Prostaglandins and leucocyte migration in inflammatory reactions

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., BW 755C and indomethacin) as well as cyproheptadine (mediator antagonist), theophylline (phosphodiesterase inhibitor) and guanabenz (alpha 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, BW 755C) 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.

Therapeutic reduction of ongoing carrageenin-induced inflammation by lipoxygenase, but not cyclooxygenase inhibitors

A variety of steroidal and nonsteroidal antiinflammatory agents (NSAs) were compared for their effectiveness against a developing acute inflammatory reaction. Only BW 755C [3-amino-1-(m-trifluoromethyl)-phenyl-2-pyrazole] was immediately effective when administered 2 h after carrageenin, as the 3-h swelling was significantly reduced. Dexamethasone, a steroidal antiinflammatory agent, produced a delayed reduction. When administered at 2 h postcarrageenin, there was no effect at 3 h; but at 6 h, dexamethasone significantly reduced the swelling. In contrast, neither of the classic NSAs, aspirin or indomethacin, were effective when administered after the carrageenin. The results demonstrating a postcarrageenin effectiveness by BW 755C and dexamethasone are discussed as a possible reflection of an action on the lipoxygenase pathways of the arachidonic cascade that is not shared by the classic NSA.

Some biochemical and pharmacological properties of an epoxide metabolite of alclofenac

The properties of an epoxide metabolite of alclofenac have been investigated in a number of in vitro and in vivo tests. Alclofenac epoxide was shown to inhibit the activity of yeast alcohol dehydrogenase and form a conjugate with cysteine. The epoxide, but not alclofenac itself, showed mutagenic effects on strains of Salmonella typhimurium sensitive to alkylating agents, but had no effect on strains sensitive to intercalating agents. In addition the epoxide was active in a cell transformation assay using as a target Syrian hamster cells. No acute toxic reactions were observed in mice treated with alclofenac epoxide and the compound was devoid of analgesic and acute antiinflammatory activity. Alclofenac epoxide was found to be a sensitising agent in the guinea-pig when administered either by injection with complete Freud's adjuvant or topically as an ethanolic solution. It is postulated that the formation of the epoxide may explain some of the therapeutic and toxicological properties of alclofenac in man.

Release of prostaglandins E and F in an algogenic reaction and its inhibition

E and F prostaglandins were measured by radioimmunoassay in the peritoneal fluid of rats which had been injected with an irritant, acetic acid. The considerable increase recorded 5 min after the injection virtually disappeared in 90 min. For the first 15 min the PGE2 level was twice that of PGF2 alpha, the levels then equalized and after 90 min the PGE2 level was less than that of PGF2 alpha. This balance between PGEs, which are hyperalgesic, and PGF2 alpha, which has often been shown to be a PGE antagonist, could regulate defence mechanisms. An examination of cells collected by washing the peritoneum revealed a large decrease between 15 and 30 min after injection of the irritant and suggested that the prostaglandins could be produced by neutrophil polynuclear cells but also by destruction of macrophages. Various types of prostaglandin biosynthesis inhibitors (non-steroid anti-inflammatory agents, non-narcotic analgesics and some monoamino-oxidase inhibitors and antioxidants) prevented prostaglandin release. Their activity on release paralleled their activity on acetic acid-induced writhing.

Inflammatory response linked to oxazolone-indued cutaneous basophil hypersensitivity: effect of different immunomodulator and anti-inflammatory drugs

The potency of cytostatic and anti-inflammatory drugs was tested on the oxazolone-induced cutaneous basophil hypersensitivity (CBH) in mice. The challenge reaction was performed early after sensitization in order to minimize B-cell expression; exudative and cellular infiltration was estimated 6 h, 24 h and 48 h after challenge. The potency of drugs was tested at three different periods of immunization: 2 days before or after sensitization or before challenge. Cytostatics act mainly when cells are being committed, a corticoid acts on inflammation linked to committed cells, NSAIDs show inconstant anti-inflammatory effects on this test. D-Penicillamine and levamisole act in the same depressive profile in normal animals. Thus the CBH model appears to be relevant in studying drug activities on inflammation linked to T-cell expression.

Aspirin, salicylate and prostaglandins

The effects of aspirin, salicylic acid and gentisic acid on the paw swellings in the arachidonic acid-potentiated and in the conventional carrageenan-induced oedema tests as well as on the content of prostaglandin-like activity and leucocyte migration in the exudate of inert implanted sponges in the rat have been studied. It is concluded that aspirin exerts two separate inhibitory effects on prostaglandin formation in vivo, a rapid action of the intact molecule on easily accessible tissues and a later action due to its metabolic conversion to salicylic acid. Salicylic acid inhibits prostaglandin biosynthesis in vivo as the salicylate ion itself and there is no formation of a subsequent 'active' metabolite.

Anti-inflammatory effects of blood platelets in the rat

A selective accumulation of blood platelets occurs at the sites of intradermal injection of zymosan and carrageenan in the rat. The inflammatory response to zymosan, assessed by the local accumulation of systemic radioactive human serum albumin, was significantly enhanced in platelet-depleted rats. Similar enhancements of the paw oedemas, caused by the subplantar injection of either carrageenan or zymosan, were also observed in thrombocytopenic animals. It is concluded that blood platelets may exert protective, i.e., anti-inflammatory, effects in some models of acute inflammation in the rat.

Comparative effects of drugs on four paw oedema models in the rat

The development of novel anti-inflammatory drugs (AID) has been claimed to be dependent on the discovery of models of inflammation that differ from those currently used for drug screening, e.g. carrageenen paw oedema and u.v. erythema. We have thus evaluated the effect of a variety of drugs in a number of novel models of inflammation in the rat produced in the hind paw. We have utilized kaolin, zymosan, anti-rat IgG (anti-IgG) and the Reversed Passive Arthus (RPA) reaction to produce these oedema models. We found that the non-steroidal AID's, e.g. aspirin, flufenamic acid, indomethacin, naproxen, and phenylbutazone, were active in all four tests. Of the nine novel AID examined, levamisole and tetramisole demonstrated considerable activity in all four tests and dapsone was especially active in the anti-IgG and RPA tests. In contrast, the anti-rheumatic d-penicillamine was inactive in all four models. Each of the ten compounds tested which has been claimed to influence complement function, was active in the RPA but not in the kaolin model. These results are discussed in the context of the aetiology of each oedema and the suspected mode of action of the various drugs.