Project description:Sepsis is the major cause of mortality across intensive care units globally, yet details of accompanying pathological molecular events are unclear. This has resulted in ineffective development of sepsis-specific biomarkers and therapies, and suboptimal treatment regimens in preventing and reversing organ damage. Here, we used pharmacoproteomics to score treatment effects in a preclinical Escherichia coli sepsis model based on changes in the organ, cell, and plasma proteome landscapes. A combination of pathophysiological read-outs and time-resolved proteome maps of organs and blood enabled the definition of time-dependent and organotypic proteotypes of dysfunction and damage that was used to guide the administration of several combinations of beta-lactam antibiotic meropenem and immunomodulatory glucocorticoid methylprednisolone. The proteome-based scoring strategy revealed three distinct response patterns defined as intervention-specific reversions, non-reversions, and specific intervention-induced effects, revealing that the intervention effects depended on the underlying proteotype and varied significantly between organs. In the later stages of the disease, administration of glucocorticoids accentuated some of the positive effects exerted by Mem leading to superior reduction of the inflammatory response in the kidneys and partial restoration of the metabolic dysfunction instigated by sepsis. Unexpectedly, antibiotics introduced sepsis-independent perturbations in the mitochondrial proteome that was to some degree counteracted by glucocorticoids. In summary, this study provides a pharmacoproteomic resource describing the time-resolved septic organ failure landscape across organs and the blood compartment, and a novel scoring strategy that captures unintended secondary drug effects as an important criterion to consider while assessing therapeutic efficacy. Such information is critically important to enable a quantitative, objective and organotypic assessment of treatment benefits and unintended effects, drug synergies of candidate treatments as well as the effect of dose and time in murine sepsis models.

Project description:Background: Sepsis involves aberrant immune responses to infection, but the exact nature of this immune dysfunction remains poorly defined. Bacterial endotoxins like lipopolysaccharide (LPS) are potent inducers of inflammation, which has been associated with the pathophysiology of sepsis, but repeated exposure can also induce a suppressive effect known as endotoxin tolerance or cellular reprogramming. It has been proposed that endotoxin tolerance might be associated with the immunosuppressive state that was primarily observed during late-stage sepsis. However, this relationship remains poorly characterised. Here we clarify the underlying mechanisms and timing of immune dysfunction in sepsis. Methods: We defined a gene expression signature characteristic of endotoxin tolerance. Gene-set test approaches were used to correlate this signature with early sepsis, both newly and retrospectively analysing microarrays from 593 patients in 11 cohorts. Then we recruited a unique cohort of possible sepsis patients at first clinical presentation in an independent blinded controlled observational study to determine whether this signature was associated with the development of confirmed sepsis and organ dysfunction. Findings: All sepsis patients presented an expression profile strongly associated with the endotoxin tolerance signature (p < 0.01; AUC 96.1%). Importantly, this signature further differentiated between suspected sepsis patients who did, or did not, go on to develop confirmed sepsis, and predicted the development of organ dysfunction. Interpretation: Our data support an updated model of sepsis pathogenesis in which endotoxin tolerance-mediated immune dysfunction (cellular reprogramming) is present throughout the clinical course of disease and related to disease severity. Thus endotoxin tolerance might offer new insights guiding the development of new therapies and diagnostics for early sepsis. For the RNA-Seq study reported here, 73 patients were recruited with deferred consent at the time of first examination in an emergency ward based on the opinion of physicians that there was a potential for the patient's condition to develop into sepsis. These were retrospectively divided into groups based on clinical features and compared to 11 non-urgent surgical controls.

Project description:An early aspect of sepsis is dysregulated activation of endothelial cells (EC), initiating a cascade of inflammatory signaling leading to leukocyte adhesion/migration and organ damage. Therapeutic targeting of ECs has been hampered by concerns regarding ECs heterogeneity from different organs. Using a combination of in vitro and in silico analysis, we present a comprehensive analysis of proteomic changes in mouse lung, kidney and liver ECs following exposure to a clinically relevant cocktail of proinflammatory cytokines. Mouse lung, liver and kidney ECs were incubated with TNFα/IL-1β/IFNγ for 4 or 24 hrs to model inflammatory responses during sepsis. Quantitative label-free global proteomics was performed on the ECs to identify differentially expressed proteins (DEP). Proteins with an abundance ratio >2.0 or <0.5 and an adjusted p<0.05 were characterized as upregulated or downregulated respectively. Gene Ontology (GO) classification was used to determine biological processes that regulate EC function during sepsis and PANTHER was used to classify the molecular function of the identified proteins. Finally, an interactive pathway was developed to investigate signaling within ECs and across organs. Proteomic analysis identified both unique and shared DEPs between the ECs specific to lung, liver and kidney. Using GO, 5 Biological Processes (BP) for each of the organ specific ECs were identified. Interestingly, 4 of the top 5 GO BPs were observed in all 3 ECs at 4 and 24 hrs: defense response to other organism, innate immune response, response to bacterium and response to cytokine. However, these BPs were found to be differentially regulated. For example, at 4 and 24 hrs, lung ECs which have the highest number and highest fold expression of upregulated proteins (189 and 316 respectively), also have higher numbers of unique upregulated proteins (124 vs 194) compared to liver (98 vs 121) and kidney ECs (109 vs 136). The liver showed the greatest number of conserved proteins between 4 and 24 hrs (56) compared to lung (50) and kidney (51). The number of common proteins between all three ECs increases from 38 at 4 hrs to 79 at 24 hrs, indicating more uniformity in ECs proteomic expression during the progression of sepsis. The PANTHER database was used to classify proteins in different functional groups (e.g. defense/immunity) at 4 and 24 hrs. Thus, BPs and PANTHER hits can provide insight into why some organs are more susceptible to sepsis early on and show that as sepsis progresses, some protein expression patterns become more uniform while additional organ specific proteins are expressed. Proteomic analysis of organ-specific ECs provides further understanding of how sepsis affects multiple organs across time and supports future proteomic, temporal studies of EC dysfunction.

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Vascular proteome responses precede organ dysfunction in a murine model of Staphylococcus aureus bacteremia

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