Ecotoxicology Biology Biomarkers: Cells, Tissues and Organs

Transcription

1 Ecotoxicology Biology 5868 Biomarkers: Cells, Tissues and Organs 2009

2 In Vitro Techniques Mouse F9 cells Retinoic acid Methoprene - insect juvenile hormone mimic Methoprene acid - metabolite

3 Transfected Cell Lines Construct cell lines that respond (i.e. signal) to desired transcriptional stimulation; e.g. - estrogen or other hormones or hormone mimics - metals - pesticides - PCBs - etc. Method: Genes containing receptor and reporter functions are constructed and inserted into a cell (ideally one without endogenous activity) Transfected cells exposed to authentic signals (e.g. hormones) and putative mimics Reporter signals indicate receptor activity/transcriptional activation Transfection techniques can be used in specific, high-throughput methods - primarily screening assays

4 ERE-GFP Plasmid Estrogen receptor response element Green fluorescent protein Xu et al., Biotechnol Bioeng 101:

5 Transient Transfection ATGCATGC RARβ2 ATGCATGC ATGCATGC RARE luciferase ATGCATGC prarβ2 RAR mrna RAR pcrbpiiluc CV-1 cell nucleus

6 Transient Transfection Retinoids prarβ2 RAR mrna RAR luciferase mrna pcrbpiiluc Luciferase + Luciferin + ATP = Light!

7 Transient Transfection Retinoid mimics prarβ2 RAR mrna RAR luciferase mrna pcrbpiiluc Light!

8 MeOH 1 μl/ml All trans-ra 1 μm Methoprene Methoprene acid Citronellal Octanoic acid 50 μm 100 μm 10 μm 25 μm 50 μm 75 μm 125 μm 100 μm 25 μm 100 μm 25 μm 100 μm RARE-lucTransfection Does methoprene (insecticide) mimic retinoic acid (vertebrate growth regulator) by binding to retinoic acid receptors and activating response elements? 120 all trans-retinoic acid methoprene Relative light units x Transiently transfect cells with plasmids for: - RAR, - RARE-luciferase Treat with methoprene & metabolites 0 9 cis-ra 0.1 μm

9 ER Dose Response MCF-7 cell culture - human - estrogen responsive Transfected with ERE-GFP plasmid Xu et al., Biotechnol Bioeng 101: E2

10 ER Xenobiotics Dose-Response MCF-7 cells - human - estrogen-responsive Transfected with ERE-β-gal (reporter) Charles GD et al., 2007 Toxicol Appl Pharmacol 218:

11 DNA Modification Genotoxicity damage by a physical or chemical agent to genetic materials such as chromosomes or DNA - mutagens - teratogens - carcinogens cisplatin adducts - clastogens (agents that cause chromosome damage) - free radicals can cause strand breakage - oxyradicals oxidize bases - metals bind phosphates or bases; e.g. Hg crosslinks DNA strands; Cu displaces Mg on PO 4 Adducts: xenobiotics bind covalently to nucleotide - alters DNA structure Chromosomal aberrations breakage or loss of segment of DNA

12 DNA Modification Mechanisms: - free radicals can cause strand breakage - oxyradicals oxidize bases - adducts: xenobiotics bind covalently to nucleotide; alters structure - metals bind phosphates or bases; e.g. - Hg crosslinks DNA strands; Cu displaces Mg on PO 4 Cellular repair mechanisms: highly active and efficient, but can be overwhelmed

13 Gene and Chromosome Damage Assay methods: - chromosome staining - flow cytometry (aneuploidy) - 32 P-labeling (adducts) - comet assay (single cell DNA assay) comet assay C. Burd & TK Archer

14 Sister Chromatid Exchange - normal process of recombination during mitosis - many xenobiotics increase the rate of SCE - increased SCE is associated with increased incidence of cancer Crossing-over and recombination during meiosis sister chromatid exchange L. normal R. Bloom s syndrome

15 Micronuclei Micronuclei individual chromosomes or chromosome fragments - no kinetochore or centrosome - membrane bound Source: Dr. Stephan Kirchner, Sabine Marget-Müller, PRNS, Roche

16 Toxicogenomics e.g. microarrays mrna expression profiles

17 2-D electrophoresis larger acidic Proteomics basic - excise protein/peptide - identify with GC-MS smaller Medicago truncatula leaf proteome

18 Proteomics Control Contaminant treated HSPs P-450s cell cycle DNA repair

19 Proteomics

20 Cytotoxicity and Histopoathology NOTE The linkage between cell/tissue level lesions and effects at higher levels of biological organization are often tenuous, at best. Cytotoxicity causing cell death Necrosis cell death resulting from toxicity or injury - coagulation necrosis coagulation of proteins; good biomarker? Inflammation often associated with toxicant-induced necrosis - often followed by scar tissue (evidence of past lesions) Edema - abnormal infiltration and excess accumulation of serous fluid

21 enhancement toxic effect Thresholds and Sensitivity threshold no threshold hormesis 0 concentration or dose

22 toxic effect Thresholds and Sensitivity Assay 1 threshold: very sensitive Assay 4 threshold: not very sensitive concentration or dose e.g. Assay 1 = mrna Assay 2 = tumor formation Assay 3 = behavioral change Assay 4 = population change

23 Cancer Neoplastic hyperplasia benign - differentiated - grow slowly (relatively) - not invasive malignant - undifferentiated - grow rapidly (in general) - invade other tissues - metastasize

24 Cancers - heritable changes in cells. Cancer - often the result of inappropriate activation of genes involved with development, differentiation, or growth; e.g. - activation of a promoter for an oncogene - inactivation of a tumor suppressor gene Triggers include: - chromosomal rearrangements - chemicals - UV (or other EM) ionizing radiation - retroviruses - mutations, deletions - damage to DNA repair mechanisms Carcinogenesis: - initiators - produce the genetic change that allows cancer to develop - promoter - enhance growth and expansion of latent tumor cells - e.g. hormones; growth factors - endocrine disrupting chemicals?

25 Respiratory Tract (Terrestrial) - principle tract for entry of pollutants - defense: - filtration - hairs, mucus - muscular constriction (trachealbronchial) - inactivation (i.e. metabolism) - alveolar cells: large alveolar cells, macrophages - removal - ciliary movement Asbestos fibers

26 Gills - intensively exposed to any waterborne contaminant - fairly simple structure accommodates histopathology - sensitive response to a wide variety of toxic processes - inflammation - edema - gas exchange - ionic regulation - necrosis - hypertrophy (increase in the size of an organ) - hyperplasia (increase in number of cells in a tissue or organ) - epithelial separation primary lamellae secondary lamellae chloride cells

27 Gastrointestinal Tract - nutrients and toxins absorbed by the same mechanisms - tissue is very well vascularized - soluble toxicants (i.e. low Kow) will be absorbed; less soluble agents carried through and eliminated with the feces - small particles (~ 50μm diam) can penetrate the intestinal wall; eventually enter the bloodstream

28 Liver Major site of detoxification reactions - blood reservoir - storage organ for some vitamins; manufacturing site for others - stores energy (glycogen) - pollutant or metabolic products can attack the liver (hepatotoxins) - e.g. CCl 4 attacks the liver Cirrhosis - excessive formation of connective tissue, followed by hardening and contraction - CCl 4 causes cirrhosis Fibrosis deposition of excessive collagen - As compounds - vinyl chloride

29 Kidneys Principal organs for excretion of both endogenous and exogenous toxins % of of the blood pumped by heart passes through the kidneys - filtration/reabsorbtion - both passive and active filtering - toxin concentration can affect active filtering mechanisms (i.e. ATPases) - filtrate contains dissolved materials, including toxins Metabolism (e.g. MFO activity) can produce less or more toxic products - trichloromethane (CHCl 3 ) and carbon tetrachloride (CCl 4 ) may be transformed into reactive, toxic products - methoxyfluorane metabolized into fluoride ions and oxalate both highly toxic - Pb, Cd, Hg both acute and chronic diseases (Cd renal cancer)