The antiangiogenic 16K prolactin impairs functional tumor neovascularization by inhibiting vessel maturation

Background

Angiogenesis, the formation of new blood vessels from existing vasculature, plays an essential role in tumor growth, invasion, and metastasis. 16K hPRL, the antiangiogenic 16-kDa N-terminal fragment of human prolactin was shown to prevent tumor growth and metastasis by modifying tumor vessel morphology.

Methodology/Principal Findings

Here we investigated the effect of 16K hPRL on tumor vessel maturation and on the related signaling pathways. We show that 16K hPRL treatment leads, in a murine B16-F10 tumor model, to a dysfunctional tumor vasculature with reduced pericyte coverage, and disruption of the PDGF-B/PDGFR-B, Ang/Tie2, and Delta/Notch pathways. In an aortic ring assay, 16K hPRL impairs endothelial cell and pericyte outgrowth from the vascular ring. In addition, 16K hPRL prevents pericyte migration to endothelial cells. This event was independent of a direct inhibitory effect of 16K hPRL on pericyte viability, proliferation, or migration. In endothelial cell-pericyte cocultures, we found 16K hPRL to disturb Notch signaling.

Conclusions/Significance

Taken together, our data show that 16K hPRL impairs functional tumor neovascularization by inhibiting vessel maturation and for the first time that an endogenous antiangiogenic agent disturbs Notch signaling. These findings provide new insights into the mechanisms of 16K hPRL action and highlight its potential for use in anticancer therapy.     

Effect of peripherally administered ghrelin on gastric emptying and acid secretion in the rat

Ghrelin is a gut peptide that is secreted from the stomach and stimulates food intake. There are ghrelin receptors throughout the gut and intracerebroventricular ghrelin has been shown to increase gastric acid secretion. The aim of the present study was to examine the effects of peripherally administered ghrelin on gastric emptying of a non-nutrient and nutrient liquid, as well as, basal and pentagastrin-stimulated gastric acid secretion in awake rats. In addition, gastric contractility was studied in vitro. Rats equipped with a gastric fistula were subjected to an intravenous infusion of ghrelin (10-500 pmol kg(-1) min(-1)) during saline or pentagastrin (90 pmol kg(-1) min(-1)) infusion. After administration of polyethylene glycol (PEG) 4000 with 51Cr as radioactive marker, or a liquid nutrient with (51)Cr, gastric retention was measured after a 20-min infusion of ghrelin (500 pmol kg(-1) min(-1)). In vitro isometric contractions of segments of rat gastric fundus were studied (10(-9) to 10(-6) M). Ghrelin had no effect on basal acid secretion, but at 500 pmol kg(-1) min(-1) ghrelin significantly decreased pentagastrin-stimulated acid secretion. Ghrelin had no effect on gastric emptying of the nutrient liquid, but significantly increased gastric emptying of the non-nutrient liquid. Ghrelin contracted fundus muscle strips dose-dependently (pD2 of 6.93+/-0.7). Ghrelin IV decreased plasma orexin A concentrations and increased plasma somatostatin concentrations. Plasma gastrin concentrations were unchanged during ghrelin infusion. Thus, ghrelin seems to not only effect food intake but also gastric motor and secretory function indicating a multifunctional role for ghrelin in energy homeostasis.     

Apoplastic oxidation of L-asparagine is involved in the control of the green algal endophyte Acrochaete operculata Correa & Nielsen by the red seaweed Chondrus crispus Stackhouse

Gametophytes of the marine alga Chondrus crispus are more resistant than tetrasporophytes to infection by the filamentous endophytic alga Acrochaete operculata. It has been shown recently that carrageenan oligosaccharides from the resistant gametophytic generation of C. crispus stimulate the secretion of L-asparagine (L-Asn) by the endophyte and that the host generates hydrogen peroxide and 2-oxo-succinamic acid after contact with this amino acid. Here the response of C. crispus to L-Asn and its effect on the pathogen is investigated. Chondrus crispus released hydrogen peroxide, ammonium ions, and a carbonyl compound into the medium when exposed to L-Asn. This response was correlated with an increase in oxygen consumption. Inhibitor studies indicated the involvement of a flavoenzyme in the reaction, which was sensitive to high concentrations of the reaction product, ammonium, and to chlorpromazine, quinacrine, and cyanide, inhibitors of L-amino acid oxidase. Cell wall macerate of C. crispus also responded to L-Asn, while protoplasts were inactive. Uptake of L-Asn into the cell was not necessary for the response, suggesting that the involved L-amino acid oxidase is apoplastic. Acrochaete operculata was more sensitive to hydrogen peroxide than C. crispus and settlement of A. operculata zoospores on C. crispus was reduced by 86% in the presence of L-Asn. This reduced settlement could be prevented with catalase. Chondrus crispus thus features an apoplastic amino acid oxidase, which is involved in the control of its endophytic pathogen. The modulation of the amino acid secretion in A. operculata by carrageenan oligosaccharides is therefore a key issue in the etiology of the association.     

Characterization and reconstitution of a 4Fe-4S adenylyl sulfate/phosphoadenylyl sulfate reductase from Bacillus subtilis

CysH1 from Bacillus subtilis encodes a 3'-phospho/adenosine-phosphosulfate-sulfonucleotide reductase (SNR) of 27 kDa. Recombinant B. subtilis SNR is a homodimer, which is bispecific and reduces adenylylsulfate (APS) and 3'-phosphoadenylylsulfate (PAPS) alike with thioredoxin 1 or with glutaredoxin 1 as reductants. The enzyme has a higher affinity for PAPS (K(m)PAPS 6.4 microm Trx-saturating, 10.7 microm Grx-saturating) than for APS (K(m) APS 28.7 microm Trx-saturating, 105 microm Grx-saturating) at a V(max) ranging from 280 to 780 nmol sulfite mg(-1) min(-1). The catalytic efficiency with PAPS as substrate is higher by a factor of 10 (K(cat)/K(m) 2.7 x 10(4)-3.6 x 10(4) liter mol(-1) s(-1). B. subtilis SNR contains one 4Fe-4S cluster per polypeptide chain. SNR activity and color were lost rapidly upon exposure to air or upon dilution. M?ssbauer and absorption spectroscopy revealed that the enzyme contained a 4Fe-4S cluster when isolated, but degradation of the 4Fe-4S cluster produced an inactive intermediate with spectral properties of a 2Fe-2S cluster. Activity and spectral properties of the 4Fe-4S cluster were restored by preincubation of SNR with the iron-sulfur cluster-assembling proteins IscA1 and IscS. Reconstitution of the 4Fe-4S cluster of SNR did not affect the reductive capacity for PAPS or APS. The interconversion of the clusters is thought to serve as oxygen-sensitive switch that suppresses SO(3) formation under aerobiosis.     

Semaphorin 3d promotes cell proliferation and neural crest cell development downstream of TCF in the zebrafish hindbrain

Neural crest cells (NCCs) are pluripotent migratory cells that are crucial to the development of the peripheral nervous system, pigment cells and craniofacial cartilage and bone. NCCs are specified within the dorsal ectoderm and undergo an epithelial to mesenchymal transition (EMT) in order to migrate to target destinations where they differentiate. Here we report a role for a member of the semaphorin family of cell guidance molecules in NCC development. Morpholino-mediated knockdown of Sema3d inhibits the proliferation of hindbrain neuroepithelial cells. In addition, Sema3d knockdown reduces markers of migratory NCCs and disrupts NCC-derived tissues. Similarly, expression of a dominant-repressor form of TCF (DeltaTCF) reduces hindbrain cell proliferation and leads to a disruption of migratory NCC markers. Moreover, expression of DeltaTCF downregulates sema3d RNA expression. Finally, Sema3d overexpression rescues reduced proliferation caused by DeltaTCF expression, suggesting that Sema3d lies downstream of Wnt/TCF signaling in the molecular pathway thought to control cell cycle in NCC precursors.     

Vaspin gene expression in human adipose tissue: association with obesity and type 2 diabetes

Recently, vaspin was identified as an adipokine with insulin-sensitizing effects, which is predominantly secreted from visceral adipose tissue in a rat model of type 2 diabetes. In this study, we examined whether vaspin mRNA expression is a marker of visceral obesity and correlates with anthropometric and metabolic parameters in paired samples of visceral and subcutaneous adipose tissue from 196 subjects with a wide range of obesity, body fat distribution, insulin sensitivity, and glucose tolerance. Vaspin mRNA expression was only detectable in 23% of the visceral and in 15% of the subcutaneous (SC) adipose tissue samples. Vaspin mRNA expression was not detectable in lean subjects (BMI<25) and was more frequently detected in patients with type 2 diabetes. No significant correlations were found between visceral vaspin gene expression and visceral fat area or SC vaspin expression. However, visceral vaspin expression significantly correlates with BMI, % body fat, and 2 h OGTT plasma glucose. Subcutaneous vaspin mRNA expression is significantly correlated with WHR, fasting plasma insulin concentration, and glucose infusion rate during steady state of an euglycemic-hyperinsulinemic clamp. Multivariate linear regression analysis revealed % body fat as strongest predictor of visceral vaspin and insulin sensitivity as strongest determinant of SC vaspin mRNA expression. In conclusion, our data indicate that induction of human vaspin mRNA expression in adipose tissue is regulated in a fat depot-specific manner and could be associated with parameters of obesity, insulin resistance, and glucose metabolism.     

Energy crops as a new bird habitat: utilization of oilseed rape fields by the rare Bluethroat (Luscinia svecica)

As part of the expanding cultivation of renewable primary products, oilseed rape has become a prominent part of the agricultural landscape of many European countries. However, the ecological impacts of increasing cultivation of oilseed rape have received little attention so far. In this study, we provide the first systematic investigation of the suitability of oilseed rape as a habitat for the Bluethroat (Luscinia svecica cyanecula), an endangered and highly specialized bird species. We conducted territorial mapping and a habitat analysis, revealing the distinct habitat requirements of L. s. cyanecula in oilseed rape fields over three breeding seasons. The soil type was identified as the crucial factor for habitat occupancy. It acts as a surrogate for soil moisture and this in turn decisively influences food availability. Ditches can further improve habitat quality, whereas reed is not a necessary structure, although it is a regular feature in the primary habitat of the Bluethroat. Occupied oilseed rape stands were structurally different from the semi-natural reed habitat, but provided similar essential habitat requirements, such as shelter from predation and moist, bare soil. Our results clearly demonstrate the utilization of oilseed rape by a rare and threatened wetland bird species and suggest that this crop may act as a secondary habitat.     

Synthesis and evaluation of substituted hexahydronaphthalenes as novel inhibitors of the Mcl-1/BimBH3 interaction

Mcl-1, an anti-apoptotic member of the Bcl-2 protein family, is overexpressed in a broad range of human cancers and plays a critical role in conferring resistance to chemotherapy. In the course of screening a natural product-like library of sesquiterpenoid analogs, we identified substituted hexahydronaphthalenes that showed activity against the Mcl-1/BimBH3 interaction in vitro. Here, we describe the synthesis of a small library of analogs and their biological evaluation. The most potent inhibitor in the series (19) exhibits an IC(50) of 8.3μM by ELISA and disrupts the interaction between endogenously expressed Mcl-1 and Bim in cultured MDA-MB-468 breast cancer cells.