Richard P. Carlson

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, 0.2 mg/ear) than (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,>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 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 ofin vivo activity of CO/LO or 5-LO inhibitors.

Etodolac selectively inhibits human prostaglandin G/H synthase 2 (PGHS-2) versus human PGHS-1

The isozymes of prostaglandin G/H synthase (PGHS) are shown to be differentially inhibited in vitro by currently marketed nonsteroidal anti-inflammatory drugs (NSAIDs) using microsomal rhPGHS-1 and rhPGHS-2. Comparison of selectivity ratios (IC50 rhPGHS-1/IC50 rhPGHS-2) demonstrated a 10-fold selectivity of etodolac (Lodine) for rhPGHS-2, whereas the other NSAIDs evaluated demonstrated no preference or a slight preference for inhibition of rhPGHS-1. In vitro enzyme results were supported by a human whole blood assay where etodolac also demonstrated a 10-fold selectivity for inhibition of PGHS-2 mediated TxB2 production. Taken together, these data may be key to explaining the clinically observed gastrointestinal safety of etodolac versus other marketed NSAIDs.

Bacterial lipopolysaccharide potentiates type II collagen-induced arthritis in mice

Collagen-induced arthritis (CIA) is an immunologically relevant animal model of human rheumatoid arthritis. Studies comparing the disease incidence in genetically susceptible male and female DBA/1LacJ mice demonstrated that under low density/low stress housing conditions, female mice had earlier onset (day 35) and higher disease incidence (25%) than the male mice (17% at day 49) when immunized with bovine type II collagen. A single subcutaneous or intraperitoneal injection of bacterial lipopolysaccharide (LPS) 17–24 days after collagen immunization greatly potentiated this standard CIA model in a dose related manner. 20–40 μg of LPS accelerated the onset of disease from day 35 to day 21 and exacerbated the clinical severity score from 0.27 to 2.00 at day 42. A similar administration of 6 μg of recombinant interleukin-β produced a comparable potentiated CIA model. The acute phase protein, serum amyloid P (SAP), was elevated in the serum at day 26 to 440 μg ml−1 for the LPS potentiated CIA mice compared to 65 μg ml−1 in the non-potentiated immunized CIA mice. There was a significant correlation (r = 0.78) between SAP levels and disease expression in the LPS treated CIA mice. The rapidity and uniformity of disease expression in this LPS potentiated CIA model will allow more and different drugs to be evaluated with a smaller number of animals.

Effect of selected antiinflammatory agents and other drugs on zymosan, arachidonic acid, PAF and carrageenan induced paw edema in the mouse

Zymosan, carrageenan, arachidonic acid and platelet activating factor (PAF) were used to induce inflammation (edema) in the paws of mice. Antiinflammatory drugs (e.g., BW755C and indomethacin) as well as cyproheptadine (mediator antagonist), theophylline (phosphodiesterase inhibitor) and guanabenz (α adrenoceptor agonist) showed the greatest efficacy in the carrageenan and zymosan models. Nonsteroidal antiinflammatory (NSAIDs) agents showed greater activity in the arachidonic acid (AA) paw edema model than the dual 5-lipoxygenase (LO)/cyclooxygenase (CO) inhibitors. The PAF model was insensitive to NSAIDs but showed some activity with drugs possessing inhibitory 5-LO activity (e.g., phenidone, BW755C) and the mediator antagonist, cyproheptadine. Suramin, a complement inhibitor, as expected, was active only against zymosan-induced edema. In conclusion, the inhibitory activities of dual 5-LO/CO inhibitors and NSAIDs were not different in the zymosan, carrageenan and AA edema models in the mouse; however, some selectivity for 5-LO inhibitors was observed in the PAF model.

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.

Comparison of antiinflammatory and antiallergic drugs in the melittin- and D49 PLa2-induced mouse paw edema models

Melittin (MLT) (10 μg/paw) and D49 (0.4 μg/paw) were injected into the hind paw of male CD-1 mice and elicited 70–80% of maximal paw edema responses at 60 and 30 min after injection, respectively. D49 paw edema was significantly inhibited by anti-histamine/serotonin agents, a PAF antagonist, a PLA2 inhibitor, and some but not all 5-LO and CO inhibitors, indicating that this edema is produced by several classes of inflammatory mediators with mast cell degranulation apparently playing a major role. In contrast, MLT paw edema was not inhibited effectively using the same pharmacological agents except theophylline, suggesting it was elicited via a different sequence of inflammatory events. In summary, D49 and MLT paw edema models were found to be ineffective models to identify experimental PLA2 compounds in our laboratory.

The antiinflammatory activity of the immunomodulator Wy-18,251 (3-(p-chlorophenyl)thiazolo[3,2-a]benzimidazole-2-acetic acid)

The antiinflammatory activity of the immuno-modulatory agent Wy-18,251 (3-(p-chlorophenyl)thiazolo-[3,2-a]benzimidazole-2-acetic acid) was examined using a variety of antiinflammatory, analgesic and antipyretic animal models in comparison to aspirin, levamisole and indomethacin. The acute antiinflammatory and analgesic activity of Wy-18,251 (ED50=100–200 mg/kg, p.o.) was similar to aspirin, but in contrast to aspirin Wy-18,251 failed to demonstrate antipyretic activity. Wy-18,251 (10–100 mg/kg, p.o.) also inhibited chronic inflammatory responses in the adjuvant- and collagen-induced arthritis models. Wy-18,251 was a modest inhibitor of prostaglandin biosynthesis but did not inhibit either 5- or 15-lipoxygenase enzymes. Wy-18,251 (up to 480 mg/kg, p.o.) produced little gastrointestinal pathology in 16 h fasted rats. The combined immunomodulatory and antiinflammatory activity of Wy-18,251 suggests that this agent may have therapeutic promise in certain immunoinflammatory diseases including rheumatoid arthritis.

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≈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.

Evidence for a role of bradykinin in experimental pain models.

Pretreatment with captopril, a kininase II inhibitor, at 10 mg/kg i.p. or s.c., significantly increased the writhing response induced by a minimum effective dose (0.75 mg/kg i.p.) of phenylbenzoquinone (PBQ), by 91–148%. 1,10-Phenanthroline, a carboxypeptidase B inhibitor (2 mg/kg i.p.), in combination with captopril enhanced the algesic effect of PBQ by 309–360%. Captopril also doubled the number of writhes induced by a minimum effective dose of BK (5 μg/kg i.p.) in PGE2-pretreated mice. The writhing responses induced by higher doses of PBQ or BK were not affected by these inhibitors. The hyperalgesic effect of BK (1 μg) injected into the hindpaw of rats was significantly increased and prolonged by coinjection of captopril (30 μg) and 1,10-phenanthroline (30 μg) and was prevented by carboxypeptidase B (1 mg). These data indicate that BK plays a role in pain in these models, a role which appears of greatest relevance at threshold algesic stimulation.

Immunomodulatory activity of WY-18, 251 (3-(P-chlorophenyl)thiazolo[3,2-a]benzimidazole-2-acetic acid

The in vitro and in vivo effects of the experimental immunomodulatory agent Wy-18,251 (3-(p-chlorophenyl)thiazolo[3,2-a]benzimidazole-2-acetic acid) were studied in comparison with levamisole and indomethacin. Levamisole (4 mg/kg, i.v.) but not Wy-18,251 (less than or equal to 10 mg/kg, i.v.) enhanced carbon clearance rates in vivo in mice. Both Wy-18,251 and levamisole (100 mg/kg, p.o.) significantly suppressed the symptoms of experimental allergic encephalomyelitis (EAE) in rats injected with spinal cord emulsion, but neither were as effective as tilorone in this model. Wy-18,251 and levamisole (1-100 mg/kg, p.o.) suppressed the in vivo generation of plaque-forming cells (PFC) in mice immunized with sheep red blood cells while indomethacin (9 mg/kg, p.o.) enhanced PFC formation. All 3 agents (10(-5) - 10(-6) M) enhanced the in vitro ovalbumin (OA)-specific and Con A- or PHA-induced proliferative response and Con A-stimulated interleukin 2 (IL-2) synthesis of rat spleen cells. Furthermore, in vivo treatment of rats with 1-10 mg/kg (p.o.) of Wy-18,251 and levamisole but not indomethacin increased the subsequent in vitro mitogen or antigen (OA) responsiveness of spleen cells. None of the drugs (10(-5) - 10(-7) M) influenced the natural killer cell (NK) activity of rat spleen cells when incorporated directly into the 51Cr release NK assay.