Examining animal testing for risk assessment: A WC-12 workshop report

In toxicology and regulatory testing, the use of animal methods has been both a cornerstone and a subject of intense debate. To continue this discourse a panel and audience representing scientists from various sectors and countries convened at a workshop held during the 12th World Congress on Alternatives and Animal Use in the Life Sciences (WC-12). The ensuing discussion focused on the scientific and ethical considerations surrounding the necessity and responsibility of defending the creation of new animal data in regulatory testing. The primary aim was to foster an open dialogue between the panel members and the audience while encouraging diverse perspectives on the responsibilities and obligations of various stakeholders (including industry, regulatory bodies, technology developers, research scientists, and animal welfare NGOs) in defending the development and subsequent utilization of new animal data. This workshop summary report captures the key elements from this critical dialogue and collective introspection. It describes the intersection of scientific progress and ethical responsibility as all sectors seek to accelerate the pace of 21st century predictive toxicology and new approach methodologies (NAMs) for the protection of human health and the environment.

Magnetic-film atom chip with 10 μm period lattices of microtraps for quantum information science with Rydberg atoms

We describe the fabrication and construction of a setup for creating lattices of magnetic microtraps for ultracold atoms on an atom chip. The lattice is defined by lithographic patterning of a permanent magnetic film. Patterned magnetic-film atom chips enable a large variety of trapping geometries over a wide range of length scales. We demonstrate an atom chip with a lattice constant of 10 μm, suitable for experiments in quantum information science employing the interaction between atoms in highly excited Rydberg energy levels. The active trapping region contains lattice regions with square and hexagonal symmetry, with the two regions joined at an interface. A structure of macroscopic wires, cutout of a silver foil, was mounted under the atom chip in order to load ultracold (87)Rb atoms into the microtraps. We demonstrate loading of atoms into the square and hexagonal lattice sections simultaneously and show resolved imaging of individual lattice sites. Magnetic-film lattices on atom chips provide a versatile platform for experiments with ultracold atoms, in particular for quantum information science and quantum simulation.

Introduction of a methoxymethyl side chain into p-phenylenediamine attenuates its sensitizing potency and reduces the risk of allergy induction

The strong sensitizing potencies of the most important primary intermediates of oxidative hair dyes, p-phenylenediamine (PPD) and p-toluylenediamine (PTD, i.e. 2-methyl-PPD) are well established. They are considered as the key sensitizers in hair dye allergic contact dermatitis. While modification of their molecular structure is expected to alter their sensitizing properties, it may also impair their color performance. With introduction of a methoxymethyl side chain we found the primary intermediate 2-methoxymethyl-p-phenylenediamine (ME-PPD) with excellent hair coloring performance but significantly reduced sensitizing properties compared to PPD and PTD: In vitro, ME-PPD showed an attenuated innate immune response when analyzed for its protein reactivity and dendritic cell activation potential. In vivo, the effective concentration of ME-PPD necessary to induce an immune response 3-fold above vehicle control (EC3 value) in the local lymph node assay (LLNA) was 4.3%, indicating a moderate skin sensitizing potency compared to values of 0.1 and 0.17% for PPD and PTD, respectively. Finally, assessing the skin sensitizing potency of ME-PPD under consumer hair dye usage conditions through a quantitative risk assessment (QRA) indicated an allergy induction risk negligible compared to PPD or PTD.

Evidence that the novobiocin-sensitive ATP-binding site of the heat shock protein 90 (hsp90) is necessary for its autophosphorylation

The 90kDa heat shock protein (Hsp90) is one of the most abundant protein and essential for all eukaryotic cells. Many proteins require the interaction with Hsp90 for proper function. Upon heat stress the expression level of Hsp90 is even enhanced. It is assumed, that under these conditions Hsp90 is required to protect other proteins from aggregation. One property of Hsp90 is its ability to undergo autophosphorylation. The N-terminal domain of Hsp90 has been shown to contain an unusual ATP-binding site. A well-known inhibitor of Hsp90 function is geldanamycin binding to the N-terminal ATP-binding site with high affinity. Recently it was shown that Hsp90 possesses a second ATP-binding site in the C-terminal region, which can be competed with novobiocin. Autophosphorylation of Hsp90 was analysed by incubation with gamma(32)P-ATP. Addition of geldanamycin did not interfere with the capability for autophosphorylation, while novobiocin indeed did. These results suggest that the C-terminal ATP-binding site is required for autophosphorylation of Hsp90.

Elicitation of the immune response to p-phenylenediamine in allergic patients: the role of dose and exposure time

BACKGROUND

Usage of hair dye products containing p-phenylenediamine (PPD) is a concern for PPD-allergic individuals.

OBJECTIVES

The present study investigates the role of dose and exposure time on elicitation of allergic contact dermatitis under conditions of permanent hair dyeing.

METHODS

Elicitation responses after application of a typical hair dye product containing 2% PPD for 30 min followed by rinsing were analysed in 38 PPD-allergic individuals with a documented history of hair dye-related allergy. Skin binding experiments in vitro were performed to distinguish the dose available for elicitation from the dose applied.

RESULTS

A positive reaction was elicited in 20 of 20 patients with grades ++ to +++ and 12 of 18 with grade + according to the classification of the International Contact Dermatitis Research Group. Under conditions of diagnostic patch testing (48 h exposure), the dose available for elicitation is more than 10-fold higher compared with the dose available for hair dyeing (30-min exposure, rinsing of product).

CONCLUSIONS

This investigation demonstrates that under simulated hair dye use conditions the actual exposure to PPD is more than an order of magnitude lower than under diagnostic patch testing, although sufficient to elicit a clearly noticeable reaction in 84% of PPD patch test-positive individuals.

Compilation of historical local lymph node data for evaluation of skin sensitization alternative methods

BACKGROUND

Within the toxicology community, considerable effort is directed toward the development of alternative methods for skin sensitization testing. The availability of high-quality, relevant, and reliable in vivo data regarding skin sensitization is essential for the effective evaluation of alternative methodologies. Ideally, data derived from humans would be the most appropriate source because the test methods are attempting to predict a toxicologic effect in humans. Unfortunately, insufficient human data of the necessary quality are available, so it is necessary to rely on the best available animal data. In recent years, the local lymph node assay (LLNA) has emerged as a practical option for assessing the skin sensitization potential of chemicals. In addition to accurately identifying skin sensitizers, the LLNA can also provide a reliable measure of relative sensitization potency, information that is pivotal to the successful management of human health risks.

OBJECTIVE

To provide a database of robust in vivo data to calibrate, evaluate, and eventually validate new approaches for skin sensitization testing.

METHODS

LLNA data derived from previously conducted studies were compiled from the published literature and unpublished sources.

RESULTS

We provide a database that comprises LLNA data on 211 individual chemicals. This extensive chemical data set encompasses both the chemical and biologic diversity of known chemical allergens. To cover the range of relative allergenic potencies, the data set includes data on 13 extreme, 21 strong, 69 moderate, and 66 weak contact allergens, classified according to each allergen's mathematically estimated concentration of chemical required to induce a threefold stimulation index. In addition, there are also 42 chemicals that are considered to be nonsensitizers. In terms of chemical diversity, the database contains data pertaining to the chemical classes represented by aldehydes, ketones, aromatic amines, quinones, and acrylates, as well as compounds that have different reactivity mechanisms. In addition to two-dimensional chemical structures, the physicochemical parameters included are log Kp, log K(o/w), and molecular weight.

CONCLUSIONS

The list of chemicals contained in the data set represents both the chemical and biologic diversity that is known to exist for chemical allergens and non-allergens. It is anticipated that this database will help accelerate the development, evaluation, and eventual validation of new approaches to skin sensitization assessment.

A novel function for the 90 kDa heat-shock protein (Hsp90): facilitating nuclear export of 60 S ribosomal subunits

Ribosomal subunits are assembled in the nucleus, and mature 40 S and 60 S subunits are exported stoichiometrically into the cytoplasm. The nuclear export of ribosomal subunits is a unidirectional, saturable and energy-dependent process. An in vitro assay for the nuclear export of 60 S ribosomal subunits involves the use of resealed nuclear envelopes. The export of ribosomal subunits from resealed nuclear envelopes is enhanced by cytoplasmic proteins. Here we present evidence that the export-promoting activity was due to the cytoplasmic 90 kDa heat-shock protein (Hsp90). Isolated, purified Hsp90 vastly enhanced the export of 60 S ribosomal subunits from resealed nuclear envelopes, while inhibition of Hsp90 function, either with the Hsp90-binding drug geldanamycin or with anti-Hsp90 antibodies, resulted in reduced release of 60 S ribosomal subunits. To confirm these findings under in vivo conditions, corresponding experiments were performed with Xenopus oocytes using microinjection techniques; the results obtained confirmed the findings obtained with resealed nuclear envelopes. These findings suggest that Hsp90 facilitates the nuclear export of 60 S ribosomal subunits, probably by chaperoning protein interactions during the export process.

Casting technique for the fabrication of pinholes for X-ray radiation

Pinholes with diameters down to 4 mum have been made in gold plates of a few hundred mum thickness. The fabrication method used is based on a casting technique. The pinholes are well suited for the collimation of (hard) X-rays from a synchrotron radiation source.

Export of ribosomal subunits from resealed rat liver nuclear envelopes

We have previously described the rat liver resealed nuclear envelope model system for the study of the selective import of nuclear proteins, and the export of poly(A)-containing mRNA [Riedel, N., Bachmann, M., Richter, H. & Fasold, H. (1987) Proc. Natl Acad. Sci. USA 83, 3540-3544]. The vesicles still respond to the importin-ATP signal for the uptake of nuclear-location-sequence (NLS)-carrying proteins. During the preparation of the vesicles and extraction of the chromatin from nuclei in cold hypotonic heparin solution, ribosomal subunits may be introduced into these envelopes, and after resealing remain stably included. Efflux from the resealed nuclear envelopes is effected by a cytoplasmatic protein fraction, and strongly enhanced in the presence of ATP. The heterogeneous nuclear RNP (hnRNP) A1, the components of importin, or GTP showed no influence on this export. The ATP-dependent efflux of mRNA is not affected by these cytoplasmic proteins in this model system.