Myeloid PTEN promotes inflammation but impairs bactericidal activities during murine pneumococcal pneumonia

Area of Science:

• Immunology
• Cell Biology
• Microbiology

Background:

• Phosphatidylinositol 3-kinase (PI3K) is crucial for immune cell chemotaxis and pathogen elimination.
• PI3K signaling also modulates immune responses, potentially limiting acute inflammation.
• The role of the PI3K pathway and its antagonist, PTEN, in bacterial infections remains unclear.

Purpose of the Study:

• To investigate the role of PTEN in myeloid cells during Streptococcus pneumoniae infection.
• To understand how PTEN deficiency impacts the immune response and disease severity.

Main Methods:

• Utilized genetically modified mice lacking myeloid cell-specific PTEN.
• Assessed survival rates and disease severity following S. pneumoniae infection.
• Analyzed inflammatory responses in macrophages in vitro and in vivo.
• Quantified neutrophil influx and bacterial load (CFUs) in lung tissues.

Main Results:

• PTEN-deficient mice showed reduced disease severity and prolonged survival.
• Pulmonary inflammation and macrophage inflammatory responses were significantly reduced.
• Neutrophil influx into the lungs was unexpectedly impaired.
• Phagocytosis by PTEN-deficient alveolar macrophages was enhanced, maintaining lung bacterial clearance.
• Reduced tissue injury was observed in PTEN-deficient mice.

Conclusions:

• Absence of myeloid cell PTEN enhances PI3K activity, dampening pulmonary inflammation.
• Impaired neutrophil influx coupled with augmented macrophage phagocytosis leads to improved outcomes.
• Targeting PTEN in myeloid cells may represent a therapeutic strategy for bacterial pneumonia.