Oehler, Elise A.

Calcific aortic valve disease (CAVD) is a highly active process, and upregulation of osteogenic signaling is thought to be a major driver to initiation and progression of disease. While previous reports by our group and others demonstrated dysregulation of antioxidants and pro-oxidants in calcified aortic valves, it remains unclear if loss of antioxidant is a causal event driving valvular calcification and dysfunction. We hypothesized that MnSOD deficiency—an essential mitochondrial antioxidant—would result in accelerated reductions of cusp separation distance, increased osteogenic signaling, and augmented calcium deposition in a hypercholesterolemic mouse model of CAVD. We used ldlr -/- / ApoB 100/100 (LA) mice that were either wild-type (LA-MnSOD +/+ ) or MnSOD-deficient (LA-MnSOD +/- ), fed a Western Diet for 3 or 6 months. We used qRT-PCR and immunohistochemistry to measure changes in pro-osteogenic signaling, histopathological analyses of calcium burden (Alizarin Red), and echocardiography to assess aortic valve function. BMP2—a pro-osteogenic marker—increased over time with Western diet feeding, though MnSOD-deficiency did not exacerbate these increases. mRNA levels of pro-osteogenic markers (Runx2, Msx2) were also unchanged with either time on diet or with experimental reduction of MnSOD. Surprisingly, protein levels of late- stage osteoblast marker, osterix, were modestly decreased at the three month time point in in LA-MnSOD +/- mice compared to age-matched wild-type littermates. Consistent with our hypothesis, however, loss of mitochondrial antioxidant capacity substantially increased osterix protein levels and calcium burden at the 6 month time point compared to age-matched wild-type littermates. Functionally, loss of mitochondrial antioxidant capacity did not alter aortic valve cusp separation distance at both 3 and 6 month time points. Collectively, these data suggest that loss of MnSOD does not alter disease initiation but instead augments osteogenic signaling and valvular calcification in established aortic valve disease. Future studies aimed at targeting mitochondrial oxidative stress could elucidate novel strategies to slow progression of established CAVD.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases (NOS), and is degraded primarily by dimethylarginine dimethylaminohydrolase-1 (DDAH1). While ADMA is elevated in patients with fibrocalcific aortic valve stenosis (FCAVD), is it unknown whether tissue levels of DDAH1 are altered in FCAVD, and whether systemic elevations in ADMA levels accelerate initiation and/or progression of FCAVD. In the present study, we measured expression of DDAH1 in normal and stenotic human aortic valves, and tested the hypothesis that increases in ADMA worsen hypertension and endothelial dysfunction and accelerate the initiation and progression of FCAVD in hypercholesterolemic mice. In tissue from humans with FCAVD, expression of DDAH1 was significantly increased compared to normal valve tissue (normal = 1.0 ± 0.1, FCAVD = 1.3 ± 0.1, ⋔⋔Ct method; p < 0.05). To experimentally alter DDAH1 levels, we used low density lipoprotein receptor-deficient, apolipoprotein B100-only (LA) mice that were either wild-type (D +/+ ) or heterozygous (D +/- ) for DDAH1. Blood pressure (tail cuff), aortic endothelial function (isolated organ bath), and aortic valve function (echocardiography), were measured at 3 and 6 month time points in these mice. Compared to LA-D +/+ mice, systolic arterial pressure was significantly increased in LA-D +/- mice at both 3 month (121±4 mmHg and 144±4 mmHg) and 6 months (138±6 mmHg and 148±4 mmHg). Aortic endothelial function progressively declined with prolonged hypercholesterolemia, but maximum relaxation to acetylcholine did not differ between LA-D +/+ and LA-D +/- mice at 3 or 6 months. While aortic valve function was similar between LA-D +/+ and LA-D +/- mice at 3 months (peak transvalvular velocity: 1.98±0.07 m/sec versus 1.94±0.06 m/s, respectively), aortic valve function was significantly worse in LA-D +/- (2.41±0.11 m/sec) compared to LA-D +/+ mice (2.20±0.09 m/sec) at 6 months (p < 0.05). In conclusion, our data support a working model in which increases in valvular DDAH1 levels protect against progression of FCAVD. Importantly, loss of DDAH1 in mice does not alter aortic valve function during early stages of FCAVD, but accelerates progression of FCAVD independently of changes in endothelial function.

Background: C-type natriuretic peptide (CNP) is of endothelial cell origin and represents the most potent anti-fibrotic peptide of the natriuretic peptide family and is important for extracellular matrix homeostasis including mediating bone growth in the young. Cardiorenal aging is associated with altered cardiac and renal structure and function that may contribute to the development of heart and kidney failure, particularly in the elderly. The impact of aging on circulating CNP and associated changes in cardiorenal structure and function are undefined. Hypothesis: We hypothesized that a decrease in endogenous plasma CNP occurs with aging and is associated with an increase in cardiorenal fibrosis and altered left ventricular (LV) and renal structure and function. Methods: Studies were performed in 2, 11 and 20 month old male Fischer rats (n = 8 –10/group). Echo was used to assess LV structure and function. Blood pressure (BP), urinary protein excretion, plasma B-type natriuretic peptide (BNP) and CNP were measured. Kidneys and LV were harvested for gross and histology analysis. Mean±SE, *p<0.05. Results: Aging from 2 to 20 months was associated with progressive reductions in plasma CNP (30±3 to 21±1* to 9±1*pg/ml). Significant and progressive cardiac and renal fibrosis were observed with aging (LV: 9±0.3 to 15±0.7* to 21±1*% and kidney: 1±0.3 to 8±2* to 17±1* %). In contrast to CNP, plasma BNP was modestly increased from the 2 to 20 month old group (21±2 to 26±1*pg/ml). The reduction in CNP and increase in BNP, the latter a biomarker for LV dysfunction, were associated with decreased EF (88±1 to 80±1*%) and increased LVEDd (6.61±0.09 to 7.48±0.09*mm). BP and urinary protein excretion were mildly elevated with aging (91±1 to 101±3* mmHg and 8±0.3 to 20±3* mg/day, respectively). Conclusion: We report for the first time that aging is associated with a progressive decline in circulating CNP and progressive cardiorenal fibrosis, systolic dysfunction and proteinuria. Further studies are warranted to explore the hypothesis that a mechanism of cardiorenal aging with altered cardiorenal structure and function may include a decrease in the bioavailability of CNP.

Thrombin plays a major role in coagulation cascade and participates in regulation of vascular function through its effects on protease-activated receptors (PARs). The effect of thrombin inhibition on vascular and aortic valve function during prolonged hypercholesterolemia, however, remains unknown. In the present study, we tested the hypothesis that direct thrombin inhibition (DTI, dabigatran etexilate) slows progression of endothelial and aortic valve dysfunction in ldlr-deficient, apolipoprotein B100-only (LA) mice. Carotid arteries from LA mice were used for studies of endothelial function in isolated organ baths, and aortic valve function was evaluated using echocardiography. In placebo-treated mice, maximum relaxation to acetylcholine was reduced following 6 and 9 months of hypercholesterolemia (maximum relaxation to acetylcholine (MR ACH ) =75%± 3.7, and 67%± 3.6, respectively), but not affected by DTI (75%± 2.5, and 62%± 3.2, respectively). Relaxation to exogenous NO donors was also unaffected by DTI. Aortic valve function progressively deteriorated at 3, 6, and 9 months in placebo-treated mice (2.1 m/s± 0.04, 2.5 m/s± 0.1, and 2.9m/s ± 0.1, respectively), and was not affected by DTI (2.0m/s± 0.1, 2.5m/s± 0.1 and 3.0m/s ± 0.4, respectively). While PAR receptor expression was detected in aorta and aortic valve tissue, expression of SPHK1 (an indicator of PAR1 activity) was not altered by DTI. Expression of CTGF in aortic valves, however, tended to be reduced by DTI. In conclusion, our data suggest that DTI does not prevent vasomotor or aortic valve dysfunction in mice with prolonged hypercholesterolemia, but may attenuate pro-fibrotic signaling in aortic valves.

Introduction While progression of calcific aortic valve stenosis (CAVS) is known to be strongly associated with activation of pro-inflammatory and pro-osteogenic pathways, effective treatments for CAVS have remained elusive. TNF-α is a pleiotropic inflammatory cytokine and is upregulated in patients with CAVS. Hence, we hypothesized that TNF-α inhibition, using the neutralizing antibody infliximab, can slow the progression of CAVS in vivo . Methods We used Ldlr -/- Apob 100/100 mice, which develop robust CAVS in an age-dependent manner, as a model. Mice were fed a Western-type diet for 6 months, then randomized into one of two groups: 1) twice-weekly infliximab injections (10 mg/kg intraperitoneally; n=10), and 2) saline injections (n=9). Aortic valve function was evaluated using echocardiography, and gene expression in aortic valves was measured using quantitative real-time PCR. Data are presented as mean ± SEM. Results During the 3 months preceding treatment initiation, aortic valve cusp separation distance decreased progressively in both groups (reduction by 0.082±0.011 mm in control group, 0.095±0.016 mm in infliximab group; p =0.27). Three months after initiation of treatment, cusp separation continued to decrease in control mice (by 0.108±0.021 mm), while progression of valve dysfunction was slower by 42% in the infliximab group (reduction of 0.063±0.009 mm; p =0.03 vs control). Expression of the pro-inflammatory genes Vcam1 and Nos2 was significantly reduced in valves of the infliximab group (by 37% and 60%, respectively). Moreover, endothelium-dependent vasodilation was improved by infliximab (improvement in maximum relaxation to acetylcholine in infliximab group 18±6% compared to control). Conclusions This study is the first to report that in vivo inhibition of TNF-α slows progression of CAVS in mice with established valve disease. This beneficial effect was accompanied by reduction in pro-inflammatory gene expression and improvement of systemic endothelial function, suggesting infliximab may exert its effects in part by increasing nitric oxide bioavailability. The findings warrant further investigation into the role of TNF-α in initiation and progression of CAVS, as well as its potential as a therapeutic target in human CAVS.

Increasing age is a major risk factor for calcific aortic valve disease (CAVD). Interestingly, SIRT6 knockout mice have a marked progeroid phenotype, and we recently reported that sirtuin enzyme expression is dramatically reduced with aging and that SIRT6 expression is reduced further in valves from patients with end-stage CAVD. It is unknown, however, whether experimentally reducing SIRT6 promotes osteogenic signaling in the valve and ultimately accelerates progression of CAVD. Thus, we used cultured mouse aortic valve interstitial cells and ldlr-deficient, apolipoprotein B100-only mice (LA) that were SIRT6 wild-type (LA-SIRT6 +/+ ) or heterozygous (LA-SIRT6 +/- ) and fed a Western diet for 3 or 12 months to determine the role of SIRT6 in valve calcification. In vitro , reduction of SIRT6 increased histone acetylation and significantly increased mRNA and protein levels of the osteogenic genes Runx2 and Sp7 in response to bone morphogenetic protein 2 (100ng/ml BMP2 for 18 hours), and siRNA knockdown of SIRT6 increased mRNA levels of Sp7 even in the absence of exogenous bone morphogens. Using high-resolution ultrasound to evaluate aortic valve function in vivo, we found that 3 month old LA-SIRT6 +/- mice did not have significant impairments in valve function compared to LA-SIRT6 +/+ mice. In contrast, 12 month old LA-SIRT6 +/- had dramatically worsened aortic valve dysfunction and stenosis compared to LA-SIRT6 +/+ mice, which was also associated with reductions in left ventricular ejection fraction. Collectively, our data strongly suggest SIRT6 plays a critical role in the tonic repression of osteogenic signaling in the aortic valve, and that age-related reductions in SIRT6 are likely to increase susceptibility to valve calcification in response to risk factors for CAVD such as hypercholesterolemia. Collectively, increasing activity of SIRT6 or reducing acetylation of its targets may serve as viable therapeutic strategies to slow progression of age-related valvular calcification and stenosis.

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthases, is primarily degraded by DDAH1. We tested the hypotheses that over expression DDAH1 reduces endothelial dysfunction and slows progression of fibrocalcific aortic valve disease (FCAVD) in hypercholesterolemic mice. We used low density lipoprotein receptor‐deficient, apolipoprotein B100‐only (LA) mice that were either wild‐type (D 0/0 ) or overexpressed human DDAH1 (D Tg/0 ). Systolic blood pressure (SBP, tail cuff), vasomotor function (isolated organ bath), and aortic valve function (echocardiography), were measured at 3 and 6 month time points. Compared to LA‐D 0/0 mice, SBP was reduced by ~15 mmHg in LA‐D Tg/0 mice at both 3 and 6 months (p < 0.05). Although aortic endothelial function progressively declined with prolonged hypercholesterolemia, there were no differences between LA‐D 0/0 and LA‐D Tg/0 mice. While aortic valve function was similar between LA‐D 0/0 and LA‐D Tg/0 mice at 3 months (peak transvalvular velocity: 1.95±0.09 m/sec versus 2.03±0.07 m/sec), overexpression of DDAH1 slowed progression of valvular dysfunction at 6 months (2.07±0.10 m/sec versus 2.30±0.05 m/sec). In conclusion, our data suggest that increasing DDAH1 may be an effective therapeutic strategy to slow progression of FCAVD, and is likely to exert protective effects independent of changes in systemic endothelial function.

Abstract Background Anthracyclines are one of the most effective chemotherapeutic agents but can lead to a decline in cardiac function. Two-dimensional (2D) speckle tracking echocardiography derived strain can predict cancer therapeutics-related cardiac dysfunction (CTRCD). However, little is known about the role of three-dimensional (3D) strain imaging in this setting. Purpose To evaluate different methods of Left Ventricular Ejection Fraction (LVEF) and strain, and to identify the best strain parameter for the prediction of CTRCD in this group of patients during treatment with anthracycline based chemotherapy. Methods Patients with Hodgkin's or non-Hodgkin's lymphoma receiving anthracycline based chemotherapy were enrolled. 2D-and 3D echocardiography was performed at 3 time points: baseline, at the completion of chemotherapy and at 1 year. 2D- and 3D LVEF (2D Modified Quinones, M-mode, 2D Biplane, 3D Philips, 3D GE and 3D TomTec), peak systolic left and right ventricular longitudinal, radial and circumferential strain and strain rate were measured. CTRCD was defined as a decrease in LVEF >10% to an absolute value of <53%. Lin's Concordance Correlation Coefficient (CCC) was calculated to compare LVEF methods. ANOVA, uni and multivariate analysis was performed. Results A total of 130 patients (79 males, mean age 57±16 years) were enrolled; 104 non-Hodgkin.3D Philips and GE (CCC 0.88 [0.84, 0.92]), 3D Philips and biplane (CCC 0.84 [0.79, 0.89]), 3D Philips and Modified Quinones (CCC 0.86 [0.82, 091]) as well as 3D Philips and M-mode (CCC 0.77 [0.70, 0.85]) showed strong correlation for LVEF. 15 patients (12%) developed CTRCD. Mean cumulative anthracycline dose was 263±65 mg/m2. 2D and 3D global longitudinal and circumferential peak systolic strain, 2D global longitudinal systolic and early diastolic strain rate, 2D global early diastolic strain rate, 2D right ventricular longitudinal peak systolic strain and systolic strain rate, 2D global radial peak systolic strain and systolic strain rate measured at the completion of chemotherapy were independent predictors of the development of CTRCD at 1 year post-chemotherapy. The strongest predictors of CTRCD were 3D global longitudinal and circumferential strain either individually (area under the curve, 0.90 and 0.95 respectively) or combined (area under the curve, 0.95) at the completion of chemotherapy; a cutoff value of <-18% in 3D global longitudinal strain had a sensitivity of 82% and specificity of 99%, while for 3D global circumferential peak systolic strain of <-24% had a sensitivity of 82% and specificity of 95%. Conclusions To our knowledge this is the first prospective trial that shows that 3D EF correlates well with other EF methods and 3D strain predicts cardiac toxicity in this group of patients with a very good sensitivity and specificity. Acknowledgement/Funding Department of Cardiovascular Medicine-Mayo Clinic Rochester MN

The balance between local asymmetric dimethylarginine (ADMA) levels and dimethylarginine dimethylaminohydrolase 1 (DDAH1) activity is a major determinant of local nitric oxide synthase activity. Previous studies suggested that increased plasma ADMA levels are strongly associated with the aortic valve stenosis, causal or mechanistic links have yet to be elucidated. Thus, the aim of this study was to investigate whether reduction or overexpression of DDAH1 protects aortic valve dysfunction in mice. To experimentally alter DDAH1 levels, we used low density lipoprotein receptor deficient, apolipoprotein B100-only (LA) mice that were either DDAH1 wild-type (D +/+ or D 0/0 ), heterozygous (D +/- ), or transgenic/overexpressing (D Tg/0 ) littermates. All mice were fed a western diet for 6 months. Reducing DDAH1 increased plasma ADMA levels (LA-D +/+ =0.89 ± 0.02 μmol/L, LA-D +/- =1.1 ± 0.02 μmol/L, p< 0.05) and blood pressure (LA-D +/+ = 125 ± 4 mmHg, LA-D +/- = 141 ± 3 mmHg, p< 0.05) following 6 months of western diet feeding. Critically, aortic valve function was significantly worse in DDAH1-deficient mice (LA-D +/+ 2.20±0.09 m/sec versus LA-D +/- =2.41±0.11 m/sec, p< 0.05) and was associated with higher levels of valve cusp calcification (Alizarin Red, LA-D +/+ = 10 ± 3% versus LA-D +/- = 20 ± 4%). Reciprocally, overexpression of DDAH1 in hypercholesterolemic littermates reduced ADMA levels (LA-D 0/0 = 1.4 ± 0.2 μmol/L, LA-D Tg/0 = 0.7 ± 0.1μmol/L, p< 0.05) and systolic blood pressure (LA-D 0/0 = 136 ± 6 mmHg, LA-D Tg/0 = 124 ± 4 mmHg, p< 0.05). Interestingly, aortic valve function was not improved by overexpression of DDAH1 (LA-D 0/0 = 2.36 ± 0.06 m/sec versus LA-D Tg/0 mice (2.43 ± 0.21 m/sec), nor was valvular calcification. These results suggest that while endogenous levels of DDAH1 expression protect against increases in circulating ADMA, blood pressure, valvular calcification, and valvular dysfunction. Interestingly, overexpression of DDAH1 does not appear to confer additional protection against progression of valvular stenosis. Collectively, our data suggest effective therapeutic harnessing of the DDAH1/ADMA/NOS axis will require targeting of downstream effector molecules—such as oxidation state of soluble guanylate cyclase—known to be pathologically altered and rate limiting in a variety of cardiovascular diseases.