Attenuation of interleukin 2-induced pulmonary vascular leak syndrome by low doses of oral methotrexate.

Pulmonary vascular leak induced in mice by interleukin 2 (IL-2) was attenuated by pretreatment with single or multiple doses of oral methotrexate. Methotrexate also attenuated pulmonary vascular leak when either larger doses of IL-2 or when lymphokine-activated killer (LAK) cells or LAK cells plus IL-2 were administered. Lymphoid infiltrates in the lungs of mice treated with IL-2 and methotrexate were significantly lower. The number of mice surviving treatment with high doses of IL-2 was also significantly increased when these mice were treated with methotrexate. Methotrexate prevented the IL-2-induced increase in the number of splenocytes that were asialo GM1+ but had no effect on Lyt 2+ or L3T4+ cell content. A marginal but significant inhibition in the generation of effector splenocytes that were cytolytic to either YAC or MCA-205 tumor targets was observed in mice treated with methotrexate and IL-2. In vivo studies indicated that methotrexate did not compromise the anti-tumor efficacy of treatment regimens that contained IL-2, LAK cells, or IL-2 and LAK cells. These results demonstrate the potential clinical utility of methotrexate in attenuating pulmonary vascular leak induced by IL-2 without compromising its efficacy. One potential mechanism of action of methotrexate is related to its ability to stimulate the release of adenosine followed by the inhibition of the adhesion of leukocytes to the IL-2-activated endothelium.

Studies evaluating the antitumor activity and toxicity of interleukin-15, a new T cell growth factor: comparison with interleukin-2.

Interleukin-15 is a new cytokine that stimulates the proliferation of T cells and other cells of the immune system. Some of the biological properties of interleukin-15 overlap that of interleukin-2. Using murine models, the present studies have shown that interleukin-15, in vivo, is three to four times more potent than interleukin-2 in generating cytolytic effector splenocytes that lyse YAC target cells. It is approximately one-third as potent as interleukin-2 in inducing specific cytolytic cells that lyse allogeneic target cells. Interleukin-15 is approximately half as potent as interleukin-2 in suppressing pulmonary metastasis induced by MCA-205 tumor cells. The dose of interleukin-15 required to induce pulmonary vascular leak in mice is six times higher than that required for interleukin-2. These results support the view that interleukin-15 exhibits a therapeutic index that is superior to interleukin-2.

Effect of CL 184,005, a platelet-activating factor antagonist in a murine model of Staphylococcus aureus-induced gram-positive sepsis.

Experiments using a murine model of heat-killed Staphylococcus aureus-induced gram-positive bacterial sepsis indicate that the lethal bacterial effects can be prevented if mice are pretreated with CL 184,005, a platelet-activating factor (PAF) antagonist. CL 184,005 was ineffective when administered after bacterial challenge. Plasma of mice pretreated with CL 184,005 contained significantly less tumor necrosis factor (TNF), suggesting that CL 184,005 interferes with TNF synthesis induced by S. aureus. Spleen-associated TNF protein was also decreased by pretreatment with CL 184,005. Although TNF levels were significantly decreased in mice treated with CL 184,005, interleukin-6 levels in serum were significantly increased. Athymic mice were also susceptible to the lethal effects of S. aureus, suggesting that T cells were not involved. When rats rendered hypotensive with S. aureus were treated with CL 184,005, their blood pressure was normalized. Mice treated with enterotoxin B were not protected if they were pretreated with CL 184,005; however, TNF levels in these mice were significantly lower, suggesting that mediators other than PAF and TNF may contribute to the lethal effects of enterotoxin.

Analogues of platelet activating factor. 8. Antagonists of PAF containing an aromatic ring linked to a pyridinium ring.

A series of platelet activating factor (PAF) antagonists containing a quaternary pyridinium ring connected through an amide, imide, or carbamate linkage to a substituted aromatic ring was prepared. Of these compounds, those containing a branched imide linkage of the form (CON-(COCH3)CH2, 37-51, and 59) generally showed excellent PAF antagonist properties in vitro. Structure-activity relationships within this series of compounds were studied extensively with respect to substituents and the position of substitution in both the aromatic and pyridinium rings. Several of these compounds (40 and 44) showed in vitro PAF antagonism at less than 0.1 microM and are as potent as CV-6209, the most potent PAF antagonist reported in the literature. Less active PAF antagonists were those bearing simple amide linkages (20-23, 27-29, and 31-35), linear imide linkages (62-63), or carbamate linkages (66 and 68), between the two aromatic rings. A number of our PAF antagonists were tested in vivo in mice and rabbits for their ability to protect these animals against a lethal injection of PAF. Those antagonists that are particularly potent (IC50 < 0.1 microM) provide excellent protection against an LD97 dose of PAF in rabbits. The relationships between structure and activity in vitro and in vivo are presented and compared to literature standards.

Analogues of platelet activating factor. 7. Bis-aryl amide and bis-aryl urea receptor antagonists of PAF.

A series of bis-aryl amide (13-57 and 66-81) and bis-aryl urea (58 and 85) antagonists of platelet-activating factor (PAF) was prepared that contain, separating the two aromatic rings, linear amide linkages of the form -(CH2)nCONH- (n = 0-2), -OCH2CONH-, and -(CH2)nNHCO- (n = 0-1), branched amide linkages of the form -(CH2)nN(COR)- (n = 1-3, R = CH3 or n-C3H7), and -N(COCH3)CH2-, and urea linkages of the form -NHCONH- and -CH2N(CONHCH3)-. These compounds were examined for their ability to inhibit PAF-induced platelet aggregation of rabbit platelets. These in vitro data were compared to similar data obtained for a number of known PAF antagonists. The compounds were evaluated in vivo, in the mouse, for their ability to prevent death induced by a lethal challenge of PAF. The relationships between the biological activity and the nature, lipophilicity, and position of substituents of the aromatic rings were studied. Best activity was observed for compounds having linkages of the type -CH2CONH-, -CH2N(COR)-, and -CH2NHCO-. Many of these compounds inhibit PAF-induced platelet aggregation with IC50's under 1 microM.

Pluronic F 127 liquid sensitizes mice to low doses of Escherichia coli lipopolysaccharide.

BACKGROUND AND METHODS: In murine models of endotoxemia, large amounts of lipopolysaccharide have to be administered to induce mortality. If mice are pretreated with D-galactosamine, the amount of lipopolysaccharide required to induce mortality is significantly lowered. Pluronic F 127 liquid is a relatively non-toxic copolymer that exhibits reverse gelation properties. Thus, it is a liquid at cold temperature and a gel at body temperature. The present studies were performed to ascertain whether the reverse gelation properties of Pluronic F 127 liquid could be used in devising a model of septic shock where a sustained delivery of lipopolysaccharide occurred. In evaluating this model, dose-response studies were conducted with lipopolysaccharide when a) it was administered intraperitoneally in saline or in Pluronic F 127 liquid, and b) it was administered intravenously to mice that had been pretreated with saline or Pluronic F 127 liquid. Mortality was followed for up to 72 hrs. RESULTS: Various doses of Escherichia coli lipopolysaccharide dissolved in saline or in Pluronic F 127 liquid were administered intraperitoneally to mice. The lethal dose of lipopolysaccharide required to kill 50% of the mice (LD50) administered in Pluronic F 127 liquid was approximately ten- to 15-fold less than the values obtained for lipopolysaccharide administered in saline. This decrease in the LD50 of lipopolysaccharide was also observed if the mice were treated intraperitoneally with Pluronic F 127 liquid and challenged 6 hrs later with iv lipopolysaccharide. The concentrations of tumor necrosis factor and interleukin-6 in the plasma were significantly higher when a low dose of lipopolysaccharide was administered to mice that had been pretreated with Pluronic F 127 liquid. While there was no effect on the liver enzymes, Pluronic F 127 liquid caused an increase in the plasma triglycerides. CONCLUSIONS: The data reported in this paper indicate that the LD50 of lipopolysaccharide is significantly decreased if it is administered in Pluronic F 127 liquid or administered to mice that have been pretreated with the Pluronic F 127 liquid. Thus, Pluronic F 127 liquid appears to sensitize mice to low levels of lipopolysaccharide. Unlike the D-galactosamine model, lipopolysaccharide can be administered as late as 6 hrs after treatment with Pluronic F 127 liquid. While the mechanisms by which Pluronic F 127 liquid sensitizes mice is not known, plasma triglycerides were increased in mice treated with this agent, suggesting that tissues responsible for the synthesis and/or degradation of triglycerides play a role in this sensitization process.

Studies of the effect of a platelet-activating factor antagonist, CL 184,005, in animal models of gram-negative bacterial sepsis.

The effect of CL 184,005, a potent and specific platelet-activating factor antagonist, has been examined in a variety of animal models relevant to gram-negative bacterial sepsis. Pretreatment of mice with CL 184,005 protected them from the lethal effects of platelet-activating factor. When rats or primates rendered hypotensive with endotoxin were treated with CL 184,005, blood pressure was normalized. Pretreatment of rats with CL 184,005 protected them from the gastrointestinal lesions induced by endotoxin. Pretreatment of rats and mice with CL 184,005 protected them from the lethal effects of endotoxin. Plasma tumor necrosis factor levels in endotoxin-treated mice were lower when the mice were pretreated with CL 184,005. These observations suggest that CL 184,005 may be potentially useful in the treatment of gram-negative bacterial sepsis, and the agent is undergoing clinical evaluation.

Analogues of platelet activating factor. 6. Mono- and bis-aryl phosphate antagonists of platelet activating factor.

A series of aryl phosphoglyceride (3, 19-61) and bis-aryl phosphate (67-135) antagonists of platelet activating factor (PAF) were prepared. A group of four bifunctional phosphorus reagents (5a-c and 7) were developed that allowed the preparation of these aryl phosphates in which the position of aromatic substitution can be varied. These compounds were examined for their ability to inhibit PAF-induced platelet aggregation of rabbit platelets. Selected compounds were also evaluated for their ability to displace [3H]PAF from its receptor on rabbit platelets. These in vitro data were compared to similar data obtained for a number of known PAF antagonists. The compounds were evaluated in vivo, in both the mouse and rabbit, for their ability to prevent death induced by a lethal challenge of PAF. The relationships between the biological activity and the nature, lipophilicity, and position of substituents of the aromatic rings were studied. Compound 105 (CL 184005) has been selected to undergo further development as a potential therapeutic agent for the treatment of septic shock in man.

Preparation of triazolo[1,5-c]pyrimidines as potential antiasthma agents.

With the use of the human basophil histamine release assay, 5-aryl-2-amino[1,2,4]triazolo[1,5-c]pyrimidines were found to be active as mediator release inhibitors. These compounds were prepared by reacting arylamidines with sodium ethyl formylacetate or with ethyl propiolate to give pyrimidinones. Treatment with phosphorus oxychloride gave a chloropyrimidine, which was converted to a hydrazinopyrimidine with hydrazine. Cyclization, using cyanogen bromide, gave the triazolo[1,5-c]pyrimidines, after a Dimroth rearrangement. Following a structure-activity evaluation, the 5-[3-(trifluoromethyl)phenyl]-2-amino (8-10), 5-(3-bromophenyl)-2-amino (8-13), 5-[3-(difluoromethoxy)-phenyl]-2-amino (8-11), and 5-(4-pyridinyl)-2-amino (6-7) compounds were found to have the best activity. They were chosen for further pharmacological and toxicological study.

Imidazo[1,5-d][1,2,4]triazines as potential antiasthma agents.

By using inhibition of histamine release from antigen-challenged, sensitized human basophils as a means of identifying a potentially prophylactic drug for the treatment of asthma, a series of substituted imidazo[1,5-d][1,2,4]triazines were found, which were active. These compounds were prepared by treating imidazolecarboxaldehydes with excess Grignard agent and then oxidizing the resulting alcohols to ketones with Jones reagent. Pyrolysis of a mixture of ketone and methyl carbazate at 200 degrees C in diphenyl ether produced the desired imidazo[1,5-d][1,2,4]triazines. Those compounds with the greatest basophil activity were tested for in vivo activity in the mouse passive cutaneous anaphylaxis (PCA) and the guinea pig passive anaphylaxis tests. The best compounds, 1-ethyl-8-methyl-6-propylimidazo[1,5-d][1,2,4]triazin-4(3H)- one (4-17) and 1,8-dimethyl-6-propylimidazo[1,5-d][1,2,4]triazin-4-(3H)-one (4-16) were chosen for further study.

Effects of age and magnesium ions on oxygen toxicity in the neonate chicken.

White Leghorn male chicks, 2-6 days and 4 weeks old, were injected with MgCl2 (2 mM Mg/kg body weight) and exposed to 100% O2 at 75 lb/in2 (approximately 5 atm). Compared to saline-injected controls, average time to onset of convulsions was delayed 37% in the younger group with no significant difference in the protective effect during days 2-6. The delay in onset of convulsions was 66% in the 4-week-old group. The protective action of Mg++ in the chick agrees closely with that reported for the mature rat. Chicks treated with Mg++ did not appear depressed. Susceptibility to hyperbaric O2 convulsions increased uniformly between the 2nd and 6th day, with time to onset of convulsions decreasing by 1.4 min/day from the 19.3 +/- 1.01 (SE) min observed at day 2 for saline controls. Between the 6th and 28th day, susceptibility was relatively stable with time to onset decreasing by about 0.2 min/day in controls.