Vascular Smooth Muscle Contractility Research Articles

Activation of β-adrenergic receptors during sexual arousal facilitates vaginal lubrication by regulating vaginal epithelial Cl(-) secretion.

Vaginal lubrication, an indicator of sexual arousal and tissue health, increases significantly during genital sexual arousal. Adrenergic alpha-receptors (AR) are an important regulator of genital physiological responses involved in mediating vascular and nonvascular smooth muscle contractility; the role of β-AR in sexual arousal, however, has not yet been investigated. The goal of this study was to reveal the functional role of β-AR in modulating vaginal lubrication during sexual arousal and the mechanisms underlying the process. The effects of adrenaline on vaginal epithelial ion transport, intracellular cyclic adenosine monophosphate (cAMP) content ([cAMP]i ), and vaginal lubrication were investigated using short-circuit current (ISC ) of rat vaginas incubated in vitro, enzyme-linked immunosorbent assay (ELISA), and measurement of vaginal lubrication in vivo, respectively. The expressions of β-AR in vaginal epithelium were analyzed by reverse transcription-polymerase chain reaction, western blot, and immunofluorescence. Changes of ISC responses; mRNA, protein expressions and localization of β-AR; [cAMP]i ; vaginal lubrication. Serosal application of adrenaline induced an increase of ISC across rat vaginal epithelium that blocked by propranolol, a β-AR antagonist, rather than phentolamine, an α-AR antagonist. β1/2-AR were both present in rat and human vaginal epithelial cells. Removing Cl(-) or application of CFTR(inh) -172, an inhibitor of cystic fibrosis transmembrane conductance regulator (CFTR), abolished adrenaline-induced ISC responses. The elevated levels of [cAMP]i induced by adrenaline were prevented by the pretreatment with propranolol. Vaginal lubrication measured in vivo showed that adrenaline or pelvic nerve stimulation caused a marked increase in vaginal lubrication, whereas pretreatment with propranolol or CFTR(inh) -172 reduced the effect. Activation of epithelial β-AR facilitates vaginal lubrication during sexual arousal by stimulating vaginal epithelial Cl(-) secretion in a cAMP-dependent pathway. Thus, vaginal epithelial β-AR might be another regulator of vaginal sexual arousal responses.

Why isn't endogenous ouabain more widely accepted?

A new idea is the most quickly acting antigen known to science . —Wilfred Trotter During the past few years, several distinguished senior colleagues who visited our department and inquired about the status of endogenous ouabain (EO) have asked, “How come I didn't know about these [published]

Inhibition of vascular calcification by block of intermediate conductance calcium-activated potassium channels with TRAM-34

Vascular calcifications are a hallmark of advanced cardiovascular disease in patients with chronic kidney disease. A key event is the transition of contractile vascular smooth muscle cells (VSMC) into an osteoblast-like phenotype, promoting a coordinated process of vascular remodeling resembling bone mineralization. Intermediate-conductance calcium-activated potassium channels (KCa3.1) are expressed in various tissues including VSMC. Aiming for novel therapeutic targets in vascular calcification, we here studied effects of KCa3.1-inhibition on VSMC calcification by the specific KCa3.1 inhibitor TRAM-34.Calcification in the murine VSMC cell line MOVAS-1 and primary rat VSMC was induced by calcification medium (CM) containing elevated levels of PO43− and Ca2+. Cell signaling, calcification markers, and release of nitric oxide and alkaline phosphatase were assessed by luciferase reporter plasmids, RT-PCR and specific enzymatic assays, respectively. KCa3.1 gene silencing was achieved by siRNA experiments.TRAM-34 at 10nmol/l, decreased CM-induced calcification and induced NO release of VSMC accompanied by decreased TGF-β signaling. The CM-induced mRNA expressions of osterix, osteocalcin, matrix-metalloproteinases (MMP)-2/-9 were reduced by TRAM-34 while osteopontin expression was increased. Further, TRAM-34 attenuated the CM- and TNF-α-induced activation of NF-κB and reduced the release of MMP-2/-9 by VSMC. Finally, TRAM-34 abrogated CM-induced apoptosis and KCa3.1 gene silencing protected VSMC from CM-induced onset of calcification.In summary, TRAM-34 interferes with calcification relevant signaling of NF-κB and TGF-β thereby blocking the phenotypic transition/calcification of VSMC.We conclude that the results provide a rationale for further studies regarding a possible therapeutic role of KCa3.1 inhibition by TRAM-34 or other inhibitors in vascular calcification.

Abstract 177: A Novel Vascular "Ring" Assay for Smooth Muscle Contractility Using Magnetic 3-Dimensional Bioprinting

The current standard for studying pharmacodynamics on vascular smooth muscle contractility is wire myography with ex vivo tissue, which suffers from high cost low throughput, limiting its widespread use. Yet, in vitro alternatives are insufficient, as they are commonly two-dimensional (2D) monolayers on rigid surfaces unlike the soft vasculature. Thus, a rapid, robust in vitro assay is needed that mimics the native three-dimensional (3D) environment, while yielding high data throughput. Towards that goal, we introduce an 3D in vitro assay in which cellularized vascular "rings" are rapidly and magnetically bioprinted. In the assay, cells are incubated with magnetic nanoparticles to render them magnetic, then printed into 3D rings (1.5 x 10^5 cells/ring) in 96-well plates. The rings will then contract or dilate over a short amount of time (<5 h) in a dose-dependent manner visually similar to vessel contraction and dilation (Fig. 1A). This measurement is label-free, meaning that the rings can be experimented on afterwards to explore pharmacodynamics. Moreover, this assay is captured using an iPod-based imaging system programmed to take images of whole plates (Fig. 1B) instead of imaging individual wells under a microscope. This assay was validated for the evaluation of drug efficacy by measuring contractility in 3D bioprinted rings of A10 rat vascular smooth muscle cells. The compounds tested were either vasodilators (blebbistatin, forskolin, verapamil) or vasoconstrictors (norepinephrine, phenylephrine, U46619). Ring contraction was compared to the presence of phosphorylated myosin light chain-2 which is related to smooth muscle concentration. Furthermore, the gene expression profiles of rings exposed to specific compounds are compared to negative controls. The result of this study is the validation of the vascular assay that rapidly prints 3D environments similar to the native blood vessel, and efficiently measures smooth muscle contraction.

Interception of the endotoxin-induced arterial hyporeactivity to vasoconstrictors

Septic shock is a severe pathophysiologic condition characterized by vasodilation, hypotension, hypoperfusion, tissue hypoxia, multiple organ failure and death. It is unclear what causes the septic vasodilation that may result from general dysfunction of vascular smooth muscles (VSMs) or selective disruption of vasomotor balances in VSMs. The latter could be due to enhanced vasorelaxation and/or depressed vasoconstriction. Understanding these may lead to pharmacological interventions to septic vasodilation. Therefore, we performed studies in isolated and perfused mesenteric arterial rings. A 20-h exposure of the rings to lipopolysaccharide (LPS, 1μg/ml) led to hyporeactivity to phenylephrine (PE). However, the responses of the LPS-treated rings to high concentrations of KCl (60mM) and ATP remained comparable to control rings, suggesting that contractility of VSMs is retained. The hyporeactivity was marginally affected by atropine, indomethacin and L-NAME, suggesting that endothelium-dependent vasorelaxation does not play a major role. In addition to PE, the LPS-treated rings were hyporeactive to dopamine, histamine and angiotensin II. They showed intermediate hyporeactivity to the thromboxane-A2 receptor agonist U46619. Little hyporeactivity to endothelin-1 (ET-1), serotonin (5-HT) and vasopressin was found. ET-1-induced vasoconstriction occurred without endothelium, whereas the effect of 5-HT was endothelium dependent. Although rings were hyporeactive to some of the vasopressors, their vasoconstriction effects were significantly potentiated by PE co-application. Taken together, these data suggest that the endotoxin-induced vasodilation may not result from general dysfunction of VSMs, neither from the endothelium-dependent vasorelaxation. The promising vascular response to various vasoconstrictors found in this study warrants further investigations of therapeutic potentials of these agents.

Defining Differences among Perivascular Cells Derived from Human Pluripotent Stem Cells

SummaryDistinguishing between perivascular cell types remains a hurdle in vascular biology due to overlapping marker expressions and similar functionalities. Clarifying and defining heterogeneities in vitro among perivascular cells could lead to improved cell-based tissue regeneration strategies and a better understanding of human developmental processes. We studied contractile vascular smooth muscle cells (vSMCs), synthetic vSMCs, and pericytes derived from a common human pluripotent stem cell source. Using in vitro cultures, we show unique cell morphology, subcellular organelle organization (namely endoplasmic reticulum, mitochondria, and stress fibers), and expression of smooth muscle myosin heavy chain and elastin for each cell type. While differences in extracellular matrix deposition and remodeling were less pronounced, the multipotency, in vivo, migratory, invasion, and contractile functionalities are distinctive for each cell type. Overall, we define a repertoire of functional phenotypes in vitro specific for each of the human perivascular cell types, enabling their study and use in basic and translational research.

The contribution of vascular smooth muscle to aortic stiffness across length scales.

The operation of the cardiovascular system in health and disease is inherently mechanical. Clinically, aortic stiffness has proven to be of critical importance as an early biomarker for subsequent cardiovascular disease; however, the mechanisms involved in aortic stiffening are still unclear. The etiology of aortic stiffening with age has been thought to primarily involve changes in extracellular matrix protein composition and quantity, but recent studies suggest a significant involvement of the differentiated contractile vascular smooth muscle cells in the vessel wall. Here, we provide an overview of vascular physiology and biomechanics at different spatial scales. The processes involved in aortic stiffening are examined with particular attention given to recent discoveries regarding the role of vascular smooth muscle.

The Inhibitory Effect of Apigenin on the Agonist-Induced Regulation of Vascular Contractility via Calcium Desensitization-Related Pathways.

Apigenin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of apigenin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Apigenin significantly relaxed fluoride-, thromboxane A2 mimetic- or phorbol ester-induced vascular contraction, which suggests that apigenin could be an anti-hypertensive that reduces agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, apigenin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels, which suggests the mechanism involving the inhibition of Rho-kinase and MEK activity and the subsequent phosphorylation of MYPT1 and ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of apigenin on agonist-induced vascular contraction regardless of endothelial function.

TRPC5.

Human canonical transient receptor potential channel 5 (TRPC5) has been cloned from the Xq23 region on chromosome X as a suspect in nonsyndromic mental retardation. TRPC5 is a Ca(2+)-permeable cation channel predominantly expressed in the CNS, including the hippocampus, cerebellum, amygdala, sensory neurons, and retina. It also shows more restricted expression in the periphery, notably in the kidney and cardiovascular system. Homotetrameric TRPC5 channels are primarily activated by receptors coupled to Gq and phospholipase C and/or Gi proteins, but TRPC5 channels may also gate in a store-dependent manner, which requires other partner proteins such TRPC1, STIM1, and Orai1. There is an impressive array of other activators of TRPC5 channels, such as nitric oxide, lysophospholipids, sphingosine-1-phosphate, reduced thioredoxin, protons, lanthanides, and calcium, and many can cause its direct activation. Moreover, TRPC5 shows constitutive activity, and it is responsive to membrane stretch and cold. Thus, TRPC5 channels have significant potential for synergistic activation and may serve as an important focal point in Ca(2+) signalling and electrogenesis. Moreover, TRPC5 functions in partnership with about 60 proteins, including TRPC1, TRPC4, calmodulin, IP3 receptors, NHERF, NCS-1, junctate, stathmin 2, Ca(2+)-binding protein 1, caveolin, and SESTD1, while its desensitisation is mediated by both protein kinases A and C. TRPC5 has a distinct voltage dependence shared only with its closest relative, TRPC4. Its unique N-shaped activation curve underlined by intracellular Mg(2+) block seems to be perfectly "shaped" to trigger action potential discharge, but not to grossly interfere with the action potential shape. The range of biological functions of TRPC5 channels is also impressive, from neurotransmission to control of axon guidance and vascular smooth muscle cell migration and contractility. Recent studies of Trpc5 gene knockouts begin to uncover its roles in fear, anxiety, seizures, and cold sensing.

Concentration-related effects of nitric oxide and endothelin-1 on human trabecular meshwork cell contractility

The contractility status of trabecular meshwork (TM) cells influences aqueous humor outflow resistance and intraocular pressure. Using human TM cells as a model, the goal of the present study was to examine concentration–response relationships of two prototypical molecules, nitric oxide (NO) and endothelin-1 (ET-1), known to differentially influence vascular smooth muscle contractility. Efficacy of ET-1, two NO donors (DETA-NO and SNP) and a cGMP analog (8-Br-cGMP) were assessed using two complementary methods: functionally in a gel contraction assay and biochemically using a myosin light chain phosphorylation assay. The NO donors DETA-NO and SNP dose dependently relaxed cultured human TM cells (EC50 for DETA-NO = 6.0 ± 2.4 μM, SNP = 12.6 ± 8.8 μM), with maximum effects at 100 μM. Interestingly, at concentrations of NO donors above 100 μM, the relaxing effect was lost. Relaxation caused by DETA-NO (100 μM) was dose dependently blocked by the soluble guanylate cyclase specific inhibitor ODQ (IC50 = 460 ± 190 nM). In contrast to the NO donors, treatment of cells with the cGMP analog, 8-Br-cGMP produced the largest relaxation (109.4%) that persisted at high concentrations (EC50 = 110 ± 40 μM). ET-1 caused a dose-dependent contraction of human TM cells (EC50 = 1.5 ± 0.5 pM), with maximum effect at 100 pM (56.1%) and this contraction was reversed by DETA-NO (100 μM). Consistent with functional data, phosphorylation status of myosin light chain was dose dependently reduced with DETA-NO, and increased with ET-1. Together, data show that TM cells rapidly change their contractility status over a wide dynamic range, well suited for the regulation of outflow resistance and intraocular pressure.

The time-of-day variation in vascular smooth muscle contractility depends on a nitric oxide signalling pathway

The dip in blood pressure during the resting-period is paradoxically associated with an increase in total peripheral resistance and occurs at a time when the vascular response to vasoconstrictor compounds is heightened, and to vasodilators reduced. However, the cellular mechanisms responsible for this time-of-day variation are not well defined. We have investigated the role of nitric oxide synthase (NOS) signalling in the control of contraction in mesenteric resistance arteries using wire myography, combined with quantitative PCR analysis of gene transcription and western blot analysis of protein. Small rings of mesenteric arteries, isolated from rats at two opposing time-points corresponding to the animal's active and resting-period, were mounted in a wire myograph. Vessels exhibited a time-of-day variation in their contractile-response to phenylephrine, with a reduced maximal contraction during the active- versus the resting-period (11.8±0.8 versus 18.6±1.2mN P<0.001). Vessels preconstricted with phenylephrine were also more responsive to vasodilation with acetylcholine during the active-period, with an EC50 of 58.6±11 versus 232±31nM in resting-period vessels (P<0.0001). These differences were abolished in the presence of l-NAME. Quantitative RT-PCR reveals a functioning peripheral circadian clock in mesenteric arteries and a 3.3-fold increase in endothelial NO synthase mRNA levels in active- versus resting-period vessels (P<0.001), which translated to a 1.7-fold increase in total eNOS protein (P<0.05). The time-of-day variation in the response of mesenteric resistance vessels to phenylephrine and acetylcholine is dependent on NOS signalling.

Synergistic Role of Protein Phosphatase Inhibitor 1 and Sarco/Endoplasmic Reticulum Ca 2+ -ATPase in the Acquisition of the Contractile Phenotype of Arterial Smooth Muscle Cells

Phenotypic modulation or switching of vascular smooth muscle cells from a contractile/quiescent to a proliferative/synthetic phenotype plays a key role in vascular proliferative disorders such as atherosclerosis and restenosis. Although several calcium handling proteins that control differentiation of smooth muscle cells have been identified, the role of protein phosphatase inhibitor 1 (I-1) in the acquisition or maintenance of the contractile phenotype modulation remains unknown. In human coronary arteries, I-1 and sarco/endoplasmic reticulum Ca2+ -ATPase expression is specific to contractile vascular smooth muscle cells. In synthetic cultured human coronary artery smooth muscle cells, protein phosphatase inhibitor 1 (I-1 target) is highly expressed, leading to a decrease in phospholamban phosphorylation, sarco/endoplasmic reticulum Ca2+ -ATPase, and cAMP-responsive element binding activity. I-1 knockout mice lack phospholamban phosphorylation and exhibit vascular smooth muscle cell arrest in the synthetic state with excessive neointimal proliferation after carotid injury, as well as significant modifications of contractile properties and relaxant response to acetylcholine of femoral artery in vivo. Constitutively active I-1 gene transfer decreased neointimal formation in an angioplasty rat model by preventing vascular smooth muscle cell contractile to synthetic phenotype change. I-1 and sarco/endoplasmic reticulum Ca2+ -ATPase synergistically induce the vascular smooth muscle cell contractile phenotype. Gene transfer of constitutively active I-1 is a promising therapeutic strategy for preventing vascular proliferative disorders.

Inositol 1,4,5-Trisphosphate (IP3) Receptor Up-regulation in Hypertension Is Associated with Sensitization of Ca2+ Release and Vascular Smooth Muscle Contractility

Resistance arteries show accentuated responsiveness to vasoconstrictor agonists in hypertension, and this abnormality relies partly on enhanced Ca(2+) signaling in vascular smooth muscle (VSM). Although inositol 1,4,5-triphosphate receptors (IP3Rs) are abundant in VSM, their role in the molecular remodeling of the Ca(2+) signaling machinery during hypertension has not been addressed. Therefore, we compared IP3R expression and function between mesenteric arteries of normotensive and hypertensive animals. Levels of IP3R transcript and protein were significantly increased in mesenteric arteries of hypertensive animals, and pharmacological inhibition of the IP3R revealed a higher contribution of IP3-dependent Ca(2+) release to vascular contraction in these arteries. Subsequently, we established cultured aortic VSM A7r5 cells as a cellular model that replicates IP3R up-regulation during hypertension by depolarizing the VSM cell membrane. IP3R up-regulation requires Ca(2+) influx through L-type Ca(2+) channels, followed by activation of the calcineurin-NFAT axis, resulting in IP3R transcription. Functionally, IP3R up-regulation in VSM is associated with enhancement and sensitization of IP3-dependent Ca(2+) release, resulting in increased VSM contraction in response to agonist stimulation.

Theoretical studies, synthesis, and biological activity of 1-[(4-methylphenyl)sulfonyl]-5-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-4-carbonitrile (C9) as a non-peptide antagonist of the arginine vasopressin V1a and V2 receptors

In this work, the synthesis of 1-[(4-methylphenyl)sulfonyl]-5-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-4-carbonitrile (C9) and the study of its biological activity as a new putative antagonist of vasopressin receptors are described. The chemical identification of the compound C9 was confirmed using 1H and 13C nuclear magnetic resonance. This compound contains a moiety core similar to those of vaptans; therefore, we decided to study the compound’s binding on vasopressin receptors (V1aR and V2R), whose models were built, refined by molecular dynamics simulations, and validated through docking studies. The biological effects of C9 on vascular smooth muscle (VSM) contractility and aquaresis were also tested. Rat aortic rings were used to test the inhibitory effect of C9 (0.0, 5.9, 59, and 590 μM) on AVP-induced VSM contraction (10 μM). The inhibition of the antidiuretic effect of vasopressin (50 μU/kg) by C9 (100 μg/kg) was determined using a water load test in rats. The results showed that C9 inhibits aortic rings’ contraction in a concentration-dependent manner, whereas C9 exhibited an aquaretic effect on urine flow. Docking studies showed that C9 reaches the vaptan binding site via the V1a and V2 receptors, which explains the similarity in their biological effects. The results indicate that C9 functions as an antagonist on both V1aR and V2R.

The role of mitochondrial bioenergetics and reactive oxygen species in coronary collateral growth

Coronary collateral growth is a process involving coordination between growth factors expressed in response to ischemia and mechanical forces. Underlying this response is proliferation of vascular smooth muscle and endothelial cells, resulting in an enlargement in the caliber of arterial-arterial anastomoses, i.e., a collateral vessel, sometimes as much as an order of magnitude. An integral element of this cell proliferation is the process known as phenotypic switching in which cells of a particular phenotype, e.g., contractile vascular smooth muscle, must change their phenotype to proliferate. Phenotypic switching requires that protein synthesis occurs and different kinase signaling pathways become activated, necessitating energy to make the switch. Moreover, kinases, using ATP to phosphorylate their targets, have an energy requirement themselves. Mitochondria play a key role in the energy production that enables phenotypic switching, but under conditions where mitochondrial energy production is constrained, e.g., mitochondrial oxidative stress, this switch is impaired. In addition, we discuss the potential importance of uncoupling proteins as modulators of mitochondrial reactive oxygen species production and bioenergetics, as well as the role of AMP kinase as an energy sensor upstream of mammalian target of rapamycin, the master regulator of protein synthesis.

Bone marrow derived cells with defective c-Myb activity protect against neointimal remodeling following injury

Purpose: We previously showed that the transcription factor c-myb regulates the differentiation of contractile vascular smooth muscle cells in embryonic stem cell-derived embryoid bodies. While we also showed that c-Myb regulates the expansion of a specific embryonic hemangiogenic progenitor, it is unclear if this population has a role in the adult animal. However, the role of c-Myb in the proliferation and potential (trans)differentiation of bone marrow (BM)-derived vs. vessel-resident cells in arterial remodelling in the adult has eluded genetic examination due to the embryonic lethality of c-myb-/- mice from hematopoietic failure. To examine the role of c-myb in BM-derived vs. vessel-resident cells, we have used a mouse harboring a non-lethal point mutation resulting in a hypomorphic (h) allele of c-myb with defective c-Myb activity. Methods and results: Histology of common carotid arteries of 12 wk-old male c-mybh/h and c-mybwt mice was performed 14 days after carotid artery wire denudation injury. Uninjured vessels from wt and h/h mice did not differ in lumen, intima, and media morphometry or I/M ratio. Following wire injury, h/h mice showed reduced intima formation (16,723±2,550 vs. 31,402±49,890 μm2; p<0.05; N=6-7/group) and I/M ratio (0.313±0.044 vs. 0.565±0.089; p<0.01) than wt controls. To determine the relative contribution of BM-derived vs. vessel cells in arterial remodeling, reciprocal BM transplants were performed in 5wk old wt and h/h mice, which were allowed to reconstitute their BM for 7 wks before wire injury. Compared to wt→wt mice, injured arteries from h/h→wt mice had decreased intima formation (19,222±2,622 vs. 8,080±1,337 μm2; p<0.0001; N= 7/group) and I/M ratio (0.491±0.068 vs. 0.217±0.01; p<0.0001). However, injured arteries from wt→h/h mice had no differences in intima formation as compared to h/h→h/h mice (14,519±486 vs. 13,437±1,175 μm2; p=NS; N= 7/group), with no differences observed in uninjured BM-transplanted control arteries. Conclusions: The blunted arterial remodelling response observed in h/h→wt mice is due to a c-Myb dependent defect in BM-derived cell populations that participate in the pathogenesis of neointimal proliferation following arterial injury.

Development of vascular smooth muscle contractility by endothelium-derived transforming growth factor β proteins

It is well established that the release of vasodilators and vasoconstrictors from vascular endothelium regulates vascular smooth muscle contraction. In this report, we investigate the role of the endothelium in the development and maintenance of constitutive vascular contractility. For that purpose, contractile activity of cultured bovine aortic smooth muscle cells (BASMCs) embedded in collagen gels was monitored by changes in gel diameter. After culturing for 5days, ATP- and high KCl solution-induced contractions were significantly enhanced in the gels that were overlaid with bovine aortic endothelial cells (BAECs) or were cultured with conditioned medium of cultured BAECs. ATP-induced Ca(2+) transients, recorded in BASMCs cultured with conditioned medium of BAECs, were markedly augmented, but high KCl-induced Ca(2+) transients were not affected. BASMCs in control gels were spindle shaped, and those in endothelium-treated gels were more elongated and interconnected. The endothelial conditioned medium also strongly affected the intracellular distribution of actin fibers. Conditioned medium of BAECs contained TGFβ1 and TGFβ2. The TGFβ receptor antagonist SB431542 as well as simultaneous treatment with TGFβ1 and TGFβ2 neutralizing antibodies completely reversed the above effects of endothelial conditioned medium on BASMCs. BAECs medium induced phosphorylation of Smad2 and increased ATP-induced phosphorylation of myosin light chain in BASMCs. The present results indicate that the release of TGFβ1 and TGFβ2 from vascular endothelium affects the contractility of vascular smooth muscle cells by altering their morphology and agonist-induced Ca(2+) mobilization.

Calcium Dynamics in Vascular Smooth Muscle

Smooth muscle cells are ultimately responsible for determining vascular luminal diameter and blood flow. Dynamic changes in intracellular calcium are a critical mechanism regulating vascular smooth muscle contractility. Processes influencing intracellular calcium are therefore important regulators of vascular function with physiological and pathophysiological consequences. In this review we discuss the major dynamic calcium signals identified and characterized in vascular smooth muscle cells. These signals vary with respect to their mechanisms of generation, temporal properties, and spatial distributions. The calcium signals discussed include calcium waves, junctional calcium transients, calcium sparks, calcium puffs, and L-type calcium channel sparklets. For each calcium signal we address underlying mechanisms, general properties, physiological importance, and regulation.

Smooth muscle-selective CPI-17 expression increases vascular smooth muscle contraction and blood pressure

Recent data revealed that protein kinase C-potentiated myosin phosphatase inhibitor of 17 kDa (CPI-17), a myosin phosphatase inhibitory protein preferentially expressed in smooth muscle, is upregulated/activated in several diseases but whether this CPI-17 increase plays a causal role in pathologically enhanced vascular smooth muscle contractility and blood pressure remains unclear. To address this possibility, we generated a smooth muscle-specific CPI-17 transgenic mouse model (CPI-17-Tg) and demonstrated that the CPI-17 transgene was selectively expressed in smooth muscle-enriched tissues, including mesenteric arteries. The isometric contractions in the isolated second-order branch of mesenteric artery helical strips from CPI-17-Tg mice were significantly enhanced compared with controls in response to phenylephrine, U-46619, serotonin, ANG II, high potassium, and calcium. The perfusion pressure increases in isolated perfused mesenteric vascular beds in response to norepinephrine were also enhanced in CPI-17-Tg mice. The hypercontractility was associated with increased phosphorylation of CPI-17 and 20-kDa myosin light chain under basal and stimulated conditions. Surprisingly, the protein levels of rho kinase 2 and protein kinase Cα/δ were significantly increased in CPI-17-Tg mouse mesenteric arteries. Radiotelemetry measurements demonstrated that blood pressure was significantly increased in CPI-17-Tg mice. However, no vascular remodeling was detected by morphometric analysis. Taken together, our results demonstrate that increased CPI-17 expression in smooth muscle promotes vascular smooth muscle contractility and increases blood pressure, implicating a pathological significant role of CPI-17 upregulation.

Smooth muscle microRNAs regulate serotonin‐induced contraction in pulmonary and systemic arteries

MicroRNA (miRNA) are short, non coding RNA that regulate mRNA expression levels and/or translational efficiency. MiRNAs are important for vascular smooth muscle development and function by regulating phenotypic modulation and contractile responses. Contractility of vascular smooth muscle is essential for regulation of blood pressure and blood flow. A number of contractile agonists can affect vascular reactivity and altered sensitivity to these agonists may play a role in vascular disease.The aim of this study was to identify the role of miRNAs in vascular responses to various contractile agonists.Vascular reactivity was assessed in isolated pulmonary arteries and aortic rings from tamoxifen‐inducible and smooth muscle specific Dicer KO mice 5 weeks post tamoxifen and in constitutive miR‐143/145 KO mice.Our results show a specific increase in the contractile response to serotonin in the pulmonary artery and aorta. This effect was not found in miR‐143/145 KO mice and is therefore likely to be dependent on other smooth muscle miRNAs. The increased contractile response to serotonin in Dicer KO vessels was reduced by Src‐inhibitors but less sensitive to Rho‐kinase inhibition.The precise mechanisms for augmented serotonin‐induced contraction in Dicer KO vessels are now under investigation and may identify a novel role for specific miRNAs in vascular disease.