Effects of Lysophosphatidic Acid on Proliferation and Cytosolic Ca++ of Human Adult Vascular Smooth Muscle Cells in Culture

doi:10.1016/S0049-3848(99)00004-3

Thrombosis Research

Volume 94, Issue 5, 1 June 1999, Pages 317-326

https://doi.org/10.1016/S0049-3848(99)00004-3 Get rights and content

Abstract

Lysophosphatidic acid (LPA) is a lipid mediator generated by activated platelets and having various effects on numerous cell types. We investigated some effects of 1-oleyl LPA on vascular smooth muscle cells cultured from adult human normal arteries. At micromolar concentrations, LPA induced a mitogenic effect ([³H]-thymidine incorporation and cell proliferation) on quiescent cells, without an additional growth factor being required. This effect was equipotent to that of 10% fetal calf serum, and it was accompanied by early (5 minutes) and late (1–3 hours) phosphorylation of mitogen-activated protein kinase. LPA inhibited cell migration through collagen coated membranes, with or without platelet-derived growth factor BB as chemoattractant. LPA induced a typical biphasic Ca²⁺ signal response made up of a rapid first phase due to Ca²⁺ release from intracellular stores followed by a second wave due to external Ca²⁺ influx. These findings support the proposal that LPA released from activated platelets is a mediator for smooth muscle cell response at the site of vessel injury in humans.

Section snippets

Materials

1-oleoyl-sn-glycero-3-phosphate (18:1 LPA), fatty acid–free bovine serum albumin (BSA), thapsigargin and neomycin were from Sigma Chemical Co. (St. Louis, MO, USA). Fetal calf serum (FCS), Dulbecco’s Modified Eagle’s Medium (DMEM), and trypsin were from Seromed (Berlin, Germany). [³H]-thymidine was from New Life Sciences Products (Boston, MA, USA), fura-2 AM from Molecular Probes Inc. (Eugene, OR, USA). Plastic material for culture and inserts for migration experiments were from Nunclon Inter

Results

LPA induces a dose-dependent mitogenic effect on VSMCs. Figure 1 shows the effects of LPA on [³H]-thymidine incorporation in serum-starved VSMCs. The increase was statistically significant at the lowest LPA concentration used (1 μM) and maximal at 5 μM (2.5-fold the value obtained in the absence of LPA and 80% of that obtained with 10% FCS). Figure 2 shows the effect of LPA on cell proliferation. Seventy-two hours after the addition of LPA, the cell number increased dose-dependently. The

Discussion

Relatively few studies have been devoted to the effects of LPA on smooth muscle cells of vascular origin 16, 17, 18, 19. The present study is the first report of LPA action on VSCMs from normal human arteries. At micromolar concentrations, LPA appears to be equipotent to 10% FCS in inducing DNA synthesis and cell division. Optimal LPA concentrations reported in this study are different from those found by others 17, 18. This may be due in part to the use of different animal species. Tokumura et

Acknowledgements

The authors thank Dr. G. Fournial and Y. Glock (Department of Vascular Surgery) for providing human mammary arteries.

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Atherosclerotic lesion progression changes lysophosphatidic acid homeostasis to favor its accumulation
2010, American Journal of Pathology
Lysophosphatidic acid (LPA) accumulates in the central atheroma of human atherosclerotic plaques and is the primary platelet-activating lipid constituent of plaques. Here, we investigated the enzymatic regulation of LPA homeostasis in atherosclerotic lesions at various stages of disease progression. Atherosclerotic lesions were induced in carotid arteries of low-density lipoprotein receptor–deficient mice by semiconstrictive collar placement. At 2-week intervals after collar placement, lipids and RNA were extracted from the vessel segments carrying the plaque. Enzymatic-and liquid chromatography-mass spectrometry–based lipid profiling revealed progressive accumulation of LPA species in atherosclerotic tissue preceded by an increase in lysophosphatidylcholine, a precursor in LPA synthesis. Plaque expression of LPA-generating enzymes cytoplasmic phospholipase A₂IVA (cPLA₂IVA) and calcium-independent PLA₂VIA (iPLA₂VIA) was gradually increased, whereas that of the LPA-hydrolyzing enzyme LPA acyltransferase α was quenched. Increased expression of cPLA₂IVA and iPLA₂VIA in advanced lesions was confirmed by immunohistochemistry. Moreover, LPA receptors 1 and 2 were 50% decreased and sevenfold upregulated, respectively. Therefore, key proteins in LPA homeostasis are increasingly dysregulated in the plaque during atherogenesis, favoring intracellular LPA production. This might at least partly explain the observed progressive accumulation of this thrombogenic proinflammatory lipid in human and mouse plaques. Thus, intervention in the enzymatic LPA production may be an attractive measure to lower intraplaque LPA content, thereby reducing plaque progression and thrombogenicity.
Roles of lysophosphatidic acid in cardiovascular physiology and disease
2008, Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
The bioactive lipid mediator lysophosphatidic acid (LPA) exerts a range of effects on the cardiovasculature that suggest a role in a variety of critical cardiovascular functions and clinically important cardiovascular diseases. LPA is an activator of platelets from a majority of human donors identifying a possible role as a regulator of acute thrombosis and platelet function in atherogenesis and vascular injury responses. Of particular interest in this context, LPA is an effective phenotypic modulator of vascular smooth muscle cells promoting the de-differentiation, proliferation and migration of these cells that are required for the development of intimal hyperplasia. Exogenous administration of LPA results in acute and systemic changes in blood pressure in different animal species, suggesting a role for LPA in both normal blood pressure regulation and hypertension. Advances in our understanding of the molecular machinery responsible for the synthesis, actions and inactivation of LPA now promise to provide the tools required to define the role of LPA in cardiovascular physiology and disease. In this review we discuss aspects of LPA signaling in the cardiovasculature focusing on recent advances and attempting to highlight presently unresolved issues and promising avenues for further investigation.
Mechanisms of lysophosphatidic acid-induced increase in intracellular calcium in vascular smooth muscle cells
2005, Cell Calcium
Although lysophosphatidic acid (LPA) is known to cause an increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) in vascular smooth muscle cells (VSMCs), the mechanisms of [Ca²⁺]_i mobilization by LPA are not fully understood. In the present study, the effect of LPA on [Ca²⁺]_i mobilization in cultured A10 VSMCs was examined by Fura-2 fluorescence technique. The expression of LPA receptors was studied by immunostaining. LPA was observed to increase [Ca²⁺]_i in a concentration-dependent manner; this increase was dependent on the concentration of extracellular Ca²⁺. Both sarcolemmal (SL) Na⁺–Ca²⁺ exchange inhibitors (amiloride, Ni²⁺ and KB-R7943) and Na⁺–H⁺ exchange inhibitor (MIA) as well as SL store-operated Ca²⁺ channel (SOC) antagonists (SK&F 96365, tyrphostin A9 and gadolinium), unlike SL Ca²⁺ channel antagonists (verapamil and diltiazem), inhibited the LPA-induced increase in [Ca²⁺]_i. In addition, sarcoplasmic reticulum (SR) Ca²⁺ channel blocker (ryanodine), SR Ca²⁺ channel opener (caffeine), SR Ca²⁺ pump ATPase inhibitor (thapsigargin) and inositol 1,4,5-trisphosphate (InsP₃) receptor antagonists (xestospongin and 2-aminoethoxydiphenyl borate) were found to inhibit the LPA-induced Ca²⁺ mobilization. Furthermore, phospholipase C (PLC) inhibitor (U 73122) and protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate) attenuated the LPA-induced increase in [Ca²⁺]_i. These results indicate that Ca²⁺ mobilization by LPA involves extracellular Ca²⁺ entry through SL Na⁺–Ca²⁺ exchanger, Na⁺–H⁺ exchanger and SL SOCs. In addition, ryanodine-sensitive and InsP₃-sensitive intracellular Ca²⁺ pools may be associated with the LPA-induced increase in [Ca²⁺]_i. Furthermore, the LPA-induced [Ca²⁺]_i mobilization in VSMCs seems to be due to the activation of both PLC and PKC.
Biology of LPA in health and disease
2004, Seminars in Cell and Developmental Biology
The functions of lysophosphatidic acid (LPA) can be broadly divided into two classes: (1) physiological and (2) pathological roles. The role of LPA in embryonic development can be seen as early as oocyte formation. It continues in postnatal homeostasis, through its ability to impart a level of protection from both stress and local injury, by regulating cellular proliferation, apoptosis, and the reorganization of cytoskeletal fibers. LPA may function as a double-edged sword. While it helps maintain homeostasis against stress and insult, it may also augment the development and spread of pathological processes, including cancers.
Molecular mechanisms of lysophosphatidic acid action
2003, Progress in Lipid Research
Epicardial and Pericoronary Adipose Tissue, Coronary Inflammation, and Acute Coronary Syndromes
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^☆: Presented in part at the XVIth Congress of the International Society for Thrombosis and Haemostasis, Florence, Italy, 6–12 June, 1997.

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Regular articleEffects of Lysophosphatidic Acid on Proliferation and Cytosolic Ca++ of Human Adult Vascular Smooth Muscle Cells in Culture☆

Abstract

Section snippets

Materials

Results

Discussion

Acknowledgements

J Biol Chem

Trends Cell Biol

Curr Opin Cell Biol

FEBS Lett

Biochimie

Cell

Biochim Biophys Res Comm

Biochim Biophys Acta

Kidney Int

Atherosclerosis

J Lipid Res

J Biol Chem

Cell

J Biol Chem

J Biol Chem

Regular article
Effects of Lysophosphatidic Acid on Proliferation and Cytosolic Ca⁺⁺ of Human Adult Vascular Smooth Muscle Cells in Culture☆