Poster 35 - Hypernociception induced by Lys49-phospholipase A2 (PLA2) involves the same sites

Poster 35. Congresso da Sociedade Brasileira de Toxinologia, 8., Symposium of the Pan American Section of the International Society on Toxinology, 8., 2004, Angra dos Reis, Brasil. Abstracts... J. Venom. Anim. Toxins incl.Trop. Dis., 2004, 10, 3, p.394.

Hypernociception induced by Lys49-phospholipase A₂ (PLA₂) involves the same sites in the C-terminal region responsible for myotoxic and membrane-damaging effects.

1 Laboratório de Fisiopatologia, Instituto Butantan, SP, Brasil, 2 Departamento de Bioquímica e Imunologia, FMRP-USP, Brasil, 3 Departamento de Química, FFCLRP-USP, Brasil.

The Lys49-PLAs2, devoid of catalytic activity, induces myotoxicity, inflammation and pain (CHACUR et al., Toxicon, 41: 667, 2003; VALENTIN & LAMBEAU, Biochim Biophys Acta, 1488: 59, 2000). Data have shown that residues in the C-terminal region of these PLA2 are important to the genesis of these phenomena (CHACUR et al., Toxicon, 41: 667, 2003; CALDERON & LOMONTE, Arch Biochem Biophys, 358: 343, 1998). This study aims to determine the residues of amino acids present in Lys49-PLA2 responsible for triggering hyperalgesia and edema. Site-directed mutagenesis was performed in recombinant BthTx-I, a Lys49-PLA2 isolated from B. jararacussu snake venom (CHIOATO et al., Biochem J, 366, 971, 2002). The R118A mutant was used since this substitution decreases PLA2 myotoxicity. In addition, K115A and K116A mutants, which contribute to the decrease of cytotoxicity and K122A mutation which decreases both activities were also used. Rats were injected by intraplantar route with mutant PLAs2 (10µg) and hyperalgesia and edema evaluated by the paw pressure test (RANDALL & SELITTO, Arch Intern Pharmacodyn, 111: 209, 1957) and by plethysmography, respectively. Native and recombinant BthTx-I were used as controls. Both toxins induced hyperalgesia and edema, which peaked at 2h (43 and 46%, 42 and 44%, respectively). The R118A mutant did not induce nociception and presented decreased edema (22%). The mutations K115A and K116A abolished hyperalgesia without interfering with the edematogenic response (37%). In addiction, the K122A mutant did not induce hyperalgesia and presented decreased inflammatory response (21%). These data indicate that the same residue present in the Lys49-PLA2 C-terminal region, responsible for myotoxicity, is also involved in the genesis of the nociceptive and inflammatory effects. Residues responsible for cytolytic activity seem to be involved only in hypernociception.