A novel RhoA/ROCK-CPI-17-MEF2C signaling pathway regulates vascular smooth muscle cell gene expression

MEF2C Directly Interacts with Pre-miRNAs and Distinct RNPs to Post-Transcriptionally Regulate miR-23a-miR-27a-miR-24-2 microRNA Cluster Member Expression

Transcriptional regulation constitutes a key step in gene expression regulation. Myocyte enhancer factor 2C (MEF2C) is a transcription factor of the MADS box family involved in the early development of several cell types, including muscle cells. Over the last decade, a novel layer of complexity modulating gene regulation has emerged as non-coding RNAs have been identified, impacting both transcriptional and post-transcriptional regulation. microRNAs represent the most studied and abundantly expressed subtype of small non-coding RNAs, and their functional roles have been widely documented. On the other hand, our knowledge of the transcriptional and post-transcriptional regulatory mechanisms that drive microRNA expression is still incipient. We recently demonstrated that MEF2C is able to transactivate the long, but not short, regulatory element upstream of the miR-23a-miR-27a-miR-24-2 transcriptional start site. However, MEF2C over-expression and silencing, respectively, displayed distinct effects on each of the miR-23a-miR-27a-miR-24-2 mature cluster members without affecting pri-miRNA expression levels, thus supporting additional MEF2C-driven regulatory mechanisms. Within this study, we demonstrated a complex post-transcriptional regulatory mechanism directed by MEF2C in the regulation of miR-23a-miR-27a-miR-24-2 cluster members, distinctly involving different domains of the MEF2C transcription factor and the physical interaction with pre-miRNAs and Ksrp, HnRNPa3 and Ddx17 transcripts.

Re-routing GPR56 signalling using Gα12/13 G protein chimeras

Adhesion G protein-coupled receptors (aGPCRs) constitute the second largest subclass of the GPCR superfamily. Although canonical GPCRs are explored pharmacologically as drug targets, no clinically approved drugs target the aGPCR family so far. The aGPCR GPR56/ADGRG1 stands out as an especially promising target, given its direct link to the monogenetic disease bilateral frontoparietal polymicrogyria and implications in cancers. Key to understanding GPCR pharmacology has been mapping out intracellular signalling activity. Detection of GPCR signalling in the Gαs /Gαi /Gαq G protein pathways is feasible with second messenger detection systems. However, in the case of Gα12/13 -coupled receptors, like GPR56, signalling detection is more challenging due to the lack of direct second messenger generation. To overcome this challenge, we engineered a Gαq chimera to translate Gα12/13 signalling. We show the ability of the chimeric GαΔ6q12myr and GαΔ6q13myr to translate basal Gα12/13 signalling of GPR56 to a Gαq readout in transcription factor luciferase reporter systems and show that the established peptide ligands (P7 and P19) function to enhance this signal. We further demonstrate the ability to directly influence the generation of second messengers in inositol-3-phosphate assays. In the future, these chimeric G proteins could facilitate basic functional studies, drug screenings and deorphanization of other aGPCRs.

Single-cell RNA sequencing reveals transcriptional changes of human choroidal and retinal pigment epithelium cells during fetal development, in healthy adult and intermediate age-related macular degeneration

Age-related macular degeneration (AMD) is the most prevalent cause of blindness in the developed world. Vision loss in the advanced stages of the disease is caused by atrophy of retinal photoreceptors, overlying retinal pigment epithelium (RPE) and choroidal endothelial cells. The molecular events that underline the development of these cell types from in utero to adult as well as the progression to intermediate and advanced stages AMD are not yet fully understood. We performed single-cell RNA-sequencing (RNA-Seq) of human fetal and adult RPE-choroidal tissues, profiling in detail all the cell types and elucidating cell type-specific proliferation, differentiation and immunomodulation events that occur up to midgestation. Our data demonstrate that progression from the fetal to adult state is characterized by an increase in expression of genes involved in the oxidative stress response and detoxification from heavy metals, suggesting a better defence against oxidative stress in the adult RPE-choroid tissue. Single-cell comparative transcriptional analysis between a patient with intermediate AMD and an unaffected subject revealed a reduction in the number of RPE cells and melanocytes in the macular region of the AMD patient. Together these findings may suggest a macular loss of RPE cells and melanocytes in the AMD patients, but given the complex processing of tissues required for single-cell RNA-Seq that is prone to technical artefacts, these findings need to be validated by additional techniques in a larger number of AMD patients and controls.

Mfge8 is expressed by pericytes in gastric antrum submucosa from patients with obesity

The main function of the stomach is to digest ingested food. Gastric antrum muscular contractions mix ingested food with digestive enzymes and stomach acid and propel the chyme through the pyloric sphincter at a rate in which the small intestine can process the chyme for optimal nutrient absorption. Mfge8 binding to α8β1 integrins helps regulate gastric emptying by reducing the force of antral smooth muscle contractions. The source of Mfge8 within gastric muscles is unclear. Since Mfge8 is a secreted protein, Mfge8 could be delivered via the circulation, or be locally secreted by cells within the muscle layers. In this study, we identify a source of Mfge8 within human gastric antrum muscles using spatial transcriptomic analysis. We show that Mfge8 is expressed in subpopulations of Mef2c+ perivascular cells within the submucosa layer of the gastric antrum. Mef2c is expressed in subpopulations of NG2+ and PDGFRB+ pericytes. Mfge8 is expressed in NG2+/Mef2c+ pericytes, but not in NG2+/Mef2c-, PDGFRB+/Mef2c-, or PDGFRB+/Mef2c+ pericytes. Mfge8 is absent from CD34+ endothelial cells but is expressed in a small population of perivascular ACTA2+ cells. We also show that α8 integrin is not expressed by interstitial cells of Cajal (ICC), supporting the findings that Mfge8 attenuates gastric antrum smooth muscle contractions by binding to α8β1 integrins on enteric smooth muscle cells. These findings suggest a novel, supplementary mechanism of regulation of gastric antrum motility by cellular regulators of capillary blood flow, in addition to the regulation of gastric antrum motility by the enteric nervous system and the SMC, ICC, and PDGFRα+ cell (SIP) syncytium.

Single-cell RNA sequencing reveals the developmental program underlying proximal-distal patterning of the human lung at the embryonic stage

The lung is the primary respiratory organ in human, in which the proximal airway and the distal alveoli are responsible for air conduction and gas exchange, respectively. However, the regulation of proximal-distal patterning at the embryonic stage of human lung development is largely unknown. Here we investigated the early lung development of human embryos at weeks 4-8 post fertilization (Carnegie stages 12-21) using single-cell RNA sequencing, and obtained a transcriptomic atlas of 169,686 cells. We observed discernible gene expression patterns of proximal and distal epithelia at week 4, upon the initiation of lung organogenesis. Moreover, we identified novel transcriptional regulators of the patterning of proximal (e.g., THRB and EGR3) and distal (e.g., ETV1 and SOX6) epithelia. Further dissection revealed various stromal cell populations, including an early-embryonic BDNF⁺ population, providing a proximal-distal patterning niche with spatial specificity. In addition, we elucidated the cell fate bifurcation and maturation of airway and vascular smooth muscle progenitor cells at the early stage of lung development. Together, our study expands the scope of human lung developmental biology at early embryonic stages. The discovery of intrinsic transcriptional regulators and novel niche providers deepens the understanding of epithelial proximal-distal patterning in human lung development, opening up new avenues for regenerative medicine.

Inhibition of tiRNA-Gly-GCC ameliorates neointimal formation via CBX3-mediated VSMCs phenotypic switching

Background and aim

tRNA-derived fragments (tRFs) are a new class of non-coding RNAs involved in a variety of pathological processes, but their biological functions and mechanisms in human aortic smooth muscle cells (HASMCs) phenotype transition and vascular intimal hyperplasia are unclear.

Methods/results

tiRNA-Gly-GCC is upregulated in synthetic HASMCs, atherosclerotic arteries, plasma, and the balloon injured carotid artery of rats. Functionally, the inhibition of tiRNA-Gly-GCC represses HASMCs proliferation, migration, and reversed dedifferentiation, whereas the overexpression of tiRNA- Gly-GCC have contrary effects. Mechanistically, tiRNA-Gly-GCC performs these functions on HASMCs via downregulating chromobox protein homolog 3 (CBX3). Finally, the inhibition of tiRNA-Gly-GCC could ameliorate neointimal formation after vascular injury in vivo.

Conclusions

tiRNA-Gly-GCC is a mediator of HASMCs phenotypic switching by targeting CBX3 and inhibition of tiRNA-Gly-GCC suppresses neointimal formation.

Transcriptional regulation of vascular smooth muscle cell proliferation, differentiation and senescence: Novel targets for therapy

Vascular smooth muscle cells (SMC) possess a unique cytoplasticity, regulated by transcriptional, translational and phenotypic transformation in response to a diverse range of extrinsic and intrinsic pathogenic factors. The mature, differentiated SMC phenotype is physiologically typified transcriptionally by expression of genes encoding "contractile" proteins, such as SMα-actin (ACTA2), SM-MHC (myosin-11) and SM22α (transgelin). When exposed to various pathological conditions (e.g., pro-atherogenic risk factors, hypertension), SMC undergo phenotypic modulation, a bioprocess enabling SMC to de-differentiate in immature stages or trans-differentiate into other cell phenotypes. As recent studies suggest, the process of SMC phenotypic transformation involves five distinct states characterized by different patterns of cell growth, differentiation, migration, matrix protein expression and declined contractility. These changes are mediated via the action of several transcriptional regulators, including myocardin and serum response factor. Conversely, other factors, including Kruppel-like factor 4 and nuclear factor-κB, can inhibit SMC differentiation and growth arrest, while factors such as yin yang-1, can promote SMC differentiation whilst inhibiting proliferation. This article reviews recent advances in our understanding of regulatory mechanisms governing SMC phenotypic modulation. We propose the concept that transcription factors mediating this switching are important biomarkers and potential pharmacological targets for therapeutic intervention in cardiovascular disease.

Molecular targets of statins and their potential side effects: Not all the glitter is gold

Statins are a class of drugs widely used worldwide to manage hypercholesterolemia and the prevention of secondary heart attacks. Currently, available statins vary in terms of their pharmacokinetic and pharmacodynamic profiles. Although the primary target of statins is the inhibition of HMG-CoA reductase (HMGR), the rate-limiting enzyme in cholesterol biosynthesis, statins exhibit many pleiotropic effects downstream of the mevalonate pathway. These pleiotropic effects include the ability to reduce myocardial fibrosis, pathologic cardiac disease states, hypertension, promote bone differentiation, anti-inflammatory, and antitumor effects through multiple mechanisms. Although these pleiotropic effects of statins may be a cause for enthusiasm, there are many adverse effects that, for the most part, are unappreciated and need to be highlighted. These adverse effects include myopathy, new-onset type 2 diabetes, renal and hepatic dysfunction. Although these adverse effects may be relatively uncommon, considering the number of people worldwide who use statins daily, the actual number of people affected becomes quite large. Also, co-administration of statins with several other medications, herbal agents, and foods, which interact through common enzymatic pathways, can have untoward clinical consequences. In this review, we address these concerns.

Serum from Patients with Severe Alcoholic Liver Cirrhosis Inhibits Proliferation and Migration of Human Coronary Artery Smooth Muscle Cells

Liver cirrhosis has been associated with an increased risk of coronary artery disease and clinical complications following percutaneous coronary revascularization. The present study is based on the hypothesis that cirrhosis may influence intimal hyperplasia following PCI. Sera from 10 patients with alcoholic liver cirrhosis and 10 age-matched healthy controls were used to stimulate cultured human coronary artery smooth muscle cells (HCASMC) for 48 h. HCASMC proliferation, migration, gene expression and apoptosis were investigated. Serum concentrations of growth factors and markers of liver function were also determined in patients and healthy controls. Treatment of HCASMC with patient sera reduced cell proliferation and migration (p < 0.05 vs. healthy controls), whereas apoptosis was unaffected (p = 0.160). Expression of genes associated with a synthetic vascular smooth muscle cell phenotype was decreased in cells stimulated with serum from cirrhotic patients (RBP1, p = 0.001; SPP1, p = 0.003; KLF4, p = 0.004). Platelet-derived growth factor-BB serum concentrations were lower in patients (p = 0.001 vs. controls). The results suggest the presence of circulating factors in patients with alcoholic liver cirrhosis affecting coronary smooth muscle cell growth. These findings may have implications for clinical outcomes following percutaneous coronary revascularization in these patients.

Copeptin, miRNA-208, and miRNA-499 as New Biomarkers for Early Detection of Acute Coronary Syndrome

cTn and CK-MB are gold standard biomarkers for acute coronary syndrome (ACS) but are less sensitive in the first 3 h after onset of symptoms. A need thus exists for novel biomarkers for early detection of ACS. We evaluated circulating copeptin, miRNA-208, and miRNA-499 as possible biomarkers for early detection of unstable angina (UA) and non-ST-segment elevation myocardial infarction (NSTEMI). Sixty-five patients with probable ACS that presented within 4 h of the onset of chest pain (23 UA and 42 NSTEMI) and 25 apparently healthy individuals were studied. Two sets of blood samples collected in the first 3 h and at 6 h after onset were analyzed for copeptin levels via ELISA and miRNA-208 and miRNA-499 expression via real-time PCR. Copeptin, miRNA-208, and miRNA-499 expression levels were significantly increased in UA and NSTEMI patients compared with controls (p < 0.001) and in NSTEMT compared with UA patients (p < 0.001). Levels were also significantly elevated in UA and NSTEMI patients with negative cardiac troponin in the first 3 h (p < 0.001). ROC curves displayed AUC for prediction of ACS of 0.96 for copeptin, 0.97 for miRNA-208, and 0.97 for miRNA-499. Their combination improved AUC to 0.98. Copeptin and miRNA-208 and miRNA-499 expression are promising biomarkers for UA and NSTEMI that present in the first 3 h of pain onset. A combination of these markers with cTn may increase the accuracy of diagnosis by avoiding the gray zone of cTn as a biomarker.

The Emerging Role of Epigenetics in Therapeutic Targeting of Cardiomyopathies

Cardiomyopathies (CMPs) are a heterogeneous group of myocardial diseases accountable for the majority of cases of heart failure (HF) and/or sudden cardiac death (SCD) worldwide. With the recent advances in genomics, the original classification of CMPs on the basis of morphological and functional criteria (dilated (DCM), hypertrophic (HCM), restrictive (RCM), and arrhythmogenic ventricular cardiomyopathy (AVC)) was further refined into genetic (inherited or familial) and acquired (non-inherited or secondary) forms. Despite substantial progress in the identification of novel CMP-associated genetic variations, as well as improved clinical recognition diagnoses, the functional consequences of these mutations and the exact details of the signaling pathways leading to hypertrophy, dilation, and/or contractile impairment remain elusive. To date, global research has mainly focused on the genetic factors underlying CMP pathogenesis. However, growing evidence shows that alterations in molecular mediators associated with the diagnosis of CMPs are not always correlated with genetic mutations, suggesting that additional mechanisms, such as epigenetics, may play a role in the onset or progression of CMPs. This review summarizes published findings of inherited CMPs with a specific focus on the potential role of epigenetic mechanisms in regulating these cardiac disorders.

Single-cell RNA-seq reveals cellular heterogeneity of mouse carotid artery under disturbed flow

Disturbed blood flow (d-flow) has been known to induce changes of the cells in the arterial wall, increasing the risk of atherosclerosis. However, the heterogeneity of the vascular cell populations under d-flow remains less understood. To generate d-flow in vivo, partial carotid artery ligation (PCL) was performed. Seven days after ligation, single-cell RNA sequencing of nine left carotid arteries (LCA) from the PCL group (10,262 cells) or control group (14,580 cells) was applied and a single-cell atlas of gene expression was constructed. The integrated analysis identified 15 distinct carotid cell clusters, including 10 d-flow-relevant subpopulations. Among endothelial cells, at least four subpopulations were identified, including Klk8hi ECs, Lrp1hi ECs, Dkk2hi ECs, and Cd36hi ECs. Analysis of GSVA and single-cell trajectories indicated that the previously undescribed Dkk2hi ECs subpopulation was mechanosensitive and potentially transformed from Klk8hi ECs under d-flow. D-flow-induced Spp1hi VSMCs subpopulation that appeared to be endowed with osteoblast differentiation, suggesting a role in arterial stiffness. Among the infiltrating cell subpopulations, Trem2hi Mφ, Birc5hi Mφ, DCs, CD4+ T cells, CXCR6+ T cells, NK cells, and granulocytes were identified under d-flow. Of note, the novel Birc5hi Mφ was identified as a potential contributor to the accumulation of macrophages in atherosclerosis. Finally, Dkk2hi ECs, and Cd36hi ECs were also found in the proatherosclerotic area of the aorta where the d-flow occurs. In conclusion, we presented a comprehensive single-cell atlas of all cells in the carotid artery under d-flow, identified previously unrecognized cell subpopulations and their gene expression signatures, and suggested their specialized functions.

Cortical organoids model early brain development disrupted by 16p11.2 copy number variants in autism

Reciprocal deletion and duplication of the 16p11.2 region is the most common copy number variation (CNV) associated with autism spectrum disorders. We generated cortical organoids from skin fibroblasts of patients with 16p11.2 CNV to investigate impacted neurodevelopmental processes. We show that organoid size recapitulates macrocephaly and microcephaly phenotypes observed in the patients with 16p11.2 deletions and duplications. The CNV dosage affects neuronal maturation, proliferation, and synapse number, in addition to its effect on organoid size. We demonstrate that 16p11.2 CNV alters the ratio of neurons to neural progenitors in organoids during early neurogenesis, with a significant excess of neurons and depletion of neural progenitors observed in deletions. Transcriptomic and proteomic profiling revealed multiple pathways dysregulated by the 16p11.2 CNV, including neuron migration, actin cytoskeleton, ion channel activity, synaptic-related functions, and Wnt signaling. The level of the active form of small GTPase RhoA was increased in both, deletions and duplications. Inhibition of RhoA activity rescued migration deficits, but not neurite outgrowth. This study provides insights into potential neurobiological mechanisms behind the 16p11.2 CNV during neocortical development.

Inhibition of miR-223 Expression Using a Sponge Strategy Decreases Restenosis in Rat Injured Carotids

OBJECTIVE

Restenosis is a frequent complication of angioplasty. It consists of a neointimal hyperplasia resulting from progression and migration of vascular smooth muscle cells (VSMC) into the vessel lumen. microRNA miR-223 has recently been shown to be involved in cardiovascular diseases including atherosclerosis, vascular calcification and arterial thrombosis. In this study, our aim was to assess the impact of miR-223 modulation on restenosis in a rat model of carotid artery after balloon injury.

METHODS

The over and down-expression of miR-223 was induced by adenoviral vectors, containing either a pre-miR-223 sequence allowing artificial miR-223 expression or a sponge sequence, trapping the native microRNA, respectively. Restenosis was quantified on stained rat carotid sections.

RESULTS

In vitro, three mRNA (Myocyte Enhancer Factor 2C (MEF2C), Ras homolog gene family, member B (RhoB) and Nuclear factor 1 A-type (NFIA)) reported as miR-223 direct targets and known to be implicated in VSMC differentiation and contractility were studied by RT-qPCR. Our findings showed that down-expression of miR-223 significantly reduced neointimal hyperplasia by 44% in carotids, and was associated with a 2-3-fold overexpression of MEF2C, RhoB and NFIA in a murine monocyte macrophage cell line, RAW 264.7 cells.

CONCLUSION

Down-regulating miR-223 could be a potential therapeutic approach to prevent restenosis after angioplasty.

FGF12 (Fibroblast Growth Factor 12) Inhibits Vascular Smooth Muscle Cell Remodeling in Pulmonary Arterial Hypertension

Loss of BMP (bone morphogenic protein) signaling induces a phenotype switch of pulmonary arterial smooth muscle cells (PASMCs), which is the pathological basis of pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). Here, we identified FGF12 (fibroblast growth factor 12) as a novel regulator of the BMP-induced phenotype change in PASMCs and elucidated its role in pulmonary vascular remodeling during PAH development. Using murine models of PAH and lung specimens of patients with PAH, we observed that FGF12 expression was significantly reduced in PASMCs. In human PASMCs, FGF12 expression was increased by canonical BMP signaling. FGF12 knockdown blocked the antiproliferative and prodifferentiation effect of BMP on human PASMCs, suggesting that FGF12 is required for the BMP-mediated acquisition of the quiescent and differentiated PASMC phenotype. Mechanistically, FGF12 regulated the BMP-induced phenotype change by inducing MEF2a (myocyte enhancer factor 2a) phosphorylation via p38MAPK signaling, thereby modulating the expression of MEF2a target genes involved in cell proliferation and differentiation. Furthermore, we observed that TG (transgenic) mice with smooth muscle cell-specific FGF12 overexpression were protected from chronic hypoxia-induced PAH development, pulmonary vascular remodeling, and right ventricular hypertrophy. Consistent with the in vitro data using human PASMCs, FGF12 TG mice showed increased MEF2a phosphorylation and a substantial change in MEF2a target gene expression, compared with the WT (wild type) controls. Overall, our findings demonstrate a novel BMP/FGF12/MEF2a pathway regulating the PASMC phenotype switch and suggest FGF12 as a potential target for the development of therapeutics for ameliorating pulmonary vascular remodeling in PAH.

BNIP3L/Nix-induced mitochondrial fission, mitophagy, and impaired myocyte glucose uptake are abrogated by PRKA/PKA phosphorylation

Lipotoxicity is a form of cellular stress caused by the accumulation of lipids resulting in mitochondrial dysfunction and insulin resistance in muscle. Previously, we demonstrated that the mitophagy receptor BNIP3L/Nix is responsive to lipotoxicity and accumulates in response to a high-fat (HF) feeding. To provide a better understanding of this observation, we undertook gene expression array and shot-gun metabolomics studies in soleus muscle from rodents on an HF diet. Interestingly, we observed a modest reduction in several autophagy-related genes. Moreover, we observed alterations in the fatty acyl composition of cardiolipins and phosphatidic acids. Given the reported roles of these phospholipids and BNIP3L in mitochondrial dynamics, we investigated aberrant mitochondrial turnover as a mechanism of impaired myocyte insulin signaling. In a series of gain-of-function and loss-of-function experiments in rodent and human myotubes, we demonstrate that BNIP3L accumulation triggers mitochondrial depolarization, calcium-dependent activation of DNM1L/DRP1, and mitophagy. In addition, BNIP3L can inhibit insulin signaling through activation of MTOR-RPS6KB/p70S6 kinase inhibition of IRS1, which is contingent on phosphatidic acids and RHEB. Finally, we demonstrate that BNIP3L-induced mitophagy and impaired glucose uptake can be reversed by direct phosphorylation of BNIP3L by PRKA/PKA, leading to the translocation of BNIP3L from the mitochondria and sarcoplasmic reticulum to the cytosol. These findings provide insight into the role of BNIP3L, mitochondrial turnover, and impaired myocyte insulin signaling during an overfed state when overall autophagy-related gene expression is reduced. Furthermore, our data suggest a mechanism by which exercise or pharmacological activation of PRKA may overcome myocyte insulin resistance.

Abbreviations: BCL2: B cell leukemia/lymphoma 2; BNIP3L/Nix: BCL2/adenovirus E1B interacting protein 3-like; DNM1L/DRP1: dynamin 1-like; FUNDC1: FUN14 domain containing 1; IRS1: insulin receptor substrate 1; MAP1LC3A/LC3: microtubule-associated protein 1 light chain 3 alpha; MFN1: mitofusin 1; MFN2: mitofusin 2; MTOR: mechanistic target of rapamycin kinase; OPA1: OPA1 mitochondrial dynamin like GTPase; PDE4i: phosphodiesterase 4 inhibitor; PLD1: phospholipase D1; PLD6: phospholipase D family member 6; PRKA/PKA: protein kinase, AMP-activated; PRKCD/PKCδ: protein kinase C, delta; PRKCQ/PKCθ: protein kinase C, theta; RHEB: Ras homolog enriched in brain; RPS6KB/p70S6K: ribosomal protein S6 kinase; SQSTM1/p62: sequestosome 1; YWHAB/14-3-3β: tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein beta

Serum response factor-cofactor interactions and their implications in disease

Serum response factor (SRF), a member of the Mcm1, Agamous, Deficiens, and SRF (MADS) box transcription factor, is widely expressed in all cell types and plays a crucial role in the physiological function and development of diseases. SRF regulates its downstream genes by binding to their CArG DNA box by interacting with various cofactors. However, the underlying mechanisms are not fully understood, therefore attracting increasing research attention due to the importance of this topic. This review's objective is to discuss the new progress in the studies of the molecular mechanisms involved in the activation of SRF and its impacts in physiological and pathological conditions. Notably, we summarized the recent studies on the interaction of SRF with its two main types of cofactors belonging to the myocardin families of transcription factors and the members of the ternary complex factors. The knowledge of these mechanisms will create new opportunities for understanding the dynamics of many traits and disease pathogenesis especially, cardiovascular diseases and cancer that could serve as targets for pharmacological control and treatment of these diseases.

Crystal Structures of Ternary Complexes of MEF2 and NKX2-5 Bound to DNA Reveal a Disease Related Protein-Protein Interaction Interface

MEF2 and NKX2-5 transcription factors interact with each other in cardiogenesis and are necessary for normal heart formation. Despite evidence suggesting that these two transcription factors function synergistically and possibly through direct physical interactions, molecular mechanisms by which they interact are not clear. Here we determined the crystal structures of ternary complexes of MEF2 and NKX2-5 bound to myocardin enhancer DNA in two crystal forms. These crystal structures are the first example of human MADS-box/homeobox ternary complex structures involved in cardiogenesis. Our structures reveal two possible modes of interactions between MEF2 and NKX2-5: MEF2 and NKX bind to adjacent DNA sites to recognize DNA in cis; and MEF2 and NKX bind to different DNA strands to interact with each other in trans via a conserved protein-protein interface observed in both crystal forms. Disease-related mutations are mapped to the observed protein-protein interface. Our structural studies provide a starting point to understand and further study the molecular mechanisms of the interactions between MEF2 and NKX2.5 and their roles in cardiogenesis.

Canonical transient receptor potential 6 channel deficiency promotes smooth muscle cells dedifferentiation and increased proliferation after arterial injury

Objective

Previous studies showed the benefit of canonical transient receptor potential 6 (TRPC6) channel deficiency in promoting endothelial healing of arterial injuries in hypercholesterolemic animals. Long-term studies utilizing a carotid wire-injury model were undertaken in wild-type (WT) and TRPC6^-/- mice to determine the effects of TRPC6 on phenotypic modulation of vascular smooth muscle cells (SMC) and neointimal hyperplasia. We hypothesized that TRPC6 was essential in the maintenance or reexpression of a differentiated SMC phenotype and minimized luminal stenosis following arterial injury.

Methods

The common carotid arteries (CCA) of WT and TRPC6^-/- mice were evaluated at baseline and 4 weeks after wire injury. At baseline, CCA of TRPC6^-/- mice had reduced staining of MYH11 and SM22, fewer elastin lamina, luminal dilation, and wall thinning. After carotid wire injury, TRPC6^-/- mice developed significantly more pronounced luminal stenosis compared with WT mice. Injured TRPC6^-/- CCA demonstrated increased medial/intimal cell number and active cell proliferation when compared with WT CCA. Immunohistochemistry suggested that expression of contractile biomarkers in medial SMC were essentially at baseline levels in WT CCA at 28 days after wire injury. By contrast, at 28 days after injury medial SMC from TRPC6^-/- CCA showed a significant decrease in the expression of contractile biomarkers relative to baseline levels. To assess the role of TRPC6 in systemic arterial SMC phenotype modulation, SMC were harvested from thoracic aortae of WT and TRPC6^-/- mice and were characterized. TRPC6^-/- SMC showed enhanced proliferation and migration in response to serum stimulation. Expression of contractile phenotype biomarkers, MYH11 and SM22, was attenuated in TRPC6^-/- SMC. siRNA-mediated TRPC6 deficiency inhibited contractile biomarker expression in a mouse SMC line.

Conclusions

These results suggest that TRPC6 contributes to the restoration or maintenance of arterial SMC contractile phenotype following injury. Understanding the role of TRPC6 in phenotypic modulation may lead to mechanism-based therapies for attenuation of IH.

After endovascular intervention and open vascular surgery, vascular smooth muscle cells (VSMC) undergo a coordinated reprogramming of gene expression to facilitate arterial healing. Down regulation of VSMC-specific contractile biomarkers (eg, SM22 and MYH11) and induction of pathways that promote cell proliferation, migration, and matrix synthesis are hallmarks of this phenotypic switch. Dysregulated phenotypic switching leads to the development of neointimal hyperplasia and vascular restenosis. Identifying pathways that regulate or constrain VSMC phenotypic modulation, therefore, has the potential to decrease neointimal hyperplasia and improve outcomes after vascular intervention. In this study, we demonstrate that depletion of the non-voltage-gated cation channel TRPC6 promotes phenotypic switching and loss of contractile biomarkers in systemic arterial VSMC. TRPC6^-/- mice developed significantly more pronounced luminal stenosis compared with wild-type mice after carotid wire injury. These results suggest that TRPC6 contributes to the restoration or maintenance of contractile phenotype in VSMC after injury. Understanding the role of TRPC6 in phenotypic switching may lead to mechanism-based therapies to mitigate restenosis.

ROCK (RhoA/Rho Kinase) in Cardiovascular-Renal Pathophysiology: A Review of New Advancements

Rho-associated, coiled-coil containing kinases (ROCK) were originally identified as effectors of the RhoA small GTPase and found to belong to the AGC family of serine/threonine kinases. They were shown to be downstream effectors of RhoA and RhoC activation. They signal via phosphorylation of proteins such as MYPT-1, thereby regulating many key cellular functions including proliferation, motility and viability and the RhoA/ROCK signaling has been shown to be deeply involved in arterial hypertension, cardiovascular–renal remodeling, hypertensive nephropathy and posttransplant hypertension. Given the deep involvement of ROCK in cardiovascular–renal pathophysiology and the interaction of ROCK signaling with other signaling pathways, the reports of trials on the clinical beneficial effects of ROCK’s pharmacologic targeting are growing. In this current review, we provide a brief survey of the current understanding of ROCK-signaling pathways, also integrating with the more novel data that overall support a relevant role of ROCK for the cardiovascular–renal physiology and pathophysiology.

Myocardin Is Involved in Mesothelial-Mesenchymal Transition of Human Pleural Mesothelial Cells

Pleural fibrosis is characterized by severe inflammation of the pleural space and pleural reorganization. Subsequent thickening of the visceral pleura contributes to lung stiffness and impaired lung function. Pleural mesothelial cells (PMCs) can become myofibroblasts via mesothelial-mesenchymal transition (MesoMT) and contribute to pleural organization, fibrosis, and rind formation. However, the mechanisms that underlie MesoMT remain unclear. Here, we investigated the role of myocardin in the induction of MesoMT. Transforming growth factor β (TGF-β) and thrombin induced MesoMT and markedly upregulated the expression of myocardin, but not myocardin-related transcription factor A (MRTF-A) or MRTF-B, in human PMCs (HPMCs). TGF-β stimulation notably induced the nuclear translocation of myocardin in HPMCs, whereas nuclear translocation of MRTF-A and MRTF-B was not observed. Several genes under the control of myocardin were upregulated in cells undergoing MesoMT, an effect that was accompanied by a dramatic cytoskeletal reorganization of HPMCs consistent with a migratory phenotype. Myocardin gene silencing blocked TGF-β- and thrombin-induced MesoMT. Although myocardin upregulation was blocked, MRTF-A and MRTF-B were unchanged. Myocardin, α-SMA, calponin, and smooth muscle myosin were notably upregulated in the thickened pleura of carbon black/bleomycin and empyema mouse models of fibrosing pleural injury. Similar results were observed in human nonspecific pleuritis. In a TGF-β mouse model of pleural fibrosis, PMC-specific knockout of myocardin protected against decrements in lung function. Further, TGF-β-induced pleural thickening was abolished by PMC-specific myocardin knockout, which was accompanied by a marked reduction of myocardin, calponin, and α-SMA expression compared with floxed-myocardin controls. These novel results show that myocardin participates in the development of MesoMT in HPMCs and contributes to the pathogenesis of pleural organization and fibrosis.

A novel MEF2C mutation in lymphoid neoplasm diffuse large B-cell lymphoma promotes tumorigenesis by increasing c-JUN expression

Diffuse large B-cell lymphoma (DLBCL) is the most aggressive non-Hodgkin lymphoma (NHL), accounting for about 31% of the newly diagnosed NHL worldwide. Although approximately 60% of patients who initially received a standard R-CHOP treatment likely have a 3-year event-free survival, many patients become refractory or relapsed due to the genetic heterogeneity of this malignancy. Hence, new treatment strategies are urgently needed. MEF2C, a member of the MEF2 transcription factor family gene, plays great important roles involved in the development of various tissues and the pathogenesis of lymphoma. However, the exact functions and molecular mechanisms of MEF2C in DLBCL are not fully investigated. By Sanger sequencing, we identified a novel point mutation of MEF2C at the p.N389 site in DLBCL patient, which was further validated by several DLBCL cell lines. Intriguingly, we found that the p.N389S mutation did not influence MEF2C expression, protein stability, and subcellular distribution, but enhanced its transcriptional activity. Furthermore, we demonstrated that MEF2C p.N389S mutation promotes DLBCL cell proliferation, cellular adhesion, and tumor formation in nude mice. On mechanism, our data revealed that MEF2C p.N389S mutation increases c-JUN expression, and c-JUN regulation mediated the oncogenic function of MEF2C p.N389S mutation on DLBCL cells. Our finding may provide a significant insight into the DLBCL and a compelling therapy target for this disease treatment.

Misoprostol regulates Bnip3 repression and alternative splicing to control cellular calcium homeostasis during hypoxic stress

The cellular response to hypoxia involves the activation of a conserved pathway for gene expression regulated by the transcription factor complex called hypoxia-inducible factor (HIF). This pathway has been implicated in both the adaptive response to hypoxia and in several hypoxic-ischemic-related pathologies. Perinatal hypoxic injury, often associated with prematurity, leads to multi-organ dysfunction resulting in significant morbidity and mortality. Using a rodent model of neonatal hypoxia and several representative cell lines, we observed HIF1α activation and down-stream induction of the cell death gene Bnip3 in brain, large intestine, and heart which was mitigated by administration of the prostaglandin E1 analog misoprostol. Mechanistically, we determined that misoprostol inhibits full-length Bnip3 (Bnip3-FL) expression through PKA-mediated NF-κB (P65) nuclear retention, and the induction of pro-survival splice variants. We observed that the dominant small pro-survival variant of Bnip3 in mouse cells lacks the third exon (Bnip3ΔExon3), whereas human cells produce a pro-survival BNIP3 variant lacking exon 2 (BNIP3ΔExon2). In addition, these small Bnip3 splice variants prevent mitochondrial dysfunction, permeability transition, and necrosis triggered by Bnip3-FL by blocking calcium transfer from the sarco/endoplasmic reticulum to the mitochondria. Furthermore, misoprostol and Bnip3ΔExon3 promote nuclear calcium accumulation, resulting in HDAC5 nuclear export, NFAT activation, and adaptive changes in cell morphology and gene expression. Collectively, our data suggests that misoprostol can mitigate the potential damaging effects of hypoxia on multiple cell types by activating adaptive cell survival pathways through Bnip3 repression and alternative splicing.

FSD-C10 Shows Therapeutic Effects in Suppressing oxidized low-density lipoprotein (ox-LDL)-Induced Human Brain Microvascular Endothelial Cells Apoptosis via Rho-Associated Coiled-Coil Kinase (ROCK)/Mitogen-Activated Protein Kinase (MAPK) Signaling

BACKGROUND ox-LDL-induced injury of brain microvascular endothelial cells (BMECs) is strongly associated with cerebral vascular diseases such as cerebral arterial atherosclerosis. ROCK inhibitor was proved to be anti-apoptotic and has been used in treating cerebral vascular diseases. Research on the neuroprotective effects of a novel ROCK inhibitor, FSD-C10, is still limited. The present study investigated the anti-apoptotic effect and underlying molecular mechanism of FSD-C10 in ox-LDL-mediated apoptosis of BMECs. MATERIAL AND METHODS ox-LDL and/or FSD-C10 were used to incubate immortalized human BMECs. MTT assay was used to assess cell viability. Cell apoptosis was evaluated by TUNEL assay. A colorimetric method was used to assess ROCK activity. Western blot analysis was used to examine the expression and phosphorylation levels of proteins. RESULTS ox-LDL incubation reduced the viability of BMECs by inducing cell apoptosis in a concentration-dependent manner. ROCK activity was also elevated by ox-LDL incubation in BMECs in a concentration-dependent manner. Expression level of Bcl2 was reduced while expression levels of Bax and active caspase3 were increased by ox-LDL treatment in a concentration-dependent manner. ox-LDL also increased the phosphorylation levels of p38, JNK, and ERK1/2 in a concentration-dependent manner. FSD-C10 treatment increased the cell viability by reducing apoptosis of BMECs exposed to ox-LDL. Moreover, FSD-C10 was found to suppress the phosphorylation levels of p38, JNK, and ERK1/2 and the expression levels of Bax and active caspase3 in ox-LDL treated BMECs. CONCLUSIONS FSD-C10 increases cell viability in ox-LDL-treated BMECs by reducing cell apoptosis. ROCK/MAPKs-mediated apoptosis appears to be the underlying molecular mechanism.

S-adenosyl methionine regulates calcium channels and inhibits uterine smooth muscle contraction in rats with infectious premature delivery through the transient receptor protein 3/protein kinase Cβ/C-kinase-activated protein phosphatase-1 inhibitor of 17 kDa signaling pathway

The aim of the present study was to investigate the effects of S-adenosyl methionine (SAMe) on infectious premature inflammatory factors and uterine contraction, and to further explore its mechanism of action via the transient receptor protein 3 (TRPC3)/protein kinase Cβ (PKCβ)/C-kinase-activated protein phosphatase-1 inhibitor of 17 kDa (CPI-17) signaling pathway, following intervention by a TRPC3 inhibitor. A rat model of premature delivery induced by lipopolysaccharide (LPS) was established. Following treatment with SAMe and inhibiting TRPC3 expression, rat serum and uterus were isolated. Hematoxylin and eosin staining was used to observe the histopathological changes in the uterus. Uterine muscle strips in vitro were selected to measure the changes in muscle tension. ELISA was utilized to measure the changes in serum inflammatory factor and oxidative stress indexes. Immunohistochemistry, western blot assay and reverse transcription-quantitative polymerase chain reaction were applied to detect calcium channel protein expression in the uterus. Western blot analysis was employed to measure the expression of TRPC3/PKCβ/CPI-17 signaling pathway-related proteins. TRPC3 was highly expressed in the uterus of rat models of premature delivery induced by LPS. Following treatment with SAMe, inflammatory cell infiltration markedly reduced in the uterus and the tension of in vitro uterine muscle strips significantly decreased. SAMe treatment suppressed inflammatory reaction and oxidative stress, and diminished L-type and T-type calcium channel protein expression. TRPC3/PKCβ/CPI-17 signaling pathway-related protein expression was also reduced. When TRPC3 expression was suppressed, the effects of SAMe against inflammation and oxidative stress were diminished. TRPC3/PKCβ/CPI-17 signaling pathway-related protein expression significantly increased. SAMe was able to reduce inflammatory reaction and oxidative stress in the uterus of rat model of infectious premature delivery induced by LPS, prolong delivery time, reduce the mortality rate of offspring rats, and serve a therapeutic role. This effect is likely achieved via the regulation of uterine contractions and childbirth through the TRPC3/PKCβ/CPI-17 signaling pathway.

Myocardin regulates mitochondrial calcium homeostasis and prevents permeability transition

Myocardin is a transcriptional co-activator required for cardiovascular development, but also promotes cardiomyocyte survival through an unclear molecular mechanism. Mitochondrial permeability transition is implicated in necrosis, while pore closure is required for mitochondrial maturation during cardiac development. We show that loss of myocardin function leads to subendocardial necrosis at E9.5, concurrent with elevated expression of the death gene Nix. Mechanistically, we demonstrate that myocardin knockdown reduces microRNA-133a levels to allow Nix accumulation, leading to mitochondrial permeability transition, reduced mitochondrial respiration, and necrosis. Myocardin knockdown elicits calcium release from the endo/sarcoplasmic reticulum with mitochondrial calcium accumulation, while restoration of microRNA-133a function, or knockdown of Nix rescues calcium perturbations. We observed reduced myocardin and elevated Nix expression within the infarct border-zone following coronary ligation. These findings identify a myocardin-regulated pathway that maintains calcium homeostasis and mitochondrial function during development, and is attenuated during ischemic heart disease. Given the diverse role of Nix and microRNA-133a, these findings may have broader implications to metabolic disease and cancer.

Diversity and plasticity in signaling pathways that regulate smooth muscle responsiveness: Paradigms and paradoxes for the myosin phosphatase, the master regulator of smooth muscle contraction

A hallmark of smooth muscle cells is their ability to adapt their functions to meet temporal and chronic fluctuations in their demands. These functions include force development and growth. Understanding the mechanisms underlying the functional plasticity of smooth muscles, the major constituent of organ walls, is fundamental to elucidating pathophysiological rationales of failures of organ functions. Also, the knowledge is expected to facilitate devising innovative strategies that more precisely monitor and normalize organ functions by targeting individual smooth muscles. Evidence has established a current paradigm that the myosin light chain phosphatase (MLCP) is a master regulator of smooth muscle responsiveness to stimuli. Cellular MLCP activity is negatively and positively regulated in response to G-protein activation and cAMP/cGMP production, respectively, through the MYPT1 regulatory subunit and an endogenous inhibitor protein named CPI-17. In this article we review the outcomes from two decade of research on the CPI-17 signaling and discuss emerging paradoxes in the view of signaling pathways regulating smooth muscle functions through MLCP.

Fasudil ameliorates the ischemia/reperfusion oxidative injury in rat hearts through suppression of myosin regulatory light chain/NADPH oxidase 2 pathway

Fasudil is a potent Rho-kinase (ROCK) inhibitor and can relax smooth muscle or cardiac muscle contraction through decreasing the phosphorylation level of myosin regulatory light chain (p-MLC₂₀ or p-MLC2v), while p-MLC2v can function as a transcription factor to promote the NADPH oxidase 2 (NOX2) expression in rat hearts subjected to ischemia/reperfusion (I/R). This study aims to explore whether fasudil can protect the rat hearts against I/R oxidative injury through suppressing NOX2 expression via reduction of p-MLC2v level. The SD rat hearts were subjected to 1h-ischemia plus 3h-reperfusion, which showed myocardial injuries (myocardial fiber loss and disarray, increase of creatine kinase release and myocardial infarction/apoptosis), increase in ROCK activity and nuclear p-MLC_2v level concomitant with up-regulation of NOX2 and H₂O₂ production; these phenomena were attenuated by fasudil in a dose-dependent manner. Next, we verified the cardioprotective effect of fasudil and the underlying mechanisms in hypoxia-reoxygenation (H/R) -treated H9c2 cells. Consistent with the results in vivo, the H/R-treated H9c2 cells showed cellular injury (increase in apoptotic ratio), elevation in ROCK activity and nuclear p-MLC_2v level, accompanied by up-regulation of NOX2 and H₂O₂ production; these effects were blocked in the presence of fasudil in a dose-dependent way. Based on these observations, we conclude that beneficial effect of fasudil against myocardial I/R or H/R oxidative injury is related to the suppression of NOX2 expression through decrease of the p-MLC2v level. Our findings also highlight that intervention of MLC2v phosphorylation by drugs may provide a novel strategy to protect heart from I/R oxidative injury.

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

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

Efficient isolation and culture of endothelial cells from venous malformation using the Rho-associated protein kinase inhibitor Y27632

BACKGROUND

The investigation of primary cells from a pathological lesion can elucidate the pathogenesis of diseases, but, for vascular malformations in humans, such basic research is still stagnant, because the isolation and culture of vascular endothelial cells (ECs) is very difficult. To obtain a sufficient amount of ECs from venous malformation (VM) this study took advantage of a Rho-associated protein kinase inhibitor, Y27632, which had been used for the efficient procurement of primary keratinocytes.

METHODS

ECs were isolated and cultured from VM lesions, combining enzymatic digestion, cell sorting, and Y27632. The proliferative effect of Y27632 on ECs was examined by proliferation assay. The characteristics of the ECs cultured with Y27632 by EC marker expression and tube formation assay were also examined.

RESULTS

Y27632 enhanced the proliferation of ECs and elongated the senescence of the cells. The expression of specific markers of ECs such as von Willebrand factor, endothelin-1, and VE-cadherin, was confirmed in the cells cultured with Y27632. In a tube formation assay, the cells cultured with Y27632 showed higher tube formation ability compared to the cells cultured without Y27632, indicating that Y27632 promoted the angiogenic capability of ECs.

CONCLUSIONS

The protocol using Y27632 offers a new EC culture methodology and provides a new option for the biological investigation of vascular malformations. This new method will contribute to other types of vascular biology research as well.

TGFβ-TAZ/SRF signalling regulates vascular smooth muscle cell differentiation

Vascular smooth muscle cells (VSMCs) do not terminally differentiate; they modulate their phenotype between proliferative and differentiated states, which is a major factor contributing to vascular diseases. TGFβ signalling has been implicated in inducing VSMC differentiation, although the exact mechanism remains largely unknown. Our goal was to assess the network of transcription factors involved in the induction of VSMC differentiation, and to determine the role of TAZ in promoting the quiescent VSMC phenotype. TGFβ robustly induces VSMC marker genes in 10T1/2 mouse embryonic fibroblast cells and the potent transcriptional regulator TAZ has been shown to retain Smad complexes on DNA. Thus, the role of TAZ in regulation of VSMC differentiation was studied. Using primary aortic VSMCs coupled with siRNA-mediated gene silencing, our studies reveal that TAZ is required for TGFβ induction of smooth muscle genes and is also required for the differentiated VSMC phenotype; synergy between TAZ and SRF, and TAZ and Myocardin (MyoC856), in regulating smooth muscle gene activation was observed. These data provide evidence of components of a novel signalling pathway that links TGFβ signalling to induction of smooth muscle genes through a mechanism involving regulation of TAZ and SRF proteins. In addition, we report a physical interaction of TAZ and MyoC856. These observations elucidate a novel level of control of VSMC induction which may have implications for vascular diseases and congenital vascular malformations.

Pyk2 inhibition promotes contractile differentiation in arterial smooth muscle

Modulation from contractile to synthetic phenotype of vascular smooth muscle cells is a central process in disorders involving compromised integrity of the vascular wall. Phenotype modulation has been shown to include transition from voltage-dependent toward voltage-independent regulation of the intracellular calcium level, and inhibition of non-voltage dependent calcium influx contributes to maintenance of the contractile phenotype. One possible mediator of calcium-dependent signaling is the FAK-family non-receptor protein kinase Pyk2, which is activated by a number of stimuli in a calcium-dependent manner. We used the Pyk2 inhibitor PF-4594755 and Pyk2 siRNA to investigate the role of Pyk2 in phenotype modulation in rat carotid artery smooth muscle cells and in cultured intact arteries. Pyk2 inhibition promoted the expression of smooth muscle markers at the mRNA and protein levels under stimulation by FBS or PDGF-BB and counteracted phenotype shift in cultured intact carotid arteries and balloon injury ex vivo. During long-term (24-96 hr) treatment with PF-4594755, smooth muscle markers increased before cell proliferation was inhibited, correlating with decreased KLF4 expression and differing from effects of MEK inhibition. The Pyk2 inhibitor reduced Orai1 and preserved SERCA2a expression in carotid artery segments in organ culture, and eliminated the inhibitory effect of PDGF stimulation on L-type calcium channel and large-conductance calcium-activated potassium channel expression in carotid cells. Basal intracellular calcium level, calcium wave activity, and store-operated calcium influx were reduced after Pyk2 inhibition of growth-stimulated cells. Pyk2 inhibition may provide an interesting approach for preserving vascular smooth muscle differentiation under pathophysiological conditions.

Fibroblast Growth Factor 12 Is a Novel Regulator of Vascular Smooth Muscle Cell Plasticity and Fate

OBJECTIVE

Vascular smooth muscle cells (VSMCs) modulate their phenotype between synthetic and contractile states in response to environmental changes; this modulation plays a crucial role in the pathogenesis of restenosis and atherosclerosis. Here, we identified fibroblast growth factor 12 (FGF12) as a novel key regulator of the VSMC phenotype switch.

APPROACH AND RESULTS

Using murine models and human specimens, we found that FGF12 was highly expressed in contractile VSMCs of normal vessel walls but was downregulated in synthetic VSMCs from injured and atherosclerotic vessels. In human VSMCs, FGF12 expression was inhibited at the transcriptional level by platelet-derived growth factor-BB. Gain- and loss-of-function experiments showed that FGF12 was both necessary and sufficient for inducing and maintaining the quiescent and contractile phenotypes of VSMCs. FGF12 inhibited cell proliferation through the p53 pathway and upregulated the key factors involved in VSMC lineage differentiation, such as myocardin and serum response factor. Such FGF12-induced phenotypic change was mediated by the p38 MAPK (mitogen-activated protein kinase) pathway. Moreover, FGF12 promoted the differentiation of mouse embryonic stem cells and the transdifferentiation of human dermal fibroblasts into SMC-like cells. Furthermore, adenoviral infection of FGF12 substantially decreased neointima hyperplasia in a rat carotid artery injury model.

CONCLUSIONS

In general, FGF family members induce a synthetic VSMC phenotype. Interestingly, the present study showed the unanticipated finding that FGF12 belonging to FGF family, strongly induced the quiescent and contractile VSMC phenotypes and directly promoted VSMC lineage differentiation. These novel findings suggested that FGF12 could be a new therapeutic target for treating restenosis and atherosclerosis.

Excitation-Contraction Coupling and Excitation-Transcription Coupling in Blood Vessels: Their Possible Interactions in Hypertensive Vascular Remodeling

Vascular smooth muscle cells (VSMC) display considerable phenotype plasticity which can be studied in vivo on vascular remodeling which occurs during acute or chronic vascular injury. In differentiated cells, which represent contractile phenotype, there are characteristic rapid transient changes of intracellular Ca2+ concentration ([Ca2+]i), while the resting cytosolic [Ca2+]i concentration is low. It is mainly caused by two components of the Ca2+ signaling pathways: Ca2+ entry via L-type voltage-dependent Ca2+ channels and dynamic involvement of intracellular stores. Proliferative VSMC phenotype is characterized by long-lasting [Ca2+]i oscillations accompanied by sustained elevation of basal [Ca2+]i. During the switch from contractile to proliferative phenotype there is a general transition from voltage-dependent Ca2+ entry to voltage-independent Ca2+ entry into the cell. These changes are due to the altered gene expression which is dependent on specific transcription factors activated by various stimuli. It is an open question whether abnormal VSMC phenotype reported in rats with genetic hypertension (such as spontaneously hypertensive rats) might be partially caused by a shift from contractile to proliferative VSMC phenotype.

Cardiac-specific miRNA in cardiogenesis, heart function, and cardiac pathology (with focus on myocardial infarction)

Cardiac miRNAs (miR-1, miR133a, miR-208a/b, and miR-499) are abundantly expressed in the myocardium. They play a central role in cardiogenesis, heart function and pathology. While miR-1 and miR-133a predominantly control early stages of cardiogenesis supporting commitment of cardiac-specific muscle lineage from embryonic stem cells and mesodermal precursors, miR-208 and miR-499 are involved in the late cardiogenic stages mediating differentiation of cardioblasts to cardiomyocytes and fast/slow muscle fiber specification. In the heart, miR-1/133a control cardiac conductance and automaticity by regulating all phases of the cardiac action potential. miR-208/499 located in introns of the heavy chain myosin genes regulate expression of sarcomeric contractile proteins. In cardiac pathology including myocardial infarction (MI), expression of cardiac miRNAs is markedly altered that leads to deleterious effects associated with heart wounding, arrhythmia, increased apoptosis, fibrosis, hypertrophy, and tissue remodeling. In acute MI, circulating levels of cardiac miRNAs are significantly elevated making them to be a promising diagnostic marker for early diagnosis of acute MI. Great cardiospecific capacity of these miRNAs is very helpful for enhancing regenerative properties and survival of stem cell and cardiac progenitor transplants and for reprogramming of mature non-cardiac cells to cardiomyocytes.

Non-muscle myosin light chain promotes endothelial progenitor cells senescence and dysfunction in pulmonary hypertensive rats through up-regulation of NADPH oxidase

Non-muscle myosin regulatory light chain (nmMLC20) is reported to exert transcriptional function in regulation of gene expression, and NADPH oxidase (NOX)-derived reactive oxygen species contribute to vascular remodeling of pulmonary artery hypertension (PAH). This study aims to determine if nmMLC20 can promote endothelial progenitor cells (EPCs) senescence and dysfunction through up-regulation of NOX in PAH rats. The rats were exposed to10% hypoxia for 3 weeks to establish a PAH model, which showed an increase in right ventricle systolic pressure, right ventricular and pulmonary vascular remodeling, and the accelerated senescence and impaired functions in EPCs, accompanied by an increase in Rho-kinase (ROCK) and NOX activities, p-nmMLC20 level, NOX expression and H2O2 content; these phenomena were reversed by fasudil, a selective inhibitor of ROCK. Next, normal EPCs were cultured under hypoxia to induce senescence in vitro. Consistent with the in vivo findings, hypoxia increased the senescence and dysfunction of EPCs concomitant with an increase in ROCK and NOX activities, p-nmMLC20 level, NOX expression and H2O2 content; these phenomena were reversed by fasudil. Knockdown of nmMLC20 showed similar results to that of fasudil except no effect on ROCK activity. Based on these observations, we conclude that nmMLC20 could promote the senescence and dysfunctions of EPCs in PAH through up-regulation of NOX in a phosphorylation-dependent manner.

A p38 Mitogen-Activated Protein Kinase-Regulated Myocyte Enhancer Factor 2-β-Catenin Interaction Enhances Canonical Wnt Signaling

Canonical Wnt/β-catenin signaling plays a major role in various biological contexts, such as embryonic development, cell proliferation, and cancer progression. Previously, a connection between p38 mitogen-activated protein kinase (MAPK) signaling and Wnt-mediated activation of β-catenin was implied but poorly understood. In the present study, we investigated potential cross talk between p38 MAPK and Wnt/β-catenin signaling. Here we show that a loss of p38 MAPK α/β function reduces β-catenin nuclear accumulation in Wnt3a-stimulated primary vascular smooth muscle cells (VSMCs). Conversely, active p38 MAPK signaling increases β-catenin nuclear localization and target gene activity in multiple cell types. Furthermore, the effect of p38 MAPK α/β on β-catenin activity is mediated through phosphorylation of a key p38 MAPK target, myocyte enhancer factor 2 (MEF2). Here we report a p38 MAPK-mediated, phosphorylation-dependent interaction between MEF2 and β-catenin in multiple cell types and primary VSMCs that results in (i) increased β-catenin nuclear retention, which is reversed by small interfering RNA (siRNA)-mediated MEF2 gene silencing; (ii) increased activation of MEF2 and Wnt/β-catenin target genes; and (iii) increased Wnt-stimulated cell proliferation. These observations provide mechanistic insight into a fundamental level of cross talk between p38 MAPK/MEF2 signaling and canonical Wnt signaling.

A conserved MADS-box phosphorylation motif regulates differentiation and mitochondrial function in skeletal, cardiac, and smooth muscle cells

Exposure to metabolic disease during fetal development alters cellular differentiation and perturbs metabolic homeostasis, but the underlying molecular regulators of this phenomenon in muscle cells are not completely understood. To address this, we undertook a computational approach to identify cooperating partners of the myocyte enhancer factor-2 (MEF2) family of transcription factors, known regulators of muscle differentiation and metabolic function. We demonstrate that MEF2 and the serum response factor (SRF) collaboratively regulate the expression of numerous muscle-specific genes, including microRNA-133a (miR-133a). Using tandem mass spectrometry techniques, we identify a conserved phosphorylation motif within the MEF2 and SRF Mcm1 Agamous Deficiens SRF (MADS)-box that regulates miR-133a expression and mitochondrial function in response to a lipotoxic signal. Furthermore, reconstitution of MEF2 function by expression of a neutralizing mutation in this identified phosphorylation motif restores miR-133a expression and mitochondrial membrane potential during lipotoxicity. Mechanistically, we demonstrate that miR-133a regulates mitochondrial function through translational inhibition of a mitophagy and cell death modulating protein, called Nix. Finally, we show that rodents exposed to gestational diabetes during fetal development display muscle diacylglycerol accumulation, concurrent with insulin resistance, reduced miR-133a, and elevated Nix expression, as young adult rats. Given the diverse roles of miR-133a and Nix in regulating mitochondrial function, and proliferation in certain cancers, dysregulation of this genetic pathway may have broad implications involving insulin resistance, cardiovascular disease, and cancer biology.

Three-Dimensional Vascular Network Assembly From Diabetic Patient-Derived Induced Pluripotent Stem Cells

OBJECTIVE

In diabetics, hyperglycemia results in deficient endothelial progenitors and cells, leading to cardiovascular complications. We aim to engineer 3-dimensional (3D) vascular networks in synthetic hydrogels from type 1 diabetes mellitus (T1D) patient-derived human-induced pluripotent stem cells (hiPSCs), to serve as a transformative autologous vascular therapy for diabetic patients.

APPROACH AND RESULTS

We validated and optimized an adherent, feeder-free differentiation procedure to derive early vascular cells (EVCs) with high portions of vascular endothelial cadherin-positive cells from hiPSCs. We demonstrate similar differentiation efficiency from hiPSCs derived from healthy donor and patients with T1D. T1D-hiPSC-derived vascular endothelial cadherin-positive cells can mature to functional endothelial cells-expressing mature markers: von Willebrand factor and endothelial nitric oxide synthase are capable of lectin binding and acetylated low-density lipoprotein uptake, form cords in Matrigel and respond to tumor necrosis factor-α. When embedded in engineered hyaluronic acid hydrogels, T1D-EVCs undergo morphogenesis and assemble into 3D networks. When encapsulated in a novel hypoxia-inducible hydrogel, T1D-EVCs respond to low oxygen and form 3D networks. As xenografts, T1D-EVCs incorporate into developing zebrafish vasculature.

CONCLUSIONS

Using our robust protocol, we can direct efficient differentiation of T1D-hiPSC to EVCs. Early endothelial cells derived from T1D-hiPSC are functional when mature. T1D-EVCs self-assembled into 3D networks when embedded in hyaluronic acid and hypoxia-inducible hydrogels. The capability of T1D-EVCs to assemble into 3D networks in engineered matrices and to respond to a hypoxic microenvironment is a significant advancement for autologous vascular therapy in diabetic patients and has broad importance for tissue engineering.

Caveolin-3 Promotes a Vascular Smooth Muscle Contractile Phenotype

Epidemiological studies have demonstrated the importance of cardiovascular diseases in Western countries. Among the cell types associated with a dysfunctional vasculature, smooth muscle (SM) cells are believed to play an essential role in the development of these illnesses. Vascular SM cells are key regulators of the vascular tone and also have an important function in the development of atherosclerosis and restenosis. While in the normal vasculature, contractile SM cells are predominant, in atherosclerotic vascular lesions, synthetic cells migrate toward the neointima, proliferate, and synthetize extracellular matrix proteins. In the present study, we have examined the role of caveolin-3 in the regulation of SM cell phenotype. Caveolin-3 is expressed in vivo in normal arterial SM cells, but its expression appears to be lost in cultured SM cells. Our data show that caveolin-3 expression in the A7r5 SM cell line is associated with increased expression of contractility markers such as SM α-actin, SM myosin heavy chain but decreased expression of the synthetic phenotype markers such as p-Elk and Klf4. Moreover, we also show that caveolin-3 expression can reduce proliferation upon treatment with LDL or PDGF. Finally, we show that caveolin-3-expressing SM cells are less sensitive to apoptosis than control cells upon treatment with oxidized LDL. Taken together, our data suggest that caveolin-3 can regulate the phenotypic switch between contractile and synthetic SM cells. A better understanding of the factors regulating caveolin-3 expression and function in this cell type will permit the development of a better comprehension of the factors regulating SM function in atherosclerosis and restenosis.

RGS5 promotes arterial growth during arteriogenesis

Arteriogenesis—the growth of collateral arterioles—partially compensates for the progressive occlusion of large conductance arteries as it may occur as a consequence of coronary, cerebral or peripheral artery disease. Despite being clinically highly relevant, mechanisms driving this process remain elusive. In this context, our study revealed that abundance of regulator of G-protein signalling 5 (RGS5) is increased in vascular smooth muscle cells (SMCs) of remodelling collateral arterioles. RGS5 terminates G-protein-coupled signalling cascades which control contractile responses of SMCs. Consequently, overexpression of RGS5 blunted Gα_q/11-mediated mobilization of intracellular calcium, thereby facilitating Gα_12/13-mediated RhoA signalling which is crucial for arteriogenesis. Knockdown of RGS5 evoked opposite effects and thus strongly impaired collateral growth as evidenced by a blockade of RhoA activation, SMC proliferation and the inability of these cells to acquire an activated phenotype in RGS5-deficient mice after the onset of arteriogenesis. Collectively, these findings establish RGS5 as a novel determinant of arteriogenesis which shifts G-protein signalling from Gα_q/11-mediated calcium-dependent contraction towards Gα_12/13-mediated Rho kinase-dependent SMC activation.

Subject Categories Vascular Biology & Angiogenesis

Transcriptional profiling reveals crosstalk between mesenchymal stem cells and endothelial cells promoting prevascularization by reciprocal mechanisms

Mesenchymal stem cells (MSCs) show great promise in blood vessel restoration and vascularization enhancement in many therapeutic situations. Typically, the co-implantation of MSCs with vascular endothelial cells (ECs) is effective for the induction of functional vascularization in vivo, indicating its potential applications in regenerative medicine. The effects of MSCs-ECs-induced vascularization can be modeled in vitro, providing simplified models for understanding their underlying communication. In this article, a contact coculture model in vitro and an RNA-seq approach were employed to reveal the active crosstalk between MSCs and ECs within a short time period at both morphological and transcriptional levels. The RNA-seq results suggested that angiogenic genes were significantly induced upon coculture, and this prevascularization commitment might require the NF-κB signaling. NF-κB blocking and interleukin (IL) neutralization experiments demonstrated that MSCs potentially secreted IL factors including IL1β and IL6 to modulate NF-κB signaling and downstream chemokines during coculture. Conversely, RNA-seq results indicated that the MSCs were regulated by the coculture environment to a smooth muscle commitment within this short period, which largely induced myocardin, the myogenic co-transcriptional factor. These findings demonstrate the mutual molecular mechanism of MSCs-ECs-induced prevascularization commitment in a quick response.

Protein phosphatase 1 catalytic isoforms: specificity toward interacting proteins

The coordinated and reciprocal action of serine-threonine protein kinases and protein phosphatases produces transitory phosphorylation, a fundamental regulatory mechanism for many biological processes. Phosphoprotein phosphatase 1 (PPP1), a major serine-threonine phosphatase, in particular, is ubiquitously distributed and regulates a broad range of cellular functions, including glycogen metabolism, cell cycle progression, and muscle relaxation. PPP1 has evolved effective catalytic machinery but in vitro lacks substrate specificity. In vivo, its specificity is achieved not only by the existence of different PPP1 catalytic isoforms, but also by binding of the catalytic moiety to a large number of regulatory or targeting subunits. Here, we will address exhaustively the existence of diverse PPP1 catalytic isoforms and the relevance of their specific partners and consequent functions.

Cadherin-11 regulates both mesenchymal stem cell differentiation into smooth muscle cells and the development of contractile function in vivo

Although soluble factors, such as transforming growth factor β1 (TGF-β1), induce mesenchymal stem cell (MSC) differentiation towards the smooth muscle cell (SMC) lineage, the role of adherens junctions in this process is not well understood. In this study, we found that cadherin-11 but not cadherin-2 was necessary for MSC differentiation into SMCs. Cadherin-11 regulated the expression of TGF-β1 and affected SMC differentiation through a pathway that was dependent on TGF-β receptor II (TGFβRII) but independent of SMAD2 or SMAD3. In addition, cadherin-11 activated the expression of serum response factor (SRF) and SMC proteins through the Rho-associated protein kinase (ROCK) pathway. Engagement of cadherin-11 increased its own expression through SRF, indicative of the presence of an autoregulatory feedback loop that committed MSCs to the SMC fate. Notably, SMC-containing tissues (such as aorta and bladder) from cadherin-11-null (Cdh11(-/-)) mice showed significantly reduced levels of SMC proteins and exhibited diminished contractility compared with controls. This is the first report implicating cadherin-11 in SMC differentiation and contractile function in vitro as well as in vivo.

Magnesium lithospermate B, an active extract of Salvia miltiorrhiza, mediates sGC/cGMP/PKG translocation in experimental vasospasm

Background. Soluble guanylyl cyclases (sGCs) and Ras homolog gene family, member A (rhoA)/Ras homolog gene family kinase(rho-kinase) plays a role in vascular smooth muscle relaxation in subarachnoid hemorrhage (SAH). It is of interest to examine the effect of MLB on rhoA/ROCK and sGC/cGMP/PKG expression. Methods. A rodent SAH model was employed. Tissue samples were for sGCα1, sGCβ1, PKG, rhoA, ROCK (Western blot), and cGMP (ELISA) measurement. Results. MLB morphologically improved convolution of the internal elastic lamina, distortion of endothelial wall, and necrosis of the smooth muscle in the SAH rats. Expressed cGMP, sGCα1, sGCβ1, and PKG in the SAH groups were reduced (P < 0.01), and MLB precondition significantly induced cGMP, sGCα1, sGCβ1, and PKG. L-NAME reversed the vasodilation effect of MLB, reduced the bioexpression of PKG and cGMP (P < 0.01), and tends to reduce sGCα1 level and induce rhoA, ROCK level in MLB precondition + SAH groups. Conclusion. These results demonstrate that sGC/cGMP/PKG and NO/ET pathways play pivotal roles in SAH-induced vasospasm. Through activating sGC/cGMP/PKG pathway and partially by inactivating rho-kinase in a NO-dependent mechanism, MLB shows promise to be an effective strategy for the treatment of this disease entity.

Genetic factors regulating lung vasculature and immune cell functions associate with resistance to pneumococcal infection

Streptococcus pneumoniae is an important human pathogen responsible for high mortality and morbidity worldwide. The susceptibility to pneumococcal infections is controlled by as yet unknown genetic factors. To elucidate these factors could help to develop new medical treatments and tools to identify those most at risk. In recent years genome wide association studies (GWAS) in mice and humans have proved successful in identification of causal genes involved in many complex diseases for example diabetes, systemic lupus or cholesterol metabolism. In this study a GWAS approach was used to map genetic loci associated with susceptibility to pneumococcal infection in 26 inbred mouse strains. As a result four candidate QTLs were identified on chromosomes 7, 13, 18 and 19. Interestingly, the QTL on chromosome 7 was located within S. pneumoniae resistance QTL (Spir1) identified previously in a linkage study of BALB/cOlaHsd and CBA/CaOlaHsd F2 intercrosses. We showed that only a limited number of genes encoded within the QTLs carried phenotype-associated polymorphisms (22 genes out of several hundred located within the QTLs). These candidate genes are known to regulate TGFβ signalling, smooth muscle and immune cells functions. Interestingly, our pulmonary histopathology and gene expression data demonstrated, lung vasculature plays an important role in resistance to pneumococcal infection. Therefore we concluded that the cumulative effect of these candidate genes on vasculature and immune cells functions as contributory factors in the observed differences in susceptibility to pneumococcal infection. We also propose that TGFβ-mediated regulation of fibroblast differentiation plays an important role in development of invasive pneumococcal disease. Gene expression data submitted to the NCBI Gene Expression Omnibus Accession No: GSE49533

SNP data submitted to NCBI dbSNP Short Genetic Variation http://www.ncbi.nlm.nih.gov/projects/SNP/snp_viewTable.cgi?handle=MUSPNEUMONIA.