Blockade of PAR-1 Signaling Attenuates Cardiac Hypertrophy and Fibrosis in Renin-Overexpressing Hypertensive Mice

Background

Although PAR‐1 (protease‐activated receptor‐1) exerts important functions in the pathophysiology of the cardiovascular system, the role of PAR‐1 signaling in heart failure development remains largely unknown. We tested the hypothesis that PAR‐1 signaling inhibition has protective effects on the progression of cardiac remodeling induced by chronic renin–angiotensin system activation using renin‐overexpressing hypertensive (Ren‐Tg) mice.

Methods and Results

We treated 12‐ to 16‐week‐old male wild‐type (WT) mice and Ren‐Tg mice with continuous subcutaneous infusion of the PAR‐1 antagonist SCH79797 or vehicle for 4 weeks. The thicknesses of interventricular septum and the left ventricular posterior wall were greater in Ren‐Tg mice than in WT mice, and SCH79797 treatment significantly decreased these thicknesses in Ren‐Tg mice. The cardiac fibrosis area and monocyte/macrophage deposition were greater in Ren‐Tg mice than in WT mice, and both conditions were attenuated by SCH79797 treatment. Cardiac mRNA expression levels of PAR‐1, TNF‐α (tumor necrosis factor‐α), TGF‐β1 (transforming growth factor‐β1), and COL3A1 (collagen type 3 α1 chain) and the ratio of β‐myosin heavy chain (β‐MHC) to α‐MHC were all greater in Ren‐Tg mice than in WT mice; SCH79797 treatment attenuated these increases in Ren‐Tg mice. Prothrombin fragment 1+2 concentration and factor Xa in plasma were greater in Ren‐Tg mice than in WT mice, and both conditions were unaffected by SCH79797 treatment. In isolated cardiac fibroblasts, both thrombin and factor Xa enhanced ERK1/2 (extracellular signal‐regulated kinase 1/2) phosphorylation, and SCH79797 pretreatment abolished this enhancement. Furthermore, gene expression of PAR‐1, TGF‐β1, and COL3A1 were enhanced by factor Xa, and all were inhibited by SCH79797.

Conclusions

The results indicate that PAR‐1 signaling is involved in cardiac remodeling induced by renin–angiotensin system activation, which may provide a novel therapeutic target for heart failure.

D-dimer and C-reactive Protein as Potential Biomarkers for Diagnosis of Trousseau's Syndrome in Patients with Cerebral Embolism

BACKGROUND

Differentiating stroke due to Trousseau's syndrome from other types of cerebral embolism is challenging, especially in patients with occult cancer. The current study aimed to determine predicting factors and biomarkers of stroke due to Trousseau's syndrome.

METHODS

This retrospective study comprised 496 consecutive patients with acute cerebral embolism, including 19, 85, 310, and, 82 patients with stroke due to Trousseau's syndrome, artery-to-artery embolism, cardioembolic stroke, and embolic stroke with undetermined source, respectively. All patients were evaluated within 72 hours of onset. The clinical characteristics, laboratory findings, and patterns on diffusion-weighted magnetic resonance imaging (DWI) were compared among the groups.

RESULTS

Plasma D-dimer and C-reactive protein (CRP) levels were significantly higher in the Trousseau's syndrome than in the other causes of cerebral embolism. Multivariate analyses demonstrated that female sex, multiple lesions on DWI, high D-dimer and CRP levels, and low platelet and low brain natriuretic peptide levels were independent predictors that could distinguish Trousseau's syndrome from the other causes of cerebral embolism. The cutoff values of D-dimer and CRP to identify stroke due to Trousseau's syndrome was 2.68 µg/mL fibrinogen equivalent units and .29 mg/dL, respectively.

CONCLUSIONS

The elevated D-dimer and CRP levels on admission in addition to specific clinical features may be useful for diagnosis of Trousseau's syndrome in patients with cerebral embolism.

P856Incidence and Outcomes of irregular protrusion after stent implantation in patients with acute myocardial infarction: An in in vivo optical coherence tomography study

Background

Irregular protrusion, a protrusion of material with an irregular surface into the lumen of the vessel after stent implantation, can only be identified by optical coherence tomography (OCT). A previous study demonstrated that irregular protrusion after stent implantation was an independent predictor of 1-year major adverse cardiac events (MACE) in CAD patients. However, the true incidence and prognostic significance of irregular protrusion after stenting in patients with ST-segment elevation myocardial infarction (STEMI) have not previously examined.

Aims

The aims of this study were the following: 1) to evaluate the incidence of irregular protrusion detected by OCT in STEMI patients after stenting; and 2) to compare the long-term outcomes between patients with and without irregular protrusion.

Methods and results

A total of 210 STEMI patients who had post-procedure OCT imaging after coronary stenting within 12 hours after symptom onset were studied. We divided them into two groups: those with irregular protrusion (n=159) and those without (n=51) after stenting. There were no significant differences in baseline characteristics between the 2 groups except that peak CK-MB levels were higher in patients with irregular protrusion than those without (289 (137–563) vs. 260 (63–349) U/L, p<0.05). During mean follow-up period of 298 days, the overall incidence of MACE defined as cardiac death, target vessel-related myocardial infarction, and target lesion revascularization was 15.3%. Kaplan-Meier curve showed that the incidence of MACE did not differ between patients with and without irregular protrusion (14.7% vs. 17.7%, p=0.53 by Log-rank).

Conclusions

Irregular protrusion after stent implantation was detected in three-fourth of STEMI patients. Although patients with irregular protrusion had a greater myocardial damage, it did not influence clinical outcomes.

Acknowledgement/Funding

Donation course from Abbott Japan

P1624Blockade of protease activated receptor-1 signaling attenuates cardiac hypertrophy and fibrosis in renin-overexpressing hypertensive mice

Introduction

Recent evidences have demonstrated that coagulation pathway is involved in cardiovascular remodeling induced by renin-angiotensin system (RAS), which finally leads to heart failure. Protease activated receptor-1 (PAR-1) is widely expressed in the vasculature and the heart, and plays important roles in pro-inflammatory process in the cardiovascular system. Recently, we demonstrated that the activity of factor Xa (FXa), which functions not only as a coagulation factor but as an agonist for PAR-1, was enhanced in renin-overexpressing hypertensive mice (Ren-Tg).

Purpose

The purpose of this study was to investigate whether inhibition of PAR-1 signaling has protective effects on the progression of heart failure induced by chronic RAS activation in Ren-Tg.

Methods and results

We treated 12–16 weeks-old male wild type mice (WT) and Ren-Tg with continuous subcutaneous infusion of PAR-1 antagonist SCH79797 (25mg/kg/day) or vehicle for 4 weeks. After treatment period, left ventricular (LV) wall thickness calculated as interventricular septum plus posterior wall thickness measured by echocardiography was greater in Ren-Tg than in WT (0.25±0.003 versus 0.18±0.002 mm), and SCH79797 attenuated the increase to 0.22±0.01 mm in Ren-Tg (both p<0.05, respectively). The ratio of heart weight to body weight was greater in Ren-Tg than in WT (6.1±0.4 versus 4.6±0.7 mg/g), and SCH79797 attenuated the increase to 5.2±0.1 mg/g (both p<0.05). The area of cardiac fibrosis evaluated by Masson-trichrome staining was greater in Ren-Tg than in WT (2.6±0.2 versus 1.4±0.3%), and SCH79797 attenuated it to 1.6±0.3% in Ren-Tg (both p<0.05). Cardiac mRNA expressions of tumor necrosis factor-α, transforming growth factor-β1, and β-myosin heavy chain were all greater in Ren-Tg than in WT, and SCH79797 attenuated the increases in Ren-Tg (all p<0.05).

Conclusions

Inhibition of PAR-1 signaling attenuates cardiac hypertrophy and fibrosis in Ren-Tg via inhibition of inflammatory cytokines production. These results support the involvement of PAR signaling in the development of heart failure induced by RAS, and may provide novel therapeutic insights for the treatment of hypertensive heart failure.

Blood Pressure-Independent Effect of Olmesartan on Albuminuria in Mice Overexpressing Renin

Enhanced renin-angiotensin activity contributes to hypertension, albuminuria, and glomerular hypertrophy. The angiotensin (Ang)-converting enzyme (ACE) 2/Ang (1-7)/Mas axis pathway acts against Ang II type 1 receptor (AT1R) signaling. We investigated whether olmesartan (Olm), an AT1R blocker, inhibits albuminuria independently of blood pressure and elucidated the potential mechanisms.Three- to 4-month-old male mice overexpressing renin in the liver (Ren-TG) were given olmesartan (5 mg/kg/day) or hydralazine (Hyd) (3.5 mg/kg/day) orally for 2 months. Ren-TG mice had higher systolic blood pressure (SBP) than wild-type (WT) mice (158.2 ± 6.3 versus 112.8 ± 8.8 mmHg, n = 3-4, P < 0.01). Ren-TG mice treated with Olm or Hyd for 2 months had lower SBP than untreated Ren-TG mice. Urinary albumin excretion (UAE) was significantly increased in Ren-TG mice compared with WT mice (78.2 ± 31.2 versus 28.6 ± 13.8 μg/day, n = 5-6, P < 0.01). Olm treatment for 2 months reduced UAE, whereas Hyd treatment did not. Olm treatment reversed decreased gene and protein expressions of ACE2 and Mas receptor (Mas 1) in the kidney of Ren-TG mice and inhibited enhanced NADPH oxidase (Nox) 4 expression, whereas Hyd treatment had no influence. Furthermore, increased reactive oxygen species (ROS) in the kidney of Ren-TG mice were decreased by Olm treatment but not by Hyd treatment.Olm treatment inhibits albuminuria and glomerular hypertrophy independently of blood pressure not only through its original AT1R blockade but also partly through the enhancement of the ACE2/Ang (1-7)/Mas axis and suppression of ROS generation.

IFN-γ and TNF-α synergistically induce microRNA-155 which regulates TAB2/IP-10 expression in human mesangial cells

BACKGROUND/AIMS

MicroRNAs are noncoding small RNA molecules that posttranscriptionally regulate gene expression. microRNA-155 (miR-155), one of the microRNAs, is involved in the control of various genes. However, the role of miR-155 in inflammatory responses in mesangial cells is not known. In the present study, we examined the expression of miR-155 in mesangial cells.

METHODS

The expression of miR-155 in cultured normal human mesangial cells treated with interferon-γ (IFN-γ) and/or tumor-necrosis factor-α (TNF-α) was examined. The cells were transfected with miR-155 mimic, siRNA against transforming growth factor-β-activated kinase-1 (TAK1)-binding protein 2 (TAB2) or siRNA against nuclear factor-κB (NF-κB).

RESULTS

IFN-γ and TNF-α synergistically induced the expression of miR-155. Transfection of cells with miR-155 mimic inhibited the expression of TAB2 and IFN-γ-inducible protein of 10 kDa (IP-10). The expression of IP-10 was suppressed by knockdown of TAB2. Induction of miR-155 was inhibited by RNA interference against TAB2 or NF-κB.

CONCLUSION

Combined stimulation with IFN-γ and TNF-α induces miR-155 via TAB2 and NF-κB. miR-155 negatively regulates TAB2, as a negative feedback system, to lower IP-10 expression. miR-155 may play a role in the regulation of inflammatory and immune reactions in the kidney.

[Effect of aging on sensitivity of blood pressure to salt]

We investigated the correlation between aging and sensitivity of blood pressure to salt. 88 non-treated essential hypertensives were divided into four groups: less than 40 years old (n = 20), 40-49 years old (n = 20), 50-59 years old (n = 39), and greater than 60 years old (n = 11). Changes of blood pressure, plasma renin activity (PRA), plasma aldosterone concentration (PAC), plasma norepinephrine (PNE), and plasma epinephrine (PE) due to salt load were compared among four groups. Salt sensitivity of blood pressure was increased with aging, and there was a positive correlation between them (r = 0.30, p < 0.01). Decrement of PRA due to salt load was decreased with aging, and there was a negative correlation between them (r = -0.35, p < 0.05). PCA and PNE were suppressed by salt load, and the decrement degrees did not change with age. PE did not change by salt load. We conclude that salt sensitivity is increased with age in essential hypertensives, and renin-angiotensin system might be involved in it.

Role of renomedullary thromboxane A2 in development of doca-salt hypertension

To clarify the role of renal thromboxane (TX)A2 in the development of deoxycorticosterone acetate (DOCA)-salt induced hypertension, relationship between systolic blood pressure and the synthesis of renal TXA2 was investigated in 18 rats without and with OKY-046 administration which suppressed the synthesis of renal TXA2. Systolic blood pressure was significantly higher in DOCA-salt group than in control and OKY groups. The synthesis of 6-keto-prostaglandin(PG)F1 alpha and TXB2 in both renal arteries and cortical slices were more enhanced in DOCA-salt and OKY groups than in control group, but there was no significant difference between DOCA-salt and OKY groups. In contrast, the synthesis of 6-keto-PGF1 alpha in renomedullary slices did not vary significantly among three groups, and that of TXB2 was more increased in DOCA-salt group than in control and OKY groups. The cumulative sodium retention was significantly greater in DOCA-salt group than in control group. Administration of OKY-046 reduced the cumulative sodium retention in DOCA-salt rats by 45% toward that of the control group. These results might suggest that the enhanced production of renomedullary TXB2 was important to the development of DOCA-salt induced hypertension.

Changes in vascular wall production of prostacyclin and thromboxane A2 in spontaneously hypertensive rats during maturation and the concomitant development of hypertension

The purpose of this study was to clarify how the metabolism of vascular prostacyclin (PGI2) and thromboxane (TX) A2 in spontaneously hypertensive rats (SHR) is involved in aging and development of hypertension. We removed the aortic walls from 5-week-old and 20 to 25-week-old SHR and age-matched Wistar Kyoto rats (WKY). At 5 weeks of age, there was no significant difference in basal and maximal (arachidonic acid 0.1 mM) 6-keto-PGF1 alpha production between SHR and WKY, but the TXB2 generation in the SHR aortic wall was markedly enhanced as compared with that in WKY. At 20 to 25 weeks of age, the SHR aortic wall synthesized about 1.5 times more 6-keto-PGF1 alpha in the basal condition and twice as much as in the maximal condition as did the WKY wall. However there was no significant difference in TXB2 production between SHR and WKY. Age-dependent increase of vascular 6-keto-PGF1 alpha was greater in SHR than in WKY. Moreover, the maximal/basal 6-keto-PGF1 alpha production ratio increased with age in SHR, but not in WKY. The synthesis of vascular TXB2 was enhanced with age in WKY, but did not change with age in SHR. These data suggest that not only the enhanced basal generation of vascular 6-keto PGF1 alpha but also a much greater reservoir of 6-keto-PGF 1 alpha synthesis in SHR was induced by both hypertension and maturity. The increased production of vascular TXB2 in young SHR may affect the development of hypertension.