Extravascular Smooth Muscle Research Articles

Phenotype and physiological significance of the endocardial smooth muscle cells in human failing hearts.

Extravascular smooth muscle cells are often observed in the endocardium of human failing hearts. Here, we characterized the phenotype of those cells and investigated their physiological significance. We examined left ventricular biopsy specimens obtained from 44 patients with dilated cardiomyopathy and 6 nonfailing hearts. In Masson trichrome-stained histological preparations, bundles of smooth muscle cells were seen localized in the endocardium in 23 of the 44 specimens (none of the 6 controls). These cells were immunopositive for α-smooth muscle actin, type 2 smooth muscle myosin, desmin, and calponin, but were negative for embryonic smooth muscle myosin, vimentin, fibronectin, and periostin. This profile is indicative of a late differentiation (contractile) smooth muscle phenotype. Electron microscopy confirmed that phenotype, revealing the cells to contain abundant myofilaments with dense bodies but little rough endoplasmic reticulum or Golgi apparatus. In the endocardial smooth muscle-positive group, the left ventricular end-systolic volume index (73±34 versus 105±50 mL/m(2); P=0.021), left ventricular peak wall stress (164±47 versus 196±43 dynes 10(3)/cm(2); P=0.023), and left ventricular end-systolic meridional wall stress (97±38 versus 121±37 dynes 10(3)/cm(2); P=0.036) were all significantly smaller, and the ejection fraction was larger (41±8.8 versus 33±9.3%; P=0.005) than in the endocardial smooth muscle-negative group. However, no histological parameters differed between the 2 groups. Endocardial smooth muscle cell bundles in hearts with dilated cardiomyopathy exhibit a mature contractile phenotype and may play a compensatory role mitigating heart failure by reducing left ventricular wall stress and systolic dysfunction.

Molecular Recognition of Tachykinin Receptor Selective Agonists: Insights from Structural Studies

This Review deals essentially with the elucidation of structural features of Tachykinin family of neuropeptides, which are known to interact through three distinct GPCR subtypes, namely NK1 (Neurokinin 1), NK2 (Neurokinin 2) and NK3 (Neurokinin 3) receptors. In mammals, Tachykinins have been shown to elicit a wide array of activities such as powerful vasodilatation, hypertensive action and stimulation of extravascular smooth muscle and are known to be involved in a variety of clinical conditions including chronic pain, Parkinson's disease, Alzheimer's disease, depression, rheumatoid arthritis, irritable bowel syndrome and asthma. This broad spectrum of action of Tachykinins is attributed to the lack of selectivity of tachykinins to their receptors. All tachykinins interact with all the three-receptor subtypes with SP preferring NK1, NKA preferring NK2 and NKB preferring NK3. This lack of specificity can be accounted for by the conformational flexibility of these short, linear peptides. Hence, identification of structural features of the agonists important for receptor binding and biological activity is of great significance in unraveling the molecular mechanisms involved in tachykinin receptor activation and also in rational design of novel therapeutic agents. Understanding structure of the ligand-receptor complex and analysis of topography of the binding pocket of the tachykinin receptor is also crucial in rational design of drugs.

Bone marrow‐derived CX3CR1 progenitors contribute to neointimal smooth muscle cellsviafractalkine CX3CR1 interaction

Smooth muscle cells play a major role in numerous vascular diseases that contribute to remodeling, repair after injury, and arteriogenesis, and the source of these cells is thought to lie within the vessel wall and the circulating blood. Currently, the precise origin and mechanism of differentiation of extravascular smooth muscle progenitor cells (SPCs) is unclear. We show here that the CX(3)CR1 mononuclear cell population of murine bone marrow provides a source of SPCs that contributes to smooth muscle cells within the neointimal plaque after vascular injury. Moreover, CX(3)CR1-fractalkine (FKN) interaction in vivo is essential for smooth muscle cell differentiation of bone marrow-derived progenitor cells at the vessel wall level. Functional competence of bone marrow-derived CX(3)CR1 positive cells to interact with FKN is also crucial in part for neointima formation following vascular injury. Finally, in a pure preparation of bone marrow-derived CX(3)CR1 positive cells, we show that in vitro smooth muscle cell differentiation increases markedly in the presence of FKN. Our data highlight a novel functional relationship between the myeloid and vascular systems and in the context of vascular injury and repair underscores a key chemokine-receptor pathway that may regulate cell fate when smooth muscle cell differentiation is required.

An Extensive System of Extravascular Smooth Muscle Cells Exists in the Choroid of the Rabbit Eye

We investigated the structural organization of the choroid especially with regard to the presence of extravascular smooth muscle (EVSM) cells in albino rabbits. The eyes were fixed by intracardiac perfusion and processed for light, confocal, and electron microscopy. An unlabeled monoclonal antibody against α-actin of smooth muscle and a horseradish-peroxidase-conjugated secondary antibody were used for immunodetection of smooth muscle actin by light microscopy. For confocal microscopy, whole mount choroids were immunostained with a fluorescein isothiocyanate-conjugated (FITC) antibody. Our investigations revealed that the choroidal vessels are enveloped by bundles of EVSM. In contrast to the circular orientation of the smooth muscle cells of the tunica media of the choroidal vessels, the cells of the EVSM system were oriented longitudinally along the external surface of the vessel wall. The EVSM cells were strongly immunopositive for smooth muscle α-actin and exhibited a green fluorescence of the FITC-labeled anti-α-actin antibody. Individual cells were elongated and spindle-shaped, had the usual ultrastructural features of smooth muscle cells and, in places, were organized as 20 layers. EVSM cells were present throughout the thickness of the choroid, but not between the fenestrated endothelial lining of the choriocapillaris and Bruch’s membrane, and extended from the optic nerve to the ciliary body where they merged with the ciliary muscles. Based on the three dimensional organization, immunoreactivity, and cellular and subcellular features of the EVSM system as well as information in the literature, we hypothesize that, functionally, this system, in conjunction with the choroidal vasculature, contributes to the myogenic control of choroidal blood flow and tissue volume, and also affects the intraocular pressure as well as the refractive and accommodative state of the eye.

PHARMACOLOGICAL PROPERTIES OF SECURIDACA LONGIPEDUNCULATA ON VASCULAR AND EXTRA-VASCULAR SMOOTH MUSCLES

Methanolic Extract of the root-bark of Securidaca longipedunculata was tested for pharmacological activity on isolated vascular and extra-vascular smooth muscle preparations. The root barks extract (50-800mg/ml) inhibited and/or abolished, in a concentration-dependent manner, the myogenic, spontaneous contractions as well as standard agonist drug-induced contractions of the smooth muscles preparations used. The rat isolated portal vein, rat isolated aortic ring, and guinea pig isolated ileum and guinea pig isolated uterus were employed in the in-vitro experiments. Since the plant extract inhibitory effects of the plant extract are unlikely to be mediated thorugh a specific receptor system, but rather, through a non-specific spasmolytic action. Key Words: Securidaca longipedunculata; Polygalaceae, Root Bark; Vascular and Extra-vascular Smooth Muscles; Inhibitory Effects; Non-specific Action Nig. J. Nat Prod. And Med. Vol.5 2001: 26-29

Molecular anatomy of the perivascular sheath in human placental stem villi: the contractile apparatus and its association to the extracellular matrix.

In previous studies, we have shown that smooth muscle cells and myofibroblast subpopulations of the perivascular stem villous sheath of the human placenta contain focal adhesion plaques and talin immunoreactivity. The close association of these cells to elastic and collagen fibres have led to the assumption of a functional myofibroelastic unit within the perivascular stem villous sheath. Interactions between the extracellular matrix and smooth muscle cells depend on a variety of structural protein assemblies. In the present study, we examined, by immunocytochemistry, whether the molecular assembly of extracellular matrix proteins and molecules of focal adhesions, known to be essential for signal transduction in smooth muscle cells, are also found in smooth muscle cells of the perivascular stem villous sheath of the human placenta. Vascular and extravascular smooth muscle cells were immunoreactive for alpha-actinin, vinculin, paxillin and tensin, the integrin chains alpha1 and beta1, and the basement membrane components laminin and heparan/-chondroitin sulfate proteoglycan perlecan. pp125(FAK) did not react. In the extracellular matrix of blood vessel walls and the perivascular stem villous sheath, we found immunoreactivity of fibronectin and collagen types I, VI and undulin (collagen type XIV). From our data we conclude that within the perivascular stem villous sheath, there exists a system of signal transduction molecules, indicating a cross talk between the smooth muscle cells of this sheath and their surrounding extracellular matrix.

Binding of antibodies against high and low molecular weight cytokeratin proteins in the human placenta with special reference to infarcts, proliferation and differentiation processes.

Recent immunocytochemical studies have shown that placental villous trophoblasts contain the high molecular weight cytokeratin (CK) proteins 5/6 and 17. In the case of CK 17, trophoblastic immunostaining was positive in villi covered by fibrinoid. CKs 5/6 and 17 are expressed by hyperproliferative cells. The aim of this investigation was to examine the location of these CKs in placental infarcts, known to be demarcated by fibrinoid and hyperproliferative trophoblasts. The results were compared with those obtained by immunostaining against Ki-67, tenascin and alpha 1-, alpha 6- and beta 1-integrins, which are involved in cell proliferation, differentiation and regenerative processes. Furthermore, the expression of the single CKs 7, 8, 10, 13, 14, 18 and 19 was investigated by immunocytochemistry and immunoblotting. While low and high molecular weight CKs were present in villous and extravillous trophoblasts, only low molecular weight CKs were detected in vascular and extravascular placental smooth muscle cells. Placental infarcts revealed different immunoreactivities in the infarct margin and centre: high molecular CKs, tenascin, Ki-67 and oncofoetal fibronectin predominated in the infarct margin, low molecular CKs, fibrin and integrins in the centre. The expression of tenascin and a defined change in the expression of CK 17 indicates villous repair and hyperproliferative mechanisms in placental infarcts.

Elastic fibres are an essential component of human placental stem villous stroma and an integrated part of the perivascular contractile sheath.

The stroma of human placental stem villi is believed to consist only of reticular and collagen fibres. In the present study we were able to show for the first time by light (orcein staining) and electron microscopy large amounts of elastic fibres in the stem villous stroma. Electron microscopically, homogeneous elastin was found alone or in association with microfibrils. In addition, microfibrils were observed forming long bands. These three structures, generally known to form elastic connective tissue, were seen in close connection with placental extravascular smooth muscle cells, which belong to the perivascular contractile sheath (PVCS) of stem villi. Elastin was associated with these smooth muscle cells and connected to collagen fibres via microfibrils. Collagen fibres were additionally interconnected by spike-like structures. Extravascular smooth muscle cells revealed numerous adhesion plaques which occupied conspicuously long cytoplasmic faces of the plasma membrane. In cryostat sections, immunoreactivity of talin, an attachment protein of adhesion plaques linking intracellular alpha-actin filaments with extracellular fibronectin, was detected in extravascular and vascular (media) smooth muscle cells. The arrangement of placental extravascular smooth muscle cells, elastic and collagen fibres suggests a functional myofibroelastic unit within the PVCS, which surrounds the large foetal blood vessels possibly contributing to elasticity and supporting tensile and/or contracting forces within the stem villi.

Effects of phorbol 12,13-dibutyrate and H-7 in extravascular smooth muscle contraction.

The effect of the activator, phorbol 12,13-dibutyrate (PDB), and the inhibitor, H-7, of protein kinase C (PKC) has been assayed in rat uterus. PDB increases the amplitude of spontaneous contractions of rat uterus and this effect does not occur in the presence of H-7 or nifedipine. PDB did not modify the KCl-induced tonic contraction but H-7 relaxed it, in a concentration-dependent way. PDB inhibited the contraction induced by oxytocin in rat uterus incubated in Ca-free solution and relaxed the tonic contraction induced by oxytocin in this medium. The relaxing effect of PDB on oxytocin-induced contraction was not modified by H-7. Thus H-7 relaxed, in a concentration-dependent way, the tonic contractions induced by oxytocin and vanadate in the rat uterus incubated in Ca-free medium. Our results suggest a dual effect of PDB related to calcium, and a direct and PKC-independent inhibitory effect of H-7.

Prostaglandin release and exogenous activity in the extravascular smooth muscle of diabetic rats

Prostaglandin release and exogenous activity in the extravascular smooth muscle of diabetic rats

Vagal stimulation and exogenous acetylcholine in isolated rat stomach: calcitonin effect on contractile activity

Calcitonin induces contraction in the vascular and extravascular smooth muscle and facilitates the transmission of the excitation in somatic motor nerve endings. These actions are Ca 2+-dependent. The calcitonin effect on autonomic nerve endings has been studied here by testing influence of calcitonin on the contractile responses of the isolated rat stomach. The organ was submitted to electrical vagal stimulation or, after denervation, to exogenous acetylcholine. Calcitonin invariably increased the muscular tone and reduced the contractile responses to vagal stimulation. Opposite effects were noted after a serotoninergic block with nicergoline. Calcitonin also increased the contractile response evoked by exogenous acetylcholine and the Ca 2+-antagonist nicardipine counteracted the facilitatory effects. We suggest that the inhibitory action of calcitonin is serotonine-dependent while the facilitatory one is Ca 2+-dependent.

The relaxant properties of human calcitonin gene-related peptide on vascular and extravascular capsular) smooth muscle of the isolated blood-perfused spleen of the anaesthetized dog.

1. The 37 amino acid human calcitonin gene-related peptide (CGRP), was injected intra-arterially into the isolated, blood perfused spleen of the dog. 2. The only vascular response observed to CGRP, once threshold had been reached (10-20 fmol), was a dose-dependent splenic arterial vasodilatation. 3. The mean intra-arterial bolus dose of CGRP to reduce the splenic arterial vascular resistance by 50% of maximum response was 0.52 +/- 0.12 pmol. This value was significantly lower than the ED50 for the non-selective beta-adrenoceptor agonist isoprenaline (P less than 0.01) in the same experiments. CGRP is the most potent splenic vasodilator yet tested. 4. The mean maximum vasodilator response to CGRP was significantly less (P less than 0.001) than that achieved with isoprenaline. 5. The time course of the splenic arterial vascular response to CGRP was substantially longer than that to isoprenaline. 6. The splenic vasodilator response to CGRP was not altered by the prior administration of the selective beta 2-adrenoceptor antagonist, ICI 118,551. 7. At all doses of CGRP that caused splenic vasodilatation there were substantial increases in spleen volume. The time course of the response and slope of the regression line suggested an active capsular relaxation component. 8. In view of its location within the spleen and high molar potency, CGRP may be considered as a potential factor in the local control of the circulation through the spleen.

The actions of the peptides, neuropeptide Y and peptide YY, on the vascular and capsular smooth muscle of the isolated, blood-perfused spleen of the dog.

The two peptides, neuropeptide Y (NPY) and peptide YY (PYY) were compared for potency on the vascular and extravascular smooth muscle of the isolated, blood-perfused spleen of the dog. The only vascular response to both NPY and PYY was vasoconstriction; the maximum effect was to arrest splenic arterial blood flow completely. On a molar basis both NPY and PYY were significantly more potent (P less than 0.01) as splenic arterial vasoconstrictors than the transmitter noradrenaline (NA). PYY was approximately 7 times more potent as a vasoconstrictor than NPY. In contrast to their potency on the vascular smooth muscle, NPY and PYY were significantly (P less than 0.01) less potent than NA in causing contraction of the splenic capsule. The two peptides were equipotent in eliciting this contraction.

Bile salts, hypotension and obstructive jaundice.

We have examined the effects of bile duct ligation on vascular and extravascular smooth muscle responsiveness to noradrenaline and tyramine using isolated rat hindlimb perfusion, and portal vein and vas deferens preparations. Bile duct ligation reduced the contractile responses to noradrenaline of vascular and extravascular smooth muscle. Exposure of smooth muscle to some bile salts caused a reduction in contractility. This effect was dependent upon bile salt type and concentration. These studies in vitro suggest that the reduced total peripheral resistance and hypotension seen in obstructive jaundice cannot be explained by a spasmolytic effect of some of the bile salts on smooth muscle.

Action of angiotensin on vascular and intestinal smooth muscle and its antagonism by saralasin

Angiotensin II was tested for its activity on rabbit aorta, lower esophageal sphincter (LES) from the rat, rat gastric fundus and rat colon. The peptide had a powerful stimulatory effect on vascular and extravascular smooth muscle beginning from concentrations of 10(-10) M. Its effect was antagonized by saralasin which acted in the different preparations to approximately the same extent: active concentrations of saralasin varied from 10(-8) M to 10(-7) M. The activity of angiotensin on the rabbit aorta appeared to be a direct one on its specific receptors. A mixed action connected with stimulation of adrenergic alpha receptors was observed in the rat LES, whereas an interference of the prostaglandin system was pointed out in the rat fundus and the rat colon. The circumstance of a similar sensitivity of the various tissues to the stimulatory effect of angiotensin and a similar degree of antagonism induced by saralasin tends to minimize the hypothesis of different subtypes of angiotensin receptors at least under the conditions of the present investigation.

Mechanism of the hypotensive effect of tetramethylpyrazine, an amide alkaloid from the stem of Jatropha podagrica.

The mechanism of the hypotensive effect of an amide alkaloid, tetramethylpyrazine (TMPZ), obtained from the stem of JATROPHA PODAGRICA H OOK (Euphorbiaceae) has been investigated in some isolated vascular and extra-vascular smooth muscle preparations. The results obtained show that the amide alkaloid inhibits the contractions of the rabbit isolated perfused central ear artery induced by periarterial electrical stimulation or intraluminally administered noradrenaline; reduces, like papaverine, the amplitude of the spontaneous myogenic contractions, and noradrenaline-evoked contractions of the rat isolated portal vein; inhibits the electrical stimulation-induced or noradrenaline-evoked contractions of the guinea-pig isolated vas deferens and reduces the periarterial electrical stimulation-induced or noradrenaline-evoked relaxations of the rabbit isolated duodenum. The antagonism produced by the amide alkaloid on the responses of these isolated tissue preparations to electrical stimulation or exogenously-added noradrenaline was similar to that elicited by phentolamine, an alpha-adrenoceptor antagonist. It is concluded that tetramethylpyrazine (TMPZ) probably causes hypotension in experimental animals by (a) dilating blood vessels, and/or (b) acting as a non-specific spasmolytic agent (like papaverine).

Active polypeptides of the amphibian skin and their synthetic analogues

Abstract

The action of bombesin on the systemic arterial blood pressure of some experimental animals.

1. The changes in blood pressure in response to parenteral administration of bombesin, the active tetradecapeptide of the skin of the European discoglossid frogs Bombina bombina and Bombina variegata variegata have been investigated in some experimental animals.2. In most species, the polypeptide elicited hypertension which was usually gradual in onset and slow to disappear. Blood pressure increases rarely exceeded 40-50 mmHg. At the beginning of an experiment some dose-response relationship could often be observed, but later tachyphylaxis developed. During an intravenous infusion of bombesin the rise in blood pressure could sometimes be maintained at a steady level as long as the infusion was continued, but at other times, the rise of pressure slowly subsided with continued administration of the polypeptide. In the rat and the chicken hypertension elicited by high doses of bombesin was often followed by secondary hypotension.3. Bombesin-induced hypertension was apparently not affected by pretreatment with either alpha- or beta-adrenergic blocking agents. Similarly secondary hypotension was not abolished by atropine. Thus, the effect of bombesin on vascular smooth muscle seems to be predominantly a direct one.4. Angiotensin was usually more potent than bombesin, and its effect on blood pressure was more rapid and of shorter duration. Tachyphylaxis to angiotensin was lacking or moderate.5. In sharp contrast to the other species, the monkey responded to bombesin with frank hypotension, which was usually proportional to the dose. In the monkey the hypotensive effect of bombesin was equal to, or greater than that of eledoisin or physalaemin and bombesin-induced hypotension was of longer duration than that of the other polypeptides. Tachyphylaxis was moderate for low and adequately spaced doses of the polypeptide, but prompt and intense for high doses. Long-lasting hypotension was obtained by intravenous infusion of bombesin, but repeated infusions caused tachyphylaxis. Bombesin-induced hypotension was not affected by pretreatment with atropine.6. Bombesin may be easily distinguished from all other known peptides active on vascular and extravascular smooth muscle by its effects on blood pressure. This does not apply to bombesin-like peptides, such as alytesin and ranatensin.

Occurrence of bombesin and alytesin in extracts of the skin of three European discoglossid frogs and pharmacological actions of bombesin on extravascular smooth muscle.

1. Methanol extracts of the skin of Bombina bombina and Bombina variegata variegata, two European discoglossid frogs, contain an active tetradecapeptide, bombesin. Alytesin, a tetradecapeptide strictly related to bombesin is present in extracts of the skin of Alytes obstetricans, another European discoglossid frog. The American frog Rana pipiens, contains in its skin ranatensin, an endecapeptide related to bombesin and alytesin.2. Passage of crude skin extracts of Bombina through a column of alumina yields eluates which may be considered free of other peptide contaminants and are suitable for the isolation of bombesin in a pure form.3. Bombesin has a stimulant action on several preparations of intestinal, uterine and urinary tract smooth muscle. Sometimes the effect is easily repeatable and shows a fair proportionality to the dose, but at other times a prompt and intense tachyphylaxis is observed. Other smooth muscle preparations are poorly sensitive or insensitive to bombesin. The rat uterus, the kitten small intestine, the guinea-pig colon and the rat urinary bladder may be used for the quantitative bioassay of bombesin.4. Bombesin-like peptides may easily be distinguished from all other naturally occurring peptides by parallel assay. They constitute a new group of active peptides possessing a peculiar spectrum of activity.

The action of caerulein on the systemic arterial blood pressure of some experimental animals.

1. The changes in blood pressure in response to parenteral administration of bombesin, the active tetradecapeptide of the skin of the European discoglossid frogs Bombina bombina and Bombina variegata variegata have been investigated in some experimental animals.2. In most species, the polypeptide elicited hypertension which was usually gradual in onset and slow to disappear. Blood pressure increases rarely exceeded 40-50 mmHg. At the beginning of an experiment some dose-response relationship could often be observed, but later tachyphylaxis developed. During an intravenous infusion of bombesin the rise in blood pressure could sometimes be maintained at a steady level as long as the infusion was continued, but at other times, the rise of pressure slowly subsided with continued administration of the polypeptide. In the rat and the chicken hypertension elicited by high doses of bombesin was often followed by secondary hypotension.3. Bombesin-induced hypertension was apparently not affected by pretreatment with either alpha- or beta-adrenergic blocking agents. Similarly secondary hypotension was not abolished by atropine. Thus, the effect of bombesin on vascular smooth muscle seems to be predominantly a direct one.4. Angiotensin was usually more potent than bombesin, and its effect on blood pressure was more rapid and of shorter duration. Tachyphylaxis to angiotensin was lacking or moderate.5. In sharp contrast to the other species, the monkey responded to bombesin with frank hypotension, which was usually proportional to the dose. In the monkey the hypotensive effect of bombesin was equal to, or greater than that of eledoisin or physalaemin and bombesin-induced hypotension was of longer duration than that of the other polypeptides. Tachyphylaxis was moderate for low and adequately spaced doses of the polypeptide, but prompt and intense for high doses. Long-lasting hypotension was obtained by intravenous infusion of bombesin, but repeated infusions caused tachyphylaxis. Bombesin-induced hypotension was not affected by pretreatment with atropine.6. Bombesin may be easily distinguished from all other known peptides active on vascular and extravascular smooth muscle by its effects on blood pressure. This does not apply to bombesin-like peptides, such as alytesin and ranatensin.