Interference of PCA 4248, a novel PAF antagonist, on antigen-induced pleurisy

pqw edema, within a period of time during which dexamethasone is known to induce lipocortin synthesis. Camuccio et af. (1989) have now shown that dexamethasone induces the synthesis of another protein, vasocortin, which inhibits dextran-induced rat paw edema and mast cell degranulation induced by concanavalin A. The purpose of the present study was to confii the involvement of PAF using the novel antagonist PCA 4240 (Ortega, 1989) and models of cross-desensitization, and to investigate in more details the effect of glucocorticoids. Intraplantar injection of 10 ug of ovoalbumin into sensitized animals led to a local inflammatory reaction that peaked 30 minutes after the challenge and decmased thereafter. Dral pretreatment of sensitixed animals with PCA 4240 (50 and 100 mg/kg) reduced anaphylactic paw edema by SC%with the two doses used @ < 0.001) while the inflammatory reaction by 1 ug of PAF was inhibited by 41% (50 mg/kg) and by 75% (100 mg/kg) (p -z 0.801). In addition, PAF-induced dessensitization cross-desensitized with antigen up to 59%. The administration of dexamethasone (0.1 mg/kg) three hours before the challenge reduced the edema by 5546, but no inhibition was seen when the drug was administered 1 hour or 12 and 1 hours before, and pre-treatment of the sensitized animals with antiallergic drugs ketotifen (5 mg/kg) inhibited the react&a GI 45% (p < 0.001) and azelastine (5 and 20 mg/kg) in 37% and 50% respectively. These results were further supported by the fact that degranulation of peritoneal mast cell from sensitized animals, challenged in vitro with 1 ug of antigen, was reduced in 40 and 75% wynen the donor mice were pre-treated s.c with 0.1 mg/kg dexamethasone, 2 or 3 hours before the in vitro challenge, whereas no effect was observed when the animals were pre-treated 1 hour bef~e and, in addition, oral pretreatment of donor mice with ketotifen (5 mg/kg) and azelastine (10 mg/kg) reduced mast cell degranulation by 63% and 55% respectively. In conclusion, the present results demonstrate that PAF participates in the anaphylactic mice paw edema. The fact that dexamethasone only interfere with paw edema and in vitro mast cell degranulation, when ghm 2 or 3 hours before, can suggests that vasocortin may be responsible for the anti-inflammatory effect of dexamethasone in this allergic reaction.

Amorim, CZ. et al., Lipids, submitted. Carnuccio,R et al., 1989, Br. J. Pham~col. (1989) 90, 32-34. Ortega,M-P.1989, abstractsubmittedto BritishPharmacologicalSociety.

1P.tu.226 1

Lima, M.C.R, Neto, H.C.C.F., Silva, P.M.R., Dias, M.T.R.P., Bozza, P.T., Perez, S.A.C., Martins, M.A.

and Cordeiro, R.S.B. Dept Fisiologia e Farmacodinrimica, Fundofio Oswald0 Cruz, Brazil

PCA 4248 (2-@henyl-thio) ethyl 5-methoxycarbonyl-2,4,6-trimethyl-l,4-dihydropyridine-3-carboxylate) was found to selectively inhibit Paf-induced rabbi& and human platelet aggregation and also the binding of Paf to human platelet and polymorphonuclear receptors. In the present work, this compound was tested for its ability to block Paf and antigen-induced pleurisy in rats. Active immunization was performed by two intraplantar injections (0.1 ml/paw) of complete Freund’s adjuvant mixtured 1: 1 wih ail ovr-%umin-saline solution (2 mg/ml). Challenge was made 14 days later by axt it injection of ovoalbumin (12.5 ug/cavity) and the pleurisy performed as described (Ortega et al., 1990). Confinning previous results (Martins et al., 1989). the it injection of Paf (1 ug/cavity) in normal rats, induced exudation at 1 h followedby an increase in the total number of mononuclear cells and neutrophils at 6 h, which fell to basal levels by 24 h. However, at this time, a marked and long lasting eosinophil accumulation was noted. The oral administration of PCA 4248 (lo-50 mg/kg) 1 h before Paf, significantly inhibited Paf-induced exudation and leukocyte recruitment, including the late eosinophil accumulation. These data support the hypothesis that PCA 4248 has a potent “in viva” Paf antagonist activity. In an other set of experiments, we observed that the it administration of antigen into actively sensitized animals induced an intense exudation and leukocyte infiltration, in which neutrophils representsthe major cellular component. As shown in table 1, the pre-treatment with PCA 4248 (25 mg/kg, po) significantly inhibited antigen-induced exudation without affect neutrophil accumulation. By contrast, two well-estab-

889 lished Paf receptor antagonists, BN 52021 and WEB 2086 at doses with supress Pal-induced exudation, did not interfere with the allergic pleurisy. In conclusion, we demonstrated that besides its clear ability to block Paf effects, 4248 has an important action on antigen-induced vasopermeation which does not seem to he related to Paf antagonism. Table 1 Effect of PAF antagonists on antigen-induced pleurisy. treatment

exudation (ul)

none PCA BN 52021 WEB 2086

930 f 270 260 f 200 827 f 100 8OOflOO

%of inlubition

total leukocytes (X106) 28.2 f 7.9 30.1 f 7.9 33.3 p 3.7 24.4 f 9.6

72.0 * 11.1 14.0

Wof inhibition

-

0.0 0.0 13.4

Each vahtes represent the mean f SEM from at least 6 animals. ( * ) represents statistically s&nificant diferences (p < 0.05). Supported by FAPERI, FINEP and CNPq.

References Martins et al., 1989. Br J Pbannacol, 96: 363. Ortega et al., 1999. Abstract in the Br. Pharmacol. Sot. London.

El

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lem 0%

Kovalev,

I.E.

All-Union ScientQiicResearch Institute of Riotechnologv. Nauchny proe.z~ 8, II 7246, Mescow, U.S.S.R.

The problem of image recognition is the central one for cybernetics. Image recognition is the main problem of the mental activity. A functional system of organism, called “immunochemical functional system of homeostasis”, was found by the author. The conception of homeostatic immunochemical functional system made it possible to elucidate the main principle of informational coding of unlimited variety of chemical structures (Kovalev, 1999; Kovalev, Polevaja, 1985). The principles of coding in the organism of the information about an unlimited scope of substances and the formation of peptide analogues of the original nonpeptide chemical structures are first formulated on the basis of the conception of the immunochemical functional system of homeostasis and the data on the pharmacological activity of antibodies to low molecular organic compounds and the corresponding antiantibodies. While being activated in biochemical systems, such as the system of cytochrome P-450, nonpeptide substances, neurotropic drugs for example, covalently bind proteins forming a conjugated antigen. This conjugate induces the synthesis of antibodies with the active center capable of recording the haptene structure. Thus the aminoacid sequence of the antibody’s active center conteins the information about the hapten chemical structure (inverse code). The antibody formed against the active center of this antibody can be considered as the direct peptirrle analog of the nonpeptide exogenic substance. The similarity of the biological activity of the basic substance and its peptide analog (antiantibody) is proved by their interaction with the same receptor (cholinoreceptor, adrenoreccptor, opiate receptor, etc.). So, this system is able to recognize of the images of unlimited amount of chemical structures, to code them with the help of aminoacide “alphabet” to remember and to safe of recieved chemical information, to create xenobiotic images in the form of peptides (direct and reversed images-antibodies and antiantibodies). In this case functional system