Cardiovascular Ramifications of Therapy-induced Endothelial Cell Senescence in Cancer Survivors

Abstract

Cancer survivorship has remarkably improved over the past decades; nevertheless, cancer survivors are burdened with multiple health complications primarily caused by their cancer therapy. Therapy-induced senescence is recognized as a fundamental mechanism contributing to adverse health complications in cancer survivors. In this mini-review, we will discuss the recent literature describing the mechanisms of cancer therapy-induced senescence. We will focus on endothelial cell senescence since it has been shown to be a key player in numerous cardiovascular complications. We will also discuss novel senotherapeutic approaches that have the potential to combat therapy-induced endothelial cell senescence.

1. Introduction

Recent years have witnessed significant improvements in the diagnosis and treatment of cancer patients [1], leading to a remarkable increase in the population of cancer survivors, now exceeding 15 million in the United States [2]. Consequently, the long-term adverse effects associated with cancer treatment have become increasingly apparent. One of those adverse effects is the accelerated aging and premature frailty induced by cancer treatment [3, 4]. Indeed, after completion of cancer treatment, cancer survivors appear to be 20 years older than their chronological age due to declining body reserves [5]. Additionally, many cancer treatments adversely affect the cardiovascular system and increase the susceptibility of cancer survivors to develop premature cardiovascular complications. Although several mechanisms have been proposed to explain the molecular mechanisms of cancer therapy-induced cardiovascular complications, the role of therapy-induced premature aging in mediating these cardiovascular complications has recently been recognized [3, 6].

Cellular senescence, one of the hallmarks of aging, has been a focus of cancer research over the past decade and was identified as an important mechanism of cell response to cancer treatments [7]. Intriguingly, strong evidence reveals that senescent cardiovascular cells play an important role in the development of multiple cardiovascular diseases (CVDs) as comprehensively reviewed in [8]. In particular, vascular senescence has been identified as a significant contributor to multiple CVDs including atherosclerosis [9], hypertension [10], and stroke [11]. Multiple types of cells are involved in vascular senescence including endothelial cells (ECs) [12], vascular smooth muscle cells [13], and endothelial progenitor cells [14].

This mini-review will focus on cancer treatment-induced endothelial senescence. First, we will discuss how endothelial senescence contributes to numerous cardiovascular health complications. Then, we will summarize and evaluate the in vivo and in vitro studies demonstrating endothelial senescence following cancer treatment and describe the underlying molecular mechanisms. Finally, we will highlight novel senotherapeutic approaches that have the potential to combat therapy-induced endothelial cell senescence and hence protect cancer survivors from cardiovascular complications.

2. Contribution of Senescent Endothelial Cells to Cardiovascular Diseases

Senescence has traditionally been considered a state of irreversible cell cycle arrest, which occurs in response to multiple stressors eventually leading to the loss of the replicative potential [15]. However, recent studies show that senescent cells can re-enter the cell cycle under certain circumstances [16]. Cellular senescence plays physiological roles in embryonic development [17] and wound healing [18]. Additionally, senescence is an important protective mechanism to suppress tumor growth following oncogenic activation [19]. However, accumulating evidence from in vivo and in vitro studies demonstrates that persistence of senescence disrupts homeostasis and contributes to aging [20, 21]. Indeed, cellular senescence is one of the seven hallmarks of aging and contributes to several age-related diseases [22, 23], including Alzheimer’s disease [24], osteoarthritis [25], and cardiovascular aging [26].

Senescent cells demonstrate characteristic alterations in morphology, structure, chromatin remodeling, metabolism, and nuclear alterations [27]. A combination of these alterations is currently used to identify senescence due to the lack of a single specific and sensitive senescence marker. Activation of the p53/p21 and p16/Rb pathways is the major contributor to cell-cycle arrest in senescent cells, thus p21^Cip1 and p16^Ink4a constitute common senescent markers [28]. Alterations in senescent cells include morphological changes, such as flattened and irregular shape, and increased lysosomal activity as evident by positive staining for senescence-associated betagalactosidase (SA-ß-gal) [29]. Of importance, senescent cells express a hallmark secretory phenotype, known as senescence-associated secretory phenotype (SASP) which includes multiple components of inflammatory cytokines, chemokines, growth factors, and extracellular matrix proteins [30]. SASP induces paracrine signaling to trigger senescence in non-senescent neighboring cells also known as the bystander effect of SASP [31]. Excessive accumulation of SASP has deleterious effects by activating a low-grade inflammatory state, called “inflammaging” [32]. Under physiological conditions, SASP influences the surrounding environment by recruiting immune cells such as neutrophils and macrophages to eliminate senescent cells [33]. On the other hand, senescent cells may induce senescence in immune cells (immunosenescence) via SASP, leading to persistent and excessive accumulation of senescent cells [34]. Thus, the ability of the immune system to recognize and eliminate senescent cells is not fully established yet.

The vascular endothelium coats the inner surface of blood vessels and plays an essential role in maintaining vascular tone and homeostasis. A recent screening of different tissues in aged wild-type mice and accelerated aged mice demonstrated that the aorta had the highest expression of the senescence markers p16^Ink4a and p21^Cip1 compared to other tissues [35]. Interestingly, SASP displays dynamic characteristics wherein both the composition and the level of expression of SASP components vary based on cell type, inducers of senescence, and time since senescence induction [27, 36]. A recent comparison of multiple cell subtypes in vitro demonstrates that senescent ECs are associated with elevated SASP expression compared to other cell types [37]. Consequently, senescent ECs play a more important role in chronic inflammation. Considering all this, premature aging of the endothelium is expected to significantly contribute to CVDs in cancer survivors.

Senescent ECs demonstrate alterations in cellular function that can induce endothelial dysfunction and vascular impairment. These alterations include decreased activity of endothelial nitric oxide synthase (eNOS) [38] and diminished production of the vasodilators nitric oxide (NO) [39] and prostacyclin (PGI2) [40]. Senescent ECs also exhibit diminished angiogenic activity [41]. Additionally, SASP produced by senescent ECs contributes to vascular dysfunction and the development of atherosclerosis. Indeed, senescent ECs have been shown to accumulate in the walls of atherosclerotic vessels [42]. The overexpression of SASP markers in senescent ECs activates the immune response that leads to invasion of monocytes into the vessel wall and initiates plaque formation [43]. Additionally, the inflammaging state induced by inflammatory SASP markers, such as IL-1α and TNF-α, together with the chemoattractant factors further increase the risk of plaque formation [44, 45]. A recent study demonstrates that CD9, a membrane protein involved in cell adhesion regulation, is expressed at greater levels in senescent ECs which could also contribute to atherosclerosis [46]. Moreover, senescent ECs express alterations in the microRNAs, which play an important role in the regulation of inflammation, apoptosis, and eNOS production [47]. Interestingly, a recent transcriptomic meta-analysis reports 38 genes with a similar trend of expression in both senescent ECs and coronary artery diseases, suggesting an association between both [48].

3. Cancer Therapy-induced Endothelial Senescence

Therapy-induced senescence is a consequence of exposure to cancer treatment, including chemotherapy and radiation, which causes cells to express senescence phenotype [6]. Importantly, growing evidence implicates that cancer therapy induces senescence in multiple cardiovascular cells and demonstrates an accelerated aging phenotype analogous to chronological aging as comprehensively reviewed in [3].

3.1. Anthracycline-induced Endothelial Senescence

Anthracyclines, including doxorubicin (DOX) and daunorubicin, are commonly used in the treatment of multiple types of cancers. However, anthracyclines are known for their cardiotoxicity that limits their clinical utility. In addition to cardiotoxicity, anthracyclines also induce vascular toxicity, characterized by endothelial dysfunction and vascular aging [49–51]. Interestingly, low doses of DOX have been shown to induce vascular senescence and premature vascular aging rather than apoptosis [52–55], causing endothelial cell dysfunction and dysregulation of the vascular tone. Another landmark study demonstrates that following DOX administration in p16–3MR mice, the majority of cardiac senescent cells were positive for CD31, which is a marker for endothelial cells, and to a lesser extent in fibroblast-like cells [6]. Intriguingly, treatment with DOX did not induce senescence in cardiomyocytes in vivo [6]. Elimination of senescent cells by ganciclovir in DOX-treated p16–3MR mice abrogated DOX-induced cardiac dysfunction [6]. Taken together, this study strongly suggests that senescent endothelial cells are key players in delayed DOX-induced cardiac dysfunction. Additionally, a recent study demonstrates that SASP released from senescent ECs following treatment with DOX stimulates platelet activation, adhesion, and aggregation [56], which can increase the risk of atherothrombotic events.

Multiple mechanisms have been proposed to mediate DOX-induced endothelial senescence. DOX induces DNA damage by promoting DNA double-strand breaks via a topoisomerase-IIβ-dependent mechanism [57], thus activating the DNA damage response (DDR). This DDR activates p53/p21 senescence pathway through ataxia telangiectasia mutated (ATM)-dependent phosphorylation eventually leading to cell cycle arrest and senescence [58]. DDR can also upregulate the p16/pRB pathway which is another important mechanism for senescence [59]. DNA damage also induces PI3K/AKT/mTOR signaling pathway resulting in p53-mediated cellular senescence [60]. The PI3K/AKT/mTOR signaling pathway activates the downstream transcription factor, NF-κB, which is an important regulator of canonical SASP. A previous study showed that DOX-treated ECs produce acute SASP phenotype through PI3K/AKT/mTOR in an NF-κB-independent manner [61]. Notably, the regulation of SASP is multifaceted with the involvement of multiple transcriptions factors and epigenetic mechanisms [62]. Additionally, the activation of AKT downregulates superoxide dismutase-2 (SOD2) via phosphorylation of FOXO transcription factors [63]. This can contribute to DOX-induced oxidative stress, which is another important mechanism mediating DOX-induced endothelial senescence.

Importantly, both the metabolism of DOX and DOX-induced mitochondrial dysfunction contribute to the production of reactive oxygen species (ROS) [64, 65]. Elevated ROS levels are demonstrated in DOX-treated ECs [61]. Higher ROS levels induce p16 signaling pathways through the p38/JNK MAPK pathway [61]. Moreover, DOX upregulates NADPH oxidase isoform 2 (Nox2), which can also contribute to oxidative stress-induced senescence in endothelial progenitor cells [66]. Notably, EC progenitors demonstrated more sensitivity to DOX-induced senescence rather than cell death [67]. Additionally, higher ROS levels activate the NLRP3 inflammasome pathway that has a contributing role in SASP secretion, especially IL-1ß, in endothelial senescence [68]. Interestingly, DOX has been shown recently to upregulate the cardiac expression of the NLRP3 inflammasome pathway in mice [69]. Future studies are needed to investigate the role of inflammasome activation in premature vascular aging following DOX treatment. Silent information regulator 2 homolog 1 (SIRT1) is another transcription factor that has an essential role in regulating senescence and SASP production. DOX downregulates the activity and the expression of SIRT1, which also contributes to mitochondrial dysfunction and DOX-induced endothelial senescence [54]. Telomere shortening is another mechanism that induces senescence. Telomerase plays an important role in preventing telomere shortening during cell division by replacing lost telomeric repeat DNA [70]. Interestingly, DOX decreases telomerase in cardiomyocytes [71–73]. However, the effect of DOX on telomerase in ECs has not been determined yet.

3.2. Radiation-induced Endothelial Senescence

Radiation therapy is another modality that plays a central role in the treatment of many different types of cancer. Around 30% of cancer survivors are treated with radiation and this number is expected to increase in the next years [74]. However, radiation also affects healthy cells and negatively impacts their function. Importantly, most of the adverse effects associated with radiation become apparent a long time after treatment. Therefore, it is important to understand the mechanisms of radiation-induced health complications, particularly cardiovascular ones including atherosclerosis, coronary heart disease, and myocardial fibrosis [75].

Radiation induces senescence in multiple cardiovascular cells including ECs [3]. Since ECs have more proliferative capacity than cardiomyocytes, they are more susceptible to radiation-induced senescence. Multiple mechanisms contribute to radiation-induced senescence. Similar to DOX, radiation causes double-strand DNA breaks and activates DDR, which triggers signaling pathways of senescence [76]. Furthermore, radiation impairs the DNA repair mechanisms within ECs [77]. Indeed, the expression of Ku86, an enzyme associated with DNA repair, is reduced in human umbilical vein endothelial cells (HUVECs) after radiation [78]. Additionally, radiation reduces the expression and activity of telomerase in ECs [79]. All these mechanisms are associated with DNA damage and telomere shortening which recruits protein kinase ATM, Rad3-related protein (ATR), and Chk2, which then activate p53 signaling and increase p16 and p21 that induce the senescent phenotype [76, 80, 81]. Post-translational modifications are associated with irradiated EC. Radiation-induced senescence increases the acetylation of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α) due to reductions in both HDAC1 and SIRT1 expression. This modification renders PGC1α inactive and unable to induce the expression of genes associated with mitochondria function and ROS detoxification, which leads to mitochondrial dysfunction, higher ROS levels, and senescence [82]. Additionally, other studies demonstrate that radiation therapy impairs mitochondrial function to generate superoxides and increase oxidative stress [80, 83, 84]. Another report shows that radiation therapy increases phospholipase A2 activity, which is associated with increased lysophosphatidylcholine and elevated ROS [85].

Receptor-mediated signaling is also affected by radiation therapy. One example is the insulin-like growth factor (IGF) signaling mechanism. Activation of IGFR-1 activates the PI3K/AKT/mTOR signaling pathway resulting in cellular senescence. Importantly, ECs exposed to radiation have an increased expression of IGFR-1 [86]. Additionally, radiation increases the expression of insulin-like growth factor-binding protein 5 (IGFBP-5) [76, 84], which binds to IGF decreasing its bioavailability and blunting signaling through IGFR1. Another example is the differentiation growth factor 15 (GDF15), which is a stress-induced marker that is associated with increased activity of pathways resulting in the survival of the cell. Radiated ECs demonstrate increased expression of GDF15 resulting in elevated ROS levels followed by ERK activation [87]. This increased signaling resulted in the increase of p16 and the induction of senescence [87]. Radiation upregulates the secretion of SASP from senescent ECs via multiple mechanisms. Radiation increases NF-κB signaling by activating NF-κB essential modulator (NEMO) following DDR [88]. The upregulation of NF-κB promotes the secretion of pro-inflammatory cytokine IL-6 [88]. Another study demonstrates that radiation increases c-jun translocation via JAK signaling which induces senescence of ECs and increases the expression of plasminogen activator inhibitor 1 (PAI-1) [89].

Importantly, radiation-induced endothelial senescence affects multiple functions in ECs responsible for the maintenance of normal vascular homeostasis. Exposure of HUVECs to radiation is associated with reduced expression of BH4 and Gch1, which leads to eNOS uncoupling and decreased bioavailability of NO [90]. Another mechanism for the reduction in NO bioavailability can be due to increased ROS production which can chelate and render NO inactive [91]. Moreover, radiation therapy has been associated with an increased expression of the vasoconstrictor, endothelin-1 (ET1), which can act to increase the vascular tone [92]. Exposure to radiation therapy also affects the angiogenic functions of senescent ECs. A number of studies demonstrate that radiation inhibits markers of angiogenesis including decreased tube formation and reduced ability of ECs to proliferate [76, 82, 83]. Radiation has also been shown to decrease VEGF, VEGFR-1, VEGFR-2, and VEGFR-3 all of which are important for the cellular signaling in angiogenesis [79, 93]. In one report, radiation induced the expression of X-linked inhibitor of apoptosis-associated factor (XAF1) mediated by bromodomain 7 transcriptional activity [94]. Increased XAF1 was associated with a p53-dependent mechanism to induce senescence and prevent angiogenesis [94]. Additionally, radiation-induced alteration in endothelial function can promote the development of atherosclerosis. Radiation increases endothelial permeability through increased activation of ADAM10, a metalloprotease that degrades VE-cadherin [95]. The degradation of factors that promote tighter cell-cell binding can potentially allow for the accumulation of lipids and monocytes that are involved in the development of atherosclerosis. Lastly, radiation increases the expression of the adhesion molecules, ICAM, VCAM, and E-selectin in senescent HUVECs [93]; and also upregulates CD44 expression which facilitates the adhesion of monocytes to senescent ECs [96].

4. Senotherapeutics as Promising Strategies Against Cancer Therapy-induced Endothelial Senescence

The past decade has witnessed the advancement of our knowledge about senescence at a staggering speed. This led to the development of multiple novel strategies that target senescence and hence have the potential to mitigate vascular dysfunction and cardiovascular complications associated with cancer treatments. These strategies are called “senotherapeutics” and can be classified into two groups: 1) senolytics which selectively remove senescent cells by promoting apoptosis and 2) senomorphics which alter the intracellular signaling to reduce SASPs and pro-inflammatory environment (Fig. 1) [97].

Fig. 1. Cancer therapy-induced senescence in endothelial cells.

Exposure of the vasculature to cancer treatments including radiation and anthracyclines induces senescence in endothelial cells. Multiple mechanisms contribute to the senescence phenotype in endothelial cells, which demonstrate characteristic alterations. Accumulation of senescent endothelial cells leads to endothelial dysfunction, which contributes to cardiovascular diseases in cancer survivors. Senotherapeutics are novel drugs that target cancer therapy-induced endothelial senescence either by targeting SASP (senomorphics) or by inducing apoptosis in senescent endothelial cells (senolytics). The figure is created with BioRender.com. eNOS, endothelial nitric oxide synthase; ET1, Endothelin-1; NAC, N-acetyl cysteine; NO, Nitric oxide; PAI-1, Plasminogen activator inhibitor-1; PGI2, prostacyclin; SA-β-gal, Senescence associated-βgalactosidase assay; SAHF, Senescence-associated heterochromatin foci; SASP, Senescence-associated secretory phenotype.

Senescent cells resist apoptosis through a variety of anti-apoptotic pathways that can differ with different cell types [36]. By targeting these anti-apoptotic pathways, senolytics selectively induce apoptosis in senescent cells. Notably, senescent HUVECs demonstrated higher expression of anti-apoptotic Bcl-xL [98], making them more sensitive to the effects of senolytics that target this pathway. Indeed, ABT-263 (navitoclax) and two specific Bcl-xL inhibitors, A1331852 and A1155463, are selective in inducing apoptosis in senescent ECs [99, 100]. ABT-263 improves endothelial function in old mice in recent findings [101], which suggests that it has the potential to improve vascular function in cancer survivors. Unfortunately, senolytics cause adverse effects that may limit their clinical utility. For example, ABT-263 may induce apoptosis in normal cells including platelets which leads to thrombocytopenia [102]. Local administration of senolytics can provide an alternative approach to mitigate these side effects. Interestingly, intramyocardial administration of ABT-263 to the hearts of ischemic reperfusion (IR)-injured rats preferentially eliminated senescent cells, decreased the expression of SASP-related genes, and restored impaired cardiac function without demonstrating any systemic toxicity [103]. Formulation of ABT-263 as a prodrug is another strategy to increase its specificity and limit its hematological toxicity [104].

Polyphenols are natural compounds that have an overall good safety profile. Several flavonoids improve endothelial function by improving mitochondrial function, and hence reducing ROS production [105]. Fisetin is a naturally occurring flavone and shares similar senolytic actions to ABT-263. Fisetin selectively targets senescent HUVECs to increase caspase 3/7 activity and trigger apoptosis [99]. However, the effects of fisetin against cancer treatment-induced endothelial dysfunction have not been reported in vivo. Quercetin is another naturally occurring flavonoid with senolytic properties. Quercetin alone or Quercetin and Dasatinib (Q+D) are able to selectively reduce the viability of senescent HUVECs after radiation exposure [98]. Targeting SASP is another strategy to modulate the senescence phenotype, decrease inflammation, and improve vascular function following cancer treatment. A recent study shows that a novel polyphenolic mix, including resveratrol and curcumin, has an anti-SASP effect in DOX-treated HUVECs [53]. Resveratrol itself has anti-aging effects mediated by the activation of SIRT1 [106]. This anti-aging effect of resveratrol is demonstrated in vivo by mitigating vascular aging in aged mice [107]. Interestingly, SIRT1 activation can also block the adhesion of monocytes to the vascular endothelium and can, therefore, protect against vascular inflammation and the development of atherosclerosis [108]. Additionally, SIRT1 activation can trigger the production of NO, which can improve the endothelial function. Considering that resveratrol has been shown to have anticancer properties on its own and to augment the chemotherapeutic benefit of other cancer treatments as reviewed in [109], resveratrol can be a promising option to protect against endothelial aging in cancer survivors and at the same time increase the chemotherapeutic benefits of cancer treatments.

Curcumin is another flavonoid recognized as a senolytic agent [110]. Importantly, curcumin displays cardioprotective effects against ionizing radiation. Curcumin administration in rats reduced pro-inflammatory cytokines, including IL-4 and IL-13, and ROS generating enzymes in whole hearts after exposure to radiation [111]. A curcumin analog, EF24, has senolytic activity against senescent HUVECs through increased proteasomal degradation of the anti-apoptotic BCL-2 proteins expressed by senescent ECs [112]. The same study demonstrates that concomitant use of ABT-263 and EF24 has synergistic senolytic effects, as both utilize different mechanisms of senolysis [112]. Chlorogenic acid, another polyphenol compound, attenuates senescence both in vitro and in vivo in a murine model of angiotensin II-induced vascular senescence [113]. This effect was mediated by activation of SIRT1 and eNOS with involvement of Nuclear factor erythroid 2-factor 2 (Nrf2)/ Heme Oxygenase-1 (HO-1) pathway [113]. To our knowledge, the effects of chlorogenic acid have not been reported in therapy-induced endothelial senescence.

As previously discussed, IGF1-PI3K/AKT/mTOR pathway activation contributes to radiation-induced endothelial senescence [86]. Using specific inhibitors of this pathway, including the PI3K inhibitor LY294002; IGF-1R inhibitor AG1024; and mTOR inhibitor rapamycin, ameliorates senescence of ECs in vitro following radiation [86]. Importantly, rapamycin targets mTOR, which affects SASP regulation, thereby, reducing the secretion of inflammatory cytokines from senescent cells [114]. Interestingly, supplementation of rapamycin in the diet of old mice downregulates the expression of senescence markers in arteries and improves endothelial function [115]. Metformin is a well-established antihyperglycemic drug for the treatment of type II diabetes. Metformin activates AMP-activated protein kinase (AMPK) which is a direct inhibitor of mTOR [116]. Interestingly, metformin has also demonstrated senomorphic properties by regulating the secretion of SASP during senescence [117]. In a previous study, metformin reduced markers of cardiac toxicity in mice after exposure to 5 Gy of ionizing radiation [118]. Metformin improves endothelial function by upregulating the expression of ROS scavengers and decreasing the expression of adhesion molecules and proinflammatory cytokines [118]. Recently, metformin was shown to modulate senescence phenotype and decreased the upregulation of senescence markers in DOX-treated ECs [119]. Vildagliptin, another antidiabetic drug, reduces senescence markers in the aortas of DOX-treated rats in a recent study [55]. This protective effect is mediated through the upregulation of its effector glucagon-like peptide 1(GLP-1) [55]. Antioxidants protect against the oxidative stress induced by cancer therapy and hence can mitigate therapy-induced senescence. Indeed, the antioxidant, N-acetyl cysteine (NAC), ameliorates radiation-induced senescence in microvascular ECs [80]. Vitamin D3 is another natural supplement shown to mitigate DOX-induced endothelial senescence [54]. This protective effect is mediated through increasing the expression of IL-10 via the AMPKα/SIRT1/FOXO3a signaling pathway.

5. Conclusions

Recent years have witnessed intense research to identify the role of cellular senescence as a mechanism of cancer therapy-induced toxicity. The effects of cancer therapy on endothelial senescence is well studied in vitro. However, the complex nature of senescence and its contributing mechanisms may hinder the translation of these findings in vivo and ultimately to humans. Eradication of senescent cells either by senolytic therapy or by genetic approaches has demonstrated protective effects against therapy-induced cardiovascular dysfunction [3, 6]. However, these approaches lead to systemic eradication of senescent cells and they do not reveal which population of senescent cells is most implicated in the cardiovascular detrimental effects of cancer treatments. Therefore, there is a clear need for more sophisticated studies to evaluate to what extent cancer treatments affect the senescence and premature aging of endothelial cells in preclinical animal models as well as in cancer survivors. This can potentially identify novel targets to inhibit therapy-induced senescence with the ultimate goal to mitigate premature aging and the cardiovascular complications of cancer therapy, thus increase the quantity and quality of life in cancer survivors.

Highlights:

• Therapy-induced cardiovascular complications are common among cancer survivors.

• Cancer therapy causes endothelial cell senescence primarily by inducing DNA damage.

• Endothelial cell senescence contributes to several cardiovascular diseases.

• Senotherapeutics may mitigate therapy-induced cardiovascular complications.

Abbreviations

ATM

Ataxia Telangiectasia Mutated

CVDs

Cardiovascular Diseases

DDR

DNA Damage Response

DOX

Doxorubicin

ECs

Endothelial Cells

eNOS

Endothelial Nitric Oxide Synthase

HUVECs

Human Umbilical Vein Endothelial Cells

NO

Nitric Oxide

ROS

Reactive Oxygen Species

SASP

Senescence-associated Secretory Phenotype

SA-β-GAL

Senescence-associated Beta Galactosidase

SIRT1

Silent Information Regulator 2 Homolog 1