Avaliação comparativa da atividade antinociceptiva e mecanismo de ação decorrente da administração de 3,4,5-trimetoxicinamato de metila (M-TMCA) e 3,4,5-trimetoxicinamato de butila (B-TMCA) em camundongos

Abstract

Natural products have been the focus of large pharmacological studies in recent decades. Phenylpropanoids, abundant in aromatic plants, have gained prominence for their various pharmacological activities, with emphasis on derivatives of cinnamic acid. 3,4,5-Trimethoxycinnamic acid (TMCA), a cinnamic derivative with well-defined pharmacological properties in the literature, such as sedatives, anticonvulsants and immunomodulators. Methyl 3,4,5-trimethoxycinnamate (M-TMCA) and butyl 3,4,5-trimethoxycinnamate (B-TMCA) are two TMCA analogues. Given the scarcity of research on the pharmacological activity of these two analogues, interest in researching the antinociceptive activity that encouraged this work arose. Therefore, the aim of the present was to evaluate the central effects resulting from the intraperitoneal administration of M-TMCA and B-TMCA in nociception models using male mice (Mus musculus – Swiss), as well as to propose the mechanism by which they act as antinociceptive drugs using in vivo and in silico studies. The experiments started with the determination of the LD50, in which it was estimated at 500 mg/kg. Then, pharmacological screening was performed, in which a depressive profile was observed for both drugs tested, due to decreased ambulation, analgesia, decreased righting reflex and decreased response to touch presented by the treated animals. Pre-treatment with M-TMCA and B-TMCA, at doses of 50, 75 and 100 mg/kg, did not change motor coordination in the rota-rod test, excluding a myorelaxant effect. Then, methodology was used to determine the antinociceptive activity of M-TMCA and B-TMCA. In the test of abdominal writhing induced by acetic acid, M-TMCA and B-TMCA reduced the number of writhes when compared to the control group, however when the doses were compared to each other, the B-TMCA at a dose of 75 mg/kg was more effective. The formalin test was performed, using the same doses, and it was observed that only B-TMCA was able to reduce the licking time in the neurogenic phase (0-5 min) of the test, however, both substances were effective in the inflammatory phase (15-30 min). Thus, B-TMCA, at a dose of 75 mg/kg was chosen to continue the studies. In an attempt to propose the possible mechanisms of action by which B-TMCA exerts its antinociceptive activity, in silico analyzes were carried out through consensus docking and molecular dynamics simulations, which demonstrated that B-TMCA acts through interactions with the enzyme COX-2 and A1 and NMDA receptors. In an attempt to prove whether B-TMCA acts on the adenosinergic receptor, caffeine (non-selective antagonist) was administered at a dose of 10 mg/kg i.p., 15 minutes before administration of B-TMCA, and the formalin test. Caffeine was able to reverse the antinociceptive effect of B-TMCA, indicating a possible involvement in the modulation of nociceptive transmission through the adenosinergic system. The glutamatergic system was also studied through the administration of MK-801 (0.15 mg/kg i.p.), a non-competitive antagonist of NMDA receptors, following the protocol of the glutamate test, in which after the administration of 20 μL of a solution of glutamate (30 μmol/paw) via intraplantar time was counted for 15 minutes. B-TMCA was able to reduce paw licking time as well as MK-801, thus suggesting a possible interaction with the glutamatergic system in reducing nociception.