Roos, Carolyn M

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.

ABSTRACT Recent studies have demonstrated an effect of neurotrophins, particularly brain‐derived neurotrophic factor (BDNF), on airway contractility [ via increased airway smooth muscle (ASM) intracellular calcium [Ca 2+ ] i ] and remodeling (ASM proliferation and extracellular matrix formation) in the context of airway disease. In the present study, we examined the role of BDNF in allergen‐induced airway inflammation using 2 transgenic models: 1 ) tropomyosin‐related kinase B (TrkB) conditional knockin (TrkBKI) mice allowing for inducible, reversible disruption of BDNF receptor kinase activity by administration of 1NMPP1, a PP1 derivative, and 2) smooth muscle‐specific BDNF knockout (BDNF fl/fl /SMMHCll Cre/0 ) mice. Adult mice were intranasally challenged with PBS or mixed allergen ( Altemaria alternata, Aspergillus fumigatus , house dust mite, and ovalbumin) for 4 wk. Our data show that administration of 1NMPP1 in TrkBKI mice during the 4‐wk allergen challenge blunted airway hyper‐responsiveness (AHR) and reduced fibronectin mRNA expression in ASM layers but did not reduce inflammation per se . Smooth muscle‐specific deletion of BDNF reduced AHR and blunted airway fibrosis but did not significantly alter airway inflammation. Together, our novel data indicate that TrkB signaling is a key modulator of AHR and that smooth muscle‐derived BDNF mediates these effects during allergic airway inflammation.—Britt, R. D., Jr., Thompson, M. A., Wicher, S. A., Manlove, L. J., Roesler, A., Fang, Y.‐H., Roos, C., Smith, L., Miller, J. D., Pabelick, C. M., Prakash, Y. S. Smooth muscle brain‐derived neurotrophic factor contributes to airway hyperreactivity in a mouse model of allergic asthma. FASEB J. 33, 3024–3034 (2019). www.fasebj.org

The purpose of this study was to characterize changes in antioxidant and age-related gene expression in aorta and aortic valve with aging, and test the hypothesis that increased mitochondrial oxidative stress accelerates age-related endothelial and aortic valve dysfunction. Wild-type (MnSOD+/+) and manganese SOD heterozygous haploinsufficient (MnSOD+/−) mice were studied at 3 and 18 mo of age. In aorta from wild-type mice, antioxidant expression was preserved, although there were age-associated increases in Nox2 expression. Haploinsufficiency of MnSOD did not alter antioxidant expression in aorta, but increased expression of Nox2. When compared with that of aorta, age-associated reductions in antioxidant expression were larger in aortic valves from wild-type and MnSOD haploinsufficient mice, although Nox2 expression was unchanged. Similarly, sirtuin expression was relatively well-preserved in aorta from both genotypes, whereas expression of SIRT1, SIRT2, SIRT3, SIRT4, and SIRT6 were significantly reduced in the aortic valve. Expression of p16ink4a, a marker of cellular senescence, was profoundly increased in both aorta and aortic valve from MnSOD+/+ and MnSOD+/− mice. Functionally, we observed comparable age-associated reductions in endothelial function in aorta from both MnSOD+/+ and MnSOD+/− mice. Interestingly, inhibition of NAD(P)H oxidase with apocynin or gp91ds-tat improved endothelial function in MnSOD+/+ mice but significantly impaired endothelial function in MnSOD+/− mice at both ages. Aortic valve function was not impaired by aging or MnSOD haploinsufficiency. Changes in antioxidant and sirtuin gene expression with aging differ dramatically between aorta and aortic valve. Furthermore, although MnSOD does not result in overt cardiovascular dysfunction with aging, compensatory transcriptional responses to MnSOD deficiency appear to be tissue specific.