Immunometabolic chaos in septic shock.

Area of Science:

• Immunology
• Metabolomics
• Critical Care Medicine

Background:

• Septic shock has high mortality, characterized by immune dysregulation transitioning from hyper-inflammation to hypo-inflammation.
• Hypo-inflammation increases susceptibility to secondary infections, but the role of plasma metabolites in this phase is unclear.
• Understanding metabolic alterations is crucial for managing septic shock's immune suppression.

Purpose of the Study:

• To investigate the impact of accumulated plasma metabolites on immune cell function during the hypo-inflammatory phase of septic shock.
• To determine if specific metabolites influence the inflammatory response of peripheral blood mononuclear cells (PBMCs).
• To identify metabolic signatures associated with endotoxin tolerance in septic shock.

Main Methods:

• Analyzed TNF protein response to lipopolysaccharide (LPS) stimulation in whole blood from septic shock patients and healthy controls.
• Performed plasma metabolomic profiling to identify accumulated metabolites in septic shock.
• Exposed healthy control PBMCs to various metabolites in vitro and assessed their LPS-induced inflammatory response.

Main Results:

• Septic shock patients exhibited endotoxin tolerance, unlike healthy controls with upregulated TNF protein.
• Significant accumulation of carbohydrate, amino acid, fatty acid, ceramide, sphingomyelin, and TCA cycle metabolites was observed in septic shock plasma.
• In vitro, some metabolites repressed while others upregulated PBMC inflammatory responses to LPS.

Conclusions:

• The endotoxin-tolerant phenotype in septic shock is linked to widespread plasma metabolite accumulation.
• These accumulated metabolites significantly modulate the immune response of circulating immune cells.
• Metabolic dysregulation plays a fundamental role in the immune suppression seen in septic shock, potentially driving secondary infections.