Spin stress contribution to the lattice dynamics of FePt.

Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments. We show that the granular microstructure is essential to support the contractive out-of-plane stresses originating from in-plane expansion via the Poisson effect that add to the uniaxial contractive stress driven by spin disorder. We prove the spin contribution by saturating the magnetic excitations with a first laser pulse and then detecting the purely expansive response to a second pulse. The contractive spin stress is reestablished on the same 100-ps time scale that we observe for the recovery of the ferromagnetic order. Finite-element modeling of the mechanical response of FePt nanosystems confirms the morphology dependence of the dynamics.

Notch inhibition counteracts Paneth cell death in absence of caspase-8.

Opposing activities of Notch and Wnt signaling regulate mucosal barrier homeostasis and differentiation of intestinal epithelial cells. Specifically, Wnt activity is essential for differentiation of secretory cells including Wnt3-producing Paneth cells, whereas Notch signaling strongly promotes generation of absorptive cells. Loss of caspase-8 in intestinal epithelium (casp8∆int) is associated with fulminant epithelial necroptosis, severe Paneth cell death, secondary intestinal inflammation, and an increase in Notch activity. Here, we found that pharmacological Notch inhibition with dibenzazepine (DBZ) is able to essentially rescue the loss of Paneth cells, deescalate the inflammatory phenotype, and reduce intestinal permeability in casp8∆int mice. The secretory cell metaplasia in DBZ-treated casp8∆int animals is proliferative, indicating for Notch activities partially insensitive to gamma-secretase inhibition in a casp8∆int background. Our data suggest that casp8 acts in the intestinal Notch network.

c-Jun N-terminal kinase 2 promotes enterocyte survival and goblet cell differentiation in the inflamed intestine.

c-Jun N-terminal kinases (JNKs) contribute to immune signaling but their functional role during intestinal mucosal inflammation has remained ill defined. Using genetic mouse models, we characterized the role of JNK1 and JNK2 during homeostasis and acute colitis. Epithelial apoptosis, regeneration, differentiation, and barrier function were analyzed in intestinal epithelium-specific (ΔIEC) or complete JNK1 and bone marrow chimeric or complete JNK2 deficient mice as well as double-knockout animals (JNK1ΔIECJNK2-/-) during homeostasis and acute dextran sulfate sodium (DSS)-induced colitis. Results were confirmed using human HT-29 cells and wild-type or JNK2-deficient mouse intestinal organoid cultures. We show that nonhematopoietic JNK2 but not JNK1 expression confers protection from DSS-induced intestinal inflammation reducing epithelial barrier dysfunction and enterocyte apoptosis. JNK2 additionally enhanced Atonal homolog 1 expression, goblet cell and enteroendocrine cell differentiation, and mucus production under inflammatory conditions. Our results identify a protective role of epithelial JNK2 signaling to maintain mucosal barrier function, epithelial cell integrity, and mucus layer production in the event of inflammatory tissue damage.

Lack of gp130 expression in hepatocytes attenuates tumor progression in the DEN model.

Chronic liver inflammation is a crucial event in the development and growth of hepatocellular carcinoma (HCC). Compelling evidence has shown that interleukin-6 (IL-6)/gp130-dependent signaling has a fundamental role in liver carcinogenesis. Thus, in the present study we aimed to investigate the role of gp130 in hepatocytes for the initiation and progression of HCC. Hepatocyte-specific gp130 knockout mice (gp130(Δhepa)) and control animals (gp130(f/f)) were treated with diethylnitrosamine (DEN). The role of gp130 for acute injury (0-144 h post treatment), tumor initiation (24 weeks) and progression (40 weeks) was analyzed. After acute DEN-induced liver injury we observed a reduction in the inflammatory response in gp130(Δhepa) animals as reflected by decreased levels of IL-6 and oncostatin M. The loss of gp130 slightly attenuated the initiation of HCC 24 weeks after DEN treatment. In contrast, 40 weeks after DEN treatment, male and female gp130(Δhepa) mice showed smaller tumors and reduced tumor burden, indicating a role for hepatocyte-specific gp130 expression during HCC progression. Oxidative stress and DNA damage were substantially and similarly increased by DEN in both gp130(f/f) and gp130(Δhepa) animals. However, gp130(Δhepa) livers revealed aberrant STAT5 activation and decreased levels of transforming growth factor-ß (TGFß), pSMAD2/3 and SMAD2, whereas phosphorylation of STAT3 at Tyr705 and Ser727 was absent. Our results indicate that gp130 deletion in hepatocytes reduces progression, but not HCC initiation in the DEN model. Gp130 deletion resulted in STAT3 inhibition but increased STAT5 activation and diminished TGF-dependent signaling. Hence, blocking gp130 in hepatocytes might be an interesting therapeutic target to inhibit the growth of HCC.

[Diagnostic value of routine ileum biopsy in patients with chronic diarrhoea--a prospective monocentric study]. / Die diagnostische Bedeutung der Ileumbiopsie bei chronischer Diarrhö--eine prospektive monozentrische Studie.

BACKGROUND AND AIMS: In patients with chronic diarrhoea of unknown origin, colonoscopy with intubation of the terminal ileum and performance of biopsies are standard in the diagnostic work-up. While the importance of random biopsies in the colon even in cases with normal endoscopic appearance has been proven in several studies, the role of biopsies in the terminal ileum under these circumstances is not well defined. PATIENTS AND METHODS: In this prospective observational 24-month study patients with chronic diarrhoea of unknown cause were included. All patients underwent colonoscopy with intubation and biopsy of the terminal ileum. These biopsies have been analysed, their diagnostic value has been compared to the endoscopic appearance and the clinical diagnosis was investigated. RESULTS: In 159 patients, the terminal ileum showed a pathological endoscopic appearance in 27 cases (17 %). In 22 (81.5 %) of these 27 patients diagnostic pathological findings were present, in 4 cases (14.8 %) non-specific histological changes were detected and in one patient (3.7 %), histology was normal. In contrast, only in one of 132 cases with normal endoscopic appearance, did histopathology show a significant pathology (celiac disease). In 30 of the 132 patients (22.7 %) with a normal endoscopic appearance, distinctive histological features were detected (slight eosinophilia or elevated mucosal immune cell count), but not classified as diagnostic. In all cases, these features were also present in simultaneously performed colonic biopsies. CONCLUSIONS: Routine biopsy of the terminal ileum, when normal endoscopic appearance is documented, does not give any additional information and cannot be recommended as a standard procedure in endoscopic work-up of chronic diarrhoea.

Selective expression of histamine receptors H1R, H2R, and H4R, but not H3R, in the human intestinal tract.

BACKGROUND AND AIMS: Histamine is known as a regulator of gastrointestinal functions, such as gastric acid production, intestinal motility, and mucosal ion secretion. Most of this knowledge has been obtained from animal studies. In contrast, in humans, expression and distribution of histamine receptors (HR) within the human gastrointestinal tract are unclear. METHODS: We analysed HR expression in human gastrointestinal tissue specimens by quantitative reverse transcription-polymerase chain reaction and immunostaining. RESULTS: We found that H1R, H2R, and H4R mRNA were expressed throughout the gastrointestinal tract, while H3R mRNA was absent. No significant differences in the distribution of HR were found between different anatomical sites (duodenum, ileum, colon, sigma, and rectum). Immunostaining of neurones and nerve fibres revealed that H3R was absent in the human enteric nervous system; however, H1R and H2R were found on ganglion cells of the myenteric plexus. Epithelial cells also expressed H1R, H2R and, to some extent, H4R. Intestinal fibroblasts exclusively expressed H1R while the muscular layers of human intestine stained positive for both H1R and H2R. Immune cells expressed mRNA and protein for H1R, H2R, and low levels of H4R. Analysis of endoscopic biopsies from patients with food allergy and irritable bowel syndrome revealed significantly elevated H1R and H2R mRNA levels compared with controls. CONCLUSIONS: We have demonstrated that H1R, H2R and, to some extent, H4R, are expressed in the human gastrointestinal tract, while H3R is absent, and we found that HR expression was altered in patients with gastrointestinal diseases.

Development of an in vitro system for the study of allergens and allergen-specific immunoglobulin E and immunoglobulin G: Fcepsilon receptor I supercross-linking is a possible new mechanism of immunoglobulin G-dependent enhancement of type I allergic reactions.

BACKGROUND: IgE-dependent activation of mast cells (MCs) is a key pathomechanism of type I allergies. In contrast, allergen-specific IgG Abs are thought to attenuate immediate allergic reactions by blocking IgE binding and by cross-linking the inhibitory Fcgamma receptor IIB on MCs. OBJECTIVES: To establish a defined in vitro system using human MCs to study the biological activity of allergens and to investigate the role of allergen-specific IgE and IgG. METHODS: Purified human intestinal MCs sensitized with different forms of specific IgE Abs were triggered by monomeric and oligomeric forms of recombinant Bet v 1, the major birch pollen allergen, in the presence or absence of allergen-specific IgG Abs. Results MCs sensitized with an anti-Bet v 1 IgE mAb or sera obtained from birch pollen allergic patients released histamine and sulphidoleukotrienes after exposure to oligomeric Bet v 1. Monomeric Bet v 1 provoked mediator release only in MCs sensitized with patients sera but not in MCs sensitized with anti-Bet v 1 IgE mAb. Interestingly, MC activation could be induced by supercross-linking of monomeric Bet v 1 bound to monovalent IgE on MCs with a secondary allergen-specific IgG pAb. By using IgG F(ab')2 fragments we provide evidence that this effect is not a result of IgG binding to Fcgamma receptors. CONCLUSION: This assay represents a new tool for the in vitro study of MC activation in response to natural and genetically modified allergens. Fcepsilon receptor I supercross-linking by allergen-specific IgG Abs provides a possible new mechanism of IgG-dependent enhancement of type I allergic reactions.

Interleukin-4 induces a switch of human intestinal mast cells from proinflammatory cells to Th2-type cells.

BACKGROUND: During the last years, mast cells have been recognized as a potent cellular source of multiple cytokines. However, little is known about the regulation of cytokine production by mature human mast cells derived from mucosal sites. METHODS: Human mast cells were isolated from intestinal mucosa and cultured for 14 days in the presence of stem cell factor (SCF) alone or in combination with IL-4. Mast cells were then stimulated by IgE receptor cross-linking or bacterial infection and cytokine production was examined by RT-PCR and ELISA. RESULTS: We found that human intestinal mast cells produce proinflammatory cytokines such as TNF-alpha, IL-1beta and IL-6 without further stimulation. Stimulation of the cells with gram-negative bacteria (Escherichia coli and others) caused an upregulation of TNF-alpha expression. Following IgE receptor cross-linking, we found additional expression of the Th2 cytokines IL-3, IL-5 and IL-13. Interestingly, mRNA for IL-3, IL-5 and IL-13 was also expressed in unstimulated mast cells provided they were cultured in the presence of SCF and IL-4. Moreover, IL-4 rendered mast cells capable of releasing IL-5 in response to bacterial challenge. CONCLUSION: In the presence of the mast cell survival factor SCF, mature human mast cells produce predominantly proinflammatory cytokines, whereas in the presence of SCF and IL-4, mast cells produce not only proinflammatory but also Th2 cytokines.

Human intestinal mast cells are capable of producing different cytokine profiles: role of IgE receptor cross-linking and IL-4.

Mast cells are recognized as a new type of immunoregulatory cells capable of producing different cytokines. So far, little is known about the cytokine profile of mature human mast cells isolated from intestinal tissue and cultured in the presence of stem cell factor (SCF). We observed that these cells express the proinflammatory cytokines TNF-alpha, IL-1 beta, IL-6, IL-8, IL-16, and IL-18 without further stimulation. Both IgE-dependent and IgE-independent agonists (e.g., Gram-negative bacteria) enhanced expression of TNF-alpha. Another set of cytokines consisting of IL-3, IL-5, IL-9, and IL-13 was expressed following activation by IgE receptor cross-linking. If mast cells were cultured in the presence of IL-4 and SCF, the production and release of IL-3, IL-5, and IL-13 was increased up to 4-fold compared with mast cells cultured with SCF alone. By contrast, IL-6 expression was completely blocked in response to culture with IL-4. In summary, our data show that mature human mast cells produce proinflammatory cytokines that may be up-regulated following triggering with IgE-independent agonists such as bacteria, whereas activation by IgE receptor cross-linking results in the expression of Th2-type cytokines. IL-4 enhances the expression of Th2-type cytokines but does not affect or even down-regulates proinflammatory cytokines.

IL-4 enhances proliferation and mediator release in mature human mast cells.

Tissue mast cells (MC) are recognized as key effector cells of immediate-type allergic reactions releasing inflammatory mediators and cytokines on stimulation with antigen, but they also might be involved in IgE-independent inflammatory and tissue repair processes. The mechanism of human MC regulation in tissue is not fully understood. Here, we show that IL-4, in synergy with stem cell factor (SCF), regulates the function of purified human MC isolated from intestinal tissue. Whereas SCF induced only marginal proliferation of MC cultured in vitro up to 4 weeks, addition of IL-4 and SCF strongly increased the proliferation rate. Moreover, IL-4, which by itself had no visible effect on human MC, enhanced the release of histamine, leukotriene C4, and IL-5 in MC triggered by IgE receptor crosslinking. The IL-4 effects occurred in a dose-dependent fashion (ED50 = 100 pg/ml) and could be totally blocked by a competitive IL-4 receptor antagonist. Our data indicate that IL-4 is an important regulator of human MC function and suggest that mature MC retain the capacity to proliferate in a particular tissue environment.

Stem cell factor-dependent survival, proliferation and enhanced releasability of purified mature mast cells isolated from human intestinal tissue.

BACKGROUND: Recently we reported about a stem cell factor (SCF)-dependent culture system for human mast cells (MC), isolated from intestinal mucosa. Here we present a method to obtain highly purified human intestinal MC. METHODS: MC were isolated from surgery specimens and purified by positive selection using the magnetic-activated cell sorting (MACStrade mark) system and subsequent culture of the MC in medium supplemented with SCF. RESULTS: In the presence of SCF, purified MC (50-85% purity after MACS) maintained in culture for up to 3 months. MC purity increased during culture and reached nearly 100%. During the first week of culture, MC numbers decreased, but after that time they started to proliferate. Cultured MC did not change their histamine content, phenotype or morphology. They were even more responsive towards IgE-dependent stimulation, which caused the release of high amounts of histamine, leukotrienes and cytokines such as TNF-alpha and IL-5. CONCLUSION: We show that mature human intestinal MC can be purified, maintained in culture, and triggered for proliferation in the presence of SCF. After culture, they are viable, release high amounts of mediators and cytokines upon stimulation, and thus are a valuable tool for further experiments on human mucosal MC.