| Increased Expression of Matrix Metalloproteinase in Clara Cell-Ablated Mice Inhaling Crystalline Silica Kazuhiro Yatera,1 Yasuo Morimoto,2 Heung-Nam Kim,3 Hiroshi Yamato,3 Isamu Tanaka,3 and Masamitsu Kido1 1Department of Respiratory Disease, 2Department of Occupational Pneumology, and 3Department of Environmental Health Engineering, University of Occupational and Environmental Health, Japan, Kitakyushu City, Fukuoka Prefecture, Japan Abstract
We investigated the function of Clara cells in vivo during exposure to inhaled crystalline silica by examining pulmonary matrix metalloproteinase (MMP) -2 and MMP-9 mRNA levels in mice. The Clara cells of male FVB/n mice (8-12 weeks old) were ablated by intraperitoneal administration of naphthalene (300 mg/kg) in a corn oil vehicle. The mice were then exposed to crystalline silica (Min-U-Sil-5 silica, 97.1 ± 9.5 mg/m2, 6 hr/day, 5 days/week) for up to 2 weeks. Transcriptional levels of mRNA extracted from the lungs were assessed by reverse transcription-polymerase chain reaction. Gene expression of both MMP-2 and MMP-9 was significantly more marked in the Clara cell-ablated group than in the group with Clara cells, indicating that Clara cells inhibit MMP expression. Our findings suggest that Clara cells inhibit pulmonary inflammation induced by crystalline silica via MMPs in vivo. Key words: Clara cell, crystalline silica, matrix metalloproteinase, naphthalene, reverse transcription-polymerase chain reaction. Environ Health Perspect 109:795-799 (2001) . [Online 3 August 2001] http://ehpnet1.niehs.nih.gov/docs/2001/109p795-799yatera/ abstract.html Address correspondence to K. Yatera, Division of Respiratory Disease, University of Occupational and Environmental Health, Japan, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu City, Fukuoka Prefecture 807-8555, Japan. Telephone: +81-93-691-7453. Fax: +81-93-601-9373. E-mail: yatera@med.uoeh-u.ac.jp We thank M. Tsunoda and M. Hirohashi for assistance with some of the experiments. This work was supported in part by the Japanese Ministry of Education and Science. Received 22 September 2000 ; accepted 15 February 2001.
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