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G Weigel

Publications and source records attributed to G Weigel.

45 records · Page 3Linked to original sources
PubMed1992

Influence of oxygen radicals generating agents on eicosanoid metabolism of human endothelial cells.

Human umbilical venous endothelial cells were incubated with increasing concentrations (0.001-10 mmol/l) of H202 or cumene hydroperoxide. PGI2 was released within the first five minutes, whereas a significant increase in TXA2-release was not observed before 10 minutes after stimulation. Furthermore the content of intracellular ATP and the level of cytosolic free Ca2+ were measured. Doses of 0.01 mmol/l H202 or cumene hydroperoxide increased the intracellular ATP-level. Doses higher than 0.1 mmol/l led to a decrease of ATP. The cytosolic free calcium (Ca2+) increased on stimulating the cells with 0.1 mmol/l cumene hydroperoxide between 120 and 240 seconds after stimulation, whereas 0.1 mmol/l H202 had no effects. These data give strong evidence, that eicosanoid-synthesis is directly started by oxygen radicals, followed by an elevation of intracellular free Ca2+.

Adenosine Triphosphate↗
PubMed1992

Effects of reactive oxygen species on eicosanoid metabolism in human endothelial cells.

The influence of reactive oxygen species (H2O2 was used as model substance) on the formation and release of PGI2 and TXA2 by cultured human endothelial cells was analyzed. In the presence of H2O2 concentrations which did not induce a general cell damage (analyzed by estimation of the cellular concentration of energy rich phosphates and extent of lipid peroxidation), the formation of both eicosanoids exhibited a sigmoidal shape with respect to time. Increasing H2O2 concentration shortened the half time of PGI2 and TXA2 production. The maximum rates of PGI2 and TXA2 formation were separated by a delay of the TXA2 production. The ratio of PGI2 and TXA2 formation was 100 to 1 at the time of maximum PGI2 formation and 1-2 to 1 at the time of maximum TXA2 formation. This effect of reactive oxygen species could contribute to the reduction of the protective function of the endothelium in hemostasis and vascular tone. Using antioxidants, the modulating function of reactive oxygen species on the eicosanoid metabolism in endothelial cells was verified.

Adenosine Triphosphate↗
PubMed1992

Functional implications of cAMP and Ca2+ on prostaglandin I2 and thromboxane A2 synthesis by human endothelial cells.

Human umbilical vein endothelial cells were incubated with ATP, ADP, thrombin, or ionophore A23187 for as long as 600 seconds. A statistically significant rise in the prostaglandin I2 (prostacyclin; PGI2) and thromboxane A2 (TxA2) release was observed after 45 seconds. The maximum amount of cytosolic free Ca2+ was reached between 20 and 30 seconds. A statistically significant elevation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels was observed only in response to ATP and ADP after 120 seconds. Furthermore, adenosine, caffeine, phorbol 12-myristate 13-acetate (PMA), and adenosine 5'-(alpha, beta-methylene)triphosphate were tested alone or in combination with ATP or thrombin. PMA inhibited ATP-stimulated eicosanoid biosynthesis but had no effect on thrombin. Of the agents used to increase cytosolic free Ca2+ concentrations, only PMA failed to provoke eicosanoid release. Similarly, only PMA failed to induce a Ca2+ flux in the absence of extracellular Ca2+. The data presented show that PGI2 and TxA2 release from human umbilical cord endothelial cells is closely associated with Ca2+ mobilized from intracellular sources. Extracellular Ca2+, as well as changes in intracellular cAMP levels, has no influence on endothelial eicosanoid synthesis, at least for short-term regulation (less than or equal to 600 seconds).

Adenosine↗
PubMed1992

Aprotinin decreases release of 6-keto-prostaglandin F1 alpha and increases release of thromboxane B2 in cultured human umbilical vein endothelial cells.

Use of the proteinase inhibitor aprotinin significantly improves hemostasis and reduces bleeding after operations in which extracorporeal circulation is used. The mechanism of action, however, has been only partially clarified. In this work we investigated whether aprotinin influenced the production and release of the eicosanoids prostacyclin, measured as the stable metabolite 6-keto-prostaglandin F1 alpha, and thromboxane A2, measured as the stable metabolite thromboxane B2, from endothelial cells. Human umbilical vein endothelial cells were incubated with different concentrations of aprotinin (5.5, 20, 55, and 100 mumol/L). The levels of 6-keto-prostaglandin F1 alpha and thromboxane B2 were measured at baseline and after thrombin stimulation. A concentration-dependent effect of aprotinin on 6-keto-prostaglandin F1 alpha synthesis was demonstrated. After incubation with 100 mumol/L of aprotinin, a 90% reduction in 6-keto-prostaglandin F1 alpha production was seen (31.69 versus 307.44 picograms per million cells; p less than 0.001). Conversely, thromboxane B2 production showed a 345% increase after incubation with aprotinin (287.80 versus 83.82 picograms per million cells; p less than 0.0001). Since 6-keto-prostaglandin F1 alpha inhibits and thromboxane B2 strongly enhances platelet aggregation, it appears that one mechanism of the clinically observed effectiveness of aprotinin lies in the altered ratio of 6-keto-prostaglandin F1 alpha: thromboxane B2 in endothelial cells, which leads to enhanced platelet aggregation and improved vessel sealing.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Aprotinin increases release of von Willebrand factor in cultured human umbilical vein endothelial cells.

Through the perioperative administration of the proteinase inhibitor aprotinin, hemostasis can be improved and postoperative bleeding reduced after cardiac operations. The mechanism of action has been only partially clarified. The goal of our study was to investigate the influence of aprotinin on the synthesis of von Willebrand factor (vWF) in human endothelial cells. Human umbilical vein endothelial cells (HUVEC) were cultivated in vitro and incubated with different aprotinin concentrations (55, 100, and 215 mol/L). With all investigated aprotinin concentrations, there was an increase in vWF synthesis compared with basal secretion (p less than 0.001). When the HUVEC were preincubated with aprotinin and stimulated with thrombin, there was a further significant increase in vWF synthesis. HUVEC that, were first incubated with aprotinin and then stimulated with thrombin demonstrated a significant increase in vWF synthesis compared with basal secretion in nonincubated cells (p less than 0.0001). Also, compared with the cells that had received thrombin stimulation alone, the combination of aprotinin incubation and thrombin stimulation led to a significantly higher vWF concentration (p less than 0.05). Because vWF is necessary for the interaction with platelet factor glycoprotein Ib and platelet adhesion, the demonstrated increase in vWF synthesis could be one of the mechanisms of action of aprotinin leading to its blood-sparing effect.

Aprotinin↗
PubMed1991

Regulation of eicosanoid release in human umbilical endothelial cells.

The concentration dependent influence of adenine nucleotides, thrombin and ionophore A 23187 on eicosanoid-production of human endothelial cells was investigated. The prostaglandin I2 (PGI2)-and thromboxane A2 (TXA2)-release were highest at concentrations of 1 mmol/l and 4 mmol/l adenine nucleotides, respectively. TXA2-release decreased at higher concentrations. Ionophore-induced eicosanoid-formation reached its maximum at 15 mumol/l for both PGI2 and TXA2. Thrombin stimulation resulted in a bell shaped concentration dependency, whereby most TXA2 was released at a concentration of 1 U/ml and most PGI2 at 5 U/ml. Intracellular cAMP showed significant (p less than 0.01) increases stimulating cells with ADP- and ATP-concentrations higher than 500 mumol/l, whereas ionophore and thrombin did hardly affect cAMP levels.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Thromboxane A2 generation by human umbilical endothelial cells.

Human umbilical endothelial cells were examined for their ability to release thromboxane A2 (TXA2) and prostacyclin (PGI2). We could show that the basal, unstimulated release of the two eicosanoids was inversely related to the cell density. At a density of 100,000 cells/cm2 TXA2 release was 0.062 +/- 0.28 fg/cell/h and PGI2 release was 0.184 +/- 0.051 fg/cell/h, whereas at a cell density of 20,000 cells/cm2 the cells released 1.075 +/- 0.055 fg TXA2/cell/h and 1.653 +/- 0.09 fg PGI2/cell/h. In stimulation experiments ATP and ADP significantly (p less than 0.001) increased the TXA2 and the PGI2 release. ANF caused a slow but still significant (p less than 0.001) enhancement of TXA2 release. Thrombin and ionophore A23187 caused the strongest stimulatory response, resulting in a significantly (p less than 0.001) increased release of both eicosanoids.

Data Interpretation, Statistical↗
PubMedDate not supplied

Different transendothelial migration behaviour pattern of blood monocytes derived from patients with benign and malignant diseases of the breast.

BACKGROUND: In this study we compared the expression of selected monocyte surface antigens with the potential to transmigrate through an endothelial layer before and after surgery from breast cancer patients (CA) and patients with benign disease of the breast (BE). MATERIALS AND METHODS: Transmigration capacity of mononuclear cells was determined after isolation by Ficoll density gradient, layered over human umbilical vein endothelial cells and cultured in a two chamber plate added with fMLP as a chemotactic stimulus. We determined monocyte phenotye (HLA-DR, FcgRI/CD64, CR1/CD11b and LFA-1/CD11a) and the phagocytosis of E. coli by flow cytometry. RESULTS: Before surgery blood monocytes had an equal expression of the measured surface antigens, but were different in regard to their interaction with endothelial cells. Monocytes derived from CA had a higher transmigration potency than those of BE. Moreover, the migration through the endothelial cell layer created different populations of monocytes. Surgical stress modified transmigrated monocytes of BE into the direction of monocytes from CA. Phagocytic capacity of peripheral blood monocytes from CA was significantly diminished and was further reduced after surgery when measured in transmigrated cells. CONCLUSION: Our study shows that monocytes from CA and BE can be discriminated in regard to their interaction with endothelial cells.

Adult↗