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Aschner M, Skalny AV, Paoliello MMB, Tinkova MN, Martins AC, Santamaria A, Lee E, Rocha JBT, Farsky SHP, Tinkov AA. Retinal toxicity of heavy metals and its involvement in retinal pathology. Food Chem Toxicol 2024; 188:114685. [PMID: 38663763 DOI: 10.1016/j.fct.2024.114685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 04/16/2024] [Accepted: 04/22/2024] [Indexed: 05/04/2024]
Abstract
The objective of the present review is to discuss epidemiological evidence demonstrating the association between toxic metal (Cd, Pb, Hg, As, Sn, Ti, Tl) exposure and retinal pathology, along with the potential underlying molecular mechanisms. Epidemiological studies demonstrate that Cd, and to a lesser extent Pb exposure, are associated with age-related macular degeneration (AMD), while the existing evidence on the levels of these metals in patients with diabetic retinopathy is scarce. Epidemiological data on the association between other toxic metals and metalloids including mercury (Hg) and arsenic (As), are limited. Clinical reports and laboratory in vivo studies have shown structural alterations in different layers of retina following metal exposure. Examination of retina samples demonstrate that toxic metals can accumulate in the retina, and the rate of accumulation appears to increase with age. Experimental studies in vivo and in vitro studies in APRE-19 and D407 cells demonstrate that toxic metal exposure may cause retinal damage through oxidative stress, apoptosis, DNA damage, mitochondrial dysfunction, endoplasmic reticulum stress, impaired retinogenesis, and retinal inflammation. However, further epidemiological as well as laboratory studies are required for understanding the underlying molecular mechanisms and identifying of the potential therapeutic targets and estimation of the dose-response effects.
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Affiliation(s)
- Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Anatoly V Skalny
- Laboratory of Ecobiomonitoring and Quality Control, Yaroslavl State University, Yaroslavl, 150003, Russia; Center of Bioelementology and Human Ecology, IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, 119435, Russia
| | - Monica M B Paoliello
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, New York, NY 10461, USA
| | | | - Airton C Martins
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Abel Santamaria
- Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico; Laboratorio de Nanotecnología y Nanomedicina, Departamento de Cuidado de La Salud, Universidad Autónoma Metropolitana-Xochimilco, Mexico City 04960, Mexico
| | - Eunsook Lee
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, FL 32307, USA
| | - Joao B T Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria 97105-900, RS, Brazil
| | - Sandra H P Farsky
- Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University of Sao Paulo, São Paulo 05508-000, SP, Brazil
| | - Alexey A Tinkov
- Laboratory of Ecobiomonitoring and Quality Control, Yaroslavl State University, Yaroslavl, 150003, Russia; Center of Bioelementology and Human Ecology, IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, 119435, Russia.
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Ebrahimi M, Ebrahimi M, Vergroesen JE, Aschner M, Sillanpää M. Environmental exposures to cadmium and lead as potential causes of eye diseases. J Trace Elem Med Biol 2024; 82:127358. [PMID: 38113800 DOI: 10.1016/j.jtemb.2023.127358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 12/04/2023] [Accepted: 12/06/2023] [Indexed: 12/21/2023]
Abstract
Humans are exposed to cadmium and lead in various regions of the world daily due to industrial development and climate change. Increasing numbers of preclinical and clinical studies indicate that heavy metals, such as cadmium and lead, play a role in the pathogenesis of eye diseases. Excessive exposure to heavy metals such as cadmium and lead can increase the risk of impaired vision. Therefore, it is essential to better characterize the role of these non-essential metals in disease etiology and progression. This article discusses the potential role of cadmium and lead in the development of age-related eye diseases, including age-related macular degeneration, cataracts, and glaucoma. Furthermore, we discuss how cadmium and lead affect ocular cells and provide an overview of putative pathological mechanisms associated with their propensity to damage the eye.
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Affiliation(s)
- Moein Ebrahimi
- School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Network of Immunity in Infection, Malignancy, and Autoimmunity, Universal Scientific Education and Research Network (USERN), Tehran, Iran
| | - Maryam Ebrahimi
- Cancer Immunology Project (CIP), Universal Scientific Education and Research Network (USERN), Tehran, Iran
| | - Joëlle E Vergroesen
- Department of Ophthalmology, Erasmus MC University Medical Center, PO Box 2040, 3000 CA Rotterdam, the Netherlands; Department of Epidemiology, Erasmus MC University Medical Center, PO Box 2040, 3000 CA Rotterdam, the Netherlands.
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Mika Sillanpää
- Department of Chemical Engineering, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, P. O. Box 17011, Doornfontein 2028, South Africa; International Research Centre of Nanotechnology for Himalayan Sustainability (IRCNHS), Shoolini University, Solan 173212, Himachal Pradesh, India; Zhejiang Rongsheng Environmental Protection Paper Co. LTD, NO.588 East Zhennan Road, Pinghu Economic Development Zone, Zhejiang 314213, PR China; Department of Civil Engineering, University Centre for Research & Development, Chandigarh University, Gharuan, Mohali, Punjab, India
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3
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Zhang J, Wang C, He Y, Wang Y, Fang X, Shi M, Chen H, Zhang J, Zou H. Peiminine alleviate coliti-like phenotype in mice induced by lead exposure. INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 2024:1-13. [PMID: 38385345 DOI: 10.1080/09603123.2024.2307344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 01/15/2024] [Indexed: 02/23/2024]
Abstract
The deleterious impact of lead (Pb) pollution on human health is evident in both domestic and occupational settings, provoking an inflammatory response across multiple tissue, limited attention has been devoted to its adverse effects on colitis and the underlying mechanisms. Peiminine (PMI) has been recognized for its anti-inflammatory properties, yet its specific anti-inflammatory effects in lead-induced colitis models remain elusive. Through the establishment of both in vivo and in vitro lead exposure models, suggests that lead exposure can induce colitis and that PMI regulates lead exposure-induced colitis by inhibiting the NF-kB signaling pathway, and alleviates the ability of lead to apoptosis and inflammation levels in intestinal epithelial cells. Consequently, these results present a promising avenue for further exploration of the molecular mechanisms underlying lead-induced colitis, evaluation of the associated risks linked to lead exposure, and the development of therapeutic interventions for colitis resulting from lead exposure.
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Affiliation(s)
- Jing Zhang
- Faculty of Life Science, Northwest University, Xi'an, China
| | - Chenchen Wang
- Department of Critical Care Medicine, the 940th Hospital of Joint Logistics Support Force of PLA, Lanzhou, Gansu, China
| | - Yixuan He
- Faculty of Life Science, Northwest University, Xi'an, China
| | - Ying Wang
- Faculty of Life Science, Northwest University, Xi'an, China
| | - Xinbei Fang
- Faculty of Life Science, Northwest University, Xi'an, China
| | - Meimei Shi
- Faculty of Life Science, Northwest University, Xi'an, China
| | - Hui Chen
- Faculty of Life Science, Northwest University, Xi'an, China
| | - Jianbin Zhang
- Department of Occupational & Environmental Health and the Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an, China
| | - Haijiang Zou
- Faculty of Life Science, Northwest University, Xi'an, China
- School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, China
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Palanirajan SK, Gummadi SN. Phospholipid scramblase 3: a latent mediator connecting mitochondria and heavy metal apoptosis. Cell Biochem Biophys 2023; 81:443-458. [PMID: 37341933 DOI: 10.1007/s12013-023-01145-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2023] [Indexed: 06/22/2023]
Abstract
Lead and mercury are the ubiquitous heavy metals triggering toxicity and initiating apoptosis in cells. Though the toxic effects of heavy metals on various organs are known, there is a paucity of information on the mechanisms that instigate the current study. A plausible role of phospholipid scramblase 3 (PLSCR3) in Pb2+ and Hg2+ induced apoptosis was investigated with human embryonic kidney (HEK 293) cells. After 12 h of exposure, ~30-40% of the cells were in the early stage of apoptosis with increased reactive oxygen species (ROS), decreased mitochondrial membrane potential, and increased intracellular calcium levels. Also, ~20% of the cardiolipin localized within the inner mitochondrial membrane was translocated to the outer mitochondrial membrane along with the mobilization of truncated Bid (t-Bid) to the mitochondria and cytochrome c from the mitochondria. The endogenous expression levels of PLSCR3, caspase 8, and caspase 3 were upregulated in Pb2+ and Hg2+ induced apoptosis. The activation and upregulation of PLSCR3 mediate CL translocation playing a potential role in initiating the heavy metal-induced apoptosis. Therefore, PLSCR3 could be the linker between mitochondria and heavy metal apoptosis.
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Affiliation(s)
- Santosh Kumar Palanirajan
- Applied and Industrial Microbiology Laboratory, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, 600 036, India
| | - Sathyanarayana N Gummadi
- Applied and Industrial Microbiology Laboratory, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, 600 036, India.
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Wang H, Wang H, Guan J, Guan W, Liu Z. Lead induces mouse skin fibroblast apoptosis by disrupting intracellular homeostasis. Sci Rep 2023; 13:9670. [PMID: 37316700 DOI: 10.1038/s41598-023-36835-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 06/10/2023] [Indexed: 06/16/2023] Open
Abstract
Lead (Pb) is a critical industrial and environmental contaminant that can cause pathophysiological changes in several cellular and organ systems and their processes, including cell proliferation, differentiation, apoptosis, and survival. The skin is readily exposed to and damaged by Pb, but the mechanisms through which Pb damages cells are not fully understood. We examined the apoptotic properties of Pb in mouse skin fibroblast (MSF) in vitro. Treatment of fibroblasts with 40, 80, and 160 μM Pb for 24 h revealed morphological alterations, DNA damage, enhanced caspase-3, -8, and -9 activities, and apoptotic cell population. Furthermore, apoptosis was dosage (0-160 μM) and time (12-48 h) dependent. Concentrations of intracellular calcium (Ca2+) and reactive oxygen species were increased, and the mitochondrial membrane potential was decreased in exposed cells. Cell cycle arrest was evident at the G0/G1 phase. The Bax, Fas, caspase-3 and -8, and p53 transcript levels were increased, whereas Bcl-2 gene expression was decreased. Based on our analysis, Pb triggers MSF apoptosis bydisrupting intracellular homeostasis. Our findings enrich the knowledge about the mechanistic function of Pb-induced cytotoxicity on human skin fibroblasts and could potentially guide future Pb health risk assessments.
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Affiliation(s)
- Hui Wang
- Jinzhou Medical University, Jinzhou, 121001, China
- Meat Processing and Safety Control Engineering Technology Research Center of Liaoning Province, Jinzhou, 121001, China
| | - Huinuan Wang
- Jinzhou Medical University, Jinzhou, 121001, China
| | - Jiawen Guan
- Jinzhou Medical University, Jinzhou, 121001, China
- Meat Processing and Safety Control Engineering Technology Research Center of Liaoning Province, Jinzhou, 121001, China
| | - Weijun Guan
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
| | - Zheng Liu
- Jinzhou Medical University, Jinzhou, 121001, China.
- Meat Processing and Safety Control Engineering Technology Research Center of Liaoning Province, Jinzhou, 121001, China.
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Wang Y, Yin N, Yang R, Faiola F. Pollution effects on retinal health: A review on current methodologies and findings. Toxicol Ind Health 2023; 39:336-344. [PMID: 37160417 DOI: 10.1177/07482337231174072] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In our daily life, we are exposed to numerous industrial chemicals that may be harmful to the retina, which is a delicate and sensitive part of our eyes. This could lead to irreversible changes and cause retinal diseases or blindness. Current retinal environmental health studies primarily utilize animal models, isolated mammalian retinas, animal- or human-derived retinal cells, and retinal organoids, to address both pre- and postnatal exposure. However, as there is limited toxicological information available for specific populations, human induced pluripotent stem cell (hiPSC)-induced models could be effective tools to supplement such data. In order to obtain more comprehensive and reliable toxicological information, we need more appropriate models, novel evaluation methods, and computational technologies to develop portable equipment. This review mainly focused on current toxicology models with particular emphasis on retinal organoids, and it looks forward to future models, analytical methods, and equipment that can efficiently and accurately evaluate retinal toxicity.
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Affiliation(s)
- Yue Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Nuoya Yin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Renjun Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Francesco Faiola
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
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Perez-Serna AA, Dos Santos RS, Ripoll C, Nadal A, Eizirik DL, Marroqui L. BCL-XL Overexpression Protects Pancreatic β-Cells against Cytokine- and Palmitate-Induced Apoptosis. Int J Mol Sci 2023; 24:5657. [PMID: 36982731 PMCID: PMC10056015 DOI: 10.3390/ijms24065657] [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: 01/23/2023] [Revised: 03/08/2023] [Accepted: 03/10/2023] [Indexed: 03/18/2023] Open
Abstract
Diabetes is a chronic disease that affects glucose metabolism, either by autoimmune-driven β-cell loss or by the progressive loss of β-cell function, due to continued metabolic stresses. Although both α- and β-cells are exposed to the same stressors, such as proinflammatory cytokines and saturated free fatty acids (e.g., palmitate), only α-cells survive. We previously reported that the abundant expression of BCL-XL, an anti-apoptotic member of the BCL-2 family of proteins, is part of the α-cell defense mechanism against palmitate-induced cell death. Here, we investigated whether BCL-XL overexpression could protect β-cells against the apoptosis induced by proinflammatory and metabolic insults. For this purpose, BCL-XL was overexpressed in two β-cell lines-namely, rat insulinoma-derived INS-1E and human insulin-producing EndoC-βH1 cells-using adenoviral vectors. We observed that the BCL-XL overexpression in INS-1E cells was slightly reduced in intracellular Ca2+ responses and glucose-stimulated insulin secretion, whereas these effects were not observed in the human EndoC-βH1 cells. In INS-1E cells, BCL-XL overexpression partially decreased cytokine- and palmitate-induced β-cell apoptosis (around 40% protection). On the other hand, the overexpression of BCL-XL markedly protected EndoC-βH1 cells against the apoptosis triggered by these insults (>80% protection). Analysis of the expression of endoplasmic reticulum (ER) stress markers suggests that resistance to the cytokine and palmitate conferred by BCL-XL overexpression might be, at least in part, due to the alleviation of ER stress. Altogether, our data indicate that BCL-XL plays a dual role in β-cells, participating both in cellular processes related to β-cell physiology and in fostering survival against pro-apoptotic insults.
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Affiliation(s)
- Atenea A. Perez-Serna
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández de Elche, 03202 Elche, Alicante, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Instituto de Salud Carlos III, Spain
| | - Reinaldo S. Dos Santos
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández de Elche, 03202 Elche, Alicante, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Instituto de Salud Carlos III, Spain
| | - Cristina Ripoll
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández de Elche, 03202 Elche, Alicante, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Instituto de Salud Carlos III, Spain
| | - Angel Nadal
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández de Elche, 03202 Elche, Alicante, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Instituto de Salud Carlos III, Spain
| | - Decio L. Eizirik
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - Laura Marroqui
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández de Elche, 03202 Elche, Alicante, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Instituto de Salud Carlos III, Spain
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Metryka E, Kupnicka P, Kapczuk P, Aszakiewicz B, Piotrowska K, Tkacz M, Gutowska I, Chlubek D, Baranowska-Bosiacka I. Lead (Pb) Accumulation in Human THP-1 Monocytes/Macrophages In Vitro and the Influence on Cell Apoptosis. Biol Trace Elem Res 2021; 199:955-967. [PMID: 32557104 PMCID: PMC7813697 DOI: 10.1007/s12011-020-02215-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 05/20/2020] [Indexed: 12/22/2022]
Abstract
In this study, we investigated the ability of THP-1 monocytes and macrophages to accumulate lead (Pb) in vitro, relative to Pb concentration and length of exposure. Moreover, we also evaluated the effect of Pb accumulation on cell viability and apoptosis. THP-1 monocytes and macrophages were cultured in the presence of Pb at 1.25 μg/dL, 2.5 μg/dL, 5 μg/dL, and 10 μg/dL. Pb accumulation was examined by inductively coupled plasma and confocal microscopy. The influence of Pb on cell viability, apoptosis, and necrosis was assessed using flow cytometry. The results showed that Pb was toxic to THP-1 monocytes/macrophages even at very low environmental concentrations. Despite the use of low concentrations, both monocytes and macrophages showed dose-dependent and time-dependent decreases in viability, with a simultaneous increase in the percentage of early and late apoptotic cells. Macrophages reacted more strongly to Pb than monocytes. When exposed to the same Pb concentrations, they showed lower viability and a higher percentage of necrotic cells. The incubation time positively correlated with Pb accumulation in a dose-dependent manner. The obtained results indicate that environmental exposure to low Pb concentrations may significantly impair the function of macrophages, with the increased number of apoptotic cells potentially contributing to the development of many pathologies in the brain and whole body.
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Affiliation(s)
- Emilia Metryka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Patrycja Kupnicka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Patrycja Kapczuk
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Beata Aszakiewicz
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Katarzyna Piotrowska
- Department of Physiology, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Marta Tkacz
- Department of Physiology, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Izabela Gutowska
- Department of Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Dariusz Chlubek
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland
| | - Irena Baranowska-Bosiacka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111, Szczecin, Poland.
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Dumbuya JS, Chen L, Shu SY, Ma L, Luo W, Li F, Wu JY, Wang B. G-CSF attenuates neuroinflammation and neuronal apoptosis via the mTOR/p70SK6 signaling pathway in neonatal Hypoxia-Ischemia rat model. Brain Res 2020; 1739:146817. [PMID: 32246916 DOI: 10.1016/j.brainres.2020.146817] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 03/19/2020] [Accepted: 03/31/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND Hypoxic-ischemic encephalopathy (HIE) is an important cause of permanent damage to the central nervous system, associated with long-lasting neurological disabilities and neurodevelopmental impairment in neonates. Granulocyte-colony stimulating factor (G-CSF) has been shown to have neuroprotective activity in a variety of experimental brain injury models and G-CSF is a standard treatment in chemotherapeutic-induced neutropenia. The underlying mechanisms are still unclear. The mTOR (mammalian target of rapamycin) signaling pathway is a master regulator of cell growth and proliferation in the nervous system. However, the effects of G-CSF treatment on the mTOR signaling pathway have not been elucidated in neonates with hypoxic-ischemic (HI) brain injury. Our study investigated the neuroprotective effect of G-CSF on neonates with hypoxic-ischemic (HI) brain injury and the possible mechanism involving the mTOR/p70S6K pathway. METHODS Sprague-Dawley rat pups at postnatal day 7 (P7) were subjected to right unilateral carotid artery ligation followed by hypoxic (8% oxygen and balanced nitrogen) exposure for 2.5 h or sham surgery. Pups received normal saline, G-CSF, G-CSF combined with rapamycin or ethanol (vehicle for rapamycin) intraperitoneally. On postnatal day 9 (P9), TTC staining for infarct volume, and Nissl and TUNEL staining for neuronal cell injury were conducted. Activation of mTOR/p70S6K pathway, cleaved caspase-3 (CC3), Bax and Bcl-2 and cytokine expression levels were determined by western blotting. RESULTS The G-CSF treated group was associated with significantly reduced infarction volume and decreased TUNEL positive neuronal cells compared to the HI group treated with saline. The expression levels of TNF-α and IL-1ß were significantly decreased in the G-CSF treated group, while IL-10 expression level was increased. The relative immunoreactivity of p-mTOR and p-p70S6K was significantly reduced in the HI group compared to sham. The HI group treated with G-CSF showed significant upregulated protein expression for p-mTOR and p-p70S6K levels compared to the HI group treated with saline. Furthermore, G-CSF treatment increased Bcl-2 expression levels and decreased CC3 and Bax expression levels in the ipsilateral hemispheres of the HI brain. The effects induced by G-CSF were all reversed by rapamycin. CONCLUSION Treatment with G-CSF decreases inflammatory mediators and apoptotic factors, attenuating neuroinflammation and neuronal apoptosis via the mTOR/p70S6K signalling pathway, which represents a potential target for treating HI induced brain damage in neonatal HIE.
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Affiliation(s)
- John Sieh Dumbuya
- Department of Pediatrics, Zhujiang Hospital of Southern Medical University, Guangzhou 510282 PR China
| | - Lu Chen
- Department of Pediatrics, Zhujiang Hospital of Southern Medical University, Guangzhou 510282 PR China
| | - Si Yun Shu
- Department of Pediatrics, Zhujiang Hospital of Southern Medical University, Guangzhou 510282 PR China
| | - Lin Ma
- Department of Radiotherapy, Chinese PLA General Hospital, Beijing 100853 PR China
| | - Wei Luo
- Department of Pediatrics, Zhujiang Hospital of Southern Medical University, Guangzhou 510282 PR China
| | - Fei Li
- Department of Pediatrics, Zhujiang Hospital of Southern Medical University, Guangzhou 510282 PR China
| | - Jang-Yen Wu
- Department of Biochemical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL, United States.
| | - Bin Wang
- Department of Pediatrics, Zhujiang Hospital of Southern Medical University, Guangzhou 510282 PR China.
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Meyer DN, Crofts EJ, Akemann C, Gurdziel K, Farr R, Baker BB, Weber D, Baker TR. Developmental exposure to Pb 2+ induces transgenerational changes to zebrafish brain transcriptome. CHEMOSPHERE 2020; 244:125527. [PMID: 31816550 PMCID: PMC7015790 DOI: 10.1016/j.chemosphere.2019.125527] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 11/27/2019] [Accepted: 11/30/2019] [Indexed: 05/24/2023]
Abstract
Lead (Pb2+) is a major public health hazard for urban children, with profound and well-characterized developmental and behavioral implications across the lifespan. The ability of early Pb2+ exposure to induce epigenetic changes is well-established, suggesting that Pb2+-induced neurobehavioral deficits may be heritable across generations. Understanding the long-term and multigenerational repercussions of lead exposure is crucial for clarifying both the genotypic alterations behind these behavioral outcomes and the potential mechanism of heritability. To study this, zebrafish (Danio rerio) embryos (<2 h post fertilization; EK strain) were exposed for 24 h to waterborne Pb2+ at a concentration of 10 μM. This exposed F0 generation was raised to adulthood and spawned to produce the F1 generation, which was subsequently spawned to produce the F2 generation. Previous avoidance conditioning studies determined that a 10 μM Pb2+ dose resulted in learning impairments persisting through the F2 generation. RNA was extracted from control- and 10 μM Pb2+-lineage F2 brains, (n = 10 for each group), sequenced, and transcript expression was quantified utilizing Quant-Seq. 648 genes were differentially expressed in the brains of F2 lead-lineage fish versus F2 control-lineage fish. Pathway analysis revealed altered genes in processes including synaptic function and plasticity, neurogenesis, endocrine homeostasis, and epigenetic modification, all of which are implicated in lead-induced neurobehavioral deficits and/or their inheritance. These data will inform future investigations to elucidate the mechanism of adult-onset and transgenerational health effects of developmental lead exposure.
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Affiliation(s)
- Danielle N Meyer
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI, USA; Institute of Environmental Health Sciences, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Emily J Crofts
- Institute of Environmental Health Sciences, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Camille Akemann
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI, USA; Institute of Environmental Health Sciences, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Katherine Gurdziel
- Applied Genome Technology Center, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Rebecca Farr
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Bridget B Baker
- Institute of Environmental Health Sciences, School of Medicine, Wayne State University, Detroit, MI, USA; Division of Laboratory Animal Resources, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Daniel Weber
- Children's Environmental Health Sciences Core Center, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Tracie R Baker
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI, USA; Institute of Environmental Health Sciences, School of Medicine, Wayne State University, Detroit, MI, USA.
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Sinkakarimi MH, Solgi E, Hosseinzadeh Colagar A. Subcellular partitioning of cadmium and lead in Eisenia fetida and their effects to sperm count, morphology and apoptosis. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 187:109827. [PMID: 31655413 DOI: 10.1016/j.ecoenv.2019.109827] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 10/14/2019] [Accepted: 10/15/2019] [Indexed: 06/10/2023]
Abstract
Earthworms and their biomarkers are considered good indicators for assessing the effects of toxic chemicals. Therefore, in this study, we exposed Eisenia fetida to lethal and sub-lethal concentrations of Cd and Pb nitrate in artificial soil for 14 and 28 days to evaluate the impact on subcellular partitioning, lethal toxicity (LC50), growth, sperm count, morphology and apoptosis (using TUNEL assay). The soluble internal pools of both metals were good predictors of the responses of biomarkers. We found sperm deformation, TUNEL positive sperms and weight loss positively and sperm count negatively correlated with the concentrations of Cd and Pb in the total internal and cytosolic fraction (p < 0.01) and to a lesser extent with Pb concentrations in the granular fraction (p < 0.05). Fourteen days LC50 for Cd and Pb were 2169 ± 322 and 6387 ± 904 μg/g, respectively. Cadmium and Pb caused a significant depression in sperm count after 14 (Cd: up to 46.9%; Pb: up to 36.24%) and 28 (Cd: up to 72.47%; Pb: up to 43.12%) days of exposure relative to the control (p < 0.05). Cadmium induced higher abnormality in sperm heads than Pb. For both metals, TUNEL positive sperms significantly increased after 14 (Cd: up to 14.17%; Pb: up to 16.33%) and 28 (Cd: up to 16.33%; Pb: up to 11.67%) days of exposure compared with the control (p < 0.05). The findings of this study, illustrate the importance of considering sperm parameters as a rapid, easy and sensitive biomarker for the evaluation of metal toxicity.
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Affiliation(s)
- Mohammad Hosein Sinkakarimi
- Department of Environment, Faculty of Natural Resource and Environment, Malayer University, 95863-65719, Malayer, Iran
| | - Eisa Solgi
- Department of Environment, Faculty of Natural Resource and Environment, Malayer University, 95863-65719, Malayer, Iran
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12
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Yun S, Chu D, He X, Zhang W, Feng C. Protective effects of grape seed proanthocyanidins against iron overload-induced renal oxidative damage in rats. J Trace Elem Med Biol 2020; 57:126407. [PMID: 31570250 DOI: 10.1016/j.jtemb.2019.126407] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 09/04/2019] [Accepted: 09/18/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND Excessive exposure to iron can cause kidney damage, and chelating drugs such as deferoxamine and deferiprone have limited usefulness in treating iron poisoning. This study was designed to investigate the protective effects of grape seed proanthocyanidins (GSPAs) against iron overload induced nephrotoxicity in rats. The roles of GSPAs in chelating iron, antioxidant activity, renal function, pathological section, and apoptosis-related gene expression were assessed. METHODS Newly weaned male Sprague-Dawley rats aged 21 days (weight, 65 ± 5 g) were randomly divided into four groups containing 10 rats each: normal control (negative) group, iron overload (positive) group, GSPAs group, and GSPAs + iron overload (test) group. Iron dextran injections (2.5 mg⋅ kg-1) and GSPAs (25 mg⋅ kg-1) were intraperitoneally and intragastrically administered to rats daily for 7 weeks, respectively. Measurements included red blood cell (RBC) count and hemoglobin (Hb) level, serum total iron-binding capacity (TIBC), renal iron content, glutathione peroxidase (GSH-Px) activity, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, total antioxidant activity (T-AOC), creatinine (CR) and blood urea nitrogen (BUN) levels, pathological changes, and apoptotic Fas, Bax expressions in the kidney tissue. Differences among the dietary groups were determined using one-way analysis of variance with post-hoc Tukey's test. P < 0.05 was considered statistically significant. RESULTS RBC count, Hb level, renal iron content, MDA content, CR and BUN levels, and Fas, Bax expressions significantly increased in the positive group than in the negative group; contrarily, TIBC, GSH-Px activity, and T-AOC significantly decreased in the positive group than in the negative group (P < 0.05). Although not statistically significant, SOD activity was slightly reduced in the positive group than in the negative group. Inflammatory cell infiltration and fibrous tissue proliferation were observed in the kidney tissue of the rats in the positive group; in contrast, the rats exhibited better recovery when GSPAs were used instead of iron alone. Compared with the positive group, RBC counts, Hb levels, renal iron contents, the MDA content, CR and BUN levels, and Fas, Bax expressions significantly decreased, whereas the TIBC, the GSH-Px and SOD activities as well as T-AOC significantly increased in the test group rats (P < 0.05). There were no significant differences in the RBC counts, Hb levels, TIBC, renal iron contents, the SOD activity and MDA content, CR and BUN levels, and Fas expression between the GSPAs and negative groups. The GSH-Px activity and T-AOC were significantly increased whereas Bax expression was significantly decreased in the GSPAs group rats than in the negative group rats (P < 0.05). The rats in the GSPAs, test, and negative groups displayed glomeruli and tubules with a clear structure; further, the epithelial cells in the renal tubules were neatly arranged. CONCLUSIONS GSPAs have protective effects on nephrotoxicity in rats with iron overload. Thus, further investigation of GSPAs as a new and natural phytochemo-preventive agent against iron overload is warranted.
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Affiliation(s)
- Shaojun Yun
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Dongyang Chu
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Xingshuai He
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Wenfang Zhang
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Cuiping Feng
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China.
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Gene networks and toxicity/detoxification pathways in juvenile largemouth bass (Micropterus salmoides) liver induced by acute lead stress. Genomics 2020; 112:20-31. [DOI: 10.1016/j.ygeno.2019.06.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/14/2019] [Accepted: 06/21/2019] [Indexed: 11/20/2022]
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Palanirajan SK, Gummadi SN. Heavy-Metals-Mediated Phospholipids Scrambling by Human Phospholipid Scramblase 3: A Probable Role in Mitochondrial Apoptosis. Chem Res Toxicol 2019; 33:553-564. [PMID: 31769662 DOI: 10.1021/acs.chemrestox.9b00406] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Human phospholipid scramblases are a family of four homologous transmembrane proteins (hPLSCR1-4) mediating phospholipids (PLs) translocation in plasma membrane upon Ca2+ activation. hPLSCR3, the only homologue localized to mitochondria, plays a vital role in mitochondrial structure, function, maintenance, and apoptosis. Upon Ca2+ activation, hPLSCR3 mediates PL translocation at the mitochondrial membrane enhancing t-bid-induced cytochrome c release and apoptosis. Mitochondria are important target organelles for heavy-metals-induced apoptotic signaling cascade and are the central executioner of apoptosis to trigger. Pb2+ and Hg2+ toxicity mediates apoptosis by increased reactive oxygen species (ROS) and cytochrome c release from mitochondria. To discover the role of hPLSCR3 in heavy metal toxicity, hPLSCR3 was overexpressed as a recombinant protein in Escherichia coli Rosetta (DE3) and purified by affinity chromatography. The biochemical assay using synthetic proteoliposomes demonstrated that hPLSCR3 translocated aminophospholipids in the presence of micromolar concentrations of Pb2+ and Hg2+. A point mutation in the Ca2+-binding motif (F258V) led to a ∼60% loss in the functional activity and decreased binding affinities for Pb2+ and Hg2+ implying that the divalent heavy metal ions bind to the Ca2+-binding motif. This was further affirmed by the characteristic spectra observed with stains-all dye. The conformational changes upon heavy metal binding were monitored by circular dichroism, intrinsic tryptophan fluorescence, and light-scattering studies. Our results revealed that Pb2+ and Hg2+ bind to hPLSCR3 with higher affinity than Ca2+ thus mediating scramblase activity. To summarize, this is the first biochemical evidence for heavy metals binding to the mitochondrial membrane protein leading to bidirectional translocation of PLs specifically toward phosphatidylethanolamine.
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Affiliation(s)
- Santosh Kumar Palanirajan
- Applied and Industrial Microbiology Laboratory, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600 036 , India
| | - Sathyanarayana N Gummadi
- Applied and Industrial Microbiology Laboratory, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600 036 , India
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Zhang T, Chen S, Chen L, Zhang L, Meng F, Sha S, Ai C, Tai J. Chlorogenic Acid Ameliorates Lead-Induced Renal Damage in Mice. Biol Trace Elem Res 2019; 189:109-117. [PMID: 30196488 DOI: 10.1007/s12011-018-1508-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 09/03/2018] [Indexed: 10/28/2022]
Abstract
Lead (Pb) exposure is a global environmental problem and its exposure can lead to serious renal damage by disturbing the pro-oxidant/antioxidant balance and facilitating inflammation. Chlorogenic acid (CGA) is one of the most abundant polyphenols in the diet and has been reported to have many biological properties such as antioxidant and anti-inflammatory. In this study, we aimed to investigate the protective efficacy and mechanism of CGA against Pb-induced nephrotoxicity in mice. The results showed that CGA inhibited Pb-induced bodyweight loss, reduced kidney coefficients, and alleviated renal function and structure. Exploration on the potential mechanism demonstrated that CGA suppressed Pb-induced inflammation in the kidney by regulating NF-κB pathway activation. Furthermore, CGA significantly increased Pb-induced reduction in the activity of SOD and GSH-Px, and reduced Pb-induced increase in the content of MDA. The expression of Bax and Bcl-2 associated with apoptosis was also significantly regulated by CGA. These data indicated that CGA may play a potential treatment strategy for Pb toxicity.
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Affiliation(s)
- Tongsen Zhang
- Department of colorectal and anal surgery, The First Bethune Hospital of Jilin University, Jilin, Changchun, 130012, People's Republic of China
| | - Si Chen
- Department of colorectal and anal surgery, The First Bethune Hospital of Jilin University, Jilin, Changchun, 130012, People's Republic of China
| | - Lei Chen
- Department of colorectal and anal surgery, The First Bethune Hospital of Jilin University, Jilin, Changchun, 130012, People's Republic of China
| | - Lixiao Zhang
- Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University, Changchun, China
| | - Fanqi Meng
- Department of colorectal and anal surgery, The First Bethune Hospital of Jilin University, Jilin, Changchun, 130012, People's Republic of China
| | - Shuang Sha
- Department of colorectal and anal surgery, The First Bethune Hospital of Jilin University, Jilin, Changchun, 130012, People's Republic of China
| | - Chunlong Ai
- Department of colorectal and anal surgery, The First Bethune Hospital of Jilin University, Jilin, Changchun, 130012, People's Republic of China
| | - Jiandong Tai
- Department of colorectal and anal surgery, The First Bethune Hospital of Jilin University, Jilin, Changchun, 130012, People's Republic of China.
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Nutritional Regulators of Bcl-xL in the Brain. Molecules 2018; 23:molecules23113019. [PMID: 30463183 PMCID: PMC6278276 DOI: 10.3390/molecules23113019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 11/15/2018] [Accepted: 11/18/2018] [Indexed: 01/12/2023] Open
Abstract
B-cell lymphoma-extra large (Bcl-xL) is an anti-apoptotic Bcl-2 protein found in the mitochondrial membrane. Bcl-xL is reported to support normal brain development and protects neurons against toxic stimulation during pathological process via its roles in regulation of mitochondrial functions. Despite promising evidence showing neuroprotective properties of Bcl-xL, commonly applied molecular approaches such as genetic manipulation may not be readily applicable for human subjects. Therefore, findings at the bench may be slow to be translated into treatments for disease. Currently, there is no FDA approved application that specifically targets Bcl-xL and treats brain-associated pathology in humans. In this review, we will discuss naturally occurring nutrients that may exhibit regulatory effects on Bcl-xL expression or activity, thus potentially providing affordable, readily-applicable, easy, and safe strategies to protect the brain.
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Zhang Z, Gao X, Guo M, Jiang H, Cao Y, Zhang N. The Protective Effect of Baicalin Against Lead-Induced Renal Oxidative Damage in Mice. Biol Trace Elem Res 2017; 175:129-135. [PMID: 27209023 DOI: 10.1007/s12011-016-0731-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 04/28/2016] [Indexed: 01/01/2023]
Abstract
Lead (Pb) exposure is a global environmental problem that can deplete body antioxidant enzymes, causing damage to various macromolecules and ultimately cell death. Pb exposure could lead to serious renal damage. Baicalin, a traditional Chinese medicine, could protect against renal injury through inhibition of oxidative stress and apoptosis. This study was designed to investigate the protective efficacy of baicalin against Pb-induced nephrotoxicity in mice and to elucidate the potential mechanisms using animal experiment. The results revealed that baicalin decreased Pb-induced bodyweight loss, declined kidney coefficients, and ameliorated renal function and structure in a dose-dependent manner. Meanwhile, baicalin dose dependently increased Pb-induced activity of SOD and GSH-Px, while the content of MDA in the kidney was decreased. In addition, baicalin enhanced the Bcl-2/Bax ratio associated with apoptosis in the kidney. These data indicated that further investigation of the use of baicalin as a new natural chemopreventive agent against Pd poisoning is warranted.
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Affiliation(s)
- Zecai Zhang
- College of Veterinary Medicine, Jilin University, Changchun, 130062, People's Republic of China
| | - Xuejiao Gao
- College of Veterinary Medicine, Jilin University, Changchun, 130062, People's Republic of China
| | - Mengyao Guo
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Haichao Jiang
- College of Veterinary Medicine, Jilin University, Changchun, 130062, People's Republic of China
| | - Yongguo Cao
- College of Veterinary Medicine, Jilin University, Changchun, 130062, People's Republic of China.
| | - Naisheng Zhang
- College of Veterinary Medicine, Jilin University, Changchun, 130062, People's Republic of China.
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18
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Chaney SY, Mukherjee S, Giddabasappa A, Rueda EM, Hamilton WR, Johnson JE, Fox DA. Increased proliferation of late-born retinal progenitor cells by gestational lead exposure delays rod and bipolar cell differentiation. Mol Vis 2016; 22:1468-1489. [PMID: 28050121 PMCID: PMC5204453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 12/22/2016] [Indexed: 10/26/2022] Open
Abstract
PURPOSE Studies of neuronal development in the retina often examine the stages of proliferation, differentiation, and synaptic development, albeit independently. Our goal was to determine if a known neurotoxicant insult to a population of retinal progenitor cells (RPCs) would affect their eventual differentiation and synaptic development. To that end, we used our previously published human equivalent murine model of low-level gestational lead exposure (GLE). Children and animals with GLE exhibit increased scotopic electroretinogram a- and b-waves. Adult mice with GLE exhibit an increased number of late-born RPCs, a prolonged period of RPC proliferation, and an increased number of late-born rod photoreceptors and rod and cone bipolar cells (BCs), with no change in the number of late-born Müller glial cells or early-born neurons. The specific aims of this study were to determine whether increased and prolonged RPC proliferation alters the spatiotemporal differentiation and synaptic development of rods and BCs in early postnatal GLE retinas compared to control retinas. METHODS C57BL/6N mouse pups were exposed to lead acetate via drinking water throughout gestation and until postnatal day 10, which is equivalent to the human gestation period for retinal neurogenesis. RT-qPCR, immunohistochemical analysis, and western blots of well-characterized, cell-specific genes and proteins were performed at embryonic and early postnatal ages to assess rod and cone photoreceptor differentiation, rod and BC differentiation and synaptic development, and Müller glial cell differentiation. RESULTS Real-time quantitative PCR (RT-qPCR) with the rod-specific transcription factors Nrl, Nr2e3, and Crx and the rod-specific functional gene Rho, along with central retinal confocal studies with anti-recoverin and anti-rhodopsin antibodies, revealed a two-day delay in the differentiation of rod photoreceptors in GLE retinas. Rhodopsin immunoblots supported this conclusion. No changes in glutamine synthetase gene or protein expression, a marker for late-born Müller glial cells, were observed in the developing retinas. In the retinas from the GLE mice, anti-PKCα, -Chx10 (Vsx2) and -secretagogin antibodies revealed a two- to three-day delay in the differentiation of rod and cone BCs, whereas the expression of the proneural and BC genes Otx2 and Chx10, respectively, increased. In addition, confocal studies of proteins associated with functional synapses (e.g., vesicular glutamate transporter 1 [VGluT1], plasma membrane calcium ATPase [PMCA], transient receptor potential channel M1 [TRPM1], and synaptic vesicle glycoprotein 2B [SV2B]) revealed a two-day delay in the formation of the outer and inner plexiform layers of the GLE retinas. Moreover, several markers revealed that the initiation of the differentiation and intensity of the labeling of early-born cells in the retinal ganglion cell and inner plexiform layers were not different in the control retinas. CONCLUSIONS Our combined gene, confocal, and immunoblot findings revealed that the onset of rod and BC differentiation and their subsequent synaptic development is delayed by two to three days in GLE retinas. These results suggest that perturbations during the early proliferative stages of late-born RPCs fated to be rods and BCs ultimately alter the coordinated time-dependent progression of rod and BC differentiation and synaptic development. These GLE effects were selective for late-born neurons. Although the molecular mechanisms are unknown, alterations in soluble neurotrophic factors and/or their receptors are likely to play a role. Since neurodevelopmental delays and altered synaptic connectivity are associated with neuropsychiatric and behavioral disorders as well as cognitive deficits, future work is needed to determine if similar effects occur in the brains of GLE mice and whether children with GLE experience similar delays in retinal and brain neuronal differentiation and synaptic development.
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Affiliation(s)
- Shawnta Y. Chaney
- College of Optometry, University of Houston, Houston, TX,Department of Biology and Biochemistry, University of Houston, Houston, TX
| | - Shradha Mukherjee
- College of Optometry, University of Houston, Houston, TX,Department of Biology and Biochemistry, University of Houston, Houston, TX
| | - Anand Giddabasappa
- College of Optometry, University of Houston, Houston, TX,Department of Biology and Biochemistry, University of Houston, Houston, TX
| | - Elda M. Rueda
- College of Optometry, University of Houston, Houston, TX
| | - W. Ryan Hamilton
- College of Optometry, University of Houston, Houston, TX,Department of Biology and Biochemistry, University of Houston, Houston, TX
| | - Jerry E. Johnson
- College of Optometry, University of Houston, Houston, TX,Department of Natural Sciences, University of Houston-Downtown; Houston, TX
| | - Donald A. Fox
- College of Optometry, University of Houston, Houston, TX,Department of Biology and Biochemistry, University of Houston, Houston, TX,Department of Pharmacology and Pharmaceutical Science, University of Houston, Houston, TX
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Eid R, Guzman DSM, Keller KA, Wiggans KT, Murphy CJ, LaDouceur EEB, Keel MK, Reilly CM. Choroidal Vasculopathy and Retinal Detachment in a Bald Eagle (Haliaeetus leucocephalus) With Lead Toxicosis. J Avian Med Surg 2016; 30:357-363. [DOI: 10.1647/2015122] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Shen XF, Huang P, Fox DA, Lin Y, Zhao ZH, Wang W, Wang JY, Liu XQ, Chen JY, Luo WJ. Adult lead exposure increases blood-retinal permeability: A risk factor for retinal vascular disease. Neurotoxicology 2016; 57:145-152. [DOI: 10.1016/j.neuro.2016.09.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Revised: 09/16/2016] [Accepted: 09/19/2016] [Indexed: 11/28/2022]
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Liu X, Huang R, Zhou X, Cai T, Chen J, Shi X, Deng H, Luo W. Presence of nano-sized chitosan-layered silicate composites protects against toxicity induced by lead ions. Carbohydr Polym 2016; 158:1-10. [PMID: 28024531 DOI: 10.1016/j.carbpol.2016.11.084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 11/28/2016] [Accepted: 11/29/2016] [Indexed: 10/20/2022]
Abstract
Protecting cells from toxicosis even apoptosis induced by a variety of toxic heavy metals stimulus has drawn more and more attentions. This study was designed to elucidate whether chitosan-organic rectorite (CS-OREC) composites exhibited any protective effects on altered oxidative stress parameter in PC12 cells exposed to lead ions (Pb2+). The cells were exposed to Pb2+ either alone or in combination with CS-OREC composites for designated time to evaluate the efficacy of the composites on Pb2+-induced toxicity. The MTT assay results showed that the cell viability of PC12 was remarkably decreased when exposed to Pb2+, but significantly retained after adding CS-OREC composites compared to that of the control. The beneficial effect of CS-OREC composites on cytotoxicity was related, at least in part, to its ability to protect against apoptosis in PC12 cells exposed to 50μM Pb2+. Their protective effect was also associated with the inhibitory effect on Pb2+-induced activation of Bax/Bcl-2, P-38, and caspase-3 pathways, while was independent on JNK pathway.
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Affiliation(s)
- Xinqin Liu
- Department of Occupational & Environmental Health, School of Public Health, Fourth Military Medical University, Xi'an 710032, China
| | - Rong Huang
- Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan 430079, China; Department of Plastic Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, China
| | - Xue Zhou
- School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Tongjian Cai
- Department of Occupational & Environmental Health, School of Public Health, Fourth Military Medical University, Xi'an 710032, China
| | - Jiajia Chen
- Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan 430079, China
| | - Xiaowen Shi
- Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan 430079, China
| | - Hongbing Deng
- Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan 430079, China.
| | - Wenjing Luo
- Department of Occupational & Environmental Health, School of Public Health, Fourth Military Medical University, Xi'an 710032, China.
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Rueda EM, Johnson JE, Giddabasappa A, Swaroop A, Brooks MJ, Sigel I, Chaney SY, Fox DA. The cellular and compartmental profile of mouse retinal glycolysis, tricarboxylic acid cycle, oxidative phosphorylation, and ~P transferring kinases. Mol Vis 2016; 22:847-85. [PMID: 27499608 PMCID: PMC4961465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Accepted: 07/21/2016] [Indexed: 10/26/2022] Open
Abstract
PURPOSE The homeostatic regulation of cellular ATP is achieved by the coordinated activity of ATP utilization, synthesis, and buffering. Glucose is the major substrate for ATP synthesis through glycolysis and oxidative phosphorylation (OXPHOS), whereas intermediary metabolism through the tricarboxylic acid (TCA) cycle utilizes non-glucose-derived monocarboxylates, amino acids, and alpha ketoacids to support mitochondrial ATP and GTP synthesis. Cellular ATP is buffered by specialized equilibrium-driven high-energy phosphate (~P) transferring kinases. Our goals were twofold: 1) to characterize the gene expression, protein expression, and activity of key synthesizing and regulating enzymes of energy metabolism in the whole mouse retina, retinal compartments, and/or cells and 2) to provide an integrative analysis of the results related to function. METHODS mRNA expression data of energy-related genes were extracted from our whole retinal Affymetrix microarray data. Fixed-frozen retinas from adult C57BL/6N mice were used for immunohistochemistry, laser scanning confocal microscopy, and enzymatic histochemistry. The immunoreactivity levels of well-characterized antibodies, for all major retinal cells and their compartments, were obtained using our established semiquantitative confocal and imaging techniques. Quantitative cytochrome oxidase (COX) and lactate dehydrogenase (LDH) activity was determined histochemically. RESULTS The Affymetrix data revealed varied gene expression patterns of the ATP synthesizing and regulating enzymes found in the muscle, liver, and brain. Confocal studies showed differential cellular and compartmental distribution of isozymes involved in glucose, glutamate, glutamine, lactate, and creatine metabolism. The pattern and intensity of the antibodies and of the COX and LDH activity showed the high capacity of photoreceptors for aerobic glycolysis and OXPHOS. Competition assays with pyruvate revealed that LDH-5 was localized in the photoreceptor inner segments. The combined results indicate that glycolysis is regulated by the compartmental expression of hexokinase 2, pyruvate kinase M1, and pyruvate kinase M2 in photoreceptors, whereas the inner retinal neurons exhibit a lower capacity for glycolysis and aerobic glycolysis. Expression of nucleoside diphosphate kinase, mitochondria-associated adenylate kinase, and several mitochondria-associated creatine kinase isozymes was highest in the outer retina, whereas expression of cytosolic adenylate kinase and brain creatine kinase was higher in the cones, horizontal cells, and amacrine cells indicating the diversity of ATP-buffering strategies among retinal neurons. Based on the antibody intensities and the COX and LDH activity, Müller glial cells (MGCs) had the lowest capacity for glycolysis, aerobic glycolysis, and OXPHOS. However, they showed high expression of glutamate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate thiokinase, GABA transaminase, and ~P transferring kinases. This suggests that MGCs utilize TCA cycle anaplerosis and cataplerosis to generate GTP and ~P transferring kinases to produce ATP that supports MGC energy requirements. CONCLUSIONS Our comprehensive and integrated results reveal that the adult mouse retina expresses numerous isoforms of ATP synthesizing, regulating, and buffering genes; expresses differential cellular and compartmental levels of glycolytic, OXPHOS, TCA cycle, and ~P transferring kinase proteins; and exhibits differential layer-by-layer LDH and COX activity. New insights into cell-specific and compartmental ATP and GTP production, as well as utilization and buffering strategies and their relationship with known retinal and cellular functions, are discussed. Developing therapeutic strategies for neuroprotection and treating retinal deficits and degeneration in a cell-specific manner will require such knowledge. This work provides a platform for future research directed at identifying the molecular targets and proteins that regulate these processes.
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Affiliation(s)
- Elda M. Rueda
- College of Optometry, University of Houston, Houston TX
| | - Jerry E. Johnson
- Department of Natural Sciences, University of Houston-Downtown, Houston TX
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | - Anand Giddabasappa
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | | | | | - Irena Sigel
- College of Optometry, University of Houston, Houston TX
| | - Shawnta Y. Chaney
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | - Donald A. Fox
- College of Optometry, University of Houston, Houston TX
- Department of Biology and Biochemistry, University of Houston, Houston TX
- Department of Pharmacology and Pharmaceutical Sciences, University of Houston, Houston TX
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Chidlow G, Wood JPM, Knoops B, Casson RJ. Expression and distribution of peroxiredoxins in the retina and optic nerve. Brain Struct Funct 2015; 221:3903-3925. [PMID: 26501408 PMCID: PMC5065902 DOI: 10.1007/s00429-015-1135-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/13/2015] [Indexed: 02/08/2023]
Abstract
Oxidative stress is implicated in various pathological conditions of the retina and optic nerve. Peroxiredoxins (Prdxs) comprise a recently characterized family of antioxidant enzymes. To date, little information exists regarding the distribution of Prdxs in the eye. Herein, we employed a combination of qRT-PCR, immunohistochemistry and Western blotting to determine the level of expression and distribution of the six Prdx isoforms in the retina and optic nerve of the rat. In addition, we performed some parallel analyses on the common marmoset (Callithrix Jacchus). In the rat, all of the Prdx transcripts were expressed in relatively high amounts in both retina and optic nerve, with abundances ranging from approximately 3–50 % of the level of the housekeeping gene cyclophilin. With regard to protein expression, each isoform was detected in the retina and optic nerve by either Western blotting and/or immunohistochemistry. Excepting Prdx4, there was a good correspondence between the rodent and primate results. In the retina, Prdx1 and Prdx2 were principally localized to neurons in the inner nuclear layer and cone photoreceptors, Prdx3 and Prdx5 displayed characteristic mitochondrial immunolabeling, while Prdx6 was associated with astrocytes and Müller cells. In the optic nerve, Prdx1 was robustly expressed by oligodendrocytes, Prdx3 and Prdx5 were observed in axons, and Prdx6 was restricted to astrocytes. The present findings augment our understanding of the distribution and expression of the Prdxs in the retina and optic nerve of rodents and primates and lay the foundation for subsequent analysis of their involvement in relevant blinding diseases.
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Affiliation(s)
- Glyn Chidlow
- Ophthalmic Research Laboratories, South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Frome Rd, Adelaide, SA, 5000, Australia. .,Department of Ophthalmology and Visual Sciences, University of Adelaide, Frome Rd, Adelaide, SA, 5000, Australia.
| | - John P M Wood
- Ophthalmic Research Laboratories, South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Frome Rd, Adelaide, SA, 5000, Australia.,Department of Ophthalmology and Visual Sciences, University of Adelaide, Frome Rd, Adelaide, SA, 5000, Australia
| | - Bernard Knoops
- Group of Animal Molecular and Cellular Biology, Institut des Sciences de la Vie (ISV), Université catholique de Louvain, 1348, Louvain-la-Neuve, Belgium
| | - Robert J Casson
- Ophthalmic Research Laboratories, South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Frome Rd, Adelaide, SA, 5000, Australia.,Department of Ophthalmology and Visual Sciences, University of Adelaide, Frome Rd, Adelaide, SA, 5000, Australia
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Landeta O, Landajuela A, Garcia-Saez A, Basañez G. Minimalist Model Systems Reveal Similarities and Differences between Membrane Interaction Modes of MCL1 and BAK. J Biol Chem 2015; 290:17004-19. [PMID: 25987560 DOI: 10.1074/jbc.m114.602193] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Indexed: 11/06/2022] Open
Abstract
Proteins belonging to the BCL2 family are key modulators of apoptosis that establish a complex network of interactions among themselves and with other cellular factors to regulate cell fate. It is well established that mitochondrial membranes are the main locus of action of all BCL2 family proteins, but it is difficult to obtain a precise view of how BCL2 family members operate at the native mitochondrial membrane environment during apoptosis. Here, we used minimalist model systems and multiple fluorescence-based techniques to examine selected membrane activities of MCL1 and BAK under apoptotic-like conditions. We show that three distinct apoptosis-related factors (i.e. the BCL2 homology 3 ligand cBID, the mitochondrion-specific lipid cardiolipin, and membrane geometrical curvature) all promote membrane association of BCL2-like structural folds belonging to both MCL1 and BAK. However, at the same time, the two proteins exhibited distinguishing features in their membrane association modes under apoptotic-like conditions. In addition, scanning fluorescence cross-correlation spectroscopy and FRET measurements revealed that the BCL2-like structural fold of MCL1, but not that of BAK, forms stable heterodimeric complexes with cBID in a manner adjustable by membrane cardiolipin content and curvature degree. Our results add significantly to a growing body of evidence indicating that the mitochondrial membrane environment plays a complex and active role in the mode of action of BCL2 family proteins.
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Affiliation(s)
- Olatz Landeta
- From the Unidad de Biofísica, Centro Mixto Centro Superior de Investigaciones Científicas (CSIC)-EuskalHerriko Unibertsitatea/Universidad del País Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain,
| | - Ane Landajuela
- From the Unidad de Biofísica, Centro Mixto Centro Superior de Investigaciones Científicas (CSIC)-EuskalHerriko Unibertsitatea/Universidad del País Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Ana Garcia-Saez
- the Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany, and the Max-Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany, and the German Cancer Research Center, BioQuant, ImNeuenheimer Feld 267, 69120 Heidelberg, Germany
| | - Gorka Basañez
- From the Unidad de Biofísica, Centro Mixto Centro Superior de Investigaciones Científicas (CSIC)-EuskalHerriko Unibertsitatea/Universidad del País Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain,
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Fox DA. Retinal and visual system: occupational and environmental toxicology. HANDBOOK OF CLINICAL NEUROLOGY 2015; 131:325-40. [PMID: 26563796 DOI: 10.1016/b978-0-444-62627-1.00017-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Occupational chemical exposure often results in sensory systems alterations that occur without other clinical signs or symptoms. Approximately 3000 chemicals are toxic to the retina and central visual system. Their dysfunction can have immediate, long-term, and delayed effects on mental health, physical health, and performance and lead to increased occupational injuries. The aims of this chapter are fourfold. First, provide references on retinal/visual system structure, function, and assessment techniques. Second, discuss the retinal features that make it especially vulnerable to toxic chemicals. Third, review the clinical and corresponding experimental data regarding retinal/visual system deficits produced by occupational toxicants: organic solvents (carbon disulfide, trichloroethylene, tetrachloroethylene, styrene, toluene, and mixtures) and metals (inorganic lead, methyl mercury, and mercury vapor). Fourth, discuss occupational and environmental toxicants as risk factors for late-onset retinal diseases and degeneration. Overall, the toxicants altered color vision, rod- and/or cone-mediated electroretinograms, visual fields, spatial contrast sensitivity, and/or retinal thickness. The findings elucidate the importance of conducting multimodal noninvasive clinical, electrophysiologic, imaging and vision testing to monitor toxicant-exposed workers for possible retinal/visual system alterations. Finally, since the retina is a window into the brain, an increased awareness and understanding of retinal/visual system dysfunction should provide additional insight into acquired neurodegenerative disorders.
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Affiliation(s)
- Donald A Fox
- Departments of Vision Sciences, Biology and Biochemistry, Pharmacology, and Health and Human Performance, University of Houston, Houston, TX, USA.
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Guo S, Zhou J, Chen X, Yu Y, Ren M, Hu G, Liu Y, Zou F. Bystander effects of PC12 cells treated with Pb²⁺ depend on ROS-mitochondria-dependent apoptotic signaling via gap-junctional intercellular communication. Toxicol Lett 2014; 229:150-7. [PMID: 24960054 DOI: 10.1016/j.toxlet.2014.05.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 05/30/2014] [Accepted: 05/30/2014] [Indexed: 12/07/2022]
Abstract
The demonstration of bystander effect, which means injured cells propagate damage to neighboring cells, in whole organisms has clear implication of the potential relevance of the non-targeted response to human health. Here we show that 10 μM lead acetate, the optimum concentration for inducing apoptosis confirmed by the expression levels of Bax and Bcl-2, can also induce rat pheochromocytoma (PC12) cells to exert bystander effects to neighboring cells. In a novel co-culture system, GFP-PC12 (Pb(2+)) cells, which were stable transfected with EF1A-eGFP and pre-exposed with lead acetate, were co-cultured with unexposed PC12 cells at a 1:5 ratio. Parachute assays demonstrated the functional gap-junctional intercellular communication (GJIC) formed between Pb(2+)-exposed and unexposed cells. The Pb(2+)-exposed cells induced very similar effects on neighboring unexposed cells to apoptosis coincide with intracellular ROS generation and the collapse of mitochondrial membrane potential (Δψm). Furthermore, carbenoxolone (CBX), a blocker of GJIC, inhibited the bystander effects. The results indicate that the Pb(2+)-induced insults propagate through GJIC between PC12 cells, while inducing the bystander cells to apoptosis via ROS-mitochondria-dependent apoptotic signaling.
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Affiliation(s)
- Shu Guo
- Department of Occupational Health and Occupational Medicine, School of Public Health and Tropical Medicine, Southern Medical University, No. 1838, North Guangzhou Road, Guangzhou 510515, PR China; Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Environmental Protection, No. 7 Yuancunxi Street, Guangzhou 510655, PR China
| | - Jin Zhou
- Department of Ophthalmology, Guangzhou Women and Children's Medical Center, No. 9 Jinsui Street, Tianhe District, Guangzhou 510623, PR China
| | - Xuemei Chen
- Department of Occupational Health and Occupational Medicine, School of Public Health and Tropical Medicine, Southern Medical University, No. 1838, North Guangzhou Road, Guangzhou 510515, PR China
| | - Yunjiang Yu
- Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Environmental Protection, No. 7 Yuancunxi Street, Guangzhou 510655, PR China
| | - Mingzhong Ren
- Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Environmental Protection, No. 7 Yuancunxi Street, Guangzhou 510655, PR China
| | - Guocheng Hu
- Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Environmental Protection, No. 7 Yuancunxi Street, Guangzhou 510655, PR China
| | - Yun Liu
- Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Environmental Protection, No. 7 Yuancunxi Street, Guangzhou 510655, PR China
| | - Fei Zou
- Department of Occupational Health and Occupational Medicine, School of Public Health and Tropical Medicine, Southern Medical University, No. 1838, North Guangzhou Road, Guangzhou 510515, PR China.
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Ahmed MB, Ahmed MI, Meki AR, Abdraboh N. Neurotoxic effect of lead on rats: Relationship to Apoptosis. Int J Health Sci (Qassim) 2014; 7:192-9. [PMID: 24421747 DOI: 10.12816/0006042] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Lead toxicity has been subjected to intensive research work, but some aspects of its mechanism needs to be elucidated. OBJECTIVES In the current study we aim to investigate the impact of lead toxicity on some different intermediates of apoptotic signaling pathway in experimental rats. DESIGN AND METHODS We measured caspase-8 and caspase-9 [by chemilumenescence], Bax and Bcl-2 [by ELISA] in Experimental rats, injected intraperitoneally with lead acetate for 7days at the dosage of 25, 50 and l00 mg/kg body weight and compared to control rats injected with deionized distilled water instead. instead. RESULTS Lead acetate significantly increased the levels of caspase 8, caspase 9 and Bax in liver, kidney and brain of experimental animals especially those with high doses. Meanwhile, caspase 8 and Bax significantly increased in brain tissue at low dose of lead, while Bcl-2 significantly increased only with advanced toxicity. Furthermore, Bax/bcl2 ratio was significantly high in kidney (p<0.05), liver (p<0.01) and brain (p<0.01) at higher doses of lead toxicity. However, brain tissues showed significant Bax/Bcl2 ratio (p<0.05) at low lead dose. A significant positive correlation was noticed between the blood level of lead and enzymatic level of caspase 8, caspase 9 and Bax in different tissues. CONCLUSION : we concluded that lead might have toxic effect through intrinsic and extrinsic induction of apoptotic pathway with prominent effect on brain tissue even at low dose.
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Affiliation(s)
| | - Maha Imam Ahmed
- Department of Medical Biochemistry, Faculty of Medicine, Qassim University, KSA
| | - Abd-Rheem Meki
- Department of Medical Biochemistry, Faculty of Medicine, Qassim University, KSA
| | - Naglaa Abdraboh
- Department of Medical Biochemistry, Faculty of Medicine, Ain Shams University Cairo, Egypt
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Cheng Y, Corbin JG, Levy RJ. Programmed cell death is impaired in the developing brain of FMR1 mutants. Dev Neurosci 2013; 35:347-58. [PMID: 23900139 DOI: 10.1159/000353248] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 05/21/2013] [Indexed: 11/19/2022] Open
Abstract
Fragile X syndrome (FXS), due to transcriptional silencing of fragile X mental retardation protein (FMRP), is characterized by excess synaptic connections and impaired dendrite maturation. Programmed cell death (PCD) is critical for synaptogenesis and elimination of aberrant neuronal connections in the developing brain; however, the role of FMRP in PCD is unknown. The aim of this work was to assess the intrinsic apoptosis pathway in the developing brain of Fmr1 mutants. To accomplish this, we evaluated two different Fmr1 mutant strains of 10-day-old male mice compared with appropriate controls. We performed immunohistochemistry for activated caspase-3 and TUNEL assays, quantified the number of neurons in neocortex and hippocampus, determined cytochrome c peroxidase activity, measured the amount of cytochrome c release from forebrain mitochondria, and assessed levels of key pro- and antiapoptotic mediators with immunoblot analysis. Both Fmr1 mutant strains demonstrated decreased apoptosis in neocortex, hippocampus, and basolateral amygdala, impaired cytochrome c and procaspase-9 release from mitochondria despite intact Bax translocation, increased expression of the antiapoptotic protein, BCL-xL, and increased number of neurons. Taken together, the data suggest that PCD is impaired due to increased BCL-xL expression and is associated with excess neurons in the developing brain of FMRP-deficient mice. It is possible that deficient PCD prevents neuron elimination and results in abnormal retention of developmentally transient neurons. Thus, defective PCD may contribute to the excess synaptic connections known to exist in Fmr1 mutants and could play a role in the behavioral phenotype of children with FXS.
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Affiliation(s)
- Ying Cheng
- Division of Anesthesiology and Pain Medicine, Children's National Medical Center, The George Washington University School of Medicine and Health Sciences, Washington, DC 20010, USA
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29
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Bogdał MN, Hat B, Kochańczyk M, Lipniacki T. Levels of pro-apoptotic regulator Bad and anti-apoptotic regulator Bcl-xL determine the type of the apoptotic logic gate. BMC SYSTEMS BIOLOGY 2013; 7:67. [PMID: 23883471 PMCID: PMC3750306 DOI: 10.1186/1752-0509-7-67] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 07/11/2013] [Indexed: 01/25/2023]
Abstract
BACKGROUND Apoptosis is a tightly regulated process: cellular survive-or-die decisions cannot be accidental and must be unambiguous. Since the suicide program may be initiated in response to numerous stress stimuli, signals transmitted through a number of checkpoints have to be eventually integrated. RESULTS In order to analyze possible mechanisms of the integration of multiple pro-apoptotic signals, we constructed a simple model of the Bcl-2 family regulatory module. The module collects upstream signals and processes them into life-or-death decisions by employing interactions between proteins from three subgroups of the Bcl-2 family: pro-apoptotic multidomain effectors, pro-survival multidomain restrainers, and pro-apoptotic single domain BH3-only proteins. Although the model is based on ordinary differential equations (ODEs), it demonstrates that the Bcl-2 family module behaves akin to a Boolean logic gate of the type dependent on levels of BH3-only proteins (represented by Bad) and restrainers (represented by Bcl-xL). A low level of pro-apoptotic Bad or a high level of pro-survival Bcl-xL implies gate AND, which allows for the initiation of apoptosis only when two stress stimuli are simultaneously present: the rise of the p53 killer level and dephosphorylation of kinase Akt. In turn, a high level of Bad or a low level of Bcl-xL implies gate OR, for which any of these stimuli suffices for apoptosis. CONCLUSIONS Our study sheds light on possible signal integration mechanisms in cells, and spans a bridge between modeling approaches based on ODEs and on Boolean logic. In the proposed scheme, logic gates switching results from the change of relative abundances of interacting proteins in response to signals and involves system bistability. Consequently, the regulatory system may process two analogous inputs into a digital survive-or-die decision.
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Affiliation(s)
- Marta N Bogdał
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw 02-106, Poland
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MENSHANOV PN, BANNOVA AV, BULYGINA VV, DYGALO NN. Acute Antiapoptotic Effects of Hydrocortisone in the Hippocampus of Neonatal Rats. Physiol Res 2013; 62:205-13. [DOI: 10.33549/physiolres.932339] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Natural glucocorticoid hydrocortisone was suggested as a potent substitution for dexamethasone in the treatment of bronchopulmonary dysplasia in neonates. The aim of this study was to investigate whether hydrocortisone is able to affect the expression of apoptotic genes and the intensity of naturally occurring cell death in the developing rat hippocampus. Hormone treatment decreased procaspase-3 and active caspase-3 levels as well as DNA fragmentation intensity in the hippocampal formation of one-week-old rats in 6 h after injection. These changes were accompanied by an upregulation of antiapoptotic protein Bcl-XL, while expression of proapoptotic protein Bax remained unchanged. The action of hydrocortisone was glucocorticoid receptor-independent, as the selective glucocorticoid receptor agonist dexamethasone did not affect either apoptotic protein levels or DNA fragmentation intensity in the hippocampal region. The data are the first evidences for in vivo antiapoptotic effects of hydrocortisone in the developing hippocampus.
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Affiliation(s)
- P. N. MENSHANOV
- Functional Neurogenomics Laboratory, Institute of Cytology and Genetics, Russian Academy of Science, Novosibirsk, Russian Federation
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31
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Oxidative and nitrosative stress and apoptosis in oral mucosa cells after ex vivo exposure to lead and benzo[a]pyrene. Toxicol In Vitro 2013; 27:915-21. [DOI: 10.1016/j.tiv.2013.01.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Revised: 12/21/2012] [Accepted: 01/02/2013] [Indexed: 11/21/2022]
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Perkins GA, Scott R, Perez A, Ellisman MH, Johnson JE, Fox DA. Bcl-xL-mediated remodeling of rod and cone synaptic mitochondria after postnatal lead exposure: electron microscopy, tomography and oxygen consumption. Mol Vis 2012; 18:3029-48. [PMID: 23288995 PMCID: PMC3534145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 12/18/2012] [Indexed: 10/29/2022] Open
Abstract
PURPOSE Postnatal lead exposure produces rod-selective and Bax-mediated apoptosis, decreased scotopic electroretinograms (ERGs), and scotopic and mesopic vision deficits in humans and/or experimental animals. Rod, but not cone, inner segment mitochondria were considered the primary site of action. However, photoreceptor synaptic mitochondria were not examined. Thus, our experiments investigated the structural and functional effects of environmentally relevant postnatal lead exposure on rod spherule and cone pedicle mitochondria and whether Bcl-xL overexpression provided neuroprotection. METHODS C57BL/6N mice pups were exposed to lead only during lactation via dams drinking water containing lead acetate. The blood [Pb] at weaning was 20.6±4.7 µg/dl, which decreased to the control value by 2 months. To assess synaptic mitochondrial structural differences and vulnerability to lead exposure, wild-type and transgenic mice overexpressing Bcl-xL in photoreceptors were used. Electron microscopy, three-dimensional electron tomography, and retinal and photoreceptor synaptic terminal oxygen consumption (QO(2)) studies were conducted in adult control, Bcl-xL, lead, and Bcl-xL/lead mice. RESULTS The spherule and pedicle mitochondria in lead-treated mice were swollen, and the cristae structure was markedly changed. In the lead-treated mice, the mitochondrial cristae surface area and volume (abundance: measure correlated with ATP (ATP) synthesis) were decreased in the spherules and increased in the pedicles. Pedicles also had an increased number of crista segments per volume. In the lead-treated mice, the number of segments/crista and fraction of cristae with multiple segments (branching) similarly increased in spherule and pedicle mitochondria. Lead-induced remodeling of spherule mitochondria produced smaller cristae with more branching, whereas pedicle mitochondria had larger cristae with more branching and increased crista junction (CJ) diameter. Lead decreased dark- and light-adapted photoreceptor and dark-adapted photoreceptor synaptic terminal QO(2). Bcl-xL partially blocked many of the lead-induced alterations relative to controls. However, spherules still had partially decreased abundance, whereas pedicles still had increased branching, increased crista segments per volume, and increased crista junction diameter. Moreover, photoreceptor and synaptic QO(2) were only partially recovered. CONCLUSIONS These findings reveal cellular and compartmental specific differences in the structure and vulnerability of rod and cone inner segment and synaptic mitochondria to postnatal lead exposure. Spherule and pedicle mitochondria in lead-exposed mice displayed complex and distinguishing patterns of cristae and matrix damage and remodeling consistent with studies showing that synaptic mitochondria are more sensitive to Ca(2+) overload, oxidative stress, and ATP loss than non-synaptic mitochondria. The lead-induced decreases in QO(2) likely resulted from the decreased spherule cristae abundance and smaller cristae, perhaps due to Bax-mediated effects as they occurred in apoptotic rod inner segments. The increase in pedicle cristae abundance and CJ diameter could have resulted from increased Drp1-mediated fission, as small mitochondrial fragments were observed. The mechanisms of Bcl-xL-mediated remodeling might occur via interaction with formation of CJ protein 1 (Fcj1), whereas the partial protection of synaptic QO(2) might result from the enhanced efficiency of energy metabolism via Bcl-xL's direct interaction with the F1F0 ATP synthase and/or regulation of cellular redox status. These lead-induced alterations in photoreceptor synaptic terminal mitochondria likely underlie the persistent scotopic and mesopic deficits in lead-exposed children, workers, and experimental animals. Our findings stress the clinical and scientific importance of examining synaptic dysfunction following injury or disease during development, and developing therapeutic treatments that prevent synaptic degeneration in retinal and neurodegenerative disorders even when apoptosis is blocked.
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Affiliation(s)
- Guy A. Perkins
- National Center for Microscopy and Imaging Research, University of California San Diego, La Jolla, CA
| | - Ray Scott
- National Center for Microscopy and Imaging Research, University of California San Diego, La Jolla, CA
| | - Alex Perez
- National Center for Microscopy and Imaging Research, University of California San Diego, La Jolla, CA
| | - Mark H. Ellisman
- National Center for Microscopy and Imaging Research, University of California San Diego, La Jolla, CA
| | - Jerry E. Johnson
- Department of Natural Sciences, University of Houston-Downtown, Houston, TX
| | - Donald A. Fox
- College of Optometry, University of Houston, Houston, TX,Department of Biology and Biochemistry, University of Houston, Houston, TX,Department of Pharmacology and Pharmaceutical Sciences, University of Houston, Houston, TX
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Baranowska-Bosiacka I, Strużyńska L, Gutowska I, Machalińska A, Kolasa A, Kłos P, Czapski GA, Kurzawski M, Prokopowicz A, Marchlewicz M, Safranow K, Machaliński B, Wiszniewska B, Chlubek D. Perinatal exposure to lead induces morphological, ultrastructural and molecular alterations in the hippocampus. Toxicology 2012; 303:187-200. [PMID: 23146751 DOI: 10.1016/j.tox.2012.10.027] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 10/29/2012] [Accepted: 10/30/2012] [Indexed: 11/16/2022]
Abstract
The aim of this paper is to examine if pre- and neonatal exposure to lead (Pb) may intensify or inhibit apoptosis or necroptosis in the developing rat brain. Pregnant experimental females received 0.1% lead acetate (PbAc) in drinking water from the first day of gestation until weaning of the offspring; the control group received distilled water. During the feeding of pups, mothers from the experimental group were still receiving PbAc. Pups were weaned at postnatal day 21 and the young rats of both groups then received only distilled water until postnatal day 28. This treatment protocol resulted in a concentration of Pb in rat offspring whole blood (Pb-B) below the threshold of 10 μg/dL, considered safe for humans.We studied Casp-3 activity and expression, AIF nuclear translocation, DNA fragmentation, as well as Bax, Bcl-2 mRNA and protein expression as well as BDNF concentration in selected structures of the rat brain: forebrain cortex (FC), cerebellum (C) and hippocampus (H). The microscopic examinations showed alterations in hippocampal neurons.Our data shows that pre- and neonatal exposure of rats to Pb, leading to Pb-B below 10 μg/dL, can decrease the number of hippocampus neurons, occurring concomitantly with ultrastructural alterations in this region. We observed no morphological or molecular features of severe apoptosis or necrosis (no active Casp-3 and AIF translocation to nucleus) in young brains, despite the reduced levels of BDNF. The potential protective factor against apoptosis was probably the decreased Bax/Bcl-2 ratio, which requires further investigation. Our findings contribute to further understanding of the mechanisms underlying Pb neurotoxicity and cognition impairment in a Pb-exposed developing brain.
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Affiliation(s)
- I Baranowska-Bosiacka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University, Powstańców Wlkp. 72, 70-111 Szczecin, Poland.
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Sharifi AM, Mousavi SH. Studying the effects of lead on DNA fragmentation and proapoptotic bax and antiapoptotic bcl-2 protein expression in PC12 cells. Toxicol Mech Methods 2012; 18:75-9. [PMID: 20020893 DOI: 10.1080/15376510701665814] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
ABSTRACT The nervous system is one of the most important targets of lead poisoning. Despite decades of study, the exact mechanism of lead toxicity has not been fully elucidated. One of the suggested mechanisms of lead toxicity is induction of apoptosis, which has not been shown yet in some neuronal cells such as pheochromocytoma cells (PC12). Therefore, the present study sought to examine the effect of lead poisoning on apoptosis in PC12 cells as a suitable model of neuronal cell study. The present results showed that lead could induce toxicity in PC12 cells after 24 hours with as little as 1 muM in a concentration-dependent manner. In Western blot analysis, the ratio of Bax/Bcl-2 protein expression in cells incubated with 3, 30, and 90 muM lead acetate significantly increased compared to controls. Additionally, a DNA laddering pattern in lead-treated cells was shown, which could indicate nuclear fragmentation. It might be concluded that lead could cause PC12 cell death, in which apoptosis or programmed cell death plays an important role.
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Affiliation(s)
- Ali M Sharifi
- Department of Pharmacology and Cellular and Molecular Research Center, School of Medicine, Iran University of Medical Sciences, P.O. Box 14155-6183, Tehran, Iran
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Fox DA, Grandjean P, de Groot D, Paule M. Developmental origins of adult diseases and neurotoxicity: epidemiological and experimental studies. Neurotoxicology 2012; 33:810-6. [PMID: 22245043 PMCID: PMC3657611 DOI: 10.1016/j.neuro.2011.12.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 12/22/2011] [Accepted: 12/22/2011] [Indexed: 10/14/2022]
Abstract
To date, only a small number of commercial chemicals have been tested and documented as developmental neurotoxicants. Moreover, an increasing number of epidemiological, clinical and experimental studies suggest an association between toxicant or drug exposure during the perinatal period and the development of metabolic-related diseases and neurotoxicity later in life. The four speakers at this symposium presented their research results on different neurotoxic chemicals relating to the developmental origins of health and adult disease (DOHaD). Philippe Grandjean presented epidemiological data on children exposed to inorganic mercury and methylmercury, and discussed the behavioral outcome measures as they relate to age and stage of brain development. Donald A. Fox presented data that low-dose human equivalent gestational lead exposure produces late-onset obesity only in male mice that is associated with neurodegeneration. Didima de Groot presented results on prenatal exposure of rats to methylazoxymethanol and discussed the results in light of the etiology of western Pacific amyotrophic lateral sclerosis and Parkinson-dementia complex. Merle G. Paule addressed the long-term changes in learning, motivation and short-term memory in aged Rhesus monkeys following acute 24 h exposure to ketamine during early development. Overall, these presentations addressed fundamental issues in the emerging areas of lifetime neurotoxicity testing, differential vulnerable periods of exposure, nonmonotonic dose-response effects and neurotoxic risk assessment. The results indicate that developmental neurotoxicity results in permanent changes, thus emphasizing the need to prevent such toxicity.
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Affiliation(s)
- Donald A. Fox
- University of Houston, College of Optometry, Department of Biology and Biochemistry, and Department of Pharmaceutical Sciences, Houston, TX, USA
| | - Philippe Grandjean
- Department of Environmental Health, Harvard School of Public Health, Boston, USA and Department of Environmental Medicine, University of Southern Denmark, Odense, Denmark,
| | - Didima de Groot
- Toxicology & Applied Pharmacology, TNO Quality of Life, Zeist, Netherlands,
| | - Merle Paule
- Division of Neurotoxicology, National Center for Toxicological Research, FDA, Jefferson, AR, USA,
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Doi N, Hoshi Y, Itokawa M, Yoshikawa T, Ichikawa T, Arai M, Usui C, Tachikawa H. Paradox of schizophrenia genetics: is a paradigm shift occurring? BEHAVIORAL AND BRAIN FUNCTIONS : BBF 2012; 8:28. [PMID: 22650965 PMCID: PMC3487746 DOI: 10.1186/1744-9081-8-28] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 04/27/2012] [Indexed: 11/10/2022]
Abstract
BACKGROUND Genetic research of schizophrenia (SCZ) based on the nuclear genome model (NGM) has been one of the most active areas in psychiatry for the past two decades. Although this effort is ongoing, the current situation of the molecular genetics of SCZ seems disappointing or rather perplexing. Furthermore, a prominent discrepancy between persistence of the disease at a relatively high prevalence and a low reproductive fitness of patients creates a paradox. Heterozygote advantage works to sustain the frequency of a putative susceptibility gene in the mitochondrial genome model (MGM) but not in the NGM. METHODS We deduced a criterion that every nuclear susceptibility gene for SCZ should fulfill for the persistence of the disease under general assumptions of the multifactorial threshold model. SCZ-associated variants listed in the top 45 in the SZGene Database (the version of the 23rd December, 2011) were selected, and the distribution of the genes that could meet or do not meet the criterion was surveyed. RESULTS 19 SCZ-associated variants that do not meet the criterion are located outside the regions where the SCZ-associated variants that could meet the criterion are located. Since a SCZ-associated variant that does not meet the criterion cannot be a susceptibility gene, but instead must be a protective gene, it should be linked to a susceptibility gene in the NGM, which is contrary to these results. On the other hand, every protective gene on any chromosome can be associated with SCZ in the MGM. Based on the MGM we propose a new hypothesis that assumes brain-specific antioxidant defenses in which trans-synaptic activations of dopamine- and N-methyl-d-aspartate-receptors are involved. Most of the ten predictions of this hypothesis seem to accord with the major epidemiological facts and the results of association studies to date. CONCLUSION The central paradox of SCZ genetics and the results of association studies to date argue against the NGM, and in its place the MGM is emerging as a viable option to account for genomic and pathophysiological research findings involving SCZ.
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Affiliation(s)
- Nagafumi Doi
- Ibaraki Prefectural Medical Center of Psychiatry, 654Asahi-machi, Kasama-shi, Ibaraki, 309-1717, Japan
| | - Yoko Hoshi
- Integrated Neuroscience Research Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya, Tokyo, 156-8506, Japan
| | - Masanari Itokawa
- Project for Schizophrenia and Affective Disorders Research, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya, Tokyo, 156-8506, Japan
| | - Takeo Yoshikawa
- Laboratory for Molecular Psychiatry, RIKEN Brain Science Institute, 2-1Hirosawa, Wako-shi, Saitama, 351-0198, Japan
| | - Tomoe Ichikawa
- Project for Schizophrenia and Affective Disorders Research, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya, Tokyo, 156-8506, Japan
| | - Makoto Arai
- Project for Schizophrenia and Affective Disorders Research, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya, Tokyo, 156-8506, Japan
| | - Chie Usui
- Department of Psychiatry, Juntendo University Nerima Hospital, 3-1-10 Takanodai, Nerima-ku, Tokyo, 177-8521, Japan
| | - Hirokazu Tachikawa
- Department of Psychiatry, Graduate School of Comprehensive Human Science, Tsukuba University, Tsukuba-shi, Ibaraki, Japan
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Mumcuoglu EU, Hassanpour R, Tasel SF, Perkins G, Martone ME, Gurcan MN. Computerized detection and segmentation of mitochondria on electron microscope images. J Microsc 2012; 246:248-65. [PMID: 22506967 DOI: 10.1111/j.1365-2818.2012.03614.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mitochondrial function plays an important role in the regulation of cellular life and death, including disease states. Disturbance in mitochondrial function and distribution can be accompanied by significant morphological alterations. Electron microscopy tomography (EMT) is a powerful technique to study the 3D structure of mitochondria, but the automatic detection and segmentation of mitochondria in EMT volumes has been challenging due to the presence of subcellular structures and imaging artifacts. Therefore, the interpretation, measurement and analysis of mitochondrial distribution and features have been time consuming, and development of specialized software tools is very important for high-throughput analyses needed to expedite the myriad studies on cellular events. Typically, mitochondrial EMT volumes are segmented manually using special software tools. Automatic contour extraction on large images with multiple mitochondria and many other subcellular structures is still an unaddressed problem. The purpose of this work is to develop computer algorithms to detect and segment both fully and partially seen mitochondria on electron microscopy images. The detection method relies on mitochondria's approximately elliptical shape and double membrane boundary. Initial detection results are first refined using active contours. Then, our seed point selection method automatically selects reliable seed points along the contour, and segmentation is finalized by automatically incorporating a live-wire graph search algorithm between these seed points. In our evaluations on four images containing multiple mitochondria, 52 ellipses are detected among which 42 are true and 10 are false detections. After false ellipses are eliminated manually, 14 out of 15 fully seen mitochondria and 4 out of 7 partially seen mitochondria are successfully detected. When compared with the segmentation of a trained reader, 91% Dice similarity coefficient was achieved with an average 4.9 nm boundary error.
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Affiliation(s)
- E U Mumcuoglu
- Health Informatics Department, Informatics Institute, Middle East Technical University, Ankara 06800, Turkey.
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Mechanisms underlying interaction of zinc, lead, and cobalt with nonspecific permeability pores in the mitochondrial membranes. NEUROPHYSIOLOGY+ 2011. [DOI: 10.1007/s11062-011-9219-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Dou C, Zhang J. Effects of lead on neurogenesis during zebrafish embryonic brain development. JOURNAL OF HAZARDOUS MATERIALS 2011; 194:277-282. [PMID: 21868162 DOI: 10.1016/j.jhazmat.2011.07.106] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 07/10/2011] [Accepted: 07/26/2011] [Indexed: 05/31/2023]
Abstract
Lead neurotoxicity has caused wide public concern in recent decades, yet little is known about its effects on cellular and molecular mechanisms during the sensitive early life stages of animals. This study examines neurological deficits caused by lead acetate (Pb) during early embryonic stages in the zebrafish (Danio rerio) and further explores its potential molecular mechanism. Zebrafish embryos showed varying levels of toxicity, which was proportional to the concentration of Pb to which the embryos were exposed. Following Pb exposure (0.2mM), embryos showed obvious neurotoxic symptoms with "sluggish" action, slow swimming movements and slow escape action. Whole mount in situ hybridization showed that gfap and huC gene expression patterns decreased significantly throughout the brains of the Pb-treated embryos, particularly in the diencephalon region. RT-PCR further proved the downregulation of the two genes. However, ngn1 and crestin gene expression patterns were similar in both the Pb-treated embryos and the control embryos. The TUNEL assay demonstrated that the reduction of nerve cells was due to increased apoptosis of neuron and glia cells. In conclusion, these findings identify that Pb-induced neurotoxicity can be caused by impaired neurogenesis, resulting in markedly increased apoptosis of special types of neural cells, neuron and glia cells.
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Affiliation(s)
- Changming Dou
- Key Laboratory of Non-point Sources Pollution Control, Ministry of Agriculture of People's Republic of China, Institute of Environmental Science and Technology, Zhejiang University, Hangzhou 310029, China.
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Fox DA, Hamilton WR, Johnson JE, Xiao W, Chaney S, Mukherjee S, Miller DB, O'Callaghan JP. Gestational lead exposure selectively decreases retinal dopamine amacrine cells and dopamine content in adult mice. Toxicol Appl Pharmacol 2011; 256:258-67. [PMID: 21703292 DOI: 10.1016/j.taap.2011.05.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 05/30/2011] [Accepted: 05/31/2011] [Indexed: 10/18/2022]
Abstract
Gestational lead exposure (GLE) produces supernormal scotopic electroretinograms (ERG) in children, monkeys and rats, and a novel retinal phenotype characterized by an increased number of rod photoreceptors and bipolar cells in adult mice and rats. Since the loss of dopaminergic amacrine cells (DA ACs) in GLE monkeys and rats contributes to supernormal ERGs, the retinal DA system was analyzed in mice following GLE. C57BL/6 female mice were exposed to low (27 ppm), moderate (55 ppm) or high (109 ppm) lead throughout gestation and until postnatal day 10 (PN10). Blood [Pb] in control, low-, moderate- and high-dose GLE was ≤ 1, ≤ 10, ~25 and ~40 μg/dL, respectively, on PN10 and by PN30 all were ≤ 1 μg/dL. At PN60, confocal-stereology studies used vertical sections and wholemounts to characterize tyrosine hydroxylase (TH) expression and the number of DA and other ACs. GLE dose-dependently and selectively decreased the number of TH-immunoreactive (IR) DA ACs and their synaptic plexus without affecting GABAergic, glycinergic or cholinergic ACs. Immunoblots and confocal revealed dose-dependent decreases in retinal TH protein expression and content, although monoamine oxidase-A protein and gene expression were unchanged. High-pressure liquid chromatography showed that GLE dose-dependently decreased retinal DA content, its metabolites and DA utilization/release. The mechanism of DA selective vulnerability is unknown. However, a GLE-induced loss/dysfunction of DA ACs during development could increase the number of rods and bipolar cells since DA helps regulate neuronal proliferation, whereas during adulthood it could produce ERG supernormality as well as altered circadian rhythms, dark/light adaptation and spatial contrast sensitivity.
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Affiliation(s)
- Donald A Fox
- College of Optometry, University of Houston, Houston, TX 77204-2020, USA.
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Giddabasappa A, Hamilton WR, Chaney S, Xiao W, Johnson JE, Mukherjee S, Fox DA. Low-level gestational lead exposure increases retinal progenitor cell proliferation and rod photoreceptor and bipolar cell neurogenesis in mice. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:71-7. [PMID: 20840909 PMCID: PMC3018503 DOI: 10.1289/ehp.1002524] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Accepted: 09/14/2010] [Indexed: 05/25/2023]
Abstract
BACKGROUND Gestational lead exposure (GLE) produces novel and persistent rod-mediated electroretinographic (ERG) supernormality in children and adult animals. OBJECTIVES We used our murine GLE model to test the hypothesis that GLE increases the number of neurons in the rod signaling pathway and to determine the cellular mechanisms underlying the phenotype. RESULTS Blood lead concentrations ([BPb]) in controls and after low-, moderate-, and high-dose GLE were ≤ 1, ≤ 10, approximately 25, and approximately 40 µg/dL, respectively, at the end of exposure [postnatal day 10 (PND10)]; by PND30 all [BPb] measures were ≤ 1 µg/dL. Epifluorescent, light, and confocal microscopy studies and Western blots demonstrated that late-born rod photoreceptors and rod and cone bipolar cells (BCs), but not Müller glial cells, increased in a nonmonotonic manner by 16-30% in PND60 GLE offspring. Retinal lamination and the rod:cone BC ratio were not altered. In vivo BrdU (5-bromo-2-deoxyuridine) pulse-labeling and Ki67 labeling of isolated cells from developing mice showed that GLE increased and prolonged retinal progenitor cell proliferation. TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) and confocal studies revealed that GLE did not alter developmental apoptosis or produce retinal injury. BrdU birth-dating and confocal studies confirmed the selective rod and BC increases and showed that the patterns of neurogenesis and gliogenesis were unaltered by GLE. CONCLUSIONS Our findings suggest two spatiotemporal components mediated by dysregulation of different extrinsic/intrinsic factors: increased and prolonged cell proliferation and increased neuronal (but not glial) cell fate. These findings have relevance for neurotoxicology, pediatrics, public health, risk assessment, and retinal cell biology because they occurred at clinically relevant [BPb] and correspond with the ERG phenotype.
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Affiliation(s)
| | | | | | - Weimin Xiao
- College of Optometry, University of Houston, Houston, Texas, USA
| | - Jerry E. Johnson
- Department of Natural Sciences, University of Houston–Downtown, Houston, Texas, USA
| | | | - Donald A. Fox
- Department of Biology and Biochemistry and
- College of Optometry, University of Houston, Houston, Texas, USA
- Department of Pharmacology and Pharmaceutical Sciences, University of Houston, Houston, Texas, USA
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Orrenius S, Nicotera P, Zhivotovsky B. Cell Death Mechanisms and Their Implications in Toxicology. Toxicol Sci 2010; 119:3-19. [DOI: 10.1093/toxsci/kfq268] [Citation(s) in RCA: 276] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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Yedjou CG, Milner JN, Howard CB, Tchounwou PB. Basic apoptotic mechanisms of lead toxicity in human leukemia (HL-60) cells. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2010; 7:2008-17. [PMID: 20623007 PMCID: PMC2898032 DOI: 10.3390/ijerph7052008] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 03/26/2010] [Accepted: 04/03/2010] [Indexed: 11/19/2022]
Abstract
Lead exposure represents a medical and public health emergency, especially in children consuming high amounts of lead-contaminated flake paints. It may also cause hematological effects to people of all ages. Recent studies in our laboratory have indicated that apoptosis may be associated with the lead-induced oxidative stress and DNA damage. However, the mechanisms underlying its effect on lymphocytes are still largely unknown. Therefore, the aim of the present study was to investigate the apoptotic mechanisms of lead nitrate [Pb(NO(3))(2)] using HL-60 cells as a test model. HL-60 cells were treated with different concentrations of Pb(NO(3))(2) for 24 h prior to cell viability assay and flow cytometry assessment. The results obtained from the trypan blue exclusion test indicated that at very low concentration, Pb(NO(3))(2) has no effect on the viability of HL-60 cells. A significant (p < 0.05) decrease in cell viability was observed when exposed to high level of Pb(NO(3))(2). Data generated from the flow cytometric assessment indicated that Pb(NO(3))(2) exposure significantly (p < 0.05) increased the proportion of annexin V positive cells (apoptotic cells) compared to the control. Pb(NO(3))(2) induced apoptosis of HL-60 cells was associated with the activation of caspase-3. In summary, these studies demonstrated that Pb(NO(3))(2) represents an apoptosis-inducing agent in HL-60 promyelocytic leukemia cells and its apoptotic mechanism functions, at least in part via, induction of phosphatidylserine externalization and caspase-3 activation.
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Affiliation(s)
- Clement G. Yedjou
- Cellomics and Toxicogenomics Research Laboratory, NIH-Center for Environmental Health, College of Science, Engineering and Technology, Jackson State University, 1400 Lynch Street, P.O. Box 18540, Jackson, MS 39217, USA; E-Mails:
(J.N.M.);
(C.B.H.);
(P.B.T.)
| | - Jessica N. Milner
- Cellomics and Toxicogenomics Research Laboratory, NIH-Center for Environmental Health, College of Science, Engineering and Technology, Jackson State University, 1400 Lynch Street, P.O. Box 18540, Jackson, MS 39217, USA; E-Mails:
(J.N.M.);
(C.B.H.);
(P.B.T.)
| | - Carolyn B. Howard
- Cellomics and Toxicogenomics Research Laboratory, NIH-Center for Environmental Health, College of Science, Engineering and Technology, Jackson State University, 1400 Lynch Street, P.O. Box 18540, Jackson, MS 39217, USA; E-Mails:
(J.N.M.);
(C.B.H.);
(P.B.T.)
| | - Paul B. Tchounwou
- Cellomics and Toxicogenomics Research Laboratory, NIH-Center for Environmental Health, College of Science, Engineering and Technology, Jackson State University, 1400 Lynch Street, P.O. Box 18540, Jackson, MS 39217, USA; E-Mails:
(J.N.M.);
(C.B.H.);
(P.B.T.)
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Lead affects apoptosis and related gene XIAP and Smac expression in the hippocampus of developing rats. Neurochem Res 2010; 35:473-9. [PMID: 19911273 DOI: 10.1007/s11064-009-0083-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2009] [Indexed: 02/05/2023]
Abstract
Lead (Pb) exposure poses devastating effects on central nervous system development of children. To replicate aspects of this neurotoxicity, we examined the effect of lead on the expression of apoptosis and of apoptosis-related genes, XIAP (X chromosome-linked inhibitor of apoptosis protein) and Smac (second mitochondrial activator of caspase), in the hippocampus of developing rats. A total of 48 rats (30-day old) were randomly divided into four groups for intragastrical perfusion of lead acetate [Pb(Ac)2]: untreated, low (2 mg/kg/d), medium (20 mg/kg/d), and high (200 mg/kg/d) dose groups. Pb content was determined in blood, and the apoptosis indexes and XIAP and Smac gene expression were analyzed in the hippocampus. There was a significant difference in apoptosis indexes (AI) between the exposed and control groups (p < 0.01). AI was highest in the high exposure group. XIAP gene expression was reduced in the exposed groups and the expression was negatively correlated with blood lead levels (BLLs) (p < 0.05). But the four groups did not differ in the expression of Smac (p > 0.05). Our data indicate that exposure to Pb(Ac)2 caused a dose-dependent and significant increase of apoptosis in the hippocampus of developing rats through depressing the expression of the XIAP but not the Smac genes.
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Fox DA, Opanashuk L, Zharkovsky A, Weiss B. Gene-chemical interactions in the developing mammalian nervous system: Effects on proliferation, neurogenesis and differentiation. Neurotoxicology 2010; 31:589-97. [PMID: 20381523 DOI: 10.1016/j.neuro.2010.03.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 03/19/2010] [Accepted: 03/22/2010] [Indexed: 12/01/2022]
Abstract
The orderly formation of the nervous system requires a multitude of complex, integrated and simultaneously occurring processes. Neural progenitor cells expand through proliferation, commit to different cell fates, exit the cell cycle, generate different neuronal and glial cell types, and new neurons migrate to specified areas and establish synaptic connections. Gestational and perinatal exposure to environmental toxicants, pharmacological agents and drugs of abuse produce immediate, persistent or late-onset alterations in behavioral, cognitive, sensory and/or motor functions. These alterations reflect the disruption of the underlying processes of CNS formation and development. To determine the neurotoxic mechanisms that underlie these deficits it is necessary to analyze and dissect the complex molecular processes that occur during the proliferation, neurogenesis and differentiation of cells. This symposium will provide a framework for understanding the orchestrated events of neurogenesis, the coordination of proliferation and cell fate specification by selected genes, and the effects of well-known neurotoxicants on neurogenesis in the retina, hippocampus and cerebellum. These three tissues share common developmental profiles, mediate diverse neuronal activities and function, and thus provide important substrates for analysis. This paper summarizes four invited talks that were presented at the 12th International Neurotoxicology Association meeting held in Jerusalem, Israel during the summer of 2009. Donald A. Fox described the structural and functional alterations following low-level gestational lead exposure in children and rodents that produced a supernormal electroretinogram and selective increases in neurogenesis and cell proliferation of late-born retinal neurons (rod photoreceptors and bipolar cells), but not Müller glia cells, in mice. Lisa Opanashuk discussed how dioxin [TCDD] binding to the arylhydrocarbon receptor [AhR], a transcription factor that regulates xenobiotic metabolizing enzymes and growth factors, increased granule cell formation and apoptosis in the developing mouse cerebellum. Alex Zharkovsky described how postnatal early postnatal lead exposure decreased cell proliferation, neurogenesis and gene expression in the dentate gyrus of the adult hippocampus and its resultant behavioral effects. Bernard Weiss illustrated how environmental endocrine disruptors produced age- and sex-dependent alterations in synaptogenesis and cognitive behavior.
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Affiliation(s)
- Donald A Fox
- University of Houston, College of Optometry, Department of Biology and Biochemistry, 4901 Calhoun Road, Houston, TX 77024-2020, USA.
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Sharifi AM, Mousavi SH, Jorjani M. Effect of chronic lead exposure on pro-apoptotic Bax and anti-apoptotic Bcl-2 protein expression in rat hippocampus in vivo. Cell Mol Neurobiol 2010; 30:769-74. [PMID: 20148304 DOI: 10.1007/s10571-010-9504-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 01/29/2010] [Indexed: 10/19/2022]
Abstract
Despite reduction in environmental lead, chronic lead exposure still possess a public health hazard, particularly in children, with devastating effects on developing CNS. To investigate the mechanism of this neurotoxicity, young and adult rats were used to study whether exposure to 500 ppm concentrations of lead could induce apoptosis in hippocampus. 2-4 and 12-14-week-old rats received lead acetate in concentration of 500 ppm for 40 days. Control animals received deionized distilled water. In lead-treated groups, the blood lead levels were increased by 3-4 folds. Light and electron microscopical study of hippocampus revealed increased apoptotic cells. Western blot analysis of Bax and Bcl-2 (pro- and anti-apoptotic gene products, respectively) indicated higher expression of Bax protein and no significant change in bcl-2 expression and accordingly increased the Bax/Bcl-2 ratio compared to control group, confirming the histological study. In conclusion, these data suggest that neurotoxicity of chronic lead exposure in hippocampus in vivo may partly be due to facilitation of apoptosis.
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Affiliation(s)
- Ali M Sharifi
- Department of Pharmacology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
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The micro-architecture of mitochondria at active zones: electron tomography reveals novel anchoring scaffolds and cristae structured for high-rate metabolism. J Neurosci 2010; 30:1015-26. [PMID: 20089910 DOI: 10.1523/jneurosci.1517-09.2010] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Mitochondria are integral elements of many nerve terminals. They must be appropriately positioned to regulate microdomains of Ca(2+) concentration and metabolic demand, but structures that anchor them in place have not been described. By applying the high resolution of electron tomography (ET) to the study of a central terminal, the calyx of Held, we revealed an elaborate cytoskeletal superstructure that connected a subset of mitochondria to the presynaptic membrane near active zones. This cytoskeletal network extended laterally and was well integrated into the nerve terminal cytoskeleton, which included filamentous linkages among synaptic vesicles. ET revealed novel features of inner membrane for these mitochondria. Crista structure was polarized in that crista junctions, circular openings of the inner membrane under the outer membrane, were aligned with the cytoskeletal superstructure and occurred at higher density in mitochondrial membrane facing the presynaptic membrane. These characteristics represent the first instance where a subcomponent of an organelle is shown to have a specific orientation relative to the polarized structure of a cell. The ratio of cristae to outer membrane surface area is large in these mitochondria relative to other tissues, indicating a high metabolic capacity. These observations suggest general principles for cytoskeletal anchoring of mitochondria in all tissues, reveal potential routes for nonsynaptic communication between presynaptic and postsynaptic partners using this novel cytoskeletal framework, and indicate that crista structure can be specialized for particular functions within cellular microdomains.
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New insights into mitochondrial structure during cell death. Exp Neurol 2009; 218:183-92. [PMID: 19464290 DOI: 10.1016/j.expneurol.2009.05.021] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 04/30/2009] [Accepted: 05/08/2009] [Indexed: 01/06/2023]
Abstract
Mitochondria play a pivotal role in the cascade of events associated with cell death pathways that are involved with several forms of neurodegeneration. Recent findings show that in the Bax/Bak-dependent pathway of apoptosis, the release of cytochrome c from mitochondria is a consequence of two carefully coordinated events: opening of crista junctions triggered by OPA1 oligomer disassembly and formation of outer membrane pores. Both steps are necessary for the complete release of pro-apoptotic proteins. The remodeling of mitochondrial structure accompanies this pathway, including mitochondrial fission, and cristae and crista junction alterations. Yet, there is controversy surrounding the timing of certain remodeling events and whether they are necessary early events required for the release of pro-apoptotic factors or are simply a downstream after-effect. Here, we analyze the current knowledge of mitochondrial remodeling during cell death and discuss what structural alterations occur to this organelle during neurodegeneration, focusing on the higher resolution structural correlates obtained by electron microscopy and electron tomography.
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Yeung CK, Chiang SWY, Chan KP, Pang CP, Lam DSC. Potassium Channel Openers Reduce the Caspase-3 Expression of Triamcinolone-Treated Retinal Pigment Epithelial (ARPE19) Cells. Cutan Ocul Toxicol 2008. [DOI: 10.1080/15569520500371636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Billen LP, Kokoski CL, Lovell JF, Leber B, Andrews DW. Bcl-XL inhibits membrane permeabilization by competing with Bax. PLoS Biol 2008; 6:e147. [PMID: 18547146 PMCID: PMC2422857 DOI: 10.1371/journal.pbio.0060147] [Citation(s) in RCA: 241] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 05/02/2008] [Indexed: 11/23/2022] Open
Abstract
Although Bcl-XL and Bax are structurally similar, activated Bax forms large oligomers that permeabilize the outer mitochondrial membrane, thereby committing cells to apoptosis, whereas Bcl-XL inhibits this process. Two different models of Bcl-XL function have been proposed. In one, Bcl-XL binds to an activator, thereby preventing Bax activation. In the other, Bcl-XL binds directly to activated Bax. It has been difficult to sort out which interaction is important in cells, as all three proteins are present simultaneously. We examined the mechanism of Bax activation by tBid and its inhibition by Bcl-XL using full-length recombinant proteins and measuring permeabilization of liposomes and mitochondria in vitro. Our results demonstrate that Bcl-XL and Bax are functionally similar. Neither protein bound to membranes alone. However, the addition of tBid recruited molar excesses of either protein to membranes, indicating that tBid activates both pro- and antiapoptotic members of the Bcl-2 family. Bcl-XL competes with Bax for the activation of soluble, monomeric Bax through interaction with membranes, tBid, or t-Bid-activated Bax, thereby inhibiting Bax binding to membranes, oligomerization, and membrane permeabilization. Experiments in which individual interactions were abolished by mutagenesis indicate that both Bcl-XL–tBid and Bcl-XL–Bax binding contribute to the antiapoptotic function of Bcl-XL. By out-competing Bax for the interactions leading to membrane permeabilization, Bcl-XL ties up both tBid and Bax in nonproductive interactions and inhibits Bax binding to membranes. We propose that because Bcl-XL does not oligomerize it functions like a dominant-negative Bax in the membrane permeabilization process. During development and under stress, cells can become committed to die via programmed cell death (apoptosis). In most cases, the permeabilization of the outer mitochondrial membrane is a key component of this commitment. The membrane permeablization step is both positively and negatively regulated by members of the Bcl-2 family of proteins. One member of this protein family with only a BH3 region, such as tBid, activates another family member, Bax, causing it to form large complexes that generate membrane-spanning pores, hence making the membrane permeable. Antiapoptotic members of the Bcl-2 family, such as Bcl-XL, are structurally similar to Bax but inhibit the membrane permeabilization process by an unknown mechanism. Two mutually exclusive models have been proposed to explain how the Bcl-2 family is operating: one states that Bcl-XL binds to tBid, thereby preventing Bax activation, while the second suggests that Bcl-XL binds directly to activated Bax. It has been difficult to sort out which interaction is important in cells, where multiple members of all three protein families are present simultaneously. Here, we describe an in vitro system containing the three recombinant proteins and the use of mutagenesis to selectively remove individual interactions. We show that Bcl-XL inhibits Bax by competing with it for binding to membranes, tBid, and activated Bax. Because Bcl-XL does not form pores, it inhibits apoptosis by acting as if it is a dominant-negative version of Bax. Bcl-XL and Bax are structurally similar members of the Bcl-2 family of cell-death-related proteins, and they compete for binding to membranes, as well as to Bcl-2 family member tBid and activated Bax. Unlike Bax, Bcl-XL is unable to oligomerize and form pores in membranes, so it inhibits membrane permeabilization--a key step during commitment to apoptosis--by functioning like a dominant-negative Bax.
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Affiliation(s)
- Lieven P Billen
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Candis L Kokoski
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Jonathan F Lovell
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Brian Leber
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - David W Andrews
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- * To whom correspondence should be addressed. E-mail:
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