The Secretome Deregulations in a Rat Model of Endotoxemic Shock

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.

Abstract 14066: O -GlcNAc Levels Stimulation is a New Potential Therapeutic Strategy at the Early Phase of Septic Shock in the Young

Background: We have shown that increase in O -GlcNAc levels, a post-translational modification involved in the stress response, at the early phase of septic shock in adult (84 days old rats) is a potential new therapeutic strategy. Most studies focus in adults while the population most affected by septic shock, young children, is rarely studied. Considering that O- GlcNAc levels are higher in the young, the impact of O- GlcNAc on septic shock in the young should be tested. Purpose: Evaluate if O- GlcNAc stimulation could improve sepsis outcomes in young. Methods: Endotoxemic shock was induced in 28 days old rats with an i.v. injection of saline (CTRL, n=10) or LPS (O111:B4, 20mg.kg -1 - LPS, n=9). 1 hour after LPS rats were randomly assigned to no therapy (LPS), fluidotherapy (saline, 10ml.kg -1 - LPS+R, n=10) ± NButGT (10 mg.kg -1 - NButGT, n=11) to increase O- GlcNAc levels. 2 hours later, physiological functions and markers of severity were measured and used in adapted Pediatric RISk of Mortality score (PRISM score). The impact of treatment on survival was evaluated on n=16 per group. Mass spectrometry (MS) study was performed to identify O -GlcNAcylated proteins. Results: LPS induce a shock (mean arterial pressure (MAP): CTRL: 67.2 ± 1.9; LPS: 50.7 ± 2.1; mmHg; p<0.05), alter biological parameters (lactates: CTRL: 3.92 ± 0.26; LPS: 6.42 ± 0.45; mmol.l -1 ; pH: CTRL: 7.27 ± 0.02; LPS: 7.15 ± 0.02; p<0.05), PRISM score (p<0.05) and is associated with multi organs dysfunction (troponin T: CTRL: 19.7 ± 4.0; LPS: 45.4 ± 11.4; ng.l -1 ; creatinine: CTRL: 15.9 ± 1.5; LPS: 25.3 ± 2.6; μmol.l -1 ; p<0.05). LPS+R has no beneficial effect while NButGT improves MAP (p<0.05), PRISM score (p<0.05) and the median survival (NButGT: 36.0; LPS+R: 13.65; hours; p<0.001) compared to LPS+R treatment. MS highlight important variations of O- GlcNAcylation particularly that of mitochondrial proteins. Conclusions: Despite higher O- GlcNAc levels, we demonstrate that O- GlcNAc stimulation is also a potential new therapeutic strategy for septic shock in young. Our results show that it is the difference between the basal levels and the post-stimulation levels which induces a protection against sepsis. Proteins identify by MS will need to be specifically studied to decipher their impact in septic shock.

O-GlcNAc stimulation: A new metabolic approach to treat septic shock

Septic shock is a systemic inflammation associated with cell metabolism disorders and cardiovascular dysfunction. Increases in O-GlcNAcylation have shown beneficial cardiovascular effects in acute pathologies. We used two different rat models to evaluate the beneficial effects of O-GlcNAc stimulation at the early phase of septic shock. Rats received lipopolysaccharide (LPS) to induce endotoxemic shock or saline (control) and fluid resuscitation (R) with or without O-GlcNAc stimulation (NButGT–10 mg/kg) 1 hour after shock induction. For the second model, rats received cecal ligature and puncture (CLP) surgery and fluid therapy with or without NButGT. Cardiovascular function was evaluated and heart and blood samples were collected and analysed. NButGT treatment efficiently increased total O-GlcNAc without modification of HBP enzyme expression.Treatment improved circulating parameters and cardiovascular function in both models, and restored SERCA2a expression levels. NButGT treatment also reduced animal mortality. In this study, we demonstrate that in septic shock O-GlcNAc stimulation improves global animal and cardiovascular function outcomes associated with a restoration of SERCA2a levels. This pre-clinical study opens avenues for a potential therapy of early-stage septic shock.