Introduction Septic shock is a systemic inflammatory response syndrome associated with organ failures. Earlier clinical diagnosis would be of benefit to a decrease in the mortality rate. However, there is currently a lack of predictive biomarkers. The secretome is the set of proteins secreted by a cell, tissue, or organism at a given time and under certain conditions. The plasma secretome is easily accessible from biological fluids and represents a good opportunity to discover new biomarkers that can be studied with nontargeted “omic” strategies. Aims To identify relevant deregulated proteins (DEP) in the secretome of a rat endotoxemic shock model. Methods Endotoxemic shock was induced in rats by intravenous injection of lipopolysaccharides (LPS, S. enterica typhi, 0.5 mg/kg) and compared to controls (Ringer Lactate, iv). Under isoflurane anesthesia, carotid cannulation allowed mean arterial blood pressure (MAP) and heart rate (HR) monitoring and blood sampling at different time points (T0 and T50 or T0 and T90, with EDTA and protease inhibitor). Samples were prepared for large-scale tandem mass spectrometry (MS-MS) based on a label-free quantification to allow identification of the proteins deregulated upon endotoxemic conditions. A Gene Ontology (GO) analysis defined several clusters of biological processes (BP) in which the DEP are involved. Results Ninety minutes after shock induction, the LPS group presents a reduction in MAP (-45%, p < 0.05) and increased lactate levels (+27.5%, p < 0.05) compared to the control group. Proteomic analyses revealed 10 and 33 DEP in the LPS group, respectively, at 50 and 90 minutes after LPS injection. At these time points, GO-BP showed alterations in pathways involved in oxidative stress response and coagulation. Conclusion This study proposes an approach to identify relevant DEP in septic shock and brings new insights into the understanding of the secretome adaptations upon sepsis.

The secretome is a set of proteins secreted by a cell at a given time and under certain conditions. The secretome, easily accessible from plasma and analyzable by a proteomic approach, represents a good opportunity to identify biomarkers in septic shock. This pathology corresponds to a systemic inflammatory response syndrome related to an infection and associated with cardiocirculatory failure leading to organ dysfunction with a mortality rate of 40%. The identification of diagnostic/prognostic biomarkers is crucial to improve patient outcome. Study the secretome of a rat model of endotoxemic shock to identify relevant deregulated proteins (DEP). Endotoxemic shock was induced by lipopolysaccharides injection (LPS, S. enterica typhi, 0.5 mg/kg, iv) and compared to controls (Ringer lactate, iv). Under isoflurane anesthesia, carotid cannulation allowed evaluation of mean arterial blood pressure (MAP), heart rate and blood sampling (T0, and T50 or T90 min on EDTA and protease inhibitor). Plasma was analyzed with tandem MS based on a label free quantification. Gene ontology (GO) analyses defined several groups of biological process (BP) in which the DEP were involved. Ninety minutes after shock induction, the LPS group present a reduction in MAP (−45%, P < 0.05) and increased lactate levels (+27%, P < 0.05). Proteomic analyses revealed 6 and 22 DEP, such as Ribonuclease 4, in the LPS group respectively at T50 and T90. At T50 and T90 Go-BP show common alterations in response to oxidative stress, tissue remodeling and coagulation. This study proposes an approach to identify DEP in septic shock. DEP need to be tested in cellular models in order to understand their role in the physiopathology of shock and to improve understanding of adaptations of the secretome during sepsis. The link between our results and patient prognosis will need to be studied for clinical use.

Septic shock is a systemic inflammatory response syndrome associated with circulation failure leading to organ failure with a mortality rate of 40%. Early diagnosis and prognosis of septic shock are necessary for timely and specific treatment but no predictive biomarkers are available. The plasma proteome is easily accessible and may contain biomarkers that can be studied with non-targeted “omic” strategies. We aim to decipher a relevant proteome signature through a non-targeted mass spectrometry (MS) analysis in a rat septic shock model. In 10-week-old Wistar rats ( n = 11/group), 30 min post-buprenorphine (0.05 mg/kg, s) endotoxemic shock was induced by lipopolysaccharides injection (LPS, S. enterica typhi, 0.5 mg/kg, iv) and compared to controls (NaCl 0.9%, iv). Under isoflurane anesthesia, carotid cannulation allowed mean arterial blood pressure (MAP), heart rate (HR) monitoring and blood sampling (T0, 50 and 150 min-EDTA with protease inhibitor). Each plasma was prepared for RPHPLC/MS by performing Proteominer, dialysis and trypsin digestion. RPHPLC-MS analysis was performed on a ESI-Q-Exactive mass spectrometer (ThermoFisher) according to a non-targeted label-free MS analysis. Data were analyzed with PEAKS and R software. LPS group present circulation failure (−40% MAP, +20% of HR vs Ctrl, P < 0.05) and an increase in lactate levels (LPS: 6.00 ± 0.86 mM, Ctrl: 1.70 ± 0.26 mM, P < 0.05). Proteomic analyses revealed 106 deregulated (21 down and 80 up-regulated) proteins with LPS. The interactome map highlighted pathways involved, as vascular homeostasis or stress responses. Some of these proteins have already been described in human septic proteome signature, demonstrating the relevance of this approach. This preliminary study revealed propose a new approach to identify relevant deregulated proteins in septic shock. The investigation of the link between our results and patients’ clinical features is in progress.