The role of autophagy in oncogenesis remains ambiguous, and mechanisms that induce autophagy and regulate its outcome in human cancers are poorly understood. The maternally imprinted Ras-related ...tumor suppressor gene aplasia Ras homolog member I (ARHI; also known as DIRAS3) is downregulated in more than 60% of ovarian cancers, and here we show that re-expression of ARHI in multiple human ovarian cancer cell lines induces autophagy by blocking PI3K signaling and inhibiting mammalian target of rapamycin (mTOR), upregulating ATG4, and colocalizing with cleaved microtubule-associated protein light chain 3 (LC3) in autophagosomes. Furthermore, ARHI is required for spontaneous and rapamycin-induced autophagy in normal and malignant cells. Although ARHI re-expression led to autophagic cell death when SKOv3 ovarian cancer cells were grown in culture, it enabled the cells to remain dormant when they were grown in mice as xenografts. When ARHI levels were reduced in dormant cells, xenografts grew rapidly. However, inhibition of ARHI-induced autophagy with chloroquine dramatically reduced regrowth of xenografted tumors upon reduction of ARHI levels, suggesting that autophagy contributed to the survival of dormant cells. Further analysis revealed that autophagic cell death was reduced when cultured human ovarian cancer cells in which ARHI had been re-expressed were treated with growth factors (IGF-1, M-CSF), angiogenic factors (VEGF, IL-8), and matrix proteins found in xenografts. Thus, ARHI can induce autophagic cell death, but can also promote tumor dormancy in the presence of factors that promote survival in the cancer microenvironment.
Tandem organic light‐emitting diodes (OLEDs) with an organic–organic intermediate connector, consisting of an n‐type doped electron‐transporting layer (e.g. Li‐doped Alq as shown in the figure) and ...nondoped hexaazatriphenylene hexacarbonitrile (HAT‐CN), exhibit reduced drive voltage, improved voltage stability, and improved power efficiency. Moreover, this intermediate connector can be formed by thermal evaporation at temperatures lower than 300 °C, which simplifies the fabrication process of the OLEDs.
Context. The Gaia mission has released the second data set (Gaia DR2), which contains parallaxes and proper motions for a large number of massive, young stars. Aims. We investigate the spiral ...structure in the solar neighborhood revealed by Gaia DR2 and compare it with that depicted by VLBI maser parallaxes. Methods. We examined three samples with different constraints on parallax uncertainty and distance errors and stellar spectral types: (1) all OB stars with parallax errors of less than 10%; (2) only O-type stars with 0.1 mas errors imposed and with parallax distance errors of less than 0.2 kpc; and (3) only O-type stars with 0.05 mas errors imposed and with parallax distance errors of less than 0.3 kpc. Results. In spite of the significant distance uncertainties for stars in DR2 beyond 1.4 kpc, the spiral structure in the solar neighborhood demonstrated by Gaia agrees well with that illustrated by VLBI maser results. The O-type stars available from DR2 extend the spiral arm models determined from VLBI maser parallaxes into the fourth Galactic quadrant, and suggest the existence of a new spur between the Local and Sagittarius arms.
Epidemics of obesity and diabetes are escalating. High-calorie/high-fat food is a major cause for these global health issues, but molecular mechanisms underlying high-fat, diet-induced obesity are ...still not well understood. The aryl hydrocarbon receptor (AhR), a transcription factor that acts as a xenobiotic sensor, mediates environmental toxicant-induced obesity, insulin resistance and development of diabetes. AhR also influences lipid metabolism and diet-induced obesity. The effects of AhR deficiency on diet-induced obesity, hepatic steatosis and insulin resistance were examined.
Male wild-type (WT), AhR null (AhR(-/-)) and AhR heterozygote (AhR(+/-)) mice were fed a normal chow diet (NCD, 10% kcal from fat) or a high-fat diet (HFD, 60% kcal from fat) for up to 14 weeks. Adiposity, adipose and liver morphology, insulin signaling, metabolic parameters and gene profiles were assessed.
AhR deficiency protected against HFD-induced obesity, hepatic steatosis, insulin resistance and inflammation. Moreover, AhR deficiency preserved insulin signaling in major metabolic tissues. These protective effects result from a higher energy expenditure in AhR-deficient mice compared with WT. Levels of transcript for both the thermogenic gene, uncoupling protein 1 (Ucp1), in brown adipose tissue and mitochondrial β-oxidation genes in muscle were significantly higher in AhR(-/-) and AhR(+/-) mice compared with WT.
This work documents a physiologically relevant function for AhR in regulation of body weight, hepatic fat deposition, insulin sensitivity and energy expenditure under HFD exposure, suggesting that AhR signaling may be developed as a potential therapeutic target for treatment of obesity and metabolic disorders.
Abstract
Aims
Adipocyte fatty acid-binding protein (A-FABP) is an adipokine implicating in various metabolic diseases. Elevated circulating levels of A-FABP correlate positively with poor prognosis ...in ischaemic stroke (IS) patients. No information is available concerning the role of A-FABP in the pathogenesis of IS. Experiments were designed to determine whether or not A-FABP mediates blood–brain barrier (BBB) disruption, and if so, to explore the molecular mechanisms underlying this deleterious effects.
Methods and results
Circulating A-FABP and its cerebral expression were increased in mice after middle cerebral artery occlusion. Genetic deletion and pharmacological inhibition of A-FABP alleviated cerebral ischaemia injury with reduced infarction volume, cerebral oedema, neurological deficits, and neuronal apoptosis; BBB disruption was attenuated and accompanied by reduced degradation of tight junction proteins and induction of matrix metalloproteinases-9 (MMP-9). In patients with acute IS, elevated circulating A-FABP levels positively correlated with those of MMP-9 and cerebral infarct volume. Mechanistically, ischaemia-induced elevation of A-FABP selectively in peripheral blood monocyte-derived macrophages and cerebral resident microglia promoted MMP-9 transactivation by potentiating JNK/c-Jun signalling, enhancing degradation of tight junction proteins and BBB leakage. The detrimental effects of A-FABP were prevented by pharmacological inhibition of MMP-9.
Conclusion
A-FABP is a key mediator of cerebral ischaemia injury promoting MMP-9-mediated BBB disruption. Inhibition of A-FABP is a potential strategy to improve IS outcome.
The process of autophagy has been described in detail at the molecular level in normal cells, but less is known of its regulation in cancer cells. Aplasia Ras homolog member I (ARHI; DIRAS3) is an ...imprinted tumor suppressor gene that is downregulated in multiple malignancies including ovarian cancer. Re-expression of ARHI slows proliferation, inhibits motility, induces autophagy and produces tumor dormancy. Our previous studies have implicated autophagy in the survival of dormant ovarian cancer cells and have shown that ARHI is required for autophagy induced by starvation or rapamycin treatment. Re-expression of ARHI in ovarian cancer cells blocks signaling through the PI3K and Ras/MAP pathways, which, in turn, downregulates mTOR and initiates autophagy. Here we show that ARHI is required for autophagy-meditated cancer cell arrest and ARHI inhibits signaling through PI3K/AKT and Ras/MAP by enhancing internalization and degradation of the epidermal growth factor receptor. ARHI-mediated downregulation of PI3K/AKT and Ras/ERK signaling also decreases phosphorylation of FOXo3a, which sequesters this transcription factor in the nucleus. Nuclear retention of FOXo3a induces ATG4 and MAP-LC3-I, required for maturation of autophagosomes, and also increases the expression of Rab7, required for fusion of autophagosomes with lysosomes. Following the knockdown of FOXo3a or Rab7, autophagolysosome formation was observed but was markedly inhibited, resulting in numerous enlarged autophagosomes. ARHI expression correlates with LC3 expression and FOXo3a nuclear localization in surgical specimens of ovarian cancer. Thus, ARHI contributes to the induction of autophagy through multiple mechanisms in ovarian cancer cells.
The epidemiology of candidaemia varies between hospitals and geographic regions. Although there are many studies from Asia, a large-scale cross-sectional study across Asia has not been performed. We ...conducted a 12-month, laboratory-based surveillance of candidaemia at 25 hospitals from China, Hong Kong, India, Singapore, Taiwan and Thailand. The incidence and species distribution of candidaemia were determined. There were 1601 episodes of candidaemia among 1.2 million discharges. The overall incidence was 1.22 episodes per 1000 discharges and varied among the hospitals (range 0.16–4.53 per 1000 discharges) and countries (range 0.25–2.93 per 1000 discharges). The number of Candida blood isolates and the total number of fungal isolates were highly correlated among the six countries (R² = 0.87) and 25 hospitals (R² = 0.77). There was a moderate correlation between incidence of candidaemia and the intensive care unit (ICU)/total bed ratio (R² = 0.47), although ICUs contributed to only 23% of candidaemia cases. Of 1910 blood isolates evaluated, Candida albicans was most frequently isolated (41.3%), followed by Candida tropicalis (25.4%), Candida glabrata (13.9%) and Candida parapsilosis (12.1%). The proportion of C. tropicalis among blood isolates was higher in haemato-oncology wards than others wards (33.7% versus 24.5%, p 0.0058) and was more likely to be isolated from tropical countries than other Asian countries (46.2% versus 18.9%, p 0.04). In conclusion, the ICU settings contribute, at least in part, to the incidence variation among hospitals. The species distribution is different from Western countries. Both geographic and healthcare factors contribute to the variation of species distribution.
Ovarian cancers migrate and metastasize over the surface of the peritoneal cavity. Consequently, dysregulation of mechanisms that limit cell migration may be particularly important in the ...pathogenesis of the disease. ARHI is an imprinted tumor-suppressor gene that is downregulated in >60% of ovarian cancers, and its loss is associated with decreased progression-free survival. ARHI encodes a 26-kDa GTPase with homology to Ras. In contrast to Ras, ARHI inhibits cell growth, but whether it also regulates cell motility has not been studied previously. Here we report that re-expression of ARHI decreases the motility of IL-6- and epidermal growth factor (EGF)-stimulated SKOv3 and Hey ovarian cancer cells, inhibiting both chemotaxis and haptotaxis. ARHI binds to and sequesters Stat3 in the cytoplasm, preventing its translocation to the nucleus and localization in focal adhesion complexes. Stat3 siRNA or the JAK2 inhibitor AG490 produced similar inhibition of motility. However, the combination of ARHI expression with Stat3 knockdown or inhibition produced greatest inhibition in ovarian cancer cell migration, consistent with Stat3-dependent and Stat3-independent mechanisms. Consistent with two distinct signaling pathways, knockdown of Stat3 selectively inhibited IL-6-stimulated migration, whereas knockdown of focal adhesion kinase (FAK) preferentially inhibited EGF-stimulated migration. In EGF-stimulated ovarian cancer cells, re-expression of ARHI inhibited FAK(Y397) and Src(Y416) phosphorylation, disrupted focal adhesions, and blocked FAK-mediated RhoA signaling, resulting in decreased levels of GTP-RhoA. Re-expression of ARHI also disrupted the formation of actin stress fibers in a FAK- and RhoA-dependent manner. Thus, ARHI has a critical and previously uncharacterized role in the regulation of ovarian cancer cell migration, exerting inhibitory effects on two distinct signaling pathways.
Pigment epithelial-derived factor (PEDF) is a potent anti-angiogenic factor whose effects are partially mediated through the induction of endothelial cell apoptosis. The pathway mediating endothelial ...cell apoptosis has not been fully established. Here we investigated the participation of peroxisome proliferator-activated receptor gamma (PPARgamma) and p53 in the apoptosis of human umbilical vein endothelial cells (HUVECs).
HUVECs pretreated with either PPARgamma antagonist or PPARgamma small interfering RNA (siRNA) suppressed PEDF-induced apoptosis as determined by TUNEL assay, annexin V-FITC/PI staining, and cleavage of procaspase-8, -9, -3. PEDF sequentially induced PPARgamma and p53 expression as observed in immunoblotting and immunofluoresence assays. PEDF also increased the transcriptional activity of PPARgamma as evident from electromobility shift assays, and p53 as determined by the phosphorylation and acetylation of p53 and the induction of Bax. The induction of p53 by PEDF was abolished by either PPARgamma antagonist or PPARgamma siRNA. PEDF-mediated HUVEC apoptosis and cleavage of procaspases were significantly attenuated by p53 siRNA.
Our observations indicate that PEDF induces HUVECs apoptosis through the sequential induction of PPARgamma and p53 overexpression. With the growing interest in anti-angiogenesis as a novel approach to cancer therapy, defining the mechanism of PEDF-mediated HUVEC apoptosis may facilitate the development of new therapeutics.
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