Neurotoxic, myotoxic and cytolytic activities of the new basic PLA ₂ isoforms BmjeTX-I and BmjeTX-II isolated from the Bothrops marajoensis (marajó lancehead) snake venom

The BmjeTX-I and BmjeTX-II isoforms of PLA₂ were purified from Bothrops marajoensis venom by ion-exchange chromatography and reverse phase HPLC. Both isoforms showed a molecular mass of 13808.89 Da (BmjeTX-I) and 13863.97 Da (BmjeTX-II) determined by based on the determined primary structures and SDS-PAGE and confirmed experimentally by MALDI-TOF mass spectrometry. Multiple alignment of BmjeTX-I and BmjeTX-II isoforms of PLA2 show high degree of homology with basic PLA₂ myotoxins from other Bothrops venoms. Ex vivo, both isoforms caused a blockade of the neuromuscular transmission in young chick biventer cer-vicis preparations in a similar way to other Bothrops species. In chick preparations, contractures to exogenous acetylcholine (55 and 110 μM) or KCl (13.4 mM) were unaltered after complete blockade for the both isoforms BmjeTX-I and BmjeTX-II of PLA₂. These results, which strongly suggested a presynaptic mechanism of action for these toxins. In mice, both isoforms induced myonecrosis and a systemic interleukin-6 response upon intramuscular injection. Both isoforms BmjeTX-I and BmjeTX-II of PLA₂ also induced moderate marked paw edema, evidencing the local increase in vascular permeability. Since both isoforms of PLA₂ exert a strong proinflammatory effect, the enzymatic hydrolysis of phospholipids might be relevant for this phenomenon and produced cytotoxicity in murine skeletal muscle C2C12 myoblasts and myotubes.