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Liu Y, LeBoeuf B, Garcia LR. G alpha(q)-coupled muscarinic acetylcholine receptors enhance nicotinic acetylcholine receptor signaling in Caenorhabditis elegans mating behavior. J Neurosci 2007; 27:1411-21. [PMID: 17287516 PMCID: PMC6673585 DOI: 10.1523/jneurosci.4320-06.2007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 11/28/2006] [Accepted: 12/12/2006] [Indexed: 11/21/2022] Open
Abstract
In this study, we address why metabotropic and ionotropic cholinergic signaling pathways are used to facilitate motor behaviors. We demonstrate that a G alpha(q)-coupled muscarinic acetylcholine receptor (mAChR) signaling pathway enhances nicotinic acetylcholine receptor (nAChR) signaling to facilitate the insertion of the Caenorhabditis elegans male copulatory spicules into the hermaphrodite during mating. Previous studies showed that ACh (acetylcholine) activates nAChRs on the spicule protractor muscles to induce the attached spicules to extend from the tail. Using the mAChR agonist Oxo M (oxotremorine M), we identified a GAR-3(mAChR)-G alpha(q) pathway that promotes protractor muscle contraction by upregulating nAChR signaling before mating. GAR-3(mAChR) is expressed in the protractor muscles and in the spicule-associated SPC and PCB cholinergic neurons. However, ablation of these neurons or impairing cholinergic transmission reduces drug-induced spicule protraction, suggesting that drug-stimulated neurons directly activate muscle contraction. Behavioral analysis of gar-3 mutants indicates that, in wild-type males, GAR-3(mAChR) expression in the SPC and PCB neurons is required for the male to sustain rhythmic spicule muscle contractions during attempts to breach the vulva. We propose that the GAR-3(mAChR)/G alpha(q) pathway sensitizes the spicule neurons and muscles before and during mating so that the male can respond to hermaphrodite vulva efficiently.
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MESH Headings
- Acetylcholine/physiology
- Animals
- Animals, Genetically Modified
- Caenorhabditis elegans/genetics
- Caenorhabditis elegans/physiology
- Caenorhabditis elegans Proteins/drug effects
- Caenorhabditis elegans Proteins/genetics
- Caenorhabditis elegans Proteins/physiology
- Carrier Proteins/genetics
- Carrier Proteins/physiology
- Disorders of Sex Development
- GTP-Binding Protein alpha Subunits, Gq-G11/deficiency
- GTP-Binding Protein alpha Subunits, Gq-G11/genetics
- GTP-Binding Protein alpha Subunits, Gq-G11/physiology
- Genitalia/innervation
- Genitalia/physiology
- Isoenzymes/deficiency
- Isoenzymes/genetics
- Isoenzymes/physiology
- Levamisole/pharmacology
- Muscarinic Agonists/pharmacology
- Muscle Contraction/physiology
- Mutation, Missense
- Neurons/physiology
- Oxotremorine/pharmacology
- Periodicity
- Phospholipase C beta
- Potassium Channels/deficiency
- Potassium Channels/genetics
- Potassium Channels/physiology
- Receptors, Muscarinic/deficiency
- Receptors, Muscarinic/genetics
- Receptors, Muscarinic/physiology
- Receptors, Nicotinic/physiology
- Recombinant Fusion Proteins/physiology
- Ryanodine Receptor Calcium Release Channel/drug effects
- Sexual Behavior, Animal/physiology
- Signal Transduction/physiology
- Syntaxin 1/deficiency
- Syntaxin 1/genetics
- Syntaxin 1/physiology
- Type C Phospholipases/deficiency
- Type C Phospholipases/genetics
- Type C Phospholipases/physiology
- Vesicular Acetylcholine Transport Proteins/deficiency
- Vesicular Acetylcholine Transport Proteins/genetics
- Vesicular Acetylcholine Transport Proteins/physiology
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Affiliation(s)
- Yishi Liu
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258
| | - Brigitte LeBoeuf
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258
| | - L. René Garcia
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258
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Patel CA, Rattan S. Spontaneously tonic smooth muscle has characteristically higher levels of RhoA/ROK compared with the phasic smooth muscle. Am J Physiol Gastrointest Liver Physiol 2006; 291:G830-7. [PMID: 16763289 DOI: 10.1152/ajpgi.00130.2006] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The internal anal sphincter (IAS) tone is important for the rectoanal continence. The RhoA/Rho kinase (ROK) pathway has been associated with the agonist-induced sustained contraction of the smooth muscle, but its role in the spontaneously tonic smooth muscle is not known. Present studies compared expression of different components of the RhoA/ROK pathway between the IAS (a truly tonic SM), the rectal smooth muscle (RSM) (a mixture of phasic and tonic), and anococcygeus smooth muscle (ASM) (a purely phasic SM) of rat. RT-PCR and Western blot analyses were performed to determine RhoA, ROCK-II, CPI-17, MYPT1, and myosin light-chain 20 (MLC20). Phosphorylated CPI-17 at threonine-38 residue (p(Thr38)-CPI-17), MYPT1 at threonine-696 residue (p(Thr696)-MYPT1), and MLC20 at threonine-18/serine-19 residues (p(Thr18/Ser19)-MLC20) were also determined in the basal state and after pretreatment with the ROK inhibitor Y 27632. In addition, we compared the effect of Y 27632 on the basal isometric tension and ROK activity in the IAS vs. the RSM. Our data show the highest levels of RhoA, ROCK-II, CPI-17, MLC20, and of phospho-MYPT1, -CPI-17, and -MLC20 in the IAS followed by in the RSM and ASM. Conversely, MYPT1 levels were lowest in the IAS and highest in the ASM. In the IAS, Y 27632 caused a concentration-dependent decrease in the basal tone, levels of phospho-MYPT1, -CPI-17, and -MLC20, and ROK activity. We conclude that RhoA/ROK plays a critical role in the basal tone in the IAS by the inhibition of MLC phosphatase via the phosphorylation of MYPT1 and CPI-17.
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Affiliation(s)
- Chirag A Patel
- Department of Medicine, Division of Gastroenterology and Hepatology, Thomas Jefferson University, 1025 Walnut St., Rm. 901, Philadelphia, PA 19107, USA
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53
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Sarna SK. Molecular, functional, and pharmacological targets for the development of gut promotility drugs. Am J Physiol Gastrointest Liver Physiol 2006; 291:G545-55. [PMID: 16565417 DOI: 10.1152/ajpgi.00122.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The science of gastrointestinal motility has made phenomenal advances during the last fifty years. Yet, there is a paucity of effective promotility drugs to treat functional bowel disorders that affect 10-29% of the U.S. population. A part of the reason for the lack of effective drugs is our limited understanding of the etiology of these diseases. In the absence of this information, mostly an ad hoc approach has been used to develop the currently available drugs, which are modestly effective or effective in only a subset of the patients with functional bowel disorders. This review discusses a grounds-up approach for development of the next generation of promotility drugs. The approach is based on our current understanding of 1) the different types of contractions that produce overall motility function of mixing and orderly net distal propulsion in major gut organs, 2) the regulatory mechanisms of these contractions, 3) which receptors and intracellular signaling molecules could be targeted to stimulate specific types of contractions to accelerate or retard transit, and 4) the strengths and limitations of animal models and experimental approaches that could screen potential promotility drugs for their efficacy in human gut propulsion in functional bowel disorders.
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Affiliation(s)
- Sushil K Sarna
- Division of Gastroenterology, Dept. of Internal Medicine, University of Texas Medical Branch at Galveston, 9.138 Medical Research Bldg., Galveston, TX 77555-1064, USA.
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Hernández M, Barahona MV, Recio P, Benedito S, Martínez AC, Rivera L, García-Sacristán A, Prieto D, Orensanz LM. Neuronal and smooth muscle receptors involved in the PACAP- and VIP-induced relaxations of the pig urinary bladder neck. Br J Pharmacol 2006; 149:100-9. [PMID: 16847435 PMCID: PMC1629402 DOI: 10.1038/sj.bjp.0706832] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE As pituitary adenylate cyclase-activating polypeptide 38 (PACAP 38)- and vasoactive intestinal peptide (VIP) are widely distributed in the urinary tract, the current study investigated the receptors and mechanisms involved in relaxations induced by these peptides in the pig bladder neck. EXPERIMENTAL APPROACH Urothelium-denuded strips were suspended in organ baths for isometric force recordings and the relaxations to VIP and PACAP analogues were investigated. KEY RESULTS VIP, PACAP 38, PACAP 27 and [Ala(11,22,28)]-VIP produced similar relaxations. Inhibition of neuronal voltage-gated Ca(2+) channels reduced relaxations to PACAP 38 and increased those induced by VIP. Blockade of capsaicin-sensitive primary afferents (CSPA), nitric oxide (NO)-synthase or guanylate cyclase reduced the PACAP 38 relaxations but failed to modify the VIP responses. Inhibition of VIP/PACAP receptors and of voltage-gated K(+) channels reduced PACAP 38 and VIP relaxations, which were not modified by the K(+) channel blockers iberiotoxin, charybdotoxin, apamin or glibenclamide. The phosphodiesterase 4 inhibitor rolipram and the adenylate cyclase activator forskolin produced potent relaxations. Blockade of protein kinase A (PKA) reduced PACAP 38- and VIP-induced relaxations. CONCLUSIONS AND IMPLICATIONS PACAP 38 and VIP relax the pig urinary bladder neck through muscle VPAC(2) receptors linked to the cAMP-PKA pathway and involve activation of voltage-gated K(+) channels. Facilitatory PAC(1) receptors located at CSPA and coupled to NO release, and inhibitory VPAC receptors at motor endings are also involved in the relaxations to PACAP 38 and VIP, respectively. VIP/PACAP receptor antagonists could be useful in the therapy of urinary incontinence produced by intrinsic sphincter deficiency.
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Affiliation(s)
- M Hernández
- Departamento de Fisiología, Fisiología Animal, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain.
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55
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Xiao ZL, Cao W, Biancani P, Behar J. Nongenomic effects of progesterone on the contraction of muscle cells from the guinea pig colon. Am J Physiol Gastrointest Liver Physiol 2006; 290:G1008-15. [PMID: 16399876 DOI: 10.1152/ajpgi.00382.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Progesterone (PG) affects muscle cells by genomic mechanisms through nuclear receptors and by nongenomic mechanisms through unidentified pathways. This study aimed to determine the pathways mediating its nongenomic actions. Experiments were performed in dissociated muscle cells from guinea pig colons. Nongenomic actions were defined as those occurring within 10 min of PG exposure. PG blocked the contraction to CCK-8 and NKA (10(-7) M) but did not impair ACh (10(-7) M) and KCl (2.5 x 10(-2) M)-induced contraction. Both CCK-8 and NKA contract muscle cells by releasing calcium from intracellular stores, whereas ACh and KCl can utilize extracellular calcium. PG also blocked the contraction induced by inositol 1,4,5-trisphosphate, thapsigargin, and caffeine, agents that contract muscle cells by releasing calcium from storage sites. The nongenomic actions of PG were transient because they were absent 1 h after the first PG dose, remaining unresponsive after a second PG dose was administered. Furthermore, PG had no effect on the contraction induced by CCK-8 and thapsigargin in muscle cells from animals pretreated with daily intramuscular PG for 4 days. Cytosolic incorporation experiments of [(3)H]PG showed that pretreatment with unlabeled PG significantly reduced the radiolabeled PG incorporation in the cytosol. We conclude that the nongenomic actions of PG on colonic muscle cells transiently blocked calcium release from storage sites, and this response became rapidly desensitized. This effect does not appear to be specific to PG because other steroid hormones such as aldosterone and testosterone can also induce it.
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Affiliation(s)
- Zuo-Liang Xiao
- Division of Gastroenterology, APC 406, Rhode Island Hospital/Brown University Medical School, 593 Eddy St., Providence, RI 02903, USA.
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56
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Zheyu C, Qinghui QI, Lixin L, Tao MA, Xu J, Zhang L, Lunan Y. Effects of emodin on Ca2+ signal transduction of smooth muscle cells in multiple organ dysfunction syndrome. J Surg Res 2005; 131:80-5. [PMID: 16271368 DOI: 10.1016/j.jss.2005.08.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 08/25/2005] [Accepted: 08/30/2005] [Indexed: 02/05/2023]
Abstract
We have made several reports on the signal transduction mechanism that emodin enhance the calcium concentrations of smooth muscle cells (SMCs) in the physiological condition by inositol [1, 4, 5]-friphosphate (IP3). The observation that IP3 concentrations in SMCs were decreased in multiple organ dysfunction syndrome (MODS) prompted us to ask whether emodin can activate SMCs to contract by way of elevating [Ca2+] and thus modulating the critical Ca2+ signal transduction pathways involved in the contraction of the SMCs in the pathological setting of MODS. To test this hypothesis, we used the rat model of MODS to explore the potential roles of emodin in Ca2+ signal transduction in the SMCs of colon in rats. ML-7 [an inhibitor of myosin light-chain kinase (MLCK)] and Calphostin C [an inhibitor of protein kinase C (PKC)] were used to observe the influence of emodin on the muscle strips and SMCs in rats after MODS. Nifedipine (an antagonist of voltage-gated Ca2+ channel), EGTA (removal of extracellular Ca2+), heparine (a specific IP3 receptor antagonist), and ryanodine were used to probe the potential mechanisms involved in emodin-mediated elevation of the global cytoplasmic Ca2+ in SMCs of colon in the rats after MODS. Our results show that emodin is capable of contract the smooth muscles of colon in rats after MODS by MLCK increasing [Ca2+] of SMCs, and by PKC enhancing the calcium sensitivity of SMCs. The mechanism by which emodin triggers elevated [Ca2+] of smooth muscles of colon in rats after MODS is likely to operate through IP3 and RyR receptors in the sarcoplasm. It is hoped that deeper insights into how emodin modulates the critical calcium signaling in SMCs might lead to the potential development of emodin in the treatment of MODS.
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Affiliation(s)
- Chen Zheyu
- Department of General Surgery of West China Hospital, Sichuan University, Chengdu, China
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57
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Abstract
Previous studies performed at our laboratory have shown that agonist-induced contraction of smooth muscle is associated with translocation of protein kinase C (PKC)-α and RhoA to the membrane and that this interaction is due to a direct protein-protein interaction. To determine the domains of PKC-α involved in direct interaction with RhoA, His-tagged PKC-α proteins of individual domains and different combinations of PKC-α domains were used to perform in vitro binding assays with the fusion protein glutathione- S-transferase (GST)-RhoA. Coimmunoprecipitation was also performed using smooth muscle cells transfected with truncated forms of PKC-α in this study. The data indicate that RhoA directly bound to full-length PKC-α, both in vitro (82.57 ± 15.26% above control) and in transfected cells. RhoA bound in vitro to the C1 domain of PKC-α [PKC-α (C1)] (70.48 ± 20.78% above control), PKC-α (C2) (72.26 ± 29.96% above control), and PKC-α (C4) (90.58 ± 26.79% above control), but not to PKC-α (C3) (0.64 ± 5.18% above control). RhoA bound in vitro and in transfected cells to truncated forms of PKC-α, PKC-α (C2, C3, and C4), and PKC-α (C3 and C4) (94.09 ± 12.13% and 85.10 ± 16.16% above control, respectively), but not to PKC-α (C1, C2, and C3) or to PKC-α (C2 and C3) (0.47 ± 1.26% and 7.45 ± 10.76% above control, respectively). RhoA bound to PKC-α (C1 and C2) (60.78 ± 13.78% above control) only in vitro, but not in transfected cells, and PKC-α (C2, C3, and C4) and PKC-α (C3 and C4) bound well to RhoA. These data suggest that RhoA bound to fragments that may mimic the active form of PKC-α. The studies using cells transfected with truncated forms of PKC-α indicate that PKC-α (C1 and C2), PKC-α (C1, C2, and C3), and PKC-α (C2 and C3) did not associate with RhoA. Only full-length PKC-α, PKC-α (C2, C3, and C4), and PKC-α (C3 and C4) associated with RhoA. The association increased upon stimulation with acetylcholine. These results suggest that the functional association of PKC-α with RhoA may require the C4 domain.
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Affiliation(s)
- Haiyan Pang
- Department of Pediatrics, University of Michigan Medical Center, 1150 W. Medical Center Drive, MSRB I, Room A520, Ann Arbor, Michigan 48109-0658, USA
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58
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Thorneloe KS, Nelson MT. Ion channels in smooth muscle: regulators of intracellular calcium and contractility. Can J Physiol Pharmacol 2005; 83:215-42. [PMID: 15870837 DOI: 10.1139/y05-016] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Smooth muscle (SM) is essential to all aspects of human physiology and, therefore, key to the maintenance of life. Ion channels expressed within SM cells regulate the membrane potential, intracellular Ca2+ concentration, and contractility of SM. Excitatory ion channels function to depolarize the membrane potential. These include nonselective cation channels that allow Na+ and Ca2+ to permeate into SM cells. The nonselective cation channel family includes tonically active channels (Icat), as well as channels activated by agonists, pressure-stretch, and intracellular Ca2+ store depletion. Cl--selective channels, activated by intracellular Ca2+ or stretch, also mediate SM depolarization. Plasma membrane depolarization in SM activates voltage-dependent Ca2+ channels that demonstrate a high Ca2+ selectivity and provide influx of contractile Ca2+. Ca2+ is also released from SM intracellular Ca2+ stores of the sarcoplasmic reticulum (SR) through ryanodine and inositol trisphosphate receptor Ca2+ channels. This is part of a negative feedback mechanism limiting contraction that occurs by the Ca2+-dependent activation of large-conductance K+ channels, which hyper polarize the plasma membrane. Unlike the well-defined contractile role of SR-released Ca2+ in skeletal and cardiac muscle, the literature suggests that in SM Ca2+ released from the SR functions to limit contractility. Depolarization-activated K+ chan nels, ATP-sensitive K+ channels, and inward rectifier K+ channels also hyperpolarize SM, favouring relaxation. The expression pattern, density, and biophysical properties of ion channels vary among SM types and are key determinants of electrical activity, contractility, and SM function.
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Affiliation(s)
- Kevin S Thorneloe
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington 05405, USA.
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59
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Amira S, Mulè F. Effects of sodium fluoride on the mechanical activity in mouse gastric preparations. Can J Physiol Pharmacol 2005; 83:367-73. [PMID: 15877111 DOI: 10.1139/y05-021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The aim of the present study was to investigate the responses induced by sodium fluoride (NaF) on gastric mechanical activity, using mouse whole-stomach preparations. The mechanical activity was recorded in vitro as changes of intraluminal pressure. In most of the preparations, NaF induced a tetrodotoxin-insensitive biphasic effect characterized by early relaxation followed by slowly developing contractile response. The contraction was dependent on the concentration of NaF, whereas the relaxation was observed at only 10-30 mmol/L NaF. The contractile effect was significantly reduced by nifedipine (an L-type Ca(2+) channel blocker), ryanodine or ruthenium red (inhibitors of Ca(2+) release from sarcoplasmic reticulum), and GF109203X (a protein kinase C inhibitor). Moreover, it was abolished by neomycin (an inhibitor of phospholipase C) and potentiated by SQ22536 (an inhibitor of adenylyl cyclase). All the drugs significantly increased the relaxation, except SQ22536, which abolished it. The present results suggest that NaF causes a complex mechanical response in the whole-stomach, which might explain gastric discomfort after fluoride ingestion. The relaxation appears owing to production of cAMP, while the contractile effects imply activation of phospholipase C, protein kinase C, influx of Ca(2+), and release of Ca(2+) from ryanodine-sensitive intracellular store.
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Affiliation(s)
- Smain Amira
- Department of Biology, Faculty of Sciences, Ferhat Abbas University, Setif, Algeria
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Wrzos HF, Tandon T, Ouyang A. Mechanisms mediating cholinergic antral circular smooth muscle contraction in rats. World J Gastroenterol 2004; 10:3292-8. [PMID: 15484303 PMCID: PMC4572298 DOI: 10.3748/wjg.v10.i22.3292] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIM: To investigate the pathway (s) mediating rat antral circular smooth muscle contractile responses to the cholinomimetic agent, bethanechol and the subtypes of muscarinic receptors mediating the cholinergic contraction.
METHODS: Circular smooth muscle strips from the antrum of Sprague-Dawley rats were mounted in muscle baths in Krebs buffer. Isometric tension was recorded. Cumulative concentration-response curves were obtained for (+)-cis-dioxolane (cD), a nonspecific muscarinic agonist, at 10-8-10-4 mol/L, in the presence of tetrodotoxin (TTX, 10-7 mol/L). Results were normalized to cross sectional area. A repeat concentration-response curve was obtained after incubation of the muscle for 90 min with antagonists for M1 (pirenzepine), M2 (methoctramine) and M3 (darifenacin) muscarinic receptor subtypes. The sensitivity to PTX was tested by the ip injection of 100 mg/kg of PTX 5 d before the experiment. The antral circular smooth muscles were removed from PTX-treated and non-treated rats as strips and dispersed smooth muscle cells to identify whether PTX-linked pathway mediated the contractility to bethanechol.
RESULTS: A dose-dependent contractile response observed with bethanechol, was not affected by TTX. The pretreatment of rats with pertussis toxin decreased the contraction induced by bethanechol. Lack of calcium as well as the presence of the L-type calcium channel blocker, nifedipine, also inhibited the cholinergic contraction, with a reduction in response from 2.5 ± 0.4 g/mm2 to 1.2 ± 0.4 g/mm2 (P < 0.05). The dose-response curves were shifted to the right by muscarinic antagonists in the following order of affinity: darifenacin (M3) > methocramine (M2) > pirenzepine (M1).
CONCLUSION: The muscarinic receptors-dependent contraction of rat antral circular smooth muscles was linked to the signal transduction pathway(s) involving pertussis-toxin sensitive GTP-binding proteins and to extracellular calcium via L-type voltage gated calcium channels. The presence of the residual contractile response after the treatment with nifedipine, suggests that an additional pathway could mediate the cholinergic contraction. The involvement of more than one muscarinic receptor (functionally predominant type 3 over type 2) also suggests more than one pathway mediating the cholinergic contraction in rat antrum.
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MESH Headings
- Anesthetics, Local/pharmacology
- Animals
- Benzofurans/pharmacology
- Bethanechol/pharmacology
- Calcium/metabolism
- Calcium Channel Blockers/pharmacology
- Cholinergic Agonists/pharmacology
- Dose-Response Relationship, Drug
- GTP-Binding Proteins/metabolism
- In Vitro Techniques
- Male
- Muscarinic Antagonists/pharmacology
- Muscle Contraction/drug effects
- Muscle Contraction/physiology
- Muscle, Smooth/physiology
- Nifedipine/pharmacology
- Pertussis Toxin/pharmacology
- Pirenzepine/pharmacology
- Pyloric Antrum/physiology
- Pyrrolidines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor, Muscarinic M1/antagonists & inhibitors
- Receptor, Muscarinic M1/metabolism
- Receptor, Muscarinic M2/antagonists & inhibitors
- Receptor, Muscarinic M2/metabolism
- Receptor, Muscarinic M3/antagonists & inhibitors
- Receptor, Muscarinic M3/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Tetrodotoxin/pharmacology
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Affiliation(s)
- Helena-F Wrzos
- Division of Gastroenterology and Hepatology, Department of Medicine, College of Medicine, Pennsylvania State University, PO Box 850, Hershey, PA 17033, USA
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61
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Sakai Y, Nobe K, Maruyama Y, Momose K, Homma I. A traditional herbal medicine, rikkunshi-to (TJ-43), prevents intracellular signaling disorders in gastric smooth muscle of diabetic rats. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2004; 32:245-56. [PMID: 15315262 DOI: 10.1142/s0192415x04001904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Prevention of diabetic gastrointestinal dysfunction is of utmost importance. The present study demonstrated that diacylglycerol kinase (DGK) activity in diabetic gastric smooth muscle in the resting state was approximately 3.5-fold greater than that in controls. However, oral administration of TJ-43 (1% of food intake) or subcutaneous insulin injection (12 units/kg/day) in streptozotocin-induced diabetic rats (DM) for 2 weeks prevented DGK abnormalities based on the control level. Increased DGK activity in the resting state of DM was inhibited significantly by R59022, neomycin or staurosporine; in contrast, these drugs did not affect DGK activity in controls, insulin-treated DM or TJ-43-treated DM. In controls, the endogenous phosphatidic acid (PA) level was inhibited significantly by R59022 or neomycin but not affected by staurosporine. On the other hand, these three drugs significantly inhibited endogenous PA levels in DM, and neomycin significantly inhibited endogenous PA levels in insulin-treated and TJ-43-treated DM. This suggests that TJ-43 could prevent alteration of DGK activity and PA formation without reduction of blood glucose levels. Moreover, these effects were greater than those of insulin treatment. Results suggested that TJ-43 treatment influenced the hyperreactivity of DGK and DAG formation via phospholipase C activity. In conclusion, TJ-43 can be recommended with respect to enhancement of the quality of life in patients displaying diabetic gastrointestinal complications.
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Affiliation(s)
- Yasushi Sakai
- Division of Physiology, Department of Occupational Therapy, School of Nursing and Rehabilitation Sciences, Showa University, Yokohama 226, Japan.
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62
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Tattoli I, Corleto VD, Taffuri M, Campanini N, Rindi G, Caprilli R, Delle Fave G, Severi C. Optimisation of isolation of richly pure and homogeneous primary human colonic smooth muscle cells. Dig Liver Dis 2004; 36:735-43. [PMID: 15571004 DOI: 10.1016/j.dld.2004.06.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Inherent properties of gastrointestinal smooth muscle can be assessed using isolated cell suspensions. Currently available isolation techniques, based on short 2-h enzymatic digestion, however, present the disadvantage of low cellular yield with brief viability. These features are an important limiting factor especially in studies in humans in which tissue may not be available daily and mixing of samples is not recommended. AIMS To optimise the isolation procedure of cells from human colon to obtain a richly pure primary smooth muscle cell preparation. METHODS Slices of circular muscle layer, obtained from surgical specimens of human colon, were incubated overnight in Dulbecco's modified eagle's medium supplemented with antibiotics, foetal bovine serum, an ATP-regenerating system and collagenase. On the following day, digested muscle strips were suspended in HEPES buffer, and spontaneously dissociated smooth muscle cells were harvested and used either immediately or maintained in suspension for up to 72 h. Cell yield, purity, viability, contractile responses, associated intracellular calcium signals and RNA and protein extraction were evaluated and compared to cell suspensions obtained with the current short digestion protocol. RESULTS AND CONCLUSION The overnight isolation protocol offers the advantage of obtaining a pure, homogeneous, long-life viable cell suspension that maintains a fully differentiated smooth muscle phenotype unchanged for at least 72 h and that allows multiple functional/biochemical studies and efficient RNA extraction from a single human specimen.
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Affiliation(s)
- I Tattoli
- Department of Clinical Sciences, University La Sapienza, Viale del Policlinico, 00161 Rome, Italy
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63
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Ma T, Qi QH, Xu J, Dong ZL, Yang WX. Signal pathways involved in emodin-induced contraction of smooth muscle cells from rat colon. World J Gastroenterol 2004; 10:1476-9. [PMID: 15133857 PMCID: PMC4656288 DOI: 10.3748/wjg.v10.i10.1476] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIM: To investigate the effects induced by emodin on single smooth muscle cells from rat colon in vitro, and to determine the signal pathways involved.
METHODS: Cells were isolated from the muscle layers of Wistar rat colon by enzymatic digestion. Cell length was measured by computerized image micrometry. Intracellular Ca2+ ([Ca2+]i) signals were studied using the fluorescent Ca2+ indicator fluo-3 and confocal microscopy. PKCα distribution at rest state or after stimulation was measured with immunofluorescence confocal microscopy.
RESULTS: (1) Emodin dose-dependently caused colonic smooth muscle cells contraction; (2) emodin induced an increase in intracellular Ca2+ concentration; (3) the contractile responses induced by emodin were respectively inhibited by preincubation of the cells with ML-7 (an inhibitor of MLCK) and calphostin C (an inhibitor of PKC); and (4) Incubation of cells with emodin caused translocation of PKCα from cytosolic area to the membrane.
CONCLUSION: Emodin has a direct contractile effect on colonic smooth muscle cell. This signal cascade induced by emodin is initiated by increased [Ca2+]i and PKCα translocation, which in turn lead to the activation of MLCK and the suppression of MLCP. Both of them contribute to the emodin-induced contraction.
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Affiliation(s)
- Tao Ma
- Department of Surgery, General Hospital of Tianjin Medical University, Tianjin 300052, China.
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64
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Shin CY, La HO, Lee YP, Lee DW, Kim DS, Huh IH, Sohn UD. The alteration of intracellular signaling on the smooth muscle cells contraction in cat esophagitis. Life Sci 2004; 74:2199-211. [PMID: 14969721 DOI: 10.1016/j.lfs.2003.09.057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2003] [Accepted: 09/30/2003] [Indexed: 11/13/2022]
Abstract
We investigated the alteration of signal transduction after acute esophagitis in cat lower esophageal sphincter (LES). Acute esophagitis (AE) was induced by perfusion with 0.1N HCl at a rate of 1 ml/min for 45 min over three consecutive days. Acetylcholine (ACh)-induced contraction was inhibited by M3>> M1 or M2 antagonists in normal LES. In AE, inhibition by M2 antagonists increased significantly, so that contraction was inhibited by M3> M2> M1 antagonists and the expression of M2 and M3 receptors were increased when compared to normal LES. In normal cells, ACh-induced contractions were antagonized by antibody against G(q/11) and the phosphatidylinositol-specific phospholipase C (PI-PLC) antagonist, U73122. The phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor, D609, or the phospholipase D inhibitor, propranolol had no effects on contraction in normal LES. However, in AE, G(q/11), and G(i3) antibodies reduced ACh-induced contraction and U73122, propranolol and D609 also reduced the contraction. In AE, we found that the expressions of G protein subtypes were increased but the expression of PLCbeta1, and PLCgamma1 were decreased when compared to normal LES. In conclusion, experimental esophagitis may alter the signal transduction by ACh in LES. ACh-induced contraction is mediated by M3 receptor, G(q/11) and PI-PLC in normal LES. However, in AE, the contractions are mediated by M2, M3 receptor, G(q/11) and G(i3). PC-PLC and PLD as PI-PLC are also involved in ACh-induced cell contraction in AE.
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Affiliation(s)
- Chang Yell Shin
- Department of Pharmacology, College of Pharmacy, Chung Ang University, Seoul 156-756, South Korea
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65
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Hernández M, Barahona MV, Recio P, Rivera L, Benedito S, Martínez AC, García-Sacristán A, Orensanz LM, Prieto D. Heterogeneity of neuronal and smooth muscle receptors involved in the VIP- and PACAP-induced relaxations of the pig intravesical ureter. Br J Pharmacol 2003; 141:123-31. [PMID: 14662737 PMCID: PMC1574168 DOI: 10.1038/sj.bjp.0705582] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The mechanisms and receptors involved in the vasoactive intestinal peptide (VIP)- and pituitary adenylate cyclase-activating polypeptide (PACAP)-induced relaxations of the pig intravesical ureter were investigated. 2. VIP, PACAP 38 and PACAP 27 concentration-dependently relaxed U46619-contracted ureteral strips with a similar potency. [Ala(11,22,28)]-VIP, a VPAC(1) agonist, showed inconsistent relaxations. 3. The neuronal voltage-gated Ca(2+) channel inhibitor, omega-conotoxin GVIA (omega-CgTX, 1 microm), reduced the VIP relaxations. Urothelium removal or blockade of capsaicin-sensitive primary afferents, nitric oxide (NO) synthase and guanylate cyclase with capsaicin (10 microm), N(G)-nitro-l-arginine (l-NOARG, 100 microm) and 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 5 microm), respectively, did not change the VIP relaxations. However, the PACAP 38 relaxations were reduced by omega-CgTX, capsaicin, l-NOARG and ODQ. 4. The VIP and VIP/PACAP receptor antagonists, [Lys(1), Pro(2,5), Arg(3,4), Tyr(6)]-VIP (1 microm) and PACAP (6-38) (0.4 microm), inhibited VIP and VIP and PACAP 38, respectively, relaxations. 5. The nonselective and large-conductance Ca(2)-activated K(+) channel blockers, tetraethylammonium (3 mm) and charybdotoxin (0.1 microm), respectively, and neuropeptide Y (0.1 microm) did not modify the VIP relaxations. The small-conductance Ca(2)-activated K(+) channel blocker apamin (1 microm) did not change the PACAP 27 relaxations. 6. The cAMP-dependent protein kinase A (PKA) blocker, 8-(4-chlorophenylthio)adenosine-3',5'-cyclic monophosphorothioate (Rp-8-CPT-cAMPS, 100 microm), reduced VIP relaxations. The phosphodiesterase 4 inhibitor rolipram and the adenylate cyclase activator forskolin relaxed ureteral preparations. The rolipram relaxations were reduced by Rp-8-CPT-cAMPS. Forskolin (30 nm) evoked a potentiation of VIP relaxations. 7. These results suggest that VIP and PACAP relax the pig ureter through smooth muscle receptors, probably of the VPAC(2) subtype, linked to a cAMP-PKA pathway. Neuronal VPAC receptors localized at motor nerves and PAC(1) receptors placed at sensory nerves and coupled to NO release, seem also to be involved in the VIP and PACAP 38 relaxations.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Apamin/pharmacology
- Capsaicin/pharmacology
- Charybdotoxin/administration & dosage
- Colforsin/pharmacology
- Cyclic AMP/analogs & derivatives
- Cyclic AMP/pharmacology
- Dose-Response Relationship, Drug
- Drug Synergism
- Female
- Guanylate Cyclase/pharmacology
- Male
- Muscle, Smooth/drug effects
- Muscle, Smooth/physiology
- NG-Nitroarginine Methyl Ester/pharmacology
- Neurons, Afferent/drug effects
- Neurons, Afferent/physiology
- Neuropeptide Y/physiology
- Neuropeptides/antagonists & inhibitors
- Neuropeptides/pharmacology
- Nitric Oxide Synthase/pharmacology
- Oxadiazoles/pharmacology
- Peptide Fragments/antagonists & inhibitors
- Peptide Fragments/pharmacology
- Pituitary Adenylate Cyclase-Activating Polypeptide
- Potassium Channels, Calcium-Activated/physiology
- Quinoxalines/pharmacology
- Receptors, Calcitonin Gene-Related Peptide
- Receptors, Peptide/antagonists & inhibitors
- Receptors, Peptide/drug effects
- Receptors, Vasoactive Intestinal Peptide/physiology
- Rolipram/antagonists & inhibitors
- Rolipram/pharmacology
- Sensory Receptor Cells/physiology
- Swine
- Tetraethylammonium/administration & dosage
- Ureter/cytology
- Ureter/drug effects
- Ureter/injuries
- Vasoactive Intestinal Peptide/antagonists & inhibitors
- Vasoactive Intestinal Peptide/pharmacology
- omega-Conotoxin GVIA/pharmacology
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Affiliation(s)
- Medardo Hernández
- Departamento de Fisiología, Facultad de Farmacia, UCM, 28040-Madrid, Spain.
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66
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Ma T, Qi QH, Jian X, Fei NX. Effects of emodin on intracellular Ca 2+ signaling in the circular smooth muscle cells of rat colon. Shijie Huaren Xiaohua Zazhi 2003; 11:1699-1702. [DOI: 10.11569/wcjd.v11.i11.1699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM To investigate whether emodin has any effects on circular smooth muscle cells of rat colon and to examine the underlying mechanisms.
METHODS Smooth muscle cells were isolated from the circular muscle layers of Wistar rat colon and cell length was measured by computerized image micrometry. Intracellular Ca2+ ([Ca2+]i) signaling was studied in smooth muscle cells using Ca2+ indicator Fluo-3 AM by laser-scanning confocal microscopy.
RESULTS Emodin dose-dependently induced smooth muscle cells contraction, caused a large, transient increase in [Ca2+]i followed by a Sustained elevation in [Ca2+]i. Emodin-induced increase in [Ca2+]i was unaffected by nifedipine, a votage-gated Ca2+-channel antagonist, and the Sustained phase of rising of [Ca2+]i was attenuated by extracellular Ca2+ removal with EGTA solution. Inhibiting Ca2+ release from ryanodine-sensitive intracellular stores by ryanodine reduced the Peak increase in [Ca2+]i. However, the application of heparine, an antagonist of IP3R, nearly abolished the Peak increase in [Ca2+]i induced by emodin.
CONCLUSION Emodin has direct excitatory effect on circular smooth muscle cells from rat colon and its effect is mediated through Ca2+-dependent pathways. Furthermore, emodin-induced Peak [Ca2+]i increase may be attributable to the Ca2+ release from IP3 sensitive stores, which promotes Ca2+ release from ryanodine-sensitive stores through CICR mechanism. Additionally, Ca2+ influx from extracellular medium contributes to the Sustained increase in [Ca2+]i.
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Affiliation(s)
- Tao Ma
- Department of Surgery, General Hospital of Tianjin Medical University, Tianjin 300052, China
| | - Qing-Hui Qi
- Department of Surgery, General Hospital of Tianjin Medical University, Tianjin 300052, China
| | - Xu Jian
- Department of Surgery, General Hospital of Tianjin Medical University, Tianjin 300052, China
| | - Nai-Xin Fei
- Department of Surgery, General Hospital of Tianjin Medical University, Tianjin 300052, China
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67
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Tong Q, Kirchgessner AL. Localization and function of metabotropic glutamate receptor 8 in the enteric nervous system. Am J Physiol Gastrointest Liver Physiol 2003; 285:G992-G1003. [PMID: 12829438 DOI: 10.1152/ajpgi.00118.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The enteric nervous system (ENS) contains glutamatergic neurons, transporters, and functional ionotropic and groups I and II metabotropic glutamate receptors (mGluRs). The aim of this study was to determine whether the ENS contains functional group III mGluRs. RT-PCR demonstrated the expression of mGluR7 and mGluR8 mRNA in rat myenteric ganglia. Western blot analysis confirmed the presence of mGluR8 protein. Immunocytochemistry, in conjunction with confocal microscopy, demonstrated mGluR8 immunoreactivity in the ENS of several species, including humans. mGluR8 immunoreactivity was localized to the membrane of nerve cell bodies that received glutamatergic input. Significant receptor internalization of mGluR8 was observed on activation, and localization to membrane was observed on blocking with the mGluR III antagonist (RS)-cyclopropyl-4-phosphonophenylglycine (CPPG). mGluR8-positive myenteric neurons contained glutamate or nitric oxide synthase (NOS), a marker of inhibitory motorneurons. Enteric group III mGluRs are functional because mGluR8 agonists inhibited forskolin-induced accumulation of cAMP in isolated myenteric ganglia, and CPPG reduced this effect. In addition, an accelerating effect on guinea pig colonic motility was observed after the application of mGluR8 agonists. Increase in motility was specific, because CPPG inhibited it. Moreover, in the presence of hexamethonium or Nomega-nitro-l-arginine methyl ester, an inhibitor of NOS, responses caused by mGluR8 agonists were abolished. mGluR8 agonists also increased longitudinal muscle contractions. These findings suggest that mGluR8 agonists increase motility by inhibiting nitrergic relaxation and possibly by facilitating cholinergic contractions.
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Affiliation(s)
- Qingchun Tong
- Dept. of Physiology and Pharmacology, Box 29, State University of New York Downstate Medical Center, 450 Clarkson Ave., Brooklyn, NY 11203, USA.
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68
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Abstract
The action of smooth muscle in the intestinal wall produces tonic contractions that maintain organ dimension against an imposed load such as a bolus of food, as well as forceful contractions that produce muscle shortening to propel the bolus along the gastrointestinal tract. These functions are regulated by intrinsic electrical and mechanical properties of smooth muscle. The complex signaling process that underlies these functions is discussed in this article. We propose a model that describes the facilitation of sustained contraction of smooth muscle cells in the gut.
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Affiliation(s)
- Khalil N Bitar
- Department of Pediatrics, University of Michigan Medical School, Ann Arbor, Michigan, USA
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69
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Ma T, Qi QH, Yang WX, Xu J, Dong ZL. Contractile effects and intracellular Ca 2+ signalling induced by emodin in circular smooth muscle cells of rat colon. World J Gastroenterol 2003; 9:1804-7. [PMID: 12918125 PMCID: PMC4611548 DOI: 10.3748/wjg.v9.i8.1804] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate whether emodin has any effects on circular smooth muscle cells of rat colon and to examine the mechanism underlying its effect.
METHODS: Smooth muscle cells were isolated from the circular muscle layer of Wistar rat colon and the cell length was measured by computerized image micrometry. Intracellular Ca2+ ([Ca2+]i) signalling was studied in smooth muscle cells using Ca2+ indicator Fluo-3 AM on a laser-scanning confocal microscope.
RESULTS: Emodin dose-dependently induced smooth muscle cells contraction. The contractile responses induced by emodin were inhibited by preincubation of the cells with ML-7 (an inhibitor of MLCK). Emodin caused a large, transient increase in [Ca2+]i followed by a sustained elevation in [Ca2+]i. The emodin –induced increase in [Ca2+]i was unaffected by nifedipine, a voltage-gated Ca2+-channel antagonist, and the sustained phase of the rising of [Ca2+]i was attenuated by extracellular Ca2+ removal with EGTA solution. Inhibiting Ca2+ release from ryanodine-sensitive intracellular stores by ryanodine reduced the peak increase in [Ca2+]i. Using heparin, an antagonist of IP3R, almost abolished the peak increase in [Ca2+]i.
CONCLUSION: Emodin has a direct excitatory effect on circular smooth muscle cells in rat colon mediated via Ca2+/ CaM dependent pathways. Furthermore, emodin-induced peak [Ca2+]i increase may be attributable to the Ca2+ release from IP3 sensitive stores, which further promote Ca2+ release from ryanodine-sensitive stores through CICR mechanism. Additionally, Ca2+ influx from extracellular medium contributes to the sustained increase in [Ca2+]i.
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Affiliation(s)
- Tao Ma
- Department of Surgery, General Hospital of Tianjin Medical University, Tianjin 300052, China.
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70
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Boittin FX, Dipp M, Kinnear NP, Galione A, Evans AM. Vasodilation by the calcium-mobilizing messenger cyclic ADP-ribose. J Biol Chem 2003; 278:9602-8. [PMID: 12486132 DOI: 10.1074/jbc.m204891200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In artery smooth muscle, adenylyl cyclase-coupled receptors such as beta-adrenoceptors evoke Ca(2+) signals, which open Ca(2+)-activated potassium (BK(Ca)) channels in the plasma membrane. Thus, blood pressure may be lowered, in part, through vasodilation due to membrane hyperpolarization. The Ca(2+) signal is evoked via ryanodine receptors (RyRs) in sarcoplasmic reticulum proximal to the plasma membrane. We show here that cyclic adenosine diphosphate-ribose (cADPR), by activating RyRs, mediates, in part, hyperpolarization and vasodilation by beta-adrenoceptors. Thus, intracellular dialysis of cADPR increased the cytoplasmic Ca(2+) concentration proximal to the plasma membrane in isolated arterial smooth muscle cells and induced a concomitant membrane hyperpolarization. Smooth muscle hyperpolarization mediated by cADPR, by beta-adrenoceptors, and by cAMP, respectively, was abolished by chelating intracellular Ca(2+) and by blocking RyRs, cADPR, and BK(Ca) channels with ryanodine, 8-amino-cADPR, and iberiotoxin, respectively. The cAMP-dependent protein kinase A antagonist N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide hydrochloride (H89) blocked hyperpolarization by isoprenaline and cAMP, respectively, but not hyperpolarization by cADPR. Thus, cADPR acts as a downstream element in this signaling cascade. Importantly, antagonists of cADPR and BK(Ca) channels, respectively, inhibited beta-adrenoreceptor-induced artery dilation. We conclude, therefore, that relaxation of arterial smooth muscle by adenylyl cyclase-coupled receptors results, in part, from a cAMP-dependent and protein kinase A-dependent increase in cADPR synthesis, and subsequent activation of sarcoplasmic reticulum Ca(2+) release via RyRs, which leads to activation of BK(Ca) channels and membrane hyperpolarization.
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Affiliation(s)
- François-Xavier Boittin
- Division of Biomedical Sciences, School of Biology, Bute Building, University of St Andrews, St Andrews, Fife, KY16 9TS, United Kingdom
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71
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Shabalina I, Wiklund C, Bengtsson T, Jacobsson A, Cannon B, Nedergaard J. Uncoupling protein-1: involvement in a novel pathway for beta-adrenergic, cAMP-mediated intestinal relaxation. Am J Physiol Gastrointest Liver Physiol 2002; 283:G1107-16. [PMID: 12381524 DOI: 10.1152/ajpgi.00193.2002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pathway for adrenergic relaxation of smooth muscle is not fully understood. As mitochondrial uncoupling protein-1 (UCP1) expression has been reported in cells within the longitudinal smooth muscle layer of organs exhibiting peristalsis, we examined whether the absence of UCP1 affects adrenergic responsiveness. Intestinal (ileal) segments were obtained from UCP1-ablated mice and from wild-type mice (C57Bl/6, 129/SvPas, and outbred NMRI). In UCP1-containing mice, isoprenaline totally inhibited contractions induced by electrical field stimulation, but in intestine from UCP1-ablated mice, a significant residual contraction remained even at a high isoprenaline concentration; the segments were threefold less sensitive to isoprenaline. Also, when contraction was induced by carbachol, there was a residual isoprenaline-insensitive contraction. Similar results were obtained with the beta(3)-selective agonist CL-316,243 and with the adenylyl cyclase stimulator forskolin. Thus the UCP1 reported to be expressed in the longitudinal muscle layer of the mouse intestine is apparently functional, and UCP1, presumably through uncoupling, may be involved in a novel pathway leading from increased cAMP levels to relaxation in organs exhibiting peristalsis.
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Affiliation(s)
- Irina Shabalina
- Wenner-Gren Institute, Arrhenius Laboratories F3, Stockholm University, SE-106 91 Stockholm, Sweden
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72
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Alcón S, Morales S, Camello PJ, Pozo MJ. Contribution of different phospholipases and arachidonic acid metabolites in the response of gallbladder smooth muscle to cholecystokinin. Biochem Pharmacol 2002; 64:1157-67. [PMID: 12234620 DOI: 10.1016/s0006-2952(02)01259-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Guinea pig gallbladder muscle strips were used to investigate the contribution of different sources of diacylglicerol (DAG) in the cholecystokinin (CCK)-induced contraction. The involvement of arachidonic acid (AA) in this response was also investigated. Three distinct pathways for DAG production were investigated with specific phospholipase (PL) inhibitors. U-73122 (10 microM) was used for inhibition of phosphoinositide-specific-PLC (PI-PLC), D-609 (100 microM) for phosphatidylcholine specific-PLC (PC-PLC), and propranolol (100 microM) for phospholipase D (PLD). Separate or combined inhibition of each of these enzymes showed that the CCK-induced output of DAG involves the parallel activation of each of these phospholipases. Thus, after inhibition of a PL subtype, the remaining subtypes were able to functionally compensate in mediating CCK-induced contraction. Inhibition of AA production via DAG-lipase or phospholipase A(2) (PLA(2)) was accomplished using RHC-80267 (40 microM), mepacrine (100 microM) and 4-BPB (100 microM). These inhibitors diminished contractile response, indicating that AA is an important modulator of CCK-induced contraction. Indomethacin (10 microM) and nordihydroguaiaretic acid (NDGA, 100 microM), which inhibit subsequent steps in AA metabolism through the cyclooxygenase and 5-lipooxygenase pathways, also inhibited contractions. Taken together, these results show that CCK redundantly activates PC-PLC, PI-PLC and PLD, to produce DAG, which in turn stimulates PKC and provides a substrate for the generation of AA. sPLA(2) is also a source of AA, whose metabolites are, in part, responsible for determining the magnitude of the CCK-evoked contraction.
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Affiliation(s)
- Soledad Alcón
- Department of Physiology, University of Extremadura, 10071 Cáceres, Spain
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73
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La J, Kim T, Sung T, Kang J, Song H, Kim H, Yang I. Rebound contraction by nitric oxide in the longitudinal muscle of porcine gastric fundus. JAPANESE JOURNAL OF PHARMACOLOGY 2002; 89:395-404. [PMID: 12233818 DOI: 10.1254/jjp.89.395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The rebound contraction induced by electrical field stimulation (EFS) and nitric oxide (NO) donor, S-nitroso-L-cysteine (cysNO), were investigated in the longitudinal muscle of porcine gastric fundus (LM-PGF). Under the presence of atropine and guanethidine, cysNO and EFS produced sequential relaxation-contraction in LM-PGF. Tetrodotoxin abolished the EFS-induced response, while leaving the cysNO-induced one unaffected. A soluble guanylate cyclase inhibitor, 1H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxalin-1-one, inhibited both cysNO and EFS-induced biphasic response. A cGMP analogue only relaxed LM-PGF. A phosphodiesterase V inhibitor, zaprinast, prolonged the cysNO and the EFS-induced relaxation and inhibited the rebound contraction. The rebound contraction was inhibited by verapamil, an L-type Ca2+ channel blocker. The cysNO and the EFS-induced biphasic response were inhibited by ryanodine plus cyclopiazonic acid or by ruthenium red, a ryanodine-receptor blocker. LM-PGF was relaxed on exposure to caffeine and then produced a verapamil-sensitive rebound contraction during the washout period. CysNO and EFS did not induce the rebound contraction in the presence of caffeine. These results suggest that the NO-induced rebound contraction involves both Ca2+-release from the ryanodine-sensitive store and Ca2+-influx through L-type channels. Although the NO-induced biphasic response is dependent on cGMP, rapid removal of cGMP seems necessary for the rebound contraction.
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Affiliation(s)
- Junho La
- Department of Veterinary Physiology, College of Veterinary Medicine, Seoul National University, Suwon, Republic of Korea
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74
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Ulker S, Cinar MG, Can C, Evinç A, Koşay S. Endotoxin-induced vascular hyporesponsiveness in rat aorta: in vitro effect of aminoguanidine. Pharmacol Res 2001; 44:22-7. [PMID: 11428906 DOI: 10.1006/phrs.2001.0814] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The current study was designed to evaluate the endotoxin-induced alterations of the mechanisms involved in Ca(2+)handling within the rat thoracic aorta and further to examine whether in vitro inhibition of inducible nitric oxide synthase (iNOS) by aminoguanidine would account for this effect or not. Endothelium denuded aortic rings from rats injected with lipopolysaccharide (LPS) (5 mg kg(-1), i.p. 18 h prior to functional studies) or saline were mounted in isolated organ baths. Various experimental conditions were studied on paired rings of the same animal which were incubated in the presence or absence of aminoguanidine (100 microM). Phenylephrine contractility in Ca(2+)-containing buffer or in Ca(2+)-free buffer, contractions induced by K(+)depolarization and CaCl(2)in depolarized muscle and by caffeine exposure were significantly decreased in LPS-treated rings and were reversed by aminoguanidine exposure. Aminoguanidine also improved the contractions recorded while switching the Ca(2+)-free buffer to Ca(2+)-containing buffer. We conclude that endotoxin induces a generalized contractile defect in vascular smooth muscle including impairment in the influx of extracellular Ca(2+)and release of Ca(2+)from intracellular stores. An increase in iNOS activation leading to excessive nitric oxide synthesis, possibly non-endothelial in origin, may account for this defect.
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Affiliation(s)
- S Ulker
- Department of Pharmacology, School of Medicine, Ege University, 35100 Bornova-Izmir, Turkey
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75
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Balsiger BM, Ohtani N, Anding WJ, Duenes JA, Sarr MG. Chronic extrinsic denervation after small bowel transplantation in rat jejunum: Effects and adaptation in nitrergic and non-nitrergic neuromuscular inhibitory mechanisms. Surgery 2001; 129:478-89. [PMID: 11283540 DOI: 10.1067/msy.2001.112070] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Extrinsic denervation of the transplanted small bowel could play a substantial role in motor dysfunction of the transplanted gut. We attempted to determine the effect of chronic extrinsic denervation on intestinal contractility. METHODS Jejunal longitudinal muscle strips were obtained from rats 1 week and 8 weeks after (1) syngeneic small bowel transplantation, (2) ischemia/reperfusion, or (3) gut transection/reanastomosis. Nonoperated rats (naive controls) and sham-operated rats (sham controls), 1 week after celiotomy/gut manipulation, served as controls. We evaluated the effects of exogenous nitric oxide, increasing doses of cholinergic and adrenergic agonists, and electrical field stimulation (EFS) in the presence or absence of N(G)-monomethyl-l-arginine, methylene blue, tetraethylammonium, or tetrodotoxin. RESULTS Spontaneous contractile activity (_chi +/- SEM), when compared with the naive controls (11.3 +/- 2.0 g.5 min/mg), was increased in all 4 groups at 1 week (15.9 +/- 10 to 19.4 +/- 2 g.5 min/mg; P < or =.03 each) but not at 8 weeks postoperatively. The inhibition of contractile activity by nitric oxide was increased in small bowel transplantation in naive controls at 8 weeks to 80% +/- 10% versus 50% +/- 7% (P <.02). EFS induced an inhibition of contractile activity that was tetraethylammonium- and tetrodotoxin-sensitive but N(G)-monomethyl-l-arginine- and methylene blue-insensitive; the maximal EFS-induced inhibition was increased at 1 week and 8 weeks but only in the small bowel transplantation groups to 103% +/- 5% and 95% +/- 7%, respectively, versus 72% +/- 8% in naive controls (P </=.05). CONCLUSIONS [corrected] Increased inhibition of contractile function after small bowel transplantation lasts at least 8 weeks and is mediated by changes in the enteric neuromuscular unit caused by extrinsic denervation.
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Affiliation(s)
- B M Balsiger
- Department of Surgery and Gastroenterology Research Unit, Mayo Clinic and Foundation, 300 First St SW, Rochester, MN 55905, USA
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76
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Di Baldassarre A, Marchisio M, Felaco M, Antonucci A, Centurione L, Grilli A, Di Valerio V, Cutroneo G, Schiavone C, Miscia S, Ianetti G. Histochemical and biochemical analysis of phospholipase C isoforms in normal human gastric mucosa cells. THE ANATOMICAL RECORD 2001; 262:440-4. [PMID: 11275974 DOI: 10.1002/ar.1052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The expression and activity of PIP2-specific phospholipase C (PLC) in healthy human gastric mucosa cells were investigated by means of Western blotting, immunohistochemistry and in vitro activity assays. The results provide direct evidence for an almost exclusive expression of the PLC beta family and at the same time supply a cellular cartography of each represented isoform of this family. In this context, the putative roles of each isoform in the signaling events regulating the gastric mucosa metabolic machinery are discussed. These data provide a unique map of the specific expression and cellular distribution of the most represented PLC isoforms in healthy human gastric mucosa cells, which may constitute a reference point in future studies aimed at highlighting possible cytochemical and biochemical hallmarks of metaplastic or malignant transformation.
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Affiliation(s)
- A Di Baldassarre
- Department of Biomorphology, School of Medicine, University of Chieti, Chieti, Italy
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77
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Liu X, Rusch NJ, Striessnig J, Sarna SK. Down-regulation of L-type calcium channels in inflamed circular smooth muscle cells of the canine colon. Gastroenterology 2001; 120:480-9. [PMID: 11159888 DOI: 10.1053/gast.2001.21167] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND & AIMS Circular smooth muscle phasic contractions and tone are suppressed during colonic inflammation, but the contributing factors are poorly understood. This study investigated if the expression level of voltage-gated long-lasting (L-type) Ca(2+) channel protein and functional Ca(2+) channel current are down-regulated in the circular muscle cells of the inflamed canine colon. METHODS L-type Ca(2+) channel expression was compared between normal and inflamed smooth muscle cells by Western immunoblots using an antibody directed against the pore-forming alpha 1C-subunit, and patch-clamp methods were used to evaluate Ca(2+) channel current density. RESULTS The expression of the L-type Ca(2+) channel protein was significantly reduced in inflamed compared with normal circular smooth muscle cell membranes, and this finding was associated with suppressed levels of Ca(2+) channel current in patch-clamped cells. The L-type Ca(2+) channel current in normal and inflamed cells increased proportionately in response to Bay K 8644, but the maximal current density was still lower in the inflamed cells. Acetylcholine increased the L-type Ca(2+) channel current in normal but not in inflamed cells. CONCLUSIONS The expression level of L-type Ca(2+) channels is down-regulated in the circular smooth muscle cell membranes of the inflamed colon, which may result in reduced Ca(2+) influx. The functional and pharmacologic properties of the channels seem normal. Although some Ca(2+) channels are still present in the inflamed cells, acetylcholine does not activate these channels, which may be caused by additional upstream defects in the receptor signaling cascade. The down-regulation of L-type Ca(2+) channel expression may suppress circular smooth muscle contractions in the inflamed colon and contribute to the abnormalities in motility and digestion observed during inflammatory disorders.
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Affiliation(s)
- X Liu
- Department of Surgery, Medical College of Wisconsin and Zablocki VA Medical Center, Milwaukee, Wisconsin, USA
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78
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Effects of flavonoids on gastrointestinal disorders. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s1572-5995(01)80019-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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79
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Carnicelli V, Di Giulio A, Romano G, Bozzi A, Oratore A, Delle Fave G, Strom R, Severi C. Regional differences in signalling transduction pathways among smooth muscle cells from rabbit colon. Cell Signal 2000; 12:683-9. [PMID: 11080621 DOI: 10.1016/s0898-6568(00)00114-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Smooth muscle cells (SMC) from the circular muscle layer of rabbit colon, taken from the proximal and distal regions that are known to have different physiological and motor activities, were used to highlight distinct regional intrinsic myogenic properties and to investigate the correlations between receptor and signalling transduction pathways. Contractile agonists were shown to be more potent on proximal than on distal SMC in inducing contraction and intracellular Ca(2+) increase. Concentration-response curves of agonists-induced Ca(2+) increase were constantly shifted to the right, though remaining parallel, with respect to contraction curves, independently of the region analysed. Using agents activating different steps of cAMP-or cGMP-mediated intracellular cascades, main regional differences were revealed as far as relaxation was concerned. Relaxation of proximal SMC was found to be essentially cGMP mediated, while that of distal SMC was cAMP mediated. In conclusion, the motor patterns of the two regions appear to be influenced by distinct regional biochemical characteristics that are intrinsic to colonic SMC.
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Affiliation(s)
- V Carnicelli
- Department of Biochemical Sciences and Technology, University of L'Aquila, 67100-L'Aquila, Via Vetoio, Italy
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80
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Murthy KS, Grider JR, Kuemmerle JF, Makhlouf GM. Sustained muscle contraction induced by agonists, growth factors, and Ca(2+) mediated by distinct PKC isozymes. Am J Physiol Gastrointest Liver Physiol 2000; 279:G201-10. [PMID: 10898764 DOI: 10.1152/ajpgi.2000.279.1.g201] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The role of protein kinase C (PKC) in sustained contraction was examined in intestinal circular and longitudinal muscle cells. Initial contraction induced by agonists (CCK-8 and neuromedin C) was abolished by 1) inhibitors of Ca(2+) mobilization (neomycin and dimethyleicosadienoic acid), 2) calmidazolium, and 3) myosin light chain (MLC) kinase (MLCK) inhibitor KT-5926. In contrast, sustained contraction was not affected by these inhibitors but was abolished by 1) the PKC inhibitors chelerythrine and calphostin C, 2) PKC-epsilon antibody, and 3) a pseudosubstrate PKC-epsilon inhibitor. GDPbetaS abolished both initial and sustained contraction, whereas a Galpha(q/11) antibody inhibited only initial contraction, implying that sustained contraction was dependent on activation of a distinct G protein. Sustained contraction induced by epidermal growth factor was inhibited by calphostin C, PKC-alpha,beta,gamma antibody, and a pseudosubstrate PKC-alpha inhibitor. Ca(2+) (0.4 microM) induced an initial contraction in permeabilized muscle cells that was blocked by calmodulin and MLCK inhibitors and a sustained contraction that was blocked by calphostin C and a PKC-alpha,beta,gamma antibody. Thus initial contraction induced by Ca(2+), agonists, and growth factors is mediated by MLCK, whereas sustained contraction is mediated by specific Ca(2+)-dependent and -independent PKC isozymes. G protein-coupled receptors are linked to PKC activation via distinct G proteins.
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Affiliation(s)
- K S Murthy
- Departments of Medicine and Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA
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81
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Shi XZ, Sarna SK. Impairment of Ca(2+) mobilization in circular muscle cells of the inflamed colon. Am J Physiol Gastrointest Liver Physiol 2000; 278:G234-42. [PMID: 10666047 DOI: 10.1152/ajpgi.2000.278.2.g234] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
This study investigated whether inflammation modulates the mobilization of Ca(2+) in canine colonic circular muscle cells. The contractile response of single cells from the inflamed colon was significantly suppressed in response to ACh, KCl, and BAY K8644. Methoxyverapamil and reduction in extracellular Ca(2+) concentration dose-dependently blocked the response in both normal and inflamed cells. The increase in intracellular Ca(2+) concentration in response to ACh and KCl was significantly reduced in the inflamed cells. However, Ca(2+) efflux from the ryanodine- and inositol 1,4, 5-trisphosphate (IP(3))-sensitive stores, as well as the decrease of cell length in response to ryanodine and IP(3), were not affected. Heparin significantly blocked Ca(2+) efflux and contraction in response to ACh in both conditions. ACh-stimulated accumulation of IP(3) and the binding of [(3)H]ryanodine to its receptors were not altered by inflammation. Ruthenium red partially inhibited the response to ACh in normal and inflamed states. We conclude that the canine colonic circular muscle cells utilize Ca(2+) influx through L-type channels as well as Ca(2+) release from the ryanodine- and IP(3)-sensitive stores to contract. Inflammation impairs Ca(2+) influx through L-type channels, but it may not affect intracellular Ca(2+) release. The impairment of Ca(2+) influx may contribute to the suppression of circular muscle contractility in the inflamed state.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Acetylcholine/pharmacology
- Animals
- Calcium/metabolism
- Calcium Channel Agonists/pharmacology
- Calcium Radioisotopes
- Cell Membrane Permeability
- Cell Size/drug effects
- Colitis/metabolism
- Cytosol/metabolism
- Dogs
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate/pharmacology
- Kinetics
- Muscle Contraction/drug effects
- Muscle, Smooth/cytology
- Muscle, Smooth/metabolism
- Potassium Chloride/pharmacology
- Ryanodine/metabolism
- Ryanodine/pharmacology
- Tritium
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Affiliation(s)
- X Z Shi
- Departments of Surgery and Physiology, Medical College of Wisconsin and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53226, USA
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82
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Stevens RJ, Weinert JS, Publicover NG. Visualization of origins and propagation of excitation in canine gastric smooth muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:C448-60. [PMID: 10484332 DOI: 10.1152/ajpcell.1999.277.3.c448] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The origin and spread of excitation were visualized with fluo 3 fluorescence in tissues isolated from canine gastric antrum. Sheets of circular muscle (5 x 6 mm) had at least 1 (30%) and up to 3 discrete slow-wave pacing sites located near the longitudinal-circular muscle boundary, whereas similarly sized longitudinal sheets had an average of 5 sites (range 3-12 sites) that initiated Ca2+ waves. Superimposed fluorescent oscillations (circular muscle) and spikes (longitudinal muscle) were seen to initiate and propagate as distinct events, separate from their underlying activities. Average propagation velocities transverse (6-7 mm/s) and parallel (39-45 mm/s) to the long axis of muscle fibers were similar for each type of event in circular and longitudinal tissues; however, distinct regions where velocities of some (but not all) events decreased by up to an order of magnitude were present. The distance propagated by individual events was limited by collisions with concurrent excitable events or recently activated regions. Complex patterns of excitation in gastrointestinal smooth muscle arise as a result of interactions between multiple pacing sites, heterogeneous conduction velocities, and the interplay of adjacent pacemaker domains.
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Affiliation(s)
- R J Stevens
- Biomedical Engineering Program, Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
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83
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Kim CD, Goyal RK, Mashimo H. Neuronal NOS provides nitrergic inhibitory neurotransmitter in mouse lower esophageal sphincter. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:G280-4. [PMID: 10444441 DOI: 10.1152/ajpgi.1999.277.2.g280] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
To identify the enzymatic source of nitric oxide (NO) in the lower esophageal sphincter (LES), studies were performed in wild-type and genetically engineered endothelial nitric oxide synthase [eNOS(-)] and neuronal NOS [nNOS(-)] mice. Under nonadrenergic noncholinergic (NANC) conditions, LES ring preparations developed spontaneous tone in all animals. In the wild-type mice, electrical field stimulation produced frequency-dependent intrastimulus relaxation and a poststimulus rebound contraction. NOS inhibitor N(omega)-nitro-L-arginine methyl ester (100 microM) abolished intrastimulus relaxation and rebound contraction. In nNOS(-) mice, both the intrastimulus relaxation and rebound contraction were absent. However, in eNOS(-) mice there was no significant difference in either the relaxation or rebound contraction from the wild-type animal. Both nNOS(-) and eNOS(-) tissues showed concentration-dependent relaxation to NO donor diethylenetriamine-NO and there was no difference in the sensitivity to the NO donor in nNOS(-), eNOS(-), or wild-type animals. These results indicate that in mouse LES, nNOS rather than eNOS is the enzymatic source of the NO that mediates NANC relaxation and rebound contraction.
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Affiliation(s)
- C D Kim
- Center for Swallowing and Motility Disorders, Brockton/West Roxbury Veterans Affairs Medical Center, Boston, Massachusetts 02132, USA
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84
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Gutiérrez AM, Kornfeld M, Persson AE. Calcium response to adenosine and ATP in rabbit afferent arterioles. ACTA PHYSIOLOGICA SCANDINAVICA 1999; 166:175-81. [PMID: 10468653 DOI: 10.1046/j.1365-201x.1999.00557.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effects of purine compounds in the renal vasculature are almost exclusively restricted to pre-glomerular vessels. Although their physiological role as extracellular messengers is not clear, there are extensive data indicating the importance of adenosine and ATP in the regulation of renal haemodynamics. This study was undertaken to characterize the calcium response of rabbit afferent arteriole to adenosine, ATP and other nucleotides. Experiments were performed in isolated afferent arterioles, microdissected from rabbit kidneys and loaded with fura-2. Intracellular calcium concentration ([Ca2+]i) was measured by video in proximal and distal parts of the afferent arteriole. Application of 100 microM adenosine or ATP increased [Ca2+]i in both arteriolar regions. In all cases the response had two well distinguishable phases: a quick peak increase and a plateau phase that equilibrated at a [Ca2+]i significantly higher than the basal level. UTP (100 microM) had no effect on the arteriole. Removal of extracellular calcium (2.5 mM EGTA) abolished only the plateau phase in response to adenosine, without significantly changing the peak increase. In contrast, the response to ATP was completely abolished in both arteriolar regions, where [Ca2+]i decreased upon application of the agonist and rapidly increased after restoration of calcium concentration to plasma level. We conclude that P1 and P2X receptors are present along the rabbit afferent arteriole and mediate calcium mobilization, with the same distribution in the proximal and distal segments.
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Affiliation(s)
- A M Gutiérrez
- Department of Physiology, University of Uppsala, Uppsala, Sweden
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85
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Flynn ER, McManus CA, Bradley KK, Koh SD, Hegarty TM, Horowitz B, Sanders KM. Inward rectifier potassium conductance regulates membrane potential of canine colonic smooth muscle. J Physiol 1999; 518:247-56. [PMID: 10373706 PMCID: PMC2269411 DOI: 10.1111/j.1469-7793.1999.0247r.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. The membrane potential of gastrointestinal smooth muscles determines the open probability of ion channels involved in rhythmic electrical activity. The role of Ba2+-sensitive K+ conductances in the maintenance of membrane potential was examined in canine proximal colon circular muscle. 2. Application of Ba2+ (1-100 microM) to strips of tunica muscularis produced depolarization of cells along the submucosal surface of the circular muscle layer. Significantly higher concentrations of Ba2+ were needed to depolarize preparations from which the submucosal and myenteric pacemaker regions were removed. 3. Elevation of extracellular [K+]o (from 5.9 to 12 mM) brought membrane potentials closer to EK (the Nernst potential for K+ ions), suggesting activation of a K+ conductance. This occurred at potentials much more negative than the activation range for delayed rectifier channels (Kv). 4. Forskolin (1 microM) caused hyperpolarization and a leftward shift in the dose-response relationship for Ba2+, suggesting that forskolin may activate a Ba2+-sensitive conductance. 5. Patch-clamp recordings from interstitial cells of Cajal (ICC) revealed the presence of a Ba2+-sensitive inward rectifier potassium conductance. Far less of this conductance was present in smooth muscle cells. 6. Kir2.1 was expressed in the circular muscle layer of the canine proximal colon, duodenum, jejunum and ileum. Kir2.1 mRNA was expressed in greater abundance along the submucosal surface of the circular muscle layer in the colon. 7. These results demonstrate that ICC express a Ba2+-sensitive conductance (possibly encoded by Kir2.1). This conductance contributes to the generation and maintenance of negative membrane potentials between slow waves.
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Affiliation(s)
- E R Flynn
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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86
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Rodier G, Magous R, Mochizuki T, Bali JP, Bataille D, Jarrousse C. A target cell to oxyntomodulin and glicentin: the antral smooth muscle cell. Ann N Y Acad Sci 1998; 865:458-62. [PMID: 9928049 DOI: 10.1111/j.1749-6632.1998.tb11215.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- G Rodier
- Laboratory Endocrinologie des Peptides et Régulation Génique INSERM U 376, Montpellier, France
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87
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Wang B, Sims SM. CCK regulates nonselective cation channels in guinea pig gastric smooth muscle cells. Am J Physiol Gastrointest Liver Physiol 1998; 274:G709-17. [PMID: 9575853 DOI: 10.1152/ajpgi.1998.274.4.g709] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
Abstract
CCK has widespread effects in the gastrointestinal tract, stimulating pancreatic secretion and contraction of smooth muscles. The cellular mechanisms by which CCK causes smooth muscle contraction are poorly understood. We investigated the effects of CCK on guinea pig gastric smooth muscle cells using patch-clamp techniques. CCK caused contraction of cells accompanied by inward current. The conductance activated by CCK was nonselective for cations and showed little voltage dependence. Because ACh also activates nonselective cation current, we examined interactions between CCK and ACh. When CCK activated inward current, ACh caused no further effect. When CCK failed to activate current, subsequent ACh-activated current was larger and no longer exhibited its characteristic voltage dependence. Intracellular dialysis with guanosine 5'-O-(3-thiotriphosphate) caused similar changes in the voltage dependence of the ACh-activated current, suggesting a role for G proteins in regulation of the current. Activation of nonselective cation current would depolarize muscle and may contribute to the excitation mediated by CCK in tissues. These findings provide evidence that multiple types of receptors converge to regulate nonselective cation current.
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Affiliation(s)
- B Wang
- Department of Physiology, University of Western Ontario, London, Canada
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88
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Kuemmerle JF, Murthy KS, Makhlouf GM. Longitudinal smooth muscle of the mammalian intestine. A model for Ca2+ signaling by cADPR. Cell Biochem Biophys 1997; 28:31-44. [PMID: 9386891 DOI: 10.1007/bf02738308] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ca2+ mobilization in muscle cells from the circular muscle layer of the mammalian intestine is mediated by IP3-dependent Ca2+ release. Ca2+ mobilization in muscle from the adjacent longitudinal muscle layer involves a distinct, phosphoinositide-independent pathway. Receptors for contractile agonists in longitudinal muscle cells are coupled via a pertussis toxin-sensitive G protein to activation of PLA2 and formation of arachidonic acid (AA). The latter activates Cl- channels resulting in depolarization of the plasma membrane and opening of voltage-sensitive Ca2+ channels. Ca2+ influx via these channels induces Ca2+ release by activating sarcoplasmic ryanodine receptor/Ca2+ channels. The increase in [Ca2+]i activates membrane-bound ADP ribosyl cyclase, and the resultant formation of cADPR enhances Ca(2+)-induced Ca2+ release.
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Affiliation(s)
- J F Kuemmerle
- Department of Physiology, Medical College of Virginia, Richmond 23298-0711, USA
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