Pharmacological characterization of crotamine effects on mice hind limb paralysis employing both ex vivo and in vivo assays: Insights into the involvement of voltage-gated ion channels in the crotamine action on skeletal muscles

PLoS Negl Trop Dis. 2018 Aug 6;12(8):e0006700. doi: 10.1371/journal.pntd.0006700. eCollection 2018 Aug.

Abstract

The high medical importance of Crotalus snakes is unquestionable, as this genus is the second in frequency of ophidian accidents in many countries, including Brazil. With a relative less complex composition compared to other genera venoms, as those from the Bothrops genus, the Crotalus genus venom from South America is composed basically by the neurotoxin crotoxin (a phospholipase A2), the thrombin-like gyroxin (a serinoprotease), a very potent aggregating protein convulxin, and a myotoxic polypeptide named crotamine. Interestingly not all Crotalus snakes express crotamine, which was first described in early 50s due to its ability to immobilize animal hind limbs, contributing therefore to the physical immobilization of preys and representing an important advantage for the envenoming efficacy, and consequently, for the feeding and survival of these snakes in nature. Representing about 10-25% of the dry weight of the crude venom of crotamine-positive rattlesnakes, the polypeptide crotamine is also suggested to be of importance for antivenom therapy, although the contribution of this toxin to the main symptoms of envenoming process remains far unknown until now. Herein, we concomitantly performed in vitro and in vivo assays to show for the first time the dose-dependent response of crotamine-triggered hind limbs paralysis syndrome, up to now believed to be observable only at high (sub-lethal) concentrations of crotamine. In addition, ex vivo assay performed with isolated skeletal muscles allowed us to suggest here that compounds active on voltage-sensitive sodium and/or potassium ion channels could both affect the positive inotropic effect elicited by crotamine in isolated diaphragm, besides also affecting the hind limbs paralysis syndrome imposed by crotamine in vivo. By identifying the potential molecular targets of this toxin, our data may contribute to open new roads for translational studies aiming to improve the snakebite envenoming treatment in human. Interestingly, we also demonstrate that the intraplantal or intraperitoneal (ip) injections of crotamine in mice do not promote pain. Therefore, this work may also suggest the profitable utility of non-toxic analogs of crotamine as a potential tool for targeting voltage-gated ion channels in skeletal muscles, aiming its potential use in the therapy of neuromuscular dysfunctions and envenoming therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Aminopyridine / administration & dosage
  • 4-Aminopyridine / pharmacology
  • Animals
  • Crotalid Venoms / administration & dosage
  • Crotalid Venoms / pharmacology*
  • Dose-Response Relationship, Drug
  • Hindlimb*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Muscle, Skeletal / drug effects*
  • Pain Measurement
  • Paralysis*
  • Potassium Channels, Voltage-Gated / antagonists & inhibitors
  • Potassium Channels, Voltage-Gated / metabolism*
  • Tetrodotoxin / administration & dosage
  • Tetrodotoxin / pharmacology
  • Voltage-Gated Sodium Channel Blockers / administration & dosage
  • Voltage-Gated Sodium Channel Blockers / pharmacology
  • Voltage-Gated Sodium Channels / metabolism*

Substances

  • Crotalid Venoms
  • Potassium Channels, Voltage-Gated
  • Voltage-Gated Sodium Channel Blockers
  • Voltage-Gated Sodium Channels
  • Tetrodotoxin
  • 4-Aminopyridine
  • crotamine

Grants and funding

This work was supported by the São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo - FAPESP No. 2013/13392-4, 2015/07019-4, and 2017/02413-1) and the National Council of Technological and Scientific Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq No. 311815/2012-0, 475739/2013-2, and 39337/2016-0). We also thank CNPq and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for the fellowships for the students. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.