Decidual macrophages participate in immune regulation at the maternal–fetal interface. Abnormal M1/M2 polarization of decidual macrophages might predispose immune maladaptation in recurrent pregnancy loss (RPL). However, the mechanism of decidual macrophage polarization is unclear. We explored the role of Estradiol (E2)-sensitive serum-glucocorticoid regulated kinase (SGK) 1 in promoting macrophage polarization and suppressing inflammation at the maternal–fetal interface. We assessed serum levels of E2 and progesterone during first trimester of pregnancy in women with or without threatened miscarriages (ended in live birth, n = 448; or early miscarriages, n = 68). For detection of SGK1 in decidual macrophages, we performed immunofluorescence labeling and western blot analysis applying decidual samples from RPL (n = 93) and early normal pregnancy (n = 66). Human monocytic THP-1 cells were differentiated into macrophages and treated with Toll-like receptor (TLR) 4 ligand lipopolysaccharide (LPS), E2, inhibitors or siRNA for in vitro analysis. Flow cytometry analysis were conducted to detect macrophages polarization. We also applied ovariectomized (OVX) mice with hormones exploring the mechanisms underlying the regulation of SGK1 activation by E2 in the decidual macrophages in vivo. SGK1 expression down regulation in the decidual macrophages of RPL was consistent with the lower concentration and slower increment of serum E2 from 4 to 12 weeks of gestation seen in these compromised pregnancies. LPS reduced SGK1 activities, but induced the pro-inflammatory M1 phenotype of THP-1 monocyte-derived macrophages and T helper (Th) 1 cytokines that favored pregnancy loss. E2 pretreatment promoted SGK1 activation in the decidual macrophages of OVX mice in vivo. E2 pretreatment amplified SGK1 activation in TLR4-stimulated THP-1 macrophages in vitro through the estrogen receptor beta (ERβ) and PI3K pathway. E2-sensitive activation of SGK1 increased M2 macrophages and Th2 immune responses, which were beneficial to successful pregnancy, by inducing ARG1 and IRF4 transcription, which are implicated in normal pregnancy. The experiments on OVX mice have shown that pharmacological inhibition of E2 promoted nuclear translocation of NF-κB in the decidual macrophages. Further more, pharmacological inhibition or knockdown of SGK1 in TLR4-stimulated THP-1 macrophages activated NF-κB by promoting its nuclear translocation, leading to increased secretion of pro-inflammatory cytokines involved in pregnancy loss. Our findings highlighted the immunomodulatory roles of E2-activated SGK1 in Th2 immune responses by priming anti-inflammatory M2 macrophages at the maternal–fetal interface, resulting in a balanced immune microenvironment during pregnancy. Our results suggest new perspectives on future preventative strategies for RPL.

中文翻译：

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SGK1 的雌激素敏感性激活诱导具有抗炎特性的 M2 巨噬细胞和母胎界面的 Th2 反应

蜕膜巨噬细胞参与母胎界面的免疫调节。蜕膜巨噬细胞异常的 M1/M2 极化可能导致复发性流产 (RPL) 中的免疫适应不良。然而，蜕膜巨噬细胞极化的机制尚不清楚。我们探讨了雌二醇 (E2) 敏感性血清糖皮质激素调节激酶 (SGK) 1 在促进巨噬细胞极化和抑制母胎界面炎症方面的作用。我们评估了有或没有先兆流产（以活产结束，n = 448；或早期流产，n = 68）的妇女在妊娠早期的血清 E2 和黄体酮水平。用于检测蜕膜巨噬细胞中的 SGK1，我们应用来自 RPL (n = 93) 和早期正常妊娠 (n = 66) 的蜕膜样本进行了免疫荧光标记和蛋白质印迹分析。人单核细胞 THP-1 细胞分化为巨噬细胞，并用 Toll 样受体 (TLR) 4 配体脂多糖 (LPS)、E2、抑制剂或 siRNA 进行处理以进行体外分析。进行流式细胞术分析以检测巨噬细胞极化。我们还对去卵巢 (OVX) 小鼠应用激素，探索体内蜕膜巨噬细胞中 E2 调节 SGK1 激活的潜在机制。RPL 蜕膜巨噬细胞中的 SGK1 表达下调与这些受损妊娠中所见的妊娠 4 至 12 周血清 E2 浓度较低和增量较慢一致。LPS 减少 SGK1 活动，但诱导了 THP-1 单核细胞衍生的巨噬细胞和 T 辅助 (Th)1 细胞因子的促炎 M1 表型，这些细胞因子有利于流产。E2 预处理促进了体内 OVX 小鼠蜕膜巨噬细胞中 SGK1 的激活。E2 预处理通过雌激素受体 β (ERβ) 和 PI3K 通路在体外增强了 TLR4 刺激的 THP-1 巨噬细胞中 SGK1 的激活。SGK1 的 E2 敏感性激活通过诱导与正常妊娠有关的 ARG1 和 IRF4 转录，增加了 M2 巨噬细胞和 Th2 免疫反应，这有利于成功妊娠。OVX 小鼠的实验表明，E2 的药理学抑制促进了蜕膜巨噬细胞中 NF-κB 的核转位。此外，TLR4 刺激的 THP-1 巨噬细胞中 SGK1 的药理学抑制或敲低通过促进其核转位激活 NF-κB，导致促炎细胞因子分泌增加，从而导致流产。我们的研究结果强调了 E2 激活的 SGK1 在 Th2 免疫反应中的免疫调节作用，通过在母胎界面启动抗炎 M2 巨噬细胞，从而在怀孕期间形成平衡的免疫微环境。我们的结果为 RPL 的未来预防策略提出了新的观点。从而在怀孕期间形成平衡的免疫微环境。我们的结果为 RPL 的未来预防策略提出了新的观点。从而在怀孕期间形成平衡的免疫微环境。我们的结果为 RPL 的未来预防策略提出了新的观点。