Targeting sortilin in immune cells reduces proinflammatory cytokines and atherosclerosis
Martin B. Mortensen, Mads Kjolby, Stine Gunnersen, Jakob V. Larsen, Johan Palmfeldt, Erling Falk, Anders Nykjaer, Jacob F. Bentzon
Martin B. Mortensen, Mads Kjolby, Stine Gunnersen, Jakob V. Larsen, Johan Palmfeldt, Erling Falk, Anders Nykjaer, Jacob F. Bentzon
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Brief Report Vascular biology

Targeting sortilin in immune cells reduces proinflammatory cytokines and atherosclerosis

Abstract

Genome-wide association studies have identified a link between genetic variation at the human chromosomal locus 1p13.3 and coronary artery disease. The gene encoding sortilin (SORT1) has been implicated as the causative gene within the locus, as sortilin regulates hepatic lipoprotein metabolism. Here we demonstrated that sortilin also directly affects atherogenesis, independent of its regulatory role in lipoprotein metabolism. In a mouse model of atherosclerosis, deletion of Sort1 did not alter plasma cholesterol levels, but reduced the development of both early and late atherosclerotic lesions. We determined that sortilin is a high-affinity receptor for the proinflammatory cytokines IL-6 and IFN-γ. Moreover, macrophages and Th1 cells (both of which mediate atherosclerotic plaque formation) lacking sortilin had reduced secretion of IL-6 and IFN-γ, but not of other measured cytokines. Transfer of sortilin-deficient BM into irradiated atherosclerotic mice reduced atherosclerosis and systemic markers of inflammation. Together, these data demonstrate that sortilin influences cytokine secretion and that targeting sortilin in immune cells attenuates inflammation and reduces atherosclerosis.

Authors

Martin B. Mortensen, Mads Kjolby, Stine Gunnersen, Jakob V. Larsen, Johan Palmfeldt, Erling Falk, Anders Nykjaer, Jacob F. Bentzon

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Figure 2

Sortilin binds IL-6 and IFN-γ with high affinity.

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Sortilin binds IL-6 and IFN-γ with high affinity. (A) Surface plasmon re...
(A) Surface plasmon resonance curves depict binding of IL-6 to immobilized soluble sortilin receptor (0–600 seconds) at IL-6 concentrations ranging 100–1,000 nM. After 600 seconds, buffer was added and IL-6 dissociated from the immobilized sortilin receptor. IL-6 bound with high affinity to sortilin. KD, 7 nM. (B) Similar experiment showing binding of IFN-γ to the immobilized soluble sortilin receptor (0–600 seconds) at IFN-γ concentrations ranging 250–1,500 nM. KD, 1 nM. (C) GST-fused sortilin propeptide (GST-Pro) was added (200–650 seconds); at 650–1,200 seconds, IL-6, GST-fused sortilin propeptide, or both were added. At 1,200 seconds, buffer was added and ligands dissociated. Binding between IL-6 and sortilin was fully inhibited by the sortilin propeptide. (D) Strong colocalization of IL-6 and sortilin at the plasma membrane after addition of IL-6 to sortilin-transfected HEK293 cells, but not control HEK293 cells. Propeptide abolished this colocalization. Nonpermeabilized cells at 4°C. Scale bars: 10 μm. (E) Different IL-6 secretion between Sort1–/– and Sort1+/+ macrophages was maintained after blocking surface sortilin with propeptide. Representative data from 2 independent experiments (mean ± SEM; n = 7). *P < 0.05, Student’s t test. (F) Coimmunoprecipitation in HEK293 cells transfected with sortilin and/or IL-6. Top: Sortilin coprecipitated with IL-6 when IL-6 was pulled down. Bottom: Cell lysates.