Development and assessment of new risk assessment methods

Title of Research:
12_S01-03

Establishment of animal testing for the prediction ofrespiratory sensitizing potential of chemicals
Principal Investigator:
Kohji Aoyama (Department of Hygiene and Health Promotion Medicine, Graduate School ofMedical and Dental Sciences, Kagoshima University)
8-35-1 Sakuragaoka, Kagoshima, 890-0031, Japan(tel)+81-99-275-5291 (e-mail) aoyama@m.kufm.kagoshima-u.ac.jp
Collaborators:
Hiroaki Kawaguchi (Laboratory of Veterinary Histopathology, Joint Faculty of Verterinary
Medicine, Kagoshima University)
1-21-1 korimoto, Kagoshima, 890-8580, Japan(tel)+81-99-285-8720 (e-mail) k3038952@kadai.jp
Kunihiko Yamashita (Corporate Research Center, R &D Management, Daicel Corporation)
1239 shinzaike, aboshi-ku, himeji, 671-1283, Japan(tel)+81-79-274-4061 (e-mail) ku_yamashita@daicel.co.jp
Summary of Research:
Respiratory allergy caused by occupational chemicals remains as a significant health concern
for industrial workers. However, to date there are no proper animal models for effectively
predicting their respiratory sensitizing potentials. The goals of this project are: (1) to develop theanimal models for evaluating the relative hazard of respiratory sensitizing chemicals; and (2) toprovide the useful information required for hazard assessment of these sensitizers in theworkplaces. we developed a small device that enables intratracheal administration of testing
substances in small animals such as mice. In this project, TDI, TMA and GA, three well-known
respiratory sensitizing chemicals and chicken ovalbumin (OVA), were evaluated. Known contact
sensitizing DNCB served as the negative control for respiratory allergens. Under light anesthesiawith diethyl ether, mice were sensitized by administering individual agents, each at 4 doses
including vehicle control, 5 times a week for a total of 3 weeks using a mouse intra-tracheal
installation device. Three days following the last installation, these mice were daily challenged
intratracheally with the corresponding agents for 3 days, and sacrificed 2 days thereafter. The
degree of airway inflammation was evaluated using semi-quantitative histological grading systems.
We found that histological scores, representing the degree of airway inflammation, increased withincreasing doses of OVA and TDI used for sensitization. Similar trends were also noted for TMAor GA-sensitized mice. They were also true for PAS staining in airway epithelial cells. In contrast,
such changes were not observed in mice treated with DNCB. Thus, our testing system confirmed
the relative sensitizing potency of these known respiratory sensitizers as previously reported incase-studies or epidemiologic studies. As the strategy for assessing the risk for respiratory
sensitizing agents in workplace, although the relationship between airway sensitization onset (asdetermined by various endpoints) and exposure dose/concentration should be first investigated,these evidence for setting exposure limit vary in substances and exposure conditions. Thus,
multi-factors, including experimental evidence, workplace exposure and clinical signs should beconsidered for properly and effectively controlling occupational respiratory allergy.
Timeline: November 1, 2012 –Topics:Presented at the 2th Annual Conferences of New LRI (31th August, 2013, Tokyo)

Annual Report 20134