Mechanisms of aging-induced impairment of endothelium-dependent relaxation: role of tetrahydrobiopterin

Abstract

Oxidative stress has been implicated as an important mechanism of vascular endothelial dysfunction induced by aging. Previous studies suggested that tetrahydrobiopterin (BH 4), an essential cofactor of endothelial NO synthase, could be a molecular target for oxidation. We tested the hypothesis that oxidative stress, in particular oxidation of BH 4, may contribute to attenuation of endothelium-dependent relaxation in aged mice. Vasomotor function of isolated carotid arteries was studied using a video dimension analyzer. Vascular levels of BH 4 and its oxidation products were measured via HPLC. In aged mice (age, 95 Ϯ 2 wk), endothelium-dependent relaxation to ACh (10 Ϫ5 to 10 Ϫ9 M) as well as endothelium-independent relaxation to the NO donor diethylammo-Ϫ5 to 10 Ϫ9 M) were significantly reduced compared with relaxation detected in young mice (age, 23 Ϯ 0.5 wk). Incubation of aged mouse carotid arteries with the cell-permeable SOD mimetic Mn(III)tetra(4-benzoic acid)porphyrin chloride normalized relaxation to ACh and DEA-NONOate. Furthermore, production of superoxide anion in aorta and serum levels of amyloid P component, which is the murine analog of C-reactive protein, was increased in old mice. In aorta, neither the concentration of BH 4 nor the ratio of reduced BH4 to the oxidation products were different between young and aged mice. Our results demonstrate that in mice, aging impairs relaxation mediated by NO most likely by increased formation of superoxide anion. Oxidation of BH 4 does not appear to be an important mechanism underlying vasomotor dysfunction in aged mouse arteries. endothelial dysfunction; nitric oxide; superoxide anion; reactive oxygen species; C-reactive protein AGING IS A RISK FACTOR for vascular disease; however, the role of aging, either as a process or as the result of longer exposure to other risks, is not well defined (16,17). In murine vascular tissue, the age-dependent changes in vasomotor function have not been characterized. Studies on rats have shown impairment of endothelium-dependent relaxation due to increased production of superoxide anions, but the source of the superoxide anions has also not been characterized (16,30). Reactive oxygen species (ROS) have been implicated in endothelial dysfunction associated with aging, hypertension, hypercholesteremia, diabetes, and cigarette smoking (3). ROS can interfere with endothelium-dependent relaxation particularly by the scavenging of NO by superoxide anion (O 2 Ϫ ⅐; Refs. 1, 3, 34).

Beneficial effects of lifelong caloric restriction on endothelial function are greater in conduit arteries compared to cerebral resistance arteries

“…This is in accordance with previous results reported by us and others Csiszar et al 2007a;Blackwell et al 2004;Modrick et al 2009;Hatake et al 1990). Lifelong CR completely prevented this age-related decline in EDD in conduit arteries (carotid), but only partially prevents the decline in cerebral resistance arteries (MCA).…”

“…Although we cannot compare absolute differences in the amount of superoxide production between arteries due (Miller et al 2005(Miller et al , 2009. Similar to previous studies, we find that scavenging superoxide improves EDD in conduit and cerebral arteries from old mice (Blackwell et al 2004;Lesniewski et al 2009;Mayhan et al 2008;Modrick et al 2009) and does not affect EDD in conduit arteries from young or old CR mice (Csiszar et al 2009). However, we demonstrate that scavenging superoxide in the MCA from young and old CR mice results in reduced EDD, which is in accordance with previous studies demonstrating reactive oxygen species contribute to the dilation of resistance arteries in skeletal muscle (Sindler et al 2013;Trott et al 2011), cardiac muscle (Miura et al 2003;Feng et al 2010;Kang et al 2011), and cerebral tissue (Drouin et al 2007).…”

“…Older humans and rodents exhibit impaired EDD in conduit arteries as well as cerebral arteries Csiszar et al 2007a;Blackwell et al 2004;Modrick et al 2009;Hatake et al 1990;Eskurza et al 2004;Celermajer et al 1994). It has been shown previously that lifelong CR can prevent the age-related decline in EDD in the aorta (Csiszar et al 2009), but the effect of CR on resistance artery EDD has not been studied.…”

Amelioration of progressive renal injury by genetic manipulation of Klotho gene

“…The superoxide dimutase is a mitochondrial enzyme that protects the cells and tissues from oxidative damage (27). In addition, superoxide dimutase mimetic compounds exert similar protective effect in blood vessels during the process of aging (28). The mice deficient in manganese superoxide dismutase exhibit increased reactive oxygen species levels and severe mitochondrial dysfunctions, including mtDNA damage and mutations (29).…”

The effects of resveratrol on aging vessels

“…Scavenging of free radicals is necessary for the appropriate functioning of the endothelium. With age, increased production of the anion superoxide (O2-) has been suggested to lead to a reduced bioavailability of NO, as O2-will scavenge NO to produce peroxynitrite (ONOO−) (Blackwell et al, 2004;Ferrer et al, 2003;Hamilton et al, 2001;Rodríguez-Mañas et al, 2009;van der Loo et al, 2000). The main sources of endothelium-derived O2-appear to be the mitochondrion, NADPH oxidase and endothelial nitric oxide synthase (eNOS) itself (Hamilton et al, 2001).…”