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Biomedical subjects

R R Harris

Publications and source records attributed to R R Harris.

At least 19 recordsLinked to original sources
PubMed1998

The role of tissue mast cells in polyacrylamide gel-induced inflammation in mice.

OBJECTIVE AND DESIGN: In the present study, we investigated the role of mast cells in a model of polyacrylamide gel (PAG)-induced inflammation in mice. SUBJECTS: Balb/c mice and two strains of mast cell deficient mice (WBB6F1/J-W/Wv, WCB6F1/J-S1/S1d). TREATMENT: Various quantities of polyacrylamide gel (Bio-Gel P4) were injected subcutaneously in the backs of mice. METHODS: Five hours after the injection of PAG the animals were euthanized, the injection sites lavaged and levels of LTB4, PGE2, TNF alpha and cells were determined. RESULTS: Subcutaneous injection of PAG caused a time-dependent response characterized by the accumulation of inflammatory cells peaking at 10 h and the formation of LTB4, PGE2 and TNF alpha, peaking at 5 h. PAG injection into W/Wv or SL/SLd mice (mice lacking mast cells) resulted in an attenuated response, i.e. LTB4 levels were reduced by 60% and minimal cell influx was seen. The lack of mast cells caused about a 30% reduction in the levels of TNF alpha found. CONCLUSIONS: These data suggest that mast cells play a prominent role in the PMN influx, TNF alpha production and eicosanoid formation in the PAG-induced inflammatory response.

Acrylic Resins↗
PubMed1997

Effect of mast cell deficiency and leukotriene inhibition on the influx of eosinophils induced by eotaxin.

Eosinophils are believed to be important cells in the pathogenesis of asthma and allergic disease. Mast cells and leukotrienes may play a role in eosinophil recruitment. Eotaxin was recently described as a specific chemoattractant for eosinophils. Therefore we examined the effects of eotaxin on eosinophil flux in the mast cell-deficient WBB6F1/J-KitW/ KitW-v (W/Wv) mice and in mice treated with zileuton or ABT-761, specific 5-lipoxygenase inhibitors. Mice were injected intraperitoneally with eotaxin and at various times later the peritoneal cavities were lavaged and cell populations determined. Murine recombinant eotaxin induced a dose-dependent increase in eosinophils, which reached a maximum at 1-2 h and subsided at 4 h in both BALB/c and W/WV littermate control mice (no other cell population was altered). However, in eotaxin-injected W/Wv mice, the peak of eosinophil influx was delayed, peaking at 2 h, and a lower number of eosinophils was seen. The specific lipoxygenase inhibitors zileuton and ABT-761 given 30 min before eotaxin caused a 63-79% reduction in the level of eosinophils seen in the lavage fluid. These data suggest that eotaxin may either be activating eosinophils to release leukotrienes or making them more responsive to leukotrienes. In addition, mast cells may be playing a role in the amplification of the eotaxin effect.

Animals↗
PubMed1997

Synthesis of indolylalkoxyiminoalkylcarboxylates as leukotriene biosynthesis inhibitors.

A series of substituted indolylalkoxyiminoalkylcarboxylates were found to be potent leukotriene biosynthesis inhibitors. The structure-activity relationships were investigated. Representative potent inhibitors identified were the quinolyl 3a (A-86885) and pyridyl 3b (A-86886) congeners with in vitro IC50s of 21 and 9 nM and in vivo leukotriene inhibition in the rat with oral ED50s of 0.9 and 1.7 mg/kg, respectively.

5-Lipoxygenase-Activating Proteins↗
PubMed1997

ABT-761 attenuates bronchoconstriction and pulmonary inflammation in rodents.

Our primary goal has been to discover leukotriene biosynthesis inhibitors with characteristics that are appropriate for use as clinical agents. The success of the use of zileuton in the treatment of asthma led us to explore further the use of the N-hydroxyurea class of 5-lipoxygenase inhibitors as longer-acting compounds with good lung penetration. A variety of in vitro and in vivo methods were used to evaluate a large number of compounds, from which ABT-761 [(R)-N-(3-(5-(4-fluorophenylmethyl)thien-2-yl)-1-methyl-2-pr opynyl)-N-hydroxyurea] was selected for study. ABT-761 exhibited potent and selective inhibition of leukotriene formation both in vitro and in vivo. More importantly, the compound potently inhibited antigen-induced bronchospasm in guinea pigs when given either prophylactically or therapeutically. In addition, ABT-761 was a potent inhibitor of eosinophil influx into the lungs of Brown Norway rats. These data provide added support for the role of leukotrienes in both bronchospasm and eosinophilic inflammation and characterize ABT-761 as a particularly potent inhibitor of leukotrienes formed in pulmonary tissues. These data combined with the excellent pharmacokinetic characteristics of the compound indicate its potential use in the treatment of leukotriene-dependent human disease.

Animals↗
PubMed1996

Pharmacological modulation of eosinophil influx into the lungs of Brown Norway rats.

A model of lung inflammation was developed in Brown Norway rats. Intense lung eosinophilia was induced by a single intravenous injection of Sephadex G-200 particles. The eosinophilia observed was preceded by an increase in cysteinyl leukotrienes found in lung lavage fluids. Theophylline and albuterol were tested in the model and found to be inactive, while dexamethasone was effective. Zileuton, a specific leukotriene inhibitor, was found to effectively inhibit leukotriene formation and the influx of eosinophils into the lungs of these Sephadex-treated animals. Studies with specific leukotriene D4 antagonists of the cysLT1 type receptor indicate that this leukotriene receptor is probably not involved directly in the eosinophilic inflammation. This model appears to be useful in characterizing potential anti-inflammatory effects of inhibitors by evaluating their ability to prevent eosinophil influx into the lung.

Animals↗
PubMed1995

Leukotrienes and alpha-naphthylisothiocyanate-induced liver injury.

alpha-naphthylisothiocyanate (ANIT) administration to rats results in periportal hepatic inflammation and injury. Glutathione (GSH) appears to be necessary for the liver injury to occur. The leukotrienes (LTs) are metabolites of arachidonic acid and potent mediators of inflammation that have been implicated in certain liver injury models. Inasmuch as GSH is a cofactor for the synthesis of cysteinyl-LTs and since inflammation is a prominent component of ANIT injury, we hypothesized that LTs are involved in producing the hepatic insult that results from ANIT administration. To test this hypothesis, rats were treated with one of several inhibitors of LT biosynthesis, A63162, Zileuton or MK-886. Each of these agents prevented the formation of LTB4 in Ca++ ionophore-stimulated whole blood from rats treated with the inhibitors. A63162 attenuated the hepatic parenchymal injury caused by ANIT and resulted in a modest decrease in ANIT-induced cholestasis. In contrast, neither Zileuton nor MK-886 attenuated liver injury. AT-125 (Acivicin) inhibits gamma-glutamyl transferase (GGT), the enzyme that catalyzes the formation of LTD4 from LTC4. AT-125 pretreatment did not prevent ANIT-induced hepatic parenchymal insult. It did, however, ameliorate the cholestasis caused by ANIT. In conclusion, the partial protection afforded by A63162 and AT-125 likely results from effects unrelated to the formation of LTs, since Zileuton and MK-886 inhibited LT synthesis without affording protection. The lack of protection by Zileuton and MK-886 in the face of LT synthesis inhibition suggests that LTs are not necessary for the expression of injury after ANIT administration.

1-Naphthylisothiocyanate↗
PubMed1995

Clinical activity of leukotriene inhibitors.

Data from the emerging clinical trials with compounds such as zileuton, ICI 204,219, Bay X1005, MK571, MK679, and MK591 are demonstrating the importance of the leukotrienes as mediators of asthma and possibly other diseases such as rheumatoid arthritis, psoriasis, and inflammatory bowel disease. One of the major questions facing the asthma community is how much improvement in the FEV1 is needed to improve the quality of life of the asthmatic patient. Comparing the various approaches to asthma treatment, there is typically 15-20% improvement in the lung function with inhaled steroids. Leukotriene interventions apparently will improve lung function to similar levels as with inhaled steroids, and thus may offer an alternative to steroids. Like the steroids, zileuton appears to also reduce the inflammatory cell influx into the antigen-challenged site, which may have the long-term effect of reversing some of the tissue alterations that occur as a result of the inflammation seen with asthma. Importantly, the reported experience to date has shown that the leukotriene modulators do not have the same side-effects as the current therapies, and thus offer the hope that both safe and effective treatment may be derived from this approach. The clinical data reported do not yet define a preferred approach to the modulation of leukotriene pathology. As more studies are published in other diseases the broad spectrum use of these inhibitors will become known.

Anti-Inflammatory Agents↗
PubMed1995

Interleukin-1 receptor antagonist inhibits proteoglycan breakdown in antigen induced but not polycation induced arthritis in the rabbit.

OBJECTIVE: To compare the alterations in proteoglycan metabolism in antigen induced arthritis and polycation induced arthritis and to determine the involvement of interleukin-1 (IL-1) in the cartilage degradation that occurs in these models of rheumatoid arthritis (RA). METHODS: The time course for loss of proteoglycan into the synovial fluid (SF) and inhibition of proteoglycan synthesis, as well as depletion of articular cartilage proteoglycan content, was compared in rabbit antigen arthritis and polycation arthritis. The ability of recombinant IL-1 receptor antagonist IL-1ra to block the acute cartilage loss at 24 h in these models was investigated, compared to its ability to block the cartilage breakdown induced by direct administration of IL-1 in rabbits. RESULTS: Initial loss of cartilage proteoglycan was accompanied by release of high levels of glycosaminoglycan (GAG) into the SF and decrease in proteoglycan synthetic rates in both antigen and polycation induced arthritis SF GAG rapidly returned to control levels, while proteoglycan synthesis and cartilage proteoglycan content remained depressed, suggesting that the inhibition in proteoglycan synthesis prevented recovery to normal levels. GAG loss from the cartilage into the SF in response to IL-1 injection, as well as other effects of IL-1 challenge, was blocked in a dose dependent manner by IL-1ra administered either intraarticularly (ED50 = 160 ng) or intravenously (iv) (ED50 = 0.09mg/kg). In the antigen induced arthritis model, IL-1ra (20 mg/kg, iv -2h) inhibited GAG release by 40%, whereas in polycation induced arthritis no inhibition was observed even with repeated administration of high doses of inhibitor. CONCLUSION: These studies suggest that sustained depression of proteoglycan synthesis may be responsible for the chronic depletion of articular cartilage proteoglycan in the antigen and the polycation model of RA. However, while IL-1 may play a role in the initial breakdown of articular cartilage in antigen induced arthritis, it does not appear to be involved in polycation induced arthritis in the rabbit.

Animals↗
PubMed1995

Optimization of the potency and duration of action of N-hydroxyurea 5-lipoxygenase inhibitors.

As in vitro glucuronidation assay and several biochemical assays were utilized to discover potent new N-hydroxyurea-containing 5-lipoxygenase inhibitors with long durations of action. The best of these, A-78773, is a racemic mixture of two enantiomers. These enantiomers were purified and the R(+)-enantiomer A-79175 was found to be superior to the S(-)-enantiomer with respect to in vitro metabolism and duration of action in the monkey. A-79175 was a potent selective inhibitor of 5-hydroxyeicosatetraenoic acid formation in rat basophilic leukemic homogenates (IC50 = 54 nM) and of calcium ionophore-induced leukotriene B4 (LTB4) formation in purified human polymorphonuclear leukocytes (IC50 = 25 nM) and human whole blood (IC50 = 80 nM). The compound inhibited LT formation in the rat with oral ED50s of 1 to 2 mg/kg. It also was a potent inhibitor of edema and inflammatory cell influx in rats and mice. A-79175 was resistant to glucuronidation and had an elimination half-life of nearly 9 hr in cynomolgus monkeys. A-79175 inhibited ex vivo LTB4 formation by monkeys for extended periods. A single 0.5-mg/kg oral dose gave > 50% inhibition of calcium ionophore-induced LTB4 formation ex vivo for 12 hr. A good correlation was found between the elimination half-life for A-78773 and its enantiomers in cynomolgus monkeys and humans. These data indicate that A-79175 is a promising long-acting agent that should be useful to delineate the importance of LTs in animal and human studies.

Animals↗
PubMed1992

Synthesis, chemical, and biological properties of vinylogous hydroxamic acids: dual inhibitors of 5-lipoxygenase and IL-1 biosynthesis.

Vinylogous hydroxamic acids (3-(N-hydroxy-N-alkylamino)-2-propen-1-ones, VHA) were prepared as antiinflammatory agents. The synthesis, chemical properties, and in vitro biological activities of these relatively unexplored compounds are described. The VHAs were prepared by condensation of the appropriate N-substituted hydroxylamine with any of the three reagents: a 1,3-dicarbonyl compound (method A); a vinylogous amide (method B); or an alkynone (method C). The VHAs exist as one or more tautomers in solution with the relative proportions of each being dependent upon the structure of the VHA, solvent, and pH. VHAs undergo some of the typical reactions of hydroxamic acids as well as those of vinylogous amides. VHAs are active as inhibitors of 5-lipoxygenase and of IL-1 biosynthesis in vitro, which do not inhibit other enzymes of the arachidonic acid cascade. They have been shown by ESR studies to bring about inhibition of soybean type 1 15-lipoxygenase by reduction of the active site iron.

Animals↗
PubMed1992

Novel 1-(pyridylphenyl)-1-phenyl-2-imidazolylethanols with topical antiinflammatory activity.

The synthesis, biological evaluation, and structure-activity relationships of a series of 1-(pyridylphenyl)-1-phenyl-2-imidazolylethanols are described. These compounds show potent dose-dependent topical antiinflammatory activity in murine models of skin inflammation. This effect is likely due to inhibition of cytochrome P450 and consequent reduction in levels of 12R-HETE in the skin. These compounds were examined for their ability to inhibit the oxidative metabolism of arachidonic acid; they specifically inhibit the formation of prostacyclins in mouse macrophages. To study the effects of structure on the in vivo activity, three general features of the molecules were varied: the position of attachment of the pyridine nucleus (A), the second aromatic residue (B), and the nitrogen base on the ethanol chain (C). 1-[4-(4-Pyridyl)phenyl]-1-(4-fluorophenyl)-2- imidazolylethanol (2a, DuP 983) shows a very attractive profile of antiinflammatory activity and has been selected for clinical evaluation as a topical antiinflammatory agent.

Administration, Topical↗
PubMed1991

Phospholipase A2 (PLA2) activity in bovine pulmonary artery endothelial cells.

We have investigated the role of recombinant human interleukin-1 beta (rIL-1 beta) and recombinant human tumor necrosis factor alpha (rTNF-alpha) on PLA2 activity, protein synthesis and eicosanoid production in bovine pulmonary artery endothelial cells. Cellular PLA2 activity increased 4-fold and production of PGE2 increased 3-fold at 1-2 hrs in the presence of 10 units/ml rIL-1 beta. PLA2 activity increased 3-fold at 30 min and PGE2 production increased 2-fold with 5 x 10(-9) M rTNF-alpha. The data show that endothelial cells respond more rapidly to rIL-1 beta (2-6 hr) and rTNF-alpha (30 min) than do chondrocytes and synovial cells (6-16 hrs), suggesting endothelial cells may play a primary role in initiating the inflammatory response.

Animals↗
PubMed1990

2-substituted-1-naphthols as potent 5-lipoxygenase inhibitors with topical antiinflammatory activity.

The synthesis, biological evaluation, and structure-activity relationships of a series of 1-naphthols bearing carbon substituents at the 2-position are described. These compounds are potent inhibitors of the 5-lipoxygenase from RBL-1 cells and also inhibit bovine seminal vesicle cyclooxygenase. Structure-activity relationships for these two enzymes are different, implying specific enzyme inhibition rather than a nonspecific antioxidant effect. 2-(Aryl-methyl)-1-naphthols are among the most potent 5-lipoxygenase inhibitors reported (IC50 values generally 0.01-0.2 microM) and show excellent antiinflammatory potency in the mouse arachidonic acid ear edema model. To study the effects of structure on in vitro and in vivo activity, four general features of the molecules were varied: the 2-substituent, the 1-hydroxyl group, substitution on the naphthalene rings, and the 1,2-disubstituted naphthalene unit itself. 2-Benzyl-1-naphthol (5a, DuP 654) shows a very attractive profile of topical antiinflammatory activity and is currently in clinical trials as a topically applied antipsoriatic agent.

Animals↗