Current concepts suggest that macrophages may play a central role in
pulmonary fibrosis by virtue of their ability to release a variety of
cytokines. In this study, the expression of
interleukin (IL)-1 alpha and beta,
platelet-derived growth factor (
PDGF) A and B, and
insulin-like growth factor (
IGF) I in BAL cells, which may be involved in fibroblast proliferation, was investigated in murine
bleomycin (BLM)-induced
pulmonary fibrosis. BAL cells were obtained at 1, 15, and 29 days from Institute for
Cancer Research mice after 10 days of intraperitoneal administration of BLM. The relative amounts of
cytokine messenger RNA (
mRNA) were evaluated by the reverse transcription-polymerase chain reaction method, which simultaneously amplified
complementary DNA for
cytokines and
beta-actin as an internal control. The level of
IL-1 beta mRNA in BLM-treated mice was increased 4.5-fold compared with that in
saline solution-treated (control) mice 1 day
after treatment, while no significant differences were observed between the two groups at 15 and 29 days. The mRNAs of
PDGF-A and
IGF-I in BLM-treated mice were sustained at levels eightfold and threefold to fourfold, respectively, those of controls over 4 weeks. No significant differences were noted in
IL-1 alpha and PDGF-B expression between the two groups. We conclude that
IL-1 beta released from macrophages may be important in the early phase of inflammatory responses and that
PDGF-A and
IGF-I may play important roles in the development of BLM-induced
pulmonary fibrosis.