Vascular Aging and Atherosclerosis: A Perspective on Aging

Vascular aging (VA) is recognized as a pivotal factor in the development and progression of atherosclerosis (AS). Although various epidemiological and clinical research has demonstrated an intimate connection between aging and AS, the candidate mechanisms still require thorough examination. This review adopts an aging-centric perspective to deepen the comprehension of the intricate relationship between biological aging, vascular cell senescence, and AS. Various aging-related physiological factors influence the physical system's reactions, including oxygen radicals, inflammation, lipids, angiotensin II, mechanical forces, glucose levels, and insulin resistance. These factors cause endothelial dysfunction, barrier damage, sclerosis, and inflammation for VA and promote AS via distinct or shared pathways. Furthermore, the increase of senescent cells inside the vascular tissues, caused by genetic damage, dysregulation, secretome changes, and epigenetic modifications, might be the primary cause of VA.

Association of Homocysteine and Risks of Long-Term Cardiovascular Events and All-Cause Death among Older Patients with Obstructive Sleep Apnea: A Prospective Study

OBJECTIVES

This study aimed to assess whether raised baseline plasma tHcy concentrations increased the risks of major adverse cardiovascular events (MACE) and all-cause death outcomes in older patients with obstructive sleep apnea (OSA).

DESIGN

A multicenter, prospective, observational study.

SETTING

Beijing, Shandong Province, Gansu Province of China.

PARTICIPANTS

A total of 1, 290 OSA patients aged 60 to 96 years from sleep centers of six hospitals in China consecutively recruited between January 2015 and October 2017.

MEASUREMENTS

Cox proportional models assessed the association between tHcy and the risk of new-onset all events among Chinese older OSA patients.

RESULTS

The final analysis (60.1% male; median age, 66 years) used data from 1, 100 subjects during a median follow-up of 42 months, a total of 105 (9.5%) patients developed MACE and 42 (3.8%) patients died. Multivariable Cox regression analysis showed higher adjusted hazard ratios (aHRs) of MACE, myocardial infarction (MI), hospitalization for unstable angina, and composite of all events with tHcy levels in the 4th quartile (HR=5.93, 95% CI: 2.79-12.59; HR=4.72, 95% CI:1.36-4.61; HR=4.26, 95% CI:1.62-5.71; HR=4.17, 95% CI:2.23-7.81) and the 3rd quartile (HR=3.79, 95% CI:1.76-8.20; HR=3.65, 95% CI:1.04-2.98; HR=2.75, 95% CI:1.08-3.76; HR=2.51, 95% CI:1.31-4.83) compared to reference tHcy levels in quartile 1, respectively, while the aHRs (95% CIs) of all-cause death showed significantly higher only in the highest tHcy level quartile than in the lowest quartile (HR=3.20, 95% CI=1.16-8.84, P=0.025) with no significant differences in risks of cardiovascular death and hospitalisation for heart failure among groups (P>0.05).

CONCLUSIONS

tHcy, a marker of prognosis for older OSA patients, was significantly associated with the increased risk of MACE and all-cause death in this population independent of BMI, smoking status, and other potential risk factors, but not all clinical components events of MACE. New therapeutic approaches for older patients with OSA should mitigate tHcy-associated risks of MACE, and even all-cause death.

Double-blind, Randomized, Placebo-controlled Trial With N-acetylcysteine for Treatment of Severe Acute Respiratory Syndrome Caused by Coronavirus Disease 2019 (COVID-19)

Background

A local increase in angiotensin 2 after inactivation of angiotensin-converting enzyme 2 by SARS-CoV-2 may induce a redox imbalance in alveolar epithelium cells, causing apoptosis, increased inflammation and, consequently, impaired gas exchange. We hypothesized that N-acetylcysteine (NAC) administration could restore this redox homeostasis and suppress unfavorable evolution in Covid-19 patients.

Objective

To determine whether NAC in high doses can avoid respiratory failure in patients with Covid-19.

Methods

It was a double-blind, randomized, placebo-controlled, unicentric trial, conducted at the Emergency Department of Hospital das Clínicas, São Paulo, Brazil. We enrolled 135 patients with severe Covid-19 (confirmed or suspected), with an oxyhemoglobin saturation of less than 94% or respiratory rate higher than 24 breaths/min. Patients were randomized to receive NAC 21 g (approximately 300 mg/kg) for 20 hours, or dextrose 5%. Primary endpoint was the need for mechanical ventilation. Secondary endpoints were time of mechanical ventilation, admission to ICU, time in ICU, and mortality.

Results

Baseline characteristics were very similar in the two groups, with no significant difference in age, sex, comorbidities, medicines taken, and disease severity. Also, groups were similar in laboratory tests and chest CT scan findings. Sixteen patients (23.9%) in the Placebo group were submitted to endotracheal intubation and mechanical ventilation, compared to 14 patients (20.6%) in the NAC group (p=0.675). No difference was observed in secondary endpoints.

Conclusion

Administration of NAC in high doses did not affect the evolution of severe Covid-19.

Na/K-ATPase/src complex mediates regulation of CD40 in renal parenchyma

Background

Recent studies have highlighted a critical role for CD40 in the pathogenesis of renal injury and fibrosis. However, little is currently understood about the regulation of CD40 in this setting.

Methods

We use novel Na/K-ATPase cell lines and inhibitors in order to demonstrate the regulatory function of Na/K-ATPase with regards to CD40 expression and function. We utilize 5/6 partial nephrectomy as well as direct infusion of a Na/K-ATPase ligand to demonstrate this mechanism exists in vivo.

Results

We demonstrate that knockdown of the α1 isoform of Na/K-ATPase causes a reduction in CD40 while rescue of the α1 but not the α2 isoform restores CD40 expression in renal epithelial cells. Second, because the major functional difference between α1 and α2 is the ability of α1 to form a functional signaling complex with Src, we examined whether the Na/K-ATPase/Src complex is important for CD40 expression. We show that a gain-of-Src binding α2 mutant restores CD40 expression while loss-of-Src binding α1 reduces CD40 expression. Furthermore, loss of a functional Na/K-ATPase/Src complex also disrupts CD40 signaling. Importantly, we show that use of a specific Na/K-ATPase/Src complex antagonist, pNaKtide, can attenuate cardiotonic steroid (CTS)-induced induction of CD40 expression in vitro.

Conclusions

Because the Na/K-ATPase/Src complex is also a key player in the pathogenesis of renal injury and fibrosis, our new findings suggest that Na/K-ATPase and CD40 may comprise a pro-fibrotic feed-forward loop in the kidney and that pharmacological inhibition of this loop may be useful in the treatment of renal fibrosis.

A critical role for both CD40 and VLA5 in angiotensin II-mediated thrombosis and inflammation

Angiotensin II (Ang-II)-induced hypertension is associated with accelerated thrombus formation in arterioles and leukocyte recruitment in venules. The mechanisms that underlie the prothrombotic and proinflammatory responses to chronic Ang-II administration remain poorly understood. We evaluated the role of CD40/CD40 ligand (CD40L) signaling in Ang-II-mediated microvascular responses and assessed whether and how soluble CD40L (sCD40L) contributes to this response. Intravital video microscopy was performed to analyze leukocyte recruitment and dihydrorhodamine-123 oxidation in postcapillary venules. Thrombus formation in cremaster muscle arterioles was induced by using the light/dye endothelial cell injury model. Wild-type (WT), CD40^-/-, and CD40L^-/- mice received Ang-II for 14 d via osmotic minipumps. Some mice were treated with either recombinant sCD40L or the VLA5 (very late antigen 5; α5β1) antagonist, ATN-161. Our results demonstrate that CD40^-/-, CD40L^-/-, and WT mice that were treated with ATN-161 were protected against the thrombotic and inflammatory effects of Ang-II infusion. Infusion of sCD40L into CD40^-/- or CD40L^-/- mice restored the prothrombotic effect of Ang-II infusion. Mice that were treated with ATN-161 and infused with sCD40L were protected against accelerated thrombosis. Collectively, these novel findings suggest that the mechanisms that underlie Ang-II-dependent thrombotic and inflammatory responses link to the signaling of CD40L via both CD40 and VLA5.-Senchenkova, E. Y., Russell, J., Vital, S. A., Yildirim, A., Orr, A. W., Granger, D. N., Gavins, F. N. E. A critical role for both CD40 and VLA5 in angiotensin II-mediated thrombosis and inflammation.

Proteomic investigation of effects of hydroxysafflor yellow A in oxidized low-density lipoprotein-induced endothelial injury

Oxidized low-density lipoprotein (ox-LDL)-induced vascular endothelial damage is a key event in early atherosclerosis. Safflower has been used to treat atherosclerotic heart disease in China for many years, but its molecular basis remains unclear. Hydroxysafflor yellow A (HSYA) is the main active ingredient of aqueous safflower extract. We identified the proteins involved in HSYA activity against ox-LDL-induced endothelial injury using isobaric tags for relative and absolute quantification-coupled two-dimensional liquid chromatography–tandem mass spectrometry. HSYA (1, 5, or 25 μM) alleviated ox-LDL-induced endothelial damage in a dose-dependent manner. We quantitated approximately 2700 protein species, of which 77 were differentially expressed following HSYA treatment. Most protein changes were related to structural molecules, metabolic enzymes, and proteins involved in signal transduction. Several differentially expressed proteins were further validated by western blot analysis. We also analysed the role of the mitochondrial membranous voltage-dependent anion-selective channel protein 2 (VDAC2) in HSYA treatment using small interfering RNA. VDAC2 functioned as a downstream anti-apoptosis effector during HSYA treatment of ox-LDL-induced endothelial impairment. These results further our understanding of the mechanisms responsible for the effects of HSYA.

Oxidative Stress-Mediated Atherosclerosis: Mechanisms and Therapies

Atherogenesis, the formation of atherosclerotic plaques, is a complex process that involves several mechanisms, including endothelial dysfunction, neovascularization, vascular proliferation, apoptosis, matrix degradation, inflammation, and thrombosis. The pathogenesis and progression of atherosclerosis are explained differently by different scholars. One of the most common theories is the destruction of well-balanced homeostatic mechanisms, which incurs the oxidative stress. And oxidative stress is widely regarded as the redox status realized when an imbalance exists between antioxidant capability and activity species including reactive oxygen (ROS), nitrogen (RNS) and halogen species, non-radical as well as free radical species. This occurrence results in cell injury due to direct oxidation of cellular protein, lipid, and DNA or via cell death signaling pathways responsible for accelerating atherogenesis. This paper discusses inflammation, mitochondria, autophagy, apoptosis, and epigenetics as they induce oxidative stress in atherosclerosis, as well as various treatments for antioxidative stress that may prevent atherosclerosis.

Oxidative stress and reactive oxygen species in endothelial dysfunction associated with cardiovascular and metabolic diseases

Reactive oxygen species (ROS) are reactive intermediates of molecular oxygen that act as important second messengers within the cells; however, an imbalance between generation of reactive ROS and antioxidant defense systems represents the primary cause of endothelial dysfunction, leading to vascular damage in both metabolic and atherosclerotic diseases. Endothelial activation is the first alteration observed, and is characterized by an abnormal pro-inflammatory and pro-thrombotic phenotype of the endothelial cells lining the lumen of blood vessels. This ultimately leads to reduced nitric oxide (NO) bioavailability, impairment of the vascular tone and other endothelial phenotypic changes collectively termed endothelial dysfunction(s). This review will focus on the main mechanisms involved in the onset of endothelial dysfunction, with particular focus on inflammation and aberrant ROS production and on their relationship with classical and non-classical cardiovascular risk factors, such as hypertension, metabolic disorders, and aging. Furthermore, new mediators of vascular damage, such as microRNAs, will be discussed. Understanding mechanisms underlying the development of endothelial dysfunction is an important base of knowledge to prevent vascular damage in metabolic and cardiovascular diseases.

Preventive and therapeutic moderate aerobic exercise programs convert atherosclerotic plaques into a more stable phenotype

The mechanisms by which exercise affects atherosclerotic plaque stability remain incompletely understood. We evaluated the effects of two training protocols on both atherosclerotic plaque structure and the signaling pathways involved in plaque rupture.

METHODS

Male low-density lipoprotein (LDL) receptor knockout mice were fed a high-fat, high-cholesterol diet (HFD). One group was subjected to moderate exercise using a treadmill for 14weeks (preventive protocol). The other group started an exercise regimen after 16weeks of the HFD (therapeutic group). Atherosclerotic plaques within the aorta were evaluated for lipid and collagen contents, as well as for inflammatory markers. Plasma cholesterol and cytokine levels were also determined.

RESULTS

The mice receiving a HFD developed hypercholesterolemia and atherosclerotic plaques within the aorta. The aortas from the animals in the preventive protocol exhibited smaller lipid cores and higher collagen content. These animals also exhibited lower CD40 expression within the plaques. The aortas of the mice in the therapeutic group exhibited higher collagen content, but no differences in either lipid core size or plaque size were noted. No differences in blood pressure, plasma cholesterol, cytokine levels, plaque size or metalloproteinase 9 expression were observed in the trained animals compared with the sedentary animals.

CONCLUSION

Moderate aerobic exercise modified atherosclerotic plaque characteristics and converted the plaques into a more stable phenotype, increasing the collagen content in response to both exercise programs. Furthermore, moderate aerobic exercise reduced the animals' fat content and decreased the activity of the CD40-CD40L signaling pathway in the preventive group.

Immunological cell type characterization and Th1-Th17 cytokine production in a mouse model of Gaucher disease

Gaucher disease is a lysosomal storage disease resulting from insufficient acid β-glucosidase (glucocerebrosidase, GCase, EC 4.2.1.25) activity and the resultant accumulation of glucosylceramide. Macrophage (Mϕ) lineage cells are thought to be the major disease effectors because of their secretion of numerous cytokines and chemokines that influence other poorly defined immunological cell populations. Increases in several such populations were identified in a Gba1 mouse model (D409V/null; 9V/null) of Gaucher disease including antigen presenting cells (APCs), i.e., Mϕ, dendritic cells (DCs), neutrophils (PMNs), and CD4(+) T cells. FACS analyses showed increases in these cell types in 9V/null liver, spleen lung, and bone marrow. T-cells or APCs enhanced activations were evident by positivity of CD40L, CD69, as well as CD40, CD80, CD86, and MHCII on the respective cells. Mϕ, and, unexpectedly, DCs, PMNs, and T cells, from 9V/null mice showed excess glucosylceramides as potential bases for activation of APCs and T cells to induce Th1 (IFNγ, IL12, TNFα,) and Th17 (IL17A/F) cytokine production. These data imply that excess glucosylceramides in these cells are pivotal for activation of APCs and T cell induction of Th1 and Th17 responses and PMN recruitment in multiple organs of this model of Gaucher disease.

CD40 ligand: a neo-inflammatory molecule in vascular diseases

CD40 Ligand (CD40L), a member of the TNF family, was initially thought to be solely implicated in thymus-dependent humoral responses. However, work by several groups showed that CD40L plays a more global role in various systems. Recent evidence has outlined an important role for CD40L in the physiopathology of the vascular system. Indeed, by interacting with its principal receptor, CD40, or with the recently identified receptors, namely αIIbβ3, α5β1, and Mac-1 integrins, CD40L displayed many biological functions in different types of vascular cells. In addition, the CD40L system was demonstrated a major player in the pathology of vascular diseases, such as atherosclerosis and restenosis. This review outlines the expression pattern and the functional properties of CD40L and its receptors at different cellular levels in the vascular system. In addition, we thoroughly describe evidence showing the implication of CD40L interactions in atherosclerosis, restenosis, and their associated clinical complications.

PPARγ expression is increased in systemic lupus erythematosus patients and represses CD40/CD40L signaling pathway

Systemic lupus erythematosus (SLE) is a heterogeneous disease involving several immune cell types and pro-inflammatory signals, including the one triggered by binding of CD40L to the receptor CD40. Peroxisome-proliferator activated receptor gamma (PPARγ) is a transcription factor with anti-inflammatory properties. Here we investigated whether CD40 and PPARγ could exert opposite effects in the immune response and the possible implications for SLE. Increased PPARγ mRNA levels were detected by real-time PCR in patients with active SLE, compared to patients with inactive SLE PPARγ/GAPDH mRNA = 2.21 ± 0.49 vs. 0.57 ± 0.14, respectively (p < 0.05) or patients with infectious diseases and healthy subjects (p < 0.05). This finding was independent of the corticosteroid therapy. We further explored these observations in human THP1 and in SLE patient-derived macrophages, where activation of CD40 by CD40L promoted augmented PPARγ gene transcription compared to non-stimulated cells (PPARγ/GAPDH mRNA = 1.14 ± 0.38 vs. 0.14 ± 0.01, respectively; p < 0.05). This phenomenon occurred specifically upon CD40 activation, since lipopolysaccharide treatment did not induce a similar response. In addition, increased activity of PPARγ was also detected after CD40 activation, since higher PPARγ-dependent transcription of CD36 transcription was observed. Furthermore, CD40L-stimulated transcription of CD80 gene was elevated in cells treated with PPARγ-specific small interfering RNA (small interfering RNA, siRNA) compared to cells treated with CD40L alone (CD80/GAPDH mRNA = 0.11 ± 0.04 vs. 0.05 ± 0.02, respectively; p < 0.05), suggesting a regulatory role for PPARγ on the CD40/CD40L pathway. Altogether, our findings outline a novel mechanism through which PPARγ regulates the inflammatory signal initiated by activation of CD40, with important implications for the understanding of immunological mechanisms underlying SLE and the development of new treatment strategies.

Angiotensin II upregulates the expression of placental growth factor in human vascular endothelial cells and smooth muscle cells

Background

Atherosclerosis is now recognized as a chronic inflammatory disease. Angiotensin II (Ang II) is a critical factor in inflammatory responses, which promotes the pathogenesis of atherosclerosis. Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family cytokines and is associated with inflammatory progress of atherosclerosis. However, the potential link between PlGF and Ang II has not been investigated. In the current study, whether Ang II could regulate PlGF expression, and the effect of PlGF on cell proliferation, was investigated in human vascular endothelial cells (VECs) and smooth muscle cells (VSMCs).

Results

In growth-arrested human VECs and VSMCs, Ang II induced PlGF mRNA expression after 4 hour treatment, and peaked at 24 hours. 10^-6 mol/L Ang II increased PlGF protein production after 8 hour treatment, and peaked at 24 hours. Stimulation with Ang II also induced mRNA expression of VEGF receptor-1 and -2(VEGFR-1 and -2) in these cells. The Ang II type I receptor (AT₁R) antagonist blocked Ang II-induced PlGF gene expression and protein production. Several intracellular signals elicited by Ang II were involved in PlGF synthesis, including activation of protein kinase C, extracellular signal-regulated kinase 1/2 (ERK1/2) and PI3-kinase. A neutralizing antibody against PlGF partially inhibited the Ang II-induced proliferation of VECs and VSMCs. However, this antibody showed little effect on the basal proliferation in these cells, whereas blocking antibody of VEGF could suppress both basal and Ang II-induced proliferation in VECs and VSMCs.

Conclusion

Our results showed for the first time that Ang II could induce the gene expression and protein production of PlGF in VECs and VSMCs, which might play an important role in the pathogenesis of vascular inflammation and atherosclerosis.