Genetic and pharmacological modifications of thrombin formation in apolipoprotein e-deficient mice determine atherosclerosis severity and atherothrombosis onset in a neutrophil-dependent manner

Update on selective treatments targeting neutrophilic inflammation in atherogenesis and atherothrombosis

Atherosclerosis is the most common pathological process underlying cardiovascular diseases. Current therapies are largely focused on alleviating hyperlipidaemia and preventing thrombotic complications, but do not completely eliminate risk of suffering recurrent acute ischaemic events. Specifically targeting the inflammatory processes may help to reduce this residual risk of major adverse cardiovascular events in atherosclerotic patients. The involvement of neutrophils in the pathophysiology of atherosclerosis is an emerging field, where evidence for their causal contribution during various stages of atherosclerosis is accumulating. Therefore, the identification of neutrophils as a potential therapeutic target may offer new therapeutic perspective to reduce the current atherosclerotic burden. This narrative review highlights the expanding role of neutrophils in atherogenesis and discusses on the potential treatment targeting neutrophil-related inflammation and associated atherosclerotic plaque vulnerability.

Inflammation and thrombosis in cardiovascular disease

PURPOSE OF REVIEW

This article will summarize recent observations that provide mechanistic insight into the molecular and cellular links between inflammation and thrombosis in the context of cardiovascular and other thromboinflammatory disease states.

RECENT FINDINGS

Several disease conditions are characterized by a thromboinflammatory state in which interactions of blood cells and components with the vascular wall perpetuate both thrombotic and inflammatory pathways. Targeting these pathways may be of benefit in inflammatory conditions and cardiovascular disease.

SUMMARY

Ongoing clinical trials should provide additional insight into the hypothesis that the thromboinflammatory state contributes to adverse clinical outcomes.

Elevated levels of circulating DNA and chromatin are independently associated with severe coronary atherosclerosis and a prothrombotic state

OBJECTIVE

Aberrant neutrophil activation occurs during the advanced stages of atherosclerosis. Once primed, neutrophils can undergo apoptosis or release neutrophil extracellular traps. This extracellular DNA exerts potent proinflammatory, prothrombotic, and cytotoxic properties. The goal of this study was to examine the relationships among extracellular DNA formation, coronary atherosclerosis, and the presence of a prothrombotic state.

APPROACH AND RESULTS

In a prospective, observational, cross-sectional cohort of 282 individuals with suspected coronary artery disease, we examined the severity, extent, and phenotype of coronary atherosclerosis using coronary computed tomographic angiography. Double-stranded DNA, nucleosomes, citrullinated histone H4, and myeloperoxidase-DNA complexes, considered in vivo markers of cell death and NETosis, respectively, were established. We further measured various plasma markers of coagulation activation and inflammation. Plasma double-stranded DNA, nucleosomes, and myeloperoxidase-DNA complexes were positively associated with thrombin generation and significantly elevated in patients with severe coronary atherosclerosis or extremely calcified coronary arteries. Multinomial regression analysis, adjusted for confounding factors, identified high plasma nucleosome levels as an independent risk factor of severe coronary stenosis (odds ratio, 2.14; 95% confidence interval, 1.26-3.63; P=0.005). Markers of neutrophil extracellular traps, such as myeloperoxidase-DNA complexes, predicted the number of atherosclerotic coronary vessels and the occurrence of major adverse cardiac events.

CONCLUSIONS

Our report provides evidence demonstrating that markers of cell death and neutrophil extracellular trap formation are independently associated with coronary artery disease, prothrombotic state, and occurrence of adverse cardiac events. These biomarkers could potentially aid in the prediction of cardiovascular risk in patients with chest discomfort.

Elevated prothrombin promotes venous, but not arterial, thrombosis in mice

OBJECTIVE

Individuals with elevated prothrombin, including those with the prothrombin G20210A mutation, have increased risk of venous thrombosis. Although these individuals do not have increased circulating prothrombotic biomarkers, their plasma demonstrates increased tissue factor-dependent thrombin generation in vitro. The objectives of this study were to determine the pathological role of elevated prothrombin in venous and arterial thrombosis in vivo, and distinguish thrombogenic mechanisms in these vessels.

APPROACH AND RESULTS

Prothrombin was infused into mice to raise circulating levels. Venous thrombosis was induced by electrolytic stimulus to the femoral vein or inferior vena cava ligation. Arterial thrombosis was induced by electrolytic stimulus or ferric chloride application to the carotid artery. Mice infused with prothrombin demonstrated increased tissue factor-triggered thrombin generation measured ex vivo, but did not have increased circulating prothrombotic biomarkers in the absence of vessel injury. After venous injury, elevated prothrombin increased thrombin generation and the fibrin accumulation rate and total amount of fibrin ≈ 3-fold, producing extended thrombi with increased mass. However, elevated prothrombin did not accelerate platelet accumulation, increase the fibrin accumulation rate, or shorten the vessel occlusion time after arterial injury.

CONCLUSIONS

These findings reconcile previously discordant findings on thrombin generation in hyperprothrombinemic individuals measured ex vivo and in vitro, and show elevated prothrombin promotes venous, but not arterial, thrombosis in vivo.