The inflammatory potential of IL-2: local induction of a specific chronic granulomatous lesion in mice.

Subcutaneous injection of recombinant human interleukin-2 (rhuIL-2) at 10(2)-10(4) U/mouse induced delayed (48 h) accumulation of mononuclear leukocytes with diffuse granulocytes, including eosinophils. Subcutaneous local infusion of rhuIL-2 or recombinant murine IL-2 (10(2)-10(4) U/mouse) via implanted Alzet miniosmotic pumps in mice induced chronic inflammatory lesions characterized by infiltration of large vacuolated mononuclear leukocytes, lymphoid cells, and eosinophil foci; neovascularization, with high endothelial-like cells, was prominent, exhibiting intravascular trapping and migration of large mononuclear leukocytes. Leukocyte infiltrates comprised T lymphocytes (CD4+; CD8+), B lymphocytes, and macrophages. Control infusions of bovine serum albumin (BSA) induced weak fibrotic lesions with sparse macrophage infiltration and minimal accumulation of lymphocytes; VLA4+ and ICAM-1+ leukocyte infiltrates were significantly greater in IL-2-induced lesions compared with BSA-induced lesions. Quantitative image analysis showed significantly increased lesion size in the IL-2-induced lesions compared with those induced by BSA infusion. The vascularity of IL-2-induced lesions assessed by immunostaining for platelet-endothelial cell adhesion molecule was increased compared with control, BSA-induced lesions mainly due to neovascularization. ICAM-1 and VCAM-1 expression was significantly enhanced in IL-2 lesions. No systemic pathological changes were observed following IL-2 infusion. We conclude that local slow-release of IL-2 causes the evolution and maintenance of a specific chronic inflammatory lesion.

Effects of an infusion of dopamine on the cardiopulmonary effects of Escherichia coli endotoxin in anaesthetised horses.

Horses with colic may be endotoxaemic and subsequently develop hypotension during anaesthesia for surgical operation. The aim of this study was to evaluate the efficacy of dopamine as a means to improve cardiovascular function in anaesthetised endotoxaemic horses. Nine horses (five in group 1 and four in group 2) were anaesthetised with thiopentone and guaifenesin and anaesthesia was maintained with halothane. After approximately one hour, facial artery pressure, heart rate, pulmonary artery pressure, cardiac output, temperature, pHa, PaCO2, PaO2, base excess, packed cell volume, plasma protein concentration and white cell count were measured (time 0). Escherichia coli endotoxin was infused intravenously over 15 minutes in both groups. Group 2 horses were given an intravenous infusion of dopamine (5 micrograms kg-1 min-1) starting five minutes after the start of the endotoxin infusion and continuing for 60 minutes. Measurements were made at 15 minute intervals for 120 minutes. In group 1, one horse died during the endotoxin infusion and in two other horses mean facial artery pressures decreased to 50 mm Hg. Total pulmonary vascular resistance and packed cell volume were significantly increased. Cardiac output, cardiac index and change in mean arterial pressure were significantly greater in group 2 horses than in group 1 horses. Conversely, diastolic pulmonary artery pressure, total vascular resistance and total pulmonary resistance were significantly less in group 2 than in group 1. PaO2, base excess and white blood cell count were significantly decreased in both groups. It was concluded that dopamine improved cardiovascular function in the presence of endotoxaemia and attenuated the rate of haemoconcentration, but had no effect on the development of decreased PaO2 or metabolic acidosis.

Efeitos de baixas doses de Flunixin Meglumine na endotoxemia experimental em cavalos / Low dose Flunixin Meglumine: effects on experimental endotoxaemia in horses

A aplicaçäo de Flunixin Meglumine antes do desafio endotoxínico causou significante supressäo na geraçäo plasmática de tramboxane e 6-Keto-prostaglandina F1 alfa em eqüinos. Na dose de 0,25 mg/kg de peso vivo, o produto provocou, em cavalos pré-medicados, significativa supressäo nos índices elevados de lactado sangüíneo. A reduçäo dos sintomas clínicos de endotoxemia por açäo do Flunixin Meglumine foi dependente, facilitando a avaliaçäo clínica do animal

Acute and chronic inflammatory responses to local administration of recombinant IL-1 alpha, IL-beta, TNF alpha, IL-2 and Ifn gamma in mice.

The contention that cytokines are important mediators of inflammation prompted the present studies which were designed to compare acute and chronic pathological effects of locally-administered recombinant (r) IL-1 alpha, IL-1 beta, TNF alpha, IL-2 and Ifn gamma. Acute (6 hr), resolving (48 hr) inflammation was induced by the following, in order of potency: rIL-1 alpha greater than rIL-1 beta greater than rTNF alpha greater than rIfn gamma = BSA (control) following a single sc. injection. However, only rIL-1 beta and rIL-2 initiated and maintained chronic granulomatous reactions when delivered locally from a sc. ethylene vinyl acetate (EVA) slow-release polymer. The predominance of macrophages in EVA-rIL-1 beta lesions contrasted with the proliferative lymphoid granulomata induced by EVA-rIL-2 implants. These "in vivo" observations reinforce the roles of both IL-1 beta and IL-2 as potent mediators of chronic immunoinflammatory disease.

Local pathological responses to slow-release recombinant interleukin-1, interleukin-2 and gamma-interferon in the mouse and their relevance to chronic inflammatory disease.

1. The present study describes the pathological responses to local administration of recombinant cytokines in subcutaneously implanted slow-release ethylene vinyl acetate (EVA) co-polymer in mice. 2. EVA-recombinant human interleukin-1 beta (10(4) units) implants induced the formation of chronic granulomatous inflammatory tissue between 4 and 7 days after implantation, characterized by predominant macrophage infiltration, neovascularization and fibrosis which persisted up to 21 days after-implantation. EVA-recombinant human interleukin-1 alpha (10(4)-10(5) units) implants induced a qualitatively similar but less intense response. 3. In contrast, recombinant human interleukin-2 (10(2)-10(4) units) implants resulted in early lymphocytic vasculitis (4 days) and the development of a predominantly lymphoid lesion comprised of lymphoblasts and significant mononuclear cell proliferation by 7 days. 4. EVA-recombinant gamma-interferon (10(3)-10(4) units) implants failed to elicit a significant tissue response; with the exception of multinucleate giant cell formation the characteristics of these lesions closely resembled the mild fibrotic responses observed for EVA-bovine serum albumin (0.5-12.5 mg) implants. 5. These observations suggest that continuous endogenous local release of interleukin-1 or interleukin-2 in vivo is sufficient for the development of specific pathological features characterizing chronic immuno-inflammatory diseases.

Pharmacological inhibition of interleukin-1 activity on T cells by hydrocortisone, cyclosporine, prostaglandins, and cyclic nucleotides.

The effects of a panel of hormones and pharmacological agents on the activation of T cells by a combination of interleukin-1 and phytohemagglutinin (IL-1/PHA) was studied. Pharmacological effects on various stages of IL-1/PHA-induced interleukin-2 (IL-2) production by the cloned murine thymoma cell line LBRM-33-1A5.7 were dissected using a multi-step assay procedure. A 4-h lag phase in the kinetics of IL-2 production allowed the operational definition of an early, IL-1-dependent programming stage, followed by an IL-2-production stage of the assay. A cell-washing procedure between these stages was introduced in order to distinguish IL-1 receptor antagonists from functional IL-1/PHA antagonists. Hydrocortisone and cyclosporine were potent inhibitors (active in the nM range) of both stages of IL-2 production, suggesting that neither is an IL-1 receptor antagonist. The cyclic adenosine monophosphate (cAMP)-elevating agents prostaglandin E2, dibutyryl cAMP, and theophylline inhibited IL-2 production during the early, IL-1-dependent programming stage. By contrast, prostaglandin F2 alpha and dibutyryl cyclic guanosine monophosphate did not appreciably inhibit IL-1/PHA activity. These results are discussed in relationship to the effects of these test agents in thymocyte IL-1 assays or mitogenesis assays and the implications toward understanding the mechanisms underlying IL-1/PHA activation of T cells.

Low dose flunixin meglumine: effects on eicosanoid production and clinical signs induced by experimental endotoxaemia in horses.

The efficacy of low doses of flunixin meglumine in reducing eicosanoid generation and clinical signs in response to experimentally induced endotoxaemia was investigated. Thromboxane B2 and 6-keto-prostaglandin F1 alpha were measured in serum and plasma by radioimmunoassay. Plasma flunixin concentrations were determined by high performance liquid chromatography and pharmacokinetic parameters derived non-compartmentally. In horses administered flunixin meglumine before endotoxin challenge, a significant suppression in plasma thromboxane B2 and 6-keto-prostaglandin F1 alpha generation was observed. Elevations in blood lactate were significantly suppressed in horses pretreated with 0.25 mg/kg bodyweight flunixin meglumine. Reduction of the clinical signs of endotoxaemia by flunixin meglumine was dose dependent. Low doses of flunixin inhibited eicosanoid production without masking all of the physical manifestations of endotoxaemia necessary for accurate clinical evaluation of the horse's status.

Effects of flunixin meglumine, phenylbutazone and a selective thromboxane synthetase inhibitor (UK-38,485) on thromboxane and prostacyclin production in healthy horses.

The efficacy of three agents which alter the metabolism of arachidonic acid was investigated in normal, conscious horses. A dose response evaluation was made of flunixin meglumine and phenylbutazone, two cyclo-oxygenase inhibitors, and of a selective thromboxane synthetase inhibitor, UK-38,485. Radioimmunoassay of thromboxane B2 (TxB2) and 6-keto prostaglandin F1 alpha (PGF1 alpha) was used to assess the concentrations of thromboxane A2 (TxA2) and prostacyclin (PGI2) respectively, in serum. Flunixin was the most potent inhibitor of serum TxB2 and 6-keto PGF1 alpha production. UK-38,485 also decreased serum TxB2 generation while significantly increasing serum 6-keto PGF1 alpha levels, thus confirming its selectivity as a thromboxane synthetase inhibitor.

Modulation of arachidonic acid metabolism in endotoxic horses: comparison of flunixin meglumine, phenylbutazone, and a selective thromboxane synthetase inhibitor.

Two cyclooxygenase inhibitors (flunixin meglumine and phenylbutazone) and a selective thromboxane synthetase inhibitor were assessed in the management of experimental equine endotoxemia. Drugs or saline solution were administered to 16 horses 15 minutes before administration of a sublethal dose of endotoxin (Escherichia coli 055:B5). Plasma concentrations of thromboxane B2 (TxB2), prostacyclin (6-keto PGF1 alpha), plasma lactate, and hematologic values and clinical appearance were monitored for 3 hours after endotoxin administration. Pretreatment with flunixin meglumine (1 mg/kg of body weight) prevented most of the endotoxin-induced changes and correlated with a significant decrease in plasma TxB2 and 6-keto PGF1 alpha concentrations, compared with concentrations in nontreated horses (ie, pretreated with saline solution). Pretreatment with phenylbutazone (2 mg/kg) attenuated the effects of endotoxin and was associated with a brief, early, significant increase in plasma TxB2 concentrations, but not in plasma 6-keto PGF1 alpha concentrations. Pretreatment with the thromboxane synthetase inhibitor did not appear to clinically benefit the horses involved; however, arachidonic acid metabolism was redirected to prostacyclin production.

Flunixin meglumine given in small doses: pharmacokinetics and prostaglandin inhibition in healthy horses.

The pharmacokinetics and inhibition of prostaglandin synthesis in conscious horses given various dosages of flunixin meglumine were studied. Plasma concentrations of flunixin were measured by high-performance liquid chromatography, and serum thromboxane B2 and 6-keto prostaglandin F1 alpha were quantitated by radioimmunoassay. Within the dosage range studied, linear pharmacokinetics were achieved. After IV administration of flunixin (1.1 mg/kg, 0.25 mg/kg, 0.1 mg/kg), significant suppression of serum thromboxane generation persisted for 12, 4, and 3 hours, respectively. Repeated administrations of flunixin (0.25 mg/kg) once every 8 hours maintained significant suppression of thromboxane generation for the duration of treatment. After treatment with flunixin was stopped, serum thromboxane generation exceeded base line (pretreatment values). Among the groups, significant alteration of 6-keto prostaglandin F1 alpha production was not observed.

Cardiopulmonary effects of prostacyclin infusion in anesthetized horses.

Prostacyclin was infused IV into 6 horses anesthetized with halothane. Three dosage rates (10, 30, and 100 ng/kg of body weight/min) were evaluated in each horse. Facial and pulmonary artery pressures, heart rate, cardiac output, blood temperature, and arterial and mixed venous pH, PCO2, and PO2 were measured. Arterial blood was collected for determination of glucose, lactate, and PCV. Mixed venous blood was sampled for assay of 6-keto-prostaglandin F1 alpha and catecholamines. Infusion of prostacyclin at 10 ng/kg/min had no effect on the variables measured, whereas the 30 ng/kg/min dosage decreased diastolic and mean arterial pressure at 15 and 30 minutes and PaO2 at 15 minutes (P less than 0.05). Prostacyclin infusion at 100 ng/kg/min significantly decreased arterial pressure, total vascular resistance, and total pulmonary resistance. Heart rate increased slightly, and cardiac output increased by 44%. Arterial PO2 decreased from 311 mm of Hg to 137 and 135 mm of Hg at 15 and 30 minutes, respectively. Blood glucose was increased. Prostacyclin infusions of 30 and 100 ng/kg/min increased blood concentrations of 6-keto-prostaglandin F1 alpha by factors of 5 and 40, respectively. Significant changes in catecholamine concentrations did not occur.