Ultrastructural aspects of mouse nerve-muscle preparation exposed toBothrops jararacussuandBothrops bilineatusvenoms and their toxins BthTX-I and Bbil-TX: Unknown myotoxic effects

Abstract

Bites by Bothrops snakes normally induce local pain, haemorrhage, oedema and myonecrosis. Mammalian isolated nerve-muscle preparations exposed to Bothrops venoms and their phospholipase A toxins (PLA ) can exhibit a neurotoxic pattern as increase in frequency of miniature end-plate potentials (MEPPs) as well as in amplitude of end-plate potentials (EPPs); neuromuscular facilitation followed by complete and irreversible blockade without morphological evidence for muscle damage. In this work, we analysed the ultrastructural damage induced by Bothrops jararacussu and Bothrops bilineatus venoms and their PLA toxins (BthTX-I and Bbil-TX) in mouse isolated nerve-phrenic diaphragm preparations (PND). Under transmission electron microscopy (TEM), PND preparations previously exposed to B. jararacussu and B. bilineatus venoms and BthTX-I and Bbil-TX toxins showed hypercontracted and loosed myofilaments; unorganized sarcomeres; clusters of edematous sarcoplasmic reticulum and mitochondria; abnormal chromatin distribution or apoptotic-like nuclei. The principal affected organelles, mitochondria and sarcoplasmic reticulum, were those related to calcium buffering and, resulting in sarcomeres and myofilaments hypercontraction. Schwann cells were also damaged showing edematous axons and mitochondria as well as myelin sheath alteration. These ultrastructural changes caused by both of Bothrops venoms and toxins indicate that the neuromuscular blockade induced by them in vitro can also be associated with nerve and muscle degeneration.

Structural determinants of the hyperalgesic activity of myotoxic Lys49-phospholipase A2

“…Here we have shown that the recombinant BthTx-I displays hyperalgesic and edematogenic responses with similar onset, intensity and time course to those observed for the native BthTx-I. The edematogenic activity of the native BthTx-1 has been previously demonstrated [ 27 , 28 ]. However, to the best of our knowledge, this is the first report showing that BthTx-I induces hyperalgesia in an experimental model of pain evaluation.…”

Bothrops lanceolatus snake venom impairs mitochondrial respiration and induces DNA release in human heart preparation

“…Firstly, we found that venom of Bothrops lanceolatus caused reduction of respiratory control ratio in human heart preparation, suggesting that efficiency of mitochondrial oxidative phosphorylation was impaired. Previous studies in human cell lines have shown that toxins isolated from Bothrops snake venom can promote mitochondrial dysfunction [17][18][19]. Changes of mitochondrial respiration induced by snake venoms in human tissue have not been previously reported.…”

Bothrops bilineatus: An Arboreal Pitviper in the Amazon and Atlantic Forest

“…A series of studies have been performed since then in order to understand the action of both crude B. bilineatus venom and isolated Bbil-TX on myotoxicity and neuromuscular impairment. From a damage perspective, both venom and toxin were capable of inducing ultrastructural muscular alterations in mouse isolated nerve-phrenic diaphragm preparations in vitro , such as hypercontraction of myofilaments, disorganization of sarcomeres, and sarcoplasmic reticulum and mitochondrial damage ( 113 , 114 ). There are no reports on in vivo myotoxicity using crude B. bilineatus venom; however, Bbil-TX has induced local myotoxicity in mice after IM administration (represented by increased levels of serum CK peaking at 2 h) with neglected systemic myotoxicity when administrated IV ( 112 ).…”

“…Moreover, they did not alter the muscle membrane resting potential or the response of endogenous and exogenous agonists, thus suggesting a presynaptic action and not muscle contraction impairment ( 113 , 115 , 116 ). Moreover, the presynaptic action of Bbil-TX involves modulation of potassium channel activity and presynaptic protein expression, as well as ultrastructural nerve alterations characterized by detachment of the axon from the myelin sheath and formation of periaxonal vacuoles ( 114 , 116 ).…”

“…inducing ultrastructural muscular alterations in mouse isolated nerve-phrenic diaphragm preparations in vitro, such as hypercontraction of myofilaments, disorganization of sarcomeres, and sarcoplasmic reticulum and mitochondrial damage (113,114). There are no reports on in vivo myotoxicity using crude B. bilineatus venom; however, Bbil-TX has induced local myotoxicity in mice after IM administration (represented by increased levels of serum CK peaking at 2 h) with neglected systemic myotoxicity when administrated IV (112).…”