IL-18 inhibition enlarges lesions, necrotic cores and thickens fibrous caps in Jak2V617F clonal hematopoiesis-driven atherosclerosis.

BackgroundInflammasome activation promotes atherosclerosis in clonal hematopoiesis (CH). Active inflammasomes secrete both IL-1{beta} and IL-18. Plasma IL-18 levels are elevated in Jak2VFCH. Genetic deficiency of IL-18 has been shown to reduce atherosclerosis in non-CH murine models. However, whether IL-18 inhibition promotes atherosclerosis in control or Jak2VF CH is unknown. Methods and resultsLdlr-/- mice were transplanted with bone marrow (BM) from Mx1-cre Jak2VF (20%) and wild-type (80%) mice or with control BM, fed a Western-type diet (WTD) for 8, 10 or 16 weeks and administered control or IL-18 IgG from 4 weeks onwards. IL-18 antibody treatment increased plaque collagen content and cap thickness. Unexpectedly, IL-18 antibody treatment increased the size of early lesions and promoted formation of advanced lesions with large necrotic cores in Jak2VF CH mice. IL-18 antibody treatment was associated with diminished interferon (IFN)-{gamma} and AIM2 levels and reduced macrophage pyroptosis especially in Jak2VF CH mice. However, IL-18 antibodies increased cleaved Caspase-3 and TUNEL+ macrophages (indicating increased apoptosis) and reduced efferocytosis. Sc-RNA-seq analysis showed that IL-18 antibody treatment reduced expression of MHC class II genes, a marker of IFN-{gamma} signaling, and of genes mediating efferocytosis (Mertk and Axl), in resident-like macrophage subpopulations in Jak2VF CH mice. Consistently, IFN-{gamma} injection increased Axl and Mertk expression in resident peritoneal macrophages. ConclusionsDespite improvements in collagen and fibrous cap thickness in Jak2VF CH mice, IL-18 antibody treatment increased advanced necrotic lesions, reflecting a shift from pyroptotic to apoptotic cell death coupled with defective efferocytosis, events which were coordinated by reduced IFN-{gamma} signaling. These findings indicate a mixed atherosclerosis phenotype resulting from IL-18 inhibition, advocating for alternative therapeutic strategies. Inhibition of IL-18 has been considered as a novel therapeutic approach to reduce atherosclerosis and stabilize atherosclerotic plaques. We show that IL-18 antibodies have adverse effects on atherosclerotic lesional necrosis, calling this approach into question. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=169 SRC="FIGDIR/small/657754v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@a93b2forg.highwire.dtl.DTLVardef@6cc057org.highwire.dtl.DTLVardef@1c7afc5org.highwire.dtl.DTLVardef@e4da82_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIInflammasome activation produces active IL-1 and IL-18 and worsens atherosclerosis in clonal hematopoiesis (CH) however the contribution of IL-18 is unknown. C_LIO_LIAntibody inhibition of IL-18 increased plaque collagen but also increased early lesion area and late lesions with large necrotic cores in Jak2VF CH mice. C_LIO_LIThere was a reversal of AIM2 inflammasome activation but a switch to apoptosis which along with reduced efferocytosis increased necrosis C_LIO_LIThese events appeared to be coordinated by reduced IFN-{gamma} which increased collagen but also decreased expression of efferocytotic genes. Our studies call into question whether inhibition of IL-18 would stabilize plaques in CH. C_LI