Plasma Proteome Profiling: Widespread Oxidative Changes in Endotoxemia Correlate with Intravascular Tissue Factor Response.

The initial response to systemic infection in sepsis syndromes is mediated by the innate immune system and results in widespread activation of inflammation and coagulation. Some of these changes are recapitulated in the human Endotoxemia model. Proteomics represents a novel approach to study the pathophysiology of disease processes, and offers the potential for identification of biomarkers that may be used for diagnostic and/or prognostic purposes. Therefore, plasma proteome profiling was performed to study the response to intravenously administered low-dose lipopolysaccharide (LPS; 2ng/kg) in 28 healthy adult male volunteers. Interleukin 6 (IL 6), which mediates the host inflammatory responses in endotoxemia and sepsis, and circulating tissue factor (TF), which initiates coagulation, were also measured as markers of these respective processes. Plasma was obtained at baseline and at 1, 2, 3, 4, 8, and 24 hours following LPS administration. Protein profiling was performed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. All individuals showed qualitative profile changes that peaked at 8 hours after LPS and reverted towards baseline at 24 hours. The spectra obtained consisted of 15 non-redundant peaks that were seen consistently in all samples, and ratios of these peaks were used in data analysis. These peaks consisted of Apolipoproteins CI, CII and CIII, and Transthyretin (TTr) and their various isoforms. Serum Amyloid A appeared at later time points following endotoxin. Six of the 28 subjects demonstrated severe oxidation of plasma proteins detected by the loss of free sulfhydryls of TTr and addition of oxygen to many proteins. Increased proteolysis of plasma proteins was also noted in these subjects, along with the appearance of new protein peaks. These 6 individuals were designated ‘high responders’. Microparticle (MP)-associated TF procoagulant activity (PCA) was measured using a recently described assay [Blood 2004 103: 4545]. The TF PCA peaked between 3-4 hours following endotoxin challenge with a 10 fold increase, on average, compared to baseline (p 175 fold compared to baseline (p