Venom of the giant ant Dinoponera quadriceps attenuates inflammatory pain in mouse cutaneous wound healing model

Arthropod venoms are potential sources of bioactive substances, providing tools for the validation of popular use and new drugs design. Ants belonging to the genus Dinoponera are used in the folk medicine to treat inflammatory conditions. It was previously demonstrated that the venom of the giant ant Dinoponera quadriceps (DqV), containing a mixture of polypeptides, elicit antinociceptive effect in mice models of chemical, mechanical and thermal nociception. The aim of this study was to evaluate DqV antiinflammatory and antihypernociceptive effects in a mice model of traumatic cutaneous wound. Colonies of D. quadriceps were collected in the ‘‘Serra de Maranguape’’ (State of Ceará, northeastern Brazil), a small mountain range located on the coastal zone, and the venom secreted by the ant glands was extracted with capillary tubes, further lyophilized and maintained at -20 ± 1ºC until use. Wounds were performed in the dorsum of Swiss mice. Animals received intravenous (i.v.) injection of DqV (50 µg -1kg day-1) during 3 days for evaluation of inflammatory parameters present in the wounds: hypernociception, leukocyte infiltrate, myeloperoxidase activity, nitrite nitrate-1 content. Data was tested by two-way ANOVA and Bonferroni’s post-hoc test. DqV reduced (2.7 folds) hypernociception at 48 hours, leukocyte infiltration by 65% at 6 hours and myeloperoxidase activity by 60% at 0.5 hour after wound induction. In conclusion, the venom extracted from D. quadriceps glands attenuates inflammation and hypernociception in mice cutaneous wounds.

Participation of the NO/cGMP/K+ATP pathway in the antinociception induced by Walker tumor bearing in rats

Implantation of Walker 256 tumor decreases acute systemic inflammation in rats. Inflammatory hyperalgesia is one of the most important events of acute inflammation. The L-arginine/NO/cGMP/K+ATP pathway has been proposed as the mechanism of peripheral antinociception mediated by several drugs and physical exercise. The objective of this study was to investigate a possible involvement of the NO/cGMP/K+ATP pathway in antinociception induced in Walker 256 tumor-bearing male Wistar rats (180-220 g). The groups consisted of 5-6 animals. Mechanical inflammatory hypernociception was evaluated using an electronic version of the von Frey test. Walker tumor (4th and 7th day post-implantation) reduced prostaglandin E2- (PGE2, 400 ng/paw; 50 µL; intraplantar injection) and carrageenan-induced hypernociception (500 µg/paw; 100 µL; intraplantar injection). Walker tumor-induced analgesia was reversed (99.3% for carrageenan and 77.2% for PGE2) by a selective inhibitor of nitric oxide synthase (L-NAME; 90 mg/kg, ip) and L-arginine (200 mg/kg, ip), which prevented (80% for carrageenan and 65% for PGE2) the effect of L-NAME. Treatment with the soluble guanylyl cyclase inhibitor ODQ (100% for carrageenan and 95% for PGE2; 8 µg/paw) and the ATP-sensitive K+ channel (KATP) blocker glibenclamide (87.5% for carrageenan and 100% for PGE2; 160 µg/paw) reversed the antinociceptive effect of tumor bearing in a statistically significant manner (P < 0.05). The present study confirmed an intrinsic peripheral antinociceptive effect of Walker tumor bearing in rats. This antinociceptive effect seemed to be mediated by activation of the NO/cGMP pathway followed by the opening of KATP channels.

Mechanical hypernociception in experimental autoimmune encephalomyelitis / Hipernocicepção mecânica em encefalomielite autoimune experimental

BACKGROUND: Pain is an important clinical manifestation in multiple sclerosis (MS) patients, though it has been neglected in clinical and experimental researches. OBJECTIVE: To investigate the nociceptive response in MOG35-55 experimental autoimmune encephalomyelitis (EAE)-induced mice. METHOD: EAE was induced in 8 to 10 week old C57BL/6 female mice with an emulsion of MOG35-55, Complete Freund Adjuvant, Mycobacterium tuberculosis H37 RA and pertussis toxin. Nociception was evaluated by the von Frey filaments method. A clinical scale ranging from 0 to 15 was used to assess motor impairment. RESULTS: Clinical evidence of disease started at day 10 and peaked at day 14 after immunization. Thereafter, there was no worsening of symptoms until day 26. The EAE-induced mice presented reduced pressure threshold at days 7th and 10th after immunization and before the onset of clinical motor signs. CONCLUSION : The hypernociception found validates MOG35-55 EAE as a model for the study of pain in multiple sclerosis.

INTRODUÇÃO: Dor é uma manifestação importante em pacientes com esclerose múltipla (EM), mas que tem sido negligenciada na pesquisas clínica e experimental. OBJETIVO: Investigar a resposta nociceptiva de camundongos com encefalomielite autoimune experimental (EAE) induzida por MOG35-55. MÉTODO: A EAE foi induzida em camundongos C57BL/6 fêmeas de 8-10 semanas com emulsão contendo MOG35-55, Adjuvante Completo de Freund, Mycobacterium tuberculosis cepa H37 RA e toxina pertussis. A nocicepção foi medida pelo método de filamentos de von Frey. Uma escala clínica variando de 0 a 15 foi utilizada para avaliar a debilidade motora dos animais. RESULTADOS: Os sinais clínicos da doença iniciaram-se no dia 10 e a gravidade máxima foi alcançada no dia 14 após a imunização. Não houve piora dos sintomas até o dia 26. Os camundongos induzidos com EAE apresentaram diminuição do limiar de pressão nos dias 7 e 10 após a imunização e antes do início dos sinais motores. CONCLUSÃO: A hipernocicepção verificada valida a EAE induzida por MOG35-55 como um modelo para estudos de dor em esclerose múltipla.

Antinociception synergy between the peripheral and spinal sites of the heme oxygenase-carbon monoxide pathway

We have shown that the peripheral and spinal cord heme oxygenase (HO)-carbon monoxide (CO)-soluble guanylate cyclase-cGMP pathways play an important role in antinociception in the rat experimental formalin model. Our objective was to determine if there is synergism between peripheral (paw) and spinal HO-CO pathways in nociception. Rats were handled and adapted to the experimental environment for a few days before the formalin test, in which 50 µL of a 1 percent formalin was injected subcutaneously into the dorsal surface of the right hind paw. The animals were then observed for 1 h and the frequency of flinching behavior was taken to represent the nociceptive response. Thirty minutes before the test, rats were pretreated with intrathecal injections of the HO inhibitor, zinc deuteroporphyrin 2,4-bis glycol (ZnDPBG) or heme-lysinate, which is a substrate of the HO pathway. The paw treatments took place 20 min before the test. Low doses of ZnDPBG did not increase nociception, while a low heme-lysinate dose did not change flinching behavior after paw or spinal injections. Combined subactive spinal (50 nmol) and peripheral (40 nmol) low doses of ZnDPBG induced hypernociception (increase of 80 percent in the first and 25 percent in the second phase flinching), whereas combined spinal-peripheral heme-lysinate (50 and 30 nmol) led to second phase antinociception (40 percent reduction in flinching). These findings suggest a synergy between the peripheral and spinal HO-CO pathways. Local activation of the HO system probably regulates the nociception initiation in peripheral tissue and participates in buffering the emerging nociceptive signals at the peripheral and spinal sites of action. In short, an antinociceptive synergy exists between peripheral and spinal HO pathways, which may reduce the doses required and side effects.