Activation of group IVC phospholipase A(2) by polycyclic aromatic hydrocarbons induces apoptosis of human coronary artery endothelial cells.

Exposure to environmental pollutants, such as polycyclic aromatic hydrocarbons (PAHs) found in coal tar mixtures and tobacco sources, is considered a significant risk factor for the development of heart disease in humans. The goal of this study was to determine the influence of PAHs present at a Superfund site on human coronary artery endothelial cell (HCAEC) phospholipase A(2) (PLA(2)) activity and apoptosis. Extremely high levels of 12 out of 15 EPA high-priority PAHs were present in both the streambed and floodplain sediments at a site where an urban creek and its adjacent floodplain were extensively contaminated by PAHs and other coal tar compounds.

Phospholipase A2 regulation of bovine endometrial (BEND) cell prostaglandin production.

Background: Prostaglandins (PG), produced by the uterine endometrium, are key regulators of several reproductive events, including estrous cyclicity, implantation, pregnancy maintenance and parturition. Phospholipase A2 (PLA2) catalyzes the release of arachidonic acid from membrane phospholipids, the rate-limiting step in PG biosynthesis. The bovine endometrial (BEND) cell line has served as a model system for investigating regulation of signaling mechanisms involved in uterine PG production but information concerning the specific PLA2 enzymes involved and their role in regulation of this process is limited.

Tumor promoting properties of a cigarette smoke prevalent polycyclic aromatic hydrocarbon as indicated by the inhibition of gap junctional intercellular communication via phosphatidylcholine-specific phospholipase C.

Inhibition of gap junctional intercellular communication (GJIC) and the activation of intracellular mitogenic pathways are common hallmarks of epithelial derived cancer cells. We previously determined that the 1-methyl and not the 2-methyl isomer of anthracene, which are prominent cigarette smoke components, activated extracellular receptor kinase, and inhibited GJIC in WB-F344 rat liver epithelial cells. Using these same cells, we show that an immediate upstream response to 1-methylanthracene was a rapid (<1 min) release of arachidonic acid.

Distinct phospholipase A2 enzymes regulate prostaglandin E2 and F2alpha production by bovine endometrial epithelial cells.

Background: The rate-limiting step in prostaglandin (PG) biosynthesis is catalyzed by phospholipase A2 (PLA2) enzymes which hydrolyze arachidonic acid from membrane phospholipids. Despite their importance in uterine PG production, little is known concerning the specific PLA2 enzymes that regulate arachidonic acid liberation in the uterine endometrium. The objectives of this study were to evaluate the expression and activities of calcium-independent Group VI and Group IVC PLA2 (PLA2G6 and PLA2G4C) and calcium-dependent Group IVA PLA2 (PLA2G4A) enzymes in the regulation of bovine uterine endometrial epithelial cell PG production.

Gestation age-related increase in 50-kDa rat uterine calcium-independent phospholipase A2 expression influences uterine sensitivity to polychlorinated biphenyl stimulation.

Phospholipase A2 (PLA2) enzymes catalyze the rate-limiting step in eicosanoid production by liberating arachidonic acid from membrane phospholipids. There is limited information regarding the expression pattern and activity of uterine PLA2 enzymes during pregnancy. Polychlorinated biphenyls (PCBs) are a group of persistent environmental toxicants previously associated with decreased gestation length that are capable of activating PLA2.

Evaluation of polycyclic aromatic hydrocarbons in the activation of early growth response-1 and peroxisome proliferator activated receptors.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental and food contaminants with known or suspected carcinogenic properties. In this study, we have evaluated whether PAHs activate the early growth response (EGR-1) gene and bind to peroxisome proliferator-activated receptor alpha (PPAR alpha) and delta (PPAR beta/delta) in cell culture systems. Luciferase reporter systems were employed and several PAHs were evaluated for their ability to activate EGR-1 and PPARs.

EGR1 is a novel target for AhR agonists in human lung epithelial cells.

The transcription factor early growth response 1 (EGR1) was previously identified as a potential novel target of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in human lung epithelial cells by toxicogenomic analysis. EGR1 has been implicated in the pathogenesis of vascular disease and is altered by a number of factors that include stress, inflammation, and hypoxia. Depending on its downstream targets or protein interactions, EGR1 regulates important biological processes that include cell growth, apoptosis, and differentiation.

Leptin augments alveolar macrophage leukotriene synthesis by increasing phospholipase activity and enhancing group IVC iPLA2 (cPLA2gamma) protein expression.

Leptin is a hormone secreted by adipocytes in correlation with total body fat mass. In addition to regulating energy homeostasis, leptin modulates immune functions such as macrophage phagocytosis and cytokine synthesis. Previously, we reported defective leukotriene synthesis in macrophages from leptin-deficient mice that could be restored with exogenous leptin.

In vitro inhibition of growth and induction of apoptosis in cancer cell lines by thymoquinone.

Thymoquinone (TQ) is likely responsible for the chemotherapeutic effects of N. sativa extract; however, the cellular mechanisms remain ill-defined. TQ-induced cytotoxicity was investigated using canine osteosarcoma (COS31), its cisplatin-resistant variant (COS31/rCDDP), human breast adenocarcinoma (MCF7), human ovarian adenocarcinoma (BG-1) and Madin-Darby canine (MDCK) cell lines.

Polycyclic aromatic hydrocarbons present in cigarette smoke cause endothelial cell apoptosis by a phospholipase A2-dependent mechanism.

Smoking is a major risk factor for endothelial cell injury and subsequent coronary artery disease. Epidemiological studies implicate the phospholipase A2/arachidonic acid cascade in the mechanism by which smoking causes heart disease. However, specific components of cigarette smoke that activate this pathway have not been identified.

Beta-adrenergic and arachidonic acid-mediated growth regulation of human breast cancer cell lines.

Adenocarcinoma of the mammary gland is the leading type of cancer in women. Among these breast cancers those that are estrogen-responsive respond well to existing therapeutic regimens while estrogen non-responsive cancers metastasize widely, demonstrate a high relapse rate, and respond poorly to therapy. Over-expression of the arachidonic acid-metabolizing enzymes cyclooxygenase-2 and lypoxygenases is frequently observed in breast cancer, particularly the non-estrogen-responsive type, suggesting a role of the arachidonic acid (AA) cascade in the growth regulation of these malignancies.

4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, a nicotine derivative, induces apoptosis of endothelial cells.

Smoking causes endothelial cell (EC) injury; however, neither the components of cigarette smoke nor the mechanisms responsible for this injury are understood. The nitrosated derivative of nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), has been implicated in the carcinogenic effects of tobacco; however, the effects of NNK on the cardiovascular system are largely unknown. NNK binds to beta1- and beta2-adrenergic receptors.

Activation of neutrophil calcium-dependent and -independent phospholipases A2 by organochlorine compounds.

The production of reactive oxygen species by organochlorine pesticides has been implicated in the toxicity and carcinogenicity of these compounds; however, the mechanism by which these agents stimulate the production of oxygen radicals is unknown. Phospholipase A2 (PLA2)-mediated release of arachidonic acid has been shown to play an essential role in superoxide anion (O2-) production in neutrophils exposed to various physiologic and pharmacologic agents. Therefore, studies were performed to determine if the organochlorine pesticides, lindane and dieldrin, activate neutrophils to produce O2- by a mechanism that requires PLA2.

The tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone is a beta-adrenergic agonist and stimulates DNA synthesis in lung adenocarcinoma via beta-adrenergic receptor-mediated release of arachidonic acid.

Lung cancer is the leading cause of death in the United States, and it demonstrates a strong etiological association with smoking. The nicotine-derived nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) reproducibly induces pulmonary adenocarcinomas (ACs) in laboratory rodents and is considered an important contributing factor to the high lung cancer burden observed in smokers. It has been shown that the development of NNK-induced ACs in mice is reduced by inhibitors of cyclooxygenase and lipoxygenase and that the growth of human AC cell lines is regulated by beta-adrenergic receptors.

Mediators of anaphylaxis but not activated neutrophils augment cholinergic responses of equine small airways.

Neutrophilic inflammation in small airways (SA) and bronchospasm mediated via muscarinic receptors are features of chronic obstructive pulmonary disease in horses (COPD). Histamine, serotonin, and leukotrienes (LTs) are reported to be involved in the exacerbation of COPD, and currently, histamine has been shown to increase tension response to electrical field simulation (EFS) in equine SA. We tested the effects of these mediators and the effects of activated neutrophils on the cholinergic responses in SA.

Distinct phospholipases A2 regulate the release of arachidonic acid for eicosanoid production and superoxide anion generation in neutrophils.

Arachidonic acid (AA) released from membrane phospholipids by phospholipase A2 (PLA2) is important as a substrate for eicosanoid formation and as a second messenger for superoxide anion (O2-) generation in neutrophils. Different isoforms of PLA2 in neutrophils might mobilize AA for different functions. To test this possibility, we sought to characterize the PLA2s that are activated by the neutrophil stimuli, Aroclor 1242, a mixture of polychlorinated biphenyls, and A23187, a calcium ionophore.

Protein tyrosine kinase involvement in the production of superoxide anion by neutrophils exposed to Aroclor 1242, a mixture of polychlorinated biphenyls.

Neutrophils produce superoxide anion (O2-) when exposed in vitro to Aroclor 1242, a mixture of polychlorinated biphenyls (PCBs). The mechanism for this effect shares some similarities with the mechanism by which the physiologic agonist f-Met-Leu-Phe (fMLP) activates neutrophils. Since production of O2- in response to fMLP involves GTP-binding proteins and protein tyrosine kinases (PTKs), the current study was undertaken to determine whether these signalling pathways are involved in PCB-induced neutrophil activation.

Phospholipase A2 is involved in the mechanism of activation of neutrophils by polychlorinated biphenyls.

Aroclor 1242, a mixture of polychlorinated biphenyls (PCBs), activates neutrophils to produce superoxide anion (O2-) by a mechanism that involves phospholipase C-dependent hydrolysis of membrane phosphoinositides; however, subsequent signal transduction mechanisms are unknown. We undertook this study to determine whether phospholipase A2-dependent release of arachidonic acid is involved in PCB-induced O2- production. We measured O2- production in vitro in glycogen-elicited, rat neutrophils in the presence and absence of the inhibitors of phospholipase A2: quinacrine, 4-bromophenacyl bromide (BPB), and manoalide.

Aroclor 1242 stimulates the production of inositol phosphates in polymorphonuclear neutrophils.

Exposure in vitro to the mixture of polychlorinated biphenyls (PCBs), Aroclor 1242, stimulates superoxide anion (O2-) production and degranulation in rat polymorphonuclear neutrophils (PMNs). The mechanism by which PCBs activate PMNs is unknown. Phospholipase C-dependent hydrolysis of membrane phosphoinositides is an important early event in PMN activation in response to several agonists including N-formyl-methionyl-leucyl phenylalanine (fMLP); therefore, the present study was undertaken to determine whether Aroclor 1242 stimulates the production of inositol phosphates in isolated rat PMNs.

Dirofilaria immitis: depression of endothelium-dependent relaxation of canine femoral artery seen in vivo does not persist in vitro.

In heartworm-infected dogs, circulating filarial factors appear to be responsible for the seasonal depression of endothelium-dependent responses seen in the in vivo femoral artery. The effect of heartworm infection on vascular responses of the femoral artery in vitro, when the vessel is not constantly exposed to circulating factors, is unknown. Experiments were designed to test the hypothesis that in vivo exposure to circulating filarial factors leads to changes in the magnitude and mechanism of endothelium-dependent relaxation that are demonstrable in vitro.

Dirofilaria immitis: do filarial cyclooxygenase products depress endothelium-dependent relaxation in the in vitro rat aorta?

Endothelial cells modulate the function of their underlying smooth muscle. Thus, altered endothelial behavior could be important in the pathogenesis of vascular and lymphatic diseases, including human and animal filariasis. Endothelium-dependent relaxation is depressed in both in vivo canine femoral artery of dogs infected with Dirofilaria immitis and in vitro rat aorta exposed to adult D.

Depression of endothelium-dependent relaxation in aorta from rats with Brugia pahangi lymphatic filariasis.

A role for altered endothelial cell function is emerging in the pathogenesis of disease. We have previously demonstrated that Dirofilaria immitis, the canine heartworm, depresses endothelium-dependent responses and alters the mechanism of relaxation in the in vivo femoral artery of infected dogs. Exposure of rat aorta to the parasite or parasite-conditioned medium selectively depresses endothelium-dependent relaxation.

Depression of endothelium-dependent relaxation by filarial parasite products.

Endothelium-dependent relaxation is depressed in the femoral artery of dogs with heartworm, Dirofilaria immitis, infection. Moreover, in infected dogs, the mechanism of relaxation is different. Because D.

Complications of blind-stitch abomasopexy: 20 cases (1980-1985).

Over a 5-year period, 20 adult Holstein cows were admitted to the New York State College of Veterinary Medicine because of complications following blind-stitch percutaneous abomasopexy for correction of left-displaced abomasum. Of the 20 cows, 16 were treated surgically, 2 were treated medically, and 2 were admitted to the pathology service for necropsy. Complications associated with the blind-stitch technique included peritonitis, cellulitis, abomasal displacement or evisceration, complete forestomach obstruction, and thrombophlebitis of the subcutaneous abdominal vein.

Ultrasonographic diagnosis of aorto-iliac thrombosis.

A linear array 5 mHz ultrasonic scanner was used to diagnose aorto-iliac thrombosis in a 3 year old Standardbred gelding. There are no reports in the literature of utilization of ultrasonography for visualization of an aortic thrombus. The technique is fairly non-invasive, requiring only a rectal examination with a linear array probe.