Estrogen-sensitive activation of SGK1 induces M2 macrophages with anti-inflammatory properties and a Th2 response at the maternal–fetal interface

Abstract

Background 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. Methods 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. Results 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. Conclusion 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.

Imbalance polarization of M1/M2 macrophages in miscarried uterus

“…Some research found that LPS can exert an impact on the differentiation of monocytes to macrophages. Th1 cytokine, like LPS and IFN-ϒ induces monocyte differentiation to M1 macrophage [ 34 , 41 , 42 ]; Th2 cytokine, like IL-10, IL-4, IL-13 can induce monocyte differentiation to M2 macrophage [ 8 , 22 , 43 , 44 ].…”

“…Many research have found that the balance of M1/M2 macrophage proportion in the uterus significantly impacts early pregnancy [ 18 , 19 ]. M1 macrophages induce pro-inflammatory response and host defense upon uteroplacental infection; M2 macrophages take up to 50% of total macrophages in early to mid-pregnancy uterus and are thought to exert immunosuppressive effect and mediate fetal-maternal immune tolerance [ 5 , 20 – 22 ]. Successful pregnancy needs to keep a proper percentage of M1 and M2 macrophage in the uterus.…”

Untargeted metabolomics analysis reveals the metabolic disturbances and exacerbation of oxidative stress in recurrent spontaneous abortion

“…M1 macrophages, characterized by classical activation, exhibit reduced susceptibility to glutamate metabolism [ 32 ]. Upon activation, these macrophages promptly initiate a proinflammatory response to the occurrence of reproductive system-associated events by detecting microbial components, including signaling lipoprotein, and damaged-associated molecular patterns that are released from shed abortive material resulting from sudden symptoms of miscarriage [ 33 ]. Additionally, M1 macrophages are closely linked to organism metabolism [ 34 ], as they rely on aerobic glycolysis to generate ATP, which leads to increased glucose and glutamine consumption while simultaneously inhibiting metabolism.…”

The role of serum-glucocorticoid regulated kinase 1 in reproductive viability: implications from prenatal programming and senescence

“…Studies have shown that SGK1 localizes to the acrosome during the course of epididymal maturation, and could be involved in endowing sperm with basal motility by phosphorylating and inactivating of glycogen synthase kinase 3 (GSK3) [ 55 ] and downregulating the abundance of β-catenin protein in the BTB [ 57 ]. Other studies have shown that SGK1 promotes the proliferation and anti-apoptosis of immature SCs [ 58 ] through PI3K, PDK1, AKT signaling pathways [ 59 , 60 ], regulates the protein synthesis and cytoskeleton of mature SCs to change the structure of BTB [ 60 ], and promotes spermatogenesis. In addition, SGK1 highlights the role of FoxO3a in regulating oxidative stress [ 61 ], which can damage BTB by destroying BTB-associated junction proteins and inducing apoptosis of Sertoli cells, leading to testicular damage and spermatogenesis disorders [ 62 ], which could lead to male infertility [ 63 ].…”