Perinatal exposure to octabromodiphenyl ether mixture, DE-79, alters the vasopressinergic system in adult rats.

Polybrominated diphenyl ethers (PBDEs) are persistent environmental pollutants considered as neurotoxicants and endocrine disruptors with important biological effects ranging from alterations in growth, reproduction, and effects on the hypothalamus-pituitary-adrenal axis. The vasopressinergic (AVPergic) system is a known target for pentaBDEs mixture (DE-71) and the structurally similar chemicals, polychlorinated biphenyls. However, the potential adverse effects of mixtures containing octaBDE compounds, like DE-79, on the AVPergic system are still unknown. The present study aims to examine the effects of perinatal DE-79 exposure on the AVPergic system. Dams were dosed from gestational day 6 to postnatal day 21 at doses of 0 (control), 1.7 (low) or 10.2 (high) mg/kg/day, and male offspring from all doses at 3-months-old were subjected to normosmotic and hyperosmotic challenge. Male offspring where later assessed for alterations in osmoregulation (i.e. serum osmolality and systemic vasopressin release), and both vasopressin immunoreactivity (AVP-IR) and gene expression in the hypothalamic paraventricular and supraoptic nuclei. Additionally, to elucidate a possible mechanism for the effects of DE-79 on the AVPergic system, both neuronal nitric oxide synthase immunoreactivity (nNOS-IR) and mRNA expression were investigated in the same hypothalamic nuclei. The results showed that perinatal DE-79 exposure AVP-IR, mRNA expression and systemic release in adulthood under normosmotic conditions and more evidently under hyperosmotic stimulation. nNOS-IR and mRNA expression were also affected in the same nuclei. Since NO is an AVP regulator, we propose that disturbances in NO could be a mechanism underlying the AVPergic system disruption following perinatal DE-79 exposure leading to osmoregulation deficits.

Perinatal exposure to organohalogen pollutants decreases vasopressin content and its mRNA expression in magnocellular neuroendocrine cells activated by osmotic stress in adult rats.

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are environmental pollutants that produce neurotoxicity and neuroendocrine disruption. They affect the vasopressinergic system but their disruptive mechanisms are not well understood. Our group reported that rats perinatally exposed to Aroclor-1254 (A1254) and DE-71 (commercial mixtures of PCBs and PBDEs) decrease somatodendritic vasopressin (AVP) release while increasing plasma AVP responses to osmotic activation, potentially emptying AVP reserves required for body-water balance. The aim of this research was to evaluate the effects of perinatal exposure to A1254 or DE-71 (30mgkg/day) on AVP transcription and protein content in the paraventricular and supraoptic hypothalamic nuclei, of male and female rats, by in situ hybridization and immunohistochemistry. cFOS mRNA expression was evaluated in order to determine neuroendocrine cells activation due to osmotic stimulation. Animal groups were: vehicle (control); exposed to either A1254 or DE-71; both, control and exposed, subjected to osmotic challenge. The results confirmed a physiological increase in AVP-immunoreactivity (AVP-IR) and gene expression in response to osmotic challenge as reported elsewhere. In contrast, the exposed groups did not show this response to osmotic activation, they showed significant reduction in AVP-IR neurons, and AVP mRNA expression as compared to the hyperosmotic controls. cFOS mRNA expression increased in A1254 dehydrated groups, suggesting that the AVP-IR decrease was not due to a lack of the response to the osmotic activation. Therefore, A1254 may interfere with the activation of AVP mRNA transcript levels and protein, causing a central dysfunction of vasopressinergic system.

Perinatal exposure to Aroclor 1254 disrupts thyrotropin-releasing hormone mRNA expression in the paraventricular nucleus of male and female rats.

Polychlorinated biphenyls (PCBs) are industrial pollutants that act as endocrine disruptors and alter thyroid function. However, it is still unclear whether PCBs can affect hypothalamic thyrotropin releasing hormone (Trh) mRNA expression through TH signaling disruption. As salt-loading dehydration induces tertiary hypothyroidism in the hypothalamic parvocellular paraventricular nuclei (paPVN), and perinatal exposure to Aroclor 1254 (A1254) disrupts the hydric balance in rats, we hypothesized that TRH synthesis could be altered during dehydration in TRH neurons that control the hypothalamic-pituitary-thyroid (HPT) axis activity in rats perinatally exposed to A1254. We examined Trh mRNA expression in the paPVN and the response to salt-loading dehydration (hyperosmotic (hyper) stress) in the progeny of Wistar pregnant rats receiving 0 mg/kg BW (control) or 30 mg/kg BW A1254 daily from gestational days 10-19. Three-month-old offspring were subjected to normosmotic or hyper conditions and Trh mRNA, glucocorticoid receptor (GR) mRNA expression were measured in the PVN by RT-PCR. TRH mRNA and TRH+ neurons were measured in the paPVN by fluorescent in situ hybridization (FISH). As expected, Trh mRNA levels were decreased in the paPVN of male and female rats in the hyper group. Basal Trh mRNA expression and serum TSH were decreased in male rats in the A1254 group. Notably, Trh mRNA levels were further decreased in the paPVN of male and female A1254 + hyper rats, in which the GR mRNA expression was significantly decreased. These results support the hypothesis that perinatal exposure to A1254 results in inadequate adaptive response of the HPT axis in adulthood and contributes to dysregulation of the HPT axis response to salt-loading dehydration.

Origin of thyrotropin-releasing hormone neurons that innervate the tuberomammillary nuclei.

Hypophysiotropic thyrotropin-releasing hormone (TRH) neurons function as metabolic sensors that regulate the thyroid axis and energy homeostasis. Less is known about the role of other hypothalamic TRH neurons. As central administration of TRH decreases food intake and increases histamine in the tuberomammillary nuclei (TMN), and TMN histamine neurons are densely innervated by TRH fibers from an unknown origin, we mapped the location of TRH neurons that project to the TMN. The retrograde tracer, cholera toxin B subunit (CTB), was injected into the TMN E1-E2, E4-E5 subdivisions of adult Sprague-Dawley male rats. TMN projecting neurons were observed in the septum, preoptic area, bed nucleus of the stria terminalis (BNST), perifornical area, anterior paraventricular nucleus, peduncular and tuberal lateral hypothalamus (TuLH), suprachiasmatic nucleus and medial amygdala. However, CTB/pro-TRH178-199 double-labeled cells were only found in the TuLH. The specificity of the retrograde tract-tracing result was confirmed by administering the anterograde tracer, Phaseolus vulgaris leuco-agglutinin (PHAL) into the TuLH. Double-labeled PHAL-pro-TRH boutons were identified in all subdivisions of the TMN. TMN neurons double-labeled for histidine decarboxylase (Hdc)/PHAL, Hdc/Trh receptor (Trhr), and Hdc/Trh. Further confirmation of a TuLH-TRH neuronal projection to the TMN was established in a transgenic mouse that expresses Cre recombinase in TRH-producing cells following microinjection of a Cre recombinase-dependent AAV that expresses mCherry into the TuLH. We conclude that, in rodents, the TRH innervation of TMN originates in part from TRH neurons in the TuLH, and that this TRH population may contribute to regulate energy homeostasis through histamine Trhr-positive neurons of the TMN.

Sex-dependent and -independent regulation of thyrotropin-releasing hormone expression in the hypothalamic dorsomedial nucleus by negative energy balance, exercise, and chronic stress.

The dorsomedial nucleus of the hypothalamus (DMH) is part of the brain circuits that modulate organism responses to the circadian cycle, energy balance, and psychological stress. A large group of thyrotropin-releasing hormone (Trh) neurons is localized in the DMH; they comprise about one third of the DMH neurons that project to the lateral hypothalamus area (LH). We tested their response to various paradigms. In male Wistar rats, food restriction during adulthood, or chronic variable stress (CVS) during adolescence down-regulated adult DMH Trh mRNA levels compared to those in sedentary animals fed ad libitum; two weeks of voluntary wheel running during adulthood enhanced DMH Trh mRNA levels compared to pair-fed rats. Except for their magnitude, female responses to exercise were like those in male rats; in contrast, in female rats CVS did not change DMH Trh mRNA levels. A very strong negative correlation between DMH Trh mRNA levels and serum corticosterone concentration in rats of either sex was lost in CVS rats. CVS canceled the response to food restriction, but not that to exercise in either sex. TRH receptor 1 (Trhr) cells were numerous along the rostro-caudal extent of the medial LH. In either sex, fasting during adulthood reduced DMH Trh mRNA levels, and increased LH Trhr mRNA levels, suggesting fasting may inhibit the activity of TRHDMH->LH neurons. Thus, in Wistar rats DMH Trh mRNA levels are regulated by negative energy balance, exercise and chronic variable stress through sex-dependent and -independent pathways.

Role of nociceptin/orphanin FQ and the pseudopeptide [Phe1Psi(CH2NH)Gly2]-nociceptin(1-13)-NH2 and their interaction with classic opioids in the modulation of thermonociception in the land snail Helix aspersa.

The role in nociception of nociceptin/orphanin FQ (N/OFQ) and its receptor, the opioid receptor-like 1 (NOP), remains unclear because this peptide has been implicated in both suppression and enhancement of nociception. The present work characterises the effects of N/OFQ and the NOP receptor antagonist, the pseudopeptide [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) (Phe(1)Psi), on thermonociception in the snail Helix aspersa using the hot plate assay. Additionally, the possible interaction of each of these compounds with morphine or dynorphin A(1-17) and naloxone was studied. Compounds were administered into the hemocoel cavity of H. aspersa and the latency to the aversive withdrawal behaviour recorded. Dose-response and time course curves were done. N/OFQ and naloxone produced a similar dose-dependent pronociceptive effect; however, N/OFQ reached its peak effect earlier and was 30 times more potent than naloxone. [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) and the opioid agonists, morphine and dynorphin A(1-17) produced antinociception with a similar efficacy, but [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) reached its peak effect more rapidly and lasted longer than that of dynorphin A(1-17) and morphine. [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) was 50 times less potent than dynorphin A(1-17), but 30 times more potent than morphine. N/OFQ significantly reduced morphine and dynorphin A(1-17)-induced antinociception. Combined administration of low doses of [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) and morphine or dynorphin A(1-17) produced a potent antinociceptive effect. Sub-effective doses of naloxone and N/OFQ also synergised to produce pronociception. Data suggest that these two opioid classes regulate nociception through parallel systems. The H. aspersa model appears as a valuable experimental preparation to continue the study of these opioid receptor systems.

Permanently compromised NADPH-diaphorase activity within the osmotically activated supraoptic nucleus after in utero but not adult exposure to Aroclor 1254.

Stimulated vasopressin (VP) release from magnocellular neuroendocrine cells in the supraoptic nucleus (SON) of hyperosmotic rats is inhibited by treatment with the industrial polychlorinated biphenyl (PCB) mixture, Aroclor 1254. Because VP responses to hyperosmotic stimulation are regulated by nitric oxide (NO) signaling, we studied NO synthase (NOS) activity in the SON of hyperosmotic rats as potential target of PCB-induced disruption of neuroendocrine processes necessary for osmoregulation. To examine PCB-induced changes in NOS activity under normosmotic and hyperosmotic conditions, male Sprague-Dawley rats were exposed to Aroclor 1254 (30mg/kg/day) in utero and NADPH-diaphorase (NADPH-d) activity was assessed in SON sections at three ages: postnatal day 10, early adult (3-5 months) or late adult (14-16 months). Hyperosmotic treatment increased mean NADPH-d staining density of oil hyperosmotic controls by 19.9% in early adults and 58% in late adulthood vs normosmotic controls. In utero exposure to PCBs reduced hyperosmotic-induced upregulation of NADPH-d activity to control levels in early adults and by 28% in late adults. Basal NADPH-d was reduced in postnatal rats. Rats receiving PCB exposure as early adults orally for 14 days displayed normal responses. Our findings show that developmental but not adult exposure to PCBs significantly reduces NOS responses to hyperosmolality in neuroendocrine cells. Moreover, reduced NADPH-d activity produced by in utero exposure persisted in stimulated late adult rats concomitant with reduced osmoregulatory capacity vs oil controls (375±9 vs 349±5mOsm/L). These findings suggest that developmental PCBs permanently compromise NOS signaling in the activated neuroendocrine hypothalamus with potential osmoregulatory consequences.

The nociceptin/orphanin FQ-like opioid peptide in nervous periesophageal ganglia of land snail Helix aspersa.

The neuropeptide nociceptin/orphanin FQ (N/OFQ) and its receptor are members of the endogenous opioid peptide family. In mammals N/OFQ modulates a variety of biological functions such as nociception, food intake, endocrine, control of neurotransmitter release, among others. In the molluscs Cepea nemoralis and Helix aspersa the administration of N/OFQ produces a thermopronociceptive effect. However, little is known about its existence and anatomic distribution in invertebrates. The aim of this study was to provide a detailed anatomical distribution of N/OFQ like peptide immunoreactivity (N/OFQ-IL), to quantify the tissue content of this peptide, as well as to demostrate molecular evidence of N/OFQ mRNA in the nervous tissue of periesophageal ganglia of the land snail H. aspersa. Immunohistochemical, immunocytochemical, radioimmunoanalysis (RIA) and reverse transcription-polymerase chain reaction (RT-PCR) techniques were used. With regard to RT-PCR, the primers to detect expression of mRNA transcripts from H. aspersa were derived from the rat N/OFQ opioid peptide. We show a wide distribution of N/OFQ-IL in neurons and fibers in all perioesophageal ganglia, fibers of the neuropile, nerves, periganglionar connective tissue, aortic wall and neurohemal sinuses. The total amount of N/OFQ-IL in the perioesophageal ganglia (7.75 ± 1.75 pmol/g of tissue) quantified by RIA was similar to that found in mouse hypothalamus (10.1 ± 1.6 pmol/g of tissue). In this study, we present molecular evidence of N/OFQ mRNA expression. Some N/OFQ-IL neurons have been identified as neuroendocrine or involved in olfaction, hydro-electrolyte regulation, feeding, and thermonociception. Therefore, we suggest that N/OFQ may participate in these snail functions.

Contaminantes ambientales neurotóxicos cercanos a nuestra vida diaria / Neurotoxic enviromental contaminants near our daily life

Chemical substances play an important role in life quality; they are present in household items and consumer products like furniture, cloths, toys, etc. However some of these substances could be dangerous for health and environment. Among the best known are the organohalogens pollutants like the polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). These substances persist in the enviroment, they bioaccumulate and may cause adverse effects in humans health. There is increasing evidence that organohalogens cause neurotoxicity in rats and human brains during development. We have been studying the neurotoxicity of Aroclor 1254 (PCB mixture) and DE-71 (PBDE mixture) in collaboration with Currás-Collazo team (UC-MEXUS/CONACYT grants). We show in this paper the principal results of our research related with molecules that participate in the osmoregulatory system, learning and memory as vasopressin, PACAP and nitric oxide synthase. We exposed pregnant rats to this organohalogens perinatally; the pups were allowed to grow until three months old for an osmotic challenge. Brains were processed for immunfloures-cence, other group was used to evaluate memory with the passive inhibitory avoidance test and Western-blot was done for presynaptic proteins Synapsin I and Synaptophysin. We found a disruption in the content of VP, PACAP and nNOS suggesting that the PCB and PBDE exposure alter the function of hypothalamic neurons that regulates osmosis and water balance. We demonstrated also that PBDE treatment modifies systolic pressure and plasmatic osmolality compared with controls suggesting a cardiovascular alteration caused by PBDEs. We found an alteration in the nNOS activity in Aroclor-1254 treated rats. Memory test and presynaptic proteins expression showed an important reduction in males, suggesting that PCBs alters the expression and activity of nitric oxide and learning and memory. Therefore, due to the neurotoxicity of the organohalogens and its constant contact with humans there is a big concern about the lack of adequate legislation in Mexico and monitoring programs to evaluate the degree of contamination in the population, especially in infants as well as the regions most affected by such contamination.

Las sustancias químicas son importantes en nuestra calidad de vida; éstas están presentes en artículos domésticos y de consumo humano. Algunas son nocivas para la salud y el medio ambiente, como los contaminantes organohalogenados, los bifenilos policlorinados (PCB) y los éteres difenílicos polibrominados (PBDE). Existe evidencia de su neurotoxicidad en las ratas y los humanos sobre todo cuando la exposición es durante el desarrollo. Nuestro grupo se ha interesado en estudiar la neurotoxicicidad de los PCB y PBDE sobre la regulación del equilibrio hidroelectrolítico, el aprendizaje y la memoria, en colaboración con la doctora Currás-Collazo. En este artículo presentamos los hallazgos principales de estos estudios. Expusimos a ratas gestantes a estos organohalogenados y las crías se estudiaron a los tres meses de edad; se sometieron al modelo de estrés osmótico o a la prueba de aprendizaje y memoria (evitación pasiva). Los cerebros se procesaron para inmunofluorescencia para VP, nNOS, PACAP o histoquímica de la NADPH-d, Western-blot para nNOS y las proteínas presinápticas sinapsina I y sinaptofisina. Nuestros resultados mostraron en las ratas tratadas con los PCB y PBDE sometidas a estrés osmótico alteraciones en el contenido de VP, PACAP y NOS y un incremento en la presión sistólica y la osmolaridad plasmática al compararla con controles, sugiriendo que los PBDE alteran la función cardiovascular y osmorregulatoria. La prueba de aprendizaje mostró una disminución significativa de la adquisición y/o consolidación del aprendizaje y memoria en las ratas macho tratadas y alteraciones en la actividad de la NOS, la expresión de la nNOS y las sinapsina y sinaptofisina, lo que sugiere que la exposición perinatal a los PCB altera el aprendizaje y la memoria. Debido a la neurotoxicidad de los organohalogenados y a que estamos expuestos a ellos en nuestra vida diaria existe una gran preocupación por la falta de una legislación adecuada en México y programas de monitoreo para evaluar el grado de contaminación en la población mexicana especialmente en los infantes, así como las regiones más afectadas por dicha contaminación.

Nitric oxide synthase inhibition during synaptic maturation decreases synapsin I immunoreactivity in rat brain.

During the development of the brain, nitric oxide and synapsins, the latter being phosphoproteins associated to presynaptic membrane vesicles, are abundant in presynaptic terminals and play important and similar roles in neurotransmitter release, morphogenesis, synaptogenesis, and synaptic plasticity. These mechanisms are fundamental for neuronal development and plasticity and constitute important factors for the formation of neuroanatomical structures. Neural nitric oxide synthase (nNOS), synapsin I, and nNOS adapter protein (CAPON) constitute a ternary complex necessary for specific NO and synapsin functions at a presynaptic level. It is not known whether NO absence may affect the presence and/or activity of synapsins during brain development. To understand the role of NO in synaptogenesis, we studied the effects of NOS inhibition on synapsin I expression at a postnatal stage. Rat pups were treated with a competitive NOS antagonist, N-nitro-L-arginine methyl ester, from postnatal days 3 to 23. Control pups received exclusively an equivalent volume of saline solution. Histochemical and immunochemical techniques for NADPH-d and synapsin I, respectively, were carried out. NOS inhibition elicited a significant reduction in synapsin I immunoreactive density and NADPH-d activity in the brain in the analyzed areas-prefrontal cortex, hippocampus, and dorsal thalamus. These data show that the alterations originated by NO and synapsin deficiencies produce a diminution in synaptic density. Thus, functions that depend on the formation of synaptic connections such as learning and memory could be affected by NO deficiency.

Los contaminantes ambientales bifenilos policlorinados (PCB) y sus efectos sobre el Sistema Nervioso y la salud / The polychlorinated biphenyls (PCBS) environmental pollutants and their effects on the Nervous System and health

Environmental pollution is a world-wide issue which is a matter for concern among the international community. Great industrialized cities are the most polluted and Mexico City is among them. However, pollution affects places which are far away from contaminated urban areas, thus damaging eco-systems. Environmental pollution is responsible for an alarming and increasing list of illnesses in humans, animals and plants. This has generated an international interest in this problem. From the 187 chemical agents considered toxic for living organisms, the Inter-Government Committee for the Negotiation of Persistent Organic Pollutants (Pops) has catalogued 12 as the most hazardous for life. Among them are the so-called polychlorinated biphenyls (PCBs). PCBs are a family of 209 structurally chlorinated compounds made up of chlorine, carbon and hydrogen. These compounds are chemically and thermally stable, insoluble in water, non-flammable, electrically resistant, with low volatility at normal temperatures, and bio-degradable only at high temperatures (1200°C). One of their main disadvantages is that they are subject to a process of bioaccumulation where their concentration increases along the food chain. Their physical properties make them widely used in industry, mainly in the electrical and building areas. Not long after PCBs were manufactured, it was determined that food for human intake such as milk, fish and eggs, to mention just a few, presented higher PCBs concentrations than those allowed by the Organism for US Environmental Protection (0.0005mg/l). It has been demonstrated that PCBs can cause damage to the endocrine, immunologic and Nervous Systems, among others. The underlying mechanism of action of these compounds is through the activation of the aril hydrocarbon receptor (AhR), a ligand-dependent cytosolic transcription factor. PCBs act like ligands and, given their lipophilic properties, enter cells by passive diffusion. Two co-chaperone proteins are bound to AhR to form an oligomer which dissociates when binding to a PCB. After ligand binding, a heterodimer is formed which translocates into the nucleus and links to specific DNA regions; this in turn regulates the transcription velocity of specific genes and produces genetic alterations that modify processes and functions in the cell. PCBs belong in the group of chemicals considered endocrine disruptors. Damage caused by these compounds can be irreversible. In the endocrine system they interfere with the production and regulation of steroid and thyroid hormones, acting as agonists or antagonists of hormone receptors. They impair endocrine metabolic pathways, such as those of thyroid hormones (T3 and T4), and inhibit carrier proteins such as transthyretin. Contaminants that harm the endocrine system also affect the reproductive function and disrupt various aspects of sexuality. In males, PCBs inhibit the synthesis of testosterone, alter masculinity, reduce sperm motility and the capacity of binding and penetrating the ovule, induce changes in the shape of the penis as well as its size, retard or inhibit testicle descent, and can generate testicular cancer. In females, they can cause early menarche (first menstruation), enhanced duration of menstrual bleeding, urogenital malformations, endometriosis, spontaneous abortion, fetal death, premature delivery and low-weight in offspring. Our group, as well as other research groups, has encountered that PCB administration to gestating rats causes an increment in offspring mortality, fetal miscarriages, low bodily weight of the offspring and a reduction in the number of males per litter. The immunological system is sensitive to chemicals such as PCBs which originate an immunological response; they act as immunotoxins that cause thymus atrophy, affect innate immunity, compromise host resistance and immunity mediated by B and T cells, as well as humoral immunity. PCBs and their metabolites are carcinogenic and act as general cancer promoters by enhancing the effects of other substances through the generation of oxygen reactive compounds that can induce DNA oxidative damage. Chronic PCB exposure can cause chromosomal aberrations; these compounds have been related to all types of cancer: mammary gland, liver, biliary tract, gastrointestinal, skin (especially malignant melanomas), lung, pancreas and brain. There is evidence that organisms are more vulnerable to PCB exposure during the early embryonic stages. These compounds can cross the placenta and affect the fetus; when they are present in human milk they keep the offspring under high PCB levels thus altering development. In addition, they can contribute to the interruption of growth and development of brain, organs and tissues. As a result, malfunctions or miscarriage occur. PCBs are involved in the neurodegeneration process since they affect dopaminergic neurons in caudate nucleus, ventral tegmental area and substantia nigra. These compounds disrupt neuronal mechanisms such as vesicular transport and dopamine release which lead to cellular death similar to that described for diseases such as Parkinson's. Perinatal exposure to PCBs is associated with neurodevelopmental deficiencies of infants which consist of dysfunctions at the neuropsychological level such as in verbal learning (syllables, words and concepts), performance functions, changes in attention and psychomotor development. Acute or chronic exposure to PCBs is associated with cephalea, insomnia, nervousness, irritability, depression and anxiety; these symptoms in turn modify behavior. At the neurophysiological level, these contaminants impair excitatory and inhibitory synaptic transmission in the hippocampus, inhibit long-term potentiation and synaptic plasticity, alter some mechanisms of cell signaling (GABAergic pathway), and deteriorate learning and memory. Recently, these compounds have been related to cognitive alterations. Our group demonstrated that the administration of PCB-77 and Aroclor 1254 during gestation inhibits the enzymatic activity of nitric oxide synthase (NOS) in 10-day postnatal pups. These rats presented degenerative morphological neuronal changes such as shrinking, picnosis, loss of neurites, neuronal death and decrease in the number of nitrergic neurons in the paraventricular and supraoptic hypothalamic nuclei. We also reported that in these nuclei a decrease in immunoreactivity to vasopressin and neuronal NOS is observed. The evidence in PCB studies is conclusive. The exposure to these environmental toxins interferes with the functioning of various organs and systems such as the endocrine and Nervous Systems, not only in humans but also in animals. These contaminants pose a risk factor for a wide number of neurodegenerative alterations.

La contaminación ambiental es un grave problema mundial que actualmente preocupa a la comunidad internacional. Las grandes ciudades industrializadas, como la de México, son las más contaminadas. Sin embargo, la contaminación llega hasta zonas alejadas de donde se produce y afecta los ecosistemas. La contaminación es responsable de una alarmante y creciente lista de enfermedades en el hombre, los animales y las plantas. Los bifenilos policlorados (PCB) se catalogaron dentro de los 12 contaminantes orgánicos más tóxicos para los organismos vivos. Sus propiedades físicas hicieron que se usaran ampliamente en la industria. No son biodegradables y se acumulan en el ambiente, se transfieren dentro de la cadena alimenticia y tienden a concentrarse más al final de ésta, por lo que en los alimentos se determinaron concentraciones que sobrepasaban los límites establecidos por el Organismo de Protección del Ambiente de los Estados Unidos. Se demostró que los PCB afectan la función de los sistemas endocrino, inmunológico y nervioso, entre otros. El mecanismo de acción descrito para los PCB, es por medio de la activación del receptor aril hidrocarburo, un factor de transcripción citosólico dependiente de ligando. Los PCB actúan como ligandos y son lipofílicos, por lo que entran a la célula y llegan al núcleo para unirse al ADN, lo cual altera la trascripción de genes específicos y provoca alteraciones genéticas que conducen a cambios en los procesos y funciones celulares. Los PCB interfieren con la producción y regulación de las hormonas esteroides y tiroideas al actuar como antagonistas o agonistas de los receptores hormonales. Afectan la función reproductora y alteran diferentes aspectos de la sexualidad. Como otros grupos de investigación, el nuestro ha observado que la administración de PCB a ratas gestantes causa un incremento de la mortalidad de las crías, pérdida fetal, peso corporal bajo y una reducción en el número de machos por camada. Los PCB actúan como inmunotoxinas que causan la atrofia del timo y afectan la respuesta inmune. Los PCB y sus metabolitos son carcinogénicos debido a la generación de especies reactivas de oxígeno que pueden producir daño oxidativo al ADN, provocar aberraciones cromosómicas y generar cáncer de mama, hígado, tracto biliar, gastrointestinal, cerebral, etc. Los organismos son más vulnerables a la exposición de los PCB durante las etapas tempranas del desarrollo embrionario. Los PCB atraviesan la placenta y llegan al feto, permanecen en la leche materna y mantienen niveles altos en las crías. Los PCB afectan así el desarrollo del Sistema Nervioso, los órganos y los tejidos, y pueden llevar a la pérdida fetal. También se asocian a deficiencias en el neurodesarrollo del niño y a alteraciones neuropsicológicas en la atención, el aprendizaje y el desarrollo psicomotor. La exposición aguda o crónica a los PCB se asocia con cefalea, insomnio, nerviosismo, irritabilidad, depresión y ansiedad. Los PCB participan en el proceso de neurodegeneración al afectar el sistema dopaminérgico. En el nivel neurofisiológico, afectan la transmisión sináptica excitatoria e inhibitoria hipocampal; inhiben la potenciación a largo plazo y la plasticidad sináptica; alteran mecanismos de señalización celular como el GABAérgico, en el aprendizaje y la memoria, y producen alteraciones cognoscitivas. Nuestro grupo demostró que la administración de los PCB durante la gestación inhibe la actividad de la enzima sintasa del óxido nítrico y provoca cambios neuronales morfológicos degenerativos en los núcleos paraventricular y supraóptico hipotalámicos. Las evidencias de los estudios realizados con los PCB son concluyentes en cuanto a que la exposición a estos tóxicos ambientales interfiere con el funcionamiento de diferentes órganos y sistemas y a que son un factor de riesgo para un amplio número de alteraciones neurodegenerativas. Actualmente, las poblaciones están expuestas a concentraciones que exceden los niveles límite tolerables recomendados por la Organización Mundial de la Salud. Nuestro grupo está analizando las alteraciones de estos contaminantes en el nivel neuroendocrino y en algunos aspectos del aprendizaje y la memoria. Dada la relevancia de los efectos de los PCB en la salud y de la falta en México de una valoración de los niveles de los PCB existentes en personas y alimentos, es importante que las instituciones de salud fomenten y apoyen las investigaciones en esta área.

Los opioides como péptidos ancestrales: estudio inmunohistoquímico en el molusco Helix aspersa y en el anfibio Ambystoma mexicanum / Opioids as ancestral peptides: inmunohistochemical study in the Helix aspersa mollusk and in the amphibious Ambystoma mexicanum

Existe una variedad de estudios multidisciplinarios de tipo farmacológico, fisiológico e inmunohistoquímico que han sido de gran utilidad en las investigaciones de la biología comparada de los péptidos opioides, y las posibles funciones en las que participan a lo largo de la escala filogenética. Se ha encontrado que estos péptidos y sus receptores específicos, se han mantenido estables a través de la evolución. Además, se ha demostrado que los opioides están distribuidos ampliamente a lo largo de la escala filogénetica. Nuestro grupo ha realizado estudios inmunohistoquímicos para leucina encefalina, metionina encefalia, dinorfina 1-8 y beta-endorfina en dos especies: el caracol de jardín Helix aspersa y el ajolote Ambystoma mexicanum. Los resultados obtenidos en el Helix aspersa mostraron inmunorreactividad a la leucina encefalina en interneuronas de la vía sensorial del tentáculo, en interneuronas de los ganglios parietales, y en neuronas neurosecretoras del cuerpo dorsal del mesocerebro, principalmente. La inmunorreactividad a metionina tuvo una distribución más amplia. Se encontró que la inmunorreactividad a encefalinas tiene una variación estacional. Así mismo, se encontró por medio de inmunohistoquímica y HPLC, inmunorreactividad al octapéptido Met-5Arg-Gly-Leu en el anillo periesofágico de este organismo. Se estudió la liberación de encefalinas en estos ganglios y se encontró que es provocada por alto potasio y dependiente de calcio. En el Ambystoma mexicanum se demostró la existencia de inmunorreactividad a metionina encefalina a dinorfina, se encontró únicamente en fibras de la eminencia media y el lóbulo posterior; la inmunorreactividad a leucina encefalina se distribuyó en algunas fibras del lóbulo posterior y de la eminencia media, y en una gran cantidad de células del lóbulo anterior. Este último hallazgo sugirió que este péptido pudiera tener un papel hormonal. La distribución de encefalinas en el cerebro del A. mexicanum fue muy similar a la encontrada en los mamíferos y otros vertebrados. En telencéfalo, la concentración principalmente en el complejo estrioamigdalino y en la región septal. En diencéfalo, se localizó en los núcleos habenulares e hipotalámicos. De los datos presentados en este trabajo, se pudo conluir que los péptidos opioides tienen una distribución parecida en organismos representativos de diferentes grupos taxonómicos, y cuya función es similar dentro de estos grupos

El Receptor ORL-1 y su péptido endógeno, La nociceptina/orfanina FQ: nuevos miembros de la familia de los opioides / The opoid receptor like-1 and its endogenous peptide nociceptin/orphanin FQ: new members of the opioid family

A la clonación de receptores opioides d, µ y ? siguió la identificación y secuenciación de otro miembro de la familia opioide, el receptor ORL-1 (por sus siglas en ingles, opioid receptor like-1). No obstante, su gran homología con receptores µ, d y ?, los ligandos opioides endógenos, como la ß-endorfina, la dinorfina A y las encefalinas, no presentan gran afinidad por este receptor. Después del descubrimiento del ORL-1, se aisló su péptido endógeno; éste tiene gran afinidad (nanomolar) para su receptor. Dos grupos de investigación independientes reportaron con este péptido: el grupo de Meunier lo llamó nociceptina y el grupo de Reinscheid, orfanina FQ. El ORL-1 y la nociceptina/orfanina FQ (N/OFQ) tienen una distribución anatómica amplia en el sistema nervioso, principalmente en los núcleos olfatorios, corteza cerebral, hipocampo, región septal, ganglios basales, tálamo, hipotálamo, puente, bulbo, pedúnculos cerebrales, médula espinal y retina, lo que evidencia su participación en diversas funciones cerebrales. La administración de la N/OFQ puede producir hiperalgesia, alodinia, efectos antiopioides o analgesia. Estos efectos dependen básicamente de la dosis y de la vía de administración. Además, alteraciones en la locomoción, en el comportamiento exploratorio motivacional, en la ansiedad, memoria, alimentación y modulación neuroendocrina. La N/OFQ se deriva de un precursor de alto peso molecular, la prepronociceptina (PPNOC), el cual contiene una sola copia de la secuencia de aminoácidos de la N/OFQ. El gen de la PPNOC está conservado en cinco especies animales estudiadas (rata, ratón, porcino, bovino y humano) y se expresa predominantemente en hipotálamo mesencéfalo, núcleos del lemnisco lateral, oliva superior, núcleo trigeminal espinal y médula espinal. Debido al reciente descubrimiento de este péptido y su receptor, además de su amplia distribución en el sistema nervioso resulta obvio que su participación en la fisiología y sus probables implicaciones farmacológicas todavía no están completas. La presencia de la N/OFQ en especies de los primeros niveles de la escala filogenética como son los moluscos Helix aspersa, H. pomatia y Cepaea nemoralis, donde se demostró también que la administración de N/OFQ tiene un efecto pronociceptivo similar a la hiperalgesia de los mamíferos, sugieren que este nuevo sistema opioide tiene un origen filogenético temprano y una continuidad funcional durante el curso de la evolución