Is blockade of the Renin-Angiotensin system able to reverse the structural and functional remodeling of the left ventricle in severe aortic stenosis?

: In experimental aortic stenosis (AS), blockade of the renin-angiotensin system attenuates AS-related left ventricular (LV) dysfunction and improves survival. We tested whether candesartan, an angiotensin II type 1 receptor blocker, favorably influences LV structure and function and improves exercise capacity in AS patients. Fifty-one patients with severe AS were randomized to receive candesartan (target dose 16 mg/d) or placebo. Eight patients discontinued treatment and the remaining 43 patients underwent echocardiography, walking test, and measurement of plasma N-terminal B-type natriuretic peptide (Nt-proBNP) before and after an average of 5-month treatment. No statistically significant changes in LV diameters, mass, or function were seen. The median 6-minute walking distance decreased from 390 to 368 m with candesartan (P = 0.003) and from 380 to 370 m with placebo (P = 0.523), reflecting natural progression of AS. Concomitantly, median Nt-proBNP increased from 319 to 414 ng/L with candesartan (P = 0.170) and from 413 to 561 ng/L with placebo (P = 0.035). No change with candesartan was statistically significantly different from the corresponding change with placebo. In conclusion, candesartan was well tolerated but had no favorable effects on the LV or effort tolerance. The benefits found in experimental AS of blocking the renin-angiotensin system could not be reproduced in patients with severe AS.

MicroRNA-125b and chemokine CCL4 expression are associated with calcific aortic valve disease.

Calcific aortic valve disease (CAVD) is a progressive pathological condition with no effective pharmacological therapy. To identify novel molecular pathways as potential targets for pharmacotherapy, we studied microRNA (miRNA) profiles of heavily stenotic aortic valves (AS). One of the most upregulated miRNAs in AS valves compared to control valves was miR-125b (1.4-fold; P < 0.05). To identify CAVD-related changes in gene expression, DNA microarray analysis was performed, including an intermediate fibro(sclero)tic stage of the disease. This revealed changes especially in genes related to inflammation and immune response, including chemokine (C-C motif) ligand 3 (CCL3) and 4 (CCL4). CCL3 mRNA level was increased 3.9-fold (P < 0.05) when AS valves were compared to control valves, and a 2.5-fold increase (P < 0.05) in CCL4 gene expression was observed when fibro(sclero)tic valves were compared to control valves. Both CCL3 and CCL4 localized to macrophages by immunofluorescence. To identify chemokine-miRNA target pairs, data from miRNA target prediction databases were combined with valvular miRNA and mRNA expression profiles. MiR-125b was computationally predicted to target CCL4, as confirmed experimentally in cultured human THP-1 macrophages. Collectively, miR-125b and CCL4 appear to be involved in the progression of CAVD and may offer novel therapeutic and diagnostic strategies related to this disease.

Dietary plant stanols or sterols neither accumulate in stenotic aortic valves nor influence their structure or inflammatory status.

BACKGROUND & AIMS: Consumption of plant stanols and plant sterols decreases LDL cholesterol level and increases serum concentrations of plant stanols/sterols, but it is practically unexplored whether also their tissue concentrations increase. Thus, the aim of this study was to assess whether consuming plant stanols/sterols increases their concentrations in stenotic aortic valves and affect the valvular structure (collagen and elastin) or inflammation (macrophages and mast cells). METHODS: In a randomized, double-blind controlled intervention patients with severe aortic stenosis consumed margarine without (n = 11) or with 2 g of plant stanols (n = 12) or sterols (n = 13) until valve replacement surgery (2.6 months, on average). The effects of sitostanol and sitosterol on the expression and secretion of proinflammatory cytokines by cultured aortic valve myofibroblasts were also assessed. RESULTS: Control-related LDL-cholesterol was diminished by 16% (p < 0.05) by plant stanol and by 11% (NS) by plant sterol consumption, respectively. In the resected valves, cholesterol, plant stanol and sterol levels were similar in all groups. Consumed plant stanols or sterols had no effect on valvular structure or mast cell or macrophage numbers in valves. Incubation of cultured myofibroblasts derived from stenotic valves with sitostanol or sitosterol decreased mRNA expression of the monocyte chemotactic protein-1 (p < 0.05) and interleukin-1 beta (p < 0.05). CONCLUSIONS: In this study, plant stanol/sterol consumption did not affect cholesterol, plant stanol or sterol levels in stenotic aortic valves; neither did they influence the structure or the inflammatory status of the valves. However, these findings need to be confirmed in a larger-scale intervention. ClinicalTrials.govRegister #NCT00738933.

Potential pathological roles for oxidized low-density lipoprotein and scavenger receptors SR-AI, CD36, and LOX-1 in aortic valve stenosis.

OBJECTIVE: To clarify the potential mechanisms by which oxidized low-density lipoprotein (oxLDL) could contribute to the progression of aortic valve stenosis (AVS). METHODS: We investigated a total of 46 stenotic and 20 control human aortic valves. The mRNA expression levels of scavenger receptor class A type 1 (SR-A1), CD36, Lectin-like oxidized LDL receptor-1 (LOX-1), and scavenger receptor class B type 1 (SR-B1) were studied using qPCR. Their cellular distribution in the valves was assessed by immunohistochemistry, and the potential effects of oxLDL were studied in cultured myofibroblasts isolated from the aortic valves. RESULTS: In AVS, the proinflammatory SR-A1 and the angiogenic LOX-1 were upregulated (p = 0.003 and p = 0.002), whereas the antiangiogenic CD36 was downregulated (p = 0.02). The expression of the atheroprotective SR-B1 remained unchanged. Immunohistochemistry revealed that SR-A1 was expressed by macrophages, whereas the expression of CD36 and LOX-1 was confined to myofibroblasts and endothelial cells in the diseased valves. In cultured valvular myofibroblasts, mast cell-derived components and TNF-α induced LOX-1 expression (p = 0.05 and p < 0.001), whereas oxLDL promoted the expression of proinflammatory cytokines. Furthermore, the expression of osteoprotegerin, an inhibitor of valvular calcification, decreased in response to oxLDL. Finally, myofibroblasts derived from stenotic valves accumulated more DiI-labeled oxLDL than myofibroblasts derived from macroscopically healthy valves (p = 0.035), so revealing enhanced foam cell-forming potential of myofibroblasts in the diseased valves. CONCLUSION: This study unveils the presence of SR-A1, CD36, and LOX-1 in aortic valves and suggests potential mechanisms by which they may contribute to the pathological angiogenesis, inflammation, calcification, and lipid accumulation in AVS.

Modified lipoprotein-derived lipid particles accumulate in human stenotic aortic valves.

In aortic stenosis plasma lipoprotein-derived lipids accumulate in aortic valves. Here, we first compared the lipid compositions of stenotic aortic valves and atherosclerotic plaque cores. Both pathological tissues were found to be enriched in cholesteryl linoleate, a marker of extracellularly accumulated lipoproteins. In addition, a large proportion of the phospholipids were found to contain arachidonic acid, the common precursor of a number of proinflammatory lipid mediators. Next, we isolated and characterized extracellular lipid particles from human stenotic and non-stenotic control valves, and compared them to plasma lipoproteins from the same subjects. The extracellular valvular lipid particles were isolated from 15 stenotic and 14 non-stenotic aortic valves. Significantly more apoB-100-containing lipid particles were found in the stenotic than in the non-stenotic valves. The majority of the lipid particles isolated from the non-stenotic valves had sizes (23±6.2 nm in diameter) similar to those of plasma low density lipoprotein (LDL) (22±1.5 nm), while the lipid particles from stenotic valves were not of uniform size, their sizes ranging from 18 to more than 500 nm. The lipid particles showed signs of oxidative modifications, and when compared to isolated plasma LDL particles, the lipid particles isolated from the stenotic valves had a higher sphingomyelin/phosphatidylcholine -ratio, and also higher contents of lysophosphatidylcholine and unesterified cholesterol. The findings of the present study reveal, for the first time, that in stenotic human aortic valves, infiltrated plasma lipoproteins have undergone oxidative and lipolytic modifications, and become fused and aggregated. The generated large lipid particles may contribute to the pathogenesis of human aortic stenosis.