Vascular Smooth Muscle Hypertrophy Research Articles

The role and mechanism of FTO in pulmonary vessels

ABSTRACT Pulmonary vascular remodeling (PVR) is the main factor of pulmonary hypertension (PH). The pathological characteristics of PVR are vascular smooth muscle hyperplasia, hypertrophy, and extensive damage. In vivo experiments, the expression of FTO in PH rat lung tissues of different rat models of hypoxia PH was observed by immunohistochemical method. mRNA microarray analysis was used to analyze the differential expressed genes in rat lung tissues. In vitro experiments, we developed models of overexpression and knockdown of FTO to study the effect of FTO protein expression on cell apoptotic, cell cycle, and the abundance of m6A. The expression of FTO was increased in PH rats. FTO knockdown can inhibit the proliferation of PASMCs, thereby regulating the cell cycle and reducing the expression of Cyclin D1 and the abundance of m6A, while overexpression of FTO leads to increased expression of Cyclin D1 and the abundance of m6A. FTO destroys the stability of Cyclin D1 by regulating the abundance of Cyclin D1 m6A, causing cell cycle arrest and inducing cell proliferation, thus inducing the occurrence and development of PVR in PH.

Exosomes as Intercellular Messengers in Hypertension.

People living with hypertension have a higher risk of developing heart diseases, and hypertension remains a top cause of mortality. In hypertension, some detrimental changes occur in the arterial wall, which include physiological and biochemical changes. Furthermore, this disease is characterized by turbulent blood flow, increased fluid shear stress, remodeling of the blood vessels, and endothelial dysfunction. As a complex disease, hypertension is thought to be caused by an array of factors, its etiology consisting of both environmental and genetic factors. The Mosaic Theory of hypertension states that many factors, including genetics, environment, adaptive, neural, mechanical, and hormonal perturbations are intertwined, leading to increases in blood pressure. Long-term efforts by several investigators have provided invaluable insight into the physiological mechanisms responsible for the pathogenesis of hypertension, and these include increased activity of the sympathetic nervous system, overactivation of the renin–angiotensin–aldosterone system (RAAS), dysfunction of the vascular endothelium, impaired platelet function, thrombogenesis, vascular smooth muscle and cardiac hypertrophy, and altered angiogenesis. Exosomes are extracellular vesicles released by all cells and carry nucleic acids, proteins, lipids, and metabolites into the extracellular environment. They play a role in intercellular communication and are involved in the pathophysiology of diseases. Since the discovery of exosomes in the 1980s, numerous studies have been carried out to understand the biogenesis, composition, and function of exosomes. In this review, we will discuss the role of exosomes as intercellular messengers in hypertension.

MSCs attenuate hypoxia induced pulmonary hypertension by activating P53 and NF-kB signaling pathway through TNFα secretion

Hypoxia could cause vascular smooth muscle hypertrophy, leading to high pulmonary circulation resistance, pulmonary artery (PA) pressure, even pulmonary arterial hypertension (PAH). Recent studies have demonstrated the ability of mesenchymal stem cell (MSC) to ameliorate PAH but the mechanism was controversial. In this study, we revealed that the growth rate of pulmonary artery smooth muscle cells (PASMCs) treated with hypoxia was significantly increased than normal and showed lower expression of potassium channels. However, cells co-cultured with MSC showed decreased proliferation capability and down-regulated expression of ion channel of PAMSCs. The protein array data showed that the changes of PAMSCs was substantially associated with a high level of tumor necrosis factor alpha (TNFα) secretion from MSC. We further demonstrated that TNFα rescued the cell behavior of PAMSCs through activating the expression of P53 and NF-kB and inducing cell cycle arrest by P21/CDK2/CDK4 downregulation. These findings suggested that MSCs could attenuate abnormal function of PAMSCs by TNFα secretion, which was more or less associated with the beneficial effects of MSC on improving PAH.

Nrf2 as a Potential Mediator of Cardiovascular Risk in Metabolic Diseases.

Free radicals act as secondary messengers, modulating a number of important biological processes, including gene expression, ion mobilization in transport systems, protein interactions and enzymatic functions, cell growth, cell cycle, redox homeostasis, among others. In the cardiovascular system, the physiological generation of free radicals ensures the integrity and function of cardiomyocytes, endothelial cells, and adjacent smooth muscle cells. In physiological conditions, there is a balance between free radicals generation and the activity of enzymatic and non-enzymatic antioxidant systems. Redox imbalance, caused by increased free radical’s production and/or reduced antioxidant defense, plays an important role in the development of cardiovascular diseases, contributing to cardiac hypertrophy and heart failure, endothelial dysfunction, hypertrophy and hypercontractility of vascular smooth muscle. Excessive production of oxidizing agents in detriment of antioxidant defenses in the cardiovascular system has been described in obesity, diabetes mellitus, hypertension, and atherosclerosis. The transcription factor Nrf2 (nuclear factor erythroid 2–related factor 2), a major regulator of antioxidant and cellular protective genes, is primarily activated in response to oxidative stress. Under physiological conditions, Nrf2 is constitutively expressed in the cytoplasm of cells and is usually associated with Keap-1, a repressor protein. This association maintains low levels of free Nrf2. Stressors, such as free radicals, favor the translocation of Nrf2 to the cell nucleus. The accumulation of nuclear Nrf2 allows the binding of this protein to the antioxidant response element of genes that code antioxidant proteins. Although little information on the role of Nrf2 in the cardiovascular system is available, growing evidence indicates that decreased Nrf2 activity contributes to oxidative stress, favoring the pathophysiology of cardiovascular disorders found in obesity, diabetes mellitus, and atherosclerosis. The present mini-review will provide a comprehensive overview of the role of Nrf2 as a contributing factor to cardiovascular risk in metabolic diseases.

Elevated muscle sympathetic nerve activity is independently associated with common carotid artery wall thickness in humans

Aging is characterized by increased wall thickness and stiffening of the large elastic arteries (i.e., aorta and carotid arteries), although the mechanisms involved are incompletely understood. Studies in vitro demonstrate hypertrophy of vascular smooth muscle following chronic sympathetic‐adrenergic stimulation. In addition, higher measures of sympathetic nerve activity, which typically occur with advancing age, are associated with greater intima‐media thickness (IMT) of the large peripheral arteries such as the common femoral arteries. Therefore, we tested the hypothesis that the age‐related increase in large elastic artery (carotid) IMT would be independently associated with higher sympathetic nerve activity. In a cohort of 88 young and middle‐age/older adults (age: 19–73 yr, 52% men) with no history of cardiovascular disease, we performed assessments of muscle sympathetic nerve activity (MSNA, microneurography), common carotid IMT (ultrasonography), and ambulatory 24‐hr mean arterial pressure (MAP). As expected, advancing age was significantly correlated with higher MSNA burst frequency (R=0.54, P<0.001), carotid IMT (R=0.51, P<0.001), and ambulatory 24‐hr MAP (R=0.18, P=0.047). Results from multiple regression analysis that included MSNA burst frequency and traditional cardiovascular disease (CVD) risk factors that were also significantly correlated with carotid IMT (age, BMI, history of hypertension or borderline hypertension, family history of hypertension, and ambulatory 24‐hour MAP) showed that MSNA burst frequency (P=0.031), age (P=0.003), and ambulatory 24‐hour MAP (P=0.003) were independent determinants of carotid IMT (model R2=0.47, P<0.001). When expressing carotid IMT relative to lumen diameter (carotid IMT‐to‐lumen diameter ratio), multiple regression analysis showed that only MSNA burst frequency (P=0.02) was an independent determinant (model R2=0.36, P<0.001). These findings demonstrate an independent association between MSNA and carotid IMT and suggest that the age‐related increase in sympathetic‐adrenergic tone may contribute importantly to increased wall thickness of the large elastic arteries.Support or Funding InformationAHA (17POST33440101), T32 HL07121, NHLBI (P01HL014388), U54 TR001356 and AHA (13DG143400012).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hyperleptinemia positively associated with central arterial stiffness in hemodialysis patients

ObjectiveLeptin plays a role in stimulating vascular inflammation, vascular smooth muscle hypertrophy, and augmenting blood pressure, which contributes to the pathogenesis of atherosclerosis and leads to arterial stiffness. This vascular damage, measured by carotid-femoral pulse wave velocity (cfPWV), is recognized as an independent predictor of cardiovascular mortality in hemodialysis (HD) patients. The aim of this study was to evaluate the relationship between serum leptin and arterial stiffness in HD patients.Patients and methodsIn 112 of the 126 HD patients were eligible and their biochemical data were collected for analysis. Serum leptin level was measured using a commercial enzyme-linked immunosorbent assay kit. Carotid-femoral pulse wave velocity was measured by a validated tonometry system (SphygmoCor). Those have cfPWV values above 10 m/s are defined as the high arterial stiffness group.ResultsAmong the participants, thirty-eight of them who were in the high arterial stiffness group, had a higher prevalence of diabetes mellitus (p = 0.002), age (p = 0.029), body mass index (BMI, p = 0.018), body fat mass (p = 0.001), hemoglobin (p = 0.040), and serum leptin levels (P<0.001). Multivariable logistic regression analysis showed that leptin (odds ratio [OR] 1.09; 95% confidence interval [CI] 1.04–1.14; p <0.001), diabetes (OR 7.17; CI 1.39–37.00; p = 0.019), body fat mass (OR 1.16; CI 1.02–1.33; p = 0.027); and hemoglobin (OR 2.11; CI 1.15–3.87; p = 0.015) were independently associated with arterial stiffness in HD patients.ConclusionIn our study, hyperleptinemia was positively correlated to the high cfPWV and thus was related to high arterial stiffness in HD patients.

Vasopressin V1A receptor mediates cell proliferation through GRK2-EGFR-ERK1/2 pathway in A7r5 cells

Abnormal proliferation and hypertrophy of vascular smooth muscle (VSMC), as the main structural component of the vasculature, is an important pathological mechanism of hypertension. Recently, increased levels of arginine vasopressin (AVP) and copeptin, the C-terminal fragment of provasopressin, have been shown to correlate with the development of preeclampsia. AVP targets on the Gq-coupled vasopressin V1A receptor and the Gs-coupled V2 receptor in VSMC and the kidneys to regulate vascular tone and water homeostasis. However, the role of the vasopressin receptor on VSM cell proliferation during vascular remodeling is unclear. Here, we studied the effects of AVP on the proliferation of the rat VSMC-derived A7r5 cells. AVP, in a time- and concentration-dependent manner, promoted A7r5 cell proliferation as indicated by the induction of proliferating cell nuclear antigen expression, methylthiazolyldiphenyl-tetrazolium reduction and incorporation of 5’-bromodeoxyuridine into cellular DNA. These effects, coupled with the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), were blocked by a V1A receptor antagonist SR45059 but not by a V2 receptor antagonist lixivaptan. Although acute activation of V1A receptor induced ERK1/2 phosphorylation via a protein kinase C-dependent pathway, this effect was not involved in cell proliferation. Cell proliferation and ERK1/2 phosphorylation in response to prolonged stimulation with AVP were abolished by inhibition of G protein-coupled receptor kinase 2 (GRK2) and epidermal growth factor receptor (EGFR) using specific inhibitors or small hairpin RNA knock-down. These results suggest that activation of V1A, but not V2 receptor, produces a cell proliferative signal in A7r5 cells via a GRK2/EGFR/ERK1/2–dependent mechanism.

Epigenetic Mechanisms: New Targets for Heart Failure Pharmacopuncture.

Pharmacopuncture treatments are proposed for cardiovascular disease and heart failure [1]. Heart failure results from complex environment-gene interactions. β-adrenergic receptors and protein kinase A (PKA) interact with histones and related segments of deoxyribonucleic acid (DNA) at promoter regions of genes for messenger ribo nucleic acid (mRNA) transcription. This increases cardiac muscle mass and contractility in normal hearts. In heart failure, activation of β-adrenergic receptors and PKA promote pathological hypertrophy and decreased contractility. Experimental models show that prenatal exposure to hypoxia, cocaine, or nicotine increases susceptibility to heart failure when animals reach adulthood. Hypermethylation of DNA is an epigenetic mechanism associated with downregulation of the protein kinase C (PKC) gene in such models of heart failure. Downregulation of PKC is also produced by the stress-related hormone norepinephrine with upregulation of the hypoxia-inducible differentiation regulator Nix in norepinephrine-induced cardiac fibrosis [2]. Norepinephrine is also the main mediator of sympathetic neural activity. Sympathetic neural overactivity, a significant cofactor in human heart failure, is, therefore, implicated as a cofactor in this epigenetic mechanism for heart failure. Other epigenetic mechanism for cardiac hypertrophy and heart failure involve endothelin- 1 induced downregulation of the cardiac myocyte differentiation factor RE1-silencing transcription signaler (REST) and GATA zinc-finger domain-containing protein-1 (GATAD1) induced inhibition of histone deacetylase (HDAC-2) in cardiac myocytes harvested from autosomal-recessive dilated cardiac myopathy patients with heart failure [3]. In contrast, both the HDAC-2 in cardiac myocytes and the HDAC-1 in cardiac fibroblasts are upregulated in experimental animal models of congestive heart failure [4]. A prominent role for inflammation in heart failure is suggested by tumor necrosis factor (TNF-α), a proinflammatory cytokine, inducing hypermethylation of the sarcoplasmic reticulum calcium ATPase (SERCA-2A) gene in cardiac myocytes, associated with diastolic dysfunction and heart failure. An important role for epigenetic mechanisms in heart failure is also suggested by HDAC-dependent stimulation of the stress-apoptosis intracellular signaling pathway, which induces hypertrophy of both cardiac and vascular smooth muscle [5].

Beneficial effects of aqueous extract of stem bark of Terminalia arjuna (Roxb.), An ayurvedic drug in experimental pulmonary hypertension

Ethnopharmacological relevanceThe stem bark of Terminalia arjuna (Roxb.) is widely used in Ayurveda in various cardiovascular diseases. Many animal and clinical studies have validated its anti-ischemic, antihypertensive, antihypertrophic and antioxidant effects.Pulmonary hypertension (PH) is a fatal disease which causes right ventricular hypertrophy and right heart failure. Pulmonary vascular smooth muscle hypertrophy and increased oxidative stress are major pathological features of PH. As available limited therapeutic options fail to reduce the mortality associated with PH, alternative areas of therapy are worth exploring for potential drugs, which might be beneficial in PH. Aim of the studyThe effect of a standardised aqueous extract of the stem bark of Terminalia arjuna (Roxb.) in preventing monocrotaline (MCT)-induced PH in rat was investigated. Materials and methodsThe study was approved by Institutional Animal Ethics Committe.Male Wistar rats (150–200g) were randomly distributed into five groups; Control, MCT (50mg/kg subcutaneously once), sildenafil (175µg/kg/day three days after MCT for 25 days), and Arjuna extract (TA125 and TA250 mg/kg/day orally after MCT for 25 days). PH was confirmed by right ventricular weight to left ventricular plus septum weight (Fulton index), right ventricular systolic pressure (RVSP), echocardiography, percentage medial wall thickness of pulmonary arteries (%MWT). Oxidative stress in lung was assessed by super oxide dismutase (SOD), catalase, reduced glutathione (GSH) and thiobarbituric acid reactive substance (TBARS). The protein expressions of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX-1) in lung and gene expression of Bcl2 and Bax in heart were analyzed by Western blot and RT PCR respectively. ResultsMCT caused right ventricular hypertrophy (0.58±0.05 vs 0.31±0.05; P<0.001 vs. control) and increase in RVSP (33.5±1.5 vs 22.3±4.7mm of Hg; P<0.001). Both sildenafil and Arjuna prevented hypertrophy and RVSP. Pulmonary artery acceleration time to ejection time ratio in echocardiography was decreased in PH rats (0.49±0.05 vs 0.32±0.06; P<0.001) which was prevented by sildenafil (0.44±0.06; P<0.01) and TA250 (0.45±0.06; P<0.01). % MWT of pulmonary arteries was increased in PH and was prevented by TA250. Increase in TBARS (132.7±18.4 vs 18.8±1.6nmol/mg protein; P<0.001) and decrease in SOD (58.4±14.1 vs 117.4±26.9U/mg protein; P<0.001) and catalase (0.30±0.05 vs 0.75±0.31U/mg protein; P<0.001) were observed in lung tissue of PH rats, which were prevented by sildenafil and both the doses of Arjuna extract. Protein expression of NOX1 was significantly increased in lung and gene expression of Bcl2/Bax ratio was significantly decreased in right ventricle in MCT-induced PH, both were significantly prevented by Arjuna and sildenafil. ConclusionsAqueous extract of Terminalia arjuna prevented MCT-induced pulmonary hypertension which may be attributed to its antioxidant as well as its effects on pulmonary arteriolar wall thickening.

Isolation, Culture, and Characterization of Vascular Smooth Muscle Cells.

Smooth muscle cells (SMC) are the predominant cell type involved in the pathogenesis of atherosclerosis, vascular calcification and restenosis after angioplasty; however, they are also important in the de novo formation of blood vessels through differentiation of mesenchymal cells under the influence of mediators secreted by endothelial cells. In angiogenesis, vascular SMC are formed by proliferation of existing SMC or maturation and differntiation of pericytes. Experimental findings have demonstrated a potential role of putative smooth muscle progenitor cells in the circulation or within adult tissues and the perivascular adventitia in the development of atherosclerotic plaques, restenosis and angiogenesis. Modulation of vascular smooth muscle phenotype, SMC migration and hypertrophy are now recognized as key events in the development of vascular diseases. This has led to an increase in experimental research on SMC function in response to growth factors, extracellular matrix components, modified lipoproteins, biomechanical forces and other pro-atherogenic and pro-angiogenic mediators to address the cellular mechanisms involved. This chapter highlights well established methodologies used for vascular SMC and pericyte isolation and culture as well as their characterisation. A better understanding of vascular SMC and pericyte biology and their phenotypic modulation is required to identify therapeutic strategies to target angiogenesis and treat cardiovascular diseases.

Vascular oxidative stress promotes aortic stiffening (867.2)

Oxidative stress correlates with arterial stiffness in clinical studies. Reactive oxygen species (ROS) contribute to blood pressure elevation, vascular smooth muscle hypertrophy and vascular dysfunction in hypertension. We hypothesized that vascular ROS induce aortic stiffening, which in turn promotes systolic hypertension with aging. We created mice overexpressing p22phox in smooth muscle (tgsm/p22phox mice), which have a constitutive increase in vascular ROS production. Six month old tgsm/p22phox mice were normotensive at baseline (118±6 systolic, mmHg), but had increased aortic stiffness as indicated by the leftward shift on stress‐strain curves. Aortic collagen level, as detected by hydroxyproline content, was increased in tgsm/p22phox mice compared to age‐matched C57Bl/6 mice (76.3±11.9 vs. 43.2±7.2 ng/μg total protein). At 9 months of age, aortic stiffening did not further increase but these mice developed mild hypertension (137±11 systolic), demonstrating that excessive ROS first promotes aortic stiffening and subsequently hypertension. Tempol, a superoxide dismutase mimetic, normalized blood pressure (117±10 systolic), reduced vascular collagen deposition (37.5±9.5 ng/μg) and prevented aortic stiffening in these mice, suggesting a role of vascular ROS in aging‐induced aortic stiffening. ROS oxidize arachidonic acid to produce isoketals, known to cross‐link lysines and promote protein cross‐linking, which could lead to vascular stiffening. Immunohistochemistry indicated a marked increase of isoketals in the aorta and peri‐aortic fat of tgsm/p22phox mice, which was prevented by 2‐hydroxybenzylamine (2‐HOBA), a scavenger of isoketals. 2‐HOBA also reduced blood pressure, prevented collagen deposition and aortic stiffening in tgsm/p22phox mice treated from 3 months to 9 months of age. We conclude that ROS promote aortic stiffening and that this might in part be due to isoketal formation and protein crosslinking.Grant Funding Source: Supported by NIH R01 grant HL105294

The Role of Mercury in Cardiovascular Disease

Mercury toxicity is highly correlated with hypertension, coronary heart disease (CHD), myocardial infarction (MI), stroke and other cardiovascular disease. Mercury has a high affinity for sulfhydryl (-SH) groups, which inactivates numerous enzymatic reactions, amino acids, and sulfur-containing antioxidants [NAC (n-acetyl cysteine, ALA (alpha lipoic acid), GSH (glutathione)], with subsequent decreased oxidant defense and increased oxidative stress. Mercury binds to metallothionein and substitutes for zinc, copper, and other trace metals reducing the effectiveness of metalloenzymes. Mercury induces mitochondrial dysfunction with reduction in ATP, depletion of glutathione, and increased lipid peroxidation. Selenium and fish containing omega 3 fatty acids or omega 3 fatty acids supplements with DHA and EPA antagonize mercury toxicity. The overall vascular effects of mercury include increased oxidative stress, inflammation, reduced oxidative defense, thrombosis, vascular smooth muscle dysfunction and hypertrophy, endothelial dysfunction, dyslipidemia, immune and mitochondrial dysfunction. The clinical consequences of mercury toxicity include hypertension, CHD, MI, cardiac arrhythmias, reduced heart rate variability, increased carotid IMT and carotid artery obstruction, CVA, generalized atherosclerosis, renal dysfunction, renal insufficiency and proteinuria. Pathological and biochemical findings correlate with the clinical manifestations of mercury toxicity. Mercury diminishes the protective effect of fish and omega-3 fatty acids. Mercury inactivates COMT (catecholamine 0 methyl transferase), which increases serum and urinary epinephrine, norepinephrine, and dopamine. This effect will increase blood pressure and may be a clinical clue to mercury- induced heavy metal toxicity. Mercury toxicity should be evaluated in any patient with hypertension, CHD, MI, CVD, CVA or other vascular disease. Specific testing for acute and chronic toxicity and total body burden using hair, toenail, urine and serum should be done with both baseline and provocation methods.

Intracellular Transactivation of Epidermal Growth Factor Receptor byα1A-Adrenoceptor Is Mediated by Phosphatidylinositol 3-Kinase Independently of Activation of Extracellular Signal Regulated Kinases 1/2 and Serine-Threonine Kinases in Chinese Hamster Ovary Cells

Transactivation of epidermal growth factor receptor (EGFR) by α1-adrenoceptor (α1-AR) is implicated in contraction and hypertrophy of vascular smooth muscle (VSM). We examine whether all α1-AR subtypes transactivate EGFR and explore the mechanism of transactivation. Chinese hamster ovary (CHO) cells stably expressing one subtype of α1-AR were transiently transfected with EGFR. The transactivation mechanism was examined both by coexpression of a chimeric erythropoietin (EPO)-EGFR with an extracellular EPO and intracellular EGFR domain, and by pharmacologic inhibition of external and internal signaling routes. All three α1-AR subtypes transactivated EGFR, which was dependent on the increase in intracellular calcium. The EGFR kinase inhibitor AG1478 [4-(3'-chloroanilino)-6,7-dimethoxyquinazoline] abrogated α1A-AR and α1D-AR induced phosphorylation of EGFR, but both the inhibition of matrix metalloproteinases by GM6001 [(R)-N4-hydroxy-N(1)-[(S)-2-(1H-indol-3-yl)-1-methylcarbamoyl-ethyl]-2-isobutyl-succinamide] or blockade of EGFR by cetuximab did not. Stimulation of α1A-AR and α1D-AR also induced phosphorylation of EPO-EGFR chimeric receptors. Moreover, α1A-AR stimulation enhanced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 and serine-threonine kinases (Akt), which were both unaffected by AG1478, indicating that ERK1/2 and Akt phosphorylation is independent of EGFR transactivation. Accordingly, inhibitors of ERK1/2 or Akt did not influence the α1A-AR-mediated EGFR transactivation. Inhibition of calcium/calmodulin-dependent kinase II (CaMKII), phosphatidylinositol 3-kinase (PI3K), and Src, however, did block EGFR transactivation by α1A-AR and α1D-AR. These findings demonstrate that all α1-AR subtypes transactivate EGFR, which is dependent on an intracellular signaling route involving an increase in calcium and activation of CaMKII, PI3K, and Src, but not the of ERK1/2 and Akt pathways.

1700 Expression of the Nuclear Factor of Activated T Cells MRNA in Human Fetal Lung

Background and AimsThe nuclear factor of activated T cells (NFAT) is a family of four transcription factors (c1, c2, c3 and c4) involved in vascular smooth muscle differentiation, contractility and...

Smooth muscle in tissue remodeling and hyper-reactivity: Airways and arteries

Smooth muscle comprises a key functional component of both the airways and their supporting vasculature. Dysfunction of smooth muscle contributes to and exacerbates a host of breathing-associated pathologies such as asthma, chronic obstructive pulmonary disease and pulmonary hypertension. These diseases may be marked by airway and/or vascular smooth muscle hypertrophy, proliferation and hyper-reactivity, and related conditions such as fibrosis and extracellular matrix remodeling. This review will focus on the contribution of airway or vascular smooth dysfunction to common airway diseases.

Bosentan and Sildenafil reduce pulmonary arterial hypertension in rats induced by semaxanib and a low oxygen environment

Previous work has demonstrated the development of increased pulmonary artery pressures, hypertrophy of the pulmonary arterial vascular smooth muscle, and proliferation of the endothelial vascular lumen in rats following extended exposure to hypoxia and VEGF‐receptor antagonists. We validated this model of pulmonary arterial hypertension (PAH) by evaluating its utility as a clinically relevant paradigm to determine the efficacy of test articles against PAH. Male SD rats (240–370 g) were kept inside a hypoxic tent. Atmospheric oxygen was reduced to 13.5% using an oxygen scrubber. Rats received a single dose of semaxanib (200 mg/kg, s.c.) and were maintained inside the tent for 3 weeks. Rats received oral doses of vehicle (20% cyclodextrin, 10mL/kg once daily), bosentan (BS‐ 300mg/kg once daily) or sildenafil (SL‐ 30mg/kg twice daily). At day 21, pulmonary and systemic arterial pressures and thoracic organ weights were measured. BS and SL‐treated rats exhibited systolic, diastolic and mean pulmonary arterial pressures (21 and 19; 16 and 15; 18 and 17 mmHg, respectively) that were significantly lower compared to the vehicle (30, 22 and 26 mmHg, respectively). There was a trend toward decreased right ventricle to left ventricle weight ratio when comparing BS and SL with the vehicle. There were no significant differences in mean arterial pressure among rats treated with BS and SL as compared to vehicle. In summary, oral administration of BS and SL reduces PAH induced semaxanib and a low oxygen environment in a clinically relevant model.

MicroRNAs in Hypertension: Mechanisms and Therapeutic Targets

Hypertension is a complex, multifactorial disease, and its development is determined by a combination of genetic susceptibility and environmental factors. Several mechanisms have been implicated in the pathogenesis of hypertension: increased activity of the sympathetic nervous system, overactivation of the renin-angiotensin aldosterone system (RAAS), dysfunction of vascular endothelium, impaired platelet function, thrombogenesis, vascular smooth muscle and cardiac hypertrophy, and altered angiogenesis. MicroRNAs are short, noncoding nucleotides regulating target messenger RNAs at the post-transcriptional level. MicroRNAs are involved in virtually all biologic processes, including cellular proliferation, apoptosis, and differentiation. Thus, microRNA deregulation often results in impaired cellular function and disease development, so microRNAs have potential therapeutic relevance. Many aspects of the development of essential hypertension at the molecular level are still unknown. The elucidation of these processes regulated by microRNAs and the identification of novel microRNA targets in the pathogenesis of hypertension is a highly valuable and exciting strategy that may eventually led to the development of novel treatment approaches for hypertension. This article reviews the potential role of microRNAs in the mechanisms associated with the development and consequences of hypertension and discusses advances in microRNA-based approaches that may be important in treating hypertension.

α1‐Adrenoceptor‐mediated contraction of rat aorta is partly mediated via transactivation of the epidermal growth factor receptor

High level of plasma catecholamines is a risk factor for vascular diseases such as hypertension and atherosclerosis. Catecholamines induce hypertrophy of vascular smooth muscle through α(1) -adrenoceptors, which in cell culture involves the transactivation of epidermal growth factor receptor (EGFR). We hypothesized that EGFR transactivation was also involved in contractions of rat aorta mediated by α(1) -adrenoceptors. Thoracic aorta was isolated from 12-14 week old male Wistar rats. In vitro aortic contractile responses to cumulative doses of phenylephrine were characterized in the absence and presence of the EGFR kinase inhibitors, AG1478 and DAPH, in intact and endothelium-denuded rings. Involvement of signal transduction pathways was investigated by using heparin and inhibitors of Src, matrix metalloproteinase (MMP), extracellular signal-regulated kinase (ERK)1/2 and phosphatidyl inositol 3-kinase (PI3K). Phosphorylation of EGFR and ERK1/2 was measured after short-term phenylephrine or EGF stimulation in aorta segments in the presence of AG1478 and the PI3K inhibitor, wortmannin. AG1478 and DAPH concentration dependently attenuated phenylephrine-induced contractile responses in intact or endothelium-denuded aortic rings. Inhibition of PI3K (wortmannin and LY294002) but not heparin or inhibitors of Src or MMP, prevented the effect of AG1478 on the responses to phenylephrine. Phenylephrine induced phosphorylation of EGFR, which was partially blocked by AG1478. Phenylephrine also increased phosphorylation of ERK1/2, time-dependently and was blocked by AG1478 and wortmannin. Contractions of rat thoracic aorta mediated by α(1) -adrenoceptors involved transactivation of EGFR, mediated via a PI3K and ERK1/2 dependent pathway.

G protein-coupled receptor kinase 2 and arrestin2 regulate arterial smooth muscle P2Y-purinoceptor signalling

AimsProlonged P2Y-receptor signalling can cause vasoconstriction leading to hypertension, vascular smooth muscle hypertrophy, and hyperplasia. G protein-coupled receptor signalling is negatively regulated by G protein-coupled receptor kinases (GRKs) and arrestin proteins, preventing prolonged or inappropriate signalling. This study investigates whether GRKs and arrestins regulate uridine 5′-triphosphate (UTP)-stimulated contractile signalling in adult Wistar rat mesenteric arterial smooth muscle cells (MSMCs).Methods and resultsMesenteric arteries contracted in response to UTP challenge: When an EC50 UTP concentration (30 µM, 5 min) was added 5 min before (R1) and after (R2) the addition of a maximal UTP concentration (Rmax: 100 µM, 5 min), R2 responses were decreased relative to R1, indicating desensitization. UTP-induced P2Y-receptor desensitization of phospholipase C signalling was studied in isolated MSMCs transfected with an inositol 1,4,5-trisphosphate biosensor and/or loaded with Ca2+-sensitive dyes. A similar protocol (R1/R2 = 10 µM; Rmax = 100 µM, applied for 30 s) revealed markedly reduced R2 when compared with R1 responses. MSMCs were transfected with dominant-negative GRKs or siRNAs targeting specific GRK/arrestins to probe their respective roles in P2Y-receptor desensitization. GRK2 inhibition, but not GRK3, GRK5, or GRK6, attenuated P2Y-receptor desensitization. siRNA-mediated knockdown of arrestin2 attenuated UTP-stimulated P2Y-receptor desensitization, whereas arrestin3 depletion did not. Specific siRNA knockdown of the P2Y2-receptor almost completely abolished UTP-stimulated IP3/Ca2+ signalling, strongly suggesting that our study is specifically characterizing this purinoceptor subtype.ConclusionThese new data highlight roles of GRK2 and arrestin2 as important regulators of UTP-stimulated P2Y2-receptor responsiveness in resistance arteries, emphasizing their potential importance in regulating vasoconstrictor signalling pathways implicated in vascular disease.

Involved Intrinsic Apoptotic Pathway in the Varicocele and Varicose Veins

Disordered programmed cell death may play a role in the development of venous diseases. Tissue hypoxia caused by blood stagnation and venous hypertension is the similar etiology of varicocele and varicose veins. We studied the vascular histopathology and determined whether there is the same apoptotic pathway in both venous diseases. The study groups consisted of 1-cm venous segments obtained from 10 patients during vascular stripping surgery for varicose saphenous vein and 1 cm of internal spermatic veins obtained from 12 patients during left varicocele repair. The control samples of 1 cm internal spermatic vein were obtained from 10 male patients who underwent left inguinal herniorrhaphy. The three layers of vascular histology were measured and compared by Masson trichrome stain, and the apoptotic proteins including Bcl-2, Fas, cleaved caspase-9, cleaved caspase-8, and cleaved caspase-3 were detected. Data were analyzed using the one-way analysis of variance with Tukey's comparison test. The relative thickness of intima and adventitia layer was smaller in both study groups than in the control group. But a significant hypertrophy of media layer was observed in the varicocele and varicose veins than in the control group (p < 0.05). Overexpression of Bcl-2 and decreased expressions of cleaved caspase-9 and cleaved caspase-3 was observed in both study groups. There is no statistical difference in Fas and cleaved caspase-8 expressions in the control and study groups. Our data showed vascular smooth muscle hypertrophy in the diseased vessels. The same dysregulation of apoptosis through intrinsic pathway was demonstrated in varicocele and varicose veins under tissues hypoxia. This mechanism of reduced apoptosis might contribute to the dilated and thickened walls of both venous diseases.