Amplification of the COX/TXS/TP receptor pathway enhances uridine diphosphate-induced contraction by advanced glycation end products in rat carotid arteries

Advanced glycation end products (AGEs) play a pivotal role in vascular functions under various pathophysiological conditions. Although uridine diphosphate (UDP) is an important extracellular nucleotide, the relationship between AGEs and UDP regarding their effect on vascular functions remains unclear. Therefore, we investigated the effects of AGE-bovine serum albumin (AGE-BSA) on UDP-mediated responses in rat thoracic aorta and carotid arteries. In rat thoracic aorta, UDP-induced relaxation was observed and this relaxation was similar between control (1.0 v/v% PBS) and AGE-BSA-treated (0.1 mg/mL for 60 min) groups. In contrast, contraction but not relaxation was obtained following UDP application to carotid arteries with and without endothelia; contraction was greater in the AGE-BSA-treated group than in the control group. The difference in UDP-induced contraction between the two groups was not abolished by the use of a nitric oxide synthase (NOS) inhibitor, whereas it was abolished by the use of cyclooxygenase (COX), thromboxane synthase (TXS), and thromboxane-prostanoid (TP) receptor antagonist. Further, the difference in UDP-induced contraction was not abolished by the use of a cPLA₂ inhibitor, whereas it was abolished by the use of an iPLA₂ inhibitor. UDP increased TXA₂ release in both groups, and its level was similar in both groups. Moreover, the release of PGE₂, PGF_2α, and PGI₂ was similar among the groups. Under NOS inhibition, TP receptor agonist-induced contraction increased in the AGE-BSA-treated group (vs. control group). In conclusion, the increase in UDP-induced carotid arterial contraction by AGE-BSA can be attributed to an increase in the COX/TXS/TP receptor pathway, particularly, TP receptor signaling.

Transcriptional control of a novel long noncoding RNA Mymsl in smooth muscle cells by a single Cis-element and its initial functional characterization in vessels

Differentiated vascular smooth muscle cells (VSMCs) are crucial in maintaining vascular homeostasis. While the coding transcriptome of the differentiated VSMC phenotype has been defined, we know little about its noncoding signature. Herein, we identified a Myocardin-induced muscle specific long noncoding RNA (lncRNA) (Mymsl) downregulated upon VSMC phenotypic modulation. We demonstrated an essential role of a proximal consensus CArG element in response to MYOCD/SRF in vitro. To validate the in vivo role of this CArG element, we generated CArG mutant mice via CRISPR-Cas9 genome editing. While the CArG mutation had no impact on the expression of surrounding genes, it abolished Mymsl expression in SMCs, but not skeletal and cardiac muscle. Chromatin immunoprecipitation assays (ChIPs) showed decreased SRF binding to CArG region in mutants whereas the enrichment of H3K79Me2 remained the same. RNA-seq analysis showed a downregulation of matrix genes in aortas from Mymsl knockout mice, which was further validated in injured carotid arteries. Our study defined the transcriptional control of a novel lncRNA in SMCs via a single transcription factor binding site, which may offer a new strategy for generating SMC-specific knockout mouse models. We also provided in vivo evidence supporting the potential importance of Mymsl in vascular pathophysiology.

Cilostazol inhibits hyperglucose-induced vascular smooth muscle cell dysfunction by modulating the RAGE/ERK/NF-κB signaling pathways

Background

Increasing evidence suggests that high glucose (HG) causes abnormalities in endothelial and vascular smooth muscle cell function (VSMC) and contributes to atherosclerosis. Receptor for advanced glycation end-products (RAGE) has been linked to the pathogenesis of both the macrovascular and microvascular complications of diabetes. Cilostazol is used to treat diabetic vasculopathy by ameliorating HG-induced vascular dysfunction.

Objectives

In this study, we investigated whether the cilostazol suppression of HG-induced VSMC dysfunction is through RAGE signaling and its possible regulation mechanism.

Method

We investigated the effect of HG and cilostazol on RAGE signaling in A7r5 rat VSMCs. Aortic tissues of streptozotocin (STZ) diabetic mice were also collected.

Results

Aortic tissue samples from the diabetic mice exhibited a significantly decreased RAGE expression after cilostazol treatment. HG increased RAGE, focal adhesion kinase (FAK), matrix metalloproteinase-2 (MMP-2), intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expressions, and was accompanied with increased reactive oxygen species (ROS), cell proliferation, adhesion and migration. Cilostazol significantly reversed HG-induced RAGE, ROS, downstream gene expressions and cell functions. RAGE knockdown significantly reversed the expressions of HG-induced vasculopathy related gene expressions and cell functions. Cilostazol with RAGE knockdown had additive effects on downstream ERK/NF-κB signaling pathways, gene expressions and cell functions of A7r5 rat VSMCs in HG culture.

Conclusions

Both in vitro and in vivo experimental diabetes models showed novel signal transduction of cilostazol-mediated protection against HG-related VSMC dysfunction, and highlighted the involvement of RAGE signaling and downstream pathways.

Sulodexide promotes arterial relaxation via endothelium-dependent nitric oxide-mediated pathway

Sulodexide (SDX) is a highly purified glycosaminoglycan with antithrombotic and profibrinolytic properties and reported benefits in thrombotic and atherosclerotic vascular disorders. However, the effects of SDX on vascular function are unclear. We tested whether SDX affects vascular relaxation and examined the potential underlying mechanisms. Isolated segments of male rat abdominal aorta and mesenteric artery were suspended in a tissue bath, and the changes in arterial contraction/relaxation were measured. The α-adrenergic receptor agonist phenylephrine (Phe) (10^-9-10^-5 M) caused concentration-dependent aortic and mesenteric artery contraction that was reduced in tissues pretreated with SDX (1 mg/ml). In aortic and mesenteric arterial segments precontracted with submaximal concentration of Phe (3 × 10^-7-6 × 10^-7 M), SDX (0.001-1 mg/ml) caused concentration-dependent relaxation. To test the role of endothelium, SDX-induced relaxation was compared with that of acetylcholine (ACh), a known activator of endothelium-dependent relaxation. In Phe precontracted aorta, ACh relaxation was abolished and SDX relaxation was significantly inhibited by endothelium removal or the nitric oxide synthase (NOS) inhibitor N_ω-nitro-l-arginine methyl ester (L-NAME), suggesting a role of NO. In mesenteric artery, ACh relaxation was abolished by endothelium removal, partially blocked by L-NAME, and completely blocked by a mixture of indomethacin, a cyclooxygenase inhibitor and blocker of the PGI₂-cAMP pathway, and tetraethylammonium, a blocker of K⁺ channels and EDHF-dependent hyperpolarization pathway. In comparison, SDX relaxation of mesenteric artery was almost completely inhibited by endothelium removal or NOS inhibitor L-NAME. SDX enhanced vascular relaxation and increased nitrate/nitrite production in response to all ACh concentrations in the aorta, but only to low ACh concentrations (<10^-7 M) in mesenteric artery. SDX did not affect aortic or mesenteric artery endothelium-independent relaxation to the NO donor sodium nitroprusside. Thus, SDX promotes arterial relaxation via a mechanism involving endothelium-dependent NO production; an effect that could enhance vasodilation and decrease vasoconstriction in vascular disorders.

Downregulation of AT2R decreases the responsiveness of BKCa channels to angiotensin II in patients with hypertension

Angiotensin II (Ang II) modulates blood pressure via Ang II type 1 receptor (AT₁R) and type 2 receptor (AT₂R). The activation of AT₂R relaxes vascular tone through opening large-conductance Ca²⁺-activated potassium (BK_Ca) channels in vascular smooth muscle cells (SMCs). In the present study, we studied the role of the AT₂R-BK_Ca pathway in patients with hypertension. The mesenteric arterial SMCs (MSMCs) were obtained from normotensive patients (NP) and hypertensive patients (HP). BK_Ca currents were recorded with patch clamp and the expressions of mRNAs and proteins of AT₁R/AT₂R were analyzed by RT-PCR and Western blotting, respectively. Ang II significantly increased the macroscopic BK_Ca currents at the whole cell level, while increased the open probability and decreased the mean close time of BK_Ca channels at the single channel level with AT₁R blockade by valsartan in NP. However, Ang II had no effect on the BK_Ca currents at the same condition in HP. Furthermore, the expressions of mRNA and protein of AT₂R but not AT₁R were markedly decreased in the MSMCs of HP compared to that of NP. The data suggest that AT₂R is well functioned in the MSMCs in NP but not in HP and deficiency in the AT₂R-BK_Ca pathway may contribute to the development of hypertension.

Myogenic tone contributes to the regulation of permeability in mesenteric microvessels

The microvascular endothelium plays a key role in regulating solute permeability in the gut, but the contribution of vascular smooth muscle to barrier function is unknown. We sought to determine the role of vascular smooth muscle and its myogenic tone in the vascular barrier to solutes in mesenteric microvessels. We determined vascular permeability to 4.4 kDa and 70 kDa dextrans in isolated mouse mesenteric arteries at increasing pressure increments. The myogenic response was simultaneously monitored using video edge-detection of vessel diameter and wall thickness. We expressed permeability as the apparent permeability coefficient, or the solute flux per second normalized to surface area and concentration gradient. We compared the effects of myogenic tone, L-type calcium channel blockade, calcium elimination, and endothelial removal on the permeability of each dextran. We found arteries resisted changes in 4.4 kDa and 70 kDa dextran permeability coefficients at intravascular pressures associated with myogenic tone. Manipulations that reduced or eliminated myogenic tone (L-type calcium channel blockade or calcium elimination) caused vasodilation and increased permeability coefficients. Thus, the maintenance of a reactive mesenteric vascular smooth muscle layer and its myogenic tone prevents increases in vascular permeability that would otherwise occur with increasing pressure. Conditions that impact vascular tone, such as trauma, stroke, or major surgery could diminish the gut-vascular barrier against dissemination of the microbiome.

A Disintegrin and Metalloproteinase (ADAM) and ADAM with thrombospondin motifs (ADAMTS) family in vascular biology and disease

A Disintegrin and Metalloproteinase (ADAM) is a family of proteolytic enzymes that possess sheddase function and regulate shedding of membrane-bound proteins, growth factors, cytokines, ligands and receptors. Typically, ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and a characteristic transmembrane domain. Most ADAMs are activated by proprotein convertases, but can also be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C activators. A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) is a family of secreted enzymes closely related to ADAMs. Like ADAMs, ADAMTS members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but they lack a transmembrane domain and instead have characteristic thrombospondin motifs. Activated ADAMs perform several functions and participate in multiple cardiovascular processes including vascular smooth muscle cell proliferation and migration, angiogenesis, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs may also be involved in pathological conditions and cardiovascular diseases such as atherosclerosis, hypertension, aneurysm, coronary artery disease, myocardial infarction and heart failure. Like ADAMs, ADAMTS have a wide-spectrum role in vascular biology and cardiovascular pathophysiology. ADAMs and ADAMTS activity is naturally controlled by endogenous inhibitors such as tissue inhibitors of metalloproteinases (TIMPs), and their activity can also be suppressed by synthetic small molecule inhibitors. ADAMs and ADAMTS can serve as important diagnostic biomarkers and potential therapeutic targets for cardiovascular disorders. Natural and synthetic inhibitors of ADAMs and ADAMTS could be potential therapeutic tools for the management of cardiovascular diseases.

Subchronic stress effects on vascular reactivity in C57BL/6 strain mice

BACKGROUND AND AIMS

There is a close relationship between psychosocial stress and the development of cardiovascular diseases. It has been reported that there are different alterations in endothelial function in this relationship. However, results obtained in different experimental stress models are controversial. Herein, we studied the effects of subchronic stress induced by movement restraint on several cardiovascular responses and plasma corticosterone concentration in male adult mice.

METHODS

Experiments were performed in adult male mice of C57BL/6 strain. Animals were allocated into three groups: Control group A, without manipulation; Control group B, with manipulation (quantitation of blood pressure); and Experimental group, with quantitation of blood pressure and exposure to movement restraint. In vivo, heart rate and blood pressure were registered. In vitro, in aortic rings, vascular reactivity was analyzed. Additionally, plasma corticosterone concentration was quantified.

RESULTS

In vivo, subchronic stress did not produce changes on heart rate either on blood pressure. In vitro, aortic rings with and without endothelium from control group B and experimental group showed: 1) a significant decrease in the maximal tension developed in response to phenylephrine; 2) this decrease was reverted by L-NAME. However, aortic rings from all groups, developed the same tension in response to high K⁺ solution. In aortic rings from animals of the experimental group, an increase in the maximal relaxation induced by carbachol was observed. This relaxation was prevented and/or reversed by L-NAME. Plasma corticosterone concentration was higher in the experimental group than that in the control group A.

CONCLUSIONS

Exposition to subchronic movement restraint did not produce alterations in neurovegetative responses in this strain mice. But according to vasomotor responses observed, the results suggest that this subchronic stress model induces an increase in the synthesis/release of nitric oxide, both from endothelial cells and vascular smooth muscle. In accordance with the aforementioned results, we propose that C57BL/6 mice strain is sensitive to subchronic movement restraint stress model.

Hibiscus acid from Hibiscus sabdariffa (Malvaceae) has a vasorelaxant effect on the rat aorta

Hibiscus sabdariffa (Malvaceae) is a plant that is widely recognised for its antihypertensive properties; however the constituent(s) responsible for this biological activity are presently unknown. The aim of this study was to identify the potential compounds that are responsible for the vasorelaxant activity of H. sabdariffa. Thereafter, the mechanisms involved in producing the vasorelaxation were investigated. The plant was extracted consecutively with hexane, ethyl acetate and methanol. The methanolic extract was subjected to bioassay-guided fractionation in order to isolate pure compounds that possessed vasorelaxant activity. The vascular effects of the pure compounds were studied on the rat aorta in vitro using myography techniques. Hibiscus acid produced a concentration-dependent relaxation of the rat aorta pre-contracted with either phenylephrine (3 μM) or KCl (60 mM), irrespective of the presence of the endothelium. When the tissue was pre-contracted with phenylephrine, the concentration required to produce 50% relaxation (IC₅₀), was 0.09 ± 0.01 mg/ml. Hibiscus acid had no effect on the phasic contraction induced by phenylephrine in Ca²⁺-free physiological solution; but it did affect the component of the contraction that is due to Ca²⁺ influx. In parallel studies, garcinia acid, a diastereoisomer of hibiscus acid, was found to have an almost identical vasorelaxant effect. The vasorelaxant action of both compounds is most likely due to the inhibition of Ca²⁺ influx via voltage-dependent Ca²⁺ channels.

Baicalin relaxes vascular smooth muscle and lowers blood pressure in spontaneously hypertensive rats

Scutellaria baicalensis Georgi is an extensively used medicinal herb for the treatment of hypertension in traditional Chinese medicine. Baicalin is the most abundant flavone compound present in Scutellaria baicalensis Georgi and endothelium-dependent vascular activities of baicalin have been suggested. However, the pharmacological implications and mechanisms of baicalin under hypertensive conditions remain to be investigated. The current study examined the blood pressure-lowering effect of baicalin in a spontaneously hypertensive rat (SHR) model. Moreover, vascular activities and mechanisms of baicalin were investigated under hypertensive conditions. The results demonstrate that baicalin treatment lowers the blood pressure in SHRs in vivo. Ex vivo vascular reactivity assay reveals that baicalin relaxes phenylephrine (PE)-constricted SHR aortas in an endothelium-independent manner. Baicalin attenuates Angiotensin II (Ang II) or potassium chloride (KCl)-induced vasoconstriction in SHR aortas as well. Baicalin also relaxes SHR aortas in the presence of different Ca²⁺ channel blockers such as nifedipine and SKF96365 in response to PE-induced constriction. Most importantly, ATP-sensitive potassium channel (K_ATP) blockade partially abrogated the vasorelaxant effect of baicalin. In summary, the current study demonstrates for the first time that intracellular Ca²⁺ regulation in vascular smooth muscle is mechanistically implicated in the vasorelaxant effect of baicalin under hypertensive conditions. Furthermore, activated K_ATP channels are in part required for the vasorelaxant effect of baicalin under hypertensive conditions. Thus, the work here sheds novel pharmacological and mechanistic insights into the blood pressure-lowering effect of baicalin, which may help better understand the therapeutic application of Scutellaria baicalensis Georgi in the treatment of hypertension.

Pregnancy-Induced Physiologic Adaptation of the Abdominal Aorta Is Associated with Changes in Gene Expression and Genomic Methylation

BACKGROUND/AIMS

Ten-eleven translocation 2 (Tet2), a DNA demethylase enzyme, has been identified as a master epigenetic regulator of vascular smooth muscle cell plasticity. We hypothesized that pregnancy will induce significant adaptive changes in aortic biomechanics that correlate with the Tet family gene expression.

METHODS

Abdominal aortas from pregnant and nonpregnant mice were dissected and cannulated. Intraluminal pressure was adjusted using a pressure-servo system while using a video dimension analyzer to measure the lumen diameter. Quantitative polymerase chain reaction and immunoblot was used to analyze the expression of Tet genes. Global genomic methylation was assessed with the luminometric methylation assay.

RESULTS

Compared to the nonpregnant (NP, 706 ± 8 µm) control group, the aortic luminal diameter was significantly increased in both E18.5 (836 ± 14 µm) and PP30 (889 ± 16 µm) mice. Distensibility was reduced in E18.5 (90 ± 4%) mice and returned to NP values (108 ± 2%) in PP30 (108 ± 3%) mice. Tet2 transcription decreased at the beginning of pregnancy and subsequently increased in late gestation, inversely corresponding to changes in global methylation.

CONCLUSION

Physiologic changes in the aorta were accompanied by changes in gene expression and genomic methylation, suggesting an epigenetic component to maternal vascular remodeling during pregnancy.

Effect of reperfusion on vascular smooth muscle reactivity in three contraction models

BACKGROUND

Ischemia and reperfusion remain inseparable elements of numerous medical procedures such as by-pass surgery, organ transplantation or other cardiology and intervention radiology. The contraction of the smooth muscle of the vessel is considered to be one of the basic components leading to impaired perfusion, an increase in the oxygen deficit of the endothelium of the vessel, and subsequently also to tissues vascularized by the vessel. Main aim of this study was to evaluate the effect of ischemia and reperfusion on vascular smooth muscle cells stimulated pharmacologically with mastoparan-7 (direct G-protein activator) in comparison to stimulation of G-protein coupled receptor agonist - phenylephrine, and direct calcium channel activator - Bay K8644.

MATERIAL AND METHODS

Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force in our model was measured by increased level of perfusion pressure with a constant flow.

RESULTS

Concentration-response curves obtained for phenylephrine, mastoparan-7 and Bay K8644 presented a sigmoidal relation. Ischemia induced hyporreactivity of vessels, whereas during reperfusion the significant time related hyperreactivity for phenylephrine and mastoparan-7 only but not for Bay K8644. These reactions were secondary to the modulation of calcium influx from intra- and extracellular calcium stores.

CONCLUSIONS

Results of our experiments suggest that mastoparan-7 significantly induces contraction of vascular smooth muscle cells not only for controls but in the presence of ischemia and reperfusion too. Potential therapeutic applications of the observed reactions are important. They may include regenerative processes within the nervous system, studies on the improvement of blood flow within the microcirculation, or antimicrobial activity. Modulation of the G protein-phospholipase C response may also be an interesting point of action of future drugs modifying the response to stimulation during ischemia in particular, such activities could take place during the transport of organs for transplantation.

Smooth muscle cell-driven vascular diseases and molecular mechanisms of VSMC plasticity

Vascular smooth muscle cells (VSMCs) are the major cell type in blood vessels. Unlike many other mature cell types in the adult body, VSMC do not terminally differentiate but retain a remarkable plasticity. Fully differentiated medial VSMCs of mature vessels maintain quiescence and express a range of genes and proteins important for contraction/dilation, which allows them to control systemic and local pressure through the regulation of vascular tone. In response to vascular injury or alterations in local environmental cues, differentiated/contractile VSMCs are capable of switching to a dedifferentiated phenotype characterized by increased proliferation, migration and extracellular matrix synthesis in concert with decreased expression of contractile markers. Imbalanced VSMC plasticity results in maladaptive phenotype alterations that ultimately lead to progression of a variety of VSMC-driven vascular diseases. The nature, extent and consequences of dysregulated VSMC phenotype alterations are diverse, reflecting the numerous environmental cues (e.g. biochemical factors, extracellular matrix components, physical) that prompt VSMC phenotype switching. In spite of decades of efforts to understand cues and processes that normally control VSMC differentiation and their disruption in VSMC-driven disease states, the crucial molecular mechanisms and signalling pathways that shape the VSMC phenotype programme have still not yet been precisely elucidated. In this article we introduce the physiological functions of vascular smooth muscle/VSMCs, outline VSMC-driven cardiovascular diseases and the concept of VSMC phenotype switching, and review molecular mechanisms that play crucial roles in the regulation of VSMC phenotypic plasticity.

Modulation of nitric oxide-stimulated soluble guanylyl cyclase activity by cytoskeleton-associated proteins in vascular smooth muscle

Soluble guanylyl cyclase (sGC, EC 4.6.1.2) is a key enzyme in the regulation of vascular tone. In view of the therapeutic interest of the NO/cGMP pathway, drugs were developed that either increase the NO sensitivity of the enzyme or activate heme-free apo-sGC. However, modulation of sGC activity by endogenous agents is poorly understood. In the present study we show that the maximal activity of NO-stimulated purified sGC is significantly increased by cytosolic preparations of porcine coronary arteries. Purification of the active principle by several chromatographic steps resulted in a protein mixture consisting of 100, 70, and 40 kDa bands on SDS polyacrylamide gel electrophoresis. The respective proteins were identified by LC-MS/MS as gelsolin, annexin A6, and actin, respectively. Further purification resulted in loss of activity, indicating an interaction of sGC with a protein complex rather than a single protein. The partially purified preparation had no effect on basal sGC activity or enzyme activation by the heme mimetic BAY 60-2770, suggesting a specific effect on the conformation of the NO-bound heterodimeric holoenzyme. Since the three proteins identified are all related to contractile elements of smooth muscle, our data suggest that regulation of vascular tone involves a modulatory interaction of sGC with the cytoskeleton.

Important roles of the Ca2+-sensing receptor in vascular health and disease

Ca²⁺-sensing receptor (CaSR), a member of G protein-coupled receptor family, is widely expressed in the vascular system, including perivascular neurons, vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). When stimulated, CaSR can further increase the cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt) in two ways: intracellular Ca²⁺ release from endo/sarcoplasmic reticulum (ER/SR) and extracellular Ca²⁺ entry through Ca²⁺-permeable cation channels. In endothelium, increased Ca²⁺ subsequently activate nitric oxide synthase (NOS) and intermediate conductance Ca²⁺-activated K⁺ channels (IKCa), resulting in vasodilation through NOS-mediated NO release or membrane hyperpolarization. In VSMCs, CaSR-induced intracellular Ca²⁺ increase causes blood vessel constriction. CaSR activation predominantly induces vasorelaxation of whole vascular tissues through VECs-dependent mechanisms; however, CaSR-induced Ca²⁺ signaling in VSMCs may play a braking role in CaSR-mediated vasorelaxation. Emerging evidence reveals the importance of CaSR in the regulation of vascular tone and blood pressure. Here, we summarized recent advances in CaSR-mediated vascular reaction and the underlying mechanisms in different species, including humans. In addition, several studies have demonstrated that CaSR dysfunction may be associated with some fatal vascular diseases, such as pulmonary arterial hypertension, primary hypertension, diabetes, acute myocardial infarction and vascular calcification. With the advance of studies on CaSR in vascular health and disease, it is expected positive modulators or negative modulators of CaSR used for the treatment of specific diseases may be promising therapeutic options for the prevention and/or treatment of vascular diseases.

Transforming growth factor β1 suppresses proinflammatory gene program independent of its regulation on vascular smooth muscle differentiation and autophagy

Transforming growth factor β (TGFβ) signaling plays crucial roles in maintaining vascular integrity and homeostasis, and is established as a strong activator of vascular smooth muscle cell (VSMC) differentiation. Chronic inflammation is a hallmark of various vascular diseases. Although TGFβ signaling has been suggested to be protective against inflammatory aortic aneurysm progression, its exact effects on VSMC inflammatory process and the underlying mechanisms are not fully unraveled. Here we revealed that TGFβ1 suppressed the expression of a broad array of proinflammatory genes while potently induced the expression of contractile genes in cultured primary human coronary artery SMCs (HCASMCs). The regulation of TGFβ1 on VSMC contractile and proinflammatory gene programs appeared to occur in parallel and both processes were through a SMAD4-dependent canonical pathway. We also showed evidence that the suppression of TGFβ1 on VSMC proinflammatory genes was mediated, at least partially through the blockade of signal transducer and activator of transcription 3 (STAT3) and NF-κB pathways. Interestingly, our RNA-seq data also revealed that TGFβ1 suppressed gene expression of a battery of autophagy mediators, which was validated by western blot for the conversion of microtubule-associated protein light chain 3 (LC3) and by immunofluo-rescence staining for LC3 puncta. However, impairment of VSMC autophagy by ATG5 deletion failed to rescue TGFβ1 influence on both VSMC contractile and proinflammatory gene programs, suggesting that TGFβ1-regulated VSMC differentiation and inflammation are not attributed to TGFβ1 suppression on autophagy. In summary, our results demonstrated an important role of TGFβ signaling in suppressing proinflammatory gene program in cultured primary human VSMCs via the blockade on STAT3 and NF-κB pathway, therefore providing novel insights into the mechanisms underlying the protective role of TGFβ signaling in vascular diseases.

A Simple Method for Normalization of Aortic Contractility

Vascular contractile function changes in proliferative vascular diseases, e.g. atherosclerosis, and is documented using isolated blood vessels; yet, many laboratories differ in their approach to quantification. Some use raw values (e.g., mg, mN); others use a "percentage of control agonist" approach; and others normalize by blood vessel characteristic, e.g. length, mass, etc. A lack of uniformity limits direct comparison of contractility outcomes. To address this limitation, we developed a simple 2-step normalization method: (1) measure blood vessel segment length (mm), area (mm2) and calculate volume (mm3); then, (2) normalize isometric contraction (mN) by segment length and volume. Normalized aortic contractions but not raw values were statistically different between normal chow and high-fat diet-fed mice, supporting the practical utility and general applicability of normalization. It is recommended that aortic contractions be normalized to segment length and/or volume to reduce variability, enhance efficiency, and to foster universal comparisons across isometric myography platforms, laboratories, and experimental settings.

Biomimetic soft fibrous hydrogels for contractile and pharmacologically responsive smooth muscle

The ability to assess changes in smooth muscle contractility and pharmacological responsiveness in normal or pathological-relevant vascular tissue environments is critical to enable vascular drug discovery. However, major challenges remain in both capturing the complexity of in vivo vascular remodeling and evaluating cell contractility in complex, tissue-like environments. Herein, we developed a biomimetic fibrous hydrogel with tunable structure, stiffness, and composition to resemble the native vascular tissue environment. This hydrogel platform was further combined with the combinatory protein array technology as well as advanced approaches to measure cell mechanics and contractility, thus permitting evaluation of smooth muscle functions in a variety of tissue-like microenvironments. Our results demonstrated that biomimetic fibrous structure played a dominant role in smooth muscle function, while the presentation of adhesion proteins co-regulated it to various degrees. Specifically, fibre networks enabled cell infiltration and upregulated expression of actomyosin proteins in contrast to flat hydrogels. Remarkably, fibrous structure and physiologically relevant stiffness of hydrogels cooperatively enhanced smooth muscle contractility and pharmacological responses to vasoactive drugs at both the single cell and intact tissue levels. Together, this study is the first to demonstrate alterations of human vascular smooth muscle contractility and pharmacological responsiveness in biomimetic soft, fibrous environments with a cellular array platform. The integrated platform produced here could enable investigations for pathobiology and pharmacological interventions by developing a broad range of patho-physiologically relevant in vitro tissue models.

STATEMENT OF SIGNIFICANCE

Engineering functional smooth muscle in vitro holds the great potential for diseased tissue replacement and drug testing. A central challenge is recapitulating the smooth muscle contractility and pharmacological responses given its significant phenotypic plasticity in response to changes in environment. We present a biomimetic fibrous hydrogel with tunable structure, stiffness, and composition that enables the creation of functional smooth muscle tissues in the native-like vascular tissue microenvironment. Such fibrous hydrogel is further combined with the combinatory protein array technology to construct a cellular array for evaluation of smooth muscle phenotype, contraction, and cell mechanics. The integrated platform produced here could be promising for developing a broad range of normal or diseased in vitro tissue models.

Sphingosine-1-phosphate receptor 1 regulates neointimal growth in a humanized model for restenosis

OBJECTIVE

The main objective of this study was to define a role of sphingosine-1-phosphate receptor 1 (S1PR1) in the arterial injury response of a human artery. The hypotheses were tested that injury induces an expansion of S1PR1-positive cells and that these cells accumulate toward the lumen because they follow the sphingosine-1-phosphate gradient from arterial wall tissue (low) to plasma (high).

METHODS

A humanized rat model was used in which denuded human internal mammary artery (IMA) was implanted into the position of the abdominal aorta of immunosuppressed Rowett nude rats. This injury model is characterized by medial as well as intimal hyperplasia, whereby intimal cells are of human origin. At 7, 14, and 28 days after implantation, grafts were harvested and processed for fluorescent immunostaining for S1PR1 and smooth muscle α-actin. Nuclei were stained with 4',6-diamidine-2'-phenylindole dihydrochloride. Using digitally reconstructed, complete cross sections of grafts, intimal and medial areas were measured, whereby the medial area had virtually been divided into an outer (toward adventitia) and inner (toward lumen) layer. The fraction of S1PR1-positive cells was determined in each layer by counting S1PR1-positive and S1PR1-negative cells.

RESULTS

The fraction of S1PR1-postive cells in naive IMA is 58.9% ± 6.0% (mean ± standard deviation). At day 28 after implantation, 81.6% ± 4.4% of medial cells were scored S1PR1 positive (P < .01). At day 14, the ratio between S1PR1-positive and S1PR1-negative cells was significantly higher in the lumen-oriented inner layer (9.3 ± 2.1 vs 6.0 ± 1.0; P < .01). Cells appearing in the intima at day 7 and day 14 were almost all S1PR1 positive. At day 28, however, about one-third of intimal cells were scored S1PR1 negative.

CONCLUSIONS

From these data, we conclude that denudation of IMA specifically induces the expansion of S1PR1-positive cells. Based on the nonrandom distribution of S1PR1-positive cells, we consider the possibility that much like lymphocytes, S1PR1-positive smooth muscle cells also use S1PR1 to recognize the sphingosine-1-phosphate gradient from tissue (low) to plasma (high) and so migrate out of the media toward the intima of the injured IMA.

Calcium- and voltage-gated BK channels in vascular smooth muscle

Ion channels in vascular smooth muscle regulate myogenic tone and vessel contractility. In particular, activation of calcium- and voltage-gated potassium channels of large conductance (BK channels) results in outward current that shifts the membrane potential toward more negative values, triggering a negative feed-back loop on depolarization-induced calcium influx and SM contraction. In this short review, we first present the molecular basis of vascular smooth muscle BK channels and the role of subunit composition and trafficking in the regulation of myogenic tone and vascular contractility. BK channel modulation by endogenous signaling molecules, and paracrine and endocrine mediators follows. Lastly, we describe the functional changes in smooth muscle BK channels that contribute to, or are triggered by, common physiological conditions and pathologies, including obesity, diabetes, and systemic hypertension.

Mechanisms underlying the relaxation by A484954, a eukaryotic elongation factor 2 kinase inhibitor, in rat isolated mesenteric artery

Eukaryotic elongation factor 2 kinase (eEF2K) is a calmodulin-related protein kinase which regulates protein translation. A484954 is an inhibitor of eEF2K. In the present study, we investigated the acute effects of A484954 on contractility of isolated blood vessels. Isometric contraction of rat isolated aorta and main branch of superior mesenteric artery (MA) was measured. Expression of an inward rectifier K⁺ (K_ir) channel subtype mRNA and protein was examined. A484954 caused relaxation in endothelium-intact [E (+)] and -denuded [E (-)] aorta or MA precontracted with noradrenaline (NA). The relaxation was higher in MA than aorta. The relaxation was partially inhibited by a nitric oxide (NO) synthase inhibitor, N^G-nitro-l-arginine methyl ester (300 μM) in E (+) MA. The relaxation was significantly smaller in MA precontracted with high K⁺ than NA. The A484954-induced relaxation was significantly inhibited by a K_ir channel blocker, BaCl₂ (1 mM) compared with vehicle control in E (-) MA. Expression of K_ir2.2 mRNA and protein was significantly higher in MA than aorta. We for the first time revealed that A484954 induces relaxation through opening smooth muscle K_ir (K_ir2.2) channel and through endothelium-derived NO in MA.

Regulation of vascular function and blood pressure by circadian variation in redox signalling

There is accumulating evidence that makes the link between the circadian variation in blood pressure and circadian variations in vascular contraction. The importance of vascular endothelium-derived redox-active and redox-derived species in the signalling pathways involved in controlling vascular smooth muscle contraction are well known, and when linked to the circadian variations in the processes involved in generating these species, suggests a cellular mechanism for the circadian variations in blood pressure that links directly to the peripheral circadian clock. Relaxation of vascular smooth muscle cells involves endothelial-derived relaxing factor (EDRF) which is nitric oxide (NO) produced by endothelial NO synthase (eNOS), and endothelial-derived hyperpolarising factor (EDHF) which includes hydrogen peroxide (H₂O₂) produced by NADPH oxidase (Nox). Both of these enzymes appear to be under the direct control of the circadian clock mechanism in the endothelial cells, and disruption to the clock results in endothelial and vascular dysfunction. In this review, we focus on EDRF and EDHF and summarise the recent findings on the influence of the peripheral circadian clock mechanism on processes involved in generating the redox species involved and how this influences vascular contractility, which may account for some of the circadian variations in blood pressure and peripheral resistance. Moreover, the direct link between the peripheral circadian clock and redox-signalling pathways in the vasculature, has a bearing on vascular endothelial dysfunction in disease and aging, which are both known to lead to dysfunction of the circadian clock.

The Endothelin System: A Critical Player in the Pathophysiology of Preeclampsia

PURPOSE OF REVIEW

Preeclampsia (PE) is a disorder of pregnancy typically characterized by new-onset hypertension and proteinuria after gestational week 20. Although preeclampsia is one of the leading causes of maternal and perinatal morbidity and death worldwide, the mechanisms of the pathogenesis of the disorder remain unclear and treatment options are limited. Placental ischemic events and the release of placental factors appear to play a critical role in the pathophysiology. These factors contribute to a generalized systemic vascular endothelial dysfunction and result in increased systemic vascular resistance and hypertension.

RECENT FINDINGS

There is increasing evidence to suggest that endothelin-1 (ET-1) in the maternal vascular endothelium is a critical final common pathway, whereby placental ischemic factors cause cardiovascular and renal dysfunction in the mother. Multiple studies report increased levels of ET-1 in PE. A number of experimental models of PE are also associated with elevated tissue levels of prepro-ET-1 mRNA. Moreover, experimental models of PE (placental ischemia, sFlt-1 excess, TNF-α excess, and AT1-AA infusion) have proven to be responsive to ET type A receptor antagonism. Recent studies also suggest that abnormalities in ET type B receptor signaling may also play a role in PE. Although numerous studies highlight the importance of the ET system in the pathogenesis of PE, further work is needed to determine whether ET receptor antagonists could provide an effective therapy for the management of this disease.

Calcium phosphate particles stimulate interleukin-1β release from human vascular smooth muscle cells: A role for spleen tyrosine kinase and exosome release

AIMS

Calcium phosphate (CaP) particle deposits are found in several inflammatory diseases including atherosclerosis and osteoarthritis. CaP, and other forms of crystals and particles, can promote inflammasome formation in macrophages leading to caspase-1 activation and secretion of mature interleukin-1β (IL-1β). Given the close association of small CaP particles with vascular smooth muscle cells (VSMCs) in atherosclerotic fibrous caps, we aimed to determine if CaP particles affected pro-inflammatory signalling in human VSMCs.

METHODS AND RESULTS

Using ELISA to measure IL-1β release from VSMCs, we demonstrated that CaP particles stimulated IL-1β release from proliferating and senescent human VSMCs, but with substantially greater IL-1β release from senescent cells; this required caspase-1 activity but not LPS-priming of cells. Potential inflammasome agonists including ATP, nigericin and monosodium urate crystals did not stimulate IL-1β release from VSMCs. Western blot analysis demonstrated that CaP particles induced rapid activation of spleen tyrosine kinase (SYK) (increased phospho-Y525/526). The SYK inhibitor R406 reduced IL-1β release and caspase-1 activation in CaP particle-treated VSMCs, indicating that SYK activation occurs upstream of and is required for caspase-1 activation. In addition, IL-1β and caspase-1 colocalised in intracellular endosome-like vesicles and we detected IL-1β in exosomes isolated from VSMC media. Furthermore, CaP particle treatment stimulated exosome secretion by VSMCs in a SYK-dependent manner, while the exosome-release inhibitor spiroepoxide reduced IL-1β release.

CONCLUSIONS

CaP particles stimulate SYK and caspase-1 activation in VSMCs, leading to the release of IL-1β, at least in part via exosomes. These novel findings in human VSMCs highlight the pro-inflammatory and pro-calcific potential of microcalcification.

FOXM1 promotes pulmonary artery smooth muscle cell expansion in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive vascular remodeling disease characterized by a persistent elevation of pulmonary artery pressure, leading to right heart failure and premature death. Exaggerated proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs) is a key component of vascular remodeling. Despite major advances in the field, current therapies for PAH remain poorly effective in reversing the disease or significantly improving long-term survival. Because the transcription factor FOXM1 is necessary for PASMC proliferation during lung morphogenesis and its overexpression stimulates proliferation and evasion of apoptosis in cancer cells, we thus hypothesized that upregulation of FOXM1 in PAH-PASMCs promotes cell expansion and vascular remodeling. Our results showed that FOXM1 was markedly increased in distal pulmonary arteries and isolated PASMCs from PAH patients compared to controls as well as in two preclinical models. In vitro, we showed that miR-204 expression regulates FOXM1 levels and that inhibition of FOXM1 reduced cell proliferation and resistance to apoptosis through diminished DNA repair mechanisms and decreased expression of the pro-remodeling factor survivin. Accordingly, inhibition of FOXM1 with thiostrepton significantly improved established PAH in two rat models. Thus, we show for the first time that FOXM1 is implicated in PAH development and represents a new promising target.

KEY MESSAGES

FOXM1 is overexpressed in human PAH-PASMCs and PAH animal models. FOXM1 promotes PAH-PASMC proliferation and resistance to apoptosis. Pharmacological inhibition of FOXM1 improves established PAH in the MCT and Su/Hx rat models. FOXM1 may be a novel therapeutic target in PAH.