Murine Vascular Smooth Muscle Cells Research Articles

MiRNA-221 and -222 increase in exosomes upon insulin stimulation of human vascular smooth muscle cells lacking the insulin-like growth factor 1 receptor

As a result of increased vascular inflammation, patients with Type 2 diabetes experience a near 4-fold increase in their risk for heart attack and stroke. miR-221 and -222 are two microRNAs that are upregulated in the vasculature of Type 2 diabetic patients. miR-221/222 act by downregulating the cyclin-dependent kinase inhibitor, p27Kip1, in vascular smooth muscle cells (VSMCs) and exosome-mediated proinflammatory effects on endothelial cells and macrophages. Loss of the insulin-like growth factor receptor (IGFR) in VSMCs can unmask the insulin receptor (IR) and increase insulin signaling. We have demonstrated that the loss of IGFR, coupled with physiological insulin stimulation, promotes an increased expression of miR-221/-222 in murine VSMCs. Respectively, miR-221/222 content in VSMC-derived exosomes increases and p27Kip1 mRNA expression decreases in VSMCs. We asked whether the effect of loss of IGFR in human coronary artery smooth muscle cells (HCASMCs) would also lead to an increase in miR-221/-222 content of VSMC-derived exosomes. Transfection with a CRISPR-cas9 plasmid targeting IGFR resulted in a 50% decrease in IGFR mRNA in HCASMCs, when compared to transfection with negative control CRISPR plasmids. Droplet digital PCR was used to measure expression of miR-221 and miR-222 in the exosomes derived from both sets of HCASMCs. There was no change in the miR-221/222 content of exosomes derived from HCASMCs transfected with the negative control CRISPR following stimulation with 1nM insulin (7.27± 4.75 vs. 11.33 ± 1.09 copies of miR-221 and 6.43 ± 0.43 vs. 4.68 ± 0.02 copies of miR-222). In contrast, there was a 2 to 3-fold increase in miR-221/222 content in exosomes that were derived from HCASMCs with IGFR knockdown following stimulation with 1nM insulin (14.96 ± 0.3 vs. 35.66 ± 3.08 copies of miR-221 and 9.12 ± 1.19 vs.15.44 ± 5.36 copies of miR-222). We conclude that loss of IGFR coupled with physiological insulin stimulation increases the miR-221/222 content of exosomes of HCASMCs, recapitulating the effects of IGFR loss seen in murine VSMCs as well as the effects of diabetes on VSMCs. This model system will allow additional studies connecting the loss of IGFR to the cardiovascular complications of diabetes. Tulane University School of Medicine, Biomedical Sciences Program. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Spatiotemporal ATF3 Expression Determines VSMC Fate in Abdominal Aortic Aneurysm.

Abdominal aortic aneurysm (AAA) is a catastrophic disease with little effective therapy, likely due to the limited understanding of the mechanisms underlying AAA development and progression. ATF3 (activating transcription factor 3) has been increasingly recognized as a key regulator of cardiovascular diseases. However, the role of ATF3 in AAA development and progression remains elusive. Genome-wide RNA sequencing analysis was performed on the aorta isolated from saline or Ang II (angiotensin II)-induced AAA mice, and ATF3 was identified as the potential key gene for AAA development. To examine the role of ATF3 in AAA development, vascular smooth muscle cell-specific ATF3 knockdown or overexpressed mice by recombinant adeno-associated virus serotype 9 vectors carrying ATF3, or shRNA-ATF3 with SM22α (smooth muscle protein 22-α) promoter were used in Ang II-induced AAA mice. In human and murine vascular smooth muscle cells, gain or loss of function experiments were performed to investigate the role of ATF3 in vascular smooth muscle cell proliferation and apoptosis. In both Ang II-induced AAA mice and patients with AAA, the expression of ATF3 was reduced in aneurysm tissues but increased in aortic lesion tissues. The deficiency of ATF3 in vascular smooth muscle cell promoted AAA formation in Ang II-induced AAA mice. PDGFRB (platelet-derived growth factor receptor β) was identified as the target of ATF3, which mediated vascular smooth muscle cell proliferation in response to TNF-alpha (tumor necrosis factor-α) at the early stage of AAA. ATF3 suppressed the mitochondria-dependent apoptosis at the advanced stage by upregulating its direct target BCL2. Our chromatin immunoprecipitation results also demonstrated that the recruitment of NFκB1 and P300/BAF/H3K27ac complex to the ATF3 promoter induces ATF3 transcription via enhancer activation. NFKB1 inhibitor (andrographolide) inhibits the expression of ATF3 by blocking the recruiters NFKB1 and ATF3-enhancer to the ATF3-promoter region, ultimately leading to AAA development. Our results demonstrate a previously unrecognized role of ATF3 in AAA development and progression, and ATF3 may serve as a novel therapeutic and prognostic marker for AAA.

Macrophage-derived GSDMD promotes abdominal aortic aneurysm and aortic smooth muscle cells pyroptosis

Macrophage is a vital factor in determining the fate of abdominal aortic aneurysm (AAA). The crosstalk between macrophage and other cells plays a crucial role in the development of aneurysm. Gasdermin D (GSDMD) is a vital executive protein of pyroptosis, which is a novel programmed cell death associated with inflammation. In this study, we identified aortic macrophage as the main expressing cell of GSDMD in AAA. Using Gsdmd-/-ApoE-/- mouse and AAV-F4/80-shGSDMD, we demonstrated the potential role of macrophage-derived GSDMD in AAA and aortic pyroptosis induced by Ang II in vivo. In vitro experiments showed that GSDMD promotes the pyroptosis of mouse primary peritoneal macrophages (MPMs), murine aortic vascular smooth muscle cells (MOVAS) and primary smooth muscle cells. Mechanistically, a mouse cytokine antibody array showed that Gsdmd-/- inhibited LPS + nigericin (LN)- induced secretion of multiple cytokines from MPMs. Furthermore, GSDMD is involved in the crosstalk between MPMs and MOVAS via cytokine secretion. This study provides a novel fundamental insight into macrophage-derived GSDMD in AAA and showed that GSDMD could be a promising therapeutic target for AAA.

Rapid sol-gel reversible thermosensitive collagen for 3D cell culture

Collagen is usually dissolved in the acid solution and neutralized to mix cells for three-dimensional (3D) cell culture. During this process, the acid collagen solution must be precisely adjusted into the pH neutral on the ice platform; after mixing cells, the collagen/cells solution need more than 30 min to gelate at 37 ℃; moreover, the cells embedded in the collagen/cells hydrogel have to be harvested through collagen enzymolysis with enzyme such as collagenase if necessary. Herein, we developed the rapid sol-gel reversible thermosensitive collagen (RRTC) for 3D cell culture. The pH neutral collagen solution could directly mix cells at room temperature; the RRTC/cells solution could gelate in 60 s or less at 37 ℃; especially, the cells embedded in the RRTC/cells hydrogel could be harvested through hydrogel phase transformation from gel to sol. The L929 cells, human umbilical vein endothelial cells (HUVEC), Sp2/0 cells, murine aortic vascular smooth muscle cells (MOVAS), rat intestinal epithelial cells (IEC-6) and human chondrocytes were 3D cultured via the RRTC and grew well. The cells could proliferate by about 10 times in 14 days and preserve the high cell viability of over 90 %. The experiments of mouse skin regeneration demonstrated the RRTC solution could in situ quickly gelate on the skin wound for the skin regeneration. Therefore, this novel collagen biomaterial could be used as an efficient tool to fabricate 3D cell culture and have more clinical applications.

Branched-chain amino acid catabolic defect in vascular smooth muscle cells drives thoracic aortic dissection via mTOR hyperactivation

Metabolic reprogramming of vascular smooth muscle cell (VSMC) plays a critical role in the pathogenesis of thoracic aortic dissection (TAD). Previous researches have mainly focused on dysregulation of fatty acid or glucose metabolism, while the impact of amino acids catabolic disorder in VSMCs during the development of TAD remains elusive. Here, we identified branched-chain amino acid (BCAA) catabolic defect as a metabolic hallmark of TAD. The bioinformatics analysis and data from human aorta revealed impaired BCAA catabolism in TAD individuals. This was accompanied by upregulated branched-chain α-ketoacid dehydrogenase kinase (BCKDK) expression and BCKD E1 subunit alpha (BCKDHA) phosphorylation, enhanced vascular inflammation, and hyperactivation of mTOR signaling. Further in vivo experiments demonstrated that inhibition of BCKDK with BT2 (a BCKDK allosteric inhibitor) treatment dephosphorylated BCKDHA and re-activated BCAA catabolism, attenuated VSMCs phenotypic switching, alleviated aortic remodeling, mitochondrial reactive oxygen species (ROS) damage and vascular inflammation. Additionally, the beneficial actions of BT2 were validated in a TNF-α challenged murine VSMC cell line. Meanwhile, rapamycin conferred similar beneficial effects against VSMC phenotypic switching, cellular ROS damage as well as inflammatory response. However, co-treatment with MHY1485 (a classic mTOR activator) reversed the beneficial effects of BT2 by reactivating mTOR signaling. Taken together, the in vivo and in vitro evidence showed that impairment of BCAA catabolism resulted in aortic accumulation of BCAA and further caused VSMC phenotypic switching, mitochondrial ROS damage and inflammatory response via mTOR hyperactivation. BCKDK and mTOR signaling may serve as the potential drug targets for the prevention and treatment of TAD.

Gasdermin D affects aortic vascular smooth muscle cell pyroptosis and Ang II-induced vascular remodeling

Vascular smooth muscle cells (VSMCs) are primarily responsible for vasoconstriction and the regulation of blood pressure1. Pyroptosis, a particular form of regulated cell death, is involved in multiple vascular injuries, including hypertensive vascular dysfunction. This pyroptotic cell death is mediated by the pore-forming protein of Gasdermin D (GSDMD). This study was designed to examine the direct effect of GSDMD on smooth muscle cell pyroptosis and vascular remodeling. Findings revealed that GSDMD was activated in Angiotensin (Ang) II- treated aortas. We then showed that genetic deletion of Gsdmd reduced vascular remodeling and aorta pyroptosis induced by Ang II in vivo. Aberrant expression of GSDMD by recombinant AAV9 virus carrying Gsdmd cDNA aggravated the level of pyroptosis in aortas of Ang II mice. Gain- and loss-of- function analysis further confirmed that GSDMD regulated the pyroptosis of murine aortic vascular smooth muscle cells (MOVAS) in an in vitro model of tumor necrosis factor (TNF)-α treatment, which was achieved by transfecting expressing plasmid or siRNA, respectively. Overall, this study provided evidence supporting the active involvement of GSDMD in smooth muscle cell pyroptosis and Ang II-induced mice vascular injury. This finding lends credence to GSDMD as a potential therapeutic target for hypertensive vascular remodeling via inhibiting pyroptosis.

Nuclear Receptor NR1D1 Regulates Abdominal Aortic Aneurysm Development by Targeting the Mitochondrial Tricarboxylic Acid Cycle Enzyme Aconitase-2.

Metabolic disorder increases the risk of abdominal aortic aneurysm (AAA). NRs (nuclear receptors) have been increasingly recognized as important regulators of cell metabolism. However, the role of NRs in AAA development remains largely unknown. We analyzed the expression profile of the NR superfamily in AAA tissues and identified NR1D1 (NR subfamily 1 group D member 1) as the most highly upregulated NR in AAA tissues. To examine the role of NR1D1 in AAA formation, we used vascular smooth muscle cell (VSMC)-specific, endothelial cell-specific, and myeloid cell-specific conditional Nr1d1 knockout mice in both AngII (angiotensin II)- and CaPO4-induced AAA models. Nr1d1 gene expression exhibited the highest fold change among all 49 NRs in AAA tissues, and NR1D1 protein was upregulated in both human and murine VSMCs from AAA tissues. The knockout of Nr1d1 in VSMCs but not endothelial cells and myeloid cells inhibited AAA formation in both AngII- and CaPO4-induced AAA models. Mechanistic studies identified ACO2 (aconitase-2), a key enzyme of the mitochondrial tricarboxylic acid cycle, as a direct target trans-repressed by NR1D1 that mediated the regulatory effects of NR1D1 on mitochondrial metabolism. NR1D1 deficiency restored the ACO2 dysregulation and mitochondrial dysfunction at the early stage of AngII infusion before AAA formation. Supplementation with αKG (α-ketoglutarate, a downstream metabolite of ACO2) was beneficial in preventing and treating AAA in mice in a manner that required NR1D1 in VSMCs. Our data define a previously unrecognized role of nuclear receptor NR1D1 in AAA pathogenesis and an undescribed NR1D1-ACO2 axis involved in regulating mitochondrial metabolism in VSMCs. It is important that our findings suggest αKG supplementation as an effective therapeutic approach for AAA treatment.

Platelet TGF-β1 inhibits the migration and proliferation of smooth muscle cells in aneurysms

BackgroundThe study explored the role of platelet TGF-β1 from the perspective of inhibiting the excessive proliferation, migration and invasion of murine aortic vascular smooth muscle cells (MASMCs). MethodThe platelets were first extracted from C57BL/6 mice, and the TGF-β1 protein was obtained after the purification of protein. In vitro, the concentrations of angiotensin Ⅱ (Ang Ⅱ) and TGF-β1 for intervention were screened by testing the viability of MASMCs, followed by the analysis concerning the effects of platelets, Ang Ⅱ and TGF-β1 on the proliferation, migration, invasion, and the expressions of pathway-related proteins in MASMCs. In vivo, an Ang Ⅱ-induced mouse model was established. TGF-β1 was injected into the tail of mice as a therapeutic agent, and its action mechanism was further verified by the treatment of inhibitor SB505124. The results of the cell experiment were validated by evaluating the maximum diameter of abdominal aorta, the proportion of total weight, the changes of both pathology and the expressions of pathway-related proteins in the mice. Result0.5 ng/mL Ang Ⅱ and 15 ng/mL TGF-β1 were chosen for treatment. The following results of cell functional experiments and Western blot assay demonstrated that Ang Ⅱ promoted the proliferation, migration and invasion of MASMCs via regulating related pathways, the effects of which were evidently reversed by TGF-β1 and platelets. Consistent results were also observed in the animal experiments, where TGF-β1 effectively alleviated Ang Ⅱ-induced abdominal aortic injury in mice. ConclusionTGF-β1 in platelets inhibits Ang Ⅱ-induced proliferation, migration and invasion of MASMCs.

17β-estradiol reduces NF-κB expression induced by increased crosstalk between KLF5 and ERα in murine vascular smooth muscle cells

Pathological vascular remodeling and cell proliferation play vital roles in many proliferative vascular diseases. Estrogen can protect the cardiovascular system, but its exact molecular mechanism is unknown. Here we report that 17β-estradiol (E2) suppressed vascular smooth muscle cells (VSMCs) proliferation and inflammation. qRT-PCR and Western blot demonstrated that E2 decreased NF-κB p50 expression and reduced VSMCs proliferation and inflammation. Mechanistically, a dual luciferase reporter assay and chromatin immunoprecipitation suggested that KLF5 promoted NF-κB p50 expression by binding to the NF-κB p50 promoter, whereas E2 reduced the effect of KLF5 binding to the NF-κB p50 promoter and inhibited NF-κB p50 expression. Furthermore, a coimmunoprecipitation assay and immunofluorescence staining showed that the interaction between KLF5 and ERα increased in VSMCs treated with E2, which in turn decreased NF-κB p50 expression levels. Altogether, we reveal that E2 inhibits VSMCs proliferation and inflammation by reducing NF-κB expression induced by an increased interaction between KLF5 and ERα. These data provide further insights into how E2 inhibits vascular proliferation and inflammation.

Dantrolene reduces platelet-derived growth factor (PDGF)-induced vascular smooth muscle cell proliferation and neointimal formation following vascular injury in mice

Dantrolene is a ryanodine receptor blocker that is used clinically for treatment of malignant hyperthermia. This study was conducted using murine aortic vascular smooth muscle cells (MOVAS) and a mouse arterial injury model to investigate the inhibitory effect of dantrolene on smooth muscle cell proliferation and migration.We investigated whether dantrolene suppressed platelet-derived growth factor (PDGF)-induced vascular smooth muscle cell proliferation and migration in vitro. The effect of dantrolene on smooth muscle phenotype was evaluated using immunostaining. In addition, smooth muscle cell proliferation and phenotype switching were tested by applying dantrolene around blood vessels using a mouse arterial injury model. Dantrolene inhibited PDGF-induced cell proliferation and migration of MOVAS. Dantrolene also inhibited the switch from contractile to synthetic phenotype both in vitro and in vivo.Dantrolene is effective at inhibiting vascular smooth muscle cell proliferation, migration, and neointimal formation following arterial injury in mice.

Ginsenoside Rg-1 prevents elevated cytosolic Ca2+ via store-operated Ca2+ entry in high-glucose–stimulated vascular endothelial and smooth muscle cells

BackgroundGinsenoside Rg-1 (Rg-1), a triterpenoid saponin abundantly present in Panax ginseng, is a type of naturally occurring steroid with known anti-diabetic and anti-inflammatory effects. In this study, we sought to confirm the effects and mechanisms of action of Rg-1 on store-operated Ca2+ entry (SOCE) in human vascular endothelial cell line (EA) and murine aortic vascular smooth muscle cell line (MOVAS) cells exposed to high glucose.MethodsCytosolic Ca2+ concentrations in EA and MOVAS cells were measured by monitoring fluorescence of the ratiometric Ca2+-indicator, Fura-2 AM.ResultsHigh glucose significantly increased Ca2+ influx by abnormally activating SOCE in EA and MOVAS cells. Notably, this high glucose-induced increase in SOCE was restored to normal levels in EA and MOVAS cells by Rg-1. Moreover, Rg-1 induced reductions in SOCE in cells exposed to high glucose were significantly inhibited by the plasma membrane Ca2+ ATPase (PMCA) blocker lanthanum, the Na+/K+-ATPase blocker ouabain, or the Na+/Ca2+ exchanger (NCX) blockers Ni2+ and KB-R7943. These observations suggest that the mechanism of action of Rg-1 inhibition of SOCE involves PMCA and Na+/K+-ATPase, and an increase in Ca2+ efflux via NCXs in both EA and MOVAS cells exposed to high glucose.ConclusionsThese findings indicate that Rg-1 may protect vascular endothelial and smooth muscle cells from Ca2+ increases following exposure to hyperglycemic conditions.

Evaluation of perfusion-driven cell seeding of small diameter engineered tissue vascular grafts with a custom-designed seed-and-culture bioreactor.

Tissue engineering commonly entails combining autologous cell sources with biocompatible scaffolds for the replacement of damaged tissues in the body. Scaffolds provide functional support while also providing an ideal environment for the growth of new tissues until host integration is complete. To expedite tissue development, cells need to be distributed evenly within the scaffold. For scaffolds with a small diameter tubular geometry, like those used for vascular tissue engineering, seeding cells evenly along the luminal surface can be especially challenging. Perfusion-based cell seeding methods have been shown to promote increased uniformity in initial cell distribution onto porous scaffolds for a variety of tissue engineering applications. We investigate the seeding efficiency of a custom-designed perfusion-based seed-and-culture bioreactor through comparisons to a static injection counterpart method and a more traditional drip seeding method. Murine vascular smooth muscle cells were seeded onto porous tubular electrospun polycaprolactone scaffolds, 2 mm in diameter and 30 mm in length, using the three methods, and allowed to rest for 24 hours. Once harvested, scaffolds were evaluated longitudinally and circumferentially to assess the presence of viable cells using alamarBlue and live/dead cell assays and their distribution with immunohistochemistry and scanning electron microscopy. On average, bioreactor-mediated perfusion seeding achieved 35% more luminal surface coverage when compared to static methods. Viability assessment demonstrated that the total number of viable cells achieved across methods was comparable with slight advantage to the bioreactor-mediated perfusion-seeding method. The method described is a simple, low-cost method to consistently obtain even distribution of seeded cells onto the luminal surfaces of small diameter tubular scaffolds.

The Functional Interaction of EGFR with AT1R or TP in Primary Vascular Smooth Muscle Cells Triggers a Synergistic Regulation of Gene Expression.

In vivo, cells are simultaneously exposed to multiple stimuli whose effects are difficult to distinguish. Therefore, they are often investigated in experimental cell culture conditions where stimuli are applied separately. However, it cannot be presumed that their individual effects simply add up. As a proof-of-principle to address the relevance of transcriptional signaling synergy, we investigated the interplay of the Epidermal Growth Factor Receptor (EGFR) with the Angiotensin-II (AT1R) or the Thromboxane-A2 (TP) receptors in murine primary aortic vascular smooth muscle cells. Transcriptome analysis revealed that EGFR-AT1R or EGFR-TP simultaneous activations led to different patterns of regulated genes compared to individual receptor activations (qualitative synergy). Combined EGFR-TP activation also caused a variation of amplitude regulation for a defined set of genes (quantitative synergy), including vascular injury-relevant ones (Klf15 and Spp1). Moreover, Gene Ontology enrichment suggested that EGFR and TP-induced gene expression changes altered processes critical for vascular integrity, such as cell cycle and senescence. These bioinformatics predictions regarding the functional relevance of signaling synergy were experimentally confirmed. Therefore, by showing that the activation of more than one receptor can trigger a synergistic regulation of gene expression, our results epitomize the necessity to perform comprehensive network investigations, as the study of individual receptors may not be sufficient to understand their physiological or pathological impact.

Cell tension controlling pathways and nutrient availability regulate plasma membrane ATP synthase trafficking

Introduction: The interplay between mechanical stress and cell metabolism is an emerging topic. However, the mechanotransduction pathways coordinating cell metabolism to the tensional status of the cell are poorly understood. Here, we provide several evidences suggesting that caveolae – mechanosensitive plasma membrane invaginations-, nutrient availability and cell tension controlling conditions are important for the biology of mitochondrial ATP synthase. Material and Methods: For achieving the caveolar interactome, plasma membrane biotinylation and co-localization experiments, we have used human retinal pigment epithelial-1 (RPE-1) cells, murine vascular aortic smooth muscle (MOVAS) cells and mouse embryonic fibroblasts (MEF). We used proximity-dependent biotin identification (BioID) and mass spectrometry to obtain the different interactomes of caveolar components. For plasma membrane (PM) localization of the ATP synthase we used PM biotinylation under different metabolic and mechanical conditions (nutrient starving, cell confluence). To study co-localization, we performed Proximity Ligation Assays (PLAs) in combination with mitochondrial and caveolar markers. Results: First, we have identified the interactome of all core caveolar components. Among the interactors, we identified subunits α and β of the mitochondrial ATP synthase, which interact with most of the caveolar components. Apart from its main localization at the inner mitochondrial membrane, the ATP synthase has also been detected in the PM, facing the extracellular space; this pool is known as ecto-ATP synthase. We show that the interaction with Caveolin-1 (Cav1), one of the main components of caveolae, occurs outside caveolae and mitochondria. In addition, the presence of ecto- ATP synthase at the PM is dependent on Cav1. Furthermore, conditions regulating cell tension, and metabolic challenges that promote autophagy, impinge on ecto-ATP synthase trafficking Conclusions: This study has characterized the interactome of caveolar components and has focused on the subunits α and β of the ATP synthase, which are also present at the PM. These subunits interact with Cav-1, but this interaction seems to occur in intracellular trafficking vesicles. Moreover, this process could be altered by mechanical cues and nutrient deprivation. Thus, our study suggests that trafficking routes regulating PM residents, and regulated by several caveolar components, are linked to nutrient starvation and mitochondrial biology.

Epigenetic Upregulation of H19 and AMPK Inhibition Concurrently Contribute to S-Adenosylhomocysteine Hydrolase Deficiency-Promoted Atherosclerotic Calcification.

S-adenosylhomocysteine (SAH) is a risk factor of cardiovascular disease; inhibition of SAH hydrolase (SAHH) results in SAH accumulation and induces endothelial dysfunction and atherosclerosis. However, the effect and mechanism of SAHH in atherosclerotic calcification is still unclear. We aimed to explore the role and mechanism of SAHH in atherosclerotic calcification. The relationship between SAHH and atherosclerotic calcification was investigated in patients with coronary atherosclerotic calcification. Different in vivo genetic models were used to examine the effect of SAHH deficiency on atherosclerotic calcification. Human aortic and murine vascular smooth muscle cells (VSMCs) were cultured to explore the underlying mechanism of SAHH on osteoblastic differentiation of VSMCs. The expression and activity of SAHH were decreased in calcified human coronary arteries and inversely associated with coronary atherosclerotic calcification severity, whereas plasma SAH and total homocysteine levels were positively associated with coronary atherosclerotic calcification severity. Heterozygote knockout of SAHH promoted atherosclerotic calcification. Specifically, VSMC-deficient but not endothelial cell-deficient or macrophage-deficient SAHH promoted atherosclerotic calcification. Mechanistically, SAHH deficiency accumulated SAH levels and induced H19-mediated Runx2 (runt-related transcription factor 2)-dependent osteoblastic differentiation of VSMCs by inhibiting DNMT3b (DNA methyltransferase 3b) and leading to hypomethylation of the H19 promoter. On the contrary, SAHH deficiency resulted in lower intracellular levels of adenosine and reduced AMPK (AMP-activated protein kinase) activation. Adenosine supplementation activated AMPK and abolished SAHH deficiency-induced expression of H19 and Runx2 and osteoblastic differentiation of VSMCs. Finally, AMPK activation by adenosine inhibited H19 expression by inducing Sirt1 (sirtuin-1)-mediated histone H3 hypoacetylation and DNMT3b-mediated hypermethylation of the H19 promoter in SAHH deficiency VSMCs. We have confirmed a novel correlation between SAHH deficiency and atherosclerotic calcification and clarified a new mechanism that epigenetic upregulation of H19 and AMPK inhibition concurrently contribute to SAHH deficiency-promoted Runx2-dependent atherosclerotic calcification.

Extracellular Vesicles From LPS-Treated Macrophages Aggravate Smooth Muscle Cell Calcification by Propagating Inflammation and Oxidative Stress

Background: Vascular calcification (VC) is a cardiovascular complication associated with a high mortality rate among patients with diseases such as atherosclerosis and chronic kidney disease. During VC, vascular smooth muscle cells (VSMCs) undergo an osteogenic switch and secrete a heterogeneous population of extracellular vesicles (EVs). Recent studies have shown involvement of EVs in the inflammation and oxidative stress observed in VC. We aimed to decipher the role and mechanism of action of macrophage-derived EVs in the propagation of inflammation and oxidative stress on VSMCs during VC. Methods: The macrophage murine cell line RAW 264.7 treated with lipopolysaccharide (LPS-EK) was used as a cellular model for inflammatory and oxidative stress. EVs secreted by these macrophages were collected by ultracentrifugation and characterized by transmission electron microscopy, cryo-electron microscopy, nanoparticle tracking analysis, and the analysis of acetylcholinesterase activity, as well as that of CD9 and CD81 protein expression by western blotting. These EVs were added to a murine VSMC cell line (MOVAS-1) under calcifying conditions (4 mM Pi—7 or 14 days) and calcification assessed by the o-cresolphthalein calcium assay. EV protein content was analyzed in a proteomic study and EV cytokine content assessed using an MSD multiplex immunoassay. Results: LPS-EK significantly decreased macrophage EV biogenesis. A 24-h treatment of VSMCs with these EVs induced both inflammatory and oxidative responses. LPS-EK-treated macrophage-derived EVs were enriched for pro-inflammatory cytokines and CAD, PAI-1, and Saa3 proteins, three molecules involved in inflammation, oxidative stress, and VC. Under calcifying conditions, these EVs significantly increase the calcification of VSMCs by increasing osteogenic markers and decreasing contractile marker expression. Conclusion: Our results show that EVs derived from LPS-EK–treated-macrophages are able to induce pro-inflammatory and pro-oxidative responses in surrounding cells, such as VSMCs, thus aggravating the VC process.

Sulfiredoxin-1 Inhibits PDGF-BB-Induced Vascular Smooth Muscle Cell Proliferation and Migration by Enhancing the Activation of Nrf2/ARE Signaling.

Sulfiredoxin1 (Srxn1), an endogenous antioxidant protein, is involved in cardiovascular diseases. In this study, we aimed to investigate the role of Srxn1 in VSMCs and its molecular mechanism. The murine vascular smooth muscle cells MOVAS were treated with different doses of platelet-derived growth factor-BB (PDGF-BB); then, Srxn1 expression was detected using reverse transcription-quantitative polymerase chain reaction and western blot analysis. MTT and wound healing assay were used to examine the effect of Srxn1 on MOVAS cell proliferation and migration. Reactive oxygen species (ROS) production, malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity in MOVAS cells were detected using corresponding commercial kits. Moreover, the expression of proliferating cell nuclear antigen (PCNA), matrix metalloproteinase 2 (MMP-2), and nuclear factor erythroid-2-related factor 2 (Nrf2) /antioxidant response element (ARE) signaling-related proteins was detected using western blot analysis. In our study, PDGF-BB dose-dependently increased Srxn1 expression in MOVAS cells, and Srxn1 expression was increased with time dependence in PDGF-BB-treated MOVAS cells. The knockdown of Srxn1 increased PDGF-BB-induced the proliferation, migration, ROS production, MDA level, and the protein expression of PCNA and MMP-2, as well as decreased SOD activity and the expression of Nrf2/ARE signaling-related proteins in PDGF-BB-stimulated MOVAS cells. However, the overexpression of Srxn1 showed the opposite results to those of knockdown of Srxn1. Moreover, the inhibitory effects of Srxn1 overexpression on PDGF-BB induced proliferation, migration, ROS production, and MDA level and the promotion of Srxn1 overexpression on PDGF-BB induced SOD activity were partially reversed by the knockdown of Nrf2. Srxn1 inhibited PDGF-BB-induced proliferation, migration, and oxidative stress through activating Nrf2/ARE signaling.

Abstract MP08: Telomerase Reverse Transcriptase Mediates Osteogenesis In Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) is the leading heart valve disorder in the US. It is characterized by an active accumulation of calcium nodules on the aortic valve leaflets which lead to stiffening and remodeling of the valve leaflets causing valve dysfunction, cardiac failure and increased stroke risk. Inflammation and mechanical stresses contribute to CAVD pathogenesis. However, the mechanisms driving the fibrocalcific remodeling of the aortic valve are currently ill-defined. Multiple studies have revealed that the catalytic subunit of telomerase reverse transcriptase (TERT) can induce gene transcription and its overexpression primes mesenchymal stem cells to differentiate into osteoblasts, suggesting that TERT has a role in the activation of osteogenic transcriptional programs. We hypothesized that TERT contributes to early events leading to calcification of the valve leaflet. In human calcified valve tissue, we found that TERT protein is highly expressed in areas of calcification compared to control valve tissue, with no effect on telomere length. Alpha-SMA, a VIC activation marker, and RUNX2, a key transcription factor involved in the osteogenic differentiation of osteoblast, were also elevated in CAVD tissue. Under osteogenic differentiation conditions, human valve interstitial cells (VICs) upregulated TERT, RUNX2, and alpha-SMA protein levels and calcified, while CAVD VICs calcified de novo. Inflammatory stimuli intensified in vitro calcification, and induced TERT, RUNX2, and alpha-SMA protein expression. PLA and ChIP analysis showed that TERT interacts with interacted with Signal Transducer and Activator of Transcription 5A/B (STAT5) and together bind to RUNX2 promoter, respectively. shRNA-mediated TERT downregulation reduced expression of RUNX2 and alpha-SMA and genetic deletion of Tert in murine mesenchymal stem cells and vascular smooth muscle cells prevented calcification. These data provide evidence that TERT is required for calcification, regulates the transition of quiescent VICs into calcifying VICs, and that STAT5 functions as a TERT-interacting partner for DNA binding.

Characterization of murine cytomegalovirus infection and induction of calcification in Murine Aortic Vascular Smooth Muscle Cells (MOVAS)

Human cytomegalovirus (HCMV) is a widespread pathogen that causes lifelong latent infection in the majority of the world population. HCMV is associated with increased incidence and severity of many cardiovascular diseases including myocarditis, atherosclerosis, and transplant vasculopathy. Due to the species-restricted nature of cytomegalovirus infection, murine cytomegalovirus (MCMV) is a useful model that recapitulates many of the features of HCMV infection of the cardiovascular system. While in vivo MCMV studies are able to answer many questions regarding pathogenesis of infection, in vitro experiments using cell lines are useful tools to further understand the potential underlying mechanisms. In this study, we characterize MCMV infection of the murine aortic smooth muscle cell line (MOVAS). Our findings demonstrate that MOVAS cells are permissive for MCMV infection, form plaques under carboxymethyl cellulose overlay, and produce progeny virus similar to NIH 3T3 murine embryonic fibroblasts. In addition, MCMV infection induces calcification in MOVAS cells similar to that seen in the epicardium of MCMV-infected hearts. We conclude that MOVAS cells are a useful in vitro tool for studying CMV-mediated cardiac calcification.

Hypomethylation of Rnase6 Promoter Enhances Proliferation and Migration of Murine Aortic Vascular Smooth Muscle Cells and Aggravates Atherosclerosis in Mice

Background: Accumulating evidence has implicated DNA methylation in the progression of atherosclerosis (AS). Rnase6 has been reported to be upregulated in AS development, but the specific regulatory mechanism remains unclear.Material/Methods: Peripheral blood and sclerotic plaque tissues from 25 AS patients were collected to detect Rnase6 expression. Methylation-specific polymerase chain reaction (MSP) was used to detected Rnase6 methylation levels in the peripheral blood of AS patients. Rnase6 expression was knocked down or DNA methyltransferase 1 (DNMT1) was overexpressed in OX-LDL-treated mouse aortic smooth muscle cells (MOVAS), and cell proliferation, migration, ROS content, and inflammatory factor secretion levels were detected. 740 Y-P, a PI3K specific agonist, was introduced to verify the effect of Rnase6 promoter hypomethylation on the PI3K/Akt signaling pathway. We knocked down Rnase6 expression in ApoE−/− mice fed with a high-fat diet to examine Rnase6 promoter methylation levels. Plaque areas and inflammatory factor secretion were examined in AS mice overexpressing DNMT1.Results: Rnase6 expression was upregulated in the peripheral blood and plaque tissues of AS patients, accompanied by decreased methylation levels of the Rnase6 promoter. Interfering with Rnase6 expression or overexpressing DNMT1 in OX-LDL stimulated MOVAS inhibited cell proliferation and migration, decreased ROS content and inflammatory factor secretion, and inhibited PI3K pathway protein expression. Rnase6 expression was decreased in the peripheral blood and plaque tissues of si-Rnase6-injected mice, and Rnase6 promoter methylation was increased. Mice overexpressing DNMT1 showed less plaque areas in the aortic root and lower secretion levels of inflammatory factors.Conclusion: Hypomethylation of the promoter of Rnase6 enhanced the proliferation and migration of OX-LDL treated MOVAS, upregulated ROS content and inflammatory factor secretion levels in the cells, and activated the PI3K/Akt signaling pathway.