Synoviocyte-mediated expansion of inflammatory T cells in rheumatoid synovitis is dependent on CD47-thrombospondin 1 interaction

Fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis elicit spontaneous proliferation of autologous T cells in an HLA-DR and CD47 costimulation-dependent manner. T cell costimulation through CD47 is attributed to specific interaction with thrombospondin-1 (TSP1), a CD47 ligand displayed on FLS. CD47 binding by FLS has broad biological impact that includes adhesion and the triggering of specific costimulatory signals. TSP1(+) FLS are highly adhesive to T cells and support their aggregation and growth in situ. Long-term cultures of T cells and FLS form heterotypic foci that are amenable to propagation without exogenous growth factors. T cell adhesion and aggregate formation on TSP1(+) FLS substrates are inhibited by CD47-binding peptides. In contrast, FLS from arthroscopy controls lack adhesive or T cell growth-promoting activities. CD47 stimulation transduces a costimulatory signal different from that of CD28, producing a gene expression profile that included induction of ferritin L chain, a component of the inflammatory response. Ferritin L chain augments CD3-induced proliferation of T cells. Collectively, these results demonstrate the active role of FLS in the recruitment, activation, and expansion of T cells in a CD47-dependent manner. Because TSP1 is abundantly expressed in the rheumatoid synovium, CD47-TSP1 interaction is proposed to be a key component of an FLS/T cell regulatory circuit that perpetuates the inflammatory process in the rheumatoid joint.     

Refinement of Pig Retroperfusion Technique: Global Retroperfusion with Ligation of the Azygos Connection Preserves Hemodynamic Function in an Acute Infarction Model in Pigs (Sus scrofa domestica)

In ischemic hearts, venous retroperfusion is a potential myocardial revascularization strategy. This study aimed to refine the technical and functional aspects of a pig model of acute myocardial infarction and retroperfusion with respect to the azygos connection. Global retroperfusion after ligation of the ramus interventricularis paraconalis (equivalent to the left anterior descending artery in humans) was performed in 16 Landrace pigs (Sus scrofa domestica). Coronary sinus perfusion was performed in 8 pigs (P+) but not in the other 8 (P–), and the azygos vein was ligated (L+) 4 of the 8 pigs in each of these groups but left open (L–) in the remaining animals. Hemodynamic performance (for example, cardiac output, stroke volume) was significantly better in P+L+ pigs that underwent coronary sinus perfusion with ligation of the azygos vein compared with all other animals. In addition, troponin I release was significant lower in P+L+ pigs (1.7 ± 1.3 ng/mL) than in P–L– (5.47 ± 2.1 ng/mL), P–L+ (6.63 ± 2.4 ng/mL), and P+L– (4.81 ± 2.3 ng/mL) pigs. Effective retrograde flow and thus hemodynamic stability was achieved by ligation of the azygos vein. Therefore, experiments focusing on global retroperfusion will benefit from effective inhibition of the blood flow through the azygos vein.Abbreviations: ACS, aorta-to-coronary–sinus shunt, CS, coronary sinus, L, ligation, LAD, left anterior descending artery, P, perfusionAnimal models are used frequently to investigate myocardial revascularization techniques, and researchers have studied global or selective venous retroperfusion in dogs,²² pigs,⁹ and sheep.³³ The goal underlying retrograde coronary sinus (CS) perfusion is perfusion of the ischemic myocardium proximal to the occlusion or stenosis. This method frequently is used for delivering cardioplegic solutions during cardiac surgery. In addition, both clinical^{2,3,6,16,28,30} and experimental ^{11,21,25,34,37,42} studies have validated the efficiency of CS retroperfusion.Interpreting the results from experimental animal models and follow-up examinations of patients who have undergone venous revascularization has led to controversy.^9,37 In particular, technical problems with some studies have been identified. Previous animal studies on interspecies anatomic differences in mammals^4,7,19 have concentrated on the venous connections of the vessels draining the myocardium and have demonstrated a need for further feasibility studies of the pig model (German Landrace pigs, Sus scrofa domestica) that focus on hemodynamic performance.We wanted to characterize in detail the contribution of the azygos vein connection in swine during retroperfusion after myocardial infarction and hypothesized that ligation of the azygos vein would preserve hemodynamic function after ligation of the left anterior descending artery (LAD) in a global retroperfusion model in pigs.     

Unchecked CD70 expression on T cells lowers threshold for T cell activation in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by premature immune aging with accumulation of degenerate T cells deficient for CD28. Gene expression profiling of CD4(+)CD28(-) and CD4(+)CD28(+) T cells to discover disease-promoting activities of CD28(-) T cells identified expression of CD70 as a most striking difference. Hence, CD70 was significantly more expressed in CD4 T cells from RA patients compared with age-matched controls (p < 0.006). The underlying mechanism was a failure to repress CD70 expression after activation-dependent induction. This defect in RA was not related to differential promoter demethylation. CD70 on bystander CD4(+)CD28(-) T cells functioned by lowering the threshold for T cell activation; admixture of CD4(+)CD28(-) T cells augmented TCR-induced responses of autologous naive CD4(+)CD28(+) T cells, particularly of low-avidity T cells. The data support a model in which CD70 expressed on T cells causes degeneracy in T cell responses and undermines tolerance mechanisms that normally control T cell autoreactivity.     

Structure of a 14-3-3 coordinated hexamer of the plant plasma membrane H+ -ATPase by combining X-ray crystallography and electron cryomicroscopy

Regulatory 14-3-3 proteins activate the plant plasma membrane H(+)-ATPase by binding to its C-terminal autoinhibitory domain. This interaction requires phosphorylation of a C-terminal, mode III, recognition motif as well as an adjacent span of approximately 50 amino acids. Here we report the X-ray crystal structure of 14-3-3 in complex with the entire binding motif, revealing a previously unidentified mode of interaction. A 14-3-3 dimer simultaneously binds two H(+)-ATPase peptides, each of which forms a loop within the typical 14-3-3 binding groove and therefore exits from the center of the dimer. Several H(+)-ATPase mutants support this structure determination. Accordingly, 14-3-3 binding could result in H(+)-ATPase oligomerization. Indeed, by using single-particle electron cryomicroscopy, the 3D reconstruction of the purified H(+)-ATPase/14-3-3 complex demonstrates a hexameric arrangement. Fitting of 14-3-3 and H(+)-ATPase atomic structures into the 3D reconstruction map suggests the spatial arrangement of the holocomplex.     

Giant cell arteritis: immune and vascular aging as disease risk factors

Susceptibility for giant cell arteritis increases with chronological age, in parallel with age-related restructuring of the immune system and age-induced remodeling of the vascular wall. Immunosenescence results in shrinkage of the naïve T-cell pool, contraction of T-cell diversity, and impairment of innate immunity. Aging of immunocompetent cells forces the host to take alternative routes for protective immunity and confers risk for pathogenic immunity that causes chronic inflammatory tissue damage. Dwindling immunocompetence is particularly relevant as the aging host is forced to cope with an ever growing infectious load. Immunosenescence coincides with vascular aging during which the arterial wall undergoes dramatic structural changes and medium and large arteries lose their pliability and elasticity. On the molecular level, elastic fibers deteriorate and matrix proteins accumulate biochemical modifications. Thus, the aging process impacts the two major biologic systems that liaise to promote giant cell arteritis; the immune system and the vessel wall niche.     

Long-term evaluation of a selective retrograde coronary venous perfusion model in pigs (Sus scrofa domestica)

The lack of suitable target vessels remains a challenge for aortocoronary bypass grafting in end-stage coronary heart disease. This study aimed to investigate the arterialization of cardiac veins as an alternative myocardial revascularization strategy in an experimental long-term model in pigs. Selective retrograde perfusion of a coronary vein (aorta to coronary vein bypass, retrobypass) before ligation of the ramus interventricularis paraconalis (equivalent to the left anterior descending artery in humans) was performed in 20 German Landrace pigs (Sus scrofa domestica). Retroperfusion of the left anterior descending vein was performed in 10 pigs (RP+) but not in the other 10 (RP-), and the vena cordis magna was ligated (L+) in 5 pigs in each of these groups but left open (L-) in the remaining animals. Hemodynamic performance (for example, cardiac output) was significantly better in the group that underwent selective retroperfusion with proximal ligation of vena cordis magna (RP+L+; 4.1 L/min) compared with the other groups (RP+L-, 2.5 L/min; RP-L+, 2.2 L/min; RP-L-, 1.9 L/min). Long-term survival was significantly better in RP+L+ pigs (112±16 d) than in all other groups. Histologic follow-up studies showed significantly less necrosis in the RP+L+ group compared with all other groups. Venous retroperfusion is an effective technique to achieve long-term survival after acute occlusion of the left anterior descending artery in a pig model. In this model, proximal ligation of vena cordis magna is essential.     

Isolation and characterisation of an equol-producing mixed microbial culture from a human faecal sample and its activity under gastrointestinal conditions

Only about one third of humans possess a microbiota capable of transforming the dietary isoflavone daidzein into equol. Little is known about the dietary and physiological factors determining this ecological feature. In this study, the in vitro metabolism of daidzein by faecal samples from four human individuals was investigated. One culture produced the metabolites dihydrodaidzein and O-desmethylangolensin, another produced dihydrodaidzein and equol. From the latter, a stable and transferable mixed culture transforming daidzein into equol was obtained. Molecular fingerprinting analysis (denaturing gradient gel electrophoresis) showed the presence of four bacterial species of which only the first three strains could be brought into pure culture. These strains were identified as Lactobacillus mucosae EPI2, Enterococcus faecium EPI1 and Finegoldia magna EPI3, and did not produce equol in pure culture. The fourth species was tentatively identified as Veillonella sp strain EP. It was found that hydrogen gas in particular, but also butyrate and propionate, which are all colonic fermentation products from poorly digestible carbohydrates, stimulated equol production by the mixed culture. However, when fructo-oligosaccharides were added, equol production was inhibited. Furthermore, the equol-producing capacity of the isolated culture was maintained upon its addition to a faecal culture originating from a non-equol-producing individual.