Long-term clopidogrel administration following severe coronary injury reduces proliferation and inflammation via inhibition of nuclear factor-kappaB and activator protein 1 activation in pigs

How selective antagonists and genetic modification have helped characterise the expression and functions of vascular P2Y receptors

Vascular P2Y receptors mediate many effects, but the role of individual subtypes is often unclear. Here we discuss how subtype-selective antagonists and receptor knockout/knockdown have helped identify these roles in numerous species and vessels. P2Y1 receptor-mediated vasoconstriction and endothelium-dependent vasodilation have been characterised using the selective antagonists, MRS2179 and MRS2216, whilst AR-C118925XX, a P2Y2 receptor antagonist, reduced endothelium-dependent relaxation, and signalling evoked by UTP or fluid shear stress. P2Y2 receptor knockdown reduced endothelial signalling and endothelial P2Y2 receptor knockout produced hypertensive mice and abolished vasodilation elicited by an increase in flow. UTP-evoked vasoconstriction was also blocked by AR-C118925XX, but the effects of P2Y2 receptor knockout were complex. No P2Y4 receptor antagonists are available and P2Y4 knockout did not affect the vascular actions of UTP and UDP. The P2Y6 receptor antagonist, MRS2578, identified endothelial P2Y6 receptors mediating vasodilation, but receptor knockout had complex effects. MRS2578 also inhibited, and P2Y6 knockout abolished, contractions evoked by UDP. P2Y6 receptors contribute to the myogenic tone induced by a stepped increase in vascular perfusion pressure and possibly to the development of atherosclerosis. The P2Y11 receptor antagonists, NF157 and NF340, inhibited ATP-evoked signalling in human endothelial cells. Vasoconstriction mediated by P2Y12/P2Y13 and P2Y14 receptors was characterised using the antagonists, cangrelor, ticagrelor, AR-C67085 and MRS2211 or PPTN respectively. This has yet to be backed up by receptor knockout experiments. Thus, subtype-selective antagonists and receptor knockout/knockdown have helped identify which P2Y subtypes are functionally expressed in vascular smooth muscle and endothelial cells and the effects that they mediate.

Research progress of NF-κB signaling pathway and thrombosis

Venous thromboembolism is a very common and costly health problem. Deep-vein thrombosis (DVT) can cause permanent damage to the venous system and lead to swelling, ulceration, gangrene, and other symptoms in the affected limb. In addition, more than half of the embolus of pulmonary embolism comes from venous thrombosis, which is the most serious cause of death, second only to ischemic heart disease and stroke patients. It can be seen that deep-vein thrombosis has become a serious disease affecting human health. In recent years, with the deepening of research, inflammatory response is considered to be an important pathway to trigger venous thromboembolism, in which the transcription factor NF-κB is the central medium of inflammation, and the NF-κB signaling pathway can regulate the pro-inflammatory and coagulation response. Thus, to explore the mechanism and make use of it may provide new solutions for the prevention and treatment of thrombosis.

The Function and Regulation of Platelet P2Y12 Receptor

In addition to the key role in hemostasis and thrombosis, platelets have also been wildly acknowledged as immune regulatory cells and involving in the pathogenesis of inflammation-related diseases. Since purine receptor P2Y12 plays a crucial role in platelet activation, P2Y12 antagonists such as clopidogrel, prasugrel, and ticagrelor have been widely used in cardiovascular diseases worldwide in recent decades due to their potent antiplatelet and antithrombotic effects. Meanwhile, the role of P2Y12 in inflammatory diseases has also been extensively studied. Relatively, there are few studies on the regulation of P2Y12. This review first summarizes the various roles of P2Y12 in the process of platelet activation, as well as downstream effects and signaling pathways; then introduces the effects of P2Y12 in inflammatory diseases such as sepsis, atherosclerosis, cancer, autoimmune diseases, and asthma; and finally reviews the current researches on P2Y12 regulation.

Ticagrelor and clopidogrel suppress NF-κB signaling pathway to alleviate LPS-induced dysfunction in vein endothelial cells

Background

Ticagrelor and clopidogrel, P2Y₁₂ receptor antagonists, can prevent thrombotic events and are used to treat cardiovascular diseases such as acute coronary syndrome and chronic obstructive pulmonary disease, in which inflammation is involved. Moreover, NF-B is the central regulator of inflammation. Thus, we suspected that ticagrelor and clopidogrel are involved in the regulation of the NF-ΚB signaling pathway.

Methods

After human umbilical vein endothelial cells (HUVECs) were cultured with ticagrelor or clopidogrel and given lipopolysaccharide (LPS) and CD14, the mRNA levels of related inflammatory factors, the protein level and subcellular localization of molecules in the NF-ΚB signaling pathway, cell viability, apoptosis and the cell cycle, cell migration, and vascular formation were detected using quantitative polymerase chain reaction (qPCR), western blotting and immunofluorescence assay, CCK-8, flow cytometry, transwell assay, and matrigel, respectively. All data was expressed as the mean ± S.D. The statistical significance of data was assessed by an unpaired two-tailed t-test.

Results

Ticagrelor and clopidogrel can inhibit the degradation of IKBα and phosphorylation of p65, prevent p65 from entering the nucleus, reduce the production of TNFα, IL-1, IL-8, IL-6 and IL-2, and alleviate the decrease in cell viability, cell migration and angiogenesis, the changes of cell cycle and apoptosis induced by LPS.

Conclusions

Ticagrelor and clopidogrel alleviate cellular dysfunction through suppressing NF-ΚB signaling pathway.

Role of NF-κB in Platelet Function

Platelets are megakaryocyte-derived fragments lacking nuclei and prepped to maintain primary hemostasis by initiating blood clots on injured vascular endothelia. Pathologically, platelets undergo the same physiological processes of activation, secretion, and aggregation yet with such pronouncedness that they orchestrate and make headway the progression of atherothrombotic diseases not only through clot formation but also via forcing a pro-inflammatory state. Indeed, nuclear factor-κB (NF-κB) is largely implicated in atherosclerosis and its pathological complication in atherothrombotic diseases due to its transcriptional role in maintaining pro-survival and pro-inflammatory states in vascular and blood cells. On the other hand, we know little on the functions of platelet NF-κB, which seems to function in other non-genomic ways to modulate atherothrombosis. Therein, this review will resemble a rich portfolio for NF-κB in platelets, specifically showing its implications at the levels of platelet survival and function. We will also share the knowledge thus far on the effects of active ingredients on NF-κB in general, as an extrapolative method to highlight the potential therapeutic targeting of NF-κB in coronary diseases. Finally, we will unzip a new horizon on a possible extra-platelet role of platelet NF-κB, which will better expand our knowledge on the etiology and pathophysiology of atherothrombosis.

Platelets, inflammation and anti-inflammatory effects of antiplatelet drugs in ACS and CAD

Platelets play a pivotal role in chronic inflammation leading to progression of atherosclerosis and acute coronary events. Recent discoveries on novel mechanisms and platelet-dependent inflammatory targets underpin the role of platelets to maintain a chronic inflammatory condition in cardiovascular disease. There is strong and clinically relevant crosslink between chronic inflammation and platelet activation. Antiplatelet therapy is a cornerstone in the prevention and treatment of acute cardiovascular events. The benefit of antiplatelet agents has mainly been attributed to their direct anti-aggregatory impact. Some anti-inflammatory off-target effects have also been described. However, it is unclear whether these effects are secondary due to inhibition of platelet activation or are caused by direct distinct mechanisms interfering with inflammatory pathways. This article will highlight novel platelet associated targets that contribute to inflammation in cardiovascular disease and elucidate mechanisms by which currently available antiplatelet agents evolve anti-inflammatory capacities, in particular by carving out the differential mechanisms directly or indirectly affecting platelet mediated inflammation. It will further illustrate the prognostic impact of antiplatelet therapies by reducing inflammatory marker release in recent cardiovascular trials.

Effect of P2Y12 inhibitors on inflammation and immunity

Platelet P2Y12 inhibitors form a major part of the treatment strategy for patients with acute coronary syndromes (ACS) due to the importance of the platelet P2Y12 receptor in mediating the pathophysiology of arterial thrombosis. It has been increasingly recognised that platelets also have a critical role in inflammation and immune responses. P2Y12 inhibitors reduce platelet release of pro-inflammatory α-granule contents and the formation of pro-inflammatory platelet-leukocyte aggregates. These are important mediators of inflammation in a variety of different contexts. Clinical evidence shows that P2Y12 inhibition by clopidogrel is associated with a reduction in platelet-related mediators of inflammation, such as soluble P-selectin and CD40L, following atherothrombosis. Clopidogrel in addition to aspirin, compared to aspirin alone, also reduces markers of systemic inflammation such as tumour necrosis factor (TNF) α and C-reactive protein (CRP) following ACS. The more potent thienopyridine P2Y12 inhibitor, prasugrel, has been shown to decrease platelet P-selectin expression and platelet-leukocyte aggregate formation compared to clopidogrel. The PLATO study suggested that the novel P2Y12 inhibitor ticagrelor might improve clinical outcomes from pulmonary infections and sepsis compared to clopidogrel in patients with ACS. Ticagrelor is a more potent P2Y12 inhibitor than clopidogrel and also inhibits cellular adenosine uptake via equilibrative nucleoside transporter (ENT) 1, whereas clopidogrel does not. Further examination of the involvement of these mechanisms in inflammation and immunity is therefore warranted.

Genetic determined low response to thienopyridines is associated with higher systemic inflammation in smokers

AIM

To investigate whether the interactions of CYP2C19*2 and CYP2C19*17 with smoking are associated with the levels of P2Y12 receptor inhibition and CRP, in on-thienopyridine post-stenting patients.

METHODS & RESULTS

At 1-month follow-up, the interactions of smoking and CYP2C19 polymorphisms on the vasodilator-stimulated phosphoprotein - platelet reactivity index (VASP PRI), and CRP were explored in three metabolizing groups (1128 patients) as follow: poor metabolizers (*2 carriers/*17 noncarriers); intermediate metabolizers (*2 carriers/*17 carriers or *2 noncarriers/*17 noncarriers); and ultrarapidmetabolizers (*2 allele noncarriers/*17 carriers). The interactions of metabolizing status and smoking was significant for CRP (p = 0.001) but not for VASP PRI (p = 0.734).

CONCLUSION

Interaction between CYP2C19 polymorphisms and smoking modifies on-treatment CRP level of post-stenting, on-thienopyridine patients. This effect seems to be independent to the level of P2Y12 receptor inhibition.

Changes in inflammatory biomarkers in patients treated with ticagrelor or clopidogrel

BACKGROUND

Inflammation is a key factor in the development of atherosclerotic disease and acute coronary syndromes (ACS). The P2Y(12) receptor antagonists ticagrelor (AZD6140) and clopidogrel may have anti-inflammatory effects. The objective of this analysis from the Dose Confirmation Study Assessing Anti-Platelet Effects of AZD6140 vs Clopidogrel in NSTEMI 2 (DISPERSE 2) trial was to compare ticagrelor and clopidogrel for effects on the inflammatory biomarkers C-reactive protein (CRP), interleukin 6 (IL-6), myeloperoxidase (MPO), and soluble CD40 ligand (sCD40L).

HYPOTHESIS

Ticagrelor inhibits the P2Y(12) receptor and inflammation to a greater extent than clopidogrel in nonST-segment elevation ACS (NSTE-ACS) patients.

METHODS

In a double-blind, double-dummy, multicenter trial, 990 patients who had been hospitalized within the previous 48 hours with NSTE-ACS were randomized to receive ticagrelor 90 mg twice daily, ticagrelor 180 mg twice daily, or clopidogrel 300 mg initially and then 75 mg once daily. Within the ticagrelor groups, patients were also randomized to receive or not receive a loading dose of ticagrelor 270 mg initially. All patients received standard treatment for ACS, which included 325 mg aspirin initially and 75 to 100 mg aspirin each day subsequently. Inflammatory biomarkers were measured at baseline, upon hospital discharge, and after 4 weeks.

RESULTS

Inflammatory biomarker measurements were not significantly different among treatment groups at baseline, discharge, and 4 weeks.

CONCLUSIONS

Ticagrelor and clopidogrel appeared not to differ in this study with respect to the inflammatory biomarkers CRP, IL-6, MPO, and sCD40L in patients with NSTE-ACS.