inositol-1-4-5-trisphosphate and Neoplasms

Plasma membrane Ca(2+) ATPases (PMCAs) are intimately involved in the control of intracellular Ca(2+) concentration. They reduce Ca(2+) in the cytosol not only by direct ejection, but also by controlling the formation of inositol-1,4,5-trisphosphate and decreasing Ca(2+) release from the endoplasmic reticulum Ca(2+) pool. In mammals four genes (PMCA1-4) are expressed, and alternative RNA splicing generates more than twenty variants. The variants differ in their regulatory characteristics. They localize into highly specialized membrane compartments and respond to the incoming Ca(2+) with distinct temporal resolution. The expression pattern of variants depends on cell type; a change in this pattern can result in perturbed Ca(2+) homeostasis and thus altered cell function. Indeed, PMCAs undergo remarkable changes in their expression pattern during tumorigenesis that might significantly contribute to the unbalanced Ca(2+) homeostasis of cancer cells. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

Topics: Animals; Calcium; Calcium Signaling; Cell Membrane; Homeostasis; Humans; Inositol 1,4,5-Trisphosphate; Isoenzymes; Neoplasms; Plasma Membrane Calcium-Transporting ATPases

The anti-apoptotic protein Bcl-2 is a versatile regulator of cell survival. Its interactions with its own pro-apoptotic family members are widely recognized for their role in promoting the survival of cancer cells. These interactions are thus being targeted for cancer treatment. Less widely recognized is the interaction of Bcl-2 with the inositol 1,4,5-trisphosphate receptor (InsP3R), an InsP3-gated Ca(2+) channel located on the endoplasmic reticulum. The nature of this interaction, the mechanism by which it controls Ca(2+) release from the ER, its role in T-cell development and survival, and the possibility of targeting it as a novel cancer treatment strategy are summarized in this review. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.

Topics: Apoptosis; Calcium; Calcium Signaling; Cell Survival; Endoplasmic Reticulum; Gene Expression Regulation; Humans; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Ion Channel Gating; Ion Transport; Lymphocytes; Neoplasms; Proto-Oncogene Proteins c-bcl-2

The surge in genetic and genomic investigations over the past 5 years has resulted in many discoveries of causative variants relevant to disease pathophysiology. Although phospholipase C (PLC) enzymes have long been recognized as important components in intracellular signal transmission, it is only recently that this approach highlighted their role in disease development through gain-of-function mutations. In this review we describe the new findings that link the PLCγ family to immune disorders and cancer, and illustrate further efforts to elucidate the molecular mechanisms that underpin their dysfunction.

Topics: Animals; Diglycerides; Humans; Immune System Diseases; Inositol 1,4,5-Trisphosphate; Models, Biological; Models, Molecular; Mutation; Neoplasms; Phospholipase C gamma; Protein Conformation; Second Messenger Systems

In the last decade, the availability of genetically modified animals has revealed interesting roles for phosphoinositide 3-kinases (PI3Ks) as signaling platforms orchestrating multiple cellular responses, both in health and pathology. By acting downstream distinct receptor types, PI3Ks nucleate complex signaling assemblies controlling several biological process, ranging from cell proliferation and survival to immunity, cancer, metabolism and cardiovascular control. While the involvement of these kinases in modulating immune reactions and neoplastic transformation has long been accepted, recent progress from our group and others has highlighted new and unforeseen roles of PI3Ks in controlling cardiovascular function. Hence, the view is emerging that pharmacological targeting of distinct PI3K isoforms could be successful in treating disorders such as myocardial infarction and heart failure, besides inflammatory diseases and cancer. Currently, PI3Ks represent attractive drug targets for companies interested in the development of novel and safe treatments for such diseases. Numerous hit and lead compounds are now becoming available and, for some of them, clinical trials can be envisaged in the near future. In the following sections, we will outline the impact of specific PI3K isoforms in regulating different cellular contexts, including immunity, metabolism, cancer and cardiovascular system, both in physiological and disease conditions.

Topics: Animals; Diglycerides; Enzyme Inhibitors; Gene Expression Regulation; Heart Failure; Humans; Immunity, Innate; Inflammation; Inositol 1,4,5-Trisphosphate; Isoenzymes; Myocardial Infarction; Neoplasms; Phosphatidylinositol 3-Kinases; Phosphatidylinositol 4,5-Diphosphate; Phosphoinositide-3 Kinase Inhibitors; Second Messenger Systems

Phosphoinositide 3-kinases (PI3Ks) control cell growth, proliferation, cell survival, metabolic activity, vesicular trafficking, degranulation, and migration. Through these processes, PI3Ks modulate vital physiology. When over-activated in disease, PI3K promotes tumor growth, angiogenesis, metastasis or excessive immune cell activation in inflammation, allergy and autoimmunity. This chapter will introduce molecular activation and signaling of PI3Ks, and connections to target of rapamycin (TOR) and PI3K-related protein kinases (PIKKs). The focus will be on class I PI3Ks, and extend into current developments to exploit mechanistic knowledge for therapy.

Topics: Autoimmunity; Cell Transformation, Neoplastic; Diglycerides; Enzyme Inhibitors; Eukaryotic Cells; Gene Expression Regulation, Neoplastic; Humans; Hypersensitivity; Inositol 1,4,5-Trisphosphate; Isoenzymes; Neoplasms; Phosphatidylinositol 3-Kinases; Phosphatidylinositol 4,5-Diphosphate; Phosphoinositide-3 Kinase Inhibitors; Second Messenger Systems; TOR Serine-Threonine Kinases

Novel sites of oxytocin receptor expression have recently been detected in central nervous system, cardiomyocytes, endothelial cells, various carcinoma cells, etc. These and other discoveries have greatly expanded the classical biological roles of oxytocin, which are stimulation of uterine smooth muscle contraction at parturition and milk ejection during lactation. It is becoming clear that the great diversity of oxytocin actions in the brain and peripheral organs is paralleled by activation of a diversity of signalling pathways. On the other hand, until now only one single oxytocin receptor type has been detected. This receptor belongs to G protein-coupled receptors and in dependence on cell conditions it binds to different G proteins; this phenomenon is called receptor-G protein promiscuity. Thus, in the same cells oxytocin can activate multiple responses at the same time. Recently, the oxytocinergic system has also been implicated in the growth modulation of various neoplastic cells, where it may inhibit or stimulate cell proliferation in dependence on cell type and activated metabolic pathways. The discovery of novel oxytocin receptor-linked signalling cascades brings interesting knowledge opening new avenues for research in oncology and molecular pharmacology with perspectives of finding new therapeutic agents.

Topics: Animals; Cell Proliferation; Humans; Inositol 1,4,5-Trisphosphate; Neoplasms; Neoplastic Processes; Oxytocin; Protein Subunits; Proto-Oncogene Proteins c-akt; Receptors, Oxytocin; Signal Transduction

Signal transduction capacity in human cancer cells is constitutively up-regulated by the markedly increased steady-state activities of the three synthetic enzymes, PI kinase, PIP kinase and PLC, which catalyze the conversion of PI to the second messengers IP3 and DAG. This evidence is supported by the elevated concentration of IP3 in human colon, ovarian and breast carcinoma samples and rat hepatocellular carcinomas and sarcoma. The decrease in activities of the two specific phosphatases in the degradative pathway of signal transduction provides an amplified capacity for IP3 production. The elevated second messenger concentrations should lead to increased calcium release and protein kinase C activation. These biochemical alterations should confer selective biological advantages to cancer cells. The malignancy-linked rise in the activity of the signal transduction pathway can be down-regulated by drugs (tiazofurin, ribavirin, tamoxifen) or through inhibition of the kinases by flavonoids (quercetin, genistein) which lead to a reduction of IP3 concentration. As a result, carcinoma cells in culture stop proliferating and are destroyed. The stringent linkage of signal transduction with neoplasia provides novel targets for clinical chemotherapy.

Topics: 1-Phosphatidylinositol 4-Kinase; Animals; Cell Proliferation; Down-Regulation; Drug Synergism; Genistein; Half-Life; Humans; Inositol 1,4,5-Trisphosphate; Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Quercetin; Ribavirin; Signal Transduction; Tamoxifen; Tumor Cells, Cultured; Type C Phospholipases

Heat shock proteins (HSPs) are detected in all cells, prokaryotic and eukaryotic. In vivo and in vitro studies have shown that various stressors transiently increase production of HSPs as protection against harmful insults. Increased levels of HSPs occur after environmental stresses, infection, normal physiological processes, and gene transfer. Although the mechanisms by which HSPs protect cells are not clearly understood, their expression can be modulated by cell signal transducers, such as changes in intracellular pH, cyclic AMP, Ca2+, Na+, inositol trisphosphate, protein kinase C, and protein phosphatases. Most of the HSPs interact with other proteins in cells and alter their function. These and other protein-protein interactions may mediate the little understood effects of HSPs on various cell functions. In this review, we focus on the structure of the HSP-70 family (HSP-70s), regulation of HSP-70 gene expression, their cytoprotective effects, and the possibility of regulating HSP-70 expression through modulation of signal transduction pathways. The clinical importance and therapeutic potential of HSPs are discussed.

Topics: Animals; Autoimmune Diseases; Calcium; Communicable Diseases; Cyclic AMP; Forecasting; Heat Stress Disorders; HSP70 Heat-Shock Proteins; Humans; Hydrogen-Ion Concentration; Immune System Diseases; Inositol 1,4,5-Trisphosphate; Neoplasms

Inositol trisphosphate receptor (IP

Topics: Antineoplastic Agents; Apoptosis; Autophagy; Calcium; Calcium Signaling; Carcinogenesis; Cell Proliferation; Datasets as Topic; Gene Regulatory Networks; Humans; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Molecular Docking Simulation; Neoplasms; Protein Interaction Mapping; Protein Interaction Maps

The uncontrolled proliferation of cancer cells requires functional mitochondrial metabolism, which uses Ca(2+) as a cofactor. IP3 receptors (IP3Rs) from endoplasmic reticulum (ER) Ca(2+) stores provide the supply of Ca(2+) to mitochondria. A new study by Cardenas et al. shows that, in contrast to normal cells, cancer cells critically depend on ER-mitochondrial Ca(2+) fluxes for their survival by sustaining the production of mitochondrial substrates used for nucleotide biosynthesis and proliferation.

Topics: AMP-Activated Protein Kinases; Calcium; Calcium Channels; Cell Death; Cell Proliferation; Endoplasmic Reticulum; Enzyme Activation; G1 Phase Cell Cycle Checkpoints; Gene Expression; Humans; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Ion Transport; Macrocyclic Compounds; Mitochondria; Neoplasms; Organ Specificity; Oxazoles; Pyruvic Acid; RNA, Small Interfering; Tumor Cells, Cultured; Voltage-Dependent Anion Channels

Extracellular acidification is a hallmark of a number of debilitating pathologies including cancer, ischemia and inflammation. We have recently shown that in human granule precursor tumour cells a fall in extracellular pH triggers increases in intracellular Ca(2+) concentration through activation of G-protein coupled proton-sensing receptors coupling to phospholipase C. This pH-dependent rise in cytosolic Ca(2+) led to activation of the extracellular signal-regulated kinase ERK, providing a mechanistic explanation of how extracellular acidification can promote tumour growth. We now find that differentiation of granule precursor tumour cells profoundly affects their ability to respond to extracellular acidification with gene transcription. Differentiating cells have a lower Ca(2+) release probability from intracellular Ca(2+) stores upon acidification and cells that respond have a significantly smaller and slower Ca(2+) signal than proliferating cells. Importantly, Ca(2+) release in differentiating cells fails to evoke ERK phosphorylation. This altered responsiveness of differentiating cells is not due to reduced proton-sensing receptor expression or diminished Ca(2+) store content. Rather, our results suggest that in differentiating cells, the proton-sensing receptor couples less effectively to phospholipase C activation and IP(3) formation. Hence, the ability of human granule cells to respond to extracellular acidification by generating Ca(2+) signals and ERK activation is state-dependent, being lost upon differentiation.

Topics: Acids; Calcium Signaling; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Extracellular Signal-Regulated MAP Kinases; Extracellular Space; Fibroblast Growth Factor 2; Humans; Hydrogen-Ion Concentration; Inositol 1,4,5-Trisphosphate; Intracellular Space; Neoplasms; Phosphorylation; Receptors, G-Protein-Coupled; TRPC Cation Channels

We have recently shown that the Ca2+ response in endothelial cells evoked by readdition of Ca2+ to the medium after store depletion caused by a submaximal concentration of agonist can involve Ca2+ release from Ca2+ stores sensitive to both inositol 1,4, 5-trisphosphate and ryanodine. The present experiments were performed to determine whether this mechanism might also exist in other types of cell. For this purpose, we used the human carcinoma cell line A431, which has a varied resting [Ca2+]i. We found that the amplitude of the Ca2+ response evoked by Ca2+ readdition did not correlate with the amplitude of the preceding UTP-evoked Ca2+ release, but did positively correlate with the initial [Ca2+]i. An inspection of the two patterns of response seen in this study (the large biphasic and small plateau-shaped Ca2+ responses) revealed that there is an accelerating rise in [Ca2+]i during the biphasic response. Application of ryanodine during the plateau-shaped Ca2+ response reversibly transformed it into the biphasic type. Unlike ryanodine, caffeine did not itself evoke Ca2+ release, but it caused a further [Ca2+]i rise when [Ca2+]i had already been elevated by thapsigargin. These data suggest that in A431 cells, as in endothelial cells, the readdition of Ca2+ after agonist-evoked store depletion can evoke Ca2+-induced Ca2+ release. This indicates that Ca2+ entry may be overestimated by this widely used protocol.

Topics: Caffeine; Calcium; Culture Media; Endothelium; Humans; Inositol 1,4,5-Trisphosphate; Neoplasms; Ryanodine; Thapsigargin; Tumor Cells, Cultured; Uridine Triphosphate

The purpose of this paper was to clarify critical aspects of the behavior of signal transduction activity in normal and cancer cells. 1. Signal transduction activity in the conversion of phosphatidylinositol through PI and PIP kinases and PLC to IP3 is regulated at multiple sites. In liver, hepatomas and human carcinomas PIP kinase is the rate limiting enzyme and PLC activity is present in great excess. 2. The steady-state signal transduction activity as measured by the three enzyme activities and IP3 concentration was markedly up-regulated in rat hepatomas of different growth rates. The steady-state specific activities of the three signal transduction enzymes were elevated in ovarian carcinomas as compared to normal ovary. Increased enzyme activities were also observed in human breast carcinoma cells as compared to normal human breast parenchymal cells. In breast, ovarian and rat hepatoma cells as they go through lag, log and plateau phases, IP3 concentration in the early lag phase increased 4.5- to 20-fold and PI and PIP kinase activities peaked in mid-log phase. These events returned to baseline levels in the plateau phase. PLC activity did not change. 3. The bone marrow PI and PIP kinase activities in 3-day starvation were decreased to 13% and IP3 concentration was reduced to 24%; at 1-day refeeding they returned to normal. PLC activity changed little. These alterations are in line with the rapid t1/2 degradation rates (12 min) of PI and PIP kinases observed in studies with cycloheximide. By contrast, PLC has a long half-life. 4. The molecular action of tiazofurin entails inhibition of IMP DH activity, decrease in GTP and IP3 concentrations, reduction of ras and myc oncogene expression, and signal transduction enzyme activities. These events are followed by induced differentiation and apoptosis. There are also decreases in enzyme activities which have rapid turnover, including TdR kinase, dTMP synthase, and GPRT. In vitro studies indicated that these events are abrogated by addition of guanine which restores GTP concentrations. Therefore, most or all these events were brought about by the reduced GTP concentration in the tiazofurin target cells. 5. Quercetin and genistein are able to inhibit PI and PIP kinase activities and reduce IP3 concentration in vivo and in tissue culture systems. These flavonoids are also inhibitors of cell proliferation and clonogenic ability in rat hepatoma 3924A and in human OVCAR-5 and MDA-MB-435 cells. Quercetin down-regul

Topics: 1-Phosphatidylinositol 4-Kinase; Animals; Antineoplastic Agents; Apoptosis; Cell Differentiation; Cell Division; Dose-Response Relationship, Drug; Genistein; Humans; IMP Dehydrogenase; Inositol 1,4,5-Trisphosphate; Neoplasms; Phosphatidylinositols; Phosphotransferases (Alcohol Group Acceptor); Quercetin; Rats; Ribavirin; Signal Transduction; Tumor Cells, Cultured; Type C Phospholipases

(1) In all examined rat and human tissues and cells, PIP kinase activity was rate-limiting and PLC activity was present in great excess. (2) The steady-state activities of the signal transduction enzymes, PI kinase, PIP kinase and PLC, and the concentration of the end product, IP3, were determined in rat liver and hepatomas of different malignancies. The activities of all three enzymes were elevated in the hepatomas in a non-random fashion. A generalization emerged that the enzyme with the lowest activity in liver, PIP kinase, increased to the highest extent and the enzyme with the highest activity in liver, PLC, increased to the smallest extent in rapidly growing hepatomas. The IP3 concentration in the hepatomas was elevated in a progression-linked fashion. (3) The three signal transduction enzyme activities were elevated in human ovarian carcinoma samples and in human breast carcinoma cells. (4) When human breast carcinoma MDA-MB-435 cells were allowed to go through lag, log and plateau phases, the IP3 concentration reached a 20-fold peak at 12 hr after plating. The elevation in IP3 concentration preceded the rise in PI and PIP kinase activities which increased 11-fold in the log phase. The IP3 concentration and PI and PIP kinase activities returned to their baseline levels when the plateau phase was reached. The PLC activity did not change significantly during the whole period. (5) Administration of cycloheximide i.p. in rats revealed short half-lives in the bone marrow for the two kinases (8 min) and a long half-life for PLC (> 6 hr). In a group of 10 enzymes, the half-lives of the kinases were the shortest. In cycloheximide-injected rats, the bone marrow IP3 concentration was reduced to about 50% in 30 min. The reduction of IP3 concentration is attributed to the decline to 15 and 12%, respectively, in PI and PIP kinase activities since PLC activity did not change. (6) In 3-day starved rats, the bone marrow PI and PIP kinase were reduced to activities (13%) that were markedly lower than the decrease in the protein concentration (to 55%). By contrast, the PLC activity was preferentially maintained (to 78%) over the protein level. Under starvation, the IP3 concentration decreased (to 24%), indicating that starvation can markedly disrupt IP3 homeostasis. Refeeding returned the enzymic activities and the IP3 concentration to the normal level in bone marrow in 24 hr. (7) Comparison of the absolute activities of PI and PIP kinases and PLC showed that PLC is

Topics: Animals; Carcinoma, Hepatocellular; Cell Count; Cycloheximide; Diet; Diglycerides; Humans; Inositol 1,4,5-Trisphosphate; Ischemia; Mice; Neoplasms; Phosphatidylinositols; Phosphotransferases (Alcohol Group Acceptor); Rats; Signal Transduction; Tumor Cells, Cultured; Type C Phospholipases

Mitogenic signalling mechanisms emerged as novel targets for tumor chemotherapy. Current strategies for pharmacological interventions are briefly discussed. Phospholipid analogues are treated in greater detail. It is shown here that this new class of antitumor agents acts as inhibitors of mitogenic signal transduction. The common target of all phospholipid analogues studied so far is the phosphatidylinositol (PI)-specific phospholipase C (PLC). This results in an attenuated formation of inositol-1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). The reduction in IP3-levels leads to a depressed release of Ca2+ from internal stores, and the reduced formation of DAG interferes with the growth factor-induced activation of protein-kinase C (PKC). In addition to the effect on PI-specific PLC, most phospholipid analogues inhibit PKC directly by interacting with the regulatory domain of the enzyme. This effect, however, is not observed with all phospholipid analogues. Some potent growth inhibitory representatives from this group like hexadecylphosphoserine or hexadecylphosphonoserine do not affect PKC in cell-free extracts. It is concluded, therefore, that the direct inhibition of PKC is not required for the growth-inhibitory activity of these agents. The ability of phospholipid analogues to interact with PKC was also not found to be correlated the occurrence of unwanted side effects. Phospholipid analogues have also been found to act as inhibitors of phospholipase D (PLD). However, in this case the correlation to the growth inhibitory potency of various phospholipid analogues was less clear, so that the contribution of the PLD inhibition to the growth inhibitory effect of these agents still remains to be established. The inhibition of the thrombin-induced rise in cytosolic free Ca2+ by phospholipid analogues is reversible by washing the cells in phospholipid-free medium. These findings suggest that phospholipid analogues do not cause persistent membrane damage and may act as cytostatic rather than cytotoxic agents.

Topics: Antineoplastic Agents; Calcium; Enzyme Inhibitors; Inositol 1,4,5-Trisphosphate; Molecular Structure; Neoplasms; Phospholipase D; Phospholipids; Phosphorylcholine; Phosphoserine; Protein Kinase C; Signal Transduction; Sodium-Hydrogen Exchangers; Thrombin; Type C Phospholipases

1. A systematic study is reported on the control of 1-phosphatidylinositol 4-kinase (PI kinase) and PI 4-phosphate 5-kinase (PIP kinase), enzymes of the phosphatidylinositol phosphorylation pathway which leads to the production of second messengers. IP3 and DAG. In liver of normal male, adult, fed Wistar rats the steady state activity of PI kinase was 0.5 +/- 0.01 and that of PIP kinase was 0.046 +/- 0.003 nmol/hr/mg protein. The concentration of IP3 was 1.8 +/- 0.1 pmol/mg protein. 2. That the two kinases have short half-lives was observed in starvation. where in the rat liver or bone marrow activities rapidly decreased and on refeeding were restored in a day. Injection to rats of the protein synthetic inhibitor, cycloheximide, yielded t1/2 = 80 min for the two enzymes in bone marrow and t1/2 = 80 min in liver. 3. Linkage of the signal transduction enzymes with proliferation was shown by the high activities as compared to liver of these enzymes in rat organs of high cell renewal capacity, e.g., thymus, bone marrow, spleen and testes. 4. Linkage with malignant proliferation was indicated by the observation that in rat hepatomas the enzyme activities increased 5- to 9-fold and were highest in rapidly growing hepatoma 3924A (29- and 45-fold). 5. In human primary ovarian carcinoma PI and PIP kinase activities were elevated 4.4 and 2.9-fold, respectively, and in OVCAR-5 cells, 32- and 11-fold, respectively. Similar increases were observed in MDA-MB-435 human breast carcinoma cells in comparison with normal breast parenchymal cells. 6. The linkage of signal transduction enzyme activities with malignant proliferation was also observed in experiments when human breast carcinoma cells were plated in flasks and expressed their proliferative capacity in the log phase. PI and PIP kinase activities steadily and coordinately increased to a peak 11-fold rise in mid-log phase. In late log and plateau phases the kinase activities gradually declined to the starting level. Similar observations were made for the two enzymes in human ovarian carcinoma OVCAR-5 cells and in rat hepatoma 3924A cells in tissue culture. 7. In animals injected with cycloheximide the bone marrow PI and PIP kinase activities exhibited t1/2 = 0.12 hr, the shortest decay rate in comparison with 8 enzymes of purine and pyrimidine biosynthesis with t1/2 = 0.6 to 4.3 hr. 8. Injection of tiazofurin decreased PI and PIP kinase activities in the bone marrow with t1/2 = 82 and 78 min, respectively.(ABSTRACT

Topics: 1-Phosphatidylinositol 4-Kinase; Animals; Cell Division; Diet; Fasting; Female; Humans; Inositol 1,4,5-Trisphosphate; Male; Neoplasms; Phosphatidylinositols; Phosphotransferases (Alcohol Group Acceptor); Quercetin; Rats; Rats, Wistar; Ribavirin; Signal Transduction; Tumor Cells, Cultured

Vascular permeability factor (VPF), a tumor-secreted heparin-binding protein (Mr approximately 38,000), is responsible for increased vessel permeability and fluid accumulation associated with tumor growth. Vascular permeability factor also promotes the growth of human umbilical vein endothelial cells (EC) and bovine pulmonary ECs in vitro. It is shown for the first time that guinea pig VPF (half-maximal and maximal dose approximately 0.4 and 22 pmol/l (picomolar), respectively), as well as human VPF, are potent stimuli for human ECs resulting in [Ca2+]i increases (maximal three- to fourfold) and inositol triphosphate (IP3) formation. Unlike the maximal responses to thrombin and histamine, the [Ca2+]i response to a maximal VPF dose was preceded by a characteristic 10- to 15-second delay. Guinea pig VPF also selectively increased [Ca2+]i in cultured aortic and pulmonary artery ECs, but not aortic smooth muscle cells, human fibroblasts, or neutrophils. Affinity-purified rabbit antibody (raised to a synthetic peptide representing VPF N-terminal amino acids 1 to 24) adsorbed all vessel permeability-increasing activity, EC growth-promoting activity, and specifically all activity responsible for increasing EC [Ca2+]i. Similar to other mediators that increase [Ca2+]i in cultured ECs, VPF also induced a 200% increase in von Willebrand factor release. Together these data indicate that VPF acts directly on ECs and that rapid cellular events in its in vivo/in vitro actions are likely to involve phospholipase C activation, [Ca2+]i increase, and von Willebrand factor release.

Topics: Calcium; Cells, Cultured; Cytosol; Endothelial Growth Factors; Endothelium, Vascular; Humans; Inositol 1,4,5-Trisphosphate; Lymphokines; Neoplasms; Osmolar Concentration; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors; von Willebrand Factor