Histopathological evaluation of the ocular-irritation potential of shampoos, make-up removers and cleansing foams in the bovine corneal opacity and permeability assay

Grading criteria of histopathological evaluation in BCOP assay by various staining methods

This study was performed to provide information on classifying eye irritating chemicals using the BCOP assay. After the BCOP assay, bovine corneas were classified by IVIS presented in OECD test guideline 437, and three special staining methods (H&E, MT, and PAS) were performed for histopathological evaluation. Non-irritant chemicals (IVIS ≤ 3), showed intact structures. In the 3 < IVIS ≤ 55 group, epithelial cell edema was observed by H&E staining, and loose collagen bundles were confirmed by MT staining. In PAS staining, bleaching of the epithelium and reduced visibility of the basement membrane were observed. Severe irritant chemicals (IVIS > 55) showed large increases edema and nuclear condensation by H&E staining. Loose collagen bundles and vacuoles around keratocytes were also observed by MT staining. Bleaching of the epithelial layer, reduction in visibility, and thickness of the basement membrane were confirmed by PAS staining. Based on the stepwise histopathological analysis, we set the criteria and grades for histopathological evaluation and found that eye irritation was increased following the irritation degree of test chemicals. Further histopathological study will support and lead to improvements in the BCOP assay.

Human-relevant approaches to assess eye corrosion/irritation potential of agrochemical formulations

There are multiple in vitro and ex vivo eye irritation and corrosion test methods that are available as internationally harmonized test guidelines for regulatory use. Despite their demonstrated usefulness to a broad range of substances through inter-laboratory validation studies, they have not been widely adopted for testing agrochemical formulations due to a lack of concordance with parallel results from the traditional regulatory test method for this endpoint, the rabbit eye test. The inherent variability of the rabbit test, differences in the anatomy of the rabbit and human eyes, and differences in modelling exposures in rabbit eyes relative to human eyes contribute to this lack of concordance. Ultimately, the regulatory purpose for these tests is protection of human health, and, thus, there is a need for a testing approach based on human biology. This paper reviews the available in vivo, in vitro and ex vivo test methods with respect to their relevance to human ocular anatomy, anticipated exposure scenarios, and the mechanisms of eye irritation/corrosion in humans. Each of the in vitro and ex vivo methods described is generally appropriate for identifying non-irritants. To discriminate among eye irritants, the human three-dimensional epithelial and full thickness corneal models provide the most detailed information about the severity of irritation. Consideration of the mechanisms of eye irritation, and the strengths and limitations of the in vivo, in vitro and ex vivo test methods, show that the in vitro/ex vivo methods are as or more reflective of human biology and less variable than the currently used rabbit approach. Suggestions are made for further optimizing the most promising methods to distinguish between severe (corrosive), moderate, mild and non-irritants and provide information about the reversibility of effects. Also considered is the utility of including additional information (e.g. physical chemical properties), consistent with the Organization for Economic Cooperation and Development's guidance document on an integrated approach to testing and assessment of potential eye irritation. Combining structural and functional information about a test substance with test results from human-relevant methods will ensure the best protection of humans following accidental eye exposure to agrochemicals.

Generation of Ophthalmic Nanosuspension of Prednisolone Acetate Using a Novel Technology

PURPOSE

Prednisolone Acetate (PAC) is currently marketed as micronized ophthalmic suspension. The microsuspension has poor dose accuracy and efficacy due to aggregation, slow dissolution rate and limited corneal residence. The ophthalmic nanosuspension of PAC shall show enhanced solubility, dissolution rate and corneal adhesion due to small particle size and increased surface area.

METHODS

In the current work, we prepared ophthalmic formulation of PAC using a novel, spray drying based technology. Firstly, PAC nanocrystalline solid dispersions (NCSD) were prepared using Mannitol (MAN) as the crystallization inducing excipient and two separate stabilizers, Polyvinyl Alcohol (PAC_MAN_PVA) and Vitamin E Tocopheryl Polyethylene Glycol Sulphosuccinate (PAC_MAN_TPGS). The NCSD was dispersed in an aqueous vehicle to obtain an ophthalmic nanosuspension.

RESULTS

The composition, PAC_MAN_PVA (0.3:0.67:0.03%), was pursued due to absence of crystal growth on storage at 40°C/75%RH for 3 months. The resulting nanosuspension showed crystal size, osmolality and viscosity of 590 ± 165 nm, 297 ± 6 mOsm/L and 11 ± 8cP respectively. In 1%w/v SLS media, the nanosuspension showed rapid and complete dissolution of PAC in 120 s. Ex-vivo goat corneal permeation and adhesion study revealed that in comparison to microsuspension, a higher fraction (6.2 times) of nanosuspension adhered to the cornea. Safety studies performed using corneal histopathology and Hen Egg Test- Chorio Allantoic Membrane (HET-CAM) assay showed no physical change in cornea or capillary damage, respectively.

CONCLUSIONS

The NCSD can be explored for generation of ophthalmically acceptable nanosuspensions of poorly soluble drugs.

Cellular viability and death biomarkers enables the evaluation of ocular irritation using the bovine corneal opacity and permeability assay

The BCOP assay is used in the identification of chemicals that cause no ocular irritation or serious damage. However, this method has not been found to adequately discriminate between mild from moderate ocular irritation (category 2A/2B), based upon the animal data. In this study, we aimed to establish methods for discerning ocular irritation by chemicals. We used the BCOP assay and the fluorescence staining methods based on biomarkers for cellular viability and death. The potential for ocular irritation by 12 chemicals from different UN GHS categories was assessed by the BCOP assay. Cryosections of bovine corneas were obtained. The necrotic nucleus was TUNEL labeled, cytoplasmic f-actin was stained by phalloidin while the nucleus was stained by DAPI. The depth of injury (DOI) was then measured. According to BCOP assay, in vivo data of Draize eye test and DOI, the results showed that category NC irritants caused ≤ 10 % epithelial DOI, irritants of category 2B caused >10 % epithelial DOI and showed no stromal damage, while category 2A showed damage to the stroma. Based on these results, the GHS prediction model could distinguish between GHS 2A and 2B. Authenticating the viability of BCOP by DOI measurements can provide a more reliable basis for classifying ocular irritants.

Strategy Combining Nonanimal Methods for Ocular Toxicity Evaluation

Historically, the ocular toxicity of manufactured consumer materials has been evaluated using the rabbit in vivo Draize rabbit eye test. The animal data obtained were used by the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS) to define the classification and labelling (C&L) for eye damage/irritation endpoint. However, the Draize test, a method which was never formally validated, has been widely criticized because of its technical limitations. In addition, ethical and economic issues and advances in scientific knowledge, and political and public pressures have made animal experimentation unsustainable. This scenario has consequently led to the development of nonanimal testing and protocols/approaches with considerable predictive value and relevance for humans. It is widely accepted that one single nonanimal method cannot cover all the criteria of damage/inflammation assessed by regulatory adopted in vivo animal testing. Thus, integrated testing strategies (ITS) have been proposed, including a tiered testing approach combining different nonanimal testing with different endpoints, which have been used for regulatory purposes, on a case-by-case basis and within integrated approaches to testing and assessment (IATA), to identify materials according to their ability to trigger eye damage. In particular, the top-down and bottom-up approaches have been recommended for the C&L of materials, which cause serious eye damage or eye irritation, respectively. This chapter describes detailed protocols for eye irritation testing based on cells (Short Time Exposure-STE, OECD No. 491/2017), a vascularized membrane (the Hen's Egg Test-Chorioallantoic Membrane-HET-CAM) and corneal tissue (Bovine Corneal Opacity and Permeability-BCOP, OECD No. 437/2017), which can be applied using top-down or bottom-up approaches. In addition, it suggests making a corneal histomorphometric evaluation as an additional parameter in the BCOP method to differentiate materials that cause serious eye tissue damage (UN GHS Cat. 1) from materials that have reversible eye irritation effects (UN GHS Cat. 2).

Innovative strategy based on mechanisms to substitute animal testing for ocular toxicity assessment of agrochemical formulations market in Brazil

Considering the successful employment of alternative methods for eye toxicity assessment of products for regulatory purposes, and the recent advances in Brazilian legislative scenario, which adopted the UN GHS classification system for agrochemical formulations toxicity assessment, there is an emerging demand for strategies that allow the evaluation of such products. Based on this, the present study aimed to address the applicability of a mechanistic-based defined approach for eye toxicity assessment of agrochemical formulations. It was investigated the opacity/permeability, depth and location of corneal injury in bovine cornea, and vascular events in chorioallantoic membrane induced for different Brazilian agrochemicals using a Sequential Testing Strategy (STS). Cytotoxicity induced by the agrochemical formulations was evaluated by Short Time exposure (STE) (OECD TG 491) assay (step 1), corneal injury was investigated by standard Bovine Corneal Opacity and Permeability (BCOP) (OECD TG 437) followed by histopathological evaluation (step 2), and Hen Chorionic-allantoic Membrane test (HET-CAM) was used to evaluate vascular injury (step 3). The results demonstrated that the proposed defined approach enabled a classification corresponding UN GHS classification of agrochemical formulations while minimizing the use of live animals. Therefore, this approach may be useful for categorization of agrochemicals in Brazil according to the new regulatory scenario.

Assessing the dyeing efficiency and irritation potentials of plant hair dyes: A multi-analytical in vitro approach

BACKGROUND

The interest toward dyeing hairs with plant colorants has grown in popularity considering its low-toxic nature. However, researches reporting plant hair dyes are limited and the potential adverse effects of irritation are unclear.

OBJECTIVES

This study is aimed to provide an avenue by which to more accurately assess the dyeing efficiency and irritation potentials of plant hair dyes.

METHODS

Four extracted plant colorants were incorporated in hydrogel hair dyes that were directly applied on unbleached gray human hairs. Their dyeing performances and the effect of an iron (Ⅱ) mordant were photometrically measured in CIELab coordinates and color strength. The eye and skin irritancy was assessed by combining various in vitro methods, including bovine corneal opacity and permeability (BCOP) assay in combination with histopathological analysis, Hen's egg test on chick chorioallantoic membrane (HET-CAM) and a test on reconstructed human epidermis models.

RESULTS

The investigated hair dyes exhibited desirable dyeing efficiency on human hairs. Post-treatment with the iron (Ⅱ) mordant caused a significant increase in color strength with subtle changes to the hue of dyed color. In the irritation testing, the four hair dyes were categorized as slight-to-mild eye irritants but possessed no skin irritation potential, while the mordant was determined as a non-irritant.

CONCLUSIONS

The results demonstrate the efficacy of a multi-analytical approach for in vitro assessment of various plant colorants for hair dyeing. The investigated plant extracts are suitable for producing viable colors on human hairs and may serve as a low-irritating alternative to the synthetic hair dyes.

Toxic Keratoconjunctivitis

Toxic keratoconjunctivitis (TK) is an underrecognized complication of ophthalmic drug use and various environmental or occupational exposures. A detailed history and clinical examination are important to identify the offending agent(s). Common drug-related causes of TK include preservatives in ophthalmic medications, topical antimicrobials, and topical anesthetics. Alternatives to benzalkonium chloride as well as preservative-free formulations should be considered in patients requiring long-term topical medication. More advanced cases of TK may require preservative-free topical steroids and/or antibiotics, and occasionally surgical intervention. Early recognition and appropriate management of TK may help prevent permanent ocular and visual damage.