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Updated: May 21, 2026
Generation of In-Frame Gene Deletion Mutants in Pseudomonas aeruginosa and Testing for Virulence Attenuation in a Simple Mouse Model of Infection
Published on: January 8, 2020
Impaired pulmonary defense against Pseudomonas aeruginosa in VEGF gene inactivated mouse lung
Ellen C Breen1, Jaret L Malloy, Kechun Tang
1Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0623, USA. ebreen@ucsd.edu
Abstract:
Repeated bacterial and viral infections are known to contribute to worsening lung function in several respiratory diseases, including asthma, cystic fibrosis, and chronic obstructive pulmonary disease (COPD). Previous studies have reported alveolar wall cell apoptosis and parenchymal damage in adult pulmonary VEGF gene ablated mice. We hypothesized that VEGF expressed by type II cells is also necessary to provide an effective host defense against bacteria in part by maintaining surfactant homeostasis. Therefore, Pseudomonas aeruginosa (PAO1) levels were evaluated in mice following lung-targeted VEGF gene inactivation, and alterations in VEGF-dependent type II cell function were evaluated by measuring surfactant homeostasis in mouse lungs and isolated type II cells. In VEGF-deficient lungs increased PAO1 levels and pro-inflammatory cytokines, TNFα and IL-6, were detected 24 h after bacterial instillation compared to control lungs. In vivo lung-targeted VEGF gene deletion (57% decrease in total pulmonary VEGF) did not alter alveolar surfactant or tissue disaturated phosphatidylcholine (DSPC) levels. However, sphingomyelin content, choline phosphate cytidylyltransferase (CCT) mRNA, and SP-D expression were decreased. In isolated type II cells an 80% reduction of VEGF protein resulted in decreases in total phospholipids (PL), DSPC, DSPC synthesis, surfactant associated proteins (SP)-B and -D, and the lipid transporters, ABCA1 and Rab3D. TPA-induced DSPC secretion and apoptosis were elevated in VEGF-deficient type II cells. These results suggest a potential protective role for type II cell-expressed VEGF against bacterial initiated infection.
Insights
Vascular Endothelial Growth Factor (VEGF) from type II cells helps defend lungs against bacterial infections by maintaining surfactant homeostasis. VEGF deficiency impairs this defense, increasing bacterial load and inflammation.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Immunology
Background:
- Repeated respiratory infections worsen lung function in diseases like asthma, cystic fibrosis, and COPD.
- Previous research linked pulmonary VEGF gene ablation in mice to alveolar cell apoptosis and lung damage.
- The role of VEGF in type II cells for host defense against bacteria and surfactant homeostasis was unclear.
Purpose of the Study:
- To investigate the necessity of type II cell-expressed VEGF for host defense against bacterial infections.
- To determine if VEGF maintains surfactant homeostasis, contributing to lung defense.
- To evaluate the impact of VEGF deficiency on type II cell function and bacterial clearance.
Main Methods:
- Lung-targeted VEGF gene inactivation in mice.
- Evaluation of Pseudomonas aeruginosa (PAO1) levels post-infection.
- Measurement of surfactant homeostasis in lungs and isolated type II cells.
- Analysis of pro-inflammatory cytokines (TNFα, IL-6), phospholipids, surfactant proteins (SP-B, SP-D), and lipid transporters (ABCA1, Rab3D).
Main Results:
- VEGF-deficient lungs showed increased PAO1 levels and pro-inflammatory cytokines (TNFα, IL-6) 24 hours after infection.
- In vivo VEGF deletion decreased sphingomyelin, CCT mRNA, and SP-D.
- Isolated type II cells with reduced VEGF showed decreased phospholipids, DSPC synthesis, SP-B, SP-D, ABCA1, and Rab3D.
- VEGF-deficient type II cells exhibited elevated TPA-induced DSPC secretion and apoptosis.
Conclusions:
- Type II cell-expressed VEGF plays a protective role in host defense against bacterial infections.
- VEGF is crucial for maintaining surfactant homeostasis and type II cell function.
- VEGF deficiency compromises lung defense mechanisms, leading to increased susceptibility to bacterial pathogens.
