MiR-122 knockdown regulates vascular smooth muscle cells phenotypic switching through enhanced FOXO3 expression.

Vascular smooth muscle cells (VSMCs) phenotypic switching is identified as enhanced dedifferentiation, proliferation, and migration ability of VSMCs, in which microRNAs have been identified as important regulators of the process. The present study is aimed to explore the pathophysiological effect of miR-122 on VSMC phenotypic modulation. Here, the result showed that the decreased miR-122 expression was found in VSMCs subjected to platelet-derived growth factor-BB (PDGF-BB) treatment. Next, we investigated the response of miR-122 knockdown in VSMCs with PDGF-BB stimulation. MiR-122 silencing showed increased proliferation and migration capability, whereas attenuated the differentiation markers expression. The above results were reversed by miR-122 overexpression. Finally, we further demonstrated that FOXO3 was an important target for miR-122. Collectively, we demonstrated that miR-122 silencing promoted VSMC phenotypic modulation partially through upregulated FOXO3 expression that indicated miR-122 may be a novel therapeutic target for neointimal formation.

ALK7 Promotes Vascular Smooth Muscle Cells Phenotypic Modulation by Negative Regulating PPARγ Expression.

As a receptor for transforming growth factor-ß, nodal and activin, activin receptor-like kinase 7 (ALK7) previously acts as a suppressor of tumorigenesis and metastasis, which has emerged to play a key role in cardiovascular diseases. However, the potential effect and molecular mechanism of ALK7 on vascular smooth muscle cells' (VSMCs) phenotypic modulation have not been investigated. Using cultured mouse VSMCs with platelet-derived growth factor-BB administration, we observed that ALK7 showed a significantly increased expression in VSMCs accompanied by decreased VSMCs differentiation marker genes. Loss-of-function study demonstrated that ALK7 knockdown inhibited platelet-derived growth factor-BB-induced VSMCs phenotypic modulation characterized by increased VSMCs differentiation markers, reduced proliferation, and migration of VSMCs. Such above effects were reversed by ALK7 overexpression. Notably, we noticed that ALK7 silencing dramatically enhanced PPARγ expression, which was required for the attenuated effect of ALK7 knockdown on VSMCs phenotypic modulation. Collected, we identified that ALK7 acted as a novel and positive regulator for VSMCs phenotypic modulation partially through inactivation of PPARγ, which suggested that neutralization of ALK7 might act as a promising therapeutic strategy of intimal hyperplasia.

The Ubiquitin E3 Ligase TRAF6 Exacerbates Ischemic Stroke by Ubiquitinating and Activating Rac1.

Stroke is one of the leading causes of morbidity and mortality worldwide. Inflammation, oxidative stress, apoptosis, and excitotoxicity contribute to neuronal death during ischemic stroke; however, the mechanisms underlying these complicated pathophysiological processes remain to be fully elucidated. Here, we found that the expression of tumor necrosis factor receptor-associated factor 6 (TRAF6) was markedly increased after cerebral ischemia/reperfusion (I/R) in mice. TRAF6 ablation in male mice decreased the infarct volume and neurological deficit scores and decreased proinflammatory signaling, oxidative stress, and neuronal death after cerebral I/R, whereas transgenic overexpression of TRAF6 in male mice exhibited the opposite effects. Mechanistically, we demonstrated that TRAF6 induced Rac1 activation and consequently promoted I/R injury by directly binding and ubiquitinating Rac1. Either functionally mutating the TRAF6 ubiquitination site on Rac1 or inactivating Rac1 with a specific inhibitor reversed the deleterious effects of TRAF6 overexpression during I/R injury. In conclusion, our study demonstrated that TRAF6 is a key promoter of ischemic signaling cascades and neuronal death after cerebral I/R injury. Therefore, the TRAF6/Rac1 pathway might be a promising target to attenuate cerebral I/R injury.SIGNIFICANCE STATEMENT Stroke is one of the most severe and devastating neurological diseases globally. The complicated pathophysiological processes restrict the translation of potential therapeutic targets into medicine. Further elucidating the molecular mechanisms underlying cerebral ischemia/reperfusion injury may open a new window for pharmacological interventions to promote recovery from stroke. Our study revealed that ischemia-induced tumor necrosis factor receptor-associated factor 6 (TRAF6) upregulation binds and ubiquitinates Rac1 directly, which promotes neuron death through neuroinflammation and neuro-oxidative signals. Therefore, precisely targeting the TRAF6-Rac1 axis may provide a novel therapeutic strategy for stroke recovery.

Reduced atherosclerosis lesion size, inflammatory response in miR-150 knockout mice via macrophage effects.

Atherosclerosis is considered to be a chronic inflammatory disease that can lead to severe clinically important cardiovascular events. miR-150 is a small noncoding RNA that significantly enhances inflammatory responses by upregulating endothelial cell proliferation and migration, as well as intravascular environmental homeostasis. However, the exact role of miR-150 in atherosclerosis remains unknown. Here, we investigated the effect of miR-150 deficiency on atherosclerosis development. Using double-knockout (miR-150-/- and ApoE-/-) mice, we measured atherosclerotic lesion size and stability. Meanwhile, we conducted in vivo bone marrow transplantation to identify cellular-level components of the inflammatory response. Compared with mice deficient only in ApoE, the double-knockout mice had significantly smaller atherosclerotic lesions and displayed an attenuated inflammatory response. Moreover, miR-150 ablation promoted plaque stabilization via increases in smooth muscle cell and collagen content and decreased macrophage infiltration and lipid accumulation. The in vitro experiments indicated that an inflammatory response with miR-150 deficiency in atherosclerosis results directly from upregulated expression of the cytoskeletal protein, PDZ and LIM domain 1 (PDLIM1), in macrophages. More importantly, the decreases in phosphorylated p65 expression and inflammatory cytokine secretion induced by miR-150 ablation were reversed by PDLIM1 knockdown. These findings suggest that miR-150 is a promising target for the management of atherosclerosis.

Interferon Regulatory Factor 4 Inhibits Neointima Formation by Engaging Krüppel-Like Factor 4 Signaling.

BACKGROUND: The mechanisms underlying neointima formation remain unclear. Interferon regulatory factors (IRFs), which are key innate immune regulators, play important roles in cardiometabolic diseases. However, the function of IRF4 in arterial restenosis is unknown. METHODS: IRF4 expression was first detected in human and mouse restenotic arteries. Then, the effects of IRF4 on neointima formation were evaluated with universal IRF4-deficient mouse and rat carotid artery injury models. We performed immunostaining to identify IRF4-expressing cells in the lesions. Smooth muscle cell (SMC)-specific IRF4-knockout (KO) and -transgenic (TG) mice were generated to evaluate the effects of SMC-IRF4 on neointima formation. We used microarray, bioinformatics analysis, and chromatin immunoprecipitation assay to identify the downstream signals of IRF4 and to verify the targets in vitro. We compared SMC-IRF4-KO/Krüppel-like factor 4 (KLF4)-TG mice with SMC-IRF4-KO mice and SMC-specific IRF4-TG/KLF4-KO mice with SMC-specific IRF4-TG mice to investigate whether the effect of IRF4 on neointima formation is KLF4-dependent. The effect of IRF4 on SMC phenotype switching was also evaluated. RESULTS: IRF4 expression in both the human and mouse restenotic arteries is eventually downregulated. Universal IRF4 ablation potentiates neointima formation in both mice and rats. Immunostaining indicated that IRF4 was expressed primarily in SMCs in restenotic arteries. After injury, SMC-IRF4-KO mice developed a thicker neointima than control mice. This change was accompanied by increased SMC proliferation and migration. However, SMC-specific IRF4-TG mice exhibited the opposite phenotype, demonstrating that IRF4 exerts protective effects against neointima formation. The mechanistic study indicated that IRF4 promotes KLF4 expression by directly binding to its promoter. Genetic overexpression of KLF4 in SMCs largely reversed the neointima-promoting effect of IRF4 ablation, whereas ablation of KLF4 abolished the protective function of IRF4, indicating that the protective effects of IRF4 against neointima formation are KLF4-dependent. In addition, IRF4 promoted SMC dedifferentiation. CONCLUSIONS: IRF4 protects arteries against neointima formation by promoting the expression of KLF4 by directly binding to its promoter. Our findings suggest that this previously undiscovered IRF4-KLF4 axis plays a key role in vasculoproliferative pathology and may be a promising therapeutic target for the treatment of arterial restenosis.

Mindin deficiency in macrophages protects against foam cell formation and atherosclerosis by targeting LXR-ß.

Mindin, which is a highly conserved extracellular matrix protein, has been documented to play pivotal roles in regulating angiogenesis, inflammatory processes, and immune responses. The aim of the present study was to assess whether mindin contributes to the development of atherosclerosis. A significant up-regulation of Mindin expression was observed in the serum, arteries and atheromatous plaques of ApoE-/- mice after high-fat diet treatment. Mindin-/-ApoE-/- mice and macrophage-specific mindin overexpression in ApoE-/- mice (Lyz2-mindin-TG) were generated to evaluate the effect of mindin on the development of atherosclerosis. The Mindin-/-ApoE-/- mice exhibited significantly ameliorated atherosclerotic burdens in the entire aorta and aortic root and increased atherosclerotic plaque stability. Moreover, bone marrow transplantation further demonstrated that mindin deficiency in macrophages was largely responsible for the alleviated atherogenesis. The Lyz2-mindin-TG mice exhibited the opposite phenotype. Mindin deficiency enhanced foam cell formation by increasing the expression of cholesterol effectors, including ABCA1 and ABCG1. The mechanistic study indicated that mindin ablation promoted LXR-ß expression via a direct interaction. Importantly, LXR-ß inhibition largely reversed the ameliorating effect of mindin deficiency on foam cell formation and ABCA1 and ABCG1 expression. The present study demonstrated that mindin deficiency serves as a novel mediator that protects against foam cell formation and atherosclerosis by directly interacting with LXR-ß.

Oncostatin M receptor ß deficiency attenuates atherogenesis by inhibiting JAK2/STAT3 signaling in macrophages.

Oncostatin M (OSM) is a secreted cytokine mainly involved in chronic inflammatory and cardiovascular diseases through binding to OSM receptor ß (OSMR-ß). Recent studies demonstrated that the presence of OSM contributed to the destabilization of atherosclerotic plaque. To investigate whether OSMR-ß deficiency affects atherosclerosis, male OSMR-ß-/-ApoE-/- mice were generated and utilized. Here we observed that OSMR-ß expression was remarkably upregulated in both human and mouse atherosclerotic lesions, which were mainly located in macrophages. We found that OSMR-ß deficiency significantly ameliorated atherosclerotic burden in aorta and aortic root relative to ApoE-deficient littermates and enhanced the stability of atherosclerotic plaques by increasing collagen and smooth muscle cell content, while decreasing macrophage infiltration and lipid accumulation. Moreover, bone marrow transplantation of OSMR-ß-/- hematopoietic cells to atherosclerosis-prone mice displayed a consistent phenotype. Additionally, we observed a relatively reduced level of JAK2 and signal transducer and activator of transcription (STAT)3 in vivo and under Ox-LDL stimulation in vitro. Our findings suggest that OSMR-ß deficiency in macrophages improved high-fat diet-induced atherogenesis and plaque vulnerability. Mech-anistically, the protective effect of OSMR-ß deficiency on atherosclerosis may be partially attributed to the inhibition of the JAK2/STAT3 activation in macrophages, whereas OSM stimulation can activate the signaling pathway.

LILRB4 deficiency aggravates the development of atherosclerosis and plaque instability by increasing the macrophage inflammatory response via NF-κB signaling.

Atherosclerosis is a chronic inflammatory disease. LILRB4 is associated with the pathological processes of various inflammatory diseases. However, the potential function and underlying mechanisms of LILRB4 in atherogenesis remain to be investigated. In this study, LILRB4 expression was examined in both human and mouse atherosclerotic plaques. The effects and possible mechanisms of LILRB4 in atherogenesis and plaque instability were evaluated in LILRB4-/-ApoE-/- and ApoE-/- mice fed a high-fat diet. We found that LILRB4 was located primarily in macrophages, and its expression was up-regulated in atherosclerotic lesions from human coronary arteries and mouse aortic roots. LILRB4 deficiency significantly accelerated the development of atherosclerotic lesions and increased the instability of plaques, as evidenced by the increased infiltration of lipids, decreased amount of collagen components and smooth muscle cells. Moreover, LILRB4 deficiency in bone marrow-derived cells promoted the development of atherosclerosis. In vivo and in vitro analyses revealed that the pro-inflammatory effects of LILRB4 deficiency were mediated by the increased activation of NF-κB signaling due to decreased Shp1 phosphorylation. In conclusion, the present study indicates that LILRB4 deficiency promotes atherogenesis, at least partly, through reduced Shp1 phosphorylation, which subsequently enhances the NF-κB-mediated inflammatory response. Thus, targeting the "LILRB4-Shp1" axis may be a novel therapeutic approach for atherosclerosis.

MicroRNA-183 as a Novel Regulator Protects Against Cardiomyocytes Hypertrophy via Targeting TIAM1.

BACKGROUND: MicroRNAs serve as important regulators of the pathogenesis of cardiac hypertrophy. Among them, miR-183 is well documented as a novel tumor suppressor in previous studies, whereas it exhibits a downregulated expression in cardiac hypertrophy recently. The present study was aimed to examine the effect of miR-183 on cardiomyocytes hypertrophy. METHODS: Angiotensin II (Ang II) was used for establishment of cardiac hypertrophy model in vitro. Neonatal rat ventricular cardiomyocytes transfected with miR-183 mimic or negative control were further utilized for the phenotype analysis. Moreover, the bioinformatics analysis and luciferase reporter assays were used for exploring the potential target of miR-183 in cardiomyocytes. RESULTS: We observed a significant decreased expression of miR-183 in hypertrophic cardiomyocytes. Overexpression of miR-183 significantly attenuated the cardiomyocytes size morphologically and prohypertrophic genes expression. Moreover, we demonstrated that TIAM1 was a direct target gene of miR-183 verified by bioinformatics analysis and luciferase reporter assays, which showed a decreased mRNA and protein expression in the cardiomyocytes transfected with miR-183 upon Ang II stimulation. Additionally, the downregulated TIAM1 expression was required for the attenuated effect of miR-183 on cardiomyocytes hypertrophy. CONCLUSIONS: Taken together, these evidences indicated that miR-183 acted as a cardioprotective regulator for the development of cardiomyocytes hypertrophy via directly regulation of TIAM1.

RIP2 Knockdown Attenuates Vascular Smooth Muscle Cells Activation via Negative Regulating Myocardin Expression.

BACKGROUND: RIP2 is an adaptor protein contributing to the activation of nuclear factor-κB induced by TNF receptor-associated factor (TRAF) and nucleotide oligomerization domain (NOD)-dependent signaling implicated in innate and adaptive immune response. Beyond regulation of immunity, we aimed to elucidate the role of RIP2 in vascular smooth muscle cell (VSMC) phenotypic modulation. METHODS AND RESULTS: In the current study, we observed that RIP2 showed an increased expression in VSMCs with PDGF-BB stimulation in a dose-dependent manner. Knockdown of RIP2 expression mediated by adenovirus dramatically accelerated the expression of VSMC-specific differentiation genes induced by PDGF-BB. Silencing of RIP2 inhibited proliferative and migratory ability of VSMCs. Additionally, we demonstrated that RIP2 knockdown can promoted myocardin expression. Furthermore, RIP2 inhibition also can attenuate the formation of intimal hyperplasia. CONCLUSIONS: These findings suggested that RIP2 played an important role in regulation of VSMCs differentiation, migration, and proliferation that may due to affect myocardin expression. Our results indicated that RIP2 may be a novel therapeutic target for intimal hyperplasia.

Attenuated macrophage activation mediated by microRNA-183 knockdown through targeting NR4A2.

Atherosclerosis is considered a chronic inflammatory disease, and macrophages function as important mediators in the development of atherogenesis. MicroRNA (miR)-183 is a small non-coding RNA that acts as a novel tumor suppressor and has recently been proposed to affect cardiac hypertrophy. However, the exact role and underlying mechanism of miR-183 in macrophage activation remain unknown. In the present study, miR-183 showed upregulated expression in atheromatous plaques and in bone marrow-derived macrophages (BMDMs) subjected to stimulation with oxidized low-density lipoproteins. Using a miR-183 loss-of-function strategy, it was demonstrated that miR-183 knockdown significantly increased resolving M2 macrophage marker expression but decreased proinflammatory M1 macrophage marker expression, as well as attenuated NF-κB activation. Moreover, decreased foam-cell formation accompanied by upregulation of genes involved in cholesterol efflux and downregulation of genes implicated in cholesterol influx was found in BMDMs transfected with a miR-183 inhibitor. Mechanistically, macrophage activation mediated by miR-183 silencing was partially attributed to direct upregulation of NR4A2 expression in BMDMs. Thus, the present study suggests that neutralizing miR-183 may be a potential therapeutic strategy for the treatment of atherosclerosis.

Association Between Unstable Angina and CXCL17: a New Potential Biomarker.

Atherosclerosis and chemokines are strongly related, but the role of the chemokine CXCL17 in atherogenesis is still poorly understood. We aim to investigate the serum CXCL17 levels in different stages of patients with coronary heart disease and explore whether these differences contribute to atherosclerosis. In the current prospective study, we enrolled 48 patients with unstable angina (UA), 51 patients with stable angina (SA) and 41 patients for the control group (CG). All subjects were diagnosed by coronary angiography and Gensini score was used to evaluate the severity of coronary artery disease. The CXCL17 levels were determined using ELISA, while lipid metabolism indicators and high sensitivity C-reactive protein (hs-CRP) were detected by automatic biochemical analyzer. We observed that the unstable angina group had higher CXCL17 levels compared with the stable angina and the control group. The logistic regression analysis showed that CXCL17 was an independent risk factor for unstable angina. Our results showed that CXCL17 was also statistically correlated with hs-CRP, while it was irrelevant with Gensini score. CXCL17 levels were associated with activity of inflammatory response and the instability of atherosclerotic plaques. These results suggest that CXCL17 elevation may be a potential new biomarker of unstable angina.

Tollip Negatively Regulates Vascular Smooth Muscle Cell-Mediated Neointima Formation by Suppressing Akt-Dependent Signaling.

BACKGROUND: Tollip, a well-established endogenous modulator of Toll-like receptor signaling, is involved in cardiovascular diseases. The aim of this study was to investigate the role of Tollip in neointima formation and its associated mechanisms. METHODS AND RESULTS: In this study, transient increases in Tollip expression were observed in platelet-derived growth factor-BB-treated vascular smooth muscle cells and following vascular injury in mice. We then applied loss-of-function and gain-of-function approaches to elucidate the effects of Tollip on neointima formation. While exaggerated neointima formation was observed in Tollip-deficient murine neointima formation models, Tollip overexpression alleviated vascular injury-induced neointima formation by preventing vascular smooth muscle cell proliferation, dedifferentiation, and migration. Mechanistically, we demonstrated that Tollip overexpression may exert a protective role in the vasculature by suppressing Akt-dependent signaling, which was further confirmed in rescue experiments using the Akt-specific inhibitor (AKTI). CONCLUSIONS: Our findings indicate that Tollip protects against neointima formation by negatively regulating vascular smooth muscle cell proliferation, dedifferentiation, and migration in an Akt-dependent manner. Upregulation of Tollip may be a promising strategy for treating vascular remodeling-related diseases.

Restoration of Circulating MFGE8 (Milk Fat Globule-EGF Factor 8) Attenuates Cardiac Hypertrophy Through Inhibition of Akt Pathway.

Cardiac hypertrophy occurs in response to numerous stimuli like neurohumoral stress, pressure overload, infection, and injury, and leads to heart failure. Mfge8 (milk fat globule-EGF factor 8) is a secreted protein involved in various human diseases, but its regulation and function during cardiac hypertrophy remain unexplored. Here, we found that circulating MFGE8 levels declined significantly in failing hearts from patients with dilated cardiomyopathy. Correlation analyses revealed that circulating MFGE8 levels were negatively correlated with the severity of cardiac dysfunction and remodeling in affected patients. Deleting Mfge8 in mice maintained normal heart function at basal level but substantially exacerbated the hypertrophic enlargement of cardiomyocytes, reprogramming of pathological genes, contractile dysfunction, and myocardial fibrosis after aortic banding surgery. In contrast, cardiac-specific Mfge8 overexpression in transgenic mice significantly blunted aortic banding-induced cardiac hypertrophy. Whereas MAPK (mitogen-activated protein kinase) pathways were unaffected in either Mfge8-knockout or Mfge8-overexpressing mice, the activated Akt/PKB (protein kinase B)-Gsk-3ß (glycogen synthase kinase-3ß)/mTOR (mammalian target of rapamycin) pathway after aortic banding was significantly potentiated by Mfge8 deficiency but suppressed by Mfge8 overexpression. Inhibition of Akt with MK-2206 blocked the prohypertrophic effects of Mfge8 deficiency in angiotensin II-treated neonatal rat cardiomyocytes. Finally, administering a recombinant human MFGE8 in mice in vivo alleviated cardiac hypertrophy induced by aortic banding. Our findings indicate that Mfge8 is an endogenous negative regulator of pathological cardiac hypertrophy and may, thus, have potential both as a novel biomarker and as a therapeutic target for treatment of cardiac hypertrophy.

Dickkopf-3 Ablation Attenuates the Development of Atherosclerosis in ApoE-Deficient Mice.

BACKGROUND: Dickkopf-3 (DKK3) is a negative regulator of the Wnt/ß-catenin signaling pathway, which is involved in inflammation. However, little is known about the relationship between DKK3 expression and the progression of atherosclerosis. The aim of the present study was to define the role of DKK3 and its potential mechanism in the development of atherosclerosis. METHODS AND RESULTS: Immunofluorescence analysis showed that DKK3 was strongly expressed in macrophages of atherosclerotic plaques from patients with coronary heart disease and in hyperlipidemic mice. The expression level was significantly increased in atherogenesis. DKK3-/-ApoE-/- mice exhibited a significant decrease in atherosclerotic lesions in the entire aorta, aortic sinus, and brachiocephalic arteries. Transplantation of bone marrow from DKK3-/-ApoE-/- mice into lethally irradiated ApoE-/- recipients resulted in a reduction of atherosclerotic lesions, compared with the lesions in recipients transplanted with ApoE-/- donor cells, suggesting that the effect of DKK3 deficiency was largely mediated by bone marrow-derived cells. A reduction in the necrotic core size, accompanied by increased collagen content and smooth muscle cells and decreased accumulation of macrophages and lipids, contributed to the stability of plaques in DKK3-/-ApoE-/- mice. Furthermore, multiple proinflammatory cytokines exhibited marked decreases in DKK3-/-ApoE-/- mice. Finally, we observed that DKK3 ablation increased ß-catenin expression in the nuclei of macrophages both in vivo and in vitro. CONCLUSIONS: DKK3 expression in macrophages is involved in the pathogenesis of atherosclerosis through modulation of inflammation and inactivation of the Wnt/ß-catenin pathway.