title: Dynamics of sterol synthesis during development of Leishmania spp. parasites to their virulent form.
abstract: BACKGROUND
  The Leishmania spp. protozoa, the causative agents of the "neglected" tropical disease leishmaniasis, are transmitted to mammals by sand fly vectors. Within the sand fly, parasites transform from amastigotes to procyclic promastigotes, followed by development of virulent (metacyclic) promastigote forms. The latter are infectious to mammalian hosts. Biochemical components localized in the parasite plasma membrane such as proteins and sterols play a pivotal role in Leishmania pathogenesis. Leishmania spp. lack the enzymes for cholesterol synthesis, and the dynamics of sterol acquisition and biosynthesis in parasite developmental stages are not understood. We hypothesized that dynamic changes in sterol composition during metacyclogenesis contribute to the virulence of metacyclic promastigotes.
  
  
  METHODS
  Sterols were extracted from logarithmic phase or metacyclic promastigotes grown in liquid culture with or without cholesterol, and analyzed qualitatively and quantitatively by gas chromatograph-mass spectrometry (GC-MS). TriTrypDB was searched for identification of genes involved in Leishmania sterol biosynthetic pathways.
  
  
  RESULTS
  In total nine sterols were identified. There were dynamic changes in sterols during promastigote metacyclogenesis. Cholesterol in the culture medium affected sterol composition in different parasite stages. There were qualitative and relative quantitative differences between the sterol content of virulent versus avirulent parasite strains. A tentative sterol biosynthetic pathway in Leishmania spp. promastigotes was identified.
  
  
  CONCLUSIONS
  Significant differences in sterol composition were observed between promastigote stages, and between parasites exposed to different extracellular cholesterol in the environment. These data lay the foundation for further investigating the role of sterols in the pathogenesis of Leishmania spp. infections.
authors.affiliation: Department of Biomedical Sciences and One Health Center for Zoonoses and Tropical Veterinary Medicine, Ross University School of Veterinary Medicine, P.O. Box 334, Basseterre, St. Kitts, West Indies, ᅟ. chyao@rossvet.edu.kn.
authors.forename: Chaoqun
authors.initials: C
authors.lastname: Yao
authors.affiliation: Departments of Internal Medicine, Microbiology and Epidemiology, University of Iowa, Iowa City, IA, USA.|Iowa City VA Medical Center, Iowa City, IA, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Wilson
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D007891:Leishmania / Q000737:chemistry* / Q000254:growth & development*; D013261:Sterols / Q000032:analysis*
chemical_list: D013261:Sterols
keywords: Leishmania; Metacyclogenesis; Promastigotes; Sterol; Sterol biosynthetic pathway; Virulence