Autophagic regulation of smooth muscle cell biology

Intrinsic Gata4 expression sensitizes the aortic root to dilation in a Loeys-Dietz syndrome mouse model

Loeys-Dietz syndrome (LDS) is an aneurysm disorder caused by mutations that decrease transforming growth factor-β (TGF-β) signaling. Although aneurysms develop throughout the arterial tree, the aortic root is a site of heightened risk. To identify molecular determinants of this vulnerability, we investigated the heterogeneity of vascular smooth muscle cells (VSMCs) in the aorta of Tgfbr1 M318R/+ LDS mice by single cell and spatial transcriptomics. Reduced expression of components of the extracellular matrix-receptor apparatus and upregulation of stress and inflammatory pathways were observed in all LDS VSMCs. However, regardless of genotype, a subset of Gata4-expressing VSMCs predominantly located in the aortic root intrinsically displayed a less differentiated, proinflammatory profile. A similar population was also identified among aortic VSMCs in a human scRNAseq dataset. Postnatal VSMC-specific Gata4 deletion reduced aortic root dilation in LDS mice, suggesting that this factor sensitizes the aortic root to the effects of impaired TGF-β signaling.

Endothelial HIFα/PDGF-B to smooth muscle Beclin1 signaling sustains pathological muscularization in pulmonary hypertension

Mechanisms underlying maintenance of pathological vascular hypermuscularization are poorly delineated. Herein, we investigated retention of smooth muscle cells (SMCs) coating normally unmuscularized distal pulmonary arterioles in pulmonary hypertension (PH) mediated by chronic hypoxia with or without Sugen 5416, and reversal of this pathology. With hypoxia in mice or culture, lung endothelial cells (ECs) upregulated hypoxia-inducible factor 1α (HIF1-α) and HIF2-α, which induce platelet-derived growth factor B (PDGF-B), and these factors were reduced to normoxic levels with re-normoxia. Re-normoxia reversed hypoxia-induced pulmonary vascular remodeling, but with EC HIFα overexpression during re-normoxia, pathological changes persisted. Conversely, after establishment of distal muscularization and PH, EC-specific deletion of Hif1a, Hif2a, or Pdgfb induced reversal. In human idiopathic pulmonary artery hypertension, HIF1-α, HIF2-α, PDGF-B, and autophagy-mediating gene products, including Beclin1, were upregulated in pulmonary artery SMCs and/or lung lysates. Furthermore, in mice, hypoxia-induced EC-derived PDGF-B upregulated Beclin1 in distal arteriole SMCs, and after distal muscularization was established, re-normoxia, EC Pdgfb deletion, or treatment with STI571 (which inhibits PDGF receptors) downregulated SMC Beclin1 and other autophagy products. Finally, SMC-specific Becn1 deletion induced apoptosis, reversing distal muscularization and PH mediated by hypoxia with or without Sugen 5416. Thus, chronic hypoxia induction of the HIFα/PDGF-B axis in ECs is required for non-cell-autonomous Beclin1-mediated survival of pathological distal arteriole SMCs.

Recent advances of myotubularin-related (MTMR) protein family in cardiovascular diseases

Belonging to a lipid phosphatase family containing 16 members, myotubularin-related proteins (MTMRs) are widely expressed in a variety of tissues and organs. MTMRs preferentially hydrolyzes phosphatidylinositol 3-monophosphate and phosphatidylinositol (3,5) bis-phosphate to generate phosphatidylinositol and phosphatidylinositol 5-monophosphate, respectively. These phosphoinositides (PIPs) promote membrane degradation during autophagosome-lysosomal fusion and are also involved in various regulatory signal transduction. Based on the ability of modulating the levels of these PIPs, MTMRs exert physiological functions such as vesicle trafficking, cell proliferation, differentiation, necrosis, cytoskeleton, and cell migration. It has recently been found that MTMRs are also involved in the occurrence and development of several cardiovascular diseases, including cardiomyocyte hypertrophy, proliferation of vascular smooth muscle cell, LQT1, aortic aneurysm, etc. This review summarizes the functions of MTMRs and highlights their pathophysiological roles in cardiovascular diseases.

Sanhuang decoction inhibits autophagy of periodontal ligament fibroblasts during orthodontic tooth movement by activating PI3K-Akt-mTOR pathway

BACKGROUND

Orthodontic tooth movement (OTM) is a typical treatment that corrects malaligned teeth by applying mechanical forces. However, mechanical overload often leads to damage of PDL fibroblasts. Sanhuang decoction (SHD) is commonly used to inhibit inflammation and oxidative stress. However, the mechanism of SHD for OTM treatment is still unclear. Therefore, this study attempts to explore the underlying mechanism through relevant experiments.

METHODS

In the present paper, we established a OTM rat model and further explored the effects of SHD on the PDL of OTM rats. The OTM model and effects of SHD were determined by micro-CT, and the PDL pathological changes, PDL width and capillaries in PDL were observed by H&E staining. Subsequently, the ROS levels in PDL was determined using flow cytometry analysis with DCFH-DA staining, MDA contents and antioxidative enzymes activities were also measured using commercial kits. Furthermore, the autophagy of PDL fibroblasts and proteins in the PI3K/Akt/mTOR pathway were detected using immunoluminescence, qPCR and western blotting assays.

RESULTS

The results showed SHD treatment can alleviate the decrease of PDL cells and capillaries induced by OTM, and improve the MDA and ROS levels in PDL, as well as enhance the activities of SOD and GSH-Px. Further experiments indicated SHD decreased the autophagy levels of PDL fibroblasts via promoting the phosphorylation levels of mTOR, PI3K and Akt proteins.

CONCLUSION

SHD inhibited autophagy of periodontal ligament fibroblasts during orthodontic tooth movement by inhibiting oxidative stress via activating PI3K-Akt-mTOR pathway. Our present findings suggested SHD treatment would be useful for management of the possible disorders occurs in orthodontic tooth movement therapy.

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.

Lipotoxicity, glucotoxicity and some strategies to protect vascular smooth muscle cell against proliferative phenotype in metabolic syndrome

Metabolic syndrome (MetS) is a risk factor for the development of cardiovascular disease (CVD) and atherosclerosis through a mechanism that involves vascular smooth muscle cell (VSMC) proliferation, lipotoxicity and glucotoxicity. Several molecules found to be increased in MetS, including free fatty acids, fatty acid binding protein 4, leptin, resistin, oxidized lipoprotein particles, and advanced glycation end products, influence VSMC proliferation. Most of these molecules act through their receptors on VSMCs by activating several signaling pathways associated with ROS generation in various cellular compartments. ROS from NADPH-oxidase and mitochondria have been found to promote VSMC proliferation and cell cycle progression. In addition, most of the natural or synthetic substances described in this review, including pharmaceuticals with hypoglycemic and hypolipidemic properties, attenuate VSMC proliferation by their simultaneous modulation of cell signaling and their scavenging property due to the presence of a phenolic ring in their structure. This review discusses recent data in the literature on the role that several MetS-related molecules and ROS play in the change from contractile to proliferative phenotype of VSMCs. Hence the importance of proposing an appropriate strategy to prevent uncontrolled VSMC proliferation using antioxidants, hypoglycemic and hypolipidemic agents.

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.

Neutrophil extracellular traps induce abdominal aortic aneurysm formation by promoting the synthetic and proinflammatory smooth muscle cell phenotype via Hippo-YAP pathway

The neutrophil plays an important role during abdominal aortic aneurysm (AAA) formation by undergoing histone citrullination with peptidyl arginine deiminase 4 (encoded by Padi4) and releasing neutrophil extracellular traps (NETs). However, the specific role of NETs during AAA formation is elusive. We found the levels of NET components in serum and tissues were found to be significantly associated with the clinical outcome of AAA patients. Furthermore, we reported that NETs induced the synthetic and proinflammatory smooth muscle cells (SMCs) phenotype and promoted AAA formation in a Hippo-YAP pathway-dependent manner by in vitro and in vivo experiments. Padi4 or Yap global knockout mice, exhibited significantly less synthetic and proinflammatory phenotypes of SMCs and developed AAA with lower frequency and severity compared with those of controls. Further studies indicated that the phenotypic switch of SMCs was associated with NETs-regulated enrichment status of H3K4me3 and H3K27me3 at promoters of synthetic and proinflammatory genes in SMCs. Cumulatively, these data suggest that NETs contribute to AAA formation by promoting the synthetic and proinflammatory phenotype of SMCs via inhibiting the Hippo-YAP pathway. A better understanding of the molecular mechanisms that regulate NETs and SMC phenotype is important to provide suitable cellular targets to prevent AAA.

Lactate promotes vascular smooth muscle cell switch to a synthetic phenotype by inhibiting miR-23b expression

Recent research indicates that lactate promotes the switching of vascular smooth muscle cells (VSMCs) to a synthetic phenotype, which has been implicated in various vascular diseases. This study aimed to investigate the effects of lactate on the VSMC phenotype switch and the underlying mechanism. The CCK-8 method was used to assess cell viability. The microRNAs and mRNAs levels were evaluated using quantitative PCR. Targets of microRNA were predicted using online tools and confirmed using a luciferase reporter assay. We found that lactate promoted the switch of VSMCs to a synthetic phenotype, as evidenced by an increase in VSMC proliferation, mitochondrial activity, migration, and synthesis but a decrease in VSMC apoptosis. Lactate inhibited miR-23b expression in VSMCs, and miR-23b inhibited VSMC's switch to the synthetic phenotype. Lactate modulated the VSMC phenotype through downregulation of miR-23b expression, suggesting that overexpression of miR-23b using a miR-23b mimic attenuated the effects of lactate on VSMC phenotype modulation. Moreover, we discovered that SMAD family member 3 (SMAD3) was the target of miR-23b in regulating VSMC phenotype. Further findings suggested that lactate promotes VSMC switch to synthetic phenotype by targeting SMAD3 and downregulating miR-23b. These findings suggest that correcting the dysregulation of miR-23b/SMAD3 or lactate metabolism is a potential treatment for vascular diseases.

Palmitic acid inhibits vascular smooth muscle cell switch to synthetic phenotype via upregulation of miR-22 expression

Synthetic phenotype switch of vascular smooth muscle cells (VSMCs) has been shown to play key roles in vascular diseases. Mounting evidence has shown that fatty acid metabolism is highly associated with vascular diseases. However, how fatty acids regulate VSMC phenotype is poorly understood. Hence, the effects of palmitic acid (PA) on VSMC phenotype were determined in this study. The effect of the PA on VSMCs was measured by live/dead and EdU assays, as well as flow cytometry. Migration ability of VSMCs was evaluated using transwell assay. The underlying targets of miR-22 were predicted using bioinformatics online tools, and confirmed by luciferase reporter assay. The RNA and protein expression of certain gene was detected by qRT-PCR or western blot. PA inhibited VSMC switch to synthetic phenotype, as manifested by inhibiting VSMC proliferation, migration, and synthesis. PA upregulated miR-22 in VSMCs, and miR-22 mimics exerted similar effects as PA treatment, inhibiting VSMC switch to synthetic phenotype. Inhibition of miR-22 using miR-22 inhibitor blocked the impacts of PA on VSMC phenotype modulation, suggesting that PA modulated VSMC phenotype through upregulation of miR-22 expression. We found that ecotropic virus integration site 1 protein homolog (EVI1) was the target of miR-22 in regulation of VSMC phenotype. Overexpression of miR-22 or/and PA treatment attenuated the inhibition of EVI1 on switch of VSMCs. These findings suggested that PA inhibits VSMC switch to synthetic phenotype through upregulation of miR-22 thereby inhibiting EVI1, and correcting the dysregulation of miR-22/EVI1 or PA metabolism is a potential treatment to vascular diseases.

Sex Differences in Molecular Mechanisms of Cardiovascular Aging

Cardiovascular disease (CVD) is still the leading cause of illness and death in the Western world. Cardiovascular aging is a progressive modification occurring in cardiac and vascular morphology and physiology where increased endothelial dysfunction and arterial stiffness are observed, generally accompanied by increased systolic blood pressure and augmented pulse pressure. The effects of biological sex on cardiovascular pathophysiology have long been known. The incidence of hypertension is higher in men, and it increases in postmenopausal women. Premenopausal women are protected from CVD compared with age-matched men and this protective effect is lost with menopause, suggesting that sex-hormones influence blood pressure regulation. In parallel, the heart progressively remodels over the course of life and the pattern of cardiac remodeling also differs between the sexes. Lower autonomic tone, reduced baroreceptor response, and greater vascular function are observed in premenopausal women than men of similar age. However, postmenopausal women have stiffer arteries than their male counterparts. The biological mechanisms responsible for sex-related differences observed in cardiovascular aging are being unraveled over the last several decades. This review focuses on molecular mechanisms underlying the sex-differences of CVD in aging.

miR-145-5p affects autophagy by targeting CaMKIIδ in atherosclerosis

BACKGROUND

Atherosclerosis (AS) is a chronic progressive inflammatory disease involving many cells. miR-145-5p mediates the biological phenotypes of human aortic vascular smooth muscle cells (HAVSMCs) and influences the progression of AS, but the potential mechanism needs further study.

METHODS

Total RNA was extracted from patient plasma and arteries to determine the expression of miR-145-5p. The CaMKIIδ pathway and genes were predicted as the target of miR-145-5p by bioinformatics approaches. The interaction between miR-145-5p and CaMKIIδ was confirmed by RT-qPCR and Dual Luciferase Reporter Assay System. Western blot analysis, immunofluorescence staining, transmission electron microscopy (TEM) and protein tracing on HAVSMCs transduced with mCherry-GFP-LC3 lentiviral vectors to determine the mechanism by which miR-145-5p affects the atherosclerotic disease process.

RESULTS

The expression of miR-145-5p was downregulated in blood and arteries specimens of patients with coronary stenosis. Correspondingly, CaMKIIδ was upregulated and miR-145-5p was downregulated in hypoxic HAVSMCs. CaMKIIδ was predicted and confirmed as a downstream target of miR-145-5p. In addition, CaMKIIδ induced the upregulation of autophagy-related proteins by activating the AMPK/mTOR/ULK1 signalling pathway. Moreover, we confirmed that miR-145-5p inhibits CaMKIIδ expression by binding to a specific sequence in the CaMKIIδ 3' UTR and affects autophagy. Crucially, CaMKIIδ was promoted by the downregulation of miR-145-5p and then activating autophagy in HAVSMCs through the AMPK/mTOR/ULK1 signalling pathway to affect the AS progress.

CONCLUSIONS

miR-145-5p regulates CaMKIIδ, leading to altered autophagy in HAVSMCs. This alteration plays an important role in AS progression.

Nkx2-3 induces autophagy inhibiting proliferation and migration of vascular smooth muscle cells via AMPK/mTOR signaling pathway

Vascular remodeling and restenosis are common complications after percutaneous coronary intervention. Excessive proliferation and migration of vascular smooth muscle cells (VSMCs) play important roles in intimal hyperplasia-induced vascular restenosis. NK2 Homeobox 3 (Nkx2-3), a critical member of Nkx family, is involved in tissue differentiation and organ development. However, the role of Nkx2-3 in VSMCs proliferation and migration remains unknown. In this study, we used carotid balloon injury model and platelet-derived growth factor-BB (PDGF)-treated VSMCs as in vivo and in vitro experimental models. EdU assay and CCK-8 assay were used to detect cell proliferation. Migration was measured by scratch test. Hematoxylin and eosin staining and immunohistochemistry staining were used to evaluate the intimal hyperplasia. The autophagy level was detected by fluorescent mRFP-GFP-LC3 in vitro and by transmission electron microscopy in vivo. It was shown that Nkx2-3 was upregulated both in balloon injured carotid arteries and PDGF-stimulated VSMCs. Adenovirus-mediated Nkx2-3 overexpression inhibited intimal hyperplasia after balloon injury, and suppressed VSMCs proliferation and migration induced by PDGF. Conversely, silencing of Nkx2-3 by small interfering RNA exaggerated proliferation and migration of VSMCs. Furthermore, we found that Nkx2-3 enhanced autophagy level, while the autophagy inhibitor 3-MA eliminated the inhibitory effect of Nkx2-3 on VSMCs proliferation and migration both in vivo and in vitro. Moreover, Nkx2-3 promoted autophagy in VSMCs by activating the AMP-activated protein kinase/mammalian target of rapamycin (AMPK/mTOR) signaling pathway. These results demonstrated for the first time that Nkx2-3 inhibited VSMCs proliferation and migration through AMPK/mTOR-mediated autophagy.

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.

Sodium propionate exerts anticancer effect in mice bearing breast cancer cell xenograft by regulating JAK2/STAT3/ROS/p38 MAPK signaling

Propionate is a short-chain fatty acid (SCFA) mainly produced from carbohydrates by gut microbiota. Sodium propionate (SP) has shown to suppress the invasion in G protein-coupled receptor 41 (GPR41) and GPR43-overexpressing breast cancer cells. In this study we investigated the effects of SP on the proliferation, apoptosis, autophagy, and antioxidant production of breast cancer cells. We showed that SP (5-20 mM) dose-dependently inhibited proliferation and induced apoptosis in breast cancer cell lines JIMT-1 (ER-negative and HER2-expressing) and MCF7 (ER-positive type), and this effect was not affected by PTX, thus not mediated by the GPR41 or GPR43 SCFA receptors. Meanwhile, we demonstrated that SP treatment increased autophagic and antioxidant activity in JIMT-1 and MCF7 breast cancer cells, which might be a compensatory mechanism to overcome SP-induced apoptosis, but were not sufficient to overcome SP-mediated suppression of proliferation and induction of apoptosis. We revealed that the anticancer effect of SP was mediated by inhibiting JAK2/STAT3 signaling which led to cell-cycle arrest at G0/G1 phase, and increasing levels of ROS and phosphorylation of p38 MAPK which induced apoptosis. In nude mice bearing JIMT-1 and MCF7 cells xenograft, administration of SP (20 mg/mL in drinking water) significantly suppressed tumor growth by regulating STAT3 and p38 in tumor tissues. These results suggest that SP suppresses proliferation and induces apoptosis in breast cancer cells by inhibiting STAT3, increasing the ROS level and activating p38. Therefore, SP is a candidate therapeutic agent for breast cancer.

Non-syndromic thoracic aortic aneurysm: cellular and molecular insights

Thoracic aortic aneurysm (TAA) develops silently and asymptomatically and is a major cause of mortality. TAA prevalence is greatly underestimated, it is usually diagnosed incidentally, and its treatment consists mainly of prophylactic surgery based on the aortic diameter. The lack of effective drugs and biological markers to identify and stratify TAAs by risk before visible symptoms results from scant knowledge of its pathophysiological mechanisms. Here we integrate the structural impairment affecting non-syndromic non-familial TAA with the main cellular and molecular changes described so far and consider how these changes are interconnected through specific pathways. The ultimate goal is to define much-needed novel markers of TAA, and so the potential of previously identified molecules to aid in early diagnosis/prognosis is also discussed. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Jujuboside B Inhibits Neointimal Hyperplasia and Prevents Vascular Smooth Muscle Cell Dedifferentiation, Proliferation, and Migration via Activation of AMPK/PPAR-γ Signaling

The uncontrolled proliferation and migration of vascular smooth muscle cells is a critical step in the pathological process of restenosis caused by vascular intimal hyperplasia. Jujuboside B (JB) is one of the main biologically active ingredients extracted from the seeds of Zizyphus jujuba (SZJ), which has the properties of anti-platelet aggregation and reducing vascular tension. However, its effects on restenosis after vascular intervention caused by VSMCs proliferation and migration remain still unknown. Herein, we present novel data showing that JB treatment could significantly reduce the neointimal hyperplasia of balloon-damaged blood vessels in Sprague-Dawley (SD) rats. In cultured VSMCs, JB pretreatment significantly reduced cell dedifferentiation, proliferation, and migration induced by platelet-derived growth factor-BB (PDGF-BB). JB attenuated autophagy and reactive oxygen species (ROS) production stimulated by PDGF-BB. Besides, JB promoted the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ). Notably, inhibition of AMPK and PPAR-γ partially reversed the ability of JB to resist the proliferation and migration of VSMCs. Taken as a whole, our findings reveal for the first time the anti-restenosis properties of JB in vivo and in vitro after the endovascular intervention. JB antagonizes PDGF-BB-induced phenotypic switch, proliferation, and migration of vascular smooth muscle cells partly through AMPK/PPAR-γ pathway. These results indicate that JB might be a promising clinical candidate drug against in-stent restenosis, which provides a reference for further research on the prevention and treatment of vascular-related diseases.

Celastrol ameliorates vascular neointimal hyperplasia through Wnt5a-involved autophagy

Neointimal hyperplasia caused by the excessive proliferation of vascular smooth muscle cells (VSMCs) is the pathological basis of restenosis. However, there are few effective strategies to prevent restenosis. Celastrol, a pentacyclic triterpene, has been recently documented to be beneficial to certain cardiovascular diseases. Based on its significant effect on autophagy, we proposed that celastrol could attenuate restenosis through enhancing autophagy of VSMCs. In the present study, we found that celastrol effectively inhibited the intimal hyperplasia and hyperproliferation of VSMCs by inducing autophagy. It was revealed that autophagy promoted by celastrol could induce the lysosomal degradation of c-MYC, which might be a possible mechanism contributing to the reduction of VSMCs proliferation. The Wnt5a/PKC/mTOR signaling pathway was found to be an underlying mechanism for celastrol to induce autophagy and inhibit the VSMCs proliferation. These observations indicate that celastrol may be a novel drug with a great potential to prevent restenosis.

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.

Regulation of Autophagic Signaling by Mechanical Loading and Inflammation in Human PDL Fibroblasts

Autophagy (cellular self-consumption) is a crucial adaptation mechanism during cellular stress conditions. This study aimed to examine how this important process is regulated in human periodontal ligament (PDL) fibroblasts by mechanical and inflammatory stress conditions and whether the mammalian target of rapamycin (mTOR) signaling pathway is involved. Autophagy was quantified by flow cytometry. Qualitative protein phosphorylation profiling of the mTOR pathway was carried out. Effects of mTOR regulation were assessed by quantification of important synthesis product collagen 1, cell proliferation and cell death with real-time PCR and flow cytometry. Autophagy as a response to mechanical or inflammatory treatment in PDL fibroblasts was dose and time dependent. In general, autophagy was induced by stress stimulation. Phosphorylation analysis of mTOR showed regulatory influences of mechanical and inflammatory stimulation on crucial target proteins. Regulation of mTOR was also detectable via changes in protein synthesis and cell proliferation. Physiological pressure had cell-protective effects (p = 0.025), whereas overload increased cell death (p = 0.003), which was also promoted in long-term inflammatory treatment (p < 0.001). Our data provide novel insights about autophagy regulation by mechanical and inflammatory stress conditions in human PDL fibroblasts. Our results suggest some involvement of the mTOR pathway in autophagy and cell fate regulation under the named conditions.

Metformin alleviates β-glycerophosphate-induced calcification of vascular smooth muscle cells via AMPK/mTOR-activated autophagy

The aim of the present study was to investigate the effect of metformin on β-glycerophosphate-induced calcification of vascular smooth muscle cells (VSMCs) and the possible mechanisms underlying this. Using an established VSMC calcification model, VSMCs were first treated with β-glycerophosphate, before metformin, 3-methyladenine and compound C were added to the cell cultures in different combinations. Calcium deposition in the cells was examined by Alizarin Red S staining and using the O-cresolphthalein complexone method. To assess the occurrence of autophagy, autophagosomes inside the cells were studied using a transmission electron microscope and green fluorescent microtubule-associated protein 1 light chain 3 (LC3) puncta were examined using a fluorescent microscope. Additionally, protein expression levels of α-smooth muscle actin (α-SMA), runt-related transcription factor 2 (RUNX2), LC3II/I, beclin 1 and 5' adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway-associated proteins were determined by western blot analysis. Metformin increased the number of autophagosomes, green fluorescent LC3 puncta and the levels of LC3II/I, beclin 1, α-SMA and phosphorylated (p)-AMPK in the VSMCs that were treated with β-glycerophosphate when compared to controls; whereas, calcium deposition and the expression levels of RUNX2 and p-mTOR were found to be decreased. Treating the VSMCs with 3-methyladenine or compound C reversed the effects of metformin. The results of the present study suggested that metformin may alleviate β-glycerophosphate-induced calcification of VSMCs, which may be attributed to the activation of AMPK/mTOR signaling pathway-dependent autophagy.

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.

Downregulation of Lysosomal Acid Ceramidase Mediates HMGB1-Induced Migration and Proliferation of Mouse Coronary Arterial Myocytes

High-mobility group box 1 protein (HMGB1) has been reported to trigger lysosome destabilization causing a wide of inflammatory diseases. The present study tested whether a lysosomal enzyme, acid ceramidase (AC), plays a critical role in HMGB1-induced alteration in ceramide metabolism and whether such HMGB1-AC interaction is associated with abnormal migration and proliferation of vascular smooth muscle cells (SMCs). We first observed that the expression of AC in the medial layer of mouse coronary arterial wall and colocalization of AC with a lysosome marker Lamp-1. In primary cultured coronary arterial myocytes (CAMs), AC expression and colocalization with Lamp-1 were significantly up-regulated by AC inducer, genistein, but down-regulated by AC inhibitor, N-oleoylethanolamine (NOE). HMGB1 dose-dependently decreased the colocalization of AC with Lamp-1 and reduced mRNA and protein expressions of AC in CAMs, but reversed by genistein. Consistently, HMGB1 significantly induced increases in the levels of long-chain ceramides in CAMs, which were not further enhanced by NOE but blocked by genistein. More importantly, HMGB1 promoted migration and proliferation of CAMs, which were not further increased by NOE but reduced by genistein. Lastly, CAMs isolated from smooth muscle-specific AC knockout mice (AC gene Asah1) exhibited increased ceramide levels and enhanced the migration and proliferation, which resembles the effects of HMGB1 on wild-type CAMs. Together, these results suggest that HMGB1 promotes SMC migration and proliferation via inhibition of AC expression and ceramide accumulation.

TMEM16A ameliorates vascular remodeling by suppressing autophagy via inhibiting Bcl-2-p62 complex formation

Rationale: Transmembrane member 16A (TMEM16A) is a component of calcium-activated chloride channels that regulate vascular smooth muscle cell (SMC) proliferation and remodeling. Autophagy, a highly conserved cellular catabolic process in eukaryotes, exerts important physiological functions in vascular SMCs. In the current study, we investigated the relationship between TMEM16A and autophagy during vascular remodeling. Methods: We generated a transgenic mouse that overexpresses TMEM16A specifically in vascular SMCs to verify the role of TMEM16A in vascular remodeling. Techniques employed included immunofluorescence, electron microscopy, co-immunoprecipitation, and Western blotting. Results: Autophagy was activated in aortas from angiotensin II (AngII)-induced hypertensive mice with decreased TMEM16A expression. The numbers of light chain 3B (LC3B)-positive puncta in aortas correlated with the medial cross-sectional aorta areas and TMEM16A expression during hypertension. SMC-specific TMEM16A overexpression markedly inhibited AngII-induced autophagy in mouse aortas. Moreover, in mouse aortic SMCs (MASMCs), AngII-induced autophagosome formation and autophagic flux were blocked by TMEM16A upregulation and were promoted by TMEM16A knockdown. The effect of TMEM16A on autophagy was independent of the mTOR pathway, but was associated with reduced kinase activity of the vacuolar protein sorting 34 (VPS34) enzyme. Overexpression of VPS34 attenuated the effect of TMEM16A overexpression on MASMC proliferation, while the effect of TMEM16A downregulation was abrogated by a VPS34 inhibitor. Further, co-immunoprecipitation assays revealed that TMEM16A interacts with p62. TMEM16A overexpression inhibited AngII-induced p62-Bcl-2 binding and enhanced Bcl-2-Beclin-1 interactions, leading to suppression of Beclin-1/VPS34 complex formation. However, TMEM16A downregulation showed the opposite effects. Conclusion: TMEM16A regulates the four-way interaction between p62, Bcl-2, Beclin-1, and VPS34, and coordinately prevents vascular autophagy and remodeling.

Calcium Phosphate Bions Cause Intimal Hyperplasia in Intact Aortas of Normolipidemic Rats through Endothelial Injury

Calcium phosphate bions (CPBs) are formed under blood supersaturation with calcium and phosphate owing to the mineral chaperone fetuin-A and representing mineralo-organic particles consisting of bioapatite and multiple serum proteins. While protecting the arteries from a rapid medial calcification, CPBs cause endothelial injury and aggravate intimal hyperplasia in balloon-injured rat aortas. Here, we asked whether CPBs induce intimal hyperplasia in intact rat arteries in the absence of cardiovascular risk factors. Normolipidemic Wistar rats were subjected to regular (once/thrice per week over 5 weeks) tail vein injections of either spherical (CPB-S) or needle-shaped CPBs (CPB-N), magnesium phosphate bions (MPBs), or physiological saline (n = 5 per group). Neointima was revealed in 3/10 and 4/10 rats which received CPB-S or CPB-N, respectively, regardless of the injection regimen or blood flow pattern in the aortic segments. In contrast, none of the rats treated with MPBs or physiological saline had intimal hyperplasia. The animals also did not display signs of liver or spleen injury as well as extraskeletal calcium deposits. Serum alanine/aspartate transaminases, interleukin-1β, MCP-1/CCL2, C-reactive protein, and ceruloplasmin levels did not differ among the groups. Hence, CPBs may provoke intimal hyperplasia via direct endothelial injury regardless of their shape or type of blood flow.

Critical role of histone demethylase Jumonji domain-containing protein 3 in the regulation of neointima formation following vascular injury

Aims

Jumonji domain-containing protein 3 (JMJD3), also called lysine specific demethylase 6B (KDM6b), is an inducible histone demethylase which plays an important role in many biological processes, however, its function in vascular remodelling remains unknown. We aim to demonstrate that JMJD3 mediates vascular neointimal hyperplasia following carotid injury, and proliferation and migration in platelet-derived growth factor BB (PDGF-BB)-induced vascular smooth muscle cells (VSMCs).

Methods and results

By using both genetic and pharmacological approaches, our study provides the first evidence that JMJD3 controls PDGF-BB-induced VSMCs proliferation and migration. Furthermore, our in vivo mouse and rat intimal thickening models demonstrate that JMJD3 is a novel mediator of neointima formation based on its mediatory effects on VSMCs proliferation, migration, and phenotypic switching. We further show that JMJD3 ablation by small interfering RNA or inhibitor GSK J4 can suppress the expression of NADPH oxidase 4 (Nox4), which is correlated with H3K27me3 enrichment around the gene promoters. Besides, deficiency of JMJD3 and Nox4 prohibits autophagic activation, and subsequently attenuates neointima and vascular remodelling following carotid injury. Above all, the increased expression of JMJD3 and Nox4 is further confirmed in human atherosclerotic arteries plaque specimens.

Conclusions

JMJD3 is a novel factor involved in vascular remodelling. Deficiency of JMJD3 reduces neointima formation after vascular injury by a mechanism that inhibits Nox4-autophagy signalling activation, and suggesting JMJD3 may serve as a perspective target for the prevention and treatment of vascular diseases.

Regulation of the autophagy-marker Sequestosome 1 in periodontal cells and tissues by biomechanical loading

PURPOSE

Orthodontic treatment is based on the principle of force application to teeth and subsequently to the surrounding tissues and periodontal cells. Sequestosome 1 (SQSTM1) is a well-known marker for autophagy, which is an important cellular mechanism of adaptation to stress. The aim of this study was to analyze whether biomechanical loading conditions regulate SQSTM1 in periodontal cells and tissues, thereby providing further information on the role of autophagy in orthodontic tooth movement.

METHODS

Periodontal ligament (PDL) fibroblasts were exposed to cyclic tensile strain of low magnitude (3%, CTSL), and the regulation of autophagy-associated targets was determined with an array-based approach. SQSTM1 was selected for further biomechanical loading experiments with dynamic and static tensile strain and assessed via real-time polymerase chain reaction (RT-PCR) and immunoblotting. Signaling pathways involved in SQSTM1 activation were analyzed by using specific inhibitors, including an autophagy inhibitor. Finally, SQSTM1 expression was analyzed in gingival biopsies and histological sections of rats in presence and absence of orthodontic forces.

RESULTS

Multiple autophagy-associated targets were regulated by CTSL in PDL fibroblasts. All biomechanical loading conditions tested increased the SQSTM1 expression significantly. Stimulatory effects of CTSL on SQSTM1 expression were diminished by inhibition of the c‑Jun N‑terminal kinase (JNK) pathway and of autophagy. Increased SQSTM1 levels after CTSL were confirmed by immunoblotting. Orthodontic force application also led to significantly elevated SQTSM1 levels in the gingiva and PDL of treated animals as compared to control.

CONCLUSIONS

Our in vitro and in vivo findings provide evidence of a role of SQSTM1 and thereby autophagy in orthodontic tooth movement.

Autophagy in periodontal ligament fibroblasts under biomechanical loading

Autophagy (cellular self-consumption) is an adaptive stress response and an important aspect of adaption to mechanical loading. If mechanical forces are associated with autophagy regulation in periodontal ligament (PDL) fibroblasts is still unknown. The aim of this study was to analyze the influence of force magnitude on autophagy regulation and subsequently on cell death in human PDL fibroblasts. Autophagy-associated genes were analyzed with a specific PrimePCR assay after 24 h of stimulation with high (STSH) and low magnitudes (STSL) of static tensile strain applied to PDL fibroblasts. Based on the results, targets were selected for further real-time PCR analysis. The autophagic flux was assessed by immunoblotting for autophagy marker microtubule-associated protein 1, light chain 3, and by autophagosome staining. Cell death was determined by TUNEL assay and Cell Death Detection ELISA^PLUS. Autophagy was induced pharmacologically by rapamycin and inhibited by chloroquine. For statistical analysis, the Kruskal Wallis test followed by the post-hoc Dunnett's test was used. Static tensile strain had regulatory effects on mRNA expression of multiple autophagy-associated targets. Stimulation with STSH induced mRNA expression changes in more autophagy-associated targets than STSL. The autophagic flux was induced by STSH while STSL had no significant effect on autophagosome formation. Furthermore, autophagy inhibition led to increased cell death. Low magnitudes of tensile strain seem to have cell-protective properties. Taken together, our findings provide novel insights about autophagy regulation by biomechanical loading in human PDL fibroblasts. Our results suggest a gradual response of autophagy to static tensile strain in human PDL fibroblasts.

Smooth muscle cell and arterial aging: basic and clinical aspects

Arterial aging engages a plethora of key signalling pathways that act in concert to induce vascular smooth muscle cell (VSMC) phenotypic changes leading to vascular degeneration and extracellular matrix degradation responsible for alterations of the mechanical properties of the vascular wall. This review highlights proof-of-concept examples of components of the extracellular matrix, VSMC receptors which connect extracellular and intracellular structures, and signalling pathways regulating changes in mechanotransduction and vascular homeostasis in aging. Furthermore, it provides a new framework for understanding how VSMC stiffness and adhesion to extracellular matrix contribute to arterial stiffness and how interactions with endothelial cells, platelets, and immune cells can regulate vascular aging. The identification of the key players of VSMC changes operating in large and small-sized arteries in response to increased mechanical load may be useful to better elucidate the causes and consequences of vascular aging and associated progression of hypertension, arteriosclerosis, and atherosclerosis.

Glucagon-Like Peptide-1 Receptor Agonist Attenuates Autophagy to Ameliorate Pulmonary Arterial Hypertension through Drp1/NOX- and Atg-5/Atg-7/Beclin-1/LC3β Pathways

Mitochondrial dysfunction is associated with cardiovascular diseases and diabetes. Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling, and the abnormal proliferation, apoptosis and migration of pulmonary arterial smooth muscle cells (PASMCs). The glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide, has been shown to prevent pulmonary hypertension in monocrotaline-exposed rats. The aim of this study was to investigate the effect of liraglutide on autophagy, mitochondrial stress and apoptosis induced by platelet-derived growth factor BB (PDGF-BB). PASMCs were exposed to PDGF-BB, and changes in mitochondrial morphology, fusion-associated protein markers, and reactive oxygen species (ROS) production were examined. Autophagy was assessed according to the expressions of microtubule-associated protein light chain 3 (LC3)-II, LC3 puncta and Beclin-1. Western blot analysis was used to assess apoptosis, mitochondrial stress and autophagy markers. Liraglutide significantly inhibited PDGF-BB proliferation, migration and motility in PASMCs. PDGF-BB-induced ROS production was mitigated by liraglutide. Liraglutide increased the expression of α-smooth muscle actin (α-SMA) and decreased the expression of p-Yes-associated protein (p-YAP), inhibited autophagy-related protein (Atg)-5, Atg-7, Beclin-1 and the formation of LC3-β and mitochondrial fusion protein dynamin-related (Drp)1. Therefore, liraglutide can mitigate the proliferation of PASMCs via inhibiting cellular Drp1/nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) pathways and Atg-5/Atg-7/Beclin-1/LC3β-dependent pathways of autophagy in PAH.

Vasculoprotective effects of Centella asiatica, Justicia gendarussa and Imperata cylindrica decoction via the NOXs-ROS-NF-κB pathway in spontaneously hypertensive rats

Background and aim

Centella asiatica, Justicia gendarussa and Imperata cylindrica decoction (CJID) is efficacious for hypertension. NADPH (nicotinamide adenine dinucleotide phosphate) oxidase (NOX)-induced reactive oxygen species (ROS) generation modulates nuclear factor kappa B (NF-κB) activation and thus mediates hypertension-induced vascular remodeling. This research aims to investigate the anti-remodeling effect of CJID through the mechanism of NOXs-ROS-NF-κB pathway in spontaneously hypertensive rats (SHRs).

Experimental procedure

CJID was orally administered once a day for five weeks in SHRs and normotensive-WKY (Wistar Kyoto) rats. All rats were sacrificed at the end of study and different assays were performed to determine whether CJID ameliorates vascular remodeling in SHRs, such as histological examination; lactate dehydrogenase (LDH), nitric oxide (NO), malondialdehyde (MDA) and superoxide dismutase (SOD) assays; superoxide and hydrogen peroxide (H₂O₂) generation assays, immunohistochemistry and immunofluorescence assays. . Changes in levels of inducible nitric oxide synthase (iNOS), NF-κB-p65, NF-κB inhibitor alpha/IκBα (inhibitory kappa B- alpha), phosphorylation of IκBα (p-IκBα) and NOX1, NOX2, NOX4 in the thoracic aorta were determined.

Results

Vascular remodeling indicators, media thickness, collagen and elastic accumulation in the thoracic aorta, of SHRs-treated CJID were attenuated. Redox homeostasis, aortic superoxide and hydrogen peroxide generation were decreased in SHRs-treated group. Aortic iNOS, p-IκBα, NF-κB-p65 and NOX1, NOX2, NOX4 expressions were suppressed.

Conclusions

CJI treatment diminishes oxidative stress response in the thoracic aorta of SHRs via regulation of NOXs-ROS-NF-κB signaling pathway. These findings indicate that CJI possess protective effect against hypertension-induced vascular remodeling in SHRs.

Is there a role for autophagy in ascending aortopathy associated with tricuspid or bicuspid aortic valve?

Autophagy is a conserved process by which cytoplasmatic elements are sequestered in vesicles and degraded after their fusion with lysosomes, thus recycling the precursor molecules. The autophagy-mediated removal of redundant/harmful/damaged organelles and biomolecules plays not only a replenishing function, but protects against stressful conditions through an adaptive mechanism. Autophagy, known to play a role in several pathological conditions, is now gaining increasing attention also in the perspective of the identification of the pathogenetic mechanisms at the basis of ascending thoracic aortic aneurysm (TAA), a localized or diffused dilatation of the aorta with an abnormal widening greater than 50 percent of the vessel's normal diameter. TAA is less frequent than abdominal aortic aneurysm (AAA), but is encountered with a higher percentage in patients with congenital heart disease or known genetic syndromes. Several biological aspects of TAA pathophysiology remain to be elucitated and therapeutic needs are still widely unmet. One of the most controversial and epidemiologically important forms of TAA is that associated with the congenital bicuspid malformation of the aortic valve (BAV). Dysregulated autophagy in response, for example, to wall shear stress alterations, has been demonstrated to affect the phenotype of vascular cells relevant to aortopathy, with potential consequences on signaling, remodeling, and angiogenesis. The most recent findings and hypotheses concerning the multiple aspects of autophagy and of its dysregulation are summarized, both in general and in the context of the different vascular cell types and of TAA progression, with particular reference to BAV-related aortopathy.

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.

A rapamycin derivative, biolimus, preferentially activates autophagy in vascular smooth muscle cells

Although rapamycin is a well-known conformational inhibitor of mTORC1, it is now widely used for treating arterial restenosis. Various rapamycin analogues (rapalogue) have been made for applying to drug-eluting stents. Here we show that two major rapalogues, everolimus and biolimus, exert a differential effect on the mTORC1-mediated signaling pathways in vascular smooth muscle cells. In balloon-injured carotid arteries, both rapalogues strongly inhibit neointimal hyperplasia. Signaling pathway analyses reveal that everolimus exert cytotoxicity by increasing cellular reactive oxygen species and consequently reduce energy metabolism. By contrast, biolimus confers a preferential induction of autophagy by more strongly activating major autophagy regulator, ULK1, in vascular smooth muscle cells than everolimus does. As a consequence, the implantation of biolimus-eluting stent reduces endothelial loss, which in turn reduces inflammation, in porcine coronary arteries. Thus, this study reveals that a chemical derivatization can cause a change among mTORC1-dependent signaling pathways in vascular smooth muscle cells, thereby enabling to elicit a differential efficacy on arterial restenosis.

Smooth muscle cell-driven vascular diseases and molecular mechanisms of VSMC plasticity

Vascular smooth muscle cells (VSMCs) are the major cell type in blood vessels. Unlike many other mature cell types in the adult body, VSMC do not terminally differentiate but retain a remarkable plasticity. Fully differentiated medial VSMCs of mature vessels maintain quiescence and express a range of genes and proteins important for contraction/dilation, which allows them to control systemic and local pressure through the regulation of vascular tone. In response to vascular injury or alterations in local environmental cues, differentiated/contractile VSMCs are capable of switching to a dedifferentiated phenotype characterized by increased proliferation, migration and extracellular matrix synthesis in concert with decreased expression of contractile markers. Imbalanced VSMC plasticity results in maladaptive phenotype alterations that ultimately lead to progression of a variety of VSMC-driven vascular diseases. The nature, extent and consequences of dysregulated VSMC phenotype alterations are diverse, reflecting the numerous environmental cues (e.g. biochemical factors, extracellular matrix components, physical) that prompt VSMC phenotype switching. In spite of decades of efforts to understand cues and processes that normally control VSMC differentiation and their disruption in VSMC-driven disease states, the crucial molecular mechanisms and signalling pathways that shape the VSMC phenotype programme have still not yet been precisely elucidated. In this article we introduce the physiological functions of vascular smooth muscle/VSMCs, outline VSMC-driven cardiovascular diseases and the concept of VSMC phenotype switching, and review molecular mechanisms that play crucial roles in the regulation of VSMC phenotypic plasticity.

Transforming growth factor β1 suppresses proinflammatory gene program independent of its regulation on vascular smooth muscle differentiation and autophagy

Transforming growth factor β (TGFβ) signaling plays crucial roles in maintaining vascular integrity and homeostasis, and is established as a strong activator of vascular smooth muscle cell (VSMC) differentiation. Chronic inflammation is a hallmark of various vascular diseases. Although TGFβ signaling has been suggested to be protective against inflammatory aortic aneurysm progression, its exact effects on VSMC inflammatory process and the underlying mechanisms are not fully unraveled. Here we revealed that TGFβ1 suppressed the expression of a broad array of proinflammatory genes while potently induced the expression of contractile genes in cultured primary human coronary artery SMCs (HCASMCs). The regulation of TGFβ1 on VSMC contractile and proinflammatory gene programs appeared to occur in parallel and both processes were through a SMAD4-dependent canonical pathway. We also showed evidence that the suppression of TGFβ1 on VSMC proinflammatory genes was mediated, at least partially through the blockade of signal transducer and activator of transcription 3 (STAT3) and NF-κB pathways. Interestingly, our RNA-seq data also revealed that TGFβ1 suppressed gene expression of a battery of autophagy mediators, which was validated by western blot for the conversion of microtubule-associated protein light chain 3 (LC3) and by immunofluo-rescence staining for LC3 puncta. However, impairment of VSMC autophagy by ATG5 deletion failed to rescue TGFβ1 influence on both VSMC contractile and proinflammatory gene programs, suggesting that TGFβ1-regulated VSMC differentiation and inflammation are not attributed to TGFβ1 suppression on autophagy. In summary, our results demonstrated an important role of TGFβ signaling in suppressing proinflammatory gene program in cultured primary human VSMCs via the blockade on STAT3 and NF-κB pathway, therefore providing novel insights into the mechanisms underlying the protective role of TGFβ signaling in vascular diseases.

Anti-apoptotic effects of autophagy via ROS regulation in microtubule-targeted and PDGF-stimulated vascular smooth muscle cells

Autophagy has been studied as a therapeutic strategy for cardiovascular diseases. However, insufficient studies have been reported concerning the influence of vascular smooth muscle cells (VSMCs) through autophagy regulation. The aim of the present study was to determine the effects of VSMCs on the regulation of autophagy under in vitro conditions similar to vascular status of the equipped microtubule target agent-eluting stent and increased release of platelet-derived growth factor-BB (PDGF-BB). Cell viability and proliferation were measured using MTT and cell counting assays. Immunofluorescence using an anti-α-tubulin antibody was performed to determine microtubule dynamic formation. Cell apoptosis was measured by cleavage of caspase-3 using western blot analysis, and by nuclear fragmentation using a fluorescence assay. Autophagy activity was assessed by microtubule-associated protein light chain 3-II (LC-II) using western blot analysis. Levels of intracellular reactive oxygen species (ROS) were measured using H₂DCFDA. The proliferation and viability of VSMCs were inhibited by microtubule regulation. Additionally, microtubule-regulated and PDGF-BB-stimulated VSMCs increased the cleavage of caspase-3 more than only the microtubule-regulated condition, similar to that of LC3-II, implying autophagy. Inhibitory autophagy of microtubule-regulated and PDGF-BB-stimulated VSMCs resulted in low viability. However, enhancement of autophagy maintained survival through the reduction of ROS. These results suggest that the apoptosis of conditioned VSMCs is decreased by the blocking generation of ROS via the promotion of autophagy, and proliferation is also inhibited. Thus, promoting autophagy as a therapeutic target for vascular restenosis and atherosclerosis may be a good strategy.

NF-κB-Mediated Inflammation in the Pathogenesis of Intracranial Aneurysm and Subarachnoid Hemorrhage. Does Autophagy Play a Role?

The rupture of saccular intracranial aneurysms (IA) is the commonest cause of non-traumatic subarachnoid hemorrhage (SAH)—the most serious form of stroke with a high mortality rate. Aneurysm walls are usually characterized by an active inflammatory response, and NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) has been identified as the main transcription factor regulating the induction of inflammation-related genes in IA lesions. This transcription factor has also been related to IA rupture and resulting SAH. We and others have shown that autophagy interacts with inflammation in many diseases, but there is no information of such interplay in IA. Moreover, NF-κB, which is a pivotal factor controlling inflammation, is regulated by autophagy-related proteins, and autophagy is regulated by NF-κB signaling. It was also shown that autophagy mediates the normal functioning of vessels, so its disturbance can be associated with vessel-related disorders. Early brain injury, delayed brain injury, and associated cerebral vasospasm are among the most serious consequences of IA rupture and are associated with impaired function of the autophagy⁻lysosomal system. Further studies on the role of the interplay between autophagy and NF-κB-mediated inflammation in IA can help to better understand IA pathogenesis and to identify IA patients with an increased SAH risk.

Celosins inhibit atherosclerosis in ApoE-/- mice and promote autophagy flow

ETHNOPHARMACOLOGICAL RELEVANCE

Semen celosiae is a traditional Chinese medicine for purging hepatic pathogenic fire and removing nebula to improve eyesight, treating hepatopyretic vertigo and hypertension. It possesses a serial of potential bioactivities such as hepatoprotection, anti-tumor and anti-inflammatory, anti-diabetes. The triterpenoid saponins celosins from it were proved to have hepatoprotection, lipid lowing and anti-inflammatory. However, the anti-atherosclerosis activities were not reported to date.

AIM OF THE STUDY

This study was designed to examine the therapeutic effects of celosins (CES), the active constituents extracted from Semen celosiae.

MATERIALS AND METHODS

Atherosclerosis model by feeding high fat diet for 12 weeks in ApoE^-/- mice and foam cell model by ox-LDL-treated peritoneal macrophages were performed. The lipid plaque was measured by histopathological analysis. The LC3 dots in the aortic root lesion examined through tissue immunofluorescence. The peritoneal macrophage phagocytosis, formation of foam cells, genes associated protein expression and autophagy flux were measured on foam cell model by oxidized low-density lipoprotein (Ox-LDL) stimulating peritoneal macrophages. The mRNA expression of CD36, SR-A1, ABCA1 and ABCG1 were determined by Real-Time PCR method. The expressions of LC3 and beclin 1 were measured using Western blot.

RESULTS

CES (10, 30, 90mg/kg; p.o.) administrated for 4 weeks significantly reduced the prevalence of the relative area of plaque in mouse aorta, and showed the therapeutic effect on atherosclerosis. In the tissue section of immunofluorescence for aortic root, compared with high fat diet model group, the number of autophagy bodies in CES group increased significantly, suggesting that inhibiting atherosclerosis effect of CES may be related to its promoting autophagy. In vitro, CES significantly reduced phagocytosis of macrophages on lipid and formation rate of foam cells. CES down-regulated the mRNA expression of CD36 and SR-A1 while up-regulated mRNA expression of ABCA1 and ABCG1. Further, CES increased the autophagy specific protein LC3 and beclin 1, and it also increased the level of autophagy in the cells, and promoted the process of autophagy.

CONCLUSIONS

The therapeutic effect of CES on atherosclerosis may be related to the promotion of autophagy.

Homocysteine up-regulates ETB receptors via suppression of autophagy in vascular smooth muscle cells

The change of autophagy is implicated in cardiovascular diseases (CVDs). Homocysteine (Hcy) up-regulates endothelin type B (ET_B) receptors in vascular smooth muscle cells (VSMCs). However, it is unclear whether autophagy is involved in Hcy-induced-up-regulation of ET_B receptors in VSMCs. The present study was designed to examine the hypothesis that Hcy up-regulates ET_B receptors by inhibiting autophagy in VSMCs. Hcy treated the rat superior mesenteric artery (SMA) without endothelium in the presence and absence of AICAR, rapamycin or MHY1485 for 24 h. The contractile responses to sarafotoxin 6c (S6c) (an ET_B receptor agonist) were studied using a sensitive myograph. Levels of protein expression were determined using Western blot analysis. Punctate staining of LC3B was exanimated by immunofluorescence using confocal microscopy. The results showed that Hcy inhibited AMPK, and activated mTOR, followed by impairing autophagy, and increased the levels of ET_B receptor protein expression and the ET_B receptor-mediated contractile responses to S6c in SMA without endothelium. However, these effects were reversed by AICAR or rapamycin. Additionally, MHY1485 up-regulated the AICAR-inhibited ET_B receptor-mediated contractile response and the levels of ET_B receptor protein expression in presence of Hcy. In conclusion, this suggested that Hcy up-regulated ET_B receptors by inhibiting autophagy in VSMCs via AMPK/mTOR signaling pathway.

Characterization of Carotid Smooth Muscle Cells during Phenotypic Transition

Vascular smooth muscle cells (VSMCs) are central players in carotid atherosclerosis plaque development. Although the precise mechanisms involved in plaque destabilization are not completely understood, it is known that VSMC proliferation and migration participate in plaque stabilization. In this study, we analyzed expression patterns of genes involved in carotid atherosclerosis development (e.g., transcription factors of regulation of SMC genes) of VSMCs located inside or outside the plaque lesion that may give clues about changes in phenotypic plasticity during atherosclerosis. VSMCs were isolated from 39 carotid plaques extracted from symptomatic and asymptomatic patients by endarterectomy. Specific biomarker expression, related with VSMC phenotype, was analyzed by qPCR, western immunoblot, and confocal microscopy. MYH11, CNN1, SRF, MKL2, and CALD1 were significantly underexpressed in VSMCs from plaques compared with VSMCs from a macroscopically intact (MIT) region, while SPP1, KLF4, MAPLC3B, CD68, and LGALS3 were found significantly upregulated in plaque VSMCs versus MIT VSMCs. The gene expression pattern of arterial VSMCs from a healthy donor treated with 7-ketocholesterol showed high similarity with the expression pattern of carotid plaque VSMCs. Our results indicate that VSMCs isolated from plaque show a typical SMC dedifferentiated phenotype with macrophage-like features compared with VSMCs isolated from a MIT region of the carotid artery. Additionally, MYH11, KLF5, and SPP1 expression patterns were found to be associated with symptomatology of human carotid atherosclerosis.

Small-Vessel Vasculopathy Due to Aberrant Autophagy in LAMP-2 Deficiency

Lysosomal associated membrane protein 2 (LAMP2) is physiologically implicated in autophagy. A genetic LAMP2 defect causes Danon disease, which consists of two major phenotypes of myopathy and cardiomyopathy. In addition, arteriopathy may manifest on rare occasions but the pathological basis remains unknown. We encountered two Danon families that developed small-vessel vasculopathy in the coronary or cerebral arteries. To investigate the underlying mechanisms, we characterized the biological features of LAMP-2–deficient mice and cultured cells. LAMP-2–deficient mice at 9–24 months of age showed medial thickening with luminal stenosis due to proliferation of vascular smooth muscle cells (VSMC) in muscular arteries. Ultrastructural analysis of VSMC revealed various autophagic vacuoles scattered throughout the cytoplasm, suggesting impaired autophagy of long-lived metabolites and degraded organelles (i.e., mitochondria). The VSMC in Lamp2 null mice expressed more vimentin but less α-smooth muscle actin (α-SMA), indicating a switch from contractile to synthetic phenotype. Silencing of LAMP2 in cultured human brain VSMC showed the same phenotypic transition with mitochondrial fragmentation, enhanced mitochondrial respiration, and overproduction of reactive oxygen species (ROS). These findings indicate that LAMP-2 deficiency leads to arterial medial hypertrophy with the phenotypic conversion of VSMC, resulting from age-dependent accumulation of cellular waste generated by aberrant autophagy.

The Anti-atherosclerotic Effect of Paeonol against Vascular Smooth Muscle Cell Proliferation by Up-regulation of Autophagy via the AMPK/mTOR Signaling Pathway

Introduction: Paeonol (2′-hydroxy-4′-methoxyacetophenone), isolated from moutan cortex, is an active component and has been shown to have anti-atherosclerotic and anti-proliferation effects on vascular smooth muscle cells (VSMCs). However, the possible role of Paeonol in protecting against VSMC proliferation as related to autophagy has yet to be elucidated.

Materials and Methods: The athero-protective effects of Paeonol were evaluated in apoE^-/- mice. The effects of Paeonol on VSMC proliferation and autophagy were examined by staining α-SMA and LC3II spots in the media layer of apoE^-/- mice, respectively. CCK8 and BrdU assays were used to investigate the effects of Paeonol on cell proliferation in vitro. The autophagic levels in VSMCs were evaluated by detecting LC3II accumulation and p62 degradation by immunoblot analysis. To investigate if Paeonol could prevent VSMCs proliferation through autophagy induction, we tested the change in autophagy and cell proliferation by inhibition of autophagy. The levels of the AMPK/mTOR pathway in autophagy regulation were detected by immunoblot analysis. An AMPK inhibitor and si-AMPK transfection in VSMCs was used to confirm whether AMPK activity plays a key role in autophagy regulation of Paeonol.

Results:In vivo experiments confirmed that Paeonol restricted atherosclerosis development and decreased the amount of VSMCs in the media layer of apoE^-/- mice. Paeonol increased protein levels of LC3II and the presence of autophagosomes in the media layer of arteries, which implies that Paeonol may induce VSMCs autophagy in vivo. Paeonol showed potential in inhibiting ox-LDL-induced proliferation in vitro experiments. Paeonol dose-dependently enhanced the formation of acidic vesicular organelles and autophagosmomes, up-regulated the expression of LC3II and increased p62 degradation. The autophagy inhibitor CQ obviously attenuated Paeonol-induced autophagy and the anti-proliferation effect in VSMCs. In addition, Paeonol induced phosphorylation of AMPK and reduced phosphorylation of mTOR. An AMPK inhibitor reversed the Paeonol-induced p-mTOR/mTOR decrease. Paeonol induced LC3II conversion, increased p62 degradation and inhibited cell proliferation in VSMCs, the effects of which were abolished by si-AMPK.

Conclusion: These results imply that Paeonol inhibits proliferation of VSMCs by up-regulating autophagy, and activating the AMPK/mTOR signaling pathway, providing new insights into the anti-atherosclerosis activity of Paeonol.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

Perpetual change: autophagy, the endothelium, and response to vascular injury

Current studies of vascular health, aging, and autophagy emphasize how the endothelium adapts to stress and contributes to disease. The endothelium is far from an inert barrier to blood-borne cells, pathogens, and chemical signals; rather, it actively translates circulating mediators into tissue responses, changing rapidly in response to physiologic stressors. Macroautophagy-the cellular ingestion of effete organelles and protein aggregates to provide anabolic substrates to fuel bioenergetics in times of stress-plays an important role in endothelial cell homeostasis, vascular remodeling, and disease. These roles include regulating vascular tone, sustaining or limiting cell survival, and contributing to the development of atherosclerosis secondary to infection, inflammation, and angiogenesis. Autophagy modulates these critical functions of the endothelium in a dynamic and perpetual response to tissue and intravascular cues.