Oscillatory shear stress promotes endothelial senescence and atherosclerosis via STING activation

Endothelial dysfunction is an initiating factor in atherosclerosis. Endothelial cells (ECs) are constantly subject to blood flow shear stress, and atherosclerotic plaques tend to occur in aortic bends or bifurcations impaired by low oscillatory shear stress (OSS). However, the mechanism that how OSS affects the initiation and progression of atherosclerosis remains to be explored. Here, we first reported that OSS can promote endothelial dysfunction and atherogenesis in vivo and in vitro by activating STING pathway. Mechanistically, at atherosclerosis-prone areas, OSS caused mitochondria damage in ECs, leading to the leakage of mitochondrial DNA (mtDNA) into the cytoplasm. The cytoplasmic mtDNA was recognized by cGAS to produce cGAMP, activating the STING pathway and leading to endothelial senescence, which resulted in endothelial dysfunction and atherosclerosis. We found that STING was activated in plaques of atherosclerotic patients and in aortic arch ECs of high-fat diet (HFD)-fed ApoeKO mice, as well as in ECs exposed to OSS. STING-specific deficiency in ECs attenuates endothelial senescence and resulted in a significant reduction in aortic arch plaque area in HFD-fed ApoeKO mice. Consistently, specific deficiency or pharmacological inhibition of STING attenuated OSS-induced senescence and endothelial dysfunction. Pharmacological depletion of mtDNA ameliorated OSS-induced senescence and endothelial dysfunction. Taken together, our study linked hemodynamics and endothelial senescence, and revealed a novel mechanism by which OSS leads to endothelial dysfunction. Our study provided new insights into the development of therapeutic strategies for endothelial senescence and atherosclerosis.

Therapeutic efficacies of mitochondria-targeted esculetin and metformin in the improvement of age-associated atherosclerosis via regulating AMPK activation

Atherosclerosis, in general, is an age-associated cardiovascular disease wherein a progressive decline in mitochondrial function due to aging majorly contributes to the disease development. Mitochondria-derived ROS due to dysregulated endothelial cell function accentuates the progression of atherosclerotic plaque formation. To circumvent this, mitochondrially targeted antioxidants are emerging as potential candidates to combat metabolic abnormalities. Recently, we synthesized an alkyl TPP+ tagged esculetin (Mito-Esc), and in the current study, we investigated the therapeutic efficacies of Mito-Esc and metformin, a well-known anti-diabetic drug, in the amelioration of age-associated plaque formation in the aortas of 12 months aged Apoe-/- and 20 months aged C57BL/6 mice, in comparison to young C57BL/6 control mice. Administration of Mito-Esc or metformin significantly reduced age-induced atherosclerotic lesion area, macrophage polarization, vascular inflammation, and senescence. Further, chronic passaging of human aortic endothelial cells (HAEC) with either Mito-Esc or metformin significantly delayed cellular senescence via the activation of the AMPK-SIRT1/SIRT6 axis. Conversely, depletion of either AMPK/SIRT1/SIRT6 caused premature senescence. Consistent with this, Mito-Esc or metformin treatment attenuated NFkB-mediated inflammatory signaling and enhanced ARE-mediated anti-oxidant responses in comparison to late passage control HAECs. Importantly, culturing of HAECs for several passages with either Mito-Esc or metformin significantly improved mitochondrial function. Overall, Mito-Esc and metformin treatments delay age-associated atherosclerosis by regulating vascular senescence via the activation of AMPK-SIRT1/SIRT6 axis.

Mitochondria-targeted esculetin and metformin delay endothelial senescence by promoting fatty acid β-oxidation: Relevance in age-associated atherosclerosis

Impaired mitochondrial fatty acid β-oxidation (FAO) plays a role in the onset of several age-associated diseases, including atherosclerosis. In the current work, we investigated the efficacies of mitochondria-targeted esculetin (Mito-Esc) and metformin in enhancing FAO in human aortic endothelial cells (HAECs), and its relevance in the delay of cellular senescence and age-associated atherosclerotic plaque formation in Apoe-/- mice. Chronic culturing of HAECs with either Mito-Esc or metformin increased oxygen consumption rates (OCR), and caused delay in senescence features. Conversely, etomoxir (CPT1 inhibitor) reversed Mito-Esc- and metformin-induced OCR, and caused premature endothelial senescence. Interestingly, Mito-Esc, unlike metformin, in the presence of etomoxir failed to preserve OCR. Thereby, underscoring Mito-Esc's exclusive reliance on FAO as an energy source. Mechanistically, chronic culturing of HAECs with either Mito-Esc or metformin led to AMPK activation, increased CPT1 activity, and acetyl-CoA levels along with a concomitant reduction in malonyl-CoA levels, and lipid accumulation. Similar results were observed in Apoe-/- mice aorta and liver tissue with a parallel reduction in age-associated atherosclerotic plaque formation and degeneration of liver with either Mito-Esc or metformin administration. Together, Mito-Esc and metformin by potentiating FAO, may have a role in the delay of cellular senescence by modulating mitochondrial function.

γ-Oryzanol ameliorates fine dust-induced premature endothelial senescence and dysfunction via attenuating oxidative stress

Various cardiovascular diseases are associated with endothelial senescence, and a recent study showed that fine dust (FD)-induced premature endothelial senescence and dysfunction is associated with increased oxidative stress. The aim of the present study was to investigate protective effect of rice bran extract (RBE) and its major component of γ-Oryzanol (γ-Ory) against FD-induced premature endothelial senescence. Porcine coronary artery endothelial cells (PCAECs) were treated with FD alone or with RBE or γ-Ory. Senescence-associated β-galactosidase (SA-β-gal) activity, expression of cell cycle regulatory proteins, and oxidative stress levels were evaluated. The results indicated that SA-β-gal activity in the FD-treated PCAECs was attenuated by RBE and γ-Ory. Additionally, γ-Ory inhibited FD-induced cell cycle arrest, restored cell proliferation, and reduced the expression of cell cycle regulatory proteins. γ-Ory also inhibited oxidative stress and prevented senescence-associated NADPH oxidase and LAS activity in FD-exposed ECs suggesting that γ-Ory could protect against FD-induced ECs senescence and dysfunction.

Klotho ameliorates angiotension-II-induced endothelial senescence via restoration of autophagy by inhibiting Wnt3a/GSK-3β/mTOR signaling: A potential mechanism involved in prognostic performance of Klotho in coronary atherosclerotic disease

OBJECTIVE

We aimed to evaluate the prognostic performance of circulating Klotho in coronary atherosclerotic disease (CAD), and to further explore the effect of Klotho on stress-mediated endothelial senescence and underlying mechanism.

METHODS

A cohort of 295 patients had a 12-month follow-up for major adverse cardiovascular events (MACE). Serum Klotho was detected by enzyme linked immunosorbent assay. Cell viability, SA-β-Gal staining, the expression of P53 and P16 were analyzed for endothelial senescence. Oxidative stress was evaluated by measurement of reactive oxygen species, superoxide dismutase and malondialdehyde. LC3, P62, Wnt3a, GSK-3β and mTOR were analyzed by western blotting. Autophagosome formation was detected by adenovirus transfection.

RESULTS

In epidemiological analysis, low Klotho (≤295.9 pg/ml) was significantly associated with MACE risk (HR=2.266, 95 %CI 1.229-4.176). In experimental analysis, Klotho alleviated endothelial senescence and oxidative stress caused by Ang-II exposure; Klotho restored impaired autophagic flux to ameliorate Ang-II induced endothelial senescence; Ang-II activated Wnt3a/GSK-3β/mTOR signaling to inhibit autophagy, whereas Klotho restored autophagy through blockade of Wnt3a/GSK-3β/mTOR signaling; Klotho ameliorated endothelial senescence by suppressing Wnt3a/GSK-3β/mTOR pathway under Ang-II exposure.

CONCLUSIONS

Prognostic significance of Klotho in CAD is potentially ascribed to its anti-endothelial senescence effect via autophagic flux restoration by inhibiting Wnt3a/ GSK-3β/mTOR signaling.

IL-17A promotes endothelial cell senescence by up-regulating the expression of FTO through activating JNK signal pathway

Endothelial aging is a sign of vascular aging that predisposes patients to vascular disease. We explored the effects of IL-17A on endothelial cell aging and determined the potential underlying mechanisms. In human umbilical vein endothelial cells, IL-17A promoted senescence, evidenced as increased positive staining of senescence-associated β-galactosidase, increased proportion of cells arrested at G0/G1 stage, and upregulated p21 and p16 expression. IL-17A increased the expression of the m6A methylase FTO. We then investigated the relationship between FTO and endothelial cell aging. After interfering with FTO expression by siRNA, we observed that FTO induced endothelial cell aging. An increase in the expression of p-Jun N-terminal kinases (JNK) increased after IL-17A treatment indicated, that the JNK signaling pathway affected FTO expression. Moreover, the addition of the JNK signaling pathway inhibitor SP600125 blocked the effect of IL-17A on FTO expression. In conclusion, our findings revealed that IL-17A can promote endothelial cell aging by activating the JNK signaling pathway and upregulating FTO expression. This discovery can help in the identification of new therapeutic targets against endothelial cell aging and related vascular complications.

Capsaicin ameliorates intermittent high glucose-mediated endothelial senescence via the TRPV1/SIRT1 pathway

BACKGROUND

Patients with diabetes have accelerated vascular aging when compared with healthy individuals. Hyperglycemia, especially intermittent high glucose (IHG), is the main cause of vascular endothelial senescence. Capsaicin, a major component of chili pepper is thought to contribute to cardiovascular protection by spicy food.

OBJECTIVE

To investigate the pathway related with the effects of capsaicin on endothelial cell senescence induced by IHG.

METHODS

HUVECs were exposed to IHG (5 mM or 33 mM glucose, alternating every 12 hours for 3 days) and treated with capsaicin at 0.3, 1 and 3 μM. To determine endothelial cell senescence, we examined the senescence-related β-galactosidase staining, cell cycle arrest, cell viability, as well as production of reactive oxygen species (ROS). To evaluate the involvement of TRPV1/[Ca²⁺]i/CaMKII/AMPK/SIRT1 pathway in anti- senescence effects of capsaicin, HUVECs were treated with CAPZ (a TRPV1 antagonist), BAPTA-AM (an intracellular calcium chelator), KN62 (a CaMKII antagonist), compound C (an AMPK inhibitor), or EX527 (a SIRT1 inhibitor). To knockdown TRPV1, HUVECs were transfected with shRNA lentivirus targeting TRPV1. The levels of SIRT1, p21, TRPV1, AMPK and phospho-AMPK were evaluated by western blotting.

RESULTS

IHG suppressed the levels of SIRT1 and enhanced endothelial senescence. Capsaicin upregulated SIRT1 expression and downregulated the senescence marker, p21, thereby protecting endothelial cells from IHG-induced senescence as indicated by relieved G0/G1 phase arrest, improved cell viabilities, and reduced counts of senescent cells and ROS production. Pre-treatment with CAPZ, BAPTA-AM, KN62 or compound C abrogated the anti-senescence effects of capsaicin. Capsaicin restored AMPK phosphorylation and IHG-inhibited TRPV1 expression. Moreover, TRPV1 silencing suppressed SIRT1 expression and abolished the anti-senescence effects of capsaicin.

CONCLUSION

Capsaicin elevates SIRT1 levels through TRPV1/[Ca²⁺]i/CaMKII/AMPK pathway and suppresses IHG-mediated endothelial cell senescence. This study provides initial evidence that capsaicin is a potential candidate for the prevention of vascular aging in diabetes.

RESOLVIN E1 ATTENUATES DOXORUBICIN-INDUCED ENDOTHELIAL SENESCENCE BY MODULATING NLRP3 INFLAMMASOME ACTIVATION

Endothelial cell senescence contributes to chronic inflammation and endothelial dysfunction, while favoring cardiovascular disorders and frailty. Senescent cells acquire a pro-inflammatory secretory phenotype that further propagates inflammation and senescence to neighboring cells. Cell senescence can be provoked by plethora of stressors, including inflammatory molecules and chemotherapeutic drugs. Doxorubicin (Doxo) is a powerful anthracycline anticancer drug whose clinical application is constrained by a dose-limiting cardiovascular toxicity. We here investigated whether cell senescence can contribute to the vascular damage elicited by Doxo. In human umbilical vein endothelial cells (HUVEC) cultures, Doxo (10-100 nM) increased the number of SA-β-gal positive cells and the levels of γH2AX, p21 and p53, used as markers of senescence. Moreover, we identified Doxo-induced senescence to be mediated by the nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome, a key player of the immune innate system capable of releasing interleukin (IL)-1β. In fact, IL-1β itself mimicked the stimulatory action of Doxo on both NLRP3 activation and cellular senescence, while the pharmacological blockade of IL-1 receptors markedly attenuated the pro-senescence effects of Doxo. In search of additional pharmacological strategies to attenuate Doxo-induced endothelial senescence, we identified resolvin E1 (RvE1), an endogenous pro-resolving mediator, as capable of reducing cell senescence induced by both Doxo and IL-1β by interfering with the increased expression of pP65, NLRP3, and pro-IL-1β proteins and with the formation of active NLRP3 inflammasome complexes. Overall, RvE1 and the blockade of the NLRP3 inflammasome-IL-1β axis may offer a novel therapeutic approach against Doxo-induced cardiovascular toxicity and subsequent sequelae.

Exosomes Derived from Senescent Endothelial Cells Contain Distinct Pro-angiogenic miRNAs and Proteins

Exosomes from senescence cells play pivotal roles in endothelium dysfunction. We investigated the exosomal angiogenic cargo of endothelial cells (ECs) in a model of senescence in vitro. After inducing aging by H₂O₂, the expression of P53, P21, and P16 was investigated by western blotting, while the expression of FMR1, miR-21, and miR-126 were measured by real-time PCR (q-PCR). Oil Red O dye was used to stain cells. Acetylcholinesterase (AChE) assay, transmission electron microscopy (TEM), and western blotting characterized Exosomes. Exosomal miR-21, miR-126, matrix metallopeptidase-9 (MMP-9), and tumor necrosis factor- ɑ (TNF-ɑ) proteins were measured by Q-PCR and western blotting. A wound-healing assay was used to explore the effect of exosomes on ECs migration rate. The results showed that the expression of P53, P21, P16, FMR1, and miR-21 was increased in treated cells as compared with control cells (P < 0.05). In addition, the expression of miR-126 was decreased in treated cells (P < 0.05). The number of Oil Red O-positive-treated cells increased (P < 0.05). The AChE activity of exosomes from treated cells was increased (P < 0.05). In comparison with control cells, an increase in the expression levels of exosomal miR-21 and TNF-ɑ of treated cells coincided with a decrease in the expression levels of miR-126 and MMP-9 levels (P < 0.05). We found that the migration rate of ECs co-cultured with exosomes from treated cells was decreased (P < 0.05). The data indicate ECs under H₂O₂ condition produce exosomes with distinct cargo that may be useful as a biomarker of age-related vascular disease.

C1q/TNF-related protein-9 attenuates palmitic acid-induced endothelial cell senescence via increasing autophagy

Autophagy is an important process in the pathogenesis of atherosclerosis. C1q/tumor necrosis factor-related protein 9 (CTRP9) is the closest adiponectin paralog. CTRP9 has anti-aging and anti-atherogenic effects, but its roles in autophagy and endothelial senescence are currently unknown. This study aimed to evaluate whether CTRP9 prevents palmitic acid (PA)-induced endothelial senescence by promoting autophagy. After no treatment or pre-treatment of human umbilical vein endothelial cells with CTRP9 prior to PA treatment, the level of senescence was measured by senescence associated acidic β-galactosidase staining and the level of hyperphosphorylated pRB protein. Autophagy was evaluated by LC3 conversion and the level of p62/SQSTM1, a protein degraded during autophagy. Autophagosome-lysosome fusion was detected by fluorescence microscopy. Pre-treatment with CTRP9 attenuated PA-induced endothelial senescence. CTRP9 increased the conversion of LC3-I to LC3-II and decreased p62 levels in a time- and dose-dependent manner. Although both CTRP9 and PA treatment increased LC3 conversion, treatment with PA increased the expression level of p62 and decreased the fusion of autophagosomes and lysosomes, which represented decreased autophagic flux. However, pre-treatment with CTRP9 recovered the autophagic flux inhibited by PA. AMP-activated kinase (AMPK) activation was involved in LC3 conversion and decreased p62 levels induced by CTRP9. CTRP9 inhibits PA-induced endothelial senescence by recovering autophagy and autophagic flux through AMPK activation.

Endothelial cell senescence: A machine learning-based meta-analysis of transcriptomic studies

Numerous systemic vascular dysfunction that leads to age-related diseases is highly associated with endothelial cell (EC) senescence; thus, identifying consensus features of EC senescence is crucial in understanding the mechanisms and identifying potential therapeutic targets. Here, by utilizing a total of 8 screened studies from different origins of ECs, we have successfully obtained common features in both gene and pathway level via sophisticated machine learning algorithms. A total of 400 differentially expressed genes (DEGs) were newly discovered with meta-analysis when compared to the usage of individual studies. The generated parsimonious model established 36 genes and 57 pathways features with non-zero coefficient, suggesting remarkable association of phosphoglycerate dehydrogenase and serine biosynthesis pathway with endothelial cellular senescence. For the cross-validation process to measure model performance of 36 deduced features, leave-one-study-out cross-validation (LOSOCV) was employed, resulting in an overall area under the receiver operating characteristic (AUROC) of 0.983 (95 % CI, 0.952, 1.000) showing excellent discriminative performance. Moreover, pathway-level analysis was performed by Pathifier algorithm, obtaining a total of 698 pathway deregulation scores from the 10,416 merged genes. In this process, high dimensional data was eventually narrowed down to 57 core pathways with AUROC value of 0.982 (95 % CI, 0.945, 1.000). The robust model with high performance underscores the merit of utilizing sophisticated meta-analysis in finding consensus features of endothelial cell senescence, which may lead to the development of therapeutic targets and advanced understanding of vascular dysfunction pathogenesis with further elucidation.

SIRT3 protects endothelial cells from high glucose-induced senescence and dysfunction via the p53 pathway

Hyperglycemia induces endothelial cells (ECs) dysfunction and vascular complications by accelerating ECs senescence. It also induces downregulation of sirtuins (SIRTs). However, the molecular mechanism involved in the regulation of ECs senescence by SIRT3 remains unclear. Here, we showed that high glucose (HG) decreased the expression level of SIRT3 in human umbilical vein endothelial cells (HUVECs), increased the proportion of cells expressing senescence-associated galactosidase (SA-gal), and HG damaged the cell's ability to form tubule networks on Matrigel. However, transfection with adenoviral construct including SIRT3 significantly inhibited HG-induced SA-gal activity, decreased p53 acetylation level at the site Lys 320 (k320), and overexpression of SIRT3 antagonized high glucose-induced angiogenic dysfunction. Our results suggested a possible molecular mechanism involving HG-SIRT3-p53 in ECs senescence.

Ageing enhances the shedding of splenocyte microvesicles with endothelial pro-senescent effect that is prevented by a short-term intake of omega-3 PUFA EPA:DHA 6:1

BACKGROUND

Ageing is associated with progressive endothelial senescence and dysfunction, and cardiovascular risk. Circulating endothelial microvesicles (MVs) are pro-senescent and pro-inflammatory endothelial effectors in acute coronary syndrome. Omega-3 PUFA intake was claimed beneficial in cardiovascular prevention.

PURPOSE

To investigate whether the intake of the omega-3 formulation EPA:DHA 6:1 by middle-aged and old rats reduces the shedding of pro-senescent microvesicles from cultured spleen leukocytes (SMVs) and clarify the underlying mechanisms in target coronary primary endothelial cells (ECs).

METHODS

Middle-aged male Wistar rats (M, 48-week old) received 500 mg/kg/d of either EPA:DHA 6:1, EPA:DHA 1:1, or vehicle (CTL) for 7 days, old rats (72-week old) for 14 days. Spleen-derived leukocytes were prepared and cultured for 24 h and MVs collected from supernatants (SMVs). Cultured ECs were prepared from freshly isolated porcine coronary arteries. Senescence-associated β-galactosidase activity (SA-β-gal) was assessed by C12FDG, protein expression by Western blot analysis, oxidative stress by dihydroethidium using confocal microscopy, and procoagulant MVs by prothrombinase assay. The pro-senescent potential of SMVs from middle-aged rats (M-SMVs) was analyzed by comparison with young (Y, 12-week) and old (O) rats.

RESULTS

The shedding of SMVs significantly increased with age and was inhibited by EPA:DHA 6:1 intake that also prevented ROS accumulation in spleen. Incubation of ECs with 10 nM SMVs from middle-aged and old but not those from young rats induced premature senescence after 48 h. The pro-senescent effect of M-SMVs was prevented by Losartan and associated with endothelial oxidative stress. M-SMVs induced an up-regulation of senescence markers (p16, p21, p53), pro-atherothrombotic (VCAM-1, ICAM-1, tissue factor) and pro-inflammatory markers (pNF-κB, COX-2) and proteins of the angiotensin system (ACE, AT1-R). Conversely, endothelial NO synthase was down-regulated. Intake of EPA:DHA 1:1 and 6:1 by middle-aged rats decreased SMV shedding by 14% and 24%, respectively. Only EPA:DHA 6:1 intake abolished the M-SMVs-induced endothelial senescence and reduced the pro-senescent action of O-SMVs by 45%. Protection of ECs was not observed in response to SMVs from EPA:DHA 1:1 treated rats.

CONCLUSION

Ingestion of EPA:DHA 6:1 by middle-aged or old rats, respectively abolished or limited both the shedding of SMVs and their pro-senescent, pro-thrombotic and pro-inflammatory effects in ECs, most likely by triggering the local angiotensin system. EPA:DHA 6:1 may help to delay ageing-related endothelial dysfunction.

CO ameliorates endothelial senescence induced by 5-fluorouracil through SIRT1 activation

Endothelial senescence is the main risk factor that contributes to vascular dysfunction and the progression of vascular disease. Carbon monoxide (CO) plays an important role in preventing vascular dysfunction and in maintaining vascular physiology or homeostasis. The application of exogenous CO has been shown to confer protection in several models of cardiovascular injury or disease, including hypertension, atherosclerosis, balloon-catheter injury, and graft rejection. However, the mechanism by which CO prevents endothelial senescence has been largely unexplored. The aim of this study was to evaluate the effects of CO on endothelial senescence and to investigate the possible mechanisms underlying this process. We measured the levels of senescence-associated-β-galactosidase activity, senescence-associated secretory phenotype, reactive oxygen species (ROS) production, and stress granule in human umbilical vein endothelial cells and the WI-38 human diploid fibroblast cell line. We found that 5-fluorouracil (5FU)-induced ROS generation was inhibited by CO-releasing molecules (CORM)-A1 treatment, and endothelial senescence induced by 5FU was attenuated by CORM-A1 treatment. The SIRT1 inhibitor EX527 reversed the inhibitory effect of CO on the 5FU-induced endothelial senescence. Furthermore, SIRT1 deficiency abolished the stress granule formation by CO. Our results suggest that CO alleviates the endothelial senescence induced by 5FU through SIRT1 activation and may hence have therapeutic potential for the treatment of vascular diseases.

Appropriate dose of ethanol exerts anti-senescence and anti-atherosclerosis protective effects by activating ALDH2

Moderate alcohol consumption has been shown to reduce atherosclerosis-associated diseases. As shown in our earlier works, ethanol has a dose-dependent protective effects against endothelial cellular senescence by activating aldehyde dehydrogenase 2 (ALDH2) in vitro. However, whether ethanol administration possesses anti-atherosclerosis properties and whether ALDH2 is involved in the underlying mechanisms are unknown. In the present study, we revealed that the appropriate dose of ethanol reduced atherosclerotic plaque formation, and upregulated ALDH2 expression and activity in ApoE^-/- mice. ALDH2 deficiency blocked the protection of ethanol against atherosclerotic plaque formation by inhibiting endothelium senescence. In contrast, Alda-1, which is a specific enzymatic agonist of ALDH2, enhanced the anti-senescence and anti-atherosclerosis effects of the appropriate dose of ethanol. Furthermore, following ALDH2 knockdown, resveratrol (an anti-aging compound) recovered the beneficial effects of ethanol against endothelial senescence in vitro. Thus, these results suggest that the appropriate dose of ethanol has protective effects against endothelial senescence and atherosclerosis by activating ALDH2.

The senescent status of endothelial cells affects proliferation, inflammatory profile and SOX2 expression in bone marrow-derived mesenchymal stem cells

Human aging is a physiological process characterized by a chronic low-grade inflammation. Senescence may affect endothelial cells, subsequently involved in the most common age-related diseases (ARDs), as well as mesenchymal stem cells (MSCs) with an impairment of their properties in tissues regeneration. Endothelial cells seem to be able to exert a paracrine effect on BM-MSCs through the secretion of pro-inflammatory factors. This work is aimed to evaluate if the senescent status of human umbilical vein endothelial cells (HUVECs) could affect bone marrow derived MSCs (BM-MSCs) proliferative ability and stemness. HUVECs were cultured until the senescence status. Young (passage 3) and senescent HUVECs (passage 13) were indirectly co-cultured with BM-MSCs for 8 days in order to evaluate the effect of their senescence status on proliferative ability and stemness of MSCs. The co-culture of senescent HUVECs with BM-MSCs was associated with a reduced proliferative ability of BM-MSCs, an enforced pro-inflammatory phenotype of BM-MSCs (increased synthesis of proinflammatory cytokines such as IL-6 and TNF-α) and an increased expression of miR-126a-3p, in association with a significant decrease of SOX2, a stemmness- associated gene, targeted by miR-126a-3p. A more general IPA analysis, revealed as miR-126a-3p also modulates the expression of IRS1, IRS2, IL6ST and PIK3R2, all targets that enforce the hypothesis that senescent endothelial cells may reduce the proliferative ability and the stemness phenotype of bone marrow-derived mesenchymal stem cells.

Long-term stimulation of angiotensin II induced endothelial senescence and dysfunction

The role of angiotensin II (Ang II) in hypertension has been clarified, but recent studies show that aging-associated arterial changes and those with hypertension as well as atherosclerosis may have some common pathogenesis. This study aimed to clarify the effects of Ang II on endothelial senescence by establishing a replicative senescence model of human umbilical vein endothelial cells (HUVECs) in vitro. The population-doubling level (PDL) was calculated, PDL5 and PDL25 respectively referred to cells cultured for 2 days and 30 days. Compared with Ang II-treated young PDL5 cells, chronic stimulation of Ang II significantly promoted the senescence-associated β-galactosidase activity and expression of senescence-related genes p16 and p21, slowed down cell growth rate, and decreased expression of longevity-related genes sirtuin1 as well as telomerase activity in senescent PDL25 cells (all P < 0.05). Moreover, expression of pro-inflammatory cytokines and adhesion molecules were up-regulated in Ang II-treated PDL25 cells (all P < 0.05). Ang II-induced senescent progression and inflammation were attenuated by angiotensin receptor blocker valsartan. In young PDL5 cells, Ang II promoted the endothelial viability including cell proliferation, migration, angiogenesis and cell adhesion to monocytes; however, chronic stimulation of Ang II suppressed the cell viability, promoted cell adhesion and apoptosis in senescent PDL25 cells, which could be ameliorated by short-term valsartan, but long-term valsartan had no effects. In addition, Ang II-induced senescent features could be partly recovered if Ang II was stopped at PDL20. These findings suggested that chronic stimulation of Ang II can accelerate the endothelial senescence process which is implicated in aging-related atherosclerosis.

ALDH2 mediates the dose-response protection of chronic ethanol against endothelial senescence through SIRT1/p53 pathway

Aldehyde dehydrogenase 2 (ALDH2) plays essential roles in drinking-associated diseases or effects. As we have previously reported, ALDH2 mediates acute ethanol-induced eNOS activation in vitro. However, whether chronic ethanol treatment has a dose-response endothelial protection, as well as the possible mediating role of ALDH2 involved, is unclear. Here, we show that appropriate dose of ethanol preserved the expression and activity of ALDH2 and eNOS, and alleviated senescence-associated phenotypes in human aortic endothelial cells. Furthermore, ALDH2 deficiency impairs the dose-response protection of ethanol against endothelial senescence by promoting the accumulation of 4-HNE, the formation of 4-HNE-SIRT1 protein adducts and the subsequent decrease in SIRT1-dependent p53 deacetylation. Collectively, our data indicate that ALDH2 mediates the protection of appropriate ethanol by modulating SIRT1/p53-dependent endothelial senescence.

Caveolin1/protein arginine methyltransferase1/sirtuin1 axis as a potential target against endothelial dysfunction

Endothelial dysfunction (ED), an established response to cardiovascular risk factors, is characterized by increased levels of soluble molecules secreted by endothelial cells (EC). Evidence suggest that ED is an independent predictor of cardiac events and that it is associated with a deficiency in production or bioavailability of nitric oxide (NO) and/or an imbalance in the relative contribution of endothelium-derived relaxing and contracting factors. ED can be reversed by treating cardiovascular risk factors, hence, beyond ambiguity, ED contributes to initiation and progression of atherosclerotic disease. Majority of cardiovascular risk factors act by a common pathway, oxidative stress (OS), characterized by an imbalance in bioavailability of NO and reactive oxygen species (ROS). Enhanced ROS, through several mechanisms, alters competence of EC that leads to ED, reducing its potential to maintain homeostasis and resulting in development of cardiovascular disease (CVD). Influential mechanisms that have been implicated in the development of ED include (i) presence of elevated levels of NOS inhibitor, asymmetric dimethylarginine (ADMA) due to augmented enzyme activity of protein arginine methyl transferase-1 (PRMT1); (ii) decrease in NO generation by endothelial nitric oxide synthase (eNOS) uncoupling, or by reaction of NO with free radicals and (iii) impaired post translational modification of protein (PTM) such as eNOS, caveolin-1 (cav1) and sirtuin-1 (SIRT1). However, the inter-related mechanisms that concur to developing ED is yet to be understood. The events that possibly overlay include OS-induced sequestration of SIRT1 to caveolae facilitating cav1-SIRT1 association; potential increase in lysine acetylation of enzymes such as eNOS and PRMT1 leading to enhanced ADMA formation; imbalance in acetylation-methylation ratio (AMR); diminished NO generation and ED. Here we review current literature from research showing interdependent association between cav1-PRMT1-SIRT1 to the outcomes of experimental and clinical research aiming to preserve endothelial function with gene- or pharmaco-therapy.

Vascular Aging: Implications for Cardiovascular Disease and Therapy

The incidence and prevalence of cardiovascular disease is highest among the elderly, in part, due to deleterious effects of advancing age on the heart and blood vessels. Aging, a known cardiovascular risk factor, is progressively associated with structural and functional changes to the vasculature including hemodynamic disturbance due to increased oxidative stress, premature cellular senescence and impairments in synthesis and/or secretion of endothelium-derived vasoactive molecules. These molecular and physiological changes lead to vessel wall stiffening and thickening, as well as other vascular complications that culminate to loss of vascular tone regulation and endothelial function. Intriguingly, the vessel wall, a biochemically active structure composed of collagen, connective tissue, smooth muscle and endothelial cells, is adversely affected by processes involved in premature or normal aging. Notably, the inner most layer of the vessel wall, the endothelium, becomes senescent and dysfunctional with advancing age. As a result, its ability to release vasoactive molecules such as acetylcholine (ACh), prostacyclin (PGI2), endothelium-derived hyperpolarizing factor (EDHF), and nitric oxide (NO) is reduced and the cellular response to these molecules is also impaired. By contrast, the vascular endothelium increases its generation and release of reactive oxygen (ROS) and nitrogen (RNS) species, vasoconstrictors such as endothelin (ET) and angiotensin (AT), and endogenous inhibitors of NO synthases (NOSs) to block NO. This skews the balance of the endothelium in favor of the release of highly tissue reactive and harmful molecules that promote DNA damage, telomere erosion, senescence, as well as stiffened and hardened vessel wall that is prone to the development of hypertension, diabetes, atherosclerosis and other cardiovascular risk factors. This Review discusses the impact of advancing age on cardiovascular health, and highlights the cellular and molecular mechanisms that underlie age-associated vascular changes. In addition, the role of pharmacological interventions in preventing or delaying age-related cardiovascular disease is discussed.

The Redox-sensitive Induction of the Local Angiotensin System Promotes Both Premature and Replicative Endothelial Senescence: Preventive Effect of a Standardized Crataegus Extract

Endothelial senescence, characterized by an irreversible cell cycle arrest, oxidative stress, and downregulation of endothelial nitric oxide synthase (eNOS), has been shown to promote endothelial dysfunction leading to the development of age-related vascular disorders. This study has assessed the possibility that the local angiotensin system promotes endothelial senescence in coronary artery endothelial cells and also the protective effect of the Crataegus extract WS1442, a quantified hawthorn extract. Serial passaging from P1 to P4 (replicative senescence) and treatment of P1 endothelial cells with the eNOS inhibitor L-NAME (premature senescence) promoted acquisition of markers of senescence, enhanced ROS formation, decreased eNOS expression, and upregulation of angiotensin-converting enzyme (ACE) and AT1 receptors. Increased SA-β-gal activity and the upregulation of ACE and AT1R in senescent cells were prevented by antioxidants, an ACE inhibitor, and by an AT1 receptor blocker. WS1442 prevented SA-β-gal activity, the downregulation of eNOS, and oxidative stress in P3 cells. These findings indicate that the impairment of eNOS-derived nitric oxide formation favors a pro-oxidant response triggering the local angiotensin system, which, in turn, promotes endothelial senescence. Such a sequence of events can be effectively inhibited by a standardized polyphenol-rich extract mainly by targeting the oxidative stress.