Related Experiment Video
Updated: Dec 18, 2025
Methods to Inhibit Bacterial Pyomelanin Production and Determine the Corresponding Increase in Sensitivity to Oxidative Stress
Published on: August 31, 2015
Brd4 inhibition ameliorates Pyocyanin-mediated macrophage dysfunction via transcriptional repression of reactive
Feimei Zhu1, Feng Xiong2, Jinchen He1
1Department of Pathophysiology, West China College of Basic medical sciences & Forensic Medicine, Sichuan University, 610041, Chengdu, China.
Abstract:
Macrophages play critical roles in the first-line immune defense against airway infections caused by Pseudomonas aeruginosa (PA). The redox-active phenazine-pyocyanin (PCN), as one of the most essential virulence factors, facilities PA-related infection via a wide spectrum of cellular oxidative damages. However, little is known for PCN cytotoxicity in macrophages. In this study, besides showing PCN-mediated reactive oxygen species (ROS) indeed involved in macrophage viability and function impairment, we at the first time demonstrated a novel role of reactive nitrogen species (RNS) pathway causing cellular damage in PCN-challenged macrophages. Using small molecule inhibitor JQ1 targeting Bromodomain and extra-terminal family proteins, we showed restrained iNOS-dependent nitric oxide (NO) production correlated with abolished Brd4 recruitment to the NOS2 (encoding inducible nitric oxide synthase-iNOS) promoter. Application of JQ1 diminished PCN-mediated peroxynitrite (ONOO-) that followed ROS and NO induction, restored macrophage survival and bacteria clearance as well as repressed local inflammation in PA/PCN-challenged mice lungs. Our results uncover a novel link between PCN-mediated macrophage dysfunction and reactive free radicals that rely on Brd4-dependent transcription modulation of multiple stress-response genes, suggesting Brd4 could be a promising therapeutic target in treating PA-related lung infection.
Insights
Pseudomonas aeruginosa
Area of Science:
- Immunology
- Microbiology
- Cellular Biology
Background:
- Macrophages are crucial for immune defense against Pseudomonas aeruginosa (PA) infections.
- Phenazine-pyocyanin (PCN), a PA virulence factor, causes oxidative damage, but its effect on macrophages is unclear.
- Understanding PCN's impact on macrophage function is vital for treating PA infections.
Purpose of the Study:
- To investigate PCN's cytotoxicity in macrophages.
- To elucidate the roles of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in PCN-induced macrophage damage.
- To explore Bromodomain and extra-terminal (BET) proteins as potential therapeutic targets.
Main Methods:
- Assessed PCN-induced ROS and RNS production in macrophages.
- Utilized the small molecule inhibitor JQ1 to target BET proteins and iNOS.
- Evaluated macrophage viability, bacterial clearance, and lung inflammation in a mouse model.
Main Results:
- PCN impairs macrophage viability and function through ROS and novel RNS pathways.
- JQ1 inhibited iNOS-dependent nitric oxide (NO) production by preventing Brd4 recruitment to the NOS2 promoter.
- JQ1 treatment reduced peroxynitrite formation, improved macrophage survival and bacterial clearance, and decreased lung inflammation in vivo.
Conclusions:
- PCN-induced macrophage dysfunction involves ROS, RNS, and Brd4-dependent transcriptional modulation.
- Targeting Brd4 with inhibitors like JQ1 shows therapeutic potential against PA infections.
- This study reveals a new mechanism of PCN toxicity and a promising therapeutic strategy.
