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Cyclic AMP response element (CRE) binding protein (CREB) is a nuclear transcription factor that regulates the transcription of several genes containing the CRE sites on their promoters. CREB is activated by phosphorylation on a key serine residue, Ser311, in response to a wide variety of extracellular stimuli including angiotensin II (Ang II). Ang II is an important vasoactive peptide and mitogen for vascular smooth muscle cells (VSMC) that in addition to regulating the contractile response in VSMC also plays an important role in phenotypic switch of VSMC from contractile to a synthetic state. The synthetic VSMC are known to exhibit proliferative and migratory properties due to hyperactivation of Ang II-induced signaling events. Ang II has been shown to induce CREB phosphorylation/activation and transcription of genes implicated in proliferation, growth, and migration. Here, we have highlighted some key studies that have demonstrated an important role of CREB in Ang II-mediated gene transcription, proliferation, hypertrophy, and migration of VSMC. Key words: angiotensin II, CREB, VSMC, MAPK, PKB/Akt. La proteine CREB liant le CRE (de l'anglais << cyclic AMP response element >>) constitue un facteur de transcription nucleaire qui participe a la regulation de la transcription de plusieurs genes comprenant les sites du CRE sur leurs promoteurs. La proteine CREB est activee par une phosphorylation de la Ser311, un residu serine cle, en reaction a une grande variete de stimuli extracellulaires, y compris l'angiotensine II (Ang II). L'Ang II est un peptide vasoactif et un agent mitogene important dans les cellules musculaires lisses vasculaires (CMLV) qui, en plus de participer a la regulation de la reaction contractile des CMLV, joue un role important dans la commutation phenotypique des CMLV de l'etat contractile a un etat synthetique. Il est connu que les CMLV synthetiques sont dotees de proprietes proliferatives et migratoires en raison d'evenements de signalisation engendres par l'hyperactivation de l'Ang II. Il a ete montre que l'Ang II engendre la phosphorylation et l'activation de la proteine CREB ainsi que la transcription de genes participant a la proliferation, a la croissance et a la migration. Ici, nous avons mis de l'avant certaines etudes cles, qui ont montre un role important de la proteine CREB dans la transcription de genes medies par l'Ang II ainsi que dans la proliferation l'hypertrophie et la migration des CMLV. [Traduit par la Redaction] Mots-cles : angiotensine II, CREB, CMLV, MAPK, PKB/Akt., Introduction Cyclic AMP response element binding protein (CREB) is an important transcription factor that was originally discovered as a regulator of somatostatin gene transcription in response to forskolin-induced elevation in [...]

Interstitial cells of Cajal (ICCs) are pacemaker cells in the intestine, and their function can be compromised by loss of C-KIT expression. Macrophage activation has been identified in intestine affected by Hirschsprung disease-associated enterocolitis (HAEC). In this study, we examined proinflammatory macrophage activation and explored the mechanisms by which it downregulates C-KIT expression in ICCs in colon affected by HAEC. We found that macrophage activation and TNF-[alpha] production were dramatically increased in the proximal dilated colon of HAEC patients and 3-week-old [Ednrb.sup.-/-] mice. Moreover, ICCs lost their [C-KIT.sup.+] phenotype in the dilated colon, resulting in damaged pacemaker function and intestinal dysmotility. However, macrophage depletion or TNF-[alpha] neutralization led to recovery of ICC phenotype and restored their pacemaker function. In isolated ICCs, TNF-[alpha]-mediated phosphorylation of p65 induced overexpression of microRNA-221 (miR-221), resulting in suppression of C-KIT expression and pacemaker currents. We also identified a TNF-[alpha]/NF-[kappa]B/miR-221 pathway that downregulated C-KIT expression in ICCs in the colon affected by HAEC. These findings suggest the important roles of proinflammatory macrophage activation in a phenotypic switch of ICCs, representing a promising therapeutic target for HAEC., Introduction Hirschsprung disease (HSCR) is a birth defect characterized by the absence of ganglion cells in the distal bowel (1). HSCR-associated enterocolitis (HAEC), the most common and serious complication of [...]

The purpose of this study was to explore the potential contracting effect of leptin on isolated guinea pig tracheal smooth muscle (TSM), the possible mechanism, and the impact of epithelium denudation or allergen sensitization, respectively. An in vitro experiment investigated the effect of leptin at a concentration of 250-1000 nmol/L on isolated guinea pig TSM with an intact or denuded epithelium. Ovalbumin and IgE were used to test the impact of active and passive sensitization. The isolated TSM strips were incubated in Krebs solution and aerated with carbogen (95% [O.sub.2] and 5% C[O.sub.2]) via an automated tissue organ bath system (n = 4 for each group). Isometric contractions were recorded digitally using iox2 data acquisition software. The possible mechanism of leptin-induced TSM contraction was examined by preincubation with leptin receptor (Ob-R) antagonist. Leptin had significant concentration-dependent contraction effects on guinea pig TSM (p < 0.05). Epithelium denuding and active or passive sensitization significantly increased the potency of the leptin. Preincubation with a leptin receptor (Ob-R) antagonist significantly reduced the contraction effects, suggesting an Ob-R-mediated mechanism. Leptin had a contracting effect on airway smooth muscles potentiated by either epithelium denuding or sensitization, and the Ob-R mechanism was a possible effect mediator. Key words: airway smooth muscles, guinea pig, leptin, Ob-R. Cette etude portait sur l'eventuel effet contractile de la leptine sur le muscle lisse tracheal (MLT) de cobaye, le mode d'action possible et l'incidence de la denudation de l'endothelium ou de la sensibilisation aux allergenes. A l'aide d'experiences in vitro, nous avons etudie l'effet de la leptine a certaines concentrations (250-1000 nmol/L) sur le MLT isole de cobaye avec un epithelium intact ou denude. Nous avons evalue l'incidence de la sensibilisation active ou passive a l'aide d'ovalbumine et d'IgE. Nous avons incube les bandelettes de MLT isolees dans une solution de Krebs ventilee a l'aide de carbogene ([O.sub.2] a 95 % et C[O.sub.2] a 5 %) dans un bain de tissu organique automatise (n = 4 pour chaque groupe). Nous avons enregistre les contractions isometriques numerisees a l'aide du logiciel d'acquisition de donnees iox2. Nous avons examine le mode d'action eventuel des contractions du MLT provoquees par la leptine apres une incubation en presence d'un antagoniste des recepteurs de la leptine (Ob-R). Nous avons observe que la leptine avait des effets contractiles marques et proportionnels a la concentration sur le MLT de cobaye (p < 0,05). La denudation de l'epithelium et la sensibilisation active ou passive entrainaient une augmentation notable de la puissance de la leptine. L'incubation prealable en presence d'un antagoniste des recepteurs de la leptine (Ob-R) entrainait clairement une diminution des effets contractiles, ce qui laisse entrevoir la presence d'un mode d'action medie par les Ob-R En conclusion, la leptine a eu un effet contractile sur le muscle lisse des voies respiratoires qui etait potentialise par la denudation de l'endothelium ou par la sensibilisation, et le mode d'action lie au recepteur Ob-R constituait un mediateur de l'effet possible. [Traduit par la Redaction] Mots-des: muscle lisse des voies respiratoires, cobaye, leptine, Ob-R., Introduction Leptin is a pro-inflammatory cytokine protein synthesized by human adipocytes with the serum levels being directly linked to the mass of the adipose tissue (Paz-Filho et al. 2015). Generated [...]

Statins are determined to have various pleiotropic effects apart from their lipid-lowering properties. Herein, we investigated the direct effects of atorvastatin on gastric smooth muscle tone. Atorvastatin effectively relaxed isolated rat gastric fundus strips precontracted with acetylcholine, potassium chloride, and serotonin. Incubation of the strips with nitric oxide synthase inhibitor, L-NOARG ([10.sup.-4] M, 20 min), L-type voltage-operated [Ca.sup.2+] channel (VOCC) blocker, nifedipine ([10.sup.-6] M, 30 min), [K.sub.ATP] channel blocker, glibenclamide ([10.sup.-5] M, 30 min), or precursor of cholesterol, mevalonate ([10.sup.- 2] M, 45 min) did not change the relaxations to atorvastatin. However, pretreatment of fundus strips with atorvastatin (3x[10.sup.-5]-3x[10.sup.-4] M, 30 min) inhibited the contractions to calcium chloride ([10.sup.-4]-[10.sup.-1] M), acetylcholine ([10.sup.-4] M), and caffeine (20 mM) in the calcium-free medium. Moreover, atorvastatin reduced the contractions induced by sarco-endoplasmic reticulum [Ca.sup.2+]-ATPase (SERCA) inhibitor, cyclopiazonic acid ([10.sup.-7]-3x[10.sup.-5] M). The current study demonstrated that atorvastatin produces an acute relaxant effect on gastric fundus strips, which appears to be mediated by several [Ca.sup.2+]-signalling mechanisms such as the blockade of L-type VOCC-independent [Ca.sup.2+] entry, decrease in smooth muscle [Ca.sup.2+] sensitivity, inhibition of I[P.sub.3]- and ryanodine-sensitive intracellular stores to mediate [Ca.sup.2+] release, as well as the activation of SERCA. This acute relaxing effect seems unlikely to be related with nitric oxide, [K.sub.ATP] channels, and the mevalonate pathway. Key words: atorvastatin, rat gastric fundus, [Ca.sup.2+] entry, intracellular [Ca.sup.2+] stores, SERCA. Il est etabli que les statines ont differents effets pleiotropiques en dehors de leurs proprietes d'abaissement des taux de lipides. Ici, nous avons etudie les effets directs de l'atorvastatine sur le tonus du muscle lisse gastrique. L'atorvastatine entrainait avec efficacite une relaxation de bandelettes isolees de fondus gastrique avec une precontraction a l'aide d'acetylcholine, de chlorure de potassium et de serotonine. L'incubation des bandelettes en presence d'L-NOARG (un inhibiteur de l'oxyde nitrique synthase; [10.sup.-4] M, 20 min), de nifedipine (un bloqueur des canaux [Ca.sup.2+] voltage dependants (CCVD) de type L; [10.sup.-6] M, 30 min), de glibenclamide (un bloqueur des canaux [K.sub.ATP]; [10.sup.-5] M, 30 min) ou de mevalonate (un precurseur du cholesterol; [10.sup.-2] M, 45 min) n'entrainait pas de modifications des relaxations obtenues avec l'atorvastatine. Cependant, l'exposition prealable des bandelettes de fondus gastrique a l'atorvastatine (3x[10.sup.-5] a 3x[10.sup.-4] M, 30 min) permettait d'inhiber les contractions sous chlorure de calcium ([10.sup.-4] a [10.sup.-1] M), acetylcholine ([10.sup.-4] M) et cafeine (20 mM) dans le milieu ne contenant pas de calcium. En outre, l'atorvastatine entrainait une diminution des contractions provoquees par l'acide cyclopiazonique (un inhibiteur de la [Ca.sup.2+]ATPase du reticulum sarco-endoplasmique (SERCA pour << sarco-endoplasmic reticulum [Ca.sup.2+]-ATPase >>); [10.sup.-7] a 3x[10.sup.-5] M). La presente etude a montre que l'atorvastatine a un effet de relaxation aigue sur des bandelettes de fundus gastrique qui semble medie par plusieurs modes d'action de signalisation du [Ca.sup.2+] comme l'inhibition de l'entree de [Ca.sup.2+] independante des CCDV de type L, la diminution de la sensibilite du muscle lisse au [Ca.sup.2+], l'inhibition de la mediation de la liberation du [Ca.sup.2+] des stores intracellulaires sensibles a l'[IP.sub.3] et a la ryanodine, ainsi que l'activation de la SERCA. Cet effet de relaxation aigue ne semble pas etre lie aux voies de signalisation de l'oxyde nitrique, des canaux [K.sub.ATP] et du mevalonate. [Traduit par la Redaction] Mots-cles: atorvastatine, fondus gastrique de rat, entree de [Ca.sup.2+], stores intracellulaires de [Ca.sup.2+], SERCA., Introduction Statins, which competitively inhibit the rate-limiting enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase in cholesterol biosynthesis, are the most effective drugs in lowering plasma cholesterol levels. Accumulating evidence indicated [...]

For more than 50 years, the methylation of mammalian actin at histidine 73 has been known to occur.sup.1. Despite the pervasiveness of His73 methylation, which we find is conserved in several model animals and plants, its function remains unclear and the enzyme that generates this modification is unknown. Here we identify SET domain protein 3 (SETD3) as the physiological actin His73 methyltransferase. Structural studies reveal that an extensive network of interactions clamps the actin peptide onto the surface of SETD3 to orient His73 correctly within the catalytic pocket and to facilitate methyl transfer. His73 methylation reduces the nucleotide-exchange rate on actin monomers and modestly accelerates the assembly of actin filaments. Mice that lack SETD3 show complete loss of actin His73 methylation in several tissues, and quantitative proteomics analysis shows that actin His73 methylation is the only detectable physiological substrate of SETD3. SETD3-deficient female mice have severely decreased litter sizes owing to primary maternal dystocia that is refractory to ecbolic induction agents. Furthermore, depletion of SETD3 impairs signal-induced contraction in primary human uterine smooth muscle cells. Together, our results identify a mammalian histidine methyltransferase and uncover a pivotal role for SETD3 and actin His73 methylation in the regulation of smooth muscle contractility. Our data also support the broader hypothesis that protein histidine methylation acts as a common regulatory mechanism.SETD3 methylates mammalian actin at His73, and SETD3 deficiency impairs stimulus-induced contraction in primary human uterine smooth muscle cells and leads to maternal dystocia in mice., Author(s): Alex W. Wilkinson [sup.1] , Jonathan Diep [sup.2] , Shaobo Dai [sup.3] , Shuo Liu [sup.1] , Yaw Shin Ooi [sup.2] , Dan Song [sup.4] , Tie-Mei Li [sup.1] [...]

cAMP has been shown to inhibit vascular smooth muscle cell proliferation and exerts a vasculoprotective effect. An upregulation of the early growth response protein-1 (Egr-1) expression has been linked with the development of atherosclerosis and intimal hyperplasia. We have recently demonstrated that angiotensin-II (Ang-II) stimulates Egr-1 expression via [Ca.sup.2+]/ERK-mediated cAMP-response element binding protein (CREB) activation. However, whether Ang-II-induced signaling leading to Egr-1 expression is modulated by cAMP remains unexplored. Therefore, in the present studies, we have examined the effect of cAMP on Ang-II-induced expression of Egr-1 and associated signaling pathways. Isoproterenol (ISO) and forskolin (FSK) attenuated Ang-II-induced Egr-1 expression in a dose-dependent fashion. In addition, dibutyryl-cAMP and benzoyl-cAMP, as well as isobutylmethylxanthine, attenuated Ang-II-induced Egr-1 expression. Moreover, inhibition of Ang-II-induced Egr-1 expression was accompanied by an increase in the phosphorylation of the vasodilator-activated phosphoprotein (VASP), and this was associated with a concomitant decrease in ERK phosphorylation. Blockade of PKA using H89 decreased VASP phosphorylation, restored Ang-II-induced ERK phosphorylation, and abolished ISO- and FSK-mediated inhibition of Ang-II-induced Egr-1 expression. In summary, these results suggest that PKA-mediated suppression of Ang-II-induced Egr-1 expression and phosphorylation of ERK maybe among the mechanisms by which cAMP exerts its vasculoprotective effects. Key words: angiotensin-II, Egr-1, cAMP, VSMC, PKA, ERK, VASP. Plusieurs etudes demontrent que l'AMPc inhibe la proliferation des cellules musculaires lisses vasculaires et exerce un effet vasculoprotecteur. L'expression de la proteine 1 de reponse de croissance precoce (Egr-1 pour <>) est liee a la pathogenese de l'atherosclerose et de l'hyperplasie intimale. Recemment, nous avons montre que l'angiotensine-II (Ang-II) stimule l'expression de l'Egr-1 par l'intermediaire de l'activation de la proteine CREB (pour <>). Toutefois, la possibilite que la signalisation favorisee par l'Ang-II et menant a l'expression de la proteine Egr-1 soit modulee par l'AMPc n'a pas encore ete exploree. Par consequent, dans les presents travaux, nous avons etudie l'effet de l'AMPc sur l'expression de l'Egr-1 favorisee par l'Ang-II, ainsi que les voies de signalisation associees. L'isoproterenol (ISO) et la forskoline (FSK) ont entraine une attenuation proportionnelle a la dose de l'augmentation de l'expression de l'Egr-1 favorisee par l'Ang-II. De plus, la dibutyryl-AMPc et la benzoyl-AMPc, ainsi que l'isobutylmethylxanthine ont entraine une attenuation de l'expression de l'Egr-1 favorisee par l'Ang-II. En outre, l'inhibition de l'expression de l'Egr-1 favorisee par l'Ang-II etait accompagnee d'une augmentation de la phosphorylation de la VASP (pour <>), augmentation qui etait concomitante a la diminution de la phosphorylation de l'ERK. L'inhibition de la PKA a l'aide d'H89 a entraine une diminution de la phosphorylation de la VASP, le retablissement de la phosphorylation d'ERK favorisee par l'Ang-II et l'abolition de l'inhibition de l'expression de l'Erg-1 favorisee par l'Ang-II et mediee par l'ISO et la FSK. En resume, ces resultats laissent entendre que l'inhibition de l'expression de l'Erg-1 favorisee par l'Ang-II et mediee par la PKA, ainsi que la phosphorylation d'ERK pourraient compter parmi les modes d'action sous-jacents aux effets vasculoprotecteurs de l'AMPc. [Traduit par la Redaction] Mots-cles: angiotensine-II, Egr-1, AMPc, cellules musculaires lisses vasculaires, PKA, ERK, VASP., Introduction Aberrant proliferation and migration of vascular smooth muscle cells (VSMC) are believed to contribute to abnormal vascular function leading to the pathogenesis of vascular diseases (Rivard and Andres 2000). [...]

Accumulating lines of evidence indicate that high leptin levels are associated with adverse cardiovascular health in obese individuals. Proatherogenic effects of leptin include endothelial cell activation and vascular smooth muscle cell proliferation and migration. Ursolic acid (UA) has been reported to exhibit multiple biological effects including antioxidant and anti-inflammatory properties. In this study, we investigated the effect of UA on leptin-induced biological responses in rat vascular smooth muscle cells (VSMCs). A-10 VSMCs were treated with leptin in the presence or absence of UA. Intracellular reactive oxygen species (ROS) was probed by 2',7'-dichlorofluorescein diacetate. The expression of extracellular signal-regulated kinase (ERK)1/2, phospho-(ERK)1/2, nuclear factor-kappa B (NF-[kappa]B) p65 and p50, and matrix metalloproteinase-2 (MMP2) was determined by Western blotting. Immunocytochemistry and confocal laser scanning microscopy were also used for the detection of NF-[kappa]B. The secretion of MMP2 was detected by gelatin zymography. UA exhibited antioxidant activities in vitro. In rat VSMCs, UA effectively inhibited cell growth and the activity of MMP2 induced by leptin. These suppressive effects appeared by decreasing the activation of (ERK)1/2, the nuclear expression and translocation of NF-[kappa]B, and the production of ROS. UA appeared to inhibit leptin-induced atherosclerosis, which may prevent the development of obesity-induced cardiovascular diseases. Key words: atherosclerosis, leptin, obesity, ursolic acid, vascular smooth muscle cells. De plus en plus de donnees de differentes sources montrent que l'augmentation des taux de leptine est associee aune mauvaise sante cardiovasculaire chez les personnes obeses. Les effets proatherogenes de la leptine comprennent l'activation des cellules endotheliales ainsi que la proliferation et la migration des cellules musculaires lisses vasculaires (CMLV). On a rapporte que l'acide ursolique (AU) a de multiples effets biologiques, y compris des proprietes anti-oxydantes et anti-inflammatoires. Dans ces travaux, nous avons etudie l'effet de l'AU sur les reactions biologiques induites par la leptine dans les CMLV de rat. Nous avons expose des CMLV de la lignee A-10 a de la leptine en presence ou en absence d'AU. Nous avons sonde les derives reactifs de l'oxygene (ou ROS pour << reactive oxygen species >>) a l'aide de diacetate de 2',7'-dichlorofluoresceine. A l'aide de l'immunobuvardage de Western, nous avons mesure l'expression extracellulaire de l' (ERK)1/2 (pour << signal-regulated kinase >>), de la phospho-(ERK)1/2, des sous-unites p65 et p50 du facteur nucleaire kappa B (NF-[kappa]B) et de la metalloproteinase matricielle 2 (MMP2). Nous avons aussi utilise l'immunohistochimie et la microscopie confocale par balayage pour detecter le NF-[kappa]B. Nous avons detecte la secretion de MMP2 a l'aide de la zymographie en gelatine. L'AU a montre une activite anti-oxydante in vitro. Dans les CMLV de rat, l'AU a inhibe efficacement la croissance cellulaire et l'activite de la MMP2 induites par la leptine. Ces effets suppresseurs sont apparus en diminuant l'activation de l'(ERK)1/2, l'expression et la translocation du NF-[kappa]B dans le noyau et la production de ROS. L'AU semblait permettre d'inhiber l'atherosclerose induite par la leptine, ce qui pourrait permettre de prevenir l'apparition de maladies cardiovasculaires induites par l'obesite. [Traduit par la Redaction] Mots-cles: atherosclerose, leptine, obesite, acide ursolique, cellules musculaires lisses vasculaires., Introduction Obesity is considered an alarming issue of public health because of its predisposition to multiple disorders, including atherosclerosis, diabetes mellitus, and cancer (Avogaro and de Kreutzenberg 2005; Karastergiou and [...]

The objective of this study was to observe the effects of moderate-intensity training on the activity of heme oxygenase (HO) and expression of HO-1 mRNA in the aorta and the cardiac muscle of spontaneously hypertensive rats (SHRs). After 9 weeks of swimming exercise, the activity of HO and expression of HO-1 mRNA in the SHRs were measured. The resting blood pressure in the exercise group was increased by 1.7% (P > 0.05), whereas it was significantly elevated by 10.3% (P < 0.01) in the SHR rats. Compared with animals in the control and sedentary groups, the expression level of HO-1 mRNA of aorta and cardiac muscle in the exercise group was significantly enhanced (P < 0.01). The HO activity and the content of plasma carbon monoxide (CO) in the sedentary group were dramatically decreased (P < 0.05 and P < 0.01, respectively) compared with the control group. HO activity and content of plasma CO in the exercise group were significantly higher compared with those in the sedentary group (P < 0.05 and P < 0.01, respectively). The HO/CO metabolic pathway might be involved in the regulation of blood pressure of the SHR models. Key words: exercise, spontaneously hypertensive rats, HO activity, HO-1 mRNA expression, cardiac and vascular smooth muscle. Cette etude avait pour objectif d'observer les effets de l'entrainement physique d'intensite moderee sur l'activite de l'heme oxygenase (HO) et l'expression de l'ARNm du gene HO-1 dans l'aorte et le muscle cardiaque de rats spontanement hypertendus (SHR). Apres un entrainement a la nage de 9 semaines, nous avons mesure l'activite de ces deux parametres chez les rats SHR. Nous avons observe que la tension arterielle au repos augmentait legerement (de 1,7 %; P < 0,05) dans le groupe soumis a l'entrainement, alors qu'elle augmentait de facon marquee (de 10,3 %; P < 0,01) chez les rats SHR. Par ailleurs, le taux d'expression de l'ARNm du gene HO-1 dans l'aorte et dans le muscle cardiaque a augmente de facon plus marquee dans le groupe soumis a l'entrainement que dans les groupes de rats temoins et sedentaires (P < 0,01). En outre, l'activite de l'HO et le taux plasmatique de monoxyde de carbone (CO) etaient augmentes considerablement (P < 0,05 et P < 0,01) chez les rats sedentaires comparativement aux temoins. De plus, l'activite de l'HO et les taux plasmatiques de CO etaient nettement plus eleves chez les rats entraines que chez les sedentaires (P < 0,05 et P < 0,01). En definitive, ces travaux montrent que la voie metabolique de l'HO et du CO pourrait jouer un role sur le plan de la regulation de la tension arterielle dans les modeles de rats SHR. [Traduit par la Redaction] Mots-cles: entrainement physique, rats spontanement hypertendus, activite de l'HO, expression de l'ARNm du gene HO-1, muscles cardiaque et vasculaire lisse., Introduction Heme oxygenase (HO) is the initial enzyme that catalyzes the degradation of heme. The main physiological function of HO is to produce bilirubin, free iron, and carbon monoxide (CO). [...]

Airway smooth muscle (ASM) plays a central role in the excessive narrowing of the airway that characterizes the primary functional impairment in asthma. This phenomenon is known as airway hyper-responsiveness (AHR). Emerging evidence suggests that the development and maintenance of ASM force involves dynamic reorganization of the subcellular filament network in both the cytoskeleton and the contractile apparatus. In this review, evidence is presented to support the view that regulation of ASM contraction extends beyond the classical actomyosin interaction and involves processes within the cytoskeleton and at the interfaces between the cytoskeleton, the contractile apparatus, and the extracellular matrix. These processes are initiated when the muscle is activated, and collectively they cause the cytoskeleton and the contractile apparatus to undergo structural transformation, resulting in a more connected and solid state that allows force generated by the contractile apparatus to be transmitted to the extracellular domain. Solidification of the cytoskeleton also serves to stiffen the muscle and hence the airway. Oscillatory strain from tidal breathing and deep inspiration is believed to be the counter balance that prevents hypercontraction and stiffening of ASM in vivo. Dysregulation of this balance could lead to AHR seen in asthma. Key words: asthma, Rho-kinase, cytoskeleton, cross-bridge, length adaptation, force adaptation. Le muscle lisse respiratoire (MLR) joue un role central dans le retrecissement excessif des voies respiratoires qui caracterise la principale deterioration fonctionnelle associee a l'asthme. Ce phenomene est connu sous le nom d'hyperreactivite bronchique (HRB). Une donnee nouvelle suggere que le developpement et le maintien de la force du MLR implique la reorganization dynamique du reseau de filaments subcellulaires du cytosquelette et de l'appareil contractile. Dans cet article de revue, les auteurs presentent une preuve qui appuie la vision que la contraction du MLR va au-dela de l'interaction classique de l'actomyosine et implique des processus a l'interieur du cytosquelette et a l'interface entre le cytosquelette, l'appareil contractile et la matrice extracellulaire. Ces processus sont inities lorsque le muscle est active, et ils provoquent collectivement une transformation structurale du cytosquelette et de l'appareil contractile resultant en un etat mieux connecte et solide qui permet a la force generee par l'appareil contractile de se transmettre au domaine extracellulaire. La solidification du cytosquelette sert aussi a durcir le muscle et, consequemment, les voies respiratoires. On croit que la pression oscillatoire de la respiration courante et de l'inspiration profonde constitue la contrebalance qui previent l'hyper-contraction et le durcissement du MLR in vivo. La deregulation de cette balance pourrait conduire a l'HRB observee dans l'asthme. [Traduit par la Redaction] Mots-cles: asthme, Rho-kinase, cytosquelette, ponts transversaux, adaptation de la longueur, adaptation de la force., Introduction The regulation of the mechanical properties of smooth muscle, such as the ability to generate force and maintain tensile stiffness, is fundamental to the proper functioning of the muscle. [...]

Airway inflammation is a key aspect of diseases such as asthma. Several inflammatory cytokines (e.g., TNFα and IL-13) increase cytosolic [Ca.sup.2+] ([[[Ca.sup.2+]].sub.cyt]) responses to agonist stimulation and [Ca.sup.2+] sensitivity of force generation, thereby enhancing airway smooth muscle (ASM) contractility (hyper-reactive state). Inflammation also induces ASM proliferation and remodeling (synthetic state). In normal ASM, the transient elevation of [[[Ca.sup.2+]].sub.cyt] induced by agonists leads to a transient increase in mitochondrial [Ca.sup.2+] ([[[Ca.sup.2+]].sub.mito]) that may be important in matching ATP production with ATP consumption. In human ASM (hASM) exposed to TNFα and IL-13, the transient increase in [[[Ca.sup.2+]].sub.mito] is blunted despite enhanced [[[Ca.sup.2+]].sub.cyt] responses. We also found that TNFα and IL-13 induce reactive oxidant species (ROS) formation and endoplasmic/sarcoplasmic reticulum (ER/SR) stress (unfolded protein response) in hASM. ER/SR stress in hASM is associated with disruption of mitochondrial coupling with the ER/SR membrane, which relates to reduced mitofusin 2 (Mfn2) expression. Thus, in hASM it appears that TNFα and IL-13 result in ROS formation leading to ER/SR stress, reduced Mfn2 expression, disruption of mitochondrion-ER/SR coupling, decreased mitochondrial [Ca.sup.2+] buffering, mitochondrial fragmentation, and increased cell proliferation. Key words: inflammation, ER/SR stress, airway, asthma, unfolded protein response. L'inflammation de voies respiratoires est un aspect cle de maladies comme l'asthme. Plusieurs cytokines inflammatoires (ex. TNFα et IL-13) augmentent le [Ca.sup.2+] cytosolique ([[[Ca.sup.2+]].sub.cyt]) en reponse a une stimulation par un agoniste et la sensibilite de la generation de forces au calcium, augmentant ainsi la contractilite du muscle lisse respiratoire (MLR) (etat d'hyperreactivite). L'inflammation induit aussi la proliferation et le remodelage des cellules du MLR (etat de synthese). Chez le MLR, l'elevation transitoire de [[[Ca.sup.2+]].sub.cyt] induite par un agoniste mene a une augmentation transitoire du [Ca.sup.2+] mitochondrial ([[[Ca.sup.2+]].sub.mito]) qui peut etre importante pour arrimer la production d'ATP a sa consommation. Chez les cellules de MLR humain (hMLR) exposees au TNFα et a l'IL-13, l'augmentation transitoire de [[[Ca.sup.2+]].sub.mito] est attenuee malgre l'augmentation de [[[Ca.sup.2+]].sub.cyt]. Les auteurs trouvent aussi que le TNFα et l'IL-13 induisent la formation d'especes reactives d'oxygene (ERO) et un stress du reticulum endoplasmique/ sarcoplasmique (RE/RS) (reponse aux proteines depliees) chez les hMLR. Le stress RE/RS chez les hMLR est associe au decouplage de la mitochondrie a la membrane du RE/RS, phenomene relie a la reduction de l'expression de la mitofusine 2 (Mfn2). Ainsi, chez les hMLR, il semble que le TNFα et l'IL-13 induisent la formation d'ERO conduisant a un stress du RE/RS, a la reduction de l'expression de Mfn2, au decouplage de la mitochondrie au RE/RS, a la diminution du tamponnage du [Ca.sup.2+] mitochondrial, a la fragmentation mitochondriale et a l'augmentation de la proliferation cellulaire. [Traduit par la Redaction] Mots-cles: inflammation, stress du RE/RS, voies respiratoires, asthme, reponse aux proteines depliees., Introduction Asthma affects more than 20 million people in the USA (~10% of the population), and more than 300 million people world-wide (GINA 2012). It is now recognized that inflammation [...]

The standard method for measuring the phosphorylation of the regulatory myosin light chain (MLC20) in smooth muscle is extraction of the light chain using a urea extraction buffer, urea-glycerol gel electrophoresis of the soluble portion of the extract (supernatant) and Western blot analysis. The undissolved portion of the tissue during extraction (the pellet) is usually discarded. Because the pellet contains a finite amount of MLC20, omission of the pellet could result in inaccurate measurement of MLC20 phosphorylation. In this study we compared the level of tracheal smooth muscle MLC20 phosphorylation in the supernatant alone, with that in the complete tissue homogenate (supernatant and pellet) using the standard method. The supernatant fraction showed the well-known double bands representing phosphorylated and un-phosphorylated MLC20. The dissolved pellet fraction showed varying amounts of un-phosphorylated and phosphorylated MLC20. There was a small but statistically significant overestimation of the percent MLC20 phosphorylation if the pellet was not taken into consideration. The overestimation was 7% ± 2% (mean ± SEM) (p < 0.05) in unstimulated muscle and 2% ± 1% (p < 0.05) in acetylcholine (10-6 mol/L) stimulated muscle. This finding suggests that for accurate estimation of the stoichiometry of MLC20 phosphorylation it is necessary to consider the contribution from the pellet portion of the muscle tissue homogenate. Key words: urea-glycerol gel electrophoresis, MLC20 phosphorylation, supernatant and pellet, Western blots. La methode standard pour mesurer la phosphorylation de la chaine legere de la myosine regulatrice (MLC20) dans le muscle lisse consiste en une extraction de la chaine legere dans un tampon d'extraction comprenant de l'uree, une electrophorese sur gel d'uree-glycerol de la portion soluble de l'extrait (surnageant) et d'un buvardage Western. La portion tissulaire non dissoute lors de l'extraction (culot) est habituellement jetee. Parce que le culot contient une faible quantite de MLC20, l'omission du culot pourrait resulter en une mesure imprecise de la phosphorylation de la MLC20. Dans cette etude, les auteurs ont compare le niveau de phosphorylation de MLC20 du muscle lisse tracheal dans le surnageant seul a celui de l'homogenat tissulaire complet (surnageant et culot) a l'aide de la methode standard. La fraction du surnageant montrait les doubles bandes bien connues representant la MLC20 phosphorylee et non phosphorylee. La fraction dissoute du culot contenait des quantites variables de MLC20 phosphorylee et non phosphorylee. Il y avait une legere mais significative surestimation du pourcentage de MLC20 phosphorylee si le culot n'etait pas considere. La surestimation etait de7%±2% (moyenne ± ESM) (p < 0,05) dans le muscle non stimule et de 2%[+ or -]1%(p < 0,05) dans le muscle stimule a l'acetylcholine (10-6 mol/L). Ces donnees suggerent que l'estimation precise de la strechiometrie de la phosphorylation de la MLC20 necessite de considerer la contribution de la portion du culot issue de l'homogenat de tissu musculaire. [Traduit par la Redaction] Mots-cles: electrophorese sur gel uree-glycerol, phosphorylation de la MLC20, surnageant et culot, buvardages Western., Introduction The crucial step for the initiation of the ATP-dependent actomyosin interaction in smooth muscle is the phosphorylation of the myosin light chain 20 (MLC20) (Frearson et al. 1976; Sobieszek [...]

The sole of crawling gastropods is a unique model for studying the function of smooth muscles and ciliated epithelium. The gastropod snail Lymnaea stagnalis glides over the substratum without visible muscular contraction in its sole; consequently, the gliding was thought to be due to sole cilia. However, we have shown that the sole muscles in Lymnaea are phasic smooth muscles. They contribute extensively to gliding rate, which is directly correlated with the sole length (longitudinal sole muscle tonus) that varies widely during gliding. Here, we show that the linear relationship between gliding rate and sole length in Lymnaea may be modified. Serotonin increases gliding rate and has no effect on sole length. Dopamine contracts the sole and, consequently, slows the gliding rate, while ergometrine (a blocker of dopamine receptors) relaxes the sole and increases gliding rate. These influences on locomotion rate and sole length are similar to those obtained earlier for Helix lucorum, in which the substances changed the number and contraction force of muscle cells involved in peristaltic locomotory waves. Taken together, the data obtained here for Lymnaea and earlier for Helix describe the fundamental mechanisms for controlling phasic smooth muscles., Introduction In vertebrates and invertebrates, studying the function of smooth musculature and ciliated epithelia in visceral ducts and organs may injure the tissues, leading to a loss of data. The [...]

Activation of cells intrinsic to the vessel wall is central to the initiation and progression of vascular inflammation. As the dominant cellular constituent of the vessel wall, vascular smooth muscle [...]

Triton X-100 (TX-100) is a nonionic detergent frequently used at millimolar concentrations to disrupt cell membranes and solubilize proteins. At low micromolar concentrations, TX-100 has been reported to inhibit the function of potassium channels. Here, we have used electrophysiological and functional techniques to examine the effects of TX-100 on another class of ion channels, L-type voltage-operated calcium channels (VOCCs). TX-100 (30 nmol-L-1 to 3 µmol x [L.sup.-1]) caused reversible concentration-dependent inhibition of recombinant L-type VOCC ([Ca.sub.V] 1.2) currents and of native L-type VOCC currents recorded from rat vascular smooth muscle cells and cardiac myocytes, and murine and human pancreatic β-cells. In functional studies, TX-100 (165 nmol x [L.sup.-1] to 3.4 µmol x [L.sup.-1]) caused concentration-dependent relaxation of rat isolated mesenteric resistance arteries prestimulated with phenylephrine or KCl. This effect was independent of the endothelium. TX-100 (1.6 µmol x [L.sup.-1]) inhibited depolarization-induced exocytosis in both murine and human isolated pancreatic β-cells. These data indicate that at concentrations within the nanomolar to low micromolar range, TX-100 significantly inhibits L-type VOCC activity in a number of cell types, an effect paralleled by inhibition of cell functions dependent upon activation of these channels. This inhibition occurs at concentrations below those used to solubilize proteins and may compromise the use of solutions containing TX-100 in bioassays. Key words: Triton X-100, voltage-operated calcium channel, vascular smooth muscle, cardiac myocyte, pancreatic β- cell. Le Triton X-100 (TX-100) est un detergent non ionique frequemment utilise a des concentrations millimolaires afin de desorganiser les membranes cellulaires et solubiliser les proteines. On rapporte qu'a de faibles concentrations millimolaires, le TX-100 inhibe la fonction des canaux potassiques. Nous avons utilise ici des techniques electro-physiologiques et fonctionnelles afin d'examiner les effets du TX-100 surun autre type de canaux ioniques, les canaux calciques dependants du voltage (CCDV) de type L. Le TX-100 (30 nmol x [L.sup.-1] -3 [micron]mol x [L.sup.-1]) provoquait une inhibition reversible et dependante de la concentration des courants du CCDV de type L recombinant [Ca.sub.V] 1.2 et des courants du CCDV de type L sauvage, enregistres a partir de cellules vasculaires musculaires lisses et de myocytes cardiaques ainsi que de cellules β du pancreas de souris et humaines. Lors des etudes fonctionnelles, le TX-100 (165 nmol x [L.sup.-1] - 3.4 [micron]mol x [L.sup.-1]) provoquait une relaxation dependante de la concentration des arteres mesenteriques isolees de rat, stimulees prealablement a la phenylephrine ou au KCl. Cet effet etait independant de l'endothelium. Le TX-100 (1.6 [micron]mol x [L.sup.-1]) inhibait l'exocytose induite par la depolarisation chez les cellules p du pancreas de souris et humaines. Ces donnees indiquent qu'a des concentrations allant du nanomolaire au micromolaire faible, le TX-100 inhibe significativement l'activite des CCDV de type L chez plusieurs cellules, un effet qui coincide avec l'inhibition des fonctions cellulaires dependantes de l'activation de ces canaux. Cette inhibition survient a des concentrations inferieures a celles utilisees pour solubiliser les proteines, ce qui peut compromettre l'utilisation de solutions contenant du TX-100 dans les tests biologiques. [Traduit par la Redaction] Mots-cles: Triton X-100, canal calcique dependant du voltage, muscle vasculaire lisse, myocytes cardiaques, cellules β du pancreas., Introduction Triton X-100 (TX-100; [C.sub.14][H.sub.22]O[([C.sub.2][H.sub.4]O).sub.n]) is a nonionic detergent commonly used at millimolar concentrations for the purification of membrane proteins (Brutsaert et al. 1988; Mink et al. 2005; Maurice et [...]

The results of our study show that whole-cell and nuclear levels of NADPH oxidase-1 (NOX1) are similar in human vascular endothelial cells (hVECs) and smooth muscle cells (hVSMCs), but lower in human endocardial endothelial cells (hEECs). NOX2 levels were higher in hVECs and lower in hVSMCs. NOX3 levels were the same in hVECs and hVSMCs, but lower in hEECs. NOX4 levels were similar in all of the cell types. NOX4 levels were higher in hVECs than in hVSMCs. NOX5 was also present throughout the 3 cell types, including their nuclei, in the following order: hEECs > hVSMCs > hVECs. The level of basal reactive oxygen species (ROS) was highest in hVECs and lowest in hVSMCs. However, the [Ca.sup.2+] level was highest in hVSMCs and lowest in hVECs. These findings suggest that all types of NOXs exist in hEECs, hVECs, and hVSMCs, although their density and distribution are cell-type dependent. The density of the different NOXs correlated with the ROS level, but not with the [Ca.sup.2+] level. In conclusion, NOXs, including NOX3, exist in cardiovascular cells and their nuclei. The nucleus is a major source of ROS generation. The nuclear NOXs may contribute to ROS and [Ca.sup.2+] homeostasis, which may affect cell remodeling, including the formation of nuclear T-tubules in vascular diseases and aging. Key words: NOX, [Ca.sup.2+], ROS, human endocardial endothelial cells, human vascular endothelial cells, human vascular smooth muscle cells, nuclear GPCR, nuclear [Ca.sup.2+], confocal microscopy, free radicals. Nos resultats ont montre que les niveaux de NADPH oxydase-1 (NOX1) dans la cellule entiere par rapport au noyau sont similaires chez les cellules endotheliales vasculaires (hCEV) et les cellules de muscle lisse vasculaires (hCMLV) humaines, mais plus faibles chez les cellules endotheliales endocardiques (hCEE) humaines. Le niveau de NOX2 etait plus eleve chez les hCEV et plus faible chez les hCMLV. Le niveau de NOX3 etait plus eleve chez les hCEV et plus faible chez les hCEE. Les niveaux de NOX4 etaient similaires chez tous les types de cellules. Ces niveaux etaient plus eleves chez les hCEV que chez les hCMLV. NOX5 etait aussi presente dans les trois types cellulaires incluant dans leur noyau selon l'ordre suivant : hCEE > hCMLV > hCEV. Le niveau basal d'ERO le plus eleve se trouvait chez les hCEVet le plus faible chez les hCMLV. Cependant, le niveau de [Ca.sup.2+] le plus eleve se trouvait chez les hCMLV et le plus faible chez les hCEV. Ces donnees suggerent que tous les types de NOX existent chez les hCEE, les hCEV et les hCMLV, toutefois, leur densite et leur distribution dependent du type cellulaire. La densite des differentes NOX correlait avec le niveau d'ERO mais pas avec le niveau de [Ca.sup.2+]. En conclusion, les NOX, incluant NOX3 existent chez les cellules cardiovasculaires et dans leurs noyaux. Le noyau est la principale source d'ERO. Les NOX nucleaires peuvent contribuer a l'homeostasie des ERO et du [Ca.sup.2+], ce qui peut affecter le remodelage cellulaire incluant la formation des tubules T nucleaires dans les maladies vasculaires et lors du vieillissement. [Traduit par la Redaction] Mots-cles : NOX, [Ca.sup.2+], ERO, cellules endotheliales endocardiques humaines, cellules endotheliales vasculaires humaines, cellules de muscle lisse vasculaires humaines, GPCR nucleaire, [Ca.sup.2+] nucleaire, microscopie confocale, radicaux libres., Introduction In the vasculature, superoxide and other reactive oxygen species (ROS) can be derived from several sources (Lassegue and Clempus 2003; Bedard and Krause 2007; Williams and Griendling 2007; Petry [...]

The purpose of the present study was to compare the differences between the role of volume-regulated [Cl.sup.-] channels (VRCCs) in veins and arteries. We used the whole cell patch clamp and fluorescence imaging techniques to evaluate swelling-induced [Cl.sup.-] current ([I.sub.Cl,vol]) and changes in the intracellular concentrations of [Cl.sup.-] ([[Cl.sup.-]].sub.i]) induced by hypotonic solutions in rat femoral artery cells (FASMCs) and vein smooth muscle cells (FVSMCs). [I.sub.Cl,vol] and [[Cl.sup.-]].sub.i] decline induced by hypotonic solution were more prominent in FASMCs than in FVSMCs. [I.sub.Cl,vol] and the alterations in [[[Cl.sup.-]].sub.i] were gradually increased as the number of cell passages increased. However, the regulatory function of tyrosine protein phosphorylation in volume-regulated chloride movement is prominent in veins. The expression of ClC-3 was higher in FASMCs than in FVSMCs. VRCC activity is more pronounced in rat femoral arteries than in veins. VRCC activity and tyrosine protein phosphorylation regulative function increase gradually as vascular cells switch from contractile to proliferative phenotypes. Key words: volume-regulated [Cl.sup.-] channels, femoral artery and vein, smooth muscle cells, phenotypic modulation. La presente etude visait a comparer le role des canaux chlorures regules par le volume (CCRV) dans les veines et les arteres. Nous avons utilise la technique de patch clamp sur cellules totales ainsi que des techniques d'imagerie en fluorescence afin d'evaluer le courant [Cl.sup.-] induit par le gonflement cellulaire ([I.sub.Cl,vol]) et les changements de concentrations intracellulaires de [Cl.sup.-] ([[[Cl.sup.-]].sub.i]) induits par des solutions hypotoniques chez des cellules de l'artere femorale (FASMC) et de veines de muscle lisse (FVSMC) du rat. Le declin du [I.sub.Cl,vol] et des [[[Cl.sup.-]].sub.i] induit par une solution hypotonique etait plus marque dans les FASMC que dans les FVSMC. Le [I.sub.Cl,vol] et les changements de [[[Cl.sup.-]].sub.i] etaient graduellement augmentes en fonction du nombre de passages cellulaires. Cependant la fonction regulatrice de la phosphorylation sur tyrosine des proteines sur le mouvement du chlorure regule par le volume etait plus marquee dans les veines. L'expression de CIC-3 etait plus elevee dans les FASMC que dans les FVSMC. L'activite des CCRV est plus prononcee dans l'artere femorale que dans les veines chez le rat. L'activite des CCRV et la fonction regulatrice de la phosphorylation sur tyrosine des proteines augmentent graduellement lorsque les cellules vasculaires passent d'un phenotype contractile a un phenotype proliferatif. Mots-cles : canaux chlorure regules par le volume, veine et artere femorales, cellules de muscle lisse vasculaire, modulation phenotypique. [Traduit par la Redaction], Introduction Arteries and veins are different types of vessels, and have different structures and functions. Usually, arteries transfer blood from the heart to tissues and regulate blood pressure. Veins, as [...]

During lung development, parabronchial SMC (PSMC) progenitors in the distal mesenchyme secrete fibro-blast growth factor 10 (Fgf10), which acts on distal epithelial progenitors to promote their proliferation. β-catenin signaling within [...]

We present a systematic quantitative analysis of power-law force relaxation and investigate logarithmic superposition of force response in relaxed porcine airway smooth muscle (ASM) strips in vitro. The term logarithmic superposition describes linear superposition on a logarithmic scale, which is equivalent to multiplication on a linear scale. Additionally, we examine whether the dynamic response of contracted and relaxed muscles is dominated by cross-bridge cycling or passive dynamics. The study shows the following main findings. For relaxed ASM, the force response to length steps of varying amplitude (0.25-4% of reference length, both lengthening and shortening) are well-fitted with power-law functions over several decades of time ([10.sup.-2] to [10.sup.3] s), and the force response after consecutive length changes is more accurately fitted assuming logarithmic superposition rather than linear superposition. Furthermore, for sinusoidal length oscillations in contracted and relaxed muscles, increasing the oscillation amplitude induces greater hysteresivity and asymmetry of force-length relationships, whereas increasing the frequency dampens hysteresivity but increases asymmetry. We conclude that logarithmic superposition is an important feature of relaxed ASM, which may facilitate a more accurate prediction of force responses in the continuous dynamic environment of the respiratory system. In addition, the single power-function response to length changes shows that the dynamics of cross-bridge cycling can be ignored in relaxed muscle. The similarity in response between relaxed and contracted states implies that the investigated passive dynamics play an important role in both states and should be taken into account. smooth muscle dynamics; power-law force relaxation doi: 10.1152/ajplung.00023.2010.

Stretch sensitivity of [Ca.sup.2+]-activated large-conductance [K.sup.+] channels ([BK.sub.Ca]) has been observed in a variety of cell types and considered to be a potential mechanism in mechanoelectric transduction (MET). Mechanical stress is a major stimulator for the smooth muscle in the gastrointestinal (GI) tract. However, much about the role and mechanism of MET in GI smooth muscles remains unknown. The [BK.sub.Ca] shows a functional diversity due to intensive Slo I alternative splicing and different [alpha]/[beta]-subunit assembly in various cells. The stress-regulated exon (STREX) insert is suggested to be an indispensable domain for the mechanosensitivity of [BK.sub.Ca]. The purpose of this study was to determine whether the [BK.sub.Ca] in colonic myocytes of the adult mouse is sensitive to mechanical stimulation and whether the STREX insert is a crucial segment for the [BK.sub.Ca] mechanosensitivity. The [alpha]- and [beta]1-subunit mRNAs and the [alpha]-subunit protein of the [BK.sub.Ca] channels were detected in the colonic muscularis. We found that the [BK.sub.Ca] STREX-lacking variant was abundantly expressed in the smooth muscle, whereas the STREX variant was not detectable. We demonstrated that the STREX-lacking [BK.sub.Ca] channels were also sensitive to membrane stretch. We suggest that in addition to the STREX domain, there are other additional structures in the channel responsible for mechanically coupling with the cell membrane. calcium-activated large-conductance potassium channels; Slo I alternative splicing; stretch; colon; patch clamp doi: 10.1152/ajpgi.00268.2010.

The wall of hollow organs of vertebrates is a unique structure able to generate active tension and maintain a nearly constant passive stiffness over a large volume range. These properties are predominantly attributable to the smooth muscle cells that line the organ wall. Although smooth muscle is known to possess plasticity (i.e., the ability to adapt to large changes in cell length through structural remodeling of contractile apparatus and cytoskeleton), the detailed structural basis for the plasticity is largely unknown. Dense bodies, one of the most prominent structures in smooth muscle cells, have been regarded as the anchoring sites for actin filaments, similar to the Z-disks in striated muscle. Here, we show that the dense bodies and intermediate filaments formed cable-like structures inside airway smooth muscle cells and were able to adjust the cable length according to cell length and tension. Stretching the muscle cell bundle in the relaxed state caused the cables to straighten, indicating that these intracellular structures were connected to the extracellular matrix and could support passive tension. These plastic structures may be responsible for the ability of smooth muscle to maintain a nearly constant tensile stiffness over a large length range. The finding suggests that the structural plasticity of hollow organs may originate from the dense-body cables within the smooth muscle cells. muscle mechanics; stiffness; ultrastructure; three-dimensional electron microscopy doi: 10.1152/ajplung.00087.2010.