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Peplomycin, a bleomycin derivative, induces myofibroblasts in pulmonary fibrosis
T Osaki1, K Yoneda, Y Tatemoto
1Department of Oral Surgery, Kochi Medical School, Kochi, Japan.
Abstract:
To analyse the mechanism by which a bleomycin derivative, peplomycin (PLM) induces pulmonary fibrosis, we investigated differentiation of rat pulmonary fibroblasts to myofibroblasts (MF). In intraperitoneally PLM (5 mg/kg/day)-injected rats, the peripheries of lungs adjacent to the pleura revealed advanced fibrosis with a small number of alpha-smooth muscle actin (alpha-SMA)-positive MF, which ultrastructurally possessed abundant microfilaments and cellular organelles. In the fibrotic tissue, the expression of alpha-SMA-mRNA was detected by in situ reverse transcription-polymerase (RT-PCR). The message was strong just after a 2-week administration of PLM then decreased thereafter, although fibrosis advanced. When pulmonary fibroblasts were separated from saline-injected rats (N-Fib) and cultivated for 7 days in the presence of 5 mg/mL PLM, alpha-SMA protein was weakly expressed, while the majority of pulmonary fibroblasts separated from PLM-injected rats (P-Fib) became positive for alpha-SMA in 7-day cultivation and the expression of alpha-SMA in P-Fib was strongly increased by cultivation in the presence of PLM and transforming growth factor-beta (TGF-beta), but not basic fibroblast growth factor (bFGF) or platelet-derived growth factor (PDGF), although the cell proliferation was most strongly enhanced by bFGF and only slightly by PLM and TGF-beta. The alpha-SMA-positive cells expressed vimentin, but only weakly expressed desmin. Additionally, P-Fib generated larger amounts of TGF-beta and bFGF than were generated by N-Fib. These results indicate that PLM induces pulmonary fibrosis by differentiating fibroblasts to alpha-SMA-positive MF, and that bFGF and TGF-beta play each critical role in the different phases of PLM-induced pulmonary fibrosis by inducing fibroblast proliferation and transformation, respectively.
Insights
Peplomycin (PLM) causes pulmonary fibrosis by transforming lung fibroblasts into myofibroblasts. Transforming growth factor-beta (TGF-beta) and basic fibroblast growth factor (bFGF) are key factors in this process.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Toxicology
Background:
- Pulmonary fibrosis is a debilitating lung disease with complex mechanisms.
- Peplomycin (PLM), a bleomycin derivative, is known to induce lung injury.
- Understanding the cellular mechanisms of PLM-induced pulmonary fibrosis is crucial for developing treatments.
Purpose of the Study:
- To elucidate the mechanism by which peplomycin (PLM) induces pulmonary fibrosis.
- To investigate the differentiation of rat pulmonary fibroblasts into myofibroblasts (MF) induced by PLM.
- To determine the roles of growth factors like TGF-beta and bFGF in this process.
Main Methods:
- Administration of PLM to rats and analysis of lung tissue for fibrosis and alpha-smooth muscle actin (alpha-SMA)-positive MF.
- In situ reverse transcription-polymerase (RT-PCR) to detect alpha-SMA mRNA expression.
- In vitro cultivation of rat pulmonary fibroblasts (N-Fib and P-Fib) with PLM, TGF-beta, bFGF, and PDGF to assess alpha-SMA expression and cell proliferation.
Main Results:
- PLM induced pulmonary fibrosis and alpha-SMA-positive MF in rat lungs.
- In vitro, PLM induced alpha-SMA expression in fibroblasts, with enhanced effects when combined with TGF-beta.
- Basic fibroblast growth factor (bFGF) primarily promoted fibroblast proliferation, while TGF-beta induced fibroblast transformation into MF.
Conclusions:
- Peplomycin (PLM) induces pulmonary fibrosis by promoting the differentiation of fibroblasts into alpha-SMA-positive myofibroblasts.
- Both fibroblast proliferation (driven by bFGF) and transformation (driven by TGF-beta) are critical in distinct phases of PLM-induced pulmonary fibrosis.