FFA4 inhibits bleomycin-induced pulmonary fibrosis in mice by suppressing IL-33
Jingjing Feng1, Hao Dong2, Songlou Yin1
1The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221000, China.
Background:
Interstitial lung disease is one of the most severe pulmonary complications of connective tissue diseases and is associated with high mortality and poor prognosis due to the lack of effective therapies. Free fatty acid receptor 4, a receptor activated by long-chain unsaturated fatty acids, participates in the regulation of inflammatory responses; however, its direct role and underlying mechanisms in ILD-related pulmonary fibrosis have not yet been reported.
Methods:
In this study, we investigated the effect of FFA4 on pulmonary fibrosis using both in vivo and in vitro models. A bleomycin-induced pulmonary fibrosis model was established in wild-type and FFAR4 knockout mice. In vitro, a Transwell co-culture system consisting of RAW264.7 macrophages and NIH3T3 fibroblasts was constructed. Transfection, transcriptomic analysis, dual-luciferase reporter assays, RT-qPCR, and Western blotting were performed to explore the molecular mechanisms mediated by FFA4. In addition, pharmacological interventions with the FFA4 agonist CpdA and the NF-κB inhibitor BAY11-7082 were used to evaluate the role of the NF-κB-IL-33 signaling axis in inflammation-driven fibrotic responses.
Results:
FFA4 expression was reduced in the bleomycin-induced fibrosis model. In both the co-culture system and the mouse model, FFA4 deficiency significantly increased IL-33 expression and aggravated pulmonary fibrosis. In contrast, activation of FFA4 with CpdA reduced IL-33 expression and attenuated pulmonary fibrosis. Moreover, BAY11-7082 also suppressed IL-33 expression. Genetic deletion and pharmacological activation experiments further confirmed that the inhibitory effect of CpdA on IL-33 expression was dependent on FFA4.
Conclusions:
Collectively, these findings demonstrate that FFA4 restrains inflammatory signal amplification and suppresses pulmonary fibrosis progression by regulating the NF-κB-IL-33 signaling axis, suggesting that FFA4 may serve as a potential therapeutic target for pulmonary fibrosis.
Insights
Free fatty acid receptor 4 (FFA4) restrains pulmonary fibrosis by regulating the NF-κB-IL-33 pathway. Activating FFA4 suppresses fibrosis, suggesting it as a therapeutic target for interstitial lung disease.
Area of Science:
- Pulmonary Medicine
- Immunology
- Molecular Biology
Background:
- Interstitial lung disease (ILD) is a severe complication of connective tissue diseases with high mortality.
- Current therapies for ILD-related pulmonary fibrosis are limited.
- The role of Free Fatty Acid Receptor 4 (FFA4) in pulmonary fibrosis remains uncharacterized.
Purpose of the Study:
- To investigate the effect of FFA4 on pulmonary fibrosis.
- To elucidate the molecular mechanisms underlying FFA4's role in fibrosis.
- To explore FFA4 as a potential therapeutic target for pulmonary fibrosis.
Main Methods:
- Established a bleomycin-induced pulmonary fibrosis model in wild-type and FFA4 knockout mice.
- Utilized a Transwell co-culture system of macrophages and fibroblasts.
- Performed transcriptomic analysis, dual-luciferase reporter assays, RT-qPCR, and Western blotting.
- Employed pharmacological interventions with an FFA4 agonist (CpdA) and an NF-κB inhibitor (BAY11-7082).
Main Results:
- FFA4 expression was decreased in a bleomycin-induced fibrosis model.
- FFA4 deficiency exacerbated pulmonary fibrosis and increased IL-33 expression.
- Activation of FFA4 with CpdA attenuated pulmonary fibrosis and reduced IL-33 expression.
- NF-κB inhibition also suppressed IL-33 expression, indicating the involvement of the NF-κB-IL-33 axis.
Conclusions:
- FFA4 restrains inflammatory signal amplification and suppresses pulmonary fibrosis progression.
- FFA4 regulates pulmonary fibrosis via the NF-κB-IL-33 signaling axis.
- FFA4 represents a potential therapeutic target for pulmonary fibrosis.
