1
|
The Causal Relationship between Endothelin-1 and Hypertension: Focusing on Endothelial Dysfunction, Arterial Stiffness, Vascular Remodeling, and Blood Pressure Regulation. Life (Basel) 2021; 11:life11090986. [PMID: 34575135 PMCID: PMC8472034 DOI: 10.3390/life11090986] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/13/2021] [Accepted: 09/17/2021] [Indexed: 12/01/2022] Open
Abstract
Hypertension (HTN) is one of the most prevalent diseases worldwide and is among the most important risk factors for cardiovascular and cerebrovascular complications. It is currently thought to be the result of disturbances in a number of neural, renal, hormonal, and vascular mechanisms regulating blood pressure (BP), so crucial importance is given to the imbalance of a number of vasoactive factors produced by the endothelium. Decreased nitric oxide production and increased production of endothelin-1 (ET-1) in the vascular wall may promote oxidative stress and low-grade inflammation, with the development of endothelial dysfunction (ED) and increased vasoconstrictor activity. Increased ET-1 production can contribute to arterial aging and the development of atherosclerotic changes, which are associated with increased arterial stiffness and manifestation of isolated systolic HTN. In addition, ET-1 is involved in the complex regulation of BP through synergistic interactions with angiotensin II, regulates the production of catecholamines and sympathetic activity, affects renal hemodynamics and water–salt balance, and regulates baroreceptor activity and myocardial contractility. This review focuses on the relationship between ET-1 and HTN and in particular on the key role of ET-1 in the pathogenesis of ED, arterial structural changes, and impaired vascular regulation of BP. The information presented includes basic concepts on the role of ET-1 in the pathogenesis of HTN without going into detailed analyses, which allows it to be used by a wide range of specialists. Also, the main pathological processes and mechanisms are richly illustrated for better understanding.
Collapse
|
2
|
Johansson M, Ulfenborg B, Andersson CX, Heydarkhan-Hagvall S, Jeppsson A, Sartipy P, Synnergren J. Cardiac hypertrophy in a dish: a human stem cell based model. Biol Open 2020; 9:bio052381. [PMID: 32878883 PMCID: PMC7522030 DOI: 10.1242/bio.052381] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 08/23/2020] [Indexed: 12/23/2022] Open
Abstract
Cardiac hypertrophy is an important and independent risk factor for the development of heart failure. To better understand the mechanisms and regulatory pathways involved in cardiac hypertrophy, there is a need for improved in vitro models. In this study, we investigated how hypertrophic stimulation affected human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs). The cells were stimulated with endothelin-1 (ET-1) for 8, 24, 48, 72, or 96 h. Parameters including cell size, ANP-, proBNP-, and lactate concentration were analyzed. Moreover, transcriptional profiling using RNA-sequencing was performed to identify differentially expressed genes following ET-1 stimulation. The results show that the CMs increase in size by approximately 13% when exposed to ET-1 in parallel to increases in ANP and proBNP protein and mRNA levels. Furthermore, the lactate concentration in the media was increased indicating that the CMs consume more glucose, a hallmark of cardiac hypertrophy. Using RNA-seq, a hypertrophic gene expression pattern was also observed in the stimulated CMs. Taken together, these results show that hiPSC-derived CMs stimulated with ET-1 display a hypertrophic response. The results from this study also provide new molecular insights about the underlying mechanisms of cardiac hypertrophy and may help accelerate the development of new drugs against this condition.
Collapse
Affiliation(s)
- Markus Johansson
- Systems Biology Research Center, School of Bioscience, Department for Biology and Bioinformatics, University of Skövde, SE-541 28 Skövde, Sweden
- Department of Molecular and Clinical Medicine, Institute of Medicine, The Sahlgrenska Academy at University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Benjamin Ulfenborg
- Systems Biology Research Center, School of Bioscience, Department for Biology and Bioinformatics, University of Skövde, SE-541 28 Skövde, Sweden
| | | | - Sepideh Heydarkhan-Hagvall
- Systems Biology Research Center, School of Bioscience, Department for Biology and Bioinformatics, University of Skövde, SE-541 28 Skövde, Sweden
- Bioscience, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals, R&D AstraZeneca, 431 50 Gothenburg, Sweden
| | - Anders Jeppsson
- Department of Molecular and Clinical Medicine, Institute of Medicine, The Sahlgrenska Academy at University of Gothenburg, 405 30 Gothenburg, Sweden
- Department of Cardiothoracic Surgery, Sahlgrenska University Hospital, 413 45 Gothenburg, Sweden
| | - Peter Sartipy
- Systems Biology Research Center, School of Bioscience, Department for Biology and Bioinformatics, University of Skövde, SE-541 28 Skövde, Sweden
- Late-stage Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, 431 50 Gothenburg, Sweden
| | - Jane Synnergren
- Systems Biology Research Center, School of Bioscience, Department for Biology and Bioinformatics, University of Skövde, SE-541 28 Skövde, Sweden
| |
Collapse
|
3
|
Li X, Augustine A, Sun D, Li L, Fliegel L. Activation of the Na +/H + exchanger in isolated cardiomyocytes through β-Raf dependent pathways. Role of Thr 653 of the cytosolic tail. J Mol Cell Cardiol 2016; 99:65-75. [PMID: 27555478 DOI: 10.1016/j.yjmcc.2016.08.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 08/04/2016] [Accepted: 08/19/2016] [Indexed: 10/21/2022]
Abstract
The mammalian Na+/H+ exchanger isoform 1 (NHE1) is a ubiquitous plasma membrane protein that is a key regulator of intracellular pH in isolated cardiomyocytes. A 500 amino acid membrane domain removes protons and is regulated by a 315 amino acid cytosolic domain. In the myocardium, aberrant regulation of NHE1 contributes to ischemia reperfusion damage and to heart hypertrophy. We examined mechanisms of regulation of NHE1 in the myocardium by endothelin and β-Raf. Endothelin stimulated NHE1 activity and activated Erk-dependent pathways. Inhibition of β-Raf reduced NHE1 activity and Erk-pathway activation. We demonstrated that myocardial β-Raf binds to the C-terminal 182 amino acids of the NHE1 protein and that β-Raf is associated with NHE1 in intact cardiomyocytes. NHE1 was phosphorylated in vivo and the protein kinase inhibitor sorafenib reduced NHE1 phosphorylation levels. Immunoprecipitates of β-Raf from cardiomyocytes phosphorylated the C-terminal 182 amino acids of NHE1 and mass spectrometry analysis showed that amino acid Thr653 was phosphorylated. Mutation of this amino acid to Ala resulted in defective activity while mutation to Asp restored the activity. The results demonstrate that Thr653 is an important regulatory amino acid of NHE1 that is activated through β-Raf dependent pathways by phosphorylation either directly or indirectly by β-Raf, and this affects NHE1 activity.
Collapse
Affiliation(s)
- Xiuju Li
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Aruna Augustine
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Difei Sun
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
| | - Liang Li
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
| | - Larry Fliegel
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| |
Collapse
|
4
|
Endothelin-1-induced remodelling of murine adult ventricular myocytes. Cell Calcium 2016; 59:41-53. [DOI: 10.1016/j.ceca.2015.12.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 12/17/2015] [Accepted: 12/22/2015] [Indexed: 11/30/2022]
|
5
|
Fontoura D, Oliveira-Pinto J, Tavares-Silva M, Leite S, Vasques-Nóvoa F, Mendes-Ferreira P, Lourenço AP, Leite-Moreira AF. Myocardial and anti-inflammatory effects of chronic bosentan therapy in monocrotaline-induced pulmonary hypertension. Rev Port Cardiol 2014; 33:213-22. [PMID: 24780128 DOI: 10.1016/j.repc.2013.09.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 09/17/2013] [Indexed: 11/17/2022] Open
Abstract
INTRODUCTION AND OBJECTIVES Endothelin-1 antagonists are increasingly used in the treatment of pulmonary hypertension despite the lack of knowledge of their myocardial and systemic effects. We assessed the right ventricular myocardial and systemic effects of endothelin-1 antagonists in monocrotaline-induced pulmonary hypertension. METHODS Male Wistar rats (180-200 g, n=57) randomly received 60 mg/kg monocrotaline or vehicle subcutaneously. Two days later, bosentan was randomly started (300 mg/kg/day) by oral route in a subgroup of monocrotaline-injected rats, while the other monocrotaline-injected and control rats received vehicle. At 25-30 days, invasive hemodynamic assessment was performed under anesthesia, arterial blood samples were collected for gas analysis and plasma was extracted for quantification of endothelin-1, cytokines, nitrates and 6-keto-prostaglandin F1α. Right ventricular myocardium was collected for assessment of cyclooxygenase and nitric oxide synthase activity and gene expression. RESULTS The monocrotaline group developed pulmonary hypertension, low cardiac output, right ventricular hypertrophy and dilation, changes in gene expression and inflammatory activation that were attenuated in the group treated with bosentan. From a functional point of view, this group had improved right ventricular function and preserved ventriculo-vascular coupling, without deterioration in arterial gas parameters or systemic hypotension. In molecular terms, they showed reduced endothelin-1 and cytokine levels, decreased right ventricular inducible nitric oxide synthase and cyclooxygenase-2 activity and increased nitrate plasma levels compared with the non-treated group. CONCLUSIONS In this study we demonstrate that besides attenuating pulmonary hypertension, bosentan has beneficial hemodynamic, myocardial and anti-inflammatory effects.
Collapse
Affiliation(s)
- Dulce Fontoura
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal
| | - José Oliveira-Pinto
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Marta Tavares-Silva
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal; Department of Cardiology, São João Hospital Centre, E.P.E., Porto, Portugal
| | - Sara Leite
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Francisco Vasques-Nóvoa
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal; Department of Internal Medicine, São João Hospital Centre, E.P.E., Porto, Portugal
| | - Pedro Mendes-Ferreira
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal
| | - André P Lourenço
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal; Department of Anaesthesiology, São João Hospital Centre, E.P.E., Porto, Portugal.
| | - Adelino F Leite-Moreira
- Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Porto, Portugal; Department Cardiothoracic Surgery, São João Hospital Centre, E.P.E., Porto, Portugal
| |
Collapse
|
6
|
Fontoura D, Oliveira‐Pinto J, Tavares‐Silva M, Leite S, Vasques‐Nóvoa F, Mendes‐Ferreira P, Lourenço AP, Leite‐Moreira AF. Myocardial and anti‐inflammatory effects of chronic bosentan therapy in monocrotaline‐induced pulmonary hypertension. REVISTA PORTUGUESA DE CARDIOLOGIA (ENGLISH EDITION) 2014. [DOI: 10.1016/j.repce.2013.09.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
|
7
|
Sobhy K, El-Korashy R, Ahmed M, Fayed F. Right ventricular diastolic dysfunction in asthmatic patients. EGYPTIAN JOURNAL OF CHEST DISEASES AND TUBERCULOSIS 2014. [DOI: 10.1016/j.ejcdt.2013.09.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
8
|
Perjés Á, Kubin A, Kónyi A, Szabados S, Cziráki A, Skoumal R, Ruskoaho H, Szokodi I. Physiological regulation of cardiac contractility by endogenous reactive oxygen species. Acta Physiol (Oxf) 2012; 205:26-40. [PMID: 22463609 DOI: 10.1111/j.1748-1716.2012.02391.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Increased production of reactive oxygen species (ROS) has been linked to the pathogenesis of congestive heart failure. However, emerging evidence suggests the involvement of ROS in the regulation of various physiological cellular processes in the myocardium. In this review, we summarize the latest findings regarding the role of ROS in the acute regulation of cardiac contractility. We discuss ROS-dependent modulation of the inotropic responses to G protein-coupled receptor agonists (e.g. β-adrenergic receptor agonists and endothelin-1), the potential cellular sources of ROS (e.g. NAD(P)H oxidases and mitochondria) and the proposed end-targets and signalling pathways by which ROS affect contractility. Accumulating new data supports the fundamental role of endogenously generated ROS to regulate cardiac function under physiological conditions.
Collapse
Affiliation(s)
| | - A.M. Kubin
- Department of Pharmacology and Toxicology; Institute of Biomedicine; Biocenter Oulu; University of Oulu; Oulu; Finland
| | - A. Kónyi
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| | - S. Szabados
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| | - A. Cziráki
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| | - R. Skoumal
- Department of Pharmacology and Toxicology; Institute of Biomedicine; Biocenter Oulu; University of Oulu; Oulu; Finland
| | - H. Ruskoaho
- Department of Pharmacology and Toxicology; Institute of Biomedicine; Biocenter Oulu; University of Oulu; Oulu; Finland
| | - I. Szokodi
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| |
Collapse
|
9
|
Perjés Á, Kubin A, Kónyi A, Szabados S, Cziráki A, Skoumal R, Ruskoaho H, Szokodi I. Physiological regulation of cardiac contractility by endogenous reactive oxygen species. Acta Physiol (Oxf) 2012. [DOI: 10.1111/j.1748-1716.2011.02391.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
| | - A.M. Kubin
- Department of Pharmacology and Toxicology; Institute of Biomedicine; Biocenter Oulu; University of Oulu; Oulu; Finland
| | - A. Kónyi
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| | - S. Szabados
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| | - A. Cziráki
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| | - R. Skoumal
- Department of Pharmacology and Toxicology; Institute of Biomedicine; Biocenter Oulu; University of Oulu; Oulu; Finland
| | - H. Ruskoaho
- Department of Pharmacology and Toxicology; Institute of Biomedicine; Biocenter Oulu; University of Oulu; Oulu; Finland
| | - I. Szokodi
- Heart Institute; Medical School; University of Pécs; Pécs; Hungary
| |
Collapse
|
10
|
Uehara Y, Azuma Y, Minai K, Yoshida H, Yoshimura M, Shimizu M. Endothelin-1 prolongs intracellular calcium transient decay in neonatal rat cardiac myocytes. Heart Vessels 2011; 27:98-105. [DOI: 10.1007/s00380-011-0133-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 03/04/2011] [Indexed: 01/08/2023]
|
11
|
Kohan DE, Rossi NF, Inscho EW, Pollock DM. Regulation of blood pressure and salt homeostasis by endothelin. Physiol Rev 2011; 91:1-77. [PMID: 21248162 DOI: 10.1152/physrev.00060.2009] [Citation(s) in RCA: 276] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Endothelin (ET) peptides and their receptors are intimately involved in the physiological control of systemic blood pressure and body Na homeostasis, exerting these effects through alterations in a host of circulating and local factors. Hormonal systems affected by ET include natriuretic peptides, aldosterone, catecholamines, and angiotensin. ET also directly regulates cardiac output, central and peripheral nervous system activity, renal Na and water excretion, systemic vascular resistance, and venous capacitance. ET regulation of these systems is often complex, sometimes involving opposing actions depending on which receptor isoform is activated, which cells are affected, and what other prevailing factors exist. A detailed understanding of this system is important; disordered regulation of the ET system is strongly associated with hypertension and dysregulated extracellular fluid volume homeostasis. In addition, ET receptor antagonists are being increasingly used for the treatment of a variety of diseases; while demonstrating benefit, these agents also have adverse effects on fluid retention that may substantially limit their clinical utility. This review provides a detailed analysis of how the ET system is involved in the control of blood pressure and Na homeostasis, focusing primarily on physiological regulation with some discussion of the role of the ET system in hypertension.
Collapse
Affiliation(s)
- Donald E Kohan
- Division of Nephrology, University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA.
| | | | | | | |
Collapse
|
12
|
Oikonomidis DL, Baltogiannis GG, Kolettis TM. Do endothelin receptor antagonists have an antiarrhythmic potential during acute myocardial infarction? Evidence from experimental studies. J Interv Card Electrophysiol 2010; 28:157-65. [DOI: 10.1007/s10840-010-9493-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 05/05/2010] [Indexed: 11/24/2022]
|
13
|
Time course and mechanisms of left ventricular systolic and diastolic dysfunction in monocrotaline-induced pulmonary hypertension. Basic Res Cardiol 2009; 104:535-45. [PMID: 19288153 DOI: 10.1007/s00395-009-0017-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Revised: 01/27/2009] [Accepted: 02/24/2009] [Indexed: 10/21/2022]
Abstract
Although pulmonary hypertension (PH) selectively overloads the right ventricle (RV), neuroendocrine activation and intrinsic myocardial dysfunction have been described in the left ventricle (LV). In order to establish the timing of LV dysfunction development in PH and to clarify underlying molecular changes, Wistar rats were studied 4 and 6 weeks after subcutaneous injection of monocrotaline (MCT) 60 mg/kg (MCT-4, n = 11; MCT-6, n = 11) or vehicle (Ctrl-4, n = 11; Ctrl-6, n = 11). Acute single beat stepwise increases of systolic pressure were performed from baseline to isovolumetric (LVPiso). This hemodynamic stress was used to detect early changes in LV performance. Neurohumoral activation was evaluated by measuring angiotensin-converting enzyme (ACE) and endothelin-1 (ET-1) LV mRNA levels. Cardiomyocyte apoptosis was evaluated by TUNEL assay. Extracellular matrix composition was evaluated by tenascin-C mRNA levels and interstitial collagen content. Myosin heavy chain (MHC) composition of the LV was studied by protein quantification. MCT treatment increased RV pressures and RV/LV weight ratio, without changing LV end-diastolic pressures or dimensions. Baseline LV dysfunction were present only in MCT-6 rats. Afterload elevations prolonged tau and upward-shifted end-diastolic pressure dimension relations in MCT-4 and even more in MCT-6. MHC-isoform switch, ACE upregulation and cardiomyocyte apoptosis were present in both MCT groups. Rats with severe PH develop LV dysfunction associated with ET-1 and tenascin-C overexpression. Diastolic dysfunction, however, could be elicited at earlier stages in response to hemodynamic stress, when only LV molecular changes, such as MHC isoform switch, ACE upregulation, and myocardial apoptosis were present.
Collapse
|
14
|
Chu L, Norota I, Ishii K, Endoh M. Wortmannin inhibits the increase in myofilament Ca(2+) sensitivity induced by cross-talk of endothelin-1 with norepinephrine in canine ventricular myocardium. J Pharmacol Sci 2009; 109:193-202. [PMID: 19234363 DOI: 10.1254/jphs.08228fp] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Endothelin-1 (ET-1) modulates cardiac contractility by cross-talk with norepinephrine (NE) in canine ventricular myocardium. The present experiments were performed to investigate the influence of wortmannin that has inhibitory action on phosphatidylinositol 3-kinase (PI3-K) (IC50 = 3 nM) and myosin light chain kinase (MLCK) (IC50 = 200 nM) on Ca(2+) signaling and the inotropic effects of ET-1 induced by cross-talk with NE. Experiments were carried out in isolated canine ventricular trabeculae and indo-1/AM-loaded single ventricular cardiomyocytes. ET-1 alone elicited a transient small negative inotropic effect (NIE). In the presence of NE at low (1-10 nM) and high (100 nM) concentrations, ET-1 induced a long-lasting positive inotropic effect (PIE) or a marked sustained NIE, respectively. Wortmannin up to 300 nM did not affect the contractility; and at 1 microM and higher, it decreased the basal contraction without suppressing Ca(2+) transients. Wortmannin (1 microM) inhibited the long-lasting PIE of ET-1 without affecting the ET-1-induced increase in Ca(2+) transients. Wortmannin at the same concentration did not affect the ET-1-induced transient and sustained NIE and the PIE mediated by beta-adrenoceptor stimulation. These results imply that wortmannin exerts selective inhibitory action on the increase in myofilament Ca(2+) sensitivity induced by cross-talk of ET-1 with NE probably through an inhibition of MLCK in canine ventricular myocardium.
Collapse
Affiliation(s)
- Li Chu
- Department of Cardiovascular Pharmacology, Yamagata University School of Medicine, Japan
| | | | | | | |
Collapse
|
15
|
Krüger M, Sachse C, Zimmermann WH, Eschenhagen T, Klede S, Linke WA. Thyroid Hormone Regulates Developmental Titin Isoform Transitions via the Phosphatidylinositol-3-Kinase/ AKT Pathway. Circ Res 2008; 102:439-47. [DOI: 10.1161/circresaha.107.162719] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Titins, giant sarcomere proteins with major mechanical/signaling functions, are expressed in 2 main isoform classes in the mammalian heart: N2B (3000 kDa) and N2BA (>3200 kDa). A dramatic isoform switch occurs during cardiac development, from fetal N2BA titin (3700 kDa) expressed before birth to a mix of smaller N2BA/N2B isoforms found postnatally; adult rat hearts almost exclusively have N2B titin. The isoform switch, which can be reversed in chronic human heart failure, alters myocardial distensibility and mechanosignaling. Here we determined factors regulating this switch using, as a model system, primary cardiomyocyte cultures prepared from embryonic rats. In standard culture, the mean N2B percentage initially was 14% and increased by ≈60% within 1 week, resembling the in vivo switching. The titin isoform transition was independent of endothelin-1–induced myocyte hypertrophy and was not altered by pacing, contractile arrest, or cell stretch; however, it was modestly impaired by decreasing substrate rigidity and strongly dependent on serum components. Angiotensin II significantly promoted the transition. The mean N2B proportion in 1-week-old cultures dropped 20% to 25% in hormone-reduced medium, but addition of 3,5,3′-triiodo-
l
-thyronine (T3) nearly restored the proportion to that found in standard culture. This T3 effect was not prevented by bisphenol A, a specific inhibitor of the classic genomic pathway of T3 action. In contrast, the titin switch could be stalled by the phosphatidylinositol 3-kinase inhibitor LY294002, which decreased the proportion of N2B mRNA transcripts within hours and suppressed a rapid T3-induced increase in Akt phosphorylation. Also, angiotensin II, but not endothelin-1 or cell stretch, enhanced Akt phosphorylation. Thus, although matrix stiffness modulates developmental titin isoform transitions, these transitions are mainly regulated through phosphatidylinositol 3-kinase/Akt-dependent signaling triggered particularly by T3 via a rapid action pathway.
Collapse
Affiliation(s)
- Martina Krüger
- From the Physiology and Biophysics Unit (M.K., C.S., S.K., W.A.L.), University of Muenster, Germany; and Institute of Experimental and Clinical Pharmacology and Toxicology (W.H.Z., T.E.), University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Christine Sachse
- From the Physiology and Biophysics Unit (M.K., C.S., S.K., W.A.L.), University of Muenster, Germany; and Institute of Experimental and Clinical Pharmacology and Toxicology (W.H.Z., T.E.), University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Wolfram H. Zimmermann
- From the Physiology and Biophysics Unit (M.K., C.S., S.K., W.A.L.), University of Muenster, Germany; and Institute of Experimental and Clinical Pharmacology and Toxicology (W.H.Z., T.E.), University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Thomas Eschenhagen
- From the Physiology and Biophysics Unit (M.K., C.S., S.K., W.A.L.), University of Muenster, Germany; and Institute of Experimental and Clinical Pharmacology and Toxicology (W.H.Z., T.E.), University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Stefanie Klede
- From the Physiology and Biophysics Unit (M.K., C.S., S.K., W.A.L.), University of Muenster, Germany; and Institute of Experimental and Clinical Pharmacology and Toxicology (W.H.Z., T.E.), University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Wolfgang A. Linke
- From the Physiology and Biophysics Unit (M.K., C.S., S.K., W.A.L.), University of Muenster, Germany; and Institute of Experimental and Clinical Pharmacology and Toxicology (W.H.Z., T.E.), University Medical Center Hamburg Eppendorf, Hamburg, Germany
| |
Collapse
|
16
|
Murray DB, Gardner JD, Brower GL, Janicki JS. Effects of nonselective endothelin-1 receptor antagonism on cardiac mast cell-mediated ventricular remodeling in rats. Am J Physiol Heart Circ Physiol 2008; 294:H1251-7. [PMID: 18178727 DOI: 10.1152/ajpheart.00622.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of this study was to investigate the effect a nonselective endothelin-1 (ET-1) receptor antagonist (bosentan) had on the acute myocardial remodeling process including left ventricular (LV) mast cells and matrix metalloproteinase (MMP) activity secondary to volume overload. Additionally, we investigated the overall functional outcome of preventative endothelin receptor antagonism during 14 days of chronic volume overload. LV tissue from sham-operated (Sham), untreated-fistula (Fist), and bosentan (100 mg.kg(-1).day(-1))-treated animals (Fist + Bos) was analyzed for mast cell density, MMP activity, and myocardial collagen volume fraction at 1 and 5 days after the creation of an aortocaval fistula. When compared with untreated fistulas, bosentan treatment prevented the marked increase in LV mast cell density at 1 day postfistula (3.1 +/- 0.3 vs. 1.3 +/- 0.3 LV mast cells/mm2, Fist vs. Fist + Bos, P <or= 0.01). Additionally, the substantial increase in MMP-2 activation in the untreated fistula at 1 day was prevented following bosentan treatment (1.6 +/- 0.3 vs. 0.9 +/- 0.1 arbitrary activity units, Fist vs. Fist + Bos, P <or= 0.01). The marked decrease in collagen volume fraction seen in the Fist group (1.4 +/- 0.1 vs. 0.8 +/- 0.1% myocardial tissue, Sham vs. Fist, P <or= 0.01) was significantly attenuated following bosentan treatment at both the 1- and 5-day time points. Lastly, a 2-wk preventative treatment with bosentan resulted in significant attenuation of the increase in LV end-systolic and -diastolic volumes compared with those in untreated fistula hearts. In summary, nonselective ET-1 antagonism prevents the acute increases in cardiac mast cell density and MMP activation induced secondary to chronic volume overload. By preventing these events, ET-1 antagonism was efficacious in attenuating ventricular dilatation and limiting the development of structural and functional deficits in the first 2 wk of chronic volume overload. Accordingly, these results are the first to demonstrate that cardiac mast cells are responsive to the endogenous endothelin system in vivo. Another novel finding from this study is that chronic nonspecific endothelin antagonism may inadvertently potentiate ET-1-mediated signaling.
Collapse
Affiliation(s)
- David B Murray
- University of South Carolina, School of Medicine, Department of Cell and Developmental Biology and Anatomy, Columbia, SC 29208, USA
| | | | | | | |
Collapse
|
17
|
Fu M, Wu M, Wang JF, Qiao YJ, Wang Z. Disruption of the intracellular Ca2+ homeostasis in the cardiac excitation-contraction coupling is a crucial mechanism of arrhythmic toxicity in aconitine-induced cardiomyocytes. Biochem Biophys Res Commun 2007; 354:929-36. [PMID: 17276394 DOI: 10.1016/j.bbrc.2007.01.082] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Accepted: 01/15/2007] [Indexed: 11/18/2022]
Abstract
Aconitine is an effective ingredient in Aconite tuber, an important traditional Chinese medicine. Aconitine is also known to be a highly toxic diterpenoid alkaloid with arrhythmogenic effects. In the present study, we have characterized the properties of arrhythmic cytotoxicity and explored the possible mechanisms of aconitine-induced cardiomyocytes. Results show that aconitine induces significant abnormity in the spontaneous beating rate, amplitude of spontaneous oscillations and the relative intracellular Ca(2+) concentration. Also, mRNA transcription levels and protein expressions of SR Ca(2+) release channel RyR(2) and sarcolemmal NCX were elevated in aconitine-induced cardiomyocytes. However, co-treatment with ruthenium red (RR), a RyR channel inhibitor, could reverse the aconitine-induced abnormity in intracellular Ca(2+) signals. These results demonstrate that disruption of intracellular Ca(2+) homeostasis in the cardiac excitation-contraction coupling (EC coupling) is a crucial mechanism of arrhythmic cytotoxicity in aconitine-induced cardiomyocytes. Moreover, certain inhibitors appear to play an important role in the detoxification of aconitine-induced Ca(2+)-dependent arrhythmias.
Collapse
Affiliation(s)
- Min Fu
- School of Medicine, Tsinghua University, Beijing, PR China
| | | | | | | | | |
Collapse
|
18
|
Lourenço AP, Roncon-Albuquerque R, Brás-Silva C, Faria B, Wieland J, Henriques-Coelho T, Correia-Pinto J, Leite-Moreira AF. Myocardial dysfunction and neurohumoral activation without remodeling in left ventricle of monocrotaline-induced pulmonary hypertensive rats. Am J Physiol Heart Circ Physiol 2006; 291:H1587-94. [PMID: 16679394 DOI: 10.1152/ajpheart.01004.2005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In monocrotaline (MCT)-induced pulmonary hypertension (PH), only the right ventricle (RV) endures overload, but both ventricles are exposed to enhanced neuroendocrine stimulation. To assess whether in long-standing PH the left ventricular (LV) myocardium molecular/contractile phenotype can be disturbed, we evaluated myocardial function, histology, and gene expression of autocrine/paracrine systems in rats with severe PH 6 wk after subcutaneous injection of 60 mg/kg MCT. The overloaded RV underwent myocardial hypertrophy ( P < 0.001) and fibrosis ( P = 0.014) as well as increased expression of angiotensin-converting enzyme (ACE) (8-fold; P < 0.001), endothelin-1 (ET-1) (6-fold; P < 0.001), and type B natriuretic peptide (BNP) (15-fold; P < 0.001). Despite the similar upregulation of ET-1 (8-fold; P < 0.001) and overexpression of ACE (4-fold; P < 0.001) without BNP elevation, the nonoverloaded LV myocardium was neither hypertrophic nor fibrotic. LV indexes of contractility ( P < 0.001) and relaxation ( P = 0.03) were abnormal, however, and LV muscle strips from MCT-treated compared with sham rats presented negative ( P = 0.003) force-frequency relationships (FFR). Despite higher ET-1 production, BQ-123 (ETA antagonist) did not alter LV MCT-treated muscle strip contractility distinctly ( P = 0.005) from the negative inotropic effect exerted on shams. Chronic daily therapy with 250 mg/kg bosentan (dual endothelin receptor antagonist) after MCT injection not only attenuated RV hypertrophy and local neuroendocrine activation but also completely reverted FFR of LV muscle strips to positive values. In conclusion, the LV myocardium is altered in advanced MCT-induced PH, undergoing neuroendocrine activation and contractile dysfunction in the absence of hypertrophy or fibrosis. Neuroendocrine mediators, particularly ET-1, may participate in this functional deterioration.
Collapse
Affiliation(s)
- André P Lourenço
- Serviço de Fisiologia, Faculdade de Medicina da Universidade do Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Penna C, Rastaldo R, Mancardi D, Cappello S, Pagliaro P, Westerhof N, Losano G. Effect of endothelins on the cardiovascular system. J Cardiovasc Med (Hagerstown) 2006; 7:645-52. [PMID: 16932076 DOI: 10.2459/01.jcm.0000242996.19077.ba] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Endothelins (ETs) exert a persistent constrictor effect on the vessels via an increase in intracellular Ca2+ concentration due to the activation of Na+/H+ and Na+/Ca2+ exchangers of the vascular smooth muscle fibres. They also produce a transient dilator effect via the activation of endothelial nitric oxide synthase mediated by protein kinase B/Akt. ETA and ETB2 receptors are involved in vasoconstriction, whereas transient vasodilatation depends on the activation of ETB1 receptors. Depending on animal species and experimental conditions, ETs can also play a role in cardiac muscle contraction and induce either an increase or a decrease in contractility. It is likely that only ETA, and not ETB, receptors are involved in the ET-induced increase in myocardial contractility. As in the case of vasoconstriction, this inotropic effect depends on an increase in intracellular Ca2+ concentration induced by Na+/H+ and Na+/Ca2+ exchangers. Activation of the Na+/H+ exchanger is stimulated by protein kinase C, which is activated by diacylglycerol released in response to ET activity. It has also been proposed that the positive inotropic effect can occur without the contribution of the Na+/Ca2+ exchanger, if the cell alkalinisation produced by the Na/H exchanger improves myofibrillar Ca2+ sensitivity. A reduction in contractility has been attributed to the involvement of the Gi protein/protein kinase G pathway or to the activation of protein kinase C without an increase in intracellular Ca2+ concentration or in myofibrillar Ca2+ sensitivity. The chronic effect of ETs on the myocardium results in hypertrophy and prevention of apoptosis, two processes that are together responsible for the contradictory effect of ETs in heart failure.
Collapse
Affiliation(s)
- Claudia Penna
- Department of Clinical and Biological Sciences, University of Turin, Turin, Italy
| | | | | | | | | | | | | |
Collapse
|
20
|
Green JJ, Robinson DA, Wilson GE, Simpson RU, Westfall MV. Calcitriol modulation of cardiac contractile performance via protein kinase C. J Mol Cell Cardiol 2006; 41:350-9. [PMID: 16815434 DOI: 10.1016/j.yjmcc.2006.05.019] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 05/01/2006] [Accepted: 05/22/2006] [Indexed: 10/24/2022]
Abstract
Vitamin D(3) deficiency enhances cardiac contraction in experimental studies, yet paradoxically this deficiency is linked to congestive heart failure in humans. Activated vitamin D(3) (1alpha,25-dihydroxyvitamin D(3)) or calcitriol, decreases peak force and activates protein kinase C (PKC) in isolated perfused hearts. However, the direct influence of this hormone on adult cardiac myocyte contractile function is not well understood. Our aim is to investigate whether 1alpha,25-dihydroxyvitamin D(3) acutely modulates contractile function via PKC activation in adult rat cardiac myocytes. Sarcomere shortening and re-lengthening were measured in electrically stimulated myocytes isolated from adult rat hearts, and the vitamin D(3) response (10(-10) to 10(-7) M) was compared to shortening observed under basal conditions. Maximum changes in sarcomere shortening and relaxation were observed with 10(-9) M 1alpha,25-dihydroxyvitamin D(3). This dose decreased peak shortening, and accelerated contraction and relaxation rates within 5 min of administration, and changes in the Ca(2+) transient contributed to the peak shortening and relaxation effects. The PKC inhibitor, bis-indolylmaleimide (500 nM) largely blocked the acute influence of the most potent dose (10(-9) M) on contractile function. While peak shortening and shortening rate returned to baseline within 30 min, there was a sustained acceleration of relaxation that continued over 60 min. Phosphorylation of the Ca(2+) regulatory proteins, phospholamban, and cardiac troponin I correlated with the accelerated relaxation observed in response to acute application of 1alpha,25-dihydroxyvitamin D(3). Accelerated relaxation continued to be observed after chronic addition of 1alpha,25-dihydroxyvitamin D(3) (e.g. 2 days), yet this sustained increase in relaxation was not associated with increased phosphorylation of phospholamban or troponin I. These results provide evidence that 1alpha,25-dihydroxyvitamin D(3) directly modulates adult myocyte contractile function, and protein kinase C plays an important signaling role in the acute response. Phosphorylation of key Ca(2+) regulatory proteins by this kinase contributes to the enhanced relaxation observed in response to acute, but not chronic calcitriol.
Collapse
Affiliation(s)
- John J Green
- Department of Surgery, Cardiac Surgery Section, Ann Arbor, MI 48109, USA
| | | | | | | | | |
Collapse
|
21
|
Proven A, Roderick HL, Conway SJ, Berridge MJ, Horton JK, Capper SJ, Bootman MD. Inositol 1,4,5-trisphosphate supports the arrhythmogenic action of endothelin-1 on ventricular cardiac myocytes. J Cell Sci 2006; 119:3363-75. [PMID: 16882691 DOI: 10.1242/jcs.03073] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although ventricular cardiomyocytes express inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] receptors, it is unclear how these Ca2+ channels contribute to the effects of Gq-coupled agonists. Endothelin-1 augmented the amplitude of pacing-evoked Ca2+ signals (positive inotropy), and caused an increasing frequency of spontaneous diastolic Ca2+-release transients. Both effects of endothelin-1 were blocked by an antagonist of phospholipase C, suggesting that Ins(1,4,5)P3 and/or diacylglycerol production was necessary. The endothelin-1-mediated spontaneous Ca2+ transients were abolished by application of 2-aminoethoxydiphenyl borate (2-APB), an antagonist of Ins(1,4,5)P3 receptors. Incubation of electrically-paced ventricular myocytes with a membrane-permeant Ins(1,4,5)P3 ester provoked the occurrence of spontaneous diastolic Ca2+ transients with the same characteristics and sensitivity to 2-APB as the events stimulated by endothelin-1. In addition to evoking spontaneous Ca2+ transients, stimulation of ventricular myocytes with the Ins(1,4,5)P3 ester caused a positive inotropic effect. The effects of endothelin-1 were compared with two other stimuli, isoproterenol and digoxin, which are known to induce inotropy and spontaneous Ca2+ transients by overloading intracellular Ca2+ stores. The events evoked by isoproterenol and digoxin were dissimilar from those triggered by endothelin-1 in several ways. We propose that Ins(1,4,5)P3 receptors support the development of both inotropy and spontaneous pro-arrhythmic Ca2+ signals in ventricular myocytes stimulated with a Gq-coupled agonist.
Collapse
MESH Headings
- Animals
- Arrhythmias, Cardiac/etiology
- Arrhythmias, Cardiac/metabolism
- Boron Compounds/pharmacology
- Calcium/metabolism
- Calcium Channels/metabolism
- Calcium Signaling
- Digoxin/pharmacology
- Endothelin-1/pharmacology
- Heart Ventricles/drug effects
- Heart Ventricles/metabolism
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors
- Isoproterenol/pharmacology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Rats
- Rats, Wistar
- Receptors, Cytoplasmic and Nuclear/metabolism
- Type C Phospholipases/pharmacology
Collapse
Affiliation(s)
- Andrew Proven
- Calcium Group, Laboratory of Molecular Signalling, Babraham Institute, Babraham, Cambridge, CB2 4AT, UK
| | | | | | | | | | | | | |
Collapse
|
22
|
Mühlhäuser U, Zolk O, Rau T, Münzel F, Wieland T, Eschenhagen T. Atorvastatin desensitizes beta-adrenergic signaling in cardiac myocytes via reduced isoprenylation of G-protein gamma-subunits. FASEB J 2006; 20:785-7. [PMID: 16467371 DOI: 10.1096/fj.05-5067fje] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Statins exert pleiotropic, cholesterol-independent effects by reducing isoprenylation of monomeric GTPases. Here we examined whether statins also reduce isoprenylation of gamma-subunits of heterotrimeric G-proteins and thereby affect beta-adrenergic signaling and regulation of force in cardiac myocytes. Neonatal rat cardiac myocytes (NRCM) were treated with atorvastatin (0.1-10 micromol/l; 12-48 h) and examined for adenylyl cyclase regulating G-protein alpha- (Galpha), beta- (Gbeta), and gamma- (Ggamma) subunits and cAMP accumulation. Engineered heart tissue (EHT) from NRCM was used to evaluate contractile consequences. In atorvastatin-treated NRCM, a second band of Ggamma3 with a lower apparent molecular weight appeared in cytosol and particulate fractions that was absent in vehicle-treated NRCM, but also seen after GGTI-298, a geranylgeranyl transferase inhibitor. In parallel, Gbeta accumulated in the cytosol and total cellular content of Galphas was reduced. In atorvastatin-treated NRCM, the cAMP-increasing effect of isoprenaline was reduced. Likewise, the positive inotropic effect of isoprenaline was desensitized and reduced after treatment with atorvastatin. The effects of atorvastatin were abolished by mevalonate and/or geranylgeranyl pyrophosphate, but not by farnesyl pyrophosphate or squalene. Taken together, the results of this study show that atorvastatin desensitizes NRCM to beta-adrenergic stimulation by a mechanism that involves reduced isoprenylation of Ggamma and subsequent reductions in the cellular content of Galphas.
Collapse
Affiliation(s)
- Ulrike Mühlhäuser
- Institute of Experimental and Clinical Pharmacology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | | | | | | | | |
Collapse
|
23
|
Miura M, Hata Y, Hirayama K, Kita T, Noda Y, Fujisawa K, Shimokawa H, Ishibashi T. Critical role of the Rho-kinase pathway in TGF-beta2-dependent collagen gel contraction by retinal pigment epithelial cells. Exp Eye Res 2005; 82:849-59. [PMID: 16310190 DOI: 10.1016/j.exer.2005.09.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Revised: 09/20/2005] [Accepted: 09/27/2005] [Indexed: 10/25/2022]
Abstract
Retinal pigment epithelial cells (RPEs) are thought to be one of the main components of fibrous membrane observed in eyes with proliferative vitreo-retinopathy. We investigated the signalling mechanisms of TGF-beta2-dependent collagen gel contraction by RPEs. An in vitro type I collagen gel contraction assay was performed to evaluate the effect of TGF-beta2 on gel contraction. The expression of alpha-smooth muscle actin (alpha-SMA) and the phosphorylation state of myosin light chain (MLC) were analyzed by Western blotting. The involvement of protein kinases such as p44/42 mitogen-activated protein kinase (MAPK), protein kinase C (PKC), p38 MAPK and phosphatidylinositol-3 kinase was investigated. The contribution of Rho-kinase and/or MLC-kinase was also evaluated using respective kinase inhibitors (Y27632, hydroxyfasudil and ML7). Additionally, RPEs were immunostained to examine whether the expression of alpha-SMA detected in our western blotting correlated to the stress fiber formation within the cells. TGF-beta2 caused time (0-5 days)-and dose (0 10 ng ml(-1))-dependent gel contraction associated with overexpression of alpha-SMA and phosphorylation of MLC (p < 0.01, respectively). PKC inhibitor (GF109203X, 5 microM) and p38 MAPK inhibitor (SB203580, 10 microM) significantly attenuated TGF-beta2-elicited gel contraction via partial downregulation of both alpha-SMA expression and MLC phosphorylation (p < 0.01, respectively). The gel contraction was prominently inhibited in the presence of Y27632 (10 microM) or hydroxyfasudil (10 microM) with strong suppression of MLC phosphorylation but had no significant effect on alpha-SMA expression. Treatment with ML7, in contrast, resulted in a marginal inhibition of MLC phosphorylation and gel contraction. Finally, pretreatment of the cells with Y27632 or hydroxyfasudil prevented the formation of stress fiber within the cells. These results indicate that TGF-beta2-dependent myofibroblastic transdifferentiation and MLC phosphorylation by RPEs involve both PKC and p38 MAPK pathways at least in part. Myofibroblastic transdifferentiation of RPEs appears to be independent of the Rho-kinase pathway, and the presence of alpha-SMA does not necessarily reflect the contractile potential of a cell. While Rho-kinase inhibitors are incapable of preventing myofibroblastic transdifferentiation itself, this pathway could be one of the critical targets of cell-mediated contraction of the tissue containing fibrillar collagens by transdifferentiated RPEs.
Collapse
Affiliation(s)
- Muneki Miura
- Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | | | | | | | | | | | | | | |
Collapse
|