Adoptive transfer of experimental allergic encephalomyelitis after in vitro treatment with recombinant murine interleukin-12. Preferential expansion of interferon-gamma-producing cells and increased expression of macrophage-associated inducible nitric oxide synthase as immunomodulatory mechanisms

In an adoptive transfer model of experimental allergic encephalomyelitis, stimulation of lymph node cells with proteolipid protein and recombinant murine interleukin (rmIL)-12 before cell transfer accelerated the onset and exacerbates clinical disease. In vitro stimulation with proteolipid protein in the presence of rmIL-12 was associated with an increase in interferon-gamma-producing cells and a decrease in IL-4-producing cells, indicating a preferential expansion of Th1 effector cells. This was supported by the finding that severe disease with rapid onset could be transferred with as few as 10 x 10(6) rmIL-12-stimulated lymph node cells. Immunohistochemical analysis confirmed that the accelerated onset of disease after in vitro stimulation with rmIL-12 coincided with an acute inflammatory response in the central nervous system. At peak disease, both control and rmIL-12 treatment groups exhibited extensive cellular infiltration with characteristic perivascular cuffing. No notable differences in either the cellular composition or cytokine expression within the lesions were seen between groups. However, the frequency of macrophages that stained positively for inducible nitric oxide synthase was increased in animals challenged with rmIL-12-treated lymph node cells. The results suggest that, in addition to promoting the preferential expansion of interferon-gamma-producing cells by rmIL-12 in vitro, secondary in vivo effects leading to macrophage activation and inducible nitric oxide synthase expression may contribute to the severe and protracted course of central nervous system inflammation in this model.

In vivo studies with interleukin-12 alone and in combination with monocyte colony-stimulating factor and/or fractionated radiation treatment

Interleukin-12 (IL-12) was found to be an active anti-tumor agent in 3 established murine solid tumors: B16 melanoma, Lewis lung carcinoma and renal cell carcinoma (RenCa). IL-12 was well tolerated over a 100-fold dose range. Only the high-dose treatment of IL-12 resulted in a clear reduction in the number of lung metastases from B16 melanoma and Lewis lung carcinoma. Treatment of animals bearing Lewis lung carcinoma with IL-12 in combination with fractionated radiation therapy was markedly dose-modifying, indicating that IL-12 was acting synergistically with radiation. Treatment of animals bearing the same tumor with monocyte colony-stimulating factor (M-CSF) along with fractionated radiation therapy resulted in a parallel increase in tumor growth delay with increasing dose of M-CSF, indicating that M-CSF was affecting a subpopulation of tumor cells in addition to those killed by radiation therapy. The combination of IL-12 with M-CSF was most effective with radiation therapy, especially in the clinically relevant dosages of 2 and 3 Gy per fraction. By isobologram analysis, IL-12 and M-CSF, along with fractionated radiation therapy, resulted in a greater-than-additive (synergistic) tumor response.

Evaluation of recombinant human factor IX: pharmacokinetic studies in the rat and the dog

The pharmacokinetics of intravenously administered recombinant human factor IX (rhFIX) were studied in Sprague-Dawley rats and Beagle dogs. Rats received rhFIX (50 IU/kg once daily) for 28 days, and the plasma half-life was 5 h. Anti-Human Factor IX serum antibody levels were found in only 1 of 12 rats. The pharmacokinetic profiles of rhFIX or Mononine, a purified human plasma-derived factor IX, after single 100 IU/kg i.v. doses in dogs, were similar. Peak plasma concentrations of rhFIX and Mononine were 4-5 micrograms/ml. The mean plasma half-lives were 13.2 +/- 1.6 h for rhFIX and 13.3 +/- 1.6 h for Mononine. Dogs also received rhFIX (40 IU/kg i.v., daily) for 28 days or Mononine (40 IU/kg i.v. daily) for 14 days. Anti-human Factor IX serum antibody levels were determined for each compound. Pharmacokinetic half-lives decreased in these treated dogs which developed antihuman Factor IX antibodies. The antibody responses in 28 day rhFIX (40 IU/kg) dogs were similar to 14 day Mononine (40 IU/kg) dogs.

Healing of large segmental defects in rat femurs is aided by RhBMP-2 in PLGA matrix

Recombinant human bone morphogenetic protein-2 (rhBMP-2) can be used to enhance the repair of congenital or acquired bone pathologies when formulated in the appropriate carrier. Poly [D,L-(lactide-co-glycolide)] (PLGA) has been shown to be an effective carrier of rhBMP-2. We investigated several particle sizes PLGA and several doses of rhBMP-2 in a rat orthotopic model. We also investigated the effects of a fibrinolytic inhibitory agent, epsilon aminocaproic acid (EACA), on the healing response. Our data indicate that higher doses of rhBMP-2 resulted in increased failure torque (408 +/- 70 N-mm or 60% of the intact value) and higher incidence of union (100%). The induced bone in femurs treated with the smaller particle size PLGA achieved the greatest torsional stiffness and strength. The presence of rhBMP-2 was necessary for new bone to form, but the presence of EACA did not change these results; the use of the PLGA carrier appeared to increase bone strength and stiffness. In fact, with higher doses of rhBMP-2 in PLGA, the stiffness of the new bone was equal to that of intact controls (64 +/- 20 N-mm/deg [intact femurs] versus 45 +/- 10 N-mm/degree [medium dose in small PLGA], 61 +/- 17 N-mm/degree [high dose in small PLGA], and 36 +/- 11 N-mm/degree [medium dose in large PLGA]; P > .05). In conclusion, PLGA implanted with rhBMP-2 effectively aided in healing large segmental defects in rat femurs.

Recombinant human bone morphogenetic protein-2 is superior to demineralized bone matrix in repairing craniotomy defects in rats

The purpose of this study was to measure bone-regenerative effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) in rat calvarial critical-size defects (CSDs). CSDs (8 mm in diameter) were treated with either 1) 2.2 micrograms rhBMP-2 combined with insoluble collagenous bone matrix (ICBM), 2) 6.5 micrograms rhBMP-2 plus ICBM, 3) ICBM alone, or 4) demineralized bone matrix (DBM), for 7, 14, or 21 days. Multiple linear regression showed that rhBMP-2 had a significant time- and dose-dependent effect on bone regeneration (P < .05). After 7 days, new calcifying cartilage and remineralizing ICBM, with an occasional zone of new woven bone, was evident in defects treated with rhBMP-2/ICBM. By 14 days, both doses of rhBMP-2 reconstituted with ICBM had induced more bone formation than ICBM alone or DBM, and 6.5 micrograms was superior to 2.2 micrograms. There was no evidence of adverse cellular response. This study shows for the first time that rhBMP-2 could restore osseous form to a calvarial defect. In addition, osteoregeneration was accelerated by the higher dose of rhBMP-2.

Recombinant human macrophage colony-stimulating factor reduces plasma cholesterol and carrageenan granuloma foam cell formation in Watanabe heritable hyperlipidemic rabbits

Previous studies have demonstrated that short-term administration of recombinant human macrophage colony-stimulating factor (rhM-CSF) reduces plasma cholesterol in rabbits, nonhuman primates, and human subjects. This study extended the dose schedule of rhM-CSF to 8 weeks of continuous intravenous infusion (CIV) in the Watanabe heritable hyperlipidemic (WHHL) rabbit and expanded the scope to include an assessment of macrophage-derived foam cell development. Ten male WHHL rabbits were injected subcutaneously with 1% carrageenan to promote formation of a macrophage-rich foam cell granuloma. Rabbits were infused with either vehicle or rhM-CSF at 100 micrograms/kg per day (weeks 1 through 5) followed by 300 micrograms/kg per day (weeks 6 through 8). rhM-CSF (100 micrograms/kg per day) decreased total plasma cholesterol by 45% at 2 weeks compared with controls. The gradual return of plasma cholesterol toward control concentrations over the subsequent 3 weeks correlated with the appearance of circulating antibodies specific to rhM-CSF. Granuloma weights at harvest (8 weeks after infusion) were significantly lower (2.8 +/- 0.7 g, mean +/- SEM) in rhM-CSF-treated rabbits relative to controls (7.1 +/- 1.5 g, P < .05). Granulomas from rabbits treated with rhM-CSF contained lower concentrations of cholesterol (2.0 +/- 0.7 versus 6.1 +/- 1.5 micrograms/mg, P < .03) and cholesteryl ester (0.7 +/- 0.4 versus 3.9 +/- 1.2 micrograms/mg, P < .03) than controls. Histological evaluation revealed that granulomas from the rhM-CSF-treated rabbits were more fibrous and contained fewer foam cells than those from controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Resolution of cutaneous leishmaniasis: interleukin 12 initiates a protective T helper type 1 immune response

Resistance to Leishmania major in mice is associated with the appearance of distinct T helper type 1 (Th1) and Th2 subsets. T cells from lymph nodes draining cutaneous lesions of resistant mice are primarily interferon gamma (IFN-gamma)-producing Th1 cells. In contrast, T cells from susceptible mice are principally Th2 cells that generate interleukin 4 (IL-4). Although existing evidence is supportive of a role for IFN-gamma in the generation of Th1 cells, additional factors may be required for a protective response to be maintained. A potential candidate is IL-12, a heterodimeric cytokine produced by monocytes and B cells that has multiple effects on T and natural killer cell function, including inducing IFN-gamma production. Using an experimental leishmanial model we have observed that daily intraperitoneal administration at the time of parasite challenge of either 0.33 micrograms IL-12 (a consecutive 5 d/wk for 5 wk) or 1.0 micrograms IL-12 per mouse (only a consecutive 5 d) caused a > 75% reduction in parasite burden at the site of infection, in highly susceptible BALB/c mice. Delay of treatment by 1 wk had less of a protective effect. Concomitant with these protective effects was an increase in IFN-gamma and a decrease in IL-4 production, as measured by enzyme-linked immunosorbent assay of supernatants generated from popliteal lymph node cells stimulated with leishmanial antigen in vitro. The reduction in parasite numbers induced by IL-12 therapy was still apparent at 10 wk postinfection. In addition, we observed that the administration of a rabbit anti-recombinant murine IL-12 polyclonal antibody (200 micrograms i.p. every other day for 25 d) at the time of infection to resistant C57Bl/6 mice exacerbated disease. These effects were accompanied by a shift in IFN-gamma production in vitro by antigen-stimulated lymph node cells indicative of a Th2-like response. These findings suggest that IL-12 has an important role in initiating a Th1 response and protective immunity.

Novel agents that promote bone regeneration

Regulation of bone growth is controlled partly by local growth factors, which have effects on bone including the differentiation of precursor cells, osteoblast proliferation, the stimulation of matrix synthesis and angiogenesis. These factors are hypothesized to have a role in augmenting bone repair. In the past year, recombinant technology has provided sufficient material to allow extensive in vivo evaluation of this hypothesis.

Correlation of leukocyte interleukin-1 production with the stimulation of prostaglandin and tissue factor synthesis by human umbilical vein endothelial cells

Human leukocyte suspensions (neutrophils 80-85%, monocyte 15-20%) were incubated alone or with cultured human umbilical vein endothelial cells. Leukocytes were either directly added to the endothelial cell cultures or separated from them by a 0.4 micron insert filter. Supernatants or cell lysates were obtained at 0.5, 1, 2, and 4 hours of incubation. Supernatants were assayed for the prostacyclin (PGI2) metabolite 6-keto prostaglandin F1 alpha and prostaglandin E2 (PGE2) by radioimmunoassay and for interleukin-1 (IL-1) by the thymocyte co-mitogen assay. Cell lysates were analyzed for cell-associated procoagulant activity (PCA). Co-incubation of endothelial cells with leukocytes stimulated the synthesis of PGI2, PGE2, and PCA. These biochemical changes correlated partially with the release of IL-1 beta. The results suggest that IL-1 released in monocyte neutrophil co-cultures can produce prothrombotic (increased PCA expression) and inflammatory changes (increased synthesis of vasodilatory and permeability enhancing PGI2 and PGE2) in endothelial cells. Neutrophils may represent a source of the released IL-1 and/or may act to stimulate monocyte release of this cytokine and thus play an important role in vascular pathology by a mechanism unrelated to their more direct cytotoxic activity.

Proliferative and lipid metabolism response to balloon angioplasty in canine renal arteries

The mechanisms responsible for reocclusion after percutaneous transluminal angioplasty are still poorly understood. The effects of angioplasty on arterial morphology, deoxyribonucleic acid (DNA) synthesis (3H-thymidine incorporation) and lipid metabolism (14C-oleate incorporation) were studied in renal arteries of 24 male mongrel dogs. Balloon-dilated (identified by Evans blue dye accumulation) and adjacent normal arterial segments were collected 90 min and 2, 5 and 14 days after the procedure. The immediate vascular response was endothelial cell denudation and platelet accumulation. Two weeks after angioplasty, healing of the luminal surface by "endothelial-like" cells, mild smooth muscle cell proliferation and an angiogenic response with capillary growth into the media were observed. DNA synthesis was increased in balloon-dilated segments at day 5 compared with adjacent nonballoon-dilated artery. This increase in DNA synthesis persisted in the 2 week postangioplasty segments. Additionally, angioplasty produced both quantitative and qualitative changes in arterial lipid synthesis. The most dramatic change was an increase in sterol esterification that was apparent as early as 90 min after angioplasty; the change persisted through day 5 but diminished toward baseline by day 14. Angioplasty-induced alterations of arterial metabolism parallel aspects of the atherogenic process and may be involved in the pathogenesis of postangioplasty reocclusion, particularly in the presence of additional risk factors, such as hyperlipemia.

1,4-Dihydronaphthoquinones as water-soluble inhibitors of 5-lipoxygenase

The acetate derivatives of 1,4-dihydronaphthoquinones showed significant inhibition of 5-lipoxygenase. Among them, 1-acetyl-2-n-butyl-4-methoxy-naphthalene and 1-acetyl-2, 3-diethyl- 4- methoxy-naphthalene were found to be the best inhibitors. A series of HCl salts of the amino acid esters and other derivatives of the two parent molecules, 1-hydroxy-2-n-butyl-4-methoxy-naphthalene and 1-hydroxy-2, 3-diethyl-4-methoxynaphthalene, were synthesized as water-soluble potential inhibitors of 5-lipoxygenase to improve the formulation characteristics of this class of compounds. The derivatives were evaluated for leukotriene (LT) C4/D4 and LTB4 inhibitory activity. The HCl salts of the L-valine esters from the two parent molecules exhibited the best potency for inhibition of LTC4/D4 (IC50 0.11-0.90 microM) in ionophore A23187-stimulated rat mononuclear cells and of LTB4 in A23187-stimulated rat blood (55.5-79.2% inhibition) following a single oral dose of 50 mg/kg.

In vivo demonstration of enhanced arterial constrictor response to serotonin following focal endothelial cell loss

Arterial sensitivity to vasospasm was assessed prior to and 2 weeks following a 15-min period of external compression of the superficial femoral artery in dogs. Compression was achieved by placing a plastic cuff around the artery to produce a 40-60% reduction in the artery cross-sectional area. An additional six dogs were used to assess morphologic changes produced in the artery immediately and at 2 weeks after compression. Angiography following intraarterial infusions of serotonin (10 and 30 micrograms/min), norepinephrine (0.1 microgram/min), ergonovine (20 micrograms/min), and the thromboxane mimic U-46,619 (0.1 microgram/min) demonstrated a specific sensitivity to serotonin 2 weeks after the 15-min application of external arterial compression. The serotonin response was antagonized by the specific serotonin (5-HT2) receptor antagonist, ketanserin. Scanning electron microscopy of the acutely injured luminal surface revealed loss of endothelium and deposition of platelets. Patchy areas with intact endothelium and migrating leukocytes were located within the denuded sites. Two weeks after constrictor placement, the compressed area appeared as a raised or semiraised lesion in which the orientation and shape of the luminal cells were distinctly delineated from the adjacent noninjured segments. However, the luminal cells appeared to be endothelium that had regrown over the previously denuded area. The results of this study demonstrate, in an in vivo model, an enhancement in serotonin-mediated vasoconstriction following intimal injury and repair and support the suggestion that endothelial damage or dysfunction may play a role in the pathophysiology of arterial spasm.

Suppression of aortic atherosclerosis in cholesterol-fed rabbits by purified rabbit interferon

The effectiveness of rabbit interferon in suppressing atherosclerosis was evaluated in rabbits fed a diet containing 1% cholesterol. Ten male New Zealand White rabbits received intramuscular injections of 1 million units of interferon twice a week, while a control group of 10 rabbits received injections of buffer. Both groups had average serum cholesterol levels of over 2000 mg/dl during the 8-week experimental period. Interferon treatment resulted in no significant hypolipidemic effect or changes in lipoprotein composition. Atherosclerotic lesions in aortas were quantified both macroscopically and microscopically. Interferon treatment decreased the grossly visible lesion area significantly from 25 +/- 4% to 8 +/- 1% (mean +/- SEM, p less than 0.005) compared to the untreated group. Microscopic analysis of serial cross-sections of aortic segments revealed significant (p less than 0.01) reductions in both lesion size and frequency in the interferon-treated group. Electron microscopy also showed that interferon treatment reduced the pathological effects of cholesterol feeding. Tissue analysis showed that total aortic cholesterol was reduced by 28% by interferon treatment, while the aortic phospholipid concentration was increased by 25%. The possibility exists that the interferon preparation used contained other biological response modifiers and that the observed effects may be totally unrelated with interferon. These results suggest that the mechanism of atherosclerosis suppression in these cholesterol-fed rabbits is not related to the lowering of serum cholesterol but may be associated with inhibition of lesion initiation.

1,4-Dihydronaphthoquinones, hydroindoloquinones, benzofurans, and benzothiophenes as inhibitors of 5-lipoxygenase. Synthesis and structure-activity studies

A series of substituted 1,4-dihydronaphthoquinones, hydroindoloquinones, benzofuran-4,7-dihydroquinones, and benzothiophene-4,7-dihydroquinones were synthesized and evaluated for inhibitory activity against 5-lipoxygenase. These compounds were found to be active in vitro for LTC4/D4 inhibition with the potencies (IC50's) ranging from 0.2 to 85 microM. Active 1,4-dihydronaphthoquinone acetates (IC50 less than 20 microM) were evaluated in an ex vivo LTB4 inhibition assay. The acetates of 1,4-dihydronaphthoquinones containing the alkyl substituent(s) (2-n-butyl, 11, and 2,3-diethyl, 15) exhibited the best activity in LTC4/D4 inhibition (IC50 = 0.2-0.4 microM, in vitro) as well as in LTB4 inhibition (60-75% inhibition).

Interleukin-1 induced vascular pathology "in vivo": a scanning electron-microscopy study

Ethylene vinyl acetate (EVA) discs containing either 50 U interleukin-1 (IL-1) or 250 mg bovine serum albumin as control were implanted around the exposed jugular veins of rabbits. After 24 hr, the veins were examined by scanning electron-microscopy. Compared with minor changes in control vein lumena, those of EVA-IL-1 treated veins showed extensive endothelial cell denudation and exposure of basement membrane associated with platelet accumulation and adherence/subendothelial migration of leucocytes. These observations suggest that locally-released IL-1 provokes significant vascular pathological changes "in vivo" and emphasise the importance of this cytokine as a mediator of inflammatory and thrombotic/atherosclerotic diseases.

Comparison of lipid accumulation and metabolism in carrageenan-induced granulomas to aorta and blood monocytes of normal and cholesterol-fed rabbits

New Zealand rabbits (six each) were either maintained on a standard chow diet (ND) or the chow diet supplemented with cholesterol/peanut oil (HD) for 2 weeks. After 2 weeks, each animal had 15 ml of a 1% carrageenan gel injected subcutaneously into the midabdominal area. Rabbits were maintained on the diets for an additional 4 weeks. At sacrifice, blood was collected both for serum and for monocyte isolation and granulomas and aorta were excised. Tissues were assayed for lipid composition and lipid metabolism. Electron and light microscopies were performed on granuloma tissue. Granulomas from ND animals did not stain with oil red O. Granulomas from HD animals had homogenous oil red O staining indicating lipid accumulation. Granulomas from both ND and HD animals consisted of macrophages. Macrophages from ND rabbits accumulated follicular carrageenan but not lipid, while HD macrophages had the appearance of foam cells. Granuloma lipid content and metabolism closely paralleled the aorta and blood monocytes. The HD tissue had increased acylCoA:cholesterol acetyltransferase (ACAT) activity and lipid composition changes reflective of the atherosclerotic process. ND granulomas had no elevation of lipid content or ACAT. The carrageenan-induced granulomas provide a useful model for studying the biochemical and morphologic changes characteristic of arteries undergoing atherogenic change.

Ciprostene, a stable prostacyclin analog, produces peripheral vasodilation, platelet inhibition and increased clot dissolution in the cat

The effect of the stable prostacyclin analog ciprostene on hemodynamic parameters, platelet aggregation and clot dissolution was examined in the sodium pentobarbital anesthetized cat. Hemodynamic and platelet aggregation effects were measured in 5 cats following infusion of 5, 10, 20, 40 and 80 micrograms/kg/min of ciprostene. Drug was dissolved in Tyrode's buffer (pH 7.4) and all doses were infused for 20 minute intervals in ascending order. The hemodynamic data were consistent with peripheral vasodilation. The total peripheral resistance and mean aortic pressure decreased with increasing dose. No change in heart rate, cardiac index, or left ventricle dP/dt (contractility) was observed. All doses infused produced inhibition of ADP induced platelet aggregation. In vivo fibrinolytic activity was assessed with an aortic thrombus positioned at the bifurcation of the aorta. Five cats were infused with vehicle and 5 cats each were infused with 8 and 20 micrograms/kg/min ciprostene respectively. All infusions were via a 4F catheter positioned in the aorta proximal to the thrombus. Infusion time was 3 hours. Infusion of 8 micrograms/kg/min did not enhance dissolution of the aortic thrombus. However, the 20 micrograms/kg/min infusion significantly reduced the thrombus weight (mean = 13.2 mg) compared to vehicle (mean = 38.7 mg) (p less than 0.03). The results suggest that ciprostene is a potent vasodilator and platelet inhibitor with clot dissolution properties.

Heparin inhibits fibrin, but not leukocytes, in a model of deep-vein thrombosis

Previous studies with models of deep-vein thrombosis (DVT) have demonstrated that leukocyte (PMN)-mediated vein injury may be an initiating event in DVT (14, 17). Since heparin (H) can prevent DVT, we studied its effect on vascular injury and thrombosis in our model. Three groups of rabbits were treated with H either sc (73 and 147 U/kg) or iv (662 U/kg). Scanning electron microscopy revealed that the 73 U/kg sc dose was ineffective. All veins had PMN accumulation, fibrin deposition and complex thrombus formation. There was no increase in anti-Xa activity; activated partial thromboplastin times (APTT) and whole blood clotting times were normal. The 147 U/kg sc and the intravenous dose did not inhibit PMN-mediated vein injury. The endothelium was sloughed by migrating PMNs, basement membrane was exposed, and platelets adhered to it. Thrombosis was completely absent in the iv dose group. This correlated with increased anti-Xa activity and prolonged APTT and whole blood clotting times. Our results indicate that heparin does not inhibit the PMN adhesion and migration which produces vascular injury. However, the anticoagulant activity of heparin effectively reduces fibrin deposition and complex thrombus formation.

Use of ultrasound for noninvasive study of blood vessel responsiveness

To provide a noninvasive means for studying individual macroscopic blood vessels, an ultrasound scanner was modified to provide a recording of blood vessel diameter. The instrument has A- and B-modes of signal display. The B-mode is used to position the probe and the A-mode to measure vessel diameter. The A-mode has two electronic gates for tracking the echo from each of two structures, i.e., near and far wall of vessel. The front gate was modified to pick up the falling rather than rising edge of a peak generated by the vessel wall. An analog signal proportional to the distance between gates was derived for recording with a strip-chart recorder. Probe holders were constructed to optimize positioning and holding of probe. Stability was excellent (reading varied 0.05 mm over 1 h). Axial resolution was between 0.3 and 0.73 mm. Discrepancy of measurements of plastic tubing made by ocular and ultrasound varied from 1.1 to 4.6%. Discrepancy with lightly fixed vessels was 2.7-8.2%. Ex vivo measurements on vessels with viable smooth muscle were more variable, perhaps because of actual change during measurements. Changes in vessel diameter induced by change in hydrostatic pressure and exposure to histamine were recorded.

Beneficial effects of U-63,557A, a thromboxane synthetase inhibitor, in an ovine model of pregnancy-induced hypertension

Pregnancy-induced hypertension was induced in five ewes (gestational day 135; term 150 days) by 72 hours of food deprivation. Maternal arterial pressure, uterine blood flow, platelet function, renal function, and plasma levels of 6-ketoprostaglandin F1 alpha and thromboxane B2 were measured before and during hypertension and after three intravenous injections of U-63,557A; sodium 5-(3'-pyridinylmethyl) benzofuran-2-carboxylate, monohydrate (30 mg/kg every 8 hours). Blood pressure increased (p less than 0.03), and returned to normal after U-63,557A. Left uterine artery blood flow increased after U-63,557A (p less than 0.03). Creatinine clearance decreased during hypertension (p less than 0.03) and increased after U-63,557A. Urine protein increased during hypertension (p less than 0.03) and decreased after treatment. Platelet count dropped during hypertension (p less than 0.03) and was elevated after treatment. Collagen lag phase decreased during hypertension (p less than 0.03) and increased after treatment. After U-63,557A, 6-ketoprostaglandin F1 alpha levels were higher (p less than 0.04) than baseline or hypertensive values. Administration of a thromboxane synthetase inhibitor caused resolution of hemodynamic, renal, and coagulation dysfunctions that occurred in ovine pregnancy-induced hypertension.

A study of atherosclerotic lesion development in the injured pulmonary arteries of dogs with induced hyperlipemia

Studies of experimental atherosclerosis in the dog demonstrate that many months at plasma cholesterol concentrations greater than 750 mg/dl are required to produce lipid containing atherosclerotic lesions. Since it has been recognized for many years that vascular injury in combination with hyperlipemia will result in rapid formation of atherosclerotic lesions, we attempted to combine vascular injury with hyperlipemia as a means of accelerating this process in the dog. Injury was produced in pulmonary arteries with experimental Dirofilaria immitis (DI or heartworm) infection. This filarial parasite produces characteristic lipid-free lesions containing smooth muscle cells and occasional monocytes and collagen. Plasma cholesterol was increased by feeding 10 dogs an essential fatty acid-deficient diet (EFAD) for 90 days. Five of the EFAD dogs were infected with 30 to 31 adult DI worms to produce pulmonary artery injury. The remaining 5 EFAD dogs were not subjected to any form of vascular injury. An additional 5 control dogs were not subjected to vascular injury nor to the EFAD diet. The arteries of dogs infected with DI developed myointimal proliferative lesions which contained smooth muscle cells and macrophages. In addition, the EFAD diet produced significant elevations in LDL but not VLDL plasma cholesterol in all 10 dogs fed the diet. However, the plasma cholesterol was less than 750 mg/dl in all EFAD-fed dogs. Although smooth muscle cells and macrophages in the pulmonary arteries of DI-infected dogs were focal points for lipid accumulation, cholesterol content of these injured arteries was not increased compared to noninjured EFAD dogs. The results suggest that even severe vascular injury does not reduce the threshold of 750 mg/dl required to produce significant lipid accumulation in canine arteries.

Human protein C induces anticoagulation and increased fibrinolytic activity in the cat

The effect of activated human Protein C (PCa) infusion on the coagulation and fibrinolytic systems of the cat was examined. Cats received bolus i.v. injections of PCa of 3 micrograms/mL (n = 7), 10 micrograms/mL (n = 2) or 16 micrograms/mL (n = 1) of calculated total blood volume. Control cats (n = 7) received either unactivated Protein C (10 micrograms/mL) or the activation vehicle containing heparin and antithrombin in tris-saline buffer. Citrated blood samples were drawn prior to infusion and 5, 10, 20, 40, 60, 120 and 180 minutes post infusion. PCa caused an immediate, dose dependent increase in anticoagulation as measured by APTT which began to normalize within 20 minutes. PCa also increased fibrinolytic activity measured by euglobulin clot lysis time and an 125I whole blood clot lysis assay. However, the profibrinolytic effect of PCa did not parallel the anticoagulant effect. In all treated cats, maximum fibrinolytic activity did not occur until 40-120 minutes after infusion. Control cats demonstrated no significant change in coagulation or fibrinolytic activity. Our results demonstrate that infusion of activated human Protein C can induce anticoagulation and fibrinolytic activity in the cat.

Leukocyte mediated vein injury and thrombosis is reduced by a lipoxygenase inhibitor

We have previously demonstrated an in vivo model of deep vein thrombosis which suggests that the neutrophil promotes vascular injury and thrombosis following blood flow stasis. Since leukotrienes are potent mediators of vascular injury and neutrophil (PMN) chemotaxis, we wished to determine if in vivo inhibition of 5-lipoxygenase would reduce neutrophil mediated events in our model. Lipoxygenase was inhibited in vivo with 2,3-diethyl-4-methoxy,1-naphthalenol acetate (U-66,855). The in vivo activity of U-66,855 was demonstrated in 4 cats. Each animal was treated with 5 mg/kg of U-66,855 intravenously. Blood cell leukotriene B4 (LTB4) and thromboxane A2, via its metabolite thromboxane B2 (TBX2) was assessed before and 30, 60, and 120 min after dosing. Blood cell LTB4 and TBX2 production was stimulated by A23187 (24 microM) and assayed by radioimmunoassay. We exposed and isolated a 3-cm segment of the jugular veins from 10 additional cats 5 of which were treated with U-66,855 (5 mg/kg, iv). In order to assess the effect of stasis, the jugular veins were ligated at the thoracic inlet for 2 hr after which the veins were perfused, fixed in 2.5% glutaraldehyde, and prepared for electron microscopy. U-66,855 reduced LTB4 production significantly (P less than 0.01), but not TBX2. In untreated cats, PMNs adhered to and migrated underneath the venous endothelium. Additionally, platelets, fibrin and formed thrombi were found on the basement membrane exposed by the migrating neutrophils. In contrast, we observed significantly reduced PMN adhesion as well as no fibrin deposition in veins obtained from cats treated with U-66,855. The results suggest that 5-lipoxygenase inhibition can significantly reduce undesirable neutrophil/vessel wall interactions.

Feline polymorphonuclear leukocytes respond chemotactically to leukotriene B4 and activated serum but not to F-Met-Leu-Phe

The chemotactic response of feline polymorphonuclear leukocytes (PMNs) to three types of chemoattractants was studied. Feline PMNs responded to leukotriene B4 as well as to agarose-activated autologous and homologous serum. However, no response was obtained to N-formylmethionylleucylphenylalanine (FMLP), and four similar peptides that activate the FMLP receptor (N-formylnorleucylleucylphenylalanine, N-formylmethionylphenylalanine, methionylleucylphenylalanine, and pepstatin). Thus, feline PMNs are similar to equine, porcine, bovine and canine PMNs which also do not respond chemotactically to these peptides.

Tolerance and pharmacology of ciprostene, a stable epoprostenol (prostacyclin) analogue in humans

Safety, tolerance, and pharmacology of 9-beta-methylcarbacyclin calcium (ciprostene calcium) was investigated in healthy male volunteers. This stable prostacyclin analogue was infused intravenously into groups of 12, 11, and three volunteers for three, six, and eight hours, respectively, in doses up to 480 ng/kg/min. Based on the tolerance data obtained, a single-blind, placebo-controlled study was conducted. Seven subjects were infused for 8 hr/d for three days with ciprostene at a maximum dose of 160 ng/kg/min and seven subjects received placebo. One subject from each group did not complete the infusion schedule, and they were not included in the final analysis. During infusion of ciprostene, consistent changes in blood pressure and heart rate did not occur. Most frequent adverse drug reactions consisted of headache, restlessness, nausea, perspiration, flushing, and jaw pain. As compared with placebo, ADP-induced platelet aggregation was inhibited during the infusion period (P = .048). Significant (P = .04) elevations of platelet cyclic AMP were observed in subjects during infusion of ciprostene. Pre- versus postinfusion routine laboratory evaluations, fibrinogen concentration, antiplasmin activity, and plasminogen and template bleeding times remained unchanged. Placebo- and drug-treated subjects had a daily postinfusion shortening of euglobulin clot lysis time (ECLT). The preinfusion minus postinfusion ECLT for ciprostene subjects on days 2 and 3 (133 and 118 min, respectively) compared with placebo (239 and 217 min) suggest a trend to increased fibrinolytic activity. Based on the outcome of this trial, it is estimated that ciprostene is about 15 times less potent than prostacyclin.(ABSTRACT TRUNCATED AT 250 WORDS)