Activation of peroxisome proliferator-activated receptor α in megakaryocytes reduces platelet-derived growth factor-BB in platelets.

AIM: Platelet-derived growth factor (PDGF)-BB plays a crucial role in atherosclerosis and vascular remodeling by promoting the migration and proliferation of vascular smooth muscle cells. The objective of this study was to clarify the pleiotropic effect of peroxisome proliferator-activated receptor α (PPARα) activators on PDGF-BB expression in megakaryocytes and platelets. METHODS AND RESULTS: The expression of PPARα in a human erythroleukemia (HEL) cells was clearly detected by reverse transcriptase-PCR and immunofluorescence microscopy. The expression level of PPARα in HEL cells was unchanged regardless of differentiation into megakaryocytic cells by treatment with phorbol 12-myristate 13 acetate (TPA). The TPA-induced expression of PDGF-B mRNA and PDGF-BB protein levels in culture media was significantly decreased by treatment with PPARα activators, Wy14643 and fenofibric acid, in a dose-dependent manner. PDGF-BB expression induced by inflammatory cytokines, including interleukin-1ß or interleukin-6, was also significantly suppressed by treatment with PPARα activators. Immunohistochemistry of human bone marrow showed the expression of PPARα in both the nucleus and cytoplasm of megakaryocytes. In addition, PDGF-BB levels in platelets were significantly decreased from 1,800±870 to 1,470±840 pg/10(5) platelets (mean±SD, p<0.05) by treatment with 300 mg fenofibrate once daily for 4 weeks in 13 patients with dyslipidemia. CONCLUSIONS: Activation of PPARα in megakaryocytes reduces PDGF-BB expression in platelets. PPARα activators may exert vasculo-protective action through suppression of PDGF-BB production in a megakaryocyte/platelet pathway.

Decrease in plasma brain natriuretic peptide level in the early phase after the start of carvedilol therapy is a novel predictor of long-term outcome in patients with chronic heart failure.

OBJECTIVE: The purpose of the present study was to determine whether change in plasma brain natriuretic peptide (BNP) level at an early phase of carvedilol therapy is a predictor of improvement in cardiac function and long-term prognosis in patients with systolic chronic heart failure (CHF). METHODS AND RESULTS: Neurohumoral factors and haemodynamics were examined in 64 patients with systolic CHF (left ventricular ejection fraction (LVEF) below 45%) before and one month (early phase) and 3 to 6 months (late phase) after the start of carvedilol therapy. These patients were followed up for a mean period of 57 months. Plasma BNP levels were already decreased in the early phase before improvement of LVEF in response to carvedilol therapy. Univariate and multivariate linear regression analyses showed that Delta log brain natriuretic peptide (BNP)E (= log BNP at baseline--log BNP at early phase) (P < 0.0001) was a significant independent predictor of improvement in LVEF in the late phase. Cardiac events occurred in I I patients during the follow-up period. In addition, multivariate Cox proportional hazards regression analysis showed that Delta log BNPE (P = 0.0045) and systolic blood pressure at baseline (P = -0.048) were significant independent predictors of the development of cardiac events. CONCLUSIONS: Decrease in plasma BNP level in the early phase of carvedilol therapy is a novel predictor of not only improvement of LVEF in the late phase but also prognosis in patients with systolic CHF.

Intra-vascular ultrasound findings of diffuse coronary atherosclerotic change in systemic lupus erythematosus with secondary antiphospholipid syndrome.

Systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) are autoimmune inflammatory diseases associated with juvenile atherosclerosis and thrombosis, respectively. A 44-year-old woman who had SLE with secondary APS had been treated with corticosteroid therapy, however, her inflammatory marker had never been within a normal range in her clinical course, and finally acute myocardial infarction was developed. Intra-vascular ultrasound also revealed diffuse coronary atherosclerosis progression for her age, which might result from SLE and APS, including vascular inflammation.

Aspirin inhibits thrombin action on endothelial cells via up-regulation of aminopeptidase N/CD13 expression.

OBJECTIVE: We hypothesized that aspirin may exhibit its anti-atherosclerotic effects via mechanisms other than cyclooxygenase inhibition in platelets. METHODS AND RESULTS: Using enhanced subtraction hybridization analysis, we found in human umbilical vein endothelial cells (HUVECs) that aspirin up-regulates the expression of aminopeptidase N (APN/CD13) mRNA and its surface protein levels in a dose-dependent manner. Enzymatic activity of APN/CD13 on HUVECs was increased approximately 1.5-fold by 1 mmol L(-1) of aspirin, and treatment with bestatin, an inhibitor for APN/CD13 metalloprotease activity, attenuated the enhanced activities of APN/CD13. Since activated thrombin receptor is reported to be inactivated by APN/CD13 in vitro, protective actions of aspirin on HUVECs by thrombin stimulation were examined, resulting in the suppression of endothelin-1 and reactive oxygen species productions in HUVECs. These inhibitory actions of aspirin were partially abrogated by bestatin. CONCLUSIONS: Aspirin may exert its anti-atherothrombotic effects in part via the inhibition of thrombin action by up-regulating APN/CD13 on endothelial cells.

Androgen receptor gene knockout male mice exhibit impaired cardiac growth and exacerbation of angiotensin II-induced cardiac fibrosis.

Androgen has anabolic effects on cardiac myocytes and has been shown to enhance left ventricular enlargement and function. However, the physiological and patho-physiological roles of androgen in cardiac growth and cardiac stress-induced remodeling remains unclear. We aimed to clarify whether the androgen-nuclear androgen receptor (AR) system contributes to the cardiac growth and angiotensin II (Ang II)-stimulated cardiac remodeling by using systemic AR-null male mice. AR knock-out (ARKO) male mice, at 25 weeks of age, and age-matched wild-type (WT) male mice were treated with or without Ang II stimulation (2.0 mg/kg/day) for 2 weeks. ARKO mice with or without Ang II stimulation showed a significant reduction in the heart-to-body weight ratio compared with those of WT mice. In addition, echocardiographic analysis demonstrated impairments of both the concentric hypertrophic response and left ventricular function in Ang II-stimulated ARKO mice. Western blot analysis of the myocardium revealed that activation of extracellular signal-regulated kinases (ERK) 1/2 and ERK5 by Ang II stimulation were lower in ARKO mice than those of WT mice. Ang II stimulation caused more prominent cardiac fibrosis in ARKO mice than in WT mice with enhanced expression of types I and III collagen and transforming growth factor-beta1 genes and with increased Smad2 activation. These results suggest that, in male mice, the androgen-AR system participates in normal cardiac growth and modulates cardiac adaptive hypertrophy and fibrosis during the process of cardiac remodeling under hypertrophic stress.

Disruption of nuclear vitamin D receptor gene causes enhanced thrombogenicity in mice.

Vitamin D metabolites influence the expression of various genes involved in calcium homeostasis, cell differentiation, and regulation of the immune system. Expression of these genes is mediated by the activation of the nuclear vitamin D receptor (VDR). Previous studies have shown that a hormonally active form of vitamin D, 1alpha,25-dihydroxyvitamin D3, exerts anticoagulant effects in cultured monocytic cells. To clarify whether activation of VDR plays any antithrombotic actions in vivo, hemostatic/thrombogenic systems were examined in normocalcemic VDR knock-out (KO) mice on a high calcium diet and compared with wild type and hypocalcemic VDRKO mice that were fed a regular diet. Platelet aggregation was enhanced significantly in normocalcemic VDRKO mice compared with wild type and hypocalcemic VDRKO mice. Aortic endothelial nitric-oxide (NO) synthase expression and urinary NOx excretions were reduced in hypocalcemic VDRKO mice, but not in normocalcemic VDRKO mice. Northern blot and RT-PCR analyses revealed that the gene expression of antithrombin in the liver as well as that of thrombomodulin in the aorta, liver and kidney was down-regulated in hypo- and normocalcemic VDRKO mice. Whereas tissue factor mRNA expression in the liver and kidney was up-regulated in VDRKO mice regardless of plasma calcium level. Furthermore, VDRKO mice manifested an exacerbated multi-organ thrombus formation after exogenous lipopolysaccharide injection regardless of the calcemic conditions. These results demonstrate that activation of nuclear VDR elicits antithrombotic effects in vivo, and suggest that the VDR system may play a physiological role in the maintenance of antithrombotic homeostasis.

Heparin cofactor II is a novel protective factor against carotid atherosclerosis in elderly individuals.

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 306 Japanese elderly individuals (154 men and 152 women; age, 40 to 91 years; 68.9+/-11.1 years, mean+/-SD). 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 (r=0.119, P<0.05; r=0.196, P<0.001; and r=0.227, P<0.0001, respectively). In contrast, high-density lipoprotein (HDL) cholesterol and HCII activity were negatively correlated with MPT values (r=-0.117, P<0.05, and r=-0.202, P<0.0005, 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 (P<0.001 and P<0.05, 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.

High plasma heparin cofactor II activity is associated with reduced incidence of in-stent restenosis after percutaneous coronary intervention.

BACKGROUND: Thrombin plays an important role in the development of atherosclerosis and restenosis after percutaneous coronary intervention. Because heparin cofactor II (HCII) inhibits thrombin action in the presence of dermatan sulfate, which is abundantly present in arterial wall, HCII may affect vascular remodeling by modulating thrombin action. We hypothesized that patients with high plasma HCII activity may show a reduced incidence of in-stent restenosis (ISR). METHODS AND RESULTS: Sequential coronary arteries (n=166) with NIR stent (Boston Scientific Corp) implantation in 134 patients were evaluated before, immediately after, and at 6 months after percutaneous coronary intervention. Patients were divided into the following groups: high HCII (> or =110%, 45 lesions in 36 patients), normal HCII (> or =80% and <110%, 81 lesions in 66 patients), and low HCII (<80%, 40 lesions in 32 patients). Percent diameter stenosis at follow-up in the high-HCII group (18.7%) was significantly lower (P=0.046) than that in the normal-HCII group (30.3%) or the low-HCII group (29.0%). The ISR rate in the high-HCII group (6.7%) was significantly lower than that in the low-HCII group (30.0%) (P=0.0039). Furthermore, multivariate analysis demonstrated that high plasma HCII activity is an independent factor in reducing the incidence of angiographic restenosis (odds ratio, 0.953/1% increase of HCII; 95% CI, 0.911 to 0.998). CONCLUSIONS: 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.