for sensory irritants. A National Toxicology Program (NTP) database that included chemicals with both an RD50 and established STELs was used to fit several linear regression models. A strong correlation between RD50s and STELs was identified, with a predictive equation of ln (STEL) (ppm) = 0.86 * ln (RD50) (ppm) - 2.42 and an R2 value of 0.75. This model supports the use of RD50s to derive STELs for chemicals without existing exposure recommendations. Further, for data-poor sensory irritants, predicted RD50 values from in silico quantitative structure activity relationship (QSAR) models can be used to derive STELs. Hence, in silico methods and statistical modeling can present a path forward for establishing reliable OELs and improving worker safety and health.

Identification of true chemical respiratory allergens: Current status, limitations and recommendations.

Asthma in the workplace is an important occupational health issue. It comprises various subtypes: occupational asthma (OA; both allergic asthma and irritant-induced asthma) and work-exacerbated asthma (WEA). Current regulatory paradigms for the management of OA are not fit for purpose. There is therefore an important unmet need, for the purposes of both effective human health protection and appropriate and proportionate regulation, that sub-types of work-related asthma can be accurately identified and classified, and that chemical respiratory allergens that drive allergic asthma can be differentiated according to potency. In this article presently available strategies for the diagnosis and characterisation of asthma in the workplace are described and critically evaluated. These include human health studies, clinical investigations and experimental approaches (structure-activity relationships, assessments of chemical reactivity, experimental animal studies and in vitro methods). Each of these approaches has limitations with respect to providing a clear discrimination between OA and WEA, and between allergen-induced and irritant-induced asthma. Against this background the needs for improved characterisation of work-related asthma, in the context of more appropriate regulation is discussed.

Research progress in the development of 3D skin models and their application to in vitro skin irritation testing.

Toxicological assessment of chemicals is crucial for safeguarding human health and the environment. However, traditional animal experiments are associated with ethical, technical, and predictive limitations in assessing the toxicity of chemicals to the skin. With the recent development of bioengineering and tissue engineering, three-dimensional (3D) skin models have been commonly used as an alternative for toxicological studies. The skin consists of the subcutaneous, dermis, and epidermis. All these layers have crucial functions such as physical and biological protection and thermoregulation. The epidermis is the shallowest layer protecting against external substances and media. Because the skin is the first contact point for many substances, this organ is very significant for assessing local toxicity following skin exposure. According to the classification of the United Nations Global Harmonized System, skin irritation is a major potentially hazardous characteristic of chemicals, and this characteristic must be accurately assessed and classified for enhancing chemical safety management and preventing and reducing chemical accidents. This review discusses the research progress of 3D skin models and introduces their application in assessing chemical skin irritation.

Itch and Pain Behaviors in Irritant Contact Dermatitis Produced by Sodium Lauryl Sulfate in Mice.

Irritant contact dermatitis (ICD) is a nonspecific skin inflammation caused by irritants, leading to itch and pain. We tested whether differential responses to histamine-dependent and -independent pruritogens can be evoked in ICD induced by sodium lauryl sulfate (SLS). An ICD mouse model was established with 5% SLS in acetone versus a vehicle topically applied for 24 h to the cheek. Site-directed itch- and pain-like behaviors, occurring spontaneously and in response to mechanical, thermal, and chemical stimuli (histamine, ß-alanine, BAM8-22, and bradykinin) applied to the cheek, were recorded before (day 0) and after irritant removal (days 1, 2, 3, and 4). Skin inflammation was assessed through visual scoring, ultrasound, and measurements of skin thickness. SLS-treated mice exhibited hyperalgesia-like behavior in response to mechanical and heat stimuli on day 1 compared to the controls. SLS mice exhibited more spontaneous wipes (pain) but not scratching bouts (itch) on day 1. Pruritogen injections caused more scratching but not wiping in SLS-treated mice compared to the controls. Only bradykinin increased wiping behavior compared to saline. SLS-treated mice developed noticeable erythema, scaling, and increased skin thickness on days 1 and 2. SLS induced cutaneous inflammation and behavioral signs of spontaneous pain and itching, hyperalgesia to mechanical and heat stimuli and a chemical algogen, and enhanced itch response to pruritogens. These sensory reactions preceded the inflammation peak and lasted up to two days.

Ocular irritation reversibility assessment of a laundry detergent using the Porcine Corneal Opacity Reversibility Assay (PorCORA): a focused study.

Consumer product manufacturers utilise a spectrum of alternative ocular irritation assays, as these tests do not require the use of live animals. Despite their usefulness, no regulatory-accepted assay assesses the reversibility of ocular damage, a key criterion of GHS ocular classification, like the rabbit eye test (i.e., Draize Rabbit Eye Test [DRET]) . The Porcine Corneal Opacity Reversibility Assay (PorCORA), an ex vivo intact corneal tissue culture model, predicts the reversibility of damage by ocular irritants. Inclusion of the damage reversibility endpoint in the PorCORA supplements other alternative test methods for ocular irritation, by assessing induced eye damage and the ability of this damage to reverse (heal) without the use of live animals to distinguish between Globally Harmonised System of Classification and Labelling of Chemicals (GHS) ocular classifications. In this focused study, results of a Bovine Corneal Opacity and Permeability (BCOP) test of a laundry detergent, neat and 10% dilution, (product mixture from S.C. Johnson & Son, Inc. [SCJ]) classified the product into GHS Category 1; however, the BCOP test cannot assess the reversibility of ocular damage. The laundry detergent was evaluated using the PorCORA, where ocular damage induced by the detergent was fully reversed within seven days. Evaluation of the reversibility of ocular damage using the PorCORA in this focused study can add strength to the weight-of-evidence (WoE) analysis approach in ocular hazard assessment. This WoE approach strengthens the argument that the PorCORA can be used to supplement BCOP data, and that this laundry detergent is not an irreversible eye irritant.

Defined approaches to classify agrochemical formulations into EPA hazard categories developed using EpiOcularTM reconstructed human corneal epithelium and bovine corneal opacity and permeability assays.

Many sectors have seen complete replacement of the in vivo rabbit eye test with reproducible and relevant in vitro and ex vivo methods to assess the eye corrosion/irritation potential of chemicals. However, the in vivo rabbit eye test remains the standard test used for agrochemical formulations in some countries. Therefore, two defined approaches (DAs) for assessing conventional agrochemical formulations were developed, using the EpiOcularTM Eye Irritation Test (EIT) [Organisation for Economic Co-operation and Development (OECD) test guideline (TG) 492] and the Bovine Corneal Opacity and Permeability (OECD TG 437; BCOP) test with histopathology. Presented here are the results from testing 29 agrochemical formulations, which were evaluated against the United States Environmental Protection Agency's (EPA) pesticide classification system, and assessed using orthogonal validation, rather than direct concordance analysis with the historical in vivo rabbit eye data. Scientific confidence was established by evaluating the methods and testing results using an established framework that considers fitness for purpose, human biological relevance, technical characterisation, data integrity and transparency, and independent review. The in vitro and ex vivo methods used in the DAs were demonstrated to be as or more fit for purpose, reliable and relevant than the in vivo rabbit eye test. Overall, there is high scientific confidence in the use of these DAs for assessing the eye corrosion/irritation potential of agrochemical formulations.

Evaluation of eye irritation potential of experimental cosmetic formulations containing glycolic acid, salicylic acid and ethanol using the Bovine Corneal Opacity and Permeability Assay.

OBJECTIVE: Prototype cosmetic formulations containing short-chain acids and alcohols intended to be applied in the proximity of the eyes are sometimes evaluated for ocular irritation potential using the validated Bovine Corneal Opacity and Permeability Assay (OECD TG 437). We evaluated the eye irritation potential of nine experimental cosmetic formulations designed and prepared by Avon Global Reserach and Development to differ only in the concentrations of Ethanol, Glycolic Acid and Salicylic Acid. METHODS: We analysed the data generated using the BCOP assay. The opacity and permeability values obtained following the exposure of bovine corneas to experimental cosmetic formulations were combined into a single In Vitro Irritancy Score used to rank eye irritation potential. Histopathological examination of treated corneas was used to provide additional information about the depth and degree of the injury and to support the prediction of eye irritation potential of each experimental cosmetic formulation. RESULTS: The In Vitro Irritancy Scores and histopathological analysis showed that experimental formulations containing only Ethanol, Glycolic Acid, or Salicylic Acid alone had, at most, a mild ocular irritation potential. The experimental formulations containing both Ethanol and Glycolic Acid had a mild ocular irritation potential, while the experimental formulations containing both Ethanol and Salicylic Acid had a moderate ocular irritation potential. Severe ocular irritation potential was induced by an experimental formulation containing a combination of Glycolic Acid and Salicylic Acid and it was further accentuated by the addition of Ethanol to the formulation. Our data indicate a possible synergistic effect on eye irritation potential of Ethanol, Glycolic Acid and Salicylic Acid in at least some experimental cosmetic formulations. Further, our results provide insight on an apparent concentration-dependent ocular irritation potential effect of combinations of Glycolic Acid, Salicylic Acid and Ethanol in at least one experimental cosmetic formulation. CONCLUSIONS: The results presented herein emphasise the need to consider in vitro testing of prototype cosmetic formulations containing combinations of Ethanol, Glycolic Acid and Salicylic Acid rather than relying on any predicted additive effect on ocular irritation based solely on previously generated results of similar formulations containing Ethanol, Glycolic Acid or Salicylic Acid alone. Further work is required to understand the significance of these observations and to elucidate the mechanisms responsible for the apparent synergistic effects of Glycolic Acid, Salicylic Acid and Ethanol and eye irritation potential suggested by our results.

Hydroquinone-induced skin irritant reaction could be achieved by activating mast cells via mas-related G protein-coupled receptor X2.

Hydroquinone (HQ) is one of the most effective drugs to treat hyperpigmentary disorders, but often causes skin irritation in clinic. Mast cell plays an important role in contact dermatitis and triggering pseudo-allergic reactions via MRGPRX2. Whether HQ-induced skin irritant reaction through activating mast cells via MRGPRX2 remains unknown. To investigate the role of mast cells in HQ-induced skin irritant reaction and verify whether MRGPRX2 participated in the HQ effect on mast cells which contributed to the pathogenesis of skin irritant reaction, a mouse model of HQ-induced skin irritation was established to observe the local and systemic inflammation associated with mast cell receptor MrgprB2. Human mast cell LAD2 was used to verify the effect of HQ on mast cells via MRGPRX2 by knocking down with siRNA. As a result, mast cells were involved in the development of HQ-induced irritant reaction, and local inflammation is closely related to mast cell receptor MrgprB2. HQ could activate mast cells via MRGPRX2, causing changes in calcium concentration, degranulation and release of inflammatory cytokines which lead to skin irritant reaction. In conclusion, HQ-induced skin irritant reaction could be skin pseudo-allergic reactions achieved by activating mast cells via MRGPRX2.

Predicting the Safety of Ocular Iontophoresis Using Reconstructed Human Corneal Epithelial Cells.

We aimed to investigate eye damage caused by ocular iontophoresis (IP) based on an in vitro eye irritation test using a reconstructed human corneal cell. In this study, the LabCyte CORNEA-MODEL was selected as the reconstructed corneal cell. The test procedure was performed according to Test Guideline No.492 of the Organisation for Economic Co-operation and Development, which was partially revised for the IP. From the relationship between the cell viability of the cornea model and the electric field intensity [current density (mA/cm2) × application time (min)] of the IP, we predicted that the intensity values of 465 mA/cm2 × min and 930 mA/cm2 × min caused reversible eye irritation and irreversible eye damage, respectively. However, further studies are required to improve the accuracy and reproducibility of the prediction. This report provides essential knowledge on the clinical safety of ocular IP.

Safety data sheets as an information pathway on hazards of occupationally used cleaning agents.

To investigate consistency and accessibility of asthma and skin allergy hazard information in safety data sheets (SDSs) for cleaning agents on the Swedish market, we compiled a database of 504 SDSs and 351 therein declared ingredients. Labelling of products was compared to that of ingredients according to harmonised classification. For each ingredient, also notified classification and three additional sources on sensitising properties were compared. Product labelling most frequently indicated corrosion and irritation hazards. Only 3% of products were labelled as skin sensitisers and none as asthmagens. According to harmonised classification, 9% of products contained skin sensitisers, using other information sources increased the number to 46%. While 2% of products contained respiratory sensitisers according to harmonised classification, the number increased to 17% when using other information sources. Furthermore, sensitisers were declared across several sections of the SDSs, hampering easy access of such information. In conclusion, there are inconsistencies in hazard identification of cleaning agents and their ingredients. Hence, SDSs may not altogether fulfil its hazard information role. Improved criteria for identifying sensitisers and respiratory irritants are warranted. Additionally, we argue that all ingredients should be listed in section 3 regardless of concentration, to facilitate access of information about sensitising properties.

Skin and eye irritancy assessment of six lactic acid bacteria strains.

Here we investigate the suitability of in vitro models to assess the skin and eye irritation potential of six microbial strains. Acute skin irritation was tested according to the unmodified and modified OECD test guideline (OECD TG) 439, while acute eye irritation was examined using the OECD TG 491 and 492. The OECD TG 439 guideline, modified to introduce 8-10 µg/mL of streptomycin during the recovery phase and use of test items containing 100% microbial product instead of finished formulae, was found to be suitable for skin irritation evaluation. On the other hand, the OECD TG 491 procedure was the most appropriate for evaluating eye irritation. None of the six microbial strains, namely, Lactiplantibacillus plantarum (IMI 507026, IMI 507027, IMI 507028), Lacticaseibacillus rhamnosus (IMI 507023), and Pediococcus pentosaceus (IMI 507024, IMI 507025), tested in this study caused skin or eye irritation under the study condition.

Difficulties in translating in vitro hazards of local acute irritants to relevant human risk: Learnings from Captan and Folpet.

In order to assess the regulatory value of New Approach Methodologies (NAMs), authors should provide their opinion on the physiological and exposure relevance of observed in vitro effects for correlation with predicted in vivo effects. Further, peer-reviewers should be encouraged to request such information during review. This is critical to scientifically transition to animal-free, reliable, robust and -- most importantly -- relevant regulatory toxicology and risk assessment approaches. Recently published studies using NAMs for the fungicides Captan and Folpet illustrate the difficulties and limitations of applying NAMs to adequately assess the toxicological relevance of these substances.

Validation study for in vitro skin irritation test using reconstructed human skin equivalents constructed by layer-by-layer cell coating technology.

The aim of this study is to validate an in vitro skin irritation test (SIT) using three-dimensional reconstructed human epidermal (RhE) skin equivalents prepared by layer-by-layer (LbL) method (LbL-3D Skin) in a series of interlaboratory studies. The goal of these validation studies is to evaluate the ability of this in vitro test to reliably discriminate skin irritant from nonirritant chemicals, as defined by OECD and UN GHS. This me-too validation study is to assess the within- and between-laboratory reproducibility, as well as the predictive capacity, of the LbL-3D Skin SIT in accordance with performance standards for OECD TG 439. The developed skin model, LbL-3D Skin had a highly differentiated epidermis and dermis, similar to the validated reference methods (VRM) and native human skin. The quality parameters (cell survival in controls, tissue integrity, and barrier function) were similar to VRM and in accordance with OECD TG 439. The LbL-3D Skin SIT validation study was performed by three participating laboratories and consisted of three independent tests using 20 reference chemicals. The results obtained with the LbL-3D Skin demonstrated high within-laboratory and between-laboratory reproducibility, as well as high accuracy for use as a stand-alone assay to distinguish skin irritants from nonirritants. The predictive potency of LbL-3D Skin SIT using total 54 test chemicals were comparable to those in other RhE models in OECD TG 439. The validation study demonstrated that LbL-3D Skin has proven to be a robust and reliable method for predicting skin irritation.

Relationship between formaldehyde exposure, respiratory irritant effects and cancers: a review of reviews.

OBJECTIVES: Formaldehyde is an organic compound used in the production of resins, paper, wood plywood, solvents and cleaning products. Formaldehyde is also present when tobacco is smoked. Formaldehyde has been defined as an irritant and is classified as a human carcinogen by the International Agency for Research on Cancer. The purpose of this study was to demonstrate the following two distinct correlations: (1) the association between formaldehyde exposure and development of irritant diseases affecting the respiratory tract, mainly asthma; and (2) the association between formaldehyde exposure and development of neoplastic diseases. STUDY DESIGN: This was an umbrella review. METHODS: A search was conducted in the three main electronic databases of scientific literature: PubMed, Scopus and Web of Science. The search included systematic reviews and meta-analyses published in the previous 10 years. Initially, titles and abstracts of retrieved articles were evaluated, then full-text assessments of selected articles took place. Data extraction and quality assessment were performed according to Assessing the Methodological Quality of Systematic Reviews (AMSTAR) score. RESULTS: A total of 630 articles were initially collected. Nine articles concerning the association between formaldehyde exposure and asthma were included in the present review, and the majority of these reported good association. In addition, 27 articles investigating the association between formaldehyde exposure and neoplastic diseases were included in the review. These studies showed that nasopharyngeal cancer and leukaemia were the most represented neoplastic diseases; however, only a weak association was reported between formaldehyde exposure and cancer. CONCLUSIONS: Although the studies included in this review did not show a strong association between exposure to formaldehyde and irritant or neoplastic diseases, the World Health Organisation recommends that levels of formaldehyde do not exceed the threshold value of 0.1 mg/m3 (0.08 ppm) for a period of 30 min. It is recommended that preventive measures, such as ventilation in workplaces with high exposure to formaldehyde and environmental monitoring of formaldehyde concentrations, are implemented.

In Silico Prediction of Eye Irritation Using Hansen Solubility Parameters and Predicted pKa Values.

An in silico method has been developed that permits the binary differentiation between pure liquids causing serious eye damage or eye irritation, and pure liquids with no need for such classification, according to the UN GHS system. The method is based on the finding that the Hansen Solubility Parameters (HSP) of a liquid are collectively important predictors for eye irritation. Thus, by applying a two-tier approach in which in silico-predicted pKa values (firstly) and a trained model based solely on in silico-predicted HSP data (secondly) were used, we have developed, and validated, a fully in silico approach for predicting the outcome of a Draize test (in terms of UN GHS Cat. 1/Cat. 2A/Cat. 2B or UN GHS No Cat.) with high validation set performance (sensitivity = 0.846, specificity = 0.818, balanced accuracy = 0.832) using SMILES only. The method is applicable to pure non-ionic liquids with molecular weight below 500 g/mol, fewer than six hydrogen bond donors (e.g. nitrogen-hydrogen or oxygen-hydrogen bonds) and fewer than eleven hydrogen bond acceptors (e.g. nitrogen or oxygen atoms). Due to its fully in silico characteristics, this method can be applied to pure liquids that are still at the desktop design stage and not yet in production.

Further optimisation of a macromolecular ocular irritation test (OptiSafeTM).

PURPOSE: OptiSafeTM (OS) is a shelf stable, nonanimal test for ocular irritation. A recent database search found that half of the OS false positive (FP) materials were associated with reactive oxygen chemistries but were not eye irritants in vivo (based on historical rabbit studies by other groups). We hypothesized that naturally occurring tear antioxidants protect the eye from reactive chemistries in vivo and that specific tear chemistries might help explain why some materials are FP for nonanimal tests but are reported as nonirritants in the live animal. To test this hypothesis, a prior study evaluated tear antioxidants and found that the tear antioxidant ascorbic acid, added at human physiological tear levels to the OS test, specifically reduced the measured values for these FPs but did not reduce the true-positive rate. Based on these findings, the OS test method was further optimized. The purpose of the current study was to comprehensively evaluate the performance of the further optimized test method for detection of ocular irritants. MATERIALS AND METHODS: The OS test measures chemically induced damage to macromolecules and relates these measured values to ocular irritancy. To improve the performance of OS, we made updates to the material to be tested physiochemical handling procedures, prediction model, and test method to include tear-level concentrations of ascorbic acid. We then retested the 78 chemicals from the prior OS-coded validation study in triplicate and compared the accuracy of the 'nonirritant versus irritant' prediction for the further optimized method with the prior results. RESULTS: We report that for the detection of 'nonirritant' versus 'irritant' (GHS NC versus categories 2B/A and 1) test substances, the further optimized OS test with ascorbic acid compared with the original version has a FP rate that is reduced from 40.0 to 22.2%, the false-negative (FN) rate remains at 0.0%, and the accuracy improved from 80.3% to 89.2%. CONCLUSION: A comparison to OECD-adopted tests demonstrates that the further optimized OS test, like the original method, has a higher accuracy and lower FN rate for the detection of 'nonirritants' versus 'irritants' (GHS Category NC versus 2B/A and 1) than the other eye irritation tests (BCOP, EpiOcularTM Eye Irritation Test, ICE, Ocular Irritection®, and STE).

Farnesoid X receptor regulates lung macrophage activation and injury following nitrogen mustard exposure.

Nitrogen mustard (NM) is a cytotoxic vesicant known to cause acute lung injury which progresses to fibrosis; this is associated with a sequential accumulation of pro- and anti-inflammatory macrophages in the lung which have been implicated in NM toxicity. Farnesoid X receptor (FXR) is a nuclear receptor involved in regulating lipid homeostasis and inflammation. In these studies, we analyzed the role of FXR in inflammatory macrophage activation, lung injury and oxidative stress following NM exposure. Wild-type (WT) and FXR-/- mice were treated intratracheally with PBS (control) or NM (0.08 mg/kg). Bronchoalveolar lavage fluid (BAL) and lung tissue were collected 3, 14 and 28 d later. NM caused progressive histopathologic alterations in the lung including inflammatory cell infiltration and alveolar wall thickening and increases in protein and cells in BAL; oxidative stress was also noted, as reflected by upregulation of heme oxygenase-1. These changes were more prominent in male FXR-/- mice. Flow cytometric analysis revealed that loss of FXR resulted in increases in proinflammatory macrophages at 3 d post NM; this correlated with upregulation of COX-2 and ARL11, markers of macrophage activation. Markers of anti-inflammatory macrophage activation, CD163 and STAT6, were also upregulated after NM; this response was exacerbated in FXR-/- mice at 14 d post-NM. These findings demonstrate that FXR plays a role in limiting macrophage inflammatory responses important in lung injury and oxidative stress. Maintaining or enhancing FXR function may represent a useful strategy in the development of countermeasures to treat mustard lung toxicity.

Effect of dexamethasone treatment at variable therapeutic windows in reversing nitrogen mustard-induced corneal injuries in rabbit ocular in vivo model.

Nitrogen mustard (NM) is an analogue of the potent vesicating agent sulfur mustard, with well-established ocular injury models in rabbit eyes to study vesicant-induced ocular toxicity. The effects of NM-exposure to eyes may include irritation, redness, inflammation, fibrosis, epithelial degradation, blurred vision, partial/complete blindness, which may be temporary or permanent, depending on the route, duration, and dosage of exposure. Effective countermeasures against vesicant exposure are presently not available and are warranted in case of any terrorist activity or accidental leakage from stockpiles. Herein, our focus was to evaluate whether dexamethasone (DEX), an FDA approved potent corticosteroid with documented anti-inflammatory activities, could be an effective treatment modality. Accordingly, utilizing NM-induced corneal injuries in rabbit ocular in vivo model, we examined and compared the efficacy of DEX treatments when administration was started at early (2 h), intermediate (4 h), and late (6 h) therapeutic windows of intervention after NM-exposure and administered every 8 h thereafter. The effects of NM-exposure and DEX treatments were evaluated on clinical (corneal opacity, ulceration, and neovascularization), biological (epithelial thickness, epithelial-stromal separation, blood vessels density, and inflammatory cell and keratocyte counts) and molecular (COX-2 and VEGF expression) parameters, at day 1, 3, 7 and 14. Results indicated that DEX treatment markedly and effectively reversed the NM-induced injury markers in rabbit corneas. Early administration of DEX at 2 h was found to be most effective in reversing NM-induced corneal injuries, followed by DEX 4 h and DEX 6 h administration initiation, indicating that DEX has best efficacy at the early therapeutic window in our study model.

Mixtures-Inclusive In Silico Models of Ocular Toxicity Based on United States and International Hazard Categories.

Computational modeling grounded in reliable experimental data can help design effective non-animal approaches to predict the eye irritation and corrosion potential of chemicals. The National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) has compiled and curated a database of in vivo eye irritation studies from the scientific literature and from stakeholder-provided data. The database contains 810 annotated records of 593 unique substances, including mixtures, categorized according to UN GHS and US EPA hazard classifications. This study reports a set of in silico models to predict EPA and GHS hazard classifications for chemicals and mixtures, accounting for purity by setting thresholds of 100% and 10% concentration. We used two approaches to predict classification of mixtures: conventional and mixture-based. Conventional models evaluated substances based on the chemical structure of its major component. These models achieved balanced accuracy in the range of 68-80% and 87-96% for the 100% and 10% test concentration thresholds, respectively. Mixture-based models, which accounted for all known components in the substance by weighted feature averaging, showed similar or slightly higher accuracy of 72-79% and 89-94% for the respective thresholds. We also noted a strong trend between the pH feature metric calculated for each substance and its activity. Across all the models, the calculated pH of inactive substances was within one log10 unit of neutral pH, on average, while for active substances, pH varied from neutral by at least 2 log10 units. This pH dependency is especially important for complex mixtures. Additional evaluation on an external test set of 673 substances obtained from ECHA dossiers achieved balanced accuracies of 64-71%, which suggests that these models can be useful in screening compounds for ocular irritation potential. Negative predictive value was particularly high and indicates the potential application of these models in a bottom-up approach to identify nonirritant substances.