Decidualization of the endometrial stroma is an essential differentiation process for embryo implantation and maintenance of pregnancy. We previously reported that protein phosphatase 2A (PP2A) acts as a key mediator during cAMP‐induced decidualization of human endometrial stromal cells (hESCs). However, the mechanism underlying its activation has remained obscure in hESCs. In the present study, we aimed to reveal the mechanism that induces the nitration of PP2A catalytic subunit (PP2Ac) during cAMP‐induced decidualization of hESCs. First, cAMP‐induced PP2Ac nitration was significantly repressed using L‐NAME, an inhibitor of nitric oxide synthase (NOS). Among several NOS isoforms, only inducible NOS (iNOS) was highly expressed in hESCs, indicating that iNOS directly induces the nitration of PP2Ac. Second, cAMP‐induced iNOS expression and PP2Ac nitration were decreased by treatment with TSA, an inhibitor of histone deacetylase 5 (HDAC5). cAMP‐induced phosphorylation of CaMKII and HDAC5 was suppressed by treatment with U73122 (an inhibitor of phospholipase C) or transfection of PLCε siRNA. Finally, small G protein Rap1 and its guanine nucleotide exchange factor Epac1 were found to be involved in cAMP‐induced PP2A activation. Taken together, our results suggest that PP2Ac nitration during cAMP‐induced decidualization of hESCs is induced through the Epac1‐Rap1‐PLCε‐CaMKII‐HDAC5‐iNOS signaling pathway.

中文翻译：

---

人子宫内膜基质细胞蜕膜化过程中通过 Epac1/PLCε/CaMKII/HDAC5/iNOS 级联反应增加蛋白磷酸酶 2A 的硝化作用

子宫内膜间质的蜕膜化是胚胎植入和妊娠维持的重要分化过程。我们之前报道过，蛋白磷酸酶 2A (PP2A) 在 cAMP 诱导的人子宫内膜基质细胞 (hESC) 蜕膜化过程中充当关键介质。然而，其激活的机制在 hESC 中仍然不清楚。在本研究中，我们旨在揭示在 cAMP 诱导的 hESC 蜕膜化过程中诱导 PP2A 催化亚基 (PP2Ac) 硝化的机制。首先，使用一氧化氮合酶 (NOS) 抑制剂 L-NAME 显着抑制了 cAMP 诱导的 PP2Ac 硝化。在几种 NOS 亚型中，只有诱导型 NOS (iNOS) 在 hESC 中高表达，表明 iNOS 直接诱导 PP2Ac 的硝化。第二，通过用组蛋白去乙酰化酶 5 (HDAC5) 抑制剂 TSA 处理，cAMP 诱导的 iNOS 表达和 PP2Ac 硝化降低。cAMP 诱导的 CaMKII 和 HDAC5 磷酸化被 U73122（一种磷脂酶 C 抑制剂）处理或转染 PLCε siRNA 所抑制。最后，发现小 G 蛋白 Rap1 及其鸟嘌呤核苷酸交换因子 Epac1 参与了 cAMP 诱导的 PP2A 激活。总之，我们的结果表明，cAMP 诱导的 hESC 蜕膜过程中的 PP2Ac 硝化是通过 Epac1-Rap1-PLCε-CaMKII-HDAC5-iNOS 信号通路诱导的。发现小 G 蛋白 Rap1 及其鸟嘌呤核苷酸交换因子 Epac1 参与 cAMP 诱导的 PP2A 激活。总之，我们的结果表明，cAMP 诱导的 hESC 蜕膜过程中的 PP2Ac 硝化是通过 Epac1-Rap1-PLCε-CaMKII-HDAC5-iNOS 信号通路诱导的。发现小 G 蛋白 Rap1 及其鸟嘌呤核苷酸交换因子 Epac1 参与 cAMP 诱导的 PP2A 激活。总之，我们的结果表明，cAMP 诱导的 hESC 蜕膜过程中的 PP2Ac 硝化是通过 Epac1-Rap1-PLCε-CaMKII-HDAC5-iNOS 信号通路诱导的。