The effect of cyclooxygenase inhibition on the ocular hypotensive action of topical carbonic anhydrase inhibitors in rabbits.

Experiments were undertaken in normal albino rabbits to determine if cyclooxygenase inhibition by nonsteroidal anti-inflammatory drugs modified the ocular hypotensive activities of topically applied MK-507, MK-927 and L-662,583, three water-soluble carbonic anhydrase inhibitors (CAI). Cyclooxygenase was inhibited either by systemic indomethacin or by topically administered flurbiprofen, and epinephrine was included as a positive control. Both a 1-hr pretreatment with indomethacin (5 mg/kg i.p.) and topically applied 0.03% flurbiprofen antagonized the ocular hypotensive effect of one drop (50 microliters) of 1% epinephrine. Two percent solutions of the three CAIs were instilled three times with 10 min between each drop in order to obtain a meaningful and reproducible reduction in intraocular pressure (IOP). This dosage schedule elicited a peak decline in IOP ranging from 4.6 mm Hg to 6.2 mm Hg which was achieved via a local action within the eye. The ocular hypotensive effects of MK-507, MK-927 and L-662,583 were unaltered either by a 1-hr pretreatment with indomethacin (5 mg/kg i.p.) or by topically administered 0.03% flurbiprofen. These studies indicate that the IOP lowering actions of the three CAIs, unlike that of epinephrine, in rabbits are not mediated by endogenous prostaglandins and/or other prostanoids.

Effect of a 5-lipoxygenase (5-LO)/cyclooxygenase (CO) inhibitor, WY-47, 288, on cutaneous models of inflammation.

WY-47,288 (2-[(1-naphthalenyloxy)methyl]quinoline) demonstrated topical antiinflammatory activity in several animal models of skin inflammation. Application of WY-47,288 to mouse ear surfaces inhibited arachidonic acid (ED50 = 0.3 mg/ear) and tetradecanoylphorbol acetate (TPA)-induced inflammation (40% at 1 mg/ear). Administration of WY-47,288 (1 mg/ear) at 30 min and 5 h after TPA reduced ear edema and epidermal proliferation by 50%. WY-47,288 also inhibited oxazolone-induced contact hypersensitivity in mouse ears (ED50 = 0.4 mg/ear) and UVB-induced guinea pig skin erythema (ED50 approximately 0.25 mg/spot). These antiinflammatory effects may be due to inhibition of 5-lipoxygenase (5-LO) and cyclooxygenase (CO) since the synthesis of 5-LO and CO products by rat neutrophils and mouse macrophages was dose-dependently reduced by WY-47,288. By contrast, WY-47,288 demonstrated no appreciable inhibition of 12-LO (rabbit platelet), 15-LO (soybean) or phospholipase A2 (human platelet). Furthermore, no systemic adverse effects were observed after topical, parenteral or oral administration of WY-47,288, suggesting that WY-47,288 is a safe topical 5-LO/CO inhibitor for treating skin inflammation.

Pharmacologic modulation of PAF-induced mortality in mice.

The effect of antiinflammatory drugs, phosphodiesterase inhibitors, leukotriene and mediator antagonists and other drug classes were evaluated in a PAF-induced mortality model in mice. By the oral route of administration (-1 hr), dapsone (ED50 = 25 mg/kg), BW 755C (ED50 = 29 mg/kg), theophylline (ED50 = 30 mg/kg) and LY-171,883 (ED50 = 50 mg/kg) protected against PAF-induced lethality in the mouse. Other drugs that afforded protection when given at various dosing schedules and routes were NDGA (100 mg/kg, -18 hr p.o.), diphenyldisulfide (100 mg/kg, -18 hr p.o.), diphenyldisulfide (200 mg/kg, -18 hr p.o.), dexamethasone (1 mg/kg, -3 hr p.o.), dipyridamole (2 mg/kg, -2 min i.v.) and kadsurenone (10 mg/kg, -2 min i.v.). Nonsteroidal antiinflammatory drugs (NSAIDs) such as indomethacin were inactive and the combination of AA-861, a putative 5-LO inhibitor, and indomethacin also failed to prevent PAF-induced lethality. Therefore, our pharmacological data do not consistently support the notion that PAF-induced lethality is due unequivocally to leukotrienes derived from 5-lipoxygenase metabolism.

Correlation between mouse skin inflammation induced by arachidonic acid and eicosanoid synthesis.

We and others have shown that arachidonic acid (AA), when applied topically to ear surfaces, causes an intense acute inflammatory reaction within minutes (as measured by ear thickness). In this study, we have investigated the cellular and biochemical changes associated with this phenomenon and have attempted to correlate these changes with the induction of inflammation. Measurement of vascular permeability by the accumulation of [125I]albumin showed that significant plasma exudation was observed at 15 min in AA-treated ears. Furthermore, the increase in [125I]albumin was time related and was nearly 10-fold greater than control at 1 h. No time-related change in plasma exudation was observed with control ears. Measurement of LTC4 by radioimmunoassay showed that there was a significant increase in LTC4 synthesis at 15 min after AA treatment. Maximal LTC4 synthesis occurred at 15 min and subsequently decreased to 30% of peak level at 30 min. Histological examination and myeloperoxidase measurement indicated that few neutrophils were present at these early time points and suggested that cells other than neutrophils are contributing to LTC4 synthesis. Ear thickness, [125I]albumin accumulation and leukotriene C4 (LTC4) synthesis in AA-treated ears were reduced significantly by topically administered mixed lipoxygenase (LO) and cyclooxygenase inhibitors such as BW755C and phenidone. Therefore, we suggest that AA-induced ear inflammation is a suitable screen for detecting LO inhibitors in vivo.

Immunomodulating activity of Wy-41,770 (5H-dibenzo[A,D]cyclohepten-5-ylidene) acetic acid.

The immunomodulatory effects of Wy-41,770 (5H-dibenzo[a,d]cyclohepten-5-ylidene) acetic acid, were compared to levamisole and indomethacin in several in vivo models. In the Jerne plaque assay, Wy-41,770 (1 and 100 mg/kg, p.o.) administered on day 1 after sensitization suppressed IgM plaque forming cells (PFC) while levamisole was active when given on days 1 and 2 after sensitization. In contrast, indomethacin administered on days 2 and 3 after sensitization increased PFC. In the rat experimental allergic encephalomyelitis (EAE) model, Wy-41,770 reduced limb paralysis at 10 and 100 mg/kg, p.o. when dosed before sensitization. Indomethacin was active too when predosed in the rat EAE model. In the methylated bovine serum albumin model (MBSA) delayed hypersensitivity (DH) model in mouse, Wy-41,770 (10 mg/kg, p.o.) given on day 1 prior to sensitization and day 2 after sensitization in subliminally sensitized animals augmented the DH response while inhibiting the subliminal DH response when administered at 6 hr after challenge. Levamisole showed similar activity in this subliminal model while indomethacin given 6 hr post challenge was inhibitory. All three drugs were inactive in mice normally sensitized to MBSA at the same drug regimens. In guinea pigs, subliminally sensitized to tuberculin, Wy-41,770 (10 and 100 mg/kg, p.o.) and levamisole augmented the DH response. No changes in DH response were observed for both drugs in normally sensitized guinea pigs. In the rat adjuvant arthritic model, Wy-41,770 (5 and 15 mg/kg, p.o.) inhibited day 16 uninjected paw edema and restored significantly the depressed proliferative responses to mitogen by spleen cells taken from the same arthritic rats at day 16. The moderate immunomodulatory activity of Wy-41,770 may contribute along with its antiinflammatory activity, towards the treatment of arthritic diseases.

Effects of thiazinamium chloride on histamine release from rat peritoneal mast cells and on phosphodiesterase activity in guinea pig lung.

The effect of thiazinamium Cl (TCl) on histamine release from rat peritoneal mast cells (RPMC) was investigated. Although TCl inhibited compound 48/80-induced histamine release moderately (IC50 value 40 microM), the drug was a weaker inhibitor of ovalbumin-induced histamine release (100 microM, -21%). In contrast, promethazine HCl (PHCl) was more effective against antigen-induced histamine release (IC50 value 13 microM) than against compound 48/80-induced histamine release (100 microM, -53%). Disodium cromoglycate (DSCG) was effective against both antigen and compound 48/80-induced release of histamine with IC50 values of 7 and 1 microM, respectively. Neither TCl nor DSCG at 1 mM increased spontaneous release of histamine from RPMC, whereas PHCl induced spontaneous release by over 50% at 1 mM. TCl did not inhibit phosphodiesterase (PDE) activity in guinea pig lung at 1 mM, whereas theophylline and DSCG inhibited PDE with IC50 values of 1.1 and 0.32 mM, respectively. These data suggest that high local concentrations of TCl may reduce histamine release during an asthmatic attack and improve its effectiveness as a bronchoprotectant.

Modulation of mouse ear edema by cyclooxygenase and lipoxygenase inhibitors and other pharmacologic agents.

Inhibitors of arachidonic acid (AA) metabolism and other pharmacologic agents were evaluated against ear edema produced in mice by tetradecanoylphorbol acetate (TPA) or AA. Drugs were administered orally and topically either 30 min prior to AA or 30 min after TPA, except for steroids which were administered 2.5-3 hr prior to AA. Several cyclooxygenase (CO) inhibitors including indomethacin, aspirin, piroxicam and timegadine were without effect when administered orally against either irritant; the same drugs inhibited TPA edema when they were administered topically. Mixed CO/lipoxygenase (LO) inhibitors, phenidone and BW755C, were active orally against AA edema (ED50S of 84 and 65 mg/kg, respectively) and against TPA edema (ED50S of 235 and 88 mg/kg, respectively). Phenidone was more active topically against AA edema (ED50, 0.1 mg/ear) than BW755C (ED50, 2.8 mg/ear); however, BW755C was more active topically against TPA edema (ED50, 0.2 mg/ear) than phenidone (ED50, 0.6 mg/ear). Methylprednisolone was very effective in the AA (oral ED50, 17 mg/kg; topical ED50, greater than 1 mg/ear) and TPA models (oral ED50, 4.3 mg/kg; topical ED50, 0.03 mg/ear. MK-447 was topically and orally effective only in the TPA model. Not surprisingly, drugs were more effective topically than orally in both mouse ear edema assays. The models were somewhat selective for CO and CO/LO inhibitors; however, dapsone was orally effective in the ear models, and a number of mediator antagonists and CNS drugs, especially anti-psychotics, were topically active primarily against TPA edema. These models may be useful for the detection of in vivo activity of CO/LO or 5-LO inhibitors.

The topical effects of Wy-41,195 [2-cyano-3-(methylamino)phenylamino] oxoacetic acid, sodium salt and disodium cromoglycate in the rat passive eyelid anaphylaxis.

Wy-41,195 demonstrated significant inhibitory effects (54-60%) when administered topically at 0.25-2% concentrations in a rat passive eyelid anaphylaxis assay. In contrast, topically applied disodium cromoglycate (DSCG) showed non significant inhibition at these concentrations. The potency of Wy-41,195 was more than 8 times greater than DSCG, and this compound may be an effective topical agent in man in preventing allergic and associated conditions.

Comparison of inflammatory changes in established type II collagen- and adjuvant-induced arthritis using outbred Wistar rats.

Type II collagen- and adjuvant-induced arthritis in outbred Wistar rats were compared using parameters that measured the inflammatory response, cellular and humoral immunity, blood protein changes, drug metabolism and histopathological and bony changes of the inflamed paws. There was a lesser incidence (40-70%) and severity of collagen disease than the adjuvant model (incidence approximately 100%). The use of MDP increased the incidence and severity of collagen arthritis. The acute phase protein response (plasma fibrinogen) was similar in both models during the peak of inflammatory response. Drug metabolism was inhibited in both type II collagen boosted with MDP or M. butyricum sensitized rats with arthritis; however, arthritic rats sensitized with collagen alone produced no inhibition. Only collagen arthritic rats produced type II collagen antibody and exhibited delayed hypersensitivity to type II collagen. Bony changes as assessed by radiographic evaluation were more severe in adjuvant arthritic rats than in the collagen arthritic model; histopathological findings from these animals confirmed this observation. The primary lesions in both models were periosteal reaction of the bone and ankylosis. Several classes of antiarthritic drugs were compared in both models using paw edema measurements and bony changes by radiographic evaluation. Drugs with inhibitory activity in both models were indomethacin, methylprednisolone, D-penicillamine and gold sodium thiomalate. Levamisole, chloroquine and auranofin were inactive in both models.

Effects of oral aspirin and oxaprozin on the development of lupus-like disease in MRL/1 mice.

We examined the effects of two prostaglandin synthetase inhibitors, aspirin and oxaprozin, on the development of lupus-like disease in MRL/1 mice. Daily oral administration of 100 mg/kg of these compounds over a period of 3 months significantly reduced thymic lymphoid hyperplasia. In addition, aspirin but not oxaprozin significantly lowered total lymphocyte counts in the peripheral blood. Other drug-related changes, including reduced hyperplasia in the spleen and lymph nodes and an improvement in kidney vasculitis by aspirin, did not reach statistical significance. Neither aspirin nor oxaprozin influenced the circulating levels of anti-ds DNA antibodies or the severity of kidney glomerulonephritis. While the overall effects of these cyclooxygenase inhibitors were not dramatic, the results do indicate that further studies are warranted to determine the precise therapeutic role, if any, for PG-synthetase inhibitors in lupus-like disease.