Combined spatial and enzymatic regulation of Csk by cAMP and protein kinase a inhibits T cell receptor signaling

Raft-associated Csk controls signaling through the T cell receptor (TCR) and was mainly anchored to Cbp/PAG (phosphoprotein associated with glycosphingolipid-enriched membrane domains). Treatment of cells with the cAMP-elevating agent prostaglandin E(2) (PGE(2)) augmented the level of Cbp/PAG phosphorylation with a concomitant increase in amounts of Csk bound to Cbp/PAG. While TCR-triggering resulted in transient dissociation of Csk from Cbp/PAG/rafts allowing TCR-induced tyrosine phosphorylation to occur, pretreatment with PGE(2) reduced Csk dissociation upon TCR triggering. This correlated with lowered TCR-induced phosphorylation of CD3 zeta-chain and linker for activation of T cells. Moreover, competition of endogenous Csk from lipid rafts abolished PGE(2)-mediated inhibition of TCR-induced zeta-chain phosphorylation and activation of the nuclear factor of activated T cells (NFAT) activator protein 1 (AP-1). Finally, raft-associated Csk already activated via Cbp/PAG binding, gained additional increase in phosphotransferase activity upon protein kinase A-mediated phosphorylation of Csk. We propose that cAMP regulates Csk via both spatial and enzymatic mechanisms, thereby inhibiting signaling through the TCR.     

Inhibition of antigen-specific T cell proliferation and cytokine production by protein kinase A type I

cAMP inhibits biochemical events leading to T cell activation by triggering of an inhibitory protein kinase A (PKA)-C-terminal Src kinase pathway assembled in lipid rafts. In this study, we demonstrate that activation of PKA type I by Sp-8-bromo-cAMPS (a cAMP agonist) has profound inhibitory effects on Ag-specific immune responses in peripheral effector T cells. Activation of PKA type I inhibits both cytokine production and proliferative responses in both CD4(+) and CD8(+) T cells in a concentration-dependent manner. The observed effects of cAMP appeared to occur endogenously in T cells and were not dependent on APC. The inhibition of responses was not due to apoptosis of specific T cells and was reversible by a PKA type I-selective cAMP antagonist. This supports the notion of PKA type I as a key enzyme in the negative regulation of immune responses and a potential target for inhibiting autoreactive T cells.     

Lactobacillus acidophilus Autolysins Inhibit Helicobacter pylori In Vitro

Antibacterial activity of 17 strains of lactobacilli was tested against 10 strains of H. pylori. The inhibition observed was related to the acid production and the low pH attained. No relationship between CagA phenotype of H. pylori strains and tolerance to lactic acid was observed. In mixed cultures, L. acidophilus CRL 639 showed an autolytic behavior after 24 h of culture. At this moment, H. pylori CCUG17874 showed a decrease of 2 log-cycle, and no viable count was detected after 48 h. The bactericidal effect of L. acidophilus CRL 639 in mixed cultures is related to a proteinaceous compound released after cell lysis. Received: 19 June 2000 / Accepted: 12 July 2000     

Benefits of a Working Memory Training Program for Inattention in Daily Life: A Systematic Review and Meta-Analysis

Background

Many common disorders across the lifespan feature impaired working memory (WM). Reported benefits of a WM training program include improving inattention in daily life, but this has not been evaluated in a meta-analysis. This study aimed to evaluate whether one WM training method has benefits for inattention in daily life by conducting a systematic review and meta-analysis.

Methods

We searched Medline and PsycINFO, relevant journals and contacted authors for studies with an intervention and control group reporting post-training estimates of inattention in daily life. To reduce the influence of different WM training methods on the findings, the review was restricted to trials evaluating the Cogmed method. A meta-analysis calculated the pooled standardised difference in means (SMD) between intervention and control groups.

Results

A total of 622 studies were identified and 12 studies with 13 group comparisons met inclusion criteria. The meta-analysis showed a significant training effect on inattention in daily life, SMD=-0.47, 95% CI -0.65, -0.29, p<.00001. Subgroup analyses showed this significant effect was observed in groups of children and adults as well as users with and without ADHD, and in studies using control groups that were active and non-adaptive, wait-list and passive as well as studies using specific or general measures. Seven of the studies reported follow-up assessment and a meta-analysis showed persisting training benefits for inattention in daily life, SMD=-0.33, 95% CI -0.57 -0.09, p=.006. Additional meta-analyses confirmed improvements after training on visuospatial WM, SMD=0.66, 95% CI 0.43, 0.89, p<.00001, and verbal WM tasks, SMD=0.40, 95% CI 0.18, 0.62, p=.0004.

Conclusions

Benefits of a WM training program generalise to improvements in everyday functioning. Initial evidence shows that the Cogmed method has significant benefits for inattention in daily life with a clinically relevant effect size.     

The effect of pH,bile and calcium on the adhesion ability of probiotic enterococci of animal origin to the porcine jejunal epithelial cell line IPEC-J2

Examination of adhesion ability using a quantitative assay based on radiolabelled bacteria showed that 10 Enterococcus strains exhibited adhesion ability from 2 to 4%. Enterococcus faecium EF2019 (isolate from rabbit faeces, deponed to Czech Culture of Microorganisms in Brno, CCM 7420) showed the highest adhesion ability (4.0 ± 0.4%). With regard to survival, all strains displayed good resistance towards 0.3% oxgall and HCl (pH 3.0). Pretreatment of strains with HCl (pH 3.0) significantly reduced their adhesion. Pretreatment of strains by oxgall significantly reduced the adhesion capacity of E. faecium EF2019, EF1839 and EF319 strains, while the adhesion ability of E. faecium EE3 (isolate from canine feed) slightly increased. Furthermore, addition of calcium (200 mmol/l) significantly increased (P < 0.001) the adhesion ability for all strains tested. The adhesion ability of the isolates from rabbits, EF1839 and EF529, as well as the isolate EE3 (strain from canine feed) increased from 2–3% up to 50–55% upon calcium addition. Despite, in general low adhesive properties, strains can survive passage through the gastrointestinal tract.     

Gastric inflammatory markers and interleukins in patients with functional dyspepsia treated with astaxanthin

The chronic active inflammation caused by Helicobacter pylori is dominated by neutrophils, macrophages, lymphocytes and plasma cells. Several interleukins are involved in the inflammatory process. The aim of this study was to investigate the effect of astaxanthin on gastric inflammation in patients with functional dyspepsia. Forty-four consecutive patients were included, and biopsies were examined for IL-4, IL-6, IL-8, IL-10, interferon-gamma, CD4, CD8, CD14, CD19, CD25 and CD30. Patients were randomized: 21 patients were treated with 40 mg of astaxanthin daily, and 23 patients were treated with a placebo. There was a significant decrease in gastric inflammation in H. pylori-positive patients from both groups. There were no significant changes in the density of H. pylori or in any of the interleukins during or after treatment. There was a significant up-regulation of CD4 and down-regulation of CD8 in patients with H. pylori treated with astaxanthin. Astaxanthin had an effect on the inflammation and on the density of H. pylori in mice in a study where the diet could be standardized without antioxidants (Bennedsen et al., 1999). These dietary conditions are impossible in studies involving humans, and may be due to the minor effect when the host have access to antioxidants in their diet.     

MiniReview: bioinformatic study of bile responses in Campylobacterales

Campylobacter, Helicobacter and Wolinella are genera of the order Campylobacterales, belonging to the class Epsilonproteobacteria. Their habitats are various niches in the gastrointestinal tract of higher animals, where they may come into contact with bile. Microorganisms in these environments require mechanisms of resistance to the surface-active amphipathic molecules with potent antimicrobial activities present in bile. This review summarizes current knowledge on the molecular responses to bile by Campylobacterales and other bacterial species that inhabit the intestinal tract and belong to the phyla Proteobacteria, Bacteriodetes, Firmicutes and Actinobacteria. To date, 125 specific genes have been implicated in bile responses, of which 10 are found in Campylobacterales. Genome database searches, analyses of protein sequence and domain similarities, and gene ontology data integration were performed to compare the responses to bile of these bacteria. The results showed that 33 proteins of bacteria belonging to the four phyla had similarities equal to or greater than 50-46% proteins of Campylobacterales. Domain architecture analyses revealed that 151 Campylobacterales proteins had similar domain composition and organization to 60 proteins known to participate in the tolerance to bile in other bacteria. The proteins CmeB, CmeF and CbrR of Campylobacter jejuni involved in bile tolerance were homologous to 42 proteins identified in the Proteobacteria, Bacteriodetes and Firmicutes. On the other hand, the proteins CiaB, CmeA, CmeC, CmeD, CmeE and FlaAsigma(28) also involved in the response to bile of C. jejuni, did not have homologues in other bacteria. Among the bacteria inhabiting the gastrointestinal tract, the Campylobacterales seem to have evolved some mechanisms of bile resistance similar to those of other bacteria, as well as other mechanisms that appear to be characteristic of this order.     

Application of measurements of transepithelial electrical resistance of intestinal epithelial cell monolayers to evaluate probiotic activity

Among five potentially probiotic lactobacilli investigated, Lactobacillus plantarum MF1298 and Lactobacillus salivarius DC5 showed the highest increase in the transepithelial electrical resistance (TER) of polarized monolayers of Caco-2 cells, and this increase was shown to be dose dependent. Furthermore, preincubation with MF1298 attenuated a decrease in TER induced by Listeria monocytogenes.     

Helicobacter pylori antibodies and gastric cancer: a gender-related difference

Helicobacter pylori has been proposed as a causative agent of gastric cancer. The aim of this study was to define serum antibodies response against different H. pylori antigens in patients with gastric cancer. Serum samples were collected from 115 Lithuanian patients with non-cardia gastric cancer and 110 age- and sex-matched controls without cancer. Heat-stable, low-molecular-mass, and outer membrane proteins were used as antigens to analyze serum IgG antibody response against H. pylori by enzyme-linked immunosorbent assay. Seroprevalence of H. pylori using low-molecular-mass antigen was significantly higher in gastric cancer patients, compared to controls (77% versus 57%, p<0.05). Significant differences in the prevalence of H. pylori infection between gastric cancer patients and controls were found in females using all three studied antigens: heat-stable (98% versus 84%, p<0.05), low-molecular-mass (88% versus 48%, p<0.05) and outer membrane proteins (78% versus 57%, p<0.05). In males, no significant differences were revealed between gastric cancer patients and controls. There may be other cofactors in addition to H. pylori that are important for the development of gastric cancer. H. pylori seems, however, to be a more important for development of gastric cancer in females than in males or males may have more confounding risk factors for gastric cancer than females.     

TCR- and CD28-mediated recruitment of phosphodiesterase 4 to lipid rafts potentiates TCR signaling

Ligation of the TCR along with the coreceptor CD28 is necessary to elicit T cell activation in vivo, whereas TCR triggering alone does not allow a full T cell response. Upon T cell activation of human peripheral blood T cells, we found that the majority of cAMP was generated in T cell lipid rafts followed by activation of protein kinase A. However, upon TCR and CD28 coligation, beta-arrestin in complex with cAMP-specific phosphodiesterase 4 (PDE4) was recruited to lipid rafts which down-regulated cAMP levels. Whereas inhibition of protein kinase A increased TCR-induced immune responses, inhibition of PDE4 blunted T cell cytokine production. Conversely, overexpression of either PDE4 or beta-arrestin augmented TCR/CD28-stimulated cytokine production. We show here for the first time that the T cell immune response is potentiated by TCR/CD28-mediated recruitment of PDE4 to lipid rafts, which counteracts the local, TCR-induced production of cAMP. The specific recruitment of PDE4 thus serves to abrogate the negative feedback by cAMP which is elicited in the absence of a coreceptor stimulus.