STAT4 knockout protects LPS-induced lung injury by increasing of MDSC and promoting of macrophage differentiation

Area of Science:

• Immunology
• Pathology
• Molecular Biology

Background:

• Signal transducer and activator of transcription 4 (STAT4) signaling is implicated in inflammation and organ injury during severe bacterial infections.
• The precise role of STAT4 in the pathogenesis of lung injury, particularly in response to lipopolysaccharide (LPS), is not fully elucidated.

Purpose of the Study:

• To investigate the mechanism of STAT4 signaling in lipopolysaccharide (LPS)-induced lung injury.
• To determine the impact of STAT4 deficiency on lung inflammation, immune cell infiltration, and cytokine production.

Main Methods:

• Utilized STAT4-deficient (STAT4(-/-)) mice and wild-type controls.
• Induced lung injury using lipopolysaccharide (LPS) administration.
• Assessed lung injury severity, protein leakage, inflammatory cell infiltration (including CD11b(+)Gr-1(+) myeloid-derived suppressor cells (MDSCs) and macrophages), and cytokine levels (TNF-α, IL-1β, IL-6, IL-10) in bronchoalveolar lavage fluid.

Main Results:

• STAT4 deficiency significantly reduced lethality, protein leakage, edema, inflammatory infiltration, and hemorrhage in LPS-induced lung injury.
• LPS challenge led to a marked increase in circulating CD11b(+)Gr-1(+) myeloid-derived suppressor cells (MDSCs) in STAT4(-/-) mice, accompanied by increased macrophage infiltration in the lungs.
• STAT4-deficient mice exhibited decreased levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and increased levels of the anti-inflammatory cytokine IL-10 in bronchoalveolar lavage fluid.

Conclusions:

• STAT4 plays a crucial role in mediating LPS-induced lung injury.
• The accumulation of myeloid-derived suppressor cells (MDSCs) and macrophages is critical in the pathogenesis of LPS-induced lung injury, modulated by STAT4 signaling.
• Targeting STAT4-dependent pathways for modulating MDSCs and macrophage polarization offers a potential therapeutic strategy to mitigate lung inflammation and damage.