RESUMEN
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. Adenocarcinomas of the lungs, pancreas and colon also frequently over-express AA-metabolizing enzymes, and recent evidence suggests that the growth-regulating AA-cascade in these malignancies is under beta-adrenergic control. Our current experiments have therefore tested the hypothesis that in analogy to these findings adenocarcinomas of the breast are also regulated by beta-adrenergic receptors via stimulation of the AA-cascade. Analysis of DNA synthesis by [3H]-thymidine incorporation assays in three estrogen-responsive and three estrogen non-responsive cell lines derived from human breast cancers demonstrated a significant reduction in DNA synthesis by beta-blockers and inhibitors of cyclooxygenase or lipoxygenases in all cell lines. Analysis of AA-release in one of the most responsive cell lines demonstrated a time-dependent increase in AA-release in response to the beta-adrenergic agonist isoproterenol. Analysis by RT-PCR revealed expression of beta2-adrenergic receptors in all cell lines whereas beta1-adrenergic receptors were not found in two of the estrogen non-responsive cell lines. Our data suggest that a significant subset of human breast cancers is under control of beta-adrenergic receptors via stimulation of the AA-cascade. These findings open up novel avenues for the prevention and clinical management of breast cancer, particularly the non-estrogen-responsive types. Moreover, our findings suggest that cardiovascular disease and adenocarcinomas in a variety of organ systems, including the breast may share common risk factors and benefit from similar preventive and treatment strategies.
Asunto(s)
Antagonistas Adrenérgicos beta/farmacología , Ácido Araquidónico/metabolismo , Neoplasias de la Mama/patología , Inhibidores de la Ciclooxigenasa/farmacología , Inhibidores de la Lipooxigenasa/farmacología , Agonistas Adrenérgicos beta/farmacología , Araquidonato 5-Lipooxigenasa/metabolismo , Aspirina/farmacología , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/genética , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , ADN/biosíntesis , Replicación del ADN/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Estrógenos/farmacología , Femenino , Humanos , Isoenzimas/antagonistas & inhibidores , Isoproterenol/farmacología , Proteínas de la Membrana , Neoplasias Hormono-Dependientes/tratamiento farmacológico , Neoplasias Hormono-Dependientes/metabolismo , Prostaglandina-Endoperóxido Sintasas , ARN Mensajero/metabolismo , Receptores Adrenérgicos beta 2/genética , Receptores Adrenérgicos beta 2/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Tumorales Cultivadas/efectos de los fármacos , Células Tumorales Cultivadas/metabolismoRESUMEN
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. Because beta-adrenergic receptor activation causes arachidonic acid (AA) release and cellular injury, we postulated that NNK causes EC injury by a mechanism that involves beta-adrenergic-mediated release of AA. NNK stimulated [3H]AA release from ECs, and this effect was mediated by both beta1- and beta2-adrenergic receptors because pretreatment with atenolol or ICI 118,551 inhibited the response. NNK also induced EC apoptosis, as measured by terminal deoxyribonucleotide transferase-mediated dUTP nick-end labeling and annexin V staining. NNK-mediated apoptosis was attenuated by pretreatment with atenolol or ICI 118,551. Furthermore, depletion of cellular AA by incubation with eicosapentaenoic acid abolished the apoptotic effect of NNK. These data suggest that NNK causes EC apoptosis by a mechanism that involves beta1- and beta2-adrenergic receptor-mediated release of AA.
Asunto(s)
Apoptosis/efectos de los fármacos , Carcinógenos/farmacología , Endotelio Vascular/citología , Nitrosaminas/farmacología , Animales , Aorta/citología , Ácido Araquidónico/farmacocinética , Arteriosclerosis/patología , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Etiquetado Corte-Fin in Situ , Nicotina/farmacocinética , Receptores Adrenérgicos beta/metabolismo , Fumar/efectos adversos , Porcinos , TritioRESUMEN
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. Production of O2- and 3H-AA release increased with similar kinetics and concentration-response relations in neutrophils activated with either dieldrin or lindane. Significant release of 3H-AA was seen in neutrophils stimulated with dieldrin or lindane in calcium-free medium and in the presence of the intracellular calcium chelator BAPTA-AM, suggesting that these agents stimulate a PLA2 that does not require calcium for activation. In addition, both O2- production and 3H-AA release were inhibited in a concentration-dependent manner by BEL, a mechanism-based inhibitor of calcium-independent PLA2. These data suggest that dieldrin and lindane stimulate O2- production by a mechanism that involves PLA2. However, release of 3H-AA was not abrogated completely by BEL nor, in the case of dieldrin, preserved entirely in the absence of calcium. This suggests that more than one isoform of PLA2 is activated by dieldrin and by lindane, and that one isoform is calcium-dependent.
Asunto(s)
Dieldrín/farmacología , Hexaclorociclohexano/farmacología , Insecticidas/farmacología , Activación Neutrófila/efectos de los fármacos , Neutrófilos/enzimología , Fosfolipasas A/metabolismo , Animales , Ácido Araquidónico/metabolismo , Calcio/metabolismo , Calcio/farmacología , Quelantes/farmacología , Relación Dosis-Respuesta a Droga , Ácido Egtácico/análogos & derivados , Ácido Egtácico/farmacología , Fosfolipasas A2 Grupo VI , Masculino , Naftalenos/farmacología , Inhibidores de Fosfodiesterasa/farmacología , Fosfolipasas A/antagonistas & inhibidores , Fosfolipasas A2 , Pironas/farmacología , Ratas , Ratas Sprague-Dawley , Superóxidos/metabolismoRESUMEN
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. On the basis of structural similarities of NNK with classic beta-adrenergic agonists, we tested the hypothesis that NNK stimulates the growth of human AC cells via agonist-binding to beta-adrenergic receptors, resulting in the release of arachidonic acid (AA). In support of this hypothesis, radioreceptor assays with transfected CHO cell lines stably expressing the human beta1- or beta2-adrenergic receptor demonstrated high affinity binding of NNK to each of these receptors. Two human AC cell lines expressed beta1- and beta2-adrenergic receptors by reverse transcription-PCR and responded to NNK with the release of AA and an increase in DNA synthesis. Beta-adrenergic antagonists completely blocked the release of AA and increase in DNA synthesis. The cyclooxygenase inhibitor aspirin and the 5-lipoxygenase inhibitor MK-886 both partially inhibited DNA synthesis in response to NNK. Our findings identify the direct interaction of NNK with beta-adrenergic, AA-dependent pathways as a novel mechanism of action which may significantly contribute to the high cancer-causing potential of this nitrosamine. Moreover, NNK may also contribute to the development of smoking-related nonneoplastic disease via this mechanism.
Asunto(s)
Agonistas Adrenérgicos beta/farmacología , Ácido Araquidónico/metabolismo , Carcinógenos/farmacología , Replicación del ADN/efectos de los fármacos , Nitrosaminas/farmacología , Receptores Adrenérgicos beta/genética , Adenocarcinoma , Animales , Araquidonato 5-Lipooxigenasa/metabolismo , Células CHO , Cricetinae , ADN de Neoplasias/efectos de los fármacos , Humanos , Indoles/farmacología , Inhibidores de la Lipooxigenasa/farmacología , Neoplasias Pulmonares , Ratones , Ensayo de Unión Radioligante , Receptores Adrenérgicos beta/fisiología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transfección , Células Tumorales CultivadasRESUMEN
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. Histamine, serotonin, and LTD4 had a synergistic effect on EFS responses and only an additive effect on the tension response to exogenous ACh or methacholine. Atropine and TTX entirely eliminated the EFS-induced tension response in the presence of all three inflammatory mediators, indicating that augmentation of the EFS response applies only to the endogenous cholinergic response. Neutrophils isolated from control and COPD-affected horses were activated by zymosan, producing 18.1 +/- 2.3 and 25.0 +/- 2.3 nmol superoxide. 10(6) cells-1. 30 min-1, respectively. However, in contrast to the profound effect of mediators, incubation of SA for over 1 h in a suspension of up to 30 x 10(6) zymosan-treated neutrophils/ml did not significantly affect EFS responses of SA isolated from either control or COPD-affected horses. We conclude that in equine SA 1) the endogenous cholinergic responses are subject to strong facilitation by inflammatory mediators; 2) activated neutrophils do not affect cholinergic responses in SA; and 3) in acute bouts of equine COPD, histamine, LTD4, and serotonin (mediators primarily associated with type I allergic reaction) rather than mediators derived from neutrophils most likely contribute to increased cholinergic airway tone.
Asunto(s)
Anafilaxia/etiología , Fibras Colinérgicas/fisiología , Caballos/fisiología , Mediadores de Inflamación/fisiología , Activación Neutrófila/fisiología , Sistema Respiratorio/inervación , Animales , Femenino , Histamina/farmacología , Enfermedades de los Caballos/fisiopatología , Leucotrieno D4/farmacología , Enfermedades Pulmonares Obstructivas/veterinaria , Masculino , Neutrófilos/fisiología , Serotonina/farmacologíaRESUMEN
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. Both Aroclor 1242 and A23187 caused release of [3H]AA; however, O2- production was seen only in response to Aroclor 1242. Eicosanoids accounted for >85% of the radioactivity recovered in the supernatant of A23187-stimulated cells but <20% of the radioactivity recovered from cells exposed to Aroclor 1242. Omission or chelation of calcium abolished A23187-induced AA release, but did not alter AA release in Aroclor 1242-stimulated neutrophils. AA release and O2- production in response to Aroclor 1242 were inhibited by bromoenol lactone (BEL), an inhibitor of calcium-independent PLA2. BEL, however, did not alter Calcium-independent activity was inhibited >80% by BEL, whereas calcium-dependent activity was inhibited <5%. Furthermore, calcium-independent, but not calcium-dependent, PLA2 activity was significantly enhanced by Aroclor 1242. These data suggest that Aroclor 1242 and A23187 activate distinct isoforms of PLA2 that are linked to different functions: Aroclor 1242 activates a calcium-independent PLA2 that releases AA for the generation of O2-, and A23187 activates a calcium-dependent PLA2 that mobilizes AA for eicosanoid production.
Asunto(s)
Ácido Araquidónico/metabolismo , Eicosanoides/biosíntesis , Neutrófilos/enzimología , Neutrófilos/inmunología , Fosfolipasas A/fisiología , Superóxidos/metabolismo , Animales , Arocloros/farmacología , Calcimicina/farmacología , Sistema Libre de Células/efectos de los fármacos , Sistema Libre de Células/enzimología , Activación Enzimática/efectos de los fármacos , Masculino , Naftalenos/farmacología , Activación Neutrófila/efectos de los fármacos , Neutrófilos/metabolismo , Fosfolipasas A2 , Pironas/farmacología , Ratas , Ratas Sprague-DawleyRESUMEN
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. Neutrophils exposed to Aroclor 1242 or fMLP produced significant O2-. Pretreatment of intact neutrophils with pertussis toxin or cholera toxin or exposure of permeabilized cells to GDPbetaS significantly inhibited O2- production in fMLP-treated neutrophils but did not alter the response to Aroclor 1242. Pretreatment with genistein, an inhibitor of PTKs, significantly inhibited O2- production in both Aroclor 1242- and fMLP-treated neutrophils; however, daidzein, a structural analogue of genistein which lacks activity against PTKs, was without effect. Exposure of neutrophils to Aroclor 1242 resulted in an increase within 1 min in tyrosine phosphorylation of proteins in the 40 and 60 kDa molecular mass ranges which persisted for up to 10 min. Similar results were obtained with 2,2',4,4'-tetrachlorobiphenyl (2,2',4,4'-TCB), a PCB congener that stimulates O2- production. In contrast, 3,3',4,4',5-pentachlorobiphenyl (3,3',4,4',5-PeCB), a congener that does not generate O2-, caused only a transient increase in tyrosine phosphorylation of proteins in the 40 kDa range with no effect on 60 kDa proteins. These data suggest that Aroclor 1242 activates neutrophils to produce O2- by a mechanism that requires tyrosine kinase activity; however, heterotrimeric G-proteins are not likely to be involved.
Asunto(s)
Arocloros/toxicidad , Neutrófilos/efectos de los fármacos , Bifenilos Policlorados/toxicidad , Proteínas Tirosina Quinasas/metabolismo , Superóxidos/metabolismo , Animales , Proteínas de Unión al GTP/metabolismo , Genisteína , Isoflavonas/farmacología , Masculino , N-Formilmetionina Leucil-Fenilalanina/farmacología , Activación Neutrófila , Neutrófilos/metabolismo , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Ratas , Ratas Sprague-DawleyRESUMEN
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. All three agents significantly decreased the amount of O2- detected during stimulation of neutrophils with Aroclor 1242. Similar inhibition occurred when neutrophils were activated with the classical stimuli, formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate. The effects of BPB and manoalide were not a result of cytotoxicity or other nonspecific effects, although data suggest that quinacrine is an O2- scavenger. Significant release of 3H-arachidonic acid preceded O2- production in neutrophils stimulated with Aroclor 1242 or fMLP. Manoalide, at a concentration that abolished O2- production, also inhibited the release of 3H-arachidonate. Aspirin, zileuton, or WEB 2086 did not affect Aroclor 1242-induced O2- production, suggesting that eicosanoids and platelet-activating factor are not needed for neutrophil activation by PCBs. Activation of phospholipase A2 and O2- production do not appear to involve the Ah receptor because a congener with low affinity, but not one with high affinity for this receptor, stimulated the release of arachidonic acid and O2-. These data suggest that Aroclor 1242 stimulates neutrophils to produce O2- by a mechanism that involves phospholipase A2-dependent release of arachidonic acid.
Asunto(s)
Ácido Araquidónico/metabolismo , Neutrófilos/efectos de los fármacos , Fosfolipasas A/metabolismo , Bifenilos Policlorados/toxicidad , Superóxidos/metabolismo , Animales , Arocloros/farmacología , Aspirina/farmacología , Inhibidores de la Ciclooxigenasa/farmacología , Hidroxiurea/análogos & derivados , Hidroxiurea/farmacología , Técnicas In Vitro , Inhibidores de la Lipooxigenasa/farmacología , Masculino , N-Formilmetionina Leucil-Fenilalanina/farmacología , Activación Neutrófila , Neutrófilos/metabolismo , Fosfolipasas A/antagonistas & inhibidores , Fosfolipasas A2 , Bifenilos Policlorados/farmacología , Quinacrina/farmacología , Ratas , Terpenos/farmacología , Acetato de Tetradecanoilforbol/farmacologíaRESUMEN
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. PMNs elicited with glycogen from rat peritoneum were labeled with myo-[2-3H]inositol, and the effect of fMLP and Aroclor 1242 on accumulation of [3H]inositol phosphates was determined. Both fMLP (in the presence of cytochalasin B) and Aroclor 1242 induced rapid breakdown of inositol-containing phospholipids. Peak accumulation of [3H]inositol phosphates occurred within 5 sec in response to Aroclor 1242 and within 15-30 sec in response to fMLP. In cytochalasin B-treated PMNs, significant O2- generation occurred within 5 min of exposure to fMLP or Aroclor 1242. 2,2',4,4'-Tetrachlorobiphenyl (TCB), but not 3,3',4,4'-TCB, stimulates O2- production and degranulation in isolated rat PMNs. To determine whether inositol phosphate accumulation parallels PMN activation, [3H]inositol monophosphate (IP) production was measured in response to Aroclor 1242, 2,2'4,4'-TCB, and 3,3'4,4'-TCB in LiCl-treated cells. Both Aroclor 1242 and 2,2',4,4'-TCB, but not 3,3',4,4'-TCB, caused significant accumulation of [3H]IP. Previous reports indicate that cytochalasin B enhances PMN activation in response to fMLP by increasing the production of inositol phosphates. Pretreatment of PMNs with cytochalasin B significantly enhanced O2- production in cells exposed to Aroclor 1242 but did not alter [H]IP accumulation. These data suggest that treatment of rat PMNs with Aroclor 1242 stimulates PI turnover and are consistent with the hypothesis that hydrolysis of membrane phospholipids is important in PMN activation by PCBs. The enhancing effect of cytochalasin B on PCB-induced O2- production, however, likely involves other mechanisms.
Asunto(s)
Arocloros/farmacología , Fosfatos de Inositol/biosíntesis , Neutrófilos/efectos de los fármacos , Neutrófilos/metabolismo , Transducción de Señal/efectos de los fármacos , Secuencia de Aminoácidos , Animales , Arocloros/farmacocinética , Membrana Celular/metabolismo , Citocalasina B/farmacología , Cinética , Masculino , Datos de Secuencia Molecular , N-Formilmetionina Leucil-Fenilalanina/farmacología , Activación Neutrófila/efectos de los fármacos , Bifenilos Policlorados/toxicidad , Ratas , Ratas Sprague-Dawley , Transducción de Señal/fisiología , Estimulación Química , Superóxidos/metabolismoRESUMEN
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. Rings of femoral artery from heartworm-infected and noninfected control dogs were suspended in muscle baths, and dose-response relationships to endothelium-dependent (methacholine) and -independent (sodium nitroprusside) vasodilators were done. To determine the mechanism of relaxation, dose-response relationships were also done in the presence of an inhibitor of nitric oxide synthase (L-NAME), an inhibitor of guanylate cyclase (methylene blue), or an inhibitor of cyclooxygenase (mefenamic acid). Heartworm infection did not depress endothelium-dependent relaxation of the femoral artery in vitro. Furthermore, the mechanism of relaxation in heartworm and control femoral artery is identical. These data suggest that the effect of circulating filarial factors that alter the magnitude and mechanism of relaxation in systemic vessels in heartworm-infected dogs rapidly disappears in their absence. This results has important bearing on the dynamics of heartworm-induced pathophysiological changes during infection and could influence the nature and chronology of responses to therapy.
Asunto(s)
Dirofilaria immitis/fisiología , Dirofilariasis/fisiopatología , Enfermedades de los Perros/fisiopatología , Endotelio Vascular/fisiología , Arteria Femoral/fisiopatología , Animales , Arginina/análogos & derivados , Arginina/farmacología , Técnicas de Cultivo , Dirofilariasis/parasitología , Enfermedades de los Perros/parasitología , Perros , Relación Dosis-Respuesta a Droga , Femenino , Arteria Femoral/efectos de los fármacos , Masculino , Ácido Mefenámico/farmacología , Cloruro de Metacolina/farmacología , Azul de Metileno/farmacología , Relajación Muscular/efectos de los fármacos , Relajación Muscular/fisiología , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/fisiopatología , NG-Nitroarginina Metil Éster , Óxido Nítrico/antagonistas & inhibidores , Nitroprusiato/farmacología , Estaciones del AñoRESUMEN
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. immitis. The experiments reported here were designed to determine if filarial cyclooxygenase products could depress endothelium-dependent relaxation in vitro. Pretreatment of the parasites, but not the vascular ring, with either indomethacin or aspirin, prevented filarial-induced depression of relaxation. Analysis of heartworm-conditioned medium by gas chromatography--mass spectrometry revealed two peaks in the biologically active medium that were not present in the control. One peak had a retention time and chromatographic profile characteristic of derivatized PGD2 standard, and the other was not identified. Incubation of the vascular ring with PGD2 mimicked filarial-induced depression of endothelium-dependent relaxation at low, but not high, concentrations of acetylcholine. Thus, filarial PGD2 may be involved in altered endothelium-dependent relaxation seen in heartworm-infected dogs.
Asunto(s)
Aorta Torácica/parasitología , Dirofilaria immitis/metabolismo , Endotelio Vascular/fisiología , Prostaglandina D2/fisiología , Vasodilatación , Acetilcolina/farmacología , Animales , Aorta Torácica/efectos de los fármacos , Aorta Torácica/fisiología , Aspirina/farmacología , Femenino , Técnicas In Vitro , Indometacina/farmacología , Masculino , Prostaglandina D2/farmacología , Ratas , Ratas Endogámicas , Vasodilatación/efectos de los fármacosRESUMEN
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. D. immitis is closely related to the major human filarial pathogens. This study was designed to examine the effect of chronic infection with the filarial nematode Brugia pahangi on endothelium-mediated responses of the rat aorta in vitro. We tested the hypothesis that endothelium-dependent responses are depressed in the aorta from rats infected with B. pahangi. Rings of thoracic and abdominal aorta were suspended in muscle baths for measurement of isometric tension. Dose-response relations to norepinephrine, endothelium-dependent dilators (acetylcholine, histamine, and A23187), and nitroglycerin were done. In some experiments, inhibitors of cyclooxygenase (indomethacin and aspirin), guanylate cyclase (methylene blue), and nitric oxide formation (N-nitro-L-arginine methyl ester; L-NOARG) were used. No differences in vascular reactivity were detected in the thoracic aorta. In contrast, endothelium-dependent responses in abdominal aorta of Brugia-infected rats were significantly depressed when compared with control aorta from noninfected rats. Acetylcholine relaxation was further depressed by indomethacin and aspirin. After L-NOARG, acetylcholine relaxation in control abdominal aorta was completely abolished; however, in abdominal aorta of Brugia-infected rats, acetylcholine still caused relaxation. Methylene blue inhibited acetylcholine relaxation in both control and Brugia-infected abdominal aorta; however, relaxation in Brugia-infected aorta was significantly greater than control. This study demonstrates that endothelium-dependent relaxation can be altered by chronic experimental filarial infection in the absence of direct contact between the blood vessel and the parasite. The mechanism of relaxation in the Brugia-infected abdominal aorta appears to be altered when compared with control, suggesting that parasites are capable of modulating vascular reactivity by inducing changes in endothelial cell behavior. The mechanism may involve parasite-induced local inflammation or alterations in endothelial cell metabolism. Understanding how chronic experimental filarial infection alters vascular reactivity may enhance our understanding of the pathogenesis of human filariasis.
Asunto(s)
Aorta/fisiopatología , Brugia , Filariasis Linfática/fisiopatología , Endotelio Vascular/fisiopatología , Vasodilatación , Animales , Arginina/análogos & derivados , Arginina/farmacología , Filariasis Linfática/parasitología , Indometacina/farmacología , Masculino , Azul de Metileno/farmacología , Nitroarginina , Nitroglicerina/farmacología , Norepinefrina/farmacología , Ratas , Ratas Endogámicas Lew , Vasodilatadores/farmacologíaRESUMEN
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. immitis is located primarily in the pulmonary circulation, these findings suggested that D. immitis releases biologically active mediators that alter distal endothelium-dependent relaxation. We tested this hypothesis in vitro. Rings of rat aorta were exposed to D. immitis (alone, in 1,000 mol wt or 100 mol wt cutoff dialysis tubing, and bioassay with conditioned medium). D. immitis alone depressed relaxation to acetylcholine, carbachol, and A23187. Nitroglycerin relaxation was not affected. Depression of acetylcholine relaxation was seen with D. immitis alone, in 1,000 mol wt dialysis tubing, and bioassay with conditioned medium. However, acetylcholine relaxation with D. immitis in 100 mol wt dialysis tubing was not different from control. It appears that D. immitis releases a small, stable, biologically active factor that alters endothelium-dependent relaxation. Its exact nature is unknown. The study of endothelial cell behavior in filariasis and modulation of endothelial cell function by filarial factors may provide important clues in understanding the pathogenesis of parasitic diseases.
Asunto(s)
Dirofilaria immitis/metabolismo , Endotelio Vascular/fisiología , Filarioidea/metabolismo , Vasodilatación , Acetilcolina/farmacología , Animales , Calcimicina/farmacología , Carbacol/farmacología , Diálisis/instrumentación , Dirofilariasis/fisiopatología , Relación Dosis-Respuesta a Droga , Indometacina/farmacología , Masculino , Nitroglicerina/farmacología , Norepinefrina/farmacología , Ratas , Ratas Endogámicas , Vasodilatación/efectos de los fármacosRESUMEN
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. Because of the various complications associated with blind-stitch percutaneous abomasopexy, we concluded that it is not an appropriate procedure for correction of left displaced abomasum in valuable cattle, but may be used as an alternative for salvage in less valuable cows.
Asunto(s)
Abomaso/cirugía , Enfermedades de los Bovinos/cirugía , Complicaciones Posoperatorias/veterinaria , Gastropatías/veterinaria , Animales , Bovinos , Femenino , Estudios Retrospectivos , Gastropatías/cirugíaRESUMEN
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. Arteriography is the only other method described for actual visualization of a thrombus. This procedure is technically difficult and highly invasive.