Implications of autophagy for vascular smooth muscle cell function and plasticity

From defense to dysfunction: Autophagy's dual role in disease pathophysiology

Autophagy is a fundamental pillar of cellular resilience, indispensable for maintaining cellular health and vitality. It coordinates the meticulous breakdown of cytoplasmic macromolecules as a guardian of cell metabolism, genomic integrity, and survival. In the complex play of biological warfare, autophagy emerges as a firm defender, bravely confronting various pathogenic, infectious, and cancerous adversaries. Nevertheless, its role transcends mere defense, wielding both protective and harmful effects in the complex landscape of disease pathogenesis. From the onslaught of infectious outbreaks to the devious progression of chronic lifestyle disorders, autophagy emerges as a central protagonist, convolutedly shaping the trajectory of cellular health and disease progression. In this article, we embark on a journey into the complicated web of molecular and immunological mechanisms that govern autophagy's profound influence over disease. Our focus sharpens on dissecting the impact of various autophagy-associated proteins on the kaleidoscope of immune responses, spanning the spectrum from infectious outbreaks to chronic lifestyle ailments. Through this voyage of discovery, we unveil the vast potential of autophagy as a therapeutic linchpin, offering tantalizing prospects for targeted interventions and innovative treatment modalities that promise to transform the landscape of disease management.

MG-132 activates sodium palmitate-induced autophagy in human vascular smooth muscle cells and inhibits senescence via the PI3K/AKT/mTOR axis

OBJECTIVE

This study aimed to reveal the role and mechanism of MG-132 in delaying hyperlipidemia-induced senescence of vascular smooth muscle cells (VSMCs).

METHODS

Immunohistochemistry and hematoxylin-eosin staining confirmed the therapeutic effect of MG-132 on arterial senescence in vivo and its possible mechanism. Subsequently, VSMCs were treated with sodium palmitate (PA), an activator (Recilisib) or an inhibitor (Pictilisib) to activate or inhibit PI3K, and CCK-8 and EdU staining, wound healing assays, Transwell cell migration assays, autophagy staining assays, reactive oxygen species assays, senescence-associated β-galactosidase staining, and Western blotting were performed to determine the molecular mechanism by which MG-132 inhibits VSMC senescence. Validation of the interaction between MG-132 and PI3K using molecular docking.

RESULTS

Increased expression of p-PI3K, a key protein of the autophagy regulatory system, and decreased expression of the autophagy-associated proteins Beclin 1 and ULK1 were observed in the aortas of C57BL/6J mice fed a high-fat diet (HFD), and autophagy was inhibited in aortic smooth muscle. MG-132 inhibits atherosclerosis by activating autophagy in VSMCs to counteract PA-induced cell proliferation, migration, oxidative stress, and senescence, thereby inhibiting VSMC senescence in the aorta. This process is achieved through the PI3K/AKT/mTOR signaling pathway.

CONCLUSION

MG-132 activates autophagy by inhibiting the PI3K/AKT/mTOR pathway, thereby inhibiting palmitate-induced proliferation, migration, and oxidative stress in vascular smooth muscle cells and suppressing their senescence.

Elucidating the crosstalk between endothelial-to-mesenchymal transition (EndoMT) and endothelial autophagy in the pathogenesis of atherosclerosis

Atherosclerosis, a chronic systemic inflammatory condition, is implicated in most cardiovascular ischemic events. The pathophysiology of atherosclerosis involves various cell types and associated processes, including endothelial cell activation, monocyte recruitment, smooth muscle cell migration, involvement of macrophages and foam cells, and instability of the extracellular matrix. The process of endothelial-to-mesenchymal transition (EndoMT) has recently emerged as a pivotal process in mediating vascular inflammation associated with atherosclerosis. This transition occurs gradually, with a significant portion of endothelial cells adopting an intermediate state, characterized by a partial loss of endothelial-specific gene expression and the acquisition of "mesenchymal" traits. Consequently, this shift disrupts endothelial cell junctions, increases vascular permeability, and exacerbates inflammation, creating a self-perpetuating cycle that drives atherosclerotic progression. While endothelial cell dysfunction initiates the development of atherosclerosis, autophagy, a cellular catabolic process designed to safeguard cells by recycling intracellular molecules, is believed to exert a significant role in plaque development. Identifying the pathological mechanisms and molecular mediators of EndoMT underpinning endothelial autophagy, may be of clinical relevance. Here, we offer new insights into the underlying biology of atherosclerosis and present potential molecular mechanisms of atherosclerotic resistance and highlight potential therapeutic targets.

Traditional Chinese medicine and its active substances reduce vascular injury in diabetes via regulating autophagic activity

Due to its high prevalence, poor prognosis, and heavy burden on healthcare costs, diabetic vascular complications have become a significant public health issue. Currently, the molecular and pathophysiological mechanisms underlying diabetes-induced vascular complications remain incompletely understood. Autophagy, a highly conserved process of lysosomal degradation, maintains intracellular homeostasis and energy balance via removing protein aggregates, damaged organelles, and exogenous pathogens. Increasing evidence suggests that dysregulated autophagy may contribute to vascular abnormalities in various types of blood vessels, including both microvessels and large vessels, under diabetic conditions. Traditional Chinese medicine (TCM) possesses the characteristics of "multiple components, multiple targets and multiple pathways," and its safety has been demonstrated, particularly with minimal toxicity in liver and kidney. Thus, TCM has gained increasing attention from researchers. Moreover, recent studies have indicated that Chinese herbal medicine and its active compounds can improve vascular damage in diabetes by regulating autophagy. Based on this background, this review summarizes the classification, occurrence process, and related molecular mechanisms of autophagy, with a focus on discussing the role of autophagy in diabetic vascular damage and the protective effects of TCM and its active compounds through the regulation of autophagy in diabetes. Moreover, we systematically elucidate the autophagic mechanisms by which TCM formulations, individual herbal extracts, and active compounds regulate diabetic vascular damage, thereby providing new candidate drugs for clinical treatment of vascular complications in diabetes. Therefore, further exploration of TCM and its active compounds with autophagy-regulating effects holds significant research value for achieving targeted therapeutic approaches for diabetic vascular complications.

Effect of reactive oxygen, nitrogen, and sulfur species on signaling pathways in atherosclerosis

Atherosclerosis is a chronic inflammatory disease in which fats, lipids, cholesterol, calcium, proliferating smooth muscle cells, and immune cells accumulate in the intima of the large arteries, forming atherosclerotic plaques. A complex interplay of various vascular and immune cells takes place during the initiation and progression of atherosclerosis. Multiple reports indicate that tight control of reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) production is critical for maintaining vascular health. Unrestricted ROS and RNS generation may lead to activation of various inflammatory signaling pathways, facilitating atherosclerosis. Given these deleterious consequences, it is important to understand how ROS and RNS affect the signaling processes involved in atherogenesis. Conversely, RSS appears to exhibit an atheroprotective potential and can alleviate the deleterious effects of ROS and RNS. Herein, we review the literature describing the effects of ROS, RNS, and RSS on vascular smooth muscle cells, endothelial cells, and macrophages and focus on how changes in their production affect the initiation and progression of atherosclerosis. This review also discusses the contribution of ROS, RNS, and RSS in mediating various post-translational modifications, such as oxidation, nitrosylation, and sulfation, of the molecules involved in inflammatory signaling.

The Key Role of Liraglutide in Preventing Autophagy of Vascular Smooth Muscle Cells in High Glucose Conditions

Background

The glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide (LIRA) is a potential hypoglycemic drug with anti-atherosclerosis (AS) effects. Autophagy in the vascular smooth muscle cells (VSMCs) facilitates AS. However, the role of autophagy in the anti-AS mechanism of LIRA remains unclear.

Aims

To examine the role and mechanisms of autophagy in LIRA’s improvement of the biological characteristics of VSMCs in high glucose conditions.

Study Design

Experimental animal study.

Methods

VSMCs isolated from the thoracic aorta of male SD rats were subjected to a high glucose (HG) condition (25 mM) in Dulbecco’s Modified Eagle’s Medium with or without LIRA, the GLP-1 receptor antagonist exendin9-39 (Exe9-39), a phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002), and autophagy inhibitors (3-methyladenine [3-MA] and bafilomycin A1 [Baf A1]). Acridine orange staining, western blotting, transmission electron microscopy, and mCherry-GFP-LC3 transfection were performed to evaluate the autophagy flux. Additionally, VSMC migration, calcification, proliferation, and apoptosis in HG conditions were observed.

Results

Addition of LIRA alone or in combination with autophagy inhibitors significantly downregulated Beclin, increased the LC3-II/LC3-I ratio, and upregulated p62 in VSMCs in HG conditions. Furthermore, autophagolysosome formation was markedly curbed after treatment with LIRA and/or autophagy inhibitors. Inhibition of autophagy by LIRA and/or the autophagy inhibitors attenuated VSMC phenotype conversion, proliferation, migration, and calcification and promoted VSMC apoptosis in HG conditions. This protective role of LIRA was augmented by LY294002, but inhibited by Exe9-39.

Conclusion

LIRA plays a significant role in the improvement of the biological features of VSMCs in HG conditions.

Nanogels with covalently bound and releasable trehalose for autophagy stimulation in atherosclerosis

Atherosclerosis, cholesterol-driven plaque formation in arteries, is a complex multicellular disease which is a leading cause of vascular diseases. During the progression of atherosclerosis, the autophagic function is impaired, resulting in lipid accumulation-mediated foam cell formation. The stimulation of autophagy is crucial for the recovery of cellular recycling process. One of the potential autophagy inducers is trehalose, a naturally occurring non-reducing disaccharide. However, trehalose has poor bioavailability due to its hydrophilic nature which results in poor penetration through cell membranes. To enhance its bioavailability, we developed trehalose-releasing nanogels (TNG) for the treatment of atherosclerosis. The nanogels were fabricated through copolymerization of 6-O-acryloyl-trehalose with the selected acrylamide-type monomers affording a high trehalose conjugation (~ 58%, w/w). TNG showed a relatively small hydrodynamic diameter (dH, 67 nm) and a uniform spherical shape and were characterized by negative ζ potential (-18 mV). Thanks to the trehalose-rich content, TNG demonstrated excellent colloidal stability in biological media containing serum and were non-hemolytic to red blood cells. In vitro study confirmed that TNG could stimulate autophagy in foam cells and enhance lipid efflux and in vivo study in ApoE-/- mice indicated a significant reduction in atherosclerotic plaques, while increasing autophagic markers. In conclusion, TNG hold great promise as a trehalose delivery system to restore impaired autophagy-mediated lipid efflux in atherosclerosis and subsequently reduce atherosclerotic plaques.

Association between intracerebral hemorrhage and cholesterol levels, and molecular mechanism underlying low cholesterol inhibiting autophagy in cerebral arterial smooth muscle cells leading to cell necrosis

BACKGROUND

An association between cholesterol and intracerebral hemorrhage (ICH) has been reported, but the mechanism is unclear.

METHODS

In this cross-sectional study, participants aged 50-75 years were selected using multistage stratified cluster sampling. All samples completed a questionnaire (age, gender, medication, etc.) and were examined (blood lipid, height, blood pressure, etc.) for risk factors. Multivariable logistic regression was used to analyze the association between cholesterol levels and ICH risk, after adjusting for age, smoking, hypertension, and other factors. We cultured rat cerebral artery smooth muscle cells at different cholesterol concentrations. The autophagy pathway was identified by transcriptome sequencing. The results were then validated using real-time polymerase chain reaction and western blot.

RESULTS

We included 39,595 patients, among whom 286 had ICH. The study showed that a low level of low-density lipoprotein cholesterol (LDL-C) was a risk factor of ICH (odds ratio 2.912, 95% confidence interval 1.460-5.806; P = 0.002). Cell experiments showed that lower cholesterol levels could significantly induce rat cerebral artery smooth muscle cell necrosis. In low-cholesterol groups, expression of the autophagy marker LC3 protein was significantly decreased and p62 protein was significantly increased. In western blot and comparison with the control group, the low cholesterol PI3K/Akt/mTOR signaling pathway was significantly activated in the autophagy pathway, resulting in its inhibition, which in turn led to smooth muscle cell death.

CONCLUSION

Low cholesterol levels may inhibit autophagy through PI3K/Akt/mTOR signaling and induce arterial smooth muscle cell necrosis, thereby increasing the risk of ICH.

LncRNA RASSF8-AS1 knockdown displayed antiproliferative and proapoptotic effects through miR-188-3p/ATG7 pathway in ox-LDL-treated vascular smooth muscle cells

BACKGROUND

Long noncoding RNA (lncRNA)-mediated changes in gene expression contribute to atherosclerosis (AS) development. However, the roles of numerous lncRNAs in AS have not been fully elucidated. Here, we aimed to investigate the potential role of lncRNA RASSF8-AS1 (RASSF8-AS1) in autophagy of human aortic vascular smooth muscle cells (HA-VSMCs).

METHODS

RASSF8-AS1 expression in patients with AS was extracted from the Gene Expression Omnibus (GEO) database. RASSF8-AS1 and microRNA-188-3p (miR-188-3p) expression was analyzed in 20 enrolled patients with AS. HA-VSMCs were treated with oxidized low-density lipoprotein (ox-LDL) (25, 50, 75, and 100 µg/mL) for 24 h. Loss- or gain-of-function of RASSF8-AS1, miR-1883p, and autophagy-related 7 (ATG7) was studied using the transfected HA-VSMCs. Cell viability was assessed using Cell Counting Kit-8 (CCK-8). Apoptosis was detected with annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI). Relative luciferase reporter assay was used to confirm the targeting relationship of miR-188-3p to RASSF8-AS1 or ATG7. Gene expression was detected by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot.

RESULTS

RASSF8-AS1 was enriched in the serum of patients with AS and ox-LDL-treated HA-VSMCs. Ox-LDL induced proliferation and autophagy while inhibiting the apoptosis of HA-VSMCs, which was abated by RASSF8-AS1 knockdown. RASSF8-AS1 downregulated miR-188-3p of ox-LDL-treated HA-VSMCs. RASSF8-AS1 knockdown caused an increase in miR-188-3p, which inhibited proliferation and autophagy and induced the apoptosis of ox-LDL-treated HA-VSMCs. miR-188-3p inhibited ATG7 expression in ox-LDL-treated HA-VSMCs. RASSF8-AS1 elevated ATG7 and induced autophagy through sponging miR-188-3p in ox-LDL-treated HA-VSMCs.

CONCLUSIONS

RASSF8-AS1 regulated autophagy by targeting miR-188-3p, a messenger RNA-binding miRNA that increases ATG7 level, which may be a new target molecule for the prevention and prognosis of AS.

Methyltransferase-like 3 suppresses phenotypic switching of vascular smooth muscle cells by activating autophagosome formation

Prevention of neointima formation is the key to improving long-term outcomes after stenting or coronary artery bypass grafting. RNA N⁶ -methyladenosine (m⁶ A) methylation has been reported to be involved in the development of various cardiovascular diseases, but whether it has a regulatory effect on neointima formation is unknown. Herein, we revealed that methyltransferase-like 3 (METTL3), the major methyltransferase of m⁶ A methylation, was downregulated during vascular smooth muscle cell (VSMC) proliferation and neointima formation. Knockdown of METTL3 facilitated, while overexpression of METTL3 suppressed the proliferation of human aortic smooth muscle cells (HASMCs) by arresting HASMCs at G2/M checkpoint and the phosphorylation of CDC2 (p-CDC2) was inactivated by METTL3. On the other hand, the migration and synthetic phenotype of HASMCs were enhanced by METTL3 knockdown, but inhibited by METTL3 overexpression. The protein levels of matrix metalloproteinase 2 (MMP2), MMP7 and MMP9 were reduced, while the expression level of tissue inhibitor of metalloproteinase 3 was increased in HASMCs with METTL3 overexpression. Moreover, METTL3 promoted the autophagosome formation by upregulating the expression of ATG5 (autophagy-related 5) and ATG7. Knockdown of either ATG5 or ATG7 largely reversed the regulatory effects of METTL3 overexpression on phenotypic switching of HASMCs, as evidenced by increased proliferation and migration, and predisposed to synthetic phenotype. These results indicate that METTL3 inhibits the phenotypic switching of VSMCs by positively regulating ATG5-mediated and ATG7-mediated autophagosome formation. Thus, enhancing the level of RNA m⁶ A or the formation of autophagosomes is the promising strategy to delay neointima formation.

Autophagy in Atherosclerotic Plaque Cells: Targeting NLRP3 Inflammasome for Self-Rescue

Atherosclerosis (AS) is a lipid-driven disorder of the artery intima characterized by the equilibrium between inflammatory and regressive processes. A protein complex called NLRP3 inflammasome is involved in the release of mature interleukin-1β (IL-1β), which is connected to the initiation and progression of atherosclerosis. Autophagy, which includes macroautophagy, chaperone-mediated autophagy (CMA), and microautophagy, is generally recognized as the process by which cells transfer their constituents to lysosomes for digestion. Recent studies have suggested a connection between vascular inflammation and autophagy. This review summarizes the most recent studies and the underlying mechanisms associated with different autophagic pathways and NLRP3 inflammasomes in vascular inflammation, aiming to provide additional evidence for atherosclerosis research.

Iron corroded granules inhibiting vascular smooth muscle cell proliferation

In-stent restenosis after interventional therapy remains a severe clinical complication. Current evidence indicates that neointimal hyperplasia induced by vascular smooth muscle cell (VSMC) proliferation is a major cause of restenosis. Thus, inhibiting VSMC proliferation is critical for preventing in-stent restenosis. The incidence of restenosis was reduced in nitrided iron-based stents (hereafter referred to as iron stents). We hypothesized that the corroded granules produced by the iron stent would prevent in-stent restenosis by inhibiting VSMC proliferation. To verify this hypothesis, we introduced a dynamic circulation device to analyze the components of corroded granules. To investigate the effects of corroded granules on VSMC proliferation, we implanted the corroded iron stent into the artery of the atherosclerotic artery stenosis model. Moreover, we explored the mechanism underlying the inhibition of VSMC proliferation by iron corroded granules. The results indicated that iron stent produced the corroded granules after implantation, and the main component of the corrosion granules was iron oxide. Remarkably, the corroded granules reduced the neointimal hyperplasia in an atherosclerotic artery stenosis model, and iron corroded granules decreased the neointimal hyperplasia by inhibiting VSMC proliferation. In addition, we revealed that corroded granules reduced VSMC proliferation by activating autophagy through the AMPK/mTOR signaling pathway. Importantly, safety of iron corroded granules was evaluated and proved to be satisfactory hemocompatibility in rabbit model. Overall, the role of corroded granules in restenosis prevention was described for the first time. This finding highlighted the implication of corroded granules produced by iron stent in inhibiting VSMC proliferation, pointing to a new direction to prevent in-stent restenosis.

CD137-CD137L Aggravates Calcification of Vascular Smooth Muscle Cell and Vasculature of ApoE-/- Mice Via Rab7-Mediated Autophagy

Vascular calcification is an independent risk factor for acute cardiovascular events and a predictor of adverse prognosis; the abnormal fusion and degradation of autophagosomes and lysosomes are closely related to the calcification of VSMC and aortic AS plaque in ApoE-/- mice. Rab7 is a member of the Ras protein family and acts as a molecular switch in the fusion between autophagosomes and lysosomes. In this study, we found that the activation of the CD137-CD137L signal promoted calcification by inhibiting the expression and activity of Rab7, which regulates the degradation of autophagic cargo in vascular smooth muscle cells (VSMCs) and aortic atherosclerosis (AS) plaques in ApoE-/- mice. Knockdown of Rab7 impaired its tethering with the downstream molecule FYVE and coiled-coil containing 1 (FYCO1), which transports autophagosomes to lysosomes through microtubule motor kinesins and fuses with lysosomes to degrade the autophagic content. Overexpression of Rab7-alleviated calcification caused by the activation of the CD137 signaling pathway. In addition, FYCO1 knockdown promoted calcification even though the expression and activity of Rab7 were normal. Our results suggest that Rab7 is the target of CD137 signaling; Rab7 cannot interact with its downstream molecule FYCO1 when its activity and expression were inhibited by the activation of CD137 signaling pathway, thus inhibiting the autophagic degradation and promoting calcification.

Targeting autophagy in atherosclerosis: Advances and therapeutic potential of natural bioactive compounds from herbal medicines and natural products

Atherosclerosis (AS) is the most common causes of cardiovascular disease characterized by the formation of atherosclerotic plaques in the arterial wall, and it has become a dominant public health problem that seriously threaten people worldwide. Autophagy is a cellular self-catabolism process, which is critical to protect cellular homeostasis against harmful conditions. Emerging evidence suggest that dysregulated autophagy is involved in the development of AS. Therefore, pharmacological interventions have been developed to inhibit the AS via autophagy induction. Among various AS treating methods, herbal medicines and natural products have been applied as effective complementary and alternative medicines to ameliorate AS and its associated cardiovascular disease. Recently, mounting evidence revealed that natural bioactive compounds from herbs and natural products could induce autophagy to suppress the occurrence and development of AS, by promoting cholesterol efflux, reducing plaque inflammation, and inhibiting apoptosis or senescence. In the present review, we highlight recent findings regarding possible effects and molecular mechanism of natural compounds in autophagy-targeted mitigation of atherosclerosis, aiming to provide new potential therapeutic strategies for the atherosclerosis treatment preclinically and clinically.

Cellular senescence and abdominal aortic aneurysm: From pathogenesis to therapeutics

As China’s population enters the aging stage, the threat of abdominal aortic aneurysm (AAA) mainly in elderly patients is becoming more and more serious. It is of great clinical significance to study the pathogenesis of AAA and explore potential therapeutic targets. The purpose of this paper is to analyze the pathogenesis of AAA from the perspective of cellular senescence: on the basis of clear evidence of cellular senescence in aneurysm wall, we actively elucidate specific molecular and regulatory pathways, and to explore the targeted drugs related to senescence and senescent cells eliminate measures, eventually improve the health of patients with AAA and prolong the life of human beings.

Dexlansoprazole prevents pulmonary artery hypertension by inhibiting pulmonary artery smooth muscle cell to fibroblast transition

OBJECTIVES

To validate that dexlansoprazole, an anti-acid drug, can prevent pulmonary artery hypertension (PAH) in preclinical animal models and find the possible mechanism of action of dexlansoprazole for this new indication.

METHODS

The efficacy of dexlansoprazole to attenuate PAH in vivo was evaluated in PAH animal models. Plasma guanosine 3', 5'-cyclic phosphate (cGMP) in PAH rats was measured by enzyme linked immunosorbent assay (ELISA). To investigate the anti-PAH effect of dexlansoprazole in vitro, proliferation and migration assays of primary cultured pulmonary artery smooth muscle cells (PASMCs) were performed. Furthermore, dexlansoprazole's function on fibroblast transition of vascular smooth muscle cells (VSMC) was explored by single cell ribonucleic acid (RNA) sequencing and RNAscope.

RESULTS

Dexlansoprazole could attenuate the pathologic process in monocrotaline (MCT)-, hypoxia-induced PAH rats and SU5416/hypoxia (SuHy)-induced PAH mice. The intervention with dexlansoprazole significantly inhibited elevated right ventricular systolic pressure (RVSP), right ventricular hypertrophy, and pulmonary vascular wall thickness. Furthermore, plasma cGMP in MCT-induced PAH rats was restored after receiving dexlansoprazole. In vitro, dexlansoprazole could inhibit PASMCs' proliferation and migration stimulated by platelet derived growth factor-BB (PDGF-BB). Moreover, dexlansoprazole significantly ameliorated pulmonary vascular remodeling by inhibiting VSMC phenotypic transition to fibroblast-like cells in a VSMC-specific multispectral lineage-tracing mouse.

CONCLUSIONS

Dexlansoprazole can prevent PAH through promoting cGMP generation and inhibiting pulmonary vascular remodeling through restraining PASMCs' proliferation, migration, and phenotypic transition to fibroblast-like cells. Consequently, PAH might be a new indication for dexlansoprazole.

New insight into dyslipidemia‐induced cellular senescence in atherosclerosis

Atherosclerosis, characterized by lipid‐rich plaques in the arterial wall, is an age‐related disorder and a leading cause of mortality worldwide. However, the specific mechanisms remain complex. Recently, emerging evidence has demonstrated that senescence of various types of cells, such as endothelial cells (ECs), vascular smooth muscle cells (VSMCs), macrophages, endothelial progenitor cells (EPCs), and adipose‐derived mesenchymal stem cells (AMSCs) contributes to atherosclerosis. Cellular senescence and atherosclerosis share various causative stimuli, in which dyslipidemia has attracted much attention. Dyslipidemia, mainly referred to elevated plasma levels of atherogenic lipids or lipoproteins, or functional impairment of anti‐atherogenic lipids or lipoproteins, plays a pivotal role both in cellular senescence and atherosclerosis. In this review, we summarize the current evidence for dyslipidemia‐induced cellular senescence during atherosclerosis, with a focus on low‐density lipoprotein (LDL) and its modifications, hydrolysate of triglyceride‐rich lipoproteins (TRLs), and high‐density lipoprotein (HDL), respectively. Furthermore, we describe the underlying mechanisms linking dyslipidemia‐induced cellular senescence and atherosclerosis. Finally, we discuss the senescence‐related therapeutic strategies for atherosclerosis, with special attention given to the anti‐atherosclerotic effects of promising geroprotectors as well as anti‐senescence effects of current lipid‐lowering drugs.

Vitamin D receptor deficiency increases systolic blood pressure by upregulating the renin‑angiotensin system and autophagy

The vitamin D receptor (VDR) may regulate blood pressure via multiple pathways. The present study investigated the underlying mechanism by which VDR deficiency increases blood pressure. A total of 16 8-week-old male littermate mice were randomly divided into the VDR knockout and wild-type groups (VDR^-/- and VDR^+/+, respectively). Blood pressure was measured using a four-channel PowerLab data acquisition and ADI software analysis system. After euthanasia, vascular smooth muscle cells (VSMCs) were isolated from the VDR^-/- and VDR^+/+ mice. Oxidative stress, renin-angiotensin system (RAS) activation and autophagy markers were measured in the isolated VSMCs using reverse transcription-quantitative PCR (RT-qPCR), western blotting and transmission electron microscopy (TEM) assays. Mean systolic pressure was significantly higher in the VDR^-/- mice compared with the VDR^+/+ mice. RT-qPCR and western blotting analyses indicated that RAS markers (angiotensin II and II type 1 receptor) were significantly upregulated, oxidative stress was increased (evidenced by reduced superoxide dismutase and peroxiredoxin-4) and autophagy was activated (upregulation of autophagy related protein 7, Beclin 1 and microtubule-associated proteins 1A/1B light chain 3A) in the VDR^-/- VSMCs compared with the VDR^+/+ VSMCs. TEM demonstrated that there were more autophagy bodies in the VDR^-/- VSMCs compared with the VDR^+/+ VSMCs. In conclusion, VDR deficiency was associated with high blood pressure. The mechanism underlying the increase in blood pressure caused by VDR deficiency may involve activation of the RAS, as well as increased oxidative stress and autophagy of VSMCs.

Autophagy, Pyroptosis, and Ferroptosis: New Regulatory Mechanisms for Atherosclerosis

Atherosclerosis is a chronic inflammatory disorder characterized by the gradual buildup of plaques within the vessel wall of middle-sized and large arteries. The occurrence and development of atherosclerosis and the rupture of plaques are related to the injury of vascular cells, including endothelial cells, smooth muscle cells, and macrophages. Autophagy is a subcellular process that plays an important role in the degradation of proteins and damaged organelles, and the autophagy disorder of vascular cells is closely related to atherosclerosis. Pyroptosis is a proinflammatory form of regulated cell death, while ferroptosis is a form of regulated nonapoptotic cell death involving overwhelming iron-dependent lipid peroxidation. Both of them exhibit distinct features from apoptosis, necrosis, and autophagy in morphology, biochemistry, and genetics. However, a growing body of evidence suggests that pyroptosis and ferroptosis interact with autophagy and participate in the development of cancers, degenerative brain diseases and cardiovascular diseases. This review updated the current understanding of autophagy, pyroptosis, and ferroptosis, finding potential links and their effects on atherogenesis and plaque stability, thus providing ways to develop new pharmacological strategies to address atherosclerosis and stabilize vulnerable, ruptured plaques.

SP1-mediated transcriptional activation of PTTG1 regulates the migration and phenotypic switching of aortic vascular smooth muscle cells in aortic dissection through MAPK signaling

Pituitary tumor-transforming gene 1 (PTTG1) has been found to be associated with the process of cell proliferation and invasion, and is highly expressed in aortic dissection (AD). However, its potential role and underlying mechanism in AD remain uncertain. This study aims at elucidating the roles of specificity protein 1 (SP1) and PTTG1 in the migration and phenotypic switching of aortic vascular smooth muscle cells (VSMCs) in AD. Aortic samples were collected from 35 patients with AD for examination of PTTG1 expression in the tissues by qPCR, western blot and immunofluorescence. Human aortic vascular smooth muscle cells (HAVSMCs) were stimulated with platelet-derived growth factor-BB (PDGF-BB) to establish the cellular model of AD. PTTG1 expression in VSMCs was also examined by qPCR and western blot. Cell viability was detected by CCK-8, cell proliferation by EdU staining and cell migration by wound healing and transwell. Western blot was then performed to assay migration-related proteins. After interference with PTTG1, the levels of smooth muscle pthenotypic switch markers smooth muscle protein 22 alpha (SM22-α) and osteopontin (OPN) were detected by qPCR, western blot and immunofluorescence. The binding of SP1 and PTTG1 was verified with dual-luciferase reporter assay and chromatin immunoprecipitation assay (ChIP). PTTG1 overexpression was found in AD patients. Interference with PTTG1 attenuated the proliferation and migration of PDGF-BB-stimulated HAVSMCs, in addition to their switching from contractile phenotype to synthetic phenotype. Transcription factor SP1 was up-regulated in PDGF-BB-stimulated HAVSMCs, combined with PTTG1 promoter sequence and regulated PTTG1 expression, whose overexpression reversed the effects of PTTG1 interference on cell proliferation, migration and phenotypic switching. SP1 transcriptional activation of PTTG1 activated MAPK/ERK signaling pathway. In conclusion, SP1 transcriptional activation of PTTG1 regulates the migration and phenotypic transformation of HAVSMCs in AD by MAPK Signaling.

β-Hydroxybutyric Inhibits Vascular Calcification via Autophagy Enhancement in Models Induced by High Phosphate

Background: Vascular calcification (VC) is a landmark of aging, while β-hydroxybutyric acid (BHB) induced by calorie restriction has been identified as a promising factor to extend the lifespan. However, the effect of BHB on VC and the potential mechanism remain unknown. Methods: A total of 160 subjects with or without metabolic abnormalities (MAs) were assigned to four groups according to different calcification severities. The association between BHB, MAs, and VC was investigated via mediation analysis. Then, with high phosphate-induced calcification models, the effect of BHB on arterial ring calcification and osteogenic phenotypic differentiation of vascular smooth muscle cells (VSMCs) was investigated. Hereafter the expressions of autophagy biomarkers, autophagy flux, and effects of autophagy inhibitors on VC were detected. Results: Severe VC was observed in the elderly, accompanied with a higher proportion of hypertension, chronic kidney disease, and lower estimated glomerular filtration rate. The serum BHB level was an independent influencing factor of VC severities. With mediation analysis, BHB was determined as a significant mediator in the effects of MAs on VC, and the indirect effect of BHB accounted for 23% of the total effect. Furthermore, BHB directly inhibited arterial ring calcification and osteogenic phenotypic differentiation in VSMCs, accompanied with autophagy enhancement in VSMCs. In accordance, the inhibition of autophagy counteracted the protective effect of BHB on VC. Conclusion: The present study demonstrated that BHB mediated the effects of MAs on VC; then, it further elucidated that BHB could inhibit arterial and VSMC calcification via autophagy enhancement.

Self-eating and Heart: The Emerging Roles of Autophagy in Calcific Aortic Valve Disease

Autophagy is a self-degradative pathway by which subcellular elements are broken down intracellularly to maintain cellular homeostasis. Cardiac autophagy commonly decreases with aging and is accompanied by the accumulation of misfolded proteins and dysfunctional organelles, which are undesirable to the cell. Reduction of autophagy over time leads to aging-related cardiac dysfunction and is inversely related to longevity. However, despite the increasing interest in autophagy in cardiac diseases and aging, the process remains an undervalued and disregarded object in calcific valvular disease. Neither the nature through which autophagy is triggered nor the interplay between autophagic machinery and targeted molecules during aortic valve calcification are fully understood. Recently, the upregulation of autophagy has been shown to result in cardioprotective effects against cell death as well as its origin. Here, we review the evidence that shows how autophagy can be both beneficial and detrimental as it pertains to aortic valve calcification in the heart.

Aberrant Mitochondrial Dynamics: An Emerging Pathogenic Driver of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is defined as a progressive segmental dilation of the abdominal aorta and is associated with high mortality. The characterized features of AAA indicate several underlying mechanisms of AAA formation and progression, including reactive oxygen species production, inflammation, and atherosclerosis. Mitochondrial functions are critical for determining cell fate, and mitochondrial dynamics, especially selective mitochondrial autophagy, which is termed as mitophagy, has emerged as an important player in the pathogenesis of several cardiovascular diseases. The PARKIN/PARIS/PGC1α pathway is associated with AAA formation and has been proposed to play a role in mitochondrial dynamics mediated by the PINK/PARKIN pathway in the pathogenesis underlying AAA. This review is aimed at deepening our understanding of AAA formation and progression, which is vital for the development of potential medical therapies for AAA.

Deletion of Ulk1 inhibits neointima formation by enhancing KAT2A/GCN5-mediated acetylation of TUBA/α-tubulin in vivo

ULK1 (unc-51 like autophagy activating kinase) has a central role in initiating macroautophagy/autophagy, a process that contributes to atherosclerosis and neointima hyperplasia, or excessive tissue growth that leads to vessel dysfunction. However, the role of ULK1 in neointima formation remains unclear. We aimed to determine how Ulk1 deletion affected neointima formation and to investigate the underlying mechanisms. We measured autophagy activity, vascular smooth muscle cell (VSMC) migration and neointima hyperplasia in cultured VSMCs and ligation-injured mouse carotid arteries from male wild-type (WT, C57BL/6 J) and VSMC-specific ulk1 knockout (ulk1 KO) mice. Carotid artery ligation in WT mice increased ULK1 protein expression, and concurrently increased autophagic flux and neointima formation. Treating human aortic smooth muscle cells (HASMCs) with PDGF (platelet derived growth factor) increased ULK1 expression, activated autophagy, and promoted cell migration. Further, smooth muscle cell-specific deletion of Ulk1 suppressed autophagy, inhibited VSMC migration, and impeded neointima hyperplasia. Mechanistically, Ulk1 deletion inhibited autophagic degradation of histone acetyltransferase protein KAT2A/GCN5 (K[lysine] acetyltransferase 2A), resulting in accumulation of KAT2A that directly acetylated TUBA/α-tubulin and subsequently increased protein levels of acetylated TUBA. The acetylation of TUBA increased microtubule stability and inhibited VSMC directional migration and neointima formation. Finally, local transfection of Kat2a siRNA decreased TUBA acetylation and prevented the attenuation of vascular injury-induced neointima formation in ulk1 KO mice. These findings suggest that Ulk1 deletion inhibits neointima formation by reducing autophagic degradation of KAT2A and increasing TUBA acetylation in VSMCs.Abbreviations: ACTA2/α-SMA: actin, alpha 2, smooth muscle, aorta; ACTB: actin beta; ATAT1: alpha tubulin acetyltransferase 1; ATG: autophagy related; BECN1: beclin 1; BP: blood pressure; CAL: carotid artery ligation; CQ: chloroquine diphosphate; EC: endothelial cells; EEL: external elastic layer; FBS: fetal bovine serum; GAPDH: glyceraldehyde 3-phosphate dehydrogenase; HASMCs: human aortic smooth muscle cells; HAT1: histone acetyltransferase 1; HDAC: histone deacetylase; IEL: inner elastic layer; IP: immunoprecipitation; KAT2A/GCN5: K(lysine) acetyltransferase 2A; KAT8/hMOF: lysine acetyltransferase 8; MAP1LC3: microtubule associated protein 1 light chain 3; MYH11: myosin heavy chain 11; PBS: phosphate-buffered saline; PDGF: platelet derived growth factor; PECAM1/CD31: platelet and endothelial cell adhesion molecule 1; RAC3: Rac family small GTPase 3; SIRT2: sirtuin 2; SPP1/OPN: secreted phosphoprotein 1; SQSTM1/p62: sequestosome 1; TAGLN/SM22: transgelin; TUBA: tubulin alpha; ULK1: unc-51 like autophagy activating kinase; VSMC: vascular smooth muscle cell; VVG: Verhoeff Van Gieson; WT: wild type.

Ozanimod, an S1PR1 ligand, attenuates hypoxia plus glucose deprivation-induced autophagic flux and phenotypic switching in human brain VSM cells

Vascular smooth muscle (VSM) cell phenotypic expression and autophagic state are dynamic responses to stress. Vascular pathologies, such as hypoxemia and ischemic injury, induce a synthetic VSM phenotype and autophagic flux resulting in a loss of vascular integrity and VSM cell death respectfully. Both clinical pilot and experimental stroke studies demonstrate that sphingosine-1-phosphate receptor (S1PR) modulation improves stroke outcome; however, specific mechanisms associated with a beneficial outcome at the level of the cerebrovasculature have not been clearly elucidated. We hypothesized that ozanimod, a selective S1PR type 1 ligand, will attenuate VSM synthetic phenotypic expression and autophagic flux in primary human brain VSM cells following acute hypoxia plus glucose deprivation (HGD; in vitro ischemic-like injury) exposure. Cells were treated with ozanimod and exposed to normoxia or HGD. Crystal violet staining, standard immunoblotting, and immunocytochemical labeling techniques assessed cellular morphology, vacuolization, phenotype, and autophagic state. We observed that HGD temporally decreased VSM cell viability and concomitantly increased vacuolization, both of which ozanimod reversed. HGD induced a simultaneous elevation and reduction in levels of pro- and antiautophagic proteins respectfully, and ozanimod attenuated this response. Protein levels of VSM phenotypic biomarkers, smoothelin and SM22, were decreased following HGD. Furthermore, we observed an HGD-induced epithelioid and synthetic morphological appearance accompanied by disorganized cytoskeletal filaments, which was rescued by ozanimod. Thus, we conclude that ozanimod, a selective S1PR₁ ligand, protects against acute HGD-induced phenotypic switching and promotes cell survival, in part, by attenuating HGD-induced autophagic flux thus improving vascular patency in response to acute ischemia-like injury.

Lysosome (Dys)function in Atherosclerosis-A Big Weight on the Shoulders of a Small Organelle

Atherosclerosis is a progressive insidious chronic disease that underlies most of the cardiovascular pathologies, including myocardial infarction and ischemic stroke. The malfunctioning of the lysosomal compartment has a central role in the etiology and pathogenesis of atherosclerosis. Lysosomes are the degradative organelles of mammalian cells and process endogenous and exogenous substrates in a very efficient manner. Dysfunction of these organelles and consequent inefficient degradation of modified low-density lipoproteins (LDL) and apoptotic cells in atherosclerotic lesions have, therefore, numerous deleterious consequences for cellular homeostasis and disease progression. Lysosome dysfunction has been mostly studied in the context of the inherited lysosomal storage disorders (LSDs). However, over the last years it has become increasingly evident that the consequences of this phenomenon are more far-reaching, also influencing the progression of multiple acquired human pathologies, such as neurodegenerative diseases, cancer, and cardiovascular diseases (CVDs). During the formation of atherosclerotic plaques, the lysosomal compartment of the various cells constituting the arterial wall is under severe stress, due to the tremendous amounts of lipoproteins being processed by these cells. The uncontrolled uptake of modified lipoproteins by arterial phagocytic cells, namely macrophages and vascular smooth muscle cells (VSMCs), is the initial step that triggers the pathogenic cascade culminating in the formation of atheroma. These cells become pathogenic "foam cells," which are characterized by dysfunctional lipid-laden lysosomes. Here, we summarize the current knowledge regarding the origin and impact of the malfunctioning of the lysosomal compartment in plaque cells. We further analyze how the field of LSD research may contribute with some insights to the study of CVDs, particularly how therapeutic approaches that target the lysosomes in LSDs could be applied to hamper atherosclerosis progression and associated mortality.

Regulation of autophagy by controlling Erk1/2 and mTOR for platelet-derived growth factor-BB-mediated vascular smooth muscle cell phenotype shift

AIMS

Vascular smooth muscle cell (VSMC) phenotype shift is involved in the pathophysiology of vascular injury or platelet-derived growth factor (PDGF)-induced abnormal proliferation and migration of VSMCs. We aimed to investigate the underlying mechanism involved in PDGF-mediated signaling pathways and autophagy regulation followed by VSMC phenotype shift.

MAIN METHODS

The proliferation, migration and apoptosis of cultured rat aortic VSMCs were measured, and cells undergoing phenotype shift and autophagy were examined. Specific inhibitors for target proteins in signaling pathways were applied to clarify their roles in regulating cell functions.

KEY FINDINGS

PDGF-BB stimulation initiated autophagy activation and synthetic phenotype transition by decreasing α-smooth muscle-actin (SMA), calponin and myosin heavy chain (MHC) and increasing osteopontin (OPN) expression. However, U0126, a potent extracellular signal-regulated kinase 1/2 (Erk1/2) inhibitor, decreased PDGF-BB-induced LC3 expression, while rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), increased it. Furthermore, U0126 decreased the expresseion of autophagy-related genes (Atgs) such as beclin-1, Atg7, Atg5, and Atg12-Atg5 complex, indicating that Erk1/2 is a regulator of PDGF-BB-induced VSMC autophagy. Regardless of autophagy inhibition by U0126 or activation by rapamycin, the PDGF-BB-induced decrease in SMA, calponin and MHC and increase in OPN expression were inhibited. Furthermore, PDGF-BB-stimulated VSMC proliferation, migration and proliferating cell nuclear antigen (PCNA) expression were inhibited by U0126 and rapamycin.

SIGNIFICANCE

These findings suggest that PDGF-BB-induced autophagy is strongly regulated by Erk1/2, an mTOR-independent pathway, and any approach for targeting autophagy modulation is a potential therapeutic strategy for addressing abnormal VSMC proliferation and migration.

YAP accelerates vascular senescence via blocking autophagic flux and activating mTOR

Yes-associated protein (YAP), a major effector of the Hippo signalling pathway, is widely implicated in vascular pathophysiology processes. Here, we identify a new role of YAP in the regulation of vascular senescence. The inhibition or deficiency and overexpression of YAP were performed in human umbilical vein endothelial cells (HUVECs) and isolated vascular tissues. Cellular and vascular senescence was assessed by analysis of the senescence-associated β-galactosidase (SA-β-gal) and expression of senescence markers P16, P21, P53, TERT and TRF1. We found that YAP was highly expressed in old vascular tissues, inhibition and knockdown of YAP decreased senescence, while overexpression of YAP increased the senescence in both HUVECs and vascular tissues. In addition, autophagic flux blockage and mTOR pathway activation were observed during YAP-induced HUVECs and vascular senescence, which could be relieved by the inhibition and knockdown of YAP. Moreover, YAP-promoted cellular and vascular senescence could be relieved by mTOR inhibition. Collectively, our findings indicate that YAP may serve as a potential therapeutic target for ageing-associated cardiovascular disease.

mTORC1 (Mechanistic Target of Rapamycin Complex 1) Signaling in Endothelial and Smooth Muscle Cells Is Required for Vascular Function

mTORC1 (Mechanistic target of rapamycin complex 1) serves as a molecular hub and intracellular energy sensor that regulate various cellular processes. Emerging evidence points to mTORC1 signaling as a critical regulator of cardiovascular function with implications for cardiovascular disease. Here, we show that selective disruption of mTORC1, through conditional Raptor gene deletion, in endothelial or smooth muscle cells alter vascular function. Endothelial cell-specific Raptor deletion results in reduced relaxation responses evoked by acetylcholine in the aorta but not in the mesenteric artery. Of note, endothelial-specific Raptor deletion did not affect endothelial-independent vasorelaxation nor the contractile responses of the aorta or mesenteric artery. Interestingly, endothelial Raptor haploinsufficiency did not alter vascular endothelial function but attenuated the endothelial dysfunction evoked by angiotensin II. Smooth muscle cell-specific conditional deletion of Raptor reduces both endothelial- and smooth muscle-dependent relaxation responses as well as receptor-dependent and -independent contractility in the aorta. This was associated with activation of autophagy signaling. Notably, the changes in vascular function evoked by endothelial and smooth muscle Raptor deletion were independent of changes in blood pressure and heart rate. Together, these data suggest that vascular mTORC1 signaling is a critical regulator of vascular endothelial and smooth muscle function. mTORC1 signaling may represent a potential target for the treatment of vascular diseases associated with altered mTORC1 activity.

Vascular Cells Proteome Associated with Bradykinin and Leptin Inflammation and Oxidative Stress Signals

Among the primary contributors to cardiovascular diseases are inflammation and oxidative imbalance within the vessel walls as well as the fibrosis of rat aortic smooth muscle cell (RASMC). Bradykinin (BK) and leptin are inflammatory modulators that are linked to vascular injury. In this study, we employed tandem LC-MS/MS to identify protein signatures that encompass protein abundance in RASMC treated with BK or leptin followed by systems biology analyses to gain insight into the biological pathways and processes linked to vascular remodeling. In the study, 1837 proteins were identified in control untreated RASMC. BK altered the expression of 72 (4%) and 120 (6.5%) proteins, whereas leptin altered the expression of 189 (10.2%) and 127 (6.5%) proteins after 24 and 48 h, respectively, compared to control RASMC. BK increased the protein abundance of leptin receptor, transforming growth factor-β. On the other hand, leptin increased the protein abundance of plasminogen activator inhibitor 1 but decreased the protein abundance of cofilin. BK and leptin induced the expression of inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) and pathway analysis revealed the activation of mitogen-activated protein kinases (MAPKs) and AKT pathways. The proteome profile in response to BK and leptin revealed mechanistic interplay of multiple processes that modulate inflammation and oxidative stress signals in the vasculature.

The role of autophagy in abdominal aortic aneurysm: protective but dysfunctional

Autophagy, an evolutionarily conserved mechanism that promotes cell survival by recycling nutrients and degrading long-lived proteins and dysfunctional organelles, is an important defense mechanism, and its attenuation has been well documented in senescence and aging-related diseases. Abdominal aortic aneurysm (AAA), a well-known aging-related disease, has been defined as a chronic degenerative process in the abdominal aortic wall; however, the complete mechanism is unknown, and a clinical treatment is lacking. Accumulating evidence has recently revealed that numerous drugs that can induce autophagy are effective in the treatment of AAA. The purpose of this systematic review was to focus on the cross-talk between autophagy and high-risk factors and the potential pathogenesis of AAA to understand not only the host defense and pathogenesis but also potential treatments.

Advanced glycation end-products suppress autophagy by AMPK/mTOR signaling pathway to promote vascular calcification

Vascular calcification is closely linked to patients in diabetes mellitus and chronic kidney disease. Advanced glycation end-products (AGEs) are associated with osteogenic differentiation of vascular smooth muscle cell (VSMC), vascular calcification, and autophagy that takes part in the process. However, the underlying mechanism of the effects of AGEs on the phenotypic transition and autophagy of VSMCs is not clearly understood. In this study, we cultured the rat VSMC line (A7R5) and thoracic aorta organ with bovine serum albumin (BSA) or AGEs (AGEs-BSA) and detected proteins expression by Western blotting or immunofluorescence. Autophagosome was observed by transmission electron microscopy (TEM). The mineralization and calcific nodules were identified by Alizarin Red S and Von Kossa staining. AGEs significantly downregulated p-AMPKα expression and upregulated p-mTOR expression and then increased the expression of osteoblastic differentiation, while suppressing autophagy in a time-dependent pattern. Pretreatment with autophagy activator rapamycin and AMPK activator AICAR both upregulated the autophagy level and downregulated the effects of AGEs on osteoblastic differentiation of VSMCs. Moreover, the result from rat thoracic aorta culture also confirmed that AGEs promote vascular calcification in a time-dependent manner. Thus, our study showed that AGEs quicken vascular calcification and suppress autophagy associated with AMPK/mTOR signaling pathway.

Vascular autophagy in health and disease

Homeostasis is maintained within organisms through the physiological recycling process of autophagy, a catabolic process that is intricately involved in the mobilization of nutrients during starvation, recycling of cellular cargo, as well as initiation of cellular death pathways. Specific to the cardiovascular system, autophagy responds to both chemical (e.g. free radicals) and mechanical stressors (e.g. shear stress). It is imperative to note that autophagy is not a static process, and measurement of autophagic flux provides a more comprehensive investigation into the role of autophagy. The overarching themes emerging from decades of autophagy research are that basal levels of autophagic flux are critical, physiological stressors may increase or decrease autophagic flux, and more importantly, aberrant deviations from basal autophagy may elicit detrimental effects. Autophagy has predominantly been examined within cardiac or vascular smooth muscle tissue within the context of disease development and progression. Autophagic flux within the endothelium holds an important role in maintaining vascular function, demonstrated by the necessary role for intact autophagic flux for shear-induced release of nitric oxide however the underlying mechanisms have yet to be elucidated. Within this review, we theorize that autophagy itself does not solely control vascular homeostasis, rather, it works in concert with mitochondria, telomerase, and lipids to maintain physiological function. The primary emphasis of this review is on the role of autophagy within the human vasculature, and the integrative effects with physiological processes and diseases as they relate to the vascular structure and function.

The Class III PI3K/Beclin-1 Autophagic Pathway Participates in the mmLDL-Induced Upregulation of ETA Receptor in Mouse Mesenteric Arteries

Minimally modified low-density lipoprotein (mmLDL) is a risk factor for cardiovascular diseases. The current study explored the effect of mmLDL on the endothelin type A (ETA) receptor in mouse mesenteric arteries in vivo, as well as the role of autophagy in this process. mmLDL was injected via the caudal vein, and the Class III PI3K autophagic pathway inhibitor 3-methyladenine (3-MA) was injected intraperitoneally. The animals were divided into physiological saline (NS), mmLDL, and mmLDL + 3-MA groups. The dose-effect curve of endothelin-1- (ET-1-) induced mesenteric artery contraction was measured using myography, while ET_A receptor mRNA expression was detected using real-time polymerase chain reactions, and the protein levels of the ET_A receptor, class III PI3K, Beclin-1, LC3 II/I, p62, NF-κB, and p-NF-κB were observed using Western blot analysis. mmLDL significantly strengthened ET-1-induced contraction (the E_max value increased from 184.87 ± 7.46% in the NS group to 319.91 ± 20.31% in the mmLDL group (P < 0.001), and the pEC₅₀ value increased from 8.05 ± 0.05 to 9.11 ± 0.09 (P < 0.01). In addition to upregulating the protein levels of Class III PI3K, Beclin-1, and LC3 II/I and downregulating that of p62, mmLDL significantly increased the mRNA expression and protein level of the ET_A receptor and increased the protein level of p-NF-κB. However, these effects were significantly inhibited by 3-MA. mmLDL activates autophagy via the Class III PI3K/Beclin-1 pathway and upregulates the ET_A receptor via the downstream NF-κB pathway. Understanding the effect of mmLDL on the ET_A receptor and the underlying mechanisms may provide a new idea for the prevention and treatment of cardiovascular diseases.

Mitophagy in Cardiovascular Diseases

Cardiovascular diseases are one of the leading causes of death. Increasing evidence has shown that pharmacological or genetic targeting of mitochondria can ameliorate each stage of these pathologies, which are strongly associated with mitochondrial dysfunction. Removal of inefficient and dysfunctional mitochondria through the process of mitophagy has been reported to be essential for meeting the energetic requirements and maintaining the biochemical homeostasis of cells. This process is useful for counteracting the negative phenotypic changes that occur during cardiovascular diseases, and understanding the molecular players involved might be crucial for the development of potential therapies. Here, we summarize the current knowledge on mitophagy (and autophagy) mechanisms in the context of heart disease with an important focus on atherosclerosis, ischemic heart disease, cardiomyopathies, heart failure, hypertension, arrhythmia, congenital heart disease and peripheral vascular disease. We aim to provide a complete background on the mechanisms of action of this mitochondrial quality control process in cardiology and in cardiac surgery by also reviewing studies on the use of known compounds able to modulate mitophagy for cardioprotective purposes.

Autophagic degradation of KAT2A/GCN5 promotes directional migration of vascular smooth muscle cells by reducing TUBA/α-tubulin acetylation

Macroautophagy/autophagy, a fundamental process for degradation of macromolecules and organelles, occurs constitutively at a basal level and is upregulated in response to stress. Whether autophagy regulates protein acetylation and microtubule stability in vascular smooth muscle cells (VSMCs) migration, however, remains unknown. Here, we demonstrate that the histone acetyltransferase KAT2A/GCN5 (lysine acetyltransferase 2) binds directly to the autophagosome protein MAP1LC3/LC3 (microtubule associated protein 1 light chain 3) via a conserved LC3-interacting region (LIR) domain. This interaction is required for KAT2A sequestration in autophagosomes and degradation by lysosomal acid hydrolases. Suppression of autophagy results in KAT2A accumulation. KAT2A functions as an acetyltransferase to increase TUBA/α-tubulin acetylation, promote microtubule polymerization and stability, ultimately inhibiting directional cell migration. Our findings indicate that deacetylation of TUBA and perturbation of microtubule stability via selective autophagic degradation of KAT2A are essential for autophagy-promoting VSMC migration. Abbreviations: ACTB: actin beta; ATAT1: alpha tubulin acetyltransferase 1; ATG: autophagy-related; BECN1: beclin 1; CQ: chloroquine; FBS: fetal bovine serum; GST: glutathione S-transferase; H4K16ac: histone H4 lysine 16 acetylation; HASMCs: human aortic smooth muscle cells; HBSS: Hank's buffered salt solution; HDAC6: histone deacetylase 6; hMOF: human males absent on the first; IP: immunoprecipitation; KAT2A/GCN5: lysine acetyltransferase 2A; Lacta: lactacystin; LIR: LC3-interaction region; MAP1LC3: microtubule associated protein 1 light chain 3; MEFs: mouse embryonic fibroblasts; MTOC: microtubule-organizing center; PE: phosphatidylethanolamine; PtdIns3K: class III phosphatidylinositol 3-kinase; RUNX2: runt-related transcription factor 2; SIRT1: sirtuin 1; SIRT2: sirtuin 2; SQSTM1/p62: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1; VSMCs: vascular smooth muscle cells; WT: wild-type.

Microparticles and autophagy: a new frontier in the understanding of atherosclerosis in rheumatoid arthritis

Microparticles (MPs) are small membrane vesicles released by many cell types under physiological and pathological conditions. In the last years, these particles were considered as inert cell debris, but recently many studies have demonstrated they could have a role in intercellular communication. Increased levels of MPs have been reported in various pathological conditions including infections, malignancies, and autoimmune diseases, such as rheumatoid arthritis (RA). RA is an autoimmune systemic inflammatory disease characterized by chronic synovial inflammation, resulting in cartilage and bone damage with accelerated atherosclerosis increasing mortality. According to the literature data, also MPs could have a role in endothelial dysfunction, contributing to atherosclerosis in RA patients. Moreover many researchers have shown that a dysregulated autophagy seems to be involved in endothelial dysfunction. Autophagy is a reparative process by which cytoplasmic components are sequestered in double-membrane vesicles and degraded on fusion with lysosomal compartments. It has been shown in many works that basal autophagy is essential to proper vascular function. Taking into account these considerations, we hypothesized that in RA patients MPs could contribute to atherosclerosis process by dysregulation of endothelial autophagy process.

Vascular smooth muscle cell death, autophagy and senescence in atherosclerosis

In the present review, we describe the causes and consequences of loss of vascular smooth muscle cells (VSMCs) or their function in advanced atherosclerotic plaques and discuss possible mechanisms such as cell death or senescence, and induction of autophagy to promote cell survival. We also highlight the potential use of pharmacological modulators of these processes to limit plaque progression and/or improve plaque stability. VSMCs play a pivotal role in atherogenesis. Loss of VSMCs via initiation of cell death leads to fibrous cap thinning and promotes necrotic core formation and calcification. VSMC apoptosis is induced by pro-inflammatory cytokines, oxidized low density lipoprotein, high levels of nitric oxide and mechanical injury. Apoptotic VSMCs are characterized by a thickened basal lamina surrounding the cytoplasmic remnants of the VSMC. Inefficient clearance of apoptotic VSMCs results in secondary necrosis and subsequent inflammation. A critical determinant in the VSMC stress response and phenotypic switching is autophagy, which is activated by various stimuli, including reactive oxygen and lipid species, cytokines, growth factors and metabolic stress. Successful autophagy stimulates VSMC survival, whereas reduced autophagy promotes age-related changes in the vasculature. Recently, an interesting link between autophagy and VSMC senescence has been uncovered. Defective VSMC autophagy accelerates not only the development of stress-induced premature senescence but also atherogenesis, albeit without worsening plaque stability. VSMC senescence in atherosclerosis is likely a result of replicative senescence and/or stress-induced premature senescence in response to DNA damaging and/or oxidative stress-inducing stimuli. The finding that VSMC senescence can promote atherosclerosis further illustrates that normal, adequate VSMC function is crucial in protecting the vessel wall against atherosclerosis.

Role of autophagy in atherosclerosis: foe or friend?

Athrosclerosis is conceived as a chronic inflammatory status affecting cells from vascular walls. Different mechanisms and pathological features are evident at the onset of atherosclerotic changes via the engaging different cells from the vascular wall and circulatory cells. Attempts are currently focused on the detection of cell compensatory mechanisms against atherosclerotic changes to restore cell function and/or postpone severe vasculitis. Autophagy is an intracellular self-digesting process commonly protrudes exhausted organelles and injured cytoplasmic constituents via double-lipid bilayer membrane vesicles out the target cells. Recent investigations point to the critical and defensive role of autophagy in the vascular cells behavioral function such as endothelial cells and smooth muscle cells against different insults. Autophagy response and related effectors could be modulated in the favor to restore cell function and reduce pro-inflammatory status under pathological conditions. In this review, the recent findings were collected regarding the role of autophagy during atherosclerotic changes. We aimed to answer the question of how autophagy stimulation and/or inhibition could provide a promising effect on developing a sophisticated treatment for AS.

Tricyclic antidepressant amitriptyline inhibits autophagic flux and prevents tube formation in vascular endothelial cells

Amitriptyline is a tricyclic antidepressant and an inhibitor of lysosomal acid sphingomyelinase (ASM). Amitriptyline is well known for its cardiovascular side effects and toxicity in psychiatric patients. However, the mechanisms underlying the cardiovascular side effects of amitriptyline remain largely undefined. This study aimed to determine the effects of amitriptyline on angiogenic capability of vascular endothelial cells in physiological settings and identify its mechanism of action. The ex vivo aortic ring angiogenesis and in vitro-cultured endothelial cell tube formation assay were used to assess the effects of amitriptyline on endothelial angiogenic capability. It was demonstrated that amitriptyline impaired the angiogenesis of aortic rings, which was similar to that found in aortic rings with haploinsufficiency of the ASM gene. In cultured mouse microvascular endothelial cells (MVECs), amitriptyline impaired the proliferation and tube formation under basal condition, which were accompanied by attenuated angiogenic signalling pathways such as endothelial nitric oxide synthase, Akt and Erk1/2 pathways. Mechanistically, amitriptyline inhibited autophagic flux without affecting autophagosome biogenesis at basal condition. ASM gene silencing or autophagy inhibition mimics the inhibitory effects of amitriptyline on endothelial cell proliferation and tube formation. Collectively, our data suggest that amitriptyline inhibits endothelial cell proliferation and angiogenesis via blockade of ASM-autophagic flux axis. It is implicated that the cardiovascular side effects of amitriptyline may be associated with its inhibitory action on physiological angiogenesis.

Chemerin stimulates aortic smooth muscle cell proliferation and migration via activation of autophagy in VSMCs of metabolic hypertension rats

Vascular remodeling is a characteristic pathogenesis of hypertension and a main cause of abnormal construction and function of organs because of hypertension. Chemerin is a new adipokine that is elevated in states of obesity and metabolic syndrome (MS). However, the molecular mechanisms behind these pathological processes are not fully clarified. An animal model of metabolic hypertension was created to evaluate the role of metabolic chemerin in hypertension. In this study, the expression of chemerin/CMKLR-1 and autophagy in the arteries of metabolic hypertension rats undergoing vascular remodeling was investigated and the effect and mechanisms on the regulation of human aortic smooth muscle cells (HA-SMCs) were explored. The vascular remodeling in vivo was more serious in the metabolic hypertensive rat model, and the expression of chemerin and its receptor CMKLR1 were remarkably higher in the media layer of the thoracic aorta and the mesenteric artery in metabolic hypertension rats. In addition, there was an increased number of autophagosomes in SMCs and an up-regulation of the autophagy-related protein LC3 and beclin-1 levels in metabolic hypertension rats. In vitro, chemerin significantly stimulated HA-SMC proliferation and migration, as determined by MTT assay and scratch assay, respectively. Chemerin significantly increased LC3 and beclin-1 levels, as measured by western blot analysis, while this effect was inhibited by the autophagy inhibitor 3-MA. It is demonstrated that chemerin stimulates SMC proliferation and migration via autophagy, which may lead to vascular structural remodeling in metabolic hypertension.

Angiotensin II-Regulated Autophagy Is Required for Vascular Smooth Muscle Cell Hypertrophy

Hypertension is a disease associated to increased plasma levels of angiotensin II (Ang II). Ang II can regulate proliferation, migration, ROS production and hypertrophy of vascular smooth muscle cells (VSMCs). However, the mechanisms by which Ang II can affect VSMCs remain to be fully elucidated. In this context, autophagy, a process involved in self-digestion of proteins and organelles, has been described to regulate vascular remodeling. Therefore, we sought to investigate if Ang II regulates VSMC hypertrophy through an autophagy-dependent mechanism. To test this, we stimulated A7r5 cell line and primary rat aortic smooth muscle cells with Ang II 100 nM and measured autophagic markers at 24 h by Western blot. Autophagosomes were quantified by visualizing fluorescently labeled LC3 using confocal microscopy. The results showed that treatment with Ang II increases Beclin-1, Vps34, Atg-12-Atg5, Atg4 and Atg7 protein levels, Beclin-1 phosphorylation, as well as the number of autophagic vesicles, suggesting that this peptide induces autophagy by activating phagophore initiation and elongation. These findings were confirmed by the assessment of autophagic flux by co-administering Ang II together with chloroquine (30 μM). Pharmacological antagonism of the angiotensin type 1 receptor (AT1R) with losartan and RhoA/Rho Kinase inhibition prevented Ang II-induced autophagy. Moreover, Ang II-induced A7r5 hypertrophy, evaluated by α-SMA expression and cell size, was prevented upon autophagy inhibition. Taking together, our results suggest that the induction of autophagy by an AT1R/RhoA/Rho Kinase-dependent mechanism contributes to Ang II-induced hypertrophy in VSMC.

TNFα expressed on the surface of microparticles modulates endothelial cell fate in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is associated with a high prevalence of atherosclerosis. Recently increased levels of microparticles (MPs) have been reported in patients with RA. MPs could represent a link between autoimmunity and endothelial dysfunction by expressing tumor necrosis factor alpha (TNFα), a key cytokine involved in the pathogenesis of RA, altering endothelial apoptosis and autophagy. The aim of this study was to investigate TNFα expression on MPs and its relationship with endothelial cell fate.

Methods

MPs were purified from peripheral blood from 20 healthy controls (HC) and from 20 patients with RA, before (time (T)0) and after (T4) 4-month treatment with etanercept (ETA). Surface expression of TNFα was performed by flow cytometry analysis. EA.hy926 cells, an immortalized endothelial cell line, were treated with RA-MPs purified at T0 and at T4 and also, with RA-MPs in vitro treated with ETA. Apoptosis and autophagy were then evaluated.

Results

RA-MPs purified at T0 expressed TNFα on their surface and this expression significantly decreased at T4. Moreover, at T0 RA-MPs, significantly increased both apoptosis and autophagy levels on endothelial cells, in a dose-dependent manner. RA-MPs did not significantly change these parameters after 4 months of in vivo treatment with ETA.

Conclusions

Our data demonstrate that MPs isolated from patients with RA exert a pathological effect on endothelial cells by TNFα expressed on their surface. In vivo and in vitro treatment with ETA modulates this effect, suggesting anti-TNF therapy protects against endothelial damage in patients with RA.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1768-8) contains supplementary material, which is available to authorized users.

Contribution of p62/SQSTM1 to PDGF-BB-induced myofibroblast-like phenotypic transition in vascular smooth muscle cells lacking Smpd1 gene

Accumulating evidence indicates a critical role of autophagy in regulating vascular smooth muscle cell (SMC) homeostasis in atherogenesis. However, little is known about the modulatory role of autophagy in PDGF-BB-induced SMC transition towards the synthetic phenotype and extracellular matrix remodeling. We recently demonstrated that acid sphingomyelinase (ASM, encoded by Smpd1 gene) controls autophagy maturation in coronary arterial SMCs. Here, we demonstrate that PDGF-BB stimulation causes a myofibroblast-like non-canonical synthetic phenotype transition in Smpd1^−/− SMCs. These non-canonical phenotypic changes induced by PDGF-BB in Smpd1^−/− SMCs were characterized by increased expression of fibroblast-specific protein (FSP-1), massive deposition of collagen type I, decreased cell size, elevated inflammatory status with enhanced cytokine release and adhesion molecule expression. Mechanistically, PDGF-BB induces prolonged Akt activation that causes decreased autophagosome biogenesis and thereby exaggerates p62/SQSTM1 accumulation in Smpd1^−/− SMCs. More importantly, Akt inhibition or p62/SQSTM1 gene silencing attenuates PDGF-BB-induced phenotypic changes in Smpd1^−/− SMCs. This first demonstration of a p62/SQSTM1-dependent myofibroblast-like phenotypic transition in Smpd1^−/− SMCs suggests that ASM-mediated autophagy pathway contributes to maintaining the arterial smooth muscle homeostasis in situation of vascular remodeling during atherosclerosis.

Alpha-lipoic acid regulates the autophagy of vascular smooth muscle cells in diabetes by elevating hydrogen sulfide level

Dysfunctional vascular smooth muscle (VSM) plays a vital role in the process of atherosclerosis in patients with type 2 diabetes mellitus (T2DM). Alpha-lipoic acid (ALA) can prevent the altered VSM induced by diabetes. However, the precise mechanism underlying the beneficial effect of ALA is not well understood. This study aimed to determine whether ALA ameliorates VSM function by elevating hydrogen sulfide (H₂S) level in diabetes and whether this effect is associated with regulation of autophagy of VSM cells (VSMCs). We found decreased serum H₂S levels in Chinese patients and rats with type 2 diabetes mellitus (T2DM). ALA treatment could increase H₂S level, which reduced the autophagy-related index and activation of the 5'-monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway, thereby protecting vascular function in rats with T2DM. Propargylglycine (PPG), a cystathionine-γ-lyase inhibitor, could weaken the ALA effect. In cultured VSMCs, high glucose level also reduced H₂S level, upregulated the autophagy-related index and activated the AMPK/mTOR pathway, which were reversed by concomitant application of sodium hydrosulfide (NaHS, an H₂S donor) or ALA. The protective effect of NaHS or ALA was attenuated by rapamycin (an autophagy activator), 5-amino-1-β-d-ribofuranosyl-imidazole-4-carboxamide (an AMPK activator) or PPG. In contrast, Compound C (an AMPK inhibitor) enhanced the effect of ALA or NaHS. ALA may have a protective effect on VSMCs in T2DM by elevating H₂S level and downregulating autophagy via the AMPK/mTOR pathway. This study provides a new target for addressing diabetic macroangiopathy.

Defective autophagy in vascular smooth muscle cells enhances cell death and atherosclerosis

Macroautophagy/autophagy is considered as an evolutionarily conserved cellular catabolic process. In this study, we aimed to elucidate the role of autophagy in vascular smooth muscle cells (SMCs) on atherosclerosis. SMCs cultured from mice with SMC-specific deletion of the essential autophagy gene atg7 (Atg7cKO) showed reduced serum-induced cell growth, increased cell death, and decreased cell proliferation rate. Furthermore, 7-ketocholestrerol enhanced apoptosis and the expression of CCL2 (chemokine [C-C motif] ligand 2) with the activation of TRP53, the mouse ortholog of human and rat TP53, in SMCs from Atg7cKO mice. In addition, Atg7cKO mice crossed with Apoe (apolipoprotein E)-deficient mice (apoeKO; Atg7cKO:apoeKO) showed reduced medial cellularity and increased TUNEL-positive cells in the descending aorta at 10 weeks of age. Intriguingly, Atg7cKO: apoeKO mice fed a Western diet containing 1.25% cholesterol for 14 weeks showed a reduced survival rate. Autopsy of the mice demonstrated the presence of aortic rupture. Analysis of the descending aorta in Atg7cKO:apoeKO mice showed increased plaque area, increased TUNEL-positive area, decreased SMC-positive area, accumulation of macrophages in the media, and adventitia and perivascular tissue, increased CCL2 expression in SMCs in the vascular wall, medial disruption, and aneurysm formation. In conclusion, our data suggest that defective autophagy in SMCs enhances atherosclerotic changes with outward arterial remodeling.

Formononetin protects against balloon injury‑induced neointima formation in rats by regulating proliferation and migration of vascular smooth muscle cells via the TGF‑β1/Smad3 signaling pathway

The present study investigated the effects of formononetin (FMN) against balloon injury‑induced neointima formation in vivo and platelet‑derived growth factor (PDGF)‑BB‑induced proliferation and migration of vascular smooth muscle cells (VSMCs) in vitro, and explored the underlying mechanisms. A rat model of carotid artery injury was established, in order to examine the effects of FMN on balloon injury‑induced neointima formation. Histological observation of the carotid artery tissues was conducted by hematoxylin and eosin staining. VSMC proliferation during neointima formation was observed by proliferating cell nuclear antigen staining. Subsequently, rat aortic VSMCs were isolated, and the effects of FMN on PDGF‑BB‑induced VSMC proliferation and migration were determined using Cell Counting Kit‑8 and Transwell/wound healing assays, respectively. Immunohistochemical and immunocytochemical staining was applied to measure the expression of transforming growth factor (TGF)‑β in carotid artery tissues and VSMCs, respectively. SMAD family member 3 (Smad3)/phosphorylated (p)‑Smad3 expression was examined by western blotting. FMN treatment significantly inhibited the abnormal proliferation of smooth muscle cells in neointima, and alterations to the vascular structure were attenuated. In addition, pretreatment with FMN effectively inhibited the proliferation of PDGF‑BB‑stimulated VSMCs (P<0.05). FMN also reduced the number of cells that migrated to the lower surface of the Transwell chamber and decreased wound‑healing percentage (P<0.05). The expression levels of TGF‑β were decreased by FMN treatment in vivo and in vitro, and Smad3/p‑Smad3 expression was also markedly inhibited. In conclusion, FMN significantly protected against balloon injury‑induced neointima formation in the carotid artery of a rat model; this effect may be associated with the regulation of VSMC proliferation and migration through altered TGF‑β1/Smad3 signaling.