Polymorphonuclear myeloid-derived suppressor cells link inflammation and damage response after trauma

Area of Science:

• Immunology
• Trauma Pathophysiology
• Cell Biology

Background:

• Effective resolution of posttraumatic inflammation and restoration of homeostasis are critical for patient recovery.
• Myeloid-derived suppressor cells (MDSCs) modulate the immune response after trauma, but their origins and mechanisms remain unclear.
• Polymorphonuclear MDSCs (PMN-MDSCs) are implicated in posttraumatic inflammation, with limited understanding of their specific role and activation pathways.

Purpose of the Study:

• To investigate the role of PMN-MDSCs in the posttraumatic inflammatory response.
• To identify the mechanisms and inducers of PMN-MDSC activation following trauma.
• To explore the clinical significance of PMN-MDSCs in trauma patients, particularly those with infection.

Main Methods:

• Characterization of PMN-MDSCs using lectin-type oxidized LDL receptor 1 (LOX1) in human trauma patients.
• Analysis of intracellular reactive oxygen species (ROS) and signaling pathways (NF-κB, TGF-β1) in MDSCs.
• Assessment of immune cell balance (Treg/Th17, Th2/Th1) and cytokine profiles.
• Experimental manipulation of PMN-MDSCs in a mouse trauma model (transfer and antibody-mediated depletion).

Main Results:

• Trauma activates LOX1+ PMN-MDSCs, associated with increased ROS and NF-κB signaling.
• Activated PMN-MDSCs modulate immune balance towards an anti-inflammatory state by regulating Treg/Th17 and Th2/Th1 ratios.
• Higher numbers of LOX1+ PMN-MDSCs correlate with better clinical outcomes in infected trauma patients.
• TGF-β1 may induce LOX1+ PMN-MDSCs in the posttraumatic cytokine milieu.
• Transfer of trauma-derived PMN-MDSCs alleviated inflammation in mice, while Gr1 agonistic antibody exacerbated it.

Conclusions:

• PMN-MDSCs are activated by trauma and play a significant role in regulating the posttraumatic inflammatory response.
• LOX1+ PMN-MDSCs are a key cellular component in managing immune dysregulation after trauma.
• Targeting PMN-MDSCs may offer a novel therapeutic strategy for improving outcomes in trauma patients.