Neuromuscular and phospholipase activities of venoms from three subspecies of Bothrops neuwiedi (B. n. goyazensis, B. n. paranaensis and B. n. diporus)

Biochemical and pharmacological characterization of PhTX-I a new myotoxic phospholipase A2 isolated from Porthidium hyoprora snake venom

This paper reports the biochemical and pharmacological characterization of a new myotoxic PLA(2) (EC 3.1.1.4) called PhTX-I, purified from Porthidium hyoprora venom by one step analytical chromatography reverse phase HPLC. The homogeneity of the PhTX-I fraction and its molecular mass were initially evaluated by SDS-PAGE and confirmed by MALDI-TOF spectrometry, indicating a molecular mass of 14.249Da and constituted of a single polipeptidic chain. Amino acid sequence was determined by "de novo sequencing," in tandem mass spectrometry, belonging to D49-PLA(2) enzyme class and exhibiting high identity (44-90%) with other myotoxics PLA(2) from snake venoms. The enzymatic investigation showed maximal activity at pH 8 and 35-45°C. This activity was dependent on Ca(2+), other cations (Mg(2+), Mn(2+), Cd(2+) and Zn(2+)) reduced notably the enzymatic activity, suggesting that the arrangement of the catalytic site presents an exclusive structure for Ca(2+). Ex vivo, whole venom and PhTX-I PLA(2) caused blockade of the neuromuscular transmission in young chick biventer cervicis preparations similar to other isolated snake venom toxins from the Bothrops genus. In vivo, both induced local myotoxicity and systemic interleukin-6 response upon intramuscular injection, additionally, induced moderate footpad edema. In vitro, both induced low cytotoxicity in skeletal muscle myoblasts, however PhTX-I PLA(2) was able to lyse myotubes.

Neuromuscular activity of BaTX, a presynaptic basic PLA2 isolated from Bothrops alternatus snake venom

We have previously isolated a Lys49 phospholipase A(2) homolog (BaTX) from Bothrops alternatus snake venom using a combination of molecular exclusion chromatography and reverse phase HPLC and shown its ability to cause neuromuscular blockade. In this work, we describe a one-step procedure for the purification of this toxin and provide further details of its neuromuscular activity. The toxin was purified by reverse phase HPLC and its purity and molecular mass were confirmed by SDS-PAGE, MALDI-TOF mass spectrometry, amino acid analysis and N-terminal sequencing. BaTX (0.007-1.4 microM) produced time-dependent, irreversible neuromuscular blockade in isolated mouse phrenic nerve-diaphragm and chick biventer cervicis preparations (time to 50% blockade with 0.35 microM toxin: 58+/-4 and 24+/-1 min, respectively; n=3-8; mean+/-S.E.) without significantly affecting the response to direct muscle stimulation. In chick preparations, contractures to exogenous acetylcholine (55 and 110 microM) or KCl (13.4 mM) were unaltered after complete blockade by all toxin concentrations. These results, which strongly suggested a presynaptic mechanism of action for this toxin, were reinforced by (1) the inability of BaTX to interfere with the carbachol-induced depolarization of the resting membrane, (2) a significant decrease in the frequency and amplitude of miniature end-plate potentials, and (3) a significant reduction (59+/-4%, n=12) in the quantal content of the end-plate potentials after a 60 min incubation with the toxin (1.4 microM). In addition, a decrease in the organ bath temperature from 37 degrees C to 24 degrees C and/or the replacement of calcium with strontium prevented the neuromuscular blockade, indicating a temperature-dependent effect possibly mediated by enzymatic activity.

Neuromuscular action of venom from the South American colubrid snake Philodryas patagoniensis

Snakes of the opisthoglyphous genus Philodryas are widespread in South America and cause most bites by colubrids in this region. In this study, we examined the neurotoxic and myotoxic effects of venom from Philodryas patagoniensis in biventer cervicis and phrenic nerve-diaphragm preparations and we compared the biochemical activities of venoms from P. patagoniensis and Philodryas olfersii. Philodryas patagoniensis venom (40 microg/mL) had no effect on mouse phrenic nerve-diaphragm preparations but caused time-dependent neuromuscular blockade of chick biventer cervicis preparations. This blockade was not reversed by washing. The highest concentration of venom tested (40 microg/mL) significantly reduced (p<0.05) the contractures to exogenous acetylcholine (55 microM and 110 microM) and K(+) (13.4 mM) after 120 min; lower concentrations of venom had no consistent or significant effect on these responses. Venom caused a concentration- and time-dependent release of creatine kinase (CK) from biventer cervicis preparations. Histological analysis showed contracted muscle fibers at low venom concentrations and myonecrosis at high concentrations. Philodryas venoms had low esterase and phospholipase A(2) but high proteolytic activities compared to the pitviper Bothrops jararaca. SDS-PAGE showed that the Philodryas venoms had similar electrophoretic profiles, with most proteins having a molecular mass of 25-80 kDa. Both of the Philodryas venoms cross-reacted with bothropic antivenom in ELISA, indicating the presence of proteins immunologically related to Bothrops venoms. RP-HPLC of P. patagoniensis venom yielded four major peaks, each of which contained several proteins, as shown by SDS-PAGE. These results indicate that P. patagoniensis venom has neurotoxic and myotoxic components that may contribute to the effects of envenoming by this species.