Redox balance in the aged endothelium

Renoprotective Effect of a Dipeptidyl Peptidase-4 Inhibitor on Aging Mice

Dipeptidyl peptidase 4 (DPP-4) inhibitors exert pleiotropic effects beyond glycemic control. We investigated the renoprotective effects of DPP-4 inhibitors on aging mice mediated by the renin-angiotensin system (RAS). C57BL/6 mice were divided into three groups: the two-month-old mice (YM group), the eighteen-month-old mice (AM group) and the eighteen-month-old, linagliptin-treated mice (AM + LIN group). Renal function was improved, based on serum creatinine and cystatin-C levels (p < 0.05 compared with the AM group for both parameters). Fibrotic areas and the levels of proteins related to fibrosis improved in the AM + LIN group (p < 0.001 compared with the AM group for all parameters). In the AM + LIN group, the DPP-4-positive area and activity and expressions of DPP-4 were decreased (p < 0.05 compared with the AM group for all parameters). The levels of proteins related to the RAS, including prorenin receptor, angiotensin-converting enzyme, angiotensin II and angiotensin 1 receptor, were decreased in the AM + LIN group (p < 0.05, p < 0.01, p < 0.05, and p < 0.01 compared with the AM group, respectively). NADPH oxidase 2 and NADPH oxidase 4 levels decreased in the AM + LIN group (p < 0.001 compared with the AM group for both proteins), whereas the levels of endothelial nitric oxide synthase (eNOS) phosphorylated at serine¹¹⁷⁷ and superoxide dismutase 1 were increased (p < 0.01 compared with the AM group for both proteins). DPP-4 inhibitors may exert renoprotective effects via prorenin receptor/angiotensin-converting enzyme/angiotensin II/angiotensin 1 receptor axis.

Stimulation of KLF14/PLK1 pathway by thrombin signaling potentiates endothelial dysfunction in Type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) promotes a high oxidative stress and hypercoagulable state that drives microvascular injury and multiple-organ abnormality. Elevated thrombin activity underlies T2DM-linked endothelial dysfunction, but the mechanistic links between T2DM/oxidative stress axis and thrombin-associated endothelial pathologies are incompletely understood. In this work, immunohistochemical studies and quantitative analysis using isolated endothelial cells (ECs) identified accumulated Kru¨ppel-like family of transcription factor 14 (KLF14) deposits in ECs from multiple organs as distinct features of T2DM mice. KLF14 upregulation in ECs, which was stimulated by thrombin treatment, was dependent on multiple pathways including calcium mobilization, activation of PKC and AMPK pathways. Functionally, inhibition of endogenous KLF14 expression significantly attenuated thrombin-induced endotheliocyte proliferation, endothelial cell migration and oxidative stress. Molecularly, by directly binding the promoter, KLF14 functions as a transcriptional activator of PLK1, a polo-like kinase whose overexpression induced excessive reactive oxygen species (ROS) production. Transient knockdown of PLK1 was sufficient to suppress KLF14 overexpression-potentiated endothelial dysfunction. Collectively, these data provide proof of concept that deregulation of KLF14/PLK1 cascade plays a key role in thrombin-induced endothelial dysfunction and targeting KLF14 or PLK1 may limit thrombin-associated pathologies in T2DM patients.

The protective effect of resveratrol on vascular aging by modulation of the renin-angiotensin system

BACKGROUND AND AIMS

This study evaluated the effects of resveratrol on arterial aging and the renin-angiotensin system (RAS) in mice and vascular smooth muscle cells (VSMCs).

METHODS

Aging mice were divided into control and resveratrol groups. Histological changes, inflammation, oxidative stress, RAS components, and the expression of AMP-activated protein kinase (AMPK), silent information regulator T1 (SIRT1), peroxisome proliferator-activated receptor-γ co-activator 1α (PGC-1α), and anti-oxidative enzymes was measured in thoracic aortas of 24-month-old mice. The effect of resveratrol on fibrosis, cell senescence, and RAS components was also investigated in VSMCs stimulated by angiotensin (Ang) II.

RESULTS

Aorta media thickness, inflammation, fibrosis, and oxidative stress were significantly lower in the resveratrol group than in the control group. Resveratrol treatment decreased serum Ang II level and the aortic expression of prorenin receptor (PRR) and angiotensin converting enzyme (ACE), and increased serum Ang-(1-7) level and the expression of ACE2, Ang II type 2 receptor (AT2R), and Mas receptor (MasR). Resveratrol increased the expression of phosphorylated AMPK, SIRT1, PGC-1α, phosphorylated endothelial nitric oxide synthase and superoxide dismutase 1 and 2, and decreased that of NADPH oxidase 2 and 4. In Ang II-stimulated VSMCs, resveratrol treatment markedly decreased the number of senescence associated β-galactosidase stained cells and pro-fibrotic protein expression and increased the expression of AT2R and MasR.

CONCLUSIONS

Resveratrol protects against arterial aging and this effect is associated with reduced activity of the PRR-ACE-Ang II axis and stimulation of the ACE2-Ang-(1-7)-ATR2-MasR axis.

The Antioxidant Machinery of Young and Senescent Human Umbilical Vein Endothelial Cells and Their Microvesicles

We examine the antioxidant role of young and senescent human umbilical vein endothelial cells (HUVECs) and their microvesicles (MVs). Proteomic and Western blot studies have shown young HUVECs to have a complete and well-developed antioxidant system. Their MVs also contain antioxidant molecules, though of a smaller and more specific range, specialized in the degradation of hydrogen peroxide and the superoxide anion via the thioredoxin-peroxiredoxin system. Senescence was shown to be associated with a large increase in the size of the antioxidant machinery in both HUVECs and their MVs. These responses might help HUVECs and their MVs deal with the more oxidising conditions found in older cells. Functional analysis confirmed the antioxidant machinery of the MVs to be active and to increase in size with senescence. No glutathione or nonpeptide antioxidant (ascorbic acid and vitamin E) activity was detected in the MVs. Endothelial cells and MVs seem to adapt to higher ROS concentrations in senescence by increasing their antioxidant machinery, although this is not enough to recover completely from the senescence-induced ROS increase. Moreover, MVs could be involved in the regulation of the blood plasma redox status by functioning as ROS scavengers.

FELLOW EYE CHANGES IN PATIENTS WITH NONISCHEMIC CENTRAL RETINAL VEIN OCCLUSION: Assessment of Perfused Foveal Microvascular Density and Identification of Nonperfused Capillaries

PURPOSE

Eyes fellow to nonischemic central retinal vein occlusion (CRVO) were examined for abnormalities, which might explain their increased risk for future occlusion, using adaptive optics scanning light ophthalmoscope fluorescein angiography.

METHODS

Adaptive optics scanning light ophthalmoscope fluorescein angiography foveal microvascular densities were calculated. Nonperfused capillaries adjacent to the foveal avascular zone were identified. Spectral domain optical coherence tomography, ultrawide field fluorescein angiographies, and microperimetry were also performed.

RESULTS

Ten fellow eyes of nine nonischemic CRVO and 1 nonischemic hemi-CRVO subjects and four affected eyes of three nonischemic CRVO and one nonischemic hemi-CRVO subjects were imaged. Ninety percent of fellow eyes and 100% of affected eyes demonstrated at least 1 nonperfused capillary compared with 31% of healthy eyes. Fellow eye microvascular density (35 ± 3.6 mm(-1)) was significantly higher than that of affected eyes (25 ± 5.2 mm(-1)) and significantly lower than that of healthy eyes (42 ± 4.2 mm(-1)). Compared with healthy controls, spectral domain optical coherence tomography thicknesses showed no significant difference, whereas microperimetry and 2/9 ultrawide field fluorescein angiography revealed abnormalities in fellow eyes.

CONCLUSION

Fellow eye changes detectable on adaptive optics scanning light ophthalmoscope fluorescein angiography reflect subclinical pathology difficult to detect using conventional imaging technologies. These changes may help elucidate the pathogenesis of nonischemic CRVO and help identify eyes at increased risk of future occlusion.

Age-Associated Changes in the Vascular Renin-Angiotensin System in Mice

Background. This study evaluated whether the change in the renin-angiotensin system (RAS) is associated with arterial aging in mice. Methods. Histologic changes and expressions of transforming growth factor-β (TGF-β), collagen IV, fibronectin, angiotensin II (Ang II), angiotensin-converting enzyme (ACE), angiotensin-converting enzyme 2 (ACE2), angiotensin II type 1 receptor (AT1R), angiotensin II type 2 receptor (AT2R), prorenin receptor (PRR), Mas receptor (MasR), endothelial nitric oxide synthase (eNOS), NADPH oxidase 2 and oxidase 4 (Nox2 and Nox4), 8-hydroxy-2′-deoxyguanosine (8-OHdG), 3-nitrotyrosine, and superoxide dismutase 1 and dismutase 2 (SOD1 and SOD2) were measured in the thoracic aortas from 2-month-old, 12-month-old, and 24-month-old C57/BL6 mice. Results. Twenty-four-month-old mice showed significantly increased aortic media thickness and expressions of TGF-β, collagen IV, and fibronectin, compared to 2-month-old and 12-month-old mice. The expressions of PRR, ACE, and Ang II, and AT1R-positive area significantly increased, whereas expressions of ACE2 and MasR and AT2R-positive area decreased with age. The expressions of phosphorylated serine¹¹⁷⁷-eNOS, SOD1, and SOD2 decreased, and the 8-OHdG-positive area and the 3-nitrotyrosine-positive area increased with age. The expression of Nox2 significantly increased with age, but that of Nox4 did not change. Conclusions. The enhanced PRR-ACE-Ang II-AT1R axis and reduced ACE2-MasR axis were associated with arterial aging in mice.

Aging-related changes in oxidative stress response of human endothelial cells

BACKGROUND

Oxidative stress is strongly associated with aging and age-related diseases and plays a crucial role in endothelial dysfunction development.

AIM

To better understand the molecular mechanisms of aging and stress response in humans, we examined changes to young and older human endothelial cells over time (72, 96 and 120 h), before and after H2O2-induced stress.

METHODS

We measured the expression of the deacetylase Sirtuin 1 (Sirt1) and its transcriptional target Forkhead box O3a (Foxo3a); TBARS, a well-known marker of overall oxidative stress, and catalase activity as index of antioxidation. Moreover, we quantified levels of cellular senescence by senescence-associated β galactosidase (SA-βgal) assay.

RESULTS

Under oxidative stress induction older cells showed a progressive decrease of Sirt1 and Foxo3a expression, persistently high TBARS levels with high, but ineffective Cat activity to counteract such levels. In addition cellular senescence drastically increased in older cells compared with Young cells both in presence and in the absence of oxidative stress.

DISCUSSION

By following the cell behavior during the time course, we can hypothesize that while in young cells an oxidative stress induction stimulated an adequate response through activation of molecular factor crucial to counteract oxidative stress, the older cells are not able to adequately adapt themselves to external stress stimuli.

CONCLUSIONS

During their life, endothelial cells impair the ability to defend themselves from oxidative stress stimuli. This dysfunction involves the pathway of Sirt1 a critical regulator of oxidative stress response and cellular lifespan, underlining its crucial role in endothelial homeostasis control during aging and age-associated diseases.

Molecular pathways of arterial aging

The incidence of stroke and myocardial infarction increases in aged patients and it is associated with an adverse outcome. Considering the aging population and the increasing incidence of cardiovascular disease, the prediction for population well-being and health economics is daunting. Accordingly, there is an unmet need to focus on fundamental processes underlying vascular aging. A better understanding of the pathways leading to arterial aging may contribute to design mechanism-based therapeutic approaches to prevent or attenuate features of vascular senescence. In the present review, we discuss advances in the pathophysiology of age-related vascular dysfunction including nitric oxide signalling, dysregulation of oxidant/inflammatory genes, epigenetic modifications and mechanisms of vascular calcification as well as insights into vascular repair. Such an overview highlights attractive molecular targets for the prevention of age-driven vascular disease.