Endokrinní disrupce I - obratlovci J. Vondráček Endokrinní disrupce n* I endokrinní disruptor - látka, která interferuje se syntézou, sekrecí, transportem, vazbou na receptor, aktivitou receptoru nebo eliminací hormonu v těle; dosud byla pozornost věnována hlavně látkám interferujícím s pohlavními hormony - estrogeny a androgeny, a thyroidními hormony; řada pesticidů či jejich metabolitů je v exp. podmínkách schopná chovat se jako estrogeny, antiandrogeny apod. pozn.: problematické koncentrace a epidemiologické studie; Endokrinní disruptory Steroids Iľp-Estradioi Pharmaceuticals Diethylstilbestrol Ethynyl Estradiol Fungal Products CH D * Zearalenone Pollutants í ! II DDT PCB Bisphenoí A Nortylphenol Kepone Plant Products Genisteir» (isoflavone) I T Ltiteolin (flavone) Resveratrol (stilbene) Coumestrol (coumarin) Fig. 5. Chemicals found in the environment reported to be estrogenic. This list is not comprehensive, but illustrates representative structures of estrogenic compounds from various sources. Information on these compounds is contained in the text. Výzkum endokrinní disrupce je soustředěn do dvou oblastí: • obratlovci, kteří alespoň část svého životního cyklu tráví ve vodném prostředí - ryby, obojživelníci -expozice vodou, potravou; • terestričtí obratlovci - expozice především v rámci potravního řetězce; • nejohroženější skupina - vrcholoví konzumenti -dravci. https://www.epa.qov/endocrine-disruption Biomagnifikace a bioakumulace DDT t'ürttrrttfdlJorti LrtUréiuŕ of 10 ulil Liu n lim*!* Endocrine Disruption in Wildlife Endocrine Disruption in Lab - Eggshell thinning in raptors from DDT - Beak, skeletal, reproductive abnormalities from PCBs (bald eagles, gulls, cormorants) - Intersex fish below UK sewage effluents from estradiol, alkylphenols • Decreased plasma sex steroids, egg and gonadal size; delayed sexual maturity from dioxin below paper mills (Great Lakes white suckers) • Poorly developed testes, small penises, low testosterone; abnormal ovaries; males with high estradiol; poor hatchling success from DDE (Lake Apopka alligators) - Masculinization of females by kepone, DDT, methoxychlor - Disruption of estrous cycle by atrazine, choroquine - Hypospadias, vaginal pouches, reduced sperm production in males exposed to vinclozolin in utero - Impaired testosterone synthesis, and spermatogenesis; decreased anogenital distance, delayed testis decent, impaired and feminized behavior of rats by dioxin -Acceleration of puberty and loss of fertility in females by many estrogenic chemicals - Delay of puberty, binding to androgen receptor; nipple retention in males by many estrogenic chemicals -Atrophy of the thymus by PCBs and dioxin Evidence for ED in Humans Genital malformation (boys), vaginal cancer, infertility (girls) exposed in utero to DES Neurological effects, decreased growth, developmental abnormalities (e.g., penis size) in children exposed in utero to PCBs Altered girl/boy ratio after population exposure to dioxin (Saveso, Italy) Shortened lactation associated with DDE Decreased sperm count and quality Increased prostate, testicular, breast cancer Endocrine (hormonal) system regulates Metabolic function and equilibrium Reproduction G r o wt h/d eve I o p m e n t Pineal Hypothalamus Pituitary-- Thyroid Paratfiyroids Thymus Adrenals ■ Pancreas Ovary There are over 50 different hormones Environmental estrogens (xenoestrogens) I ► Sources o pesticides o plastics c> pharmaceuticals c> some cleansers c> Contraception Ovs. phytoestrogens c> antiherbivore compounds in many plant species c> lignans (many fruits, vegetables), isoflavones (soy) Možnosti účinků environmentálních estrogenů na buněčné úrovni Decision Network Growth Factor Receptor Ligands Nuclear ER 1 mí i'ioi n>i DMA Binding Ligen! B ind nq Donwi Domin h ERct «CH NH, ff, DHABkidng Lnisrxi Dinding Domii Darmi n GOCH phosphorylation cascade c ore pressors 3 4 ubiqufflnlzation QR accumulation and destruction Membrane ER cell cycle activation DNA i nl er act ion APfSP 11 elh er ed TARGET GENE ACTIVATlON (MODULATION) Environmentálni estrogeny: p-Alkyl phenols Dietľiylstil bestrol Benzyl butyl p h Hralate Figure 2 S tru ctures o f some xen oestrogen s. Environmentálni anti-androgeny Fig. 2. Structural diversity among environmental chemicals reported to be antiandrogenie. The steroidal androgen. 5a-dihydroxytestosterone !5n-DHT) and its pharmaceutical antagonist, hydroxyflutamide, are shown for comparison. p,p 'DDE is a persistent contaminant, while the remaining are currently used pesticides: fenitrothion, an insecticide; Imuran, an herbicide; and vinclozolin, a fungicide. Xenoestrogens and xenoandrogens can Mimic or partly mimic a the sex steroid hormones estrogens and androgens (the male sex hormone) by binding to hormone receptors or influencing cell signaling pathways. Those that act like estrogen are called environmental estrogens. Modify the making and function of hormone receptors. Block, prevent and alter hormonal binding to hormone receptors or influencing cell signaling pathways. Chemicals that block or antagonize hormones are labeled anti-estrogens or anti-androgens. Alter production and breakdown of natural hormones. Interakce A h R a ER: E2 CYP1A1 ^CYP1B1 t Decreased E2 $\ Tf(-) ■*■ Inhibition of E2-induccd genes iDRE Coactivator binding re-ct Inhibition of E2-1 nd need genre E2 ^ „ Limiting levels of reactivators E2 #2 #3 #4 ERn coi-ji-retj.iiH Male fish living near municipal sewage outlets in England had both male and female sex characteristics and their livers produced vitellogenin, a female egg-yolk protein not normally found in males t> cancers of the female and male reproductive tract ► malformed Fallopian tubes, uterus and cervix c> altered bone density and structure <> abnormal blood hormone levels o reduced fertility o altered sexual behavior modified immune system Biosynteza steroidnich hormonu a endokrinni disrupce: HO HO I 7(it-OH-Prcgncncbnc Cholesterol iC holesTera I side-chain cleavage Pregnenolone Progesterone Androgens A Testosterone -Estrogens I_I (+ Progesterone) Gonadal steroids I 7(Ji-OH-Progestcrcnc Cortisol I_ Corti oostcno ne Aldosterone _I Adrenal steroids In vitro model: buňky H295R Buněčná linie odvozená od karcinomu kůry nadledvinek, která je schopna in vitro produkovat většinu steroidogenních enzymů: • aktivita enzymů; • exprese enzymů na úrovni mRNAa proteinu (A) cholesterol i CYP17 C Y PI 7 pregnenolone-► I 7-OH-pregnenolone-dehydroepiíindrostercne ,Sm>2' ■■■ (DHEA) CYPI7 if \ progesterone-^ 17-OH-pre geste tone androstciicdione S> Ul ** O j« o <•> o -r-1--1-1- h4 - Tp * * B □ □ ■n 100- O go- I 150-, I 1 S 10 concentration of test substances (mm) mety r apone l "I MeSO^- D DE ketoconazoie o £ 100' o o o 50- fi concentration of test substances (log Ml ■ metyrapone * ketocona^ole Effects of test substances on Cortisol and 11-deoxycortisol formation in H295R cells, assumed to represent CYP11B and CYP21 activity. 300 FIG. 2. Effect of 4-hydroxyandrostenedione (4-HA; 1 jliM), DDT, three of its metabolites (1 or 10 (jlM) or 8-bromo-eyclic adenosine monophosphate (SBr-cAMP: 300 jllM) on aromatase activity in H295R cells. Exposures were for 24 h, in quadruplicate, * Significantly lower than control. Testy estrogenity a antiestrogenity In vitro assav Measured endnoint Ad van Ui »es IJ m i tali o tis ľ-Sc reen Ligand-bindina (EDSTAC)a E R-binding lo l:Rľ GST pull-down/ľRET/ (wo-hybrid assay Transticth atii m assav in yeast or mammalian cells (EDSTAC )a Analysis of gene expression Analysis of enzyme activity Analysis of steroidogenesis (EDSTAC)a Proliferation of I!Rot-positive cells Binding affinity to ERct or ERß Rinding tiffin ity of Era or ERßMo ERL Ligand-dependent association of I IRct or ERß with co-activators I: Rot or ERß med i tue d activation of reporter Expression of ER-regulafced genes Activity of ER-regúl tiled enzvmes Induction/inhibition of estroaen biosvnthesis Measures physiologic til endpoinl of estrogen action, measures estrogens and ant iestro gens Simple, high-throughput method 11 igh-throughput method, various I í R lis can be used Analysis of molecular interaction, defined ER subtype or ER domain as well as co-activators can be used, measures estrogens and antiestro-gens 11 igh-throughput method, measures estrogens and anliestrogens, can be done in metabolic competent cells to account for (anti)-estrogenic metabolites Analysis of physiological response, versatile, measures estrogens and anfie Strogen s Analysis of physiological response, measures estrogens and anliestrogens Analysis of physiological response, measures ER-independent pathways No defined ER expression, no mechanistic data Does not measure ER activation, does not measure physiological response Does not measure ER activation, low sensitivity, does not measure physiological response Does not measure direct ER activation, low throughput, does not measure physiological response Does not measure physiological response Low throughput Cell lines or primary cell cultures with active marker enzymes suitable only Cells with active steroido-Qenesis suitable onlv Anti-androgenic compounds in the environment There are a number of commonly used environmental chemicals that have been identified as having anti-androgenic properties. These chemicals have been administered to pregnant rodents during the period of reproductive tract development. When the male pups were examined, they displayed many of the abnormalities associated with flutamide administration. Some chemicals (vinclozolin, procymidone, linuron, p,p'-DDE (1,1,1-dichloro-2,2-bis(pchlorophenyl)ethane) act as androgen receptor antagonists, others (phthalate esters) reduce androgen synthesis, but it is likely that other modes of action are also involved in the toxicity induced by these compounds. There are major problems in comparing the published studies of the effects of anti-androgenic compounds / inconsistent protocols. Human impact???? Polycyklické aromatické uhlovodíky mají anti- androgenní účinek: Antiandrogenní účinky PCB: Interakce polutantů s endokrinní dráhou = velmi složitý proces: * i STEROIDOGENESIS PCDD/Fs, COPLANAR AND MONO-ORTHO-CHLORINATED PCBs A CYP1A1 CYP1A2 CYP1B1 ENHANCED METABOLISM LEADING TO DECREASED CONCENTRATIONS OF ESTROGENS IN BLOOD ANTIESTROGENICITY MEDIATED THROUGH DIRECT INTERACTIONS OF THE AhR WITH iDRE, COMPETITION OF AhR WITH ER FOR COFACTORS, INDUCTION OF INHIBITORY FACTORS OR INDUCTION OF ER DEGRADATION NONCOPLANAR PCBs ANTIESTROGENICITY MEDIATED THROUGH DIRECT SUPRESSION OF ER ACTIVATION Efekty spojené s deregulací hladiny retinoidů: • Funkce RA; • Vznik končetin; • Vývoj nervové soustavy; • Vývojové abnormality obojživelníků; • Narušení hladin vitaminu A; ^ľ"^ 3,4-didehydro-RA Struktura a syntéza kyseliny retinové 3,4-didehydro-retinol 14-hydroxy-reíro-retingl -Q-l 4 18 retinol retiny! palmitate ^^^^^^^^^^^ retina) KIC. 3. Absorption. distribution, and tnclabolism of nal occuning íolinoids. urally 9,13-di-ris-RA FIC. 2. Structures of na t urally occuning rotinoids. A : B c D : E i F Transcriptional activation DNA Hinge ■ Ligand-binding domains (AF-1) binding region ■ Helerodimerization : 1 domain : Transcription activation (AF-2) (RARE) j N-Cor?SMRT binding domains B Early response genes Secondary response genes Gene product (e.g. transcription factors STATs, RARs, c/EBP, etc.) Inhibition of cell growth, Induction of differentiation, apo ptosis Fig. 1 - Structure and functions of retinoid receptors. A) Schematic representation of retinoid receptor protein depicting various functional domains. B) A molecular model for retinoid action. The liganded RAR forms heterodimer with RXR, binds to specific regulatory sequences (RARE) in the promoter region of target genes. Transactivation of such early response genes is a primary event of retinoid action. In addition to this, the products of early response genes can activate the transcription of secondary genes. Transactivation of these genes therefore represents secondary action of retinoids since their transcription requires protein synthesis. This cascade of ie events leads to secondary and tertiary events that eventually produce a phenotype that is characteristic of retinoid action. RA a vývojové poruchy •Abnormalities caused by exogenous agents (certain chemicals or viruses, radiation, or hyperthermia) are called developmental disruptions. The agents responsible for these disruptions are called teratogens. Most teratogens produce their effects only during certain critical periods of development. The most critical time for any organ is when it is growing and forming its structures. Different organs have different critical periods, but the time from period from day 15 through day 60 of gestation is critical for many human organs. • Retinoic acid is important in forming the anterior-posterior axis of the mammalian embryo and also in forming the limbs. In these instances, retinoic acid is secreted from discrete cells and works in a small area. However, if retinoic acid is present in large amounts, cells that normally would not receive such high concentrations of this molecule will respond to it. Inside the developing embryo, vitamin A and 13-c/s-retinoic acid become isomerized to the developmentally active forms of retinoic acid, all-frans-retinoic acid and 9-c/s-retinoic acid. Some of the Hox genes have retinoic acid response elements in their promoters. • In the early 1980s, the drug Accutane® (the trade name for isoretinoin, or 13-c/s-retinoic acid) was introduced as a treatment for severe acne. Women who took this drug during pregnancy had an increased number of spontaneous abortions and children born with a range of birth defects. RA reguluje vznik a vývoj končetin There are discrete positions where limb fields are generated. Researchers have precisely localized the limb fields of many vertebrate species. Interestingly, in all land vertebrates, there are only four limb buds per embryo, and they are always opposite each other with respect to the midline. Although the limbs of different vertebrates differ with respect to which somite level they arise from, their position is constant with respect to the level of Hox gene expression along the anterior-posterior axis. For instance, in fishes (in which the pectoral and pelvic fins correspond to the anterior and posterior limbs, respectively), amphibians, birds, and mammals, the forelimb buds are found at the most anterior expression region of Hoxc-6, the position of the first thoracic vertebra. Retinoic acid appears to be critical for the initiation of limb bud outgrowth, since blocking the synthesis of retinoic acid with certain drugs prevents limb bud initiation, suggested that a gradient of retinoic acid along the anterior-posterior axis might activate certain homeotic genes in particular cells and thereby specify them to become included in the limb field. ^egs regenerating from retinoic acid-treated tadpole tail. (A) The tail of a balloon frog tadpole treated with retinoic acid after mputation will form limbs from the amputation site. (B) Normal tail generation in a Rana temporaries tadpole 4 weeks after amputation. A all neural tube can be seen above a large notochord, and the muscles are arranged in packets. No cartilage or bone is present. (C) A retinoic acid-treated tadpole tail makes limb buds (arrows) as well as pelvic cartilage and bone. The cartilaginous rudiment of the femur can be seen the right limb bud. dorsal view aide visw dorsal view s'ide view I Expression domains of Hox genes in a mouse. The photographs show whole embryos displaying the expression domains of two genes of the HoxB complex (blue stain). These domains can be revealed by in situ hybridization or, as in these examples, by constructing transgenic mice containing the control sequence of a Hox gene coupled to a LacZ 7\ reporter gene, whose product is detected histochemically. Each gene is "J expressed in a long expanse of tissue with a sharply defined anterior 'llimit. The earlier the position of the gene in its chromosomal complex, nthe more anterior the anatomical limit of its expression. Thus, with minor (■exceptions, the anatomical domains of the successive genes form a nested set, ordered according to the ordering of the genes in the chromosomal complex. A (A) Teratogenesis in frogs. (A) Wild green frog {Rana clamitans) with an eye deformity, collected in New Hampshire in 1999 by K. Babbitt. (B) Xenopus tadpole with eye deformities caused by incubating newly fertilized eggs in water containing methoprenic acid, a by-product of methoprene. (C) One of several pathways by which methoprene can decay into teratogenic compounds such as methoprenic acid. (D) An isomer of retinoic acid showing the structural similarities to methoprenic acid. RA reguluje vývoj CNS Top panel: At left, retinoic acid activates gene expression in a subset of cells in the normal developing forebrain of a midgestation mouse embryo (blue areas indicate p-galactosidase reaction product, an indicator of gene expression in this experiment); at right, after maternal ingestion of a small quantity of retinoic acid (0.00025 mg/g of maternal weight), gene expression is ectopically activated throughout the forebrain. Bottom panel: At left, the brain of a normal mouse at term; at right, the grossly abnormal brain of a mouse whose mother ingested this same amount of retinoic acid at mid-gestation. PHAHs a PAHs narušují funkci a strukturu štítné žlázy a hladiny thyroidních hormonů a retinoidů 3.3,4ř4H,5-pentaCB CH2QH I3C Figw 'e 5 2 3 J* 8 -Td r a c h I or o di benzo-p - dioxin (TC DD) and related comp oun d s that b ind to the Ah R. PHAHs modulují hladiny retinoidů - mobilizace zásob vitaminu A v játrech o O o e (0 o. ÍD X 300 250 200 - 150 •2 100 50 - X _ Vi.J i - |b 1«: Ilji <>-•:■ í Dams Fetus ■:::::í X. £:::::r:":4 JS. T í.- : : I ■■.■.+.v;- -> i -ní - - i r Male Female Male Female GD20 PND21 PND90 FIG. 3. Hepatic retinol concentrations, expressed as percentage of control values, mean ± SEM, from dams, their fetuses (jV = 6), male and female neonates (A' = 8-10), and adult offspring {N = 10) following maternal exposure to 0 □, 5 M, or 25 □ mg Aroclor 1254/kg on Days 10-16 of gestation. *lndicates a significant difference from controls, p < 0.05. GD20, Gestation Day 20; PND21, Postnatal Day 21; PND90, Postnatal Day 90. BPA moduluje hladiny retinoidních receptoru v průběhu embryogenéze - myši ochs o.p'.rjDT OH p-Alkylphenols □CH3 p,p'-Methoxychlor OH Bisphenol-A Diethyl st i I bestrol ^C02(CH2}jCH3 Benzyl butyl p h t hal ate Figure 2 Structures of some xen oestrogen s. Funkce thyroidních hormonů v ontogenezi a vliv organických polutantů: • Funkce thyroidních hormonů v metamorfóze • Funkce thyroidních hormonů ve vývoji nervové soustavy; Hypotéza - environmentálni polutanty jako kauzální faktor neurologických poruch (autismus, poruchy učení, hyperaktivita, nádorová onemocnění, juvenilní formy diabetes); T3 a T4 mají zásadní význam pro iniciaci metamorfózy obojživelníků Fig, 1. Schematic representation of the hormonal regulation of amphibian metamorphosis. In response to environmental cues, the dormant thyroid gland of the tadpole is activated to produce the thyroid hormones T4 and by the hypothalamic and pituitary hormones TR1\ CRF and TSH. Thyroid hormone (TH) is obligatorily required to initiate and maintain the metamorphosis, its action being potentiated by giucocortieoid hormone and retarded by prolactin. Nutr., nutritional factors; TE^IL thyrorrophin-reieasing hormone; CRF, cortcotrophin-releasing factor; TSEh thyoid-stimulating hormone; T4, l-thyroxine; T3, ľriíodo-l-thyroníne; GC, glucocorticoid hormone. T3 a T4 mají zásadní význam pro iniciaci metamorfózy obojživelníků ^ Table 1 Diversity of morphological and biochemical responses to thyroid hormone during amphibian metamorphosis Tissue Response Morphologic;) I Biochemical I? rain Liver Eye Skin Limb bud, lung Tail, gills f, pancreas system Restructuring; axon guidance and growth; ceil lu mover Functional differentiation; restructuring Repositioning; new retinal neurones; altered lens Restructuring; keratinisation; granular gland formation De novo morphogenesis of bone, skin, muscle, nerve, etc. Total tissue regression and removal Major remodelling of tissues Redistribution of immune cell populations Growth, differentiation, apoptosis i elJ division; apoptosis; protein synthesis Induction of albumin and urea cycle enzymes; larval-adult haemoglobin switch Visual pigment switch; induction of pVcrystallin Induction of collagen, 63 kDa keratin, magainin Cell proliferation; gene expression Programmed cell death; induction of lytic enzymes New structural and functional constituents Aquisition of new immunocompetencc Induction of myosin heavy chain Conception 12 woeks 24 WGeks Birth 4 weeks Hypothalamus 6 weeks Cochlea 1 & weeks 7 weeks Hippocampus 5 weeks Synaptogenesis, myelinogenesis, gliogenesis 7 weeks Sexual differentiations—urogenitalia Figure 1. Role of thyroid hormones in fetal neurologic development in relation to timing of several landmark stages of development. Figure adapted from Howdeshell (2002), Možné mechanismy disrupce funkce thyroidních hormonů • Inhibition of active transport of inorganic iodide into the follicular cell • Interference with the sodium/iodide transporter system • Inhibition of thyroid peroxidases to convert inorganic iodide into organic iodide to couple iodinated tyrosyl moieties into thyroid hormone • Damage to follicular cells • Inhibition or enhancement of thyroid hormone release into the blood • Inhibition or activation of the conversion of T4 to T3 by 5'-monodeiodinase at various sites in the body, for example, the fetal brain • Enhancement or interference of the metabolism and excretion of thyroid hormone by liver uridine diphosphate • Interference with transport of thyroid hormones • Vitamin A (retinol) disturbances • Blocking of or interfering with thyroid receptors Možné mechanismy disrupce funkce thyroidních hormonů The complexity of the development of both the neurologic and thyroid systems offers numerous opportunities for chemicals to interfere as the systems develop, mature, and function. Briefly, there are chemicals that interfere with iodine uptake (the herbicides 2,4-D and mancozeb, several PCB congeners, and thiocyanates) and peroxidation at the molecular level (the herbicides aminotriazole and thioureas, the insecticides endosulfan and malathion, and PCBs). They also interfere with the protein transporter that provides a pathway for iodine to enter the cell (military and aerospace chemicals, perchlorates). Certain antagonists (PCBs, the herbicides aminotriazole and dimethoate, and the insecticide fenvalerate) prevent the release of thyroid hormone from the cell and inhibit conversion of T4 to triiodothyronine (T3). Various chemicals enhance excessive excretion of thyroid hormones, some through activation of the cytochrome P450 system (dioxin, hexachlorobenzene, and fenvalerate). Some PCBs, phthalates, and other widely used chemicals compete for sites on the thyroid transport proteins that deliver thyroid hormones throughout the body New research focuses on the role of chemicals as they interfere with vitamin A (retinols). Hydroxylovane PCB During normal enzyme detoxification of PCBs in the maternal liver, certain PCB congeners are hydroxylated. This metabolic step enhances the binding affinity of the hydroxylated PCBs to TTR. Through their high-affinity binding the hydroxylated congeners displace essential fT4 that must get to the fetal brain to be converted to fT3. Hydroxylated PCBs also interfere with the normal excretion of thyroid hormones by inhibiting their sulfation. PCB hydroxylates also have estrogenic and antithyroid properties. 4-OII-PCB107 Thyroidní disrupce u volně žijících obratlovců: Obojživelníci Gutleb and co-workers did a series of exposure studies with Xenopus laevis and Rana temporaria. They found increased incidence of mortality in tadpoles weeks after they ceased dosing the animals. Over an 80-day period, 47.5% of the tadpoles died. The X. laevis exposed to 7.7 pM and 0.64 nM PCB 126 exhibited swimming disorders prior to death. Both increased mortality and reduced T4 concentrations occurred in a dose-response manner in X. laevis. Severe eye and tail malformations increased in the froglets in a dose-response manner after approximately 60-68 days. Ptáci Thyroid hormones in birds have been investigated for their role in migration and courtship. Preventing migrating species from breeding out of season is especially critical for their survival. From the 1950s through to the 1970s, fish-eating birds in the Great Lakes were experiencing very poor reproductive success. Keith suggested that the high embryo mortality and low chick survival in herring gulls nesting in upper Green Bay in the mid 1960s was both the result of a) the effects of the chemical residues from the mother on the embryo and b) the effects of the adult's contamination on its parental behavior. Thyroidní disrupce u volně žijících obratlovců: Ryby Migration of salmonids is linked with THs effecting a sequence of behaviors. In the laboratory, increases in T4 led to less display of aggressive behavior such as territoriality. Elevated concentrations of both T3 and T4 reduced the fishes' preference for shade to more open areas (phototaxis). T3 treatment caused the fish to swim with the current rather than against the flow (rheotaxis). Savci PCBs and dioxins have been shown to alter thyroid function in rodents by multiple mechanisms, including direct toxic effects on the thyroid gland, induction of thyroid hormone metabolism via the UDP-glucuronyl transferases, and interactions with thyroid hormone plasma transport proteins, particularly transthyretin. A number of investigators have evaluated the effects of maternal PCB exposure on thyroid function of rat pups. Pup serum thyroxine (T4) levels are markedly reduced by PCB or dioxin exposure, but the levels of the active form of the hormone, triiodothyronine (T3), are generally unchanged, or only slightly reduced. Deregulace PPAR a reprodukce PPAR a karcinogenita Li gand - independ ent activation domain (AF-1) I DBD DNA Binding Domain (2 zinc fingers) Li gand -depe ndent activation domain (AF-2) LBD-Dim. Ligand Binding and Dimerization Domains Ligand a "^*\ ^ 9-ci'j-retinoicacid [PPAR Y RXR ] I—' AGGTCANAGGTCA TCCAGTNTCCAGT er Ciglitazone XX w (t p KU Pioglita/.üiic ch, Troglitazone CT « Rosiglitazone FKi. 1. General structure anil mechanism of action of PPAlls, PPAR isoforms share a c<> in m on do in a in structure and molecular mechanism of action. Membrane phospholipids Phospho lipase A2 Arachidomc acid Linoieic acid OxLDL Cycloxygenase Lipoxygenases Lipoxygenases 15-deoxy PG-J2 LTB4, 8-HETE, 15-HETE 9-HODE, 13-HODE COjH linoieic acid 15^eoxy-Alil4-PGJ2 "C02H HO 9-HODE COjH eicosapentaenoic acid /—CO,H H /— 0H 8(S)-HETE 'C02H OH 13-H0DE Ftaláty jako Ugandy PPAR Mo no ethyl í M EP) M onobutyl í M BP) M on ope ntyl (M PPi O Figure 1. Structurally related phthalate monoesters. Diesters of o-phthalic acid are quickly metabolized in vivo to their active metabolites, the monesters. The length and structure of the side chain is important for toxicity. Ftalaty jako ligandy PPAR TABLE 1 Siimmmy of E fleets of in Utero Exposure to Phthalates on the Developing Male Reproductive Tract E nd poi n I me asu red" DBP DEHP BBP D1NP Testis i Weight 1 1 1 - Sperm number l l l Degeneration/atrophy of l l l seminiferous tubules Leydi^cell hyperplasia/aggregates l l l Leydigcell adenoma 1 1 Cryplorchidi sm l l l x organs Epididymis: ... wt, agenesis/malformed l l l - Penis: delayed/incomplete preputial 1 1 1 - separation, hypospadias, . wlofglans Prostate: ... wt, agenesis l l l - Seminal vesicle: ... wt 1 1 1 — Vasdeferens: ... wt, malformed/agenesis +■ iscellaneous Anogenilal distance (...) l l l I Nipple retention 1 1 1 ER:ER B ERE Phthakues | RX R Up- or down-regulation Rc