Interstitial pneumonia (IP) is characterized by various degrees of pulmonary fibrosis and inflammation. Estrogens have been demonstrated to play important roles in physiological and pathological conditions of human lung, but significance of estrogens has remained unknown in human IP. Therefore, we measured estrogen concentrations and immunolocalized aromatase and estrogen receptor β (ERβ) in IP tissues. Estradiol concentration was significantly (2.8-fold) higher in IP than normal lung tissues, and aromatase activity evaluated by estradiol/testosterone ratio was also significantly (7.2-fold) elevated in IP tissues. Aromatase immunoreactivity in alveolar epithelial cells was significantly frequent in IP than normal lung or inflammatory lung disease other than IP, and it was positively associated with ERβ immunoreactivity in these cells of IP. These results suggest that estradiol concentration is locally increased in human IP tissue by aromatase, and increased estrogens may play an important role in the development of IP through ERβ in the alveolar epithelial cells.
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