PHOSPHOLIPASE A2 AND MASTOPARAN FROM Polybia paulista WASP VENOM ON MICE SKELETAL MUSCLE

ROCHA T. (1), BARROS L.L.S. (1), SANTOS L.D. (2), DE SOUZA, B.M. (2), PALMA M.S. (2), CRUZ-HÖFLING M.A. (1)

(1) Dept. Histology & Embryology, Inst. Biology, UNICAMP, Campinas, SP, Brazil, (2)Center of Studies of Social Insects, Inst. Biosciences, UNESP, Rio Claro, SP, Brazil.

Allergic reactions caused by wasp bites in humans is well-known. However, the action of the venom on the muscle fibers still remains unclear. Here we compared the myotoxic potency of mastoparan and phospholipase A2 (PLA2) (2.5 ug/uL) from P. paulista venom injected (i.m.) in the tibial anterior (TA) muscle of Balb/c mice. Time course of the changes were followed at degenerative (3 and 24 h) and regenerative (3 and 7 d) periods (n=6). Saline-injected groups were used as controls. The muscles were fixed in 4% paraformaldehyde and processed for embedding in paraffin. Histological sections (5 um) were stained with Hematoxylin-Eosin and the percentage of the damaged fibers was calculated and statistically analysed (p<0.05). A median of 900 fibers were counted. The controls showed normal morphology. At 3 h, 1.6% of the muscle fibers injected with PLA2 presented densely-clumped myofibrils intermingled with empty-looking sarcoplasmic areas. Inflammatory infiltrate foci were widespread and strong mainly during the intermediate phase (24 h), when just 1.1% of the muscle fibers were affected. In contrast, 27.3% (3 h) and 17.7% (24 h) of the muscles fibers were affected by mastoparan. In the late phase (3 d), whereas the muscles treated with PLA2 do not present small regenerating cells, but 1% of affected muscles fibers, the muscles treated with mastoparan presented 43.4% of regenerating cells against 6.7% of damaged cells. In the final phase (7 d), whilst regenerating area corresponded to 5.4% for PLA2, it represented 66.5% for mastoparan. The inflammatory infiltrate in the muscles treated with PLA2 still persisted. We conclude that despite PLA2 is poorly myotoxic, its inflammatory effect predominates over mastoparan. Interestingly, the regenerating process is faster in the mastoparan, than in PLA2’s.

KEY WORDS: caspases, mitochondrial damage, immunohistochemistry, western blotting

SUPPORT: CNPq, FAPESP, CAPES, Instituto Milênio

CORRESPONDENCE: THALITA ROCHA, DHE, IB, UNICAMP, CP 6109, 13083-863 Campinas, SP, Brazil, 55 19 35216250, tharocha@yahoo.com