Atividade analgesica das interleucinas 4, 10 e 13 (IL-4, IL-10 e il-13) na dor inflamatoria experimental : papel de celulas residentes e citocinas

Abstract

The release of cyclo-oxigenase products and sympathomimetics amines, the final mediators of inflammatory pain, is preceded by the generation of cytokines by resident cells. In recent years a number of cytokines such as IL-4, IL-10, IL-13, IL-6, TGF-β e IFN-α have been described to inhibit the production of TNF-α, IL-1β, IL-6 and IL-8 (cytokines regarded as pró-inflammatory) and possibly to exert their modulatory effect on macrophages and mast cells. Since it is known the capacity of those cytokines to inhibit the production of pro-inflammatory cytokines and the pivotal role of resident cells in the development of inflammatory pain we have decided to test the possibility of IL-4, IL-13 and IL-10 to modulate inflammatory pain. In short, IL-4 (1 – 5ng/animal), IL-13 (0.4 - 2.5ng/animal) or IL-10 (0.4 - 10ng/animal) was given 30 min before acetic acid (AAc) or zymosan (Zym) administration in the writhing model. IL-4 (2.5 e 5 ng/animal), IL-13 (1 e 2.5 ng/animal) or IL-10 (2 e 10 ng/animal) were injected, ip, 30 min before Zym (1 mg/animal; intra-articular) in the rat knee joint incapacitation test up to the 4th hour (the number of leukocytes was determined in the articular exsudate 6 hours later). Doses of those cytokines that exerted maximum effect in the writhing test were also injected 30 min before the hot plate test. These same doses were injected ip before naloxone administration in the AAc-induced writhing model in mice. TNF-α and IL-1β were determined in the supernatant of a macrophage culture which were collected from peritoneal fluid of mice treated with Zym and pre-treated with the cytokines under test. Our results show that interleukins 4, 13 and 10 inhibit writhing response in mice induced by AAc or Zym up to 58.7, 89.2 and 52%, and up to 62.6, 61.7 and 74.4%, respectively (p<0.05). Similar results were observed in the rat knee joint incapacitation test induced by Zym: 49.2, 56.6, 69,9% of inhibition (p<0.05). The same interleukins were able to inhibit Zym-induced leukocyte influx into articular cavity (53.8, 92.1 e 62% of inhibition, respectively - p<0,05). The analgesic activity of IL-4, IL-13 and IL-10 seems to be peripheral, since these cytokines presented no effect in the reaction time of the animals on hot plate test. This antinociceptive effect seems to have no relation with endogen opioid release since naloxone (opioid receptor antagonist) had no effect in reverting the antinociceptive effect of cytokines in the AAc-induced writhing in mice. However, IL-4 and IL-10 inhibit the release of TNF-α (42 e 41.2%, respectively - p<0.05) and of IL-1β (61.9 e 80.9%, respectively - p<0,05) by macrophages stimulated in vivo by Zym, indicating that their antinociceptive activities may be due to the inhibition of those cytokines release by resident cells.