A novel mechanism for inflammation-induced preterm birth via PR-A phosphorylation

早产（PTB）影响美国10-15%的怀孕，并导致大多数新生儿死亡和发病。为了预防PTB，需要更清楚地了解人类分娩的激素控制。在这方面，类固醇激素黄体酮（P4）通过核P4受体（PR）异构体PR- a和PR- b起作用，是一个关键因素。在大多数妊娠期，P4/PR可促进子宫静止，阻滞产程，P4/PR信号中断可触发分娩。然而，这些关键的P4/PR作用的机制尚不清楚。子宫和妊娠组织的感染/炎症是足月和早产的主要驱动因素，但这些影响的机制也不确定。我们提出的研究通过探索一种通过PR- a磷酸化形式连接炎症和肌内膜细胞P4/PR信号的机制来解决这些主要的知识空白，我们假设PR- a在炎症诱导分娩的因果途径中起核心作用。我们发表的初步数据表明，P4/PR-B通过与il -1ß-应答基因子集启动子上的激活蛋白1 （AP-1）转录因子相互作用并抑制其转录活性，从而抑制肌内膜细胞对促炎刺激的反应性。我们的数据还表明，丝氨酸344/345位点磷酸化的P4/PR-A （pSer344/345-PRA）与AP-1相互作用，破坏P4/PR-B的抗炎活性。我们还发现，在促炎刺激下，肌内膜细胞中pSer344/345-PRA的产生是由丝裂原活化蛋白激酶（MAPKs）催化的。基于这些数据，我们假设：1)P4/PR-B通过与AP-1结合抑制炎症基因启动子亚群的转录，在肌内膜细胞中发挥抗炎活性；2) pSer344/345-PRA通过破坏PR-B/AP-1相互作用抑制P4/PR-B的抗炎活性，3)在促炎症刺激下，肌层细胞中pSer344/345-PRA的产生是由特异性MAPKs催化的。这一假设将在人类子宫肌瘤细胞系和从剖腹产分娩中获得的人类子宫肌瘤以及恒河猴和小鼠炎症诱导分娩模型中进行验证。具体目标1：确定P4/PR-B在肌内膜细胞中发挥抗炎活性的机制，以及pSer344/345-PRA如何影响这种活性；特异性目的2：确定pSer344/345- PRA在子宫肌瘤细胞中的生成是如何被控制的。该研究具有开创性和创新性，将促进对人类分娩基础生物学的理解，并有助于开发基于P4/ pr的有效抗炎疗法，以促进子宫静止和预防早产。

Preterm birth (PTB) affects 10-15% of pregnancies in the US and causes the majority of neonatal mortality and morbidity. To prevent PTB a clearer understanding is needed of the hormonal control of human parturition. In this regard, the steroid hormone progesterone (P4) acting via the nuclear P4 receptor (PR) isoforms, PR-A and PR-B, is a critical factor. For most of pregnancy P4/PR promotes uterine quiescence and blocks labor, and disruption of P4/PR signaling triggers parturition. The mechanism for these critical P4/PR actions are, however, unclear. Infection/inflammation in the uterine and gestational tissues are major drivers of term and preterm parturition, but the mechanism for these effects are also uncertain. The proposed research addresses these major knowledge gaps by exploring a mechanism linking inflammation and P4/PR signaling in myometrial cells via a phosphorylated form of PR-A that we hypothesize plays a central role in the causal pathway for inflammation-induced parturition. Our published and preliminary data suggest that P4/PR-B inhibits myometrial cell responsiveness to pro-inflammatory stimuli by interacting with and repressing the transcriptional activity of the activator protein 1 (AP-1) transcription factors at promotors of a subset of IL-1ß-responsive genes. Our data also suggest that P4/PR-A upon phosphorylation at the serine-344/345 locus (pSer344/345-PRA) interacts with AP-1 to disrupt P4/PR-B anti-inflammatory activity. We also found that generation of pSer344/345-PRA in myometrial cells is catalyzed by mitogen activated protein kinases (MAPKs) in response to pro-inflammatory stimuli. Based on those data we hypothesize that: 1) P4/PR-B exerts anti-inflammatory activity in myometrial cells by binding to AP-1 to inhibit transcription at a subset of inflammatory gene promoters; 2) pSer344/345-PRA inhibits P4/PR-B anti-inflammatory activity by disrupting the PR-B/AP-1 interaction, and 3) generation of pSer344/345-PRA in myometrial cells is catalyzed by specific MAPKs in response to pro-inflammation stimuli. This hypothesis will be tested in human myometrial cell lines and human myometrium obtained from c-section deliveries, and Rhesus macaque and mouse models of inflammation induced parturition. Two Specific Aims will be achieved: Specific Aim 1: Determine the mechanism by which P4/PR-B exerts anti-inflammatory activity in myometrial cells and how this is affected by pSer344/345-PRA; and Specific Aim 2: Determine how pSer344/345- PRA generation is controlled in myometrial cells. The proposed research is novel and groundbreaking and will advance understanding of the fundamental biology of human parturition and contribute to the development of effective P4/PR-based anti-inflammatory therapies to promote uterine quiescence and prevent preterm birth.