Citations

Previous studies have reported increases in oxidative stress due to reductions in antioxidant enzymes in calcified regions of stenotic human aortic valves. Whether reductions in antioxidant enzymes are adaptive, maladaptive, or an epiphenomenon in calcifying aortic valves remains unclear. Thus, the purpose of this study was to test whether overexpression of catalase reduces valvular calcification and slows progression of aortic valve stenosis in mice. Wild type (WT) mice with calcific aortic valve disease (ldlr-deficient, apoB100-only) were crossed with transgenic mice that overexpress human catalase (TG). All mice were fed a western diet (TD88137; Harlan Teklad). Functional echocardiogram data was collected and analyzed at early (3 months) and advanced (12 months) stages of valve disease, and valves were OCT embedded, sectioned, and stained for calcium levels (Alizarin Red). The transgenic valves show a slight increase in calcification compared to wild type counterparts. While there were no differences in valve function between genotypes at the early time point, cusp separation was decreased in the transgenic mice (0.74 ± 0.02 mm) compared to their wild-type littermates (0.84 ± 0.03 mm) at the 12 month time point (p < 0.05). In a subset of animals, valve calcification also tended to increase in transgenic mice at both time points compared to their wild-type littermates. In conclusion, overexpression of catalase resulted in a surprising finding of accelerated valvular calcification and stenosis. Interestingly, this finding aligns with the findings from several negative clinical trials testing antioxidant therapies in humans with atherosclerosis, suggests that the net impact of changing redox balance on disease progression are highly context dependent, and that increasing antioxidant capacity may not be a viable strategy to slow progression of calcific aortic valve disease in humans.

Endothelial dysfunction and arterial stiffening major risk factors associated with progression of atherosclerosis and increased risk of acute coronary events. Recent data suggest sirtuins may play a role in protecting against a variety age-related diseases, and we recently reported that sirtuins are reduced in the aging vasculature. The roles of SIRT3 (a deacetylase that is largely restricted to the mitochondria) in the regulation of vasomotor function and arterial stiffness, however, remains poorly understood. Therefore, we hypothesized that genetic inactivation of SIRT3 in hypercholesterolemic mice will impair endothelial function and reduce vascular compliance compared to hypercholesterolemic mice with normal levels of SIRT3. We used Ldlr -/- /ApoB 100/100 (LA) mice that were either wild-type for SIRT3 (LA-SIRT3 +/+ ) or null for SIRT3 (LA-SIRT3 -/- ) and fed a western diet for 12 months. At time of sacrifice, aorta was removed for isolated organ chamber baths to measure changes in endothelium-dependent relaxation to acetylcholine (ACH), and carotid arteries were harvested to assess changes in vascular compliance using a pressurized cannulation system. Surprisingly, losses of SIRT3 did not impair relaxation to ACH in aorta compared to LA-SIRT3 +/+ mice (38.2±4.4%, 37.0±4.4%, respectively). Furthermore, reductions in SIRT3 did not impact vascular compliance or distensibility in carotid arteries from the same animals. In conclusion, in contrast to our hypothesis, inactivation of SIRT3 does not impact vasomotor function or conduit vessel compliance in advanced atherosclerosis. Importantly, this and may be explained by a “floor-effect”, and future work examining the effect of SIRT3 overexpression on vascular function and pathology will be instrumental in determining its biological role and ultimate therapeutic utility.

Activation of NADPH oxidase is a major contributor to hypertension, reactive oxygen species generation, endothelial dysfunction and increased vascular distensibility in angiotensin II (AngII)‐induced hypertension. Since exercise has been associated with increased antioxidant enzyme expression in blood vessels, we hypothesized that exercise training would improve endothelial function and vascular distensibility in mice with AngII‐induced hypertension. C57BL/6J mice received saline or AngII (1000 ng/kg/min) via osmotic minipumps, and were assigned to sedentary or treadmill exercise groups (13 m/min for 30 minutes, 5 days/week) for 14 days. Endothelium‐dependent relaxation in response to acetylcholine and arterial distensibility were assessed in carotid arteries using a pressurized arteriograph system. Gene expression was examined by qRT‐PCR. In AngII‐treated sedentary mice, endothelium‐dependent relaxation was impaired, while distensibility was higher than in saline‐infused sedentary mice. Compared to AngII‐infused sedentary mice, however, endothelium‐dependent relaxation was partially improved, and distensibility normalized in AngII‐infused exercised mice. In response to exercise, mRNA levels of SOD1 and SOD2 in aorta were increased, while mRNA levels of NOX2 were reduced. We conclude that exercise training can dramatically improve endothelial dysfunction and reverse derangements in carotid distensibility following prolonged AngII‐induced hypertension. Additional work examining mechanisms underlying our observed transcriptional changes will be critical to development of novel therapeutic targets.

We previously reported that MnSOD‐deficiency does not cause overt vasomotor dysfunction in aged or hypercholesterolemic mice. To determine whether increasing MnSOD protects against vasomotor dysfunction and deleterious molecular changes in atherosclerosis, we crossed hypercholesterolemic mice with mice overexpressing MnSOD to test the hypothesis that lifelong increases in MnSOD protect against vasomotor dysfunction. We used Ldlr ‐/‐ /ApoB 100/100 mice that were wild‐type (MnSOD 0/0 ) or transgenic (MnSOD Tg/0 ) and fed a western diet for 6 months. We used organ bath chambers to measure aortic endothelium‐dependent relaxation (relaxation to acetylcholine, Ach), and mRNA from aortic arch was used for qRT‐PCR. Surprisingly, relaxation to Ach was unchanged between MnSOD 0/0 and MnSOD Tg/0 mice, as was relaxation to sodium nitroprusside. As expected, gene expression of MnSOD was significantly increased in the MnSOD Tg/0 mice compared to MnSOD 0/0 mice. Unlike our findings in MnSOD +/‐ mice, however (where Nox2 was increased), Nox2 expression was unchanged between MnSOD 0/0 and MnSOD Tg/0 mice. Importantly, markers of osteogenesis such as Runx2 and BMP2 were unchanged between genotypes. Furthermore, MnSOD overexpression did not alter cellular senescence markers. Collectively, our data support the surprising conclusion that physiologically relevant increases in MnSOD do not significantly affect endothelial function or molecular regulators of histopathological changes in advanced atherosclerosis in hypercholesterolemic mice.

Physical resilience, defined as the ability to resist and respond to challenges and return to homeostasis, has been postulated to be a determinant of healthspan and lifespan. To test this premise, we have begun to optimize a standardized, clinically relevant battery of resilience challenges, including anesthesia and cisplatin chemotherapy, and recovery outcome measures in younger (2–3 month) and older (26–29 month) mice. We have also started to test whether interventions shown to increase murine lifespan‐acarbose, rapamycin, and 17a‐estradiol‐impact the resilience of older mice. Our preliminary data demonstrate that younger mice (n = 10) have faster dorsal to sternal recumbence recovery time compared to older mice (n = 8) (39 ± 1 sec vs. 67 ± 6 sec, p < 0.001) following a 5‐minute 4% isoflurane anesthesia challenge. In response to a 5‐day cisplatin (2 mg/kg/day) challenge, both younger (n=5) and older (n=4) mice lost a significant percent of their baseline body weight (younger mice −10.6 ± 0.8% and older mice −13.2 ± 2.1%, p = 0.26), however, older mice failed to regain body weight 11 days after the challenge (younger mice −0.9 ± 0.8% and older mice −9.8 ± 0.8%, p < 0.01). Changes in body weight in younger and older mice were largely attributable to the loss/regain of fat mass. Interestingly, 8 weeks of either acarbose (1,000 ppm) or 17α‐estradiol (14.4 ppm) administration to older female mice improved body weight recovery after the cisplatin challenge, while rapamycin (14 ppm) had no appreciable effect. Our preliminary results demonstrate that younger mice, as expected, have greater resilience than older mice to clinically relevant physical challenges. The age at which physical resilience starts to decline requires further investigation. Our early observations suggest interventions that extend health‐ and lifespan may impact resilience in older mice. Ultimately, a standardized battery of resilience challenges may provide a new framework for testing and translating interventions that target the fundamental biology of aging. Support or Funding Information This work was supported by grant AG52958 from the National Institutes of Health. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Sirtuin 3 (SIRT3)—a deacetylase localized to the mitochondria—deacetylates a number of mitochondria‐specific proteins, including the mitochondrial antioxidant enzyme MnSOD. We previously reported that genetic inactivation of SIRT3 impairs endothelial function and increases pro‐osteogenic markers in early stages of atherosclerosis. While recent data suggest that the molecular and phenotypic effects of SIRT enzyme inactivation can act in a highly sex‐dependent manner, we have not systematically studied sex differences in our unique mouse strains. Here, we report our first effort to explore the presence of molecular and phenotypic sex differences following inactivation of SIRT3 in hypercholesterolemic mice. We used female and male Ldlr −/− /ApoB 100/100 mice that were either wild‐type (LA‐SIRT3 +/+ ) or null for SIRT3 (LA‐SIRT3 −/− ). Following 3 months of western diet feeding, we assessed endothelial function of aorta using isolated organ bath chambers and measured changes in gene expression using qRT‐PCR. We did not observe sex differences at baseline in hypercholesterolemic mice, as endothelium‐dependent relaxation to acetylcholine (ACH) was similar between female LA‐SIRT3 +/+ and their male LA‐SIRT3 +/+ littermates (61.1%±2.2, 57.9%±2.7; respectively). Interestingly, genetic inactivation of SIRT3 did not impair responses to ACH in female LA‐SIRT3 −/− mice (61.1%±4.2), whereas responses to ACH were modestly impaired in male LA‐SIRT3 −/− mice (53.9%±1.9). Consistent with SIRT3's role as a post‐translational protein modifier, expression of MnSOD was unchanged across all sexes and genotypes. Expression of genes related to pathophysiological changes in atherosclerotic plaques did change in a highly sex‐dependent manner, however, as osterix gene expression levels (related to plaque calcification) were markedly increased in male LA‐SIRT3 −/− compared to their sex‐matched wild‐type littermates and to their female counterparts. Surprisingly, while female LA‐SIRT3 −/− mice showed dramatic increases in expression of interleukin 6 (related to inflammation) compared to their wild‐type littermates, male LA‐SIRT3 −/− had robust reductions in expression in interleukin 6 compared to their LA‐SIRT3 +/+ littermates. Collectively, these data suggest there are significant, sex‐dependent molecular and phenotypic effects of SIRT3 inactivation in hypercholesterolemic mice, which may also drive a paradoxical dissociation between pro‐osteogenic and pro‐inflammatory signaling under conditions of mitochondrial dysfunction. Support or Funding Information NHLBI R01‐HL111121 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Increased oxidative stress is associated with initiation and progression of atherosclerosis. While catalase catalyzes the breakdown of hydrogen peroxide (H 2 O 2 ) to water, it is unclear whether overexpression of catalase is sufficient to protect against cardiovascular dysfunction and advanced plaque formation. Therefore, we hypothesized overexpression of catalase in hypercholesterolemic mice following 3 months or 12 months of Western diet feeding will have preserved endothelial function, reduced H 2 O 2 levels, reduced levels of osteogenic markers, and reduced calcium burden in atherosclerotic plaques. We used Ldlr − / − ApoB 100/100 (LA) mice (hypercholesterolemic mice with a more “humanized” lipid profile) that were either expressed endogenous levels of murine catalase (LA‐Cat 0/0 ) or overexpressed one copy of a human catalase construct (LA‐Cat Tg/0 ). These mice were fed a Western Diet (TD88137) for either 3 months (early disease) or 12 months (late disease). Following 3 months or 12 months on diet, we assessed endothelial function using isolated organ chambers, quantified H 2 O 2 production (staining of frozen cross‐sections of aorta with CM‐H2DCFDA), measured changes of gene expression in aortic arch (qRT‐PCR), and performed histopathological analyses of intimal plaque calcium burden (Alizarin Red). Following 3 months on diet, endothelium‐dependent relaxation to acetylcholine (ACH) was unchanged between LA‐Cat 0/0 and LA‐Cat Tg/0 mice, and we did not find substantive molecular or histopathological differences in aortic tissue between the two genotypes. Interestingly, and contrast to our hypothesis, endothelium‐dependent relaxation was modestly but not significantly impaired in LA‐Cat Tg/0 mice compared to LA‐Cat 0/0 mice after 12 months of western diet feeding. Evaluation of female mice alone, however, revealed profoundly impaired endothelium‐dependent relaxation in LA‐Cat Tg/0 . While H 2 O 2 levels were slightly reduced in LA‐Cat Tg/0 at 3 months, H 2 O 2 levels were not reduced by catalase overexpression following 12 months of Western diet feeding. In further contrast to our original hypothesis, expression of the osteogenic genes osterix and osteopontin were modestly increased in LA‐Cat Tg/0 mice following 3 months on diet compared to their wild‐type littermates, and further increased at the 12 month time point. Functionally, the molecular changes in 12 month animals were associated with increases in intimal plaque calcium burden in LA‐Cat Tg/0 (12.3% ± 2.5%) compared to their wild‐type littermates (7.8% ±1.2%). In conclusion, these data are in line with previous negative clinical trials of antioxidant treatment strategies, and suggest targeting a single antioxidant enzyme/reactive oxygen species to delay initiation or slow progression of atherosclerosis is not a viable therapeutic target, and may in fact paradoxically lead to deleterious changes in plaque composition and endothelial dysfunction. Support or Funding Information NHLBI HL111121 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

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.

We have previously shown that global reductions in mitochondrial antioxidant capacity and induction of reactive oxygen species (ROS)‐induced ROS‐release (RI‐RR) do not impair endothelial function in young mice due to compensatory increases in an apparent NAD(P)H oxidase‐derived endothelium‐derived hyperpolarizing factor (EDHF). In the present study, we hypothesized that endothelial MnSOD is a major determinant of the functional consequences of RI‐RR, and NAD(P)H oxidase‐derived H 2 O 2 is the major compensatory EDHF released from endothelium when MnSOD is reduced. MnSOD was reduced in endothelium by crossing MnSOD FL/FL mice with mice carrying cre‐recombinase driven by a Tie‐2 promoter (Cre + ). Aorta from Cre + /MnSOD +/+ and Cre + /MnSOD FL/+ mice were used for studies of endothelial function. Maximum relaxation to acetylcholine (M R , ACH ) was not affected between Cre +/ / MnSOD +/+ and Cre + /MnSOD FL/+ mice (61%±1.9, 61%±2.6; respectively). Incubation with apocynin did not change M R , ACH in Cre + / MnSOD +/+ mice (63%±2.0), but significantly impaired M R , ACH in Cre +/ MnSOD FL/+ (42%±4.7). Incubation with catalase did not effect M R , ACH in Cre + /MnSOD +/+ mice, but substantially impaired M R , ACH in Cre + /MnSOD FL/+ mice (61%±1.2, 48%±1.7). We conclude that inducing RI‐RR in endothelium by reducing MnSOD elicits a compensatory increase in EDHF production, most likely from an increase in NOX2‐derived H 2 O 2 . NHLBI

Endothelial dysfunction and vascular calcification are major problems associated with prolonged hypercholesterolemia and aging, and are strongly associated with increases in TNFα. We hypothesized that inhibition of TNF‐α would reduce inflammatory and pro‐osteogenic gene expression in aorta, leading to improved endothelial function and reductions in intimal plaque calcification. We used hypercholesteremic mice (Ldlr −/− , apoB 100/100 ) fed Western Diet for 6 months, at which point they received either intraperitoneal injections of saline (CTRL) or Infliximab (INX) for 3 additional months. Expression of the pro‐inflammatory genes TNF‐α, VCAM, and ICAM were all reduced in the INX group (qRT‐PCR). INX treatment improved endothelium‐dependent relaxation compared to the CTRL group (acetylcholine responses in isolated organ chamber; 50.7±3.4%, 43.7±3.7%; respectively), but treatment did not affect relaxation to nitroprusside. Furthermore, expression of the osteogenic gene MSX2 was reduced in INX mice, PPARγ target gene expression was increased, and intimal plaque calcification was reduced in aorta (Alizarin Red; CTRL = 13.7±2.9%, INX = 5.4±1.3%, respectively). In conclusion, blockade of TNF‐α may be a viable therapeutic target to reduce inflammation, improve endothelial dysfunction, and attenuate vascular calcification in the advanced atherosclerotic lesions commonly found in aging humans. NHLBI