High altitude increases circulating interleukin-6, interleukin-1 receptor antagonist and C-reactive protein

Hypoxic pulmonary vasoconstriction is associated with but may not be sufficient for the development of high-altitude pulmonary oedema (HAPO). Hypoxia is known to induce an inflammatory response in immune cells and endothelial cells. It has been speculated that hypoxia-induced inflammatory cytokines at high altitude may contribute to the development of HAPO by causing capillary leakage in the lung. We were interested if such an inflammatory response, possibly involved in a later development of HAPO, is detectable at high altitude in individuals without HAPO. We examined the plasma levels of interleukin 6 (IL-6), interleukin 1 receptor antagonist (IL-1ra) and C-reactive protein (CRP) in two independent studies: study A, Jungfraujoch, Switzerland, three overnight stays at 3458 m, n=12; study B: Capanna Regina Margherita, Italy, 3 overnight stays at 3647 m and one overnight stay at 4559 m, n=10. In both studies, probands showed symptoms of acute mountain sickness but no signs of HAPO. At the Jungfraujoch, IL-6 increased from 0.1+/-0.03 pg/ml to 2. 0+/-0.5 pg/ml (day 2, P=0.03), IL-1ra from 101+/-21 to 284+/-73 pg/ml (day 2, P=0.01), and CRP from 1.0+/-0.4 to 5.8+/-1.5 micrograms/ml (day 4, P=0.01). At the Capanna Margherita, IL-6 increased from 0. 5+/-0.2 pg/ml to 2.0+/-0.8 pg/ml (P=0.02), IL-1ra from 118+/-25 to 213+/-28 pg/ml (P=0.02), and CRP from 0.4+/-0.03 to 3.5+/-1.1 micrograms/ml (P=0.03). IL-8 was below the detection limit of the ELISA (<25 pg/ml) in both studies. The increase of IL-6 and IL-1ra in response to high altitude was delayed and preceded the increase of CRP. We conclude that: (1) circulating IL-6, IL-1ra and CRP are upregulated in response to hypobaric hypoxic conditions at high altitude, and (2) the moderate systemic increase of these inflammatory markers may reflect considerable local inflammation. The existence and the kinetics of high altitude-induced cytokines found in this study support the hypothesis that inflammation is involved in the development of HAPO.     

An 18 kDa Scaffold Protein Is Critical for Staphylococcus epidermidis Biofilm Formation

Virulence of the nosocomial pathogen Staphylococcus epidermidis is crucially linked to formation of adherent biofilms on artificial surfaces. Biofilm assembly is significantly fostered by production of a bacteria derived extracellular matrix. However, the matrix composition, spatial organization, and relevance of specific molecular interactions for integration of bacterial cells into the multilayered biofilm community are not fully understood. Here we report on the function of novel 18 kDa Small basic protein (Sbp) that was isolated from S. epidermidis biofilm matrix preparations by an affinity chromatographic approach. Sbp accumulates within the biofilm matrix, being preferentially deposited at the biofilm–substratum interface. Analysis of Sbp-negative S. epidermidis mutants demonstrated the importance of Sbp for sustained colonization of abiotic surfaces, but also epithelial cells. In addition, Sbp promotes assembly of S. epidermidis cell aggregates and establishment of multilayered biofilms by influencing polysaccharide intercellular-adhesin (PIA) and accumulation associated protein (Aap) mediated intercellular aggregation. While inactivation of Sbp indirectly resulted in reduced PIA-synthesis and biofilm formation, Sbp serves as an essential ligand during Aap domain-B mediated biofilm accumulation. Our data support the conclusion that Sbp serves as an S. epidermidis biofilm scaffold protein that significantly contributes to key steps of surface colonization. Sbp-negative S. epidermidis mutants showed no attenuated virulence in a mouse catheter infection model. Nevertheless, the high prevalence of sbp in commensal and invasive S. epidermidis populations suggests that Sbp plays a significant role as a co-factor during both multi-factorial commensal colonization and infection of artificial surfaces.     

Sequestration, metabolism and partial synthesis of tertiary pyrrolizidine alkaloids by the neotropical leaf-beetle Platyphora boucardi

Platyphora boucardi leaf-beetles sequester tertiary pyrrolizidine alkaloids of the lycopsamine type acquired from their host-plant Prestonia portobellensis (Apocynaceae) and synthesize their own alkaloids from exogenous retronecine and aliphatic 2-hydroxy acids. Tracer studies with [14C]rinderine and its N-oxide revealed that P. boucardi sequesters both alkaloidal forms with the same efficiency, but accumulates exclusively tertiary alkaloids. There is no substantial alkaloid accumulation in the body outside the defensive glands. Feeding studies with [2H][14C]rinderine confirmed that P. boucardi specifically epimerizes rinderine to its stereoisomers intermedine and lycopsamine. Feeding studies with [2H][14C]retronecine proved the ability of P. boucardi to synthesize O7- and O9-(2-hydroxyisovaleryl)-retronecine and O7-lactyl-O9-(2-hydroxyisovaleryl)-retronecine. Both, alkaloids of the lycopsamine type and self-synthesized retronecine esters accumulate in the defensive secretions at concentrations up to 38 mM and 33 mM, respectively. The different biochemical strategies to maintain pro-toxic pyrrolizidine alkaloids and to prevent self-poisoning, developed by specialized insects, are compared. There are two major findings: (1) the chemical defense mediated by plant acquired pyrrolizidine alkaloids in the taxonomically related palaearctic Oreina and neotropical Platyphora leaf beetles have been evolved independently, since the biochemical mechanisms of storing and maintaining the alkaloids is completely different in the two genera; (2) unexpected parallels exist between taxonomically unrelated Coleoptera and Lepidoptera in their ability to synthesize the same retronecine esters and to catalyze the same site-specific epimerizations of the lycopsamine stereoisomers.     

Ethanolic Echinacea purpurea Extracts Contain a Mixture of Cytokine-Suppressive and Cytokine-Inducing Compounds,Including Some That Originate from Endophytic Bacteria

Echinacea preparations, which are used for the prevention and treatment of upper respiratory infections, account for 10% of the dietary supplement market in the U.S., with sales totaling more than $100 million annually. In an attempt to shed light on Echinacea''s mechanism of action, we evaluated the effects of a 75% ethanolic root extract of Echinacea purpurea, prepared in accord with industry methods, on cytokine and chemokine production from RAW 264.7 macrophage-like cells. We found that the extract displayed dual activities; the extract could itself stimulate production of the cytokine TNF-α, and also suppress production of TNF-α in response to stimulation with exogenous LPS. Liquid:liquid partitioning followed by normal-phase flash chromatography resulted in separation of the stimulatory and inhibitory activities into different fractions, confirming the complex nature of this extract. We also studied the role of alkylamides in the suppressive activity of this E. purpurea extract. Our fractionation method concentrated the alkylamides into a single fraction, which suppressed production of TNF-α, CCL3, and CCL5; however fractions that did not contain detectable alkylamides also displayed similar suppressive effects. Alkylamides, therefore, likely contribute to the suppressive activity of the extract but are not solely responsible for that activity. From the fractions without detectable alkylamides, we purified xanthienopyran, a compound not previously known to be a constituent of the Echinacea genus. Xanthienopyran suppressed production of TNF-α suggesting that it may contribute to the suppressive activity of the crude ethanolic extract. Finally, we show that ethanolic extracts prepared from E. purpurea plants grown under sterile conditions and from sterilized seeds, do not contain LPS and do not stimulate macrophage production of TNF-α, supporting the hypothesis that the macrophage-stimulating activity in E. purpurea extracts can originate from endophytic bacteria. Together, our findings indicate that ethanolic E. purpurea extracts contain multiple constituents that differentially regulate cytokine production by macrophages.     

Thiocyanate catalyzes myeloperoxidase-initiated lipid oxidation in LDL

There is evidence that LDL oxidation may render the lipoprotein atherogenic. The myeloperoxidase-hydrogen peroxide (MPO/H2O2) system of activated phagocytes may be involved in this process. Chloride is supposed to be the major substrate for MPO, generating reactive hypochlorous acid (HOCl), modifying LDL. The pseudo-halide thiocyanate (SCN-) has been shown to be a suitable substrate for MPO, forming reactive HOSCN/SCN*. As relatively abundant levels of SCN- are found in plasma of smokers--a well-known risk group for cardiovascular disease--the ability of SCN- to act as a catalyst of LDL atherogenic modification by MPO/H2O2 was tested. Measurement of conjugated diene and lipid hydroperoxide formation in LDL preparations exposed to MPO/H2O2 revealed that SCN- catalyzed lipid oxidation in LDL. Chloride did not diminish the effect of SCN- on lipid oxidation. Surprisingly, SCN inhibited the HOCl-mediated apoprotein modification in LDL. Nitrite--recently found to be a substrate for MPO--showed some competing properties. MPO-mediated lipid oxidation was inhibited by heme poisons (azide, cyanide) and catalase. Ascorbic acid was the most effective compound in inhibiting the SCN- -catalyzed reaction. Bilirubin showed some action, whereas tocopherol was ineffective. When LDL oxidation was performed with activated human neutrophils, which employ the MPO pathway, SCN- catalyzed the cell-mediated LDL oxidation. The MPO/H2O2/SCN- system may have the potential to play a significant role in the oxidative modification of LDL--an observation further pointing to the link between the long-recognized risk factors of atherosclerosis: elevated levels of LDL and smoking.     

Metabololipidomic and proteomic profiling reveals aberrant macrophage activation and interrelated immunomodulatory mediator release during aging

Macrophages adapt distinct pro-inflammatory (M1-like) and pro-resolving (M2-like) phenotypes with specific tasks in the immune response and tissue homeostasis. Altered macrophage responses with age are causative for unresolved inflammation, so-called inflammaging, and lead to higher infection susceptibility with unfavorable progression. Here, we reveal molecular determinants of age-related changes in phenotypic functions of murine peritoneal macrophages (PM) by employing comprehensive mass spectrometry-based proteomics (4746 protein groups) and metabololipidomics (>40 lipid mediators). Divergent expression of various macrophage-specific marker proteins and signaling pathways indicates aberrant PM phenotypes in old mice which detrimentally impact their capabilities to release immunomodulatory chemokines and cytokines. We show that aging strikingly compromises the polarization process of macrophages to adapt either pro-inflammatory or pro-resolving phenotypes, thereby yielding aberrant and afunctional macrophage subtypes that cannot be readily assigned to either a typical M1 or M2 phenotype. In particular, the phenotypic adaptation of the bacteria-challenged metabololipidome in macrophages related to inflammation is severely limited by age, which persists across ex vivo polarization towards M1 and M2a macrophages. Our results establish distinct age-associated PM phenotypes outside of the simplified M1 and M2 dichotomy and challenge the dogma of increased pro-inflammatory macrophage pre-activation due to aging by revealing maladaptive functions throughout all phases of inflammation, including resolution.     

The Database of European Forest Insect and Disease Disturbances: DEFID2

Insect and disease outbreaks in forests are biotic disturbances that can profoundly alter ecosystem dynamics. In many parts of the world, these disturbance regimes are intensifying as the climate changes and shifts the distribution of species and biomes. As a result, key forest ecosystem services, such as carbon sequestration, regulation of water flows, wood production, protection of soils, and the conservation of biodiversity, could be increasingly compromised. Despite the relevance of these detrimental effects, there are currently no spatially detailed databases that record insect and disease disturbances on forests at the pan-European scale. Here, we present the new Database of European Forest Insect and Disease Disturbances (DEFID2). It comprises over 650,000 harmonized georeferenced records, mapped as polygons or points, of insects and disease disturbances that occurred between 1963 and 2021 in European forests. The records currently span eight different countries and were acquired through diverse methods (e.g., ground surveys, remote sensing techniques). The records in DEFID2 are described by a set of qualitative attributes, including severity and patterns of damage symptoms, agents, host tree species, climate-driven trigger factors, silvicultural practices, and eventual sanitary interventions. They are further complemented with a satellite-based quantitative characterization of the affected forest areas based on Landsat Normalized Burn Ratio time series, and damage metrics derived from them using the LandTrendr spectral–temporal segmentation algorithm (including onset, duration, magnitude, and rate of the disturbance), and possible interactions with windthrow and wildfire events. The DEFID2 database is a novel resource for many large-scale applications dealing with biotic disturbances. It offers a unique contribution to design networks of experiments, improve our understanding of ecological processes underlying biotic forest disturbances, monitor their dynamics, and enhance their representation in land-climate models. Further data sharing is encouraged to extend and improve the DEFID2 database continuously. The database is freely available at https://jeodpp.jrc.ec.europa.eu/ftp/jrc-opendata/FOREST/DISTURBANCES/DEFID2/ .     

Myrmecovory in Neotropical primates

Primates - Ants are the dominant group of animals in many habitats, particularly in tropical rainforests. High abundance and formation of large colonies convert them into a potential food source...     

Mechanism of collagen folding propagation studied by Molecular Dynamics simulations

Collagen forms a characteristic triple helical structure and plays a central role for stabilizing the extra-cellular matrix. After a C-terminal nucleus formation folding proceeds to form long triple-helical fibers. The molecular details of triple helix folding process is of central importance for an understanding of several human diseases associated with misfolded or unstable collagen fibrils. However, the folding propagation is too rapid to be studied by experimental high resolution techniques. We employed multiple Molecular Dynamics simulations starting from unfolded peptides with an already formed nucleus to successfully follow the folding propagation in atomic detail. The triple helix folding was found to propagate involving first two chains forming a short transient template. Secondly, three residues of the third chain fold on this template with an overall mean propagation of ~75 ns per unit. The formation of loops with multiples of the repeating unit was found as a characteristic misfolding event especially when starting from an unstable nucleus. Central Gly→Ala or Gly→Thr substitutions resulted in reduced stability and folding rates due to structural deformations interfering with folding propagation.