Adenine nucleotides modulate phosphatidylcholine metabolism in aortic endothelial cells

Abstract

ATP and ADP, in concentrations ranging from 1-100 microM, increased the release of [3H]choline and [3H]phosphorylcholine (P-choline) from bovine aortic endothelial cells (BAEC) prelabelled with [3H]choline. This action was detectable within 5 minutes and was maintained for at least 40 minutes. ATP and ADP were equiactive, and their action was mimicked by their phosphorothioate analogs (ATP gamma S and ADP beta S) and adenosine 5'-(beta, gamma imido) triphosphate (APPNP), but not by AMP, adenosine, and adenosine 5'-(alpha, beta methylene)triphosphate (APCPP): these results are consistent with the involvement of P2Y receptors. ATP also induced an intracellular accumulation of [3H]choline: the intracellular level of [3H]choline was increased 30 seconds after ATP addition and remained elevated for a least 20 minutes. The action of ATP on the release of choline metabolites was reproduced by bradykinin (1 microM), the tumor promoter phorbol 12-myristate 13-acetate (PMA, 50 nM), and the calcium ionophore A23187 (0.5 microM). Down-regulation of protein kinase C, following a 24-hour exposure of endothelial cells to PMA, abolished the effects of PMA and ATP on the release of choline and P-choline, whereas the response to A23187 was maintained. These results suggest that in aortic endothelial cells, ATP produces a sustained activation of a phospholipase D hydrolyzing phosphatidylcholine. The resulting accumulation of phosphatidic acid might have an important role in the modulation of endothelial cell function by adenine nucleotides. Stimulation of phospholipase D appears to involve protein kinase C, activated following the release of diacylglycerol from phosphatidylinositol bisphosphate by a phospholipase C coupled to the P2Y receptors (Pirotton et al., 1987a).

Evidence for a nucleotide receptor on adrenal medullary endothelial cells linked to phospholipase C and phospholipase D

“…Activation of phospholipase C has been clearly demonstrated for nucleotide receptors in BAME cells (this paper), PC12 cells (Murrin & Boarder, 1992), hepatocytes (Keppens et al, 1992), airway epithelial cells (Brown et al, 1991) and sheep anterior pituitary cells (Davidson et al, 1990). Phospholipase D activation has been reported by ourselves and others (Martin & Michaelis, 1988;Pirotton et al, 1990) to be a consequence of purinoceptor stimulation of large vessel endothelium. We have recently shown that these cells contain a mixture of both P2y and nucleotide receptors , and so the phospholipase D response may in part be a nucleotide receptor response.…”

“…Phospholipase D is also activated I Author for correspondence. in large vessel endothelium by purinoceptor stimulation (Martin & Michaelis, 1989;Pirotton et al, 1990). Endothelial cells from different regions of the vasculature exhibit a high degree of variability in ultrastructural (Majno, 1965) and biochemical (Gerritsen, 1987) characteristics.…”

Regulatory mechanisms for thrombomodulin expression in human umbilical vein endothelial cells in vitro

“…Internalization and degradation of TM may be induced and is followed by increased TM expression due to PMA-induced up-regulation of TM mRNA. However, it may be possible that enhancement of TM activity by prolonged incubation with PMA results from down-regulation of protein kinase C, after activation of the enzyme, in cell membranes as reported by Pirotton et al (1990) in bovine aortic endothelial cells.…”

Extracellular ATP and ADP stimulate proliferation of porcine aortic smooth muscle cells

“…These results could have some significance in wound healing, for it has been pointed out that wound healing is defective in paraplegics and in areas of facial paralysis. Recent studies have provided evidence for increased formation of phosphatidic acid (PA) by ATP in endothelial cells via stimulation of phosphatidylcholine (PC) breakdown (Martin and Michaelis, 1989;Pirotton et al, 1990). The mitogenic effect of PA (reviewed in Knauss et al, 1990) and of lysophosphatidic acid (LPA) (van Corven et al, 1989) were recently reported.…”