Biology subjects

Megens, R. T. A.

Publications and source records attributed to Megens, R. T. A..

2 recordsLinked to original sources

bioRxiv2021

MIF-2/D-DT is an atypical atherogenic chemokine that promotes advanced atherosclerosis and hepatic lipogenesis

Atherosclerosis is the underlying cause of cardiovascular diseases (CVDs) such as myocardial infarction and ischemic stroke. It is a lipid-triggered chronic inflammatory condition of the arterial vascular wall that is driven by various inflammatory pathways including atherogenic cytokines and chemokines. D-dopachrome tautomerase (D-DT), also known as macrophage migration inhibitory factor-2 (MIF-2), belongs to the MIF protein family, which is best known for its pathogenic role in a variety of inflammatory and immune conditions including CVDs. While MIF is well known as a promoter of atherogenic processes, MIF-2 has not been studied in atherosclerosis. Here, we investigated atherosclerosis in hyperlipidemic Mif-2-/-Apoe-/- mice and studied the role of MIF-2 in various atherogenic assays in vitro. We found that global Mif-2 deficiency as well as its pharmacological blockade by 4-CPPC protected against atherosclerotic lesion formation and vascular inflammation in models of early and advanced atherogenesis. On cellular level, MIF-2 promoted monocyte migration in 2D and 3D and monocyte arrest on aortic endothelial monolayers, promoted B-cell chemotaxis in vitro and B-cell homing in vivo, and increased macrophage foam cell formation. Dose curves and direct comparison in a 3D migration set-up suggest that MIF-2 may be a more potent chemokine than MIF for monocytes and B cells. We identify CXCR4 as a novel receptor for MIF-2. The evidence relies on a CXCR4 inhibitor, CXCR4 internalization experiments, MIF-2/CXCR4 binding studies by yeast-CXCR4 transformants, and fluorescence spectroscopic titrations with a soluble CXCR4 surrogate. Of note, Mif-2-/-Apoe-/- mice exhibited decreased plasma cholesterol and triglyceride levels, lower body weights, smaller livers, and profoundly reduced hepatic lipid accumulation compared to Apoe-/- mice. Mechanistic experiments in Huh-7 hepatocytes suggest that MIF-2 regulates the expression and activation of sterol-regulatory element binding protein-1 and -2 (SREBP-1, SREBP-2) to induce lipogenic downstream genes such as FASN and LDLR, while it attenuated the activation of the SREBP inhibiting AMPK pathway. Studies using receptor Inhibitors showed that SREBP activation and hepatic lipoprotein uptake by MIF-2 is mediated by both CXCR4 and CD74. Lastly and in line with a combined role of MIF-2 in vascular inflammation and hepatic lipid accumulation, MIF-2 was found to be profoundly upregulated in unstable human carotid plaques, underscoring a critical role for MIF-2 in advanced stages of atherosclerosis. Together, these data identify MIF-2 as a novel atherogenic chemokine and CXCR4 ligand that not only promotes lesion formation and vascular inflammation but also strongly affects hepatic lipogenesis in an SREBP-mediated manner, possibly linking atherosclerosis and hepatic steatosis.

immunology↗

bioRxiv2021

Heterocomplexes between the Atypical Chemokine MIF and the CXC-Motif Chemokine CXCL4L1 Regulate Inflammation and Thrombus Formation

To fulfil their orchestrating function in immune cell trafficking in homeostasis and disease, a network of 49 chemokines and 23 receptors capitalizes on features of specificity, redundancy, and functional selectivity such as biased agonism. The discovery of the chemokine interactome, i.e. heteromeric chemokine-chemokine interactions, even across CC- and CXC-class borders, has further expanded the complexity within the network. Moreover, some inflammatory mediators, which are not structurally linked to classical CC-, CXC-, CX3C-, or C-chemokines, can bind to chemokine receptors and behave as atypical chemokines (ACKs). We identified the cytokine macrophage migration inhibitory factor (MIF) as an ACK that binds to the chemokine receptors CXCR2 and CXCR4 to promote atherogenic leukocyte recruitment. Here, we hypothesized that chemokine-chemokine interactions extend to ACKs and that MIF may form heterocomplexes with classical chemokines. We tested this hypothesis, applying an unbiased chemokine protein binding array. The platelet chemokine CXCL4L1, but not its variant CXCL4 or the CXCR2/CXCR4 ligands CXCL8 or CXCL12, was identified as a candidate interactor. MIF/CXCL4L1 complexation was verified by co-immunoprecipitation, surface plasmon-resonance analysis, and microscale thermophoresis, which also established high-affinity binding (KD{asymp}100-150 nM). The binding interface was predicted by peptide array-based mapping and molecular docking. We next determined whether heterocomplex formation modulates inflammatory and atherogenic activities of MIF. MIF-elicited T-cell chemotaxis as assessed in a 3D-matrix-based live cell-imaging set-up was abrogated, when cells were co-incubated with MIF and CXCL4L1. Heterocomplexation also blocked MIF-triggered migration of Egfp+ microglia in cortical cultures in situ. Of note, CXCL4L1 blocked the binding of Alexa-MIF to a soluble ectodomain mimic of CXCR4 and co-incubation with CXCL4L1 attenuated MIF-triggered dynamic mass redistribution in HEK293-CXCR4 transfectants, indicating that complex formation interferes with MIF/CXCR4 pathways. As MIF and CXCL4L1 are abundant platelet products, we finally tested their role in platelet activation. Multi-photon microscopy, FLIM- FRET, and proximity ligation assay visualized heterocomplexes in platelet aggregates and clinical human thrombus sections. Moreover, heterocomplex formation inhibited MIF- stimulated thrombus formation under flow and skewed the morphology of adhering platelets from a large to a small lamellipodia phenotype. Together, our study establishes a novel molecular interaction, adding to the complexity of the chemokine interactome and chemokine/receptor network. MIF/CXCL4L1, or more generally, ACK/CXC-motif chemokine heterocomplexes may be promising target structures to modulate inflammation and thrombosis.

immunology↗