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B B Weksler

Publications and source records attributed to B B Weksler.

At least 19 recordsLinked to original sources
PubMed1992

Fucoidan is a non-anticoagulant inhibitor of intimal hyperplasia.

We previously reported that heparin inhibits the proliferation of fibroblasts and vascular smooth muscle cells (SMC), in part, by binding to and increasing the antiproliferative activity of transforming growth factor-beta 1 (TGF-beta 1). We now report that certain other polyanions which are structurally distinct from heparin, such as fucoidan and polyinosinic acid, are more avid ligands for TGF-beta 1 and more potent antiproliferative agents than heparin. Fucoidan possessed more potent antiproliferative activity than heparin against rat and bovine aortic SMC in vitro, though possessing much lower anticoagulant activity than heparin. Furthermore, fucoidan suppressed in vivo intimal hyperplasia when continuously infused into rats subjected to balloon-catheter injury. Unlike heparin, which also suppressed intimal hyperplasia, fucoidan did not cause systemic anticoagulation. Thus, fucoidan may be useful as a non-anticoagulant inhibitor of post-angioplasty intimal hyperplasia.

Animals↗
PubMed1991

Heparanase activity in cultured endothelial cells.

This study was undertaken to identify a heparan sulfate (HS) degradation endoglycosidase (heparanase) in cultured endothelial cells (EC) and to characterize the requirements for its release and subsequent degradation of HS side chains in the subendothelial extracellular matrix (ECM). Intact EC, EC lysates, or EC conditioned media from different sources were incubated with metabolically Na2(35)SO4-labeled ECM produced by bovine EC. The released sulfated products were analyzed by gel filtration on Sepharose 6B. Human umbilical vein endothelial cells (HUVEC) and human saphenous vein endothelial cells (HSVEC) lysates expressed heparanase activity as indicated by release of most of the radioactivity from ECM as HS fragments that are one-fifth to one-sixth the size of the intact HS side chains. These fragments were sensitive to deamination with nitrous acid and were not produced in the presence of heparin. Rabbit coronary microvascular EC and bovine brain capillary EC lysates showed less heparanase activity (30-35%), whereas bovine aortic and corneal EC showed no activity. Intact HUVEC, plated directly on the labeled ECM, expressed low enzyme activity that was not changed when cells were exposed to various agents. Exposure of HUVEC to interleukin-1, phorbol myristate acetate, tumor necrosis factor, endotoxin, thrombin, calcium ionophore A23187, fibroblast growth factor, or radiation did not induce release of the enzyme to the medium or degradation of HS in the ECM, as long as the cells remained viable. EC differ from various normal and malignant cells that degrade HS by virtue of their inability to release the enzyme. We suggest that heparanase release during vessel wall injury may regulate the growth of EC and smooth muscle by release of HS degradation products in processes such as wound healing, neovascularization, and atherosclerosis.

Animals↗
PubMed1991

Naproxen-induced recurrent aseptic meningitis.

Aseptic meningitis has been linked to treatment with several nonsteroidal antiinflammatory drugs (e.g., ibuprofen, tolmetin, sulindac), particularly in patients with disturbed immunity. Naproxen, however, has only once been reported to cause meningitis. We report a case of recurrent aseptic meningitis related to prolonged naproxen usage in a 38-year-old woman with longstanding, minimally symptomatic systemic lupus erythematosus (SLE). Two years after starting naproxen, she experienced three separate episodes of meningitis within a period of 10 months; each episode was preceded by resumption of naproxen administration or an increase in drug dosage. There was no clinical or serologic evidence for the flare-ups of her SLE. Discontinuation of naproxen was followed by prompt recovery once the relationship of the drug to her symptoms was realized. Off the drug, the patient has remained free of meningeal symptoms for more than 18 months. Nonsteroidal antiinflammatory agents should be considered as possible causal agents in evaluating meningitis of obscure etiology.

Adult↗
PubMed1990

Modulation of muscarinic-receptor expression in human embryonic lung fibroblasts by platelet-derived growth factor.

Platelet-derived growth factor (PDGF) is known to have regulatory control of a large number of cellular components, including various receptors. We show that muscarinic acetylcholine receptors of the m2 subtype on CCL 137 human fibroblasts in culture are affected by PDGF treatment. A time-dependent down-regulation is observed in steady-state RNA levels, followed by a decrease in ligand-binding capacity. Minimum RNA levels are attained at 11 h; minimum binding capacity is observed after 24 h of treatment. To our knowledge, this is the first example of negative gene control by PDGF.

Cell Line↗
PubMed1990

Heparin and acidic fibroblast growth factor interact to decrease prostacyclin synthesis in human endothelial cells by affecting both prostaglandin H synthase and prostacyclin synthase.

Prostaglandin production by cultured human endothelial cells varies with growth conditions. We observed a marked diminution in both spontaneous and inducible production of prostacyclin (PGI2) by human umbilical vein and saphenous vein endothelial cells when they were cultured in the presence of the heparin-binding growth factor, acidic fibroblast growth factor (aFGF) and heparin, compared with PGI2 production during culture in medium lacking these factors. Decreased PGI2 production was related to duration of exposure of the cells to aFGF and heparin and depended on the concentration of both substances. Heparin (1-100 micrograms/ml) strongly potentiated the effects of aFGF but had a limited and variable effect alone. The decrease in PGI2 production correlated with a reduction in the cellular content of immunoreactive prostaglandin H synthase and prostacyclin synthase. Arachidonate deacylation was not decreased. In addition, the eicosanoid profile of endothelial cells was changed by exposure to aFGF and heparin. These studies indicate that heparin acts as a modulator of prostaglandin synthesis in endothelial cells through its interaction with aFGF, mediated by alterations in two key enzymes in the arachidonate metabolic pathway.

Arachidonic Acid↗
PubMed1989

Selenium deficiency inhibits prostacyclin release and enhances production of platelet activating factor by human endothelial cells.

Selenium is an essential component of glutathione peroxidase, an enzyme which protects cells against peroxidation and controls concentrations of intracellular peroxides. Since selenium deficiency is clinically associated with an increased degree of atherosclerosis, the effects of selenium deficiency on prostacyclin (PGI2) and platelet activating factor (PAF) production by cultured human umbilical vein endothelial cells (HUVEC) were investigated. In selenium-deficient HUVEC, histamine-induced PGI2 synthesis was significantly decreased when compared to selenium-supplemented HUVEC; in contrast, histamine-induced PAF production was increased by selenium deficiency. Histamine-induced inositol trisphosphate and [Ca2+]i responses and the conversion of PGG2 and PGH2 to PGI2 were not altered by selenium deficiency. However, selenium deficiency decreased the conversion of exogenous arachidonate to PGI2 and markedly suppressed glutathione peroxidase activity. These results suggest that selenium deficiency, by decreasing glutathione peroxidase activity, makes HUVEC susceptible to peroxide-induced inhibition of the cyclooxygenase activity of PGH2 synthase, resulting in decreased PGI2 production. These changes may alter platelet function in vivo and thus play a role in the increased incidence of atherosclerosis reported in selenium-deficient individuals.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Transforming growth factor-beta activity is potentiated by heparin via dissociation of the transforming growth factor-beta/alpha 2-macroglobulin inactive complex.

The control of smooth muscle cell (SMC) proliferation is determined by the combined actions of mitogens, such as platelet-derived growth factor, and the opposing action of growth inhibitory agents, such as heparin and transforming growth factor-beta (TGF-beta). The present studies identify an interaction between heparin and TGF-beta in which heparin potentiates the biological action of TGF-beta. Using a neutralizing antibody to TGF-beta, we observed that the short term antiproliferative effect of heparin depended upon the presence of biologically active TGF-beta. This effect was observed in rat and bovine aortic SMC and in CCL64 cells, but not in human saphenous vein SMC. Binding studies demonstrated that the addition of heparin (100 micrograms/ml) to medium containing 10% plasma-derived serum resulted in a 45% increase in the specific binding of 125I-TGF-beta to cells. Likewise, heparin induced a twofold increase in the growth inhibitory action of TGF-beta at concentrations of TGF-beta near its apparent dissociation constant. Using 125I-labeled TGF-beta, we demonstrated that TGF-beta complexes with the plasma component alpha 2-macroglobulin, but not with fibronectin. Heparin increases the electrophoretic mobility of TGF-beta apparently by freeing TGF-beta from its complex with alpha 2-macroglobulin. Dextran sulfate, another highly charged antiproliferative molecule, but not chondroitin sulfate or dermatan sulfate, similarly modified TGF-beta's mobility. Relatively high, antiproliferative concentrations of heparin (1-100 micrograms/ml) were required to dissociate the TGF-beta/alpha 2-macroglobulin complex. Thus, it appears that the antiproliferative effect of heparin may be partially attributed to its ability to potentiate the biological activity of TGF-beta by dissociating it from alpha 2-macroglobulin, which normally renders it inactive. We suggest that heparin-like agents may be important regulators of TGF-beta's biological activity.

Animals↗
PubMed1989

Human leukocyte cathepsin G and elastase specifically suppress thrombin-induced prostacyclin production in human endothelial cells.

Polymorphonuclear leukocytes (PMN) when activated release products that can potentially injure endothelial cells or alter endothelial function. Exposure of cultured human umbilical vein endothelial cells to cathepsin G and elastase isolated from human PMN at concentrations reached in vivo (100 ng/mL to 10 micrograms/mL) selectively inhibited thrombin-induced prostacyclin production and the thrombin-induced rise in cytosolic free calcium ([Ca++]i) concentration. These proteases also blocked thrombin-induced release of arachidonic acid from prelabeled endothelial cells (EC). In contrast, induction of prostacyclin (PGI2) production by arachidonate, histamine, or the calcium ionophore A23187 was not altered by treatment of EC with these proteases. The effects of the proteases were concentration-dependent, were blocked by serum or serum protease inhibitors, and were reversed when the endothelial cells were further cultured for 24 hours in the absence of the proteases. Elastase, but not cathepsin G, also produced detachment of endothelial cells. Thus, the major leukocyte proteases selectively suppress thrombin-induced prostacyclin production by human vascular endothelial cells and may alter the hemostatic balance at sites of PMN activation.

Arachidonic Acid↗
PubMed1988

Aging and arteriosclerosis. The increased proliferation of arterial smooth muscle cells isolated from old rats is associated with increased platelet-derived growth factor-like activity.

In vivo studies have suggested that the aorta from an old animal responds to injury with an exaggerated proliferation of smooth muscle cells (SMCs) compared with the response of this aorta from a young animal. In this study we compared proliferation of SMCs derived from uninjured old (less than 19 mo) and young (3-4 mo) rat aortas. Old SMCs grew more rapidly than young SMCs in the presence of medium containing competence factors (10% FCS or platelet-derived growth factor [PDGF]) as well as in their absence (2% PDS or serum-free media) as determined both by a short-term thymidine incorporation assay and by cell counts. Lysates prepared from old SMCs that had been grown in the absence of serum or PDGF stimulated proliferation of target cells more than lysates prepared from young SMCs; the effect was inversely related to cell density of the SMCs. This stimulatory effect of lysates was completely blocked by antibody to PDGF. After the growth-promoting activity of lysates was eliminated by anti-PDGF, growth-inhibiting activity was revealed. Lysates prepared from old SMCs had significantly less capacity to inhibit target cell growth. In the presence of exogenous heparin both the serum- or PDGF-stimulated proliferation and serum-free proliferation of old SMCs were decreased to the level of proliferation of young SMCs. These results suggest that the balance between growth-promoting and growth-inhibiting factors is altered in SMCs from old rats. This may contribute to the increased proliferative capacity of these cells in culture and may facilitate the development of atherosclerosis with age.

Aging↗
PubMed1988

Wheat germ agglutinin inhibits thrombin-induced rises in cytosolic free calcium and prostacyclin synthesis by human umbilical vein endothelial cells.

To characterize the endothelial cell surface membrane glycoproteins that mediate thrombin stimulation of PGI2 synthesis by human umbilical vein endothelial cells (HUVEC), HUVEC were stimulated with thrombin in the presence or absence of different lectins. Of the lectins tested, only wheat germ agglutinin (WGA) inhibited thrombin-induced rises in cytosolic free calcium [( Ca2+]i), measured using Quin 2-loaded HUVEC and PGI2 production measured by radioimmunoassay. However, WGA by itself had no influence on baseline [Ca2+]i or PGI2 production and did not inhibit histamine-induced rises in [Ca2+]i. The inhibition of thrombin-induced rises in [Ca2+]i and PGI2 production by WGA was dose dependent, with half-maximal inhibition occurring at 2 micrograms/ml. WGA also inhibited thrombin-induced release of 3H-arachidonic acid. These effects of WGA were reversed by N-acetyl-glucosamine (GlcNAc) and N-acetyl-neuraminic acid, which bind specifically to WGA, but not by unrelated sugars. Succinylated WGA (succ-WGA), a chemically modified derivative of WGA that binds to GlcNAc but, unlike native WGA, not to sialoglycoproteins, did not inhibit thrombin-induced rises in [Ca2+]i and PGI2 production. These results suggest that thrombin induces rises in [Ca2+]i and PGI2 production by interacting with an endothelial surface membrane sialoglycoprotein.

Acetylglucosamine↗
PubMed1988

A rapid fluorometric DNA assay for the measurement of cell density and proliferation in vitro.

Many research efforts require the accurate determination of cell density in vitro. However, physical cell counting is inaccurate, time-intensive and requires removal of the cells from their growth environment, thereby introducing a host of potential artifacts. The current studies document a very simple method of determining cell density in microtiter wells via DNA-enhanced fluorescence. Fixed cells are stained with the A-T intercalating DNA stains DAPI or Hoechst 33342 and then fluorescence is quantified in a plate fluorometer. Fluorescence is shown to be linearly related to cell density as determined by two physical counting methods. The validity of the method is established in determining serum-stimulated growth of smooth muscle cells and in mitogen-induced growth of endothelial cells. The fixed cells can be stored for prolonged periods, thus allowing time-course proliferation assays without interassay variations. The fixed cells are also suitable for determinations of antigens of interest by ELISA. This method is potentially valuable in many in vitro systems where the quantification of cell density and proliferation is necessary.

Animals↗
PubMed1987

Correlation between thrombin-induced prostacyclin production and inositol trisphosphate and cytosolic free calcium levels in cultured human endothelial cells.

Cultured human umbilical vein endothelial cells (HUVEC) stimulated with thrombin are known to synthesize prostacyclin at least in part from arachidonate released by phospholipase A2, an enzyme directly activated by calcium. In this study, thrombin stimulation of Quin 2-loaded HUVEC caused rapid and dose-dependent rises in inositol trisphosphate (IP3) and cytosolic free calcium (Ca2+i) levels which preceded a similarly dose-dependent rise in prostacyclin production measured as 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) by radioimmunoassay (ED50 = 0.6-0.7 units/ml for all three effects). Thrombin induced these effects in the absence of extracellular calcium (EGTA) or in the presence of either 8-bromo-cAMP or the calmodulin inhibitor W7. Thrombin inactivated with either diisopropyl fluorophosphate or D-Phe-Pro-Arg-chloromethyl ketone was inactive. In contrast, Quin 2-loaded cultured bovine aortic endothelial cells failed to respond to thrombin, although stimulation with trypsin elevated IP3 and Ca2+i levels and increased 6-keto-PGF1 alpha production. Restimulation of HUVEC with thrombin or histamine 5 min after an initial stimulation with thrombin (2 units/ml for 5 min) failed to induce a second rise in either IP3 or Ca2+i levels or further production of 6-keto-PGF1 alpha, whereas restimulation with ionomycin in the presence or absence of extracellular calcium elevated Ca2+i levels and induced further 6-keto-PGF1 alpha production. However, if the initial stimulation with thrombin was terminated by addition of D-Phe-Pro-Arg-chloromethyl ketone within 10-60 s, restimulation with a second dose of thrombin induced second rises in both IP3 and Ca2+i levels and additional 6-keto-PGF1 alpha production that were greatest when the initial thrombin stimulus was briefest. These results are consistent with the conclusion that IP3 acts as a second messenger by which thrombin elevates Ca2+i levels and initiates prostacyclin synthesis in HUVEC and that in vivo endothelial cells may be stimulated multiple times to synthesize prostacyclin if each period of stimulation is brief.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Effect of preoperative antiplatelet drugs on vascular prostacyclin synthesis.

Patients undergoing aortocoronary bypass using autogenous saphenous veins were randomly divided into three comparable groups. Group 1 (n = 10) acted as a control, Group 2 (n = 14) received 80 mg of aspirin at midnight before the operation, and Group 3 (n = 12) received 80 mg of aspirin and 75 mg of dipyridamole at midnight and an additional 75-mg dose of dipyridamole at 6 AM. The purpose was to determine which regimen would maximally inhibit platelet function without depressing vascular prostacyclin synthesis. Serum thromboxane A2, saphenous vein wall and aortic wall prostacyclin, platelet aggregation, and bleeding time were measured in all patients. None was restarted on a regimen of aspirin or dipyridamole postoperatively. Aspirin alone and in combination with dipyridamole significantly inhibited thromboxane A2 and platelet aggregation in all treated patients but spared venous prostacyclin synthesis. Aortic prostacyclin synthesis was partially inhibited in both treated groups. Chest tube drainage was comparable in all three groups. These results indicate that the combination of aspirin and dipyridamole offers no measurable advantage over aspirin alone in the perioperative period.

Aspirin↗
PubMed1987

Regulation of prostaglandin synthesis in human vascular cells.

Prostacyclin (PGI2) synthesis in human vascular tissue is mainly regulated by the activity of enzymes that metabolize arachidonic acid, and especially by the activity of cyclooxygenase. The activity of this enzyme depends upon the balance between its synthesis and its inactivation by peroxidated metabolites or drugs. Cyclooxygenase in vascular endothelial cells is strongly inhibited by aspirin, but is rapidly resynthesized. The resynthesis proceeds more rapidly in endothelium than in smooth muscle cells. Growth factors for vascular cells strongly influence cyclooxygenase production and activity. PDGF both releases arachidonate and stimulates cyclooxygenase synthesis in fibroblasts and smooth muscle cells, and ECGF enhances new enzyme synthesis. By contrast, we find that the endothelial growth factor depresses PGI2 synthesis in human endothelial cells in a time and concentration-dependent manner. This inhibitory effect is potentiated by heparin. The inhibition correlates with a decrease in the content of immunoreactive cyclooxygenase within the endothelial cells when they are grown in the presence of ECGF and heparin. These findings suggest that proliferation selectively suppresses the function of prostaglandin synthesis in endothelial cells.

Arachidonic Acid↗
PubMed1987

Herpes simplex virus infection in human arterial cells. Implications in arteriosclerosis.

Herpesviruses have been implicated as etiologic factors in the pathogenesis of human arteriosclerosis. We have examined the pathobiological effects of human herpes simplex virus (HSV-1) infection in influencing lipid accumulation and metabolism in human and bovine arterial smooth muscle cells (SMC). Significantly greater amounts of saturated cholesteryl esters (CE) and triacylglycerols (TG) accumulate in HSV-1-infected human and bovine arterial SMC than uninfected cells. This CE accumulation results, in part, from decreased CE hydrolysis. Furthermore, arachidonate-stimulated, HSV-1-infected arterial SMC have a reduced capacity to produce prostacyclin (an agonist of intracellular CE hydrolytic activity) than uninfected, stimulated SMC. It appears that HSV-1 may induce lipid accumulation in arterial SMC similar, in part, to the lipid accumulation observed in vivo during human atherogenesis. Thus, herpesviruses may contribute to lipid accumulation, which is a characteristic feature of atherosclerosis.

Animals↗