Succinate is an inflammatory signal that induces IL-1β through HIF-1α

Macrophages activated by the Gram-negative bacterial product lipopolysaccharide switch their core metabolism from oxidative phosphorylation to glycolysis. Here we show that inhibition of glycolysis with 2-deoxyglucose suppresses lipopolysaccharide-induced interleukin-1β but not tumour-necrosis factor-α in mouse macrophages. A comprehensive metabolic map of lipopolysaccharide-activated macrophages shows upregulation of glycolytic and downregulation of mitochondrial genes, which correlates directly with the expression profiles of altered metabolites. Lipopolysaccharide strongly increases the levels of the tricarboxylic-acid cycle intermediate succinate. Glutamine-dependent anerplerosis is the principal source of succinate, although the 'GABA (γ-aminobutyric acid) shunt' pathway also has a role. Lipopolysaccharide-induced succinate stabilizes hypoxia-inducible factor-1α, an effect that is inhibited by 2-deoxyglucose, with interleukin-1β as an important target. Lipopolysaccharide also increases succinylation of several proteins. We therefore identify succinate as a metabolite in innate immune signalling, which enhances interleukin-1β production during inflammation.

Identification of a candidate tumour suppressor gene, MMAC1, at chromosome 10q23.3 that is mutated in multiple advanced cancers

Deletions involving regions of chromosome 10 occur in the vast majority (> 90%) of human glioblastoma multiformes. A region at chromosome 10q23-24 was implicated to contain a tumour suppressor gene and the identification of homozygous deletions in four glioma cell lines further refined the location. We have identified a gene, designated MMAC1, that spans these deletions and encodes a widely expressed 5.5-kb mRNA. The predicted MMAC1 protein contains sequence motifs with significant homology to the catalytic domain of protein phosphatases and to the cytoskeletal proteins, tensin and auxilin. MMAC1 coding-region mutations were observed in a number of glioma, prostate, kidney and breast carcinoma cell lines or tumour specimens. Our results identify a strong candidate tumour suppressor gene at chromosome 10q23.3, whose loss of function appears to be associated with the oncogenesis of multiple human cancers.

Bidirectional cytokine interactions in the maternal-fetal relationship: is successful pregnancy a TH2 phenomenon?

Pregnant females are susceptible to intracellular pathogens and are biased towards humoral rather than cell-mediated immunity. Since TH1 cytokines compromise pregnancy and TH2 cytokines are produced at the maternal-fetal interface, we hypothesize that these TH2 cytokines inhibit TH1 responses, improving fetal survival but impairing responses against some pathogens.

A novel class of evolutionarily conserved genes defined by piwi are essential for stem cell self-renewal

Germ-line stem cells (GSCs) serve as the source for gametogenesis in diverse organisms. We cloned and characterized the Drosophila piwi gene and showed that it is required for the asymmetric division of GSCs to produce and maintain a daughter GSC but is not essential for the further differentiation of the committed daughter cell. Genetic mosaic and RNA in situ analyses suggest that piwi expression in adjacent somatic cells regulates GSC division. piwi encodes a highly basic novel protein, well conserved during evolution. We isolated piwi homologs in Caenorhabditis elegans and humans and also identified Arabidopsis piwi-like genes known to be required for meristem cell maintenance. Decreasing C. elegans piwi expression reduces the proliferation of GSC-equivalent cells. Thus, piwi represents a novel class of genes required for GSC division in diverse organisms.

Obesity increases sensitivity to endotoxin liver injury: implications for the pathogenesis of steatohepatitis

Genetically obese fatty/fatty rats and obese/obese mice exhibit increased sensitivity to endotoxin hepatotoxicity, quickly developing steatohepatitis after exposure to low doses of lipopolysaccharide (LPS). Among obese animals, females are more sensitive to endotoxin liver injury than males. LPS induction of tumor necrosis factor alpha (TNF alpha), the proven affecter of endotoxin liver injury, is no greater in the livers, white adipose tissues, or sera of obese animals than in those of lean controls. Indeed, the lowest serum concentrations of TNF occur in female obese rodents, which exhibit the most endotoxin-induced liver injury. Several cytokines that modulate the biological activity of TNF are regulated abnormally in the livers of obese animals. After exposure to LPS, mRNA of interferon gamma, which sensitizes hepatocytes to TNF toxicity, is overexpressed, and mRNA levels of interleukin 10, a TNF inhibitor, are decreased. The phagocytic activity of liver macrophages and the hepatic expression of a gene encoding a macrophage-specific receptor are also decreased in obesity. This new animal model of obesity-associated liver disease demonstrates that hepatic macrophage dysfunction occurs in obesity and suggests that this might promote steatohepatitis by sensitizing hepatocytes to endotoxin.

A tunable topological insulator in the spin helical Dirac transport regime

Helical Dirac fermions-charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum-are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics. Prominent examples include the anomalous quantization of magneto-electric coupling, half-fermion states that are their own antiparticle, and charge fractionalization in a Bose-Einstein condensate, all of which are not possible with conventional Dirac fermions of the graphene variety. Helical Dirac fermions have so far remained elusive owing to the lack of necessary spin-sensitive measurements and because such fermions are forbidden to exist in conventional materials harbouring relativistic electrons, such as graphene or bismuth. It has recently been proposed that helical Dirac fermions may exist at the edges of certain types of topologically ordered insulators-materials with a bulk insulating gap of spin-orbit origin and surface states protected against scattering by time-reversal symmetry-and that their peculiar properties may be accessed provided the insulator is tuned into the so-called topological transport regime. However, helical Dirac fermions have not been observed in existing topological insulators. Here we report the realization and characterization of a tunable topological insulator in a bismuth-based class of material by combining spin-imaging and momentum-resolved spectroscopies, bulk charge compensation, Hall transport measurements and surface quantum control. Our results reveal a spin-momentum locked Dirac cone carrying a non-trivial Berry's phase that is nearly 100 per cent spin-polarized, which exhibits a tunable topological fermion density in the vicinity of the Kramers point and can be driven to the long-sought topological spin transport regime. The observed topological nodal state is shown to be protected even up to 300 K. Our demonstration of room-temperature topological order and non-trivial spin-texture in stoichiometric Bi(2)Se(3).M(x) (M(x) indicates surface doping or gating control) paves the way for future graphene-like studies of topological insulators, and applications of the observed spin-polarized edge channels in spintronic and computing technologies possibly at room temperature.

Metformin reverses fatty liver disease in obese, leptin-deficient mice

There is no known treatment for fatty liver, a ubiquitous cause of chronic liver disease. However, because it is associated with hyperinsulinemia and insulin-resistance, insulin-sensitizing agents might be beneficial. To evaluate this possibility, insulin-resistant ob/ob mice with fatty livers were treated with metformin, an agent that improves hepatic insulin-resistance. Metformin improved fatty liver disease, reversing hepatomegaly, steatosis and aminotransferase abnormalities. The therapeutic mechanism likely involves inhibited hepatic expression of tumor necrosis factor (TNF) alpha and TNF-inducible factors that promote hepatic lipid accumulation and ATP depletion. These findings suggest a mechanism of action for metformin and identify novel therapeutic targets in insulin-resistant states.

Failure of B-cell differentiation in mice lacking the transcription factor EBF

Early B-cell factor (EBF) is a cell type-specific transcription factor that is expressed at all antigen-independent stages of B-lymphocyte differentiation and participates in the regulation of the mb-1 gene. Here we show, by targeted gene disruption in mice, that EBF is necessary for the generation of immunoglobulin-expressing B cells. EBF-deficient mice lack B cells that have rearranged their immunoglobulin D and JH gene segments, but contain B220+CD43+ progenitor cells that express germline mu and IL-7 receptor transcripts. Various non-lymphoid tissues that express EBF are apparently normal in homozygous mutant mice, including olfactory neurons in which EBF was identified as Olf-1 (refs 5, 6). Together, these data suggest that EBF plays a specific and important role in the transcriptional control of B-cell differentiation at a stage before Ig (immunoglobulin) gene rearrangement but after commitment of cells to the B-lymphoid lineage.

Amyloid beta protein forms ion channels: implications for Alzheimer's disease pathophysiology

Amyloid beta protein (AbetaP) is the major constituent of senile plaques associated with Alzheimer's disease (AD). However, its mechanistic role in AD pathogenesis is poorly understood. Globular and nonfibrillar AbetaPs are continuously released during normal metabolism. Using techniques of atomic force microscopy, laser confocal microscopy, electrical recording, and biochemical assays, we have examined the molecular conformations of reconstituted globular AbetaPs as well as their real-time and acute effects on neuritic degeneration. Atomic force microscopy (AFM) of AbetaP1-42 shows globular structures that do not form fibers in physiological-buffered solution for up to 8 h of continuous imaging. AFM of AbetaP1-42 reconstituted in a planar lipid bilayer reveals multimeric channel-like structures. Consistent with these AFM resolved channel-like structures, biochemical analysis demonstrates that predominantly monomeric AbetaPs in solution form stable tetramers and hexamers after incorporation into lipid membranes. Electrophysiological recordings demonstrate the presence of multiple single channel currents of different sizes. At the cellular level, AbetaP1-42 allows calcium uptake and induces neuritic abnormality in a dose- and time-dependent fashion. At physiological nanomolar concentrations, rapid neuritic degeneration was observed within minutes; at micromolar concentrations, neuronal death was observed within 3-4 h. These effects are prevented by zinc (an AbetaP channel blocker) and by the removal of extracellular calcium, but are not prevented by antagonists of putative AbetaP cell surface receptors. Thus, AbetaP channels may provide a direct pathway for calcium-dependent AbetaP toxicity in AD.

A novel group of pumilio mutations affects the asymmetric division of germline stem cells in the Drosophila ovary

Germline stem cells play a pivotal role in gametogenesis; yet little is known about how they are formed, how they divide to self-renew, and how these processes are genetically controlled. Here we describe the self-renewing asymmetric division of germline stem cells in the Drosophila ovarian germline, as marked by the spectrosome, a cytoplasmic structure rich in membrane skeletal proteins. The ontogeny of the spectrosome marks the lineage of germline stem cells. We identified two new groups of mutations in which the divisional asymmetry is disrupted. The first, which we refer to as ovarette (ovt) mutations, was shown to correspond to a novel class of mutations in the pumilio locus. Since pumilio is known to posttranscriptionally repress the expression of target genes at earlier stages of germ cell development, our results suggest that a similar activity is needed to maintain germ line stem cells. We have also identified a second and novel gene, piwi, whose mutations abolish germline stem cell division.

The enhanced tumorigenic activity of a mutant epidermal growth factor receptor common in human cancers is mediated by threshold levels of constitutive tyrosine phosphorylation and unattenuated signaling

Deregulation of signaling by the epidermal growth factor receptor (EGFR) is common in human malignancy progression. One mutant EGFR (variously named DeltaEGFR, de2-7 EGFR, or EGFRvIII), which occurs frequently in human cancers, lacks a portion of the extracellular ligand-binding domain due to genomic deletions that eliminate exons 2 to 7 and confers a dramatic enhancement of brain tumor cell tumorigenicity in vivo. In order to dissect the molecular mechanisms of this activity, we analyzed location, autophosphorylation, and attenuation of the mutant receptors. The mutant receptors were expressed on the cell surface and constitutively autophosphorylated at a significantly decreased level compared with wild-type EGFR activated by ligand treatment. Unlike wild-type EGFR, the constitutively active DeltaEGFR were not down-regulated, suggesting that the altered conformation of the mutant did not result in exposure of receptor sequence motifs required for endocytosis and lysosomal sorting. Mutational analysis showed that the enhanced tumorigenicity was dependent on intrinsic tyrosine kinase activity and was mediated through the carboxyl terminus. In contrast with wild-type receptor, mutation of any major tyrosine autophosphorylation site abolished these activities suggesting that the biological functions of DeltaEGFR are due to low constitutive activation with mitogenic effects amplified by failure to attenuate signaling by receptor down-regulation.

High prevalence of left ventricular systolic and diastolic asynchrony in patients with congestive heart failure and normal QRS duration

OBJECTIVE

To study the possible occurrence of left ventricular (LV) systolic and diastolic asynchrony in patients with systolic heart failure (HF) and narrow QRS complexes.

DESIGN

Prospective study.

SETTING

University teaching hospital.

PATIENTS

200 subjects were studied by echocardiography. 67 patients had HF and narrow QRS complexes (< or = 120 ms), 45 patients had HF and wide QRS complexes (> 120 ms), and 88 served as normal controls.

INTERVENTIONS

Echocardiography with tissue Doppler imaging was performed using a six basal, six mid-segmental model.

MAIN OUTCOME MEASURES

Severity and prevalence of systolic and diastolic asynchrony, as assessed by the maximal difference in time to peak myocardial systolic contraction (T(S)) and early diastolic relaxation (T(E)), and the standard deviation of T(S) (T(S)-SD) and of T(E) (T(E)-SD) of the 12 LV segments.

RESULTS

The mean (SD) maximal difference in T(S) (controls 53 (23) ms v narrow QRS 107 (54) ms v wide QRS 130 (51) ms, both p < 0.001 v controls) and in T(S)-SD (controls 17.0 (7.8) ms v narrow QRS 33.8 (16.9) ms v wide QRS 42.0 (16.5) ms, both p < 0.001 v controls) was prolonged in the narrow QRS group compared with normal controls. Similarly, the maximal difference in T(E) (controls 59 (19) ms v narrow QRS 104 (71) ms v wide QRS 148 (87) ms, both p < 0.001 v controls) and in T(E)-SD (controls 18.5 (5.8) ms v narrow QRS 33.3 (27.7) ms v wide QRS 48.6 (30.2) ms, both p < 0.001 v controls) was prolonged in the narrow QRS group. The prevalence of systolic and diastolic asynchrony was 51% and 46%, respectively, in the narrow QRS group, and 73% and 69%, respectively, in the wide QRS group. Stepwise multiple regression analysis showed that a low mean myocardial systolic velocity from the six basal LV segments and a large LV end systolic diameter were independent predictors of systolic asynchrony, while a low mean myocardial early diastolic velocity and QRS complex duration were independent predictors of diastolic asynchrony.

CONCLUSIONS

LV systolic and diastolic mechanical asynchrony is common in patients with HF with narrow QRS complexes. As QRS complex duration is not a determinant of systolic asynchrony, it implies that assessment of intraventricular synchronicity is probably more important than QRS duration in considering cardiac resynchronisation treatment.

T-cell activation by the CD28 ligand B7 is required for cardiac allograft rejection in vivo

Organ graft rejection is a T-cell-dependent process. The activation of alloreactive T cells requires stimulation of the T-cell receptor/CD3 complex by foreign major histocompatibility complex (MHC)-encoded gene products. However, accumulating evidence suggests that, in addition to T-cell receptor occupancy, other costimulatory signals are required to induce T-cell activation. Previously, the CD28 receptor expressed on T cells has been shown to serve as a surface component of a signal transduction pathway that can provide costimulation. In vitro, interaction of CD28 with its natural ligand B7 expressed on the surface of activated B cells or macrophages can act as a costimulus to induce proliferation and lymphokine production in antigen receptor-activated T cells. We now report evidence that stimulation of T cells by the CD28 ligand B7 is a required costimulatory event for the rejection of a MHC-incompatible cardiac allograft in vivo. These results demonstrate that the B7/CD28 activation pathway plays an important role in regulating in vivo T-cell responses.

Long-term acceptance of major histocompatibility complex mismatched cardiac allografts induced by CTLA4Ig plus donor-specific transfusion

Allograft rejection is a T cell-dependent process. Productive T cell activation by antigen requires antigen engagement of the T cell receptor as well as costimulatory signals delivered through other T cell surface molecules such as CD28. Engagement of CD28 by its natural ligand B7 can be blocked using a soluble recombinant fusion protein, CTLA4Ig. Administration of CTLA4Ig blocks antigen-specific immune responses in vitro and in vivo, and we have shown that treatment of rats with a 7-d course of CTLA4Ig at the time of transplantation leads to prolonged survival of cardiac allografts (median 30 d), although most grafts are eventually rejected. Here, we have explored additional strategies employing CTLA4Ig in order to achieve long-term allograft survival. Our data indicate that donor-specific transfusion (DST) plus CTLA4Ig can provide effective antigen-specific immunosuppression. When DST is administered at the time of transplantation followed by a single dose of CTLA4Ig 2 d later, all animals had long-term graft survival (> 60 d). These animals had delayed responses to donor-type skin transplants, compared with normal rejection responses to third-party skin transplants. Furthermore, donor-matched second cardiac allografts were well tolerated with minimal histologic evidence of rejection. These data indicate that peritransplant use of DST followed by subsequent treatment with CTLA4Ig can induce prolonged, often indefinite, cardiac allograft acceptance. These results may be clinically applicable for cadaveric organ and tissue transplantation in humans.

piwi encodes a nucleoplasmic factor whose activity modulates the number and division rate of germline stem cells

piwi represents the first class of genes known to be required for stem cell self-renewal in diverse organisms. In the Drosophila ovary, piwi is required in somatic signaling cells to maintain germline stem cells. Here we show that piwi encodes a novel nucleoplasmic protein present in both somatic and germline cells, with the highly conserved C-terminal region essential for its function. Removing PIWI protein from single germline stem cells significantly decreases the rate of their division. This suggests that PIWI has a second role as a cell-autonomous promoter of germline stem cell division. Consistent with its dual function, over-expression of piwi in somatic cells causes an increase both in the number of germline stem cells and the rate of their division. Thus, PIWI is a key regulator of stem cell division - its somatic expression modulates the number of germline stem cells and the rate of their division, while its germline expression also contributes to promoting stem cell division in a cell-autonomous manner.

The Drosophila fusome, a germline-specific organelle, contains membrane skeletal proteins and functions in cyst formation

Oogenesis in Drosophila takes place within germline cysts that support polarized transport through ring canals interconnecting their 15 nurse cells and single oocyte. Developing cystocytes are spanned by a large cytoplasmic structure known as the fusome that has been postulated to help form ring canals and determine the pattern of nurse cell-oocyte interconnections. We identified the adducin-like hts product and alpha-spectrin as molecular components of fusomes, discovered a related structure in germline stem cells and documented regular associations between fusomes and cystocyte centrosomes. hts mutations completely eliminated fusomes, causing abnormal cysts containing a reduced number of cells to form. Our results imply that Drosophila fusomes are required for ovarian cyst formation and suggest that membrane skeletal proteins regulate cystocyte divisions.

Growth suppression of glioma cells by PTEN requires a functional phosphatase catalytic domain

Deletions of all or part of chromosome 10 are the most common genetic alterations in high-grade gliomas. The PTEN gene (also called MMAC1 and TEP1) maps to chromosome region 10q23 and has been implicated as a target of alteration in gliomas and also in other cancers such as those of the breast, prostate, and kidney. Here we sought to provide a functional test of its candidacy as a growth suppressor in glioma cells. We used a combination of Northern blot analysis, protein truncation assays, and sequence analysis to determine the types and frequency of PTEN mutations in glioma cell lines so that we could define appropriate recipients to assess the growth suppressive function of PTEN by gene transfer. Introduction of wild-type PTEN into glioma cells containing endogenous mutant alleles caused growth suppression, but was without effect in cells containing endogenous wild-type PTEN. The ectopic expression of PTEN alleles, which carried mutations found in primary tumors and have been shown or are expected to inactivate its phosphatase activity, caused little growth suppression. These data strongly suggest that PTEN is a protein phosphatase that exhibits functional and specific growth-suppressing activity.

Obesity induces expression of uncoupling protein-2 in hepatocytes and promotes liver ATP depletion

Uncoupling protein 2 (UCP2) uncouples respiration from oxidative phosphorylation and may contribute to obesity through effects on energy metabolism. Because basal metabolic rate is decreased in obesity, UCP2 expression is predicted to be reduced. Paradoxically, hepatic expression of UCP2 mRNA is increased in genetically obese (ob/ob) mice. In situ hybridization and immunohistochemical analysis of ob/ob livers demonstrate that UCP2 mRNA and protein expression are increased in hepatocytes, which do not express UCP2 in lean mice. Mitochondria isolated from ob/ob livers exhibit an increased rate of H+ leak which partially dissipates the mitochondrial membrane potential when the rate of electron transport is suppressed. In addition, hepatic ATP stores are reduced and these livers are more vulnerable to necrosis after transient hepatic ischemia. Hence, hepatocytes adapt to obesity by up-regulating UCP2. However, because this decreases the efficiency of energy trapping, the cells become vulnerable to ATP depletion when energy needs increase acutely.

Observation of time-reversal-protected single-dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3

We show that the strongly spin-orbit coupled materials Bi2Te3 and Sb2Te3 and their derivatives belong to the Z2 topological-insulator class. Using a combination of first-principles theoretical calculations and photoemission spectroscopy, we directly show that Bi2Te3 is a large spin-orbit-induced indirect bulk band gap (delta approximately 150 meV) semiconductor whose surface is characterized by a single topological spin-Dirac cone. The electronic structure of self-doped Sb2Te3 exhibits similar Z2 topological properties. We demonstrate that the dynamics of spin-Dirac fermions can be controlled through systematic Mn doping, making these materials classes potentially suitable for topological device applications.

Mitochondrial adaptations to obesity-related oxidant stress

It is not known why viable hepatocytes in fatty livers are vulnerable to necrosis, but associated mitochondrial alterations suggest that reactive oxygen species (ROS) production may be increased. Although the mechanisms for ROS-mediated lethality are not well understood, increased mitochondrial ROS generation often precedes cell death, and hence, might promote hepatocyte necrosis. The aim of this study is to determine if liver mitochondria from obese mice with fatty hepatocytes actually produce increased ROS. Secondary objectives are to identify potential mechanisms for ROS increases and to evaluate whether ROS increase uncoupling protein (UCP)-2, a mitochondrial protein that promotes ATP depletion and necrosis. Compared to mitochondria from normal livers, fatty liver mitochondria have a 50% reduction in cytochrome c content and produce superoxide anion at a greater rate. They also contain 25% more GSH and demonstrate 70% greater manganese superoxide dismutase activity and a 35% reduction in glutathione peroxidase activity. Mitochondrial generation of H(2)O(2) is increased by 200% and the activities of enzymes that detoxify H(2)O(2) in other cellular compartments are abnormal. Cytosolic glutathione peroxidase and catalase activities are 42 and 153% of control values, respectively. These changes in the production and detoxification of mitochondrial ROS are associated with a 300% increase in the mitochondrial content of UCP-2, although the content of beta-1 ATP synthase, a constitutive mitochondrial membrane protein, is unaffected. Supporting the possibility that mitochondrial ROS induce UCP-2 in fatty hepatocytes, a mitochondrial redox cycling agent that increases mitochondrial ROS production upregulates UCP-2 mRNAs in primary cultures of normal rat hepatocytes by 300%. Thus, ROS production is increased in fatty liver mitochondria. This may result from chronic apoptotic stress and provoke adaptations, including increases in UCP-2, that potentiate necrosis.

Eradication of established intracranial rat gliomas by transforming growth factor beta antisense gene therapy

Like human gliomas, the rat 9L gliosarcoma secretes the immunosuppressive transforming growth factor beta (TGF-beta). Using the 9L model, we tested our hypothesis that genetic modification of glioma cells to block TGF-beta expression may enhance their immunogenicity and make them more suitable for active tumor immunotherapy. Subcutaneous immunizations of tumor-bearing animals with 9L cells genetically modified to inhibit TGF-beta expression with an antisense plasmid vector resulted in a significantly higher number of animals surviving for 12 weeks (11/11, 100%) compared to immunizations with control vector-modified 9L cells (2/15, 13%) or 9L cells transduced with an interleukin 2 retroviral vector (3/10, 30%) (P < 0.001 for both comparisons). Histologic evaluation of implantation sites 12 weeks after treatment revealed no evidence of residual tumor. In vitro tumor cytotoxicity assays with lymph node effector cells revealed a 3- to 4-fold increase in lytic activity for the animals immunized with TGF-beta antisense-modified tumor cells compared to immunizations with control vector or interleukin 2 gene-modified tumor cells. These results indicate that inhibition of TGF-beta expression significantly enhances tumor-cell immunogenicity and supports future clinical evaluation of TGF-beta antisense gene therapy for TGF-beta-expressing tumors.