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Applicability of Scrape Loading-Dye Transfer Assay for Non-Genotoxic Carcinogen Testing. Int J Mol Sci 2021; 22:ijms22168977. [PMID: 34445682 PMCID: PMC8396440 DOI: 10.3390/ijms22168977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/30/2021] [Accepted: 07/31/2021] [Indexed: 12/27/2022] Open
Abstract
Dysregulation of gap junction intercellular communication (GJIC) is recognized as one of the key hallmarks for identifying non-genotoxic carcinogens (NGTxC). Currently, there is a demand for in vitro assays addressing the gap junction hallmark, which would have the potential to eventually become an integral part of an integrated approach to the testing and assessment (IATA) of NGTxC. The scrape loading-dye transfer (SL-DT) technique is a simple assay for the functional evaluation of GJIC in various in vitro cultured mammalian cells and represents an interesting candidate assay. Out of the various techniques for evaluating GJIC, the SL-DT assay has been used frequently to assess the effects of various chemicals on GJIC in toxicological and tumor promotion research. In this review, we systematically searched the existing literature to gather papers assessing GJIC using the SL-DT assay in a rat liver epithelial cell line, WB-F344, after treating with chemicals, especially environmental and food toxicants, drugs, reproductive-, cardio- and neuro-toxicants and chemical tumor promoters. We discuss findings derived from the SL-DT assay with the known knowledge about the tumor-promoting activity and carcinogenicity of the assessed chemicals to evaluate the predictive capacity of the SL-DT assay in terms of its sensitivity, specificity and accuracy for identifying carcinogens. These data represent important information with respect to the applicability of the SL-DT assay for the testing of NGTxC within the IATA framework.
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Wong P, Laxton V, Srivastava S, Chan YWF, Tse G. The role of gap junctions in inflammatory and neoplastic disorders (Review). Int J Mol Med 2017; 39:498-506. [PMID: 28098880 PMCID: PMC5360388 DOI: 10.3892/ijmm.2017.2859] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 12/23/2016] [Indexed: 12/29/2022] Open
Abstract
Gap junctions are intercellular channels made of connexin proteins, mediating both electrical and biochemical signals between cells. The ability of gap junction proteins to regulate immune responses, cell proliferation, migration, apoptosis and carcinogenesis makes them attractive therapeutic targets for treating inflammatory and neoplastic disorders in different organ systems. Alterations in gap junction profile and expression levels are observed in hyperproliferative skin disorders, lymphatic vessel diseases, inflammatory lung diseases, liver injury and neoplastic disorders. It is now recognized that the therapeutic effects mediated by traditional pharmacological agents are dependent upon gap junction communication and may even act by influencing gap junction expression or function. Novel strategies for modulating the function or expression of connexins, such as the use of synthetic mimetic peptides and siRNA technology are considered.
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Affiliation(s)
- Pui Wong
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, SAR, P.R. China
| | - Victoria Laxton
- Intensive Care Department, Royal Brompton and Harefield NHS Foundation Trust, London SW3 6NP
| | | | - Yin Wah Fiona Chan
- School of Biological Sciences, University of Cambridge, Cambridge CB2 1AG, UK
| | - Gary Tse
- Department of Medicine and Therapeutics
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, SAR, P.R. China
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Connexin43 hemichannels contributes to the disassembly of cell junctions through modulation of intracellular oxidative status. Redox Biol 2016; 9:198-209. [PMID: 27567473 PMCID: PMC5007435 DOI: 10.1016/j.redox.2016.08.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 07/28/2016] [Accepted: 08/18/2016] [Indexed: 12/25/2022] Open
Abstract
Connexin (Cx) hemichannels regulate many cellular processes with little information available regarding their mechanisms. Given that many pathological factors that activate hemichannels also disrupts the integrity of cellular junctions, we speculated a potential participation of hemichannels in the regulation of cell junctions. Here we tested this hypothesis. Exposure of renal tubular epithelial cells to Ca2+-free medium led to disassembly of tight and adherens junctions, as indicated by the reduced level of ZO-1 and cadherin, disorganization of F-actin, and severe drop in transepithelial electric resistance. These changes were preceded by an activation of Cx43 hemichannels, as revealed by extracellular efflux of ATP and intracellular influx of Lucifer Yellow. Inhibition of hemichannels with chemical inhibitors or Cx43 siRNA greatly attenuated the disassembly of cell junctions. Further analysis using fetal fibroblasts derived from Cx43 wide-type (Cx43+/+), heterozygous (Cx43+/-) and knockout (Cx43-/-) littermates showed that Cx43-positive cells (Cx43+/+) exhibited more dramatic changes in cell shape, F-actin, and cadherin in response to Ca2+ depletion, as compared to Cx43-null cells (Cx43-/-). Consistently, these cells had higher level of protein carbonyl modification and phosphorylation, and much stronger activation of P38 and JNK. Hemichannel opening led to extracellular loss of the major antioxidant glutathione (GSH). Supplement of cells with exogenous GSH or inhibition of oxidative sensitive kinases largely prevented the above-mentioned changes. Taken together, our study indicates that Cx43 hemichannels promote the disassembly of cell junctions through regulation of intracellular oxidative status. The mechanisms about the coordinated regulation of cell junctions are obscure. Ca2+ depletion activates hemichannels and disrupts cell junctions. Hemichannel opening exaggerates oxidative stress via efflux of GSH. Blocking hemichannels attenuates oxidative stress and cell junction disassembly. Hemichannels regulate cell junctions via modulation of intracellular redox status.
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Babica P, Zurabian R, Kumar ER, Chopra R, Mianecki MJ, Park JS, Jaša L, Trosko JE, Upham BL. Methoxychlor and Vinclozolin Induce Rapid Changes in Intercellular and Intracellular Signaling in Liver Progenitor Cells. Toxicol Sci 2016; 153:174-85. [PMID: 27413106 DOI: 10.1093/toxsci/kfw114] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Methoxychlor (MXC) and vinclozolin (VIN) are well-recognized endocrine disrupting chemicals known to alter epigenetic regulations and transgenerational inheritance; however, non-endocrine disruption endpoints are also important. Thus, we determined the effects of MXC and VIN on the dysregulation of gap junctional intercellular communication (GJIC) and activation of mitogen-activated protein kinases (MAPKs) in WB-F344 rat liver epithelial cells. Both chemicals induced a rapid dysregulation of GJIC at non-cytotoxic doses, with 30 min EC50 values for GJIC inhibition being 10 µM for MXC and 126 µM for VIN. MXC inhibited GJIC for at least 24 h, while VIN effects were transient and GJIC recovered after 4 h. VIN induced rapid hyperphosphorylation and internalization of gap junction protein connexin43, and both chemicals also activated MAPK ERK1/2 and p38. Effects on GJIC were not prevented by MEK1/2 inhibitor, but by an inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC), resveratrol, and in the case of VIN, also, by a p38 inhibitor. Estrogen (ER) and androgen receptor (AR) modulators (estradiol, ICI 182,780, HPTE, testosterone, flutamide, VIN M2) did not attenuate MXC or VIN effects on GJIC. Our data also indicate that the effects were elicited by the parental compounds of MXC and VIN. Our study provides new evidence that MXC and VIN dysregulate GJIC via mechanisms involving rapid activation of PC-PLC occurring independently of ER- or AR-dependent genomic signaling. Such alterations of rapid intercellular and intracellular signaling events involved in regulations of gene expression, tissue development, function and homeostasis, could also contribute to transgenerational epigenetic effects of endocrine disruptors.
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Affiliation(s)
- Pavel Babica
- *Department of Experimental Phycology and Ecotoxicology, Institute of Botany, Brno 60200, Czech Republic; RECETOX, Faculty of Science, Masaryk University, Brno 62500, Czech Republic; Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824;
| | - Rimma Zurabian
- Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824; Department of Microbiology and Parasitology, Faculty of Medicine, National Autonomous University of Mexico, CdMx, 04510, Mexico
| | - Esha R Kumar
- Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
| | - Rajus Chopra
- Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
| | - Maxwell J Mianecki
- Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
| | - Joon-Suk Park
- Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824; Laboratory Animal Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, Korea
| | - Libor Jaša
- *Department of Experimental Phycology and Ecotoxicology, Institute of Botany, Brno 60200, Czech Republic; RECETOX, Faculty of Science, Masaryk University, Brno 62500, Czech Republic
| | - James E Trosko
- Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
| | - Brad L Upham
- Department of Pediatrics and Human Development, and Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
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Mudawal A, Singh A, Yadav S, Mishra M, Singh PK, Chandravanshi LP, Mishra J, Khanna VK, Bandyopadhyay S, Parmar D. Similarities in lindane induced alterations in protein expression profiling in different brain regions with neurodegenerative diseases. Proteomics 2015; 15:3875-82. [DOI: 10.1002/pmic.201400407] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 08/10/2015] [Accepted: 09/04/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Anubha Mudawal
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
- Academy of Scientific & Innovative Research; CSIR-IITR Campus; Lucknow India
| | - Anshuman Singh
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
| | - Sanjay Yadav
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
- Academy of Scientific & Innovative Research; CSIR-IITR Campus; Lucknow India
| | - Manisha Mishra
- Plant Molecular Biology Laboratory; CSIR-National Botanical Research Institute (CSIR-NBRI); Lucknow India
| | - Pradhyumna Kumar Singh
- Plant Molecular Biology Laboratory; CSIR-National Botanical Research Institute (CSIR-NBRI); Lucknow India
| | - Lalit Pratap Chandravanshi
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
| | - Juhi Mishra
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
| | - Vinay K. Khanna
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
- Academy of Scientific & Innovative Research; CSIR-IITR Campus; Lucknow India
| | - Sanghamitra Bandyopadhyay
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
- Academy of Scientific & Innovative Research; CSIR-IITR Campus; Lucknow India
| | - Devendra Parmar
- Developmental Toxicology Laboratory; Systems Toxicology and Health Risk Assessment Group; CSIR-Indian Institute of Toxicology Research (CSIR-IITR); Lucknow India
- Academy of Scientific & Innovative Research; CSIR-IITR Campus; Lucknow India
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Muto T, Tien T, Kim D, Sarthy VP, Roy S. High glucose alters Cx43 expression and gap junction intercellular communication in retinal Müller cells: promotes Müller cell and pericyte apoptosis. Invest Ophthalmol Vis Sci 2014; 55:4327-37. [PMID: 24938518 DOI: 10.1167/iovs.14-14606] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
PURPOSE To investigate whether high glucose (HG) alters connexin 43 (Cx43) expression and gap junction intercellular communication (GJIC) activity in retinal Müller cells, and promotes Müller cell and pericyte loss. METHODS Retinal Müller cells (rMC-1) and cocultures of rMC-1 and retinal pericytes were grown in normal (N) or HG (30 mM glucose) medium. Additionally, rMC-1 transfected with Cx43 small interfering RNA (siRNA) were grown as cocultures with pericytes, and rMC-1 transfected with Cx43 plasmid were grown in HG. Expression of Cx43 was determined by Western blotting and immunostaining and GJIC was assessed by scrape-loading dye transfer (SLDT) technique. Apoptosis was analyzed by TUNEL or differential staining assay, and Akt activation by assessing Akt phosphorylation. RESULTS In monocultures of rMC-1 and cocultures of rMC-1 and pericytes, Cx43 protein level, number of Cx43 plaques, GJIC, and Akt phosphorylation were significantly reduced in HG medium. Number of TUNEL-positive cells was also significantly increased in rMC-1 monocultures and in rMC-1 and pericyte cocultures grown in HG medium. Importantly, when rMC-1 transfected with Cx43 siRNA were grown as cocultures with pericytes, a significant decrease in GJIC, and increase in TUNEL-positive cells was observed, concomitant with decreased Akt phosphorylation. Upregulation of Cx43 rescued rMC-1 from HG-induced apoptosis. CONCLUSIONS Gap junction communication between Müller cells and pericytes is essential for their survival. Downregulation of Cx43 that is HG induced and impairment of GJIC activity in Müller cells contributes to loss of glial and vascular cells associated with the pathogenesis of diabetic retinopathy.
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Affiliation(s)
- Tetsuya Muto
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
| | - Thomas Tien
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
| | - Dongjoon Kim
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
| | - Vijay P Sarthy
- Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
| | - Sayon Roy
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
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Chi Y, Gao K, Li K, Nakajima S, Kira S, Takeda M, Yao J. Purinergic control of AMPK activation by ATP released through connexin 43 hemichannels - pivotal roles in hemichannel-mediated cell injury. J Cell Sci 2014; 127:1487-99. [PMID: 24496445 DOI: 10.1242/jcs.139089] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Connexin hemichannels regulate many cell functions. However, the molecular mechanisms involved remain elusive. Hemichannel opening causes loss of ATP, we therefore speculated a potential role for AMPK in the biological actions of hemichannels. Activation of hemichannels by removal of extracellular Ca(2+) led to an efflux of ATP and a weak activation of AMPK. Unexpectedly, dysfunction of hemichannels markedly potentiated AMPK activation, which was reproduced by promotion of extracellular ATP degradation or inhibition of P2 purinoceptors but counteracted by exogenous ATP. Further analysis revealed that ATP induced a purinoceptor-dependent activation of Akt and mTOR. Suppression of Akt or mTOR augmented AMPK activation, whereas activation of Akt by transfection of cells with myristoylated Akt, a constitutively active form of Akt, abolished AMPK activation. In a pathological model of hemichannel opening triggered by Cd(2+), disclosure of hemichannels similarly enhanced AMPK activity, which protected cells from Cd(2+)-induced cell injury through suppression of mTOR. In summary, our data point to a channel-mediated mechanism for the regulation of AMPK through a purinergic signaling pathway. Furthermore, we define AMPK as a pivotal molecule that underlies the regulatory effects of hemichannels on cell survival.
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Affiliation(s)
- Yuan Chi
- Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi 409-3898, Japan
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Chen H, Zhao L, Chu G, Kito G, Yamauchi N, Shigeyoshi Y, Hashimoto S, Hattori MA. FSH induces the development of circadian clockwork in rat granulosa cells via a gap junction protein Cx43-dependent pathway. Am J Physiol Endocrinol Metab 2013; 304:E566-75. [PMID: 23299500 DOI: 10.1152/ajpendo.00432.2012] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The present study was designed to assess the relationship between gap junctions and the maturation of a clock system in rat granulosa cells stimulated by follicle-stimulating hormone (FSH). Immature and mature granulosa cells were prepared by puncturing the ovaries of diethylstilbestrol- and equine chorionic gonadotropin (eCG)-treated mouse Period2 (Per2)-dLuc reporter gene transgenic rats, respectively. Mature granulosa cells exposed to dexamethasone (DXM) synchronization displayed several Per2-dLuc oscillations and a rhythmic expression of clock genes. Intriguingly, we observed clear evidence that the FSH stimulation significantly increased the amplitude of Per2 oscillations in the granulosa cells, which was confirmed by the elevation of the Per2 and Rev-erbα (Nr1d1) mRNA levels. FSH also induced a major phase-advance shift of Per2 oscillations. The mature granulosa cells cultured for 2 days with FSH expressed higher mRNA levels of Per2, Rev-erbα, Bmal1 (Arnt1), Lhcgr, and connexin (Cx) 43 (Gja1) compared with the immature granulosa cells. Consistently, our immunofluorescence results revealed abundant Cx43 protein in antral follicles stimulated with eCG and weak or no fluorescence signal of Cx43 in primary and preantral follicles. Similar results were confirmed by Western blotting analysis. Two gap junction blockers, lindane and carbenoxolone (CBX), significantly decreased the amplitude of Per2 oscillations, which further adhered significant decreases in Per2 and Rev-erbα transcript levels. In addition, both lindane and CBX induced a clear phase-delay shift of Per2 oscillations. These findings suggest that FSH induces the development of the clock system by increasing the expression of Cx43.
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Affiliation(s)
- Huatao Chen
- Department of Animal and Marine Bioresource Sciences, Graduate School of Agriculture, Kyushu University, Fukuoka, Japan
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9
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Chen CA, Wang TY, Varadharaj S, Reyes LA, Hemann C, Talukder MAH, Chen YR, Druhan LJ, Zweier JL. S-glutathionylation uncouples eNOS and regulates its cellular and vascular function. Nature 2011; 468:1115-8. [PMID: 21179168 DOI: 10.1038/nature09599] [Citation(s) in RCA: 430] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 10/12/2010] [Indexed: 02/07/2023]
Abstract
Endothelial nitric oxide synthase (eNOS) is critical in the regulation of vascular function, and can generate both nitric oxide (NO) and superoxide (O(2)(•-)), which are key mediators of cellular signalling. In the presence of Ca(2+)/calmodulin, eNOS produces NO, endothelial-derived relaxing factor, from l-arginine (l-Arg) by means of electron transfer from NADPH through a flavin containing reductase domain to oxygen bound at the haem of an oxygenase domain, which also contains binding sites for tetrahydrobiopterin (BH(4)) and l-Arg. In the absence of BH(4), NO synthesis is abrogated and instead O(2)(•-) is generated. While NOS dysfunction occurs in diseases with redox stress, BH(4) repletion only partly restores NOS activity and NOS-dependent vasodilation. This suggests that there is an as yet unidentified redox-regulated mechanism controlling NOS function. Protein thiols can undergo S-glutathionylation, a reversible protein modification involved in cellular signalling and adaptation. Under oxidative stress, S-glutathionylation occurs through thiol-disulphide exchange with oxidized glutathione or reaction of oxidant-induced protein thiyl radicals with reduced glutathione. Cysteine residues are critical for the maintenance of eNOS function; we therefore speculated that oxidative stress could alter eNOS activity through S-glutathionylation. Here we show that S-glutathionylation of eNOS reversibly decreases NOS activity with an increase in O(2)(•-) generation primarily from the reductase, in which two highly conserved cysteine residues are identified as sites of S-glutathionylation and found to be critical for redox-regulation of eNOS function. We show that eNOS S-glutathionylation in endothelial cells, with loss of NO and gain of O(2)(•-) generation, is associated with impaired endothelium-dependent vasodilation. In hypertensive vessels, eNOS S-glutathionylation is increased with impaired endothelium-dependent vasodilation that is restored by thiol-specific reducing agents, which reverse this S-glutathionylation. Thus, S-glutathionylation of eNOS is a pivotal switch providing redox regulation of cellular signalling, endothelial function and vascular tone.
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Affiliation(s)
- Chun-An Chen
- Davis Heart and Lung Research Institute and Division of Cardiovascular Medicine, Department of Internal Medicine, College of Medicine, Ohio State University, Columbus, Ohio 43210, USA
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The correlation between lipid peroxidation in different brain regions and the severity of lindane-induced seizures in rats. Mol Cell Biochem 2009; 333:243-50. [PMID: 19693653 DOI: 10.1007/s11010-009-0225-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Accepted: 08/06/2009] [Indexed: 02/08/2023]
Abstract
The aim of this study was to investigate the dynamics of lipid peroxidation and the possible correlation between lipid peroxidation in different brain regions and behavioral manifestations in lindane-induced seizures in rats. Male Wistar rats were divided into the following groups: 1. control, saline-treated group; 2. dimethylsulfoxide (DMSO)-treated group; 3. lindane-treated group (8 mg/kg), intraperitoneally. Animals were sacrificed 0.5 or 4 h after treatment and the malondialdehyde level and superoxide dismutase (SOD) activity were determined in various brain regions spectrophotometrically. Behavioral changes were classified according to the descriptive scale (0--no response, 1--head nodding, lower jaw twitching; 2--myoclonic body jerks, bilateral forelimb clonus with full rearing; 3--progression to generalized clonic convulsions followed by tonic extension of fore- and hind limbs and tail; 4--status epilepticus). A significant rise in the malondialdehyde level was detected in the cerebral cortex, hippocampus, and thalamus of lindane-treated animals 0.5 and 4 h after administration (P < 0.05). SOD activity (total and mitochondrial) was significantly decreased in the hippocampus and the cortex of lindane-treated animals at both time points (P < 0.05). An initial fall in SOD activity was detected in the thalamus 4 h after lindane administration (P < 0.05). A positive correlation between seizure severity and the malondialdehyde level was found in the hippocampus at both time points (P < 0.01). These results suggest that lipid peroxidation may contribute to the neurotoxic effects of lindane in early acute lindane intoxication and that behavioral manifestations correlate with lipid peroxidation in the hippocampus of lindane-treated rats.
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Hattis D, Chu M, Rahmioglu N, Goble R, Verma P, Hartman K, Kozlak M. A preliminary operational classification system for nonmutagenic modes of action for carcinogenesis. Crit Rev Toxicol 2009; 39:97-138. [PMID: 19009457 DOI: 10.1080/10408440802307467] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This article proposes a system of categories for nonmutagenic modes of action for carcinogenesis. The classification is of modes of action rather than individual carcinogens, because the same compound can affect carcinogenesis in more than one way. Basically, we categorize modes of action as: (1) co-initiation (facilitating the original mutagenic changes in stem and progenitor cells that start the cancer process) (e.g. induction of activating enzymes for other carcinogens); (2) promotion (enhancing the relative growth vs differentiation/death of initiated clones (e.g. inhibition of growth-suppressing cell-cell communication); (3) progression (enhancing the growth, malignancy, or spread of already developed tumors) (e.g. suppression of immune surveillance, hormonally mediated growth stimulation for tumors with appropriate receptors by estrogens); and (4) multiphase (e.g., "epigenetic" silencing of tumor suppressor genes). A priori, agents that act at relatively early stages in the process are expected to manifest greater relative susceptibility in early life, whereas agents that act via later stage modes will tend to show greater susceptibility for exposures later in life.
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Affiliation(s)
- D Hattis
- George Perkins Marsh Institute, Clark University, Worcester, Massachusetts, USA
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Sexton K, Hattis D. Assessing cumulative health risks from exposure to environmental mixtures - three fundamental questions. ENVIRONMENTAL HEALTH PERSPECTIVES 2007; 115:825-32. [PMID: 17520074 PMCID: PMC1867955 DOI: 10.1289/ehp.9333] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 09/26/2006] [Indexed: 05/02/2023]
Abstract
Differential exposure to mixtures of environmental agents, including biological, chemical, physical, and psychosocial stressors, can contribute to increased vulnerability of human populations and ecologic systems. Cumulative risk assessment is a tool for organizing and analyzing information to evaluate the probability and seriousness of harmful effects caused by either simultaneous and/or sequential exposure to multiple environmental stressors. In this article we focus on elucidating key challenges that must be addressed to determine whether and to what degree differential exposure to environmental mixtures contributes to increased vulnerability of exposed populations. In particular, the emphasis is on examining three fundamental and interrelated questions that must be addressed as part of the process to assess cumulative risk: a) Which mixtures are most important from a public health perspective? and b) What is the nature (i.e., duration, frequency, timing) and magnitude (i.e., exposure concentration and dose) of relevant cumulative exposures for the population of interest? c) What is the mechanism (e.g., toxicokinetic or toxicodynamic) and consequence (e.g., additive, less than additive, more than additive) of the mixture's interactive effects on exposed populations? The focus is primarily on human health effects from chemical mixtures, and the goal is to reinforce the need for improved assessment of cumulative exposure and better understanding of the biological mechanisms that determine toxicologic interactions among mixture constituents.
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Affiliation(s)
- Ken Sexton
- University of Texas School of Public Health, Brownsville Regional Campus, Brownsville, Texas 78520-4956, USA.
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Gianazza E, Crawford J, Miller I. Detecting oxidative post-translational modifications in proteins. Amino Acids 2006; 33:51-6. [PMID: 17021655 DOI: 10.1007/s00726-006-0410-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2006] [Accepted: 08/30/2006] [Indexed: 10/24/2022]
Abstract
Oxidative stress induces various post-translational modifications (PTM); some are reversible in vivo via enzymatic catalysis. The present paper reviews specific procedures for the detection of oxidative PTM in proteins, most of them including electrophoresis. Main topics are carbonylated and glutathionylated proteins as well as modification of selected amino acids (Cys, Tyr, Met, Trp, Lys).
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Affiliation(s)
- E Gianazza
- Gruppo di Studio per la Proteomica e la Struttura delle Proteine, Dipartimento di Scienze Farmacologiche, Università degli Studi di Milano, Milano, Italy.
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Salameh A, Dhein S. Pharmacology of gap junctions. New pharmacological targets for treatment of arrhythmia, seizure and cancer? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1719:36-58. [PMID: 16216217 DOI: 10.1016/j.bbamem.2005.09.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Revised: 08/25/2005] [Accepted: 09/06/2005] [Indexed: 11/26/2022]
Abstract
Intercellular communication in many organs is maintained via intercellular gap junction channels composed of connexins, a large protein family with a number of isoforms. This gap junction intercellular communication (GJIC) allows the propagation of action potentials (e.g., in brain, heart), and the transfer of small molecules which may regulate cell growth, differentiation and function. The latter has been shown to be involved in cancer growth: reduced GJIC often is associated with increased tumor growth or with de-differentiation processes. Disturbances of GJIC in the heart can cause arrhythmia, while in brain electrical activity during seizures seems to be propagated via gap junction channels. Many diseases or pathophysiological conditions seem to be associated with alterations of gap junction protein expression. Thus, depending on the target disease opening or closure of gap junctions may be of interest, or alteration of connexin expression. GJIC can be affected acutely by changing gap junction conductance or--more chronic--by altering connexin expression and membrane localisation. This review gives an overview on drugs affecting GJIC.
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Affiliation(s)
- Aida Salameh
- Clinic I for Internal Medicine, Department of Cardiology, University of Leipzig, Johannisallee 32, 04103 Leipzig, Germany.
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Loch-Caruso R, Upham BL, Harris C, Trosko JE. Divergent roles for glutathione in lindane-induced acute and delayed-onset inhibition of rat myometrial gap junctions. Toxicol Sci 2005; 85:694-702. [PMID: 15716478 DOI: 10.1093/toxsci/kfi123] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Previous studies have shown that the insecticide lindane (gamma-hexachlorocyclohexane) induces a biphasic inhibition of gap junction intercellular communication that is accompanied by oxidative stress. The present study investigates the hypothesis that depletion of cellular glutathione (GSH) is a mechanistic link between lindane-induced oxidative stress and inhibition of myometrial gap junctions. Exposure to 100 or 200 microM lindane rapidly (within 1 min) increased myometrial cell generation of superoxide, as measured by superoxide dismutase-inhibitable cytochrome c reduction, and superoxide production remained elevated for up to 60 min of exposure. To measure gap junction communication, Lucifer yellow dye was injected into myometrial cells, and dye transfer to adjoining cells was monitored. Cells were exposed to lindane with or without GSH modulators, and dye transfer was determined at the end of a 1-h exposure to 100 microM lindane (acute phase) and 24 h after termination of lindane exposure (secondary phase). The acute phase of lindane-induced inhibition of dye transfer was prevented by GSH depletion with L-buthionine-[S,R]-sulfoximine (BSO) and enhanced by GSH augmentation with GSH monoethyl ester or L-2-oxothiazolidine-4-carboxylate (OTC). In contrast, the secondary, delayed-onset phase of lindane-induced inhibition of dye transfer was enhanced by GSH depletion with BSO and prevented by GSH augmentation with GSH monoethyl ester or OTC. Changes in cellular GSH by the pharmacological modulators were confirmed by high performance liquid chromatography. These results suggest that GSH is required in the acute phase but protects against the secondary phase of lindane-induced inhibition of myometrial gap junctions.
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Affiliation(s)
- Rita Loch-Caruso
- Toxicology Program, Department of Environmental Health, University of Michigan, Ann Arbor, MI 48109-2029, USA.
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