Ceramide mediates Ox-LDL-induced human vascular smooth muscle cell calcification via p38 mitogen-activated protein kinase signaling

Emerging role of sphingolipids and extracellular vesicles in development and therapeutics of cardiovascular diseases

Sphingolipids are eighteen carbon alcohol lipids synthesized from non-sphingolipid precursors in the endoplasmic reticulum (ER). The sphingolipids serve as precursors for a vast range of moieties found in our cells that play a critical role in various cellular processes, including cell division, senescence, migration, differentiation, apoptosis, pyroptosis, autophagy, nutrition intake, metabolism, and protein synthesis. In CVDs, different subclasses of sphingolipids and other derived molecules such as sphingomyelin (SM), ceramides (CERs), and sphingosine-1-phosphate (S1P) are directly related to diabetic cardiomyopathy, dilated cardiomyopathy, myocarditis, ischemic heart disease (IHD), hypertension, and atherogenesis. Several genome-wide association studies showed an association between genetic variations in sphingolipid pathway genes and the risk of CVDs. The sphingolipid pathway plays an important role in the biogenesis and secretion of exosomes. Small extracellular vesicles (sEVs)/ exosomes have recently been found as possible indicators for the onset of CVDs, linking various cellular signaling pathways that contribute to the disease progression. Important features of EVs like biocompatibility, and crossing of biological barriers can improve the pharmacokinetics of drugs and will be exploited to develop next-generation drug delivery systems. In this review, we have comprehensively discussed the role of sphingolipids, and sphingolipid metabolites in the development of CVDs. In addition, concise deliberations were laid to discuss the role of sEVs/exosomes in regulating the pathophysiological processes of CVDs and the exosomes as therapeutic targets.

Loss of ceramide synthase 5 inhibits the development of experimentally induced aortic valve stenosis

AIM

Inflammation and calcification are hallmarks in the development of aortic valve stenosis (AVS). Ceramides mediate inflammation and calcification in the vascular tissue. The highly abundant d18:1,16:0 ceramide (C16) has been linked to increased cardiovascular mortality and obesity. In this study, we investigate the role of ceramide synthase 5 (CerS5), a critical enzyme for C16 ceramide synthesis, in the development of AVS, particularly in conjunction with a high-fat/high-cholesterol diet (Western diet, WD).

METHODS

We used wild-type (WT) and CerS5-/- mice on WD or normal chow in a wire injury model. We measured the peak velocity to determine AVS development and performed histological analysis of the aortic valve area, immune cell infiltration (CD68 staining), and calcification (von Kossa). In vitro experiments involved measuring the calcification of human aortic valvular interstitial cells (VICs) and evaluating cytokine release from THP-1 cells, a human leukemia monocytic-like cell line, following CerS5 knockdown.

RESULTS

CerS5-/- mice showed a reduced peak velocity compared to WT only in the experiment with WD. Likewise, we observed reduced immune cell infiltration and calcification in the aortic valve of CerS5-/- mice, but only on WD. In vitro, calcification was reduced after knockdown of CerS5 in VICs, while THP-1 cells exhibited a decreased inflammatory response following CerS5 knockdown.

CONCLUSION

We conclude that CerS5 is an important mediator for the development of AVS in mice on WD and regulates critical pathophysiological hallmarks of AVS formation. CerS5 is therefore an interesting target for pharmacological therapy and merits further investigation.

eIF2α-mediated integrated stress response links multiple intracellular signaling pathways to reprogram vascular smooth muscle cell fate in carotid artery plaque

Background

Carotid arterial atherosclerotic stenosis is a well-recognized pathological basis of ischemic stroke; however, its underlying molecular mechanisms remain unknown. Vascular smooth muscle cells (VSMCs) play fundamental roles in the initiation and progression of atherosclerosis. Organelle dynamics have been reported to affect atherosclerosis development. However, the association between organelle dynamics and various cellular stresses in atherosclerotic progression remain ambiguous.

Methods

In this study, we conducted transcriptomics and bioinformatics analyses of stable and vulnerable carotid plaques. Primary VSMCs were isolated from carotid plaques and subjected to histopathological staining to determine their expression profiles. Endoplasmic reticulum (ER), mitochondria, and lysosome dynamics were observed in primary VSMCs and VSMC cell lines using live-cell imaging. Moreover, the mechanisms underlying disordered organelle dynamics were investigated using comprehensive biological approaches.

Results

ER whorls, a representative structural change under ER stress, are prominent dynamic reconstructions of VSMCs between vulnerable and stable plaques, followed by fragmented mitochondria and enlarged lysosomes, suggesting mitochondrial stress and lysosomal defects, respectively. Induction of mitochondrial stress alleviated ER stress and autophagy in an eukaryotic translation initiation factor (eIF)-2α-dependent manner. Furthermore, the effects of eIF2α on ER stress, mitochondrial stress, and lysosomal defects were validated using clinical samples.

Conclusion

Our results indicate that morphological and functional changes in VSMC organelles, especially in ER whorls, can be used as reliable biomarkers for atherosclerotic progression. Moreover, eIF2α plays an important role in integrating multiple stress-signaling pathways to determine the behavior and fate of VSMCs.

Vascular calcification and cellular signaling pathways as potential therapeutic targets

Increased vascular calcification (VC) is observed in patients with cardiovascular diseases such as atherosclerosis, diabetes, and chronic kidney disease. VC is divided into three types according to its location: intimal, medial, and valvular. Various cellular signaling pathways are associated with VC, including the Wnt, mitogen-activated protein kinase, phosphatidylinositol-3 kinase/Akt, cyclic nucleotide-dependent protein kinase, protein kinase C, calcium/calmodulin-dependent kinase II, adenosine monophosphate-activated protein kinase/mammalian target of rapamycin, Ras homologous GTPase, apoptosis, Notch, and cytokine signaling pathways. In this review, we discuss the literature concerning the key cellular signaling pathways associated with VC and their role as potential therapeutic targets. Inhibitors to these pathways represent good candidates for use as potential therapeutic agents for the prevention and treatment of VC.

Hypoxia-induced signaling in the cardiovascular system: pathogenesis and therapeutic targets

Hypoxia, characterized by reduced oxygen concentration, is a significant stressor that affects the survival of aerobic species and plays a prominent role in cardiovascular diseases. From the research history and milestone events related to hypoxia in cardiovascular development and diseases, The "hypoxia-inducible factors (HIFs) switch" can be observed from both temporal and spatial perspectives, encompassing the occurrence and progression of hypoxia (gradual decline in oxygen concentration), the acute and chronic manifestations of hypoxia, and the geographical characteristics of hypoxia (natural selection at high altitudes). Furthermore, hypoxia signaling pathways are associated with natural rhythms, such as diurnal and hibernation processes. In addition to innate factors and natural selection, it has been found that epigenetics, as a postnatal factor, profoundly influences the hypoxic response and progression within the cardiovascular system. Within this intricate process, interactions between different tissues and organs within the cardiovascular system and other systems in the context of hypoxia signaling pathways have been established. Thus, it is the time to summarize and to construct a multi-level regulatory framework of hypoxia signaling and mechanisms in cardiovascular diseases for developing more therapeutic targets and make reasonable advancements in clinical research, including FDA-approved drugs and ongoing clinical trials, to guide future clinical practice in the field of hypoxia signaling in cardiovascular diseases.

Identifying lipid traces of atherogenic mechanisms in human carotid plaque

BACKGROUND AND AIMS

Lipids play an important role in atherosclerotic plaque development and are interesting candidate predictive biomarkers. However, the link between circulating lipids, accumulating lipids in the vessel wall, and plaque destabilization processes in humans remains largely unknown. This study aims to provide new insights into the role of lipids in atherosclerosis using lipidomics and mass spectrometry imaging to investigate lipid signatures in advanced human carotid plaque and plasma samples.

METHODS

We used lipidomics and desorption electrospray ionization mass spectrometry imaging (DESI-MSI) to investigate lipid signatures of advanced human carotid plaque and plasma obtained from patients who underwent carotid endarterectomy (n = 14 out of 17 whose plaque samples were analyzed by DESI-MSI). Multivariate data analysis and unsupervised clustering were applied to identify lipids that were the most discriminative species between different patterns in plaque and plasma. These patterns were interpreted by quantitative comparison with conventional histology.

RESULTS

Lipidomics detected more than 300 lipid species in plasma and plaque, with markedly different relative abundances. DESI-MSI visualized the spatial distribution of 611 lipid-related m/z features in plaques, of which 330 m/z features could be assigned based on exact mass, comparison to the lipidomic data, and high mass resolution MSI. Matching spatial lipid patterns to histological areas of interest revealed several molecular species that were colocalized with pertinent disease processes in plaque including specific sphingomyelin and ceramide species with calcification, phospholipids and free fatty acids with inflammation, and triacylglycerols and phosphatidylinositols with fibrin-rich areas.

CONCLUSIONS

By comparing lipid species in plaque and plasma, we identified those circulating species that were also prominently present in plaque. Quantitative comparison of lipid spectral patterns with histology revealed the presence of specific lipid species in destabilized plaque areas, corroborating previous in vitro and animal studies.

The therapeutic potential of sphingolipids for cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide and Inflammation plays a critical role in the development of CVD. Despite considerable progress in understanding the underlying mechanisms and various treatment options available, significant gaps in therapy necessitate the identification of novel therapeutic targets. Sphingolipids are a family of lipids that have gained attention in recent years as important players in CVDs and the inflammatory processes that underlie their development. As preclinical studies have shown that targeting sphingolipids can modulate inflammation and ameliorate CVDs, targeting sphingolipids has emerged as a promising therapeutic strategy. This review discusses the current understanding of sphingolipids' involvement in inflammation and cardiovascular diseases, the existing therapeutic approaches and gaps in therapy, and explores the potential of sphingolipids-based drugs as a future avenue for CVD treatment.

Mitophagy in atherosclerosis: from mechanism to therapy

Mitophagy is a type of autophagy that can selectively eliminate damaged and depolarized mitochondria to maintain mitochondrial activity and cellular homeostasis. Several pathways have been found to participate in different steps of mitophagy. Mitophagy plays a significant role in the homeostasis and physiological function of vascular endothelial cells, vascular smooth muscle cells, and macrophages, and is involved in the development of atherosclerosis (AS). At present, many medications and natural chemicals have been shown to alter mitophagy and slow the progression of AS. This review serves as an introduction to the field of mitophagy for researchers interested in targeting this pathway as part of a potential AS management strategy.

Sphingolipids and Atherosclerosis: The Dual Role of Ceramide and Sphingosine-1-Phosphate

Sphingolipids are bioactive molecules that play either pro- and anti-atherogenic roles in the formation and maturation of atherosclerotic plaques. Among SLs, ceramide and sphingosine-1-phosphate showed antithetic properties in regulating various molecular mechanisms and have emerged as novel potential targets for regulating the development of atherosclerosis. In particular, maintaining the balance of the so-called ceramide/S1P rheostat is important to prevent the occurrence of endothelial dysfunction, which is the trigger for the entire atherosclerotic process and is strongly associated with increased oxidative stress. In addition, these two sphingolipids, together with many other sphingolipid mediators, are directly involved in the progression of atherogenesis and the formation of atherosclerotic plaques by promoting the oxidation of low-density lipoproteins (LDL) and influencing the vascular smooth muscle cell phenotype. The modulation of ceramide and S1P levels may therefore allow the development of new antioxidant therapies that can prevent or at least impair the onset of atherogenesis, which would ultimately improve the quality of life of patients with coronary artery disease and significantly reduce their mortality.

miR-146-5p restrains calcification of vascular smooth muscle cells by suppressing TRAF6

Vascular calcification is a prominent manifestation of advanced atherosclerosis. Tumor necrosis factor-receptor-associated factors (TRAFs) were reported to participate in atherosclerosis development. In this study, the role and mechanism of TRAF6 in vascular calcification were explored. To induce the vascular calcification, oxidized low-density lipoprotein (Ox-LDL) was applied to treat vascular smooth muscle cells (VSMCs). TRAF6 protein expression in VSMCs was assessed by western blotting. Osteogenic differentiation of VSMCs was assessed by alkaline phosphatase activity analysis. Mineral deposition in VSMCs was evaluated by von Kossa staining. VSMC proliferation, migration, apoptosis, inflammation, and reactive oxygen species (ROS) generation were detected using cell counting kit-8, Transwell, flow cytometry, reverse transcriptase quantitative polymerase chain reaction (RT-qPCR), and dichlorodihydrofluorescein diacetate staining, respectively. Luciferase reporter assay was utilized to identify the binding relationship between miR-146-5p and TRAF6 in VSMCs. We found that Ox-LDL administration induced the calcification of VSMCs and elevated the TRAF6 level. TRAF6 knockdown restrained VSMC calcification, proliferation, migration, inflammation, and ROS generation caused by Ox-LDL. Mechanically, TRAF6 was targeted by miR-146-5p in VSMCs. Furthermore, TRAF6 overexpression offset the inhibitory effects of miR-146-5p upregulation on vascular calcification in VSMCs under the Ox-LDL condition. Overall, miR-146-5p restrains the calcification of VSMCs by suppressing TRAF6.

Ablation of Sphingosine Kinase 1 Protects Cornea from Neovascularization in a Mouse Corneal Injury Model

The purpose of this study was to investigate the role of sphingosine kinase 1 (SphK1), which generates sphingosine-1-phosphate (S1P), in corneal neovascularization (NV). Wild-type (WT) and Sphk1 knockout (Sphk1^−/−) mice received corneal alkali-burn treatment to induce corneal NV by placing a 2 mm round piece of Whatman No. 1 filter paper soaked in 1N NaOH on the center of the cornea for 20 s. Corneal sphingolipid species were extracted and identified using liquid chromatography/mass spectrometry (LC/MS). The total number of tip cells and those positive for ethynyl deoxy uridine (EdU) were quantified. Immunocytochemistry was done to examine whether pericytes were present on newly forming blood vessels. Cytokine signaling and angiogenic markers were compared between the two groups using multiplex assays. Data were analyzed using appropriate statistical tests. Here, we show that ablation of SphK1 can significantly reduce NV invasion in the cornea following injury. Corneal sphingolipid analysis showed that total levels of ceramides, monohexosyl ceramides (HexCer), and sphingomyelin were significantly elevated in Sphk^−/− corneas compared to WT corneas, with a comparable level of sphingosine among the two genotypes. The numbers of total and proliferating endothelial tip cells were also lower in the Sphk1^−/− corneas following injury. This study underscores the role of S1P in post-injury corneal NV and raises further questions about the roles played by ceramide, HexCer, and sphingomyelin in regulating corneal NV. Further studies are needed to unravel the role played by bioactive sphingolipids in maintenance of corneal transparency and clear vision.

Vascular Smooth Muscle Cell Neutral Sphingomyelinase 2 in the Release of Exosomes and Vascular Calcification

Vascular calcification (VC) is the pathological precipitation of calcium salts in the walls of blood vessels. It is a risk factor for cardiovascular events and their associated mortality. VC can be observed in a variety of cardiovascular diseases and is most prominent in diseases that are associated with dysregulated mineral homeostasis such as in chronic kidney disease. Local factors and mechanisms underlying VC are still incompletely understood, but it is appreciated that VC is a multifactorial process in which vascular smooth muscle cells (VSMCs) play an important role. VSMCs participate in VC by releasing extracellular vesicles (EVs), the extent, composition, and propensity to calcify of which depend on VSMC phenotype and microenvironment. Currently, no targeted therapy is available to treat VC. In-depth knowledge of molecular players of EV release and the understanding of their mechanisms constitute a vital foundation for the design of pharmacological treatments to combat VC effectively. This review highlights our current knowledge of VSMCs in VC and focuses on the biogenesis of exosomes and the role of the neutral Sphingomyelinase 2 (nSMase2).

The Role of Obesity, Inflammation and Sphingolipids in the Development of an Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a local dilatation of the vessel equal to or exceeding 3 cm. It is a disease with a long preclinical period commonly without any symptoms in its initial stage. Undiagnosed for years, aneurysm often leads to death due to vessel rupture. The basis of AAA pathogenesis is inflammation, which is often associated with the excess of adipose tissue, especially perivascular adipose tissue, which synthesizes adipocytokines that exert a significant influence on the formation of aneurysms. Pro-inflammatory cytokines such as resistin, leptin, and TNFα have been shown to induce changes leading to the formation of aneurysms, while adiponectin is the only known compound that is secreted by adipose tissue and limits the development of aneurysms. However, in obesity, adiponectin levels decline. Moreover, inflammation is associated with an increase in the amount of macrophages infiltrating adipose tissue, which are the source of matrix metalloproteinases (MMP) involved in the degradation of the extracellular matrix, which are an important factor in the formation of aneurysms. In addition, an excess of body fat is associated with altered sphingolipid metabolism. It has been shown that among sphingolipids, there are compounds that play an opposite role in the cell: ceramide is a pro-apoptotic compound that mediates the development of inflammation, while sphingosine-1-phosphate exerts pro-proliferative and anti-inflammatory effects. It has been shown that the increase in the level of ceramide is associated with a decrease in the concentration of adiponectin, an increase in the concentration of TNFα, MMP-9 and reactive oxygen species (which contribute to the apoptosis of vascular smooth muscle cell). The available data indicate a potential relationship between obesity, inflammation and disturbed sphingolipid metabolism with the formation of aneurysms; therefore, the aim of this study was to systematize the current knowledge on the role of these factors in the pathogenesis of abdominal aortic aneurysm.

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.

Protein kinases in cardiovascular diseases

ABSTRACT

Cardiovascular disease (CVD) remains the leading cause of death worldwide. Therefore, exploring the mechanism of CVDs and critical regulatory factors is of great significance for promoting heart repair, reversing cardiac remodeling, and reducing adverse cardiovascular events. Recently, significant progress has been made in understanding the function of protein kinases and their interactions with other regulatory proteins in myocardial biology. Protein kinases are positioned as critical regulators at the intersection of multiple signals and coordinate nearly every aspect of myocardial responses, regulating contractility, metabolism, transcription, and cellular death. Equally, reconstructing the disrupted protein kinases regulatory network will help reverse pathological progress and stimulate cardiac repair. This review summarizes recent researches concerning the function of protein kinases in CVDs, discusses their promising clinical applications, and explores potential targets for future treatments.

Apocynum Leaf Extract Suppresses the Progress of Atherosclerosis in Rats via the FKN/SYK/p38 Signal Pathway

To investigate the antiatherosclerotic effects of flavonoids extracted from Apocynum venetum (AVF) leaves in atherosclerotic rats and the underlying mechanisms, a total of 72 male Wistar rats were randomly divided into six groups: control group, model group, simvastatin group, low-dose AVF group, medium-dose AVF group, and high-dose AVF group. Atherosclerosis in rats was induced with a high-fat diet and an intraperitoneal injection of VD₃ once daily for three contiguous days at a total injection dose of 70 U/kg. At the end of the 13^th week, total serum cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) contents were measured. The hematoxylin-eosin (HE) staining was applied to evaluate the morphological changes. The ELISA method was used to detect related inflammatory factors and oxidative stress indicators. The corresponding protein expression and the mRNA level were detected by western blot analysis and reverse transcriptase PCR. HE staining showed that the thoracic aorta wall was thickened, and the aortic subendothelial foam cells and lipid vacuoles were reduced in the medium/high-AVF groups. Similarly, the TC, TG, LDL-C, and malondialdehyde (MDA) levels in the model group were significantly higher, but the HDL-C level and superoxide dismutase (SOD) activity were lower than those of the control group, and these effects were ameliorated by treatment with simvastatin or AVF. ELISA results showed that compared with the control group, the model group C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) results were significantly increased, and the medium AVF and high AVF could significantly reduce the expression of related inflammatory factors. The AVF inhibited intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin mRNA and related protein expression in the aorta in atherosclerotic rats. Western blot analysis also showed that AVF can significantly reduce the protein expression of fractalkine (FKN), spleen tyrosine kinase (SYK), and p38 mitogen-activated protein kinase (p38) in the rat aorta. We believe that the AVF can effectively reduce blood lipid levels in rats with atherosclerosis and delay atherosclerotic progression by inhibiting excessive inflammatory factors and inhibiting related adhesion factors. The underlying mechanism may be related to the FKN/SYK/p38 signaling pathway activity. Our results contribute to validating the traditional use of the Apocynum leaf extract in the treatment of atherosclerosis.

Acid sphingomyelinase promotes SGK1-dependent vascular calcification

In chronic kidney disease (CKD), hyperphosphatemia is a key factor promoting medial vascular calcification, a common complication associated with cardiovascular events and high mortality. Vascular calcification involves osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs), but the complex signaling events inducing pro-calcific pathways are incompletely understood. The present study investigated the role of acid sphingomyelinase (ASM)/ceramide as regulator of VSMC calcification. In vitro, both, bacterial sphingomyelinase and phosphate increased ceramide levels in VSMCs. Bacterial sphingomyelinase as well as ceramide supplementation stimulated osteo-/chondrogenic transdifferentiation during control and high phosphate conditions and augmented phosphate-induced calcification of VSMCs. Silencing of serum- and glucocorticoid-inducible kinase 1 (SGK1) blunted the pro-calcific effects of bacterial sphingomyelinase or ceramide. Asm deficiency blunted vascular calcification in a cholecalciferol-overload mouse model and ex vivo isolated-perfused arteries. In addition, Asm deficiency suppressed phosphate-induced osteo-/chondrogenic signaling and calcification of cultured VSMCs. Treatment with the functional ASM inhibitors amitriptyline or fendiline strongly blunted pro-calcific signaling pathways in vitro and in vivo. In conclusion, ASM/ceramide is a critical upstream regulator of vascular calcification, at least partly, through SGK1-dependent signaling. Thus, ASM inhibition by repurposing functional ASM inhibitors to reduce the progression of vascular calcification during CKD warrants further study.

Regulatory role of mammalian target of rapamycin signaling in exosome secretion and osteogenic changes in smooth muscle cells lacking acid ceramidase gene

Acid ceramidase (murine gene code: Asah1) (50 kDa) belongs to N-terminal nucleophile hydrolase family. This enzyme is located in the lysosome, which mediates conversion of ceramide (CER) into sphingosine and free fatty acids at acidic pH. CER plays an important role in intracellular sphingolipid metabolism and its increase causes inflammation. The mammalian target of rapamycin complex 1 (mTORC1) signaling on late endosomes (LEs)/lysosomes may control cargo selection, membrane biogenesis, and exosome secretion, which may be fine controlled by lysosomal sphingolipids such as CER. This lysosomal-CER-mTOR signaling may be a crucial molecular mechanism responsible for development of arterial medial calcification (AMC). Torin-1 (5 mg/kg/day), an mTOR inhibitor, significantly decreased aortic medial calcification accompanied with decreased expression of osteogenic markers like osteopontin (OSP) and runt-related transcription factor 2 (RUNX2) and upregulation of smooth muscle 22α (SM22-α) in mice receiving high dose of Vitamin D (500 000 IU/kg/day). Asah1^fl/fl /SM^Cre mice had markedly increased co-localization of mTORC1 with lysosome-associated membrane protein-1 (Lamp-1) (lysosome marker) and decreased co-localization of vacuolar protein sorting-associated protein 16 (VPS16) (a multivesicular bodies [MVBs] marker) with Lamp-1, suggesting mTOR activation caused reduced MVBs interaction with lysosomes. Torin-1 significantly reduced the co-localization of mTOR vs Lamp-1, increased lysosome-MVB interaction which was associated with reduced accumulation of CD63 and annexin 2 (exosome markers) in the coronary arterial wall of mice. Using coronary artery smooth muscle cells (CASMCs), P_i -stimulation significantly increased p-mTOR expression in Asah1^fl/fl /SM^Cre CASMCs as compared to WT/WT cells associated with increased calcium deposition and mineralization. Torin-1 blocked P_i -induced calcium deposition and mineralization. siRNA mTOR and Torin-1 significantly reduce co-localization of mTORC1 with Lamp-1, increased VPS16 vs Lamp-1 co-localization in P_i -stimulated CASMCs, associated with decreased exosome release. Functionally, Torin-1 significantly reduces arterial stiffening as shown by restoration from increased pulse wave velocity and decreased elastin breaks. These results suggest that lysosomal CER-mTOR signaling may play a critical role for the control of lysosome-MVB interaction, exosome secretion and arterial stiffening during AMC.

miR-33a-5p Suppresses ox-LDL-Stimulated Calcification of Vascular Smooth Muscle Cells by Targeting METTL3

Oxidized low-density lipoprotein (ox-LDL) accumulation in the vascular wall plays a pivotal role in the development of atherosclerosis and vascular calcification. However, few studies focus on the regulatory roles of microRNAs in ox-LDL stimulated vascular calcification. The aim of the present study was to investigate how miR-33a-5p regulated vascular calcification stimulated by ox-LDL. In the present study, miR-33a-5p was downregulated during vascular smooth muscle cells (VSMCs) calcification and upon ox-LDL treatment. ox-LDL significantly stimulated VSMCs calcification, while miR-33a-5p overexpression by its mimics transfection inhibited alkaline phosphatase (ALP) activity, mineralization and marker genes associated with VSMCs calcification even in the presence of ox-LDL. Methyltransferase like 3 (METTL3) was the target gene of miR-33a-5p. METTL3 was upregulated during VSMCs calcification and upon ox-LDL treatment. When VSMCs were transfected with miR-33a-5p mimics, METTL3 was downregulated. METTL3 downregulation by siRNA method decreased VSMCs calcification even in the presence of ox-LDL. Taken together, these results suggest miR-33a-5p suppresses VSMCs calcification stimulated by ox-LDL via targeting METTL3, highlighting the critical role of miR-33a-5p/METTL3 in vascular calcification.

Exosomal miR-512-3p derived from mesenchymal stem cells inhibits oxidized low-density lipoprotein-induced vascular endothelial cells dysfunction via regulating Keap1

Atherosclerosis (AS) is a prevalent chronic inflammatory vascular disease. Upregulated oxidized low-density lipoprotein (ox-LDL) in the serum has been found to induce endothelial cells (ECs) apoptosis by increasing oxidative stress and promoting inflammatory response, which are essential mechanisms of AS development. Mesenchymal stem cells (MSCs), which secrete exosomes to transport microRNAs (miRNAs) and regulate cell functions, have become a research focus in recent years. The results of this study manifested that MSCs-derived exosomes were phagocytosed by EC. In addition, miR-512-3p enriched by MSCs- derived exosomes markedly inhibited ox-LDL-mediated EC damage, namely, accelerated EC proliferation, inhibited Caspase-3 activation and cell apoptosis, inhibited the levels of inflammatory cytokines (tumor necrosis factor-α, interleukin (IL)-1β, and IL-6) and oxidative factor MDA, and increased the contents of SOD and GSH-PX. Mechanistically, Keleh-like ECH-associated protein 1 (Keap1) was proved to be a functional target of miR-512-3p. Furthermore, silencing Keap1 limited ox-LDL-mediated EC cell dysfunction, while over-expressing Keap1 mitigated the exosomal miR-512-3p-mediated protective effect in Ox-LDL-induced EC. The above results confirmed that miR-512-3p shuttled by MSCs-derived exosomes protected EC against ox-LDL by targeting Keap1.

Long noncoding RNA SNHG14 regulates ox-LDL-induced atherosclerosis cell proliferation and apoptosis by targeting miR-186-5p/WIPF2 axis

To investigate the role of small nucleolus RNA host gene 14 (SNHG14) in the progression of atherosclerosis (AS), bioinformatics analysis, and other relevant experiments (cell counting kit-8, flow cytometry, quantitative real-time polymerase chain reaction, luciferase reporter, RNA immunoprecipitation, RNA pull-down, and western blot assays) were done. The current study revealed that SNHG14 level was high in the serum of AS patients and oxidized low-density lipoprotein (ox-LDL)-induced AS cell lines. Besides, we found that SNHG14 accelerated cell proliferation while inhibited cell apoptosis in ox-LDL-induced AS cell lines. Next, SNHG14 was confirmed to be a sponge for miR-186-5p in AS cells, and it was validated that SNHG14 regulated AS cell proliferation and apoptosis by sponging miR-186-5p. Moreover, we uncovered that WAS-interacting protein family member 2 (WIPF2) was a downstream target of miR-186-5p in AS cells. Finally, it was demonstrated that miR-186-5p modulated AS cell proliferation and apoptosis via targeting WIPF2. To conclude, our research disclosed that SNHG14 affected ox-LDL-induced AS cell proliferation and apoptosis through miR-186-5p/WIPF2 axis, which may provide a theoretical basis for the treatment and diagnosis of AS.

Puerarin protects vascular smooth muscle cells from oxidized low-density lipoprotein-induced reductions in viability via inhibition of the p38 MAPK and JNK signaling pathways

Puerarin belongs to the family of flavonoids extracted from Pueraria lobata (Wild.) Ohwi, which exhibits antioxidative, anti-inflammatory, anti-hyperglycemic, antitumor, anti-hypertensive and anti-atherosclerotic activities. In the present study, the effects of puerarin on oxidized low-density lipoprotein (ox-LDL)-stimulated vascular smooth muscle cells (VSMCs) were explored to understand the mechanisms underlying the anti-atherosclerotic effects of puerarin. VSMCs were treated with various concentrations of puerarin (0, 20, 40 and 80 µM) prior to stimulation with ox-LDL (50 µg/ml). VSMC viability was evaluated by performing MTT and Cell Counting Kit-8 assays. Moreover, superoxide dismutase (SOD) and malondialdehyde (MDA) levels were measured by performing ELISAs. The mRNA expression levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were determined via reverse transcription-quantitative PCR. Western blotting was conducted to assess the levels of p38-MAPK and JNK phosphorylation. The results indicated that puerarin inhibited ox-LDL-induced VSMC viability. Moreover, puerarin significantly decreased the mRNA expression levels of IL-6 and TNF-α, significantly reduced the production of MDA and significantly increased SOD activity in ox-LDL-stimulated VSMCs. Puerarin also inhibited ox-LDL-induced phosphorylation of p38 and JNK in VSMCs. The results suggested that puerarin reduced ox-LDL-induced VSMC viability via inhibition of the p38 MAPK and JNK signaling pathways. The present study provided theoretical evidence that puerarin may serve as a therapeutic agent to reduce the development of atherosclerosis.

Duchenne muscular dystrophy (DMD) cardiomyocyte-secreted exosomes promote the pathogenesis of DMD-associated cardiomyopathy

Cardiomyopathy is a leading cause of early mortality in Duchenne muscular dystrophy (DMD). There is a need to gain a better understanding of the molecular pathogenesis for the development effective therapies. Exosomes (exo) are secreted vesicles and exert effects via their RNA, lipid and protein cargo. The role of exosomes in disease pathology is unknown. Exosomes derived from stem cells have demonstrated cardioprotection in the murine DMD heart. However, it is unknown how the disease status of the donor cell type influences exosome function. Here, we sought to determine the phenotypic responses of DMD cardiomyocytes (DMD-iCMs) after long-term exposure to DMD cardiac exosomes (DMD-exo). DMD-iCMs were vulnerable to stress, evidenced by production of reactive oxygen species, the mitochondrial membrane potential and cell death levels. Long-term exposure to non-affected exosomes (N-exo) was protective. By contrast, long-term exposure to DMD-exo was not protective, and the response to stress improved with inhibition of DMD-exo secretion in vitro and in vivo The microRNA (miR) cargo, but not exosome surface peptides, was implicated in the pathological effects of DMD-exo. Exosomal surface profiling revealed N-exo peptides associated with PI3K-Akt signaling. Transcriptomic profiling identified unique changes with exposure to either N- or DMD-exo. Furthermore, DMD-exo miR cargo regulated injurious pathways, including p53 and TGF-beta. The findings reveal changes in exosomal cargo between healthy and diseased states, resulting in adverse outcomes. Here, DMD-exo contained miR changes, which promoted the vulnerability of DMD-iCMs to stress. Identification of these molecular changes in exosome cargo and effectual phenotypes might shed new light on processes underlying DMD cardiomyopathy.This article has an associated First Person interview with the first author of the paper.

The role of oxidized phospholipids in the development of disease

Oxidized phospholipids (OxPLs), complex mixtures of phospholipid oxidation products generated during normal or pathological processes, are increasingly recognized to show bioactive effects on many cellular signalling pathways. There is a growing body of evidence showing that OxPLs play an important role in many diseases, so it is essential to define the specific role of OxPLs in different diseases for the design of disease therapies. In vastly diverse pathological processes, OxPLs act as pro-inflammatory agents and contribute to the progression of many diseases; in addition, they play a role in anti-inflammatory processes, promoting the dissipation of inflammation and inhibiting the progression of some diseases. In addition to participating in the regulation of inflammatory responses, OxPLs affect the occurrence and development of diseases through other pathways, such as apoptosis promotion. In this review, the different and even opposite effects of different OxPL molecular species are discussed. Furthermore, the specific effects of OxPLs in various diseases, as well as the receptor and cellular mechanisms involved, are summarized.

Circulating Receptor Activator of Nuclear Factor kB Ligand and triglycerides are associated with progression of lower limb arterial calcification in type 2 diabetes: a prospective, observational cohort study

Background

Lower limb arterial calcification is a frequent, underestimated but serious complication of diabetes. The DIACART study is a prospective cohort study designed to evaluate the determinants of the progression of lower limb arterial calcification in 198 patients with type 2 diabetes.

Methods

Lower limb arterial calcification scores were determined by computed tomography at baseline and after a mean follow up of 31.20 ± 3.86 months. Serum RANKL (Receptor Activator of Nuclear factor kB Ligand) and bone remodeling, inflammatory and metabolic parameters were measured at baseline. The predictive effect of these markers on calcification progression was analyzed by a multivariate linear regression model.

Results

At baseline, mean ± SD and median lower limb arterial calcification scores were, 2364 ± 5613 and 527 respectively and at the end of the study, 3739 ± 6886 and 1355 respectively. Using multivariate analysis, the progression of lower limb arterial log calcification score was found to be associated with (β coefficient [slope], 95% CI, p-value) baseline log(calcification score) (1.02, 1.00–1.04, p < 0.001), triglycerides (0.11, 0.03–0.20, p = 0.007), log(RANKL) (0.07, 0.02–0.11, p = 0.016), previous ischemic cardiomyopathy (0.36, 0.15–0.57, p = 0.001), statin use (0.39, 0.06–0.72, p = 0.023) and duration of follow up (0.04, 0.01–0.06, p = 0.004).

Conclusion

In patients with type 2 diabetes, lower limb arterial calcification is frequent and can progress rapidly. Circulating RANKL and triglycerides are independently associated with this progression. These results open new therapeutic perspectives in peripheral diabetic calcifying arteriopathy.

Trial registration NCT02431234

Inflammation and cardiovascular diseases: lessons from seminal clinical trials

Inflammation has been long regarded as a key contributor to atherosclerosis. Inflammatory cells and soluble mediators play critical roles throughout arterial plaque development and accordingly, targeting inflammatory pathways effectively reduces atherosclerotic burden in animal models of cardiovascular (CV) diseases. Yet, clinical translation often led to inconclusive or even contradictory results. The Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) followed by the Colchicine Cardiovascular Outcomes Trial (COLCOT) were the first two randomized clinical trials to convincingly demonstrate the effectiveness of specific anti-inflammatory treatments in the field of CV prevention, while other phase III trials-including the Cardiovascular Inflammation Reduction Trial one using methotrexate-were futile. This manuscript reviews the main characteristics and findings of recent anti-inflammatory Phase III trials in cardiology and discusses their similarities and differences in order to get further insights into the contribution of specific inflammatory pathways on CV outcomes. CANTOS and COLCOT demonstrated efficacy of two anti-inflammatory drugs (canakinumab and colchicine, respectively) in the secondary prevention of major adverse CV events (MACE) thus providing the first confirmation of the involvement of a specific inflammatory pathway in human atherosclerotic CV disease (ASCVD). Also, they highlighted the NOD-, LRR-, and pyrin domain-containing protein 3 inflammasome-related pathway as an effective therapeutic target to blunt ASCVD. In contrast, other trials interfering with a number of inflammasome-independent pathways failed to provide benefit. Lastly, all anti-inflammatory trials underscored the importance of balancing the risk of impaired host defence with an increase in infections and the prevention of MACE in CV patients with residual inflammatory risk.

Apelin-13 attenuates high glucose-induced calcification of MOVAS cells by regulating MAPKs and PI3K/AKT pathways and ROS-mediated signals

Vascular calcification (VC) is an inducement of many cardiovascular diseases. Clinic evidences have confirmed that diabetes was the independent risk factor for VC, and the mechanism has not been well explored. Apelin as a ligand molecule is widely found in the cardiovascular system and showed potential in inhibiting VC, but the inhibitory effect and mechanism of apelin-13 against high glucose-induced VC have not been investigated yet. Herein, apelin-13 was employed to inhibit high glucose-induced VC in mouse aortic vascular smooth muscle cells (MOVAS), and the underlying mechanism was explored. The results showed that apelin-13 significantly inhibited high glucose-induced cells proliferation, migration and invasion of MOVAS cells. Apelin-13 also effectively attenuated high glucose-induced calcification by inhibiting alkaline phosphatase (ALP) activity and expression. Further investigation revealed that apelin-13 dramatically suppressed high glucose-induced DNA damage through inhibiting reactive oxide species (ROS) generation. Moreover, apelin-13 also effectively improved high glucose-induced dysfunction of MAPKs and PI3K/AKT. Inhibition of ERK by inhibitor (U0126) significantly blocked high glucose-induced calcification, which further confirmed the significance of MAPKs. Taken together, these results suggested that apelin-13 had the potential to attenuate high glucose-induced calcification of MOVAS cells by inhibiting ROS-mediated DNA damage and regulating MAPKs and PI3K/AKT pathways. Our findings validated the strategy of using apelin-13 maybe a novel way in treating high glucose-mediated VC.

Electronegative low-density lipoprotein of patients with metabolic syndrome induces pathogenesis of aorta through disruption of the stimulated by retinoic acid 6 cascade

AIMS/INTRODUCTION

Electronegative low-density lipoprotein (L5) is the most atherogenic fraction of low-density lipoprotein and is elevated in people with metabolic syndrome (MetS), whereas the retinol-binding protein 4 receptor (stimulated by retinoic acid 6 [STRA6]) cascade is disrupted in various organs of patients with obesity-related diseases. Our objective was to investigate whether L5 from MetS patients capably induces pathogenesis of aorta through disrupting the STRA6 cascade.

MATERIAL AND METHODS

We examined the in vivo and in vitro effects of L5 on the STRA6 cascade and aortic atherogenic markers. To investigate the role of this cascade on atherosclerotic formation, crbp1 transfection was carried out in vitro.

RESULTS

This study shows that L5 activates atherogenic markers (p38 mitogen-activated protein kinases, pSmad2 and matrix metallopeptidase 9) and simultaneously suppresses STRA6 signals (STRA6, cellular retinol-binding protein 1, lecithin-retinol acyltransferase, retinoic acid receptor-α and retinoid X receptor-α) in aortas of L5-injected mice and L5-treated human aortic endothelial cell lines and human aortic smooth muscle cell lines. These L5-induced changes of the STRA6 cascade and atherogenic markers were reversed in aortas of LOX1-/- mice and in LOX1 ribonucleic acid-silenced human aortic endothelial cell lines and human aortic smooth muscle cell lines. Furthermore, crbp1 gene transfection reversed the disruption of the STRA6 cascade, the phosphorylation of p38 mitogen-activated protein kinases and Smad2, and the elevation of matrix metallopeptidase 9 in L5-treated human aortic endothelial cell lines.

CONCLUSIONS

This study shows that L5 from MetS patients induces atherogenic markers by disrupting STRA6 signaling. Suppression of STRA6 might be one novel pathogenesis of aorta in patients with MetS.

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.

Arterial Medial Calcification through Enhanced small Extracellular Vesicle Release in Smooth Muscle-Specific Asah1 Gene Knockout Mice

Arterial medial calcification (AMC) involves an increased small extracellular vesicle (sEV) secretion and apatite calcium precipitation in the arterial wall. The mechanisms mediating AMC remain poorly understood. In the present study, smooth muscle-specific acid ceramidase (Ac) gene knockout mice (Asah1^fl/fl/SM^Cre) were used to demonstrate the role of lysosomal ceramide signaling pathway in AMC. Asah1^fl/fl/SM^Cre mice were found to have more severe AMC in both aorta and coronary arteries compared to their littermates (Asah1^fl/fl/SM^wt and WT/WT mice) after receiving a high dose vitamin D. These mice also had pronounced upregulation of osteopontin and RUNX2 (osteogenic markers), CD63, AnX2 (sEV markers) and ALP expression (mineralization marker) in the arterial media. In cultured coronary arterial smooth muscle cells (CASMCs) from Asah1^fl/fl/SM^Cre mice, high dose of P_i led to a significantly increased calcium deposition, phenotypic change and sEV secretion compared to WT CASMCs, which was associated with reduced lysosome-multivesicular body (MVB) interaction. Also, GW4869, sEV release inhibitor decreased sEV secretion and calcification in these cells. Lysosomal transient receptor potential mucolipin 1 (TRPML1) channels regulating lysosome interaction with MVBs were found remarkably inhibited in Asah1^fl/fl/SM^Cre CASMCs as shown by GCaMP3 Ca²⁺ imaging and Port-a-Patch patch clamping of lysosomes. Lysosomal Ac in SMCs controls sEV release by regulating lysosomal TRPML1 channel activity and lysosome-MVB interaction, which importantly contributes to phenotypic transition and AMC.

Endoplasmic Reticulum Stress Contributes to Indomethacin-Induced Glioma Apoptosis

The dormancy of cellular apoptotic machinery has been highlighted as a crucial factor in therapeutic resistance, recurrence, and poor prognosis in patients with malignancy, such as malignant glioma. Increasing evidence indicates that nonsteroidal anti-inflammatory drugs (NSAIDs) confer chemopreventive effects, and indomethacin has been shown to have a novel chemotherapeutic application targeting glioma cells. To extend these findings, herein, we studied the underlying mechanisms of apoptosis activation caused by indomethacin in human H4 and U87 glioma cells. We found that the glioma cell-killing effects of indomethacin involved both death receptor- and mitochondria-mediated apoptotic cascades. Indomethacin-induced glioma cell apoptosis was accompanied by a series of biochemical changes, including reactive oxygen species generation, endoplasmic reticulum (ER) stress, apoptosis signal-regulating kinase-1 (Ask1) activation, p38 hyperphosphorylation, protein phosphatase 2A (PP2A) activation, Akt dephosphorylation, Mcl-1 and FLICE-inhibiting protein (FLIP) downregulation, Bax mitochondrial distribution, and caspases 3/caspase 8/caspase 9 activation. Data on pharmacological inhibition related to oxidative stress, ER stress, free Ca²⁺, and p38 revealed that the axis of oxidative stress/ER stress/Ask1/p38/PP2A/Akt comprised an apoptotic cascade leading to Mcl-1/FLIP downregulation and glioma apoptosis. Since indomethacin is an emerging choice in chemotherapy and its antineoplastic effects have been demonstrated in glioma tumor-bearing models, the findings further strengthen the argument for turning on the aforementioned axis in order to activate the apoptotic machinery of glioma cells.

SNHG6 modulates oxidized low-density lipoprotein-induced endothelial cells injury through miR-135a-5p/ROCK in atherosclerosis

BACKGROUND

Plenty of long non-coding RNAs (lncRNAs) play vital roles in the progression of atherosclerosis. Small nucleolar RNA host gene 6 (SNHG6) is a well known lncRNA that is aberrantly high expressed in atherosclerosis patients. However, its function and basic mechanism in atherosclerosis events have not been well clarified.

METHODS

The expression patterns of SNHG6, miR-135a-5p, ROCK1 and ROCK2 in clinical samples and cells were detected by RT-qPCR assays. Cell Counting Kit-8 (CCK-8), flow cytometry assays, ELISA and reactive oxygen species (ROS) and malondialdehyde (MDA) detection, were performed to assess cell viability, apoptosis, inflammation and oxidative stress, respectively. Western blot analysis was carried out to examine the protein levels of Bax, Bcl-2, and SNHG6. Luciferase reporter and RIP assays were used to confirm the true interaction between SNHG6 and miR-135a-5p, or miR-135a-5p and ROCK.

RESULTS

The levels of SNHG6, ROCK1 and ROCK2 were notably increased and miR-135a-5p was decreased in atherosclerosis patients and oxidized low-density lipoprotein (ox-LDL)-treated HUVECs. Knockdown of SNHG6 alleviated ox-LDL-induced injury of HUVECs, while this effect was partly reversed by miR-135a-5p inhibitor. Moreover, overexpression of ROCKs aggravated miR-135a-5p-alleviated atherosclerosis cell injury. SNHG6 contributed to ROCK expression through sequestering miR-135a-5p as a molecular sponge.

CONCLUSION

SNHG6 functions as a promoter in atherosclerosis events by targeting miR-135a-5p/ROCK axis in ox-LDL-stimulated HUVECs. This finding will help to develop a novel therapeutic strategy for atherosclerosis.

Medial calcification in the arterial wall of smooth muscle cell-specific Smpd1 transgenic mice: A ceramide-mediated vasculopathy

Arterial medial calcification (AMC) is associated with crystallization of hydroxyapatite in the extracellular matrix and arterial smooth muscle cells (SMCs) leading to reduced arterial compliance. The study was performed to test whether lysosomal acid sphingomyelinase (murine gene code: Smpd1)-derived ceramide contributes to the small extracellular vesicle (sEV) secretion from SMCs and consequently leads to AMC. In Smpd1trg /SMcre mice with SMC-specific overexpression of Smpd1 gene, a high dose of Vit D (500 000 IU/kg/d) resulted in increased aortic and coronary AMC, associated with augmented expression of RUNX2 and osteopontin in the coronary and aortic media compared with their littermates (Smpd1trg /SMwt and WT/WT mice), indicating phenotypic switch. However, amitriptyline, an acid sphingomyelinase (ASM) inhibitor, reduced calcification and reversed phenotypic switch. Smpd1trg /SMcre mice showed increased CD63, AnX2 and ALP levels in the arterial wall, accompanied by reduced co-localization of lysosome marker (Lamp-1) with multivesicular body (MVB) marker (VPS16), a parameter for lysosome-MVB interaction. All these changes related to lysosome fusion and sEV release were substantially attenuated by amitriptyline. Increased arterial stiffness and elastin disorganization were found in Smpd1trg /SMcre mice as compared to their littermates. In cultured coronary arterial SMCs (CASMCs) from Smpd1trg /SMcre mice, increased Pi concentrations led to markedly increased calcium deposition, phenotypic change and sEV secretion compared with WT CASMCs, accompanied by reduced lysosome-MVB interaction. However, amitriptyline prevented these changes in Pi -treated CASMCs. These data indicate that lysosomal ceramide plays a critical role in phenotype change and sEV release in SMCs, which may contribute to the arterial stiffness during the development of AMC.

Adipocyte Hypoxia-Inducible Factor 2α Suppresses Atherosclerosis by Promoting Adipose Ceramide Catabolism

Obesity-induced adipose dysfunction is a major contributor to atherosclerosis. Cold exposure has been reported to affect atherosclerosis through regulation of adipose function, but the mechanism has not been well clarified. Here, adipocyte hypoxia-inducible factor 2α (HIF-2α) was upregulated after mild cold exposure at 16°C and mediated cold-induced thermogenesis. Adipocyte HIF-2α deficiency exacerbated Western-diet-induced atherosclerosis by increasing adipose ceramide levels, which blunted hepatocyte cholesterol elimination and thermogenesis. Mechanistically, Acer2, the gene encoding alkaline ceramidase 2, was identified as a novel target gene of HIF-2α, triggering ceramide catabolism. Adipose overexpression of ACER2 rescued adipocyte HIF-2α-deficiency-induced exacerbation of atherosclerosis. Furthermore, activation of adipose HIF-2α by the HIF prolyl hydroxylase inhibitor FG-4592 had protective effects on atherosclerosis, accompanied by a reduction in adipose and plasma ceramide and plasma cholesterol levels. This study highlights adipocyte HIF-2α as a putative drug target against atherosclerosis.

The biphasic effects of the oxLDL/β2GPI/anti-β2GPI complex on VSMC proliferation and apoptosis

In our previous study, the oxLDL/β₂GPI/anti-β₂GPI complex was demonstrated to further enhance the foam cell formation and migration of VSMC, as well as the expression of inflammatory cytokines, via the TLR4/NF-κB pathway. However, sparse information is available on other pro-atherogenic pathogenic effects of the oxLDL/β₂GPI/anti-β₂GPI complex, such as effects on proliferation and apoptosis. In the present study, we focused on the biphasic effects and underlying mechanisms of the oxLDL/β₂GPI/anti-β₂GPI complex on VSMC survival. The data showed that short exposure to the oxLDL/β₂GPI/anti-β₂GPI complex could activate NF-κB and ERK1/2 pathways and stimulate cell proliferation in VSMC. In contrast, longer exposure increased the level of p38 pathway activation and cell apoptosis. Additionally, the promotion effect of the oxLDL/β₂GPI/anti-β₂GPI complex on both proliferation and apoptosis, as well as signaling pathway activation, was stronger than that of the other control groups. The use of selective blockers showed that TLR4/NF-κB and ERK1/2 partly mediated oxLDL/β₂GPI/anti-β₂GPI complex-induced proliferation and had an inhibitory effect on complex-stimulated apoptosis. Conversely, TLR2/p38 partly mediated oxLDL/β₂GPI/anti-β₂GPI complex-induced apoptosis and had a negative effect on complex-stimulated proliferation. Specific inhibitors of NF-κB and ERK1/2 activation could augment the oxLDL/β₂GPI/anti-β₂GPI complex-induced phosphorylation of p38 and vice versa. Under pretreatment with NADPH oxidase inhibitors, intracellular ROS generation was confirmed to participate in oxLDL/β₂GPI/anti-β₂GPI complex-induced proliferation and apoptosis, as well as the phosphorylation of NF-κB and MAPKs. Taken together, our data clearly revealed that the oxLDL/β₂GPI/anti-β₂GPI complex had biphasic effects on VSMC survival, partly mediated by ROS-induced NF-κB and MAPKs activation. The TLR4/NF-κB and TLR2/p38 pathways played supporting roles in this dual effects-initiated signal network, and there is a trade-off relationship between the phosphorylation of NF-κB, ERK1/2 and p38. The dual effects of the oxLDL/β₂GPI/anti-β₂GPI complex on VSMC survival contribute to the development of the structure typical of atherosclerotic lesions, particularly focal excessive growth alternating with necrosis.

Role of p38 MAPK in Atherosclerosis and Aortic Valve Sclerosis

Atherosclerosis and aortic valve sclerosis are cardiovascular diseases with an increasing prevalence in western societies. Statins are widely applied in atherosclerosis therapy, whereas no pharmacological interventions are available for the treatment of aortic valve sclerosis. Therefore, valve replacement surgery to prevent acute heart failure is the only option for patients with severe aortic stenosis. Both atherosclerosis and aortic valve sclerosis are not simply the consequence of degenerative processes, but rather diseases driven by inflammatory processes in response to lipid-deposition in the blood vessel wall and the aortic valve, respectively. The p38 mitogen-activated protein kinase (MAPK) is involved in inflammatory signaling and activated in response to various intracellular and extracellular stimuli, including oxidative stress, cytokines, and growth factors, all of which are abundantly present in atherosclerotic and aortic valve sclerotic lesions. The responses generated by p38 MAPK signaling in different cell types present in the lesions are diverse and might support the progression of the diseases. This review summarizes experimental findings relating to p38 MAPK in atherosclerosis and aortic valve sclerosis and discusses potential functions of p38 MAPK in the diseases with the aim of clarifying its eligibility as a pharmacological target.

Whole Body Vibration Retards Progression of Atherosclerosis via Insulin-Like Growth Factor 1 in Apolipoprotein E-Deficient Mice

Whole body vibration (WBV) has a marked impact on lipid metabolism and the endocrine system, which is related to the progression of atherosclerosis (AS). To investigate the effects of WBV, we measured the atherosclerotic plaque area of apolipoprotein E-knockout (ApoE^−/−) AS mice, which were trained by WBV (15 Hz, 30 min) for 12 weeks. Simultaneously, serum levels of lipids, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 1 receptor (IGF-1R), interleukin 6 (IL-6), and the mRNA and protein levels of the same in the aorta were compared between the control and WBV groups. The results indicated that WBV significantly reduced the atherosclerotic plaque area with lower very low-density lipoprotein (VLDL) and oxidized low-density lipoprotein (ox-LDL) in the blood. Moreover, the levels of IGF-1 in serum and expression of IL-6, IGF-1R, and p-IGF-1R protein in the mice aorta decreased significantly in the WBV group. In addition, we found that serum IGF-1 in mice increased to the highest concentration in 30 min after WBV for 10, 30, 60, and 120 minutes. These results suggested that appropriate WBV may delay the progression of AS, which was associated with acutely elevated serum IGF-1 and lower levels of IGF-1 and IL-6 in the aorta for long-term treatment.

Identification of Lysophosphatidylcholines and Sphingolipids as Potential Biomarkers for Acute Aortic Dissection via Serum Metabolomics

OBJECTIVES

Acute aortic dissection (AAD) is a severe clinical emergency with a high mortality, and is easily misdiagnosed in its early stage. This study aimed at discovering serum metabolomic markers with the potential to diagnose AAD and distinguish between two subtypes of AAD.

METHODS

Thirty-five patients with AAD, including 20 with Stanford type A and 15 with Stanford type B were enrolled in this study, together with 20 healthy controls. All patients with AAD were admitted within 72 h of onset. Serum metabolomics profiles were determined by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and the data were analysed by principal component analysis and partial least squares discriminant analysis.

RESULTS

A total of 17 metabolites differing between the control and AAD groups were finally screened and identified as lysophosphatidylcholines (LPC) and sphingolipids including sphinganine, phytosphingosine, sphingomyelin, and ceramide. Compared with those in the healthy control group, LPC levels were significantly lower in both the Stanford type A and type B AAD groups. Interestingly, sphingolipids, including sphinganine, phytosphingosine, and ceramide, were remarkably reduced in the Stanford type A AAD group, but not in the Stanford type B AAD group. Subgroup analysis showed that the changes in LPC and sphingolipid levels were unrelated to hypertension or gender.

CONCLUSIONS

The present results indicate that LPCs and sphingolipids are significantly altered in patients with AAD, and several sphingolipids, such as sphinganine, phytosphingosine, and ceramide, were dramatically decreased in patients with Stanford type A AAD. A combination of these two families of metabolites could serve as a potential biomarker for the diagnosis of AAD and distinguishing between Stanford type A and Stanford type B.

[Quercetin attenuates Ox-LDL-induced calcification in vascular smooth muscle cells by regulating ROS-TLR4 signaling pathway]

OBJECTIVE

To determine whether quercetin inhibits oxidized low-density lipoprotein (Ox-LDL)-induced osteogenic differentiation and calcification of vascular smooth muscle cells (VSMCs) and understand the underlying mechanism.

METHODS

The calcification of human VSMCs following Ox-LDL treatment was assessed using alizarin red staining and by detecting ALP activity. The mRNA expressions of the bone-related genes including Msx2, BMP2 and Osterix, and the contractile proteins including SMA and SM22a were analyzed using qPCR. The effects of quercetin were investigated on OxLDL-induced VSMC calcification and changes in ALP activity, expressions of Msx2, BMP2, Osterix, SMA and SM22a, ROS levels and SOD activity. The effect of Toll like receptor 4 (TLR4) silencing mediated by siRNA transfection on cell calcification, ALP activity, gene expressions and ROS levels were investigated.

RESULTS

Ox-LDL treatment promoted VSMC calcification and up-regulated TLR4 expression. Quercetin treatment significantly attenuated Ox-LDL-induced VSMC calcification, reduced ALP activity, down-regulated the expression levels of Msx2, BMP2 and Osterix, and up-regulated the expressions of vascular smooth muscle contractile proteins SMA and SM22a. In addition, Quercetin treatment markedly increased SOD activity, reduced ROS levels and TLR4 expression in VSMCs. Silencing TLR4 expression using TLR4 siRNA also significantly decreased calcification of the VSMCs.

CONCLUSIONS

Quercetin inhibits Ox-LDL-induced VSMC calcification in VSMCs possibly by targeting the ROS/TLR4 signaling pathway.

Exosomes, the message transporters in vascular calcification

Vascular calcification (VC) is caused by hydroxyapatite deposition in the intimal and medial layers of the vascular wall, leading to severe cardiovascular events in patients with hypertension, chronic kidney disease and diabetes mellitus. VC occurrences involve complicated mechanism networks, such as matrix vesicles or exosomes production, osteogenic differentiation, reduced cell viability, aging and so on. However, with present therapeutic methods targeting at VC ineffectively, novel targets for VC treatment are demanded. Exosomes are proven to participate in VC and function as initializers for mineral deposition. Secreted exosomes loaded with microRNAs are also demonstrated to modulate VC procession in recipient vascular smooth muscle cells. In this review, we targeted at the roles of exosomes during VC, especially at their effects on transporting biological information among cells. Moreover, we will discuss the potential mechanisms of exosomes in VC.

Lipoprotein(a) and oxidized phospholipids in calcific aortic valve stenosis

PURPOSE OF REVIEW

As the incidence of calcific aortic valve stenosis increases with the aging of the population, improved understanding and novel therapies to reduce its progression and need for aortic valve replacement are urgently needed.

RECENT FINDINGS

Lipoprotein(a) is the only monogenetic risk factor for calcific aortic stenosis. Elevated levels are a strong, causal, independent risk factor, as demonstrated in epidemiological, genome-wide association studies and Mendelian randomization studies. Lipoprotein(a) is the major lipoprotein carrier of oxidized phospholipids, which are proinflammatory and promote calcification of vascular cells, two key pathophysiological drivers of aortic stenosis. Elevated plasma lipoprotein(a) and oxidized phospholipids predict progression of pre-existing aortic stenosis and need for aortic valve replacement. The failure of statin trials in pre-existing aortic stenosis may be partially due to an increase in lipoprotein(a) and oxidized phospholipid levels caused by statins. Antisense oligonucleotides targeted to apo(a) are in Phase 2 clinical development and shown to lower both lipoprotein(a) and oxidized phospholipids.

SUMMARY

Lipoprotein(a) and oxidized phospholipids are key therapeutic targets in calcific aortic stenosis. Strategies aimed at potent lipoprotein(a) lowering to normalize levels and/or to suppress the proinflammatory effects of oxidized phospholipids may prevent progression of this disease.

Polysaccharide from Fuzi protects against Ox‑LDL‑induced calcification of human vascular smooth muscle cells by increasing autophagic activity

Polysaccharide from Fuzi (FPS) is a water‑soluble polysaccharide isolated from the traditional Chinese herbal medicine Fuzi. It has been demonstrated to protect hepatocytes against ischemia‑reperfusion injury through its potent antioxidant effects, and to attenuate starvation‑induced cytotoxicity in H9c2 cells by increasing autophagic activity. In the present study, Alizarin Red S staining was used to detect mineral deposition and reverse transcription‑quantitative polymerase chain reaction was used to detect the core binding factor α1 and smooth muscle 22α mRNA expression. To analyze autophagic activity, western blotting was used to detect microtubule‑associated protein 1A/1B light chain 3 and nucleoporin P62 expression. In addition, green fluorescent protein‑LC3 dots‑per‑cell was observed by fluorescence microscopy. It was demonstrated that oxidized low‑density lipoprotein (Ox‑LDL) could increase the calcification of human vascular smooth muscle cells (VSMCs) in a concentration‑dependent manner, and that FPS treatment had a significant protective effect against Ox‑LDL‑induced calcification of human VSMCs. Furthermore, FPS treatment alleviated the Ox‑LDL‑induced downregulation of autophagic activity, and the protective effect of FPS on Ox‑LDL‑induced calcification was attenuated by the autophagy inhibitor 3‑methyladenine. In conclusion, the present study demonstrated for the first time to the best of the authors' knowledge that FPS can protect against Ox‑LDL‑induced vascular calcification in human VSMCs, and that this likely occurs via the activation of autophagy. This supports the hypothesis that autophagy may be an endogenous protective mechanism counteracting vascular calcification, and that FPS may be used as a potential therapeutic for vascular calcification.

Sphingosine 1-phosphate activation of ERM contributes to vascular calcification

Vascular calcification is the deposition of mineral in the artery wall by vascular smooth muscle cells (VSMCs) in response to pathological stimuli. The process is similar to bone formation and is an independent risk factor for cardiovascular disease. Given that ceramide and sphingosine 1-phosphate (S1P) are involved in cardiovascular pathophysiology and biomineralization, their role in VSMC matrix mineralization was investigated. During phosphate-induced VSMC mineralization, endogenous S1P levels increased accompanied by increased sphingosine kinase (SK) activity and increased mRNA expression of SK1 and SK2. Consistent with this, mineralization was increased by exogenous S1P, but decreased by C2-ceramide. Mechanistically, exogenous S1P stimulated ezrin-radixin-moesin (ERM) phosphorylation in VSMCs and ERM phosphorylation was increased concomitantly with endogenous S1P during mineralization. Moreover, inhibition of acid sphingomyelinase and ceramidase with desipramine prevented increased S1P levels, ERM activation, and mineralization. Finally, pharmacological inhibition of ERM phosphorylation with NSC663894 decreased mineralization induced by phosphate and exogenous S1P. Although further studies will be needed to verify these findings in vivo, this study defines a novel role for the SK-S1P-ERM pathways in phosphate-induced VSMC matrix mineralization and shows that blocking these pathways with pharmacological inhibitors reduces mineralization. These results may inform new therapeutic approaches to inhibit or delay vascular calcification.

MIAT promotes proliferation and hinders apoptosis by modulating miR-181b/STAT3 axis in ox-LDL-induced atherosclerosis cell models

BACKGROUND

Plenty of lncRNAs and microRNAs have been identified to be critical mediators in the progression of atherosclerosis (AS). Myocardial infarction-associated transcript (MIAT) were aberrantly high expressed and closely associated with the pathogenesis of AS. However, its molecular mechanism has not been well characterized.

METHODS

The expression patterns of MIAT and microRNA-181b (miR-181b) in clinical samples and cells were measured by RT-qPCR assays. Luciferase reporter assay and RIP assays were used to manifest the potential interaction between MIAT, miR-181b and signal transducer and activator of transcription 3 (STAT3). Cell Counting Kit-8 (CCK-8), Propidium Iodide (PI) staining, Terminal dexynucleotidyl transferase(TdT)-mediated dUTP nick end labeling (TUNEL) and western blot assays were carried out to detect cell proliferation, cell cycle distribution, apoptosis, and STAT3 protein level, respectively.

RESULTS

MIAT expression was up-regulated and miR-181b expression was down-regulated in AS patients serum and oxidized low-density lipoprotein (ox-LDL) induced AS cells model. MIAT facilitated cell proliferation, accelerated cell cycle progression and inhibited apoptosis in ox-LDL-induced AS cell lines, while this effect was partly reversed by miR-181b overexpression. Moreover, MIAT enhanced STAT3 expression through sequestering miR-181b as a molecular sponge. Furthermore, MiR-181b hindered cell growth, induced cell cycle arrest and promoted apoptosis by directly targeting STAT3.

CONCLUSION

MIAT performed as an induction factor of AS by regulating miR-181b/STAT3 axis in ox-LDL-induced AS cell lines, offering a new insight into the potential application of MIAT in AS treatment.

The Contribution of Singlet Oxygen to Insulin Resistance

Insulin resistance contributes to the development of diabetes and cardiovascular dysfunctions. Recent studies showed that elevated singlet oxygen-mediated lipid peroxidation precedes and predicts diet-induced insulin resistance (IR), and neutrophils were suggested to be responsible for such singlet oxygen production. This review highlights literature suggesting that insulin-responsive cells such as endothelial cells, hepatocytes, adipocytes, and myocytes also produce singlet oxygen, which contributes to insulin resistance, for example, by generating bioactive aldehydes, inducing endoplasmic reticulum (ER) stress, and modifying mitochondrial DNA. In these cells, nutrient overload leads to the activation of Toll-like receptor 4 and other receptors, leading to the production of both peroxynitrite and hydrogen peroxide, which react to produce singlet oxygen. Cytochrome P450 2E1 and cytochrome c also contribute to singlet oxygen formation in the ER and mitochondria, respectively. Endothelial cell-derived singlet oxygen is suggested to mediate the formation of oxidized low-density lipoprotein which perpetuates IR, partly through neutrophil recruitment to adipose tissue. New singlet oxygen-involving pathways for the formation of IR-inducing bioactive aldehydes such as 4-hydroperoxy-(or hydroxy or oxo)-2-nonenal, malondialdehyde, and cholesterol secosterol A are proposed. Strategies against IR should target the singlet oxygen-producing pathways, singlet oxygen quenching, and singlet oxygen-induced cellular responses.

Roles of platelet-derived growth factor in vascular calcification

Vascular calcification (VC) is prevalent in aging, and patients with hypertension, chronic kidney disease (CKD), or diabetes. VC is regarded as an active and complex process that involves multiple mechanisms responsible for calcium deposition in vessel wall. In light of the complicated pathogenesis of VC, effective therapy for ameliorating VC is limited. Thus, it is urgent to explore the potential mechanisms and find new targets for the therapy of VC. Platelet-derived growth factor (PDGF), a potent mitogen, and chemoattractant have been found to disturb the vascular homeostasis by inducing inflammation, oxidative stress, and phenotype transition, all of which accelerate the process of VC. The aim of current review is to present a review about the roles of PDGF in affecting VC and to establish a potential target for treating VC.

Roles of aldosterone in vascular calcification: An update

Both clinical and experimental studies have demonstrated that vascular calcification (VC) is a common pathology shared in many chronic diseases such as chronic kidney disease (CKD) and diabetes. It's an independent risk factor for cardiovascular events. Since the pathogenesis of VC is complicated, current therapies have limited effects on the regression of VC. Therefore, it is urgent to investigate the potential mechanisms and find new targets for the treatment of VC. Aldosterone (Aldo), a mineralocorticoid hormone, is the metabolite of renin-angiotensin-aldosterone system (RAAS) activation, which can exert genomic and non-genomic effects on the cardiovascular system. Recent data suggests that Aldo can promote VC. Here, we summarized the roles of Aldo in the process of VC and a series of findings indicated that Aldo could act as a potentially therapeutic target for treating VC.

Suppression of EC-SOD by oxLDL During Vascular Smooth Muscle Cell Proliferation

Reactive oxygen species (ROS) produced by endothelial cells and macrophages play important roles in atherogenesis because they promote the formation of oxidized low-density lipoproteins (oxLDL). Extracellular-superoxide dismutase (EC-SOD) is mainly produced by vascular smooth muscle cells (VSMCs), is secreted into the extracellular space, and protects cells from the damaging effects of the superoxide anion. Thus, the expression of EC-SOD in VSMCs is crucial for protecting cells against atherogenesis; however, oxLDL-induced changes in the expression of EC-SOD in VSMCs have not yet been examined. We herein showed that oxLDL decreased EC-SOD mRNA and protein levels by binding to lectin-like oxidized LDL receptor-1 (LOX-1). Moreover, we demonstrated the significant role of mitogen-activated protein kinase (MEK)/extracellular-regulated protein kinase (ERK) signaling in oxLDL-elicited reductions in the expression of EC-SOD and proliferation of VSMCs. The results obtained with the FCS treatment indicate that oxLDL-elicited reductions in the expression of EC-SOD are related to the proliferation of VSMCs. We herein showed for the first time that luteolin, a natural product, restored oxLDL-induced decreases in the expression of EC-SOD and proliferation of VSMCs. Collectively, the results of the present study suggest that oxLDL accelerates the development of atherosclerosis by suppressing the expression of EC-SOD and also that luteolin has potential as a treatment for atherosclerosis. J. Cell. Biochem. 117: 2496-2505, 2016. © 2016 Wiley Periodicals, Inc.