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Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice
Published on: March 17, 2014
Substance P affects growth factors in Pseudomonas aeruginosa-infected mouse cornea
Megan E B Foldenauer1, Sharon A McClellan, Ronald P Barrett
1Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Purpose:
This study analyzed the influence of substance P (SP) on growth factors related to wound healing in mice in the presence of infectious keratitis.
Methods:
Naturally resistant mice were injected intraperitoneally with SP or phosphate-buffered saline and infected with Pseudomonas aeruginosa, and corneal messenger RNA (mRNA) levels of growth factors and apoptosis genes were tested. Enzyme-linked immunosorbent assay determined the protein levels, whereas immunohistochemistry tested the distribution, macrophage phenotype, and cell quantitation. In vitro, macrophages were stimulated with lipopolysaccharide (LPS; with or without SP) and mRNA levels of proinflammatory and antiinflammatory cytokines and apoptosis genes were tested.
Results:
After SP, epidermal growth factor mRNA and protein levels were disparately regulated early, with no differences later in the disease. Hepatocyte growth factor and fibroblast growth factor-7 mRNA and protein levels were increased after SP treatment. Enumerating dual-labeled stromal cells revealed no difference between SP-treated versus phosphate-buffered saline-treated groups in the percentage of epidermal growth factor-labeled fibroblasts or macrophages, but there were significant increases in both hepatocyte growth factor- and fibroblast growth factor-7-labeled cells. Type 2 (M2) macrophages and caspase-3 mRNA levels were decreased, whereas B-cell lymphoma-2 mRNA expression was increased after SP treatment. In vitro, mRNA levels of several proinflammatory cytokines and B-cell lymphoma-2 were elevated, whereas transforming growth factor β was decreased after macrophage stimulation with SP (with LPS) over LPS alone. (Mice: n = 105 control; 105 experimental.)
Conclusions:
These data show that treatment with SP in infectious keratitis elevates growth factors but also adversely affects the disease by enhancing the inflammatory response and its sequelae.
Insights
Substance P (SP) treatment in infectious keratitis increased growth factors essential for wound healing in mice. However, SP also worsened the disease by intensifying inflammation and its consequences.
Area of Science:
- Ophthalmology
- Immunology
- Molecular Biology
Background:
- Infectious keratitis, a serious eye infection, can impair wound healing.
- Substance P (SP) is a neuropeptide with known roles in inflammation and tissue repair.
Purpose of the Study:
- To investigate the effect of Substance P (SP) on growth factors crucial for wound healing during infectious keratitis in a mouse model.
- To analyze the impact of SP on inflammatory and apoptotic pathways in the cornea.
Main Methods:
- Mice with infectious keratitis were treated with SP or saline, followed by analysis of corneal gene and protein expression for growth factors and apoptosis markers.
- Macrophage responses to SP and lipopolysaccharide (LPS) were assessed in vitro by measuring cytokine and apoptosis gene expression.
Main Results:
- SP treatment increased levels of hepatocyte growth factor and fibroblast growth factor-7, but epidermal growth factor regulation was transient.
- SP promoted M2 macrophage polarization and altered apoptosis-related gene expression (decreased caspase-3, increased B-cell lymphoma-2).
- In vitro, SP enhanced pro-inflammatory cytokine production and B-cell lymphoma-2 expression in macrophages stimulated with LPS.
Conclusions:
- Substance P (SP) administration in infectious keratitis upregulates key growth factors involved in corneal wound repair.
- Despite promoting growth factors, SP exacerbates the inflammatory response and associated pathological processes in infectious keratitis.
