Cheng-Po Sung

Carvedilol inhibits vascular smooth muscle cell proliferation.

The antiproliferative properties of carvedilol, a newly developed multiple-action antihypertensive agent, were evaluated in early passage cultured rat aortic vascular smooth muscle cells. Carvedilol (10-7-10-5 M) produced concentration-dependent decreases in basal and endothelin-1-stimulated mitogenesis of rat aortic vascular smooth muscle cells. The IC50 for inhibition of [3H]thymidine incorporation by carvedilol in both basal and endothelin-1-stimulated rat aortic vascular smooth muscle cells was approximately 1 μM. Carvedilol (10 μM) inhibited basal mitogenesis by approximately 65%, and endothelin-1-stimulated mitogenesis by approximately 95%. Carvedilol (1–10 μM) also produced significant concentration-dependent inhibition of the mitogenic response mediated by thrombin (0.5 U/ml), epidermal growth factor (1 nM), platelet-derived growth factor (1 nM), and angiotensin II (5 nM). Endothelin-1− or PDGF A/B-induced increases in cell number were also significantly inhibited by carvedilol (10 μM). The antimitogenic effect of carvedilol on cell growth was reversible. The inhibitory effect of carvedilol was not shared by other β-adrenoceptor antagonists such as labetalol (10 μM), celiprolol (10 μM), or sotalol (10 μM), which did not significantly affect [3H]thymidine incorporation in rat vascular smooth muscle cells. Propranolol (10 μM) was the only β-adrenoceptor antagonist tested that inhibited [3H]thymidine incorporation, with effects of approximately 50 and 75% on basal and endothelin-1-mediated stimulation, respectively. In contrast, celiprolol (10 μM) produced significant stimulation of DNA synthesis (125% over basal). The calcium channel antagonist nifedipine (10 μM) inhibited basal and endothelin-1-mediated mitogenesis by 58 and 72%, respectively. The present studies demonstrate that the novel multiple-action antihypertensive agent carvedilol produced antimitogenic effects in rat vascular smooth muscle, a property that may be beneficial for suppressing the progression of vascular hypertrophy associated with hypertension.

CGRP stimulates the adhesion of leukocytes to vascular endothelial cells

Calcitonin gene-related peptide (CGRP) stimulates the adhesiveness of human umbilical vein endothelial cells for U937 cells and human neutrophils in a dose- and time-dependent manner. The onset of CGRP-induced adhesives of HUVEC was rapid (30 min), independent of protein synthesis, and lasted over 24 h in the continuous presence of the peptide. The stimulatory effect of CGRP was completely blocked by the CGRP antagonist, CGRP(8-37). The present study provides evidence in support of the potential role of sensory nerve-derived neuropeptides in the modulation of leukocyte adhesion to vascular endothelial cells.

Biosynthesis and modulation of endothelin from bovine pulmonary arterial endothelial cells

The biosynthesis and modulation of the vasoconstrictor peptide endothelin was studied in the conditioned medium from cultured bovine pulmonary artery endothelial (BPAE) cells. Conditioned medium from cultured BPAE cells produced contraction of isolated rabbit aortic rings. Incubation of BPAE cells with the protease inhibitors TPCK or isatoic anhydride attenuated the extent of conditioned medium-induced contractions. Incubation of BPAE cells with thrombin produced an enhancement of conditioned medium-induced contraction by approximately 25%. Endothelin levels in conditioned medium were measured by RIA and incubation of BPAE cells with TPCK or isatoic anhydride significantly reduced endothelin levels, whereas incubation with thrombin or transforming growth factor beta-1 stimulated the levels of endothelin in the conditioned medium. These data indicate that endothelin may be modulated by certain protease inhibitors and by platelet and immune cell mediators and suggest a potential new mode of vascular tone regulation.

Endothelial thromboxane receptors: biochemical characterization and functional implications

We have identified thromboxane specific receptors in membrane preparations of bovine pulmonary artery endothelial cells using a potent thromboxane specific antagonist, [125I]-PTA-OH in a binding assay. The binding was specific and saturable. Neither thromboxane B2, prostaglandin D2 nor prostaglandin F2 alpha displaced the ligand (0.1 nM) at concentrations up to 10 microM. However, binding was displaced by IPTA-OH greater than SQ29548 greater than U46619. In addition, we observed that thromboxane mimetic U46619 significantly lowered the basal production of prostacyclin and also markedly suppressed bradykinin-stimulated prostacyclin released by endothelial cells. We propose that an important biological effect of thromboxane on vascular endothelial cells may be the suppression of prostacyclin production.

Evidence for Involvement of Protein Kinase C in Expression of Intracellular Adhesion Molecule-1 (ICAM-1) by Human Vascular Endothelial Cells

Potent activators of protein kinase C (PKC), such as phorbol dibutyrate and octylindolactam V, stimulated expression of intercellular adhesion molecule 1 (ICAM-1) by human umbilical vein endothelial cells (HUVEC) in a concentration-dependent manner. Expression of PKC activator-induced ICAM-1 in HUVEC was inhibited by the PKC inhibitor, H-7. Furthermore, cytokine (TNF alpha, LPS)-induced ICAM-1 expression was inhibited by the potent PKC inhibitor, H-7, and not by the cAMP-dependent protein kinase (PKA) specific inhibitor, H-89. These data suggest that PKC is involved in cytokine- and inflammatory agent-induced upregulation of ICAM-1 expression in HUVEC.

Involvement of Protein Kinase C in Cytokine-Induced Tissue Factor Production in Human Vascular Endothelial Cells

Cultured vascular endothelial cells demonstrate procoagulant activity following stimulation by cytokines and other inflammatory agents. Tissue factor is a cell surface membrane protein, which functions as a receptor and essential cofactor for Factor VII triggering the blood coagulation process. The mechanism(s) by which cytokine/inflammatory agents stimulate the production of tissue factor is still unclear. We hypothesized that protein kinase C (PKC) may be involved in cytokine/inflammatory agent-induced up-regulation of tissue factor in human vascular endothelial cells. The production of tissue factor by human umbilical endothelial cells (HUVEC) was enhanced markedly (5-10 fold) by TNFα (100 U/ml), IL-1 (10 U/ml) or LPS (100 ng/ml). Phorbol esters (PMA or PDBu) stimulated the production of tissue factor by HUVEC in a concentration-dependent manner, while the biologically inactive analog of PDBu, 4α-PDBu was inactive. Maximal stimulation by PMA (10-12 fold) was obtained at 200 nM and the ED50 was 50 nM. P...