Vascular Ageing Features Caused by Selective DNA Damage in Smooth Muscle Cell

SIRT-associated attenuation of cellular senescence in vascular wall

This review focuses on the vital function that SIRT1 and other sirtuins play in promoting cellular senescence in vascular smooth muscle cells, which is a key element in the pathogenesis of vascular aging and associated cardiovascular diseases. Vascular aging is a gradual process caused by the accumulation of senescent cells, which results in increased vascular remodeling, stiffness, and diminished angiogenic ability. Such physiological alterations are characterized by a complex interplay of environmental and genetic variables, including oxidative stress and telomere attrition, which affect gene expression patterns and trigger cell growth arrest. SIRT1 has been highlighted for its potential to reduce cellular senescence through modulation of multiple signaling cascades, particularly the endothelial nitric oxide (eNOS)/NO signaling pathway. It also modulates cell cycle through p53 inactivation and suppresses NF-κB mediated expression of adhesive molecules at the vascular level. The study also examines the therapeutic potential of sirtuin modulation in vascular health, identifying SIRT1 and its sirtuin counterparts as potential targets for reducing vascular aging. This study sheds light on the molecular basis of vascular aging and the beneficial effects of sirtuins, paving the way for the development of tailored therapies aimed at enhancing vascular health and prolonging life.

Ercc1 DNA repair deficiency results in vascular aging characterized by VSMC phenotype switching, ECM remodeling, and an increased stress response

Cardiovascular diseases are the number one cause of death globally. The most important determinant of cardiovascular health is a person's age. Aging results in structural changes and functional decline of the cardiovascular system. DNA damage is an important contributor to the aging process, and mice with a DNA repair defect caused by Ercc1 deficiency display hypertension, vascular stiffening, and loss of vasomotor control. To determine the underlying cause, we compared important hallmarks of vascular aging in aortas of both Ercc1Δ/- and age-matched wildtype mice. Additionally, we investigated vascular aging in 104 week old wildtype mice. Ercc1Δ/- aortas displayed arterial thickening, a loss of cells, and a discontinuous endothelial layer. Aortas of 24 week old Ercc1Δ/- mice showed phenotypical switching of vascular smooth muscle cells (VSMCs), characterized by a decrease in contractile markers and a decrease in synthetic markers at the RNA level. As well as an increase in osteogenic markers, microcalcification, and an increase in markers for damage induced stress response. This suggests that Ercc1Δ/- VSMCs undergo a stress-induced contractile-to-osteogenic phenotype switch. Ercc1Δ/- aortas showed increased MMP activity, elastin fragmentation, and proteoglycan deposition, characteristic of vascular aging and indicative of age-related extracellular matrix remodeling. The 104 week old WT mice showed loss of cells, VSMC dedifferentiation, and senescence. In conclusion, Ercc1Δ/- aortas rapidly display many characteristics of vascular aging, and thus the Ercc1Δ/- mouse is an excellent model to evaluate drugs that prevent vascular aging in a short time span at the functional, histological, and cellular level.

Adiponectin secretion by perivascular adipose tissue supports impaired vasodilation in a mouse model of accelerated vascular smooth muscle cell and adipose tissue aging

OBJECTIVE

Perivascular adipose tissue (PVAT) function during aging has not been investigated in detail so far and its effect on vasodilation remains to be fully elucidated. The aim of this study was to investigate endothelium-dependent vasodilation of thoracic aorta in a mouse model of accelerated, selective vascular smooth muscle and PVAT aging, induced by SM22α-Cre-driven genetic deletion of the endonuclease ERCC1 (SMC-KO mice) versus healthy littermates (LM). We hypothesized that PVAT enhances vasodilation in LM, possibly through adiponectin secretion, which might be compromised in SMC-KO animals.

METHODS

Thoracic aorta was isolated from SMC-KO animals and LM and segments with and without PVAT were mounted in wire myography setups. The endothelium-dependent vasodilation was assessed via acetylcholine dose-response curves and pathway contribution was studied. Moreover, adiponectin secretion was measured after stimulating the aortic segments with PVAT with acetylcholine.

RESULTS

Adiponectin, secreted by PVAT, led to increased NO-contribution to endothelium-dependent vasodilation in healthy LM, although this did not increase maximum relaxation due to loss of EDH. Endothelium-dependent vasodilation was decreased in SMC-KO animals due to reduced NO-contribution and complete EDH loss. Despite strong lipodystrophy the PVAT partially compensated for lost vasodilation in SMC-KO. LM PVAT contained acetylcholinesterase that attenuated acetylcholine responses. This was lost in SMC-KO.

CONCLUSIONS

PVAT-derived adiponectin is able to partially compensate for age-related decline in NO-mediated vasodilation, even during strong lipodystrophy, in conditions of absence of compensating EDH. In aorta with healthy PVAT acetylcholinesterase modulates vascular tone, but this is lost during aging, further compensating for decreased acetylcholine responsiveness. Thus, preservation of adiponectin levels, through relatively increased production in lipodystrophic PVAT, and reduction of cholinesterase might be regulatory mechanisms of the PVAT to preserve cholinergic vasodilation during aging.

Pharmacological modulation of vascular ageing: A review from VascAgeNet

Vascular ageing, characterized by structural and functional changes in blood vessels of which arterial stiffness and endothelial dysfunction are key components, is associated with increased risk of cardiovascular and other age-related diseases. As the global population continues to age, understanding the underlying mechanisms and developing effective therapeutic interventions to mitigate vascular ageing becomes crucial for improving cardiovascular health outcomes. Therefore, this review provides an overview of the current knowledge on pharmacological modulation of vascular ageing, highlighting key strategies and promising therapeutic targets. Several molecular pathways have been identified as central players in vascular ageing, including oxidative stress and inflammation, the renin-angiotensin-aldosterone system, cellular senescence, macroautophagy, extracellular matrix remodelling, calcification, and gasotransmitter-related signalling. Pharmacological and dietary interventions targeting these pathways have shown potential in ameliorating age-related vascular changes. Nevertheless, the development and application of drugs targeting vascular ageing is complicated by various inherent challenges and limitations, such as certain preclinical methodological considerations, interactions with exercise training and sex/gender-related differences, which should be taken into account. Overall, pharmacological modulation of endothelial dysfunction and arterial stiffness as hallmarks of vascular ageing, holds great promise for improving cardiovascular health in the ageing population. Nonetheless, further research is needed to fully elucidate the underlying mechanisms and optimize the efficacy and safety of these interventions for clinical translation.

Clinical Impact and Mechanisms of Nonatherosclerotic Vascular Aging: The New Kid to Be Blocked

Ischemic cardiovascular disease and stroke remain the leading cause of global morbidity and mortality. During aging, protective mechanisms in the body gradually deteriorate, resulting in functional, structural, and morphologic changes that affect the vascular system. Because atherosclerotic plaques are not always present along with these alterations, we refer to this kind of vascular aging as nonatherosclerotic vascular aging (NAVA). To maintain proper vascular function during NAVA, it is important to preserve intracellular signalling, prevent inflammation, and block the development of senescent cells. Pharmacologic interventions targeting these components are potential therapeutic approaches for NAVA, with a particular emphasis on inflammation and senescence. This review provides an overview of the pathophysiology of vascular aging and explores potential pharmacotherapies that can improve the function of aged vasculature, focusing on NAVA.

Methods for Assessment of Nucleotide Excision Repair Efficiency

Nucleotide excision repair (NER) is responsible for removing a wide variety of bulky adducts from DNA, thus contributing to the maintenance of genome stability. The efficiency with which proteins of the NER system recognize and remove bulky adducts depends on many factors and is of great clinical and diagnostic significance. The review examines current concepts of the NER system molecular basis in eukaryotic cells and analyzes methods for the assessment of the NER-mediated DNA repair efficiency both in vitro and ex vivo.

Hallmarks of cardiovascular ageing

Normal circulatory function is a key determinant of disease-free life expectancy (healthspan). Indeed, pathologies affecting the cardiovascular system, which are growing in prevalence, are the leading cause of global morbidity, disability and mortality, whereas the maintenance of cardiovascular health is necessary to promote both organismal healthspan and lifespan. Therefore, cardiovascular ageing might precede or even underlie body-wide, age-related health deterioration. In this Review, we posit that eight molecular hallmarks are common denominators in cardiovascular ageing, namely disabled macroautophagy, loss of proteostasis, genomic instability (in particular, clonal haematopoiesis of indeterminate potential), epigenetic alterations, mitochondrial dysfunction, cell senescence, dysregulated neurohormonal signalling and inflammation. We also propose a hierarchical order that distinguishes primary (upstream) from antagonistic and integrative (downstream) hallmarks of cardiovascular ageing. Finally, we discuss how targeting each of the eight hallmarks might be therapeutically exploited to attenuate residual cardiovascular risk in older individuals.

Model Systems to Study the Mechanism of Vascular Aging

Cardiovascular diseases are the leading cause of death globally. Within cardiovascular aging, arterial aging holds significant importance, as it involves structural and functional alterations in arteries that contribute substantially to the overall decline in cardiovascular health during the aging process. As arteries age, their ability to respond to stress and injury diminishes, while their luminal diameter increases. Moreover, they experience intimal and medial thickening, endothelial dysfunction, loss of vascular smooth muscle cells, cellular senescence, extracellular matrix remodeling, and deposition of collagen and calcium. This aging process also leads to overall arterial stiffening and cellular remodeling. The process of genomic instability plays a vital role in accelerating vascular aging. Progeria syndromes, rare genetic disorders causing premature aging, exemplify the impact of genomic instability. Throughout life, our DNA faces constant challenges from environmental radiation, chemicals, and endogenous metabolic products, leading to DNA damage and genome instability as we age. The accumulation of unrepaired damages over time manifests as an aging phenotype. To study vascular aging, various models are available, ranging from in vivo mouse studies to cell culture options, and there are also microfluidic in vitro model systems known as vessels-on-a-chip. Together, these models offer valuable insights into the aging process of blood vessels.

Serum sclerostin level is positively associated with endothelial dysfunction measured by digital thermal monitoring in patients with type 2 diabetes: A prospective cross-sectional study

Sclerostin and dickkopf-1 (DKK1), extracellular inhibitors of the canonical Wnt/β-catenin signaling pathway, have been associated with vascular aging and atherosclerosis. This study aimed to assess the correlation of sclerostin and DKK1 concentrations with endothelial function measured using vascular reactivity index (VRI) in patients with type 2 diabetes mellitus (T2DM). Fasting blood samples were collected from 100 patients with T2DM. Endothelial function and VRI were measured using digital thermal monitoring and circulating sclerostin and DKK1 levels by enzyme-linked immunosorbent assays. VRI values < 1.0, 1.0-1.9, and > 2.0 indicated poor, intermediate, and good vascular reactivity, respectively. Overall, 30, 38, and 32 patients had poor, intermediate, and good vascular reactivity, respectively. Older age, higher serum glycated hemoglobulin, urinary albumin-to-creatinine ratio, and sclerostin as well as lower hypertension prevalence, systolic blood pressure, and diastolic blood pressure (DBP) were associated with poor VRI. Multivariable forward stepwise linear regression analysis showed that DBP (β = 0.294, adjusted R2 change = 0.098, P < .001), log-glycated hemoglobin (β = -0.235, adjusted R2 change = 0.050, P = .002), log-urine albumin-to-creatinine ratio (β = -0.342, adjusted R2 change = 0.227, P < .001), and log-sclerostin level (β = -0.327, adjusted R2 change = 0.101, P < .001) were independently associated with VRI. Serum sclerostin, along with glycated hemoglobin and albumin-to-creatinine ratio, exhibited a negative correlation with VRI, while DBP showed a positive correlation with VRI. These factors can independently predict endothelial dysfunction in patients with T2DM.

A landscape of Long non-coding RNAs reveals the leading transcriptome alterations in murine aorta during aging

Considerable studies have given convincing evidence of a forefront position for vascular aging in preventing cardiovascular disease. Various functions of Long non-coding RNAs (lncRNAs) are becoming increasingly distinct in aging-related diseases. This study aims at a better insight into the expression profile and mechanisms of lncRNAs in vascular senescence. High-throughput sequencing was used to detect the differential expression (DE) of lncRNAs and mRNAs in the aorta of 96 W and 8 W-old mice, while 1423 lncRNAs and 80 mRNAs were differentially expressed. By performing GO and KEGG enrichment analysis, we found that DE lncRNAs were mainly involved in purine metabolism and cGMP-PKG signaling pathways. In addition, a co-expression functional network of DE lncRNAs and DE mRNAs was constructed, and ENSMUST00000218874 could interact with 41 DE mRNAs, suggesting that it may play an essential role in vascular senescence. This study reveals DE lncRNAs in naturally aging vascular, which may provide new ideas and targets for aging-related cardiovascular diseases.

DNA repair in cardiomyocytes is critical for maintaining cardiac function in mice

Heart failure has reached epidemic proportions in a progressively ageing population. The molecular mechanisms underlying heart failure remain elusive, but evidence indicates that DNA damage is enhanced in failing hearts. Here, we tested the hypothesis that endogenous DNA repair in cardiomyocytes is critical for maintaining normal cardiac function, so that perturbed repair of spontaneous DNA damage drives early onset of heart failure. To increase the burden of spontaneous DNA damage, we knocked out the DNA repair endonucleases xeroderma pigmentosum complementation group G (XPG) and excision repair cross-complementation group 1 (ERCC1), either systemically or cardiomyocyte-restricted, and studied the effects on cardiac function and structure. Loss of DNA repair permitted normal heart development but subsequently caused progressive deterioration of cardiac function, resulting in overt congestive heart failure and premature death within 6 months. Cardiac biopsies revealed increased oxidative stress associated with increased fibrosis and apoptosis. Moreover, gene set enrichment analysis showed enrichment of pathways associated with impaired DNA repair and apoptosis, and identified TP53 as one of the top active upstream transcription regulators. In support of the observed cardiac phenotype in mutant mice, several genetic variants in the ERCC1 and XPG gene in human GWAS data were found to be associated with cardiac remodelling and dysfunction. In conclusion, unrepaired spontaneous DNA damage in differentiated cardiomyocytes drives early onset of cardiac failure. These observations implicate DNA damage as a potential novel therapeutic target and highlight systemic and cardiomyocyte-restricted DNA repair-deficient mouse mutants as bona fide models of heart failure.

Aging results in DNA damage and telomere dysfunction that is greater in endothelial versus vascular smooth muscle cells and is exacerbated in atheroprone regions

Aging increases the risk of atherosclerotic cardiovascular disease which is associated with arterial senescence; however, the mechanisms responsible for the development of cellular senescence in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) remain elusive. Here, we study the effect of aging on arterial DNA damage and telomere dysfunction. Aging resulted in greater DNA damage in ECs than VSMCs. Further, telomere dysfunction-associated DNA damage foci (TAF: DNA damage signaling at telomeres) were elevated with aging in ECs but not VMSCs. Telomere length was modestly reduced in ECs with aging and not sufficient to induce telomere dysfunction. DNA damage and telomere dysfunction were greatest in atheroprone regions (aortic minor arch) versus non-atheroprone regions (thoracic aorta). Collectively, these data demonstrate that aging results in DNA damage and telomere dysfunction that is greater in ECs than VSMCs and elevated in atheroprone aortic regions.

Soluble guanylate cyclase activator BAY 54-6544 improves vasomotor function and survival in an accelerated ageing mouse model

DNA damage is a causative factor in ageing of the vasculature and other organs. One of the most important vascular ageing features is reduced nitric oxide (NO)soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) signaling. We hypothesized that the restoration of NO-sGC-cGMP signaling with an sGC activator (BAY 54-6544) may have beneficial effects on vascular ageing and premature death in DNA repair-defective mice undergoing accelerated ageing. Eight weeks of treatment with a non-pressor dosage of BAY 54-6544 restored the decreased in vivo microvascular cutaneous perfusion in progeroid Ercc1∆/- mice to the level of wild-type mice. In addition, BAY 54-6544 increased survival of Ercc1∆/- mice. In isolated Ercc1∆/- aorta, the decreased endothelium-independent vasodilation was restored after chronic BAY 54-6544 treatment. Senescence markers p16 and p21, and markers of inflammation, including Ccl2, Il6 in aorta and liver, and circulating IL-6 and TNF-α were increased in Ercc1∆/- , which was lowered by the treatment. Expression of antioxidant genes, including Cyb5r3 and Nqo1, was favorably changed by chronic BAY 54-6544 treatment. In summary, BAY 54-6544 treatment improved the vascular function and survival rates in mice with accelerated ageing, which may have implication in prolonging health span in progeria and normal ageing.

Pharmacological developments in antihypertensive treatment through nitric oxide-cGMP modulation

Treatment of hypertension until now has been directed at inhibition of vasoconstriction, of cardiac contractility and of blood volume regulation. Despite the arsenal of drugs available for this purpose, the control of target blood pressure is still a difficult goal to reach in outpatients. The nitric oxide-cyclic guanosine monophosphate signaling is one of the most important mediators of vasodilation. It might therefore be a potential and most welcome drug target for optimization of the treatment of hypertension. In this chapter we review the problems that can occur in this signaling system, the attempts that have been made to correct these problems, and those that are still under investigation. Recently developed, clinically safe medicines that are currently approved for other applications, such as myocardial infarction, await to be tested for essential systemic hypertension. We conclude that despite many years of research without translation, stimulation of nitric oxide-cyclic guanosine monophosphate is still a viable strategy in the prevention of the health risk posed by chronic hypertension.

The Effects of Acute and Chronic Selective Phosphodiesterase 1 Inhibition on Smooth Muscle Cell-Associated Aging Features

Age-related cardiovascular diseases (CVDs) remain among the leading global causes of death, and vascular smooth muscle cell (VSMC) remodeling plays an essential role in its pathology. Reduced NO-cGMP pathway signaling is a major feature and pathogenic mechanism underlying vasodilator dysfunction. Recently, we identified phosphodiesterase (PDE) 1, an enzyme that hydrolyzes and inactivates the cyclic nucleotides cAMP and cGMP, and thereby provides a potential treatment target for restoring age-related vascular dysfunction due to aging of VSMC. Based on this hypothesis, we here tested the effects of PDE1 inhibition in a model of SMC-specific accelerated aging mice. SMC-KO and their WT littermates received either vehicle or the PDE1 inhibitor lenrispodun for 8 weeks. Vascular function was measured both in vivo (Laser Doppler technique) and ex vivo (organ bath). Moreover, we deployed UV irradiation in cell culture experiments to model accelerated aging in an in vitro situation. SMC-KO mice display a pronounced loss of vasodilator function in the isolated aorta, the cutaneous microvasculature, and mesenteric arteries. Ex vivo, in isolated vascular tissue, we found that PDE1 inhibition with lenrispodun improves vasodilation, while no improvement was observed in isolated aorta taken from mice after chronic treatment in vivo. However, during lenrispodun treatment in vivo, an enhanced microvascular response in association with upregulated cGMP levels was seen. Further, chronic lenrispodun treatment decreased TNF-α and IL-10 plasma levels while the elevated level of IL-6 in SMC-KO mice remained unchanged after treatment. PDE1 and senescence markers, p16 and p21, were increased in both SMC-KO aorta and cultured human VSMC in which DNA was damaged by ultraviolet irradiation. This increase was lowered by chronic lenrispodun. In contrast, lenrispodun increased the level of PDE1A in both situations. In conclusion, we demonstrated that PDE1 inhibition may be therapeutically useful in reversing aspects of age-related VSMC dysfunction by potentiating NO-cGMP signaling, preserving microvascular function, and decreasing senescence. Yet, after chronic treatment, the effects of PDE1 inhibition might be counteracted by the interplay between differential PDE1A and C expression. These results warrant further pharmacodynamic profiling of PDE enzyme regulation during chronic PDE1 inhibitor treatment.