Acta Tropica 117 (2011) 161–164 Contents lists available at ScienceDirect Acta Tropica journal homepage: www.elsevier.com/locate/actatropica Short communication Semicarbazide-sensitive amine oxidase kills African trypanosomes in vitro Qiao-Ping Wang, De-Hua Lai, Zhi Li, Feng-Jun Li, Zhao-Rong Lun ∗ Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Diseases Control of Ministry of Education, Zhongshan Medical College, Sun Yat-Sen (Zhongshan) University, Guangzhou 510275, PR China article info Article history: Received 22 June 2010 Received in revised form 25 November 2010 Accepted 25 November 2010 Available online 8 December 2010 Keywords: SSAO Trypanosome Formaldehyde Hydrogen peroxidase In vitro abstract The African trypanosome Trypanosoma brucei is the cause of sleeping sickness in humans and Nagana in animals. Here we report that semicarbazide-sensitive amine oxidases (SSAOs), enzymes that are abound in T. brucei mammal hosts, eliminate trypanosomes by oxidation of its substrate in vitro. SSAO and its endogenous substrate methylamine are not toxic to T. brucei, but parasites were killed in the presence of both of them. SSAO inhibitors antagonized the SSAO-methylamine induced toxicity on T. brucei. The trypanocidal activity was mainly associated with formaldehyde generated in the SSAO mediated oxida- tion of methylamine. This finding suggests that SSAO may play some roles in non-specific defense of trypanosome infection in mammals. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Protozoan parasites are susceptible to products generated dur- ing the oxidation of polyamines mediated by polyamine oxidase (PAO) and the oxidation of xanthine by xanthine oxidase (XO) (Ferrante et al., 1982,1984; Muranjan et al., 1997; Rzepczyk et al., 1984; Wang et al., 1999). In cattle trypanosomiasis, Trypanosoma brucei, is killed by the oxidation product of XO, hydrogen peroxide (H 2 O 2 )(Muranjan et al., 1997; Wang et al., 1999) which plays an important role in control the parasitaemia in the early infection in African Cape buffalo (Wang et al., 1999). Beside XO and PAO, source of antiparasitic H 2 O 2 could also come from other oxidases. For instance, semicarbazide-sensitive amine oxidases (SSAOs) exist in many mammalian species, catalyzing primary amines into aldehyde, hydrogen peroxide and ammonia (O’Sullivan et al., 2004). The physiological sub- strates of SSAOs include methylamine, aminoacetone, tyramine, 2-phenylethylamine and 5-hydroxytryptamine (O’Sullivan et al., 2004; Yu et al., 2003). SSAOs present in both tissue-bound iso- forms and soluble isoforms (plasma SSAO) (O’Sullivan et al., 2004). Soluble SSAOs originate from tissue-bound SSAOs (Stolen et al., 2004). Tissue-bound SSAOs are mostly located on the mem- brane of smooth muscle cells, adipocytes and vascular endothelial cells. Vascular adhesion protein-1 (VAP-1), an adhesion protein in endothelial cells, displays SSAO activity (Stolen et al., 2004). ∗ Corresponding author. Tel.: +86 20 84115079; fax: +86 20 84036215. E-mail address: lsslzr@mail.sysu.edu.cn (Z.-R. Lun). SSAOs-mediated oxidative deamination is toxic to endothelial cells and vascular smooth muscle cells (Yu and Zuo, 1993, 1996; Hernandez et al., 2006). SSAOs are involved in the develop- ment of vascular damages in diabetes, heart failure, inflammation and even Alzheimer’s disease (AD) (O’Sullivan et al., 2004). Here we report that SSAO mediated oxidation of methylamine killed T. brucei in vitro. 2. Material and methods 2.1. Preparation of human umbilical artery SSAO and rVAP-1 Human umbilical SSAOs were isolated as previously described (Yu and Zuo, 1996). Briefly, umbilical arteries were washed three times with chilled phosphate buffer (0.01 M, pH 6.8) and sliced into small pieces, and then were homogenized by FS-2 Polytron homogenizer (Jintan, China) in the same chilled buffer. The crude homogenate was centrifuged at 800 × g for 10 min and the resulting supernatant was subjected to ultracentrifugation at 32 000 × g for 30 min. The final supernatant containing soluble SSAO was steril- ized through a 0.22 m filter and stored at -80 ◦ C. The recombinant human VAP-1 (rVAP-1) was a gift from Biotie Therapies, Turku, Finland. 2.2. Trypanocidal assays Bloodstream forms of T. brucei brucei strain STIB 920 were cultured in HMI-11 medium at 37 ◦ C with 5% CO 2 for try- panocidal assays. To determine the antiparasitic effects of SSAO, 0001-706X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.actatropica.2010.11.010