Articular inflammation induced by an enzymatically-inactive Lys49 phospholipase A2: activation of endogenous phospholipases contributes to the pronociceptive effect.
BACKGROUND
Arthritis is a set of inflammatory conditions that induce aching, stiffness, swelling, pain and may cause functional disability with severe consequences to the patient's lives. These are multi-mediated pathologies that cannot be effectively protected and/or treated. Therefore, the aim of this study was to establish a new model of acute arthritis, using a Lys49-PLA2(Bothrops aspermyotoxin II; MT-II) to induce articular inflammation.


METHODS
The articular inflammation was induced by MT-II (10 μg/joint) injection into the left tibio-tarsal or femoral-tibial-patellar joints. Cellular influx was evaluated counting total and differential cells that migrated to the joint. The plasma extravasation was determined using Evans blue dye. The edematogenic response was evaluated measuring the joint thickness using a caliper. The articular hypernociception was determined by a dorsal flexion of the tibio-tarsal joint using an electronic pressure-meter test. The mediators involved in the articular hypernociception were evaluated using receptor antagonists and enzymatic inhibitors.


RESULTS
Plasma extravasation in the knee joints was observed 5 and 15 min after MT-II (10 μg/joint) injection. MT-II also induced a polymorphonuclear cell influx into the femoral-tibial-patellar joints observed 8 h after its injection, a period that coincided with the peak of the hyperalgesic effect. Hyperalgesia was inhibited by the pretreatment of the animals with cyclooxygenase inhibitor indomethacin, with type-2 cyclooxygenase inhibitor celecoxib, with AACOCF3and PACOCF3,inhibitors of cytosolic and Ca2+-independent PLA2s, respectively, with bradykinin B2receptor antagonist HOE 140, with antibodies against TNFα, IL-1β, IL-6 and CINC-1 and with selective ET-A (BQ-123) and ET-B (BQ-788) endothelin receptors antagonists. The MT-II-induced hyperalgesia was not altered by the lipoxygenase inhibitor zileuton, by the bradykinin B1receptor antagonist Lys-(Des-Arg9,Leu8)-bradykinin, by the histamine and serotonin antagonists promethazine and methysergide, respectively, by the nitric oxide inhibitor LNMMA and by the inhibitor of matrix 1-, 2-, 3-, 8- and 9- metalloproteinases GM6001 (Ilomastat).


CONCLUSIONS
These results demonstrated the multi-mediated characteristic of the articular inflammation induced by MT-II, which demonstrates its relevance as a model for arthritis mechanisms and treatment evaluation.
Special Laboratory of Pain and Signaling, Butantan Institute, Av. Vital Brazil, 1500, São Paulo, SP CEP 05503-900 Brazil.|Healthy Sciences Institute, Paulista University (UNIP), São Paulo, SP Brazil.
Renata Gonçalves
RG
Dias
Laboratory of Pathophysiology, Butantan Institute, São Paulo, SP Brazil.|Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP Brazil.
Sandra Coccuzzo
SC
Sampaio
Special Laboratory of Pain and Signaling, Butantan Institute, Av. Vital Brazil, 1500, São Paulo, SP CEP 05503-900 Brazil.
Morena Brazil
MB
Sant'Anna
Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil.
Fernando Queiroz
FQ
Cunha
Clodomiro Picado Institute, Faculty of Microbiology, University of Costa Rica, San José, Costa Rica.
José María
JM
Gutiérrez
Clodomiro Picado Institute, Faculty of Microbiology, University of Costa Rica, San José, Costa Rica.
Bruno
B
Lomonte
Special Laboratory of Pain and Signaling, Butantan Institute, Av. Vital Brazil, 1500, São Paulo, SP CEP 05503-900 Brazil.
Yara
Y
Cury
Special Laboratory of Pain and Signaling, Butantan Institute, Av. Vital Brazil, 1500, São Paulo, SP CEP 05503-900 Brazil.
Gisele
0000-0001-6784-8266
G
Picolo
Arthritis; Bothrops asper; Lys49-PLA2; Myotoxin II; Phospholipase