Lack of action of exogenously administered T3 on the fetal rat brain despite expression of the monocarboxylate transporter 8

Mutations of the monocarboxylate transporter 8 gene (MCT8, SLC16A2) cause the Allan-Herndon-Dudley syndrome, an X-linked syndrome of severe intellectual deficit and neurological impairment. Mct8 transports thyroid hormones (T4 and T3), and the Allan-Herndon-Dudley syndrome is likely caused by lack of T3 transport to neurons during critical periods of fetal brain development. To evaluate the role of Mct8 in thyroid hormone action in the fetal brain we administered T4 or T3 to thyroidectomized pregnant dams treated with methyl-mercapto-imidazol to produce maternal and fetal hypothyroidism. Gene expression was then measured in the fetal cerebral cortex. T4 increased Camk4, Sema3c, and Slc7a3 expression, but T3 was without effect. To investigate the cause for the lack of T3 action we analyzed the expression of organic anion transport polypeptide (Oatp14, Slco1c1), a T4 transporter, and Mct8 (Slc16a2), a T4 and T3 transporter, by confocal microscopy. Both proteins were present in the brain capillaries forming the blood-brain barrier and in the epithelial cells of the choroid plexus forming the blood-cerebrospinal fluid barrier. It is concluded that T4 from the maternal compartment influences gene expression in the fetal cerebral cortex, possibly after transport via organic anion transporter polypeptide and/or Mct8, and conversion to T3 in the astrocytes. On the other hand, T3 does not reach the target neurons despite the presence of Mct8. The data indicate that T4, through local deiodination, provides most T3 in the fetal rat brain. The role of Mct8 as a T3 transporter in the fetal rat brain is therefore uncertain. Copyright © 2011 by The Endocrine Society.This work was supported by Grants SAF2008-01168 and SAF2008-00429E from the Ministry of Science and Innovation, Spain, the European Union Integrated Project CRESCENDO (LSHM-CT-2005-018652), and by the Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III. D.D. was supported by the I3P program of the Consejo Superior de Investigaciones Científicas, Spain and by a postdoctoral fellowship from The Japanese Society for the Promotion of Science.Peer Reviewe

Uridine 5′-triphosphate promotes in vitro Schwannoma cell migration through matrix metalloproteinase-2 activation

In response to peripheral nerve injury, Schwann cells adopt a migratory phenotype and modify the extracellular matrix to make it permissive for cell migration and axonal re-growth. Uridine 5′-triphosphate (UTP) and other nucleotides are released during nerve injury and activate purinergic receptors expressed on the Schwann cell surface, but little is known about the involvement of purine signalling in wound healing. We studied the effect of UTP on Schwannoma cell migration and wound closure and the intracellular signaling pathways involved. We found that UTP treatment induced Schwannoma cell migration through activation of P2Y2 receptors and through the increase of extracellular matrix metalloproteinase-2 (MMP-2) activation and expression. Knockdown P2Y2 receptor or MMP-2 expression greatly reduced wound closure and MMP-2 activation induced by UTP. MMP-2 activation evoked by injury or UTP was also mediated by phosphorylation of all 3 major mitogen-activated protein kinases (MAPKs): JNK, ERK1/2, and p38. Inhibition of these MAPK pathways decreased both MMP-2 activation and cell migration. Interestingly, MAPK phosphorylation evoked by UTP exhibited a biphasic pattern, with an early transient phosphorylation 5 min after treatment, and a late and sustained phosphorylation that appeared at 6 h and lasted up to 24 h. Inhibition of MMP-2 activity selectively blocked the late, but not the transient, phase of MAPK activation. These results suggest that MMP-2 activation and late MAPK phosphorylation are part of a positive feedback mechanism to maintain the migratory phenotype for wound healing. In conclusion, our findings show that treatment with UTP stimulates in vitro Schwannoma cell migration and wound repair through a MMP-2-dependent mechanism via P2Y2 receptors and MAPK pathway activation. © 2014 Lamarca et al.This research was supported by an unrestricted research grant from Ferrer S.A. (Barcelona, Spain) and by grant SAF2011-23550 from Ministerio de Economia y Competitividad of SpainPeer Reviewe

Actividad biológica de análogos de triyodotironina

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Bioquímica. Fecha de lectura: 18 de Junio de 200

Direct action of triiodothyronine on gene expression in the neonatal brain and cerebellum

[ES]: Las hormonas tiroideas tienen un papel fundamental en el desarrollo y el funcionamiento de diversos órganos, especialmente el cerebro. Las hormonas tiroideas ejercen sus funciones mediante la interacción de la triyodotironina (T3) con receptores nucleares y la regulación de la expresión de genes. En este trabajo hemos estudiado los efectos del hipotiroidismo y de la administración de T3 en la expresión de genes de cerebro y cerebelo durante el periodo posnatal en la rata. Se obtuvieron neonatos hipotiroideos mediante la administración de antiroideos a la madre durante la gestación y la lactancia. Se les administró T3 a dosis diarias de 15 ng/g de peso desde el día posnatal 10 hasta el 15, y se los sacrificó 24 h tras la última inyección. El hipotiroidismo produjo un aumento de las concentraciones de colesterol y disminución de la expresión de D1 en hígado y de Serca-2 en corazón, que fueron normalizados tras el tratamiento con T3. En el encéfalo, el hipotiroidismo redujo la expresión de los genes del núcleo estriado Ngrn y Rasd2, así como de los genes de cerebelo que codifican sinaptotagmina 12 (Syt12), hairless (Hr), neurotrofina 3 (Nt3) y RevErbAa (Nrd1d), que también se normalizaron tras la administración de T3, lo que indica que durante el periodo posnatal esta hormona llega directamente y tiene actividad en el cerebro. En paralelo, se ha estudiado la posible acción de un análogo de la T3, que se une in vitro preferentemente al receptor tiroideo a (TRa). Sin embargo, este compuesto no tuvo efecto alguno en los parámetros estudiados. Para comprobar si la falta de acción de este compuesto se debe a una rápida metabolización, se comparó su actividad con la de la T3 en ensayos de transactivación del gen indicador cloranfenicol acetiltransferasa en células Cos7 que expresan de forma transitoria, mediante transfección, TRa o TRb. Los resultados indican que Kb430 carece de actividad.[EN]: Thyroid hormones play a major role in the development and function of several organs, especially the brain. The actions of thyroid hormones are exerted through the interaction of T3 with nuclear receptors and regulation of gene expression. The present study analyzed the effects of hypothyroidism and T3 administration on gene expression in the rat brain and cerebellum during the postnatal period. To obtain hypothyroid pups, antithyroid drugs were administered to pregnant rats from gestational day 9, and after delivery. T3 was administered to the pups, at single daily doses of 5 ng/g body weight from postnatal day 11 to 15. The pups were sacrificed 24 hours after the last injection. Hypothyroid neonates showed increased cholesterol levels and decreased expression of D1 in liver and of Serca-2 in heart, which were normalized with T3 treatment. In the brain, there was decreased expression of Ngrn and Rasd2 in the striatum and of the genes encoding sinatotagmin12 (Syt12), hairless (Hr), neurotrofina3 (Nt3) and RevErbA (Nrd1d) in the cerebellum, which were also normalized by T3 treatment. These results demonstrate that during the postnatal period, T3 reaches the brain and directly influences gene expression in this organ. In parallel, we studied the possible actions of a T3 analog, Kb430, which in vitro binds preferentially to thyroid receptor (TR ). This compound had no effect on any of the parameters studied. To investigate whether the lack of activity of this compound was due to rapid metabolism, we compared its activity with that of T3 in T3 receptor transactivation assays using the reporter gene chloramphenicol acetyl transferase in Cos7 cells transiently expressed through TR or TR transfection. The results indicate that Kb430 lacks biological activity.Este trabajo ha sido financiado con los proyectos BFU2005-01740 del Ministerio de Educación y Ciencia y el proyecto integrado de la Unión Europea CRECENDO (LSHM-CT-2005-018652).Peer Reviewe

A combined approach identifies a limited number of new thyroid hormone target genes in post-natal mouse cerebellum

Thyroid hormones act directly on gene transcription in the post-natal developing cerebellum, controlling neuronal, and glial cell differentiation. We have combined three experimental approaches to identify the target genes that are underlying this phenomenon: 1) a microarray analysis of gene expression to identify hormone responsive genes in the cerebellum of Pax8-/- mice, a transgenic mouse model of congenital hypothyroidism; 2) a similar microarray analysis on primary culture of cerebellum neurons; and 3) a bioinformatics screen of conserved putative-binding sites in the mouse genome. This identifies surprisingly a small set of target genes, which, for some of them, might be key regulators of cerebellum development and neuronal differentiation. © 2007 Society for Endocrinology.This work was supported by French Ministery of Research (ACI Biologie Cellulaire, Moléculaire et Structurale) Ligue contre le Cancer (équipe labellisée) the CASCADE European Network of Excellence (EU contract no. FOOD-CT-2004-506319) the CRESCENDO EU integrated project.Peer Reviewe

MCT8-D2 knock-out mice present hyperactivity and deep alterations in their metabolic rates during the dark phase

Trabajo presentado en el FENS Regional Meeting, celebrado en Belgrado (Serbia) del 10 al 13 de julio de 2019

New metabolic insights in the study of Allan-Herndon-Dudley Syndrome: metabolic characterization of MCT8 and DIO2 knock-out mice

Trabajo presentado en el FENS (Federation of European Neuroscience Societies) 2020 Virtual Forum, celebrado en modalidad virtual del 11 al 15 de julio de 2020

Thyroid hormone action in the adult brain: Gene expression profiling of the effects of single and multiple doses of triiodo-L-thyronine in the rat striatum

et al.Thyroid hormones have profound effects on mood and behavior, but the molecular basis of thyroid hormone action in the adult brain is relatively unknown. In particular, few thyroid hormone-dependent genes have been identified in the adult brain despite extensive work carried out on the developing brain. In this work we performed global analysis of gene expression in the adult rat striatum in search for genomic changes taking place after administration of T3 to hypothyroid rats. The hormone was administered in two different schedules: 1) a single, large dose of 25 µg per 100 g body weight (SD) or 2) 1.5 µg per 100 g body weight once daily for 5 d (RD). Twenty-four hours after the single or last of multiple doses, gene expression in the striatum was analyzed using Codelink microarrays. SD caused up-regulation of 149 genes and down-regulation of 88 genes. RD caused up-regulation of 18 genes and down-regulation of one gene. The results were confirmed by hybridization to Affymetrix microarrays and by TaqMan PCR. Among the genes identified are genes involved in circadian regulation and the regulation of signaling pathways in the striatum. These results suggest that thyroid hormone is involved in regulation of striatal physiology at multiple control points. In addition, they may explain the beneficial effects of large doses of thyroid hormone in bipolar disorders.Peer reviewe

Evaluation of synaptogenesis in MCT8 deficiency

Trabajo presentado al 17 National Congress of the Spanish Society of Neuroscience (SENC), celebrado en Alicante (España) del 27 al 30 de septiembre de 2017.Peer Reviewe

MCT8 deficiency: The road to therapies for a rare disease

Allan-Herndon-Dudley syndrome is a rare disease caused by inactivating mutations in the SLC16A2 gene, which encodes the monocarboxylate transporter 8 (MCT8), a transmembrane transporter specific for thyroid hormones (T3 and T4). Lack of MCT8 function produces serious neurological disturbances, most likely due to impaired transport of thyroid hormones across brain barriers during development resulting in severe brain hypothyroidism. Patients also suffer from thyrotoxicity in other organs due to the presence of a high concentration of T3 in the serum. An effective therapeutic strategy should restore thyroid hormone serum levels (both T3 and T4) and should address MCT8 transporter deficiency in brain barriers and neural cells, to enable the access of thyroid hormones to target neural cells. Unfortunately, targeted therapeutic options are currently scarce and their effect is limited to an improvement in the thyrotoxic state, with no sign of any neurological improvement. The use of thyroid hormone analogs such as TRIAC, DITPA, or sobetirome, that do not require MCT8 to cross cell membranes and whose controlled thyromimetic activity could potentially restore the normal function of the affected organs, are being explored to improve the cerebral availability of these analogs. Other strategies aiming to restore the transport of THs through MCT8 at the brain barriers and the cellular membranes include gene replacement therapy and the use of pharmacological chaperones. The design of an appropriate therapeutic strategy in combination with an early diagnosis (at prenatal stages), will be key aspects to improve the devastating alterations present in these patients.This work was supported by the Spanish Ministry of Economy and Competitiveness, grant number SAF2017-86342-R (MINECO/AEI/FEDER, UE) to AG-F, the Sherman Foundation (Grant Number OTR02211) to AG-F and SB-L, and the BBSRC (Grant Number BB/R016879/1) to SB-L. CG-M is a recipient of a contract from the Center for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid. The cost of this publication has been paid in part by FEDER funds.Peer reviewe