Pathophysiological role for oxidative stress in geriatric vascular dysfunction

Age-related trends of blood pressure levels by apolipoprotein E genotype: the Bambuì Cohort Study of Ageing (1997-2008)

The role of apolipoprotein E (apoE) polymorphisms in regulating blood pressure (BP) is still not clear. The aim of this study was to examine longitudinal changes in BP levels by apoE genotypes in a population-based prospective cohort of elderly subjects, and explore interactions with plasma lipids and uric acid. Subjects whose apoE genes had been genotyped at baseline (1408, representing 80.8% of all the elderly residents in Bambuì city, south-eastern Brazil; age range 60-95 years) were included in the analysis. Repeated BP measurements were obtained in four waves. Multi-level random-effects pattern-mixture models were used to evaluate the age-related BP trajectories, accounting for non-ignorable dropouts/deaths and handling heterogeneities as random parameter variations. Subjects with the ɛ4/4 genotype and high levels of low-density lipoprotein cholesterol had higher systolic BP levels at 60 years of age than those with the other genotypes (154.5 vs. 133.2 mm Hg, P=0.020), but this was not the case among the older subjects. Systolic BP increased more rapidly with age in the ɛ2 carriers, leading to significantly higher levels among the oldest. This relationship seemed to be modulated by uric acid levels, as it was present in the subjects with the ɛ2/3 genotype and high uric acid levels, and in those with the ɛ2/4 genotype and low or normal uric acid levels. The differences in systolic BP between the genotypes were age dependent, and the shift between the ɛ4 and ɛ2 alleles suggest that these alleles are involved in the different mechanisms leading to increased BP in middle-aged and elderly subjects.

An integrated view of oxidative stress in aging: basic mechanisms, functional effects, and pathological considerations

Aging is an inherently complex process that is manifested within an organism at genetic, molecular, cellular, organ, and system levels. Although the fundamental mechanisms are still poorly understood, a growing body of evidence points toward reactive oxygen species (ROS) as one of the primary determinants of aging. The "oxidative stress theory" holds that a progressive and irreversible accumulation of oxidative damage caused by ROS impacts on critical aspects of the aging process and contributes to impaired physiological function, increased incidence of disease, and a reduction in life span. While compelling correlative data have been generated to support the oxidative stress theory, a direct cause-and-effect relationship between the accumulation of oxidatively mediated damage and aging has not been strongly established. The goal of this minireview is to broadly describe mechanisms of in vivo ROS generation, examine the potential impact of ROS and oxidative damage on cellular function, and evaluate how these responses change with aging in physiologically relevant situations. In addition, the mounting genetic evidence that links oxidative stress to aging is discussed, as well as the potential challenges and benefits associated with the development of anti-aging interventions and therapies.

Augmented sympathetic vasoconstriction in exercising forearms of postmenopausal women is reversed by oestrogen therapy

Sympathetic vasoconstriction is normally attenuated in exercising muscles of young men and women. Recent evidence indicates that such modulation, termed functional sympatholysis, may be impaired in older men. Whether a similar impairment occurs in older women, and what role oestrogen deficiency might play in this impairment, are not known. Based on the strong positive correlation between circulating oestrogen levels and functional sympatholysis previously reported in female rats, we hypothesized that sympatholysis would be impaired in oestrogen-deficient postmenopausal women, and that this impairment would be reversed by oestrogen replacement. To test these hypotheses, we measured vasoconstrictor responses in the forearms of pre- and postmenopausal women using near infrared spectroscopy to detect decreases in muscle oxygenation in response to reflex activation of sympathetic nerves evoked by lower body negative pressure (LBNP). In eight premenopausal women, LBNP decreased muscle oxygenation by 20 +/- 1% in resting forearm, but only by 3 +/- 2% in exercising forearm (P < 0.05). In contrast, in eight postmenopausal women, LBNP decreased muscle oxygenation by 15 +/- 3% in resting forearm, and by 12 +/- 4% in exercising forearm (P > 0.05). After 1 month of transdermal oestradiol replacement in these women, the normal effect of exercise to blunt sympathetic vasoconstriction was restored (rest, -19 +/- 3%; exercise, -2 +/- 3%; P < 0.05). These data indicate that functional sympatholysis is impaired in oestrogen-deficient postmenopausal women. The effect of short-term unopposed oestrogen replacement to correct this impairment implicates a role for oestrogen in the sympathetic neural control of muscle haemodynamics during exercise.

Role of Corticotropin-Releasing Factor Receptor Type 2β in Urocortin-Induced Vasodilation of Rat Aortas

Urocortin has a high affinity for the corticotropin-releasing factor receptor type 2beta (CRF-R2beta). This study was conducted to reveal the role of CRF-R2beta in blood vessels. CRF-R2beta expressions were detected both in smooth muscle and endothelium from Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) aortas, and there was no significant difference between them. Urocortin reduced phenylephrine-induced contraction of aorta with endothelium dose-dependently in both rats. However, deendothelialization significantly but not completely (about 50%) reduced the vasodilation. The reduction of vasodilatory action of urocortin by deendothelialization was age-dependent in SHR. An adenylyl cyclase inhibitor, SQ22536, significantly inhibited urocortin-induced relaxation in denuded WKY and SHR aortas, while in preparations with endothelium, neither SQ22536 nor L-NMMA reduced the relaxation. However, simultaneous addition of both drugs significantly reduced the relaxation. In contrast to young rats (7-week-old), in aged rats (19-week-old), L-NMMA successfully reduced urocortin-induced relaxation of aorta with endothelium. These results suggest that urocortin relaxes aorta at least partly via two signal pathways, that is, an increase in intracellular cAMP by binding to CRF-R2beta expressed in smooth muscle cells and NO production from endothelium evoked by binding to the receptors expressed in endothelium and that aging increases the role of the latter system.