Novel Tocolytic Strategy: Modulating Cx43 Activity by S-Nitrosation

Area of Science:

• Reproductive biology
• Pharmacology
• Cellular signaling

Background:

• Current tocolytics are largely ineffective for delaying preterm birth.
• Understanding the mechanisms of spontaneous preterm labor (sPTL) is crucial for developing new treatments.
• Nitric oxide (NO)-mediated protein S-nitrosation (SNO) is key to myometrial relaxation, not cyclic nucleotides.

Purpose of the Study:

• To investigate the role of connexin-43 (Cx43) in spontaneous preterm labor (sPTL).
• To determine if Cx43 S-nitrosation by NO influences myometrial contractility.
• To evaluate the potential of Cx43 inhibition and NO-mediated SNO as a novel tocolytic strategy.

Main Methods:

• Protein analysis of human myometrium from sPTL cases.
• Assessment of Cx43 S-nitrosation and phosphorylation.
• Pharmacologic inhibition of Cx43 using 18β-glycyrrhetinic acid (18β-GA).
• Activation of NO synthase with nebivolol.
• Evaluation of contractile dynamics in myometrial tissue.

Main Results:

• Cx43 is downregulated in sPTL myometrium.
• NO-mediated S-nitrosation of Cx43 correlates with increased Cx43 phosphorylation (inhibiting gap junctions) and increased hemichannel (HC) open-state probability (promoting quiescence).
• Pharmacologic inhibition of Cx43 with 18β-GA and NO synthase activation with nebivolol individually reduced myometrial contractility.
• Co-administration of 18β-GA and nebivolol additively reduced contractions, nearly eliminating them.

Conclusions:

• Cx43 is a critical contractile-associated protein dysregulated in sPTL.
• NO-mediated S-nitrosation of Cx43 plays a significant role in myometrial quiescence.
• Targeting Cx43 and its S-nitrosation with 18β-GA and nebivolol presents a novel therapeutic approach for sPTL.