Background-Thrombin plays a crucial role in atherothrombotic changes. Because heparin cofactor II (HCII) inhibits thrombin actions after binding to dermatan sulfate at injured arterial walls, HCII may negatively regulate thrombin actions in vascular walls. We hypothesized that plasma HCII activity is a preventive factor against atherosclerotic changes, especially in elderly individuals who already have atherosclerotic vascular injuries. Methods and Results-Maximum plaque thickness (MPT) in the carotid artery was measured by ultrasonography in 306Japanese elderly individuals (154 men and 152 women; age, 40 to 91 years; 68.9Ϯ11.1 years, meanϮSD). The relevance of cardiovascular risk factors including plasma HCII activity to the severity of MPT was statistically evaluated. Plasma HCII activity decreased with age. Simple linear regression analysis after adjustments for age and sex showed that lipoprotein(a), glycosylated hemoglobin A1c, and presence of diabetes mellitus significantly contributed to an increase in MPT values (rϭ0.119, PϽ0.05; rϭ0.196, PϽ0.001; and rϭ0.227, PϽ0.0001, respectively). In contrast, high-density lipoprotein (HDL) cholesterol and HCII activity were negatively correlated with MPT values (rϭϪ0.117, PϽ0.05, and rϭϪ0.202, PϽ0.0005, respectively). Multiple regression analysis revealed that plasma HCII activity and HDL cholesterol independently contributed to the suppression of MPT values and that the antiatherogenic contribution of HCII activity was stronger than that of HDL cholesterol (PϽ0.001 and PϽ0.05, respectively). Conclusions-These results suggest that HCII can be a novel and independent antiatherogenic factor. Moreover, HCII is a stronger predictive factor than HDL cholesterol against carotid atherosclerosis in elderly individuals. (Circulation.

atherosclerosis. However, the in vivo effects and the molecular mechanism underlying the action of HCII during vascular remodeling remain elusive. To clarify the role of HCII in vascular remodeling, we generated HCII-deficient mice by gene targeting. In contrast to a previous report, HCII -/-mice were embryonically lethal. In HCII +/-mice, prominent intimal hyperplasia with increased cellular proliferation was observed after tube cuff and wire vascular injury. The number of protease-activated receptor-1-positive (PAR-1-positive) cells was increased in the thickened vascular wall of HCII +/-mice, suggesting enhanced thrombin action in this region. Cuff injury also increased the expression levels of inflammatory cytokines and chemokines in the vascular wall of HCII +/-mice. The intimal hyperplasia in HCII +/-mice with vascular injury was abrogated by human HCII supplementation. Furthermore, HCII deficiency caused acceleration of aortic plaque formation with increased PAR-1 expression and oxidative stress in apoE-KO mice. These results demonstrate that HCII protects against thrombin-induced remodeling of an injured vascular wall by inhibiting thrombin action and suggest that HCII is potentially therapeutic against atherosclerosis without causing coagulatory disturbance.

The results demonstrate that HCII may have a hitherto unrecognized effect in inhibiting ISR. The effect of HCII may be mediated by inactivating thrombin in injured arteries, thereby inhibiting vascular smooth muscle cell migration and proliferation.

Background: Increased serum lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerosis. We previously reported that aspirin reduced Lp(a) production by cultured hepatocytes via the reduction of apolipoprotein(a) [apo(a)] gene transcription. Methods: We evaluated both the effect of aspirin treatment (81 mg/day) on serum Lp(a) concentrations and the correlation between the degree of reduction in serum Lp(a) and the type of apo(a) isoform in 70 patients with coronary artery disease or cerebral infarction. Results: Aspirin lowered serum Lp(a) concentrations to ∼80% of the baseline values in patients with high Lp(a) concentrations (>300 mg/L). The percentage of decrease in serum Lp(a) was larger in patients with high Lp(a) than in patients with low Lp(a) (<300 mg/L), irrespective of apo(a) isoform size. The decreases in serum Lp(a) in high Lp(a) patients with both the high-molecular-weight and the low-molecular-weight isoforms were positively correlated with the baseline Lp(a) concentrations. Conclusions: Because the secretory efficiencies of apo(a) in the same isoform are likely to be similar, the difference in serum Lp(a) concentrations in patients having the same apo(a) isoform depends on the transcriptional activity of the apo(a) gene. These findings suggest that aspirin decreases serum Lp(a) concentrations via a decrease in apo(a) gene transcription more effectively in patients with high transcriptional activity of this gene.