Biomarkers of Endothelial Activation Are Associated with Poor Outcome in Critical Illness

Background

Endothelial activation plays a role in organ dysfunction in the systemic inflammatory response syndrome (SIRS). Angiopoietin-1 (Ang-1) promotes vascular quiescence while angiopoietin-2 (Ang-2) mediates microvascular leak. Circulating levels of Ang-1 and Ang-2 in patients with SIRS could provide insight on risks for organ dysfunction and death distinct from inflammatory proteins. In this study, we determined if biomarkers of endothelial activation and inflammation exhibit independent associations with poor outcomes in SIRS.

Methods

We studied 943 critically ill patients with SIRS admitted to an Intensive Care Unit (ICU) of an academic medical center. We measured plasma levels of endothelial markers (Ang-1, Ang-2, soluble vascular cell adhesion molecule-1 (sVCAM-1)) and inflammatory markers (interleukin-6 (IL-6), interleukin-8 (IL-8), granulocyte-colony stimulating factor (G-CSF), soluble tumor necrosis factor receptor-1 (sTNFR-1)) within 24 hours of enrollment. We tested for associations between each marker and 28 day mortality, shock, and day 3 sequential organ failure assessment (SOFA) score. For 28 day mortality, we performed sensitivity analysis for those subjects with sepsis and those with sterile inflammation. We used multivariate models to adjust for clinical covariates and determine if associations identified with endothelial activation markers were independent of those observed with inflammatory markers.

Results

Higher levels of all biomarkers were associated with increased 28 day mortality except levels of Ang-1 which were associated with lower mortality. After adjustment for comorbidities and sTNFR-1 concentration, a doubling of Ang-1 concentration was associated with lower 28 day mortality (Odds ratio (OR) = 0.81; p<0.01), shock (OR = 0.82; p<0.001), and SOFA score (β = -0.50; p<0.001), while Ang-2 concentration was associated with increased mortality (OR = 1.55; p<0.001), shock (OR = 1.51; p<0.001), and SOFA score (β = +0.63; p<0.001). sVCAM-1 was not independently associated with SIRS outcomes.

Conclusions

In critically ill patients with SIRS, early measurements of Ang-1 and Ang-2 are associated with death and organ dysfunction independently of simultaneously-measured markers of inflammation.     

Protective Role of Plant Sterol and Stanol Esters in Liver Inflammation: Insights from Mice and Humans

The inflammatory component of non–alcoholic steatohepatitis (NASH) can lead to irreversible liver damage. Therefore there is an urgent need to identify novel interventions to combat hepatic inflammation. In mice, omitting cholesterol from the diet reduced hepatic inflammation. Considering the effects of plant sterol/stanol esters on cholesterol metabolism, we hypothesized that plant sterol/stanol esters reduces hepatic inflammation. Indeed, adding plant sterol/stanol esters to a high-fat-diet reduced hepatic inflammation as indicated by immunohistochemical stainings and gene expression for inflammatory markers. Finally, adding sterol/stanol esters lowered hepatic concentrations of cholesterol precursors lathosterol and desmosterol in mice, which were highly elevated in the HFD group similarly as observed in severely obese patients with NASH. In vitro, in isolated LPS stimulated bone marrow derived macrophages desmosterol activated cholesterol efflux whereas sitostanol reduced inflammation. This highly interesting observation that plant sterol/stanol ester consumption leads to complete inhibition of HFD-induced liver inflammation opens new venues in the treatment and prevention of hepatic inflammation.     

Generic inhibition of amyloidogenic proteins by two naphthoquinone-tryptophan hybrid molecules

Amyloid formation is associated with several human diseases including Alzheimer's disease (AD), Parkinson's disease, Type 2 Diabetes, and so forth, no disease modifying therapeutics are available for them. Because of the structural similarities between the amyloid species characterizing these diseases, (despite the lack of amino acid homology) it is believed that there might be a common mechanism of toxicity for these conditions. Thus, inhibition of amyloid formation could be a promising disease-modifying therapeutic strategy for them. Aromatic residues have been identified as crucial in formation and stabilization of amyloid structures. This finding was corroborated by high-resolution structural studies, theoretical analysis, and molecular dynamics simulations. Amongst the aromatic entities, tryptophan was found to possess the most amyloidogenic potential. We therefore postulate that targeting aromatic recognition interfaces by tryptophan could be a useful approach for inhibiting the formation of amyloids. Quinones are known as inhibitors of cellular metabolic pathways, to have anti- cancer, anti-viral and anti-bacterial properties and were shown to inhibit aggregation of several amyloidogenic proteins in vitro. We have previously described two quinone-tryptophan hybrids which are capable of inhibiting amyloid-beta, the protein associated with AD pathology, both in vitro and in vivo. Here we tested their generic properties and their ability to inhibit other amyloidogenic proteins including α-synuclein, islet amyloid polypeptide, lysozyme, calcitonin, and insulin. Both compounds showed efficient inhibition of all five proteins examined both by ThT fluorescence analysis and by electron microscope imaging. If verified in vivo, these small molecules could serve as leads for developing generic anti-amyloid drugs.     

Inhibition of herpes simplex virus type 1 infection by silver nanoparticles capped with mercaptoethane sulfonate

Interactions between biomolecules and nanoparticles suggest the use of nanoparticles for various medical interventions. The attachment and entry of herpes simplex virus type 1 (HSV-1) into cells involve interaction between viral envelope glycoproteins and cell surface heparan sulfate (HS). Based on this mechanism, we designed silver nanoparticles that are capped with mercaptoethane sulfonate (Ag-MES). These nanoparticles are predicted to target the virus and to compete for its binding to cellular HS through their sulfonate end groups, leading to the blockage of viral entry into the cell and to the prevention of subsequent infection. Structurally defined Ag-MES nanoparticles that are readily redispersible in water were sonochemically synthesized. No toxic effects of these nanoparticles on host cells were observed. Effective inhibition of HSV-1 infection in cell culture by the capped nanoparticles was demonstrated. However, application of the soluble surfactant MES failed to inhibit viral infection, implying that the antiviral effect of Ag-MES nanoparticles is imparted by their multivalent nature and spatially directed MES on the surface. Our results suggest that capped nanoparticles may serve as useful topical agents for the prevention of infections with pathogens dependent on HS for entry.     

Beclin 1 self‐association is independent of autophagy induction by amino acid deprivation and rapamycin treatment

Autophagy, a process of self‐digestion of cellular constituents, regulates the balance between protein synthesis and protein degradation. Beclin 1 represents an important component of the autophagic machinery. It interacts with proteins that positively regulate autophagy, such as Vps34, UVRAG, and Ambra1, as well as with anti‐apoptotic proteins such as Bcl‐2 via its BH3‐like domain to negatively regulate autophagy. Thus, Beclin 1 interactions with several proteins may regulate autophagy. To identify novel Beclin 1 interacting proteins, we utilized a GST‐Beclin 1 fusion protein. Using mass spectroscopic analysis, we identified Beclin 1 as a protein that interacts with GST‐Beclin 1. Further examination by cross linking and co‐immunoprecipitation experiments confirmed that Beclin 1 self‐interacts and that the coiled coil and the N‐terminal region of Beclin 1 contribute to its oligomerization. Importantly, overexpression of vps34, UVRAG, or Bcl‐x_L, had no effect on Beclin 1 self‐interaction. Moreover, this self‐interaction was independent of autophagy induction by amino acid deprivation or rapamycin treatment. These results suggest that full‐length Beclin 1 is a stable oligomer under various conditions. Such an oligomer may provide a platform for further protein–protein interactions. J. Cell. Biochem. 110: 1262–1271, 2010. Published 2010 Wiley‐Liss, Inc.     

Tibetan 'wind' and 'wind' illnesses: towards a multicultural approach to health and illness

This article discusses the Tibetan notion of rlung, usually translated as: 'wind', but perhaps better understood as a close equivalent of pneuma in the Greek tradition, or qi in the Chinese tradition. The article focuses on the way rlung provides a useful prism through which concepts of health, illness and disease may be observed in a cross-cultural perspective. An analysis of syndromes linked with rlung in a Tibetan cultural context illuminates some of the ways in which culture determines particular syndromes. The article raises a number of questions which are relevant for a more general multicultural approach to concepts of health, illness and disease. The article argues that notions of rlung/pneuma/wind/ qi constitute a particularly interesting area for an exploration of culture-bound syndromes, as they reside in the meeting point between material and non-material, physical and mental, as well as the psychological, spiritual and religious. They are hence fundamental for a more cross-cultural approach to the mind-body problem. The article also deals with the significance of history of medicine, particularly histories of medicine, which attempt to widen the scope of the traditional Eurocentric narrative of the history of medicine, in dealing with questions such as concepts of health and illness. Allowing alternative narratives-whether narratives of patients, other cultures or historical ones-can enhance our understanding of what health, illness and disease are. Discussing perceptions of the body as culturally defined is not only important from a philosophical or historical point of view, but also has important practical ramifications, which are particularly crucial in our global age.     

Determinants of heterogeneity, excitation and conduction in the sinoatrial node: a model study

The sinoatrial node (SAN) is a complex structure that exhibits anatomical and functional heterogeneity which may depend on: 1) The existence of distinct cell populations, 2) electrotonic influences of the surrounding atrium, 3) the presence of a high density of fibroblasts, and 4) atrial cells intermingled within the SAN. Our goal was to utilize a computer model to predict critical determinants and modulators of excitation and conduction in the SAN. We built a theoretical "non-uniform" model composed of distinct central and peripheral SAN cells and a "uniform" model containing only central cells connected to the atrium. We tested the effects of coupling strength between SAN cells in the models, as well as the effects of fibroblasts and interspersed atrial cells. Although we could simulate single cell experimental data supporting the "multiple cell type" hypothesis, 2D "non-uniform" models did not simulate expected tissue behavior, such as central pacemaking. When we considered the atrial effects alone in a simple homogeneous "uniform" model, central pacemaking initiation and impulse propagation in simulations were consistent with experiments. Introduction of fibroblasts in our simulated tissue resulted in various effects depending on the density, distribution, and fibroblast-myocyte coupling strength. Incorporation of atrial cells in our simulated SAN tissue had little effect on SAN electrophysiology. Our tissue model simulations suggest atrial electrotonic effects as plausible to account for SAN heterogeneity, sequence, and rate of propagation. Fibroblasts can act as obstacles, current sinks or shunts to conduction in the SAN depending on their orientation, density, and coupling.