Redox stress in Marfan syndrome: Dissecting the role of the NADPH oxidase NOX4 in aortic aneurysm.

Marfan syndrome (MFS) is characterized by the formation of ascending aortic aneurysms resulting from altered assembly of extracellular matrix fibrillin-containing microfibrils and dysfunction of TGF-ß signaling. Here we identify the molecular targets of redox stress in aortic aneurysms from MFS patients, and investigate the role of NOX4, whose expression is strongly induced by TGF-ß, in aneurysm formation and progression in a murine model of MFS. Working models included aortae and cultured vascular smooth muscle cells (VSMC) from MFS patients, and a NOX4-deficient Marfan mouse model (Fbn1C1039G/+-Nox4-/-). Increased tyrosine nitration and reactive oxygen species levels were found in the tunica media of human aortic aneurysms and in cultured VSMC. Proteomic analysis identified nitrated and carbonylated proteins, which included smooth muscle α-actin (αSMA) and annexin A2. NOX4 immunostaining increased in the tunica media of human Marfan aorta and was transcriptionally overexpressed in VSMC. Fbn1C1039G/+-Nox4-/- mice aortas showed a reduction of fragmented elastic fibers, which was accompanied by an amelioration in the Marfan-associated enlargement of the aortic root. Increase in the contractile phenotype marker calponin in the tunica media of MFS mice aortas was abrogated in Fbn1C1039G/+-Nox4-/- mice. Endothelial dysfunction evaluated by myography in the Marfan ascending aorta was prevented by the absence of Nox4 or catalase-induced H2O2 decomposition. We conclude that redox stress occurs in MFS, whose targets are actin-based cytoskeleton members and regulators of extracellular matrix homeostasis. Likewise, NOX4 have an impact in the progression of the aortic dilation in MFS and in the structural organization of the aortic tunica media, the VSMC phenotypic modulation, and endothelial function.

Differences in the Thoracic Aorta by Region and Sex in a Murine Model of Marfan Syndrome.

Marfan syndrome (MFS) is a hereditary disorder of the connective tissue that causes life-threatening aortic aneurysm, which initiates at the aortic root and can progress into the ascending portion. However, analysis of ascending aorta reactivity in animal models of MFS has remained elusive. Epidemiologic evidence suggests that although MFS is equally prevalent in men and women, men are at a higher risk of aortic complications than non-pregnant women. Nevertheless, there is no experimental evidence to support this hypothesis. The aim of this study was to explore whether there are regional and sex differences in the thoracic aorta function of mice heterozygous for the fibrillin 1 (Fbn1) allele encoding a missense mutation (Fbn1C1039G/+), the most common class of mutation in MFS. Ascending and descending thoracic aorta reactivity was evaluated by wire myography. Ascending aorta mRNA and protein levels, and elastic fiber integrity were assessed by qRT-PCR, Western blotting, and Verhoeff-Van Gieson histological staining, respectively. MFS differently altered reactivity in the ascending and descending thoracic aorta by either increasing or decreasing phenylephrine contractions, respectively. When mice were separated by sex, contractions to phenylephrine increased progressively from 3 to 6 months of age in MFS ascending aortas of males, whereas contractions in females were unchanged. Endothelium-dependent relaxation was unaltered in the MFS ascending aorta of either sex; an effect related to augmented endothelium-dependent hyperpolarization-type dilations. In MFS males, the non-selective cyclooxygenase (COX) inhibitor indomethacin prevented the MFS-induced enhancement of phenylephrine contractions linked to increased COX-2 expression. In MFS mice of both sexes, the non-selective nitric oxide synthase inhibitor L-NAME revealed negative feedback of nitric oxide on phenylephrine contractions, which was associated with upregulation of eNOS in females. Finally, MFS ascending aortas showed a greater number of elastic fiber breaks than the wild-types, and males exhibited more breaks than females. These results show regional and sex differences in Fbn1C1039G/+ mice thoracic aorta contractility and aortic media injuries. The presence of more pronounced aortic alterations in male mice provides experimental evidence to support that male MFS patients are at increased risk of suffering aortic complications.

Cardiovascular Benefits of Moderate Exercise Training in Marfan Syndrome: Insights From an Animal Model.

BACKGROUND: Marfan syndrome (MF) leads to aortic root dilatation and a predisposition to aortic dissection, mitral valve prolapse, and primary and secondary cardiomyopathy. Overall, regular physical exercise is recommended for a healthy lifestyle, but dynamic sports are strongly discouraged in MF patients. Nonetheless, evidence supporting this recommendation is lacking. Therefore, we studied the role of long-term dynamic exercise of moderate intensity on the MF cardiovascular phenotype. METHODS AND RESULTS: In a transgenic mouse model of MF (Fbn1C1039G/+), 4-month-old wild-type and MF mice were subjected to training on a treadmill for 5 months; sedentary littermates served as controls for each group. Aortic and cardiac remodeling was assessed by echocardiography and histology. The 4-month-old MF mice showed aortic root dilatation, elastic lamina rupture, and tunica media fibrosis, as well as cardiac hypertrophy, left ventricular fibrosis, and intramyocardial vessel remodeling. Over the 5-month experimental period, aortic root dilation rate was significantly greater in the sedentary MF group, compared with the wild-type group (∆mm, 0.27±0.07 versus 0.13±0.02, respectively). Exercise significantly blunted the aortic root dilation rate in MF mice compared with sedentary MF littermates (∆mm, 0.10±0.04 versus 0.27±0.07, respectively). However, these 2 groups were indistinguishable by aortic root stiffness, tunica media fibrosis, and elastic lamina ruptures. In MF mice, exercise also produced cardiac hypertrophy regression without changes in left ventricular fibrosis. CONCLUSIONS: Our results in a transgenic mouse model of MF indicate that moderate dynamic exercise mitigates the progression of the MF cardiovascular phenotype.