Tier 3 — preclinical

Fisetin Alleviated Bleomycin-Induced Pulmonary Fibrosis Partly by Rescuing Alveolar Epithelial Cells From Senescence

Zhang L, Tong X, Huang J, Wu M, Zhang S, Wang D, Liu S, Fan H

Frontiers in Pharmacology 2020 11:553690

Bibliography

DOI: 10.3389/fphar.2020.553690
PubMed: PMID 33381023
PubMed Central: PMC7768023
Funding: Supported by the National Key R&D Program of China (2017YFC1309703), China Postdoctoral Science Foundation (2020M673259), the 1·3·5 Project for Disciplines of Excellence, Clinical Research Incubation Project, West China Hospital, and Post-Doctor Research Project, West China Hospital, Sichuan University (2020XHB013).
Competing interests: The authors declare no competing financial or commercial relationships.

Study snapshot

Design	Mouse model of bleomycin (BLM)-induced idiopathic pulmonary fibrosis (4 groups: control, fisetin-alone, BLM-alone, BLM+fisetin), paired with in vitro alveolar epithelial cell (A549) senescence and fibroblast (HELF) transdifferentiation assays using BLM-conditioned media, with and without the AMPK inhibitor Compound C.
Model	Male C57BL/6J mice (bleomycin intratracheal instillation, 2.5 mg/kg) and human A549 alveolar epithelial / HELF lung fibroblast cell lines in vitro.
Sample	70 mice randomly divided into 4 groups (in vivo); in vitro assays performed with n≥3 independent experiments.
Intervention	Fisetin 100 mg/kg intragastric every other day for 3 weeks (in vivo, from day 7 post-BLM); fisetin 5-10 μM in vitro.
Duration	28 days (in vivo, mice euthanised on day 28 post-BLM instillation); in vitro assays over 2-3 days per experiment.
Endpoints	Body weight and survival rate; Lung wet-to-dry weight ratio; Histopathology: inflammation and fibrosis scores (H&E, Masson's trichrome); Hydroxyproline (collagen) content; SA-beta-galactosidase-positive senescent cell counts; p16, p21, collagen I, alpha-SMA expression (Western blot / qRT-PCR); TGF-beta/Smad3, AMPK, NF-kB p65 phosphorylation (Western blot); BALF cytokines: IL-1beta, IL-6, TNF-alpha, TGF-beta, MMP-9 (ELISA)

What the study showed, in plain terms

Idiopathic pulmonary fibrosis has no fully satisfactory treatment, and senescent alveolar epithelial cells are thought to drive its progression. This study asked whether fisetin, already known as a senolytic in other tissues, could help in the lung.

Chinese researchers gave mice bleomycin to trigger pulmonary fibrosis, then treated some with oral fisetin. They also modelled cellular senescence directly in lung cell cultures.

Fisetin reduced weight loss, lung inflammation, collagen deposition and fibrosis scores in bleomycin-treated mice. At the cellular level, it lowered markers of alveolar epithelial cell senescence (p16, p21, SA-beta-gal) and reduced the inflammatory secretions (SASP) those senescent cells release, apparently by activating AMPK and suppressing NF-kB and TGF-beta/Smad3 signalling — an AMPK inhibitor blocked the protective effect.

Bottom line: a mechanistically coherent mouse and cell-culture study suggesting fisetin may have a role in pulmonary fibrosis via its senotherapeutic activity, but it has not been tested in human IPF patients.

Key findings

Fisetin (100 mg/kg, every other day for 3 weeks) alleviated bleomycin-induced weight loss, lung inflammation, collagen deposition and fibrosis scores in mice, and reduced alveolar epithelial cell senescence markers (p16, p21, SA-beta-gal) both in vivo and in vitro. Mechanistically, fisetin activated AMPK and suppressed NF-kB and TGF-beta/Smad3 signalling; an AMPK inhibitor (Compound C) blocked fisetin's anti-senescence and anti-fibrotic effects.

What this study can and cannot tell us

Mouse and cell-line model only; no human pulmonary fibrosis data. Fisetin showed a non-significant trend toward improved survival rather than a statistically significant one. A549 is a lung cancer-derived cell line used as an alveolar epithelial cell proxy, which may not fully represent primary alveolar epithelium behaviour.