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MRP8/14 enhances corneal susceptibility to Pseudomonas aeruginosa Infection by amplifying inflammatory responses
Qiuchan Deng1, Mingxia Sun, Kun Yang
1Department of Immunology, Zhongshan School of Medicine, Institute of Human Virology, Sun Yat-sen University, Guangzhou, China.
Purpose:
We explored the role of myeloid-related protein 8 and 14 (MRP8/14) in Pseudomonas aeruginosa (PA) keratitis.
Methods:
MRP8/14 mRNA levels in human corneal scrapes and mouse corneas infected by PA were tested using real-time PCR. MRP8/14 protein expression in C57BL/6 (B6) corneas was confirmed using Western blot assay and immunohistochemistry. B6 mice were injected subconjunctivally with siRNA for MRP8/14, and then infected with PA. Bacterial plate counts and myeloperoxidase assays were used to determine the bacterial load and polymorphonuclear neutrophil (PMN) infiltration in infected B6 corneas. Pro-inflammatory cytokine levels in vivo and in vitro were examined with PCR and ELISA. In murine macrophage-like RAW264.7 cells, phagocytosis and bacterial killing were assessed using plate count assays, and reactive oxygen species (ROS) and nitric oxide (NO) levels were tested with flow cytometry and Griess assay, respectively.
Results:
MRP8/14 expression levels were increased significantly in human corneal scrapes and B6 corneas after PA infection. Silencing of MRP8/14 in B6 corneas significantly reduced the severity of corneal disease, bacterial clearance, PMN infiltration, and pro-inflammatory cytokine expression after PA infection. In vitro studies demonstrated further that silencing of MRP8/14 suppressed pro-inflammatory cytokine production, bacterial killing, and ROS production, but not phagocytosis or NO production.
Conclusions:
Our study demonstrated a dual role for MRP8/14 in bacterial keratitis. Although MRP8/14 promotes bacterial clearance by enhancing ROS production, it functions more importantly as an inflammatory amplifier at the ocular surface by enhancing pro-inflammatory cytokine expression, thus contributing to the corneal susceptibility.
Insights
Myeloid-related protein 8 and 14 (MRP8/14) plays a dual role in Pseudomonas aeruginosa keratitis. While enhancing bacterial clearance via reactive oxygen species, it primarily amplifies inflammation, increasing corneal susceptibility.
Area of Science:
- Ophthalmology
- Immunology
- Microbiology
Background:
- Pseudomonas aeruginosa (PA) keratitis is a severe ocular infection.
- The role of myeloid-related proteins (MRPs) in PA keratitis is not fully understood.
Purpose of the Study:
- To investigate the role of myeloid-related protein 8 and 14 (MRP8/14) in Pseudomonas aeruginosa (PA) keratitis.
- To elucidate the mechanisms by which MRP8/14 influences the host response to PA infection.
Main Methods:
- Quantified MRP8/14 mRNA and protein expression in human and murine corneas post-PA infection.
- Utilized siRNA to silence MRP8/14 in a murine keratitis model.
- Assessed bacterial load, neutrophil infiltration, and pro-inflammatory cytokine levels.
- Investigated in vitro effects on phagocytosis, bacterial killing, reactive oxygen species (ROS), and nitric oxide (NO) production.
Main Results:
- MRP8/14 expression was significantly upregulated in infected corneas.
- Silencing MRP8/14 reduced disease severity, bacterial load, neutrophil infiltration, and pro-inflammatory cytokines.
- In vitro, MRP8/14 silencing impaired bacterial killing and ROS production but not phagocytosis or NO production.
Conclusions:
- MRP8/14 exhibits a dual role in PA keratitis.
- It contributes to bacterial clearance through ROS production.
- MRP8/14 primarily acts as an inflammatory amplifier, increasing corneal susceptibility.
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