Novel Tocolytic Strategy: Modulating Cx43 Activity by S-Nitrosation.

Novel Tocolytic Strategy: Modulating Cx43 Activity by S-Nitrosation.

Currently available tocolytics are ineffective at significantly delaying preterm birth. This is due in part to our failure to better understand the mechanisms that drive spontaneous preterm labor (sPTL). Cyclic nucleotides are not the primary contributors to myometrial quiescence, but instead nitric oxide (NO)-mediated protein S-nitrosation (SNO) is integral to the relaxation of the tissue. Connexin-43 (Cx43), a myometrial “contractile-associated protein” that functions as either a gap junction channel or an hemichannel (HC), was the focus of this study. Protein analysis determined that Cx43 is downregulated in sPTL myometrium. Furthermore, Cx43 is S-nitrosated by NO, which correlates with an increase of phosphorylated Cx43 at serine 368 (Cx43-pS368 -gap junction inhibition) as well as an increase in the HC open-state probability (quiescence). Pharmacologic inhibition of Cx43 with 18β-glycyrrhetinic acid (18β-GA) exhibits a negative inotropic effect on the myometrium in a dose-dependent manner, as does administration of nebivolol, an NO synthase activator that increases total protein SNOs. When 18β-GA and nebivolol were coadministered at their IC50 values, the effect on contractile dynamics was additive and all but eliminated contractions. The development of new tocolytics demands a better understanding of the underlying mechanisms of sPTL. Here it has been shown that 18β-GA and nebivolol leverage dysregulated pathways in the myometrium, resulting in a novel approach for the treatment of sPTL. Although there are many known causes of preterm labor (PTL), the mechanisms of “spontaneous” PTL (sPTL) remain obfuscated, which is why treating this condition is so challenging. Here we have identified that connexin-43 (Cx43), an important contractile-associated protein, is dysregulated in sPTL myometrium and that the pharmacologic inhibition of Cx43 and its S-nitrosation with 18β-glycyrrhetinic acid and nebivolol, respectively, significantly blunts contraction in human myometrial tissue, presenting a novel approach to tocolysis that leverages maladjusted pathways in women who experience sPTL.

目前可用的宫缩抑制剂在显著延迟早产方面效果不佳。这部分是由于我们未能更好地理解驱动自发性早产（sPTL）的机制。环核苷酸不是子宫肌静止的主要因素，而一氧化氮（NO）介导的蛋白质S - 亚硝基化（SNO）对组织的松弛至关重要。连接蛋白 - 43（Cx43）是一种子宫肌“收缩相关蛋白”，可作为缝隙连接通道或半通道（HC）发挥作用，是本研究的重点。蛋白质分析确定Cx43在sPTL子宫肌中表达下调。此外，Cx43被NO进行S - 亚硝基化，这与丝氨酸368位点磷酸化的Cx43（Cx43 - pS368——缝隙连接抑制）增加以及HC开放状态概率（静止）增加相关。用18β - 甘草次酸（18β - GA）对Cx43进行药理抑制以剂量依赖的方式对子宫肌产生负性肌力作用，NO合酶激活剂奈必洛尔增加总蛋白质SNOs时也是如此。当18β - GA和奈必洛尔以其半数抑制浓度（IC50）值共同给药时，对收缩动力学的影响是累加的，并且几乎消除了收缩。新的宫缩抑制剂的研发需要更好地理解sPTL的潜在机制。在此已表明18β - GA和奈必洛尔利用了子宫肌中失调的通路，为sPTL的治疗提供了一种新方法。 尽管早产（PTL）有许多已知原因，但“自发性”PTL（sPTL）的机制仍然不清楚，这就是治疗这种疾病如此具有挑战性的原因。在此我们已经确定连接蛋白 - 43（Cx43）这一重要的收缩相关蛋白在sPTL子宫肌中失调，并且分别用18β - 甘草次酸和奈必洛尔对Cx43及其S - 亚硝基化进行药理抑制，可显著减弱人子宫肌组织的收缩，为宫缩抑制提供了一种新方法，该方法利用了发生sPTL的女性中失调的通路。