thyronines and Disease-Models--Animal

3-iodothyronamine (T1AM) and the recently developed analog SG-2 are rapidly emerging as promising multi-target neuroprotective ligands able to reprogram lipid metabolism and to produce memory enhancement in mice. To elucidate the molecular mechanisms underlying the multi-target effects of these novel drug candidates, here we investigated whether the modulation of SIRT6, known to play a key role in reprogramming energy metabolism, might also drive the activation of clearing pathways, such as autophagy and ubiquitine-proteasome (UP), as further mechanisms against neurodegeneration. We show that both T1AM and SG-2 increase autophagy in U87MG cells by inducing the expression of SIRT6, which suppresses Akt activity thus leading to mTOR inhibition. This effect was concomitant with down-regulation of autophagy-related genes, including Hif1α, p53 and mTOR. Remarkably, when mTOR was inhibited a concomitant activation of autophagy and UP took place in U87MG cells. Since both compounds activate autophagy, which is known to sustain long term potentiation (LTP) in the entorhinal cortex (EC) and counteracting AD pathology, further electrophysiological studies were carried out in a transgenic mouse model of AD. We found that SG-2 was able to rescue LTP with an efficacy comparable to T1AM, further underlying its potential as a novel pleiotropic agent for neurodegenerative disorders treatment.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Autophagosomes; Autophagy; Cell Line, Tumor; Disease Models, Animal; Entorhinal Cortex; Gangliosides; Gene Expression Regulation; Humans; Long-Term Potentiation; Mice, Transgenic; Neuroprotective Agents; Sirtuins; Thyronines; TOR Serine-Threonine Kinases

This study aims to show how 3-iodothyronamine (T1AM) protects against spinal cord injury (SCI) in rats. We randomly divided adult female Sprague-Dawley rats (N=54) into three equal groups: (1) untreated control (n=18) (2) T1AM (n=18) (3) T1AM+EPPTB (n=18). The clamp method was used to produce SCI at the T10 segment, and the following data were collected 3, 5, and 7 days after the injury plus treatment. The mean BBB scores of both the control and T1AM+EPPTB groups were 1.5±0.5, 3.5±0.5, and 4.5±0.5 on days 3, 5, and 7 after SCI, respectively, whereas those for the T1AM group were 3.3±0.5, 5.3±0.5, and 7.5±0.5, a significant difference from the first two groups mentioned on each day (all

Topics: Animals; Apoptosis; Disease Models, Animal; Female; In Situ Nick-End Labeling; Injections, Intraperitoneal; Motor Activity; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries; Thyronines

3-iodothyronamine (T1AM) and its oxidative product, 3-iodotyhyroacetic acid (TTA1A), are known to stimulate learning and induce hyperalgesia in mice. We investigated whether i)TA1 may be generated in vivo from T1AM, ii) T1AM shares with TA1 the ability to activate the histaminergic system. Tandem mass spectrometry was used to measure TA1 and T1AM levels in i) the brain of mice following intracerebroventricular (i.c.v.) injection of T1AM (11μgkg(-1)), with or without pretreatment with clorgyline, (2.5mgkg(-1) i.p.), a monoamine oxidase inhibitor; ii) the medium of organotypic hippocampal slices exposed to T1AM (50nM). In addition, learning and pain threshold were evaluated by the light-dark box task and the hot plate test, respectively, in mice pre-treated subcutaneously with pyrilamine (10mgkg(-1)) or zolantidine (5mgkg(-1)), 20min before i.c.v. injection of T1AM (1.32 and 11μgkg(-1)). T1AM-induced hyperalgesia (1.32 and 11μgkg(-1)) was also evaluated in histidine decarboxylase (HDC(-/-)) mice. T1AM and TA1 brain levels increased in parallel in mice injected with T1AM with the TA1/T1AM averaging 1.7%. Clorgyline pre-treatment reduced the increase in both T1AM and TA1. TA1 was the main T1AM metabolite detected in the hippocampal preparations. Pretreatment with pyrilamine or zolantidine prevented the pro-learning effect of 1.32 and 4μgkg(-1) T1AM while hyperalgesia was conserved at the dose of 11μgkg(-1) T1AM. T1AM failed to induce hyperalgesia in HDC(-/-) mice at all the doses. In conclusion, TA1 generated from T1AM, but also T1AM, appears to act by modulating the histaminergic system.

Topics: Animals; Avoidance Learning; Behavior, Animal; Biotransformation; Disease Models, Animal; Hippocampus; Histamine; Histamine Antagonists; Histidine Decarboxylase; Hyperalgesia; Injections, Intraventricular; Male; Mice, 129 Strain; Mice, Knockout; Monoamine Oxidase Inhibitors; Oxidation-Reduction; Pain Threshold; Signal Transduction; Tandem Mass Spectrometry; Thyroid Hormones; Thyronines

High doses of GH, used to induce anabolism in prolonged critically ill patients, unexpectedly increased mortality. To further explore underlying mechanisms, a valid animal model is needed. Such a model is presented in this study. Seven days after arterial and venous cannulae placement, male New Zealand White rabbits were randomly allocated to a control or a critically ill group. To induce prolonged critical illness, a template controlled 15% deep dermal burn injury was imposed under combined general and regional (paravertebral) anesthesia. Subsequently, critically ill rabbits received supplemental analgesia and were parenterally fed with glucose, insulin, amino acids, and lipids. On d 1 and d 8 after randomization, acute and chronic spontaneous hormonal profiles of GH, TSH, and PRL secretion were obtained by sampling blood every 15 min for 7 h. Furthermore, GH, TSH, and PRL responses to an iv bolus of GH-releasing peptide 2 (GHRP-2) + TRH were documented on d 0, 1, and 8. Hemodynamic status and biochemical parameters were evaluated on d 0, 1, 3, 5, and 8, after which animals were killed and relative wet weight and water content of organs was determined. Compared with controls, critically ill animals exhibited transient metabolic acidosis on d 1 and weight loss, organ wasting, systolic hypertension, and pronounced anemia on d 8. On d 1, pulsatile GH secretion doubled in the critically ill animals compared with controls, and decreased again on d 8 in the presence of low plasma IGF-I concentrations from d 1 to d 8. GH responses to GHRP-2 + TRH were elevated on d 1 and increased further on d 8 in the critically ill animals. Mean TSH concentrations were identical in both groups on d 1 and 8, in the face of dramatically suppressed plasma T(4) and T(3) concentrations in the critically ill animals. PRL secretion was impaired in the critically ill animals exclusively on d 8. TSH and PRL responses to GHRP-2 and TRH were increased only on d 1. In conclusion, this rabbit model of acute and prolonged critical illness reveals several of the clinical, biochemical, and endocrine manifestations of the human counterpart.

Topics: Animals; Body Weight; Critical Illness; Disease Models, Animal; Growth Hormone; Hemodynamics; Male; Neurosecretory Systems; Oligopeptides; Organ Size; Oxygen Consumption; Prolactin; Rabbits; Stress, Physiological; Thyronines; Thyrotropin; Thyrotropin-Releasing Hormone; Triiodothyronine; Up-Regulation

A few synthetic peptides corresponding to amino acid sequences on human thyroglobulin (Tg) have been reported to induce moderate thyroiditis or activate mouse Tg (MTg)-primed T cells to transfer thyroiditis in mice susceptible to experimental autoimmune thyroiditis. Using three pairs of 12-mer peptides (1-12, 2549-2560, 2559-2570), with thyroxine (T4) or noniodinated thyronine (T0) at the conserved, hormonogenic site 5, 2553, or 2567 respectively, we reported that iodination was not required for a Tg hormonogenic site to be a thyroiditogenic autoepitope. To determine the relative importance of MHC class II and T cell receptor (TCR) repertoire, we compared two EAT-susceptible k and s (CBA and A.SW) haplotypes and their respective MHC-identical strain (C57BR and SJL) with approximately 50% genomic deletion of TCR Vbeta genes. Whereas k and s strains develop MTg-induced EAT, vigorous immunization with peptides containing T4 or T0 at either 5 or 2553, but not at 2567, led to mild (10-20%) thyroiditis only in some mice of either k strain. TCR Vbeta gene differences played a minor role. T cell responses to all peptide pairs were quite similar in CBA and C57BR mice, and both hT0(2553) and hT4(2553) reciprocally primed and stimulated their T cells. In adoptive transfer, SJL mice were somewhat more responsive to peptide activation than A.SW but much weaker than k strains. By comparing T4- and T0-containing peptides in different haplotypes, we show further that antigenicity of conserved hormonogenic sites is intrinsic, dependent more on amino acid sequence and binding to appropriate class II molecules and less on TCR repertoire or iodination of T0.

Topics: Adoptive Transfer; Amino Acid Sequence; Animals; Conserved Sequence; Disease Models, Animal; Epitopes; Female; Genes, MHC Class II; Lymphocyte Activation; Mice; Mice, Inbred A; Mice, Inbred CBA; Receptors, Antigen, T-Cell, alpha-beta; T-Lymphocytes; Thyroglobulin; Thyroiditis, Autoimmune; Thyronines; Thyroxine

We hypothesized earlier that conserved T cell epitopes and those unique to mouse thyroglobulin (MTg) contributed to its total thyroiditogenicity in murine autoimmune thyroiditis. Recent studies of synthetic peptides from human Tg (HTg) revealed no immunodominant epitopes. The role of iodine residues, considered by some to render Tg immunogenic, became unclear, since only one 12-mer peptide contained thyroxine (T4) positioned at hormonogenic site 2553. It primed T cells for thyroiditis transfer, but noniodinated peptide containing thyronine (T0) was not compared. To determine 1) whether other primary hormonogenic sites were likewise immunogenic and 2) whether iodination was requisite for this and other sites to be an autoepitope, we derivatized three pairs of 12-mer peptides, 1-12, 2549-2560, 2559-2570, containing T0 or T4 at positions 5, 2553, or 2567, respectively. The six peptides were used to stimulate MTg-primed cells in vitro and to immunize mice. None directly induced thyroiditis; peptide Abs were the lowest in mice given hT0(2567) or hT4(2567). Of the three T4-containing peptides, hT4(5) and hT4(2553), but not hT4(2567), stimulated MTg-primed or HTg-primed T cells in vitro, with hT4(2553) being the stronger. Comparing hT0(2553) with hT4(2553), both activated MTg-primed, or peptide-primed, T cells to transfer thyroiditis. The marked immunogenicity of noniodinated hT0(2553) and the poor antigenicity of hT4(5) and hT4(2567) demonstrate that immunogenicity of a conserved hormonogenic site is dependent more on its amino acid sequence than on T4 substitution. Iodination may enhance antigenicity and/or binding affinity, but it is not required for a Tg hormonogenic site to be an autoepitope.

Topics: Amino Acid Sequence; Animals; Autoantibodies; Cross Reactions; Disease Models, Animal; Epitopes; Female; Humans; Immunization, Passive; Iodine; Mice; Mice, Inbred CBA; Molecular Sequence Data; T-Lymphocytes; Thyroglobulin; Thyroid Hormones; Thyroiditis, Autoimmune; Thyronines; Thyroxine