Type 3 deiodinase expression in inflammatory spinal cord lesions in rat experimental autoimmune encephalomyelitis

Deiodinase Types 1 and 3 and Proinflammatory Cytokine Values May Discriminate Depressive Disorder Patients from Healthy Controls

INTRODUCTION

Depressive disorders are multifactorial diseases in that a variety of factors may play a role in their etiology, including inflammation and abnormalities in the thyroid hormone (TH) metabolism and levels. The purpose of this study was to evaluate iodothyronine deiodinases (DIOs) and DIO-interacting cytokines as possible biomarkers in the diagnosis of depressive disorders.

METHODS

This study enrolled 73 patients diagnosed with recurrent depressive disorder (rDD) and 54 controls. The expressions of DIO1, DIO2, DIO3, IL1B, IL6, TNFA, and IFNG genes, encoding three types of DIOs (1, 2, and 3), interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ, were assessed using the polymerase chain reaction in blood cells and an enzymatic immunoassay method in serum. The levels of examined molecules between patients and controls were compared, and correlations and diagnostic values were evaluated.

RESULTS

Lower levels of DIO2 and higher levels of IL1B, IL6, and TNFA were found in patients compared to controls. The protein concentrations of DIO1 and DIO2 were lower, while that of DIO3 was higher, in patients than in controls. Serum IL-1β, IL-6, and TNF-α were also higher in patients than in controls. The area under the curve (AUC) of the IL-1β, IL-6, DIO1, and DIO3 proteins was >0.7 for discriminating patients with rDD from controls.

CONCLUSIONS

The expressions of genes for DIO2, IL-1β, IL-6, and TNF-α may have a role in the estimation of processes present in depressive disorders. We can cautiously claim that DIO1 and DIO3 and pivotal cytokines, mainly IL-1β and IL-6, may play a role in depression diagnosis, and further studies are suggested to explain the exact role of these molecules in larger samples with more precise methods.

Synthetic Thyroid Hormone Receptor-β Agonists Promote Oligodendrocyte Precursor Cell Differentiation in the Presence of Inflammatory Challenges

Oligodendrocytes and their precursors are the cells responsible for developmental myelination and myelin repair during adulthood. Their differentiation and maturation processes are regulated by a complex molecular machinery driven mainly by triiodothyronine (T3), the genomic active form of thyroid hormone, which binds to thyroid hormone receptors (TRs), regulating the expression of target genes. Different molecular tools have been developed to mimic T3 action in an attempt to overcome the myelin repair deficit that underlies various central nervous system pathologies. In this study, we used a well-established in vitro model of neural stem cell-derived oligodendrocyte precursor cells (OPCs) to test the effects of two compounds: the TRβ1 ligand IS25 and its pro-drug TG68. We showed that treatment with TG68 induces OPC differentiation/maturation as well as both the natural ligand and the best-known TRβ1 synthetic ligand, GC-1. We then described that, unlike T3, TG68 can fully overcome the cytokine-mediated oligodendrocyte differentiation block. In conclusion, we showed the ability of a new synthetic compound to stimulate OPC differentiation and overcome inflammation-mediated pathological conditions. Further studies will clarify whether the compound acts as a pro-drug to produce the TRβ1 ligand IS25 or if its action is mediated by secondary mechanisms such as AMPK activation.

Hormones in experimental autoimmune encephalomyelitis (EAE) animal models

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) in which activated immune cells attack the CNS and cause inflammation and demyelination. While the etiology of MS is still largely unknown, the interaction between hormones and the immune system plays a role in disease progression, but the mechanisms by which this occurs are incompletely understood. Several in vitro and in vivo experimental, but also clinical studies, have addressed the possible role of the endocrine system in susceptibility and severity of autoimmune diseases. Although there are several demyelinating models, experimental autoimmune encephalomyelitis (EAE) is the oldest and most commonly used model for MS in laboratory animals which enables researchers to translate their findings from EAE into human. Evidences imply that there is great heterogeneity in the susceptibility to the induction, the method of induction, and the response to various immunological or pharmacological interventions, which led to conflicting results on the role of specific hormones in the EAE model. In this review, we address the role of endocrine system in EAE model to provide a comprehensive view and a better understanding of the interactions between the endocrine and the immune systems in various models of EAE, to open up a ground for further detailed studies in this field by considering and comparing the results and models used in previous studies.

Cognitive analysis of metabolomics data for systems biology

Cognitive computing is revolutionizing the way big data are processed and integrated, with artificial intelligence (AI) natural language processing (NLP) platforms helping researchers to efficiently search and digest the vast scientific literature. Most available platforms have been developed for biomedical researchers, but new NLP tools are emerging for biologists in other fields and an important example is metabolomics. NLP provides literature-based contextualization of metabolic features that decreases the time and expert-level subject knowledge required during the prioritization, identification and interpretation steps in the metabolomics data analysis pipeline. Here, we describe and demonstrate four workflows that combine metabolomics data with NLP-based literature searches of scientific databases to aid in the analysis of metabolomics data and their biological interpretation. The four procedures can be used in isolation or consecutively, depending on the research questions. The first, used for initial metabolite annotation and prioritization, creates a list of metabolites that would be interesting for follow-up. The second workflow finds literature evidence of the activity of metabolites and metabolic pathways in governing the biological condition on a systems biology level. The third is used to identify candidate biomarkers, and the fourth looks for metabolic conditions or drug-repurposing targets that the two diseases have in common. The protocol can take 1-4 h or more to complete, depending on the processing time of the various software used.

Thyroid Hormone and Neural Stem Cells: Repair Potential Following Brain and Spinal Cord Injury

Neurodegenerative diseases are characterized by chronic neuronal and/or glial cell loss, while traumatic injury is often accompanied by the acute loss of both. Multipotent neural stem cells (NSCs) in the adult mammalian brain spontaneously proliferate, forming neuronal and glial progenitors that migrate toward lesion sites upon injury. However, they fail to replace neurons and glial cells due to molecular inhibition and the lack of pro-regenerative cues. A major challenge in regenerative biology therefore is to unveil signaling pathways that could override molecular brakes and boost endogenous repair. In physiological conditions, thyroid hormone (TH) acts on NSC commitment in the subventricular zone, and the subgranular zone, the two largest NSC niches in mammals, including humans. Here, we discuss whether TH could have beneficial actions in various pathological contexts too, by evaluating recent data obtained in mammalian models of multiple sclerosis (MS; loss of oligodendroglial cells), Alzheimer’s disease (loss of neuronal cells), stroke and spinal cord injury (neuroglial cell loss). So far, TH has shown promising effects as a stimulator of remyelination in MS models, while its role in NSC-mediated repair in other diseases remains elusive. Disentangling the spatiotemporal aspects of the injury-driven repair response as well as the molecular and cellular mechanisms by which TH acts, could unveil new ways to further exploit its pro-regenerative potential, while TH (ant)agonists with cell type-specific action could provide safer and more target-directed approaches that translate easier to clinical settings.

Combination therapy of apo-transferrin and thyroid hormones enhances remyelination

The current study presents two different approaches with a view to elucidating the interaction between thyroid hormones (TH) and apo-transferrin (aTf) and their role in myelination and remyelination. First, in vitro assays were conducted to determine the single and combined effects of aTf and triiodothyronine (T3) on oligodendroglial cell lineage proliferation and oligodendrocyte (OLG) maturation in primary cultures. Results revealed higher proliferation rates upon single aTf treatment but Control values upon T3 and aTf + T3 treatments. In addition, both aTf and T3 accelerated OLG maturation, with the greatest effects being exerted by combined aTf + T3 administration in terms of both myelin basic protein (MBP) expression and morphological complexity. Second, in vivo assays were carried out to establish single and combined effects of aTf and T3, as well as TH receptor (THR) inhibitor I-850, on remyelination following a CPZ-induced demyelination protocol. Results showed an increase in myelin deposition and the number of mature remyelinating OLG upon single treatments, but a synergic effect upon combined aTf + T3 treatment which was prevented by THR inhibition. It may be thus concluded that combined treatment yielded the most beneficial effects on OLG maturation parameters in vitro and remyelinating capacity in vivo when compared to single treatments. These findings may help explore the development of new target molecules in the treatment of demyelinating diseases.

Phase I randomized trial of liothyronine for remyelination in multiple sclerosis: A dose-ranging study with assessment of reliability of visual outcomes

BACKGROUND

Thyroid hormone promotes remyelination in multiple sclerosis (MS) animal models through a variety of mechanisms. Liothyronine (L-T3) is a short-acting thyroid hormone with demonstrated safety and tolerability for short-term and chronic use in euthyroid adults with other health conditions, but has not been studied in people with MS. The objectives of this single-center, phase I, placebo-controlled, clinical trial were to determine the safety, tolerability, and optimal dosing of L-T3 in people with MS in preparation for a phase 2 remyelination clinical trial. Secondary goals included exploration of the reliability of functional and clinical measurements of myelination in the anterior visual pathway over one week.

METHODS

Groups of six clinically stable people with MS were randomized in a 4:2 ratio to receive L-T3 or placebo. The first group received 50 mcg total daily dose (TDD) of L-T3, with escalating doses of L-T3 in subsequent groups, up to potentially 150 mcg TDD in the final group. Prior to enrollment for the next dose-escalated group, all safety measures for the prior dose were reviewed. The maximum tolerated dose (MTD) was considered to be the dose below which two or more participants experienced dose limiting symptoms or one participant experienced a serious adverse event. After the MTD was reached, no further patients were enrolled. Visual evoked potentials (VEP) P100 latency with two different check sizes (17' and 34') and Sloan low contrast letter acuity (LCLA) were measured pre- and post-treatment. To determine whether there was a treatment effect, the placebo and L-T3 groups were compared using a clustered bootstrap regression estimation. A linear mixed effects model was used to determine test-retest reliability of VEP and LCLA in all eyes.

RESULTS

Between May 2016 and November 2016, 15 people with MS were randomized to L-T3 (n = 10) or placebo (n = 5). Subjects were adherent to the study drug and the MTD was 75 mcg TDD. No serious adverse events were observed and the most common adverse events were poor sleep and loose stools. No treatment effect of L-T3 was observed over one week. Therefore, data from patients on L-T3 and placebo were pooled to explore VEP and LCLA reliability. The intraclass correlations of VEP 17', VEP 34' and LCLA were 0.836, 0.860, and 0.932, respectively. The mean differences in values between visits 1 and 2 for VEP 17' and 34' and LCLA were 1.9 ms/eye (SD 6.5), 0.4 ms/eye (6.3), and 0.8/eye (3.6), respectively.

CONCLUSIONS

This study confirms the short-term safety and tolerability of L-T3 in people with MS, with 75 mcg TDD as the MTD. Our results also support that, despite small variations over one week, VEP with various check sizes and Sloan LCLA are reliable functional and clinical outcome measures that could be used in remyelination clinical trials in MS. A future phase 2 clinical trial to investigate the efficacy of L-T3 as a remyelination therapy may be warranted. This trial was registered on clinicaltrials.gov (NCT02760056).

Assessment of serum levels of DIO1 and DIO3 in patients diagnosed with COPD

PURPOSE

Chronic obstructive pulmonary disease is the most common chronic lung disease, which may be caused by different pathological processes, including inflammation. Furthermore, signs of changes in thyroid hormone levels are found in some patients. Deiodinases (DIOs) are selenoproteins (enzymes) involved in the synthesis of thyroid hormones. It has been found that these molecules are involved in inflammatory processes. We carried out this preliminary study to investigate the levels of two deiodinases, i.e. type 1 deiodinase (DIO1) and type 3 deiodinase (DIO3), and their possible association with COPD and specific clinical parameters.

PATIENTS AND METHODS

Serum levels of DIO1 and DIO3 as well as lung function parameters were measured in 50 patients suffering from COPD and 30 healthy control subjects. The Mann-Whitney U test and Pearson's correlation coefficient were used to compare and correlate data.

RESULTS

Serum levels of DIO1 and DIO3 were significantly elevated in COPD patients (97.9 ± 55.6 versus 28.2 ± 28.3 U/L for DIO1 and 19.6 ± 10.7 versus 6.4 ± 6.3 U/L for DIO3; p < 0.001). No correlation between serum levels of the examined DIOs and other sociodemographic and clinical parameters was identified in this study.

CONCLUSION

For the first time we observed that peripheral DIO1 and DIO3 concentrations were elevated in COPD; hence, we may cautiously begin considering these molecules as potential circulating biomarkers of COPD. It may also be beneficial to conduct further studies to confirm and clarify their potential role.

Oligodendroglial Lineage Cells in Thyroid Hormone-Deprived Conditions

Oligodendrocytes are supporting glial cells that ensure the metabolism and homeostasis of neurons with specific synaptic axoglial interactions in the central nervous system. These require key myelinating glial trophic signals important for growth and metabolism. Thyroid hormone (TH) is one such trophic signal that regulates oligodendrocyte maturation, myelination, and oligodendroglial synaptic dynamics via either genomic or nongenomic pathways. The intracellular and extracellular transport of TH is facilitated by a specific transmembrane transporter known as the monocarboxylate transporter 8 (MCT8). Dysfunction of the MCT8 due to mutation, inhibition, or downregulation during brain development leads to inherited hypomyelination, which manifests as psychomotor retardation in the X-linked inherited Allan-Herndon-Dudley syndrome (AHDS). In particular, oligodendroglial-specific MCT8 deficiency may restrict the intracellular T3 availability, culminating in deficient metabolic communication between the oligodendrocytes and the neurons they ensheath, potentially promulgating neurodegenerative adult diseases such as multiple sclerosis (MS). Based on the therapeutic effects exhibited by TH in various preclinical studies, particularly related to its remyelinating potential, TH has now entered the initial stages of a clinical trial to test the therapeutic efficacy in relapsing-remitting MS patients (NCT02506751). However, TH analogs, such as DITPA or Triac, may well serve as future therapeutic options to rescue mature oligodendrocytes and/or promote oligodendrocyte precursor cell differentiation in an environment of MCT8 deficiency within the CNS. This review outlines the therapeutic strategies to overcome the differentiation blockade of oligodendrocyte precursors and maintain mature axoglial interactions in TH-deprived conditions.

Dissecting thyroid hormone transport and metabolism in dendritic cells

We reported thyroid hormone (TH) receptor expression in murine dendritic cells (DCs) and 3,5,3'-triiodothyronine (T₃)-dependent stimulation of DC maturation and ability to develop a Th1-type adaptive response. Moreover, an increased DC capacity to promote antigen-specific cytotoxic T-cell activity, exploited in a DC-based antitumor vaccination protocol, was revealed. However, putative effects of the main circulating TH, l-thyroxine (T₄) and the mechanisms of TH transport and metabolism at DC level, crucial events for TH action at target cell level, were not known. Herein, we show that T₄ did not reproduce those registered T₃-dependent effects, finding that may reflect a homoeostatic control to prevent unspecific systemic activation of DCs. Besides, DCs express MCT10 and LAT2 TH transporters, and these cells mainly transport T₃ with a favored involvement of MCT10 as its inhibition almost prevented T₃ saturable uptake mechanism and reduced T₃-induced IL-12 production. In turn, DCs express iodothyronine deiodonases type 2 and 3 (D2, D3) and exhibit both enzymatic activities with a prevalence towards TH inactivation. Moreover, T₃ increased MCT10 and LAT2 expression and T₃ efflux from DCs but not T₃ uptake, whereas it induced a robust induction of D3 with a parallel slight reduction in D2. These findings disclose pivotal events involved in the mechanism of action of THs on DCs, providing valuable tools for manipulating the immunogenic potential of these cells. Furthermore, they broaden the knowledge of the TH mechanism of action at the immune system network.

Inflammation severely alters thyroid hormone signaling in the central nervous system during experimental allergic encephalomyelitis in rat: Direct impact on OPCs differentiation failure

Differentiation of oligodendrocyte precursor cells (OPCs) into myelinating oligodendrocytes is severely impaired by inflammatory cytokines and this could lead to remyelination failure in inflammatory/demyelinating diseases. Due to the role of thyroid hormone in the maturation of OPCs and developmental myelination, in this study we investigated (i) the possible occurrence of dysregulation of thyroid hormone signaling in the CNS tissue during experimental neuroinflammation; (ii) the possible impact of inflammatory cytokines on thyroid hormone signaling and OPCs differentiation in vitro. The disease model is the experimental allergic encephalomyelitis in female Dark-Agouti rats, whereas in vitro experiments were carried out in OPCs derived from neural stem cells. The main results are the following: (i) a strong upregulation of cytokine mRNA expression level was found in the spinal cord during experimental allergic encephalomyelitis; (ii) thyroid hormone signaling in the spinal cord (thyroid hormone receptors; deiodinase; thyroid hormone membrane transporter) is substantially downregulated, due to the upregulation of the thyroid hormone inactivating enzyme deiodinase 3 and the downregulation of thyroid hormone receptors, as investigated at mRNA expression level; (iii) when exposed to inflammatory cytokines, deiodinase 3 is upregulated in OPCs as well, and OPCs differentiation is blocked; (iv) deiodinase 3 inhibition by iopanoic acid recovers OPCs differentiation in the presence on inflammatory cytokines. These data suggest that cellular hypothyroidism occurs during experimental allergic encephalomyelitis, possibly impacting on thyroid hormone-dependent cellular processes, including maturation of OPCs into myelinating oligodendrocytes. GLIA 2016;64:1573-1589.

Polymorphisms of iodothyronine deiodinases (DIO1, DIO3) genes are not associated with recurrent depressive disorder

BACKGROUND

Depressive disorder is characterized by disturbances in the hypothalamic-pituitary-thyroid (HPT) axis and in the metabolism of thyroid hormones (TH). The evidence for changes in TH levels is observed in human sera and cerebrospinal fluid as well as in animal model studies. Iodothyronine deiodinases (DIOs) type 1, 2 and 3 (DIO1, DIO2, DIO3) are important enzymes for the synthesis and determination of TH concentration. This study aims to examine the link between recurrent depressive disorders (rDD) and two functionally known polymorphisms DIO1a-C/T (rs11206244) and DIO1b-A/G (rs12095080) within the DIO1 gene encoding DIO1 and two polymorphisms DIO3-C/T (rs17716499), DIO3-A/C (rs7150269) within the DIO3 gene encoding DIO3.

METHODS

Both variants were genotyped in 254 rDD patients and 197 healthy subjects using polymerase chain reaction. Basic methods and statistical analyses were used to estimate genetic variants in the risk of the disease.

RESULTS

No significant associations were found between the polymorphisms examined here and rDD. There were no significant associations between genotypes distribution and demographic/medical variables. Odds ratios (ORdis) and corresponding 95% confidence interval (95% CI) were calculated, for example: for CC genotype of DIO1a C/T (ORdis=0.86, 95% CI: 0.59, 1.25).

CONCLUSION

Functional variants within the DIO1 gene, which affect TH levels and polymorphisms in DIO3, are not confirmed to be associated with rDD. Nevertheless, considering previous data which indicate that the DIO1 gene is related to the depression, further studies on a larger sample size are recommended.

Rats with altered behaviour following nerve injury show evidence of centrally altered thyroid regulation

The co-morbidity of mood disturbance, in a proportion of patients, is now described across a wide range of chronic disease states. Similarly, a 'Low Thyroid Syndrome' is also reported in a proportion of individuals with chronic diseases. Here, we report on central changes in an animal model of inflammatory stress in which altered social behaviour, representing social disability, persists in a sub-group of rats following injury. We showed in an earlier study that rats with social disability following injury have significantly decreased peripheral thyroid hormones, with no increase in Thyroid Stimulating Hormone (TSH). Only rats identified by behavioural change showed changes in hypothalamic gene expression. In whole hypothalamus extracted RNA, relative expression of mRNA for Thyrotrophin-releasing hormone (TRH) was significantly down-regulated in disabled rats (p=0.039) and deiodinase 3 up-regulated (p=0.006) compared to controls. Specifically in the paraventricular nucleus (PVN), numbers of immunoreactive cells for deiodinase 3-like and thyroid hormone receptor beta-like proteins were decreased in the sub-group with disability compared to the control group (p=0.031 and p=0.011 respectively). In rats with behavioural change post-injury, down-regulation of TRH provides an explanation for the failure of the hypothalamo-pituitary-thyroid (HPT) axis to respond to the post-injury decrease in thyroxine. Decreased local expression of deiodinase 3 protein, resulting in a local increase in T3, offers an explanation for down regulation of TRH in the hypophysiotrophic TRH neurons. It is possible that, in a sub-group of animals identified behaviourally, a mechanism resulting in hypothalamic down-regulation of the HPT axis persists following inflammatory injury.

Selenium supplementation alters gene expression profiles associated with innate immunity in whole-blood neutrophils of sheep

Footrot (FR) is a common, contagious bacterial disease of sheep that results in lameness and significant economic losses for producers. We previously reported that sheep affected with FR have lower whole-blood (WB) selenium (Se) concentrations and that Se supplementation in conjunction with routine control practices accelerates recovery from FR. To determine whether oral Se-yeast administered at supranutritional levels (>4.9 mg Se/week) alters the ability of sheep to resist or recover from FR infection, 60 ewes with and 60 ewes without FR were drenched once weekly for 62.5 weeks with 0, 4.9, 14.7, or 24.5 mg organic Se-yeast (30 ewes per treatment group). Footrot prevalence and severity were measured at 0, 20, 28, 40, and 60 weeks of Se supplementation. Genomic expression of eight WB-neutrophil genes for selenoproteins and seven WB-neutrophil genes for proteins involved in innate immunity was determined at the end of the treatment period using SYBR Green and quantitative polymerase chain reaction methodology. Supranutritional Se-yeast supplementation successfully increased Se status in sheep but did not prevent FR. Supranutritional Se-yeast supplementation increased WB-neutrophil expression of genes involved in innate immunity: L-selectin, interleukin-8 receptor, and toll-like receptor 4, which were or tended to be lower in ewes affected with FR. Furthermore, supranutritional Se-yeast supplementation altered the expression of selenoprotein genes involved in innate immunity, increasing selenoprotein S and glutathione peroxidase 4 and decreasing iodothyronine deiodinases 2 and 3. In conclusion, supranutritional Se-yeast supplementation does not prevent FR, but does alter WB-neutrophil gene expression profiles associated with innate immunity, including reversing those impacted by FR.

Functional and molecular evidence of myelin- and neuroprotection by thyroid hormone administration in experimental allergic encephalomyelitis

AIMS

Recent data in mouse and rat demyelination models indicate that administration of thyroid hormone (TH) has a positive effect on the demyelination/remyelination balance. As axonal pathology has been recognized as an early neuropathological event in multiple sclerosis, and remyelination is considered a pre-eminent neuroprotective strategy, in this study we investigated whether TH administration improves nerve impulse propagation and protects axons.

METHODS

We followed up the somatosensory evoked potentials (SEPs) in triiodothyronine (T3)-treated and untreated experimental allergic encephalomyelitis (EAE) Dark-Agouti female rats during the electrical stimulation of the tail nerve. T3 treatment started on the 10th day post immunization (DPI) and a pulse administration was continued until the end of the study (33 DPI). SEPs were recorded at baseline (8 DPI) and the day after each hormone/ vehicle administration.

RESULTS

T3 treatment was associated with better outcome of clinical and neurophysiological parameters. SEPs latencies of the two groups behaved differently, being briefer and closer to control values (=faster impulse propagation) in T3-treated animals. The effect was evident on 24 DPI. In the same groups of animals, we also investigated axonal proteins, showing that T3 administration normalizes neurofilament immunoreactivity in the fasciculus gracilis and tau hyperphosphorylation in the lumbar spinal cord of EAE animals. No sign of plasma hyperthyroidism was found; moreover, the dysregulation of TH nuclear receptor expression observed in the spinal cord of EAE animals was corrected by T3 treatment.

CONCLUSIONS

T3 supplementation results in myelin sheath protection, nerve conduction preservation and axon protection in this animal model of multiple sclerosis.

Beyond low plasma T3: local thyroid hormone metabolism during inflammation and infection

Decreased serum thyroid hormone concentrations in severely ill patients were first reported in the 1970s, but the functional meaning of the observed changes in thyroid hormone levels, together known as nonthyroidal illness syndrome (NTIS), remains enigmatic. Although the common view was that NTIS results in overall down-regulation of metabolism in order to save energy, recent work has shown a more complex picture. NTIS comprises marked variation in transcriptional and translational activity of genes involved in thyroid hormone metabolism, ranging from inhibition to activation, dependent on the organ or tissue studied. Illness-induced changes in each of these organs appear to be very different during acute or chronic inflammation, adding an additional level of complexity. Organ- and timing-specific changes in the activity of thyroid hormone deiodinating enzymes (deiodinase types 1, 2, and 3) highlight deiodinases as proactive players in the response to illness, whereas the granulocyte is a novel and potentially important cell type involved in NTIS during bacterial infection. Although acute NTIS can be seen as an adaptive response to support the immune response, NTIS may turn disadvantageous when critical illness enters a chronic phase necessitating prolonged life support. For instance, changes in thyroid hormone metabolism in muscle during critical illness may be relevant for the pathogenesis of myopathy associated with prolonged ventilator dependence. This review focuses on NTIS as a timing-related and organ-specific response to illness, occurring independently from the decrease in serum thyroid hormone levels and potentially relevant for disease progression.

Triiodothyronine administration ameliorates the demyelination/remyelination ratio in a non-human primate model of multiple sclerosis by correcting tissue hypothyroidism

Remyelination failure is a key landmark in chronic progression of multiple sclerosis (MS), the most diffuse demyelinating disease in human, but the reasons for this are still unknown. It has been shown that thyroid hormone administration in the rodent models of acute and chronic demyelinating diseases improved their clinical course, pathology and remyelination. In the present study, we translated this therapeutic attempt to experimental allergic encephalomyelitis (EAE) in the non-human primate Callithrix Jacchus (marmoset). We report that short protocols of triiodothyronine treatment shifts the demyelination/remyelination balance toward remyelination, as assessed by morphology, immunohistochemistry and molecular biology, and improves the clinical course of the disease. We also found that severely ill animals display hypothyroidism and severe alteration of deiodinase and thyroid hormone receptor mRNAs expression in the spinal cord, which was completely corrected by thyroid hormone treatment. We therefore suggest that thyroid hormone treatment improves myelin sheath morphology in marmoset EAE, by correcting the dysfunction of thyroid hormone cellular effectors.

Consumptive hypothyroidism resulting from hepatic vascular tumors in an athyreotic adult

CONTEXT

Consumptive hypothyroidism is a rare syndrome resulting from increased catabolism of T(4) and T(3) by increased type 3 iodothyronine deiodinase (D3) activity. Consumptive hypothyroidism has primarily been described as a paraneoplastic syndrome in infants as well as in two adults with D3-expressing tumors.

OBJECTIVE

The aim of the study was to report the third case of consumptive hypothyroidism in an adult and the first in an athyreotic patient.

DESIGN, SETTING, AND PATIENT

We present a 38-yr-old athyreotic female who was euthyroid on a stable therapeutic dose of thyroid hormone for many years and then developed marked hyperthyrotropinemia, coincident with the discovery of large D3-expressing hepatic vascular tumors. The patient also had low serum T(3) and elevated serum rT(3). Hyperthyrotropinemia transiently worsened after surgical resection of the vascular tumors and then persisted for 3 wk after the operation, despite further increases in levothyroxine therapy.

INTERVENTION

The patient's vascular tumor and adjacent normal liver parenchyma were probed with a polyclonal antibody directed against D3.

MAIN OUTCOME MEASURES AND RESULTS

D3 immunostaining of the patient's vascular tumor was positive, with no significant immunoreactivity in the adjacent normal hepatic tissue.

CONCLUSIONS

This is the third case report of consumptive hypothyroidism in an adult and the first in an athyreotic individual. This case demonstrates that hyperthyrotropinemia may persist after partial liver resection, possibly from the hepatic resection itself.

The complex world of oligodendroglial differentiation inhibitors

Myelination is a central nervous system (CNS) process wherein oligodendrocyte-axon interactions lead to the establishment of myelin sheaths that stabilize, protect, and electrically insulate axons. In inflammatory demyelinating diseases such as multiple sclerosis (MS), the degeneration and eventual loss of functional myelin sheaths slows and blocks saltatory conduction in axons, which results in clinical impairment. However, remyelination can occur, and lesions can be partially repaired, resulting in clinical remission. The recruitment and activation of resident oligodendrocyte precursor cells (OPCs) play a critical role in the repair process because these cells have the capacity to differentiate into functional myelinating cells. Mature oligodendrocytes, however, are thought to have lost the capacity to develop new myelin sheaths and frequently undergo programmed cell death in MS. The endogenous capacity to generate new oligodendrocytes in MS is limited, and this is predominantly due to the presence of inhibitory components that block OPC differentiation and maturation. Here, we present an overview of recently identified negative regulators of oligodendroglial differentiation and their potential relevance for CNS repair in MS. Because currently available immunomodulatory drugs for MS mainly target inflammatory cascades outside the brain and fail to repair existing lesions, achieving more efficient lesion repair constitutes an important goal for future MS therapies.

Left-ventricular remodeling after myocardial infarction is associated with a cardiomyocyte-specific hypothyroid condition

Similarities in cardiac gene expression in hypothyroidism and left ventricular (LV) pathological remodeling after myocardial infarction (MI) suggest a role for impaired cardiac thyroid hormone (TH) signaling in the development of heart failure. Increased ventricular activity of the TH-degrading enzyme type 3 deiodinase (D3) is recognized as a potential cause. In the present study, we investigated the cardiac expression and activity of D3 over an 8-wk period after MI in C57Bl/6J mice. Pathological remodeling of the noninfarcted part of the LV was evident from cardiomyocyte hypertrophy, interstitial fibrosis, and impairment of contractility. These changes were maximal and stable from the first week onward, as was the degree of LV dilation. A strong induction of D3 activity was found, which was similarly stable for the period examined. Plasma T(4) levels were transiently decreased at 1 wk after MI, but T(3) levels remained normal. The high D3 activity was associated with increased D3 mRNA expression at 1 but not at 4 and 8 wk after MI. Immunohistochemistry localized D3 protein to cardiomyocytes. In vivo measurement of TH-dependent transcription activity in cardiomyocytes using a luciferase reporter assay indicated a 48% decrease in post-MI mice relative to sham-operated animals, and this was associated with a 50% decrease in LV tissue T(3) concentration. In conclusion, pathological ventricular remodeling after MI in the mouse leads to high and stable induction of D3 activity in cardiomyocytes and a local hypothyroid condition.

Inflammation induced neurological handicap processes in multiple sclerosis: new insights from preclinical studies

Multiple sclerosis (MS) is described as originating from incompletely explained neuroinflammatory processes, dysfunction of neuronal repair mechanisms and chronicity of inflammation events. Blood-borne immune cell infiltration and microglia activation are causing both neuronal destruction and myelin loss, which are responsible for progressive motor deficiencies, organic and cognitive dysfunctions. MRI as a non-invasive imaging method offers various ways to visualise de- and remyelination, neuronal loss, leukocyte infiltration, blood-brain barrier modification and new sensors are emerging to detect inflammatory lesions at an early stage. We describe studies performed on experimental autoimmune encephalomyelitis (EAE) animal models of MS that shed new light on mechanisms of functional impairments to understand the neurological handicap in MS. We focus on examples of neuroinflammation-mediated inhibition of CNS repair involving adult neurogenesis in the sub-ventricular zone and hippocampus and such experimentally observed inhibitions could reflect deficient plasticity and activation of compensatory mechanisms in MS. In parallel with cognitive decline, organic deficits such as bladder dysfunction are described in most of MS patients. Neuropharmacological interventions, electrical stimulation of nerves, MRI and histopathology follow-up studies helped in understanding the operating events to remodel the neurological networks and to compensate the inflammatory lesions both in spinal cord and in cortical regions. At the molecular level, the local production of reactive products is a well-described phenomenon: oxidative species disturb cellular physiology and generate new molecular epitopes that could further promote immune reactions. The translational research from EAE animal models to MS patient cohorts helps in understanding the mechanisms of the neurological handicap and in development of new therapeutic concepts in MS.