1
|
Loss of E-Cadherin Leads to Druggable Vulnerabilities in Sphingolipid Metabolism and Vesicle Trafficking. Cancers (Basel) 2021; 14:cancers14010102. [PMID: 35008266 PMCID: PMC8749886 DOI: 10.3390/cancers14010102] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 12/23/2021] [Indexed: 01/02/2023] Open
Abstract
Simple Summary Germline loss of the CDH1 gene is the primary genetic basis for hereditary diffuse gastric cancer, a disease resulting in elevated risk of both diffuse gastric cancer and lobular breast cancer. Current preventative treatment consists of prophylactic total gastrectomy, a therapy with several associated long-term morbidities. To address the lack of targeted molecular therapies for hereditary diffuse gastric cancer, we have utilized a synthetic lethal approach to identify candidate compounds that can specifically kill CDH1-null cells. Inhibitors of sphingolipid metabolism and vesicle trafficking pathways were identified as promising candidate compounds in a cell line model of CDH1 loss, then further validated in murine-derived organoid models of hereditary diffuse gastric cancer. With further research, these findings may lead to the development of novel chemoprevention strategies for the treatment of hereditary diffuse gastric cancer. Abstract Germline inactivating variants of CDH1 are causative of hereditary diffuse gastric cancer (HDGC), a cancer syndrome characterized by an increased risk of both diffuse gastric cancer and lobular breast cancer. Because loss of function mutations are difficult to target therapeutically, we have taken a synthetic lethal approach to identify targetable vulnerabilities in CDH1-null cells. We have previously observed that CDH1-null MCF10A cells exhibit a reduced rate of endocytosis relative to wildtype MCF10A cells. To determine whether this deficiency is associated with wider vulnerabilities in vesicle trafficking, we screened isogenic MCF10A cell lines with known inhibitors of autophagy, endocytosis, and sphingolipid metabolism. Relative to wildtype MCF10A cells, CDH1−/− MCF10A cells showed significantly greater sensitivity to several drugs targeting these processes, including the autophagy inhibitor chloroquine, the endocytosis inhibitors chlorpromazine and PP1, and the sphingosine kinase 1 inhibitor PF-543. Synthetic lethality was confirmed in both gastric and mammary organoid models of CDH1 loss, derived from CD44-Cre/Cdh1fl/fl/tdTomato mice. Collectively, these results suggest that both sphingolipid metabolism and vesicle trafficking represent previously unrecognised druggable vulnerabilities in CDH1-null cells and may lead to the development of new therapies for HDGC.
Collapse
|
2
|
Yokoyama K, Irie M, Tsuchiya N, Yamauchi E, Kawashima M, Miyayama T, Fukuda H, Yamauchi R, Umeda K, Takata K, Tanaka T, Inomata S, Morihara D, Takeyama Y, Shakado S, Sakisaka S, Hirai F. Irsogladine maleate alters expression of a tight junction protein in portal hypertensive gastropathy. J Gastroenterol Hepatol 2021; 36:1208-1215. [PMID: 32926748 DOI: 10.1111/jgh.15259] [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] [Received: 01/09/2020] [Revised: 08/22/2020] [Accepted: 09/06/2020] [Indexed: 12/09/2022]
Abstract
BACKGROUND AND AIM Portal hypertensive gastropathy (PHG) is characterized by noninflammatory edema and vasodilatation of the lamina propria of the mucosal epithelium. In addition, the alterations of intercellular junction proteins and dilatation of the endothelial gaps have been reported. In this study, we examined whether irsogladine maleate (IM), a gastric mucosal protective agent, has the potential to improve PHG by restoration of tight junctions (TJs). METHODS Twenty-four patients with PHG were registered and randomly assigned into two groups: 12 patients in the IM-administration group and 12 patients in the non-administration group. In the administration group, IM (4 mg/day) was administered orally for 12 weeks. Gastric mucosa with a red color in patients with PHG were obtained endoscopically on the registration day and 12 weeks later. The endoscopic findings were evaluated, an immunohistochemical analysis of claudin-3 (a TJ protein) expression in gastric mucosal tissues by a laser microscope was performed, and claudin-3 expression was quantified by western blot analysis. RESULTS Irsogladine maleate improved the degree of PHG in 2/12 patients endoscopically, in contrast to none of the 12 patients in the non-administration group. Immunohistochemical analysis showed that expression of claudin-3 increased in 8/12 patients in the IM-administration group and 2/12 patients in the non-administration group (P = 0.036). Western blot analysis revealed that the increase in claudin-3 after 12 weeks was significantly higher in the IM-administration group than in the non-administration group (P = 0.010). CONCLUSIONS The present pilot study suggested that IM might improve the gastric mucosa in PHG through restoration of TJ-protein claudin-3.
Collapse
Affiliation(s)
- Keiji Yokoyama
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Makoto Irie
- Department of Gastroenterology and Medicine, Fukuoka University Nishijin Hospital, Fukuoka, Japan
| | - Naoaki Tsuchiya
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Eri Yamauchi
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Motoko Kawashima
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Takashi Miyayama
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Hiromi Fukuda
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Ryo Yamauchi
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Kaoru Umeda
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Kazuhide Takata
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Takashi Tanaka
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Shinjiro Inomata
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Daisuke Morihara
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Yasuaki Takeyama
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Satoshi Shakado
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Shotaro Sakisaka
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Fumihito Hirai
- Department of Gastroenterology and Medicine, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| |
Collapse
|
3
|
Toxicologic Evaluation for Amorphous Silica Nanoparticles: Genotoxic and Non-Genotoxic Tumor-Promoting Potential. Pharmaceutics 2020; 12:pharmaceutics12090826. [PMID: 32872498 PMCID: PMC7559769 DOI: 10.3390/pharmaceutics12090826] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 08/20/2020] [Accepted: 08/27/2020] [Indexed: 11/17/2022] Open
Abstract
Amorphous silica nanoparticles (SiO2NPs) have been widely used in medicine including targeted drug/DNA delivery, cancer therapy, and enzyme immobilization. Nevertheless, SiO2NPs should be used with caution due to safety concerns associated with unique physical and chemical characteristics. The objective of this study was to determine the effects of SiO2NPs on genotoxic and non-genotoxic mechanisms associated with abnormal gap junctional intercellular communication (GJIC) in multistage carcinogenesis. The SiO2NPs exhibited negative responses in standard genotoxicity tests including the Ames test, chromosome aberration assay, and micronucleus assay. In contrast, the SiO2NPs significantly induced DNA breakage in comet assay. Meanwhile, SiO2NPs inhibited GJIC based on the results of scrape/loading dye transfer assay for the identification of non-genotoxic tumor-promoting potential. The reduction in expression and plasma membrane localization of Cx43 was detected following SiO2NP treatment. Particularly, SiO2NP treatment increased Cx43 phosphorylation state, which was significantly attenuated by inhibitors of extracellular signal-regulated kinases 1/2 (ERK1/2) and threonine and tyrosine kinase (MEK), but not by protein kinase C (PKC) inhibitor. Taken together, in addition to a significant increase in DNA breakage, SiO2NP treatment resulted in GJIC dysregulation involved in Cx43 phosphorylation through the activation of mitogen-activated protein kinase (MAPK) signaling. Overall findings of the genotoxic and non-genotoxic carcinogenic potential of SiO2NPs provide useful toxicological information for clinical application at an appropriate dose.
Collapse
|
4
|
Kim SJ, Oh HW, Chang JW, Kim SJ. Recovery of Tendon Characteristics by Inhibition of Aberrant Differentiation of Tendon-Derived Stem Cells from Degenerative Tendinopathy. Int J Mol Sci 2020; 21:ijms21082687. [PMID: 32294907 PMCID: PMC7215446 DOI: 10.3390/ijms21082687] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 04/09/2020] [Accepted: 04/10/2020] [Indexed: 11/16/2022] Open
Abstract
The inhibition of the aberrant differentiation of tendon-derived stem cells (TDSCs) is a major target for the regeneration of damaged tendon tissues, as tendinopathy can be caused by the aberrant differentiation of TDSCs. We investigated whether the possible aberrant differentiation of TDSCs can be prevented by using adequate inhibitors. TDSCs extracted from chemically induced tendinopathy and injury-with-overuse tendinopathy models were cultured with 18α-glycyrrhetinic acid (AGA) and T0070907 to block osteogenic differentiation and adipogenic differentiation, respectively. The optimal dose of AGA decreased the osteogenic-specific marker Runx2 (Runt-related transcription factor 2), and T0070907 blocked the adipogenic-specific marker peroxisome proliferator-activated receptor gamma (PPARγ) in mRNA levels. We also found that AGA induced tenogenic differentiation in mRNA levels. However, T0070907 did not affect the tenogenic differentiation and regenerative capacity of TDSCs. We expect that optimal doses of AGA and T0070907 can prevent tendinopathy by inhibiting osteogenic and adipogenic differentiation, respectively. In addition, AGA and T0070907 may play important roles in the treatment of tendinopathy.
Collapse
Affiliation(s)
- Sun Jeong Kim
- Department of Physical and Rehabilitation Medicine, Stem Cell & Regenerative Medicine Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351, Korea;
- R&D Center, ENCell Co. Ltd., Seoul 06072, Korea
| | - Hae Won Oh
- Division of Health Policy and Administration, School of Public Health, University of Illinois, Chicago, IL 60612, USA;
| | - Jong Wook Chang
- R&D Center, ENCell Co. Ltd., Seoul 06072, Korea
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul 06351, Korea
- Stem Cell & Regenerative Medicine Institute, Samsung Medical Center, Seoul 06351, Korea
- Correspondence: (J.W.C.); (S.J.K.); Tel.: +82-2-3410-6048 (J.W.C.); +82-2-576-0100 (S.J.K.)
| | - Sang Jun Kim
- Seoul Jun Research Center, Seoul Jun Rehabilitation Clinic, Seoul 06737, Korea
- Correspondence: (J.W.C.); (S.J.K.); Tel.: +82-2-3410-6048 (J.W.C.); +82-2-576-0100 (S.J.K.)
| |
Collapse
|
5
|
Yang W, Lampe PD, Kensel-Hammes P, Hesson J, Ware CB, Crisa L, Cirulli V. Connexin 43 Functions as a Positive Regulator of Stem Cell Differentiation into Definitive Endoderm and Pancreatic Progenitors. iScience 2019; 19:450-460. [PMID: 31430690 PMCID: PMC6708988 DOI: 10.1016/j.isci.2019.07.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 05/04/2019] [Accepted: 07/18/2019] [Indexed: 01/05/2023] Open
Abstract
Efficient stem cell differentiation into pancreatic islet cells is of critical importance for the development of cell replacement therapies for diabetes. Here, we identify the expression pattern of connexin 43 (Cx43), a gap junction (GJ) channel protein, in human embryonic stem cell (hESC)-derived definitive endoderm (DE) and primitive gut tube cells, representing early lineages for posterior foregut (PF), pancreatic progenitors (PP), pancreatic endocrine progenitors (PE), and islet cells. As the function of GJ channels is dependent on their gating status, we tested the impact of supplementing hESC-derived PP cell cultures with AAP10, a peptide that promotes Cx43 GJ channel opening. We found that this treatment promotes the expression of DE markers FoxA2 and Sox17, leads to a more efficient derivation of DE, and improves the yield of PF, PP, and PE cells. These results demonstrate a functional involvement of GJ channels in the differentiation of embryonic stem cells into pancreatic cell lineages.
Collapse
Affiliation(s)
- Wendy Yang
- Department of Medicine, UW Diabetes Institute, University of Washington, 850 Republican Street, S475, Seattle, WA 98109, USA
| | - Paul D Lampe
- Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Patricia Kensel-Hammes
- Department of Medicine, UW Diabetes Institute, University of Washington, 850 Republican Street, S475, Seattle, WA 98109, USA
| | - Jennifer Hesson
- Institute for Stem Cell and Regenerative Medicine, University of Washington, 850 Republican Street, S480, Seattle, WA 98109, USA
| | - Carol B Ware
- Institute for Stem Cell and Regenerative Medicine, University of Washington, 850 Republican Street, S480, Seattle, WA 98109, USA
| | - Laura Crisa
- Department of Medicine, UW Diabetes Institute, University of Washington, 850 Republican Street, S475, Seattle, WA 98109, USA; Institute for Stem Cell and Regenerative Medicine, University of Washington, 850 Republican Street, S480, Seattle, WA 98109, USA; Department of Pharmacology, University of Washington, Seattle, WA, USA.
| | - Vincenzo Cirulli
- Department of Medicine, UW Diabetes Institute, University of Washington, 850 Republican Street, S475, Seattle, WA 98109, USA; Institute for Stem Cell and Regenerative Medicine, University of Washington, 850 Republican Street, S480, Seattle, WA 98109, USA; Department of Pharmacology, University of Washington, Seattle, WA, USA.
| |
Collapse
|
6
|
Abstract
Purpose of Review Considerable progress has been made in the field of stem cell research; nonetheless, the use of stem cells for regenerative medicine therapies, for either endogenous tissue repair or cellular grafts post injury, remains a challenge. To better understand how to maintain stem cell potential in vivo and promote differentiation ex vivo, it is fundamentally important to elucidate the interactions between stem cells and their surrounding partners within their distinct niches. Recent Findings Among the vast array of proteins depicted as mediators for cell-to-cell interactions, connexin-comprised gap junctions play pivotal roles in the regulation of stem cell fate both in vivo and in vitro. Summary This review summarizes and illustrates the current knowledge regarding the multifaceted roles of Cx43, specifically, in various stem cell niches.
Collapse
Affiliation(s)
- Nafiisha Genet
- Department of Medicine, Genetics and Biomedical Engineering, Yale Cardiovascular Research Center, Vascular Biology Therapeutics Program, New Haven, USA.,2Yale Stem Cell Center Yale University School of Medicine, 300 George St, New Haven, CT 06511 USA
| | - Neha Bhatt
- Department of Medicine, Genetics and Biomedical Engineering, Yale Cardiovascular Research Center, Vascular Biology Therapeutics Program, New Haven, USA.,2Yale Stem Cell Center Yale University School of Medicine, 300 George St, New Haven, CT 06511 USA
| | - Antonin Bourdieu
- Department of Medicine, Genetics and Biomedical Engineering, Yale Cardiovascular Research Center, Vascular Biology Therapeutics Program, New Haven, USA.,2Yale Stem Cell Center Yale University School of Medicine, 300 George St, New Haven, CT 06511 USA
| | - Karen K Hirschi
- Department of Medicine, Genetics and Biomedical Engineering, Yale Cardiovascular Research Center, Vascular Biology Therapeutics Program, New Haven, USA.,2Yale Stem Cell Center Yale University School of Medicine, 300 George St, New Haven, CT 06511 USA
| |
Collapse
|
7
|
Abu Khamidakh AE, Dos Santos FC, Skottman H, Juuti-Uusitalo K, Hyttinen J. Semi-automatic Method for Ca 2+ Imaging Data Analysis of Maturing Human Embryonic Stem Cells-Derived Retinal Pigment Epithelium. Ann Biomed Eng 2016; 44:3408-3420. [PMID: 27225993 DOI: 10.1007/s10439-016-1656-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/17/2016] [Indexed: 10/21/2022]
Abstract
Ca2+ is a second messenger controlling vital cellular processes, including cell maturation. Changes in Ca2+ signaling during maturation of human embryonic stem cell-derived retinal pigment epithelial cells (hESC-RPE) have not been assessed previously. The aim of this study was to investigate maturation-dependent changes in transient intracellular Ca2+ ([Ca2+] i ) increases in hESC-RPE. For this, we developed image analysis tools to evaluate cell-specific Ca2+ signals from the entire field of view. Spontaneous and mechanically induced transient [Ca2+] i increases (STIs and MITIs) were analyzed in hESC-RPEs cultured for 9 or 28 days, altogether from more than 80,000 cells. Both cultures showed STIs: the longer culture time resulted in twofold increase of amount of cells with STIs. Mechanical stimulation induced intercellular Ca2+ waves in cells from both time points, but longer culture time reduced Ca2+ wave spreading. Depletion of intracellular Ca2+ stores decreased cell fraction with STIs and MITIs at both time points, and absence of extracellular Ca2+ had similar effect on cells with STIs. To conclude, hESC-RPE cells undergo significant Ca2+ signaling re-arrangements during a short maturation period increasing cell fraction with STIs, while decreasing coordinated cell response to mechanical stimulation. This knowledge and proposed analysis tools can be used for assessment of hESC-RPE maturation in vitro.
Collapse
Affiliation(s)
- Amna E Abu Khamidakh
- Department of Electronics and Communications Engineering, BioMediTech, Tampere University of Technology, Biokatu 6, FM-1, 33520, Tampere, Finland.
| | - Florentino Caetano Dos Santos
- Department of Electronics and Communications Engineering, BioMediTech, Tampere University of Technology, Biokatu 6, FM-1, 33520, Tampere, Finland
| | - Heli Skottman
- BioMediTech, University of Tampere, Biokatu 12, FM-5, 33520, Tampere, Finland
| | - Kati Juuti-Uusitalo
- BioMediTech, University of Tampere, Biokatu 12, FM-5, 33520, Tampere, Finland
| | - Jari Hyttinen
- Department of Electronics and Communications Engineering, BioMediTech, Tampere University of Technology, Biokatu 6, FM-1, 33520, Tampere, Finland.
| |
Collapse
|
8
|
Schrobback K, Klein TJ, Woodfield TBF. The importance of connexin hemichannels during chondroprogenitor cell differentiation in hydrogel versus microtissue culture models. Tissue Eng Part A 2015; 21:1785-94. [PMID: 25693425 DOI: 10.1089/ten.tea.2014.0691] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Appropriate selection of scaffold architecture is a key challenge in cartilage tissue engineering. Gap junction-mediated intercellular contacts play important roles in precartilage condensation of mesenchymal cells. However, scaffold architecture could potentially restrict cell-cell communication and differentiation. This is particularly important when choosing the appropriate culture platform as well as scaffold-based strategy for clinical translation, that is, hydrogel or microtissues, for investigating differentiation of chondroprogenitor cells in cartilage tissue engineering. We, therefore, studied the influence of gap junction-mediated cell-cell communication on chondrogenesis of bone marrow-derived mesenchymal stromal cells (BM-MSCs) and articular chondrocytes. Expanded human chondrocytes and BM-MSCs were either (re-) differentiated in micromass cell pellets or encapsulated as isolated cells in alginate hydrogels. Samples were treated with and without the gap junction inhibitor 18-α glycyrrhetinic acid (18αGCA). DNA and glycosaminoglycan (GAG) content and gene expression levels (collagen I/II/X, aggrecan, and connexin 43) were quantified at various time points. Protein localization was determined using immunofluorescence, and adenosine-5'-triphosphate (ATP) was measured in conditioned media. While GAG/DNA was higher in alginate compared with pellets for chondrocytes, there were no differences in chondrogenic gene expression between culture models. Gap junction blocking reduced collagen II and extracellular ATP in all chondrocyte cultures and in BM-MSC hydrogels. However, differentiation capacity was not abolished completely by 18αGCA. Connexin 43 levels were high throughout chondrocyte cultures and peaked only later during BM-MSC differentiation, consistent with the delayed response of BM-MSCs to 18αGCA. Alginate hydrogels and microtissues are equally suited culture platforms for the chondrogenic (re-)differentiation of expanded human articular chondrocytes and BM-MSCs. Therefore, reducing direct cell-cell contacts does not affect in vitro chondrogenesis. However, blocking gap junctions compromises cell differentiation, pointing to a prominent role for hemichannel function in this process. Therefore, scaffold design strategies that promote an increasing distance between single chondroprogenitor cells do not restrict their differentiation potential in tissue-engineered constructs.
Collapse
Affiliation(s)
- Karsten Schrobback
- 1Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Australia
| | - Travis Jacob Klein
- 1Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Australia
| | - Tim B F Woodfield
- 1Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Australia
| |
Collapse
|
9
|
Jing D, Baik AD, Lu XL, Zhou B, Lai X, Wang L, Luo E, Guo XE. In situ intracellular calcium oscillations in osteocytes in intact mouse long bones under dynamic mechanical loading. FASEB J 2013; 28:1582-92. [PMID: 24347610 DOI: 10.1096/fj.13-237578] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Osteocytes have been hypothesized to be the major mechanosensors in bone. How in situ osteocytes respond to mechanical stimuli is still unclear because of technical difficulties. In vitro studies have shown that osteocytes exhibited unique calcium (Ca(2+)) oscillations to fluid shear. However, whether this mechanotransduction phenomenon holds for in situ osteocytes embedded within a mineralized bone matrix under dynamic loading remains unknown. Using a novel synchronized loading/imaging technique, we successfully visualized in real time and quantified Ca(2+) responses in osteocytes and bone surface cells in situ under controlled dynamic loading on intact mouse tibia. The resultant fluid-induced shear stress on the osteocyte in the lacunocanalicular system (LCS) was also quantified. Osteocytes, but not surface cells, displayed repetitive Ca(2+) spikes in response to dynamic loading, with spike frequency and magnitude dependent on load magnitude, tissue strain, and shear stress in the LCS. The Ca(2+) oscillations were significantly reduced by endoplasmic reticulum (ER) depletion and P2 purinergic receptor (P2R)/phospholipase C (PLC) inhibition. This study provides direct evidence that osteocytes respond to in situ mechanical loading by Ca(2+) oscillations, which are dependent on the P2R/PLC/inositol trisphosphate/ER pathway. This study develops a novel approach in skeletal mechanobiology and also advances our fundamental knowledge of bone mechanotransduction.
Collapse
Affiliation(s)
- Da Jing
- 1351 Engineering Terrace, Mail Code 8904, 1210 Amsterdam Ave., Columbia University, New York, NY 10027, USA.
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Yang Y, Qin SK, Wu Q, Wang ZS, Zheng RS, Tong XH, Liu H, Tao L, He XD. Connexin-dependent gap junction enhancement is involved in the synergistic effect of sorafenib and all-trans retinoic acid on HCC growth inhibition. Oncol Rep 2013; 31:540-50. [PMID: 24317203 PMCID: PMC3896525 DOI: 10.3892/or.2013.2894] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 11/19/2013] [Indexed: 12/11/2022] Open
Abstract
Increasing gap junction activity in tumor cells provides a target by which to enhance antineoplastic therapies. Previously, several naturally occurring agents, including all-trans retinoic acid (ATRA) have been demonstrated to increase gap junctional intercellular communication (GJIC) in a number of types of cancer cells. In the present study, we investigated in vitro whether ATRA modulates the response of human hepatocellular carcinoma (HCC) cells to sorafenib, the only proven oral drug for advanced HCC, and the underlying mechanisms. HepG2 and SMMC-7721 cells were treated with sorafenib and/or ATRA, and cell proliferation and apoptosis were analyzed; the role of GJIC was also explored. We found that ATRA, at non-toxic concentrations, enhanced sorafenib-induced growth inhibition in both HCC cell lines, and this effect was abolished by two GJIC inhibitors, 18-α-GA and oleamide. Whereas lower concentrations of sorafenib (5 µM) or ATRA (0.1 or 10 µM) alone modestly induced GJIC activity, the combination of sorafenib plus ATRA resulted in a strong enhancement of GJIC. However, the action paradigm differed in the HepG2 and SMMC-7721 cells, with the dominant effect of GJIC dependent on the cell-specific connexin increase in protein amounts and relocalization. RT-PCR assay further revealed a transcriptional modification of the key structural connexin in the two cell lines. Thus, a connexin-dependent gap junction enhancement may play a central role in ATRA plus sorafenib synergy in inhibiting HCC cell growth. Since both agents are available for human use, the combination treatment represents a future profitable strategy for the treatment of advanced HCC.
Collapse
Affiliation(s)
- Yan Yang
- Department of Medical Oncology, The First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, P.R. China
| | - Shu-Kui Qin
- Department of Medical Oncology, PLA Cancer Center, Nanjing Bayi Hospital, Nanjing 210002, P.R. China
| | - Qiong Wu
- Department of Medical Oncology, The First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, P.R. China
| | - Zi-Shu Wang
- Department of Medical Oncology, The First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, P.R. China
| | - Rong-Sheng Zheng
- Department of Medical Oncology, The First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, P.R. China
| | - Xu-Hui Tong
- Department of Pharmacy, Bengbu Medical College, Bengbu 233000, P.R. China
| | - Hao Liu
- Department of Pharmacy, Bengbu Medical College, Bengbu 233000, P.R. China
| | - Liang Tao
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, P.R. China
| | - Xian-Di He
- Department of Intensive Care, The First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, P.R. China
| |
Collapse
|
11
|
Chapman K, Holmes M, Seckl J. 11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action. Physiol Rev 2013; 93:1139-206. [PMID: 23899562 DOI: 10.1152/physrev.00020.2012] [Citation(s) in RCA: 563] [Impact Index Per Article: 51.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.
Collapse
Affiliation(s)
- Karen Chapman
- Endocrinology Unit, Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | | | | |
Collapse
|
12
|
Abu Khamidakh A, Juuti-Uusitalo K, Larsson K, Skottman H, Hyttinen J. Intercellular Ca2+ wave propagation in human retinal pigment epithelium cells induced by mechanical stimulation. Exp Eye Res 2013; 108:129-39. [DOI: 10.1016/j.exer.2013.01.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 01/10/2013] [Accepted: 01/14/2013] [Indexed: 01/19/2023]
|
13
|
Lu XL, Huo B, Park M, Guo XE. Calcium response in osteocytic networks under steady and oscillatory fluid flow. Bone 2012; 51:466-73. [PMID: 22750013 PMCID: PMC3412915 DOI: 10.1016/j.bone.2012.05.021] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 05/04/2012] [Accepted: 05/05/2012] [Indexed: 02/05/2023]
Abstract
The fluid flow in the lacunar-canalicular system of bone is an essential mechanical stimulation on the osteocyte networks. Due to the complexity of human physical activities, the fluid shear stress on osteocyte bodies and processes consists of both steady and oscillatory components. In this study, we investigated and compared the intracellular calcium ([Ca(2+)](i)) responses of osteocytic networks under steady and oscillatory fluid flows. An in vitro osteocytic network was built with MLO-Y4 osteocyte-like cells using micro-patterning techniques to simulate the in vivo orderly organization of osteocyte networks. Sinusoidal oscillating fluid flow or unidirectional steady flow was applied on the cell surface with 2Pa peak shear stress. It was found that the osteocytic networks were significantly more responsive to steady flow than to oscillatory flow. The osteocytes can release more calcium peaks with higher magnitudes at a faster speed under steady flow stimulation. The [Ca(2+)](i) signaling transients under the steady and oscillatory flows have significantly different spatiotemporal characters, but a similar responsive percentage of cells. Further signaling pathway studies using inhibitors showed that endoplasmic reticulum (ER) calcium store, extracellular calcium source, ATP, PGE(2) and NO related pathways play similar roles in the [Ca(2+)](i) signaling of osteocytes under either steady or oscillating flow. The spatiotemporal characteristics of [Ca(2+)](i) transients under oscillating fluid flow are affected more profoundly by pharmacological treatments than under the steady flow. Our findings support the hypothesis that the [Ca(2+)](i) responses of osteocytic networks are significantly dependent on the profiles of fluid flow.
Collapse
Affiliation(s)
- X. Lucas Lu
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY 10027
- Department of Mechanical Engineering, University of Delaware, Newark, DE 19716
| | - Bo Huo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY 10027
- Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Miri Park
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY 10027
- Department of Mechanical Engineering, University of Delaware, Newark, DE 19716
| | - X. Edward Guo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY 10027
- Address correspondence to: Professor X. Edward Guo, Department of Biomedical Engineering, Columbia University, 351 Engineering Terrace, 1210 Amsterdam Avenue, New York, NY 10027, Telephone: (212) 854-6196, Fax: (212) 854-8725,
| |
Collapse
|
14
|
Lu XL, Huo B, Chiang V, Guo XE. Osteocytic network is more responsive in calcium signaling than osteoblastic network under fluid flow. J Bone Miner Res 2012; 27:563-74. [PMID: 22113822 PMCID: PMC3343217 DOI: 10.1002/jbmr.1474] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Osteocytes, regarded as the mechanical sensor in bone, respond to mechanical stimulation by activating biochemical pathways and mediating the cellular activities of other bone cells. Little is known about how osteocytic networks respond to physiological mechanical stimuli. In this study, we compared the mechanical sensitivity of osteocytic and osteoblastic networks under physiological-related fluid shear stress (0.5 to 4 Pa). The intracellular calcium ([Ca(2+)](i)) responses in micropatterned in vitro osteoblastic or osteocytic networks were recorded and analyzed. Osteocytes in the network showed highly repetitive spikelike [Ca(2+)](i) peaks under fluid flow stimulation, which are dramatically different from those in the osteoblastic network. The number of responsive osteocytes in the network remained at a constant high percentage (>95%) regardless of the magnitude of shear stress, whereas the number of responsive osteoblasts in the network significantly depends on the strength of fluid flow. All spatiotemporal parameters of calcium signaling demonstrated that osteocytic networks are more sensitive and dynamic than osteoblastic networks, especially under low-level mechanical stimulations. Furthermore, pathway studies were performed to identify the molecular mechanisms responsible for the differences in [Ca(2+)](i) signaling between osteoblastic and osteocytic networks. The results suggested that the T-type voltage-gated calcium channels (VGCC) expressed on osteocytes may play an essential role in the unique kinetics of [Ca(2+)](i) signaling in osteocytic networks, whereas the L-type VGCC is critical for both types of cells to release multiple [Ca(2+)](i) peaks. The extracellular calcium source and intracellular calcium store in ER-, ATP-, PGE₂-, NO-, and caffeine-related pathways are found to play similar roles in the [Ca(2+)](i) signaling for both osteoblasts and osteocytes. The findings in this study proved that osteocytic networks possess unique characteristics in sensing and processing mechanical signals.
Collapse
Affiliation(s)
- X Lucas Lu
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | | | | | | |
Collapse
|
15
|
Yao J, Huang T, Fang X, Chi Y, Zhu Y, Wan Y, Matsue H, Kitamura M. Disruption of gap junctions attenuates aminoglycoside-elicited renal tubular cell injury. Br J Pharmacol 2010; 160:2055-68. [PMID: 20649601 DOI: 10.1111/j.1476-5381.2010.00860.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Gap junctions play important roles in the regulation of cell phenotype and in determining cell survival after various insults. Here, we investigated the role of gap junctions in aminoglycoside-induced injury to renal tubular cells. EXPERIMENTAL APPROACH Two tubular epithelial cell lines NRK-E52 and LLC-PK1 were compared for gap junction protein expression and function by immunofluorescent staining, Western blot and dye transfer assay. Cell viability after exposure to aminoglycosides was evaluated by WST assay. Gap junctions were modulated by transfection of the gap junction protein, connexin 43 (Cx43), use of Cx43 siRNA and gap junction inhibitors. KEY RESULTS NRK-E52 cells expressed abundant Cx43 and were functionally coupled by gap junctional intercellular communication (GJIC). Exposure of NRK-E52 cells to aminoglycosides, G418 and hygromycin, increased Cx43 phosphorylation and GJIC. The aminoglycosides also decreased cell viability that was prevented by gap junction inhibitors and Cx43 siRNA. LLC-PK1 cells were gap junction-deficient and resistant to aminoglycoside-induced cytotoxicity. Over-expression of a wild-type Cx43 converted LLC-PK1 cells to a drug-sensitive phenotype. The gap junction inhibitor alpha-glycyrrhetinic acid (alpha-GA) activated Akt in NRK-E52 cells. Inhibition of the Akt pathway enhanced cell toxicity to G418 and abolished the protective effects of alpha-GA. In addition, gentamycin-elicited cytotoxicity in NRK-E52 cells was also significantly attenuated by alpha-GA. CONCLUSION AND IMPLICATIONS Gap junctions contributed to the cytotoxic effects of aminoglycosides. Modulation of gap junctions could be a promising approach for prevention and treatment of aminoglycoside-induced renal tubular cell injury.
Collapse
Affiliation(s)
- Jian Yao
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Abstract
Gap junctions are protein channels between cells that allow direct electrical and metabolic coupling via the exchange of biomolecules and ions. Their expression, though ubiquitous in most mammalian cell types, is especially important for the proper functioning of cardiac and neuronal systems. Many existing methods for studying gap junction communication suffer from either unquantifiable data or difficulty of use. Here, we measure the extent of dye spread and effective diffusivities through gap junction connected cells using a quantitative microfluidic cell biology platform. After loading dye by hydrodynamic focusing of calcein/AM, dye transfer dynamics into neighboring, unexposed cells can be monitored via timelapse fluorescent microscopy. By using a selective microfluidic dye loading over a confluent layer of cells, we found that high expression of gap junctions in C6 cells transmits calcein across the monolayer with an effective diffusivity of 3.4 x 10(-13) m(2)/s, which are highly coupled by Cx43. We also found that the gap junction blocker 18alpha-GA works poorly in the presence of serum even at high concentrations (50 microM); however, it is highly effective down to 2.5 microM in the absence of serum. Furthermore, when the drug is washed out, dye spread resumes rapidly within 1 min for all doses, indicating the drug does not affect transcriptional regulation of connexins in these Cx43+ cells, in contrast to previous studies. This integrated microfluidic platform enables the in situ monitoring of gap junction communication, yielding dynamic information about intercellular molecular transfer and pharmacological inhibition and recovery.
Collapse
Affiliation(s)
- Sisi Chen
- Biomolecular Nanotechnology Center, Berkeley Sensor & Actuator Center, Department of Bioengineering, University of California-Berkeley, 408C Stanley Hall, CA 94720-1762, USA
| | | |
Collapse
|
17
|
Huo B, Lu XL, Costa KD, Xu Q, Guo XE. An ATP-dependent mechanism mediates intercellular calcium signaling in bone cell network under single cell nanoindentation. Cell Calcium 2010; 47:234-41. [PMID: 20060586 DOI: 10.1016/j.ceca.2009.12.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Revised: 10/07/2009] [Accepted: 12/07/2009] [Indexed: 11/15/2022]
Abstract
To investigate the roles of intercellular gap junctions and extracellular ATP diffusion in bone cell calcium signaling propagation in bone tissue, in vitro bone cell networks were constructed by using microcontact printing and self-assembled monolayer technologies. In the network, neighboring cells were interconnected through functional gap junctions. A single cell at the center of the network was mechanically stimulated by using an AFM nanoindenter. Intracellular calcium ([Ca2+](i)) responses of the bone cell network were recorded and analyzed. In the untreated groups, calcium propagation from the stimulated cell to neighboring cells was observed in 40% of the tests. No significant difference was observed in this percentage when the intercellular gap junctions were blocked. This number, however, decreased to 10% in the extracellular ATP-pathway-blocked group. When both the gap junction and ATP pathways were blocked, intercellular calcium waves were abolished. When the intracellular calcium store in ER was depleted, the indented cell can generate calcium transients, but no [Ca2+](i) signal can be propagated to the neighboring cells. No [Ca2+](i) response was detected in the cell network when the extracellular calcium source was removed. These findings identified the biochemical pathways involved in the calcium signaling propagation in bone cell networks.
Collapse
Affiliation(s)
- Bo Huo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | | | | | | | | |
Collapse
|
18
|
Lefkimmiatis K, Moyer MP, Curci S, Hofer AM. "cAMP sponge": a buffer for cyclic adenosine 3', 5'-monophosphate. PLoS One 2009; 4:e7649. [PMID: 19888343 PMCID: PMC2766031 DOI: 10.1371/journal.pone.0007649] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Accepted: 10/06/2009] [Indexed: 11/18/2022] Open
Abstract
Background While intracellular buffers are widely used to study calcium signaling, no such tool exists for the other major second messenger, cyclic AMP (cAMP). Methods/Principal Findings Here we describe a genetically encoded buffer for cAMP based on the high-affinity cAMP-binding carboxy-terminus of the regulatory subunit RIβ of protein kinase A (PKA). Addition of targeting sequences permitted localization of this fragment to the extra-nuclear compartment, while tagging with mCherry allowed quantification of its expression at the single cell level. This construct (named “cAMP sponge”) was shown to selectively bind cAMP in vitro. Its expression significantly suppressed agonist-induced cAMP signals and the downstream activation of PKA within the cytosol as measured by FRET-based sensors in single living cells. Point mutations in the cAMP-binding domains of the construct rendered the chimera unable to bind cAMP in vitro or in situ. Cyclic AMP sponge was fruitfully applied to examine feedback regulation of gap junction-mediated transfer of cAMP in epithelial cell couplets. Conclusions This newest member of the cAMP toolbox has the potential to reveal unique biological functions of cAMP, including insight into the functional significance of compartmentalized signaling events.
Collapse
Affiliation(s)
- Konstantinos Lefkimmiatis
- VA Boston Healthcare System and the Department of Surgery, Brigham and Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts, United States of America
| | - Mary Pat Moyer
- INCELL Corporation LLC, San Antonio, Texas, United States of America
| | - Silvana Curci
- VA Boston Healthcare System and the Department of Surgery, Brigham and Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts, United States of America
| | - Aldebaran M. Hofer
- VA Boston Healthcare System and the Department of Surgery, Brigham and Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
19
|
Huo B, Lu XL, Hung CT, Costa KD, Xu Q, Whitesides GM, Guo XE. Fluid Flow Induced Calcium Response in Bone Cell Network. Cell Mol Bioeng 2008; 1:58-66. [PMID: 20852730 DOI: 10.1007/s12195-008-0011-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In our previous work, bone cell networks with controlled spacing and functional intercellular gap junctions had been successfully established by using microcontact printing and self assembled monolayers technologies [Guo, X. E., E. Takai, X. Jiang, Q. Xu, G. M. Whitesides, J. T. Yardley, C. T. Hung, E. M. Chow, T. Hantschel, and K. D. Costa. Mol. Cell. Biomech. 3:95-107, 2006]. The present study investigated the calcium response and the underlying signaling pathways in patterned bone cell networks exposed to a steady fluid flow. The glass slides with cell networks were separated into eight groups for treatment with specific pharmacological agents that inhibit pathways significant in bone cell calcium signaling. The calcium transients of the network were recorded and quantitatively evaluated with a set of network parameters. The results showed that 18α-GA (gap junction blocker), suramin (ATP inhibitor), and thapsigargin (depleting intracellular calcium stores) significantly reduced the occurrence of multiple calcium peaks, which were visually obvious in the untreated group. The number of responsive peaks also decreased slightly yet significantly when either the COX-2/PGE(2) or the NOS/nitric oxide pathway was disrupted. Different from all other groups, cells treated with 18α-GA maintained a high concentration of intracellular calcium following the first peak. In the absence of calcium in the culture medium, the intracellular calcium concentration decreased slowly with fluid flow without any calcium transients observed. These findings have identified important factors in the flow mediated calcium signaling of bone cells within a patterned network.
Collapse
Affiliation(s)
- Bo Huo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, 351 Engineering Terrace, 1210 Amsterdam Avenue, Mail Code 8904, New York, NY 10027, USA
| | | | | | | | | | | | | |
Collapse
|
20
|
Nagasawa K, Chiba H, Fujita H, Kojima T, Saito T, Endo T, Sawada N. Possible involvement of gap junctions in the barrier function of tight junctions of brain and lung endothelial cells. J Cell Physiol 2006; 208:123-32. [PMID: 16547974 DOI: 10.1002/jcp.20647] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Gap-junction plaques are often observed with tight-junction strands of vascular endothelial cells but the molecular interaction and functional relationships between these two junctions remain obscure. We herein show that gap-junction proteins connexin40 (Cx40) and Cx43 are colocalized and coprecipitated with tight-junction molecules occludin, claudin-5, and ZO-1 in porcine blood-brain barrier (BBB) endothelial cells. Gap junction blockers 18beta-glycyrrhetinic acid (18beta-GA) and oleamide (OA) did not influence expression of Cx40, Cx43, occludin, claudin-5, junctional adhesion molecule (JAM)-A, JAM-B, JAM-C, or ZO-1, or their subcellular localization in the porcine BBB endothelial cells. In contrast, these gap-junction blocking agents inhibited the barrier function of tight junctions in cells, determined by measurement of transendothelial electrical resistance and paracellular flux of mannitol and inulin. 18beta-GA also significantly reduced the barrier property in rat lung endothelial (RLE) cells expressing doxycycline-induced claudin-1, but did not change the interaction between Cx43 and either claudin-1 or ZO-1, nor their expression levels or subcellular distribution. These findings suggest that Cx40- and/or Cx43-based gap junctions might be required to maintain the endothelial barrier function without altering the expression and localization of the tight-junction components analyzed.
Collapse
Affiliation(s)
- Kunihiko Nagasawa
- Department of Pathology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | | | | | | | | | | | | |
Collapse
|
21
|
Rodríguez-Sinovas A, García-Dorado D, Ruiz-Meana M, Soler-Soler J. Protective effect of gap junction uncouplers given during hypoxia against reoxygenation injury in isolated rat hearts. Am J Physiol Heart Circ Physiol 2006; 290:H648-56. [PMID: 16183732 DOI: 10.1152/ajpheart.00439.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has been shown that cell-to-cell chemical coupling may persist during severe myocardial hypoxia or ischemia. We aimed to analyze the effects of different, chemically unrelated gap junction uncouplers on the progression of ischemic injury in hypoxic myocardium. First, we analyzed the effects of heptanol, 18α-glycyrrhetinic acid, and palmitoleic acid on intracellular Ca2+ concentration during simulated hypoxia (2 mM NaCN) in isolated cardiomyocytes. Next, we analyzed their effects on developed and diastolic tension and electrical impedance in 47 isolated rat hearts submitted to 40 min of hypoxia and reoxygenation. All treatments were applied only during the hypoxic period. Cell injury was determined by lactate dehydrogenase (LDH) release. Heptanol, but not 18α-glycyrrhetinic acid nor palmitoleic acid, attenuated the increase in cytosolic Ca2+ concentration induced by simulated ischemia in cardiomyocytes and delayed rigor development (rigor onset at 7.31 ± 0.71 min in controls vs. 14.76 ± 1.44 in heptanol-treated hearts, P < 0.001) and the onset of the marked changes in electrical impedance (tissue resistivity: 4.02 ± 0.29 vs. 7.75 ± 1.84 min, P = 0.016) in hypoxic rat hearts. LDH release from hypoxic hearts was minimal and was not significantly modified by drugs. However, all gap junction uncouplers, given during hypoxia, attenuated LDH release during subsequent reoxygenation. Dose-response analysis showed that increasing heptanol concentration beyond the level associated with maximal effects on cell coupling resulted in further protection against hypoxic injury. In conclusion, gap junction uncoupling during hypoxia has a protective effect on cell death occurring upon subsequent reoxygenation, and heptanol has, in addition, a marked protective effect independent of its uncoupling actions.
Collapse
Affiliation(s)
- Antonio Rodríguez-Sinovas
- Laboratorio de Investigación Cardiovascular, Hospitals Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain
| | | | | | | |
Collapse
|
22
|
Martin PEM, Wall C, Griffith TM. Effects of connexin-mimetic peptides on gap junction functionality and connexin expression in cultured vascular cells. Br J Pharmacol 2005; 144:617-27. [PMID: 15678088 PMCID: PMC1576046 DOI: 10.1038/sj.bjp.0706102] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. We have investigated the effects of connexin-mimetic peptides homologous to the Gap 26 and Gap 27 domains of Cxs 37, 40 and 43 against gap junctional communication and connexin expression in rat aortic endothelial cells (RAECs) and A7r5 myocytes. 2. Immunostaining and Western blot analysis confirmed the presence of gap junction plaques containing Cx43, but not Cx40, in RAECs, whereas plaques containing Cxs 40 and 43 were evident in A7r5 cells. Expression of Cx37 was limited in RAECs and absent from A7r5 cells. 3. Under control conditions calcein-loaded RAECs transferred dye to approximately 70% of subjacent A7r5 cells after coculture for 4-5 h. Dye transfer was inhibited by a peptide targeted to Cxs 37 and 43 ((37,43)Gap 27), but minimally affected by peptides targeted to Cxs 37 and 40 ((37,40)Gap 26 and (40)Gap 27). These findings suggest that the myoendothelial gap junctions that couple RAECs and A7r5 cells are constructed principally from Cx43. 4. Inhibition of dye transfer from RAECs to A7r5 cells cocultured in the presence of (37,43)Gap 27 plus (37,40)Gap 26 for 5 h was fully reversible. 5. In A7r5 cells, endogenous expression of Cx40 and Cx43 was unaffected by incubation with (37,43)Gap 27, (37,40)Gap 26, either individually or in combination, and the peptide combination did not impair connexin trafficking or the de novo formation of gap plaques in A7r5 cells transfected to express Cx43-GFP. 6. Treatment of A7r5 cells with (37,43)Gap 27 plus (37,40)Gap 26 abolished synchronized oscillations in intracellular [Ca2+] induced by the alpha1-adrenoceptor agonist phenylephrine. 7. The reversibility and lack of effect of the peptides on plaque formation suggests that they may be considered ideal probes for functional studies of connexin-mediated communication in the vascular wall.
Collapse
Affiliation(s)
- Patricia E M Martin
- Department of Diagnostic Radiology, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff CF14 4XN.
| | | | | |
Collapse
|
23
|
Griffith TM. Endothelium-dependent smooth muscle hyperpolarization: do gap junctions provide a unifying hypothesis? Br J Pharmacol 2005; 141:881-903. [PMID: 15028638 PMCID: PMC1574270 DOI: 10.1038/sj.bjp.0705698] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
An endothelium-derived hyperpolarizing factor (EDHF) that is distinct from nitric oxide (NO) and prostanoids has been widely hypothesized to hyperpolarize and relax vascular smooth muscle following stimulation of the endothelium by agonists. Candidates as diverse as K(+) ions, eicosanoids, hydrogen peroxide and C-type natriuretic peptide have been implicated as the putative mediator, but none has emerged as a 'universal EDHF'. An alternative explanation for the EDHF phenomenon is that direct intercellular communication via gap junctions allows passive spread of agonist-induced endothelial hyperpolarization through the vessel wall. In some arteries, eicosanoids and K(+) ions may themselves initiate a conducted endothelial hyperpolarization, thus suggesting that electrotonic signalling may represent a general mechanism through which the endothelium participates in the regulation of vascular tone.
Collapse
Affiliation(s)
- Tudor M Griffith
- Department of Diagnostic Radiology, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN.
| |
Collapse
|
24
|
Takeda Y, Ward SM, Sanders KM, Koh SD. Effects of the gap junction blocker glycyrrhetinic acid on gastrointestinal smooth muscle cells. Am J Physiol Gastrointest Liver Physiol 2005; 288:G832-41. [PMID: 15528254 DOI: 10.1152/ajpgi.00389.2004] [Citation(s) in RCA: 28] [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
In the tunica muscularis of the gastrointestinal (GI) tract, gap junctions form low-resistance pathways between pacemaker cells known as interstitial cells of Cajal (ICCs) and between ICC and smooth muscle cells. Coupling via these junctions facilitates electrical slow-wave propagation and responses of smooth muscle to enteric motor nerves. Glycyrrhetinic acid (GA) has been shown to uncouple gap junctions, but previous studies have shown apparent nonspecific effects of GA in a variety of tissues. We tested the effects of GA using isometric force measurements, intracellular microelectrode recordings, the patch-clamp technique, and the spread of Lucifer yellow within cultured ICC networks. In murine small intestinal muscles, beta-GA (10 muM) decreased phasic contractions and depolarized resting membrane potential. Preincubation of GA inhibited the spread of Lucifer yellow, increased input resistance, and decreased cell capacitance in ICC networks, suggesting that GA uncoupled ICCs. In patch-clamp experiments of isolated jejunal myocytes, GA significantly decreased L-type Ca(2+) current in a dose-dependent manner without affecting the voltage dependence of this current. The IC(50) for Ca(2+) currents was 1.9 muM, which is lower than the concentrations used to block gap junctions. GA also significantly increased large-conductance Ca(2+)-activated K(+) currents but decreased net delayed rectifier K(+) currents, including 4-aminopyridine and tetraethylammonium-resistant currents. In conclusion, the reduction of phasic contractile activity of GI muscles by GA is likely a consequence of its inhibitory effects on gap junctions and voltage-dependent Ca(2+) currents. Membrane depolarization may be a consequence of uncoupling effects of GA on gap junctions between ICCs and smooth muscles and inhibition of K(+) conductances in smooth muscle cells.
Collapse
Affiliation(s)
- Yukari Takeda
- Univ. of Nevada School of Medicine, 352 Anderson Medical Bldg., Reno, NV 89557, USA
| | | | | | | |
Collapse
|
25
|
Hewitt A, Barrie R, Graham M, Bogus K, Leiter JC, Erlichman JS. Ventilatory effects of gap junction blockade in the RTN in awake rats. Am J Physiol Regul Integr Comp Physiol 2004; 287:R1407-18. [PMID: 15308490 DOI: 10.1152/ajpregu.00404.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that carbenoxolone, a pharmacological inhibitor of gap junctions, would reduce the ventilatory response to CO(2) when focally perfused within the retrotrapezoid nucleus (RTN). We tested this hypothesis by measuring minute ventilation (V(E)), tidal volume (V(T)), and respiratory frequency (F(R)) responses to increasing concentrations of inspired CO(2) (Fi(CO(2)) = 0-8%) in rats during wakefulness. We confirmed that the RTN was chemosensitive by perfusing the RTN unilaterally with either acetazolamide (AZ; 10 microM) or hypercapnic artificial cerebrospinal fluid equilibrated with 50% CO(2) (pH approximately 6.5). Focal perfusion of AZ or hypercapnic aCSF increased V(E), V(T), and F(R) during exposure to room air. Carbenoxolone (300 microM) focally perfused into the RTN decreased V(E) and V(T) in animals <11 wk of age, but V(E) and V(T) were increased in animals >12 wk of age. Glyzyrrhizic acid, a congener of carbenoxolone, did not change V(E), V(T), or F(R) when focally perfused into the RTN. Carbenoxolone binds to the mineralocorticoid receptor, but spironolactone (10 microM) did not block the disinhibition of V(E) or V(T) in older animals when combined with carbenoxolone. Thus the RTN is a CO(2) chemosensory site in all ages tested, but the function of gap junctions in the chemosensory process varies substantially among animals of different ages: gap junctions amplify the ventilatory response to CO(2) in younger animals, but appear to inhibit the ventilatory response to CO(2) in older animals.
Collapse
Affiliation(s)
- Amy Hewitt
- Department of Biology, St. Lawrence University, Canton, NY 13617, USA
| | | | | | | | | | | |
Collapse
|
26
|
Rodriguez-Sinovas A, García-Dorado D, Ruiz-Meana M, Soler-Soler J. Enhanced effect of gap junction uncouplers on macroscopic electrical properties of reperfused myocardium. J Physiol 2004; 559:245-57. [PMID: 15218064 PMCID: PMC1665057 DOI: 10.1113/jphysiol.2004.065144] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Transient inhibition of gap junction (GJ)-mediated communication with heptanol during myocardial reperfusion limits infarct size. However, inhibition of cell coupling in normal myocardium may be arrhythmogenic. The purpose of this study was to test the hypothesis that the consequences of GJ inhibition may be magnified in reperfused myocardium compared with normal tissue, thus allowing the inhibition of GJs in reperfused tissue while only minimally modifying overall macroscopic cell coupling in normal myocardium. Concentration-response curves were defined for the effects of heptanol, 18alpha-glycyrrhetinic acid, halothane, and palmitoleic acid on conduction velocity, tissue electrical impedance, developed tension and lactate dehydrogenase (LDH) release in normoxically perfused rat hearts (n= 17). Concentrations lacking significant effects on tissue impedance were added during the initial 15 min of reperfusion in hearts submitted to 60 min (n= 43) or 30 min (n= 35) of ischaemia. These concentrations markedly increased myocardial electrical impedance (resistivity and phase angle) in myocardium reperfused after either 30 or 60 min of ischaemia, and reduced reperfusion-induced LDH release after 1 h of ischaemia by 83.6, 57.9, 51.7 and 52.5% for heptanol, 18alpha-glycyrrhetinic acid, halothane and palmitoleic acid, respectively. LDH release was minimal in hearts submitted to 30 min of ischaemia, independently of group allocation. In conclusion, the present results strongly support the hypothesis that intercellular communication in postischaemic myocardium may be effectively reduced by concentrations of GJ inhibitors affecting only minimally overall electrical impedance in normal myocardium. Reduction of cell coupling during initial reperfusion was consistently associated with attenuated lethal reperfusion injury.
Collapse
Affiliation(s)
- Antonio Rodriguez-Sinovas
- Laboratorio de Investigación Cardiovascular, Servicio de Cadiología, Hospitals Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain
| | | | | | | |
Collapse
|
27
|
Martin PEM, Hill NS, Kristensen B, Errington RJ, Griffith TM. Ouabain exerts biphasic effects on connexin functionality and expression in vascular smooth muscle cells. Br J Pharmacol 2004; 141:374-84. [PMID: 14971424 PMCID: PMC1574206 DOI: 10.1038/sj.bjp.0705671] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2003] [Revised: 09/08/2003] [Accepted: 09/20/2003] [Indexed: 11/08/2022] Open
Abstract
1. We have compared the effects of ouabain on the maintenance of gap junctional communication in rat aortic A7r5 smooth muscle cells, monkey COS-1 fibroblasts and human HeLa epithelial cells. 2. Ouabain (1 mM) interrupted dye coupling between confluent A7r5 cells within approximately 1 h, and high concentrations of ouabain were similarly required to reduce coupling between COS-1 cells selected to express the rat alpha1 Na+/K+-ATPase subunit, which is ouabain resistant. By contrast, low concentrations of ouabain (1-10 microM) attenuated dye transfer in wild-type COS-1 and HeLa cells, whose endogenous alpha1 subunits possess relatively high affinity for the glycoside (Ki approximately 0.3 vs approximately 100 microM) Ouabain-induced reductions in dye transfer therefore correlated with the ability of the glycoside to bind to the Na+/K+-ATPase isoenzymes expressed in these different cell lines. 3. No consistent relationship between inhibition of intercellular dye transfer and secondary changes in [Ca2+]i or pHi could be identified following incubation with ouabain. 4. In separate experiments, the effects of ouabain on real-time trafficking of connexin (Cx) protein were monitored by time-lapse microscopy of A7r5 cells transfected to express a fluorescent Cx43-green fluorescent protein (GFP) and the ability of the glycoside to modulate endogenous expression of Cx40 and Cx43 evaluated in A7r5 cells by immunochemical and Western blot analysis. 5. Ouabain (1 mM) depressed vesicular trafficking of Cx43-GFP after approximately 1 h, and caused a time-dependent loss of endogenous Cx40 and Cx43 protein that was first evident at 2 h and almost complete after 4 h. These effects of ouabain on Cx expression were reversed 90 min following washout of the glycoside. 6. We conclude that ouabain exerts biphasic effects on intercellular communication that involve an initial decrease in gap junctional permeability followed by a global reduction in the expression of Cx protein. Further studies are necessary to establish to what extent these actions of ouabain reflect inversion of the normal [Na+]i/[K+]i ratio and/or conversion of the Na+/K+-ATPase into a general signal transducer that regulates downstream protein synthesis.
Collapse
Affiliation(s)
- Patricia E M Martin
- Department of Diagnostic Radiology, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN
| | - Nathan S Hill
- Department of Diagnostic Radiology, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN
| | - Bo Kristensen
- Biomembrane Center, The August Krogh Institute, Universitetsparken 13, Copenhagen, DK-2100, Denmark
| | - Rachael J Errington
- Department of Medical Biochemistry, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN
| | - Tudor M Griffith
- Department of Diagnostic Radiology, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN
| |
Collapse
|
28
|
Guo Y, Martinez-Williams C, Rannels DE. Gap junction-microtubule associations in rat alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2003; 285:L1213-21. [PMID: 14604851 DOI: 10.1152/ajplung.00066.2003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Connexin 43 (Cx43) is a predominant gap junction (GJ) protein expressed by alveolar epithelial cells (AEC) in primary cell culture. Cx43 trafficking, assembly, and turnover are regulated by multiple mechanisms, including those mediated by integrins, by extracellular matrix, and by the cytoskeleton. Immunocytochemical double labeling demonstrates association of microtubules with internalization of Cx43-positive GJ plaques. Antibodies against the α5-integrin subunit block cell-matrix interactions without effect on tubulin expression, whereas inhibition of MAP kinase kinase by PD-98059 reduces tubulin expression, based on both Western blot and immunostaining. To examine direct association of microtubules (MT) with GJ plaques, we treated day 3 AEC for 0.5-24 h with colchicine, an inhibitor of tubulin polymerization. After 60 min, MTs were disassembled, whereas Western blot analysis showed no change in tubulin expression. In parallel, colchicine initiated redistribution of immunopositive Cx43 from the membrane to the cytosol. These observations support the premise that direct association of the cytoskeleton with gap junctions plays a significant role in regulation of Cx43 expression and distribution through integrin-mediated signal transduction pathways.
Collapse
Affiliation(s)
- Yihe Guo
- Department of Cellular & Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | | | | |
Collapse
|
29
|
Martin PEM, Hill NS, Kristensen B, Errington RJ, Griffith TM. Ouabain exerts biphasic effects on connexin functionality and expression in vascular smooth muscle cells. Br J Pharmacol 2003; 140:1261-71. [PMID: 14645140 PMCID: PMC1574142 DOI: 10.1038/sj.bjp.0705556] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2003] [Revised: 09/08/2003] [Accepted: 09/20/2003] [Indexed: 11/09/2022] Open
Abstract
1. We have compared the effects of ouabain on the maintenance of gap junctional communication in rat aortic A7r5 smooth muscle cells, monkey COS-1 fibroblasts and human HeLa epithelial cells. 2. Ouabain (1 mM) interrupted dye coupling between confluent A7r5 cells within approximately 1 h, and high concentrations of ouabain were similarly required to reduce coupling between COS-1 cells selected to express the rat alpha1 Na+/K+-ATPase subunit, which is ouabain resistant. By contrast, low concentrations of ouabain (1-10 microM) attenuated dye transfer in wild-type COS-1 and HeLa cells, whose endogenous alpha1 subunits possess relatively high affinity for the glycoside (Ki approximately 0.3 vs approximately 100 microM) Ouabain-induced reductions in dye transfer therefore correlated with the ability of the glycoside to bind to the Na+/K+-ATPase isoenzymes expressed in these different cell lines. 3. No consistent relationship between inhibition of intercellular dye transfer and secondary changes in [Ca2+]i or pHi could be identified following incubation with ouabain. 4. In separate experiments, the effects of ouabain on real-time trafficking of connexin protein were monitored by time-lapse microscopy of A7r5 cells transfected to express a fluorescent Cx43-green fluorescent protein (GFP) and the ability of the glycoside to modulate endogenous expression of connexins (Cx) 40 and 43 evaluated in A7r5 cells by immunochemical and Western blot analysis. 5. Ouabain (1 mM) depressed vesicular trafficking of Cx43-GFP after approximately 1 h, and caused a time-dependent loss of endogenous Cx40 and Cx43 protein that was first evident at 2 h and almost complete after 4 h. These effects of ouabain on Cx expression were reversed approximately 90 min following washout of the glycoside. 6. We conclude that ouabain exerts biphasic effects on the intercellular communication that involve an initial decrease in gap junctional permeability followed by a global reduction in the expression of Cx protein. Further studies are necessary to establish to what extent these actions of ouabain reflect inversion of the normal [Na+]i/[K+]i ratio and/or conversion of the Na+/K+-ATPase into a general signal transducer that regulates downstream protein synthesis.
Collapse
Affiliation(s)
- Patricia E M Martin
- Department of Diagnostic Radiology, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK.
| | | | | | | | | |
Collapse
|
30
|
Isakson BE, Seedorf GJ, Lubman RL, Evans WH, Boitano S. Cell-cell communication in heterocellular cultures of alveolar epithelial cells. Am J Respir Cell Mol Biol 2003; 29:552-61. [PMID: 12748060 DOI: 10.1165/rcmb.2002-0281oc] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The mammalian alveolar epithelium is composed of alveolar type I (AT1) and alveolar type II (AT2) cells that together coordinate tissue function. We used a heterocellular culture model of AT1 and AT2 cells to determine pathways for intercellular signaling between these two phenotypes. Gap junction protein (connexin) profiles of AT1 and AT2 cells in heterocellular cultures were similar to those seen in rat lung alveolar sections. Dye coupling studies revealed functional gap junctions between and among each cell phenotype. Localized mechanical stimulation resulted in propagated changes of intracellular Ca2+ to AT1 or AT2 cells independent of the stimulated cell phenotype. Ca2+ communication that originated after AT1 cell stimulation was inhibited by gap junction blockers, but not by an inhibitor of extracellular nucleotide signaling (apyrase). Conversely, Ca2+ communication after stimulation of AT2 cells was not significantly reduced by gap junction inhibitors. However, apyrase significantly reduced Ca2+ communication from AT2 to AT1 cells, but not from AT2 to AT2 cells. In conclusion, AT1 and AT2 cells have unique connexin profiles that allow for functional coupling and distinct intercellular pathways for coordination of Ca2+ signaling.
Collapse
Affiliation(s)
- Brant E Isakson
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, AZ 85724, USA
| | | | | | | | | |
Collapse
|
31
|
Zhang W, Green C, Stott NS. Bone morphogenetic protein-2 modulation of chondrogenic differentiation in vitro involves gap junction-mediated intercellular communication. J Cell Physiol 2002; 193:233-43. [PMID: 12385001 DOI: 10.1002/jcp.10168] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Undifferentiated mesenchymal cells in the limb bud integrate a complex array of local and systemic signals during the process of cell condensation and chondrogenic differentiation. To address the relationship between bone morphogenetic protein (BMP) signaling and gap junction-mediated intercellular communication, we examined the effects of BMP-2 and a gap junction blocker 18 alpha glycyrrhetinic acid (18alpha-GCA) on mesenchymal cell condensation and chondrogenic differentiation in an in vitro chondrogenic model. We find that connexin43 protein expression significantly correlates with early mesenchymal cellular condensation and chondrogenesis in high-density limb bud cell culture. The level of connexin43 mRNA is maximally upregulated 48 h after treatment with recombinant human BMP-2 with corresponding changes in protein expression. Inhibition of gap junction-mediated intercellular communication with 2.5 microM 18alpha-GCA decreases chondrogenic differentiation by 50% at 96 h without effects on housekeeping genes. Exposure to 18alpha-GCA for only the first 24-48 h after plating does not affect condensation or later chondrogenic differentiation suggesting that gap junction-mediated intercellular communication is not critical for the initial phase of condensation but is important for the onset of differentiation. 18alpha-GCA can also block the chondrogenic effects of BMP-2 without effects on cell number or connexin43 expression. These observations demonstrate 18alpha-GCA-sensitive regulation of intercellular communication in limb mesenchymal cells undergoing chondrogenic differentiation and suggest that BMP-2 induced chondrogenic differentiation may be mediated in part through the modulation of connexin43 expression and gap junction-mediated intercellular communication.
Collapse
Affiliation(s)
- Wei Zhang
- Department of Surgery, Faculty of Medicine and Health Sciences, University of Auckland, Auckland, New Zealand
| | | | | |
Collapse
|
32
|
Kolomytkin OV, Marino AA, Waddell DD, Mathis JM, Wolf RE, Sadasivan KK, Albright JA. IL-1beta-induced production of metalloproteinases by synovial cells depends on gap junction conductance. Am J Physiol Cell Physiol 2002; 282:C1254-60. [PMID: 11997239 DOI: 10.1152/ajpcell.01166.2000] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Synovial cells can form networks connected by gap junctions. The purpose of this study was to obtain evidence for a necessary role of gap junction intercellular communication in protein secretion by synovial cells. We developed a novel assay to measure the enzymatic activity of metalloproteinases (MMPs) produced by synovial cells in response to interleukin-1beta (IL-1beta) and employed the assay to explore the biological function of gap junctions. IL-1beta produced a dose-dependent increase in MMP activity that was blocked by exposure to the gap junction inhibitors 18alpha-glycyrrhetinic acid and octanol for as few as 50 min. The inhibitors produced an immediate and marked reduction in intercellular communication, as assessed by transient current analysis using the nystatin perforated-patch method. These observations suggest that communication through gap junctions early in IL-1beta signal transduction is critical to the process of cytokine-regulated secretion of MMPs by synovial cells.
Collapse
Affiliation(s)
- Oleg V Kolomytkin
- Department of Orthopaedic Surgery, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130, USA
| | | | | | | | | | | | | |
Collapse
|
33
|
Irimia D, Karlsson JOM. Kinetics and mechanism of intercellular ice propagation in a micropatterned tissue construct. Biophys J 2002; 82:1858-68. [PMID: 11916845 PMCID: PMC1301983 DOI: 10.1016/s0006-3495(02)75536-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Understanding the effects of cell-cell interaction on intracellular ice formation (IIF) is required to design optimized protocols for cryopreservation of tissue. To determine the effects of cell-cell interactions during tissue freezing, without confounding effects from uncontrolled factors (such as time in culture, cell geometry, and cell-substrate interactions), HepG2 cells were cultured in pairs on glass coverslips micropatterned with polyethylene glycol disilane, such that each cell interacted with exactly one adjacent cell. Assuming the cell pair to be a finite state system, being either in an unfrozen state (no ice in either cell), a singlet state (IIF in one cell only), or a doublet state (IIF in both cells), the kinetics of state transitions were theoretically modeled and cryomicroscopically measured. The rate of intercellular ice propagation, estimated from the measured singlet state probability, increased in the first 24 h of culture and remained steady thereafter. In cell pairs cultured for 24 h and treated with the gap junction blocker 18beta-glycyrrhetinic acid before freezing, the intercellular ice propagation rate was lower than in untreated controls (p < 0.001), but significantly greater than zero (p < 0.0001). These results suggest that gap junctions mediate some, but not all, mechanisms of ice propagation in tissue.
Collapse
Affiliation(s)
- Daniel Irimia
- Department of Bioengineering, University of Illinois, Chicago, Illinois 60607, USA
| | | |
Collapse
|
34
|
Tare M, Coleman HA, Parkington HC. Glycyrrhetinic derivatives inhibit hyperpolarization in endothelial cells of guinea pig and rat arteries. Am J Physiol Heart Circ Physiol 2002; 282:H335-41. [PMID: 11748079 DOI: 10.1152/ajpheart.2002.282.1.h335] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glycyrrhetinic acid (GA) derivatives have been used to implicate gap junctions in vasorelaxation attributed to endothelium-derived hyperpolarizing factor (EDHF). The aim of this study was to assess whether GA compounds affect endothelial cell hyperpolarization. Membrane potentials were recorded from dye-identified endothelial and smooth muscle cells of guinea pig coronary and rat mesenteric arteries. GA derivatives had varied effects on the resting membrane potential: depolarization, hyperpolarization, or no effect, depending on the artery. 18alpha-GA (50 microM) had a small variable effect on ACh-induced hyperpolarizations in endothelial cells. 18beta-GA (30 microM) and carbenoxolone (100 microM) significantly reduced ACh-induced hyperpolarizations in both endothelial and smooth muscle cells. Smooth muscle action potentials in rat tail arteries were smaller and slower in the presence of 18beta-GA. Nerve-induced excitatory junction potentials were inhibited by 18beta-GA and carbenoxolone, whereas the time course of their decay initially increased and then decreased. In conclusion, the GA compounds had a range of effects. Their inhibition of the EDHF hyperpolarization and relaxation in the smooth muscle may stem from the inhibition of endothelial cell hyperpolarization.
Collapse
Affiliation(s)
- Marianne Tare
- Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia
| | | | | |
Collapse
|
35
|
Yamazaki J, Kitamura K. Cell-to-cell communication via nitric oxide modulation of oscillatory Cl(-) currents in rat intact cerebral arterioles. J Physiol 2001; 536:67-78. [PMID: 11579157 PMCID: PMC2278835 DOI: 10.1111/j.1469-7793.2001.00067.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. Diffusion-mediated changes in ion channel function within blood vessels have not been demonstrated directly in a patch-clamp study. Here, we examined the hypothesis that endothelium-derived diffusible bioactive substances would modify endothelin-1 (ET-1)-evoked membrane currents in smooth muscle cells situated within intact arterioles. 2. In pieces of arterioles dissected from the rat cerebral pial membrane, patch electrodes were placed on single smooth muscle cells identified under the microscope. Under perforated patch-clamp conditions, ET-1 evoked an oscillatory inward current at negative potentials in such cells in the presence of the gap junction disrupter 18alpha-glycyrrhetinic acid. ET-1 also elicited an oscillation superimposed on a membrane depolarization in current-clamp mode. 3. The oscillatory current exhibited an outwardly rectifying current-voltage relationship, a sensitivity to niflumic acid, a requirement for inositol 1,4,5-trisphosphate (IP(3))- and caffeine-sensitive Ca(2+) stores and for external Ca(2+) and a rank order of anion permeabilities characteristic of Ca(2+)-activated Cl(-) currents (I(Ca(Cl))). 4. This oscillatory response was inhibited by bradykinin (an effect distinct from the electrical propagation of hyperpolarization) and this effect was attenuated by the NO-synthase inhibitor N(omega)-nitro-L-arginine and by the NO scavenger oxyhaemoglobin but not by the cyclo-oxygenease inhibitor indomethacin. 8-Bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) and nitroprusside closely mimicked the effect of bradykinin. 5. The present patch-clamp study has revealed diffusion-mediated cell-to-cell interaction in an intact blood vessel: bradykinin appears to cause NO to move from endothelium to smooth muscle, there to inhibit an ET-1-evoked oscillatory I(Ca(Cl)) via the NO-cGMP pathway.
Collapse
Affiliation(s)
- J Yamazaki
- Department of Pharmacology, Fukuoka Dental College, Sawara-ku, Fukuoka 814-0193, Japan.
| | | |
Collapse
|
36
|
Ruiz-Meana M, Garcia-Dorado D, Lane S, Pina P, Inserte J, Mirabet M, Soler-Soler J. Persistence of gap junction communication during myocardial ischemia. Am J Physiol Heart Circ Physiol 2001; 280:H2563-71. [PMID: 11356611 DOI: 10.1152/ajpheart.2001.280.6.h2563] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During myocardial ischemia, severe ATP depletion induces rigor contracture followed by intracellular Ca2+ concentration ([Ca2+]i) rise and progressive impairment of gap junction (GJ)-mediated electrical coupling. Our objective was to investigate whether chemical coupling through GJ allows propagation of rigor in cardiomyocytes and whether it persists after rigor development. In end-to-end connected adult rat cardiomyocytes submitted to simulated ischemia the interval between rigor onset was 3.7 ± 0.7 s, and subsequent [Ca2+]i rise was virtually identical in both cells, whereas in nonconnected cell pairs the interval was 71 ± 12 s and the rate of [Ca2+]i rise was highly variable. The GJ blocker 18α-glycyrrhetinic acid increased the interval between rigor onset and the differences in [Ca2+]i between connected cells. Transfer of Lucifer yellow demonstrated GJ permeability 10 min after rigor onset in connected cell pairs, and 30 min after rigor onset in isolated rat hearts submitted to nonflow ischemia but was abolished after 2 h of ischemia. GJ-mediated communication allows propagation of rigor in ischemic myocytes and persists after rigor development despite acidosis and increased [Ca2+]i.
Collapse
Affiliation(s)
- M Ruiz-Meana
- Department of Cardiology, Hospital General Vall d'Hebron, Barcelona 08035, Spain
| | | | | | | | | | | | | |
Collapse
|
37
|
Jiang F, Dusting GJ. Endothelium-dependent vasorelaxation independent of nitric oxide and K(+) release in isolated renal arteries of rats. Br J Pharmacol 2001; 132:1558-64. [PMID: 11264250 PMCID: PMC1572700 DOI: 10.1038/sj.bjp.0703965] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. We investigated whether K(+) can act as an endothelium-derived hyperpolarizing factor (EDHF) in isolated small renal arteries of Wistar-Kyoto rats. 2. Acetylcholine (0.001 - 3 microM) caused relaxations that were abolished by removal of the endothelium. However, acetylcholine-induced relaxations were not affected by the nitric oxide (NO) synthase inhibitor N:(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM), by L-NAME plus the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, 1 microM) or by L-NAME plus the cyclo-oxygenase inhibitor indomethacin (10 microM). In rings precontracted with high-K(+)(60 mM) physiological salt solution in the presence of L-NAME, acetylcholine-induced relaxations were abolished. 3. L-NAME-resistant relaxations were abolished by the large-conductance Ca(2+)-activated K(+) channel inhibitor charybdotoxin plus the small-conductance Ca(2+)-activated K(+) channel inhibitor apamin, while the inward rectifier K(+) channel inhibitor Ba(2+) or the gap junction inhibitor 18alpha-glycyrrhetinic acid had no effect. Acetylcholine-induced relaxation was unchanged by ouabain (10 microM) but was partially inhibited by a higher concentration (100 microM). 4. In half of the tissues tested, K(+)(10 mM) itself produced L-NAME-resistant relaxations that were blocked by ouabain (10 microM) and partially reduced by charybdotoxin plus apamin, but not affected by 18alpha-glycyrrhetinic acid or Ba(2+). However, K(+) did not induce relaxations in endothelium-denuded tissues. 5. In conclusion, acetylcholine-induced relaxations in this tissue are largely dependent upon hyperpolarization mechanisms that are initiated in the endothelium but do not depend upon NO release. K(+) release cannot account for endothelium-dependent relaxation and cannot be an EDHF in this artery. However, K(+) itself can initiate endothelium-dependent relaxations via a different pathway from acetylcholine, but the mechanisms of K(+)-induced relaxations remain to be clarified.
Collapse
Affiliation(s)
- F Jiang
- Howard Florey Institute, The University of Melbourne, Victoria 3010, Australia.
| | | |
Collapse
|
38
|
Alford AI, Rannels DE. Extracellular matrix fibronectin alters connexin43 expression by alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2001; 280:L680-8. [PMID: 11238008 DOI: 10.1152/ajplung.2001.280.4.l680] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alveolar type II epithelial cells undergo phenotypic changes and establish gap junction intercellular communication as they reach confluence in primary culture. The pattern of gap junction protein (connexin) expression changes in parallel. Although connexin (Cx)43 mRNA and protein increase significantly by culture day 2, Cx26 and Cx32 expression decline. Along with increasing Cx43 expression, the cells assemble fibronectin derived both from serum in the culture medium and from de novo synthesis into the extracellular matrix (ECM). The present studies indicate that this ECM regulates Cx43 expression. Culture of type II cells in DMEM containing 8-10% fetal bovine serum (FBS) promotes assembly of a fibronectin-rich ECM that stimulates expression of both Cx43 mRNA and protein. Although Cx43 protein expression increased in response to FBS in a dose-dependent manner, fibronectin also elevated Cx43 protein in the absence of FBS. Anti-fibronectin antibody significantly reduced the serum-dependent increase in Cx43 expression. These results support the premise that fibronectin in the ECM contributes to the regulation of Cx43 expression by alveolar epithelial cells in primary culture.
Collapse
Affiliation(s)
- A I Alford
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17033, USA
| | | |
Collapse
|
39
|
Isakson BE, Evans WH, Boitano S. Intercellular Ca2+ signaling in alveolar epithelial cells through gap junctions and by extracellular ATP. Am J Physiol Lung Cell Mol Physiol 2001; 280:L221-8. [PMID: 11159000 DOI: 10.1152/ajplung.2001.280.2.l221] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inter- and extracellular-mediated changes in intracellular Ca2+ concentration ([Ca2+]i) can ensure coordinated tissue function in the lung. Cultured rat alveolar epithelial cells (AECs) have been shown to respond to secretagogues with increases in [Ca2+]i and have been shown to be gap junctionally coupled. However, communication of [Ca2+]i changes in AECs is not well defined. Monolayers of AECs were mechanically perturbed and monitored for [Ca2+]i changes. Perturbation of AECs was administered by a glass probe to either mechanically stimulate or mechanically wound individual cells. Both approaches induced a change in [Ca2+]i in the stimulated cell that was propagated to neighboring cells (Ca2+ waves). A connexin mimetic peptide shown to uncouple gap junctions eliminated Ca2+ waves in mechanically stimulated cells but had no effect on mechanically wounded cells. In contrast, apyrase, an enzyme that effectively removes ATP from the extracellular milieu, had no effect on mechanically stimulated cells but severely restricted mechanically wounded Ca2+ wave propagation. We conclude that AECs have the ability to communicate coordinated Ca2+ changes using both gap junctions and extracellular ATP.
Collapse
Affiliation(s)
- B E Isakson
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071-3166, USA
| | | | | |
Collapse
|
40
|
Guo Y, Martinez-Williams C, Yellowley CE, Donahue HJ, Rannels DE. Connexin expression by alveolar epithelial cells is regulated by extracellular matrix. Am J Physiol Lung Cell Mol Physiol 2001; 280:L191-202. [PMID: 11158997 DOI: 10.1152/ajplung.2001.280.2.l191] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extracellular matrix (ECM) proteins promote attachment, spreading, and differentiation of cultured alveolar type II epithelial cells. The present studies address the hypothesis that the ECM also regulates expression and function of gap junction proteins, connexins, in this cell population. Expression of cellular fibronectin and connexin (Cx) 43 increase in parallel during early type II cell culture as Cx26 expression declines. Gap junction intercellular communication is established over the same interval. Cells plated on a preformed, type II cell-derived, fibronectin-rich ECM demonstrate accelerated formation of gap junction plaques and elevated gap junction intercellular communication. These effects are blocked by antibodies against fibronectin, which cause redistribution of Cx43 protein from the plasma membrane to the cytoplasm. Conversely, cells cultured on a laminin-rich ECM, Matrigel, express low levels of Cx43 but high levels of Cx26, reflecting both transcriptional and translational regulation. Cx26 and Cx43 thus demonstrate reciprocal regulation by ECM constituents.
Collapse
Affiliation(s)
- Y Guo
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
| | | | | | | | | |
Collapse
|
41
|
Boitano S, Evans WH. Connexin mimetic peptides reversibly inhibit Ca(2+) signaling through gap junctions in airway cells. Am J Physiol Lung Cell Mol Physiol 2000; 279:L623-30. [PMID: 11000121 DOI: 10.1152/ajplung.2000.279.4.l623] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effect of peptides with sequences derived from connexins, the constituent proteins of gap junctions, on mechanically stimulated intercellular Ca(2+) signaling in tracheal airway epithelial cells was studied. Three peptides with sequences corresponding to connexin extracellular loop regions reversibly restricted propagation of Ca(2+) waves to neighboring cells. Recovery of communication began within 10 min of removal of the peptides, with inhibition totally reversed by 20-40 min. The peptides were shown to be more effective in inhibiting Ca(2+) waves than glycyrrhetinic acid or oleamide. Inhibition of intercellular Ca(2+) waves by connexin mimetic peptides did not affect the Ca(2+) response to extracellular ATP. Although the intracellular Ca(2+) response of tracheal epithelial cells to ATP was greatly reduced by either pretreatment with high doses of ATP or application of apyrase, mechanically stimulated intercellular Ca(2+) signaling was not affected by these agents. We conclude that connexin mimetic peptides are effective and reversible inhibitors of gap junctional communication of physiologically significant molecules that underlie Ca(2+) wave propagation in tracheal epithelial cells and propose a potential mechanism for the mode of action of mimetic peptides.
Collapse
Affiliation(s)
- S Boitano
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071-3166, USA.
| | | |
Collapse
|
42
|
Ko K, Arora P, Lee W, McCulloch C. Biochemical and functional characterization of intercellular adhesion and gap junctions in fibroblasts. Am J Physiol Cell Physiol 2000; 279:C147-57. [PMID: 10898726 DOI: 10.1152/ajpcell.2000.279.1.c147] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Despite their significance in wound healing, little is known about the molecular determinants of cell-to-cell adhesion and gap junctional communication in fibroblasts. We characterized intercellular adherens junctions and gap junctions in human gingival fibroblasts (HGFs) using a novel model. Calcein-labeled donor cells in suspension were added onto an established, Texas red dextran (10 kDa)-labeled acceptor cell monolayer. Cell-to-cell adhesion required Ca(2+) and was >30-fold stronger than cell-to-fibronectin adhesion at 15 min. Electron micrographs showed rapid formation of adherens junction-like structures at approximately 15 min that matured by approximately 2-3 h; distinct gap junctional complexes were evident by approximately 3 h. Immunoblotting showed that HGF expressed beta-catenin and that cadherins and connexin43 were recruited to the Triton-insoluble cytoskeletal fraction in confluent cultures. Confocal microscopy localized the same molecules to intercellular contacts of acceptor and donor cells. There was extensive calcein dye transfer in a cohort of Texas red dextran-labeled cells, but this was almost completely abolished by the gap junction inhibitor beta-glycyrrhetinic acid and the connexin43 mimetic peptide GAP 27. This donor-acceptor cell model allows large numbers (>10(5)) of cells to form synchronous cell-to-cell contacts, thereby enabling the simultaneous functional and molecular studies of adherens junctions and gap junctions.
Collapse
Affiliation(s)
- K Ko
- Medical Research Council Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada M5S 3E2.
| | | | | | | |
Collapse
|
43
|
Murai T, Muraki K, Imaizumi Y, Watanabe M. Levcromakalim causes indirect endothelial hyperpolarization via a myo-endothelial pathway. Br J Pharmacol 1999; 128:1491-6. [PMID: 10602328 PMCID: PMC1571792 DOI: 10.1038/sj.bjp.0702956] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Effects of K+ channel opener, levcromakalim, on vascular endothelial cells were examined. Under voltage- and current-clamp conditions, application of acetylcholine to dispersed endothelial cells isolated from rabbit superior mesenteric artery (dispersed RMAECs) produced hyperpolarization and outward currents. On the other hand, dispersed RMAECs did not respond to levcromakalim. 2. When membrane potential was recorded from endothelium in a mesenteric arterial segment, exposure to levcromakalim in a concentration range of 0.1 to 3 microM caused concentration-dependent hyperpolarization. The hyperpolarization was observed in the absence of external Ca2+ and was inhibited by 10 microM glibenclamide. 3. The presence of 1 mM heptanol did not affect the levcromakalin-induced hyperpolarization, whereas treatment of the mesenteric arterial segment with 20 microM 18 beta-glycyrrhetinic acid significantly reduced the hyperpolarization. The response to acetylcholine of RMAECs in an arterial segment with 18 beta-glycyrrhetinic acid was, however, similar to that without 18 beta-glycyrrhetinic acid. 4. These suggest that although RMAECs themselves are functionally insensitive to levcromakalim, those in an arterial segment are hyperpolarized by levcromakalim via myo-endothelial electrical communication.
Collapse
MESH Headings
- Animals
- Cell Communication/drug effects
- Cell Communication/physiology
- Cromakalim/pharmacology
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/physiology
- Gap Junctions/drug effects
- Gap Junctions/physiology
- Glycyrrhetinic Acid/pharmacology
- In Vitro Techniques
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Mesenteric Artery, Superior/drug effects
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Potassium Channels/drug effects
- Potassium Channels/physiology
- Rabbits
- Vasodilator Agents/pharmacology
Collapse
Affiliation(s)
- Takeshi Murai
- Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
| | - Katsuhiko Muraki
- Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
- Author for correspondence:
| | - Yuji Imaizumi
- Department of Pharmacology & Therapeutics, Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
| | - Minoru Watanabe
- Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
| |
Collapse
|