Alan J. Lewis

On the ability of prostaglandin E1, and arachidonic acid to modulate experimentally induced oedema in the rat paw.

1 Prostaglandins E1 and E2 but not prostaglandin F2α, arachidonic acid or linolenic acid, produced slight oedema when injected into the rat hindpaw. 2 Prostaglandin E1 potentiated hindpaw oedema produced by carrageenan, kaolin, bradykinin and trypsin but not that produced by 5‐hydroxytryptamine (5‐HT), histamine, dextran B or compound 48/80. Carrageenan‐ and bradykinin‐induced paw oedemas were also potentiated by prostaglandin E2. Arachidonic acid potentiated responses to carrageenan and kaolin but not responses to bradykinin, trypsin, 5‐HT, histamine, dextran B or compound 48/80. Linolenic acid did not potentiate hindpaw oedema induced by carrageenan. 3 Potentiation of carrageenan‐induced oedema by prostaglandin E1 was not diminished by pretreatment with indomethacin, hydrocortisone or cyproheptadine. However, arachidonic acid potentiation of carrageenan oedema was reduced by pretreatment with non‐steroidal anti‐inflammatory drugs but not by anti‐inflammatory steroids or by paracetamol. 4 The enhancement of the response to carrageenan and kaolin by prostaglandins E1, E2 and arachidonic acid is discussed in terms of kinin mediation.

Differential effects of putative lipoxygenase inhibitors on arachidonic acid metabolism in cell-free and intact cell preparations

The effects of nordihydroguairetic acid (NDGA), 3-amino-1-trifluoromethyl-)-phenyl-2-pyrazoline (BW755c), eicostatetraynoic acid (ETYA), phenidone, quercetin, and indomethacin (INDO) on the synthesis of 15-hydroxyeicosatatetraenoic acid (15-HETE) from soybean 15-lipoxygenase, leukotriene B4 (LTB4 from 5-lipoxygenase, and prostaglandin E2 (PGE2 from cyclooxygenase enzymes of rat neutrophils and mouse peritoneal macrophages were investigated. All of the drugs caused a dose-related inhibition of increased oxygen consumption by soybean 15-lipoxygenase in the presence of arachidonic acid and the rank order of potency was phenidone ≥ BW755c > ETYA > quercetin > NDGA > indomethacin. The reduction in oxygen consumption correlated with a reduction of 15-HETE formation as identified by high-performance liquid chromatography. Apart from indomethacin, these drugs were also effective against the rat neutrophil 5-lipoxygenase, although the rank order of potency did not correlate with that obtained with soybean 15-lipoxygenase. Furthermore, in both A23187-activated rat neutrophils and zymosan-activated mouse peritoneal macrophages the synthesis of prostaglandins was inhibited by all of these drugs. In the neutrophils, the rank order of potency was INDO > ETYA > BW755c > quercetin > NDGA > phenidone, whereas in mouse peritoneal macrophages, the order was INDO > ETYA > BW755c > NDGA > quercetin > phenidone. These results suggest that putative lipoxygenase inhibitors exhibit both qualitative and quantitative differences in their effects on both lipoxygenases and cyclooxygenases.

The role of copper in inflammatory disorders

Copper was believed to be of therapeutic value as long ago as 1000 years s.c.; in particular, copper bracelets and foods high in copper were thought to be beneficial in treating arthritic conditions [ll. In 1945, patients with rheumatoid arthritis (RA) were shown to exhibit higher than normal serum copper levels [2]. Nevertheless, during the 1940s to early 1970s parenterally-administered copper complexes were used successfully in the treatment of arthritic conditions [3]. However, the possible acceptance of this form of therapy was impeded by the concomitant development of anti-inflammatory steroids and aspirin-like nonsteroidal anti-imflammatory drugs. It was not until 1960 that Bonta placed the clinical studies on a more scientific footing when he showed that copper compounds possessed anti-inflammatory effects in animals [4]. Sorenson confirmed and extended these findings and he opened a new chapter in the copper story by claiming that copper complexes of anti-inflammatories were indeed the active forms of these drugs [5, 6]. He also speculated that antiarthritic agents might promote tissue distribution of elevated serum copper in RA patients which was a physiological response to the inflammation (Fig. 1). The use of copper to treat RA was rationalized by suggesting that this physiological response was insufficient to quell the ongoing inflammatory processes and, consequently, exogenous help was needed. The modulatory role for copper was supported by the studies of Milanino and associates who demonstrated that exacerbation of inflammation occurred in rats on a copper-deficient diet [7]. Numerous multidisciplinary groups have subsequently re-examined the paradoxical role of copper in inflammation emphasizing the therapeutic usefulness of copper, in inflammatory conditions. Two excellent reviews [6, 8] and two books [9, 10] on the subject have recently been published covering much of this research.

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 AIDs, 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.

Action of gold salts in some inflammatory and immunological models

Several gold salts were compared in kaolin-induced rat paw oedema, u.v. erythema in guinea pigs, delayed type hypersensitivity and humoral immunity in mice, and adjuvant-induced arthritis in the rat. In the latter the additional parameters of serum gold and copper levels and lysosomal enzyme activity were determined. In addition, the in vitro inhibition of several lysosomal enzymes derived from mouse macrophages was studied. The gold compounds examined were aurothiomalate, aurothioglucose, triethylphosphine gold chloride (SK & F 36914) and its glucopyranoside derivative (SK & F D-39162), triphenylphosphine gold chloride and sodium gold chloride dihydrate.SK & F 36914 and SK & F D-39162 had significant activity after oral dosage upon paw kaolin and u.v. erythema in rats and guinea pigs, respectively. Gastric swelling also occurred.In Wistar rats, adjuvant arthritis was little affected by the gold salts but in the Lewis rats there was suppression. In both strains there was less elevation in serum copper levels with treatment by SK & F 36914 and SK & F D-39162, but not by aurothiomalate.None of the compounds had any measurable effect on delayed hypersensitivity or humoral antibody levels in mice.The in vitro activities of cathepsin B1 and cathepsin D were inhibited by all the gold compounds. Reactivity of gold dependent on compound solubility and the nature of the gold ligand.Considerable differences exist between the profiles of activity for the different gold salts evaluated.These observations indicate that some gold salts do possess anti-inflammatory activity with a potency similar to that of indomethacin.

A comparison of the anti-inflammatory effects of copper aspirinate and other copper salts in the rat and guinea pig.

A comparison of the anti-inflammatory (AI) activity of copper compounds in models of kaolin-induced paw oedema and u.v. erythema in the rat and guinea pig is described. The results demonstrated considerable species variation, the guinea pig being more sensitive to the AI and irritant effects of copper aspirinate and the other copper compounds. The route of administration of these compounds was also an important factor in interpreting AI activity obtained. Indeed, the counter-irritation effects of the copper compounds may be largely responsible for the AI activity obtained after subcutaneous administration.The comparison between copper aspirinate and aspirin, performed in order to determine whether a copper complex of an AI drug was more active than the parent AI compound, failed to produce a clear difference in activity although copper aspirinate was more effective than aspirin in certain cases.It is concluded that this study highlights the complexities of copper therapy against inflammatory processes and furthermore indicates the importance of species, the model of inflammation and route of drug administration in interpreting data obtained with copper containing compounds.

THE EFFECT OF SYSTEMICALLY AND TOPICALLY APPLIED DRUGS ON ULTRAVIOLET‐INDUCED ERYTHEMA IN THE RAT

1 Exposure of the skin of rats to u.v. light (>295 nm) for 30 s or longer elicited a delayed erythema response, the rate of onset increasing with the period of irradiation. The erythema was still present at 24 h and was replaced by scab formation in 48 hours. 2 Both topically applied steroidal and non‐steroidal anti‐inflammatory drugs reduced the erythema formation when administered immediately after u.v. exposure. Propyl gallate, an antioxidant with sun screening properties in man, also possessed topical anti‐erythemic activity. 3 Both steroidal and non‐steroidal anti‐inflammatory drugs, systemically administered 1 h before u.v. exposure, reduced the erythema. However, the steroidal compounds were less effective than the nonsteroids and reduced the intensity of erythema by less than 50%. Antagonists of 5‐hydroxytryptamine (5‐HT) reduced the erythema but several other drugs with different pharmacological activities were ineffective. 4 Neither topical nor systemic treatments of any of the drugs examined suppressed the scab formation at 48 hours. 5 These results and those using other selective blocking agents indicate that in the mediation of the erythema reaction prostaglandins may play a major role and 5‐HT perhaps a minor one but that H1 histamine receptors and α‐ and β‐adrenoceptors have no significant role.

Mechanisms of phytohaemagglutinin-P-, concanavalin-A- and kaolin-induced oedemas in the rat

Subplantar administration of either Phytohaemagglutinin-P (PHA), Concanavalin-A (Con A) or kaolin into the rat hind paw produced a dose related oedema which was still present at 48 h. Both of the lectins were more inflammagenic than kaolin on a weight per weight basis. As a result of studies using mediator inhibitors and depletors it appears that 5HT, but not histamine, may play a role in the early phases (0.5-1.5 h) of both PHA and Con A responses. Neither mediator appears to be involved in the kaolin oedema. Kinins are also likely mediators of the inflammatory response to all three irritants and could be detected in irritant injected air blebs in the rat. Prostaglandins are unlikely to play a significant role in PHA or Con A oedema since indomethacin-induced inhibition of their synthesis has only a slight inhibitory effect on the lectin induced paw oedemas and only small amounts of prostaglandin-like material could be detected in PHA or Con A blebs. However, kaolin oedema appears to have a significant prostaglandin component since large amounts of prostaglandin-like materials were detected in kaolin blebs and also indomethacin reduced the kaolin induced paw oedema. Other mediators of the inflammatory process such as complement are likely to be involved in all three irritant induced oedemas.

The anti-inflammatory profile of dapsone in animal models of inflammation.

Dapsone has been shown to possess anti-inflammatory activity in a variety of animal models. It possesses oral anti-oedema activity especially pronounced in novel models of acute inflammation, viz. anti-IgG and reversed passive Arthus oedemas. However, it is not very active in the guinea pig u.v. erythema model. It is effective in chronic models such as adjuvant arthritis and the cotton pellet granuloma although multiple administration may also produce cyanosis. Antipyretic and analgesic effects for dapsone have been demonstrated and are similar to those produced by phenylbutazone. It inhibits zymosan-induced β-glucuronidase release from cultured macrophages and also the activity of this enzyme. Dapsone does not appear to be ulcerogenic in the rat.

Changes in colonic tissue levels of inflammatory mediators in a guinea-pig model of immune colitis.

An immune colitis based on a delayed-type hypersensitivity reaction was induced in dinitrochlorobenzene (DNCB)-sensitized guinea-pigs by intrarectal challenge with DNCB. A low challenge dose (0.25% DNCB) induced mild inflammatory changes in the distal colon and rectum characterized by goblet cell depletion. A higher challenge concentration (5% DNCB) resulted in severe colonic ulceration with crypt abscess formation. The inflammatory mediators, histamine, 5-hydroxytryptamine (5HT), glandular kallikrein and PGE2 were measured in freeze-dried colonic mucosae. Histamine content was three times control (p<0.01) in 0.25% DNCB induced colitis, although no significant change was observed in 5% DNCB challenged animals. Mucosal 5HT content was significantly reduced (p<0.01) after both challenges. Glandular kallikrein content did not differ from control, while PGE2 was significantly (p<0.05) increased at both challenge doses. The possible significance of these changes with respect to severity of inflammation and aetiology of colitis is discussed.