MASTOPARAN FROM Polybia paulista WASP VENOM IN SKELETAL MUSCLE APOPTOSIS

ROCHA T. (1), BARROS L.L.S. (1), 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.

Our previous studies with light and transmission electron microscopy (TEM) showed that the mastoparan (I-N-W-L-K-L-G-K-M-V-I-D-A-L-NH2) from P. paulista wasp venom causes marked mitochondria changes together with myonecrosis in the tibial anterior (TA) muscle of Balb/c mice. However, although the pathologic states of the necrotic process of the fibers caused by mastoparan closely resemble those by snake venoms, apoptotic-looking fibers were seen after i.m. injection of the P. paulista wasp whole venom. In this study, we investigate possible apoptotic events in different time intervals (from 3 h to 21 d) after TA i.m. injection of 2.5  ug/uL mastoparan by examining the expression of caspases 9 and 3 seen by Western Blotting (WB) and Immunohistochemistry (IH). Saline solution-injected muscles were used as control. Controls were negative for caspase 9 and 3 in all periods. Myonecrotic fibers of mastoparan injected TA was strongly positive for caspase 9 and 3 which appeared expressed in the empty-looking sarcoplasmic areas at 3 and 24 h, but was negative at 3, 7 and 21 days. WB of the proteins confirmed the IH results, since a significant reduction of the bands were seen 3, 7 and 21 d in relation to that of 3 and 24 h. We concluded that mastoparan can mediate cell death by apoptosis involving a caspase 9 and 3 activating mechanism at early (3 h) and intermediate (24 h) phases, probably explaining the mitochondrial alterations seen by TEM. Mastoparan has been reported to facilitate the opening of the mitochondrial permeability transition pore through an apparent bimodal mechanism of action. The decrease of caspase 9 expression, seen on late (3 d) and final phases (7 and 21 d) probably reduced the caspase 3 activation mechanisms and consequently in the death by apoptosis. These phases correspond to regenerative periods of muscle fibers after toxin effect.

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

SUPPORT: CNPq, FAPESP, CAPES, Instituto do Milênio

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