Caractérisation du rôle du neuromédine U récepteur 2 dans le déclenchement du travail préterme et développement de modulateurs peptidiques de son activité utérotonique pour prévenir la naissance prématurée

Seventy-five percent of preterm births are due to preterm labor in which myometrial contractions are caused by uterine activation proteins, more expressed in an inflammatory context. Moreover, being born premature highly increase risks of neonatal mortality and morbidities and/or long-term complications. For now, the pharmacological options mostly used in clinic are the ones that preserve or induce the quiescence of the uterus. However, tocolytics (agents inhibiting contractions) are not efficient enough to prolong gestation for more than 48 hours and induce numerous maternal and fetal side effects. We recently discovered that neuropeptides called neuromedins U (NmU) and S (NmS) favor uterine contractions by inducing intracellular calcium release via the neuromedin U receptor 2 (NmUR2). We wanted to elucidate the implication of this pro-contractile system in the onset of term and preterm uterine labor as well as the mechanism of action of NmU-R2 in murine myometrial myocytes. We also characterized five small antagonist peptides against NmU-R2, designed in our laboratory, in order to select the best candidate for the development of a new tocolytic. Until now, our data show that: 1) NmU and NmS induce uterine contraction ex vivo, uterine labor in vivo and intracellular calcium release in vitro in a dose-dependant, gestational age-dependant and NmU-R2-dependant manner; 2) a transient activation (5-15 minutes) of Akt and Erk1/2 occurs after in vitro stimulation with NmU or NmS; 3) p38, JNK, c-jun are not involved in the signaling pathway of NmU-R2; 4) the knockdown of NmU-R2 significantly inhibits Akt and Erk1/2 activation and considerably reduce the intracellular calcium release, showing that these effects induced by NmU and NmS are NmU-R2-dependant; 5) the signaling of NmU-R2 is exclusive to the end of the gestation as we approach uterine labor; 6) peptide 5 inhibits uterine contraction ex vivo (40-50% inhibition); 7) these uterine contractions are not inhibited by the scrambled peptide; 8) peptides 4 and 5 inhibit the intracellular calcium release in a dose-dependant manner (IC50 of the dose-response curve for peptide 5: 23nM); 9) the phosphorylation of Akt (but not of Erk1/2) is inhibited in a dose-dependant manner by peptide 5. Therefore, our results suggest that NmU-R2 plays a role in the uterine contraction, in the induction of preterm labor associated with infection and that its signaling activates Erk1/2, Akt and the calcium release in myometrial myocytes within term uterus. In addition, peptide 5 possesses antagonist properties against NmU-R2, suggesting it as the best candidate for a potential tocolytic agent targeting NmU-R2 to prevent preterm labor. In the near future, it is planned to continue the characterization of the anti-NmU-R2 candidate peptide in order to pursue the development of the molecule and find a new potential therapy to prevent premature birth.

Keyphrases: Contraction, Calcium, NmU-R2, Neuromedin U, Neuromedin S, Contraction, Calcium, Uterine labor, Preterm labor, Prematurity, Tocolytic, Pregnancy