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Apoptotic bodies unleash functional CXCL12 expression through microRNA-126

ABSTRACT: Apoptosis plays a pivotal role in embryogenesis and postnatal cell homeostasis, involving DNA or subcellular fragmentation, and shedding of small membranous microvesicles termed apoptotic bodies (AB). Following DNA damage, hypoxia, or vascular injury, the chemokine CXCL12 has been implicated in the recruitment of progenitor cells for tissue regeneration through its receptor CXCR4 and in mechanisms counteracting apoptosis. Whether AB deliver alarm signals for regenerative responses to neighbouring cells beyond recruitment or eat-me signals for phagocytes and relevance to diseases with abundant apoptosis, eg atherosclerosis, remains unknown. Here we show that endothelial cell-derived AB are generated during diet-induced atherosclerosis and can be transferred to recipient endothelial or smooth muscle cells to induce functional expression of CXCL12. This is mediated through miRNA-126 enriched in AB, which acts by silencing RGS16 translation and unlocking CXCR4 to unleash an auto-regulatory feedback loop inducing CXCL12. Injection of AB promoted mobilization and incorporation of progenitor cells, reducing diet-induced atherosclerosis in apolipoprotein E-deficient mice, and local transfer of microRNA-126 inhibited collar-induced arterial plaque formation. This was associated with increased smooth muscle content but decreased macrophage and apoptotic cell content, all features of plaque stability. Our data identify a new mechanism, by which AB confer microRNA-126 as a paracrine alarm messenger to enhance CXCR4 signals and CXCL12 expression, thereby limiting or repairing vascular damage. This adds to the important functions of microRNAs in health and disease and may extend to progenitor cell recruitment during other forms of tissue repair or homeostasis.

ORGANISM(S): Mus musculus Rattus norvegicus Homo sapiens

PROVIDER: GSE12696 | GEO | 2010/08/31

SECONDARY ACCESSION(S): PRJNA112707

REPOSITORIES: GEO

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Project description:Apoptosis plays a pivotal role in embryogenesis and postnatal cell homeostasis, involving DNA or subcellular fragmentation, and shedding of small membranous microvesicles termed apoptotic bodies (AB). Following DNA damage, hypoxia, or vascular injury, the chemokine CXCL12 has been implicated in the recruitment of progenitor cells for tissue regeneration through its receptor CXCR4 and in mechanisms counteracting apoptosis. Whether AB deliver alarm signals for regenerative responses to neighbouring cells beyond recruitment or eat-me signals for phagocytes and relevance to diseases with abundant apoptosis, eg atherosclerosis, remains unknown. Here we show that endothelial cell-derived AB are generated during diet-induced atherosclerosis and can be transferred to recipient endothelial or smooth muscle cells to induce functional expression of CXCL12. This is mediated through miRNA-126 enriched in AB, which acts by silencing RGS16 translation and unlocking CXCR4 to unleash an auto-regulatory feedback loop inducing CXCL12. Injection of AB promoted mobilization and incorporation of progenitor cells, reducing diet-induced atherosclerosis in apolipoprotein E-deficient mice, and local transfer of microRNA-126 inhibited collar-induced arterial plaque formation. This was associated with increased smooth muscle content but decreased macrophage and apoptotic cell content, all features of plaque stability. Our data identify a new mechanism, by which AB confer microRNA-126 as a paracrine alarm messenger to enhance CXCR4 signals and CXCL12 expression, thereby limiting or repairing vascular damage. This adds to the important functions of microRNAs in health and disease and may extend to progenitor cell recruitment during other forms of tissue repair or homeostasis. AB were isolated from supernatants of apoptotic, serum-starved human umbilical vein endothelial cells (HUVECs) by sequential centrifugation steps. Total RNA was isolated from AB or HUVECs and microRNA was purified using the mirVanaTM miRNA Isolation Kit (Ambion). microRNA obtained from 10 µg of total RNA was labeled using the mirVanaTM miRNA Labeling Kit (Ambion) and fluorescent Cy3 (Molecular Probes), and hybridized to the Ambion mirVanaTM miRNA Bioarray (1566 v.1). Hybridized mirVana miRNA Bioarrays were scanned and quantified by using ImaGene 5.5.4 (Bio Discovery). Resulted signal intensities were background corrected and then normalized using variance stabilization normalization. (Huber, 2002).

Project description:Nathaniel L. Coggins, Danielle Trakimas, S. Laura Chang, Anna Ehrlich, Paramita Ray, Kathryn E. Luker, Jennifer J. Linderman & Gary D. Luker. CXCR7 controls competition for recruitment of β-arrestin 2 in cells expressing both CXCR4 and CXCR7. PLoS ONE 9, 6 (2014). Chemokine CXCL12 promotes growth and metastasis of more than 20 different human cancers, as well as pathogenesis of other common diseases. CXCL12 binds two different receptors, CXCR4 and CXCR7, both of which recruit and signal through the cytosolic adapter protein β-arrestin 2. Differences in CXCL12-dependent recruitment of β-arrestin 2 in cells expressing one or both receptors remain poorly defined. To quantitatively investigate parameters controlling association of β-arrestin 2 with CXCR4 or CXCR7 in cells co-expressing both receptors, we used a systems biology approach combining real-time, multi-spectral luciferase complementation imaging with computational modeling. Cells expressing only CXCR4 maintain low basal association with β-arrestin 2, and CXCL12 induces a rapid, transient increase in this interaction. In contrast, cells expressing only CXCR7 have higher basal association with β-arrestin 2 and exhibit more gradual, prolonged recruitment of β-arrestin 2 in response to CXCL12. We developed and fit a data-driven computational model for association of either CXCR4 or CXCR7 with β-arrestin 2 in cells expressing only one type of receptor. We then experimentally validated model predictions that co-expression of CXCR4 and CXCR7 on the same cell substantially decreases both the magnitude and duration of CXCL12-regulated recruitment of β-arrestin 2 to CXCR4. Co-expression of both receptors on the same cell only minimally alters recruitment of β-arrestin 2 to CXCR7. In silico experiments also identified β-arrestin 2 as a limiting factor in cells expressing both receptors, establishing that CXCR7 wins the "competition" with CXCR4 for CXCL12 and recruitment of β-arrestin 2. These results reveal how competition for β-arrestin 2 controls integrated responses to CXCL12 in cells expressing both CXCR4 and CXCR7. These results advance understanding of normal and pathologic functions of CXCL12, which is critical for developing effective strategies to target these pathways therapeutically.

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Apoptotic bodies unleash functional CXCL12 expression through microRNA-126

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