BEHAVIORAL AND NEURAL EFFECTS IN QUAIL EXPOSED TO XENOESTROGENS DURING EMBRYONIC DEVELOPMENT

Size: px

Start display at page:

Download "BEHAVIORAL AND NEURAL EFFECTS IN QUAIL EXPOSED TO XENOESTROGENS DURING EMBRYONIC DEVELOPMENT"

Felix West
5 years ago
Views:

1 BEHAVIORAL AND NEURAL EFFECTS IN QUAIL EXPOSED TO XENOESTROGENS DURING EMBRYONIC DEVELOPMENT Panzica G.C.*, Mura E., Viglietti-Panzica C.* UNIVERSITY OF TORINO, ITALY Dept. Anatomy, Pharmacology and Forensic Medicine *NIT, INN, GRIDES

Belgium) Mary Ann Ottinger (College Park, USA) Supported by

2 ACKNOWLEDGEMENTS These studies have been performed with the support of other research groups Jacques Balthazart (Liege, Belgium) Mary Ann Ottinger (College Park, USA) Supported by Regione Piemonte, Fondazione CRT, and University of Torino

Hormones and Brain Gonadal, adrenal, and thyroid hormones affect the brain directly through hormone receptors located in discrete populations of neurons.

3 Hormones and Brain Gonadal, adrenal, and thyroid hormones affect the brain directly through hormone receptors located in discrete populations of neurons. The secretion of hormones is also under the control of neural and pituitary factors. Therefore the brain-endocrine axis has a delicately balanced state that can be altered in various ways, and any agent that interfere with normal hormone secretion can alter brain functions.

4 Gender differences in the brain Gender differences are present in the brain of all vertebrates: Differences in gross anatomy Differences in the volume of brain nuclei Differences in neural connectivity Differences in cell size or shape Differences in enzyme expression, in neurotrasmitters and neuropeptides Sexually dimorphic circuits may be related or not to the control of sexually dimorphic functions

5 Brain Sexual Differentiation Brain sexually dimorphic circuits and functions are organized during the embryonic period (in birds) or immediately after birth (in mammals). Alterations of hormonal balance during this period generally result in permanent alterations of neural circuits and of related functions, including behavior. This phase of the development is defined critical period. The critical period is specie-specific and hormonespecific.

6 Endocrine disrupting chemicals (EDCs) can interact with living beings during all the phases of the life. Panzica et al., 2007 During embryonic or early postnatal life they can, in particular, interfere with the mechanisms leading to brain sexual differentiation Alteration of brain sexual differentiation may heavily impact development of neural circuits controlling several behaviors, in particular those involved in the control of reproduction and social behaviors

7 BRAIN EFFECTS OF EDCs Several nervous circuitries in vertebrates are affected by precocious exposure to EDCs : The rat SDN-POA The hippocampus The catecholaminergic system (Locus coeruleus, AVPV) Several peptidergic circuits These effects may explain functional alterations that have been observed in animals exposed to EDCs during development.

8 Animal models Several studies investigated cellular effects of EDCs in in vitro systems or in lower vertebrates. In recent years, several laboratories, including our, started to investigate the effects of precocious exposure to EDCs on both behavior and neural circuits in higher vertebrates. In particular, we used two different experimental approaches for birds and mammals, trying to mimic the real mode of exposure to EDCs that may happens during pre- and postnatal development.

9 CRITICAL PERIOD FOR SEXUAL DIFFERENTIATION OF BEHAVIOR IN BIRDS Exogenous Estradiol or Testosterone administered during embryonic critical period (before day 12) irreversibly destroy male copulatory behavior

10 THE SEXUALLY DIMORPHIC PARVOCELLULAR VT SYSTEM Panzica et al BST and POM project to Lateral Septum, in addition POM is projecting to several brainstem regions showing sexually dimorphic AVT innervation

These effects are in parallel with irreversible effects on the differentiation

11 Embryonic administration of E2 demasculinizes the male VT system Embryonic administration of an inhibitor of aromatase masculinizes the female VT system These effects are in parallel with irreversible effects on the differentiation of male copulatory behavior 24th Conference of European Comparative Endocrinologists

12 VASOTOCIN AND CONTROL OF REPRODUCTION IN JAPANESE QUAIL AVT is found in regions related to the control of sexual activities (POM controlling male copulatory behavior) Balthazart et al., 1997 AVT-ir fibers are found in close contact with aromatase-ir and GnRH-ir elements Panzica et al., 1999 AVT i.cv. administration inhibits male copulatory behavior Castagna et al., 1998 AVT parvocellular sexually dimorphic system is under the control of estradiol for its differentiation during the embryonic life and expression in the adult Panzica et al., 1998 The sexually dimorphic AVT system in quail may therefore represent a model to test the estrogenic activity of pollutants that affect male quail sexual behavior Panzica et al., 2002

13 XENOESTROGENS AND AVT The paradigm is that xenoestrogens may alter the animal physiology through their binding to estrogen receptor. In quail model this means that a xenoestrogen administered during embryonic life, should reduce or abolish male copulatory behavior and interfere with the differentiation of the AVT system

14 EXPERIMENTAL PROCEDURE Behavioral tests Injection Hatching sacrifice 3 17 Incubation day Postnatal weeks 7 8

15 We used three compounds Diethylstilbestrol (DES), a synthetic compound, formerly used as an abortion preventing agent, which is now present as a pollutant in the environment. DES Genistein, a phytoestrogen found in the soy. It binds mainly to ERbeta DES GENISTEIN Ethylene,1,1-dichloro-2,2-bis-pchlorophenyl (DDE) a metabolite of DDT with antiandrogenic action DDE

16 Effects of EDCs on Male copulatory behavior Viglietti Panzica et al, 2005 Viglietti Panzica et al, 2007 Mura et al, submitted Embryonic treatments with DES, Genistein or DDE significantly decrease male copulatory behavior

17 Viglietti Panzica et al, 2005 Viglietti Panzica et al, 2007 Mura et al, submitted Effects of EDCs on VT system

18 * ERα * BST * * * ERβ * * * * * BST * * * * * VT * * * VT X E 2 DES GEN DDE POM POM X MALE COPULATORY BEHAVIOR MALE COPULATORY BEHAVIOR

19 Summary The sexually dimorphic AVT-parvocellular system is very sensitive, during embryonic development, to xenoestrogens Anatomical alterations of this system are parallel to the alteration of the male copulatory behavior Both indicators are, therefore, very useful to detect estrogenic potentialities in different types of putative endocrine disruptors XE may deeply interfere with the organization and differentiation of that parts of the central nervous system that are organizing at the time of exposure and of the related behaviors

20 CONCLUSIONS In the majority of studies involving high vertebrates and xenoestrogens (XE) the doses were very high and the administration route largely artificial (i.e. intraperitoneal injection) Our studies demonstrated that XE may interfere with the differentiation of the central nervous system, even when they are administered at levels comparable to the environmental doses and through more natural routes, as accumulation within the eggs (quails) or treatments of the mothers (mice). Limited exposure and low doses may result in alterations of neural circuits that profoundly impact reproduction or social behavior, as the NO-circuits (involved in the regulation of dopamine system), the kisspeptin system and the vasotocin system of birds Data collected in our and other laboratories should stimulate a critical reanalysis of the way to determine the safe exposure levels to EDCs for wild species as well as for human, considering among the factors to be analyzed the behavior and related neural circuits.

Deadline December 15th 5th International Meeting on STEROIDS AND NERVOUS SYSTEM Torino (Italy) February 13-18 2009

21 Deadline December 15th 5th International Meeting on STEROIDS AND NERVOUS SYSTEM Torino (Italy) February Organizers GC Panzica (Torino) RC Melcangi (Milano)

22 QuickTime e un decompressore sono necessari per visualizzare quest'immagine. ERα ERβ 17th day old embryos alpha beta Different expression of ERα and β in quail embryo. ERβ is more expressed than ERα

β-receptor is largely diffused within these nuclei during the embryonic

development. PPT is an agonist of a-receptor.

23 Estrogen Receptor Alpha or Beta? Two estrogen receptors (α and β) are present in BST, SL and POM β-receptor is largely diffused within these nuclei during the embryonic life, whereas α- receptor appears only later at the end of the development. PPT is an agonist of a-receptor. Quail embryos exposed to PPT don t have alterations of both sexual behavior and VTimmunoreactivity CONTROL PPT EE2 EE2 is an agonist for both receptors

24 THE RAT VASOPRESSIN SYSTEM The The parvocellular system system of of SCN SCN is is not not sexually dimorphic and and sends sends axons axons to to telencephalic and and thalamic regions regions The The parvocellular system system of of BST BST and and MA MA is is sexually dimorphic and and sends sends axons axons to to several several extrahypothalamic regions regions including the the lateral lateral septum, the the hippocampus and and the the brainstem BST PVN The The magnocellular system system (PVN (PVN and and SON) SON) sends sends axons axons to to the the neurohypophysis SCN SON MA

THE RAT VASOPRESSIN SYSTEM MALE FEMALE + T

1985 MA VP-ir VP-irneurons and and fibers

than than in in females females even even if

25 THE RAT VASOPRESSIN SYSTEM MALE FEMALE + T MALE FEMALE + T BST De Vries et al MA VP-ir VP-irneurons and and fibers fibers are are denser denser in in males males than than in in females females even even if if females females are are treated treated with with T in in adulthood. This This sex sex dimorphism can can be be reversed by by early early postnatal treatments.

26 VASOTOCIN AND CONTROL OF REPRODUCTION AVT is found in regions related to the control of sexual activities (POM controlling male copulatory behavior) AVT-ir fibers are found in close contact with aromatase-ir and GnRH-ir elements AVT i.cv. administration inhibits male copulatory behavior

27 BSTm and POM neurons project to SL in quail Post-mortem DiI in SL retrogradely labels BSTm and POM neurons Balthazart et al., 1994

28 VASOTOCIN AND CONTROL OF REPRODUCTION AVT is found in regions related to the control of sexual activities (POM controlling male copulatory behavior) AVT-ir fibers are found in close contact with aromatase-ir and GnRH-ir elements AVT i.cv. administration inhibits male copulatory behavior

29 Aromatase-producing neurons Balthazart et al., 1997 GnRH-I producing elements Panzica et al., 1999

30 VASOTOCIN AND CONTROL OF REPRODUCTION AVT is found in regions related to the control of sexual activities (POM controlling male copulatory behavior) AVT-ir fibers are found in close contact with aromatase-ir and GnRH-ir elements AVT i.cv. administration inhibits male copulatory behavior

stimulates male prevents the VT-induced inhibition of sexual behavior

31 AVT and COPULATORY BEHAVIOR Central administration of AVT inhibits male copulatory behavior Administration of AVT receptor antagonist stimulates male copulatory behavior Administration of AVT receptor antagonist prevents the VT-induced inhibition of sexual behavior Castagna et al. 1998

32 THE SEXUALLY DIMORPHIC PARVOCELLULAR VASOTOCIN SYSTEM OF THE JAPANESE QUAIL EFFECTS OF GONADAL STEROIDS In the adult male the expression of AVT-ir elements and AVT mrna is under the control of Testosterone (T) or its estrogenic metabolite Estradiol (E2) Sexual differentiation of AVT system is dependent by the absence of E2 during the embryonic development

The Sexually Dimorphic Medial Preoptic Nucleus of Quail: A Key Brain Area Mediating Steroid Action on Male Sexual Behavior

FRONTIERS IN NEUROENDOCRINOLOGY 17, 51 125 (1996) Article No. 0002 The Sexually Dimorphic Medial Preoptic Nucleus of Quail: A Key Brain Area Mediating Steroid Action on Male Sexual Behavior GIAN CARLO