Denuja Karunakaran1,2, My-Anh Nguyen1,3, Michele Geoffrion1, Dianne Vreeken4, Zachary Lister1, Henry S Cheng5, Nicola Otte2, Patricia Essebier2, Hailey Wyatt1, Joshua W Kandiah1, Richard Jung1, Francis J Alenghat6, Ana Mompeon1, Richard Lee7, Calvin Pan8, Emma Gordon2, Adil Rasheed1, Aldons J Lusis8, Peter Liu1, Ljubica Perisic Matic9, Ulf Hedin, Jason E Fish6, Liang Guo10, Frank Kolodgie10, Renu Virmani10, Janine M van Gils4, Katey J Rayner1,3. 1. University of Ottawa Heart Institute, Canada (D.K., M.-A.N., M.G., Z.L., H.W., J.W.K., R.J., A.M., A.R., P.L., K.J.R.). 2. Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia (D.K., N.O., P.E., E.G.). 3. Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ontario, Canada (M.-A.N., K.J.R.). 4. Leiden University Medical Center, The Netherlands (D.V., J.M.v.G.). 5. Toronto General Research Hospital Institute, University Health Network, Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada (H.S.C.). 6. Cardiology, Department of Medicine, University of Chicago, IL (F.J.A., J.E.F.). 7. Cardiovascular Antisense Drug Discovery Group, Ionis Pharmaceuticals, Carlsbad, CA (R.L.). 8. David Geffen School of Medicine, University of California Los Angeles (C.P., A.J.L.). 9. Vascular Surgery Division, Department of Molecular Medicine and Surgery, Karolinska Institute, Sweden (L.P.M.). 10. CVPath Institute Inc., Gaithersburg, MD (L.G., F.K., R.V.).
Abstract
BACKGROUND: Chronic activation of the innate immune system drives inflammation and contributes directly to atherosclerosis. We previously showed that macrophages in the atherogenic plaque undergo RIPK3 (receptor-interacting serine/threonine-protein kinase 3)-MLKL (mixed lineage kinase domain-like protein)-dependent programmed necroptosis in response to sterile ligands such as oxidized low-density lipoprotein and damage-associated molecular patterns and that necroptosis is active in advanced atherosclerotic plaques. Upstream of the RIPK3-MLKL necroptotic machinery lies RIPK1 (receptor-interacting serine/threonine-protein kinase 1), which acts as a master switch that controls whether the cell undergoes NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells)-dependent inflammation, caspase-dependent apoptosis, or necroptosis in response to extracellular stimuli. We therefore set out to investigate the role of RIPK1 in the development of atherosclerosis, which is driven largely by NF-κB-dependent inflammation at early stages. We hypothesize that, unlike RIPK3 and MLKL, RIPK1 primarily drives NF-κB-dependent inflammation in early atherogenic lesions, and knocking down RIPK1 will reduce inflammatory cell activation and protect against the progression of atherosclerosis. METHODS: We examined expression of RIPK1 protein and mRNA in both human and mouse atherosclerotic lesions, and used loss-of-function approaches in vitro in macrophages and endothelial cells to measure inflammatory responses. We administered weekly injections of RIPK1 antisense oligonucleotides to Apoe-/- mice fed a cholesterol-rich (Western) diet for 8 weeks. RESULTS: We find that RIPK1 expression is abundant in early-stage atherosclerotic lesions in both humans and mice. Treatment with RIPK1 antisense oligonucleotides led to a reduction in aortic sinus and en face lesion areas (47.2% or 58.8% decrease relative to control, P<0.01) and plasma inflammatory cytokines (IL-1α [interleukin 1α], IL-17A [interleukin 17A], P<0.05) in comparison with controls. RIPK1 knockdown in macrophages decreased inflammatory genes (NF-κB, TNFα [tumor necrosis factor α], IL-1α) and in vivo lipopolysaccharide- and atherogenic diet-induced NF-κB activation. In endothelial cells, knockdown of RIPK1 prevented NF-κB translocation to the nucleus in response to TNFα, where accordingly there was a reduction in gene expression of IL1B, E-selectin, and monocyte attachment. CONCLUSIONS: We identify RIPK1 as a central driver of inflammation in atherosclerosis by its ability to activate the NF-κB pathway and promote inflammatory cytokine release. Given the high levels of RIPK1 expression in human atherosclerotic lesions, our study suggests RIPK1 as a future therapeutic target to reduce residual inflammation in patients at high risk of coronary artery disease.
BACKGROUND: Chronic activation of the innate immune system drives inflammation and contributes directly to atherosclerosis. We previously showed that macrophages in the atherogenic plaque undergo RIPK3 (receptor-interacting serine/threonine-protein kinase 3)-MLKL (mixed lineage kinase domain-like protein)-dependent programmed necroptosis in response to sterile ligands such as oxidized low-density lipoprotein and damage-associated molecular patterns and that necroptosis is active in advanced atherosclerotic plaques. Upstream of the RIPK3-MLKL necroptotic machinery lies RIPK1 (receptor-interacting serine/threonine-protein kinase 1), which acts as a master switch that controls whether the cell undergoes NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells)-dependent inflammation, caspase-dependent apoptosis, or necroptosis in response to extracellular stimuli. We therefore set out to investigate the role of RIPK1 in the development of atherosclerosis, which is driven largely by NF-κB-dependent inflammation at early stages. We hypothesize that, unlike RIPK3 and MLKL, RIPK1 primarily drives NF-κB-dependent inflammation in early atherogenic lesions, and knocking down RIPK1 will reduce inflammatory cell activation and protect against the progression of atherosclerosis. METHODS: We examined expression of RIPK1 protein and mRNA in both human and mouseatherosclerotic lesions, and used loss-of-function approaches in vitro in macrophages and endothelial cells to measure inflammatory responses. We administered weekly injections of RIPK1 antisense oligonucleotides to Apoe-/- mice fed a cholesterol-rich (Western) diet for 8 weeks. RESULTS: We find that RIPK1 expression is abundant in early-stage atherosclerotic lesions in both humans and mice. Treatment with RIPK1 antisense oligonucleotides led to a reduction in aortic sinus and en face lesion areas (47.2% or 58.8% decrease relative to control, P<0.01) and plasma inflammatory cytokines (IL-1α [interleukin 1α], IL-17A [interleukin 17A], P<0.05) in comparison with controls. RIPK1 knockdown in macrophages decreased inflammatory genes (NF-κB, TNFα [tumor necrosis factor α], IL-1α) and in vivo lipopolysaccharide- and atherogenic diet-induced NF-κB activation. In endothelial cells, knockdown of RIPK1 prevented NF-κB translocation to the nucleus in response to TNFα, where accordingly there was a reduction in gene expression of IL1B, E-selectin, and monocyte attachment. CONCLUSIONS: We identify RIPK1 as a central driver of inflammation in atherosclerosis by its ability to activate the NF-κB pathway and promote inflammatory cytokine release. Given the high levels of RIPK1 expression in humanatherosclerotic lesions, our study suggests RIPK1 as a future therapeutic target to reduce residual inflammation in patients at high risk of coronary artery disease.
Authors: Tingting Wang; Yan Dong; Li Yao; Fan Lu; Chenxi Wen; Zhuo Wan; Li Fan; Zhelong Li; Te Bu; Mengying Wei; Xuekang Yang; Yi Zhang Journal: Bioact Mater Date: 2022-02-15