title: Extracellular lipid droplets promote hemozoin crystallization in the gut of the blood fluke Schistosoma mansoni.
abstract: Hemozoin (Hz) is a heme crystal produced upon hemoglobin digestion as the main mechanism of heme disposal in several hematophagous organisms. Here, we show that, in the helminth Schistosoma mansoni, Hz formation occurs in extracellular lipid droplets (LDs). Transmission electron microscopy of adult worms revealed the presence of numerous electron-lucent round structures similar to LDs in gut lumen, where multicrystalline Hz assemblies were found associated to their surfaces. Female regurgitates promoted Hz formation in vitro in reactions partially inhibited by boiling. Fractionation of regurgitates showed that Hz crystallization activity was essentially concentrated on lower density fractions, which have small amounts of pre-formed Hz crystals, suggesting that hydrophilic-hydrophobic interfaces, and not Hz itself, play a key catalytic role in Hz formation in S. mansoni. Thus, these data demonstrate that LDs present in the gut lumen of S. mansoni support Hz formation possibly by allowing association of heme to the lipid-water interface of these structures.
authors.affiliation: Instituto de Bioquímica Médica, Programa de Biologia Molecular e Biotecnologia, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
authors.forename: Juliana B R
authors.initials: JB
authors.lastname: Corrêa Soares
authors.forename: Clarissa M
authors.initials: CM
authors.lastname: Maya-Monteiro
authors.forename: Paula R B
authors.initials: PR
authors.lastname: Bittencourt-Cunha
authors.forename: Geórgia C
authors.initials: GC
authors.lastname: Atella
authors.forename: Flávio A
authors.initials: FA
authors.lastname: Lara
authors.forename: Joana C P
authors.initials: JC
authors.lastname: d'Avila
authors.forename: Diego
authors.initials: D
authors.lastname: Menezes
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Vannier-Santos
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Oliveira
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Egan
authors.forename: Marcus F
authors.initials: MF
authors.lastname: Oliveira
mesh_terms: D000818:Animals; D003460:Crystallization; D005260:Female; D006420:Hemeproteins / Q000737:chemistry* / Q000187:drug effects*; D057927:Hydrophobic and Hydrophilic Interactions; D007422:Intestines / Q000737:chemistry; D008055:Lipids / Q000494:pharmacology*; D012550:Schistosoma mansoni / Q000033:anatomy & histology
chemical_list: D006420:Hemeproteins; D008055:Lipids; C020753:hemozoin