Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(2): 545-556, April-June 2021 (Published Apr. 19, 2021) 545 Rostelato-Ferreira, S., Vettorazzo, O.B., Tribuiani, N., Leal, A.P., Dal Belo, C.A., Rodrigues-Simioni, L., Floriano, R.S., Oshima- Franco, Y. (2021). Action of heparin and acetylcholine modulators on the neurotoxicity of the toad Rhinella schneideri (Anura: Bufonidae) in Brazil. Revista de Biología Tropical, 69(2), 545- 556. DOI 10.15517/rbt.v69i2.44539 DOI 10.15517/rbt.v69i2.44539 Action of heparin and acetylcholine modulators on the neurotoxicity of the toad Rhinella schneideri (Anura: Bufonidae) in Brazil Sandro Rostelato-Ferreira1,2; Orcid: 0000-0002-8987-434X Orlando B. Vettorazzo2; Orcid: 0000-0003-4731-4771 Natália Tribuiani2; Orcid: 0000-0002-7661-475X Allan P. Leal3; Orcid: 0000-0002-4689-4615 Cháriston A. Dal Belo3,4; Orcid: 0000-0001-7010-650 Léa Rodrigues-Simioni5; Orcid: 0000-0002-8712-6639 Rafael S. Floriano6; Orcid: 0000-0003-0759-5863 Yoko Oshima-Franco2*; Orcid: 0000-0002-4972-8444 1. Institute of Health Sciences, Paulista University (UNIP), Sorocaba, São Paulo, Brazil; [email protected] 2. Graduate Program in Pharmaceutical Sciences, University of Sorocaba (UNISO), Sorocaba, São Paulo, Brazil; [email protected], [email protected], [email protected] (*Correspondence) 3. Graduate Program in Toxicological Biochemistry, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul, Brazil; [email protected] 4. Laboratory of Neurobiology and Toxinology (Lanetox), Federal University of Pampa (UNIPAMPA), São Gabriel, Rio Grande do Sul, Brazil; [email protected] 5. Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas 13083-970, São Paulo, Brazil; [email protected] 6. Graduate Program in Health Sciences, University of Western São Paulo (UNOESTE), Presidente Prudente, São Paulo, Brazil; [email protected] Received 17-XI-2020. Corrected 11-III-2021. Accepted 23-III-2021. ABSTRACT Introduction: Rhinella schneideri is a toad widely distributed in South America and its poison is characterized by inducing cardiotoxicity and neurotoxicity. Objective: In this work, we investigated pharmacological strate- gies to attenuate the peripheral neurotoxicity induced by R. schneideri poison in avian neuromuscular prepara- tion. Methods: The experiments were carried out using isolated chick biventer cervicis preparation subjected to field stimulation for muscle twitches recordings or exposed to acetylcholine and potassium chloride for contrac- ture responses. Results: Poison (10 μg/ml) produced complete neuromuscular blockade in chick biventer cervi- cis preparation within approximately 70 min incubation (times for 50 and 90 % blockade: 15 ± 3 min and 40 ± 2 min, respectively; P < 0.05, N= 5); contracture responses to exogenous acetylcholine and KCl were unaffected by poison indicating no specificity with postsynaptic receptors or myotoxicity, respectively. Poison (10 μg/ml)- induced neuromuscular blockade was not prevented by heparin (5 and 150 IU/ml) under pre- or post-treatment conditions. Incubation at low temperature (23-25 °C) abolished the neuromuscular blockade; after raising the temperature to 37 °C, the complete neuromuscular blockade was slightly slower than that seen in preparations directly incubated at 37 °C (times for 50 and 90 % blockade: 23 ± 2 min and 60 ± 2.5 min, respectively; P < 0.05, N= 4). Neostigmine (3.3 μM) did not reverse the neuromuscular blockade in BC preparation whereas 3,4-diaminopyridine (91.6 μM) produced a partial and sustained reversal of the twitch responses (29 ± 7.8 % of maximal reversal reached in approximately 40 min incubation; P < 0.05, N= 4). Conclusions: R. schneideri poison induces potent peripheral neurotoxicity in vitro which can be partially reversible by 3,4-diaminopyridine. Key words: amphibian poison; paratoid gland secretion; chick biventer cervicis preparation; neuromuscular blockade; reversal. 546 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 69(2): 545-556, April-June 2021 (Published Apr. 19, 2021) Rhinella genus (Bufonidae) comprises 94 including the chemical identification and struc- species distributed in Central (Panama) and tural characterization of bufadienolides, e.g., South America (Paraguay, Bolivia, Argenti- marinobufagenin, bufalin, telocinobufagin, hel- na, Uruguay and Brazil), with approximately lebrigenin, 20S21R-epoxymarinobufagin and 30 of them found in Brazil (Pereyra et al., β-sitosterol, which exhibit cytotoxic activity, 2016; Wake, 2020). The secretion produced modulatory action on the complement cascade, by amphibian paratoid glands is composed by anti-inflammatory activity, inhibitory action numerous active components such as biogenic of serine protease, presynaptic neuromuscular amines, peptides, steroids (bufadienolides and blocking activity and anticonvulsant action bufotoxins), alkaloids (batrachotoxin ‘tetrodo- (Cunha-Filho et al., 2010; Anjolette et al., toxin’), and proteins (Gregerman, 1952; Zel- 2015; Sousa-Filho et al., 2016; Shibao, Anjo- nik, 1965; Mahan & Biggers, 1977; O’Rourke, lette, Lopes, & Arantes, 2015; Freitas et al., Chen, Hirst, Rao, & Shaw, 2004), compris- 2017; Rostelato-Ferreira et al., 2018; Baldo et ing the main protection mechanism against al., 2019; Zheng et al., 2020). potential predators (Clarke, 1997; Kowalski, Heparin has been successfully used to Marciniak, Rosiński, & Rychlik, 2018). These neutralize the neurotoxic and myotoxic activi- components, especially those bufadienolides ties of Bothrops (Viperidae: Crotalinae) ‘pit- and bufotoxins, have been considered potential viper’ snake venoms (Melo & Suarez-Kurtz, therapeutic tools for exhibiting cancer inhibi- 1988a; Melo & Suarez-Kurtz, 1988b; Melo & tory activity (Meng et al., 2009), apoptosis Ownby, 1999; Calil-Elias, Martinez, & Melo, suppressive action (Qi et al., 2010) and anti- 2002; Rostelato-Ferreira et al., 2010) and their microbial activity (Tempone et al., 2008). The major phospholipase A2 (PLA2) (Lomonte, paratoid gland secretion and their components, Moreno, Tarkowski, Hanson, & Maccarana, e.g., non-enzymatic presynaptic active toxin 1994a; Lomonte, Tarkowski, Bagge, & Han- (730.6 Da) isolated from R. schneideri poison son, 1994b; Rodrigues et al., 2004a; Perchuc et (Rostelato-Ferreira et al., 2018), can induce al., 2010; Rostelato-Ferreira et al., 2010). The neurotoxicity characterized by suppression of action of heparin against the effects produced the motor acetylcholine release (Rostelato- by amphibian poisons on the motor neurotrans- Ferreira, Dal Belo, Cruz-Höfling, Hyslop, & mitter release has not been previously investi- Rodrigues-Simioni, 2011; Rostelato-Ferreira, gated, however, the acid-basic characteristics Dal Belo, Leite, Hyslop, & Rodrigues-Simioni, of steroid derivatives and biogenic amines 2014; Rostelato-Ferreira et al., 2018), includ- found in toad venoms may suggest an even- ing cardiotoxicity consisted in arrhythmia and tual interaction with heparin (Zelnik, 1965). In ventricular failure mostly by antagonizing Na+/ addition, acetylcholine (ACh) release modulat- K+ ATPase of cardiomyocytes (Toledo & Jared, ing drugs, e.g., neostigmine, an acetylcholin- 1995; Sakate & Oliveira, 2000; Gadelha, Lima, esterase inhibitor, and 3.4-diaminopyridine, a Batista, Melo, & Soto-Blanco, 2014; Leal voltage-gated potassium channel blocker, show et al., 2020). R. marinus and R. vulgaris are to be effective in counteract the neuromuscular responsible for causing the most cases of paralysis caused by animal venoms and iso- envenomation in domestic animals (Sakate & lated toxins by promoting the increase of ace- Oliveira, 2000; Sakate & Oliveira, 2001). tylcholine release in motor nerve terminal (Ng In recent years, several biological proper- et al., 2017; Floriano et al., 2019; Neely, Sabir, ties have been characterized from Rhinella & Kohli, 2020). In this work, we have tested schneideri ‘Schneider’s toad’ poison (Rostela- different pharmacological strategies in order to to-Ferreira et al., 2011; Rostelato-Ferreira et al., counteract the neuromuscular action induced 2014; Abdelfatah, Lu, Schmeda-Hirschmann, by R. schneideri poison in avian isolated prepa- & Efferth, 2019; Leal et al., 2020), a species ration by applying heparin and acetylcholine widely distributed in Brazil (Wake, 2020), (ACh) release modulating drugs. Revista de Biología Tropical, ISSN: 2215-2075, Vol. 69(2): 545-556, April-June 2021 (Published Apr. 19, 2021) 547 MATERIALS AND METHODS 4-6 V) with stimuli being delivered from a LE 12406 TC stimulator (Panlab, Barcelona, Reagents and poison: Acetylcholine chlo- Spain) and the muscle twitches recorded using ride, neostigmine methylsulfate, 3.4-diamino- an MLT0201 force-displacement transducer pyridine and heparin sodium salt were obtained coupled to a Quad Bridge Amp and PowerLab from Sigma-Aldrich Chemical Co. (St. Louis, 4/35 data acquisition system connected to a MO, USA). All salts used to prepare the physi- LabChart Pro v. 6.0 (ADInstruments Pty Ltd., ological solutions were of analytical grade. The 2020) software (all from ADInstruments Pty methanolic extract of R. schneideri poison was Ltd., Sydney, Australia). Muscle contractures provided by Universidade Federal do Pampa to exogenous acetylcholine (ACh, 110 μM) and (UNIPAMPA, São Gabriel, RS, Brazil) through potassium chloride (KCl, 20 mM) were evoked Dr. Cháriston A. Dal Belo. R. schneideri poi- in the absence of electric stimulation, before son