Arterial stiffening with ageing is associated with transforming growth factor-β1-related changes in adventitial collagen: reversal by aerobic exercise

Abstract

We tested the hypothesis that carotid artery stiffening with ageing is associated with transforming growth factor-β1 (TGF-β1)-related increases in adventitial collagen and reductions in medial elastin, which would be reversed by voluntary aerobic exercise. Ex vivo carotid artery incremental stiffness was greater in old (29-32 months, n = 11) vs. young (4-7 months, n = 8) cage control B6D2F1 mice (8.84 ± 1.80 vs. 4.54 ± 1.18 AU, P < 0.05), and was associated with selective increases in collagen I and III and TGF-β1 protein expression in the adventitia (P < 0.05), related to an increase in smooth muscle α-actin (SMαA) (myofibroblast phenotype) (P < 0.05). In cultured adventitial fibroblasts, TGF-β1 induced increases in superoxide and collagen I protein (P < 0.05), which were inhibited by Tempol, a superoxide dismutase. Medial elastin was reduced with ageing, accompanied by decreases in the pro-synthetic elastin enzyme, lysyl oxidase, and increases in the elastin-degrading enzyme, matrix metalloproteinase 2. Fibronectin was unchanged with ageing, but there was a small increase in calcification (P < 0.05). Increased incremental stiffness in old mice was completely reversed (3.98 ± 0.34 AU, n = 5) by 10-14 weeks of modest voluntary wheel running (1.13 ± 0.29 km day −1 ), whereas greater voluntary wheel running (10.62 ± 0.49 km day −1 ) had no effect on young mice. The amelioration of carotid artery stiffness by wheel running in old mice was associated with reductions in collagen I and III and TGF-β1, partial reversal of the myofibroblast phenotype (reduced SMαA) and reduced calcification (all P < 0.05 vs. old controls), whereas elastin and its modulating enzymes were unaffected. Adventitial TGF-β1-related oxidative stress may play a key role in collagen deposition and large elastic artery stiffening with ageing and the efficacious effects of voluntary aerobic exercise.

Nicotinamide mononucleotide supplementation reverses vascular dysfunction and oxidative stress with aging in mice

“…In contrast, elastin, the main structural protein conferring elasticity, is reduced in old arteries (Zieman et al ., 2005; Diez, 2007; Fleenor et al ., 2012b). We have previously shown in mice (Fleenor et al ., 2012a) and cultured aortic fibroblasts (Fleenor et al ., 2010) that oxidative stress contributes to some or all of the age‐associated structural changes seen within the arteries. In the present study, we demonstrate that 8 weeks of NMN supplementation reverses the accumulation of whole‐vessel collagen type I and enhances arterial elastin in old mice (Fig.…”

“…We have observed reductions in aortic collagen in old mice subjected to other short‐term late‐life behavioral or pharmacological interventions (Fleenor et al ., 2010, 2012a, 2013; LaRocca et al ., 2013), although not in every case (Fleenor et al ., 2012b). Interestingly, NMN also induced a partial restoration of aortic elastin to levels not significantly different from young control animals.…”

“…Interestingly, NMN also induced a partial restoration of aortic elastin to levels not significantly different from young control animals. We have not previously observed an increase in aortic elastin with any other late‐life lifestyle or pharmacological intervention in mice (Fleenor et al ., 2010, 2012a,b), although lifelong CR protects against the loss of elastic properties within the arteries, including elastin degradation (Fornieri et al ., 1999; Donato et al ., 2013). Thus, it is possible that NMN may partially restore the loss of arterial elastin by mimicking the effects of CR, although further studies would be needed to provide direct support for this mechanism.…”

“…Immunohistochemistry was used to determine aortic expression of collagen type I, elastin, and MnSOD as previously described (Fleenor et al ., 2010, 2012b). Thoracic aorta segments, cleared of perivascular fat and other surrounding tissue, were frozen in OCT compound in liquid nitrogen‐cooled isopentane.…”

“…A common mechanism that contributes to both vascular endothelial dysfunction and large elastic artery stiffness with aging is excessive superoxide‐associated vascular oxidative stress (Seals et al ., 2011; Fleenor et al ., 2012a; Bachschmid et al ., 2013). Increased vascular production of superoxide occurs with aging and reduces the bioavailability of the vasoprotective and vasodilatory molecule nitric oxide (NO), while also causing alterations in major structural proteins (collagen and elastin) in the large elastic arteries (i.e., the aorta and carotid arteries) (Deanfield et al ., 2007; Fleenor et al ., 2010; Seals et al ., 2014). These changes contribute directly to age‐related endothelial dysfunction and increased arterial stiffness (Lakatta & Levy, 2003; Seals et al ., 2011).…”