Anti-inflammatory/antiarthritic ketonic bisphosphonic acid esters.

Bisphosphonate ester 2 is an inhibitor of inflammation, but is devoid of antiarthritic effects. SAR studies on a series of related bisphosphonate esters resulted in compounds 6e, 6i, 6j, and 6m, which exhibited excellent inhibition of an arthritis model, in addition to potent anti-inflammatory effects.

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.

Carbonyl-containing bisphosphonate esters as novel antiinflammatory and antiarthritic agents.

A study of the decomposition of the pyrazoline bisphosphonate ester 2 identified 3 as the sole bisphosphonate component. Evaluation in a delayed-type hypersensitivity granuloma model of chronic inflammation in mice (DTH-GRA) showed 3 to be a potent inhibitor of granuloma formation (sc, 10 mg/kg, 45%), but in a murine model of antigen-induced arthritis (AIA), no significant inhibition was observed. As a result, new ketonic bisphosphonate tetraethyl esters were synthesized from vinylidenebisphosphonic acid tetraethyl ester 4 and activated carbonyl compounds in 13-84% yield. 6 significantly inhibited the pathology of both the DTH-GRA (sc, 25 mg/kg, 45%) and AIA models (sc, 25 mg/kg, 55%). Other compounds in the series were not as potent. Our results show that bisphosphonate ester 6 can inhibit the chronic inflammatory response associated with cutaneous granuloma formation and erosive arthritis.

Pyrazoline bisphosphonate esters as novel antiinflammatory and antiarthritic agents.

Vinylidenebisphosphonic acid tetraethyl ester (1) and diazo ketones 7a-1 in ether at 22 degrees C yield pyrazoline bisphosphonate tetraethyl esters 8a-1 in moderate to good yield. These compounds were evaluated in animal models of arthritis: rat adjuvant-induced polyarthritis (AIP) and murine antigen-induced arthritis (AIA) and a murine model of chronic inflammation, the delayed type hypersensitivity granuloma reaction (DTH-GRA). (5-Benzoyl-2,4-dihydro-3H-pyrazol-3-ylidene)-bisphosphonic acid tetraethyl ester (8a), and [5-(3-fluorobenzoyl)-2,4-dihydro-3H-pyraxol-3-ylidene]- bisphosphonic acid tetraethyl ester (8d) significantly inhibited the arthritis models, AIP (15 mg/kg) and AIA (25 mg/kg), as well as the DTH-GRA (25 mg/kg). Conversion of 8a to the corresponding bisphosphonic acid, 10a, resulted in loss of activity. Compounds with alkyl substituents on the pyrazoline nitrogen, 9a-d, were inactive in the DTH-GRA. These results show that 8a and 8d have novel antiinflammatory activity and are capable of inhibiting chronic arthritis and inflammation in animals. Such compounds might be useful in man for treating chronic tissue injury associated with arthropathies such as inflammatory joint disease as well as other chronic inflammatory diseases.

Chasing the elusive animal model of late-phase bronchoconstriction: studies in dogs, guinea pigs and rats.

Antigen inhalation in sensitized dogs, guinea pigs and rats resulted in a marked, late-phase, eosinophil-rich, influx of inflammatory cells into the bronchial lumen. Attempts to demonstrate an associated late-phase bronchoconstriction were disappointing. We were unable to demonstrate a late-phase bronchoconstriction in either rats or dogs, even when dogs were pretreated with metyrapone to reduce blood cortisol levels. In ovalbumin-sensitized guinea pigs, challenged with low doses of ovalbumin, we observed an immediate bronchoconstriction, a late-phase bronchopulmonary eosinophilia but no late-phase bronchoconstriction. However, inhalation of very high doses of antigen in mepyramine-treated sensitized guinea pigs did induce a moderate late-phase bronchoconstriction.

Contribution of leukotriene B4 to airway inflammation and the effect of antagonists.

Inhalation of aerosols of ovalbumin in sensitized guinea pigs produced a marked, bronchoalveolar eosinophilia 24 hr after challenge. The lung eosinophilia was not prevented by the cyclooxygenase inhibitors, indomethacin or PAF antagonists (WEB-2086 and L-652731) but was inhibited by methylprednisolone, the 5-LO inhibitor, U-66858 and a series of structural analogs of LTB4, U-75302, U-77692, U-75485 and U-78489. The effectiveness of LTB4 antagonists but not PAF antagonists in vivo was consistent with in vitro studies in which LTB4 was shown to be far more chemotactic than PAF for guinea pig eosinophils. LTB4 elicited maximal directional migration of guinea pig eosinophils at concentrations from 10(-7) M to 10(-9) M while PAF showed no effect over the same concentration range. The structural analogs of LTB4 were shown to inhibit LTB4 induced chemotaxis of guinea pig eosinophils and produced a dose-related inhibition of binding of LTB4 to guinea pig eosinophil membranes. To add further proof to the hypothesis that LTB4 contributed to the antigen-induced lung eosinophilia we attempted to measure LTB4 release into BAL fluid immediately after and at various time points up to 24 hr after antigen inhalation. However, using a sensitive radioimmunoassay (detection limit 10 pg/ml) very low levels of LTB4 (24.9-67.9 pg/ml) or its metabolite, 20-OH LTB4 (24.9-98.2 pg/ml) were detected in BAL fluid and these levels did not increase significantly following antigen provocation. Inhalation of LTB4 aerosols in unsensitized Brown-Norway rats or inhalation of aerosols of ovalbumin in sensitized Brown-Norway rats also produced a marked "late-phase" eosinophil-rich influx of inflammatory cells into the lungs. The lung eosinophilia in the rat was prevented by two structurally unrelated leukotriene B4 (LTB4) antagonists, U-75302 and Ly255283. These data implicate LTB4 as a mediator of allergen-induced bronchopulmonary eosinophilia. Leukotriene B4 antagonists may provide leads for the development of compounds which inhibit the chronic airway inflammation associated with asthma in man.

Novel inhibitors of pulmonary eosinophil accumulation.

The effects of representatives of three classes of compounds were investigated on antigen-induced bronchopulmonary eosinophilia in sensitized Brown-Norway rats. Rats were sensitized by 3 weekly inhalation provocations with aerosols of ovalbumin. Twenty-four hours after a fourth weekly antigen provocation, cell populations were enumerated following bronchoalveolar lavage (BAL) in animals treated with test compounds or the appropriate vehicle. A marked eosinophil-rich influx of inflammatory cells into the bronchial lumen followed the antigen provocation in sensitized animals. Dose-related inhibitions of antigen-induced lung eosinophilia were demonstrated with: 1) glucocorticoids, given po (methylprednisolone acetate, U-8210) or by inhalation (methylprednisolone suleptanate, U-67590A); 2)the non-glucocorticoid 21-amino steroid, U-75412E, and 3) the leukotriene B4 antagonist, U-75302. The steroids methylprednisolone and U-75412E were tested for glucocorticoid activity using phorbol ester-differentiated U937 (human macrophage) cells. Methylprednisolone but not U-75412E produced a dose-dependent inhibition of lipopolysaccharide-stimulated thromboxane synthesis by the U937 cells. Leukotriene B4 antagonists and the novel 21-aminosteroid, U-75412E, which lacks glucorticoid activity, provide leads for the development of compounds which inhibit the chronic airway inflammation associated with asthma in man.

Murine delayed-type hypersensitivity granuloma: an improved model for the identification and evaluation of different classes of anti-arthritic drugs.

The present study examined the effects of five different classes of anti-inflammatory/immunoregulatory drugs using a mouse model of mBSA-induced delayed-type hypersensitivity granuloma (DTH GRA) to measure immune-mediated chronic inflammatory tissue formation. The compounds were administered orally daily following induction of DTH GRA (days 0 to 4); granulomata were quantitated gravimetrically on day 5. NSAIDs, with the exception of flurbiprofen, showed little activity in comparison with the steroids dexamethasone (1-3 mg/kg/day, orally) and prednisolone (3-10 mg/kg/day, orally), which caused significant suppression of DTH GRA tissue (65-76% and 26-68%, respectively). The "immunoregulatory" compounds levamisole and D(-)penicillamine were inactive, whereas cyclophosphamide (5-50 mg/kg/day, orally) reduced the response by 24-83%. The "interferon alpha-inducers" Tilorone, U-54,461, and U-56,499 were also potent inhibitors of the DTH GRA response; U-54,462, a weak interferon alpha-inducer, was inactive. Cyclosporin A (50-100 mg/kg/day, orally) suppressed DTH GRA most effectively when administered on days 3 and 4 (66% and 97%) of the five-day granuloma response (treatment was ineffective when given on days 1 and 2). We conclude that the DTH GRA response described above may be useful for evaluating different types of unique therapeutic agents that are effective in the treatment of chronic immuno-inflammatory disease such as rheumatoid arthritis.