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Human Macrophage Long Intergenic Non-coding RNA, SIMALR, Suppresses Inflammatory Macrophage Apoptosis via Netrin 1

ABSTRACT: Long noncoding RNAs (lncRNAs) have emerged as novel regulators of macrophage biology and related inflammatory cardiovascular diseases. However, studies focused on lncRNAs in human macrophage subtypes, particularly human lncRNAs that are not conserved in rodents, are limited. Through RNA-seq of human monocyte-derived macrophages, we identified Suppressor of Inflammatory Macrophage Apoptosis lncRNA (SIMALR), a human macrophage-specific long intergenic noncoding RNA, to be highly induced in LPS/IFNγ-stimulated macrophages. Treatment of LPS/IFNγ stimulated THP1 human macrophages with SIMALR antisense oligonucleotides induced apoptosis of inflammatory macrophages, as shown by increased protein expression of cleaved PARP, caspase 9, caspase 3, and Annexin V+. RNA-seq of control versus SIMALR knockdown in LPS/IFNγ-stimulated human monocyte derived macrophages showed NTN1 to be significantly decreased upon SIMALR knockdown. As expected, NTN1 knockdown in LPS/IFNγ-stimulated macrophages induced apoptosis. This apoptotic phenotype was attenuated by adding recombinant NTN1 after SIMALR knockdown. Furthermore, NTN1 promoter-luciferase reporter activity was increased in HEK293T cells treated with lentiviral overexpression of SIMALR. NTN1 promoter activity is known to require HIF1α. RNA immunoprecipitation and microscopy studies suggest that SIMALR may interact with HIF1α to regulate NTN1 transcription, thereby regulating apoptosis of macrophages. In translational studies, SIMALR was found to be expressed in macrophages in human carotid atherosclerotic plaques of symptomatic patients. SIMALR is a non-conserved, human macrophage lincRNA expressed in human atherosclerosis that regulates macrophage apoptosis. SIMALR partners with HIF1α to regulate NTN1, which is a known macrophage survival factor. This work illustrates the importance of interrogating the functions of non-conserved human lincRNAs and exploring their translational and therapeutic potential in human atherosclerosis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE212381 | GEO | 2022/11/23

REPOSITORIES: GEO

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Project description:Through deep RNA-seq of human monocyte-derived macrophages, we identified RP11-184M15.1, a human macrophage-specific lincRNA, to be highly induced in the cytoplasm of IL-4-stimulated macrophage. Preliminary data showed that treatment of IL-4-stimulated THP1 human macrophages with RP11-184M15.1 small interfering RNA (siRNA) repressed apoptosis of resolving macrophages, as shown by decreased Annexin V+ macrophages, and reduced protein expression of cleaved PARP. Biotinylated RP11-184M15.1 pulldown coupled with mass spectrometry indicated an interaction between RP11-184M15.1 and zinc finger RNA-binding protein (ZFR). RIP corroborated the proposed interaction between RP11-184M15.1 and ZFR. RNAInter revealed mRNAs predicted to interact with ZFR, and some of those genes (e.g., ALYREF, CCNYL1) were also differentially expressed in RNA-seq data of control versus RP11-184M15.1 knockdown in IL-4-stimulated THP1 macrophages. qPCR validated that ALYREF and CCNYL1 expression are reduced with RP11-184M15.1 knockdown. In contrast, with ZFR siRNA, ALYREF and CCNYL1 mRNA expressions were elevated. Thus, a hypothesis to be further tested is that RP11-184M15.1 interacts with ZFR to regulate mRNA stability in IL-4-stimulated macrophages. Nuclear RNA export factor 1 (NXF1) was also validated by RIP to interact with RP11-184M15.1. NXF1 is a known interacting partner of ALYREF in the transcription-export (TREX) complex. With RP11-184M15.1 knockdown, the protein level of ALYREF decreased, and Ingenuity Pathway Analysis (IPA) of RNA-seq data of control versus RP11-184M15.1 knockdown revealed that THO complex subunit 5 homolog (THOC5), another component of the TREX complex, may be an upstream regulator. In addition, past studies have revealed that ALYREF and NXF1 are involved in nuclear export of inflammatory mRNAs and proinflammatory macrophage phenotype, respectively. With RP11-184M15.1 knockdown, there was decreased expression of inflammatory macrophage-associated genes. It may be possible that RP11-184M15.1 functions in mRNA export, along with NXF1 and ALYREF.

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Human Macrophage Long Intergenic Non-coding RNA, SIMALR, Suppresses Inflammatory Macrophage Apoptosis via Netrin 1

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