Toxicon 58 (2011) 28–34 Contents lists available at ScienceDirect Toxicon journal homepage: www.elsevier.com/locate/toxicon A comparative study of the effects of venoms from five rear-fanged snake species on the growth of Leishmania major: Identification of a protein with inhibitory activity against the parasite María E. Peichoto a,b,*, Flávio L. Tavares b, Gregory DeKrey b, Stephen P. Mackessy b a Cátedra de Farmacología, Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Sargento Cabral 2139, 3400 Corrientes, Argentina b School of Biological Sciences, University of Northern Colorado, 501 20th St., CB 92, Greeley, CO 80639-0017, USA article info abstract Article history: Leishmania parasites of several species cause cutaneous and visceral disease to millions of Received 25 November 2010 people worldwide, and treatment for this vector-borne protozoan parasite typically involves Received in revised form 24 April 2011 administration of highly toxic antimonial drugs. Snake venoms are one of the most Accepted 27 April 2011 concentrated enzyme sources in nature, displaying a broad range of biological effects, and Available online 12 May 2011 several drugs now used in humans were derived from venoms. In this study, we compared the effects of the venoms of the South American rear-fanged snakes Philodryas baroni (PbV), Keywords: Philodryas olfersii olfersii (PooV) and Philodryas patagoniensis (PpV), and the North American Antileishmanial activity Hypsiglena torquata texana rear-fanged snakes Hypsiglena torquata texana (HttV) and Trimorphodon biscutatus lambda Philodryas baroni (TblV), on the growth of Leishmania major, a causative agent of cutaneous leishmaniasis. Philodryas olfersii olfersii Different concentrations of each venom were incubated with the log-phase promastigote Philodryas patagoniensis stage of L. major. TblV showed significant anti-leishmanial activity (IC50 of 108.6 mg/mL) at its Phospholipase A2 highest concentrations; however, it induced parasite proliferation at intermediate Trimorphodon biscutatus lambda concentrations. PpV was not very active in decreasing the parasitic growth, and a high final concentration (1.7 mg/mL) was necessary to inhibit proliferation by only 51.5% Æ 3.6%. PbV, PooV and HttV, at final concentrations of 562, 524 and 438 mg/mL respectively, had no significant effect on L. major growth. The phospholipase A2 of TblV (trimorphin) was isolated and assayed as for crude venom, and it also exhibited dose-dependent biphasic effects on the parasite culture, with potent cytotoxicity at higher concentrations (IC50 of 0.25 mM; 3.6 mg/mL) and stimulation of proliferation at very low concentrations. Anti-leishmanial activity of TblV appears to be solely due to the action of trimorphin. This is the first report of anti-leishmanial activity of rear-fanged snake venoms, and these results suggest novel possibilities for discovering new protein-based drugs that might be used as possible agents against leishmaniasis as well as tools to study the biology of Leishmania parasites. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Leishmania following the bite of an infected sandfly (commonly Phlebotomus sp.). It is a severe disease affecting Leishmaniasis is an anthropozoonosis caused by cuta- millions of people in Africa, America, Europe and Asia neous infection with protozoan parasites of the genus (Desjeux, 1992). Because of its prevalence and morbidity, this disease has been considered a serious health problem by the World Health Organization (WHO) and is statisti- * Corresponding author. Universidad Nacional del Nordeste, Facultad cally the second most important parasitic disease world- de Ciencias Veterinarias, Cátedra de Farmacología, Sargento Cabral 2139, 3400 Corrientes, Argentina. Tel./fax: þ54 3783 425753. wide (Rath et al., 2003). E-mail addresses: [email protected], mepeichoto@conicet. Currently, the main drugs used for the treatment of gov.ar (M.E. Peichoto). patients are pentavalent antimonials, whereas the antifungal 0041-0101/$ – see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.toxicon.2011.04.018 M.E. Peichoto et al. / Toxicon 58 (2011) 28–34 29 drug amphotericin B (a polyene macrolide antibiotic) is and 0456), and maintained in the UNC Animal Facility. Four considered an efficient treatment option for many captive-born specimens of P. baroni were obtained from the antimonial-resistant strains of Leishmania (Rosenthal et al., Dallas Zoological Park and were also maintained in the UNC 2009). Other drugs, such as allopurinol, miltefosine and Animal Facility. All housing and handling procedures were pentamidine also represent important options for leish- approved by the UNC-IACUC (protocols #9204.1 & 9401). maniasis treatment (Loiseau and Bories, 2006). However, Extraction of snakes utilized a previously published effective new anti-leishmanial compounds are needed due method (Hill and Mackessy, 1997; Rosenberg, 1992). to the high costs, development of parasite resistance and side After extraction, all venoms were centrifuged, lyophi- effects related to those drugs currently in use. Importantly, lized and kept frozen at À20 C. When required, venoms no licensed human vaccine for leishmaniasis is available. were dissolved in 0.01 M phosphate buffer saline (PBS), pH A productive, more recent approach to the search for 7.4, and filtered through a 0.22 mm Millipore filter to more efficient and less toxic chemotherapeutic agents has remove insoluble material and to sterilize. been the screening of natural compounds able to inhibit protistan growth. Snake venoms, one of the most concen- 2.2. Protein concentration determination trated enzyme sources in nature, are complex mixtures of proteins, peptides and small organic molecules whose Protein concentration was assayed in triplicate accord- composition varies phylogenetically and as a function of ing to Bradford (1976) as modified by BioRad Inc. (Hercules, other factors, overall displaying a broad range of biological CA, USA), using bovine gamma globulin as a standard. effects (Mackessy, 2010). Previous studies have shown that the venom of the front-fanged snakes Bothrops marajoensis 2.3. Purification of phospholipase A2 (PLA2) from TblV (Costa Torres et al., 2010),Bothropsmoojeni(Tempone et al., 2001), Bothrops jararaca (Gonçalves et al., 2002), Crotalus TblV was dissolved in 25 mM HEPES buffer containing durissus terrificus, Crotalus durissus cascavella, Crotalus dur- 100 mM NaCl (pH 6.8). Two hundred microliters (4 mg) of issus collilineatus (Passero et al., 2007), Cerastes cerastes and the venom was injected onto a TSKgel G2000 SWXL size Naja haje (Fernandez-Gomez et al., 1994) can inhibit the exclusion column (7.8 mm i.d., 30 cm, 5 mm) (TOSOH growth of different Leishmania species. However, at present Bioscience LLC, Tokyo, Japan) at a flow rate of 0.15 mL/min no venoms from rear-fanged snakes, most species of which using the same buffer (Waters HPLC), and chromatograms do not represent a risk to humans, have been evaluated for were recorded using Empower software. Fractions were anti-protist activity. collected and assayed for PLA2 activity (see below). Selected Ò Ò There is tremendous potential for discovering novel fractions were electrophoresed on NuPAGE Novex 12% bioactive compounds in rear-fanged snake venoms, Bis-Tris gels (Invitrogen, Inc., Carlsbad, CA, USA). Active because this is the most speciose group of advanced snakes fractions were pooled and applied to a Protein and Peptide and relatively few studies have investigated their compo- C18 column (5 mm, 4.6 mm i.d. Â 250 mm) (VYDAC, Hes- sition and biological activities (Mackessy, 2002). The peria, CA, USA) equilibrated with solvent A [0.1% (v/v) tri- current study evaluates new sources of potential anti- fluoroacetic acid (TFA) in Milli-Q water], using a Waters leishmanial compounds from rear-fanged snake venoms. HPLC system. Bound proteins were eluted with 0–100% In this study, we compared the effects of the venoms of the increasing linear gradient of solvent B [0.1% TFA/80% South American rear-fanged snakes Philodryas baroni (PbV), acetonitrile (ACN)] at a flow rate of 1 mL/min for 90 min. Philodryas olfersii olfersii (PooV) and Philodryas patago- The elution profile was monitored at 220 and 280 nm. niensis (PpV), and the North American rear-fanged snakes Hypsiglena torquata texana (HttV) and Trimorphodon bis- 2.4. PLA2 activity assay cutatus lambda (TblV), as well as a purified PLA2 from T. b. lambda venom, on the growth of the promastigote stage of PLA2 enzyme activity was determined by the method of Leishmania major, a causative agent of cutaneous leish- Holzer and Mackessy (1996), using 4-nitro-3-(octanoyloxy) maniasis, as an initial screen of their potential anti-leish- benzoic acid as substrate. The assay buffer was 10 mM Tris– manial activity. HCl (pH 8.0) containing 10 mM CaCl2 and 100 mM NaCl. 2. Materials and methods 2.5. SDS-PAGE 2.1. Rear-fanged snake venoms Crude venoms and purified PLA2 fractions were sub- jected to SDS-PAGE using NuPage Bis-Tris gels (Invitrogen, Pools of P. patagoniensis and P. o. olfersii venoms were Inc., Carlsbad, CA, USA), MES/SDS running buffer and 24 mg obtained from wild specimens captured in northeastern venom/lane as described previously (Weldon and Argentina and then maintained at the serpentarium of the Mackessy, 2010). Following staining with Coomassie bril- local Zoo, Corrientes, Argentina. Specimens were extracted liant blue R-250 and destaining, the gel was imaged using an by introducing a 100-mL micropipette under each fang, AlphaImager (Cell Biosciences, Inc., Santa Clara, CA, USA). according to a procedure described previously (Ferlan et al., 1983). 2.6. Mass spectrometry Hypsiglena torquata and T. biscutatus venoms were ob- tained from wild specimens captured in Colorado and In order to determine the molecular mass of the purified Arizona, USA (scientific collecting permits MCKSY000221 PLA2, approximately 1 mg protein in 50% ACN containing 30 M.E. Peichoto et al. / Toxicon 58 (2011) 28–34 0.1% TFA was spotted onto a MALDI sample holder, mixed variance (ANOVA) with the Holm-Sidak method for with an equal volume of 10 mg/mL sinapinic acid in 50% multiple comparisons versus control group.