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Cholico GN, Fling RR, Sink WJ, Nault R, Zacharewski T. Inhibition of the urea cycle by the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin increases serum ammonia levels in mice. J Biol Chem 2024; 300:105500. [PMID: 38013089 PMCID: PMC10731612 DOI: 10.1016/j.jbc.2023.105500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/26/2023] [Accepted: 11/18/2023] [Indexed: 11/29/2023] Open
Abstract
The aryl hydrocarbon receptor is a ligand-activated transcription factor known for mediating the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. TCDD induces nonalcoholic fatty liver disease (NAFLD)-like pathologies including simple steatosis that can progress to steatohepatitis with fibrosis and bile duct proliferation in male mice. Dose-dependent progression of steatosis to steatohepatitis with fibrosis by TCDD has been associated with metabolic reprogramming, including the disruption of amino acid metabolism. Here, we used targeted metabolomic analysis to reveal dose-dependent changes in the level of ten serum and eleven hepatic amino acids in mice upon treatment with TCDD. Bulk RNA-seq and protein analysis showed TCDD repressed CPS1, OTS, ASS1, ASL, and GLUL, all of which are associated with the urea cycle and glutamine biosynthesis. Urea and glutamine are end products of the detoxification and excretion of ammonia, a toxic byproduct of amino acid catabolism. Furthermore, we found that the catalytic activity of OTC, a rate-limiting step in the urea cycle was also dose dependently repressed. These results are consistent with an increase in circulating ammonia. Collectively, the repression of the urea and glutamate-glutamine cycles increased circulating ammonia levels and the toxicity of TCDD.
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Affiliation(s)
- Giovan N Cholico
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA
| | - Russell R Fling
- Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA; Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Warren J Sink
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA
| | - Rance Nault
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA
| | - Tim Zacharewski
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA.
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Taivassalo T, Hepple RT. Integrating Mechanisms of Exacerbated Atrophy and Other Adverse Skeletal Muscle Impact in COPD. Front Physiol 2022; 13:861617. [PMID: 35721564 PMCID: PMC9203961 DOI: 10.3389/fphys.2022.861617] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 05/11/2022] [Indexed: 11/13/2022] Open
Abstract
The normal decline in skeletal muscle mass that occurs with aging is exacerbated in patients with chronic obstructive pulmonary disease (COPD) and contributes to poor health outcomes, including a greater risk of death. There has been controversy about the causes of this exacerbated muscle atrophy, with considerable debate about the degree to which it reflects the very sedentary nature of COPD patients vs. being precipitated by various aspects of the COPD pathophysiology and its most frequent proximate cause, long-term smoking. Consistent with the latter view, recent evidence suggests that exacerbated aging muscle loss with COPD is likely initiated by decades of smoking-induced stress on the neuromuscular junction that predisposes patients to premature failure of muscle reinnervation capacity, accompanied by various alterations in mitochondrial function. Superimposed upon this are various aspects of COPD pathophysiology, such as hypercapnia, hypoxia, and inflammation, that can also contribute to muscle atrophy. This review will summarize the available knowledge concerning the mechanisms contributing to exacerbated aging muscle affect in COPD, consider the potential role of comorbidities using the specific example of chronic kidney disease, and identify emerging molecular mechanisms of muscle impairment, including mitochondrial permeability transition as a mechanism of muscle atrophy, and chronic activation of the aryl hydrocarbon receptor in driving COPD muscle pathophysiology.
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Affiliation(s)
- Tanja Taivassalo
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, United States
| | - Russell T. Hepple
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, United States
- Department of Physical Therapy, University of Florida, Gainesville, FL, United States
- *Correspondence: Russell T. Hepple,
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3
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Thome T, Miguez K, Willms AJ, Burke SK, Chandran V, de Souza AR, Fitzgerald LF, Baglole C, Anagnostou ME, Bourbeau J, Jagoe RT, Morais JA, Goddard Y, Taivassalo T, Ryan TE, Hepple RT. Chronic aryl hydrocarbon receptor activity phenocopies smoking-induced skeletal muscle impairment. J Cachexia Sarcopenia Muscle 2022; 13:589-604. [PMID: 34725955 PMCID: PMC8818603 DOI: 10.1002/jcsm.12826] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/30/2021] [Accepted: 09/11/2021] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Chronic obstructive pulmonary disease (COPD) patients exhibit skeletal muscle atrophy, denervation, and reduced mitochondrial oxidative capacity. Whilst chronic tobacco smoke exposure is implicated in COPD muscle impairment, the mechanisms involved are ambiguous. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that activates detoxifying pathways with numerous exogenous ligands, including tobacco smoke. Whereas transient AHR activation is adaptive, chronic activation can be toxic. On this basis, we tested the hypothesis that chronic smoke-induced AHR activation causes adverse muscle impact. METHODS We used clinical patient muscle samples, and in vitro (C2C12 myotubes) and in vivo models (mouse), to perform gene expression, mitochondrial function, muscle and neuromuscular junction morphology, and genetic manipulations (adeno-associated virus-mediated gene transfer). RESULTS Sixteen weeks of tobacco smoke exposure in mice caused muscle atrophy, neuromuscular junction degeneration, and reduced oxidative capacity. Similarly, smoke exposure reprogrammed the muscle transcriptome, with down-regulation of mitochondrial and neuromuscular junction genes. In mouse and human patient specimens, smoke exposure increased muscle AHR signalling. Mechanistically, experiments in cultured myotubes demonstrated that smoke condensate activated the AHR, caused mitochondrial impairments, and induced an AHR-dependent myotube atrophy. Finally, to isolate the role of AHR activity, expression of a constitutively active AHR mutant without smoke exposure caused atrophy and mitochondrial impairments in cultured myotubes, and muscle atrophy and neuromuscular junction degeneration in mice. CONCLUSIONS These results establish that chronic AHR activity, as occurs in smokers, phenocopies the atrophy, mitochondrial impairment, and neuromuscular junction degeneration caused by chronic tobacco smoke exposure.
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Affiliation(s)
- Trace Thome
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Kayla Miguez
- Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada
| | - Alexander J Willms
- Research Institute of the McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - Sarah K Burke
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | | | - Angela R de Souza
- Research Institute of the McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - Liam F Fitzgerald
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Carolyn Baglole
- Research Institute of the McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | | | - Jean Bourbeau
- Research Institute of the McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - R Thomas Jagoe
- Research Institute of the McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - Jose A Morais
- Research Institute of the McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - Yana Goddard
- Department of Medicine, University of Florida, Gainesville, FL, USA
| | - Tanja Taivassalo
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, USA
| | - Terence E Ryan
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Russell T Hepple
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA.,Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, USA
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4
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Luo Y, Xie HQ, Chen Y, Xia Y, Sha R, Liu Y, Ma Y, Xu T, Xu L, Wah-Keung Tsim K, Zhao B. Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure on acetylcholinesterase during myogenic differentiation of contractile rat primary skeletal muscle cells. Chem Biol Interact 2019; 308:164-169. [DOI: 10.1016/j.cbi.2019.05.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 04/30/2019] [Accepted: 05/13/2019] [Indexed: 12/12/2022]
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5
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Xie HQ, Xia Y, Xu T, Chen Y, Fu H, Li Y, Luo Y, Xu L, Tsim KWK, Zhao B. 2,3,7,8-Tetrachlorodibenzo-p-dioxin induces alterations in myogenic differentiation of C2C12 cells. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2018; 235:965-973. [PMID: 29751400 DOI: 10.1016/j.envpol.2017.12.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 11/07/2017] [Accepted: 12/06/2017] [Indexed: 06/08/2023]
Abstract
Dioxin-induced toxicities that affect the development of the motor system have been proposed since many years. However, cellular evidence and the molecular basis for the effects are limited. In this study, a cultured mouse myoblast cell line, C2C12, was utilized to examine the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on myogenic differentiation and expression of acetylcholinesterase (AChE), a neuromuscular transmission-related gene. The results showed that TCDD exposure at 10-10 M repressed the myotube formation of C2C12 cells by disturbing the fusion process and suppressing the expression of myosin heavy chain, a myobute structural protein, and not by induction of cytotoxicity. Furthermore, TCDD dose dependently suppressed the transcriptional expression and enzymatic activity of AChE during the myogenic differentiation, particularly in the middle stage. However, the administration of aryl hydrocarbon receptor antagonists, CH223191 and alpha-naphthoflavone, did not completely reverse the TCDD-induced downregulation of muscular AChE during myogenic differentiation. These findings suggest that low dose exposure to dioxin may result in disturbances of muscle differentiation and neuromuscular transmission.
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Affiliation(s)
- Heidi Q Xie
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Yingjie Xia
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Tuan Xu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Yangsheng Chen
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Hualing Fu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Yunping Li
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Yali Luo
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Li Xu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China
| | - Karl W K Tsim
- Division of Life Science, Center for Chinese Medicine and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay Road, Hong Kong, China
| | - Bin Zhao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center of Eco-Environment Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, China.
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Yazan LS, Ong YS, Zaaba NE, Ali RM, Foo JB, Tor YS. Anti-breast cancer properties and toxicity of Dillenia suffruticosa root aqueous extract in BALB/c mice. Asian Pac J Trop Biomed 2015. [DOI: 10.1016/j.apjtb.2015.09.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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7
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Sangeetha M, Eazhisai Vallabi D, Sali VK, Thanka J, Vasanthi HR. Sub-acute toxicity profile of a modified resveratrol supplement. Food Chem Toxicol 2013; 59:492-500. [DOI: 10.1016/j.fct.2013.06.037] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 06/15/2013] [Accepted: 06/19/2013] [Indexed: 12/16/2022]
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8
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Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin administration and high-fat diet on the body weight and hepatic estrogen metabolism in female C3H/HeN mice. Toxicol Appl Pharmacol 2007; 226:107-18. [PMID: 17945325 DOI: 10.1016/j.taap.2007.08.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Revised: 08/23/2007] [Accepted: 08/23/2007] [Indexed: 12/23/2022]
Abstract
We studied the effect of administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by i.p. injection once every 2 weeks in combination with a high-fat (HF) diet for 8 or 16 weeks on the body and organ weight changes as well as on the hepatic enzyme activity for estrogen metabolism in C3H/HeN female mice. Administration of TCDD at 100 microg/kg b.w. once every 2 weeks for 8 weeks increased the body weight by 46% in the HF diet-fed animals, but not in the regular diet-fed animals. This is the first observation suggesting that TCDD at a high dose (100 microg/kg b.w.), but not at lower doses (1 or 10 microg/kg b.w.), may have a strong obesity-inducing effect in C3H/HeN mice fed an HF diet. While TCDD increased liver weight and decreased thymus weight in animals, these effects were enhanced by feeding animals an HF diet. Metabolism studies showed that TCDD administration for 8 or 16 weeks increased the liver microsomal activity for the 2- and 4-hydroxylation of 17 beta-estradiol in animals fed a control diet, but surprisingly not in animals fed an HF diet. Treatment with TCDD dose-dependently increased the hepatic activity for the O-methylation of catechol estrogens in both control and HF diet-fed animals, and it also decreased the levels of liver microsomal sulfatase activity for hydrolysis of estrone-3-sulfate. TCDD did not significantly affect the hepatic enzyme activity for the glucuronidation or esterification of endogenous estrogens. It is suggested that enhanced metabolic inactivation of endogenous estrogens by hepatic estrogen-metabolizing enzymes in TCDD-treated, control diet-fed animals contributes importantly to the reduced incidence of estrogen-associated tumors in animals treated with TCDD.
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9
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Wang Y, Watford M. Glutamine, insulin and glucocorticoids regulate glutamine synthetase expression in C2C12 myotubes, Hep G2 hepatoma cells and 3T3 L1 adipocytes. BIOCHIMICA ET BIOPHYSICA ACTA 2007; 1770:594-600. [PMID: 17197094 PMCID: PMC1850228 DOI: 10.1016/j.bbagen.2006.11.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 10/26/2006] [Accepted: 11/16/2006] [Indexed: 10/23/2022]
Abstract
The cell-specific regulation of glutamine synthetase expression was studied in three cell lines. In C2C12 myotubes, glucocorticoids increased the abundance of both glutamine synthetase protein and mRNA. Culture in the absence of glutamine also resulted in very high glutamine synthetase protein abundance but mRNA levels were unchanged. Glucocorticoids also increased the abundance of glutamine synthetase mRNA in Hep G2 hepatoma cells but this was not reflected in changes in protein abundance. Culture of Hep G2 cells without glutamine resulted in very high levels of protein, again with no change in mRNA abundance. Insulin was without effect in both C2C12 and Hep G2 cells. In 3T3 L1 adipocytes glucocorticoids increased the abundance of both glutamine synthetase mRNA and protein, insulin added alone had no effect but in the presence of glucocorticoids resulted in lower mRNA levels than seen with glucocorticoids alone, although protein levels remained high under such conditions. In contrast to the other cell lines glutamine synthetase protein levels were relatively unchanged by culture in the absence of glutamine. The results support the hypothesis that in myocytes, and hepatomas, but not in adipocytes, glutamine acts to moderate glutamine synthetase induction by glucocorticoids.
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Affiliation(s)
- Yanxin Wang
- Department of Nutritional Sciences, Thompson Hall, Cook College, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA
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10
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Konno S. Hydroxyl Radical Formation in Skeletal Muscle of Rats with Glucocorticoid-Induced Myopathy. Neurochem Res 2005; 30:669-75. [PMID: 16176071 DOI: 10.1007/s11064-005-2755-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Steroid myopathy is a well-known adverse effect of glucocorticoids that causes muscle weakness and atrophy; however, its pathogenic mechanism is still unclear. Recently, oxidative stress was reported to contribute to steroid myopathy, but there is no report that actually attempts to measure hydroxyl radical. I developed an animal model of steroid myopathy in rat with dexamethasone (9-Fluoro-11beta,17, 21-trihydroxy-16alpha-methylpregna-1,4-diene-3,20-dione), and measured hydroxyl radical using the salicylate trapping method. There was significant dose-dependent relation between both 2,5- and 2,3-dihydroxybenzoic acids and dexamethasone in the treated group, compared to the control group. These results suggest that hydroxyl radical plays a role in the pathogenesis of steroid myopathy.
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Affiliation(s)
- Shingo Konno
- Department of Neurology, Toho University School of Medicine, Oohashi Hospital, 2-17-6 Oohashi, 153-8515, Meguro-ku, Tokyo, Japan.
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11
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Birnbaum LS, Tuomisto J. Non-carcinogenic effects of TCDD in animals. FOOD ADDITIVES AND CONTAMINANTS 2000; 17:275-88. [PMID: 10912242 DOI: 10.1080/026520300283351] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Exposure to TCDD and related chemicals leads to a plethora of effects in multiple species, tissues, and stages of development. Responses range from relatively simple biochemical alterations through overtly toxic responses, including lethality. The spectrum of effects shows some species variability, but many effects are seen in multiple wildlife, domestic, and laboratory species, ranging from fish through birds and mammals. The same responses can be generated regardless of the route of exposure, although the administered dose may vary. The body burden appears to be the most appropriate dosimetric. Many of the effects often attributed to TCDD are associated with relatively high doses: lethality, wasting, lymphoid and gonadal atrophy, chloracne, hepatotoxicity, adult neurotoxicity, and cardiotoxicity. Changes in multiple endocrine and growth factor systems have been reported in a manner which is tissue, sex, and age-dependent. The most sensitive adverse effects observed in multiple species appear to be developmental, including effects on the developing immune, nervous, and reproductive systems. Such effects have been observed at maternal body burdens in the range of 30-80 ng/kg in both non-human primates and rodents. Biochemical effects on cytokine expression and metabolizing enzymes occur at body burdens which are within a factor of ten of the clearly adverse developmental responses. Thus, effects on the immune system, learning, and the developing reproductive system of multiple animals occur at body burdens which are close to those present in the background human population.
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Affiliation(s)
- L S Birnbaum
- National Health and Environmental Effects Research Laboratory, United States Environmental Protection Agency, Research Triangle Park, NC 27711-2055, USA
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12
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De Krey GK, Kerkvliet NI. Suppression of cytotoxic T lymphocyte activity by 2,3,7,8-tetrachlorodibenzo-p-dioxin occurs in vivo, but not in vitro, and is independent of corticosterone elevation. Toxicology 1995; 97:105-12. [PMID: 7716775 DOI: 10.1016/0300-483x(94)02929-o] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Previous studies have shown that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent immunosuppressive compound. In our laboratory, TCDD and structurally related polychlorinated biphenyls (PCBs) have been shown to suppress alloantigen-specific cytotoxic T lymphocyte (CTL) activity in C57B1/6 mice. PCB-induced CTL suppression occurs coincident with significant elevation of plasma glucocorticoid (GC) levels (> 500 ng/ml). Since GC elevation can cause immune suppression, this study was conducted to determine if TCDD-induced CTL suppression is correlated with elevation of plasma corticosterone (CS), the major GC in mice. Single oral doses of TCDD (2.5-40 micrograms/kg) induced a dose-dependent suppression of CTL activity with a calculated 50% immunosuppressive dose (ID50) occurring at 7.2 micrograms/kg. When total lytic units (LU)/spleen were calculated, the ID50 was 2.8 micrograms/kg. In contrast, plasma CS levels were not significantly altered at doses below 40 micrograms/kg. These data suggest that TCDD-induced CTL suppression is not dependent on CS elevation. The direct effect of TCDD on CTL generation was tested by adding TCDD at 10(-13)-10(-9) M to in vitro mixed lymphocyte-tumor cell (MLTC) cultures. No alteration of CTL activity was observed after 5 days of culture at any TCDD concentration. In contrast, CS alone significantly suppressed CTL activity in vitro. CS-induced CTL suppression in vitro was neither enhanced nor inhibited by the presence of TCDD. These results suggest that TCDD causes CTL suppression in vivo by a mechanism that does not involve CS.
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Affiliation(s)
- G K De Krey
- Department of Agricultural Chemistry, Oregon State University, Corvallis 97331, USA
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13
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Aoki Y, Silbergeld EK, Max SR, Fowler BA. Alterations in protein synthesis in rat liver cells by in vitro and in vivo exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Biochem Pharmacol 1991; 42:1195-201. [PMID: 1888329 DOI: 10.1016/0006-2952(91)90254-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Alterations in protein synthesis in rat liver cells were examined following in vitro and in vivo exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Primary cultured rat liver parenchymal cells were exposed to 1 nM TCDD for 23 and 47 hr. Synthesis of two proteins with molecular weights (Mr) of 26,000 and 39,000 (designated 26k-P and 39k-P, respectively), other than cytochrome P450, was increased markedly in the cells. These proteins did not have the same antigens as cytochromes P450IA1 and P450IA2. Synthesis of three proteins with Mrs of 24,000, 25,000 and 29,000, respectively, was decreased by TCDD. TCDD was administered to rats at a dose of 100 micrograms/kg body weight. The amount of five proteins (two proteins with Mr of 26,000, one of 36,000 and two of 39,000) was increased in TCDD-treated rat liver. However, the proteins increased in vivo by TCDD were distinguishable from 26k-P and 39k-P by two dimensional gel electrophoresis.
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Affiliation(s)
- Y Aoki
- National Institute for Environmental Studies, Ibaraki, Japan
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14
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Stohs SJ, Abbott BD, Lin FH, Birnbaum LS. Induction of ethoxyresorufin-O-deethylase and inhibition of glucocorticoid receptor binding in skin and liver of haired and hairless HRS/J mice by topically applied 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicology 1990; 65:123-36. [PMID: 2274963 DOI: 10.1016/0300-483x(90)90083-s] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The biochemical changes associated with the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been reported to include alterations in glucocorticoid and epidermal growth factor receptors and mixed function oxidase (MFO) induction. TCDD induces MFO activity in skin of both haired and hairless HRS/J mice. However, epidermal hyperplasia and hyperkeratosis are produced only in the skin of hairless mice. Therefore, since steroid and growth factor responses are implicated in cell proliferation and differentiation, these mice constitute a model system for assessing the possible roles of glucocorticoid and epidermal growth factor receptors in the toxicity of TCDD. The effect of dermal TCDD application (12 micrograms/kg in 100 microliters acetone) on ethoxyresorufin-O-deethylase (EROD) activity, glucocorticoid receptor binding and epidermal growth factor receptors in liver and skin of hairless and haired mice was determined. No differences existed in the basal number of cytosolic glucocorticoid receptors (Bmax) or the apparent equilibrium binding constants (Kd) in control liver, dorsal skin and abdominal skin of male and female hairless mice and haired male mice. Seven days after topical application of TCDD, decreases of approximately 38% were observed in the hepatic Bmax of the glucocorticoid receptors in both haired and hairless mice. However, in dorsal skin, TCDD decreased Bmax by approximately 40% in hairless mice but only 18% in haired mice. The dexamethasone-glucocorticoid receptor complex from both liver and skin of control and TCDD treated mice had similar sedimentation co-efficients in sucrose density gradients. TCDD had no effect on the Kd of glucocorticoid receptors of skin or liver in haired and hairless mice. No difference was observed in the time-dependent increases in hepatic EROD activity between haired and hairless mice after dermal application of TCDD. However, the maximum induction of EROD activity in microsomes from the skin of haired mice was only 60% of the activity observed in hairless animals. The induction of EROD by TCDD did not correlate temporally with the decrease in glucocorticoid receptor binding. The application of TCDD to the skin of hairless mice resulted in epidermal hyperplasia and dermal keratinization, while little change was observed in the general morphology of the skin of haired mice following dermal application. The application of TCDD had no effect on the incidence and distribution of epidermal growth factor receptors in skin of haired and hairless mice as determined immunohistochemically. Thus, the biochemical effects of TCDD are not only strain dependent, but tissue specific. Furthermore, decreases in glucocorticoid and epidermal growth factor receptors do not appear to be general markers of TCDD toxicity.
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Affiliation(s)
- S J Stohs
- Systemic Toxicology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
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Tombaugh GC, Sapolsky RM. Hippocampal glutamine synthetase: insensitivity to glucocorticoids and stress. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 258:E894-7. [PMID: 1970712 DOI: 10.1152/ajpendo.1990.258.5.e894] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Glucocorticoids enhance the neurotoxic potential of several insults to the rat hippocampus that involve overactivation of glutamatergic synapses. These hormones also stimulate the synthesis of glutamine synthetase (GS) in peripheral tissue. Because this enzyme helps regulate glutamate metabolism in the central nervous system, glucocorticoid induction of GS in the brain may underlie the observed synergy. We have measured GS activity in the hippocampus and skeletal muscle (plantaris) of adult rats after bilateral adrenalectomy (ADX), corticosterone (Cort) replacement, or stress. No significant changes in GS were observed in hippocampal tissue, whereas muscle GS was significantly elevated after Cort treatment or stress and was reduced after ADX. These results suggest that Cort-induced shifts in GS activity probably do not explain Cort neurotoxicity, although the stress-induced rise in muscle GS may be relevant to certain types of myopathy.
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Affiliation(s)
- G C Tombaugh
- Department of Biological Sciences, Stanford University, California 94305
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Ryan RP, Sunahara GI, Lucier GW, Birnbaum LS, Nelson KG. Decreased ligand binding to the hepatic glucocorticoid and epidermal growth factor receptors after 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,4,7,8-hexachlorodibenzofuran treatment of pregnant mice. Toxicol Appl Pharmacol 1989; 98:454-64. [PMID: 2718174 DOI: 10.1016/0041-008x(89)90174-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
2,3,4,7,8-Pentachlorodibenzofuran (PeCDF) and 1,2,3,4,7,8-hexachlorodibenzofuran (HCDF) are environmental contaminants which mimic many of the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Like TCDD, these polychlorinated dibenzofurans (PCDFs) induce hepatic benzo[a]pyrene hydroxylase activity (BPH) and possess high affinity for the Ah receptor. Another similarity of these PCDFs to TCDD is their ability to induce teratogenic effects such as cleft palate and hydronephrosis in mice. Recent studies have shown that TCDD modifies the equilibrium binding kinetics of the rat liver cytosolic glucocorticoid receptor (GRc) and the hepatic plasma membrane epidermal growth factor (EGF) receptor. To gain a better understanding of the action of halogenated hydrocarbons on these cytosolic and membrane-bound receptor systems during pregnancy, we investigated the biochemical effects of PeCDF and HCDF on the binding kinetics of maternal mouse liver GRc and EGF receptors and the induction of BPH activities. Pregnant C57BL/6N mice were treated once daily on gestation Days 10 through 13 with PeCDF (0-30 micrograms/kg) or HCDF (0-300 micrograms/kg). Hepatic [3H]dexamethasone and [125I]EGF equilibrium binding studies indicated that all doses of PeCDF tested (10, 20, and 30 micrograms/kg) significantly reduced the GRc and EGF receptor maximum binding capacities but did not affect the binding affinities of these receptors when compared to corn oil-treated control pregnant mice. Similar effects were observed for doses of HCDF greater than or equal to 100 micrograms/kg. These data suggest that the dibenzofuran-mediated decreases in GRc and EGF receptor binding capacities are similar to those caused by TCDD. Although the mechanism of action is not yet clear, our results indicate that halogenated aromatic compounds in addition to TCDD have profound effects on both steroid and growth factor receptor systems.
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Affiliation(s)
- R P Ryan
- Laboratory of Biochemical Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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Abstract
Despite continuing controversies related to public policy, information on the molecular biology of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has advanced significantly over the past decade. Current understanding of the biological mechanisms of TCDD action is based upon the interactions of TCDD with a genetically expressed cytosolic macromolecule that functions as a receptor in many cells across many species. The Ah receptor recognizes TCDD and structurally similar molecules and serves as the transducing step whereby TCDD alters gene expression through the association of the TCDD:receptor complex with specific TCDD-responsive elements on the genome. Understanding these molecular events and their relevance to the organ-level manifestations of TCDD toxicity may be critical to formulating scientifically based assessments of the risk of TCDD exposure.
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Affiliation(s)
- E K Silbergeld
- Toxic Chemicals Program, Environmental Defense Fund, Washington, DC 20036
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Affiliation(s)
- E K Silbergeld
- Toxic Chemicals Program, Environmental Defense Fund, Washington, DC 20036
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