Department of Pharmacology, Myometrial Function Group, University of Nevada, Reno School of Medicine, Reno, NV
Department of Pharmacology, Myometrial Function Group, University of Nevada, Reno School of Medicine, Reno, NV.
J Pharmacol Exp Ther. 2021 Mar;376(3):444-453. doi: 10.1124/jpet.120.000427. Epub 2020 Dec 31.
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 -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 -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 18-glycyrrhetinic acid (18-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 18-GA and nebivolol were coadministered at their IC 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 18-GA and nebivolol leverage dysregulated pathways in the myometrium, resulting in a novel approach for the treatment of sPTL. SIGNIFICANCE STATEMENT: 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 -nitrosation with 18-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导致自发性早产 (sPTL) 的机制。环核苷酸不是子宫静止的主要贡献者，而是一氧化氮 (NO) 介导的蛋白质 - 亚硝化为组织的松弛是必不可少的。连接蛋白-43 (Cx43) 是一种子宫肌“收缩相关蛋白”，可作为间隙连接通道或半通道 (HC) 发挥作用，是本研究的重点。蛋白质分析表明，Cx43 在 sPTL 子宫肌中下调。此外，Cx43 被 NO 亚硝化，这与磷酸化 Cx43 在丝氨酸 368 处的增加 (Cx43-pS368-间隙连接抑制) 以及 HC 开放状态概率的增加 (静止) 相关。用 18-甘草次酸 (18-GA) 抑制 Cx43 的药理作用以剂量依赖性方式对子宫肌产生负性变力作用，NO 合酶激活剂 nebivolol 也是如此，它增加总蛋白 SNOs。当 18-GA 和 nebivolol 在其 IC 值下共同给药时，对收缩动力学的影响是相加的，几乎消除了收缩。新型宫缩抑制剂的开发需要更好地理解 sPTL 的潜在机制。在这里已经表明，18-GA 和 nebivolol 利用子宫肌中失调的途径，为治疗 sPTL 提供了一种新方法。意义声明：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，这就是为什么治疗这种情况如此具有挑战性的原因。在这里，我们已经确定连接蛋白-43 (Cx43)，一种重要的收缩相关蛋白，在 sPTL 子宫肌中失调，并且 Cx43 的药理抑制及其与 18-甘草次酸和 nebivolol 的 - 亚硝化分别显着减弱人子宫组织的收缩，为经历 sPTL 的女性提供了一种利用失调途径的新型宫缩抑制剂方法。
