Development and assessment of new risk assessment methods

Title of Research:
12_S01-03-2

Establishment of animal testing for the prediction of respiratory
sensitizing potential of chemicals
Principal Investigator:
Kohji Aoyama, PhD (Assistant Professor, Kagoshima University, Department of Hygiene andHealth Promotion Medicine, Graduate School of Medicine and Dental Sciences)
8-35-1 Sakuragaoka, Kagoshima, 890-8544, 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 VeterinaryMedicine, 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 shinazaike, aboshi-ku, Himeji, 671-1283, Japan(tel)+81-79-274-4061 (e-mail)ku_yamashita@daicel.jp
Summary of Research:
Currently, there is no test for evaluating the respiratory sensitizing potential of chemicals. The
purpose of this project is the establishment of animal testing methods for predicting respiratory
sensitizers and for evaluating their relative respiratory sensitizing potency. We have developed arespiratory sensitization testing method using intratracheal administration.
In the second stage, we verified the effectiveness of the testing method using several new but
known respiratory sensitizers. Test substances used were phthalic anhydride (PA), methyl tetrahydrophthalic anhydride (MTHPA), maleic anhydride (MA), and hexamethylene diisocyanate (HDI),
which are well-known respiratory sensitizers. We used oxazolone (OX) and chlorobenzene (CB),which are a skin sensitizer and non-sensitizer, respectively. Mice were sensitized by intratracheal
instillation of individual chemicals, each at three concentrations, on 5 days per week for 3 weeks.
Three days following the last installation, mice were challenged with the corresponding agents forthree days, and were sacrificed 2 days later. The degree of Th2 type-allergic inflammation in lungs
was determined using an allergic inflammation score based on the histopathological grading.
PA and MTHPA elicited weak Th2-type allergic inflammatory responses in a dose-related manner.
It was difficult to identify a respiratory sensitizing potency for MA under the test conditions,although Th2-type allergic inflammatory responses were elicited in the lungs of mice sensitizedwith MA. With HDI, Th2-type allergic inflammatory responses were elicited in elicitation-control
and low-concentration groups; the reason for this is unknown. OX showed the same levels ofallergic inflammation scores as the vehicle-control group. No allergic inflammatory reaction to CB
was found at non-sensitizing potency. The relative sensitizing potency, based on the relationshipbetween sensitizing concentrations and allergic inflammation scores, could be used to compare
the potency of PA, MTHPA, OX, and CB. Thus, the present test method could separate PA andMTHPA from OX and CB, and confirmed the usefulness of evaluating relative sensitizing potency.
Further studies should be conducted on enhancing the elicitation reaction for weak respiratory
sensitizers.
Timeline:
November 1, 2013 – February 28, 2015
Topics:Presented at the 3th Annual Conferences of New LRIPublications:
88th Annual Meeting of Japan Society for Occupational Health, Osaka, May 2015