Vascular superoxide and hydrogen peroxide production and oxidative stress resistance in two closely related rodent species with disparate longevity

Young blood-mediated cerebromicrovascular rejuvenation through heterochronic parabiosis: enhancing blood-brain barrier integrity and capillarization in the aged mouse brain

Age-related cerebromicrovascular changes, including blood-brain barrier (BBB) disruption and microvascular rarefaction, play a significant role in the development of vascular cognitive impairment (VCI) and neurodegenerative diseases. Utilizing the unique model of heterochronic parabiosis, which involves surgically joining young and old animals, we investigated the influence of systemic factors on these vascular changes. Our study employed heterochronic parabiosis to explore the effects of young and aged systemic environments on cerebromicrovascular aging in mice. We evaluated microvascular density and BBB integrity in parabiotic pairs equipped with chronic cranial windows, using intravital two-photon imaging techniques. Our results indicate that short-term exposure to young systemic factors leads to both functional and structural rejuvenation of cerebral microcirculation. Notably, we observed a marked decrease in capillary density and an increase in BBB permeability to fluorescent tracers in the cortices of aged mice undergoing isochronic parabiosis (20-month-old C57BL/6 mice [A-(A)]; 6 weeks of parabiosis), compared to young isochronic parabionts (6-month-old, [Y-(Y)]). However, aged heterochronic parabionts (A-(Y)) exposed to young blood exhibited a significant increase in cortical capillary density and restoration of BBB integrity. In contrast, young mice exposed to old blood from aged parabionts (Y-(A)) rapidly developed cerebromicrovascular aging traits, evidenced by reduced capillary density and increased BBB permeability. These findings underscore the profound impact of systemic factors in regulating cerebromicrovascular aging. The rejuvenation observed in the endothelium, following exposure to young blood, suggests the existence of anti-geronic elements that counteract microvascular aging. Conversely, pro-geronic factors in aged blood appear to accelerate cerebromicrovascular aging. Further research is needed to assess whether the rejuvenating effects of young blood factors could extend to other age-related cerebromicrovascular pathologies, such as microvascular amyloid deposition and increased microvascular fragility.

Chronological and reproductive aging-associated changes in resistance to oxidative stress in post-reproductive female mice

Effort toward reproduction is often thought to negatively influence health and survival. Reproduction has been shown to influence metabolism, but the pathways and mechanisms have yet to be thoroughly elucidated. In the current experiments, our aim was to dissect the role of young and old ovarian tissues in the response to oxidative stress, through changes in liver oxidative stress response proteins. Liver proteins were analyzed in control mice at 4, 13, and 27 months of age and compared to 23-month-old mice which received young ovarian tissue transplants (intact or follicle-depleted) at 13 months of age. In control mice, of the 29 oxidative stress response proteins measured, 31% of the proteins decreased, 52% increased, and 17% were unchanged from 13 to 27 months. The greatest changes were seen during the period of reproductive failure, from 4 to 13 months of age. In transplanted mice, far more proteins were decreased from 13 to 23 months (93% in follicle-containing young ovary recipients; 62% in follicle-depleted young ovary recipients). Neither transplant group reflected changes seen in control mice between 13 and 27 months. Estradiol levels in transplant recipient mice were not increased compared with age-matched control mice. The current results suggest the presence of a germ cell- and estradiol-independent ovarian influence on aging-associated changes in the response to oxidative stress, which is manifest differently in reproductive-aged adults and post-reproductive-aged mice. The results presented here separate chronological and ovarian aging and the influence of estradiol in the response to aging-associated oxidative stress and support a novel, estradiol-independent role for the ovary in female health and survival.

Rejuvenation of cerebromicrovascular function in aged mice through heterochronic parabiosis: insights into neurovascular coupling and the impact of young blood factors

Age-related impairment of neurovascular coupling (NVC; "functional hyperemia") is a critical factor in the development of vascular cognitive impairment (VCI). Recent geroscience research indicates that cell-autonomous mechanisms alone cannot explain all aspects of neurovascular aging. Circulating factors derived from other organs, including pro-geronic factors (increased with age and detrimental to vascular homeostasis) and anti-geronic factors (preventing cellular aging phenotypes and declining with age), are thought to orchestrate cellular aging processes. This study aimed to investigate the influence of age-related changes in circulating factors on neurovascular aging. Heterochronic parabiosis was utilized to assess how exposure to young or old systemic environments could modulate neurovascular aging. Results demonstrated a significant decline in NVC responses in aged mice subjected to isochronic parabiosis (20-month-old C57BL/6 mice [A-(A)]; 6 weeks of parabiosis) when compared to young isochronic parabionts (6-month-old, [Y-(Y)]). However, exposure to young blood from parabionts significantly improved NVC in aged heterochronic parabionts [A-(Y)]. Conversely, young mice exposed to old blood from aged parabionts exhibited impaired NVC responses [Y-(A)]. In conclusion, even a brief exposure to a youthful humoral environment can mitigate neurovascular aging phenotypes, rejuvenating NVC responses. Conversely, short-term exposure to an aged humoral milieu in young mice accelerates the acquisition of neurovascular aging traits. These findings highlight the plasticity of neurovascular aging and suggest the presence of circulating anti-geronic factors capable of rejuvenating the aging cerebral microcirculation. Further research is needed to explore whether young blood factors can extend their rejuvenating effects to address other age-related cerebromicrovascular pathologies, such as blood-brain barrier integrity.

Phenotypic molecular features of long-lived animal species

One of the challenges facing science/biology today is uncovering the molecular bases that support and determine animal and human longevity. Nature, in offering a diversity of animal species that differ in longevity by more than 5 orders of magnitude, is the best 'experimental laboratory' to achieve this aim. Mammals, in particular, can differ by more than 200-fold in longevity. For this reason, most of the available evidence on this topic derives from comparative physiology studies. But why can human beings, for instance, reach 120 years whereas rats only last at best 4 years? How does nature change the longevity of species? Longevity is a species-specific feature resulting from an evolutionary process. Long-lived animal species, including humans, show adaptations at all levels of biological organization, from metabolites to genome, supported by signaling and regulatory networks. The structural and functional features that define a long-lived species may suggest that longevity is a programmed biological property.

Mitochondrial ROS production, oxidative stress and aging within and between species: Evidences and recent advances on this aging effector

Mitochondria play a wide diversity of roles in cell physiology and have a key functional implication in cell bioenergetics and biology of free radicals. As the main cellular source of oxygen radicals, mitochondria have been postulated as the mediators of the cellular decline associated with the biological aging. Recent evidences have shown that mitochondrial free radical production is a highly regulated mechanism contributing to the biological determination of longevity which is species-specific. This mitochondrial free radical generation rate induces a diversity of adaptive responses and derived molecular damage to cell components, highlighting mitochondrial DNA damage, with biological consequences that influence the rate of aging of a given animal species. In this review, we explore the idea that mitochondria play a fundamental role in the determination of animal longevity. Once the basic mechanisms are discerned, molecular approaches to counter aging may be designed and developed to prevent or reverse functional decline, and to modify longevity.

MiR-27b attenuates mitochondrial oxidative stress and inflammation in endothelial cells

MiR-27b is highly expressed in endothelial cells (EC) but its function in this context is poorly characterized. This study aims to investigate the effect of miR-27b on inflammatory pathways, cell cycle, apoptosis, and mitochondrial oxidative imbalances in immortalized human aortic endothelial cells (teloHAEC), human umbilical vein endothelial cells (HUVEC), and human coronary artery endothelial cells (HCAEC) exposed to TNF-α. Treatment with TNF-α downregulates the expression of miR-27b in all EC lines, promotes the activation of inflammatory pathways, induces mitochondrial alteration and reactive oxygen species accumulation, fostering the induction of intrinsic apoptosis. Moreover, miR-27b mimic counteracts the TNF-α-related cytotoxicity and inflammation, as well as cell cycle arrest and caspase-3-dependent apoptosis, restoring mitochondria redox state, function, and membrane polarization. Mechanistically, hsa-miR-27b-3p targets the 3'untranslated regions of FOXO1 mRNA to downregulate its expression, blunting the activation of the Akt/FOXO1 pathway. Here, we show that miR-27b is involved in the regulation of a broad range of functionally intertwined phenomena in EC, suggesting its key role in mitigating mithochondrial oxidative stress and inflammation, most likely through targeting of FOXO1. Overall, results reveal for the first time that miR-27b could represent a possible target for future therapies aimed at improving endothelial health.

Physiological Evidence for Delayed Age-related Hearing Loss in Two Long-lived Rodent Species (Peromyscus leucopus and P. californicus)

Deer mice (genus Peromyscus) are an emerging model for aging studies due to their longevity relative to rodents of similar size. Although Peromyscus species are well-represented in genetic, developmental, and behavioral studies, relatively few studies have investigated auditory sensitivity in this genus. Given the potential utility of Peromyscus for investigations of age-related changes to auditory function, we recorded auditory brainstem responses (ABRs) in two Peromyscus species, P. californicus, and P. leucopus, across the lifespan. We compared hearing sensitivity and ABR wave metrics measured in these species with measurements from Mus musculus (CBA/CaJ strain) to assess age-related effects on hearing across species. Recordings in young animals showed that all species had similar hearing ranges and thresholds with peak sensitivity ranging from 8 to 16 kHz; however, P. californicus and P. leucopus were more sensitive to frequencies below 8 kHz. Although M. musculus showed significant threshold shifts across a broad range of frequencies beginning at middle age and worsening among old individuals, older Peromyscus mice retained good sensitivity to sound across their lifespan. Middle-aged P. leucopus had comparable thresholds to young for frequencies below 24 kHz. P. leucopus also had notably large ABRs that were robust to age-related amplitude reductions, although response latencies increased with age. Old P. californicus were less sensitive to mid-range tones (8-16 kHz) than young individuals; however, there were no significant age-effects on ABR amplitudes or latencies in this species. These results indicate that longevity in Peromyscus mice may be correlated with delayed aging of the auditory system and highlight these species as promising candidates for longitudinal hearing research.

Evolved reductions in body temperature and the metabolic costs of thermoregulation in deer mice native to high altitude

The evolution of endothermy was instrumental to the diversification of birds and mammals, but the energetic demands of maintaining high body temperature could offset the advantages of endothermy in some environments. We hypothesized that reductions in body temperature help high-altitude natives overcome the metabolic challenges of cold and hypoxia in their native environment. Deer mice (Peromyscus maniculatus) from high-altitude and low-altitude populations were bred in captivity to the second generation and were acclimated as adults to warm normoxia or cold hypoxia. Subcutaneous temperature (Tsub, used as a proxy for body temperature) and cardiovascular function were then measured throughout the diel cycle using biotelemetry. Cold hypoxia increased metabolic demands, as reflected by increased food consumption and heart rate (associated with reduced vagal tone). These increased metabolic demands were offset by plastic reductions in Tsub (approx. 2°C) in response to cold hypoxia, and highlanders had lower Tsub (approx. 1°C) than lowlanders in both environmental treatments. Empirical and theoretical evidence suggested that these reductions could together reduce metabolic demands by approximately 10-30%. Therefore, plastic and evolved reductions in body temperature can help mammals overcome the metabolic challenges at high altitude and may be a valuable energy-saving strategy in some non-hibernating endotherms in extreme environments.

Genetic variation in HIF-2α attenuates ventilatory sensitivity and carotid body growth in chronic hypoxia in high-altitude deer mice

KEY POINTS

High-altitude natives of many species have experienced natural selection on the gene encoding HIF-2α, Epas1, including high-altitude populations of deer mice. HIF-2α regulates ventilation and carotid body growth in hypoxia, so the genetic variants in Epas1 in high-altitude natives may underlie evolved changes in control of breathing. Deer mice from controlled crosses between high- and low-altitude populations were used to examine the effects of Epas1 genotype on an admixed genomic background. The high-altitude variant was associated with reduced ventilatory chemosensitivity and carotid body growth in chronic hypoxia, but had no effects on haematology. The results help us better understand the genetic basis for the unique physiological phenotype of high-altitude natives.

ABSTRACT

The gene encoding HIF-2α, Epas1, has experienced a history of natural selection in many high-altitude taxa, but the functional role of mutations in this gene are still poorly understood. We investigated the influence of the high-altitude variant of Epas1 in North American deer mice (Peromyscus maniculatus) on control of breathing and carotid body growth during chronic hypoxia. We created hybrids between high- and low-altitude populations of deer mice to disrupt linkages between genetic loci so physiological effects of Epas1 alleles (Epas1^H and Epas1^L , respectively) could be examined on an admixed genomic background. In general, chronic hypoxia (4 weeks at 12 kPa O₂ ) enhanced ventilatory chemosensitivity (assessed as the acute ventilatory response to hypoxia), increased total ventilation and arterial O₂ saturation during progressive poikilocapnic hypoxia, and increased haematocrit and blood haemoglobin content across genotypes. However, effects of chronic hypoxia on ventilatory chemosensitivity were attenuated in mice that were homozygous for the high-altitude Epas1 allele (Epas1^H/H ). Carotid body growth and glomus cell hyperplasia, which was strongly induced in Epas1^L/L mice in chronic hypoxia, was not observed in Epas1^H/H mice. Epas1 genotype also modulated the effects of chronic hypoxia on metabolism and body temperature depression in hypoxia, but had no effects on haematological traits. These findings confirm the important role of HIF-2α in modulating ventilatory sensitivity and carotid body growth in chronic hypoxia, and show that genetic variation in Epas1 is responsible for evolved changes in the control of breathing and metabolism in high-altitude deer mice. Abstract figure legend ventilation and carotid body growth in hypoxia, so we investigated the role genetic variants in Epas1 in highaltitude deer mice on the control of breathing. In the lab, hybrids between high- and lowaltitude populations of deer mice were created to disrupt linkages between genetic loci so physiological effects of Epas1 alleles (Epas1H and Epas1L, respectively) could be examined on an admixed genomic background. The high-altitude variant was associated with reduced ventilatory chemosensitivity and carotid body growth after 4 weeks of chronic hypoxia, compared to mice homozygous for the low-altitude allele (Epas1LL). These results help us better understand the genetic basis for the unique physiological phenotype of high-altitude natives. This article is protected by copyright. All rights reserved.

Old blood from heterochronic parabionts accelerates vascular aging in young mice: transcriptomic signature of pathologic smooth muscle remodeling

Vascular aging has a central role in the pathogenesis of cardiovascular diseases contributing to increased mortality of older adults. There is increasing evidence that, in addition to the documented role of cell-autonomous mechanisms of aging, cell-nonautonomous mechanisms also play a critical role in the regulation of vascular aging processes. Our recent transcriptomic studies (Kiss T. et al. Geroscience. 2020;42(2):727-748) demonstrated that circulating anti-geronic factors from young blood promote vascular rejuvenation in aged mice. The present study was designed to expand upon the results of this study by testing the hypothesis that circulating pro-geronic factors also contribute to the genesis of vascular aging phenotypes. To test this hypothesis, through heterochronic parabiosis, we determined the extent to which shifts in the vascular transcriptome (RNA-seq) are modulated by the old systemic environment. We reanalyzed existing RNA-seq data, comparing the transcriptome in the aorta arch samples isolated from isochronic parabiont aged (20-month-old) C57BL/6 mice [A-(A); parabiosis for 8 weeks] and young isochronic parabiont (6-month-old) mice [Y-(Y)] and also assessing transcriptomic changes in the aortic arch in young (6-month-old) parabiont mice [Y-(A); heterochronic parabiosis for 8 weeks] induced by the presence of old blood derived from aged (20-month-old) parabionts. We identified 528 concordant genes whose expression levels differed in the aged phenotype and were shifted towards the aged phenotype by the presence of old blood in young Y-(A) animals. Among them, the expression of 221 concordant genes was unaffected by the presence of young blood in A-(Y) mice. GO enrichment analysis suggests that old blood-regulated genes may contribute to pathologic vascular remodeling. IPA Upstream Regulator analysis (performed to identify upstream transcriptional regulators that may contribute to the observed transcriptomic changes) suggests that the mechanism of action of pro-geronic factors present in old blood may include inhibition of pathways mediated by SRF (serum response factor), insulin-like growth factor-1 (IGF-1) and VEGF-A. In conclusion, relatively short-term exposure to old blood can accelerate vascular aging processes. Our findings provide additional evidence supporting the significant plasticity of vascular aging and the existence of circulating pro-geronic factors mediating pathological remodeling of the vascular smooth muscle cells and the extracellular matrix.

Turn-On Fluorescence Sensing of Oxygen with Dendrimer-Encapsulated Platinum Nanoparticles as Tunable Oxidase Mimics for Spatially Resolved Measurement of Oxygen Gradient in a Human Gut-on-a-Chip

Turn-on type fluorescence sensing of O₂ is considered a promising approach to developing ways to measure O₂ in microenvironments with spatially distributed O₂ levels. As a class of nanomaterials with a high degree of control over composition and structure, dendrimer-encapsulated nanoparticles (DENs) are promising candidates to mimic biological enzymes. Here, we report a strategy to monitor spatially distributed O₂ across a three-dimensional (3D) human intestinal epithelial layer in a gut-on-a-chip in a turn-on fluorescence sensing manner. The strategy is based on the oxidase-mimetic activity of Pt DENs for catalytic oxidation of nonfluorescent Amplex Red to highly fluorescent resorufin in the presence of O₂. We synthesized Pt DENs using two different types of dendrimers (i.e., amine-terminated or hydroxyl-terminated generation 6 polyamidoamine (PAMAM) dendrimers) with six different Pt²⁺/dendrimer ratios (i.e., 55, 200, 220, 550, 880, and 1320). After clarifying the intrinsic oxidase-mimetic activity of Pt DENs, we determined tunable oxidase-mimetic activity of Pt DENs, especially with fine-tuning the ratios of the Pt precursor ions and dendrimers. Particularly, the optimal Pt DENs having a Pt²⁺/dendrimer ratio of 1320 exhibited an ∼117-fold increase in the oxidase-mimetic activity for catalyzing the aerobic oxidation of Amplex Red to resorufin compared to one having a Pt²⁺/dendrimer ratio of 200. This study exemplified a simple yet effective approach for spatially resolved imaging of O₂ using metal nanoparticle-based oxidase mimics in microphysiological environments like a human gut-on-a-chip.

Sirtuin 6 Protects Against Oxidative Stress and Vascular Dysfunction in Mice

Objective: Sirtuin deacetylases are major regulators of organismal aging, and while depletion of sirtuin 6 (SIRT6) in mice results in a profound progeroid phenotype, the role of SIRT6 in the regulation of vasomotor function is unknown. Thus, our objective was to test the hypothesis that reductions in SIRT6 elicit endothelial dysfunction in young, genetically altered mice.

Results and Approach: We used young (3 month old), littermate-matched, SIRT6 wild-type (WT), and SIRT6 heterozygous (HET) mice. SIRT6 expression (qRT-PCR) was reduced by 50% in HET mice. Carotid vessel responses to acetylcholine, sodium nitroprusside, U46619, and serotonin were examined in isolated organ chamber baths. Relaxation in response to acetylcholine (ACH) was impaired in HET mice compared to littermate-matched WT controls (67 ± 3% versus 76 ± 3%, respectively; p < 0.05), while responses to sodium nitroprusside were unchanged. Short-term incubation of carotid rings with the NAD(P)H oxidase inhibitor, apocynin, significantly improved in vessels from HET mice but not their WT littermates. Peak tension generated in response to either U46619 or serotonin was significantly blunted in HET mice compared to their WT littermates.

Conclusion: These data suggest that SIRT6 is a key regulator of vasomotor function in conduit vessels. More specifically, we propose that SIRT6 serves as a tonic suppressor of NAD(P)H oxidase expression and activation, as inhibition of NAD(P)H oxidase improved endothelial function in SIRT6 haploinsufficient mice. Collectively, SIRT6 activation and/or histone acetyltransferase inhibition may be useful therapeutic approaches to reduce endothelial dysfunction and combat age-associated cardiovascular disease.

Animal reservoirs of SARS-CoV-2: calculable COVID-19 risk for older adults from animal to human transmission

The current COVID-19 pandemic, caused by the highly contagious respiratory pathogen SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), has already claimed close to three million lives. SARS-CoV-2 is a zoonotic disease: it emerged from a bat reservoir and it can infect a number of agricultural and companion animal species. SARS-CoV-2 can cause respiratory and intestinal infections, and potentially systemic multi-organ disease, in both humans and animals. The risk for severe illness and death with COVID-19 significantly increases with age, with older adults at highest risk. To combat the pandemic and protect the most susceptible group of older adults, understanding the human-animal interface and its relevance to disease transmission is vitally important. Currently high infection numbers are being sustained via human-to-human transmission of SARS-CoV-2. Yet, identifying potential animal reservoirs and potential vectors of the disease will contribute to stronger risk assessment strategies. In this review, the current information about SARS-CoV-2 infection in animals and the potential spread of SARS-CoV-2 to humans through contact with domestic animals (including dogs, cats, ferrets, hamsters), agricultural animals (e.g., farmed minks), laboratory animals, wild animals (e.g., deer mice), and zoo animals (felines, non-human primates) are discussed with a special focus on reducing mortality in older adults.

Regulation of Age-Related Protein Toxicity

Proteome damage plays a major role in aging and age-related neurodegenerative diseases. Under healthy conditions, molecular quality control mechanisms prevent toxic protein misfolding and aggregation. These mechanisms include molecular chaperones for protein folding, spatial compartmentalization for sequestration, and degradation pathways for the removal of harmful proteins. These mechanisms decline with age, resulting in the accumulation of aggregation-prone proteins that are harmful to cells. In the past decades, a variety of fast- and slow-aging model organisms have been used to investigate the biological mechanisms that accelerate or prevent such protein toxicity. In this review, we describe the most important mechanisms that are required for maintaining a healthy proteome. We describe how these mechanisms decline during aging and lead to toxic protein misassembly, aggregation, and amyloid formation. In addition, we discuss how optimized protein homeostasis mechanisms in long-living animals contribute to prolonging their lifespan. This knowledge might help us to develop interventions in the protein homeostasis network that delay aging and age-related pathologies.

Is the NDUFV2 subunit of the hydrophilic complex I domain a key determinant of animal longevity?

Complex I, a component of the electron transport chain, plays a central functional role in cell bioenergetics and the biology of free radicals. The structural and functional N module of complex I is one of the main sites of the generation of free radicals. The NDUFV2 subunit/N1a cluster is a component of this module. Furthermore, the rate of free radical production is linked to animal longevity. In this review, we explore the hypothesis that NDUFV2 is the only conserved core subunit designed with a regulatory function to ensure correct electron transfer and free radical production, that low gene expression and protein abundance of the NDUFV2 subunit is an evolutionary adaptation needed to achieve a longevity phenotype, and that these features are determinants of the lower free radical generation at the mitochondrial level and a slower rate of aging of long-lived animals.

Circulating anti-geronic factors from heterochonic parabionts promote vascular rejuvenation in aged mice: transcriptional footprint of mitochondrial protection, attenuation of oxidative stress, and rescue of endothelial function by young blood

Aging-induced functional and phenotypic alterations of the vasculature (e.g., endothelial dysfunction, oxidative stress) have a central role in morbidity and mortality of older adults. It has become apparent in recent years that cell autonomous mechanisms alone are inadequate to explain all aspects of vascular aging. The present study was designed to test the hypothesis that age-related changes in circulating anti-geronic factors contribute to the regulation of vascular aging processes in a non-cell autonomous manner. To test this hypothesis, through heterochronic parabiosis we determined the extent, if any, to which endothelial function, vascular production of ROS, and shifts in the vascular transcriptome (RNA-seq) are modulated by the systemic environment. We found that in aortas isolated from isochronic parabiont aged (20-month-old) C57BL/6 mice [A-(A); parabiosis for 8 weeks] acetylcholine-induced endothelium-dependent relaxation was impaired and ROS production (dihydroethidium fluorescence) was increased as compared with those in aortas from young isochronic parabiont (6-month-old) mice [Y-(Y)]. The presence of young blood derived from young parabionts significantly improved endothelium-dependent vasorelaxation and attenuated ROS production in vessels of heterochronic parabiont aged [A-(Y)] mice. In aortas derived from heterochronic parabiont young [Y-(A)] mice, acetylcholine-induced relaxation and ROS production were comparable with those in aortas derived from Y-(Y) mice. Using RNA-seq we assessed transcriptomic changes in the aortic arch associated with aging and heterochronic parabiosis. We identified 347 differentially expressed genes in A-(A) animals compared with Y-(Y) controls. We have identified 212 discordant genes, whose expression levels differed in the aged phenotype, but have shifted back toward the young phenotype by the presence of young blood in aged A-(Y) animals. Pathway analysis shows that vascular protective effects mediated by young blood-regulated genes include mitochondrial rejuvenation. In conclusion, a relatively short-term exposure to young blood can rescue vascular aging phenotypes, including attenuation of oxidative stress, mitochondrial rejuvenation, and improved endothelial function. Our findings provide additional evidence supporting the significant plasticity of vascular aging and evidence for the existence of anti-geronic factors capable of exerting rejuvenating effects on the aging vasculature.

Microvascular contributions to age-related macular degeneration (AMD): from mechanisms of choriocapillaris aging to novel interventions

Aging of the microcirculatory network plays a central role in the pathogenesis of a wide range of age-related diseases, from heart failure to Alzheimer's disease. In the eye, changes in the choroid and choroidal microcirculation (choriocapillaris) also occur with age, and these changes can play a critical role in the pathogenesis of age-related macular degeneration (AMD). In order to develop novel treatments for amelioration of choriocapillaris aging and prevention of AMD, it is essential to understand the cellular and functional changes that occur in the choroid and choriocapillaris during aging. In this review, recent advances in in vivo analysis of choroidal structure and function in AMD patients and patients at risk for AMD are discussed. The pathophysiological roles of fundamental cellular and molecular mechanisms of aging including oxidative stress, mitochondrial dysfunction, and impaired resistance to molecular stressors in the choriocapillaris are also considered in terms of their contribution to the pathogenesis of AMD. The pathogenic roles of cardiovascular risk factors that exacerbate microvascular aging processes, such as smoking, hypertension, and obesity as they relate to AMD and choroid and choriocapillaris changes in patients with these cardiovascular risk factors, are also discussed. Finally, future directions and opportunities to develop novel interventions to prevent/delay AMD by targeting fundamental cellular and molecular aging processes are presented.

Mechanisms of Vascular Aging

Aging of the vasculature plays a central role in morbidity and mortality of older people. To develop novel treatments for amelioration of unsuccessful vascular aging and prevention of age-related vascular pathologies, it is essential to understand the cellular and functional changes that occur in the vasculature during aging. In this review, the pathophysiological roles of fundamental cellular and molecular mechanisms of aging, including oxidative stress, mitochondrial dysfunction, impaired resistance to molecular stressors, chronic low-grade inflammation, genomic instability, cellular senescence, epigenetic alterations, loss of protein homeostasis, deregulated nutrient sensing, and stem cell dysfunction in the vascular system are considered in terms of their contribution to the pathogenesis of both microvascular and macrovascular diseases associated with old age. The importance of progeronic and antigeronic circulating factors in relation to development of vascular aging phenotypes are discussed. Finally, future directions and opportunities to develop novel interventions to prevent/delay age-related vascular pathologies by targeting fundamental cellular and molecular aging processes are presented.

Calcium and electrical signaling in arterial endothelial tubes: New insights into cellular physiology and cardiovascular function

The integral role of the endothelium during the coordination of blood flow throughout vascular resistance networks has been recognized for several decades now. Early examination of the distinct anatomy and physiology of the endothelium as a signaling conduit along the vascular wall has prompted development and application of an intact endothelial "tube" study model isolated from rodent skeletal muscle resistance arteries. Vasodilatory signals such as increased endothelial cell (EC) Ca²⁺ ([Ca²⁺ ]_i ) and hyperpolarization take place in single ECs while shared between electrically coupled ECs through gap junctions up to distances of millimeters (≥2 mm). The small- and intermediate-conductance Ca²⁺ activated K⁺ (SK_Ca /IK_Ca or K_Ca 2.3/K_Ca 3.1) channels function at the interface of Ca²⁺ signaling and hyperpolarization; a bidirectional relationship whereby increases in [Ca²⁺ ]_i activate SK_Ca /IK_Ca channels to produce hyperpolarization and vice versa. Further, the spatial domain of hyperpolarization among electrically coupled ECs can be finely tuned via incremental modulation of SK_Ca /IK_Ca channels to balance the strength of local and conducted electrical signals underlying vasomotor activity. Multifunctional properties of the voltage-insensitive SK_Ca /IK_Ca channels of resistance artery endothelium may be employed for therapy during the aging process and development of vascular disease.

Thrombospondin-1, Free Radicals, and the Coronary Microcirculation: The Aging Conundrum

SIGNIFICANCE

Successful matching of cardiac metabolism to perfusion is accomplished primarily through vasodilation of the coronary resistance arterioles, but the mechanism that achieves this effect changes significantly as aging progresses and involves the contribution of reactive oxygen species (ROS). Recent Advances: A matricellular protein, thrombospondin-1 (Thbs-1), has been shown to be a prolific contributor to the production and modulation of ROS in large conductance vessels and in the peripheral circulation. Recently, the presence of physiologically relevant circulating Thbs-1 levels was proven to also disrupt vasodilation to nitric oxide (NO) in coronary arterioles from aged animals, negatively impacting coronary blood flow reserve.

CRITICAL ISSUES

This review seeks to reconcile how ROS can be successfully utilized as a substrate to mediate vasoreactivity in the coronary microcirculation as "normal" aging progresses, but will also examine how Thbs-1-induced ROS production leads to dysfunctional perfusion and eventual ischemia and why this is more of a concern in advancing age.

FUTURE DIRECTIONS

Current therapies that may effectively disrupt Thbs-1 and its receptor CD47 in the vascular wall and areas for future exploration will be discussed. Antioxid. Redox Signal. 27, 785-801.

Endothelial Cell Inflammation and Antioxidant Capacity are Associated With 6-Minute Walk Performance in Patients With Symptomatic Peripheral Artery Disease

We determined whether 6-minute walk total distance and pain-free distance were associated with circulating biomarkers of antioxidant capacity and inflammation and with cultured endothelial cell inflammation, oxidative stress, and apoptosis in 251 patients with symptomatic peripheral artery disease (PAD). In multivariate analyses, pain-free distance during the 6-minute walk test was negatively associated with dyslipidemia ( P < .001), chronic kidney disease ( P = .004), and transient transfection, nuclear factor κ-Light-Chain-Enhancer of activated B (NF-κB) cultured endothelial cells ( P = .007) and was positively associated with height ( P = .008). Furthermore, total distance walked during the 6-minute walk test was negatively associated with cultured endothelial cell NF-κB ( P < .001), coronary artery disease ( P = .009), and body mass index ( P = .022) and was positively associated with ankle-brachial index ( P < .001), male sex ( P < .001), and hydroxyl radical antioxidant capacity ( P < .001). The 6-minute walk performance in symptomatic patients with PAD was associated with vascular biomarkers, as walking distances were negatively associated with cultured endothelial cell inflammation and positively associated with circulating antioxidant capacity. The clinical implication is that behavioral interventions designed to alleviate endothelial cell inflammation and increase circulating antioxidant capacity, such as exercise and antioxidant intake, may improve ambulation of patients with PAD during submaximal exercise that is typically performed during daily activities.

Oxidative stress in carotid arteries of patients submitted to carotid endarterectomy. The role of aging process

PURPOSE

To evaluated the role of oxidative stress on aging process in patients submitted to carotid endarterectomy.

METHODS

Twenty patients were divided into two groups: older group (≥ 70 years old); and the younger group (< 70 years old). We evaluated the reactive oxygen species (ROS) concentration, nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, superoxide dismutase (SOD) and catalase (CAT) activities as so as nitrite levels in fragments of carotid arteries harvested during carotid endarterectomy for treatment of high grade carotid stenosis.

RESULTS

We observed a higher levels of ROS and NADPH oxidase activity in the older group (p<0.05). Furthermore, the nitrite concentration was lower in the older group (14.55 ± 5.61 x 10-3 versus 26.42 ± 8.14 x 10-3 µM; p=0.0123). However, the activities of antioxidant enzymes (CAT and SOD) were similar in both the groups.

CONCLUSIONS

: Arterial aging is associated with increased concentrations of oxygen species and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity as so as nitrite reduction in human carotid artery specimens. Maybe therapies that block NADPH oxidase activity and enhance nitrite stores would be a good strategy to reduce the effect of oxidative stress in arterial aging.

Cerebral microhemorrhages: mechanisms, consequences, and prevention

The increasing prevalence of multifocal cerebral microhemorrhages (CMHs, also known as "cerebral microbleeds") is a significant, newly recognized problem in the aging population of the Western world. CMHs are associated with rupture of small intracerebral vessels and are thought to progressively impair neuronal function, potentially contributing to cognitive decline, geriatric psychiatric syndromes, and gait disorders. Clinical studies show that aging and hypertension significantly increase prevalence of CMHs. CMHs are also now recognized by the National Institutes of Health as a major factor in Alzheimer's disease pathology. Moreover, the presence of CMHs is an independent risk factor for subsequent larger intracerebral hemorrhages. In this article, we review the epidemiology, detection, risk factors, clinical significance, and pathogenesis of CMHs. The potential age-related cellular mechanisms underlying the development of CMHs are discussed, with a focus on the structural determinants of microvascular fragility, age-related alterations in cerebrovascular adaptation to hypertension, the role of oxidative stress and matrix metalloproteinase activation, and the deleterious effects of arterial stiffening, increased pulse pressure, and impaired myogenic autoregulatory protection on the brain microvasculature. Finally, we examine potential treatments for the prevention of CMHs based on the proposed model of aging- and hypertension-dependent activation of the reactive oxygen species-matrix metalloproteinases axis, and we discuss critical questions to be addressed by future studies.

The GH/IGF-1 axis in a critical period early in life determines cellular DNA repair capacity by altering transcriptional regulation of DNA repair-related genes: implications for the developmental origins of cancer

Experimental, clinical, and epidemiological findings support the concept of developmental origins of health and disease (DOHAD), suggesting that early-life hormonal influences during a sensitive period around adolescence have a powerful impact on cancer morbidity later in life. The endocrine changes that occur during puberty are highly conserved across mammalian species and include dramatic increases in circulating GH and IGF-1 levels. Importantly, patients with developmental IGF-1 deficiency due to GH insensitivity (Laron syndrome) do not develop cancer during aging. Rodents with developmental GH/IGF-1 deficiency also exhibit significantly decreased cancer incidence at old age, marked resistance to chemically induced carcinogenesis, and cellular resistance to genotoxic stressors. Early-life treatment of GH/IGF-1-deficient mice and rats with GH reverses the cancer resistance phenotype; however, the underlying molecular mechanisms remain elusive. The present study was designed to test the hypothesis that developmental GH/IGF-1 status impacts cellular DNA repair mechanisms. To achieve that goal, we assessed repair of γ-irradiation-induced DNA damage (single-cell gel electrophoresis/comet assay) and basal and post-irradiation expression of DNA repair-related genes (qPCR) in primary fibroblasts derived from control rats, Lewis dwarf rats (a model of developmental GH/IGF-1 deficiency), and GH-replete dwarf rats (GH administered beginning at 5 weeks of age, for 30 days). We found that developmental GH/IGF-1 deficiency resulted in persisting increases in cellular DNA repair capacity and upregulation of several DNA repair-related genes (e.g., Gadd45a, Bbc3). Peripubertal GH treatment reversed the radiation resistance phenotype. Fibroblasts of GH/IGF-1-deficient Snell dwarf mice also exhibited improved DNA repair capacity, showing that the persisting influence of peripubertal GH/IGF-1 status is not species-dependent. Collectively, GH/IGF-1 levels during a critical period during early life determine cellular DNA repair capacity in rodents, presumably by transcriptional control of genes involved in DNA repair. Because lifestyle factors (e.g., nutrition and childhood obesity) cause huge variation in peripubertal GH/IGF-1 levels in children, further studies are warranted to determine their persisting influence on cellular cancer resistance pathways.

Peromyscus as a model of human disease

Animals of the genus Peromyscus have been a particularly informative model for many areas of study, including behavior, evolution, anatomy, physiology and genetics. While their use in modeling human disease and pathology has been relatively restricted, certain qualities of Peromyscine mice may make them a good candidate for such studies. Pathophysiological conditions where Peromyscus may be of particular value involve aging, reactive oxygen species-associated pathologies, metabolism and detoxification, diabetes, and certain cancers. In this review article we will summarize pathological conditions where Peromyscus have been used effectively, we will discuss factors limiting the use of Peromyscus in studying pathology and we will indicate areas at which the use of this model may be of special value.

Physiological levels of thrombospondin-1 decrease NO-dependent vasodilation in coronary microvessels from aged rats

Aging and cardiovascular disease are associated with the loss of nitric oxide (NO) signaling and a decline in the ability to increase coronary blood flow reserve (CFR). Thrombospondin-1 (Thbs-1), through binding of CD47, has been shown to limit NO-dependent vasodilation in peripheral vascular beds via formation of superoxide (O2 (-)). The present study tests the hypothesis that, similar to the peripheral vasculature, blocking CD47 will improve NO-mediated vasoreactivity in coronary arterioles from aged individuals, resulting in improved CFR. Isolated coronary arterioles from young (4 mo) or old (24 mo) female Fischer 344 rats were challenged with the NO donor, DEA-NONO-ate (1 × 10(-7) to 1 × 10(-4) M), and vessel relaxation and O2 (-) production was measured before and after Thbs-1, αCD47, and/or Tempol and catalase exposure. In vivo CFR was determined in anesthetized rats (1-3% isoflurane-balance O2) via injected microspheres following control IgG or αCD47 treatment (45 min). Isolated coronary arterioles from young and old rats relax similarly to exogenous NO, but addition of 2.2 nM Thbs-1 inhibited NO-mediated vasodilation by 24% in old rats, whereas young vessels were unaffected. Thbs-1 increased O2 (-) production in coronary arterioles from rats of both ages, but this was exaggerated in old rats. The addition of CD47 blocking antibody completely restored NO-dependent vasodilation in isolated arterioles from aged rats and attenuated O2 (-) production. Furthermore, αCD47 treatment increased CFR from 9.6 ± 9.3 (IgG) to 84.0 ± 23% in the left ventricle in intact, aged animals. These findings suggest that the influence of Thbs-1 and CD47 on coronary perfusion increases with aging and may be therapeutically targeted to reverse coronary microvascular dysfunction.

Animal models of aging research: implications for human aging and age-related diseases

Aging is characterized by an increasing morbidity and functional decline that eventually results in the death of an organism. Aging is the largest risk factor for numerous human diseases, and understanding the aging process may thereby facilitate the development of new treatments for age-associated diseases. The use of humans in aging research is complicated by many factors, including ethical issues; environmental and social factors; and perhaps most importantly, their long natural life span. Although cellular models of human disease provide valuable mechanistic information, they are limited in that they may not replicate the in vivo biology. Almost all organisms age, and thus animal models can be useful for studying aging. Herein, we review some of the major models currently used in aging research and discuss their benefits and pitfalls, including interventions known to extend life span and health span. Finally, we conclude by discussing the future of animal models in aging research.

Red Raspberries and Their Bioactive Polyphenols: Cardiometabolic and Neuronal Health Links

Diet is an essential factor that affects the risk of modern-day metabolic diseases, including cardiovascular disease, diabetes mellitus, obesity, and Alzheimer disease. The potential ability of certain foods and their bioactive compounds to reverse or prevent the progression of the pathogenic processes that underlie these diseases has attracted research attention. Red raspberries (Rubus idaeus L.) are unique berries with a rich history and nutrient and bioactive composition. They possess several essential micronutrients, dietary fibers, and polyphenolic components, especially ellagitannins and anthocyanins, the latter of which give them their distinctive red coloring. In vitro and in vivo studies have revealed various mechanisms through which anthocyanins and ellagitannins (via ellagic acid or their urolithin metabolites) and red raspberry extracts (or the entire fruit) could reduce the risk of or reverse metabolically associated pathophysiologies. To our knowledge, few studies in humans are available for evaluation. We review and summarize the available literature that assesses the health-promoting potential of red raspberries and select components in modulating metabolic disease risk, especially cardiovascular disease, diabetes mellitus, obesity, and Alzheimer disease-all of which share critical metabolic, oxidative, and inflammatory links. The body of research is growing and supports a potential role for red raspberries in reducing the risk of metabolically based chronic diseases.

LDL biochemical modifications: a link between atherosclerosis and aging

Atherosclerosis is an aging disease in which increasing age is a risk factor. Modified low-density lipoprotein (LDL) is a well-known risk marker for cardiovascular disease. High-plasma LDL concentrations and modifications, such as oxidation, glycosylation, carbamylation and glycoxidation, have been shown to be proatherogenic experimentally in vitro and in vivo. Atherosclerosis results from alterations to LDL in the arterial wall by reactive oxygen species (ROS). Evidence suggests that common risk factors for atherosclerosis raise the likelihood that free ROS are produced from endothelial cells and other cells. Furthermore, oxidative stress is an important factor in the induction of endothelial senescence. Thus, endothelial damage and cellular senescence are well-established markers for atherosclerosis. This review examines LDL modifications and discusses the mechanisms of the pathology of atherosclerosis due to aging, including endothelial damage and oxidative stress, and the link between aging and atherosclerosis.

Impact of age and sex on the development of atherosclerosis and expression of the related genes in apoE deficient mice

Development of atherosclerosis is a chronic pathological process. ApoE deficient (apoE(-/-)) mice spontaneously develop atherosclerotic lesions. However, the impact of age and sex on lesions and expression of the related genes have not been fully elucidated. In this study, we collected blood and tissue samples from normal chow fed male and female apoE(-/-) mice at different ages, and determined serum lipids, PCSK9 levels, en face aortic lesions and expression of some pro- or anti-atherogenic genes. We determined that lesion development was clearly associated with age, and more lesions in males than females (12.6 ± 1.7% vs. 8.9 ± 1.1% at 8 months old, P < 0.05). Associated with age, serum total, LDL- and HDL-cholesterol and PCSK9 levels increased with more PCSK9 in females than males (313 ± 31 ng/mL vs. 239 ± 28 ng/mL at 8 months old, P < 0.05); expression of liver LDLR and ABCA1 decreased while of SR-BI increased; expression of macrophage ABCA1 and SR-BI decreased but of CD36 increased. Estrogen and tamoxifen induced ABCA1 and SR-BI expression, respectively, in macrophages isolated from female mice at the different age. Taken together, our study suggests that aging facilitates lesion development in apoE(-/-) mice with greater effect on male mice. The lesion development is also related to expression of pro- or anti-atherogenic genes in tissues, particularly in macrophages.

Age-related cellular changes in the long-lived bivalve A. islandica

One of the biggest challenges to studying causes and effects of aging is identifying changes in cells that are related to senescence instead of simply the passing of chronological time. We investigated two populations of the longest living non-colonial metazoan, Arctica islandica, with lifespans that differed sixfolds. Of four investigated parameters (nucleic acid oxidation, protein oxidation, lipid oxidation, and protein instability), only nucleic acid oxidation increased with age and correlated with relative lifespan. Nucleic acid oxidation levels increased significantly faster and were significantly higher in the shorter-lived than the longer-lived population. In contrast, neither protein oxidation, lipid oxidation, nor protein stability changed over time. Protein resistance to unfolding stress when treated with urea was significantly lower overall in the shorter-lived population, and lipid peroxidation levels were higher in the longer-lived population. With the exception of nucleic acid oxidation, damage levels of A. islandica do not change with age, indicating excellent cellular maintenance in both populations. Since correlations between nucleic acid oxidation and age have also been shown previously in other organisms, and nucleic acid oxidation accumulation rate correlates with relative age in both investigated populations, nucleic acid oxidation may reflect intrinsic aging mechanisms.

Treatment with the cytochrome P450 ω-hydroxylase inhibitor HET0016 attenuates cerebrovascular inflammation, oxidative stress and improves vasomotor function in spontaneously hypertensive rats

BACKGROUND AND PURPOSE

Hypertension increases cerebrovascular oxidative stress and inflammation and impairs vasomotor function. These pathological alterations lead to dysregulation of cerebral blood flow and exacerbate atherogenesis, increasing the morbidity of ischaemic cerebrovascular diseases and promoting vascular cognitive impairment. We aimed to test the hypothesis that increased production of the arachidonic acid metabolite 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) contributes to hypertension-induced cerebrovascular alterations.

EXPERIMENTAL APPROACH

We treated male spontaneously hypertensive rats (SHR) with HET0016 (N-hydroxy-N'-(4-butyl-2-methylphenyl)-formamidine), an inhibitor of 20-HETE synthesis. In middle cerebral arteries (MCAs) of SHRs, we focused on vasomotor responses and end points that are highly relevant for cellular reactive oxygen species (ROS) production, inflammatory cytokine expression and NF-κB activation.

KEY RESULTS

SHRs treated with HET0016 remained hypertensive (SHR + HET0016: 149 ± 8 mmHg, Wistar-Kyoto rat: 115 ± 4 mmHg; P < 0.05.), although their systolic blood pressure was decreased compared to untreated SHRs (191 ± 6 mmHg). In MCAs of SHRs, flow-induced constriction was increased, whereas ACh- and ATP-induced dilations were impaired. This functional impairment was reversed by treatment with HET0016. Treatment with HET0016 also significantly decreased oxidative stress in MCAs of SHRs (as shown by dihydroethidium staining and analysis of vascular 5-nitrotyrosine, 4-hydroxynonenal and carbonyl content) and inhibited cerebrovascular inflammation (shown by the reduced mRNA expression of TNFα, IL-1β and IL-6). Treatment of SHRs with HET0016 also attenuated vascular NF-κB activation. In vitro treatment with 20-HETE significantly increased vascular production of ROS and promoted NF-κB activation in cultured cerebromicrovascular endothelial cells.

CONCLUSIONS AND IMPLICATIONS

Taken together, treatment with HET0016 confers anti-oxidative and anti-inflammatory effects in the cerebral arteries of SHRs by disrupting 20-HETE-mediated autocrine/paracrine signalling pathways in the vascular wall. It is likely that HET0016-induced decreases in blood pressure also potentiate the cerebrovascular protective effects of the drug.

Whole food versus supplement: comparing the clinical evidence of tomato intake and lycopene supplementation on cardiovascular risk factors

Cardiovascular disease (CVD) is a major contributor to morbidity and mortality in the United States and worldwide. A link between diet and CVD is well established, with dietary modification a foundational component of CVD prevention and management. With the discovery of bioactive components beyond the essential nutrients of foods, a new era of nutritional, medical, botanical, physiologic, and analytical sciences has unfolded. The ability to identify, isolate, purify, and deliver single components has expanded the dietary supplement business and health opportunity for consumers. Lycopene is an example of a food component that has attracted attention from scientists as well as food, agriculture, and dietary supplement industries. A major question, however, is whether delivering lycopene through a supplement source is as effective as or more effective than consuming lycopene through whole food sources, specifically the tomato, which is the richest source of lycopene in the Western diet. In this review, we examined clinical trials comparing the efficacy of lycopene supplements with tomato products on intermediate CVD risk factors including oxidative stress, inflammation, endothelial function, blood pressure, and lipid metabolism. Overall, the present review highlights the need for more targeted research; however, at present, the available clinical research supports consuming tomato-based foods as a first-line approach to cardiovascular health. With the exception of blood pressure management where lycopene supplementation was favored, tomato intake provided more favorable results on cardiovascular risk endpoints than did lycopene supplementation. Indeed, future research that is well designed, clinically focused, mechanistically revealing, and relevant to human intake will undoubtedly add to the growing body of knowledge unveiling the promise of tomatoes and/or lycopene supplementation as an integral component of a heart-healthy diet.

Resveratrol encapsulated in novel fusogenic liposomes activates Nrf2 and attenuates oxidative stress in cerebromicrovascular endothelial cells from aged rats

Resveratrol (3,4',5-trihydroxystilbene) is a plant-derived polyphenolic trans-stilbenoid, which exerts multifaceted antiaging effects. Here, we propose a novel delivery system for resveratrol, which significantly increases its cellular uptake into aged cells. Combination of resveratrol with a positively charged lipid component to "conventional" liposomes converts these lipid vesicles to a robust fusogenic system. To study their cellular uptake and cellular effects, we treated primary cerebromicrovascular endothelial cells isolated from aged F344xBN rats with resveratrol encapsulated in fusogenic liposomes (FL-RSV). To demonstrate effective cellular uptake of FL-RSV, accumulation of the lipophilic tracer dye, DiR, and resveratrol in cerebromicrovascular endothelial cells was confirmed using flow cytometry and confocal microscopy and high-performance liquid chromatography electrochemical detection. Treatment of aged cerebromicrovascular endothelial cells with FL-RSV activated Nrf2 (assessed with a reporter gene assay), significantly decreased cellular production of reactive oxygen species (assessed by a flow cytometry-based H2DCFDA fluorescence method), and inhibited apoptosis. Taken together, encapsulation of resveratrol into novel fusogenic liposomes significantly enhances the delivery of resveratrol into aged cells, which subsequently results in rapid activation of cellular Nrf2-driven antioxidant defense mechanisms. Our studies provide proof-of-concept for the development of a novel, translationally relevant interventional strategy for prevention and/or control of oxidative stress-related pathophysiological conditions in aging.

Nox2-induced production of mitochondrial superoxide in angiotensin II-mediated endothelial oxidative stress and hypertension

AIMS

Angiotensin II (AngII)-induced superoxide (O2(•-)) production by the NADPH oxidases and mitochondria has been implicated in the pathogenesis of endothelial dysfunction and hypertension. In this work, we investigated the specific molecular mechanisms responsible for the stimulation of mitochondrial O2(•-) and its downstream targets using cultured human aortic endothelial cells and a mouse model of AngII-induced hypertension.

RESULTS

Western blot analysis showed that Nox2 and Nox4 were present in the cytoplasm but not in the mitochondria. Depletion of Nox2, but not Nox1, Nox4, or Nox5, using siRNA inhibits AngII-induced O2(•-) production in both mitochondria and cytoplasm. Nox2 depletion in gp91phox knockout mice inhibited AngII-induced cellular and mitochondrial O2(•-) and attenuated hypertension. Inhibition of mitochondrial reverse electron transfer with malonate, malate, or rotenone attenuated AngII-induced cytoplasmic and mitochondrial O2(•-) production. Inhibition of the mitochondrial ATP-sensitive potassium channel (mitoK(+)ATP) with 5-hydroxydecanoic acid or specific PKCɛ peptide antagonist (EAVSLKPT) reduced AngII-induced H2O2 in isolated mitochondria and diminished cytoplasmic O2(•-). The mitoK(+)ATP agonist diazoxide increased mitochondrial O2(•-), cytoplasmic c-Src phosphorylation and cytoplasmic O2(•-) suggesting feed-forward regulation of cellular O2(•-) by mitochondrial reactive oxygen species (ROS). Treatment of AngII-infused mice with malate reduced blood pressure and enhanced the antihypertensive effect of mitoTEMPO. Mitochondria-targeted H2O2 scavenger mitoEbselen attenuated redox-dependent c-Src and inhibited AngII-induced cellular O2(•-), diminished aortic H2O2, and reduced blood pressure in hypertensive mice.

INNOVATION AND CONCLUSIONS

These studies show that Nox2 stimulates mitochondrial ROS by activating reverse electron transfer and both mitochondrial O2(•-) and reverse electron transfer may represent new pharmacological targets for the treatment of hypertension.

A heart that beats for 500 years: age-related changes in cardiac proteasome activity, oxidative protein damage and expression of heat shock proteins, inflammatory factors, and mitochondrial complexes in Arctica islandica, the longest-living noncolonial animal

Study of negligibly senescent animals may provide clues that lead to better understanding of the cardiac aging process. To elucidate mechanisms of successful cardiac aging, we investigated age-related changes in proteasome activity, oxidative protein damage and expression of heat shock proteins, inflammatory factors, and mitochondrial complexes in the heart of the ocean quahog Arctica islandica, the longest-lived noncolonial animal (maximum life span potential: 508 years). We found that in the heart of A. islandica the level of oxidatively damaged proteins did not change significantly up to 120 years of age. No significant aging-induced changes were observed in caspase-like and trypsin-like proteasome activity. Chymotrypsin-like proteasome activity showed a significant early-life decline, then it remained stable for up to 182 years. No significant relationship was observed between the extent of protein ubiquitination and age. In the heart of A. islandica, an early-life decline in expression of HSP90 and five mitochondrial electron transport chain complexes was observed. We found significant age-related increases in the expression of three cytokine-like mediators (interleukin-6, interleukin-1β, and tumor necrosis factor-α) in the heart of A. islandica. Collectively, in extremely long-lived molluscs, maintenance of protein homeostasis likely contributes to the preservation of cardiac function. Our data also support the concept that low-grade chronic inflammation in the cardiovascular system is a universal feature of the aging process, which is also manifest in invertebrates.

Oxidative stress and vascular inflammation in aging

Vascular aging, a determinant factor for cardiovascular disease and health status in the elderly, is now viewed as a modifiable risk factor. Impaired endothelial vasodilation is a early hallmark of arterial aging that precedes the clinical manifestations of vascular dysfunction, the first step to cardiovascular disease and influencing vascular outcomes in the elderly. Accordingly, the preservation of endothelial function is thought to be an essential determinant of healthy aging. With special attention on the effects of aging on the endothelial function, this review is focused on the two main mechanisms of aging-related endothelial dysfunction: oxidative stress and inflammation. Aging vasculature generates an excess of the reactive oxygen species (ROS), superoxide and hydrogen peroxide, that compromise the vasodilatory activity of nitric oxide (NO) and facilitate the formation of the deleterious radical, peroxynitrite. Main sources of ROS are mitochondrial respiratory chain and NADPH oxidases, although NOS uncoupling could also account for ROS generation. In addition, reduced antioxidant response mediated by erythroid-2-related factor-2 (Nrf2) and downregulation of mitochondrial manganese superoxide dismutase (SOD2) contributes to the establishment of chronic oxidative stress in aged vessels. This is accompanied by a chronic low-grade inflammatory phenotype that participates in defective endothelial vasodilation. The redox-sensitive transcription factor, nuclear factor-κB (NF-κB), is upregulated in vascular cells from old subjects and drives a proinflammatory shift that feedbacks oxidative stress. This chronic NF-κB activation is contributed by increased angiotensin-II signaling and downregulated sirtuins and precludes adequate cellular response to acute ROS generation. Interventions targeted to recover endogenous antioxidant capacity and cellular stress response rather than exogenous antioxidants could reverse oxidative stress-inflammation vicious cycle in vascular aging. Lifestyle attitudes such as caloric restriction and exercise training appear as effective ways to overcome defective antioxidant response and inflammation, favoring successful vascular aging and decreasing the risk for cardiovascular disease.

Impaired vascular endothelial growth factor A and inflammation in patients with peripheral artery disease

We compared apoptosis, cellular oxidative stress, and inflammation of cultured endothelial cells treated with sera from 130 patients with peripheral artery disease (PAD) and a control group of 36 patients with high burden of comorbid conditions and cardiovascular risk factors. Second, we compared circulating inflammatory, antioxidant capacity, and vascular biomarkers between the groups. The groups were not significantly different (P > .05) on apoptosis, hydrogen peroxide, hydroxyl radical antioxidant capacity, and nuclear factor κ-light-chain enhancer of activated B cells. Circulating tumor necrosis factor α (TNF-α; P = .016) and interleukin 8 (IL-8; P = .006) were higher in the PAD group, whereas vascular endothelial growth factor A (VEGF-A; P = .023) was lower. The PAD does not impair the endothelium beyond that which already occurs from comorbid conditions and cardiovascular risk factors in patients with claudication. However, patients with PAD have lower circulating VEGF-A than the control group and higher circulating inflammatory parameters of TNF-α and IL-8.

Aging impairs electrical conduction along endothelium of resistance arteries through enhanced Ca2+-activated K+ channel activation

OBJECTIVE

Intercellular conduction of electrical signals underlies spreading vasodilation of resistance arteries. Small- and intermediate-conductance Ca(2+)-activated K(+) channels of endothelial cells serve a dual function by initiating hyperpolarization and modulating electrical conduction. We tested the hypothesis that regulation of electrical signaling by small- and intermediate-conductance Ca(2+)-activated K(+) channels is altered with advancing age.

APPROACH AND RESULTS

Intact endothelial tubes (60 µm wide; 1-3 mm long) were freshly isolated from male C57BL/6 mouse (Young: 4-6 months; Intermediate: 12-14 months; Old: 24-26 months) superior epigastric arteries. Using dual intracellular microelectrodes, current was injected (± 0.1-3 nA) at site 1 while recording membrane potential (Vm) at site 2 (separation distance: 50-2000 µm). Across age groups, greatest differences were observed between Young and Old. Resting Vm in Old (-38 ± 1 mV) was more negative (P<0.05) than Young (-30 ± 1 mV). Maximal hyperpolarization to both direct (NS309) and indirect (acetylcholine) activation of small- and intermediate-conductance Ca(2+)-activated K(+) channels was sustained (ΔVm ≈-40 mV) with age. The length constant (λ) for electrical conduction was reduced (P<0.05) from 1630 ± 80 µm (Young) to 1320 ± 80 µm (Old). Inhibiting small- and intermediate-conductance Ca(2+)-activated K(+) channels with apamin+charybdotoxin or scavenging hydrogen peroxide (H2O2) with catalase improved electrical conduction (P<0.05) in Old. Exogenous H2O2 (200 µmol/L) in Young evoked hyperpolarization and impaired electrical conduction; these effects were blocked by apamin+charybdotoxin.

CONCLUSIONS

Enhanced current loss through Ca2+-activated K+ channel activation impairs electrical conduction along the endothelium of resistance arteries with aging. Attenuating the spatial domain of electrical signaling will restrict the spread of vasodilation and thereby contribute to blood flow limitations associated with advanced age.

Aging decreases antioxidant effects and increases lipid peroxidation in the Apolipoprotein E deficient mouse

In this study, to study the effect of aging and Apolipoprotein E (ApoE) deficiency on antioxidant ability in mice, we examined whether lipid peroxidation is promoted by aging in ApoE deficient (ApoE(-/-)) mice, which have a shorter lifespan than normal mice. The levels of thiobarbituric acid-reactive substances (TBARS), a biomarker of lipid peroxidation, were measured in plasma and liver in ApoE(-/-) mice aged 12 weeks (young) and 52 weeks (early stage of senescence). TBARS in plasma and liver were significantly increased by aging. Next, we examined the reasons why lipid peroxidation was promoted by aging, based on measurement of protein and mRNA levels for antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in liver in ApoE(-/-) mice aged 12 and 52 weeks. The levels of superoxide dismutase 1 and 2 in liver were significantly decreased by aging. The mRNA level of catalase was also significantly decreased and the mRNA levels of superoxide dismutase 1, superoxide dismutase 2 and glutathione peroxidase 1 all showed a tendency to decrease with age. These results suggest that lipid peroxidation is caused by reduction of antioxidant activity with aging and that this promotes senescence and shortens lifespan in ApoE(-/-) mice.

Ionizing radiation promotes the acquisition of a senescence-associated secretory phenotype and impairs angiogenic capacity in cerebromicrovascular endothelial cells: role of increased DNA damage and decreased DNA repair capacity in microvascular radiosensitivity

Cerebromicrovascular rarefaction is believed to play a central role in cognitive impairment in patients receiving whole-brain irradiation therapy. To elucidate the mechanism underlying the deleterious effects of γ-irradiation on the cerebral microcirculation, rat primary cerebromicrovascular endothelial cells (CMVECs) were irradiated in vitro. We found that in CMVECs, γ-irradiation (2-8 Gy) elicited increased DNA damage, which was repaired less efficiently in CMVECs compared with neurons, microglia, and astrocytes. Increased genomic injury in CMVECs associated with increased apoptotic cell death. In the surviving cells, γ-irradiation promotes premature senescence (indicated by SA-β-galactosidase positivity and upregulation of p16 (INK4a) ), which was associated with impaired angiogenic capacity (decreased proliferation and tube-forming capacity). γ-Irradiated CMVECs acquired a senescence-associated secretory phenotype, characterized by upregulation of proinflammatory cytokines and chemokines (including IL-6, IL-1α, and MCP-1). Collectively, increased vulnerability of γ-irradiated CMVECs and their impaired angiogenic capacity likely contribute to cerebromicrovascular rarefaction and prevent regeneration of the microvasculature postirradiation. The acquisition of a senescence-associated secretory phenotype in irradiated CMVECs is biologically highly significant as changes in the cytokine microenvironment in the hippocampus may affect diverse biological processes relevant for normal neuronal function (including regulation of neurogenesis and the maintenance of the blood brain barrier).

Aging decreases antioxidant effects and increases lipid peroxidation in the Apolipoprotein E deficient mouse

In this study, to study the effect of aging and Apolipoprotein E (ApoE) deficiency on antioxidant ability in mice, we examined whether lipid peroxidation is promoted by aging in ApoE deficient (ApoE^−/−) mice, which have a shorter lifespan than normal mice. The levels of thiobarbituric acid-reactive substances (TBARS), a biomarker of lipid peroxidation, were measured in plasma and liver in ApoE^−/− mice aged 12 weeks (young) and 52 weeks (early stage of senescence). TBARS in plasma and liver were significantly increased by aging. Next, we examined the reasons why lipid peroxidation was promoted by aging, based on measurement of protein and mRNA levels for antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in liver in ApoE^−/− mice aged 12 and 52 weeks. The levels of superoxide dismutase 1 and 2 in liver were significantly decreased by aging. The mRNA level of catalase was also significantly decreased and the mRNA levels of superoxide dismutase 1, superoxide dismutase 2 and glutathione peroxidase 1 all showed a tendency to decrease with age. These results suggest that lipid peroxidation is caused by reduction of antioxidant activity with aging and that this promotes senescence and shortens lifespan in ApoE^−/− mice.

Vascular aging: chronic oxidative stress and impairment of redox signaling-consequences for vascular homeostasis and disease

Characteristic morphological and molecular alterations such as vessel wall thickening and reduction of nitric oxide occur in the aging vasculature leading to the gradual loss of vascular homeostasis. Consequently, the risk of developing acute and chronic cardiovascular diseases increases with age. Current research of the underlying molecular mechanisms of endothelial function demonstrates a duality of reactive oxygen and nitrogen species in contributing to vascular homeostasis or leading to detrimental effects when formed in excess. Furthermore, changes in function and redox status of vascular smooth muscle cells contribute to age-related vascular remodeling. The age-dependent increase in free radical formation causes deterioration of the nitric oxide signaling cascade, alters and activates prostaglandin metabolism, and promotes novel oxidative posttranslational protein modifications that interfere with vascular and cell signaling pathways. As a result, vascular dysfunction manifests. Compensatory mechanisms are initially activated to cope with age-induced oxidative stress, but become futile, which results in irreversible oxidative modifications of biological macromolecules. These findings support the 'free radical theory of aging' but also show that reactive oxygen and nitrogen species are essential signaling molecules, regulating vascular homeostasis.

Reduced mitochondrial ROS, enhanced antioxidant defense, and distinct age-related changes in oxidative damage in muscles of long-lived Peromyscus leucopus

Comparing biological processes in closely related species with divergent life spans is a powerful approach to study mechanisms of aging. The oxidative stress hypothesis of aging predicts that longer-lived species would have lower reactive oxygen species (ROS) generation and/or an increased antioxidant capacity, resulting in reduced oxidative damage with age than in shorter-lived species. In this study, we measured ROS generation in the young adult animals of the long-lived white-footed mouse, Peromyscus leucopus (maximal life span potential, MLSP = 8 yr) and the common laboratory mouse, Mus musculus (C57BL/6J strain; MLSP = 3.5 yr). Consistent with the hypothesis, our results show that skeletal muscle mitochondria from adult P. leucopus produce less ROS (superoxide and hydrogen peroxide) compared with M. musculus. Additionally, P. leucopus has an increase in the activity of antioxidant enzymes superoxide dismutase 1, catalase, and glutathione peroxidase 1 at young age. P. leucopus compared with M. musculus display low levels of lipid peroxidation (isoprostanes) throughout life; however, P. leucopus although having elevated protein carbonyls at a young age, the accrual of protein oxidation with age is minimal in contrast to the linear increase in M. musculus. Altogether, the results from young animals are in agreement with the predictions of the oxidative stress hypothesis of aging with the exception of protein carbonyls. Nonetheless, the age-dependent increase in protein carbonyls is more pronounced in short-lived M. musculus, which supports enhanced protein homeostasis in long-lived P. leucopus.

Resistance to genotoxic stresses in Arctica islandica, the longest living noncolonial animal: is extreme longevity associated with a multistress resistance phenotype?

Bivalve molluscs are newly discovered models of successful aging. Here, we test the hypothesis that extremely long-lived bivalves are not uniquely resistant to oxidative stressors (eg, tert-butyl hydroperoxide, as demonstrated in previous studies) but exhibit a multistress resistance phenotype. We contrasted resistance (in terms of organismal mortality) to genotoxic stresses (including topoisomerase inhibitors, agents that cross-link DNA or impair genomic integrity through DNA alkylation or methylation) and to mitochondrial oxidative stressors in three bivalve mollusc species with dramatically differing life spans: Arctica islandica (ocean quahog), Mercenaria mercenaria (northern quahog), and the Atlantic bay scallop, Argopecten irradians irradians (maximum species life spans: >500, >100, and ~2 years, respectively). With all stressors, the short-lived A i irradians were significantly less resistant than the two longer lived species. Arctica islandica were consistently more resistant than M mercenaria to mortality induced by oxidative stressors as well as DNA methylating agent nitrogen mustard and the DNA alkylating agent methyl methanesulfonate. The same trend was not observed for genotoxic agents that act through cross-linking DNA. In contrast, M mercenaria tended to be more resistant to epirubicin and genotoxic stressors, which cause DNA damage by inhibiting topoisomerases. To our knowledge, this is the first study comparing resistance to genotoxic stressors in bivalve mollusc species with disparate longevities. In line with previous studies of comparative stress resistance and longevity, our data extends, at least in part, the evidence for the hypothesis that an association exists between longevity and a general resistance to multiplex stressors, not solely oxidative stress. This work also provides justification for further investigation into the interspecies differences in stress response signatures induced by a diverse array of stressors in short-lived and long-lived bivalves, including pharmacological agents that elicit endoplasmic reticulum stress and cellular stress caused by activation of innate immunity.