AUTHOR=Kettunen Sanna , Ruotsalainen Anna-Kaisa , Örd Tiit , Suoranta Tuisku , Heikkilä Janne , Kaikkonen Minna U. , Laham-Karam Nihay , Ylä-Herttuala Seppo 

TITLE=Deletion of the murine ortholog of human 9p21.3 locus promotes atherosclerosis by increasing macrophage proinflammatory activity

JOURNAL=Frontiers in Cardiovascular Medicine

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2023.1113890

DOI=10.3389/fcvm.2023.1113890

ISSN=2297-055X

ABSTRACT=<sec><title>Background</title><p>Several genome-wide association studies have reported a risk locus for coronary artery disease (CAD) in the 9p21. 3 chromosomal region. This region encodes a lncRNA in the INK4 locus (<italic>ANRIL</italic>) and its genetic variance has a strong association with CAD, but its mechanisms in atherogenesis remain unclear.</p></sec><sec><title>Objectives</title><p>This study aimed to investigate the role of the murine ortholog of human 9p21.3 locus in atherogenesis in hypercholesterolemic mice.</p></sec><sec><title>Methods</title><p>Murine 9p21.3 ortholog knockout mice (Chr4<sup>Δ70<italic>kb</italic>/Δ70<italic>kb</italic></sup>) were crossbred with <italic>Ldlr</italic><sup>−/−</sup><italic>ApoB</italic><sup>100/100</sup> mice, and atherosclerotic plaque size and morphology were analyzed on a standard or a high-fat diet (HFD). The hematopoietic cell-specific effect of Chr4<sup>Δ70<italic>kb</italic>/Δ70<italic>kb</italic></sup> on atherosclerotic plaque development was studied <italic>via</italic> bone marrow (BM) transplantation, where Chr4<sup>Δ70<italic>kb</italic>/Δ70<italic>kb</italic></sup> or wild-type BM was transplanted into <italic>Ldlr</italic><sup>−/−</sup><italic>ApoB</italic><sup>100/100</sup> mice. The role of Chr4<sup>Δ70<italic>kb</italic>/Δ70<italic>kb</italic></sup> in macrophage M1/M2 polarization was studied. In addition, single-cell sequencing data from human and mouse atheroma were analyzed to show the expression profiles of <italic>ANRIL</italic> and its murine equivalent, <italic>Ak148321</italic>, in the plaques.</p></sec><sec><title>Results</title><p>Both systemic and hematopoietic Chr4<sup>Δ70<italic>kb</italic>/Δ70<italic>kb</italic></sup> increased atherosclerosis in <italic>Ldlr</italic><sup>−/−</sup><italic>ApoB</italic><sup>100/100</sup> mice after 12 weeks of HFD. The systemic Chr4<sup>Δ70<italic>kb</italic>/Δ70<italic>kb</italic></sup> also elevated the number of circulating leukocytes. Chr4<sup>Δ70<italic>kb</italic>/Δ70<italic>kb</italic></sup> BMDMs showed enhanced M1 polarization <italic>in vitro</italic>. Single-cell sequencing data from human and mouse atheroma revealed that <italic>ANRIL</italic> and <italic>Ak148321</italic> were mainly expressed in the immune cells.</p></sec><sec><title>Conclusion</title><p>These data demonstrate that both systemic and BM-specific deletion of the murine 9p21.3 risk locus ortholog promotes atherosclerosis and regulates macrophage pro-inflammatory activity, suggesting the inflammation-driven mechanisms of the risk locus on atherogenesis.</p></sec>