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Hypoxia Sensing in Resident Cardiac Macrophages Regulates Monocyte Fate Specification following Ischemic Heart Injury

ABSTRACT: Myocardial infarction initiates cardiac remodeling and is central to heart failure pathogenesis. Following myocardial ischemia reperfusion injury, monocytes enter the heart and differentiate into diverse subpopulations of macrophages. The mechanisms and dynamics of monocyte differentiation within this context are unknown. We investigated the role of macrophage hypoxia sensing on monocyte differentiation following reperfused myocardial infarction. We show that deletion of Hif1α, a hypoxia response transcription factor, in resident cardiac macrophages led to increased remodeling and overrepresentation of a macrophage subset marked by arginase 1 (Arg1) expression. Arg1+ macrophages displayed an inflammatory gene signature and were predicted to represent an intermediate state within the monocyte differentiation cascade. Lineage tracing of Arg1+ macrophages revealed the existence of a monocyte differentiation trajectory consisting of multiple transcriptionally distinct macrophage states. We further showed that deletion of Hif1α in resident cardiac macrophages resulted in arrested progression through this trajectory and accumulation of an inflammatory intermediate state marked by persistent Arg1 expression. Depletion of the Arg1+ trajectory also results in increased heart remodeling following ischemic injury, likely due to the beneficial effects of macrophages downstream of Arg1+ macrophage differentiation. Collectively, our findings unveil distinct trajectories of monocyte differentiation and identify hypoxia sensing as an important determinant of monocyte differentiation following myocardial infarction.

ORGANISM(S): Mus musculus

PROVIDER: GSE251991 | GEO | 2024/09/02

REPOSITORIES: GEO

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Project description: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.

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Hypoxia Sensing in Resident Cardiac Macrophages Regulates Monocyte Fate Specification following Ischemic Heart Injury

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