Background-The endoplasmic reticulum (ER) responds to various stresses by upregulation of ER chaperones, but prolonged ER stress eventually causes apoptosis. Although apoptosis is considered to be essential for the progression and rupture of atherosclerotic plaques, the influence of ER stress and apoptosis on rupture of unstable coronary plaques remains unclear. Methods and Results-Coronary artery segments were obtained at autopsy from 71 patients, and atherectomy specimens were obtained from 40 patients. Smooth muscle cells and macrophages in the fibrous caps of thin-cap atheroma and ruptured plaques, but not in the fibrous caps of thick-cap atheroma and fibrous plaques, showed a marked increase of ER chaperone expression and apoptotic cells. ER chaperones also showed higher expression in atherectomy specimens from patients with unstable angina pectoris than in specimens from those with stable angina. Expression of 7-ketocholesterol was increased in the fibrous caps of thin-cap atheroma compared with thick-cap atheroma. Treatment of cultured coronary artery smooth muscle cells or THP-1 cells with 7-ketocholesterol induced upregulation of ER chaperones and apoptosis, whereas these changes were prevented by antioxidants. We also investigated possible signaling pathways for ER-initiated apoptosis and found that the CHOP (a transcription factor induced by ER stress)-dependent pathway was activated in unstable plaques. In addition, knockdown of CHOP expression by small interfering RNA decreased ER stress-dependent death of cultured coronary artery smooth muscle cells and THP-1 cells. Conclusions-Increased ER stress occurs in unstable plaques. Our findings suggest that ER stress-induced apoptosis of smooth muscle cells and macrophages may contribute to plaque vulnerability.

Summary.  Background: Thrombus formation through the activation of tissue factor (TF) and factor (F) XI is a critical event in the onset of cardiovascular disease. TF expressed in atherosclerotic plaques and circulating blood is an important determinant of thrombogenicity that contributes to fibrin‐rich thrombus formation after plaque disruption. However, the contribution of FXI to thrombus formation on disrupted plaques remains unclear. Methods: A mouse monoclonal antibody against FXI and activated FXI (FXIa) (XI‐5108) was generated by immunization with activated human FXI. Prothrombin time (PT), activated partial thromboplastin time (APTT), bleeding time, and ex vivo platelet aggregation in rabbits were measured before and after an intravenous bolus injection of XI‐5108. We investigated the role of FXI upon arterial thrombus growth in the rabbit iliac artery in the presence of repeated balloon injury. Results: The XI‐5108 antibody reacted to the light chain of human and rabbit FXI/FXIa, and inhibited FXIa‐initiated FXa and FXIa generation. Fibrin‐rich thrombi developed on the injured neointima that was obviously immunopositive for glycoprotein IIb‐IIIa, fibrin, TF, and FXI. Intravenous administration of XI‐5108 (3.0 mg kg−1) remarkably reduced thrombus growth, and the APTT was significantly prolonged. However, PT, bleeding time and platelet aggregation were not affected. Conclusions: These results indicate that plasma FXI plays a potent role in thrombus growth on the injured neointima. Inhibition of plasma FXI activity might help to reduce thrombus growth on ruptured plaques without prolonging bleeding time.

Summary. Background: Thrombus propagation on disrupted plaque is a major cause of acute coronary events and serious complication after coronary intervention. 5-hydroxytryptamine (5-HT) is a potent vasoactive and platelet-aggregating substance that is predominantly mediated by 5-HT 2A receptor. However, the roles of 5-HT 2A receptor in occlusive thrombus formation on disrupted plaque remain obscure. Objective: We investigated the role of 5-HT 2A receptor in thrombus formation using a rabbit model of repeated balloon-injury. Methods: Three weeks after a first balloon-injury of the femoral arteries, luminal diameter, neointimal growth, and vasoconstriction by 5-HT in vitro were examined. Thrombus propagation and the role of 5-HT 2A receptor after a second balloon-injury were evaluated using sarpogrelate, a selective 5-HT 2A receptor antagonist. Results: Three weeks after the first balloon-injury, luminal stenosis was evident in the femoral arteries, where the neointima expressed tissue factor and 5-HT 2A receptor. The hypercontractile response of the stenotic arteries to 5-HT was significantly reduced by sarpogrelate. Balloon-injury of the neointima with substantially reduced blood flow promoted the formation of occlusive thrombus that was immunoreactive against glycoprotein IIb-IIIa, 5-HT 2A receptor and fibrin. Intravenous injection of sarpogrelate significantly inhibited ex vivo platelet aggregation induced by adenosine 5¢-diphosphate, thrombin and collagen alone as well as with 5-HT, and significantly prevented occlusive thrombus formation in vivo. Conclusions: The 5-HT 2A receptor appears to play a crucial role in occlusive thrombus formation in diseased arteries via platelet aggregation and vasoconstriction. Inhibition of 5-HT 2A receptor might help reduce the onset of acute coronary events and of acute coronary occlusion after the intervention.

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BackgroundCardiovascular diseases, including acute myocardial infarction (AMI), are leading causes of death among the Japanese, who have the longest life expectancy in the world. Over the past 50 years in Japan, the percentage of elderly individuals has increased 4-fold, from 5.7% in 1960 to 23.1% in 2010. To explore medical practices and emergency care for AMI in this aging society, the Japan Acute Myocardial Infarction Registry (JAMIR) was established as a nationwide real-world database.MethodsJAMIR conducted retrospective analysis of 20,462 AMI patients (mean age, 68.8 ± 13.3 years; 15,281 men [74.7%]) hospitalized between January 2011 and December 2013.ResultsThe rates of ambulance use and emergency PCI were 78.9% and 87.9%, respectively. The median door-to-balloon time was 80 min (interquartile range, 53–143 min). Overall in-hospital mortality was 8.3%, including 6.6% due to cardiac death. JAMIR included 4837 patients aged ≥80 years (23.6%). In this age group, patients who underwent PCI (79.9%) had significantly lower in-hospital mortality than those who did not (11.1% vs. 36.9%, P < 0.001).ConclusionsThe large JAMIR database, with 24% of AMI patients aged ≥80 years, could provide useful information about medical care in an aging society. The reasonable in-hospital outcomes observed may justify consideration of PCI for patients with AMI aged ≥80 years.

Summary. Background: Plaque erosion is a cause of atherothrombosis that preferentially occurs on smooth muscle cell (SMC)-and proteoglycan-rich rather than lipid-rich plaques. However, its underlying mechanisms remain unknown. Objective: To determine whether disturbed blood flow induces erosive injury and thrombus formation on SMC-rich neointima. Methods: Three weeks after balloon injury, SMC-rich neointima with increased tissue factor (TF) activity developed in rabbit femoral arteries that were narrowed with a vascular occluder to disturb blood flow after stenosis. Neointimal injury and thrombus formation were assessed at 15, 30, and 180 min after the vascular narrowing. Results: Endothelial detachment, platelet adhesion and neointimal cell apoptosis became evident at the post-stenotic regions of all femoral arteries (n = 5) within 15 min of narrowing. Mural thrombi composed of platelet and fibrin developed after 30 min, and then occlusive thrombi were generated in three out of five vessels after 180 min. The identical vascular narrowing of normal femoral arteries also induced endothelial detachment with small platelet thrombi at poststenotic regions, but fibrin and occlusive thrombi did not develop. Computational simulation analysis indicated that oscillatory shear stress contributes to the development of erosive damage to the neointima. Conclusions: These results suggest that disturbed post-stenotic blood flow can induce erosive injury in SMC-rich plaques and promote thrombus formation that results in vascular events.

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Aims  Frailty is characterized by reduced biological reserves and weakened resistance to stressors, and is common in older adults. This study evaluated the prognostic implications of frailty at hospitalization in elderly patients with acute myocardial infarction (AMI) who undergo percutaneous coronary intervention (PCI). Methods and results  We prospectively analysed 546 AMI patients aged ≥80 years undergoing PCI from 2009 to 2017. Frailty was classified based on impairment in walking (unassisted, assisted, and wheelchair/non-ambulatory), cognition (normal, mildly impaired, moderately to severely impaired), and basic activities of daily living. Impairment in each domain was scored as 0, 1, or 2, and patients were categorized into the following three groups based on total score: no frailty (0), mild frailty (1–2), moderate-to-severe frailty (≥3). The median follow-up period was 589 days. Of the 546 patients, 27.8% were frail (mild or moderate-to-severe), and this proportion significantly increased to 35.5% at discharge (P &lt; 0.001). Compared to non-frail patients, frail patients were older, less likely to be male, and had a higher rate of advanced Killip class. Major bleeding (no frailty, 9.6%; mild frailty, 16.9%; moderate-to-severe frailty, 31.8%; P &lt; 0.001) and in-hospital mortality (no frailty, 8.4%; mild frailty, 15.4%; moderate-to-severe frailty, 27.3%; P &lt; 0.001) increased as frailty worsened. After adjusting for confounders, frailty was independently associated with higher mid-term all-cause mortality (hazard ratio, 1.81; 95% confidence interval, 1.23–2.65; P = 0.002). Conclusion  Frailty in AMI patients aged ≥80 years undergoing PCI was associated with major bleeding, in-hospital death, and mid-term mortality.