Epidemiology and Management of the 2013-16 West African Ebola Outbreak.

The 2013-16 West African Ebola outbreak is the largest, most geographically dispersed, and deadliest on record, with 28,616 suspected cases and 11,310 deaths recorded to date in Guinea, Liberia, and Sierra Leone. We provide a review of the epidemiology and management of the 2013-16 Ebola outbreak in West Africa aimed at stimulating reflection on lessons learned that may improve the response to the next international health crisis caused by a pathogen that emerges in a region of the world with a severely limited health care infrastructure. Surveillance efforts employing rapid and effective point-of-care diagnostics designed for environments that lack advanced laboratory infrastructure will greatly aid in early detection and containment efforts during future outbreaks. Introduction of effective therapeutics and vaccines against Ebola into the public health system and the biodefense armamentarium is of the highest priority if future outbreaks are to be adequately managed and contained in a timely manner.

Targeting angiogenic processes by combination rofecoxib and ionizing radiation.

Tumor growth and angiogenesis are interdependent. Cyclooxygenase (COX) catalyzes the synthesis of prostaglandins from arachidonic acid. Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit COX-mediated synthesis of prostaglandins. COX-1 is constitutively expressed in a wide range of tissues, whereas COX-2 is cytokine inducible. Enhanced COX-2 expression has been attributed a key role in the development of inflammation and related processes observed in pathologically altered disease states. Two specific COX-2 inhibitors, namely rofecoxib (Vioxx) and celecoxib (Celebrex), both oral agents and U.S. Food and Drug Administration approved, have been shown preclinically and clinically to have efficacy comparable to that of NSAIDs for relief of pain and inflammation in osteoarthritis, with decreased risk of gastrointestinal damage. Little is known about how angiogenesis is affected by the combination of rofecoxib and radiation. We have evaluated the combination of rofecoxib, at various concentrations, and radiation on cytokine-induced angiogenesis in vitro. We have found that rofecoxib inhibited endothelial cell proliferation, migration, and tube formation (differentiation) at clinically relevant doses. In combination with radiation, inhibition of endothelial cell function further increased twofold. The combination of rofecoxib and radiation suggests a complementary strategy with clinical ramifications to target angiogenesis-dependent malignancies.

A differential outcomes effect using biologically neutral outcomes in delayed matching-to-sample with pigeons.

The differential outcomes effect (DOE) pertains to enhanced conditional discrimination performance if each correct stimulus-choice sequence is always followed by a different outcome (e.g., food vs. water) compared to when each correct sequence is followed equally often by either outcome. The present experiments sought evidence of a DOE in pigeons, using biologically neutral outcomes. Experiment 1 replicated findings with rats demonstrating that a DOE can occur when one outcome is a biologically neutral light and the other is the absence of that light. Experiment 2 extended these findings by demonstrating a DOE when two biologically neutral outcomes of similar sensory and associative properties were employed.

Revascularization of ischemic tissues with SIKVAV and neuropeptide Y (NPY).

Angiogenesis, the process of new vessel growth, is necessary for many normal physiological and pathological processes such as tumor growth, wound healing and ischemia. We have recently examined in vitro and in vivo the ability of two potent angiogenic compounds, SIKVAV (a peptide derived from the alpha chain of laminin-1) and Neuropeptide Y (NPY) to revascularize ischemic tissue. These compounds were tested in an ex vivo capillary sprouting angiogenesis assay that uses rat aortic rings. Both NPY and SIKVAV in the presence of VEGF, stimulated the formation of long sprouts at concentrations of 1 ng NPY (0.2 pmol/L) and 100 micrograms SIKVAV. In comparison very little sprouting occurred in the control rings and 50 ng of VEGF alone was required to induce equivalent number of sprouts as NPY. SIKVAV and NPY were further tested in vivo in a rat hindlimb ischemic model. Both compounds (500 micrograms SIKVAV and 10 ng of NPY) were embedded in the rat hind limb following unilateral ligation of the femoral artery 1 cm proximal to the adductor hiatus. After two weeks control peptides show little or no revascularization of the hindlimb distal to the ligation; however, both SIKVAV and NPY demonstrated a two-fold increase in new vessels in the region proximal to the ligation. Histological sections of latex perfused hindlimb demonstrated that ligated limbs had very few latex-filled dermal capillaries. Limbs treated with SIKVAV and NPY, however, demonstrated normal distribution in the dermal capillary beds. These data indicate that both SIKVAV and NPY are potent angiogenic factors that show promising potential clinical application to the revascularization of ischemic tissue.

Effects of microenvironmental extracellular pH and extracellular matrix proteins on angiostatin's activity and on intracellular pH.

Antiangiogenic agents target migratory and proliferative endothelial cells (EC) in the process of forming new vessels, resulting in growth inhibition or cell death. Here we have shown that the antiangiogenic activity of angiostatin on EC is enhanced in culture when the microenvironmental extracellular pH (pH(e)) is reduced to levels similar to that of many tumors. In a migration/scratch assay and during tube formation, angiostatin in combination with reduced pH(e) synergistically resulted in an increased EC death--an effect not seen with either stimulus individually. Lowering of pH(e) decreased intracellular pH (pH(i)), and a further lowering of pH(i) occurred when low pH(e) was combined with angiostatin. These data suggest that low pH(e) plays a role in the relative specificity and efficacy of angiostatin for tumor neovasculature and indicate roles for both pH(e) and pH(i) in the mechanism of angiostatin action. A receptor for angiostatin, the alpha-subunit of ATP synthase, was found on the surface of EC. We show that cell surface receptor distribution is increased on Matrigel, a basement-like matrix, as opposed to fibronectin or RGD peptide substrates, and redistributed to a more punctuate appearance at low pH(e). Furthermore, positive cell surface histochemical staining for alpha-ATP synthase was blocked by preincubation with angiostatin. These data indicate that substrate and pH(e) are critical parameters in the evaluation of this antiangiogenic substance, and probably for others as well.

The role of laminin-1 in the modulation of radiation damage in endothelial cells and differentiation.

Microvascular dysfunction due to endothelial damage is often associated with the ionizing radiation used during cancer therapy. This radiation-induced capillary injury is a major factor in the inhibition of new vessel growth (angiogenesis) and in disease states such as radiation-induced pneumonitis and nephropathy. Many studies have examined the effects of radiation on endothelial cell function; however, little is known regarding the role the basement membrane plays in radiation-induced endothelial cell damage and angiogenesis. Therefore, we examined the effects of gamma radiation on aortic explants, and in vitro on three endothelial cell types (of artery, vein and capillary origin) irradiated with or without the basement membrane glycoprotein laminin-1. As expected, irradiation inhibited angiogenic sprouting of the aortic explants, endothelial cell proliferation, attachment, migration and differentiation in vitro in a dose-dependent manner. However, the effect of radiation on several of these processes in angiogenesis was reduced when the cells were irradiated on laminin-1. To further evaluate the effects of radiation on endothelial cells, we examined the expression of the vascular endothelial cell growth factor (VEGF) kinase domain region receptor in endothelial cells irradiated in the presence and absence of laminin-1. In endothelial cells irradiated on laminin-1, KDR expression increased 2.5-fold over control levels. Therefore, although radiation has a dose-dependent inhibitory effect on processes associated with angiogenesis in vitro, the presence of the basement membrane glycoprotein laminin-1 during irradiation decreases these effects.

Estradiol enhances endothelial cell interactions with extracellular matrix proteins via an increase in integrin expression and function.

Premenopausal women have a lower cardiovascular risk and a higher incidence of several autoimmune diseases involving blood vessels than men. Although the precise effects of estrogens on the cardiovascular system are largely unknown, recent data suggest that estrogens can exert direct regulatory effects on endothelial cells. In the present study, we show that 17beta-estradiol increases human umbilical vein endothelial cell attachment to the extracellular matrix proteins laminin-1, type IV collagen, type I collagen, and fibronectin. Estradiol enhanced adhesion most significantly to laminin-1 and to fibronectin-derived synthetic peptides containing an RGD sequence. Upon exposure to estradiol, an increase in beta1, alpha5 and alpha6 integrin mRNA was observed in subconfluent cells which was abrogated by treatment with cycloheximide. This increase was followed by a later enhancement in surface expression of the above integrins. In addition, integrin-mediated signaling was also enhanced by estrogens since an increase in tyrosine-phosphorylation of focal adhesion kinase induced by cell attachment was observed in estrogen-treated endothelial cells. Since integrins have an important role in mediating endothelial cell attachment, migration and differentiation, the increase in integrin expression and function induced by estradiol may be an important mechanism through which estrogens can promote neovascularization and vessel repair.

Thymosin beta4 enhances endothelial cell differentiation and angiogenesis.

When human umbilical vein endothelial cells (HUVEC) differentiate into capillary-like tubes, there is a five-fold upregulation of the mRNA for thymosin beta4 (Tbeta4) (Grant et al. J Cell Sci 1995; 108: 3685-94 [1]) and this endogenous expression plays an important role in endothelial cell attachment to and spreading on matrix components. We now show that exogenous addition of thymosin beta4 (in the ng-microg range) to HUVEC in culture can induce several biological responses. These responses include increased tube formation in vitro. Additionally, exogenous thymosin beta4 enhances vascular sprouting in the coronary artery ring angiogenesis assay. Measurements of these vascular sprouts show a doubling of the vessel area (via increased branching) with as little as 100 ng of synthetic thymosin beta4. These processes appear to involve the binding of thymosin beta4 to an unknown cell surface receptor and internalization of the protein. This cell surface-binding appears not to be mediated through the thymosin beta4-actin binding domain LKTET. An increase in thymosin beta4 cytoplasmic staining in HUVEC exposed 10 microg of the peptide appears to occur without increased mRNA translation. In summary Tbeta4 induces an increase in cell-matrix attachment, proliferation, tube formation, internalization of the peptide and rearrangement of the actin cytoskeleton. The data now defines both an autocrine and paracrine role for thymosin beta4 in vessel formation.

Neuropeptide Y: a novel angiogenic factor from the sympathetic nerves and endothelium.

Sympathetic nerves have long been suspected of trophic activity, but the nature of their angiogenic factor has not been determined. Neuropeptide Y (NPY), a sympathetic cotransmitter, is the most abundant peptide in the heart and the brain. It is released during nerve activation and ischemia and causes vasoconstriction and smooth muscle cell proliferation. Here we report the first evidence that NPY is angiogenic. At low physiological concentrations, in vitro, it promotes vessel sprouting and adhesion, migration, proliferation, and capillary tube formation by human endothelial cells. In vivo, in a murine angiogenic assay, NPY is angiogenic and is as potent as a basic fibroblast growth factor. The NPY action is specific and is mediated by Y1 and Y2 receptors. The expression of both receptors is upregulated during cell growth; however, Y2 appears to be the main NPY angiogenic receptor. Its upregulation parallels the NPY-induced capillary tube formation on reconstituted basement membrane (Matrigel); the Y2 agonist mimics the tube-forming activity of NPY, whereas the Y2 antagonist blocks it. Endothelium contains not only NPY receptors but also peptide itself, its mRNA, and the "NPY-converting enzyme" dipeptidyl peptidase IV (both protein and mRNA), which terminates the Y1 activity of NPY and cleaves the Tyr1-Pro2 from NPY to form an angiogenic Y2 agonist, NPY3-36. Endothelium is thus not only the site of action of NPY but also the origin of the autocrine NPY system, which, together with the sympathetic nerves, may be important in angiogenesis during tissue development and repair.

VE-Cadherin mediates endothelial cell capillary tube formation in fibrin and collagen gels.

Various cell adhesion molecules mediate the diverse functions of the vascular endothelium, such as cell adhesion, neutrophil migration, and angiogenesis. In order to identify cell adhesion molecules important for angiogenesis, we used an in vitro model (Chalupowicz, Chowdhury, Bach, Barsigian, and Martinez, J. Cell Biol. 130, 207-215, 1995) in which human umbilical vein endothelial cell monolayers are induced to form capillary-like tubes when a second gel, composed of either fibrin or collagen, is formed overlying the apical surface. In the present investigation, we observed that a monoclonal antibody directed against the first extracellular domain of human vascular endothelial cadherin (VE-cadherin, cadherin 5) inhibited the formation of capillary tubes formed between either fibrin or collagen gels. Moreover, when added to preformed capillary tubes, this antibody disrupted the capillary network. In contrast, monoclonal antibodies directed against the extracellular domain of N-cadherin, the alphavbeta3 integrin, and PECAM-1 failed to inhibit capillary tube formation. During capillary tube formation, Western blot and RT-PCR analysis revealed no marked change in VE-cadherin expression. Immunocytochemical studies demonstrated that VE-cadherin was concentrated at intercellular junctions in multicellular capillary tubes. Thus, VE-cadherin plays a specific role in fibrin-induced or collagen-induced capillary tube formation and is localized at areas of intercellular contact where it functions to maintain the tubular architecture. Moreover, its function at tubular intercellular junctions is distinct from that at intercellular junctions present in confluent monolayers, since only the former was inhibited by monoclonal antibodies.

Thrombin promotes endothelial cell alignment in Matrigel in vitro and angiogenesis in vivo.

We have tested the effect of thrombin on endothelial cell tube formation in vitro and angiogenesis in vivo. Thrombin induces the differentiation of endothelial cells into capillary structures in a dose-dependent fashion (0.1-0.3 units thrombin/ml) on Matrigel, a laminin-rich reconstituted basement membrane matrix. At higher thrombin concentrations (1.0 unit/ml), a suppression of tube formation is evident, probably due to downregulation (desensitization) of the thrombin receptor. D-Phe-Pro-Arg-CH2Cl-thrombin is without effect when used alone, but it abolishes the tube-promoting effect of thrombin when used in combination with thrombin, indicating the involvement of the catalytic site of thrombin. Activation of protein kinase C (PKC) seems to be the transduction mechanism involved in the stimulation of tube formation by thrombin. Ro-318220 (3 micrograms/ml), a specific inhibitor of PKC, completely abolishes the stimulatory effect of thrombin. In the in vivo Matrigel system of angiogenesis, there is a 10-fold increase in endothelial cell infiltration in response to thrombin. These results provide evidence for the angiogenesis-promoting effect of thrombin in vivo and the induction by thrombin of the angiogenic phenotype of endothelial cells in vitro in the absence of other cell types such as smooth muscle cells, pericytes, and inflammatory cells.

A role for perlecan in the suppression of growth and invasion in fibrosarcoma cells.

Perlecan is a major heparan sulfate proteoglycan of basement membranes and cell surfaces. Because of its strategic location and ability to store and protect growth factors, perlecan has been implicated in the control of tumor cell growth and metastatic behavior. To test the role of perlecan in malignancy, we generated several stably transfected clones of HT-1080, a human fibrosarcoma cell line, harboring a perlecan cDNA in the antisense orientation. Surprisingly, clones with a reduced synthesis of perlecan mRNA and protein core grew faster, formed larger colonies in semisolid agar, and induced faster formation of s.c. tumors in nude mice than the wild-type cells. Their growth properties in vitro were independent of exogenous basic fibroblast growth factor. Reduction of perlecan expression was associated with three distinct properties typical of tumor cells with a more aggressive phenotype: enhanced migration through 8-microm-pore filter, increased invasion in Matrigel-coated filters, and heightened adhesiveness to type IV collagen substrata. These results thus provide the first evidence that perlecan may inhibit the growth and invasiveness of fibrosarcoma cells in a basic fibroblast growth factor-independent pathway and raise the possibility that perlecan may prevent the infiltration of host tissues in mesenchymal neoplasms.

Regulation of capillary formation by laminin and other components of the extracellular matrix.

The process of angiogenesis (vessel formation) and the resulting stabilization of the mature vessel are complex events that are highly regulated and require signals from both serum and the extracellular matrix. Endothelial cells rest on a specialized thin extracellular matrix known as the basement membrane. Endothelial cells lining normal blood vessels are usually quiescent. When a proper stimulus is present, angiogenesis beings when endothelial cells degrade their basement membrane and invade the surrounding extravascular matrix. Formation of new vessels involves the migration and proliferation of cells. To assist the cells in their migration, the extravascular matrix provides an environment rich in stromal collagen fibers, fibrin, hyaluoronic acid, vitronectin and fibronectin. Once the endothelial cells assemble to form a new vessel, the cells secrete a basement membrane that helps to stabilize and maintain the vessel wall. The basement membrane adheres tightly to cells comprising the vessel wall, provides inductive signals, and plays a important role in the homeostasis of new vessels. We have demonstrated that two major components of the basement membrane, laminin and collagen IV, possess endothelial cell binding sites which regulate vessel stability. In this chapter, we will define the role of these molecules in endothelial cell behavior.

Matrigel induces thymosin beta 4 gene in differentiating endothelial cells.

We performed differential cDNA hybridization using RNA from endothelial cells cultured for 4 hours on either plastic or basement membrane matrix (Matrigel), and identified early genes induced during the morphological differentiation into capillary-like tubes. The mRNA for one clone, thymosin beta 4, was increased 5-fold. Immunostaining localized thymosin beta 4 in vivo in both growing and mature vessels as well as in other tissues. Endothelial cells transfected with thymosin beta 4 showed an increased rate of attachment and spreading on matrix components, and an accelerated rate of tube formation on Matrigel. An antisense oligo to thymosin beta 4 inhibited tube formation on Matrigel. The results suggest that thymosin beta 4 is induced and likely involved in differentiating endothelial cells. Thymosin beta 4 may play a role in vessel formation in vivo.

Abscess drainage techniques.

Percutaneous abscess drainage of infected and sterile collections within the body is a cost and clinically effective technique. The principles and pitfalls of the technique are outlined and an algorithm is included to aid patient management.

Estrogen promotes angiogenic activity in human umbilical vein endothelial cells in vitro and in a murine model.

BACKGROUND: Angiogenesis is a critical event in wound healing, tumor growth, and the inflammatory vasculitides. Since women have a higher incidence of many vasculitic diseases, we examined the effects of female sex steroids, particularly estradiol, on human umbilical vein endothelial cell (HUVEC) behavior in vitro and on angiogenesis in vivo. METHODS AND RESULTS: HUVECs were grown in estrogen-free medium before each assay. Exogenous 17 beta-estradiol (1 to 5 nmol/L) increased cell attachment to laminin, types I and IV collagen, and fibronectin, as well as to tissue culture plastic. After a confluent monolayer of cells was "wounded" by scraping, estradiol-treated (10(-8) mol/L) cells migrated into the wound three times faster than untreated cells. Cell proliferation on plastic and on laminin increased threefold to fivefold, respectively, in the presence of estradiol. Estradiol also enhanced the ability of HUVECs to organize into tubular networks when plated on a reconstituted basement membrane, Matrigel. Estradiol effects on both the "wounding" assay and tube formation were blocked by the specific estrogen receptor antagonist ICI 182,780. Ovariectomy markedly decreased in vivo vascularization of Matrigel plugs coinjected with basic fibroblast growth factor in mice. With estrogen replacement, angiogenesis was increased to the levels observed in nonovariectomized mice. CONCLUSIONS: These studies demonstrate that, in vitro and in vivo, estradiol enhances endothelial cell activities important in neovascularization and suggest a promoting influence of estrogens on angiogenesis.

Angiogenesis as a component of epithelial-mesenchymal interactions.

Here we review the role of angiogenesis as it pertains to the interactions between the epithelium and the mesenchyme, especially during tumor growth and metastasis. We illustrate and discuss several models of angiogenesis including endothelial tube formation on Matrigel. Finally, we examine angiogenic factors using the Matrigel model and investigate several other matrix molecules for their importance in angiogenesis and epithelial/stromal interactions.

E-selectin-mediated dynamic interactions of breast- and colon-cancer cells with endothelial-cell monolayers.

The molecular mechanisms involved in the dynamic interaction of human breast carcinoma cells with the endothelial cell lining of lymphatic vessels and post-capillary blood venules are largely unknown. In the present study, laminar flow assays were used to investigate the ability of various normal breast cells and of breast- and colon-tumor cells to adhere to human umbilical cord endothelial cell monolayers. MCF-10A breast, MCF-7 and T-47D breast-carcinoma and clone A, RKO, and HT-29 colon-carcinoma cells accumulated and rolled, in the presence of flow, on tumor necrosis factor (TNF)-stimulated but not on unstimulated endothelial cell monolayers. Non-tumor and tumor cells continued to form transient adhesions with TNF-stimulated endothelial cells even when the flow rate was increased to levels found in arteries. Incubation of TNF-stimulated endothelial cells with an E-selectin-specific monoclonal antibody (MAb) partially or completely inhibited dynamic interactions and diminished adhesion strength, whereas integrin beta 1- and integrin alpha 6-specific MAbs had no effect. A set of highly invasive breast-carcinoma cells (MDA-231, BT-549, HS-578t) neither adhered to nor rolled on resting or TNF-stimulated endothelial cell monolayers. However, after 5 min of static incubation, a fraction of these cells attached strongly to resting and TNF-stimulated endothelial cells and this static adhesion could not be blocked by an E-selectin-specific monoclonal antibody. Our results suggest that E-selectin is a major homing receptor in the metastasis of some breast and colon cancers.

Inhibitors of basement membrane collagen synthesis prevent endothelial cell alignment in matrigel in vitro and angiogenesis in vivo.

BACKGROUND: The formation of a basement membrane is the last step in the development of a new blood vessel. Matrigel, a laminin-rich reconstituted basement membrane matrix induces the differentiation of endothelial cells into capillary-like structures. EXPERIMENTAL DESIGN: The effect of inhibitors of basement membrane collagen synthesis, tricyclodecan-9-yl xanthate (D609) and 8,9-dihydroxy-7-methyl-benzo[b] quinolizinium bromide (GPA 1734), was investigated on endothelial cell tube formation on Matrigel in vitro and in an angiogenesis assay in C57 black mice in vivo. RESULTS: D609 and GPA 1734 caused a dose-dependent decrease in tube formation in vitro with complete inhibition at 50 micrograms/ml for D609 and 15 micrograms/ml for GPA 1734. The inhibitory effect on capillary tube formation by both agents was reversible. Tube formation correlated well with collagenous protein biosynthesis. Parallel studies on endothelial cells cultured on plastic indicate that cell viability, proliferation, attachment, and morphology were not affected by the presence of these collagen inhibitors at doses that blocked tube formation and collagen biosynthesis. D609 and GPA 1734 also inhibited endothelial cell infiltration in response to SIKVAV in an in vivo angiogenesis model system. CONCLUSIONS: These results indicate that newly synthesised collagen is a prerequisite for expression of the endothelial cell phenotype for tube formation and that prevention of collagenous protein biosynthesis inhibits tube formation and angiogenesis in vivo.