146 research outputs found
Regulation of AKT phosphorylation at Ser473 and Thr308 by endoplasmic reticulum stress modulates substrate specificity in a severity dependent manner.
Endoplasmic reticulum (ER) stress is a common factor in the pathophysiology of diverse human diseases that are characterised by contrasting cellular behaviours, from proliferation in cancer to apoptosis in neurodegenerative disorders. Coincidently, dysregulation of AKT/PKB activity, which is the central regulator of cell growth, proliferation and survival, is often associated with the same diseases. Here, we demonstrate that ER stress modulates AKT substrate specificity in a severity-dependent manner, as shown by phospho-specific antibodies against known AKT targets. ER stress also reduces both total and phosphorylated AKT in a severity-dependent manner, without affecting activity of the upstream kinase PDK1. Normalisation to total AKT revealed that under ER stress phosphorylation of Thr308 is suppressed while that of Ser473 is increased. ER stress induces GRP78, and siRNA-mediated knock-down of GRP78 enhances phosphorylation at Ser473 by 3.6 fold, but not at Thr308. Substrate specificity is again altered. An in-situ proximity ligation assay revealed a physical interaction between GRP78 and AKT at the plasma membrane of cells following induction of ER stress. Staining was weak in cells with normal nuclear morphology but stronger in those displaying rounded, condensed nuclei. Co-immunoprecipitation of GRP78 and P-AKT(Ser473) confirmed the immuno-complex consists of non-phosphorylated AKT (Ser473 and Thr308). The interaction is likely specific as AKT did not bind to all molecular chaperones, and GRP78 did not bind to p70 S6 kinase. These findings provide one mechanistic explanation for how ER stress contributes to human pathologies demonstrating contrasting cell fates via modulation of AKT signalling
In vitro and in vivo effects of the PPAR-alpha agonists fenofibrate and retinoic acid in endometrial cancer.
UNLABELLED: Fenofibrate, an agonist of PPAR-alpha, in doses above 25 microM, inhibits proliferation and induces apoptosis in Ishikawa endometrial cancer cells. We show that these effects are potentiated by retinoic acid, an agonist of the retinoid-X-receptor. DNA content analysis shows that G1/S phase progression through the cell cycle is inhibited. Independent Component Analysis of gene microarray experiments demonstrated downregulation of Cyclin D1 (CCND1) and associated changes in cell cycle gene expression. Expression of PPAR-alpha mRNA was reduced by >75% using RNA-interference but this resulted in only minor changes in biological effects. A nude mouse model of endometrial carcinoma was used to investigate the effect of fenofibrate in vivo but failed to show consistent inhibition of tumour growth. CONCLUSION: The combination of fenofibrate and retinoic acid is a potent inhibitor of Ishikawa endometrial cancer cell growth in vitro
The Effect of an Oxytocin Receptor Antagonist (Retosiban, GSK221149A) on the Response of Human Myometrial Explants to Prolonged Mechanical Stretch.
Multiple pregnancy is a major cause of spontaneous preterm birth, which is related to uterine overdistention. The objective of this study was to determine whether an oxytocin receptor antagonist, retosiban (GSK221149A), inhibited the procontractile effect of stretch on human myometrium. Myometrial biopsies were obtained at term planned cesarean delivery (n = 12). Each biopsy specimen was dissected into 8 strips that were exposed in pairs to low or high stretch (0.6 or 2.4 g) in the presence of retosiban (1 μM) or vehicle (dimethylsulfoxide) for 24 hours. Subsequently, we analyzed the contractile responses to KCl and oxytocin in the absence of retosiban. We found that incubation under high stretch in vehicle alone increased the response of myometrial explants to both KCl (P = .007) and oxytocin (P = .01). However, there was no statistically significant effect of stretch when explants were incubated with retosiban (P = .3 and .2, respectively). Incubation with retosiban in low stretch had no statistically significant effect on the response to either KCl or oxytocin (P = .8 and >.9, respectively). Incubation with retosiban in high stretch resulted in a statistically significant reduction (median fold change, interquartile range, P) in the response to both KCl (0.74, 0.60-1.03, P = .046) and oxytocin (0.71, 0.53-0.91, P = .008). The greater the effect of stretch on explants from a given patient, the greater was the inhibitory effect of retosiban (r = -0.65, P = .02 for KCl and r= -0.73, P = .007 for oxytocin). These results suggest that retosiban prevented stretch-induced stimulation of human myometrial contractility. Retosiban treatment is a potential approach for preventing preterm birth in multiple pregnancy.This is the author accepted manuscript. The final version is available from the Endocrine Society via http://dx.doi.org/10.1210/en.2015-137
Models of endometriosis and their utility in studying progression to ovarian clear cell carcinoma.
Endometriosis is a common benign gynaecological condition affecting at least 10% of women of childbearing age and is characterized by pain--frequently debilitating. Although the exact prevalence is unknown, the economic burden is substantial (∼$50 billion a year in the USA alone) and it is associated with considerable morbidity. The development of endometriosis is inextricably linked to the process of menstruation and thus the models that best recapitulate the human disease are in menstruating non-human primates. However, the use of these animals is ethically challenging and very expensive. A variety of models in laboratory animals have been developed and the most recent are based on generating menstrual-like endometrial tissue that can be transferred to a recipient animal. These models are genetically manipulable and facilitate precise mechanistic studies. In addition, these models can be used to study malignant transformation in epithelial ovarian carcinoma. Epidemiological and molecular evidence indicates that endometriosis is the most plausible precursor of both clear cell and endometrioid ovarian cancer (OCCA and OEA, respectively). While this progression is rare, understanding the underlying mechanisms of transformation may offer new strategies for prevention and therapy. Our ability to pursue this is highly dependent on improved animal models but the current transgenic models, which genetically modify the ovarian surface epithelium and oviduct, are poor models of ectopic endometrial tissue. In this review we describe the various models of endometriosis and discuss how they may be applicable to developing our mechanistic understanding of OCCA and OEA.CMK was funded by a grant from CRUK (A13095). Part of the research work disclosed in this publication is funded by the Strategic Educational Pathways Scholarship (Malta) to CB. The scholarship is part-financed by the European Union-European Social Fund (ESF) under Operational Programme II-Cohesion Policy 2007-2013, "Empowering People for More Jobs and a Better Quality of Life”. JDB is supported by CRUK (A15601).This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/path.465
Soluble FLT1 sensitizes endothelial cells to inflammatory cytokines by antagonizing VEGF receptor-mediated signalling.
AIMS: Pre-eclampsia affects 5-7% of pregnancies, and is a major cause of maternal and foetal death. Elevated serum levels of placentally derived splice variants of the vascular endothelial growth factor (VEGF) receptor, soluble fms-like tyrosine kinase-1 (sFLT1), are strongly implicated in the pathogenesis but, as yet, no underlying mechanism has been described. An excessive inflammatory-like response is thought to contribute to the maternal endothelial cell dysfunction that characterizes pre-eclampsia. We hypothesized that sFLT1 antagonizes autocrine VEGF-A signalling, rendering endothelial cells more sensitive to pro-inflammatory factors also released by the placenta. We tested this by manipulating VEGF receptor signalling and treating endothelial cells with low doses of tumour necrosis factor-α (TNF-α). METHODS AND RESULTS: Application of recombinant sFLT1 alone did not activate human umbilical vein endothelial cells (HUVECs). However, antagonizing the autocrine actions of endothelial VEGF-A and/or placenta growth factor (PlGF) by pre-incubation with recombinant sFLT1, anti-FLT1, anti-VEGF receptor 2 (KDR), anti-VEGF-A, VEGF receptor tyrosine kinase inhibitor SU5614, or knocking-down FLT1 or KDR transcripts rendered cells more sensitive to low doses of TNF-α. Each treatment increased activation, as measured by increases in endothelial intercellular adhesion molecule 1 (ICAM1), vascular cell adhesion molecule 1 (VCAM1), endothelin 1 (ET-1), von Willebrand factor (vWF), and leucocyte adhesion, and led to reduction in AKT Ser⁴⁷³ and endothelial nitric oxide synthase (eNOS) Ser¹¹⁷⁷ phosphorylation. CONCLUSIONS: Our data describe a mechanism by which sFLT1 sensitizes endothelial cells to pro-inflammatory factors, providing an explanation for how placental stress may precipitate the pre-eclamptic syndrome
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Three-dimensional modeling of human placental terminal villi.
INTRODUCTION: Placental transport is the main factor affecting the health and development of the fetus. Due to the placenta's geometrical and mathematical complexity, the structure-function relations of placental terminal villi have not been successfully modeled. Hence, a novel modeling approach is proposed. METHODS: Computational models of four different specimens were generated from the three-dimensional reconstruction of confocal laser scanning microscopic image stacks. To evaluate the capabilities of the proposed methodology, stationary oxygen diffusion transport was calculated in the terminal villus volumes. RESULTS: The reconstructions automatically provided the spatial arrangement of the fetal capillaries inside the terminal villi. The surface and volume ratios between the fetal capillaries and the villus were also calculated, and the effects of model parameters on the placental diffusive capacity were assessed by parametric analysis. DISCUSSION: The potential of three-dimensional reconstructions combined with finite element analysis as a research tool for the human placenta was tested. The methodology herein could serve in the future as a simulation platform for complicated in vivo and in vitro scenarios.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.placenta.2016.05.00
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Placental energy metabolism in health and disease-significance of development and implications for preeclampsia.
The placenta is a highly metabolically active organ fulfilling the bioenergetic and biosynthetic needs to support its own rapid growth and that of the fetus. Placental metabolic dysfunction is a common occurrence in preeclampsia although its causal relationship to the pathophysiology is unclear. At the outset, this may simply be seen as an "engine out of fuel." However, placental metabolism plays a vital role beyond energy production and is linked to physiological and developmental processes. In this review, we discuss the metabolic basis for placental dysfunction and propose that the alterations in energy metabolism may explain many of the placental phenotypes of preeclampsia such as reduced placental and fetal growth, redox imbalance, oxidative stress, altered epigenetic and gene expression profiles, and the functional consequences of these aberrations. We propose that placental metabolic reprogramming reflects the dynamic physiological state allowing the tissue to adapt to developmental changes and respond to preeclampsia stress, whereas the inability to reprogram placental metabolism may result in severe preeclampsia phenotypes. Finally, we discuss common tested and novel therapeutic strategies for treating placental dysfunction in preeclampsia and their impact on placental energy metabolism as possible explanations into their potential benefits or harm.I.L.M.H. Aye is funded by a Next Generation Fellowship from the Centre for
20 Trophoblast Research, University of Cambridg
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Three-dimensional morphological analysis of placental terminal villi.
Transport of nutrients and waste between the maternal and fetal circulations during pregnancy takes place at the final branches of the placental villous trees. Therefore, and unsurprisingly, pregnancy complications have been related to the maldevelopment of terminal villi. However, a deep analysis of placental villous morphology has been limited by tissue processing and imaging techniques. In this proof-of-principle study, placental lobules were fixed by perfusion and small clumps of villi were stained, sectioned optically and reconstructed. Morphological and network analyses were suggested and demonstrated on samples of normal placentas. The results show that most parameters are almost constant within a placenta but that there exists an inter-individual variation. Network analysis suggests that the feto-placental capillary network has several paths within an individual villus, serving as an efficient transport system. Three-dimensional reconstruction from confocal laser scanning microscopy images is a potent technique able to quantify placental architecture and capture the significant irregularities in vessel diameter and membrane thickness. This approach has the potential to become a powerful tool to further our understanding of the differences in placental structure which may underlie pregnancy complications
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Screening for fetal growth restriction using fetal biometry combined with maternal biomarkers.
Fetal growth restriction is a major determinant of perinatal morbidity and mortality. Screening for fetal growth restriction is a key element of prenatal care but it is recognized to be problematic. Screening using clinical risk assessment and targeting ultrasound to high-risk women is the standard of care in the United States and United Kingdom, but the approach is known to have low sensitivity. Systematic reviews of randomized controlled trials do not demonstrate any benefit from universal ultrasound screening for fetal growth restriction in the third trimester, but the evidence base is not strong. Implementation of universal ultrasound screening in low-risk women in France failed to reduce the risk of complications among small-for-gestational-age infants but did appear to cause iatrogenic harm to false positives. One strategy to making progress is to improve screening by developing more sensitive and specific tests with the key goal of differentiating between healthy small fetuses and those that are small through fetal growth restriction. As abnormal placentation is thought to be the major cause of fetal growth restriction, one approach is to combine fetal biometry with an indicator of placental dysfunction. In the past, these indicators were generally ultrasonic measurements, such as Doppler flow velocimetry of the uteroplacental circulation. However, another promising approach is to combine ultrasonic suspicion of small-for-gestational-age infant with a blood test indicating placental dysfunction. Thus far, much of the research on maternal serum biomarkers for fetal growth restriction has involved the secondary analysis of tests performed for other indications, such as fetal aneuploidies. An exemplar of this is pregnancy-associated plasma protein A. This blood test is performed primarily to assess the risk of Down syndrome, but women with low first-trimester levels are now serially scanned in later pregnancy due to associations with placental causes of stillbirth, including fetal growth restriction. The development of "omic" technologies presents a huge opportunity to identify novel biomarkers for fetal growth restriction. The hope is that when such markers are measured alongside ultrasonic fetal biometry, the combination would have strong predictive power for fetal growth restriction and its related complications. However, a series of important methodological considerations in assessing the diagnostic effectiveness of new tests will have to be addressed. The challenge thereafter will be to identify novel disease-modifying interventions, which are the essential partner to an effective screening test to achieve clinically effective population-based screening
Morphological and molecular changes in the murine placenta exposed to normobaric hypoxia throughout pregnancy.
Chronic hypoxia is a common complication of pregnancy, arising through malperfusion of the placenta or pregnancy at high altitude. The present study investigated the effects of hypoxia on the growth of the placenta, which is the organ that interfaces between the mother and her fetus. Mice were housed in an hypoxic environment for the whole of gestation. An atmosphere of 13% oxygen induced fetal growth restriction (1182 ± 9 mg, n = 90 vs. 1044 ± 11 mg, n = 62, P < 0.05) but enhanced placental weight (907 ± 11 mg, n = 90 vs. 998 ± 15 mg, n = 62,P < 0.05). Stereological analyses revealed an increase in the volume of maternal blood spaces in the placenta, consistent with increased flow. At the molecular level, we observed activation of the protein kinase B (Akt)-mechanistic target of rapamycin growth and proliferation pathway. Chronic hypoxia also triggered mild endoplasmic reticulum stress, a conserved homeostatic response that mediates translational arrest through phosphorylation of eukaryotic initiation factor 2 subunit α. Surprisingly, although subunits of the mitochondrial electron transport chain complexes were reduced at the protein level, there was no evidence of intracellular energy depletion. Finally, we demonstrated sex-specific placental responses to chronic hypoxia. Placentas from male fetuses were heavier (1082 ± 2 mg, n = 30 vs. 928 ± 2 mg, n = 34, P < 0.05) and less susceptible to hypoxia-induced oxidative stress than those from females. Their capacity to adapt may explain why male fetuses were significantly less growth restricted at embryonic day 18.5 than their female counterparts. These findings are consistent with the concept that male fetuses are more aggressive with respect to their nutrient demands, which may place them at greater risk of adverse outcomes under limiting conditions.This study was supported by a grant from the Wellcome Trust
(084804/2/08/Z).This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1113/JP27107
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