title: A role for the endocannabinoid system in premature luteal regression and progesterone withdrawal in lipopolysaccharide-induced early pregnancy loss model.
abstract: What is the role of the endocannabinoid system (eCS) in the alterations of the endocrine system in a murine model of lipopolysaccharide (LPS)-induced miscarriage?
  
  
  
  In 7-days pregnant wild type, but not cannabinoid receptor type 1 knockout (CB1-KO) mice, LPS increased COX-2 expression and prostaglandin F2α(PGF2α) production in the uterus leading to lower expression of prolactin receptor in the ovary and a marked regression of corpora lutea (CL), suggesting that the eCS mediates the deleterious effects of LPS on reproductive events.
  
  
  
  Appropriate systemic progesterone levels are critical for a successful pregnancy outcome. Precocious loss of luteal progesterone (P4) secretion leads to miscarriage in rodents. We have previously shown that LPS administration to pregnant mice induces embryonic resorption accompanied by a dramatic decrease in systemic progesterone levels in a murine model of inflammatory miscarriage, with the eCS mediating these LPS-induced deleterious effects.
  
  
  
  CD1 wild-type (WT) and CB1-KO mice were randomly allocated to Vehicle (saline; i.p.) or LPS (0.5 μg/g body weight; i.p.) treated groups: (WT-Vehicle; WT-LPS; CB1-KO-Vehicle and CB1-KO-LPS). A single injection was given on day 7 of pregnancy and tissues (blood, ovary, uterus) were collected 6, 12, 24 and 48 h later. P4 and PGF2α plasma levels were determined by radioimmunoassay. Cyclooxygenase-2 (COX-2) mRNA (RT-PCR) and protein (Western blot) content in uterus was assayed. COX-2 and prolactin receptor (PrlR) mRNA levels in the ovary were assayed by RT-PCR. Tissue morphology of the CL was assessed by haematoxylin-eosin staining.
  
  
  
  Treatment of 7-day pregnant WT mice with LPS induced a P4 withdrawal (p < 0.05), increased in uterine COX-2 mRNA and protein expression (p < 0.05) as well as an increase in uterine PGF2αproduction (p < 0.05). These changes were absent in LPS-treated 7-day pregnant CB1-KO mice. In ovarian tissues, LPS treatment to 7-day pregnant WT mice induced a downregulation of PrlR mRNA expression (p < 0.05) together with an increase in COX-2 mRNA expression (p < 0.05) and PGF2αcontent (p < 0.05). These effects were absent in the CB1-KO mice. Collectively, our results suggest a role for the eCS mediating LPS-induced deleterious effects on reproductive tissues.
  
  
  
  An important caveat of this study is the endocrine differences between mice and humans during pregnancy (e.g. P4 is produced by the CL throughout pregnancy in mice, whereas this is not the case in humans), which limits the extrapolation of the results presented here.
  
  
  
  Our findings provide new insights in the role of the endocannabinoid system in the physiopathology of reproduction as well as the role of this endogenous system as a mediator of LPS deleterious effects on reproductive tissues.
  
  
  
  None.
  
  
  
  Dr Ana María Franchi was funded by Agencia Nacional para la Promoción Científica y Tecnológica (PICT 2010/0813 and PICT 2013/0097) and by Consejo Nacional de Investigaciones Científicas y Técnicas (PIP 2012/0061). The authors have no competing interests.
authors.affiliation: Laboratory of Physiopathology of Pregnancy and Labor, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: Julieta Aylen
authors.initials: JA
authors.lastname: Schander
authors.affiliation: Laboratory of Physiopathology of Pregnancy and Labor, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: Fernando
authors.initials: F
authors.lastname: Correa
authors.affiliation: Laboratory of Physiopathology of Pregnancy and Labor, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Bariani
authors.affiliation: Laboratory of Physiopathology of Pregnancy and Labor, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: Julieta
authors.initials: J
authors.lastname: Blanco
authors.affiliation: Laboratory of Molecular Endocrinology, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: Cora
authors.initials: C
authors.lastname: Cymeryng
authors.affiliation: Laboratory of Reproductive Immunology, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: Federico
authors.initials: F
authors.lastname: Jensen
authors.affiliation: Laboratory of Physiopathology of Pregnancy and Labor, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina manuwolfson@gmail.com.
authors.forename: Manuel Luis
authors.initials: ML
authors.lastname: Wolfson
authors.affiliation: Laboratory of Physiopathology of Pregnancy and Labor, Center for Pharmacological and Botanical Studies, National Research Council, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: Ana María
authors.initials: AM
authors.lastname: Franchi
mesh_terms: D000022:Abortion, Spontaneous / Q000188:drug therapy* / Q000378:metabolism*; D000818:Animals; D003338:Corpus Luteum / Q000378:metabolism; D063388:Endocannabinoids / Q000378:metabolism*; D005260:Female; D008070:Lipopolysaccharides / Q000633:toxicity*; D008183:Luteal Phase / Q000378:metabolism*; D003341:Luteolysis / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D011247:Pregnancy; D011374:Progesterone / Q000378:metabolism*; D011863:Radioimmunoassay
chemical_list: D063388:Endocannabinoids; D008070:Lipopolysaccharides; D011374:Progesterone
keywords: COX-2; PGF2α; endocannabinoid system; luteolysis; progesterone; prolactin receptor