Inducible nitric oxide synthase contributes to immune dysfunction following trauma

Area of Science:

• Immunology
• Trauma Research
• Nitric Oxide Biology

Background:

• Trauma induces persistent adaptive immune depression, increasing morbidity and mortality.
• This immune paralysis involves impaired T-cell function and a shift towards a TH2 phenotype.
• Inducible nitric oxide synthase (iNOS) is upregulated after injury, but its role in adaptive immune dysfunction is unclear.

Purpose of the Study:

• To investigate the role of iNOS-derived nitric oxide (NO) in post-traumatic adaptive immune suppression.
• To determine if iNOS regulates T-lymphocyte function and cytokine production following severe injury.

Main Methods:

• Utilized a murine model of severe peripheral tissue injury.
• Examined iNOS expression in splenic macrophages and myeloid-derived suppressor cells.
• Employed iNOS knockout mice, an iNOS inhibitor, and a nitric oxide scavenger to assess NO's impact.

Main Results:

• iNOS was rapidly upregulated in splenic macrophages and myeloid-derived suppressor cells post-trauma.
• iNOS-derived NO was essential for the depression in T-lymphocyte proliferation.
• iNOS-derived NO significantly reduced interferon-gamma and interleukin-2 production in the spleen 48 hours after trauma.

Conclusions:

• iNOS plays a critical role in regulating immune suppression following trauma.
• Targeting sustained NO production by iNOS may be a therapeutic strategy to mitigate post-traumatic immune depression.