title: Antimicrobial host defence peptide, LL-37, as a potential vaginal contraceptive.
abstract: OBJECTIVE
  Does antimicrobial peptide, LL-37, inhibit sperm fertilizing ability?
  
  
  CONCLUSIONS
  Our results indicate that LL-37 inhibits mouse and human sperm fertilizing ability.
  
  
  BACKGROUND
  LL-37, a cationic antimicrobial peptide, exerts its microbicidal effects through the disruption of microbial cytoplasmic membranes following its interaction with microbial surface anionic phospholipids. ALL-38 (an LL-37 close analogue: LL-37 + Ala at the N-terminus) is produced in the vagina 2-6 h post-intercourse from its precursor hCAP-18, a seminal plasma component. At this time, motile sperm have already swum into the uterine cavity, thus unexposed to ALL-38. Since sperm contain a substantial amount of acidic sulfogalactosylglycerolipid (SGG) on their surface, treatment of sperm with LL-37 may cause their membrane disruption in an analogous manner to that occurring on microbial membranes.
  
  
  METHODS
  Mouse/human sperm treated (2-30 min) with LL-37 in a physiological concentration range (up to 10.8 µM) were assessed for SGG-dependent LL-37 binding, and parameters relevant to fertilizing ability, namely motility and intactness of the sperm acrosome and plasma membrane. Ability of mouse sperm to fertilize eggs in vitro was also evaluated. Each study was performed with greater than or equal to three different sperm samples. The efficacy of LL-37 to inhibit sperm fertilizing ability in vivo was determined in female mice (n = 26 each for LL-37 treatment and no treatment), using sperm retrieved from 26 males.
  
  
  METHODS
  Human sperm samples were donated by fertile men. LL-37 was chemically synthesized and was biotinylated for sperm binding studies. Sperm motility was assessed by videomicroscopy and the acrosomal status by Coomassie blue staining of acrosome-intact mouse sperm or the exposure of CD46, an inner acrosomal membrane protein, of acrosome reacted human sperm. Sperm membrane permeabilization/disruption was assessed by the loss of hypo-osmotic swelling response, an incorporation of Sytox Green (a membrane impermeable fluorescent DNA dye), and electron microscopy. Mouse IVF was scored by the presence of two pronuclei in eggs 6 h post-insemination. Ability of mouse sperm to fertilize eggs in vivo was determined by the pregnancy outcome of female mice injected transcervically with sperm with or without LL-37.
  
  
  RESULTS
  Biotinylated LL-37 bound to both mouse and human sperm and the binding was partially dependent on sperm surface SGG. Mouse and human sperm became immotile and underwent a premature acrosome reaction upon treatment with LL-37 at 3.6 and 10.8 µM, respectively. The initial action of LL-37 on both mouse and human sperm appeared to be through permeabilization/disruption of sperm surface membranes evidenced by the loss of hypo-osmotic swelling response, Sytox Green staining and electron microscopy revealing ultrastructural damage. Mouse sperm treated with 3.6 µM LL-37 lost the ability to fertilize eggs both in vitro and in vivo. All 26 female mice inseminated with sperm and LL-37 did not become pregnant. No apparent damage to the reproductive tract was observed as revealed by histological characterization in LL-37-inseminated mice and these females resumed fecundity following mating with fertile males.
  
  
  CONCLUSIONS
  Direct demonstration that LL-37 treated human sperm fail to fertilize eggs was limited by legal restrictions on obtaining human eggs for such use.
  
  
  CONCLUSIONS
  Our results reveal selective inhibitory effects of LL-37 on sperm fertilizing ability in mice without apparent impairment to the female reproductive tract. LL-37 is therefore a promising candidate to be developed into a vaginal contraceptive with microbicidal activity.
  
  
  BACKGROUND
  This work was supported by Grand Challenges Explorations grant from the Bill & Melinda Gates Foundation (OPP1024509), Canadian Institutes of Health Research (MOP119438 & CCI82413) and International Collaboration and Exchanges NSFC of China (No.30611120525). There are no competing interests to declare.
authors.affiliation: Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada K1H 8L6.
authors.forename: Nopparat
authors.initials: N
authors.lastname: Srakaew
authors.forename: Charlene D
authors.initials: CD
authors.lastname: Young
authors.forename: Arpornrad
authors.initials: A
authors.lastname: Sae-wu
authors.forename: Hongbin
authors.initials: H
authors.lastname: Xu
authors.forename: Krista L
authors.initials: KL
authors.lastname: Quesnel
authors.forename: Riccardo
authors.initials: R
authors.lastname: di Brisco
authors.forename: Kessiri
authors.initials: K
authors.lastname: Kongmanas
authors.forename: Duriya
authors.initials: D
authors.lastname: Fongmoon
authors.forename: Greanggrai
authors.initials: G
authors.lastname: Hommalai
authors.forename: Wattana
authors.initials: W
authors.lastname: Weerachatyanukul
authors.forename: Susan H
authors.initials: SH
authors.lastname: Hall
authors.forename: Yong-Lian
authors.initials: YL
authors.lastname: Zhang
authors.forename: Luigi
authors.initials: L
authors.lastname: Panza
authors.forename: Laura
authors.initials: L
authors.lastname: Franchini
authors.forename: Federica
authors.initials: F
authors.lastname: Compostella
authors.forename: Terry W
authors.initials: TW
authors.lastname: Pearson
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hancock
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Oko
authors.forename: Louis S
authors.initials: LS
authors.lastname: Hermo
authors.forename: Nongnuj
authors.initials: N
authors.lastname: Tanphaichitr
mesh_terms: D000177:Acrosome / Q000187:drug effects; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D003270:Contraceptive Agents; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D006801:Humans; D008297:Male; D051379:Mice; D013081:Sperm Motility / Q000187:drug effects; D013084:Sperm-Ovum Interactions / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects*; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D003270:Contraceptive Agents; D054804:Cathelicidins
keywords: LL-37; sperm fertilizing ability; sperm plasma membrane; vaginal contraceptive