Impact of medical therapy on atheroma volume measured by different cardiovascular imaging modalities

Renin and aldosterone are not associated with vulnerable plaque characteristics in patients with carotid artery disease

BACKGROUND

The renin-angiotensin-aldosterone system is increasingly being recognized to play an important role in the development and clinical course of cardiovascular diseases. Renin-angiotensin-aldosterone system activation is associated with clinical outcome in various populations of cardiovascular patients, such as patients with coronary artery, peripheral artery, and cerebrovascular disease. In this study, we investigated the associations between plasma renin and aldosterone concentrations and atherosclerotic plaque characteristics and secondary vascular events in patients undergoing carotid endarterectomy.

METHODS AND RESULTS

Baseline plasma renin and aldosterone concentrations from 506 subjects undergoing carotid endarterectomy (mean age, 67 ± 9 years; 65% male) were correlated with histopathologic characteristics and inflammatory protein concentrations of the excised atherosclerotic plaque. Ordinal logistic regression (for ordinal outcome parameters) or linear regression (for linear outcome) analysis did not show a statistically significant relationship between plasma renin or aldosterone concentrations and plaque fat, thrombus, calcifications, collagen, smooth muscle cells, or macrophage content. Neither could any association be found with intraplaque inflammatory mediators. During a median follow-up of 3 years, 102 (20%) patients experienced a major secondary vascular event (composite of stroke, myocardial infarction, leg amputation, vascular death, or coronary revascularization or peripheral intervention). In multivariable Cox regression analysis, including both renin and aldosterone, baseline renin concentrations were associated with the occurrence of secondary events.

CONCLUSIONS

In patients with established atherosclerotic disease undergoing carotid endarterectomy, plasma renin and aldosterone concentrations were not associated with atherosclerotic plaque characteristics. Plasma renin concentration was positively associated with the occurrence of major secondary vascular events.

Suppressive effects of irbesartan on inflammation and apoptosis in atherosclerotic plaques of apoE-/- mice: molecular imaging with 14C-FDG and 99mTc-annexin A5

OBJECTIVES

To investigate the effects of irbesartan on inflammation and apoptosis in atherosclerotic plaques by histochemical examination and molecular imaging using (14)C-FDG and (99m)Tc-annexin A5.

BACKGROUND

Irbesartan has a peroxisome proliferator-activated receptor gamma (PPARγ) activation property in addition to its ability to block the AT1 receptor. Accordingly, irbesartan may exert further anti-inflammatory and anti-apoptotic effects in atherosclerotic plaques. However, such effects of irbesartan have not been fully investigated. Molecular imaging using (18)F-FDG and (99m)Tc-annexin A5 is useful for evaluating inflammation and apoptosis in atherosclerotic plaques.

METHODS

Female apoE(-/-) mice were treated with irbesartan-mixed (50 mg/kg/day) or irbesartan-free (control) diet for 12 weeks (n = 11/group). One week after the treatment, the mice were co-injected with (14)C-FDG and (99m)Tc-annexin A5, and cryostat sections of the aortic root were prepared. Histochemical examination with Movat's pentachrome (plaque size), Oil Red O (lipid deposition), Mac-2 (macrophage infiltration), and TUNEL (apoptosis) stainings were performed. Dual-tracer autoradiography was carried out to evaluate the levels of (14)C-FDG and (99m)Tc-annexin A5 in plaques (%ID×kg). In vitro experiments were performed to investigate the mechanism underlying the effects.

RESULTS

Histological examination indicated that irbesartan treatment significantly reduced plaque size (to 56.4%±11.1% of control), intra-plaque lipid deposition (53.6%±20.2%) and macrophage infiltration (61.9%±20.8%) levels, and the number of apoptotic cells (14.5%±16.6%). (14)C-FDG (43.0%±18.6%) and (99m)Tc-annexin A5 levels (45.9%±16.8%) were also significantly reduced by irbesartan treatment. Irbesartan significantly suppressed MCP-1 mRNA expression in TNF-α stimulated THP-1 monocytes (64.8%±8.4% of un-treated cells). PPARγ activation was observed in cells treated with irbesartan (134%±36% at 3 µM to 3329%±218% at 81 µM) by a PPARγ reporter assay system.

CONCLUSIONS

Remissions of inflammation and apoptosis as potential therapeutic effects of irbesartan on atherosclerosis were observed. The usefulness of molecular imaging using (18)F-FDG and (99m)Tc-annexin A5 for evaluating the therapeutic effects of irbesartan on atherosclerosis was also suggested.

Measuring and targeting aldosterone and renin in atherosclerosis-a review of clinical data

Our understanding of the development and progression of atherosclerosis has increased substantially over the past decades. A significant role for the renin-angiotensin-aldosterone system (RAAS) in this process has gained appreciation in recent years. Preclinical and clinical studies have associated components of the RAAS with various cardiovascular disease conditions. Classically known for its contribution to hypertension, dysregulation of the system is now also believed to promote vascular inflammation, fibrosis, remodeling, and endothelial dysfunction, all intimately related to atherosclerosis. The reduction in cardiovascular mortality and morbidity, as seen with the use of angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, supports the concept that RAAS is involved in the pathogenesis of atherosclerotic disease. However, the underlying molecular mechanisms of the pathophysiology remain to be completely understood. Evidence points toward additional benefit from therapeutic approaches aiming at more complete inhibition of the system and the possible utility of renin or aldosterone in the prediction of cardiovascular outcome. This review will summarize the current knowledge from clinical studies regarding the presumptive role of renin and aldosterone in the prediction and management of patients with atherosclerosis. For this purpose, a literature search was performed, focusing on available clinical data regarding renin or aldosterone and cardiovascular outcome.