Sandra E. Reznik

The Role of Endothelin-1 in Endotoxin-Triggered Release of Placental Pro-inflammatory Cytokines

Sandra E. Reznik, College of Pharmacy and Health Sciences, Department of Pharmaceutical Sciences; Students: Prathamesh Mahajan, Roopali V. Donepudi, Francine Einstein

Abstract
Background:  Premature delivery, defined as delivery occurring before 37 weeks’ gestation, occurs in 12% of all births, and accounts for nearly half of long-term neurological morbidity, and 60 to 80% of perinatal mortality, excluding infants with congenital anomalies.  We have previously shown that both the endothelin-converting enzyme-1 (ECE-1) inhibitor phosphoramidon and the selective endothelin receptor A antagonist BQ-123 control PTB in a dose-dependent fashion.  In addition, we have found that a novel synthetic ET A receptor antagonist synthesized by our group rescues mice from lipopolysaccharide (LPS)-induced PTB.  Finally, we have been able to prevent PTB in LPS-stimulated animals, using RNA silencing with ECE-1 RNAi.

Objective:  Our aim was to test the hypothesis that ET-1 contributes to the cause of preterm birth by up-regulating pro-inflammatory cytokines.

Methods:  Chorionic villous explants were prepared from full term human placentae obtained from Albert Einstein Hospital, Bronx, NY and cultured in Dulbecco’s Modified Eagle’s medium (DMEM) under aseptic conditions. The explants were divided into four groups:  sham, endotoxin-treated, endotoxin plus low concentration BQ-123-treated and endotoxin plus high concentration BQ-123-treated.  Explant supernatants from all groups were collected 24 hours after the addition of endotoxin and evaluated for changes in levels of interleukin 1b(IL-1b) and tumor necrosis factor a(TNF a by Western blotting analysis.

Results:  Villous explants treated with LPS released significantly higher amounts of both IL-1b and TNF ainto culture media than sham explants.  This pro-inflammatory response was reversed, in a concentration-dependent fashion, with the ET A receptor antagonist BQ-123.

Conclusion:  IL-1b and TNF a, pro-inflammatory cytokines closely linked to infection-associated PTB, are ET-1 dependent.  The mechanism of action of ET-1 blocking agents in tocolysis involves decreased ET-1-dependent release of these mediators.  Further evaluation of inflammatory mediators affected by ET-1 action may lead to the identification of novel targets for preventive therapy for PTB.