A Proteomics-Based Assessment of Inflammation Signatures in Endotoxemia.

We have previously shown that multimers of plasma pentraxin-3 (PTX3) were predictive of survival in patients with sepsis. To characterize the release kinetics and cellular source of plasma protein changes in sepsis, serial samples were obtained from healthy volunteers (n = 10; three time points) injected with low-dose endotoxin (lipopolysaccharide [LPS]) and analyzed using data-independent acquisition MS. The human plasma proteome response was compared with an LPS-induced endotoxemia model in mice. Proteomic analysis of human plasma revealed a rapid neutrophil degranulation signature, followed by a rise in acute phase proteins. Changes in circulating PTX3 correlated with increases in neutrophil-derived proteins following LPS injection. Time course analysis of the plasma proteome in mice showed a time-dependent increase in multimeric PTX3, alongside increases in neutrophil-derived myeloperoxidase (MPO) upon LPS treatment. The mechanisms of oxidation-induced multimerization of PTX3 were explored in two genetic mouse models: MPO global knock-out (KO) mice and LysM Cre Nox2 KO mice, in which NADPH oxidase 2 (Nox2) is only deficient in myeloid cells. Nox2 is the enzyme responsible for the oxidative burst in neutrophils. Increases in plasma multimeric PTX3 were not significantly different between wildtype and MPO or LysM Cre Nox2 KO mice. Thus, PTX3 may already be stored and released in a multimeric form. Through in vivo neutrophil depletion and multiplexed vascular proteomics, PTX3 multimer deposition within the aorta was confirmed to be neutrophil dependent. Proteomic analysis of aortas from LPS-injected mice returned PTX3 as the most upregulated protein, where multimeric PTX3 was deposited as early as 2 h post-LPS along with other neutrophil-derived proteins. In conclusion, the rise in multimeric PTX3 upon LPS injection correlates with neutrophil-related protein changes in plasma and aortas. MPO and myeloid Nox2 are not required for the multimerization of PTX3; instead, neutrophil extravasation is responsible for the LPS-induced deposition of multimeric PTX3 in the aorta.

Constant light exposure aggravates POMC-mediated muscle wasting associated with hypothalamic alteration of circadian clock and SIRT1 in endotoxemia rats.

Constant light exposure is widespread in the intensive care unit (ICU) and could increase the rate of brain dysfunction as delirium and sleep disorders in critical patients. And the activation of hypothalamic neuropeptides is proved to play a crucial role in regulating hypercatabolism, especially skeletal muscle wasting in critical patients, which could lead to serious complications and poor prognosis. Here we investigated the hypothesis that constant light exposure could aggravate skeletal muscle wasting in endotoxemia rats and whether it was associated with alterations of circadian clock and hypothalamic proopiomelanocortin(POMC) expression. Fifty-four adult male Sprague-Dawley rats were intraperitoneally injected with lipopolysaccharide(LPS) or saline, subjected to constant light or a 12:12 h light-dark cycle for 7 days. On day 8, rats were sacrificed across six time points in 24 h and hypothalamus tissues and skeletal muscle were obtained. Rates of muscle wasting were measured by 3-methylhistidine(3-MH) and tyrosine release as well as expression of two muscle atrophic genes, muscle ring finger 1(MuRF-1) and muscle atrophy F-box(MAFbx). The expression of circadian clock genes, silent information regulator 1(SIRT1), POMC and hypothalamic inflammatory cytokines were also detected. Results showed that LPS administration significantly increased hypothalamic POMC expression, inflammatory cytokine levels and muscle wasting rates. Meanwhile constant light exposure disrupted the circadian rhythm, declined the expression of SIRT1 as well as aggravated hypothalamic POMC overexpression and skeletal muscle wasting in rats with endotoxemia. Taken together, the results demonstrated that constant light exposure could aggravate POMC-mediated skeletal muscle wasting in endotoxemia rats, which is associated with alteration of circadian clocks and SIRT1 in the hypothalamus.

Micro-autoradiographic assessment of cell types contributing to 2-deoxy-2-[(18)F]fluoro-D-glucose uptake during ventilator-induced and endotoxemic lung injury.

PURPOSE: The aim of the study was to use micro-autoradiography to investigate the lung cell types responsible for 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) uptake in murine models of acute lung injury (ALI). PROCEDURES: C57/BL6 mice were studied in three groups: controls, ventilator-induced lung injury (VILI), and endotoxin. VILI was produced by high tidal volumes and zero end-expiratory pressure and endotoxin ALI, by intranasal administration. Following FDG injection, the lungs were processed and exposed to autoradiographic emulsion. Grain density over cells was used to quantify FDG uptake. RESULTS: Neutrophils, macrophages, and type 2 epithelial cells presented higher grain densities during VILI and endotoxin ALI than controls. Remarkably, cell grain density in specific cell types was dependent on the injury mechanism. Whereas macrophages showed high grain densities during endotoxin ALI, similar to those exhibited by neutrophils, type 2 epithelial cells demonstrated the second highest grain density (with neutrophils as the highest) during VILI. CONCLUSIONS: In murine models of VILI and endotoxin ALI, FDG uptake occurs not only in neutrophils but also in macrophages and type 2 epithelial cells. FDG uptake by individual cell types depends on the mechanism underlying ALI.

Quantitative in vivo assessment of arginine utilization and nitric oxide production in endotoxemia.

BACKGROUND: Until recently no methods were available to quantitate nitric oxide (NO) production in vivo. The advent of stable isotope techniques has allowed quantitation of NO production in different animal models and human disease states. METHODS: In vivo NO production was assessed with the use of stable isotope labeled arginine. Enrichments of metabolites were measured by liquid chromatography-mass spectrometry (LC-MS). Knock-out mice were used to assess the influence of knocking out inducible NOS (iNOS) or constitutively expressed NOS (cNOS) on arginine-NO metabolism. Pig models were used to assess the role of individual organs on arginine-NO fluxes. RESULTS: In mice under basal conditions cNOS mediates half of the NO production. After endotoxin challenge NO production doubles as a result of iNOS induction and cNOS-mediated NO production is downregulated. In larger animal models (pig) whole body NO production is augmented after endotoxin challenge, largely resulting from NO production in liver, intestine and kidney. Arginine supplementation increases NO production in pigs in liver, intestine and kidney both in the basal state and after endotoxin challenge. CONCLUSIONS: Stable isotope techniques employing LC-MS allow in vivo assessment of NO production in small and large animal models and in patients. This allows definition of the role that iNOS and cNOS-mediated NO production play in several disease states.

Gastric and esophageal intramucosal PCO2 (PiCO2) during endotoxemia: assessment of raw PiCO2 and PCO2 gradients as indicators of hypoperfusion in a canine model of septic shock.

STUDY OBJECTIVES: To validate capnometric recirculating gas tonometry (CRGT) for continuously monitoring gut intramucosal PCO2 (PiCO2) in a septic shock model, and to compare gastric vs esophageal PCO2 vs intramucosal-arterial PCO2 gradients. INTERVENTIONS: CRTG catheters were placed in the stomach and esophagus of six anesthetized dogs. A saline solution filled balloon tonometry (ST) catheter was also placed in the stomach. After equilibration, 3 mg/kg Escherichia coli lipopolysaccharide (LPS) was administered IV. PiCO2 measurements were made at 0, 45, and 90 min post-LPS by ST and continuously by CRGT. RESULTS: Baseline PiCO2 was 41.5+/-1.9 (+/-SE) in the stomach by CRGT, 38.0+/-1.0 by ST, and 43.0+/-4.4 mm Hg in the esophagus (p=not significant). Gastric PiCO2 by CRGT increased to 47.0+/-2.4 mm Hg by 25 min post-LPS (p<0.05), whereas gastric (ST) and esophageal PiCO2 increased significantly by 45 min post-LPS. Good agreement was observed between gastric CRGT and ST measurements (mean bias, 1.3 mm Hg). The PiCO2-PaCO2 gradient increased post-LPS, but was significant only for gastric CRGT measurements 90 min post-LPS infusion. CONCLUSION: CRGT provided continuous gastric PiCO2 measurements that were in close agreement with ST but detected changes earlier than the conventional technique. Continuous esophageal PiCO2 represents a valid alternative for assessing gastric PiCO2.