The enhancer RNA lnc-SLC4A1-1 epigenetically regulates unexplained recurrent pregnancy loss (URPL) by activating CXCL8 and NF-kB pathway

Backgrounds: Enhancer RNAs (eRNAs) are subsets of lncRNAs and transcribed from enhancers, whose regulatory effects on gene expressions are an emerging area of interest. However, the roles of eRNAs in regulating the trophoblates and unexplained recurrent pregnancy loss (URPL), still remain elusive. Methods: We profiled eRNAs in the villus tissues from URPL patients and matched normal controls by RNA-seq and VISTA Enhancer Browser. Results: We identified lnc-SLC4A1-1, which was transcribed from an active enhancer marked with H3K27ac and H3K4me1 and so-called eRNA, highly expressed in villus of URPL patients. Gain-of-function experiments indicated that lnc-SLC4A1-1 facilitated the trophoblast cells migration and apoptosis. Mechanistically, as eRNAs, lnc-SLC4A1-1 retained in the nuclei and recruited transcription factor NF-κB to bind to CXCL8, resulting in increased H3K27ac in CXCL8 promoter and subsequent elevation of CXCL8 expression. Activation of CXCL8 exacerbated inflammatory reactions in trophoblast cells by inducing TNF-α and IL-1β, whose effects could be blocked by antagonist of lnc-SLC4A1-1. Interpretation: Therefore, these findings indicate that as an eRNA, lncSLC4A1-1 alters trophoblast functions through activation of immune responses and regulating NF-κB/CXCL8 axis. Our study provides new insights in understanding the lncRNA/eRNA's functions in pathological pregnancy, potentially informing on therapeutic strategies for URPL. Funding Statement: This work was supported by the National Natural Science Foundation of China (81671461, 81402706 and 81630085), National Key Research and Development Program (2016YFC1000207) and the Priority Academic Program for the Development of Jiangsu Higher Education Institutions (Public Health and Preventive Medicine). Declaration of Interests: The authors state: "None declared." Ethics Approval Statement: This study was approved by the Institutional Ethics Committee of Nanjing Medical University. All activities involved in this study were done under full compliance with government policies and the Helsinki Declaration. All experiments protocol was approved by the Institutional Review Board of Nanjing Medical University prior to the study.