title: The effect of estradiol, progesterone, and melatonin on estrous cycling and ovarian aromatase expression in intact female mice.
abstract: OBJECTIVE
  Melatonin and progesterone levels decline during the perimenopause. Both hormones inhibit estrogen action and endometrial cancer, but little is known about how they act in combination. Therefore, the interplay of progesterone (P4) and melatonin was investigated in intact female mice.
  
  
  METHODS
  Three P4 doses, low (25mg), mid (50mg), and high (100mg), combined with 0.5mg 17β-estradiol (E), were administered in the diet (per 1800kcal) for 30 days. Hormone therapy (HT) with the low P4 dose (estradiol/low progesterone replacement therapy (EPLRT)) was used to create an excess estrogen environment to mimic perimenopause. Half the mice were treated with melatonin (M) 15mg/L in the drinking water at night.
  
  
  RESULTS
  The unbalanced EPLRT treatment increased estrogen-regulated responses. Specifically, mice treated with EPLRT had significantly higher levels of ovarian aromatase mRNA versus control, which was prevented in the presence of higher doses of P4 and/or the addition of melatonin. The number of days in estrus also increased in EPLRT-treated versus control mice with no change in the length or number of complete estrous cycles. Melatonin, combined with all doses of P4, increased the number of days spent in estrus, but not the length or number of estrous cycles compared to melatonin alone; however, two-way ANOVA revealed a significant interaction between melatonin and P4 dose for days in estrus and for number of cycles. Although none of the E2 and P4 combinations significantly affected uterine weight compared to control, melatonin addition to the low or mid P4 HT resulted in slightly higher uterine weights compared to melatonin-treated mice. Melatonin significantly increased uterine estrogen receptor alpha (ERα) and progesterone receptor A levels compared to control animals. HT, added in combination with melatonin, reduced ERα levels back to control levels, but PR levels remained elevated albeit intermediary to those achieved with melatonin alone.
  
  
  CONCLUSIONS
  The findings that melatonin supplementation inhibits ovarian aromatase expression and increases uterine receptors in mice given an HT that mimics perimenopause may have important clinical applications for the improvement of menopause-related conditions, like menorrhagia, associated with high levels of E2 and low levels of P4.
authors.affiliation: Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA, United States.
authors.forename: C D
authors.initials: CD
authors.lastname: Bondi
authors.affiliation: Department of Physiology and Pharmacology, School of Medicine, University of Cantabria, Santander, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Alonso-Gonzalez
authors.affiliation: Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA, United States.
authors.forename: W P
authors.initials: WP
authors.lastname: Clafshenkel
authors.affiliation: Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA, United States.
authors.forename: M P
authors.initials: MP
authors.lastname: Kotlarczyk
authors.affiliation: Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA, United States.
authors.forename: B R
authors.initials: BR
authors.lastname: Dodda
authors.affiliation: Department of Physiology and Pharmacology, School of Medicine, University of Cantabria, Santander, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Sanchez-Barcelo
authors.affiliation: Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA, United States; Center for Applied Research and Intellectual Property Development, Clarion University, Clarion, PA, United States.
authors.forename: V L
authors.initials: VL
authors.lastname: Davis
authors.affiliation: Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA, United States. Electronic address: wittp@duq.edu.
authors.forename: P A
authors.initials: PA
authors.lastname: Witt-Enderby
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics* / Q000378:metabolism; D004347:Drug Interactions; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000032:analysis; D030762:Estrous Cycle / Q000187:drug effects*; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D008550:Melatonin / Q000494:pharmacology*; D008593:Menopause; D051379:Mice; D009929:Organ Size / Q000187:drug effects; D010053:Ovary / Q000201:enzymology*; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D014599:Uterus / Q000033:anatomy & histology / Q000737:chemistry
chemical_list: D047628:Estrogen Receptor alpha; D012333:RNA, Messenger; D011980:Receptors, Progesterone; C101118:progesterone receptor A; D011374:Progesterone; D004958:Estradiol; D001141:Aromatase; D008550:Melatonin
keywords: Aromatase; Estrogen; Hormone replacement therapy; Melatonin; Progesterone; Selective estrogen enzyme modulator (SEEM)