Neurotoxicity of Micrurus lemniscatus lemniscatus (South American coralsnake) venom in vertebrate neuromuscular preparations in vitro and neutralization by antivenom

Abstract

We investigated the effect of South American coral snake (Micrurus lemniscatus lemniscatus) venom on neurotransmission in vertebrate nerve-muscle preparations in vitro. The venom showed calcium-dependent PLA2 activity and caused irreversible neuromuscular blockade (0.1-30 µg/ml) in chick biventer cervicis (BC) and mouse phrenic nerve-diaphragm (PND) preparations. In BC preparations, contractures to exogenous acetylcholine and carbachol (CCh), but not KCl, were abolished by venom concentrations ≥0.3 µg/ml; in PND preparations, the amplitude of the tetanic response was progressively attenuated, but with little tetanic fade. In low Ca 2+ physiological solution, venom (10 µg/ml) caused neuromuscular blockade in PND preparations within ~10 min that was reversible by washing; the addition of Ca 2+ immediately after the blockade temporarily restored the twitch responses, but did not prevent the progression to irreversible blockade. Venom (10 µg/ml) did not depolarize diaphragm muscle, prevent depolarization by CCh, or cause muscle contracture or histological damage. Venom (3 µg/ml) had a biphasic effect on the frequency of miniature end-plate potentials, but did not affect their amplitude; there was a progressive decrease in the amplitude of evoked end-plate potentials. The amplitude of compound action potentials in mouse sciatic nerve was unaffected by venom (10 µg/ml). Pre-incubation of venom with coral snake antivenom (Instituto Butantan) at the recommended antivenom:venom ratio did not neutralize the neuromuscular blockade in PND preparations, but total neutralization was achieved with a 10-fold greater volume of antivenom. The addition of antivenom after 50% and 80% blockade restored the twitch responses. These results show that M. l. lemniscatus venom causes potent, irreversible neuromuscular blockade, without myonecrosis. This blockade is apparently mediated by pre-and postsynaptic neurotoxins and can be reversed by coralsnake antivenom.

Forty Years of the Description of Brown Spider Venom Phospholipases-D

“…However, the treatment of loxoscelism based on serum therapy is still controversial, since its efficacy varies according to the different types of accidents, the species involved and mainly the delay in the beginning of the treatment after the bite [2,3,5,85,87]. This variation in the efficacy of antivenoms also happens with some snake antivenoms, mainly regarding neutralization of venom activities from different species of the same genus, and authors suggest the use of a greater antivenom:venom ratio to circumvent this problem [88]. However, the lack of effectiveness of these anti-loxoscelic sera could be related to their low titers of anti-PLD antibodies, and thus fail to neutralize these toxins after envenoming.…”

Effects of Mlx-8, a phospholipase A2 from Brazilian coralsnake Micrurus lemniscatus venom, on muscarinic acetylcholine receptors in rat hippocampus

“…Currently, Micrurus lemniscatus is a species composed of three subspecies (M. l. carvalhoi, M. l. helleri and M. l. lemniscatus). Particularly, M. l. carvalhoi is distributed along the Brazilian east coast from the northeast to southeast of the country and in parts of central, central-western, southeastern and southern Brazil, as well as eastern Paraguay and northeastern Argentina [7,8]. Moreover, the venom of this animal is composed of approximately 70% three-finger toxins (3FTxs) and 10% phospholipase A 2 (PLA 2 ) toxins [9].…”

Cardiovascular activity of Micrurus lemniscatus lemniscatus (South American coralsnake) venom

“…are represented by more than 80 species widely distributed throughout the Americas (Campbell and Lamar, 2004;Roze, 1996;Silva Jr. et al, 2016) Several biological activities have been described for Micrurus venoms, such as intense pain (Nishioka et al, 1993;Vital Brazil et al, 1976/1977Vital Brazil and Vieira, 1996), edema (Cecchini et al, 2005;Gutiérrez et al, 1980;Moraes et al, 2003;Urdaneta et al, 2005), myonecrosis (Arroyo et al, 1987;Barros et al, 1994;Gutiérrez et al, 1992;Gutiérrez et al, 1986;Moraes et al, 2003), haemorrhage (Barros et al, 1994;Ramsey et al, 1972), nephrotoxicity (Braga et al, 2020;De Roodt et al, 2012) and interference with the complement system (Tanaka et al, 2012). However, the peripheral neurotoxicity is the most relevant clinical manifestation of envenomation by coralsnakes and it represents the principal cause of death due to rapid neuromuscular blockade (Bucaretchi et al, 2016a,b;Floriano et al, 2019;Risk et al, 2016;Warrell, 2004). The neurotoxicity of Micrurus venoms is mediated by two major groups of toxins: three-finger toxins (3FTx), classic -neurotoxins that block post-synaptic nicotinic (cholinergic) receptors, and a variety of phospholipase A2 (PLA2), some of which act as -neurotoxins causing potent presynaptic blockade of neurotransmitter release (Aird et al, 2017 In comparison to the well-studied neurotoxic effects of Micrurus venoms, the cardiotoxic and vascular effects of these venoms have been poorly investigated with only a relatively small number of studies describing the hypotensive effects of coralsnakes venoms in the 1970s (Ramsey et al, 1971;Ramsey et al, 1972;Vital Brazil et al, 1976/1977Weiss and McIsaac, 1971).…”