Role of chemokines in promoting instability of coronary atherosclerotic plaques and the underlying molecular mechanism

Fractalkine Signalling (CX3CL1/CX3CR1 Axis) as an Emerging Target in Coronary Artery Disease

Acute myocardial infarction (MI) is the most common and dramatic complication of atherosclerosis, which, despite successful reperfusion therapy, can lead to incident heart failure (HF). HF occurs when the healing process is impaired due to adverse left ventricular remodelling, and can be the result of so-called ischaemia/reperfusion injury (IRI), visualised by the development of intramyocardial haemorrhage (IMH) or microvascular obstruction (MVO) in cardiac MRI. Thus far, translation of novel pharmacological strategies from preclinical studies to target either IRI or HF post MI have been largely unsuccessful. Anti-inflammatory therapies also carry the risk of affecting the immune system. Fractalkine (FKN, CX3CL1) is a unique chemokine, present as a transmembrane protein on the endothelium, or following cleavage as a soluble ligand, attracting leukocyte subsets expressing the corresponding receptor CX3CR1. We have shown previously that the fractalkine receptor CX3CR1 is associated with MVO in patients undergoing primary PCI. Moreover, inhibition of CX3CR1 with an allosteric small molecule antagonist (KAND567) in the rat MI model reduces acute infarct size, inflammation, and IMH. Here we review the cellular biology of fractalkine and its receptor, along with ongoing studies that introduce CX3CR1 as a future target in coronary artery disease, specifically in patients with myocardial infarction.

Large Extracellular Vesicle-Associated Rap1 Accumulates in Atherosclerotic Plaques, Correlates With Vascular Risks and Is Involved in Atherosclerosis

RATIONALE

Metabolic syndrome (MetS) is a cluster of interrelated risk factors for cardiovascular diseases and atherosclerosis. Circulating levels of large extracellular vesicles (lEVs), submicrometer-sized vesicles released from plasma membrane, from MetS patients were shown to induce endothelial dysfunction, but their role in early stage of atherosclerosis and on vascular smooth muscle cells (SMC) remain to be fully elucidated.

OBJECTIVE

To determine the mechanisms by which lEVs lead to the progression of atherosclerosis in the setting of MetS.

METHODS AND RESULTS

Proteomic analysis revealed that the small GTPase, Rap1 was overexpressed in lEVs from MetS patients compared with those from non-MetS subjects. Rap1 was in GTP-associated active state in both types of lEVs, and Rap1-lEVs levels correlated with increased cardiovascular risks, including stenosis. MetS-lEVs, but not non-MetS-lEVs, increased Rap1-dependent endothelial cell permeability. MetS-lEVs significantly promoted migration and proliferation of human aortic SMC and increased expression of proinflammatory molecules and activation of ERK (extracellular signal-regulated kinase) 5/p38 pathways. Neutralization of Rap1 by specific antibody or pharmacological inhibition of Rap1 completely prevented the effects of lEVs from MetS patients. High-fat diet-fed ApoE^-/- mice displayed an increased expression of Rap1 both in aortas and circulating lEVs. lEVs accumulated in plaque atherosclerotic lesions depending on the progression of atherosclerosis. lEVs from high-fat diet-fed ApoE^-/- mice, but not those from mice fed with a standard diet, enhanced SMC proliferation. Human atherosclerotic lesions were enriched in lEVs expressing Rap1.

CONCLUSIONS

These data demonstrate that Rap1 carried by MetS-lEVs participates in the enhanced SMC proliferation, migration, proinflammatory profile, and activation of ERK5/p38 pathways leading to vascular inflammation and remodeling, and atherosclerosis. These results highlight that Rap1 carried by MetS-lEVs may be a novel determinant of diagnostic value for cardiometabolic risk factors and suggest Rap1 as a promising therapeutic target against the development of atherosclerosis. Graphical Abstract: A graphical abstract is available for this article.

Impact on rats from acute intratracheal inhalation exposures to WTC dusts

Background: Studies have revealed the increased incidence of health disorders in First Responders (FR) who were at Ground Zero over the initial 72 hr after the World Trade Center (WTC) collapses. Previous studies in rats exposed to WTC dusts using exposure scenarios that mimicked FR mouthbreathing showed exposure led to altered expression of genes whose products could be involved in lung ailments. Nevertheless, it was uncertain if repeated exposures (as occurred in earliest days post-disaster) might have given rise to long-term changes in the lungs/other organs, in white blood cell (WBC) profiles, and/or systemic expression of select (mostly immune-related) proteins.Methods: To examine this, rats were exposed on 2 consecutive days (2 hr/d, intratracheal inhalation) to WTC dusts and then examined over a 1-yr period thereafter. At select times post-exposure, organ (lung, heart, liver, kidney, spleen) weights, WBC profiles, and blood levels of a variety of proteins were evaluated.Results: The study showed that over the 1-yr period, there were nominal effects on organ weights (absolute, index) as a result of the dust exposures. There were significant changes (relative to in naïve rats) in WBC profiles, with exposed rats having increased monocyte-macrophage and decreased lymphocyte percentages. The study also found that dust exposure led to significant systemic increases in many proteins, including MCP-1, RANTES, MMP-9, RAGE, and Galectin-3.Conclusions: These results provide further support for our longstanding hypothesis that the WTC dusts could potentially have acted as direct inducers of many of the health effects that have been seen in the exposed FR.

Levetiracetam inhibits THP-1 monocyte chemotaxis and adhesion via the synaptic vesicle 2A

Long-term therapy with older antiepileptic drugs (AEDs), but not levetiracetam (LEV), may increase the risk of atherosclerosis (AS), suggesting that LEV may have a potential anti-AS effect. The synaptic vesicle 2A (SV2A) is known to the specific binding site of LEV. Numerous studies have documented that SV2A is a membrane protein specifically expressed in nervous system. Interestingly, our previous research showed that SV2A also existed in human CD8+ T lymphocytes. Therefore, we hypothesized that LEV was associated with decreased risk of AS by regulating monocytes chemotaxis and adhesion. We showed that SV2A protein were detected in THP-1 human monocytic leukemia cells. LEV (300 μM) inhibited the chemotaxis and adhesion of THP-1 cells after transfection with plasmids expressing SV2AWT, but not SV2AR383Q which was a known functional mutation site of human SV2A. Furthermore, RT-PCR and western blot analysis demonstrated that LEV (300 μM) decreased the expression level of chemokine-related receptors (CX3CL1, CCR1, CCR2, and CCR5),and reduced levels of phosphorylated AKT (p-AKT) in THP-1 cells with SV2AWT expressing plasmids. Taken together, these findings indicated that LEV has an inhibitory effect on THP-1 monocyte adhesion and chemotaxis, suggesting that SV2A may serve as a novel therapeutic target to prevent AS.

Colchicine as a Novel Therapy for Suppressing Chemokine Production in Patients With an Acute Coronary Syndrome: A Pilot Study

PURPOSE

Existing literature reports that colchicine inhibits inflammasome activation and downstream inflammatory cytokine production and stabilizes coronary plaque. However, colchicine's effect on chemokines, which orchestrate multiple atheroinflammatory pathways, is unknown.

METHODS

Patients with acute coronary syndrome (ACS) were randomly assigned to colchicine (1.5 mg PO) (n = 12; mean age, 65.2 years) or no treatment (n = 13; mean age, 62.2 years). Blood samples were collected during cardiac catheterization within 24 hours of colchicine administration from the coronary sinus, aortic root, and right atrium. Patients with colchicine-naive stable angina (SAP) (n = 13; mean age, 66.8 years) were additionally sampled. Serum chemokine levels were analyzed with ELISA. In parallel, monocytes from healthy donors were isolated and subjected to colchicine treatment.

FINDINGS

Transcoronary (TC) levels of chemokine ligand 2 (CCL2) and C-X3-C motif chemokine ligand 1 (CX3CL1) were significantly elevated in patients with ACS versus patients with SAP (P < 0.01). TC chemokine ligand 5 (CCL5) levels were not significantly (P = 0.084) elevated in patients with ACS versus patients with SAP. Colchicine treatment markedly reduced TC levels of CCL2, CCL5, and CX3CL1 in patients with ACS (P < 0.05). In vitro colchicine suppressed CCL2 gene expression in stimulated monocytes (P < 0.05). Colchicine treatment reduced the intracellular concentration of all 3 chemokines (P < 0.01) and impaired monocyte chemotaxis (P < 0.05).

IMPLICATIONS

Here, we report for the first time that short-term colchicine therapy significantly reduces the local production of coronary chemokines, in part by attenuating production of these mediators by monocytes. These data provide further evidence of colchicine's beneficial role in patients with ACS.