1
|
Van Campenhout R, Leroy K, Cooreman A, Tabernilla A, Cogliati B, Kadam P, Vinken M. Connexin-Based Channels in the Liver. Compr Physiol 2022; 12:4147-4163. [PMID: 35950654 DOI: 10.1002/cphy.c220007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Connexin proteins oligomerize in hexameric structures called connexin hemichannels, which then dock to form gap junctions. Gap junctions direct cell-cell communication by allowing the exchange of small molecules and ions between neighboring cells. In this way, hepatic gap junctions support liver homeostasis. Besides serving as building blocks for gap junctions, connexin hemichannels provide a pathway between the intracellular and the extracellular environment. The activation of connexin hemichannels is associated with acute and chronic liver pathologies. This article discusses the role of gap junctions and connexin hemichannels in the liver. © 2022 American Physiological Society. Compr Physiol 12:1-17, 2022.
Collapse
Affiliation(s)
- Raf Van Campenhout
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Kaat Leroy
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Axelle Cooreman
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Andrés Tabernilla
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Bruno Cogliati
- School of Veterinary Medicine and Animal Science, Department of Pathology, University of São Paulo, São Paulo, Brazil
| | - Prashant Kadam
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Mathieu Vinken
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| |
Collapse
|
2
|
Kar R, Batra N, Riquelme MA, Jiang JX. Biological role of connexin intercellular channels and hemichannels. Arch Biochem Biophys 2012; 524:2-15. [PMID: 22430362 PMCID: PMC3376239 DOI: 10.1016/j.abb.2012.03.008] [Citation(s) in RCA: 174] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 02/16/2012] [Accepted: 03/06/2012] [Indexed: 12/11/2022]
Abstract
Gap junctions (GJ) and hemichannels (HC) formed from the protein subunits called connexins are transmembrane conduits for the exchange of small molecules and ions. Connexins and another group of HC-forming proteins, pannexins comprise the two families of transmembrane proteins ubiquitously distributed in vertebrates. Most cell types express more than one connexin or pannexin. While connexin expression and channel activity may vary as a function of physiological and pathological states of the cell and tissue, only a few studies suggest the involvement of pannexin HC in acquired pathological conditions. Importantly, genetic mutations in connexin appear to interfere with GJ and HC function which results in several diseases. Thus connexins could serve as potential drug target for therapeutic intervention. Growing evidence suggests that diseases resulting from HC dysfunction might open a new direction for development of specific HC reagents. This review provides a comprehensive overview of the current studies of GJ and HC formed by connexins and pannexins in various tissue and organ systems including heart, central nervous system, kidney, mammary glands, ovary, testis, lens, retina, inner ear, bone, cartilage, lung and liver. In addition, present knowledge of the role of GJ and HC in cell cycle progression, carcinogenesis and stem cell development is also discussed.
Collapse
Affiliation(s)
| | | | - Manuel A Riquelme
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900
| | - Jean X. Jiang
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900
| |
Collapse
|
3
|
Roh DS, Funderburgh JL. Rapid changes in connexin-43 in response to genotoxic stress stabilize cell-cell communication in corneal endothelium. Invest Ophthalmol Vis Sci 2011; 52:5174-82. [PMID: 21666237 DOI: 10.1167/iovs.11-7272] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
PURPOSE To determine how corneal endothelial (CE) cells respond to acute genotoxic stress through changes in connexin-43 (Cx43) and gap junction intercellular communication (GJIC). METHODS Cultured bovine CE cells were exposed to mitomycin C or other DNA-damaging agents. Changes in the levels, stability, binding partners, and trafficking of Cx43 were assessed by Western blot analysis and immunostaining. Live-cell imaging of a Cx43-green fluorescent protein (GFP) fusion protein was used to evaluate internalization of cell surface Cx43. Dye transfer and fluorescent recovery after photobleaching (FRAP) assessed GJIC. RESULTS After genotoxic stress, Cx43 accumulated in large gap junction plaques, had reduced zonula occludens-1 binding, and displayed increased stability. Live-cell imaging of Cx43-GFP plaques in stressed CE cells revealed reduced gap junction internalization and degradation compared to control cells. Mitomycin C enhanced transport of Cx43 from the endoplasmic reticulum to the cell surface and formation of gap junction plaques. Mitomycin C treatment also protected GJIC from disruption after cytokine treatment. DISCUSSION These results show a novel CE cell response to genotoxic stress mediated by marked and rapid changes in Cx43 and GJIC. This stabilization of cell-cell communication may be an important early adaptation to acute stressors encountered by CE.
Collapse
Affiliation(s)
- Danny S Roh
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
| | | |
Collapse
|
4
|
Vinken M, Decrock E, De Vuyst E, De Bock M, Vandenbroucke RE, De Geest BG, Demeester J, Sanders NN, Vanhaecke T, Leybaert L, Rogiers V. Connexin32 hemichannels contribute to the apoptotic-to-necrotic transition during Fas-mediated hepatocyte cell death. Cell Mol Life Sci 2010; 67:907-18. [PMID: 19960225 PMCID: PMC11115707 DOI: 10.1007/s00018-009-0220-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Revised: 11/16/2009] [Accepted: 11/18/2009] [Indexed: 12/19/2022]
Abstract
The present study was set up to investigate the fate of connexin32 and its channels in hepatocellular apoptosis. Primary hepatocyte cultures were exposed to Fas ligand and cycloheximide, and modifications in connexin32 expression and localization, and gap junction functionality were studied. We found that gap junction functionality rapidly declined upon progression of cell death, which was associated with a decay of the gap junctional connexin32 protein pool. Simultaneously, levels of newly synthesized connexin32 protein increased and gathered in a hemichannel configuration. This became particularly evident towards the end stages of the cell death process and was not reflected at the transcriptional level. We next either silenced connexin32 expression or inhibited connexin32 hemichannel activity prior to cell death induction. Both approaches resulted in a delayed termination of the cell death response. We conclude that connexin32 hemichannels facilitate the apoptotic-to-necrotic transition, which typically occurs in the final stage of hepatocellular apoptosis.
Collapse
Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Vrije Universiteit Brussel, Belgium.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Straub AC, Johnstone SR, Heberlein KR, Rizzo MJ, Best AK, Boitano S, Isakson BE. Site-specific connexin phosphorylation is associated with reduced heterocellular communication between smooth muscle and endothelium. J Vasc Res 2009; 47:277-86. [PMID: 20016202 DOI: 10.1159/000265562] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 07/08/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Myoendothelial junctions (MEJs) represent a specialized signaling domain between vascular smooth muscle cells (VSMC) and endothelial cells (EC). The functional consequences of phosphorylation state of the connexins (Cx) at the MEJ have not been explored. METHODS/RESULTS Application of adenosine 3',5'-cyclic monophosphate sodium (pCPT) to mouse cremasteric arterioles reduces the detection of connexin 43 (Cx43) phosphorylated at its carboxyl terminal serine 368 site (S368) at the MEJ in vivo. After single-cell microinjection of a VSMC in mouse cremaster arterioles, only in the presence of pCPT was dye transfer to EC observed. We used a vascular cell co-culture (VCCC) and applied the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (PMA) or fibroblast growth factor-2 (FGF-2) to induce phosphorylation of Cx43 S368. This phosphorylation event was associated with a significant reduction in dye transfer and calcium communication. Using a novel method to monitor increases in intracellular calcium across the in vitro MEJ, we noted that PMA and FGF-2 both inhibited movement of inositol 1,4,5-triphosphate (IP(3)), but to a lesser extent Ca(2+). CONCLUSION These data indicate that site-specific connexin phosphorylation at the MEJ can potentially regulate the movement of solutes between EC and VSMC in the vessel wall.
Collapse
Affiliation(s)
- Adam C Straub
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
| | | | | | | | | | | | | |
Collapse
|
6
|
Vinken M, Doktorova T, Decrock E, Leybaert L, Vanhaecke T, Rogiers V. Gap junctional intercellular communication as a target for liver toxicity and carcinogenicity. Crit Rev Biochem Mol Biol 2009; 44:201-22. [PMID: 19635038 DOI: 10.1080/10409230903061215] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Direct communication between hepatocytes, mediated by gap junctions, constitutes a major regulatory platform in the control of liver homeostasis, ranging from hepatocellular proliferation to hepatocyte cell death. Inherent to this pivotal task, gap junction functionality is frequently disrupted upon impairment of the homeostatic balance, as occurs during liver toxicity and carcinogenicity. In the present paper, the deleterious effects of a number of chemical and biological toxic compounds on hepatic gap junctions are discussed, including environmental pollutants, biological toxins, organic solvents, pesticides, pharmaceuticals, peroxides, metals and phthalates. Particular attention is paid to the molecular mechanisms that underlie the abrogation of gap junction functionality. Since hepatic gap junctions are specifically targeted by tumor promoters and epigenetic carcinogens, both in vivo and in vitro, inhibition of gap junction functionality is considered as a suitable indicator for the detection of nongenotoxic hepatocarcinogenicity.
Collapse
Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium.
| | | | | | | | | | | |
Collapse
|
7
|
Abstract
Evidence is accumulating that some forms of cell death, like apoptosis, are not only governed by the complex interplay between extracellular and intracellular signals but are also strongly influenced by intercellular communicative networks. The latter is provided by arrays of channels consisting of connexin proteins, with gap junctions directly connecting the cytoplasm of neighboring cells and hemichannels positioned as pores that link the cytoplasm to the extracellular environment. The role of gap junctions in cell death communication has received considerable interest and recently hemichannels have joined in as potentially toxic pores adding their part to the cell death process. However, despite a large body of existing evidence, especially for gap junctions, the exact contribution of the connexin channel family still remains controversial, as both gap junctions and hemichannels may furnish cell death as well as cell survival signals. An additional layer of complexity is formed by the fact that connexin proteins as such, beyond their channel function, may influence the cell death process. We here review the current knowledge on connexins and their channels in cell death and specifically address the molecular mechanisms that underlie connexin-related signaling. We also briefly focus on pannexins, a novel set of connexin-like proteins that have been implicated in cellular responses to pathological insults.
Collapse
|
8
|
Vinken M, Henkens T, De Rop E, Fraczek J, Vanhaecke T, Rogiers V. Biology and pathobiology of gap junctional channels in hepatocytes. Hepatology 2008; 47:1077-88. [PMID: 18058951 DOI: 10.1002/hep.22049] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The present review provides the state of the art of the current knowledge concerning gap junctional channels and their roles in liver functioning. In the first part, we summarize some relevant biochemical properties of hepatic gap junctional channels, including their structure and regulation. In the second part, we discuss the involvement of gap junctional channels in the occurrence of liver cell growth, liver cell differentiation, and liver cell death. We further exemplify their relevance in hepatic pathophysiology. Finally, a number of directions for future liver gap junctional channel research are proposed, and the up-regulation of gap junctional channel activity as a novel strategy in (liver) cancer therapy is illustrated.
Collapse
Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
| | | | | | | | | | | |
Collapse
|
9
|
Jin EJ, Lee SY, Jung JC, Bang OS, Kang SS. TGF-beta3 inhibits chondrogenesis of cultured chick leg bud mesenchymal cells via downregulation of connexin 43 and integrin beta4. J Cell Physiol 2007; 214:345-53. [PMID: 17620312 DOI: 10.1002/jcp.21202] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Transforming growth factor beta (TGF-beta) is a multifunctional cytokine that regulates a number of biological responses including chemotaxis, cell cycle progression, differentiation, and apoptosis of cells. Even though temporal and spatial expression of TGF-beta3 suggests its role in chick limb development, it is not well characterized how TGF-beta3 regulates chondrogenic differentiation of limb bud mesenchymal cells. In this study, differential display polymerase chain reaction (DD-PCR) screening and reverse transcription PCR analysis revealed that the mRNA expression of the gap junction protein, connexin 43 (Cx43), was significantly decreased during the first treatment of TGF-beta3 for 24 h in cultured chick leg bud mesenchymal cells. Treatment of these cells with lindane, a general gap junction blocker, or expression of dominant negative Cx43 increased apoptotic cell death and decreased the level of integrin beta4 protein, in a manner similar to that observed when these cells were exposed to TGF-beta3. Similarly, exposure of cultured leg chondroblasts to a functional blocking antibody against integrin-beta4 induced an increase in apoptosis. Treatment of cells with TGF-beta3 decreased the membrane translocation of PKC-alpha, leading to activation of ERK. The increase in apoptotic cell death triggered by TGF-beta3 and dominant negative Cx43 was blocked by inhibition of ERK but increased by inhibition of PKC. Collectively, these data indicate that, in cultured chick leg bud mesenchyme cells, TGF-beta3 treatment downregulates Cx43 and induces apoptotic cell death via downregulation of integrin beta4, activation of ERK and suppression of PKC-alpha activation.
Collapse
Affiliation(s)
- Eun-Jung Jin
- Department of Biology, College of Natural Sciences (BK21), Kyungpook National University, Daegu, Korea
| | | | | | | | | |
Collapse
|
10
|
Francis RJB, Lo CW. Primordial germ cell deficiency in the connexin 43 knockout mouse arises from apoptosis associated with abnormal p53 activation. Development 2006; 133:3451-60. [PMID: 16887824 DOI: 10.1242/dev.02506] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Connexin 43 knockout (Cx43alpha1KO) mice exhibit germ cell deficiency, but the underlying cause for the germ cell defect was unknown. Using an Oct4-GFP reporter transgene, we tracked the distribution and migration of primordial germ cells (PGCs) in the Cx43alpha1KO mouse embryo. Analysis with dye injections showed PGCs are gap-junction-communication competent, with dye coupling being markedly reduced in Cx43alpha1-deficient PGCs. Time-lapse videomicroscopy and motion analysis showed that the directionality and speed of cell motility were reduced in the Cx43alpha1KO PGCs. This was observed both in E8.5 and E11.5 embryos. By contrast, PGC abundance did not differ between wild-type and heterozygous/homozygous Cx43alpha1KO embryos until E11.5, when a marked reduction in PGC abundance was detected in the homozygous Cx43alpha1KO embryos. This was accompanied by increased PGC apoptosis and increased expression of activated p53. Injection of alpha-pifithrin, a p53 antagonist, inhibited PGC apoptosis and prevented the loss of PGC. Analysis using a cell adhesion assay indicated a reduction in beta1-integrin function in the Cx43alpha1KO PGCs. Together with the abnormal activation of p53, these findings suggest the possibility of anoikis-mediated apoptosis. Overall, these findings show Cx43alpha1 is essential for PGC survival, with abnormal p53 activation playing a crucial role in the apoptotic loss of PGCs in the Cx43alpha1KO mouse embryos.
Collapse
Affiliation(s)
- Richard J B Francis
- Laboratory of Developmental Biology, National Heart Lung and Blood Institute, National Institutes of Health, Building 50/Room 4537, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | | |
Collapse
|
11
|
Gorbe A, Becker DL, Dux L, Krenacs L, Krenacs T. In differentiating prefusion myoblasts connexin43 gap junction coupling is upregulated before myoblast alignment then reduced in post-mitotic cells. Histochem Cell Biol 2005; 125:705-16. [PMID: 16341870 DOI: 10.1007/s00418-005-0121-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/17/2005] [Indexed: 02/05/2023]
Abstract
Previously we have shown that during in vivo muscle regeneration differentiating rat primary myoblasts transiently upregulate connexin43 (Cx43) gap junctions and leave cell cycle synchronously. Here, we studied the temporal regulation of Cx expression in relation to functional dye coupling in allogenic primary myoblast cultures using western blotting, immuno-confocal microscopy and dye transfer assays. As in vivo, Cx43 was the only Cx isotype out of Cx26, 32, 37, 40, 43 and 45 found in cultured rat myoblasts by immunostaining. Cultured myoblasts showed similar temporal regulation of Cx43 expression and phenotypic maturation to those regenerating in vivo. Cx43 protein was progressively upregulated in prefusion myoblasts, first by the cytoplasmic assembly in sparse myoblast meshworks and then in cell membrane particles in aligned cells. Dye injection using either Lucifer Yellow alone, Cascade Blue with a non-junction permeant FITC-dextran revealed an extensive gap junction coupling between the sparse interacting myoblasts and a reduced communication between the aligned, but still prefused cells. The aligned myoblasts, uniformly upregulate p21(waf1/cip1) and p27(kip1) cell cycle control proteins. Taken together, in prefusion myoblasts less membrane-bound Cx43 was found to mediate substantially more efficient dye coupling in the growing cell fraction than those in the aligned post-mitotic myoblasts. These and our in vivo results in early muscle differentiation are consistent with the role of Cx43 gap junctions in synchronizing cell cycle control of myoblasts to make them competent for a coordinated syncytial fusion.
Collapse
Affiliation(s)
- Aniko Gorbe
- Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | | | | | | | | |
Collapse
|
12
|
Albright CD, Klem E, Shah AA, Gallagher P. Breast cancer cell-targeted oxidative stress: enhancement of cancer cell uptake of conjugated linoleic acid, activation of p53, and inhibition of proliferation. Exp Mol Pathol 2005; 79:118-25. [PMID: 15992797 DOI: 10.1016/j.yexmp.2005.05.005] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 05/18/2005] [Indexed: 11/20/2022]
Abstract
We investigated the mechanism of inhibition of cell proliferation by mixed isomers of CLA (9-cis, 11-trans CLA; 10-trans, 12-cis CLA) on human, non-tumorigenic MCF10A cells that were derived from mammary ductal epithelial cells and MCF7 cells that were derived from a well differentiation mammary adenocarcinoma. When treated in the log phase of growth, the uptake of CLA by MCF7 exceeded the levels measured in MCF10A cells. Treatment with CLA in the presence of HPO doubled the incorporation of CLA in MCF7 cells, independent of the isomer, but reduced the incorporation of CLA by MCF10A cells. CLA caused tumor cell-targeted increased expression of 4-hydroxy-2-nonenal (4HNE), a product of lipid peroxidation, and decreased proliferation in MCF7 cells, as measured by the incorporation of bromodeoxyuridine (BrdU) and expression of phosphorylated histone H3, and the effects of CLA in combination with HPO on mitosis were greater than the effects of either agent alone. Decreased cell proliferation in CLA-treated MCF7 cells coincided with increased nuclear localization of phosphorylated, activated p53 protein, and decreased nuclear localization of the transcription factor FKHRSer256. Importantly, CLA-treated MCF7 cells were more sensitive than MCF10A cells to HPO-induced 4HNE, expression of p53, and decreased mitotic activity. These studies suggest that tumor cell-targeted increased sensitivity to oxidative stress and activation of p53 play important roles in the regulation of human breast cancer cell proliferation by CLA.
Collapse
Affiliation(s)
- Craig D Albright
- Department of Nutrition, McGavran-Greenberg Building, School of Public Health and School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7461, USA.
| | | | | | | |
Collapse
|
13
|
Albright CD, Mar MH, Craciunescu CN, Song J, Zeisel SH. Maternal dietary choline availability alters the balance of netrin-1 and DCC neuronal migration proteins in fetal mouse brain hippocampus. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 159:149-54. [PMID: 16109446 PMCID: PMC1592522 DOI: 10.1016/j.devbrainres.2005.07.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Revised: 07/07/2005] [Accepted: 07/16/2005] [Indexed: 12/11/2022]
Abstract
Alterations in maternal dietary choline availability during days 12-17 of pregnancy led to an increase in the level of immunoreactive netrin-1 and a decrease in the level of DCC protein in the developing fetal mouse brain hippocampus compared with controls. Changes in the expression of cell migration cues during development could account for some of the lifelong consequences of maternal dietary choline availability for cognitive and memory processes.
Collapse
|
14
|
Albright CD, da Costa KA, Craciunescu CN, Klem E, Mar MH, Zeisel SH. Regulation of choline deficiency apoptosis by epidermal growth factor in CWSV-1 rat hepatocytes. Cell Physiol Biochem 2005; 15:59-68. [PMID: 15665516 PMCID: PMC2424026 DOI: 10.1159/000083653] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/12/2004] [Indexed: 11/19/2022] Open
Abstract
Previous studies show that acute choline deficiency (CD) triggers apoptosis in cultured rat hepatocytes (CWSV-1 cells). We demonstrate that prolonged EGF stimulation (10 ng/mL x 48 hrs) restores cell proliferation, as assessed by BrdU labeling, and protects cells from CD-induced apoptosis, as assessed by TUNEL labeling and cleavage of poly(ADP-ribose) polymerase. However, EGF rescue was not accompanied by restoration of depleted intracellular concentrations of choline, glycerphosphocholine, phosphocholine, or phosphatidylcholine. In contrast, we show that EGF stimulation blocks apoptosis by restoring mitochondrial membrane potential (Delta Psi(m)), as determined using the potential-sensitive dye chloromethyl-X-rosamine, and by preventing the release and nuclear localization of cytochrome c. We investigated whether EGF rescue involves EGF receptor phosphorylation and activation of the down-stream cell survival factor Akt. Compared to cells in control medium (CT, 70 micromol choline x 48 hrs), cells in CD medium (5 micromol choline) were less sensitive to EGF-induced (0-300 ng/mL x 5 min) receptor tyrosine phosphorylation. Compared to cells in CT medium, cells in CD medium treated with EGF (10 ng/mL x 5 min) exhibited higher levels of phosphatidylinositol 3-kinase (PI3K)-dependent phosphorylation of AktSer473. Inactivation of PI3K was sufficient to block EGF-stimulated activation of Akt, restoration of mitochondrial Delta Psi(m), and prevention of cytochrome c release. These studies indicate that stimulation with EGF activates a cell survival response against CD-apoptosis by restoring mitochondrial membrane potential and preventing cytochrome c release and nuclear translocation which are mediated by activation of Akt in hepatocytes.
Collapse
Affiliation(s)
- Craig D Albright
- Department of Nutrition, School of Public Health and School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7461, USA
| | | | | | | | | | | |
Collapse
|
15
|
Koval M. Sharing signals: connecting lung epithelial cells with gap junction channels. Am J Physiol Lung Cell Mol Physiol 2002; 283:L875-93. [PMID: 12376339 DOI: 10.1152/ajplung.00078.2002] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gap junction channels enable the direct flow of signaling molecules and metabolites between cells. Alveolar epithelial cells show great variability in the expression of gap junction proteins (connexins) as a function of cell phenotype and cell state. Differential connexin expression and control by alveolar epithelial cells have the potential to enable these cells to regulate the extent of intercellular coupling in response to cell stress and to regulate surfactant secretion. However, defining the precise signals transmitted through gap junction channels and the cross talk between gap junctions and other signaling pathways has proven difficult. Insights from what is known about roles for gap junctions in other systems in the context of the connexin expression pattern by lung cells can be used to predict potential roles for gap junctional communication between alveolar epithelial cells.
Collapse
Affiliation(s)
- Michael Koval
- Department of Physiology and Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
| |
Collapse
|
16
|
Albright CD, Grimley PM, Jones RT, Resau JH. Differential effects of TPA and retinoic acid on cell-cell communication in human bronchial epithelial cells. Exp Mol Pathol 2002; 72:62-7. [PMID: 11784124 DOI: 10.1006/exmp.2001.2411] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Understanding how normal and immortalized bronchial epithelial cells respond to modulators of gap junctional communication will increase our understanding of the process of tumor promotion. In the present study we compared to effects of retinoic acid (RA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) on the rate of fluorescent dye transfer via gap junctions in primary human tracheo-bronchial epithelial cells (TBE) and SV40 large T-antigen immortalized, non-tumorigenic bronchial epithelial cells (BEAS-2B). RA in the physiological range (0.001-1 microM) inhibited cell proliferation (DNA synthesis, mitotic index) more in primary TBE cells than BEAS-2B cells. Also in RA-treated cells, decreased cell proliferation was coupled to decreased gap junctional communication (GJC) in TBE but not in BEAS-2B cells. TPA strongly suppressed GJC and proliferation in primary TBE cells, whereas BEAS-2B exhibited increased GJC and retained a significant fraction of cells undergoing DNA synthesis. Our studies show that an uncoupling of GJC and cell proliferation is associated with a differential response to the growth inhibitory effects of RA and phorbol esters in immortalized compared to primary human bronchial epithelial cells.
Collapse
Affiliation(s)
- Craig D Albright
- Department of Nutrition, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | | | | | | |
Collapse
|
17
|
Connexin Interacting Proteins. HEART CELL COUPLING AND IMPULSE PROPAGATION IN HEALTH AND DISEASE 2002. [DOI: 10.1007/978-1-4615-1155-7_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
|