Pathogen specific, IRF3-dependent signaling and innate resistance to human kidney infection

The mucosal immune system identifies and fights invading pathogens, while allowing non-pathogenic organisms to persist. Mechanisms of pathogen/non-pathogen discrimination are poorly understood, as is the contribution of human genetic variation in disease susceptibility. We describe here a new, IRF3-dependent signaling pathway that is critical for distinguishing pathogens from normal flora at the mucosal barrier. Following uropathogenic E. coli infection, Irf3(-/-) mice showed a pathogen-specific increase in acute mortality, bacterial burden, abscess formation and renal damage compared to wild type mice. TLR4 signaling was initiated after ceramide release from glycosphingolipid receptors, through TRAM, CREB, Fos and Jun phosphorylation and p38 MAPK-dependent mechanisms, resulting in nuclear translocation of IRF3 and activation of IRF3/IFNβ-dependent antibacterial effector mechanisms. This TLR4/IRF3 pathway of pathogen discrimination was activated by ceramide and by P-fimbriated E. coli, which use ceramide-anchored glycosphingolipid receptors. Relevance of this pathway for human disease was supported by polymorphic IRF3 promoter sequences, differing between children with severe, symptomatic kidney infection and children who were asymptomatic bacterial carriers. IRF3 promoter activity was reduced by the disease-associated genotype, consistent with the pathology in Irf3(-/-) mice. Host susceptibility to common infections like UTI may thus be strongly influenced by single gene modifications affecting the innate immune response.     

Hydrurus‐related golden algae (Chrysophyceae) cause yellow snow in polar summer snowfields

In polar regions, melting snow fields can be occupied by striking blooms of chrysophycean algae, which cause yellowish slush during summer. Samples were harvested at King George Island (South Shetland Islands, Maritime Antarctica) and at Spitsbergen (Svalbard archipelago, High Arctic). The populations live in an ecological niche, where water‐logged snow provides a cold and ephemeral ecosystem, possibly securing the survival of psychrophilic populations through the summer. A physiological adaptation to low temperatures was shown by photosynthesis measurements. The analysis of soluble carbohydrates showed the occurrence of glycerol and sugars, which may play a role in protection against intracellular freezing. Although both populations were made of unicells with Ochromonas‐alike morphology, investigation by molecular methods (18S rDNA sequencing) revealed unexpectedly a very close relationship to the mountain‐river dwelling Hydrurus foetidus (Villars) Trevisan. However, macroscopic thalli typical for the latter species were never found in snow, but are known from nearby localities, and harvested samples of snow algae exposed to dryness evolved a similar pervading, ‘fishy’ smell. Moreover, in both habitats tetrahedal zoospores with four elongate spikes were found, similar to what is known from Hydrurus. Our molecular results go along with earlier reports, where chrysophycean sequences of the same taxonomic affiliation were isolated from snow. This points to a distinct group of photoautotrophic, Hydrurus‐related chrysophytes, which are characteristic for long‐lasting, slowly melting snow packs in certain cold regions of the world.     

Effect of Calcitriol in Combination with Corticosterone, Interleukin-1β, and Transforming Growth Factor-β1 on Nerve Growth Factor Secretion in an Astroglial Cell Line

Abstract: In astrocytes, nerve growth factor (NGF) synthesis has been described to be stimulated by the cytokines interleukin-1β (IL-1β) and transforming growth factor-β1 (TGF-β1) and inhibited by corticosterone. As all three factors are present in the brain under certain conditions, we investigated the effect of their combined application on NGF secretion in the astroglial cell line RC7 and, in addition, studied the effect of calcitriol (1α,25-dihydroxyvitamin D₃). Calcitriol stimulated NGF secretion, whereas corticosterone reduced basal levels of NGF secretion as well as inhibited the NGF secretion induced by IL-1β, calcitriol, and TGF-β1. Calcitriol had an additive effect when applied together with IL-1β and a synergistic effect when applied with TGF-β1. Moreover, calcitriol not only counteracted the inhibitory effect of corticosterone on NGF secretion stimulated by TGF-β1 but even augmented it to a level more than threefold higher than that reached with TGF-β1 alone. Due to the trophic effect of NGF on basal forebrain cholinergic neurons, these findings might be of therapeutic relevance under conditions where cholinergic function is impaired and the endogenous levels of corticosterone, IL-1β, or TGF-β1 are elevated.     

Prion protein (PrP) with amino-proximal deletions restoring susceptibility of PrP knockout mice to scrapie.

The 'protein only' hypothesis postulates that the prion, the agent causing transmissible spongiform encephalopathies, is PrP(Sc), an isoform of the host protein PrP(C). Protease treatment of prion preparations cleaves off approximately 60 N-terminal residues of PrP(Sc) but does not abrogate infectivity. Disruption of the PrP gene in the mouse abolishes susceptibility to scrapie and prion replication. We have introduced into PrP knockout mice transgenes encoding wild-type PrP or PrP lacking 26 or 49 amino-proximal amino acids which are protease susceptible in PrP(Sc). Inoculation with prions led to fatal disease, prion propagation and accumulation of PrP(Sc) in mice expressing both wild-type and truncated PrPs. Within the framework of the 'protein only' hypothesis, this means that the amino-proximal segment of PrP(C) is not required either for its susceptibility to conversion into the pathogenic, infectious form of PrP or for the generation of PrP(Sc).     

PTPN22 1858C>T gene polymorphism in patients with SLE: association with serological and clinical results

To assess the association between PTPN22 1858C>T gene polymorphism and susceptibility to, and clinical presentation of, systemic lupus erythematosus (SLE). Our study included 135 SLE patients (120 women and 15 men; mean age 45.1 years; mean course of disease from 0.5 to 31 years) and 201 healthy subjects. The PTPN22 1858C>T gene polymorphism was genotyped by polymerase chain reaction restriction fragment length polymorphism. A significantly higher incidence of genotype CT in patients with SLE (36.3 %) was found, compared with the control group (24.9 %). The frequencies of C1858 and T1858 alleles were 78.1 and 21.9 % in SLE patients and 86.1 and 13.9 % in controls, respectively. Significantly higher SLE susceptibility was observed in patients carrying at least one T allele (p = 0.009; OR 1.86; 95 % CI 0.14–3.05). Significant association of the PTPN22 T1858 allele (CT + TT vs.CC) and secondary antiphospholipid syndrome was observed (p = 0.049). In SLE patients carrying the T1858 allele, higher levels of antiphospholipid antibodies (anticardiolipin antibodies and/or lupus anticoagulant) were found (p = 0.030; OR 2.17; 95 % CI 1.07–4.44).     

Angiopoietin-1 is associated with cerebral vasospasm and delayed cerebral ischemia in subarachnoid hemorrhage

Background  

Angiopoietin-1 (Ang-1) and -2 (Ang-2) are keyplayers in the regulation of endothelial homeostasis and vascular proliferation. Angiopoietins may play an important role in the pathophysiology of cerebral vasospasm (CVS). Ang-1 and Ang-2 have not been investigated in this regard so far.     

A genetic study of the human low-voltage electroencephalogram

Summary The studied phenotype, the low-voltage electroencephalogram (LVEEG), is characterized by the absence of an alpha rhythm from the resting EEG. In previous studies, evidence was found for a simple autosomal-dominant mode of inheritance of the LVEEG. Such a polymorphism in brain function can be used as a research model for the stepwise elucidation of the molecular mechanism involved in those aspects of neuronal activity that are reflected in the EEG. Linkage with the variable number of tandem repeats (VNTR) marker CMM6 (D20S19) and localization of an LVEEG (EEGV1) gene on 20q have previously been reported, and genetic heterogeneity has been demonstrated. This latter result has been corroborated by studing new marker (MS214). The phenotype of the LVEEG is described here in greater detail. Its main characteristic is the absence of rhythmic alpha activity, especially in occipital leads, whereas other wave forms such as beta or theta waves may be present. Analysis of 17 new families (some of them large), together with 60 previously described nuclear families, supports the genetic hypothesis of an autosomal-dominant mode of inheritance. Problems connected with the analysis of linkage heterogeneity, exclusion mapping, and the study of multipoint linkage are discussed. A possible explanation of the localization of LVEEG in the close vicinity of another gene influencing synchronization of the normal EEG, the gene for benign neonatal epilepsie, is given.     

A plasmid-based vector system for the cloning and expression of Helicobacter pylori genes encoding outer membrane proteins

Helicobacter pylori produces a number of proteins associated with the outer membrane, including adhesins and the vacuolating cytotoxin. We observed that the functional expression of such proteins is deleterious to Escherichia coli, the host bacterium used for gene cloning. Therefore, a general method was developed for the functional expression of such genes on a shuttle vector in H. pylori, which has been termed SOMPES (Shuttle vector-based Outer Membrane Protein Expression System). The intact, active gene is reconstituted by recombination in H. pylori from partial gene sequences cloned on an E. coli-H. pylori shuttle vector. This system was established in an H. pylori strain carrying a precise, unmarked chromosomal deletion of the vacA gene, which was constructed by adapting the streptomycin sensitivity system to H. pylori. It is based on the expression of the H. pylori rpsL gene as a counterselectable marker in the genetic background of an rpsL mutant. The utility of this approach is demonstrated by the expression of a recombinant gene encoding vacuolating cytotoxin (vacA) and a recombinant gene encoding an adherence-associated outer membrane protein (alpA) in H. pylori. Received: 10 May 1999 / Accepted: 7 July 1999     

Are gastropods, rather than ants, important dispersers of seeds of myrmecochorous forest herbs?

Seed dispersal by ants (myrmecochory) is widespread, and seed adaptations to myrmecochory are common, especially in the form of fatty appendices (elaiosomes). In a recent study, slugs were identified as seed dispersers of myrmecochores in a central European beech forest. Here we used 105 beech forest sites to test whether myrmecochore presence and abundance is related to ant or gastropod abundance and whether experimentally exposed seeds are removed by gastropods. Myrmecochorous plant cover was positively related to gastropod abundance but was negatively related to ant abundance. Gastropods were responsible for most seed removal and elaiosome damage, whereas insects (and rodents) played minor roles. These gastropod effects on seeds were independent of region or forest management. We suggest that terrestrial gastropods can generally act as seed dispersers of myrmecochorous plants and even substitute myrmecochory, especially where ants are absent or uncommon.