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A Murine Model of Fetal Exposure to Maternal Inflammation to Study the Effects of Acute Chorioamnionitis on Newborn Intestinal Development
Published on: June 24, 2020
Antimicrobial peptide LL37 ameliorated experimental inflammation induced neonatal lung injury through macrophage
Xiaoling Zhang1, Zhu Wang1, Shuzhe Xiao2
1Department of Neonatology, Guangdong Women and Children Hospital, Southern University of Science and Technology, 521 Xingnan Avenue, Guangzhou, 511442, China; Guangzhou Medical University, Guangdong Neonatal ICU Medical Quality Control Center, National Key Clinical Specialty Construction Unit, 521 Xingnan Avenue, Guangzhou, 511442, China.
Background:
Previous studies have shown that the lung tissues of preterm infants with bronchopulmonary dysplasia (BPD) are infiltrated by pro-inflammatory macrophages. The Wnt5a/frizzled-5/CaMKII signaling pathway plays a critical role in regulating macrophage activation. The antimicrobial peptide LL37, an important paracrine factor secreted by cord blood mesenchymal stem cells, modulates macrophages. Lower LL37 levels are associated with a higher risk of BPD. However, whether LL37 protects against inflammation-induced lung injury and its underlying mechanisms remain unclear.
Methods:
Macrophages derived from human myeloid leukemia mononuclear cells (THP-1) and human type II alveolar epithelial cells (A549) were co-cultured. Lipopolysaccharide (LPS) and/or LL37 were added, and CRISPR-Cas9 was used to silence Wnt5a expression in THP-1 cells. An inflammation-induced lung injury mouse model was established by the intraperitoneal injection of LPS during early life after birth. Mice were treated with intraperitoneal injections of either LL37 or an LL37-neutralizing antibody. Inflammatory cytokine expression, macrophage phenotypes, apoptosis, proliferation of type II alveolar epithelial cells, and expression of the Wnt5a/frizzled-5/CaMKII pathway were investigated. In addition, macrophage infiltration and polarization as well as alveolar development in mouse lung tissues were assessed.
Results:
After LL37 intervention or Wnt5a gene silencing, the expression of inflammatory cytokines in THP-1 cells decreased, pro-inflammatory macrophages decreased, and anti-inflammatory macrophages increased. In the mouse model, LL37 treatment reduced macrophage infiltration, pulmonary alveolar diameter, and the severity of lung fibrosis. The protective effect of LL37 was partially neutralized by the addition of an LL37-neutralizing antibody. LL37 intervention inhibited the Wnt5a/frizzled-5/CaMKII pathway.
Conclusion:
LL37 ameliorated inflammation-induced lung injury by inhibiting macrophage activation and the inflammatory response. This protective effect may be mediated through downregulation of the macrophage Wnt5a/frizzled-5/CaMKII pathway. These findings provide novel insights and potential targets for the early prevention of lung injury and establish a foundation for translational research on stem cell therapy for BPD.
Insights
The antimicrobial peptide LL37 reduces lung injury by decreasing pro-inflammatory macrophages and inhibiting the Wnt5a/frizzled-5/CaMKII pathway. This offers potential for preventing bronchopulmonary dysplasia (BPD) in infants.
Area of Science:
- Pulmonary Medicine
- Immunology
- Cell Biology
Background:
- Bronchopulmonary dysplasia (BPD) in preterm infants is linked to pro-inflammatory macrophages in lung tissue.
- The Wnt5a/frizzled-5/CaMKII pathway regulates macrophage activation, and lower levels of the antimicrobial peptide LL37 correlate with increased BPD risk.
Purpose of the Study:
- To investigate the protective effects of LL37 against inflammation-induced lung injury.
- To elucidate the underlying mechanisms of LL37's action, particularly its impact on macrophage activation and the Wnt5a pathway.
Main Methods:
- Co-culture of human macrophages (THP-1) and alveolar epithelial cells (A549) with LPS and/or LL37.
- CRISPR-Cas9 gene silencing of Wnt5a in THP-1 cells.
- Establishment of an LPS-induced lung injury mouse model treated with LL37 or an LL37-neutralizing antibody.
Main Results:
- LL37 intervention and Wnt5a silencing decreased inflammatory cytokines and pro-inflammatory macrophages while increasing anti-inflammatory macrophages.
- In vivo, LL37 treatment reduced macrophage infiltration, improved alveolar diameter, and lessened lung fibrosis, with partial neutralization by an antibody.
- LL37 inhibited the Wnt5a/frizzled-5/CaMKII pathway.
Conclusions:
- LL37 ameliorates inflammation-induced lung injury by suppressing macrophage activation and inflammation via downregulation of the Wnt5a/frizzled-5/CaMKII pathway.
- These findings suggest LL37 as a potential therapeutic target for preventing lung injury and offer a basis for stem cell therapy research in BPD.
